716 research outputs found
Topological features of the deconfinement transition
The first order transition between the confining and the center symmetry
breaking phases of the SU(3) Yang-Mills theory is marked by discontinuities in
various thermodynamics functions, such as the energy density or the value of
the Polyakov loop. We investigate the non-analytical behaviour of the
topological susceptibility and its higher cumulant around the transition
temperature and make the connection to the curvature of the phase diagram in
the plane and to the latent heat.Comment: 13 pages, 10 figure
Surface collective modes in the topological insulators BiSe and BiSbTeSe
We used low-energy, momentum-resolved inelastic electron scattering to study
surface collective modes of the three-dimensional topological insulators
BiSe and BiSbTeSe. Our goal was to
identify the "spin plasmon" predicted by Raghu and co-workers [S. Raghu, et
al., Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary
collective mode is a surface plasmon arising from the bulk, free carrers in
these materials. This excitation dominates the spectral weight in the bosonic
function of the surface, , at THz energy scales, and
is the most likely origin of a quasiparticle dispersion kink observed in
previous photoemission experiments. Our study suggests that the spin plasmon
may mix with this other surface mode, calling for a more nuanced understanding
of optical experiments in which the spin plasmon is reported to play a role.Comment: 5 pages, 4 figure
Tumor Necrosis Factor-Alpha Signaling May Contribute to Chronic West Nile Virus Post-Infectious Proinflammatory State
Background: West Nile virus (WNV) causes a spectrum of human disease ranging from a febrile illness (WNV fever) to severe neuroinvasive disease (meningitis, encephalitis, acute flaccid paralysis). Since WNV gained entry into North America in 1999, clinicians caring for WNV survivors have observed persistent neurological symptoms occurring long-after the production of neutralizing antibodies and clearance of the virus. Accordingly, alternative pathogeneses other than direct viral invasion have been hypothesized to explain these post-infectious symptoms. The dominant hypothesis is that antiviral inflammatory responses triggered initially to clear WNV may persist to promote a post-infectious proinflammatory state.
Methods: In 4 serologically-confirmed WNV patients with persistent post-infectious symptoms (3 WNV fever, 1 neuroinvasive disease), we ordered a comprehensive cytokine panel at weeks 8, 10, 12, and 36 months post-onset of illness, respectively, to better understand the pathophysiology of the protracted symptoms.
Results: All patients had abnormally elevated tumor necrosis factor alpha (TNF-α), a major molecule triggering antiviral cytokines and chronic inflammation in many human autoimmune diseases, but heretofore not reported to be upregulated in human WNV infection. Three patients also had elevations of other proinflammatory proteins. Major symptoms included fatigue, arthralgias, myalgias, generalized or multifocal pain or weakness, imbalance, headaches, cognitive problems, and symptoms of dysautonomia.
Conclusion: The findings provide support for an extended post-infectious proinflammatory state that may contribute to chronic inflammation and long-term morbidity in some WNV survivors and further suggest that TNF-α may play a pathogenic role in initiating this inflammatory environment. Clinical trials may be warranted to determine if TNF-α inhibitors or other immunosuppressive agents can improve patient outcomes
Anomalous density fluctuations in a strange metal.
A central mystery in high-temperature superconductivity is the origin of the so-called strange metal (i.e., the anomalous conductor from which superconductivity emerges at low temperature). Measuring the dynamic charge response of the copper oxides, [Formula: see text], would directly reveal the collective properties of the strange metal, but it has never been possible to measure this quantity with millielectronvolt resolution. Here, we present a measurement of [Formula: see text] for a cuprate, optimally doped Bi2.1Sr1.9CaCu2O8+x (Tc = 91 K), using momentum-resolved inelastic electron scattering. In the medium energy range 0.1-2 eV relevant to the strange metal, the spectra are dominated by a featureless, temperature- and momentum-independent continuum persisting to the electronvolt energy scale. This continuum displays a simple power-law form, exhibiting q2 behavior at low energy and q2/ω2 behavior at high energy. Measurements of an overdoped crystal (Tc = 50 K) showed the emergence of a gap-like feature at low temperature, indicating deviation from power law form outside the strange-metal regime. Our study suggests the strange metal exhibits a new type of charge dynamics in which excitations are local to such a degree that space and time axes are decoupled
Post-Outburst Phase of McNeil's Nebula (V1647 Orionis)
We present a detailed study of the post-outburst phase of McNeil's nebula
(V1647 Ori) using optical B,V,R,I and NIR J,H,K photometric and low resolution
optical spectroscopic observations. The observations were carried out with the
HFOSC, NIRCAM, TIRCAM and NICMOS cameras on the 2m HCT and 1.2m PRL telescopes
during the period 2004 Feb-2005 Dec. The optical/NIR observations show a
general decline in brightness of the exciting source of McNeil's nebula (V1647
Ori). Our recent optical images show that V1647 Ori has faded by more than 3
mags since Feb 2004. The optical/NIR photometric data also show a significant
variation in the mags (Delta V = 0.78 mag, Delta R = 0.44 mag, Delta I = 0.21
mag, Delta J = 0.24 mag and Delta H = 0.20 mag) of V1647 Ori within a period of
one month, which is possibly undergoing a phase similar to eruptive variables,
like EXors or FUors. The optical spectra show a few features such as strong
Halpha emission with blue-shifted absorption and the CaII IR triplet (8498A,
8542A and 8662A) in emission. As compared to the period just after outburst,
there is a decrease in the depth and extent of the blue-shifted absorption
component, indicating a weakening in the powerful stellar wind. The presence of
the CaII IR triplet in emission confirms that V1647 Ori is a PMS star. The
long-term, post-outburst photometric observations of V1647 Ori suggest an EXor,
rather than an FUor event. An optical/IR comparison of the region surrounding
McNeil's nebula shows that the optical nebula is more widely and predominantly
