Sheathless capillary electrophoresis/electrospray mass spectrometry using a carbon-coated fused-silica capillary

A simple procedure was developed for preparing a carbon-coated fused-silica capillary for use in sheathless capillary electrophoresis/electrospray mass spectrometry (CE/ESI-MS). The tapered capillary tip was smeared with a marker pen before coating with carbon using a soft pencil. The layer from the ink of the marker pen was critical to the preparation of the carbon-coated capillary. The fabrication of a carbon-coated fused-silica capillary tip requires less than 1 min. The stability of this carbon-coated fused-silica capillary is examined, and its utility in on-line sheathless CE/ESI-MS is demonstrated with the separation of berberine, coptisine, and palmatine chlorides. Although the carbon-coated fused-silica capillary tip is not as rugged as a gold-coated capillary, it is durable enough for sheathless CE/ESI-MS applications. Moreover, it is easy to refurbish the column once the performance of the tip is degraded.     

The finite element analysis of composite laminates and shell structures subjected to low velocity impact

In this investigation, the composite laminate and shell structures subjected to low velocity impact are studied by the ANSYS/LS-DYNA finite element software. The contact force is calculated by the modified Hertz contact law in conjunction with the loading and unloading processes. In the case of composite laminate, the impact-induced damage including matrix cracking and delamination are predicted by the appropriated failure criteria and the damaged area are plotted. Two types of shell structure, cylindrical and spherical shells, are considered in this paper. The effects of various parameters, such as shell curvature, clamped or simple supported boundary conditions and impactor velocity are examined through the parametric study. Numerical results show that structures with greater stiffness, such as smaller curvature and clamped boundary condition, result to a larger contact force and a smaller deflection. The impact response of the structure is proportional to the impactor velocity.     

Semi-natural Forested Landscape under a Bark Beetle Outbreak: a case study of the Bohemian Forest (Czech Republic)

Long-term and lasting human interference in forest ecosystems in the Bohemian Forest has resulted in the loss of some equilibrium mechanisms and hence increased susceptibility to ecological disturbances. Two methods for estimating bark beetle outbreaks in spruce forests are reported: an assessment of the susceptibility of individual trees to attack according to crown structure characteristics; and the use of remotely sensed data and image processing techniques to quantify changes in forest cover. The results document a significant increase in the area of highly damaged and dead forest classes, from 1% in 1987 to 16% in 1998, and a decrease in the area of healthy and moderately damaged spruce classes from 71% in 1987 to 52% in 1998. A possible approach to managing mountain Norway spruce ecosystems invaded by bark beetle in the Bohemian Forest is proposed.     

Synthesis and characterization of water-soluble diazonium salts as contrast-enhancement materials

Water soluble aromatic diazonium double salts, p-diazodiphenylamine chloride zinc chloride (DZS-1) and p-diazoanisol chloride zinc chloride (DZS-2), have been evaluated as photobleachable dyes for contrast enhancement lithography. After testing the bleaching characteristics, aqueous solutions of DZS-1 and poly(vinyl alcohol) were used as a contrast enhancement material. Thermal stability, resist contrast, exposure parameters and other bleaching characteristics of the photobleachable membranes were investigated. A. commercial i-line photoresist was used to evaluate the contrast ratio of the DZS-1/PVA CEL layer. The contrast ratio obtained in this investigation is 1.67.     

Denitrifying kinetics involving the distributed ratio of reductases

A suspended-growth batch reactor was used to denitrify synthetic wastewater containing various proportions of nitrate and nitrite. A competitive phenomenon between nitrate- and nitrite-reductase was studied utilizing various proportions of nitrate and nitrite in an anaerobic environment with a temperature of 30°C and methanol as carbon source. By using a non-linear regression technique, biokinetic constants of the maximum specific reduction rates of nitrate and nitrite (k₁, k₂) and the Monod half-saturation coefficients of nitrate and nitrite (K_s1, K_s2) for the proposed two-step denitrifying kinetics were 1·29 day^?1, 0·89 day^?1 and 14·3 mg NO-N dm^?3, 10.9 mg NO-N dm^?3, respectively. The result obtained from a series of chemostat studies indicated the Monod-type kinetic model was more accurate when the distributed ratio of nitrate- and nitrite-reductase in the proposed two-step denitrifying kinetics was taken into account.     

