WorldWideScience

Sample records for synthesis structure determination

  1. A General Chemistry Experiment Incorporating Synthesis and Structural Determination

    Science.gov (United States)

    van Ryswyk, Hal

    1997-07-01

    An experiment for the general chemistry laboratory is described wherein gas chromatography-mass spectroscopy (GC-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) are used to characterize the products of a series of microscale reactions on vanillin. A single sophisticated instrument can be incorporated into the laboratory given sufficient attention to the use of sampling accessories and software macros. Synthetic experiments coupled with modern instrumental techniques can be used in the general chemistry laboratory to illustrate the concepts of synthesis, structure, bonding, and spectroscopy.

  2. Synthesis and Structural Determination of Temocapril Sulfoxide Hydrochlorides

    International Nuclear Information System (INIS)

    Seong, Seok Bong; Moon, Jong Taik; Kim, Jung Ahn; Choo, Dong Joon; Lee, Jae Yeol

    2012-01-01

    Impurity (or related substance) control in pharmaceutical products is a primary goal of drug development. Stringent international regulatory requirements have been in place for several years as outlined in the International Conference on Harmonization (ICH) Guidelines Q3A (R), Q3B (R) and Q3C. According to ICH guidelines, impurities associated with the manufacture of a drug substance, also known as an active pharmaceutical ingredient (API), are classified into the following categories: (1) organic impurities (process and drug-related); (2) inorganic impurities (3) residual solvents. Many potential impurities result from the API manufacturing process including starting materials, isomers, intermediates, reagents, solvents, catalysts and reaction by-products. These potential impurities should be investigated to determine process control mechanisms for their removal and the need for specification controls at appropriate points in the process. The suggested structures of the impurities can be synthesized and will provide the final evidence for their structures, previously determined by spectroscopic methods. Therefore it is essential to know the structure of these impurities in the bulk drug in order to alter the reaction condition and to reduce the quantity of impurity to an acceptable level. Isolation, identification and quantification of impurities help the pharmaceutical company to obtain a pure substance with less toxicity and safety in drug therapy

  3. Methodology in structural determination and synthesis of insect pheromone

    Directory of Open Access Journals (Sweden)

    Guo-Qiang Lin

    1991-01-01

    Full Text Available By means of ethereal washing of insect pheromone glands of female moths, GC-MS detection along with microchemical reactions and electroantennogram (EAG survey, six economically important insect species were targeted for pheromone identification. The discovery of a natural pheromone inhibitor, chemo-selectivity and species isolation by pheromone will be described. The modified triple bond migration and triethylamine liganded vinyl cuprate were applied for achiral pheromone synthesis in double bond formation. Some optically active pheromones and their stereoisomers were synthesized through chiral pool or asymmetric synthesis. Some examples of chiral recognition of insects towards their chiral pheromones will be discussed. A CaH2 and silica gel catalyzed Sharpless Expoxidation Reaction was found in shortening the reaction time.

  4. Benzofuranyl Esters: Synthesis, Crystal Structure Determination, Antimicrobial and Antioxidant Activities

    Directory of Open Access Journals (Sweden)

    C. S. Chidan Kumar

    2015-09-01

    Full Text Available A series of five new 2‐(1‐benzofuran‐2‐yl‐2‐oxoethyl 4-(un/substitutedbenzoates 4(a–e, with the general formula of C8H5O(C=OCH2O(C=OC6H4X, X = H, Cl, CH3, OCH3 or NO2, was synthesized in high purity and good yield under mild conditions. The synthesized products 4(a–e were characterized by FTIR, 1H-, 13C- and 1H-13C HMQC NMR spectroscopic analysis and their 3D structures were confirmed by single-crystal X-ray diffraction studies. These compounds were screened for their antimicrobial and antioxidant activities. The tested compounds showed antimicrobial ability in the order of 4b < 4a < 4c < 4d < 4e and the highest potency with minimum inhibition concentration (MIC value of 125 µg/mL was observed for 4e. The results of antioxidant activities revealed the highest activity for compound 4e (32.62% ± 1.34% in diphenyl-2-picrylhydrazyl (DPPH radical scavenging, 4d (31.01% ± 4.35% in ferric reducing antioxidant power (FRAP assay and 4a (27.11% ± 1.06% in metal chelating (MC activity.

  5. Cell-free protein synthesis for structure determination by X-ray crystallography.

    Science.gov (United States)

    Watanabe, Miki; Miyazono, Ken-ichi; Tanokura, Masaru; Sawasaki, Tatsuya; Endo, Yaeta; Kobayashi, Ichizo

    2010-01-01

    Structure determination has been difficult for those proteins that are toxic to the cells and cannot be prepared in a large amount in vivo. These proteins, even when biologically very interesting, tend to be left uncharacterized in the structural genomics projects. Their cell-free synthesis can bypass the toxicity problem. Among the various cell-free systems, the wheat-germ-based system is of special interest due to the following points: (1) Because the gene is placed under a plant translational signal, its toxic expression in a bacterial host is reduced. (2) It has only little codon preference and, especially, little discrimination between methionine and selenomethionine (SeMet), which allows easy preparation of selenomethionylated proteins for crystal structure determination by SAD and MAD methods. (3) Translation is uncoupled from transcription, so that the toxicity of the translation product on DNA and its transcription, if any, can be bypassed. We have shown that the wheat-germ-based cell-free protein synthesis is useful for X-ray crystallography of one of the 4-bp cutter restriction enzymes, which are expected to be very toxic to all forms of cells retaining the genome. Our report on its structure represents the first report of structure determination by X-ray crystallography using protein overexpressed with the wheat-germ-based cell-free protein expression system. This will be a method of choice for cytotoxic proteins when its cost is not a problem. Its use will become popular when the crystal structure determination technology has evolved to require only a tiny amount of protein.

  6. Synthesis/literature review for determining structural layer coefficients (SLC) of bases.

    Science.gov (United States)

    2014-12-01

    FDOTs current method of determining a base material structural layer coefficient (SLC) is detailed in the : Materials Manual, Chapter 2.1, Structural Layer Coefficients for Flexible Pavement Base Materials. : Currently, any new base material not a...

  7. Synthesis and structural determination of twisted MoS2 nanotubes

    International Nuclear Information System (INIS)

    Santiago, P.; Schabes-Retchkiman, P.; Ascencio, J.A.; Mendoza, D.; Perez-Alvarez, M.; Espinosa, A.; Reza-SanGerman, C.; Camacho-Bragado, G.A.; Jose-Yacaman, M.

    2004-01-01

    In the present work we report the synthesis of MoS 2 nanotubes with diameters greater than 10 nm using a template method. The length and properties of these nanotubes are a direct result of the preparation method. High-resolution transmission electron microscopy is used to study the structure of these highly curved entities. Molecular dynamics simulations of MoS 2 nanotubes reveal that one of the stable forms of the nanotubes is a twisted one. The twisting of the nanotubes produces a characteristic contrast in the images, which is also studied using simulation methods. The analysis of the local contrast close to the perpendicular orientation shows geometrical arrays of dots in domain-like structures, which are demonstrated to be a product of the atomic overlapping of irregular curvatures in the nanotubes. The configuration of some of the experimentally obtained nanotubes is demonstrated to be twisted with a behavior suggesting partial plasticity. (orig.)

  8. Strontium substituted hydroxyapatites: Synthesis and determination of their structural properties, in vitro and in vivo performance

    Energy Technology Data Exchange (ETDEWEB)

    Kaygili, Omer, E-mail: okaygili@firat.edu.tr [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Keser, Serhat [Department of Chemistry, Faculty of Science, Firat University, 23119 Elazig (Turkey); Kom, Mustafa [Department of Surgery, Faculty of Veterinary Medicine, Firat University, 23119 Elazig (Turkey); Eroksuz, Yesari [Department of Pathology, Faculty of Veterinary Medicine, Firat University, 23119 Elazig (Turkey); Dorozhkin, Sergey V. [Kudrinskaja square 1-155, Moscow 123242 (Russian Federation); Ates, Tankut [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Ozercan, Ibrahim H. [Department of Pathology, School of Medicine, Firat University, 23119 Elazig (Turkey); Tatar, Cengiz; Yakuphanoglu, Fahrettin [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey)

    2015-10-01

    The objective of this study is to present a detailed report related to the synthesis and characterization of strontium substituted hydroxyapatites. Based on this purpose, hydroxyapatite (HAp) bioceramics with different amounts of strontium (e.g., 0, 0.45, 0.90, 1.35, 1.80 and 2.25 at.%) were prepared using a sol–gel method. The effects of Sr substitution on the structural properties and biocompatibility of the samples were studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques, in vitro and in vivo tests. All the samples composed of the nanoparticles ranging from 21 to 27 nm. The presence of Sr at low levels influenced the crystal size, crystallinity degree, lattice parameters and volume of the unit cell of the HAp. Both in vitro conditions and soaking period in simulated body fluid (SBF) significantly affected these properties. Especially, the (Ca + Sr)/P molar ratio gradually decreases with increasing soaking period in SBF. Animal experiments revealed the bone formation and osseointegration for all samples, and as compared with other groups, more reasonable, were observed for the sample with the lowest Sr content. - Highlights: • Sr content affects the structural properties of hydroxyapatite. • Bone formation and osseointegration are observed for all the samples. • In vitro conditions cause a significant change in the (Ca + Sr)/P ratio.

  9. Synthesis, three-dimensional structure, conformation and correct chemical shift assignment determination of pharmaceutical molecules by NMR and molecular modeling

    Energy Technology Data Exchange (ETDEWEB)

    Azeredo, Sirlene O.F. de; Sales, Edijane M.; Figueroa-Villar, José D., E-mail: jdfv2009@gmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Grupo de Ressonância Magnética Nuclear e Química Medicinal

    2017-07-01

    This work includes the synthesis of phenanthrenequinone guanylhydrazone and phenanthro[9,10-e][1,2,4]triazin-3-amine to be tested as intercalate with DNA for treatment of cancer. The other synthesized product, 2-[(4-chlorophenylamino)methylene]malononitrile, was designed for future determination of its activity against leishmaniasis. A common problem about some articles on the literature is that some previously published compounds display error of their molecular structures. In this article it is shown the application of several procedures of nuclear magnetic resonance (NMR) to determine the complete molecular structure and the non questionable chemical shift assignment of the synthesized compounds, and also their analysis by molecular modeling to confirm the NMR results. To determine the capacity of pharmacological compounds to interact with biological targets is determined by docking. This work is to motivate the application of NMR and molecular modeling on organic synthesis, being a process that is very important for the study of the prepared compounds as interactions with biological targets by NMR. (author)

  10. Synthesis, three-dimensional structure, conformation and correct chemical shift assignment determination of pharmaceutical molecules by NMR and molecular modeling

    International Nuclear Information System (INIS)

    Azeredo, Sirlene O.F. de; Sales, Edijane M.; Figueroa-Villar, José D.

    2017-01-01

    This work includes the synthesis of phenanthrenequinone guanylhydrazone and phenanthro[9,10-e][1,2,4]triazin-3-amine to be tested as intercalate with DNA for treatment of cancer. The other synthesized product, 2-[(4-chlorophenylamino)methylene]malononitrile, was designed for future determination of its activity against leishmaniasis. A common problem about some articles on the literature is that some previously published compounds display error of their molecular structures. In this article it is shown the application of several procedures of nuclear magnetic resonance (NMR) to determine the complete molecular structure and the non questionable chemical shift assignment of the synthesized compounds, and also their analysis by molecular modeling to confirm the NMR results. To determine the capacity of pharmacological compounds to interact with biological targets is determined by docking. This work is to motivate the application of NMR and molecular modeling on organic synthesis, being a process that is very important for the study of the prepared compounds as interactions with biological targets by NMR. (author)

  11. Synthesis and Single Crystal X-Ray Structure Determination of 3,3',5 ...

    African Journals Online (AJOL)

    Single crystal structure determination at 100 K revealed needle-like crystals in an orthorhombic crystal system. The asymmetric unit of the cell consists of an isolated chloride ion, one half of a tetrahedral [MnCl4]2- anion, a [H2Me4bpz]2+ dication and one half of a molecule of water. Keywords: Crystal Engineering, Hydrogen ...

  12. Isolation, structural determination, synthesis and quantitative determination of impurities in Intron-A, leached from a silicone tubing.

    Science.gov (United States)

    Chan, Tze-Ming; Pramanik, Birendra; Aslanian, Robert; Gullo, Vincent; Patel, Mahesh; Cronin, Bart; Boyce, Chris; McCormick, Kevin; Berlin, Mike; Zhu, Xiaohong; Buevich, Alexei; Heimark, Larry; Bartner, Peter; Chen, Guodong; Pu, Haiyan; Hegde, Vinod

    2009-02-20

    Investigation of unexpected levels of impurities in Intron product has revealed the presence of low levels of impurities leached from the silicone tubing (Rehau RAU-SIK) on the Bosch filling line. In order to investigate the effect of these compounds (1a, 1b and 2) on humans, they were isolated identified and synthesized. They were extracted from the tubing by stirring in Intron placebo at room temperature for 72 h and were enriched on a reverse phase CHP-20P column, eluting with gradient aqueous ACN and were separated by HPLC. Structural elucidation of 1a, 1b and 2 by MS and NMR studies demonstrated them to be halogenated biphenyl carboxylic acids. The structures were confirmed by independent synthesis. Levels of extractable impurities in first filled vials of actual production are estimated to be in the range of 0.01-0.55 microg/vial for each leached impurity. Potential toxicity of these extractables does not represent a risk for patients under the conditions of clinical use.

  13. Structure determination of LpxA from the lipopolysaccharide-synthesis pathway of Acinetobacter baumannii

    International Nuclear Information System (INIS)

    Badger, John; Chie-Leon, Barbara; Logan, Cheyenne; Sridhar, Vandana; Sankaran, Banumathi; Zwart, Peter H.; Nienaber, Vicki

    2012-01-01

    Crystal structures of the LpxA protein from A. baumannii were solved in apo forms that were suitable for structure-based antibacterial drug discovery. Acinetobacter baumannii is a Gram-negative pathogenic bacterium which is resistant to most currently available antibiotics and that poses a significant health threat to hospital patients. LpxA is a key enzyme in the biosynthetic pathway of the lipopolysaccharides that are components of the bacterial outer membrane. It is a potential target for antibacterial agents that might be used to fight A. baumannii infections. This paper describes the structure determination of the apo form of LpxA in space groups P2 1 2 1 2 1 and P6 3 . These crystal forms contained three and one protein molecules in the asymmetric unit and diffracted to 1.8 and 1.4 Å resolution, respectively. A comparison of the conformations of the independent protein monomers within and between the two crystal asymmetric units revealed very little structural variation across this set of structures. In the P6 3 crystal form the enzymatic site is exposed and is available for the introduction of small molecules of the type used in fragment-based drug discovery and structure-based lead optimization

  14. Structure determination of LpxD from the lipopolysaccharide-synthesis pathway of Acinetobacter baumannii

    International Nuclear Information System (INIS)

    Badger, John; Chie-Leon, Barbara; Logan, Cheyenne; Sridhar, Vandana; Sankaran, Banumathi; Zwart, Peter H.; Nienaber, Vicki

    2012-01-01

    Crystal structures of the protein LpxD from A. baumannii were solved in apo forms that are suitable for structure-based antibacterial drug discovery. Acinetobacter baumannii is a Gram-negative bacterium that is resistant to many currently available antibiotics. The protein LpxD is a component of the biosynthetic pathway for lipopolysaccharides in the outer membrane of this bacterium and is a potential target for new antibacterial agents. This paper describes the structure determination of apo forms of LpxD in space groups P2 1 and P4 3 22. These crystals contained six and three copies of the protein molecule in the asymmetric unit and diffracted to 2.8 and 2.7 Å resolution, respectively. A comparison of the multiple protein copies in the asymmetric units of these crystals reveals a common protein conformation and a conformation in which the relative orientation between the two major domains in the protein is altered

  15. Synthesis and atomic structure determination of Al8V5 gamma-brass

    International Nuclear Information System (INIS)

    Mizutani, Uichiro

    2006-01-01

    Many structurally complex compounds like quasicrystals and their approximants are known to be stabilized at a particular electron per atom ratio e/a, regardless of constituent elements involved. This has been often referred to as the Hume-Rothery electron concentration rule. We consider the understanding of the Hume-Rothery stabilization mechanism to be best deepened by performing both ab initio LMTO-ASA and FLAPW band calculations for the complex compound whose atomic structure is experimentally determined. Admittedly, however, a computing time increases rapidly beyond practical level with increasing the number of atoms in a unit cell. Among various candidates, we chose a series of gamma-brasses containing 52 atoms in a unit cell by taking a full advantage of the facts that it exists in as many as 24 binary alloy systems and that its unit cell is just in size to be handled even in more time-consuming FLAPW method. We have so far studied the stability mechanism of Cu 5 Zn 8 and Cu 9 Al 4 , both being regarded as its prototype, and TM 2 Zn 11 gamma-brasses containing late transition elements TM=Fe, Co, Ni and Pd. In the present work, we chose the gamma-brass consisting of early transition metal element V and trivalent element Al. An almost single phase Al 8 V 5 gamma-brass was ultimately synthesized by overcoming metallurgical difficulties encountered. Its atomic structure was determined by using the Brandon model as a starting structure in the Rietveld structure analysis for powdered diffraction spectra taken at the beam line BL02B2 of 8 GeV synchrotron radiation facility, SPring-8, Japan. The atomic structure suitable for band calculations was then proposed by eliminating quenched-in chemical disorder, i.e., partial mixing of Al and V atoms at given sites with minimum sacrifice. (author)

  16. Synthesis and Structure Determination of Large-Pore Zeolite SCM-14.

    Science.gov (United States)

    Luo, Yi; Smeets, Stef; Peng, Fei; Etman, Ahmed S; Wang, Zhendong; Sun, Junliang; Yang, Weimin

    2017-11-27

    SCM-14 (Sinopec Composite Material No. 14), a new stable germanosilicate zeolite with a 12×8×8-ring channel system, was synthesized using commercially available 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs) in fluoride medium. The framework structure of SCM-14 was determined using rotation electron diffraction (RED), and refined against synchrotron X-ray powder diffraction (SXPD) data for both as-made and calcined materials. The framework structure of SCM-14 is closely related to that of three known zeolites: mordenite (MOR), GUS-1 (GON), and IM-16 (UOS). SCM-14 has the same projection as that of mordenite and GUS-1 when viewed along the 12-ring channels, and possesses two more straight 8-ring channels running perpendicular to the 12-ring channels. The structure of SCM-14 can be constructed by either the same layers as that of GUS-1 or the same columns as that of IM-16. Based on their structural relationship, three topologically reasonable hypothetical zeolites were predicted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Fully convergent chemical synthesis of ester insulin: determination of the high resolution X-ray structure by racemic protein crystallography.

    Science.gov (United States)

    Avital-Shmilovici, Michal; Mandal, Kalyaneswar; Gates, Zachary P; Phillips, Nelson B; Weiss, Michael A; Kent, Stephen B H

    2013-02-27

    Efficient total synthesis of insulin is important to enable the application of medicinal chemistry to the optimization of the properties of this important protein molecule. Recently we described "ester insulin"--a novel form of insulin in which the function of the 35 residue C-peptide of proinsulin is replaced by a single covalent bond--as a key intermediate for the efficient total synthesis of insulin. Here we describe a fully convergent synthetic route to the ester insulin molecule from three unprotected peptide segments of approximately equal size. The synthetic ester insulin polypeptide chain folded much more rapidly than proinsulin, and at physiological pH. Both the D-protein and L-protein enantiomers of monomeric DKP ester insulin (i.e., [Asp(B10), Lys(B28), Pro(B29)]ester insulin) were prepared by total chemical synthesis. The atomic structure of the synthetic ester insulin molecule was determined by racemic protein X-ray crystallography to a resolution of 1.6 Å. Diffraction quality crystals were readily obtained from the racemic mixture of {D-DKP ester insulin + L-DKP ester insulin}, whereas crystals were not obtained from the L-ester insulin alone even after extensive trials. Both the D-protein and L-protein enantiomers of monomeric DKP ester insulin were assayed for receptor binding and in diabetic rats, before and after conversion by saponification to the corresponding DKP insulin enantiomers. L-DKP ester insulin bound weakly to the insulin receptor, while synthetic L-DKP insulin derived from the L-DKP ester insulin intermediate was fully active in binding to the insulin receptor. The D- and L-DKP ester insulins and D-DKP insulin were inactive in lowering blood glucose in diabetic rats, while synthetic L-DKP insulin was fully active in this biological assay. The structural basis of the lack of biological activity of ester insulin is discussed.

  18. Dihydroxycoumarin Schiff base synthesis and structure determination from powder diffraction data

    Czech Academy of Sciences Publication Activity Database

    Rohlíček, Jan; Ketata, I.; Ben Ayed, T.; Ben Hassen, R.

    2013-01-01

    Roč. 1051, NOV (2013), s. 280-284 ISSN 0022-2860 Grant - others:AV ČR(CZ) AP0701 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378271 Keywords : powder diffraction * structure solution * Schiff base * dihydroxycoumarine Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.599, year: 2013

  19. Synthesis and Structure Determination of Di-tert-butyltin (IV) Dithiocarbamate)

    International Nuclear Information System (INIS)

    Amirah Faizah Abdul Muthalib; Ibrahim Baba; Yang Farina Abdul Aziz; Mohd Wahid Samsudin

    2013-01-01

    New diorganotin (IV) dithiocarbamate complexes have been synthesized from di-tert-butyltin (IV) dichloride, N-dialkylamine and carbon disulphide. Elemental and gravimetric analysis confirmed the general formula of these complexes as (t- C 4 H 9 ) 2 Sn[S 2 CNR 1 R 2 ] 2 (R 1 = CH 3 , C 2 H 5 , C 7 H 7 dan R 2 = C 2 H 5 , C 6 H 11 , iC 3 H 7 , CH 3 , C 2 H 5 , C 4 H 9 , C 7 H 7 ). The structures of these complexes have been elucidated on the basis of infrared, ultraviolet, 1 H, 13 C and 119 Sn NMR spectroscopy and X-ray crystallography. The infrared spectra of these complexes showed three main peaks for v(C-N), v(C-S) and v(Sn-S) bands that appeared in the region of 1447-1496, 947-988 and 352-370 cm -1 , respectively. The 13 C NMR spectrum showed the chemical shift for ?(N 13 CS 2 ) in the range of 199.1-201.8 ppm. X-ray single crystal structure (C 4 H 9 ) 2 Sn[S 2 CN(CH 3 )(iC 3 H 7 )] 2 demonstrated a six-coordination geometry around the tin atom adopting a monoclinic system with a space group of P2/n with a = 11.2934(11) Angstrom, b = 7.0175(7) Angstrom, c = 15.6894(15) Angstrom; β = 95.016(1) degree. The (N-benzyl-N-ethyl dithiocarbamato)chloride di-tert-butyltin(IV) and (N,N-dibenzyl dithiocarbamato)chloride-di-(tert-butyl)tin(IV) formed a different geometry with one dithiocarbamate ligand and one chlorine atom attached to the tin centre to form a five-coordinate structure. Crystal of (N-benzyl-N-ethyl dithiocarbamato)chloride di-tert-butyltin(IV) adopts a triclinic system with space group of P1 and cell parameter of a = 8.6140 (2) Angstrom, b = 10.9604 (3) Angstrom, c = 11.4765 (3) Angstrom; α = 91.858 (2) degree, β = 96.193 (2) degree, γ = 96.011 (2) degree, while (N,N-dibenzyl dithiocarbamato)chloride-di-(tert-butyl)tin(IV) adopts a monoclinic system with space group of P2 i with cell parameter a = 9.0600 (2) Angstrom, b = 10.9238 (2) Angstrom, c = 12.7845 (3) Angstrom; β= 102.759 (2) degree. (author)

  20. Synthesis and biosynthesis of 13C, 15N labeled deoxynucleosides useful for biomolecular structural determinations

    International Nuclear Information System (INIS)

    Ashburn, D.A.; Garcia, K.; Hanners, J.L.; Silks, L.A. III; Unkefer, C.J.

    1994-01-01

    Currently, there is a great emphasis on elucidating the structure, function, and dynamics of DNA. Much of the research involved in this study utilizes nuclear magnetic resonance (NMR) spectroscopy. Effective use of NMR spectroscopy (more than 10,000 mw) in this arena requires stable isotope enrichment. Herein, the authors present strategies for the site-specific isotopic labeling of the purine bases adenosine and guanosine and the biosynthesis of [U- 13 C, 15 N] DNA from methylotrophic bacteria. With commercially available 6-chloropurine, an effective 2-step route leads to [6- 15 N]-2'-deoxadenosine (dA). The resulting [6- 15 N]-dA is used in a series of reactions to synthesize [2- 13 C, 1,2'- 15 N 2 ]-2'-deoxyguanosine or any combination thereof. An improved biosynthesis of labeled DNA has been accomplished using Methylobacterium extorquens AS1. Each liter of growth medium contains 4g of methanol to yield 1 gram of lyophilized cells. As much as 200 mg of RNA per liter of culture has been obtained. The authors are currently developing large scale isolation protocols. General synthetic pathways to oligomeric DNA are presented

  1. Synthesis and biosynthesis of 13C-, 15N-labeled deoxynucleosides useful for biomolecular structural determinations

    International Nuclear Information System (INIS)

    Ashburn, D.A.; Garcia, K.; Hanners, J.L.; Silks, L.A. III; Unkefer, C.J.

    1994-01-01

    Currently, there is a great emphasis on elucidating the structure, function, and dynamics of DNA. Much of the research involved in this study uses nuclear magnetic resonance (NMR) spectroscopy. Effective use of NMR spectroscopy for DNA molecules with mw > 10,000 requires stable isotope enrichment. We present strategies for site-specific isotopic labeling of the purine bases adenosine and guanosine and the biosynthesis of (U- 13 C, 15 N) DNA from methylotropic bacteria. With commercially available 6-chloropurine, an effective two-step route leads to 2'-deoxy-(amino- 15 N)adenosine (dA). The resulting d(amino- 15 N)A is used in a series of reactions to synthesize 2'-deoxy-(2- 13 C,1,amino- 15 N 2 )guanosine or any combination thereof. An improved biosynthesis of labeled DNA has been accomplished using Methylobacterium extorquens AS1. Each liter of growth medium contains 4 g of methanol to yield 1 g of lyophilized cells. As much as 200 mg of RNA per liter of culture has been obtained. We are currently developing large-scale isolation protocols. General synthetic pathways to oligomeric DNA will be presented

  2. Synthesis and Structure Determination of a New Au20 Nanocluster Protected by Tripodal Tetraphosphine Ligands

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing [Brown Univ., Providence, RI (United States); Zhang, Qianfan [Brown Univ., Providence, RI (United States); Williard, Paul G. [Brown Univ., Providence, RI (United States); Wang, Lai-Sheng [Brown Univ., Providence, RI (United States)

    2014-03-31

    We report the synthesis and structure determination of a new Au20 nanocluster coordinated by four tripodal tetraphosphine (PP3) ligands {PP3 = tris[2-(diphenylphosphino)ethyl]phosphine}. Single-crystal Xray crystallography and electrospray ionization mass spectrometry show that the cluster assembly can be formulated as [Au20(PP3)4]Cl4. The Au20 cluster consists of an icosahedral Au13 core and a seven-Au-atom partial outer shell arranged in a local C3 symmetry. One PP3 ligand coordinates to four Au atoms in the outer shell, while the other three PP3 ligands coordinate to one Au atom from the outer shell and three Au atoms from the surface of the Au13 core, giving rise to an overall chiral 16-electron Au cluster core with C3 symmetry.

  3. Two-Dimensional Nuclear Magnetic Resonance Structure Determination Module for Introductory Biochemistry: Synthesis and Structural Characterization of Lyso-Glycerophospholipids

    Science.gov (United States)

    Garrett, Teresa A.; Rose, Rebecca L.; Bell, Sidney M.

    2013-01-01

    In this laboratory module, introductory biochemistry students are exposed to two-dimensional [superscript 1]H-nuclear magnetic resonance of glycerophospholipids (GPLs). Working in groups of three, students enzymatically synthesized and purified a variety of 2-acyl lyso GPLs. The structure of the 2-acyl lyso GPL was verified using [superscript…

  4. Proof of the Structure of the Stemodia chilensis Tetracyclic Diterpenoid (+)-19-Acetoxystemodan-12-ol by Synthesis from (+)-Podocarpic Acid: X-ray Structure Determination of a Key Intermediate.

    Science.gov (United States)

    Leonelli, Francesca; Mostarda, Azzurra; De Angelis, Luca; Lamba, Doriano; Demitri, Nicola; La Bella, Angela; Ceccacci, Francesca; Migneco, Luisa M; Marini Bettolo, Rinaldo

    2016-04-22

    The first synthesis of (+)-19-acetoxystemodan-12-ol (1), a stemodane diterpenoid isolated from Stemodia chilensis, is described. The structure was supported by an X-ray crystallographic analysis of intermediate (+)-9a, which confirmed the proposed structure and excluded the structure of (-)-19-hydroxystemod-12-ene as a possible candidate for the Chilean Calceolaria diterpenoid to which the (-)-19-hydroxystemar-13-ene structure (9b) had been erroneously assigned.

  5. Synthesis and chlorination of manganese-columbine by means of a solid-gas reaction. Determination of crystalline structures

    International Nuclear Information System (INIS)

    Gonzales, J.; Ruiz, M. del C.

    1997-01-01

    Full text. The synthesis of mangano-columbite was carried out as follows: Mixing of N B 203 and Mn Cl 2 with an 10% weight excess of the latter in order to compensate for losses due to volatilization; grinding of the mixture in an agate mortar with agate handle in order to achieve close contact between the two solids; calcination of the sample in a quartz crucible at temperatures between 610 and 620 C (fusion temperature for Mn Cl2) in N2 current for six hours. After this time, temperature was increased at a eat of 50 C/h until reaching 800 C. This temperature was maintained for two hours in order to eliminate Mn Cl2 excess; cooling of the obtained product in N2 current. XRD analysis showed that the obtained products is a mangano-columbite. The mineral in natural state presents and orthorhombic structure. The structure of the synthesized product, though corresponding to mangano-columbite according to DRX, should be confirmed by means of an additional technique such as EXAFS. Th mangano-columbite obtained was subsequently chlorinated at 900 deg C for two hours to obtain conversions close to 50%, at 101 kPa, with a chlorine molar fraction of 1 and a flow of 50 cm3/min. By XRD it can be observed that the chlorination residue presents unreacted mangano-columbite and niobium oxide in an unknown phase, whose crystalline structure is currently under study. Measurements to be performed by means Synchrotron Radiation (EXAFS and XANES) might help elucidate this new structure. (author)

  6. Determination of the X-ray structure of the snake venom protein omwaprin by total chemical synthesis and racemic protein crystallography.

    Science.gov (United States)

    Banigan, James R; Mandal, Kalyaneswar; Sawaya, Michael R; Thammavongsa, Vilasak; Hendrickx, Antoni P A; Schneewind, Olaf; Yeates, Todd O; Kent, Stephen B H

    2010-10-01

    The 50-residue snake venom protein L-omwaprin and its enantiomer D-omwaprin were prepared by total chemical synthesis. Radial diffusion assays were performed against Bacillus megaterium and Bacillus anthracis; both L- and D-omwaprin showed antibacterial activity against B. megaterium. The native protein enantiomer, made of L-amino acids, failed to crystallize readily. However, when a racemic mixture containing equal amounts of L- and D-omwaprin was used, diffraction quality crystals were obtained. The racemic protein sample crystallized in the centrosymmetric space group P2(1)/c and its structure was determined at atomic resolution (1.33 A) by a combination of Patterson and direct methods based on the strong scattering from the sulfur atoms in the eight cysteine residues per protein. Racemic crystallography once again proved to be a valuable method for obtaining crystals of recalcitrant proteins and for determining high-resolution X-ray structures by direct methods.

  7. synthesis and structures

    Indian Academy of Sciences (India)

    Priya Saxena

    2017-08-29

    Aug 29, 2017 ... to a single crystal X-ray diffraction study for 1, 2 and 4-7. Keywords. Sterically .... 2.2b Mono-Schiff base 2: A suspension of I (1.00 g,. 2.27 mmol) and ...... bridge Crystallographic Data Centre, CCDC, 12 Union. Road, Cambridge .... H-C 2014 Rational design and synthesis of porous poly- mer networks: ...

  8. Structural synthesis of parallel robots

    CERN Document Server

    Gogu, Grigore

    This book represents the fifth part of a larger work dedicated to the structural synthesis of parallel robots. The originality of this work resides in the fact that it combines new formulae for mobility, connectivity, redundancy and overconstraints with evolutionary morphology in a unified structural synthesis approach that yields interesting and innovative solutions for parallel robotic manipulators.  This is the first book on robotics that presents solutions for coupled, decoupled, uncoupled, fully-isotropic and maximally regular robotic manipulators with Schönflies motions systematically generated by using the structural synthesis approach proposed in Part 1.  Overconstrained non-redundant/overactuated/redundantly actuated solutions with simple/complex limbs are proposed. Many solutions are presented here for the first time in the literature. The author had to make a difficult and challenging choice between protecting these solutions through patents and releasing them directly into the public domain. T...

  9. Mechanism of mechanochemical synthesis of complex oxides and the peculiarities of their nano-structurization determining sintering

    Directory of Open Access Journals (Sweden)

    Zyryanov V.V.

    2005-01-01

    Full Text Available A mechanism of superfast mechanosynthesis reaction for oxide systems is proposed on the base of a dynamics study. The threshold effect and linear dependence of the chemical response on the effective temperature of the reaction zone are established. Major factors are determined: molecular mass of reagents, enthalpy and difference of reagents in Mohs’s hardness, which also influence the composition of the primary product. Primary acts are characterized by a superfast roller mechanism of mass transfer with the formation of a transient dynamic state (D*. Secondary acts slowly approximate the composition of the product to the composition of the starting mixture by diffusion mass transfer in a deformation mixing regime with a contribution of a rotation (roller mechanism. The list of structure types for complex oxides derived by mechanosynthesis includes perovskites, fluorites, pyrochlors, sheelites, and some other ones. Powders of crystal products display multilevel structurization. In all studied complex oxides strong disordering of the “anti-glass” type was observed. The mechanism of sintering was studied in BaTiO3 powders of different origin and in metastable complex oxides derived by mechanosynthesis. The major contribution in shrinkage belongs to rearrangements of crystalline particles as a whole. Structure transformations accompany, as a rule, sintering of inhomogeneous powders derived by mechanosynthesis.

  10. Detonation-synthesis nanodiamonds: synthesis, structure, properties and applications

    Energy Technology Data Exchange (ETDEWEB)

    Dolmatov, Valerii Yu [Federal State Unitary Enterprise Special Design-Technology Bureau (FSUE SDTB) ' ' Tekhnolog' ' at the St Petersburg State Institute of Technology (Technical University) (Russian Federation)

    2007-04-30

    The review outlines the theoretical foundations and industrial implementations of modern detonation synthesis of nanodiamonds and chemical purification of the nanodiamonds thus obtained. The structure, key properties and promising fields of application of detonation-synthesis nanodiamonds are considered.

  11. Detonation-synthesis nanodiamonds: synthesis, structure, properties and applications

    International Nuclear Information System (INIS)

    Dolmatov, Valerii Yu

    2007-01-01

    The review outlines the theoretical foundations and industrial implementations of modern detonation synthesis of nanodiamonds and chemical purification of the nanodiamonds thus obtained. The structure, key properties and promising fields of application of detonation-synthesis nanodiamonds are considered.

  12. Combining Sustainable Synthesis of a Versatile Ruthenium Dihydride Complex with Structure Determination Using Group Theory and Spectroscopy

    Science.gov (United States)

    Armstrong, Christopher; Burnham, Jennifer A. J.; Warminski, Edward E.

    2017-01-01

    A good-yielding two-step synthesis of RuH[subscript 2](CO)(PPh[subscript 3])[subscript 3] using conventional or microwave-assisted reflux techniques is described for use in undergraduate teaching laboratories. RuH[subscript 2](CO)(PPh[subscript 3])[subscript 3] is synthesized from RuCl[subscript 3]·xH[subscript 2]O, PPh[subscript 3], and KOH in…

  13. Synthesis for Structure Rewriting Systems

    Science.gov (United States)

    Kaiser, Łukasz

    The description of a single state of a modelled system is often complex in practice, but few procedures for synthesis address this problem in depth. We study systems in which a state is described by an arbitrary finite structure, and changes of the state are represented by structure rewriting rules, a generalisation of term and graph rewriting. Both the environment and the controller are allowed to change the structure in this way, and the question we ask is how a strategy for the controller that ensures a given property can be synthesised.

  14. Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

    Directory of Open Access Journals (Sweden)

    James C. Anderson

    2013-08-01

    Full Text Available Piperazirum, isolated from Arum palaestinum Boiss, was originally assigned as r-3,c-5-diisobutyl-c-6-isopropylpiperazin-2-one. The reported structure was synthesised diastereoselectively using a key nitro-Mannich reaction to set up the C5/C6 relative stereochemistry. The structure was unambiguously assigned by single crystal X-ray diffraction but the spectroscopic data did not match those reported for the natural product. The structure of the natural product must therefore be revised.

  15. Structural determinants of HIV-1 nucleocapsid protein for cTAR DNA binding and destabilization, and correlation with inhibition of self-primed DNA synthesis.

    Science.gov (United States)

    Beltz, Hervé; Clauss, Céline; Piémont, Etienne; Ficheux, Damien; Gorelick, Robert J; Roques, Bernard; Gabus, Caroline; Darlix, Jean-Luc; de Rocquigny, Hugues; Mély, Yves

    2005-05-20

    The nucleocapsid protein (NC) of human immunodeficiency virus type 1 (HIV-1) is formed of two highly conserved CCHC zinc fingers flanked by small basic domains. NC is required for the two obligatory strand transfers in viral DNA synthesis through its nucleic acid chaperoning properties. The first DNA strand transfer relies on NC's ability to bind and destabilize the secondary structure of complementary transactivation response region (cTAR) DNA, to inhibit self-priming, and to promote the annealing of cTAR to TAR RNA. To further investigate NC chaperone properties, our aim was to identify by fluorescence spectroscopy and gel electrophoresis, the NC structural determinants for cTAR binding and destabilization, and for the inhibition of self-primed DNA synthesis on a model system using a series of NC mutants and HIV-1 reverse transcriptase. NC destabilization and self-priming inhibition properties were found to be supported by the two fingers in their proper context and the basic (29)RAPRKKG(35) linker. The strict requirement of the native proximal finger suggests that its hydrophobic platform (Val13, Phe16, Thr24 and Ala25) is crucial for binding, destabilization and inhibition of self-priming. In contrast, only partial folding of the distal finger is required, probably for presenting the Trp37 residue in an appropriate orientation. Also, Trp37 and the hydrophobic residues of the proximal finger appear to be essential for the propagation of the melting from the cTAR ends up to the middle of the stem. Finally, both N-terminal and C-terminal basic domains contribute to cTAR binding but not to its destabilization.

  16. Synthesis by two methods and crystal structure determination of a new pyrochlore-related compound Sm{sub 2}FeTaO{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Martinez, Leticia M., E-mail: lettorresg@yahoo.com [Departamento de Ecomateriales y Energia, Facultad de Ingenieria Civil, Universidad Autonoma de Nuevo Leon, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Ruiz-Gomez, Miguel A. [Departamento de Ecomateriales y Energia, Facultad de Ingenieria Civil, Universidad Autonoma de Nuevo Leon, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, Av. Manuel Nava 6, San Luis Potosi, S.L.P. 78290 (Mexico); Figueroa-Torres, M.Z.; Juarez-Ramirez, Isaias [Departamento de Ecomateriales y Energia, Facultad de Ingenieria Civil, Universidad Autonoma de Nuevo Leon, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Moctezuma, Edgar [Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, Av. Manuel Nava 6, San Luis Potosi, S.L.P. 78290 (Mexico); and others

    2012-04-16

    Graphical abstract: The monoclinic (space group C2/c) structure of a new compound, Sm{sub 2}FeTaO{sub 7} shows an alternating Sm-O and Fe/Ta-O layers. In the Fe/Ta-O layer, Fe/Ta1 and Fe/Ta3 cations are coordinated by six oxygen atoms, forming irregular octahedral interconnected into a hexagonal tungsten bronze (HTB) type network. The HTB layer is a fundamental framework in the pyrohlore-related structure. Highlights: Black-Right-Pointing-Pointer Pyrochlore-related compound Sm{sub 2}FeTaO{sub 7} prepared by solid state reaction and sol-gel. Black-Right-Pointing-Pointer Sm{sub 2}FeTaO{sub 7} crystallizes with a monoclinic crystal structure and space group C2/c. Black-Right-Pointing-Pointer The compound is synthesized by sol-gel at lower temperature and time than solid state. Black-Right-Pointing-Pointer Surface area of sol-gel Sm{sub 2}FeTaO{sub 7} is 10 times higher than that prepared by solid state. - Abstract: This paper reports on the synthesis of a new pyrochlore-related compound Sm{sub 2}FeTaO{sub 7} by both solid state reaction and sol-gel synthesis routes. Structural features were determined by X-ray powder diffraction and Rietveld refinement and were corroborated using Transmission Electron Microscopy (TEM). The results revealed that Sm{sub 2}FeTaO{sub 7} crystallized in the monoclinic system with space group C2/c and the following cell parameters: a = 13.1307(5) Angstrom-Sign , b = 7.5854(3) Angstrom-Sign , c = 11.6425(4) Angstrom-Sign and {beta} = 100.971(2) Degree-Sign . The monoclinic structure of Sm{sub 2}FeTaO{sub 7} showed an arrangement of alternating Sm-O and Fe/Ta-O layers and two types of irregular octahedra of Fe/Ta-O, which are interconnected into a hexagonal tungsten bronze (HTB)-type network. On the other hand, Sm{sub 2}FeTaO{sub 7} prepared by sol-gel was obtained with lower particle sizes than the solid state produced compound. The difference in particle size causes a difference of one order of magnitude in the specific surface area. In

  17. Synthesis and structural characterization of lithium

    Indian Academy of Sciences (India)

    synthesis and characterization of two new iminophos- phonamine ligands ... structures. 2.3 General synthetic method for ligands (1 and 2) ... 2.3b General method for the Synthesis of ligands ...... studies are currently underway in our laboratory.

  18. Zinc(II) halide complexes with 2-methoxyaniline ligand: Synthesis, characterization, thermal analyses, crystal structure determination and luminescent properties

    Science.gov (United States)

    Amani, Vahid

    2018-03-01

    Three new mononuclear zinc(II) complexes, [Zn(2-MeO-C6H4NH2)2X2] (X is Cl in 1, Br in 2 and I in 3), were prepared from the reactions of ZnX2 with 2-methoxyaniline (2-MeO-C6H4NH2) ligand in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurements by slow evaporation of methanol solution at room temperature. The three complexes were thoroughly characterized by thermogravimetric analysis, elemental analysis (CHNO), spectral methods (IR, UV-Vis, 13C{1H}NMR, 1H NMR and luminescence), and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the zinc(II) cation is four-coordinated in a distorted tetrahedral configuration by two N atoms from two 2-methoxyanyline ligands and two halide anions. Also, in these complexes intermolecular interactions, for example Nsbnd H⋯X hydrogen bonds (in 1-3), Csbnd H⋯X hydrogen bonds (in 3), Csbnd H⋯π interactions (in 1 and 2) and π⋯π interactions (in 3), are effective in the stabilization of the crystal structures. In addition, the luminescence spectra of all complexes in methanolic solution show that the intensity of their emission bands is stronger than that for free 2-methoxyaniline ligand.

  19. Component mode synthesis in structural dynamics

    International Nuclear Information System (INIS)

    Reddy, G.R.; Vaze, K.K.; Kushwaha, H.S.

    1993-01-01

    In seismic analysis of Nuclear Reactor Structures and equipments eigen solution requires large computer time. Component mode synthesis is an efficient technique with which one can evaluate dynamic characteristics of a large structure with minimum computer time. Due to this reason it is possible to do a coupled analysis of structure and equipment which takes into account the interaction effects. Basically in this the method large size structure is divided into small substructures and dynamic characteristics of individual substructure are determined. The dynamic characteristics of entire structure are evaluated by synthesising the individual substructure characteristics. Component mode synthesis has been applied in this paper to the analysis of a tall heavy water upgrading tower. Use of fixed interface normal modes, constrained modes, attachment modes in the component mode synthesis using energy principle and using Ritz vectors have been discussed. The validity of this method is established by solving fixed-fixed beam and comparing the results obtained by conventional and classical method. The eigen value problem has been solved using simultaneous iteration method. (author)

  20. Mononuclear mercury(II) complexes containing bipyridine derivatives and thiocyanate ligands: Synthesis, characterization, crystal structure determination, and luminescent properties

    Science.gov (United States)

    Amani, Vahid; Alizadeh, Robabeh; Alavije, Hanieh Soleimani; Heydari, Samira Fadaei; Abafat, Marzieh

    2017-08-01

    A series of mercury(II) complexes, [Hg(Nsbnd N)(SCN)2] (Nsbnd N is 4,4‧-dimethyl-2,2‧-bipyridine in 1, 5,5‧-dimethyl-2,2‧-bipyridine in 2, 6,6‧-dimethyl-2,2‧-bipyridine in 3 and 6-methyl-2,2‧-bipyridine in 4), were prepared from the reactions of Hg(SCN)2 with mentioned ligands in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurement by methanol diffusion into a DMSO solution. The four complexes were thoroughly characterized by spectral methods (IR, UV-Vis, 13C{1H}NMR, 1H NMR and luminescence), elemental analysis (CHNS) and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the mercury(II) cation is four-coordinated in a distorted tetrahedral configuration by two S atoms from two thiocyanate anions and two N atoms from one chelating 2,2‧-bipyridine derivative ligand. Also, in these complexes intermolecular interactions, for example Csbnd H⋯N hydrogen bonds (in 1-4), Csbnd H⋯S hydrogen bonds (in 1, 2 and 4), π … π interactions (in 2-4), Hg⋯N interactions (in 2) and S⋯S interactions (in 4), are effective in the stabilization of the crystal structures and the formation of the 3D supramolecular complexes. Furthermore, the luminescence spectra of the title complexes show that the intensity of their emission bands are stronger than the emission bands for the free bipyridine derivative ligands.

  1. Synthesis and biosynthesis of {sup 13}C-, {sup 15}N-labeled deoxynucleosides useful for biomolecular structural determinations

    Energy Technology Data Exchange (ETDEWEB)

    Ashburn, D.A.; Garcia, K.; Hanners, J.L.; Silks, L.A. III; Unkefer, C.J. [Los Alamos National Laboratory, NM (United States)

    1994-12-01

    Currently, there is a great emphasis on elucidating the structure, function, and dynamics of DNA. Much of the research involved in this study uses nuclear magnetic resonance (NMR) spectroscopy. Effective use of NMR spectroscopy for DNA molecules with mw > 10,000 requires stable isotope enrichment. We present strategies for site-specific isotopic labeling of the purine bases adenosine and guanosine and the biosynthesis of (U-{sup 13}C, {sup 15}N) DNA from methylotropic bacteria. With commercially available 6-chloropurine, an effective two-step route leads to 2{prime}-deoxy-(amino-{sup 15}N)adenosine (dA). The resulting d(amino-{sup 15}N)A is used in a series of reactions to synthesize 2{prime}-deoxy-(2-{sup 13}C,1,amino-{sup 15}N{sub 2})guanosine or any combination thereof. An improved biosynthesis of labeled DNA has been accomplished using Methylobacterium extorquens AS1. Each liter of growth medium contains 4 g of methanol to yield 1 g of lyophilized cells. As much as 200 mg of RNA per liter of culture has been obtained. We are currently developing large-scale isolation protocols. General synthetic pathways to oligomeric DNA will be presented.

  2. Synthesis, crystal structure determination and antiproliferative activity of novel 2-amino-4-aryl-4,10-dihydro[1,3,5]triazino[1,2- a]benzimidazoles

    Science.gov (United States)

    Hranjec, Marijana; Pavlović, Gordana; Karminski-Zamola, Grace

    2012-01-01

    This manuscript describes the synthesis of novel 2-amino-4-aryl-4,10-dihydro-[1,3,5]triazino[1,2- a]benzimidazoles as hydrochloride salts 4a-n and 5b which were prepared in the reaction of cyclocondensation between 2-guanidinobenzimidazole and versatile heteroaromatic aldehydes. Structures of all prepared compounds have been studied by using 1H and 13C NMR, IR and UV/Vis spectroscopy. The crystal and molecular structure of 4f was determined by X-ray diffraction on single crystals. The molecule of 2-amino-4-(4'-methylphenyl)-4,10-dihydro[1,3,5]triazino[1,2- a]benzimidazole hydrochloride 4f (C 16H 16N 5+·Cl -) exists in the solid state in one of the possible tautomeric forms, being protonated at the one of the nitrogen atoms of the 1,4-dihydrotriazine ring. The molecule is highly delocalized within the 4,10-dihydro[1,3,5]triazino[1,2- a]benzimidazole moiety with the highest deviation from the plane for the methine carbon atom and the protonated nitrogen atom of the 1,4-dihydrotriazine ring. The cations are joined via N-H⋯N hydrogen bonds into R22(8) centrosymmetric dimers. Cation dimers are further connected with Cl - ions via N-H⋯Cl and C-H⋯Cl hydrogen bonds into 2D chains spreading along the b axis. The obtained single-crystal X-ray structure determination unequivocally confirms tautomeric form of the compound present in the solid-state and can represent tantative pattern for other prepared compounds. All prepared compounds were tested on their antiproliferative activity in vitro on several human cancer cell lines. Compound 4m was the most active one (IC 50 ≈ 20 μM), while compounds 4d, 4f, 4k, 4l4m showed moderate, but non-selective, antiproliferative activity with IC 50 25-60 μM.

  3. Determinants of capital structure.

    Science.gov (United States)

    McCue, M J; Ozcan, Y A

    1992-01-01

    This study analyzes the determinants of hospital capital structure in a new market setting that are created by the financial pressures of prospective payment and the intense price competition among hospitals. Using California data, the study found hospital system affiliation, bed size, growth rate in revenues, operating risk, and asset structure affected both short- and long-term debt borrowings. In addition, percentage of uncompensated care, profitability, and payer mix influenced short-term borrowings while market conditions and ownership affected long-term borrowings. Most significant of all is the finding that smaller hospitals tend to borrow more, possibly because they cannot generate funds internally.

  4. Synthesis, radiometric determination of functional groups, complexation

    International Nuclear Information System (INIS)

    Pompe, S.; Bubner, M.; Schmeide, K.; Heise, K.H.; Bernhard, G.; Nitsche, H.

    2000-01-01

    The interaction behavior of humic acids with uranium(VI) and the influence of humic substances on the migration behavior of uranium was investigated. A main focus of this work was the synthesis of four different humic acid model substances and their characterization and comparison to the natural humic acid from Aldrich. A radiometric method for the determination of humic acid functional groups was applied in addition to conventional methods for the determination of the functionality of humic acids. The humic acid model substances show functional and structural properties comparable to natural humic acids. Modified humic acids with blocked phenolic OH were synthesized to determine the influence of phenolic OH groups on the complexation behavior of humic acids. A synthesis method for 14 C-labeled humic acids with high specific activity was developed. The complexation behavior of synthetic and natural humic acids with uranium(VI) was investigated by X-ray absorption spectroscopy, laser-induced fluorescence spectroscopy and FTIR spectroscopy. The synthetic model substances show an interaction behavior with uranium(VI) that is comparable to natural humic acids. This points to the fact that the synthetic humic acids simulate the functionality of their natural analogues very well. For the first time the influence of phenolic OH groups on the complexation behavior of humic acids was investigated by applying a modified humic acid with blocked phenolic OH groups. The formation of a uranyl hydroxy humate complex was identified by laserspectroscopic investigations of the complexation of Aldrich humic acid with uranium(VI) at pH 7. The migration behavior of uranium in a sandy aquifer system rich is humic substances was investigated in column experiments. A part of uranium migrates non-retarded through the sediment, bound to humic colloids. The uranium migration behavior is strongly influenced by the kinetically controlled interaction processes of uranium with the humic colloids

  5. Synthesis and structure determination of the novel aluminophosphate TL-1: A new layered compound with corner-sharing AlX{sub 6} chains

    Energy Technology Data Exchange (ETDEWEB)

    Pastero, Linda [Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, I-10125 Torino (Italy); Interdepartmental Centre “Nanostructured Interfaces and Surfaces-NIS”, Via Quarello 15A, 10135 Torino (Italy); CrisDi – Interdepartmental Center for Crystallography, Università di Torino, Via Pietro Giuria 7, I-10125 Torino (Italy); Arletti, Rossella, E-mail: rossella.arletti@unito.it [Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, I-10125 Torino (Italy); Interdepartmental Centre “Nanostructured Interfaces and Surfaces-NIS”, Via Quarello 15A, 10135 Torino (Italy); CrisDi – Interdepartmental Center for Crystallography, Università di Torino, Via Pietro Giuria 7, I-10125 Torino (Italy); Cámara, Fernando [Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, I-10125 Torino (Italy); Interdepartmental Centre “Nanostructured Interfaces and Surfaces-NIS”, Via Quarello 15A, 10135 Torino (Italy); CrisDi – Interdepartmental Center for Crystallography, Università di Torino, Via Pietro Giuria 7, I-10125 Torino (Italy); Gigli, Lara [Dipartimento di Scienze della Terra, Università di Torino, Via Valperga Caluso 35, I-10125 Torino (Italy); Interdepartmental Centre “Nanostructured Interfaces and Surfaces-NIS”, Via Quarello 15A, 10135 Torino (Italy); Cagnoni, Monica [Dipartimento di Chimica, Università di Torino, Via Pietro Giuria 7, I-10125 Torino (Italy)

    2016-10-15

    A novel layered aluminophosphate (TL-1) has been synthesized. Crystals grow as pseudo-hexagonal thin platelets and their whole morphology depends on the synthesis conditions. The structure was solved by single-crystal X-ray diffraction using charge flipping methods. The synthesized layered material, with composition [AlPO{sub 4}F(H{sub 2}O)]-(H{sub 10}C{sub 4}ON){sub 4}, crystallizes in the monoclinic space group P2{sub 1}/a with a=9.2282(5) Å, b=6.9152(4) Å, c=14.4615(9) Å, β=101.57(1)°. The novel compound has corner sharing AlO{sub 3}F{sub 2}(H{sub 2}O) octahedral chains running along [010], where fluorine atoms are at the shared apices, three oxygen atoms are shared with PO{sub 4} tetrahedra while the sixth oxygen pertain to an H{sub 2}O molecule. The stability field of the novel material is enclosed in the HF/Al{sub 2}O{sub 3} ratio ranging between 1 and 4 and the HF/morpholine ratio lower than 3. At temperature lower than 190 °C, the synthesis results is a pure aluminophosphate sample (low alumina/morpholine ratio). A treatment with H{sub 2}CO{sub 3} leads to a complete morpholine removal, as shown by in situ Raman spectroscopy. Powder X-ray diffraction reveals that, after morpholine extraction, the material collapses. The collapse is irreversible. - Highlights: • A new layered aluminophosphate was obtained and characterized. • The crystal structure is a sequence of aluminophosphate and organic layers. • The stability field of the new phase was defined by changing chemistry and T. • The templating agent can be removed by using a CO{sub 2} aqueous solution. • The decomposition of the morpholine induce a collapse in the structure.

  6. SYNTHESIS, CRYSTAL STRUCTURE AND MAGNETIC ...

    African Journals Online (AJOL)

    Preferred Customer

    Much of the current effort on such extended hybrid metal organic complexes is ... In this paper, we report the synthesis, single crystal X-ray diffraction analysis and ..... with g = 2.0 (0.37 cm3 mol−1 K), and smoothly increases to a value of 0.45 ...

  7. SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURES ...

    African Journals Online (AJOL)

    B. S. Chandravanshi

    ABSTRACT. Reaction of [VO(acac)2] (acac = acetylacetonate) with ... Single crystal X-ray structural studies indicate that the hydrazone ligands coordinate to ..... Molecular structure of complex (1) at 30% probability displacement. Figure 4.

  8. SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURE ...

    African Journals Online (AJOL)

    Preferred Customer

    Reaction of [MoO2(acac)2] (where acac = acetylacetonate) with N'-(2-hydroxy-4- ... Single crystal X-ray structural studies indicate that the hydrazone ligand coordinates .... Molecular structure of the complex at 30% probability displacement.

  9. Structured synthesis of MEMS using evolutionary approaches

    DEFF Research Database (Denmark)

    Fan, Zhun; Wang, Jiachuan; Achiche, Sofiane

    2008-01-01

    In this paper, we discuss the hierarchy that is involved in a typical MEMS design and how evolutionary approaches can be used to automate the hierarchical synthesis process for MEMS. The paper first introduces the flow of a structured MEMS design process and emphasizes that system-level lumped...

  10. SYNTHESIS, CHARACTERIZATION, AND CRYSTAL STRUCTURE ...

    African Journals Online (AJOL)

    a

    KEY WORDS: Barium, Crystal structure, 2,6-Pyridinedicarboxylic acid .... The rational design of novel metal-organic frameworks has attracted great ..... Bond, A.D.; Jones, W. Supramolecular Organization and Materials Design, Jones, W.; Rao,.

  11. Determinants of Glycosaminoglycan (GAG Structure

    Directory of Open Access Journals (Sweden)

    Kristian Prydz

    2015-08-01

    Full Text Available Proteoglycans (PGs are glycosylated proteins of biological importance at cell surfaces, in the extracellular matrix, and in the circulation. PGs are produced and modified by glycosaminoglycan (GAG chains in the secretory pathway of animal cells. The most common GAG attachment site is a serine residue followed by a glycine (-ser-gly-, from which a linker tetrasaccharide extends and may continue as a heparan sulfate, a heparin, a chondroitin sulfate, or a dermatan sulfate GAG chain. Which type of GAG chain becomes attached to the linker tetrasaccharide is influenced by the structure of the protein core, modifications occurring to the linker tetrasaccharide itself, and the biochemical environment of the Golgi apparatus, where GAG polymerization and modification by sulfation and epimerization take place. The same cell type may produce different GAG chains that vary, depending on the extent of epimerization and sulfation. However, it is not known to what extent these differences are caused by compartmental segregation of protein cores en route through the secretory pathway or by differential recruitment of modifying enzymes during synthesis of different PGs. The topic of this review is how different aspects of protein structure, cellular biochemistry, and compartmentalization may influence GAG synthesis.

  12. Synthesis, structural and electrical characterizations of thermally ...

    African Journals Online (AJOL)

    Synthesis, structural and electrical characterizations of thermally evaporated Cu 2 SnS 3 thin films. ... The surface profilometer shows that the deposited films are rough. The XRD spectra identified the ... The electrical resistivity of the deposited Cu2SnS3 film is 2.55 x 10-3 Ωcm. The conductivity is in the order of 103 Ω-1cm-1.

  13. Synthesis and structure determination of a stable organometallic uranium(V) imine complex and its isolobal anionic U(IV)-ate complex

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, M.; Botoshanskii, M.; Eisen, M.S. [Schulich Faculty of Chemistry, and Institute of Catalysis Science and Technology, Technion Israel Institute of Technology, Haifa (Israel); Bannenberg, Th.; Tamm, M. [Institut fur Anorganische und Analytische Chemie, Technische Universitat Braunschweig (Germany)

    2010-06-15

    The reaction of one equivalent of Cp*{sub 2}UCl{sub 2} with 2-(trimethylsilyl-imino)-1,3-di-tert-butyl-imidazoline in boiling toluene afforded a one electron oxidation of the uranium metal and the opening of the N-heterocyclic ring, resulting in the formation of an organometallic uranium(V) imine complex. This complex crystallized with one molecule of toluene in the unit cell, and its solid-state structure was determined by X-ray diffraction analysis. When the same reaction was performed in perdeuterated toluene, a myriad of organometallic complexes were obtained, however, when equimolar amounts of water were used in toluene, the same complex was obtained, and its solid state characterization shows two independent molecules in the unit cell with an additional water molecule. For comparison of the geometric parameters, the corresponding isolobal anionic uranium(IV) complex [Cp*{sub 2}UCl{sub 3}]{sup -} was synthesized by the reaction of Cp*{sub 2}UCl{sub 2} with 1,3-di-tert-butyl-imidazolium chloride, and the resulting U(IV)-ate complex was characterized by X-ray diffraction analysis. (authors)

  14. Catalytic NH3 Synthesis using N2 /H2 at Molecular Transition Metal Complexes: Concepts for Lead Structure Determination using Computational Chemistry.

    Science.gov (United States)

    Hölscher, Markus; Leitner, Walter

    2017-09-07

    While industrial NH 3 synthesis based on the Haber-Bosch-process was invented more than a century ago, there is still no molecular catalyst available which reduces N 2 in the reaction system N 2 /H 2 to NH 3 . As the many efforts of experimentally working research groups to develop a molecular catalyst for NH 3 synthesis from N 2 /H 2 have led to a variety of stoichiometric reductions it seems justified to undertake the attempt of systematizing the various approaches of how the N 2 molecule might be reduced to NH 3 with H 2 at a transition metal complex. In this contribution therefore a variety of intuition-based concepts are presented with the intention to show how the problem can be approached. While no claim for completeness is made, these concepts intend to generate a working plan for future research. Beyond this, it is suggested that these concepts should be evaluated with regard to experimental feasibility by checking barrier heights of single reaction steps and also by computation of whole catalytic cycles employing density functional theory (DFT) calculations. This serves as a tool which extends the empirically driven search process and expands it by computed insights which can be used to rationalize the various challenges which must be met. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Marine Nucleosides: Structure, Bioactivity, Synthesis and Biosynthesis

    Directory of Open Access Journals (Sweden)

    Ri-Ming Huang

    2014-12-01

    Full Text Available Nucleosides are glycosylamines that structurally form part of nucleotide molecules, the building block of DNA and RNA. Both nucleosides and nucleotides are vital components of all living cells and involved in several key biological processes. Some of these nucleosides have been obtained from a variety of marine resources. Because of the biological importance of these compounds, this review covers 68 marine originated nucleosides and their synthetic analogs published up to June 2014. The review will focus on the structures, bioactivities, synthesis and biosynthetic processes of these compounds.

  16. Crystal structure determination of Efavirenz

    International Nuclear Information System (INIS)

    Popeneciu, Horea; Dumitru, Ristoiu; Tripon, Carmen; Borodi, Gheorghe; Pop, Mihaela Maria

    2015-01-01

    Needle-shaped single crystals of the title compound, C 14 H 9 ClF 3 NO 2 , were obtained from a co-crystallization experiment of Efavirenz with maleic acid in a (1:1) ratio, using methanol as solvent. Crystal structure determination at room temperature revealed a significant anisotropy of the lattice expansion compared to the previously reported low-temperature structure. In both low- and room temperature structures the cyclopropylethynyl fragment in one of the asymmetric unit molecules is disordered. While at low-temperature only one C atom exhibits positional disorder, at room temperature the disorder is present for two C atoms of the cyclopropane ring

  17. Structural determination of organic compounds

    International Nuclear Information System (INIS)

    Kintzinger, J.P.

    1991-01-01

    This paper reports that the current methods available in high-field NMR spectroscopy are such that the tridimensional structure determination of any rigid molecule containing only carbon and hydrogen atoms may be achieved. The connectivities between carbon-carbon, carbon-hydrogen, and hydrogen-hydrogen atoms are determined by multipulse and two-dimensional (2D) experiments. These connectivity patterns or maps allow a step-by-step reconstruction of the molecular structures. From the carbon-carbon connectivity map, the carbon framework of the molecule is obtained, whereas the carbon-hydrogen pattern allows determination of the positions of the hydrogen atoms on their corresponding carbon atoms. High-field spectrometers are then necessary to remove fortuitous degeneracy and to reduce the proton spectra to a nearly first-order one, allowing an easy measurement of the chemical shifts and the coupling constants

  18. Structure, bioactivity, and synthesis of methylated flavonoids.

    Science.gov (United States)

    Wen, Lingrong; Jiang, Yueming; Yang, Jiali; Zhao, Yupeng; Tian, Miaomiao; Yang, Bao

    2017-06-01

    Methylated flavonoids are an important type of natural flavonoid derivative with potentially multiple health benefits; among other things, they have improved bioavailability compared with flavonoid precursors. Flavonoids have been documented to have broad bioactivities, such as anticancer, immunomodulation, and antioxidant activities, that can be elevated, to a certain extent, by methylation. Understanding the structure, bioactivity, and bioavailability of methylated flavonoids, therefore, is an interesting topic with broad potential applications. Though methylated flavonoids are widely present in plants, their levels are usually low. Because developing efficient techniques to produce these chemicals would likely be beneficial, we provide an overview of their chemical and biological synthesis. © 2017 New York Academy of Sciences.

