Bibliothek

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Noise-assisted traffic of spikes through neuronal junctions (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 11 (2001), S. 581-586 
    Details
    ISSN: 1089-7682
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The presence of noise, i.e., random fluctuations, in the nervous system raises at least two different questions. First, is there a constructive role noise can play for signal transmission in a neuron channel? Second, what is the advantage of the power spectra observed for the neuron activity to be shaped like 1/fk? To address these questions a simple stochastic model for a junction in neural spike traffic channels is presented. Side channel traffic enters main channel traffic depending on the spike rate of the latter one. The main channel traffic itself is triggered by various noise processes such as Poissonian noise or the zero crossings of Gaussian 1/fk noise whereas the variation of the exponent k gives rise to a maximum of the overall traffic efficiency. It is shown that the colored noise is superior to the Poissonian and, in certain cases, to deterministic, periodically ordered traffic. Further, if this periodicity itself is modulated by Gaussian noise with different spectral exponents k, then such modulation can lead to noise-assisted traffic as well. The model presented can also be used to consider car traffic at a junction between a main and a side road and to show how randomness can enhance the traffic efficiency in a network. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1379308
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Charge separation technique for metal–oxide–silicon capacitors in the presence of hydrogen deactivated dopants (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8206-8208 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An improved charge separation technique for metal–oxide–silicon (MOS) capacitors is presented which accounts for the deactivation of substrate dopants by hydrogen at elevated irradiation temperatures or small irradiation biases. Using high-frequency capacitance–voltage measurements, radiation-induced inversion voltage shifts are separated into components due to oxide trapped charge, interface traps, and deactivated dopants, where the latter is computed from a reduction in Si capacitance. In the limit of no radiation-induced dopant deactivation, this approach reduces to the standard midgap charge separation technique used widely for the analysis of room-temperature irradiations. The technique is demonstrated on a p-type MOS capacitor irradiated with 60Co γ rays at 100 °C and zero bias, where the dopant deactivation is significant.© 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.373522
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Dual-Frequency Ultrasound Examination of Skin and Subcutis Thickness in Breast Cancer-Related Lymphedema (2004)
    Oxford, UK : Blackwell Science Inc
    The @breast journal 10 (2004), S. 0 
    Details
    ISSN: 1524-4741
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract:  Breast cancer-related lymphedema (BCRL) is a chronic swelling of the arm that sometimes follows breast cancer treatment. Clinically, both skin and subcutis are swollen. Edema is considered to be predominantly subcutaneous and of an even distribution. The purpose of this study was to quantify the degree and uniformity of skin and subcutis swelling around the forearms of women with BCRL. Ten women with BCRL were recruited. Both forearms were examined using 20 MHz ultrasound to visualize the skin and 7 MHz ultrasound to visualize the subcutis. Skin thickness was between the bottom of the entry-echo and the skin–subcutis boundary. Subcutis thickness was measured between the skin–subcutis boundary and the subcutis–muscle boundary. Both average skin thickness (1.97 ± 1.00 mm) and average subcutis thickness (10.32 ± 5.63 mm) were greater in the ipsilateral arm than in the contralateral arm (skin 1.12 ± 0.14 mm, subcutis 5.58 ± 2.04 mm, p 〈 0.01, t-test). The degree of increase in skin thickness did not vary around the arm (p 〉 0.05, ANOVA), while the degree of increase in subcutis thickness did vary (p 〈 0.05). Skin thickness correlated negatively with subcutis thickness in the contralateral arm, but correlated positively in the ipsilateral arm. The skin and subcutis are thickened in the ipsilateral arm of patients with BCRL. Skin thickness is increased uniformly around the arm and correlates strongly with the degree of swelling, while subcutis swelling varies. The measurement of skin thickness using ultrasound may form a useful clinical tool in the diagnosis of lymphedema and also aid further investigation of therapeutic techniques. 
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1075-122X.2004.21458.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    Effects of Soil Carbon Amendment on Nitrogen Availability and Plant Growth in an Experimental Tallgrass Prairie Restoration (2004)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 12 (2004), S. 0 
    Details
    ISSN: 1526-100X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Restoration of tallgrass prairie on former agricultural land is often impeded by failure to establish a diverse native species assemblage and by difficulties with nonprairie, exotic species. High levels of available soil nitrogen (N) on such sites may favor fast-growing exotics at the expense of more slowly growing prairie species characteristic of low-N soils. We tested whether reducing N availability through soil carbon (C) amendments could be a useful tool in facilitating successful tallgrass prairie restoration. We added 6 kg/m2 hardwood sawdust to experimental plots on an abandoned agricultural field in the Sandusky Plains of central Ohio, United States, increasing soil C by 67% in the upper 15 cm. This C amendment caused a 94% reduction in annual net N mineralization and a 27% increase in soil moisture but had no effect on total N or pH. Overall, plant mass after one growing season was reduced by 64% on amended compared with unamended soil, but this effect was less for prairie forbs (−34%) than for prairie grasses (−67%) or exotics (−62%). After the second growing season, only exotics responded significantly to the soil C amendment, with a 40% reduction in mass. The N concentration of green-leaf tissue and of senescent leaf litter was also reduced by the soil C treatment in most cases. We conclude that soil C amendment imparts several immediate benefits for tallgrass prairie restoration––notably reduced N availability, slower plant growth, and lower competition from exotic species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1061-2971.2004.00284.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    Hexavalent Chromium and Lung Cancer in the Chromate Industry: A Quantitative Risk Assessment (2004)
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Publishing, Inc.
