Evaluation of steric and substituent effects in phenols by competitive reactions of dimethyl ether ions in a quadrupole ion trap

Competitive reactions of dimethyl ether ions are used to probe the steric and substituent effects of substituted phenols and anisoles in a quadrupole ion trap. The relative percentages of protonation and methylene substitution from the reactions of dimethyl ether ions show a correlation with size, location, and number of subsrituents on the aromatic ring. Although gas-phase basicity measurements of the phenols show no discernible correlation with the percentages of competitive reactions, semiempirical calculations show a good correlation between the trend in heats of formation and the trend in methylene substitution percentage. Reactions with deuterated compounds show that the methylene substitution reaction occurs on the ring.     

Crystal and magnetic structures of afeIIFeIII(C2O4)3 (A = organic cation): two-dimensional honeycomb ferrimagnets

Ferrimagnetic tris-oxalato-ferrate(II,III) salts with general formula AFeIIFeIII(C2O4)3 (A = quaternary ammonium, phosphonium) all crystallise in two-dimensional hexagonal honeycomb lattices but while some show conventional Néel type Q magnetisation at low temperature others show negative Néet type N magnetisation below a compensation temperature Tcomp. The compounds having negative magnetisation show a discontinuity in the magnetisation at a temperature between Tcomp and Tc suggesting a magneto-strictive transition. For the type Q compounds, hysteresis and frequency dependent AC susceptibility show that the low temperature magnetic state is glassy, either because of frustration of random anisotropy domains below a blocking temperature, or imbalance in the fractions of FeII and FeIII.     

Synthesis of new siloxane urethane block copolymers and their properties

Siloxane urethane block copolymers were prepared with siloxanes as the soft segment. Films were cast from a variety of solvents. Solvent has an effect on the segregation of soft and hard segments. Surface studies, including ESCA, EDS, and FT-IR, show well segregated block copolymers with enhanced siloxane on the surface. DSC studies show a low mp (-44°C) for the soft segment and a T_g for the hard segment above room temperature. These materials show higher thermal stability compared to polyether urethane block copolymers. These copolymers also show relatively good resistance to exposure to oxygen plasma and show improved flame retardancy compared to nonsiliconated, polyether polyurethane block copolymers. © 1994 John Wiley & Sons, Inc.     

分子内电荷转移荧光探针1-酮-2-（对二甲氨基苯亚甲基）四氢萘与人血清白蛋白作用

采用荧光及紫外光谱研究了1-酮-2-（对二甲氨基苯亚甲基）-四氢萘（KDTN）与人血清白蛋白（HSA）相互作用的光谱特性。 结果表明,静态猝灭和非辐射能量转移是导致KDTN对HSA荧光猝灭的主要原因。 测得17、27和37 ℃ 3个温度下的结合常数K_A分别为1.633×10⁸、0.7998×10⁸和0.347×10⁸ L/mol,结合位点数n分别为1.7、1.6和1.7;据Forster偶极 偶极非辐射能量转移理论,计算得到KDTN与HSA在3个温度下的作用距离r分别为2.64、2.59和2.64 nm;能量转移效率E分别为0.5100、0.4797和0.4210。 热力学参数表明,二者主要以范德华力或氢键结合;用同步荧光技术研究了KDTN对HSA构象的影响,结果表明,KDTN的加入对HSA构象影响不大。     

Syntheses and Complexing Properties of Polyethers

Diaza-18-crown-6 with two 8-hydroxyquinolines as side arms show high selective complexing ability with metal ions^[1,2] and with two aminophenols exhibit strange property^[3]. 8 diaza-18-crown-6 ethers containing sidearms^[4] and 7 podands were synthesized. Their complexing ability with metal ions were studied, the results show that they present high complexing capability for metal ions. The polyethers containing 8-hydroquinoline fragment show high selectivities for Hg²⁺,Ni²⁺ and their complexes with Eu³⁺ and Tb³⁺ show strong luminescence.     

