53,547 research outputs found
Elliptic Flow from a Transversally Thermalized Fireball
The agreement of elliptic flow data at RHIC at central rapidity with the
hydrodynamic model has led to the conclusion of very rapid thermalization. This
conclusion is based on the intuitive argument that hydrodynamics, which assumes
instantaneous local thermalization, produces the largest possible elliptic flow
values and that the data seem to saturate this limit. We here investigate the
question whether incompletely thermalized viscous systems may actually produce
more elliptic flow than ideal hydrodynamics. Motivated by the extremely fast
primordial longitudinal expansion of the reaction zone, we investigate a toy
model which exhibits thermalization only in the transverse directions but
undergoes collisionless free-streaming expansion in the longitudinal direction.
For collisions at RHIC energies, elliptic flow results from the model are
compared with those from hydrodynamics. With the final particle yield and
\kt-distribution fixed, the transversally thermalized model is shown not to
be able to produce the measured amount of elliptic flow. This investigation
provides further support for very rapid local kinetic equilibration at RHIC. It
also yields interesting novel results for the elliptic flow of massless
particles such as direct photons.Comment: revtex4, 15 pages + 10 embedded EPS figure
Heteropolymer Sequence Design and Preferential Solvation of Hydrophilic Monomers: One More Application of Random Energy Model
In this paper, we study the role of surface of the globule and the role of
interactions with the solvent for designed sequence heteropolymers using random
energy model (REM). We investigate the ground state energy and surface monomer
composition distribution. By comparing the freezing transition in random and
designed sequence heteropolymers, we discuss the effects of design. Based on
our results, we are able to show under which conditions solvation effect
improves the quality of sequence design. Finally, we study sequence space
entropy and discuss the number of available sequences as a function of imposed
requirements for the design quality
Landau (\Gamma,\chi)-automorphic functions on \mathbb{C}^n of magnitude \nu
We investigate the spectral theory of the invariant Landau Hamiltonian
\La^\nu acting on the space of
-automotphic functions on \C^n, for given real number ,
lattice of \C^n and a map such that the
triplet satisfies a Riemann-Dirac quantization type
condition. More precisely, we show that the eigenspace
{\mathcal{E}}^\nu_{\Gamma,\chi}(\lambda)=\set{f\in
{\mathcal{F}}^\nu_{\Gamma,\chi}; \La^\nu f = \nu(2\lambda+n) f};
\lambda\in\C, is non trivial if and only if . In such
case, is a finite dimensional vector space
whose the dimension is given explicitly. We show also that the eigenspace
associated to the lowest Landau level of
\La^\nu is isomorphic to the space, {\mathcal{O}}^\nu_{\Gamma,\chi}(\C^n),
of holomorphic functions on \C^n satisfying g(z+\gamma) = \chi(\gamma)
e^{\frac \nu 2 |\gamma|^2+\nu\scal{z,\gamma}}g(z), \eqno{(*)} that we can
realize also as the null space of the differential operator
acting on
functions on \C^n satisfying .Comment: 20 pages. Minor corrections. Scheduled to appear in issue 8 (2008) of
"Journal of Mathematical Physics
Ultrahigh Transmission Optical Nanofibers
We present a procedure for reproducibly fabricating ultrahigh transmission
optical nanofibers (530 nm diameter and 84 mm stretch) with single-mode
transmissions of 99.95 0.02%, which represents a loss from tapering of
2.6 10 dB/mm when normalized to the entire stretch. When
controllably launching the next family of higher-order modes on a fiber with
195 mm stretch, we achieve a transmission of 97.8 2.8%, which has a loss
from tapering of 5.0 10 dB/mm when normalized to the
entire stretch. Our pulling and transfer procedures allow us to fabricate
optical nanofibers that transmit more than 400 mW in high vacuum conditions.
