1,455 research outputs found
Study of the growth parameters involved in synthesizing boron carbide filaments Final report
Boron carbide whiskers - growth, mechanical properties and crystalline perfection, and incorporation in composite material
Parametric Evolution for a Deformed Cavity
We consider a classically chaotic system that is described by a Hamiltonian
H(Q,P;x), where (Q,P) describes a particle moving inside a cavity, and x
controls a deformation of the boundary. The quantum-eigenstates of the system
are |n(x)>. We describe how the parametric kernel P(n|m) = , also
known as the local density of states, evolves as a function of x-x0. We
illuminate the non-unitary nature of this parametric evolution, the emergence
of non-perturbative features, the final non-universal saturation, and the
limitations of random-wave considerations. The parametric evolution is
demonstrated numerically for two distinct representative deformation processes.Comment: 13 pages, 8 figures, improved introduction, to be published in Phys.
Rev.
Study of the growth parameters involved in synthesizing boron carbide filaments
Growth and deposition zone geometry effects on boron carbide whisker production, mechanical properties, and composite application
Reduction of circulating cholesterol and apolipoprotein levels during sepsis
Sepsis with multiple organ failure is frequently associated with a substantial decrease of cholesterol levels. This decrease of cholesterol is strongly associated with mortality suggesting a direct relation between inflammatory conditions and altered cholesterol homeostasis. The host response during sepsis is mediated by cytokines and growth factors, which are capable of influencing lipid metabolism. Conversely lipoproteins are also capable of modulating cytokine production during the inflammatory response. Therefore the decrease in circulating cholesterol levels seems to play a crucial role in the pathophysiology of sepsis. In this review the interaction between cytokines and lipid metabolism and its clinical consequences will be discussed
Localization in Strongly Chaotic Systems
We show that, in the semiclassical limit and whenever the elements of the
Hamiltonian matrix are random enough, the eigenvectors of strongly chaotic
time-independent systems in ordered bases can on average be exponentially
localized across the energy shell and decay faster than exponentially outside
the energy shell. Typically however, matrix elements are strongly correlated
leading to deviations from such behavior.Comment: RevTeX, 5 pages + 3 postscript figures, submitted to Phys. Rev. Let
Quantum-Mechanical Non-Perturbative Response of Driven Chaotic Mesoscopic Systems
Consider a time-dependent Hamiltonian with periodic driving
. It is assumed that the classical dynamics is chaotic,
and that its power-spectrum extends over some frequency range
. Both classical and quantum-mechanical (QM) linear
response theory (LRT) predict a relatively large response for
, and a relatively small response otherwise, independently
of the driving amplitude . We define a non-perturbative regime in the
space, where LRT fails, and demonstrate this failure numerically.
For , where , the system may have a relatively
strong response for , and the shape of the response
function becomes dependent.Comment: 4 pages, 2 figures, revised version with much better introductio
Quelle rĂ©gulation pour lâarrĂȘt dâun protocole de recherche clinique de thĂ©rapie gĂ©nique somatique ? Ătat des lieux auprĂšs des cliniciens-chercheurs europĂ©ens
Depuis 2002, le dĂ©bat sur les risques associĂ©s Ă la thĂ©rapie gĂ©nique est initiĂ© suite Ă lâannonce
que deux enfants inclus dans un essai thérapeutique impliquant une thérapie génique ont
développé des effets indésirables important. En Janvier 2005, le débat sur les risques reprit suite
Ă lâinterruption du protocole sur les enfants bulle du Pr Fischer Ă lâhĂŽpital Necker de Paris. Nous
avons donc étudié le processus impliqué ainsi que la réflexion éthique associée aux décisions
dâarrĂȘt de protocole de recherche. Notre travail a Ă©tĂ© menĂ© par une Ă©quipe pluridisciplinaire
combinant chercheurs en santé, généticiens et éthiciens. Nous avons étudié la participation des
chercheurs, des patients, des institutions officielles, des comitĂ©s dâĂ©thique ainsi que des
associations de patients dans le processus de dĂ©cision dâinterruption dâun protocole de recherche.Nous avons Ă©galement analysĂ© les critĂšres jugĂ©s les plus pertinents dans lâarrĂȘt dâun protocole
de recherche. Enfin nous avons analysé le point de vue des personnes directement impliquées
dans la thĂ©rapie gĂ©nique au moyen dâun questionnaire. Toutes les personnes contactĂ©es ont
présenté un poster de recherche au congrÚs de la Société Européenne de Thérapie Génique. 62
personnes dâautant dâĂ©quipes de recherche diffĂ©rentes, de 17 pays, sur les 350 contactĂ©s ont
rĂ©pondu. Selon eux, la dĂ©cision dâarrĂȘt dâun protocole de recherche doit ĂȘtre prise suite Ă une
consultation des chercheurs, des patients, du ministĂšre de tutelle, dâune agence nationale de
rĂ©gulation ou dâun comitĂ© dâĂ©thique ; la lĂ©gitimitĂ© Ă©tant accordĂ©e Ă des dĂ©cisions prises en
commun par les chercheurs, les patients et les comitĂ©s dâĂ©thique. Les incidents sĂ©rieux et de façon
plus surprenante, les incidents moins graves sont jugés comme étant des critÚres suffisants pour
interrompre un essai. Nous avons fini par analyser les conséquences éthiques, telles que balance
bĂ©nĂ©fice/risque, processus de rĂ©gulation ou responsabilitĂ©, de ces critĂšres sur lâarrĂȘt dâun protocole
de recherche.In 2002, the debate on the risks of gene therapy was initiated following the annoucement that two
children included in a clinical trial developed serious adverse effects. In January 2005, the debate
was reignited following the interruption of the âbubble kids protocolâ at the HĂŽpital Necker in Paris.
