教学课程资源库 更多>>

关键词： PCM   TRC   Composite material   Mechanical behaviour   Physicochemical investigation  

摘要： The present paper presents a multiscale and multiphysics study that focuses on the development of an innovative composite material, which combines a cementitious matrix modified by a phase-change material (PCM) with textile reinforcement (PCM-TRC). The development of this composite has been guided by the conjunction of several factors, among which it is appropriate to emphasise the lightweight of the composite due to the reduced covers in textile reinforced concrete (TRC) coupled to the high thermal inertia due to the addition of PCM microcapsules. This research focuses on the effect of PCM on the mechanical and physicochemical properties of TRC. Special emphasis is placed on providing the phenomenological explanation for the resulting mechanical behaviour of TRC according to the rate and state of the PCM. It has been found that the ductile mechanical behaviour of TRC composites is maintained in the presence of microencapsulated PCM;however, the mechanical performance of PCM-TRC decreases with the PCM rate. This is due to the disorder caused by PCM at the matrix and interface scales. Furthermore, it has been found that the PCM state (solid or liquid) can affect the mechanical performance of both the PCM-mortar matrix and PCM-TRC composite. This is due to PCM expansion during phase change from the solid to the liquid state, which can induce matrix microcracking.

关键词： pearling fraction   physicochemical properties   protein   protein conformation   wheat  

摘要： Backgrounds and objectives The protein from various parts of the wheat kernel has different physicochemical properties, which is one of the reasons for the different processing characteristics of the corresponding flour made from these parts. In this study, wheat kernels were pearled into seven fractions from the outermost to the innermost layers to evaluate the quantitative and conformational properties of protein fractions from different pearling fractions. Findings The crude protein and protein fraction content was lower in the corresponding pearling fractions that were closer to the center of the endosperm. The albumin and SDS-soluble protein contents in the total protein from the pearling fractions exhibited a similar trend, whereas the dry gluten content exhibited an opposite trend. The average molar mass (M-w), polydispersity index (M-w/M-n), and density (rho) of the SDS-soluble protein were decreased, but there was no significant difference in theR(gz). And the G ' plateau values of glutenin macropolymer (GMP) were increased. Conclusions Protein conformation of the inner endosperm was looser than the other pearling fractions. Loose network wrapped more protein that led to the increased proportion of dry gluten. And it may increase aggregate entanglement that attributed to GMP became more elastic. Significance and novelty The changes in protein conformation in pearling fractions of wheat kernels further explained changes in physicochemical properties of protein from different pearling fractions.

关键词： Fish   Shellfish   Muscle proteins   Stability   Structure   Characterization   Physiological functions  

摘要： Fish and marine invertebrates constitute an important part of the human diet worldwide, and their muscles are the major edible parts. The muscles are a rich source of proteins, which in other terms determines the nutritional value and the quality of seafood products. Though the fish skeletal muscle proteins share many similarities with their mammalian counterparts, there exist great differences in their biological activity and structural stability. While the muscles of shellfish or aquatic invertebrates share many properties and general structural features with their vertebrate counterparts, they have unique characteristics. Therefore, understanding the biochemical and physicochemical properties of their major protein components is needed from the viewpoint of effective utilization of aquatic bioresources. Thus, in this review, we aimed to assemble the basis of such differences and also to understand the benefits of these proteins as the targets for studies on the structure-stability relationship of proteins.

关键词： Macrolide lactone   Nanotechnology   Raman scattering   Skin-related autoimmune disorders   Stability testing  

