641 research outputs found
Quantum enhanced positioning and clock synchronization
A wide variety of positioning and ranging procedures are based on repeatedly
sending electromagnetic pulses through space and measuring their time of
arrival. This paper shows that quantum entanglement and squeezing can be
employed to overcome the classical power/bandwidth limits on these procedures,
enhancing their accuracy. Frequency entangled pulses could be used to construct
quantum positioning systems (QPS), to perform clock synchronization, or to do
ranging (quantum radar): all of these techniques exhibit a similar enhancement
compared with analogous protocols that use classical light. Quantum
entanglement and squeezing have been exploited in the context of
interferometry, frequency measurements, lithography, and algorithms. Here, the
problem of positioning a party (say Alice) with respect to a fixed array of
reference points will be analyzed.Comment: 4 pages, 2 figures. Accepted for publication by Natur
Searching for sterile neutrinos in ice
Oscillation interpretation of the results from the LSND, MiniBooNE and some
other experiments requires existence of sterile neutrino with mass eV
and mixing with the active neutrinos . It has
been realized some time ago that existence of such a neutrino affects
significantly the fluxes of atmospheric neutrinos in the TeV range which can be
tested by the IceCube Neutrino Observatory. In view of the first IceCube data
release we have revisited the oscillations of high energy atmospheric neutrinos
in the presence of one sterile neutrino. Properties of the oscillation
probabilities are studied in details for various mixing schemes both
analytically and numerically. The energy spectra and angular distributions of
the events have been computed for the simplest mass, and
mixing schemes and confronted with the IceCube data. An
illustrative statistical analysis of the present data shows that in the
mass mixing case the sterile neutrinos with parameters required by
LSND/MiniBooNE can be excluded at about level. The
mixing scheme, however, can not be ruled out with currently available IceCube
data.Comment: 41 pages, 16 figures. Accepted for publication in JHEP. Minor changes
from the previous versio
Single to Double Hump Transition in the Equilibrium Distribution Function of Relativistic Particles
We unveil a transition from single peaked to bimodal velocity distribution in
a relativistic fluid under increasing temperature, in contrast with a
non-relativistic gas, where only a monotonic broadening of the bell-shaped
distribution is observed. Such transition results from the interplay between
the raise in thermal energy and the constraint of maximum velocity imposed by
the speed of light. We study the Bose-Einstein, the Fermi-Dirac, and the
Maxwell-J\"uttner distributions, all exhibiting the same qualitative behavior.
We characterize the nature of the transition in the framework of critical
phenomena and show that it is either continuous or discontinuous, depending on
the group velocity. We analyze the transition in one, two, and three
dimensions, with special emphasis on two-dimensions, for which a possible
experiment in graphene, based on the measurement of the Johnson-Nyquist noise,
is proposed.Comment: 5 pages, 5 figure
The Demise of Multidrug-Resistant HIV-1: the National Time Trend in Portugal
OBJECTIVES:
Despite a decreasing mortality and morbidity in treated HIV-1 patients, highly active antiretroviral treatment (HAART) can still fail due to the development of drug resistance. Especially, multidrug-resistant viruses pose a threat to efficient therapy. We studied the changing prevalence of multidrug resistance (MDR) over time in a cohort of HIV-1-infected patients in Portugal.
PATIENTS AND METHODS:
We used data of 8065 HIV-1-infected patients followed from July 2001 up to April 2012 in 22 hospitals located in Portugal. MDR at a specific date of sampling was defined as no more than one fully active drug (excluding integrase and entry inhibitors) at that time authorized by the Portuguese National Authority of Medicines and Health Products (INFARMED), as interpreted with the Rega algorithm version 8.0.2. A generalized linear mixed model was used to study the time trend of the prevalence of MDR.
RESULTS:
We observed a statistically significant decrease in the prevalence of MDR over the last decade, from 6.9% (95% CI: 5.7-8.4) in 2001-03, 6.0% (95% CI: 4.9-7.2) in 2003-05, 3.7% (95% CI: 2.8-4.8) in 2005-07 and 1.6% (95% CI: 1.1-2.2) in 2007-09 down to 0.6% (95% CI: 0.3-0.9) in 2009-12 [OR=0.80 (95% CI: 0.75-0.86); P<0.001]. In July 2011 the last new case of MDR was seen.
