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Unique Structure (unique + structure)
Selected AbstractsUnique structure of ZnO films deposited by chemical bath depositionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2009Dewei Chu Abstract The unique structure of ZnO films obtained from aqueous solution method was investigated. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analyses indicate that unique morphology and structure of the region where precipitation on the substrate may occur in parallel with other regions. This is accompanied by a decrease of the electrical resistivity in the absorbed region. A possible mechanism for the resistivity transformation was discussed. [source] Inkjet-Printed Single-Droplet Organic Transistors Based on Semiconductor Nanowires Embedded in Insulating PolymersADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Jung Ah Lim Fabrication of organic field-effect transistors (OFETs) using a high-throughput printing process has garnered tremendous interest for realizing low-cost and large-area flexible electronic devices. Printing of organic semiconductors for active layer of transistor is one of the most critical steps for achieving this goal. The charge carrier transport behavior in this layer, dictated by the crystalline microstructure and molecular orientations of the organic semiconductor, determines the transistor performance. Here, it is demonstrated that an inkjet-printed single-droplet of a semiconducting/insulating polymer blend holds substantial promise as a means for implementing direct-write fabrication of organic transistors. Control of the solubility of the semiconducting component in a blend solution can yield an inkjet-printed single-droplet blend film characterized by a semiconductor nanowire network embedded in an insulating polymer matrix. The inkjet-printed blend films having this unique structure provide effective pathways for charge carrier transport through semiconductor nanowires, as well as significantly improve the on-off current ratio and the environmental stability of the printed transistors. [source] Purification and characterization of cathepsin B-like cysteine protease from cotyledons of daikon radish, Raphanus sativusFEBS JOURNAL, Issue 21 2008Akihiko Tsuji Plant cathepsin B-like cysteine protease (CBCP) plays a role in disease resistance and in protein remobilization during germination. The ability of animal cathepsin B to function as a dipeptidyl carboxypeptidase has been attributed to the presence of a dihistidine (His110-His111) motif in the occluding loop, which represents a unique structure of cathepsin B. However, a dihistidine motif is not present in the predicted sequence of the occluding loop of plant CBCP, as determined from cDNA sequence analysis, and the loop is shorter. In an effort to investigate the enzymatic properties of plant CBCP, which possesses the unusual occluding loop, we have purified CBCP from the cotyledons of daikon radish (Raphanus sativus) by chromatography through Sephacryl S-200, DEAE,cellulose, hydroxyapatite and organomercurial,Sepharose. The molecular mass of the enzyme was estimated to be 28 kDa by SDS/PAGE under reducing conditions. The best synthetic substrate for CBCP was t -butyloxycarbonyl Leu-Arg-Arg-4-methylcoumaryl 7-amide, as is the case with human cathepsin B. However, the endopeptidase activity of CBCP towards glucagon and adrenocorticotropic hormone showed broad cleavage specificity. Human cathepsin B preferentially cleaves model peptides via its dipeptidyl carboxypeptidase activity, whereas daikon CBCP displays both endopeptidase and exopeptidase activities. In addition, CBCP was found to display carboxymonopeptidase activity against the substrate o -aminobenzoyl-Phe-Arg-Phe(4-NO2). Daikon CBCP is less sensitive (1/7000) to CA-074 than human cathepsin B. Expression analysis of CBCP at the protein and RNA levels indicated that daikon CBCP activity in cotyledons is regulated by post-transcriptional events during germination. [source] Structure of a 2-aminoethyl phosphate-containing O-specific polysaccharide of Proteus penneri 63 from a new serogroup O68FEBS JOURNAL, Issue 2 2000Aleksander S. Shashkov Lipopolysaccharide of Proteus penneri strain 63 was degraded by mild acid to give a high molecular mass O-specific polysaccharide that was isolated by gel-permeation chromatography. Sugar and methylation analyses and NMR spectroscopic studies, including two-dimensional 1H,1H COSY, TOCSY rotating-frame NOE spectroscopy, H-detected 1H,13C and 1H,31P heteronuclear multiple-quantum coherence (HMQC), and 1H,13C HMQC-TOCSY experiments, demonstrated the following structure of the polysaccharide: where FucNAc is 2-acetamido-2,6-dideoxygalactose and PEtn is 2-aminoethyl phosphate. The polysaccharide studied shares some structural features, such as the presence of d -GlcNAc6PEtn and an ,- L -FucNAc-(1,3)- d -GlcNAc disaccharide, with other Proteus O-specific polysaccharides. A marked cross-reactivity of P. penneri 63 O-antiserum with P. vulgaris O12 was observed and substantiated by a structural similarity of the O-specific polysaccharides of the two strains. In spite of this, the polysaccharide of P. penneri 63 has the unique structure among Proteus O-antigens, and therefore a new, separate serogroup, O68, is proposed for this strain. [source] Structures of two cell wall-associated polysaccharides of a Streptococcus mitis biovar 1 strainFEBS JOURNAL, Issue 24 2000A unique teichoic acid-like polysaccharide, the group O antigen which is a C-polysaccharide in common with pneumococci The cell wall of Streptococcus mitis biovar 1 strain SK137 contains the C-polysaccharide known as the common antigen of a closely related species Streptococcus pneumoniae, and a teichoic acid-like polysaccharide with a unique structure. The two polysaccharides are different entities and could be partially separated by gel chromatography. The structures of the two polysaccharides were determined by chemical methods and by NMR spectroscopy. The teichoic acid-like polymer has a heptasaccharide phosphate repeating unit with the following structure: The structure neither contains ribitol nor glycerol phosphate as classical teichoic acids do, thus we have used the expression teichoic acid-like for this polysaccharide. The following structure of the C-polysaccharide repeating unit was established: where AAT is 2-acetamido-4-amino-2,4,6-trideoxy- d -galactose. It has a carbohydrate backbone identical to that of one of the two structures of C-polysaccharide previously identified in S. pneumoniae. C-polysaccharide of S. mitis is characterized by the presence, in each repeating unit, of two residues of phosphocholine and both galactosamine residues in the N-acetylated form. Immunochemical analysis showed that C-polysaccharide constitutes the Lancefield group O antigen. Studies using mAbs directed against the backbone and against the phosphocholine moiety of the C-polysaccharide revealed several different patterns of these epitopes among 95 S. mitis and Streptococcus oralis strains tested and the exclusive presence of the group O antigen in the majority of S. mitis biovar 1 strains. [source] Vertically Aligned Single-Walled Carbon Nanotubes by Chemical Assembly , Methodology, Properties, and ApplicationsADVANCED MATERIALS, Issue 13 2010Peng Diao Abstract Single-walled carbon nanotubes (SWNTs), as one of the most promising one-dimension nanomaterials due to its unique structure, peculiar chemical, mechanical, thermal, and electronic properties, have long been considered as an important building block to construct ordered alignments. Vertically aligned SWNTs (v-SWNTs) have been successfully prepared by using direct growth and chemical assembly strategies. In this review, we focus explicitly on the v-SWNTs fabricated via chemical assembly strategy. We provide the readers with a full and systematic summary covering the advances in all aspects of this area, including various approaches for the preparation of v-SWNTs using chemical assembly techniques, characterization, assembly kinetics, and electrochemical properties of v-SWNTs. We also review the applications of v-SWNTs in electrochemical and bioelectrochemical sensors, photoelectric conversion, and scanning probe microscopy. [source] Nanoporous Structures Prepared by an Electrochemical Deposition Process,ADVANCED MATERIALS, Issue 19 2003H.-C. Shin Free-standing metal foam structures with nano-dendritic walls of copper and tin are fabricated by an electrochemical deposition process. This unique structure is attributed to the concurrent generation of hydrogen bubbles with extremely fast metal deposition at high cathodic current densities. The Figure shows a typical example of the foam-like structure of tin deposits with walls composed of nano-dendritic branches. [source] Raman spectra indicative of unusual water structure in crystals formed from a room-temperature ionic liquidJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2006Hiroko Miki Abstract Formation of crystals with unusual water structure has been found to take place in an ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate (bmim[FeCl4]). The Raman spectrum of a crystal formed in bmim[FeCl4] showed two prominent Raman bands ascribed to H2O. Another crystal formed in bmim[FeCl4] exposed to D2O atmosphere showed Raman bands of H2O, HOD and D2O. These findings indicate that an unusually high concentration of water is contained in the crystals. The observed Raman bands of the HOH, HOD and DOD bending modes are unusually narrow, implying an unknown unique structure of water. Copyright © 2006 John Wiley & Sons, Ltd. [source] Inverse Opal Structure of Nitrogen-Doped Titanium Oxide with Enhanced Visible-Light Photocatalytic ActivityJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008Qi Li Nitrogen-doped titanium oxide inverse opal structure was synthesized to combine both chemical and physical modifications on n -TiO2 by the polystyrene sphere self-assembly followed by a sol,gel process. Enhanced visible-light absorption and subsequently enhanced photodegradation efficiency were observed in this unique structure, which can be attributed to both nitrogen-doping effect and inverse opal structure effect. Our work suggests that the coupling of photonic band gap structure with photocatalytic materials is a promising approach to achieve maximum enhancement for various photocatalytic materials, especially for environmental applications and solar cell devices. [source] Formation of Silicon-Doped Boron Nitride Bamboo Structures Via Pyrolysis of a Polymeric PrecursorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Yi Fan In this paper, we report the growth of bamboo-like silicon-doped boron nitride nanotubes via catalyst-assisted pyrolysis of a boron-containing polymeric precursor. The morphologies and structures of the nanotubes were characterized using electron microscopy and Raman spectroscopy. Two types of nanotubes are observed, one from a base-growth mode and the other from a tip-growth mode. The type II nanotubes contain encapsulated catalytic nanoparticles at the tip of every compartment. This unique structure is a promising candidate for applications in many nanodevices. [source] Morphology and reproduction of Nipponomysella subtruncata (Yokoyama), a galeommatoidean bivalve commensal with the sipunculan Siphonosoma cumanense (Keferstein) in JapanJOURNAL OF ZOOLOGY, Issue 4 2001J. Lützen Abstract The shell and anatomy of Nipponomysella subtruncata is described. The bivalve is attached singly or in groups of up to nine on Siphonosoma cumanense, a burrowing intertidal sipunculan in south-west Japan. The species is a protandrous hermaphrodite. Specimens 1.4,2.5 mm long are males, which between 2.1 and 3 mm in length reverse sex and remain females. Reproduction peaks in summer and the annual number of clutches is small. Ripe oocytes, 84,88 ,m diameter, are spawned into the suprabranchial cavity where they develop into 107-,m-long straight-hinged veligers. Following a planktotrophic period of unknown duration, the c. 360-,m-long spat normally settle upon and attach to the shells of larger, predominantly female, individuals. At a length of 1,1.6 mm they detach again and live separately thereafter. Sperm are transferred in spermatophores and stored within paired, mushroom-shaped receptacles located posteriorly in the female's suprabranchial cavity. The receptacles first appear in large males or in specimens in the process of reversing sex. Stored sperm probably survive long enough to fertilize more than one clutch. The anatomy of Nipponomysella is characteristic of the Montacutidae, and is of especial interest because of the unique structure of the sperm receptacles. [source] Out of Place and Out of Line: Positioning the Police in the Regulation of Financial MarketsLAW & POLICY, Issue 3 2008JAMES W. WILLIAMS In November of 2003, the Royal Canadian Mounted Police launched a major initiative to combat securities fraud in Canada. Spurred by the Enron scandals in the United States, this involved the establishment of a series of specialized white-collar crime units with the express mandate of investigating serious cases of securities fraud and protecting investors from the worst of the market's abuses. After four years of activity, these units have produced little in the way of tangible results and have been widely criticized in legal, financial, and regulatory communities. Drawing on thirty-five interviews with members of these units, as well as outside stakeholders including Crown Attorneys and private litigators, this article examines the activities of these Integrated Market Enforcement Teams and highlights a number of barriers to the successful execution of their designated mandate. While factors such as procedural restrictions and limited expertise are certainly relevant, this analysis reveals that the IMET teams are more fundamentally constrained by their position in a broader regulatory field. Understanding this field, and its unique structure and politics, is essential in coming to terms with both the possibilities and limitations of securities enforcement in an increasingly complex financial world. [source] Thermo-Responsive Organic/Inorganic Hybrid Hydrogels based on Poly(N -vinylcaprolactam)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2003Wouter Loos Abstract A new type of ,intelligent' hydrogels has been developed in the form of organic/inorganic hybrid materials by making use of the sol-gel technology. Poly(N -vinylcaprolactam) (PVCL) has been incorporated in these materials for its thermo-responsive properties. The synthesis of