978 resultados para Structure Z c (3900)


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Two mimics of the intermediate in the reaction catalyzed by ketol-acid reductoisomerase (KARI) were synthesized. Their structures were established on the basis of elemental analyses, IR, H-1 NMR and GC/mass detector. The crystal structure of compound 2 was found to be a substituted dioxane, formed by the condensation of two molecules. The two compounds showed some herbicidal activity on the basis of tests using rape root and barnyard grass growth inhibition. However, the herbicidal effect was weaker in greenhouse tests. (c) 2004 Society of Chemical Industry.

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Highly ordered rodlike periodic mesoporous organosilicas (PMO) were successfully synthesized using 1.2-bis(trimethoxysilyl)ethane as an precursor and triblock copolymer P123 as a template at low acid concentration and in the presence of inorganic salts (KCl). The role of acid and salt as well as the effects of synthesis temperature and reactant mole ratio in the control of morphology and the formation of ordered mesostructure was systematically examined. It was found that the addition of inorganic salt can dramatically expand the range of the synthesis parameters to produce highly ordered PMO structure and improve the quality of PMO materials. The morphology of PMOs was significantly dependent on the induction time for precipitation. The uniform PMO rods can only be synthesized in a narrow range of acid and salt concentrations. The results also show that the optimized salt concentration (I M) and low acidity (0.167 M) were beneficial to the formation of not only highly ordered mesostructure but also rodlike morphology. Increasing acidity resulted in fast hydrolysis reaction and short rod or plate-like particles. Highly ordered rod can also be prepared at low temperature (35 degrees C) with high salt amount (1.5 M) or high temperature (45 degrees C) with low salt amount (0.5 M). Optimum reactant molar composition at 40 degrees C is 0.035P123:8KCl:1.34HCI:444H(2)O:1.0bis(trimethoxysilyl)ethane. Lower or higher SiO2/PI23 ratio led to the formation of uniform meso-macropores or pore-blocking effect. (c) 2005 Elsevier Inc. All rights reserved.

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Details on the general discussion session of the 2004 Hume-Rothery Symposium on "The Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries" is presented. The symposium was held on Mar 17, 2004 at the Charlotte Convention Center in Charlotte NC.

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A test oracle provides a means for determining whether an implementation behaves according to its specification. A passive test oracle checks that the correct behaviour has been implemented, but does not implement the behaviour itself. In previous work, we have presented a method that allows us to derive passive C++ test oracles from formal specifications written in Object-Z. We describe the "Warlock" prototype tool that supports the method. Warlock is built on top of an existing Object-Z type checker and generates oracle code for a substantial subset of the Object-Z language. We describe the architecture of Warlock and its application to a number of Object-Z specifications. We also discuss its current limitations.

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The structure and thermal properties of yttrium alumino-phosphate glasses, of nominal composition (Y2O3)(0.31-z)(Al2O3)(z)(P2O5)(0.69) with 0 less than or similar to z less than or similar to 0.31, were studied by using a combination of neutron diffraction, Al-27 and P-31 magic angle spinning nuclear magnetic resonance, differential scanning calorimetry and thermal gravimetric analysis methods. The Vickers hardness of the glasses was also measured. The data are compared to those obtained for pseudo-binary Al2O3-P2O5 glasses and the structure of all these materials is rationalized in terms of a generic model for vitreous phosphate materials in which Y3+ and Al3+ act as modifying cations that bind only to the terminal (non-bridging) oxygen atoms of PO4 tetrahedra. The results are used to help elucidate the phenomenon of rare-earth clustering in phosphate glasses which can be reduced by substituting Al3+ ions for rare-earth R3+ ions at fixed modifier content.

