61,566 research outputs found
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Small scale energy release driven by supergranular flows on the quiet Sun
No full textIn this article we present data and modelling for the quiet Sun that strongly suggest a ubiquitous small-scale atmospheric heating mechanism that is driven solely by converging supergranular flows.
A possible energy source for such events is the power transfer to the plasma via the work done on the magnetic field by photospheric convective flows, which exert drag of the footpoints of magnetic structures. In this paper we present evidence of small scale energy release events driven directly by the hydrodynamic forces that act on the magnetic elements in the photosphere, as a result of supergranular scale flows. We show strong spatial and temporal correlation between quiet Sun soft X-ray emission (from <i>Yohkoh</i> and <i>SOHO</i> MDI-derived flux removal events driven by deduced photospheric flows.
We also present a simple model of heating generated by flux submergence, based on particle acceleration by converging magnetic mirrors.
In the near future, high resolution soft X-ray images from XRT on the <i>Hinode</i> satellite will allow definitive, quantitative verification of our results
Latest results on Jovian disk X-rays from XMM-Newton
No full textWe present the results of a spectral study of the soft X-ray emission (0.2–2.5 keV) from low-latitude (‘disk’) regions of Jupiter. The data were obtained during two observing campaigns with XMM-Newton in April and November 2003. While the level of the emission remained approximately the same between April and the first half of the November observation, the second part of the latter shows an enhancement by about 40% in the 0.2–2.5 keV flux. A very similar, and apparently correlated increase, in time and scale, was observed in the solar X-ray and EUV flux.
The months of October and November 2003 saw a period of particularly intense solar activity, which appears reflected in the behavior of the soft X-rays from Jupiter's disk. The X-ray spectra, from the XMM-Newton EPIC CCD cameras, are all well fitted by a coronal model with temperatures in the range 0.4–0.5 keV, with additional line emission from Mg XI (1.35 keV) and Si XIII (1.86 keV): these are characteristic lines of solar X-ray spectra at maximum activity and during flares.
The XMM-Newton observations lend further support to the theory that Jupiter's disk X-ray emission is controlled by the Sun, and may be produced in large part by scattering, elastic and fluorescent, of solar X-rays in the upper atmosphere of the planet
SunSmart? Skin cancer knowledge and preventive behaviour in a British population representative sample
No full textThe incidence of skin cancer has risen rapidly in the UK over the last 20 years, prompting public health organizations to try and raise awareness of the dangers of sun exposure and the need to practice sun-safe behaviour. This study aimed to assess baseline levels of sun-safe knowledge and behaviour in a British population-representative sample, prior to the launch of Cancer Research UK's 'SunSmart' campaign. A face-to-face survey was conducted through the Office for National Statistics as part of their Omnibus survey. In total, 1848 men and women aged 18 and over were interviewed. Knowledge of what to do to reduce skin cancer risk was modest. Two-thirds mentioned avoiding the sun by seeking shade, 50% mentioned covering up and only 43% said to use high factor sunscreen. Practice of sun-safe behaviours was also poor, with only one-third saying they sought shade, covered up or used high factor sunscreen to protect themselves from the sun. Men and those from lower socioeconomic groups were least informed and least likely to report using sun-protective behaviours. Increases in both knowledge and use of appropriate sun-protective behaviours are needed if skin cancer incidence rates are to decrease
Serum levels of Adrenocorticotropic hormone and thyroid stimulating hormone are associated with suicidal thoughts in patients with major depressive disorder
No full textBackground: Patients with major depressive disorder (MDD) have a substantially higher prevalence of suicidal thoughts than is seen in non-depressed individuals in the general population. Potential biological correlates of suicidal thoughts in first-episode MDD are relatively under-investigated. We examined suicidal thoughts and their associations with clinical features and endocrine measures in patients with first-episode, drug-naïve (FEDN) MDD using a cross-sectional design. Method: 91 FEDN patients meeting DSM-IV diagnosis of MDD were recruited. Depressive and anxiety symptoms, suicidal thoughts and other aspects of psychopathology were assessed by the Hamilton Depression Rating Scale (HAMD), HamiltonAnxiety Rating Scale (HAMA), and Brief Psychiatric Rating Scale (BPRS). Sociodemographic characteristics(including age, sex, marriage, education, working status), life experiences (Life Event Scale, LES) and clinical features were recorded systematically. Serum levels of cortisol, adrenocorticotropic hormone(ACTH), stimulating thyroid hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) were measured. Results: There were 52 patients with suicidal thoughts and 39 without. Serum levels of ACTH and HAMD scores (t=-2.80, p=0.006 and t=-2.14, p=0.04, respectively) differed significantly between groups with and without suicidal thoughts, whereas there were no between-group differences in cortisol, TSH,FT4, or FT3 levels. After controlling for potential demographic and clinical variables, logistic regression analysis indicated that ACTH levels were positively associated with suicidal thoughts (OR=1.047, 95% CI:1.017~1.077, p=0.002), whereas TSH levels were negatively associated with suicidal thoughts (OR=0.557,95% CI: 0.365~0.849, p=0.006). Conclusion: Our study indicates high serum ACTH and low TSH levels were associated with suicidal thoughts in patients with first-episode drug-naïve MDD. Further research using a prospective study design is warranted to examine how these associations might change over time
Measurements of K S 0 - K L 0 asymmetries in the decays Λ c + → p K L , S 0 , p K L , S 0 π + π − and p K L , S 0 π 0
