In Situ Transmission Electron Microscopy Observations of the Growth Process of Fe_3O_4–Ag Nanoparticles

The properties of nanocrystals are highly dependent on their morphology, composition and structure. To obtain full control over their properties, the behavior of nanocrystals under external stimuli, such as heat treatment, needs to be understood. Herein, to in situ observe their microstructure and morphology changes, Fe_3O_4–Ag heterodimers were selected as a model system. Their structural changes after heat treatment were investigated by in situ transmission electron microscopy. A combination of real-time imaging with elemental analysis enabled observation of the transformation of Fe_3O_4–Ag heterodimers having a loose interface configuration to those with a Janus structure at the atomic scale after heating from room temperature to 600 °C. After incubation at 600 °C for 32 min, two kinds of Janus structures could be seen, including a clear linear interface in the Fe_3O_4–Ag heterodimers and a semi-crescent-shaped interface between the Ag and Fe_3O_4 nanoparticles(NPs). These dynamic observations provide unique insights into NP growth mechanisms, which are essential for understanding and controlling the structure and morphology of nanoparticles.     

In‐Plane Potential Gradient Induces Low Frictional Energy Dissipation during the Stick‐Slip Sliding on the Surfaces of 2D Materials

Understanding the nanoscale friction properties of 2D materials and further manipulating their friction behaviors is of great significance for the development of various micro/nanodevices. Recent studies, taking advantage of the close relationship between friction and surface charges, use an external out‐of‐plane electric field to control the interfacial friction. Nevertheless, friction increases with the application of the out‐of‐plane electric field in most cases. Here, an in‐plane potential gradient is applied for the investigation of the contribution of electric charges to friction on the surfaces of 2D materials. Experimental results show that the friction between an atomic force microscope tip and the flakes of 2D materials decreases with the application of the in‐plane potential gradient, and the higher the potential gradient, the greater the friction decrease. By comparing the in situ atomic‐level stick‐slip maps before and after the application of the in‐plane potential gradient, it is proposed that the promotion of low friction dissipative motion during the stick‐slip process owing to the presence of the potential gradient gives rise to the friction reduction. These results not only help to reveal the origin of friction, but also provide a novel way to manipulate friction through an electrically‐controlled sliding process.     

Trajectory-Based User Encounter Prediction Over Wireless Sensor Networks

Wireless Personal Communications - People or friends may encounter with each other offline, when they have a location proximity. With the rapid development of the wireless sensor network, smart...     

Synergistic extraction of heavy rare earths by mixture of α-aminophosphonic acid HEHAMP and HEHEHP

Synergistic extraction of heavy rare earths(REs) were investigated in chloride media by the mixture of(2-ethylhexylamino)methyl phosphonic acid mono-2-ethylhexyl ester(HEHAMP) and 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester(HEHEHP). The maximum synergistic enhancement coefficients(R) of Lu, Yb, Tm, Er, Y and Ho are 2.89, 2.76, 2.54, 2.14, 2.14 and 2.06, respectively, when the mole fraction X_(HEHAMP) is 0.5. The synergistic separation factors of the heavy REs are obtained(β_(Y/Ho)=1.31,β_(Er/Y)= 1.61,β_(Tm/Er)= 1.78, β_(Yb/Tm)= 1.76, β_(Lu/Yb) = 1.20). The extracted complex is determined to be RE[H(EHAMP)_2][H(EHEHP)_2]_2 by the slope analysis method. The loading capacities of the mixtures consisting of 15% HEHAMP and 15% HEHEHP for Y and Lu are about 26.59 g/L(Yb_2 O_3) and 27.25 g/L(Lu_2 O_3),respectively.     

2,2''-二氯氢化偶氮苯合成方法进展

对２，２′－二氯氢化偶氮苯（ＤＨＢ）的各种合成方法进行了综述，并提出了今后研究开发的方向。     

Long‐term effects of daily hemodialysis on vascular access outcomes: A prospective controlled study

Daily hemodialysis has been associated with surrogate markers of improved survival among hemodialysis patients. A potential disadvantage of daily hemodialysis is that frequent vascular access cannulations may affect long‐term vascular access patency. The study design was a 4‐year, nonrandomized, contemporary control, prospective study of 77 subjects in either 3‐h daily hemodialysis (six 3‐h dialysis treatments weekly; n = 26) or conventional dialysis (three 4‐h dialysis treatments weekly; n = 51). Outcomes of interest were vascular access procedures (fistulagram, thrombectomy and access revision). Total access procedures (fistulagram, thrombectomy and access revision) were 543.2 (95% confidence interval [CI]: 432.9, 673.0) per 1000 person‐years in the conventional dialysis group vs. 400.8 (95% CI: 270.2, 572.4) per 1000 person‐years in the daily hemodialysis dialysis group (incidence rate ratio = 0.74 with 95% CI: from 0.40 to 1.36, P = 0.33), after adjusting for age, gender, diabetes status, serum phosphorus, hemoglobin level and erythropoietin dose, there was no significant differences in incidence rate of total access procedures (P‐value > 0.05). There was no difference in time to first access revision between the daily dialysis and the conventional dialysis groups after adjustment for covariates (hazard ratio = 0.99 95% CI: 0.42, 2.36, P = 0.96). Daily hemodialysis is not associated with increased vascular access complications, or increased vascular access failure rates.     

化肥工业生产废料中钴的分光光度测定

应用分光光度法研究了化肥工业生产废料中钴的测定．确定了被测溶液的酸度、显色剂用量、加热时间、放置时间、络合比．对离子干扰影响进行了实验，用标准加入法测定了化肥工业生产废料中的钴，回收率９９％．该法可作为从化肥工业生产废料中提取钴的分析方法．