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Novel dendritic monomers derived from cystamine (Cy) were firstly synthesized in this research. Then, these monomers were used as crosslinkers to prepare three series of thermosensitive hydrogels with 2-(2-methoxyethoxy) ethyl methacrylate (MEMA). The effects of these crosslinkers on the hydrogel’s properties such as swelling behavior, mechanical properties, decomposability and thermoreversibility were investigated and compared with the hydrogel crosslinked by N,N′-bisacrylyl cystamine. The results showed that the equilibrium swelling ratio (SReq) of the hydrogel was affected by the hydrophilic group on the structure of the crosslinker and branch distribution of dendrimer crosslinker. More hydrophilic groups led to higher SReq; however, more complex branch distribution occupied the storage space of water and thus reduced the SReq. The prepared hydrogels all showed apparent thermoreversibility, and the critical gel transition temperature (CGTT) of these hydrogels increased with an increase of hydrophilic group in the crosslinker. Their CGTT showed a range from 26 °C (pure polymer) to 45 °C. More importantly, disulfide bonds in the synthesized hydrogel could be decomposed in the presence of cysteine. This result was confirmed by the change of swelling ratio and mechanical properties before and after they were treated with cysteine. The hydrogels decomposed by cysteine showed higher swelling ratio than the pristine hydrogels. And for mechanical properties, the shear modulus, Young’s modulus and effective crosslinking density of the decomposed hydrogels are lower than the pristine hydrogels. In summary, a thermoresponsive and cysteine-responsive hydrogel has been developed.

This paper details the development and application of a novel pressure-tight sampler with a metal seal capable of acquiring high-purity fluid samples from deep-sea hydrothermal vents. The sampler has a titanium diaphragm valve for sampling and a flexible titanium foil bag to store the fluid sample. Hence, all parts of the sampler in contact with the sample are made of titanium without elastomer O-ring seals to minimize the organic carbon blank of the sampler, which makes it suitable for collecting organic samples. A pressure-tight structure was specially designed to maintain the sample at in situ pressure during the recovery of the sampler. The sampler has been successfully tested in a sea trial from November 2018 to March 2019, and pressure-tight hydrothermal fluid samples have been collected.

Three crosslinkers, poly(ethylene glycol) diacrylate (PEGDA), glycerol ethoxylate triacrylate (GETA) and citric acid-(PEG acrylate)3 (CA-PEGTA) derived from poly(ethylene glycol) (PEG) were synthesized at first. The three series of poly (N-isopropylacrylamide) (PNIPAAm) hydrogels were prepared by photopolymerization with the crosslinkers and compared with a hydrogel based on commercial crosslinker, N,N′-methylene bis-acrylamide (NMBA). The influence of the crosslinker structures and contents on the swelling behaviour, mechanical properties, and drug release of the hydrogels was investigated. The results showed that the hydrogels based on PEGDA and NMBA exhibited the highest and the lowest swelling ratio, respectively. The content of crosslinker of all hydrogel series showed good thermosensitivity and thermo-reversibility. The critical gel transition temperature (CGTT) appeared at 32 °C for the hydrogel based on NMBA, but appeared at about 34 °C for other hydrogels due to higher hydrophilicity of the crosslinker. In the mechanical properties, three-arms crosslinker GETA and CA-PEGTA led to higher mechanical strength than a linear crosslinker PEGDA. A hydrogel based on GETA (NG6) showed the highest shear modulus of 656.9 kPa and Young’s modulus of 1655.0 kPa. The hydrogels containing higher content of crosslinker revealed lower swelling ratio and higher mechanical strength. In the drug release, the hydrogels with higher swelling ratios showed higher drug absorbed. The highest release percentage of caffeine and vitamin B12 for hydrogel based on PEGDA (NP6) could reach 68.3% and 75.4%, respectively. In addition, the bound water and toxicity of the hydrogels were also investigated.

Waste printed circuit boards (WPCBs) are an essential component in electronic waste (e-waste), and contain a number of valuable metals (e.g., Cu, Sn) as well as non-metal resources (e.g., brominated epoxy resin). Currently, most of the non-metals are disposed of in landfills, causing environmental problems. In this study, a combination of pyrolysis and physical separation is proposed to recover valuable resources, including both metals and non-metals, from WPCBs. The WPCBs were pyrolyzed at 700°C under a nitrogen atmosphere. Pyrolysis oil and gas can be reused as fuel for the pyrolysis of WPCBs. Metals like copper, tin, and iron in the pyrolysis residues were separated by selective crushing, sieving, gravity separation, and magnetic separation. Finally, rich copper (Cu 82.21%, Sn 1.47%), rich tin (Cu 53.20%, Sn 13.43%), rich iron (Fe > 63%), and non-metal products were obtained, and the total recoveries of copper, tin, and iron were 95%, 86%, and 76%, respectively.