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[-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4)iron(II)] bis(hexafluorophosphate), [Fe(btzb)3](PF6)2, crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity at about T1/2 = 174 K and a hysteresis of about 4 K between T1/2 and the low-spin state. The spin transition has been independently followed by magnetic susceptibility measurements, 57Fe-Mssbauer spectroscopy, and variable temperature far and midrange FTIR spectroscopy. The title compound crystallizes in the trigonal space group P30(No. 147) with a unit cell content of one formula unit plus a small amount of disordered solvent. The lattice parameters were determined by X-ray diffraction at several temperatures between 100 and 300 K. Complete crystal structures were resolved for 9 of these temperatures between 100 (only low spin, LS) and 300 K (only high spin, HS), Z = 1 [Fe(btzb)3](PF 6)2: 300 K (HS), a = 11.258(6) , c = 8.948(6) , V = 982.2(10) 3; 100 K (LS), a = 10.989(3) , c = 8.702(2) , V = 910.1(4) 3. The molecular structure consists of octahedral coordinated iron(II) centers bridged by six N4,N4 coordinating bis(tetrazole) ligands to form three 3-dimensional networks. Each of these three networks is symmetry related and interpenetrates each other within a unit cell to form the interlocked structure. The FeN bond lengths change between 1.993(1) at 100 K in the LS state and 2.193(2) at 300 K in the HS state. The nearest Fe separation is along the c-axis and identical with the lattice parameter c.

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* Dedicated to the memory of Prof. N. Obreshkoff

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The reaction of Cs4[Re6Te8(CN)6]2H2O with Cu(en)2Cl2 in water affords crystals of a cluster complex [{Cu(H2O)(en) 2}{Cu(en)2}Re6Te8(CN)6]3H2O. The structure of the compound is determined by single crystal X-ray diffraction (a = 10.8082(4) , b = 16.5404(6) , c = 24.6480(7) , = 92.696(1), V = 4401.5(3) 3, Z = 4, space group P21/n, R 1 = 0.0331, wR 2 (all data) = 0.0652). In the complex, cluster [Re6Te8(CN)6]4- anions are linked by Cu2+ cations into zigzag chains through cyanide bridges. The coordination environment of the copper cations is complemented by ethylenediamine molecules. Each of the cluster anions is additionally coordinated by a terminal fragment {Cu(H2O)(en)2}. 2014 Pleiades Publishing, Ltd.

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Signaturformel: A-H4 (1 Bl. vacat), Fingerprint nach Ex. der UB Frankfurt, Vorlageform des Erscheinungsvermerks: Gedruckt zu Wienn in Osterreich/ durch Hans Synbriener

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We present Spitzer IRS mid-infrared spectra for 15 gravitationally lensed, 24 m-selected galaxies, and combine the results with four additional very faint galaxies with IRS spectra in the literature. The median intrinsic 24 m flux density of the sample is 130 Jy, enabling a systematic survey of the spectral properties of the very faint 24 m sources that dominate the number counts of Spitzer cosmological surveys. Six of the 19 galaxy spectra (32%) show the strong mid-IR continuua expected of AGNs; X-ray detections confirm the presence of AGNs in three of these cases, and reveal AGNs in two other galaxies. These results suggest that nuclear accretion may contribute more flux to faint 24 m-selected samples than previously assumed. Almost all the spectra show some aromatic (PAH) emission features; the measured aromatic flux ratios do not show evolution from z = 0. In particular, the high signal-to-noise mid-IR spectrum of SMM J163554.2+661225 agrees remarkably well with low-redshift, lower luminosity templates. We compare the rest-frame 8 m and total infrared luminosities of star-forming galaxies, and find that the behavior of this ratio with total IR luminosity has evolved modestly from z = 2 to z = 0. Since the high aromatic-to-continuum flux ratios in these galaxies rule out a dominant contribution by AGNs, this finding implies systematic evolution in the structure and/or metallicity of infrared sources with redshift. It also has implications for the estimates of star-forming rates inferred from 24 m measurements, in the sense that at z ~ 2, a given observed frame 24 m luminosity corresponds to a lower bolometric luminosity than would be inferred from low-redshift templates of similar luminosity at the corresponding rest wavelength.

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General note: Title and date provided by Bettye Lane.

