1,354,391 research outputs found
General analysis of dark radiation in sequestered string models
No full textAbstract: We perform a general analysis of axionic dark radiation produced from the decay of the lightest modulus in the sequestered LARGE Volume Scenario. We discuss several cases depending on the form of the Kähler metric for visible sector matter fields and the mechanism responsible for achieving a de Sitter vacuum. The leading decay channels which determine dark radiation predictions are to hidden sector axions, visible sector Higgses and SUSY scalars depending on their mass. We show that in most of the parameter space of split SUSY-like models squarks and sleptons are heavier than the lightest modulus. Hence dark radiation predictions previously obtained for MSSM-like cases hold more generally also for split SUSY-like cases since the decay channel to SUSY scalars is kinematically forbidden. However the inclusion of string loop corrections to the Kähler potential gives rise to a parameter space region where the decay channel to SUSY scalars opens up, leading to a significant reduction of dark radiation production. In this case, the simplest model with a shift-symmetric Higgs sector can suppress the excess of dark radiation ΔNeff to values as small as 0.14, in perfect agreement with current experimental bounds. Depending on the exact mass of the SUSY scalars all values in the range 0.14 ≲ ΔNeff ≲ 1.6 are allowed. Interestingly dark radiation overproduction can be avoided also in the absence of a Giudice-Masiero coupling
Effect of prolonged administration of transdermal estradiol on flow-mediated endothelium-dependent and endothelium-independent vasodilation in healthy women
No full textIn 15 postmenopausal women with no cardiovascular risk factors, hormone replacement with transdermal estradiol (50 microg/day for 2 months) did not enhance flow-mediated endothelium-dependent vasodilation, reduce endothelium-independent vasodilation, and did not modify the pulsatility index and blood flow of the brachial artery. The present data do not support a positive effect of replacement with transdermal estradiol on vessel vasodilation in healthy, postmenopausal women
Effect of prolonged administration of transdermal estradiol on flow-mediated endothelium-dependent and endothelium-independent vasodilation in healthy women
No full textIn 15 postmenopausal women with no cardiovascular risk factors, hormone replacement with transdermal estradiol (50 microg/day for 2 months) did not enhance flow-mediated endothelium-dependent vasodilation, reduce endothelium-independent vasodilation, and did not modify the pulsatility index and blood flow of the brachial artery. The present data do not support a positive effect of replacement with transdermal estradiol on vessel vasodilation in healthy, postmenopausal women
Global embedding of fibre inflation models
No full textWe present concrete embeddings of fibre inflation models in globally consistent type IIB Calabi-Yau orientifolds with closed string moduli stabilisation. After performing a systematic search through the existing list of toric Calabi-Yau manifolds, we find several examples that reproduce the minimal setup to embed fibre inflation models. This involves Calabi-Yau manifolds with h1,1 = 3 which are K3 fibrations over a P1 base with an additional shrinkable rigid divisor. We then provide different consistent choices of the underlying brane set-up which generate a non-perturbative superpotential suitable for moduli stabilisation and string loop corrections with the correct form to drive inflation. For each Calabi-Yau orientifold setting, we also compute the effect of higher derivative contributions and study their influence on the inflationary dynamics
Relationship between atrial function, left ventricular isovolumic relaxation time, and early filling in dual chamber-paced patients
No full textThis investigation was performed to study atrial systolic function in response to modification of atrioventricular delay in a sample of 36 patients with a DDD pacemaker implanted for complete atrioventricular block. The relation between atrial systolic performance and diastolic-related parameters was also evaluated. Isovolumic relaxation time, early diastolic peak velocity, late (atrial) diastolic peak velocity, atrial filling fraction, and atrial ejection force were recorded at a pacing rate of 70 impulses/min and at atrioventricular delay of 200, 150, and 100 msec. Our data showed that the progressive shortening of atrioventricular delay induced a gradual increase in early peak velocity (median value 46 to 53 to 61.5 cm/sec, respectively, at 200, 150, and 100 msec intervals) and a gradual decrease in isovolumic relaxation time (median 92.6 to 81.5 to 69.7 msec at 200, 150, and 100 msec, respectively), atrial peak velocity (59 to 52 to 44.5 cm/sec at 200, 150, and 100 msec, respectively), atrial filling fraction (50.5% to 40% to 23.5% at 200, 150, and 