Authors:H. Gao, F. Zhao, R. Hu, H. Zhao, and H. Zhang
A method for estimating the critical temperatures (Tb) of thermal explosion for energetic materials is derived from Semenov’s thermal explosion theory and the non-isothermal kinetic
equation dα/dt=A0TBf(α)e−E/RT using reasonable hypotheses. The final formula of calculating the value of Tb is
(Tb−Te0=1. The data needed for the method, E and Te0, can be obtained from analyses of the non-isothermal DSC curves. When B=0.5 the critical temperature (Tb) of thermal explosion of azido-acetic-acid-2-(2-azido-acetoxy)-ethylester (EGBAA) is determined as 475.65 K.
Authors:Z. Dang, F. Zhao, S. Li, C. Yin, and R. Hu
The thermal decomposition characteristics of1,7-diazido-2,4,6-trinitrazaheptane (DATH) and multi-component systems containing
DATH were studied by using DSC, TG and DTG techniques. Three –NO2 groups in the DATH molecule break away first from the main chain when DATH is heated up to 200C. Following this process,
the azido groups and the residual molecule decompose rapidly to release a great deal of heat within a short time. In the multi-component
systems, DATH undergoes a strong interaction with the binder of the double-base propellant and a weak interaction with RDX.
The burning rates of the two propellants were determined by using a Crawford bomb. The results showed that the burning rate
rises by about 19–66% when 23.5%DATH is substituted for RDX in a minimum smoke propellant. Meanwhile, the N2 level in the combustion gases is enhanced, which is valuable for a reduction of the signal level of the solid propellant.
Microcalorimetry was applied to study the toxic action of two cobalt compounds such as bis(salicylideniminato-3-propyl)methylaminocobalt(II)
(denoted as Co(II)) and Co(III) sepulchrate trichloride (denoted as Co(sep)3+) on (E. coli) DH5α. The power-time curves of the E. coli DH5α growth were determined, and the thermokinetics parameters such as the growth rate constant k, the maximum power output Pm and the time (tm) corresponding to the Pm were obtained. The half-inhibitory concentrations (IC50) of Co(II) and Co(sep)3+ to E. coli DH5α were 15 and 42.1 mg mL−1, respectively.
The experimental results revealed that the toxicity of the Co(II) compound was larger than that of Co(sep)3+. On the other hand, the scanning electron microscopy (SEM) demonstrated that the two cobalt compounds had the same toxic
mechanism on E. coli DH5α, which was attributed to the damage of cell wall of the bacteria caused by both Co(II) and Co(sep)3+. Furthermore, accumulation of intracellular cobalt of E. coli DH5α, due to the interaction of Co(II) or Co(sep)3+ and E. coli DH5α, has been found by using inductively coupled plasma (ICP) analytical technique.
Authors:L. Yang, F. Xu, L. Sun, Z. Zhao, and C. Song
Microcalorimetry was applied to study the effect of cephalosporins (cefazolin sodium and cefonicid sodium) on the E. coli growth. The microbial activity was recorded as power-time curves through an ampoule method with a TAM Air Isothermal Microcalorimeter
at 37°C. The parameters such as the growth rate constant (k), inhibitory ratio (I), the maximum power output (Pm) and the time corresponding to the maximum power output (tm) were calculated. The change tendencies of k, with the increasing of concentration (C) of the two cephalosporins, are similar which show that cefazolin sodium and cefonicid sodium have the same inhibitory mechanism.
The experimental results reveal that cefonicid sodium has a stronger antibacterial activity towards E. coli than that of cefazolin sodium and this was coincide with the clinical manifestations.
Authors:B. Yan, H. X. Ma, N. N. Zhao, T. Mai, J. R. Song, F. Q. Zhao, and R. Z. Hu
As N-2′,4′-dinitrophenyl-3,3-dinitroazetidine (DNPDNAZ) is an important derivative of 3,3-dinitroazetidine, its thermal behavior was studied under 0.1 and 2 MPa by the differential scanning calorimetry (DSC) method. The results of this study show that there are one melting process and two exothermic decomposition processes. Its kinetic parameters of the intense exothermic decomposition process were obtained from the analysis of the DSC curves. The activation energy and the mechanism function under 0.1 MPa are 167.26 kJ mol−1 and f(α) = 3(1 + α)2/3[(1 + α)1/3− 1]−1/2, respectively, and the said parameters under 2 MPa are 169.30 kJ mol−1 and f(α) = 3(1 + α)2/3[(1 + α)1/3− 1]−1/2, respectively. The specific heat capacity of DNPDNAZ was determined using a continuous Cp mode of micro-calorimeter. Using the relationship between Cp and T with the thermal decomposition parameters, the time of the thermal decomposition from initialization to thermal explosion (adiabatic time-to-explosion, tTIAD), the self-accelerating decomposition temperature (TSADT), thermal ignition temperature (TTIT), critical temperatures of thermal explosion (Tb), and half-life (t1/2) were obtained to evaluate its thermal safety under different pressures.
