Chern-Simons Gravity in Four Dimensions

Five dimensional Chern-Simons theory with (anti-)de Sitter SO(1,5) or SO(2,4) gauge invariance presents an alternative to General Relativity with cosmological constant. We consider the zero-modes of its Kaluza-Klein compactification to four dimensions. Solutions with vanishing torsion are obtained in the cases of a spherically symmetric 3-space and of a homogeneous and isotropic 3-space, which reproduce the Schwarzshild-de Sitter and $\Lambda$CDM cosmological solutions of General Relativity. We also check that vanishing torsion is a stable feature of the solutions.Comment: 25 pages, Late

Behaviour of Charged Spinning Massless Particles

We revisit the classical theory of a relativistic massless charged point particle with spin and interacting with an external electromagnetic field. In particular, we give a proper definition of its kinetic energy and its total energy, the latter being conserved when the external field is stationary. We also write the conservation laws for the linear and angular momenta. Finally, we find that the particle's velocity may differ from $c$ as a result of the spin---electromagnetic field interaction, without jeopardizing Lorentz invariance.Comment: PDFtex file, 20 pages, 3 figures Revised version published in Symmetry (Basel

A Topological-like Model for Gravity in 4D Space-time

In this paper we consider a model for gravity in 4-dimensional space-time originally proposed by Chamseddine, which may be derived by dimensional reduction and truncation from a 5-dimensional Chern-Simons theory. Its topological origin makes it an interesting candidate for an easier quantization, e.g., in the Loop Quantization framework. The present paper is dedicated to a classical analysis of the model's properties. Cosmological solutions as well as wave solutions are found and compared with the corresponding solutions of Einstein's General Relativity with cosmological constant.Comment: 24 pages, 2 figures, PDFLatex. Typos corrected. Subsection 2.2.1 is new and subsection 2.2.3 (old subsection 2.2.2) has been improve

Asymmetric Reversal in Inhomogeneous Magnetic Heterostructures

Asymmetric magnetization reversal is an unusual phenomenon in antiferromagnet / ferromagnet (AF/FM) exchange biased bilayers. We investigated this phenomenon in a simple model system experimentally and by simulation assuming inhomogeneously distributed interfacial AF moments. The results suggest that the observed asymmetry originates from the intrinsic broken symmetry of the system, which results in local incomplete domain walls parallel to the interface in reversal to negative saturation of the FM. Magneto-optic Kerr effect unambiguously confirms such an asymmetric reversal and a depth-dependent FM domain wall in accord with the magnetometry and simulations.Comment: 4 pages, 4 figure

On the Necessity of Time and Resource Issues to Support Collaboration in E-learning Standards

In this paper we motivate the necessity of time+resource metadata in current e-learning standards to support collaborative activities. Learning Objects (LOs) are currently defined in a very independent way from each other, which makes it difficult to use them in a real scenario where students interact and have their own constraints. We present some challenging features that, at least, should be discussed when elaborating new e-learning standards.Garrido Tejero, A.; Morales, L.; Serina, I. (2011). On the Necessity of Time and Resource Issues to Support Collaboration in E-learning Standards. IEEE Learning Technology Newsletter. 13:39-41. http://hdl.handle.net/10251/35041S39411

