Search Results
You are looking at 21 - 30 of 45 items for
- Author or Editor: S. Sun x
- Refine by Access: All Content x
Summary
The new PGAA facility using diffracted neutron beam was developed in Korea. The basic characteristics of the facility were studied in detail. A general formalism of the k 0 factor as extended to non-1/v absorber and arbitrary neutron spectrum was discussed and the actual data for Cd, Sm, Eu, Gd have been measured and determined successfully owing to the simple nature of the diffracted neutron spectrum. The k 0 factors for B, N, Si, P, S and Cl were also determined and showed consistent results with previously reported ones. At an early stage, feasibility of boron concentration analysis and measurement of thermal neutron capture cross sections has been studied. The PGAA facility is now open to users. A considerable amount of beam time is already dedicated to studies on the elemental analysis.
Low-temperature heat capacities and standard molar enthalpy of formation of the complex
Zn(Val)SO4·H2O(s) (Val=L-α-valine)
Abstract
Low-temperature heat capacities of a solid complex Zn(Val)SO4·H2O(s) were measured by a precision automated adiabatic calorimeter over the temperature range between 78 and 373 K. The initial dehydration temperature of the coordination compound was determined to be, T D=327.05 K, by analysis of the heat-capacity curve. The experimental values of molar heat capacities were fitted to a polynomial equation of heat capacities (C p,m) with the reduced temperatures (x), [x=f (T)], by least square method. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the complex relative to the standard reference temperature 298.15 K were given with the interval of 5 K.
Enthalpies of dissolution of the [ZnSO4·7H2O(s)+Val(s)] (Δsol H m,l 0) and the Zn(Val)SO4·H2O(s) (Δsol H m,2 0) in 100.00 mL of 2 mol dm−3 HCl(aq) at T=298.15 K were determined to be, Δsol H m,l 0=(94.588±0.025) kJ mol−1 and Δsol H m,2 0=–(46.118±0.055) kJ mol−1, by means of a homemade isoperibol solution–reaction calorimeter. The standard molar enthalpy of formation of the compound was determined as: Δf H m 0 (Zn(Val)SO4·H2O(s), 298.15 K)=–(1850.97±1.92) kJ mol−1, from the enthalpies of dissolution and other auxiliary thermodynamic data through a Hess thermochemical cycle. Furthermore, the reliability of the Hess thermochemical cycle was verified by comparing UV/Vis spectra and the refractive indexes of solution A (from dissolution of the [ZnSO4·7H2O(s)+Val(s)] mixture in 2 mol dm−3 hydrochloric acid) and solution A’ (from dissolution of the complex Zn(Val)SO4·H2O(s) in 2 mol dm−3 hydrochloric acid).
Abstract
The low-temperature molar heat capacities of CoPc and CoTMPP were measured by temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 223 to 413 K for the first time. No phase transition or thermal anomaly was observed in the experimental temperature range for CoPc. However, a structural change was found to be nonreversible for CoTMPP in the temperature range of 368–403 K, which was further validated by the results of IR and XRD. The molar enthalpy ΔH m and entropy ΔS m of phase transition of the CoTMPP were determined to be 3.301 kJ mol−1 and 8.596 J K−1 mol−1, respectively. The thermodynamic parameters of CoPc and CoTMPP such as entropy and enthalpy relative to reference temperature 298.15 K were derived based on the above molar heat capacity data. Moreover, the thermal stability of these two compounds was further investigated through TG measurements. Three steps of mass loss were observed in the TG curve for CoPc and five steps for CoTMPP.
Abstract
The two complexes of [Ln(CA)3bipy]2 (Ln = Tb and Dy; CA = cinnamate; bipy = 2,2′-bipyridine) were prepared and characterized by elemental analysis, infrared spectra, ultraviolet spectra, thermogravimetry and differential thermogravimetry techniques. The thermal decomposition behaviors of the two complexes under a static air atmosphere can be discussed by thermogravimetry and differential thermogravimetry and infrared spectra techniques. The non-isothermal kinetics was investigated by using a double equal-double steps method, the nonlinear integral isoconversional method and the Starink method. The mechanism functions of the first decomposition step of the two complexes were determined. The thermodynamic parameters (ΔH ≠ , ΔG ≠ and ΔS ≠ ) and kinetic parameters (activation energy E and the pre-exponential factor A) of the two complexes were also calculated.
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.
