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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4324-4330 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a new Monte Carlo method for estimating the chemical potential of model polymer systems. The method is based on the gradual insertion of a penetrable "ghost'' polymer into the system and is effective for large chain lengths and at high densities. Insertion of the ghost chain is facilitated by use of an expanded ensemble, in which weighted transitions are permitted between states characterizing the strength of the excluded volume and thermal interactions experienced by the ghost chain. We discuss the implementation and optimization of the method within the framework of the bond fluctuation model and demonstrate its precision by a calculation of the finite-size corrections to the chemical potential.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 719-724 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We are presenting a new method to measure the chemical potential of polymer chains in computer simulations which has virtually no limitations in chain length. The method uses a thermodynamic integration over the excluded volume interaction of a ghost chain to determine its excess chemical potential. It is exemplified with a Monte Carlo simulation of the athermal bondflucutation model for various densities and the chain lengths N=20,50,80. Furthermore, the osmotic equation of state and the entropy density are determined.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nutrition 33 (1994), S. 164-166 
    ISSN: 1436-6215
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 50 (1994), S. 442-446 
    ISSN: 1420-9071
    Keywords: Glucagon ; endocrine pancreas ; exocrine pancreas ; islet-acinar axis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Intravenous glucagon inhibits exocrine pancreatic secretion in vivo, but exogenous glucagon does not affect exocrine secretion in vitro. Recent work, however, suggested that endogenous glucagon may be involved in the regulation of exocrine secretion even in vitro. We therefore investigated the effects of exogenous and endogenous glucagon on exocrine secretion by the isolated perfused rat pancreas in the presence of 1.8 mM glucose. Exogenous glucagon did not affect CCK-stimulated amylase output. 20 mM arginine stimulated glucagon release, but did not affect basal enzyme secretion. CCK-stimulated amylase output, however, was significantly inhibited in the presence of arginine. This inhibitory effect of arginine on exocrine pancreatic secretion could be blocked by glucagon antibodies, but not by nonspecific gammaglobulins. Thus exogenous glucagon failed to affect exocrine pancreatic secretion in vitro, but endogenously released glucagon or a glucagon-like peptide inhibited amylase release in the isolated perfused pancreas. We conclude that glucagon or a glucagon-like peptide may be a mediator in the islet-acinar axis.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1440
    Keywords: Nicotine ; Biphasic action ; Suggestibility ; Nicotine serum levels ; Cardiovascular measures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Based on previous observations that sensory suggestibility might be related to cholinergic drug effects, and that individual susceptibility to nicotine as defined by response differences to various doses is lower in males, nonsmokers, and highly suggestible subjects, the present study investigated whether nicotine serum blood levels, cardiovascular responses, and sensory suggestibility show differences according to gender and smoking habit, and whether differences in nicotine susceptibility measured by a discrimination task by subjective ratings on activation can be reproduced in the direction predicted by the previous data. In a doubleblind threefold cross-over design 48 subjects divided according to smoking habit, gender, and sensory suggestibility were tested in balanced order under the influence of an oral dose of 0, 0.014, or 0.028 mg/kg body weight of nicotine. Results revealed higher serum levels of nicotine in males and smokers, a dose-dependent increase in heart rate and systolic and diastolic blood pressure, partly interacting with gender or smoking habit (females and nonsmokers showing larger increase with the low doses), and a change in suggestibility in the expected direction (decrease with the low dose, increase with the large one only in female nonsmokers). A fourfold interaction among dose, smoking habit, gender, and suggestibility for the discrimination task partly reproduced the observations of higher nicotine susceptibility in females and nonsmokers, whereas suggestibility did not seem to reveal the expected changes. Also, on a subjective level larger doses were necessary to make male smokers feel activated, while the other groups showed the biphasic response pattern to the two nicotine doses. In conclusion, the data justify further research on the concept of nicotine susceptibility defined by biphasic effects of nicotine on vigilance.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 72 (1994), S. 568-579 
    ISSN: 1432-1440
    Keywords: Intermediary metabolism ; Basal metabolism ; Postprandial metabolism ; Energy metabolism ; Energy expenditure ; Glucose metabolism ; Lipid metabolism ; Nutrition ; Nutritional state ; Hyperinsulinemia ; Exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1440
