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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 41 (1998), S. 1523-1528 
    ISSN: 1530-0358
    Keywords: Diverticular disease ; Complications ; Surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: The natural history of patients admitted because of acute diverticulitis is largely unknown, and the selection of patients for surgical treatment varies notably. This study presents our experience concerning the outcome for 366 patients admitted during a 10-year period. METHODS: Three hundred sixty-six patients admitted to our hospital with acute diverticulitis from 1981 to 1990 were identified from a computer database, and their clinical data up to the end of 1996 were reviewed from the database and patient records. RESULTS: There were significantly more males than females in the age group less than 50 years old, and young males underwent surgical treatment during the first treatment period more frequently than the others. Young patients were operated on without mortality, and all their temporary colostomies were closed. Older patients died more often of diseases unrelated to the diverticular disease during the years after the first episode of acute diverticulitis. Recurrences of diverticular disease developed in 22 percent of patients, and they were significantly more common in patients less than 50 years old than in the older age groups. Males less than 50 years old more often developed complications of diverticular disease after two hospital admissions. CONCLUSIONS: Males first admitted when less than 50 years of age undergo more primary operations and develop more recurrences of diverticular disease than do older people. Based on our data, however, we recommend surgery for all patients after two episodes of acute diverticulitis that resolves after conservative treatment with antibiotics.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 41 (1998), S. 654-657 
    ISSN: 1530-0358
    Keywords: Ileoanal reconstruction ; Complications ; Blind loop ; Surgical management ; Surgical technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: To demonstrate a simple and effective repair of a poorly constructed ileal J-pouch with an extensive long efferent limb. METHOD: A retrospective case review was performed. RESULTS: The surgical procedure described preserves additional ileum and enlarges the ileal reservoir. The procedure succeeded in resolving the patient's complaints of partial obstruction, weight loss, and increased stool frequency. At five-month follow-up, the patient was doing well with three to six stools daily. Evaluation of the new ileal J-pouch showed no signs of inflammation, and the pouch size measured more than 20 cm compared with 12 cm preoperatively. CONCLUSIONS: Repair of a long efferent limb by this simple stapling technique is feasible, simple, and effective, with an excellent clinical result. It preserves valuable small intestine and enlarges the capacity of the reservoir, leading to better functional outcome.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 41 (1998), S. 1023-1028 
    ISSN: 1530-0358
    Keywords: Diverticulitis ; Computed tomography ; Hospital costs ; Complications ; Surgery ; Accuracy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: The purpose of this study was to evaluate the use and timing of computed tomography in the treatment of patients with acute left-sided diverticulitis. METHODS: We reviewed our four-year experience of 47 patients with the diagnosis of acute diverticulitis. We have evaluated the benefits of admissionvs. delayed computed tomography in patients with this diagnosis. RESULTS: Of the 47 patients, 17 were diagnosed on clinical grounds alone, treated, and released. Thirty patients had their clinical diagnoses of diverticulitis evaluated with either computed tomographic scan (26) or laparotomy (4). Eleven of those 30 (36 percent) patients were found to have normal computed tomographic scans, indicating inaccurate clinical diagnosis, and all patients who underwent laparotomy had the pathologic diagnosis of diverticulitis. Six of the 47 patients had abscesses, but only 2 were identified at the time of admission. The remaining four abscesses were identified on delayed computed tomographic scans after failure of medical therapy. Thirty-seven hospital days were used by patients with inaccurate diagnoses before their computed tomographic scans. Analysis of cost revealed that a computed tomographic scan for all 47 patients would have cost less than the expense of admission for just the 11 patients who had normal computed tomographic scans. CONCLUSION: Routine admission computed tomographic scan for patients with acute diverticulitis leads to more accurate diagnosis, earlier identification of complications, and possible decreased hospital costs.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 41 (1998), S. 1587-1589 
    ISSN: 1530-0358
    Keywords: Ileal-pouch-anal-anal anastomosis ; Complications ; Surgical technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: A novel technique is described for pouch reconstruction after failed restorative proctocolectomy and pouch excision. METHODS: Surgery was undertaken in two patients who had undergone restorative proctocolectomy with subsequent excision of the ileal J-pouch after necrosis. At revisional surgery it was technically impossible to form a pouch using the terminal ileum because of mesenteric shortening. A new 18-cm J-pouch was formed with a jejunal segment. After selective division of axial vessels, adequate length was obtained to allow formation of a jejunal-pouchanal anastomosis. The small bowel distal to the pouch was interposed between the proximal jejunum and J-pouch and a defunctioning stoma was made. RESULTS: The postoperative course was uneventful in both cases. The functional results at 3 and 12 months after stoma closure were good, with five to seven bowel movements per day and complete continence. CONCLUSION: Shortening of the terminal ileal mesentery may preclude the formation of an ileal pouch in patients undergoing salvage surgery after failed restorative proctocolectomy. This novel technique of jejunal J-pouch formation and small-bowel interposition has value as an alternative to definitive ileostomy or Kock's pouch in such patients.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 41 (1998), S. 254-257 
    ISSN: 1530-0358
    Keywords: Insufficiency fractures ; Radiation injury effects ; Radiotherapy ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: The report contained herein presents a patient who developed severe back pain because of bilateral sacral insufficiency fractures after pelvic radiation for rectal carcinoma. METHODS: This is a case report and review of the literature for a rare complication of pelvic radiation. RESULT: The patient was diagnosed by computerized tomography and radionuclide bone scans. Bed rest and analgesia followed by rehabilitation provided good relief of the symptoms. CONCLUSION: A rare complication of pelvic radiation is insufficiency fractures of the pelvis. Early detection is important, because significant morbidity may result from delaying treatment. Unawareness of this complication may lead to diagnostic difficulties and unnecessary work-up.
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  • 6
    ISSN: 1534-4681
    Keywords: Pelvic exenteration ; Gynecologic malignancy ; Complications ; Antibiotics ; Heparin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Since pelvic exenteration for the treatment of recurrent gynecologic malignancy first was described, reported rates of morbidity and mortality have declined steadily. However, the factors responsible for this decline have never been clearly delineated. Methods: We reviewed the charts of 154 patients who underwent pelvic exenteration for gynecologic malignancy between 1954 and 1994. Charts were abstracted for details of the surgical procedure, pathologic findings, postoperative management, short- and long-term complications, time to recurrence, and overall survival. Results: Seventy-two patients (47%) experienced 95 identifiable postoperative complications, resulting in death in 22 patients (14%). The rate of infectious complications declined to a statistically significant degree between the first two decades and latter two decades of the study (odds ratio [OR] 0.28, 95% CI 0.11–0.69). The use of routine prophylactic antibiotics was associated with this decline in infectious complications (OR 0.25, 95% CI 0.07–0.83). The use of preoperative subcutaneous heparin was associated with a reduction in thrombotic complications from 5 of 100 patients to 0 of 54 patients (P=.11), as well as a significant reduction in overall risk of complications (OR 0.53, 95% CI 0.33–0.85) and risk of postoperative mortality (OR 0.19, 95% CI 0.05–0.80). There was a significant reduction in overall risk of postoperative complications with both intensive care unit monitoring postoperatively (OR 0.65, 95% CI 0.43–0.99) and routine postoperative monitoring with a pulmonary artery catheter (OR 0.61, 95% CI 0.38–0.98). Conclusions: Routine use of prophylactic antibiotics, prophylactic subcutaneous heparin, and intensive postoperative monitoring appear to have reduced morbidity from pelvic exenteration.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Clinical oral investigations 2 (1998), S. 73-76 
    ISSN: 1436-3771
    Keywords: Key words Inferior alveolar nerve ; Complications ; Endodontic treatment ; Surgical therapy ; Apicectomia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Overextension of filling material into the mandibular canal after root treatment in the lower jaw is a rare but serious complication. Mechanical compression, chemical neurotoxicity and local infection may cause irreversible nerve damage. A report on 11 patients with neurological complaints of the inferior alveolar nerve after endodontic treatment is summarised. The neurological findings are dominated by hypaesthesia and dysaesthesia. Half of the patients reported pain. Hyperaesthesia is found much more rarely. Nearly all the patients had a combination of one or more symptoms. Initial X-rays showed root filling material in the area of the mandibular canal. Nine cases were treated with apicectomy and decompression of the nerve; in two cases, extraction of the tooth was necessary. Only one patient reported persistent pain after surgery. If neurological complaints appear after root filling in the lower jaw, a nerve injury due to root filling material should be ruled out. In cases of overfilling, immediate apicectomy and decompression of the nerve with conservation of the tooth is often the treatment of choice; the tooth may be preserved and the best chance of avoiding permanent nerve damage is provided.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Neurosurgical review 21 (1998), S. 254-259 
    ISSN: 1437-2320
    Keywords: Complications ; fiberoptic device ; intracranial pressure monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Seventy-five patients with intracranial hypertension whose Glasgow Coma Score (GCS) was 8 or below and in whom intracranial pressure (ICP) was monitored were examined for complications of this procedure. In 20 of the 75 patients we used only an intraparenchymal fiberoptic ICP monitoring transducer, while, in the remaining 55 patients, who required CSF drainage, a ventricular drainage set (VDS) was used in addition to ICP monitoring. The duration of monitoring with the ICP transducer alone was approximately 5.1 ± 2.6 das (min. 1, max. 13) and that of ICP monitoring with VDS was 6.2 ± 3.1 days (min. 1, max. 13). In 8 cases a total of 9 complications were experienced (12 %). These complications were infection in 3 cases (4 %), epidural hematoma in 2 cases (2.7 %), disconnection in 2 cases (2.7 %) and contusion in 2 cases (2.7 %). Although none of the 44 patients who were monitored for less than 5 days experienced infection, 3 of the 31 patients monitored for longer than 5 days did experience infection (9.7 %) (p 〈 0.05). None of the 20 patients who underwent ICP monitoring only experienced infection. However, 3 of the 55 patients in whom the ventricular drainage set was implanted in addition to the transducer for ICP monitoring experienced infection (p 〈 0.05). Owing to its minimally invasive nature, low complication rate, and accuracy in monitoring the parenchyma pressure, the Camino fiberoptic intraparenchymal monitor has become the system of choice in our clinic.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Rechtsmedizin 8 (1998), S. 73-76 
    ISSN: 1434-5196
    Keywords: Key words Laparoscopy ; Complications ; Carbon ; dioxide embolism ; Confirmation ; Schlüsselwörter Laparoskopie ; Komplikationen ; Kohlendioxid-Embolie ; Nachweis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Es wird der Fall einer 30 Jahre alt gewordenen Patientin vorgestellt, welche während einer beabsichtigten gynäkologischen laparoskopischen Operation trotz sofortiger Reanimationsmaßnahmen akut starb. Die klinische Symptomatik entsprach einer akuten Gasembolie, insbesondere wegen einer sonographisch verifizierten intravasalen Gaspulsation. Bei der Obduktion 2 Tage postmortem wurde eine frische Perforation der linken Vena iliaca communis festgestellt. Eine Gasembolie des Herzens konnte nicht nachgewiesen werden. Es wird auf besondere physiko-chemische Bedingungen einer tödlichen CO2-Gasembolie hingewiesen. Voraussetzungen für den postmortalen Gasnachweis sind: umgehende Obduktion und Verzicht auf Kühlung der Leiche.
