Seismology of the Sun : Inference of Thermal, Dynamic and Magnetic Field Structures of the Interior

Recent overwhelming evidences show that the sun strongly influences the Earth's climate and environment. Moreover existence of life on this Earth mainly depends upon the sun's energy. Hence, understanding of physics of the sun, especially the thermal, dynamic and magnetic field structures of its interior, is very important. Recently, from the ground and space based observations, it is discovered that sun oscillates near 5 min periodicity in millions of modes. This discovery heralded a new era in solar physics and a separate branch called helioseismology or seismology of the sun has started. Before the advent of helioseismology, sun's thermal structure of the interior was understood from the evolutionary solution of stellar structure equations that mimicked the present age, mass and radius of the sun. Whereas solution of MHD equations yielded internal dynamics and magnetic field structure of the sun's interior. In this presentation, I review the thermal, dynamic and magnetic field structures of the sun's interior as inferred by the helioseismology.Comment: To be published in the proceedings of the meeting "3rd International Conference on Current Developments in Atomic, Molecular, Optical and Nano Physics with Applications", December 14-16, 2011, New Delhi, Indi

Star Formation and Dynamics in the Galactic Centre

The centre of our Galaxy is one of the most studied and yet enigmatic places in the Universe. At a distance of about 8 kpc from our Sun, the Galactic centre (GC) is the ideal environment to study the extreme processes that take place in the vicinity of a supermassive black hole (SMBH). Despite the hostile environment, several tens of early-type stars populate the central parsec of our Galaxy. A fraction of them lie in a thin ring with mild eccentricity and inner radius ~0.04 pc, while the S-stars, i.e. the ~30 stars closest to the SMBH (<0.04 pc), have randomly oriented and highly eccentric orbits. The formation of such early-type stars has been a puzzle for a long time: molecular clouds should be tidally disrupted by the SMBH before they can fragment into stars. We review the main scenarios proposed to explain the formation and the dynamical evolution of the early-type stars in the GC. In particular, we discuss the most popular in situ scenarios (accretion disc fragmentation and molecular cloud disruption) and migration scenarios (star cluster inspiral and Hills mechanism). We focus on the most pressing challenges that must be faced to shed light on the process of star formation in the vicinity of a SMBH.Comment: 68 pages, 35 figures; invited review chapter, to be published in expanded form in Haardt, F., Gorini, V., Moschella, U. and Treves, A., 'Astrophysical Black Holes'. Lecture Notes in Physics. Springer 201

THE RATE OF BINARY BLACK HOLE MERGERS INFERRED FROM ADVANCED LIGO OBSERVATIONS SURROUNDING GW150914

A transient gravitational-wave signal, GW150914, was identi fi ed in the twin Advanced LIGO detectors on 2015 September 2015 at 09:50:45 UTC. To asse ss the implications of this discovery, the detectors remained in operation with unchanged con fi gurations over a period of 39 days around the time of t he signal. At the detection statistic threshold corresponding to that observed for GW150914, our search of the 16 days of simultaneous two-detector observational data is estimated to have a false-alarm rate ( FAR ) of < ́ -- 4.9 10 yr 61 , yielding a p -value for GW150914 of < ́ - 210 7 . Parameter estimation follo w-up on this trigger identi fi es its source as a binary black hole ( BBH ) merger with component masses ( )( ) = - + - + mm M ,36,29 12 4 5 4 4 at redshift = - + z 0.09 0.04 0.03 ( median and 90% credible range ) . Here, we report on the constraints these observations place on the rate of BBH coalescences. Considering only GW150914, assuming that all BBHs in the universe have the same masses and spins as this event, imposing a search FAR threshold of 1 per 100 years, and assuming that the BBH merger rate is constant in the comoving frame, we infer a 90% credible range of merger rates between – -- 2 53 Gpc yr 31 ( comoving frame ) . Incorporating all search triggers that pass a much lower threshold while accounting for the uncerta inty in the astrophysical origin of each trigger, we estimate a higher rate, ranging from – -- 13 600 Gpc yr 31 depending on assumptions about the BBH mass distribution. All together, our various rate estimat es fall in the conservative range – -- 2 600 Gpc yr 31

Repositioning of the global epicentre of non-optimal cholesterol

High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol�which is a marker of cardiovascular risk�changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95 credible interval 3.7 million�4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world. © 2020, The Author(s), under exclusive licence to Springer Nature Limited

Doppler flow velocity waveform analysis in high risk pregnancies: A randomized controlled trial

Objective— To test whether the introduction of Doppler waveform analysis into the ultrasound department of a tertiary level hospital reduces neonatal morbidity and improves obstetric management. Design— A randomized controlled trial. Setting— Department of Ultrasound, King Edward Memorial Hospital, Perth, Western Australia. Subjects— 505 women with pregnancy abnormalities referred to an ultrasound department for fetal investigation during the third trimester. Intervention— Continuous wave Doppler studies of umbilical and utero-placental arterial circulations. Results were revealed to patients and clinicians. Main outcome measures— Principal end point was the duration of neonatal stay in hospital; other end points included the number and type of fetal heart rate monitoring studies, obstetric interventions, frequency of fetal distress, birthweight, Apgar scores and need for neonatal intensive care. Results— There was no effect on the duration of neonatal stay in hospital. Small trends in obstetric management were observed with study group patients having fewer contraction stress tests, less likelihood of antepartum fetal distress, and more likelihood of fetal distress after induction of labour leading to emergency cacsarean section. Depressed Apgar scores were more frequent in the study group. Conclusion— Introduction of Doppler waveform studies did not result in reduced neonatal morbidity but did have a small effect on obstetric management. For each institution the role of Doppler studies in late pregnancy will be influenced by the usage of other tests of fetal welfare already entrenched in clinical practice

Changes in temporal and spatial associations between pairs of cattle during the process of familiarisation

Mixing unfamiliar individuals is a common practice in livestock production systems. However, a change in social structure can create social stresses, which can adversely affect animal welfare and reduce production. In this study, social interaction metrics were used to investigate interaction and behavioural differences between familiar and unfamiliar pairs. These differences were used to characterise features of the familiarisation process between pairs of unfamiliar steers. Proximity loggers quantified the frequency and duration of close proximity encounters between animals while visual observations evaluated the distance and movement between individuals within pairs and described their behaviour. Fifteen pairs of familiar steers and 15 pairs of unfamiliar steers were observed over 5 weeks. Each pair was monitored for 5 days in a 3 ha paddock with contact between adjacent pairs prevented by a 20 m buffer zone. Unfamiliar pairs initially maintained further distance apart than familiar pairs, but after 3 days their distances were similar to familiar pairs. Unfamiliar pairs had increased (P < 0.05) movement towards and away from each other while familiar pairs tended to spend more (P < 0.10) time lying and standing and less (P < 0.05) time grazing than unfamiliar pairs. The results confirm that familiarity affects proximity between pairs of steers and that differences in behaviour and movement patterns between familiar and unfamiliar pairs emphasise the disruptive effect of introducing new individuals. The decrease in proximity between unfamiliar pairs over time suggests familiarisation between pairs begins early (after 3 days). However, overall familiar pairs had more close proximity encounters per hour than unfamiliar pairs (3.8 and 2.3 contacts/h, respectively. P < 0.01) and showed a tendency to spend more time lying and standing than unfamiliar pairs: these differences were constant over the 5-day period indicating that complete familiarisation had not occurred within 5 days. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved