Adsorption isotherms for the system n-heptane/ethanol/HDPE

The equilibrium isotherms for the adsorption of n-heptane and ethanol on high density polyethylene (HDPE) are reported at 27–110°C and at 20–100 mmHg.

The experimental apparatus and procedures are described for three methods, namely flow, static and chromatographic.

The obtained results are discussed on the basis of the Henry law for adsorbates at low coverage on solids.     

从大木尺度现象看柳林香严寺毗卢殿建造年代之复杂性*

采用共沉淀法制备了高分散80%Ni/Al_2O_3催化剂,经350℃焙烧,得高分散NiO/Al_2O_3(NiO粒径～3 nm),将其以CS_2硫化(310℃, 4 h)或PPh_3磷化(320℃, 36 h),分别获得了高分散的硫化镍(Ni_3S_2和Ni_3S_4, 5.8 nm)和Ni_2P(7.0nm),在二苯并噻吩(DBT)的加氢脱硫(HDS)反应中, Ni_2P的活性远高于NiS_x(360℃时DBT的转化率分别为100%和75%).若将NiS_x用PPh_3磷化,则NiS_x全部转化为Ni_2P(13.3 nm),其HDS活性远高于原来的NiS_x且与直接磷化获得的Ni_2P(7.0 nm)相当.反之,若将Ni_2P用CS_2硫化,则Ni_2P物相不变,粒径也没有长大,表明Ni_2P物相远比NiS_x稳定,且其HDS活性高于直接磷化的Ni_2P,表明其Ni_2P表面可能生成了HDS活性更高的某种Ni-P-S物种.     

Exploiting the complementary nature of LC/MALDI/MS/MS and LC/ESI/MS/MS for increased proteome coverage

The goal of this work was to evaluate the improvement in proteome coverage of complex protein mixtures gained by analyzing samples using both LC/ESI/MS/MS and LC/MALDI/MS/MS. Parallel analyses of a single sample were accomplished by interfacing a Probot fractionation system with a nanoscale LC system. The Probot was configured to perform a post-column split such that a fraction (20%) of the column effluent was sent for on-line LC/ESI/MS/MS data acquisition, and the majority of the sample (80%) was mixed with a matrix solution and deposited onto the MALDI target plate. The split-flow approach takes advantage of the concentration sensitive nature of ESI and provides sufficient quantity of sample for MALDI/MS/MS. Hybrid quadrupole time-of-flight mass spectrometers were used to acquire LC/ESI/MS/MS data and LC/MALDI/MS/MS data from a tryptic digest of a preparation of mammalian mitochondrial ribosomes. The mass spectrometers were configured to operate in a data dependent acquisition mode in which precursor ions observed in MS survey scans are automatically selected for interrogation by MS/MS. This type of acquisition scheme maximizes the number of peptide fragmentation spectra obtained and is commonly referred to as shotgun analysis. While a significant degree of overlap (63%) was observed between the proteins identified in the LC/ESI/MS/MS and LC/MALDI/MS/MS data sets, both unique peptides and unique proteins were observed by each method. These results demonstrate that improved proteome coverage can be obtained using a combination of these ionization techniques.     

Fe/Co和Ni/Co镍黄铁矿型析氢反应电催化剂

作为析氢反应的电催化剂,富金属的过渡金属硫化物因能克服富硫金属催化剂所存在的如导电性有限和缺乏必要的纳米结构等不足,近年来受到越来越多的关注.本文介绍了具有镍黄铁矿型结构的三元富金属硫化物复合材料FexCo9-xS8和Ni_yCo_9-yS₈(x=y=0-4.5)的合成、表征及其电催化研究.首先,研究了二元钴化合物Co₉S₈中Co逐步被Fe或Ni取代直至4.5当量的变化过程.硫镍铁矿复合物中组分的变化有助于不同温度下酸性介质中的质子还原.其次,在还原电催化条件下,复合物中元素化学计量变化对其电化学活化/失活行为有决定性的影响.与Co₉S₈相比,Co缺陷复合材料表现出了更高的HER性能.Ni/Co化合物通常表现出比类似结构Fe/Co化合物更高的电催化析氢活性.     

