掺假藕粉中木薯淀粉和甘薯淀粉的鉴别-差示扫描量热法

为了对掺入藕粉中的其他淀粉种类进行鉴别,本研究通过差示扫描量热仪对藕粉等常见几种淀粉的糊化过程进行考察发现,藕粉与其他淀粉在糊化吸热峰上有着明显的差别。根据藕粉与木薯淀粉和甘薯淀粉等在糊化吸热峰上的差异,以糊化吸热峰作为特征指标,对掺假藕粉中掺入的木薯淀粉和甘薯淀粉进行定性或定量鉴别实验。同理,此方法也可用于检验与藕粉在糊化吸热峰上有明显差异的用于藕粉掺假的其他淀粉种类,如马铃薯淀粉,玉米淀粉等。此方法将弥补前期发表的基于淀粉颗粒超微形貌特征的可食用淀粉种类扫描电镜鉴别方法的不足。     

Thermal properties of doughs formulated with enzymes and starters

 Thermal properties (gelatinization, amylose-lipid complex dissociation and amylopectin retrogradation) of bread samples formulated with two different quality wheat flours, two enzymes (α-amylase/pentosanase, lipase and their mixture), and three microbial sourdough starters were studied with a differential scanning calorimeter. The carbohydrases modified gelatinization temperature and enthalpy, whilst the lipase modified the amylose-lipid complex dissociation. The enthalpy of amylopectin retrogradation was significantly influenced only by the storage of breads. Second-order interactive effects of enzymes with flour or starter were found for gelatinization and/or amylose-lipid complex dissociation parameters. Some interesting relationships were observed between thermal and textural properties of fresh and stored breads. Received: 22 September 1998 / Revised version: 28 October 1998     

Thermal expansion and heat capacity of Gd6UO12(s)

Gd₆UO₁₂(s) was synthesized by citrate–nitrate combustion method. Thermal expansion measurements of this compound were carried out in the temperature range of 298–1273 K by high temperature X-ray powder diffractometry and compared with other rare earth compounds of similar stoichiometry reported in literature. Heat capacity of Gd₆UO₁₂(s) was also measured by differential scanning calorimetry in the temperature range of 330–720 K. Enthalpy, entropy and free energy functions for Gd₆UO₁₂(s) were computed.     

On the Nature of Interaction Between Fullerene and Aniline

Interaction between fullerene C₆₀ and N,N-dialkyl-substituted anilines was studied by gas-liquid chromatography (GLC) and titration calorimetry. The GLC study was performed at 140-200°C in the poly(tetramethylbenzene) solvent with ultra-high solubility of C₆₀. No interaction of the C₆₀-aniline type was registered under such conditions. Calorimetric titration performed at 25°C in a non-aromatic solvent confirmed the lack of complex formation. Minute exoeffect registered is explained by suppressing of the rotation motion of the C₆₀ molecules accompanied by energy dissipation for the aniline environment.     

Toxicity of unwanted intermediates and products formed during accidental thermal decomposition of chemicals

The problem of the formation of unwanted substances that can occur during thermal decomposition of chemicals is studied from a toxicological point of view. Two species, ethyl parathion (a widely used pesticide) and cumene hydroperoxide (an intermediate for the industrial production of phenol and acetone), are selected for this investigation. The hazards associated to their accidental thermal decomposition are estimated on the basis of the (known) intermediates and products formed by means of a computational tool (ECOSAR programme) and assessed experimentally by means of algal bioassays. Green alga Pseudokirchneriella is used as target organism for all the toxicological assessments. The results of these tests on the samples collected during the thermal decomposition of the two studied species indicate that in the case of ethyl parathion the decomposition process gives rise to a mixture of compounds which are more toxic than the parent species. On the other hand, the decomposition of cumene hydroperoxide in cumene results into the formation of different species whose toxicity towards the adopted organism is lower than that shown by the starting compound. A procedure is proposed to ascertain when it is necessary or it is avoidable to carry out further investigations that involve the analytical resolution of mixtures resulting from the thermal decomposition process. This approach is suggested as a preliminary screening to identify the hazards associated with an accidental decomposition either of pure chemicals or of mixtures of compounds.     

