11,349 research outputs found
Universal few-body physics in a harmonic trap
Few-body systems with resonant short-range interactions display universal
properties that do not depend on the details of their structure or their
interactions at short distances. In the three-body system, these properties
include the existence of a geometric spectrum of three-body Efimov states and a
discrete scaling symmetry. Similar universal properties appear in 4-body and
possibly higher-body systems as well. We set up an effective theory for
few-body systems in a harmonic trap and study the modification of universal
physics for 3- and 4-particle systems in external confinement. In particular,
we focus on systems where the Efimov effect can occur and investigate the
dependence of the 4-body spectrum on the experimental tuning parameters.Comment: 20 pages, 10 figures, final version, new references adde
Simulating the impact of the Smith Cloud
We investigate the future evolution of the Smith Cloud by performing
hydrodynamical simulations of the cloud impact onto the gaseous Milky Way
Galactic disk. We assume a local origin for the cloud and thus do not include a
dark matter component to stabilize it. Our main focus is the cloud's influence
on the local and global star formation rate (SFR) of the Galaxy and whether or
not it leads to an observable event in the far future. Our model assumes two
extremes for the mass of the Smith Cloud, an upper mass limit of 10
M and a lower mass limit of 10 M, compared to the
observational value of a few 10 M. In addition, we also make the
conservative assumption that the entirety of the cloud mass of the extended
Smith Cloud is concentrated within the tip of the cloud. We find that the
impact of the low-mass cloud produces no noticeable change in neither the
global SFR nor the local SFR at the cloud impact site within the galactic disk.
For the high-mass cloud we find a short-term (roughly 5 Myr) increase of the
global SFR of up to 1 M yr, which nearly doubles the normal
Milky Way SFR. This highly localized starburst should be observable.Comment: 14 pages, 5 figure
Relationship of management factors with prevalence of respiratory problems in beira antelope (Dorcotragus megalotis)
Most of the Beira antelopes (Dorcatragus megalotis) that ever lived at Al Wabra Wildlife Preservation (AWWP) showed respiratory signs and since winter 2005/2006 many Beiras have diedfrom a Fibrinous Pleuropneumonia Syndrome (FPPS) with Mycoplasma spp. as suspectedcausative agent. Neither therapies with different drugs nor vaccinations yielded a sustained success against the respiratory disease so far. This study aimed to test if there is a relationship between management factors and the prevalence of respiratory problems, in order to find indications whether changes in management might decrease the risk of respiratory diseases. For this reason, environmental factors such as temperature and humidity as well as individual appearance (coughing, nasal discharge etc.) and feeding of vitamin/mineral supplements were recorded daily for over a year. There was a noticeable increase of affected Beiras during winter months
Biochemische Serumparameter bei in Gefangenschaft gehaltenen Gazellen
Objective: This study aimed at comparing serum parameters of clinically healthy gazelles of Al Wabra Wildlife Preservation (AWWP), Qatar, with reference ranges of domestic and other wild ruminants, in order to gain, on the one hand, insight into the nutritional status of the animals, and, on the other hand, to establish reference ranges for the investigated species. Material and methods: Serum biochemistry parameters and mineral levels were measured in 250 clinically healthy individuals of the species Soemmering's gazelle (Gazella soemmerringii), Speke's gazelle (Gazella spekei), Dorcas gazelle (Gazella dorcas), Saudi gazelle (Gazella saudiya), Mountain gazelle (Gazella gazella), Arabian goitered gazelle (Gazella subgutturosa marica) and Chinkara Pakistani gazelle (Gazella benetti). Results: With respect to the nutritional status, the supplementation with trace elements (selenium, copper, zinc, iron) was adequate at AWWP according to measured serum levels. In contrast, serum levels of phosphorus, total protein and albumin indicated a suboptimal feeding situation, most likely due to the low quality of the roughage available in the region. The levels of sodium, potassium, calcium, magnesium, choride, triglycerides, cholesterol, creatinine, ALT- as well as GGT avtivity were -as in other wild ruminants-within the reference range of domestic ruminants, which therefore should be applicable to ruminants in general. The contents of glucose, blood urea nitrogen, creatine kinase and ALP, in contrast, seem to be generally elevated in wild ruminants. While other wild ruminants display an AST activity comparable to those of domestic ruminants, gazelles of both this and other studies had elevated values of this enzyme. Conclusion and clinical relevance: These peculiarities need to be accounted for when interpreting blood values
Ascent control studies of the 049 and ATP parallel burn solid rocket motor shuttle configurations
The control authority approach is discussed as a major problem of the parallel burn soil shuttle configuration due to the many resulting system impacts regardless of the approach. The major trade studies and their results, which led to the recommendation of an SRB TVC control authority approach are presented
Recent Developments in the Nuclear Many-Body Problem
The study of quantum chromodynamics (QCD) over the past quarter century has
had relatively little impact on the traditional approach to the low-energy
nuclear many-body problem. Recent developments are changing this situation. New
experimental capabilities and theoretical approaches are opening windows into
the richness of many-body phenomena in QCD. A common theme is the use of
effective field theory (EFT) methods, which exploit the separation of scales in
physical systems. At low energies, effective field theory can explain how
existing phenomenology emerges from QCD and how to refine it systematically.
More generally, the application of EFT methods to many-body problems promises
insight into the analytic structure of observables, the identification of new
expansion parameters, and a consistent organization of many-body corrections,
with reliable error estimates.Comment: 15 pages, 10 figures, plenary talk at the 11th Conference on Recent
Progress in Many-Body Theories (MB 11), Manchester, England, 9-13 Jul 200
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