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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 1356-1358 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Crystals of the molbindin ModG (subunit Mr = 14359 Da), a cytoplasmic molybdate-binding protein from Azotobacter vinelandii, were grown by vapour diffusion. Both apo and tungstate-bound forms were crystallized and X-ray data were collected at 100 K. Apo-ModG crystallizes in space group P6322, with unit-cell dimensions a = b = 90.62, c = 79.46 Å. Native data to a resolution of 2.5 Å were collected from a single crystal, which showed a marked improvement in diffraction quality after annealing. Data from a single-site gold derivative were also collected at 2.7 Å resolution. Crystals of the ligand-bound form of ModG belong to space group P321, with unit-cell parameters a = b = 50.57, c = 79.29 Å. X-ray data to a resolution of 2.0 Å were collected.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Graduate Center for Cloud Physics Research at UMR has developed a cloud simulation facility to study phenomena occurring in terrestrial clouds and fogs. The facility consists of a pair of precision cooled-wall expansion chambers along with extensive supporting equipment. The smaller of these chambers, described in this article, is fully operational, and is capable of simulating a broad range of in-cloud thermodynamic conditions. It is currently being used to study water drop growth and evaporation for drops nucleated (activated) on well-characterized aerosol particles. Measurements have been made not only for continuous expansions (simulated updraft) but also for cyclic conditions, i.e., sequences of expansion-compression cycles resulting in alternating drop growth and evaporation. The larger of the two cloud chambers is nearing completion and will provide a broader range of conditions than the smaller chamber. The facility is supported by a fully implemented aerosol laboratory which routinely produces well-characterized condensation nuclei. The aerosol laboratory contains extensive instrumentation designed to both shape and measure the size distribution and nucleating characteristics of the generated aerosol. The cloud simulation facility also includes a humidifier to bring an air sample to a known humidity before it is put into the cloud chamber. A systematic program to infer effective condensation coefficients (of water vapor on cloud drop) under a variety of well-controlled simulated in-cloud conditions is now under way. Analysis of current experiments with standard drop growth theory indicates a variation of condensation coefficient with observation time, with values sufficiently low to explain one of the current mysteries in cloud physics: viz., the broad spread of drop sizes observed in natural clouds. This article includes a description and performance specifications of the smaller cloud simulation chamber.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-2592
    Keywords: T-cell ontogeny ; suppressor/helper cells ; thymic hormone ; interleukin 2 (IL2) ; severe combined immunodeficiency disease (SCID)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the present study of human bone marrow lymphocytes, we analyze a newly recognized population of T suppressor-cell precursors which are found in marrow only and which have the potential to inhibit immunoglobulin (Ig) productionin vitro. Following exposure to interleukin 2 (IL2), suppressor precursors acquire E receptor, T3 determinants, suppressor function, and lectin responsiveness. To distinguish this population within the framework of T-cell ontogeny, it was compared to a previously described population of thymus-dependent helper T-cell precursors which express helper function following exposure to thymus-derived mediators. The two populations are completely distinct and can be separated on density gradients. Suppressor precursors expressed T8 and TAC (IL2-receptor) antigens prior toin vitro induction with IL2. The thymic hormone-dependent cells expressed T4 but not T8 or TAC determinants. In two patients with severe combined immunodeficiency disease (SCID), IL2-responsive precursor cells appeared only late after thymus epithelium transplantation, perhaps best explained by a model in which thymus-dependent differentiation pathways precede, induce, or seed pathways of extrathymic T-cell differentiation. The large pool size of over 1011 suppressor and helper precursor cells present in adult bone marrow suggests that these populations may play an important role in immune homeostasis.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-2800
    Keywords: erectile impotence ; testosterone ; luteinizing hormone ; follicle stimulating hormone ; penile tumescence ; sleep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract Five physically healthy young males suffering from erectile impotence and five normal controls of similar age are the subjects of this preliminary report. All were studied in the sleep laboratory during 3 to 5 nights with the last two devoted to sequential hormonal sampling by means of an indwelling venous catheter. Electroencephalogram, eye movements, and penile tumescence were monitored continually through the night. Plasma LH, FSH, and testosterone were measured every 20 minutes by radioimmunoassay. There were no differences between the patients with erectile impotence and normal controls in all sleep parameters investigated, including mean tumescent time, time in simultaneous REM and tumescence, and number of full and partial tumescent episodes. Marked fluctuations in plasma LH, FSH, and testosterone were observed during sleep without differences noted between the two groups. Mean plasma LH, but not FSH or testosterone, was significantly lower in the impotent men. There were no significant differences in mean plasma gonadotrophins and testosterone between tumescent episodes and nontumescent periods in either group. A significant relation was found in normals, but not in the men with erectile dysfunction, between the occurrence of REM sleep and abrupt elevations in testosterone. Testosterone levels during REM sleep with tumescence were also consistently higher than during the condition of non-REM without tumescence in the normal, but not in the impotent, group.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archives of sexual behavior 15 (1986), S. 285-291 
    ISSN: 1573-2800
    Keywords: sleep ; prolactin ; estradiol ; impotence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract There are no investigations of sleep-related changes in circulating prolactin and estradiol in impotent men without known organic pathology. This study compares plasma levels of both hormones during sleep in 17 physically healthy patients with erectile impotence and 11 normal controls. Five men had never been able to achieve intercourse (primary impotent group) and 12 suffered from a lifelong history of intermittent erectile failure (secondary impotent group). The subjects, aged 23 to 36, were studied in a sleep laboratory from 3 to 6 nights with the last two devoted to sequential blood sampling every 20 min. Samples were pooled during consecutive 2-hr periods from 11 PM to 7 AM for hormonal assessment. There were no statistical differences in sleep measures among groups. Mean prolactin and estradiol values for all subjects were within the normal range. Both impotent groups showed a significant nocturnal increase in prolactin concentration and no time-related changes in plasma estradiol. There were no statistical differences in the plasma concentration of both hormones among groups or between study nights. The results suggest that severe and long-lasting erectile failure may occur in physically healthy individuals without associated abnormalities in circulating prolactin and estradiol.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of sexual behavior 22 (1993), S. 207-215 
