Structure and Properties of Nanocomposites Formed by the Occlusion of Block Copolymer Worms and Vesicles Within Calcite Crystals

This article describes an experimentally versatile strategy for producing inorganic/organic nanocomposites, with control over the microstructure at the nano‐ and mesoscales. Taking inspiration from biominerals, CaCO₃ is coprecipitated with anionic diblock copolymer worms or vesicles to produce single crystals of calcite occluding a high density of the organic component. This approach can also be extended to generate complex structures in which the crystals are internally patterned with nano‐objects of differing morphologies. Extensive characterization of the nanocomposite crystals using high resolution synchrotron powder X‐ray diffraction and vibrational spectroscopy demonstrates how the occlusions affect the short and long‐range order of the crystal lattice. By comparison with nanocomposite crystals containing latex particles and copolymer micelles, it is shown that the effect of these occlusions on the crystal lattice is dominated by the interface between the inorganic crystal and the organic nano‐objects, rather than the occlusion size. This is supported by in situ atomic force microscopy studies of worm occlusion in calcite, which reveal flattening of the copolymer worms on the crystal surface, followed by burial and void formation. Finally, the mechanical properties of the nanocomposite crystals are determined using nanoindentation techniques, which reveal that they have hardnesses approaching those of biogenic calcites.     

Detection of polyomavirus DNA in human brain tumors

AIM: To investigate surgically resected human brain tumors for the presence of polyomavirus DNA. MATERIALS AND METHODS: 65 samples of surgically resected human brain tumors (57 tumors were of neuroectodermal genesis, 4--mesenchimal, 4--metastatic tumors) were examined for the presence of viral DNA by PCR analysis. RESULTS: DNA of polyomaviruses was found in oligodendroligomas (66.7% of cases), oligodendroastrocytomas (66.7% of cases) and glioblastomas (40% of cases). In metastatic tumors viral infection had not been detected. No correlation between the grade of brain tumors and infection with polyomavirus DNA has been revealed. CONCLUSION: Our data point to importance of investigation of the brain tumors and cerebrospinal fluid for determination of viral infection.     

Micromechanical modelling of poly(ethylene terephthalate) using a layered two-phase approach

The aim of this study is to assess the interactions between the constituent phases of poly(ethylene terephthalate) and thereby analyse the validity of a hybrid interaction model in a mean-field micromechanical model based on layered two-phase inclusions. Two different modelling approaches are used to simulate the behaviour of semicrystalline polymers. The first approach is the micromechanical model based on interactions of the crystalline lamellae and the adjacent amorphous layers. The second approach is a two-scale finite-element model of the spherulitic microstructure. Isotropic poly(ethylene terephthalate) is selected as the model material. The deformation mechanisms at the microscopic scale are examined. Various crystal geometries are used in the finite-element model to analyse the case when the crystalline regions do not form an interconnected network. It is shown that the predictions of the microscopic deformation measures obtained with the micromechanical and the finite-element models are similar. Experimental evaluation of the elastic moduli has been performed to further estimate the applicability of the micromechanical model to PET.     

Numerical implementation of the S-matrix algorithm for modeling of relief diffraction gratings

A new numerical implementation is developed to calculate the diffraction efficiency of relief diffraction gratings. In the new formulation, vectors containing the expansion coefficients of electric and magnetic fields on boundaries of the grating layer are expressed by additional constants. An S-matrix algorithm has been systematically described in detail and adapted to a simple matrix form. This implementation is suitable for the study of optical characteristics of periodic structures by using modern object-oriented programming languages and different standard mathematical software. The modeling program has been developed on the basis of this numerical implementation and tested by comparison with other commercially available programs and experimental data. Numerical examples are given to show the usefulness of the new implementation.     

Loss of swiss cheese in Neurons Contributes to Neurodegeneration with Mitochondria Abnormalities,Reactive Oxygen Species Acceleration and Accumulation of Lipid Droplets in Drosophila Brain

Various neurodegenerative disorders are associated with human NTE/PNPLA6 dysfunction. Mechanisms of neuropathogenesis in these diseases are far from clearly elucidated. Hereditary spastic paraplegia belongs to a type of neurodegeneration associated with NTE/PNLPLA6 and is implicated in neuron death. In this study, we used Drosophila melanogaster to investigate the consequences of neuronal knockdown of swiss cheese (sws)—the evolutionarily conserved ortholog of human NTE/PNPLA6—in vivo. Adult flies with the knockdown show longevity decline, locomotor and memory deficits, severe neurodegeneration progression in the brain, reactive oxygen species level acceleration, mitochondria abnormalities and lipid droplet accumulation. Our results suggest that SWS/NTE/PNPLA6 dysfunction in neurons induces oxidative stress and lipid metabolism alterations, involving mitochondria dynamics and lipid droplet turnover in neurodegeneration pathogenesis. We propose that there is a complex mechanism in neurological diseases such as hereditary spastic paraplegia, which includes a stress reaction, engaging mitochondria, lipid droplets and endoplasmic reticulum interplay.     

Investigation of the operation time dependence of the yield of ammonia conversion to nitrogen(II) oxide by platinum catalyst sets

The origins of changes in the catalytic activity of platinum catalysts in the ammonia oxidation process are studied. A general mathematical model for the dependence of the catalyst activity on the operation time of a single platinum gauze is proposed. Simplified expressions for the catalytic activity of two basic types of catalyst sets are obtained. Optimization of the catalyst operation mode is investigated and an optimal mode is selected based on the industrial data. © 2001 Society of Chemical Industry     

Engineering of a Plant Isoprenyl Diphosphate Synthase for Development of Irregular Coupling Activity

We performed mutagenesis on a regular isoprenyl diphosphate synthase (IDS), neryl diphosphate synthase from Solanum lycopersicum (SlNPPS), that has a structurally related analogue performing non-head-to-tail coupling of two dimethylallyl diphosphate (DMAPP) units, lavandulyl diphosphate synthase from Lavandula x intermedia (LiLPPS). Wild-type SlNPPS catalyses regular coupling of isopentenyl diphosphate (IPP) and DMAPP in cis-orientation resulting in the formation of neryl diphosphate. However, if the enzyme is fed with DMAPP only, it is able to catalyse the coupling of two DMAPP units and synthesizes two irregular monoterpene diphosphates; their structures were elucidated by the NMR analysis of their dephosphorylation products. One of the alcohols is lavandulol. The second compound is the trans-isomer of planococcol, the first example of an irregular cyclobutane monoterpene with this stereochemical configuration. The irregular activity of SlNPPS constitutes 0.4 % of its regular activity and is revealed only if the enzyme is supplied with DMAPP in the absence of IPP. The exchange of asparagine 88 for histidine considerably enhanced the non-head-to-tail coupling. While still only observed in the absence of IPP, irregular activity of the mutant reaches 13.1 % of its regular activity. The obtained results prove that regular IDS are promising starting points for protein engineering aiming at the development of irregular activities and leading to novel monoterpene structures.