A generalized family of anisotropic compact object in general relativity

We present model for anisotropic compact star under the general theory of relativity of Einstein. In the study a 4-dimensional spacetime has been considered which is embedded into the 5-dimensional flat metric so that the spherically symmetric metric has class 1 when the condition $e^{\lambda}=\left(\,1+C\,e^{\nu} \,{\nu'}^2\,\right)$ is satisfied ($\lambda$ and $\nu$ being the metric potentials along with a constant $C$). A set of solutions for the field equations are found depending on the index $n$ involved in the physical parameters. The interior solutions have been matched smoothly at the boundary of the spherical distribution to the exterior Schwarzschild solution which necessarily provides values of the unknown constants. We have chosen the values of $n$ as $n=2$ and $n$=10 to 20000 for which interesting and physically viable results can be found out. The numerical values of the parameters and arbitrary constants for different compact stars are assumed in the graphical plots and tables as follows: (i) LMC X-4 : $a=0.0075$, $b=0.000821$ for $n=2$ and $a=0.0075$, $nb=0.00164$ for $n\ge 10$, (ii) SMC X-1: $a=0.00681$, $b=0.00078$ for $n=2$, and $a=0.00681$, $nb=0.00159$ for $n \ge 10$. The investigations on the physical features of the model include several astrophysical issues, like (i) regularity behavior of stars at the centre, (ii) well behaved condition for velocity of sound, (iii) energy conditions, (iv) stabilty of the system via the following three techniques - adiabatic index, Herrera cracking concept and TOV equation, (v) total mass, effective mass and compactification factor and (vi) surface redshift. Specific numerical values of the compact star candidates LMC X-4 and SMC X-1 are calculated for central and surface densities as well as central pressure to compare the model value with actual observational data.Comment: 20 pages, 9 figures, 2 Table

Topological Insulator Magnetic Tunnel Junctions: Quantum Hall Effect and Fractional Charge via Folding

We provide a characterization of tunneling between coupled topological insulators in 2D and 3D under the influence of a ferromagnetic layer. We explore conditions for such systems to exhibit integer quantum Hall physics and localized fractional charge, also taking into account interaction effects for the 2D case. We show that the effects of tunneling are topologically equivalent to a certain deformation or folding of the sample geometry. Our key advance is the realization that the quantum Hall or fractional charge physics can appear in the presence of only a \emph{single} magnet unlike previous proposals which involve magnetic domain walls on the surface or edges of topological insulators respectively. We give illustrative topological folding arguments to prove our results and show that for the 2D case our results are robust even in the presence of interactions.Comment: 5 pages, 2 figure

Study of Doppler waveforms in pregnancy induced hypertension and its correlation with perinatal outcome

Background: Objectives of current study were to study the significance of Doppler in PIH using middle cerebral artery and umbilical artery blood flow and to analyze the role of Doppler in PIH in predicting perinatal outcome.Methods: Hundred cases of women with pregnancy induced hypertension between 28-40 weeks of gestation were studied for umbilical artery and middle cerebral artery Doppler waveforms. The perinatal outcome results were documented and analyzed statistically using percentage and Chi-square test.Results: Adverse perinatal outcome was significantly associated with oligohydramnios (P <0.0001) and grade 3 placental maturity (P <0.01). Absent end diastolic flow waveform in umbilical artery was associated with mortality of 27.78% and reverse end diastolic waveform with mortality of 100%.  UA PI has the highest sensitivity (88.88%) and positive predictive value (69.56%) in predicting low birth weight. Cerebroplacental ratio (MCA/UA) had highest sensitivity (94.42%), PPV (86.42%), accuracy (90%) for predicting adverse perinatal outcome than UAPI and MCA PI. MCA PI had low specificity in predicting adverse perinatal outcome.Conclusions: Pregnancy induced hypertension is associated with significant fetal morbidity and mortality. Oligohydramnios in PIH patients is associated with adverse pregnancy outcome. Presence of absent end diastolic flow and reversed end diastolic flow in umbilical artery is an ominous sign with high perinatal mortality. Reversed end diastolic flow is more ominous than absent end diastolic flow. Cerebroplacental ratio (MCA/UA PI) is a better predictor of adverse perinatal outcome, with highest diagnostic accuracy, sensitivity, and positive predictive value, than either vessel Doppler indices considered alone. Colour Doppler study is a simple, quick, non-invasive procedure and is found to be the most accurate among the other tests for antepartum fetal surveillance

A True Human Tail in a Neonate : Case report and literature review

A true human tail is a benign vestigial caudal cutaneous structure composed of adipose, connective tissue, muscle, vessels, nerves and mechanoreceptors. A true human tail can be distinguished from a pseudotail as the latter is commonly associated with underlying spinal dysraphism, which requires specialised management. True human tails are very rare, with fewer than 40 cases reported to date. We report a healthy one-day-old male newborn who was referred to the Bharath Hospital, Kottayam, Kerala, India, in 2014 with a cutaneous appendage arising from the lumbosacral region. Magnetic resonance imaging of the spine ruled out spinal dysraphism. The appendage was removed by simple surgical excision. Clinicians should emphasise use of ‘true tail’ and ‘pseudotail’ as specific disparate terms as the clinical, radiological and histological findings of these conditions differ significantly, along with management strategies and outcomes

Accessing nanotube bands via crossed electric and magnetic fields

We investigate the properties of conduction electrons in single-walled armchair carbon nanotubes in the presence of mutually orthogonal electric and magnetic fields transverse to the tube's axis. We find that the fields give rise to an asymmetric dispersion in the right- and left-moving electrons along the tube as well as a band-dependent interaction. We predict that such a nanotube system would exhibit spin-band-charge separation and a band-dependant tunneling density of states. We show that in the quantum dot limit, the fields serve to completely tune the quantum states of electrons added to the nanotube. For each of the predicted effects, we provide examples and estimates that are relevant to experiment.Comment: 4 pages, 2 figure