Black hole - D-brane correspondence: An example

We explore the connection between D-branes and black holes in one particular case: a $D3$-brane compactified to four dimensions on $T^6/Z_3$. Using the $D$-brane boundary state description we show the equivalence with a double extremal N=2 black hole solution of four dimensional supergravity.Comment: 15 pages, LaTeX. Contribution by C. Nunez to the conference Quantum Gravity in the Southern Cone, Bariloche 7-10 January 1998; to appear in the proceeding

Hyperinsulinism-hyperammonaemia syndrome: novel mutations in the GLUD1 gene and genotype-phenotype correlations

Background: Activating mutations in the GLUD1 gene (which encodes for the intra-mitochondrial enzyme glutamate dehydrogenase, GDH) cause the hyperinsulinism–hyperammonaemia (HI/HA) syndrome. Patients present with HA and leucine-sensitive hypoglycaemia. GDH is regulated by another intra-mitochondrial enzyme sirtuin 4 (SIRT4). Sirt4 knockout mice demonstrate activation of GDH with increased amino acid-stimulated insulin secretion. Objectives: To study the genotype–phenotype correlations in patients with GLUD1 mutations. To report the phenotype and functional analysis of a novel mutation (P436L) in the GLUD1 gene associated with the absence of HA. Patients and methods: Twenty patients with HI from 16 families had mutational analysis of the GLUD1 gene in view of HA (n=19) or leucine sensitivity (n=1). Patients negative for a GLUD1 mutation had sequence analysis of the SIRT4 gene. Functional analysis of the novel P436L GLUD1 mutation was performed. Results: Heterozygous missense mutations were detected in 15 patients with HI/HA, 2 of which are novel (N410D and D451V). In addition, a patient with a normal serum ammonia concentration (21 µmol/l) was heterozygous for a novel missense mutation P436L. Functional analysis of this mutation confirms that it is associated with a loss of GTP inhibition. Seizure disorder was common (43%) in our cohort of patients with a GLUD1 mutation. No mutations in the SIRT4 gene were identified. Conclusion: Patients with HI due to mutations in the GLUD1 gene may have normal serum ammonia concentrations. Hence, GLUD1 mutational analysis may be indicated in patients with leucine sensitivity; even in the absence of HA. A high frequency of epilepsy (43%) was observed in our patients with GLUD1 mutations

Analyzing Learners Behavior in MOOCs: An Examination of Performance and Motivation Using a Data-Driven Approach

Massive Open Online Courses (MOOCs) have been experiencing increasing use and popularity in highly ranked universities in recent years. The opportunity of accessing high quality courseware content within such platforms, while eliminating the burden of educational, financial and geographical obstacles has led to a rapid growth in participant numbers. The increasing number and diversity of participating learners has opened up new horizons to the research community for the investigation of effective learning environments. Learning Analytics has been used to investigate the impact of engagement on student performance. However, extensive literature review indicates that there is little research on the impact of MOOCs, particularly in analyzing the link between behavioral engagement and motivation as predictors of learning outcomes. In this study, we consider a dataset, which originates from online courses provided by Harvard University and Massachusetts Institute of Technology, delivered through the edX platform [1]. Two sets of empirical experiments are conducted using both statistical and machine learning techniques. Statistical methods are used to examine the association between engagement level and performance, including the consideration of learner educational backgrounds. The results indicate a significant gap between success and failure outcome learner groups, where successful learners are found to read and watch course material to a higher degree. Machine learning algorithms are used to automatically detect learners who are lacking in motivation at an early time in the course, thus providing instructors with insight in regards to student withdrawal

ARPES studies of cuprate Fermiology: superconductivity, pseudogap, and quasiparticle dynamics

We present angle-resolved photoemission spectroscopy (ARPES) studies of the cuprate high-temperature superconductors which elucidate the relation between superconductivity and the pseudogap and highlight low-energy quasiparticle dynamics in the superconducting state. Our experiments suggest that the pseudogap and superconducting gap represent distinct states, which coexist below T$_c$. Studies on Bi-2212 demonstrate that the near-nodal and near-antinodal regions behave differently as a function of temperature and doping, implying that different orders dominate in different momentum-space regions. However, the ubiquity of sharp quasiparticles all around the Fermi surface in Bi-2212 indicates that superconductivity extends into the momentum-space region dominated by the pseudogap, revealing subtlety in this dichotomy. In Bi-2201, the temperature dependence of antinodal spectra reveals particle-hole asymmetry and anomalous spectral broadening, which may constrain the explanation for the pseudogap. Recognizing that electron-boson coupling is an important aspect of cuprate physics, we close with a discussion of the multiple 'kinks' in the nodal dispersion. Understanding these may be important to establishing which excitations are important to superconductivity.Comment: To appear in a focus issue on 'Fermiology of Cuprates' in New Journal of Physic

