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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9067-9077 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational excitation of an Ar55 cluster in collisions with He (Ekin=25 meV) is investigated by using classical trajectories and a highly approximate quantum mechanical method (vibrationally sudden approximation). The energy transfer from the helium atom to the cluster (ΔE) is calculated as a function of the scattering angle θ. It is found (i) that predominantly the modes corresponding to the cluster atoms in the outer shell are excited and (ii) that the probability for multi-phonon (Δn≥2) excitations steadily increases with the scattering angle. The results of both sets of calculations are generally in good agreement with measured energy loss spectra over the entire range of scattering angles. In the region θ(approximate)15°–30°, which—because single-phonon transitions dominate—is most important for determining the frequency distribution of the cluster, the quantum mechanical calculations are superior to classical mechanics; the latter fails to conserve zero-point energy and therefore leads to unrealistic energy transfer below ΔE(approximately-less-than)2 meV. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 565-570 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting tunnel junctions (STJs) are promising as high energy resolution x-ray detectors. However, the theoretical limit of the energy resolution of STJs has not yet been reached for several reasons. In many cases quasiparticle losses limit the energy resolution. We have investigated STJs with different multilayer structures by means of low temperature scanning electron microscopy. By measuring the quasiparticle lifetime of Nb junctions with and without Ta passivation at the surface, we have identified quasiparticle losses at the surface of nonpassivated junctions as the dominant loss process. The temperature dependence of the quasiparticle lifetime gives information about the loss mechanism. The influence of quasiparticle traps on the effective quasiparticle lifetime is discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2181-2183 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present here a low-temperature (Ts〈630 °C) process for the selective epitaxial growth of Si that employs atomic hydrogen. Modulation of both the substrate temperature and the flux of atomic hydrogen gives alternating growth and suppression/etching cycles, resulting in a significant increase in selectivity. Epitaxial thin-film quality is essentially unaffected, as verified by in situ analysis via low-energy electron diffraction, and ex situ analysis via scanning electron and atomic-force microscopy. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2604-2606 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nucleation of copper on TiN and SiO2 surfaces has been investigated using a collimated molecular beam of hexafluroacetylacetonate copper(I) trimethylvinylsilane in ultrahigh vacuum. The Cu thin film precursor was delivered using a bubbler with H2 as the carrier gas and the substrate temperature was varied from 150 to 260 °C. Ex situ analysis of thin film morphology and microstructure has been conducted using scanning electron microscopy. On SiO2 surfaces the Cu nuclei density reaches a maximum near 5×1010 cm−2, nearly independent of substrate temperature. In contrast, on TiN surfaces the maximum nuclei density is strongly dependent on temperature, varying nearly two orders of magnitude from 150 to 260 °C. On TiN the nucleation process is described well by established kinetic models where a maximum in nuclei density (Nmax) is predicted with respect to the time, and where this quantity exhibits an Arrhenius dependence on substrate temperature. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. A clonal culture of the peritrich Epistylis pygmaeum was used for all observations and experiments. Motile cells preferentially attached to the eggs of three species of Brachionus but also attached to the body of adult B. angularis. Zooids on the transitory egg substratum developed only short stalks, while those on the body often developed long stalks and branched colonies. Selection for the eggs positions the ciliate near the cloaca, and thus high concentrations of fine particulate material excreted by the host. Settlement on eggs occurred equally well in the light and dark, and on moving and stationary eggs.2. Motile Epistylis cells attached to a wide variety of rotifer and crustacean zooplankton, but exhibited