Differential scanning calorimetry study of diffusional and martensitic phase transformations in some 9 wt-%Cr low carbon ferritic steels

Abstract

The results of a comprehensive characterisation study of different phase transformations that take place upon heating and cooling in some low carbon, 9 wt-%Cr steels with varying concentrations of microalloying additions are presented in this paper. The steels investigated include: standard 9Cr–1Mo grade, V and Nb added modified 9Cr variety, controlled silicon added versions of plain 9Cr variety, (Ni+Mn) content controlled modified 9Cr welding consumables and one composition of W, Ta added reduced activation steel. The various on-heating diffusional phase changes up to the melting range and subsequent rapid cooling induced martensitic transformations are investigated in a controlled manner using differential scanning calorimetry under different heating and cooling rates, in the range 1–100 K min^?1. In addition to the accurate determination of Ac₁, Ac₃, M₂₃C₆, MX carbide dissolution and δ-ferrite formation temperatures upon heating, the melting range and the associated fusion enthalpy have also been established for these steels. The effect of prolonged thermal aging at temperatures of 823–873 K on austenite formation characteristics has also been investigated for standard and modified 9Cr–1Mo steels. The critical cooling rate for the formation of martensite on cooling from single phase austenite region is estimated to be about 4–5 K min^?1 for all 9Cr steels investigated in this study. The effect of holding at 1273 K in the austenite region on martensite start temperature M_s, has also been evaluated as a part of this study. The experimental results are discussed in the light of the prevailing understanding of the physical metallurgy of high chromium low carbon steels.     

浮力变化的量热法与辐射力天平法测量超声功率比较研究

辐射力天平法测量超声功率,一般只适合测量较小功率的平面波超声功率。根据介质吸收热量发生体积变化、浮力变化的原理,设计并实现了蓖麻油吸收靶,建立了采用天平的量热法超声功率测量装置,解决了传统量热法需精确测量温度场分布的问题。经与辐射力天平法装置的比较,验证了所建立超声功率测量装置的有效性,并将进一步推广至大功率、非平面波超声功率的测量。     

Preparation and characterization of pyrolytic oil through pyrolysis of neem seed and study of performance,combustion and emission characteristics in CI engine

This paper deals with production of pyrolytic oil from neem seed and using this pyrolytic oil in the form of blend with fossil diesel to study the performance and emission characteristics in CI engine. Thermal and catalytic pyrolysis of non edible neem seed was performed in a slow fixed bed pyrolyser to produce pyrolytic oil. Maximum pyrolytic oil obtained in thermal pyrolysis was 55% wt and in catalytic pyrolysis was 60% wt using both Al₂O₃ and K₂CO₃ catalysts followed by 41% wt and 38% wt for zeolite and kaolin catalysts respectively. The catalytic pyrolysis improved pH and calorific values of 12.4% and 14.4% respectively as compared to thermal pyrolysis. Blends of neem seed catalytic pyrolytic oil (NB) with fossil diesel in the ratio of 5% (NB5) and 10% (NB10) by volume were tested on an unmodified CI engine. Brake thermal efficiency (BTE) was lower at part load conditions and higher at full load condition up to 3.7% in the case of blends as compared to fossil diesel operation. Higher Brake Specific Fuel Consumption (BSFC) was observed in the case of NB5 blend on all load conditions, up to 23.9%. Reduction in emission levels were observed for HC (46.9%), CO (42.2%), CO₂ (29.8%) and NOx (20.7%) at full load condition. This study observed that neem seed catalytic pyrolytic oil is a potential renewable and sustainable green fuel.     

Influence of compositional ratio on microstructure and martensitic transformation of CuZr shape memory alloys

In the present work the effect of Cu/Zr atomic ratio on structural and calorimetric properties of this high temperature shape memory alloy (HTSMA) is studied. It has been discussed the changes induced by Cu/Zr ratio on the martensitic transformation temperatures and the corresponding transformation heats coupled with the phases microstructure. The modification of the Cu content in the range ±2% at, around the equiatomic composition, does not drastically change the thermal properties of the alloys. Moreover, the Cu/Zr ratio strongly influences the microstructure in terms of the presence and amount of the other characteristic phases, Cu₁₀Zr₇ and CuZr₂, in the place of the CuZr phase. The understanding of the basic properties of the binary system can be of great help for further investigations on CuZr based systems with other alloying elements.     

Structure and transformation behaviour of rapidly solidified Ni–Al–Hf alloys

Rapidly solidified Ni–Al–Hf alloys of ternary eutectic compositions were studied by X-ray diffractometry, transmission electron microscopy and differential scanning calorimetry. Ni₆₆Hf₂₀Al₁₄ amorphous alloy with relatively high Hf/Al ratio showed high tensile strength of 1600 MPa and high thermal stability against crystallization. The formation of a nanoscale metastable intermetallic compound having a body-centered cubic lattice with a lattice parameter of a=1.22 nm was observed in the alloys with higher Al than Hf content. The transformation of an amorphous+metastable cubic mixture to AlNi₃ produces AlNi₃ of the same composition as the AlNi₃ phase formed on rapid solidification. Pm m AlNi₃ phase can dissolve up to 11 at.% Hf.