Biodegradable amphiphilic triblock copolymer bearing pendant glucose residues: Preparation and specific interaction with Concanavalin A molecules

A novel biodegradable amphiphilic block copolymer PLGG-PEG-PLGG bearing pendant glucose residues is successfully prepared by the coupling reaction of 3-(2-aminoethylthio) propyl-R-D-glucopyranoside with the pendant carboxyl groups of PLGG-PEG-PLGG in the presence of N,N'-carbonyldiimidazole. The polymer PLGG-PEG-PLGG, i.e., poly {(lactic acid)-co-[(glycolic acid)-alt-(L-glutamic acid)]}-block-poly(ethylene glycol)-block-poly{( lactic acid)-co-[( glycolic acid)-alt-(L-glutamic acid)]}, is prepared by ring-opening copolymerization of L-lactide (LLA) with (3s)-benzoxylcarbonylethylmorpholine-2,5-dione (BEMD) in the presence of dihydroxyl PEG with molecular weight of 2000 as macroinitiator and Sn(Oct)(2) as catalyst, and then by catalytic hydrogenation. The glucose-grafted copolymer shows a lower degree of cytotoxicity to ECV-304 cells and improved specific recognition and binding with Concanavalin A (Con A). Therefore, this kind of glucose-grafted copolymer may find biomedical applications.

Synthesis using electrospinning and stabilization of single layer macroporous films and fibrous networks of poly(vinyl alcohol)

We demonstrated in this paper an electrospinning technique could be employed to prepare the single layer macroporous films and fibrous networks of poly(vinyl alcohol) (PVA). A crucial element using electrospinning on the development of these electrospun structures was to shorten the distance of from the needle tip to the collector (L), which resulted in the bond of the wet fibers deposited on the collector at the junctions. The morphologies and average pore size of electrospun structures of PVA were mainly predominated by L and the time of collecting wet fibers on the collector. In addition, experimental results showed that an increase of the PVA concentration or a decrease of the applied voltage could also diminish slightly the average pore size of electrospun productions. Furthermore, a 60 degrees C absolute ethanol soak to PVA electrospun production led them to be able to stabilize in water for 1 month against disintegration. Differential scanning calorimetry (DSC) demonstrated that the 60 degrees C ethanol soak enhanced the degree of crystallinity of PVA production. The structural characteristic of macroporous films and networks in combination with their easy processability suggests potential utility in issue engineering applications.

Determination of Hg(II) in waters by on-line preconcentration using Cyanex 923 as a sorbent - Cold vapor atomic absorption spectrometry

Using a solid phase extraction mini-column home-made from a neutral extractant Cyanex 923, inorganic Hg could be on-line preconcentrated and simultaneously separated from methyl mercury. The preconcentrated Hg (11) was then eluted with 10% HNO3 and subsequently reduced by NaBH4 to form Hg vapor before determination by cold vapor atomic absorption spectrometry (CVAAS). Optimal conditions for and interferences on the Hg preconcentration and measurement were at 1% HCl, for a 25 mL sample uptake volume and a 10 mL min(-1) sample loading rate. The detection limit was 0.2 ng L-1 and much lower than that of conventional method (around 15.8 ng L-1). The relative standard deviation (RSD) is 1.8% for measurements of 40 ng L-1 of Hg and the linear working curve is from 20 to 2000 ng L-1 (with a correlation coefficient of 0.9996). The method was applied in determination of inorganic Hg in city lake and deep well water (from Changchun, Jilin, China), and recovery test results for both samples were satisfactory.

Preparation of TiO2 nanocrystallites by hydrolyzing with gaseous water and their photocatalytic activity

TiO2 nanocrystallites were prepared front precursors tetra-n-butyl titanate (Ti(OC4H9)(4)) and titanium tetrachloride (TiCl4). The precursors were hydrolyzed by gaseous water in autoclave, and then calcined at predetermined testing temperatures. The samples were characterized by X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectra (FT-IR), and UV-vis diffuse reflectance spectra (DRS). The photocatalytic activities of the samples were evaluated by the photobleaching of methylene blue (MB) in aqueous solution and the photocatalytic oxidation of propylene in gas phase at ambient temperature. The results showed that the anatase phase nanocrystalline TiO2 could be obtained at relatively low temperatures (for precursor Ti(OC4H9)4 at I I VC and for TiCl4 at 140 degrees C, respectively), and that the as prepared samples exhibited high photocatalytic activities to photobleach MB in aqueous solution. As the calcination temperatures increasing. the decolor ratio of MB increased and reached the maximum value of nearly 100% at 600 degrees C, and then decreased. The photobleaching of MB by all samples followed the pseudo-first-order kinetics with respect to MB concentration.

