Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 62 (1990), S. 519-528 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The aim of our investigation is to understand the mechanisms which control the movement of the human arm. The arm is here considered as a redundant system: the shoulder, elbow and wrist joints, which provide three degrees of freedom, combine to move the hand in a horizontal plane, i.e. a two dimensional space. Thus the system has one extra degree of freedom. Earlier investigations of the static situation led to the hypothesis that independent cost functions were attached to each of the three joints and that the configuration chosen for a given target position is that which provides the minimum total cost (Cruse 1986). The aim of the current investigation was to look for measurable values corresponding to the hypothetical cost functions. Experiments using pointers of different lengths attached to the hand showed that the strategy in choosing the joint angles are independent of the limb length. The muscle force necessary to reach a given angle is increased by a spring mounted across a joint. In this situation the angles of the loaded joint are changed for a given target point to give way to the force effect. This leads to the conclusion that the hypothetical cost functions are not independent of the physiological costs necessary to hold the joint at a given angle. The cost functions seem to depend on joint angle and on the force which is necessary to hold the joint in a given position. Cost functions are measured by psychophysical methods. The results showU-shaped curves which can be approximated by parabolas. The position of minimum cost (maximum comfort) for one joint showed no or weak dependency on the angles of the other joints. For each subject these “psychophysical” cost functions are compared with the hypothetical cost functions. The comparison showed reasonable agreement. This supports the assumption that the psychophysically measured “comfort functions” provide a measure for the hypothetical cost functions postulated to explain the targeting movements. Targeting experiments using a four joint arm which has two extra degrees of freedom showed a much larger scatter compared to the three joint arm. Nevertheless, the results still conform to the hypothesis that also in this case the minimum cost principle is applied to solve the redundancy problem. As the cost function for the whole arm shows a large minimum valley, quite a large range of arm positions is possible of about equal total costs. The scatter does not result from pure randomness but seems to be mainly produced by the fact that the angles at the end of the movement depend on the value of the joint angles at the beginning of the movement.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 62 (1990), S. 549-555 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract In an earlier investigation (Cruse and Brüwer 1987) an algorithmic model was proposed which describes targeting movements of a human arm when restricted to a horizontal plane. As three joints at shoulder, elbow and wrist are allowed to move, the system is redundant. Two models are discussed here which replace this algorithmic model by a network model. Both networks solve the static problem, i.e. they provide the joint angles which the arm has to adopt in order to reach a given point in the workspace. In the first model the position of this point is given in the form ofx —y coordinates, the second model obtains this information by means of a retina-like input layer. The second model is expanded by a simple procedure to describe movements from a start to an end point. The results qualitatively correspond to those obtained from human subjects. The advantages of the network models in comparison to the algorithmic model are discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Der Chirurg 71 (2000), S. 1277-1280 
    ISSN: 1433-0385
    Keywords: Keywords: Necrotizing fasciitis – Crohn's disease – Inflammatory bowel disease – Group F streptococci. ; Schlüsselwörter: Nekrotisierende Fasciitis – Morbus Crohn – chronisch entzündliche Darmerkrankung – Streptokokken Gruppe F.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die nekrotisierende Fasciitis, in der Regel durch Streptokokken der Gruppe A als Leiterreger ausgelöst, bedeutet für den betroffenen Patienten einen ernst zu nehmenden und lebensbedrohlichen Zustand, der optimalerweise binnen 24 Std der chirurgischen Sanierung zugeführt werden muß. Klinisch stellt sich die Infektion als hochakuter Verlauf mit Vernichtungsschmerz und unter Umständen dem Nachweis bullöser Formationen bzw. freier Gasbildung dar. Zwar bieten CT und MRT flankierende diagnostische Hilfen, eine definitive Sicherung muß allerdings bioptisch mit Anzüchtung des Erregers und pathologischem Nachweis vorhandener Fasciennekrosen erfolgen. Die breite Eröffnung der entsprechenden Region mit Débridement bis hin zur Amputation der betroffenen Extremität wird angestrebt, die antibiotische Therapie kann adjuvant nach Resistogramm erfolgen. Im Rahmen chronisch entzündlicher Darmerkrankungen, wie im hier vorliegenden Fall ein Morbus Crohn, existieren bisher nahezu keine literarischen Nennungen. Das therapeutische Management in dieser speziellen (immunsupprimierten) Situation soll infolgedessen anhand eines entsprechenden Beispiels gezeigt werden.
