2,849 research outputs found
Potential one-forms for hyperk\"ahler structures with torsion
It is shown that an HKT-space with closed parallel potential 1-form has
-symmetry. Every locally conformally hyperk\"ahler manifold
generates this type of geometry. The HKT-spaces with closed parallel potential
1-form arising in this way are characterized by their symmetries and an
inhomogeneous cubic condition on their torsion.Comment: 16 pages, Latex, no figure
Impaired endothelial function of the retinal vasculature in hypertensive patients
<p><b>Background and Purpose:</b> Arterial hypertension constitutes a central factor in the pathogenesis of stroke. We examined endothelial function of the retinal vasculature as a model of the cerebral circulation.</p>
<p><b>Methods:</b> Thirty-eight young subjects (19 hypertensive and 19 normotensive) were treated with the AT1-receptor blocker candesartan cilexetil and placebo, each over 7 days. Retinal capillary flow and blood flow velocity in the central retinal artery were assessed with scanning laser Doppler flowmetry and pulsed Doppler ultrasound, respectively. NG-monomethyl-L-arginine (L-NMMA) was infused to inhibit nitric oxide (NO) synthesis. Diffuse luminance flicker was applied to stimulate NO release.</p>
<p><b>Results:</b> In normotensive subjects, L-NMMA decreased retinal capillary flow by 8.2%±13% (P<0.05) and flickering light increased mean blood flow velocity in the central retinal artery by 19%±29% (P<0.01). In contrast, no significant change to these provocative tests was seen in hypertensive subjects. Treatment with candesartan cilexetil restored a normal pattern of reactivity in retinal capillaries (L-NMMA: decrease in perfusion by 10%±17%, P<0.05) and the central retinal artery (flicker: increase in mean blood flow velocity by 42%±31%, P<0.001) in hypertensive patients.</p>
<p><b>Conclusions:</b> Endothelial function of the retinal vasculature is impaired in early essential hypertension but can be improved by AT1-receptor blockade.</p>
Breaking the Silence: The role of gossip in organizational culture
From the early 1980s, the number of studies pertaining to organizational culture expanded considerably to the point where it could reasonably be argued that the field had reached a level of maturity. Perhaps indicative of this maturity was the publication of the first handbook of organizational culture and climate (Ashkanasy et al. 2000). The commencement of academic interest in the topic of organizational culture generally coincided with the publication of two books mainly aimed at practitioners—Peters and Waterman’s, In search of excellence (1982) and Deal and Kennedy’s, Corporate cultures: the rites and rituals of corporate life (1982). This is not to suggest that these books account exclusively for the intellectual curiosity generated in the function and purpose of culture for an organization as there were well-known examples which had earlier sought to address the issue of organizational cultures (e.g. Pettigrew 1979). Nonetheless, these tomes were influential in raising interest in, and scope for, research on organizational culture
Arago (1810): the first experimental result against the ether
95 years before Special Relativity was born, Arago attempted to detect the
absolute motion of the Earth by measuring the deflection of starlight passing
through a prism fixed to the Earth. The null result of this experiment gave
rise to the Fresnel's hypothesis of an ether partly dragged by a moving
substance. In the context of Einstein's Relativity, the sole frame which is
privileged in Arago's experiment is the proper frame of the prism, and the null
result only says that Snell's law is valid in that frame. We revisit the
history of this premature first evidence against the ether theory and calculate
the Fresnel's dragging coefficient by applying the Huygens' construction in the
frame of the prism. We expose the dissimilar treatment received by the ray and
the wave front as an unavoidable consequence of the classical notions of space
and time.Comment: 16 pages. To appear in European Journal of Physic
My gal : (she has some wonderful ways)
https://digitalcommons.library.umaine.edu/mmb-vp/3303/thumbnail.jp
Relativity tests by complementary rotating Michelson-Morley experiments
We report Relativity tests based on data from two simultaneous
Michelson-Morley experiments, spanning a period of more than one year. Both
were actively rotated on turntables. One (in Berlin, Germany) uses optical
Fabry-Perot resonators made of fused silica; the other (in Perth, Australia)
uses microwave whispering-gallery sapphire resonators. Within the standard
model extension, we obtain simultaneous limits on Lorentz violation for
electrons (5 coefficients) and photons (8) at levels down to ,
improved by factors between 3 and 50 compared to previous work.Comment: 5 pages revtex, 2 figure
Guest Editors’ Introduction to the Special Issue on FIFO Work
This special edition of the Australian Bulletin of Labour is concerned with the recent and much-hyped phenomenon of Fly-In Fly-Out (FIFO) workers. We stress that our focus is on FIFO, not on the related question of work and employment in the resources sector, or on the broader impact of the resources sector on the regions and communities where it is located. There have been recent special editions of other journals on these matters: one assessing the impact of the Australian resources sector on rural societies (Rural Society 22, 2 2013) and another examining the dynamics and pattern of development in the Pilbara (Australian Geographer 44, 3 2013), as well as an inquiry—reported in 2013—undertaken by the Australian House of Representatives Standing Committee on Regional Australia (FHRE 2013)
Diagnosis of glaucoma by indirect classifiers
Objectives: Demonstration of the applicability of a framework called indirect classification to the example of glaucoma classification. Indirect classification combines medical a priori knowledge and statistical classification methods. The method is compared to direct classification approaches with respect to the estimated misclassification error. Methods: Indirect classification is applied using classification trees and the diagnosis of glaucoma. Misclassification errors are reduced by bootstrap aggregation. As direct classification methods linear discriminant analysis, classification trees and bootstrap aggregated classification trees are utilized in the problem of glaucoma diagnosis. Misclassification rates are estimated via 10-fold cross-validation. Results: Indirect classification techniques reduce the misclassification error in the context of glaucoma classification compared to direct classification methods. Conclusions: Embedding a priori knowledge into statistical classification techniques can improve misclassification results. Indirect classification offers a framework to realize this combination
Superconformal Multi-Black Hole Moduli Spaces in Four Dimensions
Quantum mechanics on the moduli space of N supersymmetric Reissner-Nordstrom
black holes is shown to admit 4 supersymmetries using an unconventional
supermultiplet which contains 3N bosons and 4N fermions. A near-horizon limit
is found in which the quantum mechanics of widely separated black holes
decouples from that of strongly-interacting, near-coincident black holes. This
near-horizon theory is shown to have an enhanced D(2,1;0) superconformal
symmetry. The bosonic symmetries are SL(2,R) conformal symmetry and SU(2)xSU(2)
R-symmetry arising from spatial rotations and the R-symmetry of N=2
supergravity.Comment: 23 pages, harvmac. v2: many typos fixe
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