5,273 research outputs found
Quantum dichotomies and coherent thermodynamics beyond first-order asymptotics
We address the problem of exact and approximate transformation of quantum
dichotomies in the asymptotic regime, i.e., the existence of a quantum channel
mapping into with an
error (measured by trace distance) and into
exactly, for a large number . We derive
second-order asymptotic expressions for the optimal transformation rate
in the small, moderate, and large deviation error regimes, as well as the
zero-error regime, for an arbitrary pair of initial states
and a commuting pair of final states. We also prove that
for and given by thermal Gibbs states, the derived
optimal transformation rates in the first three regimes can be attained by
thermal operations. This allows us, for the first time, to study the
second-order asymptotics of thermodynamic state interconversion with fully
general initial states that may have coherence between different energy
eigenspaces. Thus, we discuss the optimal performance of thermodynamic
protocols with coherent inputs and describe three novel resonance phenomena
allowing one to significantly reduce transformation errors induced by
finite-size effects. What is more, our result on quantum dichotomies can also
be used to obtain, up to second-order asymptotic terms, optimal conversion
rates between pure bipartite entangled states under local operations and
classical communication.Comment: 51 pages, 6 figures, comments welcom
Gamma-rays from binary system with energetic pulsar and Be star with aspherical wind: PSR B1259-63/SS2883
At least one massive binary system containing an energetic pulsar, PSR
B1259-63/SS2883, has been recently detected in the TeV gamma-rays by the HESS
telescopes. These gamma-rays are likely produced by particles accelerated in
the vicinity of the pulsar and/or at the pulsar wind shock, in comptonization
of soft radiation from the massive star. However, the process of gamma-ray
production in such systems can be quite complicated due to the anisotropy of
the radiation field, complex structure of the pulsar wind termination shock and
possible absorption of produced gamma-rays which might initiate leptonic
cascades. In this paper we consider in detail all these effects. We calculate
the gamma-ray light curves and spectra for different geometries of the binary
system PSR B1259-63/SS2883 and compare them with the TeV gamma-ray
observations. We conclude that the leptonic IC model, which takes into account
the complex structure of the pulsar wind shock due to the aspherical wind of
the massive star, can explain the details of the observed gamma-ray light
curve.Comment: 12 pages, 11 figures, accepted for publication in MNRA
A new carbohydrate-active oligosaccharide dehydratase is involved in the degradation of ulvan
Marine algae catalyze half of all global photosynthetic production of carbohydrates. Owing to their fast growth rates, Ulva spp. rapidly produce substantial amounts of carbohydrate-rich biomass and represent an emerging renewable energy and carbon resource. Their major cell wall polysaccharide is the anionic carbohydrate ulvan. Here, we describe a new enzymatic degradation pathway of the marine bacterium Formosa agariphila for ulvan oligosaccharides involving unsaturated uronic acid at the nonreducing end linked to rhamnose-3-sulfate and glucuronic or iduronic acid (Delta-Rha3S-GlcA/IdoA-Rha3S). Notably, we discovered a new dehydratase (P29_PDnc) acting on the nonreducing end of ulvan oligosaccharides, i.e., GlcA/IdoARha3S, forming the aforementioned unsaturated uronic acid residue. This residue represents the substrate for GH105 glycoside hydrolases, which complements the enzymatic degradation pathway including one ulvan lyase, one multimodular sulfatase, three glycoside hydrolases, and the dehydratase P29_PDnc, the latter being described for the first time. Our research thus shows that the oligosaccharide dehydratase is involved in the degradation of carboxylated polysaccharide
Progress with the Upgrade of the SPS for the HL-LHC Era
The demanding beam performance requirements of the High Luminosity (HL-) LHC
project translate into a set of requirements and upgrade paths for the LHC
injector complex. In this paper the performance requirements for the SPS and
the known limitations are reviewed in the light of the 2012 operational
experience. The various SPS upgrades in progress and still under consideration
are described, in addition to the machine studies and simulations performed in
2012. The expected machine performance reach is estimated on the basis of the
present knowledge, and the remaining decisions that still need to be made
concerning upgrade options are detailed.Comment: 3 p. Presented at 4th International Particle Accelerator Conference
(IPAC 2013
Cerium-Doped Fused-Silica Fibers as Wavelength Shifters
We have evaluated the performance of a Ce-doped fused-silica fiber as
wavelength shifter coupled to a CeF crystal using electron beams at CERN.
The pulse shape and collection efficiency were measured using irradiated (100
kGy) and un-irradiated fibers. In addition, we evaluated the light yield of
various Ce-doped fibers and explored the possibility of using them in the
future, including for precision timing applications in a high-luminosity
collider environment.Comment: 11 pages, 7 figure
Testing sequential quantum measurements: how can maximal knowledge be extracted?
The extraction of information from a quantum system unavoidably implies a
modification of the measured system itself. It has been demonstrated recently
that partial measurements can be carried out in order to extract only a portion
of the information encoded in a quantum system, at the cost of inducing a
limited amount of disturbance. Here we analyze experimentally the dynamics of
sequential partial measurements carried out on a quantum system, focusing on
the trade-off between the maximal information extractable and the disturbance.
