36,428 research outputs found
Multicomponent gas sorption Joule-Thomson refrigeration
The present invention relates to a cryogenic Joule-Thomson refrigeration capable of pumping multicomponent gases with a single stage sorption compressor system. Alternative methods of pumping a multicomponent gas with a single stage compressor are disclosed. In a first embodiment, the sorbent geometry is such that a void is defined near the output of the sorption compressor. When the sorbent is cooled, the sorbent primarily adsorbs the higher boiling point gas such that the lower boiling point gas passes through the sorbent to occupy the void. When the sorbent is heated, the higher boiling point gas is desorbed at high temperature and pressure and thereafter propels the lower boiling point gas out of the sorption compressor. A mixing chamber is provided to remix the constituent gases prior to expansion of the gas through a Joule-Thomson valve. Other methods of pumping a multicomponent gas are disclosed. For example, where the sorbent is porous and the low boiling point gas does not adsorb very well, the pores of the sorbent will act as a void space for the lower boiling point gas. Alternatively, a mixed sorbent may be used where a first sorbent component physically adsorbs the high boiling point gas and where the second sorbent component chemically absorbs the low boiling point gas
Flexible thermal apparatus for mounting of thermoelectric cooler
A flexible heat transfer apparatus used to flexibly connect and thermally couple a thermoelectric cooler to an object to be cooled is disclosed. The flexible heat transfer apparatus consists of a pair of flexible corrugated sheets made from high thermal conductivity materials such as copper, aluminum, gold, or silver. The ridges of the corrugated sheets are oriented perpendicular to one another and bonded sandwich-fashion between three plates to define an upper section and a lower section. The upper section provides X flexure, the lower section provides Y flexure, and both sections together provide Z flexure
Fuel economy and exhaust emissions characteristics of diesel vehicles: Test results of a prototype Fiat 131 NA 2.4 liter automobile
The vehicle was tested on a chassis dynamometer over selected drive cycles and steady-state conditions. Two fuels were used, a U.S. no. 2 diesel and a European diesel fuel. The vehicle was tested with retarded timing and with and without an oxidation catalyst. Particulate emission rates were calculated from dilution tunnel measurements and large volume particulate samples were collected for biological and chemical analysis. It was determined that while the catalyst was generally effective in reducing hydrocarbon and carbon monoxide levels, it was also a factor in increasing particulate emissions. Increased particulate emission rates were particularly evident when the vehicle was operated on the European fuel which has a high sulfur content
Two-loop electroweak contributions to
A review is given on the quantum correction in the -- mass
correlation at the electroweak two-loop level, as derived from the calculation
of the muon lifetime in the Standard Model. Exact results for and
the -mass prediction including corrections with
fermion loops are presented and compared with previous results of a
next-to-leading order expansion in the top-quark mass.Comment: 14 pages, including 4 figures. Presented at the 5th International
Symposium on Radiative Corrections, (RADCOR-2000), Carmel CA, USA, 11-15
September 200
Finite-Temperature Properties of Ba(Zr,Ti)O Relaxors From First Principles
A first-principles-based technique is developed to investigate properties of
Ba(Zr,Ti)O relaxor ferroelectrics as a function of temperature. The use of
this scheme provides answers to important, unresolved and/or controversial
questions, such as: what do the different critical temperatures usually found
in relaxors correspond to? Do polar nanoregions really exist in relaxors? If
yes, do they only form inside chemically-ordered regions? Is it necessary that
antiferroelectricity develops in order for the relaxor behavior to occur? Are
random fields and random strains really the mechanisms responsible for relaxor
behavior? If not, what are these mechanisms? These {\it ab-initio-based}
calculations also leads to a deep microscopic insight into relaxors.Comment: 3 figures + Supplemen
High Sensitivity Array Observations of the QSO BRI 1335-0417
We present sensitive phase-referenced VLBI results on the radio continuum
emission from the QSO BRI 1335--0417. The observations were carried out
at 1.4 GHz using the High Sensitivity Array (HSA). Our sensitive VLBI image at
mas ( kpc) resolution shows continuum
emission in BRI 1335--0417 with a total flux density of Jy,