These results, published as parameters in our previous work, present an
improvement of two orders of magnitude less loss for the fundamental mode and
an increase in transmission of more than 300% for higher-order modes, when
following the protocols detailed in this paper. We extract from the
transmission during the pull, the only reported spectrogram of a fundamental
mode launch that does not include excitation to asymmetric modes; in stark
contrast to a pull in which our cleaning protocol is not followed. These
results depend critically on the pre-pull cleanliness and when properly
following our pulling protocols are in excellent agreement with simulations.Comment: 32 pages, 10 figures, accepted to AIP Advance
The universal functorial equivariant Lefschetz invariant
We introduce the universal functorial equivariant Lefschetz invariant for
endomorphisms of finite proper G-CW-complexes, where G is a discrete group. We
use K_0 of the category of "phi-endomorphisms of finitely generated free
RPi(G,X)-modules". We derive results about fixed points of equivariant
endomorphisms of cocompact proper smooth G-manifolds.Comment: 33 pages; shortened version of the author's PhD thesis, supervised by
Wolfgang Lueck, Westfaelische Wilhelms-Universitaet Muenster, 200
Heavy Quarkonia and Quark Drip Lines in Quark-Gluon Plasma
Using the potential model and thermodynamical quantities obtained in lattice
gauge calculations, we determine the spontaneous dissociation temperatures of
color-singlet quarkonia and the `quark drip lines' which separate the region of
bound states from the unbound region. The dissociation temperatures
of and in quenched QCD are found to be 1.62 and
respectively, in good agreement with spectral function analyses. The
dissociation temperature of in full QCD with 2 flavors is found to be
1.42. For possible bound quarkonium states with light quarks, the
characteristics of the quark drip lines severely limit the stable region close
to the phase transition temperature. Bound color-singlet quarkonia with light
quarks may exist very near the phase transition temperature if their effective
quark mass is of the order of 300-400 MeV and higher.Comment: 8 pages, 2 figures, in LaTex, invited talk presented at the
International Conference on Strangeness in Quark Matter, UCLA, March 26-31,
200
Intermodal Energy Transfer in a Tapered Optical Fiber: Optimizing Transmission
We present an experimental and theoretical study of the energy transfer
between modes during the tapering process of an optical nanofiber through
spectrogram analysis. The results allow optimization of the tapering process,
and we measure transmission in excess of 99.95% for the fundamental mode. We
quantify the adiabaticity condition through calculations and place an upper
bound on the amount of energy transferred to other modes at each step of the
tapering, giving practical limits to the tapering angle.Comment: 29 pages, 17 figure
Recommended from our members
Management of Agitation During the COVID-19 Pandemic
The coronavirus disease 2019 (COVID-19) pandemic caused by the coronavirus SARS-CoV-2 has radically altered delivery of care in emergency settings. Unprecedented hardship due to ongoing fears of exposure and threats to personal safety, along with societal measures enacted to curb disease transmission, have had broad psychosocial impact on patients and healthcare workers alike. These changes can significantly affect diagnosing and managing behavioral emergencies such as agitation in the emergency department. On behalf of the American Association for Emergency Psychiatry, we highlight unique considerations for patients with severe behavioral symptoms and staff members managing symptoms of agitation during COVID-19. Early detection and treatment of agitation, precautions to minimize staff hazards, coordination with security personnel and psychiatric services, and avoidance of coercive strategies that cause respiratory depression will help mitigate heightened risks to safety caused by this outbreak
Recommended from our members
Knowledge, attitudes and practices of medical staff towards obesity management in patients with spinal cord injuries: an International survey of four western European countries
Objective: To (1) examine the opinions of medical staff working in spinal cord injury (SCI) centres (SCICs); (2) evaluate their knowledge, attitudes and practices towards obesity prevention and management; (3) report the number of beds and dietitians available at each SCIC. Methods: A 37-item questionnaire was sent to 23 SCICs in the UK, the Netherlands, Belgium and the Republic of Ireland between September 2012 and January 2013. Results: Eighteen SCICs returned the questionnaires for analysis. All respondents stated that they had an interest in obesity treatment but only 2.3% of the respondents received training in obesity management. Sixty-one percent of staff did not consider body mass index (BMI) to be appropriate for use in SCI patients and subsequently less than half of the respondents use BMI routinely. The majority of respondents reported that they are confident in dealing with overweight (74.5%) and obese (66.1%) SCI adults, less than half (44.1%) are confident in treating overweight and obese SCI children. Respondents also indicated the need for nationally adopted guidelines and a lack of physical activity provision. There were 17.5 whole-time equivalent (WTE) dietitians recorded in 22 SCICs, equivalent to 47.8 beds per WTE dietitians (range 10–420). Non-UK SCIC dietitians are significantly better resourced than in UK SCICs (beds per WTE dietitian: 36 vs 124, P=0.035). Conclusion: Medical staff expressed the need to participate in obesity prevention and management. Appropriate training should be considered for all medical staff and the development of specific weight management guidelines and dietetic provision should be considered
Detection of antibody-dependent complement mediated inactivation of both autologous and heterologous virus in primary HIV-1 infection
Specific CD8 T-cell responses to human immunodeficiency virus type 1 (HIV-1) are induced in primary infection and make an important contribution to the control of early viral replication. The importance of neutralizing antibodies in containing primary viremia is questioned because they usually arise much later. Nevertheless antienvelope antibodies develop simultaneously with, or even before, peak viremia. We determined whether such antibodies might control viremia by complement-mediated inactivation (CMI). In each of seven patients studied, antibodies capable of CMI appeared at or shortly after the peak in viremia, concomitantly with detection of virus-specific T-cell responses. The CMI was effective on both autologous and heterologous HIV-1 isolates. Activation of the classical pathway and direct viral lysis were at least partly responsible. Since immunoglobulin G (IgG)-antibodies triggered the CMI, specific memory B cells could also be induced by vaccination. Thus, consideration should be given to vaccination strategies that induce IgG antibodies capable of CMI
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