CONCLUSIONS:
The prevalence of multidrug-resistant HIV-1 is decreasing over time in Portugal, reflecting the increasing efficiency of HAART and the availability of new drugs. Therefore, in designing a new drug, safety and practical aspects, e.g. less toxicity and ease of use, may need more attention than focusing mainly on efficacy against resistant strains.info:eu-repo/semantics/publishedVersio
Professional competences of nurse to work in Intensive Care Units: an integrative review
α-Galactosylceramide and peptide-based nano-vaccine synergistically induced a strong tumor suppressive effect in melanoma
α-Galactosylceramide (GalCer) is a glycolipid widely known as an activator of Natural killer T (NKT) cells, constituting a promising adjuvant against cancer, including melanoma. However, limited clinical outcomes have been obtained so far. This study evaluated the synergy between GalCer and major histocompatibility complex (MHC) class I and MHC class II melanoma-associated peptide antigens and the Toll-Like Receptor (TLR) ligands CpG and monophosphoryl lipid A (MPLA), which we intended to maximize following their co-delivery by a nanoparticle (NP). This is expected to improve GalCer capture by dendritic cells (DCs) and subsequent presentation to NKT cells, and simultaneously induce an anti-tumor specific T-cell mediated immunity. The combination of GalCer with melanoma peptides and TLR ligands successfully restrained tumor growth. The tumor volume in these animals was 5-fold lower than the ones presented by mice immunized with NPs not containing GalCer. However, tumor growth was controlled at similar levels by GalCer entrapped or in its soluble form, when mixed with antigens and TLR ligands. Those two groups showed an improved infiltration of T lymphocytes into the tumor, but only GalCer-loaded nano-vaccine induced a prominent and enhanced infiltration of NKT and NK cells. In addition, splenocytes of these animals secreted levels of IFN-γ and IL-4 at least 1.5-fold and 2-fold higher, respectively, than those treated with the mixture of antigens and adjuvants in solution. Overall, the combined delivery of the NKT agonist with TLR ligands and melanoma antigens via this multivalent nano-vaccine displayed a synergistic anti-tumor immune-mediated efficacy in B16F10 melanoma mouse model. STATEMENT OF SIGNIFICANCE: Combination of α-galactosylceramide (GalCer), a Natural Killer T (NKT) cell agonist, with melanoma-associated antigens presented by MHC class I (Melan-A:26) and MHC class II (gp100:44) molecules, and Toll-like Receptor (TLR) ligands (MPLA and CpG), within nanoparticle matrix induced a prominent anti-tumor immune response able to restrict melanoma growth. An enhanced infiltration of NKT and NK cells into tumor site was only achieved when the combination GalCer, antigens and TLR ligands were co-delivered by nanovaccine
Quantum anti-Zeno effect without wave function reduction
We study the measurement-induced enhancement of the spontaneous decay (called
quantum anti-Zeno effect) for a two-level subsystem, where measurements are
treated as couplings between the excited state and an auxiliary state rather
than the von Neumann's wave function reduction. The photon radiated in a fast
decay of the atom, from the auxiliary state to the excited state, triggers a
quasi-measurement, as opposed to a projection measurement. Our use of the term
"quasi-measurement" refers to a "coupling-based measurement". Such frequent
quasi-measurements result in an exponential decay of the survival probability
of atomic initial state with a photon emission following each
quasi-measurement. Our calculations show that the effective decay rate is of
the same form as the one based on projection measurements. What is more
important, the survival probability of the atomic initial state which is
obtained by tracing over all the photon states is equivalent to the survival
probability of the atomic initial state with a photon emission following each
quasi-measurement to the order under consideration. That is because the
contributions from those states with photon number less than the number of
quasi-measurements originate from higher-order processes.Comment: 7 pages, 3 figure
Experimental non-classicality of an indivisible quantum system
Quantum theory demands that, in contrast to classical physics, not all
properties can be simultaneously well defined. The Heisenberg Uncertainty
Principle is a manifestation of this fact. Another important corollary arises
that there can be no joint probability distribution describing the outcomes of
all possible measurements, allowing a quantum system to be classically
understood. We provide the first experimental evidence that even for a single
three-state system, a qutrit, no such classical model can exist that correctly
describes the results of a simple set of pairwise compatible measurements. Not
only is a single qutrit the simplest system in which such a contradiction is
possible, but, even more importantly, the contradiction cannot result from
entanglement, because such a system is indivisible, and it does not even allow
the concept of entanglement between subsystems.Comment: 11 pages, 4 figures, 2 table
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