6,096 research outputs found
Approaching Space Time Through Velocity in Doubly Special Relativity
We discuss the definition of velocity as dE/dp, where E,p are the energy and
momentum of a particle, in Doubly Special Relativity (DSR). If this definition
matches dx/dt appropriate for the space-time sector, then space-time can in
principle be built consistently with the existence of an invariant length
scale. We show that, within different possible velocity definitions, a
space-time compatible with momentum-space DSR principles can not be derived.Comment: 11 pages, no figures, minor changes, references added, final version
to appear in PR
Modified Special Relativity on a fluctuating spacetime
It was recently proposed that deformations of the relativistic symmetry, as
those considered in Deformed Special Relativity (DSR), can be seen as the
outcome of a measurement theory in the presence of non-negligible (albeit
small) quantum gravitational fluctuations [1,2]. In this paper we explicitly
consider the case of a spacetime described by a flat metric endowed with
stochastic fluctuations and, for a free particle, we show that DSR-like
nonlinear relations between the spaces of the measured and classical momenta,
can result from the average of the stochastic fluctuations over a scale set be
the de Broglie wavelength of the particle. As illustrative examples we consider
explicitly the averaging procedure for some simple stochastic processes and
discuss the physical implications of our results.Comment: 7 pages, no figure
Non-linear diffusive acceleration of heavy nuclei in supernova remnant shocks
We describe a semi-analytical approach to non-linear diffusive shock
acceleration in the case in which nuclei other than protons are also
accelerated. The structure of the shock is determined by the complex interplay
of all nuclei, and in turn this shock structure determines the spectra of all
components. The magnetic field amplification upstream is described as due to
streaming instability of all nuclear species. The amplified magnetic field is
then taken into account for its dynamical feedback on the shock structure as
well as in terms of the induced modification of the velocity of the scattering
centers that enters the particle transport equation. The spectra of accelerated
particles are steep enough to be compared with observed cosmic ray spectra only
if the magnetic field is sufficiently amplified and the scattering centers have
high speed in the frame of the background plasma. We discuss the implications
of this generalized approach on the structure of the knee in the all-particle
cosmic ray spectrum, which we interpret as due to an increasingly heavier
chemical composition above eV. The effects of a non trivial chemical
composition at the sources on the gamma ray emission from a supernova remnant
when gamma rays are of hadronic origin are also discussed.Comment: 23 pages, 5 figures, minor changes to reflect the published versio
Radiative decays of light vector mesons in a quark level linear sigma model
We calculate the P0 to gamma gamma, V0 to P0 gamma and V0to V'0 gamma gamma
decays in the framework of a U(3)xU(3) linear sigma model which includes
constituent quarks. For the first two decays this approach improves results
based on the anomalous Wess-Zumino term, with contributions due to SU(3)
symmetry breaking and vector mixing. The phi to (omega,rho) gamma gamma decays
are dominated by resonant eta' exchange . Our calculation for the later decays
improves and update similar calculations in the -closely related- framework of
vector meson dominance. We obtain BR(phi to rho gamma gamma)=2.5x10^{-5} and
BR(phi to omega gamma gamma)=2.8x10^{-6} within the scope of the
high-luminosity phi factories.Comment: 8 pages, submitted to Phys. Rev.
Deformed Special Relativity as an effective theory of measurements on quantum gravitational backgrounds
In this article we elaborate on a recently proposed interpretation of DSR as
an effective measurement theory in the presence of non-negligible (albeit
small) quantum gravitational fluctuations. We provide several heuristic
arguments to explain how such a new theory can emerge and discuss the possible
observational consequences of this framework.Comment: 11 pages, no figure
Impact of total automation consolidating first-line laboratory tests on diagnostic blood loss
Background: Blood loss for laboratory testing may contribute to hospital-acquired anemia. When implementing the core laboratory (core-lab) section, we consolidated first-line tests decreasing the number of tubes previously dispatched to different sites. Here, hypothesized benefits of the amount of blood volume drawn were explored.
Methods: We retrieved, using a laboratory information system (LIS), the number of tubes received by laboratories interested in the change from all clinical wards in a year-based period, i.e. 2013 for pre-core-lab and 2015 for core-lab system, respectively. Data were expressed as the overall number of tubes sent to laboratories, the corresponding blood volume, and the number of laboratory
tests performed, normalized for the number of inpatients.
Results: After consolidation, the average number of blood tubes per inpatient significantly decreased (12.6 vs. 10.7, p\u2009<\u20090.001). However, intensive care units (ICUs) did not reduce the number of tubes per patient, according to the needs of daily monitoring of their clinical status. The average blood volume sent to laboratories did not vary significantly because serum tubes for core-lab required higher volumes for testing up to 55 analytes in the same transaction. Finally, the number of requested tests per
patient during the new osystem slightly decreased ( 122.6%).
