2,478 research outputs found
On leading spiral arms in close pairs of galaxies
It is explained why one can observe a leading spiral pattern in close pairs of galaxies where the direction of the orbital momentum of the satellite is opposite to the direction of the spin of the spiral galaxy
Tropospheric limitations on the accuracy of phase measurement of coordinates in astronomy
The effect of tropospheric fluctuation on the accuracy of phase measurements of coordinates is discussed. The nature of the averaging of the tropospheric effects, if N coordinate measurements of duration T with period mu are made, is investigated. Various averaging modes depending on the relation of the various time parameters are investigated. Equations taking into account the correlations between individual observations are presented. It is shown that the correlation interval between the individual observations is always greater than the fluctuation period of tropospheric inhomogeneities typical for a given baseline
Restoring the full velocity field in the gaseous disk ofthe spiral galaxy NGC 157
We analyse the line-of-sight velocity field of ionized gas in the spiral
galaxy NGC 157 which has been obtained in the H\alpha emission at the 6m
telescope of SAO RAS. The existence of systematic deviations of the observed
gas velocities from pure circular motion is shown. A detailed investigation of
these deviations is undertaken by applying a Fourier analysis of the azimuthal
distributions of the line-of-sight velocities at different distances from the
galactic center. As a result of the analysis, all the main parameters of the
wave spiral pattern are determined: the corotation radius, the amplitudes and
phases of the gas velocity perturbations at different radii, and the velocity
of circular rotation of the disk corrected for the velocity perturbations due
to spiral arms. At a high confidence level, the presence of the two giant
anticyclones in the reference frame rotating with the spiral pattern is shown;
their sizes and the localization of their centers are consistent with the
results of the analytic theory and of numerical simulations. Besides the
anticyclones, the existence of cyclones in residual velocity fields of spiral
galaxies is predicted. In the reference frame rotating with the spiral pattern
these cyclones have to reveal themselves in galaxies where a radial gradient of
azimuthal residual velocity is steeper than that of the rotation velocity
(abridged).Comment: 23 pages including 25 eps-figures. Accepted for publication in A&
Spectral density asymptotics for Gaussian and Laguerre -ensembles in the exponentially small region
The first two terms in the large asymptotic expansion of the
moment of the characteristic polynomial for the Gaussian and Laguerre
-ensembles are calculated. This is used to compute the asymptotic
expansion of the spectral density in these ensembles, in the exponentially
small region outside the leading support, up to terms . The leading form
of the right tail of the distribution of the largest eigenvalue is given by the
density in this regime. It is demonstrated that there is a scaling from this,
to the right tail asymptotics for the distribution of the largest eigenvalue at
the soft edge.Comment: 19 page
Dynamic stabilization of non-spherical bodies against unlimited collapse
We solve equations, describing in a simplified way the newtonian dynamics of
a selfgravitating nonrotating spheroidal body after loss of stability. We find
that contraction to a singularity happens only in a pure spherical collapse,
and deviations from the spherical symmetry stop the contraction by the
stabilising action of nonlinear nonspherical oscillations. A real collapse
happens after damping of the oscillations due to energy losses, shock wave
formation or viscosity. Detailed analysis of the nonlinear oscillations is
performed using a Poincar\'{e} map construction. Regions of regular and chaotic
oscillations are localized on this map.Comment: MNRAS, accepted, 7 pages, 9 figure
Effect of angular momentum distribution on gravitational loss-cone instability in stellar clusters around massive BH
Small perturbations in spherical and thin disk stellar clusters surrounding
massive a black hole are studied. Due to the black hole, stars with
sufficiently low angular momentum escape from the system through the loss cone.
We show that stability properties of spherical clusters crucially depend on
whether the distribution of stars is monotonic or non-monotonic in angular
momentum. It turns out that only non-monotonic distributions can be unstable.