the hybrid hydrogels was achieved by the in situ formation of an inorganic silica phase in the presence of an aqueous solution of high molecular weight PVCL. This methodology results in the preparation of micro-heterogeneous systems in which silica particles of nanometer dimensions act as physical cross-links for the PVCL molecules. Hydrogen bonds between the remaining non-condensed silanol groups and the PVCL carbonyl functions, together with physical entanglements, are responsible for the strong interactions between the organic and inorganic phases. Stress-strain tests on highly swollen materials demonstrated that the unique structure of these thermo-responsive hybrid hydrogels improves the mechanical stability to a great extent as compared to conventional hydrogels. Transmission measurements demonstrate that the presence of the inorganic phase does not influence the cloud point temperatures of PVCL significantly. On the other hand, the response of the reinforced hybrid hydrogels to temperature becomes less pronounced for increasing silica fractions. The reversibility of the swelling/deswelling process has been demonstrated by swelling experiments as a function of temperature. PVCL/SiO2 hybrid hydrogels. [source] Mechanical, dielectric, and magnetic properties of the silicone elastomer with multi-walled carbon nanotubes as a nanofillerPOLYMER ENGINEERING & SCIENCE, Issue 9 2007Il-Seok Park Silicone elastomer and multi-walled carbon nanotubes (MWCNTs) composites, applicable as actuators and controllable dampers, were studied. Dynamic mechanical analysis (DMA) and vibrating sample magnetometry (VSM) were used to investigate the mechanical and magnetic properties of silicone elastomers and MWCNTs composites. Also, measurement of their dielectric property was conducted. The addition of MWCNT was able to tailor the damping and dielectric properties of the silicone elastomer. In this study, a 0.7 wt% of MWCNT composite demonstrated an attractive condition for the damping and the dielectric property. Exceedingly, the modulus increased with the application of a magnetic field. The good filler effect with the small addition of the MWCNTs content is caused by their unique structure, catalytic effect, and magnetic property. POLYM. ENG. SCI., 47:1396,1405, 2007. © 2007 Society of Plastics Engineers [source] Structure of OsmC from Escherichia coli: a salt-shock-induced proteinACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2004Dong Hae Shin The crystal structure of an osmotically inducible protein (OsmC) from Escherichia coli has been determined at 2.4,Ĺ resolution. OsmC is a representative protein of the OsmC sequence family, which is composed of three sequence subfamilies. The structure of OsmC provides a view of a salt-shock-induced protein. Two identical monomers form a cylindrically shaped dimer in which six helices are located on the inside and two six-stranded ,-sheets wrap around these helices. Structural comparison suggests that the OsmC sequence family has a peroxiredoxin function and has a unique structure compared with other peroxiredoxin families. A detailed analysis of structures and sequence comparisons in the OsmC sequence family revealed that each subfamily has unique motifs. In addition, the molecular function of the OsmC sequence family is discussed based on structural comparisons among the subfamily members. [source] CULTURAL CIRCUMCISION IN EU PUBLIC HOSPITALS , AN ETHICAL DISCUSSIONBIOETHICS, Issue 8 2009MARGHERITA BRUSA ABSTRACT The paper explores the ethical aspects of introducing cultural circumcision of children into the EU public health system. We reject commonplace arguments against circumcision: considerations of good medical practice, justice, bodily integrity, autonomy and the analogy from female genital mutilation. From the unique structure of patient-medicine interaction, we argue that the incorporation of cultural circumcision into EU public health services is a kind of medicalization, which does not fit the ethos of universal healthcare. However, we support a utilitarian argument that finds hospital-based circumcision safer than non-medicalized alternatives. The argument concerning medicalization and the utilitarian argument both rely on preliminary empirical data, which depend on future validation. [source] General and Facile Syntheses of Metal Silicate Porous Hollow NanostructuresCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2010Jun Zheng Abstract Porous hollow nanostructures have attracted intensive interest owing to their unique structure and promising applications in various fields. A facile hydrothermal synthesis has been developed to prepare porous hollow nanostructures of silicate materials through a sacrificial-templating process. The key factors, such as the concentration of the free metal cation and the alkalinity of the solution, are discussed. Porous hollow