Low-flux, in-cocktail neutron activation analysis was used to quantify atmospheric tracer aerosols. Liquid scintillation was necessary to reduce the experimental uncertainty due to low sample activity. Activation of the tracers was performed in-cocktail since the short half lives of the nuclides did not allow time for sample preparation. Most of the tested cocktails proved inadequate for such analysis because of activation of their components. Neutron and gamma induced luminescence, and neutron generated bubbles in suspensions introduced further difficulties. Only a few cocktails showed activity levels after irradiation comparable to background. This method allowed substantial cost reduction by eliminating the need for irradiation in a research reactor.
A procedure for determining Pu in environmental soil using238Pu as a yield tracer is described. The method involves radiochemical separation and electrodeposition onto a stainless steel disc followed by alpha-spectrometric measurement with a solid-state detector. In order to eliminate error in calculation caused by238Pu contained in original samples, a new calculating method is introduced in this paper. By using this method, the activity of238Pu contained in original samples can be substracted from the total activity of samples, to which the238Pu tracer is added. This procedure has been applied satisfactorily to the determination of Pu in a soil reference sample, which was supplied by the Institute of Metrological Science of China.
Authors:Q. Zhang, Z. Qian, L. Pan, H. Li and H. Zhu
Berberine, a primary pharmacological active constitute of Coptidis Rhizoma, could inhibit neuronal apoptosis in cerebral ischemia. Here, we aimed to investigate whether and how HIF-1 is implicated in the anti-apoptosis effect of berberine on neurons under hypoxia/ischemia. Viability of PC12 cells treated with berberine prior to or following CoCl2-induced hypoxia was evaluated. Annexin V-PI staining was employed to analyse cell apoptosis ratio. HIF-1α and apoptosis-associated molecules were detected via Western blotting. TUNEL and immunohistochemistry were used to demonstrate apoptosis, HIF-1α and p53 levels in cerebral tissue of middle cerebral artery occlusion (MCAO) rats. Berberine pretreatment promoted PC12 cells survival and inhibited apoptosis under hypoxia condition. At the same time, it decreased cell viability and enhancement of apoptosis were observed with berberine treatment under hypoxia. Decreased HIF-1α, caspase 9, caspase 3 and increased Bcl-2/Bax ratio were responsible for the anti-apoptosis of berberine pretreatment. However, pro-apoptosis by berberine under hypoxia was indicated with opposing regulation of those molecules. Significant reduction of apoptosis, HIF-1α and p53 were found in cerebral tissue of MCAO rats treated with berberine. The present study suggests that berberine regulates neuronal apoptosis in cerebral ischemia, which might be dependent on the degree of cell injury. HIF-1 and the followed apoptotic pathway are involved in those effects of berberine.
The aim of this study is to investigate the melting/freezing characteristics of paraffin by adding Cu nanoparticles. Cu/paraffin composite phase change materials (PCMs) were prepared by a two-step method. The effects of Cu nanoparticles on the thermal conductivity and the phase change heat transfer of PCMs were investigated by the Hot Disk thermal constants analyzer and infrared monitoring methods, respectively. The maximum thermal conductivity enhancements up to 14.2% in solid state and 18.1% in liquid state are observed at the 2 wt% Cu/paraffin. The photographs of infrared monitoring suggest that the melting and freezing rates of Cu/paraffin are enhanced. For 1 wt% Cu/paraffin, the melting and freezing times can be saved by about 33.3 and 31.6%, respectively. The results provide that adding nanoparticles is an efficient way to enhance the phase change heat transfer of PCMs.
Novel magnetic solid-phase extraction using carboxylated multiwalled carbon nanotubes was proposed with ultra high-performance liquid chromatography–tandem mass spectrometry for the determination of silodosin in biological samples. The effects of various experimental parameters including adsorbent amount, pH, adsorption time, desorption conditions, and adsorbent reusability were systematically validated. Under the optimized conditions, the calibration curve was linear within the concentration range of 1.0–800 ng mL−1 with the correlation coefficient of 0.9997 and the lower limit of detection was 0.3 ng mL−1. The extraction recoveries were over 90.0% with relative standard deviation (RSD) of less than 5.0%. All these results suggested that magnetic extraction method can be used for enrichment and quantification of silodosin in biological samples.
