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Sample records for synthesis revised structure

  1. Synthesis and Structural Revision of Cyslabdan.

    PubMed

    Ohtawa, Masaki; Hishinuma, Yusuke; Takagi, Eiji; Yamada, Takafumi; Ito, Fumihiro; Arima, Shiho; Uchida, Ryuji; Kim, Yong-Pil; Ōmura, Satoshi; Tomoda, Hiroshi; Nagamitsu, Tohru

    2016-01-01

    Cyslabdan was isolated from the culture broth of Streptomyces sp. K04-0144 as a new potentiator of imipenem activity against methicillin-resistant Staphylococcus aureus. We accomplished the synthesis of cyslabdan according to a previously reported structure. However, we subsequently found that this structure was incorrect; our analysis of natural cyslabdan showed that it possessed R stereochemistry at the C8 position, not S, as had previously been reported. Thus, we completed the protecting-group-free synthesis of the correct structure of cyslabdan, which is described herein. PMID:27581641

  2. Bioinspired total synthesis and structural revision of yuremamine, an alkaloid from the entheogenic plant Mimosa tenuiflora.

    PubMed

    Calvert, Matthew B; Sperry, Jonathan

    2015-04-11

    Guided by a biosynthetic hypothesis, a serendipitous total synthesis of yuremamine has resulted in its structural revision from the putative pyrroloindole (1) to the flavonoidal indole (2), which was initially proposed as a biosynthetic intermediate. PMID:25756921

  3. Total synthesis and structural revision of mycalol, an anticancer natural product from the marine source.

    PubMed

    Seetharamsingh, B; Rajamohanan, P R; Reddy, D Srinivasa

    2015-04-01

    The total synthesis of an anticancer (anaplastic thyroid) natural lipid mycalol has been accomplished for the first time. Synthesis of originally proposed structure necessitated the revision of structure in which the position of acetate group moved from C20 to C19 and a change in stereochemistry of the glycerol unit. PMID:25763453

  4. Total Synthesis and Structural Revision of Antibiotic CJ-16,264**

    PubMed Central

    Nicolaou, K. C.; Shah, Akshay A.; Korman, Henry; Khan, Tabrez; Shi, Lei; Worawalai, Wisuttaya; Theodorakis, Emmanuel A.

    2015-01-01

    The total synthesis and structural revision of antibiotic CJ-16,264 is described. Starting with citronellal, the quest for the target molecule featured a novel bis-transannular Diels–Alder reaction that casted stereoselectively the decalin system and included the synthesis of six isomers before demystification of its true structure. PMID:26096055

  5. Substrate-Controlled Asymmetric Total Synthesis and Structure Revision of (-)-Bisezakyne A.

    PubMed

    Shin, Iljin; Lee, Dongjoo; Kim, Hyoungsu

    2016-09-01

    The first asymmetric total synthesis and subsequent structure revision of (-)-bisezakyne A, a Laurencia C15 acetogenin from Alpysia oculifera, has been accomplished. Our substrate-controlled synthesis of this oxolane natural product features a highly stereoselective "protecting-group-dependent" intramolecular amide enolate alkylation strategy for the synthesis of the key 9,10-trans-9,12-cis-10-hydroxytetrahydrofuran intermediate through "nonchelate" control. In addition, our synthesis determined the absolute configuration of the halogenated marine natural product. PMID:27551943

  6. Synthesis of (+/-)-nosyberkol (isotuberculosinol, revised structure of edaxadiene) and (+/-)-tuberculosinol.

    PubMed

    Maugel, Nathan; Mann, Francis M; Hillwig, Matthew L; Peters, Reuben J; Snider, Barry B

    2010-06-01

    Me(2)AlCl-catalyzed Diels-Alder reaction of N-tigloyloxazolidinone with 6,6-dimethyl-1-vinylcyclohexene selectively provided the exo adduct, which was converted to nosyberkol (isotuberculosinol) and tuberculosinol. The spectral data for nosyberkol are identical with those reported for edaxadiene, whose structure is revised accordingly. PMID:20462237

  7. Concise total synthesis and structural revision of (+)-pestalazine B.

    PubMed

    Pérez-Balado, Carlos; de Lera, Angel R

    2010-11-21

    A convergent synthesis of the proposed structure of (+)-pestalazine B has been achieved in 4 steps using the N-alkylation of an unprotected tryptophan diketopiperazine with a 3a-bromopyrrolidinoindoline as the key step. Although its structure was confirmed by X-ray analysis, the spectroscopic data did not match those of the natural product. The versatility of the methodology allowed the preparation of several diastereomers, and the database generated led to the proposal of an isomeric structure for the natural alkaloid where the d-leucine and d-phenylalanine residues exchanged positions, which was corroborated by total synthesis. PMID:20848034

  8. Synthesis of (±)-Serralongamine A and the Revised Structure of Huperzine N.

    PubMed

    Saborit, Gisela V; Bosch, Caroline; Parella, Teodor; Bradshaw, Ben; Bonjoch, Josep

    2016-03-18

    A revised structure for the Lycopodium alkaloid huperzine N is proposed and confirmed by synthesis. The key synthetic steps involve an epimerization of a cis-5-oxodecahydroquinoline to the corresponding trans isomer and a coupling, followed by a diastereoselective hydrogenation using Wilkinson's catalyst to incorporate the pyridylmethyl moiety. This route allowed the alkaloid serralongamine A to be synthesized for the first time, and two additional steps led to the revised structure of huperzine N, both products bearing an unusual decahydroquinoline stereostructure. PMID:26927208

  9. Synthesis-Guided Structure Revision of the Sarcodonin, Sarcoviolin and Hydnellin Natural Product Family

    PubMed Central

    Lin, David W.; Masuda, Takeshi; Biskup, Moritz B.; Nelson, Jonathan D.; Baran, Phil S.

    2011-01-01

    A sweeping structural revision of the sarcodonin natural product family (published structures: 1a–13a) is proposed after extensive studies aimed at their chemical synthesis. Key features of revised structure 1b include replacement of the N,N-dioxide moiety with an oxime, ring opening of the central diketopiperazine, and transposition of the terphenyl wing from the 1β-2β position of 1a to the 2β-3β position of 1b. This structure revision arose from the serendipitous synthesis of a benzodioxane aminal (44) whose structure was unambiguously determined by X-Ray crystallography and whose spectral properties bore considerable resemblance to the published data for the sarcodonins. A versatile new method for O-arylation of hydroxamic acids is also reported herein, as well as a manganese(III)-mediated α-oxidation of hydroxamic acids to aminals. PMID:21250718

  10. Total synthesis and structure revision of the (-)-maduropeptin chromophore.

    PubMed

    Komano, Kazuo; Shimamura, Satoshi; Norizuki, Yutaro; Zhao, Donglin; Kabuto, Chizuko; Sato, Itaru; Hirama, Masahiro

    2009-09-01

    The proposed structure of the maduropeptin chromophore, the biologically active component of the highly potent chromoprotein antitumor antibiotics, was stereoselectively synthesized but did not satisfy the spectra of the natural product. We demonstrated that the correct structure is diastereomeric, which possesses an antipodal sugar moiety. PMID:19655742

  11. Total Synthesis, Structure Revision, and Absolute Configuration of (−)-Brevenal

    PubMed Central

    Fuwa, Haruhiko; Ebine, Makoto; Bourdelais, Andrea J.; Baden, Daniel G.; Sasaki, Makoto

    2008-01-01

    Total synthesis of structure 1 originally proposed for brevenal, a nontoxic polycyclic ether natural product isolated from the Florida red tide dinoflagellate, Karenia brevis, was accomplished. The key features of the synthesis involved (i) convergent assembly of the pentacyclic polyether skeleton based on our developed Suzuki–Miyaura coupling chemistry and (ii) stereoselective construction of the multi-substituted (E,E)-dienal side chain by using copper(I) thiophen-2-carboxylate (CuTC)-promoted modified Stille coupling. The disparity of NMR spectra between the synthetic material and the natural product required a revision of the proposed structure. Detailed spectroscopic comparison of synthetic 1 with natural brevenal, coupled with the postulated biosynthetic pathway for marine polyether natural products, suggested that the natural product was most likely represented by 2, the C26 epimer of the proposed structure 1. The revised structure was finally validated by completing the first total synthesis of (−)-2, which also unambiguously established the absolute configuration of the natural product. PMID:17177450

  12. Enantioselective Total Synthesis of (−)-Citrinadin A and Revision of its Stereochemical Structure

    PubMed Central

    Bian, Zhiguo; Marvin, Christopher C.; Martin, Stephen F.

    2013-01-01

    The first enantioselective total synthesis of (−)-citrinadin A has been accomplished in 20 steps from commercially available materials via an approach that minimizes refunctionalization and protection/deprotection operations. The cornerstone of this synthesis features an asymmetric vinylogous Mannich addition of a dienolate to a chiral pyridinium salt to set the initial chiral center. A sequence of substrate-controlled reactions, including a highly stereoselective epoxidation/ring opening sequence and an oxidative rearrangement of an indole to furnish a spirooxindole, are then used to establish the remaining stereocenters in the pentacyclic core of (−)-citrinadin A. The successful synthesis of citrinadin A led to a revision of the stereochemical structure of the core substructure of the citrinadins. PMID:23837457

  13. One-Pot Synthesis of 5-Hydroxy-4H-1,3-thiazin-4-ones: Structure Revision, Synthesis, and NMR Shift Dependence of Thiasporine A.

    PubMed

    Seitz, Tobias; Fu, Peng; Haut, Franz-Lucas; Adam, Lutz; Habicht, Marija; Lentz, Dieter; MacMillan, John B; Christmann, Mathias

    2016-07-01

    An annulation of arylthioamides with 3-bromopyruvic acid chloride to 5-hydroxy-4H-1,3-thiazin-4-ones has been developed. The initial condensation affords two regioisomeric thiazolinone intermediates in a temperature-dependent manner. The synthesis of the 2-aminophenylthiazinone derivative led to the revision of the previously proposed structure of thiasporine A. Synthesis of the revised structure and NMR analysis revealed that thiasporine A had been isolated as a carboxylate. PMID:27286418

  14. Total Synthesis of Viridicatumtoxin B and Analogues Thereof: Strategy Evolution, Structural Revision, and Biological Evaluation

    PubMed Central

    2015-01-01

    The details of the total synthesis of viridicatumtoxin B (1) are described. Initial synthetic strategies toward this intriguing tetracycline antibiotic resulted in the development of key alkylation and Lewis acid-mediated spirocyclization reactions to form the hindered EF spirojunction, as well as Michael–Dieckmann reactions to set the A and C rings. The use of an aromatic A-ring substrate, however, was found to be unsuitable for the introduction of the requisite hydroxyl groups at carbons 4a and 12a. Applying these previous tactics, we developed stepwise approaches to oxidize carbons 12a and 4a based on enol- and enolate-based oxidations, respectively, the latter of which was accomplished after systematic investigations that revealed critical reactivity patterns. The herein described synthetic strategy resulted in the total synthesis of viridicatumtoxin B (1), which, in turn, formed the basis for the revision of its originally assigned structure. The developed chemistry facilitated the synthesis of a series of viridicatumtoxin analogues, which were evaluated against Gram-positive and Gram-negative bacterial strains, including drug-resistant pathogens, revealing the first structure–activity relationships within this structural type. PMID:25317739

  15. Total Synthesis and Structural Revision of Vannusals A and B. Synthesis of the True Structures of Vannusals A and B

    PubMed Central

    Ortiz, Adrian; Zhang, Hongjun; Guella, Graziano

    2010-01-01

    Having determined, through total synthesis, that the originally assigned structure of vannusals A and B were incorrect, we set out to uncover the identity of the true structures of these novel marine natural products. Our search was based on intelligence gathered by NMR spectroscopy and chemical synthesis and took us through the total synthesis of eight diastereomeric vannusal B structures [2, d-2, 3, d-3, 4, d-4, 5, and d-5, Figure 1]. The true structures of vannusals A and B were finally determined to be d-5 and d-1, respectively. Their total synthesis was based on a highly convergent and efficient strategy that involved fragments vinyl iodide (−)-6 and aldehyde (±)-94, and featured a stereoselective lithium-mediated coupling reaction and a samarium-induced cyclization process that forged the final ring of the carbon framework. The synthetic strategies and technologies developed in these investigations expand the scope of chemical synthesis and render these compounds readily available for biological evaluation, while the NMR spectroscopic insights gained should prove useful in future structural determination endeavors. PMID:20443558

  16. Convergent and Modular Synthesis of Candidate Precolibactins. Structural Revision of Precolibactin A.

    PubMed

    Healy, Alan R; Vizcaino, Maria I; Crawford, Jason M; Herzon, Seth B

    2016-04-27

    The colibactins are hybrid polyketide-nonribosomal peptide natural products produced by certain strains of commensal and extraintestinal pathogenic Escherichia coli. The metabolites are encoded by the clb gene cluster as prodrugs termed precolibactins. clb(+) E. coli induce DNA double-strand breaks in mammalian cells in vitro and in vivo and are found in 55-67% of colorectal cancer patients, suggesting that mature colibactins could initiate tumorigenesis. However, elucidation of their structures has been an arduous task as the metabolites are obtained in vanishingly small quantities (μg/L) from bacterial cultures and are believed to be unstable. Herein we describe a flexible and convergent synthetic route to prepare advanced precolibactins and derivatives. The synthesis proceeds by late-stage union of two complex precursors (e.g., 28 + 17 → 29a, 90%) followed by a base-induced double dehydrative cascade reaction to form two rings of the targets (e.g., 29a → 30a, 79%). The sequence has provided quantities of advanced candidate precolibactins that exceed those obtained by fermentation, and is envisioned to be readily scaled. These studies have guided a structural revision of the predicted metabolite precolibactin A (from 5a or 5b to 7) and have confirmed the structures of the isolated metabolites precolibactins B (3) and C (6). Synthetic precolibactin C (6) was converted to N-myristoyl-d-asparagine and its corresponding colibactin by colibactin peptidase ClbP. The synthetic strategy outlined herein will facilitate mechanism of action and structure-function studies of these fascinating metabolites, and is envisioned to accommodate the synthesis of additional (pre)colibactins as they are isolated. PMID:27025153

  17. Chemical synthesis of dendrotoxin-I: revision of the reported structure.

    PubMed

    Nishio, H; Inui, T; Nishiuchi, Y; De Medeiros, C L; Rowan, E G; Harvey, A L; Katoh, E; Yamazaki, T; Kimura, T; Sakakibara, S

    1998-05-01

    Dendrotoxin I (DTX-I) is a 60-residue peptide from the venom of the black mamba snake Dendroaspis polylepis, which binds to neuronal K+ channels. The structure reported previously for DTX-I was synthesized for the first time by a solution procedure. The synthetic product was confirmed to have the correct primary and disulfide structure determined by peptide mapping, sequence analysis and mass measurements. Comparison of synthetic DTX-I with the natural one by high-performance liquid chromatography and capillary zone electrophoresis, as well as by sequence analysis, revealed that the Asn residue at position 12 in the synthetic peptide was Asp in the natural product. Synthesis of DTX-I with Asp at position 12 gave a peptide identical with the natural product in all aspects. NMR analysis of synthetic [Asn12]- and [Asp12]-DTX-I also supported our findings that the Asn residue at position 12 in the DTX-I molecule should be revised as Asp. [Asn12]- and [Asp12]-DTX-I had very similar binding affinities when tested against radiolabeled dendrotoxin binding to rat brain synaptosomal membranes. PMID:9606015

  18. Synthesis of (±)-Nosyberkol (Isotuberculosinol, Revised Structure of Edaxadiene) and (±)-Tuberculosinol

    PubMed Central

    Maugel, Nathan; Mann, Francis M.; Hillwig, Matthew L.; Peters, Reuben J.

    2010-01-01

    Me2AlCl-catalyzed Diels–Alder reaction of N-tigloyloxazolidinone with 6,6-dimethyl-1-vinylcyclohexene selectively provided the exo adduct, which was converted to nosyberkol (isotuberculosinol) and tuberculosinol. The spectral data for nosyberkol are identical to those reported for edaxadiene, whose structure is revised accordingly. PMID:20462237

  19. Structure Revision of Similanamide to PF1171C by Total Synthesis.

    PubMed

    Masuda, Yuichi; Tanaka, Ren; Ganesan, A; Doi, Takayuki

    2015-09-25

    The total synthesis of the proposed structure of similanamide, a cyclic hexapeptide recently isolated from the marine sponge-associated fungus Aspergillus similanensis KUFA 0013, was achieved by solid-phase synthesis of a linear precursor and solution-phase macrolactamization. The NMR spectra of our synthetic final product were not identical to those of the isolated material and led us to conclude that similanamide is identical to PF1171C, a previously reported diastereomeric hexapeptide. PMID:26348363

  20. Facile synthesis of de-O-sulfated salacinols: revision of the structure of neosalacinol, a potent alpha-glucosidase inhibitor.

    PubMed

    Tanabe, Genzoh; Xie, Weijia; Ogawa, Ai; Cao, Changnian; Minematsu, Toshie; Yoshikawa, Masayuki; Muraoka, Osamu

    2009-04-15

    Facile synthesis of de-O-sulfated salacinols (3) was developed by employing the coupling reaction of an epoxide, 1,2-anhydro-3,4-di-O-benzyl-D-erythritol (9) with 2,3,5-tri-O-benzyl-1,4-dideoxy-1,4-epithio-D-arabinitol (10) as the key reaction. The reported structure of a potent alpha-glucosidase inhibitor named neosalacinol (8), isolated recently from Ayurvedic medicine Salacia oblonga, was proved incorrect, and revised to be de-O-sulfated salacinol formate (3c) by comparison of the spectroscopic properties with those of the authentic specimen synthesized. Discrepancies and confusion in the literature concerning the NMR spectroscopic properties of salacinol (1) have also been clarified. PMID:19307117

  1. Misassigned natural products and their revised structures.

    PubMed

    Yoo, Hye-Dong; Nam, Sang-Jip; Chin, Young-Won; Kim, Min-Sun

    2016-02-01

    Natural products are a major pipeline for drug development and are responsible for more than 50 % of drugs on the market. NMR is a fundamental and powerful tool for the structure determination of natural products. It is essential to provide unambiguous chemical structure information on natural products in drug development research, including the structure-activity relationship, derivatization and pharmacokinetic/pharmacodynamic studies. Advancement of NMR instruments has made it possible to deal with nanomole-scale natural products for structure elucidation, but misinterpretation of NMR spectra still occurs. We review 21 natural products with revised chemical structures and the methods used for those revisions. PMID:26310208

  2. Total Synthesis of Sarcophytonolide H and Isosarcophytonolide D: Structural Revision of Isosarcophytonolide D and Structure-Antifouling Activity Relationship of Sarcophytonolide H.

    PubMed

    Takamura, Hiroyoshi; Kikuchi, Takahiro; Endo, Noriyuki; Fukuda, Yuji; Kadota, Isao

    2016-05-01

    The first total syntheses of sarcophytonolide H and the originally proposed and correct structures of isosarcophytonolide D have been achieved via transannular ring-closing metathesis (RCM). These total syntheses culminated in the stereostructural confirmation of sarcophytonolide H and the reassignment of isosarcophytonolide D, respectively. The antifouling activity of the synthetic sarcophytonolide H and its analogues was also evaluated. PMID:27093115

  3. Synthesis and Structural Reassignment of Plakinidone.

    PubMed

    Xu, Ze-Jun; Tan, Dong-Xing; Wu, Yikang

    2015-10-16

    In connection with its first synthesis, plakinidone was structurally revised to a five-membered lactone. The key evidence for the previous assignment of this natural product as a perlactone was proven to be a misinterpretation of the MS data because of unawareness of a facile air oxidation. The synthetic samples also allowed for detection of differences in (13)C NMR for diastereomers of remote stereogenic centers, along with the influence of the air oxidation on the optical rotation. PMID:26434640

  4. Total synthesis and stereochemical revision of (+)-aeruginosin 298-A.

    PubMed

    Wipf, P; Methot, J L

    2000-12-28

    [structure:see text] Novel routes toward both enantiomers of the bicyclic proline surrogate 2-carboxy-6-hydroxyoctahydroindole, i.e., Choi, were developed on the basis of the oxidative cyclization of L-tyrosine. Synthesis of the proposed sequence of (+)-aeruginosin 298-A did not provide the natural product. Incorporation of a D-leucine residue, in contrast, led to the total synthesis of this thrombin inhibitor. PMID:11150202

  5. A Unified Strategy for Enantioselective Total Synthesis of Cladiellin and Briarellin Diterpenes: Total Synthesis of Briarellins E and F, and the Putative Structure of Alcyonin and Revision of Its Structure Assignment

    PubMed Central

    Corminboeuf, Olivier; Overman, Larry E.; Pennington, Lewis D.

    2009-01-01

    Enantioselective total syntheses of briarellin E (12) and briarellin F (13), as well as the structure originally proposed for the cladiellin diterpene alcyonin (10), have been realized. Comparison of the spectral data for synthetic 10, natural alcyonin, cladiellisin (33), and cladiellaperoxide (34), as well as chemical transformations of 10 and natural alcyonin, suggest that the structure of this coral metabolite is allylic peroxide 11. The unified approach detailed herein can be used to access both C4-deoxygenated and C4-oxygenated cladiellins and briarellins. The central step in these syntheses is acid-promoted condensation of (Z)-α,β-unsaturated aldehydes 17 with cyclohexadienyl diols 18, to form intermediates 16 incorporating the hexahydroisobenzofuran core and five stereocenters of these marine diterpenes (Scheme 1). PMID:19534538

  6. Control Augmented Structural Synthesis

    NASA Technical Reports Server (NTRS)

    Lust, Robert V.; Schmit, Lucien A.

