979 research outputs found
UNDERGROUND WIRELESS COMMUNICATION CHANNEL MODELING AND SIMULATION USING 0.3GMSK MODULATION CONSIDERING PENETRATION AND SCATTERING LOSS
Wireless communication inside mines and tunnels is very different from that in terrestrial environment because of the strong attenuation of signals. Here, we are developing an empirical model for the underground wireless communication channel based on experimental data which help in predicting the average received signal strength at a given distance from transmitter. The model aims at adding correction factors to the available outdoor and indoor propagation models such as Okumara-hata model, cost231 model, ITU indoor propagation models etc. Modeling is done by choosing the most appropriate model among the available ones and performing regression methods to the model based on experimental data. Correction factors are then added based on two parameters which we are considering namely- Penetration and Scattering loss for 0.3GMSK
HI in Abell 3128
We discuss Australia Telescope Compact Array (ATCA) HI 21cm data for the
galaxy cluster A3128. Our observations are intentionally relatively shallow,
and a blind search through our data cube yields (tentative) detections of only
two galaxies, of which one is probably spurious.
A3128 is part of the ESO Nearby Abell Cluster Survey (ENACS); redshifts are
available for 193 galaxies in the A3128 region. For 148 of these galaxies the
redshifts are such that the HI emission (if any) would lie within our data
cube. We use the known redshifts of these galaxies to coadd their spectra and
thus improve our sensitivity to HI emission. The technique is fairly successful
-- the coadded spectra allow detection of an average mass content of ~ 9x10^8
Msun, almost an order of magnitude lower than for direct detection of
individual objects.
By dividing the total galaxy sample into subsamples we find that the gas
content of late type galaxies that lie outside the X-ray emitting core of the
cluster is substantially higher than that of those within the core. Even
outside the X-ray emitting region the distribution of gas-rich galaxies in the
cluster is not uniform, we find that gas-rich galaxies are concentrated in the
east of the cluster. This is consistent with earlier analyses of the kinematics
of the galaxies in A3128 which indicate the presence of subclustering.
In summary we find that coadding spectra is a powerful tool for the study of
HI in cluster galaxies, and suggest that this technique could be applied to
substantially increase the redshift range over which such observations could be
carried out.Comment: 8pages, 7 figures accepted for publication in A&
Some experience in the production of high silicon Fe-Mn at TISCO Joda Plant
The paper describes the experience gained over the last few years in the production of Silico manganese at Ferro Manganese Plant, Joda.
The quality of the quartzite is a very important factor governing the level of silicon in the alloys. An alloy of 16% silicon could be produced successfully with 96% SiO2 in the quartzite.
Trials in the production of the alloy and the improvement effected of its grade has also been discussed
Constraining the variation of fundamental constants using 18cm OH lines
We describe a new technique to estimate variations in the fundamental
constants using 18cm OH absorption lines. This has the advantage that all lines
arise in the same species, allowing a clean comparison between the measured
redshifts. In conjunction with one additional transition (for example, an
HCO line), it is possible to simultaneously measure changes in ,
and . At present, only the 1665 MHz and 1667 MHz lines
have been detected at cosmological distances; we use these line redshifts in
conjunction with those of HI 21cm and mm-wave molecular absorption in a
gravitational lens at to constrain changes in the above three
parameters over the redshift range . While the constraints
are relatively weak ( 1 part in ), this is the first
simultaneous constraint on the variation of all three parameters. We also
demonstrate that either one (or more) of , and must vary with
cosmological time or there must be systematic velocity offsets between the OH,
HCO and HI absorbing clouds.Comment: 5 pages, no figures. Accepted for publication in Phys. Rev. Let
Resolving the mystery of the dwarf galaxy HIZSS003
The nearby galaxy HIZSS003 was recently discovered during a blind HI survey
of the zone of avoidance (Henning et al. 2000). Follow up VLA as well as
optical and near-IR imaging and spectroscopy (Massey et al. 2003; Silva et al.
2005) confirm that it is a low metallicity dwarf irregular galaxy. However
there were two puzzling aspects of the observations, (i) current star
formation, as traced by H emission, is confined to a small region at
the edge of the VLA HI image and (ii) the metallicity of the older RGB stars is
higher than that of the gas in HII region. We present high spatial and velocity
resolution Giant Meterwave Radio Telescope (GMRT) observations that resolve
these puzzles by showing that HIZSS003 is actually a galaxy pair and that the
HII region lies at the center of a much smaller companion galaxy (HIZSS003B) to
the main galaxy (HIZSS003A). The HI emission from these two galaxies overlaps
in projection, but can be separated in velocity space. HIZSS003B has an HI mass
of 2.6 X 10^6 M, and a highly disturbed velocity field. Since the
velocity field is disturbed, an accurate rotation curve cannot be derived,
however, the indicative dynamical mass is ~5 X 10^7 M. For the bigger
galaxy HIZSS003A we derive an HI mass of 1.4 X 10^7 M. The velocity
field of this galaxy is quite regular and from its rotation curve we derive a
total dynamical mass of ~6.5 X 10^8 M.Comment: 5 pages, 4 figures. Accepted for publication in MNRAS Letter
Sequence and structural features of binding site residues in protein-protein complexes: comparison with protein-nucleic acid complexes
<p>Abstract</p> <p>Background</p> <p>Protein-protein interactions are important for several cellular processes. Understanding the mechanism of protein-protein recognition and predicting the binding sites in protein-protein complexes are long standing goals in molecular and computational biology.</p> <p>Methods</p> <p>We have developed an energy based approach for identifying the binding site residues in protein–protein complexes. The binding site residues have been analyzed with sequence and structure based parameters such as binding propensity, neighboring residues in the vicinity of binding sites, conservation score and conformational switching.</p> <p>Results</p> <p>We observed that the binding propensities of amino acid residues are specific for protein-protein complexes. Further, typical dipeptides and tripeptides showed high preference for binding, which is unique to protein-protein complexes. Most of the binding site residues are highly conserved among homologous sequences. Our analysis showed that 7% of residues changed their conformations upon protein-protein complex formation and it is 9.2% and 6.6% in the binding and non-binding sites, respectively. Specifically, the residues Glu, Lys, Leu and Ser changed their conformation from coil to helix/strand and from helix to coil/strand. Leu, Ser, Thr and Val prefer to change their conformation from strand to coil/helix.</p> <p>Conclusions</p> <p>The results obtained in this study will be helpful for understanding and predicting the binding sites in protein-protein complexes.</p
Conjugate 18cm OH Satellite Lines at a Cosmological Distance
We have detected the two 18cm OH satellite lines from the
source PKS1413+135, the 1720 MHz line in emission and the 1612 MHz line in
absorption. The 1720 MHz luminosity is , more than
an order of magnitude larger than that of any other known 1720 MHz maser. The
profiles of the two satellite lines are conjugate, implying that they arise in
the same gas. This allows us to test for any changes in the values of
fundamental constants, without being affected by systematic uncertainties
arising from relative motions between the gas clouds in which the different
lines arise. Our data constrain changes in ,
where ; we find ,
consistent with no changes in , and .Comment: 5 pages, 1 figure. Minor changes to match published versio
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