nanostructures of magnesium silicate, nickel silicate, and iron silicate have been successfully prepared by using SiO2 spheres as the template, as well as a silicon source. Several yolk,shell structures have also been fabricated by a similar process that uses silica-coated composite particles as a template. As-prepared mesoporous magnesium silicate hollow spheres showed an excellent ability to remove Pb2+ ions in water treatment owing to their large specific surface and unique structures. [source] Flow cytometric and morphological characterization of platelet-rich plasma gelCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2006Juan Emilio Fernández-Barbero Abstract Background of problems: Platelet-rich plasma (PRP) gel is derived from an autogenous preparation of concentrated platelets and is widely used in implant dentistry as a vector for cell growth factors. However, limited data are available on its structure and composition. The present study was aimed at providing a flow cytometric and ultrastructural characterization of PRP gel. Materials and methods: Twenty PRP gel samples were obtained from healthy volunteers. These PRP gel specimens were prepared for transmission (TEM) and scanning electron microscopy (SEM) examination of their morphological ultrastructure. Flow cytometry with CD41-PE monoclonal antibody was used to detect platelet cells, as this antibody recognizes human-platelet-specific antigen CD41. Results: Both SEM and TEM showed that PRP gel contains two components: a fibrillar material with striated band similar to fibrin filaments, and a cellular component that contains human platelet cells. Both techniques indicated that no morphological elements were bound between the cellular component and the fibrillar material. The cells were confirmed as platelet cells by flow cytometric study after incubation with specific monoclonal antibody CD41-PE. Conclusion: PRP gel contains a fibrillar and a cellular (largely human platelet cell) component. This unique structure may be capable of acting as a vehicle for carrying of cells that are essential for soft/hard tissue regeneration. [source] Two different unique cardiac isoforms of protein 4.1R in zebrafish, Danio rerio, and insights into their cardiac functions as related to their unique structuresDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 7 2010Kenji Murata Protein 4.1R (4.1R) has been identified as the major component of the human erythrocyte membrane skeleton. The members of the protein 4.1 gene family are expressed in a tissue-specific alternative splicing manner that increases their functions in each tissue; however, the exact roles of cardiac 4.1R in the developing myocardium are poorly understood. In zebrafish (ZF), we identified two heart-specific 4.1R isoforms, ZF4.1RH2 and ZF4.1RH3, encoding N-terminal 30 kDa (FERM) domain and spectrin-actin binding domain (SABD) and C-terminal domain (CTD), separately. Applying immunohistochemistry using specific antibodies for 30 kDa domain and CTD separately, the gene product of ZF4.1RH2 and ZF4.1RH3 appeared only in the ventricle and in the atrium, respectively, in mature hearts. During embryogenesis, both gene expressions are expressed starting 24 h post-fertilization (hpf). Following whole-mount in situ hybridization, ZF4.1RH3 gene expression was detected in the atrium of 37 hpf embryos. These results indicate that the gene product of ZF4.1RH3 is essential for normal morphological shape of the developing heart and to support the repetitive cycles of its muscle contraction and relaxation. [source] Electrical properties of structured HIPS/gamma-irradiated UHMWPE/carbon black blendsPOLYMER ENGINEERING & SCIENCE, Issue 4 2000O. Breuer HIPS/UHMWPE and HIPS/XL-UHMWPE containing carbon black (CB) are unique systems in which CB is attracted to the PE, and thus structuring takes place affecting the morphology and the resultant electrical properties. UHMWPE, having a very high viscosity, was chosen as the dispersed phase within HIPS in place of a conventional polymer in order to explore possibilities of obtaining unique structures that would induce the CB to segregate and form a conductive network. XL-UHMWPE particles also constitute an interesting dispersed phase, maintaming their highly porous and intricate structure even subsequent to melt processing. In both cases the CB is located at the interface; however, differences in resistivity values are observed. When low UHMWPE or XL-UHMWPE contents are incorporated, the HIPS/XL-UHMWPE/CB compositions have lower resistivities due to the heterogeneity of the interface, even at high shear rates. When high UHMWPE or XL-UHMWPE contents are utilized, the trends reverse: HIPS/UHMWPE/CB depict enhanced conductivity, due to the dominance of UHMWPE particle coalescence and the resultant decrease in surface area. This is contrary to what happens with the XL-UHMWPE