450 research outputs found
Kinematics of Tycho-2 Red Giant Clump Stars
Based on the Ogorodnikov-Milne model, we analyze the proper motions of 95 633
red giant clump (RGC) stars from the Tycho-2 Catalogue. The following Oort
constants have been found: A = 15.9+-0.2 km/s/kpc and B = -12.0+-0.2 km/s/kpc.
Using 3632 RGC stars with known proper motions, radial velocities, and
photometric distances, we show that, apart from the star centroid velocity
components relative to the Sun, only the model parameters that describe the
stellar motions in the XY plane differ significantly from zero. We have studied
the contraction (a negative K-effect) of the system of RGC stars as a function
of their heliocentric distance and elevation above the Galactic plane. For a
sample of distant (500--1000 pc) RGC stars located near the Galactic plane
(|Z|<200 pc) with an average distance of d=0.7 kpc, the contraction velocity is
shown to be Kd= -3.5+-0.9 km/s; a noticeable vertex deviation, lxy = 9.1+-0.5
degrees, is also observed for them. For stars located well above the Galactic
plane (|Z|>=200 pc), these effects are less pronounced, Kd = -1.7+-0.5 km/s and
lxy = 4.9+-0.6 degrees. Using RGC stars, we have found a rotation around the
Galactic X axis directed toward the Galactic center with an angular velocity of
-2.5+-0.3 km/s/kpc, which we associate with the warp of the Galactic
stellar-gaseous disk.Comment: 23 pages, 7 figures, 4 table
Magnetic behaviour of non-interacting colloidal iron oxide nanoparticles in physiological solutions
Magnetic properties of colloidal nanoparticles (NPs) depend on various
parameters, such as size, size distribution, interparticle distance, shape,
condition of synthesis and stabilizing surfactants. Nowadays, those magnetic
nanoparticles (MNPs) are preferably produced in hydrophobic organic solvents,
while biomedical applications need hydrophilic properties. Thus, a major
challenge is the hydrophilization of the particles, while avoiding
destabilization and aggregation. Here we present magnetic characteristics of
non-interacting, highly crystalline iron oxide NPs in physiological solutions
that are coated with modified polyacrylic acid. The magnetic analysis
comprised both static and dynamic magnetic behaviour of 4 nm NPs. The NPs have
been further characterized by transmission electron microscopy (TEM) and
energy dispersive X-ray spectroscopy (EDX)
Особливості формування ентомокомплекс в екосистемах Ялтинського гірничо-лісового природного заповідника
The results of research of entomocomplex at the territory of Yalta Mountain-Forest Nature Reserve are presented. The influence of height above sea level on insects’ number is shown. Spatial, cenotical and biomorphic structures of entomocomplex is analyzed.Изложены результаты исследований ентомокомплекс на территории Ялтинского горно-лесного природного заповедника. Показано влияние высоты над уровнем моря на численность насекомых. Проанализированы пространственную, ценотическая, биоморфичну структуры ентомокомплекс.Викладено результати досліджень ентомокомплексів на території Ялтинського гірсько-лісового природного заповідника. Показано вплив висоти над рівнем моря на чисельність комах. Проаналізовано просторову, ценотичну, біоморфічну структури ентомокомплексів
Lipopolysaccharides and outer membrane proteins as main structures involved in complement evasion strategies of non-typhoidal Salmonella strains
Non-typhoidal Salmonella (NTS) infections pose a serious public health problem. In addition to the typical course of salmonellosis, an infection with Salmonella bacteria can often lead to parenteral infections and sepsis, which are particularly dangerous for children, the elderly and immunocompromised. Bacterial resistance to serum is a key virulence factor for the development of systemic infections. Salmonella, as an enterobacterial pathogen, has developed several mechanisms to escape and block the antibacterial effects of the complement system. In this review, we discuss the relevance of outer membrane polysaccharides to the complement evasion mechanisms of NTS strains. These include the influence of the overall length and density of the lipopolysaccharide molecules, modifications of the O-antigen lipopolysaccharide composition and the role of capsular polysaccharides in opsonization and protection of the outer membrane from the lytic action of complement. Additionally, we discuss specific outer membrane protein complement evasion mechanisms, such as recruitment of complement regula-tory proteins, blocking assembly of late complement components to form the membrane attack complex and the proteolytic cleavage of complement proteins.Peer reviewe
