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A collinear-beam thermal lens detector has been constructed and its properties were characterized. Its application to the high-performance liquid chromatography (HPLC) separation of a mixture of five anthraquinone dyes dissolved in water shows a linear response over 3.5 orders of magnitude and a detection limit that is subnanomolar in the dye concentrations. These results are compared with those obtained previously using cavity ring-down spectroscopy (CRDS) in a Brewster's angle flow cell (Bechtel, K. L.; Zare, R. N.; Kachanov, A. A.; Sanders, S. S.; Paldus, B. A.Anal. Chem. 2005, 77, 1177–1182). The peak-to-peak baseline noise of the thermal lensing detection is 3.5 × 10-8 absorbance units (AU) with a path length of 200 μm, whereas the peak-to-peak baseline noise of CRDS detection is ∼2 × 10-7 AU with a path length of 300 μm. Both of these figures of merit should be compared to the peak-to-peak baseline noise of one of the best commercial UV-vis HPLC detection systems, which is ∼5 × 10-6 AU with a path length of 10mm (1-s integration time). Therefore, the thermal lensing technique has a demonstrated sensitivity of subnanomolar detection that is ∼140 times better than that of the best commercial UV—vis detector and ∼5 times better than that of CRDS. [ABSTRACT FROM AUTHOR]

Evanescent-wave cavity ring-down spectroscopy has been applied to a planar fused-silica surface covered with crystal violet (CV+) cations to characterize the silanol groups indirectly. A radiation-polarization dependence of the adsorption isotherm of CV+ at the CH3CN/silica interface is measured and fit to a two-site Langmuir equation to determine the relative populations of two different types of isolated silanol groups. CV- binding at type I sites yields a free energy of adsorption of -29.9 ± 0.2 kJ/mol and a saturation surface density of (7.4 ± 0.5) × 1012 cm-2, whereas the values of -17.9 ± 0.4 kJ/mol and (3.1 ± 0.4) × 1013 cm-2 are obtained for the type II sites. The CV+ cations, each with a planar area of ∼120 Å2, seem to be aligned randomly while lying over the SiO- type I sites, thereby suggesting that this type of site may be surrounded by a large empty surface area (>480 Å2). In contrast, the CV+ cations on a type II sites are restricted with an average angle of ∼40° tilted off the surface normal, suggesting that the CV+ cations on these sites are grouped closely together. The average tilt angle increases with increasing concentration of crystal violet so that CV+ cations may be separated from each other to minimize the repulsion of nearby CV+ and SiOH sites. [ABSTRACT FROM AUTHOR]

It is believed that a transition region may exist between the bulk adhesive and the adherend, which would play an important role in the performance of the joint. Epoxy/aluminum joints were studied using a nano-indenter and an atomic force microscope (AFM). Some samples were based on direct bonding of aluminum specimens with the epoxy adhesive and some used aluminum samples pre-coated with a softer epoxy system to simulate a soft interphase. The topography of indented samples was measured using AFM and the image was used to define the indentation positions. Results were interpreted in terms of three types of interactions of the indenter with the sample in the interface region: (a) direct contact of the indenter with both phases during indentation, (b) contact of the indenter with a single phase but for which the indentation response was directly affected by the adjacent phase and (c) contact with a modified resin phase near the interface the: 'interphase'. The importance of sample surface preparation was also studied. Results showed that polishing the surface often resulted in formation of ridges and troughs near the interface which resulted in artifacts, which could be interpreted as indicating the presence of a soft interphase. [ABSTRACT FROM AUTHOR]

INTRODUCTION: In transfusion medicine, antibodies that cause RBCs positive DATs, may interfere with patients' phenotyping. Traditionally, these antibodies were removed using various antibody elution methodologies. However, the elution agents and conditions used have been only partially successful; and no one method is superior. The purpose of this study was to develop a general and efficient method to separate non-sensitized from sensitized RBCs using Sephadex-based cell-affinity adsorbents. METHODS: First, we coupled Sephadex support with Staphylococcal Protein G (SpG) with or without NHS. Then we simulated clinical conditions by mixing different ratios of sensitized and non-sensitized RBCs in vitro. Sensitized cells were prepared by mixing antibody with corresponding antigen-positive RBCs. Finally, we checked the sensitization status of absorbed RBCs after absorption with modified Sephadex support. RESULTS: The number of sensitized RBCs bound to Sephadex-based cell-affinity adsorbents is approximately 5×10(8) RBCs/mL support. Activated Sephadex could separate sensitized from non-sensitized RBCs. Conclusion Sephadex-based cell-affinity adsorbents with an NHS spacer arm have bigger capacity for binding RBCs than unmodified Sephadex. The Sephadex-based cell-affinity adsorbents readily separate non-sensitized RBCs from sensitized RBCs, thus providing a new strategy to type the blood for transfused patients.

In order to reveal the biological diversity and the evolution of microbial community structure in the process of sludge cultivation and acclimation at the start-up stage of simultaneous partial nitrification and denitrification (SNAD) process, polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the microbial community structure in different operating periods. And molecular cloning was used for species identification and phylogenetic analysis. The 16S rDNA sequence analysis of the characteristic bands of the DGGE profile of total bacteria showed that the bacterial populations in the sludge were rich in diversity, and β- proteobacteria were slightly more abundant and maintained a relatively stable dominant position. With the operation of the reactor, the secondary populations were strengthened and became new dominant communities, such as Firmicutes, γ- proteobacteria, Bacteroides and so on. The 16S rDNA sequence analysis of the characteristic bands of the DGGE profile of ammonia-oxidizing bacteria showed that the strains obtained by sequencing basically belonged to Nitrosomonas of β-proteobacteria. The fast growth rate of this genus made it the dominant ammonia-oxidizing bacteria (AOB) in the activated sludge systems. [ABSTRACT FROM AUTHOR]

In this study, the preparation characteristics of coated electrodes were used to remove organic matter from wastewater. The effects of low concentration range in different current densities and pH on the removal of organic substances, chemical oxygen demand (COD) and ammonia nitrogen (NH3 -N) by the coated electrode were explored. The experimental results indicated that the removal efficiency of NH3 -N and COD achieved the optimum value when the electric current density was 8-10 mA/cm2 , the pH value was mild alkaline or neutral, and the electrolysis time was about 30 min. The preparation process of coated electrode and the mechanism of degradation of organic matter in wastewater were investigated. The coated electrode was analyzed by blending Energy Dispersive X-Ray (EDX) and Scanning Electron Microscope (SEM). The results indicated that the titanium-based ruthenium coated electrode was more suitable for practical application. [ABSTRACT FROM AUTHOR]