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Crystalline
Kinds of Crystalline Terms modified by Crystalline Selected AbstractsHighly Crystalline, Idiomorphic Na2Ti6O13 Whiskers Grown from a NaCl Flux at a Relatively Low TemperatureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2010Katsuya Teshima Abstract Well-developed, highly crystalline Na2Ti6O13 whiskers were successfully grown by cooling a NaCl flux at a relatively low temperature of 700 °C. The obtained Na2Ti6O13 whiskers were colorless and transparent. The whiskers grown at 700 °C were single phase and exhibit the lowest sizes of up to about 3.5 ,m,×,0.1 ,m. From the results of SEM, XRD, and TEM, it was confirmed that the Na2Ti6O13 whiskers have very good crystallinity and elongated in the [lang]010[rang] directions. Furthermore, the whiskers exhibited good photocatalytic activity under ultraviolet light irradiation. It is reasonable to suppose that NaCl can be adequately used to synthesize high quality and well-developed titanate whiskers in an environmentally friendly process of crystal growth. [source] The Relationship Between 27Al Quadrupolar Parameters and AlF63, Octahedron Connectivity in Crystalline and Glassy Fluoroaluminates,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2007Monique Body Abstract 27Al SATRAS and MQ-MAS spectra were recorded for eight crystalline compounds, from the CaF2,AlF3 and BaF2,AlF3 binary and BaF2,CaF2,AlF3 ternary systems, and four glass compositions with different CaF2/BaF2/AlF3 contents. For the crystalline phases, the reconstruction of the spectra leads to the precise determination of the NMR parameters. For the glassy phases, the 27Al SATRAS spectra have been reconstructed using quadrupolar parameter distributions. The main finding of this study is the dependence of the quadrupolar frequency on the type of AlF63, octahedron connectivity. For crystalline phases the experimental ,Q values range between 75 kHz and 510 kHz for structures built up from isolated octahedra, and are between 560 kHz and 1250 kHz for structures built up from isolated chains of cis -connected octahedra, and are between 1530 kHz and 1580 kHz for structures built up from isolated chains of trans -connected octahedra. In the glassy phases the maximum of the quadrupolar frequency distribution shifts toward larger values and its width increases with increasing AlF3 content, and subsequently with the number of connected octahedra. The range of the ,Q values seems to indicate that when the octahedra are connected, cis connections occur most frequently. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Crystalline , -Alumina Deposited in an Industrial Coating Unit for Demanding Turning Operations,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2010Kirsten Bobzin Crystalline PVD ,-Al2O3 - coatings offer great potential for their use in high-speed cutting operations. They promise high hot hardness and high oxidation resistance at elevated temperatures. This is important for coatings that are used for machining of materials with low thermal conductivity such as stainless steel or Inconel 718 because heat generated during cutting can barely be dissipated by the chip. Because of the prevailing bonding forces of alumina, adhesion-related sticking can be reduced even for dry cutting. Furthermore, the high formation enthalpy of alumina prevents chemical reactions with frictional partners. The present work gives an overview of the deposition of ,-Al2O3 thin films on WC/Co-cutting inserts by using pulsed MSIP (magnetron sputter ion plating) PVD technology. To improve adhesion, a (Ti,Al)N bond coat was employed. The samples were analyzed using common thin film test equipment. Cutting tests and pin-on-disk examinations were carried out to test the coating's performance. For turning operations, the difficult-to-machine austenitic steel 1.4301 (X5CrNi18-10) was used. In comparison to a state-of-the-art (Ti,Al)N coating, (Ti,Al)N/,-Al2O3 showed a longer tool life. [source] Analyses of the Performance Potential of Oxidic PVD Wear-Protection Coatings on Cutting Tools Using the Example of Crystalline ,-Al2O3,ADVANCED ENGINEERING MATERIALS, Issue 7 2008F. Klocke This paper focuses on the high performance potential of oxidic PVD coatings on cutting tools using the example of crystalline ,-Al2O3. The materials used during the cutting processes were the nickel-based alloy, Inconel 718, in wet-cut drilling and milling as well as a quenched and tempered steel in dry-cut milling. The conclusion that may be drawn from these analyses is that oxidic PVD coatings are characterised by outstanding wear behaviour and can contribute to a significant increase in cutting performance. [source] Butadiene,isoprene copolymerization with V(acac)3 -MAO.