Measurements and predictive models for the N-methyl-2-pyrrolidone/water/methanol system

This work reports on the properties and structure of N-methyl-2-pyrrolidone in binary and ternary liquid mixtures with water and/or methanol. A comprehensive set of thermophysical properties have been measured at 298.15 K and 0.1 MPa over the whole composition range. On the basis of the derived excess and mixing properties, the fluid structure was analyzed by looking into the forces and geometry factors that effectively control the mixture behavior. Application of the inverted Kirkwood-Buff theory provides a reasonable link between the macroscopic properties and the microscopic features. A density functional theory computation was carried out to analyze the structure and energy features of the hydrogen bonded complexes formed between the components. Use of semiempirical models in the framework of molecular-based equations of state according to the PC-SAFT approach led to unsatisfactory predicted thermophysical properties. The conclusions arrived at give away the existence of strong heteroassociations and hydrogen bonding self-associations that determine the complex nature of the fluid structure.     

PVTx relationships and solid-liquid equilibria for the m-xylene-p-xylene system under high pressures

PVTx relationships of the m-xylene-p-xylene system have been measured with a glass piezometer at 283.15 and 298.15 K and pressures up to 200 MPa, or up to the point of solidification of m-xylene where this occurred at a lower pressure. Freezing pressures of m-xylene were observed as a discontinuity in the volume at increasing pressure. Approximate solid-liquid equilibria under high pressures were obtained from the freezing pressure measurement. The Carnahan-Starling-van der Waals (CS-vdW) equation of state was used to correlate the PVTx data. The solid-liquid equilibria under high pressures were calculated with the CS-vdW equation of state for the liquid phase and a simple equation of state for the solid phase. In order to test the validity of the calculation method, the solid-liquid equilibrium relationships of the benzene-cyclohexane system were also calculated. It was found that the solid molar volume should be treated as a function of temperature and/or pressure to fit the experimental data.     

铂-氢钨青铜电极的制备及对氢氧化的电催化

采用电化学还原法在表面改性的碳布上,通过改变催化剂沉积顺序及氢钨青铜沉积时间制备铂-氢钨青铜复合催化剂,所得电极作为质子交换膜燃料电池(PEMFC)阳极。利用X射线衍射(XRD)、热重分析(TG)、扫描电子显微镜(SEM)、循环伏安(CV)及单电池极化性能测试研究了催化剂的组成、沉积量、分散性及其对氢氧化的电催化活性。实验结果表明,氢钨青铜沉积时间及催化剂沉积顺序对电极催化性能有显著影响,当氢钨青铜沉积时间为10 min,先沉积氢钨青铜、后沉积铂所得Pt/HxWO3电极对氢氧化具有最佳的催化活性。适量的氢钨青铜才能与铂形成较好的协同催化效应。     

Hm and Vm thermodynamic surfaces for binary mixtures in the near critical region

Even for such simple mixtures as (argon+methane), the excess enthalpy H^E_m and the excess volume V^E_m in the near critical region are about two orders of magnitude higher than for the liquid mixture at low temperatures and pressures near ambient conditions. Mixtures for which the critical temperatures are close together, and for which the critical pressures are far apart, have similar H^E_m (x,p,T) and V^E_m (x,p,T) surfaces, and near critical isotherms show double maxima in the supercritical fluid region. Mixtures for which the critical pressures are close together, and the critical temperatures are far apart, also have similar H^E_m (x,p,T) and V^E_m (x,p,T) surfaces, but isobars on the surfaces are ‘S’ shaped. The shapes of these near-critical excess-function surfaces can be understood from an inspection of the enthalpy, or residual enthalpy curves of the mixture and of the pure components. Examples of both are given. Attention is drawn to the large value that these excess functions can have close to a pure component critical point.     

