The Early X-ray Afterglows of Optically Bright and Dark Gamma-Ray Bursts

A systematic study on the early X-ray afterglows of both optically bright and dark gamma-ray bursts （B-GRBs and D-GRBs） observed by Swift is presented. Our sample includes 25 GRBs of which 13 are B-GRBs and 12 are D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes （Fx）, the gamma-ray fluxes （Sγ）, and the ratio （Rγ,x） are similar for the two kinds of GRBs, that any observed differences should be simply statistical fluctuation. These results indicate that the progenitors of the two kinds of GRBs are of the same population with comparable total energies of explosion. The suppression of optical emission in the D-GRBs should result from circumburst but not from their central engine.

A literature review of research exploring the experiences of overseas nurses in the United Kingdom[2002-2017]

Objectives: The goals of this work were to critically explore the challenges faced by overseas nurses during their working careers in the UK, to critically explore the available support for overseas nurses, and to make recommendations on how to minimize the effects of these challenges, as well as how to provide more support for overseas nurses during their working careers in the UK.Methods: A systematic and comprehensive literature review was conducted to explore the said objectives. A search was conducted in the Cumulative Index to Nursing and Allied Health Literature(CINAHL), Scopus, and Academic Search Complete databases for relevant research. Inclusion and exclusion criteria were used to select the included articles. A total of 8 studies including 6 qualitative studies,1 quantitative study, and 1 mixed-method study were selected for literature review. The validity and reliability of these 8 studies were analyzed by using 2 appraisal tools.Results: This review reveals 4 challenges, which overseas nurses experience in the past 15 years, including cultural differences,communication issues, unequal opportunities, and de-skilling. These challenges have a negative impact on overseas nurses' emotions and career development. The formal and informal supports are revealed in this review. Various supports can help overseas nurses to work better.Conclusions: This review reveals 4 challenges faced by overseas nurses, including cultural differences, communication issues,and unequal opportunities and de-skilling. These challenges naturally have a profound negative impact on the emotions and career development of overseas nurses. Additionally, the formal and informal support systems available to these nurses are reviewed. Various support systems can help overseas nurses work more effectively.

Comparison between Swift and pre-Swift gamma-ray bursts

The gamma-ray burst （GRB） mission Swift has made a much deeper GRB survey than any previous one. I present a systematical comparison between GRB samples detected with pre-Swift missions and those from Swift, in order to investigate whether they show any statistical difference. Our Swift GRB sample includes the bursts detected by Swift/BAT before 2007 September. With both flux-limited surveys and redshift-known GRB samples, I show that, apparently, the observed distributions of the redshifts, T90, and log N- log P are significantly different, but not for the spectral hardness ratio, fluence and Eiso. The redshifts of the Swift GRB sample are statistically larger than those of pre-Swift GRBs, with a mean of 1.95±0.17 compared to ～ 1 for pre-Swift GRBs. The cosmological effect on the observables is thus considerable. This effect on the spectral hardness ratio, fluence and Eiso is cancelled out, and the distributions of these quantities indeed do not show significant differences between the Swift and pre-Sw/ft GRBs. Taking this effect into account, I found that the corrected distributions of T90 for long GRBs and log N - log P observed with Swift/BAT are also consistent with those observed with CGRO/BATSE. These results indicate that the Swift and pre-Swift GRBs are from the same population.

Swift/BAT Observations of X-Ray Flashes

An analysis of prompt gamma-rays of X-ray flashes （XRFs） observed with the Swift/BAT has been presented. Our sample includes 235 bursts. It is found that the BAT detection ratio of XRFs to typical Gamma-ray bursts （GRBs） is 42：193, for division at Г= 2 （roughly corresponding Ep ～ 50 keV）, Г being the power law index of the BAT spectrum and Ep, the peak energy （Ep） of the vfv, spectrum. This is consistent with the HETE-2 observations. For both XRFs and GRBs F are almost normally distributed in the range of 1 to 2.8, similar that observed with HETE-2. The distribution of F for the entire set of GRBs/XRFs is not available due to poor statistics on the peak at Г 〉 2.3. This result probably indicates that the BAT spectrum of a typical XRF could have a Г of roughly 2.3, if they indeed are a distinct soft component of the GRB population. By comparing the fluence and the peak flux in different energy bands, it is found that the XRFs are ordinarily softer than the GRBs, but during the peak time the spectra of both GRBs and XRF are similar, showing that the dominant radiation mechanisms of both GRBs and XRFs are similar.

On the Existence and Uniqueness of Solutions to Stochastic Differential Equations Driven by G-Brownian Motion with Integral-Lipschitz Coefficients

In this paper, we study the existence and uniqueness of solutions to stochastic differential equations driven by G-Brownian motion （GSDEs） with integral-Lipschitz coefficients.