3,760 research outputs found
Управління трудовим потенціалом при створенні інноваційної продукції
Super-resolution microscopy (SRM) bypasses the diffraction limit, a physical barrier that restricts the optical resolution to roughly 250 nm and was previously thought to be impenetrable. SRM techniques allow the visualization of subcellular organization with unprecedented detail, but also confront biologists with the challenge of selecting the best-suited approach for their particular research question. Here, we provide guidance on how to use SRM techniques advantageously for investigating cellular structures and dynamics to promote new discoveries
Magnetic hysteresis in Ising-like dipole-dipole model
Using zero temperature Monte Carlo simulations we have studied the magnetic
hysteresis in a three-dimensional Ising model with nearest neighbor exchange
and dipolar interaction. The average magnetization of spins located inside a
sphere on a cubic lattice is determined as a function of magnetic field varied
periodically. The simulations have justified the appearance of hysteresis and
allowed us to have a deeper insight into the series of metastable states
developed during this process.Comment: REVTEX, 10 pages including 4 figure
Psychometric properties and validation of the Spanish versions of the overall anxiety and depression severity and impairment scales
Background: Anxiety and depressive disorders are the most frequent disorders for which patients seek care in public health settings in Spain. This study aimed at validating the Overall Anxiety Severity and Impairment Scale (OASIS) and the Overall Depression Severity and Impairment Scale (ODSIS), which are brief screening scales for anxiety and depression consisting of only five items each.
Methods: The study was conducted in a Spanish clinical sample receiving outpatient mental health treatment (N = 339). A subsample of participants (n = 219) was assessed before and after receiving a course of cognitive-behavioral treatment.
Results: The results revealed excellent internal consistency estimates (Cronbach's alpha for the OASIS and the ODSIS was 0.87 and 0.94, respectively), along with promising convergent and discriminant validity and test-criterion relationships (i.e., moderate correlation with other measures of depression and anxiety, as well as with neuroticism, quality of life, adjustment, and negative affect). A one-dimensional structure was obtained for the OASIS and the ODSIS. The ROC analyses indicated an area under the curve of 0.83 for the OASIS and the ODSIS when predicting moderate-to-severe anxiety and depression, respectively. Good sensitivity to therapeutic change was also evidence and the analysis of the sensitivity as a function of 1-specificity area suggested a cutoff value of 10 for both scales.
Limitations: Inter-rater reliability of diagnoses with the ADIS-IV interview could not be investigated and the results obtained may not be generalizable to other samples and health settings.
Conclusions: The availability of these two short and psychometrically sound measures should make screening of anxiety and depressive symptoms in routine care more feasible
Practical approximation scheme for the pion dynamics in the three-nucleon system
We discuss a working approximation scheme to a recently developed formulation
of the coupled piNNN-NNN problem. The approximation scheme is based on the
physical assumption that, at low energies, the 2N-subsystem dynamics in the
elastic channel is conveniently described by the usual 2N-potential approach,
while the explicit pion dynamics describes small, correction-type effects.
Using the standard separable-expansion method, we obtain a dynamical equation
of the Alt-Grassberger-Sandhas (AGS) type. This is an important result, because
the computational techniques used for solving the normal AGS equation can also
be used to describe the pion dynamics in the 3N system once the matrix
dimension is increased by one component. We have also shown that this
approximation scheme treats the conventional 3N problem once the pion degrees
of freedom are projected out. Then the 3N system is described with an extended
AGS-type equation where the spin-off of the pion dynamics (beyond the 2N
potential) is taken into account in additional contributions to the driving
term. These new terms are shown to reproduce the diagrams leading to modern
3N-force models. We also recover two sets of irreducible diagrams that are
commonly neglected in 3N-force discussions, and conclude that these sets should
be further investigated, because a claimed cancellation is questionable.Comment: 18 pages, including 5 figures, RevTeX, Eps
Light-front Ward-Takahashi Identity for Two-Fermion Systems
We propose a three-dimensional electromagnetic current operator within
light-front dynamics that satisfies a light-front Ward-Takahashi identity for
two-fermion systems. The light-front current operator is obtained by a
quasi-potential reduction of the four-dimensional current operator and acts on
the light-front valence component of bound or scattering states. A relation
between the light-front valence wave function and the four-dimensional
Bethe-Salpeter amplitude both for bound or scattering states is also derived,
such that the matrix elements of the four-dimensional current operator can be
fully recovered from the corresponding light-front ones. The light-front
current operator can be perturbatively calculated through a quasi-potential
expansion, and the divergence of the proposed current satisfies a
Ward-Takahashi identity at any given order of the expansion. In the
quasi-potential expansion the instantaneous terms of the fermion propagator are
accounted for by the effective interaction and two-body currents. We exemplify
our theoretical construction in the Yukawa model in the ladder approximation,
investigating in detail the current operator at the lowest nontrivial order of
the quasi-potential expansion of the Bethe-Salpeter equation. The explicit
realization of the light-front form of the Ward-Takahashi identity is verified.
