Characterization and evaluation of the photocatalytic properties of wormhole-like mesoporous silica incorporating TiO2, prepared using different hydrothermal and calcination temperatures

TiO₂?CSiO₂ mesoporous materials were synthesised by deposition of TiO₂ nanoparticles prepared by the sol?Cgel method on to the internal pore surface of wormhole-like mesoporous silica. In this work we synthesised wormhole-like mesoporous silica of different surface area by changing the hydrothermal temperature (70, 100, or 130?°C). Subsequent to this, titania solution was deposited on to the inner surface of the pores and this was followed by calcination at different temperatures (400, 600, or 800?°C). The effect of different hydrothermal and calcination temperature on the photocatalytic properties was evaluated. The samples were characterized by N₂-sorption, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The effect of different hydrothermal and calcination temperatures on the photocatalytic properties was evaluated by measuring the degradation of methylene blue in aqueous solution under UV light irradiation (mercury lamp, 125?W). The results indicated that appropriate surface area and degree of crystallinity are two important factors for obtaining high photocatalytic efficiency. Samples prepared at a hydrothermal temperature of 100?°C and calcined at 800?°C had the best photocatalytic performance, because of the highest surface area and high crystallinity.     

Analytical method for the accurate determination of tricothecenes in grains using LC-MS/MS: a comparison between MRM transition and MS3 quantitation

The current food crisis demands unambiguous determination of mycotoxin contamination in staple foods to achieve safer food for consumption. This paper describes the first accurate LC-MS/MS method developed to analyze tricothecenes in grains by applying multiple reaction monitoring (MRM) transition and MS(3) quantitation strategies in tandem. The tricothecenes are nivalenol, deoxynivalenol, deoxynivalenol-3-glucoside, fusarenon X, 3-acetyl-deoxynivalenol, 15-acetyldeoxynivalenol, diacetoxyscirpenol, and HT-2 and T-2 toxins. Acetic acid and ammonium acetate were used to convert the analytes into their respective acetate adducts and ammonium adducts under negative and positive MS polarity conditions, respectively. The mycotoxins were separated by reversed-phase LC in a 13.5-min run, ionized using electrospray ionization, and detected by tandem mass spectrometry. Analyte-specific mass-to-charge (m/z) ratios were used to perform quantitation under MRM transition and MS(3) (linear ion trap) modes. Three experiments were made for each quantitation mode and matrix in batches over 6 days for recovery studies. The matrix effect was investigated at concentration levels of 20, 40, 80, 120, 160, and 200 μg kg(-1) (n = 3) in 5 g corn flour and rice flour. Extraction with acetonitrile provided a good overall recovery range of 90-108% (n = 3) at three levels of spiking concentration of 40, 80, and 120 μg kg(-1). A quantitation limit of 2-6 μg kg(-1) was achieved by applying an MRM transition quantitation strategy. Under MS(3) mode, a quantitation limit of 4-10 μg kg(-1) was achieved. Relative standard deviations of 2-10% and 2-11% were reported for MRM transition and MS(3) quantitation, respectively. The successful utilization of MS(3) enabled accurate analyte fragmentation pattern matching and its quantitation, leading to the development of analytical methods in fields that demand both analyte specificity and fragmentation fingerprint-matching capabilities that are unavailable under MRM transition.     

Characteristics of a vacuum spark triggered by the transient hollowcathode discharge electron beam

The discharge characteristics of a vacuum spark triggered by the transient hollow cathode discharge (THCD) electron beam is investigated over a wide variety of discharge conditions. Two systems of the vacuum spark device have been considered-the first system powered by eight 2700-pF doorknob capacitors charged to a voltage of 40 kV (input energy of 17.6 J); while the second system employs a single 1.85-μF Maxwell capacitor discharged at a voltage of 20 kV (input energy of 370 J). The operating pressure of these systems has been varied over the range of 10 ^-2 to 10^-5 mbar in order to examine the effect of the operating pressure on the plasma formation of the vacuum spark discharge. The effectiveness of plasma heating has been found to be significantly enhanced in the two vacuum spark systems studied here. In particular, the plasma of the 17.6 J system has been observed to be heated to a condition hot enough to emit in the X-ray region when the operating pressure is reduced from 10^-2 to 10^-5 mbar. Similarly, in the case of the 370 J system, hot spot formation is also observed to occur only at a low operating pressure of 10^-4 mbar     

A Note on Partitions into Distinct Parts and Odd Parts

Bousquet-Mélou and Eriksson showed that the number of partitions of n into distinct parts whose alternating sum is k is equal to the number of partitions of n into k odd parts, which is a refinement of a well-known result by Euler. We give a different graphical interpretation of the bijection by Sylvester on partitions into distinct parts and partitions into odd parts, and show that the bijection implies the above statement.     

