Potential bile acid metabolites. 1. The epimeric 3ϵ,7α,12β-trihydroxy-5β-cholanic acids. Raney nickel as an epimerizing catalyst.

The epimeric 3α,7α,12β- and 3β,7α,12β-trihydroxy-5β-cholanic acids have been prepared. Under ambient hydrogenation conditions with Raney nickel as catalyst the axial 3β-ester ($\text{4b}$) is epimerized to the 3α-compound ($\text{2b}$).     

Effects of polystyrene-encapsulated magnesium hydroxide on rheological and flame-retarding properties of HIPS composites

In this study, polystyrene (PS)-encapsulated magnesium hydroxide (Mg(OH)₂) was successfully prepared by in situ polymerization of styrene on the surface of Mg(OH)₂ in a high-speed mixer. A large amount of PS chemically bonded on Mg(OH)₂ surface was confirmed by means of FT-IR, TGA and SEM. A series of composites of high impact polystyrene (HIPS) were prepared by melt blending in a co-rotating twin-screw extruder. The effects of PS-encapsulated filler on the properties of HIPS composites were studied by SEM, rheology and combustion tests (horizontal burning tests and cone calorimetry). The dispersion and adhesion patterns of PS-encapsulated Mg(OH)₂ in HIPS matrix were investigated through FT-IR and SEM. The experimental results demonstrated that comparing to the composites containing untreated filler, the rheological and flame retardant properties of those containing PS-encapsulated filler were found to be significantly improved. This improvement is mostly attributed to a better dispersion of the encapsulated filler and a strong adhesion between the filler and matrix.     

UO2、UC2和UCO分子的结构和热力学性质

用密度泛函B3LYP方法,计算了UO2、UC2和UCO分子的结构和热力学函数,计算了固体U的振动内能Ev、振动和电子熵Sev,以及U在不同气氛（O2、C2、CO）中形成UO2、UC2和UCO晶体的ΔHfΘ、ΔSfΘ和ΔGfΘ.结果表明,UO2晶体最稳定.     

碘掺杂的3-乙基-5-[2-(3-乙基-2苯并噻唑啉基)亚乙基]罗丹宁的结构与电性能

The merocyanine dye 3-ethyl-5-(2-(3-ethyl-2-benzothiazolinylidene)-ethylidene)-rhodanine (BTER) known as Agfa-10 has been found to have a good photoconductivity as solution cast film. In this paper iodine-doped BTER was obtained by doping with iodine vapor. Its structure was investigated with the following characteristies. 1 The doped iodine had been excited as I_3~- anion. 2 Because the electron located on the sulphur atom was transferred to iodine, the charge transfer complex of (BTER-I_3) formed. 3 During the iodine doping process, BTER changed from α-form to β-modification. These had been identified by X-ray diffraction, VIS-absorption spectra and SEM picture.4 From the volt-Ampere curve obtained from sandwich cell, when E≤2.2×10~(-1) V·cm~(-1), the room temperature electrical conductivity of BTER and BTER-I_3 were found to be 2.22×10~(-10) s·cm~(-1) and 2.6×10~(-7) S·cm~(-1), respectively.     

Spectrophotometric Determination of Zirconium in Monazite Sand

A sensitive spectrophotometric method was developed for the determination of zirconium in monazite sand. The zirconium ion was previously separated from the other interfering elements by a 0.5 M thenoyltrifluoroacetone (TTA)-xylene extraction, then determined with Arsenazo III in 9 M HCl medium. Zirconium reacted with Arsenazo III to form an emeraled green coloured complex having maximum absorbance at 665 nm in 9 M HCl medium. The color was stable for at least 2 hours. Effects of time, HCl concentration, gelatine and various ions have been studied. The system confirms the Beer's law over the concentration range investigated. Optimum condition range for measurement in 1.0 cm quartz cell is 0.1–0.5 μg/ml of zirconium. The molar absorptivity is 1.51×10⁵ liter mole^?1 cm^?1. The metal-ligand ratio of 1:4 was confirmed by Job's Continuous Variation method and the conditional stability constant of Zirconium-Arsenazo III Complex in 4 M HCl and 9 M HCl were also determined by this method.     

