Microcalorimetry

A specific heat measuring instrument, with the capacity for the application of magnetic fields up to 9 T, resorting to microcalorimetry chips from the company Xensor Integration, has been successfully assembled and its functioning specifications are reported in the current paper.
With this instrument is it possible to perform specific heat measurements with applied magnetic fields up to 9 T in milligram samples. This offers our group the possibility to calculate the actual adiabatic temperature change of a material, as well as providing reliable and precise information on any phase transition that may be influenced by the application of a magnetic field.

Microcalorimetric and biological methods were carried out to determine the toxicity of dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) to wild strain of Bacillus thuringiensis. Thermokinetic parameters were obtained from the power-time curves, showing that the peak-heat output power, total heat output, and number of colonies decreased with the increases in concentration of DMA and MMA. In addition, the generation time and peak maximal time increased with the increases in the dosage of DMA and MMA. The half inhibitory concentrations of DMA and MMA were 99.02 and 142.02 microg mL(-1), respectively for the wild strain of B. thuringiensis. DMA shows higher toxicity to bacteria than MMA. The toxicity resistance of B. thuringiensis against organoarsenic(V) is quite high for the wild strain. Our work demonstrates that microcalorimetry is a very sensitive, simple, and useful technique for in vitro investigation of the toxic effect of organoarsenic(V) on microbial activity.

Given the potentiality of Fe2P based alloys for magnetocaloric application, this thesis covers various offshoot material systems related to this rich family of compounds, such as the (Mn,Fe)3(Si,P), (Mn,Co)3(Si,P) and the (Fe,Co)3(Si,P). Also covered is the assembly of a microcalorimetery setup meant for the study of certain fundamental qualities of these systems, as well as an economical optimization of the (Mn,Fe)2(P,Ge) system.

Palm shell based activated carbon prepared by K2CO3 activation is used as precursor in the production of carbon molecular sieve by chemical vapor deposition (CVD) method using benzene as depositing agent. The influences of deposition temperature, time, and flow rate of benzene on pore development of carbon molecular sieve (CMS) and methane (CH4) adsorption capacity were investigated. The parameters that varied are the deposition temperature range of 600 to 1000 °C, time from 5.0 to 60 min, and benzene flow rate from 3.0 to 15 mL/min. The results show that in all cases, increasing the deposition temperature, time, and flow rate of benzene result in a decrease in adsorption capacity of N2, pore volume and pore diameter of CMS. The BET surface area of CMS (approximately 1065 m2/g) and the adsorption capacity of CH4 were at a maximum value at a deposition temperature of 800 °C, time of 20 min and benzene flow rate of 6 mL/min. The product has a good selectivity for separating CH4 from carbon dioxide (CO2), nitrogen (N2), and oxygen (O2). © 2007 Elsevier B.V. All rights reserved.

http://ac.els-cdn.com/S0378382007000240/1-s2.0-S0378382007000240-main.pdf?_tid=51fe81f2-2364-11e4-87fa-00000aab0f6c&acdnat=1407987630_f432a70dc1530cea5ed9f86db5a9fdca 
http://www.sciencedirect.com/science/article/pii/S0378382007000240

The interactions of the cationic cellulose ether derivatives JR400 and LM200 with cationic surfactants differing in both the alkyl chain length and head group composition were investigated using microcalorimetric techniques. The presence of polymer-induced surfactant aggregation and polymerbound aggregates was detected for the majority of the surfactants investigated. The thermodynamic properties of the premicellar aggregation, the binding, and the micellization of the surfactants in the presence of polymers were evaluated and analysed in terms of the strength of the interactions between the polymer and the surfactants. The nature of these aggregates was also evaluated using conductivity, fluorescence spectroscopy, and dye solubilization techniques.

Beech and pine wood blocks were treated with 1,3-dimethylol-4,5-dihydroxyethylen urea (DMDHEU) to increasing weight percent gains (WPG). The resistance of the treated specimens against Trametes versicolor and Coniophora puteana, determined as mass loss, increased with increasing WPG of DMDHEU. Metabolic activity of the fungi in the wood blocks was assessed as total esterase activity (TEA) based on the hydrolysis of fluorescein diacetate and as heat or energy production determined by isothermal micro-calorimetry. Both methods revealed that the fungal activity was related with the WPG and the mass loss caused by the fungi. Still, fungal activity was detected even in wood blocks of the highest WPG and showed that the treatment was not toxic to the fungi. Energy production showed a higher consistency with the mass loss after decay than TEA; higher mass loss was more stringently reflected by higher heat production rate. Heat production did not proceed linearly, possibly due to the inhibition of fungal activity by an excess of carbon dioxide.

Palm shell based activated carbon prepared by K 2 CO 3 activation is used as precursor in the production of carbon molecular sieve by chemical vapor deposition (CVD) method using benzene as depositing agent. The influences of deposition temperature, time, and flow rate of ...

