6,663 research outputs found
Vanishing conductivity of quantum solitons in polyacetylene
Quantum solitons or polarons are supposed to play a crucial role in the
electric conductivity of polyacetylene, in the intermediate doping regime. We
present an exact fully quantized calculation of the quantum soliton
conductivity in polyacetylene and show that it vanishes exactly. This is
obtained by applying a general method of soliton quantization, based on
order-disorder duality, to a Z(2)-symmetric complex extension of the TLM
dimerization effective field theory. We show that, in this theory,
polyacetylene solitons are sine-Gordon solitons in the phase of the complex
field.Comment: To appear in J. Phys. A: Math. Theor., 15 page
Plasma adrenomedullin is associated with short-term mortality and vasopressor requirement in patients admitted with sepsis
Introduction: The incidence of death among patients admitted for severe sepsis or septic shock is high. Adrenomedullin (ADM) plays a central role in initiating the hyperdynamic response during the early stages of sepsis. Pilot studies indicate an association of plasma ADM with the severity of the disease. In the present study we utilized a novel sandwich immunoassay of bioactive plasma ADM in patients hospitalized with sepsis in order to assess the clinical utility.Methods: We enrolled 101 consecutive patients admitted to the emergency department with suspected sepsis in this study. Sepsis was defined by fulfillment of at least two systemic inflammatory response syndrome (SIRS) criteria plus clinical suspicion of infection. Plasma samples for ADM measurement were obtained on admission and for the next four days. The 28-day mortality rate was recorded.Results: ADM at admission was associated with severity of disease (correlation with Acute Physiology and Chronic Health Evaluation II (APACHE II) score: r = 0.46; P <0.0001). ADM was also associated with 28-day mortality (ADM median (IQR): survivors: 50 (31 to 77) pg/mL; non-survivors: 84 (48 to 232) pg/mL; P <0.001) and was independent from and additive to APACHE II (P = 0.02). Cox regression analysis revealed an additive value of serial measurement of ADM over baseline assessment for prediction of 28-day mortality (P < 0.01). ADM was negatively correlated with mean arterial pressure (r = -0.39; P <0.0001), and it strongly discriminated those patients requiring vasopressor therapy from the others (ADM median (IQR): no vasopressors 48 (32 to 75) pg/mL; with vasopressors 129 (83 to 264) pg/mL, P <0.0001).Conclusions: In patients admitted with sepsis, severe sepsis or septic shock plasma ADM is strongly associated with severity of disease, vasopressor requirement and 28-day mortality
Sulle orme del consumatore affinity analysis e knowledge visualization per il processo decisionale
L\u2019articolo analizza i reali comportamenti di acquisto dell\u2019acquirente all\u2019interno del punto vendita e individua i pattern latenti pi\uf9 significativi attraverso un\u2019analisi di affinit\ue0 di 128.364 scontrini estratti da un dataset di 715.662 transazioni effettuate in un anno. Lo studio individua le strutture associative pi\uf9 ricorrenti relativamente alla singola merceologia. Attraverso la tecnica della Market Basket Analysis \ue8 stato possibile individuare le categorie merceologiche che creano \u201cpoli d\u2019attrazione\u201d sul punto vendita stimolando acquisti di altre categorie. In particolar modo, applicando le regole associative sul punto vendita \ue8 stato possibile identificare le \u201caree calde\u201d e le \u201caree fredde\u201d. L\u2019articolo evidenzia quindi alcune riflessioni sulle strategie che possono adottare gli store manager
Multimarginal Optimal Transport Maps for one dimensional Repulsive Costs
We study a multimarginal optimal transportation problem in one dimension. For a symmetric, repulsive cost function, we show that given a minimizing transport plan, its symmetrization is induced by a cyclical map, and that the symmetric optimal plan is unique. The class of costs that we consider includes, in particular, the Coulomb cost, whose optimal transport problem is strictly related to the strong interaction limit of Density Functional Theory. In this last setting, our result justifies some qualitative properties of the potentials observed in numerical experiments
Evidence of a non-conservative mass transfer for XTE J0929-314
Context. In 1998 the first accreting millisecond pulsar, SAX J1808.4-3658,
was discovered and to date 18 systems showing coherent, high frequency (> 100
Hz) pulsations in low mass X-ray binaries are known. Since their discovery,
this class of sources has shown interesting and sometimes puzzling behaviours.
