1,270 research outputs found
On local comparison between various metrics on Teichmüller spaces
International audienceThere are several Teichmüller spaces associated to a surface of infinite topological type, after the choice of a particular basepoint ( a complex or a hyperbolic structure on the surface). These spaces include the quasiconformal Teichmüller space, the length spectrum Teichmüller space, the Fenchel-Nielsen Teichmüller space, and there are others. In general, these spaces are set-theoretically different. An important question is therefore to understand relations between these spaces. Each of these spaces is equipped with its own metric, and under some hypotheses, there are inclusions between these spaces. In this paper, we obtain local metric comparison results on these inclusions, namely, we show that the inclusions are locally bi-Lipschitz under certain hypotheses. To obtain these results, we use some hyperbolic geometry estimates that give new results also for surfaces of finite type. We recall that in the case of a surface of finite type, all these Teichmüller spaces coincide setwise. In the case of a surface of finite type with no boundary components (and possibly with punctures), we show that the restriction of the identity map to any thick part of Teichmüller space is globally bi-Lipschitz with respect to the length spectrum metric and the classical Teichmüller metric on the domain and on the range respectively. In the case of a surface of finite type with punctures and boundary components, there is a metric on the Teichmüller space which we call the arc metric, whose definition is analogous to the length spectrum metric, but which uses lengths of geodesic arcs instead of lengths of closed geodesics. We show that the restriction of the identity map restricted to any ``relative thick" part of Teichmüller space is globally bi-Lipschitz, with respect to any of the three metrics: the length spectrum metric, the Teichmüller metric and the arc metric on the domain and on the range
Fundamental Strings as Black Bodies
We show that the decay spectrum of massive excitations in perturbative string
theories is thermal when averaged over the (many) initial degenerate states. We
first compute the inclusive photon spectrum for open strings at the tree level
showing that a black body spectrum with the Hagedorn temperature emerges in the
averaging. A similar calculation for a massive closed string state with winding
and Kaluza-Klein charges shows that the emitted graviton spectrum is thermal
with a "grey-body" factor, which approaches one near extremality. These results
uncover a simple physical meaning of the Hagedorn temperature and provide an
explicit microscopic derivation of the black body spectrum from a unitary
matrix.Comment: some changes in the Discussion section and in the reference list. 11
pages, Late
Sewing Constraints and Non-Orientable Open Strings
We extend to non-orientable surfaces previous work on sewing constraints in
Conformal Field Theory. A new constraint, related to the real projective plane,
is described and is used to illustrate the correspondence with a previous
construction of open-string spectra.Comment: phyzzx, 11 pages and 4 figures, ROM2F-93/3
Characterization of ellipses as uniformly dense sets with respect to a family of convex bodies
Let K \subset R^N be a convex body containing the origin. A measurable set G
\subset R^N with positive Lebesgue measure is said to be uniformly K-dense if,
for any fixed r > 0, the measure of G \cap (x + rK) is constant when x varies
on the boundary of G (here, x + rK denotes a translation of a dilation of K).
We first prove that G must always be strictly convex and at least C1,1-regular;
also, if K is centrally symmetric, K must be strictly convex, C1,1-regular and
such that K = G - G up to homotheties; this implies in turn that G must be
C2,1- regular. Then for N = 2, we prove that G is uniformly K-dense if and only
if K and G are homothetic to the same ellipse. This result was already proven
by Amar, Berrone and Gianni in [3]. However, our proof removes their regularity
assumptions on K and G and, more importantly, it is susceptible to be
generalized to higher dimension since, by the use of Minkowski's inequality and
an affine inequality, avoids the delicate computations of the higher-order
terms in the Taylor expansion near r = 0 for the measure of G\cap(x+rK) (needed
in [3])
Influence of Blackberry Plants on the Aroma Profile of Vitis vinifera L. cv. Pinot Noir
V. vinifera cv. Pinot noir vines were grown in pots together with blackberry plants and the effect of this association on the grape aroma was assessed. Preliminary data showed that vines that cohabited with blackberry had a different aroma profile compared to vine grown alone. The association with blackberry increased the concentration of 30 out 74 free aroma compounds and of 24 out 95 bound ones. No aroma compound was identified exclusively in the treated grapes
Path integral evaluation of Dbrane amplitudes
We extend Polchinski's evaluation of the measure for the one-loop closed
string path integral to open string tree amplitudes with boundaries and
crosscaps embedded in Dbranes. We explain how the nonabelian limit of
near-coincident Dbranes emerges in the path integral formalism. We give a
