ABSTRACT Filament eruptions often lead to coronal mass ejections (CMEs), which can affect critical technological systems in space and on the ground when they interact with the geo-magnetosphere at ...high speeds. Therefore, it is important to investigate the acceleration mechanisms of CMEs in solar/space physics. Based on observations and simulations, the resistive magnetic reconnection and the ideal instability of magnetic flux ropes have been proposed to accelerate CMEs. However, it remains uncertain whether both of them play a comparable role during a particular eruption. It has been extremely difficult to separate their contributions as they often work in a close time sequence during one fast acceleration phase. Here we report an intriguing filament eruption event, which shows two apparently separated fast acceleration phases and provides us an excellent opportunity to address the issue. Through analyzing the correlations between velocity (acceleration) and soft (hard) X-ray profiles, we suggest that the instability and magnetic reconnection make a major contribution during the first and second fast acceleration phases, respectively. Further, we find that both processes have a comparable contribution to the filament acceleration in this event.
In porous media subject to applied magnetic field, the internal field arises out of susceptibility contrast of the constituents. We have examined the spatial inhomogeneity of the internal fields in a ...random pack of spheres using numerical computation. We find that the pair-correlation function of the internal field (
K
2) is a close approximation to the structure factor of the material, thus
K
2 can be used to characterize pore geometry. The magnetic length scale
Λ
M exhibited in
K
2 is shown to be related to the fluid transport in the medium.
In this paper, the exponential periodicity and stability of neural networks with Lipschitz continuous activation functions are investigated, without assuming the boundedness of the activation ...functions and the differentiability of time-varying delays, as needed in most other papers. The neural networks contain reaction-diffusion terms and both variable and unbounded delays. Some sufficient conditions ensuring the existence and uniqueness of periodic solution and stability of neural networks with reaction-diffusion terms and both variable and unbounded delays are obtained by analytic methods and inequality technique. Furthermore, the exponential converging index is also estimated. The methods, which does not make use of Lyapunov functional, is simple and valid for the periodicity and stability analysis of neural networks with variable and/or unbounded delays. The results extend some previous results. Two examples are given to show the effectiveness of the obtained results.
In recent studies, we proposed that source properties of type II radio bursts can be inferred through a causal relationship between the special shape of the type II dynamic spectrum (e.g., bump or ...break) and simultaneous extreme ultraviolet (EUV)/white light imaging observations (e.g., CME-shock crossing streamer structures). As a further extension of these studies, in this paper we examine the coronal mass ejection (CME) event on 2007 December 31 associated with a multiple type II radio burst. We identify the presence of two spectral bump features on the observed dynamic spectrum. By combining observational analyses of the radio spectral observations and the EUV-white light imaging data, we conclude that the two spectral bumps result from a CME-shock propagating across dense streamers on the southern and northern sides of the CME. It is inferred that the corresponding two type II emissions originate separately from the two CME-shock flanks where the shock geometries are likely quasi-perpendicular or oblique. Since the emission lanes are bumped as a whole within a relatively short time, it suggests that the type II radio bursts with bumps of this study are emitted from spatially confined sources (with a projected lateral dimension smaller than 0.05-0.1 R sub(middot in circle) at a fundamental frequency level of 20-30 MHz).
A novel laminated Ti–TiBw/Ti composite containing Ti layers and TiBw/Ti composite layers were successfully fabricated by the reaction hot-pressing technique. The TiB whiskers and their network ...distribution structure play an effective role in microstructural evolution of the Ti matrix during the sintering and cooling processes. Interestingly, the morphology and size of grains in the laminated Ti–TiBw/Ti composites exhibit gradient distribution. The Ti layer comprises coarse lath-like grains while the TiBw/Ti composite layer contains two different sizes of equiaxed grains. A combination of high strength and ductility can be obtained by incorporating a low volume fraction of in-situ TiBw through the grain refinement mechanism and the laminated structure. The TiBw/Ti composite layer with high strain hardening rate delays localized necking of the Ti layer. The novel laminated structure of Ti–TiBw/Ti composite allocates stress and strain reasonably well and reveals a prolonged uniform plastic deformation capability.
The frequency dependence of the quasi-quantized energy release is reported for the first time in 14 bursts with pulsations of seconds at 1.0, 2.0, 3.75, 9.4, 17, and 35 GHz, observed by the Nobeyama ...Radio Polarimeters (NoRP). There is a linear correlation between the repetition rate of pulsations and the radio flux during the burst, the so-called
R
–
S
relation, at each burst frequency. The slope in the linear fitting, which is equivalent to the energy release in an individual pulse, becomes maximum at a particular frequency around 10 GHz, which can be explained by electrons accelerated in solar flares with maximum energy density around this frequency or coronal height.
