微生物最适生长酸度的微量热法研究

The bacterial growth thermogram curves under different acidities were determined. From these thermogram curves, the growth rate constants(k) at different acidities were calculated and the equation correlating of k with PH could be established. From these k-pH equations,the optimum acidity of bacteria growth could be obtained. These models provide a good method for the study of the metabolism of bacteria.     

Description of the shape of thermoanalytical curves : Part 1. Empirical Parameters for the Characterization of Peaks in Differential Scanning Calorimetry

Thermoanalytical curves of the derivative type can be described by using empirical parameters as properties of the peak shape, including the temperatures at characteristic points of the peak, temperature differences, mathematical moments, etc. The reproducibility of differential scanning calorimetric curves of the thermal decomposition of aluminium hydroxide is evaluated on the basis of these parameters. The importance of correct and consistent choice of baseline is demonstrated.     

细胞代谢的热化学研究——鉴别静息细胞代谢的新方法

探讨微生物代谢的一个主要方面是研究在限制性营养物质(例如不含氮源)中静息细胞在非生长条件下的代谢(简称静息代谢),即由于缺乏某些必要营养成份使细胞不能繁殖,但因含有各种酶系统,细胞仍能发酵其它营养物。通常获取静息细胞的方法是:让细菌(以幼龄菌为宜)在培养基中生长一定时期,再加生理盐水或缓冲液,洗涤、离心分离、洗去细胞上的培养基而得,忽略了细胞的内源代谢阶段。在有些代谢研究中,为了排除内源代谢的干扰,把沉淀再放置一至二个传代时间(对于大肠杆菌为35分钟),这时认为细胞进入静息状态。从生物热化学的观点考虑,处在内源代谢状态的细胞和静息细胞应有不同的热效应。     

吡喃并[3,2-c]吡啶-5-酮衍生物与血清白蛋白相互作用的光谱和分子对接研究

通过荧光光谱和紫外-可见吸收光谱法,在模拟生理条件下,研究了吡喃并[3,2-c]吡啶-5-酮衍生物-2-氨基-7-甲基-3-氰基-4-(4-甲苯)-吡喃并[3,2-c]吡啶-5-酮(AMP)与牛血清白蛋白(BSA)的相互作用。探讨了AMP对BSA的荧光猝灭过程的猝灭机理。不同温度下的Stern-Volmer曲线和紫外-可见吸收光谱表明:该衍生物主要以静态猝灭的方式使牛血清白蛋白的荧光猝灭。热力学参数表明两者之间的作用力类型主要为疏水作用力。用同步荧光技术考察了这一衍生物对牛血清白蛋白构象的影响。分子对接表明,该衍生物可能位于白蛋白的疏水腔IIA处。     

Synthesis and mesomorphic characterization of azoesters with a coumarin ring

We have synthesized a homologous series of azoesters consisting of a coumaryl moiety as the end group. Eleven derivatives of this series exhibit mesomorphism. The nematic mesophase is exhibited from ethyl homologue onward, while the smectic phase commences at the pentyl derivative and is exhibited along with the nematic phase up to the hexadecyl derivative. The N-I transition temperatures curves show the usual odd-even effect. All the compounds in this series are thermally stable and exhibit a wide mesomorphic range of nearly 120°C. Their thermal stabilities and other characteristics are discussed.     

Synthesis and mesomorphic characterization of azoesters with a coumarin ring

We have synthesized a homologous series of azoesters consisting of a coumaryl moiety as the end group. Eleven derivatives of this series exhibit mesomorphism. The nematic mesophase is exhibited from ethyl homologue onward, while the smectic phase commences at the pentyl derivative and is exhibited along with the nematic phase up to the hexadecyl derivative. The N-I transition temperatures curves show the usual odd-even effect. All the compounds in this series are thermally stable and exhibit a wide mesomorphic range of nearly 120°C. Their thermal stabilities and other characteristics are discussed.     

微量量热法测定细菌生长的热谱

活体中细胞内的各种代谢过程都件随着一定的热效应,若使用具有足够灵敏的量热计对它进行探测,就提供了一种研究活细胞代谢过程及共有关特性的新方法。当用量热计连续跟踪监测细胞(如细菌)生长繁殖过程热效应的变化时,便获得该细胞生长的“热谱”。近期的研究实践证明,量热学方法用来进行细菌基本生长的研究是可行的。Boling等曾用Batch型量热计检测了某些细菌的生长热谱(见图1),但有些谱图不完整,因在它们的图     

量热法研究Cr3+水解聚合作用的热力学性质

水合多价金属离子在水溶液中发生水解聚合是一种普遍现象，铬（Ⅲ）离子就是这样的金属离子，具有水解聚合特征，铬（Ⅲ）的许多应用常与其水解特性有关［1］，虽然早在1907年Bjerrum［2］已经指出，但迄今为止，有关它的水解聚合的研究报道仍然较少［3］，而用微量热法研究Cr3十水解聚合作用的热力学还未见报道．Cr3＋水解聚合状态与其浓度有关，在低浓度和较高浓度下发现水解聚合产物不同．在较高浓度下形成单羟联的聚合质点，此观点曾相继由Hall［4］、戴安邦［5］等人提出并得到了验证．之后，戴安邦等人对Cr3＋的水解聚合作用进行了…     

Thermal decomposition of basic lead carbonate

TG and DTA curves of the thermal decomposition of basic lead carbonate, 2PbCO₃ Pb(OH)₂, are presented and compared with the thermogram of normal lead carbonate PbCO₃. The appearance of different intermediate compounds at identical experimental conditions is ascribed to the degree of perfection of the carbonate crystals. Poorly developed basic lead carbonate crystals, formed in the presence of polyglutamic acid, give no recognizable intermediate compounds.     