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 20074 copolymers, Crystalline, amorphous trans - Abstract Butadiene-isoprene copolymerization with the system V(acac)3 -MAO was examined. Crystalline or amorphous copolymers were obtained depending on isoprene content. Both butadiene and isoprene units exhibit a trans -1,4 structure and are statistically distributed along the polymer chain. Polymer microstructure, comonomer composition, and distribution along the polymer chain were determined by 13C and 1H NMR analysis. The thermal and X-ray behaviors of the copolymers were also investigated and compared with results from solid-state 13C NMR experiments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4635,4646, 2007 [source] Inorganic Crystalline and Amorphous Fibers , Science and TechnologyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2006Hong Li No abstract is available for this article. [source] Variable-temperature studies of the 4-isopropylphenol crystal structure from X-ray diffraction.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2002Comparison of thermal expansion, molecular dynamics with spectroscopic results Crystalline 4-isopropylphenol, C9H12O, an optically non-linear material, was studied by X-ray diffraction in order to determine its structure at several temperatures in the 95,300,K range. The thermal expansion coefficients have been calculated from the lattice parameters' dependence on temperature. The rigid-body analysis of the anisotropic displacement parameters including the correlation with the internal motion of large amplitude provided the values of the molecular translation and libration tensors at the temperatures studied and was used to characterize the torsional motion of the isopropyl group. The calculated normal modes and internal torsion frequency were compared with the wave numbers at the maximum of bands in the low-frequency Raman scattering, FTIR and inelastic neutron scattering spectra. [source] Two 1-substituted 4-nitroimidazolesACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2001Maciej Kubicki Crystalline 4-nitro-1-phenylimidazole, C9H7N3O2, (I), and 4,-nitro-1-phenyl-4,1,-biiimidazole, C12H9N5O2, (II), contain C,H,O and C,H,N hydrogen bonds, connecting the molecules into infinite chains. The aromatic fragments in both compounds are nearly planar. The dihedral angles between the benzene and imidazole rings are 26.78,(5)° in (I) and 29.36,(8)° in (II). [source] Crystalline, Mixed-Valence Manganese Analogue of Prussian Blue: Magnetic, Spectroscopic, X-Ray and Neutron Diffraction Studies.CHEMINFORM, Issue 13 2005Silvio Decurtins Abstract For Abstract see ChemInform Abstract in Full Text. [source] Structural Analysis for Crystalline and Amorphous LnFe2Dx (Ln: Ho, Tb) by X-Ray/Neutron Diffraction and Reverse Monte Carlo Modeling.CHEMINFORM, Issue 41 2004Keiji Itoh Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Preparation and Properties of a Huge, Crystalline, and Water-Soluble Compound (C72H132N12Br6S12) That Possesses Six Carbenium Salt Units.CHEMINFORM, Issue 2 2002Juzo Nakayama Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Low-Temperature Heat Capacity and Thermal Decomposition of Crystalline [Ho(Thr)(H2O)5] Cl3CHINESE JOURNAL OF CHEMISTRY, Issue 8 2003Xiao-Zheng First page of article [source] Sonochemical synthesis and characterization of ZnO nanorod/Ag nanoparticle compositesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2009Fei Li Abstract A simple sonochemical route for the synthesis of Ag nanoparticles on ZnO nanorods is reported. Ultrasonic irradiation of a mixture of ZnO nanorods, Ag(NH3)2+, and formaldehyde in an aqueous medium yields ZnO nanorod/Ag nanoparticle composites. The powder X-ray diffraction of the ZnO/Ag composites shows additional diffraction peaks corresponding to the face-center-cubic structured Ag crystalline, apart from the signals from the ZnO nanorods. Scanning electron microscopy and transmission electron microscopy images of the ZnO/Ag composites reveal that the ZnO nanorods are coated with Ag nanoparticles with a mean size of several tens nanometer. The absorption band of ZnO/Ag composites is distinctly broadened and red-shifted, indicating the strong interfacial interaction between ZnO nanorods and Ag nanoparticles. This sonochemical method is simple, mild and readily scaled up, affording a simple way for synthesis of other composites. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystalline bismuth oxide nanorods fabricated on Pt-coated substrates using a trimethylbismuth and oxygen mixtureCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2008Hyoun Woo Kim Abstract The current work reports the fabrication of crystalline Bi2O3 nanorods on Pt-coated Si substrates using trimethylbismuth and O2 as the bismuth and the oxygen sources, respectively, in the metalorganic chemical vapor deposition process. Their microstructures were characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The obtained nanorods were crystalline, with their diameters in the range of 20,200 nm. The absence of tip-nanoparticle and the presence of predeposited Bi2O3 layer indicated that the growth was dominated by a vapor-solid process. The photoluminescence measurements of the Bi2O3 nanorods at room temperature exhibited an emission band peaked at around 422 nm. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanical properties of single crystalline and glassy lithium triborateCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2008I. P. Shakhverdova Abstract Mechanical properties of LiB3O5 single crystal plates with different orientation as well as of glass with the same composition have been investigated. The nano- (H) and microhardness (HM), the reduced Young's modulus (Er) and the crack behaviour of the samples were studied. Both hardness and Young's modulus of glass appeared smaller in comparison to corresponding single crystal data (H , 7 , 8 GPa, HM , 6 GPa, Er , 70 , 80 GPa for glass and H , 10 , 15 GPa, HM , 6 ,11 GPa, Er , 93 , 155 GPa for single crystal). H, Er, and the plane of crack propagation proved orientation-dependent. Cracks in the glass sample were not observed up to 0.49 N microindentation load, whereas for the single crystal the cracks appeared already at 0.098N. In single crystals the observed cleavage planes {211} and/or {412} are oriented nearly parallel to planes of B-O rings. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystal structure of a polar nematogen 4-(trans- 4-undecylcyclohexyl) isothiocyanatobenzeneCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2007S. Biswas Abstract Crystal and molecular structures of a nematogenic compound 4-(trans- 4-undecylcyclohexyl) isothiocyanatobenzene (11CHBT) have been determined by direct methods using single crystal X-ray diffraction data. The compound (C24H37N1S1) crystallizes in the monoclinic system with the space group P21/c and Z = 4. The unit cell parameters are a = 5.5539(11) Å, b = 8.1341(10) Å, c = 51.494(5) Å, and (= 91.127(14)0. The structure was refined to Rw = 0.051. The molecule is found to be slightly bow-shaped though the alkyl chain is in all- trans conformation. The phenyl ring and the alkyl chain are planar and the cyclohexyl group is in chair conformation. The isothiocyanato groups are almost linear. Parallel imbricated mode of packing of the molecules is found in the crystalline state which is precursor to the nematic phase structure. There are many van der Waals' interactions particularly in the isothiocyanato benzene part of the molecule. Of the various associated pairs of molecules the one having anti-parallel configuration with overlaps in the isothiocyanato phenyl group probably exists in both the crystalline and the nematic phases. