Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar

The relativistic plasma flows onto neutron stars that are accreting material from stellar companions can be used to probe strong-field gravity as well as the physical conditions in the supranuclear-density interiors of neutron stars. Plasma inhomogeneities orbiting a few kilometres above the stars are observable as X-ray brightness fluctuations on the millisecond dynamical timescale of the flows. Two frequencies in the kilohertz range dominate these fluctuations: the twin kilohertz quasi-periodic oscillations (kHz QPOs). Competing models for the origins of these oscillations (based on orbital motions) all predict that they should be related to the stellar spin frequency, but tests have been difficult because the spins were not unambiguously known. Here we report the detection of kHz QPOs from a pulsar whose spin frequency is known. Our measurements establish a clear link between kHz QPOs and stellar spin, but one not predicted by any current model. A new approach to understanding kHz QPOs is now required. We suggest that a resonance between the spin and general relativistic orbital and epicyclic frequencies could provide the observed relation between QPOs and spin.Comment: Published in the 2003 July 3 issue of Natur

Effectiveness of mindful walking intervention on nature on sleep quality and mood among university student during Covid-19:A randomised control study

OBJECTIVE: The aim of this project was to conduct a randomised control study to examine whether outdoor mindful walking in nature can effectively improve university students’ sleep quality, mood, and mindfulness during the Covid-19 pandemic in the U.K. METHODS: Participants were measured at T(0) (pre-study baseline), T(1) (pre-intervention), T(2) (post-intervention), and T(3) (follow-up). A total of 104 participants (female = 94) who were experiencing sleep difficulties were randomly allocated to either an experimental (i.e., nature) or control (i.e., urban) walking environment. Participants in each walking condition independently undertook a daily 35-minute walk for a week (7 days). Subjective sleep quality, total mood disturbance, mindfulness, and degree of nature connectedness, and participants’ perspectives on the intervention, were collected. RESULTS: Findings suggest that both groups resulted in significant improvements in participants' trait mindfulness, sleep quality and mood after the intervention. However, mindful walking in nature did not bring additional mental health benefits to participants relative to those who walked an urban environment. Participants provided their perspectives about the intervention, which will assist with future intervention development. CONCLUSIONS: Findings contribute to the evidence-base on the effectiveness of outdoor mindful walking interventions for enhancing mental health. These findings contribute new knowledge on how mindful walking outdoors reduces university students’ mood disturbances and improves sleep quality and mindfulness level

Finite size scaling analysis of intermittency moments in the two dimensional Ising model

Finite size scaling is shown to work very well for the block variables used in intermittency studies on a 2-d Ising lattice. The intermittency exponents so derived exhibit the expected relations to the magnetic critical exponent of the model. Email contact: [email protected]: Saclay-T93/063 Email: [email protected]

Swings between rotation and accretion power in a millisecond binary pulsar

It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales.Comment: 43 pages, 9 figures, 4 table. Published by Nature on 26 Sep 2013. Includes Supplementary information. Minor differences with published version may exis

Replication of LDL SWAs hits in PROSPER/PHASE as validation for future (pharmaco)genetic analyses

<p><b>Background:</b> The PHArmacogenetic study of Statins in the Elderly at risk (PHASE) is a genome wide association study in the PROspective Study of Pravastatin in the Elderly at risk for vascular disease (PROSPER) that investigates the genetic variation responsible for the individual variation in drug response to pravastatin. Statins lower LDL-cholesterol in general by 30%, however not in all subjects. Moreover, clinical response is highly variable and adverse effects occur in a minority of patients. In this report we first describe the rationale of the PROSPER/PHASE project and second show that the PROSPER/PHASE study can be used to study pharmacogenetics in the elderly.</p> <p><b>Methods:</b> The genome wide association study (GWAS) was conducted using the Illumina 660K-Quad beadchips following manufacturer's instructions. After a stringent quality control 557,192 SNPs in 5,244 subjects were available for analysis. To maximize the availability of genetic data and coverage of the genome, imputation up to 2.5 million autosomal CEPH HapMap SNPs was performed with MACH imputation software. The GWAS for LDL-cholesterol is assessed with an additive linear regression model in PROBABEL software, adjusted for age, sex, and country of origin to account for population stratification.</p> <p><b>Results:</b> Forty-two SNPs reached the GWAS significant threshold of p = 5.0e-08 in 5 genomic loci (APOE/APOC1; LDLR; FADS2/FEN1; HMGCR; PSRC1/CELSR5). The top SNP (rs445925, chromosome 19) with a p-value of p = 2.8e-30 is located within the APOC1 gene and near the APOE gene. The second top SNP (rs6511720, chromosome 19) with a p-value of p = 5.22e-15 is located within the LDLR gene. All 5 genomic loci were previously associated with LDL-cholesterol levels, no novel loci were identified. Replication in WOSCOPS and CARE confirmed our results.</p> <p><b>Conclusion:</b> With the GWAS in the PROSPER/PHASE study we confirm the previously found genetic associations with LDL-cholesterol levels. With this proof-of-principle study we show that the PROSPER/PHASE study can be used to investigate genetic associations in a similar way to population based studies. The next step of the PROSPER/PHASE study is to identify the genetic variation responsible for the variation in LDL-cholesterol lowering in response to statin treatment in collaboration with other large trials.</p&gt