    Notes: Abstract. Necrotizing fasciitis is a life-threatening infection, commonly caused by group A streptococci, which has to be treated by surgical exploration and debridement during the first 24 h. Clinical clues are severe pain, in some cases followed by the appearance of bullous formations, and the detection of gas in the soft tissues by computed tomography or MRI. In addition to that, the infection is characterized by rapid inflammatory progression, producing a highly life-threatening situation. Diagnosis is finally based on surgical exploration obtaining specimens for culture and histopathologic examination. Debridement and exploration, in some cases amputation of the extremity, are indicated as soon as possible. Antibiotic therapy increases efficacy too, but there is no substitute for surgical treatment. Inflammatory bowel disease (Crohn's disease in this case) followed by necrotizing fasciitis is rarely mentioned in the literature. Therapeutic management in a situation of immunosuppression is discussed by illustration of an actual case.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Der Chirurg 70 (1999), S. 627-634 
    ISSN: 1433-0385
    Keywords: Key words: Ileostomy ; Coloproctectomy ; “High-output” syndrome ; Short-bowel syndrome ; metabolism. ; Schlüsselwörter: Stomaphysiologie ; Coloproktektomie ; „High-output-Syndrom“ ; Kurzdarmsyndrom.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die Anlage eines Kunstafters kann neben der psychologischen Belastung auch metabolische Konsequenzen haben. Während Colostomata nur geringe physiologische Probleme bedingen, kann eine Ileostomie eine echte Risikosituation darstellen. Wasser- und Elektrolytbalance wie auch die Versorgung des Körpers mit Nährstoffen, Vitaminen und Spurenelementen sind essentielle Leistungen des Dünndarms. Unter besonderen Bedingungen wie „High-output-Syndrom“ oder Kurzdarmsyndrom sind z. T. schwerwiegende Folgen, wie z. B. Niereninsuffizienz, zu beobachten. Die Grundlagen therapeutischer Eingriffsmöglichkeiten wie enterale und parenterale Substitution werden dargestellt.
    Notes: Summary. In addition to psychological stress, stomas may lead to metabolic consequences. Colostomies normally cause only minor physiological problems; however, patients with ileostomies are at risk for severe metabolic disturbances. The small intestine essentially manages the balance of water and electrolytes and the absorption of nutrition. In special circumstances such as “high output” or short-bowel syndrome, dangerous consequences like kidney disorders may arise. Basic therapeutic strategies such as enteral or parenteral substitution are discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 57 (1987), S. 137-144 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract The movements studied involved moving the tip of a pointer attached to the hand from a given starting point to a given end point in a horizontal plane. Three joints — the shoulder, elbow and wrist —were free to move. Thus the system represented a redundant manipulator. The coordination of the movements of the three joints was recorded and analyzed. The study concerned how the joints are controlled during a movement. The results are used to evaluate several current hypotheses for motor control. Basically, the incremental changes are calculated so as to move the tip of the manipulator along a straight line in the workspace. The values of the individual joints seem to be determined as follows. Starting from the initial values the incremental changes in the three joint angles represent a compromise between two criteria: 1) the amount of the angular change should be about the same in the three joints, and 2) the angular changes should minimize the total cost of the arm position as determined by cost functions defined for each joint as a function of angle. By itself, this mechanism would produce strongly curved trajectories in joint space which could include additional acceleration and deceleration in a joint. These are reduced by the influence of a third criterion which fits with the mass-spring hypothesis. Thus the path is calculated as a compromise between a straight line in workspace and a straight line in joint space. The latter can produce curved paths in the workspace such as were actually found in the experiments. A model calculation shows that these hypotheses can qualitatively describe the experimental findings.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of colorectal disease 14 (1999), S. 41-46 
    ISSN: 1432-1262