    Notes: Abstract We report a case of a 30-year-old patient who – after unsuccessfull resuscitation – died during gynecological laparoscopy. Prefinal symptoms corresponded to acute gas embolism, particularly as ultrasonic examination revealed an intravascular gas pulsation. At autopsy, 2 days postmortem, a punction of the left common iliac vein was discovered but gas bubbles in the right heart could not be confirmed. Preconditions for fatal carbon dioxide embolism are stressed. To prove the presence of carbon dioxide gas postmortem, autopsy has to be performed as soon as possible and the corpse has to be stored without cooling.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Der Chirurg 69 (1998), S. 773-776 
    ISSN: 1433-0385
    Keywords: Key words: Laparoscopy ; Complications ; Carbon dioxide embolism ; Confirmation. ; Schlüsselwörter: Laparoskopie ; Komplikationen ; Kohlendioxid-Embolie ; Nachweis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Tödliche Komplikationen bei endoskopischen Eingriffen sind insgesamt selten. Als häufigste Ursache wurden Verletzungen großer intraabdominaler Gefäße mit nachfolgender Blutung, aber auch mit Kohlendioxid (CO2)-Embolie beobachtet. Es wird der Fall einer 30 Jahre alt gewordenen Patientin vorgestellt, welche zu Beginn einer gynäkologisch-laparoskopischen Operation trotz sofortiger Reanimationsmaßnahmen akut starb. Die klinische Symptomatik entsprach einer akuten Gasembolie, insbesondere wegen einer sonographisch verifizierten Gaspulsation. Bei der Obduktion 2 Tage post mortem wurde eine frische Perforation der linken V. iliaca communis festgestellt. Eine Gasembolie des Herzens konnte nicht nachgewiesen werden. Dafür können die physikochemischen Eigenschaften des CO2 maßgeblich sein. Voraussetzungen für den postmortalen Gasnachweis sind: umgehende Obduktion und Verzicht auf Kühlung der Leiche.
    Notes: Summary. Fatal complications during laparoscopy mostly originate from injury to major pelvic vessels, causing severe hemorrhage or carbon dioxide embolism. We report a case of a 30-year-old patient who – after unsuccessful resuscitation – died during gynecologic laparoscopy. The noted signs corresponded to acute gas embolism, particularly as ultrasound revealed intravascular gas pulsation. At autopsy, 2 days post mortem, a puncture of the left common iliac vein was discovered. Despite this, gas bubbles in the right heart could not be confirmed. Preconditions for fatal carbon dioxide embolism are stressed. To prove the presence of carbon dioxide gas post mortem, autopsy has to be performed as soon as possible and the corpse has to be stored without cooling.
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  • 11
    ISSN: 1279-8517
    Keywords: Ureter ; Abnormalities ; Embryology ; Calculi ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Partial ureteral duplication in an inverted Y is evidenced by the presence of a ureter duplicated at a variable level before reaching the bladder, in either an orthotopic or an ectopic position. A case of ureteral duplication at the level of the renal hilum with opening of a ureter at the level of the epididymis is reported. The description of this original case is compared with the data in the literature. The stages of organogenesis of the superior excretory pathway leading to ureteral ectopia and ureteral anomalies of number are reviewed.
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  • 12
    ISSN: 1279-8517
    Keywords: Ureter ; Abnormalities ; Embryology ; Calculi ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé La duplication urétérale partielle en Y inversé se traduit par la présence d'un uretère se dédoublant à une hauteur variable avant d'atteindre la vessie, de façon orthotopique ou ectopique. Un cas de dédoublement urétéral au niveau du hile du rein avec abouchement d'un uretère ectopique au niveau de l'épididyme est rapporté. La description de ce cas original permet sa confrontation aux données de la littérature. Les étapes de l'organogenèse de la voie excrétrice supérieure aboutissant aux ectopies urétérales et aux anomalies urétérales de nombre sont rappelées.
    Notes: Summary Partial ureteral duplication in an inverted Y is evidenced by the presence of a ureter duplicated at a variable level before reaching the bladder, in either an orthotopic or an ectopic position. A case of ureteral duplication at the level of the renal hilum with opening of a ureter at the level of the epididymis is reported. The description of this original case is compared with the data in the literature. The stages of organogenesis of the superior excretory pathway leading to ureteral ectopia and ureteral anomalies of number are reviewed.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    International journal of legal medicine 111 (1998), S. 93-96 
    ISSN: 1437-1596
    Keywords: Key words Cardiopulmonary resuscitation ; Active compression-decompression ; Complications ; Iatrogenic injury ; Myocardial rupture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract An 84-year-old woman was unsuccessfully resuscitated for 3 min using standard cardiopulmonary resuscitation (CPR), followed by 15 min of active compression-decompression (ACD). The autopsy revealed that death was due to myocardial infarction complicated by rupture of the infarcted area and pericardial tamponade was diagnosed. Furthermore, a series of rib fractures, a transverse fracture of the sternum, rupture of the pericardial sac, the right ventricle, both atria and lacerations of the ascending aorta, were found with no signs of a vital reaction. To our knowledge, such extensive cardiac injury after CPR has not been previously reported. It is suggested that the pre-existing pericardial tamponade, the age of the patient and the application of the ACD-device to incorrect areas of the chest contributed to the extent of the cardiac injury. This case further adds to the suspicion of an increased risk of cardiac injuries when using an ACD device for cardiac massage.
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  • 14
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Intubation ; tracheal: retrograd-geführt ; fiberoptisch ; Technik ; Komplikationen ; Training ; Key words Tracheal intubation ; Retrograde-guided fiberoptic technique ; Complications ; Training
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Retrograde or fiberoptic intubation techniques are recommended for patients in whom intubation is difficult; however, each method has its own limitations. Good results have been reported with a combination of both techniques, i.e. retrograde passage of a guidewire through the cricothyroid membrane to guide a fiberoptic bronchoscope. The practicality, success and complication rates of our retrograde-guided fiberoptic bronchoscopic technique (RGFT) were studied prospectively in 93 patients with obstructing tumors scheduled for laryngectomy. The technique showed itself to be successful, practical and safe, with negligible complications in 89/93 patients (96%). The ability to insert the bronchoscope by means of a guidewire and to direct the intubation procedure optically was found to be advantageous. Limitations were found in two patients with extreme obesity and in two other patients with advanced obstructive carcinomas of the larynx. Additionally, use of the tracheal puncture allows the RGFT to be integrated into clinical medical education as a preparatory exercise for emergency coniotomy.
    Notes: Zusammenfassung Retrograde und fiberoptische Intubationstechniken werden für schwierig zu intubierende Patienten empfohlen, weisen aber jeweils methodenspezifische Limitationen auf. Gute Erfolge wurden mit einer Kombination beider Techniken, d.h. der retrograden Passage eines Führungsdrahts durch die Membrana cricothyreoidea und nachfolgenden Führung des Fiberbronchoskops beschrieben. In einer prospektiven Studie an 93 Patienten mit Hyopharynx-Larynx-Karzinom, die für eine Laryngektomie vorgesehen waren, wurden Durchführbarkeit, Erfolgsrate und Komplikationsrate der „retrograd-geführten fiberbronchoskopischen Technik” (RGFT) untersucht. Die Technik erwies sich bei 89/93 Patienten (96%) als relativ einfaches, praktikables und sicheres Verfahren mit vernachlässigbaren Komplikationen, das aufgrund der Führung des Bronchoskops durch den Führungsdraht sowie die optische Kontrolle des Intubationsvorgangs vorteilhaft war. Limitationen fanden sich bei 2 Patienten mit Adipositas permagna sowie bei 2 weiteren Patienten mit obstruierendem Larynxkarzinom. Aufgrund der erforderlichen Trachealpunktion ist die RGFT darüber hinaus als Vorübung zur Notfallkoniotomie unter optimalen Bedingungen in die klinische Routine integrierbar.
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  • 15
    ISSN: 1433-0385
    Keywords: Key words: ASA score ; Risk evaluation ; Complications ; Laparoscopic cholecystectomy ; Contraindications. ; Schlüsselwörter: ASA-Klassifikation ; Risikoeinschätzung ; Komplikationen ; laparoskopische Cholecystektomie ; Kontraindikation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die laparoskopischen Cholecystektomie bietet eine Reihe von Vorteilen, denen eine erhöhte Gefährdung kardiopulmonal vorgeschädigter Patienten durch die hämodynamischen und respiratorischen Auswirkungen des Pneumoperitoneums gegenübersteht. In der Zeit von Juni 1990 bis Dezember 1995 wurden 19 Hochrisikopatienten (ASA IV) laparoskopisch und 26 Patienten mit gleichem operativem Risiko (ASA IV) konventionell cholecystektomiert. Bei insgesamt 11,1 % (n = 5) an intraoperativen, kardiopulmonalen Komplikationen traten diese in beiden Gruppen annähernd gleichhäufig auf. Allgemeine, postoperative Komplikationen sahen wir in 33,3 % (n = 15) aller Fälle, wobei die konventionell operierten Patienten vermehrt betroffen waren [46,2 % (n = 12) vs. 15,8 % (n = 3), p = 0,03]. Die Liegedauer war in der Gruppe der offen operierten Patienten mit 11,6 ± 5,6 Tagen im Vergleich zu 7,6 ± 5 (Gruppe der laparoskopisch operierten Patienten) verlängert (p = 0,01). Die Einstufung als Hochrisikopatient bedeutet insgesamt eine Erhöhung der perioperativen Komplikationsrate, wobei bei gleichem intraoperativen Risiko die postoperative Komplikationsrate bei laparoskopischer Cholecystektomie niedriger ist.
    Notes: Summary. Laparoscopic cholecystectomy offers many advantages, but cardiopulmonary impaired patients may be endangered by the haemodynamic and respiratory effects of the pneumoperitoneum. Between June 1990 and December 1995, laparoscopic cholecystectomies were performed on 19 high-risk patients (ASA IV) and conventional cholecystectomies on 26 patients with the same operative risk (ASA IV). Out of 45 patients, 5 (11.1 %) suffered intraoperative cardiopulmonal complications. Three belonged to the group with laparoscopic cholecystectomy (15,8 %) and two to the group with open laparotomy (7.7 %). General postoperative complications occured in 15 cases (33.3 %), whereby patients of the conventional cholcystectomy group were concerned more often [46.2 % (n = 12) versus 15.8 % (n = 3), P = 0.03]. The number of days spent in hospital after open cholecystectomy was higher (P = 0.01) (11.6 ± 5.6 days in the laparotomy group versus 7.6 ± 5.0 days in the laparoscopy group). The classification as a high-risk patient indicates an elevation of the perioperative rate of complications in laparoscopic and open cholecystectomy, whereby the rate of postoperative complications is lower in the laparoscopic group.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Der Chirurg 69 (1998), S. 1035-1044 
    ISSN: 1433-0385
    Keywords: Key words: Ileoanal Pouch ; Redo-Operation ; Complications ; Pouchitis. ; Schlüsselwörter: Ileoanaler Pouch ; Redo-Operationen ; Komplikationen ; Pouchitis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die Komplikationsrate nach ileoanaler Pouchrekonstruktion wird in der Literatur mit bis zu 60 % angegeben. Diese Rate beinhaltet allerdings auch postoperative Komplikationen – wie z. B. Ileus, Narbenbruch –, die nach jedem Eingriff auftreten können. Betrachtet man ausschließlich die Pouch-bezogene, also die das Verfahren betreffende Komplikationsrate, so werden zwischen 15 und 25 % angegeben. Dabei zeigen sich als Hauptrisikofaktoren eine erhöhte Spannung der ileoanalen Anastomose, Anastomoseninsuffizienz, ein fehlender Stomaschutz, ein präoperativ undiagnostizierter Morbus Crohn und die Unerfahrenheit des Chirurgen. Wir klassifizierten die Pouchkomplikationen in 5 Kategorien: 1. chirurgische Komplikationen (Anastomoseninsuffizienz, Blutung, pelvine Sepsis, Fisteln), 2. technische Probleme (langer S-Pouch-Auslaß, Rectum-Cuff-Stenose, Pouchsteg), 3. funktionelle Probleme (Analsphincterinsuffizienz, Nachtinkontinenz, hypermotiler Pouch, Evakuationsstörungen), 4. Pouchitis und 5. Pouchneoplasien. Die Pathogenese, Diagnostik und medikamentöse und chirurgische Therapie wird eingehend analysiert. In einer eigenen Serie von 11 Pouch-Redo-Operationen wurde bei 6 Pouchfisteln (3mal mit Morbus Crohn), 3 Fehlkonstruktionen, einem langen S-Pouch-Auslaß sowie einer chronischen Pouchitis in 6 Fällen ein langfristiger Erhalt erreicht. In 3 Fällen mußte der Pouch komplett exstirpiert werden, in 2 Fällen persistierte das Loop-Ileostoma. Aufgrund der technischen Komplexität der Operation, dem nötigen Verständnis der Pathophysiologie sowie der Verfügbarkeit und Beherrschung der nötigen Diagnostik sollte diese Operation nur in darauf spezialisierten Zentren vorgenommen werden.