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photoelectrical properties of crystalline titanium dioxide thin films after thermo-annealingCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2007R. Sathyamoorthy Abstract This paper reports the photoelectrical properties of sol gel derived titanium dioxide (TiO2) thin films annealed at different temperatures (425-900°C). The structure of the as-grown film was found to be amorphous and it transforms to crystalline upon annealing. The trap levels are studied by thermally stimulated current (TSC) measurements. A single trap level with activation energy of 1.5 eV was identified. The steady state and transient photocurrent was measured and the results are discussed on the basis of structural transformation. The photocurrent was found to be maximum for the films annealed at 425°C and further it decreases with annealing at higher temperatures. The photoconduction parameters such as carrier lifetime, lifetime decay constant and photosensitivity were calculated and the results are discussed as a function of annealing temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phase transition behavior and structure of the thermotropic liquid crystal 6-{[(4,-{[(undecyl)carbonyl]oxy}biphenyl-4yl)carbonyl]oxy}-1-hexyneCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2006Leijing Liu Abstract The phase transition behaviors and corresponding structures of 6-{[(4,-{[(undecyl)carbonyl]oxy}biphenyl-4yl)carbonyl]oxy}-1-hexyne (A4EE11) were investigated using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and wide angle X-ray diffraction (WAXD). In comparison with the published homologues, 5-{[(4,-heptoxy-biphenyl-4-yl)carbonyl]oxy}-1-pentyne (A3EO7) which shows a monotropic smectic A (SmA) phase and a metastable monotropic smectic C (SmC) phase; 5-{[(4,-heptoxy-biphenyl-4-yl)oxy]carbonyl}- 1-pentyne (A3E'O7) that exhibits three enantiotropic stable liquid crystalline (LC) phases, SmA phase, SmC phase and smectic X (SmX) phase; 5-{[(4,-heptoxy-biphenyl-4-yl)carbonyl]oxy}-1-undecyne (A9EO7) which has a monotropic SmA phase and a metastable crystal phase, A4EE11 integrates the enantiotropy, monotropy and metastability of the LC phases of those three compounds. Upon cooling from isotropic state to room temperature, in the temperature range of 62.0 to 58.5°C, A4EE11 shows an enantiotropic smectic A (SmA) phase with a layer spacing d=32.69Å. Further lowering the temperature, it enters into a metastable monotropic smectic B (SmB) phase with a longer layer spacing d=34.22Å which has a tendency towards crystallization. The metastability of the liquid crystalline phase may associate to the linkage order of the ester bridge between the mesogenic core and the flexible spacer. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Raman and Rayleigh scattering study of crystalline polyoxyethyleneglycolsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005M. Kozielski Abstract Results of the study of Raman and Rayleigh scattering in crystalline polyoxyethyleneglycols (PEG) and PEG 1500 aqueous solution are reported. The conformational changes of the polymer chain have been studied as a function of PEG water solution concentration and molecular weight. Intensity ratios of the gauche and trans conformation around C,C and C,O bonds have been estimated from the Raman spectra. Moreover, from the Raman band parameters the values of the order parameters versus aqueous solution concentration have been determined. The influence of an external electric field on these parameters has been analysed. Mutual orientation of polyoxyethyleneglycol chains in the crystalline and liquid state has been studied on the basis of the angular correlation parameters obtained from the Rayleigh band intensity as a function of aqueous solution concentration and molecular weight. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Improving the dissolution and oral bioavailability of the poorly water-soluble drug aloe-emodin by solid dispersion with polyethylene glycol 6000DRUG DEVELOPMENT RESEARCH, Issue 5 2009Hao-gang Duan Abstract Solid dispersions (SDs) of aloe-emodin (AE) and polyethylene glycol 6000 (PEG6000) with different drug loadings were prepared, characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) and evaluated for solubility and in vitro release. The oral bioavailability of AE from SD in rats was compared with the crystalline drug. Plasma concentrations of AE were determined by HPLC. After administration of crystalline AE (35,mg·kg,1) in rats, the AUC0-600 and Cmax were 