As an effective and universal acaricide, amitraz is widely used on beehives against varroasis caused by the mite Varroa jacobsoni. Its residues in honey pose a great danger to human health. In this study, a sensitive, rapid, and environmentally friendly surface-enhanced Raman spectroscopy method (SERS) was developed for the determination of trace amount of amitraz in honey with the use of silver nanorod (AgNR) array substrate. The AgNR array substrate fabricated by an oblique angle deposition technique exhibited an excellent SERS activity with an enhancement factor of ~107. Density function theory was employed to assign the characteristic peak of amitraz. The detection of amitraz was further explored and amitraz in honey at concentrations as low as 0.08 mg/kg can be identified. Specifically, partial least square regression analysis was employed to correlate the SERS spectra in full-wavelength with Camitraz to afford a multiple-quantitative amitraz predicting model. Preliminary results show that the predicted concentrations of amitraz in honey samples are in good agreement with their real concentrations. Compared with the conventional univariate quantitative model based on single peak’s intensity, the proposed multiple-quantitative predicting model integrates all the characteristic peaks of amitraz, thus offering an improved detecting accuracy and anti-interference ability.

Polyphenylene sulfide (PPS) superfine fiber is a promising high efficient material for high temperature dedusting. In this paper, the PPS superfine fiber was prepared by melt-electrospinning for the first time. In order to produce the finer fibers, the polypropylene (PP) was added to PPS and the effects of blending ratio, spinning voltage, spinning temperature, and spinning distance on resultant fibers were investigated systematically. The superfine fibers of PPS with an average diameter of 4.12 μm were successfully prepared at the optimized condition, which was one third of that by melt-spinning method. With the decrease of 76.21 % fibers diameter, the filter efficiency increased from 87.03 % to 98.05 %. The presented method provides a new way for the scalable and green fabrication of PPS superfine fibers.

Pyrolysis has recently received much attention as a promising technology for recycling all the valuable materials from wastes. This study investigated the thermal degradation behaviors of the waste steel tailings and the recovery of iron from waste steel tailings using magnetic separation after pyrolysis. Thermogravimetric (TG) and differential thermogravimetric (DTG) analyses were performed to study the mass loss characteristics. The main pyrolysis temperature range of the waste steel tailings was approximately from 100 to 800 ℃ and the total mass loss was about 30%. The pyrolysis process of waste steel tailings could be classified into four stages. The optimum pyrolysis temperature and pyrolysis time of waste steel tailings were at 700 ℃ for 60 min. The pyrolysis residues generated during the process under optimal condition were detailed analyzed by X-ray powder diffraction (XRD). The result showed that the phase composition of iron in the pyrolysis residues was magnetite. The results of magnetic separation showed that the recovery of iron was 92.66%.

In milk and milk products, the matrix is complex and the interfering components are large, so it is difficult to separate and enrich formaldehyde. In this study, combined with Surface-Enhanced Raman Scattering (SERS) technology, the self-developed green capture device was used to realize the integration of separation, enrichment and detection of formaldehyde. Firstly, we use fluid dynamics to simulate the heat-fluid coupling working mechanism of the enrichment chemical mechanical device. By exploring the steady-state and transient changes of separation and enrichment gas flow under different working conditions, we designed a purge and separation device with small dead volume and high separation efficiency. We further optimized the purge air velocity and heating voltage to increase sample recovery and shorten the separation and enrichment time of the target. As a result, we have realized the application of green and efficient pre-treatment, which is rapid and green. Finally, we used derivatization strategy to enhance the Raman scattering and combined with colloidal gold nanoparticles (AuNPs) to realize SERS analysis. According to this method, we detected formaldehyde in boxed milk, milk powder and raw milk. Thus, we realized a rapid detection method of formaldehyde in milk from various sources, including exogenous and endogenous formaldehyde.