    Notes: Summary. The overall rate of complications after ileal pouch–anal anastomosis is 60 %. This rate, however, includes complications such as bowel-obstruction and hernias. Pouch-related complications occur after ileal pouch–anal anastomosis with a frequency of 15–25 %. In an analysis of the recent literature the main risk factors are: tension of the ileal pouch–anal anastomosis, anastomotic leakage, lack of protective ileostomy, preoperatively undiagnosed Crohn's disease and the experience of the surgeon. We classified pouch related-complications into (1) surgical complications (leakage, bleeding, pelvic sepsis, fistulas); (2) technical problems (long S-pouch spout, rectal cuff stenosis, etc.); (3) functional problems (anal sphincter insufficiency, night incontinence, hypermotility, evacuation disorders); (4) pouchitis; (5) pouch neoplasias. Pathogenesis, diagnostic features, and medical and surgical therapy are discussed in detail. In our own series of 11 pouch-redo operations we had 6 pouch fistulas (3 related to Crohn's disease, 3 postoperative fistulas), 3 wrongly constructed pouches, 1 chronic pouchitis and 1 long S-pouch spout. In 3 cases the pouch had to be excised completely. Two patients remained with a permanent ileostomy. In 6 patients the pouch could be preserved on long term. Due to the technical complexity, the need to understand pathophysiology and the need for a differentiated diagnostic procedure, this operation should be performed only in specialised centers.
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  • 17
    ISSN: 1433-0385
    Keywords: Key words: Percutaneous dilatational tracheostomy ; Translaryngeal tracheostomy ; Complications ; Results ; Minimally invasive surgery. ; Schlüsselwörter: Punktionstracheostomie ; translaryngeale Tracheostomie ; Komplikationen ; Ergebnisse ; minimal-invasive Chirurgie.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die Punktionstracheostomie (PT) und die translaryngeale Tracheostomie (TLT) sind relativ neuartige, minimal-invasive Methoden zur Behandlung von langzeitbeatmeten Intensivpatienten. Beide Verfahren werden erstmals innerhalb einer prospektiv-randomisierten Studie an 50 Intensivpatienten (34 m., 16 w., Alter: 18–84 Jahre) hinsichtlich ihrer Frühkomplikationsrate und der perioperativen methodenbedingten Beeinträchtigung der Beatmung verglichen. Bei je 25 Patienten wurde eine PT bzw. eine TLT durchgeführt. Perioperativ wurde in beiden Gruppen keine Hypoxie beobachtet, allerdings war ein Abfall des PaO2 um mehr als 50 mm Hg während der TLT 9mal, bei der PT nur 3mal festzustellen (p = 0,051). Außerdem war der mittlere Anstieg des PaCO2 in der TLT-Gruppe signifikant höher (5,2 ± 6,7 vs. 11,6 ± 8,4 mm Hg; p 〈 0,01). In der PT-Gruppe kam perioperativ keine Komplikation vor, nach TLT mußte einmal zur PT konvertiert werden, nachdem die Kanülenspitze disloziert war. Postoperativ trat einmal eine vorzeitige akzidentelle Dekanülierung nach PT und eine Blutung nach TLT auf. PT und TLT sind bei entsprechender klinischer Erfahrung sichere Methoden. Da bei der TLT unter Umständen mit einer erheblichen Hyperkapnie und einem Abfall des arteriellen Sauerstoffpartialdruckes zu rechnen ist, sollte dieses Verfahren nur bei Patienten ohne spezielle Risiken angewandt werden.
    Notes: Summary. Percutaneous dilatational tracheostomy (PT) and translaryngeal tracheostomy (TLT) are relatively new minimally invasive methods for critically ill patients. To compare the perioperative procedural safety we analyzed the severity of perioperative blood gas changes in a prospective randomized clinical study in 50 patients (34 men, 16 women; age 18–84 years). Additionally, early complications were documented. Twenty-five PTs and 25 TLTs were performed under tracheoscopic guidance. Perioperative hypoxia did not occur in either group; however, a decrease of PaO2 of more than 50 mm Hg was noticed in nine patients during TLT versus three patients with PT (P = 0.051). The mean increase of PaCO2 was significantly higher in the TLT-group (5.2 ± 6.7 vs 11.6 ± 8.4 mm Hg; P 〈 0.01). In the PT group no perioperative complications arose; in the TLT group one procedure was not successful and had to be converted to a PT. Postoperatively, one premature decannulation (PT group) and one bleeding (TLT group) were noticed. PT and TLT are safe methods. Early complications are rare in experienced hands. TLT tends to cause relevant hypercarbia and should therefore be restricted to patients without special risks.
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  • 18
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    Der Chirurg 69 (1998), S. 604-612 
    ISSN: 1433-0385
    Keywords: Key words: Laparoscopy ; Retroperitoneoscopy ; Nephrectomy ; Complications ; Reintervention ; Conversion. ; Schlüsselwörter: Laparoskopie ; Retroperitoneoskopie ; Nephrektomie ; Komplikationen ; Reintervention ; Konversion.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Der retroperitoneale Zugang findet breite Anwendung bei offenen Operationen in der Urologie. Mit Einführung der Ballondissektionstechnik konnte dieser anatomische Zugang auch für laparoskopische Operationen genutzt werden. Material und Methode: Zwischen 12/1992 und 10/1997 wurden 200 retroperitoneale Operationen an 197 Patienten (Alter 4–82 Jahre) durchgeführt: 78 Nephrektomien, 50 Nierencystenresektionen, 14 Nephropexien, 11 Ureterolysen, 8 retroperitoneale Lymphadenektomien, 8 Nierenbiopsien, 6 Adrenalektomien, 6 Heminephrektomien, 6 Pyeloplastiken, 5 Ureterolithotomien, 6 Ureterocutaneostomien sowie 2 andere. 38 Patienten (19 %) waren bereits abdominell , 22 (11 %) an Niere und Ureter voroperiert. Die Präparation des Retroperitonealraums erfolgte in 14 Fällen mit Hilfe eines Ballonkatheters, in 93 Fällen mittels eines Ballontrokarsystems, während in den letzten 93 Fällen eine Präparation des Retroperitoneums mit dem Zeigefinger sich als ausreichend erwies. Ergebnisse: Die Eingriffe wurden wie folgt klassifiziert: 76 einfache Operationen (z. B. Nierenbiopsie, Nierencystenresektion, Ureterocutaneostomie), 102 schwierige (z. B. Adrenalektomie, Nephrektomie, Nephropexie) und 22 sehr schwierige Eingriffe (z. B. Pyeloplastik, Heminephrektomie, Lymphadenektomie). Während der ersten 50 Fälle zeigte sich eine signifikante Lernkurve, welche sich in einer höheren Operationszeit und Komplikations- sowie Konversionsrate widerspiegelte. Abhängig vom Schwierigkeitsgrad des Eingriffs betrugen die mittlere Operationszeiten 45–100 min bei leichten Eingriffen, 95–185 min bei schwierigen und 185–240 min bei sehr schwierigen Operationen. In den letzten 50 Fällen war die Komplikations-, Konversions- sowie Reinterventionsrate mit offenen Eingriffen vergleichbar (2, 4 und 2 %). Schlußfolgerung: Nach mehr als 200 retroperitoneoskopischen Eingriffen wurde die Zugangstechnik bedeutend vereinfacht, so daß das Verfahren heute standardisiert, sicher und reproduzierbar ist.
    Notes: Summary. A retroperitoneal access is most commonly applied for open procedures in urology. With introduction of the balloon dissecting technique, this anatomical route could also be used for laparoscopic surgery. Materials and Methods: From 12/1992 to 10/1997, a total of 200 retroperitoneoscopic procedures have been performed in 197 patients (age 4–82 years): 78 nephrectomies, 50 renal cyst resections, 14 nephropexies, 11 ureterolyses, 8 retroperitoneal lymph-node dissections, 8 renal biopsies, 6 adrenalectomies, 6 heminephrectomies, 6 pyeloplasties, 5 ureterolithotomies, 6 ureterocutaneostomies and 2 others. Thirty-eight patients (19 %) had undergone previous abdominal surgery; 22 (11 %) had had kidney and ureter operations. Dissection of the retroperitoneal space was done with a balloon catheter in 14 or a balloon trocar system in 93 cases, and in the last 93 patients digital dissection with the index finger proved to be sufficient. Results: We classified 76 as simple (i. e., renal biopsy, renal cyst resections, ureterocutaneostomy) and 102 as difficult (i.e. adrenalectomy, nephrectomy, nephropexy) and 22 (11 %) as very difficult operations (i. e., pyeloplasty, heminephrectomy, lymphadenectomy). There has been a significant learning curve during the first 50 cases as reflected by increased operating time and complications and the conversion rate to open surgery. After that, the OR times mainly depended on the difficulty of the procedure, averaging 45–100 min for an easy retroperitoneoscopy, 95–185 min for a difficult and 185–240 min for a very difficult operation. In the last 50 cases, the complications, conversion and reintervention rate have become comparable to open surgery (2, 4 and 2 %). Conclusions: After more than 200 cases of retroperitoneoscopy, the access technique has been significantly simplified. The procedure is standardized, safe and reproducible.
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  • 19
    ISSN: 1433-0385
    Keywords: Key words: Hernia inguinalis ; Laparoscopic hernioplasty ; Complications ; Recurrences ; Learning curve. ; Schlüsselwörter: Leistenbruch ; laparoskopische Hernioplastik ; Komplikationen ; Rezidive ; Lernkurve.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. In der vorliegenden Studie werden erstmals an einem sehr großen Krankengut von 3400 Hernienreparationen prospektiv Risiko, Nutzen und Kosten der laparoskopischen Hernioplastik in der transabdominellen Technik mit präperitonealer Plazierung eines Polypropylennetzes untersucht. Die medianen Operationszeiten betrugen für die einseitige Primärhernie 45 min, für die einseitige Rezidivhernie 50 min und für die doppelseitige Hernie 76 min. Die Komplikationsfrequenz zeigte eine signifikante Abhängigkeit von den einzelnen Schritten der Methodenentwicklung sowie der individuellen Lernkurve. Das gleiche gilt für die Rezidivrate. Während anfänglich die Rate größerer Komplikationen bei 2,75 %, bei den kleineren Komplikationen bei 11 % und die Rezidivrate bei 4,5 % lag, betragen die entsprechenden Zahlen aktuell 0,4 %, 4,4 % bzw. 0,5 %. Die laparoskopische Hernioplastik erwies sich als gleich effektiv in der Behandlung der Primärhernie, der Rezidivhernie und der doppelseitigen Hernie. Die große Zahl von insgesamt 11 Operateuren zeigt, daß die laparoskopische Hernioplastik erlernbar ist und auch in einer Ausbildungsklinik sicher, effizient und kosteneffektiv durchgeführt werden kann.
    Notes: Summary. In the present study, for the first time the aspects of risk, benefit and the costs of laparoscopic hernioplasty in the transabdominal technique with preperitoneal placement of a polypropylene mesh are examined prospectively in a very large group of patients with 3,400 hernia repairs. The median operation time was 45 min for unilateral primary hernias, 50 min for unilateral recurrent hernias and 76 min for bilateral hernias. The frequency of complications showed a significant dependence on the individual steps in the development of the method and the individual learning curve. The same is true for the rate of recurrency. Whereas initially the rate of serious complications was 2.75 %, the rate of minor complications 11 % and the rate of recurrences 4.5 % the corresponding figures are at present 0.4 %, 4.4 % and 0.5 %. Laparoscopic hernioplasty proved to be equally as effective in the treatment of primary hernias, recurrent hernias and bilateral hernias. The large number of 11 surgeons participating proves that laparoscopic hernioplasty can be learned and that even in a teaching hospital it can be performed safely, efficiently and cost-effectively.