393.6±77.1,mg·min·l,1 and 1.87±0.30,mg·l,1, respectively. For the PEG6000 SD of AE, AUC0-600 and Cmax were boosted to 1310.5±111.9,mg·min·l,1 and 5.86±0.47,mg·l,1, respectively. The results indicated that the oral bioavailability of AE was increased significantly. Simultaneously, the Tmax value of AE for AE crystalline was decreased from 75.6±17.3,min to 44.8±14.8,min for SD. The earlier Tmax for AE from SD indicated the higher extent of absorption for SD due to their improved dissolution rate in rat intestine. This SD approach can therefore be used to enhanced dissolution and bioavailability for poorly water-soluble drugs. Drug Dev Res, 2009. © 2009 Wiley-Liss, Inc. [source] Synthesis and Characterisation of a New Cu(O2CNAllyl2)2 Carbamato Complex and an Unusual Polymeric CuI Complex [CuI4Cl4(NHAllyl2)4]n: New Insights into Metal Carbamato ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2009Alberto Albinati Abstract Transition-metal N,N -dialkylcarbamato complexes represent an interesting class of compounds that can be conveniently used as precursors for the controlled formation of inorganic compounds, typically oxides. They can also be used as convenient precursors for chemical grafting of metal oxides on oxide surfaces as well as for the synthesis of inorganic,organic hybrid materials. In this last case, the presence of double bonds on the complex would enable its covalent embedding into a polymer matrix through reaction with suitable monomers. To this aim, we addressed the synthesis of an allyl-functionalised copper carbamato complex. During the synthesis of the N,N -diallylcarbamato complex Cu(O2CNAllyl2)2 (Cu1), the formation of the crystalline and unusual polymeric CuI complex [CuI4Cl4(NHAllyl2)4]n (Cu2) was observed. The new compound was characterised by X-ray single crystal diffraction and FTIR, 1H and 13C NMR spectroscopic analysis. In an attempt to investigate the redox mechanism and the equilibria leading to the formation of the observed unusual CuI polymeric complex, gas chromatography coupled with mass spectrometry (GC,MS) experiments were carried out, which allowed us to identify 3,4-dimethylpyrrole as the oxidation product of the reaction, leading to the reduction of CuII to CuI.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Phosphonylation of 2-Amino- and 2-Amido-3-bromopyridines and 2-Amino-3-chloroquinoxalines with Triethyl PhosphiteEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2009M. Shaker S. Adam Abstract The Tavs reaction of 2-amino- and 2-acylamido-3-bromopyridines 1 and 2 with triethyl phosphite in the presence of palladium acetate or chloride allows the synthesis of 2-amino- and 2-acylamidopyridine-3-phosphonates 3 and 4. A second ring nitrogen atom causes strong activation and leads to excellent yields in the phosphonylation of 2-amino-3-chloroquinoxalines. 2,3-Dichloroquinoxaline does not need a catalyst and undergoes double phosphonylation with sodium diethyl phosphite under Michaelis,Becker conditions. The results show an activating influence of pyridine nitrogen (,M) and deactivating influence of the amino group (+M). The reactivity of 1 and 2 in the Tavs coupling is compared with that of the 3-NH-2-bromopyridine position isomers and 2-bromoanilines and discussed in terms of the opposite effects of pyridine and amino(amido) nitrogen and different position of the N atoms towards the reaction site. The advantage of the Tavs reaction is the easy optimization because neither auxiliary ligands are required nor a base to trap the halide or a solvent. Triethyl phosphite itself acts as ligand and forms Pd0{P(OEt)3}n in the initial phase of the reaction. The structures of the products and the expected intramolecular N,H···O=P hydrogen bridging bonds were proven by solution NMR and by X-ray crystal structure analysis of single crystalline 3c.