In the current study, via utilizing a mixed-ligand method, two new coordination polymers (CPs) of {[Zn5(pmbcd)2(μ3-OH)2(H2O)4(DMF)2]·4DMF}n (1) and {[Zn2(pmbcd)(bpea)2]·2H2O·2DMF}n (2) (in which bpea = 1,2-bis(4-pyridyl)ethane and H4pmbcd = 9,9′-(1,4-phenylenebis(methylene))bis(9H-carbazole-3,6-dicarboxylic acid)) have been successfully prepared using a tetracarboxylate ligand H4pmbcd without or with the present of the second co-ligand bpea. Furthermore, in the water, the complex 1 containing Zn5 clusters exhibits the strong blue luminescence, which can only be selectively quenched via the contaminant Fe3+ ion. For the treatment of liver cancer, the Cell Counting Kit-8 assay was implemented for the assessment of the compounds’ inhibition on the HepG2 liver cancer cells viability. Moreover, the prolyl hydroxylase-3 relative expression in HepG2 liver cancer cells was also detected by the real time reverse transcription polymerase chain reaction.

Waste printed circuit boards (WPCBs) are an integral part of e-waste, and they contain many valuable metals like Cu, Sn, etc. In order to recycle metal from WPCBs, electrostatic separation, wet gravity separation, air current separation, etc., have been used to separate metals from nonmetals, and the metal product has usually contained a high grade of copper and a low grade of tin. Because copper and tin can form an alloy, it is difficult to separate the two by smelting. Therefore, selective flotation of copper and copper-tin alloy (solder) was investigated in this study, with the aim of decreasing the content of tin in the rich copper product. Under optimized conditions, a rich copper concentrate with Cu grade of 61.12%, Cu recovery of 75.93%, Sn grade of 1.78%, Sn recovery of 8.46%, and a rich tin tailings with Sn grade of 40.93%, Sn recovery of 91.54%, Cu grade of 40.50%, Cu recovery of 24.07% were obtained. Moreover, during the flotation process, the adsorption capacity of ammonium dibutyl dithiophosphate (ADD) on the surface of copper was significantly higher than that on the surface of solder, which is the main reason for the flotation separation of copper and solder. Cu(II) on the surface of copper and solder was reduced to a lower valence state by ADD, and the ADD was oxidized to (ADD)2; but the (ADD)2 did not stably adsorb on the surface of either copper or solder. The adsorption product of ADD on the surface of copper and solder was Cu(I)-ADD precipitate; the adsorption sites of ADD on the solder surface were copper atoms.

We demonstrate a competitive coordination strategy for the synthesis of H-MOF nanostructures, such as two-dimensional H-MOF nanosheets and H-MOF nanocubes, evolving through an etching process tuned by a competitive ligand., Metal–organic frameworks (MOFs) usually have micropores smaller than 2 nm, which may restrict their applications in some cases. Hierarchical-pore MOFs (H-MOFs) are a new family of MOF materials, possessing both micro- and mesopores to address this problem. Here we demonstrate a competitive coordination strategy for the synthesis of H-MOF nanostructures, such as two-dimensional (2D) H-MOF nanosheets and H-MOF nanocubes, evolving through an etching process tuned by a competitive ligand. The as-synthesized 2D H-MOF nanosheets can serve as a substrate to in situ immobilize Pd nanoparticles to achieve a surfactant-free Pd catalyst, by means of a simple soaking method of Pd2+ precursors. Combined with the unique structure and gas adsorption capacity of H-MOF-5, the Pd-H-MOF-5 catalyst exhibits superior catalytic performance.

The aim of the present study was to investigate the effects of hepatic blood inflow on liver function, liver ultrastructure and the regeneration of future liver remnant (FLR) following major hepatectomy in rats with liver cirrhosis. A rat model of cirrhosis was established through intraperitoneal injection of carbon tetrachloride for 8 consecutive weeks. Extensive liver resection and different blood inflow models by portal vein (PV) and/or hepatic artery (HA) stenosis were conducted on the cirrhosis rats. Animal models were constructed as follows: Control (group A), low-flow PV + high-flow HA (group B), low-flow PV + low-flow HA (group C), high-flow PV + high-flow HA (group D) and high-flow PV + low-flow HA (group E). Hepatic blood inflow was detected by laser speckle contrast analysis, liver function and pathological changes were analyzed, Masson staining was used to identify the fibrosis of the liver and Periodic acid-Schiff staining was used to identify glycogen synthesis and hepatocyte function. The liver cell ultrastructure was evaluated by transmission electron microscopy, and the expression of Ki-67 in hepatocytes and the weight of the FLR were recorded to determine the regeneration of the FLR. Five days after major hepatectomy and liver blood inflow modulation, pathological examination of the livers from groups B and C revealed less congestion and less extensive hepatocellular injury. The serum alanine aminotransferase level of group B at 1, 3 and 5 days after hepatectomy and blood inflow modulation was 460.9±31.7, 331.0±22.0 and 285.6±15.8 U/l, respectively (control group: 676.9±41.7, 574.9±28.0 and 436.1±32.7 U/l, respectively; P

