166 research outputs found
Stationary States in Bistable System Driven by L\'evy Noise
We study the properties of the probability density function (PDF) of a
bistable system driven by heavy tailed white symmetric L\'evy noise. The shape
of the stationary PDF is found analytically for the particular case of the
L\'evy index \alpha = 1 (Cauchy noise). For an arbitrary L\'evy index we employ
numerical methods based on the solution of the stochastic Langevin equation and
space fractional kinetic equation. In contrast with the bistable system driven
by Gaussian noise, in the L\'evy case the positions of maxima of the stationary
PDF do not coincide with the positions of minima of the bistable potential. We
provide a detailed study of the distance between the maxima and the minima as a
function of the potential's depth and L\'evy noise parameters.Comment: Accepted to EPJS
Management of patent ductus arteriosus in premature infants.
Closure of hemodynamically significant patent ductus arterios (HSPDA) is one of the most important questions in modern neonatal intensive care, especially for preterm babies. Long-term functioning of the hemodynamically significant arterial duct leads to a large number of complications in premature babies, such as: bronchopulmonary dysplasia, periventricular leucomalacia, intraventricular hemorrhage, retinopathy of the premature. To prevent all these complications, the PDA should be closed pharmacologically or surgically as soon as possible without any hesitation. COX inhibitors are commonly used nowa days. Ibuprofen and indomethacin show the equal efficacy and no significant adverse events. But some patients still need surgical treatment. The aim of the study was to determine the feasibility, effectiveness and safety of using various volumes of infusion in combination with COX inhibitors and to determine its effect on the timing of the closure of PDA. 91 premature infants with a gestational age of 26-31 weeks with manifestations of respiratory distress syndrome and НSPDA were studied retrospectively. Premies were divided into 2 groups. Research groups were representative as to gestational age, gender, and weight (1205.0±435.0 g). Therapy for PDA closure included the use of various volumes of restrictive or liberal infusion therapy (from 50 to 100 ml/kg/day) and COX inhibitors (indomethacin, ibuprofen). The volume of infusion therapy was limited in the first group. Preemies received 53.5±6.4 ml/kg/day on DOL1 and 2. From the third day urine excretion increased and the volume of infusion therapy also raised to 63.6±5.6 ml/kg/day, and on day 5 – to 89.7±6.8 ml/kg/day. In the second group there was no strict limitation of the volume of infusion therapy (especially in the first 5 days). Delayed period of PDA closure (on average from 14.55±0.56 DOL) was associated with absence of limitation of the infusion volume. In the first group, volume of infusion therapy was restricted in the first 5 days, and the closure of the ductus arteriosus occurred extremely early (on 2.35±0.48 DOL). COX inhibitors were prescribed according to the standard scheme: in the first 3 days indomethacin was administered orally in doses of 0.2/0.1/0.1 mg/kg/day. If the premature baby had symptoms of intestinal paresis ( this restricted oral administration of indomethacin), ibuprofen was prescribed in a three-day course in doses of 10/5/5 mg/kg/day intravenously or 20/10/10 mg/kg/day in rectal form. In all groups, standard PDA closure therapy was used. In the more remote periods (14 and 28 days), there was no fundamental difference in the volume of infusion in all groups. For early PDA closure limitation of infusion therapy in the first 3-5 days in combination with COX is principle
Strategy of protection against hazardous channel and hydrological processes in rivers of developed territories and territories with focal development