particles, where the surface area increases with their higher contents, since they do not coalesce. [source] Caged and clustered structures of endothelin inhibitor BQ123, cyclo(- d -Trp- d -Asp, -Pro- d -Val-Leu-),Na+, forming five and six coordination bonds between sodium ions and peptidesACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2001Mitsunobu Doi BQ123 is a cyclic pentapeptide and a potent endothelin-1 inhibitor. The crystal structure of the BQ123 sodium salt was determined as the first example of an endothelin inhibitor. Four independent molecules and many solvent molecules were found in the asymmetric unit; the total weight was about 3000,Da. The precise structure including the solvent molecules was determined using high-resolution data collected on a synchrotron source. Sodium ions formed unique structures with five and six coordination bonds and their forms were distinguished into three classes. An ion was sandwiched by two BQ123 molecules. This peptide,sodium (2:1) complex showed a cage-like structure and octahedral coordination was observed. Sodium ions also formed a cluster composed of hydrated water molecules and peptides. Two sodium ions were contained in this cluster, making five coordination bonds. Despite having the same coordination numbers, these ions were distinguishable by differences in the polyhedra. One was trigonal bipyramidal (having six planes) and the other was square pyramidal (having five planes). Both shapes were very similar to each other, although the synchrotron data clearly revealed slight geometrical differences. [source] Design of peptides with branched ,-carbon dehydro-residues: syntheses, crystal structures and molecular conformations of two peptides, (I) N -Carbobenzoxy-,Val-Ala-Leu-OCH3 and (II) N -Carbobenzoxy-,Ile-Ala-Leu-OCH3CHEMICAL BIOLOGY & DRUG DESIGN, Issue 2 2003R. Vijayaraghavan Abstract: Highly specific structures can be designed by inserting dehydro-residues into peptide sequences. The conformational preferences of branched , -carbon residues are known to be different from other residues. As an implication it was expected that the branched , -carbon dehydro-residues would also induce different conformations when substituted in peptides. So far, the design of peptides with branched , -carbon dehydro-residues at (i + 1) position has not been reported. It may be recalled that the nonbranched , -carbon residues induced , -turn II conformation when placed at (i + 2) position while branched , -carbon residues induced , -turn III conformation. However, the conformation of a peptide with a nonbranched , -carbon residue when placed at (i + 1) position was not found to be unique as it depended on the stereochemical nature of its neighbouring residues. Therefore, in order to induce predictably unique structures with dehydro-residues at (i + 1) position, we have introduced branched , -carbon dehydro-residues instead of nonbranched , -carbon residues and synthesized two peptides: (I) N -Carbobenzoxy-,Val-Ala-Leu-OCH3 and (II) N -Carbobenzoxy-,Ile-Ala-Leu-OCH3 with ,Val and ,Ile, respectively. The crystal structures of peptides (I) and (II) have been determined and refined to R-factors of 0.065 and 0.063, respectively. The structures of both peptides were essentially similar. Both peptides adopted type II , -turn conformations with torsion angles; (I): ,1 = ,38.7 (4)°, ,1 = 126.0 (3)°; ,2 = 91.6 (3)°, ,2 = ,9.5 (4)° and (II): ,1 = ,37.0 (6)°, ,1 = 123.6 (4)°, ,2 = 93.4 (4), ,2 = ,11.0(4)° respectively. Both peptide structures were stabilized by intramolecular 4,1 hydrogen bonds. The molecular packing in both crystal structures were stabilized in each by two identical hydrogen bonds N1,O1, (,x, y + 1/2, ,z) and N2,O2, (,x + 1, y + 1/2, ,z) and van der Waals interactions. [source] General and Facile Syntheses of Metal Silicate Porous Hollow NanostructuresCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2010Jun Zheng Abstract Porous hollow nanostructures have attracted intensive interest owing to their unique structure and promising applications in various fields. A facile hydrothermal synthesis has been developed to prepare porous hollow nanostructures of silicate materials through a sacrificial-templating process. The key factors, such as the concentration of the free metal cation and the alkalinity of the solution, are discussed. Porous hollow nanostructures of magnesium silicate, nickel silicate, and iron silicate have been successfully prepared by using SiO2 spheres as the template, as well as a silicon source. Several yolk,shell structures have also been fabricated by a similar process that uses silica-coated composite particles as a template. As-prepared mesoporous magnesium silicate hollow spheres showed an excellent ability to remove Pb2+ ions in water treatment owing to their large specific surface and unique structures. [source] | ||||||||||||||||||||||||||||