1,829 research outputs found
Ground-state baryons in nonperturbative quark dynamics
We review the results obtained in an Effective Hamiltonian (EH) approach for
the three-quark systems. The EH is derived starting from the Feynman--Schwinger
representation for the gauge-invariant Green function of the three quarks
propagating in the nonperturbative QCD vacuum and assuming the minimal area law
for the asymptotic of the Wilson loop. It furnishes the QCD consistent
framework within which to study baryons. The EH has the form of the
nonrelativistic three-quark Hamiltonian with the perturbative Coulomb-like and
nonperturbative string interactions and the specific mass term. After outlining
the approach, methods of calculations of the baryon eigenenergies and some
simple applications are explained in details. With only two parameters: the
string tension and the strong coupling constant
a unified quantitative description of the ground state light
and heavy baryons is achieved. The prediction of masses of the doubly heavy
baryons not discovered yet are also given. In particular, a mass of
for the lightest baryon is found by employing the hyperspherical
formalism to the three quark confining potential with the string junction.Comment: 25 pages, 4 figures included, LaTeX 2e; to be published in Phys.
Atom. Nuc
Low-lying spectrum of the Y-string three-quark potential using hyper-spherical coordinates
We calculate the energies of three-quark states with definite permutation
symmetry (i.e. of SU(6) multiplets) in the N=0,1,2 shells, confined by the
Y-string three-quark potential. The exact Y-string potential consists of one,
so-called three-string term, and three angle-dependent two-string terms. Due to
this technical complication we treat the problem at three increasingly accurate
levels of approximation: 1) the (approximate) three-string potential expanded
to first order in trigonometric functions of hyper-spherical angles; 2) the
(approximate) three-string potential to all orders in the power expansion in
hyper-spherical harmonics, but without taking into account the transition(s) to
two-string potentials; 3) the exact minimal-length string potential to all
orders in power expansion in hyper-spherical harmonics, and taking into account
the transition(s) to two-string potentials. We show the general trend of
improvement %convergence of these approximations: The exact non-perturbative
corrections to the total energy are of the order of one per cent, as compared
with approximation 2), yet the exact energy differences between the
-plets are shifted to 2:2:0.9,
from the Bowler and Tynemouth separation rule 2:2:1, which is obeyed by
approximation 2) at the one per cent level. The precise value of the energy
separation of the first radial excitation ("Roper") -plet
from the -plet depends on the approximation, but does not become
negative, i.e. the "Roper" remains heavier than the odd-parity
-plet in all of our approximations.Comment: 19 pages, 6 figure
Sub-wavelength lithography over extended areas
We demonstrate a systematic approach to sub-wavelength resolution
lithographic image formation on films covering areas larger than a wavelength
squared. For example, it is possible to make a lithographic pattern with a
feature size resolution of by using a particular -photon, multi-mode entangled state, where , and banks of birefringent
plates. By preparing a statistically mixed such a state one can form any pixel
pattern on a pixel grid occupying a square
with a side of wavelengths. Hence, there is a trade-off between
the exposed area, the minimum lithographic feature size resolution, and the
number of photons used for the exposure. We also show that the proposed method
will work even under non-ideal conditions, albeit with somewhat poorer
performance.Comment: 8 pages, 8 figures, 1 table. Written in RevTe
Electron shakeoff following the ÎČ+ decay of trapped 35Ar+ ions
The electron shakeoff of 35Cl atoms resulting from the ÎČ+ decay of 35Ar+ ions has been investigated using a Paul trap coupled to a recoil-ion spectrometer. The charge-state distribution of the recoiling daughter nuclei is compared to theoretical calculations accounting for shakeoff and Auger processes. The calculations are in excellent agreement with the experimental results and enable one to identify the ionization reaction routes leading to the formation of all charge states.D.R. acknowledges support from the Spanish ministry of Economy and Competitiveness under the project FPA2010-14803 and the action AIC10-D000562
Numerical approximation of the Euler-Poisson-Boltzmann model in the quasineutral limit
This paper analyzes various schemes for the Euler-Poisson-Boltzmann (EPB)
model of plasma physics. This model consists of the pressureless gas dynamics
equations coupled with the Poisson equation and where the Boltzmann relation
relates the potential to the electron density. If the quasi-neutral assumption
is made, the Poisson equation is replaced by the constraint of zero local
charge and the model reduces to the Isothermal Compressible Euler (ICE) model.
