2,609 research outputs found
Studies of interstellar vibrationally-excited molecules
Several molecules thus far have been detected in the ISM in vibrationally-excited states, including H2, SiO, HC3N, and CH3CN. In order for vibrational-excitation to occur, these species must be present in unusually hot and dense gas and/or where strong infrared radiation is present. In order to do a more thorough investigation of vibrational excitation in the interstellar medium (ISM), studies were done of several mm-wave transitions originating in excited vibrational modes of HCN, an abundant interstellar molecule. Vibrationally-excited HCN was recently detected toward Orion-KL and IRC+10216, using a 12 meter antenna. The J=3-2 rotational transitions were detected in the molecule's lowest vibrational state, the bending mode, which is split into two separate levels, due to l-type doubling. This bending mode lies 1025K above ground state, with an Einstein A coefficient of 3.6/s. The J=3-2 line mode of HCN, which lies 2050K above ground state, was also observed toward IRC+10216, and subsequently in Orion-KL. Further measurements of vibrationally-excited HCN were done using a 14 meter telescope, which include the observations of the (0,1,0) and (0,2,0) modes towards Orion-KL, via their J=3-2 transitions at 265-267 GHz. The spectrum of the J=3-2 line in Orion taken with the 14 meter telescope, is shown, along with a map, which indicates that emission from vibrationally-excited HCN arises from a region probably smaller than the 14 meter telescope's 20 arcsec beam
DataWarp: Building Applications which Make Progress in an Inconsistent World
The usual approach to dealing with imperfections in data is to attempt to eliminate them. However, the nature of modern systems means this is often futile. This paper describes an approach which permits applications to operate notwithstanding inconsistent data. Instead of attempting to extract a single, correct view of the world from its data, a DataWarp application constructs a collection of interpretations. It adopts one of these and continues work. Since it acts on assumptions, the DataWarp application considers its recent work to be provisional, expecting eventually most of these actions will become definitive. Should the application decide to adopt an alternative data view, it may then need to void provisional actions before resuming work. We describe the DataWarp architecture, discuss its implementation and describe an experiment in which a DataWarp application in an environment containing inconsistent data achieves better results than its conventional counterpart
Biosynthesis of valine and isoleucine. II. Formation of α-acetolactate and α-aceto-α-hydroxybutyrate in Neurospora crassa and Escherichia coli
This article does not have an abstract
Microsphere plate detectors used with a compact Mott polarimeter for time-of-flight studies
A compact retarding-potential Mott polarimeter combined with microsphere plates (MSP) as electron detectors was built to perform spin-resolved time-of-flight electron spectroscopy. The comparison of the performance of MSP and channeltron detectors shows that the MSP detector has a better time resolution but a lower efficiency. The overall time resolution of the system was determined to be 350 ps using synchrotron radiation pulses
Conformal submanifolds, distinguished submanifolds, and integrability
For conformal geometries of Riemannian signature, we provide a comprehensive
and explicit treatment of the core local theory for embedded submanifolds of
arbitrary dimension. This is based in the conformal tractor calculus and
includes a conformally invariant Gauss formula leading to conformal versions of
the Gauss, Codazzi, and Ricci equations. It provides the tools for
proliferating submanifold conformal invariants, as well for extending to
conformally singular Riemannian manifolds the notions of mean curvature and of
minimal and CMC submanifolds. A notion of distinguished submanifold is defined
by asking the tractor second fundamental form to vanish. We show that for the
case of curves this exactly characterises conformal geodesics (a.k.a. conformal
circles) while for hypersurfaces it is the totally umbilic condition. So, for
other codimensions, this unifying notion interpolates between these extremes,
and we prove that in all dimensions this coincides with the submanifold being
weakly conformally circular, meaning that ambient conformal circles remain in
the submanifold. Stronger notions of conformal circularity are then
characterised similarly. Next we provide a very general theory and construction
of quantities that are necessarily conserved along distinguished submanifolds.
This first integral theory thus vastly generalises the results available for
conformal circles in [56]. We prove that any normal solution to an equation
from the class of first BGG equations can yield such a conserved quantity, and
show that it is easy to provide explicit formulae for these. Finally we prove
that the property of being distinguished is also captured by a type of moving
incidence relation. This second characterisation is used to show that, for
suitable solutions of conformal Killing-Yano equations, a certain zero locus of
the solution is necessarily a distinguished submanifold.Comment: 87 page
Simulation of phosphorus implantation into silicon with a single-parameter electronic stopping power model
We simulate dopant profiles for phosphorus implantation into silicon using a
new model for electronic stopping power. In this model, the electronic stopping
power is factorized into a globally averaged effective charge Z1*, and a local
charge density dependent electronic stopping power for a proton. There is only
a single adjustable parameter in the model, namely the one electron radius rs0
which controls Z1*. By fine tuning this parameter, we obtain excellent
agreement between simulated dopant profiles and the SIMS data over a wide range
of energies for the channeling case. Our work provides a further example of
implant species, in addition to boron and arsenic, to verify the validity of
the electronic stopping power model and to illustrate its generality for
studies of physical processes involving electronic stopping.Comment: 11 pages, 7 figures. See http://bifrost.lanl.gov/~reed
Biosynthesis of valine and isoleucine. III. α-keto-β-hydroxy acid reductase and α-hydroxy-β-keto acid reductoisomerase
This article does not have an abstract
The Impact of Fault Zone Architecture in Modelling the Fluid Overpressure Driven Faulting and Seismicity of the Colfiorito Seismic Sequence
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