TG/DTG/DTA for the oxidation behavior characterization of vegetable and animal fats

TG/DTG/DTA curves can be used to estimate alimentary fats quality and antioxidants insertion efficiency. Sunflower oil obtained from Carnia hybrid and pork lard were used as matrices for the non-isothermal measurements. The first stage of non-isothermal decomposition is mostly important for the characterization of the fats thermal stability. The corresponding onset temperature is a good value for the comparison of different fats thermal stability or for the effectiveness evaluation in case of antioxidant insertion. In this study, it can be seen a considerable improvement of the fats thermal stability by adding small amounts from a natural antioxidant liquid mixture (obtained by alcoholic maceration of equal amounts of seven plants, namely: milfoil, rosemary, marjoram, thyme, lovage, oregano, and basil). Chlorophylls removal from the plant extract using two different adsorbents was accompanied by a four time decrease of the antiradical activity (measured by the DPPH method) with Sephadex LH20 and seventeen times decrease when activated carbon was used.     

Ring-closing metathesis for the synthesis of 2H- and 4H-chromenes

Six 4H-chromenes were synthesized from substituted phenols using vinylstannylation and ring-closing metathesis (RCM) as key steps. In addition, a different approach involving amongst other steps, an aryl allyl isomerization and RCM afforded a set of seven 2H-chromenes from phenolic precursors.     

SOS-LUX- and LAC-FLUORO-TEST for the quantification of genotoxic and/or cytotoxic effects of heavy metal salts

The constantly increasing industrial, agricultural and domestic activities with their growing risk of contaminating fresh water and ground water by discharged compounds lead to an increasing concern focused on the quality of water. Because of their simplicity and sensitivity, bacterial tests play an important role in the detection and screening of genotoxins or cytotoxins in water.One of those bacterial tests is the SOS-LUX- and LAC-FLUORO-TEST, which is a combination of two bioassays, that simultaneously measures the genotoxicity (SOS-LUX-TEST) and the cytotoxicity (LAC-FLUORO-TEST) of substances and mixtures of substances.The SOS-LUX-TEST is based on genetically modified Salmonella typhimurium TA1535 bacteria, which have been transformed with the plasmid pPLS-1 carrying the promoterless lux operon of Photobacterium leiognathi as reporter element under the control of a DNA damage-dependent SOS promoter from ColD as sensing element. This system reacts in a dose-dependent manner to agents which induce DNA damages inside these bacterial cells with the production of bioluminescence that can easily be measured.The analogous LAC-FLUORO-TEST has been developed for the detection of cellular responses to cytotoxins. It is based on the constitutive expression of green fluorescent protein (GFP) mediated by the bacterial protein expression vector pGFPuv (Clontech, Palo Alto, USA). In response to cytotoxic agents, this system reacts with a dose-dependent reduction of GFP-fluorescence.A panel of recombinant S. typhimurium strains carrying either the SOS-LUX plasmid or the fluorescence-mediating lac-GFPuv plasmid was used to determine in parallel on one microplate the genotoxic and the cytotoxic potential of heavy metal salts like K₂Cr₂O₇, CrCl₃, ZnSO₄, CuSO₄, NiSO₄, KH₂AsO₄ and As₂O₃ at the same time. Light and fluorescence emission of untreated and chemical-treated cells were measured in a microplate luminometer-fluorometer-photometer combination and the luminescence induction as well as the fluorescence reduction were used to determine the genotoxic and/or cytotoxic potential of the heavy metal salts.     

CGC/AED and CGC/ECD/NPD comparison for the determination of acaricides in honey after hexane/acetone extraction

Summary The performance of a gas chromatographic system coupled to an atomic emission detector (GC/AED) is tested by comparison with a two-dimensional gas chromatographic system equipped with capillary columns of different polarity and simultaneous electron capture and nitrogen-phosphorus detection (ECD/NPD), for the determination of the acaricides chlordimeform, bromopropylate, amitraz and coumaphos on spiked honey samples. The acaricides were extracted with ann-hexane/acetone mixture (8020, v/v) with a further clean-up step on an octadecylsilane cartridge. The 193 nm carbon emission line is the best choice in terms of sensitivity whereas the ECD/NPD system gives better selectivity.     