    1988-01-01

    A methodology for control augmented structural synthesis is proposed for a class of structures which can be modeled as an assemblage of frame and/or truss elements. It is assumed that both the plant (structure) and the active control system dynamics can be adequately represented with a linear model. The structural sizing variables, active control system feedback gains and nonstructural lumped masses are treated simultaneously as independent design variables. Design constraints are imposed on static and dynamic displacements, static stresses, actuator forces and natural frequencies to ensure acceptable system behavior. Multiple static and dynamic loading conditions are considered. Side constraints imposed on the design variables protect against the generation of unrealizable designs. While the proposed approach is fundamentally more general, here the methodology is developed and demonstrated for the case where: (1) the dynamic loading is harmonic and thus the steady state response is of primary interest; (2) direct output feedback is used for the control system model; and (3) the actuators and sensors are collocated.

  7. Structure A, architectural sections & details. Drawing no. H2, revised ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Structure A, architectural sections & details. Drawing no. H2, revised as-built dated October 11, 1951. Original drawing by Black & Veatch, consulting engineers, Kansas City, Missouri, prepared for the U.S. Department of the Army, Office of Engineers, Military Construction Division, Washington, D.C. dated October 1. - Travis Air Force Base, Building No. 925, W Street, Fairfield, Solano County, CA

  8. Revision of the oligosaccharide structures of yeast carboxypeptidase Y

    SciTech Connect

    Ballou, L.; Hernandez, L.M.; Alvarado, E.; Ballou, C.E. )

    1990-05-01

    The N-linked oligosaccharides from baker's yeast carboxypeptidase Y were analyzed by {sup 1}H NMR and specific mannosidase digestion and found to be identical to those from the Saccharomyces cerevisiae mnn9 mutant bulk mannoprotein. The results support the view that the mnn mutants make oligosaccharides that are a true reflection of the normal biosynthetic pathway and confirm that a recently revised yeast oligosaccharide structure is applicable to wild-type mannoproteins.

  9. Total synthesis of xiamenmycin C and all of its stereoisomers: stereochemical revision.

    PubMed

    Yao, Yang-Yang; Liu, Xiao-Yu; Li, Xiao-Yu; Yang, Hong-Guang; Li, Li; Jiao, Xiao-Zhen; Xie, Ping

    2016-10-01

    Xiamenmycin C, a potent anti-fibrotic natural product, and all of its stereoisomers have been synthesized and their structures were fully characterized. Based on this study, the originally proposed structure of xiamenmycin C has been accordingly revised to be 2R,3S. PMID:27256638

  10. Coibacins A and B: Total Synthesis and Stereochemical Revision

    PubMed Central

    Carneiro, Vânia M. T.; Avila, Carolina M.; Balunas, Marcy J.; Gerwick, William H.; Pilli, Ronaldo A.

    2014-01-01

    The interface between synthetic organic chemistry and natural products was explored in order to unravel the structure of coibacin A, a metabolite isolated from the marine cyanobacterium cf. Oscillatoria sp. that exhibits selective antileishmanial activity and potent anti-inflammatory properties. Our synthetic plan focused on a convergent strategy that allows rapid access to the desired target by coupling of three key fragments involving E-selective Wittig and modified Julia olefinations. CD measurements and comparative HPLC analyses between the natural product and four synthetic stereoisomers led to determination of its absolute configuration thus correcting the original assignment at C-5 and unambiguously establishing those at C-16 and C-18. Additionally, we have synthesized coibacin B based on the assignment of configuration for coibacin A. PMID:24359482

  11. 78 FR 19541 - Proposed Revision to Design of Structures, Components, Equipment and Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-01

    ... published in the Federal Register (FR) on March 1, 2013 (78 FR 13911), that announced the request for comments on the proposed revisions in Chapter 3, ``Design of Structures, Components, Equipment, and Systems... COMMISSION Proposed Revision to Design of Structures, Components, Equipment and Systems AGENCY:...

  12. 78 FR 15755 - Proposed Revision to Design of Structures, Components, Equipment and Systems; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-12

    ... March 1, 2013 (41 FR 13911), that announced the solicitation for comments of the proposed revision in Chapter 3, ``Design of Structures, Components, Equipment, and Systems'' and is soliciting public comment... COMMISSION Proposed Revision to Design of Structures, Components, Equipment and Systems; Correction...

  13. Synthesis : Convection, structure and evolution

    NASA Astrophysics Data System (ADS)

    Schatzman, E.

    1997-12-01

    Lectures and discussions at the SCORe workshop have given a general idea of our present understanding of convection and oscillations and its application to the special case of the Sun. This {\\it SYNTHESIS} is just an attempt to present what seems to me to be the most important results, to draw attention to forgotten physical processes and to approach some important unsolved questions.

  14. Approximation concepts for efficient structural synthesis

    NASA Technical Reports Server (NTRS)

    Schmit, L. A., Jr.; Miura, H.

    1976-01-01

    It is shown that efficient structural synthesis capabilities can be created by using approximation concepts to mesh finite element structural analysis methods with nonlinear mathematical programming techniques. The history of the application of mathematical programming techniques to structural design optimization problems is reviewed. Several rather general approximation concepts are described along with the technical foundations of the ACCESS 1 computer program, which implements several approximation concepts. A substantial collection of structural design problems involving truss and idealized wing structures is presented. It is concluded that since the basic ideas employed in creating the ACCESS 1 program are rather general, its successful development supports the contention that the introduction of approximation concepts will lead to the emergence of a new generation of practical and efficient, large scale, structural synthesis capabilities in which finite element analysis methods and mathematical programming algorithms will play a central role.

  15. Xanthane sesquiterpenoids: structure, synthesis and biological activity.

    PubMed

    Vasas, Andrea; Hohmann, Judit

    2011-04-01

    The aim of this review is to survey the naturally occurring xanthanes and xanthanolides, their structures, biological activities, structure–activity relationships and synthesis. There has been no comprehensive review of this topic previously. On the basis of 126 references, 112 compounds are summarized. PMID:21321751

  16. Synthesis and structures of metal chalcogenide precursors

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Duraj, Stan A.; Eckles, William E.; Andras, Maria T.

    1990-01-01

    The reactivity of early transition metal sandwich complexes with sulfur-rich molecules such as dithiocarboxylic acids was studied. Researchers recently initiated work on precursors to CuInSe2 and related chalcopyrite semiconductors. Th every high radiation tolerance and the high absorption coefficient of CuInSe2 makes this material extremely attractive for lightweight space solar cells. Their general approach in early transition metal chemistry, the reaction of low-valent metal complexes or metal powders with sulfur and selenium rich compounds, was extended to the synthesis of chalcopyrite precursors. Here, the researchers describe synthesis, structures, and and routes to single molecule precursors to metal chalcogenides.

  17. Total Synthesis and Stereochemical Revision of the Anti-Tuberculosis Peptaibol Trichoderin A.

    PubMed

    Kavianinia, Iman; Kunalingam, Lavanya; Harris, Paul W R; Cook, Gregory M; Brimble, Margaret A

    2016-08-01

    The first total synthesis of the postulated structure of the aminolipopeptide trichoderin A and its epimer are reported. A late-stage solution phase C-terminal coupling was employed to introduce the C-terminal aminoalcohol moiety. This methodology provides a foundation to prepare analogues of trichoderin A to establish a structure-activity relationship. NMR spectroscopic analysis established that the C-6 position of the 2-amino-6-hydroxy-4-methyl-8-oxodecanoic acid (AHMOD) residue in trichoderin A possesses an (R)-configuration as opposed to the originally proposed (S)-configuration. PMID:27467118

  18. Tetrabromidocuprates(II)-Synthesis, Structure and EPR.

    PubMed

    Zabel, André; Winter, Alette; Kelling, Alexandra; Schilde, Uwe; Strauch, Peter

    2016-01-01

    Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several "onium" cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g‖ and g⊥) of the tensors could be determined and information on the structural changes in the [CuBr₄](2-) anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids. PMID:27104522

  19. Structural shape optimization in multidisciplinary system synthesis

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, Jaroslaw

    1988-01-01

    Structural shape optimization couples with other discipline optimization in the design of complex engineering systems. For instance, the wing structural weight and elastic deformations couple to aerodynamic loads and aircraft performance through drag. This coupling makes structural shape optimization a subtask in the overall vehicle synthesis. Decomposition methods for optimization and sensitivity analysis allow the specialized disciplinary methods to be used while the disciplines are temporarily decoupled, after which the interdisciplinary couplings are restored at the system level. Application of decomposition methods to structures-aerodynamics coupling in aircraft is outlined and illustrated with a numerical example of a transport aircraft. It is concluded that these methods may integrate structural and aerodynamic shape optimizations with the unified objective of the maximum aircraft performance.

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

    PubMed Central

    Huang, Ri-Ming; Chen, Yin-Ning; Zeng, Ziyu; Gao, Cheng-Hai; Su, Xiangdong; Peng, Yan

    2014-01-01

    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. PMID:25474189

  1. Improved approximations for control augmented structural synthesis

    NASA Technical Reports Server (NTRS)

    Thomas, H. L.; Schmit, L. A.

    1990-01-01

    A methodology for control-augmented structural synthesis is presented for structure-control systems which can be modeled as an assemblage of beam, truss, and nonstructural mass elements augmented by a noncollocated direct output feedback control system. Truss areas, beam cross sectional dimensions, nonstructural masses and rotary inertias, and controller position and velocity gains are treated simultaneously as design variables. The structural mass and a control-system performance index can be minimized simultaneously, with design constraints placed on static stresses and displacements, dynamic harmonic displacements and forces, structural frequencies, and closed-loop eigenvalues and damping ratios. Intermediate design-variable and response-quantity concepts are used to generate new approximations for displacements and actuator forces under harmonic dynamic loads and for system complex eigenvalues. This improves the overall efficiency of the procedure by reducing the number of complete analyses required for convergence. Numerical results which illustrate the effectiveness of the method are given.

  2. Synthesis and molecular structure of gold triarylcorroles.

    PubMed

    Thomas, Kolle E; Alemayehu, Abraham B; Conradie, Jeanet; Beavers, Christine; Ghosh, Abhik

    2011-12-19

    A number of third-row transition-metal corroles have remained elusive as synthetic targets until now, notably osmium, platinum, and gold corroles. Against this backdrop, we present a simple and general synthesis of β-unsubstituted gold(III) triarylcorroles and the first X-ray crystal structure of such a complex. Comparison with analogous copper and silver corrole structures, supplemented by extensive scalar-relativistic, dispersion-corrected density functional theory calculations, suggests that "inherent saddling" may occur for of all coinage metal corroles. The degree of saddling, however, varies considerably among the three metals, decreasing conspicuously along the series Cu > Ag > Au. The structural differences reflect significant differences in metal-corrole bonding, which are also reflected in the electrochemistry and electronic absorption spectra of the complexes. From Cu to Au, the electronic structure changes from noninnocent metal(II)-corrole(•2-) to relatively innocent metal(III)-corrole(3-). PMID:22111600

  3. Application of optimality criteria in structural synthesis

    NASA Technical Reports Server (NTRS)

    Terai, K.

    1974-01-01

    The rational use of optimality criteria was investigated for a class of structural synthesis problems where materials, configuration and applied load conditions are specified, and the minimum weight design is to be determined. The potential of hybrid methods of structural optimization for dealing with relatively large design problems involving practical complexity was explored. The reduced basis concept in design space was used to decrease the number of generalized design variables dealt with by the mathematical programming algorithm. Optimality criteria methods for obtaining design vectors associated with displacement, system buckling and natural frequency constraints are presented. A stress ratio method was used to generate a basis design vector representing the stress constraints. The finite element displacement method was used as the basic structural analysis tool. Results for several examples of truss systems subject to stress, displacement and minimum size constraints are presented. An assessment of these results indicates the effectiveness of the hybrid method developed.

  4. Nanostructured lead sulfide: synthesis, structure and properties

    NASA Astrophysics Data System (ADS)

    Sadovnikov, S. I.; Gusev, A. I.; Rempel, A. A.

    2016-07-01

    The theoretical and experimental results of recent studies dealing with nanostructured lead sulfide are summarized and analyzed. The key methods for the synthesis of nanostructured lead sulfide are described. The crystal structure of PbS in nanopowders and nanofilms is discussed. The influence of the size of nanostructure elements on the optical and thermal properties of lead sulfide is considered. The dependence of the band gap of PbS on the nanoparticle (crystallite) size for powders and films is illustrated. The bibliography includes 222 references.

  5. Structural, Item, and Test Generalizability of the Psychopathy Checklist-Revised to Offenders with Intellectual Disabilities

    ERIC Educational Resources Information Center

    Morrissey, Catrin; Cooke, David; Michie, Christine; Hollin, Clive; Hogue, Todd; Lindsay, William R.; Taylor, John L.

    2010-01-01

    The Psychopathy Checklist-Revised (PCL-R) is the most widely used measure of psychopathy in forensic clinical practice, but the generalizability of the measure to offenders with intellectual disabilities (ID) has not been clearly established. This study examined the structural equivalence and scalar equivalence of the PCL-R in a sample of 185 male…

  6. Factor Structure of Scores from the Conners' Rating Scales-Revised among Nepali Children

    ERIC Educational Resources Information Center

    Pendergast, Laura L.; Vandiver, Beverly J.; Schaefer, Barbara A.; Cole, Pamela M.; Murray-Kolb, Laura E.; Christian, Parul

    2014-01-01

    This study used exploratory and confirmatory factor analyses to examine the structures of scores from the Conners' Teacher and Parent Rating Scales-Revised (CTRS-R and CPRS-R, respectively; Conners, 1997). The scales were administered to 1,835 parents and 1,387 teachers of children in Nepal's Sarlahi district, a region where no other measures of…

  7. Interval Estimation of Revision Effect on Scale Reliability via Covariance Structure Modeling

    ERIC Educational Resources Information Center

    Raykov, Tenko

    2009-01-01

    A didactic discussion of a procedure for interval estimation of change in scale reliability due to revision is provided, which is developed within the framework of covariance structure modeling. The method yields ranges of plausible values for the population gain or loss in reliability of unidimensional composites, which results from deletion or…

  8. Computer applications for engineering/structural analysis. Revision 1

    SciTech Connect

    Zaslawsky, M.; Samaddar, S.K.

    1991-12-31

    Analysts and organizations have a tendency to lock themselves into specific codes with the obvious consequences of not addressing the real problem and thus reaching the wrong conclusion. This paper discusses the role of the analyst in selecting computer codes. The participation and support of a computation division in modifying the source program, configuration management, and pre- and post-processing of codes are among the subjects discussed. Specific examples illustrating the computer code selection process are described in the following problem areas: soil structure interaction, structural analysis of nuclear reactors, analysis of waste tanks where fluid structure interaction is important, analysis of equipment, structure-structure interaction, analysis of the operation of the superconductor supercollider which includes friction and transient temperature, and 3D analysis of the 10-meter telescope being built in Hawaii. Validation and verification of computer codes and their impact on the selection process are also discussed.

  9. Superheavy Elements -- Synthesis, Structure and Reaction Mechanism

    SciTech Connect

    Ackermann, Dieter

    2006-08-14

    The exciting results search for superheavy elements which have been achieved in the recent years have triggered a broad range of activities. Apart from experiments to attempt the synthesis of new elements, nuclear structure investigations in the transactinide region has become possibly for Z up to 108 or 110. Heavy element chemistry has successfully placed Hs in the periodic table and is no attacking element 112. The development of accelerators and experimental methods promises advances to enable the extension of these investigations in regions closer to the ''island of stability''. Mass measurements using ion traps and neutron rich unstable beam species for the systematic investigation of nuclear structure and reaction mechanisms for heavy neutron rich system are believed to complete the variety of tools in future.

  10. Some approximation concepts for structural synthesis

    NASA Technical Reports Server (NTRS)

    Schmit, L. A., Jr.; Farshi, B.

    1974-01-01

    An efficient automated minimum weight design procedure is presented which is applicable to sizing structural systems that can be idealized by truss, shear panel, and constant strain triangles. Static stress and displacement constraints under alternative loading conditions are considered. The optimization algorithm is an adaptation of the method of inscribed hyperspheres and high efficiency is achieved by using several approximation concepts including temporary deletion of noncritical constraints, design variable linking, and Taylor series expansions for response variables in terms of design variables. Optimum designs for several planar and space truss examples problems are presented. The results reported support the contention that the innovative use of approximation concepts in structural synthesis can produce significant improvements in efficiency.

  11. Some approximation concepts for structural synthesis.

    NASA Technical Reports Server (NTRS)

    Schmit, L. A., Jr.; Farshi, B.

    1973-01-01

    An efficient automated minimum weight design procedure is presented which is applicable to sizing structural systems that can be idealized by truss, shear panel, and constant strain triangles. Static stress and displacement constraints under alternative loading conditions are considered. The optimization algorithm is an adaptation of the method of inscribed hyperspheres and high efficiency is achieved by using several approximation concepts including temporary deletion of noncritical constraints, design variable linking, and Taylor series expansions for response variables in terms of design variables. Optimum designs for several planar and space truss example problems are presented. The results reported support the contention that the innovative use of approximation concepts in structural synthesis can produce significant improvements in efficiency.

  12. Betulin Phosphonates; Synthesis, Structure, and Cytotoxic Activity.

    PubMed

    Chrobak, Elwira; Bębenek, Ewa; Kadela-Tomanek, Monika; Latocha, Małgorzata; Jelsch, Christian; Wenger, Emmanuel; Boryczka, Stanisław

    2016-01-01

    Betulin derivatives are a widely studied group of compounds of natural origin due to their wide spectrum of biological activities. This paper describes new betulin derivatives, containing a phosphonate group. The allyl-vinyl isomerization and synthesis of acetylenic derivatives have been reported. Structural identification of products as E and Z isomers has been carried out using ¹H-, (13)C-, (31)P-NMR, and crystallographic analysis. The crystal structure in the orthorhombic space group and analysis of crystal packing contacts for 29-diethoxyphosphoryl-28-cyclopropylpropynoyloxy-lup-20E(29)-en-3β-ol 8a are reported. All new compounds were tested in vitro for their antiproliferative activity against human T47D (breast cancer), SNB-19 (glioblastoma), and C32 (melanoma) cell lines. PMID:27571057

  13. Total Synthesis, Stereochemical Revision, and Biological Reassessment of Mandelalide A: Chemical Mimicry of Intrafamily Relationships.

    PubMed

    Willwacher, Jens; Heggen, Berit; Wirtz, Conny; Thiel, Walter; Fürstner, Alois

    2015-07-13

    Mandelalide A and three congeners had recently been isolated as the supposedly highly cytotoxic principles of an ascidian collected off the South African coastline. Since these compounds are hardly available from the natural source, a concise synthesis route was developed, targeting structure 1 as the purported representation of mandelalide A. The sequence involves an iridium-catalyzed two-directional Krische allylation and a cobalt-catalyzed carbonylative epoxide opening as entry points for the preparation of the major building blocks. The final stages feature the first implementation of terminal acetylene metathesis into natural product total synthesis, which is remarkable in that this class of substrates had been beyond the reach of alkyne metathesis for decades. Synthetic 1, however, proved not to be identical with the natural product. In an attempt to clarify this issue, NMR spectra were simulated for 20 conceivable diastereomers by using DFT followed by DP4 analysis; however, this did not provide a reliable assignment either. The puzzle was ultimately solved by the preparation of three diastereomers, of which compound 6 proved identical with mandelalide A in all analytical and spectroscopic regards. As the entire "northern sector" about the tetrahydrofuran ring in 6 shows the opposite configuration of what had originally been assigned, it is highly likely that the stereostructures of the sister compounds mandelalides B-D must be corrected analogously; we propose that these natural products are accurately represented by structures 68-70. In an attempt to prove this reassignment, an entry into mandelalides C and D was sought by subjecting an advanced intermediate of the synthesis of 6 to a largely unprecedented intramolecular Morita-Baylis-Hillman reaction, which furnished the γ-lactone derivative 74 as a mixture of diastereomers. Whereas (24R)-74 was amenable to a hydroxyl-directed dihydroxylation by using OsO4 /TMEDA as the reagent, the sister

  14. Revised structure of the orthoborate YBO{sub 3}

    SciTech Connect

    Chadeyron, G.; El-Ghozzi, M.; Mahiou, R.; Arbus, A.; Cousseins, J.C.

    1997-02-01

    The YBO{sub 3} orthoborate was prepared by a flux evaporation process and the diffraction lines of its X-ray pattern were indexed on the basis of single crystal data. Crystal structure was determined (R = 0.035) in the P6{sub 3}/m space group from data recorded on a four-circle automatic diffractometer, with cell parameters a = 3.776 (1) {Angstrom}, c = 8.806 (4) {Angstrom}. The structure consists of a three-dimensional network made up of eightfold coordinated yttrium atoms and fourfold coordinated boron atoms. The structure exhibits two nonequivalent environments for the yttrium ions, which is confirmed by luminescence studies using the En{sup 3+} ion as structural probe. This work was completed by {sup 11}B NMR and IR studies, which show that boron has tetrahedral coordination.

  15. Simulation of Aircraft Engine Blade-Out Structural Dynamics. Revised

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles; Carney, Kelly; Gallardo, Vicente

    2001-01-01

    A primary concern of aircraft structure designers is the accurate simulation of the blade-out event and the subsequent windmilling of the engine. Reliable simulations of the blade-out event are required to insure structural integrity during flight as well as to guarantee successful blade-out certification testing. The system simulation includes the lost blade loadings and the interactions between the rotating turbomachinery and the remaining aircraft structural components. General-purpose finite element structural analysis codes such as MSC NASTRAN are typically used and special provisions are made to include transient effects from the blade loss and rotational effects resulting from the engine's turbomachinery. The present study provides the equations of motion for rotordynamic response including the effect of spooldown speed and rotor unbalance and examines the effects of these terms on a cantilevered rotor. The effect of spooldown speed is found to be greater with increasing spooldown rate. The parametric term resulting from the mass unbalance has a more significant effect on the rotordynamic response than does the spooldown term. The parametric term affects both the peak amplitudes as well as the resonant frequencies of the rotor.