二维氢键层状Mg(Ⅱ)配合物的合成、晶体结构及其抗菌活性(英文)

A new complex hexaaquamagnesium(Ⅱ) bis [2-(thiosemicarbazonomethyl)-benzoato],has been prepared and characterized by elemental analysis,IR spectra,molar conductivity and single-crystal X-ray diffraction. The results of crystal structure show that each Mg(Ⅱ) ion is coordinated with six oxygen atoms from water molecules and the complex formed two dimensional layered structure through intramolecule and intermolecule hydrogen bonds. The antibacterial assay of the magnesium(Ⅱ) complex and the ligand were tested using a modified version of the 2-fold serial dilution method,the results show that the complex show considerable antibacterial activity against escherichia coli,bacillus subtilis and staphylococcus white,and the ligand did not show antibacterial activity.     

Molecular Dynamics Simulations and NMR Experimental Study of Oxidized Glutathione in Aqueous Solution

All-atom molecular simulations and NMR experiments have been used to study the conformations and interactions of oxidized glutathione (GSSG) in aqueous solution. The simulations are characterized by the radius of gyration, intramolecular distance, root-mean-square deviation and solvent-accessible surface area. The variations in these properties show time dependences. Interestingly, the two chains connected by the disulfide linkage in GSSG show different flexibilities in aqueous solution. The conformations of GSSG can convert from ??extended?? to ??folded?? states. Also, the two different kinds of amide hydrogen atoms in cysteine (Cys) and glycin (Gly) show different capabilities in forming N?CH?O hydrogen bonds with water molecules. Temperature-dependent NMR results show agreements with the MD simulations.     

Nonlinear optics in quantum confined semiconductor particles

The field of nonlinear optics is dominated by the search for materials which show a large nonlinear optical response. Physical confinement of charge carriers, whether in 1, 2 or 3 dimensions, can greatly enhance the nonlinear optical behaviour. We have studied the nonlinear optical properties of small particles, in the size range 100-10Å which provide 3-D charge confinement. The larger particles are too big to show significant quantum confinement effects. Smaller particles show distinct confinement effects and a large optical nonlinearity.     

氯原子与丙烷反应的准经典轨线研究

氢原子取代反应为化学反应动力学的研究提供了许多有用的信息,人们对这些轻原子转移反应在理论和实验上都进行了大量研究［１］．最近,一些实验对Ｃｌ原子与烃反应提供了直接信息．Ｓｉｍｐｓｏｎ等［２］利用核抽取的方法测量相关态和散射分布来研究Ｃｌ原子与振动激发态...     

Raman, fluorescence, and time-resolved light scattering as optical diagnostic techniques to separate diseased and normal biomedical media.

Studies of Raman scattering, fluorescence and time-resolved light scattering were conducted on cancer and normal biomedical media. Fourier transform Raman spectroscopic measurements were performed on human normal, benign and cancerous tissues from gynecological (GYN) tracts. A comparison of the intensity differences between various Raman modes as well as the number of Raman lines, enables one to distinguish normal GYN tissues from diseased tissues. Fluorescence spectroscopic measurements on human breast tissues show that the ratio of fluorescence intensity at 340 nm to that at 440 nm can be used to distinguish between cancerous and non-cancerous tissues. Separate studies on normal and cancerous breast cell lines show spectral differences. The measurements of back-scattered ultrafast laser pulses from human breast tissues show differences in the scattered pulse profiles for different tissues. These studies show that various optical techniques have the potential to be used in medical diagnostic applications.     