Applications of LC/ESI-MS/MS and UHPLC/Qq-TOF-MS for the determination of 141 pesticides in tea

This paper presents the applications of LC-electrospray ionization (ESI)/MS/MS and ultra-HPLC (UHPLC)/ESI quadrupole (Qq)-time-of-flight (TOF) MS for the determination of 141 pesticides in tea. Pesticides were extracted and cleaned up from tea with a modified quick, easy, cheap, effective, rugged, and safe method using graphitized carbon black and primary-secondary amine sorbents. Quantification was achieved using matrix-matched standard calibration curves with isotopically labeled standards or a chemical analog as internal standards in an analytical range from 5 to 500 microg/kg. The LC/ESI-MS/MS served as a reliable tool to quantify the pesticides due to its superior sensitivity and good repeatability. Its method performance characteristics that include overall recovery, intermediate precision, and measurement uncertainty were evaluated according to a statistically designed experiment, i.e., a nested design. About 87% of the pesticides had recoveries between 81 and 110%; 94% had an intermediate precision < or = 20%; and 90% showed measurement uncertainty < or = 40%. About 92% of the pesticides were able to be detected at 5 microg/kg with an S/N > or = 3. The UHPLC/Qq-TOF-MS showed much less sensitivity and poorer repeatability compared to the LC/ESI-MS/MS, and, therefore, it was primarily used for confirmatory purposes based on the accurate mass measurement and isotopic patterns.     

非整比Li4-xTi5SnyO12化合物的合成及电化学性能的研究

采用流变相法合成了锡掺杂的非整比锂钛氧尖晶石化合物,并研究了不同比例的Sn髧离子掺杂对锂钛氧尖晶石结构及性能的影响。采用XRD、SEM技术对合成材料的晶体结构和微观形貌进行表征,采用恒流充、放电系统及交流阻抗测试法对合成材料的电化学性能进行了测试,结果表明:Sn髧离子掺杂在一定程度上改善了锂钛氧尖晶石作为负极材料时,不同的掺杂量,对材料的电化学性能影响不同,其中Li4-xTi5Sn0·3O12材料的性能为最佳,当电池在较低电流密度下(50 mA·g-1)充、放电时,Li4-xTi5Sn0·3O12材料的首次放电比容量为236 mAh·g-1,在随后提高充、放电倍率过程中(由1C增到4C进行充、放电),当循环105次后,Li4-xTi5Sn0·3O12材料的放电比容量仍保持在109.8 mAh·g-1,与纯样品或其它非整比掺杂样品锂钛氧尖晶石比较,Li4-xTi5Sn0·3O12表现优良的电化学循环性能。本文还对锡掺杂导致锂钛尖晶石材料性能改善的原因也进行了初步探索。     

Hyphenated HPLC/ICP-MS and HPLC/ICP-OES techniques for the characterization of metal and non-metal species

Ion-pair and ion-exchange chromatography were used for the separation of model substances like metal-EDTA and metal-peptide complexes. Real samples like food extracts and human serum were separated by size-exclusion chromatography. The HLPC/ICP coupling was simply realized by connecting the column outlet of the chromatographic system with the nebulizer of the element specific detection systems ICP-OES and ICP-MS, respectively. In food extracts a correlation was found between zinc and sulfur as well as between copper and phosphorus; all measured metals were exclusively present in the 10–14 kD range. Copper in the 68 kD region was found to be correlated with sulfur in serum.Dedicated to Prof. Dr. Wilhelm Fresenius on the occasion on his 80th birthday     

Structures and phase diagram for the system CaTiO3-La2/3TiO3

High-resolution neutron and synchrotron X-ray powder diffraction have been used to examine various compositions across the system (1−x)CaTiO₃−xLa_2/3TiO₃. The structures at room temperature were determined according to composition: in Pbnm for 0?x?0.5, Ibmm for 0.5<x<0.7, then I4/mcm for 0.7?x<0.9, and finally in Cmmm for x?0.9. Although the four structures are the same as those proposed previously in an X-ray diffraction study, the phase boundaries are somewhat different, in particular the Pbnm↔Ibmm phase boundary has been extended from x?0.4 to x>0.5 in the current study based on our high-resolution neutron diffraction data. From in situ measurements to identify structures above room temperature, an approximate composition-temperature phase diagram has been constructed, involving four temperature-induced phase transitions: Pbnm→I4/mcm, Ibmm→I4/mcm, I4/mcm→Pm3¯m and Cmmm→P4/mmm.     