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  • 20
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Kopf-Hals-Tumoren ; PEG ; Komplikationen ; Langzeiternährung ; Key words Head and neck cancer ; PEG ; Complications ; Long-term nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Percutaneous endoscopically controlled gastrostomy (PEG) enables patients suffering from a tumor of the upper aerodigestive tract to receive direct gastric feedings. The procedure also avoids the social stigma of a nasal feeding tube. The results of 630 PEG procedures used in 555 patients suffering from various head and neck cancers are reported. The mean age of the patients was 58.0 years with a range from 11 to 92 years. The PEG procedure was carried out under local anesthesia in 60% of the cases and with general anesthesia in 40%. In 512 patients the initial PEG procedure was successful while 43 of the patients required a second PEG procedure after loss of the PEG. In 19 patients the PEG procedure was not successful because of tumor obstruction or it was not possible to perform endoscopy. Twenty-four patients were successfully treated in a second or third session. Altogether 97% (n = 563) of all 555 patients and 92% (n = 579) of all PEG procedures were successful. The mean duration of PEG use was 243 days (range: 0–2271 days). In 66 patients (10.5%) complications occurred but severe complications developed in only 8 patients (1.3%). Operative interventions were necessary in two cases. No deaths resulted from the PEG. These findings show that the PEG technique is safe to do with only few complications when performed by a skilled team.
    Notes: Zusammenfassung Die perkutane endoskopisch kontrollierte Gastrostomie (PEG) emöglicht Patienten mit Tumoren des oberen Aerodigestivtraktes eine direkte intragastrale Ernährung unter Ausschaltung der sowohl durch den Tumor selbst als auch die Tumortherapie stark alterierten Schluckstraße und erspart ihnen die soziale Stigmatisierung durch eine Nasensonde. Die Ergebnisse von 630 PEG-Prozeduren bei 555 Patienten mit Kopf-Hals-Tumoren werden vorgestellt. Die Patienten waren zum Zeitpunkt der PEG-Anlage im Durchschnitt 58,0 (11–92) Jahre alt. Der Eingriff erfolgte in 60% in Lokalanästhesie, in 40% in Intubationsnarkose. 512 Patienten wurden primär erfolgreich mit einer PEG versorgt. Von diesen 512 Patienten unterzogen sich 43 Patienten im Beobachtungszeitraum erneut einer erfolgreichen PEG-Prozedur nach Sondenverlust. Bei 19 Patienten war die Anlage einer PEG wegen endoskopisch – auch nach Bougierungsbehandlung – nicht passierbarer Tumorobstruktion oder fehlender Darstellbarkeit der Diaphanoskopie nicht möglich. Weitere 24 Patienten wurden nach zunächst erfolglosen Versuchen mit einer PEG versorgt. Somit war bei 97% (n = 536) der 555 Patienten bzw. bei 92% (n = 579) der 630 PEG-Prozeduren die PEG-Anlage erfolgreich. Bei einer mittleren Sondentragedauer von 243 (Spanne 0–2271) Tagen beobachteten wir bei insgesamt 10,5% (n = 66) der PEG-Anlagen Komplikationen, davon in nur 1,3% (n = 8) schwere Komplikationen; lediglich bei zwei Patienten war eine operative Intervention notwendig. Durch die Methode bedingte Todesfälle ereigneten sich nicht. Die Technik der PEG erweist sich damit in den Händen des erfahrenen Endoskopikers als sicher, komplikationsarm und den Patienten wenig belastend.
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  • 21
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Fibrinolyse ; Intrazerebrale Blutung ; CT ; Kontrastmittel ; Komplikation ; Key words Fibrinolysis ; Cerebral hemorrhage ; Computed tomography ; Contrast medium ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary
    Notes: Zusammenfassung
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  • 22
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    International journal of legal medicine 111 (1998), S. 154-156 
    ISSN: 1437-1596
    Keywords: Key words Air embolism ; Gastroscopy ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract Although venous air embolism is a known complication in medical practice in general, only a single case of upper gastrointestinal endoscopy complicated by venous air embolism with consecutive acute cardiovascular failure has so far been described in literature. Here we show that gastroscopy may be accompanied by massive, i.e. fatal venous air embolism. If a vessel in the gastrointestinal tract is exposed but does not collapse (in the case of a gastric ulcer, for example) air insufflated under pressure by the gastroscope may lead to a fatal air embolism. Our tests using a commercial gastroscope revealed that an overpressure of up to 43 kPa (kiloPascals) is reached without the rinsing function while an overpressure of up to 45 kPa is measured if the rinsing function is operated simultaneously. The maximum flow rates without resistance were 100 ml/min for rinsing liquid (purified water) and 2000 ml/min for air. Our results suggest that air insufflation by the gastroscope may result in a critical air embolism within very few seconds on condition that a connection with the vascular system exists. However, this complication is extremely rarely encountered. We propose that CO2 should be administered in place of air or alternatively the maximum pressure should be considerably reduced to avoid a fatal outcome in routinely performed gastroscopical examinations.
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  • 23
    ISSN: 1437-9813
    Keywords: Key words Esophageal atresia ; Tracheoesophageal fistula ; Prognosis ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The management of esophageal atresia (EA) and tracheoesophageal fistula (TEF) has improved markedly over the years, with a current overall survival of 80%–90%. This however, is not the case in developing countries, where mortality continues to be high. The results of treatment of 41 consecutive cases EA and/or TEF have been analyzed to determine factors pertinent to the outcome. The distribution of anomalies and a postoperative survival of 86.8% were comparable to those from developed countries. Aspiration pneumonia was unusually frequent in our patients (78%), but did not adversely influence outcome. Associated congenital anomalies as well as low birth weight continue to be important predictors of outcome in our setting. Our post-operative complications were similar to those from developed countries apart from a high incidence of stricture formation. This was attributed to gastroesophageal reflux, non-ventilation post-operatively, and the use of silk sutures to construct the anastomosis.
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  • 24
    ISSN: 1432-2161
    Keywords: Key words Osteochondroma ; Complications ; MR imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To demonstrate the value of MR imaging in the diagnosis and differentiation of the various symptomatic complications of osteochondromas, providing pathological correlation with emphasis on the usefulness of MR imaging as a single imaging modality in these patients. Design. We retrospectively reviewed all MR examinations of clinically symptomatic osteochondromas (30 patients) performed at our institution between March 1990 and October 1997. Patients. Thirty patients had clinically symptomatic osteochondromas during the study period. Twenty patients were male and 10 were female. There were five cases of multiple osteochondromatosis. Pathological correlation was available in 24 patients. Results and conclusion . Symptomatic complications included fracture (7%), osseous deformity limiting range of motion (23%), vascular injury (7%), neurological compromise (10%), bursa formation (27%) and malignant transformation (27%). MR imaging was able to diagnose or suggest the etiology for the clinical symptomatology in all cases, demonstrating that it is an ideal imaging modality in the diagnostic evaluation of symptomatic complications of osteochondromas and often avoids the need for further imaging.
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  • 25
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    European journal of pediatrics 157 (1998), S. 666-672 
    ISSN: 1432-1076
    Keywords: Key words Multicystic dysplastic kidney ; Complications ; Nephrectomy ; Renal function ; Contralateral anomalies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A clinical study of 204 patients with unilateral multicystic renal dysplasia referred to 30 nephrology departments was undertaken to assess the frequency of complications in children who underwent nephrectomy (n=40) versus those who were treated conservatively (n=164). Six patients required antihypertensive treatment, 30 (13% of girls, 17% of boys) had at least one episode of urinary tract infection. The number of clinical complications did not differ in patients who underwent nephrectomy in comparison to those who did not. The dysplastic kidney decreased in size in 65% of kidneys with repeated ultrasound values; no change occurred in 16%, while an increase in maximal diameter was observed in 19%. Contralateral kidney length of more than 2 standard deviation scores (SDS) was seen in 30% of patients. There is evidence for a slight impairment of renal function in the whole study group given by a median of serum creatinine level of 0.63 SDS in all patients available for analysis. Among those 35 patients with contralateral anomalies (mainly obstructive changes and vesico-ureteral reflux), all 3 patients with contralateral changes suggestive of hypoplasia and 22% with obstruction, but only 1/7 (14%) with reflux showed elevated serum creatinine level 〉2 SDS. Conclusion Renal function seems to be slightly impaired in patients with unilateral multicystic renal dysplasia. The apparent tendency to regression of the dysplastic kidney and no difference in the number of complications justify a conservative management rather than operative intervention.
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  • 26
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    Intensive care medicine 24 (1998), S. 194-196 
    ISSN: 1432-1238
    Keywords: Key words Horner's syndrome ; Internal jugular vein ; Cannulation ; Pulmonary artery ; Catheterization ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present two cases of Horner's syndrome occurring following uncomplicated internal jugular venous cannulation. An awareness of this potential complication will reduce confusion over the aetiology of anisocoria in critically ill patients. This consideration is important, since lesions in the central nervous system or carotid dissection following trauma might otherwise be suspected.
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  • 27
    ISSN: 1432-1238
    Keywords: Key words Percutaneous dilatational tracheostomy ; Complications ; Results ; Tracheal stenosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: To analyze perioperative and postoperative complications and long-term sequelae following percutaneous dilatational tracheostomy (PDT). Design: A prospective clinical study of patients undergoing PDT. Setting: Seven intensive care units at a University hospital Patients: 326 intensive care patients (202 male, 124 female; age: 11–95 years) with indications for tracheostomy. Interventions: Using tracheoscopic guidance, 337 PDTs were performed according to Ciaglias' method. In 106 decannulated patients, tracheal narrowing was assessed by plain tracheal radiography. Results: Two procedure-related deaths were seen (0.6 %). Perioperative and postoperative complications occurred with 9.5 % of the PDTs. One of 106 patients, who were followed-up for at least 6 months, showed a clinically relevant tracheal stenosis. Subclinical tracheal stenosis of at least 10 % of the cross-sectioned area was recognized in 46 of 106 patients (43.4 %). In the univariate analysis, the degree of stenosis was influenced by the age of the patient (p = 0.044), the duration of intubation prior to PDT (p = 0.042) and by the duration of cannulation (p = 0.006). These parameters had no statistical significance in a multiple regression model. Conclusion: When performed by experienced physicians, percutaneous dilatational tracheostomy under fiberoptic guidance is a safe method. The risks of early complications and of clinically relevant tracheal stenoses are low. Subclinical tracheal stenoses are found in about 40 % of patients following PDT.
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  • 28
    ISSN: 1432-198X
    Keywords: Key words: Outpatient ; Percutaneous renal biopsy ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Although several retrospective reports suggest that pediatric outpatient renal biopsies may be done in a safe and cost-effective manner, risk factors and the natural history of major complications following this procedure have not been clearly delineated. In an effort to determine the minimal observation period required to detect major post-renal biopsy complications in children and to establish clinical parameters predictive of these complications, a retrospective review of 177 percutaneous renal biopsies was performed. The overall major complication rate was 3.4%, while the minor complication rate was 14.1%. The mean percentage change in hemoglobin 4 – 10 h postbiopsy in patients with major bleeding complications was significantly greater than patients with minor bleeding complications. Using a 16% drop in hemoglobin 4 – 10 h postbiopsy, the sensitivity and specificity of identifying a major bleeding complication was 100% and 98%, respectively, while the positive and negative predictive value was 68% and 100%, respectively. All patients with major complications due to excess sedation or immediate bleeding were diagnosed within 11 h of the biopsy. Automated renal biopsies offered several safety and efficiency advantages compared with non-automated methods. Our results suggest that outpatient pediatric renal biopsies should be encouraged provided certain precautions are taken to reduce the risk of developing major complications.
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  • 29
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    European radiology 8 (1998), S. 371-376 
    ISSN: 1432-1084
    Keywords: Key words: MR mammography ; Breast ; Implants ; Augmentation ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Mammographic evaluation of the augmented breast is challenging, since breast implants obscure significant amount of breast tissue while diminishing the effect of compression. Posttherapeutic scarring can make mammographic interpretation even more difficult. MRI has thus evolved into the modality of choice for diagnosing implant complications as well as detection of primary or recurrent breast cancer in these patient population. The present article attemps to give an overview of the MR findings of different breast augmentation and reconstruction techniques, i. e. prosthetic breast implants, breast reconstruction with autogenous tissue, free silicone injections and fat grafts, and their complications.
