1,466 research outputs found
A dual output polarimeter devoted to the study of the Cosmic Microwave Background
We have developed a correlation radiometer at 33 GHz devoted to the search
for residual polarization of the Cosmic Microwave Background (CMB). The two
instruments`s outputs are linear combination of two Stokes Parameters (Q and U
or U and V). The instrument is therefore directly sensitive to the polarized
component of the radiation (respectively linear and circular). The radiometer
has a beam-width oif 7 or 14 deg, but it can be coupled to a telescope
increasing the resolution. The expected CMB polarization is at most a part per
milion. The polarimeter has been designed to be sensitive to this faint signal,
and it has been optimized to improve its long term stability, observing from
the ground. In this contribution the performances of the instrument are
presented, together with the preliminary test and observations.Comment: 12 pages, 6 figures, in print on the Proc. SPIE Conf. - August 200
EFFECTS OF ASCORBIC ACID ON MICROSOMAL DRUG METABOLISM *
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73764/1/j.1749-6632.1975.tb29272.x.pd
Growth of Rhodococcus sp. strain BCP1 on gaseous n-alkanes: New metabolic insights and transcriptional analysis of two soluble di-iron monooxygenase genes
Rhodococcus sp. strain BCP1 was initially isolated for its ability to grow on gaseous n-alkanes, which act as inducers for the co-metabolic degradation of low-chlorinated compounds. Here, both molecular and metabolic features of BCP1 cells grown on gaseous and short-chain n-alkanes (up to n-heptane) were examined in detail. We show that propane metabolism generated terminal and sub-terminal oxidation products such as 1- and 2-propanol, whereas 1-butanol was the only terminal oxidation product detected from n-butane metabolism. Two gene clusters, prmABCD and smoABCD-coding for Soluble Di-Iron Monooxgenases (SDIMOs) involved in gaseous n-alkanes oxidation-were detected in the BCP1 genome. By means of Reverse Transcriptase-quantitative PCR (RT-qPCR) analysis, a set of substrates inducing the expression of the sdimo genes in BCP1 were assessed as well as their transcriptional repression in the presence of sugars, organic acids, or during the cell growth on rich medium (Luria-Bertani broth). The transcriptional start sites of both the sdimo gene clusters were identified by means of primer extension experiments. Finally, proteomic studies revealed changes in the protein pattern induced by growth on gaseous- (n-butane) and/or liquid (n-hexane) short-chain n-alkanes as compared to growth on succinate. Among the differently expressed protein spots, two chaperonins and an isocytrate lyase were identified along with oxidoreductases involved in oxidation reactions downstream of the initial monooxygenase reaction step
Effect of ascorbic acid on the consequences of acute alcohol consumption in humans
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109850/1/cptclpt198765.pd
Universal power law in the orientational relaxation in thermotropic liquid crystals
We observe a surprisingly general power law decay at short to intermediate
times in orientational relaxation in a variety of model systems (both calamitic
and discotic, and also discrete) for thermotropic liquid crystals. As all these
systems transit across the isotropic-nematic phase boundary, two power law
relaxation regimes, separated by a plateau, emerge giving rise to a step-like
feature (well-known in glassy liquids) in the single-particle second-rank
orientational time correlation function. In contrast to its probable dynamical
origin in supercooled liquids, we show that the power law here can originate
from the thermodynamic fluctuations of the orientational order parameter,
driven by the rapid growth in the second-rank orientational correlation length.Comment: Submitted to Physical Review Letter
TRIS II: search for CMB spectral distortions at 0.60, 0.82 and 2.5 GHz
With the TRIS experiment we have performed absolute measurements of the sky
brightness in a sky circle at at the frequencies
0.60, 0.82 and 2.5 GHz. In this paper we discuss the techniques used to
separate the different contributions to the sky emission and give an evaluation
of the absolute temperature of the Cosmic Microwave Background. For the
black-body temperature of the CMB we get: at GHz; at GHz; at
GHz. The first error bar is statistic (1) while the second
one is systematic. These results represent a significant improvement with
respect to the previous measurements. We have also set new limits to the
free-free distortions, ,
and slightly improved the Bose-Einstein upper limit, , both at 95% confidence level.Comment: accepted for publication in The Astrophysical Journa
TRIS III: the diffuse galactic radio emission at
We present values of temperature and spectral index of the galactic diffuse
radiation measured at 600 and 820 MHz along a 24 hours right ascension circle
at declination . They have been obtained from a subset of
absolute measurements of the sky temperature made with TRIS, an experiment
devoted to the measurement of the Cosmic Microwave Background temperature at
decimetric-wavelengths with an angular resolution of about .
Our analysis confirms the preexisting picture of the galactic diffuse
emission at decimetric wavelength and improves the accuracy of the measurable
quantities. In particular, the signal coming from the halo has a spectral index
in the range above 600 MHz, depending on the sky position. In the
disk, at TRIS angular resolution, the free-free emission accounts for the 11%
of the overall signal at 600 MHz and 21% at 1420 MHz. The polarized component
of the galactic emission, evaluated from the survey by Brouw and Spoelstra,
affects the observations at TRIS angular resolution by less than 3% at 820 MHz
and less than 2% at 600 MHz. Within the uncertainties, our determination of the
galactic spectral index is practically unaffected by the correction for
polarization.
Since the overall error budget of the sky temperatures measured by TRIS at
600 MHz, that is 66 mK(systematic)18 mK (statistical), is definitely smaller
than those reported in previous measurements at the same frequency, our data
have been used to discuss the zero levels of the sky maps at 150, 408, 820 and
1420 MHz in literature. Concerning the 408 MHz survey, limiting our attention
to the patch of sky corresponding to the region observed by TRIS, we suggest a
correction of the base-level of K.Comment: Accepted for publication in the Astrophysical Journa
How glassy are orientational dynamics of rodlike molecules near the isotropic-nematic transition?
In an attempt to quantitatively characterize the recently observed slow
dynamics in the isotropic and nematic phase of liquid crystals, we investigate
the single-particle orientational dynamics of rodlike molecules across the
isotropic-nematic transition in computer simulations of a family of model
systems of thermotropic liquid crystals. Several remarkable features of glassy
dynamics are on display including non-exponential relaxation, dynamical
heterogeneity, and non-Arrhenius temperature dependence of the orientational
relaxation time. In order to obtain a quantitative measure of glassy dynamics
in line with the estbalished methods in supercooled liquids, we construct a
relaxation time versus scaled inverse temperature plot, and demonstrate that
one can indeed define a 'fragility index' for thermotropic liquid crystals,
that depends on density and aspect ratio. The values of the fragility parameter
are surprisingly in the range one observed for glass forming liquids. A
plausible correlation between the energy landscape features and the observed
fragility is discussed.Comment: 7 figures and 8 page
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