Two hundred and ninety F9 recombinant inbred lines (RILs) derived from the bread wheat cultivar Gaocheng 8901 and the waxy wheat cultivar Nuomai 1 were used in determining the high-molecular-weight glutenin subunit (HMW-GS) and waxy protein subunit combinations and their effects on the dough quality and texture profile analysis (TPA) of cooked Chinese noodles. Seven alleles were detected at Glu-1 loci. There were two alleles found at each of the Wx-A1, Wx-B1 and Wx-D1 loci. Eight allelic combinations were observed for HMW-GS, LMW-GS and waxy proteins, respectively. Both the 1/7+8/5+10 and 1/7+8/5+12 combinations contributed to dough elasticity, and the 1/7+8/5+10 combination also provided better TPA characteristics. Compared to Wx protein, HMW-GS was more important on dough alveogram properties. LMW-GS significantly affected springiness and cohesiveness; HMW-GS mainly affected the hardness; Wx×LMW-GS significantly affected the springiness, cohesiveness and chewiness; HMW-GS×Wx×LMW-GS mainly influenced the springiness and chewiness. But HMW-GS×LMW-GS only affected the spinginess. These indicated the TPA of noodles was significantly affected by the interactions between glutenin and Wx proteins.
A total of 232 accessions of tetraploid species, durum wheat (Triticum turgidum L. ssp. durum Desf., 2n=4x=28, AABB) with a widespread origin of various countries were used in this study. Their high molecular weight glutenin subunit (HMW-GS) composition was identified by Matrix-assisted laser desorption/ionization time-of-flight Mass Spectrometry (MALDI-TOF-MS). Among all accessions analyzed, 194 were homogeneous for HMW-GS, 38 were heterogeneous, and 62 possessed unusual or new subunits. The results revealed a total of 43 alleles, including 5 at Glu-A1 and 38 at Glu-B1, resulting in 60 different allele combinations. The Glu-B1 locus displayed higher variation compared with Glu-A1. Glu-A1c (55.2%) and Glu-B1aj (17.7%) were the most frequent alleles at Glu-A1 and Glu-B1, respectively. Two allele types (“null” and 1) at the Glu-A1 locus and three allele types (7OE + 8, 14+15, 8) at the Glu-B1 locus appeared to be the common types in the 232 accessions. A total of 23 new alleles represented by unusual subunits were detected at the Glu-A1 and the Glu-B1 locus.
The powdery mildew resistance gene Pm2 is effective in China. Bulked segregant analysis (BSA) was used to search for microsatellite markers linked to Pm2 . Twenty-one microsatellite primer pairs located on chromosome 5DS were screened; three polymorphic loci Xcfd81 -5DS, Xgwm190 -5DS, and Xcfd18 -5DS were linked to Pm2 using an F 2 population from Chinese Spring × C114118 (with Pm2 ) consisting of 814 individuals. The genetic distances between Pm2 and the three markers were: 2.0cM, 34.2cM and 44.2cM, respectively. Microsatellite marker Xcfd81 -5DS could be used in marker assisted selection for Pm2 provided any chosen Pm2 source also carries the relevant marker.
Phyllostachys edulis (PES), the most important bamboo species in China, is widely distributed in East Asia. Flavonoids, which are important bioactive natural compounds, often have similar structures, making their structural elucidation difficult. The aim of this study was to represent valuable, reliable mass spectral data for the identification of flavonoids in plant leaves. Ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC–Q-TOF-MS/MS) method was established for characterization and identification of the major flavonoids in PES leaf extract. A total of 13 flavonoids were simultaneously characterized, and their proposed characteristic product ions and fragmentation pathways were investigated. Thirteen compounds were separated on an Agilent Zorbax RRHD SB-C18 column (150 mm × 2.1 mm, 1.8 μm). On the basis of comparing with the 4 reference standards and the literature data, the other 9 flavonoids were identified by tandem mass spectrometry (MS/MS). Eight compounds (compounds 1, 4, 5, 8, 9, 10, 11, and 12) were found in PES leaves for the first time. An efficient UPLC–QTOF-MS/MS method was successfully applied for the structural identification of flavonoids in PES leaves. These results have practical applications for the rapid identification and structural characterization of these compounds in crude bioactive extracts or mixtures.
Abstract
Polyimide BTDA-ODA sample was prepared by polycondensation or step-growth polymerization method. Its low temperature heat capacities were measured by an adiabatic calorimeter in the temperature range between 80 and 400 K. No thermal anomaly was found in this temperature range. A DSC experiment was conducted in the temperature region from 373 to 673 K. There was not phase change or decomposition phenomena in this temperature range. However two glass transitions were found at 420.16 and 564.38 K. Corresponding heat capacity increments were 0.068 and 0.824 J g–1 K–1, respectively. To study the decomposition characteristics of BTDA-ODA, a TG experiment was carried out and it was found that this polyimide started to decompose at ca 673 K.