We also show the relevance of instantaneous terms and of the pair contribution
to the two-body current and the Ward-Takahashi identity.Comment: 48 pages, 3 figure
Generalized isothermic lattices
We study multidimensional quadrilateral lattices satisfying simultaneously
two integrable constraints: a quadratic constraint and the projective Moutard
constraint. When the lattice is two dimensional and the quadric under
consideration is the Moebius sphere one obtains, after the stereographic
projection, the discrete isothermic surfaces defined by Bobenko and Pinkall by
an algebraic constraint imposed on the (complex) cross-ratio of the circular
lattice. We derive the analogous condition for our generalized isthermic
lattices using Steiner's projective structure of conics and we present basic
geometric constructions which encode integrability of the lattice. In
particular, we introduce the Darboux transformation of the generalized
isothermic lattice and we derive the corresponding Bianchi permutability
principle. Finally, we study two dimensional generalized isothermic lattices,
in particular geometry of their initial boundary value problem.Comment: 19 pages, 11 figures; v2. some typos corrected; v3. new references
added, higlighted similarities and differences with recent papers on the
subjec
Light-Front Bethe-Salpeter Equation
A three-dimensional reduction of the two-particle Bethe-Salpeter equation is
proposed. The proposed reduction is in the framework of light-front dynamics.
It yields auxiliary quantities for the transition matrix and the bound state.
The arising effective interaction can be perturbatively expanded according to
the number of particles exchanged at a given light-front time. An example
suggests that the convergence of the expansion is rapid. This result is
particular for light-front dynamics. The covariant results of the
Bethe-Salpeter equation can be recovered from the corresponding auxiliary
three-dimensional ones. The technical procedure is developed for a two-boson
case; the idea for an extension to fermions is given. The technical procedure
appears quite practicable, possibly allowing one to go beyond the ladder
approximation for the solution of the Bethe-Salpeter equation. The relation
between the three-dimensional light-front reduction of the field-theoretic
Bethe-Salpeter equation and a corresponding quantum-mechanical description is
discussed.Comment: 42 pages, 5 figure
Characterization of growth and metabolism of the haloalkaliphile Natronomonas pharaonis
Natronomonas pharaonis is an archaeon adapted to two extreme conditions: high salt concentration and alkaline pH. It has become one of the model organisms for the study of extremophilic life. Here, we present a genome-scale, manually curated metabolic reconstruction for the microorganism. The reconstruction itself represents a knowledge base of the haloalkaliphile's metabolism and, as such, would greatly assist further investigations on archaeal pathways. In addition, we experimentally determined several parameters relevant to growth, including a characterization of the biomass composition and a quantification of carbon and oxygen consumption. Using the metabolic reconstruction and the experimental data, we formulated a constraints-based model which we used to analyze the behavior of the archaeon when grown on a single carbon source. Results of the analysis include the finding that Natronomonas pharaonis, when grown aerobically on acetate, uses a carbon to oxygen consumption ratio that is theoretically near-optimal with respect to growth and energy production. This supports the hypothesis that, under simple conditions, the microorganism optimizes its metabolism with respect to the two objectives. We also found that the archaeon has a very low carbon efficiency of only about 35%. This inefficiency is probably due to a very low P/O ratio as well as to the other difficulties posed by its extreme environment
Why is the three-nucleon force so odd?
By considering a class of diagrams which has been overlooked also in the most
recent literature on three-body forces, we extract a new contribution to the
three-nucleon interaction which specifically acts on the triplet odd states of
the two nucleon subsystem. In the static approximation, this 3N-force
contribution is fixed by the underlying 2N interaction, so in principle there
are no free parameters to adjust. The 2N amplitude however enters in the 3NF
diagram in a form which cannot be directly accessed or constrained by NN
phase-shift analysis. We conclude that this new 3N-force contribution provides
a mechanism which implies that the presence of the third nucleon modifies the
p-wave (and possibly the f-wave) components of the 2N subsystem in the
triplet-isotriplet channels.Comment: 10 Pages, 7 figures, RevTeX, twocolumn, epsf (updated version with
minor changes
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