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<p>FtsZ, a bacterial tubulin homologue, is a cytoskeleton protein that plays key roles in cytokinesis of almost all prokaryotes. FtsZ assembles into protofilaments (pfs), one subunit thick, and these pfs assemble further to form a Z ring at the center of prokaryotic cells. The Z ring generates a constriction force on the inner membrane, and also serves as a scaffold to recruit cell-wall remodeling proteins for complete cell division in vivo. FtsZ can be subdivided into 3 main functional regions: globular domain, C terminal (Ct) linker, and Ct peptide. The globular domain binds GTP to assembles the pfs. The extreme Ct peptide binds membrane proteins to allow cytoplasmic FtsZ to function at the inner membrane. The Ct linker connects the globular domain and Ct peptide. In the present studies, we used genetic and structural approaches to investigate the function of Escherichia coli (E. coli) FtsZ. We sought to examine three questions: (1) Are lateral bonds between pfs essential for the Z ring? (2) Can we improve direct visualization of FtsZ in vivo by engineering an FtsZ-FP fusion that can function as the sole source of FtsZ for cell division? (3) Is the divergent Ct linker of FtsZ an intrinsically disordered peptide (IDP)?</p><p> One model of the Z ring proposes that pfs associate via lateral bonds to form ribbons; however, lateral bonds are still only hypothetical. To explore potential lateral bonding sites, we probed the surface of E. coli FtsZ by inserting either small peptides or whole FPs. Of the four lateral surfaces on FtsZ pfs, we obtained inserts on the front and back surfaces that were functional for cell division. We concluded that these faces are not sites of essential interactions. Inserts at two sites, G124 and R174 located on the left and right surfaces, completely blocked function, and were identified as possible sites for essential lateral interactions. Another goal was to find a location within FtsZ that supported fusion of FP reporter proteins, while allowing the FtsZ-FP to function as the sole source of FtsZ. We discovered one internal site, G55-Q56, where several different FPs could be inserted without impairing function. These FtsZ-FPs may provide advances for imaging Z-ring structure by super-resolution techniques.</p><p> The Ct linker is the most divergent region of FtsZ in both sequence and length. In E. coli FtsZ the Ct linker is 50 amino acids (aa), but for other FtsZ it can be as short as 37 aa or as long as 250 aa. The Ct linker has been hypothesized to be an IDP. In the present study, circular dichroism confirmed that isolated Ct linkers of E. coli (50 aa) and C. crescentus (175 aa) are IDPs. Limited trypsin proteolysis followed by mass spectrometry (LC-MS/MS) confirmed Ct linkers of E. coli (50 aa) and B. subtilis (47 aa) as IDPs even when still attached to the globular domain. In addition, we made chimeras, swapping the E. coli Ct linker for other peptides and proteins. Most chimeras allowed for normal cell division in E. coli, suggesting that IDPs with a length of 43 to 95 aa are tolerated, sequence has little importance, and electrostatic charge is unimportant. Several chimeras were purified to confirm the effect they had on pf assembly. We concluded that the Ct linker functions as a flexible tether allowing for force to be transferred from the FtsZ pf to the membrane to constrict the septum for division.</p>

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Durante las tres ltimas dcadas, numerosos/as arquelogos/as han discutido extensamente sobre el ritual funerario original de las poblaciones del sur ibrico entre los siglos ix y vi a.c., esto es, cremacin o inhumacin. Este debate est adems conectado con la existencia o no de complejidad social antes de la llegada fenicia, con la aparicin de una lite orientalizada y con la adopcin de nuevos objetos y prcticas por las poblaciones locales. En este artculo hago uso del concepto deleuziano de desterritorializacin y lo asocio con el de frontera desarrollado por anzalda para interpretar la sociedad del sur ibrico. Para ello, analizo la evidencia funeraria indgena y cuestiono la divisin estricta entre cremacin e inhumacin en la regin; as como examino la profundidad y significado de los cambios funerarios en las comunidades locales.

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Graphene, with its unique electronic and structural qualities, has become an important playground for studying adsorption and assembly of various materials including organic molecules. Moreover, organic/graphene vertical structures assembled by van der Waals interaction have potential for multifunctional device applications. Here, we investigate structural and electrical properties of vertical heterostructures composed of C60 thin film on graphene. The assembled film structure of C60 on graphene is investigated using transmission electron microscopy, which reveals a uniform morphology of C60 film on graphene with a grain size as large as 500 nm. The strong epitaxial relations between C60 crystal and graphene lattice directions are found, and van der Waals ab initio calculations support the observed phenomena. Moreover, using C60-graphene heterostructures, we fabricate vertical graphene transistors incorporating n-type organic semiconducting materials with an on/off ratio above 3 10(3). Our work demonstrates that graphene can serve as an excellent substrate for assembly of molecules, and attained organic/graphene heterostructures have great potential for electronics applications.