11,635 research outputs found
Stimulated Raman Adiabatic Passage via bright state in Lambda medium of unequal oscillator strengths
We consider the population transfer process in a Lambda-type atomic medium of
unequal oscillator strengths by stimulated Raman adiabatic passage via
bright-state (b-STIRAP) taking into account propagation effects. Using both
analytic and numerical methods we show that the population transfer efficiency
is sensitive to the ratio q_p/q_s of the transition oscillator strengths. We
find that the case q_p>q_s is more detrimental for population transfer process
as compared to the case where . For this case it is possible to
increase medium dimensions while permitting efficient population transfer. A
criterion determining the interaction adiabaticity in the course of propagation
process is found. We also show that the mixing parameter characterizing the
population transfer propagates superluminally
Infrared-temperature variability in a large agricultural field
The combined effect of water carved gullies, varying soil color, moisture state of the soil and crop, nonuniform phenology, and bare spots was measured for commercially grown barley planted on varying terrain. For all but the most rugged terrain, over 80% of the area within 4, 16, 65, and 259 ha cells was at temperatures within 3 C of the mean cell temperature. The result of using relatively small, 4 ha instantaneous field of views for remote sensing applications is that either the worst or the best of conditions is often observed. There appears to be no great advantage in utilizing a small instantaneous field of view instead of a large one for remote sensing of crop canopy temperatures. The two alternatives for design purposes are then either a very high spatial resolution, of the order of a meter or so, where the field is very accurately temperature mapped, or a low resolution, where the actual size seems to make little difference
Performance of the SERT 2 spacecraft after 4 and one-half years in space
The SERT 2 satellite, launched in February, 1970, has recently been reactivated after being dormant for a year. The satellite orientation was changed to spin stabilization in 1973 and the satellite is now coning such that the active side of the solar arrays move into and out of the sun every 23 days. There is sufficient power to operate the ion thrusters for seven days of this cycle. The 2 ion thruster system was successfully operated; the electrical short in the accelerating grids had cleared during the year long dormant phase
Unusually Luminous Giant Molecular Clouds in the Outer Disk of M33
We use high spatial resolution (~7pc) CARMA observations to derive detailed
properties for 8 giant molecular clouds (GMCs) at a galactocentric radius
corresponding to approximately two CO scale lengths, or ~0.5 optical radii
(r25), in the Local Group spiral galaxy M33. At this radius, molecular gas
fraction, dust-to-gas ratio and metallicity are much lower than in the inner
part of M33 or in a typical spiral galaxy. This allows us to probe the impact
of environment on GMC properties by comparing our measurements to previous data
from the inner disk of M33, the Milky Way and other nearby galaxies. The outer
disk clouds roughly fall on the size-linewidth relation defined by
extragalactic GMCs, but are slightly displaced from the luminosity-virial mass
relation in the sense of having high CO luminosity compared to the inferred
virial mass. This implies a different CO-to-H2 conversion factor, which is on
average a factor of two lower than the inner disk and the extragalactic
average. We attribute this to significantly higher measured brightness
temperatures of the outer disk clouds compared to the ancillary sample of GMCs,
which is likely an effect of enhanced radiation levels due to massive star
formation in the vicinity of our target field. Apart from brightness
temperature, the properties we determine for the outer disk GMCs in M33 do not
differ significantly from those of our comparison sample. In particular, the
combined sample of inner and outer disk M33 clouds covers roughly the same
range in size, linewidth, virial mass and CO luminosity than the sample of
Milky Way GMCs. When compared to the inner disk clouds in M33, however, we find
even the brightest outer disk clouds to be smaller than most of their inner
disk counterparts. This may be due to incomplete sampling or a potentially
steeper cloud mass function at larger radii.Comment: Accepted for Publication in ApJ; 7 pages, 4 figure
Anti-malarial drugs: how effective are they against Plasmodium falciparum gametocytes?
<p>Abstract</p> <p>Background</p> <p>Recent renewed emphasis on the eradication of malaria has highlighted the need for more tools with which to achieve this ambitious goal. One high priority area is the need to determine the gametocytocidal activity of both currently used anti-malarial drugs and those in the development pipeline. However, testing the activity of compounds against <it>Plasmodium falciparum </it>gametocytes is technically challenging both <it>in vivo </it>and <it>in vitro</it>.</p> <p>Methods</p> <p>Here the use of a simple robust assay to screen a panel of currently used and experimental anti-malarial drugs against mature <it>P. falciparum </it>gametocytes is described.</p> <p>Results</p> <p>Eight of 44 compounds tested reduced gametocyte viability by at least 50% and three showed IC<sub>50 </sub>values in nM range.</p> <p>Conclusions</p> <p>There is a need to identify new compounds with activity against late stage gametocytes and the information provided by this <it>in vitro </it>assay is a valuable first step, which can guide future clinical studies.</p
Strand Coating for the Superconducting Cables of the LHC Main Magnets
The electrical resistance of contacts between strands in the Rutherford type superconducting cables has a major effect on the eddy current loss in cables, and on the dynamic magnetic field error in the LHC main magnets. In order to guarantee the value and constancy of the contact resistance, various metallic coatings were studied from the electrical and mechanical points of view in the past. We report on the molten bath Sn95wt.Ag5wt. coating, oxidized thermally in air after the cabling is completed, that we adopted for the cables of the LHC main magnets. The value of the con-tact resistance is determined by the strand coating and cabling procedures, oxidation heat treatment, and the magnet coil cu-ring and handling. Chemical analysis helps to understand the evolution of the contacts. We also mention results on two electrolytic coatings resulting in higher contact resistance
Examination of contacts between strands by electrical measurements and topographical analysis
The contact resistance (crossing and adjacent) between the strands of Rutherford type superconducting cables has been proven to be an essential parameter for the behaviour of the main magnets in accelerators like the LHC. A strong development program has been launched at CERN. Contact resistances were measured by means of a DC method at 4.2 K. The strand deformation and the chemical conditions at the contacts were analyzed in order to interpret the electrical resistances measured by a 3 contacts method on individual strands as well as the resistances measured independently on cables
Magnetohydrostatic solar prominences in near-potential coronal magnetic fields
We present numerical magnetohydrostatic solutions describing the
gravitationally stratified, bulk equilibrium of cool, dense prominence plasma
embedded in a near-potential coronal field. These solutions are calculated
using the FINESSE magnetohydrodynamics equilibrium solver and describe the
morphologies of magnetic field distributions in and around prominences and the
cool prominence plasma that these fields support. The equilibrium condition for
this class of problem is usually different in distinct subdomains, separated by
free boundaries, across which solutions are matched by suitable continuity or
jump conditions describing force balance. We employ our precise finite element
elliptic solver to calculate solutions not accessible by previous analytical
techniques with temperature or entropy prescribed as free functions of the
magnetic flux function, including a range of values of the polytropic index,
temperature variations mainly across magnetic field lines and photospheric
field profiles sheared close to the polarity inversion line. Out of the many
examples computed here, perhaps the most noteworthy is one which reproduces
precisely the three-part structure often encountered in observations: a cool
dense prominence within a cavity/flux rope embedded in a hot corona. The
stability properties of these new equilibria, which may be relevant to solar
eruptions, can be determined in the form of a full resistive MHD spectrum using
a companion hyperbolic stability solver.Comment: To appear in ApJ August 200
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