We compare a numerical strategy based on the EPB model to a strategy using a
reformulation (called REPB formulation). The REPB scheme captures the
quasi-neutral limit more accurately
Srs2 removes deadly recombination intermediates independently of its interaction with SUMO-modified PCNA
Saccharomyces cerevisiae Srs2 helicase plays at least two distinct functions. One is to prevent recombinational repair through its recruitment by sumoylated Proliferating Cell Nuclear Antigen (PCNA), evidenced in postreplication-repair deficient cells, and a second one is to eliminate potentially lethal intermediates formed by recombination proteins. Both actions are believed to involve the capacity of Srs2 to displace Rad51 upon translocation on single-stranded DNA (ssDNA), though a role of its helicase activity may be important to remove some toxic recombination structures. Here, we described two new mutants, srs2R1 and srs2R3, that have lost the ability to hinder recombinational repair in postreplication-repair mutants, but are still able to remove toxic recombination structures. Although the mutants present very similar phenotypes, the mutated proteins are differently affected in their biochemical activities. Srs2R1 has lost its capacity to interact with sumoylated PCNA while the biochemical activities of Srs2R3 are attenuated (ATPase, helicase, DNA binding and ability to displace Rad51 from ssDNA). In addition, crossover (CO) frequencies are increased in both mutants. The different roles of Srs2, in relation to its eventual recruitment by sumoylated PCNA, are discussed
Identification of cryptolepine metabolites in rat and human hepatocytes and metabolism and pharmacokinetics of cryptolepine in Sprague Dawley rats
YesBackground: This study aims at characterizing the in vitro metabolism of cryptolepine using human and rat
hepatocytes, identifying metabolites in rat plasma and urine after a single cryptolepine dose, and evaluating the
single-dose oral and intravenous pharmacokinetics of cryptolepine in male Sprague Dawley (SD) rats.
Methods: The in vitro metabolic profiles of cryptolepine were determined by LC-MS/MS following incubation with
rat and human hepatocytes. The in vivo metabolic profile of cryptolepine was determined in plasma and urine
samples from Sprague Dawley rats following single-dose oral administration of cryptolepine. Pharmacokinetic
parameters of cryptolepine were determined in plasma and urine from Sprague Dawley rats after single-dose
intravenous and oral administration.
Results: Nine metabolites were identified in human and rat hepatocytes, resulting from metabolic pathways
involving oxidation (M2-M9) and glucuronidation (M1, M2, M4, M8, M9). All human metabolites were found in rat
hepatocyte incubations except glucuronide M1. Several metabolites (M2, M6, M9) were also identified in the urine
and plasma of rats following oral administration of cryptolepine. Unchanged cryptolepine detected in urine was
negligible. The Pharmacokinetic profile of cryptolepine showed a very high plasma clearance and volume of
distribution (Vss) resulting in a moderate average plasma half-life of 4.5 h. Oral absorption was fast and plasma
exposure and oral bioavailability were low.
Conclusions: Cryptolepine metabolism is similar in rat and human in vitro with the exception of direct glucuronidation
in human. Clearance in rat and human is likely to include a significant metabolic contribution, with proposed primary
human metabolism pathways hydroxylation, dihydrodiol formation and glucuronidation. Cryptolepine showed extensive
distribution with a moderate half-life.Funded by Novartis Pharma under the Next Generation Scientist Program
Physical activity to improve cognition in older adults: can physical activity programs enriched with cognitive challenges enhance the effects? A systematic review and meta-analysis
: EPHPP quality rating scores (DOCX 38 kb
Continuous variable entanglement and quantum state teleportation between optical and macroscopic vibrational modes through radiation pressure
We study an isolated, perfectly reflecting, mirror illuminated by an intense
laser pulse. We show that the resulting radiation pressure efficiently
entangles a mirror vibrational mode with the two reflected optical sideband
modes of the incident carrier beam. The entanglement of the resulting
three-mode state is studied in detail and it is shown to be robust against the
mirror mode temperature. We then show how this continuous variable entanglement
can be profitably used to teleport an unknown quantum state of an optical mode
onto the vibrational mode of the mirror.Comment: 18 pages, 10 figure
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