Excess volumes for binary liquid mixtures of methylethylketone with methylene chloride, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene and cyclohexane at various temperatures

Dilatometric measurements of excess volumes V^E have been made for binary liquid mixtures of methylethylketone with methylene chloride (CH₂Cl₂), 1,2-dichloroethane (CH₂ClCH₂Cl) and tetrachloroethylene (CCl₂CCl₂) at 293.15 and 303.15 K, for mixtures of methylethylketone with trichloroethylene (CHClCCl₂) at 298.15 and 308.15 K, and for mixtures of methylethylketone with cyclohexane (c-C₆H₁₂) at 303.15 K. The values of V^E have been found to be highly positive for methylethylketone + c-C₆H₁₂, slightly positive for methylethylketone + CH₂Cl₂ and methylethylketone + CCl₂CCl₂, and slightly negative for methylethylketone + CHClCCl₂ and methylethylketone + CH₂ClCH₂Cl. The results indicate the existence of specific interactions of methylethylketone with CH₂Cl₂, CH₂ClCH₂Cl, CHClCCl₂ and CCl₂CCl₂.     

PHOTOOXIDATION AND ELECTRON-TRANSFER PROCESSES IN FREE-BASE TETRAPHENYLPORPHIN PROBED BY RESONANCE RAMAN SPECTROSCOPY

Abstract
We report here the resonance Raman studies of photooxidation of free base tetraphenylporphin (H₂TPP) in the presence of external electron acceptors such as CCl₄ and chloranil under selective laser irradiation. From the dependence of photooxidation on the concentration of electron acceptors, polarity of solvents, excitation lines and temperatures, we have inferred that a weak triplet exciplex formed between the excited H₂TPP and electron acceptor in non-polar solvents serves as transient species and the light-induced intermolecular charge transfer from H₂TPP to the electron acceptor is the primary process involved in photooxidation. Observation of partial photooxidation in the rigid matrix at low temperatures has been interpreted to be due to long-range quantum mechanical electron tunneling process. Almost complete photooxidation is observed in a soft matrix as the donor and acceptor molecules can attain favorable relative orientation and separation for electron transfer during the excited state lifetime of the exciplex.     

13X分子筛负载Fe催化剂上1,4-二氧六环在空气中完全氧化(英文)

采用浸渍法制备了不同Fe含量的13X分子筛负载的Fe催化剂(Fe/X13),运用N_2吸附-脱附法测得其BET比表面积和BJH孔径分布,采用X射线衍射、扫描电镜、程序升温还原和NH_3程序升温脱附法表征了该催化剂的织构性质.在固定床流动反应器中,以空气为氧化剂、在100-400℃范围内考察了Fe/X13催化剂上1,4-二氧六环的完全氧化反应性能,研究了反应温度、金属担载量和气体空速(GHSV)等条件对催化氧化降解二氧六环反应性能的影响,并在400℃测定了该催化剂反应50h的稳定性,结果表明,6 wt%Fe/13X催化剂表现出最高的催化性能,在400℃,GHSV=24000 h~(-1)的条件下,二氧六环转化率为97%,生成CO和CO_2的选择性达95%,降解产物还包括少量的乙醛、乙二醇-甲酸酯、乙二醇二甲酸、1,4-二氧六环-2醇、1,4-二氧六环-2酮及2-甲氧基1,3二氧戊环.基于这些经色谱-质谱联用仪检测出的产物,提出了可能的1,4-二氧六环降解机理。     

Effect of Salicylic Acid on the Activity of PAL and PHB Geranyltransferase and Shikonin Derivatives Production in Cell Suspension Cultures of Arnebia euchroma (Royle) Johnst—a Medicinally Important Plant Species

Cell suspension cultures of Arnebia euchroma were established from the friable callus on liquid Murashige and Skoog medium supplemented with 6-benzylaminopurine (10.0 μM) and indole-3-butyric acid (5.0 μM). Salicylic acid was used to study its effect on the enzymes which participate in shikonin biosynthesis with respect to metabolite (shikonin) content in the cell suspension culture of A. euchroma. In our study, phenylalanine ammonia lyase and PHB geranyltransferase were selected from the entire biosynthetic pathway. Results showed that phenylalanine ammonia lyase is responsible for growth and PHB geranyltransferase for metabolite production. Salicylic acid exhibited an inverse relationship with the metabolite content (shikonin); salicylic acid (100 μM) completely inhibited shikonin biosynthesis. The results presented in the current study can be successfully employed for the metabolic engineering of its biosynthetic pathway for the enhancement of shikonin, which will not only help in meeting its industrial demand but also lead to the conservation of species in its natural habitat.     

MSn,LC‐MS‐TOF and LC‐PDA studies for identification of new degradation impurities of bupropion

Three new degradation impurities of bupropion were characterized through high performance liquid chromatography coupled to photodiode array detection and to time‐of‐flight mass spectrometry. Bupropion was subjected to the ICH prescribed stress conditions. It degraded to seven impurities (I–VII) in alkaline hydrolytic conditions which were optimally resolved on an XTerra C₁₈ column (250 × 4.6 mm, 5 µm) with a ternary mobile phase comprising ammonium formate (20 mm , pH 4.0), methanol and acetonitrile (75:10:15, v/v). The degradation impurities (III–V and VII) were characterized on the basis of mass fragmentation pattern of drug, accurate mass spectral and photodiode array data of the drug and degradation impurities. Compound V was found to be a known degradation impurity [1‐hydroxy‐1‐(3‐chlorophenyl)propan‐2‐one], whereas III, IV and VII were characterized as 2‐hydroxy‐2‐(3′‐chlorophenyl)‐3,5,5‐trimethylmorpholine, (2,4,4‐trimethyl‐1,3‐oxazolidin‐2‐yl)(3‐chlorophenyl)‐methanone and 2‐(3′‐chlorophenyl)‐3,5,5‐trimethylmorphol‐2‐ene, respectively. Compound III was a known metabolite of the drug. This additional information on the degradation impurities can help in the development of a new stability‐indicating assay method to monitor the stability of the drug product during its shelf‐life as well as in development of a drug product with increased shelf‐life. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of high hydrostatic pressure on to life of the tiny animal tardigrade

