216 research outputs found
THz transition radiation of electron bunch laser-accelerated in long-scale near-critical density plasmas
Direct laser electron acceleration in near-critical density plasma produces
collimated electron beams with high charge (up to C). This regime
could be of interest for high energy THz radiation generation, as many of the
mechanisms have a scaling . In this work we focused specifically
on challenges that arise during numerical investigation of transition radiation
in such interaction. Detailed analytical calculations that include both
diffraction and decoherence effects of characteristics of transition radiation
in the THz range were conducted with the input parameters obtained from 3D PIC
and hydrodynamic simulations. The calculated characteristics of THz radiation
are in good agreement with the experimentally measured ones. Therefore, this
approach can be used both to optimize properties of THz radiation and
distinguish the transition radiation contribution if several mechanisms of THz
radiation generation are considered
Impact of fiscal, monetary and structural economic policies on the growth rates of leading economies : 2000-2016
The article analyzes the impact of measures and instruments of fiscal, monetary, and structural economic policies on the growth rates of the economies of many countries around the world from 2000 to 2016, considering the provisions of the structural theory of development. The dynamics of the following indicators of national economies is analyzed: GDP growth rate; total tax rate, central government debt; domestic credit to the private sector; consumer price inflation; high-tech exports as a share of country industrial exports and in value terms. It was revealed that for balanced long-term growth of the economy, it is necessary that the structure of the national economy should include industries whose exported goods are characterized by high elasticity of demand, and goods imported by low elasticity of demand. Selective tools of state stimulating economic policy should be aimed at industries that can generate innovations and promote the dissemination of the results of technological progress.peer-reviewe
Laser-driven pointed acceleration of electrons with preformed plasma lens
The simultaneous laser-driven acceleration and angular manipulation of the
fast electron beam is experimentally demonstrated. The bunch of multi-MeV
energy charged particles is generated during the propagation of the femtosecond
laser pulse through the near-critical plasma slab accompanied by plasma
channeling. Plasma is formed by the controlled breakdown of a thin-tape target
by a powerful nanosecond prepulse. The electron beam pointing approach is based
on the refraction of a laser pulse in the presence of a strong radial density
gradient in the breakdown of the tape with a small displacement of the
femtosecond laser beam relative to the breakdown symmetry axis. A shift of
several micrometers makes it possible to achieve beam deflection by an angle up
to 10 degrees with acceptable beam charge and spectrum conservation. This opens
up opportunities for in-situ applications for scanning objects with an electron
beam and the multistage electron beam energy gain in consecutive laser
accelerators without bulk magnetic optics for particles. Experimental findings
are supported by numerical Particle-In-Cell calculations of laser-plasma
acceleration and hydrodynamic simulations.Comment: Submitted to PPC
Transition Metall-Free C-H/C-H and C-LI/C-H Coupling in the Synthesis of New Azaheterocycles Derivatives
The study was carried out with the financial support of the Russian Foundation for Basic Research in the framework of a research project 18-33-00226 and Russian Science Foundation as part of a research project 18-73-00088
Debris Disks in NGC 2547
We have surveyed the 30 Myr-old cluster NGC 2547 for planetary debris disks
using Spitzer. At 4.5-8 um we are sensitive to the photospheric level down to
mid-M stars (0.2 Msol) and at 24 um to early-G stars (1.2 Msol). We find only
two to four stars with excesses at 8 um out of ~400-500 cluster members,
resulting in an excess fraction <~1 percent at this wavelength. By contrast,
the excess fraction at 24 um is ~40 percent (for B-F types). Out of four
late-type stars with excesses at 8 um two marginal ones are consistent with
asteroid-like debris disks. Among stars with strong 8 um excesses one is
possibly from a transitional disk, while another one can be a result of a
catastrophic collision. Our survey demonstrates that the inner 0.1-1 AU parts
of disks around solar-type stars clear out very thoroughly by 30 Myrs of age.