At the same time the instability in disk clusters is possible for both types of
distributions.Comment: 14 pages, 7 figures, submitted to MNRA
Wilcoxon-Mann-Whitney odds ratio: A statistical measure for ordinal outcomes such as EDSS
Background: In many clinical situations, ordinal scales afford the primary method of semi-quantifying patient outcomes. In the field of multiple sclerosis, the primary ordinal scale is the Expanded Disability Status Scale. Predominant methods of ordinal scale statistical analysis provide a p-value without effect size or rely heavily on the assumption of proportionality of odds, subjecting them to lack of power and error. The Wilcoxon-Manny-Whitney Odds is a statistical method which provides significant information such as p-value, effect size, number needed to treat, confidence intervals, and is largely assumption-free. However, its utility has not been demonstrated in the field of multiple sclerosis. Methods: Three clinical studies in the field of multiple sclerosis were selected which utilized ordinal scale outcomes at group or individual levels. Data from these studies was extracted using WebPlotDigitizer, and a custom Wilxocon-Mann-Whitney Odds software was applied to each dataset to re-analyze the main outcomes of the studies. Results: Re-analysis of the manuscript by Muraro et al., 2017 demonstrated that autologous stem cell transplantation for relapsing remitting multiple sclerosis resulted in a 65% chance of improving from any Expanded Disability Status Scale category, although not significant. Re-analysis of the manuscript by Songthammawat et al., 2019 demonstrated chance of improvement with intravenous methylprednisolone and concurrent plasma exchange was 185% versus 32% in intravenous methylprednisolone with add-on plasma exchange, although not significant. Re-analysis of Kister et al., 2012 demonstrated the chances of mobility or cognition scores generally favored decline at every 5-year increment of study, and although statistically significant, these were smaller effect sizes ranging from an 11% chance of improvement to a 66% chance of decline over a 5-year interval. Discussion: The Wilcoxon-Mann-Whitney Odds simplifies ordinal data analysis with its robust largely assumption-free nature. In the place of numerous statistical tests, this single test provides effect size estimate, number needed to treat, p-values, and confidence intervals. Importantly, the Wilcoxon-Mann-Whitney Odds effect size calculation is intuitively applicable to both individual and population-levels. Further, the Wilcoxon-Mann-Whitney Odds allows intuitive description of the progression of large cohorts over time, and we were able to clearly convey the odds of mobility and cognitive decline over 30 years in a large multiple sclerosis cohort. Overall, the Wilcoxon-Mann-Whitney Odds is a powerful and robust statistical test with significant promise within the field of multiple sclerosis
TRAIL Coated Genetically Engineered Immunotherapeutic Nano-Ghosts Vesicles Target Human Melanoma-Avoiding the Need for High Effective Therapeutic Concentration of TRAIL
Cancer cell therapy using cytotoxic T lymphocytes (CTL) or mesenchymal stem cells (MSC) possesses hurdles due to the cells, susceptibility to host induced changes. Here, versatile inanimate broadly applicable nanovesicles, termed immunotherapeutic-nano-ghosts (iNGs), are armed with inherent surface-associated targeting and therapeutic capabilities in which the promise and benefits of MSC therapy and T cell immunotherapy are combined into one powerful off-the-shelf approach for treating malignant diseases. To mimic the cytotoxic or immunosuppressive functions of T cells, iNG are produced from MSC that were genetically engineered (GE) or metabolically manipulated to express additional membrane-bound proteins, endowing the NGs derived therefrom with additional surface-associated functions such as tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL). iNGs from GE-MSCs (GE-iNGs) show superior TRAIL retention and induce apoptosis in different cancer cell lines in vitro. In vivo studies on a human melanoma model demonstrate that a systemic, three-day frequency, administration of GE-iNGs result in tumor inhibition comparable to a six orders of magnitude higher concentration of soluble TRAIL. The iNGs are therefore a promising nanovesicle platform that can affect tumors in a non-immunogenic manner while avoiding the need for a highly effective therapeutic concentration
Elliptical motions of stars in close binary systems
Motions of stars in close binary systems with a conservative mass exchange
are examined. It is shown that Paczynski-Huang model widely used now for
obtaining the semi-major axis variation of a relative stars orbit is incorrect,
because it brings about large mistakes. A new model suitable for elliptical
orbits of stars is proposed. Both of reactive and attractive forces between
stars and a substance of the flowing jet are taken into account. A possibility
of a mass exchange at presence of accretion disk is considere
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