Authors:F. McDaniel, S. Matteson, D. Weathers, J. Duggan, D. Marble, I. Hassan, Z. Zhao, and J. Anthony
Accelerator Mass Spectcrometry (AMS) is being used for both radionuclide dating and stable isotope trace element determination with limits of high sensitivity. The areas of applications of radionuclide AMS include oceanography, terrestrial studies, glaciology, hydrology, environmental studies, meteorology, archaeology, anthropology, analysis of crude oils, biomedical and materials sciences, etc. The techniques and applications of radionuclide AMS are reviewed. The applications of stable element AMS include the measurements of trace impurities in electronic and other materials. The techniques and applications of stable element AMS are discussed with particular emphasis on electronic materials such as Si, GaAs, and HgCdTe. The design of the University of North Texas stable element AMS facility built in collaboration with Texas Instruments Incorporated is discussed.
Authors:L. Yang, S. Qiu, F. Xu, L. Sun, Z. Zhao, J. Liang, and C. Song
The effects of Amoxicillin Sodium and Cefuroxime Sodium on the growth of E. coli DH5α were investigated by microcalorimetry. The metabolic power-time curves of E. coli DH5α growth were determined by using a TAM air isothermal microcalorimeter at 37�C. By evaluation of the obtained parameters,
such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (Pm) and the time of the maximum heat power (tm), one found that the inhibitory activity of Amoxicillin Sodium vs. E. coli DH5α is enhanced with the increasing of the Amoxicillin Sodium concentration, and the Cefuroxime Sodium has a stimulatory effect on the E. coli DH5α growth when the concentration is about 1 μg mL−1. The IC50 for the Amoxicillin Sodium and the Cefuroxime Sodium are 1.6 and 2.0 μg mL−1, respectively, it implicates that the E. coli DH5α is more sensitive to Amoxicillin Sodium than Cefuroxime Sodium.
Authors:L. Yang, F. Xu, L. Sun, Z. Tan, H. Tan, Z. Zhao, and J. Liang
technique based on the bacterial heat output was applied to evaluate the influence
of antibiotics PIP (Piperacillin Sodium)
and composite preparation of PIP and SBT (Sulbactam
Sodium) on the growth of E. coli
DH5α. The power–time curves of the growth metabolism of E. coli DH5α were studied using a TAM Air Isothermal
Microcalorimeter at 37C. By analyzing the power–time curves, the
parameters such as growth rate constants (k),
inhibitory ratio (I), the maximum heat
power (Pm) and the
time of the maximum heat power (tm)
were obtained. The results show that different concentrations of antibiotics
affect the growth metabolism of E. coli
DH5α. The PIP in the concentration range of 0–0.05 g mL–1
has a stimulatory effect on the E. coli
DH5α growth, while the PIP of higher concentrations (0.05 –0.25
g mL–1) can inhibit its growth. It seems
that the composite preparation composed of PIP and SBT cannot improve the
inhibitory effect on E. coli DH5α
as compared with the PIP.
Authors:B. Feng, Z.B. Xu, X. Wang, F. Jiang, G.J. Zhao, C. Xiang, and T. Wang
High molecular weight (HMW) glutenin subunits are important seed storage proteins in wheat and its related species. Novel HMWglutenin subunits in Aegilops tauschii accession of TA2484 were detected and characterized. SDS-PAGE analysis revealed the y-type subunit from TA2484 displayed similar electrophoretic mobility compared to that of 1Dy12 subunit. However, the electrophoretic mobility of x-type subunit was faster than that of 1Dx2 subunit. The primary structure of the two cloned subunits from TA2484 was similar to that of the x- and y-type subunits reported before. However, the 148 residues of the x-type subunit, which contained the sequence element GHCPTSLQQ, in the middle of the repetitive domain was quite different from other x-type subunits. Moreover, the 68 residues in this region were identical to those of the y-type subunits from the same accession. Consequently, 1Dx2.3*t (x-type subunit of TA2484) contains an extra cystenin residue located at the repetitive domain, which is novel compared to the x-type subunits reported so far. Phylogenetic analysis indicated that two subunits from accession TA2484 were in the x- and y-type subunit cluster, but bootstrapping value of 100% gave high support for the spilt between two subunits (1Dx2.3*t and 1Dy12.3*t) and their alleles, respectively. A hypothesis on the genetic mechanism generating this novel sequence of 1Dx2.3*t subunit is suggested.