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  • 1995-1999  (423)
  • 1950-1954  (15)
  • 1945-1949  (13)
  • 1
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Proteins that bind with high affinity to specific DNA sequences often do so through hydrogen bonding and electrostatic interactions between the DNA major groove and defined protein structural elements, such as helix-turn-helix motifs, β-ribbon recognition elements and Zn-binding domains1. ...
    Type of Medium: Electronic Resource
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  • 2
    Title: Datenreisende : die Kultur der Computernetz
    Author: Wetzstein, Thomas A.
    Contributer: Dahm, Hermann , Steinmetz, Linda , Lentes, Anja , Schampaul, Stephan , Eckert, Roland
    Publisher: Opladen :Westdeutscher Verlag,
    Year of publication: 1995
    Pages: 341 S.
    Type of Medium: Book
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 34 (1995), S. 5060-5065 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2528-2532 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A CsI salt-based cathode which is capable of producing a modest perveance, 10 s of A/cm2 electron beam for several microseconds pulse lengths, and has little susceptibility to diode closure has been experimentally characterized. This explosive field-emission CsI-coated carbon fiber cathode has operated in modest 10−5 Torr vacuums at voltages up to 160 kV, and can easily be configured to provide space-charge-limited solid or annular electron beams in arbitrarily large diameter configurations. The CsI cathode has demonstrated negligible closure for 2 μs pulses, and has operated for 200 shots with no degradation in cathode performance. Data on the operating performance of this salt cathode, including effective gap time history and streak photographs demonstrating uniformity of the current density, are presented. A comparison of CsI cathode performance with a velvet explosive field emitting cathode used in electron-beam production is also presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 4532-4535 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A power supply for "triggerless," repetitively pulsed cathodic arcs has been developed. It is based on a thyristor-switched, high-voltage, high-current, pulse-forming network (PFN). It can provide high pulsed currents (up to 2 kA), with duration of 600 μs, and pulse repetition rate of up to 10 Hz. Higher repetition rates are possible at lower current. The rectangular pulse shape and amplitude are reproducible to within a few percent. Cathodic arc initiation is extremely reliable because the charging voltage is much higher than the minimum starting voltage for the triggerless arc initiation method. The energy utilization efficiency is very high by intentionally mismatching load and PFN impedances and by using an efficiency-enhancing diode; the stored energy is dissipated primarily in the arc.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The observation that many chronic wounds are ischemic has spurred a series of studies evaluating the response of cells exposed to hypoxia. To date, these studies have shown largely beneficial effects from hypoxia, such as increased cellular replication and procollagen synthesis. These findings are counter-intuitive from a clinical standpoint because cellular growth and synthetic function are known to be retarded in chronic ischemic wounds. We have established an in vitro system in which human dermal fibroblasts grown chronically at 5 ± 3 mm Hg will proliferate at a rate three times slower than those fibroblasts grown under standard culture conditions (namely an oxygen partial pressure of 150 mm Hg). No phenotypic changes are noted in chronically hypoxic cells, and the growth-retarding effects are reversible when the cells are returned to standard oxygen conditions. Competitive reverse transcription-polymerase chain reaction showed that acute exposure to hypoxia (up to 1 week) results in a 6.3-fold increase in the relative expression of transforming growth factor-β1 messenger RNA, whereas chronic exposure to hypoxia leads to a 3.1-fold decrease in this message. Collagen production measured at both the mRNA and protein level is also decreased in the setting of chronic hypoxia. We propose that this system may be the most appropriate setting for studying the role of oxygen on dermal fibroblasts in ischemic, nonhealing wounds.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Impaired wound healing as a result of age is a well-documented phenomenon. However, the overall deficit in healing is substantially increased when the healing wound of an aged animal is ischemic. We hypothesized that both of these deficits are cytokine mediated. We have studied the messenger RNA expression of platelet-derived growth factor receptor-β, using the rabbit dermal ulcer model of wound repair, in young (3 to 6 months) and aged (48 months and 60 months) rabbits under normal and ischemic conditions. Platelet-derived growth factor receptor-β mRNA expression was measured with the use of quantitative reverse transcriptase-polymerase chain reaction with incorporation of a synthetic, nonhomologous DNA fragment complementary to platelet-derived growth factor receptor-β primers as a competitive internal standard. Results in young rabbits showed a large upregulation of platelet-derived growth factor receptor-β mRNA expression after wounding. In both aged animal groups, platelet-derived growth factor receptor-β expression was found to be significantly decreased in nonischemic wounds relative to young nonischemic controls. Ischemia was found to have little effect on platelet-derived growth factor receptor-β mRNA expression in young animals relative to matched controls. However, ischemia induced a large decrease in the platelet-derived growth factor receptor-β mRNA levels of wounds of aged animals relative to paired aged nonischemic wounds. Results suggest an age-related delay in platelet-derived growth factor receptor-β mRNA expression in healing wounds, as well as an age-related decline in responsiveness to confounding ischemia.