教学课程资源库 更多>>

关键词： photoreduction   serpentinization   wetting   drying   hydrolysis   polymerization   condensing agents   RNA   replication   catalysts   ribozymes   protocells  

摘要： The material and energetic resources for the abiotic syntheses of substances, which provide the formation of prebiological structures have been analyzed. It has been shown that one-carbon compounds including formaldehyde and hydrogen cyanide could be the main starting substances. Volcanic activity and photochemical action of solar UV rays are considered as possible energetic resources. Amino acids, lipids, carbohydrates, and nucleotides had been synthesized by reactions between starting substances and photoreduction of their products in a sulfur-containing environment. The wetting/drying cycles in water pools promoted the polymerization of monomers (amino acids and nucleotides). Among the resulting oligonucleotides, ribozymes could occur, some of which could catalyze the processes of elongation of oligonucleotides. The extended RNA-like structures acquired new functions including the ability to catalyze the replication of RNA. The lipid-like peptides and fatty acids performed the role of the primitive membranes, thus forming protocells. Details of the described processes have been discussed.

关键词： phenacene-type compounds   thiophene ring   cross-coupling   alkyl side chains   UV-vis absorption   p-type organic semiconductors   organic field-effect transistor (OFET)  

摘要： We report the design, synthesis, and physicochemical properties of an array of phenanthro[2,1-b:7,8-b']dithiophene (PDT-2) derivatives by introducing five types of alkyl (CnH2n+1;n = 8, 10, 12, 13, and 14) or two types of decylthienyl groups at 2,7-positions of the PDT-2 core. Systematic investigation revealed that the alkyl length and the type of side chains have a great effect on the physicochemical properties. For alkylated PDT-2, the solubility was gradually decreased as the chain length was increased. For instance, C-8-PDT-2 exhibited the highest solubility (5.0 g/L) in chloroform. Additionally, substitution with 5-decylthienyl groups showed poor solubility in both chloroform and toluene, whereas PDT-2 with 4-decylthienyl groups resulted in higher solubility. Furthermore, UV-vis absorption of PDT-2 derivatives substituted by decylthienyl groups showed a redshift, indicating the extension of their pi-conjugation length. This work reveals that modification of the conjugated core by alkyl or decylthienyl side chains may be an efficient strategy by which to change the physicochemical properties, which might lead to the development of high-performance organic semiconductors.

关键词： Waxy maize   High temperature   Plant growth regulator   Starch granule size  

摘要： Plant growth regulators (PGR) can be used to alleviate heat injury on the starch quality of crops. In this study, two waxy maize hybrids with exogenous cytokinin or spermine at silking stage were exposed to post-silking ambient temperature (AT;28/20 degrees C) and high temperature (HT;35/27 degrees C) during grain filling. Results indicated that spraying exogenous cytokinin or spermine increased the grain weight and starch content at both temperature regimes. The starch granule size, amylopectin chain length, and relative crystallinity differed between two hybrids and were affected by PGRs and temperatures. Peak viscosity decreased at HT, unaffected by cytokinin, and increased by spermine at both temperature regimes. The retrogradation percentage at HT with PGR was lower than that without PGR in both hybrids. In conclusion, spraying exogenous cytokinin or spermine at silking stage can increase peak viscosity and reduce retrogradation percentage at HT, thereby alleviating the detrimental effects of post-silking heat injury.

关键词： Medicinal plants   Antimicrobial properties   Mono-floral honeys   Antioxidant   Phenolic compounds  