Golden gravitational lensing systems from the Sloan Lens ACS Survey. II. SDSS J1430+4105: A precise inner total mass profile from lensing alone

We study the SLACS strong lensing system SDSSJ1430+4105 at z=0.285. The lensed source (z=0.575) of this system has a complex morphology with several subcomponents. Its subcomponents span a radial range from 4 to 10kpc in the lens plane. Therefore we can constrain the slope of the total projected mass profile around the Einstein radius (R_E) from lensing alone. We measure a density profile that is slightly but not significantly shallower than isothermal at R_E. We decompose the mass of the lensing galaxy into a de Vaucouleurs (deV) component to trace the stars and an additional dark component. The spread of multiple image components over a large radial range also allows us to determine the amplitude of the deV and dark matter components separately. We get a mass to light ratio of M_deV/L_B~5.5\pm1.5M/L_sun,B and a dark matter fraction within R_E of ~20 to 40%. Modelling the star formation history assuming composite stellar populations at solar metallicity to the galaxy's photometry yields a mass to light ratio of M_star,salp/L_B~4.0_{-1.3}^{+0.6}M/L_sun,B and M_star,chab/L_B~2.3_{-0.8}^{+0.3}M/L_sun,B for Salpeter and Chabrier IMFs, respectively. Hence, the mass to light ratio derived from lensing is more Salpeter-like, in agreement with results for massive Coma galaxies and other nearby massive early type galaxies. We examine the consequences of the galaxy group in which the lensing galaxy is embedded, showing that it has little influence on the mass to light ratio obtained for the deV component of the lensing galaxy. Finally, we decompose the projected, azimuthally averaged 2D density distribution of the deV and dark matter component of the lensing signal into spherically averaged 3D density profiles. We can show that the 3D dark and luminous matter density within R_E~0.6R_eff of this SLACS galaxy is similar to the values of Coma galaxies with the same velocity dispersions.Comment: 24 pages, 21 figures, 11 tables, accepted for publication by MNRA

長者學習研究計劃2011-2012 : 計劃介紹及教材冊

有見長者的學歷及學習能力日高，長者的需求亦有所不同，對長者需求的研究實是需要的。加上部份長者表示希望參與較高層次的學習活動及貢獻社會，故嶺南大學服務研習處舉辦長者學習研究計劃2011-2012，培訓長者成為研究人員，期望由長者的角度出發，為長者學習 的長遠發展作出研究及提出建議。 計劃目標： • 培養長者對學術研究的興趣； • 提供研究技巧培訓課程； • 分析學苑現有課程的成效； • 探討長者學習的政策及制定長遠發展方向； • 透過長幼參與研究計劃，增加兩代溝通，促進跨代共融。 本手冊收錄了有關計劃詳情以及課程教材。https://commons.ln.edu.hk/osl_book/1002/thumbnail.jp

Accreting Black Holes

This chapter provides a general overview of the theory and observations of black holes in the Universe and on their interpretation. We briefly review the black hole classes, accretion disk models, spectral state classification, the AGN classification, and the leading techniques for measuring black hole spins. We also introduce quasi-periodic oscillations, the shadow of black holes, and the observations and the theoretical models of jets.Comment: 41 pages, 18 figures. To appear in "Tutorial Guide to X-ray and Gamma-ray Astronomy: Data Reduction and Analysis" (Ed. C. Bambi, Springer Singapore, 2020). v3: fixed some typos and updated some parts. arXiv admin note: substantial text overlap with arXiv:1711.1025

Predicted interaction of human Ribosomal Protein S15 with Fragile X Mental Retardation Protein

In addition to the central role of ribosome biogenesis, the human ribosomal protein S15 (RPS15) has extra-ribosomal roles that include its association with a congenital disease and a few types of cancer. However, current knowledge of its functions in the context of extra-ribosomal activities remains fragmented. An approach to gain insights into the interaction between RPS15 and possible protein partners is via Bioinformatics strategies. Based on the sequence-to-structure-to-function paradigm, structural data of a protein can be computationally analysed to derive logical interacting partners. This method can include three-dimensional model construction, structural neighbour prediction, and molecular docking analysis. By using this approach, we have constructed RPS15 3D-structural models that have allowed the prediction of 23 structural neighbours. Of these, two that are from human origin were further analysed and only one have logical prospect of binary protein-protein interactions. Further analysis of this structural neighbour revealed 7 candidate docking partners. From these, our molecular docking analysis demonstrated two most logical dock models of interactions between RPS15 with two different domains of the Fragile X Mental Retardation Protein 1 (FMRP1) protein. Hence, we have provided in silico evidence of de novo protein-protein interaction between RPS15 and the Fragile X Mental Retardation Protein 1 (FMRP1)