  19. Synthesis of Structures Related to Antifreeze Glycoproteins

    OpenAIRE

    Fyrner, Timmy

    2005-01-01

    In this thesis, synthesis of structures related to antifreeze glycoproteins (AFGPs) are presented. Synthetic routes to a protected carbohydrate derivative, 2,3,4,6-tetra-O-benzyl-β-galactopyranosyl-(1→3)-2-deoxy-2-azido-4,6-di-O-benzyl-β-D-thio-1-galactopyranoside, and a tBu-Ala-Thr-Ala-Fmoc tripeptide, are described. These compounds are meant to be used in the assembly of AFGPs and analogues thereof. A Gal-GlcN disaccharide was synthesized via glycosylation between the donor, bromo-2-O-benzo...

  20. A new oxidovanadium(IV) Schiff base complex containing asymmetric tetradentate ONN′O′ Schiff base ligand: synthesis, characterization, crystal structure determination, thermal study and catalytic activity

    Czech Academy of Sciences Publication Activity Database

    Grivani, G.; Ghavami, A.; Eigner, Václav; Dušek, Michal; Khalaji, A.D.

    2015-01-01

    Roč. 26, č. 6 (2015), s. 779-784 ISSN 1001-8417 R&D Projects: GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : oxidovanadium(IV) * Schiff base * crystal structure * nanoparticle * epoxidation Subject RIV: CC - Organic Chemistry Impact factor: 1.947, year: 2015

  1. Synthesis and X-ray crystal structure determination of N-p-methylphenyl-4-benzoyl-3,4-diphenyl-2-azetidinone

    Czech Academy of Sciences Publication Activity Database

    Kabak, M.; Senöz, H.; Elmali, A.; Adar, V.; Svoboda, I.; Dušek, Michal; Fejfarová, Karla

    2010-01-01

    Roč. 55, č. 7 (2010), s. 1220-1222 ISSN 1063-7745 Institutional research plan: CEZ:AV0Z10100521 Keywords : molecular structure * carbon * azetidione Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.644, year: 2010

  2. In vivo determination of arterial collagen synthesis in atherosclerotic rabbits

    International Nuclear Information System (INIS)

    Opsahl, W.P.; DeLuca, D.J.; Ehrhart, L.A.

    1986-01-01

    Collagen and non-collagen protein synthesis rates were determined in vivo in tissues from rabbits fed a control or atherogenic diet supplemented with 2% peanut oil and 0.25% cholesterol for 4 months. Rabbits received a bolus intravenous injection of L-[ 3 H]-proline (1.0 mCi/kg) and unlabeled L-proline (7 mmoles/kg) in 0.9% NaCl. Plasma proline specific activity decreased only 20% over 5 hr and was similar to the specific activity of free proline in tissues. Thoracic aortas from atherosclerotic rabbits exhibited raised plaques covering at least 75% of the surface. Thoracic intima plus a portion of the media (TIM) was separated from the remaining media plus adventitia (TMA). Dry delipidated weight, total collagen content, and collagen as a percent of dry weight were increased significantly in the TIM of atherosclerotic rabbits. Collagen synthesis rates and collagen synthesis as a percent of total protein synthesis were likewise increased both in the TIM and in the abdominal aortas. No differences from controls either in collagen content or collagen synthesis rates were observed in the TMA, lung or skin. These results demonstrate for the first time in vivo that formation of atherosclerotic plaques is associated with increased rates of collagen synthesis. Furthermore, as previously observed with incubations in vitro, collagen synthesis was elevated to a greater extent than noncollagen protein synthesis in atherosclerotic aortas from rabbits fed cholesterol plus peanut oil

  3. Synthesis of lever-blade dampers with enhanced mechanical structure

    Directory of Open Access Journals (Sweden)

    Igor I. Sydorenko

    2015-03-01

    Full Text Available Since the torsion bar represents just an elastic element, the energy dissipation in suspensions problem is highly relevant for its application. Currently in quality of a dissipation device in torsion suspension are used the hydraulic dampers with movable members reciprocating translational motion respectively to the housing or lever-type hydraulic shock absorbers of piston and vane types, with the movable member’s rotational movement respectively to the housing. These dampers are implementing only throttle-valve performance type, associated with these devices’ functional capacities and depending on design constraints. The paper presents a synthesis of innovative lever-blade dampers, whose performance is not related to the value of working chambers inner pressure. Their essential peculiarity relates to the mechanical control loop presence in the structure that determines a close relationship between the performance and the value of the shock absorber movable element displacement relatively to the body. In the process of synthesis carried out tested are the appropriate methods, built on the basis of technical systems’ modeling with modified kinematic graphs. The synthesis results are shown in the form of two structurally implemented samples. Performed is a comparative analysis of the samples with their basic performance determining.

  4. Wall grid structure for interior scene synthesis

    KAUST Repository

    Xu, Wenzhuo

    2015-02-01

    We present a system for automatically synthesizing a diverse set of semantically valid, and well-arranged 3D interior scenes for a given empty room shape. Unlike existing work on layout synthesis, that typically knows potentially needed 3D models and optimizes their location through cost functions, our technique performs the retrieval and placement of 3D models by discovering the relationships between the room space and the models\\' categories. This is enabled by a new analytical structure, called Wall Grid Structure, which jointly considers the categories and locations of 3D models. Our technique greatly reduces the amount of user intervention and provides users with suggestions and inspirations. We demonstrate the applicability of our approach on three types of scenarios: conference rooms, living rooms and bedrooms.

  5. Superheavy Element Synthesis and Nuclear Structure

    International Nuclear Information System (INIS)

    Ackermann, D.

    2009-01-01

    The search for the next closed proton and neutron shells beyond 2 08P b has yielded a number of exciting results in terms of the synthesis of new elements [1,2,3]. The superheavy elements (SHE), however, are a nuclear structure phenomenon. They owe their existence to the quantum mechanical origin of shell correction energies without which they would not be bound. In recent years the development of efficient experimental set-ups including separators and advanced particle and photon detection arrangements allowed for more and more detailed nuclear structure studies for nuclei at and beyond Z=100. A review of those recent achievements is given in ref. [4]. Among the most interesting features is the observation of K-isomeric states. Experimentally about 14 cases have been identified in the region of Z>96 as shown in Fig. 1. K-isomers or indications of their existence have been found for almost all even-Z elements in the region Z=100 to 110. We could recently establish and/or confirm such states in the even-even isotopes 2 52,254N o [5]. The heaviest nucleus where such a state was found is 2 70D s with Z=110 as we reported in 2001 [6]. Those nuclear structure studies lay out the grounds for a detailed understanding of these heavy and high-Z nuclear systems, and contribute at the same time valuable information to preparation of strategies to successfully continue the hunt for the localisation of the next spherical proton and neutron shells after 2 08P b. The recent activities for both SHE synthesis and nuclear structure investigations at GSI will be reported.(author)

  6. Synthesis of carbon nano structures by plasma discharge

    International Nuclear Information System (INIS)

    Jimenez L, M.L.

    2007-01-01

    Due to the great quantity of applications of carbon neocarcinostatin (NEC) in diverse areas like: synthesis of super-resistant materials, hydrogen storage, nano sensors generation and nano catalysts, one has seen the necessity to generate new synthesis processes of these materials as well as to already improve those existent. The present work has as objective to optimize the NEC synthesis process by means of the electric arc method which uses alternating current to high frequencies (HF), obtaining relatively clean products; that is to say, it hardly presents amorphous material neither impurities. They stand out the obtaining of carbon nano fibers (NFC) by means of a luminescent-arc discharge, in a gas mixture He-CH 4 with 34% at.Ni/10.32%at.Y like catalyst; to a frequency of 42 k Hz and low power (300 W). This method benefits the agglomeration of the particles in both electrodes due to the high frequencies. The time of duration of the process oscillates between 5 and 20 minutes. The obtained product was characterized by scanning electron microscopy (MEB), transmission electron microscopy (MET) to determine the type of obtained NEC and by X-ray diffraction analysis and Raman spectroscopy to determine the purity of the samples. The NFC are relatively free of amorphous coal. The surface and structural analysis indicates that the fibers have a half diameter of 80 nm. It is also made, a study by optical emission spectroscopy of the plasma using the Swan band to determine the temperature. (Author)

  7. Synthesis and Crystal Structure Determination of a Nickel(II Complex of an Acyclic Pentadentate (N5 Mono Schiff Base Ligand

    Directory of Open Access Journals (Sweden)

    R. V. Parish

    2001-10-01

    Full Text Available The asymmetrical tripodal tetraamine ligand N[(CH23NH2]2[(CH22NH2] (ppe was condensed with 2-acetylpyridine in the presence of nickel(II ion. In ethanolwater solution the reaction stops after the first stage of condensation, and a new nickel(II complex of an acyclic pentadentate (N5 mono Schiff base ligand was obtained. X-ray structure analysis of the resulting complex, [Ni(ppe-py(H2O](ClO42, indicates that condensation with 2-acetylpyridine is at the propylene chain of ppe. The geometry around the nickel ion is distorted octahedral in which the sixth co-ordination group is a solvent molecule.

  8. New pyrrole inhibitors of monoamine oxidase: synthesis, biological evaluation, and structural determinants of MAO-A and MAO-B selectivity.

    Science.gov (United States)

    La Regina, Giuseppe; Silvestri, Romano; Artico, Marino; Lavecchia, Antonio; Novellino, Ettore; Befani, Olivia; Turini, Paola; Agostinelli, Enzo

    2007-03-08

    A series of new pyrrole derivatives have been synthesized and evaluated for their monoamine oxidase (MAO) A and B inhibitory activity and selectivity. N-Methyl,N-(benzyl),N-(pyrrol-2-ylmethyl)amine (7) and N-(2-benzyl),N-(1-methylpyrrol-2-ylmethyl)amine (18) were the most selective MAO-B (7, SI = 0.0057) and MAO-A (18, SI = 12500) inhibitors, respectively. Docking and molecular dynamics simulations gave structural insights into the MAO-A and MAO-B selectivity. Compound 18 forms an H-bond with Gln215 through its protonated amino group into the MAO-A binding site. This H-bond is absent in the 7/MAO-A complex. In contrast, compound 7 places its phenyl ring into an aromatic cage of the MAO-B binding pocket, where it forms charge-transfer interactions. The slightly different binding pose of 18 into the MAO-B active site seems to be forced by a bulkier Tyr residue, which replaces a smaller Ile residue present in MAO-A.

  9. Structure determination of enterovirus 71

    Energy Technology Data Exchange (ETDEWEB)

    Plevka, Pavel; Perera, Rushika; Cardosa, Jane; Kuhn, Richard J.; Rossmann, Michael G. (Purdue); (Sentinext)

    2013-02-20

    Enterovirus 71 is a picornavirus that causes hand, foot and mouth disease but may induce fatal neurological illness in infants and young children. Enterovirus 71 crystallized in a body-centered orthorhombic space group with two particles in general orientations in the crystallographic asymmetric unit. Determination of the particle orientations required that the locked rotation function excluded the twofold symmetry axes from the set of icosahedral symmetry operators. This avoided the occurrence of misleading high rotation-function values produced by the alignment of icosahedral and crystallographic twofold axes. Once the orientations and positions of the particles had been established, the structure was solved by molecular replacement and phase extension.

  10. Synthesis, structural and ferromagnetic properties of La1–x Kx ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Synthesis, structural and ferromagnetic properties of La1–KMnO3 (0.0≤ 0.25) phases by solution combustion method ... Structural parameters were determined by the Rietveld refinement method using powder XRD data. Parent ... The ratio of the Mn3+/Mn4+ was determined by the iodometric titration.

  11. Non linear structures seismic analysis by modal synthesis

    International Nuclear Information System (INIS)

    Aita, S.; Brochard, D.; Guilbaud, D.; Gibert, R.J.

    1987-01-01

    The structures submitted to a seismic excitation, may present a great amplitude response which induces a non linear behaviour. These non linearities have an important influence on the response of the structure. Even in this case (local shocks) the modal synthesis method remains attractive. In this paper we will present the way of taking into account, a local non linearity (shock between structures) in the seismic response of structures, by using the modal synthesis method [fr

  12. Synthesis of Carbon nano structures by plasma discharge

    International Nuclear Information System (INIS)

    Jimenez L, M.L.

    2007-01-01

    Due to the great quantity of applications of the carbon nano structures (NEC) in diverse areas like: synthesis of super-resistant materials, hydrogen storage, nano sensors generation and nano catalysts, it has seen the necessity to generate new processes of synthesis of this materials as well as to already improve those existent. The present work has as objective to optimize the NEC synthesis process by means of the electric arc method which uses alternating current to high frequencies (HF), obtaining relatively clean products; that is to say, it hardly presents amorphous material neither sludges. They stand out the obtaining of carbon nano fibers (NFC) by means of a luminescent-arch discharge, in a gas mixture of He-CH 4 with 34% at. Ni/10.32% at.Y like catalyst; at a frequency of 42 kHz and low power (300 W). This method benefits the amass of the particles in both electrodes due to the high frequencies. The time of duration of the process oscillates between 5 and 20 minutes. The obtained product was characterized by scanning electron microscopy (MEB), transmission electron microscopy (MET) to determine the NEC type obtained and by X-ray diffraction analysis and Raman spectroscopy for determining the purity of the samples. The NFC is relatively free of amorphous coal. The surface and structural analysis indicates that the fibers have a half diameter of 80 nm. It is also made, a study by optical emission spectroscopy of plasma using the Swan band for determining the temperature. (Author)

  13. Determination of human muscle protein fractional synthesis rate

    DEFF Research Database (Denmark)

    Bornø, Andreas; Hulston, Carl J; van Hall, Gerrit

    2014-01-01

    In the present study, different MS methods for the determination of human muscle protein fractional synthesis rate (FSR) using [ring-(13)C6 ]phenylalanine as a tracer were evaluated. Because the turnover rate of human skeletal muscle is slow, only minute quantities of the stable isotopically...

  14. Synthesis, Crystal Structure, Density Function Theory, Molecular ...

    African Journals Online (AJOL)

    Tropical Journal of Pharmaceutical Research ... Purpose: To determine the exact structure and antimicrobial activity of 2-(3-(4 phenylpiperazin-1-yl) ... Besides HOMO– LUMO energy gap was performed at B3LYP/6-31G (d,p) level of theory.

  15. Ultrafast Hydro-Micromechanical Synthesis of Calcium Zincate: Structural and Morphological Characterizations

    Directory of Open Access Journals (Sweden)

    Vincent Caldeira

    2017-01-01

    Full Text Available Calcium zincate is a compound with a large panel of application: mainly known as an advantageous replacement of zinc oxide in negative electrodes for air-zinc or nickel-zinc batteries, it is also used as precursor catalyst in biodiesel synthesis and as antifungal compound for the protection of limestone monuments. However, its synthesis is not optimized yet. In this study, it was elaborated using an ultrafast synthesis protocol: Hydro-Micromechanical Synthesis. Two other synthesis methods, Hydrochemical Synthesis and Hydrothermal Synthesis, were used for comparison. In all cases, the as-synthesized samples were analyzed by X-ray diffraction, scanning electron microscopy, and LASER diffraction particle size analysis. Rietveld method was used to refine various structural parameters and obtain an average crystallite size, on a Hydro-Micromechanical submicronic sample. X-ray single crystal structure determination was performed on a crystal obtained by Hydrochemical Synthesis. It has been shown that regardless of the synthesis protocol, the prepared samples always crystallize in the same crystal lattice, with P21/c space group and only differ from their macroscopic textural parameters. Nevertheless, only the Hydro-Micromechanical method is industrially scalable and enables a precise control of the textural parameters of the obtained calcium zincate.

  16. Organoactinide chemistry: synthesis, structure, and solution dynamics

    International Nuclear Information System (INIS)

    Brennan, J.G.

    1985-12-01

    This thesis considers three aspects of organoactinide chemistry. In chapter one, a bidentate phosphine ligand was used to kinetically stabilize complexes of the type Cp 2 MX 2 . Ligand redistribution processes are present throughout the synthetic work, as has often been observed in uranium cyclopentadienyl chemistry. The effects of covalent M-L bonding on the solution and solid state properties of U(III) coordination complexes are considered. In particular, the nature of the more subtle interaction between the metal and the neutral ligand are examined. Using relative basicity data obtained in solution, and solid state structural data (and supplemented by gas phase photoelectron measurements), it is demonstrated that the more electron rich U(III) centers engage in significant U → L π-donation. Trivalent uranium is shown to be capable of acting either as a one- or two-electron reducing agent toward a wide variety of unsaturated organic and inorganic molecules, generating molecular classes unobtainable via traditional synthetic approaches, as well as offering an alternative synthetic approach to molecules accessible via metathesis reactions. Ligand redistribution processes are again observed, but given the information concerning ligand lability, this reactivity pattern is applied to the synthesis of pure materials inaccessible from redox chemistry. 214 refs., 33 figs., 10 tabs

  17. Synthesis and structure of cerium nitrosocarbonylcyanmethanid complex

    International Nuclear Information System (INIS)

    Gerasimenko, H.; Scopenko, V.V.; Kapshuk, A.A.

    1998-01-01

    Full text: The complex compound [CeL 4 Dy 2 ]Na*2Ac (where L- nitrosocarbonylcyanmethanid, Dy -- dipyridile, Ac - acetone) were synthesised by interaction of cerium chloride and sodium nitrosocarbonylcyanmethanid from acetone solution. After two hours of mixing the dipyridil solution in acetone was added for complex stabilization. After filtration solution was put to desiccator for crystallisation. The complex was studied using IR- and UV-spectroscopy. The structure of the complex was determined using X-ray structure analysis. It was found that the structure of the complex belongs to orthorhombic Pna2(1) syngony with the unit cell parameters 17.010, 16.280 and 16.340Angstroms, respectively. It was found that cerium in the compound was eight co-ordinated. Four nitroso ligands were co-ordinated by bidentate bridge method and two dipyridiles by bidentate-cycle method

  18. Synthesis and X-ray structure of the dysprosium(III) complex derived ...

    African Journals Online (AJOL)

    Synthesis and X-ray structure of the dysprosium(III) complex derived from the ligand 5-chloro-1 ... Bulletin of the Chemical Society of Ethiopia ... synthesized and its crystal structure determined by single X-ray diffraction at room temperature.

  19. Combustion synthesis and structural characterization of Li–Ti mixed

    Indian Academy of Sciences (India)

    Combustion synthesis and structural characterization of Li–Ti mixed nanoferrites ... were prepared by combustion method at lower temperatures compared to the ... first time at low temperatures, using PEG which acts as a new fuel and oxidant.

  20. Total synthesis of the proposed structure of trichodermatide A.

    Science.gov (United States)

    Myers, Eddie; Herrero-Gómez, Elena; Albrecht, Irina; Lachs, Jennifer; Mayer, Peter; Hanni, Matti; Ochsenfeld, Christian; Trauner, Dirk

    2014-10-17

    A short total synthesis of the published structure of racemic trichodermatide A is reported. Our synthesis involves a Knoevenagel condensation/Michael addition sequence, followed by the formation of tricyclic hexahydroxanthene-dione and a diastereoselective bis-hydroxylation. The final product, the structure of which was confirmed by X-ray crystallography, has NMR spectra that are very similar, but not identical, to those of the isolated natural product. Quantum chemically computed (13)C shifts agree well with the present NMR measurements.

  1. Solution NMR structure determination of proteins revisited

    International Nuclear Information System (INIS)

    Billeter, Martin; Wagner, Gerhard; Wuethrich, Kurt

    2008-01-01

    This 'Perspective' bears on the present state of protein structure determination by NMR in solution. The focus is on a comparison of the infrastructure available for NMR structure determination when compared to protein crystal structure determination by X-ray diffraction. The main conclusion emerges that the unique potential of NMR to generate high resolution data also on dynamics, interactions and conformational equilibria has contributed to a lack of standard procedures for structure determination which would be readily amenable to improved efficiency by automation. To spark renewed discussion on the topic of NMR structure determination of proteins, procedural steps with high potential for improvement are identified

  2. PROSPECTIVE TEACHERS’ COGNITIVE STRUCTURES CONCERNING PROTEIN SYNTHESIS AND THEIR DEGREE OF UNDERSTANDING

    Directory of Open Access Journals (Sweden)

    Cem Gerçek

    2018-02-01

    Full Text Available The purpose of education is to actualise meaningful learning. Therefore, researching the issues on how students process information and how they configure it is important for meaningful learning. The issue of protein synthesis contains a number of abstract topics and concepts. Hence, it is important in biology teaching to be informed of students’ cognitive structures concerning protein synthesis. This research aims to analyse prospective teachers’ cognitive structures about protein synthesis and their degree of understanding the subject. The research group was composed of 17 volunteering prospective teachers who had been chosen through purposeful sampling. The data were collected via semi-structured interviews. Flow maps and content analysis were used in analysing the data. The results demonstrated that prospective teachers had too many misconceptions about protein synthesis and that their knowledge extent and rich connection are inadequate. The prospective teachers’ degree of understanding protein synthesis was divided into three categories. The results obtained in this research suggested that teachers should be careful in teaching the subject of protein synthesis. Students’ prior knowledge and their misconceptions should be determined and content or contexts to facilitate them to learn an abstract subject such as protein synthesis should be presented.

  3. Wall grid structure for interior scene synthesis

    KAUST Repository

    Xu, Wenzhuo; Wang, Bin; Yan, Dongming

    2015-01-01

    We present a system for automatically synthesizing a diverse set of semantically valid, and well-arranged 3D interior scenes for a given empty room shape. Unlike existing work on layout synthesis, that typically knows potentially needed 3D models

  4. The Synthesis and Crystal Structure of Two New Hydrazone Compounds

    Directory of Open Access Journals (Sweden)

    Li-Hua Wang

    2016-05-01

    Full Text Available Two new hydrazone compounds, 4-formylimidazole-4-hydroxybenzhydrazone dihydrate (1 and 2-nitrobenzaldehyde-2-furan formylhydrazone (2, were synthesized via the classical synthesis method. Their structure was determined via elemental analysis and X-ray single crystal diffraction analysis. Compound 1 crystallizes in triclinic, space group P-1 with a = 7.0321(14 Å, b = 7.3723(15 Å, c = 13.008(3 Å, α = 98.66(3°, β = 101.69(3°, γ = 92.25(3°, V = 651.2(2 Å3, Z = 2, Dc = 1.358 g·cm−3, μ = 0.106 mm−1, F(000 = 280, and final R1 = 0.0564, wR2 = 0.1420. Compound 2 crystallizes in monoclinic, space group P21/c with a = 17.3618(9 Å, b = 9.1506(4 Å, c = 15.5801(7 Å, β = 104.532(5°, V = 2396.05(19 Å3, Z = 8, Dc = 1.437 g·cm−3, μ = 0.111 mm−1, F(000 = 1072, and final R1 = 0.0633, wR2 = 0.1649. Compound 1 forms a 2D-layered structure via the interactions of 1D chains and Compound 2 forms a 3D network structure via the interactions of 1D chains.

  5. Total chemical synthesis and X-ray structure of kaliotoxin by racemic protein crystallography.

    Science.gov (United States)

    Pentelute, Brad L; Mandal, Kalyaneswar; Gates, Zachary P; Sawaya, Michael R; Yeates, Todd O; Kent, Stephen B H

    2010-11-21

    Here we report the total synthesis of kaliotoxin by 'one pot' native chemical ligation of three synthetic peptides. A racemic mixture of D- and L-kaliotoxin synthetic protein molecules gave crystals in the centrosymmetric space group P1 that diffracted to atomic-resolution (0.95 Å), enabling the X-ray structure of kaliotoxin to be determined by direct methods.

  6. 3-cyanoindole-based inhibitors of inosine monophosphate dehydrogenase: synthesis and initial structure-activity relationships.

    Science.gov (United States)

    Dhar, T G Murali; Shen, Zhongqi; Gu, Henry H; Chen, Ping; Norris, Derek; Watterson, Scott H; Ballentine, Shelley K; Fleener, Catherine A; Rouleau, Katherine A; Barrish, Joel C; Townsend, Robert; Hollenbaugh, Diane L; Iwanowicz, Edwin J

    2003-10-20

    A series of novel small molecule inhibitors of inosine monophosphate dehydrogenase (IMPDH), based upon a 3-cyanoindole core, were explored. IMPDH catalyzes the rate determining step in guanine nucleotide biosynthesis and is a target for anticancer, immunosuppressive and antiviral therapy. The synthesis and the structure-activity relationships (SAR), derived from in vitro studies, for this new series of inhibitors is given.

  7. Monte Carlo determination of heteroepitaxial misfit structures

    DEFF Research Database (Denmark)

    Baker, J.; Lindgård, Per-Anker

    1996-01-01

    We use Monte Carlo simulations to determine the structure of KBr overlayers on a NaCl(001) substrate, a system with large (17%) heteroepitaxial misfit. The equilibrium relaxation structure is determined for films of 2-6 ML, for which extensive helium-atom scattering data exist for comparison...

  8. Functional coordination polymers and MOFs from reactions of the lanthanides and barium with azole ligands. Synthesis and characterization with a focus on structure determination from X-ray powder diffraction data

    International Nuclear Information System (INIS)

    Rybak, Jens-Christoph

    2012-01-01

    This thesis deals with the synthesis and characterization of coordination polymers and MOFs of the lanthanides and barium with different azolic N-heterocycles. A total of 18 new organic-inorganic hybrid materials, as well as a series of co-doped compounds is presented. Besides the structural characterization of these materials from X-ray diffraction powder data, the focus of the investigations is on the thermal and photoluminescence spectroscopic properties. The lanthanides La - Lu, except Eu and Pm, can be reacted with 1H-1,2,3-triazole to give the series of the isotypic dense 3D-MOFs 3 ∞ [Ln(Tz * ) 3 ]. Investigation of the photoluminescence properties of these compounds reveals a broad range of different luminescence phenomena, including the first observation of an intrinsic inner-filter effect of the Ln 3+ -ions. The structure of this isotypic series of compounds was solved and refined from X-ray powder diffraction data. A 2D-polymorph of these compounds 2 ∞ [Ln(Tz * ) 3 ], is observed for Ln = Sm, Tb and was characterized by single crystal data. The reaction of Eu with 1H-benzotriazole yields the 1D-coordination polymer 1 ∞ [Eu(Btz) 2 (BtzH) 2 ], which is the first example of a divalent rare earth benzotriazolate. Analysis of the thermal properties reveals the transformation to the 3D-MOF 3 ∞ [Eu(Btz) 2 ] at higher temperatures. The structure of this material was also solved from X-ray powder diffraction data. Investigation of the photoluminescence properties of the co-doped compounds 3 ∞ [Ba 1-x Eu x (Im) 2 ], which were obtained from reaction of the salt-like hydrides BaH 2 and EuH 2 with imidazole, show that the synthesis of luminescent MOF materials by co-doping of non-luminescent networks with luminescence centers is possible. The structure of these materials was solved from X-ray powder diffraction data of the undoped compound 3 ∞ [BaEu(Im) 2 ]. Structural characterization of materials from X-ray powder diffraction data is an important aspect

  9. Synthesis route and structural properties of nanoferrites

    Energy Technology Data Exchange (ETDEWEB)

    Zaharieva, Katerina; Cherkezova-Zheleva, Zara; Kunev, Boris; Shopska, Maya; Mitov, Ivan [Institute of Catalysis, Bulgarian Academy of Sciences, Sofia (Bulgaria)

    2013-07-01

    The nano dimensional magnesium ferrite materials Mg{sub 0.25}Fe{sub 2.75}O{sub 4} , Mg{sub 0.5}Fe{sub 2.5}O{sub 4} and MgFe{sub 2}O{sub 4} with different stoichiometry were prepared by co-precipitation procedure using MgCl{sub 2} •6H{sub 2}O, FeCl{sub 2} •4H{sub 2}O and FeCl{sub 3} •6H{sub 2}O and NaOH as precipitant. The physicochemical methods - X-ray diffraction analysis, Moessbauer spectroscopy and FTIR spectroscopy were performed to investigate the structural properties of obtained nano size magnesium ferrite type samples. The registered experimental data were determined the presence of spinel ferrites and additional precursor phases as iron oxihydroxides and double layered hydroxides in ferrite materials MgxFe{sub 3-x}O{sub 4} (x=0.5;1). In the case of magnesium ferrite sample Mg{sub x}Fe{sub 3-x}O{sub 4} (x=0.25) the existence of non-stoichiometric spinel ferrite and intermediate phase - iron oxihydroxides were observed only. Key words: magnesium ferrites, co-precipitation, physicochemical methods.

  10. Synthesis route and structural properties of nanoferrites

    International Nuclear Information System (INIS)

    Zaharieva, Katerina; Cherkezova-Zheleva, Zara; Kunev, Boris; Shopska, Maya; Mitov, Ivan

    2013-01-01

    The nano dimensional magnesium ferrite materials Mg 0.25 Fe 2.75 O 4 , Mg 0.5 Fe 2.5 O 4 and MgFe 2 O 4 with different stoichiometry were prepared by co-precipitation procedure using MgCl 2 •6H 2 O, FeCl 2 •4H 2 O and FeCl 3 •6H 2 O and NaOH as precipitant. The physicochemical methods - X-ray diffraction analysis, Moessbauer spectroscopy and FTIR spectroscopy were performed to investigate the structural properties of obtained nano size magnesium ferrite type samples. The registered experimental data were determined the presence of spinel ferrites and additional precursor phases as iron oxihydroxides and double layered hydroxides in ferrite materials MgxFe 3-x O 4 (x=0.5;1). In the case of magnesium ferrite sample Mg x Fe 3-x O 4 (x=0.25) the existence of non-stoichiometric spinel ferrite and intermediate phase - iron oxihydroxides were observed only. Key words: magnesium ferrites, co-precipitation, physicochemical methods

  11. Hydrothermal synthesis, structure and characterization of new ...

    Indian Academy of Sciences (India)

    Unknown

    Keywords. Hydrothermal; crystal structure; solid electrolyte; iron (III) pyrophosphate. 1. Introduction ... tion, structure and electrical conductivity and the higher values of ..... type cavity structure. Acknowledgements. The authors would like to express their thanks to DST,. New Delhi, for financial assistance under the projects.

  12. Synthesis, characterization and crystal structure determination of a new vanadium(IV) Schiff base complex (VOL.sub.2./sub.) and investigation of its catalytic activity in the epoxidation of cyclooctene

    Czech Academy of Sciences Publication Activity Database

    Grivani, G.; Tahmasebi, V.; Khalaji, A.D.; Fejfarová, Karla; Dušek, Michal

    2013-01-01

    Roč. 51, č. 1 (2013), s. 54-60 ISSN 0277-5387 R&D Projects: GA ČR(CZ) GAP204/11/0809 Institutional support: RVO:68378271 Keywords : vanadium (IV) * Schiff base * single crystal * structure determination * catalysis * epoxidation Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 2.047, year: 2013

  13. Synthesis, Structure, Stability and Redispersion of Gold-based Nanoparticles

    Science.gov (United States)

    Tiruvalam, Ram Chandra

    Nanoscale gold has been shown to possess an intriguing combination of unexpected optical, photochemical and catalytic properties. The ability to control the size, shape, morphology, composition and dispersion of gold-based nanostructures is key to optimizing their performance for nanotechnology applications. The advanced electron microscopy studies described in this thesis analyze three important aspects of gold and gold-palladium alloy nanoparticles: namely, (i) the ability to synthesize gold nanoparticles of controlled size and shape in an aqueous medium; (ii) the colloidal preparation of designer gold-palladium alloys for selective oxidation catalysis; and (iii) the ability to disperse gold as finely and homogeneously as possible on a metal oxide or carbon support. The ability to exploit the nanoscale properties of gold for various engineering applications often depends on our ability to control size and shape of the nanoscale entity by careful manipulation of the synthesis parameters. We have explored an aqueous based synthesis route, using oleylamine as both a reductant and surfactant, for preparing gold nanostructures. By systematically varying synthesis parameters such as oleylamine concentration, reaction temperature, and aging time it is possible to identify processing regimens that generate Au nanostructures having either pseudo-spherical, faceted polyhedral, nanostar or wire shaped morphologies. Furthermore, by quenching the reaction partway through it is possible to create a class of metastable Au-containing structures such as nanocubes, nanoboxes and nanowires. Possible formation mechanisms for these gold based nano-objects are discussed. There is a growing interest in using supported bimetallic AuPd alloy nanoparticles for selective oxidation reactions. In this study, a systematic series of size controlled AuPd bimetallic particles have been prepared by colloidal synthesis methods. Particles having random alloy structures, as well as `designer

  14. Synthesis, structural and optical properties of nanoparticles (Al, V ...

    Indian Academy of Sciences (India)

    The synthesis by the sol–gel method, structural and optical properties of ZnO, Zn0.99Al0.01O (AlZ),. Zn0.9V0.1O (VZ) ... drops of the resulting suspension containing the synthesized .... ZnO films on silicon substrate, they thought that this emis-.

  15. Synthesis and structural characterization of a calcium coordination ...

    Indian Academy of Sciences (India)

    Synthesis and structural characterization of a calcium coordination polymer based on a μ3-bridging. tetradentate binding mode of glycine. SUBRAMANIAN NATARAJAN*a, BIKSHANDARKOIL R. SRINIVASANb , J. KALYANA SUNDARa, K. RAVIKUMARc , R.V. KRISHNAKUMARd , J. SURESHe,. aSchool of Physics, ...

  16. Structural determinants of students' employability: Influence of ...

    African Journals Online (AJOL)

    Structural determinants of students' employability: Influence of career ... greatest influence on students' employability, followed by decision-making skills, and ... efforts in developing app-ropriate strategies so as to engage undergraduates with ...

  17. Synthesis of Efficient Structures for Concurrent Computation.

    Science.gov (United States)

    1983-10-01

    formal presentation of these techniques, called virtualisation and aggregation, can be found n [King-83$. 113.2 Census Functions Trees perform broadcast... Functions .. .. .. .. ... .... ... ... .... ... ... ....... 6 4 User-Assisted Aggregation .. .. .. .. ... ... ... .... ... .. .......... 6 5 Parallel...6. Simple Parallel Structure for Broadcasting .. .. .. .. .. . ... .. . .. . .... 4 Figure 7. Internal Structure of a Prefix Computation Network

  18. Protein Structure Determination Using Chemical Shifts

    DEFF Research Database (Denmark)

    Christensen, Anders Steen

    is determined using only chemical shifts recorded and assigned through automated processes. The CARMSD to the experimental X-ray for this structure is 1.1. Å. Additionally, the method is combined with very sparse NOE-restraints and evolutionary distance restraints and tested on several protein structures >100...

  19. Hydrothermal synthesis, crystal structure and luminescence property ...

    Indian Academy of Sciences (India)

    The design and construction of ... dination polymers. It is difficult to design coordination .... The first endotherm at about 180 ... graphic data for coordination polymer 1. ... Sheldrick G M 1997 SHELXS-97: Program for solution of crystal structures ...

  20. Synthesis, structure and electronic structure of a new polymorph of CaGe2

    International Nuclear Information System (INIS)

    Tobash, Paul H.; Bobev, Svilen

    2007-01-01

    Reported are the flux synthesis, the crystal structure determination, the properties and the band structure calculations of a new polymorph of CaGe 2 , which crystallizes with the hexagonal space group P6 3 mc (no. 186) with cell parameters of a=3.9966(9) and c=10.211(4)A (Z=2; Pearson's code hP6). The structure can be viewed as puckered layers of three-bonded germanium atoms, ∼ 2 [Ge 2 ] 2- , which are stacked along the direction of the c-axis in an ABAB-fashion. The germanium polyanionic layers are separated by the Ca cations. As such, this structure is closely related to the structure of the other CaGe 2 polymorph, which crystallizes with the rhombohedral CaSi 2 type in the R3-bar m space group (No. 166), where the ∼ 2 [Ge 2 ] 2- layers are arranged in an AA'BB'CC'-fashion, and are also interspaced by Ca 2+ cations. LMTO calculations suggest that in spite of the formal closed-shell configuration for all atoms and the apparent adherence to the Zintl rules for electron counting, i.e., Ca 2+ [3b-Ge 1- ] 2 ), the phase will be a poor metal due to a small Ca-3d-Ge-4p band overlap. Magnetic susceptibility measurements as a function of the temperature indicate that the new CaGe 2 polymorph exhibits weak, temperature independent, Pauli-paramagnetism

  1. Synthesis, structural and surface morphological characterizations of ...

    African Journals Online (AJOL)

    Sulfated zirconia (SZ) nanoparticles (NPs) were successfully synthesized and deposited via chemical route called sol-gel technique. The structural, morphological, and optical properties the samples were investigated by X-ray diffraction (XRD), Energy Dispersive X-ray Spectrometry (EDX), Scanning Electron Microscopy ...

  2. Synthesis, characterization and crystal structure of a ...

    African Journals Online (AJOL)

    The Mo atom in the complex is in octahedral coordination. Thermal stability of the complex has also been studied. KEY WORDS: Molybdenum complex, Hydrazone ligand, Crystal structure, X-ray diffraction, Thermal property. Bull. Chem. Soc. Ethiop. 2014, 28(3), 409-414. DOI: http://dx.doi.org/10.4314/bcse.v28i3.10 ...

  3. Synthesis, molecular structure, spectroscopic investigations and ...

    Indian Academy of Sciences (India)

    MS received 29 December 2015; revised 9 April 2016; accepted 25 May 2016 ... B, open form blue. Scheme 1. Structures and Photochromic reaction of the title compound. 2. Experimental. 2.1 Materials and measurements. The mid-IR spectra were obtained in the ... segment is put between two parallel Au(111) surfaces,.

  4. Synthesis, crystal structure, thermal analysis and dielectric ...

    Indian Academy of Sciences (India)

    [13] Perry C H and Lowdes R P 1969 J. Chem. Phys. 51 3648. [14] Sheldrick G M 1997 SHELXS9, Program for the Refinement of Crystal Structures (Germany: University of Gottingen). [15] Loukil M, Kabadou A, Salles Ph and Ben Salah A 2004 Chem. Phys. 300 247. [16] Rolies M M and De Ranter C J 1978 Acta Crystallogr.

  5. Ligand-protected gold clusters: the structure, synthesis and applications

    International Nuclear Information System (INIS)

    Pichugina, D A; Kuz'menko, N E; Shestakov, A F

    2015-01-01

    Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Au n with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au 15 and Au 25 ) and on anchorage to a support surface (Au 25 /SiO 2 , Au 20 /C, Au 10 /FeO x ) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR) n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters M x Au n L m (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR) x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active

  6. Ligand-protected gold clusters: the structure, synthesis and applications

    Science.gov (United States)

    Pichugina, D. A.; Kuz'menko, N. E.; Shestakov, A. F.

    2015-11-01

    Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Aun with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au15 and Au25) and on anchorage to a support surface (Au25/SiO2, Au20/C, Au10/FeOx) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR)n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters MxAunLm (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR)x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active sites. The bibliography includes 345 references.

  7. Capital Structure Determinants and Governance Structure Variety in Franchising

    NARCIS (Netherlands)

    T. Jiang (Tao)

    2009-01-01

    textabstractThis thesis investigates two questions: the determinants of capital structure in franchising and its subsequent impact on the franchise financing decisions; and the efficient governance structure choice in franchising. We posit that firms franchise in order to benefit from the reduced

  8. Efficient Product Customization by Structure Synthesis

    OpenAIRE

    Maurer, M.;Rupp, T.;Lindemann, U.

    2017-01-01

    The presented approach describes a new strategy for creating product structures, which are suitable for further customer driven product customization – i.e. the customization can be carried out within less time and for lower costs. The required input data is knowledge on the interconnectivity between product components and knowledge of principal scopes of customization demands (e.g. which components or functions customers would like to individualize, which ones are unknown or hidden). By mean...

  9. Synthesis and structure of vanillin azomethines

    Directory of Open Access Journals (Sweden)

    Jasmina M. Jovanović

    2009-10-01

    Full Text Available Vanillin is most prominent as the principal flavor and aroma compound in vanilla. Vanillin has been used as a chemical intermediate in the production of pharmaceuticals and other fine chemicals.The two intermediates, assigned as intermediates I and II, were prepared by using vanillin and 1-butylbromide or 2-chloroacetic acid, respectively. The condensation of intermediates with 2,3- -diaminopyridine gave azomethines. Their structure was established by using elemental microanalysis, as well as UV/Vis, FTIR and 1H-NMR spectra. Synthesized compounds were tested for their antifungal activity against Candida albicans, Candida lipolytica and Sacharomyces cerevisiae.

  10. Structural Amendment and Stereoselective Synthesis of Mutisianthol.

    Science.gov (United States)

    Ho, Tse-Lok; Lee, Kwang-Yuan; Chen, Chun-Kuei

    1997-05-16

    cis-1-(5-Acetoxy-3,6-dimethyl-1-indanyl)-2-methyl-1-propene synthesized from 3,6-dimethyl-1-indanone was found to be different from mutisianthol by spectral comparison. The presence of a high-field signal in the NMR spectrum of the final product and various intermediates, characteristic of the cis-1,3-dialkylindanes but absent in the spectrum of the natural terpene, suggests a revision of the structure of mutisianthol to the trans isomer. The trans-indane which was subsequently obtained indeed exhibits data fully agreeable with mutisianthol. A similar stereochemical revision for jungianol is also indicated.

  11. Synthesis, structure, and properties of azatriangulenium salts

    DEFF Research Database (Denmark)

    Laursen, B.W.; Krebs, Frederik C

    2001-01-01

    amines and, by virtue of its stepwise and irreversible nature, provides a powerful tool for the preparation of a wide variety of new heterocyclic carbenium salts. Several derivatives of the three new oxygen- and/or nitrogen-bridged triangulenium salts, azadioxa- (6), diazaoxa- (7......), and triazatriangulenium (4), have been synthesized and their physicochemical properties have been investigated. Crystal structures for compounds 2 b-PF6: 2d-PF6, 4b-BF4, 4c-BF4, 6e-BF4, and 8 are reported. The different packing modes found for the triazatriagulenium salts are discussed in relation to the electrostatic...

  12. Superheavy Element Synthesis And Nuclear Structure

    International Nuclear Information System (INIS)

    Ackermann, D.; Block, M.; Burkhard, H.-G.; Heinz, S.; Hessberger, F. P.; Khuyagbaatar, J.; Kojouharov, I.; Mann, R.; Maurer, J.; Antalic, S.; Saro, S.; Venhart, M.; Hofmann, S.; Leino, M.; Uusitalo, J.; Nishio, K.; Popeko, A. G.; Yeremin, A. V.

    2009-01-01

    After the successful progress in experiments to synthesize superheavy elements (SHE) throughout the last decades, advanced nuclear structure studies in that region have become feasible in recent years thanks to improved accelerator, separation and detection technology. The means are evaporation residue(ER)-α-α and ER-α-γ coincidence techniques complemented by conversion electron (CE) studies, applied after a separator. Recent examples of interesting physics to be discovered in this region of the chart of nuclides are the studies of K-isomers observed in 252,254 No and in 270 Ds.

  13. Advances on surface structural determination by LEED

    International Nuclear Information System (INIS)

    Soares, Edmar A; De Carvalho, Vagner E; De Castilho, Caio M C

    2011-01-01

    In the last 40 years, low energy electron diffraction (LEED) has proved to be the most reliable quantitative technique for surface structural determination. In this review, recent developments related to the theory that gives support to LEED structural determination are discussed under a critical analysis of the main theoretical approximation-the muffin-tin calculation. The search methodologies aimed at identifying the best matches between theoretical and experimental intensity versus voltage curves are also considered, with the most recent procedures being reviewed in detail. (topical review)

  14. Synthesis of silicon nanowires and novel nano-dendrite structures

    International Nuclear Information System (INIS)

    Sinha, Saion; Gao Bo; Zhou, Otto

    2004-01-01

    We report a study on the effects of various parameters on the synthesis of silicon nanowires (5--50 nm in diameter) by pulsed laser ablation. A novel silicon nanodendrite structure is observed by changing some of the growth parameters abruptly. This growth mechanism is explained by a qualitative model. These nanodendrites show a promise of being used as a template in fabricating nanocircuits. Thermal quantum confinement effects were also observed on the silicon nanowires and have been reported

  15. Representing Personal Determinants in Causal Structures.

    Science.gov (United States)

    Bandura, Albert

    1984-01-01

    Responds to Staddon's critique of the author's earlier article and addresses issues raised by Staddon's (1984) alternative models of causality. The author argues that it is not the formalizability of causal processes that is the issue but whether cognitive determinants of behavior are reducible to past stimulus inputs in causal structures.…

  16. Capital Structure Determinants and Governance Structure Variety in Franchising

    OpenAIRE

    Jiang, Tao

    2009-01-01

    textabstractThis thesis investigates two questions: the determinants of capital structure in franchising and its subsequent impact on the franchise financing decisions; and the efficient governance structure choice in franchising. We posit that firms franchise in order to benefit from the reduced franchisees’ operational risks by limiting the debt level, such that the franchisor can bear more debt and gain tax-deduction benefits. Specific hypotheses are based on various theories like resource...

  17. Cyclotetraphosphinophosphonium ions: synthesis, structures, and pseudorotation.

    Science.gov (United States)

    Dyker, C Adam; Riegel, Susanne D; Burford, Neil; Lumsden, Michael D; Decken, Andreas

    2007-06-13

    The first derivatives of catenated cyclotetraphosphinophosphonium cations, [(PhP)4PPhMe]+ (8a), [(MeP)4PMe2]+ (8b), [(CyP)4PPh2]+ (8d), [(CyP)4PMe2]+ (8e), [(PhP)4PPh2]+ (8f), [(PhP)4PMe2]+ (8g), are synthesized as trifluoromethanesulfonate (triflate, OSO2CF3-) salts through the reaction of cyclopentaphosphines (PhP)5 (4a) or (MeP)5 (4b) with methyl triflate (MeOTf) or by a net phosphenium ion [PR2+, R = Ph, Me; from R2PCl and trimethylsilyltriflate (Me3SiOTf)] insertion into the P-P bond of either cyclotetraphosphine (CyP)4 (3c) or cyclopentaphosphines (PhP)5 (4a) or (MeP)5 (4b). Although more conveniently prepared from 4a, compound 8a[OTf] can also be formed from (PhP)4 (3a) and MeOTf, and derivatives 8f[OTf] and 8g[OTf] are also accessible through reactions of 3a and R2PCl/Me3SiOTf with R = Ph or Me, respectively. A tetrachlorogallate salt of [(PhP)4PPhtBu]+ (8c) has been synthesized by alkylation of 4a with tBuCl/GaCl3. 31P[1H] NMR parameters for all derivatives of 8 have been determined by iterative simulation of experimental data. Derivatives 8a[OTf], 8b[OTf], 8c[GaCl4], 8e[OTf], 8f[OTf], and 8g[OTf] and have been characterized by X-ray crystallography, showing the most favorable all-trans configuration of substituents for the phosphine centers, thus minimizing steric interactions. Each derivative adopts a unique envelope or twist conformation of C1 symmetry. The effective C2 symmetry observed for 8b, d, e, f, and g in solution, signified by their 31P[1H] NMR AA'BB'X spin systems, implies a rapid conformational exchange for derivatives of 8. The core frameworks of the cations in the solid state are viewed as snapshots of different conformational isomers within the solution-phase pseudorotation process.

  18. DNA nanotubes for NMR structure determination of membrane proteins.

    Science.gov (United States)

    Bellot, Gaëtan; McClintock, Mark A; Chou, James J; Shih, William M

    2013-04-01

    Finding a way to determine the structures of integral membrane proteins using solution nuclear magnetic resonance (NMR) spectroscopy has proved to be challenging. A residual-dipolar-coupling-based refinement approach can be used to resolve the structure of membrane proteins up to 40 kDa in size, but to do this you need a weak-alignment medium that is detergent-resistant and it has thus far been difficult to obtain such a medium suitable for weak alignment of membrane proteins. We describe here a protocol for robust, large-scale synthesis of detergent-resistant DNA nanotubes that can be assembled into dilute liquid crystals for application as weak-alignment media in solution NMR structure determination of membrane proteins in detergent micelles. The DNA nanotubes are heterodimers of 400-nm-long six-helix bundles, each self-assembled from a M13-based p7308 scaffold strand and >170 short oligonucleotide staple strands. Compatibility with proteins bearing considerable positive charge as well as modulation of molecular alignment, toward collection of linearly independent restraints, can be introduced by reducing the negative charge of DNA nanotubes using counter ions and small DNA-binding molecules. This detergent-resistant liquid-crystal medium offers a number of properties conducive for membrane protein alignment, including high-yield production, thermal stability, buffer compatibility and structural programmability. Production of sufficient nanotubes for four or five NMR experiments can be completed in 1 week by a single individual.

  19. Metal Oxide Nano structures: Synthesis, Properties, and Applications

    International Nuclear Information System (INIS)

    Xu, L. H.; Patil, D. S.; Yang, J.; Xiao, J.

    2015-01-01

    In recent years, nano structured materials have attracted wide attention due to their fascinating optical and electrical properties, which make these materials potentially suitable for applications in electronics, optics, photonics, and sensors. Some metal oxides show a wide variety of morphologies such as nano wires, nano rods, nano tubes, nano rings, and nano belts. Synthesis and investigation of these metal-oxide nano structures are beneficial not only for understanding the fundamental phenomena in low dimensional systems, but also for developing new-generation nano devices with high performance.

  20. Ionothermal synthesis and crystal structures of metal phosphate chains

    International Nuclear Information System (INIS)

    Wragg, David S.; Le Ouay, Benjamin; Beale, Andrew M.; O'Brien, Matthew G.; Slawin, Alexandra M.Z.; Warren, John E.; Prior, Timothy J.; Morris, Russell E.

    2010-01-01

    We have prepared isostructural aluminium and gallium phosphate chains by ionothermal reactions in 1-ethyl-3-methylimidazolium bromide and 1-ethylpyridinium bromide under a variety of conditions. The chains can be prepared as pure phases or along with three dimensional framework phases. The chains are favoured at shorter heating times and the crystallinity can be improved by addition of transition metal acetates and amines which are not included in the final structure. The chain can be prepared with or without the presence of hydrofluoric acid. - Graphical abstract: Chain structures prepared from ionic liquid solvents under a wide variety of synthesis conditions.

  1. Characterization structural and morphology ZSM-5 zeolite by hydrothermal synthesis

    International Nuclear Information System (INIS)

    Silva, V.J.; Crispim, A.C.; Queiroz, M.B.; Laborde, H.M.; Rodrigues, M.G.F.; Menezes, R.R.

    2009-01-01

    Solid acids are catalytic materials commonly used in the chemical industry. Among these zeolites are the most important business processes including water treatment, gas separation, and cracking long hydrocarbon chains to produce high octane gasoline. Its synthesis, characterization and applications have been widely studied. The objective this study was to synthesize the ZSM-5 zeolite for future use in separation processes and catalysis. The zeolite ZSM-5 was prepared by hydrothermal synthesis at 170°C, using silica, deionized water and the director of structures (TPABr - tetrapropylammonium bromide). The materials were characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and semiquantitative chemical analysis by X ray fluorescence (XRF). According to the XRD was possible to observe the formation of ZSM-5 zeolite, with peaks intense and well defined. The SEM showed the formation of individual particles, clean, rounded shapes. (author)

  2. Simultaneous determination of protein structure and dynamics

    DEFF Research Database (Denmark)

    Lindorff-Larsen, Kresten; Best, Robert B.; DePristo, M. A.

    2005-01-01

    at the atomic level about the structural and dynamical features of proteins-with the ability of molecular dynamics simulations to explore a wide range of protein conformations. We illustrate the method for human ubiquitin in solution and find that there is considerable conformational heterogeneity throughout......We present a protocol for the experimental determination of ensembles of protein conformations that represent simultaneously the native structure and its associated dynamics. The procedure combines the strengths of nuclear magnetic resonance spectroscopy-for obtaining experimental information...... the protein structure. The interior atoms of the protein are tightly packed in each individual conformation that contributes to the ensemble but their overall behaviour can be described as having a significant degree of liquid-like character. The protocol is completely general and should lead to significant...

  3. SYNTHESIS OF THE TECHNICAL CONTROL SYSTEMS WITH VARIABLE STRUCTURE

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available Change. Also the object as a result of an adverse effect is considered. The formal problem definition of synthesis of hardy management system is considered. Model choice criteria ensemble is set. The rule of choice algorithm implementation on the basis of different reference functions is provided. The conclusion is drawn that in case of preliminary processing of the available prior data it is possible to select reference functions correctly which reflect physical processes more precisely. The mathematical description of a dynamic object on the basis of a differential equation, or its decision is provided. Defini- tion of function of a trend is given. Criteria for selection of model of damage are given. The recommendation of modifica- tion of Demark trends algorithm by means of the sliding Yazvinsky's window and a method of self-organization for in- crease of accuracy of creation of a predictive model of damage is made. It is offered to realize a model choice by means of more complex logical analysis of an observed vector in the appropriate situation. Logic-functional control task definition is given and approach to its decision is formulated. The conclusion about what the task of synthesis management system con- sists of is given. This article describes the method of synthesis of control system with variable structure provides increasing survivability control system in a significant change of the external environment, as well as the object itself from the adverse impacts.

  4. Effect of preparation conditions on fractal structure and phase transformations in the synthesis of nanoscale M-type barium hexaferrite

    Energy Technology Data Exchange (ETDEWEB)

    Pashkova, E.V. [V.I. Vernadskii Institute of General and Inorganic Chemistry, 32/34 Prospect Palladina, Kyiv-142, 03680 (Ukraine); Solovyova, E.D., E-mail: solovyovak@mail.ru [V.I. Vernadskii Institute of General and Inorganic Chemistry, 32/34 Prospect Palladina, Kyiv-142, 03680 (Ukraine); Kotenko, I.E., E-mail: Hab2420@yahoo.com [National Technical University of Ukraine ' KPI' , Pr. Pobedy, 37, Kyiv-57 (Ukraine); Kolodiazhnyi, T.V., E-mail: kolodiazhnyi.taras@nims.go.jp [National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Belous, A.G., E-mail: belous@ionc.kar.net [V.I. Vernadskii Institute of General and Inorganic Chemistry, 32/34 Prospect Palladina, Kyiv-142, 03680 (Ukraine)

    2011-10-15

    The conditions of the synthesis of carbonate-hydroxide precursors (pH of FeOOH precipitation and heat treatment regimes) were studied in terms of their effect on the fractal structure and physical-chemical properties of precursors. Phase transformations which occur during the synthesis of nanosize M-type barium hexaferrite (BHF) were studied as well. The first structural level of precursors' aggregation for mass fractals, the correlation between fractal dimension and precursors' activity during the synthesis of BHF were determined. Synthesis parameters for the precursors with the optimal fractal structure were determined. These data permit an enhancement of the filtration coefficient of the precipitates by a factor of 4-5, obtaining substantial decrease in the temperature required for synthesis of a single-phase BHF, and monodispersed plate-like nanoparticles (60 nm diameter) with the shape anisotropy and good magnetic characteristics (saturation magnetization (M{sub s})=68,7 emu/g and coercitivity (H{sub c})=5440 Oe). - Highlights: > The nanosize M-type BHF obtained by precipitation of hydroxicarbonates technique. > Optimal fractal structure of a precursor for nanosize M-type BHF has been determined. > The precursor precipitated at pH 4.3 allows getting monodisperse particles of BHF.

  5. Structure-based synthesis from natural products to drug prototypes

    International Nuclear Information System (INIS)

    Hanessian, S.

    2009-01-01

    X-Ray crystallographic data available from complexes of natural and synthetic molecules with the enzyme thrombin has aided to the design and synthesis of truncated and hybrid molecules exhibiting excellent inhibition in vitro. The vital importance of natural products for the well-being of man has been known lor millennia. Their therapeutic benefits to alleviate pain or cure diseases continue to rank natural products among the primary sources of potential drugs. Great advances have been made in the methods of isolation, identification, and structure elucidation of some of the most complex natural products in recent years. The advent of molecular biology and genetic mapping has also aided in our understanding of the intriguing biosynthetic pathways leading to various classes of therapeutically relevant antibiotic, anticancer, and related natural products. Elegant and practical methodology has been developed leading to the total synthesis of virtually every class of medicinally important natural product. In some cases, natural products or their chemically modified congeners have been manufactured by total synthesis on an industrial level which is a testament to the ingenuity of process chemists. In spite of their potent activities HI enzymatic ox receptor-mediated assays, not all natural products are amenable to being developed as marketable drags. In many instances unfavorable pharmacological effects cannot be overcome without drastic structural and functional modifications, which may also result in altered efficacy. Structure modification through truncation, functional group variations, isosteric replacements, and skeletal rigidifications aided by molecular modeling, X ray crystallography of protein targets, or NMR data are valid objectives in the context of small molecule drug discovery starting with bioactive natural products. A large proportion of these pertain to chemotherapeutic agents against cancer

  6. The extended evolutionary synthesis: its structure, assumptions and predictions

    Science.gov (United States)

    Laland, Kevin N.; Uller, Tobias; Feldman, Marcus W.; Sterelny, Kim; Müller, Gerd B.; Moczek, Armin; Jablonka, Eva; Odling-Smee, John

    2015-01-01

    Scientific activities take place within the structured sets of ideas and assumptions that define a field and its practices. The conceptual framework of evolutionary biology emerged with the Modern Synthesis in the early twentieth century and has since expanded into a highly successful research program to explore the processes of diversification and adaptation. Nonetheless, the ability of that framework satisfactorily to accommodate the rapid advances in developmental biology, genomics and ecology has been questioned. We review some of these arguments, focusing on literatures (evo-devo, developmental plasticity, inclusive inheritance and niche construction) whose implications for evolution can be interpreted in two ways—one that preserves the internal structure of contemporary evolutionary theory and one that points towards an alternative conceptual framework. The latter, which we label the ‘extended evolutionary synthesis' (EES), retains the fundaments of evolutionary theory, but differs in its emphasis on the role of constructive processes in development and evolution, and reciprocal portrayals of causation. In the EES, developmental processes, operating through developmental bias, inclusive inheritance and niche construction, share responsibility for the direction and rate of evolution, the origin of character variation and organism–environment complementarity. We spell out the structure, core assumptions and novel predictions of the EES, and show how it can be deployed to stimulate and advance research in those fields that study or use evolutionary biology. PMID:26246559

  7. Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

    Directory of Open Access Journals (Sweden)

    Nina Gonsior

    2012-03-01

    Full Text Available The synthesis of a heterocyclic mesomeric betaine by quaternization reaction of 1-butylimidazole and tetrabromo-1,4-benzoquinone is presented. The structure was verified by means of X-ray single-crystal analysis, NMR and IR spectroscopy. Inclusion complexes of the heterocyclic mesomeric betaine with randomly methylated (1.8 β-cyclodextrin were investigated by UV–vis spectroscopy. Furthermore, the reaction conditions were applied to poly(vinylimidazole and 1,4-bis(1H-imidazol-1-ylbutane to obtain functionalized polymer networks and condensate polymers, respectively.

  8. Synthesis of resorcinolic lipids bearing structural similarities to cytosporone A

    International Nuclear Information System (INIS)

    Santos, Edson dos Anjos dos; Beatriz, Adilson; Lima, Denis Pires de; Marques, Maria Rita; Leite, Carla Braga

    2009-01-01

    Inspired by the structure and biological activities of resorcinolic lipids and, particularly cytosporone A- a potent inhibitor of plantule germination and growth, we have performed the synthesis of the analogs 3-heptyl-3-hydroxy-5,7-dimethoxy-2-benzofuran-1(3H)-one (1) and 3-heptyl-3-hydroxy-4,6-dimethoxy-2-benzofuran-1(3H)-one (2). The intermediates and products were submitted to allelopathic test using Lactuca sativa L. seeds. Target compound 1 showed an inhibitory effect on germination and growth of hypocotyl and radicle in millimolar range. (author)

  9. Synthesis of resorcinolic lipids bearing structural similarities to cytosporone A

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Edson dos Anjos dos; Beatriz, Adilson; Lima, Denis Pires de [Universidade Federal Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil). Centro de Ciencias Exatas e Tecnologia. Dept. de Quimica], e-mail: dlima@nin.ufms.br; Marques, Maria Rita; Leite, Carla Braga [Universidade Federal Mato Grosso do Sul (UFMS), Campo Grande, MS (Brazil). Centro de Ciencias Biologicas. Dept. de Morfofisiologia

    2009-07-01

    Inspired by the structure and biological activities of resorcinolic lipids and, particularly cytosporone A- a potent inhibitor of plantule germination and growth, we have performed the synthesis of the analogs 3-heptyl-3-hydroxy-5,7-dimethoxy-2-benzofuran-1(3H)-one (1) and 3-heptyl-3-hydroxy-4,6-dimethoxy-2-benzofuran-1(3H)-one (2). The intermediates and products were submitted to allelopathic test using Lactuca sativa L. seeds. Target compound 1 showed an inhibitory effect on germination and growth of hypocotyl and radicle in millimolar range. (author)

  10. Synthesis of resorcinolic lipids bearing structural similarities to cytosporone A

    Directory of Open Access Journals (Sweden)

    Edson dos Anjos dos Santos

    2009-01-01

    Full Text Available Inspired by the structure and biological activities of resorcinolic lipids and, particularly cytosporone A- a potent inhibitor of plantule germination and growth, we have performed the synthesis of the analogs 3-heptyl-3-hydroxy-5,7-dimethoxy-2-benzofuran-1(3H-one (1 and 3-heptyl-3-hydroxy-4,6-dimethoxy-2-benzofuran-1(3H-one (2. The intermediates and products were submitted to allelopathic test using Lactuca sativa L. seeds. Target compound 1 showed an inhibitory effect on germination and growth of hypocotyl and radicle in milimolar range.

  11. High Resolution Powder Diffraction and Structure Determination

    International Nuclear Information System (INIS)

    Cox, D. E.

    1999-01-01

    It is clear that high-resolution synchrotrons X-ray powder diffraction is a very powerful and convenient tool for material characterization and structure determination. Most investigations to date have been carried out under ambient conditions and have focused on structure solution and refinement. The application of high-resolution techniques to increasingly complex structures will certainly represent an important part of future studies, and it has been seen how ab initio solution of structures with perhaps 100 atoms in the asymmetric unit is within the realms of possibility. However, the ease with which temperature-dependence measurements can be made combined with improvements in the technology of position-sensitive detectors will undoubtedly stimulate precise in situ structural studies of phase transitions and related phenomena. One challenge in this area will be to develop high-resolution techniques for ultra-high pressure investigations in diamond anvil cells. This will require highly focused beams and very precise collimation in front of the cell down to dimensions of 50 (micro)m or less. Anomalous scattering offers many interesting possibilities as well. As a means of enhancing scattering contrast it has applications not only to the determination of cation distribution in mixed systems such as the superconducting oxides discussed in Section 9.5.3, but also to the location of specific cations in partially occupied sites, such as the extra-framework positions in zeolites, for example. Another possible application is to provide phasing information for ab initio structure solution. Finally, the precise determination of f as a function of energy through an absorption edge can provide useful information about cation oxidation states, particularly in conjunction with XANES data. In contrast to many experiments at a synchrotron facility, powder diffraction is a relatively simple and user-friendly technique, and most of the procedures and software for data analysis

  12. Controllable synthesis and crystal structure determined upconversion luminescence properties of Tm{sup 3+} (Er{sup 3+}) ions doped YbF{sub 3} and NaYbF{sub 4} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Tao [Institute of Photonics, Faculty of Science, Ningbo University, Ningbo 315211 (China); Qin, Weiping, E-mail: wpqin@jlu.edu.cn [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Zhou, Jun [Institute of Photonics, Faculty of Science, Ningbo University, Ningbo 315211 (China)

    2014-04-01

    Graphical abstract: - Highlights: • The synthesis of YbF{sub 3} and NaYbF{sub 4} crystals was successfully fulfilled by hydrothermal method. • The phase and morphology of products were adjusted by changing the hydrothermal conditions. • Relatively enhanced ultraviolet upconversion emissions were observed in YbF{sub 3} nanocrystals. • The crystalline phase impact on the upconversion luminescence was systematically studied. - Abstract: The synthesis of YbF{sub 3} and NaYbF{sub 4} crystals was successfully fulfilled by a facial hydrothermal method. The phase and morphology of the products were adjusted by changing the surfactant additive and fluorine source and tuning the pH value of the initial solution. The products with various morphologies range from octahedral nanoparticles, corn-like nanobundles, nanospheres, microrods, and hollow microprisms were prepared at different conditions. The growth mechanism of these products has been systematically studied. Impressively, relatively enhanced high order ultraviolet (UV) upconversion (UC) luminescence was observed in Tm{sup 3+} (Er{sup 3+}) ions doped YbF{sub 3} nanocrystals (NCs) compared with NaYbF{sub 4} microcrystals under the excitation of 980 nm infrared laser. The investigation results reveal that the crystal symmetry of matrix has significant effect on the spectra and lifetimes of the doping lanthanide ions. The simply synthesized water soluble YbF{sub 3} NCs with efficient UV UC luminescence may find potential application in biochemistry.