Generating self-accelerating Airy beams using a digital micromirror device

We report a new approach for generating an Airy beam by using a digital micromirror device (DMD) and a holographic technique where the DMD loads the desired hologram. Unique characteristics of an Airy beam, such as the non-diffraction and self-acceleration properties, were demonstrated to prove the successful construction of this type of waveform. Experimental results showed good agreement with theoretical calculations. This approach can also be used to generate other special beams.     

Effects of temperature and solvent concentration on the solvent crystallization of palm-based dihydroxystearic acid with isopropyl alcohol

Palm-based dihydroxystearic acid of 69.55% purity was produced in a 500-kg-per-batch operation pilot plant and purified through solvent crystallization in a custom fabricated simultaneous batch crystallizer unit. The effects of temperature and solvent concentration on yield, particle size distribution and purity were studied. The purity was higher, while the yield and particle size were lower and smaller, respectively, at higher temperature and solvent concentration. The solvent crystallization process efficiency was rated at 66–69% when carried out with 70–80% isopropyl alcohol at 20 °C.     

Nitrile‐functionalized Hg(II)‐ and Ag(I)‐N‐heterocyclic carbene complexes: synthesis,crystal structures,nuclease and DNA binding activities

Various nitrile‐functionalized benzimidazol‐2‐ylidene carbene complexes of Hg(II) and Ag(I) were synthesized by the interaction of 1‐benzyl/1‐butyl‐3‐(cyano‐benzyl)‐3 H‐benzimidazol‐1‐ium mono/dihexafluorophosphate with Hg(OAc)₂/Ag₂O in acetonitrile. Two of the benzimidazolium salts were structurally characterized by single crystal X‐ray diffraction technique. Structures of reported compounds were characterized by ¹ H, ¹³C NMR, FT‐IR, UV–visible spectroscopic techniques, and molar conductivity and elemental analyses. For bis‐benzimidazolium salt, dinuclear Hg(II)– and Ag(I)–carbene complexes were obtained. Nuclease activity and binding interactions of the synthesized benzimidazolium salts and their Ag(I)–carbene complexes with DNA were studied using agarose gel electrophoresis and, absorption spectroscopy and viscosity measurements, respectively. Ag(I)–carbene complexes showed higher DNA binding activity compared to their respective benzimidazolium salts. However, a benzimidazolium salt and two of the Ag(I) complexes showed remarkably higher nuclease activity both, in the presence and absence of an oxidizing agent. Copyright © 2012 John Wiley & Sons, Ltd.     

Metallic nanocavity-enhanced second harmonic generation from a KNbO3 nonlinear nanowire

We propose and experimentally investigate a self-aligned metallic nanocavity that can enhance second harmonic signals from a single KNbO₃ nanowire. With pump beams in the spectral proximity of the metallic nanocavity resonance, second harmonic intensity is observed to be >1800 times stronger than that of a typical bare nanowire under the same illumination conditions. By studying spectral features and polarization characteristics, we confirm that the nonlinear enhancement originates from the locally intensified electric field of a surface plasmon-polariton mode. This simple and robust scheme represents a powerful platform to study single nanowire nonlinearity.     

PaDEL‐DDPredictor: Open‐source software for PD‐PK‐T prediction

ADMET (absorption, distribution, metabolism, excretion, and toxicity)‐related failure of drug candidates is a major issue for the pharmaceutical industry today. Prediction of PD‐PK‐T properties using in silico tools has become very important in pharmaceutical research to reduce cost and enhance efficiency. PaDEL‐DDPredictor is an in silico tool for rapid prediction of PD‐PK‐T properties of compounds from their chemical structures. It is free and open‐source software that, has both graphical user interface and command line interface, can work on all major platforms (Windows, Linux, and MacOS) and supports more than 90 different molecular file formats. The software can be downloaded from http://padel.nus.edu.sg/software/padelddpredictor . © 2012 Wiley Periodicals, Inc.