This paper proposes a novel method to derive the junction temperature of a Silicon Carbide Schottky Barrier Diode (SiC SBD) when it is in operation. There is a correlation between the switching waveforms and the temperature, due to the material parameters and the carrier vary with the temperature. Estimating the Turn-on-delay time as a temperature sensitive electrical parameter (TSEP), the chip temperature in operation can be evaluated. The experiment is based on signal loop — dealing with the output signal of the chip by the peripheral circuits, then putting it as the switching signal to the chip. Thus, each minimal turn-on-delay time — at nanosecond level — can be accumulated to be a time span at microsecond or second level and the value is averaged to evaluate the turn-on-delay time.

Two kinds of assembly structures (nanorolls and hollow spindles) based on the palladium substituted Wells–Dawson polyoxometalate (Pd-POM) were synthesised and showed high catalytic activity for both the Suzuki–Miyaura coupling reaction and semihydrogenation reaction., The challenge with single-atom catalysts (SACs) is in designing a highly definite structure with accurate location of the single atom and high catalytic efficiency. The noble metal substituted polyoxometalates seem to be a kind of SAC because of their well resolved crystal structure. Here, we got two kinds of assembly structures (nanorolls and hollow spindles) based on the palladium substituted Wells–Dawson polyoxometalate (Pd-POM), which consists of isolated Pd atoms. Both the nanorolls and hollow spindles showed high catalytic activity for both the Suzuki–Miyaura coupling reaction and semihydrogenation reaction. The difference of the chemical surroundings between the nanorolls and hollow spindles leads to their discrepancy in the catalytic activity of semihydrogenation.

We have synthesized spiral ultrathin-nanosheets with overgrown edges of NiFe, CoNi and CoFe bimetallic hydroxides which show excellent performance for the OER., The structure of edges may dramatically influence the properties of nanomaterials, so the rational design or control over the structures of the edges is required. Here we synthesized spiral ultrathin-nanosheets with overgrown edges (SUNOE) of NiFe, CoNi and CoFe bimetallic hydroxides by governing the growth rates of different directions in screw dislocation driven growth (SDDG) in nonaqueous solvents. The driving force for the SDDG is supersaturation, which could be controlled by the concentration of the different precursors, thus achieving non-uniform structures of the edges and inner sheets. NiFe, CoNi and CoFe bimetallic hydroxides possess layered structures, in which overgrown edges may prevent them from re-stacking. The as prepared SUNOE all show good performance for the oxygen evolution reaction (OER) in the electrolysis of water, and the lowest onset potential was 1.45 V (vs. RHE) (the lowest potential when the current density reached 10 mA cm–2 was 1.51 V (vs. RHE)).

Background Sortase A (SrtA) is a transpeptidase found in Staphylococcus aureus, which is widely used in site-specific protein modification. However, SrtA was expressed in Escherichia coli (E. coli) in rather low level (ranging from several milligrams to 76.9 mg/L at most). The present study aims to optimize fermentation conditions for improving SrtA expression in E. coli. Results Under the optimized media (0.48 g/L glycerol, 1.37 g/L tryptone, 0.51 g/L yeast extract, MOPS 0.5 g/L, PBS buffer 180 mL/L) and condition (30 °C for 8 h) in a 7-L fermentor, the enzyme activity and the yield of SrtA reached 2458.4 ± 115.9 U/mg DCW and 232.4 ± 21.1 mg/L, respectively, which were higher by 5.8- and 4.5-folds compared with initial conditions, respectively. The yield of SrtA also represented threefold increase than the previously reported maximal level. In addition, the enzymatic characterizations of SrtA (optimal temperature, optimal pH, the influence of metal irons, and tolerance to water-soluble organic solvents) were determined. Conclusions Enhanced expression of SrtA was achieved by optimization of medium and condition. This result will have potential application for production levels of SrtA on an industry scale. Moreover, the detailed enzymatic characterizations of SrtA were examined, which will provide a useful guide for its future application. Electronic supplementary material The online version of this article (doi:10.1186/s40643-017-0143-y) contains supplementary material, which is available to authorized users.