Water vapor adsorption on silica gel was investigated using Tian–Calvet-type microcalorimetry. Differential heat of adsorption data was obtained. The setup of microcalorimetry was used volumetric system to determine adsorption isotherms of water vapor–silica gel. The Langmuir model was used in the interpretation of the adsorption data. The Clausius–Clapeyron diagram was also given. Effective mass diffusivity of water vapor in the silica gel particle as a function of temperature was also determined. The silica gel, which was degassed under vacuum at 10−7 mbar and 120 °C for 18 h, was found to adsorb 0.6, 0.98, 1.1, 1.4, 2, 3.5, 11, 13, and 14 wt% water vapor at 120, 110, 100, 90, 75, 60, 40, 35, and 30 °C, respectively. The diffusivities of water vapor inside the silica gel for short- and long-range periods were described using kinetics data as a function of temperature in the Arrhenius form.

ABSTRACT Treatment of Varroa destructor (Anderson and Trueman) mites with propolis has displayed both narcotic and lethal effects. The length of narcosis and rate of mortality showed dependence on the concentration of propolis used, the duration of contact time and the extraction procedure. Investigation of the action of propolis on the heat production rate of Varroa mites was performed by means of a Biocalorimeter (BCP 600). Calorimetric results point to the fact that even weak propolis concentrations with feeble lethal effects have a strong influence on the specific heat production rate. Thus, treatment with a 20% propolis solution in 40% ethanol resulted in a mortality rate of only 34% but dropped the heat production rate by 75%, a corresponding 5% propolis solution had no lethal effect but reduced the specific heat production rate still by 37% and treatment with a 0.5% propolis solution in 55% ethanol resulted in a non-significant mortality rate of 7% but reduced the specific heat production rate by 29%. Propolis showed a strong impact on the structure of the calorimetric power–time (p–t) curves. The usually highly structured p–t curves were smoothed due to treatment even with weak propolis concentrations.

Purpose Use RH-perfusion microcalorimetry and other analytical techniques to measure the interactions between water vapor and amorphous pharmaceutical solids; use these measurements and a mathematical model to provide a mechanistic understanding of observed calorimetric events. Materials Isothermal microcalorimetry was used to characterize interactions of water vapor with a model amorphous system, spray-dried raffinose. Differential scanning calorimetry was used to measure glass transition temperature, T g. High-sensitivity differential scanning calorimetry was used to measure enthalpy relaxation. X-ray powder diffraction (XRPD) was used to confirm that the spray-dried samples were amorphous. Scanning electron microscopy (SEM) was used to examine particle morphology. Gravimetric vapor sorption was used to measure moisture sorption isotherms. Thermogravimetric analysis (TGA) was used to measure loss on drying. Results A moisture-induced thermal activity trace (MITAT) provides a rapid measure of the dependence of molecular mobility on moisture content at a given storage temperature. At some relative humidity threshold, RHm, the MITAT exhibits a dramatic increase in the calorimetric rate of heat flux. Simulations using calorimetric data indicate that this thermal event is a consequence of enthalpy relaxation. Conclusions RH-perfusion microcalorimetry is a useful tool to determine the onset of moisture-induced physical instability of glassy pharmaceuticals and could find a broad application to determine appropriate storage conditions to ensure long-term physical stability. Remarkably, thermal events measured on practical laboratory timescales (hours to days) are relevant to the stability of amorphous materials on much longer, pharmaceutically relevant timescales (years). The mechanistic understanding of these observations in terms of enthalpy relaxation has added further value to the use of RH-perfusion calorimetry as a rapid means to characterize the molecular mobility of amorphous solids.

Sulfate-reducing bacteria (SRB) were isolated from anaerobic sludge of yeast factory wastewater treatment plant by cultivation on Postgate C medium. Microcalorimetry was used to monitor the anaerobic digestion processes and to measure the growth rates of sulfate-reducing bacteria. The maximum growth rates determined by microcalorimetry and ATP analysis were different—μmax(dQ/dt) = 0.165 ± 0.008 h−1 and μmax(NATP) = 0.207 ± 0.013 h−1. Experiments on the cultivation of SRB from yeast industry wastewater treatment plant in batch culture showed that during the first 20 h the concentration of sulfate decreased from 78.3mMdown to 62.2mMwhile the increase of sulfide production was negligible. Perceptible amount of sulfide (7.82 mM) appeared on the 33.5 h of fermentation together with a peak on the power–time curve and considerable increase in the cell count (1.26 × 109). First steps of sulfate metabolism (activation of sulfate by ATP sulfurylase, production of H2) are accompanied by endothermic heat effects, therefore the values of thermal power remain moderate until the evolution of sulfide starts. The influence of green microalgae Chlorococcum sp. preparation Biotreat 100) on the growth characteristics of microorganisms was also studied. Identification of one SRB strain was started by sequencing of PCR-amplified 16S rRNA gene. Two sets of primers were used for PCR amplification, both specific for domain Bacteria but giving different gene fragments. PCR-products were purified with JETQUICK kit according to the manufacturer instructions.