999 research outputs found
Kernel regression estimates of time delays between gravitationally lensed fluxes
Strongly lensed variable quasars can serve as precise cosmological probes,
provided that time delays between the image fluxes can be accurately measured.
A number of methods have been proposed to address this problem. In this paper,
we explore in detail a new approach based on kernel regression estimates, which
is able to estimate a single time delay given several datasets for the same
quasar. We develop realistic artificial data sets in order to carry out
controlled experiments to test of performance of this new approach. We also
test our method on real data from strongly lensed quasar Q0957+561 and compare
our estimates against existing results.Comment: Updated to match published versio
Complicated septic shock caused by Achromobacter xylosoxidans bacteremia in a patient with acute lymphoblastic leukaemia
Infections caused by Achromobacter xylosoxidans cause significant morbidity and mortality in debilitated individuals. Eradication of these infections requires prolonged therapy with antimicrobial agents and removal of any infected central venous catheter. The outcome is usually poor in patients with high risk malignancy, septic complications, and/or multi-organ dysfunction
Crossover of thermal to shot noise in chaotic cavities
We study the crossover between thermal and shot-noise power in a chaotic
quantum dot in the presence of non-ideal contacts at finite temperature. The
result explicitly demonstrates that the temperature affect the
suppression-amplification effect present in the main quantum noise. In
particular, the weak localization contribution to the noise has an anomalous
thermal behavior when one let the barriers vary, indicating the presence of a
critical point related to specific value of the tunneling barriers. We also
show how to get to the opaque limit of the quantum dot at finite temperature.Comment: 6 pages, 5 figures. To be published in Europhysics Letter
Tribal casinos in California: the last vestige of indoor smoking
Background. High levels of airborne particles from secondhand smoke have been reported in California Indian casinos. Yet, little is known regarding the smoking status of casino patrons, their avoidance of secondhand smoke while visiting, and their views on a hypothetical smoking ban. Methods. Predictors of visiting an Indian casino were assessed among participants of the 2008 California Tobacco Survey (n = 10, 397). Exposure to and avoidance of secondhand smoke were subsequently analyzed among a subset of participants who had visited a casino in the year prior to the survey (n = 3, 361). Results. Ethnic minorities, older individuals, current smokers and residents of sparsely populated regions of California were more likely than other demographic groups to visit a tribal casino. Avoidance of secondhand smoke was more frequent among the never smokers than former and current smokers, particularly those who last visited a casino lacking physical separation between non-smoking and smoking sections. The never smokers versus current smokers disproportionately expressed a willingness to extend their stay and visit again if smoking were prohibited. Conclusions. If casinos became smoke free, then it is anticipated that they would be visited by a significantly larger number of Californians, including both patrons and those who otherwise would not have visited a casino. © 2012 Timberlake et al; licensee BioMed Central Ltd
Quantum to Classical Transition in a Single-Ion Laser
Stimulated emission of photons from a large number of atoms into the mode of
a strong light field is the principle mechanism for lasing in "classical"
lasers. The onset of lasing is marked by a threshold which can be characterised
by a sharp increase in photon flux as a function of external pumping strength.
The same is not necessarily true for the fundamental building block of a laser:
a single trapped atom interacting with a single optical radiation mode. It has
been shown that such a "quantum" laser can exhibit thresholdless lasing in the
regime of strong coupling between atom and radiation field. However, although
theoretically predicted, a threshold at the single-atom level could not be
experimentally observed so far. Here, we demonstrate and characterise a
single-atom laser with and without threshold behaviour by changing the strength
of atom-light field coupling. We observe the establishment of a laser threshold
through the accumulation of photons in the optical mode even for a mean photon
number substantially lower than for the classical case. Furthermore,
self-quenching occurs for very strong external pumping and constitutes an
intrinsic limitation of single-atom lasers. Moreover, we find that the
statistical properties of the emitted light can be adjusted for weak external
pumping, from the quantum to the classical domain. Our observations mark an
important step towards fundamental understanding of laser operation in the
few-atom limit including systems based on semiconductor quantum dots or
molecules.Comment: 19 pages, 4 figures, 10 pages supplement, accepted by Nature Physic
Propagation of squeezed radiation through amplifying or absorbing random media
We analyse how nonclassical features of squeezed radiation (in particular the
sub-Poissonian noise) are degraded when it is transmitted through an amplifying
or absorbing medium with randomly located scattering centra. Both the cases of
direct photodetection and of homodyne detection are considered. Explicit
results are obtained for the dependence of the Fano factor (the ratio of the
noise power and the mean current) on the degree of squeezing of the incident
state, on the length and the mean free path of the medium, the temperature, and
on the absorption or amplification rate.Comment: 8 pages, 4 figure
PerchĂ© unâimprovvisa caduta di capelli merita unâaccurata e completa visita dermatologica?
Il lupus eritematoso Ăš una patologia sistemica autoimmune ad andamento cronico recidivante, caratterizzata da un ampio spettro clinico, che varia da una forma a coinvolgimento sistemico a una esclusivamente cutanea. Presentiamo il caso di una donna di colore di 42 anni con importante disagio psicologico dovuto a un rapido diradamento al cuoio capelluto. Allâesame obiettivo si rilevava la presenza di due ampie aree di alopecia cicatriziale in sede parietale e occipitale. La diagnosi differenziale di alopecia cicatriziale al cuoio capelluto comprende principalmente lichen planus pilaris, lupus eritematoso discoide, follicolite decalvante e alopecia di Brocq. Ad una piĂč approfondita valutazione clinica si riscontravano chiazze ipercromiche nella conca auricolare e lesioni infiltrate ipercheratosiche con ulcerazione centrale localizzate ai gomiti e in regione retro-auricolare. Lâinsieme di tali reperti clinici deponeva per lupus eritematoso discoide. Tale diagnosi veniva confermata dal quadro istologico e dalla presenza di depositi granulari di IgG alla giunzione dermo-epidermica evidenziati con lâimmunofluorescenza diretta. Questo caso testimonia lâimportanza di un accurato esame obiettivo dermatologico al fine di un corretto approccio clinico. Nello specifico, lâorientamento diagnostico veniva suggerito dalla concomitanza di tipiche lesioni al corpo e al cuoio capelluto
Negativity of the Wigner function as an indicator of nonclassicality
A measure of nonclassicality of quantum states based on the volume of the
negative part of the Wigner function is proposed. We analyze this quantity for
Fock states, squeezed displaced Fock states and cat-like states defined as
coherent superposition of two Gaussian wave packets.Comment: 10 pages, 7 figure
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