Chitosan/anionic surfactant complex membranes for the pervaporation separation of methanol/MTBE and characterization of the polymer/surfactant system

For the separation of methanol/MTBE (methyl tert-butyl ether) mixtures, methanol selective chitosan composite membranes were prepared and tested for pervaporation experiments. When anionic surfactants are added into the cationic chitosan solution, the solution viscosity was drastically decreased due to the collapsed chain conformation. Pervaporation characteristics of surfactant modified chitosan membrane were substantially improved due to the decreased membrane thickness and possible enhanced affinity to methanol. Rheological data of the casting solution was measured using viscometer and the surface morphology of the surfactant complexed chitosan membrane was investigated by atomic force microscopy (AFM).     

Structure/Property Relationships for Polyamide 6 / Organoclay Nanocomposites in the Melt and in the Solid State

Commercial nanocomposites of polyamide 6 prepared by melt compounding with organoclays were characterized by complex viscosities and relaxation time spectra derived from storage and loss shear moduli measured in the melt state at 230°C, and by wide- and small-angle X-ray scattering, differential scanning calorimetry and stretching calorimetry in the solid state. In the melt state, the decrease of ∼ 25 % (compared to the pristine sample) in Newtonian viscosity at the lowest clay loading (2.5 %) suggested a lower equilibrium elasticity modulus of an entangled melt, as the small amounts of organoclay nanoparticles acted as specific “diluents” for the initial entanglement network. However, by increasing the clay loading this effect disappeared due to the importance of strong interactions at the nanoparticle/melt interface, leading to the formation of a fairly thick boundary interphase (BI) around the nanoparticles and ending up in the build-up of an “infinite cluster” of clay nanoparticles coated with BI at the highest (albeit still unusually low) clay loading (7.5 %). In the solid state, organoclay nanoparticles proved to induce the crystallographic α → γ transformation of PA6 , while the matrix crystallinity in nanocomposites remained essentially unchanged. In the range of elastic (reversible) behavior below the apparent yield strains ϵ* , the highest Young's moduli E and the lowest linear thermal expansion coefficients α_L were observed for dried nanocomposites, while the lowest E and the highest α_L corresponded to the moisturized, pristine PA6. The endothermal process of shape distortion of the lamellar crystals was assumed to precede the onset of the exothermal process of lamellar fragmentation in the range of inelastic (irreversible) behaviour of PA6 above ϵ* . The energy balance of the inelastic behaviour of nanocomposites was dominated by the endothermal process of lamellar shape distortion.     

Comparison of GC/MSD and GC/AED for the determination of organotin compounds in the environment

Summary Methods are described for the analysis of environmental samples like water, sediment and suspended matter for the determination of all organotin compounds (OTs) that are currently used as biocides: tributyltin (TBT), triphenyltin (TPT), tricyclohexyltin (TCT) and fenbutatin oxide (FBTO). In water also five degradation products (di and mono substituted analogs) can be determined. Alkylation using a Grignard reagent was used to obtain OT derivatives amenable to gas chromatography (GC). Both methylation and pentylation have been employed for derivatization prior to GC analysis. The present results show that derivatization efficiencies for TPT, TCT and FBTO at trace levels are higher using methylation than pentylation. Detection limits for each type of sample matrix were determined using GC/Mass Selective Detection (GC/MSD) and GC/Atomic Emission Detection (AED). In sediment and suspended matter only tri-substituted OTs (i.e. the parent compounds) could be determined. Detection limits ranged from 0.2 to 10 ng/g dry weight. FBTO, not previously detected in environmental samples, was found at levels of 4 and 11 ng/g in a suspended matter sample and a sediment sample, respectively. In water the OTs and their degradation products were determined at levels of 1–10 ng/l (as tin) using 200 ml water samples.     

N-Halosuccinimide/SiCl4 as general, mild and efficient systems for the α-monohalogenation of carbonyl compounds and for benzylic halogenation

Combinations of N-halosuccinimide and tetrachlorosilane in acetonitrile were found to be efficient systems for the selective α-monohalogenation of carbonyl compounds as well as for benzylic halogenation under mild conditions.