In particular, apart from a few exceptions, they are all transient with very
long X-ray quiescent periods implying a quite low averaged mass accretion rate
onto the neutron star. Among these sources, XTE J0929-314 has been detected in
outburst just once in about 15 years of continuous monitoring of the X-ray sky.
Aims. We aim to demonstrate that a conservative mass transfer in this system
will result in an X-ray luminosity that is higher than the observed, long-term
averaged X-ray luminosity. Methods. Under the hypothesis of a conservative mass
transfer driven by gravitational radiation, as expected for this system given
the short orbital period of about 43.6 min and the low mass of the companion
implied by the mass function derived from timing techniques, we calculate the
expected mass transfer rate in this system and predict the long-term averaged
X-ray luminosity. This is compared with the averaged, over 15 years, X-ray flux
observed from the system, and a lower limit of the distance to the source is
inferred. Results. This distance is shown to be > 7.4 kpc in the direction of
the Galactic anticentre, implying a large height, > 1.8 kpc, of the source with
respect to the Galactic plane, placing the source in an empty region of the
Galaxy. We suggest that the inferred value of the distance is unlikely.
(abridged)Comment: 6 pages, 2 figures, accepted for publication in Astronomy &
Astrophysics (A&A
An entropy minimization approach to second-order variational mean-field games
We propose an entropy minimization viewpoint on variational mean-field games with diffusion and quadratic Hamiltonian. We carefully analyze the time discretization of such problems, establish Gamma-convergence results as the time step vanishes and propose an efficient algorithm relying on this entropic interpretation as well as on the Sinkhorn scaling algorithm
Progress in understanding colour confinement
New results from lattice are presented,which demonstrate that monopoles
condense in the vacuum of confined phase of QCD, which is thus a dual
superconductor. Monopoles defined by different abelian projections appear to be
physically equivalent.Comment: 5 pages,4 figures. Presented by A.Di Giacomo at QCD98 Montpellier
July199
Multiple stellar populations in Magellanic Cloud clusters. V. The split main sequence of the young cluster NGC1866
One of the most unexpected results in the field of stellar populations of the
last few years, is the discovery that some Magellanic-Cloud globular clusters
younger than ~400 Myr, exhibit bimodal main sequences (MSs) in their
color-magnitude diagrams (CMDs). Moreover, these young clusters host an
extended main sequence turn off (eMSTO) in close analogy with what is observed
in most ~1-2 Gyr old clusters of both Magellanic Clouds.
We use high-precision Hubble-Space-Telescope photometry to study the young
star cluster NGC1866 in the Large Magellanic Cloud. We discover an eMSTO and a
split MS. The analysis of the CMD reveals that (i) the blue MS is the less
populous one, hosting about one-third of the total number of MS stars; (ii)
red-MS stars are more centrally concentrated than blue-MS stars; (iii) the
fraction of blue-MS stars with respect to the total number of MS stars drops by
a factor of ~2 in the upper MS with F814W <~19.7.
The comparison between the observed CMDs and stellar models reveals that the
observations are consistent with ~200 Myr old highly-rotating stars on the
red-MS, with rotation close to critical value, plus a non-rotating stellar
population spanning an age interval between ~140 and 220 Myr, on the blue-MS.
Noticeable, neither stellar populations with different ages only, nor coeval
stellar models with different rotation rates, properly reproduce the observed
split MS and eMSTO. We discuss these results in the context of the eMSTO and
multiple MS phenomenon.Comment: 11 pages, 11 figures, accepted for publication in MNRA
A matrix model for the topological string II: The spectral curve and mirror geometry
In a previous paper, we presented a matrix model reproducing the topological
string partition function on an arbitrary given toric Calabi-Yau manifold.
Here, we study the spectral curve of our matrix model and thus derive, upon
imposing certain minimality assumptions on the spectral curve, the large volume
limit of the BKMP "remodeling the B-model" conjecture, the claim that
Gromov-Witten invariants of any toric Calabi-Yau 3-fold coincide with the
spectral invariants of its mirror curve.Comment: 1+37 page
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