The unpredictable toxicity of insecticides may cause behavior disorder of biological organisms. In order to assess the role of acetylcholinesterase (AChE) in swimming behavior of Daphnia magna, a correlation analysis of both parameters in 24 h exposure of deltamethrin (DM) and methomyl (MT) was investigated. The behavior responses of D. magna in DM (13.36 μg/L and 33.40 μg/L) and MT (19.66 μg/L and 49.15 μg/L) suggested that recovery behavior in the adjustment phase was crucial, and behavior homeostasis provided them with an optimal way to achieve a wider tolerance against environmental stress. During the experiment, positive effects on AChE activity occurred in the beginning of the exposure. Even though the de novo synthesis of AChE in D. magna might help it recover, the AChE inhibition in different treatments could be observed. Some induction effects on AChE activity at the beginning of exposure occurred, and a 50% decrease may cause toxic effects on behavior. In most treatments, the results showed that both behavior strength and AChE activity stayed in the same field within a correlation circle. These results illustrated that the environmental stress caused by both DM and MT could inhibit AChE activity and subsequently induce a stepwise behavior response, though both pesticides affect it as direct and indirect inhibitors, respectively.

This study aimed to improve the storage quality of figs by determining how spraying calcium nitrate on fig fruits and naphthaleneacetic acid (NAA) on leaves before plucking the fruits affect their storage quality. Storage experiments were performed on 4-year-old Bo JiHong, and results showed that all treatments contributed to improving the fruits’ hardness and alleviating the changes in several factors, including fruit-rot rate, soluble solids, titratable acid, and vitamin C content. In particular, the change rates of these factors for the calcium-alone treatment group decreased by 0%–15%, 6.2%–27.1%, 13.4%–32.4%, and 29.5%–31.3%, respectively, compared with the control group. Meanwhile, the change rates for the calcium + NAA treatment group decreased by 55%–70%, 34.7%–50.7%, 27.8%–54.8%, and 35.2%–60%, respectively, compared with the control group. These finding indicated that the consumption of nutrients inside the fruits was greatly diminished, the fruit shape was maintained, and the storage quality of figs was enhanced. The optimal storage effect was achieved by applying 0.5% Ca(NO3)2 + 30 mg· L–1 NAA.

Flavin mononucleotide (FMN) plays an important role in living systems. Accurate probing and characterizing of FMN is the key to understanding the contribution of FMN coenzyme in biological processes. We demonstrate a way to get a bright surface-enhanced Raman spectroscopy (SERS) signal while simultaneously quenching the fluorescence background through silver nanorod (AgNR) array substrates fabricated by the oblique angle deposition method. The AgNR array substrates show a good SERS activity with an enhancement factor of ∼4.2 × 104. Meanwhile, the characteristic peaks of FMN are assigned by the density function theory calculation. An exponential relationship is demonstrated between SERS intensity and FMN concentration in the concentration range of 0.1 to 100 mg / L. This SERS-based method enabled the rapid and highly sensitive detection of FMN, holding great promise for expanding SERS application in biochemistry and food safety fields.

This study investigated the feasibility of using an alkaline pressure oxidative leaching process to treat lead smelter flue dust containing extremely high levels of arsenic with the aim of achieving the selective separation of arsenic. The effects of different parameters including NaOH concentration, oxygen partial pressure, liquid-to-solid ratio, temperature, and time for the extraction of arsenic were investigated based on thermodynamic calculation. The results indicated that the leaching efficiency of arsenic reached 95.6% under the optimized leaching conditions: 80 g/L of NaOH concentration, 1.0 MPa of oxygen partial pressure, 8 mL/g of liquid-to-solid ratio, 120 &deg, C of temperature, 2.0 h of time. Meanwhile, the leaching efficiencies of antimony, cadmium, indium and lead were less than 4.0%, basically achieving the selective separation of arsenic from lead smelter flue dust. More than 99.0% of arsenic was converted into calcium arsenate product and thus separated from the leach solution by a causticization process with CaO after other metal impurities were removed from the solution with the addition of Na2S. The optimized causticization conditions were established as: 4.0 of the mole ratio of calcium to arsenic, temperature of 80 &deg, C, reaction time of 2.0 h. The resulting product of calcium arsenate may be used for producing metallic arsenic.

Cavitation-accelerated aqueous enzymatic extraction (CAEE) of seed oil from Cucurbita pepo was performed. An enzyme cocktail comprised of cellulose, pectinase and proteinase can work synergistically in releasing the oil. The CAEE extraction conditions were optimized by a Plackett-Burman design followed by a central composite methodology. A maximal extraction yield of 58.06% was achieved under optimal conditions of vacuum degree -0.07, enzyme amount 1.05% and extraction time 69min. As compared to soxhlet extraction (SE)-derived oil, CAEE-derived oil exhibited similar physical properties and better oxidation stability. In addition, chemical composition analyzing showed that the content of linoleic acid obtained by CAEE (47.67%) was higher than that of SE (44.51%). Moreover, the IC50 of oil obtained by CAEE and SE, as measured by α-amylase inhibition assay, were 40.68μg/mL and 45.46μg/mL. All results suggest that CAEE represents an excellent alternative protocol for production of oil from oil-bearing materials.