The characterisation of a novel, covalently modified, amphiphilic alginate derivative, which retains gelling and non-toxic properties

The characterisation of a novel amphiphilic material, Alg-C4, produced from butanol linked by esterification to alginate is presented. The novel derivative retains the gelling and non-toxic properties of native alginate. FTIR spectra of Alg-C4 contained the characteristic hydroxyl and carboxyl bands, but also featured additional peaks at 1736 and 1134 cm(-1), indicating the presence of ester bonds. NMR studies showed the presence of butyl groups. The endothermic peak and exothermic peak present in the DSC thermogram of native alginate were also apparent in the Alg-C4 thermogram, but had shifted to lower temperatures (from 106 to 87 degrees C and from 254 to 247 degrees C, respectively). In addition, the exothermic peak was significantly reduced for Alg-C4 (5 mW compared to 20 mW in native alginate). Scanning electron microscopy was used to examine surface topography. The native alginate beads appeared smooth while Alg-C4 beads had a different, rougher appearance. Using circular dichroism it was found that the ratio of mannuronic to guluronic residues in the Alg-C4 was markedly increased compared to the native alginate (1.33 to 2.47), suggesting the preferential esterification of butanol to the guluronic residues. Exposure of ovarian granulosa cells in vitro to the Alg-C4 material demonstrated that granulosa cell viability (MTT test) was unchanged when compared to native alginate, which is regarded as non-toxic. The novel material is very stable, giving identical FTIR, DSC and gelling performance after 12 months storage at temperatures ranging from 10 to 20 degrees C. The data support the successful preparation of a stable modified alginate with characteristic hydrophilic properties and, in addition, a novel hydrophobic character.     

A new method for the simultaneous determination of the size and shape of pores: the thermoporometry

A thermodynamic study of the liquid—solid phase transformations in porous materials provides the relationships between the size of the pores in which solidification takes place and the temperature of the triple point of the divided liquid, on the one hand, and between this temperature and the apparent solidification energy on the other hand.The experimental study of the phase transformations, carried out by means of a microcalorimeter, gives the values of the parameters necessary to calculate the free solid = liquid interphase extension energy γ_ls at different temperatures. A formula γ_ls  f(T) is given for water and benzene. Once this factor is known, it is possible to study the numerical relationship between pore-radius and freezing energy at the equilibrium temperature.By using these relations together with the solidification thermogram (the recording of the power evolved by the solidification of a capillary condensate during a linear decrease of temperature) the authors have been able to determine pore distribution curves. An emphasis is put on the comparison between this method, thermoporometry, and the B.J.H. method.Last of all the comparison of the experimental data for solidification and melting provide information concerning pore shape by means of the evaluation of a thermodynamic shape factor or by a method of simulation of porous material.     

模拟热谱曲线法(Ⅱ)──不可逆连串-级反应的热动力学研究

研究连串反应的动力学有十分重要的意义,文献［1,2]建立了两种连串一级反应的热动力学研究法．我们在前文[1]的基础上,建立了模拟热谱曲线法．该法可以直接从热导式量热计的热谱曲线上解析出连串一级反应中两步反应的速率常数．应用该法测定了邻苯二甲酸二乙酯和丁二酸...     

Phase and state transition effects on dielectric, mechanical, and thermal properties of polyols

The present study investigated the glass transition, crystallisation and melting behaviour of erythritol, xylitol, and glucitol (sorbitol) using dielectric analysis (DEA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Sorbitol and xylitol were plasticised by water and their glass transition temperatures decreased when water content was increased. Erythritol crystallised rapidly, and its water plasticisation behaviour could not be determined. Melting of the crystalline polyols occurred at their specific melting temperatures. Melts of erythritol and xylitol crystallised on recooling and no glass transition was apparent on reheating. Quench cooled sorbitol melt remained amorphous and showed a glass transition on reheating. Glass transition and crystallisation were apparent in the DSC thermogram and the dielectric and the dynamic mechanical spectra of mixtures of amorphous and crystalline xylitol.     

