VAPOR-LIQUID EQUILIBRIA PREDICTION FOR SYSTEMS CONTAINING UNSATURATED HYDROCARBONS THE UNIFAC MODEL FOR PREDICTING BOILING TEMPERATURE

The original UNIFAC method is used to predict isobaric boiling temperatures for one ternary and twelve binary systems containing isomeric n-alkenes and. n-alkynes as one component. Boiling temperatures are calculated using group interaction parameters available in the literature and determined by the authors. In most cases an agreement between the experimental and predicted values is acceptable for engineering purposes     

'Strain effect' descriptors for ATP and ADP derivatives with modified phosphate groups

Semiempirical AM1 calculations were carried out for quantum chemically optimized conformations of ATP and ADP and their modified phosphate derivatives with the oxygen atoms intervening between phosphorus atoms substituted by imido or methylene groups or the double-bonded oxygen atoms substituted by sulfur. In addition to the calculation of conventional geometric and energetic parameters, the effect of these substitutions was quantified in terms of conformational 'strain energy'. The latter has been defined as the energy of transformation of the parent nucleotide (ATP or ADP) from the optimum conformation to the conformation optimized for its phosphate-modified analog. The results of calculations revealed that conformational 'strain' of phosphate-modified nucleotides depends not only on the nature of the substituent but also on its position. The respective effect had the largest magnitude when the substitution was made between two terminal phosphorus atoms. Given that the 'strain energy' characterizes the geometrical aspects of the interaction of nucleotide molecules with receptors and enzymes, an attempt was made to correlate it with the corresponding biological activities. Such correlation was significant in the case of highly specific binding sites for universal ligands like ATP.     

A tabu search heuristic for the single vehicle pickup and delivery problem with time windows

The single vehicle pickup and delivery problem with time windows is a generalization of the traveling salesman problem. In such a problem, a number of transportation requests have to be satisfied by one vehicle, each request having constraints to respect: a pickup at its origin and a delivery at its destination, and a time window at each location. The capacity of the vehicle has to be respected. The aim is to minimize the total distance traveled by the vehicle. A number of exact and approximate solution methods exists in the literature, but to the authors knowledge none of them make use of metaheuristics, still promising with other vehicle routing problems. In this paper we present tabu search and probabilistic tabu search. Results obtained on classical traveling salesman problems and a class of randomly generated instances indicate that our approach often produces optimal solutions in a relatively short execution time.     

Silver halide photonic crystal fibers for the middle infrared

Photonic crystal fibers are normally holey silica fibers, which are opaque in the mid- and far-infrared. We have fabricated novel fibers by multiple extrusions of silver halide crystalline materials, which are highly transparent in the mid-infrared. These fibers are composed of two solid materials; The core consists of pure AgBr, and the cladding includes AgCl fiberoptic elements arranged in two concentric hexagonal rings around the core. Flexible fibers of outer diameter 1 mm and length of approximately 1 m were fabricated, and their optical properties were measured. These fibers exhibited core-clad behavior and would be extremely useful for IR laser power transmission, IR radiometry, and IR spectroscopy.     

Langmuir monolayers of gold nanoparticles

We report an experimental study of Langmuir monolayers of dodecanethiol-ligated gold nanoparticles with in situ optical microscopy and X-ray scattering. The particle spacing increases with thiol concentration but does not depend on surface pressure. Compression beyond the full coverage of the monolayers causes the monolayers to wrinkle. With the presence of excess thiol molecules, the wrinkles unfold back to monolayer upon the expansion of the surface area. A theoretical model based on van der Waals' attraction and tunable steric repulsion is adopted to explain this reversibility.     

Physico‐chemical,thermal, and mechanical approaches for the characterization of solubilized and solid state chitosans

This study was conducted on the both solid and solubilized chitosans to propose an approach for the physico‐chemical, thermal and mechanical characterizations of this polysaccharide. The polysaccharide used was a 90% deacetylated chitosan having a molecular weight of 98.4 kDa. The flow property of chitosan solutions was evaluated revealing a shear‐thinning behavior. The thermal characterization was carried out by studying heat specific capacity, glass transition temperature, and thermal conductivity on chitosan dried specimens (solid state). Their T_g were measured by DSC and confirmed by DMA at 102 and 122°C depending on concentrations of initial chitosan solutions. The mechanical characterization was conducted by analyzing Young modulus, tensile strength, and elongation at break of chitosan specimens. They exhibited a higher elongation at break and a lower tensile strength when made from high concentrated chitosan solution (9% w/v). Differences in mechanical behavior of specimens were explained by differences of crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41257.     

