443 research outputs found
Vector Meson Photoproduction with an Effective Lagrangian in the Quark Model
A quark model approach to the photoproduction of vector mesons off nucleons
is proposed. Its starting point is an effective Lagrangian of the interaction
between the vector meson and the quarks inside the baryon, which generates the
non-diffractive s- and u- channel resonance contributions. Additional t-channel
and exchanges are included for the and
production respectively to account for the large diffractive behavior in the
small region as suggested by Friman and Soyeur. The numerical results are
presented for the and productions in four isospin channels with
the same set of parameters, and they are in good agreement with the available
data not only in and productions but also in the charged
productions where the additional t-channel exchange does not
contribute so that it provides an important test to this approach. The
investigation is also extended to the photoproduction, and the initial
results show that the non-diffractive behavior of the productions in the
large region can be described by the s- and u- channel contributions with
significantly smaller coupling constants, which is consistent with the findings
in the similar studies in the QHD framework. The numerical investigation has
also shown that polarization observables are essential for identifying
so-called "missing resonances".Comment: 36 pages, 10 PS figures, extended version of nucl-th/9711061 and
nucl-th/9803021, submitted to PR
Umweltgerechte ProzessfĂŒhrung und Zustandserkennung in Chemieanlagen mit neuronalen Netzen - Teilvorhaben 2: Konzipierung und Erprobung des Zustandserkennungsverfahrens
Im Rahmen des Teilvorhabens wurde ein Online-Monitoring-System fĂŒr stark exotherme Reaktionen entwickelt, das das Bedienungspersonal bei der optimalen und umweltgerechten ProzessfĂŒhrung von komplexen oder sicherheitstechnisch schwierigen Semibatch-Prozessen in RĂŒhrkesselreaktoren (Batch-Reaktoren) unterstĂŒtzen soll. Das Monitoring-System (MoSys) basiert auf dimensionslosen Stoff- und WĂ€rmebilanzen mit adaptiven Komponenten. MoSys muss zuerst mit den Prozessdaten von normalen und unerwĂŒnschten Batch-VerlĂ€ufen angelernt werden, die im Miniplant unter den Bedingungen des Industrieprozesses durchgefĂŒhrt wurden. Die Adaption der Bilanzmodelle an die Zielanlage erfolgt durch zweischichtige Perceptron-Netze. Um eine vollstĂ€ndige MaĂstabsĂŒbertragung zu gewĂ€hrleisten, sollte MoSys mit Prozessdaten von mindestens einem normalen Batch-Verlauf in der Chemieanlage angepasst und validiert werden. MoSys wurde sowohl fĂŒr eine homogene exotherme Veresterungsreaktion als auch fĂŒr einen komplexen heterogenen exothermen Hydrierprozess konzipiert. Experimentelle Tests wurden fĂŒr die Veresterung in einer Pilotanlage und fĂŒr die Hydrierung in einer industriellen Chemieanlage durchgefĂŒhrt. Zur Industrieerprobung wurde MoSys in ein Batch-Informations-Management-System (BIMS) integriert, das auch entwickelt und in das Prozessleitsystem (PLS) einer Mehrzweckanlage im Feinchemie-Werk Radebeul (Degussa AG) implementiert wurde. Dadurch konnten die MoSys-Ausgaben simultan mit wichtigen Prozesssignalen auf den Terminals des PLS visualisiert werden. Zum Beispiel werden der Hydrierungsfortschritt, das vorhergesagte Reaktionsende und die KonzentrationsverlĂ€ufe des Edukts, Zwischenprodukts und Produkts auf den Terminals der Operatorstationen angezeigt. Wenn unerwĂŒnschte BetriebszustĂ€nde auftreten, wird das Bedienungspersonal frĂŒhzeitig alarmiert und Anweisungen fĂŒr GegenmaĂnahmen, die nur vom Operator ausgefĂŒhrt werden dĂŒrfen, werden auf den Terminals angezeigt. Die LeistungsfĂ€higkeit von MoSys/BIMS konnte wĂ€hrend zweier Hydrierungs-Produktionskampagnen nachgewiesen werden
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Overview of mathematical approaches used to model bacterial chemotaxis II: bacterial populations
We review the application of mathematical modeling to understanding the behavior of populations of chemotactic bacteria. The application of continuum mathematical models, in particular generalized KellerâSegel models, is discussed along with attempts to incorporate the microscale (individual) behavior on the macroscale, modeling the interaction between different species of bacteria, the interaction of bacteria with their environment, and methods used to obtain experimentally verified parameter values. We allude briefly to the role of modeling pattern formation in understanding collective behavior within bacterial populations. Various aspects of each model are discussed and areas for possible future research are postulated
Improved Culture Medium (TiKa) for Mycobacterium avium Subspecies Paratuberculosis (MAP) Matches qPCR Sensitivity and Reveals Significant Proportions of Non-viable MAP in Lymphoid Tissue of Vaccinated MAP Challenged Animals.
