162 research outputs found
Decoherence and entanglement degradation of a qubit-qutrit system in non-inertial frames
We study the effect of decoherence on a qubit-qutrit system under the
influence of global, local and multilocal decoherence in non-inertial frames.
We show that the entanglement sudden death can be avoided in non-inertial
frames in the presence of amplitude damping, depolarizing and phase damping
channels. However, degradation of entanglement is seen due to Unruh effect. It
is shown that for lower level of decoherence, the depolarizing channel degrades
the entanglement more heavily as compared to the amplitude damping and phase
damping channels. However, for higher values of decoherence parameters,
amplitude damping channel heavily degrades the entanglement of the hybrid
system. Further more, no ESD is seen for any value of Rob's acceleration.Comment: 16 pages, 5 .eps figures, 1 table; Quantum Information Processing,
published online, 5 July, 201
SU(3) symmetry breaking in lower fp-shell nuclei
Results of shell-model calculations for lower fp-shell nuclei show that SU(3)
symmetry breaking in this region is driven by the single-particle spin-orbit
splitting. However, even though states of the yrast band exhibit SU(3) symmetry
breaking, the results also show that the yrast band B(E2) values are
insensitive to this fragmentation of the SU(3) symmetry; specifically, the
quadrupole collectivity as measured by B(E2) transition strengths between low
lying members of the yrast band remain high even though SU(3) appears to be
broken. Results for and using the Kuo-Brown-3
two-body interaction are given to illustrate these observations.Comment: Updated to the published versio
The Stellar Content and Star Formation History of the late-type spiral galaxy NGC 300 from Hubble Space Telescope observations
We present the first WFPC2 V, I photometry for the Sculptor Group galaxy NGC
300 in four fields ranging from the centre to the outer edge. We have made the
first measurement of the star formation histories in two disk fields: the
oldest stars were born at similar epochs and formation activity increased but
at different mean rates. The main disk stellar population is predominantly old,
consisting of RGB and AGB stars, based on a synthetic colour magnitude diagram
analysis. Z is found to have been more metal poor than 0.006 (or 0.33Zsolar)
with no evidence for significant change in the mean Z value over time in both
disk fields. In the central region, we find a dearth of bright stars with
respect to the two disk fields that cannot be explained by observational
effects. Taken at face value, this finding would agree with the Davidge (1998)
report of suppressed star formation there during the past 1Gyr with respect to
his disk fields at larger radii; but the possibility of significant central
extinction affecting our finding remains. We have also determined the first
distance modulus estimate based on the tip of the red giant branch method: on
the Cepheid distance scale of Ferrarese et al. (2000) we find (m-M)o =
26.56+/-0.07 (+/-0.13) mag; and a similar value from the Cepheid-independent
empirical method by Lee et al. (1993), both in good agreement with the Cepheid
distance determined by Freedman et al. (2001). A discrepancy between this and
the theoretical calibration of the red giant branch tip magnitude method
remains. Finally, we report a newly detected young (up to about 10Myr) stellar
association of about average size (~140pc) in one of the disk fields.Comment: 47 pages, 12 figures (the quality of Figures 1 and 6 has been
degraded), Corrected minor textual errors and two reference omissions to
match the version to be published in The Astronomical Journa
Cross section measurements of 155,157Gd(n, γ) induced by thermal and epithermal neutrons
© SIF, Springer-Verlag GmbH Germany, part of Springer Nature 2019Neutron capture cross section measurements on 155Gd and 157Gd were performed using the time-of-flight technique at the n_TOF facility at CERN on isotopically enriched samples. The measurements were carried out in the n_TOF experimental area EAR1, at 185 m from the neutron source, with an array of 4 C6D6 liquid scintillation detectors. At a neutron kinetic energy of 0.0253 eV, capture cross sections of 62.2(2.2) and 239.8(8.4) kilobarn have been derived for 155Gd and 157Gd, respectively, with up to 6% deviation relative to values presently reported in nuclear data libraries, but consistent with those values within 1.6 standard deviations. A resonance shape analysis has been performed in the resolved resonance region up to 181 eV and 307 eV, respectively for 155Gd and 157Gd, where on average, resonance parameters have been found in good agreement with evaluations. Above these energies and up to 1 keV, the observed resonance-like structure of the cross section has been analysed and characterised. From a statistical analysis of the observed neutron resonances we deduced: neutron strength function of 2. 01 (28) × 10 - 4 and 2. 17 (41) × 10 - 4; average total radiative width of 106.8(14) meV and 101.1(20) meV and s-wave resonance spacing 1.6(2) eV and 4.8(5) eV for n + 155Gd and n + 157Gd systems, respectively.Peer reviewedFinal Accepted Versio
Optimal Design of a Trickle Bed Reactor for Light Fuel Oxidative Desulfurization based on Experiments and Modelling