摘要： Tacrolimus (TAC) or FK506 is a macrolide lactone isolated from the bacterial fermentation of Streptomyces tsukubaensis which belongs to the group of calcineurin inhibitors. Its main mechanism of action is to act on the immune system. In addition, this drug has been widely explored for skin disorders. However, TAC shows high molecular weight, high hydrophobicity, and low water solubility that can limit its ability to effectively permeate through the skin. Hence, it becomes imperative to develop a percutaneous drug delivery system for increasing its permeation in relation to the conventional ointment and for reducing the dose and the adverse effects as erythema, itching, and burning. Therefore, the aim of this work was to investigate the stability of colloidal suspensions of TAC-loaded poly(epsilon-caprolactone) (PCL) nanoparticles that were stored at room temperature for 120 days. In that sense, pH, particle size, polydispersity index (PDI), zeta potential, and Raman spectroscopy were performed. Significant decrease of pH (p < 0.05) occurred after 60 days for TAC-loaded nanoparticles prepared at high drug concentration (NC-3, 3 ***(-1)). Loaded formulation showed significant pH changes (p < 0.05 to p < 0.001) after 90 of experiment. Non-loaded nanoparticles revealed significant pH increase (p < 0.05) after 120 days. Particle size and PDI had no statistical difference (p> 0.05) during the time interval investigated. Zeta potential presented statistically significant difference (p < 0.05) only for TAC-loaded nanoparticles after 120 days. The results obtained from Raman spectroscopy showed the suitability of the technique on the evaluation of stability TAC-loaded PCL nanoparticles. The analysis of Raman results demonstrated that the degradation mechanism occurred mainly in amorphous domains of PCL and resulted in an increased polymer crystallinity. Taking all these into account, TAC-loaded nanoparticles had a suitable stability within 60 days of preparation and can be

关键词： Refrigeration  

摘要： Efforts have been made to extend the poor shelf life of cassava roots through low-temperature storage like refrigeration, but the effects of this onlafun(fermented cassava flour) had not been investigated. This study determined the chemical composition oflafunobtained from cassava roots refrigerated for 1-3 weeks and the physicochemical and sensory properties of its cooked paste. Refrigerated storage (4 degrees C) slightly reduced the whiteness oflafunand appearance of the cooked *** refrigerated cassava roots showed similar titratable acidity values (approx. 0.53%), but varying pH values (4.10-5.25). Carbohydrate was the major macro-component oflafun(approx. 84%), while calcium (40.13-60.11 mg/100 g), sodium (39.60-48.70 mg/100 g), magnesium (20.12-40.99 mg/100 g), and potassium (24.92-32.01 mg/100 g) were the major minerals. An increase in the swelling index and peak viscosity oflafunsuggests an alteration in starch composition due to refrigeration. Cooked paste fromlafunprepared from refrigerated cassava showed comparable quality with the control. Practical applications Refrigeration is a low-temperature method of preservation that could be used to reduce the rate of biochemical and microbiological changes during storage and hence to extend the shelf life of fresh and processed foods. This study demonstrates the possibility of extending the shelf life of cassava roots using refrigeration without significant changes in the properties oflafunand cooked paste obtained from the stored roots. Furthermore, refrigerated storage could be used by small-holder farmers through cooperatives and government interventions to store cassava roots for at least 3 weeks before use.

关键词： Riverine network   Carbon metabolism   Bacterial production   Bacterial respiration   Nutrients   Rio Grande  

摘要： Although freshwater systems comprise a small portion of land surface, they play a pivotal role in landscape carbon (C) cycling. Carbon processing by heterotrophic bacteria is critical, contributing to ecosystem production and dissolved organic carbon (DOC) processing. Riverine bacterial C metabolism is related to a diversity of factors, including (1) physiochemical conditions and inorganic nutrient concentrations and (2) DOC quality and quantity;however, the relative importance of these factors in influencing C metabolism across arid fluvial networks remains equivocal. This study examined C metabolism by heterotrophic bacterioplankton in the Rio Grande drainage, an arid river network in Texas, USA. We examined spatial variation in physicochemical and inorganic nutrient conditions, bacterial C metabolism, and DOC lability across the drainage and assessed whether variation in bacterial C metabolism was more related to physicochemical-inorganic nutrient conditions or DOC quantity and lability. Across the drainage, hydrology and landscape position influenced physicochemical conditions, bacterial abundance, phytoplankton biomass, and bacterial C metabolism and the proportion of variation in bacterial C metabolism explained by physicochemical/inorganic nutrient and DOC quality-quantity gradients was approximately equal. Bacterial abundance and production were associated with greater NH(4)(+)and DOC concentrations and phytoplankton biomass, whereas bacterial respiration and growth efficiency were driven by DOC color and suspended particulate concentrations. Results indicate that aspects of bacterial C metabolism are influenced by different environmental factors related to autochthonous and allochthonous inputs to riverine systems, which has implications for C transformation, sequestration, and transport to the ocean.