Energy Return Characteristics of EVA and E-TPU Midsoles During a Drop Jump

Expanded Thermoplastic Polyurethane (E-TPU) is a material used in shoe midsoles that has been described as having greater energy return than traditional Ethylene Vinyl-Acetate (EVA) midsole material. PURPOSE: The purpose of this study was to compare the landing and energy return characteristics of shoes using EVA and E-TPU midsoles. METHODS: Ten collegiate female athletes (19.7±1.0 yrs, 75.74±10.9 kg, 1.72±0.08 m) volunteered and provided informed consent to participate in this study. Participants performed five drop jumps from a height of 50 cm under two conditions; while wearing EVA midsole shoes and while wearing E-TPU midsole shoes. Peak force, rate of loading and impulse were measured from a Bertec force plate sampled at 1000 Hz during the initial landing phase of the drop jump. Coefficient of Restitution (COR) was determined by measuring the bounce height of a 1 in steel ball bearing dropped from a 1 m height onto the shoes. All measures were compared between midsole conditions using paired t-tests. RESULTS: Peak vertical force when landing with the EVA shoe (3265.6±554.2 N) was not different (p=0.19) than when landing with the E-TPU shoe (3406.6± 590.3 N). Similar rates of loading (p=0.71) were found for the EVA shoes (56106.3±9995.8 N/s) and the E-TPU shoes (54232.4±12167.0). Likewise impulse was not different (p=0.30) between the EVA shoe (710.5±177.7 Ns) and E-TPU shoe (693.9±162.6 Ns). However, COR was slightly higher (p=0.01) in the E-TPU shoe (0.67±.05) than the EVA shoe (0.66±0.02). CONCLUSION: The difference in COR values coupled with the similar landing characteristics observed for the different midsole materials may suggest that individuals are able to compensate for material differences by using different physiological strategies such as using different muscle stiffness during the landing phase depending on midsole material. Further testing to examine physiological measures during these movements is warranted

Contextualizing women’s agency in marital negotiations:Muslim and Hindu women in Karnataka, India

We use 36 in-depth interviews, with 18 Muslim and 18 Hindu women in Karnataka, India, to explore the relationships between women’s educational attainments and women’s exercise of agency in spousal selection and the timing of marriage. We have outlined three kinds of agency, namely, convinced, resistance, and complicit, and the contexts in which they were deployed by our participants during their marriage negotiations. Our examination of the role of education across this spectrum of agential capacities during marriage negotiations suggests that the linkages between education and agency are not straightforward. Rather, the normative context, and how parents and daughters interact with it when fixing marriages, makes the use of agency by the woman and by their parents much more complicated than standard narratives that claim that “modern” education for girls will inevitably enable women to play decisive roles in realizing their personal preferences. Our data lead us to challenge this framework and we argue that the link between education and agency is not always positive and linear, as it widely thought to be

Protective Effect of Bombyx mori L Cocoon (Abresham) and its Formulations against Isoproterenol-Induced Cardiac Damage

Purpose: To investigate the potential activity of Bombyx mori and its formulations against isoproterenol (ISO) induced cardiotoxicity.Methods: Wistar rats were orally pretreated with the ethanol extract of Bombyx mori cocoons in two doses (250 and 500 mg/kg) for 30 days; rats were similarly pretreated with its polyherbal formulations incorporating Khamira Abresham sada (KAS) and Khamira Abresham Hakim Arshadwala (KAHAW) (800 mg/kg), standard drug metoprolol (10 mg/kg) and normal saline for 30 days. Cardiotoxicity was induced by administration of isoproterenol (ISO, 85 mg/kg, subcutaneous) given twice on days 29 and 30 in all six pre-treated groups (n = 6) except the normal control. Cardiotoxicity was assessed by morphological and biochemical evaluation and further confirmed by histopathological studies.Results: Pretreatment with Bombyx mori (500 mg/kg), KAHAW and KAS significantly decreased (p < 0.01) the heart weight:body weight (HW:BW) ratio; significantly decreases the elevated activities of the cardiac marker enzymes, namely, asparate transaminase (AST) (p < 0.01), alanine transaminase (ALT) (p < 0.01), lactate dehydrogenase (LDH) (p < 0.01) ,creatinine kinase (CK-MB) (p < 0.01) and thiobarbituric acid reactive substances (TBARS) (p < 0.01) similar to the standard drug metoprolol (p < 0.01) in ISO-injected rats. Pre-treatment of rats with Bombyx mori (500 mg/kg), KAS, KAHAW and metoprolol challenged with ISO also showed absence of troponin. Pretreatment with B. mori (500 mg/kg), KAHAW and KAS significantly increased the activities of Superoxide dismutase (SOD) (p < 0.01), Tissue glutathione (GSH) (p < 0.01) and catalase (p < 0.01) similar to the standard drug metoprolol (p < 0.01).Conclusion: The findings of this study indicate that Bombyx mori as well as its polyherbal formulations exerts potent cardioprotection against isoproterenol-induced cardiotoxicity. This effect is comparable with that of metoprolol.Keywords: Bombyx mori, Myocardial necrosis, Oxidative stress, Cardiotoxicity, Khamira Abresham, Metoprolol, Isoprotereno

Radiative decays of heavy and light mesons in a quark triangle approach

The radiative meson decays $V\to P\gamma$ and $P\to \gamma\gamma$ are analyzed using the quark triangle diagram. Experimental data yield well determined estimates of the universal quark-antiquark-meson couplings $g_{Vq\bar{q}'}$ and $g_{Pq\bar{q}'}$ for the light meson sector. Also predictions for the ratios of neutral to charged heavy meson decay coupling constants are given and await experimental confirmation.Comment: 31 pages of RevTex, 5 figures, Postscript version available at http://info.utas.edu.au/docs/physics/theory/Publications/9548.html, scheduled to appear in Phys. Rev. D, vol 53, issue 11, 199