    Risk analysis 24 (2004), S. 0 
    Details
    ISSN: 1539-6924
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Energietechnik
    Notizen: The purpose of this investigation was to estimate excess lifetime risk of lung cancer death resulting from occupational exposure to hexavalent-chromium-containing dusts and mists. The mortality experience in a previously studied cohort of 2,357 chromate chemical production workers with 122 lung cancer deaths was analyzed with Poisson regression methods. Extensive records of air samples evaluated for water-soluble total hexavalent chromium were available for the entire employment history of this cohort. Six different models of exposure-response for hexavalent chromium were evaluated by comparing deviances and inspection of cubic splines. Smoking (pack-years) imputed from cigarette use at hire was included in the model. Lifetime risks of lung cancer death from exposure to hexavalent chromium (assuming up to 45 years of exposure) were estimated using an actuarial calculation that accounts for competing causes of death. A linear relative rate model gave a good and readily interpretable fit to the data. The estimated rate ratio for 1 mg/m3-yr of cumulative exposure to hexavalent chromium (as CrO3), with a lag of five years, was RR= 2.44 (95% CI = 1.54–3.83). The excess lifetime risk of lung cancer death from exposure to hexavalent chromium at the current OSHA permissible exposure limit (PEL) (0.10 mg/m3) was estimated to be 255 per 1,000 (95% CI: 109–416). This estimate is comparable to previous estimates by U.S. EPA, California EPA, and OSHA using different occupational data. Our analysis predicts that current occupational standards for hexavalent chromium permit a lifetime excess risk of dying of lung cancer that exceeds 1 in 10, which is consistent with previous risk assessments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.0272-4332.2004.00512.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Conversion of Atrial Fibrillation by the Experimental Antiarrhythmic Drug Tedisamil in Two Canine Models (2001)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 12 (2001), S. 0 
    Details
    ISSN: 1540-8167
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Tedisamil Conversion of AF in Two Canine Models. Introduction: Tedisamil is an experimental bradycardic agent possessing action potential-prolonging effects. It has been proven effective in terminating ventricular arrhythmias in several animal models and atrial flutter in a conscious dog model. There are no reports to date evaluating tedisamil's efficacy in terminating atrial fibrillation (AF). Methods and Results: Two different canine models of AF were used. One group of dogs (n = 6) was subjected to 28 days of chronic fibrillatory pacing at 50 Hz using an implantable neural stimulator. Sustained AF was achieved in all dogs within 14 days of initiating pacing. A second set of dogs (n = 5) had AF induced via bilateral vagal stimulation. Tedisamil 1 mg/kg was 100% effective in terminating AF in both models. Cardioversion was associated with a statistically significant prolongation of the fibrillatory cycle length immediately before return to normal sinus rhythm in both models. A dose-response trial was performed in the vagal AF group as well as in a second group of three dogs that underwent chronic fibrillatory pacing. The efficacy of tedisamil was dose dependent, with limited efficacy at 0.1 and 0.3 mg/kg intravenously in both models. Tedisamil was able to prevent reinduction of sustained AF 30 minutes after administration of 1 mg/kg in the chronic pacing model in all dogs. Side effects included minor hypersalivation in most dogs receiving the 1 mg/kg dose. No ventricular ectopy or arrhythmias were observed. Conclusion: Tedisamil is effective for conversion of sustained AF to normal sinus rhythm in two different models of AF.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.01138.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    Prospective Assessment after Pediatric Cardiac Ablation: (2004)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 15 (2004), S. 0 
    Details
    ISSN: 1540-8167
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Introduction: A multicenter prospective study was designed and implemented to assess the short- and longer-term results and risks associated with radiofrequency (RF) ablation in children. Methods and Results: Patients recruited for the study were aged 0 to 16 years with supraventricular tachycardia due to accessory pathways or AV nodal reentrant tachycardia (AVNRT), excluding patients with nontrivial congenital heart disease. A national registry also was established, and contributing centers were encouraged to enroll all pediatric patients, aged 0 to 21 years, undergoing ablation at their center. This report summarizes acute results of these procedures. For analysis, subjects were divided into three groups: the prospective cohort (n = 481), cohort-eligible registry participants (n = 504), and not cohort eligible registry participants (n = 1,776). Prospectively enrolled cohort patients were similar to cohort-eligible patients in terms of demographic and other patient characteristics. Overall success rates for RF ablation were high (95.7%), with higher success rates for left-sided and particularly left free-wall pathways (97.8%) than right free-wall pathways (90.8%). Complications of both electrophysiologic study and RF ablation were infrequent (4.2% and 4.0%, respectively), and there were no deaths. AV block was uncommon overall (1.2%) and was limited to ablation in AVNRT (2.1%) and septal accessory pathways (3.0%). Conclusion: Despite the multicenter and prospective design, the study demonstrates high success rates and low complication rates, which are comparable to prior single-center retrospective studies. These results may serve as the current best benchmark for expected results in the pediatric population, aged 0 to 16 years, both in terms of acute success rates and the occurrence of complications. (J Cardiovasc Electrophysiol, Vol. 15, pp. 759-770, July 2004)