In 2012-2015, the Makkaveev Research Laboratory of Soil Erosion and Fluvial Processes of MSU, Department of Geography, carried out a research, including analysis of hydrological and channel regimes of the Tom river in the Kuznetsk basin (Kuzbass) and the Katun river up to Uimonsky (the Altai), intra-mountain drainage basins, the survey of floodplains and eroded banks, and modelling of floods occurring in floodplains. As a result, a concept has been developed to improve protection measures against hazardous hydrological and channel processes. More than 200 engineering and organisational events were suggested as part of the concept. Given the dense network of river banks and the high potential damage caused by floods in Kuzbass, the continuous protection of cities, large residential and commercial areas, as well as sections of roads and railways subject to erosion is a priority in the flood control concept. In the case of the Katun river basin, characterized by local development, low population density, and relatively small damage caused by floods, the emphasis is put on organisational measures: prevention, evacuation of people and property, insurance and compensation. Selective engineering structures should, as a matter of priority, reduce the dangerous erosion of river banks and ensure a high level of protection of the territory against floods
Spatial and Wavenumber Resolution of Doppler Reflectometry
Doppler reflectometry spatial and wavenumber resolution is analyzed within
the framework of the linear Born approximation in slab plasma model. Explicit
expression for its signal backscattering spectrum is obtained in terms of
wavenumber and frequency spectra of turbulence which is assumed to be radially
statistically inhomogeneous. Scattering efficiency for both back and forward
scattering (in radial direction) is introduced and shown to be inverse
proportional to the square of radial wavenumber of the probing wave at the
fluctuation location thus making the spatial resolution of diagnostics
sensitive to density profile. It is shown that in case of forward scattering
additional localization can be provided by the antenna diagram. It is
demonstrated that in case of backscattering the spatial resolution can be
better if the turbulence spectrum at high radial wavenumbers is suppressed. The
improvement of Doppler reflectometry data localization by probing beam focusing
onto the cut-off is proposed and described. The possibility of Doppler
reflectometry data interpretation based on the obtained expressions is shown.Comment: http://stacks.iop.org/0741-3335/46/114
Evolution and global collapse of trapped Bose condensates under variations of the scattering length
We develop the idea of selectively manipulating the condensate in a trapped
Bose-condensed gas, without perturbing the thermal cloud. The idea is based on
the possibility to modify the mean field interaction between atoms (scattering
length) by nearly resonant incident light or by spatially uniform change of the
trapping magnetic field. For the gas in the Thomas-Fermi regime we find
analytical scaling solutions for the condensate wavefunction evolving under
arbitrary variations of the scattering length . The change of from
positive to negative induces a global collapse of the condensate, and the final
stages of the collapse will be governed by intrinsic decay processes.Comment: 4 pages, LaTeX, other comments are at
http://WWW.amolf.nl/departments/quantumgassen/TITLE.HTM
Management of patent ductus arteriosus in premature infants
Closure of hemodynamically significant patent ductus arterios (HSPDA) is
one of the most important questions in modern neonatal intensive care, especially for preterm babies. Long-term
functioning of the hemodynamically significant arterial duct leads to a large number of complications in premature
babies, such as: bronchopulmonary dysplasia, periventricular leucomalacia, intraventricular hemorrhage, retinopathy
of the premature. To prevent all these complications, the PDA should be closed pharmacologically or surgically as
soon as possible without any hesitation. COX inhibitors are commonly used nowa days. Ibuprofen and indomethacin
show the equal efficacy and no significant adverse events. But some patients still need surgical treatment. The aim of
the study was to determine the feasibility, effectiveness and safety of using various volumes of infusion in combination with COX inhibitors and to determine its effect on the timing of the closure of PDA. 91 premature infants with a
gestational age of 26-31 weeks with manifestations of respiratory distress syndrome and НSPDA were studied
retrospectively. Premies were divided into 2 groups. Research groups were representative as to gestational age, gender,
and weight (1205.0±435.0 g). Therapy for PDA closure included the use of various volumes of restrictive or liberal
infusion therapy (from 50 to 100 ml/kg/day) and COX inhibitors (indomethacin, ibuprofen). The volume of infusion
therapy was limited in the first group. Preemies received 53.5±6.4 ml/kg/day on DOL1 and 2. From the third day urine
