Time evolution of rolling tachyons for a brane-antibrane pair

A precise form of the time evolution of rolling tachyons corresponding to a brane-antibrane pair is investigated by solving the Hamiltonian equations of motion under the assumption that in a region far away from branes the tachyon vacuum is almost already achieved, even at the beginning of the rolling.Comment: 10 pages, 2 figures. Addition of references in v2, inclusion of more details in v

Tgif1 Counterbalances The Activity Of Core Pluripotency Factors In Mouse Embryonic Stem Cells

Core pluripotency factors, such as Oct4, Sox2, and Nanog, play important roles in maintaining embryonic stem cell (ESC) identity by autoregulatory feedforward loops. Nevertheless, the mechanism that provides precise control of the levels of the ESC core factors without indefinite amplification has remained elusive. Here, we report the direct repression of core pluripotency factors by Tgif1, a previously known terminal repressor of TGF beta/activin/nodal signaling. Overexpression of Tgif1 reduces the levels of ESC core factors, whereas its depletion leads to the induction of the pluripotency factors. We confirm the existence of physical associations between Tgif1 and Oct4, Nanog, and HDAC1/2 and further show the level of Tgif1 is not significantly altered by treatment with an activator/inhibitor of the TGF beta/activin/nodal signaling. Collectively, our findings establish Tgif1 as an integral member of the core regulatory circuitry of mouse ESCs that counterbalances the levels of the core pluripotency factors in a TGF beta/activin/nodal-independent manner.Cancer Prevention Research Institute of Texas (CPRIT) R1106Molecular Bioscience

Seizures and antiepileptic drugs in patients with spontaneous intracerebral hemorrhages

AbstractPurposePatients with intracerebral hemorrhage (ICH) are often initiated on antiepileptic drugs without a clear indication. We compared the percentage of patients with spontaneous ICH who had seizures at onset or during hospitalization, and examined empiric use of antiepileptic drugs (AEDs) in these patients in 2 cohorts 10 years apart.MethodsUsing a clinical data registry at a tertiary care adult hospital, we retrospectively selected admissions for spontaneous ICH between 1/1/99–12/31/00 (Cohort A, n=30) and 1/1/09–12/31/10 (Cohort B, n=108). Clinical, neurophysiological and radiological data were collected in both cohorts.ResultsIn Cohorts A and B respectively, AEDs were started in 53.3% and 50.0%, and continued on discharge in 50.0% and 20.4% of patients; 86.6% and 59.1% of patients discharged on AEDs did not have a clinical/electrographic seizure or epileptiform EEG findings. Seizures occurred in 6.6% and 13.0% in Cohorts A and B respectively. The presence of a seizure at presentation (p=0.01) and during hospitalization (p=0.02) were predictors for continuing AED on discharge.ConclusionIn both cohorts, a significant number of patients were discharged on AEDs without a clear indication, though there is a change in practice between the two cohorts

Inflationary Perturbations: the Cosmological Schwinger Effect

This pedagogical review aims at presenting the fundamental aspects of the theory of inflationary cosmological perturbations of quantum-mechanical origin. The analogy with the well-known Schwinger effect is discussed in detail and a systematic comparison of the two physical phenomena is carried out. In particular, it is demonstrated that the two underlying formalisms differ only up to an irrelevant canonical transformation. Hence, the basic physical mechanisms at play are similar in both cases and can be reduced to the quantization of a parametric oscillator leading to particle creation due to the interaction with a classical source: pair production in vacuum is therefore equivalent to the appearance of a growing mode for the cosmological fluctuations. The only difference lies in the nature of the source: an electric field in the case of the Schwinger effect and the gravitational field in the case of inflationary perturbations. Although, in the laboratory, it is notoriously difficult to produce an electric field such that pairs extracted from the vacuum can be detected, the gravitational field in the early universe can be strong enough to lead to observable effects that ultimately reveal themselves as temperature fluctuations in the Cosmic Microwave Background. Finally, the question of how quantum cosmological perturbations can be considered as classical is discussed at the end of the article.Comment: 49 pages, 6 figures, to appear in a LNP volume "Inflationary Cosmology