We have thus investigated the ethical stakes involved in decisions to stop protocols. This work was
carried out by a multidisciplinary team combining ethics researchers and geneticists. We studied
the specific participation of researchers, patients, official institution, ethics committees and patient
associations in the processes that can lead to an interruption of trial.We also analysed the criterion
judged most relevant for halting a trial. Finally, we analyzed the perspective of the actors implicated
directly in the provision of gene therapy, by means of a questionnaire. All the individuals contacted
had presented a scientific poster at the European Society of Gene Therapy. 62 out of 350 persons,
from 17 countries, responded to our questionnaire. According to these respondants, decisions to stop
a trial should be taken after consultation with researchers, patients, the ministry, national agencies
or ethics committees. Legitimacy was accorded to joint decision-making by researchers, patients and
committees. Serious incidents, and surprisingly less serious incidents, clearly emerge as criterion for
stopping a trial. We conclude by analyzing the ethical consequences, such as risk/benefit ratios,
regulatory processes and responsibility, associated with these criterions and decisions to stop a trial
Marine stratocumulus aerosolâcloud relationships in the MASEâII experiment: Precipitation susceptibility in eastern Pacific marine stratocumulus
Journal of Geophysical Research, Vol. 114, D24203The article of record as published may be located at http://dx.doi.org/10.1029/2009JD012774.Observational data on aerosol-cloud-drizzle relationships in marine stratocumulus are
presented from the second Marine Stratus/Stratocumulus Experiment (MASE-II)
carried out in July 2007 over the eastern Pacific near Monterey, California. Observations,
carried out in regions of essentially uniform meteorology with localized aerosol
enhancements due to ship exhaust (ââship tracksââ), demonstrate, in accord with those from
numerous other field campaigns, that increased cloud drop number concentration Nc and
decreased cloud top effective radius re are associated with increased subcloud aerosol
concentration
E10 and a "small tension expansion" of M Theory
A formal ``small tension'' expansion of D=11 supergravity near a spacelike
singularity is shown to be equivalent, at least up to 30th order in height, to
a null geodesic motion in the infinite dimensional coset space E10/K(E10) where
K(E10) is the maximal compact subgroup of the hyperbolic Kac-Moody group
E10(R). For the proof we make use of a novel decomposition of E10 into
irreducible representations of its SL(10,R) subgroup. We explicitly show how to
identify the first four rungs of the E10 coset fields with the values of
geometric quantities constructed from D=11 supergravity fields and their
spatial gradients taken at some comoving spatial point.Comment: 4 page
Global Diffusion in a Realistic Three-Dimensional Time-Dependent Nonturbulent Fluid Flow
We introduce and study the first model of an experimentally realizable
three-dimensional time-dependent nonturbulent fluid flow to display the
phenomenon of global diffusion of passive-scalar particles at arbitrarily small
values of the nonintegrable perturbation. This type of chaotic advection,
termed {\it resonance-induced diffusion\/}, is generic for a large class of
flows.Comment: 4 pages, uuencoded compressed postscript file, to appear in Phys.
Rev. Lett. Also available on the WWW from http://formentor.uib.es/~julyan/,
or on paper by reques
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