328 research outputs found
Relativistic quark models of baryons with instantaneous forces
This is the first of a series of three papers treating light baryon resonances (up to 3 GeV) within a relativistically covariant quark model based on the three-fermion Bethe-Salpeter equation with instantaneous two- and three-body forces. In this paper we give a unified description of the theoretical background and demonstrate how to solve the Bethe-Salpeter equation by a reduction to the Salpeter equation. The specific new features of our covariant Salpeter model with respect to the usual nonrelativistic quark model are discussed in detail. The purely theoretical results obtained in this paper will be applied numerically to explicit quark models for light baryons in two subsequent papers
Molecular dynamic simulation of a homogeneous bcc -> hcp transition
We have performed molecular dynamic simulations of a Martensitic bcc->hcp
transformation in a homogeneous system. The system evolves into three
Martensitic variants, sharing a common nearest neighbor vector along a bcc
direction, plus an fcc region. Nucleation occurs locally, followed by
subsequent growth. We monitor the time-dependent scattering S(q,t) during the
transformation, and find anomalous, Brillouin zone-dependent scattering similar
to that observed experimentally in a number of systems above the transformation
temperature. This scattering is shown to be related to the elastic strain
associated with the transformation, and is not directly related to the phonon
response.Comment: 11 pages plus 8 figures (GIF format); to appear in Phys. Rev.
Inflammatory and metabolic responses to high-fat meals with and without dairy products in men.
Postprandial inflammation is an important factor for human health since chronic low-grade inflammation is associated with chronic diseases. Dairy products have a weak but significant anti-inflammatory effect on postprandial inflammation. The objective of the present study was to compare the effect of a high-fat dairy meal (HFD meal), a high-fat non-dairy meal supplemented with milk (HFM meal) and a high-fat non-dairy control meal (HFC meal) on postprandial inflammatory and metabolic responses in healthy men. A cross-over study was conducted in nineteen male subjects. Blood samples were collected before and 1, 2, 4 and 6 h after consumption of the test meals. Plasma concentrations of insulin, glucose, total cholesterol, LDL-cholesterol, HDL-cholesterol, TAG and C-reactive protein (CRP) were measured at each time point. IL-6, TNF-α and endotoxin concentrations were assessed at baseline and endpoint (6 h). Time-dependent curves of these metabolic parameters were plotted, and the net incremental AUC were found to be significantly higher for TAG and lower for CRP after consumption of the HFM meal compared with the HFD meal; however, the HFM and HFD meals were not different from the HFC meal. Alterations in IL-6, TNF-α and endotoxin concentrations were not significantly different between the test meals. The results suggest that full-fat milk and dairy products (cheese and butter) have no significant impact on the inflammatory response to a high-fat meal
Recombinant human erythropoietin in the treatment of chemotherapy-induced anemia and prevention of transfusion requirement associated with solid tumors: A randomized, controlled study
Background: Anemia is a common side effect of anticancer chemotherapy. Blood transfusion, previously the only available treatment for chemotherapy-induced anemia, may result insome clinical or subclinical adverse effects in the recipients. Recombinant human erythropoietin (rhEPO) provides a new treatment modality for chemotherapy-induced anemia. Patients and methods: To evaluate the effect of rhEPO onthe need for blood transfusions and on hemoglobin (Hb)concentrations, 227 patients with solid tumors and chemotherapy-induced anemia were enrolled in a randomized, controlled, clinical trial. Of 189 patients evaluable for efficacy, 101 received 5000 IU rhEPO daily s.c, while 88 patients received no treatment during the 12-week controlled phase of the study. Results: The results demonstrate a statistically significant reduction in the need for blood transfusions (28% vs. 42%, P = 0.028) and in the