In particular we consider two different regimes of measurement, demonstrating
that, by exploiting an adaptive strategy, an optimal trade-off between the two
quantities can be found, as observed in a single measurement process. Such
experimental result, achieved for two sequential measurements, can be extended
to N measurement processes.Comment: 5 pages, 3 figure
Risk stratification for progression of IgA nephropathy using a decision tree induction algorithm
Background. Immunoglobulin A nephropathy (IgAN) is the most common form of glomerulonephritis, and many patients are at risk of at least slow progression. However, prediction of the renal outcome in individual patients remains difficult
Fermi LAT Observations of LS I +61 303: First detection of an orbital modulation in GeV Gamma Rays
This Letter presents the first results from the observations of LSI +61 303
using Large Area Telescope data from the Fermi Gamma-Ray Space Telescope
between 2008 August and 2009 March. Our results indicate variability that is
consistent with the binary period, with the emission being modulated at 26.6
+/- 0.5 days. This constitutes the first detection of orbital periodicity in
high-energy gamma rays (20 MeV-100 GeV, HE). The light curve is characterized
by a broad peak after periastron, as well as a smaller peak just before
apastron. The spectrum is best represented by a power law with an exponential
cutoff, yielding an overall flux above 100 MeV of 0.82 +/- 0.03(stat) +/-
0.07(syst) 10^{-6} ph cm^{-2} s^{-1}, with a cutoff at 6.3 +/- 1.1(stat) +/-
0.4(syst) GeV and photon index Gamma = 2.21 +/- 0.04(stat) +/- 0.06(syst).
There is no significant spectral change with orbital phase. The phase of
maximum emission, close to periastron, hints at inverse Compton scattering as
the main radiation mechanism. However, previous very high-energy gamma ray
(>100 GeV, VHE) observations by MAGIC and VERITAS show peak emission close to
apastron. This and the energy cutoff seen with Fermi suggest the link between
HE and VHE gamma rays is nontrivial.Comment: 7 pages, 5 figures, accepted for publication in ApJ Letters 21 July
200
Insights into the Transposable Mobilome of Paracoccus spp. (Alphaproteobacteria)
Several trap plasmids (enabling positive selection of transposition events) were used to identify a pool of functional transposable elements (TEs) residing in bacteria of the genus Paracoccus (Alphaproteobacteria). Complex analysis of 25 strains representing 20 species of this genus led to the capture and characterization of (i) 37 insertion sequences (ISs) representing 9 IS families (IS3, IS5, IS6, IS21, IS66, IS256, IS1182, IS1380 and IS1634), (ii) a composite transposon Tn6097 generated by two copies of the ISPfe2 (IS1634 family) containing two predicted genetic modules, involved in the arginine deiminase pathway and daunorubicin/doxorubicin resistance, (iii) 3 non-composite transposons of the Tn3 family, including Tn5393 carrying streptomycin resistance and (iv) a transposable genomic island TnPpa1 (45 kb). Some of the elements (e.g. Tn5393, Tn6097 and ISs of the IS903 group of the IS5 family) were shown to contain strong promoters able to drive transcription of genes placed downstream of the target site of transposition. Through the application of trap plasmid pCM132TC, containing a promoterless tetracycline resistance reporter gene, we identified five ways in which transposition can supply promoters to transcriptionally silent genes. Besides highlighting the diversity and specific features of several TEs, the analyses performed in this study have provided novel and interesting information on (i) the dynamics of the process of transposition (e.g. the unusually high frequency of transposition of TnPpa1) and (ii) structural changes in DNA mediated by transposition (e.g. the generation of large deletions in the recipient molecule upon transposition of ISPve1 of the IS21 family). We also demonstrated the great potential of TEs and transposition in the generation of diverse phenotypes as well as in the natural amplification and dissemination of genetic information (of adaptative value) by horizontal gene transfer, which is considered the driving force of bacterial evolution
Long-term monitoring of the high-energy gamma-ray emission from LS I +61{\deg} 303 and LS 5039
The Fermi Large Area Telescope (LAT) reported the first definitive GeV
detections of the binaries LS I +61\degree 303 and LS 5039 in the first year
after its launch in June, 2008. These detections were unambiguous as a
consequence of the reduced positional uncertainty and the detection of
modulated gamma-ray emission on the corresponding orbital periods. An analysis
of new data from the LAT, comprising 30 months of observations, identifies a
change in the gamma-ray behavior of LS I +61\degree 303. An increase in flux is
detected in March 2009 and a steady decline in the orbital flux modulation is
observed. Significant emission up to 30GeV is detected by the LAT; prior
datasets led to upper limits only. Contemporaneous TeV observations no longer
detected the source, or found it -in one orbit- close to periastron, far from
the phases at which the source previously appeared at TeV energies. The
detailed numerical simulations and models that exist within the literature do
not predict or explain many of these features now observed at GeV and TeV
energies. New ideas and models are needed to fully explain and understand this
behavior. A detailed phase-resolved analysis of the spectral characterization
of LS I +61\degree 303 in the GeV regime ascribes a power law with an
exponential cutoff spectrum along each analyzed portion of the system's orbit.
The on-source exposure of LS 5039 is also substantially increased with respect
to our prior publication. In this case, whereas the general gamma-ray
properties remain consistent, the increased statistics of the current dataset
allows for a deeper investigation of its orbital and spectral evolution.Comment: 12 pages, 13 figures, accepted for publication in Ap
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