some pronounced selectivity. They readily settled on the eggs of other rotifers (Epiphanes, Polyarthra), on the carapace of several cladocerans (Ceriodaphnia, Daphnia, Diaphanosoma), and on the egg sacs of a copepod (Tropocyclops). They settled less readily on the bodies of the rotifers Asplanchna and Synchaeta, and rarely or never settled on the rotifer Keratella, the cladocerans Bosmina and Scapholeberis, and the body of the copepod.3. Epistylis populations initiated with a single zooid on Brachionus increased exponentially and often contained several hundred attached zooids and motile cells after 3 days at 20 °C. Observations of a culture initiated from a single telotroch provided new information about peritrich life cycles: (1) motile cells reproduced themselves at a rapid rate (λ = 4.26 day−1); (2) telotrochs produced or transformed into swimming zooids and vice versa. Functions of the two types of motile cells remain to be clarified. Telotrochs likely are specialised for finding and attaching to hosts. Swimming zooids can feed and reproduce, producing both their own cell type and telotrochs. Together, they should enhance dispersal and population growth, especially when hosts are rare.4. Life-table experiments with two species of Brachionus showed that colonisation by Epistylis had no effect on adult survival but significantly decreased fecundity, by 29% in both cases. Zooids attached to eggs could be a weight burden, increase drag, and possibly inhibit egg development. Those on the body of B. angularis also could interfere with coronal cilia, inhibiting feeding and further slowing locomotion. The ability of E. pygmaeum to select and then interfere with its hosts indicates that this epibiont has the potential to influence the species structure of zooplankton communities.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Propanidid ; Liposomen ; Propofol ; Hämodynamik ; Histamin ; Katecholamine ; Key words Propanidid ; Liposomes ; Propofol ; Haemodynamics ; Histamine ; Catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Background. Propanidid was widely used as a short-acting i.v. anaesthetic until it was withdrawn due to severe haemodynamic side effects. It was presumed that anaphylactoid reactions with massive histamine release were caused by the solvent cremophor rather than by propanidid itself. A new liposomal preparation of propanidid was examined in this animal study and compared with propanidid in cremophor solution and with propofol. Methods. Eighteen pigs were randomly assigned to one of the following groups: Group 1 (n=6): Propanidid in liposomal preparation (PropaLip; Braun Melsungen, Germany). Anaesthesia was induced with 60 mg/kg, followed by continuous infusion of 400 mg/kg·h. Group 2 (n=6): Propanidid in cremophor solution (PropaCrem; Sombrevin, Gedeon Richter, Budapest) 15 mg/kg, 100 mg/kg·h. Group 3 (n=6): Propofol (Disoprivan, Zeneca, Plankstadt, Germany) 5 mg/kg, 20 mg/kg·h. After induction and tracheal intubation, the animals were ventilated with 50% oxygen in air. Basic monitoring included noninvasive blood pressure measurements, electrocardiographic monitoring, and capnography. In a short surgical procedure, arterial and pulmonary artery catheters were placed via the right carotid artery and right internal jugular vein, respectively. As soon as the animals responded to a pain stimulus a second anaesthetic induction was performed, followed by a 60-min continuous infusion of the agent studied with invasive haemodynamic monitoring including arterial and pulmonary arterial pressures and cardiac output. Blood samples were taken for the measurement of serum levels of adrenaline, noradrenaline, cortisol, aldosterone, adrenocorticotropic hormone, and histamine. Results. Intubation conditions and quality of anaesthesia were best in propofol animals, followed by PropaCrem animals. In spite of the large dose of 410 mg/kg·h, resulting in a volume load of as much as 16.4 ml/kg·h, the PropaLip animals showed evidence of poor anaesthetic quality. In group 1 we recorded the highest increases in heart rate (91 vs. 115/min), cardiac output (5.4 vs. 7.7 l/min), plasma catecholamine levels, and histamine concentrations (124–268 ng/ml). Conclusions. In our animal study, propanidid in liposomal preparation failed to show promise as a new anaesthetic agent. Our results are discussed in view of a drug targeting the cells of the reticuloendothelial system, especially the liver, where liposomes are eliminated from the blood. This may result in the transport of propanidid to one of its major places of inactivation.