Broken Heart, Broken Mind

Introduction: Takostubo Cardiomyopathy (TCM) is a unique condition of reversible cardiac dysfunction precipitated by emotional or physical stress. Studies are emerging noting an association with Amyotrophic Lateral Sclerosis (ALS). This is hypothesized to be secondary to baseline elevation of catecholamines in these individuals. Case Presentation: A 53-year-old female with background of anxiety, presented with acute onset chest pain. Initial evaluation revealed elevated troponins without ST changes on EKG. Echocardiogram showed EF 28% with apical ballooning and left heart catheterization was unremarkable. Her echocardiogram improved 2 weeks later, consistent with TCM. During this evaluation it was noted she was significantly dysarthric. On further history she revealed progressive odynophagia for the past year, generalized muscle weakness for the past few months, and dysarthria for 4-6 weeks. Neurological exam demonstrated both upper and lower motor neuron findings of diffuse muscle atrophy, fasciculations as well as brisk peripheral reflexes, jaw jerk and bilateral Hoffmans. MRI brain/spine imaging showed no significant abnormalities and EMG indicated lower motor neuron changes. CPK, anti-MUSK, anti-acetylcholine receptor antibodies were normal and extensive evaluation of paraneoplastic, vitamin and autoimmune disease were negative. An ALS diagnosis was made. Due to worsening respiratory status she required intubation with subsequent tracheostomy placement and ultimately was discharged to a long-term care facility. Conclusion: This case highlights the uncommon association of TCM in ALS with a unique scenario where it was the presenting feature of the disease. Physicians should be vigilant for neurological symptoms in patients presenting with chest discomfort or risk missing the diagnosis.https://scholarlycommons.henryford.com/merf2020caserpt/1020/thumbnail.jp

A case of portal hypertension due to a superior mesenteric arteriovenous fistula

Introduction: Superior mesenteric arteriovenous fistula (SMAVF) is an infrequent vascular disorder characterized by abnormal communication between high-pressure superior mesenteric artery and low-pressure superior mesenteric vein. This allows blood to bypass the intestinal capillary bed and produces portal hypertension leading to ascites and gastro-esophageal variceal bleeding. Although SMAVF can be congenital, most reported cases have been due to abdominal trauma or iatrogenic causes. Here, we report a case of SMAVF presenting as severe ascites. Case presentation: A 61-year-old female presented to the emergency department with a 1-week history of abdominal distention and discomfort. Her past medical history was significant for abdominal hysterectomy complicated by bowel resection. Initial evaluation was remarkable for severe hyponatremia and severe abdominal and pelvic ascites evidenced on computed tomography. A paracentesis was performed, fluid analysis was negative for spontaneous bacterial peritonitis. The Serum Ascites Albumin Gradient was elevated (\u3e1.1 g/dL). The hospital course was complicated by gastrointestinal bleeding requiring blood transfusions. An upper endoscopy revealed bleeding esophageal varices that were banded. A magnetic resonance of the abdomen revealed a large SMAVF between causing increased portal vein blood flow and pressure; the patient subsequently underwent embolization of the SMAVF. The patient clinically improved and was discharged on stable condition. On follow-up after discharge, cross sectional imaging revealed improved appearance of the mesenteric vasculature and resolution of the ascites. Discussion: This case illustrates the for clinicians to be vigilant for rare but reversible causes of portal hypertension that can mimic cirrhosis in order to provide appropriate diagnosis and management.https://scholarlycommons.henryford.com/merf2020caserpt/1028/thumbnail.jp

The Nighttime Fears Scale: Development and psychometric evidence of a standardized self-report scale to assess nighttime fears in children

Nighttime fears are highly prevalent in children and are linked to children’s distress and internalizing problems, especially childhood anxiety. Although its assessment may be critical, there is a lack of available standardized self-reports. This study aimed to describe the development and psychometric evaluation of the Nighttime Fears Scale (NFS), a new standardized self-report for assessing nighttime fears in school-aged children. The construction of the scale was based on prior relevant research and involvement of researchers and clinicians, experts in childhood anxiety, and fears. A total of 794 Spanish-speaking children (51.1 % girls) aged 8–12 years completed the NFS along with measures of anxiety, sleep problems, internalizing and externalizing problems, and positive behaviors. Exploratory and confirmatory factor analyses supported a four-factor structure of the NFS, consisting of 21 items measuring a range of potentially fear-provoking stimuli at nighttime. Strong internal consistency (alphas ranging from .87 to .94), adequate test-retest reliability, and evidence of convergent, divergent and incremental validity was found. This study provides initial support for the use of the NFS by clinicians and researchers, suggesting that it is a promising tool for a rapid and easily-administered assessment to identify the presence and intensity levels of a set of common children’s nighttime fears