6,131 research outputs found
The problem of formalization of some nonstandard semantics
I shall propose the formalization of some nonstandard semantics in sequential form
Relation between parameters of dust and parameters of molecular and atomic gas in extragalactic star-forming regions
The relationships between atomic and molecular hydrogen and dust of various
sizes in extragalactic star-forming regions are considered, based on
observational data from the Spitzer and Herschel infrared space telescopes, the
Very Large Array (atomic hydrogen emission) and IRAM (CO emission). The source
sample consists of approximately 300 star-forming regions in 11 nearby
galaxies. Aperture photometry has been applied to measure the fluxes in eight
infrared bands (3.6, 4.5, 5.8, 8, 24, 70, 100, and 160m), the atomic
hydrogen (21cm) line and CO (2--1) lines.
The parameters of the dust in the starforming regions were determined via
synthetic-spectra fitting, such as the total dust mass, the fraction of
polycyclic aromatic hydrocarbons (PAHs), etc. Comparison of the observed fluxes
with the measured parameters shows that the relationships between atomic
hydrogen, molecular hydrogen, and dust are different in low- and
high-metallicity regions. Low-metallicity regions contain more atomic gas, but
less molecular gas and dust, including PAHs. The mass of dust constitutes about
of the mass of molecular gas in all regions considered. Fluxes produced
by atomic and molecular gas do not correlate with the parameters of the stellar
radiation, whereas the dust fluxes grow with increasing mean intensity of
stellar radiation and the fraction of enhanced stellar radiation. The ratio of
the fluxes at 8 and 24m, which characterizes the PAH content, decreases
with increasing intensity of the stellar radiation, possibly indicating
evolutionary variations of the PAH content. The results confirm that the
contribution of the 24m emission to the total IR luminosity of
extragalactic star-forming regions does not depend on the metallicity.Comment: Published in Astronomy Reports, 2017, vol. 61, issue
Problem aspects of University education in Russia
The article deals with the current state of higher education in Russia, which is characterized by many problems, which indicates its crisis. Reforms of the higher education system do not give the desired result, because they do not solve its problems and problems of modern society, but only retouch themВ статье рассматривается современное состояние сферы высшего образования в России, которое характеризуется множеством проблем, что свидетельствует о его кризисе. Реформы системы высшего образования не дают нужного результата, т.к. не решают его проблемы и проблемы современного общества, а только лишь их ретуширую
Tilting light's polarization plane to spatially separate the ultrafast nonlinear response of chiral molecules
Distinguishing between the left- and right-handed versions of a chiral molecule (enantiomers) is vital, but also inherently difficult. Traditional optical methods using elliptically/circularly polarized light rely on linear effects which arise beyond the electric-dipole approximation, posing major limitations for ultrafast spectroscopy. Here we show how to turn an ultrashort elliptical pulse into an efficient chiro-optical tool: by tilting its polarization plane towards its propagation direction. This forward tilt can be achieved by focusing the beam tightly, creating structured light which exhibits a nontrivial polarization pattern in space. Using state-of-the-art computational modelling, we show that our structured field realizes a near-field interferometer for efficient chiral recognition that separates the nonlinear optical response of left- and right-handed molecules in space. Our work provides a simple, yet highly efficient, way of spatially structuring the polarization of light to image molecular chirality, with extreme enantio-efficiency and on ultrafast time scales
CEP-stable Tunable THz-Emission Originating from Laser-Waveform-Controlled Sub-Cycle Plasma-Electron Bursts
We study THz-emission from a plasma driven by an incommensurate-frequency
two-colour laser field. A semi-classical transient electron current model is
derived from a fully quantum-mechanical description of the emission process in
terms of sub-cycle field-ionization followed by continuum-continuum electron
transitions. For the experiment, a CEP-locked laser and a near-degenerate
optical parametric amplifier are used to produce two-colour pulses that consist
of the fundamental and its near-half frequency. By choosing two incommensurate
frequencies, the frequency of the CEP-stable THz-emission can be continuously
tuned into the mid-IR range. This measured frequency dependence of the
THz-emission is found to be consistent with the semi-classical transient
electron current model, similar to the Brunel mechanism of harmonic generation
Cadmium-induced oxidative damage and protective action of fractioned red beet (Beta vulgaris) root juice in chickens
ArticleCadmium (Cd) is one of the most dangerous environmental bioaccumulative pollutants
that
affects
many organs in humans and animals. Present investigation was conducted
to evaluate
the protective effect of fractioned red beetroot juice on Cd
-
induced oxidative stress in chickens.