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  • 30
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    European spine journal 7 (1998), S. 104-110 
    ISSN: 1432-0932
    Keywords: Key words Ankylosing spondylitis ; Osteotomies ; Lumbar spine ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Between 1984 and 1993 we treated 21 consecutive patients who had progressive thoracic kyphosis due to ankylosing spondylitis by polysegmental posterior lumbar wedge osteotomies. In 19 patients we used the Universal Spinal Instrumentation System and in the last 2 patients the H-frame. The average correction in 20 of 21 patients at follow-up was 25.6° (range 0°–52°), with a mean segmental correction of 9.5° and a mean loss of correction after operation of 10.7° (range 0°–36°). There were no fatal complications, but in one patient no correction could be obtained during surgery and another patient was reoperated due to lack of correction. Breaking out of screws through the pedicle during compressive correction was seen in seven patients. Implant failure, such as breakage of the threaded rods and/or loosening of the junction between the pedicle screw and the rod, occurred in 9 out of 21 patients. Two patients required reoperation at long-term follow-up. Five out of seven deep wound infections required removal of the implant. Polysegmental lumbar wedge osteotomies for correction of progressive thoracic kyphosis in ankylosing spondylitis is only recommended in patients at a mild stage of the disease with mobile discs and in combination with strong instrumentation.
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  • 31
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    European spine journal 7 (1998), S. 438-444 
    ISSN: 1432-0932
    Keywords: Key words Vertebral metastases ; Complications ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The authors report their experience concerning complications of spinal metastasis surgery. The purpose of this study was to assess the frequency of such complications and analyse the factors influencing their occurrence. The records of 145 patients treated between 1982 and 1991 for metastatic disease of the spine were retrospectively reviewed for intra- and postoperative complications. Other factors such as radiation therapy, emergent nature of surgery, and neurologic deficits were analysed for potential correlations with the frequency of complications. Twenty-seven (18.6%) patients developed postoperative complications. Wound dehiscence and infection (11%) were the most frequent complications. Statistical analysis showed a significant influence of three factors: preoperative radiation therapy, paraplegia before surgery, and surgery under emergency conditions. The rate of complications in this surgery is lower than might be expected and can be significantly reduced. Surgery should be performed before radiation therapy and before appearance of substantial neurologic deficits.
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  • 32
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    European journal of trauma 24 (1998), S. 162-169 
    ISSN: 1615-3146
    Keywords: Retrograde Marknagelungstechnik ; Distale und supra/diakondyläre Femurfrakturen ; Komplikationen ; Retrograde nailing technique ; Distal and supra/diacondylar femoral fractures ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract We performed retrograde femoral nailing in 20 patients with 20 fractures of the distal femoral region. All fractures were stabilized on the day of admission after performing closed reduction. There were 15 distal femoral or supra/diacondylar fractures type A and 5 type C fractures. Four fractures were classified open (3A). Eight patients had previous surgery with implanted hip arthroplasties or dynamic hip screws. Immediate passive motion and mobilisation were begun postoperatively. All fractures healed. Follow-up was 27 months after surgery (range: 20 to 33 months). There were neither failure of the implant nor infections. In 4 patients we had loosening of interlocking screws but only 1 had to be reoperated. Two implants were chosen too long and had to be exchanged. Functional results were assessed based on the score of Leung et al. [11]. Six patients showed an excellent result, 4 a good, 3 a fair and 1 patient a poor result. We conclude retrograde interlocking femoral nailing has proven to be a minimal invasive stabilisation method for closed and open supra/diacondylar and distal femoral fractures. As there is the possibility of technical pitfalls, this technique should only be performed by well trained surgeons.
    Notes: Zusammenfassung Unsere ersten 20 mit einem retrograden Femurmarknagel versorgten Patienten wurden 27 Monate postoperativ (20 bis 33 Monate) nachuntersucht. Alle Patienten waren am Unfalltag in geschlossener Operationsweise behandelt worden. Nach der AO-Klassifikation handelte es sich um 15 distale oder supra/diakondyläre Typ-A-Frakturen und fünf Typ-C-Frakturen. Darunter waren vier offene Frakturen vom Typ 3A nach Gustilo. Bei acht Patienten waren auf der zu operierenden Seite bereits von früheren Verletzungen dynamische Hüftschrauben oder Endoprothesen implantiert. Postoperative wurden die Patienten sehr rasch ohne weitere Fixation mobilisiert. Alle Frakturen waren primär geheilt. Wir verzeichneten keinen Implantatbruch und keine Infektion. Bei vier Patienten kam es zur Lockerung von Verriegelungsbolzen, wovon ein Patient wegen der resultierenden Frakturinstabilität revidiert werden mußte. Bei zwei Pateinten wurde ein zu langer Nagel implantiert und dieser dann bei der Revisionsoperation durch einen kürzeren Nagel ersetzt. Die funktionellen Resultate wurden bei der Nachuntersuchung nach dem Score von Leung et al. [11] bewertet. Sechs Patienten zeigten exzellente Ergebnisse, vier Patienten gute, drei mäßige und ein Patient ein schlechtes Ergebnis. Nach unseren ersten Erfahrungen ist die retrograde Marknagelung von distalen Femurfrakturen eine ausgezeichnete Technik zur Frakturstabilisation sowohl von geschlossenen und offenen distalen als auch supra/diakondylären Femurfrakturen. Zudem handelt es sich um eine minimal-invasive Methode mit den sich daraus ergebenden Vorteilen. Da die Technik jedoch sehr anspruchsvoll ist, sollte sie nur von adäquat ausgebildeten und geübten Unfallchirurgen vorgenommen werden.
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  • 33
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    Arthroskopie 11 (1998), S. 98-101 
    ISSN: 1434-3924
    Keywords: Schlüsselwörter Ambulante Operationen ; Voraussetzungen ; Eigenes Procedere ; Postoperatives Management ; 4588 ambulante op. Eingriffe ; Komplikationen ; Akzeptanz ; Ausschlußkriterien ; Key words Outpatient operations ; Requirements ; Individual procedure ; Postoperative management ; 4588 outpatient operations ; Complications ; Aceptance ; Exclusion criteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: This study describes the approach that is necessary in outpatient surgery in order to carry out the operation safely. The particular procedure is discussed, and the necessity of strict postoperative management is shown. Between 1994 and 1997, the author supervised 4588 outpatient operations, of which 3020 were arthroscopic. The observed complications are listed and evaluated. Overall, outpatient surgery is well accepted by the patients. The criteria for denying a patient surgery on an outpatient basis are laid out.
    Notes: Die Arbeit schildert die Voraussetzungen, die zum ambulanten Operieren notwendig sind, um die Eingriffe sicher gestalten zu können. Das eigene Procedere des Behandlungsablaufes wird geschildert. Die Notwendigkeit eines strengen postoperativen Managementes wird dargelegt. Von 1994 bis 1997 überblicken die Autoren 4588 ambulante operative Eingriffe, davon 3020 ambulante arthroskopische Operationen. Die beobachteten Komplikationen werden aufgelistet. Insgesamt wird das ambulante Operieren vom Patienten akzeptiert. Ausschlußkriterien zum ambulanten Operieren werden aufgestellt.
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  • 34
    ISSN: 1433-0385
    Keywords: Key words: Gastric banding ; Complications ; Therapy. ; Schlüsselwörter:„Gastric banding“ ; Komplikationen ; Therapie.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Das laparoskopische „gastric banding“ hat sich zu einem etablierten Verfahren in der Chirurgie der Fettsucht entwickelt. Früh- und Spätkomplikationen sind im Vergleich zu herkömmlichen Verfahren seltener. Operationstechnisch bedingte Komplikationen sind die Magenperforation, die frühe Pouchdilatation, das Magen-slipping, Infektionen des Implantats, die Bandarrosion und Defekte des Band- und Schlauchsystems. Eine unzureichende Gewichtsabnahme und die späte Pouchdilatation sind durch die unzureichende Compliance des Patienten verursacht. In 7,5 % von 146 Patienten waren Wiedereingriffe notwendig. Erbrechen und die Unfähigkeit der Flüssigkeitszufuhr sind Symptome einer Stomaocclusion oder eines „slipping“. Die sofortige Röntgendiagnostik mit anschließender „Entblockung des Systems“ ist notfallmäßig vorzunehmen. Bei einer Pouchdilatation oder einem „slipping“ wird eine Magensonde in den Pouch plaziert. Läßt sich durch diese Maßnahmen keine Passage wiederherstellen, muß notfallmäßig die operative Korrektur erfolgen.
    Notes: Summary. Laparoscopic gastric banding has become a common procedure in bariatric surgery. Early as well as late complications are, in comparison to conventional techniques, rare. Complications arising from the operative technique are: perforation, early pouch dilatation, gastric slippage, infections of the port and the band, erosion and defects of the band tube. Insufficient weight loss and late pouch dilatation arise from unsatisfactory compliance on the part of the patient. In 7.5 % of 146 cases, reoperations were necessary. Obstruction of the pouch stoma and a slippage resulted in total food intolerance. After radiologic diagnosis the band system should be deflated first and a naso-gastric tube applied. If this does not result in the pouch collapsing, a revision operation is needed.
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  • 35
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    European journal of plastic surgery 21 (1998), S. 106-107 
    ISSN: 1435-0130
    Keywords: Key words Fingertip injury ; Nail bed ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report the long term sequel of a finger tip injury (case report). Attention to detail, particularly in repairing the nail bed and a decision at the time to either retain and repair, or excise fully, the germinal matrix could avoid long term complications.
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  • 36
    ISSN: 1434-9949
    Keywords: Chronic pancreatitis ; Complications ; Pseudocyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We describe two patients with pancreatitis. One patient had acute pancreatitis of biliary origin and presented with small joint polyarthritis and panniculitis lesions. The other patient was originally hospitalised for dyspnoea with bilateral pleural effusion, and subsequently developed migratory polyarthritis. During his hospital stay he developed panniculitis lesions and a monoclonal IgG disorder of unknown significance. Very few patients with pancreatitis develop polyarthritis and panniculitis. The appearance of pseudocysts in the pleural and mediastinal cavity in the course of pancreatitis is an infrequent complication.
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  • 37
    ISSN: 1435-0130
    Keywords: Key words Radial forearm free flap ; Oral and oropharyngeal cancer ; Squamous cell carcinoma ; Reconstruction ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The success rate of 56 free radial forearm flaps used between 1987 and 1995 in the University Hospital Groningen, The Netherlands for oral and oropharyngeal reconstructions in cancer patients, was evaluated. There were 36 men and 20 women. The most prevalent neoplasm was squamous cell carcinoma (n=52). Most tumours were stage IV (n=33). Oral tumors were most common (n=34), while oropharyngeal tumours were present in 22 patients. In 48 cases a fasciocutaneous flap was used, while an osseofasciocutaneous flap was taken in 8 patients. Recipient-site problems occurred in 31 patients (55%). There was total flap loss in 4 patients (7%) and partial flap loss in 4 (7%). Donor-site complications were seen in 18 patients (32%). Total loss of skin graft occurred in 1 patient (2%) and partial loss of skin grafts in 7 patients (13%). A fracture of the radius was observed in 2 patients. The overall success rate of the radial forearm free flap was 86%. Free vascularised tissue transfer to the oral and oropharyngeal regions should be carried out in a centre with a multidisciplinary head and neck team with experienced microsurgeons.
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  • 38
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    European archives of oto-rhino-laryngology and head & neck 255 (1998), S. 124-126 
    ISSN: 1434-4726
    Keywords: Key words Acoustic neuroma surgery ; Facial palsy ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Delayed onset of facial palsy is possibly an underestimated but distressing complication of acoustic neuroma surgery. The incidence of this complication reported in the literature has varied from 11.7 to 41%.This study reviewed retrospectively 60 primary acoustic neuroma surgeries performed by a single neurotologist. The deelayed onset of facial dysfunction was defined according to the guidelines described by of Lalwani Butt, Jackler, Pitts and Jingling in 1995. They considered either a deterioration of facial function from normal to abnormal or an increased severity of the degree of facial paralysis, which was grouped using the House-Brackmann scale system. Fifteen of the 60 patients (25%) were found to have a deterioration of facial function. The incidence of delayed facial palsy was not influenced by age, sex or tumor size. The majority of the patients had a favorable prognosis. Only three patients had a grade III–IV facial function at 1 year. It is possible that these latter cases might have benefited from intraoperative meatal facial nerve decompression, as advocated by Sargent, Kartush and Graham.