Comparing with the much slower decay of excesses at 24 and 70 um, disks clear
from the inside out, of order 10 Myr for the inner zones probed at 8 um
compared with a hundred or more Myr for those probed with the two longer
wavelengths.Comment: Accepted to ApJ, 29 pages, 13 figs. A Note in Proof concerning
cluster's age was added in the original submission of 2007 July 19. Full
Tables 1 and 2 in the electronic form together with the article with full
resolution figures are available at
http://www.astro.ufl.edu/~ngorlova/disksNGC2547
The low level of debris disk activity at the time of the Late Heavy Bombardment: a Spitzer study of Praesepe
We present 24 micron photometry of the intermediate-age open cluster
Praesepe. We assemble a catalog of 193 probable cluster members that are
detected in optical databases, the Two Micron All Sky Survey (2MASS), and at 24
micron, within an area of ~ 2.47 square degrees. Mid-IR excesses indicating
debris disks are found for one early-type and for three solar-type stars.
Corrections for sampling statistics yield a 24 micron excess fraction (debris
disk fraction) of 6.5 +- 4.1% for luminous and 1.9 +- 1.2% for solar-type
stars. The incidence of excesses is in agreement with the decay trend of debris
disks as a function of age observed for other cluster and field stars. The
values also agree with those for older stars, indicating that debris generation
in the zones that emit at 24 micron falls to the older 1-10 Gyr field star
sample value by roughly 750 Myr.
We discuss our results in the context of previous observations of excess
fractions for early- and solar-type stars. We show that solar-type stars lose
their debris disk 24 micron excesses on a shorter timescale than early-type
stars. Simplistic Monte Carlo models suggest that, during the first Gyr of
their evolution, up to 15-30% of solar-type stars might undergo an orbital
realignment of giant planets such as the one thought to have led to the Late
Heavy Bombardment, if the length of the bombardment episode is similar to the
one thought to have happened in our Solar System.
In the Appendix, we determine the cluster's parameters via boostrap Monte
Carlo isochrone fitting, yielding an age of 757 Myr (+- 36 Myr at 1 sigma
confidence) and a distance of 179 pc (+- 2 pc at 1 sigma confidence), not
allowing for systematic errors.Comment: 22 pages, 14 figures, 9 tables, emulateapj format; Accepted for
publication in The Astrophysical Journa
Gene-level association analysis of systemic sclerosis: A comparison of African-Americans and White populations
© 2018 Gorlova et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Gene-level analysis of ImmunoChip or genome-wide association studies (GWAS) data has not been previously reported for systemic sclerosis (SSc, scleroderma). The objective of this study was to analyze genetic susceptibility loci in SSc at the gene level and to determine if the detected associations were shared in African-American and White populations, using data from ImmunoChip and GWAS genotyping studies. The White sample included 1833 cases and 3466 controls (956 cases and 2741 controls from the US and 877 cases and 725 controls from Spain) and the African American sample, 291 cases and 260 controls. In both Whites and African Americans, we performed a gene-level analysis that integrates association statistics in a gene possibly harboring multiple SNPs with weak effect on disease risk, using Versatile Gene-based Association Study (VEGAS) software. The SNP-level analysis was performed using PLINK v.1.07. We identified 4 novel candidate genes (STAT1, FCGR2C, NIPSNAP3B, and SCT) significantly associated and 4 genes (SERBP1, PINX1, TMEM175 and EXOC2) suggestively associated with SSc in the gene level analysis in White patients. As an exploratory analysis we compared the results on Whites with those from African Americans. Of previously established susceptibility genes identified in Whites, only TNFAIP3 was significant at the nominal level (p = 6.13x10-3) in African Americans in the gene-level analysis of the ImmunoChip data. Among the top suggestive novel genes identified in Whites based on the ImmunoChip data, FCGR2C and PINX1 were only nominally significant in African Americans (p = 0.016 and p = 0.028, respectively), while among the top novel genes identified in the gene-level analysis in African Americans, UNC5C (p = 5.57x10-4) and CLEC16A (p = 0.0463) were also nominally significant in Whites. We also present the gene-level analysis of SSc clinical and autoantibody phenotypes among Whites. Our findings need to be validated by independent studies, particularly due to the limited sample size of African Americans
