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Various Structures (various + structure)
Selected AbstractsSynthesis of Highly Efficient Ag@AgCl Plasmonic Photocatalysts with Various StructuresCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2010Peng Wang Abstract By means of a simple ion-exchange process (using different precursors) and a light-induced chemical reduction reaction, highly efficient Ag@AgCl plasmonic photocatalysts with various self-assembled structures,including microrods, irregular balls, and hollow spheres,have been fabricated. All the obtained Ag@AgCl catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and UV-visible diffuse reflectance spectroscopy. The effect of the different morphologies on the properties of the photocatalysts was studied. The average content of elemental Ag in Ag@AgCl was found to be about 3.2,mol,%. All the catalysts show strong absorption in the visible-light region. The obtained Ag@AgCl samples exhibit enhanced photocatalytic activity for the degradation of organic contaminants under visible-light irradiation. The stability of the plasmonic photocatalysts was also investigated in detail. [source] Phase-contrast X-ray imaging with a large monolithic X-ray interferometerJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2000Tohoru Takeda To increase the field of view for large objects in phase-contrast X-ray imaging, a large monolithic X-ray interferometer has been fabricated using an available silicon ingot of diameter 10,cm. A performance study of this interferometer has been carried out using a synchrotron X-ray source. The view size of the interference pattern obtained with this interferometer was 25,mm wide and 15,mm high and its visibility was 79%. Various structures of a sliced human hepatocellular carcinoma were identified as necrosis, hemorrhagic necrosis, normal liver tissue and blood vessel. The performance of this interferometer was sufficient for phase-contrast X-ray imaging. [source] Tunneling current in gate dielectric stack in sub-45 nanometer CMOS devicesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Hitender Kumar Tyagi Abstract Direct tunneling current through dual layer SiO2/high-K dielectric structures are investigated for substrate injection. Correlation of dielectric constants and band offsets with respect to silicon has been taken into consideration in order to identify possible materials to construct these devices. The direct tunneling current in oxide/high-K dielectric structures with equivalent oxide thickness (EOT) of 2.0 nm can be significantly lower than that through single layer oxides of the same thickness. Various structures and materials of high-K stacks of interest have been examined and compared to access the reduction of gate current in these structures. It is estimated that HfO2/SiO2 dual stack structure can reduce gate leakage current by four orders of magnitude as compared with pure SiO2 layer of same EOT. The importance of interfacial layer in dual stack structure is high-lighted for the reduction of gate leakage current. The present approach is capable of modeling high-K stack structures consisting of multiple layers of different dielectrics (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A Polycrystalline Approach to the Cyclic Behaviour of f.c.c. Alloys , Intra-Granular HeterogeneityADVANCED ENGINEERING MATERIALS, Issue 9 2009Xavier Feaugas For several decades, the plastic deformation mechanisms of f.c.c. metals under cyclic loading have received considerable attention. The extensive work on this subject has gradually lead to the identification of the physical processes to be included in a formal scheme of fatigue behavior. Accordingly, we propose a review of the physical mechanisms of plastic deformation in f.c.c. metals and alloys to define the state-of-the-art and motivate future studies. The aim is to demonstrate the importance of a good knowledge of the heterogeneous nature of deformation at the intra-granular scale in defining a physical model of cyclic behavior. A large characterization of the different stages associated with the evolution of heterogeneous dislocation structures during tensile and cyclic loadings is given for an austenitic stainless steel AISI 316L. A unified view of these various structures is proposed in the form of a modified Pedersen's map [,max,=,f(,pcum), where ,max is the maximum plastic strain and ,pcum the cumulative plastic strain] in the case of tensile loading and different kinds of cyclic loading: uni-axial and multi-axial tests under stress or strain amplitude control. The specificities of each domain defined in the map are discussed in terms of long-range internal stresses in order to formalize, in a simple composite scheme, the intra-granular stress,strain field. The importance of taking into account this scheme and the nature of the different dislocations populations in a polycrystalline model is illustrated. [source] Improving the TDDFT calculation of low-lying excited states for polycyclic aromatic hydrocarbons using the Tamm,Dancoff approximationINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2008Yi-Lei Wang Abstract Full TDDFT combined with the commonly used hybrid functional B3LYP has been known to greatly underestimate the 1La excitation energies of large linear acenes. This has cast doubt on the TDDFT results for the similar 1La -type state in other conjugated ,-systems. Although increasing the amount of Hartree,Fock (HF) exchange energy in the employed functional could improve the excitation energy estimation of the 1La state, it would worsen the results for another lowest-lying excited state,1Lb. Calculations of absorption and emitting energies relative to the 1La states for a series of linear acenes showed that a TDDFT scheme incorporating the Tamm,Dancoff approximation (TDDFT/TDA) could decrease the estimation errors by a factor of about 50%, but keep the levels of 1Lb states almost unchanged. Thus, the TDDFT/TDA scheme gives an overall description for the low-lying excited states of linear acenes significantly better than the full TDDFT does. Furthermore, 16 nonlinear polycyclic aromatic hydrocarbons (PAHs) with various structures were examined to confirm the superiority of the TDDFT/TDA over the full TDDFT in its ability to describe the 1La states for conjugated ,-systems of large size. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Structural and photooxidation studies of poly(styrene oxide) prepared with Maghnite-H+ as cationic catalystJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Aïcha Hachemaoui Abstract The nature of irregularities and end-groups in poly(styrene oxide) samples prepared using Maghnite-H+ as a cationic catalyst were studied by 1H- and 13C-NMR at 200 MHz. Head-to-head (H-H) and tail-to-tail (T-T) irregularities are detected in all the samples studied. Secondary hydroxyl terminal groups are identified in polymers prepared with Maghnite-H+. Poly(styrene oxide) was found to undergo chain scission by aging at 25°C. It was confirmed that oxidation of this type of polymers results from the important sensitivity of the polyether soft segment to oxidative degradation. For this reason, the scissions due to the oxidation of the material lead to notable quantities of low molecular weight photoproducts. Among the various structures produced by the oxidative degradation process, benzoate and secondary hydroxyl groups are identified by MALDI-TOF-MS. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Systematic quantum chemical study of DNA-base tautomersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2004M. Piacenza Abstract The relative energies of the energetically low-lying tautomers of pyridone, cytosine, uracil, thymine, guanine, and iso-cytosine are studied by a variety of different quantum chemical methods. In particular, we employ density functional theory (DFT) using the six functionals HCTH407, PBE, BP86, B-LYP, B3-LYP, and BH-LYP, and the ab initio methods Hartree-Fock (HF), standard second-order Møller-Plesset perturbation theory (MP2), an improved version of it (SCS-MP2), and quadratic configuration interaction including single and double excitations (QCISD) and perturbative triple corrections [QCISD(T)]. A detailed basis set study is performed for the formamide/formamidic acid tautomeric pair. In general, large AO basis sets of at least valence triple-, quality including f-functions (TZV) are employed, which are found to be necessary for an accurate energetic description of the various structures. The performance of the more approximate methods is evaluated with QCISD(T)/TZV(2df,2dp) data taken as reference. In general it is found that DFT is not an appropriate method for the problem. For the tautomers of pyridone and cytosine, most density functionals, including the popular B3-LYP hybrid, predict a wrong energetic order, and only for guanine, the correct sequence of tautomers is obtained with all functionals. Out of the density functionals tested, BH-LYP, which includes a rather large fraction of HF exchange, performs best. A consistent description of the nonaromatic versus aromatic tautomers seems to be a general problem especially for pure, nonhybrid functionals. Tentatively, this could be assigned to the exchange potentials used while the functional itself, including the correlation part, seems to be appropriate. Out of the ab initio methods tested, the new SCS-MP2 approach seems to perform best because it effectively reduces some outliers obtained with standard MP2. It outperforms the much more costly QCISD method and seems to be a very good compromise between computational effort and accuracy. © 2003 Wiley Periodicals, Inc. J Comput Chem 1: 83,98, 2004 [source] A COMPARATIVE STUDY OF THE POTENTIAL ANTIOXIDANT ACTIVITIES OF GINSENOSIDESJOURNAL OF FOOD BIOCHEMISTRY, Issue 2010SUNGWOOK CHAE ABSTRACT Ginseng roots are believed to contain over 20 different types of ginsenosides. However, no reports exist on the antioxidant activity of ginsenosides according to their various structures. The present study involves a comparison of the various forms of ginsenosides, a series of derivatives originating from the attachment of different sugar moieties to triterpene dammarane, with respect to their intracellular reactive oxygen species scavenging activity. Among the ginsenosides, Rb2 and Rc showed the strongest antioxidant activity, followed by (in decreasing order) Rg2, Rh2, Rh1, Rf, Rg3, Rg1, Rb1, Re and Rd. Furthermore, the antioxidant activity ranks of the various forms of ginsenosides were influenced by the types of dammarane, as well as the number of sugar moieties, and substitutive groups. To the best of our knowledge, this is the first report evaluating the antioxidant properties of ginsenosides with the goal of determining their structure,activity relationship. PRACTICAL APPLICATIONS Ginseng (Panax ginseng C.A. Meyer), a member of the Araliaceae family, is traditionally considered as one of the most important medicinal plants with high ginsenoside content. Ginsenoside is a triterpenoid glycoside, which is known to have diverse physiological and pharmacological activities. However, the correlation of structure and antioxidant