This study was conducted to evaluate the adverse health effects on rabbits exposed to SO2 emitted indoors from burning coals, and compare differences between coal-biomass briquette (B.B.) and raw coal (R.C.). Thirty-six male rabbits were divided equally into three groups at random, and then exposed to burning R.C., B.B., and the third without burning coal (Control) for 90 days. Data showed that the average concentration of SO2 in 24 h in R.C. was 13.04 mg m−3, which was 5-fold greater than B.B. (2.68 mg m−3) and 31-fold higher than control (0.41 mg m−3). After 45 days, the numbers of rabbits, with increased frequency of Comet cell was highest in R.C. After 90 days, the % positive Comet cell was significant at 10.36% in R.C., 5.42% in B.B., and 1.73% in Control. There was a nonlinear dose–effect relationship between % positive Comet cell and the concentration of SO2. The incidence of interstitial pneumonia was 6/12 in R.C. and 4/12 in B.B. showing severe squamous metaplasia with atypical hyperplasia in bro...

Fluorescence of Tm3+/Er3+ codoped bismuth-silica (BS) glasses and the sensitization of Ce3+ are investigated. It shows that Ce3+ codoping with Tm3+/Er3+ in BS glasses results in a quenching of Tm3+ ion emission from 3F4 to the 3H6 level. Consequently, the 1.47 μm emission occurs after the population inversion between the 3H4 and 3F4 levels. Furthermore, the codoped glasses show the broad emission spectra over the whole S and C bands with full-width at half-maximum (FWHM) up to about 119 nm, as it combines 1.55 μm emission band of Er3+ with 1.47 μm emission band of Tm3+ under 800 nm excitation.

Raw coal (RC) is the main fuel in many, especially rural parts of China. Biomass briquette (BB), which has less SO2 emission, was developed as a cleaner alternative for RC. In this research, the cooking fuel of a group of countrywomen was switched from RC to BB and studied for health effects. Five biological indices percent of comet cell (COMET), lysozyme saliva (LYS), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) were chosen. All indices were measured three times during the 18-month experiment. Statistical analysis shows that there are significant changes in the indices. Using BB as a cooking fuel improves the function of anti-oxidation system and the nonspecific immune system, and reduces the DNA damage, which is negatively related to LYS and SOD.

In the new version of the catalogue of carbon stars, IRAS 19227+1700 is listed as a carbon-rich sta. However, in the IRAS infrared two-color diagram, it is located in the typical region of stars with rather thick oxygen-rich circurnstellar envelopes, and not in the region commonly occupied by silicate carbon stars. MoreOver, there are other pieces of evidence that show that this star not only has the main and satellite line OH maser emissions, but also has water emission close to the central star. Its IRAS low- resolution spectrum (LRS) displays dust emission features in the range of 9-12 mum, and near infrared observation has confirmed that it really possesses a hot circurnstellar envelope. Therefore, the circumstellar envelope of IRAS 19227+1700 should be completely oxygen-rich in nature, and quite possibly its central star is also oxygen-rich.

Poly-phenylquinoxaline is used as the electroluminescent(EL) materials to fabricate the thin film electroluminescent devices by the spin coating method. Doped with 1, 3, 5-triphenyl-2-pyrazoline, the EL spectrum of the devices is shifted to the blue-green region with its peak located at 465nm. The incorporation of a hole transport layer, poly-vinylcarbazole, will enhance the EL intensity, and the quantum efficiency is estimated to be 0.2%. Thus, the devices can be driven by either positive or negative bias (or ac voltage) even though the currentvoltage curve possesses a rectifying property.

