Search

The effectiveness of gene silencing to evaluate gene function is discussed.

The critical challenges for fluoride conversion cathodes lie in the absence of built-in Li source, poor capacity retention, and rate performance. For lithiated fluorides, the reason to limit their competitiveness is rooted in the facile coarsing of insulating LiF (as built-in Li source) and its insufficient splitting kinetics during charging. Previous efforts on blending LiF nanodomains with reductive metal, metal oxide, or fluoride by ball-milling method still face the problems of large overpotential and low current density. Herein we propose a strategy of dual-metal (Fe–Cu) driven LiF splitting to activate the conversion reaction of fluoride cathode. This lithiated heterostructure (LiF/Fe/Cu) with compact nanodomain contact enables a substantial charge process with considerable capacity release (300 mAh g–1) and low charge overpotential. Its reversible capacity is as high as 375–400 mAh g–1with high energy efficiency (76%), substantial pseudocapacitance contribution (>50%), and satisfactory capacity retention (at least 200 cycles). The addition of Cu nanodomains greatly catalyzes the kinetics of Fe–Cu–F formation and decomposition compared with the redox process of Fe–F, which lead to the energy and power densities exceeding 1000 Wh kg–1and 1500 W kg–1, respectively. These results indicate that LiF-driven cathode is promising as long as its intrinsic conductive network is elegantly designed.

The effect of TM-doping (Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) on atomic, electronic structures,quantum capacitance (CQ), and surface charge storage of perfect and different styles of vacancy-defected MoS2/graphene heterostructures were studied based on DFT computations. The electron density of states (DOS) around the Fermi level suggested that the enhancement of CQwas attributed to the transition-metal dopants and C/Mo/S-atoms near vacancy.

Niobium fluoride (NbF5) is introduced into the MgH2+ 1/4AlH3hydride composite by ball milling to improve the hydrogen desorption properties of the Mg–Al–H system. It is found that after being ball milled with 1 mol % of NbF5, AlH3in the composite has almost fully decomposed and forms metallic Al, which indicates that NbF5can significantly destabilize AlH3. DSC results show that NbF5addition also helps reduce the peak desorption temperature of MgH2in the composite from 324 to 280 °C. Isothermal desorption measurements demonstrate that MgH2in the doped composite can rapidly release 98% of its hydrogen after desorption at 300 °C for 1 h, while the valued is only 46% for the undoped composite. The activation energy for hydrogen desorption of MgH2in the doped composite is calculated to be 104.5 kJ/mol, much lower than that in the undoped composite (127.4 kJ/mol). These results suggest that NbF5addition dramatically improves the hydrogen desorption kinetics of the MgH2+ 1/4AlH3composite. Dehydrogenation–hydrogenation measurements reveal that the hydrogen desorption kinetics of the undoped composite declines with cycle number, whereas the NbF5-doped composite maintains good cycling stability. Microstructure studies indicate that the decline of the kinetics is attributed to the grain growth and particle agglomeration of MgH2during hydrogen sorption cycling. However, NbF5addition can suppress this grain growth through the formation of Nb/NbH layers surrounding the particles of MgH2and acting both as the impediment to grain growth of Mg/MgH2and as the gateway for hydrogen diffusion. Finally, the role that AlH3plays in the hydrogen desorption process of the Mg–Al–H composites is discussed.