Flammability studies of 3-methyl pyridine/water system

In industrial processes, information on the safety property of chemicals is essentially crucial for safe handling during unit operations. Ensuring the safe use of combustible or flammable substances in processes is unlikely without detailed investigations of their flammability characteristics and related hazards. We studied 3-methyl pyridine (3-picoline), e.g., flammability limits (LFL/UFL), maximum explosion pressure (P _max), maximum explosion pressure rise (dP/dt)_max, minimum oxygen concentration (MOC), vapor deflagration index (K _g), and characterized the influence of inert steam (H₂O) on critical parameters for 3-picoline/water mixtures at 270°C, 1 atm, various oxygen concentrations, and vapor mixing ratios (100/0, 30/70, 10/90 and 5/95 vol.%) with a 20-L-Apparatus in simulated conditions, respectively. The results showed that the flammability characteristics of 3-picoline_(aq) all increased with the oxygen concentration. However, as the composition of inert steam increased, the flammability parameters and the degree of fire and explosion hazards were significantly reduced, instead. This study elucidated the flammability properties of 3-picoline mixed with inert steam. The conclusions could be applied to proactively prevent the relevant processes from incurring fire and explosion accidents.     

Optical measurement of the deformation of giant lipid vesicles driven by a micropipet electrode

We investigate the deformation of giant lipid vesicles driven by a micropipet electrode by use of differential confocal microscopy. This optical technique provides nanometer depth resolution without mechanical contact and hence prevents large tension or perforation of the soft membrane. For dipalmitoyl phosphatidylcholine (DPPC) membranes in the gel phase, we observed deformations of several hundreds of nanometers when the driving voltage was about 0.1 V. The voltage and frequency responses of the vesicle deformation can be explained by the balance between the electroosmotic force inside the micropipet and the membrane tension. We also used DPPC:cholesterol vesicles to check the validity of this model. In the fluid phase, however, the deformation is independent of the modulation signal because micrometer-scale thermal fluctuations dominate the membrane motion.     

Mammalian cell growth studiedin situ by fourier transform infrared spectroscopy

Fourier transform infrared techniques were used to monitor mammalian cell growth plated on attenuated total reflection (ATR) crystals. Consistently, the growth kinetics plots generated from the obtained spectra demonstrated a sigmoidal curve representing a sequence of slow, rapid, then tapering cell growth which correlated well with non-spectral cell growth determinations. Significant advantages over traditional methods of measuring cell growth kinetics are demonstrated. The technique has promising potential to be used to study events in areas such as toxicology and cell biology.     

Double-Label Simultaneous Time-Resolved Fluoroimmunoassay of Phenytoin and Phenobarbital

A procedure for the simultaneous time-resolved fluoroimmunoassay for phenobarbital and phenytoin, based on the use of europium- and samarium-labeled haptens, has been investigated. These lanthanide ions are bound to the haptens by means of the anhydride of diethylenetriaminepentaacetic acid. The antibody is immobilized onto immunoplate in which samples are assayed in competitive immunoassay. After the immunoreactions and dissociation with a fluorescence enhancement solution, the fluorescence intensity is measured. The detection limits of the assay are, respectively, 20 ng/ml for phenobarbital and 50 ng/ml for phenytoin. Results obtained with the proposed methods correlate well (CV <10%). The inter-reactions between phenobarbital, phenytoin, and their antibodies are studied.     

Fragmentation processes of methylbutyl trifluoroacetates studied by tandem quadrupole mass spectrometry and isotope labeling

The fragmentation patterns of 3-methyl-2-butyl trifluoroacetate and 2-methyl-2-butyl trifluoroacetate were investigated by GC/MS/MS, with electron impact and collision-induced dissociation, on regular and isotope-labeled (deuterium and ¹⁸O) esters. The atoms found in various fragments could be traced back to specific positions in the parent molecules. In this way, molecular rearrangements potentially occurring during the formation of esters by trifluoroacetolysis of 3-methyl-2-butyl p-toluenesulfonate or trifluoroacetic acid addition to various 2-methylbutenes could be shown. Rearrangements also occurred during the fragmentation, particularly during the expulsion of the small fragments CO, C₂H₄ and F₂CO. For the decompositions of oxygen-containing ions these rearrangements were highly specific. By contrast, alkyl cations lead to fragments that are fully scrambled (statistical label distribution). Alkene radical cations ([C_nH_2n]^{+ ˙}) fragment to daughter ions that are extensively, but less than statistically scrambled. Hydrogen scrambling may also occur in fluoroalkyl cation fragments.