An Sb delta doping layer in silicon is grown at the temperature of 300°C by silicon molecular beam epitaxy and characterized by the small angle x-ray reflectivity measurement using synchrotron radiation beam. The oscillations of the reflectivity caused by dopant Sb at Q as large as 14.5 are detected. Simulation of this curve as a whole shows that the total amount of dopant Sb is 0.15 monolayer and is restricted to two atomic layers. An extremely narrow Sb delta doping structure without Sb segregation is thus obtained at the growth temperature of 300°C as verified by the experiment.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is increasingly considered as an important functional food material because of its rich nutraceutical compounds. Reserve starch is the major component of tartary buckwheat seed. However, the gene sequences and the molecular mechanism of tartary buckwheat starch synthesis are unknown so far. In this study, the complete genomic sequence and full-size cDNA coding tartary buckwheat granule-bound starch synthase I (FtGBSSI), which is responsible for amylose synthesis, were isolated and analyzed. The genomic sequence of the FtGBSSI contained 3947 nucleotides and was composed of 14 exons and 13 introns. The cDNA coding sequence of FtGBSSI shared 63.3%-75.1% identities with those of dicots and 56.6%-57.5% identities with monocots (Poaceae). In deduced amino acid sequence of FtGBSSI, eight motifs conserved among plant starch synthases were identified. A cleavage at the site IVC↓G of FtGBSSI protein produces the chloroplast transit sequence of 78 amino acids and the mature protein of 527 amino acids. The FtGBSSI mature protein showed an identity of 73.4%-77.8% with dicot plants, and 67.6%-70.4% with monocot plants (Poaceae). The mature protein was composed of 20 α-helixes and 16 β-strands, and folds into two main domains, N- and C-terminal domains. The critical residues which are involved in ADP and sugar binding were predicted. These results will be useful to modulate starch composition of buckwheat kernels with the aim to produce novel improved varieties in future breeding programs.

A new surface cleaning method for Si MBE is described in which a very weak Ge beam flux is deposited on the surface for removing the thin passivative layer of SiO2 on the Si substrate. It has proved that the SiO2 will react with Ge at a relatively low temperature (620° C), and as a result, the oxide layer becomes volatile. Here the high temperature annealing in the conventional Shiraki method is no longer required, and since the oxide layer is removed in ultra high vacuum, only very little carbon contamination may occur. Furthermore, to reduce the excessive Ge on the substrate surface, Ge is deposited at 620° C and then the sample is annealed at 700° C; the residual Ge atoms on Si substrate can be reduced to less than 0.1 monolayer (ML). Ge beam treatment turns out to be an effective low-temperature Si surface-cleaning method, especially for the heteroepitaxial growth of GexSi1-x/Si.

It is well known that the excellent pollution performance of silicone rubber (SR) insulators originates from its hydrophobicity and hydrophobicity transfer properties. With the sustainable growth of composite insulator usage in China, a convenient method should be given to judge the hydrophobicity properties and to help the utilities choose proper products. In this paper, a four-parameter method used in the evaluation of hydrophobicity status was introduced. The four parameters are hydrophobicity on clean surface, hydrophobicity loss property, hydrophobicity recovery property and hydrophobicity transfer property named H/sub c,/ H/sub l,/ H/sub r/ and H/sub t,/ respectively. Relative values of the four parameters, which were based on the research work of hydrophobicity, were also given. This method has already been used in some parts of China for its easy operation and effectiveness regarded. In addition, the mechanism of hydrophobicity transfer property was further investigated and the difference of the results between contact angle and hydrophobicity classification was also discussed in detail.

The usage of composite insulators in various contaminated areas is increasing prominently in recent years. Most of composite insulators are operating in heavy or medium pollution environment in China. As the exposure time in the field prolonging, the change of hydrophobicity and the build-up of pollution layer directly affect pollution performance of the composite insulators. This paper is based on the work of investigation on the pollution performance and aging of nearly 40 composite insulators operated in Jiamusi city, the north east area of China. These composite insulators were removed from 110 kV lines, and they are all made of HTV silicone rubber and mostly are in service for nine years. Four aspects of hydrophobicity of these insulators are studied after the measurement of pollution status.

Considering various contaminated environments in the field, research on the hydrophobicity transfer properties of different pollutants is necessary for the proper selection and maintenance of polymeric insulators. In the paper, hydrophobicity of SR polluted by several kinds of pollutants such as kieselguhr, kaolin, Tonoko, metal oxides and inorganic salts were investigated. Contact angle measurement and FTIR analysis have been used to trace the hydrophobicity transfer process. It is found that the inherent chemical properties and the physical morphology of pollutants play important roles on the hydrophobicity transfer property.

The shell model interionic and interatomic potentials are widely used to perform atomistic simulations of ionic crystals. The parameters of the potentials are obtained by fitting the data from measurements and/or electronic structure calculations of the crystal discussed. A new method of fitting shell model interatomic potential is presented for diatomic molecule from electronic structure data obtained by quantum chemical ab initio calculation in the paper. And the shell model interatomic potential for H is fitted from the electronic structure data of H2 molecule for example. To examine the method, the interatomic potential and force of H+2 molecular ion are calculated from the potential functions. The results demonstrate that the proposed new fitting procedure shows a fairly good feasibility to the shell model potential for covalent bond molecule.

