1,379 research outputs found
Newtonian and General Relativistic Models of Spherical Shells
A family of spherical shells with varying thickness is derived by using a
simple Newtonian potential-density pair. Then, a particular isotropic form of a
metric in spherical coordinates is used to construct a General Relativistic
version of the Newtonian family of shells. The matter of these relativistic
shells presents equal azimuthal and polar pressures, while the radial pressure
is a constant times the tangential pressure. We also make a first study of
stability of both the Newtonian and relativistic families of shells.Comment: 13 pages, 5 figures, accepted for publication in MNRA
Nova tehnologija proizvodnje magnezijevih traka i limova
A new production technology for magnesium strip, based on twin-roll-casting and strip rolling was developed in Freiberg Germany. By means of this economic method it is possible to produce strips in deep drawing quality with good forming properties in order to satisfy the request for low cost Mg sheets in the automotive and electronic industry. Both, coils as single sheets, were manufactured and rolled to a thickness of 1mm(0,5 mm). The technology of the new process and the properties of the twin-roll-casted material and the final sheets are presented.Nova tehnologija proizvodnje magnezijevih traka i limova. Nova tehnologija proizvodnje magnezijevih traka utemeljena dvostruko-valjanje-lijevanje i valjanje trake je razvijeno u Freibergu-NjemaÄka. Motri se, ovom ekonomiÄnom metodom je moguÄa proizvoditi trake za duboko izvlaÄenje, sa dobrim plastiÄnim svojstvima uz zadovoljavajuÄi zahtjev za nisku cijenu Mg trake za automobilsku i elektronsku industriju. Oboje, svitak i pojedinaÄne trake su poizvedene i valjane do debljine stjenke 1mm(0,5 mm). Prikazuje se tehnologija novog postupka i svojstva dvostrukog valjanog-lijevaÄkog materijala i zavrĆĄnih traka
Nova tehnologija proizvodnje magnezijevih traka i limova
A new production technology for magnesium strip, based on twin-roll-casting and strip rolling was developed in Freiberg Germany. By means of this economic method it is possible to produce strips in deep drawing quality with good forming properties in order to satisfy the request for low cost Mg sheets in the automotive and electronic industry. Both, coils as single sheets, were manufactured and rolled to a thickness of 1mm(0,5 mm). The technology of the new process and the properties of the twin-roll-casted material and the final sheets are presented.Nova tehnologija proizvodnje magnezijevih traka i limova. Nova tehnologija proizvodnje magnezijevih traka utemeljena dvostruko-valjanje-lijevanje i valjanje trake je razvijeno u Freibergu-NjemaÄka. Motri se, ovom ekonomiÄnom metodom je moguÄa proizvoditi trake za duboko izvlaÄenje, sa dobrim plastiÄnim svojstvima uz zadovoljavajuÄi zahtjev za nisku cijenu Mg trake za automobilsku i elektronsku industriju. Oboje, svitak i pojedinaÄne trake su poizvedene i valjane do debljine stjenke 1mm(0,5 mm). Prikazuje se tehnologija novog postupka i svojstva dvostrukog valjanog-lijevaÄkog materijala i zavrĆĄnih traka
Quark exchange model for charmonium dissociation in hot hadronic matter
A diagrammatic approach to quark exchange processes in meson-meson scattering
is applied to the case of inelastic reactions of the type
(Q\barQ)+(q\barq)\rightarrow (Q\barq) + (q\barQ), where and refer to
heavy and light quarks, respectively. This string-flip process is discussed as
a microscopic mechanism for charmonium dissociation (absorption) in hadronic
matter. The cross section for the reaction is
calculated using a potential model, which is fitted to the meson mass spectrum.
