常温直接沉淀法制备ZnO纳米棒

在常温下, 以PEG-400(聚乙二醇400)为表面活性剂, 采用直接沉淀法合成了ZnO纳米棒. 产物用XRD, TEM, SAED和 HRTEM等进行了表征. 结果表明, 所得ZnO为一维的纳米棒, 属于六方纤维矿的单晶结构. ZnO纳米棒的直径在20~40 nm之间, 长度在300~800 nm范围. (0001)面为ZnO纳米棒的生长方向. 讨论了ZnO相的生成和ZnO纳米棒的形成机理以及PEG-400在其形成过程中的作用.     

Flux decline behaviors in dead-end microfiltration of activated sludge and its supernatant

The properties of dead-end microfiltration were explored under constant pressure using two types of activated sludge controlled under the condition of different air flow rates. The activated sludge cultured at the air flow rate of 0.15 L min⁻¹ (the anaerobic condition) exhibited a significant flux decline compared with the case of the air flow rate of 2.33 L min⁻¹ (the aerobic condition). It was found from the results of microfiltration of the supernatant separated by centrifugation that the constituents in the supernatant caused a major cake resistance in microfiltration of the activated sludge. The average specific filtration resistance for filtration of the activated sludge was closely consistent with that for filtration of the supernatant at low pressure (49 kPa). However, the cake resistance of the microbial floc in microfiltration of the activated sludge became substantial with increasing filtration pressure because of high compressibility of the microbial floc. Moreover, the foulant and the fouling mechanism in microfiltration of the supernatant were evaluated from both microfiltration test of the supernatant and microfiltration test of the filtrate collected thereby. As a result, the effects of the pore size and material of the microfiltration membrane on the flux decline behaviors in dead-end microfiltration were reasonably elucidated.     

Comparative molecular field analysis (CoMFA) for phosphodiesterase (PDE) IV inhibitors

A comparative molecular field analysis (CoMFA) for phosphodiesterase (PDE) IV inhibitors has been performed to correlate their chemical structures with their observed biological activity. In this study, CoMFA model based on docking mode for active site of PDE IV can describe the relative change in magnitude of the steric and electrostatic fields as a function of the compounds. Pyridine N-oxide and pyridine group of each compound are aligned toward the metal ion in S2-sub pocket of PDE IV. The study provided a statistically valid model with good correlation and predictive power, and consequently we identified some key features that may be used to design new derivatives.     

Sonocrystallization of polycarbonate melts

In this paper, we showed the simplified continuous process to crystallize the polycarbonate (PC) melts using sonocrystallization which is based on ultrasonic cavitation and ‘hot spot’ theory. High power ultrasonic wave was introduced to crystallize the PC prepolymers which is generally used for solid‐state polymerization (SSP) to obtain the ultra‐high molecular weight PCs. The structure and properties of PC treated with ultrasonic wave such as torque changes and crystallinities were studied. The experimental results showed that ultrasonic wave could improve the crystallinities of PCs and sonication time was proportional to their crystallinity. This is attributed to the decrease of the specific volume and the resulting shrinkage is compensated by a flux of a polymer melt toward the crystallization front. Torque data were collected directly from the Haake internal mixer and crystallinities were evaluated from differential scanning calorimeter (DSC). This process is an environmentally benign process so that no additional solvents or treatments are needed and will be very useful in the conventional solid‐state process which is used industrially. Copyright © 2007 John Wiley & Sons, Ltd.     

Langmuir monolayers of Co nanoparticles and their patterning by microcontact printing

In this paper, we describe an easy and reliable method for the production of patterned monolayers of Co nanoparticles. A two-dimensional monolayer of Co nanoparticles is fabricated by spreading a nanoparticle solution over an air-water interface and then transferring it to a hydrophobic substrate by using the Langmuir-Blodgett (LB) method. Transmission electron microscopy (TEM) was used to show that, with increasing surface pressure, the Co nanoparticles become well-organized into a Langmuir monolayer with a hexagonal close-packed structure. By controlling the pH of the subphase, it was found that a monolayer of Co nanoparticles with long-range order could be obtained. Further, by transferring the Langmuir monolayer onto a poly(dimethoxysilane) (PDMS) mold, the selective micropatterning of the Co nanoparticles could be achieved on a patterned electronic circuit. The electronic transport properties of the Co nanoparticles showed the ohmic I-V curve.     

