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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 8 (1998), S. 65-78 
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Although the mechanisms of fibrillation are no doubt multi-faceted, the geometry of the heart may play a major role in the dynamics of wave propagation during fibrillation [A. T. Winfree, Science 266, 1003–1006 (1994)]. The ventricles are thick chambers made up of sheets of parallel muscle fibers with the direction of fibers rotating across the ventricular walls (rotational anisotropy). The thick walls of the ventricles allow reentry to develop transmurally, provided the wavelength is sufficiently small. Depending on the kinetics of heart cells, the dynamics of rotating waves in three dimensions may be fundamentally different than in two dimensions, leading to destabilization of reentry and ventricular fibrillation (VF) in thick ventricles. The atria have an intricate geometry comprised of a thin sheet of cardiac tissue attached to a very complex network of pectinate muscles. The branching geometry of the pectinate muscles may lead to destabilization of two-dimensional reentry via "long-distance" electrical connections giving rise to atrial fibrillation (AF). Therefore, although fibrillation occurs via complex three-dimensional wave propagation in the ventricles and the atria, the underlying mechanisms and factors that sustain VF and AF are probably different.© 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 58 (2003), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Transurethral vaporisation of the prostate gland (TUVP) is an emerging surgical alternative to conventional electroresection (TURP). This study examined vesical pressure and fluid absorption during TUVP in 35 patients with benign prostatic hypertrophy. The irrigating fluid was a solution of glycine 1.5% and ethanol 1%. Intraoperative intravesical pressure was monitored continuously and absorption of irrigating fluid was detected by ethanol analysis in expired breath. The incidence of absorption during TUVP was 34%. Intravesical pressures were higher amongst patients who went on to absorb than amongst patients who did not. Combining data from the current study and from 35 patients in our previous investigation into TURP (Gray et al.: Anaesthesia 2001; 56: 461–4), urological trainees operated at higher mean pressure and for longer than their consultant colleagues and their resections were significantly more likely to result in absorption. The incidence of irrigating fluid absorption during trainees’ operations appeared to be less using TUVP than using conventional TURP.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 56 (2001), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Intravesical pressure was measured continuously during 35 transurethral prostate resections using a fine suprapubic catheter. Absorption of irrigating fluid was detected by tagging it with ethanol and sampling the expired breath using an alcohol meter. Higher mean (SD) intravesical pressure was demonstrated in those patients who absorbed irrigating fluid (19.1 (7.7) mmHg) than in those who did not (12.4 (6.5) mmHg; p = 0.00004). Higher peak pressures were also demonstrated among absorbing patients. Traditional risk factors for fluid absorption, such as operator experience and resectate mass, were found to correlate with pressure exposure over time. Exposure to supranormal bladder pressure over time is the final common path for all causes of absorption. Vesical pressure monitoring may be a valuable feedback tool during difficult resections or operator training.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 298 (1982), S. 562-563 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In female mammals, one of the two X chromosomes becomes irreversibly inactivated early in embryogenesis; subsequently any somatic cell and its descendants fail to express genes carried on the inactivated chromosome4'5. X-linked genetic variants can therefore provide markers for cell population ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: New synthetic anionic membranes have been developed as replacements for the cellulose membranes currently used to remove blood toxins and water in hemodialyzers. The membranes are solvent-cast on to polyethylene sheets from copolymers of acrylic acid with various alkyl methacrylates. Membranes from copolymers of acrylic acid and n-butyl methacrylate show most promise as alternative hemodialysis membranes. The copolymers are prepared using modified emulsion copolymerization techniques with sequential monomeric additions in order to yield homogeneous polymers with the high molecular weight necessary for good film-forming characteristics. Permeability of the synthetic membranes to blood components, rates of water removal by ultrafiltration, and mechanical properties of membranes are measured and compared with standard 150 and 300PT cellulose films. Results for cellulose films confirm previous conclusions that permeability is principally proportional to the inverse molecular volume of the diffusing solute, while new anionic synthetic membranes show selectivity to basic blood solutes and operate by an “assisted diffusion” mechanism. A method is reported of improving mechanical properties while maintaining high permeability rates for blood solutes and high water ultrafiltration rates, by treating membranes with ethylene oxide gas, a clinical sterilizing agent.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 415-445 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: New synthetic polymer membranes prepared from copolymers of dimethylaminoethyl methacrylate are reported. Membrane transport characteristics are compared with those of standard cellulose films currently used in hemodialysis. The membranes are obtained as films by casting solutions of vinyl copolymers prepared by emulsion polymerization techniques. The new membranes show selectivity towards certain blood components under the test conditions used. The clinical procedure for ethylene oxide sterilization has been adapted to give chemical modification of dimethylaminoethyl methacrylate tertiary amine groups. With acrylonitrile as comonomer, polymer membranes which are both watersensitive and insoluble are obtained. The permeability of such films is controlled by varying processing time. Infrared spectra of processed and unprocessed films are discussed and reasons put forward for the change in membrane properties brought about by processing. Membrane behavior when acrylonitrile is replaced by methacrylonitrile or methyl methacrylate indicates the probable necessity of having a strongly electron-attracting comonomer for successful modification.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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