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Abstract  

As one primary component of Vitamin B3, nicotinic acid [pyridine 3-carboxylic acid] was synthesized, and calorimetric study and thermal analysis for this compound were performed. The low-temperature heat capacity of nicotinic acid was measured with a precise automated adiabatic calorimeter over the temperature rang from 79 to 368 K. No thermal anomaly or phase transition was observed in this temperature range. A solid-to-solid transition at Ttrs=451.4 K, a solid-to-liquid transition at Tfus=509.1 K and a thermal decomposition at Td=538.8 K were found through the DSC and TG-DTG techniques. The molar enthalpies of these transitions were determined to be ΔtrsHm=0.81 kJ mol-1, ΔfusHm=27.57 kJ mol-1 and ΔdHm=62.38 kJ mol-1, respectively, by the integrals of the peak areas of the DSC curves.

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Abstract  

The complex of [Nd(BA)3bipy]2 (BA = benzoic acid; bipy = 2,2′-bipyridine) has been synthesized and characterized by elemental analysis, IR spectra, single crystal X-ray diffraction, and TG/DTG techniques. The crystal is monoclinic with space group P2(1)/n. The two–eight coordinated Nd3+ ions are linked together by four bridged BA ligands and each Nd3+ ion is further bonded to one chelated bidentate BA ligand and one 2,2′-bipyridine molecule. The thermal decomposition process of the title complex was discussed by TG/DTG and IR techniques. The non-isothermal kinetics was investigated by using double equal-double step method. The kinetic equation for the first stage can be expressed as dα/dt = A exp(−E/RT)(1 − α). The thermodynamic parameters (ΔH , ΔG , and ΔS ) and kinetic parameters (activation energy E and pre-exponential factor A) were also calculated.

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The objective of this work was to research the antibacterial effects of orange pigment, which was separated from Monascus pigments, against Staphylococcus aureus. The increase of the diameter of inhibition zone treated with orange pigment indicated that orange pigment had remarkable antibacterial activities against S. aureus. Orange pigment (10 mg ml−1) had a strong destructive effect on the membrane and structure of S. aureus by the analysis of scanning electron microscopy as well as transmission electron microscopy. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) further demonstrated that the cell membrane was seriously damaged by orange pigment, which resulted in the leakage of protein from S. aureus cells. A significant decrease in the synthesis of DNA was also seen in S. aureus cells exposed to 10 mg ml−1 orange pigment. All in all, orange pigment showed excellent antibacterial effects against S. aureus.

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Abstract  

The heat capacities of 2-benzoylpyridine were measured with an automated adiabatic calorimeter over the temperature range from 80 to 340 K. The melting point, molar enthalpy, Δfus H m, and entropy, Δfus S m, of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03 kJ mol–1 and 66.07±0.05 J mol–1 K–1, respectively. The purity of the compound was calculated to be 99.60 mol% by using the fractional melting technique. The thermodynamic functions (H TH 298.15) and (S TS 298.15) were calculated based on the heat capacity measurements in the temperature range of 80–340 K with an interval of 5 K. The thermal properties of the compound were further investigated by differential scanning calorimetry (DSC). From the DSC curve, the temperature corresponding to the maximum evaporation rate, the molar enthalpy and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2 kJ mol–1 and 92.2±0.4 J K–1 mol–1, respectively, under the experimental conditions.

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Abstract  

The concentrations and distributions of total halogen (TX), extractable organohalogen (EOX) and extractable persistent organohalogen (EPOX) were determined in 20 kinds of yogurt specimens collected from Chinese supermarkets using neutron activation analysis (NAA) and gas chromatography equipped with a 63Ni electron capture detector (GC-ECD). The results indicated that the halogens in yogurt mainly existed as non-extractable organohalogen compounds. About 25–30% of EOX was EPOX. EOCl and EPOCl were the main organohalogen species in yogurt. The average concentration of the identified organochlorine, such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), was below 4% of EPOCl.

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Abstract  

The molar heat capacity, C p,m, of a complex of holmium chloride coordinated with L-aspartic acid, Ho(Asp)Cl2·6H2O, was measured from 80 to 397 K with an automated adiabatic calorimeter. The thermodynamic functions H T-H 298.15 and S T-S 298.15 were derived from 80 to 395 K with temperature interval of 5 K. The thermal stability of the complex was investigated by differential scanning calorimeter (DSC) and thermogravimetric (TG) technique, and the mechanism of thermal decomposing of the complex was determined based on the structure and the thermal analysis experiment.

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Abstract

In this paper, organic phase change materials (PCM)/Ag nanoparticles composite materials were prepared and characterized for the first time. The effect of Ag nanoparticles on the thermal conductivity of PCM was investigated. 1-tetradecanol (TD) was selected as a PCM. A series of nano-Ag-TD composite materials in aqueous solution were in-situ synthesized and characterized by means of thermal conductivity evaluation method, TG-DSC, IR, XRD and TEM. The results showed that the thermal conductivity of the composite material was enhanced as the loading of Ag nanoparticles increased. The composite materials still had relatively large phase change enthalpy. Their phase change enthalpy could be correlated linearly with the loading of TD, but their phase change temperature was a little bite lower than that of pure TD. The thermal stability of the composite materials was close to that of pure TD. It appeared that there was no strong interaction between the Ag nanoparticles and the TD. Furthermore, the experiment results indicated that the Ag nanoparticles dispersed uniformly in the materials, occurred in the forms of pure metal.

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Shewanella putrefaciens supernatant was found to increase the virulence factors of Vibrio parahaemolyticus by efficiently degrading its acylhomoserine lactone (AHL). To further reveal the regulation mechanism and its key degrading enzyme, a potential AHL-degrading enzyme acylase (Aac) from S. putrefaciens was cloned, and the influences of temperature, pH, protein modifiers, and metals on Aac were tested. Aac was significantly influenced by temperature and pH, and exhibited the highest AHL-degrading activity at temperatures of 37 °C and pH of 8. Mg2+ and Fe2+ can further increase the AHL-degrading activity. 10 mM EDTA inhibited its activity possibly by chelating the co-factors (metals) required for Aac activity. Tryptophan and arginine were identified as key components for Aac activity that are critical to its AHL-degrading activity. This study provides useful information on Aac and for V. parahaemolyticus control.

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Abstract  

As one 3-D coordination polymer, lead formate was synthesized; calorimetric study and thermal analysis for this compound were performed. The low-temperature heat capacity of lead formate was measured by a precise automated adiabatic calorimeter over the temperature range from 80 to 380 K. No thermal anomaly or phase transition was observed in this temperature range. A four-step sequential thermal decomposition mechanism for the lead formate was found through the DSC and TG-DTG techniques at the temperature range from 500 to 635 K.

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Abstract  

Molar heat capacities (C p,m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of C p,m vs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding function is as follows: for 78 K≤T≤383 K, C p,m/J mol-1 K-1=19.086X 4+15.951X 3-5.2548X 2+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {ΔH TH 298.15} and {S T-S 298.15}, were derived. Combustion energy of aspirin (Δc U m) was determined by static bomb combustion calorimeter. Enthalpy of combustion (Δc H o m) and enthalpy of formation (Δf H o m) were derived through Δc U m as - (3945.262.63) kJ mol-1 and - (736.411.30) kJ mol-1, respectively.

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