2,810 research outputs found
Differences in Neurocognitive Abilities in Premature and Full-term Infants at 5 Months of Age
It is known that prematurity is a risk for neurodevelopmental disorders. Most of the studies were dedicated to those children who have reached the preschool and primary school age. However, the impact of prematurity on neurocognitive functions in the early stages of development is not investigated thoroughly. The aim of thisresearch was to reveal the differences in neurocognitive development in premature (24 babies) and gender-matched healthy mature full-term infants (31 participants) at 5 months of age. The gestational age of preterm children was between 29 and 35 weeks. The Bayley Scales of Infant and Toddler Development (3rd Edition) were used to evaluate the neurocognitive abilities in children. The one-way ANOVA has revealedthat premature infants at 5 months of corrected age performed significantly (p ≤ 0.05) more poorly than the full-term infants on cognitive scale, receptive language, gross and fine motor. No significant differences (p ≤.05) were found between preterm and full-term children on expressive language. In view of the obtained results, itcan be assumed that the prematurity has specific (not global) negative effect on neurocognitive development at 5 months of age.
Keywords: premature infants, neurocognitive development, Bayley Scales of Infant and Toddler Development (3rd Edition
Prospects for the Bc Studies at LHCb
We discuss the motivations and perspectives for the studies of the mesons of
the (bc) family at LHCb. The description of production and decays at LHC
energies is given in details. The event yields, detection efficiencies, and
background conditions for several Bc decay modes at LHCb are estimated.Comment: 20 pages, 5 eps-figure
Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones
Bulk samples of carbon multilayer nanotubes with the structure of nested
cones (fishbone structure) suitable for transport measurements, were prepared
by compressing under high pressure (~25 kbar) a nanotube precursor synthesized
through thermal decomposition of polyethylene catalyzed by nickel. The
structure of the initial nanotube material was studied using high-resolution
transmission electron microscopy. In the low-temperature range (4.2 - 100 K)
the electric resistance of the samples changes according to the law ln \rho ~
(T_0/T)^{1/3}, where T_0 ~ 7 K. The measured magnetoresistance is quadratic in
the magnetic field and linear in the reciprocal temperature. The measurements
have been interpreted in terms of two-dimensional variable-range hopping
conductivity. It is suggested that the space between the inside and outside
walls of nanotubes acts as a two-dimensional conducting medium. Estimates
suggest a high value of the density of electron states at the Fermi level of
about 5 10^{21} eV^{-1} cm^{-3}.Comment: 8 pages, 4 figures. EM photographic images on figures 1a, 1b, 1c
attached as JPG files. For correspondence mail to [email protected]
Two-particle decays of B_c meson into charmonium states
The factorization of hard and soft contributions into the hadronic decays of
B_c meson at large recoils is explored in order to evaluate the decay rates
into the S, P and D-wave charmonia associated with rho and pi. The constraints
of approach applicability and uncertainties of numerical estimates are
discussed. The mode with the J/psi in the final state is evaluated taking into
account the cascade radiative electromagnetic decays of excited P-wave states,
that enlarges the branching ratio by 20-25%.Comment: 13 pages, LaTeX axodraw-style, 1 figure, 2 table
Gold-plated Mode of CP-Violation in Decays of B_c Meson from QCD Sum Rules
The model-independent method based on the triangle ideology is implemented to
extract the CKM-matrix angle gamma in the decays of doubly heavy long-lived
meson B_c. We analyze a color structure of diagrams and conditions to
reconstruct two reference-triangles by tagging the flavor and CP eigenstates of
D^0 meson in the fixed exclusive channels. The characteristic branching ratios
are evaluated in the framework of QCD sum rules.Comment: 11 pages, RevTeX4 file, 4 eps-figure
Ferrimagnetic mixed-spin ladders in weak and strong coupling limits
We study two similar spin ladder systems with the ferromagnetic leg coupling.
