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  • Author or Editor: Y. Zhao x
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Abstract  

Positron annihilation lifetime technique was applied to study the electric field dependence of size, intensity and size distribution of free volumes in various liquid crystals negative nematic MBBA(N-(4-methoxybenzylidene)-4-n-butylaniline), positive nematic 5CB (4-cyano-4-n-pentylbiphenyl) and cholesteric mixture of MBBA and cholesteryl oleate. Positron annihilation decay curves were obtained in the direct and alternate electric field range from 0 to 120 V/mm, and annihilation curves were resolved into four lifetime components. The relation between the free volume parameters and the variation of molecular alignment is discussed for nematic and cholesteric liquid crystals.

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Abstract  

The two complexes, [Ln(Ala)2(Im)(H2O)](ClO4)3 (Ln=Pr, Gd), were synthesized and characterized. Using a solution-reaction isoperibol calorimeter, standard enthalpies of reaction of two reactions: LnCl3⋅6H2O(s)+2Ala(s)+Im(s)+3NaClO4(s)=[Ln(Ala)2(Im)(H2O)](ClO4)3(s)+3NaCl(s)+5H2O(l) (Ln=Pr, Gd), at T=298.15 K, were determined to be (39.260.10) and (5.330.12) kJ mol–1 , respectively. Standard enthalpies of formation of the two complexes at T=298.15 K, Δf H Θ m {[Ln(Ala)2(Im)(H2O)](ClO4)3(s)} (Ln=Pr, Gd), were calculated as –(2424.23.3) and –(2443.43.3) kJ mol–1 , respectively.

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Abstract  

Inhalation of tobacco smoke is ranked second to food as a source of210Pb and210Po exposure to man. Assay of210Pb and210Po in commercially available tobacco collected from many countries have been carried out to assess the potential risk from210Po present in tobacco.The range of210Po contained in the tobacco grands varied from 10.08 to 15.0 mBq/tob or 13.0 to 20.1 mBq/g and the mean was 11.6 mBq/tob or 15.4 mBq/g. During the International Standard Smoking process about 50% of210Po present in tobaccos was transferred into the smoke and the other 50% remained in the ash and butt. About 10% of the total210Po of tobacco was inhaled by smoke through mainstream smoke. One pack-a-day smoker inhaled 24 mBq of210Po per day through smoking and the annual inhalation was 8.8 Bq. The risk of mortality from lung cancer caused by210Po in tobaccos was 18 per million persons for the above model.

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Abstract  

The two complexes, [RE(Gly)4(Im)(H2O)](ClO4)3(s)(RE = Eu, Sm), have been synthesized and characterized. The standard molar enthalpies of reaction for the following reactions, RECl3·6H2O(s)+4Gly(s)+Im(s)+3NaClO4(s) = =[RE(Gly)4(Im)(H2O)](ClO4)3(s)+3NaCl(s)+5H2O(l), were determined by solution-reaction colorimetry. The standard molar enthalpies of formation of the two complexes at T = 298.15 K were derived as Δf H m Θ {Eu(Gly)4(Im)(H2O)}(ClO4)3(s)} = = −(3396.6±2.3) kJ mol−1 and Δf H m Θ {Sm(Gly)4(Im)(H2O)}(ClO4)3(s)} = −(3472.7±2.3) kJ mol−1, respectively.

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Abstract  

The concentration of radon in an underground research facility (URF) was measured by setting up 12 sampling points in the URF and with 3 different measurement methods. All the methods were calibrated in the radon laboratory of the No. 6 Institute of Nuclear Industry. The accumulation of radon in the URF was observed before a ventilation system was applied. The reduction of radon concentration in the URF by 1-hour ventilation was also observed. Experimental result indicates that the concentration of radon in the URF increased from 15 to 50 Bq·m−3 in 5 days without ventilation, and decreased to less than 10 Bq·m−3 with 1-hour ventilation. Applying the average working time of 4 hours per day of the workers in the URF, the additional effective dose is 0.75 msv·y−1 when 1 hour ventilation is applied before entering the URF and 13 mSv·y−1 without ventilation. These figures strongly suggest that for the health of the workers, ventilation in such underground research facilities is needed.

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Abstract  

The thermal behavior of rutin extracted from the buds of Sophora japonica L. by different methods and conditions have been investigated using TG and DTG. The results showed that every sample had different mass loss, curve shape, and peak location related to varied extraction technology. The TG-DTG characteristics of the rutin sample extracted by alkali-dissolution and acid-sedimentation with the solution adjusted to pH 9 and simply borax as stabilizer were highly similar to that of standard rutin, with the maximal purity determined by spectrophotometry. Therefore, the TG-DTG patterns could be served to characterize rutin extracted from the buds of Sophora japonica L.

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Abstract  

To determine the levels of210Pb and210Po in human tissues of people in Japan, various tissue samples were obtained at autopsy from the cadavers of 22 oncologic cases, mainly in Niigata Prefecture in northern Japan, from 1986 to 1988.Wet ashing, followed by electrochemical deposition and alpha spectrometry were used to separate and determine the210Pb and210Po present. Among the tissues analyzed, the highest concentrations of210Pb and210Po were observed in bone (sternum), liver, and kidneys. The total body burden of210Pb and210Po was found to be approximately 427 pCi and 514 pCi, respectively. This estimated210Po value did not differ significantly from values found in populations in the U.S.A. and European countries.

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Abstract  

Iron doped boehmite nanofibres with varying iron content have been prepared at low temperatures using a hydrothermal treatment in the presence of poly(ethylene oxide) surfactant. The resultant nanofibres were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). TEM images showed the resulting nanostructures are predominantly nanofibres when Fe doping is no more than 5%; in contrast nanosheets were formed if Fe doping was above 5%. For the 10% Fe doped boehmite, a mixed morphology of nanofibres and nanosheets were obtained. Nanotubes instead of nanofibres were observed in samples with 20% added iron. The Fe doped boehmite and the subsequent nanofibres/nanotubes were analysed by thermogravimetric and differential thermogravimetric methods. Boehmite nanofibres decompose at higher temperatures than non-hydrothermally treated boehmite and nano-sheets decompose at lower temperatures than the nanofibres.

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Abstract  

Different scanning calorimetry and dynamic mechanical analysis are used to study the thermal behavior of composites by melt-mixing low-density polyethylene (LDPE) matrix and zinc oxide whisker (ZnOw) fillers. Micrographs of the composites illustrate that needle or wedge shaped ZnOw are distributed uniformly in the LDPE matrix. Dielectric properties of the composites are measured in a frequency range of 1-10 MHZ. The results show that the addition of ZnOw does not affect the melting behavior of LDPE, but has an important effect on the heat of fusion, dynamic mechanical behavior, and dielectric behavior of the composites.

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