243 research outputs found
Quantum effects in the radial thermal expansion of bundles of single-walled carbon nanotubes doped with 4He
The radial thermal expansion (ar) of bundles of single-walled carbon
nanotubes saturated with 4He impurities to the molar concentration 9.4% has
been investigated in the interval 2.5-9.5 K using the dilatometric method. In
the interval 2.1-3.7 K (ar) is negative and is several times higher than the
negative (ar) for pure nanotube bundles. This most likely points to 4He atom
tunneling between different positions in the nanotube bundle system. The excess
expansion was reduced with decreasing 4He concentration.Comment: 4 pages, 1 figure, will be published in Fiz.Nizk Temp. #7, 201
On the structure of subsets of an orderable group with some small doubling properties
The aim of this paper is to present a complete description of the structure
of subsets S of an orderable group G satisfying |S^2| = 3|S|-2 and is
non-abelian
Lattice distortion in hcp rare gas solids
The lattice distortion parameter has been
calculated as a function of molar volume for the hcp phases of He, Ar, Kr and
Xe. Results from both semi-empirical potentials and density functional theory
are presented. Our study shows that is negative for helium in the
entire pressure range. For Ar, Kr and Xe, however, changes sign from
negative to positive as the pressure increases, growing rapidly in magnitude at
higher pressures.Comment: Submitted to Low. Temp. Phys., 14 pages, 5 figure
Poisson's ratio in cryocrystals under pressure
We present results of lattice dynamics calculations of Poisson's ratio (PR)
for solid hydrogen and rare gas solids (He, Ne, Ar, Kr and Xe) under pressure.
Using two complementary approaches - the semi-empirical many-body calculations
and the first-principle density-functional theory calculations we found three
different types of pressure dependencies of PR. While for solid helium PR
monotonically decreases with rising pressure, for Ar, Kr, and Xe it
monotonically increases with pressure. For solid hydrogen and Ne the pressure
dependencies of PR are non-monotonic displaying rather deep minimums. The role
of the intermolecular potentials in this diversity of patterns is discussed.Comment: Fizika Nizkikh Temperatur 41, 571 (2015
The Impact of the Functional Layer Composition of Glucose Test-Strips on the Stability of Electrochemical Response
Herein, the impact of the chemical stability of RedOx mediator ferricyanide, K3
[Fe(CN)6
]
(FC), a type of buffer solution used for bioreceptor preparation, gel composition (carboxymethylcellulose, CMC, Aerosile, AS, and alginate, ALG) on the long term stability of glucose test-strips and
their analytical performance was examined. By simple addition of ALG to the functional gel aiming
to improve its viscosity, we managed to enhance the sensitivity of conventional CMC-containing
amperometric glucose test-strips from 3.3 µA/mM to 3.9 µA/mM and extend their shelf life from
8 months to 1.7 years. Moreover, during the course of investigations, it was revealed that the activity
of enzyme in dependence with the used buffer did not linearly correlate with its activity in a dried
functional layer, and the entire long-term electrochemical signal of glucose test-strips was determined
by RedOx mediator FC chemical stability. The most stable and sensitive test-strips were obtained by
the screen-printing approach from a gel containing 24 mg/mL GOx prepared in citrate buffer with
pH 6, 200 mg/mL of FC and 10 mg/mL of CMC supplemented with 25 mg/mL of ALG
Mathematics education and technology
Recent international surveys such as the Organisation for Economic Co-operation and Development (OECD) report Students, Computers and Learning ( 2015) highlight the wide gap in students’ access to, and use of, technology in secondary mathematics in participating countries. The OECD “snapshot” methodology in which 15-year-old students were asked if they (or their teachers) had performed a range of mathematical tasks using computers in the month preceding their completion of the Programme for International Student Assessment (PISA) survey revealed low levels of technology use (see Fig. 1)
Low temperature heat capacity of fullerite C60 doped with nitrogen
The heat capacity Cm of polycrystalline fullerite C60 doped with nitrogen has
been measured in the temperature interval 2 - 13 K. The contributions to heat
capacity from translational lattice vibrations (Debye contribution),
orientational vibrations of the C60 molecules (Einstein contribution) and from
the motion of the N2 molecules in the octahedral cavities of the C60 lattice
have been estimated. However, we could not find (beyond the experimental error
limits) any indications of the first - order phase transformation that had been
detected earlier in the dilatometric investigation of the orientational N2-C60
glass. A possible explanation of this fact is proposed.Comment: 4 pages, 2 figures, to be published in Fiz. Nizk. Temp. (Low Temp.
Phys.
Effects of early neonatal proinflammatory stress on the expression of BDNF transcripts in the brain regions of prepubertal male rats
Early postnatal proinflammatory stress provokes behavioral impairments in adulthood; however, underlying mechanisms are still elusive. Brain-derived neurotrophic factor (BDNF) plays a crucial role in neuroplastic changes in health as well as at pathology. The BDNF gene is transcribed to exon-specific mRNAs and the pattern of their expression depends on stimulus. We suggest that disturbances of exonspecific BDNF mRNA expression in the brain regions after stress induced by proinflammatory stimuli in early postnatal period could be one of the underlying mechanisms of consequent behavioral impairments. Thus, the aim of the study was to investigate the effects of proinflammatory stress in early postnatal ontogeny on the expression of BDNF and the patterns of expression of the BDNF gene in the neocortex and hippocampus of prepubertal male rats. The proinflammatory stress was induced by subcutaneous administration of bacterial lipopolysaccharide (LPS) to rat pups on postnatal days 3 and 5, while BDNF expression was analyzed in 36-day-old rats. BDNF polypeptide concentration was estimated by means of an enzyme-linked immunosorbent assay, while quantitative polymerase chain reaction followed by reverse transcription was used to detect exon-specific BDNF mRNA expression. The levels of BDNF and transcripts, containing common exon IX were similar in the control and LPS-treated rats. In the rats treated with LPS, the level of BDNF mRNA, containing exon IV, was lower in the neocortex, but not in the hippocampus. No changes in the expression of the transcripts containing exons I and VI were observed in any brain structure studied. We suggest that specific alterations in BDNF expression may be involved in the susceptibility to the development of behavioral impairments of animals subjected to early proinflammatory stress
Small doubling in groups
Let A be a subset of a group G = (G,.). We will survey the theory of sets A
with the property that |A.A| <= K|A|, where A.A = {a_1 a_2 : a_1, a_2 in A}.
The case G = (Z,+) is the famous Freiman--Ruzsa theorem.Comment: 23 pages, survey article submitted to Proceedings of the Erdos
Centenary conferenc
Third order dielectric susceptibility in a model quantum paraelectric
In the context of perovskite quantum paraelectrics, we study the effects of a
quadrupolar interaction , in addition to the standard dipolar one .
We concentrate here on the nonlinear dielectric response , as
the main response function sensitive to quadrupolar (in our case
antiquadrupolar) interactions. We employ a 3D quantum four-state lattice model
and mean-field theory. The results show that inclusion of quadrupolar coupling
of moderate strength () is clearly accompanied by a
double change of sign of from negative to positive, near the
quantum temperature where the quantum paraelectric behaviour sets in. We
fit our to recent experimental data for SrTiO, where the
sign change is identified close to .Comment: 22 page
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