Obesity and genetic polymorphism of ERCC2 and ERCC4 as modifiers of risk of breast cancer

To evaluate the relationship of genetic polymorphisms of ERCC2 and ERCC4 genes, both involved in nucleotide excision repair (NER), and the risk of breast cancer, a hospital-based case-control study was conducted in Korea. Histologically confirmed breast cancer cases (n = 574) and controls (n = 502) with no present or previous history of cancer were recruited from three teaching hospitals in Seoul during 1995-2001. Information on selected characteristics was collected by interviewed questionnaire. ERCC2 Asp(312)Asn (G>A) was genotyped by single-base extension assay and ERCC4 Ser(835)Ser (T>C) by dynamic allele-specific hybridization system. Although no significant association was observed between the genetic polymorphisms and the risk of breast cancer, women with both ERCC2 A allele- and ERCC4 C allele-containing genotypes showed a 2.6-fold risk (95% CI: 1.02-6.48) of breast cancer compared to women concurrently carrying the ERCC2 GG and ERCC4 TT genotypes. The breast cancer risk increased as the number of "at risk" genotypes increased with a borderline significance (P for trend = 0.07). Interactive effect was also observed between ERCC4 genotype and body mass idnex (BMI) for the breast cancer risk; the ERCC4 C allele containing genotypes posed a 1.7-fold (95% CI: 0.96-2.93) breast cancer risk in obese women (BMI>25 kg/m(2)) with a borderline significance. Our finding suggests that the combined effect of ERCC2 Asp(312)Asn and ERCC4 Ser(835)Ser genotypes might be associated with breast cancer risk in Korean women.     

Amphiphilic treelike rods at interfaces: layered stems and circular aggregation

Amphiphilic dendron-rod molecules with three hydrophilic poly(ethylene oxide) (PEO) branches attached to a hydrophobic octa-p-phenylene rod stem were investigated for their ability to form two-dimensional micellar structures on a solid surface. A treelike shape of the molecules was reported to be a major factor in the formation of nonplanar micellar structures in solution and in the bulk state (cylindrical and spherical). We observed that in these treelike amphiphilic molecules the hydrophilic terminated dendron branches assemble themselves in surface monolayers with the formation of two-dimensional layered or circular micellar structures. We suggested the formation of the planar ribbon-like structures with interdigitated layering within the loosely packed monolayers and circular, ringlike structures (2D circular aggregates) in the precollapsed state.     

Effect of plant matrix and fluid ethanol concentration on supercritical fluid extraction efficiency of schisandrin derivatives

An investigation of the effect of plant matrix on the supercritical fluid extraction efficiency of five schisandrin derivatives is reported, exhibiting a great difference with respect to extraction efficiency depending on the matrix. Pure supercritical CO2 at 60 degrees C and 34.0 MPa cannot fully recover schisandrin derivatives from the leaves as much as from the other matrices. Only 36.9% of these compounds are extracted from leaves of Schisandra chinensis by supercritical CO2 in comparison with organic solvent extraction. However, more than 80% of schisandrin derivatives are obtained from both stem and fruit parts. Ethanol addition also shows a different effect depending on plant matrix; that is, CO2 modified with 10% ethanol could enhance the yield of schisandrin derivatives from leaves by four times when compared with that of pure CO2, but it has little effect on both stems and fruits.     

Determination of diphenhydramine in biological fluids by capillary gas chromatography using nitrogen-phosphorus detection. Application to placental transfer studies in pregnant sheep

A nitrogen-phosphorus detection-gas chromatographic method, which provides improved sensitivity and selectivity for diphenhydramine, is reported. A 25 m X 0.31 mm cross-linked, 5% phenylmethyl silicone-coated fused-silica capillary column (film thickness 0.52 micron) was used for all analyses. The splitless capillary injection mode was employed with a 2-microliter sample being introduced by an automatic liquid sampler. Standard curves, using orphenadrine as an internal standard, were linear in the range 2-320 ng of diphenhydramine per 0.5 ml of sheep plasma. This represents an amount of diphenhydramine from ca. 40 pg to 6.4 ng at the detector. Chromatographic separation of diphenhydramine and orphenadrine was excellent, with no interference from endogenous plasma constituents. Applicability of the method was demonstrated by a placental transfer study in a chronically instrumented pregnant sheep following a 100 mg intravenous injection of diphenhydramine to the ewe.