The enhanced ionization(EI) behaviour of linear multiatomic molecular ions is studied in two-color(fundamental radiation:780 nm, the second harmonic:390 nm) laser fields by the numerical solution of the time-dependent Schrdinger equation with the symmetrical splitting of the short-time exponential propagator. The influence of the relative phase between the two-color laser fields on the ionization probability is given. The numerical results demonstrate that the influence of the relative phase on the ionization probability is the strongest in the range of the inter-nuclear distance where the EI occurs. The influence can be explained in terms of the field-induced over-the-barrier ionization model.

The atomic configuration and electronic structure of erbium-doped silicon are studied theoretically by using local density formalism (LDF) and discrete variational method (DVM).The influence of codoping with oxygen is also investigated.The minimum-energy atomic configuration is that erbium occupies a tetrahedral interstitial site for an isolated erbium atom.In this configuration,Er 5d levels are located near the conduction band edge of Si in shallow resonance states. With the presence of oxygen,the binding energy of the structure decreases. In this case,the minimum-energy atomic configuration is that erbium occupies a hexagonal interstitial site with six nearest neighbors of oxygen atoms. An electronic state caused by the hybridization of Er 5d,O 2p and Si 2p electrons is located 0.3eV below the conduction band edge,which might be correlated with the deep level at Ec-0.15eV observed by the experimental measurement in Er and O codoped Si.

Ion implantation and annealing have been used to switch the luminescence in Si1-xGex/Si quantum wells from a band-edge exciton process to a broad well below the band edge. The damage introduced by silicon ion implants, which leads to the formation of the platelets correlated with broad band luminescence, is related to the track of an implanted ion and the recoiled atoms in the quantum well structures. The activation energy for defect clusters is about 0.1eV, which is larger compared with the activation energy of ～0.05 eV for interstitial atoms. This indicates that the defect clusters is responsible for the deep broad photoluminescence in early MBE samples.

The admittance spectroscopy technique has been used to study the hole confinement in Si/Si1-xGex/Si and boron highly doped superthin Si quantum wells. Based on the carrier thermal emission medel of the carriers in the well, the value of activation energy derived from the admittance spectra was considered as the distance from the position of the heavy hole ground state in the well to the top of it . For Si/Si1-xGex/Si quantum wells we found the value of activation energy increased with increasing annealing time at 800℃. The phenomena could be explained the annealing-induced interdiffusion of Si and Ge, the interface broadening, the weakening of quantum confinement, the decrease of the position of the heavy hole ground state, and so the increase of the activation energy. At the annealing temperature of 900℃, we only see the decrease of the value of activation energy with increasing annealing time. For boron highly doped superthin Si quantum wells due to quantum confinement effect, we observed the activation energy are different for samples with the same doping density but different well widths.

The typical Raman spectrum from light-emitting porous silicon shows a sharp peak near 520cm －１ . The peak wavenumber decreases with the increase of porosity. The lineshape analysis shows that both phonon confinment and strain effects in nanocrystal silicon must be taken into account for the measured Raman spectra. The strain in porous silicon film is estimated and the result is consistent with that given by X-ray diffraction studies. No light scattering from amorphous phase is observed.

The growth procedure of the Si/GaP( Ⅲ )heterointerface with Si electron beam evaporation in an improved ADES-400 photo-electron spectrometer is introduced in this paper. Then the status of formation and valence band discontinuities of Si/GaP(Ⅲ ) heterointerfaces that grown under different conditions are analysed or measured in situ by photoemission. The relation of the ΔEv values with the status of the interface and the shift of atomic core levels is discussed. The growth condition of the abrupt and ordered Si/GaP(Ⅲ)heterointerfaces is determined. The value of valence band discontinuity in this case is 0.80eV. It agrees with theoretical results.

A stable hydrogen-terminated Si (100) surface was obtained by using a modified mothed. The Si (100) surface was hydrogen passivated during the ex-situ HF-dip followed by the in-situ low-temperature desorption of physisorbed residues. It was found that this procedure is very effective to eliminate the boron spike at the Si MBE layer/p-Si substrate interface. The origon of the boron spike is also discussed.

The application of HREELS to the study of the Ag(100)/Na+O2 system reveals the presence of molecularly adsorbed oxygen species at room temperature. This may help explain why alkali metals can enhance the selectivity of an Ag catalyst towards the formation of C2H4O.

The surface indium islands originated by argon ion bombardment can be removed by evaporating phosphorous on InP surface followed by annealing. A possible mechanism of elimination of In islands is proposed based on the experimental ELS and XPS data.