  16. Revision of pyrrhotite structures within a common superspace model.

    PubMed

    Izaola, Zunbeltz; González, Santiago; Elcoro, Luis; Perez-Mato, J M; Madariaga, Gotzon; García, Alberto

    2007-10-01

    The structure of pyrrhotite (Fe(1 - x)S with 0.05 < or = x < or = 0.125) has been reinvestigated in the framework of the superspace formalism. A common model with a centrosymmetric superspace group is proposed for the whole family. The atomic domains in the internal space representing the Fe atoms are parametrized as crenel functions that fulfil the closeness condition. The proposed model explains the x-dependent space groups observed and the basic features of the structures reported up to now. Our model yields for any x value a well defined ordered distribution of Fe vacancies in contrast to some of the structural models proposed in the literature. A new (3 + 1)-dimensional refinement of Fe(0.91)S using the deposited dataset [Yamamoto & Nakazawa (1982). Acta Cryst. A38, 79-86] has been performed as a benchmark of the model. The consistency of the proposed superspace symmetry and its validity for other compositions has been further checked by means of ab initio calculations of both atomic forces and equilibrium atomic positions in non-relaxed and relaxed structures, respectively. PMID:17873438

  17. `Guanigma': the revised structure of biogenic anhydrous guanine

    NASA Astrophysics Data System (ADS)

    Hirsch, Anna; Gur, Dvir; Polishchuk, Iryna; Levy, Davide; Pokroy, Boaz; Cruz-Cabeza, Aurora J.; Addadi, Lia; Kronik, Leeor; Leiserowitz, Leslie

    Living organisms display a spectrum of colors, produced by pigmentation, structural coloration, or both. A relatively well-studied system, which produces colors via an array of alternating anhydrous guanine crystals and cytoplasm, is responsible for the metallic luster of many fish. The structure of biogenic anhydrous guanine was believed to be the same as that of the synthetic one - a monoclinic polymorph. Here we re-examine the structure of biogenic guanine, using experimental X-ray and electron diffraction (ED) data exposing troublesome inconsistencies - namely, a 'guanigma'. To address this, we sought alternative candidate polymorphs using symmetry and packing considerations, then used first principles calculations to determine whether the selected candidates could be energetically stable. We identified theoretically a different monoclinic polymorph, were able to synthesize it, and to confirm using X-ray diffraction that it is this polymorph that occurs in biogenic samples. However, the ED data were still not consistent with this polymorph, but rather with a theoretically generated orthorhombic polymorph. This apparent inconsistency was resolved by showing how the ED pattern could be affected by crystal structural faults composed of offset molecular layers.

  18. Structure A, protective alarm installation details. Drawing no. H3709, revised ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Structure A, protective alarm installation details. Drawing no. H3-709, revised as-built dated August 28, 1952. Original drawing by Black & Veatch, consulting engineers, Kansas City, Missouri, prepared for the U.S. Department of the Army, Office of Engineers, Military Construction Division, Washington, D.C. dated October 1, 1951. - Travis Air Force Base, Building No. 925, W Street, Fairfield, Solano County, CA

  19. Synthesis and structures of cuprous triptycylthiolate complexes.

    PubMed

    Ferrara, Skylar J; Mague, Joel T; Donahue, James P

    2012-06-18

    A synthesis of 1-(thioacetyl)triptycene (5), a convenient protected form of 1-(thiolato)triptycene [STrip](-), is described, a key transformation being the high yield conversion of tert-butyl 1-triptycenyl sulfide (8) to 5 by a protocol employing BBr(3)/AcCl. Syntheses of the two-coordinate copper(I) compounds [Bu(4)N][Cu(STrip)(2)], [Bu(4)N]10, and [(Cu(IMes)(STrip)] (13) proceed readily by chloride displacement from CuCl and [Cu(IMes)Cl], respectively. Reaction of 10 with Ph(3)SiSH or Me(3)SiI produces the heteroleptic species [Cu(STrip)(SSiPh(3))](-) (11) and [Cu(STrip)I](-) (12), detected by mass spectrometry, in mixture with the homoleptic bis(thiolate) anions. Structural identification by X-ray crystallography of the ligand precursor molecules 9-(thioacetyl)anthracene (4, triclinic and orthorhombic polymorphs), tert-butyl 9-anthracenyl sulfide (7), 5, and tert-butyl 1-triptycenyl sulfide (8) are presented. Crystallographic characterization of bis(9-anthracenyl)sulfide (3), which features a C-S-C angle of 104.0° and twist angle of 54.8° between anthracenyl planes, is also given. A crystal structure of [Bu(4)N][(STrip)], [Bu(4)N]9, provides an experimental measure of 144.6° for the ligand cone angle. The crystal structures of [Bu(4)N]10 and 13 are reported, the former of which reveals an unexpectedly small C-S···S-C torsion angle of ∼41° (average of two values), which confers a near "cis" disposition of the triptycenyl groups with respect the S-Cu-S axis. This conformation is governed by interligand π···π and CH···π interactions. A crystal structure of an adventitious product, [Bu(4)N][(Cu-STrip)(6)(μ(6)-Br)]·[Bu(4)N][PF(6)], [Bu(4)N]14·[Bu(4)N][PF(6)] is described, which reveals a cyclic hexameric structure previously unobserved in cuprous thiolate chemistry. The Cu(6)S(6) ring displays a centrosymmetric cyclohexane chair type conformation with a Br(-) ion residing at the inversion center and held in place by apparent soft

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

    SciTech Connect

    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/sub 2/MX/sub 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 ..pi..-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.

  1. Examining the impact of gender on the factor structure of the Psychopathic Personality Inventory-Revised.

    PubMed

    Anestis, Joye C; Caron, Kelly M; Carbonell, Joyce L

    2011-09-01

    Research on the factor structure of psychopathy has yielded mixed results, supporting anywhere from one to three factors. Additionally, most of this research has used all-male samples, and the possibility of structural invariance across gender has not been examined. Using a mixed-gender sample of 360 undergraduates, the factor structure of the Psychopathic Personality Inventory-Revised was examined using confirmatory factor analysis and multiple group analysis. One-, two-, and three-factor models were tested and compared with each other. When males and females were combined, none of the three models provided adequate fit to the data. Multiple group analyses revealed partial invariance across gender for all three models. Model comparison criteria supported use of both the one- and two-factor models, taking into account variable factor structure across gender. The importance of considering structural differences based on biological sex when assessing psychopathic traits is discussed. PMID:21490056

  2. A revised structure and hydrogen bonding system in cellulose II from a neutron fiber diffraction analysis

    SciTech Connect

    Langan, P.; Nishiyama, Y.; Chanzy, H.

    1999-11-03

    The crystal and molecular structure and hydrogen bonding system in cellulose II have been revised using new neutron diffraction data extending to 1.2 {angstrom} resolution collected from two highly crystalline fiber samples of mercerized flax. Mercerization was achieved in NaOH/H{sub 2}O for one sample and in NaOD/D{sub 2}O for the other, corresponding to the labile hydroxymethyl moieties being hydrogenated and deuterated, respectively. Fourier difference maps were calculated in which neutron difference amplitudes were combined with phases calculated from two revised X-ray models of cellulose II. The revised phasing models were determined by refinement against the X-ray data set of Kolpak and Blackwell, using the LALS methodology. Both models have two antiparallel chains organized in a P2{sub 1} space group and unit cell parameters: a = 8.01 {angstrom}, b = 9.04 {angstrom}, c = 10.36 {angstrom}, and {gamma} = 117.1{degree}. One has equivalent backbone conformations for both chains but different conformations for the hydroxymethyl moieties: gt for the origin chain and tg for the center chain. The second model based on the recent crystal structures of cellotetraose, has different conformations for the two chains but nearly equivalent conformations for the hydroxymethyl moieties. On the basis of the X-ray data alone, the models could not be differentiated. From the neutron Fourier difference maps, possible labile hydrogen atom positions were identified for each model and refined using LALS. The second model is significantly different from previous proposals based on the crystal structures of cellotetraose, MD simulations of cellulose II, and any potential hydrogen-bonding network in the structure of cellulose II determined in earlier X-ray fiber diffraction studies. The exact localization of the labile hydrogen atoms involved in this bonding, together with their donor and acceptor characteristics, is presented and discussed. This study provides, for the first time

  3. 75 FR 34714 - Updated Record of Decision (ROD) for Revised Army Growth and Force; Structure Realignment Decisions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-18

    ... Department of the Army Updated Record of Decision (ROD) for Revised Army Growth and Force; Structure... Department of the Army announces the availability of an updated ROD for Army Growth and Force Structure... Army growth and force structure realignment. The Army's decision at the time grew the Army by...

  4. Meroterpenoids with New Skeletons from Myrtus communis and Structure Revision of Myrtucommulone K.

    PubMed

    Liu, Chao; Ang, Song; Huang, Xiao-Jun; Tian, Hai-Yan; Deng, Yuan-Yuan; Zhang, Dong-Mei; Wang, Ying; Ye, Wen-Cai; Wang, Lei

    2016-08-19

    Five sesquiterpene-based meroterpenoids with three kinds of new skeletons [1, 2, 3, (+)-4, and (-)-4] were isolated from the leaves of Myrtus communis. Compound 1 featured a new carbon skeleton with an unprecedented octahydrospiro[bicyclo[7.2.0]undecane-2,2'-chromene] tetracyclic ring system, which possessed two preferred conformations detected by variable-temperature NMR spectroscopy experiments. In addition, the structure of reported myrtucommulone K was revised to be compound 3. The plausible biosynthetic pathways of these meroterpenoids and their cytotoxicities are discussed. PMID:27471772

  5. Halohydrins and polyols derived from antirrhinoside: structural revisions of muralioside and epimuralioside

    PubMed

    Franzyk; Jensen; Thale; Olsen

    1999-02-01

    Treatment of the iridoid glucoside antirrhinoside (1) with pyridinium chloride in dimethylformamide gave rise to the two possible trans-halohydrins, linarioside (4) and isolinarioside (5). Pyridinium bromide gave the two analogous bromohydrins. It is shown that the iridoid glucosides 8-epi-muralioside from Linaria arcusangeli and 7,8-epi-antirrhinoside from Linaria dalmatica are both identical with isolinarioside, and therefore, these names are redundant. The structure of muralioside isolated from Cymbalaria muralis is revised to that of its 8-epimer (8), while the structure of an isomeric, new iridoid glucoside from Paulownia tomentosa has been elucidated to be 7beta-hydroxyharpagide (3), the structure originally assigned to 8. In addition, 7alpha-hydroxyharpagide (2), the known product from the base-catalyzed hydrolytic opening of 1, has been isolated from Antirrhinum majus and thus shown to be a natural product. PMID:10075758

  6. Dynamic analysis of large structures by modal synthesis techniques.

    NASA Technical Reports Server (NTRS)

    Hurty, W. C.; Hart, G. C.; Collins, J. D.

    1971-01-01

    Several criteria that may be used to evaluate the merits of some of the existing techniques for the dynamic analysis of large structures which involve division into substructures or components are examined. These techniques make use of component displacement modes to synthetize global systems of generalized coordinates and, for that reason, they have come to be known as modal synthesis or component mode methods. Two techniques have been found to be particularly useful - i.e., the modal synthesis method with fixed attachment modes, and the modal synthesis method with free attachment modes. These two methods are treated in detail, and general flow charts are presented for guidance in computer programming.

  7. Structure Elucidation of Nigricanoside A Through Enantioselective Total Synthesis

    PubMed Central

    Chen, Jie; Koswatta, Panduka; DeBergh, J. Robb; Fu, Peng; Pan, Ende; MacMillan, John B.; Ready, Joseph M.

    2016-01-01

    Nigricanoside A was isolated from green alga, and its dimethyl ester was found to display potent cytotoxicity. Its scarcity prevented a full structure elucidation, leaving total synthesis as the only means to determine its relative and absolute stereochemistry and to explore its biological activity. Here we assign the stereochemistry of the natural product through enantioselective total synthesis and provide initial studies of its cytotoxicity. PMID:26877863

  8. Revising the Child and Adolescent Perfectionism Scale: A Test of the Four-Factor Structure in a Chinese Sample

    ERIC Educational Resources Information Center

    Yang, Hongfei; Hong, Chaoqin; Tao, Xiaodan; Zhu, Lingyi

    2015-01-01

    This study examined the structure, reliability, and validity of the revised Chinese version of the Child and Adolescent Perfectionism Scale (N = 933). The results confirmed the four-factor structure of the Chinese version of the Child and Adolescent Perfectionism Scale. Implications, limitations, and suggestions for future research are provided.

  9. Experimental component mode synthesis of structures with sloppy joints

    NASA Technical Reports Server (NTRS)

    Blackwood, Gary H.; Von Flotow, A. H.

    1988-01-01

    The accuracy of component mode synthesis is investigated experimentally for substructures coupled by nonideal joints. The work is based upon a segmented experimental beam for which free-interface frequency response matrices are measured for each segment. These measurements are used directly in component mode synthesis to predict the behavior of the assembled structure; the segments are then physically joined, and the resulting frequency response of the superstructure is compared to the prediction. Rotational freeplay is then introduced into the connecting joint, and the new superstructure frequency response is compared to the original linear component mode synthesis prediction. The level of accuracy to be expected in component mode synthesis is discussed in terms of the degree of nonlinearity in the joints, mode number, and mode shapes.

  10. Synthesis and structural study of N-isopropenylbenzimidazolone

    NASA Astrophysics Data System (ADS)

    Mondieig, D.; Negrier, Ph.; Leger, J. M.; Lakhrissi, L.; El Assyry, A.; Lakhrissi, B.; Essassi, E. M.; Benali, B.; Boucetta, A.

    2015-05-01

    The synthesis and the crystal structure of the N-isopropenylbenzimidazolone (C10H10N2O) are presented. The synthesis was performed by Meth-Cohen method by reaction of o-phenylenediamine with ethyl acetoacetate in refluxed xylene. The single crystal structure was determined at room temperature by means of X-rays diffraction. The crystal system is monoclinic, with space group C2/c and eight molecules per unit cell. The unit cell dimensions are: a = 15.978(1) Å, b = 6.100(2) Å, c = 18.222(2) Å, β = 90.16(1)° and V = 1776.0(6) Å3.

  11. Application of variable metric methods to structural synthesis

    NASA Technical Reports Server (NTRS)

    Vanderplaats, G. N.; Sugimoto, H.

    1985-01-01

    Powell (1977, 1978), Biggs (1972, 1975), and Han (1976, 1977) have developed a class of variable metric methods which create an explicit, quadratic, subproblem which is to be solved for finding a search direction for design improvement. A one-dimensional search is then performed. The present paper has the objective to present this variable metric approach in the context of structural synthesis. The variable metric algorithm is modified for application to the structural synthesis problem. The application of the new procedure is illustrated with the aid of examples, taking into account a 10-bar planar truss, a 17-bar planar tower, and a cantilever beam.

  12. An advanced structural analysis/synthesis capability - ACCESS 2

    NASA Technical Reports Server (NTRS)

    Schmit, L. A.; Miura, H.

    1976-01-01

    An advanced automated design procedure for minimum-weight design of structures (ACCESS 2) is reported. Design variable linking, constraint deletion, and explicit constraint approximation are used to combine effectively finite-element and nonlinear mathematical programming techniques. The approximation-concepts approach to structural synthesis is extended to problems involving fiber composite structure, thermal effects, and natural frequency constraints in addition to the usual static stress and displacement limitations. Sample results illustrating these features are given.

  13. An advanced structural analysis/synthesis capability - ACCESS 2

    NASA Technical Reports Server (NTRS)

    Schmit, L. A.; Miura, H.

    1978-01-01

    An advanced automated design procedure for minimum weight design of structures (ACCESS 2) is reported. Design variable linking, constraint deletion, and explicit constraint approximation are used to effectively combine finite element and nonlinear mathematical programming techniques. The approximation concepts approach to structural synthesis is extended to problems involving fiber composite structure, thermal effects and natural frequency constraints in addition to the usual static stress and displacement limitations. Sample results illustrating these new features are given.

  14. Factor structure of the Bulimia Test--Revised in college women from four ethnic groups.

    PubMed

    Fernandez, Senaida; Malcarne, Vanessa L; Malacrne, Vanessa L; Wilfley, Denise E; McQuaid, John

    2006-07-01

    The factor structure of the Bulimia Test--Revised (BULIT-R) was investigated using confirmatory factor analysis (CFA) and exploratory factor analysis (EFA). The sample consisted of 2,671 female college students (African American, Asian American, Caucasian American, and Latino American). Reliability coefficients were excellent across groups. African Americans scored significantly lower on the BULIT-R than Caucasian Americans. Across groups, CFA and EFA results suggest a six-factor solution is most appropriate. Consistent across groups were factors representing bingeing, body image, purging, and extreme weight loss behaviors, while few differences were observed across groups. These findings suggest that the measure is reliable and valid for use with diverse ethnic groups. Future research should focus on culturally salient psychological correlates of disordered eating in diverse ethnic groups. PMID:16881746

  15. Factor Structure of Scores from the Conners’ Rating Scales–Revised Among Nepali Children

    PubMed Central

    Pendergast, Laura L.; Vandiver, Beverly J.; Schaefer, Barbara A.; Cole, Pamela M.; Murray-Kolb, Laura M.; Christian, Parul

    2014-01-01

    This study used exploratory and confirmatory factor analyses to examine the structures of scores from the Conners’ Teacher and Parent Rating Scales–Revised (CTRS-R and CPRS-R, respectively; Conners, 1997). The scales were administered to 1,835 parents and 1,387 teachers of children in Nepal's Sarlahi district – a region where no other measures of child psychopathology have been studied. With a Nepali sample, the findings indicate that reduced two factor models for the Conners’ scales are superior to the models identified in the scale development research. The hyperactivity and inattention factors were comparable to what has been identified in prior research, while other factors (e.g., social problems) differed substantially. Implications for use of the Conners’ scales in Nepal and cross cultural issues in the assessment of ADHD symptoms are discussed. PMID:25574454

  16. The Revised Identity Style Inventory: Factor Structure and Validity in Italian Speaking Students

    PubMed Central

    Monacis, Lucia; de Palo, Valeria; Sinatra, Maria; Berzonsky, Michael D.

    2016-01-01

    The purpose of this study was to evaluate the factor structure and convergent and discriminant validity of scores on an Italian translation of the Revised Identity Style Inventory (ISI-5) with samples of 237 adolescents (50 males, Mage = 18.04, SD = .86) and 268 university students (42 males, Mage = 22.71, SD = 3.70). Confirmatory Factor Analysis indicated that a three-factor solution provided a good fit, which was invariant across age and sex groups. The theoretically relationships between scores on the ISI and scores on measures of reasoning and identity processes, identity commitment, and social desirability were partially consistent, thus further studies are needed to give more evidence to the convergent and discriminant validity. PMID:27378980

  17. The Revised Identity Style Inventory: Factor Structure and Validity in Italian Speaking Students.

    PubMed

    Monacis, Lucia; de Palo, Valeria; Sinatra, Maria; Berzonsky, Michael D

    2016-01-01

    The purpose of this study was to evaluate the factor structure and convergent and discriminant validity of scores on an Italian translation of the Revised Identity Style Inventory (ISI-5) with samples of 237 adolescents (50 males, M age = 18.04, SD = .86) and 268 university students (42 males, M age = 22.71, SD = 3.70). Confirmatory Factor Analysis indicated that a three-factor solution provided a good fit, which was invariant across age and sex groups. The theoretically relationships between scores on the ISI and scores on measures of reasoning and identity processes, identity commitment, and social desirability were partially consistent, thus further studies are needed to give more evidence to the convergent and discriminant validity. PMID:27378980

  18. Re-assessment of offshore structures using the revised HSE fatigue guidance

    SciTech Connect

    Stacey, A.; Sharp, J.V.

    1995-12-31

    The re-assessment of existing North Sea structures is an increasingly important issue as the age of platforms increases. Over 50 from a total of approximately 180 fixed installations in the UK sector are now over 15 years old. Fatigue damage has been the main reason for repairs to North Sea structures and the risk of this continues. The fatigue guidance of the Offshore Safety Division of the Health and Safety Executive (HSE) has recently been revised and published. Fundamental changes have been made to this guidance with several new recommendations including joint classification, basic design S-N curves for welded joints, the thickness effect, the effects of environment and the treatment of low and high stress ranges. To quantify the effects of the new guidance on the fatigue life assessment of offshore strictures, the HSE commissioned a study which included a deep water and a shallow water fixed steel structure and a twin-pontoon semi-submersible. These structures are typical of those operating in the North Sea. These were re-assessed with respect to fatigue lives and the results compared with predictions based on the 1990 guidance. The results and general conclusions are presented in this paper.

  19. Factor Structure of the Luria-Nebraska Neuropsychological Battery-Children's Revision with Learning-Disabled Children.

    ERIC Educational Resources Information Center

    Snow, Jeffrey; Hynd, George W.

    1985-01-01

    Examined the factor structure of the Luria-Nebraska Neuropsychological Battery-Children's Revision in a population of learning-disabled children (N=100). Factor analysis and varimax rotation revealed three factors: a language-general intellectual factor, a reading-written expression factor, and a sensory-motor factor. (Author/MCF)

  20. The Structural and Predictive Properties of the Psychopathy Checklist-Revised in Canadian Aboriginal and Non-Aboriginal Offenders

    ERIC Educational Resources Information Center

    Olver, Mark E.; Neumann, Craig S.; Wong, Stephen C. P.; Hare, Robert D.

