Energy Distribution of a Charged Black Hole with a Minimally Coupled Scalar Field

Using three different energy-momentum complexes, the Einstein, Landau-Lifshitz, and Papapetrou prescriptions, we calculate the energy of an electrically charged black hole exact solution with a self-interacting, minimally-coupled scalar field and the asymptotic region locally an Anti-deSitter spacetime. Writing the metric in Kerr-Schild Cartesian coordinates, we demonstrate that this metric belongs to the Kerr-Schild class of solutions. Applying each of the three energy-momentum prescriptions and comparing the results, we find consistency among these complexes, suggesting their utility as localized measures of energy.Comment: 11 pages; To appear in Astrophysics and Space Scienc

Evaluating cardiac anatomy as a predictor for success after pulmonary vein isolation for the treatment of atrial fibrillation

Introduction: Atrial Fibrillation is a condition characterized by the production of ectopic beats by the heart. One common treatment for Atrial Fibrillation is catheter guided pulmonary vein isolation (PVI), however this treatment is only effective in around 60-70% of the population. Our research hopes to elucidate a link between cardiac anatomy and successful treatment of A-fib by pulmonary vein isolation. Methods: The medical records for 78 consecutive patients who underwent PVI for atrial fibrillation at Jefferson from July 2013 to March 2016 were gathered. Included in these charts were ECG-gated cardiac CT angiogram and two-year follow up history. Different variables from the imaging data such as left atrial volume, ejection fraction, and pulmonary vein area were analyzed and compared to likelihood of recurrence of A-Fib after PVI. A T-test was used to compare continuous variables in patients who had recurrence versus those that did not and a Chi-Squared Test was used to compare likelihood of recurrence in those with persistent versus paroxysmal A-Fib. Results: Recurrent atrial fibrillation was found in 32/72 (44%) of treated patients by 24 months. Univariate analysis demonstrated a higher incidence of recurrent atrial fibrillation among patients who remained on anti-arrhythmic medications 14/22 = as compared to those who did not 18/50, p = 0.03. There was a lower incidence of recurrent atrial fibrillation in males 20/52 (38%) as compared with females 12/19 (63%), though this difference was only marginally significant (p = 0.056). Multivariate analysis of additional variables with logistic regression demonstrated a marginally significant association of reduced ejection fraction with recurrent atrial fibrillation (p= 0.064). Logistic regression analysis demonstrated no significant differences in recurrence rate based upon age, paroxysmal/persistent fibrillation, left atrial volume, CHADS2 score, pulmonary vein area, and catheter type. Discussion: The only marginal predictors for recurrent atrial fibrillation after PVI were Gender and left ventricular ejection fraction. The other variables including anatomical features and the catheter type used for the procedure had no significant impact on long-term recurrence rates after PVAI. This was a surprising result given other data in the field, which seemed to indicate a link between cardiac anatomy and recurrence of A-Fib after PVI. More research should be conducted in this area, perhaps with a larger data set then was used in this study

Exact Solutions of Five Dimensional Anisotropic Cosmologies

We solve the five dimensional vacuum Einstein equations for several kinds of anisotropic geometries. We consider metrics in which the spatial slices are characterized as Bianchi types-II and V, and the scale factors are dependent both on time and a non-compact fifth coordinate. We examine the behavior of the solutions we find, noting for which parameters they exhibit contraction over time of the fifth scale factor, leading naturally to dimensional reduction. We explore these within the context of the induced matter model: a Kaluza-Klein approach that associates the extra geometric terms due to the fifth coordinate with contributions to the four dimensional stress-energy tensor.Comment: 11 page

Instabilities in droplets spreading on gels

We report a novel surface-tension driven instability observed for droplets spreading on a compliant substrate. When a droplet is released on the surface of an agar gel, it forms arms/cracks when the ratio of surface tension gradient to gel strength is sufficiently large. We explore a range of gel strengths and droplet surface tensions and find that the onset of the instability and the number of arms depend on the ratio of surface tension to gel strength. However, the arm length grows with an apparently universal law L ~ t^{3/4}

The Behavior of Kasner Cosmologies with Induced Matter

We extend the induced matter model, previously applied to a variety of isotropic cases, to a generalization of Bianchi type-I anisotropic cosmologies. The induced matter model is a 5D Kaluza-Klein approach in which assumptions of compactness are relaxed for the fifth coordinate, leading to extra geometric terms. One interpretation of these extra terms is to identify them as an ``induced matter'' contribution to the stress-energy tensor. In similar spirit, we construct a five dimensional metric in which the spatial slices possess Bianchi type-I geometry. We find a set of solutions for the five dimensional Einstein equations, and determine the pressure and density of induced matter. We comment on the long-term dynamics of the model, showing that the assumption of positive density leads to the contraction over time of the fifth scale factor.Comment: 14 page

The Mixmaster Universe in Five Dimensions

We consider a five dimensional vacuum cosmology with Bianchi type-IX spatial geometry and an extra non-compact coordinate. Finding a new class of solutions, we examine and rule out the possibility of deterministic chaos. We interpret this result within the context of induced matter theory.Comment: 13 page

Remembering 'zeal' but not 'thing':reverse frequency effects as a consequence of deregulated semantic processing

More efficient processing of high frequency (HF) words is a ubiquitous finding in healthy individuals, yet frequency effects are often small or absent in stroke aphasia. We propose that some patients fail to show the expected frequency effect because processing of HF words places strong demands on semantic control and regulation processes, counteracting the usual effect. This may occur because HF words appear in a wide range of linguistic contexts, each associated with distinct semantic information. This theory predicts that in extreme circumstances, patients with impaired semantic control should show an outright reversal of the normal frequency effect. To test this prediction, we tested two patients with impaired semantic control with a delayed repetition task that emphasised activation of semantic representations. By alternating HF and low frequency (LF) trials, we demonstrated a significant repetition advantage for LF words, principally because of perseverative errors in which patients produced the previous LF response in place of the HF target. These errors indicated that HF words were more weakly activated than LF words. We suggest that when presented with no contextual information, patients generate a weak and unstable pattern of semantic activation for HF words because information relating to many possible contexts and interpretations is activated. In contrast, LF words tend are associated with more stable patterns of activation because similar semantic information is activated whenever they are encountered

Five-Dimensional Space-Times

The set of all spatially homogeneous (4+1)-dimensional cosmologies will be explored. We will utilize a classification of these space-times based on the actions of isometry groups on these manifolds. Several exact solutions of the Einstein equations will be derived. The possibilities of dimensional reduction and isotropization will be examined. Five-dimensional generalizations of the mixmaster universe will be developed. Finally, the Einstein equations in 4+1 dimensions will be viewed as a Hamiltonian system. The absence of chaotic solutions to these equations will be shown