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.03645.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    Early Leptin Response to a Palatable Diet Predicts Dietary Obesity in Rats: Key Role of Melanocortin-4 Receptors in the Ventromedial Hypothalamic Nucleus (2000)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 74 (2000), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: We have investigated whether interactions between leptin and hypothalamic melanocortin-4 receptors (MC4-Rs) determine individual susceptibility to dietary obesity in rats. Animals with relatively high plasma leptin levels 1 week after presentation of palatable food, before weight increased significantly, subsequently showed lower food intake and weight gain after 8 weeks of palatable feeding than those with low early leptin levels. The rats with lesser weight gain also showed significantly greater down-regulation of MC4-Rs, which mediate hypophagia, in specific hypothalamic areas, namely, the arcuate, dorsomedial, and ventromedial (VMH) nuclei and the median eminence. We suggest that this reflects enhanced receptor exposure to endogenous α-melanocyte-stimulating hormone, an appetite-suppressing peptide produced by hypothalamic proopiomelanocortin neurones. It is striking that plasma leptin levels at 1 week were inversely correlated with MC4-R density in the VMH, suggesting that this is a key site of leptin action. The early leptin response to palatable feeding may therefore "program" subsequent feeding behaviour and weight gain by regulating neurones that project selectively to the VMH.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.2000.741224.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Shift in the localization of sites of hydrogen peroxide production in brain mitochondria by mitochondrial stress (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 90 (2004), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: We have determined the underlying sites of H2O2 generation by isolated rat brain mitochondria and how these can shift depending on the presence of respiratory substrates, electron transport chain modulators and exposure to stressors. H2O2 production was determined using the fluorogenic Amplex red and peroxidase system. H2O2 production was higher when succinate was used as a respiratory substrate than with another FAD-dependent substrate, α-glycerophosphate, or with the NAD-dependent substrates, glutamate/malate. Depolarization by the uncoupler p-trifluoromethoxyphenylhydrazone decreased H2O2 production stimulated by all respiratory substrates. H2O2 production supported by succinate during reverse transfer of electrons was decreased by inhibitors of complex I (rotenone and diphenyleneiodonium) whereas in glutamate/malate-oxidizing mitochondria diphenyleneiodonium decreased while rotenone increased H2O2 generation. The complex III inhibitors antimycin and myxothiazol decreased succinate-induced H2O2 production but stimulated H2O2 production in glutamate/malate-oxidizing mitochondria. Antimycin and myxothiazol also increased H2O2 production in mitochondria using α-glycerophosphate as a respiratory substrate. In substrate/inhibitor experiments maximal stimulation of H2O2 production by complex I was observed with the α-glycerophosphate/antimycin combination. In addition, three forms of in vitro mitochondrial stress were studied: Ca2+ overload, cold storage for more than 24 h and cytochrome c depletion. In each case we observed (i) a decrease in succinate-supported H2O2 production by complex I and an increase in succinate-supported H2O2 production by complex III, (ii) increased glutamate/malate-induced H2O2 generation by complex I and (iii) increased α-glycerophosphate-supported H2O2 generation by complex III. Our results suggest that all three forms of mitochondrial stress resulted in similar shifts in the localization of sites of H2O2 generation and that, in both normal and stressed states, the level and location of H2O2 production depend on the predominant energetic substrate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02489.x
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    Clinical Equivalence: A Step, A Misstep, or Just a Misnomer? (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical psychology 8 (2001), S. 0 
    Details
    ISSN: 1468-2850
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Psychologie
    Notizen: Most current approaches to assess clinical significance and clinical equivalence rely principally on concepts and methods drawn from population statistics, yet these strategies fall far short of the qualitative nature of the judgments rendered by clinicians. Just as the construct of clinical diagnosis in research settings bene-fitted by drawing upon the so-called LEAD standard (longitudinal, expert, all data) to achieve research diagnoses with the greatest clinical credibility, the concepts of “clinically significant change” or “clinically equivalent to normal” need similar standards. As an alternative, for future purposes of assessing clinical significance, I recommend the application of a “SMARTER” standard, as follows: (a) whenever possible, the method should use standardized measures, (b) it should address all relevant outcomes across settings, raters, and domains; and (c) it should make use of trained expert clinicians, trained to achieve reliability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1093/clipsy.8.4.436
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...