  13. Synthesis of an Albendazole Metabolite: Characterization and HPLC Determination

    Science.gov (United States)

    Mahler, Graciela; Davyt, Danilo; Gordon, Sandra; Incerti, Marcelo; Nunez, Ivana; Pezaroglo, Horacio; Scarone, Laura; Serra, Gloria; Silvera, Mauricio; Manta, Eduardo

    2008-01-01

    In this laboratory activity, students are introduced to the synthesis of an albendazole metabolite obtained by a sulfide oxidation reaction. Albendazole as well as its metabolite, albendazole sulfoxide, are used as anthelmintic drugs. The oxidation reagent is H[subscript 2]O[subscript 2] in acetic acid. The reaction is environmental friendly,…

  14. Synthesis, crystal structure determination, thermal and magnetic properties of the new Cu{sub 0.73}Ni{sub 0.27}(HSeO{sub 3}){sub 2} compound

    Energy Technology Data Exchange (ETDEWEB)

    Hentech, I., E-mail: hentechimen@yahoo.fr [Laboratoire des Sciences des Matériaux et de l' Environnement, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); Zehani, K. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); Kabadou, A.; Ben Salah, A.; Loukil, M. [Laboratoire des Sciences des Matériaux et de l' Environnement, Faculté des Sciences de Sfax, BP 1171, Université de Sfax, 3000 (Tunisia); Bessais, L. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France)

    2017-01-15

    A novel three-dimensional Cu{sub 0.73}Ni{sub 0.27}(HSeO{sub 3}){sub 2} compound was prepared from an aqueous solution. This compound crystallizes in the monoclinic system with P2{sub 1}/n space group and with the following cell parameters: a=6.4379(3) Å; b=7.3555(3) Å; c=5.7522(3) Å; β=93.4341(1)°; V=271.90(2) Å{sup 3} and Z=2. The reported material has been structurally characterized by X-ray powder diffraction and confirmed by scanning electron microscope and energy dispersive spectroscopy (MEB/EDS) analysis. The copper/nickel atom is surrounded by an octahedron coordination of oxygen atoms from sex hydrogenoselenites anions. The presence of (HSeO{sub 3}){sup −} has been further confirmed by IR spectroscopy and this compound exhibits a phase transition at 356 K, this transition has been detected by differential scanning calorimetry and TG-DTA measurement. The magnetic property of this material was determined. The ferromagnetic ordering is further confirmed by the magnetic field dependence of the magnetization (Hysteresis loop) at 10 K. The substitution of Cu by Ni induces a ferro-paramagnetic transition at T=31 K. Field cooled (FC) and Zero field cooled (ZFC) magnetization measurements under an applied field of 100 Oe in the temperature range of 10–300 K were performed. These measurements have been resulted the blocking temperature (T{sub B}) at around 25 K. - Highlights: • A novel three-dimensional Cu{sub 0.73}Ni{sub 0.27}(HSeO{sub 3}){sub 2} compound was prepared from an aqueous solution. • Magnetic measurements reveal the occurrence of weak ferromagnetism at low temperature for this compound. • The substitution of Cu by Ni induces a ferro-paramagnetic transition at T=31 K.

  15. Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

    International Nuclear Information System (INIS)

    Pourmortazavi, Seied Mahdi; Rahimi-Nasrabadi, Mehdi; Khalilian-Shalamzari, Morteza; Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh; Omrani, Ismail

    2012-01-01

    Graphical abstract: NiWO 4 nanoparticles were prepared via precipitation technique. Experimental parameters of procedure were optimized statistically. Highlights: ► NiWO 4 spherical nanoparticles were synthesized via direct precipitation method. ► Taguchi robust design was used for optimization of synthesis reaction parameters. ► Composition and structural properties of NiWO 4 nanoparticles were characterized. ► EDAX, XRD, SEM, FT-IR, UV–vis and photoluminescence techniques were employed. ► Catalytic activity of the product in a cyclo-addition reaction was investigated. - Abstract: Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO 4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO 4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO 4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV–vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.

  16. Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Pourmortazavi, Seied Mahdi, E-mail: pourmortazavi@yahoo.com [Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran (Iran, Islamic Republic of); Rahimi-Nasrabadi, Mehdi, E-mail: rahiminasrabadi@gmail.com [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of); Khalilian-Shalamzari, Morteza [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of); Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh [Islamic Azad University, Varamin Pishva Branch, Varamin (Iran, Islamic Republic of); Omrani, Ismail [Department of Chemistry, Imam Hossein University, Tehran (Iran, Islamic Republic of)

    2012-12-15

    Graphical abstract: NiWO{sub 4} nanoparticles were prepared via precipitation technique. Experimental parameters of procedure were optimized statistically. Highlights: Black-Right-Pointing-Pointer NiWO{sub 4} spherical nanoparticles were synthesized via direct precipitation method. Black-Right-Pointing-Pointer Taguchi robust design was used for optimization of synthesis reaction parameters. Black-Right-Pointing-Pointer Composition and structural properties of NiWO{sub 4} nanoparticles were characterized. Black-Right-Pointing-Pointer EDAX, XRD, SEM, FT-IR, UV-vis and photoluminescence techniques were employed. Black-Right-Pointing-Pointer Catalytic activity of the product in a cyclo-addition reaction was investigated. - Abstract: Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO{sub 4} nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO{sub 4} particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO{sub 4} were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV

  17. Development of nano-structured silicon carbide ceramics: from synthesis of the powder to sintered ceramics

    International Nuclear Information System (INIS)

    Reau, A.

    2008-12-01

    The materials used inside future nuclear reactors will be subjected to very high temperature and neutrons flux. Silicon carbide, in the form of SiC f /SiC nano-structured composite is potentially interesting for this type of application. It is again necessary to verify the contribution of nano-structure on the behaviour of this material under irradiation. To verify the feasibility and determine the properties of the matrix, it was envisaged to produce it by powder metallurgy from SiC nanoparticles. The objective is to obtain a fully dense nano-structured SiC ceramic without additives. For that, a parametric study of the phases of synthesis and agglomeration was carried out, the objective of which is to determine the active mechanisms and the influence of the key parameters. Thus, studying the nano-powder synthesis by laser pyrolysis allowed to produce, with high production rates, homogeneous batches of SiC nanoparticles whose size can be adjusted between 15 and 90 nm. These powders have been densified by an innovating method: Spark Plasma Sintering (SPS). The study and the optimization of the key parameters allowed the densification of silicon carbide ceramic without sintering aids while preserving the nano-structure of material. The thermal and mechanical properties of final materials were studied in order to determine the influence of the microstructure on their properties. (author)

  18. Versatile hydrothermal synthesis of one-dimensional composite structures

    Science.gov (United States)

    Luo, Yonglan

    2008-12-01

    In this paper we report on a versatile hydrothermal approach developed to fabricate one-dimensional (1D) composite structures. Sulfur and selenium formed liquid and adsorbed onto microrods as droplets and subsequently reacted with metallic ion in solution to produce nanoparticles-decorated composite microrods. 1D composites including ZnO/CdS, ZnO/MnS, ZnO/CuS, ZnO/CdSe, and FeOOH/CdS were successfully made using this hydrothermal strategy and the growth mechanism was also discussed. This hydrothermal strategy is simple and green, and can be extended to the synthesis of various 1D composite structures. Moreover, the interaction between the shell nanoparticles and the one-dimensional nanomaterials were confirmed by photoluminescence investigation of ZnO/CdS.

  19. Synthesis, Structure, and Properties of Refractory Hard-Metal Borides

    Science.gov (United States)

    Lech, Andrew Thomas

    As the limits of what can be achieved with conventional hard compounds, such as tungsten carbide, are nearing reach, super-hard materials are an area of increasing industrial interest. The refractory hard metal borides, such as ReB2 and WB4, offer an increasingly attractive alternative to diamond and cubic boron nitride as a next-generation tool material. In this Thesis, a thorough discussion is made of the progress achieved by our laboratory towards understanding the synthesis, structure, and properties of these extremely hard compounds. Particular emphasis is placed on structural manipulation, solid solution formation, and the unique crystallographic manifestations of what might also be called "super-hard metals".

  20. Synthesis of arborescent model polymer structures by living carbocationic polymerization for structure-property studies

    Science.gov (United States)

    Dos Santos Freire, Lucas

    Polyisobutylene is fully saturated, therefore exhibits outstanding chemical, oxidative and thermal stability,1 which makes it ideally suitable as a model to study mechanical and viscoelastic properties of elastomers, and to correlate properties with structure. The main objective of this dissertation was to develop a fundamental understanding of the mechanism of the synthesis of arborescent (hyperbranched) polyisobutylene (arbPIB) by inimer-type (initiator-monomer) living carbocationic polymerization. The strategy for the effective synthesis of arbPIBs consists of copolymerizing the 4-(2-methoxyisopropyl)styrene (IUPAC name: p-vinylcumyl methyl ether) (IB) via controlled/living carbocationic polymerization using TiCl4 coinitiator. In situ FTIR monitoring showed that the self-condensing vinyl polymerization (SCVP) of MeOIM is possible, and that when copolymerizing MeOIM and IB, a nearly alternating structure and multiple end groups are obtained. arbPIB was synthesized and the repeatability of the polymerization was demonstrated. It was found that higher branching was obtained with increasing [MeOIM] and that branching did not further increase if additional IB was added after the MeOIM had reacted completely. No evident changes were observed when switching solvents from Hx/MeCl to a MeCHx/MeCl mixture. Branching parameters showed that arbPIBs have a behavior between polydisperse stars and polycondensates with the number of branches increasing linearly with molecular weight. Novel arbPIB-based block copolymers (TPEs) were synthesized and it was found that copolymers with low Tg short end blocks and less than 5 mol% of a second monomer exhibit thermoplastic elastomeric properties. The materials were strongly reinforced when compounded with carbon black. arbPIB-b-PS are prospective biomaterials and the establishment of reliable methods for evaluating their short and long term properties is a subject of great importance. A dynamic fatigue testing methodology was developed

  1. Facile synthesis of a silver nanoparticles/polypyrrole nanocomposite for non-enzymatic glucose determination.

    Science.gov (United States)

    Poletti Papi, Maurício A; Caetano, Fabio R; Bergamini, Márcio F; Marcolino-Junior, Luiz H

    2017-06-01

    The present work describes the synthesis of a new conductive nanocomposite based on polypyrrole (PPy) and silver nanoparticles (PPy-AgNP) based on a facile reverse microemulsion method and its application as a non-enzymatic electrochemical sensor for glucose detection. Focusing on the best sensor performance, all experimental parameters used in the synthesis of nanocomposite were optimized based on its electrochemical response for glucose. Characterization of the optimized material by FT-IR, cyclic voltammetry, and DRX measurements and TEM images showed good monodispersion of semispherical Ag nanoparticles capped by PPy structure, with size average of 12±5nm. Under the best analytical conditions, the proposed sensor exhibited glucose response in linear dynamic range of 25 to 2500μmolL -1 , with limit of detection of 3.6μmolL -1 . Recovery studies with human saliva samples varying from 99 to 105% revealed the accuracy and feasibility of a non-enzymatic electrochemical sensor for glucose determination by easy construction and low-cost. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Facile synthesis of gold nanomaterials with unusual crystal structures.

    Science.gov (United States)

    Fan, Zhanxi; Huang, Xiao; Chen, Ye; Huang, Wei; Zhang, Hua

    2017-11-01

    Gold (Au) nanomaterials have attracted wide research attention, owing to their high chemical stability, promising catalytic properties, excellent biocompatibility, unique electronic structure and outstanding localized surface plasmon resonance (LSPR) absorption properties; all of which are closely related to their size and shape. Recently, crystal-phase-controlled synthesis of noble metal nanomaterials has emerged as a promising strategy to tune their physicochemical properties. This protocol describes the detailed experimental procedures for the crystal-phase-controlled syntheses of Au nanomaterials with unusual crystal structures under mild conditions. Briefly, pure hexagonal close-packed (hcp) Au square sheets (AuSSs) with a thickness of ∼2.4 nm are synthesized using a graphene-oxide-assisted method in which HAuCl 4 is reduced by oleylamine in a mixture of hexane and ethanol. By using pure hexane as the solvent, well-dispersed ultrathin hcp/face-centered cubic (fcc) Au nanowires with a diameter of ∼1.6 nm on graphene oxide can be obtained. Meanwhile, hcp/fcc Au square-like plates with a side length of 200-400 nm are prepared via the secondary growth of Au on the hcp AuSSs. Remarkably, hexagonal (4H) Au nanoribbons with a thickness of 2.0-6.0 nm can be synthesized with a one-pot colloidal method in which HAuCl 4 is reduced by oleylamine in a mixed solvent of hexane and 1,2-dichloropropane. It takes 17-37 h for the synthesis of these Au nanomaterials with unusual crystal structures. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) are used to characterize the resultant Au nanomaterials, which could have many promising applications, such as biosensing, near-IR photothermal therapy, catalysis and surface-enhanced Raman scattering (SERS).

  3. Structure determination by X-ray crystallography

    CERN Document Server

    Ladd, M F C

    1977-01-01

    Crystallography may be described as the science of the structure of materi­ als, using this word in its widest sense, and its ramifications are apparent over a broad front of current scientific endeavor. It is not surprising, therefore, to find that most universities offer some aspects of crystallography in their undergraduate courses in the physical sciences. It is the principal aim of this book to present an introduction to structure determination by X-ray crystal­ lography that is appropriate mainly to both final-year undergraduate studies in crystallography, chemistry, and chemical physics, and introductory post­ graduate work in this area of crystallography. We believe that the book will be of interest in other disciplines, such as physics, metallurgy, biochemistry, and geology, where crystallography has an important part to play. In the space of one book, it is not possible either to cover all aspects of crystallography or to treat all the subject matter completely rigorously. In particular, certain ...

  4. Synthesis, structure characterization and catalytic activity of nickel tungstate nanoparticles

    Science.gov (United States)

    Pourmortazavi, Seied Mahdi; Rahimi-Nasrabadi, Mehdi; Khalilian-Shalamzari, Morteza; Zahedi, Mir Mahdi; Hajimirsadeghi, Seiedeh Somayyeh; Omrani, Ismail

    2012-12-01

    Taguchi robust design was applied to optimize experimental parameters for controllable, simple and fast synthesis of nickel tungstate nanoparticles. NiWO4 nanoparticles were synthesized by precipitation reaction involving addition of nickel ion solution to the tungstate aqueous reagent and then formation of nickel tungstate nucleolus which are insoluble in aqueous media. Effects of various parameters such as nickel and tungstate concentrations, flow rate of reagent addition and reactor temperature on diameter of synthesized nickel tungstate nanoparticles were investigated experimentally by the aid of orthogonal array design. The results for analysis of variance (ANOVA) showed that particle size of nickel tungstate can be effectively tuned by controlling significant variables involving nickel and tungstate concentrations and flow rate; while, temperature of the reactor has a no considerable effect on the size of NiWO4 particles. The ANOVA results proposed the optimum conditions for synthesis of nickel tungstate nanoparticles via this technique. Also, under optimum condition nanoparticles of NiWO4 were prepared and their structure and chemical composition were characterized by means of EDAX, XRD, SEM, FT-IR spectroscopy, UV-vis spectroscopy, and photoluminescence. Finally, catalytic activity of the nanoparticles in a cycloaddition reaction was examined.

  5. Synthesis and crystal structure of chromium-bearing anhydrous wadsleyite

    Science.gov (United States)

    Sirotkina, E. A.; Bindi, L.; Bobrov, A. V.; Aksenov, S. M.; Irifune, T.

    2018-04-01

    A chromium-bearing wadsleyite (Cr- Wad) was synthesized in the model system Mg2SiO4-MgCr2O4 at 14 GPa and 1600 °C and studied from the chemical and structural point of views. Microprobe data gave the formula Mg1.930Cr0.120Si0.945O4, on the basis of 4 oxygen atoms. The crystal structure has been studied by single-crystal X-ray diffraction. The orthorhombic unit-cell parameters are: a = 5.6909(5) Å, b = 11.4640(10) Å, c = 8.2406(9) Å, V = 537.62(9) Å3, Z = 8. The structure, space group Imma, was refined to R 1 = 5.99% in anisotropic approximation using 1135 reflections with F o > 4σ( F o) and 43 parameters. Chromium was found to substitute for both Mg at the octahedral sites and Si at the tetrahedral site, according to the reaction VIMg2+ + IVSi4+ = VICr3+ + IVCr3+. On the whole, the structural topology is nearly identical to that of pure wadsleyite. The successful synthesis of Cr- Wad may be important for the thermobarometry of mantle phase associations.

  6. Magnesium substitutions in rare-earth metal germanides with the Gd5Si4 type. Synthesis, structure determination and magnetic properties of RE5-xMgxGe4 (RE=Gd-Tm, Lu and Y)

    Energy Technology Data Exchange (ETDEWEB)

    Sarrao, J L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Tobash, P H [UNIV. OF DE; Bobev, S [UNIV. OF DE

    2009-01-01

    A series of magnesium-substituted rare-earth metal germanides with a general formula RE{sub 5-x}Mg{sub x}Ge{sub 4} (x {approx} 1.0-2.3; RE =Gd-Tm, Lu, Y) have been synthesized by high-temperature reactions and structurally characterized by single-crystal X-ray diffraction. These compounds crystallize with the common Gd{sub 5}Si{sub 4} type in the orthorhombic space group Pnma (No. 62; Z =4; Pearson's code oP36) and do not appear to undergo temperature-induced crystallographic phase transitions down to 120 K. Replacing rare-earth metal atoms with Mg, up to nearly 45 % at., reduces the valence electron count and is clearly expressed in the subtle changes of the Ge-Ge and metal-metal bonding. Magnetization measurements as a function of the temperature and the applied field reveal complex magnetic structures at cryogenic temperatures, and Curie-Weiss paramagnetic behavior at higher temperatures. The observed local moment magnetism is consistent with RE+ ground states in all cases. In the magnetically ordered phases, the magnetization cannot reach saturation in fields up to 50 kOe. The structural trends across the series and the variations of hte magnetic properties as a function of the Mg content are also discussed. KEYWORDS: Rare-earth intermetallics, germanides, crystal structure,Gd{sub 5}Si{sub 4} type.

  7. Simple synthesis, structure and ab initio study of 1,4-benzodiazepine-2,5-diones

    Science.gov (United States)

    Jadidi, Khosrow; Aryan, Reza; Mehrdad, Morteza; Lügger, Thomas; Ekkehardt Hahn, F.; Ng, Seik Weng

    2004-04-01

    A simple procedure for the synthesis of pyrido[2,1-c][1,4] benzodiazepine-6,12-dione ( 1) and 1,4-benzodiazepine-2,5-diones ( 2a- 2d), using microwave irradiation and/or conventional heating is reported. The configuration of 1 was determined by single-crystal X-ray diffraction. A detailed ab initio B3LYP/6-31G* calculation of structural parameters and substituent effects on ring inversion barriers (Δ G#) and also free energy differences (Δ G0) for benzodiazepines are reported.

  8. Solid-phase synthesis of yttrium ferrites with structures of perovskite and garnet

    Energy Technology Data Exchange (ETDEWEB)

    Tkachenko, E V; Shapovalov, A G; Aksel' rod, N L; Pazdnikov, I P [Ural' skij Gosudarstvennyj Univ., Sverdlovsk (USSR)

    1980-09-01

    The solid phase synthesis of yttrium ferrites having a perovskite- and garnet-like structure has been investigated in the temperature range from 800 to 1500 deg C and temper times of up to 80 hours by reaction zone simulation and magnetic phase analysis. It is shown that for conversion degrees d<0.15 the reactions are diffusion-controlled. The rate constants and effective diffusion in the formation of YFeO/sub 3/ and Y/sub 3/Fe/sub 5/O/sub 12/ have been determined.

  9. Synthesis, characterization and crystal structure determination of a new Zn(II Schiff base complex derived from condensation of a new asymmetrical tripodal amine, 3-((4-aminobutyl(pyridin-2-ylmethylaminopropan-1-ol and 2-hydroxy-3-methoxybenzaldehyde

    Directory of Open Access Journals (Sweden)

    Majid Rezaeivala

    2017-05-01

    Full Text Available A new tripodal amine, 3-((4-aminobutyl(pyridin-2-ylmethylaminopropan-1-ol (HL has been prepared. This has been used to synthesize a new Schiff base complex by template condensation with 2-hydroxy-3-methoxybenzaldehyde in the presence of Zn(II metal ion in methanol. The complex has been characterized using spectroscopic methods and the crystal structure of [ZnL]BF4, L:3-((4-aminobutyl(pyridin-2-ylmethylaminopropan-1-ol was confirmed by single crystal X-ray diffraction studies. Single crystal X-ray structure analysis showed that in the mononuclear Zn(II complex, [ZnL]BF4 the Zn(II ion is in a distorted square pyramidal environment.

  10. Poliovirus RNA synthesis in vitro: structural elements and antibody inhibition

    International Nuclear Information System (INIS)

    Semler, B.L.; Hanecak, R.; Dorner, L.F.; Anderson, C.W.; Wimmer, E.

    1983-01-01

    The poliovirus RNA polymerase complex has been analyzed by immunoautoradiography using antibody probes derived from purified replicase (P3) region viral polypeptides. Antibody preparations made against the polio RNA polymerase, P3-4b, detected a previously unreported cellular protein that copurifies with the RNA polymerase. An IgG fraction purified from rabbit antiserum to polypeptide P3-2, a precursor fo the RNA polymerase, specifically inhibits poliovirus RNA synthesis in vitro. The authors have also immunoprecipitated a 60,000-dalton protein (P3-4a) with antiserum to protein P3-4b and have determined the precise genomic map position of this protein by automated Edman degradation. Protein P3-4a originates by cleavage of the RNA polymerase precursor at a glutamine-glucine amino acid pair not previously reported to be a viral cleavage site

  11. Synthesis and structural studies of copper sulfide nanocrystals

    Directory of Open Access Journals (Sweden)

    Peter A. Ajibade

    Full Text Available We report the synthesis and structural studies of copper sulfide nanocrystals from copper(II dithiocarbamate single molecule precursors. The optical studies of the as-prepared copper sulfide nanoparticles were carried out using UV–Visible and photoluminescence spectroscopy. The absorption spectra show absorption band edges at 287 nm and exhibit considerable blue shift that could be ascribed to the quantum confinement effects as a result of the small crystallite sizes of the nanoparticles and the photoluminescence spectra show emission curves that are red shifted with respect to the absorption band edges. The structural studies were carried out using powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The XRD patterns revealed the formation of hexagonal structure of covellite CuS with estimated crystallite sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microsphere on the surfaces and EDS spectra confirmed the presence of CuS nanoparticles. Keywords: CuS, Dithiocarbamate, Nanoparticles, Electron microscopy, AFM

  12. Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

    KAUST Repository

    Zeng, Shangjing; Wang, Runwei; Li, Ang; Huang, Weiwei; Zhang, Zongtao; Qiu, Shilun

    2016-01-01

    A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity

  13. Synthesis, crystal structure determination, biological screening and docking studies of N1-substituted derivatives of 2,3-dihydroquinazolin-4(1H)-one as inhibitors of cholinesterases.

    Science.gov (United States)

    Sultana, Nargis; Sarfraz, Muhammad; Tanoli, Saba Tahir; Akram, Muhammad Safwan; Sadiq, Abdul; Rashid, Umer; Tariq, Muhammad Ilyas

    2017-06-01

    Pursuing the strategy of developing potent AChE inhibitors, we attempted to carry out the N 1 -substitution of 2,3-dihydroquinazolin-4(1H)-one core. A set of 32 N-alkylated/benzylated quinazoline derivatives were synthesized, characterized and evaluated for their inhibition against cholinesterases. N-alkylation of the series of the compounds reported previously (N-unsubstituted) resulted in improved activity. All the compounds showed inhibition of both enzymes in the micromolar to submicromolar range. Structure activity relationship (SAR) of the 32 derivatives showed that N-benzylated compounds possess good activity than N-alkylated compounds. N-benzylated compounds 2ad and 2af were found very active with their IC 50 values toward AChE in submicromolar range (0.8µM and 0.6µM respectively). Binding modes of the synthesized compounds were explored by using GOLD (Genetic Optimization for Ligand Docking) suit v5.4.1. Computational predictions of ADMET studies reveal that all the compounds have good pharmacokinetic properties with no AMES toxicity and carcinogenicity. Moreover, all the compounds are predicted to be absorbed in human intestine and also have the ability to cross blood brain barrier. Overall, the synthesized compounds have established a structural foundation for the design of new inhibitors of cholinesterase. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Synthesis and structure determination of new open-framework chromium carboxylate MIL-105 or CrIII(OH).{O2C-C6(CH3)4-CO2}.nH2O

    International Nuclear Information System (INIS)

    Serre, Christian; Millange, Franck; Devic, Thomas; Audebrand, Nathalie; Van Beek, Wouter

    2006-01-01

    Two new three-dimensional chromium(III) dicarboxylate, MIL-105 or Cr III (OH).{O 2 C-C 6 (CH 3 ) 4 -CO 2 }.nH 2 O, have been obtained under hydrothermal conditions, and their structures solved using X-ray powder diffraction data. Both solids are structural analogs of the known Cr benzenedicarboxylate compound (MIL-53). Both contain trans corner-sharing CrO 4 (OH) 2 octahedral chains connected by tetramethylterephthalate di-anions. Each chain is linked by the ligands to four other chains to form a three-dimensional framework with an array of 1D pores channels. The pores of the high temperature form of the solid, MIL-105ht, are empty. However, MIL-105ht re-hydrates at room temperature to finally give MIL-105lt with pores channels filled with free water molecules (lt: low temperature form; ht: high temperature form). The thermal behaviour of the two solids has been investigated using TGA. Crystal data for MIL-105ht: monoclinic space group C2/c with a = 19.653(1) A, b = 9.984(1) A, c = 6.970(1) A, β = 110.67(1) o and Z = 4. Crystal data for MIL-105lt: orthorhombic space group Pnam with a = 17.892(1) A, b = 11.165(1) A, c = 6.916(1) A and Z = 4

  15. Metal-organic frameworks: structure, properties, methods of synthesis and characterization

    International Nuclear Information System (INIS)

    Butova, V V; Soldatov, M A; Guda, A A; Lomachenko, K A; Lamberti, C

    2016-01-01

    This review deals with key methods of synthesis and characterization of metal-organic frameworks (MOFs). The modular structure affords a wide variety of MOFs with different active metal sites and organic linkers. These compounds represent a new stage of development of porous materials in which the pore size and the active site structure can be modified within wide limits. The set of experimental methods considered in this review is sufficient for studying the short-range and long-range order of the MOF crystal structure, determining the morphology of samples and elucidating the processes that occur at the active metal site in the course of chemical reactions. The interest in metal-organic frameworks results, first of all, from their numerous possible applications, ranging from gas separation and storage to chemical reactions within the pores. The bibliography includes 362 references

  16. Synthesis, characterization and structural refinement of polycrystalline uranium substituted zirconolite

    International Nuclear Information System (INIS)

    Shrivastava, O.P.; Narendra Kumar; Sharma, I.B.

    2005-01-01

    Ceramic precursors of Zirconolite (CaZrTi 2 O 7 ) family have a remarkable property of substitution Zr 4+ cationic sites. This makes them potential material for nuclear waste management in 'synroc' technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a solid phase of composition CaZr 0.95 U 0.5 Ti 2 O 7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050 degC. The polycrystalline solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (15). The following unit cell parameters have been calculated: a =12.4883(15), b =7.2448(5), c 11.3973(10) and β = 100.615(9)0. The structure was refined to satisfactory completion. The Rp and Rwp are found to be 7.48% and 9.74% respectively. (author)

  17. Synthesis and conductivity of heptadecatungstovanadodiphosphoric heteropoly acid with Dawson structure

    Energy Technology Data Exchange (ETDEWEB)

    Tong Xia; Zhu Weiming [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Wu Qingyin, E-mail: qywu@zju.edu.cn [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Qian Xueyu; Liu Zhen [Department of Chemistry, Zhejiang University, Hangzhou 310027 (China); Yan Wenfu [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012 (China); Gong Jian [Key Lab of Polyoxometalate Science, the Ministry of Education, Northeast Normal University, Changchun 130024 (China)

    2011-07-21

    A new solid high-proton conductor, heptadecatungstovanadodiphosphoric heteropoly acid H{sub 7}P{sub 2}W{sub 17}VO{sub 62}.28H{sub 2}O with Dawson structure was synthesized by the stepwise acidification and the stepwise addition of element solutions. The optimal proportion of component compounds in the synthesis reaction was given. The product was characterized by chemical analysis, potentiometric titration, IR, UV, XRD, {sup 31}P NMR, TG-DTA and electrochemical impedance spectroscopy (EIS). The results indicate that H{sub 7}P{sub 2}W{sub 17}VO{sub 62}.28H{sub 2}O possesses the Dawson structure. EIS measurements show a high conductivity (3.10 x 10{sup -2} S cm{sup -1} at 26 deg. C and 75% relative humidity), with an activation energy of 32.23 kJ mol{sup -1} for proton conduction. The mechanism of proton conduction for this heteropoly acid is Vehicle mechanism.

  18. Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis

    Directory of Open Access Journals (Sweden)

    Boyce Mark

    2012-08-01

    Full Text Available Abstract Background Bluetongue virus (BTV is a double-stranded RNA (dsRNA virus of the Reoviridae family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the Orbivirus genus has not been investigated. Results Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1 as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3′ poly(A sequence identifying the 3′ end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA. Conclusions NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed

  19. Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis.

    Science.gov (United States)

    Boyce, Mark; Celma, Cristina C P; Roy, Polly

    2012-08-29

    Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus of the Reoviridae family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp) as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the Orbivirus genus has not been investigated. Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1) as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs) of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3' poly(A) sequence identifying the 3' end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA. NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed replacement of cellular protein synthesis with viral protein

  20. Synthesis of TiO 2 nanostructured reservoir with temozolomide: Structural evolution of the occluded drug

    Science.gov (United States)

    López, T.; Sotelo, J.; Navarrete, J.; Ascencio, J. A.

    2006-10-01

    Sol-gel synthesized nanostructured TiO 2 matrix were produced with different channel sizes, where drug are immersed, producing a reservoir with Temozolomide (TMZ). This drug is particularly important for the treatment of cancer tumors, which are fundamentally a consequence of the uncontrolled reproduction of human cell. In this way the chemotherapy plays an important role in the treatment of both recurrent and newly diagnosed patients. In the handling of brain tumors TMZ has been discovered as a recent and efficient second generation drug employed in the control of advanced brain gliomas, and it is a welcome addition. Its active component binds to the cancerous DNA cells, thus preventing their disordered growth, destroying them. In this work, we report the synthesis of TiO 2 nanostructured reservoir with TMZ, focusing the effort to the understanding of structural effects on the TMZ configuration by using nuclear magnetic resonance, Raman and IR spectroscopy methods. Our results establish that TMZ molecules are quite sensible to chemical processes and it produces the activation of the molecule, which is followed and understood with help of quantum molecular simulation methods. The study of the molecules allows determining the conditions that produce the activation and chemical selectivity of the molecules, which determines the conditions of synthesis. This information gives parameters for the reservoir structural and chemical optimization.

  1. The crystal structure of escherichia coli MoaB suggests a probable role in molybdenum cofactor synthesis

    International Nuclear Information System (INIS)

    Sanishvili, R.; Beasley, S.; Skarina, T; Glesne, D; Joachimiak, A; Edwards, A; Savchenko, A.; Univ. Health Network; Univ. of Toronto

    2004-01-01

    The crystal structure of Escherichia coli MoaB was determined by multiwavelength anomalous diffraction phasing and refined at 1.6 Angstrom resolution. The molecule displayed a modified Rossman fold. MoaB is assembled into a hexamer composed of two trimers. The monomers have high structural similarity with two proteins, MogA and MoeA, from the molybdenum cofactor synthesis pathway in E. Coli, as well as with domains of mammalian gephyrin and plant Cnx1, which are also involved in molybdopterin synthesis. Structural comparison between these proteins and the amino acid conservation patterns revealed a putative active site in MoaB. The structural analysis of this site allowed to advance several hypothesis which can be tested in further studies

  2. Overcoming barriers to membrane protein structure determination.

    Science.gov (United States)

    Bill, Roslyn M; Henderson, Peter J F; Iwata, So; Kunji, Edmund R S; Michel, Hartmut; Neutze, Richard; Newstead, Simon; Poolman, Bert; Tate, Christopher G; Vogel, Horst

    2011-04-01

    After decades of slow progress, the pace of research on membrane protein structures is beginning to quicken thanks to various improvements in technology, including protein engineering and microfocus X-ray diffraction. Here we review these developments and, where possible, highlight generic new approaches to solving membrane protein structures based on recent technological advances. Rational approaches to overcoming the bottlenecks in the field are urgently required as membrane proteins, which typically comprise ~30% of the proteomes of organisms, are dramatically under-represented in the structural database of the Protein Data Bank.

  3. determination of verticality of reservoir engineering structure

    African Journals Online (AJOL)

    user

    applications is 3D survey and management of oil and gas facilities and other engineering structures. This recent .... also affect ground water contamination. 2. VERTICALITY ...... The soil, water and concrete in a Reservoir at the foundation bed ...

  4. DETERMINANTS OF FINANCIAL STRUCTURE OF GREEK COMPANIES

    Directory of Open Access Journals (Sweden)

    Gargalis PANAGIOTIS

    2016-06-01

    Full Text Available Capital structure is essential for the survival, growth and performance of a firm. There has been a growing interest worldwide in identifying the factors associated with debt leverage. This article aims to investigate the factors affecting the capital structure of companies listed on the Athens Stock Exchange (ASE. The data set used is composed of indicators reflecting the financial position and performance of 40 firms listed on the ASE in 2014. Using a regression model we estimate in what extent the financial structure of companies is affected by performance indicators and other specific factors like the field of activity or the size of the firms. The results obtained show an important influence of share of tangible assets in total assets of the company on the financial leverage, as main variable selected in order to reflect the capital structure of Greek companies.

  5. Synthesis, crystal structure determination of two-dimensional ...

    Indian Academy of Sciences (India)

    Abstract. The 2-D polymeric complex (I) has the formula [Ag(phSE)(NO3)]n, which has been crystallized from methanol-acetonitrile mixture and characterized by elemental analysis and single-crystal X-ray diffraction analysis. In this polymer, each Ag(I) ion occupies distorted trigonal pyramidal geometry coordinating with two.

  6. Synthesis, crystal structures and properties of lead phosphite compounds

    International Nuclear Information System (INIS)

    Song, Jun-Ling; Hu, Chun-Li; Xu, Xiang; Kong, Fang; Mao, Jiang-Gao

    2015-01-01

    Here, we report the preparation and characterization of two lead(II) phosphites, namely, Pb_2(HPO_3)_2 and Pb_2(HPO_3)(NO_3)_2 through hydrothermal reaction or simple solution synthesis, respectively. A new lead phosphite, namely, Pb_2(HPO_3)_2, crystallizes in the noncentrosymmetric space group Cmc2_1 (no. 36), which features 3D framework formed by the interconnection of 2D layer of lead(II) phosphites and 1D chain of [Pb(HPO_3)_5]_∞. The nonlinear optical properties of Pb_2(HPO_3)(NO_3)_2 have been studied for the first time. The synergistic effect of the stereo-active lone-pairs on Pb"2"+ cations and π-conjugated NO_3 units in Pb_2(HPO_3)(NO_3)_2 produces a moderate second harmonic generation (SHG) response of ∼1.8×KDP (KH_2PO_4), which is phase matchable (type I). IR, UV–vis spectra and thermogravimetric analysis (TGA) for the two compounds were also measured. - Graphical abstract: Two lead phosphites Pb_2(HPO_3)_2 and Pb_2(HPO_3)(NO_3)_2 are studied. A new lead phosphite Pb_2(HPO_3)_2 features a unique 3D framework structure and Pb_2(HPO_3)(NO_3)_2 shows a moderate SHG response of ∼1.8×KDP (KH_2PO_4). - Highlights: • A new lead phosphite, Pb_2(HPO_3)_2 is reported. • Pb_2(HPO_3)_2 features a unique 3D framework structure. • NLO property of Pb_2(HPO_3)(NO_3)_2 is investigated. • Pb_2(HPO_3)(NO_3)_2 produces a moderate SHG response of ∼1.8×KDP (KH_2PO_4).

  7. Structural Synthesis of 3-DoF Spatial Fully Parallel Manipulators

    Directory of Open Access Journals (Sweden)

    Alfonso Hernandez

    2014-07-01

    Full Text Available In this paper, the architectures of three degrees of freedom (3-DoF spatial, fully parallel manipulators (PMs, whose limbs are structurally identical, are obtained systematically. To do this, the methodology followed makes use of the concepts of the displacement group theory of rigid body motion. This theory works with so-called ‘motion generators’. That is, every limb is a kinematic chain that produces a certain type of displacement in the mobile platform or end-effector. The laws of group algebra will determine the actual motion pattern of the end-effector. The structural synthesis is a combinatorial process of different kinematic chains’ topologies employed in order to get all of the 3-DoF motion pattern possibilities in the end-effector of the fully parallel manipulator.

  8. Synthesis and Structural Characterization of 1- and 2-Substituted Indazoles: Ester and Carboxylic Acid Derivatives

    Directory of Open Access Journals (Sweden)

    Isabel Bento

    2006-11-01

    Full Text Available A series of indazoles substituted at the N-1 and N-2 positions with ester-containing side chains -(CH2nCO2R of different lengths (n = 0-6, 9, 10 are described.Nucleophilic substitution reactions on halo esters (X(CH2nCO2R by 1H-indazole inalkaline solution lead to mixtures of N-1 and N-2 isomers, in which the N-1 isomerpredominates. Basic hydrolysis of the ester derivatives allowed the synthesis of thecorresponding indazole carboxylic acids. All compounds were fully characterised bymultinuclear NMR and IR spectroscopies, MS spectrometry and elemental analysis; theNMR spectroscopic data were used for structural assignment of the N-1 and N-2 isomers.The molecular structure of indazol-2-yl-acetic acid (5b was determined by X-raydiffraction, which shows a supramolecular architecture involving O2-H...N1intermolecular hydrogen bonds.

  9. Science achievement determinants: factorial structure of family ...

    African Journals Online (AJOL)

    The family plays an important role in determining the academic achievement ... parents' assistance, expectation, and encouragement in their children's mathematics ... suggested that cultural upbringing is a strong factor contributing to the.

  10. Structure determination by X-ray crystallography

    CERN Document Server

    Ladd, M F C

    1995-01-01

    X-ray crystallography provides us with the most accurate picture we can get of atomic and molecular structures in crystals. It provides a hard bedrock of structural results in chemistry and in mineralogy. In biology, where the structures are not fully crystalline, it can still provide valuable results and, indeed, the impact here has been revolutionary. It is still an immense field for young workers, and no doubt will provide yet more striking develop­ ments of a major character. It does, however, require a wide range of intellectual application, and a considerable ability in many fields. This book will provide much help. It is a very straightforward and thorough guide to every aspect of the subject. The authors are experienced both as research workers themselves and as teachers of standing, and this is shown in their clarity of exposition. There are plenty of iliustrations and worked examples to aid the student to obtain a real grasp of the subject.

  11. Structural determinants in the bulk heterojunction.

    Science.gov (United States)

    Acocella, Angela; Höfinger, Siegfried; Haunschmid, Ernst; Pop, Sergiu C; Narumi, Tetsu; Yasuoka, Kenji; Yasui, Masato; Zerbetto, Francesco

    2018-02-21

    Photovoltaics is one of the key areas in renewable energy research with remarkable progress made every year. Here we consider the case of a photoactive material and study its structural composition and the resulting consequences for the fundamental processes driving solar energy conversion. A multiscale approach is used to characterize essential molecular properties of the light-absorbing layer. A selection of bulk-representative pairs of donor/acceptor molecules is extracted from the molecular dynamics simulation of the bulk heterojunction and analyzed at increasing levels of detail. Significantly increased ground state energies together with an array of additional structural characteristics are identified that all point towards an auxiliary role of the material's structural organization in mediating charge-transfer and -separation. Mechanistic studies of the type presented here can provide important insights into fundamental principles governing solar energy conversion in next-generation photovoltaic devices.

  12. Some structural determinants of melody recall.

    Science.gov (United States)

    Boltz, M

    1991-05-01

    Sophisticated musicians were asked to recall, using musical notation, a set of unfamiliar folk tunes that varied in rhythmic structure and referents of tonality. The results showed that memory was facilitated by tonic triad members marking phrase endings, but only when their presence was highlighted by a corresponding pattern of temporal accents. Conversely, recall significantly declined when tonal information was either absent or obscured by rhythmic structure. Error analyses further revealed that the retention of overall pitch contour and information at phrase ending points varied as a function of these manipulations. The results are discussed in terms of a framework that links the acts of perceiving and remembering to a common attentional scheme.

  13. Overcoming barriers to membrane protein structure determination

    NARCIS (Netherlands)

    Bill, Roslyn M.; Henderson, Peter J. F.; Iwata, So; Kunji, Edmund R. S.; Michel, Hartmut; Neutze, Richard; Newstead, Simon; Poolman, Bert; Tate, Christopher G.; Vogel, Horst

    After decades of slow progress, the pace of research on membrane protein structures is beginning to quicken thanks to various improvements in technology, including protein engineering and microfocus X-ray diffraction. Here we review these developments and, where possible, highlight generic new

  14. Structural determination and gynecological tumor diagnosis using ...

    African Journals Online (AJOL)

    covalent bonding patterns and branched structures. Studies have shown that changes in protein glycosylation at the cell surface during tumorigenesis are closely related to the occurrence and development of some cancers, including pancreatic cancer, mammary cancer, prostatic cancer, colon cancer, and gastric cancer [1].

  15. Determining the structure of Carbon-60

    International Nuclear Information System (INIS)

    Wif, D.

    1994-01-01

    Carbon-60 is the most stable and best known of the carbon cage structures known collectively as the fullerenes. It is a remarkable molecule that forms a fascinating solid. Although the molecular shape of C sub 6 sub 0 is familiar - it is simply the shape of a soccer ball with 12 pentagons and 20 hexagons - the manner in which it forms a crystal structure is by no means obvious. This talk will focus on the insights which neutron scattering at ISIS has brought to our understanding of solid C sub6 sub 0. At room temperature, the structure may be regarded as forming as essentially ideal cubic-close packed molecular b ubble-raft : each molecule is reorienting so rapidly that a time-averaged picture, over as little as a nanosecond, reveals a closely spherical shell of atomic density. At 260 K, a rather unusual structural transition occurs. The molecules order but still retain cubic symmetry. Although this may not appear to be a rather dramatic change, detailed considerations show that a profound transition has occurred that bears close similarities to a solid-liquid phase transition but in two dimensions. Below 260 K, reorientation still occurs but at a dramatically reduced rate as the temperature is lowered. Indeed at around 90 K, The reorientation is so slow that thermodynamic equilibrium cannot be achieved in a reasonable timescale an orientational glass transition occurs. Although the behaviour of solid C sub 6 sub 0 undergoes dramatic changes as a function of temperature, a coherent description has evolved in which neutron scattering plays a central role. Close analogies are to be found in the study of systems as diverse as solid H sub 2 and human-rhinovirus structures. These analogies and the central role played by neutron scattering at ISIS will be emphasised in this paper. 5 figs., 10 refs. (author)

  16. Synthesis, X-ray crystal structure, DNA binding and Nuclease activity ...

    Indian Academy of Sciences (India)

    s12039-016-1125-x. Synthesis, X-ray crystal structure, DNA binding and Nuclease activity of lanthanide(III) complexes of 2-benzoylpyridine acetylhydrazone. KARREDDULA RAJA, AKKILI SUSEELAMMA and KATREDDI HUSSAIN REDDY. ∗.

  17. Vascular structure determines pulmonary blood flow distribution

    Science.gov (United States)

    Hlastala, M. P.; Glenny, R. W.

    1999-01-01

    Scientific knowledge develops through the evolution of new concepts. This process is usually driven by new methodologies that provide observations not previously available. Understanding of pulmonary blood flow determinants advanced significantly in the 1960s and is now changing rapidly again, because of increased spatial resolution of regional pulmonary blood flow measurements.

  18. Using Combustion Synthesis to Reinforce Berms and Other Regolith Structures

    Science.gov (United States)

    Rodriquez, Gary

    2013-01-01

    The Moonraker Excavator and other tools under development for use on the Moon, Mars, and asteroids will be employed to construct a number of civil engineering projects and to mine the soil. Mounds of loose soil will be subject to the local transport mechanisms plus artificial mechanisms such as blast effects from landers and erosion from surface vehicles. Some of these structures will require some permanence, with a minimum of maintenance and upkeep. Combustion Synthesis (CS) is a family of processes and techniques whereby chemistry is used to transform materials, often creating flame in a hard vacuum. CS can be used to stabilize civil engineering works such as berms, habitat shielding, ramps, pads, roadways, and the like. The method is to unroll thin sheets of CS fabric between layers of regolith and then fire the fabric, creating a continuous sheet of crusty material to be interposed among layers of loose regolith. The combination of low-energy processes, ISRU (in situ resource utilization) excavator, and CS fabrics, seems compelling as a general method for establishing structures of some permanence and utility, especially in the role of robotic missions as precursors to manned exploration and settlement. In robotic precursory missions, excavator/ mobility ensembles mine the Lunar surface, erect constructions of soil, and dispense sheets of CS fabrics that are covered with layers of soil, fired, and then again covered with layers of soil, iterating until the desired dimensions and forms are achieved. At the base of each berm, for example, is a shallow trench lined with CS fabric, fired and filled, mounded, and then covered and fired, iteratively to provide a footing against lateral shear. A larger trench is host to a habitat module, backfilled, covered with fabric, covered with soil, and fired. Covering the applied CS fabric with layers of soil before firing allows the resulting matrix to incorporate soil both above and below the fabric ply into the fused layer

  19. Synthesis, properties, structure and thermochemistry of hexa-aqua-tris (N,N-dimethylformamide) lanthanide tri fluoro methane sulfonates

    International Nuclear Information System (INIS)

    Araujo Melo, D.M. de.

    1989-01-01

    Addition compounds between several lanthanide salts and dimethylformamide (DMF) have been described in the literature. This thesis reports the synthesis and characterization of the compounds of general composition Ln (C H 3 SO 3 ) 3 . 3 DMF.6 H 3 O) (Ln = La - Ho) and Ln (C H 3 SO 3 ) 3 DMF.6 H 2 O (Ln = Er - Lu). The structure of the neodymium compound, isomorphous with the series, is also described. The enthalpy variations were determined by solution calorimetry. (author)

  20. Combustion synthesis and structural characterization of Li–Ti mixed ...

    Indian Academy of Sciences (India)

    pared by combustion method at lower temperatures compared to the conventional high temperature sintering for ... Li–Ti mixed ferrites; combustion synthesis; hysteresis. 1. ... Quantum model - VSM 6000) at an applied field of ±10 kOe.

  1. Zinc Oxide Nanostructures: From Chestnut Husk-Like Structures to Hollow Nanocages, Synthesis and Structure

    Directory of Open Access Journals (Sweden)

    Domenica Scarano

    2018-03-01

    Full Text Available Tailor-made nanostructured ZnO cages have been catalytically grown on Au and Pt films covering silicon substrates, by a controlled evaporation process, which means an accurate choice of temperatures, times, gas flows (He in the heating, He/air during the synthesis, and Au/Pt film thickness. The effect of the process parameters affecting the morphology and the structure of the obtained materials has been investigated by XRD analysis, scanning electron microscopy (SEM and atomic force microscopy (AFM microscopies, and FTIR spectroscopies. In particular, the role of the synthesis temperature in affecting the size and shape of the obtained ZnO cages has been highlighted. It will be shown that by adopting higher temperatures, the protruding nanowhiskers several microns in length, covering the cages and exhibiting both basal and prismatic faces, change into very thin and narrow structures, with extended prismatic faces, prevailing with respect to the basal ones. At an even higher process temperature, the building up of Au particles aggregates inside and/or anchored to the walls of the hollow cages, without any evidence of elongated ZnO nanostructures will be highlighted. From FTIR spectra information on lattice modes of the investigated ZnO, materials have been obtained.

  2. Structural archetypes in nickel(II) hybrid vanadates. Towards a directed hydrothermal synthesis

    International Nuclear Information System (INIS)

    Luis, R. Fernandez de; Urtiaga, M.K.; Mesa, J.L.; Rojo, T.; Arriortua, M.I.

    2009-01-01

    In the present work, we relate the modifications of the initial synthesis parameters (pH value, stoichiometry and concentration) with the different structural archetypes obtained in the {Ni/Bpy/VO} and {Ni/Bpe/VO} systems (4,4'-bipyridine (Bpy), 1,2-di(4-pyridyl) ethylene (Bpe)). The vanadium coordination is partially controlled by the hydrothermal synthesis conditions, and the final crystal structures depend on the synergetic interaction between the metal-organic subnets and the vanadium oxide subunits.

  3. Total synthesis, structure, and oral absorption of a thiazole cyclic peptide, sanguinamide A

    DEFF Research Database (Denmark)

    Nielsen, Daniel S; Hoang, Huy N; Lohman, Rink-Jan

    2012-01-01

    The first total synthesis and three-dimensional solution structure are reported for sanguinamide A, a thiazole-containing cyclic peptide from the sea slug H. sanguineus. Solution phase fragment synthesis, solid phase fragment assembly, and solution macrocyclization were combined to give (1) in 10......% yield. Spectral properties were identical for the natural product, requiring revision of its structure from (2) to (1). Intramolecular transannular hydrogen bonds help to bury polar atoms, which enables oral absorption from the gut....

  4. Synthesis and characterization of electrical conducting nanoporous carbon structures

    International Nuclear Information System (INIS)

    El Mir, L.; Kraiem, S.; Bengagi, M.; Elaloui, E.; Ouederni, A.; Alaya, S.

    2007-01-01

    Nanoporous organic xerogel compounds were prepared by sol-gel method from pyrogallol-formaldehyde (PF) mixtures in water using perchloric acid as catalyst. The preparation conditions of electrical conducting carbon (ECC) structures were explored by changing the pyrolysis temperature. The effect of this preparation parameters on the structural and electrical properties of the obtained ECCs were studied, respectively, by thermogravimetric analysis (TGA), nitrogen adsorption isotherms, IR spectroscopy and electrical conductivity measurements. The analysis of the obtained results revealed that, the polymeric insulating phase was transformed progressively with pyrolysis temperature into carbon conducting phase; this means the formation of long continuous conducting path for charge carriers when the carbon microparticles inside the structure agglomerated with thermal treatment and the samples exhibited tangible percolation behaviour where the percolation threshold can be determined by pyrolysis temperature. The temperature-dependent conductivity and the I(V) characteristics of the obtained ECC structures show a non-ohmic behaviour. The results obtained from TGA and differential thermal analyser (DTA) thermograms, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs, IR spectroscopy and X-ray diffraction revealed that, the obtained ECC structures consist of amorphous and nanoporous electrical conducting carbon materials

  5. Synthesis of Novel Mesoporous Silica Materials with Hierarchical Pore Structures

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Suk Bon; Choi, Wang Kyu; Choi, Byung Seon; Moon, Jei Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Porous materials with various pore sizes in the range of micropore (< 2 nm), mesopore (2-50 nm), and macropore (> 50 nm) are attractive due to their many emerging applications such as catalysts, separation systems, and low dielectric constant materials. The discovery of new M41S mesoporous silica families with pore sizes larger than 2 nm in diameter in 1992 extended the applications into much wider pore ranges, bringing in a new prosperous era in porous material research. The synthesis of these silica materials has been mainly accomplished through a self-assembly between surfactant molecules and inorganic species under various pH conditions. Recently, core-shell nanoparticles with a silica core and mesoporous shell under basic conditions were synthesized using the silica nanoparticles as a core, and a silica precursor (TEOS) and cationic surfactant (CTABr) as a material for the formation of the mesoporous shell. The resultant materials were very monodispersive in size and showed a narrow pore size distribution in the range of ca 2-3 nm in diameter, depending on the alkyl-chain length of the surfactants used. In this work, the mesoporous shell coated-fumed silicas (denoted as MS M-5s) were synthesized by using fumed silica instead of the silica nanoparticle as a core based on previous reports. Also, the structural properties of the MS M-5s such as the specific surface area and pore volume were easily controlled by varying the amount of the silica precursor and surfactant. The resultant materials exhibited a BET surface area of ca 279-446 m{sup 2}/g and total pore volume of ca 0.64-0.74 cm{sup 3}/g and showed a narrow pore size distribution (PSD) due to the removal of the organic surfactant molecules

  6. Comparison of bile acid synthesis determined by isotope dilution versus fecal acidic sterol output in human subjects

    International Nuclear Information System (INIS)

    Duane, W.C.; Holloway, D.E.; Hutton, S.W.; Corcoran, P.J.; Haas, N.A.

    1982-01-01

    Fecal acidic sterol output has been found to be much lower than bile acid synthesis determined by isotope dilution. Because of this confusing discrepancy, we compared these 2 measurements done simultaneously on 13 occasions in 5 normal volunteers. In contrast to previous findings, bile acid synthesis by the Lindstedt isotope dilution method averaged 16.3% lower than synthesis simultaneously determined by fecal acidic sterol output (95% confidence limit for the difference - 22.2 to -10.4%). When one-sample determinations of bile acid pools were substituted for Lindstedt pools, bile acid synthesis by isotope dilution averaged 5.6% higher than synthesis by fecal acidic sterol output (95% confidence limits -4.9 to 16.1%). These data indicate that the 2 methods yield values in reasonably close agreement with one another. If anything, fecal acidic sterol outputs are slightly higher than synthesis by isotope dilution

  7. Synthesis and crystal structure analysis of uranyl triple acetates

    Energy Technology Data Exchange (ETDEWEB)

    Klepov, Vladislav V., E-mail: vladislavklepov@gmail.com [Institute for Energy and Climate Research (IEK-6), Forschungszentrum Jülich GmbH, 52428 Jülich (Germany); Department of Chemistry, Samara National Research University, 443086 Samara (Russian Federation); Serezhkina, Larisa B.; Serezhkin, Victor N. [Department of Chemistry, Samara National Research University, 443086 Samara (Russian Federation); Alekseev, Evgeny V., E-mail: e.alekseev@fz-juelich.de [Institute for Energy and Climate Research (IEK-6), Forschungszentrum Jülich GmbH, 52428 Jülich (Germany); Institut für Kristallographie, RWTH Aachen University, 52066 Aachen (Germany)

    2016-12-15

    Single crystals of triple acetates NaR[UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 3}·6H{sub 2}O (R=Mg, Co, Ni, Zn), well-known for their use as reagents for sodium determination, were grown from aqueous solutions and their structural and spectroscopic properties were studied. Crystal structures of the mentioned phases are based upon (Na[UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 3}){sup 2–} clusters and [R(H{sub 2}O){sub 6}]{sup 2+} aqua-complexes. The cooling of a single crystal of NaMg[UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 3}·6H{sub 2}O from 300 to 100 K leads to a phase transition from trigonal to monoclinic crystal system. Intermolecular interactions between the structural units and their mutual packing were studied and compared from the point of view of the stereoatomic model of crystal structures based on Voronoi-Dirichlet tessellation. Using this method we compared the crystal structures of the triple acetates with Na[UO{sub 2}(CH{sub 3}COO){sub 3}] and [R(H{sub 2}O){sub 6}][UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 2} and proposed reasons of triple acetates stability. Infrared and Raman spectra were collected and their bands were assigned. - Graphical abstract: Single crystals of uranium based triple acetates, analytical reagents for sodium determination, were synthesized and structurally, spectroscopically and topologically characterized. The structures were compared with the structures of compounds from preceding families [M(H{sub 2}O){sub 6})][UO{sub 2}(CH{sub 3}COO){sub 3}]{sub 2} (M = Mg, Co, Ni, Zn) and Na[UO{sub 2}(CH{sub 3}COO){sub 3}]. Analysis was performed with the method of molecular Voronoi-Dirichlet polyhedra to reveal a large contribution of the hydrogen bonds into intermolecular interactions which can be a reason of low solubility of studied complexes.

  8. Dispersed metal cluster catalysts by design. Synthesis, characterization, structure, and performance

    Energy Technology Data Exchange (ETDEWEB)

    Arslan, Ilke [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Dixon, David A. [Univ. of Alabama, Tuscaloosa, AL (United States); Gates, Bruce C. [Univ. of California, Davis, CA (United States); Katz, Alexander [Univ. of California, Berkeley, CA (United States)

    2015-09-30

    To understand the class of metal cluster catalysts better and to lay a foundation for the prediction of properties leading to improved catalysts, we have synthesized metal catalysts with well-defined structures and varied the cluster structures and compositions systematically—including the ligands bonded to the metals. These ligands include supports and bulky organics that are being tuned to control both the electron transfer to or from the metal and the accessibility of reactants to influence catalytic properties. We have developed novel syntheses to prepare these well-defined catalysts with atomic-scale control the environment by choice and placement of ligands and applied state-of-the art spectroscopic, microscopic, and computational methods to determine their structures, reactivities, and catalytic properties. The ligands range from nearly flat MgO surfaces to enveloping zeolites to bulky calixarenes to provide controlled coverages of the metal clusters, while also enforcing unprecedented degrees of coordinative unsaturation at the metal site—thereby facilitating bonding and catalysis events at exposed metal atoms. With this wide range of ligand properties and our arsenal of characterization tools, we worked to achieve a deep, fundamental understanding of how to synthesize robust supported and ligand-modified metal clusters with controlled catalytic properties, thereby bridging the gap between active site structure and function in unsupported and supported metal catalysts. We used methods of organometallic and inorganic chemistry combined with surface chemistry for the precise synthesis of metal clusters and nanoparticles, characterizing them at various stages of preparation and under various conditions (including catalytic reaction conditions) and determining their structures and reactivities and how their catalytic properties depend on their compositions and structures. Key characterization methods included IR, NMR, and EXAFS spectroscopies to identify

  9. Three-Dimensional Structure Determination of Botulinum Toxin

    National Research Council Canada - National Science Library

    Stevens, Ray

    1997-01-01

    ...) Based on the structure of the neurotoxin, understand the toxins mechanism of action. We have accomplished the first goal of determining the three-dimensional structure of the 150 kD botulinum neurotoxin serotype...

  10. Three-Dimensional Structure Determination of Botulinum Toxin

    National Research Council Canada - National Science Library

    Stevens, Ray

    1998-01-01

    ...) Based on the structure of the neurotoxin, understand the toxins mechanism of action. We have accomplished the first goal of determining the three-dimensional structure of the 150 kD botulinum neurotoxin serotype...

  11. The determinants of capital structure: evidence from Dutch panel data

    OpenAIRE

    Chen, Linda H.; Lensink, Robert; Sterken, Elmer

    1999-01-01

    This paper studies the determinants of capital structure choice of Dutch firms. Our main objective is to investigate whether and to what extent the main capital structure theories can explain capital structure choice of Dutch firms. A better understanding of the capital structure determinants in a rela-tively small yet open industrialized economy is essential not only for enrich-ing empirical studies in this field, but also for the purpose of cross country asset evaluation. By estimating a pa...

  12. How structure determines correlations in neuronal networks.

    Directory of Open Access Journals (Sweden)

    Volker Pernice

    2011-05-01

    Full Text Available Networks are becoming a ubiquitous metaphor for the understanding of complex biological systems, spanning the range between molecular signalling pathways, neural networks in the brain, and interacting species in a food web. In many models, we face an intricate interplay between the topology of the network and the dynamics of the system, which is generally very hard to disentangle. A dynamical feature that has been subject of intense research in various fields are correlations between the noisy activity of nodes in a network. We consider a class of systems, where discrete signals are sent along the links of the network. Such systems are of particular relevance in neuroscience, because they provide models for networks of neurons that use action potentials for communication. We study correlations in dynamic networks with arbitrary topology, assuming linear pulse coupling. With our novel approach, we are able to understand in detail how specific structural motifs affect pairwise correlations. Based on a power series decomposition of the covariance matrix, we describe the conditions under which very indirect interactions will have a pronounced effect on correlations and population dynamics. In random networks, we find that indirect interactions may lead to a broad distribution of activation levels with low average but highly variable correlations. This phenomenon is even more pronounced in networks with distance dependent connectivity. In contrast, networks with highly connected hubs or patchy connections often exhibit strong average correlations. Our results are particularly relevant in view of new experimental techniques that enable the parallel recording of spiking activity from a large number of neurons, an appropriate interpretation of which is hampered by the currently limited understanding of structure-dynamics relations in complex networks.

  13. Potassium and magnesium succinatouranilates – Synthesis and crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, S.A., E-mail: serg.alex.novikov@gmail.com [Samara National Research University, 443086 Samara (Russian Federation); Grigoriev, M.S. [Frumkin Institute of Physical Chemistry and Electrochemistry RAS, 119071 Moscow (Russian Federation); Serezhkina, L.B.; Serezhkin, V.N. [Samara National Research University, 443086 Samara (Russian Federation)

    2017-04-15

    Single crystal X-ray diffraction has been applied to determine the structures of two new uranyl coordination polymers: K{sub 2}[(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}] (1) and [Mg(H{sub 2}O){sub 6}] [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]·2H{sub 2}O (2), where C{sub 4}H{sub 4}O{sub 4}{sup 2-} is succinate anion. Crystals of 1 and 2 contain polymeric complex anions [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]{sup 2-} with the same A{sub 2}Q{sup 02}{sub 3} crystallochemical formula (A=UO{sub 2}{sup 2+}, Q{sup 02}=C{sub 4}O{sub 4}H{sub 4}{sup 2-}), and have layered (1) or chain (2) structure. It has been found, that conformation of succinate ions is one of the factors, which affects the structure of [(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]{sup 2-} anions. IR spectra of these new compounds are in good agreement with crystallographic data. Topological analysis of the uranium dicarboxylates with A{sub 2}Q{sup 02}{sub 3} crystallochemical formula has shown the presence of five isomers which differ from each other in coordination sequences and / or dimensionality. - Graphical abstract: Crystal structures of two new uranium(VI) coordination polymers with succinate linkers, namely K{sub 2}[(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}] (1) and [Mg(H{sub 2}O){sub 6}][(UO{sub 2}){sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}]·2H{sub 2}O (2), were determined by single-crystal XRD. Crystals of studied compounds are based on 2D or 1D structural units with the same composition and crystallochemical formula. Topological isomerism in A{sub 2}Q{sup 02}{sub 3} crystallochemical group and conformations of succinate anions in uranyl complexes are under discussion. - Highlights: • Two new uranium coordination polymers were synthesized. • Their structural units have the same composition and crystallochemical formula. • In spite the same composition and CCF dimensionality of units is different. • Structural features of uranyl CPs

  14. Synthesis and structure of bis(β-dibenzoyl methanato -O,O') (aquo-O ...

    Indian Academy of Sciences (India)

    Synthesis and structure of bis(β-dibenzoyl methanato -O,O') (aquo-O) dioxouranium (VI) compound ... Keywords. β-diketonates; uranyl ion; adduct compound; crystal structure; hydrogen bonding. 1. Introduction. Structural studies on uranyl ... crystalline product obtained was filtered, washed with ether and dried. The crystal ...

  15. Determining building interior structures using compressive sensing

    Science.gov (United States)

    Lagunas, Eva; Amin, Moeness G.; Ahmad, Fauzia; Nájar, Montse

    2013-04-01

    We consider imaging of the building interior structures using compressive sensing (CS) with applications to through-the-wall imaging and urban sensing. We consider a monostatic synthetic aperture radar imaging system employing stepped frequency waveform. The proposed approach exploits prior information of building construction practices to form an appropriate sparse representation of the building interior layout. We devise a dictionary of possible wall locations, which is consistent with the fact that interior walls are typically parallel or perpendicular to the front wall. The dictionary accounts for the dominant normal angle reflections from exterior and interior walls for the monostatic imaging system. CS is applied to a reduced set of observations to recover the true positions of the walls. Additional information about interior walls can be obtained using a dictionary of possible corner reflectors, which is the response of the junction of two walls. Supporting results based on simulation and laboratory experiments are provided. It is shown that the proposed sparsifying basis outperforms the conventional through-the-wall CS model, the wavelet sparsifying basis, and the block sparse model for building interior layout detection.

  16. Language structure is partly determined by social structure.

    Directory of Open Access Journals (Sweden)

    Gary Lupyan

    Full Text Available BACKGROUND: Languages differ greatly both in their syntactic and morphological systems and in the social environments in which they exist. We challenge the view that language grammars are unrelated to social environments in which they are learned and used. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a statistical analysis of >2,000 languages using a combination of demographic sources and the World Atlas of Language Structures--a database of structural language properties. We found strong relationships between linguistic factors related to morphological complexity, and demographic/socio-historical factors such as the number of language users, geographic spread, and degree of language contact. The analyses suggest that languages spoken by large groups have simpler inflectional morphology than languages spoken by smaller groups as measured on a variety of factors such as case systems and complexity of conjugations. Additionally, languages spoken by large groups are much more likely to use lexical strategies in place of inflectional morphology to encode evidentiality, negation, aspect, and possession. Our findings indicate that just as biological organisms are shaped by ecological niches, language structures appear to adapt to the environment (niche in which they are being learned and used. As adults learn a language, features that are difficult for them to acquire, are less likely to be passed on to subsequent learners. Languages used for communication in large groups that include adult learners appear to have been subjected to such selection. Conversely, the morphological complexity common to languages used in small groups increases redundancy which may facilitate language learning by infants. CONCLUSIONS/SIGNIFICANCE: We hypothesize that language structures are subjected to different evolutionary pressures in different social environments. Just as biological organisms are shaped by ecological niches, language structures appear to adapt to the

  17. Microwave Determination of the Structure of Pyridine

    Energy Technology Data Exchange (ETDEWEB)

    Bak, B.; Hansen, L.; Rastrup-Andersen, J. [Chemical Laboratory of the University of Copenhagen, Copenhagen (Denmark)

    1954-12-15

    2‐, 3‐, and 4‐mono‐deutero‐pyridine have been prepared and the microwave spectra recorded. For each of the isotopic species 11—12 transitions (Q‐ and R‐branch lines) were localized, a number of which could be identified by their Stark effect. For all three species rotational constants of high precision were calculated. The material so provided in connection with known rotational constants for ordinary pyridine is insufficient for a complete determination of the ten geometrical parameters of the molecule. Seven models with a choice of C – H distances close to the correct value (1.075‐1.085 A) were considered one of which was shown to be consistent with electron‐diffraction work and current valence theory. In this model d(N – C(2)) = 1.340±0.005; d(C(2) – C(3)) = 1.390±0.005; d(C(3) – C(4)) = 1.400±0.005 A. The valence angles in the aromatic ring (starting with the C(6) – N – C(2) angle) are: 116° 42′; 124° 00′; 118° 36′; 118° 06′.