excretion increased and the volume of infusion therapy also raised to 63.6±5.6 ml/kg/day, and on day 5 – to
89.7±6.8 ml/kg/day. In the second group there was no strict limitation of the volume of infusion therapy (especially in
the first 5 days). Delayed period of PDA closure (on average from 14.55±0.56 DOL) was associated with absence of
limitation of the infusion volume. In the first group, volume of infusion therapy was restricted in the first 5 days, and the
closure of the ductus arteriosus occurred extremely early (on 2.35±0.48 DOL). COX inhibitors were prescribed
according to the standard scheme: in the first 3 days indomethacin was administered orally in doses of
0.2/0.1/0.1 mg/kg/day. If the premature baby had symptoms of intestinal paresis ( this restricted oral administration of
indomethacin), ibuprofen was prescribed in a three-day course in doses of 10/5/5 mg/kg/day intravenously or
20/10/10 mg/kg/day in rectal form. In all groups, standard PDA closure therapy was used. In the more remote periods
(14 and 28 days), there was no fundamental difference in the volume of infusion in all groups. For early PDA closure
limitation of infusion therapy in the first 3-5 days in combination with COX is principle
Identification of the Causes of the Destruction of the Body of the Shut-off Valve
A study was made of the causes of the emergency destruction of the shut-off valve. The fracture surface was studied, the mechanical properties of the material and the structure of the metal were evaluated. The accident was caused by deviations from standard properties and equipment overload
Russia and the Arab Spring: supporting the counter-revolution
Russia’s response to the Arab Spring ranged from apprehension to deep anxiety and diverged significantly from the US and the EU responses. While initially
welcoming the popular demands for political reform in North Africa, the Russian reaction rapidly became more critical as a result of Western military intervention into Libya and the threat of the spread of Islamist extremism. It was these twin fears which prompted the Russian leadership to adopt an uncompromizing stance towards Syria. While geopolitical factors certainly played a role in driving Russian strategy, domestic political factors were also more significant. As the Russian leadership felt internally threatened by the growing opposition within the country, conflict in the
Middle East highlighted the perceived flaws of the imposition of Western liberal democracy and the virtues of Russia’s own model of state-managed political order.
There was, as such, a significant ideational and ideological dimension to the Russian response to the Arab Spring
FRACTOGRAPHIC STUDY OF FATIGUE FAILURE OF A HIGH-PRESSURE TURBINE ROTOR BLADE
The paper presents the results of studying the fracture surface of a high-pressure turbine rotor blade with a crack. The crack grew by a fatigue mechanism, with the formation of fan-shaped scars and grooves along the crack front in the fracture. Fatigue crack propagation caused emergency fracture.Работа выполнена в рамках государственного задания МИНОБРНАУКИ России (тема «Диагностика», № АААА-А18-118020690196-3)
Stabilization of the number of Bose-Einstein condensed atoms in evaporative cooling via three-body recombination loss
The dynamics of evaporative cooling of magnetically trapped Rb atoms
is studied on the basis of the quantum kinetic theory of a Bose gas. We carried
out the quantitative calculations of the time evolution of conventional
evaporative cooling where the frequency of the radio-frequency magnetic field
is swept exponentially. This "exponential-sweep cooling" is known to become
inefficient at the final stage of the cooling process due to a serious
three-body recombination loss. We precisely examine how the growth of a
Bose-Einstein condensate depends on the experimental parameters of evaporative
cooling, such as the initial number of trapped atoms, the initial temperature,
and the bias field of a magnetic trap. It is shown that three-body
recombination drastically depletes the trapped Rb atoms as the system
approaches the quantum degenerate region and the number of condensed atoms
finally becomes insensitive to these experimental parameters. This result
indicates that the final number of condensed atoms is well stabilized by a
large nonlinear three-body loss against the fluctuations of experimental
conditions in evaporative cooling.Comment: 7 pages, REVTeX4, 8 eps figures, Phys. Rev A in pres
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