    Notes: Zusammenfassung In einer tierexperimentellen Studie wurden 18 Läuferschweine untersucht, von denen je 6 Tiere (1) Propanidid in Liposomendispersion (abgekürzt PropaLip), (2) Propanidid in Cremophor (abgekürzt PropaCrem) und (3) Propofol erhielten. Nach Narkoseeinleitung mit 60 mg/kg PropaLip, 15 mg/kg PropaCrem bzw. 5 mg/kg Propofol wurden die Tiere intubiert, für die weiteren Messungen instrumentiert und in einer anschließenden 60minütigen Narkose untersucht. Der Anästhetikaverbrauch betrug 16 mg/kg·h Propofol, 120 mg/kg·h PropaCrem und 410 mg/kg·h PropaLip. Trotz dieser hohen Dosierung und der damit verbundenen Volumenbelastung von 16,4 ml/kg·h war die Anästhesiequalität in der PropaLip-Gruppe unbefriedigend. Bei diesen Tieren traten die ausgeprägtesten Anstiege von Herzfrequenz, HZV, Katecholamin- und Histaminspiegeln auf, weitgehend konstant blieben die genannten Parameter bei der Propofolgruppe, während die PropaCrem-Tiere eine Mittelstellung einnahmen. Offenbar ist die Verfügbarkeit von Propanidid in der Liposomenpräparation schlechter als in der Cremophorlösung. Ein Zusammenhang der geringen Wirksamkeit mit der gezielten Aufnahme von Liposomen in die Zellen des RES, z.B. der Leber, wo Propanidid inaktiviert wird, wird diskutiert.
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  • 7
    ISSN: 1432-1017
    Keywords: Key words Gallstone ; Cholesterol monohydrate crystals ; Phase separation ; Light scattering ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Phospholipid/cholesterol vesicles were solu-bilized by 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). Above 30 mol% cholesterol (Ch) in the lipid vesicles several remarkable changes of the solubilization process were observed. (i) Two modes of solubilization: The effective detergent to lipid ratio Rc(M) for the formation of mixed micelles decreased from Rc(M) = 43 ± 3 at low lipid concentrations, [L]≤ 0.15 mm, to Rc(M) = 2.4 ± 0.3 above [L] = 0.5 mm (40 mol% Ch, T = 20 °C). (ii) At subsolubilizing CHAPS concentrations, filamentous and helical microstructures were formed, similar to those which were observed in native and model bile. (iii) The number of observed fibers was about two orders of magnitude higher in the presence of the negatively charged lipids phosphatidylglycerol (PG) and phosphatidic acid (PA) compared to the zwitterionic phosphatidylcholine (PC). Fiber formation began after 16–18 h using PG and PA compared to 3–4 days in the presence of PC. Screening of the charged lipids by NaCl effectively reduced the formation of fibers. Assuming binding of Na+ to the charged lipid aggregates, an intrinsic binding constant Kint = 0.6 M–1 was determined by applying the Gouy-Chapman theory. After the addition of CHAPS to PG/Ch vesicles, a fast initial solubilization of the vesicles (〈1 min) to mixed micelles (rh = 2.3 ± 0.2 nm) and small vesicles (rh = 23 ± 1 nm) was observed, followed by an intermediate period of 2 h, after which the formation of fibers occurred (〉15 h). The microstructures are visualized by darkfield and electron microscopy. The method of vesicle solubilization is compared to the dilution of concentrated micellar solutions, which is usually applied to model bile systems.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Intensive care medicine 24 (1998), S. 829-836 
    ISSN: 1432-1238
