354 research outputs found
Study of star formation in RCW 106 using far infrared observations
High resolution far-infrared observations of a large area of the star forming
complex RCW 106 obtained using the TIFR 1-metre balloon-borne telescope are
presented. Intensity maps have been obtained simultaneously in two bands
centred around 150 & 210 micron. Intensity maps have also been obtained at the
4 IRAS bands using HIRES processed IRAS data. From the 150 & 210 micron maps,
reliable maps of dust temperature and optical depth have been generated. The
star formation in this complex has occured in five linear subclumps. Using the
map at 210 micron, which has a spatial resolution superior to that of the IRAS
at 100 micron, 23 sources have been identified. The SED and luminosity of these
sources have been determined using the associations wit hthe IRAS maps.
Luminosity distribution of these sources has been obtained. Assuming these
embedded sources to be ZAMS stars and using the mass-luminosity relation, the
power law slope of the Initial Mass Function is found to be -1.73+-0.5. This
index for this very young complex is about the same as that for more evolved
complexes and clusters. Radiation transfer calculations in spherical geometry
have been undertaken to fit the SEDs of 13 sources with fluxes in both the TIFR
and IRAS bands. From this, the r^-2 density distribution in the envelopes is
ruled out. Finally, a correlation is seen between the luminosity of embedded
sources and the computed dust masses of the envelopes.Comment: Accepted for publication in MNRAS (21 pages, 8 figures & 3 tables
Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24
Recently, using Greenwich and Solar Optical Observing Network sunspot group
data during the period 1874-2006, (Javaraiah, MNRAS, 377, L34, 2007: Paper I),
has found that: (1) the sum of the areas of the sunspot groups in 0-10 deg
latitude interval of the Sun's northern hemisphere and in the time-interval of
-1.35 year to +2.15 year from the time of the preceding minimum of a solar
cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of
the smoothed monthly sunspot number) of the next cycle n+1. (2) The sum of the
areas of the spot groups in 0-10 deg latitude interval of the southern
hemisphere and in the time-interval of 1.0 year to 1.75 year just after the
time of the maximum of the cycle n correlates very well (r=0.966) with the
amplitude of cycle n+1. Using these relations, (1) and (2), the values 112 + or
- 13 and 74 + or -10, respectively, were predicted in Paper I for the amplitude
of the upcoming cycle 24. Here we found that in case of (1), the north-south
asymmetry in the area sum of a cycle n also has a relationship, say (3), with
the amplitude of cycle n+1, which is similar to (1) but more statistically
significant (r=0.968) like (2). By using (3) it is possible to predict the
amplitude of a cycle with a better accuracy by about 13 years in advance, and
we get 103 + or -10 for the amplitude of the upcoming cycle 24. However, we
found a similar but a more statistically significant (r=0.983) relationship,
say (4), by using the sum of the area sum used in (2) and the north-south
difference used in (3). By using (4) it is possible to predict the amplitude of
a cycle by about 9 years in advance with a high accuracy and we get 87 + or - 7
for the amplitude of cycle 24.Comment: 21 pages, 7 figures, Published in Solar Physics 252, 419-439 (2008
Macromolecular theory of solvation and structure in mixtures of colloids and polymers
The structural and thermodynamic properties of mixtures of colloidal spheres
and non-adsorbing polymer chains are studied within a novel general
two-component macromolecular liquid state approach applicable for all size
asymmetry ratios. The dilute limits, when one of the components is at infinite
dilution but the other concentrated, are presented and compared to field theory
and models which replace polymer coils with spheres. Whereas the derived
analytical results compare well, qualitatively and quantitatively, with
mean-field scaling laws where available, important differences from ``effective
sphere'' approaches are found for large polymer sizes or semi-dilute
concentrations.Comment: 23 pages, 10 figure
Experimental investigation of the detection mechanism in WSi nanowire superconducting single photon detectors
Quantum Matter and Optic
Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions
The osmotic virial coefficient of globular protein solutions is
calculated as a function of added salt concentration at fixed pH by computer
simulations of the ``primitive model''. The salt and counter-ions as well as a
discrete charge pattern on the protein surface are explicitly incorporated. For
parameters roughly corresponding to lysozyme, we find that first
decreases with added salt concentration up to a threshold concentration, then
increases to a maximum, and then decreases again upon further raising the ionic
strength. Our studies demonstrate that the existence of a discrete charge
pattern on the protein surface profoundly influences the effective interactions
and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek
(DLVO) theory fail for large ionic strength. The observed non-monotonicity of
is compared to experiments. Implications for protein crystallization are
discussed.Comment: 43 pages, including 17 figure
Gravitational Radiation from Compact Binary Pulsars
An outstanding question in modern Physics is whether general relativity (GR)
is a complete description of gravity among bodies at macroscopic scales.
Currently, the best experiments supporting this hypothesis are based on
high-precision timing of radio pulsars. This chapter reviews recent advances in
the field with a focus on compact binary millisecond pulsars with white-dwarf
(WD) companions. These systems - if modeled properly - provide an unparalleled
test ground for physically motivated alternatives to GR that deviate
significantly in the strong-field regime. Recent improvements in observational
techniques and advances in our understanding of WD interiors have enabled a
series of precise mass measurements in such systems. These masses, combined
with high-precision radio timing of the pulsars, result to stringent
constraints on the radiative properties of gravity, qualitatively very
different from what was available in the past.Comment: Short review chapter to appear in "Gravitational Wave Astrophysics"
by Springer-Verlag, edited by Carlos F. Sopuerta; v3: a few major corrections
and updated references. Comments are welcome
Synthesis, antileishmanial activity and QSAR studies of 2-chloro- N -arylacetamides
ABSTRACT We describe herein the synthesis and evaluation of the antileishmanial activity against promastigote forms of Leishmania amazonensis and cytotoxicity to murine macrophages of a series of 2-chloro-N-arylacetamide derivatives. All compounds were active, except one (compound 3). Compound 5 presented the most promising results, showing good antileishmanial activity (CI50=5.39±0.67 µM) and moderate selectivity (SI=6.36), indicating that further development of this class is worthwhile. Preliminary QSAR studies, although not predictive, furnished some insights on the importance of electronic character of aryl substituent to biological activity, as well as an indirect influence of hydrophobicity on activity
Calculation of the Flux of Atmospheric Neutrinos
Atmospheric neutrino-fluxes are calculated over the wide energy range from 30
MeV to 3,000 GeV for the study of neutrino-physics using the data from
underground neutrino-detectors. The atmospheric muon-flux at high altitude and
at sea level is studied to calibrate the neutrino-fluxes at low energies and
high energies respectively. The agreement of our calculation with observations
is satisfactory. The uncertainty of atmospheric neutrino-fluxes is also
studied.Comment: 51 page
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