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  • 1
    ISSN: 1572-9540
    Keywords: muon-catalyzed fusion ; deuterium ; solid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Muon-catalyzed fusion in deuterium has traditionally been studied in gaseous and liquid targets. The TRIUMF solid hydrogen layer target system has been used to study the fusion reaction rates in the solid phase at a target temperature of 3 K. Both branches of the cycle were observed; neutrons by a liquid organic scintillator, and protons by a silicon detector located inside the target system. The effective molecular formation rate from the upper hyperfine state and the spin exchange rate have been measured, and information on the branching ratio parameters has been extracted.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9540
    Keywords: muon-catalyzed fusion ; thickness measurement ; solid hydrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In experiments using the TRIUMF solid hydrogen target system, the knowledge of the target thickness and uniformity is often essential in order to extract physical parameters from the data. We have characterized the thickness and uniformity of frozen targets using the energy loss of alpha particles. An accuracy of ∼5% was achieved, a limit imposed by the uncertainty in the stopping powers: The details of the method are described, and the thickness calibration of the target is presented.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9540
    Keywords: muon-catalyzed fusion ; muonic hydrogen ; muonic atoms ; muonic molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Preliminary results are reported for an experiment at TRIUMF where a time-of-flight technique was tested for measuring the energy dependence of the rate for muon-catalyzed dt fusion. Muonic tritium atoms were created following transfer of negative muons from muonic protium in a layer of solid hydrogen (protium) containing a small fraction of tritium. The atoms escaped from the solid layer via the Ramsauer-Townsend mechanism, traversed a drift region of 18 mm, and then struck an adjacent layer of deuterium, where the muonic atom could form a molecular system. The time of detection of a fusion product (neutron or alpha) following muon arrival is dependent upon the energy of the muonic tritium atom as it traverses the drift region. By comparison of the time distribution of fusion events with a prediction based on the theoretical energy dependence of the rate, the strength of resonant formation can in principle be determined. The results extracted so far are discussed and the limitations of the method are examined.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Explants of human synovialis obtained surgically were cultivated under dialysis membrane in the multipurpose Rose chamber and in Eagle's medium enriched with 20% pooled human cord sera. Within 24 hours monocytes and lymphocytic cells emerged from the majority of explants while spindle and stellate cells appeared later on the second and third days of culture. A monolayer of cells developed in which active mitosis was observed. Between 12 to 15 days, fingerlike projections of cells adjacent to the explants branched out between the cover glass and the monolayer of mesenchymelike growth and by the twenty-fifth day had developed into anastomosing networks eventually ranging in length from 1.2 to 3.2 mm. Ciné and still phase photomicrographs decumented findings. Vascular networks developed in vitro in 85% of the total 80 Rose chambers examined over an average period of 58 days. Minute vessels, patent for only short distances, were lined with endothelial cells characterized by slender elongated nuclei and with two or three small nucleoli. In contrast, flanking fibroblasts were considerably larger with clear oval nuclei containing conspicuous nucleoli. Differential stains demonstrated reticular fibers and distinct bundles of collagen lying along the vessels, particularly in the area adjacent to the fragment. In the study of rheumatoid arthritis, where vascular lesions are known to occur, it is possible that such preparations may provide favorable test objects.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 143-149 
    ISSN: 1040-452X
    Keywords: Fertility ; Ca2+ uptake ; Head plasma membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Head plasma membranes (HPM) isolated from cryopreserved boar spermatozoa show an excessive fluidization (Buhr et al., Gamete Res 23:441-449, 1989), which might be involved in the loss of fertility. The current study assessed the ability of cold shock (5°C) and phospholipase A2 (PA2) to duplicate these effects on membrane structure and to affect 45Ca2+ uptake and gross morphological characteristics of whole, fresh boar sperm. The HPM from cold-shocked sperm showed a significantly greater rate of fluidization over time than did HPM from control sperm. Addition of PA2 (bee or snake venom, 0.1 or 10.0 ng/ml) to HPM from control sperm caused fluidization similar to cold shocking, but to a lesser degree (P 〈 0.05). Cold-shocked intact sperm exhibited severe acrosomal disruption, loss of motility, and increased 45Ca2+ uptake relative to control sperm. Addition of PA2 (bee or snake venom, 0.1, 1.0., 10.0, and 1,000 ng/ml) to control sperm had not effect on gross morphology or motility while maintaining or increasing sperm extrusion of 45Ca2+. Therefore, although PA2 can, to some extent, duplicate the effects of cold shock on HPM molecular organization, its lipid hydrolytic action is insufficient to cause all the gross disruptions of severe thermal shock. Both PA2 and cold shock disrupted HPM structure, but only cold shock increased 45Ca2+ uptake, suggesting that cold shock may be increasing 45Ca2+ uptake in areas other than the head. Cold shock disrupts sperm on three levels; membrane molecular organization, intracellular Ca2+ regulation, and gross morphology/motility.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 23 (1989), S. 441-449 
    ISSN: 0148-7280
    Keywords: boar ; spermatozoa ; membrane fluidity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Head plasma membranes were isolated from the sperm-rich fraction of boar semen and from sperm-rich semen that had been subjected to three commercial preservation processes: Ex tended for fresh insemination (extended), prepared for freezing but not frozen (cooled), and stored frozen for 3-5 weeks (frozen-thawed). Fluorescence polarization was used to determine fluidity of the membranes of all samples for 160 min at 25°C and also for membranes from the sperm-rich and extended semen during cooling and reheating (25 to 5 to 40°C, 0.4°C/min). Head plasma membranes from extended semen were initially more fluid than from other sources (P 〈 0.05). Fluidity of head membranes from all sources decreased at 25°C, but the rate of decrease was significantly lower for membranes from cooled and lower again for membranes from frozen-thawed semen. Cooling to 5°C reduced the rate of fluidity change for plasma membranes from the spernvrich fraction, while heating over 30°C caused a signifi cantly greater decrease. The presence of Ca++ (10 mM) lowered the fluidity of the head plasma membranes from sperm-rich and extended semen over time at 25°C but did not affect the membranes from the cooled or frozen-thawed semen. The change in head plasma membrane fluidity at 25°C may reflect the dynamic nature of spermatozoa membranes prior to fertilization. Extenders, preservation processes and temperature changes have a strong influence on head plasma membrane fluidity and therefore the molecular organization of this membrane.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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