    Keywords: Low-density lipoprotein apheresis ; Immunoadsorption ; Dextran sulfate cellulose adsorption ; Familial hypercholesterolemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two low-density lipoprotein (LDL) apheresis methods allowing a specific extracorporeal removal of atherogenic lipoproteins from plasma were compared concerning their efficacy and safety in the long-term therapy of severe familial hypercholesterolemia. Five patients were treated with immunoadsorption (IMA) at weekly intervals over 3 years each, and three patients received weekly therapy with dextran sulfate cellulose adsorption (DSA) for up to 2 years. The mean plasma volume processed per session to decrease total cholesterol to a target level of 100–150 mg/dl at the end of LDL apheresis was significantly lower in DSA than in IMA: 143% vs. 180% of the individual plasma volume. Both LDL apheresis procedures achieved a mean acute reduction of plasma LDL cholesterol by more than 70%. The average interval concentrations of plasma LDL cholesterol obtained without concomitant lipid-lowering medication were 151 ± 26 mg/dl compared to 351 ± 65 mg/dl at baseline in the IMA-treated patients and 139 ± 18 mg/dl compared to 359 ± 48 mg/dl at baseline in the DSA-treated patients. Two patients from the DSA group died after 2 years of study participation due to a stroke and a sudden cardiac death several days after the last plasma therapy. Treatment-related side effects were infrequent. Long-term therapy with IMA and DSA was associated with symptomatic improvement of coronary artery disease and mobilization of tissue cholesterol deposits. Analysis of coronary angiograms after 3 years of weekly LDL apheresis with IMA revealed in five patients nearly identical atherosclerotic lesions without definite regression or progression.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 175 (1994), S. 525-530 
    ISSN: 1432-1351
    Keywords: Systematic search ; Path integration ; Dead reckoning ; Desert ants ; Cataglyphis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The main navigational mechanism used by foraging desert ants of the genus Cataglyphis is path integration (dead reckoning). Any such egocentric system of navigation is prone to cumulative navigational errors. Hence, while homing Cataglyphis might have reset its path integration system and yet not arrived at the start of its foraging excursion, the nest entrance. Then it resorts to piloting or performs a systematic search for the nest. The search pattern consists of a system of loops of ever increasing size centred about the origin, i.e. the start of the search. Here we show that underlying the system of loops is a spiral search programme that gets transformed into the observed pattern of loops by the ant's idiosyncratic path-integration algorithm. The ant starts to follow a spiral course, then breaks off this course and walks towards the centre, i.e. to what its path-integration system has computed to be the origin of the search. This reset episode is followed by another spiral course, which is terminated by the next reset, and so forth. After each reset, the spiral gets wider, so that the whole pattern expands. Futhermore, every now and then the spiral might change its sign. Computer simulations based on these simple rules lead to search patterns of the kind actually recorded in Cataglyphis ants. These patterns ensure that those parts of the area in which the target (nest entrance) is most likely to be located are searched most heavily; in other words: the search density profile is adapted to the probability density function of the target.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2307
    Keywords: Prolyl 4-hydroxylase ; Pulmonary fibrosis ; Alveolar epithelium ; Protein disulphide isomerase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Polyclonal and monoclonal antibodies to the β subunit of prolyl 4-hydroxylase, the protein disulphide isomerase, were used to compare the pulmonary cells in 13 normal and in 20 fibrotic rat and mini-pig lungs made fibrotic by X-ray irradiation, using the ABC immunoperoxidase technique. In normal lungs, prominent staining of Clara cells and type II pneumocytes and weaker reactivity with alveolar macrophages, fibroblasts, endothelial and smooth muscle cells were detectable. In pulmonary disease, in which interstitial fibrosis was the characteristic feature, the immunoreactivity was increased in both the epithelial and interstitial cells. Type I pneumocytes remained negative. In the early stages of disease (3 to 4 weeks after irradiation) when little morphological alteration was seen, capillary endothelial cells had already become immunoreactive. These results underline the complex involvement and interaction of different lung cell populations in the process of pulmonary fibrogenesis.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 653-660 
    ISSN: 0392-6737
    Keywords: Macromolecular and polymer solutions (solubility, swelling, etc.) ; polymer melts ; Critical point phenomena ; Liquid-liquid transitions ; Monte Carlo and statistical methods ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The unmixing transition of both symmetrical polymer blends AB (i.e. chain lengthsN A=N B=N) and asymmetrical ones (N B/N A=2,3) is studied by large-scale Monte Carlo simulations of the bond fluctuation model. Combination of semi-grand-canonical simulation techniques, «histogram reweighting» and finitesize scaling allows an accurate location of the coexistence curve in the critical region. The variation of the critical temperature with chain length (N) is studied and compared to theoretical predictions. For the symmetrical case, use of chain lengths up toN=512 allows a rough estimation of crossover scaling functions for the crossover from Ising to mean-field exponents. The order-disorder transitions in melts of both symmetric (compositionf=N A/(N A+N B)=1/2) and asymmetric (f=3/4) block copolymers is studied for very short chains (16≤N≤60). The interplay between structure and chain configuration is emphasized. Qualitative evidence for «dumbell formation» of chains and vacancy enrichment in A-B-interfaces and near hard walls is presented.
    Type of Medium: Electronic Resource
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