Flux Expulsion - Field Evolution in Neutron Stars

Models for the evolution of magnetic fields of neutron stars are constructed, assuming the field is embedded in the proton superconducting core of the star. The rate of expulsion of the magnetic flux out of the core, or equivalently the velocity of outward motion of flux-carrying proton-vortices is determined from a solution of the Magnus equation of motion for these vortices. A force due to the pinning interaction between the proton-vortices and the neutron-superfluid vortices is also taken into account in addition to the other more conventional forces acting on the proton-vortices. Alternative models for the field evolution are considered based on the different possibilities discussed for the effective values of the various forces. The coupled spin and magnetic evolution of single pulsars as well as those processed in low-mass binary systems are computed, for each of the models. The predicted lifetimes of active pulsars, field strengths of the very old neutron stars, and distribution of the magnetic fields versus orbital periods in low-mass binary pulsars are used to test the adopted field decay models. Contrary to the earlier claims, the buoyancy is argued to be the dominant driving cause of the flux expulsion, for the single as well as the binary neutron stars. However, the pinning is also found to play a crucial role which is necessary to account for the observed low field binary and millisecond pulsars.Comment: 23 pages, + 7 figures, accepted for publication in Ap

Mobile addiction and its relationship with quality of life in medical students

Background: Quality of life is one of the most important health-related outcomes that can be affected by mobile phone addiction. This study was conducted to determine the prevalence of mobile phone addiction and its relationship with quality of life in students of Birjand University of Medical Sciences (BUMS). Methods: This cross-sectional study was conducted on 360 students in BUMS in 2018. The sample was randomly selected from each faculty using proportional stratified sampling. To collect data, a questionnaire containing the demographic variables, the PMPAS questionnaire for mobile addiction and SF-12 for quality of life were used. Data were analyzed by independent t-test and Pearson correlation coefficient in SPSS (V.18). Results: The mean age of the students was 25.1 ± 6.3 years that 75.5 were female. In terms of marital status, 60.6 were single. Nearly 75 of students were with moderate or severe mobile phone addiction. The score of mobile phone addiction was higher in single and younger students (p < 0.001). The mean score of quality of life for the students in two aspects of the physical and mental component were 50.81 and 42.86 respectively. Based on the results, there was a significant inverse relationship between scores of mental function and mobile phone addiction (r = �0.35, p < 0.001), this relation was not significant for physical function (r = �0.60, p = 0.25). Conclusions: According to the results, the prevalence of mobile phone addiction among students was high and mobile phone addiction has a negative effect on the quality of life of students, which has a negative effect on psychological performance. © 2019 INDIACLE

Aplikasi Pengenalan Tempat Wisata Propinsi Bengkulu Menggunakan Teknologi Augmented Reality (Video Playback) Berbasis Android

—Aplikasi Pengenalan Tempat Wisata Propinsi Bengkulu Menggunakan Teknologi Augmented Reality (Video Playback) Berbasis Android dibangun untuk mempermudah mempromosikan tempat – tempat wisata yang ada di Propinsi Bengkulu serta mempermudah para wisatawan untuk mengetahui bentuk wisata di Propinsi Bengkulu. Aplikasi ini dibuat dengan menggunakan Unity 3D untuk editor, Adobe Photoshop untuk desain tampilan interface, vuforia untuk pengembangan Augmented Reality dan didukung oleh sebuah samples dari Vuforia yaitu Vuforia Video playback untuk Play Video saat marker ditemukan. Pengembangan aplikasi ini diharapkan mampu untuk mempromosikan tempat wisata yang ada di Propinsi Bengkulu ke semua kalangan dimanapun berada.Kata kunci—Augmented Reality; Wisata; Propinsi Bengkulu; Androi

Fast determination of bisphenol A in spiked juice and drinking water samples by pipette tip solid phase extraction using cobalt metal organic framework as sorbent

A cobalt metal organic framework was prepared with rapid ultrasound assisted method by treatment of cobalt nitrate with pyridine 2,6-dicarboxilic acid dissolved in ethanolic media and used as a sorbent for pipette tip solid phase extraction of Bisphenol A (BPA) and its determination in spiked juice and drinking water samples by HPLC. Parameters which influence extraction efficiency such as pH, sample volume, amount of sorbent, type and volume of eluent, and number of draw/eject cycles for extraction and elusion were tested and optimized. Results showed that best extraction efficiency could be obtained at pH 3, 150 ‎µL of sample volume, 3 mg of adsorbent and 10 ‎µL of methanol as elution solvent. Numbers of draw/eject cycles for both sample extraction and elution were 7 cycles. Limit of detection and limit of quantification of this method were 0.07 and 0.3 µg L-1, respectively, with linear dynamic range of 0.3 to 300 µg L-1 for BPA. This method was applied successfully for determination of BPA in five spiked juices and drinking water samples.               KEY WORDS: Cobalt metal organic framework, Bisphenol A, Pipette-tip solid phase extraction, Juice analysis Bull. Chem. Soc. Ethiop. 2018, 32(3), 595-602.DOI: https://dx.doi.org/10.4314/bcse.v32i3.1

