环糊精对啤酒花油及风味物质稳定性影响研究

风味分析标准往往难以确定,而且不稳定,用环糊精与风味物质可制成稳定的包合物。通过选择条件制备啤酒花油-环糊精包合物,风味物质的含量在包合物稳定物质中可高达10%。β-环糊精是淀粉发酵产物,作为酿造啤酒时向其中添加所需"风味"保持剂,无毒无害,可生产绿色"风味"啤酒,对改进啤酒品质有重要的应用前景。

辅酶Q_(10)氯化钠注射液有关物质方法的建立及其有关物质稳定性研究

目的建立RP-HPLC法测定辅酶Q10氯化钠注射液有关物质的检查方法 ,并考察样品在贮藏过程中有关物质的变化情况。方法色谱柱:ZORBAXSB-C18(150mm×4.6mm,5μm);流动相:甲醇-无水乙醇(1∶1);柱温:35℃;流速:1ml/min;检测波长:275nm。采用自身对照法计算结果。结果辅酶Q10在12.8～816μg/ml线性关系良好(r=0.9993,n=6);精密度良好,RSD为1.33%(n=7);回收率为99.47%,RSD为0.71%;辅酶Q10与多种有关物质分离良好,制剂中其他成分不干扰测定。结论该方法准确可靠、简单快速,可用于该制剂有关物质的测定,同时经过稳定性考察本品在避光情况下放置,有关物质变化不大。

关于物质稳定性的教学探讨——由Na_2O_2与Na_2O稳定性引起的思考

针对现行高中《化学》教材对稳定性的概念未做明确阐述的问题,提出了关于物质稳定性概念教学的一些看法。

多能干细胞维持遗传物质稳定性的研究进展

由于功能特殊,干细胞不仅是发育生物学研究的重要模型,也在再生医学中有巨大的应用前景。但多能干细胞基因组稳定性是其得以应用的前提。相对于其他多种类型的分化细胞,多能干细胞有着独特的基因组稳定性维持能力和机制,其DNA损伤反应更加复杂也更加强大,但目前对多能干细胞如何高效维持基因组稳定性的机制仍知之甚少,有待进一步探索。简要综述近年在多能干细胞基因组稳定性调控上的研究进展。

多能干细胞维持遗传物质稳定性的调控机制

多能干细胞(pluripotent stem cells,PSCs)能无限增殖且具有发育多潜能性,在再生医学中有巨大的应用前景,但长期扩增过程中产生的遗传物质不稳定性及潜在致瘤性阻碍了临床应用。深入理解多能干细胞维持遗传物质稳定性的方式和机制具有重要的理论价值和应用前景。由于功能的特殊性,相较于体细胞,多能干细胞维持遗传物质稳定性的能力更强,并有其独特的机制。该文简要综述了近年来在多能干细胞维持遗传物质稳定性方面的研究进展,包括干细胞如何有效应对DNA复制压力、如何有效修复DNA损伤以及在DNA损伤情况下的细胞命运决定机制。

物质的生成热在有机化学中的应用

在一般的物理化学教材中,仅指出生成热是用于计算化学反应热效应的物理量,本文着重利用生成热反应了物质稳定性的实质,从几方面阐述了生成热在有机化学中的应用。

多重乳状液技术及其在香料物质缓释中的应用

对多重乳状液W/O/W的制备进行了介绍,分析了影响W/O/W乳状液稳定性的因素,阐述了研究其稳定性的一些方法,给出了其所具有的一些潜在应用价值以及其在香料物质缓释方面的应用.

