Use of calorimetry and thermal analysis to assess the heat of supplementary cementitious materials during the hydration of composite cementitious binders

Journal of Thermal Analysis and Calorimetry - The present paper focuses on the suitability, variability and versatility of thermal analysis and calorimetry methods in the study of cement hydration...     

Synthesis of trans-Non-4-EN-2-Ynoic Acid

The synthesis of the title compound has been achieved from 1 -methoxybutenyne in 77% yield in three steps. A reaction mechanism is given to explain exclusive formation of 4,5-trans-configuration.     

Specular reflectance studies of bromide adsorption on gold

Specular reflectance changes have been used to examine the specific adsorption of bromide on gold in the presence of a large excess of supporting electrolyte (NaF) which is not specifically adsorbed. A linear relation has been demonstrated between the reflectance changes and the surface excess of bromide through the examination of the time dependence of the reflectance under conditions where the rate of adsorption of the bromide is diffusion controlled and hence known. The adsorption isotherms have been found to follow Temkin behavior. The electrosorption valency has been evaluated from the charge and surface excess at constant potential and found to be ?0.49 to ?0.59, depending on the potential. Various mechanisms for the subtantial changes in reflectance attending the specific adsorption of anions are discussed. The observed effects cannot be explained on the basis of changes in the charge on the electrode and corresponding changes in the contribution of the conduction band to the surface optical properties. The principal mechanism is proposed to be modifications in the surface electronic states of the metal electrode through direct orbital interactions between the adsorbed anions and the metal.     

Ultrasound-assisted extraction in the fractionation analysis of gravitation dust sediments

Ultrasound-assisted extraction is frequently used to prepare analytical samples and is considered an alternative to conventional extraction techniques. Extraction procedures are used in the fractionation analysis for the isolation of various element species. The recoveries of elements in the ultrasonic extracts were tested by comparing these results with those of conventional extraction procedures. Contents of Cu, Pb, and Zn in extracts obtained by both the conventional and the ultrasound-assisted extraction were determined by flame atomic absorption spectrometry. The optimal conditions for the ultrasound-assisted extraction (sonication power = 90%, depth of ultrasonic probe = 4 cm) were determined, and the extraction time was shortened to 6 min (using EDTA) and to 5 min using HNO₃ extraction reagent.     

Simulation of parametric ship roll and hull twist oscillations

A new mechanical model for simulating both the ship oscillations and the induced twisting of the hull in the case of longitudinal seas is presented. Particular attention is given to the onset of parametric rolling, which may result from non-linearly coupled heave-pitch-roll motions. It is shown that in these sea conditions the phenomenon of twisting is likely to occur under a mechanism similar to that of parametric rolling.