First model includes two sorts of spins, s= 1/2 and s= 1, and the second model
comprises only s=1/2 legs coupled by a "triangular" rung exchange. The
antiferromagnetic (AF) rung coupling destroys the long-range order and
eventually makes the systems equivalent to the AF s=1/2 Heisenberg chain. We
investigate the situation by different methods in weak and strong rung coupling
limits. Particularly we compare the spin-wave theory and the bosonization
method in the weak coupling regime of the second model. We analyze the spectra
and correlations, and discuss the order parameter of these ladder systems.Comment: 12 pages, 4 figure
Mass spectra of doubly heavy Omega_QQ' baryons
We evaluate the masses of baryons composed of two heavy quarks and a strange
quark with account for spin-dependent splittings in the framework of potential
model with the KKO potential motivated by QCD with a three-loop beta-function
for the effective charge consistent with both the perturbative limit at short
distances and linear confinement term at long distances between the quarks. The
factorization of dynamics is supposed and explored in the nonrelativistic
Schroedinger equation for the motion in the system of two heavy quarks
constituting the doubly heavy diquark and the strange quark interaction with
the diquark. The limits of approach, its justification and uncertainties are
discussed. Excited quasistable states are classified by the quantum numbers of
heavy diquark composed by the heavy quarks of the same flavor.Comment: 14 pages, revtex4-file, 3 eps-figures, 5 tables, typos correcte
Physics of B_c mesons
In the framework of potential models for heavy quarkonium the mass spectrum
for the system () is considered. Spin-dependent splittings, taking
into account a change of a constant for effective coulomb interaction between
the quarks, and widths of radiative transitions between the () levels
are calculated. In the framework of QCD sum rules, masses of the lightest
vector and pseudoscalar states are estimated, scaling relation
for leptonic constants of heavy quarkonia is derived, and the leptonic constant
is evaluated. The decays are considered in the framework of
both the potential models and the QCD sum rules, where the significance of
Coulomb-like corrections is shown. The relations, following from the
approximate spin symmetry for the heavy quarks in the heavy quarkonium, are
analysed for the form factors of the semileptonic weak exclusive decays of
. The lifetime is evaluated with the account of the corrections to
the spectator mechanism of the decay, because of the quark binding into the
meson. The total and differential cross sections of the production in
different interactions are calculated. The analytic expressions for the
fragmentational production cross sections of are derived. The possibility
of the practical search in the current and future experiments at
electron-positron and hadron colliders is analysed.Comment: 81 page, latex, ihep.sty is required and attached in the end of the
file after \end{document}, figures are not availabl
Expression, Processing, and Localization of PmpD of Chlamydia trachomatis Serovar L2 during the Chlamydial Developmental Cycle
BACKGROUND: While families of polymorphic membrane protein (pmp) genes have been identified in several Chlamydia species, their function remains mostly unknown. These proteins are of great interest, however, because of their location in the outer membrane and possible role in chlamydial virulence. METHODOLOGY/PRINCIPAL FINDING: We analyzed the relative transcription of the pmpD gene, a member of the pmp gene family in C. trachomatis serovar L2, and its protein product translation and processing during the chlamydial developmental cycle. By real-time reverse transcription polymerase chain reaction, the pmpD gene was found to be upregulated at 16 to 24 four hours after infection. Using polyclonal antibodies generated against the predicted passenger domain of PmpD, we demonstrated that it is initially localized on the surface of reticulate bodies, followed by its secretion outside Chlamydia starting at 24 hours after infection. In elementary bodies, we found a approximately 157 kDa PmpD only inside the cell. Both events, the upregulation of pmpD gene transcription and PmpD protein processing and secretion, are coincidental with the period of replication and differentiation of RBs into EBs. We also demonstrated that, in the presence of penicillin, the cleavage and secretion of the putative passenger domain was suppressed. CONCLUSION/SIGNIFICANCE: Our results are in agreement with the general concept that PmpD is an autotransporter protein which is post-translationally processed and secreted in the form of the putative passenger domain outside Chlamydia at mid- to- late point after infection, coinciding with the development of RBs into EBs
Damped orbital excitations in the titanates
A possible mechanism for the removal of the orbital degeneracy in RTiO3
(where R=La, Y, ...) is considered. The calculation is based on the
Kugel-Khomskii Hamiltonian for electrons residing in the t2g orbitals of the Ti
ions, and uses a self-consistent pe rturbation expansion in the interaction
between the orbital and the spin degrees of freedom. The latter are assumed to
be ordered in a Neel state, brought about by delicate interactions that are not
included in the Kugel-Khomskii Hamiltonian. Within our model calculations, each
of the t2g bands is found to acquire a finite, temperature-dependent
dispersion, that lifts the orbital degeneracy. The orbital excitations are
found to be heavily damped over a rather wide band. Consequently, they do not
participate as a separate branch of excitations in the low-temperature
thermodynamics.eComment: 6 pages, 3 figure
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