Effective interaction parameter of linear/star polymer blends and comparison with that of linear/linear and star/star blends

The authors present a detailed study of the microscopic parameters, which control the miscibility in binary linear/star polymer blends. The effective interactions of linear/star polymer blends are studied by means of Monte Carlo simulations and comparison is made with linear/linear and star/star blends, which they also determined. Using the bond fluctuation model on a simple cubic lattice, the authors are able to simulate symmetric linear/linear, star/star, and, for the first time, linear/star blends with a moderate number of arms. The simulations were performed at a volume fraction of occupied lattice sites phi=0.5, which corresponds to dense polymer mixtures for this algorithm. In particular, we study star/star blends with 4, 8, and 12 arms and the respective linear/linear blends as well as linear/star blends, all having the same total number of units equal to 73 and 121. The authors find that linear/star blends are more miscible than the corresponding linear/linear blends, which is in agreement with recent experimental and theoretical results. They find that linear/star mixtures are less miscible than star/star blends, a result which is also verified by theoretical findings.     

Tuning reversible supramolecular polymer properties through co-monomer addition

Unlike most low molar mass organogelators, which form strong gels due to the entanglement of strong molecular aggregates such as crystalline fibres, a few reversible supramolecular polymers form viscoelastic solutions due to the formation of both rigid and dynamic filaments. By using three different bisureas which self-assemble according to the same hydrogen-bonding pattern and form such rigid reversible supramolecular polymers, we have shown that it is possible to finely tune the properties of the resulting solutions. The critical temperature below which viscoelastic solutions are obtained and the viscosity of the dilute solutions can be adjusted by changing the co-monomer content. This clearly facilitates gel formulation, which is an important step as far as applications are concerned.

By using three different bis-ureas which self-assemble according to the same hydrogen bonding pattern and form rigid reversible supramolecular polymers, we show that it is possible to finely tune the properties of the resulting viscoelastic solutions.     

氧缺陷TiO2-B作为可充电锂离子电池负极材料的第一性原理研究

利用对氧缺陷的TiO₂-B材料进行密度泛函理论的计算,阐述了氧空穴对于TiO₂-B材料的电化学性质的影响。计算研究主要聚焦于缺陷材料的锂离子迁移和电子导电性等基本问题。计算结果表明在低锂离子浓度下(x(Li/Ti)≤ 0.25),相比于无缺陷的TiO₂-B,氧缺陷TiO₂-B有着更高的插入电压和更低的b轴方向迁移活化能,意味着锂离子的嵌入也更容易,这对于可充电电池的充电过程是有利的。而在高浓度下(x(Li/Ti) = 1),锂饱和的氧缺陷TiO₂-B相较于无缺陷的TiO₂-B有着较低的插入电压,更有利于锂离子的脱嵌过程,这对于可充电电池的放电过程也是有利的。电子结构计算表明缺陷材料的禁带宽度在1.0-2.0 eV之间,低于无缺陷的材料的3.0 eV。主要态密度贡献者是Ti-Ov-3d,并且随着氧空穴的增加它的强度也变得更强。这就表明氧缺陷TiO₂-B有更好的电子导电性。     

ON THE MECHANISM OF QUENCHING OF SINGLET OXYGEN IN SOLUTION

Abstract— Bimolecular rate constants for the quenching of singlet oxygen O*₂(¹Δ_g), have been obtained for several transition-metal complexes and for β-carotene. Laser photolysis experiments of aerated solutions, in which triplet anthracene is produced and quenched by oxygen, yielding singlet oxygen which then sensitizes absorption due to triplet carotene, firmly establishes diffusion-controlled energy transfer from singlet oxygen as the quenching mechanism in the case of β-carotene. The efficient quenching of singlet oxygen by two trans-planar Schiff-base Ni(II) complexes, which have low-lying triplet ligand-field states, most probably also occurs as a result of electronic energy transfer, since an analogous Pd(II) complex and ferrocene, which both have lowest-lying triplet states at higher energies than the O*₂(¹Δ_g), state, quench much less effectively.     

Desorption kinetics of surfactants at fluid interfaces by novel coaxial capillary pendant drop experiments

Surfactants appear in multiphase fluid systems in which the interface and the adjacent bulk phase have been removed from equilibrium. Here, a new method is described for the measurement of rate constants of desorption of surface-active materials from fluid/fluid interfaces and the extent to which adsorption is reversible: the coaxial capillary pendant drop experimental technique.