直接乙醇燃料电池PtSn/C电催化剂的合成表征和性能

采用多元醇法制备了n(Pt)/n(Sn)比为2:1,3:1,4:1的PtSn/C电催化剂.通过XRD,TEM、循环伏安和氢化学吸附技术对催化剂进行了表征.TEM和XRD结果表明,不同比例的PtSn/C金属粒子的平均粒径均小于4nm,且粒径分布较窄;该系列催化剂中Pt具有fcc结构;PtSn间的相互作用使Pt晶格参数增大.循环伏安和氢化学吸附实验结果表明,加入Sn可抑制Pt对氢的吸附,Pt3Sn/C对乙醇的氧化电流比Pt4Sn/C高约1倍.用不同n(Pt)/n(Sn)比的催化剂作为直接醇类燃料电池阳极电催化剂,在相同条件下,随着Sn含量的增加,单电池最大输出功率逐渐增大,当Sn含量继续增大时,单池性能反而下降.导致不同比例PtSn催化剂活性差别的原因可能是由于Sn与Pt间的合金化程度不同和催化剂粒子尺寸效应及Sn含量对电池阻抗等几方面因素所致.对40h寿命测试前后的阳极Pt3Sn/C催化剂的分析(EnergydispersiveX-rayanalysis,EDX)结果表明,PtSn含量在测试前后均有所降低,PtSn催化剂的寿命尚有待改善.     

Kinetics of fiber heat treatment. III Poly(butylene terephthalate) fibers

Small- and wide-angle X-ray scattering (SAXS and WAXS), shrinkage, and density experiments were performed on poly(butylene terephthalate) fibers which had been isothermally crystallized at different temperatures, and at constant tension, for times ranging from 100 to 1050 ms. A consistent correlation among WAXS, SAXS, and the kinetic results is demonstrated. Shrinkage results show that the crystallization process prevails over the chain-re-coiling process. Density measurements show that the rate of crystallization increases with temperature. Pinhole X-ray photos show that the orientation of the chains within the crystals remains constant with time and temperature. WAXS diffractometer scans show the development of wide-angle Bragg peaks. SAXS shows the development of small-angle Bragg peaks, as the annealing time is increased. The two-lobe arced pattern is the characteristic pattern. The value for long spacing ranged from 100 to 120 Å, increasing with temperature.     

超顺磁/荧光双功能纳米粒子的合成、表征和生物功能化

通过反相微乳液聚合, 在热解法合成的MnFe2O4纳米粒子表面修饰了一层掺杂有荧光染料(联吡啶钌)的SiO2, 制备了同时具有超顺磁性和荧光特性的双功能纳米粒子. 再通过氨基硅烷的修饰作用, 将该双功能纳米粒子与万古霉素结合, 所得到的生物功能化的纳米粒子表现出很好的对大肠杆菌的识别和磁性分离能力. 本研究制备的超顺磁/荧光双功能纳米粒子具有磁性强、光稳定性高、制备简单、分散性好和尺寸均匀等优点, 可以推断这种新型纳米粒子在生物学、医学和分析化学等领域中将有广阔的应用前景.     

Supramolecular isomerism of a metallocyclic dipyridyldiamide ligand metal halide system generating isostructural (Hg, Co and Zn) porous materials

We show how crystallisation of supramolecular isomers of a dynamic coordination system generates a series of isostructural porous materials. These mercury, cobalt and zinc metallocyclic materials show permanent porosity and exhibit single-crystal-to-single-crystal transformations.     

A polyacrylate prepared using polyurethane surfactants: properties of emulsion and film

The designed polyurethane surfactant (PUS) was used as a macromolecular surfactant for the preparation of polyacrylate emulsion without any other surfactants and stabilizers. The resultant polymer emulsion and film properties were compared with those of the emulsion prepared with sodium dodecyl sulfate (SDS). Long shelf-life of the polymer emulsion can be achieved at proper composition. Polymer particles show core-shell and nano-scale structure with narrow distribution. Thermoanalysis results show phase separation in the polymer film, which leads to gloss decrease with the PUS content increase. Such polymer films show good water resistance and mechanical strength.     

A simple mechanistic model to interpret the effects of narcotics

In this research we will show the advantages of using a time-independent dose metric in a mechanistic model to evaluate toxic effects for different narcotic compounds on different species. We will show how different already existing QSARs can be combined within a mechanistic framework to 1) make predictions of lethal thresholds; 2) show some limitations in the use of existing QSARs; 3) show how a mechanistic framework solves some conceptual problems in current approaches and 4) show how such a framework can be used to be of aid in an experimental setup in predicting the outcome of a survival experiment. The approach we chose is based on the simplest mechanistic model available, a scaled one-compartment model to describe uptake and elimination and hazard model to link the exposure to effects on survival. Within this theoretical framework a prediction for an internal threshold for effects on survival of 3 mmol/kg bw can be made, which should be similar for different species and independent of the partitioning characteristics of the toxicant. To demonstrate this, a threshold for 51 different species was derived, which indeed appeared to lie in a relatively small range, typically between 1 and 10 mmol/kg bw.     