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects on wound healing of insulin-like growth factor-I with and without insulin-like growth factor binding protein-1 were studied in a rabbit ear dermal ulcer model under both nonischemic and ischemic conditions. Wounds 6 mm in diameter were made on the ventral surface of rabbit ears for a total of 272 wounds in the nonischemic group and 77 wounds in the ischemic group. Insulin-like growth factor-I in varying doses (1 to 43 µg) and in combination with varying molar ratios of the binding protein were added at time of wounding to each wound. Wounds were analyzed histomorphometrically on day 7 after wounding. We found that insulin-like growth factor-I or binding protein alone at varying doses did not have any effects on wound healing parameters. Low to moderate doses (1 µg and 4 µg, respectively) of the combination of insulin-like growth factor-I with the binding protein in a molar ratio of 5:1 or 11:1 showed a 52% increase (p 〈 0.05) in new granulation tissue in the nonischemic model compared with controls but did not significantly augment new granulation tissue formation in the ischemic wound model. A high dose (43 µg) at a 10:1 molar ratio of growth factor to binding protein was required to elicit significantly enhanced wound healing in ischemic wounds. These results indicate that insulin-like growth factor binding protein-1 modulates the effects of insulin-like growth factor-I in promoting wound healing in vivo and that the combination is a highly effective vulnerary compound with effects comparable in magnitude with other growth factors previously tested in this model.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Cambridge, MA, USA : Blackwell Publishing Inc
    Restoration ecology 6 (1998), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effectiveness of organic mulch as a simple means of enhancing the restoration of disturbed lands by providing a competitive edge to native perennials, such as Artemisia californica (California sagebrush), over exotic annuals, such as Avena fatua (wild oat), was studied by investigating the effect of organic amendments on microbial activity and nitrogen immobilization through both soil analysis and aboveground plant growth. The addition of organic amendment resulted in an increase in microbial activity, a parallel increase in nitrogen immobilization, and no significant differences in total soil nitrogen. It is likely that nitrogen was gradually being removed from its more available form of nitrate and being immobilized in the tissues of the increasing microbial biomass. The survival rate of planted native perennial seedlings of A. californica in organic amended plots was almost double that of control-plot seedlings, and plant volume was significantly higher. When the availability of nitrogen was reduced through increased immobilization, amended plots established an environment more conducive to native perennial shrubs, allowing them to outcompete exotic annuals for water and nutrients. This simple procedure could have major implications for enhancing the restoration of disturbed lands.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1532-849X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Purpose This study evaluated the tensile bond strength of a bisphenol glycidyl methacrylate (Bis-GMA) resin luting cement with four different surface treatments of a high Pd-Cu alloy.Materials and Methods For each surface treatment type (tin-plated, porcelain furnace oxide, air-abraded, and finished-only), 15 opposing half-dumbbell-shaped samples were cast and prepared in new Pd?Cu alloy. Samples were luted with a Bis-GMA resin luting cement at a film thickness of 80 μm using a custom alignment apparatus. Samples were stored in distilled water at 37°C for 24 hours, thermocycled for 1,000 cycles, and then stored for 30 days in distilled water at 37°C. Samples were then subjected to fracture in tension at a loading rate of 0.5 cm/min with the bond strengths calculated in megapascals (MPa). The fractured surfaces were examined using stereomicroscopy and scanning electron microscopy at various magnifications ranging from 5.5x to 500x to determine the type of bond failure (adhesive, cohesive, or mixed).Results Tensile bond strengths (mean ± SD MPa) were: tin-plated, 30 ± 15.7; porcelain furnace oxide, 23 ± 8.6; air-abraded, 8 ± 8.1; and finished-only, 4 ± 4.5. Statistical analysis of the tensile bond values using an ANCOVA and Tukey's multiple comparison test at a significance level of 0.05 indicated that there was no difference between the tin-plated and the furnace oxide groups, as well as between the air-abraded and the furnace oxide groups. However, there was significant difference between the tin-plated, the air-abraded, and the finished-only groups. The observed bond failures were predominantly mixed and cohesive in nature with only one adhesive failure.Conclusions There was no significant difference in the tensile bond strengths between the tin-plated group or the porcelain furnace oxide surface group. This suggests that the less-technique-sensitive porcelain furnace oxide surface treatment offers an alternative for achieving high metal-resin bonds to a high Pd?Cu alloy.
    Type of Medium: Electronic Resource
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