careful path integral derivation of the cylinder amplitude including the
modulus dependence of the volume of the conformal Killing group.Comment: Extended version replacing hep-th/9903184, includes discussion of
nonabelian limit, Latex, 10 page
Remotely sensed variables explain microhabitat selection and reveal buffering behaviours against warming in a climate-sensitive bird species
Fine-scale habitat selection modelling can allow a mechanistic understanding of habitat selection processes, enabling better assessments of the effects of climate and habitat changes on biodiversity. Remotely sensed data provide an ever-increasing amount of environmental and climatic variables at high spatio-temporal resolutions, and a unique opportunity to produce fine-scale habitat models particularly useful in challenging environments, such as high-elevation areas. Working at a 10-m spatial resolution, we assessed the value of remotely sensed data for investigating foraging habitat selection (in relation to topography, microclimate, land cover) in nestling-rearing white-winged snowfinch (Montifringilla nivalis), a high-elevation species highly sensitive to climate change. Adult snowfinches foraged at locations with intermediate vegetation cover and higher habitat heterogeneity, also avoiding extremely warm or extremely cold microclimates. Temperature interacted with other environmental drivers in defining habitat selection, highlighting trade-offs between habitat profitability and thermoregulation: snowfinches likely adopted mechanisms of behavioural buffering against physiologically stressful conditions by selecting for cooler, shaded and more snowy foraging grounds at higher temperatures. Our results matched those from previous studies based on accurate field measurements, confirming the species' reliance on climate-sensitive microhabitats (snow patches and low-sward grassland, in heterogeneous patches) and the usefulness of satellite-derived fine-scale modelling. Habitat suitability models built on remotely sensed predictors can provide a cost-effective method for periodic monitoring of species' habitats both at fine grain and over large extents. Fine-scale models also enhance our understanding of the actual drivers of (micro)habitat selection and of possible buffering behaviours against warming, allowing more accurate and robust distribution models, finer predictions of potential future changes and carefully targeted conservation strategies and habitat management
Can One Teach Old Drugs New Tricks? Reformulating to Repurpose Chloroquine and Hydroxychloroquine
The outbreak of the novel corona virus disease, COVID-19, has presented health care professionals with the unique challenges of trying to select appropriate pharmacological treatments with little time available for drug testing. Given the development times and manufacturing requirements for new products, Value Added Medicines (repurposing – reformulation of existing drugs) could be one possibility to beat the COVID-19 outbreak. This review explores reformulation alternatives which could be progressed with chloroquine and hydroxychloroquine; two antimalarial drugs, that are being tested on a global scale as a potential therapeutic option. The key areas for improvement have been reviewed and the potential solutions to the problems and limitations of current formulations are discussed. The pharmaceutical challenges discussed are those of highly soluble drugs, needed to be given at high doses and presenting a real bitter taste challenge with significant gastrointestinal side effects that could be translated and repurposed into fit for purpose reformulations
Impaired postural control in patients affected by tension-type headache.
Sixteen subjects, affected by chronic tension-type headache (TTH) accordingly to the International Headache Society Classification (1988) criteria, in presence of tenderness in pericranial muscles,with a mean age of 37+/-11.8 years, and ten healthy volunteer subjects, age and sex matched, were submitted to postural analysis by Static Posturography (S.Ve.P. Amplaid). Aim of the study was to evaluate whether patients with TTH have disturbed postural control, as compared to normal subjects. Postural analysis considered all posturographic variables but focused on spectral frequency analysis of body sway. In both open (OE) and closed eyes (CE) condition, spectral frequency analysis showed a significantly increased body sway at low (OE= p < or = 0.01; CE= p < or = 0.01) and middle (OE= p < or = 0.01; CE= p < or = 0.01) frequencies on the antero-posterior (y) plane and at low frequencies (OE= p < or = 0.05; CE= p < or = 0.05) on the lateral (x) plane. Statistical analysis was performed using the Student's t test for unpaired data, p value 0.05 defined significant. The proprioceptive input seems to be predominant at middle and high frequencies in maintaining posture, our results seem then to suggest a proprioceptive disturbance in TTH patients. The disturbance is likely related to chronic pericranial muscle contraction and tenderness. Posturography and spectral analysis may help not only in the diagnosis of a postural disturbance but even more in the follow-up of TTH patients, during and after a medical and/or a rehabilitative treatment
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