Study of Hadrons Produced in Proton—Carbon Interactions at 120 GeV/c Using Hadron-Production Models

Physics of Atomic Nuclei - Double differential yield of π±, K±, protons, and antiprotons as a function of laboratory momentum is presented using hadron production models. This study...     

In situ bioconversion of compactin to pravastatin by Actinomadura species in fermentation broth of Penicillium citrinum

The biocatalytic production of pravastatin from compactin by hydroxylation has found many applications in health care and pharmaceuticals. Actinomadura macra, Actinomadura madurae, and Actinomadura livida can efficiently bioconvert compactin to pravastatin. The fermentation broth (Penicillium citrinum fermented media) harvested on the eighth day contained 388.90 mg L^?1 of compactin and an undetectable level of mycotoxin (citrinin). Bioconversion by A. macra was highest (87 %) in the yeast extract-amended medium. The anti-actinomadura effects of citrinin reduce the bioconversion capacity of Actinomadura. The in situ hydroxylation of compactin produced by P. citrinum represents a preferable alternative for the use of purified compactin, as a way to reduce cost and time processing.     

Cyclic Se6 and helical infinity1[Sex] as neutral ligands in the new compounds PdBr2Se6 and PdCl2Se8

PdBr2Se6 and PdCl2Se8 are two new compounds with cyclic Se6 coordinated to PdBr2 molecules and one-dimensional helical Sex chains coordinated to PdCl2 molecules. PdBr2Se6 is a black solid with a crystal structure similar, but not equal, to PdCl2Se6. It crystallizes in the space group P1 with the lattice constants a = 4.3946(8) A, b = 7.605(1) A, c = 7.992(2) A, alpha = 66.15(2) degrees , beta = 86.44(2) degrees , gamma = 80.90(2) degrees , and Z = 1 and can be handled in air like the deep red PdCl2Se8 which crystallizes in the orthorhombic space group Pbca with the lattice constants a = 9.609(2) A, b = 8.958(2) A, c = 13.799(3) A, and Z = 4. In PdBr2Se6, two cyclic Se6 molecules (chair conformation) are directly coordinated to Pd atoms, forming Pd(Se6)2Br2 groups. These are connected to one-dimensional chains via trans-standing Se atoms. In PdCl2Se8, the selenium substructure consists of helical chains with every fifth Se atom directly coordinated to the Pd atom of a PdCl2 group. Each PdCl2 group on the other hand connects two neighboring Sex helices. The type of Sex helix found for this compound is unique and differs from all other ones reported up to now including elemental alpha-Se. A reproducible twinning observed for PdBr2Se6 crystals in the course of the X-ray single-crystal investigations is checked by transmission electron microscopy in connection with details of the atomic arrangement. The Raman spectra of PdBr2Se6 and PdCl2Se8 are compared to Raman data of elemental Se modifications and give significant support for the Se6 and helical Sex to be neutral molecules. A discussion of the results of thermal analyses gives clear evidence that cyclic Se6 and helical Sex are considerably stabilized by bonding to the PdX2 molecules because the melting temperatures of the composite materials are significantly higher than the ones of the respective elemental modifications.     

Synthesis and characterization of polycyclic structures and linear polycarbonate copolymers from a bisphenol A dimer

An o,o′‐methylene‐bridged bisphenol A (BPA) dimer 2 was synthesized by a one‐step reaction between formalin and excess BPA in the presence of a cation exchange resin in a polar aprotic solvent. Novel oligomeric polycyclic structures were synthesized by the reaction of reactive difunctional halides, methyl phosphonic dichloride, phenyl phosphonic dichloride, and dimethyl dichlorosilane with the BPA dimer under high‐dilution conditions. The yields of the polycyclics were quite high. NMR and matrix‐assisted laser desorption ionization–time of flight mass spectrometry (MALDI–TOF MS) were very useful in the characterization of the dimer and its oligomeric polycyclic analogs. These polycyclics can potentially be used as precursors for advanced thermosetting materials. A series of polycarbonate copolymers of BPA were synthesized by solution polycondensation of the methylene bridged dimer of BPA with triphosgene. Alternatively, the co‐polycarbonate containing crosslinkable moieties was synthesized by in‐situ polymerization of BPA and BPA dimer with triphosgene. The copolymers were characterized by GPC. TG/DTA and DSC were used to investigate the thermal properties of the co‐polycarbonates. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 927–935, 1999     

Space–time cloaks through birefringent Goos–H?nchen shifts

We report a theoretical demonstration for the creation of space–time holes based on birefringence of reflection,transmission, and the Goos–H?chen(GH) shifts from a chiral medium. We observed space–time holes in the reflection, transmission, and their corresponding GH-shifted beams. Two space–time holes are clearly detected in the regions of 0 t ≤ 5τ_0 and-5 w ≤ y ≤ 5 w, as well as in the regions of-5τ_0≤ t ≤ 0 and-5 w ≤ y ≤ 5 w.These space–time holes hide objects and information contents from observers and hackers. The objects and information contents are completely undetectable, and thus events can be cloaked. The results of this paper have potential applications in the invisibility of drone technology and secure communication of information in telecom industries.     