Two series of antibacterial compounds were synthesized using montmorillonite and chlorhexidine acetate (CA) by ion-exchange
reaction. The resulting samples were characterized by high-resolution thermogravimetric analysis (HRTG), Fourier transform
infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and their antibacterial activity was assayed by halo method. In this
study, the loaded amounts of CA in the resultant compounds were evaluated by the HRTG curves. CA adopts a lateral monolayer
arrangement in the resulting samples with low CA loading, while a special state with partial overlapping of organic molecules
is supposed for the resulting samples prepared at 1.0–4.0 CEC. After the intercalation with CA, the hydrophilic surfaces of
montmorillonite are changed to hydrophobic ones, reflected by the frequency shift of the symmetric ν1(O-H) stretching vibration from low to high. This study shows that the interlayer cations in raw montmorillonite have little influence
on the structure of the resulting samples. Antibacterial activity test against E. coli demonstrates that the antibacterial activity of the resulting samples strongly depends on the content of the loaded CA and
these resulting materials show a long-term antibacterial activity that can last for at least one year.
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.
Authors:J. Zhu, H. Jin, D. Dong, D. Qiang and F. Ma
The glass formation and devitrification of GaF3-based glasses were studied by differential scanning calorimetry. A comparison of various simple quantitative methods to assess
the level of stability of multicomponent fluoride glass systems is presented. Most of these methods are based on critical
temperatures. In this paper a new parameter kb(T) is added to the stability criteria. The stability of several GaF3-based glasses were experimentally evaluated and correlated with the activation energies of crystallization via this new kinetic
criterion and compared with those evaluated by other criteria.
Authors:A. Ousegui, S. Zhu, H. Ramaswamy and A. Le Bail
The evaluation of the latent heat and enthalpy of fusion of food systems
in the case of high pressure–low temperature processing is important
for modelling purposes as well as for technical applications. A high pressure
calorimeter has been designed for this purpose. The high pressure calorimeter
was used to evaluate the latent heat during a pressure scan at constant temperature.
It permits to measure the heat of phase transitions and to obtain the relationship
between the initial freezing temperature Tifp
and the average pressure while the phase transition is going on.
work presents a modelling of results obtained from an experimental approach
using a high pressure calorimeter and from a mathematical model developed
from existing data on the phase change of pure water.
work consisted in evaluating the latent heat measured in previous tests from
computations taking into account the dependence of the latent heat of fusion
of water on pressure. Models predicting the amount of frozen water in a food
matrix under atmospheric conditions were used to determine the initial amount
of frozen water in the sample. Then a stepwise procedure was operated in a
program to reproduce the pressure rise occurring during a high pressure calorimeter
test. The amount of melted ice at each pressure step was calculated using
conventional ice fraction models, which were adapted to pressure dependence
of the initial freezing temperature and the dependence of the latent heat
pressure. The comparison was satisfactory, especially at low temperatures.
Authors:M. Zhu, J. A. Duan, Y. P. Tang, J. M. Guo, E. X. Shang and Z. H. Zhu
An efficient and robust method for analyzing constituents of a well-known traditional Chinese medicine (TCM) formula SiWu decoction (SWD) contains Angelicae Sinensis Radix (ASR), Chuanxiong Rhizoma (CR), Paeoniae Radix Alba (PRA), and Rehmanniae Radix Praeparata (RRP) by ultra high-performance liquid chromatography (UHPLC)/time-of-flight mass spectrometry (TOF-MS) was established. The method efficiently applied to the separation of 75 compounds, including organic acids, phthalides, phenylpropanoid glycosides, iridoid glycosides, monoterpene glycosides, and galloyl glycosides in the complex prescription, 52 compounds in this study can be unambiguously identified or tentatively characterized. The separation was achieved within 20 min at the optimized chromatographic conditions. Our study provided a reliable and high-efficient method for the understanding of the chemical basis of SWD.