  18. Green synthesis and structural control of metal and mineral nanostructures

    DEFF Research Database (Denmark)

    Engelbrekt, Christian

    of nanoparticle formation which, however, entails the development of new methods. Two approaches to the advancement of solution synthesis of gold nanomaterials for energy technology were exploited, namely the development of techniques to study nanoparticle formation and the synthesis of active, composite...... nanomaterials. In the first approach, time-resolved chronopotentiometry, pH, conductivity and turbidity, and ultraviolet-visible light spectroscopy were employed to follow the green synthesis of gold nanoparticles. Several distinct phases were observed with all techniques providing a broad picture...... of the complex processes. Strong indications of sequential reduction were found and details about ligands and surface immobilized molecules disclosed. This platform is a widely available alternative to traditionally used synchrotron techniques. In the second approach, systematic efforts toward size and shape...

  19. Synthesis and structure of the unligated carbene of chromium

    Energy Technology Data Exchange (ETDEWEB)

    Billups, W.E.; Souchan Chang; Hauge, R.H.; Margrave, J.L. (Rice Univ., Houston, TX (United States))

    1993-04-14

    Complexes with metal-carbon double bonds have found applications as intermediates in many important catalytic reactions including cyclopropanation of alkenes by diazoalkanes, Fischer-Tropsch synthesis, olefin metathesis, Ziegler-Natta polymerization, alkane activation, and in the decomposition of transition metal alkyl complexes. However, complexes with the simplest carbene, CH[sub 2], coordinated to the metal center are relatively rare. In this paper the authors report the synthesis and characterization of the simple unligated carbene of chromium by FTIR matrix isolation spectroscopy. 7 refs., 3 figs., 4 tabs.

  20. Nanoparticle synthesis of zinc peroxide: structural and morphological characterization for bactericidal applications

    International Nuclear Information System (INIS)

    Colonia, Roberto; Martinez, Vanessa C.; Solis, Jose L.; Gomez, Monica M.

    2013-01-01

    Zinc peroxide (ZnO 2 ) nanoparticles were synthesized by sol-gel technique. The chemicals used for the synthesis were zinc acetate di-hydrate (Zn(CH 3 COO) 2. 2H 2 O) and hydrogen peroxide (H 2 O 2 ) at 30 % in an aqueous solution with sonication. The structure of the ZnO 2 nanoparticles was characterized by X-ray diffraction. While the morphology and the cluster size were determined using scanning and transmission electron microscopy. For a preliminary evaluation of the bactericidal properties of the ZnO 2 , the material was exposed to Staphylococcus aureus, Escherichia coli y Bacillus subtili, and the nanoparticles presented good bactericidal properties. (author)

  1. Tungsten disilicide (WSi{sub 2}). Synthesis, characterization, and prediction of new crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Lukovic, Jelena; Zagorac, Dejan; Zagorac, Jelena; Jordanov, Dragana; Matovic, Branko [Institute of Nuclear Sciences Vinca, Materials Science Laboratory, University of Belgrade (Serbia); Materials Science Laboratory, Center for the Synthesis, Processing and Characterization of Materials for Use in Extreme Conditions, Belgrade (Serbia); Schoen, J. Christian [Materials Science Laboratory, Max Planck Institute for Solid State Research, Stuttgart (Germany); Volkov-Husovic, Tatjana [Faculty of Technology and Metallurgy, Department for Metallurgical Engineering, University of Belgrade (Serbia)

    2017-12-13

    Transition metal silicides have attracted great attention due to their potential applications in microelectronics, ceramics, and the aerospace industry. In this study, experimental and theoretical investigations of tungsten based silicides were performed. Tungsten disilicide (WSi{sub 2}) was synthesized by simple thermal treatment at 1350 C for 4 h in an argon atmosphere. These optimal synthesis conditions were obtained by variation of temperatures and times of heating, and the structure of the final synthesized compound was determined by XRPD analysis. In addition, new modifications for WSi{sub 2} were proposed and investigated using first-principles calculations within density-functional theory (DFT). Both LDA and PBE calculations show excellent agreement with experimental observations and previous calculations for the existing modifications, where available. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Structural control in the synthesis of inorganic porous materials

    Science.gov (United States)

    Holland, Brian Thomas

    Mesoporous (2.0--50.0 nm pore diameter) and macroporous (50.0 nm on up) materials have been the basis of my studies. These materials, for many years, possessed large pore size distributions. Recently, however, it has been possible to synthesize both mesoporous and macroporous materials that possess highly ordered uniform pores throughout the material. Workers at Mobil Corporation in 1992 discovered a hexagonally arrayed mesoporous material, designated MCM-41, which exhibited uniform pores ranging from 2.0--10.0 nm in diameter. In my work MCM-41 was used as a host for the incorporation of meso-tetrakis(5-trimethylammoniumpentyl)porphyrin (TMAP-Cl) and as a model for the synthesis of mesoporous alumino- and galloaluminophosphates which were created using cluster precursors of the type MO4Al 12(OH)24(H2O)12 7+, M = Al or Ga. Macroporous materials with uniform pore sizes have been synthesized by our group with frameworks consisting of a variety of metal oxides, metals, organosilanes, aluminophosphates and bimodal pores. These materials are synthesized from the addition of metal precursors to preordered polystyrene spheres. Removal of the spheres results in the formation of macropores with highly uniform pores extending microns in length. Porous materials with uniform and adjustable pore sizes in the mesoporous and macroporous size regimes offer distinct advantages over non-ordered materials for numerous reasons. First, catalysis reactions that are based on the ability of the porous materials to impose size and shape restrictions on the substrate are of considerable interest in the petroleum and petrochemical industries. As pore diameters increase larger molecules can be incorporated into the pores, i.e., biological molecules, dyes, etc. For the macroporous materials synthesized by our group it has been envisioned that these structures may not only be used for catalysis because of increased efficiencies of flow but for more advanced applications, e.g., photonic crystals

  3. The synthesis and structural characterization of novel transition metal fluorides

    Energy Technology Data Exchange (ETDEWEB)

    Casteel, W.J. Jr.

    1992-09-01

    High purity KMF[sub 6] and K[sub 2]MF[sub 6] salts (M = Mo,Re, Ru, Os, Ir, Pt) are obtained from reduction hexafluorides. A rhombohedral unit cell is observed for KReF[sub 6]. Fluoride ion capture by Lewis acids from the hexafluorometallate (IV) salts affords high purity tetrafluorides for M = Mo, Re, Ru, Os, and Pd. The structure of RuF[sub 4] is determined from X-ray synchrotron and neutron powder data. Unit cells based on theorthorhombic PdF[sub 4] type cell are derived from X-ray powder data for ReF[sub 4] and OsF[sub 4]. Fluoride ion capture from KAgF[sub 4] provides the thermally unstable trifluoride as a bright, red, diamagnetic solid. The structure solution of AgF[sub 3] and redetermination of the AuF[sub 3] structure from X-ray synchrotron and neutron powder data demonstrate that the two are isostnictural. Thermal decomposition product of AgF[sub 3] is the mixed valence compound Ag[sup II]Ag[sub 2][sup III]F[sub 8]. Several new salts containing the (Ag - F)[sub n][sup n+] chain cation are prepared. The first linear (Ag - F)[sub n][sup n+] chain is observed in AgF[sup +]BF[sub 4 [sup [minus

  4. Structure and fertilizer properties of byproducts formed in the synthesis of EDDHA.

    Science.gov (United States)

    Hernández-Apaolaza, Lourdes; García-Marco, Sonia; Nadal, Paloma; Lucena, Juan J; Sierra, Miguel A; Gómez-Gallego, Mar; Ramírez-López, Pedro; Escudero, Rosa

    2006-06-14

    The synthesis of commercial EDDHA produces o,o-EDDHA as the main reaction product, together with a mixture of regioisomers (o,p-EDDHA and p,p-EDDHA) and other unknown byproducts also able to complex Fe3+. These compounds have been obtained by direct synthesis, and their structures have been determined by ESI-MS analysis as oligomeric EDDHA-like products, formed by polysubstitution in the phenolic rings. Short-term experiments show that the iron complexes of samples enriched in these oligomeric byproducts have adequate stability in solution, but a significant amount of them is lost after interaction with soils and soil materials. Mildly chlorotic cucumber plants are able to reduce iron better from o,p-EDDHA/Fe3+ than from the iron complexes of the oligomeric byproducts. In hydroponics, the chlorotic soybean susceptible plants have a lower potential for Fe absorption from these byproducts than from o,o-EDDHA/Fe3+ and from o,p-EDDHA/Fe3+. In the studied conditions, the iron chelates of EDDHA byproducts do not have the long-lasting effect shown by o,o-EDDHA/Fe3+ and present a less efficient fast-action effect than the o,p-EDDHA/Fe3+.

  5. Determination of atomic cluster structure with cluster fusion algorithm

    DEFF Research Database (Denmark)

    Obolensky, Oleg I.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2005-01-01

    We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters.......We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters....

  6. Synthesis, Crystal structure and Characterization of a New Oxalate ...

    Indian Academy of Sciences (India)

    in a slightly distorted octahedral environment, by two O atoms from two water molecules and four O atoms of two oxalate anions acting as chelating ligands. ... component for building up supramolecular systems and for participating in hydrogen bonding ... heating rate of 10◦C min−1. 2.2 Synthesis of the complex. Aqueous ...

  7. Synthesis and Structural Studies of Nanocrystalline Cd Zn Fe O

    African Journals Online (AJOL)

    NICO

    The synthesis of Cd0.3Zn0.7Fe2O4 nanoparticles has been achieved by a simple thermal decomposition method from the inorganic ... pure and doped spinel ferrite nanopowders. ... K. Kalimuthu, S.C. Rangasamy and M. Rakkiyasamy,. 91.

  8. Structure of catalase determined by MicroED

    Science.gov (United States)

    Nannenga, Brent L; Shi, Dan; Hattne, Johan; Reyes, Francis E; Gonen, Tamir

    2014-01-01

    MicroED is a recently developed method that uses electron diffraction for structure determination from very small three-dimensional crystals of biological material. Previously we used a series of still diffraction patterns to determine the structure of lysozyme at 2.9 Å resolution with MicroED (Shi et al., 2013). Here we present the structure of bovine liver catalase determined from a single crystal at 3.2 Å resolution by MicroED. The data were collected by continuous rotation of the sample under constant exposure and were processed and refined using standard programs for X-ray crystallography. The ability of MicroED to determine the structure of bovine liver catalase, a protein that has long resisted atomic analysis by traditional electron crystallography, demonstrates the potential of this method for structure determination. DOI: http://dx.doi.org/10.7554/eLife.03600.001 PMID:25303172

  9. Effect of synthesis parameters on polymethacrylic acid xerogel structures and equilibrium swelling

    Science.gov (United States)

    Panić, V.; Jovanović, J.; Adnadjević, B.; Velicković, S.

    2009-09-01

    Hydrogels based on crosslinked polymethacrylic acid were synthesized via free-radical polymerization in aqueous solution, using N,N'-methylene bisacrylamide as a crosslinking agent and 2,2'-azobis-[2-(2-imidazolin-2-yl)propane] dihydrochloride as an initiator. The influence of the reaction parameters (the neutralization degree of methacrylic acid and the initial monomer concentration) on the equilibrium swelling degree, the swelling kinetic parameters and the basic structural properties of xerogels was investigated. The change of synthesis parameters leads to the change of the basic structural parameters of xerogel, as well as the equilibrium swelling degree and the initial swelling rate of the hydrogels. It is found that there are power form relationships between the equilibrium swelling degree, the initial swelling rate and the structural xerogel’s properties and the change of the neutralization degree of monomer, i.e. the monomer concentration. The examined correlations proved that the crosslinking density is the crucial parameter which determines all the other investigated structural and swelling parameters.

  10. Determination of the synthesis site of the infections flacherie virus-RNA by light microscopy-autoradiography

    International Nuclear Information System (INIS)

    Almeida, I.M.G. de; Silva, D.M.

    1981-01-01

    The site of the RNA synthesis of the infectious flacherie virus in the midgut epithelial cells of the silkworm, Bombyx mori L., 1758 (Lep., Bombycidae), has been investigated using both autoradiography and light microscopy techniques. The density or ratio between silver grain and the respective cell structure (silver grain/μm 2 ) has been used as criteria to identify the site of the viral RNA synthesis. Actinomycin D selectively blocked about 60% of the cell RNA synthesis without affecting the virus RNA synthesis. The obtained data indicated that the viral RNA synthesis occurs in the nucleus of the midgut epithelial cells of the silkworm larvae. Some evidence about the viral RNA translocation from nucleus to cytoplasm and inhibition of the synthesis of normal RNA by the virus were observed. (Author) [pt

  11. SYNTHESIS, CHARACTERIZATION AND CRYSTAL STRUCTURE OF BIS-(2-HYDROXYBENZALDEHYDEDIAMINOGUANIZONE

    Directory of Open Access Journals (Sweden)

    Diana Dragancea, Vladimir B. Arion, Sergiu Shova

    2008-12-01

    Full Text Available The new ligand, bis(2-hydroxybenzaldehydediaminoguanizone (1 has been synthesized and characterized by elemental analysis, IR and 1H NMR spectroscopies. The crystal structure of the compound was determined by X-ray diffraction. The ligand C15H15N5O2·C2H5OH crystallizes in the monoclinic space group P21/c with unit cell parameters a = 8.9102(3, b = 10.0357(3, c = 19.7618(6 Å, β = 98.385(2°, Z = 4, V = 1748.21(9 Å3, R1 = 0.040. The amino form of the ligand adopts a planar conformation stabilized by two intramolecular hydrogen bonds of the type O–H···N, in which the H atoms of the central amino group are directed to the lone-pair regions of the azomethine nitrogen atoms.

  12. MWW-type titanosilicate synthesis, structural modification and catalytic applications to green oxidations

    CERN Document Server

    Wu, Peng; Xu, Le; Liu, Yueming; He, Mingyuan

    2013-01-01

    This book provides a comprehensive review of a new generation of selective oxidation titanosilicate catalysts with the MWW topology (Ti-MWW) based on the research achievements of the past 12 years. It gives an overview of the synthesis, structure modification and catalytic properties of Ti-MWW. Ti-MWW can readily be prepared by means of direct hydrothermal synthesis with crystallization-supporting agents, using dual-structure-directing agents and a dry-gel conversion technique. It also can be post-synthesized through unique reversible structure transformation and liquid-phase isomorphous subst

  13. Rapid and reliable protein structure determination via chemical shift threading.

    Science.gov (United States)

    Hafsa, Noor E; Berjanskii, Mark V; Arndt, David; Wishart, David S

    2018-01-01

    Protein structure determination using nuclear magnetic resonance (NMR) spectroscopy can be both time-consuming and labor intensive. Here we demonstrate how chemical shift threading can permit rapid, robust, and accurate protein structure determination using only chemical shift data. Threading is a relatively old bioinformatics technique that uses a combination of sequence information and predicted (or experimentally acquired) low-resolution structural data to generate high-resolution 3D protein structures. The key motivations behind using NMR chemical shifts for protein threading lie in the fact that they are easy to measure, they are available prior to 3D structure determination, and they contain vital structural information. The method we have developed uses not only sequence and chemical shift similarity but also chemical shift-derived secondary structure, shift-derived super-secondary structure, and shift-derived accessible surface area to generate a high quality protein structure regardless of the sequence similarity (or lack thereof) to a known structure already in the PDB. The method (called E-Thrifty) was found to be very fast (often chemical shift refinement, these results suggest that protein structure determination, using only NMR chemical shifts, is becoming increasingly practical and reliable. E-Thrifty is available as a web server at http://ethrifty.ca .

  14. Facile synthesis and structure characterization of hexagonal tungsten bronzes crystals

    Science.gov (United States)

    Lee, Jiann-Shing; Liu, Hao-Chuan; Peng, Gao-De; Tseng, Yawteng

    2017-05-01

    A facile molten-salt route was used to synthesize hexagonal Cs0.33WO3, Rb0.33WO3 and K0.30WO3 crystals. The three isostructural compounds were successfully prepared from the reaction of MxWO3 powders (M = Cs, Rb, K) in the CsCl/NaCl, RbCl/NaCl and KCl/NaCl fluxes, respectively. The structure determination and refinement, based on single-crystal X-ray diffraction data, are in agreement with previous works, possessing space group P63/mcm. The a and c parameters vary non-linearly with increasing radii of the M+ cations (rM) that is coordinated to twelve oxygen atoms. Both the volumes of unit-cell and WO6 octahedra vary linearly with rM, which become smaller from Cs0.33WO3 to K0.30WO3. The distortion of WO6 octahedra as well as isotropic displacement parameters increases from Cs0.33WO3 to K0.30WO3. The geometry of the WO6 octahedron becomes more regular with increasing rM. These structural trends arise from the effective size of the M+ cation.

  15. Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

    KAUST Repository

    Zeng, Shangjing

    2016-08-03

    A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity is investigated by adding an organosilane surfactant as a mesopore-generating agent.

  16. Isolation, structure, and synthesis of viridic acid, a new tetrapeptide mycotoxin of Penicillium viridicatum Westling

    International Nuclear Information System (INIS)

    Holzapfel, C.W.; Koekemoer, J.M.; Van Dyk, M.S.

    1986-01-01

    The isolation of a new toxic metabolite, viridic acid, from Penicillium viridicatum Westling is described. The chemical and spectroscopic properties of the compound are interpreted in terms of the tetrapeptide structure (N,N-dimethyl-o-aminobenzoyl)-glycyl-(N'-methyl-L-valyl)-o-aminobenzoic acid. The structure and chirality of viridic acid were confirmed by total synthesis

  17. New data structures and algorithms for logic synthesis and verification

    CERN Document Server

    Amaru, Luca Gaetano

    2017-01-01

    This book introduces new logic primitives for electronic design automation tools. The author approaches fundamental EDA problems from a different, unconventional perspective, in order to demonstrate the key role of rethinking EDA solutions in overcoming technological limitations of present and future technologies. The author discusses techniques that improve the efficiency of logic representation, manipulation and optimization tasks by taking advantage of majority and biconditional logic primitives. Readers will be enabled to accelerate formal methods by studying core properties of logic circuits and developing new frameworks for logic reasoning engines. · Provides a comprehensive, theoretical study on majority and biconditional logic for logic synthesis; · Updates the current scenario in synthesis and verification – especially in light of emerging technologies; · Demonstrates applications to CMOS technology and emerging technologies.

  18. Organized Mesoporous Alumina: Synthesis, Structure and Potential in Catalysis

    Czech Academy of Sciences Publication Activity Database

    Čejka, Jiří

    2003-01-01

    Roč. 254, - (2003), s. 327-338 ISSN 0926-860X R&D Projects: GA AV ČR IAA4040001; GA ČR GA104/02/0571; GA MŠk ME 404 Institutional research plan: CEZ:AV0Z4040901 Keywords : organized mesoporous alumina * mesoporous molecular sieves * synthesis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.825, year: 2003

  19. Uranium hetero-bimetallic complexes: synthesis, structure and magnetic properties

    International Nuclear Information System (INIS)

    Le Borgne, Th.

    2000-01-01

    The aim of this thesis is to synthesize molecular complexes with uranium and transition metal ions in close proximity, to determine the nature of the magnetic interaction between them. We decided to use Schiff bases as assembling ligands, which are unusual for uranium (IV). Although the simplest Schiff bases, such as H 2 Salen, lead to ligand exchange reactions, the bi-compartmental Schiff base H 4 L 6 (bis(3-hydroxy-salicylidene) - 2,2-dimethyl-propylene) allows the crystal structure determination of the complex [L 6 Cu(pyr)]U[L 6 Cu].2pyr, obtained by reaction of the metallo-ligand H 2 L 6 Cu with U(acac) 4 . In this manner, the complexes [L 6 Co(pyr)] 2 U and [L 6 Ni(pyr)] 2 U.pyr were also isolated, as well as the compounds in which the paramagnetic ions have been exchanged by the diamagnetic ions Zn II , Zr IV and Th IV ': [L 6 Zn(pyr)] 2 U, [L 6 Cu] 2 Zr and [L 6 Cu(pyr)]Th[L 6 Cu].2pyr. These complexes are the first which involve three metallic centres assembling by the means of a hexa-dentate Schiff base. The crystalline structures show, for all these complexes, the outstanding orthogonal arrangement of the two fragments L 6 M around the central atom which is in a dodecahedral environment of eight oxygen atoms of two Schiff bases. The syntheses of the isostructural complexes Cu2 II and Zn 2 U in which the uranium (IV) ion is close, in the first one, to the paramagnetic ion Cu II and, in the second one, to the diamagnetic ion Zn II , has allowed the use of the empiric method to determine the nature of the magnetic interaction between an f element and a transition metal. The comparison of the magnetic behaviour of two complexes Cu 2 U and Zn 2 U, expressed by the variation of χT vs T, reveals the ferromagnetic interaction in the heart of the triad Cu-U-Cu. The magnetic behaviour of the complexes Cu 2 Th et Cu 2 Zr which does not show any coupling between the two copper (II) ions and the weak antiferromagnetic interaction in the Ni 2 U compound, favour the

  20. Determination of possible effects of mineral concentration on protein synthesis by rumen microbes in vitro

    International Nuclear Information System (INIS)

    Nikolic, J.A.; Jovanovic, M.; Andric, R.

    1976-01-01

    The aim of the present investigation was to determine the effect of different concentrations of sulphide, magnesium and zinc on protein synthesis by rumen micro-organisms in vitro. Rumen content was taken from a young bull fed a diet based on maize and dried sugar beet pulp (2/1) supplemented with urea. The rate of incorporation of 35 S from Na 2 35 SO 4 in relation to the mean specific radioactivity of the sulphide pool was used to estimate the overall rate of microbial protein synthesis. It was found that the rate of protein synthesis and the net rate of utilization of ammonia-N were not affected by differences in mean sulphide concentration from 3.6-8.0 mg/litre. The rate of reduction of sulphate appeared not to be affected by the addition of sodium sulphide to the medium. The rate and efficiency of protein synthesis by rumen micro-organisms were not significantly affected by increasing the concentration of total magnesium from 8.4-15.3 mg/100 ml. The values for soluble magnesium varied widely (1.2-7.8 mg/100 ml), and appeared to be partly dependent on the pH of the medium. Zinc concentrations varying from 5.2-12.4 mg/litre did not influence the overall rate of protein synthesis, although the efficiency tended to be higher when the concentration of zinc was greater. Concentrations of soluble zinc were low (0.3-1.15 mg/litre), and not influenced by changes in the concentration of total zinc. It was concluded that increasing the concentrations of the examined elements above the basic values did not lead consistently to an improved production of microbial protein but, on the other hand, had no obvious detrimental effect on microbial metabolic activity within the limits studied. (author)

  1. Structural study of the controlled hydrothermal synthesis of LiMn2O4 and LixMnyO2

    DEFF Research Database (Denmark)

    Christiansen, Troels Lindahl; Jensen, Kirsten Marie Ørnsbjerg; Shen, Yanbin

    , a layered structure, which can also be described as a defective spinel structure. Here, we show that both LiMn2O4 and LixMnyO2 nanoparticles can be synthesized from a simple, low-temperature hydrothermal synthesis. By tuning a single synthesis parameter (Li-concentration) each of the 2 structures...

  2. The obtaining of iron acetate from processed iron comprising catalyst of ammonia synthesis

    International Nuclear Information System (INIS)

    Mansurov, M.M.; Lugovenko, A.N.; Mirzoeva, M.M.

    1993-01-01

    Present article is devoted to obtaining of iron acetate from processed iron comprising catalyst of ammonia synthesis. The method of synthesis of iron acetate from processed iron comprising catalyst of ammonia synthesis was elaborated. The structure of complex was determined.

  3. Functional and stability orientation synthesis of materials and structures in aprotic Li-O2 batteries.

    Science.gov (United States)

    Zhang, Peng; Zhao, Yong; Zhang, Xinbo

    2018-04-23

    The lithium-O2 battery is one of most promising energy storage and conversion devices due to its ultrahigh theoretical energy density and hence has broad application potential in electrical vehicles and stationary power systems. However, the present Li-O2 battery suffers from a series of challenges for its practical application, such as its low capacity and rate capability, poor round-trip efficiency and short cycle life. These challenges mainly arise from the sluggish and unsustainable discharge and charge reactions at lithium and oxygen electrodes, which determine the performance and durability of a battery. In this review, we first provide insights on the present understanding of the discharge/charge mechanism of such a battery and follow up with establishing a correlation between the specific materials/structures of the battery modules and their functionality/stability within the recent progress in electrodes, electrolytes and redox mediators. Considerable emphasis is paid to the importance of functional orientation design and the synthesis of materials/structures towards accelerating and sustaining the electrode reactions of Li-O2 batteries. Moreover, the future directions and perspectives of rationally constructed material and surface/interface structures, as well as their optimal combinations are proposed for enhancement of the electrode reaction rate and sustainability, and consequently for a better performance and durability of such batteries.

  4. De novo protein structure determination using sparse NMR data

    International Nuclear Information System (INIS)

    Bowers, Peter M.; Strauss, Charlie E.M.; Baker, David

    2000-01-01

    We describe a method for generating moderate to high-resolution protein structures using limited NMR data combined with the ab initio protein structure prediction method Rosetta. Peptide fragments are selected from proteins of known structure based on sequence similarity and consistency with chemical shift and NOE data. Models are built from these fragments by minimizing an energy function that favors hydrophobic burial, strand pairing, and satisfaction of NOE constraints. Models generated using this procedure with ∼1 NOE constraint per residue are in some cases closer to the corresponding X-ray structures than the published NMR solution structures. The method requires only the sparse constraints available during initial stages of NMR structure determination, and thus holds promise for increasing the speed with which protein solution structures can be determined

  5. Synthesis and structural characterization of nano-hydroxyapatite biomaterials prepared by microwave processing

    Science.gov (United States)

    Ramli, Rosmamuhamadani; Arawi, Ainaa Zafirah Omar; Talari, Mahesh Kumar; Mahat, Mohd Muzamir; Jais, Umi Sarah

    2012-07-01

    Synthetic hydroxyapatite, (HA, Ca10(PO4)6(OH)2), is an attractive and widely utilized bio-ceramic material for orthopedic and dental implants because of its close resemblance of native tooth and bone crystal structure. Synthetic HA exhibits excellent osteoconductive properties. Osteoconductivity means the ability to provide the appropriate scaffold or template for bone formation. Calcium phosphate biomaterials [(HA), tri-calcium phosphate (TCP) and biphasic calcium phosphate (HA/TCP)] with appropriate three-dimensional geometry are able to bind and concentrate endogenous bone morphogenetic proteins in circulation, and may become osteoinductive and can be effective carriers of bone cell seeds. This HA can be used in bio-implants as well as drug delivery application due to the unique properties of HA. Biomaterials synthesized from the natural species like mussel shells have additional benefits such as high purity, less expensive and high bio compatibility. In this project, HA-nanoparticles of different crystallite size were prepared by microwave synthesis of precursors. High purity CaO was extracted from the natural mussel shells for the synthesis of nano HA. Dried nano HA powders were analyzed using X-Ray Diffraction (XRD) technique for the determination of crystal structure and impurity content. Scanning Electron Microscopic (SEM) investigation was employed for the morphological investigation of nano HA powders. From the results obtained, it was concluded that by altering the irradiation time, nano HA powders of different crystallite sizes and morphologies could be produced. Crystallite sizes calculated from the XRD patterns are found to be in the range of 10-55 nm depending on the irradiation time.

  6. Cryo-EM Structure Determination Using Segmented Helical Image Reconstruction.

    Science.gov (United States)

    Fromm, S A; Sachse, C

    2016-01-01

    Treating helices as single-particle-like segments followed by helical image reconstruction has become the method of choice for high-resolution structure determination of well-ordered helical viruses as well as flexible filaments. In this review, we will illustrate how the combination of latest hardware developments with optimized image processing routines have led to a series of near-atomic resolution structures of helical assemblies. Originally, the treatment of helices as a sequence of segments followed by Fourier-Bessel reconstruction revealed the potential to determine near-atomic resolution structures from helical specimens. In the meantime, real-space image processing of helices in a stack of single particles was developed and enabled the structure determination of specimens that resisted classical Fourier helical reconstruction and also facilitated high-resolution structure determination. Despite the progress in real-space analysis, the combination of Fourier and real-space processing is still commonly used to better estimate the symmetry parameters as the imposition of the correct helical symmetry is essential for high-resolution structure determination. Recent hardware advancement by the introduction of direct electron detectors has significantly enhanced the image quality and together with improved image processing procedures has made segmented helical reconstruction a very productive cryo-EM structure determination method. © 2016 Elsevier Inc. All rights reserved.

  7. Structure, stereochemistry and synthesis of a variety of physiologically active plant phenols

    Energy Technology Data Exchange (ETDEWEB)

    Van Heerden, F R

    1980-01-01

    The medicinal use of various Leguminosae species by the local population led to a phytochemical study of the bark of Dalbergia nitidula, Dalbergia melanoxylon and wood of Acacia fasciculifera. Rotenoid glycoside and three new carbon bonded isoflavone glycosides were isolated from the bark of D. nitidula. The rotenoid glycoside was characterized by means of acid and enzymatic hydrolysis and its absolute configuration was determined with reference to CD comparisons. A kinetic study was done to determine the relative toxidities of the rotenoid glycoside and its aglicone. The identity and the coupling positions of the sugars was confirmed by a C-NMR investigation of the rotenoid and isoflavane glycosides. The structure of heminitidulan, a complex isoflavane from D. nitidula, was confirmed by complete synthesis. Trans- and cis-clovamide, amides made up of L-DOPA and trans- and cis-caffeic acid respectively, and four new analogous deoxyclovamides are present in the bark of D. melanoxylon. For the first time optically pure trans clovamide was obtained by direct synthesis. C-NMR and CD confirmed differentiation between trans- and cisclovamide. The therapeutic value of L-DOPA for Parkinson's Disease implies possible physiological activity for the clovamide. As well as a number of known flavonoids and peltoginoids, a tetracyclic flavonoid (peltoginoid), fasciculiferin, was found in the wood of A. fasciculifera. Although peltoginoids with a D-ring in a fully reduced or oxidised state are known, this is the first natural peltoginoid with the D-ring in an intermediate oxidation state. Fasciculiferol, till now an unknown metabolyte from A. fasciculifera, is a new member of a rare group of natural products that are generally cytotoxic. The relatively drastic reaction conditions necessary for carbocation formation from peltoginol in comparison to the analogous flavon-3, 4-diols, is attributed to steric factors which arise from the rigid conformation of the B-ring of peltoginol.

  8. The structure, stereochemistry and synthesis of a variety of physiologically active plant phenols

    International Nuclear Information System (INIS)

    Van Heerden, F.R.

    1980-03-01

    The medicinal use of various Leguminosae species by the local population led to a phytochemical study of the bark of Dalbergia nitidula, Dalbergia melanoxylon and wood of Acacia fasciculifera. Rotenoid glycoside and three new carbon bonded isoflavone glycosides were isolated from the bark of D. nitidula. The rotenoid glycoside was characterized by means of acid and enzymatic hydrolysis and its absolute configuration was determined with reference to CD comparisons. A kinetic study was done to determine the relative toxidities of the rotenoid glycoside and its aglicone. The identity and the coupling positions of the sugars was confirmed by a C-NMR investigation of the rotenoid and isoflavane glycosides. The structure of heminitidulan, a complex isoflavane from D. nitidula, was confirmed by complete synthesis. Trans- and cis-clovamide, amides made up of L-DOPA and trans- and cis-caffeic acid respectively, and four new analogous deoxyclovamides are present in the bark of D. melanoxylon. For the first time optically pure trans clovamide was obtained by direct synthesis. C-NMR and CD confirmed differentiation between trans- and cisclovamide. The therapeutic value of L-DOPA for Parkinson's Disease implies possible physiological activity for the clovamide. As well as a number of known flavonoids and peltoginoids, a tetracyclic flavonoid (peltoginoid), fasciculiferin, was found in the wood of A. fasciculifera. Although peltoginoids with a D-ring in a fully reduced or oxidised state are known, this is the first natural peltoginoid with the D-ring in an intermediate oxidation state. Fasciculiferol, till now an unknown metabolyte from A. fasciculifera, is a new member of a rare group of natural products that are generally cytotoxic. The relatively drastic reaction conditions necessary for carbocation formation from peltoginol in comparison to the analogous flavon-3, 4-diols, is attributed to steric factors which arise from the rigid conformation of the B-ring of peltoginol

  9. Synthesis and structure of two-dimensional transition-metal dichalcogenides

    KAUST Repository

    Shi, Yumeng; Zhang, Hua; Chang, Wen-Hao; Shin, Hyeon Suk; Li, Lain-Jong

    2015-01-01

    Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) exhibit unique electrical, optical, thermal, and mechanical properties, which enable them to be used as building blocks in compact and lightweight integrated electronic systems. The controllable and reliable synthesis of atomically thin TMDCs is essential for their practical application. Recent progress in large-area synthesis of monolayer TMDCs paves the way for practical production of various 2D TMDC layers. The intrinsic optical and electrical properties of monolayer TMDCs can be defined by stoichiometry during synthesis. By manipulating the lattice structure or layer stacking manner, it is possible to create atomically thin van der Waals materials with unique and unexplored physical properties. In this article, we review recent developments in the synthesis of TMDC monolayers, alloys, and heterostructures, which shine light on the design of novel TMDCs with desired functional properties.

  10. Synthesis and structure of two-dimensional transition-metal dichalcogenides

    KAUST Repository

    Shi, Yumeng

    2015-07-13

    Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) exhibit unique electrical, optical, thermal, and mechanical properties, which enable them to be used as building blocks in compact and lightweight integrated electronic systems. The controllable and reliable synthesis of atomically thin TMDCs is essential for their practical application. Recent progress in large-area synthesis of monolayer TMDCs paves the way for practical production of various 2D TMDC layers. The intrinsic optical and electrical properties of monolayer TMDCs can be defined by stoichiometry during synthesis. By manipulating the lattice structure or layer stacking manner, it is possible to create atomically thin van der Waals materials with unique and unexplored physical properties. In this article, we review recent developments in the synthesis of TMDC monolayers, alloys, and heterostructures, which shine light on the design of novel TMDCs with desired functional properties.

  11. The synthesis and structural characterization of novel transition metal fluorides

    Energy Technology Data Exchange (ETDEWEB)

    Casteel, Jr., William Jack [Univ. of California, Berkeley, CA (United States)

    1992-09-01

    High purity KMF6 and K2MF6 salts (M = Mo,Re, Ru, Os, Ir, Pt) are obtained from reduction hexafluorides. A rhombohedral unit cell is observed for KReF6. Fluoride ion capture by Lewis acids from the hexafluorometallate (IV) salts affords high purity tetrafluorides for M = Mo, Re, Ru, Os, and Pd. The structure of RuF4 is determined from X-ray synchrotron and neutron powder data. Unit cells based on theorthorhombic PdF4 type cell are derived from X-ray powder data for ReF4 and OsF4. Fluoride ion capture from KAgF4 provides the thermally unstable trifluoride as a bright, red, diamagnetic solid. The structure solution of AgF3 and redetermination of the AuF3 structure from X-ray synchrotron and neutron powder data demonstrate that the two are isostnictural. Thermal decomposition product of AgF3 is the mixed valence compound AgIIAg2IIIF8. Several new salts containing the (Ag - F)$n+\\atop{n}$ chain cation are prepared. The first linear (Ag - F)$n+\\atop{n}$ chain is observed in AgF+BF4- which crystallizes in a tetragonal unit. AgFAuF4 has a triclinic unit cell and is isostructural with CuFAuF4. AgFAuF6 has an orthorhombic unit cell and appears to be isostructural with AgFAsF6. A second mixed valence silver fluoride, AgIIAgIIIF5, is prepared, which magnetic measurements indicate is probably an AgF+ salt. Magnetic data for all of the AgF+ salts exhibit low magnitude, temperature independent paramagnetism characteristic of metallic systems. Cationic AG(II) in acidic AHF solutions is a powerful oxidizer, capable of oxidizing Xe to Xe(II) and O2 to O2+. Reactions with C6F6 and C3F6 suggest an electron capture

  12. Synthesis of computational structures for analog signal processing

    CERN Document Server

    Popa, Cosmin Radu

    2011-01-01

    Presents the most important classes of computational structures for analog signal processing, including differential or multiplier structures, squaring or square-rooting circuits, exponential or Euclidean distance structures and active resistor circuitsIntroduces the original concept of the multifunctional circuit, an active structure that is able to implement, starting from the same circuit core, a multitude of continuous mathematical functionsCovers mathematical analysis, design and implementation of a multitude of function generator structures

  13. Micro structured reactors for synthesis/decomposition of hazardous chemicals. Challenging prospects for micro structured reaction architectures (4)

    NARCIS (Netherlands)

    Rebrov, E.V.; Croon, de M.H.J.M.; Schouten, J.C.

    2004-01-01

    A review. This paper completes a series of four publications dealing with the different aspects of the applications of micro reactor technol. This article focuses on the application of micro structured reactors in the processes for synthesis/decompn. of hazardous chems., such as unsym.

  14. Determinants of capital structure and financial crisis impact: evidence

    OpenAIRE

    Proença, Pedro Miguel Correia

    2012-01-01

    Mestrado em contabilidade The objectives of this empirical work are to investigate the determinants of Portuguese SMEs capital structure, evaluate whether and how the impacts of those determinants affect the debt ratios and examine the effects of financial crisis and industry on Portuguese SMEs capital structure. The sample used considers the period 2007-2010, resulting in 12.857 Portugues e SMEs per year observations. R...

  15. Structural archetypes in nickel(II) hybrid vanadates. Towards a directed hydrothermal synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Luis, R. Fernandez de; Urtiaga, M.K. [Dpto. Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/UPV/EHU, Apdo. 644, 48080 Bilbao (Spain); Mesa, J.L.; Rojo, T. [Dpto. Quimica Inorganica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco UPV/EHU, Apdo. 644, 48080 Bilbao (Spain); Arriortua, M.I. [Dpto. Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/UPV/EHU, Apdo. 644, 48080 Bilbao (Spain)], E-mail: maribel.arriortua@ehu.es

    2009-07-01

    In the present work, we relate the modifications of the initial synthesis parameters (pH value, stoichiometry and concentration) with the different structural archetypes obtained in the {l_brace}Ni/Bpy/VO{r_brace} and {l_brace}Ni/Bpe/VO{r_brace} systems (4,4'-bipyridine (Bpy), 1,2-di(4-pyridyl) ethylene (Bpe)). The vanadium coordination is partially controlled by the hydrothermal synthesis conditions, and the final crystal structures depend on the synergetic interaction between the metal-organic subnets and the vanadium oxide subunits.

  16. Transaction cost determinants of credit governance structures of ...

    African Journals Online (AJOL)

    This paper explores transaction cost determinants of credit governance structures (CGS) of commercial banks in Tanzania. Descriptive statistics, linear regression model, binary and multinomial logistic regression models were employed for analysis. Findings revealed four modes of credit governance structures that are ...

  17. Photonic crystals based on opals and inverse opals: synthesis and structural features

    International Nuclear Information System (INIS)

    Klimonsky, S O; Abramova, Vera V; Sinitskii, Alexander S; Tretyakov, Yuri D

    2011-01-01

    Methods of synthesis of photonic crystals based on opals and inverse opals are considered. Their structural features are discussed. Data on different types of structural defects and their influence on the optical properties of opaline materials are systematized. The possibilities of investigation of structural defects by optical spectroscopy, electron microscopy, microradian X-ray diffraction, laser diffraction and using an analysis of Kossel ring patterns are described. The bibliography includes 253 references.

  18. The Determinants of Capital Structure: Some Evidence from Banks

    OpenAIRE

    Heider, Florian; Gropp, Reint

    2008-01-01

    This paper documents that standard cross-sectional determinants of firm leverage also apply to the capital structure of large banks in the United States and Europe. We find a remarkable consistency in sign, significance and economic magnitude. Like non-financial firms, banks appear to have stable capital structures at levels that are specific to each individual bank. The results suggest that capital requirements may only be of second-order importance for banks’ capital structures and confirm ...

  19. Nickel–carbon nanocomposites: Synthesis, structural changes and strengthening mechanisms

    International Nuclear Information System (INIS)

    Nunes, D.; Vilarigues, M.; Correia, J.B.; Carvalho, P.A.

    2012-01-01

    The present work investigates Ni–nanodiamond and Ni–graphite composites produced by mechanical synthesis and subsequent heat treatments. Processing of nickel–carbon nanocomposites by this powder metallurgy route poses specific challenges, as carbon phases are prone to carbide conversion and amorphization. The processing window for carbide prevention has been established through X-ray diffraction by a systematic variation of the milling parameters. Transmission electron microscopy confirmed the absence of carbide and showed homogeneous particle distributions, as well as intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained largely unaffected by mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. The results on the annealed nanocomposites showed that milling with Ni accelerated graphitization of the carbon phases during heat treatments at 973 and 1073 K in both composites. At the finer scales, the nanocomposites exhibited a remarkable microhardness enhancement (∼70%) compared with pure nanostructured nickel. The Hall–Petch relation and the Orowan–Ashby equation are used to discuss strengthening mechanisms and the load transfer ability to the reinforcing particles.

  20. Labor Market Structure and Salary Determination among Professional Basketball Players.

    Science.gov (United States)

    Wallace, Michael

    1988-01-01

    The author investigates the labor market structure and determinants of salaries for professional basketball players. An expanded version of the resource perspective is used. A three-tiered model of labor market segmentation is revealed for professional basketball players, but other variables also are important in salary determination. (Author/CH)

  1. Denotational, Causal, and Operational Determinism in Event Structures

    NARCIS (Netherlands)

    Rensink, Arend; Kirchner, H.

    1996-01-01

    Determinism of labelled transition systems and trees is a concept of theoretical and practical importance. We study its generalisation to event structures. It turns out that the result depends on what characterising property of tree determinism one sets out to generalise. We present three distinct

  2. Denotational, Causal, and Operational Determinism in Event Structures

    NARCIS (Netherlands)

    Rensink, Arend

    Determinism is a theoretically and practically important concept in labelled transition systems and trees. We study its generalisation to event structures. It turns out that the result depends on what characterising property of tree determinism one sets out to generalise. We present three distinct

  3. Synthesis, structure and luminescence properties of phosphates A1 ...

    Indian Academy of Sciences (India)

    rule and the localization of this cation in the structure, which is in agreement with the structural characterization. It appears that europium ... 1. Introduction. Atom isomorphism in complex crystalline compounds with ..... isotropic approx- imation of basis atom positions in the structures of phosphates Na0.7Eu0.1Zr2(PO4)3 and.

  4. Integral membrane protein structure determination using pseudocontact shifts

    Energy Technology Data Exchange (ETDEWEB)

    Crick, Duncan J.; Wang, Jue X. [University of Cambridge, Department of Biochemistry (United Kingdom); Graham, Bim; Swarbrick, James D. [Monash University, Monash Institute of Pharmaceutical Sciences (Australia); Mott, Helen R.; Nietlispach, Daniel, E-mail: dn206@cam.ac.uk [University of Cambridge, Department of Biochemistry (United Kingdom)

    2015-04-15

    Obtaining enough experimental restraints can be a limiting factor in the NMR structure determination of larger proteins. This is particularly the case for large assemblies such as membrane proteins that have been solubilized in a membrane-mimicking environment. Whilst in such cases extensive deuteration strategies are regularly utilised with the aim to improve the spectral quality, these schemes often limit the number of NOEs obtainable, making complementary strategies highly beneficial for successful structure elucidation. Recently, lanthanide-induced pseudocontact shifts (PCSs) have been established as a structural tool for globular proteins. Here, we demonstrate that a PCS-based approach can be successfully applied for the structure determination of integral membrane proteins. Using the 7TM α-helical microbial receptor pSRII, we show that PCS-derived restraints from lanthanide binding tags attached to four different positions of the protein facilitate the backbone structure determination when combined with a limited set of NOEs. In contrast, the same set of NOEs fails to determine the correct 3D fold. The latter situation is frequently encountered in polytopical α-helical membrane proteins and a PCS approach is thus suitable even for this particularly challenging class of membrane proteins. The ease of measuring PCSs makes this an attractive route for structure determination of large membrane proteins in general.

  5. Structural determination of intact proteins using mass spectrometry

    Science.gov (United States)

    Kruppa, Gary [San Francisco, CA; Schoeniger, Joseph S [Oakland, CA; Young, Malin M [Livermore, CA

    2008-05-06

    The present invention relates to novel methods of determining the sequence and structure of proteins. Specifically, the present invention allows for the analysis of intact proteins within a mass spectrometer. Therefore, preparatory separations need not be performed prior to introducing a protein sample into the mass spectrometer. Also disclosed herein are new instrumental developments for enhancing the signal from the desired modified proteins, methods for producing controlled protein fragments in the mass spectrometer, eliminating complex microseparations, and protein preparatory chemical steps necessary for cross-linking based protein structure determination.Additionally, the preferred method of the present invention involves the determination of protein structures utilizing a top-down analysis of protein structures to search for covalent modifications. In the preferred method, intact proteins are ionized and fragmented within the mass spectrometer.

  6. BIRTHDAY CAKE ACTIVITY STRUCTURED ARRANGEMENT FOR HELPING CHILDREN DETERMINING QUANTITIES

    Directory of Open Access Journals (Sweden)

    Neni Mariana

    2010-07-01

    Full Text Available Few researches have been concerned about relation between children’s spatialthinking and number sense. Narrowing for this small research, we focused onone component of spatial thinking, that is structuring objects, and onecomponent of number senses, that is cardinality by determining quantities. Thisstudy focused on a design research that was conducted in Indonesia in which weinvestigated pre-school children’s (between 2 and 3.5 years old ability inmaking structured arrangement and their ability to determine the quantities bylooking at the arrangements. The result shows us that some of the children wereable to make such arrangement. However, the children found difficulties eitherto determine quantities from those arrangements or to compare some structuresto easily recognize number of objects.Keywords: structures, structured arrangement, cardinality DOI: http://dx.doi.org/10.22342/jme.1.1.790.53-70

  7. Energy group structure determination using particle swarm optimization

    International Nuclear Information System (INIS)

    Yi, Ce; Sjoden, Glenn

    2013-01-01

    Highlights: ► Particle swarm optimization is applied to determine broad group structure. ► A graph representation of the broad group structure problem is introduced. ► The approach is tested on a fuel-pin model. - Abstract: Multi-group theory is widely applied for the energy domain discretization when solving the Linear Boltzmann Equation. To reduce the computational cost, fine group cross libraries are often down-sampled into broad group cross section libraries. Cross section data collapsing generally involves two steps: Firstly, the broad group structure has to be determined; secondly, a weighting scheme is used to evaluate the broad cross section library based on the fine group cross section data and the broad group structure. A common scheme is to average the fine group cross section weighted by the fine group flux. Cross section collapsing techniques have been intensively researched. However, most studies use a pre-determined group structure, open based on experience, to divide the neutron energy spectrum into thermal, epi-thermal, fast, etc. energy range. In this paper, a swarm intelligence algorithm, particle swarm optimization (PSO), is applied to optimize the broad group structure. A graph representation of the broad group structure determination problem is introduced. And the swarm intelligence algorithm is used to solve the graph model. The effectiveness of the approach is demonstrated using a fuel-pin model

  8. Development of a Probabilistic Dynamic Synthesis Method for the Analysis of Nondeterministic Structures

    Science.gov (United States)

    Brown, A. M.

    1998-01-01

    Accounting for the statistical geometric and material variability of structures in analysis has been a topic of considerable research for the last 30 years. The determination of quantifiable measures of statistical probability of a desired response variable, such as natural frequency, maximum displacement, or stress, to replace experience-based "safety factors" has been a primary goal of these studies. There are, however, several problems associated with their satisfactory application to realistic structures, such as bladed disks in turbomachinery. These include the accurate definition of the input random variables (rv's), the large size of the finite element models frequently used to simulate these structures, which makes even a single deterministic analysis expensive, and accurate generation of the cumulative distribution function (CDF) necessary to obtain the probability of the desired response variables. The research presented here applies a methodology called probabilistic dynamic synthesis (PDS) to solve these problems. The PDS method uses dynamic characteristics of substructures measured from modal test as the input rv's, rather than "primitive" rv's such as material or geometric uncertainties. These dynamic characteristics, which are the free-free eigenvalues, eigenvectors, and residual flexibility (RF), are readily measured and for many substructures, a reasonable sample set of these measurements can be obtained. The statistics for these rv's accurately account for the entire random character of the substructure. Using the RF method of component mode synthesis, these dynamic characteristics are used to generate reduced-size sample models of the substructures, which are then coupled to form system models. These sample models are used to obtain the CDF of the response variable by either applying Monte Carlo simulation or by generating data points for use in the response surface reliability method, which can perform the probabilistic analysis with an order of

  9. New alkali metal diphosphates how materials to preserve the security of the environment: CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7) synthesis and crystal structure determination

    Science.gov (United States)

    Chernyatieva, Anastasiya; Filatova, Alyona; Spiridonova, Dariya; Krivovichev, Sergey

    2013-04-01

    In this work we describe preliminary results of the synthesis and of a crystal-chemical study of synthetic phosphates with transition metals. Due to the increasing requirements for environmental safety specialists from various industries, we are searching for sustainable forms of immobilization of hazardous waste during storage. We are also developing a component-based waste for new materials. In our continued exploratory synthesis of compounds containing transition-metals, we were able to produce the new diphosphate phases CsNaCu(P2O7), Rb2Cu(P2O7) and CsNaCo(P2O7). A crystal chemical study has allowed us to identify new phosphates. Crystals of CsNaCu(P2O7) (Phase 1) is orthorhombic, crystallizes in space group Pmn21, with a = 5.147(8), b = 15.126(2), c = 9.717(2) Å, V = 756.20 Å3, R1 = 0.066 and Rb2Cu(P2O7) (Phase 2) is orthorhombic as well, crystallizes in space group Pmcn, with a = 5.183(8), b = 10.096(1), c = 15.146(3) Å, V = 793.55 Å3, R1 = 0.063, they have been obtained by high-temperature reaction of RbNO3, CsNO3, Cu(NO3)2, NaOH and (NH4)4P2O7. Synthetic crystals of the phosphate of copper and rubidium were studied in detail by us on the structures of Rb2Cu(P2O7) and Rb2Cu3(P2O7)2 - new alkali metal copper diphosphates (CHERNYATIEVA et al., 2008). Here we report the synthesis, the structure and the properties of the title compounds and we compare these phases with the previously discovered K2CuP2O7 (ELMAADI et al., 1995) and CsNaMnP2O7 (HUANG et al., 1998). These structures crystallize in other space groups, although their structures are also based on 2-D layers, formed by P2O7 groups combined with polyhedra of the transition metals (CHERNYATIEVA et al., 2012). A crystal chemical study has allowed us to identify even new diphosphates CsNaCu(P2O7) (Phase 3). Crystals of CsNaCoP2O7 is monoclinic, space group P 21/n, with a = 7,424(2), b = 7,648(1), c = 12,931(3)Å, β = 90,71(2)° , V = 734.2(3) Å3 and R1 = 0.060. The structure is based framework of Co

  10. New Diethyl Ammonium Salt of Thiobarbituric Acid Derivative: Synthesis, Molecular Structure Investigations and Docking Studies

    Directory of Open Access Journals (Sweden)

    Assem Barakat

    2015-11-01

    Full Text Available The synthesis of the new diethyl ammonium salt of diethylammonium(E-5-(1,5-bis(4-fluorophenyl-3-oxopent-4-en-1-yl-1,3-diethyl-4,6-dioxo-2-thioxohexaydropyrimidin-5-ide 3 via a regioselective Michael addition of N,N-diethylthiobarbituric acid 1 to dienone 2 is described. In 3, the carboanion of the thiobarbituric moiety is stabilized by the strong intramolecular electron delocalization with the adjacent carbonyl groups and so the reaction proceeds without any cyclization. The molecular structure investigations of 3 were determined by single-crystal X-ray diffraction as well as DFT computations. The theoretically calculated (DFT/B3LYP geometry agrees well with the crystallographic data. The effect of fluorine replacement by chlorine atoms on the molecular structure aspects were investigated using DFT methods. Calculated electronic spectra showed a bathochromic shift of the π-π* transition when fluorine is replaced by chlorine. Charge decomposition analyses were performed to study possible interaction between the different fragments in the studied systems. Molecular docking simulations examining the inhibitory nature of the compound show an anti-diabetic activity with Pa (probability of activity value of 0.229.

  11. Chemical synthesis, 3D structure, and ASIC binding site of the toxin mambalgin-2.

    Science.gov (United States)

    Schroeder, Christina I; Rash, Lachlan D; Vila-Farrés, Xavier; Rosengren, K Johan; Mobli, Mehdi; King, Glenn F; Alewood, Paul F; Craik, David J; Durek, Thomas

    2014-01-20

    Mambalgins are a novel class of snake venom components that exert potent analgesic effects mediated through the inhibition of acid-sensing ion channels (ASICs). The 57-residue polypeptide mambalgin-2 (Ma-2) was synthesized by using a combination of solid-phase peptide synthesis and native chemical ligation. The structure of the synthetic toxin, determined using homonuclear NMR, revealed an unusual three-finger toxin fold reminiscent of functionally unrelated snake toxins. Electrophysiological analysis of Ma-2 on wild-type and mutant ASIC1a receptors allowed us to identify α-helix 5, which borders on the functionally critical acidic pocket of the channel, as a major part of the Ma-2 binding site. This region is also crucial for the interaction of ASIC1a with the spider toxin PcTx1, thus suggesting that the binding sites for these toxins substantially overlap. This work lays the foundation for structure-activity relationship (SAR) studies and further development of this promising analgesic peptide. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Synthesis and characterization of Al-TON zeolite using a dialkylimizadolium as structure-directing agent

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Christian Wittee; Pergher, Sibele Berenice Castella, E-mail: chriswittee@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil); Villarroel-Rocha, Jhonny [Laboratorio de Solidos Porosos, Instituto de Fisica Aplicada, Universidad Nacional de San Luis, Chacabuco, San Luis (Argentina); Silva, Bernardo Araldi Da; Mignoni, Marcelo Luis [Universidade Regional Integrada, Erechim, RS (Brazil)

    2016-11-15

    In this work, the synthesis of zeolites using 1-butyl-3-methylimidazolium chloride [C{sub 4}MI]Cl as a structure-directing agent was investigated. The organic cation shows effectiveness and selectivity for the syntheses of TON zeolites under different reaction conditions compared to the traditional structure directing agent, 1,8-diaminooctane. The 1-butyl-3-methylimidazolium cation lead to highly crystalline materials and its role as OSDA in our synthesis conditions has been confirmed by characterization techniques. ICP-OES confirms the presence of Al in the samples and {sup 27}Al MAS NMR analysis indicated that aluminum atoms were incorporated in tetrahedral coordination. Scanning electron microscopy indicated that changing the crystallization condition (static or stirring), zeolites with different crystal size were obtained, which consequently affects the textural properties of the zeolites. Moreover, varying some synthesis parameters MFI zeolite can also be obtained. (author)

  13. Determination of radioinduced delay in DNA synthesis in two-garlic-clones cells (Allium Sativum L.)

    International Nuclear Information System (INIS)

    Perez Lezcano, A.; Perez Talavera, S.

    1989-01-01

    To contribute to tech improvement of the use of ionizing radiations as an auxiliary tool in the fitoimprovement, dose-effect curves for the 'Martinez' and 'Sancti Spiritus-3' clones were stablished by using as effect the delay induced by radiations in DNA synthesis determined by the 'Martinez' clone which induces a delay of 50% in reference to the control is approximately 11 Gy, while the dose value for the 'Sancti Spiritus-3' clone is 18 Gy, thus the 'Martinez' clones has a higher sensitivity to radiations than the other clone, therefore it coincides with what we found for these clones other indexes are used as radiosensitivity criteria

  14. Development of XAFS Into a Structure Determination Technique

    Science.gov (United States)

    Stern, E. A.

    After the detection of diffraction of x-rays by M. Laue in 1912, the technique was soon applied to structure determination by Bragg within a year. On the other hand, although the edge steps in X-Ray absorption were discovered even earlier by Barkla and both the near edge (XANES) and extended X-Ray fine structure (EXAFS) past the edge were detected by 1929, it still took over 40 years to realize the structure information contained in this X-Ray absorption fine structure (XAFS). To understand this delay a brief historical review of the development of the scientific ideas that transformed XAFS into the premiere technique for local structure determination is given. The development includes both advances in theoretical understanding and calculational capabilities, and in experimental facilities, especially synchrotron radiation sources. The present state of the XAFS technique and its capabilities are summarized.

  15. Reliability enhancement of portal frame structure by finite element synthesis

    International Nuclear Information System (INIS)

    Nakagiri, S.

    1989-01-01

    The stochastic finite element methods have been applied to the evaluation of structural response and reliability of uncertain structural systems. The structural reliability index of the advanced first-order second moment (AFOSM) method is a candidate of the measure of assessing structural safety and reliability. The reliability index can be evaluated when a baseline design of structures under interest is proposed and the covariance matrix of the probabilistic variables is acquired to represent uncertainties involved in the structure systems. The reliability index thus evaluated is not assured the largest one for the structure. There is left a possibility to enhance the structural reliability for the given covariance matrix by changing the baseline design. From such a viewpoint of structural optimization, some ideas have been proposed to maximize the reliability or to minimize the failure probability of uncertain structural systems. A method of changing the design is proposed to increase the reliability index from its baseline value to another desired value. The reliability index in this paper is calculated mainly by the method of Lagrange multiplier

  16. Stop Flow Lithography Synthesis and Characterization of Structured Microparticles

    Directory of Open Access Journals (Sweden)

    David Baah

    2014-01-01

    Full Text Available In this study, the synthesis of nonspherical composite particles of poly(ethylene glycol diacrylate (PEG-DA/SiO2 and PEG-DA/Al2O3 with single or multiple vias and the corresponding inorganic particles of SiO2 and Al2O3 synthesized using the Stop Flow Lithography (SFL method is reported. Precursor suspensions of PEG-DA, 2-hydroxy-2-methylpropiophenone, and SiO2 or Al2O3 nanoparticles were prepared. The precursor suspension flows through a microfluidic device mounted on an upright microscope and is polymerized in an automated process. A patterned photomask with transparent geometric features masks UV light to synthesize the particles. Composite particles with vias were synthesized and corresponding inorganic SiO2 and Al2O3 particles were obtained through polymer burn-off and sintering of the composites. The synthesis of porous inorganic particles of SiO2 and Al2O3 with vias and overall dimensions in the range of ~35–90 µm was achieved. BET specific surface area measurements for single via inorganic particles were 56–69 m2/g for SiO2 particles and 73–81 m2/g for Al2O3 particles. Surface areas as high as 114 m2/g were measured for multivia cubic SiO2 particles. The findings suggest that, with optimization, the particles should have applications in areas where high surface area is important such as catalysis and sieving.

  17. Synthesis and structural characterization of manganese olivine lithium phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Herrera Robles, Joel O. [Basic Science Department, IIT, Universidad Autónoma de Ciudad Juárez, Av. del Charro 460 norte Cd. Juárez, Chih. C.P. 32310 (Mexico); Fuentes Cobas, Luis E. [Centro de Investigación en Materiales Avanzados CIMAV, Complejo Industrial, M. Cervantes 120, Chihuahua C.P. 31109 (Mexico); Díaz de la Torre, Sebastián [Instituto Politécnico Nacional, Centro de Investigación e Innovación Tecnológica CIITEC, Azcapotzalco, México, D.F. C.P. 02250 (Mexico); Camacho Montes, Héctor, E-mail: hcamacho@uacj.mx [Basic Science Department, IIT, Universidad Autónoma de Ciudad Juárez, Av. del Charro 460 norte Cd. Juárez, Chih. C.P. 32310 (Mexico); Elizalde Galindo, José T.; García Casillas, Perla E.; Rodríguez González, Claudia A. [Basic Science Department, IIT, Universidad Autónoma de Ciudad Juárez, Av. del Charro 460 norte Cd. Juárez, Chih. C.P. 32310 (Mexico); Álvarez Contreras, Lorena [Centro de Investigación en Materiales Avanzados CIMAV, Complejo Industrial, M. Cervantes 120, Chihuahua C.P. 31109 (Mexico)

    2015-09-15

    Highlights: • LiMnPO{sub 4} was obtained by sol gel method and crystallization in reducing atmosphere. • Magnetic and electric properties are reported for LiMnPO{sub 4}. • Electrochemical properties are also found and enhanced by adding carbon. • SEM and HRTEM show the submicron powder nature. • The multifunctional behavior of LiMnPO{sub 4} is experimentally demonstrated. - Abstract: The manganese olivine lithium phosphate is a multifunctional material. If carbon is added to form a composite LiMnPO{sub 4}–C, electrochemical properties can be enhanced, making this material a good candidate for battery cathode. High magnetic susceptibility is reported for this compound at room temperature. In this work, the magnetic response was measured through a Field Cooling/Zero Field Cooling technique at temperature below 100 K. Weak ferroelectric properties at room temperature were measured. Even though, the promising applications and the interesting properties of this system, the attention received in the literature is relatively low. The synthesis of this material is difficult because of the rapid manganese oxidation and the need of a reducing atmosphere. In fact, only few authors report the synthesis of the pure phase. In the present work, nanostructured LiMnPO{sub 4} is obtained by sol gel chemical method and according to X-ray diffraction patterns, pure LiMnPO{sub 4} is obtained after calcination in a reducing atmosphere (10% H{sub 2} – 90% Ar). Nanostructured LiMnPO{sub 4} is a material with very interesting properties that deserves attentions.

  18. A SARS-coronovirus 3CL protease inhibitor isolated from the marine sponge Axinella cf. corrugata: structure elucidation and synthesis

    International Nuclear Information System (INIS)

    Lira, Simone P. de; Seleghim, Mirna H.R.; Berlinck, Roberto G.S.

    2007-01-01

    Two coumarin derivatives, esculetin-4-carboxylic acid methyl ester (1) and esculetin-4- carboxylic acid ethyl ester (2), have been isolated from the marine sponge Axinella cf. corrugata. Structure determination included analysis of spectroscopic data and total synthesis of compound 2. These are the first coumarin derivatives isolated from a marine sponge. The ethyl ester 2 was found to be an in vitro inhibitor of SARS 3CL-protease and an effective inhibitor of SARS-CoV replication in Vero cells at non-cytotoxic concentrations. (author)

  19. A microporous potassium vanadyl phosphate analogue of mahnertite. Hydrothermal synthesis and crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Yakubovich, Olga V. [M.V. Lomonosov Moscow State Univ. (Russian Federation). Dept. of Crystallography; Russian Academy of Science, Moscow (Russian Federation). Inst. of Geology of Deposits, Petrography, Mineralogy and Geochemistry; Steele, Ian M. [Notre Dame Univ., IN (United States). Notre Dame Integrated Imaging Facility; Kiriukhina, Galina V.; Dimitrova, Olga V. [M.V. Lomonosov Moscow State Univ. (Russian Federation). Dept. of Crystallography

    2015-09-01

    The novel phase K{sub 2.5}Cu{sub 5}Cl(PO{sub 4}){sub 4}(OH){sub 0.5}(VO{sub 2}).H{sub 2}O was prepared by hydrothermal synthesis at 553 K. Its crystal structure was determined using low-temperature (100 K) single-crystal synchrotron diffraction data and refined against F{sup 2} to R = 0.035. The compound crystallizes in the tetragonal space group I4/mmm, with unit-cell parameters a =9.8120(8), c = 19.954(1) Aa, V = 1921.1(2) Aa{sup 3}, and Z = 4. Both symmetrically independent Cu{sup 2+} sites show elongated square-pyramidal coordination. The V{sup 5+} ions reside in strongly distorted five-vertex VO{sub 5} polyhedra with 50% occupancy. The structure is based on a 3D anionic framework built from Cu- and V-centered five-vertex polyhedra and PO{sub 4} tetrahedra. Channels in the [100] and [010] directions accommodate large K atoms and H{sub 2}O molecules. The compound is a new structural representative of the topology shown by the lavendulan group of copper arsenate and phosphate minerals. Their tetragonal or pseudotetragonal crystal structures are characterized by two types of 2D slabs alternating along one axis of their unit cells. One slab, described by the formula [Cu{sub 4}X(TO{sub 4}){sub 4}]{sub 8} (where X = Cl, O and T = As, P), is common to all phases, whereas the slab content of the other set differs among the group members. We suggest interpreting this family of compounds in terms of the modular concept and also consider the synthetic phase Ba(VO)Cu{sub 4}(PO{sub 4}){sub 4} as a simplest member of this polysomatic series.