Kinetic constants are determined by desorption experiments in pendant drops in which the interface adjacent to a surfactant solution is removed from equilibrium by replacing the subphase of the drop with pure water. Further, we demonstrate that although the rate of subphase exchange is comparatively slow with respect to the desorption timescale, it is possible to resolve desorption processes which occur under local equilibrium with the adjacent bulk phase from those that are determined in part by sorption kinetics. Experiments which measure the desorption kinetic coefficient, , using a homologous series of n-alkyl (C₈, C₁₀, C₁₂, C₁₄) dimethyl phosphine oxides are presented.     

The effect of electrolyte on ionic surfactant adsorption

For submicellar solutions of ionic surfactants rigorous thermodynamic expressions are presented which show that the surfactant adsorption will not depend on electrolyte concentration c₃ at constant surfactant concentration c₁, if there is no corresponding dependence on c₁ at constant c₃. Results which indicate otherwise are inconsistent with thermodynamics.     

A MICROSECOND KINETIC STUDY OF THE PHOTOGENERATED MEMBRANE POTENTIAL OF BACTERIORHODOPSIN WITH A FAST RESPONDING DYE

Abstract— Bacteriorhodopsin is a light activated proton pump which generates proton and electric gradients across the cytoplasmic membrane of Halobacterium halobium. In this study, a dye whose fluorescence intensity responds rapidly to membrane potential was used to follow the evolution of the potential on liposomes reconstituted with bacteriorhodopsin, in the microseconds time domain. By comparing the formation kinetics of the potential to those of the long-lived intermediate species in the bacteriorhodopsin photocycle, M₄₁₂, both in H₂O and ₂H₂O suspensions, we can draw the following conclusion: the electric potential onset time is 20 μs after initiation of the illumination. The triggering of the potential is not the formation of the M₄₁₂ intermediate, which was hitherto considered to be the first species in the bacteriorhodopsin cycle which has an unprotonated Schiff base linkage at the retinal chromophore. Rather, the potential forms at the transition of the L₅₅₀ intermediate to the species X which precedes M₄₁₂ or even at the preceding conversion of K₅₉₀ to L₅₅₀.     

V_2O_5/Ti-Ce-PILC在H_2S选择性催化氧化过程中的催化性能

合成了TiO_2-CeO_2柱撑黏土负载V_2O_5催化剂,通过XRD、氮气吸附脱附、TG、FT-IR、H_2-TPR、NH_3-TPD、XPS等方法对其物理化学性质进行了表征,研究了该催化剂在H2S选择性催化氧化反应中的活性。结果表明,负载5%V_2O_5的TiO_2-CeO_2柱撑黏土在180℃下催化效果最好,且尾气中不含SO_2。V_2O_5、TiO_2和CeO_2之间的相互作用提高了催化剂的活性,CeO_2提高了催化剂的热稳定性,同时提供大量晶格氧,加强了V_2O_5的氧化还原作用,降低了反应温度;TiO_2加强了VO_x和CeO_x的再氧化,降低了硫酸盐的覆盖率,从而降低了催化剂的失活速率。     

REINVESTIGATION OF THE PHOTOPHYSICS OF 2-(2'-HYDROXY-4'-DIETHYLAMINOPHENYL)BENZOTHIAZOLE

Abstract— The photophysical properties of 2-(2'-hydroxy-4'-diethylaminophenyl) benzothiazole (HABT) have been investigated by steady-state and time-resolved spectroscopies. In n-heptane HABT exhibits both normal and tautomer emissions with ∼equal fluorescence intensity at room temperature, in contrast to a previous report in which negligible tautomer emission was observed. The normal/tautomer (400/500 nm) ratio of emission intensity increases as the temperature decreases. Two possible excited-state intramolecular proton transfer (ESIPT) mechanisms are proposed, which cannot be resolved at the present stage. One proposed mechanism incorporates state mixing between -OH and -N(C₂H₅)₂ charge transfer states, resulting in a significant energy barrier for ESIPT. An alternative mechanism is also proposed in which fast proton tunneling may take place between enol and keto forms, which are in equilibrium in the excited singlet state.     