Structural characteristics and properties of PU-modified TDE-85/MeTHPA epoxy resin

Diglycidy1-4,5-epoxycyclohexane-1,2-dicarboxylate （TDE-85）/methyl tetrahydro-phthalic anhydride （MeTHPA） epoxy resin was modified by polyurethane（PU）, and its structural characteristics and properties were studied by infrared spectrum analysis （IR）, scanning electronic microscopy （SEM）, mechanics testing and thermogravimetric analysis （TG）. The results indicate that epoxy polymeric network Ⅰ and polyurethane polymeric network Ⅱ are formed in the PU-modified TDE-85/MeTHPA epoxy resin. Meanwhile the PU-modified TDE-85/MeTHPA resins have heterogeneous structure. The miscibility between epoxy （EP） and polyurethane （PU） as well as the phase size are dominantly determined by the mass fraction of polyurethane prepolymer （PUP） in the EP/PU blends. With the increase of PUP mass fraction, the tensile strength, impact strength and thermal stability of the PU-modified TDE-85/MeTHPA epoxy resin all firstly exhibit increasing tendency, and decrease after successively reaching their maxima. When the number-average molecular mass of PPG is 1 000 and the mass fraction of PUP is 15%, the tensile strength, impact strength and thermal stability of materials obtained, compared with TDE-85/MeTHPA epoxy resin, are improved obviously.

Formation and Water Stability of Aggregates in Red Soils as Affected by Organic Matter

The water stability of aggregates in various size classes separated from 18 samples of red soils under different managements, and the mechanisms responsible for the formation of water-stable soil aggregates were studied. The results showed that the water stability of soil aggregates declined with increasing size, especially for the low organic matter soils. Organic matter plays a key role in the formation of water-stable soil aggregates. The larger the soil aggregate size, the greater the impact of organic matter on the water stability of soil aggregates. Removal of organic matter markedly disintegrated the large water-stable aggregates (> 2.0 mm) and increased the small ones (< 0.25-0.smm) to some extent, whereas removal of free iron(aluminium) oxides considerably destroyed aggregates of all sizes, especially the < 0.25-0.5 mm classes. The contents of organic matter in water-stable aggregates increased with aggregate sizes. It is concluded from this study that small water-stable aggregates (< 0.25-0.5 mm) were chiefly cemented by Fe and Al oxides whilst the large ones (> 2.0 mm) were mainly glued up by organic matter. Both free oxides and organic matter contribute to the formation and water stability of aggregates in red soils.

Effect of substrate amendment on alkaline minerals and aggregate stability in bauxite residue

Bauxite residue is an alkaline waste material in the process of alumina production due to its characteristics of higher salinity and alkalinity,which results in environmental issues and extremely restricts the sustainable development of alumina industries.In this work,we conduct a column experiment to study the effects of two amendments on aggregate stability and variations in alkaline minerals of bauxite residue.The two amendments are phosphogypsum(PG)and phosphogypsum and vermicompost(PVC).The dominant fraction in aggregate is 1–0.25 mm in diameter on the surface,which takes up 39.34%,39.38%,and 44.51%for CK,PG,and PVC,respectively.Additions of PG and PVC decreased pH,EC,ESP,exchangeable Na^+concentration and the percentage of alkaline minerals,and then increased exchangeable Ca^2+concentration in bauxite residue.There was significant positive correlation between pH and exchangeable Na^+concentration,the percentage of cancrinite,tricalcium aluminate and calcite;while negative correlation was found in pH value versus exchangeable Ca^2+concentration.Theses findings confirmed that additions of phosphogypsum and vermicompost have a stimulative effect on aggregate stability in bauxite residue.In particular,amendment neutralization(phosphogypsum+vermicompost)in column represents an advantage for large-scale simulation of vegetation rehabilitate in bauxite residue disposal areas.

Practice and design of the self-purification system for heavy metals-bearing contaminants

Many minerals in nature have self-purification capacity to hold and stabilize deleterious contaminants into their lattice structures,which can be used for treatment of heavy metals-bearing contaminants. Hydrotalcite Layer Double Hydroxide (LDH),tobermorite Calcium Silicate Hydrate (CSH) and apatite are ubiquitous minerals in nature,having higher geochemical stability and potential for binding and stabilizing heavy metals. Based on the elucidation of crystal structure property and self-purification principles of the three minerals above,this article discussed how to design the self-purification system of heavy metal-bearing contaminants.