extended to the north, whereas the IR nebula is relatively confined (dia ~ 60
arcsec), but definitely extended, to the south, too.Comment: 25 pages (4 figures in JPEG format), Accepted for the publication in
MNRAS. Preprint is also available at:
http://www.tifr.res.in/~ojha/McNeil.htm
Feasibility of free space quantum key distribution with coherent polarization states
We demonstrate for the first time the feasibility of free space quantum key
distribution with continuous variables under real atmospheric conditions. More
specifically, we transmit coherent polarization states over a 100m free space
channel on the roof of our institute's building. In our scheme, signal and
local oscillator are combined in a single spatial mode which auto-compensates
atmospheric fluctuations and results in an excellent interference. Furthermore,
the local oscillator acts as spatial and spectral filter thus allowing
unrestrained daylight operation.Comment: 12 pages, 8 figures, extensions in sections 2, 3.1, 3.2 and 4. This
is an author-created, un-copyedited version of an article accepted for
publication in New Journal of Physics (Special Issue on Quantum Cryptography:
Theory and Practice). IOP Publishing Ltd is not responsible for any errors or
omissions in this version of the manuscript or any version derived from i
Active wetting of epithelial tissues
Development, regeneration and cancer involve drastic transitions in tissue
morphology. In analogy with the behavior of inert fluids, some of these
transitions have been interpreted as wetting transitions. The validity and
scope of this analogy are unclear, however, because the active cellular forces
that drive tissue wetting have been neither measured nor theoretically
accounted for. Here we show that the transition between 2D epithelial
monolayers and 3D spheroidal aggregates can be understood as an active wetting
transition whose physics differs fundamentally from that of passive wetting
phenomena. By combining an active polar fluid model with measurements of
physical forces as a function of tissue size, contractility, cell-cell and
cell-substrate adhesion, and substrate stiffness, we show that the wetting
transition results from the competition between traction forces and contractile
intercellular stresses. This competition defines a new intrinsic lengthscale
that gives rise to a critical size for the wetting transition in tissues, a
striking feature that has no counterpart in classical wetting. Finally, we show
that active shape fluctuations are dynamically amplified during tissue
dewetting. Overall, we conclude that tissue spreading constitutes a prominent
example of active wetting --- a novel physical scenario that may explain
morphological transitions during tissue morphogenesis and tumor progression
The BLAST View of the Star Forming Region in Aquila (ell=45deg,b=0deg)
We have carried out the first general submillimeter analysis of the field
towards GRSMC 45.46+0.05, a massive star forming region in Aquila. The
deconvolved 6 deg^2 (3\degree X 2\degree) maps provided by BLAST in 2005 at
250, 350, and 500 micron were used to perform a preliminary characterization of
the clump population previously investigated in the infrared, radio, and
molecular maps. Interferometric CORNISH data at 4.8 GHz have also been used to
characterize the Ultracompact HII regions (UCHIIRs) within the main clumps. By
means of the BLAST maps we have produced an initial census of the submillimeter
structures that will be observed by Herschel, several of which are known
Infrared Dark Clouds (IRDCs). Our spectral energy distributions of the main
clumps in the field, located at ~7 kpc, reveal an active population with
temperatures of T~35-40 K and masses of ~10^3 Msun for a dust emissivity index
beta=1.5. The clump evolutionary stages range from evolved sources, with
extended HII regions and prominent IR stellar population, to massive young
stellar objects, prior to the formation of an UCHIIR.The CORNISH data have
revealed the details of the stellar content and structure of the UCHIIRs. In
most cases, the ionizing stars corresponding to the brightest radio detections
are capable of accounting for the clump bolometric luminosity, in most cases
powered by embedded OB stellar clusters
What "best practice" could be in Palliative Care: an analysis of statements on practice and ethics expressed by the main Health Organizations
<p>Abstract</p> <p>Background</p> <p>In palliative care it would be necessary to refer to a model. Nevertheless it seems that there are no official statements which state and describe that model. We carried out an analysis of the statements on practice and ethics of palliative care expressed by the main health organizations to show which dimensions of end-of-life care are taken into consideration.</p> <p>Methods</p> <p>The official documents by the most representative health organisations committed to the definition of policies and guidelines for palliative and end-of-life care had been considered. The documents were analysed through a framework of the components of end-of-life care derived from literature, which was composed of 4 main "areas" and of 12 "sub-areas".</p> <p>Results</p> <p>Overall, 34 organizations were identified, 7 international organisations, and 27 organisations operating on the national level in four different countries (Australia, Canada, UK and United States). Up to 56 documents were selected and analysed. Most of them (38) are position statements. Relevant quotations from the documents were presented by "areas" and "sub-areas". In general, the "sub-areas" of symptoms control as well as those referring to relational and social issues are more widely covered by the documents than the "sub-areas" related to "preparation" and to "existential condition". Indeed, the consistency of end-of-life choices with the patient's wishes, as well as completion and meaningfulness at the end of life is given only a minor relevance.</p> <p>Conclusions</p> <p>An integrated model of the best palliative care practice is generally lacking in the documents. It might be argued that the lack of a fixed and coherent model is due to the relevance of unavoidable context issues in palliative care, such as specific cultural settings, patient-centred variables, and family specificity. The implication is that palliative care staff have continuously to adapt their model of caring to the specific needs and values of each patient, more than applying a fixed, although maybe comprehensive, care model.</p
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