activity has never been studied thus far in ginsenosides. A relationship exists between the type and position of the sugar moieties in ginsenoside. From these results, ginsenosides Rb2 and Rc might be very useful for the development of functional food and raw materials of medicine for antioxidants preventing oxidative stress-related diseases. And structure and antioxidant relationship may be potential for evaluating the structure and function relationship of other ginsenosides in order to elucidate which part of ginsenoside is essential with regards to increasing antioxidant activity and the development of novel antioxidants to treat diseases associated with free radicals. [source] A theoretical investigation of ZnOxS1,x alloy band structurePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007H. Rozale Abstract We report the properties of ordered ZnOxS1,x alloys calculated in various structures (CuAu,I, Cu3Au, Luzonite and Famatinite) using a first-principles total-energy formalism based on the hybrid full-potential augmented plane-wave plus local orbitals (APW + lo) method, within the local-density approximation (LDA). The calculated band gaps of the alloys are direct and range from 0.49 for O-rich to 1.55 eV for S-rich ZnOxS1,x. The non linear variation of the band gap energy is related to the large electronegativity difference between O and S. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth and characterization of ZnMgTe/ZnTe layered structures grown by molecular beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010S. Imada Abstract ZnMgTe/ZnTe layered structures were grown on ZnTe substrates by molecular beam epitaxy, and the crystal structures were characterized using X-ray diffraction methods. This structure would be the waveguide for various optoelectronic devices. Therefore, the crystal quality of this layered structure would be very crucial for the realization of high performance devices. ZnMgTe is lattice mismatched to ZnTe, and the increase of the ZnMgTe layer thickness or Mg mole fraction ratio would result in the crystal quality deterioration of the layered structure. The critical layer thickness (CLT) was theoretically derived, and various structures with various ZnMgTe layer thickness and Mg mole fraction were grown. The lattice mismatch strain relief and crystal quality of those samples were investigated by means of X-ray reciprocal space mapping (RSM) and cross sectional transmission electron microscopy (TEM). The dislocation formation and the lattice mismatch relaxation were confirmed for various samples and it was revealed that the calculated CLT values could be used as an appropriate guideline to design the dislocation free and high performance device structures (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Damage Detection by Wave Propagation Observation with Laser SpeckleInterferometryPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005Alexander Schmidt For quality insurance and fault detection, one and three dimensional ESPI (Electronic Speckle Pattern Interferometry) technique is applied to various structures. These experiments are an extension of previous experiments with Holographic Interferometry [4], a related measurement technique. ESPI is a non contact, high resolution Laser measurement technique. It facilitates transient full field vibration measurements that deliver absolute deflections, either one dimensional out-of-plane or three dimensional in and out-of-plane. Experiments have been performed with a full scale concrete embedded track segment. Different known artificial defects represent various flaws and voids due to the fabrication process and operation. Wave propagation due to impact is observed and allows for damage detection. ESPI measurements are in good accordance with expectations. An in-situ measurement setup for quality management of concrete embedded railway tracks has been built. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of Vorticella convallaria calcium-binding centrin proteinsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005KATARZYNA KONIOR The stalked ciliate, Vorticella convallaria, is a good model system to study mechanochemical motility because its contractile organelles (spasmoneme and myonemes) use a mode of contraction that differs from most other eukaryotic motile systems. Since calcium triggers this contraction, we have undertaken the molecular characterization of the calcium-binding proteins associated with these organelles. We have isolated and identified seven unique centrin-like cDNAs from V. convallaria. Each encodes an acidic protein of approximately 20-kDa, containing a unique N-terminus and four potential calcium-binding domains. We predict that each centrin has a distinct function within the cell. To define these functions, we have initiated immunofluorescence localization studies utilizing various anti-centrin antibodies. Western analysis indicates that each antibody recognizes a distinct protein or subset of proteins in Vorticella. Using these antibodies, we have localized centrin to various structures within the cell; myonemes, spasmoneme, and the oral apparatus. Because each of these antibodies recognizes a different protein on Westerern analysis, we conclude that a number of calcium-binding proteins are associated with the contractile organelles. To further characterize this gene family, we have initiated immunolocalization at the ultrastructural level. This will permit subcellular localization of all Vorticella centrins and enable us to dissect the function of this multi-gene family. [source] | ||||||||||||||||