Neuro-Cells therapy improves motor outcomes and suppresses inflammation during experimental syndrome of amyotrophic lateral sclerosis in mice
Aims: Mutations in DNA/RNA-binding factor (fused-in-sarcoma) FUS and superoxide dismutase-1 (SOD-1) cause amyotrophic lateral sclerosis (ALS). They were reproduced in SOD-1-G93A (SOD-1) and new FUS[1-359]-transgenic (FUS-tg) mice, where inflammation contributes to disease progression. The effects of standard disease therapy and anti-inflammatory treatments were investigated using these mutants. Methods: FUS-tg mice or controls received either vehicle, or standard ALS treatment riluzole (8 mg/kg/day), or anti-inflammatory drug a selective blocker of cyclooxygenase-2 celecoxib (30 mg/kg/day) for six weeks, or a single intracerebroventricular (i.c.v.) infusion of Neuro-Cells (a preparation of 1.39 × 106 mesenchymal and hemopoietic human stem cells, containing 5 × 105 of CD34+ cells), which showed anti-inflammatory properties. SOD-1 mice received i.c.v.-administration of Neuro-Cells or vehicle. Results: All FUS-tg-treated animals displayed less marked reductions in weight gain, food/water intake, and motor deficits than FUS-tg-vehicle-treated mice. Neuro-Cell-treated mutants had reduced muscle atrophy and lumbar motor neuron degeneration. This group but not celecoxib-FUS-tg-treated mice had ameliorated motor performance and lumbar expression of microglial activation marker, ionized calcium-binding adapter molecule-1 (Iba-1), and glycogen-synthase-kinase-3ß (GSK-3ß). The Neuro-Cells-treated-SOD-1 mice showed better motor functions than vehicle-treated-SOD-1 group. Conclusion: The neuropathology in FUS-tg mice is sensitive to standard ALS treatments and Neuro-Cells infusion. The latter improves motor outcomes in two ALS models possibly by suppressing microglial activation. © 2019 The Authors. CNS Neuroscience & Therapeutics published by John Wiley & Sons LtdWe thank ?5-100? Russian Excellence Program, Prof. Daniel C. Anthony, Diana Babayevskaya, and Arina Kosakova for their highly valuable contribution. ?Neuro-Cells? preparation was provided by Neuroplast BV, Maastricht, Netherlands
Spitzer 24 um Excesses for Bright Galactic Stars in Bootes and First Look Survey Fields
Optically bright Galactic stars (V 1 mJy are
identified in Spitzer mid-infrared surveys within 8.2 square degrees for the
Bootes field of the NOAO Deep Wide-Field Survey and within 5.5 square degrees
for the First Look Survey (FLS). 128 stars are identified in Bootes and 140 in
the FLS, and their photometry is given. (K-[24]) colors are determined using K
magnitudes from the 2MASS survey for all stars in order to search for excess 24
um luminosity compared to that arising from the stellar photosphere. Of the
combined sample of 268 stars, 141 are of spectral types F, G, or K, and 17 of
these 141 stars have 24 um excesses with (K-[24]) > 0.2 mag. Using limits on
absolute magnitude derived from proper motions, at least 8 of the FGK stars
with excesses are main sequence stars, and estimates derived from the
distribution of apparent magnitudes indicate that all 17 are main sequence
stars. These estimates lead to the conclusion that between 9% and 17% of the
main sequence FGK field stars in these samples have 24 um infrared excesses.
This result is statistically similar to the fraction of stars with debris disks
found among previous Spitzer targeted observations of much brighter, main
sequence field stars.Comment: Accepted for publication in The Astronomical Journa
Monte Carlo calculation of the current-voltage characteristics of a two dimensional lattice Coulomb gas
We have studied the nonlinear current-voltage characteristic of a two
dimensional lattice Coulomb gas by Monte Carlo simulation. We present three
different determinations of the power-law exponent of the nonlinear
current-voltage characteristic, . The determinations rely on
both equilibrium and non-equilibrium simulations. We find good agreement
between the different determinations, and our results also agree closely with
experimental results for Hg-Xe thin film superconductors and for certain single
crystal thin-film high temperature superconductors.Comment: late
- …