    ISSN: 1573-2800
    Keywords: aging ; nocturnal penile tumescence ; testosterone ; sleep ; pituitary ; gonadal hormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract There is no information on the relationship between endogenous pituitary and gonadal hormones and nocturnal penile tumescence (NPT) in healthy aging men. Sixty-seven married volunteers ages 45–74 years were studied in the sleep laboratory for 4 nights with the last night devoted to sequential blood sampling every 20 min. Bioavailable testosterone (bT) correlated significantly with several NPT measures while total testosterone, estradiol, LH, and prolactin were mostly unrelated to NPT. All bT—NPT correlations lost their significance after adjustment by multiple regression for the effect of age on both bT and NPT variables in the total subject sample. Analysis of bT—NPT relations by age groups revealed a significant association between bT and duration NPT in men ages 55 to 64 years, but no statistical relations in younger and older age groups. Changes in the central threshold of activation of NPT as age progresses may explain the age-dependent effect of bT in sleep erections.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-2800
    Keywords: penile tumescence ; testosterone ; luteinizing hormone ; sleep ; sex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract Variations of plasma LH and testosterone in relation to sleep-related penile tumescence were assessed. Plasma LH and testosterone were measured at 10–20 min intervals in five normal adult men during 2 nights of sleep. Blood samples were obtained by means of an indwelling venous catheter while sleep was monitored polygraphically and penile tumescence recorded with a penile mercury strain gauge. Tumescent episodes were recorded in all subjects during 9 of the 10 nights of the study, and the percentage of time during sleep, which was associated with tumescence, ranged from 13% to 34%. Simultaneous REM and tumescence comprised 57.7% of total tumescent time. Abrupt elevations of plasma LH and testosterone were observed during the night without a significant relationship to stages of sleep. The mean of all hormonal determinations for the five subjects did not show significant differences in plasma LH and testosterone between fully and partially tumescent episodes and nontumescent periods. Mean testosterone during REM sleep with tumescence, a state of autonomic activation involving sexual function, was consistently higher for the five subjects than during periods free from REM and tumescence.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-2800
    Keywords: testosterone ; androgens ; luteinizing hormone ; sexual behavior ; erectile dysfunction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Psychology
    Notes: Abstract This double-blind placebo controlled, cross-over study was carried out to assess the effect of testosterone administration on sexual behavior mood, and psychological symptoms in healthy men with erectile dysfunction. Biweekly injections of 200 mg of testosterone enanthate were given over a period of 6 weeks separated by a washout period of 4 weeks. Blood samples for hormonal assessment, behavioral and psychological ratings were obtained prior to each injection. Luteinizing hormone remained significantly depressed but circulating testosterone had returned to baseline levels by 2 weeks following each hormonal injection. The ejaculatory frequency during the testosterone phase was statistically higher than during the placebo phase. There were marked, although statistically nonsignificant, increases in median frequency of reported sexual desire, masturbation, sexual experiences with partner, and sleep erections during the testosterone period. Testosterone did not have demonstrable effects on ratings of penile rigidity and sexual satisfaction. Mood variables and psychological symptoms did not change following hormonal administration. Results suggest that androgen administration to eugonadal men with erectile dysfunction may activate their sexual behavior without enhancing erectile capacity and without effects on mood and psychological symptoms.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 50 (1998), S. 53-65 
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Preliminary data are presented from a set of experiments designed to promote the use of pyrolysis-GC/MS in bioremediation. Studies were designed to aid researchers in developing a pyrolysis-GC/MS method and identifying how the method could help characterize bioremediation, particularly in organic soils. Since sample size affects the results of pyrolytic analyses, the first experiment demonstrated how an appropriate sample size might be selected for pyrolysis-GC/MS testing. In order to show how quantitative results can be obtained from pyrolysis-GC/MS, a second experiment determined the 'goodness of fit' for a standard curve relating the chromatographic area under a pyrogram to actual mass units. The third experiment investigated ways in which pyrolysis-GC/MS analyses could improve our understanding of bioremediation in organic soils contaminated with crude oil. Experimental results confirmed that differences in analyte mass affect the extent of pyrolytic cracking. In pyrograms of the test soil, the ratio of toluene to total product showed that for a sample mass between 1.8 and 2.0 mg, variability in the cracking pattern was minimized. Unlike deviations outside this range, small deviations within the range did not appreciably effect the toluene ratio. A standard curve was prepared for pyrolytic analyses by plotting the total chromatographic area of all pyrolysis products versus the mass of organic material pyrolyzed. These data were fit with a straight line having an 'R2' of 0.73. Based on a bench scale bioremediation experiment, preliminary pyrolysis-GC/MS results were used to predict that compounds derived from lignin and carbohydrates would be degraded faster in uncontaminated than contaminated soils. Appreciable degradation of both compounds, however, occurred in contaminated soils. In addition, results suggested that using pyrolysis-GC/MS to quantify the sum of all n-alkanes and the ratio of odd to even chain n-alkanes could help researchers distinguish between the degradation of petroleum and non-petroleum hydrocarbons in contaminated and uncontaminated soils.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 981-990 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To identify conditions under which gas-liquid reaction systems exhibit natural oscillations, a model is formulated in which the time scales of the elementary processes play a leading role. The steady solutions of the model problem are investigated, with the finding that at most one solution may lie in each of five temperature ranges, each range corresponding to a dominant physicochemical process.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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