    2013-01-01

    We examined the structural and predictive properties of the Psychopathy Checklist-Revised (PCL-R) in large samples of Canadian male Aboriginal and non-Aboriginal offenders. The PCL-R ratings were part of a risk assessment for criminal recidivism, with a mean follow-up of 26 months postrelease. Using multigroup confirmatory factor analysis, we were…

  1. Micro- and nanosized boron carbide: synthesis, structure and properties

    NASA Astrophysics Data System (ADS)

    Andrievski, Rostislav A.

    2012-06-01

    Methods of synthesis of powder particles, fibres (wires), tubes, films, coatings and bulk materials based on micro- and nanocrystalline and amorphous boron carbide are considered. Specific features of the electronic structure, material structure and physicochemical and mechanical properties of boron carbide and boron carbide-based composites are discussed. Their existing and potential applications are highlighted. The little studied aspects of the research area in question are specified. The bibliography includes 105 references.

  2. Facile chemical synthesis and structure characterization of copper molybdate nanoparticles

    NASA Astrophysics Data System (ADS)

    Rahimi-Nasrabadi, Mehdi; Pourmortazavi, Seied Mahdi; Khalilian-Shalamzari, Morteza

    2015-03-01

    Experimental parameters of a synthesis route were optimized by Taguchi robust design for the facile and controllable synthesis of copper molybdate nanoparticles. CuMoO4 nanoparticles were synthesized by chemical precipitation followed by hydrothermal process. Effects of different parameters of synthesis procedure, i.e. concentrations of both reagents, copper feeding flow rate and temperature of reactor on the particle size of prepared copper molybdate nanoparticles were investigated. The results of statistical optimization revealed that the size of copper molybdate particles is dependent on the procedure variables involving copper concentrations, flow rate and temperature of the reactor; while, molybdate concentration has a no considerable role in determining the size of CuMoO4 particles. Based on the results obtained by statistical optimization process, the nanoparticles of copper molybdate were prepared and then their structure and chemical composition were characterized by various techniques, i.e. SEM, TEM, XRD, EDX, FT-IR, UV-Vis and photoluminescence spectroscopy.

  3. Synthesis and Crystal Structure of Gold Nanobelts

    PubMed Central

    2015-01-01

    Gold nanobelts were synthesized by the reduction of tetrachloroauric acid with ascorbic acid in the presence of the surfactants cetyltrimethylammonium bromide and sodium dodecylsulfate. The resulting structures have rectangular cross sectional dimensions that are tens of nanometers and lengths that are tens to hundreds of micrometers. We find that the nanobelt yield and resulting structures are very sensitive to temperature which is likely due to the transition of the surfactant solution from wormlike micelles to spherical micelles. The nanobelt crystal structure contains a mixture of face centered cubic and hexagonally close packed lattice phases that can be isolated and examined individually due to the unique nanobelt size and shape. PMID:24803725

  4. Hydrothermal synthesis and structure of a potassium tantalum defect pyrochlore

    SciTech Connect

    Duan, N.; Tian, Z.R.; Willis, W.S.; Suib, S.L.; Newsam, J.M.; Levine, S.M.

    1998-09-07

    The synthesis and crystal structure of potassium tantalate (KTa{sub 2}(O,OH){sub 6}{center_dot}1.8H{sub 2}O) with a defect pyrochlore structure are reported. The compound was crystallized directly from tantalum pentoxide in basic solution under hydrothermal conditions at temperatures as low as 200 C. Ion exchange of this substance in acid yielded an H-type defect pyrochlore. Both highly crystalline K-type and H-type materials absorb argon and have BET surface areas of about 14 m{sup 2}/g. The crystal structures were refined by the Rietveld least-squares method from powder X-ray diffraction data. The final R{sub wp} and {chi}{sup 2} were 7.70% and 2.79, respectively. The high thermal stability and control of acidity of these materials, along with the simple and cheap synthesis, may find many applications in sorption, catalysis, and microelectronics.

  5. Block-Krylov component synthesis method for structural model reduction

    NASA Technical Reports Server (NTRS)

    Craig, Roy R., Jr.; Hale, Arthur L.

    1988-01-01

    A new analytical method is presented for generating component shape vectors, or Ritz vectors, for use in component synthesis. Based on the concept of a block-Krylov subspace, easily derived recurrence relations generate blocks of Ritz vectors for each component. The subspace spanned by the Ritz vectors is called a block-Krylov subspace. The synthesis uses the new Ritz vectors rather than component normal modes to reduce the order of large, finite-element component models. An advantage of the Ritz vectors is that they involve significantly less computation than component normal modes. Both 'free-interface' and 'fixed-interface' component models are derived. They yield block-Krylov formulations paralleling the concepts of free-interface and fixed-interface component modal synthesis. Additionally, block-Krylov reduced-order component models are shown to have special disturbability/observability properties. Consequently, the method is attractive in active structural control applications, such as large space structures. The new fixed-interface methodology is demonstrated by a numerical example. The accuracy is found to be comparable to that of fixed-interface component modal synthesis.

  6. Control augmented structural synthesis with dynamic stability constraints

    NASA Technical Reports Server (NTRS)

    Thomas, H. L.; Schmit, L. A., Jr.

    1989-01-01

    Dynamic stability constraints are included in a computer program that simultaneously synthesizes a structure and its control system. Two measures of stability, the real part of the system complex eigenvalues and the damping ratio, are examined. The procedure for calculating the sensitivities of the two measures of stability to changes in the structure and its control system is explained. The sensitivities are used to formulate an approximate problem that is solved at each design iteration. The effects of structural damping and noncollated controllers on the synthesis process are discussed.

  7. Synthesis and structural characterization of CZTS nanoparticles

    SciTech Connect

    Lydia, R.; Reddy, P. Sreedhara

    2013-06-03

    The CZTS nanoparticles were successfully synthesized by Chemical co-precipitation method with different pH values in the range of 6 to 8. The synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. XRD studies revealed that the CZTS nanoparticles exhibited Kesterite Structure with preferential orientation along the (112) direction. Sample at pH value of 7 reached the nearly stoichiometric ratio.

  8. Analysis of nonlinear structures via mode synthesis

    NASA Technical Reports Server (NTRS)

    Gieseke, R. K.

    1975-01-01

    An effective procedure for NASTRAN was developed that permits any number of substructures of any size to be synthesized for the purpose of developing normal modes of vibration of the complete structural system. The technique is extended to permit modal transient analysis of the subdivided system. This latter procedure permits the use of NASTRAN's ability to include nonlinear forces in the problem. The five-phase process is accomplished using standard NASTRAN rigid formats with problem-independent alter packages and DMAP sequences.

  9. Novel Synthesis and Structural Analysis of Ferrihydrite

    SciTech Connect

    Smith, Stacey J.; Page, Katharine; Kim, Hyunjeong; Campbell, Branton J.; Boerio-Goates, Juliana; Woodfield, Brian F.

    2012-07-25

    Naturally occurring ferrihydrite is both impure and difficult to isolate, so the numerous applications and interesting properties of ferrihydrite have spurred the development of various synthetic techniques. Nearly all techniques are based on the hydrolysis of an iron salt and require careful control of temperature, pH, and concentration. In this Article, we report a new synthetic method which does not require such control and is perhaps the fastest and simplest route to synthesizing ferrhydrite. XRD, TEM, BET, and chemical purity characterizations show that the chemically pure, 2-line ferrihydrite product consists of crystallites 2-6 nm in diameter which aggregate to form mesoporous, high surface area agglomerates that are attractive candidates for the many adsorption applications of ferrihydrite. X-ray PDF data were also collected for the ferrihydrite product and refined against the hexagonal structural model recently proposed by Michel et al. These analyses suggest that ferrihydrite has a consistent, repeatable structure independent of variation in the synthetic method, water content of the sample, or particle size of the crystallites, and this structure can be adequately described by the proposed hexagonal model.

  10. Synthesis and Structural Characterization of Orthorhombic Vanadium Oxide Nanorods

    NASA Astrophysics Data System (ADS)

    Garcia, L. M.; Chavira, E.; Santiago-Jacinto, P.; Rendon, L.; Marinero, E. E.; Tejada, A.; Fregoso-Israel, E.; Flores, C.

    2012-02-01

    Nanorod structures for Li storage are of interest for rechargeable battery applications. Vanadium pentoxide is a promising battery cathode material and in this work we report on the synthesis of V2O5 orthorhombic single crystal and polycrystalline nanorods by the sol-gel polymerizing acryl amide method via ethylenediamine tetra acetic acid EDTA assisted hydrothermal process. In order to determine the thermodynamic stability of nanostructured polymorphs vanadates, heat treatments were performed from 450 C to 500 ^oC with annealing times ranging from 48 to 72 h. The morphologies and structures of the nanorods were characterized by XRD, SEM and HRTEM. Thermo Gravimetric Analysis (TGA) was employed to monitor reaction mass losses during the course of the synthesis. Nanorod diameters ranging from 50 to 150 nm were observed. The lengths and diameter of the rods depended on the conditions of the preparation, such as concentration, and reaction time.

  11. Polyureas from diamines and carbon dioxide: synthesis, structures and properties.

    PubMed

    Wu, Chaoyong; Wang, Jinyao; Chang, Pingjing; Cheng, Haiyang; Yu, Yancun; Wu, Zhijian; Dong, Dewen; Zhao, Fengyu

    2012-01-14

    Polyureas were synthesized from diamines and carbon dioxide in the absence of any catalyst or solvent, analogous to the synthesis of urea from condensation of ammonia with carbon dioxide. The method used carbon dioxide as a carbonyl source to substitute highly toxic isocyanates for the synthesis of polyureas. FTIR and DFT calculations confirmed that strong bidentate hydrogen bonds were formed between urea motifs, and XRD patterns showed that the PUas were highly crystalline and formed a network structure through hydrogen bonds, which served as physical cross-links. The long chain PUas presented a microphase separated morphology as characterized by SAXS and showed a high melting temperature above 200 °C. The PUas showed high resistance to solvents and excellent thermal stability, which benefitted from their special network structures. The PUas synthesized by this method are a new kind of functional material and could serve some areas where their analogues with similar functional groups could not be applied. PMID:22120724

  12. A new approximation method for stress constraints in structural synthesis

    NASA Technical Reports Server (NTRS)

    Vanderplaats, Garret N.; Salajegheh, Eysa

    1987-01-01

    A new approximation method for dealing with stress constraints in structural synthesis is presented. The finite element nodal forces are approximated and these are used to create an explicit, but often nonlinear, approximation to the original problem. The principal motivation is to create the best approximation possible, in order to reduce the number of detailed finite element analyses needed to reach the optimum. Examples are offered and compared with published results, to demonstrate the efficiency and reliability of the proposed method.

  13. An implementation of the distributed programming structural synthesis system (PROSSS)

    NASA Technical Reports Server (NTRS)

    Rogers, J. L., Jr.

    1981-01-01

    A method is described for implementing a flexible software system that combines large, complex programs with small, user-supplied, problem-dependent programs and that distributes their execution between a mainframe and a minicomputer. The Programming Structural Synthesis System (PROSSS) was the specific software system considered. The results of such distributed implementation are flexibility of the optimization procedure organization and versatility of the formulation of constraints and design variables.

  14. Spreading Effect in Industrial Complex Network Based on Revised Structural Holes Theory

    PubMed Central

    Ye, Qing; Guan, Jun

    2016-01-01

    This paper analyzed the spreading effect of industrial sectors with complex network model under perspective of econophysics. Input-output analysis, as an important research tool, focuses more on static analysis. However, the fundamental aim of industry analysis is to figure out how interaction between different industries makes impacts on economic development, which turns out to be a dynamic process. Thus, industrial complex network based on input-output tables from WIOD is proposed to be a bridge connecting accurate static quantitative analysis and comparable dynamic one. With application of revised structural holes theory, flow betweenness and random walk centrality were respectively chosen to evaluate industrial sectors’ long-term and short-term spreading effect process in this paper. It shows that industries with higher flow betweenness or random walk centrality would bring about more intensive industrial spreading effect to the industrial chains they stands in, because value stream transmission of industrial sectors depends on how many products or services it can get from the other ones, and they are regarded as brokers with bigger information superiority and more intermediate interests. PMID:27218468

  15. Spreading Effect in Industrial Complex Network Based on Revised Structural Holes Theory.

    PubMed

    Xing, Lizhi; Ye, Qing; Guan, Jun

    2016-01-01

    This paper analyzed the spreading effect of industrial sectors with complex network model under perspective of econophysics. Input-output analysis, as an important research tool, focuses more on static analysis. However, the fundamental aim of industry analysis is to figure out how interaction between different industries makes impacts on economic development, which turns out to be a dynamic process. Thus, industrial complex network based on input-output tables from WIOD is proposed to be a bridge connecting accurate static quantitative analysis and comparable dynamic one. With application of revised structural holes theory, flow betweenness and random walk centrality were respectively chosen to evaluate industrial sectors' long-term and short-term spreading effect process in this paper. It shows that industries with higher flow betweenness or random walk centrality would bring about more intensive industrial spreading effect to the industrial chains they stands in, because value stream transmission of industrial sectors depends on how many products or services it can get from the other ones, and they are regarded as brokers with bigger information superiority and more intermediate interests. PMID:27218468

  16. Superheavy Element Synthesis And Nuclear Structure

    SciTech Connect

    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.

    2009-08-26

    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)-alpha-alpha and ER-alpha-gamma 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 {sup 252,254}No and in {sup 270}Ds.

  17. Synthesis and Structure of Technetium Trichloride

    SciTech Connect

    Poineau, Frederic; Johnstone, Erik V.; Weck, Philippe F.; Kim, Eunja; Forster, Paul M.; Scott, Brian L.; Sattelberger, Alfred P.; Czerwinski, Kenneth R.

    2010-12-07

    Technetium trichloride has been synthesized by reaction of Tc{sub 2}(O{sub 2}CCH{sub 3}){sub 4}Cl{sub 2} with HCl(g) at 300 C. The mechanism of formation mimics the one described earlier in the literature for rhenium. Tc{sub 2}(O{sub 2}CCH{sub 3}){sub 2}Cl{sub 4} [P{sub T}; a = 6.0303(12) {angstrom}, b = 6.5098(13) {angstrom}, c = 8.3072(16) {angstrom}, {alpha} = 112.082(2){sup o}, {beta} = 96.667(3){sup o}, {gamma} = 108.792(3){sup o}; Tc-Tc = 2.150(1) {angstrom}] is formed as an intermediate in the reaction at 100 C. Technetium trichloride is formed above 250 C and is isostructural with its rhenium homologue. The structure consists of Tc{sub 3}Cl{sub 9} clusters [R{sub 3}m; a = b = 10.1035(19) {angstrom}, c = 20.120(8) {angstrom}], and the Tc-Tc separation is 2.444(1) {angstrom}. Calculations on TcX{sub 3} (X = Cl, Br) have confirmed the stability of TcCl{sub 3} and suggest the existence of a polymorph of TcBr{sub 3} with the ReBr{sub 3} structure.

  18. Tetrabromidocuprates(II)—Synthesis, Structure and EPR

    PubMed Central

    Zabel, André; Winter, Alette; Kelling, Alexandra; Schilde, Uwe; Strauch, Peter

    2016-01-01

    Metal-containing ionic liquids (ILs) are of interest for a variety of technical applications, e.g., particle synthesis and materials with magnetic or thermochromic properties. In this paper we report the synthesis of, and two structures for, some new tetrabromidocuprates(II) with several “onium” cations in comparison to the results of electron paramagnetic resonance (EPR) spectroscopic analyses. The sterically demanding cations were used to separate the paramagnetic Cu(II) ions for EPR measurements. The EPR hyperfine structure in the spectra of these new compounds is not resolved, due to the line broadening resulting from magnetic exchange between the still-incomplete separated paramagnetic Cu(II) centres. For the majority of compounds, the principal g values (g‖ and g⊥) of the tensors could be determined and information on the structural changes in the [CuBr4]2− anions can be obtained. The complexes have high potential, e.g., as ionic liquids, as precursors for the synthesis of copper bromide particles, as catalytically active or paramagnetic ionic liquids. PMID:27104522

  19. The Neo Personality Inventory-Revised: Factor Structure and Gender Invariance from Exploratory Structural Equation Modeling Analyses in a High-Stakes Setting

    ERIC Educational Resources Information Center

    Furnham, Adrian; Guenole, Nigel; Levine, Stephen Z.; Chamorro-Premuzic, Tomas

    2013-01-01

    This study presents new analyses of NEO Personality Inventory-Revised (NEO-PI-R) responses collected from a large British sample in a high-stakes setting. The authors show the appropriateness of the five-factor model underpinning these responses in a variety of new ways. Using the recently developed exploratory structural equation modeling (ESEM)…

  20. Robust penalty method for structural synthesis

    NASA Technical Reports Server (NTRS)

    Kamat, M. P.

    1983-01-01

    The Sequential Unconstrained Minimization Technique (SUMT) offers an easy way of solving nonlinearly constrained problems. However, this algorithm frequently suffers from the need to minimize an ill-conditioned penalty function. An ill-conditioned minimization problem can be solved very effectively by posing the problem as one of integrating a system of stiff differential equations utilizing concepts from singular perturbation theory. This paper evaluates the robustness and the reliability of such a singular perturbation based SUMT algorithm on two different problems of structural optimization of widely separated scales. The report concludes that whereas conventional SUMT can be bogged down by frequent ill-conditioning, especially in large scale problems, the singular perturbation SUMT has no such difficulty in converging to very accurate solutions.

  1. 78 FR 48727 - Proposed Revisions to Design of Structures, Components, Equipment and Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-09

    ... System (ADAMS): You may access publicly available documents online in the NRC Library at http://www.nrc... accordingly. Terms have been revised from ``Operability'' and ``Operability Assurance'' to...

  2. Topology structure synthesis and analysis of spatial pyramid deployable truss structures for satellite SAR antenna

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Deng, Zongquan; Liu, Rongqiang; Yang, Hui; Guo, Hongwei

    2014-07-01

    Many attentions for structural synthesis are paid to planar linkages and parallel mechanisms, while design novel pyramid deployable truss structure(PDTS) of satellite SAR mainly depends on experience of designer. To design novel configuration of PDTS, a two-step topology structure synthesis and analysis approach is proposed. Firstly, a conceptual configuration of PDTS is synthesized. Weighted graph and weighted adjacency matrix are established to realize topological description for PDTS. Graph properties are then summarized to distinguish differentia between PDTS and other type structures. According to graph properties, a procedure for synthesis conceptual configuration of PDTS is presented. Secondly, join relationship of components in a PDTS is analyzed. Kinematic chain and corresponding incidence/adjacency matrix are employed to analyze join relationship of PDTS. Properties and simplified rules of kinematic chain are extracted to construct kinematic chain. A procedure for construction kinematic chain of PDTS is then established. Finally, with this two-step approach all 11 rectangular pyramid deployable structures whose folded state is planar are discovered and their kinematic chains are constructed. Based on synthesis results, a novel deployable support structure for satellite SAR is designed. The proposed research can be applied to obtain some novel PDTSs, which is of great importance to design some novel deployable support structures for satellite SAR antenna.

  3. Reduced complexity structural modeling for automated airframe synthesis

    NASA Technical Reports Server (NTRS)

    Hajela, Prabhat

    1987-01-01

    A procedure is developed for the optimum sizing of wing structures based on representing the built-up finite element assembly of the structure by equivalent beam models. The reduced-order beam models are computationally less demanding in an optimum design environment which dictates repetitive analysis of several trial designs. The design procedure is implemented in a computer program requiring geometry and loading information to create the wing finite element model and its equivalent beam model, and providing a rapid estimate of the optimum weight obtained from a fully stressed design approach applied to the beam. The synthesis procedure is demonstrated for representative conventional-cantilever and joined wing configurations.

  4. Structure, Chemical Synthesis, and Biosynthesis of Prodiginine Natural Products.

    PubMed

    Hu, Dennis X; Withall, David M; Challis, Gregory L; Thomson, Regan J

    2016-07-27

    The prodiginine family of bacterial alkaloids is a diverse set of heterocyclic natural products that have likely been known to man since antiquity. In more recent times, these alkaloids have been discovered to span a wide range of chemical structures that possess a number of interesting biological activities. This review provides a comprehensive overview of research undertaken toward the isolation and structural elucidation of the prodiginine family of natural products. Additionally, research toward chemical synthesis of the prodiginine alkaloids over the last several decades is extensively reviewed. Finally, the current, evidence-based understanding of the various biosynthetic pathways employed by bacteria to produce prodiginine alkaloids is summarized. PMID:27314508

  5. Ionothermal synthesis and crystal structures of metal phosphate chains

    SciTech Connect

    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.

    2010-07-15

    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.

  6. Application of component mode synthesis in structural dynamics

    NASA Technical Reports Server (NTRS)

    Craig, R. R.

    1986-01-01

    The principal analytical techniques used for component mode synthesis (CMS) of undamped systems and their application to structural dynamics are discussed. In the CMS, a system is divided into components or substructures, and for each of these components, the number of degrees of freedom is reduced by expressing the physical coordinates in terms of a reduced set of component modal coordinates. Among a number of component modes, a new form of component mode, called an applied force attachment mode, is described. Consideration is given to literature studies of damped structures and recent combined analytical/experimental studies.

  7. Synthesis of aircraft structures using integrated design and analysis methods

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, J.; Goetz, R. C.

    1978-01-01

    A systematic research is reported to develop and validate methods for structural sizing of an airframe designed with the use of composite materials and active controls. This research program includes procedures for computing aeroelastic loads, static and dynamic aeroelasticity, analysis and synthesis of active controls, and optimization techniques. Development of the methods is concerned with the most effective ways of integrating and sequencing the procedures in order to generate structural sizing and the associated active control system, which is optimal with respect to a given merit function constrained by strength and aeroelasticity requirements.

