Do intramolecular halogen bonds exist? Ab initio calculations and crystal structures’ evidences

Cl···O intramolecular contacts are analyzed here. Hence, the Cambridge Structural Database search was performed to find five-membered Cl–C=C–C=O pseudo-rings closed through Cl···O intramolecular contacts. Such rings were analyzed and it was found that some of Cl···O distances are smaller than the corresponding sum of van der Waals radii. Additionally ab initio MP2/6-311++G(d,p) calculations and AIM analyses were carried out here on 3-chloropropenal and its fluoro derivatives to deepen the nature of intramolecular Cl···O interactions, some of findings may indicate that they are attractive and stabilizing ones. This article is dedicated to Prof. T. M. Krygowski on the occasion of his 70th birthday.     

Sobolev’s spaces on time scales and its applications to a class of second order Hamiltonian systems on time scales

In this paper, we study the Sobolev’s spaces on time scales and their properties. As applications, we present a recent approach via variational methods and the critical point theory to obtain the existence of solutions for a class of second order Hamiltonian systems on time scales. By establishing a proper variational setting, three existence results for systems under consideration are obtained. Finally, three examples are presented to illustrate the feasibility and effectiveness of the existence results.     

Composition and polyamorphism in supercooled yttria-alumina melts

By extending recent work on liquid-liquid transitions in supercooled yttria-alumina AYx liquids we draw attention to the compositional dependence of the structure factor of the high density liquid, arguing that this is sufficiently sensitive to discriminate between liquids at the level of a few %. Comparing structure factor differences between liquids of different compositions and in the same liquid AY20 between high and low temperatures straddling the transition at 1788 K between a high density liquid (HDL) and a low density liquid (LDL) enables compositional phase separation to be ruled out. It points instead to kinetic changes in polyhedral configurational order being the drivers for this polyamorphic transformation. Rotor behaviour observed in levitated liquid drops used in the high temperature experiments enables the reversibility of the LLT transition (LLT) and the associated changes in entropy and density to be identified. Evidence for critical-like behaviour in the structural relaxation time and in the fluctuation correlation length is presented. By re-examining recent work which failed to find the structural and thermal signatures for the LLT in liquid AY20 at 1788 K we present evidence for the LLT occurring instead in liquid AY15 at 1940 K, suggesting that the liquid-liquid transition temperature in AYx liquids decreases with increasing yttria content.     

Scaling function of critical binary mixtures: Nitrobenzene-n-hexane data revisited

Ultrasonic attenuation spectra of the nitrobenzene-n-hexane mixture of critical composition have been analysed. Data between 50 kHz and 1 GHz from different sources have been included to show that at a given temperature the spectra, in addition to the critical contribution, reveal a non-critical relaxation term. Taking this additional term into account inconsistencies in the scaling function reported in the literature are avoided. In the final analysis the scaling function of the nitrobenzene-n-hexane system follows the predictions of the Bhattacharjee-Ferrell theory with critical amplitude and relaxation rate of concentration fluctuations in nice agreement with determinations from independent methods. The low-frequency attenuation data are briefly discussed with a view to a bulk viscosity approach which yields a slightly different proportionality constant in the linear regime of the scaling function than the Bhattacharjee-Ferrell theory. Evidence in favour of the latter is obtained.     

壳聚糖与尿素的相互作用及其应用研究进展

尿素能够显著破坏甲壳素/壳聚糖分子氢键结构和疏水相互作用,增加其临界胶束浓度,促进多糖大分子的溶解,并能减少其在溶液中的自聚集现象.碱-尿素水溶液可以作为一种新型的甲壳素/壳聚糖绿色溶剂,有望用于对刺激性要求较为苛刻的食品、生物医学等领域.壳聚糖衍生物特别是其与过渡金属离子的配合物具有良好的尿素吸附功能,可用于尿毒症患者血液中小分子毒物的吸附,对机体刺激性小且不吸附血清蛋白等生物大分子.有望成为血液灌流治疗法中清除尿素等小分子毒性物质的良好吸附剂.壳聚糖还可以作为包膜材料,制备壳聚糖包膜尿素,与普通的包膜尿素相比性能更为优越.     

Existence of solution for a fractional advection dispersion equation in RN

This paper is concerned with the existence of solution to the following fractional advection dispersion equation$-{\int }_{|\theta |=1}{D}_{\theta }{D}_{\theta }^{\beta }\mathit{uM}(d\theta )+b(x)u=f(x\text{,}u)\text{,}x\in {\mathbb{R}}^N\text{,}u\in H^{\alpha }({\mathbb{R}}^N)\text{,}$where $N>1\text{,}{\inf }_{{\mathbb{R}}^N}b(x)>0$, $f:{\mathbb{R}}^N\times \mathbb{R}\to \mathbb{R}$ is continuous, the constant $\beta \in (0\text{,}1)\text{,}\alpha =\frac{\beta +1}{2}\text{,}M(d\theta )$ is a Borel probability measure on the unit sphere in ${\mathbb{R}}^N$, $D_{\theta }^{\beta }$ denotes directional fractional derivative of order β in the direction of the unit vector θ. We focus our investigation on the existence of solution to the problem when M is symmetric and nonsymmetric by the Mountain Pass theorem and iterative technique. The main results of this paper emphasize the central role played by the general Borel probability measure.