3,465 research outputs found
Optical alignment system Patent
Electro-optical/computer system for aligning large structural members and maintaining correct positio
Deformations of Fuchsian Systems of Linear Differential Equations and the Schlesinger System
We consider holomorphic deformations of Fuchsian systems parameterized by the
pole loci. It is well known that, in the case when the residue matrices are
non-resonant, such a deformation is isomonodromic if and only if the residue
matrices satisfy the Schlesinger system with respect to the parameter. Without
the non-resonance condition this result fails: there exist non-Schlesinger
isomonodromic deformations. In the present article we introduce the class of
the so-called isoprincipal deformations of Fuchsian systems. Every isoprincipal
deformation is also an isomonodromic one. In general, the class of the
isomonodromic deformations is much richer than the class of the isoprincipal
deformations, but in the non-resonant case these classes coincide. We prove
that a deformation is isoprincipal if and only if the residue matrices satisfy
the Schlesinger system. This theorem holds in the general case, without any
assumptions on the spectra of the residue matrices of the deformation. An
explicit example illustrating isomonodromic deformations, which are neither
isoprincipal nor meromorphic with respect to the parameter, is also given
A New Look at Nonprofits: Health Care Policy in a Competitive Age
The importance of organizational form in American medicine has been the subject of much debate. But the character of the debate-the nonprofit form versus its competitors-has been sufficiently confused that much of the controversy should be reconsidered. That debate has been both ideological (commercialism and profit versus service and professionalism) and practical (which form is more efficient)? The challenge of public policy is to adapt public rules to the central realities of American medicine, not the shibboleths of shrill discourse. In the case of medicine, factors other than the form of legal ownership-among them, the nature of the service provided, the developmental stage of the service, the role of physicians in providing the service, and the nature of government regulation-are more important in fashioning those appropriate responses
Substantiating a political public sphere in the Scottish press : a comparative analysis
This article uses content analysis to characterize the performance of the media in a national public sphere, by setting apart those qualities that typify internal press coverage of a political event. The article looks at the coverage of the 1999 devolved Scottish election from the day before the election until the day after. It uses a word count to measure the election material in Scottish newspapers the Herald, the Press and Journal and the Scotsman, and United Kingdom newspapers the Guardian, the Independent and The Times, and categorizes that material according to discourse type, day and page selection. The article finds a number of qualities that typify the Scottish sample in particular, and might be broadly indicative of a political public sphere in action. Firstly, and not unexpectedly, it finds that the Scottish newspapers carry significantly more election coverage. Just as tellingly, though, the article finds that the Scottish papers offer a greater proportion of advice and background information, in the form of opinion columns and feature articles. It also finds that the Scottish papers place a greater concentration of both informative and evaluative material in the period before the vote, consistent with their making a contribution to informed political action. Lastly, the article finds that the Scottish sample situates coverage nearer the front of the paper and places a greater proportion on recto pages. The article therefore argues that the Scottish papers display features that distinguish them from the UK papers, and are broadly consistent with their forming part of a deliberative public sphere, and suggests that these qualities might be explored as a means of judging future media performance
Ferromagnetism in the Mott insulator Ba2NaOsO6
Results are presented of single crystal structural, thermodynamic, and
reflectivity measurements of the double-perovskite Ba2NaOsO6. These
characterize the material as a 5d^1 ferromagnetic Mott insulator with an
ordered moment of ~0.2 Bohr magnetons per formula unit and TC = 6.8(3) K. The
magnetic entropy associated with this phase transition is close to Rln2,
indicating that the quartet groundstate anticipated from consideration of the
crystal structure is split, consistent with a scenario in which the
ferromagnetism is associated with orbital ordering.Comment: 5 pages, 5 figures, added reference
An All-Cryogenic THz Transmission Spectrometer
This paper describes a THz transmission spectrometer for the spectral range
of 2-65 cm^-1 (100 GHz to 2 THz) with a spectral resolution of at least 1.8
cm^-1 (50 GHz) where the source, sample, and detector are all fully contained
in a cryogenic environment. Cyclotron emission from a two-dimensional electron