Trans Fatty Acid Contents in Selected Dietary Fats in the Estonian Market

In response to public concern, this study assessed the fatty acid (FA) composition of blended spreads, margarines and shortenings in the Estonian retail market in 2011. Special attention was paid to the trans fatty acids (TFA) composition. The changes in these characteristics of selected dietary fats in the market over recent years are also presented. Twenty-six edible fat brands, available in the Estonian retail market in 2011, were purchased and FA compositions were analyzed by chromatography. Saturated fatty acids (SFA) were the dominant group of FAs for all blended spreads (49.6 to 65.8%), and for the majority of shortenings (from 21.1 to 54.6%). Cis monounsaturated fatty acids (MUFA) were the dominant group of FAs for the majority of margarines, ranging from 25.3% to 50.5%. The total TFA for blended spreads varied from 1.18% to 9.08%, for margarines from 0.04% to 34.96% and for shortenings from 0.14% to 39.50%. Octadecenoic (C18:1) isomers were the main TFA found. Compared to 2008/2009, the industrially produced TFA (IP-TFA) content in several of the dietary fat brands was much reduced in 2011. This voluntary reformulation was probably a response to consumer demand associated with a public health campaign directed against IP-TFA in Estonian foods, and were mainly achieved by replacing TFA with SFA C12:0-C16:0. Practical Application: Present paper is directed toward public health related institutions and food industries producing foods with potentially high contents of trans fatty acids (TFA). According to the public concern TFA content in domestic blended spreads has declined significantly over the past 3 y in Estonia. The reduction in the TFA content was achieved by replacing TFA with saturated fatty acids (SFA) (C12:0-C16:0). To shift food composition toward healthier product formulations, mandatory labeling of the sum of IP-TFA and SFA (C12:0-C16:0) was recommended.     

Green synthesis,properties, and catalytic application of zeolite (P) in production of biofuels from bagasse

This study reports the technical and economic feasibilities of converting sugar cane residue (bagasse) into biofuel by using novel zeolite (P) catalyst. Using silica gel, aluminum powder, and sodium hydroxide as a precursor material, zeolite (P) has been successfully fabricated by template free hydrothermal synthesis. The as‐prepared catalyst is used for the conversion of sugarcane residue into valuable hydrocarbons by an autoclaving process. The effect of various parameters on catalytic and conventional (noncatalytic) pyrolysis was scrutinized and compared. It has been recognized that conventional pyrolysis (without catalyst) and catalytic pyrolysis (with Cat (I) and Cat (II)) produced 25.06%, 80.31%, and 55.26% of combustible liquid. The facial synthesis, high thermal stability, and economic and environmental feasibilities of the as‐synthesized zeolite (P) makes it a promising catalyst for biofuel production from biomass.     

Characterisation of steam-treated nanoporous carbide-derived carbon of TiC origin: structure and enhanced electrochemical performance

Modifications of pore size distribution and structural order of nanoporous carbide-derived carbon (CDC) materials with variety of surface areas and pore sizes were investigated using physical activation by etching with water vapour. Variable etching duration was used to explore the activation impact on the pore size distribution and the adsorption behaviour of TiC-derived carbon. A distribution of micro- and mesopores, modified during physical activation, was studied using N₂ and CO₂ adsorption. Notable impact of preceding carbon structure on the activation product was revealed by the results of scanning electron microscopy, powder X-ray diffraction and Raman spectroscopy. An infrared spectroscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy confirmed that water-induced etching of CDC followed by high-temperature treatment in inert gas atmosphere does not change notably the total amount of surface oxygen, however, leads to the changes in a composition of oxygen containing functional groups in post-activated carbon. The electrochemical evaluation was performed in triethylmethylammonium tetrafluoroborate/acetonitrile electrolyte to elaborate the structure-electrochemical properties relationships on post-activated nanoporous CDC materials. It was observed that the degree of improvement in double-layer capacitance achievable with a steam-treatment significantly depends on the preceding properties of CDC prior treatment, whereby the highest capacitance, ~?160 Fg^?1, was reached for the steam-treated TiC-derived CDC made at 800 °C, which clearly is a very promising material for the electrical double-layer capacitor.     

ZnO和Al2O3缓冲层对AZO透明导电膜薄膜性能的影响

采用射频磁控溅射法,以纯度为99.9%,质量分数98%ZnO、2%Al2O3陶瓷靶为溅射靶材,在预先沉积了ZnO和Al2O3的玻璃衬底上制备了Al2O3掺杂的ZnO薄膜。研究并对比了两种不同的缓冲层对ZnO∶Al(AZO)薄膜的微观结构和光电性能的影响。并借助X线衍射(XRD)仪、扫描电子显微镜(SEM)、紫外可见光谱仪(UV-Vis)等方法测试和分析了不同缓冲层,对AZO薄膜的形貌结构、光电学性能的影响。结果表明:加入缓冲层后,在衬底温度为200℃时,溅射30min,负偏压为60V、在氮气气氛下经300℃退火处理后,制得薄膜的可见光透过率为83%～87%,AZO薄膜的最低电阻率,从9.2×10-4Ω.cm(玻璃)分别下降到8.0×10-4Ω.cm(ZnO)和5.4×10-4Ω.cm(Al2O3)。