  20. A microporous potassium vanadyl phosphate analogue of mahnertite. Hydrothermal synthesis and crystal structure

    International Nuclear Information System (INIS)

    Yakubovich, Olga V.; Russian Academy of Science, Moscow; Steele, Ian M.; Kiriukhina, Galina V.; Dimitrova, Olga V.

    2015-01-01

    The novel phase K 2.5 Cu 5 Cl(PO 4 ) 4 (OH) 0.5 (VO 2 ).H 2 O was prepared by hydrothermal synthesis at 553 K. Its crystal structure was determined using low-temperature (100 K) single-crystal synchrotron diffraction data and refined against F 2 to R = 0.035. The compound crystallizes in the tetragonal space group I4/mmm, with unit-cell parameters a =9.8120(8), c = 19.954(1) Aa, V = 1921.1(2) Aa 3 , and Z = 4. Both symmetrically independent Cu 2+ sites show elongated square-pyramidal coordination. The V 5+ ions reside in strongly distorted five-vertex VO 5 polyhedra with 50% occupancy. The structure is based on a 3D anionic framework built from Cu- and V-centered five-vertex polyhedra and PO 4 tetrahedra. Channels in the [100] and [010] directions accommodate large K atoms and H 2 O molecules. The compound is a new structural representative of the topology shown by the lavendulan group of copper arsenate and phosphate minerals. Their tetragonal or pseudotetragonal crystal structures are characterized by two types of 2D slabs alternating along one axis of their unit cells. One slab, described by the formula [Cu 4 X(TO 4 ) 4 ] 8 (where X = Cl, O and T = As, P), is common to all phases, whereas the slab content of the other set differs among the group members. We suggest interpreting this family of compounds in terms of the modular concept and also consider the synthetic phase Ba(VO)Cu 4 (PO 4 ) 4 as a simplest member of this polysomatic series.

  1. Capital Structure Determinants of Small and Medium Enterprises in Croatia

    Directory of Open Access Journals (Sweden)

    Nataša Šarlija

    2016-09-01

    Full Text Available Most of the research about capital structure is focused towards two theories: trade off theory (TOT and pecking order theory (POT. The idea is to explore which theory works better in certain conditions and identify the key determinants that affect the capital structure of the company. However, in different countries different determinants with opposite relation to the leverage are found to be significant. Besides, most of the previous researches are oriented on listed companies. The aim of this paper is to analyse the capital structure of small and medium enterprises in Croatia through the analysis of the fundamental determinants of the capital structure. The research was conducted on a data sample of 500 SMEs in Croatia in the period of 2005–2011. On the unbalanced panel data set a linear regression is applied. Influence of determinants on leverage is estimated by a static panel model with random effect and with fixed effect estimation. Four capital structure determinants are analysed: growth, size, profitability and tangible assets. The results of this research support the pecking order theory confirming that SMEs in Croatia are primarily financed frominternally generated funds that affect profitability, growth, tangible assets and enterprise size.

  2. Origami-inspired active structures: a synthesis and review

    International Nuclear Information System (INIS)

    Peraza-Hernandez, Edwin A; Hartl, Darren J; Malak Jr, Richard J; Lagoudas, Dimitris C

    2014-01-01

    Origami, the ancient art of paper folding, has inspired the design of engineering devices and structures for decades. The underlying principles of origami are very general, which has led to applications ranging from cardboard containers to deployable space structures. More recently, researchers have become interested in the use of active materials (i.e., those that convert various forms of energy into mechanical work) to effect the desired folding behavior. When used in a suitable geometry, active materials allow engineers to create self-folding structures. Such structures are capable of performing folding and/or unfolding operations without being kinematically manipulated by external forces or moments. This is advantageous for many applications including space systems, underwater robotics, small scale devices, and self-assembling systems. This article is a survey and analysis of prior work on active self-folding structures as well as methods and tools available for the design of folding structures in general and self-folding structures in particular. The goal is to provide researchers and practitioners with a systematic view of the state-of-the-art in this important and evolving area. Unifying structural principles for active self-folding structures are identified and used as a basis for a quantitative and qualitative comparison of numerous classes of active materials. Design considerations specific to folded structures are examined, including the issues of crease pattern identification and fold kinematics. Although few tools have been created with active materials in mind, many of them are useful in the overall design process for active self-folding structures. Finally, the article concludes with a discussion of open questions for the field of origami-inspired engineering. (topical review)

  3. Synthesis and structures of two new Cu(I) frameworks bearing1,3 ...

    Indian Academy of Sciences (India)

    DOI 10.1007/s12039-016-1100-6. Synthesis and structures of two new Cu(I) frameworks bearing1,3-bis(4-pyridyl)propane and inorganic linkers. ZHAOBO HUa, BO LIb,∗, WENQIANG JUa, YUNING LIANGa and ZILU CHENa,∗. aState Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources,.

  4. Fixation of CO2 in air: Synthesis and crystal structure of a µ3-CO3 ...

    Indian Academy of Sciences (India)

    Unknown

    Fixation of CO2 in air: Synthesis and crystal structure of a ... from the reaction between copper(I) complexes and dioxygen.2,6,7 ... and co-workers from the reaction of [(L2) ..... followed by water dissociation.13h,24 While fixation of CO2 by ...

  5. Synthesis and structural characterization of piperazino-modified DNA that favours hybridization towards DNA over RNA

    DEFF Research Database (Denmark)

    Skov, Joan; Bryld, Torsten; Lindegaard, Dorthe

    2011-01-01

    We report the synthesis of two C4'-modified DNA analogues and characterize their structural impact on dsDNA duplexes. The 4'-C-piperazinomethyl modification stabilizes dsDNA by up to 5°C per incorporation. Extension of the modification with a butanoyl-linked pyrene increases the dsDNA stabilizati...

  6. Aircraft interior noise prediction using a structural-acoustic analogy in NASTRAN modal synthesis

    Science.gov (United States)

    Grosveld, Ferdinand W.; Sullivan, Brenda M.; Marulo, Francesco

    1988-01-01

    The noise induced inside a cylindrical fuselage model by shaker excitation is investigated theoretically and experimentally. The NASTRAN modal-synthesis program is used in the theoretical analysis, and the predictions are compared with experimental measurements in extensive graphs. Good general agreement is obtained, but the need for further refinements to account for acoustic-cavity damping and structural-acoustic interaction is indicated.

  7. Total synthesis of the putative structure of the novel triquinane natural product isocapnellenone

    OpenAIRE

    Mehta, Goverdhan; Murthy, Sai Krishna A; Umarye, Jayant D

    2002-01-01

    A total synthesis of the ‘putative structure’ 7, attributed to the novel triquinane sesquiterpene isolated recently from two Buddelia species has been accomplished. The spectral data for 7 is a complete mismatch with those reported for the natural product and warrants a revision of the assigned structure.

  8. Synthesis, structure analysis, anti-bacterial and in vitro anti-cancer ...

    Indian Academy of Sciences (India)

    DOI 10.1007/s12039-015-0824-z. Synthesis, structure analysis, anti-bacterial and in vitro anti-cancer activity of new Schiff base and its copper complex derived from sulfamethoxazole. I RAMA∗ and R SELVAMEENA. PG and Research Department of Chemistry, Seethalakshmi Ramaswami College,. Tiruchirappalli 620 002 ...

  9. Structural characterization of birnessite: influence of the way of synthesis; Caracterisation structurale de la birnessite: influence du protocole de synthese

    Energy Technology Data Exchange (ETDEWEB)

    Gaillot, A.C.

    2002-01-15

    Birnessite is a lamellar manganese oxide whose layers are built up of edge sharing MnO{sub 6} octahedra. The presence of hetero-valent Mn cations and/or of vacant sites in these layers leads to a charge deficit compensated for by the presence of hydrated cations in the interlayer space. Because of their high specific area and of their strong oxidative character, these ubiquitous manganese oxides play a fundamental role in the fate of organic and metallic pollutants in the environment, but our imperfect knowledge of their structure limits the understanding and the modeling of this impact. This study aimed at classifying all different kinds of birnessite obtained using existing synthesis protocols according to two relevant criteria: layer symmetry and layer stacking mode, and at determining the structure of several essential varieties using X-ray and electron diffraction. Layers of hydrothermal birnessite contain vacant sites and, as a result, possess an hexagonal symmetry. Their stacking mode is 3R. In high-temperature birnessites, adjacent layers have an opposite orientation, which results in a two-layer polytype. The symmetry of these layers, linked to the origin of the layer charge deficit, depends on the temperature of synthesis. At 800 C the presence of vacant sites results in an hexagonal symmetry (2H polytype). At 1000 C, the layer charge deficit originates from the presence of Mn{sup 3+} cations in the layer lowering the layer symmetry (2O polytype). A variety of chemical and structural heterogeneities was also described in these samples, along with the occurrence of a new type of structural disorder. Finally we proved both the fundamental link between the origin of the layer charge and the layer symmetry, and the influence of physico-chemical parameters during synthesis (temperature, average manganese oxidation degree, nature of the interlayer cation) on the structure of the obtained compound. The chemical and thermal stabilities of these birnessites are

  10. Solid state synthesis and structural refinement of polycrystalline La ...

    Indian Academy of Sciences (India)

    Perovskite structure based ceramic precursors have a characteristic property of substitution in the ``A" site of the ABO3 structure. This makes them a potential material for nuclear waste management in synthetic rock (SYNROC) technology. In order to simulate the mechanism of rare earth fixation in perovskite, La ...

  11. Bureaucratic Structure in Schools: A Refinement and Synthesis in Measurement.

    Science.gov (United States)

    Sousa, David A.; Hoy, Wayne K.

    1981-01-01

    Compares two methods of measuring bureaucratic structure, Hall's organizational inventory and the University of Aston (England) approach, and tests them using data from 55 public high schools in New Jersey. Factor analysis reveals four underlying dimensions of school structure, including organizational control, rational specialization, system…

  12. Synthesis, reactivity and structural studies of carboranyl thioethers and disulfides

    Czech Academy of Sciences Publication Activity Database

    Laromaine, A.; Teixidor, F.; Kivekäs, R.; Sillanpää, R.; Benakki, R.; Grüner, Bohumír; Vinas, C.

    -, č. 10 (2005), s. 1785-1795 ISSN 1477-9226 Grant - others:Generalitat de Catalunya(ES) 2001/SGR/0033 Keywords : molecular structure * crystal structure * closo-carboranes Subject RIV: CA - Inorganic Chemistry Impact factor: 3.003, year: 2005

  13. Synthesis of nano structures for use as toxic gas adsorbents

    International Nuclear Information System (INIS)

    Velazquez P, S.; Pacheco S, J.; Estrada M, N.; Vasquez N, C.; Garcia R, M.; Garduno A, M.; Torres R, C.; Garcia G, J.; Pacheco P, M.; Valdivia B, R.; Ramos F, F.; Cruz A, A.; Duran G, M.; Hidalgo P, M.

    2008-01-01

    The work described here is the study of adsorption of nitrogen oxides by carbon nano structures and its implementation in a plasma reactor used to treat toxic gases. By placing a bed of carbon nano structures to the plasma reactor outlet obtained and increase in the efficiency of degradation. (Author)

  14. Synthesis, structure and thermoelectric properties of La1 ...

    Indian Academy of Sciences (India)

    Structural parameters for all the compounds were confirmed by the Rietveld refinement method usingpowder X-ray diffraction (XRD) data and exhibit the rhombhohedral crystal structure with space group R-3c (No. 167). Thescanning electron microscopy study reveals that the particles are spherical in shape and sizes, in the ...

  15. In cellulo structure determination of a novel cypovirus polyhedrin

    International Nuclear Information System (INIS)

    Axford, Danny; Ji, Xiaoyun; Stuart, David I.; Sutton, Geoff

    2014-01-01

    The crystal structure of a previously unsolved type of cypovirus polyhedrin has been determined from data collected directly from frozen live insect cells. This work demonstrates that with the use of a microfocus synchrotron beam the structure of a novel viral polyhedrin could be successfully determined from microcrystals within cells, removing the preparatory step of sample isolation and maintaining a favourable biological environment. The data obtained are of high quality, comparable to that obtained from isolated crystals, and enabled a facile structure determination. A small but significant difference is observed between the unit-cell parameters and the mosaic spread of in cellulo and isolated crystals, suggesting that even these robust crystals are adversely affected by removal from the cell

  16. Birthday Cake Activity Structured Arrangement for Helping Children Determining Quantities

    Directory of Open Access Journals (Sweden)

    Neni Mariana

    2010-07-01

    Full Text Available Few researches have been concerned about relation between children’s spatial thinking and number sense. Narrowing for this small research, we focused on one component of spatial thinking, that is structuring objects, and one component of number senses, that is cardinality by determining quantities. This study focused on a design research that was conducted in Indonesia in which we investigated pre-school children’s (between 2 and 3.5 years old ability in making structured arrangement and their ability to determine the quantities by looking at the arrangements. The result shows us that some of the children were able to make such arrangement. However, the children found difficulties either to determine quantities from those arrangements or to compare some structures to easily recognize number of objects.

  17. Nucleic acid helix structure determination from NMR proton chemical shifts

    Energy Technology Data Exchange (ETDEWEB)

    Werf, Ramon M. van der; Tessari, Marco; Wijmenga, Sybren S., E-mail: S.Wijmenga@science.ru.nl [Radboud University Nijmegen, Department of Biophysical Chemistry, Institute of Molecules and Materials (Netherlands)

    2013-06-15

    We present a method for de novo derivation of the three-dimensional helix structure of nucleic acids using non-exchangeable proton chemical shifts as sole source of experimental restraints. The method is called chemical shift de novo structure derivation protocol employing singular value decomposition (CHEOPS) and uses iterative singular value decomposition to optimize the structure in helix parameter space. The correct performance of CHEOPS and its range of application are established via an extensive set of structure derivations using either simulated or experimental chemical shifts as input. The simulated input data are used to assess in a defined manner the effect of errors or limitations in the input data on the derived structures. We find that the RNA helix parameters can be determined with high accuracy. We finally demonstrate via three deposited RNA structures that experimental proton chemical shifts suffice to derive RNA helix structures with high precision and accuracy. CHEOPS provides, subject to further development, new directions for high-resolution NMR structure determination of nucleic acids.

  18. Synthesis of gold nanoparticles with different atomistic structural characteristics

    International Nuclear Information System (INIS)

    Esparza, R.; Rosas, G.; Lopez Fuentes, M.; Sanchez Ramirez, J.F.; Pal, U.; Ascencio, J.A.; Perez, R.

    2007-01-01

    A chemical reduction method was used to produce nanometric gold particles. Depending on the concentration of the main reactant compound different nanometric sizes and consequently different atomic structural configurations of the particles are obtained. Insights on the structural nature of the gold nanoparticles are obtained through a comparison between digitally-processed experimental high-resolution electron microscopy images and theoretically-simulated images obtained with a multislice approach of the dynamical theory of electron diffraction. Quantum molecular mechanical calculations, based on density functional theory, are carried out to explain the relationships between the stability of the gold nanoparticles, the atomic structural configurations and the size of nanoparticles

  19. Spore coat protein of Bacillus subtilis. Structure and precursor synthesis.

    Science.gov (United States)

    Munoz, L; Sadaie, Y; Doi, R H

    1978-10-10

    The coat protein of Bacillus subtilis spores comprises about 10% of the total dry weight of spores and 25% of the total spore protein. One protein with a molecular weight of 13,000 to 15,000 comprises a major portion of the spore coat. This mature spore coat protein has histidine at its NH2 terminus and is relatively rich in hydrophobic amino acids. Netropsin, and antibiotic which binds to A-T-rich regions of DNA and inhibits sporulation, but not growth, decreased the synthesis of this spore coat protein by 75%. A precursor spore coat protein with a molecular weight of 25,000 is made initially at t1 of sporulation and is converted to the mature spore coat protein with a molecular weight of 13,500 at t2 - t3. These data indicate that the spore coat protein gene is expressed very early in sporulation prior to the modifications of RNA polymerase which have been noted.

  20. Synthesis, crystal structures and luminescence properties of two metal carboxyphosphonates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chaonan; Feng, Pingjing; Li, Jintang, E-mail: leejt@xmu.edu.cn; Luo, Xuetao

    2017-05-15

    Two metal carboxyphosphonates, [Co{sub 2}(OOCC{sub 5}H{sub 3}NPO{sub 3}){sub 2·}(H{sub 2}O){sub 3}] (Compound1) and Zn{sub 3}[OOCC{sub 6}H{sub 3}CH(OH)PO{sub 3}]{sub 2·}2H{sub 2}O (Compound2) were successfully synthesized under the hydrothermal reactions. In compound 1, two (Co1-NO{sub 5}) octahedra link the (CPO{sub 3}) by sharing the corner, which link the two (Co2-O{sub 6}) octahedra. From a-axis the six clusters form the layer. Each layer is linked through hydrogen bond. In compound 2, the (Zn-O{sub 4}) tetrahedron and (CPO{sub 3}) tetrahedron are corner-shared, which arrange in line. From a-axis, each line forms the columnar. The thermal and luminescence properties of these compounds were investigated. - Graphical abstract: The synthesis conditions of the two compounds and the crystal morphology. Compound 1 shows the layer and the compound 2 shows the pillared-layer. - Highlights: • Two new carboxyphosphonate ligands have been prepared. • Using the two ligands, two metal carboxyphosphonates have been synthesized. • The two MOFs may be candidates for fluorescent materials.

  1. Determinants of Capital Structure in Non-Financial Companies

    OpenAIRE

    Kühnhausen, Fabian; Stieber, Harald W.

    2014-01-01

    In this paper, we evaluate firm-, industry- and country-specific factors determining a firm's capital structure. The empirical validity of several capital structure theories has been ambiguous so far. We shed light on the main drivers of leverage and depict differences in industry and country characteristics. Using a short panel data set with a large cross-section, we are able to show that firm size, industry leverage, industry growth and tax shield positively affect leverage ratios, while pr...

  2. A study on determinants of capital structure in India

    Directory of Open Access Journals (Sweden)

    Anshu Handoo

    2014-09-01

    Full Text Available The paper identifies the most important determinants of capital structure of 870 listed Indian firms comprising both private sector companies and government companies for the period 2001–2010. Ten independent variables and three dependent variables have been tested using regression analysis. It has been concluded that factors such as profitability, growth, asset tangibility, size, cost of debt, tax rate, and debt serving capacity have significant impact on the leverage structure chosen by firms in the Indian context.

  3. Sulfated oligosaccharide structures, as determined by NMR techniques

    International Nuclear Information System (INIS)

    Noseda, M.D.; Duarte, M.E.R.; Tischer, C.A.; Gorin, P.A.J.; Cerezo, A.S.

    1997-01-01

    Carrageenans are sulfated polysaccharides, produced by red seaweeds (Rhodophyta), that have important biological and physico-chemical properties. Using partial autohydrolysis, we obtained sulfated oligosaccharides from a λ-carrageenan (Noseda and Cerezo, 1993). These oligosaccharides are valuable not only for the study of the structures of the parent carrageenans but also for their possible biological activities. In this work we determined the chemical structure of one of the sulfated oligosaccharides using 1D and 2D NMR techniques. (author)

  4. Determinants of Market Structure and the Airline Industry

    Science.gov (United States)

    Raduchel, W.

    1972-01-01

    The general economic determinants of market structure are outlined with special reference to the airline industry. Included are the following facets: absolute size of firms; distributions of firms by size; concentration; entry barriers; product and service differentiation; diversification; degrees of competition; vertical integration; market boundaries; and economies of scale. Also examined are the static and dynamic properties of market structure in terms of mergers, government policies, and economic growth conditions.

  5. β-Telluroacroleins and β-tellurovinyl ketones: synthesis, reactions and structure

    International Nuclear Information System (INIS)

    Sadekov, I.D.

    2002-01-01

    Data on synthesis, reactivity, spectral characteristics and structure of new telluroorganic synthons, i.e. β-tellurovinylcarbonyl compounds, were generalized and systematized. Synthesis and reactions of β-telluroacroleins and similar cations were considered individually for each type of β-tellurovinylcarbonyl compounds. Special attention was paid to the use of the compounds for preparing tellurium-containing heterocycles. Reactions characteristics of carbonyl groups and tellurium-containing substituents, as well as transformation, as a result of which β-tellurovinylcarbonyl compounds and products of their reactions form tellurium-containing heterocycles, were discussed [ru

  6. Functional coordination polymers and MOFs from reactions of the lanthanides and barium with azole ligands. Synthesis and characterization with a focus on structure determination from X-ray powder diffraction data; Funktionale Koordinationspolymere und MOFs aus Reaktionen der Lanthanide und des Bariums mit Azol-Liganden. Synthese und Charakterisierung mit dem Fokus der Strukturbestimmung anhand von Roentgenpulverbeugungsdaten

    Energy Technology Data Exchange (ETDEWEB)

    Rybak, Jens-Christoph

    2012-07-01

    This thesis deals with the synthesis and characterization of coordination polymers and MOFs of the lanthanides and barium with different azolic N-heterocycles. A total of 18 new organic-inorganic hybrid materials, as well as a series of co-doped compounds is presented. Besides the structural characterization of these materials from X-ray diffraction powder data, the focus of the investigations is on the thermal and photoluminescence spectroscopic properties. The lanthanides La - Lu, except Eu and Pm, can be reacted with 1H-1,2,3-triazole to give the series of the isotypic dense 3D-MOFs {sup 3}{sub ∞}[Ln(Tz{sup *}){sub 3}]. Investigation of the photoluminescence properties of these compounds reveals a broad range of different luminescence phenomena, including the first observation of an intrinsic inner-filter effect of the Ln{sup 3+}-ions. The structure of this isotypic series of compounds was solved and refined from X-ray powder diffraction data. A 2D-polymorph of these compounds {sup 2}{sub ∞}[Ln(Tz{sup *}){sub 3}], is observed for Ln = Sm, Tb and was characterized by single crystal data. The reaction of Eu with 1H-benzotriazole yields the 1D-coordination polymer {sup 1}{sub ∞}[Eu(Btz){sub 2}(BtzH){sub 2}], which is the first example of a divalent rare earth benzotriazolate. Analysis of the thermal properties reveals the transformation to the 3D-MOF {sup 3}{sub ∞}[Eu(Btz){sub 2}] at higher temperatures. The structure of this material was also solved from X-ray powder diffraction data. Investigation of the photoluminescence properties of the co-doped compounds {sup 3}{sub ∞}[Ba{sub 1-x}Eu{sub x}(Im){sub 2}], which were obtained from reaction of the salt-like hydrides BaH{sub 2} and EuH{sub 2} with imidazole, show that the synthesis of luminescent MOF materials by co-doping of non-luminescent networks with luminescence centers is possible. The structure of these materials was solved from X-ray powder diffraction data of the undoped compound {sup 3}{sub

  7. Generative probabilistic models extend the scope of inferential structure determination

    DEFF Research Database (Denmark)

    Olsson, Simon; Boomsma, Wouter; Frellsen, Jes

    2011-01-01

    demonstrate that the use of generative probabilistic models instead of physical forcefields in the Bayesian formalism is not only conceptually attractive, but also improves precision and efficiency. Our results open new vistas for the use of sophisticated probabilistic models of biomolecular structure......Conventional methods for protein structure determination from NMR data rely on the ad hoc combination of physical forcefields and experimental data, along with heuristic determination of free parameters such as weight of experimental data relative to a physical forcefield. Recently, a theoretically...

  8. Rotational characterization of methyl methacrylate: Internal dynamics and structure determination

    Science.gov (United States)

    Herbers, Sven; Wachsmuth, Dennis; Obenchain, Daniel A.; Grabow, Jens-Uwe

    2018-01-01

    Rotational constants, Watson's S centrifugal distortion coefficients, and internal rotation parameters of the two most stable conformers of methyl methacrylate were retrieved from the microwave spectrum. Splittings of rotational energy levels were caused by two non equivalent methyl tops. Constraining the centrifugal distortion coefficients and internal rotation parameters to the values of the main isotopologues, the rotational constants of all single substituted 13C and 18O isotopologues were determined. From these rotational constants the substitution structures and semi-empirical zero point structures of both conformers were precisely determined.

  9. Organizational Structure as a Determinant of Job Burnout.

    Science.gov (United States)

    Bilal, Atif; Ahmed, Hafiz Mushtaq

    2017-03-01

    This exploratory study determined the impact of organizational structure, particularly participation in decision making, instrumental communication, formalization, integration, and promotional opportunity, on burnout among Pakistani pediatric nurses. Data were collected from pediatric nurses working for Punjab's largest state-run hospital. The findings revealed that participation in decision making, instrumental communication, and promotional opportunity prevented burnout. Formalization contributed to burnout but integration was not related to burnout. Quite interestingly, except for supervisory status, most control variables for this study were not significantly related to emotional burnout. Hence, the hypothesis that organizational structure is a determinant of job burnout was accepted.

  10. Structural versatility of Metal-organic frameworks: Synthesis and Characterization

    KAUST Repository

    Alsadun, Norah Sadun

    2017-01-01

    -targeted multi-nuclear Molecular Building Block (MBB) precursors to unveil materials with targeted structural characteristics is captivating. The aim of my master project in the continuous quest of the group of Prof. Eddaoudi in exploring different synthetic

  11. "Chameleon" Macromolecules: Synthesis, Structures and Applications of Stimulus Responsive Polymers

    NARCIS (Netherlands)

    Sui, Xiaofeng

    2012-01-01

    This thesis describes the preparation and characterization of addressable responsive polymer structures and their versatile applications. Stimuli responsive polymer chains including temperature responsive poly(N-isopropylacrylamide), PNIPAM, pH responsive poly(methacrylic acid), PMAA and redox

  12. Synthesis, crystal structure and Thermogravimetry of ortho-phthalic ...

    Indian Academy of Sciences (India)

    satisfied by two chelated carboxylates while fifth and sixth co-ordination positions are satisfied by monodentate ... Keywords. o-Phthalic acid; coordination polymer; X-ray crystal structure; Copper(II); EPR; TGA. 1. .... Absorption coefficient.

  13. synthesis, crystal structure and antimicrobial activity of a hetero

    African Journals Online (AJOL)

    B. S. Chandravanshi

    application in many fields [1-3]. Schiff bases ... the molecular design of extended structures starting from molecular precursors is of great interest. .... absorptions of the non-bridging and bridging cyanide groups [21], and weak and broad band.

  14. Synthesis and Antifungal Activity of Musa Phytoalexins and Structural Analogs

    Directory of Open Access Journals (Sweden)

    Adriana Gallego

    2000-07-01

    Full Text Available Several perinaphthenone/phenylphenalenone compounds were synthesized to establish a relationship between structure and antifungal activity against Mycosphaerella fijiensis. Substitutions on the unsaturated carbonyl system or addition of a phenyl group reduced antibiotic activity.

  15. Synthesis, spectral and structural properties of bis-imidazoline selones

    Indian Academy of Sciences (India)

    The solid state structures of bis-imidazoline selones were ... two biologically active selones are expected to function. ∗ .... The organic extract was washed with brine solution .... mentioned CH2 carbon and the quaternary carbon of benzene ...

  16. Organic superconductors: A current overview, synthesis, structure and theory

    International Nuclear Information System (INIS)

    Wang, H.H.; Beno, M.A.; Carlson, K.D.; Geiser, U.; Kini, A.M.; Williams, J.M.

    1990-01-01

    To date, four types of crystal packing motifs (β, θ, κ and α) are known to lead to superconductivity in the BEDT-TTF based materials, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene. The syntheses, crystal structures, physical properties and band electronic structures of these materials will be reviewed. Recent progress made in the oxygen containing analogue, BEDO-TTF [bis(ethylenedioxo)tetrathiofulvalene] will be presented. The implication and future prospect of organic superconductors will be discussed

  17. Lipases as biocatalysts for the synthesis of structured lipids.

    Science.gov (United States)

    Jala, Ram Chandra Reddy; Hu, Peng; Yang, Tiankui; Jiang, Yuanrong; Zheng, Yan; Xu, Xuebing

    2012-01-01

    Structured lipids (SL) are broadly referred to as modified or synthetic oils and fats or lipids with functional or pharmaceutical applications. Some structured lipids, such as triglycerides that contain both long-chain (mainly essential) fatty acids and medium- or short-chain fatty acids and also artificial products that mimic the structure of natural materials, namely human milk fat substitutes and cocoa butter equivalents, have been discussed. Further, other modified or synthetic lipids, such as structured phospholipids and synthetic phenolic lipids are also included in this chapter. For all the products described in this chapter, enzymatic production in industry has been already conducted in one way or another. Cocoa butter equivalents, healthy oil containing medium-chain fatty acids, phosphatidyl serine, and phenol lipids from enzyme technology have been reported for commercial operation. As the demand for better quality functional lipids is increasing, the production of structured lipids becomes an interesting area. Thus, in this chapter we have discussed latest developments as well as present industrial situation of all commercially important structured lipids.

  18. Synthesis of Carbon nano structures by plasma discharge; Sintesis de nanoestructuras de carbono por descarga de plasmaa

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez L, M L

    2007-07-01

    Due to the great quantity of applications of the carbon nano structures (NEC) in diverse areas like: synthesis of super-resistant materials, hydrogen storage, nano sensors generation and nano catalysts, it has seen the necessity to generate new processes of synthesis of this materials as well as to already improve those existent. The present work has as objective to optimize the NEC synthesis process by means of the electric arc method which uses alternating current to high frequencies (HF), obtaining relatively clean products; that is to say, it hardly presents amorphous material neither sludges. They stand out the obtaining of carbon nano fibers (NFC) by means of a luminescent-arch discharge, in a gas mixture of He-CH{sub 4} with 34% at. Ni/10.32% at.Y like catalyst; at a frequency of 42 kHz and low power (300 W). This method benefits the amass of the particles in both electrodes due to the high frequencies. The time of duration of the process oscillates between 5 and 20 minutes. The obtained product was characterized by scanning electron microscopy (MEB), transmission electron microscopy (MET) to determine the NEC type obtained and by X-ray diffraction analysis and Raman spectroscopy for determining the purity of the samples. The NFC is relatively free of amorphous coal. The surface and structural analysis indicates that the fibers have a half diameter of 80 nm. It is also made, a study by optical emission spectroscopy of plasma using the Swan band for determining the temperature. (Author)

  19. Vascular wall proteoglycan synthesis and structure as a target for the prevention of atherosclerosis

    Directory of Open Access Journals (Sweden)

    Peter J Little

    2007-03-01

    Full Text Available Peter J Little1, 2, 3, Mandy L. Ballinger1, Narin Osman1,31Cell Biology of Diabetes Laboratory, Baker Heart Research Institute, Melbourne, Australia; Monash University, Departments of 2Medicine and 3Immunology, Central and Eastern Clinical School, Alfred Hospital, Melbourne, AustraliaAbstract: Atherosclerosis is the underlying pathology of most cardiovascular disease and it represents the major cause of premature death in modern societies. Current therapies target risk factors being hypertension, hypercholesterolemia, hypertriglyceridemia and hyperglycemia when diabetes is present however the maximum efficacy of these strategies is often 30% or less. Areas of vascular biology that may lead to the development of a complementary vascular wall directed therapy are: inflammation, oxidation, endothelial dysfunction, diabetes-specific factors —hyperglycemia and advanced glycation endproducts and lipid retention by vascular matrix specifically proteoglycans. The major structural features of proteoglycans that determine low-density lipoprotein (LDL binding are the length and sulfation pattern on the glycosaminoglycan (GAG chains. Emerging data discussed in this review indicates that these structural properties are subject to considerable regulation by vasoactive substances possibly using novel signaling pathways. For example, GAG elongation stimulated by platelet-derived growth factor is not blocked by the receptor tyrosine kinase antagonist, genistein suggesting that there may be a previously unknown signaling pathway involved in this response. Thus, modifying proteoglycan synthesis and structure may represent a prime target to prevent LDL binding and entrapment in the vessel wall and thus prevent the development and progression of atherosclerosis.Keywords: proteoglycans, signaling, lipoproteins, atherosclerosis

  20. Synthesis and structural evaluation of five coordination complexes of benzenepentacarboxylic acid with aza-donor ligands

    Science.gov (United States)

    Shimpi, Manishkumar R.; Biswas, Sharmita Nandy; Sarkar, Sohini; Pedireddi, V. R.

    2016-06-01

    Synthesis and structural features of five new coordination assemblies, [Co(bpyH)(H2O)5](BPCH)·(bpyH2)0.5·(H2O) (1a), [{Cu(H2O)3}·{Cu0.5(bpy)0.5(H2O)0.5}2(μ-BPCH)] (1b), [{Cd0.5(BPCH)}2·{Cd0.5(bpy)(H2O)2}2]·6(H2O) (1c), [Cu(BPCH2)(bpyeaH)]·2(H2O) (1d) and [Cd2 (bpyea)0.5(oxalate)0.5(μ-BPC) (H2O)]·(bpyeaH2)·2(H2O) (1e), have been reported. All the assemblies were prepared by co-crystallization of benzenepentacarboxylic acid (BPCH5) either with 4,4‧-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethane (bpyea) in the presence of a transition metal ion (either Co(II), Cu(II) or Cd(II)) as the case may be. All the five compounds were synthesized by hydrothermal method and structures were determined by single crystal X-ray diffraction. All the obtained compounds, 1a-1e, exhibit distinct 3-D polymeric architectures either in the form of stacked layers or host-guest networks in which water molecules play a pivotal role providing additional stabilization by coordinate bonds as well as hydrogen bonds. Other non-covalent interactions such as C-H … π and π … π stacking also participate in the formation of exotic 3-D structures of these complexes.

  1. Synthesis and properties MFe2O4 (M = Fe, Co) nanoparticles and core-shell structures

    Science.gov (United States)

    Yelenich, O. V.; Solopan, S. O.; Greneche, J. M.; Belous, A. G.

    2015-08-01

    Individual Fe3-xO4 and CoFe2O4 nanoparticles, as well as Fe3-xO4/CoFe2O4 core/shell structures were synthesized by the method of co-precipitation from diethylene glycol solutions. Core/shell structure were synthesized with CoFe2O4-shell thickness of 1.0, 2.5 and 3.5 nm. X-ray diffraction patterns of individual nanoparticles and core/shell are similar and indicate that all synthesized samples have a cubic spinel structure. Compares Mössbauer studies of CoFe2O4, Fe3-xO4 nanoparticles indicate superparamagnetic properties at 300 K. It was shown that individual magnetite nanoparticles are transformed into maghemite through oxidation during the synthesis procedure, wherein the smallest nanoparticles are completely oxidized while a magnetite core does occur in the case of the largest nanoparticles. The Mössbauer spectra of core/shell nanoparticles with increasing CoFe2O4-shell thickness show a gradual decrease in the relative intensity of the quadrupole doublet and significant decrease of the mean isomer shift value at both RT and 77 K indicating a decrease of the superparamagnetic relaxation phenomena. Specific loss power for the prepared ferrofluids was experimentally calculated and it was determined that under influence of ac-magnetic field magnetic fluid based on individual CoFe2O4 and Fe3-xO4 particles are characterized by very low heating temperature, when magnetic fluids based on core/shell nanoparticles demonstrate higher heating effect.

  2. High-throughput determination of RNA structure by proximity ligation.

    Science.gov (United States)

    Ramani, Vijay; Qiu, Ruolan; Shendure, Jay

    2015-09-01

    We present an unbiased method to globally resolve RNA structures through pairwise contact measurements between interacting regions. RNA proximity ligation (RPL) uses proximity ligation of native RNA followed by deep sequencing to yield chimeric reads with ligation junctions in the vicinity of structurally proximate bases. We apply RPL in both baker's yeast (Saccharomyces cerevisiae) and human cells and generate contact probability maps for ribosomal and other abundant RNAs, including yeast snoRNAs, the RNA subunit of the signal recognition particle and the yeast U2 spliceosomal RNA homolog. RPL measurements correlate with established secondary structures for these RNA molecules, including stem-loop structures and long-range pseudoknots. We anticipate that RPL will complement the current repertoire of computational and experimental approaches in enabling the high-throughput determination of secondary and tertiary RNA structures.

  3. Orientation determination of interfacial beta-sheet structures in situ.

    Science.gov (United States)

    Nguyen, Khoi Tan; King, John Thomas; Chen, Zhan

    2010-07-01

    Structural information such as orientations of interfacial proteins and peptides is important for understanding properties and functions of such biological molecules, which play crucial roles in biological applications and processes such as antimicrobial selectivity, membrane protein activity, biocompatibility, and biosensing performance. The alpha-helical and beta-sheet structures are the most widely encountered secondary structures in peptides and proteins. In this paper, for the first time, a method to quantify the orientation of the interfacial beta-sheet structure using a combined attenuated total reflectance Fourier transformation infrared spectroscopic (ATR-FTIR) and sum frequency generation (SFG) vibrational spectroscopic study was developed. As an illustration of the methodology, the orientation of tachyplesin I, a 17 amino acid peptide with an antiparallel beta-sheet, adsorbed to polymer surfaces as well as associated with a lipid bilayer was determined using the regular and chiral SFG spectra, together with polarized ATR-FTIR amide I signals. Both the tilt angle (theta) and the twist angle (psi) of the beta-sheet at interfaces are determined. The developed method in this paper can be used to obtain in situ structural information of beta-sheet components in complex molecules. The combination of this method and the existing methodology that is currently used to investigate alpha-helical structures will greatly broaden the application of optical spectroscopy in physical chemistry, biochemistry, biophysics, and structural biology.

  4. One-step synthesis and structural features of CdS/montmorillonite nanocomposites.

    Science.gov (United States)

    Han, Zhaohui; Zhu, Huaiyong; Bulcock, Shaun R; Ringer, Simon P

    2005-02-24

    A novel synthesis method was introduced for the nanocomposites of cadmium sulfide and montmorillonite. This method features the combination of an ion exchange process and an in situ hydrothermal decomposition process of a complex precursor, which is simple in contrast to the conventional synthesis methods that comprise two separate steps for similar nanocomposite materials. Cadmium sulfide species in the composites exist in the forms of pillars and nanoparticles, the crystallized sulfide particles are in the hexagonal phase, and the sizes change when the amount of the complex for the synthesis is varied. Structural features of the nanocomposites are similar to those of the clay host but changed because of the introduction of the sulfide into the clay.

  5. Synthesis and structural characterization of Ce-doped bismuth titanate

    International Nuclear Information System (INIS)

    Pavlovic, Nikolina; Srdic, Vladimir V.

    2009-01-01

    Ce-modified bismuth titanate nanopowders Bi 4-x Ce x Ti 3 O 12 (x ≤ 1) have been synthesized using a coprecipitation method. DTA/TG, FTIR, XRD, SEM/EDS and BET methods were used in order to investigate the effect of Ce-substitution on the structure, morphology and sinterability of the obtained powders. The phase structure investigation revealed that after calcinations at 600 deg. C powder without Ce addition exhibited pure bismuth titanate phase; however, powders with Ce (x = 0.25, 0.5 and 0.75) had bismuth titanate pyrochlore phase as the second phase. The strongest effect of Ce addition on the structure was noted for the powder with the highest amount of Ce (x = 1) having a cubic pyrochlore structure. The presence of pure pyrochlore phase was explained by its stabilization due to the incorporation of cerium ions in titanate structure. Ce-modified bismuth titanate ceramic had a density over 95% of theoretical density and the fracture in transgranular manner most probably due to preferable distribution of Ce in boundary region

  6. Synthesis, crystal structure and biological activity of novel diester cyclophanes

    International Nuclear Information System (INIS)

    Zhang, Pengfei; Yang, Bingqin; Fang, Xianwen; Cheng, Zhao; Yang, Meipan

    2012-01-01

    A series of novel diester cyclophanes was synthesized by esterification of 1,2-benzenedicarbonyl chloride with eight different diols under high dilution conditions. The structures of the compounds were verified by elemental analysis, 1 H nuclear magnetic resonance (NMR), IR spectroscopy and high resolution mass spectrometry (HRMS). The crystal structures of two compounds were characterized by single crystal X-ray diffractometry (XRD). All the new cyclophanes were evaluated for biological activities and the results showed that some of these compounds have low antibacterial or antifungal activities (author)

  7. Synthesis, crystal structure and biological activity of novel diester cyclophanes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengfei; Yang, Bingqin; Fang, Xianwen; Cheng, Zhao; Yang, Meipan, E-mail: yangbq@nwu.edu.cn [Department of Chemistry, Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Northwest University, Shaanxi (China)

    2012-10-15

    A series of novel diester cyclophanes was synthesized by esterification of 1,2-benzenedicarbonyl chloride with eight different diols under high dilution conditions. The structures of the compounds were verified by elemental analysis, {sup 1}H nuclear magnetic resonance (NMR), IR spectroscopy and high resolution mass spectrometry (HRMS). The crystal structures of two compounds were characterized by single crystal X-ray diffractometry (XRD). All the new cyclophanes were evaluated for biological activities and the results showed that some of these compounds have low antibacterial or antifungal activities (author)

  8. Direct electron crystallographic determination of zeolite zonal structures

    International Nuclear Information System (INIS)

    Dorset, Douglas L.; Gilmore, Christopher J.; Jorda, Jose Luis; Nicolopoulos, Stavros

    2007-01-01

    The prospect for improving the success of ab initio zeolite structure investigations with electron diffraction data is evaluated. First of all, the quality of intensities obtained by precession electron diffraction at small hollow cone illumination angles is evaluated for seven representative materials: ITQ-1, ITQ-7, ITQ-29, ZSM-5, ZSM-10, mordenite, and MCM-68. It is clear that, for most examples, an appreciable fraction of a secondary scattering perturbation is removed by precession at small angles. In one case, ZSM-10, it can also be argued that precession diffraction produces a dramatically improved 'kinematical' data set. There seems to no real support for application of a Lorentz correction to these data and there is no reason to expect for any of these samples that a two-beam dynamical scattering relationship between structure factor amplitude and observed intensity should be valid. Removal of secondary scattering by the precession mode appears to facilitate ab initio structure analysis. Most zeolite structures investigated could be solved by maximum entropy and likelihood phasing via error-correcting codes when precession data were used. Examples include the projected structure of mordenite that could not be determined from selected area data alone. One anomaly is the case of ZSM-5, where the best structure determination in projection is made from selected area diffraction data. In a control study, the zonal structure of SSZ-48 could be determined from selected area diffraction data by either maximum entropy and likelihood or traditional direct methods. While the maximum entropy and likelihood approach enjoys some advantages over traditional direct methods (non-dependence on predicted phase invariant sums), some effort must be made to improve the figures of merit used to identify potential structure solutions

  9. Comparison of algorithms for determination of rotation measure and Faraday structure. I. 1100–1400 MHz

    International Nuclear Information System (INIS)

    Sun, X. H.; Akahori, Takuya; Anderson, C. S.; Farnes, J. S.; O’Sullivan, S. P.; Rudnick, L.; O’Brien, T.; Bell, M. R.; Bray, J. D.; Scaife, A. M. M.; Ideguchi, S.; Kumazaki, K.; Stepanov, R.; Stil, J.; Wolleben, M.; Takahashi, K.; Weeren, R. J. van

    2015-01-01

    Faraday rotation measures (RMs) and more general Faraday structures are key parameters for studying cosmic magnetism and are also sensitive probes of faint ionized thermal gas. A definition of which derived quantities are required for various scientific studies is needed, as well as addressing the challenges in determining Faraday structures. A wide variety of algorithms has been proposed to reconstruct these structures. In preparation for the Polarization Sky Survey of the Universe's Magnetism (POSSUM) to be conducted with the Australian Square Kilometre Array Pathfinder and the ongoing Galactic Arecibo L-band Feeds Array Continuum Transit Survey (GALFACTS), we run a Faraday structure determination data challenge to benchmark the currently available algorithms, including Faraday synthesis (previously called RM synthesis in the literature), wavelet, compressive sampling, and QU-fitting. The input models include sources with one Faraday thin component, two Faraday thin components, and one Faraday thick component. The frequency set is similar to POSSUM/GALFACTS with a 300 MHz bandwidth from 1.1 to 1.4 GHz. We define three figures of merit motivated by the underlying science: (1) an average RM weighted by polarized intensity, RM wtd , (2) the separation Δϕ of two Faraday components, and (3) the reduced chi-squared χ r 2 . Based on the current test data with a signal-to-noise ratio of about 32, we find the following. (1) When only one Faraday thin component is present, most methods perform as expected, with occasional failures where two components are incorrectly found. (2) For two Faraday thin components, QU-fitting routines perform the best, with errors close to the theoretical ones for RM wtd but with significantly higher errors for Δϕ. All other methods, including standard Faraday synthesis, frequently identify only one component when Δϕ is below or near the width of the Faraday point-spread function. (3) No methods as currently implemented work well

  10. Synthesis, structure and magnetic properties of crystallographically aligned CuCr_2Se_4 thin films

    International Nuclear Information System (INIS)

    Esters, Marco; Liebig, Andreas; Ditto, Jeffrey J.; Falmbigl, Matthias; Albrecht, Manfred; Johnson, David C.

    2016-01-01

    We report the low temperature synthesis of highly textured CuCr_2Se_4 thin films using the modulated elemental reactant (MER) method. The structure of CuCr_2Se_4 is determined for the first time in its thin film form and exhibits cell parameters that are smaller than found in bulk CuCr_2Se_4. X-ray diffraction and precession electron diffraction show a strong degree of crystallographic alignment of the crystallites, where the axis is oriented perpendicular to the substrate surface, while being rotationally disordered within the plane. Temperature and field dependent in-plane and out-of-plane magnetization measurements show that the film is ferromagnetic with a Curie temperature of 406 K CuCr_2Se_4 synthesized utilizing the MER method shows stronger magnetic anisotropy (effective anisotropy: 1.82 × 10"6 erg cm"−"3; shape anisotropy: 1.07 × 10"6 erg cm"−"3), with the easy axis lying out of plane, and a larger magnetic moment (6 μ_B/f.u.) than bulk CuCr_2Se_4. - Highlights: • Crystallographically aligned, phase pure CuCr_2Se_4 were synthesized. • The degree of alignment decreases with annealing time. • The films are ferromagnetic with the easy axis along the direction. • The magnetization is larger than bulk CuCr_2Se_4 or other CuCr_2Se_4 films made to date.

  11. Synthesis, structure and superconductivity in Ba1-xKxBiO3

    International Nuclear Information System (INIS)

    Hinks, D.G.

    1989-01-01

    Ba 1-x K x BiO 3 (with x = 0.4) has the highest T c (30 K) of any copperless compound. The superconducting transition temperature of this material is expected to be at the limit of conventional electron-phonon coupling. Since this material is much simpler than the copper containing high-T c superconductors (it is cubic in its superconducting state and only sp electrons are involved in the transport properties), it should be much easier to unravel the nature of the superconducting pairing mechanism in this system. Understanding this system may help explain superconductivity in the more complex copper-oxide materials. In this paper, the authors report on the development of a synthesis method which allows the preparation of stoichiometric, single-phase materials with x between 0.0 and 0.5. The structural phase diagram was determined using powder neutron diffraction as a function of both composition and temperature. Superconductivity only occurs in the cubic perovskite phase which is stable for x larger than 0.3. At a x = 0.3 composition the material undergoes a semiconductor to metal transition with a maximum value for T c . As the K content is further increased, T c is reduced

  12. Synthesis, Crystal Structure and Luminescence Property of a New Silver(I) Dimer with Isonicotinic Acid

    International Nuclear Information System (INIS)

    Yuan, Qi; Liu, Bing

    2005-01-01

    The absorption spectrum was calculated from reflection spectrum by the Kubelka.Munk function. The energy gap of the title compound determined by extrapolation from the linear portion of the absorption edge in a (α/S) versus energy plot is 1.91 eV, which suggests that the title compound behaves as semiconductor. Isonicotinic acid (Iso), namely 4.pyridinecarboxylate, a multi.functional chelating and/or bridging ligand, has proved to be very powerful for the construction of multi. dimensional metal.organic coordination networks. Furthermore, The isonicotinic acid complexes has raised many interests in fluorescence probing with numerous potential applications for studies of microsecond diffusion and dynamics of membranes. Metal centers are potential carriers of electrochemical, magnetic, catalytic, or optical properties that may be introduced into the inorganic.organic hybrid materials. d"1"0 metals with rich photophysical and photochemical character have focused attentions to synthesize polynuclear complexes. Considering the versatile coordination abilities of Iso, we employ the ligand to coordinate with silver nitrate to fabricate a coordination complex with excellent fluorescence property. Herein we report the synthesis, crystal structure and fluorescence property of a new d"1"0 coordination dimer [Ag_2(Iso)_2(NO_3)_2

  13. Synthesis, Crystal Structure and Luminescence Property of a New Silver(I) Dimer with Isonicotinic Acid

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Qi [Pharmacy College of Henan University, Kaifeng (China); Liu, Bing [Chinese Academy of Sciences, Fuzhou (China)

    2005-10-15

    The absorption spectrum was calculated from reflection spectrum by the Kubelka.Munk function. The energy gap of the title compound determined by extrapolation from the linear portion of the absorption edge in a (α/S) versus energy plot is 1.91 eV, which suggests that the title compound behaves as semiconductor. Isonicotinic acid (Iso), namely 4.pyridinecarboxylate, a multi.functional chelating and/or bridging ligand, has proved to be very powerful for the construction of multi. dimensional metal.organic coordination networks. Furthermore, The isonicotinic acid complexes has raised many interests in fluorescence probing with numerous potential applications for studies of microsecond diffusion and dynamics of membranes. Metal centers are potential carriers of electrochemical, magnetic, catalytic, or optical properties that may be introduced into the inorganic.organic hybrid materials. d{sup 10} metals with rich photophysical and photochemical character have focused attentions to synthesize polynuclear complexes. Considering the versatile coordination abilities of Iso, we employ the ligand to coordinate with silver nitrate to fabricate a coordination complex with excellent fluorescence property. Herein we report the synthesis, crystal structure and fluorescence property of a new d{sup 10} coordination dimer [Ag{sub 2}(Iso){sub 2}(NO{sub 3}){sub 2}].

  14. Synthesis and structural characterization of carboxyethylpyrrole-modified proteins: mediators of age-related macular degeneration.

    Science.gov (United States)

    Lu, Liang; Gu, Xiaorong; Hong, Li; Laird, James; Jaffe, Keeve; Choi, Jaewoo; Crabb, John; Salomon, Robert G

    2009-11-01

    Protein modifications in which the epsilon-amino group of lysyl residues is incorporated into a 2-(omega-carboxyethyl)pyrrole (CEP) are mediators of age-related macular degeneration (AMD). They promote both angiogenesis into the retina ('wet AMD') and geographic retinal atrophy ('dry AMD'). Blood levels of CEPs are biomarkers for clinical prognosis of the disease. To enable mechanistic studies of their role in promoting AMD, for example, through the activation of B- and T-cells, interaction with receptors, or binding with complement proteins, we developed an efficient synthesis of CEP derivatives, that is especially effective for proteins. The structures of tryptic peptides derived from CEP-modified proteins were also determined. A key finding is that 4,7-dioxoheptanoic acid 9-fluorenylmethyl ester reacts with primary amines to provide 9-fluorenylmethyl esters of CEP-modified proteins that can be deprotected in situ with 1,8-diazabicyclo[5.4.0]undec-7-ene without causing protein denaturation. The introduction of multiple CEP-modifications with a wide variety of CEP:protein ratios is readily achieved using this strategy.

  15. Document boundary determination using structural and lexical analysis

    Science.gov (United States)

    Taghva, Kazem; Cartright, Marc-Allen

    2009-01-01

    The document boundary determination problem is the process of identifying individual documents in a stack of papers. In this paper, we report on a classification system for automation of this process. The system employs features based on document structure and lexical content. We also report on experimental results to support the effectiveness of this system.

  16. New method to determine structures in thermonuclear plasmas

    International Nuclear Information System (INIS)

    Tanzi, C.P.

    1998-01-01

    The information from tomographic methods is not always sufficient to determine fast changing structures, e.g. very hot plasmas. A new method has been developed by means of which, among other things, physical mechanisms of plasma instability can be disentangled. 4 refs

  17. Dynamic Capital Structure: Dynamics, Determinants and Speed of Adjustment

    NARCIS (Netherlands)

    Tamirat, A.S.; Trujillo Barrera, A.A.; Pennings, J.M.E.

    2017-01-01

    The corporate finance literature has focused on explaining the determinants of firms target capital structure and speed of adjustment using the well-established theories such as pecking order, signaling and trade-off theories. However, less attention has been paid to understanding the financing

  18. Farm Target Capital Structure: Dynamics, Determinants and Speed of Adjustment

    NARCIS (Netherlands)

    Tamirat, A.S.; Trujillo Barrera, A.A.; Pennings, J.M.E.

    2017-01-01

    The corporate finance literature has focused on explaining the determinants of firms target capital structure and speed of adjustment using the well-established theories such as pecking order, signaling and trade-off theories. However, less attention has been paid to understanding the financing

  19. A Laboratory Exercise in the Determination of Carbohydrate Structures.

    Science.gov (United States)

    White, Bernard J.; Robyt, John F.

    1988-01-01

    Describes an experiment in which students are given a naturally occurring oligosaccharide as an unknown and are asked to determine both its monosaccharide composition and its structure. Discusses methods and experimental techniques including thin layer chromatography and the use of enzymes. (CW)

  20. Determining modulus of elasticity of ancient structural timber

    Science.gov (United States)

    Houjiang Zhang; Lei Zhu; Yanliang Sun; Xiping Wang; Haicheng Yan

    2011-01-01

    During maintenance of ancient timber architectures, it is important to determine mechanical properties of the wood component materials non-destructively and effectively, so that degraded members may be replaced or repaired to avoid structural failure. Experimental materials are four larch (Larix principis-rupprechtii Mayr.) components, which were taken down from the...

  1. Birthday Cake Activity Structured Arrangement for Helping Children Determining Quantities

    Science.gov (United States)

    Mariana, Neni

    2010-01-01

    Few researches have been concerned about relation between children's spatial thinking and number sense. Narrowing for this small research, we focused on one component of spatial thinking, that is structuring objects, and one component of number senses, that is cardinality by determining quantities. This study focused on a design research that was…

  2. Macromolecular structure determination in the post-genome era

    International Nuclear Information System (INIS)

    Kuhn, P.; Soltis, S.M.

    2001-01-01

    Recent advances in genetics, molecular biology and crystallographic instrumentation and methodology have led to a revolution in the field of Structural Molecular Biology (SMB). These combined advances have paved the way to a more complete and detailed understanding of the biological macromolecules that make up an organism, both in terms of their individual functions and also the interactions between them. In this paper we describe a large-scale, genomic approach to the three-dimensional structure determination of macromolecules and their complexes, using high-throughput methodology to streamline all aspects of the process. This task requires the development of automated high-intensity synchrotron beam lines for X-ray diffraction data collection from single crystal samples. Furthermore, these beam lines must be operated within a sophisticated software and hardware environment, which is capable of delivering a completely automated structure determination pipeline. The SMB resource at SSRL is developing a system for the structure determination steps of this process, starting with the initial characterization of the frozen sample, followed by data collection, data reduction, phase determination, and model building. This paper focuses on the data collection elements of this high-throughput system

  3. Synthesis and applications of one-dimensional nano-structured polyaniline: An overview

    International Nuclear Information System (INIS)

    Zhang Donghua; Wang Yangyong

    2006-01-01

    This paper summarizes and reviews the various synthesizing approaches of one-dimensional nano-structured polyaniline (PANI) and several potential applications of the nanomaterial. The synthesizing approaches can be generally categorized into template synthesis and non-template synthesis according to whether template(s), hard (physical template) or soft (chemical template), is (are) used or not. However, though the various approaches established, preparation of one-dimensional nano-structured PANI with controllable morphologies and sizes, especially well oriented arrays on a large scale is still a major challenge. Furthermore, the formation mechanisms of the nanostructures are still unclear. On the other hand, one-dimensional nano-structured PANI exhibits high surface area, high conductivity, as well as controllable chemical/physical properties and good environmental stability, rendering the nanomaterial promising candidate for application ranging from sensors, energy storage and flash welding to digital nonvolatile memory

  4. From bacterial to human dihydrouridine synthase: automated structure determination

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, Fiona, E-mail: fiona.whelan@york.ac.uk; Jenkins, Huw T., E-mail: fiona.whelan@york.ac.uk [The University of York, Heslington, York YO10 5DD (United Kingdom); Griffiths, Samuel C. [University of Oxford, Headington, Oxford OX3 7BN (United Kingdom); Byrne, Robert T. [Ludwig-Maximilians-University Munich, Feodor-Lynen-Strasse 25, 81377 Munich (Germany); Dodson, Eleanor J.; Antson, Alfred A., E-mail: fiona.whelan@york.ac.uk [The University of York, Heslington, York YO10 5DD (United Kingdom)

    2015-06-30

    The crystal structure of a human dihydrouridine synthase, an enzyme associated with lung cancer, with 18% sequence identity to a T. maritima enzyme, has been determined at 1.9 Å resolution by molecular replacement after extensive molecular remodelling of the template. The reduction of uridine to dihydrouridine at specific positions in tRNA is catalysed by dihydrouridine synthase (Dus) enzymes. Increased expression of human dihydrouridine synthase 2 (hDus2) has been linked to pulmonary carcinogenesis, while its knockdown decreased cancer cell line viability, suggesting that it may serve as a valuable target for therapeutic intervention. Here, the X-ray crystal structure of a construct of hDus2 encompassing the catalytic and tRNA-recognition domains (residues 1–340) determined at 1.9 Å resolution is presented. It is shown that the structure can be determined automatically by phenix.mr-rosetta starting from a bacterial Dus enzyme with only 18% sequence identity and a significantly divergent structure. The overall fold of the human Dus2 is similar to that of bacterial enzymes, but has a larger recognition domain and a unique three-stranded antiparallel β-sheet insertion into the catalytic domain that packs next to the recognition domain, contributing to domain–domain interactions. The structure may inform the development of novel therapeutic approaches in the fight against lung cancer.

  5. From bacterial to human dihydrouridine synthase: automated structure determination

    International Nuclear Information System (INIS)

    Whelan, Fiona; Jenkins, Huw T.; Griffiths, Samuel C.; Byrne, Robert T.; Dodson, Eleanor J.; Antson, Alfred A.

    2015-01-01

    The crystal structure of a human dihydrouridine synthase, an enzyme associated with lung cancer, with 18% sequence identity to a T. maritima enzyme, has been determined at 1.9 Å resolution by molecular replacement after extensive molecular remodelling of the template. The reduction of uridine to dihydrouridine at specific positions in tRNA is catalysed by dihydrouridine synthase (Dus) enzymes. Increased expression of human dihydrouridine synthase 2 (hDus2) has been linked to pulmonary carcinogenesis, while its knockdown decreased cancer cell line viability, suggesting that it may serve as a valuable target for therapeutic intervention. Here, the X-ray crystal structure of a construct of hDus2 encompassing the catalytic and tRNA-recognition domains (residues 1–340) determined at 1.9 Å resolution is presented. It is shown that the structure can be determined automatically by phenix.mr-rosetta starting from a bacterial Dus enzyme with only 18% sequence identity and a significantly divergent structure. The overall fold of the human Dus2 is similar to that of bacterial enzymes, but has a larger recognition domain and a unique three-stranded antiparallel β-sheet insertion into the catalytic domain that packs next to the recognition domain, contributing to domain–domain interactions. The structure may inform the development of novel therapeutic approaches in the fight against lung cancer

  6. Using photoelectron diffraction to determine complex molecular adsorption structures

    International Nuclear Information System (INIS)

    Woodruff, D P

    2010-01-01

    Backscattering photoelectron diffraction, particularly in the energy-scan mode, is now an established technique for determining in a quantitative fashion the local structure of adsorbates on surfaces, and has been used successfully for ∼100 adsorbate phases. The elemental and chemical-state specificity afforded by the characteristic core level photoelectron binding energies means that it has particular advantages for molecular adsorbates, as the local geometry of inequivalent atoms in the molecule can be determined in a largely independent fashion. On the other hand, polyatomic molecules present a general problem for all methods of surface structure determination in that a mismatch of intramolecular distances with interatomic distances on the substrate surface means that the atoms in the adsorbed molecule are generally in low-symmetry sites. The quantities measured experimentally then represent an incoherent sum of the properties of each structural domain that is inequivalent with respect to the substrate point group symmetry. This typically leads to greater ambiguity or precision in the structural solutions. The basic principles of the method are described and illustrated with a simple example involving molecule/substrate bonding through only one constituent atom (TiO 2 -(110)/H 2 O). This example demonstrates the importance of obtaining quantitative local structural information. Further examples illustrate both the successes and the problems of this approach when applied to somewhat more complex molecular adsorbates.

  7. Synthesis and structural characterization of a calcium coordination ...

    Indian Academy of Sciences (India)

    gly = glycine) has been isolated from the calcium chloride-glycine-water system and structurally characterized. Each Ca(II) in 1 is eight-coordinated and is bonded to eight oxygen atoms three of which are from terminal water molecules and five ...

  8. Synthesis and Spectroscopic, Thermal and Crystal Structure Studies ...

    African Journals Online (AJOL)

    NICO

    Structure Studies of Hydrazinium Hydrogensuccinate .... SMART and SAINT software packages28 were used for ... were corrected for systematic errors using SADABS29 based on ... T. Premkumar, R. Selvakumar, N.P. Rath and S. Govindarajan,. 86. S. Afr. J. .... 6 D. Gajapathy, S. Govindarajan and K.C. Patil, Thermochim.

  9. Structural higher education reform - design and evaluation: synthesis report

    NARCIS (Netherlands)

    File, Jonathan M.; Huisman, Jeroen; de Boer, Harry F.; Seeber, Marco; Vukasovic, Martina; Westerheijden, Donald F.

    2016-01-01

    This study analyses how different types of system-level (or ‘landscape’) structural reforms in higher education have been designed and implemented in selected higher education systems. In the 12 case studies that form the core of the project, the researchers examine reforms aimed at: - Increasing

  10. short communication synthesis and crystal structure of a polymeric

    African Journals Online (AJOL)

    Preferred Customer

    A new polymeric zinc(II) complex, [ZnL2(PDA)]n, has been prepared by the reaction of zinc sulfate ... complex has been characterized by single-crystal X-ray diffraction. .... Molecular structure of the complex at 30% probability displacement.

  11. Synthesis, structure, thermal, transport and magnetic properties of VN ceramics

    Czech Academy of Sciences Publication Activity Database

    Huber, Š.; Jankovský, O.; Sedmidubský, D.; Luxa, J.; Klimová, K.; Hejtmánek, Jiří; Sofer, Z.

    2016-01-01

    Roč. 42, č. 16 (2016), s. 18779-18784 ISSN 0272-8842 R&D Projects: GA ČR GA13-20507S Institutional support: RVO:68378271 Keywords : vanadium mononitride * phase transition * electronic structure * heat capacity * transport properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.986, year: 2016

  12. Synthesis of PbTe nanocubes, worm-like structures

    Indian Academy of Sciences (India)

    ... the optical bandgap energies of 1.61, 1.23 and 1.01 eV, respectively. Photoconductivity measurement shows that the prepared nanocrystalline PbTe thin films of different morphology exhibits good response. This structure induced change in optical properties may have potential applications in optoelectronics devices.

  13. Synthesis and structural characterization of CsNiP crystal

    Indian Academy of Sciences (India)

    Unknown

    The crystals obtained by this method were of good quality exhibiting ... type framework structure having Cs atoms inside it (figures. 3 and 4). This helps for .... Gopalakrishna G S, Prasad J S and Lokanath N K 2001 Proc. joint 4th and 6th ICSTR ...

  14. Structural evolution of ZTA composites during synthesis and processing

    Czech Academy of Sciences Publication Activity Database

    Exare, C.; Kiat, J. M.; Guiblin, N.; Porcher, F.; Petříček, Václav

    2015-01-01

    Roč. 35, č. 4 (2015), s. 1273-1283 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GA14-03276S Institutional support: RVO:68378271 Keywords : ceramic s * alumina–zirconia composites * structural properties * strain effect * size effect Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 2.933, year: 2015

  15. Macromolecular structure determination in the post-genome era

    CERN Document Server

    Kuhn, P

    2001-01-01

    Recent advances in genetics, molecular biology and crystallographic instrumentation and methodology have led to a revolution in the field of Structural Molecular Biology (SMB). These combined advances have paved the way to a more complete and detailed understanding of the biological macromolecules that make up an organism, both in terms of their individual functions and also the interactions between them. In this paper we describe a large-scale, genomic approach to the three-dimensional structure determination of macromolecules and their complexes, using high-throughput methodology to streamline all aspects of the process. This task requires the development of automated high-intensity synchrotron beam lines for X-ray diffraction data collection from single crystal samples. Furthermore, these beam lines must be operated within a sophisticated software and hardware environment, which is capable of delivering a completely automated structure determination pipeline. The SMB resource at SSRL is developing a system...