摘要： Honey has been widely used to treat several human pathogens. However, all honeys may not have equal potencies against different human pathogens. The purpose of the current work was to investigate the physico-chemical and antimicrobial qualities of some mono-floral honeys from Ethiopia against some human pathogen bacteria and fungi. In the study, seven different botanical origin honeys were used of which some were from plants known for their medicinal properties. The samples were tested for their major physico-chemical properties (sugar profiles, total free acids, pH, color, electric conductivity and total soluble substances) and their medicinal values as total antioxidant capacity, total phenolic content and antimicrobial properties as minimum inhibitory concentration against some human pathogens, following standard protocols. Generally, the average values of the physico-chemical properties of the samples were within the acceptable ranges of world honey quality values. The average total antioxidant value of the samples was 320.3 +/- 15.1 with range of 225.4 +/- 12.8-465.7 +/- 21.8 mu M Fe(II)/100g. Relatively higher values 421.5 +/- 23.4 and 465.7 +/- 21.8 mu M Fe(II)/100g recorded for Croton macrostachyus and Vernonia amygalina honeys respectively. The average phenolic contents of the samples varied from 233.3 +/- 24.0 to 693.3 +/- 26.8 mgGAE/kg and relatively higher values recorded for C. macrostachys and V. amygdalina honeys. The significant proportion of the tested samples showed strong antimicrobial qualities inhibiting the growth of tested pathogens at concentration of 10.5%-28.6% of MIC (% v/v). Honeys from medicinal plants (C. macrostachys and V. amygdalina) relatively showed more antimicrobial properties which could be due to the presence of plant specific phytochemicals which require further investigations. (C) 2020 Published by Elsevier B.V. on behalf of King Saud University.

关键词： acrylic acid   aldol condensation   supported catalysts   porous structure   acid centers  

摘要： The influence of the support nature on physicochemical characteristics (surface acidity, porous structure) of complex oxide compositions B-P-V-W-O(x)and their catalytic properties (activity, selectivity) in the reaction of gas-phase aldol condensation of acetic acid with formaldehyde to obtain acrylic acid was studied. It was found that the activity of catalysts varies symbolically with the size of the specific surface, and the selectivity of the formation of acrylic acid is determined by the presence of weak acid centers on the surface of the catalyst. In the presence of the catalyst B-P-V-W-O-x/TiO(2)at a temperature of 375 degrees C, acrylic acid was obtained with a yield of similar to 59% with a selectivity of formation of 92%.

关键词： Pelletizing  

摘要： Abstract: It was established that the completion degree of the processes that accompany the iron ore pellets annealing on conveyor machines depends largely on the layer’s internal heat source distribution over separate zones. And the most significant role is played by the magnetite oxidation and carbonate dissociation. During the industrial research conducted on one of the Kachkanarsk’s mining and processing plant (KMPP) conveyor machines, the influence of the original batch composition on the thermal technical indicators of the machine was studied. The consistent pattern obtained for the heat source distribution in the pellet layer along the annealing conveyor machine allows one to optimize separate zone sizes, thermal parameters of the pellets annealing and to find the heat share from the external source for optimal fuel consumption. © 2020, Allerton Press, Inc.

关键词： Fat-reduced cookies   Bran gels   Fat replacers   Physico-chemical properties  

摘要： Wheat and oat bran-based fat replacers in the form of gels were used for partial replacement of fat (30-50%) in a cookie formulation. Dough rheological properties, physical (cookie dimension, weight loss, moisture content and water activity), textural (hardness and fracturability), colour and sensory parameters were evaluated to characterize full-fat and fat-reduced cookies. Based on the obtained results it was concluded that the fat reduction in cookie formulation at the level of 30% maintained sensory properties of the full-fat cookies. Therefore, this level of fat replacement was chosen for further analysis: 30% WBG (wheat bran gel-containing cookies) and 30% OBG (oat bran gel-containing cookies) were examined in terms of nutritional and functional properties. It was revealed that fat replacement using bran gels at the level of 30% resulted in the fat-reduced added-value cookies in terms of dietary fibre, minerals and phenolics. 30% WBG cookies possessed higher dietary fibre, mineral and phenolic content in comparison to 30% OBG and the full-fat cookies.