No full textAbstract Using e + e − annihilation data sets corresponding to an integrated luminosity of 4.5 fb −1, collected with the BESIII detector at center-of-mass energies between 4.600 and 4.699 GeV, we report the first measurements of the absolute branching fractions B Λ c + → p K L 0 = (1.67 ± 0.06 ± 0.04)%, B Λ c + → p K L 0 π + π − = (1.69 ± 0.10 ± 0.05)%, and B Λ c + → p K L 0 π 0 = (2.02 ± 0.13 ± 0.05)%, where the first uncertainties are statistical and the second systematic. Combining with the known branching fractions of Λ c + → p K S 0 , Λ c + → p K S 0 π + π − , and Λ c + → p K S 0 π 0 , we present the first measurements of the K S 0 - K L 0 asymmetries R Λ c + K S , L 0 X = B Λ c + → K S 0 X − B Λ c + → K L 0 X B Λ c + → K S 0 X + B Λ c + → K L 0 X in charmed baryon decays: R Λ c + p K S , L 0 = − 0.025 ± 0.031 , R Λ c + p K S , L 0 π + π − = − 0.027 ± 0.048 and R Λ c + p K S , L 0 π 0 = − 0.015 ± 0.046 . No significant asymmetries with statistical significance are observed
Relations between x-ray timing features and spectral parameters of galactic black hole x-ray binaries
No full textWe present a study of correlations between spectral and timing parameters for a sample of black hole X-ray binary candidates. Data are taken from GX
339-4, H 1743-322, and XTE J1650-500, as the Rossi X-ray Timing Explorer
(RXTE) observed complete outbursts of these sources. In our study we investigate outbursts that happened before the end of 2009 to make use of the high-energy coverage of the HEXTE detector and select observations that
show a certain type of quasi-periodic oscillations (type-C QPOs). The spectral parameters are derived using the empirical convolution model simpl to model the Comptonized component of the emission together with a disc blackbody for the emission of the accretion disc. Additional spectral features, namely a reflection component, a high-energy cut-off, and excess emission at 6.4 keV, are taken into account. Our investigations confirm the known positive
correlation between photon index and centroid frequency of the QPOs and reveal an anti-correlation between the fraction of up-scattered photons and the QPO frequency. We show that both correlations behave as expected in the “sombrero”
geometry. Furthermore, we find that during outburst decay the correlation between photon index and QPO frequency follow a general track, independent of individual outbursts
Synthesis and characterization of compounds with the Al-O-X (X = Si, P, C) structural motif
No full textThe reactions of LAlH2 (L = HC(CMeNAr)(2), Ar = 2,6-iPr(2)C(6)H(3)) (1) with diphenylsilanediol, phenylphosphonic acid, diphenylphosphinic acid, and pyrocatechol afford compounds with the Al-O-X (X = Si, P, C) motif of composition [LAl(mu-O)](2)Si(Ph)(2) (2), [LAl(mu-O)](2)PO(Ph) (3), LAl[OPO(Ph)(2)](2) (4), and LAl(mu-O)(2)(o-C6H4) (5), respectively. Compound 2 contains the Al-O-Si-O-Al heterotrimetallic dioxide chain. Compound 3 features an Al(mu-O)](2)P four-membered ring, while compound 4 exhibits a P-O-Al-O-P chain structure. Compound 5 contains the benzo-aluminum-dioxide organic-inorganic hybrid five-membered ring. Complexes 2, 3, 4, and 5 were characterized by NMR, elementary analysis, and single-crystal X-ray diffraction
Are Chinese loess deposits essentially continuous?
No full textWe conducted a paleomagnetic examination of the last glacial loess of three representative profiles along an east-west transect in the central Loess Plateau in order to assess the continuity of Chinese loess. The results show that the Xifeng and Luochuan profiles record the Laschamp geomagnetic excursion but with different morphologies. Together with the published results from Weinan, southern plateau, our results suggest that sedimentation of the last glacial loess in the central-southern plateau was continuous at the time scale equivalent to the duration of the Laschamp excursion (~2 kyr), but probably episodic at finer time scales (<2 kyr). No geomagnetic excursion was found at the Yichuan profile near the Yellow River valley, where loess accumulation may be strongly affected by local environmental changes and thus may have been discontinuous. Both site location and time scale therefore need to be considered when considering continuity of Chinese loess.<br/
A grounded theory of female adolescent behaviour in the sun: comfort matters.
No full textThe aim of the research was to generate a grounded theory to explain the behaviour of young women in the sun. The study sought to explore the sun-related experiences of
young women in order to gain new insights into the influences upon them. The study was qualitative by design and utilised grounded theory method as developed by Glaser.
Twenty female participants, aged 14 to 17 years old were included in the study. They formed six groups. Thirteen interviews were carried out with the groups and six one-to one interviews took place with individuals. All interviews were semi-structured and were based upon the participants' experiences of being in the sun. Data was analysed using the
constant comparative method of data analysis, concordant with Glaserian grounded theory method. Five explanatory categories emerged from the data; Fitting In, Being Myself,
Being Physically Comfortable, Slipping Up and a core category of Being Comfortable. One of the issues that emerged was that some young women believed their social
acceptance depended on their appearance and they conformed to this end. The theory, derived from the categories, proposes that when in the sun, young women direct their
activities toward meeting physical and psychosocial comfort needs. Comfort matters to them because it has implications for their wellbeing. This thesis contributes to the literature about the behaviours of young women in the sun.
By increasing understanding of the factors that influence them, it also adds to the body of knowledge related to the primary prevention of skin cancer with teenage girls in the United Kingdom. The outcome of the research and its contribution to knowledge is a grounded theory, which explains the basis of the behaviours of young women in the sun. It appears that no other study has explored the experiences of UK adolescent females specifically, in
a qualitative way and with the intention of producing a theory to explain them
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