1,933 research outputs found
Molecular line study of the very young protostar IRAM 04191 in Taurus: Infall, rotation, and outflow
We present a detailed millimeter line study of the circumstellar environment
of the low-luminosity Class 0 protostar IRAM 04191+1522 in the Taurus molecular
cloud. New line observations demonstrate that the ~14000 AU radius protostellar
envelope is undergoing both extended infall and fast, differential rotation.
Radiative transfer modeling of multitransition CS and C34S maps indicate an
infall velocity v_inf ~ 0.15 km/s at r ~ 1500 AU and v_inf ~ 0.1 km/s up to r ~
11000 AU, as well as a rotational angular velocity Omega ~ 3.9 x 10^{-13}
rad/s, strongly decreasing with radius beyond 3500 AU down to a value Omega ~
1.5-3 x 10^{-14} rad/s at ~ 11000 AU. Two distinct regions, which differ in
both their infall and their rotation properties, therefore seem to stand out:
the inner part of the envelope (r ~< 2000-4000 AU) is rapidly collapsing and
rotating, while the outer part undergoes only moderate infall/contraction and
slower rotation. These contrasted features suggest that angular momentum is
conserved in the collapsing inner region but efficiently dissipated due to
magnetic braking in the slowly contracting outer region. We propose that the
inner envelope is in the process of decoupling from the ambient cloud and
corresponds to the effective mass reservoir (~0.5 M_sun) from which the central
star is being built. Comparison with the rotational properties of other objects
in Taurus suggests that IRAM 04191 is at a pivotal stage between a prestellar
regime of constant angular velocity enforced by magnetic braking and a
dynamical, protostellar regime of nearly conserved angular momentum. The
rotation velocity profile we derive for the inner IRAM 04191 envelope should
thus set some constraints on the distribution of angular momentum on the scale
of the outer Solar system at the onset of protostar/disk formation.Comment: 23 pages, 16 figures, 1 table, Accepted by Astronomy & Astrophysic
Inconsistency in Fermi's probability of the quantum states
We point out an important hidden inconsistency in Fermi's probability of the
quantum states that engendered inconsistent/inaccurate equations-of-state
extensively used in the literature to model nonideal plasma systems. The
importance of this amendment goes beyond rectifying our comprehension and
foundation of an important physical problem to influencing contemporary
research results.Comment: Accepted for Publicatio
Antibiotic resistance peculiarities of S. aureus isolates, obtained from nasal and throat mucosa of outpatients, Chernivtsi city
The purpose of this study was to determine the specificity of sensitivity to antibiotics of S. aureus strains isolated from nasal mucous membranes and tonsils, as well as to identify the factors of antibiotic resistance.
Materials and methods. The pure culture method was used to study smears of the palatine tonsils, the nose and the secret of the external auditory canal of 561, 56 and 15 cultures, respectively. Identification of isolated cultures was carried out according to morphological, tinctorial, physiological and biochemical characteristics. The sensitivity of S. aureus strains to antibiotics was studied and analyzed, 211 of which were isolated from the mucous of the palatine tonsils and 18 - from the nasal mucous. All the isolated strains of S. aureus were determined for the presence of antibiotic resistance factors (FA) -Ăź-lactamases (BL) and penicillin-binding protein (PĐ’Ps).
Results. High percentage of strains resistant to ß-lactam antibiotics and macrolides was found in both groups of studied cultures. However, the number of resistant forms to these antibiotics was higher among nasal strains. At the same time, none of the resistant strain to aminoglycosides, fluoroquinolones, lincosamides, tetracyclines, and vancomycin was detected among them. 9.57 % of the strains isolated from the tonsillar mucosa were resistant to the last one. BL and PВPs antibiotic resistance factors of isolated S. aureus strains were more frequent among nasal isolates (BL – 83.3 %, PВPs – 66.7 %) than in strains isolated from the palatine tonsils (BL – 66.3 %, PВPs – 38.6 %), P < 0.05. Sensitivity to antibiotics of S. aureus strains having both FA simultaneously (30 strains) and strains having none of them (26 strains) turned out to be different. Among the strains having both FA, 100 % were resistant to penicillin, 93.3 % to oxacillin, and 36.7 % to vancomycin. Whereas there were 3.9 %, 0.0 %, and 7.7 % strains without FA resistant to these antibiotics, respectively. Resistance to azithromycin was greater in the group of strains with FA: 26.7 % versus 7.7 % in the group without FA. The strains of both groups were highly sensitive with an insignificant difference to other studied antibiotics (aminoglycosides, fluoroquinolones, macrolides, lincosamides and tetracyclines).