    Keywords: Key words Lung injury ; Oleic acid ; Regional ventilation ; Electrical impedance ; Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: To apply electrical impedance tomography (EIT) and the new evaluation approach (the functional EIT) in monitoring the development of artificial lung injury. Design: Acute experimental trial. Setting: Operating room for animal experimental studies at a university hospital. Subjects: Five pigs (41.3 ± 4.1 kg, mean body weight ± SD). Interventions: The animals were anaesthetised and mechanically ventilated. Sixteen electrodes were attached on the thoracic circumference and used for electrical current injection and surface voltage measurement. Oleic acid was applied sequentially (total dose 0.05 ml/kg body weight) into the left pulmonary artery to produce selective unilateral lung injury. Measurements and results: The presence of lung injury was documented by significant changes of PaCO2 (40.1 mmHg vs control 37.1 mmHg), PaO2 (112.3 mmHg vs 187.5 mmHg), pH (7.35 vs 7.42), mean pulmonary arterial pressure (29.2 mmHg vs 20.8 mmHg) and chest radiography. EIT detected 1) a regional decrease in mean impedance variation over the affected left lung (–41.4 % vs control) and an increase over the intact right lung ( + 20.4 % vs control) indicating reduced ventilation of the affected, and a compensatory augmented ventilation of the unaffected lung and 2) a pronounced fall in local baseline electrical impedance over the injured lung (–20.6 % vs control) with a moderate fall over the intact lung (–10.0 % vs control) indicating the development of lung oedema in the injured lung with a probable atelectasis formation in the contralateral one. Conclusion: The development of the local impairment of pulmonary ventilation and the formation of lung oedema could be followed by EIT in an experimental model of lung injury. This technique may become a useful tool for monitoring local pulmonary ventilation in intensive care patients suffering from pulmonary disorders associated with regionally reduced ventilation, fluid accumulation and/or cell membrane changes.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Diseases of the colon & rectum 38 (1995), S. 1144-1146 
    ISSN: 1530-0358
    Keywords: Pelvic pouch surgery ; Paradoxical puborectalis contraction ; Anismus ; Nonrelaxing puborectalis ; Biofeedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Normal defecation is associated with relaxation of sphincters during the evacuation process. However, obstructive defecation is sometimes seen clinically manifested by abnormal contraction of the puborectalis during defecation rather than relaxing. This condition has not previously been described after pelvic pouch construction. PURPOSE: This study was done to evaluate patients for defecation difficulties caused by paradoxical puborectalis contraction after pelvic pouch procedures. METHODS: Prospectively, patients with defecation difficulties were questioned. They then underwent electromyography if they met particular criteria. Biofeedback was offered to all patients demonstrating paradox on electromyography. Follow-up was by clinic visits and interviews. RESULTS: After pelvic pouch construction, 13 patients were found to have paradoxical puborectalis contraction. Twelve of 13 patients elected to have biofeedback therapy. Eleven of these 12 were available for follow-up an average of eight (1–15) months after biofeedback. Nine improved, and two had no change in their defecation difficulty. Of the initial 13, 10 had an event, either pouchitis or abdominal trauma, directly before their defecation problems. CONCLUSION: Paradoxical puborectalis contraction can occur in patients after pelvic pouch surgery. It should be suspected in patients with defecation difficulties in the absence of an anatomic abnormality. Biofeedback is effective treatment.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für Gerontologie + Geriatrie 33 (2000), S. 438-446 
    ISSN: 0044-281X
    Keywords: Schlüsselwörter Aortenklappenersatz – Letalität – Morbidität –¶Überleben – 9. Lebensdekade ; Key words Aortic valve replacement – mortality – morbidity –¶survival – 9th decade of life
