Global existence and blow-up of solutions of nonlocal diffusion problems with free boundaries

In this paper, we investigate some nonlocal diffusion problems with free boundaries. We first give the existence and uniqueness of local solution by the ODE basic theory and the contraction mapping principle. Then we provide a complete classification for the global existence and finite time blow-up of solutions. Moreover, estimates of blow-up rate and blow-up time are also obtained for the blow-up solution.     

Molecular dynamics simulation of liquid CH2Cl2 with 3×3 and 5×5 site-site interactions

A molecular dynamics simulation of liquid CH₂Cl₂ is compared with the far infrared spectrum at the same state point (293K, 1 bar). Two representations of the force field are used, a 3×3 and 5×5 site-site interaction consisting of Lennard-Jones and charge terms. The far infra-red spectrum shows unambiguously that the 5×5 representation is more realistic in the sense that it reproduces the observed spectrum more closely.     

Carbazole and Diketopyrrolopyrrole-Based D-A π-Conjugated Oligomers Accessed via Direct C–H Arylation for Opto-Electronic Property and Performance Study

Five carbazole and diketopyrrolopyrrole-based donor-acceptor (D-A) new π-conjugated oligomers (π-COs) with gradually elongated lengths are facilely synthesized via a single pot of direct C–H arylation with merits of atom- and step-economy. The structure-property-performance correlations of these π-COs and their parent polymer are studied in detail by opto-electronic characterizations and bulk heterojunction (BHJ) organic photovoltaic (OPV) devices. It is found that the π-COs having longer lengths enable better performance in OPVs owing to the enhanced intermolecular interaction with the elongation of the conjugations. The above results not only highlight the powerful synthetic strategy here provided, but also reveal that π-COs with unique properties might find promising application in OPVs.     

Mechanical properties of vanadium-base binary alloys

The fabricability and tensile properties of solid-solution-strengthened vanadium-base binary alloys containing aluminium, titanium, niobium, tantalum, chromium, molybdenum or iron were studied. The alloys were prepared by non-consumable arc melting and contained 150–370 ppm O, 20–250 ppm N and 40–130 ppm C. The VTi, VNb and VTa alloys were superior to the other alloys in their fabricabilities into sheet. The tensile properties were examined between room temperature and 1000 °C. The tensile strength values of the VNb and the VTa alloys were higher than those of the VAl and the VCr alloys. The tensile strengths of the VAl, VCr and VMo alloys increased in proportion to the increase in atomic per cent of alloying element, while those of the VNb, VTa and VFe alloys increased with the square root of the atomic per cent of the alloying element.     

Methods for the homologation of benzofurancarboxylic acids using dianionic intermediates

Dianions (2), (5), and (10), can be derived from the corresponding benzofurancarboxylic acids using lithium diisopropylamide, and are useful intermediates for the homologation of the parent acids.     

Uranyl-Organic Framework as Hydrogen Atom Transfer Catalyst for Visible-Light-Driven Heterogeneous Hydroacylation of Azodicarboxylates

The direct C−H to C−N bond conversion at room temperature using heterogeneous visible-light catalysts is both interesting and challenging. Herein, we disclosed visible-light-promoted hydroacylation of azodicarboxylates using uranyl-organic framework [UO₂(OH)(cpt)]_n ( Ucpt , Hcpt=4-(4′-carboxyphenyl)-1,2,4-triazole) as an efficient heterogeneous hydrogen atom transfer photocatalyst. In this procedure, diverse benzaldehydes are compatible using dimethyl carbonate (DMC) as a green solvent at room temperature, achieving direct conversion of C−H to C−N bond with excellent yields (up to 99%). The key to excellent catalytic activity lies in the fact that the coordination of the conjugated ligand changes the HOMO energy level of Ucpt , resulting in more active sites and longer-lived photo excitons. Simultaneously, this heterogeneous photocatalyst can be easily separated and reused for seven successive cycles and maintain high catalytic activity, showing outstanding sustainability and recyclability.     

Effet Kerr magnetique microonde du type Faraday dans les semiconducteurs

The Faraday-type magneto-microwave Kerr effect in semiconductors at weak magnetic fields has been studied in the domain where the influence of the carrier inertia is low but not negligible. After stating the expressions connecting the rotation and the ellipticity of the reflected wave to the material parameters we have applied these results to the determination of Hall mobility and shown that a precise determination of this mobility must usually be realised from both rotation and ellipticity effects.The experimental study has been achieved with a recording interferential reflecto-polarimeter. This apparatus being particularly well suited to this study has not yet been used for this kind of measurements. We have thus determined precisely the Hall mobility of various semiconductor samples at 16 GHz and at room temperature.     

Topological classification of defects in crystals

Here we review the topological approach to the classification of defects in crystals, which are deviations from crystallinity. First, we illustrate this approach using the simpler case of dislocations. We show how the fact that dislocations are completely characterized by their Burgers vectors only, is related via topological considerations to the fact that a perfect crystal is exactly reproduced by translations through a lattice vector. Later, we present the developments of the French school and that of Rogula, comparing and contrasting them. These are attempts to generalize the above idea to include consideration of other transformations that leave a perfect crystal invariant. Finally, we discuss briefly some of the problems that still remain with this approach.     

Presodiation Strategies for the Promotion of Sodium-Based Energy Storage Systems

Nowadays sodium-based energy storage systems (Na-based ESSs) have been widely researched as it possesses the possibility to replace traditional energy storage media to become next generation energy storage system. However, due to the irreversible loss of sodium ions in the first cycle, development of Na-based ESSs is limited. Presodiation, as a strategy of adding excess sodium ions to the system in advance, accomplishes the enhancement of electrochemical performance. In this minireview, different presodiation strategies applied in sodium-based energy storage systems will be summarized in detail, their functions and corresponding mechanisms will be discussed as well. Furthermore, the current novel application of presodiation method in other aspects of Na-based ESSs will be mentioned additionally. At last, in the view of present research status of presodiation, issues that can be mitigated are put forward and guidelines are given on how to deliberate in-depth presodiation technology in the future, dedicating to promote the further development of Na-based ESSs.     

Promoting the Phosphidation Process using an Oxygen Vacancy Precursor for Efficient Hydrogen Evolution Reaction

Based on previous works, most of the transition metal phosphides (TMPs) were directly prepared by decomposing NaH₂PO₂ with the precursors at high temperatures, which resulted in different degrees of phosphidation in the final product. Therefore, it is necessary to design an innovative approach to enhance the degree of phosphidation in the material using crystal defects. Here, oxygen-vacancy iron oxide/iron foam (Ov-Fe₂O₃/IF) was firstly prepared by generating oxygen vacancy in situ in an iron foam through heating in vacuum conditions. Subsequently, FeP/IF was formed by phosphating Ov-Fe₂O₃/IF. Under the effects of oxygen vacancies, oxygen-vacancy iron oxide could be completely phosphatized to produce more active sites on the surface of the material. This, in turn, could result in a catalyst with exceptional hydrogen evolution activity. Thus, the successful fabrication of FeP/IF demonstrated in this work provides an effective and feasible way for the preparation of other high-efficiency catalysts.