磁性有序介孔炭的制备及药物吸附行为研究

采用纳米共铸法将磁性纳米粒子包埋到有序介孔炭的骨架中, 制成含有磁性纳米粒子的有序介孔炭(Fe/OMCs). 实验通过氮气吸附、扫描电镜、X射线衍射、磁性测试等手段对Fe/OMCs进行了系统的表征. 研究表明, Fe/OMCs基本保持了有序介孔结构, 磁性粒子在材料中以纳米α-Fe粒子的形式存在, 并且具有超顺磁特性. 盐酸四环素(TH)在Fe/OMCs上的吸附研究表明, Fe/OMCs的介孔表面积和介孔孔容是决定TH吸附量的关键因素. 脱附动力学研究表明, Fe/OMCs的孔尺寸是影响脱附速率的关键因素, 孔径越大, TH的脱附速率就越大.     

Photophysical properties of 9,10-disubstituted anthracene derivatives in solution and films

We have carried out absorption, time-resolved fluorescence, and fluorescence quantum yield measurements of four new soluble anthracene derivatives. They show natural radiative lifetimes in the range of 2.5-4.4 ns, which is 5-10 times shorter than those reported for unsubstituted anthracene. The 9,10-bis(phenylethynyl)anthracene (BPEA) derivatives show the largest fluorescence transition dipoles, which is attributed to extended π-conjugation between anthracene and phenyls through acetylene linkages. Spin-cast films of the BPEA derivatives show strong fluorescence quenching by weakly emitting low energy excitations, which is attributed to excimer-like traps. Quenching is significantly reduced when bulky dendrons are attached so that they give maximum coverage of the emitting chromophore and prevent their aggregation. The results show that anthracene derivatives can be developed into efficient solution-processable fluorescent emitters for the blue and green spectral regions.     

Structural,optical and magnetic characterization of ZnO nanorods synthesized using hydrothermal technique at low temperature

Pure ZnO nanorods were grown from aqueous solutions at low temperature (90 °C) by hydrothermal growth technique on sapphire (0001) substrate coated with ZnO thin film. X-ray diffraction results show that these nanorods crystallize in the wurtzite structure having space group P6₃mc and that they are oriented along the c-axis. Raman and photo-luminescence studies show the presence of oxygen vacancies in the ZnO nanorods. The ZnO nanorods show room temperature ferromagnetism.     

Orange-red luminescence from Cu doped CdS nanophosphor prepared using mixed Langmuir-Blodgett multilayers

Cu doped CdS nanophosphors were fabricated through Langmuir-Blodgett route for the first time. Precursors mixed Langmuir-Blodgett multilayers of cadmium arachidate-copper arachidate were used to grow doped sulfide nanoparticles within the organic matrix through postdeposition treatment with H(2)S gas. Changes in composition and layered structure of precursor multilayers were studied using Fourier transform infrared and x-ray reflection. Uptake of Cu in the multilayers was analyzed by inductively coupled plasma atomic emission spectroscopy measurements. Unannealed H(2)S exposed multilayers containing CdS nanoparticles show strong surface state emission centered at approximately 570 nm, whereas Cu doped CdS nanoparticles show orange-red luminescence. Photoluminescence (PL) spectra of annealed-Cu doped CdS nanoparticles show distinct Cu-related emission compared to annealed-undoped CdS nanoparticles. Power dependent PL measurements of annealed samples show that an efficient carrier recombination takes place at T(2) level of Cu(++). The carrier relaxation from the excitonic states to T(2) level results in the strong orange-red luminescence.