The named red beetroot juice fraction (BJF) was received by juice ultrafiltration. Per oral
administration of BJF for 10 days followed by dietar
y Cd exposure (50
mg
kg
-
1
of diet) was
evaluated in the
in vivo
experiments in chickens. The prominent increase of Cd concentration in
blood plasma, liver and kidney provoked the rise of oxidative processes activity in organs. BJF
treatment
attenuated the
Cd
-
induced oxidative stress. The changes of oxidative stress markers
-
the reduction of
hepatic and kidney malondialdehyde amount, the increase of
glutathionperoxidase level in liver and blood
catalase
activity indicated the possible antioxidative
influenc
e of BJF. Chickens exposed to Cd showed no evidence of clinical toxicity, but exhibited
some features of adverse action of this heavy metal. The increase of uric acid concentration in
blood serum is associated with protein catabolic processes intensified b
y Cd affect. Suppressive
effect of Cd on the immune response in chickens manifested in alteration of cell and humoral
immunity parameters. The data of the most investigated oxidative stress markers, biochemical
and immunological indices in Cd
-
exposed chick
ens were almost back to the values, when
received BJF
per os
during 10 days. Administration of fractioned red beetroot juice to Cd
-
treated
chickens prevented the oxidative impact of this heavy metal and provided immunomodulating
effect
Effects of Intermittent Emission: Noise Inventory for Scintillating Pulsar B0834+06
We compare signal and noise for observations of the scintillating pulsar
B0834+06, using very-long baseline interferometry and a single-dish
spectrometer. Comparisons between instruments and with models suggest that
amplitude variations of the pulsar strongly affect the amount and distribution
of self-noise. We show that noise follows a quadratic polynomial with flux
density, in spectral observations. Constant coefficients, indicative of
background noise, agree well with expectation; whereas second-order
coefficients, indicative of self-noise, are about 3 times values expected for a
pulsar with constant on-pulse flux density. We show that variations in flux
density during the 10-sec integration account for the discrepancy. In the
secondary spectrum, about 97% of spectral power lies within the pulsar's
typical scintillation bandwidth and timescale; an extended scintillation arc
contains about 3%. For a pulsar with constant on-pulse flux density, noise in
the dynamic spectrum will appear as a uniformly-distributed background in the
secondary spectrum. We find that this uniform noise background contains 95% of
noise in the dynamic spectrum for interferometric observations; but only 35% of
noise in the dynamic spectrum for single-dish observations. Receiver and sky
dominate noise for our interferometric observations, whereas self-noise
dominates for single-dish. We suggest that intermittent emission by the pulsar,
on timescales < 300 microseconds, concentrates self-noise near the origin in
the secondary spectrum, by correlating noise over the dynamic spectrum. We
suggest that intermittency sets fundamental limits on pulsar astrometry or
timing. Accounting of noise may provide means for detection of intermittent
sources, when effects of propagation are unknown or impractical to invert.Comment: 38 pages, 10 figure
Reconstruction of the time-dependent electronic wave packet arising from molecular autoionization
Autoionizing resonances are paradigmatic examples of two-path wave interferences between direct photoionization, which takes a few attoseconds, and ionization via quasi-bound states, which takes much longer. Time-resolving the evolution of these interferences has been a long-standing goal, achieved recently in the helium atom owing to progress in attosecond technologies. However, already for the hydrogen molecule, similar time imaging has remained beyond reach due to the complex interplay between fast nuclear and electronic motions. We show how vibrationally resolved photoelectron spectra of H2 allow one to reconstruct the associated subfemtosecond autoionization dynamics by using the ultrafast nuclear dynamics as an internal clock, thus forgoing ultrashort pulses. Our procedure should be general for autoionization dynamics in molecules containing light nuclei, which are ubiquitous in chemistry and biologyThis work was supported by European Research Council advanced grant 290853-XCHEM within the seventh framework program of the European Union. We also acknowledge the financial support from MINECO projects FIS2013-42002-R and FIS2016-77889-R, and the European COST (Cooperation in Science and Technology) Action XLIC CM1204, and the computer time from the Centro de Computación Científica de la Universidad Autónoma de Madrid and Marenostrum Supercomputer Center. A.P. acknowledges a Ramón y Cajal contract from the Ministerio de Economía y Competitividad (Spain). F.M. acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, grant SEV-2016-0686) and the “María de Maeztu” Programme for Units of Excellence in R&D (MDM-2014-0377). S.E.C. acknowledges funding from the Helmoltz Recognition Award. The Extreme Light Infrastructure Attosecond Light Pulse Source project (GINOP-2.3.6-15-2015-00001) was financed by the European Union and cofinanced by the European Regional Development Fun
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