  8. Optimal placement of active elements in control augmented structural synthesis

    NASA Technical Reports Server (NTRS)

    Sepulveda, A. E.; Jin, I. M.; Schmit, L. A., Jr.

    1992-01-01

    A methodology for structural/control synthesis is presented in which the optimal location of active members is treated in terms of (0,1) variables. Structural member sizes, control gains and (0,1) placement variables are treated simultaneously as design variables. Optimization is carried out by generating and solving a sequence of explicit approximate problems using a branch and bound strategy. Intermediate design variable and intermediate response quantity concepts are used to enhance the quality of the approximate design problems. Numerical results for example problems are presented to illustrate the efficacy of the design procedure set forth.

  9. The Padua Inventory: Do Revisions Need Revision?

    ERIC Educational Resources Information Center

    Gonner, Sascha; Ecker, Willi; Leonhart, Rainer

    2010-01-01

    The purpose of the present study was to examine the psychometric properties, factorial structure, and validity of the Padua Inventory-Washington State University Revision and of the Padua Inventory-Revised in a large sample of patients with obsessive-compulsive disorder (n = 228) and with anxiety disorders and/or depression (n = 213). The…

  10. Synthesis and Structural Data of Tetrabenzo[8]circulene

    PubMed Central

    Miller, Robert W.; Duncan, Alexandra K.; Schneebeli, Severin T.; Gray, Danielle L.; Whalley, Adam C.

    2015-01-01

    In 1976, the first attempted synthesis of the saddle-shaped molecule [8]circulene was reported. The next 37 years produced no advancement towards the construction of this complicated molecule. Remarkably, however, over the last six months a flurry of progress has been made with two groups reporting independent and strikingly different strategies for the synthesis of [8]circulene derivatives. Herein, we present a third synthetic method in which we target tetrabenzo[8]circulene. Our approach employs a Diels-Alder reaction and a palladium-catalyzed arylation reaction as the key steps. Despite calculations describing the instability of [8]circulene, coupled with the reported instability of synthesized derivatives of the parent molecule, the addition of four fused benzenoid rings around the periphery of the molecule provides a highly stable structure. This increased stability over the parent [8]circulene was predicted using Clar’s theory of aromatic sextets and is a result of the compound becoming fully benzenoid upon incorporation of these additional rings. The synthesized compound exhibits remarkable stability under ambient conditions – even at elevated temperatures – with no signs of decomposition over several months. The solid-state structure of this compound is significantly twisted compared to the calculated structure primarily as a result of crystal packing forces in the solid state. Despite this contortion from the lowest energy structure, a range of structural data is presented confirming the presence of localized aromaticity in this large polycyclic aromatic hydrocarbon. PMID:24615957

  11. Janus-Cube Octasilsesquioxane: Facile Synthesis and Structure Elucidation.

    PubMed

    Oguri, Naoki; Egawa, Yasunobu; Takeda, Nobuhiro; Unno, Masafumi

    2016-08-01

    A perfect "Janus-cube" octasilsesquioxane, a nanometer-scale Janus particle with two different types of substituents, was synthesized through the cross-coupling of a "half-cube" cyclic sodium siloxanolate with another half-cube cyclic fluorosiloxane. The structure was confirmed by X-ray crystallography to be a Janus cube. The overall synthesis is simple and does not require drastic separation methods compared with previous methods. The synthesis of the Janus cube demonstrates a novel siloxane bond-forming reaction involving the coupling a silanol salt and fluorosilane. The reaction is mild, does not result in acid generation, and could be applied to the construction of other novel siloxane compounds. PMID:27225052

  12. Precision synthesis, structure and function of helical polymers

    PubMed Central

    OKAMOTO, Yoshio

    2015-01-01

    Helical structures are chiral, which means that if we can synthesize a polymer having a stable one-handed helicity, the polymer is optically active. In 1979, we succeeded in the synthesis of a one-handed helical polymer from an optically inactive achiral monomer, triphenylmethyl methacrylate (TrMA). This is the first example of the asymmetric synthesis of an optically active one-handed helical polymer. The polymer (PTrMA) exhibited an unexpected high chiral recognition ability and afforded a practically useful chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) by coating it on silica gel. In addition, we also succeeded in the development of very useful CSPs for HPLC using the phenylcarbamate derivatives of polysaccharides, cellulose and amylose. These CSPs can efficiently resolve a broad range of chiral compounds, and have been used all over the world for separating and analyzing chiral compounds. PMID:26062738

  13. Precision synthesis, structure and function of helical polymers.

    PubMed

    Okamoto, Yoshio

    2015-01-01

    Helical structures are chiral, which means that if we can synthesize a polymer having a stable one-handed helicity, the polymer is optically active. In 1979, we succeeded in the synthesis of a one-handed helical polymer from an optically inactive achiral monomer, triphenylmethyl methacrylate (TrMA). This is the first example of the asymmetric synthesis of an optically active one-handed helical polymer. The polymer (PTrMA) exhibited an unexpected high chiral recognition ability and afforded a practically useful chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) by coating it on silica gel. In addition, we also succeeded in the development of very useful CSPs for HPLC using the phenylcarbamate derivatives of polysaccharides, cellulose and amylose. These CSPs can efficiently resolve a broad range of chiral compounds, and have been used all over the world for separating and analyzing chiral compounds. PMID:26062738

  14. PASS: A computer program for Preliminary Aircraft Structural Synthesis

    NASA Technical Reports Server (NTRS)

    Johnson, E. H.

    1977-01-01

    A computer code for Preliminary Aircraft Structural Synthesis provides rapid and accurate analysis for aircraft structures that can be adequately modeled by beam finite elements. The philosophy used in developing the program was to provide a basic framework that can be used for structural synthesis. It is anticipated that a user will need to add detail to this framework in order to perform his specific task. With this philosophy in mind, the program was written so that it is easily divided into segments, thereby making it readily adaptable. The theoretical portion of this manual describes the basic structure of the program and details the development of the unique beam element that is used. The present capability of the algorithm is stated and suggestions are made regarding enhancements to this capability. User information is also given that provides an overview of the program's construction, identifies the required inputs, describes the program output, provides some comments on the program use, and exhibits results for a simple example.

  15. Revision total hip arthroplasty for large medial defects with witch's hat-shaped structural allografts--minimum 10-year follow-up.

    PubMed

    Peng, Kuo-Ti; Hsu, Wei-Hsiu; Shih, Hsin-Nung; Chen, Chun-Chieh; Yeh, Jih-Hsi

    2014-02-01

    A witch's hat-shaped structural allograft can restore bone stock over acetabular medial wall during revision total hip arthroplasty, which may be of importance for future re-revisions. However, long-term results are unclear. A retrospective review of 104 consecutive hips in 96 patients was performed to determine survivorship and functions. The minimum follow-up was 10 years. Nine patients required re-revision for cup aseptic loosening with a mean time to revision of 4.5 years. Kaplan-Meier survivorship was 89.4% at the endpoint. Radiographic evaluation revealed sixteen instances of minor medial wall graft absorption without significant cup migration. The mean modified Harris Hip Scores were 36 preoperatively and 86 at last follow-up. Revision acetabular surgery using a witch's hat-shaped allograft to restore acetabular medial wall provides an excellent alternative. PMID:23810421

  16. Global sensitivity analysis in control-augmented structural synthesis

    NASA Technical Reports Server (NTRS)

    Bloebaum, Christina L.

    1989-01-01

    In this paper, an integrated approach to structural/control design is proposed in which variables in both the passive (structural) and active (control) disciplines of an optimization process are changed simultaneously. The global sensitivity equation (GSE) method of Sobieszczanski-Sobieski (1988) is used to obtain the behavior sensitivity derivatives necessary for the linear approximations used in the parallel multidisciplinary synthesis problem. The GSE allows for the decoupling of large systems into smaller subsystems and thus makes it possible to determine the local sensitivities of each subsystem's outputs to its inputs and parameters. The advantages in using the GSE method are demonstrated using a finite-element representation of a truss structure equipped with active lateral displacement controllers, which is undergoing forced vibration.

  17. Application of the Probabilistic Dynamic Synthesis Method to Realistic Structures

    NASA Technical Reports Server (NTRS)

    Brown, Andrew M.; Ferri, Aldo A.

    1998-01-01

    The Probabilistic Dynamic Synthesis method is a technique for obtaining the statistics of a desired response engineering quantity for a structure with non-deterministic parameters. The method uses measured data from modal testing of the structure as the input random variables, rather than more "primitive" quantities like geometry or material variation. This modal information is much more comprehensive and easily measured than the "primitive" information. The probabilistic analysis is carried out using either response surface reliability methods or Monte Carlo simulation. In previous work, the feasibility of the PDS method applied to a simple seven degree-of-freedom spring-mass system was verified. In this paper, extensive issues involved with applying the method to a realistic three-substructure system are examined, and free and forced response analyses are performed. The results from using the method are promising, especially when the lack of alternatives for obtaining quantitative output for probabilistic structures is considered.

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

    PubMed Central

    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

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

    PubMed

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

    2015-08-22

    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

  20. Synthesis and Structural Study of Some Pyrimidinium Hexafluoridosilicates.

    PubMed

    Pevec, Andrej

    2015-01-01

    The synthesis and spectroscopic characterization of some pyrimidinium hexafluoridosilicate salts with the formula (RH)2[SiF]6 (where R = 2-aminopyrimidine (1), cytosine (2) and 5-cyanocytosine (3)) is obtained in the reaction of SiO2 with hydrofluoric acid solution and subsequent addition of 2-aminopyrimidine, cytosine or 4-amino-2-chloropyrimidine-5-carbonitrile. The crystal structures of 1 and 3 have been determined by single-crystal X‒ray diffraction analysis. The combination of N‒H···F hydrogen bonds along with π‒π interactions between aromatic rings resulted in supramolecular architecture of cations and anions in the solid state. PMID:26085410

  1. Difluoromethylenated polyhydroxylated pyrrolidines: facile synthesis, crystal structure and biological evaluation.

    PubMed

    Wang, Ruo-Wen; Xu, Jun; Lopez, Oscar; Bols, Mikael; Qing, Feng-Ling

    2009-08-01

    In our ongoing program aimed at the design, synthesis and biological evaluation of novel gem-difluoromethylenated glycosidase inhibitors, the gem-difluoromethylenated polyhydroxylated pyrrolidines as analogues of 2,5-dideoxy-2,5-imino-D-mannitol (DMDP) were designed and prepared. The crystal structure of gem-difluoromethylenated polyhydroxylated pyrrolidine 17 contains an N-H…F intermolecular hydrogen bond. The biological assessment of gem-difluoromethylenated polyhydroxylated pyrrolidines showed that the modification by the gem-difluoromethylene group decreased the inhibitory activities of DMDP. PMID:21426093

  2. A General Chemistry Experiment Incorporating Synthesis and Structural Determination

    NASA Astrophysics Data System (ADS)

    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.

  3. An approximation based global optimization strategy for structural synthesis

    NASA Technical Reports Server (NTRS)

    Sepulveda, A. E.; Schmit, L. A.

    1991-01-01

    A global optimization strategy for structural synthesis based on approximation concepts is presented. The methodology involves the solution of a sequence of highly accurate approximate problems using a global optimization algorithm. The global optimization algorithm implemented consists of a branch and bound strategy based on the interval evaluation of the objective function and constraint functions, combined with a local feasible directions algorithm. The approximate design optimization problems are constructed using first order approximations of selected intermediate response quantities in terms of intermediate design variables. Some numerical results for example problems are presented to illustrate the efficacy of the design procedure setforth.

  4. System for Structural Synthesis Combines Finite-Element Analysis and Optimization Programs

    NASA Technical Reports Server (NTRS)

    Rogers, J. L., Jr.

    1984-01-01

    Programming System for Structural Synthesis, EAL/PROSSS, provides structural-synthesis capability by combining EAL and CONMIN computer programs with set of interface procedures. EAL is general-purpose finiteelement structural-analysis program; CONMIN is general-purpose optimization program. User supplies two smaller problem-dependent programs to define design variables, constraints, and objective function.

  5. Structural Revisions of a Class of Natural Products: Scaffolds of Aglycon Analogues of Fusicoccins and Cotylenins Isolated from Fungi.

    PubMed

    Tang, Ying; Xue, Yongbo; Du, Guang; Wang, Jianping; Liu, Junjun; Sun, Bin; Li, Xiao-Nian; Yao, Guangmin; Luo, Zengwei; Zhang, Yonghui

    2016-03-14

    The reisolation and structural revision of brassicicene D is described, and inspired us to reassign the core skeletons of brassicicenes C-H, J and K, ranging from dicyclopenta[a,d]cyclooctane to tricyclo[9.2.1.0(3,7)]tetradecane using quantum-chemical predictions and experimental validation strategies. Three novel, highly modified fusicoccanes, brassicicenes L-N, were also isolated from the fungus Alternaria brassicicola, and their structures were unequivocally established by spectroscopic data, ECD calculations, and crystallography. The reassigned structures represent the first class of bridgehead double-bond-containing natural products with a bicyclo[6.2.1]undecane carbon skeleton. Furthermore, their stabilities were first predicted with olefin strain energy calculations. Collectively, these findings extend our view of the application of computational predictions and biosynthetic logic-based structure elucidation to address problems related to the structure and stability of natural products. PMID:26916098

  6. The Structure of the Autism Diagnostic Interview-Revised: Diagnostic and Phenotypic Implications

    ERIC Educational Resources Information Center

    Snow, Anne V.; Lecavalier, Luc; Houts, Carrie

    2009-01-01

    Background: Multivariate statistics can assist in refining the nosology and diagnosis of pervasive developmental disorders (PDD) and also contribute important information for genetic studies. The Autism Diagnostic Interview-Revised (ADI-R) is one of the most widely used assessment instruments in the field of PDD. The current study investigated its…

  7. Confirming the Structural Validity of the My Class Inventory -- Short Form Revised

    ERIC Educational Resources Information Center

    Mariani, Melissa; Villares, Elizabeth; Sink, Christopher A.; Colvin, Kimberly; Kuba, Summer Perhay

    2015-01-01

    Researchers analyzed data collected from elementary school students (N = 893) to further establish the psychometric soundness of the My Class Inventory--Short Form Revised (MCI-SFR). A confirmatory factor analysis was conducted resulting in a good fit for a four-factor model, which corresponds to the instrument's four scales (Cohesion,…

  8. 78 FR 41434 - Proposed Revisions to Design of Structures, Components, Equipment and Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-10

    ... Regulatory Commission. ACTION: Standard review plan-draft section revision; request for comment. ] SUMMARY...-0800, ``Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR... are shown in the description of changes. The changes to Chapter 3 of this Standard Review Plan...

  9. Discrete-continuous variable structural synthesis using dual methods

    NASA Technical Reports Server (NTRS)

    Schmit, L. A.; Fleury, C.

    1980-01-01

    Approximation concepts and dual methods are extended to solve structural synthesis problems involving a mix of discrete and continuous sizing type of design variables. Pure discrete and pure continuous variable problems can be handled as special cases. The basic mathematical programming statement of the structural synthesis problem is converted into a sequence of explicit approximate primal problems of separable form. These problems are solved by constructing continuous explicit dual functions, which are maximized subject to simple nonnegativity constraints on the dual variables. A newly devised gradient projection type of algorithm called DUAL 1, which includes special features for handling dual function gradient discontinuities that arise from the discrete primal variables, is used to find the solution of each dual problem. Computational implementation is accomplished by incorporating the DUAL 1 algorithm into the ACCESS 3 program as a new optimizer option. The power of the method set forth is demonstrated by presenting numerical results for several example problems, including a pure discrete variable treatment of a metallic swept wing and a mixed discrete-continuous variable solution for a thin delta wing with fiber composite skins.

  10. Computational simulation for analysis and synthesis of impact resilient structure

    NASA Astrophysics Data System (ADS)

    Djojodihardjo, Harijono

    2013-10-01

    Impact resilient structures are of great interest in many engineering applications varying from civil, land vehicle, aircraft and space structures, to mention a few examples. To design such structure, one has to resort fundamental principles and take into account progress in analytical and computational approaches as well as in material science and technology. With such perspectives, this work looks at a generic beam and plate structure subject to impact loading and carry out analysis and numerical simulation. The first objective of the work is to develop a computational algorithm to analyze flat plate as a generic structure subjected to impact loading for numerical simulation and parametric study. The analysis will be based on dynamic response analysis. Consideration is given to the elastic-plastic region. The second objective is to utilize the computational algorithm for direct numerical simulation, and as a parallel scheme, commercial off-the shelf numerical code is utilized for parametric study, optimization and synthesis. Through such analysis and numerical simulation, effort is devoted to arrive at an optimum configuration in terms of loading, structural dimensions, material properties and composite lay-up, among others. Results will be discussed in view of practical applications.

  11. Structure-Controlled Synthesis of Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Li, Yan

    Single-walled carbon nanotubes (SWNTs) present structure-determined outstanding properties and SWNTs with a single (n, m) type are needed in many advanced applications. However, the chirality-specific growth of SWNTs is always a great challenge. Carbon nanotubes and their caps or catalysts can all act as the structural templates to guide the formation of SWNTs with a specified chirality. SWNT growth via a catalyzed chemical vapor deposition CVD process is normally more efficient and therefore of great interest. We developed a new family of catalyst, tungsten-based intermetallic nanocrystals, to grow SWNTs with specified chiral structures. Such intermetallic nanocrystals present unique structure and atomic arrangements, which are distinctly different from the normal alloy nanoparticles or simple metal nanocrystals, therefore can act as the template to grow SWNTs with designed (n, m) structures. Using W6Co7 catalysts, we realized the selective growth of (12, 6), (16, 0), (14, 4) and other chiralities. By the cooperation of thermodynamic and kinetic factors, SWNTs with high chirality purity can be obtained. . Structure-Controlled Synthesis of Single-Walled Carbon Nanotubes.

  12. An implementation of the programming structural synthesis system (PROSSS)

    NASA Technical Reports Server (NTRS)

    Rogers, J. L., Jr.; Sobieszczanski-Sobieski, J.; Bhat, R. B.

    1981-01-01

    A particular implementation of the programming structural synthesis system (PROSSS) is described. This software system combines a state of the art optimization program, a production level structural analysis program, and user supplied, problem dependent interface programs. These programs are combined using standard command language features existing in modern computer operating systems. PROSSS is explained in general with respect to this implementation along with the steps for the preparation of the programs and input data. Each component of the system is described in detail with annotated listings for clarification. The components include options, procedures, programs and subroutines, and data files as they pertain to this implementation. An example exercising each option in this implementation to allow the user to anticipate the type of results that might be expected is presented.

  13. Synthesis and Structural Activity Relationship Study of Antitubercular Carboxamides

    PubMed Central

    Ugwu, D. I.; Ezema, B. E.; Eze, F. U.; Ugwuja, D. I.

    2014-01-01

    The unusual structure and chemical composition of the mycobacterial cell wall, the tedious duration of therapy, and resistance developed by the microorganism have made the recurrence of the disease multidrug resistance and extensive or extreme drug resistance. The prevalence of tuberculosis in synergy with HIV/AIDS epidemic augments the risk of developing the disease by 100-fold. The need to synthesize new drugs that will shorten the total duration of effective treatment and/or significantly reduce the dosage taken under DOTS supervision, improve on the treatment of multidrug-resistant tuberculosis which defies the treatment with isoniazid and rifampicin, and provide effective treatment for latent TB infections which is essential for eliminating tuberculosis prompted this review. In this review, we considered the synthesis and structure activity relationship study of carboxamide derivatives with antitubercular potential. PMID:25610646

  14. Identification of structural interface characteristics using component mode synthesis

    NASA Technical Reports Server (NTRS)

    Huckelbridge, A. A.; Lawrence, C.

    1987-01-01

    The inability to adequately model connections has limited the ability to predict overall system dynamic response. Connections between structural components are often mechanically complex and difficult to accurately model analytically. Improved analytical models for connections are needed to improve system dynamic predictions. This study explores combining Component Mode synthesis methods for coupling structural components with Parameter Identification procedures for improving the analytical modeling of the connections. Improvements in the connection properties are computed in terms of physical parameters so the physical characteristics of the connections can be better understood, in addition to providing improved input for the system model. Two sample problems, one utilizing simulated data, the other using experimental data from a rotor dynamic test rig are presented.

  15. Identification of structural interface characteristics using component mode synthesis

    NASA Technical Reports Server (NTRS)

    Huckelbridge, A. A.; Lawrence, C.

    1987-01-01

    The inability to adequately model connections has limited the ability to predict overall system dynamic response. Connections between structural components are often mechanically complex and difficult to accurately model analytically. Improved analytical models for connections are needed to improve system dynamic predictions. This study explores combining Component Mode synthesis methods for coupling structural components with Parameter Identification procedures for improving the analytical modeling of the connections. Improvements in the connection properties are computed in terms of physical parameters so the physical characteristics of the connections can be better understood, in addition to providing improved input for the system model. Two sample problems, one utilizing simulated data, the other using experimental data from a rotor dynamic test rig, are presented.

  16. Identification of structural interface characteristics using component mode synthesis

    NASA Technical Reports Server (NTRS)

    Huckelbridge, A. A.; Lawrence, C.

    1989-01-01

    The inability to adequately model connections has limited the ability to predict overall system dynamic response. Connections between structural components are often mechanically complex and difficult to accurately model analytically. Improved analytical models for connections are needed to improve system dynamic predictions. This study explores combining Component Mode synthesis methods for coupling structural components with Parameter Identification procedures for improving the analytical modeling of the connections. Improvements in the connection properties are computed in terms of physical parameters so the physical characteristics of the connections can be better understood, in addition to providing improved input for the system model. Two sample problems, one utilizing simulated data, the other using experimental data from a rotor dynamic test rig, are presented.

