1,443 research outputs found
Electrically neutral Dirac particles in the presence of external fields: exact solutions
In the present article we present exact solutions of the Dirac equation for
electric neutral particles with anomalous electric and magnetic moments. Using
the algebraic method of separation of variables, the Dirac equation is
separated in cartesian, cylindrical and spherical coordinates, and exact
solutions are obtained in terms of special functions.Comment: 20pp, IVIC-CFLE-93/02 (this is a version without Tex problems, the
first version was corrupted
Quark mass correction to the string potential
A consistent method for calculating the interquark potential generated by the
relativistic string with massive ends is proposed. In this approach the
interquark potential in the model of the Nambu--Goto string with point--like
masses at its ends is calculated. At first the calculation is done in the
one--loop approximation and then the variational estimation is performed. The
quark mass correction results in decreasing the critical distance
(deconfinement radius). When quark mass decreases the critical distance also
decreases. For obtaining a finite result under summation over eigenfrequencies
of the Nambu--Goto string with massive ends a suitable mode--by--mode
subtraction is proposed. This renormalization procedure proves to be completely
unique. In the framework of the developed approach the one--loop interquark
potential in the model of the relativistic string with rigidity is also
calculated.Comment: 34 pages, LATE
Separation of suspended particles in microfluidic systems by directional-locking in periodic fields
We investigate the transport and separation of overdamped particles under the
action of a uniform external force in a two-dimensional periodic energy
landscape. Exact results are obtained for the deterministic transport in a
square lattice of parabolic, repulsive centers that correspond to a
piecewise-continuous linear-force model. The trajectories are periodic and
commensurate with the obstacle lattice and exhibit phase-locking behavior in
that the particle moves at the same average migration angle for a range of
orientation of the external force. The migration angle as a function of the
orientation of the external force has a Devil's staircase structure. The first
transition in the migration angle was analyzed in terms of a Poincare map,
showing that it corresponds to a tangent bifurcation. Numerical results show
that the limiting behavior for impenetrable obstacles is equivalent to the high
Peclet number limit in the case of transport of particles in a periodic pattern
of solid obstacles. Finally, we show how separation occurs in these systems
depending on the properties of the particles
Vocabulary intervention for adolescents with language disorder: a systematic review
Background: Language disorder and associated vocabulary difficulties can persist into adolescence, and can impact on long-term life outcomes. Previous reviews have shown that a variety of intervention techniques can successfully enhance students’ vocabulary skills; however, none has investigated vocabulary intervention specifically for adolescents with language disorder.
Aims: To carry out a systematic review of the literature on vocabulary interventions for adolescents with language disorder.
Methods & Procedures: A systematic search of 14 databases and other sources yielded 1320 studies, of which 13 met inclusion criteria. Inclusion criteria were: intervention effectiveness studies with a focus on enhancing oral receptive and/or expressive vocabulary skills in the study's aims; participants in the age range 11;0–16;11 with receptive and/or expressive language difficulties of any aetiology.
Main Contribution: There was a high degree of diversity between studies. Types of intervention included: semantic intervention (four studies); comparison of phonological versus semantic intervention (two); and combined phonological–semantic intervention (seven). The strongest evidence for effectiveness was found with a combined phonological–semantic approach. The evidence suggested a potential for all models of delivery to be helpful (individual, small group and whole class).
Conclusions & Implications: Tentative evidence is emerging for the effectiveness of a phonological–semantic approach in enhancing the vocabulary skills of adolescents who have language disorder. Future research needs to refine and develop the methodologies used in this diverse group of studies in order to replicate their findings and to build consensus
Synthesis of technetium hydride TcH at 27 GPa
In this work, we synthesize and investigate lower technetium hydrides at
pressures up to 45 GPa using the synchrotron X-ray diffraction, reflectance
spectroscopy, and ab initio calculations. In the Tc-H system, the hydrogen
content in TcH phases increases when the pressure rises, and at 27 GPa we
found a new hexagonal (hcp) nonstoichiometric hydride TcH. The
formation of technetium hydrides is also confirmed by the emergence of a new
reflective band at 450-600 nm in the reflectance spectra of TcH samples
synthesized at 45 GPa. On the basis of the theoretical analysis, we proposed
crystal structures for the TcH (TcH) and
TcH (TcH) phases previously obtained at 1-2 GPa. The
calculations of the electron-phonon interaction show that technetium hydrides
TcH do not possess superconducting properties due to the low
electron-phonon interaction parameter ()
Comparison of voluntary food intake and palatability of commercial weight loss diets in healthy dogs and cats
Background Obesity in dogs and cats is usually managed by dietary energy restriction using a purpose-formulated weight loss diet, but signs of hunger and begging commonly occur causing poor owner compliance. Altering diet characteristics so as to reduce voluntary food intake (VFI) can improve the likelihood of success, although this should not be at the expense of palatability. The aim of the current study was to compare the VFI and palatibility of novel commercially available canine and feline weight loss diets. Methods The relative performance of two canine (C1 and C2) and two feline (F1 and F2) diets was assessed in groups of healthy adult dogs and cats, respectively. Diets varied in energy, protein, fibre, and fat content. To assess canine VFI, 12 (study 1) and 10 (study 2) dogs were offered food in 4 meals, for 15 min on each occasion, with hourly intervals between the meals. For feline VFI, 12 cats were offered food ad libitum for a period of 18 h per day over 5 consecutive days. The palatability studies used separate panels of 37 dogs and 30 cats, with the two diets being served, side-by-side, in identical bowls. Results In dogs, VFI was significantly less for diet C1 than diet C2 when assessed on energy intake (study 1, 42% less, P = 0.032; study 2, 28% less, P = 0.019), but there was no difference in gram weight intake (study 1: P = 0.964; study 2: P = 0.255). In cats, VFI was 17% less for diet F1 than diet F2 when assessed by energy intake (P < 0.001), but there was again no difference in gram weight (P = 0.207). There was no difference in palatability between the two canine diets (P = 0.490), whilst the panel of cats diet preferred F1 to F2 (P < 0.001). Conclusion Foods with different characteristics can decrease VFI without affecting palatability in both dogs and cats. The effects seen could be due to decreased energy content, decreased fat content, increased fibre content, different fibre source, and increased protein content. Further studies are now needed to determine whether similar findings occur in obese dogs and cats on controlled weight loss programmes