100 msec, respectively), and atrial ejection force (17.2 to 14.7 to 8.5 kilodynes at 200, 150, and 100 msec, respectively). For every atrioventricular delay value detected, we found a significant correlation between isovolumic relaxation time and early peak velocity with atrial filling fraction and atrial ejection force. In addition, atrial ejection force was related directly to atrial filling fraction at studied atrioventricular delays. The two indexes of atrial systolic performance showed a parallel decrease by shortening the atrioventricular delay, and they can quantify atrial systolic performance equally in sequentially paced patients. Furthermore, our results are in accordance with the hypothesis that the interaction between the effectiveness of active left atrial emptying and isovolumetric relaxation time may play an important role in maintaining an ideal ventricular filling despite changes in atrial systolic function
Hunt for light primordial black hole dark matter with ultrahigh-frequency gravitational waves
No full textLight primordial black holes may comprise a dominant fraction of the dark matter in our Universe. This paper critically assesses whether planned and future gravitational wave detectors in the ultrahigh-frequency band could constrain the fraction of dark matter composed of subsolar primordial black holes. Adopting the state-of-the-art description of primordial black hole merger rates, we compare various signals with currently operating and planned detectors. As already noted in the literature, our findings confirm that detecting individual primordial black hole mergers with currently existing and operating proposals remains difficult. Current proposals involving gravitational wave to electromagnetic wave conversion in a static magnetic field and microwave cavities feature a technology gap with respect to the loudest gravitational wave signals from primordial black holes of various orders of magnitude. However, we point out that one recent proposal involving resonant LC circuits represents the best option in terms of individual merger detection prospects in the range (1-100) MHz. In the same frequency range, we note that alternative setups involving resonant cavities, whose concept is currently under development, might represent a promising technology to detect individual merger events. We also show that a detection of the stochastic gravitational wave background produced by unresolved binaries is possible only if the theoretical sensitivity of the proposed Gaussian beam detector is achieved. Such a detector, whose feasibility is subject to various caveats, may be able to rule out some scenarios for asteroidal mass primordial black hole dark matter. We conclude that pursuing dedicated studies and developments of gravitational wave detectors in the ultrahigh-frequency band remains motivated and may lead to novel probes on the existence of light primordial black holes
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Affleck-Dine baryogenesis in type IIB string models
No full textAbstract: We propose a possible string embedding of Affleck-Dine baryogenesis in type IIB sequestered models where the late-time decay of the lightest modulus reheats the universe to relatively low temperatures. We show that if inflation is driven by a blow-up Kähler modulus, the Affleck-Dine field can become tachyonic during inflation if the Kähler metric for matter fields has an appropriate inflaton-dependent contribution. We find that the Affleck-Dine mechanism can generate the observed baryon asymmetry for natural values of the underlying parameters which lead also to successful inflation and low-energy gaugino masses in a split supersymmetry scenario. The reheating temperature from the lightest modulus decay is high enough to allow thermal Higgsino-like dark matter
Microscopic origin of volume modulus inflation
No full textHigh-scale string inflationary models are in well-known tension with low-energy supersymmetry. A promising solution involves models where the inflaton is the volume of the extra dimensions so that the gravitino mass relaxes from large values during inflation to smaller values today. We describe a possible microscopic origin of the scalar potential of volume modulus inflation by exploiting non-perturbative effects, string loop and higher derivative perturbative corrections to the supergravity effective action together with contributions from anti-branes and charged hidden matter fields. We also analyse the relation between the size of the flux superpotential and the position of the late-time minimum and the inflection point around which inflation takes place. We perform a detailed study of the inflationary dynamics for a single modulus and a two moduli case where we also analyse the sensitivity of the cosmological observables on the choice of initial conditions
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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