A simple, efficient, and environmentally friendly membrane-assisted solvent extraction (MASE) method for the extraction and preconcentration of six pyrethroid insecticides from aquaculture seawater ...samples followed by gas chromatography-electron capture detection (GC-ECD) was successfully proposed. The operating conditions for MASE, such as the extraction solvent, solvent volume, NaCl concentration, stirring rate, extraction time, and temperature, were optimized. Compared to conventional Florisil-solid phase extraction (SPE), higher extraction recoveries (85.9% to 105.9%) of three spiked levels of the six pyrethroid pesticides in aquaculture seawater were obtained using MASE, and the RSD values were lower than 7.9%. The limits of detection (LOD, signal-to-noise ratio (S/N)=3) and quantification (LOQ, S/N = 10) were in the range of 0.0370.166 and 0.120.55 g L
1
, respectively. The results demonstrate the excellent applicability of the MASE method in analyzing the six pyrethroid pesticides in aqueous samples. The proposed method exhibited a high potential for routine monitoring analysis of pyrethroid insecticides in seawater samples.
A membrane-assisted solvent extraction (MASE) method coupled with GC-ECD exhibited a high potential for routine monitoring analysis of pyrethroid insecticides in seawater samples.
Radiosensitive cell lines derived from X‐ray cross complementing group 5 (XRCC5), SCID mice and a human glioma cell line lack components of the DNA‐dependent protein kinase, DNA‐PK, suggesting that ...DNA‐PK plays an important role in DNA double‐strand break repair. Another enzyme implicated in DNA repair, poly(ADP‐ribose) polymerase, is cleaved and inactivated during apoptosis, suggesting that some DNA repair proteins may be selectively targeted for destruction during apoptosis. Here we demonstrate that DNA‐PKcs, the catalytic subunit of DNA‐PK, is preferentially degraded after the exposure of different cell types to a variety of agents known to cause apoptosis. However, Ku, the DNA‐binding component of the enzyme, remains intact. Degradation of DNA‐PKcs was accompanied by loss of DNA‐PK activity. One cell line resistant to etoposide‐induced apoptosis failed to show degradation of DNA‐PKcs. Protease inhibitor data implicated an ICE‐like protease in the cleavage of DNA‐PKcs, and it was subsequently shown that the cysteine protease CPP32, but not Mch2alpha, ICE or TX, cleaved purified DNA‐PKcs into three fragments of comparable size with those observed in cells undergoing apoptosis. Cleavage sites in DNA‐PKcs, determined by antibody mapping and microsequencing, were shown to be the same for CPP32 cleavage and for cleavage catalyzed by extracts from cells undergoing apoptosis. These observations suggest that DNA‐PKcs is a critical target for proteolysis by an ICE‐like protease during apoptosis.
Heterosexual transmission of HIV through contact with female sex workers (FSWs) is a growing concern for the HIV/AIDS epidemic in China. Using consecutive cross-sectional surveys, we examined the ...prevalence of HIV and sexually transmitted infections (STIs), risk behaviours, HIV knowledge and the utilization of intervention services among FSWs in Shandong Province. Of 3460 participants, half reported ever having STI-related symptoms, 57.8% had ≥7 clients in the last week, half reported inconsistent use of condoms with clients and 11.2% reported ever using illicit drugs. Consistent use of condoms with clients was associated with higher education, being 20-24 years of age, being recruited from hotels, having ever received free condoms and was inversely associated with STI-related symptoms. HIV-related knowledge was associated with higher education, ever testing for HIV and inversely associated with self-reported STI-related symptoms. The low rates of condom use, high number and frequent turnover of clients, high prevalence of self-reported STIs and drug use highlight the urgency for more effective intervention in these FSWs.
Bioanalytical methods using liquid/liquid extraction (LLE) and liquid chromatography with electrospray tandem mass spectrometry (LC–MS/MS) are widely used. The organic extracts need to be evaporated ...and reconstituted, hampering further improvement of throughput and automation. In this study, we demonstrated a novel approach of eliminating these two steps in 96-well LLE by using hydrophilic interaction chromatography with MS/MS (HILIC–MS/MS) on silica column with high organic/low aqueous mobile phase. Omeprazole, its metabolite 5-OH omeprazole, and internal standard desoxyomeprazole, were extracted from 0.05
ml of human plasma using 0.5
ml of ethyl acetate in a 96-well plate. A portion (0.1
ml) of the ethyl acetate extract was diluted with 0.4
ml of acetonitrile and 10
μl was injected onto a Betasil silica column (50
mm
×
3.0
mm, 5
μm) and detected by API 3000 and 4000 with (+) ESI. Mobile phase with linear gradient elution consists of acetonitrile, water, and formic acid (from 95:5:0.1 to 73.5:26.5:0.1 in 2
min). The flow rate was 1.5
ml/min with total run time of 2.75
min. The method was validated for a low limit of quantitation at 2.5
ng/ml for both analytes. The method was also validated for specificity, reproducibility, stability and recovery. Lack of adverse matrix effect and carry-over was also demonstrated. The inter-day precision and accuracy of the quality control samples at low, medium and high concentration levels were <4.4% relative standard deviation (R.S.D.) and 4.1% relative error (R.E.) for omeprazole, and 4.5% R.S.D. and 5.6% R.E. for 5-OH omeprazole, respectively.
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