PROGRESS OF ACOUSTIC WAVE TECHNIQUE ANDITS APPLICATION IN UNDERGROUND PRESSURE MEASUREMENT

This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data processing device. On the spot, the stability of surrounding rock is studied by means of experiments on the relationship between the change process (from elastie to plastic failure zone) in surrounding rock of roadway and the change law of acoustic parameters of rock. These acoustie parameters inelude wave amplitude, spectral amplitude, spectrum area, spectral density,wave veloeity and attenuation coefficient etc.

Bio-energy in s-Helix Protein Molecules with Three Properties of Soliton-Transported Channels

We study numerically the propagating properties of soliton-transported bio-energy excited in the a-helix protein molecules with three channels in the cases of the short-time and long-time motions and its features of collision at temperature T = 0 and biological temperature T = 300 K by the dynamic equations in the improved Davydov theory and fourth-order Runge-Kutta method, respectively. From these simulation experiments we see that the new solitons in the improved model can move without dispersion at a constant speed retaining its shape and energy in the cases of motion of both short-time or T = 0 and long time or T = 300 K and can go through each other without scattering in their collisions. In these cases its lifetime is, at least, 120 ps at 300 K, in which the soliton can travel over about 700 amino acid residues. This result is consistent with analytic result obtained by quantum perturbed theory in this model. In the meanwhile, the influences of structure disorder of a-helix protein molecules, including the inhomogeneous distribution of amino acids with different masses and fluctuations of spring constant, dipole-dipole interaction, exciton-phonon coupling constant and diagonal disorder, on the solitons are also studied by the fourth-order Runge-Kutta method. The results show that the soliton still is very robust against the structure disorders and thermal perturbation of proteins at biological temperature 300 K. Therefore we can conclude that the new soliton in the a-helix protein molecules with three channels is a possible carrier of bio-energy transport and the improved model is possibly a candidate for the mechanism of this transport.

Stabilization of the Soliton Transported Bio-energy in Protein Molecules in the Improved Model

We study the stabilization of the soliton transported bio-energy by the dynamic equations in the improved Davydov theory from four aspects containing the feature of free motion and states of the soliton at the long-time motion and at biological temperature 300 K and behaviors of collision of the solitons by Runge–Kutta method and physical parameter values appropriate to the α-helix protein molecules. We prove that the new solitons can move without dispersion at a constant speed retaining its shape and energy in free and long-time motions and can go through each other without scattering. If considering further influence of the temperature effect of heat bath on the soliton, it is still thermally stable at biological temperature 300 K and in a time as long as 300 ps and amino acid spacings as large as 400, which shows that the lifetime of the new soliton is at least 300 ps, which is consistent with analytic result obtained by quantum perturbation theory. These results exhibit that the new soliton is a possible carrier of bio-energy transport and the improved model is possibly a candidate for the mechanism of this transport.

Investigation of the Drug Stability at the Amorphous State Using Thermal Analysis

Formulation of poorly water-soluble crystalline drugs in their amorphous counterpart is a common approach to enhance their biodisponibility. In this study, the amorphous forms of ketoprofen and flurbiprofen were obtained by supercooling of the melt in a DSC （differential scanning calorimetry） apparatus and then investigated, especially under the stability point of view. The average rate of molecular motions at any given temperature is probably the most important parameter to know for amorphous pharmaceutical materials, and it was used to explain and predict the stability of ketoprofen and flurbiprofen. A quantitative estimate of the product＇s behaviour upon storage is obtained with additional data, such as the heat capacity of crystalline and amorphous samples and the distribution of molecular relaxation times. Amorphous flurbiprofen demonstrated greater physical stability at any aging temperature tested, when compared to ketoprofen and a different dependence from aging temperature. Both amorphous drugs could he classified as ＂fragile＂ ones.