consistent with the flux density measured with the VLA. The size of the source
at FWHM is mas ( kpc) and the derived
intrinsic brightness temperature is K. No continuum
emission is detected at the full VLBI resolution ( mas, pc), with a 4 point source upper limit of 34 Jy
beam, or an upper limit to the intrinsic brightness temperature of
K. The highest angular resolution with at least a 4.5
detection of the radio continuum emission is mas ( kpc). At this resolution, the image shows a continuum feature in BRI
1335--0417 with a size of mas ( kpc) at FWHM,
and intrinsic brightness temperature of K. The extent of
the observed continuum sources at 1.4 GHz and the derived brightness
temperatures show that the radio emission (and thus presumably the far-infrared
emission) in BRI 1335--0417 is powered by a major starburst, with a massive
star formation rate of order a few thousand M_{\odot} {\rm yr}^{-1}z=4.4$ QSO.Comment: 13 pages, 3 figures, AJ accepte
Error bounds on block Gauss Seidel solutions of coupled\ud multiphysics problems
Mathematical models in many fields often consist of coupled sub–models, each of which describe a different physical process. For many applications, the quantity of interest from these models may be written as a linear functional of the solution to the governing equations. Mature numerical solution techniques for the individual sub–models often exist. Rather than derive a numerical solution technique for the full coupled model, it is therefore natural to investigate whether these techniques may be used by coupling in a block Gauss–Seidel fashion. In this study, we derive two a posteriori bounds for such linear functionals. These bounds may be used on each Gauss–Seidel iteration to estimate the error in the linear functional computed using the single physics solvers, without actually solving the full, coupled problem. We demonstrate the use of the bound first by using a model problem from linear algebra, and then a linear ordinary differential equation example. We then investigate the effectiveness of the bound using a non–linear coupled fluid–temperature problem. One of the bounds derived is very sharp for most linear functionals considered, allowing us to predict very accurately when to terminate our block Gauss–Seidel iteration.\ud
\ud
Copyright c 2000 John Wiley & Sons, Ltd
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Length-length and weight-length relationships of seven deep-water fishes in the Gulf of Mexico
Regression coefficients for equations of the form Y = a + bX were estimated for total length (TL) and whole weight (W) as a function of standard length (SL) and fork length (FL) and vice versa for seven deep-water fishes. All lengths were measured in millimeters and all weights in grams. There was a significant correlation between weight and length and the types of length measurements for all species. However, the amount of variation explained by each regression varied among species. Weight-length regressions were less precise than length-length regression, as they generally are, because weights of small fish measured at sea are more inaccurate than those of large fish.Marine Scienc
Chlorinated auxins–how does Arabidopsis thaliana deal with them?
Plant hormones have various functions in plants and play crucial roles in all developmental and differentiation stages. Auxins constitute one of the most important groups with the major representative indole-3-acetic acid (IAA). A halogenated derivate of IAA, 4-chloro-indole-3-acetic acid (4-Cl-IAA), has previously been identified in Pisum sativum and other legumes. While the enzymes responsible for the halogenation of compounds in bacteria and fungi are well studied, the metabolic pathways leading to the production of 4-Cl-IAA in plants, especially the halogenating reaction, are still unknown. Therefore, bacterial flavin-dependent tryptophan-halogenase genes were transformed into the model organism Arabidopsis thaliana. The type of chlorinated indole derivatives that could be expected was determined by incubating wild type A. thaliana with different Cl-tryptophan derivatives. We showed that, in addition to chlorinated IAA, chlorinated IAA conjugates were synthesized. Concomitantly, we found that an auxin conjugate synthetase (GH3.3 protein) from A. thaliana was able to convert chlorinated IAAs to amino acid conjugates in vitro. In addition, we showed that the production of halogenated tryptophan (Trp), indole-3-acetonitrile (IAN) and IAA is possible in transgenic A. thaliana in planta with the help of the bacterial halogenating enzymes. Furthermore, it was investigated if there is an effect (i) of exogenously applied Cl-IAA and Cl-Trp and (ii) of endogenously chlorinated substances on the growth phenotype of the plants
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