Synthesis and characterization of spherical Sr2CeO4 phosphors by spray pyrolysis for field emission displays

A blue emitting Sr2CeO4 phosphor with a one-dimensional structure has been prepared by a two-step spray pyrolysis (SP) method, starting from the aqueous solutions of metal nitrates with citric acid and polyethylene glycol (PEG) as additives. The material is ultimately designed for field emission displays (FEDs). X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), field emission scanning electron microscope pictures (FE-SEM) as well as photoluminescence (PL) and cathodoluminescence (CL) spectroscopy and lifetime measurements have been employed to characterize the samples. The morphology, PL and low voltage CL properties of Sr2CeO4 phosphors as-prepared using the SP method have been investigated by changing the concentration of the precursor solution, concentration of PEG, annealing temperature, acceleration voltage and filament current. The obtained Sr2CeO4 phosphor particles are spherical and of submicron size, 0.5-2 mu m. The emission spectrum of the phosphors shows a broad band with maximum at 467 nm (lifetime = 37.4 mu s; CIE chromaticity coordinates: x = 0.15 and y = 0.21), presumably due to a ligand-to-metal charge-transfer transition.

Synthesis, structural characterization and electrical property of new oxide ion conductors: La3MMo2O12 (M = In, Ga and Al)

New series of oxides, La3MMo2O12 (M = In, Ga and Al), have been prepared by the solid-state reaction. The composition and elemental distribution were analyzed by the energy-dispersive X-ray (EDX) analysis. As determined by the X-ray diffraction (XRD), these compounds have similar crystal structures that can be indexed on a monoclinic cell at room temperature. AC impedance spectra and the DC electrical conductivity measurements in various atmospheres indicate that they are oxide ion conductors with ionic conductivities between 10(-2) and 10(-3) S/cm at 800 degrees C. The conductivity decreases in the order of La3GaMo2O12 > La3AlMo2O12 > La3InMo2O12, implying that the effect of cell volume and polarization associated with In3+, Ga3+ and Al3+ play an important role in the anion transport of these materials. The reversible phase transition was observed in all these compounds as confirmed by the differential thermal analysis (DTA) and dilatometric measurements.

Determination of Nb and Ta in Nb/Ta minerals by inductively coupled plasmas optical emission spectrometry using slurry sample introduction

The determination of Nb and Ta in Nb-Ta minerals was accomplished by slurry nebulization inductively coupled plasma optical emission spectrometry (ICP-OES), using a clog-free V-groove ceramic nebulizer. Samples were first wet-ground to appropriate particle sizes with narrow size distribution and 90% of the particles in the slurry were smaller than 2.32 mu m in diameter. Subsamples were then dispersed in pH 9 aqueous solutions, and agitated in an ultrasonic bath for 15 min prior to analysis. Due to the lack of slurry standards matching well with the samples, calibration was simply carried out using aqueous solution standards. Results were compared with those obtained from a conventional fusion decomposition procedure and acid digestion procedures and a good agreement between the measured and referred values was obtained. The technique provided a good alternative for the rapid determination of Nb and/or Ta in their corresponding minerals.

Synthesis of nanocrystalline Ba(CoxZn1-x)(2)Fe16O27 by sol-gel auto-combustion method

The synthesis of nanocrystalline W-type hexaferrites Ba(CoxZn1-x)(2)Fe16O27 powders by sol-gel auto-combustion method has been investigated. The thermal decomposition process of dried gel was studied by thermogravimetry (TG), differential thermal analysis (DTA) and infrared spectra (IR). The structural and magnetic properties of resultant particles were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). The results reveal that the dried gel exhibits auto-combustion behavior. After combustion, pure nanocrystalline W-type hexaferrite phase starts to appear at the calcination temperature of 800 degrees C. The crystallinity and the grain size increase at higher temperature. The saturation magnetization and coercivity clearly depend on calcination temperature and Co content X.

Lanthanum zirconate nanofibers with high sintering-resistance

The PVP/lanthanum nitrate/zirconium oxychloride (PVP-precursor) nanofiber was prepared by electrospinning technique. Lanthanum zirconate (La2Zr2O7, LZ) in the nanofiber is formed after calcination at 800 degrees C and the nanofiber with pyrochlore structure and a diameter of 100-500 nm can be obtained by calcination of the above precursor fiber at 1000 degrees C for 12 h. The surface of the fiber is rough but the continuous microstructure is still maintained after calcination. LZ fibers stack randomly, resulting in a structure with a low contact area between the fibers. This special structure makes the fiber to have a high resistance to sintering at elevated temperatures. The BET (Brunauer-Emmett-Teller) specific surface areas of the LZ fiber and powder calcined at different temperatures are shown in this paper, and the fiber was characterized by TG-DTA (thermal gravimetry-differential thermal analysis), XRD (X-ray diffraction), N-2 absorption-desorption porosimetry and SEM (scanning electron microscopy).

Calculation of the thermal expansion coefficient for Bi2Sr2CaCu2O8

An estimation method of thermal expansion coefficient in term of lattice energy which was developed earlier for simple materials is extended to a complex material of Bi2Sr2CaCu2O8 (Bi-2212). The calculation of the chemical bond property and thermal expansion coefficient of Bi-2212 has been carried out and the theoretical values were in good agreement with the corresponding experimental results. The dependence of the thermal expansion coefficient on the different structures and on the flexible oxidation states of Bi and Cu are investigated. The results indicate that the thermal expansion coefficients of Bi-2212 are insensitive to the low lattice distortion of the average structure and the changes of formal valences of Bi and Cu ions.