Stereochemical patterns in bromofullerenes C60Br2 to C60Br12

The stabilities of different isomers of C₆₀Br_n have been calculated for n = 2 to 12. A general stereochemical pattern which emerges is the tendency to form strings created by the edge sharing of C₆Br₂ hexagonal faces. Stable structures are formed if these strings form loops, thereby eliminating string ends, which may involve the creation of C₆Br₃ hexagonal faces. A particularly stable structure is formed at C₆₀Br₆ in which the loop forms a C₁₀Br₆ fragment with a pentagonal pyramidal arrangement of six bromine atoms. Two isomers of C₆₀Br₁₂ are also particularly stable. One isomer contains two of these Br₆ pentagonal pyramids on opposite sides of the molecule, and the other isomer contains a single large loop wrapped around the middle of the molecule.     

Filling of antibonding orbitals—II Chemical bond properties

Antibonding effects, which accompany double-bonding in saturated compounds, account for many chemical bond lengths which are anomalous on the basis of electronegativity. Double-bonding influences the Pauling Electronegativity values of N, O, F, Al and Si and also widens the interbond angles in molecules such as (CH₃)₃N, (CF₃)₃N, (CH₃)₂O and (CF₃)₂O.     

Radiofrequency Irradiation Mitigated UV-B-Induced Skin Pigmentation by Increasing Lymphangiogenesis

Dermal macrophages containing melanin increase skin pigmentation since dermal melanin removal is slower than epidermal melanin removal. Lymphatic vessels are also involved in melanin clearance. We evaluated whether radiofrequency (RF) irradiation induced an increase in HSP90, which promotes lymphangiogenesis by activating the BRAF/MEK/ERK pathway and decreasing tyrosinase activity, in the UV-B exposed animal model. The HSP90/BRAF/MEK/ERK pathway was upregulated by RF. Tyrosinase activity and the VEGF-C/VEGFR 3/PI3K/pAKT1/2/pERK1/2 pathway, which increase lymphangiogenesis, as well as the expression of the lymphatic endothelial marker LYVE-1, were increased by RF. Additionally, the number of melanin-containing dermal macrophages, the melanin content in the lymph nodes, and melanin deposition in the skin were decreased by RF. In conclusion, RF increased HSP90/BRAF/MEK/ERK expression, which decreased tyrosinase activity and increased lymphangiogenesis to eventually promote the clearance of dermal melanin-containing macrophages, thereby decreasing skin pigmentation.     

锂离子电池正极材料LiCoO2的制备新方法

利用电解金属钴制得Co(OH)_2-2xR_x(其中R为有机酸和无机酸根离子)中间产物,然后根据钴含量与LiOH·H₂O)固相反应制得了LiCoO₂.通过X光衍射,扫描电镜以及激光粒度测试表明,所得的锂离子正极材料LiCoO₂结构纯正,粒度分布集中,比表面积较大:对其进行充放电实验表明,放电容量比较高,首次放电容量达到146mAh/g,循环10次后容量仍保持在142mAh/g.该法可大大降低制备LiCoO₂的生产成本,具有十分广阔的应用前景.     

STRUCTURE OF HYPSORHODOPSIN: ANALYSIS BY FOURIER TRANSFORM INFRARED SPECTROSCOPY AT 10 K

Abstract— Vibrational bands of hypsorhodopsin in the difference Fourier transform infrared spectra were identified as the bands which arose after formation of isorhodopsin by successive irradiations of bovine rhodopsin at 10 K with >500 nm light, and also as the bands disappeared upon conversion to bathorhodopsin by warming. The chromophore bands were assigned by the bands which shifted upon deuterium substitution of the polyene chain of the retinylidene chromophore. The presence of chromophore bands which shift by D₂O exchange clearly shows that the Schiff base chromophore of hypsorhodopsin is protonated. The amide I bands and several other protein bands of hypsorhodopsin appeared at the same frequencies as those of bathorhodopsin, but they are different from those of rhodopsin and isorhodopsin. Furthermore, like bathorhodopsin, hypsorhodopsin displays the C_l—H out-of-plane bending mode which is weakly coupled with C₁₂-_-–H out-of-plane mode. These facts show that hypsorhodopsin has a chromophore conformation and chromophore-opsin interaction more similar to bathorhodopsin than to rhodopsin and isorhodopsin.     

Thermal behaviour of bromine-metal fire retardant systems

Chemical reactions which occur on heating fire retardant mixtures of decabromodiphenyloxide (DBDPO) with antimony trioxide (AO) or bismuth carbonate (BC) have been studied by means of weight loss, elemental analysis, X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive system (EDS) microanalysis.