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Asymmetric Cyclopropanation of Optically Active (1-Diethoxyphosphoryl)vinyl p -Tolyl Sulfoxide with Sulfur Ylides: A Rationale for DiastereoselectivityEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 4 2005Wanda H. Midura Abstract The title sulfoxide (S)-(+)- 1a was found to react with sulfur ylides affording the corresponding cyclopropanes in high yields. With fully deuterated dimethyl(oxo)sulfonium methylide, (CD3)2S(O)CD2, the cyclopropanation reaction occurred in a highly diastereoselective manner producing the cyclopropane 4a - d2 as a major diastereomer in which the newly formed quaternary ,-carbon atom is chiral due to isotopic substitution (CH2 vs. CD2). The diastereomer 4b - d2, having the opposite configuration at the ,-carbon atom, was obtained starting form the 2,2-dideuterio substituted vinyl sulfoxide, (S)-(+)- 1a - d2, and the nondeuterated ylide. The diastereomeric ratio in both reactions was found to be ca. 10:1. The reaction of (S)-(+)- 1a with diphenylsulfonium isopropylide yielded the cyclopropane (+)- 7 as a single diastereomer. X-ray structural studies of the crystalline 1-phosphorylvinyl sulfoxide 9 as well as density functional calculations (B3LYP/6-31G*) on (1-phosphoryl)vinyl sulfoxides revealed the origin of the experimentally observed diastereoselectivities and allowed us to propose a transition state model for the cyclopropanation reaction of chiral 1-phosphorylvinyl sulfoxides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Soft magnetic materials for electrical engineering: state of the art and recent advancesEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2005F. Alves Abstract This article gives a brief description of the essential characteristics and principal applications of amorphous, crystalline and nanostructured soft magnetic materials in electrical engineering. Copyright © 2005 John Wiley & Sons, Ltd. [source] Analyses of the Performance Potential of Oxidic PVD Wear-Protection Coatings on Cutting Tools Using the Example of Crystalline ,-Al2O3,ADVANCED ENGINEERING MATERIALS, Issue 7 2008F. Klocke This paper focuses on the high performance potential of oxidic PVD coatings on cutting tools using the example of crystalline ,-Al2O3. The materials used during the cutting processes were the nickel-based alloy, Inconel 718, in wet-cut drilling and milling as well as a quenched and tempered steel in dry-cut milling. The conclusion that may be drawn from these analyses is that oxidic PVD coatings are characterised by outstanding wear behaviour and can contribute to a significant increase in cutting performance. [source] Coaxial Nanorods of MgO Core with Si Shell LayersADVANCED ENGINEERING MATERIALS, Issue 1-2 2007W. Kim This article demonstrates an approach to the synthesis of MgO/Si core-shell nanorods. The Si shell was close to amorphous, whereas the MgO core was crystalline with a cubic structure. The PL of the Si-coated products under excitation at 325 nm exhibited a visible light emission, which was almost identical to that of the uncoated ones. [source] Photoswitchable Gas Permeation Membranes Based on Liquid CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Eric G, owacki Abstract We have fabricated switchable gas permeation membranes in which a photoswitchable low-molecular-weight liquid crystalline (LC) material acts as the active element. Liquid crystal mixtures are doped with mesogenic azo dyes and infused into commercially available track-etched membranes with regular cylindrical pores (0.40 to 10.0 ,m). Tunability of mass transfer can be achieved through a combination of (1) LC/mesogenic dye composition, (2) surface-induced alignment, and (3) reversible photoinduced LC-isotropic transitions. Photo-induced isothermal phase changes in the imbibed material afford large and fully reversible changes in the permeability of the membrane to nitrogen. Both the LC and photogenerated isotropic states demonstrate a linear permeability/pressure relationship, but they show significant differences in their permeability coefficients. Liquid crystal compositions can be chosen such that the LC phase is more permeable than the isotropic,or vice versa , and can be further tuned by surface alignment. Permeability switching response times are 5 s, with alternating UV and >420-nm radiation at an intensity of 2 mW/cm2 being sufficient for complete and reversible switching. Thermal and kinetic properties of the confined LC materials are evaluated and correlated with the observed permeation properties. We demonstrate for the first time reversible permeation control of a membrane with light irradiation. [source] Biophysical characterization of