mean volume of packed red blood cells transfused (152 ml vs. 190 ml, p = 0.044) in patients treated with rhEPO compared to untreated controls. This effect was even more pronounced in patients receiving platinum-based chemotherapy (26% vs. 45%, % 0.038). During the controlled treatment phase, the median Hb values increased in the rhEPO patients while remaining unchanged in the control group. The response was seen in all tumor types. Conclusions: RhEPO administration at a dose of 5000 IU daily s.c. increases hemoglobin levels and reduces transfusionrequirements in chemotherapy-induced anemia, especially during platinum-based chemotherap
Metastable Dynamics above the Glass Transition
The element of metastability is incorporated in the fluctuating nonlinear
hydrodynamic description of the mode coupling theory (MCT) of the liquid-glass
transition. This is achieved through the introduction of the defect density
variable into the set of slow variables with the mass density and
the momentum density . As a first approximation, we consider the case
where motions associated with are much slower than those associated with
. Self-consistently, assuming one is near a critical surface in the MCT
sense, we find that the observed slowing down of the dynamics corresponds to a
certain limit of a very shallow metastable well and a weak coupling between
and . The metastability parameters as well as the exponents
describing the observed sequence of time relaxations are given as smooth
functions of the temperature without any evidence for a special temperature. We
then investigate the case where the defect dynamics is included. We find that
the slowing down of the dynamics corresponds to the system arranging itself
such that the kinetic coefficient governing the diffusion of the
defects approaches from above a small temperature-dependent value .Comment: 38 pages, 14 figures (6 figs. are included as a uuencoded tar-
compressed file. The rest is available upon request.), RevTEX3.0+eps
Broadband Dielectric Spectroscopy on Glass-Forming Propylene Carbonate
Dielectric spectroscopy covering more than 18 decades of frequency has been
performed on propylene carbonate in its liquid and supercooled-liquid state.
Using quasi-optic submillimeter and far-infrared spectroscopy the dielectric
response was investigated up to frequencies well into the microscopic regime.
We discuss the alpha-process whose characteristic timescale is observed over 14
decades of frequency and the excess wing showing up at frequencies some three
decades above the peak frequency. Special attention is given to the
high-frequency response of the dielectric loss in the crossover regime between
alpha-peak and boson-peak. Similar to our previous results in other glass
forming materials we find evidence for additional processes in the crossover
regime. However, significant differences concerning the spectral form at high
frequencies are found. We compare our results to the susceptibilities obtained
from light scattering and to the predictions of various models of the glass
transition.Comment: 13 pages, 9 figures, submitted to Phys. Rev.
KlimafolgenabschĂ€tzungen in der Wasserwirtschaft und deren Nutzen fĂŒr die Praxis
KlimafolgenClimate ImpactsDer globale Klimawandel kann regional unterschiedliche Auswirkungen haben. WĂ€hrend sich die wissenschaftliche Forschung vor allem mit der Analyse der Daten beschĂ€ftigt, ist die fachliche Praxis darum bemĂŒht, die Ergebnisse zu interpretieren und Handlungsempfehlungen daraus abzuleiten. Im Zuge des Projektes KliBiW (Globaler Klimawandel â Wasserwirtschaftliche FolgenabschĂ€tzung fĂŒr das Binnenland) wurden die Auswirkungen des Klimawandels auf die Hochwasser- und NiedrigwasserverhĂ€ltnisse in Niedersachsen untersucht. Hierzu wurden die Daten von zwei regionalen Klimamodellen (WETTREG2006 und REMO), beide angetrieben durch das Globalmodell ECHAM5/MPI-OM, rĂ€umlich interpoliert und die NiederschlĂ€ge zum Teil zeitlich disaggregiert, um hoch aufgelöste Klimainformationen bereitzuhalten. AnschlieĂend erfolgte die Kopplung mit einem hydrologischen Modellsystem (PANTA RHEI), das bereits in der Hochwasservorhersagezentrale des NLWKN im Einsatz ist. Ăber Langzeitsimulationen wurden zukĂŒnftige VerĂ€nderungen in den