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  • 39
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1-24 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We study the large time asymptotics of solutions u(x, t) of the wave equation with time-harmonic force density f(x)e-iωt, ω≥0, in the semi-strip Ω= (0, ∞)×(0, 1) for a given f∊C∞0(Ω). We assume that u satisfies the initial condition u=(∂/∂t)u=0 for t=0 and the boundary conditions u=0 for x2=0 and x2=1, and (∂/∂x1)u=αu for x1=0, with given α, -π≤α〈∞. Let Dα be the self-adjoint realization of -Δ in Ω with this boundary condition. For -π≤α〈0, Dα has eigenvalues λj=π2j2-α2, j=1, 2, … For j≥2 these eigenvalues are embedded in the continuous spectrum of Dα, σc(Dα)=[π2, ∞]. For α≥0, Dα has no eigenvalues. We consider the asymptotic behaviour of u(x, t), t→∞, as a function of α. In the case α=0 resonances of order √t at ω=πj, j=1, 2, …, were found in References 5 and 10. We prove that for α=-π there is a resonance of order t2 for ω=0 and resonances of order t for every ω〉0 (note that 0 is an eigenvalue of D-π). Moreover, for -π〈α〈0 there are resonances of order t at ω=√λj. The resonance frequencies are continuous functions of α for -π〈α〈0 and tend to πj, j=1, 2, … as α goes to zero.On the contrary in the case α〉0 there are no real resonances in the sense that the solution remains bounded in time as t→∞. Actually in this case, the limit amplitude principle is valid for all frequencies ω≥0. This rather striking behaviour of the resonances is explained in terms of the extension of the resolvent R(κ)=(Dα-κ2)-1 as a meromorphic function of κ into an appropriate Riemann surface. We find that as α crosses zero the real poles of R(κ) associated with the eigenvalues remain real, but go into a second sheet of the Riemann surface. This behaviour under perturbation is rather different from the case of complex resonances which has been extensively studied in the theory of many-body Schrödinger operators where the (real) eigenvalues embedded in the continuous spectrum turn under a small perturbation into complex poles of the meromorphic extension of the resolvent, as a function of the spectral parameter κ2. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 40
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 117-128 
    ISSN: 0170-4214
    Keywords: third-grade fluid ; existence ; uniqueness ; classical solution ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The global existence and uniqueness of classical solution of steady motions of a third-grade fluid provided assumptions on positivness of μ (coefficient of viscosity) and α1, γ (material coefficients) is proved. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 41
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 227-249 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Integral equations associated with the basic boundary value problems for the Laplace and Stokes equations are considered. The integral operators for these integral equations are interpreted as the pseudodifferential operators, and their principal symbols are calculated. The symbols are obtained in terms of the principal curvatures and the coefficients of the first quadratic form of the boundary. As a consequence, the initial approximation is suggested for the iterative methods solving the integral equations. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 42
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 327-359 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The boundary integral equation method is used to prove the convergence of the Drude-Born-Fedorov equations with variable coefficients, possibly non-smooth, to Maxwell's equations as chirality admittance tends to zero. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 43
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 565-588 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: New explicit stability conditions are derived for a linear integro-differential equation with periodic operator coefficients. The equation under consideration describes oscillations of thin-walled viscoelastic structural members driven by periodic loads. To develop stability conditions two approaches are combined. The first is based on the direct Lyapunov method of constructing stability functionals. It allows stability conditions to be derived for unbounded operator coefficients, but fails to correctly predict the critical loads for high-frequency excitations. The other approach is based on transforming the equation under consideration in such a way that an appropriate ‘differential’ part of the new equation would possess some reserve of stability. Stability conditions for the transformed equation are obtained by using a technique of integral estimates. This method provides acceptable estimates of the critical forces for periodic loads, but can be applied to equations with bounded coefficients only. Combining these two approaches, we derive explicit stability conditions which are close to the Floquet criterion when the integral term vanishes. These conditions are applied to the stability problem for a viscoelastic bar compressed by periodic forces. The effect of material and structural parameters on the critical load is studied numerically. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 44
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 653-664 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In order to maintain spectrally accurate solutions, the grids on which a non-linear physical problem is to be solved must also be obtained by spectrally accurate techniques. The purpose of this paper is to describe a pseudospectral computational method of solving integro-differential systems with quadratic performance index. The proposed method is based on the idea of relating grid points to the structure of orthogonal interpolating polynomials. The optimal control and the trajectory are approximated by the m th degree interpolating polynomial. This interpolating polynomial is spectrally constructed using Legendre-Gauss-Lobatto grid points as the collocation points, and Lagrange polynomials as trial functions. The integrals involved in the formulation of the problem are calculated by Gauss-Lobatto integration rule, thereby reducing the problem to a mathematical programming one to which existing well-developed algorithms may be applied. The method is easy to implement and yields very accurate results. An illustrative example is included to confirm the convergence of the pseudospectral Legendre method, and a comparison is made with an existing result in the literature. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 45
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 701-718 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This article establishes the existence of a trapped-mode solution to a linearized water-wave problem. The fluid occupies a symmetric horizontal channel that is uniform everywhere apart from a confined region which either contains a thin vertical plate spanning the depth of the channel or has indentations in the channel walls; the forces of gravity and surface tension are operative. A trapped mode corresponds to an eigenvalue of the composition of an inverse differential operator and a Neumann-Dirichlet operator for an elliptic boundary-value problem in the fluid domain. The existence of such an eigenvalue is established by extending previous results dealing with the case when surface tension is absent. © 1998 B.G. Teubner Stuttgart-John Wiley & Sons, Ltd.
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  • 46
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 501-517 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper an initial-boundary-value problem in one-space dimension is studied for the Broadwell model extended to a gas mixture undergoing bimolecular reactions. Techniques of semigroup of bounded positive operators in a suitable Banach space are used to prove existence and uniqueness of the solution on bounded time intervals whose length depends on the initial data. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 47
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 685-700 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In the present work, the problem of electromagnetic wave propagation in three-dimensional stratified media is studied. The method of decoupling the electric and magnetic fields is implemented, and the spectral approach is adopted, componentwise, to the vector equation involving the electric field. Operational calculus of self-adjoint, positive operators in suitable Hilbert spaces is used to solve the corresponding initial value problems. The spectral families of these operators for the cases of the whole space and of a finite layer are constructed. A discussion on the applicability of the obtained results to physical problems is also included. © 1998 B.G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 48
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 757-780 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we prove under the assumption of small initial data the global existence of a classical solution to the equations in viscoelasticity, associated with a free damping boundary condition. We also show that if we choose the initial data large enough, blow up will occur in finite time. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 49
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 797-821 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the thermoelastic plate system,utt-γΔutt+Δ2u+αΔθ=0,θt-κΔθ-αΔut=0 and we make a comparison between the models in which γ=0 and γ〉0. We conclude that in the first case the plate system is of a parabolic type, while when γ〉0 the corresponding system has a hyperbolic behaviour. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 50
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 883-894 
    ISSN: 0170-4214
    Keywords: solitary wave ; stability ; long wave-short wave resonance equations ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper concerns the orbital stability for solitary waves of the Long Wave-Short Wave resonance equations. Since the abstract results of Grillakis et al. [7, 8] cannot be applied directly, we can extend the abstract stability theory and use the detailed spectral analysis to obtain the stability of the solitary waves. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 51
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1049-1066 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider particle transport in a three-dimensional convex region V, bounded by the regular surface ∂V. We assume that particles are specularly reflected by ∂V and that a source q is assigned on ∂V; more general non-homogeneous boundary conditions are also discussed. The problem is non-linear because the boundary condition is not homogeneous. We prove existence of a unique strict solution and by using the theory of semigroups we derive the explicit expression of such a solution in terms of the boundary source q. In the appendix, we indicate how some properties of affine operators can be used to derive the solution. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1085-1105 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: A phase-field model based on the Coleman-Gurtin heat flux law is considered. The resulting system of non-linear parabolic equations, associated with a set of initial and Neumann boundary conditions, is studied. Existence, uniqueness, and regularity results are proved. An asymptotic analysis is also carried out, in the case where the coefficient of the interfacial energy term tends to 0. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 53
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1115-1148 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We apply the Child-Langmuir asymptotics of the Vlasov-Poisson system to the case of a bipolar diode, i.e. a vacuum diode where two species of particles of opposite electric charge are flowing. This leads to a simplified model which, if at least one of the two injected currents is not too large, has a unique solution. Moreover, in that case, the currents flowing inside the diode are limited by the so-called bipolar Child-Langmuir currents. In the case of large currents, other solutions may appear, and the formation of virtual electrodes may occur inside the diode. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 54
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1107-1113 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we consider the Cauchy problem for the equation∂u/∂t + u ∂u/∂x + u/x = 0 for x 〉 0, t ≥ 0, with u(x, 0) = u0-(x) for x 〈 x0, u(x, 0) = u0+(x) for x 〉 x0, u0-(x0) 〉 u0+(x0). Following the ideas of Majda, 1984 and Lax, 1973, we construct, for smooth u0- and u0+, a global shock front weak solution u(x, t) = u-(x, t) for x 〈 φ(t), u(x, t) = u+(x, t) for x 〉 φ(t), where u- and u+ are the strong solutions corresponding (respectively) to u0- and u0+ and the curve t → φ(t) is defined by dφ/dt (t) = 1/2[u-(φ(t), t) + u+(φ(t), t)], t ≥ 0 and φ(0) = x0.© 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 55
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1195-1206 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: A variational approach to a non-linear non-local identification problem related to the non-linear transport equation is studied. Introducing a similarity transformation, the problem is formulated as an identification problem for a non-linear differential equation of second order with an additional non-local condition. For the solution of the forward problem stability in H1-norm with respect to the identification parameter is obtained. Using this result the existence of a solution to the identification problem is proved. Some results of computational experiments are given. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1233-1267 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the plate equation in a polygonal domain with free edges. Its resolution by boundary integral equations is considered with double layer potentials whose variational formulation was given in Reference 25. We approximate its solution (u, (∂u/∂n)) by the Galerkin method with approximated spaces made of piecewise polynomials of order 2 and 1 for, respectively, u and (∂u/∂n). A prewavelet basis of these subspaces is built and equivalences between some Sobolev norms and discrete ones are established in the spirit of References 14, 16, 30 and 31. Further, a compression procedure is presented which reduces the number of nonzero entries of the stiffness matrix from O(N2) to O(N log N), where N is the size of this matrix. We finally show that the compressed stiffness matrices have a condition number uniformly bounded with respect to N and that the compressed Galerkin scheme converges with the same rate than the Galerkin one. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1287-1296 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The relativistic Vlasov-Maxwell-Fokker-Planck system is used in modelling distribution of charged particles in plasma. It consists of a transport equation coupled with the Maxwell system. The diffusion term in the equation models the collisions among particles, whereas the viscosity term signifies the dynamical frictional forces between the particles and the background reservoir. In the case of one space variable and two momentum variables, we prove the existence of a classical solution when the initial density decays fast enough with respect to the momentum variables. The solution which shares this same decay condition along with its first derivatives in the momentum variables is unique. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1415-1439 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider reactive mixtures of dilute polyatomic gases in full vibrational non-equilibrium. The governing equations are derived from the kinetic theory and possesses an entropy. We recast this system of conservation laws into a symmetric conservative form by using entropic variables. Following a formalism developed by the authors in a previous paper, the system is then rewritten into a normal form, that is, in the form of a quasilinear symmetric hyperbolic-parabolic system. Using a result of Vol'pert and Hudjaev, we prove local existence and uniqueness of a bounded smooth solution to the Cauchy problem. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1479-1494 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Approximate solutions of the non-linear Boltzmann equation, which have the structure of the linear combination of three global Maxwellians with arbitrary hydrodynamical parameters, are considered. Some sufficient conditions which allow the error between the left- and the right-hand sides of the equation tend to zero, and which are calculated either in the mixed metric or in the pure integral metric, are obtained. The class of the distributions, which minimized this error for the arbitrary Knudsen number, is found. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1519-1542 
