Authors:J. Ahmed, J. Zhang, Z. Song, and S. Varshney
A thermal analysis of a series of polylactides (PLA) was carried out based on the number of average molecular mass (Mn), and the nature of isomer (D, L and DL). It is confirmed that the glass transition temperature (Tg) of PLA increased as a function of molecular mass irrespective of isomer type except sample with a high polydispersity index.
The melting temperature (Tm) and enthalpy of crystal fusion (ΔHf) of L-isomer increased as the Mn was increased from 1100 to 27500. The degree of crystallinity (χc%) increased as a function of molecular mass. However no crystallization peak was detected in the lower molecular mass range
(550–1400). The non-isothermal crystallization behavior of the PLA melt was significantly influenced by the cooling rate.
Both D and L isomers exhibited insignificant difference in thermal properties and DL lactides exhibited amorphous behavior at identical molecular masses. Change in microstructure showed significant difference
between two isomers. Analysis of the FTIR spectra of these PLA samples in the range of 1200–1230 cm−1 supported DSC observation on crystallinity.
The title compound 3,3-dinitroazetidinium (DNAZ) 3,5-dinitrosalicylate (3,5-DNSA) was prepared and the crystal structure has
been determined by a four-circle X-ray diffractometer. The thermal behavior of the title compound was studied under a non-isothermal
condition by DSC and TG/DTG techniques. The kinetic parameters were obtained from analysis of the TG curves by Kissinger method,
Ozawa method, the differential method and the integral method. The kinetic model function in differential form and the value
of Ea and A of the decomposition reaction of the title compound are f(α)=4α3/4, 130.83 kJ mol−1 and 1013.80s−1, respectively. The critical temperature of thermal explosion of the title compound is 147.55 °C. The values of ΔS≠, ΔH≠ and ΔG≠ of this reaction are −1.35 J mol−1 K−1, 122.42 and 122.97 kJ mol−1, respectively. The specific heat capacity of the title compound was determined with a continuous Cp mode of mircocalorimeter. Using the relationship between Cp and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic
time-to-explosion) was obtained.
Authors:L. Chen, W. Song, J. Lv, L. Wang, and C. Xie
Aluminum (Al) nanopowders with mean diameter of about 50 nm and passivated by alumina (Al2O3) coatings were prepared by an evaporation route: laser heating evaporation. Thermal properties of the nanopowders were investigated
by simultaneous thermogravimetric-differential thermal analysis (TG-DTA) in dry oxygen environment, using a series of heating
rates (5, 10, 20, 30, 50 and 90°C min−1) from room temperature to 1200°C. With the heating rates rise, the onset and peak temperatures of the oxidation rise, and
the conversion degree of Al to Al2O3 varies. However, the specific heat release keeps relatively invariant and has an average value of 18.1 kJ g−1. So the specific heat release is the intrinsic characteristic of Al nanopowders, which can represent the ability of energy
Connexin 43 (Cx43) is the most ubiquitously expressed member of the family of connexins, constituting gap junctions and mediating cell communication, still its role in hearing loss has been little studied.
Immunohistochemistry was used to detect the expression pattern of Cx43. Spiral ganglia neurons (SGNs) and Corti co-culture were utilized to assay the re-innervation of hair cells by newborn SGNs. Gap19 was utilized to inhibit Cx43 hemichannels. Auditory brainstem responses (ABR) and endocochlear potential (E.P.) were measured to confirm the hearing loss.
The expression of Cx43 in P14 mice was higher than in P0 and P28 (adult) mice, the earlier time point coinciding with the early inner ear development. Additionally, the growth and synapse generation of fibers were inhibited after Gap 19 treatment of the co-cultures of the Corti and SGNs from newborn mice. Furthermore, the inhibition of Cx43 could increase the ABR threshold and decrease E.P. level in postnatal mice, whereas such an effect was not observed in adult mice.
The function of Cx43 is critical during the early development of mouse cochlea but is dispensable in adult mice.
Authors:X. Geng, Y. Wu, J. Song, X. Geng, J. Xing, and Z. Lei
The displacement adsorption enthalpies (ΔH) of the refolding of lysozyme (Lys) denatured by
1.8 mol L–1 guanidine hydrochloride (GuHCl)
on a moderately hydrophobic surface at 298 K, pH 7.0 and various (NH4)2SO4
concentrations were determined by using a Micro DSC-III calorimeter. The study
shows that the effect of salt concentrations on the three fractions of the
enthalpy is that with increasing (NH4)2SO4
concentrations, the molecular conformation enthalpy of the adsorbed Lys has
probably no distinct change at 1.8 mol L–1
GuHCl; the adsorption affinity enthalpy (exothermic) becomes more negative;
and the dehydration enthalpy (endothermic) decreases. At lower salt concentrations,
the dehydration, especially squeezing water molecules led by molecular conformation,
which leads to an entropy-driving process, predominates over the adsorption
affinity (also including the orderly orientation of molecular conformation),
while at higher salt concentrations, the latter is prior to the former for
contribution to ΔH and induces an
enthalpy-driving process. Also, the optimal NH4)2SO4
concentration favoring refolding and renaturing of Lys denatured by 1.8 mol
L–1 GuHCl was found.
