260 research outputs found
Multiple Quantum NMR and Entanglement Dynamics in Dipolar Coupling Spin
We investigate numerically the time dependence of the multiple quantum
coherences and entanglement in linear chains up to nine nuclear spins of 1/2
coupled by the dipole-dipole interactions. Two models are considered: (1) a
spin chain with nearest-neighbor dipole -dipole interactions; (2) a more
realistic model with interactions between all spins. It is shown that the
entangled states appear between remote particles which do not interact directly
(model 1), while the interaction between all spins (model 2) not always results
in entanglement between remote spins.Comment: 14 pages, 3 figures. accepted for publication in Physical Review
Fast and reliable mini-prep RNA extraction from Neurospora crassa
We have developed a method for isolating high quality total RNA from N. crassa mycelia that reliably yields large quantities. It is possible to extract more than 50 minipreps at once
Thermal regimes of HTS cylinders operating in devices for fault current limitation
We reveal obstacles related to the application of HTS cylinders in current
limiting devices based on the superconducting - normal state transition. It is
shown that, at the critical current density achieved presently in bulk
materials, and especially in BSCCO-2212, the required thickness of the cylinder
wall in a full-scale inductive device achieves several centimeters. A simple
mathematical model of the operation of an inductive fault current limiter (FCL)
is used to show that such cylinders cannot be cooled in admissible time after a
fault clearing and, hence, the inductive FCLs and current-limiting transformers
employing BSCCO cylinders do not return to the normal operation in the time
required. For the recovery even with a non-current pause in the circuit, the
cylinders are needed with the critical current density by an order higher than
the existed ones.Comment: 15 pages, 5 figure
Electric field formulation for thin film magnetization problems
We derive a variational formulation for thin film magnetization problems in
type-II superconductors written in terms of two variables, the electric field
and the magnetization function. A numerical method, based on this formulation,
makes it possible to accurately compute all variables of interest, including
the electric field, for any value of the power in the power law current-voltage
relation characterizing the superconducting material. For high power values we
obtain a good approximation to the critical state model solution. Numerical
simulation results are presented for simply and multiply connected films, and
also for an inhomogeneous film.Comment: 15 p., submitte
The massive star population of the Virgo Cluster galaxy NGC 4535
We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535
using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in
filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We
performed high precision point spread function fitting photometry of 24353
sources including 3762 candidate blue supergiants, 841 candidate yellow
supergiants and 370 candidate red supergiants. We estimated the ratio of blue
to red supergiants as a decreasing function of galactocentric radius. Using
Modules for Experiments in Stellar Astrophysics isochrones at solar
metallicity, we defined the luminosity function and estimated the star
formation history of the galaxy over the last 60 Myrs. We conducted a
variability search in the V and I filters using three variability indexes: the
median absolute deviation, the interquartile range and the inverse von-Neumann
ratio. This analysis yielded 120 new variable candidates with absolute
magnitudes ranging from M = 4 to 11 mag. We used the MESA
evolutionary tracks at solar metallicity, to classify the variables based on
their absolute magnitude and their position on the color-magnitude diagram.
Among the new candidate variable sources are eight candidate variable red
supergiants, three candidate variable yellow supergiants and one candidate
luminous blue variable, which we suggest for follow-up observations.Comment: Accepted by A&A, 7 pages, 7 Tables, 53 figure
Multi-frequency VLBA study of the blazar S5 0716+714 during the active state in 2004: I. Inner jet kinematics
We observed the blazar \object{0716+714} with the
VLBA during its active state in 2003-2004. In this paper we discuss
multi-frequency analysis of the inner jet (first 1 mas) kinematics. The
unprecedentedly dense time sampling allows us to trace jet components without
misidentification and to calculate the component speeds with good accuracy. In
the smooth superluminal jet we were able to identify and track three components
over time moving outwards with relatively high apparent superluminal speeds
(8.5-19.4 ), which contradicts the hypothesis of a stationary oscillating
jet in this source. Component ejections occur at a relatively high rate (once
in two months), and they are accompanied by mm-continuum outbursts.
Superluminal jet components move along wiggling trajectories, which is an
indication of actual helical motion. Fast proper motion and rapid decay of the
components suggest that this source should be observed with the VLBI at a rate
of at least once in one or two months in order to trace superluminal jet
components without confusion.Comment: 4 pages, 3 figures, Astronomy & Astrophysics Letter, language
corrections adde
Cutaneous sinus histiocytosis of face of the non-Langerhans cell histiocytoses type (cutaneous Rosai — Dorfman disease)
An extremely rare case of sinus histiocytosis of the non-Langerhans cell histiocytoses type is described in 55-year-old patient with isolated localization of cutanious lesion on the right cheek without involvement of nodular structures. Main skin lesion was an erythematous-cyanotic node with multiple milia-like lesions on the top of it. Histologically revealed feature was a large number of plasma cells, besides phenomenon of emperipolesis was described, which was first falsely perceived by pathologists as phagocytosis. In immu-nohistochemistry assay the changes were characterized by proliferation of large polygonal histiocytes with accumulation of pentalamellar markers in its cytoplasm (protein S-100, CD68)
The core shift effect in the blazar 3C 454.3
Opacity-driven shifts of the apparent VLBI core position with frequency (the
"core shift" effect) probe physical conditions in the innermost parts of jets
in active galactic nuclei. We present the first detailed investigation of this
effect in the brightest gamma-ray blazar 3C454.3 using direct measurements from
simultaneous 4.6-43 GHz VLBA observations, and a time lag analysis of 4.8-37
GHz lightcurves from the UMRAO, CrAO, and Metsahovi observations in 2007-2009.
The results support the standard Konigl model of jet physics in the VLBI core
region. The distance of the core from the jet origin r_c(nu), the core size
W(nu), and the lightcurve time lag DT(nu) all depend on the observing frequency
nu as r_c(nu)~W(nu)~ DT(nu)~nu^-1/k. The obtained range of k=0.6-0.8 is
consistent with the synchrotron self-absorption being the dominating opacity
mechanism in the jet. The similar frequency dependence of r_c(nu) and W(nu)
suggests that the external pressure gradient does not dictate the jet geometry
in the cm-band core region. Assuming equipartition, the magnetic field strength
scales with distance r as B = 0.4(r/1pc)^-0.8 G. The total kinetic power of
electron/positron jet is about 10^44 ergs/s.Comment: Accepted for publication in MNRAS; 10 pages, 6 figure
Effect of hot rolling on the microstructure and mechanical properties of a Ti-15Mo/TiB metal-matrix composite
A Ti-15Mo/TiB metal matrix composite was produced by the spark plasma sintering process at 1400 °C using a Ti-14.25 wt.% Mo-5 wt.% TiB2 powder mixture. The microstructure and mechanical properties of the composite were studied after non-isothermal rolling of specimens heated to 1000 °C to a thickness strain of ~0.
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