    ISSN: 0170-4214
    Keywords: non-hyperbolic systems ; two-phase flows ; dispersion terms ; symmetrization ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The paper considers a system of partial differential equations of convection dispersion type, modelling a stratified two-phase fluid flow. Local existence in time is proved for a sufficiently smooth initial data, given in the set of physically admissible states. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1559-1569 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we study the motion of an elastic conducting wire in a magnetic field. The motion of the conductor induces a current in the wire (Faraday's law) which, in turn produces a force on the wire. We consider the linear equation obtained by linearizing the resulting equations of motion about an equilibrium solution. This is a hyperbolic partial differential equation with a non-local term. We prove existence and uniqueness of a weak solution of an initial-boundary value problem for this equation. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1637-1654 
    ISSN: 0170-4214
    Keywords: generalized Stokes equations ; incompressible flow ; least-squares ; finite element method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we are concerned with a weighted least-squares finite element method for approximating the solution of boundary value problems for 2-D viscous incompressible flows. We consider the generalized Stokes equations with velocity boundary conditions. Introducing the auxiliary variables (stresses) of the velocity gradients and combining the divergence free condition with some compatibility conditions, we can recast the original second-order problem as a Petrovski-type first-order elliptic system (called velocity-stress-pressure formulation) in six equations and six unknowns together with Riemann-Hilbert-type boundary conditions. A weighted least-squares finite element method is proposed for solving this extended first-order problem. The finite element approximations are defined to be the minimizers of a weighted least-squares functional over the finite element subspaces of the H1 product space. With many advantageous features, the analysis also shows that, under suitable assumptions, the method achieves optimal order of convergence both in the L2-norm and in the H1-norm. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1619-1635 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the two-parameter non-linear Sturm-Liouville problems. By using the variational method on general level sets, the variational eigenvalues are obtained. The purpose of this paper is to study the properties of these variational eigenvalues with respect to the parameter of general level sets. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 187-226 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We study the limit behaviour of solution of Poisson's equation in a class of thin two-dimensional domains, both simply connected or single-hollowed, as its thickness becomes very small. The method is based on a transformation of the original problem into another posed on a fixed domain, obtention of a priori estimates and convergence results when thickness parameter tends to zero. As an important application of abstract results we obtain the limit expressions for functions appearing in elastic beam theories as torsion and warping functions. In this way, we provide a mathematical justification and a correct definition of torsion, warping and Timoshenko functions and constants that should be used in the open and closed thin-walled elastic beam theories. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 269-279 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The generalized Möbius function and Möbius inversion formula are applied to a multiplicative semigroup. A general mathematical method based on this Möbius inversion is presented to solve inversion problems of expansions with unequally weighted terms. By this method, all the inverse lattice problems in physics can be solved concisely. The solutions of four inverse lattice problems: the Fibonacci structure, the square lattice structure, the bcc and the hcp lattice structures are given. These are difficult to be solved by other methods. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 361-374 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We use the eigenfunction expansion of Green's function of Dirichlet problems to obtain sampling theorems. The analytic properties of the sampled integral transforms as well as the uniform convergence of the sampling series are proved without any restrictions on the integral transforms. We obtain a one- and multi-dimensional versions of sampling theorems. In both cases the sampling series are written in terms of Lagrange-type interpolation expansions. Some examples and the truncation error as well as the stability of the obtained sampling expansions are discussed at the end of the paper. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 393-416 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider a dynamical von Kármán system in the presence of thermal effects. Our model includes the possibility of a rotational inertia term in the system. We show that the total energy of the solution of such system decays exponentially as t→+∞. The decay rates we obtain are uniform on bounded sets of the energy space. The main ingredients of our method of proof are suitable properties of a decoupled system, the energy method and the compactness of the nonlinear map associated to the von Kármán system. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 479-488 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This short article discusses the spectrum of the Neumann Laplacian in the infinite domain Ω⊂∝n, n ≥2 created by inserting a compact obstacle P into the uniform cylinder Ω0 =(-∞, ∞)×Ω′. The main result is the existence of at least one embedded eigenvalue when P is an (n -2)-dimensional surface whose unit normal is parallel to Ω′ at each point of P . The special case when P is symmetric about {0}×Ω′ is also treated. It is shown that there is at least one symmetric eigenvector and, when P is sufficiently long, at least one antisymmetric eigenvector. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 551-564 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We prove the existence of solutions to the three-dimensional elastoplastic problem with Hencky's law and Neumann boundary conditions by elliptic regularization and the penalty method, both for the case of a smooth boundary and of an interior two dimensional crack. It is shown, in particular, that the variational solution satisfies all boundary conditions. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 251-268 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The propagation of Hölder regularity of the solutions to the 3D Euler equations is discussed. Our method is a special semi-linearization of the vorticity equation combined with the classical Schauder interior estimates. © 1998 by B.G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 433-461 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper is concerned with the solution of Maxwell equations in the modelling of the scattering of a time-harmonic electromagnetic wave by an obstacle located in a two-layered medium. The use of the Silver-Müller radiation condition in each layer is shown to provide a well-posed scattering problem. The analysis is based on the study of the Green tensor, which allows to relate the radiation condition to an integral representation formula. The analyticity properties of the scattering problem with respect to the frequency are then investigated. This gives rise to a limiting absorption principle and furnishes a characterization of the resonances. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 489-499 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We apply our recently developed distributional technique [2, 3] to study time-domain asymptotics. This enables us to present a rigorous mathematical discussion and extensions of the results given by Chapman [1] and subsequent workers in this field. The present analysis is facilitated by defining functions which are distributionally small at infinity. We find that one of the advantages of using this technique is that multidimensional extensions can be derived very easily. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 519-549 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper is concerned with a specific finite element strategy for solving elliptic boundary value problems in domains with corners and edges. First, the anisotropic singular behaviour of the solution is described. Then the finite element method with anisotropic, graded meshes and piecewise linear shape functions is investigated for such problems; the schemes exhibit optimal convergence rates with decreasing mesh size. For the proof, new local interpolation error estimates for functions from anisotropically weighted spaces are derived. Finally, a numerical experiment is described, that shows a good agreement of the calculated approximation orders with the theoretically predicted ones. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 605-617 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper presents a general method of analysis for investigating the whirl stability of a rotor-bearing system whose appendage is flexibly attached to the spinning shaft. Sufficient conditions of asymptotic stability involving system different parameters are derived based on Liapunov's theory. An inclusive analysis of the effect of the combined flexibilities of the elastic attachment of the appendage to the shaft and the two end bearings coupled with the other various parameters of the system on the dynamic stability is presented. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 665-684 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We investigate the steady compressible Navier-Stokes equations near the equilibrium state v = 0, ρ = ρ0 (v the velocity, ρ the density) corresponding to a large potential force. We introduce a method of decomposition for such equations: the velocity field v is split into a non-homogeneous incompressible part u (div (ρ0u) = (0) and a compressible (irrotational) part ∇φ. In such a way, the original complicated mixed elliptic-hyperbolic system is split into several ‘standard’ equations: a Stokes-type system for u, a Poisson-type equation for φ and a transport equation for the perturbation of the density σ = ρ - ρ0. For ρ0 = const. (zero potential forces), the method coincides with the decomposition of Novotny and Padula [21]. To underline the advantages of the present approach, we give, as an example, a ‘simple’ proof of the existence of isothermal flows in bounded domains with no-slip boundary conditions. The approach is applicable, with some modifications, to more complicated geometries and to more complicated boundary conditions as we will show in forthcoming papers. © 1998 B.G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 619-651 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider acoustic scattering from an obstacle inside an inhomogeneous structure. We prove in the paper that if the outside inhomogeneity is known then the obstacle and possible inside inhomogeneity are uniquely determined by the fixed energy far field data. The proof is based on new mapping properties of layer potentials in spaces that specify one point. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 939-967 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The linear problem for the velocity potential around a slightly curved thin finite wing is considered under the Joukowskii-Kutta hypothesis. The exponents of possible singularities of solutions at angular points on wing's trailing edge are expressed in terms of eigenvalues of mixed boundary value problems for the Beltrami-Laplace operator on the hemisphere and the semicircle. These singularities have a structure such that the circulation function turns out to be continuous in interior angular points of the trailing edge. In the case of trapezoidal shape of the wing ends there occur square-root singularities of the velocity field at the trailing edge endpoints and the same singularities, of course, are extended along the lateral sides of the wake behind the wing. It is proved that for any angular point on the trailing edge the exponents of all above-mentioned singularities form a countable set in the upper complex half-plane with the only accumulation point at infinity. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 985-1014 
    ISSN: 0170-4214
    Keywords: Vlasov-Poisson-Fokker-Planck ; long-time behaviour ; fundamental solutions ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We study the long-time behaviour of solutions of the Vlasov-Poisson-Fokker-Planck equation for initial data small enough and satisfying some suitable integrability conditions. Our analysis relies on the study of the linearized problems with bounded potentials decaying fast enough for large times. We obtain global bounds in time for the fundamental solutions of such problems and their derivatives. This allows to get sharp bounds for the decay of the difference between the solutions of the Vlasov-Poisson-Fokker-Planck equation and the solution of the free equation with the same initial data. Thanks to these bounds, we get an explicit form for the second term in the asymptotic expansion of the solutions for large times. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1067-1084 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: An initial-value problem modelling coagulation and fragmentation processes is studied. The results of earlier papers are extended to models where either one or both of the rates of coagulation and fragmentation depend on time. An abstract integral equation, involving the solution operator to the linear fragmentation part, is investigated via the contraction mapping principle. A unique global, non-negative, mass-conserving solution to this abstract equation is shown to exist. The latter solution is used to generate a global, non-negative, mass-conserving solution to the original non-autonomous coagulation and multiple-fragmentation equation. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1185-1194 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we prove the global existence and study decay property of the solutions to the initial boundary value problem for the quasi-linear wave equation with a dissipative term without the smallness of the initial data. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1207-1226 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Reaction random-walk systems are hyperbolic models to describe spatial motion (in one dimension) with finite speed and reactions of particles. Here we present two approaches which relate reaction random-walk equations with reaction diffusion equations. First, we consider the case of high particle speeds (parabolic limit). This leads to a singular perturbation analysis of a semilinear damped wave equation. A initial layer estimate is given. Secondly, we consider the case of a transcritical bifurcation. We use techniques similar to that of the Ginzburg-Landau method to find a modulation equation for the amplitude of the first unstable mode. It turns out that the modulation equation is Fisher's equation, hence near the bifurcation point travelling wave solutions are obtained. The approximation result and the corresponding estimate is given in terms of the bifurcation parameter. Both results are based on an a priori estimate for classical solutions which follows from explicit representations of the solution of the linear telegraph equation. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1365-1377 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In the article the problem of regulation of the cardiovascular system is investigated from the point of view of control process theory. This problem was reduced to finding the optimal control in the sense of speed in a bilinear system. In the first part of the article the possibility of applying Saburov's method for the solution to bilinear control problems is considered. The second part of the article is devoted to the application of this method to a concrete problem from practical medicine. The method has allowed the complete synthesis of an optimal control to be carried out  -  the sliding mode takes place and it was investigated completely. The results obtained are interesting from the point of view of control process theory, and testify to the high efficiency of the method. The final results allow concrete recommendations about the regulation of the cardiovascular system. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1399-1413 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The steady-state equations for a charged gas or fluid consisting of several components, exposed to an electric field, are considered. These equations form a system of strongly coupled, quasilinear elliptic equations which in some situations can be derived from the Boltzmann equation. The model uses the duality between the thermodynamic fluxes and the thermodynamic forces. Physically motivated mixed Dirichlet-Neumann boundary conditions are prescribed. The existence of generalized solutions is proven. The key of the proof is a transformation of the problem by using the entropic variables, or electro-chemical potentials, which symmetrize the equations. The uniqueness of weak solutions is shown under the assumption that the boundary data are not far from the thermal equilibrium. A general uniqueness result cannot be expected for physical reasons. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1343-1363 