  16. Synthesis and structure of new lanthanoid carbonate "lanthaballs".

    Science.gov (United States)

    Chesman, Anthony S R; Turner, David R; Langley, Stuart K; Moubaraki, Boujemaa; Murray, Keith S; Deacon, Glen B; Batten, Stuart R

    2015-02-02

    New insights into the synthesis of high-nuclearity polycarbonatolanthanoid complexes have been obtained from a detailed investigation of the preparative methods that initially yielded the so-called "lanthaballs" [Ln(13)(ccnm)(6)(CO(3))(14)(H(2)O)(6)(phen)(18)] Cl(3)(CO(3))·25H(2)O [α-1Ln; Ln = La, Ce, Pr; phen = 1,10-phenanthroline; ccnm = carbamoylcyanonitrosomethanide]. From this investigation, we have isolated a new pseudopolymorph of the cerium analogue of the lanthaball, [Ce(13)(ccnm)(6)(CO(3))(14)(H(2)O)(6)(phen)(18)]·C(l3)·CO(3) (β-1Ce). This new pseudopolymorph arose from a preparation in which fixation of atmospheric carbon dioxide generated the carbonate, and the ccnm ligand was formed in situ by the nucleophilic addition of water to dicyanonitrosomethanide. From a reaction of cerium(III) nitrate, instead of the previously used chloride salt, with (Et4N)(ccnm), phen, and NaHCO(3) in aqueous methanol, the new complex Na[Ce(13)(ccnm)(6)(CO(3))(14)(H(2)O)(6)(phen)(18)](NO(3))(6)·20H(2)O (2Ce) crystallized. A variant of this reaction in which sodium carbonate was initially added to Ce(NO(3))(3), followed by phen and (Et(4)N)(ccnm), also gave 2Ce. However, an analogous preparation with (Me4N)(ccnm) gave a mixture of crystals of 2Ce and the coordination polymer [CeNa(ccnm)4(phen)3]·MeOH (3), which were manually separated. The use of cerium(III) acetate in place of cerium nitrate in the initial preparation did not give a high-nuclearity complex but a new coordination polymer, [Ce(ccnm)(OAc)(2)(phen)] (4). The first lanthaball to incorporate neodymium, namely, [Nd(13)(ccnm)(4)(CO(3))14(NO(3))(4)(H(2)O)(7)(phen)(15)](NO(3))(3)·10H(2)O (5Nd), was isolated from a preparation similar to that of the second method used for 2Ce, and its magnetic properties showed an antiferromagnetic interaction. The identity of all products was established by X-ray crystallography.

  17. Direct experimental determination of the atomic structure at internal interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Browning, N.D. [Oak Ridge National Lab., TN (United States)]|[Illinois Univ., Chicago, IL (United States); Pennycook, S.J. [Oak Ridge National Lab., TN (United States)

    1995-07-01

    A crucial first step in understanding the effect that internal interfaces have on the properties of materials is the ability to determine the atomic structure at the interface. As interfaces can contain atomic disorder, dislocations, segregated impurities and interphases, sensitivity to all of these features is essential for complete experimental characterization. By combining Z-contrast imaging and electron energy loss spectroscopy (EELS) in a dedicated scanning transmission electron microscope (STEM), the ability to probe the structure, bonding and composition at interfaces with the necessary atomic resolution has been obtained. Experimental conditions can be controlled to provide, simultaneously, both incoherent imaging and spectroscopy. This enables interface structures observed in the image to be interpreted intuitively and the bonding in a specified atomic column to be probed directly by EELS. The bonding and structure information can then be correlated using bond-valence sum analysis to produce structural models. This technique is demonstrated for 25{degrees}, 36{degrees} and 67{degrees} symmetric and 45{degrees} and 25{degrees} asymmetric [001] tilt grain boundaries in SrTiO{sub 3} The structures of both types of boundary were found to contain partially occupied columns in the boundary plane. From these experimental results, a series of structural units were identified which could be combined, using continuity of gain boundary structure principles, to construct all [001] tilt boundaries in SrTiO{sub 3}. Using these models, the ability of this technique to address the issues of vacancies and dopant segregation at grain boundaries in electroceramics is discussed.

  18. Global search in photoelectron diffraction structure determination using genetic algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Viana, M L [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil); Muino, R Diez [Donostia International Physics Center DIPC, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain); Soares, E A [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil); Hove, M A Van [Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China); Carvalho, V E de [Departamento de Fisica, Icex, UFMG, Belo Horizonte, Minas Gerais (Brazil)

    2007-11-07

    Photoelectron diffraction (PED) is an experimental technique widely used to perform structural determinations of solid surfaces. Similarly to low-energy electron diffraction (LEED), structural determination by PED requires a fitting procedure between the experimental intensities and theoretical results obtained through simulations. Multiple scattering has been shown to be an effective approach for making such simulations. The quality of the fit can be quantified through the so-called R-factor. Therefore, the fitting procedure is, indeed, an R-factor minimization problem. However, the topography of the R-factor as a function of the structural and non-structural surface parameters to be determined is complex, and the task of finding the global minimum becomes tough, particularly for complex structures in which many parameters have to be adjusted. In this work we investigate the applicability of the genetic algorithm (GA) global optimization method to this problem. The GA is based on the evolution of species, and makes use of concepts such as crossover, elitism and mutation to perform the search. We show results of its application in the structural determination of three different systems: the Cu(111) surface through the use of energy-scanned experimental curves; the Ag(110)-c(2 x 2)-Sb system, in which a theory-theory fit was performed; and the Ag(111) surface for which angle-scanned experimental curves were used. We conclude that the GA is a highly efficient method to search for global minima in the optimization of the parameters that best fit the experimental photoelectron diffraction intensities to the theoretical ones.

  19. CAPITAL STRUCTURE DETERMINANTS: EVIDENCE FROM PALESTINE AND EGYPT STOCK EXCHANGES

    Directory of Open Access Journals (Sweden)

    Abdul Razak Abdul Hadi

    2017-04-01

    Full Text Available Abstract -This study is driven by the motivation to examine the capital structure determinants for Palestine Stock Exchange (PEX and Egypt Stock Exchange (EGX. Within the framework of capital structure theories, this study uses Generalized Method of Moments (GMM,1982 as an estimation model employing quarterly panel data analysis during the observed period from 2008 till 2012. The test results from GMM indicate that all the examined determinants have significant relationship with leverage. It has a negative value with liquidity, non-debt tax shield, profitability, size and growth. The Egyptian firms have some uniqueness in its trend. Current assets, debt ratio and liquidity behave positively with leverage except for growth. The other tested determinants in Egyptian companies are found to be not significant.

  20. Synthesis, Structure, and Fluorescence of a Novel Cadmium Compound

    Science.gov (United States)

    Yao, Zhong-Liang; Chen, Wen-Tong

    2017-12-01

    A novel cadmium compound, [(CdI3)2(μ2-I)]2(Me2-4,4'-H2bipy)3 (1) (Me = methyl; 4,4'-bipy = 4,4'-bipyridine) with the Me2-4,4'-H2bipy moiety generated in situ, has been prepared through a solvothermal reaction and structurally characterized by X-ray single crystal diffraction analysis. Compound 1 is characterized by an isolated structural motif, consisting of [(CdI3)2(μ2-I)]3- anions and Me2-4,4'-H2bipy2+ cations. The [(CdI3)2(μ2-I)]3- anions and Me2-4,4'-H2bipy2+ cations interconnect together via C-H···I hydrogen-bonding interactions to complete a three-dimensional (3D) supramolecular network. Solid state fluorescent spectrum reveals an emission band in the violet region.

  1. Synthesis and crystal structures of three new benzotriazolylpropanamides

    Directory of Open Access Journals (Sweden)

    Donna S. Amenta

    2017-06-01

    Full Text Available The base-catalyzed Michael addition of 2-methylacrylamide to benzotriazole afforded 3-(1H-benzotriazol-1-yl-2-methylpropanamide, C10H12N4O (1, in 32% yield in addition to small amounts of isomeric 3-(2H-benzotriazol-2-yl-2-methylpropanamide, C10H12N4O (2. In a similar manner, 3-(1H-benzotriazol-1-yl-N,N-dimethylpropanamide, C11H14N4O (3, was prepared from benzotriazole and N,N-dimethylacrylamide. All three products have been structurally characterized by single-crystal X-ray diffraction. The crystal structures of 1 and 2 comprise infinite arrays formed by N—H...O and N—H...N bridges, as well as π–π interactions, while the molecules of 3 are aggregated to simple π-dimers in the crystal.

  2. Synthesis, characterization, x-ray structure and antimicrobial activity ...

    African Journals Online (AJOL)

    intermolecular N3—H1N1•••O1 hydrogen bonds. (Table 2), resulting in the formation of zigzag layers lying parallel to (100) (Fig. 2b). The existence of π•••π interactions involving the centroid of the N4/C9-C13 pyridine ring (π•••π distance = 3.5108(18) Å) further stabilize the molecular packing. The structure of compound 2.

  3. Synthesis and characterization of JBW structure and its thermal transformation

    International Nuclear Information System (INIS)

    Hegazy, Eman Z.; Kosa, Samia A.; Abd El Maksod, Islam Hamdy

    2012-01-01

    In this paper, JBW zeolite prepared from Egyptian kaolin was investigated by means of XRD, IR, SEM, EDX and ion exchange of some heavy metals. Adsorption isotherms were used to investigate the structure and properties of the prepared zeolite. XRD analysis showed that the JBW was a pure crystalline phase with orthorhombic crystal symmetry. Thermal treatment showed that the JBW transformed into the It-Carn phase at 1000 °C through an intermediate crystalline alumino silicate phase. SEM images showed that the JBW crystallised in a cylindrical shape. However, spherical agglomerates were observed at lower magnifications. The ion exchange isotherms with Cu 2+ , Ni 2+ and Co 2+ were found to follow a Freundlich isotherm. In addition, it shows higher affinity towards Cu 2+ than other ions. - Graphical abstract: JBW zeolite structure was prepared from Egyptian kaolin and characterised. XRD analysis showed that the JBW was a pure crystalline phase with orthorhombic crystal symmetry. Thermal treatment showed that the JBW transformed into the It-Carn phase at 1000 °C through an intermediate crystalline alumino silicate phase. Highlights: ► Egyptian kaolin was successfully used to prepare pure phase of JBW Structure. ► JBW is stable till 2+ , Ni 2+ , and Co 2+ followed up Freundlich isotherm. ► Selectivity towards Cu 2+ is much higher than Co 2+ or Ni 2+ .

  4. Uranium complexes with macrosyclic polyethers. Synthesis and structural chemical analysis

    International Nuclear Information System (INIS)

    Elbasyouny, A.

    1983-01-01

    This dissertation reports about studies on the chemical coordination behaviour of uranium of oxidation stages IV and VI with regard to twelve different macrocyclic ligands. For the preparation of the complexes, for every system a different method has been developed. The elementary analysis of the various complexes including the uranium had been done by X-ray fluorescence analysis, and the structural characterization proceeded via vibrational, uv-vis and emission spectroscopy as well as 1 H-NMR and 13 C-spin-lattice relaxation time studies. Conformational analysis of the polyethers used allowed the structural changes in the complexes to be observed. The structural analysis of the hydrous uranium VI crown ether complexes yielded information of characteristic features of these types of complexes. The first coordination sphere of the uranyl ion with covalently bonded anion remains unchanged. As to the water content, there is a certain range. Depending upon the solvent used, the complexes have two or four H 2 O molecules per formula unit. (orig./EF) [de

  5. Controlled Synthesis of Manganese Dioxide Nano structures via a Facile Hydrothermal

    International Nuclear Information System (INIS)

    Pang, R.S.C.; Chin, S.F.; Ye, Ch. Ling

    2012-01-01

    Manganese dioxide nano structures with controllable morphological structures and crystalline phases were synthesized via a facile hydrothermal route at low temperatures without using any templates or surfactants. Both the aging duration and aging temperatures were the main synthesis parameters used to influence and control the rate of morphological and structural evolution of MnO 2 nano structures. MnO 2 nano structures comprise of spherical nano particulate agglomerates and highly amorphous in nature were formed at lower temperature and/or short aging duration. In contrast, MnO 2 nano structures of sea-urchin-like and nano rods-like morphologies and nanocrystalline in nature were prepared at the combined higher aging temperatures and longer aging durations. These nano structures underwent notable phase transformation from d-MnO 2 to a-MnO 2 upon prolonged hydrothermal aging duration and exhibited accelerated rate of phase transformation at higher aging temperature.

  6. X-ray structure determination and deuteration of nattokinase

    International Nuclear Information System (INIS)

    Yanagisawa, Yasuhide; Chatake, Toshiyuki; Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki; Kawaguchi, Akio; Chiba-Kamosida, Kaori; Ogawa, Megumi; Adachi, Tatsumi; Morimoto, Yukio

    2013-01-01

    X-ray structure determination and deuteration of nattokinase were performed to facilitate neutron crystallographic analysis. Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D 2 O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D 2 O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis

  7. X-ray structure determination and deuteration of nattokinase

    Energy Technology Data Exchange (ETDEWEB)

    Yanagisawa, Yasuhide [Chiba Institute of Science, 15-8 Shiomi-cho, Cho-shi, Chiba 288-025 (Japan); Chatake, Toshiyuki [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan); Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki [Kurashiki University of Science and the Arts, 2640 Nishinoura, Tsurajima-cho, Kurashiki, Okayama 712-8505 (Japan); Kawaguchi, Akio [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan); Chiba-Kamosida, Kaori [Nippon Advanced Technology Co. Ltd, J-PARC, 2-4 Shirane Shirakata, Tokai, Ibaraki 319-1195 (Japan); Ogawa, Megumi; Adachi, Tatsumi [Chiba Institute of Science, 15-8 Shiomi-cho, Cho-shi, Chiba 288-025 (Japan); Morimoto, Yukio [Kyoto University, Asashironishi 2, Kumatori, Osaka 590-0494 (Japan)

    2013-11-01

    X-ray structure determination and deuteration of nattokinase were performed to facilitate neutron crystallographic analysis. Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D{sub 2}O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D{sub 2}O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis.

  8. Overconfidence, Managerial Optimism, and the Determinants of Capital Structure

    Directory of Open Access Journals (Sweden)

    Alexandre di Miceli da Silveira

    2008-12-01

    Full Text Available This research examines the determinants of the capital structure of firms introducing a behavioral perspective that has received little attention in corporate finance literature. The following central hypothesis emerges from a set of recently developed theories: firms managed by optimistic and/or overconfident people will choose more levered financing structures than others, ceteris paribus. We propose different proxies for optimism/overconfidence, based on the manager’s status as an entrepreneur or non-entrepreneur, an idea that is supported by theories and solid empirical evidence, as well as on the pattern of ownership of the firm’s shares by its manager. The study also includes potential determinants of capital structure used in earlier research. We use a sample of Brazilian firms listed in the Sao Paulo Stock Exchange (Bovespa in the years 1998 to 2003. The empirical analysis suggests that the proxies for the referred cognitive biases are important determinants of capital structure. We also found as relevant explanatory variables: profitability, size, dividend payment and tangibility, as well as some indicators that capture the firms’ corporate governance standards. These results suggest that behavioral approaches based on human psychology research can offer relevant contributions to the understanding of corporate decision making.

  9. EFFECTS OF SYNTHESIS PARAMETERS ON THE STRUCTURE OF TITANIA NANOTUBES

    Directory of Open Access Journals (Sweden)

    M. NORANI MUTI

    2008-08-01

    Full Text Available Detection of hydrogen is crucial for industrial process control and medical applications where presence of hydrogen in breath indicates different type of health problems particularly in infants. A better performed sensor with high sensitivity, selectivity, reliability and faster response time would be critical and sought after especially for medical applications. Titanium dioxide nanotube structure is chosen as an active component in the gas sensor because of its highly sensitive electrical resistance to hydrogen over a wide range of concentrations. The objective of the work is to investigate the effect of the anodizing conditions on the structure of titania nanotubes produced by anodizing method. The anodizing parameters namely the ambient temperature and separation of electrodes are varied accordingly to find the optimum anodizing conditions for production of good quality titania nanotubes for enhanced properties based on their uniformity, coverage, pore size and crystallinity. Samples of nanotubes produced were subjected to annealing process at varying time and temperature in order to improve the crystallinity of the nanotubes. The highly ordered porous titania nanotubes produced by this method are of tabular shape and have good uniformity and alignment over large areas. The pore size of the titania nanotubes ranges from 47 to 94 nm, while the wall thickness is in the range of 17 to 26 nm. The length of the nanotubes was found to be about 280 nm. The structure of nanotubes changes from amorphous to crystalline after undergoing annealing treatment. Nanotubes have also shown to have better crystallinity if they were subjected to annealing treatment at higher temperature. The characteristics of nanotubes obtained are found to be agreeable to those that have been reported to show improved hydrogen gas sensing properties.

  10. Synthesis, reactivity, and electronic structure of molecular uranium nitrides

    OpenAIRE

    Cleaves, Peter A.

    2016-01-01

    The study of metal-ligand multiple bonding offers insight into the electronic structure and bond of metal systems. Until recently, for uranium, such systems were limited to uranyl, and terminal chalcogenide, imide and carbene complexes. In 2012, this was extended to nitrides with the first preparation of a uranium–nitride (U≡N) species isolable under standard conditions, namely [U(TrenTIPS)(N)][Na(12C4)2] (52), which is prepared by the two-electron reduction of sodium azide with a trivalent u...

  11. Synthesis and structural characterization of oaklin-catechins.

    Science.gov (United States)

    Sousa, André; Fernandes, Ana; Mateus, Nuno; De Freitas, Victor

    2012-02-15

    Condensation reactions of procyanidin dimer B4 with two representative oak wood cinnamic aldehydes (coniferaldehyde and sinapaldehyde) were conducted in winelike model solutions. Coniferaldehyde led to the formation of guaiacylcatechin-pyrylium-catechin (GCP-catechin, 737 m/z), whereas sinapaldehyde led to the formation of syringylcatechin-pyrylium-catechin (SCP-catechin, 767 m/z). The former was also structurally characterized by 1D and 2D NMR, allowing an elucidation of the formation mechanism of these oaklin-catechin adducts and demonstrating the importance of procyanidins in the formation of colored compounds through the reaction with cinnamic aldehydes extracted from oaks during storage.

  12. Alkyltributylphosphonium chloride ionic liquids: synthesis, physicochemical properties and crystal structure.

    Science.gov (United States)

    Adamová, Gabriela; Gardas, Ramesh L; Nieuwenhuyzen, Mark; Puga, Alberto V; Rebelo, Luís Paulo N; Robertson, Allan J; Seddon, Kenneth R

    2012-07-21

    A series of alkyltributylphosphonium chloride ionic liquids, prepared from tributylphosphine and the respective 1-chloroalkane, C(n)H(2n+1)Cl (where n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 or 14), is reported. This work is a continuation of an extended series of tetraalkylphosphonium ionic liquids, where the focus is on the variability of n and its impact on the physical properties, such as melting points/glass transitions, thermal stability, density and viscosity. Experimental density and viscosity data were interpreted using QPSR and group contribution methods and the crystal structure of propyl(tributyl)phosphonium chloride is detailed.

  13. Determination of the synthesis of uptake of α2-macroglobulin by cultured human glioma cells

    International Nuclear Information System (INIS)

    Druskova, E.; Bizik, J.; Grofova, M.

    1994-01-01

    Using immunological techniques, the synthesis of α 2 -macroglobulin was studied in established cell lines derived from human glioblastomas multiform. α 2 -Macroglobulin was detected in cytoplasm and in the culture medium of the analyzed cell lines. Radioimmunoprecipitation, revealed a protein with Mr corresponding to α 2 -macroglobulin in the medium conditioned by U-118MG and U-343MG cells. On the other hand, using immunoblot analysis, α 2 -macroglobulin was detected in all of the analyzed lines. In immunofluorescence test, α 2 -macroglobulin was determined also in all four cell lines, but with different staining pattern. Conditioned culture medium of U-536MG cells with the lowest level of α 2 -macroglobulin exerted the lowest mitogenic activity for human fibroblasts. (author)

  14. Colorimetric determination of TOPO during synthesis process by complexation with thiocyanate

    International Nuclear Information System (INIS)

    Achache, A.; Meddour, L.; Azzouz, A.

    1990-09-01

    We have shown up a method which permits to dose tri-n-octyl phosphine oxid (TOPO) dissolved into the cyclohexan by colorimetric technique. This leads to find out a method capable to follow the evolution of the process of the synthesis for the tri-n-octyl phosphine oxid. This method consists in mixing up TOTO-cyclohexan with thiocyanate salts, and the formation of a complex of red colour occurs. Further, the complex amount was determined by spectrophotometry U.V. under the following conditions: =487nm; the concentration of the TOPO into the cyclohexan varies in range 1 to 5 10 -4 M/L. This method previously tested on the commercial TOPO (Flukz) was further used for the titration of synthetizied TOPO

  15. Determination of kinetic parameters and Hammett ρ from the synthesis of triaryl phosphites using reaction calorimetry

    International Nuclear Information System (INIS)

    Seiceira, Rafael C.; Higa, Camila M.; Barreto, Amaro G.; Cajaiba da Silva, Joao F.

    2005-01-01

    Triaryl phosphites bearing electron donating and electron withdrawing substituents were prepared through the reaction of sodium phenoxides with phosphorus trichloride. The reactions were performed in a Mettler RC1 reaction calorimeter. The main purpose of this work was the determination of Hammett ρ from the synthesis of substituted triaryl phosphites through the interpretation of calorimetric data. The phenoxide bearing a methoxide group was the most reactive, and the one bearing the nitro group was the least reactive. It was demonstrated that the reaction rate depends mainly on the addition rate of phosphorus trichloride solution. A good correlation between the Hammet parameters (σ p + ) was obtained, indicating a reaction mechanism in which a decrease of the negative charge occurs in the transition state

  16. One dimensional coordination polymers: Synthesis, crystal structures and spectroscopic properties

    Science.gov (United States)

    Karaağaç, Dursun; Kürkçüoğlu, Güneş Süheyla; Şenyel, Mustafa; Şahin, Onur

    2016-11-01

    Two new one dimensional (1D) cyanide complexes, namely [M(4-aepy)2(H2O)2][Pt(CN)4], (4-aepy = 4-(2-aminoethyl)pyridine M = Cu(II) (1) or Zn(II) (2)), have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal and elemental analyses techniques. The crystallographic analyses reveal that 1 and 2 are isomorphous and isostructural, and crystallize in the monoclinic system and C2 space group. The Pt(II) ions are coordinated by four cyanide-carbon atoms in the square-planar geometry and the [Pt(CN)4]2- ions act as a counter ion. The M(II) ions display an N4O2 coordination sphere with a distorted octahedral geometry, the nitrogen donors belonging to four molecules of the organic 4-aepy that act as unidentate ligands and two oxygen atoms from aqua ligands. The crystal structures of 1 and 2 are similar each other and linked via intermolecular hydrogen bonding, Pt⋯π interactions to form 3D supramolecular network. Vibration assignments of all the observed bands are given and the spectral features also supported to the crystal structures of the complexes.

  17. Topology Synthesis of Structures Using Parameter Relaxation and Geometric Refinement

    Science.gov (United States)

    Hull, P. V.; Tinker, M. L.

    2007-01-01

    Typically, structural topology optimization problems undergo relaxation of certain design parameters to allow the existence of intermediate variable optimum topologies. Relaxation permits the use of a variety of gradient-based search techniques and has been shown to guarantee the existence of optimal solutions and eliminate mesh dependencies. This Technical Publication (TP) will demonstrate the application of relaxation to a control point discretization of the design workspace for the structural topology optimization process. The control point parameterization with subdivision has been offered as an alternative to the traditional method of discretized finite element design domain. The principle of relaxation demonstrates the increased utility of the control point parameterization. One of the significant results of the relaxation process offered in this TP is that direct manufacturability of the optimized design will be maintained without the need for designer intervention or translation. In addition, it will be shown that relaxation of certain parameters may extend the range of problems that can be addressed; e.g., in permitting limited out-of-plane motion to be included in a path generation problem.

  18. Stacked nickelocenes: synthesis, structural characterization, and magnetic properties.

    Science.gov (United States)

    Trtica, Sabrina; Prosenc, Marc Heinrich; Schmidt, Michael; Heck, Jürgen; Albrecht, Ole; Görlitz, Detlef; Reuter, Frank; Rentschler, Eva

    2010-02-15

    The disubstitution of 1,8-diiodonaphthalene (1) with cyclopentadienyl nucleophiles reveals 1,8-(dicyclopentadienyl)-naphthalene, which rapidly undergoes Diels-Alder reaction forming 1,8-(3a',4',7',7a'-tetrahydro-4',7'-methanoindene-7a',8'-diyl)-naphthalene (2). A subsequent retro-Diels-Alder reaction in the presence of sodium hydride yields the disodium salt of 1,8-(dicyclopentadiendiyl)-naphthalene 3. The disodium salt 3 was the starting material to obtain the paramagnetic bisnickelocene derivative 4, which structure was obtained by X-ray structure analysis, revealing two nickelocenes kept together in a stacked fashion by a 1,8-naphthalene clamp. An electronic interaction between the two nickel atoms is found as a result of cyclic voltammetry, indicating five different oxidation states +4, +3, +2, +1, and 0. The magnetic properties of 4 in solution were studied by variable temperature paramagnetic (1)H NMR spectroscopy and Evans method and revealed Curie behavior between 213 and 293 K. The magnetic susceptibility of a powdered sample of 4 was measured, and an antiferromagnetic interaction with an exchange coupling of J(12) = -31.49 cm(-1) is found. In accord with experimental data, broken symmetry density functional theory (DFT) calculations revealed four antiferromagnetically coupled electrons resulting in an open shell singlet ground state.

  19. Synthesis and structural characterization of actinide oxalate compounds

    International Nuclear Information System (INIS)

    Tamain, C.

    2011-01-01

    Oxalic acid is a well-known reagent to recover actinides thanks to the very low solubility of An(IV) and An(III) oxalate compounds in acidic solution. Therefore, considering mixed-oxide fuel or considering minor actinides incorporation in ceramic fuel materials for transmutation, oxalic co-conversion is convenient to synthesize mixed oxalate compounds, precursors of oxide solid solutions. As the existing oxalate single crystal syntheses are not adaptable to the actinide-oxalate chemistry or to their manipulation constrains in gloves box, several original crystal growth methods were developed. They were first validate and optimized on lanthanides and uranium before the application to transuranium elements. The advanced investigations allow to better understand the syntheses and to define optimized chemical conditions to promote crystal growth. These new crystal growth methods were then applied to a large number of mixed An1(IV)-An2(III) or An1(IV)-An2(IV) systems and lead to the formation of the first original mixed An1(IV)-An2(III) and An1(IV)-An2(IV) oxalate single crystals. Finally thanks to the first thorough structural characterizations of these compounds, single crystal X-ray diffraction, EXAFS or micro-RAMAN, the particularly weak oxalate-actinide compounds structural database is enriched, which is essential for future studied nuclear fuel cycles. (author) [fr

  20. (Biodegradable Ionomeric Polyurethanes Based on Xanthan: Synthesis, Properties, and Structure

    Directory of Open Access Journals (Sweden)

    T. V. Travinskaya

    2017-01-01

    Full Text Available New (biodegradable environmentally friendly film-forming ionomeric polyurethanes (IPU based on renewable biotechnological polysaccharide xanthan (Xa have been obtained. The influence of the component composition on the colloidal-chemical and physic-mechanical properties of IPU/Xa and based films, as well as the change of their properties under the influence of environmental factors, have been studied. The results of IR-, PMS-, DMA-, and X-ray scattering study indicate that incorporation of Xa into the polyurethane chain initiates the formation of a new polymer structure different from the structure of the pure IPU (matrix: an amorphous polymer-polymer microdomain has occurred as a result of the chemical interaction of Xa and IPU. It predetermines the degradation of the IPU/Xa films as a whole, unlike the mixed polymer systems, and plays a key role in the improvement of material performance. The results of acid, alkaline hydrolysis, and incubation into the soil indicate the increase of the intensity of degradation processes occurring in the IPU/Xa in comparison with the pure IPU. It has been shown that the introduction of Xa not only imparts the biodegradability property to polyurethane, but also improves the mechanical properties.

  1. Experimental determination of the structure of H3+

    International Nuclear Information System (INIS)

    Gaillard, M.J.; Gemmell, D.S.; Goldring, G.; Levine, I.; Pietsch, W.J.; Poizat, J.C.; Ratkowski, A.J.; Remillieux, J.; Vager, Z.; Zabransky, B.J.

    1978-01-01

    Three different measurements on the structure of the H 3 + molecular ion are reported. The measurements all make use of a new technique: the foil-induced dissociation of a fast molecular-ion beam. It is shown that the structure is equilaterally triangular in shape. The most probable length of side of the triangle is determined by the three measurements to be 0.97 +- 0.03 A, 0.95 +- 0.06 A, and 1.2 +- 0.2 A, respectively

  2. Sulfated oligosaccharide structures, as determined by NMR techniques

    Energy Technology Data Exchange (ETDEWEB)

    Noseda, M.D.; Duarte, M.E.R.; Tischer, C.A.; Gorin, P.A.J. [Parana Univ., Curitiba, PR (Brazil). Dept. De Bioquimica; Cerezo, A.S. [Buenos Aires Univ. Nacional (Argentina). Dept. de Quimica Organica

    1997-12-31

    Carrageenans are sulfated polysaccharides, produced by red seaweeds (Rhodophyta), that have important biological and physico-chemical properties. Using partial autohydrolysis, we obtained sulfated oligosaccharides from a {lambda}-carrageenan (Noseda and Cerezo, 1993). These oligosaccharides are valuable not only for the study of the structures of the parent carrageenans but also for their possible biological activities. In this work we determined the chemical structure of one of the sulfated oligosaccharides using 1D and 2D NMR techniques. (author) 4 refs., 8 figs., 1 tabs.

  3. Taking MAD to the extreme: ultrafast protein structure determination

    International Nuclear Information System (INIS)

    Walsh, M.A.; Dementieva, I.; Evans, G.; Sanishvili, R.; Joachimiak, A.

    1999-01-01

    Multiwavelength anomalous diffraction data were measured in 23 min from a 16 kDa selenomethionyl-substituted protein, producing experimental phases to 2.25 (angstrom) resolution. The data were collected on a mosaic 3 x 3 charge-coupled device using undulator radiation from the Structural Biology Center 19ID beamline at the Argonne National Laboratory's Advanced Photon Source. The phases were independently obtained semiautomatically by two crystallographic program suites, CCP4 and CNS. The quality and speed of this data acquisition exemplify the opportunities at third-generation synchrotron sources for high-throughput protein crystal structure determination

  4. Implantation measurements to determine tritium permeation in first wall structures

    International Nuclear Information System (INIS)

    Holland, D.F.; Causey, R.A.

    1983-01-01

    A principal safety concern for a D-T burning fusion reactor is release of tritium during routine operation. Tritium implantation into first wall structures, and subsequent permeation into coolants, is potentially an important source of tritium loss. This paper reports on an experiment in which an ion accelerator was used to implant deuterium atoms in a stainless steel disk to simulate tritium implantation in first wall structures. The permeation rate was measured under various operating conditions. These results were used in the TMAP computer code to determine potential tritium loss rates for fusion reactors

  5. DETERMINANT FACTORS OF THE CAPITAL STRUCTURE OF BRAZILIAN TECHNOLOGY COMPANIES

    Directory of Open Access Journals (Sweden)

    Camila Freitas Sant´Ana

    2015-12-01

    Full Text Available The purpose of this study is to identify determinant factors of the capital structure of Brazilian technology companies. The research was characterized as descriptive, document and quantitative, consisting of 21 companies in the communications, telecommunications and digital industry, according to the Exame magazine ranking. The analysis was established from 2009 to 2013 using panel data regression. The results indicate that the growth rate of capital and control type have a positive relationship with the general and long-term debt. However, it was found that company size, profitability and type of capital point to a negative relationship with the capital structure.

  6. Design and synthesis of diverse functional kinked nanowire structures for nanoelectronic bioprobes.

    Science.gov (United States)

    Xu, Lin; Jiang, Zhe; Qing, Quan; Mai, Liqiang; Zhang, Qingjie; Lieber, Charles M

    2013-02-13

    Functional kinked nanowires (KNWs) represent a new class of nanowire building blocks, in which functional devices, for example, nanoscale field-effect transistors (nanoFETs), are encoded in geometrically controlled nanowire superstructures during synthesis. The bottom-up control of both structure and function of KNWs enables construction of spatially isolated point-like nanoelectronic probes that are especially useful for monitoring biological systems where finely tuned feature size and structure are highly desired. Here we present three new types of functional KNWs including (1) the zero-degree KNW structures with two parallel heavily doped arms of U-shaped structures with a nanoFET at the tip of the "U", (2) series multiplexed functional KNW integrating multi-nanoFETs along the arm and at the tips of V-shaped structures, and (3) parallel multiplexed KNWs integrating nanoFETs at the two tips of W-shaped structures. First, U-shaped KNWs were synthesized with separations as small as 650 nm between the parallel arms and used to fabricate three-dimensional nanoFET probes at least 3 times smaller than previous V-shaped designs. In addition, multiple nanoFETs were encoded during synthesis in one of the arms/tip of V-shaped and distinct arms/tips of W-shaped KNWs. These new multiplexed KNW structures were structurally verified by optical and electron microscopy of dopant-selective etched samples and electrically characterized using scanning gate microscopy and transport measurements. The facile design and bottom-up synthesis of these diverse functional KNWs provides a growing toolbox of building blocks for fabricating highly compact and multiplexed three-dimensional nanoprobes for applications in life sciences, including intracellular and deep tissue/cell recordings.

  7. Synthesis and structural and electrical characterization of new materials Bi3R2FeTi3O15

    International Nuclear Information System (INIS)

    Gil Novoa, O.D.; Landínez Téllez, D.A.; Roa-Rojas, J.

    2012-01-01

    In this work we report the synthesis of polycrystalline samples of Bi 5 FeTi 3 O 15 and Bi 3 R 2 FeTi 3 O 15 new compounds with R=Nd, Sm, Gd, Dy, Ho and Yb. The materials were synthesized by the standard solid state reaction recipe from high purity (99.99%) powders. The structural characteristics of materials were analyzed by X-ray diffraction experiments. Rietveld refinement by the GSAS code was performed, taking the input data from the ICSD 74037 database. Results reveal that materials crystallized in orthorhombic single-phase structures and space group Fmm2. Measurements of polarization as a function of applied electric field were carried out using a Radiant Technology polarimeter. We determine the occurrence of hysteretic behaviors, which are characteristic of ferroelectric materials. The main values of remnant and coercive applied fields were observed for substitutions with Yb and Nd, which have the main atomic radii.

  8. Synthesis and Structural Characterization of ZnS Quantum Dots

    International Nuclear Information System (INIS)

    Selim, H.; Khalil, M.M.H.; Al-Kotb, M.S.; Kotkata, M.F.; Amer, H.H.

    2013-01-01

    Zinc sulfide QDs have been synthesized via a simple reaction of Zn (CH 3 COO) 2 and Na 2 S in the presence of sodium dodecyl sulphate (SDS) acting as an anionic capping material. The structure as well as characterization of the synthesized materials has been studied by XRD, EDX, SEM, TEM, TGA and FT-IR spectroscopy. Analysis of the obtained results revealed products of zinc blende ZnS nanoparticles with an average size of 5.3±0.2 nm in diameter distributed spherically and uniformly. The UV-visible absorption spectrum of the synthesized ZnS nanoparticles reflects an energy gap of 4.30 eV

  9. Nanocomposites: synthesis, structure, properties and new application opportunities

    Directory of Open Access Journals (Sweden)

    Pedro Henrique Cury Camargo

    2009-03-01

    Full Text Available Nanocomposites, a high performance material exhibit unusual property combinations and unique design possibilities. With an estimated annual growth rate of about 25% and fastest demand to be in engineering plastics and elastomers, their potential is so striking that they are useful in several areas ranging from packaging to biomedical applications. In this unified overview the three types of matrix nanocomposites are presented underlining the need for these materials, their processing methods and some recent results on structure, properties and potential applications, perspectives including need for such materials in future space mission and other interesting applications together with market and safety aspects. Possible uses of natural materials such as clay based minerals, chrysotile and lignocellulosic fibers are highlighted. Being environmentally friendly, applications of nanocomposites offer new technology and business opportunities for several sectors of the aerospace, automotive, electronics and biotechnology industries.

  10. 1-Hydroxyethyl-2-Substituted Phenoxymethyl Benzimidazoles: Synthesis and Crystal Structures

    International Nuclear Information System (INIS)

    Wu, J.; Wang, Z.; Gu, H.; Chen, W.; Zhao, L.; Zhao, C.

    2016-01-01

    Five novel 1-hydroxyethyl-2-substituted phenoxymethyl benzimidazoles c1-c5 were successfully synthesized by a three-step route. Firstly, five substituted phenoxymethyl acids a1-a5 were prepared by the O-carboxymethylation reaction of the starting substituted phenols under microwave irradiation. Then, these compounds reacted with o-phenylendiamine to get the key intermediates 2-substituted phenoxymethyl benzimidazoles b1-b5. At last, the target compounds were synthesized by the N-hydroxyethylation reaction of b1-b5 with 2-chloroethyl alcohol through the solid-liquid phase transfer catalysis method, where tetrabutyl ammonium bromide (TBAB) was used as the catalyst. The structures of the target compounds were well characterized and verified by elemental analysis, MS, IR, 1H NMR, 13C NMR and single crystal X-ray diffraction analysis. (author)

  11. Synthesis and structural characterization of alkali metal arsinoamides.

    Science.gov (United States)

    Chen, Xiao; Gamer, Michael T; Roesky, Peter W

    2017-12-20

    The aminoarsane Mes 2 AsN(H)Ph was prepared from Mes 2 AsCl and aniline in good yields. Deprotonation of Mes 2 AsN(H)Ph with suitable alkali metal bases resulted in the corresponding alkali metal derivatives. Thus, reaction of Mes 2 AsN(H)Ph with nBuLi, NaN(SiMe 3 ) 2 , or KH gave the metal complexes [(Mes 2 AsNPh){Li(OEt 2 ) 2 }], [(Mes 2 AsNPh){Na(OEt 2 )}] 2 , and [(Mes 2 AsNPh){K(THF)}] 2 . These are the first metal complexes ligated by an arsinoamide. All solid-state structures were established by single crystal X-ray diffraction. The lithium compounds form a monomer in the solid-state, whereas the sodium and the potassium derivatives are dimers. In the dimeric compounds intra- and intermolecular π-interaction of the aromatic rings with the metal atoms is observed.

  12. Stochastic Control Synthesis of Systems with Structured Uncertainty

    Science.gov (United States)

    Padula, Sharon L. (Technical Monitor); Crespo, Luis G.

    2003-01-01

    This paper presents a study on the design of robust controllers by using random variables to model structured uncertainty for both SISO and MIMO feedback systems. Once the parameter uncertainty is prescribed with probability density functions, its effects are propagated through the analysis leading to stochastic metrics for the system's output. Control designs that aim for satisfactory performances while guaranteeing robust closed loop stability are attained by solving constrained non-linear optimization problems in the frequency domain. This approach permits not only to quantify the probability of having unstable and unfavorable responses for a particular control design but also to search for controls while favoring the values of the parameters with higher chance of occurrence. In this manner, robust optimality is achieved while the characteristic conservatism of conventional robust control methods is eliminated. Examples that admit closed form expressions for the probabilistic metrics of the output are used to elucidate the nature of the problem at hand and validate the proposed formulations.

  13. Synthesis and optical properties of novel organic-inorganic hybrid nanolayer structure semiconductors

    International Nuclear Information System (INIS)

    Zhang Sanjun; Lanty, Gaetan; Lauret, Jean-Sebastien; Deleporte, Emmanuelle; Audebert, Pierre; Galmiche, Laurent

    2009-01-01

    We report on the synthesis of some novel organic-inorganic hybrid 2D perovskite semiconductors (R-(CH 2 ) n NH 3 ) 2 PbX 4 . These semiconductors are self-assembled intercalation nanolayers and have a multi-quantum-well energy level structure. We systematically vary the characteristic of organic groups (R-(CH 2 ) n NH 3 + ) to study the relationship between their structures and the optical properties of (R-(CH 2 ) n NH 3 ) 2 PbX 4 . From optical absorption and photoluminescence spectroscopy experiments performed on series of samples, we find some trends of choosing the organic groups to improve the optical performance of (R-(CH 2 ) n NH 3 ) 2 PbX 4 . A new organic group, which allows synthesis of nanolayer perovskite semiconductors with quite high photoluminescence efficiency and better long-term stability, has been found.

  14. Some structural aspects that are relevant for synthesis of planetary gear trains

    Energy Technology Data Exchange (ETDEWEB)

    Rajasri, I. [Pathfinder Engineering College, Hanamkonda (India); Gupta, A.V.S.S.K.S. [JNTU, Hyderabad (India); Rao, Y.V.D. [BITS-Pilani. Dept. of Mechanical Engineering, Hyderabad (India)

    2012-07-01

    Gear Trains are typically used in various mechanisms including wind turbines and robots to transmit specified motion and/or torque between two or more shafts and wind turbines need drives and overdrives that amplify the speed of turbine shaft and provide high speed at generator shaft. Planetary gear trains (PGT) are compact, easy to build and operate. Therefore PGTs are most suitable for such drives including over drives. Graph theory used in synthesis of the PGTs is also useful to identify various possible structural aspects of the PGTs. Generation of PGTs is followed by the test for isomorphism in PGTs generated. In this context various structural aspects relevant for the synthesis of PGTs is described. (Author)

  15. Synthesis and structural evaluation of freeze-cast porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Douglas F., E-mail: souzadf@outlook.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nunes, Eduardo H.M., E-mail: eduardohmn@gmail.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Pimenta, Daiana S.; Vasconcelos, Daniela C.L. [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nascimento, Jailton F.; Grava, Wilson [Petrobras/CENPES, Avenida Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ CEP:21941-915 (Brazil); Houmard, Manuel [Department of Materials Engineering and Civil Construction, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 1, sala 3304 (Brazil); Vasconcelos, Wander L., E-mail: wlv@demet.ufmg.br [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil)

    2014-10-15

    In this work we fabricated alumina samples by the freeze-casting technique using tert-butanol as the solvent. The prepared materials were examined by scanning electron microscopy and X-ray microtomography. Next, they were coated with sol–gel silica films by dip-coating. Permeability tests were carried out in order to assess the permeation behavior of the materials processed in this study. We observed that the sintering time and alumina loading showed a remarkable effect on both the structural properties and flexural strength of the freeze-cast samples. Nitrogen adsorption tests revealed that the silica prepared in this study exhibited a microporous structure. It was observed that the presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance by about one order of magnitude. Because of the similar kinetic diameters of nitrogen and carbon dioxide, the CO{sub 2}/N{sub 2} system showed a separation efficiency that was lower than that observed for the He/CO{sub 2} and He/N{sub 2} systems. We noticed that increasing the feed pressure improved the separation capacity of the obtained materials. - Highlights: • Porous alumina samples obtained by the freeze-casting technique • Microporous silica coating prepared by a simple sol–gel dip-coating methodology • Samples examined by SEM, μ-CT, and nitrogen sorption tests • Mechanical tests were carried out in the freeze-cast samples. • The presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance.

  16. One-Dimensional SnO2 Nano structures: Synthesis and Applications

    International Nuclear Information System (INIS)

    Pan, J.; Shen, H.; Mathur, S.; Pan, J.

    2012-01-01

    Nano scale semiconducting materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, like nano wires, nano belts, and nano tubes, have gained tremendous attention within the past decade. Among the variety of 1D nano structures, tin oxide (SnO 2 ) semiconducting nano structures are particularly interesting because of their promising applications in optoelectronic and electronic devices due to both good conductivity and transparence in the visible region. This article provides a comprehensive review of the recent research activities that focus on the rational synthesis and unique applications of 1D SnO 2 nano structures and their optical and electrical properties. We begin with the rational design and synthesis of 1D SnO 2 nano structures, such as nano tubes, nano wires, nano belts, and some heterogeneous nano structures, and then highlight a range of applications (e.g., gas sensor, lithium-ion batteries, and nano photonics) associated with them. Finally, the review is concluded with some perspectives with respect to future research on 1D SnO 2 nano structures

  17. Chemical synthesis and structure elucidation of bovine κ-casein (1-44)

    International Nuclear Information System (INIS)

    Bansal, Paramjit S.; Grieve, Paul A.; Marschke, Ronald J.; Daly, Norelle L.; McGhie, Emily; Craik, David J.; Alewood, Paul F.

    2006-01-01

    The caseins (α s1 , α s2 , β, and κ) are phosphoproteins present in bovine milk that have been studied for over a century and whose structures remain obscure. Here we describe the chemical synthesis and structure elucidation of the N-terminal segment (1-44) of bovine κ-casein, the protein which maintains the micellar structure of the caseins. κ-Casein (1-44) was synthesised by highly optimised Boc solid-phase peptide chemistry and characterised by mass spectrometry. Structure elucidation was carried out by circular dichroism and nuclear magnetic resonance spectroscopy. CD analysis demonstrated that the segment was ill defined in aqueous medium but in 30% trifluoroethanol it exhibited considerable helical structure. Further, NMR analysis showed the presence of a helical segment containing 26 residues which extends from Pro 8 to Arg 34 . This is First report which demonstrates extensive secondary structure within the casein class of proteins

  18. Methyl farnesoate synthesis is necessary for the environmental sex determination in the water flea Daphnia pulex.

    Science.gov (United States)

    Toyota, Kenji; Miyakawa, Hitoshi; Hiruta, Chizue; Furuta, Kenjiro; Ogino, Yukiko; Shinoda, Tetsuro; Tatarazako, Norihisa; Miyagawa, Shinichi; Shaw, Joseph R; Iguchi, Taisen

    2015-09-01

    Sex-determination systems can be divided into two groups: genotypic sex determination (GSD) and environmental sex determination (ESD). ESD is an adaptive life-history strategy that allows control of sex in response to environmental cues in order to optimize fitness. However, the molecular basis of ESD remains largely unknown. The micro crustacean Daphnia pulex exhibits ESD in response to various external stimuli. Although methyl farnesoate (MF: putative juvenile hormone, JH, in daphnids) has been reported to induce male production in daphnids, the role of MF as a sex-determining factor remains elusive due to the lack of a suitable model system for its study. Here, we establish such a system for ESD studies in D. pulex. The WTN6 strain switches from producing females to producing males in response to the shortened day condition, while the MFP strain only produces females, irrespective of day-length. To clarify whether MF has a novel physiological role as a sex-determining factor in D. pulex, we demonstrate that a MF/JH biosynthesis inhibitor suppressed male production in WTN6 strain reared under the male-inducible condition, shortened day-length. Moreover, we show that juvenile hormone acid O-methyltransferase (JHAMT), a critical enzyme of MF/JH biosynthesis, displays MF-generating activity by catalyzing farnesoic acid. Expression of the JHAMT gene increased significantly just before the MF-sensitive period for male production in the WTN6 strain, but not in the MFP strain, when maintained under male-inducible conditions. These results suggest that MF synthesis regulated by JHAMT is necessary for male offspring production in D. pulex. Our findings provide novel insights into the genetic underpinnings of ESD and they begin to shed light on the physiological function of MF as a male-fate determiner in D. pulex. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Synthesis, crystal structure and magnetic properties of U2RuGa8

    International Nuclear Information System (INIS)

    Grin', Yu.N.; Rogl', P.; Aksel'rud, L.G.; Pecharskij, V.K.; Yarmolyuk, Ya.P.

    1988-01-01

    Synthesis of a new uranium intermetallic compound of U 2 RuGa 8 composition was conducted. The compound crystallizes in Ho 2 CoGa 8 structural type, met earlier only in compounds of rare earths. Magnetic susceptibility of the compound is rather high and is practically independent of temperature in 80-300 K range. This feature is typical for paramagnetism of electron gas and testifies to the absence of localized magnetic moments on ruthenium and uranium atoms

  20. Synthesis and Structure of D3h-Symmetric Triptycene Trimaleimide

    Directory of Open Access Journals (Sweden)

    Anthony Linden

    2010-01-01

    Full Text Available A new D3h symmetric triptycene derivative has been synthesized with the aim of obtaining molecules that are able to assemble into porous structures, and can be used in the development of new ligands. The synthesis involves a Diels-Alder reaction as the key step, followed by an oxidation and the formation of a maleimide ring. Triptycene trimaleimide furnished single crystals which have been analyzed by means of X-ray diffraction.

  1. The potential for biological structure determination with pulsed neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, C.C. [CLRC Rutherford Appleton Laboratory, Chilton Didcot Oxon (United Kingdom)

    1994-12-31

    The potential of pulsed neutron diffraction in structural determination of biological materials is discussed. The problems and potential solutions in this area are outlined, with reference to both current and future sources and instrumentation. The importance of developing instrumentation on pulsed sources in emphasized, with reference to the likelihood of future expansion in this area. The possibilities and limitations of single crystal, fiber and powder diffraction in this area are assessed.

  2. The potential for biological structure determination with pulsed neutrons

    International Nuclear Information System (INIS)

    Wilson, C.C.

    1994-01-01

    The potential of pulsed neutron diffraction in structural determination of biological materials is discussed. The problems and potential solutions in this area are outlined, with reference to both current and future sources and instrumentation. The importance of developing instrumentation on pulsed sources in emphasized, with reference to the likelihood of future expansion in this area. The possibilities and limitations of single crystal, fiber and powder diffraction in this area are assessed

  3. Determining the helicity structure of third generation resonances

    International Nuclear Information System (INIS)

    Papaefstathiou, Andreas

    2011-11-01

    We examine methods that have been proposed for determining the helicity structure of decays of new resonances to third generation quarks and/or leptons. We present analytical and semi-analytical predictions and assess the applicability of the relevant variables in realistic reconstruction scenarios using Monte Carlo-generated events, including the effects of QCD radiation and multiple parton interactions, combinatoric ambiguities and fast detector simulation. (orig.)

  4. Determination of the Basin Structure Beneath European Side of Istanbul

    Science.gov (United States)

    Karabulut, Savas; Cengiz Cinku, Mulla; Thomas, Michael; Lamontagne, Maurice

    2016-04-01

    Istanbul (near North Anatolian Fault Zone:NAFZ, Turkey) is located in northern part of Sea of Marmara, an area that has been influenced by possible Marmara Earthquakes. The general geology of Istanbul divided into two stratigraphic unit such as sedimentary (from Oligocene to Quaternary Deposits) and bedrock (Paleozoic and Eocene). The bedrock units consists of sand stone, clay stone to Paleozoic age and limestone to Eocene age and sedimentary unit consist of sand, clay, mil and gravel from Oligocene to Quaternary age. Earthquake disaster mitigation studies divided into two important phases, too. Firstly, earthquake, soil and engineering structure problems identify for investigation area, later on strategic emergency plan can prepare for these problems. Soil amplification play important role the disaster mitigation and the site effect analysis and basin structure is also a key parameter for determining of site effect. Some geophysical, geological and geotechnical measurements are requeired to defined this relationship. Istanbul Megacity has been waiting possible Marmara Earthquake and their related results. In order to defined to possible damage potential related to site effect, gravity measurements carried out for determining to geological structure, basin geometry and faults in Istanbul. Gravity data were collected at 640 sites by using a Scientrex CG-5 Autogravity meter Standard corrections applied to the gravity data include those for instrumental drift, Earth tides and latitude, and the free-air and Bouguer corrections. The corrected gravity data were imported into a Geosoft database to create a grid and map of the Bouguer gravity anomaly (grid cell size of 200 m). As a previously results, we determined some lineminants, faults and basins beneath Istanbul City. Especially, orientation of faults were NW-SE direction and some basin structures determined on between Buyukcekmece and Kucukcekmece Lake.

  5. Synthesis, spectroscopic and DNA binding ability of Co{sup II}, Ni{sup II}, Cu{sup II} and Zn{sup II} complexes of Schiff base ligand (E)-1-(((1H-benzo[d]imidazol-2-yl)methylimino)methyl)naphthalen-2-ol. X-ray crystal structure determination of cobalt (II) complex

    Energy Technology Data Exchange (ETDEWEB)

    Yarkandi, Naeema H. [Chemistry Department, Faculty of Applied Science, Umm Al–Qura University, Makkah (Saudi Arabia); El-Ghamry, Hoda A., E-mail: helghamrymo@yahoo.com [Chemistry Department, Faculty of Applied Science, Umm Al–Qura University, Makkah (Saudi Arabia); Chemistry Department, Faculty of Science, Tanta University, Tanta (Egypt); Gaber, Mohamed [Chemistry Department, Faculty of Science, Tanta University, Tanta (Egypt)

    2017-06-01

    A novel Schiff base ligand, (E)-1-(((1H-benzo[d]imidazol-2-yl)methylimino)methyl)naphthalen-2-ol (HL), has been designed and synthesized in addition to its metal chelates [Co(L){sub 2}]·l2H{sub 2}O, [Ni(L)Cl·(H{sub 2}O){sub 2}].5H{sub 2}O, [Cu(L)Cl] and [Zn(L)(CH{sub 3}COO)]. The structures of the isolated compounds have been confirmed and identified by means of different spectral and physicochemical techniques including CHN analysis, {sup 1}H &{sup 13}C NMR, mass spectral analysis, molar conductivity measurement, UV–Vis, infrared, magnetic moment in addition to TGA technique. The infrared spectral results ascertained that the ligand acts as monobasic tridentate binding to the metal centers via deprotonated hydroxyl oxygen, azomethine and imidazole nitrogen atoms. The UV–Vis, magnetic susceptibility and molar conductivity data implied octahedral geometry for Co(II) & Ni(II) complexes, tetrahedral for Zn(II) complex and square planar for Cu(II) complex. X-ray structural analysis of Co(II) complex 1 has been reported and discussed. Moreover, the type of interaction between the ligand & its complexes towards salmon sperm DNA (SS-DNA) has been examined by the measurement of absorption spectra and viscosity which confirmed that the ligand and its complexes interact with DNA via intercalation interaction as concluded from the values of binding constants (K{sub b}). - Highlights: • Synthesis of Co{sup II}, Ni{sup II}, Cu{sup II} and Zn{sup II} complexes of the Schiff base ligand based on 2-(aminomethyl)benzimidazole moiety. • The constitutions and structures of the ligand and complexes were elucidated. • Molecular structure of Co{sup II} complex was confirmed by single crystal X-ray diffraction method. • The ligand and its complexes interact with SS-DNA via intercalation mods.

  6. Synthesis and crystal structure of the new vanadate AgCaVO{sub 4}. Comparison with the arcanite structure

    Energy Technology Data Exchange (ETDEWEB)

    Nenert, Gwilherm [PANalytical B.V., Almelo (Netherlands)

    2017-07-01

    We report the synthesis and the crystal structure of the new vanadate AgCaVO{sub 4} from laboratory powder X-ray data. Contrary to the previously reported AgBVO{sub 4} (B=Mg, Cd), AgCaVO{sub 4} exhibits the arcanite structure (β-K{sub 2}SO{sub 4}). Although it exhibits the same structure than arcanite, significant differences are observed. These differences are explained by deriving the atomic displacement field. The change of connectivity within the structure between β-K{sub 2}SO{sub 4} and AgCaVO{sub 4} results from a rotation of the VO{sub 4} tetrahedra giving rise to a change from a face sharing to an edge sharing octahedral chains. Additionally, the thermal expansion of AgCaVO{sub 4} has been investigated up to 800 C.

  7. MOTIVATION INTERNALIZATION AND SIMPLEX STRUCTURE IN SELF-DETERMINATION THEORY.

    Science.gov (United States)

    Ünlü, Ali; Dettweiler, Ulrich

    2015-12-01

    Self-determination theory, as proposed by Deci and Ryan, postulated different types of motivation regulation. As to the introjected and identified regulation of extrinsic motivation, their internalizations were described as "somewhat external" and "somewhat internal" and remained undetermined in the theory. This paper introduces a constrained regression analysis that allows these vaguely expressed motivations to be estimated in an "optimal" manner, in any given empirical context. The approach was even generalized and applied for simplex structure analysis in self-determination theory. The technique was exemplified with an empirical study comparing science teaching in a classical school class versus an expeditionary outdoor program. Based on a sample of 84 German pupils (43 girls, 41 boys, 10 to 12 years old), data were collected using the German version of the Academic Self-Regulation Questionnaire. The science-teaching format was seen to not influence the pupils' internalization of identified regulation. The internalization of introjected regulation differed and shifted more toward the external pole in the outdoor teaching format. The quantification approach supported the simplex structure of self-determination theory, whereas correlations may disconfirm the simplex structure.

  8. Determinants of capital structure: evidence from the Czech automotive industry

    Directory of Open Access Journals (Sweden)

    Pavlína Pinková

    2012-01-01

    Full Text Available The objective of the paper is to identify the determinants influencing the capital structure of large and medium-sized enterprises of the automotive industry in the Czech Republic. The sample consists of 100 companies belonging to NACE division 29. The data come from financial statements of selected companies and cover a period from 2006 to 2010. For the purpose of the paper quantitative research is used. The selection of appropriate dependent and independent is realized on the basis of secondary research on studies of capital structure. The analysis of variance, correlation and regression analyses have been performed to see the nature of relationship between variables. Size, tangibility, profitability and liquidity appear to be relevant determinants of capital structure. Growth is not a statistically significant determinant of leverage. It has been observed that the maturity of debt has to be considered, since the investigation of total debt only does not provide precious results. The findings do not unequivocally support either the static trade-off theory or the pecking order theory.

  9. Local magnetic structure determination using polarized neutron holography

    International Nuclear Information System (INIS)

    Szakál, Alex; Markó, Márton; Cser, László

    2015-01-01

    A unique and important property of the neutron is that it possesses magnetic moment. This property is widely used for determination of magnetic structure of crystalline samples observing the magnetic components of the diffraction peaks. Investigations of diffraction patterns give information only about the averaged structure of a crystal but for discovering of local spin arrangement around a specific (e.g., impurity) nucleus remains still a challenging problem. Neutron holography is a useful tool to investigate the local structure around a specific nucleus embedded in a crystal lattice. The method has been successfully applied experimentally in several cases using non-magnetic short range interaction of the neutron and the nucleus. A mathematical model of the hologram using interaction between magnetic moment of the atom and the neutron spin for polarized neutron holography is provided. Validity of a polarized neutron holographic experiment is demonstrated by applying the proposed method on model systems

  10. Isolation, Synthesis and Structures of Cytotoxic Ginsenoside Derivatives

    Directory of Open Access Journals (Sweden)

    Yi-nan Zheng

    2007-09-01

    Full Text Available Four known ginsenosides: ginsenoside-Rb1 (1, Rb3 (2, Rd (3 and Re (4 were isolated from the methanolic extract of the traditional Chinese medicine Panax ginseng C. A. Meyer. Further enzyme reactions and chemical modifications led us to obtain ginsenoside-M1 (5 and synthesize three novel mono-esters of ginsenoside-M1, ginsenoside-DM1 (6, PM1 (7 and SM1 (8 30 - 50% of yield via a facile and green synthetic strategy. The structures were elucidated on the basis of extensive 1D- and 2DNMR, as well as high resolution ESI-TOF mass spectroscopic analyses. The isolated and synthetic compounds were tested in an anti-tumor bioassay, and compounds 5-8 showed considerable cytotoxicity (SRB against several human cancer cell lines (breast cancer MCF-7, skin melanoma SK-MEL-2 and human ovarian carcinoma B16, but moderate effects on lung carcinoma COR-L23. The other ginsenosides showed no effects.

  11. Synthesis and crystal structure of MgB12

    International Nuclear Information System (INIS)

    Adasch, Volker; Hess, Kai-Uwe; Ludwig, Thilo; Vojteer, Natascha; Hillebrecht, Harald

    2006-01-01

    Single crystals of MgB 12 were synthesized from the elements in a Mg/Cu melt at 1600deg. C. MgB 12 crystallizes orthorhombic in space group Pnma with a=16.632(3)A, b=17.803(4)A and c=10.396(2)A. The crystal structure (Z=30, 5796 reflections, 510 variables, R 1 (F)=0.049, wR 2 (I)=0.134) consists of a three dimensional net of B 12 icosahedra and B 21 units in a ratio 2:1. The B 21 units are observed for the first time in a solid compound. Mg is on positions with partial occupation. The summation reveals the composition MgB 12.35 or Mg 0.97 B 12 , respectively. This is in good agreement with the value of MgB 11.25 as expected by electronic reasons to stabilize the boron polyhedra B 12 2- and B 21 4-

  12. Synthesis, crystal structure and applications of palladium thiosalicylate complexes

    Directory of Open Access Journals (Sweden)

    S.B. Moosun

    2017-05-01

    Full Text Available Three palladium thiosalicylate complexes [Pd(tb(bipy]·3H2O (1, [Pd2(tb2(bipy2]·(dtdb2 (2 and [Pd2(tb2(phen2]·dtdb·H2O (3 (bipy = bipyridine; phen = phenanthroline were prepared from the reaction of PdCl2(CH3CN2 with dithiosalicylic acid (dtdb which underwent cleavage to form thiobenzoate anion (tb in DMF/MeOH. Square planar geometries of the complexes with a N2SO coordination type were proposed on the basis of single crystal X-ray structural study. The presence of trapped and uncoordinated dtdb was observed in complexes 2 and 3. Complexes 1–3 were evaluated as catalysts for Heck coupling reactions of methyl acrylate with iodobenzene, and showed moderate activities at a very low catalyst loading. Complex 1 was found to inhibit the growth of bacteria and scavenge free radicals efficiently.

  13. Synthesis and textural evolution of alumina particles with mesoporous structures

    International Nuclear Information System (INIS)

    Liu Xun; Peng Tianyou; Yao Jinchun; Lv Hongjin; Huang Cheng

    2010-01-01

    Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl - in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2 O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 4 2- can promote above morphology evolution and then transformed into γ-Al 2 O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g -1 even after calcinations at 1173 K. - Graphical abstract: Co-existing Cl - is beneficial for the formation of γ-alumina nanoparticles with mesostructures during the precipitation process. Interparticle and intraparticle mesopores can be derived from acidic solution and near neutral solution, respectively.

  14. Synthesis and textural evolution of alumina particles with mesoporous structures

    Science.gov (United States)

    Liu, Xun; Peng, Tianyou; Yao, Jinchun; Lv, Hongjin; Huang, Cheng

    2010-06-01

    Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous γ-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl - in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into γ-Al 2O 3 particles with mesostructures after further calcination at 1173 K, whereas coexisting SO 42- can promote above morphology evolution and then transformed into γ-Al 2O 3 nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m 2 g -1 even after calcinations at 1173 K.

  15. Structural versatility of Metal-organic frameworks: Synthesis and Characterization

    KAUST Repository

    Alsadun, Norah S.

    2017-05-01

    Metal-Organic Frameworks (MOFs), an emerging class of porous crystalline materials, have shown promising properties for diverse applications such as catalysis, gas storage and separation. The high degree of tunability of MOFs vs other solid materials enable the assembly of advanced materials with fascinating properties for specific applications. Nevertheless, the precise control in the construction of MOFs at the molecular level remains challenging. Particularly, the formation of pre-targeted multi-nuclear Molecular Building Block (MBB) precursors to unveil materials with targeted structural characteristics is captivating. The aim of my master project in the continuous quest of the group of Prof. Eddaoudi in exploring different synthetic pathways to control the assembly of Rare Earth (RE) based MOF. After giving a general overview about MOFs, I will discuss in this thesis the results of my work on the use of tri-topic oriented organic carboxylate building units with the aim to explore the assembly/construction of new porous RE based MOFs. In chapter 2 will discuss the assembly of 3-c linkers with RE metals was then evaluated based on symmetry and angularity of the three connected linkers. The focus of chapter 3 is cerium based MOFs and heterometallic system, based on 3-c ligands with different length and symmetry. Overall, the incompatibility of 3-c ligands with the 12-c cuo MBB did not allow to any formation of higher neuclearity (˃6), but it has resulted in affecting the connectivity of the cluster.

  16. Synthesis facilitates an understanding of the structural basis for translation inhibition by the lissoclimides

    Science.gov (United States)

    Könst, Zef A.; Szklarski, Anne R.; Pellegrino, Simone; Michalak, Sharon E.; Meyer, Mélanie; Zanette, Camila; Cencic, Regina; Nam, Sangkil; Voora, Vamsee K.; Horne, David A.; Pelletier, Jerry; Mobley, David L.; Yusupova, Gulnara; Yusupov, Marat; Vanderwal, Christopher D.

    2017-11-01

    The lissoclimides are unusual succinimide-containing labdane diterpenoids that were reported to be potent cytotoxins. Our short semisynthesis and analogue-oriented synthesis approaches provide a series of lissoclimide natural products and analogues that expand the structure-activity relationships (SARs) in this family. The semisynthesis approach yielded significant quantities of chlorolissoclimide (CL) to permit an evaluation against the National Cancer Institute's 60-cell line panel and allowed us to obtain an X-ray co-crystal structure of the synthetic secondary metabolite with the eukaryotic 80S ribosome. Although it shares a binding site with other imide-based natural product translation inhibitors, CL engages in a particularly interesting and novel face-on halogen-π interaction between the ligand's alkyl chloride and a guanine residue. Our analogue-oriented synthesis provides many more lissoclimide compounds, which were tested against aggressive human cancer cell lines and for protein synthesis inhibitory activity. Finally, computational modelling was used to explain the SARs of certain key compounds and set the stage for the structure-guided design of better translation inhibitors.