Study of mass transfer in oil-water-oil multiple emulsions by differential scanning calorimetry

A multiple emulsion of the type O1/W/O2 is studied experimentally by means of differential scanning calorimetry (DSC). The aim of this work is to characterize and measure the time-dependent changes within the emulsion. In particular, interest is focused to quantify the concentration changes in the internal and external phases of the O1/W/O2 multiple emulsion. In order to accomplish the objective, the measurement and analysis carried out by DSC are based on the crystallization behavior of the emulsion. A volume of a few mm3 is periodically removed from the O1/W/O2 multiple emulsion. The sample is submitted to steady cooling and the crystallization thermogram is recorded. The experimental data provided by the crystallization thermogram makes it possible to quantify the crystallized mass for both phases, the internal and the external. In addition, the composition in each phase can also be deduced from the thermogram. To deduce the composition, a diagram of crystallization temperatures is elaborated, employing several mixtures of known composition. In addition to the main objective previously mentioned, the influence of formulation parameters such as surfactant concentration in the aqueous phase and the mass ratio of the internal and external phases are also analyzed. The experimental results made it possible to conclude that a mass transfer took place from the internal phase toward the external phase; this transfer is caused by the composition difference on both sides of the aqueous membrane. In this work we analyzed the mass transfer in the multiple emulsion carried out by a composition gradient through the aqueous membrane. The most likely mechanism of mass transfer through the aqueous membrane is a solution-diffusion of tetradecane enhanced by the micelles of the surfactant Tween 20. The model of mass transfer confirms that the osmotic pressure difference controls the kinetics of tetradecane transfer. It is also confirmed that an increment of surfactant concentration in the aqueous phase allows a faster kinetics of the tetradecane transfer.     

Equilibrium study between condensed phases by isoplethic thermal analysis when a miscibility gap is observed

Isoplethic thermal analysis was used to determine the solid-liquid-liquid equilibria in the ternary system water-sodium sulfate-piperidine. The changes in state observed on the thermogram recorded during the displacement in a quasi-binary section permit the identification of the different phases and the delimitation of the corresponding equilibrium domains. Two isotherms were established at 25°C and 40°C because these temperatures frame the peritectic decomposition of the sodium sulfate decahydrate. Miscibility gaps were completely delimited and each critical point was calculated. This study permitted to determine the optimal conditions for separating the organic phase by liquid-liquid extraction.     

STUDIES ON THERMOKINETICS.(Ⅰ)THEORY AND METHODS OP THERMOKINETICS

A chemical reaction taking place in a calorimeter is called a thermokinetic system.The recording curve of its temperature during the reaction is called a thermogram.It is very interesting to study the reaction kinetics from.its thermogram but the theory and methods of thermokinetics have not been developed into perfection yet.In this article,the thermokinetic equations of a reacting system are derived in the light of nonequilibrium thermodynamics.And the analytical expression of a thermogram can be derived from the thermokinetic equations.On this theoretical basis,a new research method in thermokinetics has been suggested     

Thermal analysis of pyrotechnical mixtures,I

The author investigated a two-component pyrotechnical mixture used in the manufacture of delay detonators. Comparing the thermogravimetric, derivative thermogravimetric and differential thermal analysis curves of components with that of mixtures containing the components in different ratios, a relation has been found between the reaction rate and ratio. Initial temperature of reaction can be defined as well. Release of oxygen and oxidation takes place separately at certain temperatures and ratios. Mixture of highest rate of reaction generates the lowest heat of reaction.     

Thermal stability of the amorphous system Ge20As14(SexS1−x)52I14

Results of thermal investigations of the amorphous five-component chalcogenide system Ge₂₀As₁₄(Se_xS_1?x)₅₂I₁₄ are presented. Differential thermal analysis (DTA), derivative differential thermal analysis (DDTA), and dilatometry were employed to determine the temperatures of softening and partial crystallization of the samples. Thermal treatment of the samples at 1000°C and recording of the corresponding thermogravimetric (TG) and derivative thermogravimetric (DTG) curves allowed an elucidation of the full mechanism of their decomposition, which proceeds via seven characteristic phase transitions.     

Thermal and surface study of phenolic resin from cashew nut shell liquid cured by plasma treatment

In this study, phenolic resins from cashew nut shell liquid (CNSL) were applied as coating on Carbon Steel 1020 samples and successfully cured by plasma treatment or with hexamethylenetetramine (HMTA). The crosslinked samples were characterized by thermal analysis using thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), and atomic force microscopy (AFM) techniques in order to evaluate the thermal stability of these samples, as well as understand and study the curing process. TG/DTG curves showed that the thermal stability of the HMTA-cured resin was slightly higher than the resin treated by plasma. According to the DSC curves, HMTA-cured resin and plasma-treated resin exhibited only transition temperatures, so both resins were predominantly amorphous. Images generated by AFM provided qualitative evaluation of the resin surfaces, demonstrating that the coating surface with best homogeneity was cured by plasma treatment.     

Thermal analysis of diazo pigments

The differential-thermal and thermogravimetric analysis of eight derivatives of 1,4-bis-(8′-hydroxy-3′,6′-disulpho-1′-naphthyl)-benzenediamide showed that these compounds have a marked exothermic effect, with maxima in the temperature range 290–340°C. The 4-nitroaniline derivative was found to undergo a blast-like decomposition in the temperature interval 285–295°C, reflected by large steps in the TG curves. The thermal analysis of diazo pigments permits determination of their applicability at higher temperatures.