It has been shown that on rapid heating to 700°C, DBDPO volatilisation competes with debromination by AO or BC leading to volatile SbBr₃ or BiBr₃ which are formed by different mechanisms. BC is rapidly transformed into BiOBr which gives BiBr₃ by further debromination of DBDPO. At high conversion (high temperature) this process is in competition with reduction of BiOBr to metallic bismuth. In the case of AO slower formation of progressively bromine-richer antimony oxybromides takes place which liberates SbBr₃ by thermal degradation.

The formation of a rod-shaped Br-Sb containing phase is shown to relate to the progression of chemical reactions which occur on heating the AO-DBDPO mixture.     

Carboxylate-induced Various Structures of Ni(II) Complexes with Fluorescence Sensing and Bifunctional Electrochemical Properties

We synthesized three new Ni(II) coordination polymers [Ni(LXHLPXH2O)2]- H2O(CP1),[Ni(LXNIP)]-2H2O(CP2) and [Ni(LXNDCXH20)2](CP3)[L=N,N′-bis(pyridme-3-yl)thiophene-2,5-dicarboxamide, H2HIP=5-hydroxyisophthalic acid, H2NIP=5-nitroisophthalic acid, H2NDC=2,6-naphthalenedicarboxylie acid] by hydrothermal method, which were characterized by means of infrared spectra(IR), TG analyses, PXRD and single-crystal X-ray diffraction. The CPI is a ID tubular structure based on [Ni-HIP]2 loops and pairs of L ligands. CP2 is a 2D 3,5-connected architecture, which consists of Ni-L linear chains and (Ni-NIP)2 double chains. CP3 is a 2D network, which features 4-connected topology. Solid-state luminescent behaviours of CP-P3 were investigated. The CPI can detect Fe^3+ ions through luminescence quenching. The electrochemical properties of CPI buk-modified carbon paste electrode(CP1-CPE) has also been investigated, which has bifunctional electrocatalytic activity for oxidation of ascorbic acid and reduction of NO2^-.     

纳米ZrO2在O2/H2气中的表面效应

用ESR方法研究了一种纳米ZrO₂在普通H₂气中升温条件下的表面效应.ZrO₂上Zr³⁺的中心量约为1×10^-7mol/g.这些Zr³⁺中心是ZrO₂表面一些O^2-配位不饱和的Zr原子点位.在普通H₂气中,ZrO₂上的Zr³⁺中心数在温度低于400℃时变化很小.但在这一温度范围内从室温升温时,由ZrO₂表面羟基的H₂还原引起的F中心量随温度的升高而增加.温度高于400℃时,ZrO₂表面的Zr³⁺及F中心可与普通H₂气中存在的少量O₂气作用产生O₂^-,并伴随ZrO₂表面羟基的脱除而形成新的Zr³⁺.     

QUENCHING OF THE EXCITED STATES OF 2-PHENYLBENZOXAZOLE BY AZIDE ANION. FLUORESCENCE AND ESR STUDY

Electron spin resonance, spin-trapping and fluorescence techniques demonstrate that 2-phenylbenzoxazole (P) participates in photo-induced reactions with alcohols and electron donors like the azide ion. Irradiation of Pat 300 nm in deaerated ethanol produces ethoxyl and hydroxyethyl radicals which can be detected with the spin trap, 5,5-dimethyl-l-pyrroline-l-oxide (DMPO). However, irradiation of P in the presence of N^-₃ leads to the appearance of the azide radical, N^-₃, which also reacts with DMPO. Studies with the nitroxyl radical, 2,2,6,6-tetramethylpiperidine-l-oxyl (TEMPO), suggest that electron transfer from the azide anion to an excited state of P yields the semi-reduced sensitizer, P^-, which in turn reacts with TEMPO. The effect of sodium azide upon the fluorescence intensity and lifetime of P in aqueous ethanol has also been studied.     

高硅煤中Si-Al-Fe-Ca四元体系碳热反应研究

研究了不同温度条件下高硅煤中矿物组成比例下的Si-Al-Fe-Ca多元体系的碳热反应以及其影响因素。通过XRD和FESEM-EDS技术对各还原产物进行分析。结果表明,Fe_2O_3对含硅矿物的碳热反应起促进作用,Fe可以有效提高Si反应活性。CaO在较低温度时与灰中的Al_2O_3和SiO_2反应形成致密的Ca-Al-Si相共熔体CaAl_2Si_2O_8,阻碍含硅矿物碳热反应的进行。随着温度的升高,继续反应生成SiC、CaAl_4O_7和CaSiO_3。热力学模拟计算与实验结果基本吻合。