With the rapid development of information and communications technology, the prevalence of cyberbullying and its influences on mental health among college students have received increasing attention. ...The purpose of this study was to survey the prevalence of cyberbullying in Chinese college students and to investigate the association between cyberbullying, emotional exhaustion and the perception of collective efficacy.
The study sample included 5315 respondents from ten different colleges in Liaoning Province. Their demographic characteristics and characteristics of online behaviors and instruments including a Cyberbullying Scale with 12 items, the Emotional Exhaustion measuring scale, and the Perception of Collective Efficacy Scale, were employed.
The prevalence of cyberbullying victimization was 26.45 % (1406/5315). Younger male college students who had more active online lives were more likely to be cyberbullying victims. Binary logistic regression analysis showed that being a cyberbullying victim (odds ratio, OR = 2.188; 95%CI, 1.841–2.600, p < 0.001) was associated with emotional exhaustion. Perceptions of collective efficacy (PCE) is negatively associated with cyberbullying and, thus, alleviate emotional exhaustion and mediate the negative effect of emotional exhaustion after it occurs.
Cyberbullying occurs quite frequently among Chinese college students. Cyberbullying is a predictor of emotional exhaustion. PCE play a bidirectional role before and after cyberbullying occurs. Our study highlights the importance of the identification of potential cyberbullying victims and of the provision of early interventions in cyberbullying among Chinese college students to improve their mental health.
•The study sample included 5315 respondents from ten different colleges in Liaoning Province.•Cyberbullying occurs quite frequently among Chinese college students.•Cyberbullying victimization n had a significant and positive predictive effect on emotional exhaustion•Perception of Collective Efficacy play a bidirectional role before and after cyberbullying occurs.
Herein, the phase evolution, densification and grain growth process of the high entropy ceramics during flash sintering were systematically characterized and quantified to understand the ...microstructural evolution for the first time. It was demonstrated that the densification rate of (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 by flash sintering in this work was generally around 60 times that of conventional sintering at 1600 °C, while the grain growth rate by flash sintering was only around 1.5–6 times that of conventional sintering, indicating that grain growth was suppressed during flash sintering. The grain growth mechanisms by flash sintering and conventional sintering could be both attributed to surface diffusion and volume diffusion. In addition, the flash sintered high-entropy ceramics as promising immobilization materials for high-level radioactive waste (HLW) exhibited excellent aqueous durability with normalized leaching rates of Nd, Gd and Zr approximately 10−6∼10−7 g m−2 d−1 after 42 days, which were much lower than most reported pyrochlore materials.
The high radiation resistance and long time stability of Gd2Zr2O7 ceramics make it a promising candidate for high level waste (HLW) immobilization materials. In this study, single phase ...nanocrystalline Gd2Zr2O7 was successfully synthesized and consolidated at temperatures around 1050 °C for only 1 min by flash sintering for the first time. The phase evolution and microstructural development during flash sintering were systematically studied and compared with the conventionally sintered samples. The flash sintered Gd2Zr2O7 exhibit defect fluorite structure, and a following heat treatment at 1400 °C could transform the Gd2Zr2O7 ceramics from defect fluorite phase into pyrochlore phase. The MCC-1 leaching test shows that the flash sintered Gd2Zr2O7 samples exhibit good aqueous durability.
Two‐step reactive flash sintering (TSRFS) was employed to achieve fast densification of high entropy pyrochlore (La0.2Nd0.2Sm0.2Eu0.2Gd0.2)2Zr2O7 with suppressed grain growth and improved ...microstructural homogeneity. Theoretical density of ∼98.15% with a grain size of ∼684 nm was achieved by TSRFS, representing only half the grain size compared with conventional one‐step reactive flash sintering (RFS), while the total holding time of TSRFS was only 1.5 times that of RFS. Although longer duration in step 1 benefited faster densification, it was demonstrated that the shorter time in step 1 not only resulted in smaller grain size in TSRFS samples with identical densities but also helps mitigate the grain size heterogeneity between sample cores and surfaces. Therefore, the art of efficiently using TSRFS lies in the reasonable manipulation of the time and power in step 1 and 2, achieving a balance between densification, grain growth, and microstructural homogeneity.