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Due to demographic changes in average life expectancy, the age of patients undergoing cardiac surgery is increasing as well. We have reviewed the short- and long-term outcome in patients over 80 years of age after aortic valve replacement.¶   From 01Jan1995 until 31Dec1998, 105 patients (76 women, 29 men between 80 and 89 years, median: 83) underwent aortic valve replacement. 42% presented with aortic stenosis, 58% with combined valve disease with leading stenosis. 53% (group A) received isolated valve replacement, 47% (group B) underwent myocardial revascularization as well. The in-hospital mortality rate was 8.9% for group A and 14.3% for group B. The follow-up time ranged between 10 and 243 weeks (median: 112 weeks). None of the patients had to be reoperated for prosthetic valve dysfunction or endocarditis. Bleeding complications due to anticoagulant therapy were not observed. Of the 11 deaths during the follow-up period, 5 (45%) were cardiac in nature and 2 (18%) related to stroke. Actuarial survival rates for group A were 98, 95 and 88% at 1, 2 and 3 years, and for group B 92, 84 and 84%, respectively. Permanent nursing care was not required 1 year after the operation by 98% of patients in group A (2 years: 95%, 3 years: 88%) and by 100% of patients in group B (2 years: 95%, 3 years: 88%). At an interval of 1 year after the operation 98% of patients in group A had not been hospitalized as a result of cardiac disorders ¶(2 years: 98%, 3 years: 94%). The rates for group B were 90, 82 and 82%.¶   Compared with younger age groups, aortic valve replacement in patients 80 years of age and older is associated with a distinctly increased mortality and morbidity. However, our data suggest that considering the poor prognosis of conservative therapy of symptomatic aortic valve disease, the functional status as well as life expectancy in this age group seems to be positively influenced by aortic valve replacement.
    Notes: Zusammenfassung Mit zunehmendem Anteil älterer Menschen an der Gesamtbevölkerung nimmt das durchschnittliche Alter der am Herzen operierten Patienten zu. Wir haben in unserem Patientengut die Kurz- und Langzeitergebnisse des Aortenklappenersatzes in der neunten Lebensdekade untersucht. Zwischen dem 1.1.1995 und dem 31.12.1998 wurden 105 Patienten (76 Frauen, 29 Männer, 80 bis 89 Jahre alt, Median: 83 Jahre) einem Aortenklappenersatz unterzogen. 42% hatten eine Aortenstenose, 58% ein kombiniertes Vitium mit führender Stenose. Bei 53% wurde ein isolierter Klappenersatz vorgenommen (Gruppe A), 47% erhielten zusätzlich eine Myokardrevaskularisation (Gruppe B). Die Krankenhausletalität betrug bei isoliertem Klappenersatz 8,9% und bei Kombinationseingriffen 14,3%. Die Nachbeobachtungszeit betrug zwischen 10 und 243 Wochen (Median: 112 Wochen). Reoperationen wegen Prothesendysfunktion oder -endokarditis sowie Blutungen aufgrund der Antikoagulation wurden nicht beobachtet. Von den 11 Todesfällen während der Nachbeobachtungsphase waren 5 (45%) kardial bedingt und 2 (18%) Folge eines Schlaganfalls. Die Überlebensrate betrug bei Patienten der Gruppe A nach einem Jahr 98%, nach zwei Jahren 95% und nach drei Jahren 88%. Für die Gruppe B waren die entsprechenden Zahlen 92, 84 und 84%. Die Freiheitsrate von Pflegebedürftigkeit war beim isolierten Aortenklappenersatz nach einem Jahr 98%, nach zwei Jahren 95%, nach drei Jahren 88% und bei Kombinationseingriffen 100, 95 und 88%. Die Freiheitsrate von erneuter stationärer Behandlung aus kardialen Gründen war in der Gruppe A nach einem Jahr 98%, nach zwei Jahren 98%, nach drei Jahren 94% und in der Gruppe B 90, 82 sowie 82%.¶  Der Aortenklappenersatz ist bei Patienten in der neunten Lebensdekade im Vergleich zu jüngeren Patienten mit einer deutlich erhöhten Letalität und Morbidität verbunden. Berücksichtigt man jedoch die infauste Prognose der konservativen Therapie klinisch manifester Aortenvitien, so weisen unsere Daten darauf hin, dass auch im hohen Alter der funktionelle Status und die Lebenserwartung durch den Klappenersatz positiv beeinflusst werden können.
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