To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Multi-wavelength flares have routinely been observed from the supermassive black hole, Sagittarius A⋆ (Sgr A⋆), at our Galactic center. The nature of these flares remains largely unclear, despite many theoretical models. We study the statistical properties of the Sgr A⋆ X-ray flares and find that they are consistent with the theoretical prediction of the self-organized criticality system with the spatial dimension S = 3. We suggest that the X-ray flares represent plasmoid ejections driven by magnetic reconnection (similar to solar flares) in the accretion flow onto the black hole. Motivated by the statistical results, we further develop a time-dependent magnetohydrodynamic (MHD) model for the multi-band flares from Sgr A⋆ by analogy with models of solar flares/coronal mass ejections (CMEs). We calculate the X-ray, infrared flare light curves, and the spectra, and find that our model can explain the main features of the flares.
The authors investigated the effects of annealing in Ar atmosphere at different temperatures (350–1100 °C) on the densification and leakage current characteristics of thermally oxidized SiO2 films on n-type 4H-SiC. A strong correlation between densification improvement and leakage current reduction was observed. Densification of the SiO2 films, which were characterized by spectroscopic ellipsometry, Fouriertransform infrared spectroscopy and atomic force microscopy, can be significantly improved after annealing at moderate temperature (600 °C). The leakage current is decreased by two orders of magnitude of the SiO2 thin film after annealing at 600 °C. Based on the studies, SiO2 film of the highest quality can be obtained after annealing at 600 °C. Improvements in the quality of the SiO2 thin films after annealing at 600 °C may be explained by the consumption and formation of carbon-related and oxygen-related defects during annealing.
While many recent advances have been made in the breeding of giant pandas ex situ, historically this species has never reproduced well in captivity. Sexual incompatibility, health problems, low fecundity and a juvenile mortality rate in excess of 70% have contributed to low reproductive success (O'Brien & Knight, 1987; O'Brien et al., 1994; Peng et al., 2001a, b). Wild- and captive-born giant pandas, particularly those captured at a young age, traditionally had difficulty producing offspring in captivity upon becoming adults (Lu & Kemf, 2001). As a result, the ex-situ giant panda population has not been self-sustaining and, until recently, its growth has relied on introducing animals captured from nature. In some cases, this included individuals that appeared ill (rescues) or cubs that were believed to be neglected or abandoned by their mothers. Later field studies, however, revealed that females often leave cubs alone for four to eight hours while foraging, and in one documented case for 52 hours (Lu et al., 1994). Recently, China has placed a general moratorium on capturing wild giant pandas for captive breeding (Lu & Kemf, 2001), a move that forces the breeding community to develop a self-sustaining population.
The goal, however, is not only ensuring demographic self-sustainability but also the maintenance of genetic diversity. The deleterious effects of inbreeding are well recognised (O'Brien, 1994a; Frankham, 1995; Hedrick & Kalinowski, 2001; Frankham et al., 2002).
The distribution of genetic diversity between Oryza sativa L. ssp. indica and O. sativa L. ssp. japonica covering different ecological zones in Yunnan was studied, and specific markers of indica/japonica subspecies, paddy/upland rice and different ecological zones were screened, using 36 microsatellite primers and 113 accessions in the Yunnan landrace rice core collection. The genetic diversity of japonica was higher than that of indica, and the ecological zone with the highest and smallest genetic diversity lay in south-east and north-east Yunnan, respectively. This distribution was consistent at morphological and isozyme levels with studies on the entire Yunnan rice resources and core collection. In addition, the results showed that, among 416 markers, there were six indica/japonica-specific markers, 15 specific markers for paddy/upland rice and three specific markers in different ecological zones. The main conclusions are that the landrace rice core collection in Yunnan genetically represents the entire landrace rice resources in Yunnan, the centre of genetic diversity at DNA level lies in south-east Yunnan, and the DNA differentiation between indica and japonica is small. Furthermore, microsatellite markers were useful for studying the genetic diversity, classification and ecotype of germplasm resources and their core collection.
Chemical bath deposition (CBD) techniques for the growth of CdS polycrystalline thin films are now well developed. However, there usually appear different structures, grain sizes and energy gaps in CdS polycrystalline films by CBD, which implies that the influence of growth process on the structures and properties of CBD CdS thin films must be considered. In this paper, the optical, compositional and structural properties of CBD CdS thin films in the reaction process have been studied by XRD, AFM, XPS and optical transmission spectra measurements. The results can be explained using atomic mechanism and lattice transition in the CdS thin films.
Email your librarian or administrator to recommend adding this to your organisation's collection.