synthetic rhamnolipidsFEBS JOURNAL, Issue 22 2006Jörg Howe Synthetic rhamnolipids, derived from a natural diacylated glycolipid, RL-2,214, produced by Burkholderia (Pseudomonas) plantarii, were analyzed biophysically. Changes in the chemical structures comprised variations in the length, the stereochemistry and numbers of the lipid chains, numbers of rhamnoses, and the occurrence of charged or neutral groups. As relevant biophysical parameters, the gel (,) to liquid crystalline (,) phase behavior of the acyl chains of the rhamnoses, their three-dimensional supramolecular aggregate structure, and the ability of the compounds to intercalate into phospholipid liposomes in the absence and presence of lipopolysaccharide-binding protein were monitored. Their biological activities were examined as the ability to induce cytokines in human mononuclear cells and to induce chemiluminescence in monocytes. Depending on the particular chemical structures, the physicochemical parameters as well as the biological test systems show large variations. This relates to the acyl chain fluidity, aggregate structure, and intercalation ability, as well as the bioactivity. Most importantly, the data extend our conformational concept of endotoxicity, based on the intercalation of naturally originating amphiphilic virulence factors into membranes from immune cells. This ,endotoxin conformation', produced by amphiphilic molecules with a hydrophilic charged backbone and apolar hydrophobic moiety, and adopting inverted cubic aggregate structures, causes high mechanical stress in target immune cells on integral proteins, eventually leading to cell activation. Furthermore, biologically inactive rhamnolipids with lamellar aggregate structures antagonize the endotoxin-induced activity in a way similar to lipid A-derived antagonists. [source] Structural evidence for a constant c11 ring stoichiometry in the sodium F-ATP synthaseFEBS JOURNAL, Issue 21 2005Thomas Meier The Na+ -dependent F-ATP synthases of Ilyobacter tartaricus and Propionigenium modestum contain membrane-embedded ring-shaped c subunit assemblies with a stoichiometry of 11. Subunit c from either organism was overexpressed in Escherichia coli using a plasmid containing the corresponding gene, extracted from the membrane using detergent and then purified. Subsequent analyses by SDS/PAGE revealed that only a minor portion of the c subunits had assembled into stable rings, while the majority migrated as monomers. The population of rings consisted mainly of c11, but more slowly migrating assemblies were also found, which might reflect other c ring stoichiometries. We show that they consisted of higher aggregates of homogeneous c11 rings and/or assemblies of c11 rings and single c monomers. Atomic force microscopy topographs of c rings reconstituted into lipid bilayers showed that the c ring assemblies had identical diameters and that stoichiometries throughout all rings resolved at high resolution. This finding did not depend on whether the rings were assembled into crystalline or densely packed assemblies. Most of these rings represented completely assembled undecameric complexes. Occasionally, rings lacking a few subunits or hosting additional subunits in their cavity were observed. The latter rings may represent the aggregates between c11 and c1, as observed by SDS/PAGE. Our results are congruent with a stable c11 ring stoichiometry that seems to not be influenced by the expression level of subunit c in the bacteria. [source] Vertical Nanostructures: Vertical (La,Sr)MnO3 Nanorods from Track-Etched Polymers Directly Buffering Substrates (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Mater. The inside cover image shows a tilted SEMFE image of La0.7Sr0.3MnO3 vertical nanorods. A. Carretero-Genevrier and co-workers have established a new method to generate vertical complex oxides nanostructures based on a sol,gel precursor solution and using track-etched polymers that act to buffer the substrate, which is described on page 892. These vertical nanorods grown at mild temperature undergo a complete structural, morphological, and chemical transformation into single crystalline (LaSr)xOy nanopyramids upon thermal activation at 1000°C. [source] | |||||||||||||||||||||||||||||||||||||