  17. Versatile hydrothermal synthesis of one-dimensional composite structures

    NASA Astrophysics Data System (ADS)

    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.

  18. ACCESS computer program for the synthesis of large structural systems

    NASA Technical Reports Server (NTRS)

    Fleury, C.; Ramanathan, R. K.; Salama, M.; Schmit, L. A., Jr.

    1982-01-01

    The structural-synthesis computer code ACCESS-3, originally limited to the optimization of relatively simple problems involving truss, membrane, and shear panel elements, has been restructured to make it applicable to structures with a larger number of degrees-of-freedom, design variables, and constraints. The modifications made allow the use of six degrees-of-freedom per node and permit the out-of-core solution of large matrix equations encountered at the analysis stage. Also, finite elements which permit pure bending as well as combined bending and membrane (axial) behavior have been added to satisfy the need for a more comprehensive set of elements. Like its predecessor, the new version of the program combines the approximation concepts with primal or dual formulations to provide an efficient optimization tool.

  19. Dual methods and approximation concepts in structural synthesis

    NASA Technical Reports Server (NTRS)

    Fleury, C.; Schmit, L. A., Jr.

    1980-01-01

    Approximation concepts and dual method algorithms are combined to create a method for minimum weight design of structural systems. Approximation concepts convert the basic mathematical programming statement of the structural synthesis problem into a sequence of explicit primal problems of separable form. These problems are solved by constructing explicit dual functions, which are maximized subject to nonnegativity constraints on the dual variables. It is shown that the joining together of approximation concepts and dual methods can be viewed as a generalized optimality criteria approach. The dual method is successfully extended to deal with pure discrete and mixed continuous-discrete design variable problems. The power of the method presented is illustrated with numerical results for example problems, including a metallic swept wing and a thin delta wing with fiber composite skins.

  20. Shock wave synthesis of aluminium nitride with rocksalt structure

    NASA Astrophysics Data System (ADS)

    Keller, K.; Schlothauer, T.; Schwarz, M.; Heide, G.; Kroke, E.

    2012-03-01

    The high pressure phase of aluminium nitride with rocksalt structure (rs) is a ceramic with high potential and a challenging material to investigate. The rs-AlN was synthesised and recovered by shock wave experiments using the flyer-plate method with multiple reflections at peak pressures between 15 and 43 GPa. Successful syntheses were carried out using AlN nanopowder with ambient pressure wurtzite structure (w-AlN) as starting material. The high pressure modification could, however, not be obtained when starting from submicron w-AlN. The recovery of rs-AlN is sensitive to the synthesis conditions as these influence the reconversion of rs-AlN to w-AlN.

  1. Hydrothermal synthesis as a route to mineralogically-inspired structures.

    PubMed

    McMillen, Colin D; Kolis, Joseph W

    2016-02-21

    The use of high temperature hydrothermal reactions to prepare crystals having mineralogically-related structures is described. Complex naturally occurring minerals can have fascinating structures and exhibit important features like low dimensionality, noncentrosymmetry, or ion channels that can provide excellent guideposts for the designed synthesis of new materials. Actual minerals, even though they may have intriguing physical properties, are often unsuitable for study because of the persistent impurities inevitably present in natural samples. Hydrothermal fluids at relatively high temperatures provide access to large, high quality single crystals of structures with mineral-like structures. This enables the study of physical properties like ionic conduction, magnetic spin frustration and non-linear optical behavior. Some fundamental considerations of the hydrothermal technique are discussed in the context of synthesizing mineralogically-inspired materials. The metal vanadates provide a surprisingly rich and diversified range of compounds and are selected to illustrate many of the concepts described here. A series of low dimensional mineral analogs featuring isolated units, chains, and layers have been prepared in the laboratory as large single crystals using a high temperature hydrothermal synthetic methods, and their physical properties are under investigation. The metal silicates are also highlighted as another promising field of exploration, since their hydrothermal synthesis surprisingly lags behind the enormous literature of the natural silicate minerals. The introduction of heteroelements, such as boron to make borosilicates, appears to also open the door to additional new materials. Many of these new materials have direct equivalents in the mineral kingdom, while others have no known analogs but are reminiscent of minerals and can be classified in the same ways. From these initial results there appears to be a very rich vein of synthetic minerals waiting

  2. Synthesis, structure and phase behavior of liquid crystalline polyurethanes

    SciTech Connect

    Papadimitrakopoulos, F.

    1993-01-01

    This dissertation describes the synthesis, structure and phase behavior of polyurethanes based on the mesogenic biphenol 4,4'-bis (6-hydroxyhexoxy)biphenyl (BHHBP) and meta substituted tolylene/phenylene diisocynates. The structure-property relationships were determined as a function of hydrogen-bonding, the position of the methyl group in the tolylene diisocyanate moiety (TDI) and the biphenol moiety. The liquid crystalline phase (mesophase) and crystalline phase were investigated primarily with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and infrared spectroscopy. The influence of H-bonding on the structure and phase behavior of 1,4-LCPU-6 was determined by the synthesis of high molecular weight N-Methyl2,4-LCPU-65, using a novel high temperature polymerization of a biscarbamoyl chloride with the BHHBP mesogenic diol. In contrast to the regular ([alpha], [omega]-hexane diol) based polyurethanes (PUs), BHHBP derived polyurethanes (LCPUs) crystallize rapidly from their melts. Hexafluoroisopropanol fast solvent-evaporation casting or rapid cooling from the melt resulted in thin films or bulk samples with a glassy mesophase morphology. During the subsequent heating scan, the mesophase to crystal transition occurs. Highly oriented fibers were obtained for the mesogenic polyurethanes. Atomistic molecular simulations coupled with X-ray intensity refinement allowed determination of the crystalline chain conformation and packing characteristics for the 2,6-LCPU-6 and 1,3-LCPU-6 (2,6-TDI and 1,3-Phenylene Diisocynate (1,3-PDI) derived LCPUs). On the basis of structural similarity and well resolved WAXS powder patterns similar analysis was extended to the regular polyurethanes as well (2,6-PU-6 and 1,3-PU-6). The good correlation polymers suggest that melting is primarily controlled by the dissociation of H-bonds in the ordered domains.

  3. Planning and Revising Written Arguments: The Effects of Two Text Structure-Based Interventions on Persuasiveness of 8th-Grade Students' Essays

    ERIC Educational Resources Information Center

    Midgette, Ekaterina; Haria, Priti

    2016-01-01

    The purpose of the study was to investigate the effects of two comprehensive argumentative writing interventions--Text Structure Instruction (TSI) and Text Structure Revision Instruction (TSRI)--on the eighth-grade students' ability to compose convincing essays that include structural elements of argumentative discourse. Both treatment groups…

  4. Synthesis and photocatalytic activity of titania microspheres with hierarchical structures

    SciTech Connect

    Cheng, Qian-Qian; Cao, Ying; Yang, Lin; Zhang, Pei-Pei; Wang, Kui; Wang, Hua-Jie

    2011-03-15

    Research highlights: {yields} Lauryl alcohol directs the formation of titania with hierarchical structures. {yields} Hierarchical structures endow the higher specific area to titania. {yields} Titania had a higher photocatalytic activity than commercial Degussa P25. {yields} The synthesis process of the target product is low-cost. -- Abstract: A combined sol-gel and solvothermal process was introduced to fabricate the titania microspheres with hierarchical structures by using lauryl alcohol as the structure-directing agent. Scanning electron microscope, high-resolution transmission electron microscope, Fourier transform infrared spectrograph and powder X-ray powder diffraction indicated that the molar ratio of lauryl alcohol, water and tetra-n-butyl titanate was the key factor for the formation of the mono-dispersed titania with anatase phase and the optimal ratio was 1.2:4:1. The diameter of the end-product was 523 {+-} 74 nm and it was composed of smaller nanoparticles with about 6.8 nm size in diameter. Photocatalytic activity of the end-product was investigated by employing Rhodamine B and Methylene blue as the model compounds. The target microspheres exhibited the higher photocatalytic efficiency compared with commercial Degussa P25 titania and this result might be due to the hierarchical structures of microspheres according to the analysis of Brunauer-Emmett-Teller specific surface areas.

  5. Synthesis, structure and bonding of hexaphenyl thorium(IV): observation of a non-octahedral structure.

    PubMed

    Pedrick, Elizabeth A; Hrobárik, Peter; Seaman, Lani A; Wu, Guang; Hayton, Trevor W

    2016-01-14

    We report herein the synthesis of the first structurally characterized homoleptic actinide aryl complexes, [Li(DME)3]2[Th(C6H5)6] (1) and [Li(THF)(12-crown-4)]2[Th(C6H5)6] (2), which feature an anion possessing a regular octahedral (1) or a severely distorted octahedral (2) geometry. The solid-state structure of 2 suggests the presence of pseudo-agostic ortho C-H···Th interactions, which arise from σ(C-H) → Th(5f) donation. The non-octahedral structure is also favoured in solution at low temperatures. PMID:26569166

  6. Alphavirus RNA synthesis and non-structural protein functions

    PubMed Central

    Rupp, Jonathan C.; Sokoloski, Kevin J.; Gebhart, Natasha N.

    2015-01-01

    The members of the genus Alphavirus are positive-sense RNA viruses, which are predominantly transmitted to vertebrates by a mosquito vector. Alphavirus disease in humans can be severely debilitating, and depending on the particular viral species, infection may result in encephalitis and possibly death. In recent years, alphaviruses have received significant attention from public health authorities as a consequence of the dramatic emergence of chikungunya virus in the Indian Ocean islands and the Caribbean. Currently, no safe, approved or effective vaccine or antiviral intervention exists for human alphavirus infection. The molecular biology of alphavirus RNA synthesis has been well studied in a few species of the genus and represents a general target for antiviral drug development. This review describes what is currently understood about the regulation of alphavirus RNA synthesis, the roles of the viral non-structural proteins in this process and the functions of cis-acting RNA elements in replication, and points to open questions within the field. PMID:26219641

  7. Graphene Oxide: Synthesis, Characterization, Electronic Structure, and Applications

    NASA Astrophysics Data System (ADS)

    Stewart, Derek A.; Mkhoyan, K. Andre

    While graphite oxide was first identified in 1855 [1, 2], the recent discovery of stable graphene sheets has led to renewed interest in the chemical structure and potential applications of graphene oxide sheets. These structures have several physical properties that could aid in the large scale development of a graphene electronics industry. Depending on the degree of oxidization, graphene oxide layers can be either semiconducting or insulating and provide an important complement to metallic graphene layers. In addition, the electronic and optical properties of these films can be controlled by the selective removal or addition of oxygen. For example, selective oxidationof graphene sheets could lead to electronic circuit fabrication on the scale of a single atomic layer. Graphene oxide is also dispersible in water and other solvents and this provides a facile route for graphene deposition on a wide range of substrates for macroelectronics applications. Although graphite oxide has been known for roughly 150 years, key questions remain in regards to its chemical structure, electronic properties, and fabrication. Answering these issues has taken on special urgency with the development of graphene electronics. In this chapter, we will provide an overview of the field with special focus on synthesis, characterization, and first principles analysis of bonding and electronic structures. Finally, we will also address some of the most promising applications for graphene oxide in electronics and other industries.

  8. Structural analogues of diosgenyl saponins: synthesis and anticancer activity.

    PubMed

    Kaskiw, Matthew J; Tassotto, Mary Lynn; Mok, Mac; Tokar, Stacey L; Pycko, Roxanne; Th'ng, John; Jiang, Zi-Hua

    2009-11-15

    Saponins display various biological activities including anti-tumor activity. Recently intensive research has been focused on developing saponins for tumor therapies. The diosgenyl saponin dioscin is one of the most common steroidal saponins and exhibits potent anticancer activity in several human cancer cells through apoptosis-inducing pathways. In this paper, we describe the synthesis of several diosgenyl saponin analogues containing either a 2-amino-2-deoxy-beta-d-glucopyranosyl residue or an alpha-l-rhamnopyranosyl-(1-->4)-2-amino-2-deoxy-beta-d-glucopyranosyl residue with different acyl substituents on the amino group. The cytotoxic activity of these compounds was evaluated in MCF-7 breast cancer cells and HeLa cervical cancer cells. Structure-activity relationship studies show that the disaccharide saponin analogues are in general less active than their corresponding monosaccharide analogues. The incorporation of an aromatic nitro functionality into these saponin analogues does not exhibit significant effect on their cytotoxic activity. PMID:19819703

  9. Revision of the design manual Structures to Resist the Effects of Accidental Explosions (TM 5-1300, NAVFAC P-397, AFM 88-22)

    NASA Astrophysics Data System (ADS)

    Caltagirone, J.; Castellano, A.; Dede, M.; Dobbs, N.

    1984-08-01

    Procedures for structures designed to resist the effects of a high energy (HE) type explosions are presently available in the Tri-Service Design Manual Structures to Resist the Effects of Accidental Explosions. However, these procedures are limited to reinforced concrete structures. Since its original publication, a considerable amount of data has been generated which brought about the requirement to revise existing procedures in the manual and incorporate new data. The format of the revised manual is described and a discussion on the contents of each of the six volumes, including the improvements made to the existing manual is given.

  10. Synthesis, structure and magnetism in copper chalcochromite spinels

    NASA Astrophysics Data System (ADS)

    Neulinger, Janell Rebecca

    The copper chalcochromites (CuCr2X4 (X = S, Se, Te)) possess a rare combination of magnetic and electronic properties compared to other chalcogenide spinet materials. A precise structural and magnetic investigation of these materials was undertaken in order to facilitate technological exploitation of these unusual properties. CuCr2Se4, several halogenated derivatives of the form CuCr2Se4 -xXx (with X = Cl, Br, or I), and CuCr2S3Cl were prepared via powder methods and chemical vapor transport growth of single crystals. A variety of X-ray diffraction techniques were employed to determine the crystal structures of the synthesis products. The materials adopt a trigonal variation of the spinet structure type; the lower-symmetry structure includes a single threefold roto-inversion axis. Halogen doping introduces systematic changes in the properties of the chalcochromites, and the effects of halogen doping were monitored by magnetometry, soft X-ray spectroscopy, and magnetic microscopy techniques. Bulk magnetic properties were characterized by SQUID and vibrating sample magnetometry, at temperatures from 5 K to above the Curie temperatures. Soft X-ray spectroscopic measurements performed at the Advanced Light Source at Lawrence Berkeley National Laboratory included X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) experiments. Dichroic spectra at the Cr L2,3 and Cu L 2,3 absorption edges confirm a ferrimagnetic model of opposing magnetic sub-lattices localized on the Cr and Cu centers; increasing levels of halogen doping suppress the contribution from the copper sublattice and reduce T C. Magnetic domain imaging using the Photoelectron Electron Microscope (PEEM) at the Advanced Light Source indicates the presence of a variety of domain morphologies, including predominantly stripe domains reflecting the uniaxial symmetry of the trigonal spinel structure. The magnetic and structural features of the copper chalcochromites mark them as robust, tunable, and

  11. A new structural analysis/synthesis capability - ACCESS. [Approximation Concepts Code for Efficient Structural Synthesis

    NASA Technical Reports Server (NTRS)

    Schmit, L. A.; Miura, H.

    1975-01-01

    The creation of an efficient automated capability for minimum weight design of structures is reported. The ACCESS 1 computer program combines finite element analysis techniques and mathematical programming algorithms using an innovative collection of approximation concepts. Design variable linking, constraint deletion techniques and approximate analysis methods are used to generate a sequence of small explicit mathematical programming problems which retain the essential features of the design problem. Organization of the finite element analysis is carefully matched to the design optimization task. The efficiency of the ACCESS 1 program is demonstrated by giving results for several example problems.

  12. Amphidinolide B: Total Synthesis, Structural Investigation and Biological Evaluation

    PubMed Central

    Lu, Liang; Zhang, Wei; Nam, Sangkil; Horne, David A.; Jove, Richard

    2013-01-01

    The total synthesis of amphidinolide B1 and the proposed structure of amphidinolide B2 has been accomplished. Key aspects of this work include the development of a practical, non-transition metal mediated method for the construction of the C13-C15 diene, the identification of α-chelation and dipole minimization models for diastereoselective methyl ketone aldol reactions, the discovery of a spontaneous Horner-Wadsworth-Emmons macrocyclization strategy and the development of a novel late stage method for construction of an allylic epoxide moiety. The originally proposed structure for amphidinolide B2 and diastereomers thereof display potent anti-tumor activities with IC50 values ranging from 3.3 nM to 94.5 nM against human solid and blood tumor cells. Of the different stereoisomers, the proposed structure of amphidinolide B2 is over 12-fold more potent than the C8,9-epimer and C18-epimer in human DU145 prostate cancer cells. These data suggest that the epoxide stereochemistry is a significant factor for anticancer activity. PMID:23406192

  13. Synthesis, base pairing and structure studies of geranylated RNA.

    PubMed

    Wang, Rui; Vangaveti, Sweta; Ranganathan, Srivathsan V; Basanta-Sanchez, Maria; Haruehanroengra, Phensinee; Chen, Alan; Sheng, Jia

    2016-07-27

    Natural RNAs utilize extensive chemical modifications to diversify their structures and functions. 2-Thiouridine geranylation is a special hydrophobic tRNA modification that has been discovered very recently in several bacteria, such as Escherichia coli, Enterobacter aerogenes, Pseudomonas aeruginosa and Salmonella Typhimurium The geranylated residues are located in the first anticodon position of tRNAs specific for lysine, glutamine and glutamic acid. This big hydrophobic terpene functional group affects the codon recognition patterns and reduces frameshifting errors during translation. We aimed to systematically study the structure, function and biosynthesis mechanism of this geranylation pathway, as well as answer the question of why nature uses such a hydrophobic modification in hydrophilic RNA systems. Recently, we have synthesized the deoxy-analog of S-geranyluridine and showed the geranylated T-G pair is much stronger than the geranylated T-A pair and other mismatched pairs in the B-form DNA duplex context, which is consistent with the observation that the geranylated tRNA(Glu) UUC recognizes GAG more efficiently than GAA. In this manuscript we report the synthesis and base pairing specificity studies of geranylated RNA oligos. We also report extensive molecular simulation studies to explore the structural features of the geranyl group in the context of A-form RNA and its effect on codon-anticodon interaction during ribosome binding. PMID:27307604

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

    NASA Astrophysics Data System (ADS)

    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

  15. Fluorinated proteins: from design and synthesis to structure and stability.

    PubMed

    Marsh, E Neil G

    2014-10-21

    Fluorine is all but absent from biology; however, it has proved to be a remarkably useful element with which to modulate the activity of biological molecules and to study their mechanism of action. Our laboratory's interest in incorporating fluorine into proteins was stimulated by the unusual physicochemical properties exhibited by perfluorinated small molecules. These include extreme chemical inertness and thermal stability, properties that have made them valuable as nonstick coatings and fire retardants. Fluorocarbons also exhibit an unusual propensity to phase segregation. This phenomenon, which has been termed the "fluorous effect", has been effectively exploited in organic synthesis to purify compounds from reaction mixtures by extracting fluorocarbon-tagged molecules into fluorocarbon solvents. As biochemists, we were curious to explore whether the unusual physicochemical properties of perfluorocarbons could be engineered into proteins. To do this, we developed a synthesis of a highly fluorinated amino acid, hexafluoroleucine, and designed a model 4-helix bundle protein, α4H, in which the hydrophobic core was packed exclusively with leucine. We then investigated the effects of repacking the hydrophobic core of α4H with various combinations of leucine and hexafluoroleucine. These initial studies demonstrated that fluorination is a general and effective strategy for enhancing the stability of proteins against chemical and thermal denaturation and proteolytic degradation. We had originally envisaged that the "fluorous interactions", postulated from the self-segregating properties of fluorous solvents, might be used to mediate specific protein-protein interactions orthogonal to those of natural proteins. However, various lines of evidence indicate that no special, favorable fluorine-fluorine interactions occur in the core of the fluorinated α4 protein. This makes it unlikely that fluorinated amino acids can be used to direct protein-protein interactions. More

  16. Factor Structure and Reliability of the Revised Conflict Tactics Scales' (CTS2) 10-Factor Model in a Community-Based Female Sample

    ERIC Educational Resources Information Center

    Yun, Sung Hyun

    2011-01-01

    The present study investigated the factor structure and reliability of the revised Conflict Tactics Scales' (CTS2) 10-factor model in a community-based female sample (N = 261). The underlying factor structure of the 10-factor model was tested by the confirmatory multiple group factor analysis, which demonstrated complex factor cross-loadings…

  17. New C20-diterpenoid alkaloids from Aconitum vilmorrianum and structural revision of 2-O-acetylorochrine and orochrine.