Investigations on the Thermodynamic Stability and Availability of Nutrients for Plants by Humic Substances Extracted from Peat Samples

This work evaluated the complexation capacity, exchange constants and availability of micronutrients for plants and humic substances extracted from peat samples. Samples of humic substances extracted from two tropical peats （HS-P1 and HS-P2） were enriched with the micronutrients Cu（II）, Co（II）, Fe（II）, Mn（II）, Ni（II） and Zn（II） and the parameters for formation of the complexes （HS-N） were evaluated at different pH. The Scatchard model was used to calculate the maximum complexation capacity and the nutrient availability was studied using exchange capacity experiments based on ultrafiltration procedure. The optimum pH for complexation was 4.5 and the order of affinity was： Fe（II） 〉 Cu（II） 〉 Co（II） 〉 Mn（II） = Ni（II） 〉 Zn（II）. The maximum complexation capacity reached 56.8 mg·g-1 Fe of HS-P1 （the highest） and 1.7 mg.g1 Zn of HS-P2 （the slightest）. The exchange experiments showed that HS-P-Fe complexes were formed preferentially. The least stable complex was formed with Zn, which was therefore, more easily available. The results contribute to understand the behavior and availability of some nutrients in soils.

Exploring aramid as emerging contender for CO_2 capture

To prevent CO_2 accumulation in the atmosphere generated from scorching of fossil fuels, carbon capture and sequestration(CCS) technology is considered as a potential route to mitigate the emissions of CO_2 from reaching the atmosphere. Power generation from sources such as gas, coal and biomass can fulfill the energy demand more readily than many other sources of electricity production. Thus these sources may be retained as important alternative option in the global energy cycle. In order to curtail CO_2, porous aramid network was fabricated by the condensation of 1,3,5-benzenetricarbonyl trichloride and 1,3-phenylenediamine in 1,4-dioxane solvent. Aramid was characterized for various analyses including FTIR, XRD, TGA, BET surface area and pore size analysis, FESEM and CO_2 adsorption measurements. Excellent thermal stability was provided by strong amide linkages in the polymer backbone. Optimum CO_2 uptake of aramid was achieved to be 23.14 mg·g^(-1) at 273 K at 0.1 MPa. The basic amide groups of network structure showed greater affinity for CO_2.Excellent thermal stability of aramid makes it a promising sorbent for CO_2 capture in adverse conditions.

Stability and Electronic Properties of Metal-N4 and Metal-N2 Complexes

Nitrogen molecules Nx have been the subject of much recent research because of their potential as high-energy materials. Many nitrogen molecules dissociate with very low barriers, including molecules such as acyclic N4 that are essentially unbound. A number of studies have reported the ability of heteroatoms to stabilize complex nitrogen molecules. In the present study, the energetic and electronic properties of scandium（Ⅰ） and titanium（Ⅱ） complexes with N2 and N4 are calculated and discussed. Dissociation energies and singlet-triplet energies are determined by theoretical calculations using second-order perturbation theory （MP2） in conjunction with the Dunning basis sets.

Effect of Microwave Radiation on Dielectric Behavior of Two Vegetable Oils

The effect of microwave （MW） heating on the dielectric properties and oxidation processes of virgin olive oil and refined sunflower oil were determined by dielectric and UV- spectroscopy. Samples were heated in the microwave oven （850 W, 2.450 MHz） for 0 to 14 minutes. The results show degradation of dielectric characteristics, conductivity and oxidative stability of investigated oils, increasing with the exposure time. UV spectrum shows only one defined peak at 206 nm for olive oil confirming the dominant presence of monounsaturated fats and four peaks for sunflower oil （203 nm, 230 nm, 269 nm and 278 nm） dependent on polyunsaturated acid fats contents. Increasing of absorbance at all peak wave lengths indicates production of lipid oxidation, due to formation of conjugated monoenes and dienes and in small amounts due to trienes and secondary products like ketoaldehydes. Dielectric constant for olive oil is stable and almost unchangeable with MW radiation while sunflower oil＇s c＇ oscillates around the origin value in greater rate. Dielectric loss e＂ decreases with increasing time of MW radiation and its maximum shifts towards higher frequencies for sunflower oil indicating shortening of the relaxation times, while for olive oil it is unchanged. Cole-Cole analysis show the presence of only one relaxation process in the oils. Conductivity of oils is increasing in similar way with increasing frequency following the Jonscher＇s power law and is not changed with MW exposure time. Olive oil has conductivity higher for four orders of magnitude than sunflower oil, which is connected to the high content of monounsaturated fats. The differences between sunflower and olive oil characteristics are discussed.