Capillary electrophoretic separation of heparin oligosaccharides under conditions amenable to mass spectrometric detection

A capillary electrophoresis method for the separation of high-molecular-mass heparin oligosaccharides compatible with mass spectral detection was developed. Structurally defined heparin oligosaccharides ranging in size from tetrasaccharide to tetradecasaccharide were used to optimize the conditions. Applying normal and reversed polarity modes, these oligosaccharides were separated by CE under various conditions. Ammonium hydrogencarbonate (30 mM at pH 8.50) used as the running electrolyte system gave good separation efficiency and resolution in the normal polarity mode. Application of this method to the separation of complicated heparin oligosaccharide mixtures required the addition of electrolyte additives. Ammonium hydrogencarbonate (30 mM), containing triethylamine (10 mM), was useful for the separation of complex oligosaccharide mixtures. Run-to-run and day-to-day precision and limits of detection were established for these separations.     

Film analysis employing subtarget effect using 355 nm Nd-YAG laser-induced plasma at low pressure

The applicability of spectrochemical analysis for liquid and powder samples of minute amount in the form of thin film was investigated using ultraviolet Nd-YAG laser (355 nm) and low-pressure ambient air. A variety of organic samples such as commercial black ink usually used for stamp pad, ginseng extract, human blood, liquid milk and ginseng powder was prepared as film deposited on the surface of an appropriate hard substrate such as copper plate or glass slide. It was demonstrated that in all cases studied, good quality spectra were obtained with very low background and free from undesirable contamination by the substrate elements, featuring ppm or even sub-ppm sensitivity and worthy of application for quantitative analysis of organic samples. The proper preparation of the films was found to be crucial in achieving the high quality spectra. It was further shown that much inferior results were obtained when the atmospheric-pressure (101 kPa) operating condition of laser-induced breakdown spectroscopy or the fundamental wavelength of the Nd-YAG laser was employed due to the excessive or improper laser ablation process.     

A density functional theory study on multiple exciton generation in lead chalcogenides

Abstract

Quantum confined structure-based solar cell is promising two folds increment of the maximum theoretical photovoltaic conversion efficiency i.e., > 60% in comparison with that of the bulk analogs e.g., silicon-based and dye sensitized solar cell (ca. 32% of maximum theoretical efficiency). The key to the significant increment is the ability of the fluorophore to exhibit multiple exciton generation upon absorption photon with sufficient energy. Small size of lead chalcogenides (PbS, PbSe, PbTe) crystals have been reported and proven experimentally could exhibit this unique property. We have investigated few clusters of narrow bandgap lead chalcogenides nanocrystals i.e., (PbS)n, (PbSe)n and (PbTe)n; which n?=?4 - 80. The cluster models were optimized using quantum chemical calculations to the lowest energy geometry at B3LYP/lanl2dz level of theory. The predicted realistic (PbS)₈₀, (PbSe)₅₀, and (PbTe)₇₄ clusters with the size, and bandgap of 4.58?nm (2.00?eV), 4.03?nm (1.51?eV), and 4.84?nm (1.55?eV) are smaller than that of their exciton Bohr radius i.e., 5.01, 13.1, and 24.8?nm respectively. Therefore, the occurrence of multi exciton generation in the clusters is hypothesized upon absorption of photon with E_photon = 2E_g.     

Antibacterial Activity of Clay Soils against Food-Borne Salmonella typhimurium and Staphylococcus aureus

Natural clays have recently been proven to possess antibacterial properties. Effective natural antimicrobial agents are needed to combat bacterial contamination on food contact surfaces, which are increasingly more prevalent in the food chain. This study sought to determine the antibacterial activity of clays against the food-borne pathogens Salmonella typhimurium ATCC 14028 and Staphylococcus aureus ATCC 13565. Soils were processed to yield leachates and suspensions from untreated and treated clays. Soil particle size, pH, cation-exchange capacity, metal composition and mineralogy were characterized. Antibacterial screening was performed on six Malaysian soils via the disc diffusion method. In addition, a time-kill assay was conducted on selected antibacterial clays after 6 h of exposure. The screening revealed that Munchong and Carey clays significantly inhibit Salmonella typhimurium (11.00 ± 0.71 mm) and S. aureus (7.63 ± 0.48 mm), respectively. Treated Carey clay leachate and suspension completely kill Salmonella typhimurium, while S. aureus viability is reduced (2 to 3 log₁₀). The untreated Carey and all Munchong clays proved ineffective as antibacterials. XRD analysis confirmed the presence of pyrite and magnetite. Treated Carey clays had a higher soluble metal content compared to Munchong; namely Al (92.63 ± 2.18 mg/L), Fe (65.69 ± 3.09 mg/L) and Mg (88.48 ± 2.29 mg/L). Our results suggest that metal ion toxicity is responsible for the antibacterial activity of these clays.     

Electrochemical Biosensors for Cancer Biomarkers Detection: Recent Advances and Challenges

Biomarkers are described as characteristics that provide information about biological conditions whether normal or pathological. Detection of biomarkers at the earliest stage of the cancer is of utmost importance for clinical diagnosis. Electrochemical biosensors allow detecting the low levels of specific analytes in blood, urine or saliva and providing a sensitive approach for direct measurement for cancer biomarker detection. Moreover, the integration of electrochemical devices with nanomaterials, such as carbon nanotubes, gold and magnetic particles offer amplification and multiplexing capabilities for simultaneous measurements of cancer biomarkers very sensitively. This review summarizes the recent developments of electrochemical biosensors systems for the detection of cancer biomarkers with emphasis on voltammetric, amperometric and impedimetric biosensors. A special attention is paid to aptamers and miRNAs that are very promising for the ultra‐sensitive and specific cancer biomarker detection.     

Maximum temperature analysis in a Li-ion battery pack cooled by different fluids

Journal of Thermal Analysis and Calorimetry - The use of Li-ion battery in electric vehicles is becoming extensive in the modern-day world owing to their high energy density and longer life. But...     

Negative refractions by triangular lattice sonic crystals in partial band gaps

This study numerically demonstrates the effects of partial band gaps on the negative refraction properties of sonic crystal. The partial band gap appearing at the second band edge leads to the efficient transmissions of scattered wave envelopes in the transverse directions inside triangular lattice sonic crystal, and therefore enhances the refraction property of sonic crystal. Numerical simulation results indicate a diagonal guidance of coupled scattered wave envelopes inside crystal structure at the partial band gap frequencies and then output waves are restored in the vicinity of the output interface of sonic crystal by combining phase coherent scattered waves according to Huygens' principles. This mechanism leads to two operations for wavefront engineering: one is spatial wavefront shifting operation and the other is convex–concave wavefront inversion operation. The effects of this mechanism on the negative refraction and wave focalization are investigated by using the finite difference time domain(FDTD) simulations. This study contributes to a better understanding of negative refraction and wave focusing mechanisms at the band edge frequencies, and shows the applications of the slab corner beam splitting and SC-air multilayer acoustic system.