Identification of nanofiltration membrane foulants

The Mery-sur-Oise plant (France) has been using nanofiltration (NF) membranes (NF200) to produce safe drinking water since 1999. However, significant fouling has been occasionally observed according to seasonal conditions, even with various pre-treatments including conventional surface water treatment followed by ozonation, acid addition to pH 6.9, anti-scalant addition, and microfiltration (6mum). Pilot-scale filtration experiments were performed to determine the effects of natural organic matter (NOM) character and ozonation on NF membrane fouling under constant operating conditions. Two parallel pilot units were operated with sand-filtered water (SFW) and sand-filtered-ozonated water (SFOW) for 3-month periods corresponding to spring and fall seasons. To identify NF foulants, Fourier transform infrared spectroscopy, fluorescence excitation emission matrix, scanning electron microscope, energy-dispersive spectrophotometry, and HPSEC-UVA-DOC-fluorescence chromatography have been used. Even though the dissolved organic carbon (DOC) and ultraviolet (UVA) levels of spring samples were lower than those of winter season, these feed waters showed higher fouling presumably due to a higher hydrophilic fraction of NOM and the presence of microorganisms. In addition, for both seasons, ozonation increased the degree of fouling mainly by a change in NOM characteristics and by the promotion of bacterial cell growth conditions. The hydrophilic NOM is not expected to be easily rejected by the relatively hydrophilic and negatively charged NF200 membrane due to its non-charged (or oppositely charged) properties, indicating a high fouling potential by NOM associated with spring samples. The adhesion of bacteria and accumulation of microalgae on the membrane may be due to the role of extracellular biopolymers released by algae upon ozonation, promoting adhesion between microorganisms and the membrane surface. Protein- and polysaccharide-like substances were found as major foulants. The reason for the minor fouling by humic substances on membranes fed with SFOW during the spring season might be a loss of membrane surface charge due to screening by significant subsequent fouling on the base of the fouling layer of extracellular materials.     

Effect of the solvent composition and annealing process on the preparation of spray freeze-dried acetaminophen powder

The analgesic and physical properties of acetaminophen powder suitable as an inhaled drug produced by spray freeze-drying (SFD) were compared with those of raw acetaminophen. A laser particle size analyzer and scanning electron microscopy (SEM) were applied to estimate physical structure and properties of the particles. A cyclooxygenase (COX) inhibitor screening assay was used to compare the antipyretic and analgesic activity of raw and SFD acetaminophen. According to SEM, SFD acetaminophen particles had various shapes and sizes with porous structures. The optimized conditions for solvent, annealing temperature, and annealing time were water/ethanol mixture (60% water and 40% ethanol), ?40°C, and 7?h, respectively. The diameter of optimized acetaminophen powder was 7.33?µm, and the aerodynamic particle size was 3.38?µm. The antipyretic and analgesic activities of acetaminophen after SFD were from 84.3 to 97.1% for COX-1 and from 91.6 to 102.9% for COX-2 compared to those of raw acetaminophen, respectively.     

Porosity and mould filling of titanium castings

A vacuum/Ar pressure casting machine was used to study porosity and mould filling of cast bridges of Ti. Two series of experiments were carried out: (1) The melting and the mould chamber were separated by a thin Ti foil until penetrated by the Ti melt. The mould chamber including the mould cavity was evacuated. (2) No separating Ti foil was applied. The pressure in the mould chamber was then controlled by diffusion of Ar through the investment. The moulds were made of two investments with different gas permeability. A standardized wax pattern for a five-unit bridge was used. Mould filling was evaluated by visual inspection and by measuring the missing lengths of the margins of the crowns. The porosity was studied by x-ray radiography and density measurements. In the first series mould filling was satisfactory in all cases, while the porosity was substantial for high Ar pressures. Without a Ti foil (second series) all castings contained little porosity, but the mould filling was adequate only for the high permeability investment. The experiments show that porosity can be avoided by maintaining small pressure differences between the melting chamber and the mould cavity. Adequate mould filling is promoted by minimal back pressures from trapped Ar gas in the mould.