  17. Structural determinants and mechanism of HIV-1 genome packaging.

    Science.gov (United States)

    Lu, Kun; Heng, Xiao; Summers, Michael F

    2011-07-22

    Like all retroviruses, the human immunodeficiency virus selectively packages two copies of its unspliced RNA genome, both of which are utilized for strand-transfer-mediated recombination during reverse transcription-a process that enables rapid evolution under environmental and chemotherapeutic pressures. The viral RNA appears to be selected for packaging as a dimer, and there is evidence that dimerization and packaging are mechanistically coupled. Both processes are mediated by interactions between the nucleocapsid domains of a small number of assembling viral Gag polyproteins and RNA elements within the 5'-untranslated region of the genome. A number of secondary structures have been predicted for regions of the genome that are responsible for packaging, and high-resolution structures have been determined for a few small RNA fragments and protein-RNA complexes. However, major questions regarding the RNA structures (and potentially the structural changes) that are responsible for dimeric genome selection remain unanswered. Here, we review efforts that have been made to identify the molecular determinants and mechanism of human immunodeficiency virus type 1 genome packaging. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. Determination of material constants of vertically aligned carbon nanotube structures in compressions

    International Nuclear Information System (INIS)

    Li, Yupeng; Kang, Junmo; Choi, Jae-Boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-01-01

    Different chemical vapour deposition (CVD) fabrication conditions lead to a wide range of variation in the microstructure and morphologies of carbon nanotubes (CNTs), which actually determine the compressive mechanical properties of CNTs. However, the underlying relationship between the structure/morphology and mechanical properties of CNTs is not fully understood. In this study, we characterized and compared the structural and morphological properties of three kinds of vertically aligned carbon nanotube (VACNT) arrays from different CVD fabrication methods and performed monotonic compressive tests for each VACNT array. The compressive stress–strain responses and plastic deformation were first compared and analyzed with nanotube buckling behaviours. To quantify the compressive properties of the VACNT arrays, a strain density energy function was used to determine their intrinsic material constants. Then, the structural and morphological effects on the quantified material constants of the VACNTs were statistically investigated and analogized to cellular materials with an open-cell model. The statistical analysis shows that density, defect degree, and the moment of inertia of the CNTs are key factors in the improvement of the compressive mechanical properties of VACNT arrays. This approach could allow a model-driven CNT synthesis for engineering their mechanical behaviours. (paper)

  19. Synthesis, structural, spectroscopic and biological studies of Schiff base complexes

    Science.gov (United States)

    Diab, M. A.; El-Sonbati, A. Z.; Shoair, A. F.; Eldesoky, A. M.; El-Far, N. M.

    2017-08-01

    Schiff base ligand 4-((pyridin-2- yl)methyleneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (PDMP) and its complexes were prepared and characterized on the basis of elemental analysis, IR, mass spectra and thermogravimetric analysis. All results confirm that the complexes have 1:1 (M: PMDP) stoichiometric formula [M(PMDP)Cl2H2O ] (M = Cu(II), Co(II), Ni(II) and Mn(II)), [Cd(PMDP)Cl2] and the ligand behaves as a bi/tridentate forming five-membered chelating ring towards the metal ions, bonding through azomethine nitrogen/exocyclic carbonyl oxygen, azomethine pyridine nitrogen and exocyclic carbonyl oxygen. The shift in the band positions of the groups involved in coordination has been utilized to estimate the metal-nitrogen and/or oxygen bond lengths. The complexes of Co(II), Ni(II) and Cu(II) are paramagnetic and the magnetic as well as spectral data suggest octahedral geometry, whereas the Cd(II) complex is tetrahedral. The XRD studies show that both the ligand and its metal complexes (1 and 3) show polycrystalline with crystal structure. Molecular docking was used to predict the binding between PMDP ligand and the receptors. The corrosion inhibition of mild steel in 2 M HCl solution by PDMP was explored utilizing potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and (EFM) electrochemical frequency modulation method. Potentiodynamic polarization demonstrated that PDMP compound is mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the protective ability. The percentage of inhibition efficiency was found to increase with increasing the inhibitor concentration.

  20. Synthesis and study of nano-structured cellulose acetate based materials for energy applications

    International Nuclear Information System (INIS)

    Fischer, F.

    2006-12-01

    Nano-structured materials have unique properties (high exchange areas, containment effect) because of their very low characteristic dimensions. The elaboration way set up in this PhD work consists in applying the classical processes for the preparation of aerogel-like materials (combining sol-gel synthesis and CO 2 supercritical extraction) to cellulosic polymers. This work is divided in four parts: a literature review, the presentation and the study of the chemical synthesis that leads to cellulose acetate-based aerogel, the characterizations (chemical, structural and thermal) of the elaborated nano-materials, and finally the study of the first carbons that were obtained after pyrolysis of the organic matrix. The formulations and the sol-gel protocol lead to chemical gels by crosslinking cellulose acetate using a poly-functional iso-cyanate. The dry materials obtained after solvent extraction with supercritical CO 2 are nano-structured and mainly meso-porous. Correlations between chemical synthesis parameters (reagent concentrations, crosslinking rate and degree of polymerisation) and porous properties (density, porosity, pore size distribution) were highlighted thanks to structural characterizations. An ultra-porous reference aerogel, with a density equals to 0,245 g.cm -3 together with a meso-porous volume of 3,40 cm 3 .g -1 was elaborated. Once in granular shape, this material has a thermal conductivity of 0,029 W.m -1 .K -1 . In addition, carbon materials produced after pyrolysis of the organic matrix and after grinding are nano-structured and nano-porous, even if important structural modifications have occurred during the carbonization process. The elaborated materials are evaluated for applications in relation with energy such as thermal insulation (organic aerogels) but also for energy conversion and storage through electrochemical way (carbon aerogels). (author)

  1. Cholesterol metabolism: use of D2O for determination of synthesis rate in cell culture

    International Nuclear Information System (INIS)

    Esterman, A.L.; Cohen, B.I.; Javitt, N.B.

    1985-01-01

    Cholesterol synthesis in cell culture in the presence of D 2 O yields a spectrum of enriched molecules having a relative abundance that indicates random substitution of deuterium for hydrogen. Quantitation of the absolute rate of cholesterol synthesis is obtained by isotope ratio mass spectrometry. Mevinolin and 26-hydroxycholesterol both decrease cholesterol synthesis rate but have a discordant effect on HMG-CoA reductase activity

  2. Defining an essence of structure determining residue contacts in proteins.

    Science.gov (United States)

    Sathyapriya, R; Duarte, Jose M; Stehr, Henning; Filippis, Ioannis; Lappe, Michael

    2009-12-01

    The network of native non-covalent residue contacts determines the three-dimensional structure of a protein. However, not all contacts are of equal structural significance, and little knowledge exists about a minimal, yet sufficient, subset required to define the global features of a protein. Characterisation of this "structural essence" has remained elusive so far: no algorithmic strategy has been devised to-date that could outperform a random selection in terms of 3D reconstruction accuracy (measured as the Ca RMSD). It is not only of theoretical interest (i.e., for design of advanced statistical potentials) to identify the number and nature of essential native contacts-such a subset of spatial constraints is very useful in a number of novel experimental methods (like EPR) which rely heavily on constraint-based protein modelling. To derive accurate three-dimensional models from distance constraints, we implemented a reconstruction pipeline using distance geometry. We selected a test-set of 12 protein structures from the four major SCOP fold classes and performed our reconstruction analysis. As a reference set, series of random subsets (ranging from 10% to 90% of native contacts) are generated for each protein, and the reconstruction accuracy is computed for each subset. We have developed a rational strategy, termed "cone-peeling" that combines sequence features and network descriptors to select minimal subsets that outperform the reference sets. We present, for the first time, a rational strategy to derive a structural essence of residue contacts and provide an estimate of the size of this minimal subset. Our algorithm computes sparse subsets capable of determining the tertiary structure at approximately 4.8 A Ca RMSD with as little as 8% of the native contacts (Ca-Ca and Cb-Cb). At the same time, a randomly chosen subset of native contacts needs about twice as many contacts to reach the same level of accuracy. This "structural essence" opens new avenues in the

  3. Synthesis and Single Crystal Structures of Substituted-1,3-Selenazol-2-amines

    Directory of Open Access Journals (Sweden)

    Guoxiong Hua

    2016-12-01

    Full Text Available The synthesis and X-ray single crystal structures of a series of new 4-substituted-1,3-selenazol-2-amines is reported. The efficient preparation of these compounds was carried out by two-component cyclization of the selenoureas with equimolar amounts of α-haloketones. The selenoureas were obtained from the reaction of Woollins’ reagent with cyanamides, followed by hydrolysis with water. All new compounds have been characterized by IR spectroscopy, multi-NMR (1H, 13C, 77Se spectroscopy, accurate mass measurement and single crystal X-ray structure analysis.

  4. The mathematical model structural-parametric synthesis of working processes in an oxygen-methane steam generator with flow swirl

    Science.gov (United States)

    Timoshinova, T. S.; Shmatov, D. P.; Kretinin, A. V.; Drozdov, I. G.

    2017-11-01

    While formulating a mathematical model of the flow and interaction between oxygen-methane fuel combustion products with tangentially swirled ballast water injected in the end of the combustion chamber in CAE product Fluent, which integrated into the ANSYS Workbench platform, the problem of structural-parametric synthesis is solved for structure optimization of the model. Equations are selected from the catalogue of Fluent physical models. Also optimization helps to find “regime” model parameters that determine the specific implementation of the model inside the synthesized structure. As a result, such solutions which were developed during creation of a numerical algorithm, as the choice of a turbulence model and the state equation, the methods for determining the thermodynamic thermophysical characteristics of combustion products, the choice of the radiation model, the choice of the resistance law for drops, the choice of the expression which allows to evaluate swirling flows lateral force, determination of the turbulent dispersion strength, choice of the mass exchange law, etc. Fields of temperature, pressure, velocity and volume fraction of phases were obtained at different ballast water mass flows. Dependence of wall temperature from mass flow of ballast water is constructed, that allows us to compare results of the experiment and mathematical modeling.

  5. Synthesis, Crystal Structure, and Topology-Symmetry Analysis of a New Modification of NaIn[IO3]4

    Science.gov (United States)

    Belokoneva, E. L.; Karamysheva, A. S.; Dimitrova, O. V.; Volkov, A. S.

    2018-01-01

    Crystals of new iodate NaIn[IO3]4 were prepared by the hydrothermal synthesis. The unit cell parameters are a = 7.2672(2) Å, b = 15.2572(6) Å, c = 15.0208(6) Å, β = 101.517(3)°, sp. gr. P21/ c. The formula was determined during the structure determination and refinement of a twinned crystal based on a set of reflections from the atomic planes of the major individual. The refinement with anisotropic displacement parameters was performed for both twin components to the final R factor of 0.050. The In and Na atoms are in octahedral coordination formed by oxygen atoms. The oxygen octahedra are arranged into columns by sharing edges, and the columns are connected by isolated umbrella-like [IO3]- groups to form layers. The new structure is most similar to the isoformular iodate NaIn[IO3]4, which crystallizes in the same sp. gr. P21/ c and is structurally similar, but has a twice smaller unit cell and is characterized by another direction of the monoclinic axis. The structural similarity and difference between the two phases were studied by topologysymmetry analysis. The formation of these phases is related to different combinations of identical one-dimensional infinite chains of octahedra.

  6. Assessment of carotid plaque vulnerability using structural and geometrical determinants

    International Nuclear Information System (INIS)

    Li, Z.Y.; Tang, T.; U-King-Im, J.; Graves, M.; Gillard, J.H.; Sutcliffe, M.

    2008-01-01

    Because many acute cerebral ischemic events are caused by rupture of vulnerable carotid atheroma and subsequent thrombosis, the present study used both idealized and patient-specific carotid atheromatous plaque models to evaluate the effect of structural determinants on stress distributions within plaque. Using a finite element method, structural analysis was performed using models derived from in vivo high-resolution magnetic resonance imaging (MRI) of carotid atheroma in 40 non-consecutive patients (20 symptomatic, 20 asymptomatic). Plaque components were modeled as hyper-elastic materials. The effects of varying fibrous cap thickness, lipid core size and lumen curvature on plaque stress distributions were examined. Lumen curvature and fibrous cap thickness were found to be major determinants of plaque stress. The size of the lipid core did not alter plaque stress significantly when the fibrous cap was relatively thick. The correlation between plaque stress and lumen curvature was significant for both symptomatic (p=0.01; correlation coefficient: 0.689) and asymptomatic patients (p=0.01; correlation coefficient: 0.862). Lumen curvature in plaques of symptomatic patients was significantly larger than those of asymptomatic patients (1.50±1.0 mm -1 vs 1.25±0.75 mm -1 ; p=0.01). Specific plaque morphology (large lumen curvature and thin fibrous cap) is closely related to plaque vulnerability. Structural analysis using high-resolution MRI of carotid atheroma may help in detecting vulnerable atheromatous plaque and aid the risk stratification of patients with carotid disease. (author)

  7. X-ray structure determination and deuteration of nattokinase.

    Science.gov (United States)

    Yanagisawa, Yasuhide; Chatake, Toshiyuki; Naito, Sawa; Ohsugi, Tadanori; Yatagai, Chieko; Sumi, Hiroyuki; Kawaguchi, Akio; Chiba-Kamosida, Kaori; Ogawa, Megumi; Adachi, Tatsumi; Morimoto, Yukio

    2013-11-01

    Nattokinase (NK) is a strong fibrinolytic enzyme, which is produced in abundance by Bacillus subtilis natto. Although NK is a member of the subtilisin family, it displays different substrate specificity when compared with other subtilisins. The results of molecular simulations predict that hydrogen arrangements around Ser221 at the active site probably account for the substrate specificity of NK. Therefore, neutron crystallographic analysis should provide valuable information that reveals the enzymatic mechanism of NK. In this report, the X-ray structure of the non-hydrogen form of undeuterated NK was determined, and the preparation of deuterated NK was successfully achieved. The non-hydrogen NK structure was determined at 1.74 Å resolution. The three-dimensional structures of NK and subtilisin E from Bacillus subtilis DB104 are near identical. Deuteration of NK was carried out by cultivating Bacillus subtilis natto in deuterated medium. The D2O resistant strain of Bacillus subtilis natto was obtained by successive cultivation rounds, in which the concentration of D2O in the medium was gradually increased. NK was purified from the culture medium and its activity was confirmed by the fibrin plate method. The results lay the framework for neutron protein crystallography analysis.

  8. Constitutional Isomers of Dendrimer-like Star Polymers: Design, Synthesis and Conformational and Structural Properties; TOPICAL

    International Nuclear Information System (INIS)

    Pople, John A.

    2001-01-01

    The design, synthesis and solution properties of six constitutional isomers of dendrimer-like star polymers is described. Each of the polymers have comparable molecular weights ((approx) 80,000 g/mol), narrow polydispersities ( and lt; 1.19) and an identical number of branching junctures (45) and surface hydroxyl functionalities (48). The only difference in the six isomers is the placement of the branching junctures. The polymers are constructed from high molecular weight poly(e-caprolactone) with branching junctures derived from 2,2'-bis(hydroxylmethyl) propionic acid (bis-MPA) emanating from a central core. The use of various generations of dendritic initiators and dendrons coupled with the ring opening polymerization of e-caprolactones allowed a modular approach to the dendrimer-like star polymer isomers. The most pronounced effects on the physical properties/morphology and hydrodynamic volume was for those polymers in which the branching was distributed throughout the sample in a dendrimer-like fashion. The versatility of this approach has provided the possibility of understanding the relationship between architecture and physical properties. Dynamic light scattering and small angle X-ray scattering techniques were used to determine the hydrodynamic radius Rh and radius of gyration Rg respectively. The relationship between Rg and molecular weight was indicative of a compact star-like structure, and did not show advanced bias towards either the dense core or dense shell models. The radial density distribution of the isomers was therefore modeled according to a many arm star polymer, and good agreement was found with experimental measures of Rh/Rg

  9. Materials-by-design: computation, synthesis, and characterization from atoms to structures

    Science.gov (United States)

    Yeo, Jingjie; Jung, Gang Seob; Martín-Martínez, Francisco J.; Ling, Shengjie; Gu, Grace X.; Qin, Zhao; Buehler, Markus J.

    2018-05-01

    In the 50 years that succeeded Richard Feynman’s exposition of the idea that there is ‘plenty of room at the bottom’ for manipulating individual atoms for the synthesis and manufacturing processing of materials, the materials-by-design paradigm is being developed gradually through synergistic integration of experimental material synthesis and characterization with predictive computational modeling and optimization. This paper reviews how this paradigm creates the possibility to develop materials according to specific, rational designs from the molecular to the macroscopic scale. We discuss promising techniques in experimental small-scale material synthesis and large-scale fabrication methods to manipulate atomistic or macroscale structures, which can be designed by computational modeling. These include recombinant protein technology to produce peptides and proteins with tailored sequences encoded by recombinant DNA, self-assembly processes induced by conformational transition of proteins, additive manufacturing for designing complex structures, and qualitative and quantitative characterization of materials at different length scales. We describe important material characterization techniques using numerous methods of spectroscopy and microscopy. We detail numerous multi-scale computational modeling techniques that complements these experimental techniques: DFT at the atomistic scale; fully atomistic and coarse-grain molecular dynamics at the molecular to mesoscale; continuum modeling at the macroscale. Additionally, we present case studies that utilize experimental and computational approaches in an integrated manner to broaden our understanding of the properties of two-dimensional materials and materials based on silk and silk-elastin-like proteins.

  10. Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials.

    Science.gov (United States)

    Hesemann, Peter; Nguyen, Thy Phung; Hankari, Samir El

    2014-04-11

    The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS) recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA), mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the "anionic templating" strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

  11. Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

    Directory of Open Access Journals (Sweden)

    Peter Hesemann

    2014-04-01

    Full Text Available The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA, mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the “anionic templating” strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

  12. Ionothermal synthesis, crystal structure, and magnetic study of Co2PO4OH isostructural with caminite.

    Science.gov (United States)

    Wang, Guangmei; Valldor, Martin; Spielberg, Eike T; Mudring, Anja-Verena

    2014-03-17

    A new framework cobalt(II) hydroxyl phosphate, Co2PO4OH, was prepared by ionothermal synthesis using 1-butyl-4-methyl-pyridinium hexafluorophosphate as the ionic liquid. As the formation of Co2PO4F competes in the synthesis, the synthesis conditions have to be judiciously chosen to obtain well-crystallized, single phase Co2PO4OH. Single-crystal X-ray diffraction analyses reveal Co2PO4OH crystallizes with space group I41/amd (a = b = 5.2713(7) Å, c = 12.907(3) Å, V = 358.63(10) Å(3), and Z = 4). Astonishingly, it does not crystallize isotypically with Co2PO4F but rather isotypically with the hydroxyl minerals caminite Mg1.33[SO4(OH)0.66(H2O)0.33] and lipscombite Fe(2–y)PO4(OH) (0 ≤ y ≤ 2/3). Phosphate tetrahedra groups interconnect four rod-packed face-sharing ∞(1){CoO(6/2)} octahedra chains to form a three-dimensional framework structure. The compound Co2PO4OH was further characterized by powder X-ray diffraction, Fourier transform–infrared, and ultraviolet–visible spectroscopy, confirming the discussed structure. The magnetic measurement reveals that Co2PO4OH undergoes a magnetic transition and presents at low temperatures a canted antiferromagnetic spin order in the ground state.

  13. Structural Ceramic Nanocomposites: A Review of Properties and Powders’ Synthesis Methods

    Science.gov (United States)

    Palmero, Paola

    2015-01-01

    Ceramic nanocomposites are attracting growing interest, thanks to new processing methods enabling these materials to go from the research laboratory scale to the commercial level. Today, many different types of nanocomposite structures are proposed in the literature; however, to fully exploit their exceptional properties, a deep understanding of the materials’ behavior across length scales is necessary. In fact, knowing how the nanoscale structure influences the bulk properties enables the design of increasingly performing composite materials. A further key point is the ability of tailoring the desired nanostructured features in the sintered composites, a challenging issue requiring a careful control of all stages of manufacturing, from powder synthesis to sintering. This review is divided into four parts. In the first, classification and general issues of nanostructured ceramics are reported. The second provides basic structure–property relations, highlighting the grain-size dependence of the materials properties. The third describes the role of nanocrystalline second-phases on the mechanical properties of ordinary grain sized ceramics. Finally, the fourth part revises the mainly used synthesis routes to produce nanocomposite ceramic powders, underlining when possible the critical role of the synthesis method on the control of microstructure and properties of the sintered ceramics. PMID:28347029

  14. A use of Ramachandran potentials in protein solution structure determinations

    International Nuclear Information System (INIS)

    Bertini, Ivano; Cavallaro, Gabriele; Luchinat, Claudio; Poli, Irene

    2003-01-01

    A strategy is developed to use database-derived φ-ψ constraints during simulated annealing procedures for protein solution structure determination in order to improve the Ramachandran plot statistics, while maintaining the agreement with the experimental constraints as the sole criterion for the selection of the family. The procedure, fully automated, consists of two consecutive simulated annealing runs. In the first run, the database-derived φ-ψ constraints are enforced for all aminoacids (but prolines and glycines). A family of structures is then selected on the ground of the lowest violations of the experimental constraints only, and the φ-ψ values for each residue are examined. In the second and final run, the database-derived φ-ψ constraints are enforced only for those residues which in the first run have ended in one and the same favored φ-ψ region. For residues which are either spread over different favored regions or concentrated in disallowed regions, the constraints are not enforced. The final family is then selected, after the second run, again only based on the agreement with the experimental constraints. This automated approach was implemented in DYANA and was tested on as many as 12 proteins, including some containing paramagnetic metals, whose structures had been previously solved in our laboratory. The quality of the structures, and of Ramachandran plot statistics in particular, was notably improved while preserving the agreement with the experimental constraints

  15. What determines the structures of native folds of proteins?

    International Nuclear Information System (INIS)

    Trovato, Antonio; Hoang, Trinh X; Banavar, Jayanth R; Maritan, Amos; Seno, Flavio

    2005-01-01

    We review a simple physical model (Hoang et al 2004 Proc. Natl Acad. Sci. USA 101 7960, Banavar et al 2004 Phys. Rev. E at press) which captures the essential physico-chemical ingredients that determine protein structure, such as the inherent anisotropy of a chain molecule, the geometrical and energetic constraints placed by hydrogen bonds, sterics, and hydrophobicity. Within this framework, marginally compact conformations resembling the native state folds of proteins emerge as competing minima in the free energy landscape. Here we demonstrate that a hydrophobic-polar (HP) sequence composed of regularly repeated patterns has as its ground state a β-helical structure remarkably similar to a known architecture in the Protein Data Bank

  16. Host Proteins Determine MRSA Biofilm Structure and Integrity

    DEFF Research Database (Denmark)

    Dreier, Cindy; Nielsen, Astrid; Jørgensen, Nis Pedersen

    Human extracellular matrix (hECM) proteins aids the initial attachment and initiation of an infection, by specific binding to bacterial cell surface proteins. However, the importance of hECM proteins in structure, integrity and antibiotic resilience of a biofilm is unknown. This study aims...... to determine how specific hECM proteins affect S. aureus USA300 JE2 biofilms. Biofilms were grown in the presence of synovial fluid from rheumatoid arteritis patients to mimic in vivo conditions, where bacteria incorporate hECM proteins into the biofilm matrix. Difference in biofilm structure, with and without...... addition of hECM to growth media, was visualized by confocal laser scanning microscopy. Two enzymatic degradation experiments were used to study biofilm matrix composition and importance of hECM proteins: enzymatic removal of specific hECM proteins from growth media, before biofilm formation, and enzymatic...

  17. An Introduction to Zeolite Synthesis Using Imidazolium-Based Cations as Organic Structure-Directing Agents.

    Science.gov (United States)

    Vinaches, Paloma; Bernardo-Gusmão, Katia; Pergher, Sibele B C

    2017-08-06

    Zeolite synthesis is a wide area of study with increasing popularity. Several general reviews have already been published, but they did not summarize the study of imidazolium species in zeolite synthesis. Imidazolium derivatives are promising compounds in the search for new zeolites and can be used to help understand the structure-directing role. Nearly 50 different imidazolium cations have already been used, resulting in a variety of zeolitic types, but there are still many derivatives to be studied. In this context, the purpose of this short review is to help researchers starting in this area by summarizing the most important concepts related to imidazolium-based zeolite studies and by presenting a table of recent imidazolium derivatives that have been recently studied to facilitate filling in the knowledge gaps.

  18. Green synthesis of ZnO nanoparticles by Aspalathus linearis: Structural & optical properties

    International Nuclear Information System (INIS)

    Diallo, A.; Ngom, B.D.; Park, E.; Maaza, M.

    2015-01-01

    This contribution reports for the 1st time on the synthesis and the main physical properties of ZnO nanoparticles synthesized by an entirely green physical-chemistral process using Aspalathus linearis's natural extract as an efficient reduction/oxidizing agent. Their structural and optical properties by electron microscopy, X-rays diffraction, Raman and X-rays photoemission spectroscopies as well as room temperature photoluminescence are reported. - Highlights: • 1st time report on synthesis of ZnO nanoparticles by a green process via Aspalathus linearis extract. • A. linearis's natural extract was used as an effective reduction/oxidizing agent. • Wurtzite nature of ZnO nanoparticles was confirmed via XRD, Raman, XPS and PL

  19. Green synthesis of ZnO nanoparticles by Aspalathus linearis: Structural & optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Diallo, A.; Ngom, B.D. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Park, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa); Nelson Mandela African Institute for Science & Technology, Arusha (Tanzania, United Republic of); Maaza, M., E-mail: Maaza@tlabs.ac.za [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, PO Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, PO Box 722, Somerset West, Western Cape (South Africa)

    2015-10-15

    This contribution reports for the 1st time on the synthesis and the main physical properties of ZnO nanoparticles synthesized by an entirely green physical-chemistral process using Aspalathus linearis's natural extract as an efficient reduction/oxidizing agent. Their structural and optical properties by electron microscopy, X-rays diffraction, Raman and X-rays photoemission spectroscopies as well as room temperature photoluminescence are reported. - Highlights: • 1st time report on synthesis of ZnO nanoparticles by a green process via Aspalathus linearis extract. • A. linearis's natural extract was used as an effective reduction/oxidizing agent. • Wurtzite nature of ZnO nanoparticles was confirmed via XRD, Raman, XPS and PL.

  20. Novel Fluorinated Indanone, Tetralone and Naphthone Derivatives: Synthesis and Unique Structural Features

    Directory of Open Access Journals (Sweden)

    Joseph C. Sloop

    2012-02-01

    Full Text Available Several fluorinated and trifluoromethylated indanone, tetralone and naphthone derivatives have been prepared via Claisen condensations and selective fluorinations in yields ranging from 22–60%. In addition, we report the synthesis of new, selectively fluorinated bindones in yields ranging from 72–92%. Of particular interest is the fluorination and trifluoroacetylation regiochemistry observed in these fluorinated products. We also note unusual transformations including a novel one pot, dual trifluoroacetylation, trifluoroacetylnaphthone synthesis via a deacetylation as well as an acetyl-trifluoroacetyl group exchange. Solid-state structural features exhibited by these compounds were investigated using crystallographic methods. Crystallographic results, supported by spectroscopic data, show that trifluoroacetylated ketones prefer a chelated cis-enol form whereas fluorinated bindone products exist primarily as the cross-conjugated triketo form.

  1. Purification and primary structure determination of human lysosomal dipeptidase.

    Science.gov (United States)

    Dolenc, Iztok; Mihelic, Marko

    2003-02-01

    The lysosomal metallopeptidase is an enzyme that acts preferentially on dipeptides with unsubstituted N- and C-termini. Its activity is highest in slightly acidic pH. Here we describe the isolation and characterization of lysosomal dipeptidase from human kidney. The isolated enzyme has the amino-terminal sequence DVAKAIINLAVY and is a homodimer with a molecular mass of 100 kDa. So far no amino acid sequence has been determined for this metallopeptidase. The complete primary structure as deduced from the nucleotide sequence revealed that the isolated dipeptidase is similar to blood plasma glutamate carboxypeptidase.

  2. Structure determination of spider silk from X-ray images

    Energy Technology Data Exchange (ETDEWEB)

    Ulrich, Stephan; Zippelius, Annette [Universitaet Goettingen, Institut fuer Theoretische Physik (Germany); Meling, Martin [Max-Planck-Institut fuer biophysikalische Chemie, Goettingen (Germany); Glisovic, Anja; Salditt, Tim [Universitaet Goettingen, Institut fuer Roentgenphysik (Germany)

    2008-07-01

    Spider silk consists of interconnected crystallites, which are typically aligned along the fiber axis. We present a method to systematically determine the structure of these crystallites. Hereby we introduce a model that calculates the scattering function G(q) which is fitted to the measured X-ray image (silk from nephila clavipes). With it, the crystallites' size, the constitution and dimensions of their unit cell, as well as their tilt with respect to the fiber axis is identified, and furthermore the effect of coherent scattering from different crystallites is investigated. The shown methods and the presented model can easily be generalized to a wide class of composite materials.

  3. Shallow lunar structure determined from the passive seismic experiment

    International Nuclear Information System (INIS)

    Nakamura, Y.; Dorman, J.; Duennebier, F.; Lammlein, D.; Latham, G.

    1975-01-01

    Data relevant to the shallow structure of the Moon obtained at the Apollo seismic stations are compared with previously published results of the active seismic experiments. It is concluded that the lunar surface is covered by a layer of low seismic velocity (Vsub(p) approximately equal to 100 ms -1 ), which appears to be equivalent to the lunar regolith defined previously by geological observations. This layer is underlain by a zone of distinctly higher seismic velocity at all of the Apollo landing sites. The regolith thicknesses at the Apollo 11, 12, and 15 sites are estimated from the shear-wave resonance to be 4.4, 3.7, and 4.4m, respectively. These thicknesses and those determined at the other Apollo sites by the active seismic experiments appear to be correlated with the age determinations and the abundances of extra-lunar components at the sites. (Auth.)

  4. Coupling Neumann development and component mode synthesis methods for stochastic analysis of random structures

    Directory of Open Access Journals (Sweden)

    Driss Sarsri

    2014-05-01

    Full Text Available In this paper, we propose a method to calculate the first two moments (mean and variance of the structural dynamics response of a structure with uncertain variables and subjected to random excitation. For this, Newmark method is used to transform the equation of motion of the structure into a quasistatic equilibrium equation in the time domain. The Neumann development method was coupled with Monte Carlo simulations to calculate the statistical values of the random response. The use of modal synthesis methods can reduce the dimensions of the model before integration of the equation of motion. Numerical applications have been developed to highlight effectiveness of the method developed to analyze the stochastic response of large structures.

  5. Synthesis and structural characterization of some trisulfide analoges of thiouracil-based antithyroid drugs

    Science.gov (United States)

    Bhabak, Krishna P.; Bhowmick, Debasish

    2012-08-01

    Thiourea-based antithyroid drugs are effectively used for the treatment of hyperthyroidism. In this paper, we describe the synthesis of new trisulfides (11-12) from the commonly used thiourea-based antithyroid drugs such as 6-n-propyl-2-thiouracil (PTU) and 6-methyl-2-thiouracil (MTU) in the reaction with I2/KI system. Structural analysis by single crystal X-ray diffraction studies revealed the stabilization of trisulfides by a lactam-lactim tautomerism facilitating effective intramolecular as well as intermolecular non-covalent interactions. Although the structures of both trisulfides were found to be quite similar, a notable difference in the intermolecular interactions was observed between compounds 11 and 12 leading to different structural patterns. Structural stabilization of these trisulfides by tautomerism followed by intramolecular as well as intermolecular H-bonds makes these molecules as perfect examples in molecular recognition with self-complementary donor and acceptor units within a single molecule.

  6. Structure-directing effects of ionic liquids in the ionothermal synthesis of metal-organic frameworks.

    Science.gov (United States)

    Vaid, Thomas P; Kelley, Steven P; Rogers, Robin D

    2017-07-01

    Traditional synthesis of metal-organic frameworks (MOFs) involves the reaction of a metal-containing precursor with an organic linker in an organic solvent at an elevated temperature, in what is termed a 'solvothermal' reaction. More recently, many examples have been reported of MOF synthesis in ionic liquids (ILs), rather than an organic solvent, in 'ionothermal' reactions. The high concentration of both cations and anions in an ionic liquid allows for the formation of new MOF structures in which the IL cation or anion or both are incorporated into the MOF. Most commonly, the IL cation is included in the open cavities of the MOF, countering the anionic charge of the MOF framework itself and acting as a template around which the MOF structure forms. Ionic liquids can also serve other structure-directing roles, for example, when an IL containing a single enantiomer of a chiral anion leads to a homochiral MOF, even though the IL anion is not itself incorporated into the MOF. A comprehensive review of ionothermal syntheses of MOFs, and the structure-directing effects of the ILs, is given.

  7. Structure-directing effects of ionic liquids in the ionothermal synthesis of metal–organic frameworks

    Directory of Open Access Journals (Sweden)

    Thomas P. Vaid

    2017-07-01

    Full Text Available Traditional synthesis of metal–organic frameworks (MOFs involves the reaction of a metal-containing precursor with an organic linker in an organic solvent at an elevated temperature, in what is termed a `solvothermal' reaction. More recently, many examples have been reported of MOF synthesis in ionic liquids (ILs, rather than an organic solvent, in `ionothermal' reactions. The high concentration of both cations and anions in an ionic liquid allows for the formation of new MOF structures in which the IL cation or anion or both are incorporated into the MOF. Most commonly, the IL cation is included in the open cavities of the MOF, countering the anionic charge of the MOF framework itself and acting as a template around which the MOF structure forms. Ionic liquids can also serve other structure-directing roles, for example, when an IL containing a single enantiomer of a chiral anion leads to a homochiral MOF, even though the IL anion is not itself incorporated into the MOF. A comprehensive review of ionothermal syntheses of MOFs, and the structure-directing effects of the ILs, is given.

  8. Simple surface structure determination from Fourier transforms of angle-resolved photoemission extended fine structure

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Y. [Pennsylvania State Univ., University Park, PA (United States)]|[Lawrence Berkeley Lab., CA (United States); Shirley, D.A. [Pennsylvania State Univ., University Park, PA (United States)

    1995-02-01

    The authors show by Fourier analyses of experimental data, with no further treatment, that the positions of all the strong peaks in Fourier transforms of angle-resolved photoemission extended fine structure (ARPEFS) from adsorbed surfaces can be explicitly predicted from a trial structure with an accuracy of about {+-} 0.3 {angstrom} based on a single-scattering cluster model together with the concept of a strong backscattering cone, and without any additional analysis. This characteristic of ARPEFS Fourier transforms can be developed as a simple method for determining the structures of adsorbed surfaces to an accuracy of about {+-} 0.1 {angstrom}.

  9. Synthesis of Uncarbonised Coconut Shell Nanoparticles: Characterisation and Particle Size Determination

    Directory of Open Access Journals (Sweden)

    S.A. Bello

    2015-06-01

    Full Text Available The possibility of using mechanical milling for the synthesis of uncarbonised coconut shell nanoparticles (UCSNPs has been investigated. UCSNPs were synthesized from discarded coconut shells (CSs using top down approach. The sundried CSs were crushed, ground and then sieved using hammer crusher, a two disc grinder and set of sieves with shine shaker respectively. The CS powders retained in the pan below 37 µm sized sieve were milled for 70 hours to obtain UCSNPS. Samples for analysis were taken at 16 and 70 hours. UCSNPs were analyzed using transmission electron microscope (TEM, scanning electron microscope (SEM with attached EDS and Gwyddion software. Samples of UCSNPs obtained at 16 and 70hours show that the deep brown colour of the initial CS powder became fading as the milling hour increased. The size determination from TEM image revealed spherical particles with an average size of 18.23 nm for UCSNPs obtained at 70 hour milling. The EDS spectrographs revealed an increase in the carbon counts with increased milling hours. This is attributable to dryness of the CS powders by the heat generated during the milling process due to absorption of kinetic energy by the CS powders from the milling balls. SEM micrographs revealed UCSNPs in agglomerated networks. The SEM micrograph/Gyweddion particles size determination showed average particles of 170.5 ±3 and 104.9 ±4.1 nm for UCSNPs obtained at 16 and 70 hours respectively. Therefore, production of UCSNPs through mechanical milling using mixture of ceramic balls of different sizes has been established especially when the particles of the sourced/initial CS powders falls below 37 µm.

  10. Mechanical synthesis of copper-carbon nanocomposites: Structural changes, strengthening and thermal stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, D., E-mail: daniela.nunes@ist.utl.pt [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Livramento, V. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Mateus, R. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Correia, J.B. [LNEG, Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal); Alves, L.C. [ITN, Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal); Vilarigues, M. [Departamento de Conservacao e Restauro e R and D Unit Vidro e da Ceramica Para as Artes, FCT-UNL, Quinta da Torre, 2829-516 Caparica (Portugal); Carvalho, P.A. [ICEMS, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Departamento de Bioengenharia, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2011-11-15

    Highlights: {yields} The study characterized Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites. {yields} Preservation of nD crystalline structure during high-energy milling was demonstrated. {yields} Higher refinement of matrix in Cu-nD comparing to Cu-G is due to a milling mechanism. {yields} Remarkable thermal stability and microhardness have been achieved in Cu-nD and Cu-G. {yields} Strengthening resulted mainly from grain refinement and second-phase reinforcement. - Abstract: Processing of copper-carbon nanocomposites by mechanical synthesis poses specific challenges as carbon phases are prone to amorphization and exhibit an intrinsically difficult bonding with copper. The present work investigates Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites produced by mechanical synthesis and subsequent heat treatments. Transmission electron microscopy observations showed homogeneous particle distributions and intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained essentially unaffected by the mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. Particle-induced X-ray emission spectroscopy showed that the total contamination originating from the milling media remained below 0.7 wt.%. The Cu-nanodiamond composite exhibited remarkable microhardness and microstructural thermal stability when compared with pure nanostructured copper.

  11. Mechanical synthesis of copper-carbon nanocomposites: Structural changes, strengthening and thermal stabilization

    International Nuclear Information System (INIS)

    Nunes, D.; Livramento, V.; Mateus, R.; Correia, J.B.; Alves, L.C.; Vilarigues, M.; Carvalho, P.A.

    2011-01-01

    Highlights: → The study characterized Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites. → Preservation of nD crystalline structure during high-energy milling was demonstrated. → Higher refinement of matrix in Cu-nD comparing to Cu-G is due to a milling mechanism. → Remarkable thermal stability and microhardness have been achieved in Cu-nD and Cu-G. → Strengthening resulted mainly from grain refinement and second-phase reinforcement. - Abstract: Processing of copper-carbon nanocomposites by mechanical synthesis poses specific challenges as carbon phases are prone to amorphization and exhibit an intrinsically difficult bonding with copper. The present work investigates Cu-nanodiamond (Cu-nD) and Cu-graphite (Cu-G) composites produced by mechanical synthesis and subsequent heat treatments. Transmission electron microscopy observations showed homogeneous particle distributions and intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of chemically extracted carbon phases demonstrated that milled nanodiamond preserved crystallinity, while an essentially amorphous nature could be inferred for milled graphite. Raman spectra confirmed that nanodiamond particles remained essentially unaffected by the mechanical synthesis, whereas the bands of milled graphite were significantly changed into the typical amorphous carbon fingerprint. Particle-induced X-ray emission spectroscopy showed that the total contamination originating from the milling media remained below 0.7 wt.%. The Cu-nanodiamond composite exhibited remarkable microhardness and microstructural thermal stability when compared with pure nanostructured copper.

  12. A new class of HIV-1 protease inhibitor: the crystallographic structure, inhibition and chemical synthesis of an aminimide peptide isostere.

    Science.gov (United States)

    Rutenber, E E; McPhee, F; Kaplan, A P; Gallion, S L; Hogan, J C; Craik, C S; Stroud, R M

    1996-09-01

    The essential role of HIV-1 protease (HIV-1 PR) in the viral life cycle makes it an attractive target for the development of substrate-based inhibitors that may find efficacy as anti-AIDS drugs. However, resistance has arisen to potent peptidomimetic drugs necessitating the further development of novel chemical backbones for diversity based chemistry focused on probing the active site for inhibitor interactions and binding modes that evade protease resistance. AQ148 is a potent inhibitor of HIV-1 PR and represents a new class of transition state analogues incorporating an aminimide peptide isostere. A 3-D crystallographic structure of AQ148, a tetrapeptide isostere, has been determined in complex with its target HIV-1 PR to a resolution of 2.5 A and used to evaluate the specific structural determinants of AQ148 potency and to correlate structure-activity relationships within the class of related compounds. AQ148 is a competitive inhibitor of HIV-1 PR with a Ki value of 137 nM. Twenty-nine derivatives have been synthesized and chemical modifications have been made at the P1, P2, P1', and P2' sites. The atomic resolution structure of AQ148 bound to HIV-1 PR reveals both an inhibitor binding mode that closely resembles that of other peptidomimetic inhibitors and specific protein/inhibitor interactions that correlate with structure-activity relationships. The structure provides the basis for the design, synthesis and evaluation of the next generation of hydroxyethyl aminimide inhibitors. The aminimide peptide isostere is a scaffold with favorable biological properties well suited to both the combinatorial methods of peptidomimesis and the rational design of potent and specific substrate-based analogues.

  13. Structure determination by photoelectron diffraction of small molecules on surfaces

    International Nuclear Information System (INIS)

    Booth, N.A.

    1998-05-01

    The synchrotron radiation based technique of Photoelectron Diffraction (PhD) has been applied to three adsorption systems. Structure determinations, are presented for each system which involve the adsorption of small molecules on the low index {110} plane of single crystal Cu and Ni substrates. For the NH 3 -Cu(110) system PhD was successful in determining a N-Cu bondlength of 2.05 ± 0.03 A as well as values for the anisotropic vibrational amplitudes of the N and an expansion of the 1st to 2nd Cu substrate layer spacing from the bulk value of 0.08 ± 0.08 A. The most significant and surprising structural parameter determined for this system was that the N atom occupies an asymmetric adsorption site. Rather than being situated in the expected high symmetry atop site the N atom was found to be offset parallel to the surface by 0.37 ± 0.12 A in the [001] azimuth. In studying the glycine-Cu(110) system the adsorption structure of an amino-acid has been quantified. The local adsorption geometries of all the atoms involved in the molecule to surface bond have been determined. The glycine molecule is found to be bonded to the surface via both its amino and carboxylate functional groups. The molecule straddles two [11-bar0] rows of the Cu substrate. The two O atoms are found to be in identical sites both approximately atop Cu atoms on the [11-bar0] rows offset parallel to the surface by 0.80 ± 0.05 A in the [001] azimuth, the O-Cu bondlength was found to be 2.03 ± 0.05 A. The N atom was also found to adsorb in an approximately atop geometry but offset parallel to the surface by 0.24 ± 0.10A in the [11-bar0] direction, the N-Cu bondlength was found to be 2.05± 0.05 A. PhD was unsuccessful in determining the positions of the two C atoms that form a bridge between the two functional groups bonded to the surface due to difficulties in separating the two inequivalent contributions to the final intensity modulation function. For the CN-Ni(110) system both PhD and Near Edge

  14. Facile and template-free method toward chemical synthesis of polyaniline film/nanotube structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Pei [Department of Electrical and Computer Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh Pennsylvania 15261; Zhu, Yisi [Materials Science Division, Argonne National Lab, Lemont Illinois 60439; Torres, Jorge [Department of Electrical and Computer Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh Pennsylvania 15261; Lee, Seung Hee [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-786 Korea; Yun, Minhee [Department of Electrical and Computer Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh Pennsylvania 15261

    2017-09-05

    A facile and template-free method is reported to synthesize a new thin film structure: polyaniline (PANI) film/nanotubes (F/N) structure. The PANI F/N is a 100-nm thick PANI film embedded with PANI nanotubes. This well-controlled method requires no surfactant or organic acid as well as relatively low concentration of reagents. Synthesis condition studies reveal that aniline oligomers with certain structures are responsible for guiding the growth of the nanotubes. Electrical characterization also indicates that the PANI F/N possesses similar field-effect transistor characteristics to bare PANI film. With its 20% increased surface-area-to-volume (S/V) ratio contributed by surface embedded nanotubes and the excellent p-type semiconducting characteristic, PANI F/N shows clear superiority compared with bare PANI film. Such advantages guarantee the PANI F/N a promising future toward the development of ultra-high sensitivity and low-cost biosensors.

  15. Synthesis and crystal structure of the rare earth borogermanate EuGeBO{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Yang; Zhuang, Yan; Guo, Sheng-Ping [Yangzhou Univ., Jiangsu (China). College of Chemistry and Chemical Engineering

    2017-03-01

    The synthesis and crystal structure of the rare earth borogermanate EuGeBO{sub 5} are reported. It is synthesized by high-temperature solid-state reaction and crystallizes in the monoclinic space group P2{sub 1}/c (no. 14) with the unit cell parameters a=4.8860(5), b=7.5229(8), c=9.9587(10) Aa, and β=91.709(3) . Its crystal structure features a polyanion-type layer (GeBO{sub 5}){sup 3-} constructed by BO{sub 4} and GeO{sub 4} tetrahedra connected alternatingly. Eu{sup 3+} ions are located in cavities and are coordinated by eight O atoms. Various structures of the related compounds REMM'O{sub 5} (RE=rare earth metal; M=Si, Ge, and Sn; M'=B, Al, and Ga) are also discussed.

  16. Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives

    Directory of Open Access Journals (Sweden)

    Carlos Macias

    2016-01-01

    Full Text Available We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores. The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

  17. Synthesis and crystal structures of a novel layered silicate SSA-1 and its microporous derivatives by topotactic transformation.

    Science.gov (United States)

    Takahashi, S; Kurita, Y; Ikeda, T; Miyamoto, M; Uemiya, S; Oumi, Y

    2016-10-18

    The synthesis of a novel layered silicate SSA-1 (SSA: silicate synthesized with a quaternary amine) was achieved in the SiO 2 -H 2 O-TEAOH (TEAOH: tetraethylammonium hydroxide - as an organic structural directing agent) system. The crystal structure of SSA-1 involved two silicate layers composed of bre [10T]-type CBU (Composite Building Unit) and TEAOH in interlayers. The topotactic transformation of SSA-1 by calcination was examined, resulting in a porous material (PML-1: porous material transformed from a layered silicate) with a 108 m 2 g -1 BET surface area and 0.035 cm 3 g -1 pore volume. PML-1 is a siliceous microporous material with silanols in the framework and possesses unique properties, such as hydrophilicity, in spite of all its silica composition. The most reasonable crystal structure of PML-1 was successfully determined on the basis of the crystal structure of SSA-1 by a combination of manual modelling, PXRD pattern simulation, DFT optimization and Rietveld analysis. Additionally, an interlayer expanded siliceous zeolite SSA-1 (IEZ-SSA-1) was also successfully prepared by silylation using trichloro(methyl)silane under acidic conditions. IEZ-SSA-1 showed hydrophilicity or hydrophobicity properties by changing the functional group of the pillar part in the interlayer. Additionally, IEZ-SSA-1 showed a large gas adsorption property (537 m 2 g -1 and 0.21 cm 3 g -1 ).

  18. Structure of human DNA polymerase iota and the mechanism of DNA synthesis.

    Science.gov (United States)

    Makarova, A V; Kulbachinskiy, A V

    2012-06-01

    Cellular DNA polymerases belong to several families and carry out different functions. Highly accurate replicative DNA polymerases play the major role in cell genome replication. A number of new specialized DNA polymerases were discovered at the turn of XX-XXI centuries and have been intensively studied during the last decade. Due to the special structure of the active site, these enzymes efficiently perform synthesis on damaged DNA but are characterized by low fidelity. Human DNA polymerase iota (Pol ι) belongs to the Y-family of specialized DNA polymerases and is one of the most error-prone enzymes involved in DNA synthesis. In contrast to other DNA polymerases, Pol ι is able to use noncanonical Hoogsteen interactions for nucleotide base pairing. This allows it to incorporate nucleotides opposite various lesions in the DNA template that impair Watson-Crick interactions. Based on the data of X-ray structural analysis of Pol ι in complexes with various DNA templates and dNTP substrates, we consider the structural peculiarities of the Pol ι active site and discuss possible mechanisms that ensure the unique behavior of the enzyme on damaged and undamaged DNA.

  19. Carbon Nanotubes Advanced Topics in the Synthesis, Structure, Properties and Applications

    CERN Document Server

    Jorio, Ado; Dresselhaus, Mildred S

    2008-01-01

    The carbon nanotubes field has evolved substantially since the publication of the bestseller "Carbon Nanotubes: Synthesis, Structure, Properties and Applications". The present volume builds on the generic aspects of the aforementioned book, which emphasizes the fundamentals, with the new volume emphasizing areas that have grown rapidly since the first volume, guiding future directions where research is needed and highlighting applications. The volume also includes an emphasis on areas like graphene, other carbon-like and other tube-like materials because these fields are likely to affect and influence developments in nanotubes in the next 5 years.

  20. Synthesis of Copper-Based Transparent Conductive Oxides with Delafossite Structure via Sol-Gel Processing

    OpenAIRE

    Götzendörfer, Stefan

    2011-01-01

    Starting off with solubility experiments of possible precursors, the present study reveals the whole development of a sol gel processing route for transparent p type semiconductive thin films with delafossite structure right to the fabrication of functional p-n junctions. The versatile sol formulation could successfully be modified for several oxide compositions, enabling the synthesis of CuAlO2, CuCrO2, CuMnO2, CuFeO2 and more. Although several differences in the sintering behaviour of powde...

  1. Gadolinium (III) 2-benzoyl-1,1,3,3-tetracyanopropenide diacetate. Synthesis and crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Karpov, Sergey V.; Kayukov, Yakov S.; Grigor' ev, Arthur A. [Department of Chemistry and Pharmaceutics, I.N. Ul' yanov Chuvash State University, Cheboksary (Russian Federation); Tafeenko, Victor A. [Department of Chemistry, Lomonosov Moscow State University (Russian Federation)

    2018-02-15

    2-Acyl-1,1,3,3-tetracyanopropenides (ATCN) is a stable organic salts, containing the carbonyl group in addition to the tetracyanoallyl (TCA) fragment in the anion. TCA anions are known as bridging ligands with variable denticity with potential application in organic electronics and as a ionic liquids components. In this communication we reporting the synthesis and crystal structure of gadolinium(III) 2-benzoyl-1,1,3,3-tetracyanopropenide diacetate - the first lanthanide ATCN. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Synthesis and structural characterization of amorphous alloys of the Fe-Ni-B type

    International Nuclear Information System (INIS)

    Cabral P, A.; Jimenez B, J.; Garcia S, I.

    2004-01-01

    It was prepared the alloy FeNiB for chemical reduction, using four p H values (5, 6, 7 and 7.5). To p H=6 partially oxidized particles were obtained, between 16 and 20%. In the synthesis to other p H values, the obtained particles were highly oxidized (65-90%) according to the X-ray diffraction results, in all the preparations the particles were partially crystallized, with crystal size that varied between 4 and 10 nm. The structure of these particles can be consider that they are formed by a nucleus due to the alloy and an oxide armor recovering it. (Author)

  3. Synthesis and processing of structural and intracellular proteins of two enteric coronaviruses

    International Nuclear Information System (INIS)

    Sardinia, L.M.

    1985-01-01

    The synthesis and processing of virus-specific proteins of two economically important enteric coronaviruses, bovine enteric coronavirus (BCV) and transmissible gastroenteritis virus (TGEV), were studied at the molecular level. To determine the time of appearance of virus-specific proteins, virus-infected cells were labeled with 35 S-methionine at various times during infection, immunoprecipitated with specific hyperimmune ascitic fluid, and analyzed by SDS-polyacrylamide gel electrophoresis. The peak of BCV protein synthesis was found to be at 12 hours postinfection (hpi). The appearance of all virus-specific protein was coordinated. In contrast, the peak of TGEV protein synthesis was at 8 hpi, but the nucleocapsid proteins was present as early as 4 hpi. Virus-infected cells were treated with tunicamycin to ascertain the types of glycosidic linkages of the glycoproteins. The peplomer proteins of both viruses were sensitive to inhibition by tunicamycin indicating that they possessed N-linked carbohydrates. The matrix protein of TGEV was similarly affected. The matrix protein of BCV, however, was resistant to tunicamycin treatment and, therefore, has O-linked carbohydrates. Only the nucleocapsid protein of both viruses is phosphorylated as detected by radiolabeling with 32 P-orthophosphate. Pulse-chase studies and comparison of intracellular and virion proteins were done to detect precursor-product relationships

  4. Production, purification, crystallization and structure determination of H-1 Parvovirus

    International Nuclear Information System (INIS)

    Halder, Sujata; Nam, Hyun-Joo; Govindasamy, Lakshmanan; Vogel, Michèle; Dinsart, Christiane; Salomé, Nathalie; McKenna, Robert; Agbandje-McKenna, Mavis

    2012-01-01

    The production, purification, crystallization and crystallographic analysis of H-1 Parvovirus, a gene-therapy vector, are reported. Crystals of H-1 Parvovirus (H-1PV), an antitumor gene-delivery vector, were obtained for DNA-containing capsids and diffracted X-rays to 2.7 Å resolution using synchrotron radiation. The crystals belonged to the monoclinic space group P2 1 , with unit-cell parameters a = 255.4, b = 350.4, c = 271.6 Å, β = 90.34°. The unit cell contained two capsids, with one capsid per crystallographic asymmetric unit. The H-1PV structure has been determined by molecular replacement and is currently being refined

  5. Epothilones as lead structures for the synthesis-based discovery of new chemotypes for microtubule stabilization.

    Science.gov (United States)

    Feyen, Fabian; Cachoux, Frédéric; Gertsch, Jürg; Wartmann, Markus; Altmann, Karl-Heinz

    2008-01-01

    Epothilones are macrocyclic bacterial natural products with potent microtubule-stabilizing and antiproliferative activity. They have served as successful lead structures for the development of several clinical candidates for anticancer therapy. However, the structural diversity of this group of clinical compounds is rather limited, as their structures show little divergence from the original natural product leads. Our own research has explored the question of whether epothilones can serve as a basis for the development of new structural scaffolds, or chemotypes, for microtubule stabilization that might serve as a basis for the discovery of new generations of anticancer drugs. We have elaborated a series of epothilone-derived macrolactones whose overall structural features significantly deviate from those of the natural epothilone scaffold and thus define new structural families of microtubule-stabilizing agents. Key elements of our hypermodification strategy are the change of the natural epoxide geometry from cis to trans, the incorporation of a conformationally constrained side chain, the removal of the C3-hydroxyl group, and the replacement of C12 with nitrogen. So far, this approach has yielded analogs 30 and 40 that are the most advanced, the most rigorously modified, structures, both of which are potent antiproliferative agents with low nanomolar activity against several human cancer cell lines in vitro. The synthesis was achieved through a macrolactone-based strategy or a high-yielding RCM reaction. The 12-aza-epothilone ("azathilone" 40) may be considered a "non-natural" natural product that still retains most of the overall structural characteristics of a true natural product but is structurally unique, because it lies outside of the general scope of Nature's biosynthetic machinery for polyketide synthesis. Like natural epothilones, both 30 and 40 promote tubulin polymerization in vitro and at the cellular level induce cell cycle arrest in mitosis. These

  6. Structure of HIV-1 protease determined by neutron crystallography

    International Nuclear Information System (INIS)

    Adachi, Motoyasu; Kuroki, Ryota

    2009-01-01

    HIV-1 protease is an aspartic protease, and plays an essential role in replication of HIV. To develop HIV-1 protease inhibitors through structure-based drug design, it is necessary to understand the catalytic mechanism and inhibitor recognition of HIV-1 protease. We have determined the crystal structure of HIV-1 protease in complex with KNI-272 to 1.9 A resolution by neutron crystallography in combination with 1.4 A resolution X-ray diffraction data. The results show that the carbonyl group of hydroxymethylcarbonyl (HMC) in KNI-272 forms a hydrogen bonding interaction with protonated Asp 25 and the hydrogen atom from the hydroxyl group of HMC forms a hydrogen bonding interaction with the deprotonated Asp125. This is the first neutron report for HIV-1/inhibitor complex and shows directly the locations of key hydrogen atoms in catalysis and in the binding of a transition-state analog. The results confirm key aspect of the presumed catalytic mechanism of HIV-1 protease and will aid in the further development of protease inhibitors. (author)

  7. Determination of subsurface geological structure with borehole gravimetry

    International Nuclear Information System (INIS)

    Clark, S.R.; Hearst, J.R.

    1983-07-01

    Conventional gamma-gamma and gravimetric density measurements are routinely gathered for most holes used for underground nuclear tests. The logs serve to determine the subsurface structural geology near the borehole. The gamma-gamma density log measures density of the rock within about 15 cm of the borehole wall. The difference in gravity measured at two depths in a borehole can be interpreted in terms of the density of an infinite, homogeneous, horizontal bed between those depths. When the gravimetric density matches the gamma-gamma density over a given interval it is assumed that the bed actualy exists, and that rocks far from the hole must be the same as those encountered adjacent to the borehole. Conversely, when the gravimetric density differs from the gamma-gamma density it is apparent that the gravimeter is being influenced by a rock mass of different density than that at the hole wall. This mismatch can be a powerful tool to deduce the local structural geology. The geology deduced from gravity mesurements in emplacement hole, U4al, and the associated exploratory hole, UE4al, is an excellent example of the power of the method

  8. Determination of scattering structures from spatial coherence measurements.

    Science.gov (United States)

    Zarubin, A M

    1996-03-01

    A new method of structure determination and microscopic imaging with short-wavelength radiations (charged particles, X-rays, neutrons), based on measurements of the modulus and the phase of the degree of spatial coherence of the scattered radiation, is developed. The underlying principle of the method--transfer of structural information about the scattering potential via spatial coherence of the secondary (scattering) source of radiation formed by this potential--is expressed by the generalization of the van Cittert-Zernike theorem to wave and particle scattering [A.M. Zarubin, Opt. Commun. 100 (1993) 491; Opt. Commun. 102 (1993) 543]. Shearing interferometric techniques are proposed for implementing the above measurements; the limits of spatial resolution attainable by reconstruction of the absolute square of a 3D scattering potential and its 2D projections from the measurements are analyzed. It is shown theoretically that 3D imaging with atomic resolution can be realized in a "synthetic aperture" electron or ion microscope and that a 3D resolution of about 6 nm can be obtained with a "synthetic aperture" X-ray microscope. A proof-of-principle optical experiment is presented.

  9. A Determination of the Neutron Spin Structure Function

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Emlyn W

    2003-08-18

    The authors report the results of the experiment E142 which measured the spin dependent structure function of the neutron, g{sub 1}{sup n}(x, Q{sup 2}). The experiment was carried out at the Stanford Linear Accelerator Center by measuring an asymmetry in the deep inelastic scattering of polarized electrons from a polarized {sup 3}He target, at electron energies from 19 to 26 GeV. The structure function was determined over the kinematic range 0.03 < BJorken x < 0.6 and 1.0 < Q{sup 2} < 5.5 (GeV/c){sup 2}. An evaluation of the integral {integral}{sub 0}{sup 1} g{sub 1}{sup n}(x,Q{sup 2})dx at fixed Q{sup 2} = 2 (GeV/c){sup 2} yields the final result {Lambda}{sub 1}{sup n} = -0.032 {+-} 0.006 (stat.) {+-} 0.009 (syst.). This result, when combined with the integral of the proton spin structure function measured in other experiments, confirms the fundamental Bjorken sum rule with O({alpha}{sub s}{sup 3}) corrections to within one standard deviation. This is a major success for perturbative Quantum Chromodynamics. Some ancillary results include the findings that the Ellis-Jaffe sum rule for the neutron is violated at the 2 {sigma} level, and that the total contribution of the quarks to the helicity of the nucleon is 0.36 {+-} 0.10. The strange sea polarization is estimated to be small and negative, {Delta}s = -0.07 {+-} 0.04.

  10. Structure and Absolute Configuration of Nyasol and Hinokiresinol via Synthesis and Vibrational Circular Dichroism Spectroscopy

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2005-01-01

    The absolute configuration of the norlignan (+)-nyasol was determined to be S by comparison of the experimental vibrational circular dichroism data with first-principle calculations taking into account the eight lowest energy conformations. The established absolute configuration of (+)-nyasol...... enables establishment of the absolute configuration of (-)-hinokiresinol, which is concluded to be S. A total synthesis and resolution of hinokiresinol has been performed to resolve the conflicting reports of the coupling constant of the vinylic protons of the disubstituted double bond in this molecule...

  11. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

    International Nuclear Information System (INIS)

    Caskey, Christopher M.; Holder, Aaron; Christensen, Steven T.; Biagioni, David; Ginley, David S.; Tumas, William; Perkins, John D.; Lany, Stephan; Zakutayev, Andriy; Shulda, Sarah; Diercks, David; Pylypenko, Svitlana; Richards, Ryan M.; Schwartz, Craig P.; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; Prendergast, David; Sun, Wenhao; Orvananos, Bernardo

    2016-01-01

    Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here, we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is N-deficient SnN with tin in the mixed II/IV valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn 3 N 4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of metastable materials. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials.

  12. Mesoporous silicas with covalently immobilized β-cyclodextrin moieties: synthesis, structure, and sorption properties

    Science.gov (United States)

    Roik, Nadiia V.; Belyakova, Lyudmila A.; Trofymchuk, Iryna M.; Dziazko, Marina O.; Oranska, Olena I.

    2017-09-01

    Mesoporous silicas with chemically attached macrocyclic moieties were successfully prepared by sol-gel condensation of tetraethyl orthosilicate and β-cyclodextrin-silane in the presence of a structure-directing agent. Introduction of β-cyclodextrin groups into the silica framework was confirmed by the results of IR spectral, thermogravimetric, and quantitative chemical analysis of surface compounds. The porous structure of the obtained materials was characterized by nitrogen adsorption-desorption measurements, powder X-ray diffraction, transmission electron microscopy, and dynamic light scattering. It was found that the composition of the reaction mixture used in β-cyclodextrin-silane synthesis significantly affects the structural parameters of the resulting silicas. The increase in (3-aminopropyl)triethoxysilane as well as the coupling agent content in relation to β-cyclodextrin leads ultimately to the lowering or complete loss of hexagonal arrangement of pore channels in the synthesized materials. Formation of hexagonally ordered mesoporous structure was observed at molar composition of the mixture 0.049 TEOS:0.001 β-CD-silane:0.007 CTMAB:0.27 NH4OH:7.2 H2O and equimolar ratio of components in β-CD-silane synthesis. The sorption of alizarin yellow on starting silica and synthesized materials with chemically attached β-cyclodextrin moieties was studied in phosphate buffer solutions with pH 7.0. Experimental results of the dye equilibrium sorption were analyzed using Langmuir, Freundlich, and Redlich-Peterson isotherm models. It was proved that the Redlich-Peterson isotherm model is the most appropriate for fitting the equilibrium sorption of alizarin yellow on parent silica with hexagonally arranged mesoporous structure as well as on modified one with chemically immobilized β-cyclodextrin groups. [Figure not available: see fulltext.

  13. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Caskey, Christopher M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Colorado School of Mines, Golden, Colorado 80401 (United States); Larix Chemical Science, Golden, Colorado 80401 (United States); Holder, Aaron; Christensen, Steven T.; Biagioni, David; Ginley, David S.; Tumas, William; Perkins, John D.; Lany, Stephan; Zakutayev, Andriy, E-mail: andriy.zakutayev@nrel.gov [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Shulda, Sarah; Diercks, David; Pylypenko, Svitlana; Richards, Ryan M. [Colorado School of Mines, Golden, Colorado 80401 (United States); Schwartz, Craig P.; Nordlund, Dennis [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Kukliansky, Alon; Natan, Amir [Tel Aviv University, Tel Aviv-Yafo (Israel); Prendergast, David; Sun, Wenhao [Lawrence Berkeley National Laboratory, Berkley, California 94720 (United States); Orvananos, Bernardo [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); and others

    2016-04-14

    Recent advances in theoretical structure prediction methods and high-throughput computational techniques are revolutionizing experimental discovery of the thermodynamically stable inorganic materials. Metastable materials represent a new frontier for these studies, since even simple binary non-ground state compounds of common elements may be awaiting discovery. However, there are significant research challenges related to non-equilibrium thin film synthesis and crystal structure predictions, such as small strained crystals in the experimental samples and energy minimization based theoretical algorithms. Here, we report on experimental synthesis and characterization, as well as theoretical first-principles calculations of a previously unreported mixed-valent binary tin nitride. Thin film experiments indicate that this novel material is N-deficient SnN with tin in the mixed II/IV valence state and a small low-symmetry unit cell. Theoretical calculations suggest that the most likely crystal structure has the space group 2 (SG2) related to the distorted delafossite (SG166), which is nearly 0.1 eV/atom above the ground state SnN polymorph. This observation is rationalized by the structural similarity of the SnN distorted delafossite to the chemically related Sn{sub 3}N{sub 4} spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of metastable materials. In addition to reporting on the discovery of the simple binary SnN compound, this paper illustrates a possible way of combining a wide range of advanced characterization techniques with the first-principle property calculation methods, to elucidate the most likely crystal structure of the previously unreported metastable materials.