Terrestrial tardigrade is known to show very strong anti-environmental character at a dehydrated state called “tun” state. It was reported to be alive after exposed to the hydrostatic pressure of 0.6 GPa, which was almost twice higher than the limit for most bacteria and multi-organisms. However, the limit of the hydrostatic pressure above which tardigrades cannot survive is unknown. We performed an experiment to put tardigrades into high hydrostatic pressure of 7.5 GPa, more than 10-times higher than investigated so far, and convinced that they can survive after exposure to 7.5 GPa for up to 12 h.     

Non-radiative depletion of the excited electronic states of 9-cyanoanthracene in presence of tetrahydronaphthols

Both steady state and time resolved spectroscopic measurements reveal that the prime process involved in quenching mechanism of the lowest excited singlet (S1) and triplet (T1) states of the well known electron acceptor 9-Cyanoanthracene (9CNA) in presence of 5,6,7,8-tetrahydro-1-naphthol (TH1N) or 5,6,7,8-tetrahydro-2-naphthol (TH2N) is H-bonding interaction. It has been confirmed that the fluorescence of 9CNA is not at all affected in presence of 5,6,7,8-tetrahydro-2-methoxy naphthalene (TH2MN) both in non-polar n-heptane (NH) and highly polar acetonitrile (ACN) media. This indicates that the H-bonding interaction is crucial for the occurrence of the quenching phenomenon observed in the present investigations with TH1N (or TH2N) donors and 9CNA acceptor. In ACN solvent both contact ion-pair (CIP) and solvent-separated (or dissociated) ions are formed due to intermolecular H-bonding interactions in the excited electronic states (both singlet and triplet). In NH environment due to stronger H-bonding interactions, the large proton shift within excited charge transfer (CT) or ion-pair complex, 1 or 3(D+-H...A-), causes the formation of the neutral radical, 3(D+H-A)*, due to the complete detachment of the H-atom. It is hinted that both TH1N and TH2N due to their excellent H-bonding ability could be used as antioxidants.     

Electrical properties and EMI shielding behavior of highly thermally stable polyaniline/colloidal graphite composites

A hybrid approach has been adopted by using a combination of colloidal graphite (CG) as a conducting filler, 5‐lithium sulfoisophthalic (LiSIPA) acid as a dopant, and polyaniline (PANI) as a matrix to prepare LiSIPA doped PANI–CG composites. The thermal stability (～300°C) and electrical conductivity (67.4 S/cm at 17.4% CG content) have been improved significantly as compared to PANI doped with conventional inorganic dopants like HCl or H₂SO₄ (130–150°C). The maximum shielding effectiveness value was found to be ?39.7 dB. X‐ray diffraction and infrared spectroscopy showed a systematic shifting of the characteristic peaks and bands with increase in the amount of CG, which indicates significant interaction exists between CG and PANI. The UV–Vis spectra showed the characteristic bands of PANI, with a shift to shorter wavelength with increase in the CG content. The interaction mechanism between doped PANI and CG in the resultant composites has been proposed. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrical conduction mechanism in nanocrystalline CdTe (nc-CdTe) thin films

The present paper reports the electrical characterization of nc-CdTe thin films in different temperature ranges. Thin films of nc-CdTe are deposited on the glass substrates by Physical Vapor Deposition (PVD) using the Inert Gas Condensation (IGC) method. The Transmission Electron Microscopy (TEM) studies are made on the CdTe nanocrystals. The surface morphology and structure of the thin films are studied by the Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) measurements. Dark conductivity measurements are made on the nc-CdTe thin films in the temperature range 110–370 K in order to identify the conduction mechanism in this temperature range. The obtained results reveal three distinct regions at high, low, and sufficiently low temperature regions with decreasing activation energies. The analysis of the high temperature conductivity data is based on the Seto’s model of thermionic emission. At very low temperatures, dc conductivity (σ _d) obeys the law: lnσT ^1/2∝T ^?1/4, indicating variable-range hopping in localized states near the Fermi level. The density of the localized states N(E _F) and various other Mott’s parameters like the degree of disorder (T _O), hopping distance (R), and hopping energy (W) near the Fermi level are calculated using dc conductivity measurements at low temperatures. Carrier type, carrier concentration, and mobility are determined from the Hall measurements. The transient photoconductivity decay measurements are performed on the nc-CdTe thin films at different intensities in order to know the nature of the decay process.     

Local structure of LiCoO(2) nanoparticles studied by Co K-edge x-ray absorption spectroscopy

We have studied the local structure of LiCoO(2) nanoparticles by Co K-edge x-ray absorption spectroscopy as a function of particle size. Extended x-ray absorption fine structure data reveal substantial changes in the near neighbor distances and the associated mean square relative displacements with decreasing particle size. X-ray absorption near edge structure spectra show clear local geometrical changes with decreasing particle size, similar to those that appear in the charging (delithiation) process. The results suggest that the LiCoO(2) nanoparticles are characterized by a large atomic disorder confined to the Co-O octahedra, similar to the distortions generated during the delithiation, and this disorder should be the primary limiting factor for a reversible diffusion of Li ions when nanoparticles of LiCoO(2) are used as cathode material in rechargeable Li ion batteries.