The interplay between osteoblast functions and the degree of nanoscale roughness induced by grain boundary grooving of nanograined materials

From the perspective of osseointegration, nanograined/ultrafine-grained (NG/UFG) metals provide surfaces that are different from conventional coarse-grained (CG) polycrystalline metals because of the high fraction of grain boundaries. We describe here the interplay between the cellular response and grain boundary grooving as a potential approach to enhance osteoblast functions and facilitate the biomechanical interlocking and anchorage. This is accomplished by making a relative comparison of osteoblast response of NG/UFG grains electrochemically grooved to different depths to induce different degree of nanoscale roughness with planar NG/UFG surfaces, under identical biological environment. Electrochemically grooved NG/UFG structures indicated significant attachment and proliferation, and consequently enhanced modulation of cellular response that was significantly different from planar (non-grooved) NG/UFG substrate. Consistent with cell attachment and proliferation, immunofluorescence microscopy and computational analysis indicated stronger vinculin signals associated with actin stress fibers in the outer regions of the cells and cellular extensions on electrochemically-grooved NG/UFG substrates. These observations are indicative of accelerated response of cell-substrate interaction and activity. The behavior is attributed to average nanoscale roughness and high surface hydrophilicity of the nanoengineered surface.     

Pr的掺杂对固溶体Ce_(4.5)Gd_(1.5)MoO_(15-δ)电性能的影响

在固溶体Ce4.5 Gd1.5MoO15-δ体系中的Ce位引入少量Pr得新氧化物Ce4.5 Gd1.5-xPrxMoO15-δ(x=0.15).通过X射线粉末衍射(XRD)对氧化物结构进行分析,交流阻抗谱潮试电性能,讨论掺杂少量Pr对Ce4.5 Gd1.5 MoO15-δ电性能的影响.结果表明,少量Pr2的掺杂可降低晶界电阻,增加离子扩散通道,降低体系的总电导激活能和晶界电导激活能.提高氧化物的总电导率和晶界电导率.600℃时掺Pr材料的晶界电导牟为1.04×10-1 s/cm,高于未掺Pr材料的晶界电导率(5.27×10-4D/cm)约1倍.     

Food habits of rodents in grain godowns of Karachi, Pakistan

The present study is based on identification of stomach contents of three commensal rodents (Rattus rattus, Rattus norvegicus, Mus sp.) and the common house shrew (Suncus murinus), which were collected from the Thole Produce Yard rice godowns, Karachi. The relative frequency of individual plant and animal food items were calculated as percentages.The stomachs of 88% of 65 R. rattus and 85% of 39 R. norvegicus contained insect remains as did the stomachs of 93% of 84 Mus sp. All stomachs of S. murinus contained remains of economically important stored-grain insect pests. It is concluded that insects can be a significant component of the diet of these commensal rodents.     

Multimodal ultrafine grain size distributions from severe plastic deformation at high strain rates

Severe plastic deformation at high strain rates in machining is explored as a vehicle for engineering grain size distributions in copper. Typical strengthening in unimodal, ultrafine grained chips is found to accompany poor ductility when generated at large strains but low strain rates. However, at higher rates, in situ heating in the deformation zone engenders dynamic recovery that results in material with a multimodal grain size distribution that is comparable in strength to the unimodal chips, but additionally possesses improved ductility.     

Optimization of BaZrO3 sintering by control of the initial powder size distribution; a factorial design statistical analysis

A factorial design statistical analysis has been conducted in order to obtain the optimum conditions in the solid state sintering process of barium zirconate bulk materials, optimum with respect to density, closed and open porosities. The optimized heat treatment permits to sinter a 99% dense barium zirconate sample at 1650 °C during only 2 h. When the temperature is higher than 1650 °C or when the heating time is longer than 2 h, a decrease in density is observed.     

Study on micro-topographical removals of diamond grain and metal bond in dry electro-contact discharge dressing of coarse diamond grinding wheel

A coarse diamond grinding wheel is able to perform smooth surface grinding with high and rigid grain protrusion, but it is very difficult to dress it. Hence, the dry electro-contact discharge (ECD) is proposed to dress #46 diamond grinding wheel for dry grinding of carbide alloy. The objective is to understand micro-topographical removals of diamond grain and metal bond for self-optimizing dressing. First, the pulse power and direct-current (DC) power were employed to perform dry ECD dressing in contrast to mechanical dressing; then the micro-topographies of diamond grains and metal bond were recognized and extracted from measured wheel surface, respectively; finally, the relationship between impulse discharge parameters and micro-topographical removals was investigated with regard to grain cutting parameters, dry grinding temperature and ground surface. It is shown that the dry ECD dressing along with spark discharge removal may enhance the dressing efficiency by about 10 times and dressing ratio by about 34 times against the mechanical dressing along with cutting removal. It averagely increases grain protrusion height by 12% and grain top angle by 23%, leading to a decrease 37% in grinding temperature and a decrease 46% in surface roughness. Compared with the DC-25V power along with arc discharges, the Pulse-25V power removes the metal bond at 0.241 mm³/min by utilizing discharge energy by 73% and diamond grain at 0.013 mm³/min through surface graphitization, respectively, leading to high and uniform grain protrusion. It is confirmed that the impulse discharge parameters are likely to control the microscopic grain protrusion topography for efficient dressing according to their relations to the micro-removal of metal bond.     

Low temperature fabrication of formamidinium based perovskite solar cells with enhanced performance by chlorine incorporation

Recently formamidinium (FA) based perovskite solar cell was demonstrated to show high performance and better stability upon partial substitution of FA with Cs cation. However, the fabrication of device required high-temperature processing on TiO₂ electrode and thus limits the use of flexible polymeric substrates. Here, we present a low temperature approach for the fabrication of p-i-n perovskite solar cells based on Cs_0.15FA_0.85PbI₃. Furthermore, we investigated the effects of chlorine on the morphology and crystallinity of the perovskite films and the corresponding photovoltaic performance. Chlorine incorporation can significantly enlarge the size of grains and improve the crystallinity of perovskite films with full surface coverage. A best power conversion efficiency of 14.5% was realized for planar perovskite solar cells with negligible hysteresis and remarkable reproducibility.     

Chlorobenzene vapor assistant annealing method for fabricating high quality perovskite films

In this study, chlorobenzene (CB) vapor assistant annealing (VAA) method is employed to make high quality perovskite films and produce high efficiency CH₃NH₃PbI_3-xCl_x perovskite solar cells. The perovskite films made by this method present several advantages such as increased crystallinity, large grain size and reduced crystal boundaries compared with those prepared by thermal annealing (TA) method, which is beneficial to charge dissociation and transport in hybrid photovoltaic device. In addition, it is found that the CB VAA method could improve the surface property of perovskite film, resulting in a preferable coverage of PCBM layer and a better interfacial contact between perovskite film and upper PCBM film. Consequently, the short circuit current density (J_sc) of the devices is significantly increased, yielding a high efficiency of 14.79% and an average efficiency of 13.40%, which is 13% higher than that of thermal annealed ones. This work not only put forward a simple and efficient approach to prepare highly efficient perovskite solar cells but also provide a new idea to improve the morphology and interfacial contact in one integration step.