AbflussverhĂ€ltnissen rĂ€umlich und zeitlich differenziert fĂŒr das Aller-Leine Gebiet identifiziert. Als BetrachtungszeitrĂ€ume dienten eine nahe Zukunftsphase (2021 â 2050) und eine ferne Zukunftsphase (2071 â 2100). Die VerĂ€nderungen verschiedener hydrologischer Hoch- und Niedrigwasser-KenngröĂen wurden gegenĂŒber einem Kontrollzeitraum (1971 â 2000) aufgezeigt. Die Auswertungen an 8 Pegeln in Einzugsgebieten >1.000 kmÂČ auf Tageswertbasis und an 6 Pegeln in Einzugsgebieten <1.000 kmÂČ auf Stundenwertbasis zeigten, dass sich die Hochwassersituation zukĂŒnftig verschĂ€rfen kann. WĂ€hrend kleinere HochwĂ€sser hĂ€ufiger auftreten können, nehmen die ScheitelabflĂŒsse insbesondere in der fernen Zukunft zu. Aussagen zu gröĂeren Ereignissen sind aufgrund der groĂen Bandbreite der Ergebnisse jedoch mit erheblichen Unsicherheiten behaftet. Die NiedrigwasserverhĂ€ltnisse zeigten eine Abnahme der AbflĂŒsse, speziell im Sommer, sowie eine Zunahme der Dauer undnder Volumendefizite bei Trockenperioden. Hierbei erschien die VariabilitĂ€t und AusprĂ€gung der Trockenheit in kleineren Einzugsgebieten etwas gröĂer. Die Nutzung dieser Erkenntnisse stellt die fachliche Praxis vor die Herausforderung, die Ergebnisse zu interpretieren und zu kommunizieren. Unsicherheiten in den Modellketten mĂŒssen berĂŒcksichtigt und, wenn möglich, quantifiziert werden. Die abgeleiteten hydrologischen Konsequenzen des Klimawandels können z.B. Anwendung finden in der gesetzlich geforderten BerĂŒcksichtigung der Auswirkungen des Klimawandels auf die Risikogebiete entsprechend der Hochwasserrisikomanagement-Richtlinie (2007/60/EG). Dieser Beitrag gibt einen Ăberblick ĂŒber wasserwirtschaftlich relevante Auswertungen von Klimamodelldaten auf unterschiedlichen rĂ€umlichen Skalen und zeigt anhand ausgewĂ€hlter Beispiele auf, wie primĂ€r im wissenschaftlichen Kontext erhobene Ergebnisse effektiv fĂŒr praxisrelevante Fragestellungen genutzt werden können
Near Infrared Intraday Variability of Mrk 421
We report results from our monitoring of the BL Lac object Mrk 421 in the
near-IR band. The observations, aimed at studying the intraday variability
(IDV) of the object, were carried out systematically over an extended (and
near-continuous) period of eight nights from the 1.2m Mount Abu Infrared
Telescope, India. There are limited studies for Mrk 421 in the band for
such an extended period. The observation epoch for this study (25 February - 5
March 2003) was chosen to significantly overlap other concurrent studies of Mrk
421 in the X-ray/-ray regions being conducted using the Rossi X-ray
timing explorer (RXTE) and the solar tower atmospheric Cherenkov effect
experiment (STACEE). Hence these results could be useful for a multi-wavelength
analysis of the variability behavior of Mrk 421. We find that Mrk 421 was quite
active during the observed period and showed significant IDV and short term
variability. A maximum variation of 0.89 magnitudes is seen over the entirety
of the observed period. Flaring activity, with typical brightness variations of
, are also seen on several occasions. The extent of the variability
observed by us is compared with the results of other similar studies of Mrk 421
in the band.Comment: accepted for publication in Astronomy & Astrophysics (6 pages, 2
figures
The Heidelberg-Moscow double beta decay experiment with enriched 76Ge. First results
Abstract The status of the Heidelberg-Moscow ÎČÎČ-experiment using isotopically enriched 76Ge is reported. The results of 14.8 mol yr (or 1.29 kg yr) of operation are presented. From these data a new half life time for the ÎČÎČ0v-decay of 76Ge to the ground state of 76Se of T 1 2 1.4 (2.5) X 10 24 yr with 90% (68%) CL can be deduced. For a possible neutrinoless decay to the first excited state a half life of 4.3(8.2)X1023 yr can be excluded with 90% (68%) CL
Maternal Low-Protein Diet or Hypercholesterolemia Reduces Circulating Essential Amino Acids and Leads to Intrauterine Growth Restriction
OBJECTIVEâWe have examined maternal mechanisms for adult-onset glucose intolerance, increased adiposity, and atherosclerosis using two mouse models for intrauterine growth restriction (IUGR): maternal protein restriction and hypercholesterolemia
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