257 research outputs found
A generalized Finch-Skea class one static solution
In the present article, we discuss relativistic anisotropic solutions of the
Einstein field equation for the spherically symmetric line element under the
class I condition. To do so we apply the embedding class one technique using
Eisland condition. Within this approach, one arrives at a particular
differential equation that links the two metric components and
. In order to obtain the full space-time description inside the
stellar configuration we ansatz the generalized form of metric component
corresponding to the Finch-Skea solution. Once the space-time geometry
is specified we obtain the complete thermodynamic description i.e. the matter
density , the radial, and tangential pressures and ,
respectively. Graphical analysis shows that the obtained model respects the
physical and mathematical requirements that all ultra-high dense collapsed
structures must obey. The diagram suggests that the solution yields
stiffer EoS as parameter increases. The graph is in agreement with
the concepts of Bejgar et al. \cite{bej} that the mass at is lesser
by few percent (for this solution ) from . This suggests
that the EoSs is without any strong high-density softening due to
hyperonization or phase transition to an exotic state.Comment: 14 figures, Accepted in European Physical Journal
Cosmological expansion and contraction from Pauli exclusion principle in -branes
We show that the Pauli exclusion principle in a system of -branes can
give rise to the expansion and contraction of the universe which is located on
an -brane. We start with a system of -branes with high symmetry, which
join mutually and form pairs of -anti--branes. The resulting symmetry
breaking creates gauge fields that live on the -branes and play the role of
graviton tensor modes, which induce an attractive force between the and
anti- branes. Consequently, the gauge fields that live on the -branes,
and the scalar fields which are attached symmetrically to all parts of these
branes, decay to fermions that attach anti-symmetrically to the upper and lower
parts of the branes, and hence the Pauli exclusion principle emerges. By
closing -branes mutually, the curvatures produced by parallel spins will be
different from the curvatures produced by anti-parallel spins, and this leads
to an inequality between the number of degrees of freedom on the boundary
surface and the number of degrees of freedom in the bulk region. This behavior
is inherited in the -brane on which the universe is located, and hence this
leads to the emergence of the universe expansion and contraction. In this
sense, the Pauli exclusion principle rules the cosmic dynamics.Comment: 27 pages. arXiv admin note: text overlap with arXiv:1607.0149
The Reliability of Red Flags in Spinal Cord Compression
Background: Acute low back pain is a common cause for presentation to the emergency department (ED). Since benign etiologies account for 95% of cases, red flags are used to identify sinister causes that require prompt management.
Objectives: We assessed the effectiveness of red flag signs used in the ED to identify spinal cord and cauda equine compression.
Patients and Methods: It was a retrospective cohort study of 206 patients with acute back pain admitted from the ED. The presence or absence of the red flag symptoms was assessed against evidence of spinal cord or cauda equina compression on magnetic resonance imaging (MRI).
Results: Overall, 32 (15.5%) patients had compression on MRI. Profound lower limb neurologic examination did not demonstrate a statistically significant association with this finding. The likelihood ratio (LR) for bowel and bladder dysfunction (sensitivity of 0.65 and specificity of 0.73) was 2.45. Saddle sensory disturbance (sensitivity of 0.27 and specificity of 0.87) had a LR of 2.11. When both symptoms were taken together (sensitivity of 0.27 and specificity of 0.92), they gave a LR of 3.46.
Conclusions: The predictive value of the two statistically significant red flags only marginally raises the clinical suspicion of spinal cord or cauda equina compression. Effective risk stratification of patients presenting to the ED with acute back pain is crucial; however, this study did not support the use of these red flags in their current form
Association of selected inflammatory markers and risk factors with pain in patients undergoing cervical or lumbar disc herniation
Introduction
Studies have suggested that radicular pain following disc herniation may be associated with local or systemic inflammatory responses produced in the vicinity of the herniated disc rather than compression of the nerve. Present study assessed the association of serum interleukin-6 (IL-6) levels, high-sensitivity C-reactive protein (hs-CRP) and related risk factors in patients undergoing discectomy following cervical disc herniation (CDH) or lumbar disc herniation (LDH).
Methods
Study recruited 77 patients undergoing discectomy for LDH and CDH. An interviewer administered questionnaire was used to obtain sociodemographic, behavioral and occupational data. IL-6 and hs-CRP levels were measured in each individual. IL-6 was analyzed by ELISA method and hs-CRP was determined using auto analyzer. Results were analyzed by using SPSS version 25.0.
Results
Significant correlation was not found with serum IL-6 and hs-CRP levels (r=0.02, p˃0.05) for acute and chronic CDH and LDH. Patients with chronic neck or back pain showed significantly (p=0.043) higher IL-6 level compared to patients with acute neck or back pain. Serum hs-CRP level was significantly higher (p=0.048) in patients with acute neck or back pain compared to patients with chronic neck or back pain. Significant association was not observed between; level of physically demanding nature of occupation (p=0.542), duration of occupation (p=0.446), type of exercise (p=0.371), type of sports (p=0.339) and CDH or LDH.