The quantitative detection of viable pathogen load is an important tool in determining the degree of infection in animals and contamination of foodstuffs. Current conventional culture methods are limited in their ability to determine these levels in Mycobacterium avium subspecies paratuberculosis (MAP) due to slow growth, clumping and low recoverability issues. The principle goal of this study was to evaluate a novel culturing process (TiKa) with unique ability to stimulate MAP growth from low sample loads and dilutions. We demonstrate it was able to stimulate a mean 29-fold increase in recoverability and an improved sensitivity of up to three logs when compared with conventional culture. Using TiKa culture, MAP clumping was minimal and produced visible colonies in half the time required by standard culture methods. Parallel quantitative evaluation of the TiKa culture approach and qPCR on MAP loads in tissue and gut mucosal samples from a MAP vaccine-challenge study, showed good correlations between colony counts (cfu) and qPCR derived genome equivalents (Geq) over a large range of loads with a 30% greater sensitivity for TiKa culture approach at low loads (two logs). Furthermore, the relative fold changes in Geq and cfu from the TiKa culture approach suggests that non-mucosal tissue loads from MAP infected animals contained a reduced proportion of non-viable MAP (mean 19-fold) which was reduced significantly further (mean 190-fold) in vaccinated "reactor" calves. This study shows TiKa culture equates well with qPCR and provides important evidence that accuracy in estimating viable MAP load using DNA tests alone may vary significantly between samples of mucosal and lymphatic origin
Correct quantum chemistry in a minimal basis from effective Hamiltonians
We describe how to create ab-initio effective Hamiltonians that qualitatively
describe correct chemistry even when used with a minimal basis. The
Hamiltonians are obtained by folding correlation down from a large parent basis
into a small, or minimal, target basis, using the machinery of canonical
transformations. We demonstrate the quality of these effective Hamiltonians to
correctly capture a wide range of excited states in water, nitrogen, and
ethylene, and to describe ground and excited state bond-breaking in nitrogen
and the chromium dimer, all in small or minimal basis sets
Opening the black box of energy modelling: Strategies and lessons learned
The global energy system is undergoing a major transition, and in energy planning and decision-making across governments, industry and academia, models play a crucial role. Because of their policy relevance and contested nature, the transparency and open availability of energy models and data are of particular importance. Here we provide a practical how-to guide based on the collective experience of members of the Open Energy Modelling Initiative (Openmod). We discuss key steps to consider when opening code and data, including determining intellectual property ownership, choosing a licence and appropriate modelling languages, distributing code and data, and providing support and building communities. After illustrating these decisions with examples and lessons learned from the community, we conclude that even though individual researchers' choices are important, institutional changes are still also necessary for more openness and transparency in energy research
Bouncing back : the wellbeing of children in international child abduction cases
This report contains the results of a three-part research project conducted in the framework of the project Enhancing the Well-being of Children in Cases of International Child Abduction (eWELL). Part I contains an overview of the results of a quantitative survey conducted among parents who have been in a situation of international parental child abduction. The quantitative survey data collection was financed by the European Commission and was undertaken by the University of Antwerp in collaboration with Centrum IKO, CFPE-Enfant Disparus, Child Focus, the French Central Authority and Missing Children Europe (MCE, the European umbrella organization for missing children). Part II provides an overview of the qualitative interview results conducted with children who were taken by to another country by one parent without the consent of the other. The qualitative data collection was co-financed by the European Commission and undertaken by the University of Antwerp, Centrum IKO, Child Focus, CFPE-Enfant Disparus, and in collaboration with the French Central Authority and Missing Children Europe (MCE, the European umbrella organization for missing children). Part III examines international parental child abduction court rulings, jurisdictions and the application of Art. 13 (2) of the 1980 Hague Convention on the Civil Aspects of International Child Abduction in Belgium, France and the Netherlands. It discusses age and maturity attainment and assessment; the involvement of intermediaries; the definition of the childâs objections to return and other relevant matters
Clinical feasibility of (neo)adjuvant taxane-based chemotherapy in older patients: analysis of >4,500 patients from four German randomized breast cancer trials
Introduction Despite the fact that people older than 65 years of age have the highest incidence of developing breast cancer, these patients are excluded from clinical trials in most cases. Furthermore, most physicians tend towards therapy regimens without the use of dose-dense, highly active taxane-based treatments because of a lack of data regarding toxicities of these compounds in older patients. Methods Pooled side-effect data were analyzed from four prospective, randomized clinical trials in which patients of different age groups (60 years, between 60 and 64 years, and 64 years) with primary breast cancer received taxane-based chemotherapy. Results Dose delays, dose reductions, hospitalization, and therapy discontinuation increased with age. Hematologic toxicities and some nonhematologic toxicities were generally more common in older patients. Leucopenia increased from 55.3% in patients aged 60 years to 65.5% in patients aged 64 years (P<0.001), and neutropenia increased from 46.9% to 57.4% (P<0.001). There was no difference, however, in clinically more relevant febrile neutropenia between the different age groups. Thrombopenia shows a similar age-dependent increase, whereas there is no difference between the age groups concerning anemia. Hot flushes and elevated liver enzymes decreased with increasing age. Conclusions The present pooled analysis of a substantial cohort of older primary breast cancer patients demonstrates that taxane-containing (neo) adjuvant chemotherapy is feasible in older patients and that toxicity can be reduced by sequential therapy regimens
Exotic state photoproduction
It is shown that the list of unusual mesons planned for a careful study in
photoproduction can be extended by the exotic states with which should be looked for in the decay
channels in the reactions and . The full classification of the states by their
quantum numbers is presented. A simple model for the spin structure of the , , and reaction amplitudes is formulated and the tentative estimates of the
corresponding cross sections at the incident photon energy
GeV are obtained: b, b, b, and b. The problem of the
signal extraction from the natural background due to the other production channels is discussed. In particular the estimates are
presented for the , , and reaction cross sections.
Our main conclusion is that the search for the exotic
states is quite feasible at JEFLAB facility. The expected yield of the events in a 30-day run at the 100% detection
efficiency approximates events.Comment: 19 pages, revtex, 1 figure in postscipt, some comments and references
added, a few minor typos corrected, to be published in Phys. Rev.
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