    PubMed

    Tang, Tian-Xing; Chen, Qi-Feng; Liu, Xiao-Yu; Jian, Xi-Xian; Wang, Feng-Peng

    2016-04-01

    Three new C20-diterpenoid alkaloids vilmorrianines E (1), F (2), and G (3) were isolated from the whole plants of Aconitum vilmorrianum, along with one artifact N-chloromethyl vilmorrianine E hydrochloride (4), as well as two known alkaloids hemsleyaconitines F (5) and G (6). The structures of 1-4 were established by HR-ESI-MS, 1D-, 2D-NMR (HMQC, HMBC, and NOESY), and single-crystal X-ray diffraction analysis. In addition, the structures of naturally occurring 2-O-acetylorochrine (7) and orochrine (8) were revised to be the known alkaloids heterophylloidine (9) and deacetyl heterophylloidine (10), respectively, on the basis of consideration of transannular effect and chemical correlations. PMID:26479584

  18. Synthesis and structure of nanocrystalline mixed Ce–Yb silicates

    SciTech Connect

    Małecka, Małgorzata A. Kępiński, Leszek

    2013-07-15

    Graphical abstract: - Highlights: • New method of synthesis of nanocrystalline mixed lanthanide silicates is proposed. • Formation of A-type (Ce{sub 1−y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} in well dispersed Ce{sub 1−x}Yb{sub x}O{sub 2−(x/2)}–SiO{sub 2} system. • Formation of Yb{sub y}Ce{sub 9.33−y}(SiO{sub 4}){sub 6}O{sub 2} in agglomerated Ce{sub 1−x}Yb{sub x}O{sub 2−(x/2)}–SiO{sub 2} system. - Abstract: This work presents results of studies on synthesis and structure of mixed, nanocrystalline Ce–Yb silicates. Using TEM, XRD and FTIR we showed that heat treatment of nanocrystalline Ce{sub 1−x}Yb{sub x}O{sub 2−(x/2)} (x = 0.3, 0.5) mixed oxide supported on amorphous silica in reducing atmosphere, results in formation of Ce–Yb mixed silicates. Dispersion of the oxide on the silica surface and thus a local lanthanide/Si atomic ratio determines the stoichiometry of the silicate. Oxide crystallites uniformly dispersed on the silica surface transformed into A-(Ce{sub 1−y}Yb{sub y}){sub 2}Si{sub 2}O{sub 7} disilicate, while the agglomerated nanoparticles converted into Yb{sub y}Ce{sub 9.33−y}(SiO{sub 4}){sub 6}O{sub 2} oxyapatite silicate as an intermediate phase.

  19. Topology synthesis and size optimization of morphing wing structures

    NASA Astrophysics Data System (ADS)

    Inoyama, Daisaku

    This research demonstrates a novel topology and size optimization methodology for synthesis of distributed actuation systems with specific applications to morphing air vehicle structures. The main emphasis is placed on the topology and size optimization problem formulations and the development of computational modeling concepts. The analysis model is developed to meet several important criteria: It must allow a rigid-body displacement, as well as a variation in planform area, with minimum strain on structural members while retaining acceptable numerical stability for finite element analysis. Topology optimization is performed on a semi-ground structure with design variables that control the system configuration. In effect, the optimization process assigns morphing members as "soft" elements, non-morphing load-bearing members as "stiff' elements, and non-existent members as "voids." The optimization process also determines the optimum actuator placement, where each actuator is represented computationally by equal and opposite nodal forces with soft axial stiffness. In addition, the configuration of attachments that connect the morphing structure to a non-morphing structure is determined simultaneously. Several different optimization problem formulations are investigated to understand their potential benefits in solution quality, as well as meaningfulness of the formulations. Extensions and enhancements to the initial concept and problem formulations are made to accommodate multiple-configuration definitions. In addition, the principal issues on the external-load dependency and the reversibility of a design, as well as the appropriate selection of a reference configuration, are addressed in the research. The methodology to control actuator distributions and concentrations is also discussed. Finally, the strategy to transfer the topology solution to the sizing optimization is developed and cross-sectional areas of existent structural members are optimized under

  20. High octane ethers from synthesis gas-derived alcohols. Quarterly technical progress report, October--December 1992, Revision 1

    SciTech Connect

    Klier, K.; Herman, R.G.; Johansson, M.A.; Feeley, O.C.

    1993-04-01

    The objective of the proposed research is to synthesize high octane ethers, primarily methyl isobutyl ether (MIBE) and methyl tertiary butyl ether (MTBE) directly from H{sub 2}/CO/CO{sub 2} coal-derived synthesis gas via alcohol mixtures that are rich in methanol and 2-methyl-l-propanol (isobutanol). The overall scheme involves gasification of coal, purification and shifting of the synthesis gas, higher alcohol synthesis, and direct synthesis of ethers. The testing of strongly acidic catalysts for the conversion of a mixture of methanol and isobutanol to ethers and hydrocarbons was continued. Under standardized test conditions the catalysts tested this quarter were: phosphotungstic acid supported on zirconia (PW{sub 12}/ZrO{sub 2}), ``niobic acid`` (Nb{sub 2}O{sub 5}{center_dot}xH{sub 2}O), and an iron and manganese doped sulfate-modified zirconia (Fe/Mn/ZrO{sub 2}/SO{sub 4}{sup 2{minus}}). The overall activity of these catalysts followed the order of Fe/Mn/ZrO{sub 2}/SO{sub 4}{sup 2{minus}} > PW{sub 12}/ZrO{sub 2} >Nb{sub 2}O{sub 5}{center_dot}xH{sub 2}O With the Fe/Mn/ZrO{sub 2}/SO{sub 4}{sup 2{minus}} catalyst approaching ZrO{sub 2}/SO{sub 4}{sup 2{minus}} in both activity and selectivity for isobutene production. The effect of the presence of water on the reaction of methanol and isobutanol over ZrO{sub 2}/SO{sub 4}{sup 2{minus}} was determined to be insignificant under the reaction conditions investigated.

  1. Lanthanide Ion Doped Upconverting Nanoparticles: Synthesis, Structure and Properties.

    PubMed

    Yan, Chenglin; Zhao, Haiguang; Perepichka, Dmitrii F; Rosei, Federico

    2016-08-01

    Lanthanide doped upconverting nanoparticles (UCNPs) have emerged as a new class of luminescent materials, with major discoveries and overall significant progress during the last decade. Unlike multiphoton absorption in organic dyes or semiconductor quantum dots, lanthanide doped UCNPs involve real intermediate quantum states and convert infrared (IR) into visible light via sequential electronic excitation. The relatively high efficiency of this process even at low radiation flux makes UCNPs particularly attractive for many current and emerging areas of technology. The aim of this article is to highlight several recent advances in this rapidly growing field, emphasizing the relationships between structure and properties of UCNPs. Additionally, various strategies developed for the synthesis of UCNPs with a focus on the various synthetic approaches that yield high-quality monodisperse samples with controlled size, shape and crystalline phase are reviewed. Emerging synthetic approaches towards designed structure to improve the optical and electronic properties of UCNPs are discussed. Finally, recent examples of applications of UCNPs in biomedical and optoelectronics research, giving our own perspectives on future directions and emerging possibilities of the field are described. PMID:27345736

  2. Xylonucleic acid: synthesis, structure, and orthogonal pairing properties

    PubMed Central

    Maiti, Mohitosh; Maiti, Munmun; Knies, Christine; Dumbre, Shrinivas; Lescrinier, Eveline; Rosemeyer, Helmut; Ceulemans, Arnout; Herdewijn, Piet

    2015-01-01

    There is a common interest for studying xeno-nucleic acid systems in the fields of synthetic biology and the origin of life, in particular, those with an engineered backbone and possessing novel properties. Along this line, we have investigated xylonucleic acid (XyloNA) containing a potentially prebiotic xylose sugar (a 3′-epimer of ribose) in its backbone. Herein, we report for the first time the synthesis of four XyloNA nucleotide building blocks and the assembly of XyloNA oligonucleotides containing all the natural nucleobases. A detailed investigation of pairing and structural properties of XyloNAs in comparison to DNA/RNA has been performed by thermal UV-melting, CD, and solution state NMR spectroscopic studies. XyloNA has been shown to be an orthogonal self-pairing system which adopts a slightly right-handed extended helical geometry. Our study on one hand, provides understanding for superior structure-function (-pairing) properties of DNA/RNA over XyloNA for selection as an informational polymer in the prebiotic context, while on the other hand, finds potential of XyloNA as an orthogonal genetic system for application in synthetic biology. PMID:26175047

  3. Thioanalogues of N-1-methylanabasine and nicotine - Synthesis and structure

    NASA Astrophysics Data System (ADS)

    Wojciechowska-Nowak, Marzena; Boczoń, Władysław; Warżajtis, Beata; Rychlewska, Urszula; Jasiewicz, Beata

    2011-03-01

    The synthesis, spectral characteristics and structures of N-1-methyl-6-(pyridin-3-yl)piperidine-2-thione ( 1) (thioanalogue of N-1-methylanabasine) and N-1-methyl-(5-pyridin-3-yl)pyrrolidine-2-thione ( 2) (thioanalogue of nicotine) are reported. Both compounds were obtained using Lawesson's reagent. The structures of compounds 1 and 2 are confirmed by NMR, IR, UV and mass spectroscopy, as well as, by X-ray diffraction analysis. Pyridine ring of compound 1 adopts a pseudo-axial orientation in solution, as well as in a solid state. A substantial lengthening of the C dbnd S bond in the crystals of 1 is interpreted as a sign of an enhanced electron delocalization within the thiolactam group due to the presence of several C sbnd H groups in the nearest vicinity of the sulfur atom. In the crystals of 2, which differ from 1 in that the relatively puckered piperidine-2-thione moiety is replaced by the flat pyrrolidine-2-thione ring, no short CH⋯S( dbnd C) contacts are observed. Instead, the packing is governed by stacking interactions between pyridine rings. The pyrrolidine and pyridine rings in 2 are nearly perpendicular to each other and the pyrrolidine moiety adopts a flattened half-chair conformation.

  4. Synthesis and structure-activity relationships of neuromuscular blocking agents.

    PubMed

    Tuba, Zoltan; Maho, Sandor; Vizi, E Sylvester

    2002-08-01

    The first use of neuromuscular blocking agents (muscle relaxants) in clinical practice (1942) revolutionised the practice of anaesthesia and started the modern era of surgery. Since 1942 introduction of tubocurarine (18) neuromuscular blocking agents have been used routinely to provide skeletal muscle relaxation during surgical procedures allowing access to body cavities without hindrance from voluntary or reflex muscle movement. After the introduction of tubocurarine and the depolarizing suxamethonium chloride (4) (1949) several nondepolarizing steroidal and nonsteroidal neuromuscular blocking agents with different onset time and duration of effect were introduced e.g. gallamine triethiodide (1) (1949), methocurine (2) (1949), alcuronium chloride (3) (1963), pancuronium bromide (9) (1968), vecuronium bromide (11) (1982), pipecuronium bromide (10) (1982), atracurium besylate (5) (1982), doxacurium chloride (6) (1991), mivacurium chloride (8) (1992), rocuronium bromide (12) (1994) cisatracurium besylate (7) (1996), and rapacuronium bromide (13) (2000). SZ 1677 (14) a steroid type nondepolarizing neuromuscular blocking agent under development (preclinical phase). This review article deals with a comprehensive survey of the progress in chemical, pharmacological and, in some respects, of clinical studies of neuromuscular blocking agents used in the clinical practice and under development, including the synthesis, structure elucidation, pharmacological actions, structure activity relationships studies of steroidal and nonsteroidal derivatives. PMID:12171561

  5. Resonant active sites in catalytic ammonia synthesis: A structural model

    NASA Astrophysics Data System (ADS)

    Cholach, Alexander R.; Bryliakova, Anna A.; Matveev, Andrey V.; Bulgakov, Nikolai N.

    2016-03-01

    Adsorption sites Mn consisted of n adjacent atoms M, each bound to the adsorbed species, are considered within a realistic model. The sum of bonds Σ lost by atoms in a site in comparison with the bulk atoms was used for evaluation of the local surface imperfection, while the reaction enthalpy at that site was used as a measure of activity. The comparative study of Mn sites (n = 1-5) at basal planes of Pt, Rh, Ir, Fe, Re and Ru with respect to heat of N2 dissociative adsorption QN and heat of Nad + Had → NHad reaction QNH was performed using semi-empirical calculations. Linear QN(Σ) increase and QNH(Σ) decrease allowed to specify the resonant Σ for each surface in catalytic ammonia synthesis at equilibrium Nad coverage. Optimal Σ are realizable for Ru2, Re2 and Ir4 only, whereas other centers meet steric inhibition or unreal crystal structure. Relative activity of the most active sites in proportion 5.0 × 10- 5: 4.5 × 10- 3: 1: 2.5: 3.0: 1080: 2270 for a sequence of Pt4, Rh4, Fe4(fcc), Ir4, Fe2-5(bcc), Ru2, Re2, respectively, is in agreement with relevant experimental data. Similar approach can be applied to other adsorption or catalytic processes exhibiting structure sensitivity.

  6. Recent Research Trends on the Enzymatic Synthesis of Structured Lipids.

    PubMed

    Kim, Byung Hee; Akoh, Casimir C

    2015-08-01

    Structured lipids (SLs) are lipids that have been chemically or enzymatically modified from their natural biosynthetic form. Because SLs are made to possess desired nutritional, physicochemical, or textural properties for various applications in the food industry, many research activities have been aimed at their commercialization. The production of SLs by enzymatic procedures has a great potential in the future market because of the specificity of lipases and phospholipases used as the biocatalysts. The aim of this review is to provide concise information on the recent research trends on the enzymatic synthesis of SLs of commercial interest, such as medium- and long-chain triacylglycerols, human milk fat substitutes, cocoa butter equivalents, trans-free or low-trans plastic fats (such as margarines and shortenings), low-calorie fats/oils, health-beneficial fatty acid-rich fats/oils, mono- or diacylglycerols, and structurally modified phospholipids. This limited review covers 108 research articles published between 2010 and 2014 which were searched in Web of Science. PMID:26189491

  7. Synthesis of ultrasmall platinum nanoparticles and structural relaxation.

    PubMed

    Liu, Chao; Li, Gao; Kauffman, Douglas R; Pang, Guangsheng; Jin, Rongchao

    2014-06-01

    We report the synthesis of ligand-protected, ultrasmall Pt nanoparticles of ∼1 nm size via a one-phase wet chemical method. Using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), we determined the mass of the nanoparticles to be ∼8 kDa. Characterization of the Pt nanoparticles was further carried out by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), optical absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS). Interestingly, we observed a large structural relaxation in the 8kDa nanoparticles (i.e. lattice parameter elongation by +10%) compared to bulk platinum. XPS analysis revealed a positive shift of Pt 4f core level energy by approximately +1 eV compared with bulk Pt, indicating charge transfer from Pt to S atom of the thiolate ligand on the particle. Compared to bulk Pt, the 5d band of Pt nanoparticles is narrower and shifts to higher binding energy. Overall, the ∼1 nm ultrasmall Pt nanoparticles exhibit quite distinct differences in electronic and structural properties compared to their larger counterparts and bulk Pt. PMID:24703677

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

    NASA Astrophysics Data System (ADS)

    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.

  9. On the proposed structures and stereocontrolled synthesis of the cephalosporolides

    PubMed Central

    Tlais, Sami F

    2012-01-01

    Summary The synthesis of four candidate stereoisomers of cephalosporolide H is described, made possible by a zinc-chelation strategy for controlling the stereochemistry of oxygenated 5,5-spiroketals. The same strategy likewise enables the first stereocontrolled synthesis of cephalosporolide E, which is typically isolated and prepared admixed with its spiroketal epimer, cephalosporolide F. PMID:23019461

  10. The Infant Behavior Questionnaire-Revised: Factor structure in a culturally and sociodemographically diverse sample in the United States.

    PubMed

    Bosquet Enlow, Michelle; White, Matthew T; Hails, Katherine; Cabrera, Ivan; Wright, Rosalind J

    2016-05-01

    The recommended factor structure for the Infant Behavior Questionnaire-Revised (IBQ-R), a widely used parent-report measure of infant temperament, has limited empirical support. Moreover, the recommended factors were developed using homogenous samples not representative of current United States (U.S.) sociodemographics. The objective of this study was to examine the factor structure of the IBQ-R in a culturally and sociodemographically diverse U.S. cohort (N=380 mother-infant dyads). Mothers were assessed during pregnancy on a range of cultural and sociodemographic characteristics and completed the IBQ-R when their infants were 6 months of age. The sample was diverse on maternal marital status, educational attainment, household income, race/ethnicity, primary language spoken, and country of birth. Initial confirmatory factor analysis for the recommended three-factor model yielded a poor fit. Modifications employed in other studies failed to improve model fit. An exploratory factor analysis revealed an acceptable model fit for a three-factor solution that showed similarities to as well as differences from the originally proposed factor structure. Additional analyses suggested lack of invariance on several factor and scale scores by maternal country of birth, race/ethnicity, and household income. The findings suggest that the commonly used IBQ-R factor structure may need to be adjusted for diverse samples and deserves further study. PMID:27088863

  11. Inositolphosphoglycan mediators structurally related to glycosyl phosphatidylinositol anchors: synthesis, structure and biological activity.

    PubMed

    Martín-Lomas, M; Khiar, N; García, S; Koessler, J L; Nieto, P M; Rademacher, T W

    2000-10-01

    The preparation of the pseudopentasaccharide 1a, an inositol-phosphoglycan (IPG) that contains the conserved linear structure of glycosyl phosphatidylinositol anchors (GPI anchors), was carried out by using a highly convergent 2+3-block synthesis approach which involves imidate and sulfoxide glycosylation reactions. The preferred solution conformation of this structure was determined by using NMR spectroscopy and molecular dynamics simulations prior to carrying out quantitative structure--activity relationship studies in connection with the insulin signalling process. The ability of 1a to stimulate lipogenesis in rat adipocytes as well as to inhibit cAMP dependent protein kinase and to activate pyruvate dehydrogenase phosphatase was investigated. Compound 1a did not show any significant activity, which may be taken as a strong indication that the GPI anchors are not the precursors of the IPG mediators. PMID:11072827

  12. Evolution, structure, and synthesis of vertebrate egg-coat proteins

    PubMed Central

    Litscher, Eveline S.; Wassarman, Paul M.

    2015-01-01

    All vertebrate eggs are surrounded by an extracellular coat that supports growth of oocytes, protects oocytes, eggs, and early embryos, and participates in the process of fertilization. In mammals (platypus to human beings) the coat is called a zona pellucida (ZP) and in non-mammals (molluscs to birds), a vitelline envelope (VE). The ZP and VE are composed of just a few proteins that are related to one another and possess a common motif, called the zona pellucida domain (ZPD). The ZPD arose more than ~600 million years ago, consists of ~260 amino acids, and has 8 conserved Cys residues that participate in 4 intramolecular disulfides. It is likely that egg-coat proteins are derived from a common ancestral gene. This gene duplicated several times during evolution and gave rise to 3–4 genes in fish, 5 genes in amphibians, 6 genes in birds, and 3–4 genes in mammals. Some highly divergent sequences, N- and C-terminal to the ZPD, have been identified in egg-coat proteins and some of these sequences may be under positive Darwinian selection that drives evolution of the proteins. These and other aspects of egg-coat proteins, including their structure and synthesis, are addressed in this review. PMID:26504367

  13. Examining the Impact of Gender on the Factor Structure of the Psychopathic Personality Inventory--Revised

    ERIC Educational Resources Information Center

    Anestis, Joye C.; Caron, Kelly M.; Carbonell, Joyce L.

    2011-01-01

    Research on the factor structure of psychopathy has yielded mixed results, supporting anywhere from one to three factors. Additionally, most of this research has used all-male samples, and the possibility of structural invariance across gender has not been examined. Using a mixed-gender sample of 360 undergraduates, the factor structure of the…

  14. Liquid Nickel Salts: Synthesis, Crystal Structure Determination, and Electrochemical Synthesis of Nickel Nanoparticles.

    PubMed

    Sniekers, Jeroen; Verguts, Ken; Brooks, Neil R; Schaltin, Stijn; Phan, Thanh Hai; Trung Huynh, Thi Mien; Van Meervelt, Luc; De Feyter, Steven; Seo, Jin Won; Fransaer, Jan; Binnemans, Koen

    2016-01-18

    New nickel-containing ionic liquids were synthesized, characterized and their electrochemistry was investigated. In addition, a mechanism for the electrochemical synthesis of nanoparticles from these compounds is proposed. In these so-called liquid metal salts, the nickel(II) cation is octahedrally coordinated by six N-alkylimidazole ligands. The different counter anions that were used are bis(trifluoromethanesulfonyl)imide (Tf2 N(-) ), trifluoromethanesulfonate (OTf(-) ) and methanesulfonate (OMs(-) ). Several different N-alkylimidazoles were considered, with the alkyl sidechain ranging in length from methyl to dodecyl. The newly synthesized liquid metal salts were characterized by CHN analysis, FTIR, DSC, TGA and viscosity measurements. An odd-even effect was observed for the melting temperatures and viscosities of the ionic liquids, with the complexes with an even number of carbon atoms in the alkyl chain of the imidazole having a higher melting temperature and a lower viscosity than the complexes with an odd number of carbons. The crystal structures of several of the nickel(II) complexes that are not liquid at room temperature were determined. The electrochemistry of the compounds with the lowest viscosities was investigated. The nickel(II) cation could be reduced but surprisingly no nickel deposits were obtained on the electrode. Instead, nickel nanoparticles were formed at 100 % selectivity, as confirmed by TEM. The magnetic properties of these nanoparticles were investigated by SQUID measurements. PMID:26643274

  15. Mapping structures of the South China Sea; a synthesis

    NASA Astrophysics Data System (ADS)

    Pubellier, Manuel; Savva, Dimitri; Aurelio, Mario; Yan, Qiu; Phach Phung, Van; Franke, Dieter; Rahman, Hadi A.; Mansor, Yazid M.; Auxiètre, Jean Luc; Meresse, Florian; Delescluse, Matthias; Pichot, Thibaud; Chan, Lung Sang; Le Gal, Virginie; Xin, Nie

    2015-04-01

    The South China Sea margin has been the focus of scientific interest in the past decade including ODP and IODP drilling, oil and gas exploration, and projects from several international teams onshore and offshore. The South China Sea, because of its narrow V shape oceanic crust, the wide extension of its rifted continental crust, and the various styles of rifting is an interesting playground to study the formation of passive margins. We present a synthesis of the main characteristics of the SCS on a structural map focused on the Late Mesozoic and Cenozoic features. The basement, similar in China, Vietnam and part of the western Philippines is undifferentiated. The Mesozoic location of the area was on the upper plate of a subduction zone, resulting in an impressive coverage of Cretaceous granites sometimes separated by narrow Cretaceous molasse basins. These granitic bodies, widespread offshore in the extended crust conditioned the location of the extension via large detachments and normal faults; later cut by steeper faults. The geometries of the faults vary from E-W to NE-SW indicating that the rifting underwent several stages with different stretching directions and a varying degree of extension which ultimately exhumed the mantle. Some faults are low angle detachments and therefore surround the granitic/metamorphic basement structures with an E-W general trend. Platform and reef carbonates occupy some of the bathymetric highs and developed mainly during Late Oligocene to Mid Miocene times and during Late Miocene times. The map also illustrates the coverage of the different units of the NW Borneo wedge, which actually develops offshore in the SE SCS and shifts to the NW of the Sulu Sea. Onshore Borneo, the sub-aerial conditions for the NW Borneo wedge resulted in intense erosion and deltas formation.