gas heated with an electrical current serves as a magnetic field tunable
source. The spectrometer is demonstrated at 4.2 K by measuring the resonant
cyclotron absorption of a second two dimensional electron gas. Unique aspects
of the spectrometer are that 1) an ultra-broadband detector is used and 2) the
emitter is run quasi-continuously with a chopping frequency of only 1 Hz. Since
optical coupling to room temperature components is not necessary, this
technique is compatible with ultra-low temperature (sub 100 mK) operation.Comment: 7 pages, 5 figures. Author affiliation and funding acknowledgements
clarifie
Non-Fermi liquid behavior of SrRuO_3 -- evidence from infrared conductivity
The reflectivity of the itinerant ferromagnet SrRuO_3 has been measured
between 50 and 25,000 cm-1 at temperatures ranging from 40 to 300 K, and used
to obtain conductivity, scattering rate, and effective mass as a function of
frequency and temperature. We find that at low temperatures the conductivity
falls unusually slowly as a function of frequency (proportional to
\omega^{-1/2}), and at high temperatures it even appears to increase as a
function of frequency in the far-infrared limit. The data suggest that the
charge dynamics of SrRuO_3 are substantially different from those of
Fermi-liquid metals.Comment: 4 pages, 3 postscript figure
Competition and Facilitation: Contrasting Effects of Artemisia Tridentata on Desert vs Montane Pines
Circumstantial evidence suggests that Artemisia tridentata may out-compete Pinus ponderosa and P. jefferyi for water at ecotones between shrub steppe and montane forest vegetation in the Great Basin. Other studies indicate that within the shrub steppe Artemisia may act as a nurse plant for a third species of pine, P. monophylla. We used field experiments to study these contrasting effects of Artemisia on P, ponderosa and P. monophylla within the contest of the distributional patterns in western Nevada of all three species on andesite, and on sites where hydrothermal activity has altered the andesite. At intermediate elevations in the Great Basin Artemisia and P. monophylla are restricted to unaltered desert soils, whereas P. ponderosa is restricted to acidic, nutrient-poor altered andesite. Although mature P. monophylla were virtually absent in our study plots on altered andesite, first- and second-year seedlings were common. On adjacent unaltered andesite, all size classes of P. monophylla occurred, and P. monophylla seedlings were associated with Artemisia shrubs. Pinus ponderosa and P. jefferyi adults and seedlings were rare on unaltered andesite, but a wide range of size classes was found on altered andesite. In experiments, all P. ponderosa seedlings on unaltered andesite were consumed by predators regardless of positive or negative spatial association with shrubs. Of the P, monophylla seedlings that germinated on unaltered andesite, all that were under shrubs survived, but only 6% of those that germinated in the intershrub spaces survived, On the open altered andesite the mortality of P. monophylla seedlings due to abiotic stress was high, with a final survival of only 3%, whereas 25% of P, ponderosa seedlings survived the iir-st growing season on altered andesite. On unaltered andesite, survival and conductance of P. ponderosa saplings was enhanced by shrub removal, but P. monophylla survival was significantly higher under shrubs than in shrub-removal plots or in intershrub spaces, In Artemisia-removal experiments, we found that Artemisia competed with P. ponderosa seedlings and saplings for water. Removal of Artemisia decreased water use efficiency (WUE) of P. monophylla seedlings. The absence of Artemisia may restrict Pinus monophylla from out-crops of altered andesite in the Great Basin, but provide refuges for P. ponderosa
Prospects for the Characterization and Confirmation of Transiting Exoplanets via the Rossiter-McLaughlin Effect
The Rossiter-McLaughlin (RM) effect is the distortion of stellar spectral
lines that occurs during eclipses or transits, due to stellar rotation. We
assess the future prospects for using the RM effect to measure the alignment of
planetary orbits with the spin axes of their parent stars, and to confirm
exoplanetary transits. We compute the achievable accuracy for the parameters of
interest, in general and for the 5 known cases of transiting exoplanets with
bright host stars. We determine the requirements for detecting the effects of
differential rotation. For transiting planets with small masses or long periods
(as will be detected by forthcoming satellite missions), the velocity anomaly
produced by the RM effect can be much larger than the orbital velocity of the
star. For a terrestrial planet in the habitable zone of a Sun-like star found
by the Kepler mission, it will be difficult to use the RM effect to confirm
transits with current instruments, but it still may be easier than measuring
the spectroscopic orbit.Comment: 18 pages, 8 figures, one table. Minor changes. Accepted to ApJ, to
appear in the Jan 20, 2007 issue (v655
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