Probing photospheric magnetic fields with new spectral line pairs

The magnetic line ratio (MLR) method has been extensively used in the measurement of photospheric magnetic field strength. It was devised for the neutral iron line pair at 5247.1 A and 5250.2 A (5250 A pair). Other line pairs as well-suited as this pair been have not been reported in the literature. The aim of the present work is to identify new line pairs useful for the MLR technique and to test their reliability. We use a three dimensional magnetohydrodynamic (MHD) simulation representing the quiet Sun atmosphere to synthesize the Stokes profiles. Then, we apply the MLR technique to the Stokes V profiles to recover the fields in the MHD cube both, at original resolution and after degrading with a point spread function. In both these cases, we aim to empirically represent the field strengths returned by the MLR method in terms of the field strengths in the MHD cube. We have identified two new line pairs that are very well adapted to be used for MLR measurements. The first pair is in the visible, Fe I 6820 A - 6842 A (whose intensity profiles have earlier been used to measure stellar magnetic fields), and the other is in the infrared (IR), Fe I 15534 A - 15542 A. The lines in these pairs reproduce the magnetic fields in the MHD cube rather well, partially better than the original 5250 A pair. The newly identified line pairs complement the old pairs. The lines in the new IR pair, due to their higher Zeeman sensitivity, are ideal for the measurement of weak fields. The new visible pair works best above 300 G. The new IR pair, due to its large Stokes V signal samples more fields in the MHD cube than the old IR pair at $1.56\,\mu$m, even in the presence of noise, and hence likely also on the real Sun. Owing to their low formation heights (100-200 km above tau_5000=1), both the new line pairs are well suited for probing magnetic fields in the lower photosphere.Comment: Accepted for publication in Astronomy & Astrophysic

Prevalence of congenital anomalies in a tertiary care centre in North Kerala, India

Background: Congenital anomalies have emerged as an important cause for neonatal morbidity and mortality. The prevalence as well as pattern of anomaly varies from place to place. Literature search reveals that India has the highest number of children with birth defects.Methods: This is a cohort study conducted in the Department of Obstetrics and Gynecology during the period 2009-2015. All mothers admitted with congenital structural defects to the fetus diagnosed by imaging and those who delivered anomalous babies were included in this study. The anomalies were classified based on ICD-10 system.Results: There were a total of 911 anomalous babies born during the study period of which 554 were males and 338 were females.19 babies had ambiguous genitalia. Anomalies were more common in multigravidae and in mothers of age group 20-29 years. Maximum number of babies were born between 37-40weeks. Maternal diabetes was associated with increased incidence of anomalies. Most common system involved was urinary system followed by musculoskeletal system.Conclusions: The prevalence of structural anomalies in the present study is 0.84%. Patients with risk factors for anomalies should undergo pre-pregnancy counselling. Routine antenatal anomaly screening with ultrasound before viability should be done for all patients so that early termination of lethal anomalies can be done

Convolutional coded dual header pulse interval modulation for line of sight photonic wireless links.

The analysis and simulation for convolutional coded dual header pulse interval modulation (CC-DH-PIM) scheme using a rate ½ convolutional code with the constraint length of 3 is presented. Decoding is implemented using the Viterbi algorithm with a hard decision. Mathematical analysis for the slot error rate (SER) upper bounds is presented and results are compared with the simulated data for a number of different modulation techniques. The authors show that the coded DH-PIM outperforms the pulse position modulation (PPM) scheme and offers >4 dB code gain at the SER of 10?4 compared to the standard DH-PIM. Results presented show that the CC-DH-PIM with a higher constraint length of 7 offers a code gain of 2 dB at SER of 10?5 compared to the CC-DH-PIM with a constraint length of 3. However, in CC-DH-PIM the improvement in the error performance is achieved at the cost of reduced transmission throughput compared to the standard DH-PIM

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