The temperature dependence of the relaxation time for the \J/Psi distribution
in a homogeneous thermal pion gas is obtained. The use of charmonium for the
diagnostics of the state of hot hadronic matter produced in ultrarelativistic
nucleus-nucleus collisions is discussed.Comment: 24 pages, 3 tables, 7 figure
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Entirely flexible on-site conditioned magnetic sensorics
The first entirely flexible integrated magnetic field sensor system is realized consisting of a flexible giant magnetoresistive bridge onâsite conditioned using highâperformance IGZOâbased readout electronics. The system outperforms commercial fully integrated rigid magnetic sensors by at least one order of magnitude, whereas all components stay fully functional when bend to a radius of 5 mm
Soft and virtual corrections to pp -> H + X at NNLO
The contributions of virtual corrections and soft gluon emission to the
inclusive Higgs production cross section pp -> H + X are computed at
next-to-next-to-leading order in the heavy top quark limit. We show that this
part of the total cross section is well behaved in the sense of perturbative
convergence, with the NNLO corrections amounting to an enhancement of the NLO
cross section by \sim 5% for LHC and 10-20% for the Tevatron. We compare our
results with an existing estimate of the full NNLO effects and argue that an
analytic evaluation of the hard scattering contributions is needed.Comment: 16 pages, 7 figures, 16 ps files embedded with epsf. Minor
modifications: references and note added, results unchange
The roles and values of wild foods in agricultural systems
Almost every ecosystem has been amended so that plants and animals can be used as food, fibre, fodder, medicines, traps and weapons. Historically, wild plants and animals were sole dietary components for hunterâgatherer and forager cultures. Today, they remain key to many agricultural communities. The mean use of wild foods by agricultural and forager communities in 22 countries of Asia and Africa (36 studies) is 90â100 species per location. Aggregate country estimates can reach 300â800 species (e.g. India, Ethiopia, Kenya). The mean use of wild species is 120 per community for indigenous communities in both industrialized and developing countries. Many of these wild foods are actively managed, suggesting there is a false dichotomy around ideas of the agricultural and the wild: hunterâgatherers and foragers farm and manage their environments, and cultivators use many wild plants and animals. Yet, provision of and access to these sources of food may be declining as natural habitats come under increasing pressure from development, conservation-exclusions and agricultural expansion. Despite their value, wild foods are excluded from official statistics on economic values of natural resources. It is clear that wild plants and animals continue to form a significant proportion of the global food basket, and while a variety of social and ecological drivers are acting to reduce wild food use, their importance may be set to grow as pressures on agricultural productivity increase.</jats:p
Heavy-flavour and quarkonium production in the LHC era: from proton-proton to heavy-ion collisions
This report reviews the study of open heavy-flavour and quarkonium production
in high-energy hadronic collisions, as tools to investigate fundamental aspects
of Quantum Chromodynamics, from the proton and nucleus structure at high energy
to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is
given to the lessons learnt from LHC Run 1 results, which are reviewed in a
global picture with the results from SPS and RHIC at lower energies, as well as
to the questions to be addressed in the future. The report covers heavy flavour
and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus
collisions. This includes discussion of the effects of hot and cold strongly
interacting matter, quarkonium photo-production in nucleus-nucleus collisions
and perspectives on the study of heavy flavour and quarkonium with upgrades of
existing experiments and new experiments. The report results from the activity
of the SaporeGravis network of the I3 Hadron Physics programme of the European
Union 7th Framework Programme
Limits on the high-energy gamma and neutrino fluxes from the SGR 1806-20 giant flare of December 27th, 2004 with the AMANDA-II detector
On December 27th 2004, a giant gamma flare from the Soft Gamma-ray Repeater
1806-20 saturated many satellite gamma-ray detectors. This event was by more
than two orders of magnitude the brightest cosmic transient ever observed. If
the gamma emission extends up to TeV energies with a hard power law energy
spectrum, photo-produced muons could be observed in surface and underground
arrays. Moreover, high-energy neutrinos could have been produced during the SGR
giant flare if there were substantial baryonic outflow from the magnetar. These
high-energy neutrinos would have also produced muons in an underground array.
AMANDA-II was used to search for downgoing muons indicative of high-energy
gammas and/or neutrinos. The data revealed no significant signal. The upper
limit on the gamma flux at 90% CL is dN/dE < 0.05 (0.5) TeV^-1 m^-2 s^-1 for
gamma=-1.47 (-2). Similarly, we set limits on the normalization constant of the
high-energy neutrino emission of 0.4 (6.1) TeV^-1 m^-2 s^-1 for gamma=-1.47
(-2).Comment: 14 pages, 3 figure
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