关键词： Chitosan   Degree of deacetylation   Genipin   Biocatalyst   beta-D-galactosidase  

摘要： The effect of the degree of deacetylation (DD) on the characteristics of the support matrix formed through chitosan (CH) and genipin (GE) crosslinking was investigated by using CH with DD of 83, 94 and 96%. The rheological properties of CH dispersions were determined in order to study the influence of DD on the CH viscosity, gel network structures and gelation temperature (Tgel). The CH exhibited the shear-thinning behavior of pseudoplastic fluids. Tgel decreased with the increase of DD and the sol-gel transition temperature of CH-83, CH-94 and CH-96 were 75, 30 and 25 degrees C, respectively. The magnitude of viscous modulus (G) was higher than the elastic modulus (G'), revealing the formation of a weak gel structure. The CH dispersions have been used in the preparation of beads and then crosslinked with GE to form support matrices. Besides, to verify how it influences in a practical application, an enzymatic immobilization was carried out using a beta-D-galactosidase (BG) as a model, which could be advantageously employed to promote hydrolysis of lactose. Scanning Electron Microscope images showed biocatalysts with multiple porous compartments. Fourier Transform Infrared Spectroscopy (FTIR) analyses confirmed chemical and physical interactions between CH, GE and BG. Thermogravimetric analysis (TGA) demonstrated that the DD of CH had a positive influence in the thermal degradation behavior of the biocatalysts up to 200 degrees C, which represents the temperature range used in most enzymatic reactions (up to 100 degrees C) in the industrial scale applications.

关键词： Accelerated co-composting   Lignocellulosic food industry waste   Empty fruit bunches   Coffee ground   Palm oil mill sludge  

摘要： Time and storage space are the main constraints facing by the current Malaysia composting industries which are handling lignocellulosic food industry waste such as empty fruit bunch (EFB), coffee ground (CG) and palm oil mill sludge (POMS). To develop an efficient accelerated composting method for lignocellulosic food industry waste in Malaysia, a new approach which combined two distinct technologies to achieve rapid composting;(i) co-composting with combination of different lignocellulosic materials and (ii) inoculation of the co-composting with mixture of microorganism were presented in this study. All the mixtures achieved thermophilic condition on the first week of composting, with 50% EFB + 50% CG combination recorded the highest temperature of 56 degrees C. The mixtures with initial C/N ratios within 25-35 showed the highest reduction in holocellulose, cellulose, hemicellulose and lignin content while compost mixture with initial C/N ratio more than 50 had a minimal reduction. The C/N ratio for 50% EFB + 25% CG + 25% POMS combination was reduced to less than 20 after 4 weeks of co-composting process while the other treatments needed longer composting duration. During thermophilic phase, higher population of bacteria (10(7)-10(8) CFU/g DW) was observed, followed by fungi (10(5)-10(6) CFU/g DW) and actinomycetes (10(5)-10(6) CFU/g DW) populations. However, higher population of actinobacteria (10(4)-10(6) CFU/g DW) compared to bacterial (10(4)-10(5) CFU/g DW) and fungal (10(3)-10(4) CFU/g DW) was found during latter stages. By reducing both the time and space required for composting lignocellulosic food industry waste, this accelerated co-composting method may be a viable option for food industries searching for a long-term, practical solution for solid biowaste disposal issues. Graphic

摘要： Background. One of the key elements of successful transplantation is effectively rinsing off the blood and preserving organs under controlled hypothermia. The aim of the study was to analyze the physicochemical parameters of Biolasol (Biochefa, Sosnowiec, Poland) and histidine-tryptophan-ketoglutarate (HTK) (Custodiol) solutions, which are recommended for perfusion and preservation of abdominal parenchymal organs. Methods. Biolasol and HTK solution were used for the study. The solutions were subjected to physicochemical analysis involving pH, density, osmolarity, viscosity, refractive index, zeta potential, hydrodynamic diameter, and rheological properties. Rheological parameters were associated with morphologic features of fluids. Results. HTK and Biolasol are non-Newtonian systems with pseudoplastic properties and yield stress. The solutions begin to flow under shear stress greater than the ultimate stress. In addition, a nonlinear relationship of their viscosity as a function of velocity gradient (shear rate) was observed. Conclusions. The solutions reproduce blood properties, which leads to the conclusion about their effective filling of the vascular bed and high efficiency in organ rinsing.