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- Author or Editor: X. Wang x
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Abstract
The thermal dehydration of La[Co(CN)6]⋅5H2O proceeded through at least three stages from the temperature range of30~230C, and an abrupt mass loss occurred around 350C and the perovskite type oxide,LaCoO3 was obtained at 1000C. After dehydration, the color of the anhydride changed from white to pale blue around 230C and furthermore, the color changed to blue around 290C. These color changes were discussed on the basis of the changes of coordination structures around Co ions. In La[Co(CN)6]⋅5H2O, Co3+ ions lie at the center of the Oh crystal field consisted of six CN– ions. However, in the pale blue specimen, Co3+ ions were situated in the center of D4h crystal field which was distorted the Oh one by lengthening of the trans CN– ions along z-axis. In the blue specimen, Co3+ ions were reduced to Co2+ ions which were situated in the Td crystal field formed by four CN–ions as [Co(CN)4]2–.
Abstract
Heat capacities of both the ingot-like and melt-spun Al-Sr alloys have been measured through the temperature range 373 to 1060 K using differential scanning calorimetry. The experimental results show that rapid solidification has a slight effect on the temperature dependence of the heat capacities of the Al-Sr alloys. The heat capacities of the melt-spun Al-Sr alloys increase more slowly than those of the ingot-like alloys with increasing temperature from 373 to 900 K. Furthermore, the effect of rapid solidification on the heat capacities becomes more obvious with increasing Sr concentration in the Al-Sr alloys. The data of the heat capacities between 373 and 900 K have been fitted with the least square method and a linear dependence on temperature was assumed for that temperature range.
Abstract
On dehydration of La[Co(CN)6]5H2O, the color of the complex, changes from white to pale blue at around 230C. Heating the pale blue specimen, the color changes to deep blue at around 290C. This deep blue specimen is easily rehydrated to a pink one. As reported previously, in the pale blue specimen, Co3+ ions are situated in the center of the D4h crystal field formed by six CN- ions. The deep blue specimen is due to the presence of [Co(CN)4]2- ions in which Co2+ was situated in a Td coordination field formed by four CN- ions and the Co-C bond length is 1.67 Ĺ. The pink species corresponded to trans-[Co(CN)4(H2O)2]2- and the bond lengths of Co-C and Co-O are 1.89 and 1.85 Ĺ, respectively. The Raman spectra of the complex observed at 25C displays two bands at 2157 and 2176 cm-1 associated with the vibration of C-N bond, and the band of 2157 cm-1 was split into two bands, 2150 and 2156 cm-1, at around 100C. When the complex was heated to around 230C, three new bands were observed at 2103, 2116 and 2141 cm-1. The bands of 2103 and 2116 cm-1 were assigned to the stretching vibration of C=N bonding to Co2+. The band of 2141 cm-1 was assigned to the stretching vibration of the inverted CN- as follows: Co-C=N-La→Co-N=C-La. The activation energy for the inversion of CN- was estimated as 67 kJ mol-1.
Abstract
The effect of excipients on the secondary structure of lyophilized proteins was studied through second-derivative Fourier transform infrared (FTIR) spectroscopic analysis. The glass transition temperature (T g), denaturation temperature (T d) and moisture content were determined by differential scanning calorimetry (DSC) and thermogravimetry (TG). T g, T d and the preservation of protein secondary structure were found to be dependent upon the type and amount of the excipient included in the formulation. Meanwhile, the lyophilized proteins easily adsorbed amounts of moisture during storage to reduce their T gs and stability.
Abstract
The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order to disclose the decomposition kinetics of charged LiCoO2 used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged LiCoO2. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E a=148.87 and 88.87 kJ mol−1 based on TG and C80 data, respectively.
Abstract
It is proposed to use 14 MeV neutrons tagged by the associated particle neutron time-of-flight technique (APnTOF) to identify the fillers of unexploded ordnances (UXO) by characterizing their carbon, nitrogen and oxygen contents. To facilitate the design and construction of a prototype system, a preliminary simulation model was developed, using the Geant4 toolkit. This work established the toolkit environment for (a) generating tagged neutrons, (b) their transport and interactions within a sample to induce emission and detection of characteristic gamma-rays, and (c) 2D and 3D-image reconstruction of the interrogated object using the neutron and gamma-ray time-of-flight information. Using the modeling, this article demonstrates the novelty of the tagged-neutron approach for extracting useful signals with high signal-to-background discrimination of an object-of-interest from that of its environment. Simulations indicated that an UXO filled with the RDX explosive, hexogen (C3H6O6N6), can be identified to a depth of 20 cm when buried in soil.
Abstract
In 1951, unsaturated prairie soil was contaminated with fission products and actinides. Fifty years later, in 2001, soil samples were collected from the contaminated site. This paper describes the techniques used to analyze these samples, including gamma-spectroscopy (GS) for 137Cs, neutron activation analysis (NAA/GS) for 238U, liquid scintillation counting (LSC) for 90Sr and inductively coupled plasma mass spectroscopy (ICP-MS) for 238U and 113mCd. As expected, ICP-MS was found to have the lowest detection level, while the techniques were ranked in order of increasing uncertainty as GS, NAA/GS, ICP-MS and LSC.
‘Egusi’ melon Citrullus lanatus (Thunb.) Matsum. & Nakai is an important vegetable crop in Nigeria, grown for its edible seeds and oils. The diverse areas in which the crop is cultivated make it a rich source of genetic resources for the species. To explore its diversity, 50 accessions of ‘egusi’ melon were collected from different agro-ecological parts of Nigeria and were evaluated using 25 simple sequence repeat (SSR) markers. A total of 49 bands were scored, of which 42 were polymorphic, accounting for 93.60% of the polymorphic loci. The PIC value ranged from 0.36–0.80. UPGMA cluster analysis revealed five distinct groups for SSR. PCA analysis revealed the distinction of the accessions NG/OE/MAR/09/014, NG/TO/APR/09/027 and A8. Based on the results of this study, SSR markers appear to be particularly useful for the estimation of genetic similarity among diverse accessions of melon.
Abstract
Both microcalorimetric determination of displacement adsorption enthalpies ΔH and measurement of adsorbed amounts of guanidine – denatured lysozyme (Lys) refolding on the surface of hydrophobic interaction chromatography (HIC) packings at 308 K were carried out and compared with that at 298 K. Study shows that both temperature and concentration of guanidine hydrochloride (GuHCl) affect the molecular mechanism of hydrophobic interaction of protein with adsorbent based on the analysis of dividing ΔH values into three kinds of enthalpy fractions. The adsorption in higher concentrations of GuHCl (>1.3 mol L–1) at 308 K is an enthalpy-driving process, and the adsorption under other GuHCl concentrations is an entropy-driving process. The fact that the Lys denatured by 1.8 mol L–1 GuHCl forms a relatively stable intermediate state under the studied conditions will not be changed by temperature.
Hydrated goethite nanorodS
Vibration spectral properties, thermal stability, and their potential application in removing cadmium ions
Abstract
Vibration spectral properties and dehydration behaviors of goethite nanorods with diameters ranging from 13 to 32 nm were investigated using infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. All goethite nanorods were highly hydrated with physisorbed and chemisorbed water. As the diameters of goethite nanorods increased, the hydroxyl deformation vibration in the a-b plane showed a significant blue shift, while the Fe-O vibration in the a-b plane shifted to lower frequencies, indicating an enhancement of O-H bond and the ionicity of Fe-O in a-b plane. The hydrated goethite nanorods are also proved to be useful in environmental remedy because of their excellent removal ability of heavy metal ions.