String Nature of Confinement in (Non-)Abelian Gauge Theories
Recent progress achieved in the solution of the problem of confinement in
various (non-)Abelian gauge theories by virtue of a derivation of their string
representation is reviewed. The theories under study include QCD within the
so-called Method of Field Correlators, QCD-inspired Abelian-projected theories,
and compact QED in three and four space-time dimensions. Various
nonperturbative properties of the vacua of the above mentioned theories are
discussed. The relevance of the Method of Field Correlators to the study of
confinement in Abelian models, allowing for an analytical description of this
phenomenon, is illustrated by an evaluation of field correlators in these
models.Comment: 100 pages, LaTeX2e, no figures, 1 table, based on the Ph.D. thesises
at the Humboldt University of Berlin (1999) (available under
http://dochost.rz.hu-berlin.de) and the Institute of Theoretical and
Experimental Physics, Moscow (2000), new results are included, extended with
respect to the journal versio
Three Year Prognosis of Patients with Myocardial Infarction Depending on the Body Weight Index: Data of the Kemerovo Acute Coronary Syndrome Registry
Aim. To study the effect of body mass index (BMI) on the 3-year prognosis of patients after myocardial infarction (MI).Material and methods. The study is based on data from a 3-year observation of patients with MI from the Kemerovo registry of acute coronary syndrome (n=1366). The characteristics of patients with MI, distributed by the BMI, were determined, the outcomes were analyzed, the risk factors and predictors for the vascular events and mortality were identified.Results. Obesity was detected in 32.2% people with MI (I degree – 22.3%; II – 7.7%; III – 2.3%), lack of BMI at 0.5%, normal BMI at 20.5%, overweight at 46.9%. Patients with different BMI showed a comparable incidence of recurring MI. In patients with normal BMI, when compared with patients with obesity, unstable angina pectoris (UA), heart failure (HF) and strokes developed often. In patients with normal BMI compared with obese patients, fewer deaths from all causes were recorded within 3 years after MI. A similar pattern with respect to the group with normal BMI in terms of high overall mortality was obtained among patients with overweight who had a lower UA. Patients with obesity was favorable in relation to the development of HF, strokes and overall mortality than patients with overweight. Differences in the 3-year outcomes in the group of patients with MI and underweight were not found when compared with patients with normal and overweight, however, they had a higher of strokes compared with patients with obesity. At patients with I degree obesity within 3 years after MI UA, HF, strokes were less. Patients with III degree obesity, the maximum frequency of total mortality was recorded. The development of death from all causes during the observation period in patients with MI and obesity was associated with: male, smoking, multivessel arterial diseases, non-endovascular reperfusion, acute HF with MI, history of vascular events and angina pectoris; whereas with overweight: multifocal atherosclerosis and arterial hypertension; with a deficit of BMI: non-reperfusion; with normal BMI: heredity for cardiovascular diseases, dyslipidemia and atrial fibrillation.Conclusion. 3 years after MI patients with obesity of the I degree are less likely than patients with obesity of II-III deaths from all causes are recorded; these patients are less likely than patients with normal weight to develop strokes, HF, UA. Thus, patients with MI and the presence of I degree obesity are characterized by better survival during 3 years of observation
On Possible Light-Torsion Mixing in Background Magnetic Field
The interaction of the light with propagating axial torsion fields in the
presence of an external magnetic field has been investigated. Axial torsion
fields appearing in higher derivative quantum gravity possess two states, with
spin one and zero, with different masses. The torsion field with spin-0 state
is a ghost that can be removed if its mass is infinite. We investigate the
possibility when the light mixes with the torsion fields resulting in the
effect of vacuum birefringence and dichroism. The expressions for ellipticity
and the rotation of light polarization axis depending on the coupling constant
and the external magnetic field have been obtained.Comment: 12 pages, title changed, shortened journal version, accepted in
Eur.Phys.J.
Bastroviruses (<i>Astroviridae</i>): genetic diversity and potential impact on human and animal health
Introduction. Bastroviruses were discovered in the Netherlands in 2016 in human stool samples and show partial genetic similarities to astroviruses and hepatitis E viruses. Their association with disease onset has not yet been established.
Materials and methods. Metagenomic sequencing of fecal samples of Nyctalus noctula bats collected in the Russian Federation in 2023 was performed. Two almost complete genomes of bastroviruses were assembled. The zoonotic potential of these viruses was assessed using machine learning methods, their recombination was studied, and phylogenetic trees were constructed.
Results. A nearly complete bastrovirus genome was de novo assembled in one of the samples, and it was used to assemble another genome in another sample. The zoonotic potential of the virus from one of these samples was estimated as high. The existence of recombination between structural and non-structural polyproteins was demonstrated.
Conclusion. Two bastrovirus genomes were assembled, phylogenetic and recombination analyses were performed, and the zoonotic potential was evaluated
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