  14. Extent of excision repair before DNA synthesis determines the mutagenic but not the lethal effect of UV radiation

    Energy Technology Data Exchange (ETDEWEB)

    Konze-Thomas, B.; Hazard, R.M.; Maher, V.M.; McCormick, J.J. (Michigan State Univ., East Lansing (USA). Carcinogenesis Lab.)

    1982-01-01

    Excision repair-proficient diploid fibroblasts from normal persons (NF) and repair-deficient cells from a xeroderma pigmentosum patient (XP12BE, group A) were grown to confluence and allowed to enter the G/sub 0/ state. Autoradiography studies of cells released from G/sub 0/ after 72 h and replated at lower densities (3-9 x 10/sup 3/ cells/cm/sup 2/) in fresh medium showed that semiconservative DNA synthesis (S phase) began approx. equal to 24 h after the replating. The task was to determine whether the time available for DNA excision repair between ultraviolet irradiation (254 nm) and the onset of DNA synthesis was critical in determining the cytotoxic and/or mutagenic effect of UV in human fibroblasts.

  15. Nitridomanganates of alkaline-earth metals. Synthesis, structure, and physical properties

    Energy Technology Data Exchange (ETDEWEB)

    Ovchinnikov, Alexander

    2016-12-02

    The main goal of the present work was the synthesis of alkaline-earth nitridomanganates (AE{sub x}Mn{sub y}N{sub z}) with extended anionic structures and the characterization of their electronic and magnetic properties. Up to now, only compounds with isolated nitridomanganate anions have been reported in the discussed ternary systems. A systematic exploratory synthesis, employing high-temperature treatment of AE nitrides and Mn under controlled N2 pressure, yielded more than ten new nitridomanganates. Their crystal structures contain anionic building blocks of different dimensionalities, ranging from isolated species to three-dimensional frameworks. In general, the formation of Mn-rich compositions was found to be driven by the emergence of Mn-Mn interactions, which creates a link between nitridometalates and transition-metal-rich binary nitrides. The obtained nitridomanganates display a plethora of interesting phenomena, such as large spin-orbit coupling, magnetic frustration, quenching of magnetism due to Mn-Mn interactions, and metal-insulator transition.

  16. Synthesis and optical properties of novel organic-inorganic hybrid nanolayer structure semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Sanjun; Lanty, Gaetan; Lauret, Jean-Sebastien [Laboratoire de Photonique Quantique et Moleculaire de l' Ecole Normale Superieure de Cachan, 61 avenue du President Wilson, 94235 Cachan (France); Deleporte, Emmanuelle, E-mail: Emmanuelle.Deleporte@lpqm.ens-cachan.fr [Laboratoire de Photonique Quantique et Moleculaire de l' Ecole Normale Superieure de Cachan, 61 avenue du President Wilson, 94235 Cachan (France); Audebert, Pierre; Galmiche, Laurent [Laboratoire de Photophysique et Photochimie Supramoleculaires et Macromoleculaires de l' Ecole Normale Superieure de Cachan, 61 avenue du President Wilson, 94235 Cachan (France)

    2009-06-15

    We report on the synthesis of some novel organic-inorganic hybrid 2D perovskite semiconductors (R-(CH{sub 2}){sub n}NH{sub 3}){sub 2}PbX{sub 4}. These semiconductors are self-assembled intercalation nanolayers and have a multi-quantum-well energy level structure. We systematically vary the characteristic of organic groups (R-(CH{sub 2}){sub n}NH{sub 3}{sup +}) to study the relationship between their structures and the optical properties of (R-(CH{sub 2}){sub n}NH{sub 3}){sub 2}PbX{sub 4}. From optical absorption and photoluminescence spectroscopy experiments performed on series of samples, we find some trends of choosing the organic groups to improve the optical performance of (R-(CH{sub 2}){sub n}NH{sub 3}){sub 2}PbX{sub 4}. A new organic group, which allows synthesis of nanolayer perovskite semiconductors with quite high photoluminescence efficiency and better long-term stability, has been found.

  17. Determining synthesis rates of individual proteins in zebrafish (Danio rerio) with low levels of a stable isotope labelled amino acid.

    Science.gov (United States)

    Geary, Bethany; Magee, Kieran; Cash, Phillip; Young, Iain S; Whitfield, Phillip D; Doherty, Mary K

    2016-05-01

    The zebrafish is a powerful model organism for the analysis of human cardiovascular development and disease. Understanding these processes at the protein level not only requires changes in protein concentration to be determined but also the rate at which these changes occur on a protein-by-protein basis. The ability to measure protein synthesis and degradation rates on a proteome-wide scale, using stable isotope labelling in conjunction with mass spectrometry is now a well-established experimental approach. With the advent of more selective and sensitive mass spectrometers, it is possible to accurately measure lower levels of stable isotope incorporation, even when sample is limited. In order to challenge the sensitivity of this approach, we successfully determined the synthesis rates of over 600 proteins from the cardiac muscle of the zebrafish using a diet where either 30% or 50% of the L-leucine was replaced with a stable isotope labelled analogue ([(2) H7 ]L-leucine]. It was possible to extract sufficient protein from individual zebrafish hearts to determine the incorporation rate of the label into hundreds of proteins simultaneously, with the two labelling regimens showing a good correlation of synthesis rates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Low-temperature synthesis and structural properties of ferroelectric K 3WO 3F 3 elpasolite

    Science.gov (United States)

    Atuchin, V. V.; Gavrilova, T. A.; Kesler, V. G.; Molokeev, M. S.; Aleksandrov, K. S.

    2010-06-01

    Low-temperature ferroelectric G2 polymorph of K 3WO 3F 3 has been prepared by chemical synthesis. Structural and chemical properties of the final product have been evaluated with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Structure parameters of G2-K 3WO 3F 3 are refined by the Rietveld method from XRD data measured at room temperature (space group Cm, Z = 2, a = 8.7350(3) Å, b = 8.6808(5) Å, c = 6.1581(3) Å, β = 135.124(3) Å, V = 329.46(3) Å 3; RB = 2.47%). Partial ordering of oxygen and fluorine atoms has been found over anion positions. Mechanism of ferroelectric phase transition in A 2BMO 3F 3 oxyfluorides is discussed.

  19. The Synthesis of Peculiar Structure of Springlike Multiwall Carbon Nanofibers/Nanotubes via Mechanothermal Method

    Directory of Open Access Journals (Sweden)

    Sahebali Manafi

    2012-01-01

    Full Text Available Mechanothermal (MT method is one of the methods used for large-scale production of carbon nanotubes/nanofibers. The different peculiar morphologies of carbon allotropes are introduced with an extraordinary structure for the first time by MT method. In this paper, the influence of milling time and annealing temperature on the crystallinity and morphology of the synthesized nanopowders was investigated. Surprisingly, in this investigation, we report the synthesis of springlike multiwalled carbon nanofibers (S-MWCNFs by a two-step annealing of milled graphite in an Ar atmosphere. On the other hand, the MT method could be used for the preparation of suitable structures with applications in nanocomposite materials, which is an important task in the era of nanotechnology.

  20. Nε-Acryloyllysine Piperazides as Irreversible Inhibitors of Transglutaminase 2: Synthesis, Structure-Activity Relationships, and Pharmacokinetic Profiling.

    Science.gov (United States)

    Wodtke, Robert; Hauser, Christoph; Ruiz-Gómez, Gloria; Jäckel, Elisabeth; Bauer, David; Lohse, Martin; Wong, Alan; Pufe, Johanna; Ludwig, Friedrich-Alexander; Fischer, Steffen; Hauser, Sandra; Greif, Dieter; Pisabarro, M Teresa; Pietzsch, Jens; Pietsch, Markus; Löser, Reik

    2018-05-24

    Transglutaminase 2 (TGase 2)-catalyzed transamidation represents an important post-translational mechanism for protein modification with implications in physiological and pathophysiological conditions, including fibrotic and neoplastic processes. Consequently, this enzyme is considered a promising target for the diagnosis of and therapy for these diseases. In this study, we report on the synthesis and kinetic characterization of N ε -acryloyllysine piperazides as irreversible inhibitors of TGase 2. Systematic structural modifications on 54 new compounds were performed with a major focus on fluorine-bearing substituents due to the potential of such compounds to serve as radiotracer candidates for positron emission tomography. The determined inhibitory activities ranged from 100 to 10 000 M -1 s -1 , which resulted in comprehensive structure-activity relationships. Structure-activity correlations using various substituent parameters accompanied by covalent docking studies provide an advanced understanding of the molecular recognition for this inhibitor class within the active site of TGase 2. Selectivity profiling of selected compounds for other transglutaminases demonstrated an excellent selectivity toward transglutaminase 2. Furthermore, an initial pharmacokinetic profiling of selected inhibitors was performed, including the assessment of potential membrane permeability and liver microsomal stability.

  1. Ultrasound-assisted synthesis of nano-structured Zinc(II)-based metal-organic frameworks as precursors for the synthesis of ZnO nano-structures.

    Science.gov (United States)

    Bigdeli, Fahime; Ghasempour, Hosein; Azhdari Tehrani, Alireza; Morsali, Ali; Hosseini-Monfared, Hassan

    2017-07-01

    A 3D, porous Zn(II)-based metal-organic framework {[Zn 2 (oba) 2 (4-bpmn)]·(DMF) 1.5 } n (TMU-21), (4-bpmn=N,N'-Bis-pyridin-4-ylmethylene-naphtalene-1,5-diamine, H 2 oba=4,4'-oxybis(benzoic acid)) with nano-rods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure was prepared and characterized by scanning electron microscopy. Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs were studied. Also {[Zn 2 (oba) 2 (4-bpmn)] (TMU-21) and {[Zn 2 (oba) 2 (4-bpmb)] (TMU-6), 4-bpmb=N,N'-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) were easily prepared by mechanochemical synthesis. Nanostructures of Zinc(II) oxide were obtained by calcination of these compounds and their de-solvated analogue as activated MOFs, at 550°C under air atmosphere. As a result of that, different Nanostructures of Zinc(II) oxide were obtained. The ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Crystal Structure of TDP-Fucosamine Acetyl Transferase (WECD) from Escherichia Coli, an Enzyme Required for Enterobacterial Common Antigen Synthesis

    International Nuclear Information System (INIS)

    Hung, M.; Rangarajan, E.; Munger, C.; Nadeau, G.; Sulea, T.; Matte, A.

    2006-01-01

    Enterobacterial common antigen (ECA) is a polysaccharide found on the outer membrane of virtually all gram-negative enteric bacteria and consists of three sugars, N-acetyl-D-glucosamine, N-acetyl-D-mannosaminuronic acid, and 4-acetamido-4,6-dideoxy-D-galactose, organized into trisaccharide repeating units having the sequence →(3)-α-D-Fuc4NAc-(1→4)-β-D-ManNAcA-(1→4)-α-D-GlcNAc-(1→). While the precise function of ECA is unknown, it has been linked to the resistance of Shiga-toxin-producing Escherichia coli (STEC) O157:H7 to organic acids and the resistance of Salmonella enterica to bile salts. The final step in the synthesis of 4-acetamido-4,6-dideoxy-D-galactose, the acetyl-coenzyme A (CoA)-dependent acetylation of the 4-amino group, is carried out by TDP-fucosamine acetyltransferase (WecD). We have determined the crystal structure of WecD in apo form at a 1.95-Angstroms resolution and bound to acetyl-CoA at a 1.66-Angstroms resolution. WecD is a dimeric enzyme, with each monomer adopting the GNAT N-acetyltransferase fold, common to a number of enzymes involved in acetylation of histones, aminoglycoside antibiotics, serotonin, and sugars. The crystal structure of WecD, however, represents the first structure of a GNAT family member that acts on nucleotide sugars. Based on this cocrystal structure, we have used flexible docking to generate a WecD-bound model of the acetyl-CoA-TDP-fucosamine tetrahedral intermediate, representing the structure during acetyl transfer. Our structural data show that WecD does not possess a residue that directly functions as a catalytic base, although Tyr208 is well positioned to function as a general acid by protonating the thiolate anion of coenzyme A.

  3. Chemical synthesis of porous web-structured CdS thin films for photosensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Gosavi, S.R., E-mail: srgosavi.taloda@gmail.com [C. H. C. Arts, S. G. P. Commerce, and B. B. J. P. Science College, Taloda, Dist., Nandurbar 425413, M. S. (India); Nikam, C.P. [B.S.S.P.M.S. Arts, Commerce and Science College, Songir, Dist., Dhule 424309, M. S. (India); Shelke, A.R.; Patil, A.M. [Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India); Ryu, S.-W. [Department of Physics, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Bhat, J.S. [Department of Physics, Karnatak University, Dharwad 580003 (India); Deshpande, N.G., E-mail: nicedeshpande@yahoo.co.in [Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India)

    2015-06-15

    The photo-activity of chemically deposited cadmium sulphide (CdS) thin film has been studied. The simple chemical route nucleates the CdS films with size up to the mean free path of the electron. Growth Kinematics of crystalline hexagonal CdS phase in the thin film form was monitored using X-ray diffraction. The time limitation set for the formation of the amorphous/nano-crystalline material is 40 and 60 min. Thereafter enhancement of the crystalline orientation along the desired plane was identified. Web-like porous structured surface morphology of CdS thin film over the entire area is observed. With decrease in synthesis time, increase of band gap energy i.e., a blue spectral shift was seen. The activation energy of CdS thin film at low and high temperature region was examined. It is considered that this activation energy corresponds to the donor levels associated with shallow traps or surface states of CdS thin film. The photo-electrochemical performance of CdS thin films in polysulphide electrolyte showed diode-like characteristics. Exposure of light on the CdS electrode increases the photocurrent. This suggests the possibility of production of free carriers via excited ions and also the light harvesting mechanism due to porous web-structured morphology. These studies hint that the obtained CdS films can work as a photosensor. - Highlights: • Photoactivity of chemically synthesized cadmium sulphide (CdS) thin films was studied. • Web-like porous structured surface morphology of CdS thin film over the entire area was observed. • Blue spectral shift with lowering of the synthesis time suggests films can act as a window layer over the absorber layer. • Porous web-structured CdS thin films can be useful in light harvesting.

  4. Chemical synthesis of porous web-structured CdS thin films for photosensor applications

    International Nuclear Information System (INIS)

    Gosavi, S.R.; Nikam, C.P.; Shelke, A.R.; Patil, A.M.; Ryu, S.-W.; Bhat, J.S.; Deshpande, N.G.

    2015-01-01

    The photo-activity of chemically deposited cadmium sulphide (CdS) thin film has been studied. The simple chemical route nucleates the CdS films with size up to the mean free path of the electron. Growth Kinematics of crystalline hexagonal CdS phase in the thin film form was monitored using X-ray diffraction. The time limitation set for the formation of the amorphous/nano-crystalline material is 40 and 60 min. Thereafter enhancement of the crystalline orientation along the desired plane was identified. Web-like porous structured surface morphology of CdS thin film over the entire area is observed. With decrease in synthesis time, increase of band gap energy i.e., a blue spectral shift was seen. The activation energy of CdS thin film at low and high temperature region was examined. It is considered that this activation energy corresponds to the donor levels associated with shallow traps or surface states of CdS thin film. The photo-electrochemical performance of CdS thin films in polysulphide electrolyte showed diode-like characteristics. Exposure of light on the CdS electrode increases the photocurrent. This suggests the possibility of production of free carriers via excited ions and also the light harvesting mechanism due to porous web-structured morphology. These studies hint that the obtained CdS films can work as a photosensor. - Highlights: • Photoactivity of chemically synthesized cadmium sulphide (CdS) thin films was studied. • Web-like porous structured surface morphology of CdS thin film over the entire area was observed. • Blue spectral shift with lowering of the synthesis time suggests films can act as a window layer over the absorber layer. • Porous web-structured CdS thin films can be useful in light harvesting

  5. Synthesis and structural characterization of coaxial nano tubes intercalated of molybdenum disulfide with carbon

    International Nuclear Information System (INIS)

    Reza San German, C.M.

    2005-01-01

    In this work the study of some fundamental aspects in the growth of unidimensional systems of coaxial nano tubes from the mold method is approached. This method is an inclusion technique of a precursor reagent into oxide nano porous alumina film (mold), and later applying some processes of synthesis it is gotten to obtain the wished material. The synthesized structures are identified later because they take place by means of the initial formation of nano tubes of MoS 2 , enclosing to carbon nano tubes by the same method, with propylene flow which generates a graphitization process that 'copy' the mold through as it flows. Binary phase MoS 2 + C nano tubes were synthesized by propylene pyrolysis inside MoS 2 nano tubes prepared by template assisted technique. The large coaxial nano tubes constituted of graphite sheets inserted between the MoS 2 layers forming the outer part, and coaxial multi wall carbon nano tubes (MWCNT) intercalated with MoS 2 inside. High resolution electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), high angle annular dark field (HAADF), gatan image filter (GIF), nano beam electron diffraction patterns (NBEDP), along with molecular dynamics simulation and quantum mechanical calculations were used to characterize the samples. The one-dimensional structures exhibit diverse morphologies such as long straight and twisted nano tubes with several structural irregularities. The inter-planar spacing between MoS 2 layers was found to increase from 6.3 to 7.4 A due to intercalation with carbon. Simulated HREM images revealed the presence of these twisted nano structures, with mechanical stretch into intercalate carbon between MoS 2 layers. Our results open up the possibility of using MoS 2 nano tubes as templates for the synthesis of new one- dimensional binary phase systems. (Author)

  6. Synthesis, structure, optical property, and electronic structure of Ba7AgGa5Se15

    International Nuclear Information System (INIS)

    Yin, Wenlong; He, Ran; Feng, Kai; Hao, Wenyu; Yao, Jiyong; Wu, Yicheng

    2013-01-01

    Graphical abstract: -- Highlights: •A new quaternary chalcogenide Ba 7 AgGa 5 Se 15 was synthesized. •It adopts a new structure type in the space group P31c of the trigonal system. •The structure contains a three-dimensional framework built from GaSe 4 and AgSe 4 tetrahedra. •Ba 7 AgGa 5 Se 15 is a direct semiconductor with the band gap of 2.60 (2) eV. •The electronic structure was calculated to explain the optical properties. -- Abstract: A new quaternary chalcogenide Ba 7 AgGa 5 Se 15 was synthesized by solid state reaction. It crystallizes in a new structure type in the noncentrosymmetric space group P31c of the trigonal system. In the structure, three Ga2Se 4 tetrahedra and one Ga1Se 4 tetrahedron are connected to each other by corner-sharing to form [Ga 4 Se 10 ] 8− anion clusters, which are further connected to AgSe 4 tetrahedra by corner-sharing to form a three-dimensional framework with Ba, Se7, and isolated Ga3Se 4 tetrahedra residing in the cavities. The optical band gap of 2.60 (2) eV for Ba 7 AgGa 5 Se 15 was deduced from the diffuse reflectance spectrum. From a band structure calculation, Ba 7 AgGa 5 Se 15 is a direct semiconductor and the transition between Se and Ba plays an important role in the band gap

  7. Investigating the Synthesis, Structure, and Catalytic Properties of Versatile Gold-Based Nanocatalvsts

    Science.gov (United States)

    Pretzer, Lori A.

    Transition metal nanomaterials are used to catalyze many chemical reactions, including those key to environmental, medicinal, and petrochemical fields. Improving their catalytic properties and lifetime would have significant economic and environmental rewards. Potentially expedient options to make such advancements are to alter the shape, size, or composition of transition metal nanocatalysts. This work investigates the relationships between structure and catalytic properties of synthesized Au, Pd-on-Au, and Au-enzyme model transition metal nanocatalysts. Au and Pd-on-Au nanomaterials were studied due to their wide-spread application and structure-dependent electronic and geometric properties. The goal of this thesis is to contribute design procedures and synthesis methods that enable the preparation of more efficient transition metal nanocatalysts. The influence of the size and composition of Pd-on-Au nanoparticles (NPs) was systematically investigated and each was found to affect the catalyst's surface structure and catalytic properties. The catalytic hydrodechlorination of trichloroethene and reduction of 4-nitrophenol by Pd-on-Au nanoparticles were investigated as these reactions are useful for environmental and pharmaceutical synthesis applications, respectively. Structural characterization revealed that the dispersion and oxidation state of surface Pd atoms are controlled by the Au particle size and concentration of Pd. These structural changes are correlated with observed Pd-on-Au NP activities for both probe reactions, providing new insight into the structure-activity relationships of bimetallic nanocatalysts. Using the structure-dependent electronic properties of Au NPs, a new type of light-triggered biocatalyst was prepared and used to remotely control a model biochemical reaction. This biocatalyst consists of a model thermophilic glucokinase enzyme covalently attached to the surface of Au nanorods. The rod-like shape of the Au nanoparticles made the

  8. Molecular structure design and soft template synthesis of aza-, oxaaza- and thiaazamacrocyclic metal chelates in the gelatin matrix

    Directory of Open Access Journals (Sweden)

    Oleg V. Mikhailov

    2017-01-01

    Full Text Available The data about of soft template synthesis proceeding in gelatin matrices in [3d-element M(II ion – (N,S- or (N,O,S-ambidentate ligson – mono- or dicarbonyl ligson] systems, have been considered and discussed. The chemical nature of the final products of template synthesis formed under these specific conditions, has been compared with the chemical nature of the final products formed by template synthesis in solutions. It has been noted that in many cases, the nature and chemical composition of these products differ substantially. Specific features of the DFT calculated molecular structures of the macrocyclic compounds that can be formed due to the template synthesis in the systems indicated above, have been discussed, too. The review covers the period 1990–2015.

  9. Synthesis and properties of ZnFe2O4 replica with biological hierarchical structure

    International Nuclear Information System (INIS)

    Liu, Hongyan; Guo, Yiping; Zhang, Yangyang; Wu, Fen; Liu, Yun; Zhang, Di

    2013-01-01

    Highlights: • ZFO replica with hierarchical structure was synthesized from butterfly wings. • Biotemplate has a significant impact on the properties of ZFO material. • Our method opens up new avenues for the synthesis of spinel ferrites. -- Abstract: ZnFe 2 O 4 replica with biological hierarchical structure was synthesized from Papilio paris by a sol–gel method followed by calcination. The crystallographic structure and morphology of the obtained samples were characterized by X-ray diffraction, field-emission scanning electron microscope, and transmittance electron microscope. The results showed that the hierarchical structures were retained in the ZFO replica of spinel structure. The magnetic behavior of such novel products was measured by a vibrating sample magnetometer. A superparamagnetism-like behavior was observed due to nanostructuration size effects. In addition, the ZFO replica with “quasi-honeycomb-like structure” showed a much higher specific capacitance of 279.4 F g −1 at 10 mV s −1 in comparison with ZFO powder of 137.3 F g −1 , attributing to the significantly increased surface area. These results demonstrated that ZFO replica is a promising candidate for novel magnetic devices and supercapacitors

  10. Synthesis, structural studies and biological properties of new TBA analogues containing an acyclic nucleotide.

    Science.gov (United States)

    Coppola, Teresa; Varra, Michela; Oliviero, Giorgia; Galeone, Aldo; D'Isa, Giuliana; Mayol, Luciano; Morelli, Elena; Bucci, Maria-Rosaria; Vellecco, Valentina; Cirino, Giuseppe; Borbone, Nicola

    2008-09-01

    A new modified acyclic nucleoside, namely N(1)-(3-hydroxy-2-hydroxymethyl-2-methylpropyl)-thymidine, was synthesized and transformed into a building block useful for oligonucleotide (ON) automated synthesis. A series of modified thrombin binding aptamers (TBAs) in which the new acyclic nucleoside replaces, one at the time, the thymidine residues were then synthesized and characterized by UV, CD, MS, and (1)H NMR. The biological activity of the resulting TBAs was tested by Prothrombin Time assay (PT assay) and by purified fibrinogen clotting assay. From a structural point of view, nearly all the new TBA analogues show a similar behavior as the unmodified counterpart, being able to fold into a bimolecular or monomolecular quadruplex structure depending on the nature of monovalent cations (sodium or potassium) coordinated in the quadruplex core. From the comparison of structural and biological data, some important structure-activity relationships emerged, particularly when the modification involved the TT loops. In agreement with previous studies we found that the folding ability of TBA analogues is more affected by modifications involving positions 4 and 13, rather than positions 3 and 12. On the other hand, the highest anti-thrombin activities were detected for aptamers containing the modification at T13 or T12 positions, thus indicating that the effects produced by the introduction of the acyclic nucleoside on the biological activity are not tightly connected with structure stabilities. It is noteworthy that the modification at T7 produces an ON being more stable and active than the natural TBA.

  11. Structure-Based Design and Synthesis of Potent and Selective Matrix Metalloproteinase 13 Inhibitors.

    Science.gov (United States)

    Choi, Jun Yong; Fuerst, Rita; Knapinska, Anna M; Taylor, Alexander B; Smith, Lyndsay; Cao, Xiaohang; Hart, P John; Fields, Gregg B; Roush, William R

    2017-07-13

    We describe the use of comparative structural analysis and structure-guided molecular design to develop potent and selective inhibitors (10d and (S)-17b) of matrix metalloproteinase 13 (MMP-13). We applied a three-step process, starting with a comparative analysis of the X-ray crystallographic structure of compound 5 in complex with MMP-13 with published structures of known MMP-13·inhibitor complexes followed by molecular design and synthesis of potent but nonselective zinc-chelating MMP inhibitors (e.g., 10a and 10b). After demonstrating that the pharmacophores of the chelating inhibitors (S)-10a, (R)-10a, and 10b were binding within the MMP-13 active site, the Zn 2+ chelating unit was replaced with nonchelating polar residues that bridged over the Zn 2+ binding site and reached into a solvent accessible area. After two rounds of structural optimization, these design approaches led to small molecule MMP-13 inhibitors 10d and (S)-17b, which bind within the substrate-binding site of MMP-13 and surround the catalytically active Zn 2+ ion without chelating to the metal. These compounds exhibit at least 500-fold selectivity versus other MMPs.

  12. Crystal Engineering: Synthesis and Structural Analysis of Coordination Polymers with Wavelike Properties

    Directory of Open Access Journals (Sweden)

    Matasebia T. Munie

    2011-10-01

    Full Text Available Supramolecular coordination polymers with wavelike structures have been synthesized by self-assembly and their structures analyzed using the sine trigonometric function. Slow evaporation of a methylene chloride-methanol solution of a 1:1 molar mixture of [M(tmhd2], where M = Co or Ni, and quinoxaline; a 1:2:1 molar mixture of [M(acac2], where M = Co or Ni, 2,2,6,6-tetramethyl-3,5-heptadione and quinoxaline; or a 1:2:1 molar mixture of [Co(acac2], dibenzoylmethane, and quinoxaline, yielded the crystalline coordination polymers. In the presence of the nitrogenous base, ligand scrambling occurs yielding the most insoluble product. The synthesis and structures of the following wavelike polymers are reported: trans-[Co(DBM2(qox]n·nH2O (2, trans-[Co(tmhd2(qox]n (3, trans-[Ni(tmhd2(qox]n (4, where DBM− = dibenzoylmethanate, tmhd− = 2,2,6,6-tetramethyl-3,5-heptadionate, and qox = quinoxaline. The wavelike structures are generated by intramolecular steric interactions and crystal packing forces between the chains. Some of the tert-butyl groups show a two-fold disorder. The sine function, φ = A sin 2πx/λ, where φ = distance (Ǻ along the polymer backbone, λ = wavelength (Ǻ, A = amplitude (Ǻ, x = distance (Ǻ along the polymer axis, provides a method to approximate and visualize the polymer structures.

  13. Structural Determinants of Autoproteolysis of the Haemophilus influenzae Hap Autotransporter▿

    Science.gov (United States)

    Kenjale, Roma; Meng, Guoyu; Fink, Doran L.; Juehne, Twyla; Ohashi, Tomoo; Erickson, Harold P.; Waksman, Gabriel; St. Geme, Joseph W.

    2009-01-01

    Haemophilus influenzae is a gram-negative bacterium that initiates infection by colonizing the upper respiratory tract. The H. influenzae Hap autotransporter protein mediates adherence, invasion, and microcolony formation in assays with respiratory epithelial cells and presumably facilitates colonization. The serine protease activity of Hap is associated with autoproteolytic cleavage and extracellular release of the HapS passenger domain, leaving the Hapβ C-terminal domain embedded in the outer membrane. Cleavage occurs most efficiently at the LN1036-37 peptide bond and to a lesser extent at three other sites. In this study, we utilized site-directed mutagenesis, homology modeling, and assays with a peptide library to characterize the structural determinants of Hap proteolytic activity and cleavage specificity. In addition, we used homology modeling to predict the S1, S2, and S4 subsite residues of the Hap substrate groove. Our results indicate that the P1 and P2 positions at the Hap cleavage sites are critical for cleavage, with leucine preferred over larger hydrophobic residues or other amino acids in these positions. The substrate groove is formed by L263 and N274 at the S1 subsite, R264 at the S2 subsite, and E265 at the S4 subsite. This information may facilitate design of approaches to block Hap activity and interfere with H. influenzae colonization. PMID:19687208

  14. New quaternary oxides with both families of second-order Jahn–Teller (SOJT) distortive cations: Solid-state synthesis, structure determination, and characterization of YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeong Hun [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of); Jeon, Beom-Yong; You, Tae-Soo [Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of); Ok, Kang Min, E-mail: kmok@cau.ac.kr [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of)

    2015-07-15

    Graphical abstract: Ball-and-stick representation of YNbTe{sub 2}O{sub 8} composed of polyhedra of SOJT distortive cations, i.e., NbO{sub 6} and TeO{sub 3}, in the ac-plane. - Highlights: • Two novel tellurite and selenite (YNbQ{sub 2}O{sub 8}; Q = Te and Se) are synthesized. • YNbQ{sub 2}O{sub 8} possess both families of second-order Jahn–Teller distortive cations. • The distortive environments and bonding nature are supported by electronic structure calculations. - Abstract: Two novel quaternary mixed metal tellurite and selenite, YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8}, respectively, have been synthesized through standard solid-state reactions using Y{sub 2}O{sub 3}, Nb{sub 2}O{sub 5}, TeO{sub 2} or SeO{sub 2} as reagents. Single crystal X-ray and powder neutron diffraction analyses have been utilized to determine the structures of the reported materials. YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8} are isostructural to each other and crystallize in the monoclinic centrosymmetric space group, C2/m (No. 12). Due to the two families of constituent second-order Jahn–Teller (SOJT) distortive cations, i.e., Nb{sup 5+} and Te{sup 4+}/Se{sup 4+}, local asymmetric environments occur from the three-dimensional frameworks. Intra-octahedral distortions along the local C{sub 4} direction and asymmetric trigonal pyramidal coordination moieties generated by stereoactive lone pairs are observed from the NbO{sub 6} octahedra and TeO{sub 3} (or SeO{sub 3}) polyhedra, respectively. Thermogravimetric analysis, infrared and UV–vis diffuse reflectance spectroscopies, elemental analysis, out-of-center distortions, dipole moment calculations, and electronic structure calculations for the reported materials are presented.

  15. Crystal Structure of the 30S Ribosomal Subunit from Thermus Thermophilus: Purification, Crystallization and Structure Determination

    International Nuclear Information System (INIS)

    Clemons, William M. Jr.; Brodersen, Ditlev E.; McCutcheonn, John P.; May, Joanna L.C.; Carter, Andrew P.; Morgan-Warren, Robert J.; Wimberly, Brian T.; Ramakrishnan, Venki

    2001-01-01

    We describe the crystallization and structure determination of the 30 S ribosomal subunit from Thermus thermophilus. Previous reports of crystals that diffracted to 10 (angstrom) resolution were used as a starting point to improve the quality of the diffraction. Eventually, ideas such as the addition of substrates or factors to eliminate conformational heterogeneity proved less important than attention to detail in yielding crystals that diffracted beyond 3 (angstrom) resolution. Despite improvements in technology and methodology in the last decade, the structure determination of the 30 S subunit presented some very challenging technical problems because of the size of the asymmetric unit, crystal variability and sensitivity to radiation damage. Some steps that were useful for determination of the atomic structure were: the use of anomalous scattering from the LIII edges of osmium and lutetium to obtain the necessary phasing signal; the use of tunable, third-generation synchrotron sources to obtain data of reasonable quality at high resolution; collection of derivative data precisely about a mirror plane to preserve small anomalous differences between Bijvoet mates despite extensive radiation damage and multi-crystal scaling; the pre-screening of crystals to ensure quality, isomorphism and the efficient use of scarce third-generation synchrotron time; pre-incubation of crystals in cobalt hexaammine to ensure isomorphism with other derivatives; and finally, the placement of proteins whose structures had been previously solved in isolation, in conjunction with biochemical data on protein-RNA interactions, to map out the architecture of the 30 S subunit prior to the construction of a detailed atomic-resolution model.

  16. New bismuth calcium oxysilicate with apatite structure: Synthesis and structural characterization

    International Nuclear Information System (INIS)

    Uvarov, Vladimir; Shenawi-Khalil, Sanaa; Popov, Inna

    2010-01-01

    New bismuth calcium silicon oxide Ca 4 Bi 4.3 (SiO 4 )(HSiO 4 ) 5 O 0.95 , with apatite structure has been synthesized. The structure was refined from powder X-ray diffraction data. The refinement revealed that the phase has P6 3 /m (176) space group with unit cell parameters a=b=9.6090(7) A, c=7.0521(7) A, V=563.9 A 3 and c/a=0.734. The R wp factor at Rietveld refinement was equal to 0.082. The synthesized phase has an unusual quantity of cation vacancies in a crystal lattice. Mechanisms of compensation of the excess charge of a lattice are considered and checked experimentally using the FT-IR spectroscopy, the thermal analysis and the XPS analysis. - Graphical abstract: The fragment Ca 4 Bi 4.3 (SiO 4 )(HSiO 4 ) 5 O 0.95 structure along c-axis in polygonal mode.

  17. Copper coordination polymers constructed from thiazole-5-carboxylic acid: Synthesis, crystal structures, and structural transformation

    Energy Technology Data Exchange (ETDEWEB)

    Meundaeng, Natthaya; Rujiwatra, Apinpus [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Prior, Timothy J., E-mail: t.prior@hull.ac.uk [Chemistry, University of Hull, Kingston upon Hull HU6 7RX (United Kingdom)

    2017-01-15

    We have successfully prepared crystals of thiazole-5-carboxylic acid (5-Htza) (L) and three new thiazole-5-carboxylate-based Cu{sup 2+} coordination polymers with different dimensionality, namely, 1D [Cu{sub 2}(5-tza){sub 2}(1,10-phenanthroline){sub 2}(NO{sub 3}){sub 2}] (1), 2D [Cu(5-tza){sub 2}(MeOH){sub 2}] (2), and 3D [Cu(5-tza){sub 2}]·H{sub 2}O (3). These have been characterized by single crystal X-ray diffraction and thermogravimetry. Interestingly, the 2D network structure of 2 can directly transform into the 3D framework of 3 upon removal of methanol molecules at room temperature. 2 can also undergo structural transformation to produce the same 2D network present in the known [Cu(5-tza){sub 2}]·1.5H{sub 2}O upon heat treatment for 2 h. This 2D network can adsorb water and convert to 3 upon exposure to air. - Highlights: • Rare examples of coordination polymers of thiazole-5-carboxylic acid were prepared. • Non-covalent interactions play a key role on the assembly of the complexes in solid state. • Structural transformation of a 2D framework to a 3D upon removal of methanol is observed.

  18. CCDC 1416891: Experimental Crystal Structure Determination : Methyl-triphenyl-germanium

    KAUST Repository

    Bernatowicz, Piotr; Shkurenko, Aleksander; Osior, Agnieszka; Kamieński, Bohdan; Szymański, Sławomir

    2015-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from

  19. Cell-free synthesis of functional antibody fragments to provide a structural basis for antibody-antigen interaction.

    Directory of Open Access Journals (Sweden)

    Takayoshi Matsuda

    Full Text Available Growing numbers of therapeutic antibodies offer excellent treatment strategies for many diseases. Elucidation of the interaction between a potential therapeutic antibody and its target protein by structural analysis reveals the mechanism of action and offers useful information for developing rational antibody designs for improved affinity. Here, we developed a rapid, high-yield cell-free system using dialysis mode to synthesize antibody fragments for the structural analysis of antibody-antigen complexes. Optimal synthesis conditions of fragments (Fv and Fab of the anti-EGFR antibody 059-152 were rapidly determined in a day by using a 30-μl-scale unit. The concentration of supplemented disulfide isomerase, DsbC, was critical to obtaining soluble antibody fragments. The optimal conditions were directly applicable to a 9-ml-scale reaction, with linear scalable yields of more than 1 mg/ml. Analyses of purified 059-152-Fv and Fab showed that the cell-free synthesized antibody fragments were disulfide-bridged, with antigen binding activity comparable to that of clinical antibodies. Examination of the crystal structure of cell-free synthesized 059-152-Fv in complex with the extracellular domain of human EGFR revealed that the epitope of 059-152-Fv broadly covers the EGF binding surface on domain III, including residues that formed critical hydrogen bonds with EGF (Asp355EGFR, Gln384EGFR, H409EGFR, and Lys465EGFR, so that the antibody inhibited EGFR activation. We further demonstrated the application of the cell-free system to site-specific integration of non-natural amino acids for antibody engineering, which would expand the availability of therapeutic antibodies based on structural information and rational design. This cell-free system could be an ideal antibody-fragment production platform for functional and structural analysis of potential therapeutic antibodies and for engineered antibody development.

  20. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    Science.gov (United States)

    Katayama, Tsukasa; Chikamatsu, Akira; Kamisaka, Hideyuki; Yokoyama, Yuichi; Hirata, Yasuyuki; Wadati, Hiroki; Fukumura, Tomoteru; Hasegawa, Tetsuya

    2015-10-01

    The substitution of hydride anions (H-) into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoOxHy thin films via the topotactic hydride doping of brownmillerite SrCoO2.5 epitaxial thin films with CaH2. The perovskite-type cation framework was maintained during the topotactic treatment owing to epitaxial stabilization. Structural and chemical analyses accompanied by X-ray absorption spectroscopy measurements revealed that the doped hydride ions form a two-dimensional network of Co-H--Co bonds, in contrast to other reported perovskite oxyhydrides, SrMO3-xHx (M = Cr, Ti, V). The SrCoOxHy thin film exhibited insulating behavior and had a direct band gap of 2.1 eV. Thus, topotactic hydride doping of transition-metal-oxide thin films on suitable substrates is a promising method for the synthesis of new transition metal oxyhydrides.

  1. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    Directory of Open Access Journals (Sweden)

    Tsukasa Katayama

    2015-10-01

    Full Text Available The substitution of hydride anions (H− into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoOxHy thin films via the topotactic hydride doping of brownmillerite SrCoO2.5 epitaxial thin films with CaH2. The perovskite-type cation framework was maintained during the topotactic treatment owing to epitaxial stabilization. Structural and chemical analyses accompanied by X-ray absorption spectroscopy measurements revealed that the doped hydride ions form a two-dimensional network of Co-H−-Co bonds, in contrast to other reported perovskite oxyhydrides, SrMO3−xHx (M = Cr, Ti, V. The SrCoOxHy thin film exhibited insulating behavior and had a direct band gap of 2.1 eV. Thus, topotactic hydride doping of transition-metal-oxide thin films on suitable substrates is a promising method for the synthesis of new transition metal oxyhydrides.

  2. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Tsukasa [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Kamisaka, Hideyuki [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Yokoyama, Yuichi; Hirata, Yasuyuki; Wadati, Hiroki [Institute for Solid State Physics, The University of Tokyo, Chiba 277-8581 (Japan); Fukumura, Tomoteru [CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Department of Chemistry, Tohoku University, Miyagi 980-8578 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Tokyo 113-0033 (Japan); CREST, Japan Science and Technology Agency (JST), Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)

    2015-10-15

    The substitution of hydride anions (H{sup −}) into transition metal oxides has recently become possible through topotactic reactions or high-pressure synthesis methods. However, the fabrication of oxyhydrides is still difficult because of their inherently less-stable frameworks. In this study, we successfully fabricated perovskite SrCoO{sub x}H{sub y} thin films via the topotactic hydride doping of brownmillerite SrCoO{sub 2.5} epitaxial thin films with CaH{sub 2}. The perovskite-type cation framework was maintained during the topotactic treatment owing to epitaxial stabilization. Structural and chemical analyses accompanied by X-ray absorption spectroscopy measurements revealed that the doped hydride ions form a two-dimensional network of Co-H{sup −}-Co bonds, in contrast to other reported perovskite oxyhydrides, SrMO{sub 3−x}H{sub x} (M = Cr, Ti, V). The SrCoO{sub x}H{sub y} thin film exhibited insulating behavior and had a direct band gap of 2.1 eV. Thus, topotactic hydride doping of transition-metal-oxide thin films on suitable substrates is a promising method for the synthesis of new transition metal oxyhydrides.

  3. InSe monolayer: synthesis, structure and ultra-high second-harmonic generation

    Science.gov (United States)

    Zhou, Jiadong; Shi, Jia; Zeng, Qingsheng; Chen, Yu; Niu, Lin; Liu, Fucai; Yu, Ting; Suenaga, Kazu; Liu, Xinfeng; Lin, Junhao; Liu, Zheng

    2018-04-01

    III–IV layered materials such as indium selenide have excellent photoelectronic properties. However, synthesis of materials in such group, especially with a controlled thickness down to monolayer, still remains challenging. Herein, we demonstrate the successful synthesis of monolayer InSe by physical vapor deposition (PVD) method. The high quality of the sample was confirmed by complementary characterization techniques such as Raman spectroscopy, atomic force microscopy (AFM) and high resolution annular dark field scanning transmission electron microscopy (ADF-STEM). We found the co-existence of different stacking sequence (β- and γ-InSe) in the same flake with a sharp grain boundary in few-layered InSe. Edge reconstruction is also observed in monolayer InSe, which has a distinct atomic structure from the bulk lattice. Moreover, we discovered that the second-harmonic generation (SHG) signal from monolayer InSe shows large optical second-order susceptibility that is 1–2 orders of magnitude higher than MoS2, and even 3 times of the largest value reported in monolayer GaSe. These results make atom-thin InSe a promising candidate for optoelectronic and photosensitive device applications.

  4. Electrospray synthesis and properties of hierarchically structured PLGA TIPS microspheres for use as controlled release technologies.

    Science.gov (United States)

    Malik, Salman A; Ng, Wing H; Bowen, James; Tang, Justin; Gomez, Alessandro; Kenyon, Anthony J; Day, Richard M

    2016-04-01

    Microsphere-based controlled release technologies have been utilized for the long-term delivery of proteins, peptides and antibiotics, although their synthesis poses substantial challenges owing to formulation complexities, lack of scalability, and cost. To address these shortcomings, we used the electrospray process as a reproducible, synthesis technique to manufacture highly porous (>94%) microspheres while maintaining control over particle structure and size. Here we report a successful formulation recipe used to generate spherical poly(lactic-co-glycolic) acid (PLGA) microspheres using the electrospray (ES) coupled with a novel thermally induced phase separation (TIPS) process with a tailored Liquid Nitrogen (LN2) collection scheme. We show how size, shape and porosity of resulting microspheres can be controlled by judiciously varying electrospray processing parameters and we demonstrate examples in which the particle size (and porosity) affect release kinetics. The effect of electrospray treatment on the particles and their physicochemical properties are characterized by scanning electron microscopy, confocal Raman microscopy, thermogravimetric analysis and mercury intrusion porosimetry. The microspheres manufactured here have successfully demonstrated long-term delivery (i.e. 1week) of an active agent, enabling sustained release of a dye with minimal physical degradation and have verified the potential of scalable electrospray technologies for an innovative TIPS-based microsphere production protocol. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  5. Determination of reactive oxygen species from ZnO micro-nano structures with shape-dependent photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    He, Weiwei; Zhao, Hongxiao; Jia, Huimin [Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, Xuchang University, Henan 461000 (China); Yin, Jun-Jie [Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, MD 20740 (United States); Zheng, Zhi, E-mail: zhengzhi99999@gmail.com [Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, Xuchang University, Henan 461000 (China)

    2014-05-01

    Graphical abstract: ZnO micro/nano structures with shape dependent photocatalytic activity were prepared by hydrothermal reaction. The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were identified precisely by electron spin resonance spectroscopy. The type of reactive oxygen species was determined by band gap structure of ZnO. - Highlights: • ZnO micro/nano structures with different morphologies were prepared by solvothermal reaction. • Multi-pod like ZnO structures exhibited superior photocatalytic activity. • The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were characterized precisely by electron spin resonance spectroscopy. • The type of reactive oxygen species was determined by band gap structure of ZnO. - Abstract: ZnO micro/nano structures with different morphologies have been prepared by the changing solvents used during their synthesis by solvothermal reaction. Three typical shapes of ZnO structures including hexagonal, bell bottom like and multi-pod formed and were characterized by scanning electron microscopy and X-ray diffraction. Multi pod like ZnO structures exhibited the highest photocatalytic activity toward degradation of methyl orange. Using electron spin resonance spectroscopy coupled with spin trapping techniques, we demonstrate an effective way to identify precisely the generation of hydroxyl radicals, superoxide and singlet oxygen from the irradiated ZnO multi pod structures. The type of reactive oxygen species formed was predictable from the band gap structure of ZnO. These results indicate that the shape of micro-nano structures significantly affects the photocatalytic activity of ZnO, and demonstrate the value of electron spin resonance spectroscopy for characterizing the type of reactive oxygen species formed during photoexcitation of semiconductors.

  6. Determination of reactive oxygen species from ZnO micro-nano structures with shape-dependent photocatalytic activity

    International Nuclear Information System (INIS)

    He, Weiwei; Zhao, Hongxiao; Jia, Huimin; Yin, Jun-Jie; Zheng, Zhi

    2014-01-01

    Graphical abstract: ZnO micro/nano structures with shape dependent photocatalytic activity were prepared by hydrothermal reaction. The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were identified precisely by electron spin resonance spectroscopy. The type of reactive oxygen species was determined by band gap structure of ZnO. - Highlights: • ZnO micro/nano structures with different morphologies were prepared by solvothermal reaction. • Multi-pod like ZnO structures exhibited superior photocatalytic activity. • The generations of hydroxyl radical, superoxide and singlet oxygen from irradiated ZnO were characterized precisely by electron spin resonance spectroscopy. • The type of reactive oxygen species was determined by band gap structure of ZnO. - Abstract: ZnO micro/nano structures with different morphologies have been prepared by the changing solvents used during their synthesis by solvothermal reaction. Three typical shapes of ZnO structures including hexagonal, bell bottom like and multi-pod formed and were characterized by scanning electron microscopy and X-ray diffraction. Multi pod like ZnO structures exhibited the highest photocatalytic activity toward degradation of methyl orange. Using electron spin resonance spectroscopy coupled with spin trapping techniques, we demonstrate an effective way to identify precisely the generation of hydroxyl radicals, superoxide and singlet oxygen from the irradiated ZnO multi pod structures. The type of reactive oxygen species formed was predictable from the band gap structure of ZnO. These results indicate that the shape of micro-nano structures significantly affects the photocatalytic activity of ZnO, and demonstrate the value of electron spin resonance spectroscopy for characterizing the type of reactive oxygen species formed during photoexcitation of semiconductors

  7. Discovery and structure determination of the orphan enzyme isoxanthopterin deaminase .

    Science.gov (United States)

    Hall, Richard S; Agarwal, Rakhi; Hitchcock, Daniel; Sauder, J Michael; Burley, Stephen K; Swaminathan, Subramanyam; Raushel, Frank M

    2010-05-25

    Two previously uncharacterized proteins have been identified that efficiently catalyze the deamination of isoxanthopterin and pterin 6-carboxylate. The genes encoding these two enzymes, NYSGXRC-9339a ( gi|44585104 ) and NYSGXRC-9236b ( gi|44611670 ), were first identified from DNA isolated from the Sargasso Sea as part of the Global Ocean Sampling Project. The genes were synthesized, and the proteins were subsequently expressed and purified. The X-ray structure of Sgx9339a was determined at 2.7 A resolution (Protein Data Bank entry 2PAJ ). This protein folds as a distorted (beta/alpha)(8) barrel and contains a single zinc ion in the active site. These enzymes are members of the amidohydrolase superfamily and belong to cog0402 within the clusters of orthologous groups (COG). Enzymes in cog0402 have previously been shown to catalyze the deamination of guanine, cytosine, S-adenosylhomocysteine, and 8-oxoguanine. A small compound library of pteridines, purines, and pyrimidines was used to probe catalytic activity. The only substrates identified in this search were isoxanthopterin and pterin 6-carboxylate. The kinetic constants for the deamination of isoxanthopterin with Sgx9339a were determined to be 1.0 s(-1), 8.0 muM, and 1.3 x 10(5) M(-1) s(-1) (k(cat), K(m), and k(cat)/K(m), respectively). The active site of Sgx9339a most closely resembles the active site for 8-oxoguanine deaminase (Protein Data Bank entry 2UZ9 ). A model for substrate recognition of isoxanthopterin by Sgx9339a was proposed on the basis of the binding of guanine and xanthine in the active site of guanine deaminase. Residues critical for substrate binding appear to be conserved glutamine and tyrosine residues that form hydrogen bonds with the carbonyl oxygen at C4, a conserved threonine residue that forms hydrogen bonds with N5, and another conserved threonine residue that forms hydrogen bonds with the carbonyl group at C7. These conserved active site residues were used to identify 24 other genes

  8. Discovery and Structure Determination of the Orphan Enzyme Isoxanthopterin Deaminase

    Energy Technology Data Exchange (ETDEWEB)

    Hall, R.S.; Swaminathan, S.; Agarwal, R.; Hitchcock, D.; Sauder, J. M.; Burley, S. K.; Raushel, F. M.

    2010-05-25

    Two previously uncharacterized proteins have been identified that efficiently catalyze the deamination of isoxanthopterin and pterin 6-carboxylate. The genes encoding these two enzymes, NYSGXRC-9339a (gi|44585104) and NYSGXRC-9236b (gi|44611670), were first identified from DNA isolated from the Sargasso Sea as part of the Global Ocean Sampling Project. The genes were synthesized, and the proteins were subsequently expressed and purified. The X-ray structure of Sgx9339a was determined at 2.7 {angstrom} resolution (Protein Data Bank entry 2PAJ). This protein folds as a distorted ({beta}/{alpha}){sub 8} barrel and contains a single zinc ion in the active site. These enzymes are members of the amidohydrolase superfamily and belong to cog0402 within the clusters of orthologous groups (COG). Enzymes in cog0402 have previously been shown to catalyze the deamination of guanine, cytosine, S-adenosylhomocysteine, and 8-oxoguanine. A small compound library of pteridines, purines, and pyrimidines was used to probe catalytic activity. The only substrates identified in this search were isoxanthopterin and pterin 6-carboxylate. The kinetic constants for the deamination of isoxanthopterin with Sgx9339a were determined to be 1.0 s{sup -1}, 8.0 {micro}M, and 1.3 x 10{sup 5} M{sup -1} s{sup -1} (k{sub cat}, K{sub m}, and k{sub cat}/K{sub m}, respectively). The active site of Sgx9339a most closely resembles the active site for 8-oxoguanine deaminase (Protein Data Bank entry 2UZ9). A model for substrate recognition of isoxanthopterin by Sgx9339a was proposed on the basis of the binding of guanine and xanthine in the active site of guanine deaminase. Residues critical for substrate binding appear to be conserved glutamine and tyrosine residues that form hydrogen bonds with the carbonyl oxygen at C4, a conserved threonine residue that forms hydrogen bonds with N5, and another conserved threonine residue that forms hydrogen bonds with the carbonyl group at C7. These conserved active site

  9. Synthesis, structural characterization and quantum chemical studies of silicon-containing benzoic acid derivatives

    Science.gov (United States)

    Zaltariov, Mirela-Fernanda; Cojocaru, Corneliu; Shova, Sergiu; Sacarescu, Liviu; Cazacu, Maria

    2016-09-01

    The present paper is concerned with the synthesis and molecular structure investigation of two new benzoic acid derivatives having trimethylsilyl tails, 4-((trimethylsilyl)methoxy) and 4-(3-(trimethylsilyl)propoxy)benzoic acids. The structures of the novel compounds have been confirmed by X-ray crystallography, Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H and 13C NMR). The theoretical studies of molecules were conducted by using the quantum chemical methods, such as Density Functional Theory (DFT B3LYP/6-31 + G**), Hartree-Fock (HF/6-31 + G**) and semiempirical computations (PM3, PM6 and PM7). The optimized molecular geometries have been found to be in good agreement with experimental structures resulted from the X-ray diffraction. The maximum electronic absorption bands observed at 272-287 nm (UV-vis spectra) have been assigned to π → π* transitions, which were in reasonable agreement with the time dependent density functional theory (TD-DFT) calculations. The computed vibrational frequencies by DFT method were assigned and compared with the experimental FTIR spectra. The mapped electrostatic potentials revealed the reactive sites, which corroborated the observation of the dimer supramolecular structures formed in the crystals by hydrogen-bonding. The energies of frontier molecular orbitals (HOMO and LUMO), energy gap, dipole moment and molecular descriptors for the new compounds were calculated and discussed.

  10. Synthesis and structural characterization of bulk Sb2Te3 single crystal

    Science.gov (United States)

    Sultana, Rabia; Gahtori, Bhasker; Meena, R. S.; Awana, V. P. S.

    2018-05-01

    We report the growth and characterization of bulk Sb2Te3 single crystal synthesized by the self flux method via solid state reaction route from high temperature melt (850˚C) and slow cooling (2˚C/hour) of constituent elements. The single crystal X-ray diffraction pattern showed the 00l alignment and the high crystalline nature of the resultant sample. The rietveld fitted room temperature powder XRD revealed the phase purity and rhombohedral structure of the synthesized crystal. The formation and analysis of unit cell structure further verified the rhombohedral structure composed of three quintuple layers stacked one over the other. The SEM image showed the layered directional growth of the synthesized crystal carried out using the ZEISS-EVOMA-10 scanning electron microscope The electrical resistivity measurement was carried out using the conventional four-probe method on a quantum design Physical Property Measurement System (PPMS). The temperature dependent electrical resistivity plot for studied Sb2Te3 single crystal depicts metallic behaviour in the absence of any applied magnetic field. The synthesis as well as the structural characterization of as grown Sb2Te3 single crystal is reported and discussed in the present letter.

  11. Structural Studies of Silver Nanoparticles Obtained Through Single-Step Green Synthesis

    Science.gov (United States)

    Prasad Peddi, Siva; Abdallah Sadeh, Bilal

    2015-10-01

    Green synthesis of silver Nanoparticles (AGNP's) has been the most prominent among the metallic nanoparticles for research for over a decade and half now due to both the simplicity of preparation and the applicability of biological species with extensive applications in medicine and biotechnology to reduce and trap the particles. The current article uses Eclipta Prostrata leaf extract as the biological species to cap the AGNP's through a single step process. The characterization data obtained was used for the analysis of the sample structure. The article emphasizes the disquisition of their shape and size of the lattice parameters and proposes a general scheme and a mathematical model for the analysis of their dependence. The data of the synthesized AGNP's has been used to advantage through the introduction of a structural shape factor for the crystalline nanoparticles. The properties of the structure of the AGNP's proposed and evaluated through a theoretical model was undeviating with the experimental consequences. This modus operandi gives scope for the structural studies of ultrafine particles prepared using biological methods.

  12. Integrated Structural Biology for α-Helical Membrane Protein Structure Determination.

    Science.gov (United States)

    Xia, Yan; Fischer, Axel W; Teixeira, Pedro; Weiner, Brian; Meiler, Jens

    2018-04-03

    While great progress has been made, only 10% of the nearly 1,000 integral, α-helical, multi-span membrane protein families are represented by at least one experimentally determined structure in the PDB. Previously, we developed the algorithm BCL::MP-Fold, which samples the large conformational space of membrane proteins de novo by assembling predicted secondary structure elements guided by knowledge-based potentials. Here, we present a case study of rhodopsin fold determination by integrating sparse and/or low-resolution restraints from multiple experimental techniques including electron microscopy, electron paramagnetic resonance spectroscopy, and nuclear magnetic resonance spectroscopy. Simultaneous incorporation of orthogonal experimental restraints not only significantly improved the sampling accuracy but also allowed identification of the correct fold, which is demonstrated by a protein size-normalized transmembrane root-mean-square deviation as low as 1.2 Å. The protocol developed in this case study can be used for the determination of unknown membrane protein folds when limited experimental restraints are available. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. An Investigation of Porous Structure of TiNi-Based SHS-Materials Produced at Different Initial Synthesis Temperatures

    Science.gov (United States)

    Khodorenko, V. N.; Anikeev, S. G.; Kokorev, O. V.; Yasenchuk, Yu. F.; Gunther, V. É.

    2018-02-01

    An investigation of structural characteristics and behavior of TiNi-based pore-permeable materials manufactured by the methods of selfpropagating high-temperature synthesis (SHS) at the initial synthesis temperatures T = 400 and 600°C is performed. It is shown that depending on the temperature regime, the resulting structure and properties of the material can differ. It is found out that the SHS-material produced at the initial synthesis temperature T = 400°C possesses the largest number of micropores in the pore wall surface structure due to a high phase inhomogeneity of the alloy. The regime of structure optimization of the resulting materials is described and the main stages of formation of the pore wall microporous surfaces are revealed. It is demonstrated that after optimization of the surface structure of a TiNi-based fine-pore alloy by its chemical etching, the fraction of micropores measuring in size less than 50 nm increased from 59 to 68%, while the number of pores larger than 1 μm increased twofold from 11 to 22%. In addition, peculiar features of interaction between certain cell cultures with the surface of the SHS-material manufactured at different initial synthesis temperatures are revealed. It is found out that the dynamics of the cell material integration depends on the pore wall surface morphology and dimensions of macropores.

  14. Synthesis of hydroxyapatite and structural refinement by X-ray diffraction

    International Nuclear Information System (INIS)

    Araujo, Jorge Correa de

    2007-01-01

    A sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by X-ray diffraction by means of the Rietveld method. Two functions were used to fit the peak profiles, modified Voigt (TCHZ) and Pearson VII. The occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. The interatomic distances from Ca1 to oxygens O1, O2 and O3 were adequate for a pure hydroxyapatite without defect at site Ca1. Besides, the use of multiple lines in planes (300) and (002) associated with the model Pearson VII resulted in good agreement with the TCHZ model with respect to the size-strain effects with an ellipsoidal shape of crystallites. In conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. The experimental results of transmission electron microscopy confirmed the predicted shape of crystals. (author)

  15. Structured mesoporous Mn, Fe, and Co oxides: Synthesis, physicochemical, and catalytic properties

    Science.gov (United States)

    Maerle, A. A.; Karakulina, A. A.; Rodionova, L. I.; Moskovskaya, I. F.; Dobryakova, I. V.; Egorov, A. V.; Romanovskii, B. V.

    2014-02-01

    Structured mesoporous Mn, Fe, and Co oxides are synthesized using "soft" and "hard" templates; the resulting materials are characterized by XRD, SEM, TEM, BET, and TG. It is shown that in the first case, the oxides have high surface areas of up to 450 m2/g that are preserved after calcination of the material up to 300°C. Even though, the surface area of the oxides prepared by the "hard-template" method does not exceed 100 m2/g; it is, however, thermally stable up to 500°C. Catalytic activity of mesoporous oxides in methanol conversion was found to depend on both the nature of the transition metal and the type of template used in synthesis.

  16. Synthesis, X-ray crystal structure and theoretical calculations of antileishmanial neolignan analogues

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Josenaide P. do; Santos, Lourivaldo S.; Carmo, Maria Carolina L. do; Brasil, Davi S.B.; Alves, Claudio N., E-mail: nahum@ufpa.b [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Inst. de Ciencias Exatas e Naturais; Santos, Regina Helena A.; Tozzo, Erica; Ferreira, Janaina G. [Universidade de Sao Paulo (IQSC/USP), Sao Carlos, SP (Brazil). Inst. de Quimica

    2010-07-01

    The synthesis and X-ray crystal diffraction structure of two analogues of neolignans, 2-(4-chlorophenyl)-1-phenylethanone (20) and 2-[(4-chlorophenyl)thio]-1-(3,4-dimethoxyphenyl) propan-1-one (12) is described. The compound 12 presents activity against intracellular Leishmania donovani and Leishmania amazonensis amastigotes that cause cutaneous and visceral leishmaniasis. In addition, the density functional theory (DFT) with the B3LYP hybrid functional was employed to calculate a set of molecular descriptors for nineteen synthetic analogues of neolignans with antileishmanial activities. Afterwards, the stepwise discriminant analysis was performed to investigate possible relationship between the molecular descriptors and biological activities. Through this analysis the compounds were classified into two groups active and inactive according to their degree of biological activities, and the more important properties were charges on some key atoms, electronic affinity and ClogP. (author)

  17. Mesoporous Structure Control of Silica in Room-Temperature Synthesis under Basic Conditions

    Directory of Open Access Journals (Sweden)

    Jeong Wook Seo

    2015-01-01

    Full Text Available Various types of mesoporous silica, such as continuous cubic-phase MCM-48, hexagonal-phase MCM-41, and layer-phase spherical silica particles, have been synthesized at room temperature using cetyltrimethylammonium bromide as a surfactant, ethanol as a cosurfactant, tetraethyl orthosilicate as a silica precursor, and ammonia as a condensation agent. Special care must be taken both in the filtering of the resultant solid products and in the drying process. In the drying process, further condensation of the silica after filtering was induced. As the surfactant and cosurfactant concentrations in the reaction mixture increased and the NH3 concentration decreased, under given conditions, continuous cubic MCM-48 and layered silica became the dominant phases. A cooperative synthesis mechanism, in which both the surfactant and silica were involved in the formation of mesoporous structures, provided a good explanation of the experimental results.

  18. Fused 1,2,3-Dithiazoles: Convenient Synthesis, Structural Characterization, and Electrochemical Properties

    Directory of Open Access Journals (Sweden)

    Lidia S. Konstantinova

    2016-05-01

    Full Text Available A new general protocol for synthesis of fused 1,2,3-dithiazoles by the reaction of cyclic oximes with S2Cl2 and pyridine in acetonitrile has been developed. The target 1,2,3-dithiazoles fused with various carbocycles, such as indene, naphthalenone, cyclohexadienone, cyclopentadiene, and benzoannulene, were selectively obtained in low to high yields. In most cases, the hetero ring-closure was accompanied by chlorination of the carbocyclic moieties. With naphthalenone derivatives, a novel dithiazole rearrangement (15→13 featuring unexpected movement of the dithiazole ring from α- to β-position, with respect to keto group, was discovered. Molecular structure of 4-chloro-5H-naphtho[1,2-d][1,2,3]dithiazol-5-one 13 was confirmed by single-crystal X-ray diffraction. Electrochemical properties of 13 were studied by cyclic voltammetry and a complex behavior was observed, most likely including hydrodechlorination at a low potential.

  19. Synthesis and computer-aided structural investigation of potentially photochromic spirooxazines

    International Nuclear Information System (INIS)

    Chi, L.

    2000-03-01

    Quantum mechanical methods, PPP-MO and ZINDO, were used to predict the electronic spectra of the ring-opened forms and ring-closed forms respectively of a series of spirooxazines. Molecular mechanics was used to optimise the molecular geometry and to calculate the molecular final energy (steric energy) using the MM2 force field method. An all-valence-electron quantum mechanical method was employed to calculate the heats of formation using AM1 parameters, and the data were used to provide a measure of the stability of the molecules. This computer-aided structural investigation has provided an enhanced understanding of the spirooxazine system and methods with the potential to predict photochromic behaviour have emerged. The synthesis of a series of heterocyclic analogues of the well-known spironaphthoxazines based on quinolines, coumarin and pyrazolones were attempted. The properties of the compounds obtained were correlated with the results of the calculations. (author)

  20. Synthesis and in vivo antimalarial activity of novel naphthoquine derivatives with linear/cyclic structured pendants.

    Science.gov (United States)

    Tang, Ling; Bei, Zhuchun; Song, Yabin; Xu, Likun; Wang, Hong; Zhang, Dongna; Dou, Yuanyuan; Lv, Kai; Wang, Hongquan

    2017-07-01

    Naphthoquine (NQ) was discovered by our institute as an antimalarial candidate in 1980s, and currently employed as an artemisinin-based combination therapy partner drug. Resistance to NQ was found in mouse model in laboratory, and might emerge in future as widely used. We herein report the design and synthesis of NQ derivatives by replacing t-butyl moiety with linear/cyclic structured pendants. All the target compounds 6a-l and intermediates 5a-h were tested for their in vivo antimalarial activity against Plasmodium berghei K173 strain in mice. Compounds 6a and 6j were found to have a comparable or slightly more potent activity (the 50% effective dose [ED 50 ], which is required to decrease parasitemia by 50%: 0.38-0.43 mg/kg) than NQ (ED 50 : 0.48 mg/kg). The newly designed compounds 6a and 6j might be promising antimalarial candidates for further research.