In this work, the hydrogen desorption properties of the novel Mg–Al–H hydrogen storage composites prepared by ball-milling the as-received magnesium hydride (MgH2) and the as-prepared aluminum hydride (AlH3) with different molar ratios (1:1, 1:0.5, and 1:0.25) are investigated systematically. Nonisothermal desorption measurements show that more than 7.51 wt % of hydrogen is released from the Mg–Al–H composites when they are heated from room temperature to 500 °C. Thermal analysis by differential scanning calorimeter (DSC) and hydrogen desorption spectrum by mass spectrometer (MS-H2) are used synchronously to study the desorption process of the Mg–Al–H. The onset hydrogen desorption temperature of MgH2in the MgH2+ AlH3composite is dramatically reduced from 320 °C for the pure MgH2to below 252 °C. The DSC/MS-H2and the X-ray diffraction (XRD) analyses show that the desorption of MgH2in the Mg–Al–H composite is composed of two steps with the reaction between MgH2and Al forming Mg17Al12as the first step and the self-decomposition of the residual MgH2as the second step. Isothermal desorptions show that the desorption kinetics of the MgH2in the Mg–Al–H composite is significantly improved. The apparent activation energy for the desorption of MgH2in the MgH2+ 0.25AlH3is reduced to 144.6 kJ/mol, which contributes to the improvement in the desorption kinetics of MgH2. The Johnson–Mehl–Avrami (JMA) kinetic studies indicate that the desorption kinetic model of MgH2in the Mg–Al–H composite is different from the pure MgH2. Concerning the reversibility, under the conditions of 300 °C and 5 MPa H2, MgH2in the Mg–Al–H composite is almost fully recovered after absorption for 5 h while it is partially recovered for the pure MgH2. Among the samples studied, the MgH2+ 0.25AlH3composite exhibits the highest reversible hydrogen storage capacity of 6.10 wt % (H/M).

ZnO nanowires were investigated at high pressures of up to 27 GPa in situ in a diamond anvil cell using synchrotron X-ray diffraction. Upon compression, a wurtzite-to-rocksalt phase transformation was observed, but both the onset and the completion pressures of this transformation were enhanced compared with all previously studied morphologies of ZnO, including nanocrystals and their bulk counterparts. Upon decompression, the rocksalt phase was found to sustain at near ambient pressure and could be recovered in a significant amount. Moreover, the pressure–volume equations of state for both the wurtzite and the rocksalt phases indicate that their bulk moduli are significantly higher than those of bulk ZnO and nanocrystals. The SEM images of the ZnO nanowires both before and after the compression suggest the pressure-induced morphology modifications, corroborating the understanding of other structure and property evolutions with pressure. Finally, possible pressure-induced phase transition mechanisms were explored by examining the cell parameters and the internal structural parameter with pressures.

Multiwalled boron nitride nanotubes (BNNTs) were compressed at room temperature in diamond anvil cells up to 35 GPa, followed by decompression. For the first time, in situ infrared absorption spectroscopy was used to monitor BNNT structural transformations. These BNNTs were found to undergo pressure-induced transformations from a hexagonal to a more closely packed wurtzite structure at 11 GPa, which is similar to that exhibited by bulk hexagonal BN (h-BN). However, when BNNTs are compressed, they exhibit quantitative differences compared with bulk h-BN in terms of transformation completeness and reversibility. Our findings provide unambiguous evidence that sp3bondings that form in significantly different yields originated from different morphologies of the starting BN materials. The unique transformation mechanism proposed for BNNTs provides new information for developing BNNTs as potential advanced materials with more desirable properties than those of carbon nanotubes.

Sex-lethal (Sxl) is an RNA-binding protein, containing two conserved RNA binding domains (RBDs) and a glycine-rich region, which functions as a regulator of alternative splicing inDrosophilasex determination. Previous work demonstrated that Sxl monomers interact cooperatively upon binding to target RNAs and that the cooperativity depends on the glycine-rich N terminus. Here we use band shift experiments to show that RNA binding patterns are altered when Sxl is combined with other proteins having similar glycine-rich domains, including mammalian heterogeneous nuclear (hn) RNP L and DrosophilaHrb87F (an hnRNP A/B homolog). Direct involvement of the Sxl glycine-rich region in protein interactions was verified by Far-Western analysis. Two interaction domains, the Sxl N terminus and the Sxl first RNA binding domain, were suggested by the yeast two-hybrid assay. In a systematic examination of the RNA binding properties of Sxl domains, it was found that the Sxl termini as well as the RBDs influence RNA binding specificity. Finally, selection of the Sxl optimal binding site (SELEX) confirms the importance of U-runs in the Sxl binding site and suggests a second type of non-U-run target that may be associated with RNA secondary structure.