The elusiveness of old neutron stars

Old neutron stars (ONSs) which have radiated away their internal and rotational energy may still shine if accreting the interstellar medium. Despite their large number, only two promising candidates have been detected so far and rather stringent limits on their observability follow from the analysis of ROSAT surveys. This contrasts with optimistic theoretical estimates that predicted a large number of sources in ROSAT fields. We have reconsidered the issue of ONSs observability, accounting for the spin and magnetic field evolution over the neutron star lifetime. In the framework of a spin-induced field decay model, we show that the total number of ONSs which are, at present, in the accretion stage is reduced by a factor ~5 over previous figures if the characteristic timescale for crustal current dissipation is ~ 10^8 - 10^9 yr. This brings theoretical predictions much closer to observational limits. Most ONSs should be at present in the propeller phase and, if subject to episodic flaring, they could be observable.Comment: 10 pages Latex, 5 ps figures. To be formatted with the AASTeX package. Accepted for publication in Ap

Bragg solitons in nonlinear PT-symmetric periodic potentials

It is shown that slow Bragg soliton solutions are possible in nonlinear complex parity-time (PT) symmetric periodic structures. Analysis indicates that the PT-symmetric component of the periodic optical refractive index can modify the grating band structure and hence the effective coupling between the forward and backward waves. Starting from a classical modified massive Thirring model, solitary wave solutions are obtained in closed form. The basic properties of these slow solitary waves and their dependence on their respective PT-symmetric gain/loss profile are then explored via numerical simulations.Comment: 6 pages, 4 figures, published in Physical Review

Petrography, geochemistry and tectonic significance of the Mahoor granitoids (Lut Block, Eastern Iran)

The Mahoor granitoids are Cu–Zn-bearing porphyries that outcrop in the central part of the Lut Block, about 135 km south-west of Nehbandan (eastern Iran). These granitoids occur mainly as dykes and stocks that intrude Eocene volcanics. Petrographically, all the studied intrusives display porphyritic textures with mm-sized phenocrysts, most commonly of plagioclase and hornblende, embedded in a fine-grained groundmass with variable amounts of plagioclase, hornblende, clinopyroxene, quartz and opaques. Hydrothermal alteration affected these granitoids, as revealed by the common occurrence of sericite, chlorite, sphene/leucoxene, epidote and calcite. Chemical classification criteria show that the intrusives may be named as gabbrodiorites, diorites, monzodiorites and tonalites. Major element geochemistry reveals that all the studied lithologies are typically metaluminous (A/CNK ≤ 0.94) and, in addition, suggest, that they constitute a suite belonging to the high-K calc-alkaline series. Magnetic susceptibility (1485 × 10-5 SI) together with mineralogical and geochemical features show that they belong to magnetite granitoid series (I-type). In primitive mantle-normalized trace element spiderdiagrams, the analysed samples display strong enrichment in LILE compared to HFSE (15.5 ≤ RbN/YN ≤ 45.9), accompanied by negative anomalies of Nb, Ta and Ti. REE chondrite-normalized plots show slight to moderate LREE enrichment (4.9 ≤ LaN/LuN ≤ 8.4) and negative Eu anomalies (Eu/Eu* ratios vary from 0.65 to 0.88). Tectonic characteristics also indicate that the study area is emplaced in a volcanic arc setting. The whole set of geochemical data suggest that the Mahoor granitoids are co-genetic, belong to the calc-alkaline series and have been originated in an active continental margin setting. Sulfide mineralizations (pyrite, chalcopyrite and sphalerite) related to these granitoids are common and occur both disseminated and as hydrothermal veins, indicating a high mineralization potential for this area

Analysing the perceptions of pedestrians and drivers to shared space

Shared space is an approach to improving streets and places where both pedestrians and vehicles are present, with layouts related more to the pedestrian scale and with features encouraging drivers to assume priority having been reduced or removed. It creates a more pedestrian-friendly environment than conventional street layouts, which are based on greater segregation between pedestrians and vehicles, while at the same time introducing uncertainty, which makes drivers engage more fully with their surroundings, leading to lower vehicle speeds and improved safety. This paper investigates the importance of certain person-, context- and design-specific factors affecting the perceptions of pedestrians and drivers to shared space. Using two web-based stated-preference surveys, two sets of responses are collected from pedestrians and drivers, who are presented with different combinations of binary factors forming scenarios. Regression analysis is carried out with logit models for each survey. The results suggest that pedestrians feel most comfortable in shared space under conditions which ensure their presence is clear to other road users – these conditions include low vehicular traffic, high pedestrian traffic, good lighting and pedestrian-only facilities. Conversely, the presence of many pedestrians and, in particular, children and elderly, makes drivers feel uneasy and, therefore, enhances their alertness