脱氧核糖核酸一级序列特殊碱基组合及相关性研究

在脱氧核糖核酸(DNA)一级序列中,4种碱基可以有16种两两组合的方式(例如,ct,ag,cg,tc等),不同的组合方式在DNA的该种序列中出现的次数也不一样,其中,cg出现的频数甚少.本文将cg所处位置及频率作为一种数学的量,计算了各物种的分子连接性指数,并以之为参数进行了物种间相似性分析.在此基础上,进一步对10种物种做了分组和归类.

原位聚合聚乙烯/蒙脱土纳米复合材料的结晶行为

用DSC研究了HDPE与MMT负载的催化剂熔融共混和原位聚合得到的两种纳米复合材料的熔融、结晶行为和等温结晶动力学.结果表明,HDPE与熔融共混样品的结晶度、平衡熔点、球晶生长速率和结晶能力大体相同;原位聚合得到的HDPE/MMT纳米复合材料的结晶度和平衡熔点高于纯HDPE;在相同过冷度条件下熔融结晶速率和结晶能力低于纯HDPE,而在相同结晶温度Tc下,熔融结晶速率和结晶能力则高于纯HDPE.纯HDPE的晶体生长侧向单位面积表面自由能最小,其次是熔融共混样品,原位聚合样品最大,且随MMT含量的增加逐渐升高.

Determination of ultra-trace concentrations of elements in high purity tellurium by inductively coupled plasma mass spectrometry after Fe(OH)(3) coprecipitation

In this work, a method was established for the determination of impurities in high purity tellurium by inductively coupled plasma mass spectrometry (ICP-MS) after Fe(OH)(3) coprecipitation. After comparison of coprecipitation ability and separation efficiency between Fe(OH), and Al(OH)(3), Fe(OH)(3) was chosen as the precipitate. A separation factor of 160 for 200 mg tellurium was obtained under conditions of pH 9 and 2 mg of Fe3(+). The 13 elements, such as Bi, Sn, Pb, In, Tl, Cd, Cu, Co, Ni, Zn, Ti, Be and Zr, could be almost completely coprecipitated under these conditions. In addition, Te memory effect imposed on the ICP-MS instrument was assessed, as well as Te matrix effect that caused the low recovery of Ga, As, Sb and V in real sample was discussed. Finally, the method was evaluated through recovery test and was applied to practical sample analysis, with detection limits of most of the elements being below 0.15 mug g(-1) and R.S.D. below or at approximately 10%, which indicated that this method could fully satisfy the requirements for analysis of 99.999% similar to 99.9999% high purity Te.

Sol-gel synthesis and photoluminescent properties of LaPO4 : A (A = Eu3+, Ce3+, Tb3+) nanocrystalline thin films

Rare-earth ion (Eu3+, Tb3+, Ce3+)- doped LaPO4 nanocrystalline thin films and their patterning were fabricated by a Pechini sol-gel process combined with soft lithography on silicon and silica glass substrates. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), scanning electron microcopy (SEM), optical microscopy, absorption and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicate that the films begin to crystallize at 700 degreesC and the crystallinity increases with increasing annealing temperature. The morphology of the thin film depends on the annealing temperature and the number of coating layers. The 1000 degreesC annealed single layer film is transparent to the naked eye, uniform and crack-free with a thickness of about 200 nm and an average grain size of 100 nm. Patterned thin films with different strip widths ( 5 - 50 mm) were obtained by micromolding in capillaries ( soft lithography). The doped rare earth ions show their characteristic emission in the nanocrystalline LaPO4 films, i.e., Eu3+ D-5(0)-F-7(J) (J = 1, 2, 3, 4), Tb3+ D-5(3,4) - F-7(J) ( J = 6, 5, 4, 3, 2) and Ce3+ 5d-4f transition emissions, respectively. Both the lifetimes and the PL intensities of Eu3+ and Tb3+ increase with increasing annealing temperature, and the optimum concentrations for them were determined to be 5 mol% and 16 mol% of La3+ in LaPO4 thin films, respectively. An energy transfer phenomenon from Ce3+ to Tb3+ has been observed in LaPO4 nanocrystalline thin films, and the energy transfer efficiency depends on the doping concentration of Tb3+ if the concentration of Ce3+ is fixed.

Patterning and luminescent properties of nanocrystallineY(2)O(3): Eu3+ phosphor films by sol-gel soft lithography

Nanocrystalline Y2O3:Eu3+ phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained, which mainly consisted of grains with an average size of 70 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped Eu3+ showed its characteristic emission in crystalline Y2O3 phosphor films due to an efficient energy transfer from Y2O3 host to them. Both the lifetimes and PL intensity of the Eu3+ increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+ were determined to be 5 mol%.