Conclusions. S. aureus strains isolated from the mucous membranes of the nose and tonsils differ in sensitivity to antibiotics and the presence of FA. The nasal strains of S. aureus are more likely to be resistant to Ăź-lactam antibiotics and macrolides. Vancomycin resistant strains of S. aureus are significantly more common among strains with FA
A Guide to Delineate the Logic of Neurovascular Signaling in the Brain
The neurovascular system may be viewed as a distributed nervous system within the brain. It transforms local neuronal activity into a change in the tone of smooth muscle that lines the walls of arterioles and microvessels. We review the current state of neurovascular coupling, with an emphasis on signaling molecules that convey information from neurons to neighboring vessels. At the level of neocortex, this coupling is mediated by: (i) a likely direct interaction with inhibitory neurons, (ii) indirect interaction, via astrocytes, with excitatory neurons, and (iii) fiber tracts from subcortical layers. Substantial evidence shows that control involves competition between signals that promote vasoconstriction versus vasodilation. Consistent with this picture is evidence that, under certain circumstances, increased neuronal activity can lead to vasoconstriction rather than vasodilation. This confounds naĂŻve interpretations of functional brain images. We discuss experimental approaches to detect signaling molecules in vivo with the goal of formulating an empirical basis for the observed logic of neurovascular control
The surprising politics of anti-immigrant prejudice: How political conservatism moderates the effect of immigrant race and religion on infrahumanisation judgements
Attitudes towards immigrants in the UK are worsening. It has been posited that these attitudes may reflect covert racial and religious prejudices, particularly among conservatives. To investigate this, two studies examined the role that immigrant race (Black/White; Study 1) and immigrant religion (Muslim/non-Muslim; Study 2) played in immigrant infrahumanisation judgements, using political conservatism as a moderating variable. There was a moderating effect of political conservatism; however, it was not in the predicted direction. The results of both studies indicated that immigrant race (Black) and immigrant religion (Muslim) predicted greater infrahumanisation when political conservatism was low. Conservatives infrahumanised all immigrants equally (and more than liberals), but liberals were more sensitive to racial/religious biases in their evaluations of immigrants
Atomic Supersymmetry, Rydberg Wave Packets, and Radial Squeezed States
We study radial wave packets produced by short-pulsed laser fields acting on
Rydberg atoms, using analytical tools from supersymmetry-based quantum-defect
theory. We begin with a time-dependent perturbative calculation for
alkali-metal atoms, incorporating the atomic-excitation process. This provides
insight into the general wave packet behavior and demonstrates agreement with
conventional theory. We then obtain an alternative analytical description of a
radial wave packet as a member of a particular family of squeezed states, which
we call radial squeezed states. By construction, these have close to minimum
uncertainty in the radial coordinates during the first pass through the outer
apsidal point. The properties of radial squeezed states are investigated, and
they are shown to provide a description of certain aspects of Rydberg atoms
excited by short-pulsed laser fields. We derive expressions for the time
evolution and the autocorrelation of the radial squeezed states, and we study
numerically and analytically their behavior in several alkali-metal atoms. Full
and fractional revivals are observed. Comparisons show agreement with other
theoretical results and with experiment.Comment: published in Physical Review
Boundary dynamics and multiple reflection expansion for Robin boundary conditions
In the presence of a boundary interaction, Neumann boundary conditions should
be modified to contain a function S of the boundary fields: (\nabla_N +S)\phi
=0. Information on quantum boundary dynamics is then encoded in the
-dependent part of the effective action. In the present paper we extend the
multiple reflection expansion method to the Robin boundary conditions mentioned
above, and calculate the heat kernel and the effective action (i) for constant
S, (ii) to the order S^2 with an arbitrary number of tangential derivatives.
Some applications to symmetry breaking effects, tachyon condensation and brane
world are briefly discussed.Comment: latex, 22 pages, no figure
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