Authors:D. H. Mu, J. Z. Du, D. J. Li, H. Q. Song, S. P. Yan, and Y. J. Gu
The comprehension of the behavior of radioactive nuclides in aquifer requires the study of the sorption processes of nuclides
in various geochemical conditions. The sorption/desorption of 65Zn(II) on surface sediments (0-2 cm) was investigated by batch method in sea water (pH 8.20, 35‰ salinity, filtered by 0.45mm)
at ambient temperature. The surface sediments were obtained from four stations around the Daya Bay of Guangdong Province (China),
where the first nuclear power station of China has been running from 1994. The sorption process is fast initially and around
39% average of sorption percentage (SP%) can be quickly obtained in 15 minutes for all the surface sediments. Then, the sorption
percentage becomes constant. In 30 days of contact time 79.6% sorption percentage and Kd=3.9. 103ml/g distribution coefficient was obtained. The value of Kdbecame constant, 4.0. 103ml/g, in contact time more than 120 hours. The distribution coefficient Kddecreases with increasing sediment concentration from 4.0 to 250 mg/l from 1.31. 104to 1.68. 103ml/g, respectively. Then the value of Kdgoes up to 5.38. 103ml/g with sediment concentration of 3000 mg/l. The desorption experiments suggest that the sorption of Zn(II) is irreversible
with a hyteresis coefficient of 66%.
Authors:D. Mu, H. Song, S. Yan, Y. Gu, D. Li, and J. Du
Three kinds of marine bivalves (wild Saccostrea cucullata, aquacultured Perna viridis and aquacultured Pinctada martens), collected from Daya Bay, the South China Sea, were used to investigate the bio-accumulation of radioruthenium in the glass
aquarium with natural seawater (pH 8.20, 35‰ salinity, filtered by 0.45 μm) at ambient temperature under laboratory feeding
conditions. The experimental results show that the stead-state of biology concentration factor (BCF, ml/g) of radioruthenium
was approached around 6 days for most species of bivalves. The values of BCF in shells are the highest in organs all the three
bivalves. The orders of BCF values (ml·g−1) are as: Perna viridis (33.2) < Saccostrea cucullata (47.0) < Pinctada martensi (208.4) for shells and Saccostrea cucullata (1.5) < Pinctada martensi (2.2) ≈ Perma viridis (2.4) for soft tissues, respectively, after exposed for 14 days. The rate constants of uptake and elimination of radioruthenium
on marine bivalves were also discussed by first-order kinetics model. The Pinctada martensi may be applicable to be an indicator for monitoring radioruthenium among the three bivalves.
Authors:S. Yu, A. Ren, J. Cheng, X. Song, C. Chen, and X. Wang
Effects of pH, ionic strength and fulvic acid on sorption of radiocobalt on montmorillonite and its Al-pillared and cross-linked
samples were studied using batch technique. The results indicate that the sorption of cobalt is strongly dependent on pH values
and independent of ionic strength. Fulvic acid enhances the sorption of cobalt slightly at low pH, but has no influence at
high pH values. Surface complexation is considered the main mechanism of cobalt sorption to montmorillonite. The sequences
of FA/Co2+ additions to the system did not affect cobalt sorption.
Authors:J. Du, H. Song, D. Mu, D. Li, S. Yan, and Y. Gu
The sorption/desorption of radioruthenium was investigated by the batch method in sea water system at ambient temperature
on the surface sediments obtained around the Daya Bay of Guangdong Province, where the first nuclear power station of China
has been running from 1994. It was found that the sorption percentage was obtained to be around 40% for all the surface sediments
in 60 minutes. Then, the sorption percentage goes up slowly. The sorption percentage of radioruthenium reached around 80%
in 113 days (2713 hours). The distribution coefficients decreased from 3.16·104 to 1.35·103 ml/g with the increasing of sediment concentration in the range of 4–10000 mg/l. The results of the desorption experiments
suggest that the sorption of radioruthenium is irreversible with 81.5% relative hysteresis coefficient.