10,620 research outputs found
A High Galactic Latitude HI 21cm-line Absorption Survey using the GMRT: II. Results and Interpretation
We have carried out a sensitive high-latitude (|b| > 15deg.) HI 21cm-line
absorption survey towards 102 sources using the GMRT. With a 3-sigma detection
limit in optical depth of ~0.01, this is the most sensitive HI absorption
survey. We detected 126 absorption features most of which also have
corresponding HI emission features in the Leiden Dwingeloo Survey of Galactic
neutral Hydrogen. The histogram of random velocities of the absorption features
is well-fit by two Gaussians centered at V(lsr) ~ 0 km/s with velocity
dispersions of 7.6 +/- 0.3 km/s and 21 +/- 4 km/s respectively. About 20% of
the HI absorption features form the larger velocity dispersion component. The
HI absorption features forming the narrow Gaussian have a mean optical depth of
0.20 +/- 0.19, a mean HI column density of (1.46 +/- 1.03) X 10^{20} cm^{-2},
and a mean spin temperature of 121 +/- 69 K. These HI concentrations can be
identified with the standard HI clouds in the cold neutral medium of the
Galaxy. The HI absorption features forming the wider Gaussian have a mean
optical depth of 0.04 +/- 0.02, a mean HI column density of (4.3 +/- 3.4) X
10^{19} cm^{-2}, and a mean spin temperature of 125 +/- 82 K. The HI column
densities of these fast clouds decrease with their increasing random
velocities. These fast clouds can be identified with a population of clouds
detected so far only in optical absorption and in HI emission lines with a
similar velocity dispersion. This population of fast clouds is likely to be in
the lower Galactic Halo.Comment: 19 pages, 19 figures. Accepted for publication in Journal of
Astrophysics & Astronom
Network Inference via the Time-Varying Graphical Lasso
Many important problems can be modeled as a system of interconnected
entities, where each entity is recording time-dependent observations or
measurements. In order to spot trends, detect anomalies, and interpret the
temporal dynamics of such data, it is essential to understand the relationships
between the different entities and how these relationships evolve over time. In
this paper, we introduce the time-varying graphical lasso (TVGL), a method of
inferring time-varying networks from raw time series data. We cast the problem
in terms of estimating a sparse time-varying inverse covariance matrix, which
reveals a dynamic network of interdependencies between the entities. Since
dynamic network inference is a computationally expensive task, we derive a
scalable message-passing algorithm based on the Alternating Direction Method of
Multipliers (ADMM) to solve this problem in an efficient way. We also discuss
several extensions, including a streaming algorithm to update the model and
incorporate new observations in real time. Finally, we evaluate our TVGL
algorithm on both real and synthetic datasets, obtaining interpretable results
and outperforming state-of-the-art baselines in terms of both accuracy and
scalability
Chain of Hardy-type local reality constraints for qubits
Non-locality without inequality is an elegant argument introduced by L. Hardy
for two qubit systems, and later generalised to qubits, to establish
contradiction of quantum theory with local realism. Interestingly, for
this argument is actually a corollary of Bell-type inequalities, viz. the
CH-Hardy inequality involving Bell correlations, but for greater than 2 it
involves -particle probabilities more general than Bell-correlations. In
this paper, we first derive a chain of completely new local realistic
inequalities involving joint probabilities for qubits, and then, associated
to each such inequality, we provide a new Hardy-type local reality constraint
without inequalities. Quantum mechanical maximal violations of the chain of
inequalities and of the associated constraints are also studied by deriving
appropriate Cirel'son type theorems. These results involving joint
probabilities more general than Bell correlations are expected to provide a new
systematic tool to investigate entanglement.Comment: 10 pages, Late
BVRI CCD photometric standards in the field of GRB 990123
The CCD magnitudes in Johnson and Cousins photometric passbands are
determined for 18 stars in the field of GRB 990123. These measurements can be
used in carrying out precise CCD photometry of the optical transient of GRB
990123 using differential photometric techniques during non--photometric sky
conditions. A comparison with previous photometry indicates that the present
photmetry is more precise.Comment: Tex file, 5 pages with 1 figure. Bull. Astron. Society India, Vol. 27
(accepted
Multidrug-resistant tuberculosis
Multidrug-resistant tuberculosis (MDR-TB) caused by Mycobacterium tuberculosis resistant to both isoniazid and rifampicin with or without resistance to other drugs is among the most worrisome elements of the pandemic of antibiotic resistance. Globally, about three per cent of all newly diagnosed patients have MDR-TB. The proportion is higher in patients who have previously received antituberculosis treatment reflecting the failure of programmes designed to ensure complete cure of patients with tuberculosis. While host genetic factors may probably contribute, incomplete and inadequate treatment is the most important factor leading to the development of MDR-TB. The definitive diagnosis of MDR-TB is difficult in resource poor low income countries because of non-availability of reliable laboratory facilities. Efficiently run tuberculosis control programmes based on directly observed treatment, short-course (DOTS) policy is essential for preventing the emergence of MDR-TB. Management of MDR-TB is a challenge which should be undertaken by experienced clinicians at centres equipped with reliable laboratory service for mycobacterial culture and in vitro sensitivity testing as it requires prolonged use of expensive second-line drugs with a significant potential for toxicity. Judicious use of drugs, supervised individualised treatment, focussed clinical, radiological and bacteriological follow up, use of surgery at the appropriate juncture are key factors in the successful management of these patients. In certain areas, currently available programme approach may not be adequate and innovative approaches such as DOTS-plus may have to be employed to effectively control MDR-TB
рдЪреЗрдиреНрдирдИ рдорд╛рддреНрд╕реНрдпрд┐рдХреА рдкреЛрддрд╛рд╢реНрд░рдп рдореЗрдВ рдмреИрдЧ рдЬрд╛рд▓ рджреНрд╡рд╛рд░рд╛ рдмреЛрдИ (рдорд▓реНрд▓реЗрдЯ) рдореБрдЬрд┐рд▓ рд╕реЗрдлреЗрд▓рд╕ рдХрд╛ рднрд╛рд░реА рдЕрд╡рддрд░рдг
рдХреГрдкрдпрд╛ рдкреВрд░рд╛ рд▓реЗрдЦрд╛ рдкрдв
- тАж