Conclusion
Though significant correlation was not observed between inflammatory markers IL-6, hs-CRP and CDH or LDH. The mean IL-6 was higher in chronic back pain and neck pain patients with LDH and CDH whereas mean hs-CRP mean was higher in acute back pain and neck pain patients. Significant association was not reported between selected known risk factors (behavioral, occupational) and CDH or LDH
On the resolution of cosmic coincidence problem and phantom crossing with triple interacting fluids
We here investigate a cosmological model in which three fluids interact with
each other involving certain coupling parameters and energy exchange rates. The
motivation of the problem stems from the puzzling `triple coincidence problem'
which naively asks why the cosmic energy densities of matter, radiation and
dark energy are almost of the same order of magnitude at the present time. In
our model, we determine the conditions under triple interacting fluids will
cross the phantom divide.Comment: 22 pages, 6 figures, to appear in Eur. Phys. J. C (2009
IInfluence of Mg/CTAB ratio on the structural, physicochemical properties and catalytic activity of amorphous mesoporous magnesium silicate catalysts
This study investigated the physicochemical and catalytic properties of mesoporous magnesium silicate catalysts prepared at various Mg/CTAB ratio (0.25, 0.50, 0.75 and 1.00). The XPS analysis detected a mixture of enstatite and magnesium carbonate species when the Mg/CTAB ratio was 0.25, and 0.50. A mixture of forsterite and magnesium carbonate species were detected when the Mg/CTAB ratio was 0.75 whereas for Mg/CTAB ratio of 1.00, enstatite and magnesium metasilicate species were detected. Catalyst with Mg/CTAB ratio of 1.00 indicated the highest catalytic activity in the oxidation of styrene. Its styrene conversion rate was 59.0% with 69.2% of styrene oxide (StO) selectivity. The H2O2 molecules were activated regio-specifically by the magnesium species to prevent rapid self-decomposition while promoting selective interaction with styrene. All the parameters that influence the styrene conversion and product selectivity were evaluated by using Analysis of variance (ANOVA) with Tukey’s test. Based on the ANOVA analysis, it showed that reaction time (h), Mg/CTAB ratio, styrene/H2O2 ratio, catalyst loading (mg) and temperature (°C) effects the styrene conversion and product selectivity (StO), significantly (p< 0.05). The oxidation of styrene was well fitted to the pseudo-first-order model. The activation energy, Ea of catalyzed styrene epoxidation reaction was calculated to be 27.7 kJmol-1. The catalysts can be reused several times without any significant loss in its activity and selectivity. The results from this study will be useful in designing and developing low cost, high activity catalysts from alkaline earth metals
Scenarios of cosmic string with variable cosmological constant
Exact solutions of the Einstein field equations with cosmic string and space
varying cosmological constant, viz., , in the
energy-momentum tensors are presented. Three cases have been studied: where
variable cosmological constant (1) has power law dependence, (2) is
proportional to the string fluid density, and (3) is purely a constant. Some
cases of interesting physical consequences have been found out such that (i)
variable cosmological constant can be represented by a power law of the type
, (ii) variable cosmological constant and cosmic string
density are interdependent to each other according to the relation
, and (iii) cosmic string density can be scaled by a
power law of the type . It is also shown that several known
solutions can be recovered from the general form of the solutions obtained
here.Comment: 15 LaTeX pages; Two new sections (Secs 4 & 5) have been include
Corporate Social Responsibility and Islamic Financial Institutions (IFIs): Management Perceptions from IFIs in Bahrain
Islamic finance is gaining greater attention in the finance industry, and this paper analyses how Islamic financial institutions (IFIs) are responding to the welfare needs of society. Using interview data with managers and content analysis of the disclosures, this study attempts to understand management perceptions of corporate social
responsibility (CSR) in IFIs. A thorough understanding of CSR by managers, as evident in the interviews, has not been translated fully into practice. The partial use of IFIs’ potential role in social welfare would add further challenges in the era of financialisation
Cosmic coincidence problem and variable constants of physics
The standard model of cosmology is investigated using time dependent
cosmological constant and Newton's gravitational constant . The
total energy content is described by the modified Chaplygin gas equation of
state. It is found that the time dependent constants coupled with the modified
Chaplygin gas interpolate between the earlier matter to the later dark energy
dominated phase of the universe. We also achieve a convergence of parameter
, with minute fluctuations, showing an evolving . Thus our
model fairly alleviates the cosmic coincidence problem which demands
at present time.Comment: 27 pages, 15 figure
A Bayesian decision support sequential model for severity of illness predictors and intensive care admissions in pneumonia.
BACKGROUND: Community-acquired pneumonia (CAP) is one of the leading causes of morbidity and mortality in the USA. Our objective was to assess the predictive value on critical illness and disposition of a sequential Bayesian Model that integrates Lactate and procalcitonin (PCT) for pneumonia. METHODS: Sensitivity and specificity of lactate and PCT attained from pooled meta-analysis data. Likelihood ratios calculated and inserted in Bayesian/ Fagan nomogram to calculate posttest probabilities. Bayesian Diagnostic Gains (BDG) were analyzed comparing pre and post-test probability. To assess the value of integrating both PCT and Lactate in Severity of Illness Prediction we built a model that combined CURB65 with PCT as the Pre-Test markers and later integrated the Lactate Likelihood Ratio Values to generate a combined CURB 65 + Procalcitonin + Lactate Sequential value. RESULTS: The BDG model integrated a CUBR65 Scores combined with Procalcitonin (LR+ and LR-) for Pre-Test Probability Intermediate and High with Lactate Positive Likelihood Ratios. This generated for the PCT LR+ Post-test Probability (POSITIVE TEST) Posterior probability: 93% (95% CI [91,96%]) and Post Test Probability (NEGATIVE TEST) of: 17% (95% CI [15-20%]) for the Intermediate subgroup and 97% for the high risk sub-group POSITIVE TEST: Post-Test probability:97% (95% CI [95,98%]) NEGATIVE TEST: Post-test probability: 33% (95% CI [31,36%]) . ANOVA analysis for CURB 65 (alone) vs CURB 65 and PCT (LR+) vs CURB 65 and PCT (LR+) and Lactate showed a statistically significant difference (P value = 0.013). CONCLUSIONS: The sequential combination of CURB 65 plus PCT with Lactate yielded statistically significant results, demonstrating a greater predictive value for severity of illness thus ICU level care
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