关键词： digestibility   heat treatment   physiochemical   water caltrop starch  

摘要： Water caltrop has a high starch content and is a promising resource of starch in Asia. Starch can be divided into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). Here, the effects of physical modification by microwave treatments, heat-moisture treatments, and pressure-heat treatments on the physiochemical and structural properties and on the in vitro digestibility of water caltrop starch is studied. The results show that, compared with native starch (NS), the solubility and swelling power of modified starch samples decrease with prolonged microwave and heat-moisture treatment. The infrared absorbance ratio at 1047 cm(-1)/1022 cm(-1) is decreased in starch samples modified by microwave treatment and pressure-heat treatment, the NS samples present a C-type crystalline pattern which changes into an A-type pattern upon microwave treatment. Water caltrop starch subjected to 50 s of microwave treatment has the highest amylose (48.78%), the highest crystallinity (42.95%), and the highest RS content (67.41%, uncooked and 48.91%, cooked). Water caltrop starch subjected to 3 h of heat-moisture treatment contains the highest SDS content (54.33%, uncooked and 60.11%, cooked).

关键词： Coagulation   Induced gelation   Sensory properties   Sweep analysis  

摘要： Plant based coagulases are becoming an area of increasing interest to the dairy and allied food industries, due to the ease and abundance of their availability, simplified, less labour intensive and more highly economic purification processes, their higher acceptability among the vegetarians. Therefore, the present study examined the potentiality of pumpkin (Cucurbita moschata) seed extract as a source of milk coagulating peptidase. The rheological behaviour of the milk gel formed by using the pumpkin seed extract was studied by taking into the consideration of viscosity, flow behaviour, gel development, gel structure, gelation time, gel stability, storage and loss modulus at varying parameter of time, temperature, frequency (1000 rad/s to 0.01 rad/s) and strain (0.1%-1000% at constant frequency 10 rad/s). The study reported that the seed extract (corresponding to a 61 kDa protein by SDS-PAGE) curdled the milk satisfactorily within a wide pH and temperature range (pH-4.5 to pH-8.5 and 20 degrees C-80 degrees C) with minimum requirement of calcium ion (0.02 M) respectively. The dynamic rheological study of the curdled milk yielded a higher storage modulus value [G'] than the loss modulus [G ''] throughout the designed experimental conditions with a loss factor [tan (eta)] of less than 1. All these values indicated a strong milk gel formed using pumpkin seed peptidase extracts. Within a shear strain of 12.8% the gel followed a linear viscoelastic response and had an activation energy of 37.8 kJ/mol. The study of peptidase sequence revealed homology with cucumicin like peptidase.

关键词： Germination   Flour   Physicochemical properties   Grain   Brown rice  

摘要： The changes in physiochemical properties of flours obtained from the four selected grains after germination were investigated. After germination, the sprout length of sorghum and millet was substantially larger than that of brown rice and oat. Germination led to a decrease in the apparent amylose content and swelling factor of flours. Gelatinization onset and peak temperatures increased after germination, while a slight decrease was found in conclusion temperature. Compared to the raw flours, the germinated flours derived from brown rice, sorghum, and millet had lower gelatinization enthalpy, whereas the germinated oat flour showed higher gelatinization enthalpy. Germination resulted in significant decrease in pasting parameters of the four flours. Amylose leaching of sorghum and millet flours increased after germination, while the brown rice and oat flours showed a significant decrease in amylose leaching. Results suggest that germination effectively altered the physicochemical properties of grain flours, which can be utilized as functional ingredient in the preparation of grain-based products.

关键词： atmosphere of the North Atlantic   aerosol and black carbon   organic and elemental carbon contents   chemical and isotopic compositions  

摘要： In summer 2018 along the route of the 71st cruise of RVAkademik Mstislav Keldyshin the North Atlantic we carried out the measurements of such atmospheric aerosol characteristics as aerosol optical depth, near-surface aerosol and black carbon concentrations, content of chemical elements in aerosol samples, and organic and elemental carbon, as well as the isotopic composition of black carbon. It is shown that the average values of most characteristics decrease severalfold during passage from the Baltic Sea to the North Atlantic (57 degrees-60 degrees N), and then to the Norwegian Sea. For instance, the average black carbon concentration decreased from 83 to 29 ng/m(3). Episodic impact of continental aerosol was noted even in remote regions of ocean. Outflow of smokes from forest fires in the north of Canada to the region of measurements (southward of Greenland) had the strongest effect on aerosol characteristics. The average concentrations of chemical elements in aerosol composition over the North Atlantic were several times larger than in the Arctic region, and smaller than in the background region of Siberia.