The hydrogen evolution reaction (HER) represents one promising solution for energy and environmental sustainability. Nickel phosphide with various morphology has been recently investigated as ...promising earth abundant electrocatalysts for HER. Compared with three or two dimensional morphology, one dimensional (1D) nickel phosphide could provide larger specific surface area and hence improves the HER electrocatalytic performance. However, most reported 1D nickel phosphides show a small length-to-diameter ratio (less than 50). Herein, ultrahigh length-to-diameter ratio Ni2P nanowires synthesized by one-step phosphorization-sulfuration treatment are reported for the first time. The as-prepared nanowires have extremely high length to diameter ratio which ranges from 500 to 1000. The formation mechanism of such morphology is illustrated by a systematic study of the morphology, microstructure and elementary distribution of the nanowire array cathode. The ultralong nanowire morphology clearly helps improve the HER performances, since the self-supported Ni2P nanowire array cathode exhibits outstanding HER electrocatalytic activity and long-term durability in all of the acidic, alkaline, and neutral conditions.
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•Ultralong Ni2P nanowire were prepared on a 3D macroporous substrate by a one-step synthesis method.•The ultralong nanowire morphology could provide large electrode/electrolyte interface (more active sites) and facilitate bubble evacuation, hence show high HER performances in all of the acidic, alkaline, and neutral condition.
LiNi1/3Co1/3Mn1/3O2 as a promising cathode material in lithium‐ion batteries was synthesized by flash/field‐assisted sintering technique for the first time. This study showed that the current‐limited ...synthesis of LiNi1/3Co1/3Mn1/3O2 could be carried out at temperatures less than 400°C for only 8 minutes, compared with the conventional pressureless sintering at 850°C for 12 hours. X‐ray diffraction results showed the phase evolution from precursor mixtures to the final LiNi1/3Co1/3Mn1/3O2 products during flash/field‐assisted sintering process and a well‐layered structure without undesirable cation mixing in the as‐formed LiNi1/3Co1/3Mn1/3O2. Combined with the lowered sintering temperatures and reduced sintering time, the excellent electrochemical performance of flash/field‐assisted sintered LiNi1/3Co1/3Mn1/3O2 materials suggested that this technique could be an energy‐efficient approach for the synthesis of lithium‐ion battery cathode materials and other materials requiring high‐temperature heat treatment.
Abstract
LiNi
1/3
Co
1/3
Mn
1/3
O
2
as a promising cathode material in lithium‐ion batteries was synthesized by flash/field‐assisted sintering technique for the first time. This study showed that the ...current‐limited synthesis of LiNi
1/3
Co
1/3
Mn
1/3
O
2
could be carried out at temperatures less than 400°C for only 8 minutes, compared with the conventional pressureless sintering at 850°C for 12 hours. X‐ray diffraction results showed the phase evolution from precursor mixtures to the final LiNi
1/3
Co
1/3
Mn
1/3
O
2
products during flash/field‐assisted sintering process and a well‐layered structure without undesirable cation mixing in the as‐formed LiNi
1/3
Co
1/3
Mn
1/3
O
2
. Combined with the lowered sintering temperatures and reduced sintering time, the excellent electrochemical performance of flash/field‐assisted sintered LiNi
1/3
Co
1/3
Mn
1/3
O
2
materials suggested that this technique could be an energy‐efficient approach for the synthesis of lithium‐ion battery cathode materials and other materials requiring high‐temperature heat treatment.
Seven cases of electrocution death by low voltage (<80 V) were studied. Autopsy was carried out and the death scene was investigated. The conditions for low-voltage electrocution death, the state of ...the victim at the time of electrocution, postmortem examination and the nature of the electricity is discussed. It was pointed out that low-voltage electrocution was related to the nature of electricity, individual characteristics and environment conditions.