Conclusions: Total laboratory automation does not automatically mean reducing iatrogenic blood loss. The new system affected the procedure of blood drawing in clinical wards by significantly reducing the number of handled tubes, producing a benefit in terms of costs, labor and time consumption. Except in ICUs, this also slightly promoted some blood saving. ICUs which engage in phlebotomizing patients daily, did not take advantage from the test consolidation
Signatures of the transition from galactic to extragalactic cosmic rays
We discuss the signatures of the transition from galactic to extragalactic
cosmic rays in different scenarios, giving most attention to the dip scenario.
The dip is a feature in the diffuse spectrum of ultra-high energy (UHE) protons
in the energy range eV, which is caused by
electron-positron pair production on the cosmic microwave background (CMB)
radiation. The dip scenario provides a simple physical description of the
transition from galactic to extragalactic cosmic rays. Here we summarize the
signatures of the pair production dip model for the transition, most notably
the spectrum, the anisotropy and the chemical composition. The main focus of
our work is however on the description of the features that arise in the
elongation rate and in the distribution of the depths of shower maximum in the dip scenario. We find that the curve for shows a
sharp increase with energy, which reflects a sharp transition from an iron
dominated flux at low energies to a proton dominated flux at
eV. We also discuss in detail the shape of the distributions for
cosmic rays of given energy and demonstrate that this represents a powerful
tool to discriminate between the dip scenario and other possible models of the
transition.Comment: Version accepted for publication in Physical Review
Imaginary chemical potential and finite fermion density on the lattice
Standard lattice fermion algorithms run into the well-known sign problem at
real chemical potential. In this paper we investigate the possibility of using
imaginary chemical potential, and argue that it has advantages over other
methods, particularly for probing the physics at finite temperature as well as
density. As a feasibility study, we present numerical results for the partition
function of the two-dimensional Hubbard model with imaginary chemical
potential.
We also note that systems with a net imbalance of isospin may be simulated
using a real chemical potential that couples to I_3 without suffering from the
sign problem.Comment: 9 pages, LaTe
Proton induced Dark Count Rate degradation in 150-nm CMOS Single-Photon Avalanche Diodes
Proton irradiation effects on a Single-Photon Avalanche Diodes (SPADs) device
manufactured using a 150-nm CMOS process are presented. An irradiation campaign
has been carried out with protons of 20 MeV and 24 MeV on several samples of a
test chip containing SPADs arrays with two different junction layouts. The dark
count rate distributions have been analyzed as a function of the displacement
damage dose. Annealing and cooling have been investigated as possible damage
mitigation approaches. We also discuss, through a space radiation simulation,
the suitability of such devices on several space mission case-studies.Comment: This is an author-created, un-copyedited version of an article
accepted for publication/published in Nuclear Instruments and Methods in
Physics Research Section A. The Version of Record is available online at
https://doi.org/10.1016/j.nima.2019.16272
Traceability validation of six enzyme measurements on the Abbott Alinity c analytical system
Background: Laboratory professionals should independently verify the correct implementation of metrological traceability of commercial measuring systems and determine if their performance is fit for purpose. We evaluated the trueness, uncertainty of measurements, and transferability of six clinically important enzyme measurements (alanine aminotransferase [ALT], alkaline phosphatase [ALP], aspartate aminotransferase [AST], creatine kinase [CK], \u3b3-glutamyltransferase [\u3b3GT], and lactate dehydrogenase [LDH]) performed on the Abbott Alinity c analytical system.
Methods: Target values and associated uncertainties were assigned to three pools for each enzyme by using the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference measurement procedures (RMPs) and the pools were then measured on the
Alinity system. Bias estimation and regression studies were performed, and the uncertainty associated with Alinity measurements was also estimated, using analytical performance specifications (APS) derived from biological variability of measurands as goals. Finally, to validate
the transferability of the obtained results, a comparison study between two Alinity systems located in Milan, Italy, and Bydgoszcz, Poland, was carried out.
Results: Correct implementation of traceability to the IFCC RMPs and acceptable measurement uncertainty fulfilling desirable (ALP, AST, LDH) or optimal APS (ALT, CK, \u3b3GT) was verified for all evaluated enzymes. An optimal alignment between the two Alinity systems located in
Milan and Bydgoszcz was also found for all enzyme measurements.
Conclusions: We confirmed that measurements of ALT, ALP, AST, CK, \u3b3GT, and LDH performed on the Alinity c analytical system are correctly standardized to the IFCC reference measurement systems and the system alignment is consistent between different platforms
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