Analysis of mandipropamid residual levels through systematic method optimization against the matrix complexity of sesame leaves using HPLC/UVD

An analytical method was developed to detect mandipropamid residues in sesame leaves using high‐performance liquid chromatography–ultraviolet detection. Samples were extracted with acetonitrile and were prepurified using a solid‐phase extraction (SPE) cartridge with an additional dispersive‐SPE (d‐SPE) sorbent application. The method was validated using an external calibration curve prepared using pure solvent. The linearity was excellent with determination coefficient = 1. The limits of detection and quantification were 0.003 and 0.01 mg/kg, respectively. Recoveries at three spiking levels – 0.1, 0.5, and 1.0 mg/kg – were in the range 80.3–90.7% with relative standard deviations <2%. This method was applied to field‐treated samples collected from two different areas, Gwangju and Muan, in the Republic of Korea and the half‐lives were similar, 5.10 and 5.41 days, respectively. The pre‐harvest residue limit was also predicted for both sites. The proposed method is sensitive and able to quantify trace amounts of mandipropamid in leafy vegetables. The combination of SPE and d‐SPE effectively removed the matrix components in sesame leaves. Copyright © 2015 John Wiley & Sons, Ltd.     

A combination of solid‐phase extraction and dispersive solid‐phase extraction effectively reduces the matrix interference in liquid chromatography–ultraviolet detection during pyraclostrobin analysis in perilla leaves

Perilla leaves contain many interfering substances; thus, it is difficult to protect the analytes during identification and integration. Furthermore, increasing the amount of sample to lower the detection limit worsens the situation. To overcome this problem, we established a new method using a combination of solid‐phase extraction and dispersive solid‐phase extraction to analyze pyraclostrobin in perilla leaves by liquid chromatography with ultraviolet absorbance detection. The target compound was quantitated by external calibration with a good determination coefficient (R² = 0.997). The method was validated (in triplicate) with three fortification levels, and 79.06– 89.10% of the target compound was recovered with a relative standard deviation <4. The limits of detection and quantification were 0.0033 and 0.01 mg/kg, respectively. The method was successfully applied to field samples collected from two different areas at Gwangju and Muan. The decline in the resiudue concentrations was best ascribed to a first‐order kinetic model with half‐lives of 5.7 and 4.6 days. The variation between the patterns was attributed to humidity. Copyright © 2015 John Wiley & Sons, Ltd.     

Various extraction methods for detection of bistrifluron residues in Asian pear using high‐performance liquid chromatography: application to dissipation patterns under open‐field conditions

The present study was carried out to develop an analytical method for the detection and quantification of bistrifluron, a benzoylphenylurea compound, in pear using high‐performance liquid chromatography with UV detection. Samples were extracted using conventional, AOAC and EN quick, easy, cheap, effective, rugged and safe ‘QuEChERS’ methods. As expected, conventional and EN‐QuEChERS methods gave higher recoveries than AOAC. In addition, interference around the analyte retention time was observed in the conventional method. Thus, the EN‐QuEChERS method was selected and validated by studying various parameters, including linearity, limit of detection, limit of quantification (LOQ), recovery and precision. Linearity was excellent, with a correlation coefficient of 0.9998. Recovery rates at three spiking levels (0.05, 0.2 and 1 mg/kg) ranged from 73.76 to 98.66%. Intra‐ and inter‐day precisions, expressed as relative standard deviations, were <6%. The LOQ of 0.05 mg/kg was considerably lower than the maximum residue limit (1 mg/kg) set by the Korean Ministry of Food and Drug Safety. The developed method was successfully applied to open‐field pear samples, in which the target analyte was slowly dissipated (55% decline) over 14 days with a half‐life of 10.19 days. Notably, the residue levels throughout the period of sample collection (14 days) were lower than the maximum residue limit, indicating that the residue was not hazardous for consumers. Copyright © 2016 John Wiley & Sons, Ltd.