YesIn this work, the performance of oxidative desulfurization (ODS) of dibenzothiophene (DBT) in light gas oil (LGO) is evaluated with a homemade manganese oxide (MnO2/γ-Al2O3) catalyst. The catalyst is prepared by Incipient Wetness Impregnation (IWI) method with air under moderate operating conditions. The effect of different reaction parameters such as reaction temperature, liquid hour space velocity and initial concentration of DBT are also investigated experimentally. Developing a detailed and a validated trickle bed reactor (TBR) process model that can be employed for design and optimization of the ODS process, it is important to develop kinetic models for the relevant reactions with high accuracy. Best kinetic model for the ODS process taking into account hydrodynamic factors (mainly, catalyst effectiveness factor, catalyst wetting efficiency and internal diffusion) and the physical properties affecting the oxidation process is developed utilizing data from pilot plant experiments. An optimization technique based upon the minimization of the sum of the squared error between the experimental and predicted composition of oxidation process is used to determine the best parameters of the kinetic models. The predicted product conversion showed very good agreement with the experimental data for a wide range of the operating condition with absolute average errors less than 5%
Multi-Scale Simulations Provide Supporting Evidence for the Hypothesis of Intramolecular Protein Translocation in GroEL/GroES Complexes
The biological function of chaperone complexes is to assist the folding of non-native proteins. The widely studied GroEL chaperonin is a double-barreled complex that can trap non-native proteins in one of its two barrels. The ATP-driven binding of a GroES cap then results in a major structural change of the chamber where the substrate is trapped and initiates a refolding attempt. The two barrels operate anti-synchronously. The central region between the two barrels contains a high concentration of disordered protein chains, the role of which was thus far unclear. In this work we report a combination of atomistic and coarse-grained simulations that probe the structure and dynamics of the equatorial region of the GroEL/GroES chaperonin complex. Surprisingly, our simulations show that the equatorial region provides a translocation channel that will block the passage of folded proteins but allows the passage of secondary units with the diameter of an alpha-helix. We compute the free-energy barrier that has to be overcome during translocation and find that it can easily be crossed under the influence of thermal fluctuations. Hence, strongly non-native proteins can be squeezed like toothpaste from one barrel to the next where they will refold. Proteins that are already fairly close to the native state will not translocate but can refold in the chamber where they were trapped. Several experimental results are compatible with this scenario, and in the case of the experiments of Martin and Hartl, intra chaperonin translocation could explain why under physiological crowding conditions the chaperonin does not release the substrate protein
Characterization of carbapenem-resistant Pseudomonas aeruginosa clinical isolates, carrying multiple genes coding for this antibiotic resistance
Bringing Molecules Back into Molecular Evolution
Much molecular-evolution research is concerned with sequence analysis. Yet these sequences represent real, three-dimensional molecules with complex structure and function. Here I highlight a growing trend in the field to incorporate molecular structure and function into computational molecular-evolution work. I consider three focus areas: reconstruction and analysis of past evolutionary events, such as phylogenetic inference or methods to infer selection pressures; development of toy models and simulations to identify fundamental principles of molecular evolution; and atom-level, highly realistic computational modeling of molecular structure and function aimed at making predictions about possible future evolutionary events
An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561
Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a
full characterisation of the planetary system orbiting the late G dwarf
TOI-561. After the identification of three transiting candidates by TESS, we
discovered two additional external planets from RV analysis. RVs cannot confirm
the outer TESS transiting candidate, which would also make the system
dynamically unstable. We demonstrate that the two transits initially associated
with this candidate are instead due to single transits of the two planets
discovered using RVs. The four planets orbiting TOI-561 include an ultra-short
period (USP) super-Earth (TOI-561 b) with period d, mass
M and radius
R, and three mini-Neptunes: TOI-561 c, with d,
M, R;
TOI-561 d, with d, M,
R; and TOI-561 e, with
d, M,
R. Having a density of g cm, TOI-561 b is the
lowest density USP planet known to date. Our N-body simulations confirm the
stability of the system and predict a strong, anti-correlated, long-term
transit time variation signal between planets d and e. The unusual density of
the inner super-Earth and the dynamical interactions between the outer planets
make TOI-561 an interesting follow-up target
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