A method to localize gamma-ray bursts using POLAR
The hard X-ray polarimeter POLAR aims to measure the linear polarization of
the 50-500 keV photons arriving from the prompt emission of gamma-ray bursts
(GRBs). The position in the sky of the detected GRBs is needed to determine
their level of polarization. We present here a method by which, despite of the
polarimeter incapability of taking images, GRBs can be roughly localized using
POLAR alone. For this purpose scalers are attached to the output of the 25
multi-anode photomultipliers (MAPMs) that collect the light from the POLAR
scintillator target. Each scaler measures how many GRB photons produce at least
one energy deposition above 50 keV in the corresponding MAPM. Simulations show
that the relative outputs of the 25 scalers depend on the GRB position. A
database of very strong GRBs simulated at 10201 positions has been produced.
When a GRB is detected, its location is calculated searching the minimum of the
chi2 obtained in the comparison between the measured scaler pattern and the
database. This GRB localization technique brings enough accuracy so that the
error transmitted to the 100% modulation factor is kept below 10% for GRBs with
fluence Ftot \geq 10^(-5) erg cm^(-2) . The POLAR localization capability will
be useful for those cases where no other instruments are simultaneously
observing the same field of view.Comment: 13 pages, 10 figure
Astrometric Control of the Inertiality of the Hipparcos Catalog
Based on the most complete list of the results of an individual comparison of
the proper motions for stars of various programs common to the Hipparcos
catalog, each of which is an independent realization of the inertial reference
frame with regard to stellar proper motions, we redetermined the vector
of residual rotation of the ICRS system relative to the extragalactic
reference frame. The equatorial components of this vector were found to be the
following: mas yr,
mas yr, and mas yr.Comment: 8 pages, 1 figur
A Search for Scalar Chameleons with ADMX
Scalar fields with a "chameleon" property, in which the effective particle
mass is a function of its local environment, are common to many theories beyond
the standard model and could be responsible for dark energy. If these fields
couple weakly to the photon, they could be detectable through the "afterglow"
effect of photon-chameleon-photon transitions. The ADMX experiment was used in
the first chameleon search with a microwave cavity to set a new limit on scalar
chameleon-photon coupling excluding values between 2*10^9 and 5*10^14 for
effective chameleon masses between 1.9510 and 1.9525 micro-eV.Comment: 4 pages, 3 figure
Central composite rotatable design approach to optimize Italia raisin drying conditions.
Considering its high demand and limited production, raisin represents an important alternative to diversify grape processed products around the world. The aim of this study was to determine the best combination between drying temperature and time required to reach the highest consumer acceptance of ?Italia? raisin produced in the semi-arid climate in Brazil. The drying conditions were combinations between drying temperatures of 50, 56, 70, 84 and 90°C and drying times of 16, 22, 35, 48 and 54 hours, following a central composite rotational design (CCRD). The best combination between drying temperature and time was estimated to be 70°C for 35 hours (h), based on overall consumer acceptance. According to the statistical analysis used, drying at 70 °C for 35h and at 59 °C for 28h results in equal overall consumer acceptance, being the second option the more economical. Taste and texture, raisin chroma values and pH were more positively correlated to overall acceptance. The results indicate that drying at 59ºC for 28 h is the most efficient drying condition for raisins from ?Italia? grapes grown in Brazilian semi-arid condition. This study uses a new approach based on the central composite rotatable design to determine the most efficient drying temperature and time for Italia raisins
Augmentation with bone marrow of donor leukocyte migration for kidney, liver, heart, and pancreas islet transplantation
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