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    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider an elastic plate with the non-deformed shape ΩΣ := Ω \ Σ, where Ω is a domain bounded by a smooth closed curve Γ and Σ ⊂ Ω is a curve with the end points {γ1, γ2}. If the force g is given on the part ΓN of Γ, the displacement u is fixed on ΓD := Γ \ ΓN and the body force f is given in Ω, then the displacement vector u(x) = (u1(x), u2(x)) has unbounded derivatives (stress singularities) near γk, k = 1, 2   u(x) = ∑2k, l=1 Kl(γk)r1/2kSCkl(θk) + uR(x)     near γk.Here (rk, θk) denote local curvilinear polar co-ordinates near γk, k = 1, 2, SCkl (θk) are smooth functions defined on [-π, π] and uR(x) ∊ {H2(near γk)}2. The constants Kl(γk),   l = 1, 2, which are called the stress intensity factors at γk (abbr. SIFs), are important parameters in fracture mechanics. We notice that the stress intensity factors Kl(γk) (l = 1, 2;  k = 1, 2) are functionals Kl(γk) = Kl(γk; L, Ω, Σ) depending on the load L, the shape of the plate Ω and the shape of the crack Σ. We say that the crack Σ is safe, if Kl(γk; Ω)2 + K2(γk; Ω)2 〈 RẼ. By a small change of Ω the shape Σ can change to a dangerous one, i.e. we have K1(γk; Ω)2 + K2(γk; Ω)2 ≥ RẼ. Therefore it is important to know how Kl(γk) depends on the shape of Ω.For this reason, we calculate the Gâteaux derivative of Kl(γk) under a class of domain perturbations which includes the approximation of domains by polygonal domains and the Hadamard's parametrization Γ(τ) := {x + τφ(x)n(x);  x ∊ Γ}, where φ is a function on Γ and n is the outward unit normal on Γ. The calculations are quite delicate because of the occurrence of additional stress singularities at the collision points {γ3, γ4} = ΓD ∩ ΓN.The result is derived by the combination of the weight function method and the Generalized J-integral technique (abbr. GJ-integral technique). The GJ-integrals have been proposed by the first author in order to express the variation of energy (energy release rate) by extension of a crack in a 3D-elastic body. This paper begins with the weak solution of the crack problem, the weight function representation of SIF's, GJ-integral technique and finish with the shape sensitivity analysis of SIF's. GJ-integral Jω(u; X) is the sum of the P-integral (line integral) Pω(u, X) and the R-integral (area integral) Rω(u, X). With the help of the GJ-integral technique we derive an R-integral expression for the shape derivative of the potential energy which is valid for all displacement fields u ∊ H1. Using the property that the GJ-integral vanishes for all regular fields u ∊ H2 we convert the R-integral expression for the shape derivative to a P-integral expression. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1543-1558 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: It is shown that a stochastic system of N interacting particles in a slab approximates, in the Boltzmann-Grad limit, a one-dimensional Boltzmann equation with diffusive boundary conditions. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons, Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1571-1591 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The asymptotic behaviour of solutions of certain semilinear elliptic Dirichlet boundary value problems defined on a semi-infinite cylinder is investigated by means of energy arguments and maximum principles. Various hypotheses are made on the form of the semilinear term, and in some cases it is found that the rate of decay of solutions is faster than the optimal decay rate for harmonic functions. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 87
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1655-1679 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper the problem of collision analysis for a mobile robot operating in a planar environment with moving objects (obstacles) is addressed. The pattern of motion of the potential obstacles cannot be predicted; only a bound on their maximum velocity is available. Based on this information, at its current position the robot constructs the Hazard Region that corresponds to the path it contemplates. If the Hazard Region contains at least one obstacle, then there is a potential for this obstacle to collide with the robot (in which case perhaps another path should be planned). We first derive the solution for Hazard Region for two standard path primitives, a straight line segment and a circular arc segment; the solution is exact, except for one special case (for which the approximation error is estimated). This result is then applied to a more complex case when the path presents a combination of those primitives. Such are, for example, the optimal (shortest) paths with constrained curvature (known as Dubins paths [3]), which connect two points, each with a prescribed direction of motion. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 88
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1681-1704 
    ISSN: 0170-4214
    Keywords: stratified medium ; acoustic waves ; self-adjoint operators ; spectrum ; limiting absorption principle ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the acoustic propagator A=-∇·c2∇ in the strip Ω={(x, z)∊∝2∣0〈z〈H} with finite width H〉0. The celerity c depends for large ∣x∣ only on the variable z and describes the stratification of Ω: it is assumed to be in L∞(Ω), bounded from below by cmin〉0, such that there exists M〉0 with c(x, z)=c1(z) if x〈 -M and c(x, z)=c2(z) if x〉M. We look at the propagator A as a ‘perturbation’ of the free propagators Aj in Ω associated to the velocities cj, j=1, 2, and implement a ‘perturbative’ method, adapting ideas of Majda and Vainberg. The spectrum of A is defined in section 2, a limiting absorption principle is proved in section 3 outside of a countable set Γ(A). The points of Γ(A) can only accumulate at the left of the thresholds of the free propagators. The needed material about Aj, j=1, 2, and some technical estimates for A are given in Appendix. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 89
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 25-42 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Considered is the rotation of a robot arm or rod in a horizontal plane about an axis through the arm's fixed end and driven by a motor whose torque is controlled. The model was derived and investigated computationally by Sakawa and co-authors in [7] for the case that the arm is described as a homogeneous Euler beam. The resulting equation of motion is a partial differential equation of the type of a wave equation which is linear with respect to the state, if the control is fixed, and non-linear with respect to the control.Considered is the problem of steering the beam, within a given time interval, from the position of rest for the angle zero into the position of rest under a certain given angle.At first we show that, for every L2-control, there is exactly one (weak) solution of the initial boundary value problem which describes the vibrating system without the end condition.Then we show that the problem of controllability is equivalent to a non-linear moment problem. This, however, is not exactly solvable. Therefore, an iteration method is developed which leads to an approximate solution of sufficient accuracy in two steps. This method is numerically implemented and demonstrated by an example. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 59-91 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: A time-dependent Ginzburg-Landau-type model of a superconducting-normal-superconducting junction is presented. The existence and the uniqueness of the solutions are proved. When the data of the model are symmetric of some kinds, the solutions turns out to be symmetric of some kinds. In this symmetric case, an approximate model with the small thickness of the normal material in the middle of the junction as coefficients of a differential system is established for the sake of numerical computations. And also the existence and the uniqueness of the solution to this approximate model are set up. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 91
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 165-185 
    ISSN: 0170-4214
    Keywords: boundary integral equations ; boundary finite element ; free edge polygonal plate ; hypersingular kernels ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We consider the problem of a polygonal plate with free edges. It is a boundary value problem for the biharmonic operator on a polygon with Neumann boundary conditions. Its resolution is studied via boundary integral equations. A variational formulation of the boundary problem obtained by a double-layer potential is given. Finally, we implement the method and give numerical results. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 92
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 129-163 
    ISSN: 0170-4214
    Keywords: wavelets on closed surfaces ; Dirichlet's and Neumann's problem ; scaling function ; scale discrete wavelets ; integral formulas ; exact fully discrete wavelet transform ; band-limited harmonic wavelets ; Runge-Walsh approximation ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: Wavelets on closed surfaces in Euclidean space ∝3 are introduced starting from a scale discrete wavelet transform for potentials harmonic down to a spherical boundary. Essential tools for approximation are integration formulas relating an integral over the sphere to suitable linear combinations of function values (resp. normal derivatives) on the closed surface under consideration. A scale discrete version of multiresolution is described for potential functions harmonic outside the closed surface and regular at infinity. Furthermore, an exact fully discrete wavelet approximation is developed in case of band-limited wavelets. Finally, the role of wavelets is discussed in three problems, namely (i) the representation of a function on a closed surface from discretely given data, (ii) the (discrete) solution of the exterior Dirichlet problem, and (iii) the (discrete) solution of the exterior Neumann problem. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 93
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 417-432 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We state a 1D model with quasi-stationary gas flows approximation for a carbon reactivity test in the production of silicon. The mathematical problem we formulate is a non-linear boundary value problem for a third-order ordinary differential equation with non-linear boundary conditions, which are non-local in time. We prove existence and uniqueness of a classical solution and provide a numerical example. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 281-325 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We present a bending model for a shallow arch, namely the type of curved rod where the curvature is of the order of the diameter of the cross section. The model is deduced in a rigorous mathematical way from classical tridimensional linear elasticity theory via asymptotic techniques, by taking the limit on a suitable re-scaled formulation of that problem as the diameter of the cross section tends to zero. This model is valid for general cases of applied forces and material, and it allows us to calculate displacements, axial stresses, bending moments and shear forces. The equations present a more general form than in the classical Bernoulli-Navier bending theory for straight slender rods, so that flexures and extensions are proved to be coupled in the most general case. © 1998 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 95
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 375-392 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this work we analyse a model for radiative heat transfer in materials that are conductive, grey and semitransparent. Such materials are for example glass, silicon, water and several gases. The most important feature of the model is the non-local interaction due to exchange of radiation. This, together with non-linearity arising from the well-known Stefan-Boltzmann law, makes the resulting heat equation non-monotone. By analysing the terms related to heat radiation we prove that the operator defining the problem is pseudomonotone. Hence, we can prove the existence of weak solution in the cases where coercivity can be obtained. In the general case, we prove the solvability of the system using the technique of sub and supersolutions. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
    Additional Material: 2 Ill.
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  • 96
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 589-603 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In the paper we study the problem of control by means of a heat source g for a thermoelastic system of equationsutt - ρ∇·p(θ, ∇u) - νΔut + DΔ2 u = f, cv(θ, ∇u)θt - κΔθ - ρθ[pθ (θ, ∇u)·∇ut] - ν∣∇ut∣2 = g, in a two-dimensional domain, where both viscosity ν and rigidity D are positive. Such a system has been considered in our former papers, and existence of solutions as well as uniqueness have been obtained. Here we prove the continuity and differentiability of solutions under somewhat stronger assumptions. An example of a control problem and necessary optimality conditions are presented. The system has an interpretation as a plate reinforced with shape memory alloy (SMA) wire mesh. © 1998 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 719-731 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The exact solutions for the KdV and the Calogero-Degasperis-Fokas mKdV equations can be obtained by the AKNS class. The technique developed relies on the construction of the wave functions which are solutions of the associated AKNS system; that is, a linear eigenvalue problem in the form of a system of first order partial differential equations. The method of characteristics is used and Bäcklund transformations (BTs) are employed to generate two new solutions from the old. © 1998 B.G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 98
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 781-795 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper we consider the boundary value problem for a semilinear equation□u(t, x)-μu(t, x)+aum(t, x)=0, μ〉0, a∊ℜ in the interior domain. We find a time global classical solution with exponential decay property by using singular hyperbolic equation. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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  • 99
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 895-906 
    ISSN: 0170-4214
    Keywords: geometrical inverse problems ; crack detection ; identifiability ; stability ; Lipschitz stability ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: This paper deals with the detection of emergent plane cracks, by using boundary measurements. An identifiability result (uniqueness of the solution) is first proved. Then, we look at the stability of this solution with respect to the measurement. A weak stability result is proved, as well as a Lipshitz stability result for straight cracks, by using domain-derivative techniques. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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    Mathematical Methods in the Applied Sciences 21 (1998), S. 1467-1477 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: In this paper, the existence, both locally and globally in time, the uniqueness of solutions and the non-existence of global solutions to the initial boundary value problem of a generalized Modification of the Improved Boussinesq equation utt-uxx-uxxtt=σ(u)xx are studied and a few examples are discussed. © 1998 B. G. Teubner Stuttgart - John Wiley & Sons, Ltd.
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