    Keywords: Key words Inflammatory bowel disease ; Permeability ; Transepithelial transport ; Immunoelectron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Crohn's disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBD) of unknown etiology. Oral absorption studies have shown an increased intestinal permeability for various sugar molecules in patients with IBD and their healthy relatives as a possible pathogenetic factor. However, the various transport pathways through the mucosal barrier have not yet been examined. This study therefore investigated whether antigens pass the epithelial barrier by a transcellular or a paracellular pathway. Mucosa of freshly resected specimens from CD (n = 10) or UC (n = 10) patients was investigated by immunoelectron microscopy and compared with healthy mucosa. Epithelial transport was studied with the antigens ovalbumin and horseradish peroxidase after defined incubation. Labeling density of subunit c of ATP synthetase was determined in mitochondria of enterocytes of all specimens. In all specimens epithelial transport of OVA and HRP was principally transcellular through enterocytes with normal ultrastructure, although some tight junctions in CD and UC were dilated. Antigens were transported within vesicles to the basolateral membrane 2.5 min after incubation. The level of enterocytes with electron-lucent cytoplasm containing a high amount of antigens was higher in CD and UC than in healthy mucosa, depending on the grade of inflammation. ATP synthetase was significantly decreased in electron-lucent cytoplasm of CD and UC to normal ultrastructure of healthy mucosa. Our study shows that ovalbumin and horseradish peroxidase taken up by the apical membrane reach the paracellular space by vesicular transport in healthy and IBD enterocytes within a few minutes. Transcellular pathway is affected in both CD and UC, which is indicated by a high level of antigens within the cytosol. We speculate that increased intestinal permeability in IBD results substantially from enhanced transcellular transport.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Der Onkologe 5 (1999), S. 929-932 
    ISSN: 1433-0415
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Patienten mit langjähriger Dauer einer chronisch entzündlichen Darmerkrankung (CED) – Colitis ulcerosa (CU) oder Morbus Crohn (MC) mit Dickdarmbeteiligung – haben ein erhöhtes Risiko, an einem kolorektalen Karzinom zu erkranken. Doch trotz koloskopisch – bioptischer Überwachungsprogramme zur Erkennung prämaligner Veränderungen (Dysplasien), erkranken immer wieder Patienten mit CED an einem manifesten Dickdarmkarzinom. Ziel dieser Studie war die Evaluation eines Patientenkollektivs mit CU oder MC und einem assoziierten kolorektalen Karzinom hinsichtlich klinischem Erscheinungsbild und Stellenwert koloskopisch–bioptischer Überwachungsprogramme.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1433-0385
    Keywords: Keywords: Intraoperative irradiation ; Gastrointestinal carcinoma ; Recurrent rectal carcinoma ; Multimodal therapy. ; Schlüsselwörter: Intraoperative Radiotherapie ; gastrointestinale Carcinome ; Rectumcarcinomrezidiv ; multimodale Therapie.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Durch intraoperative Strahlentherapie (IORT) wird unter maximaler Schonung der umliegenden strahlensensiblen Organe die Strahlendosis im Tumorbett lokal erhöht. Mit diesem Verfahren als Bestandteil eines multimodalen Therapieregimes konnten sowohl die Lokalrezidivrate als auch die Überlebensrate gegenüber konventionellen Therapieregimen beim fortgeschrittenen primären Rectumcarcinom und Carcinomrezidiv verbessert werden. Dagegen ist bisher nur in wenigen Studien über eine verbesserte Überlebensrate durch zusätzliche IORT beim fortgeschrittenen Magencarcinom berichtet worden. Beim Pankreascarcinom wird durch IORT die lokale Tumorkontrolle, nicht aber die Überlebensrate verbessert, da häufig Leber- und Peritonealmetastasen auftreten. Für das Oesophaguscarcinom liegen zur Zeit nur unzureichende Daten vor.
    Notes: Abstract. Surgery alone often fails to achieve local control in advanced gastrointestinal tumors. With multimodal therapy approaches, both local tumor control and long-term survival appear to be improved. Intraoperative radiation therapy (IORT) is an attempt to achieve higher doses of irradiation while dose-limiting structures are surgically displaced. It has been shown previously that both local tumor control and long-term survival are improved in patients undergoing surgery combined with IORT for both primary and recurrent rectal carcinoma. In advanced gastric carcinoma, IORT has achieved optimistic survival results in a few studies. In locally advanced pancreatic cancer, an apparent improvement in local control has been noted with IORT, but survival has not been prolonged because of a high incidence of both liver and peritoneal metastases. The data concerning IORT for esophageal carcinoma are not yet sufficient to allow judgement.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...