Hot particles analysis originating from failed and damaged fuels

The increase of activities of fission products and transmutation products in the primary coolant of a nuclear power plant indicates the presence of fuel rod failures. The measurement of the activity concentration of the primary coolant was able to detect fuel failures in the reactor core. Microanalytical methods for examining individual hot particles have been developed and applied to fuel failure detection under normal operation conditions as well as during the severe fuel damage that occurred in the cleaning tank incident at Unit 2 of NPP Paks in April 2003. Several faulty fuel rods can be detected simultaneously by the characterization of individual hot particles originating from the primary water. The analysis of particles originating from the damaged fuels provides information relating to the dissolution process of the fuel debris.     

Ab initio calculation of the interaction energy in the P2 binding pocket of HIV‐1 protease

Interactions at the P2 binding pocket of human immunodeficiency virus type 1 (HIV‐1) protease have been studied using calculated interaction energies for model systems that mimic this binding pocket. Models were built for the P2 pocket of HIV‐1 protease in complex with TMC114, nelfinavir, and amprenavir. A two‐step procedure was applied. In the first step, the size of the model system was confined to ～40 atoms, and the interaction energy was calculated at different computational levels. In the second step, the size of the system was increased to 138 atoms, and the calculations were only performed at the HF/6‐31G** level. The interaction energy of the HIV‐1 protease/TMC114 complex was found to be more favorable than the interaction energies of the other complexes because of the additional hydrogen bond interaction this inhibitor is able to make with the HIV‐1 protease backbone. The results of the calculations are supported by stockholder charges and electrostatic potential maps. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Characterization of gingerol-related compounds in ginger rhizome (Zingiber officinale Rosc.) by high-performance liquid chromatography/electrospray ionization mass spectrometry

This study sought to determine the utility of liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) coupled with diode array detection in identifying gingerol-related compounds from crude extracts of ginger rhizome. The fragmentation behaviors of compounds in both (-)- and (+)ESI-MS/MS were used to infer and confirm the chemical structures of several groups of compounds, including the gingerols, methylgingerols, gingerol acetates, shogaols, paradols, gingerdiols, mono- and diacetyl gingerdiols, and dehydrogingerdiones. Diode array detection at different wavelengths was used to confirm MS/MS-based identification. In total, 31 gingerol-related compounds were identified from the methanolic crude extracts of fresh ginger rhizome in this study. Three of these compounds were found to be new compounds. This study demonstrated that LC/ESI-MS/MS is a powerful on-line tool for identification of gingerol-related compounds, especially for thermally labile compounds that cannot be readily detected by GC/MS analysis.     

A green,isocyanide-based three-component reaction approach for the synthesis of multisubstituted ureas and thioureas

A one-pot, isocyanide based multicomponent protocol was presented starting from secondary amines towards (thio)urea derivatives and utilized for the construction of a diverse 27-membered chemical library. Following a green compatible microwave assisted condition, the formed N,N′-multisubstituted (thio)ureas were obtained in up to 85% yield.     

First liquid crystalline cuneane‐caged derivatives: a structure–property relationship study

The synthesis and phase behaviour of the first cuneane derivatives having liquid crystalline properties are reported. This new class of liquid crystalline materials is the homologous series of bis[4‐(n‐alkoxyphenyl)]cuneane‐2,6‐dicarboxylates. They were synthesized by two methods: either by isomerization of the previously prepared bis[4‐(n‐alkoxyphenyl)]cubane‐1,4‐dicarboxylates or by direct esterification of the cuneane‐2,6‐dicarboxylic acid. Enantiotropic nematic phases were observed for the first four homologues. The higher homologues exhibited enantiotropic smectic A phases. The bis[4‐(n‐octylphenyl]cuneane‐2,6‐dicarboxylate exhibited the SmA phase at a lower temperature than its octyloxy analogue. The mesophases were investigated and established by polarizing optical microscopy, differential scanning calorimetry and X‐ray diffraction. Quantum chemical calculations suggest elongated structure for these new liquid crystalline compounds.     

Small-angle scattering study of structural changes in the microfibril network of nanocellulose during enzymatic hydrolysis

The hydrolysis of nanofibrillated cellulose (NFC), consisting of individual cellulose fibrils, was followed using small-angle scattering techniques in order to reveal changes in the substrate structure caused by cellulose degrading enzymes. In particular, the nanoscale structure of the network of cellulose fibrils was characterized with the combination of small-angle neutron scattering and small-angle x-ray scattering. In the nanocellulose with higher xylan content, the interfibrillar distance was shown to remain unchanged during enzymatic degradation, whereas the distance increased in the nanocellulose with lower xylan content. The limiting effect of xylan on the hydrolysis and a faster hydrolysis of the more thoroughly fibrillated segments of the NFC network could be observed. Despite the extensive fibrillation of the raw material, however, the hydrolysis was eventually limited by the aggregated and heterogeneous structure of the substrate.     

Neuraminidase Based Electro-Nano Diagnostic Platforms: Development of Model Systems for Cancer Diagnosis

An electrochemical biosensor that monitored neuraminidase (NEU3), activity was developed. The analysis platform included a graphene-platinum hybrid modified gold screen printed electrode as a transducer. The detection protocol was based on observation of NEU3 activity which was used to remove sialic acid from the GD3 ganglioside. Examination of analytical characteristics resulted with two linear ranges of 10⁻⁸ U/mL–10⁻¹ and 10⁻¹ U/mL–2.53 U/mL with limit of detection values of 10⁻⁸ U/mL and 10⁻¹ U/mL, respectively. The selectivity of the developed NEU3 activity based electrochemical biosensor was tested with HeLa, VERO and A549 cell lines.     

Thio-click approach to the synthesis of stable glycomimetics

Carbon-sulfur-bridged glycomimetics were prepared by free radical hydrothiolation of the exocyclic double bond of unsaturated sugars. Reaction between benzoyl-substituted pyranoid-exoglycal and a range of thiols including peptide, 1-thioglycerol and 1-thiosugar derivatives gave β-D-configured carbon-sulfur-linked glycoconjugates with full stereoselectivity. Addition of a panel of thiols to a 3-exomethylene-glucofuranose derivative also proceeded in a stereoselective manner and afforded a series of D-allo-configured 3-deoxy-3-C-S-bridged glycoconjugates.     

Photoinitiated Thiol-ene Reactions of Enoses: A Powerful Tool for Stereoselective Synthesis of Glycomimetics with Challenging Glycosidic Linkages

Thioglycosides and C-glycosides represent pharmacologically useful classes of glycomimetics that possess a high degree of biological stability. One emerging tool for the stereoselective synthesis of thioglycosides is the photoinitiated addition of thiols to unsaturated sugars. Moreover, thiyl radical-mediated reactions of exo-glycals and 1-substituted endo-glycals offer facile routes to β-C-glycosidic structures. This Concept article summarizes the thiol-ene coupling strategies developed recently by our group and Somsák's group for the synthesis of several kinds of glycomimetics which are difficult to synthesize by conventional methods. One unusual characteristic of the thiol-ene reactions of endo-glycals is that heating inhibits, whereas cooling promotes the reaction. This unique temperature dependence as well as the effects of the enose structures and thiol configurations on the efficacy and stereoselectivity of the reactions are also discussed.     

Experimental determination of the natural frequencies of complex-shaped shells

The natural frequencies of a complex-shaped thin elastic shell under loading of two types that cause nonstationary vibrations are experimentally determined. The strains in the shell are recorded with piezoelectric strain gages, followed by the Fourier analysis of the oscillograms