In this study, geochemical compositions of elements in sulfide samples collected from the Deyin-1 hydrothermal field near the 15°S southern Mid-Atlantic Ridge (SMAR) were analyzed by the X-ray ...fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) to examine the enrichment regulations of ore-forming elements and hydrothermal mineralization.These sulfide precipitates can be classified macroscopically into three types: Fe-rich sulfide, Fe-Cu-rich sulfide and Fe-Zn-rich sulfide, and are characterized by the enrichment of base metal elements along with a sequence of Fe>Zn>Cu. Compared with sulfides from other hydrothermal fields on MAR, Zn concentrations of sulfides in the research area are significantly high, while Cu concentrations are relatively low. For all major, trace or rare-earth elements (REE), their concentrations and related characteristic parameters exhibit significant variations (up to one or two orders of magnitude), which indicates the sulfides from different hydrothermal vents or even a same station were formed at different stages of hydrothermal mineralization, and suggests the variations of chemical compositions of the hydrothermal fluid with respect to time. The hydrothermal temperatures of sulfides precipitation decreased gradually from station TVG10 (st.TVG10) to st.TVG12, and to st.TVG11, indicating that the precipitation of hydrothermal sulfides is subjected to conditions changed from high temperature to low temperature, and that the hydrothermal activity of study area was at the late stage of a general trend of evolution from strong to weak. The abnormally low concentrations of REE in sulfides and their similar chondrite-normalized REE patterns show that REEs in all sulfides were derived from a same source, but underwent different processes of migration or enrichment, or sulfides were formed at different stages of hydrothermal mineralization. The sulfides collected from the active hydrothermal vent were mainly attributed to precipitating directly from the hydrothermal fluid, while those collected from the extinct hydrothermal chimney might have already been altered by the seawater. Generally, ore-forming elements in the sulfides can be divided into three groups: Fe-based element group, Cu-based element group and Zn-based element group.The first group includes Fe, Mn, Cr, Mo, Sn, Rb and bio-enriching elements, such as P and Si, reflecting the similar characteristics to Fe in the study area. And the second group contains Cu, W, Co, Se, Te and Bi, suggesting the similar behavior with Cu. Moreover,the third group includes Zn, Hf, Hg, Cd, Ta, Ga, Pb, As, Ag, Ni and Sb, which indicates the geochemical characteristics of most dispersed trace elements controlled by Zn-bearing minerals to some extent.
A seafloor hydrothermal field, named Deyin-1 later, near 15°S southern Mid-Atlantic Ridge（SMAR） was newly found during the 22 nd cruise carried out by the China Ocean Mineral Resources Research ＆ ...Development Association（COMRA）. Sulfide samples were collected at three stations from the hydrothermal field during the26 th cruise in 2012. In this paper, mineralogical characteristics of the sulfides were analyzed with optical microscope, X-ray diffractometer, scanning electron microscope and electron microprobe to study the crystallization sequence of minerals and the process of hydrothermal mineralization. According to the difference of the ore-forming metal elements, the sulfide samples can be divided into three types：（1） the Ferich sulfide, which contains mainly pyrite and chalcopyrite;（2） the Fe-Cu-rich sulfide consisting predominantly of pyrite, chalcopyrite and isocubanite, with lesser amount of sphalerite, marmatite and pyrrhotine; and（3） the Fe-Zn-rich sulfide dominated by pyrite, sphalerite and marmatite, with variable amounts of chalcopyrite, isocubanite, pyrrhotine, marcasite, galena and gratonite. Mineral precipitations in these sulfides are in the sequence of chalcopyrite（isocubanite and possible coarse pyrite）, fine pyrite,sphalerite（marmatite）, galena, gratonite and then the minerals out of the dissolution. Two morphologically distinct generations（Py-I and Py-II） of pyrite are identified in each of the samples; inclusions of marmatite tend to exist in the coarse pyrite crystals（Py-I）. Sphalerite in the Fe-Zn-rich sulfide is characterized by a＂chalcopyrite disease＂ phenomenon. Mineral paragenetic relationships and a wide range of chemical compositions suggest that the environment of hydrothermal mineralization was largely changing. By comparison, the Fe-rich sulfide was formed in a relatively stable environment with a high temperature, but the conditions for the formation of the Fe-Cu-rich sulfide were variable. The Fe-Zn-rich sulfide was precipitated during the hydrothermal venting at relatively low temperature.
