The temperature integral cannot be analytically integrated and many simple closed-form expressions have been proposed to use
in the integral methods. This paper first reviews two types of simple approximation expressions for temperature integral in
literature, i.e. the rational approximations and exponential approximations. Then the relationship of the two types of approximations
is revealed by the aid of a new equation concerning the 1st derivative of the temperature integral. It is found that the exponential approximations are essentially one kind of rational
approximations with the form of h(x)=[x/(Ax+k)]. That is, they share the same assumptions that the temperature integral h(x) can be approximated by x/Ax+k). It is also found that only two of the three parameters in the general formula of exponential approximations are needed
to be determined and the other one is a constant in theory. Though both types of the approximations have close relationship,
the integral methods derived from the exponential approximations are recommended in kinetic analysis.
Slow pyrolysis of walnut shell which is a cheap and abundantly available solid waste was carried out using thermogravimetric
analysis. The effects of raw material heating rate on the pyrolysis properties and kinetic parameters were investigated. A
two-step consecutive reaction model were used to simulate the pyrolysis process. The kinetic parameters were established by
using the pattern search method. Comparison between experimental data and the model prediction indicated that the two-step
consecutive reaction model can better describe the slow pyrolysis of walnut shell as the formation of an intermediate during
the pyrolysis process was taken into account.
, which frequently occurs in non-isothermal thermal analysis, are presented. A series of the approximations for the temperature
integral with different complexity and accuracy are proposed from the procedure. For commonly used values of m in kinetic analysis, the deviation of most approximations from the numerical values of the integral is within 0.7%, except
the first approximation (within 4.0%). Since they are simple in calculation and hold high accuracy, the approximations are
recommended to use in the evaluation of kinetic parameters from non-isothermal kinetic analysis.
frequently occurs in non-isothermal kinetic analysis. Here E is the activation energy, R the universal gas constant and T the absolute temperature. The exponent m arises from the temperature dependence of the pre-exponential factor. This paper has proposed two new approximate formulae
for the generalized temperature integral, which are in the following forms:
where hm(x) is the equivalent form of the generalized temperature integral. For commonly used values of m in kinetic analysis, the deviations of the new approximations from the numerical values of the integral are within 0.2 and
0.03%, respectively. In contrast to other approximations, both the present approaches are simple, accurate and can be used
easily in kinetic analysis.
A novel method for separating and concentrating magnolol and honokiol from Magnoliae Cortex by solvent sublation and analysis of the compounds by high-performance liquid chromatography (HPLC) has been established. The optimum conditions for solvent sublation were use of n-butanol as sublation solvent, sample solution at pH 2, nitrogen flow 50 mL min–1, and sublation time 50 min. The floating product obtained under the optimum conditions was determined by HPLC analysis on a C18 reversed-phase column, with 22:78 (%, v/v) water-methanol as isocratic mobile phase at a flow rate of 1.00 mL min–1. When the method was used for quantification of magnolol and honokiol in Magnoliae Cortex recovery ranged from 98.1 to 106.1%, RSD was from 3.07 to 4.80%, and LOD for honokiol and magnolol were 0.94 and 1.14 ng mL–1, respectively.
Authors:H. Sun, X. Wang, Y. Liu, Z. Nan, and H. Zhang
In this paper studies on the oscillation regularity of the classical B–Z reaction system, and the calorimetric curves of the reaction system measured at three temperatures, 25, 27 and 29°C are described. A new way is presented for studying the regularity properties of chemical oscillation phenomena from the viewpoint of reaction heat effects.
Among the progenies of crossing
Triticum turgidum — Haynaldia villosa
amphiploid with synthetic hexaploid wheat
(T. carthlicum / Aegilops tauschii)
Am3, two lines (SN030713 and SN05078), with good resistance to stripe rust and powdery mildew, were developed. Cytological studies demonstrated that SN030713 contained 42 chromosomes and formed 21 bivalents at meiotic metaphase I. SN05078 contained 28 chromosomes and formed 14 bivalents. Genomic
hybridization analysis using
V genomic DNA as the probe showed SN030713 and SN05078 had no large
chromosome fragments. PCR analysis with
specific primer pHv29 showed that
genetic materials were introgressed in these two lines. SSR analysis indicated that the genomic composition of SN030713 was 2n = 6x = 42 (AABBDD), and SN05078 was 2n = 4x = 28 (AABB). Introgressed
genetic materials in SN05078 were also detected.
An improved accurate coincidence correction formula has been deduced on the basis of Cox's theory considering the complex situations of differences in pulse shaping width as well as a relative delay existing between the two channels. The correctness has been examined by experiments.
The determination of the total selenium in different materials is now a routine task for many laboratories. A few problems, however, still remain concerning the choice of an efficient digestion technique and an accurate and precise detection method. For this purpose, we investigated the action of various reagents used for the wet digestion of different materials. Efficient digestion combined with preconcentration were successfully applied to biological samples. Using PIXE, selenium can be detected at 5 ppb level in a short time. The overall performance of wet digestion and PIXE methods were tested with some standard reference materials.