  16. Uncertainty Modeling for Structural Control Analysis and Synthesis

    NASA Technical Reports Server (NTRS)

    Campbell, Mark E.; Crawley, Edward F.

    1996-01-01

    The development of an accurate model of uncertainties for the control of structures that undergo a change in operational environment, based solely on modeling and experimentation in the original environment is studied. The application used throughout this work is the development of an on-orbit uncertainty model based on ground modeling and experimentation. A ground based uncertainty model consisting of mean errors and bounds on critical structural parameters is developed. The uncertainty model is created using multiple data sets to observe all relevant uncertainties in the system. The Discrete Extended Kalman Filter is used as an identification/parameter estimation method for each data set, in addition to providing a covariance matrix which aids in the development of the uncertainty model. Once ground based modal uncertainties have been developed, they are localized to specific degrees of freedom in the form of mass and stiffness uncertainties. Two techniques are presented: a matrix method which develops the mass and stiffness uncertainties in a mathematical manner; and a sensitivity method which assumes a form for the mass and stiffness uncertainties in macroelements and scaling factors. This form allows the derivation of mass and stiffness uncertainties in a more physical manner. The mass and stiffness uncertainties of the ground based system are then mapped onto the on-orbit system, and projected to create an analogous on-orbit uncertainty model in the form of mean errors and bounds on critical parameters. The Middeck Active Control Experiment is introduced as experimental verification for the localization and projection methods developed. In addition, closed loop results from on-orbit operations of the experiment verify the use of the uncertainty model for control analysis and synthesis in space.

  17. Total synthesis of the putative structure of the proposed Banyasin A

    PubMed Central

    Gao, Xuguang; Ren, Qi; Choi, Sun; Xu, Zhengshuang; Ye, Tao

    2015-01-01

    The first total synthesis of four possible isomers of a molecule possessing the configuration proposed for Banyasin A is described. The structure synthesized appears to be different from that of the natural product. PMID:25853121

  18. Correction: Substituent interference on supramolecular assembly in urea gelators: synthesis, structure prediction and NMR.

    PubMed

    Piana, Francesca; Case, David H; Ramalhete, Susana M; Pileio, Giuseppe; Facciotti, Marco; Day, Graeme M; Khimyak, Yaroslav Z; Angulo, Jesús; Brown, Richard C D; Gale, Philip A

    2016-06-28

    Correction for 'Substituent interference on supramolecular assembly in urea gelators: synthesis, structure prediction and NMR' by Francesca Piana et al., Soft Matter, 2016, 12, 4034-4043. PMID:27254024

  19. Synthesis of (-)-Cannabimovone and Structural Reassignment of Anhydrocannabimovone through Gold(I)-Catalyzed Cycloisomerization.

    PubMed

    Carreras, Javier; Kirillova, Mariia S; Echavarren, Antonio M

    2016-06-13

    The first total synthesis of cannabimovone from Cannabis sativa and anhydrocannabimovone was achieved by means of a highly stereoselective gold(I)-catalyzed cycloisomerization. The results led to reassignment of the structure of anhydrocannabimovone. PMID:27119910

  20. Structure, Mechanics and Synthesis of Nanoscale Carbon and Boron Nitride

    NASA Astrophysics Data System (ADS)

    Rinaldo, Steven G.

    This thesis is divided into two parts. In Part I, we examine the properties of thin sheets of carbon and boron nitride. We begin with an introduction to the theory of elastic sheets, where the stretching and bending modes are considered in detail. The coupling between stretching and bending modes is thought to play a crucial role in the thermodynamic stability of atomically-thin 2D sheets such as graphene. In Chapter 2, we begin by looking at the fabrication of suspended, atomically thin sheets of graphene. We then study their mechanical resonances which are read via an optical transduction technique. The frequency of the resonators was found to depend on their temperature, as was their quality factor. We conclude by offering some interpretations of the data in terms of the stretching and bending modes of graphene. In Chapter 3, we look briefly at the fabrication of thin sheets of carbon and boron nitride nanotubes. We examine the structure of the sheets using transmission and scanning electron microscopy (TEM and SEM, respectively). We then show a technique by which one can make sheets suspended over a trench with adjustable supports. Finally, DC measurements of the resistivity of the sheets in the temperature range 600 -- 1400 C are presented. In Chapter 4, we study the folding of few-layer graphene oxide, graphene and boron nitride into 3D aerogel monoliths. The properties of graphene oxide are first considered, after which the structure of graphene and boron nitride aerogels is examined using TEM and SEM. Some models for their structure are proposed. In Part II, we look at synthesis techniques for boron nitride (BN). In Chapter 5, we study the conversion of carbon structures of boron nitride via the application of carbothermal reduction of boron oxide followed by nitridation. We apply the conversion to a wide variety of morphologies, including aerogels, carbon fibers and nanotubes, and highly oriented pyrolytic graphite. In the latter chapters, we look at the

  1. A Test and Cross-Validation of the Revised Two-Factor Study Process Questionnaire Factor Structure among Western University Students

    ERIC Educational Resources Information Center

    Immekus, Jason C.; Imbrie, P. K.

    2010-01-01

    The Revised Two-Factor Study Process Questionnaire (R-SPQ-2F) is a measure of university students' approach to learning. Original evaluation of the scale's psychometric properties was based on a sample of Hong Kong university students' scores. The purpose of this study was to test and cross-validate the R-SPQ-2F factor structure, based on separate…

  2. SSME/side loads analysis for flight configuration, revision A. [structural analysis of space shuttle main engine under side load excitation

    NASA Technical Reports Server (NTRS)

    Holland, W.

    1974-01-01

    This document describes the dynamic loads analysis accomplished for the Space Shuttle Main Engine (SSME) considering the side load excitation associated with transient flow separation on the engine bell during ground ignition. The results contained herein pertain only to the flight configuration. A Monte Carlo procedure was employed to select the input variables describing the side load excitation and the loads were statistically combined. This revision includes an active thrust vector control system representation and updated orbiter thrust structure stiffness characteristics. No future revisions are planned but may be necessary as system definition and input parameters change.

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

    NASA Technical Reports Server (NTRS)

    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

  4. Synthesis and crystal structure characterisation of sodium neptunate compounds

    NASA Astrophysics Data System (ADS)

    Smith, A. L.; Raison, P. E.; Konings, R. J. M.

    2011-06-01

    The present work reports studies of the chemical reactions between neptunium dioxide and sodium oxide either in the presence of oxygen or inert gas (Ar), leading to compounds with hexavalent, heptavalent or pentavalent/tetravalent neptunium, respectively. Solid state synthesis with different NpO 2/Na 2O ratios led to the following polycrystalline compounds: Na 2Np 2O 7 monoclinic (P12 11), α-Na 2NpO 4 orthorhombic (Pbam), β-Na 2NpO 4 orthorhombic (Pbca), β-Na 4NpO 5 tetragonal (I4/mmm), Na 5NpO 6 monoclinic (C2/m) and a cubic compound (Fm-3m) that could either be Na 3NpO 4 or Na 4NpO 4. The crystal structures of the α-Na 2NpO 4 and Na 2Np 2O 7 compounds were refined by Rietveld analysis. Evolution of the cell parameters of α-Na 2NpO 4 was also followed as a function of temperature up to 1273 K by X-ray diffraction. The corresponding linear thermal expansion coefficients along the different axis were determined: αa = 41.3 × 10 -6 K -1, αb = 35.0 × 10 -6 K -1, αc ˜ 0 K -1. From the high temperature X-ray diffraction experiment it was also possible to evidence formation of diverse phases at different temperatures and to review parts of the Na-Np-O system.

  5. Barium borohydride chlorides: synthesis, crystal structures and thermal properties.

    PubMed

    Grube, Elisabeth; Olesen, Cathrine H; Ravnsbæk, Dorthe B; Jensen, Torben R

    2016-05-10

    Here we report the synthesis, mechanism of formation, characterization and thermal decomposition of new barium borohydride chlorides prepared by mechanochemistry and thermal treatment of MBH4-BaCl2, M = Li, Na or K in ratios 1 : 1 and 1 : 2. Initially, orthorhombic barium chloride, o-BaCl2 transforms into o-Ba(BH4)xCl2-x, x ∼ 0.15. Excess LiBH4 leads to continued anion substitution and a phase transformation into hexagonal barium borohydride chloride h-Ba(BH4)xCl2-x, which accommodates higher amounts of borohydride, possibly x ∼ 0.85 and resembles h-BaCl2. Thus, two solid solutions are in equilibrium during mechano-chemical treatment of LiBH4-BaCl2 (1 : 1) whereas LiBH4-BaCl2 (2 : 1) converts to h-Ba(BH4)0.85Cl1.15. Upon thermal treatment at T > ∼200 °C, h-Ba(BH4)0.85Cl1.15 transforms into another orthorhombic barium borohydride chloride compound, o-Ba(BH4)0.85Cl1.15, which is structurally similar to o-BaBr2. The samples with M = Na and K have lower reactivity and form o-Ba(BH4)xCl2-x, x ∼ 0.1 and a solid solution of sodium chloride dissolved in solid sodium borohydride, Na(BH4)1-xClx, x = 0.07. The new compounds and reaction mechanisms are investigated by in situ synchrotron radiation powder X-ray diffraction (SR-PXD), Fourier transform infrared spectroscopy (FT-IR) and simultaneous thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), mass spectroscopy (MS) and temperature programmed photographic analysis (TPPA). PMID:27109871

  6. PWR containment structures license renewal industry report: Revision 1. Final report

    SciTech Connect

    Deng, D.; Renfro, J.; Statton, J.

    1994-07-01

    Reinforced concrete, prestressed concrete, and freestanding steel PWR containment structures and components have been evaluated relative to the effects of age-related degradation mechanisms; the capability of current design limits, inservice examination, testing, repair, refurbishment, and other programs to manage these effects; and the assurance that these structures and components can continue to perform their intended safety functions in the license renewal term. This industry report (IR), one of a series of ten, provides a generic technical basis for evaluation of PWR containment structures and components for license renewal.

  7. Total Synthesis of Pinnatoxins A and G and Revision of the Mode of Action of Pinnatoxin A

    PubMed Central

    Araoz, Romulo; Servent, Denis; Molgó, Jordi; Iorga, Bogdan I.; Fruchart-Gaillard, Carole; Benoit, Evelyne; Gu, Zhenhua; Stivala, Craig; Zakarian, Armen

    2012-01-01

    Pinnatoxins belong to an emerging class of potent marine toxins of the cyclic imine group. Detailed studies of their biological effects have been impeded by unavailability of the complex natural product from natural sources. This work describes the development of a robust, scalable synthetic sequence relying on a convergent strategy that delivered a sufficient amount of the toxin for detailed biological studies and its commercialization for use by other research groups and regulatory agencies. A central transformation in the synthesis is the highly diastereoselective Ireland–Claisen rearrangement of a complex α,α-disubstituted allylic ester based on a unique mode for stereoselective enolization through a chirality match between the substrate and the lithium amide base. With synthetic pinnatoxin A, a detailed study has been performed that provides conclusive evidence for its mode of action as a potent inhibitor of nicotinic acetylcholine receptors selective for the human neuronal α7 subtype. The comprehensive electrophysiological, biochemical, and computational studies support the view that the spiroimine subunit of pinnatoxins is critical for blocking nicotinic acetylcholine receptor subtypes, as evidenced by analyzing the effect of a synthetic analogue of pinnatoxin A containing an open form of the imine ring. Our studies have paved the way for the production of certified standards to be used for mass-spectrometric determination of these toxins in marine matrices and for the development of tests to detect these toxins in contaminated shellfish. PMID:21644584

  8. Total synthesis of pinnatoxins A and G and revision of the mode of action of pinnatoxin A.

    PubMed

    Araoz, Romulo; Servent, Denis; Molgó, Jordi; Iorga, Bogdan I; Fruchart-Gaillard, Carole; Benoit, Evelyne; Gu, Zhenhua; Stivala, Craig; Zakarian, Armen

    2011-07-13

    Pinnatoxins belong to an emerging class of potent marine toxins of the cyclic imine group. Detailed studies of their biological effects have been impeded by unavailability of the complex natural product from natural sources. This work describes the development of a robust, scalable synthetic sequence relying on a convergent strategy that delivered a sufficient amount of the toxin for detailed biological studies and its commercialization for use by other research groups and regulatory agencies. A central transformation in the synthesis is the highly diastereoselective Ireland-Claisen rearrangement of a complex α,α-disubstituted allylic ester based on a unique mode for stereoselective enolization through a chirality match between the substrate and the lithium amide base. With synthetic pinnatoxin A, a detailed study has been performed that provides conclusive evidence for its mode of action as a potent inhibitor of nicotinic acetylcholine receptors selective for the human neuronal α7 subtype. The comprehensive electrophysiological, biochemical, and computational studies support the view that the spiroimine subunit of pinnatoxins is critical for blocking nicotinic acetylcholine receptor subtypes, as evidenced by analyzing the effect of a synthetic analogue of pinnatoxin A containing an open form of the imine ring. Our studies have paved the way for the production of certified standards to be used for mass-spectrometric determination of these toxins in marine matrices and for the development of tests to detect these toxins in contaminated shellfish. PMID:21644584

  9. 78 FR 13911 - Proposed Revision to Design of Structures, Components, Equipment and Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-01

    ...,'' Section 3.7.3, ``Seismic Subsystem Analysis,'' Section 3.8.1, ``Concrete Containment,'' Section 3.8.3, ``Concrete And Steel Internal Structures of Steel Or Concrete Containments, ``Section 3.8.4, ``Other...

  10. Visual weld acceptance criteria: Volume 1, Visual weld acceptance criteria for structural welding at nuclear power plants (NCIG-01, Revision 2): Final report

    SciTech Connect

    Not Available

    1987-09-01

    The Nuclear Construction Issues Group (NCIG) was formed to resolve common problems being experienced at nuclear power plants in the assurance of hardware quality for which common solutions likely existed. The initial activity undertaken by this group was development of visual weld acceptance criteria and inspection guidance for structural welds. This report, Volume 1, documents the results of this NCIG activity in describing the visual weld acceptance criteria for structural welding at nuclear power plants (NCIG-01, Revision 2).

  11. Structural Design Requirements and Factors of Safety for Spaceflight Hardware: For Human Spaceflight. Revision A

    NASA Technical Reports Server (NTRS)

    Bernstein, Karen S.; Kujala, Rod; Fogt, Vince; Romine, Paul

    2011-01-01

    This document establishes the structural requirements for human-rated spaceflight hardware including launch vehicles, spacecraft and payloads. These requirements are applicable to Government Furnished Equipment activities as well as all related contractor, subcontractor and commercial efforts. These requirements are not imposed on systems other than human-rated spacecraft, such as ground test articles, but may be tailored for use in specific cases where it is prudent to do so such as for personnel safety or when assets are at risk. The requirements in this document are focused on design rather than verification. Implementation of the requirements is expected to be described in a Structural Verification Plan (SVP), which should describe the verification of each structural item for the applicable requirements. The SVP may also document unique verifications that meet or exceed these requirements with NASA Technical Authority approval.

  12. A revised version of the transfer matrix method to analyze one-dimensional structures

    NASA Technical Reports Server (NTRS)

    Nitzsche, F.

    1983-01-01

    A new and general method to analyze both free and forced vibration characteristics of one-dimensional structures is discussed in this paper. This scheme links for the first time the classical transfer matrix method with the recently developed integrating matrix technique to integrate systems of differential equations. Two alternative approaches to the problem are presented. The first is based upon the lumped parameter model to account for the inertia properties of the structure. The second releases that constraint allowing a more precise description of the physical system. The free vibration of a straight uniform beam under different support conditions is analyzed to test the accuracy of the two models. Finally some results for the free vibration of a 12th order system representing a curved, rotating beam prove that the present method is conveniently extended to more complicated structural dynamics problems.

  13. Revised structure of trans-resveratrol: Implications for its proposed antioxidant mechanism.

    PubMed

    Zarychta, Bartosz; Gianopoulos, Christopher G; Pinkerton, A Alan

    2016-03-01

    The crystal structure of trans-resveratrol has been redetermined by X-ray diffraction. The newly refined structure demonstrates that the previously reported, dynamically disordered hydrogen-bonding network is rather the superposition of two crystallographically independent molecules of trans-resveratrol. This latter arrangement possesses a well-defined hydrogen-bonding network in a unit cell of double the previously reported volume. While not meant as a criticism of the proposed antioxidant mechanism itself, the present studies clearly show that the X-ray diffraction data should no longer be used for its additional support. PMID:26856924

  14. Structural allograft and cemented long-stem prosthesis for complex revision hip arthroplasty: use of a trochanteric claw plate improves final hip function

    PubMed Central

    Lemoine, Camille Thevenin; Kerboull, Marcel; Courpied, Jean Pierre

    2007-01-01

    Extensive bone loss raises formidable challenges in total hip revision. The aim of this study was to evaluate the results of reconstruction using a cemented long-stem and massive structural allograft implanted in a filleted proximal femur, with and without the use of a trochanteric claw plate. Between 1988 and 2001, 44 revisions were performed in 42 patients. After a transtrochanteric approach, the femur was cut longitudinally. A long, cemented Charnley-type prosthesis was used, and flaps of the residual femur were folded around the allograft. The greater trochanter was reinserted with wires in all revisions, and with both wires and a claw plate in 20 revisions. Mean follow-up was 7.15 years (range: 3–16); seven patients, died and four were lost to follow-up. The follow-up exceeded five years in 34 patients. The major complication was nonunion of the greater trochanter, which occurred in 25 cases. Six dislocations, one recurrence of infection, two mechanical loosening, and two fractures below the stem were also recorded. The use of a trochanteric claw plate significantly improved final hip stability, even in patients with nonunion. Femoral reconstruction with a massive structural allograft is reliable and long-lived, and serious complications and long-term resorption are uncommon. The use of a trochanteric claw plate significantly improves final hip stability. Level of evidence: Therapeutic study, level III (retrospective comparative study). PMID:18008098

  15. 78 FR 59732 - Revisions to Design of Structures, Components, Equipment, and Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-27

    ...: Jonathan.DeGange@nrc.gov . SUPPLEMENTARY INFORMATION: On March 1, 2013 (73 FR 13911), the NRC published for..., ``Seismic Subsystem Analysis,'' Section 3.8.1, ``Concrete Containment,'' Section 3.8.3, ``Concrete and Steel Internal Structures of Steel or Concrete Containments,'' Section 3.8.4, ``Other Seismic Category...

  16. Revised structural phase transitions in the archetype KMnF3 perovskite crystal

    NASA Astrophysics Data System (ADS)

    Kapusta, Joanna; Daniel, Philippe; Ratuszna, Alicja

    1999-06-01

    Reinvestigation of the structural and vibrational properties of the typical perovskite KMnF3, exhibiting two antiferrodistortive structural phase transitions, was performed using x-ray powder diffraction and Raman spectroscopy in the range between 30 and 300 K. The x-ray-diffraction work has unambiguously shown that a monoclinic distortion (ra-b+c- tilt system P21/m space group) is observed at low temperature below TC2=91 K. This result corresponds with the Raman temperature study which shows that this transition, in spite of its first-order character, can be associated with a group-subgroup relation between tetragonal and monoclinic symmetries. Additionally, existence of a large structural disorder far above the cubic to tetragonal transition (TC1=186 K) is suggested by the two following experimental indications: (i) persistence of hard modes of the tetragonal phase in the cubic symmetry, and (ii) existence of Raman broad bands in normally inactive ideal cubic phase, which are interpreted by the folding of the whole phonons branches of the cubic Brillouin zone. This last observation allows us to follow the evolution of the cubic R'15 soft mode versus temperature, based only on the Raman-scattering data, in full agreement with previous inelastic neutron data. The results of Raman investigations into KMnF3 are discussed in more general framework of structural disorder in perovskite systems which exhibit anisotropic correlation between octahedra.

  17. Mercy Mission and Transformative Change: Evaluation of a Revised Governance Structure

    ERIC Educational Resources Information Center

    Affenito, Sandra G.; Artz, Judy; Carlson, Vivian

    2014-01-01

    The University of St. Joseph, a Mercy institution, was founded during the Great Depression to provide women a gateway to higher education for careers in fields that would serve the well-being of society. Recently, the institution has undergone changes to modernize its organizational structure. Consistent with its commitment to educate people of…

  18. Optimal Full Information Synthesis for Flexible Structures Implemented on Cray Supercomputers

    NASA Technical Reports Server (NTRS)

    Lind, Rick; Balas, Gary J.

    1995-01-01

    This paper considers an algorithm for synthesis of optimal controllers for full information feedback. The synthesis procedure reduces to a single linear matrix inequality which may be solved via established convex optimization algorithms. The computational cost of the optimization is investigated. It is demonstrated the problem dimension and corresponding matrices can become large for practical engineering problems. This algorithm represents a process that is impractical for standard workstations for large order systems. A flexible structure is presented as a design example. Control synthesis requires several days on a workstation but may be solved in a reasonable amount of time using a Cray supercomputer.

  19. An Exploration of the Four-Factor Structure of the Drinking Motives Questionnaire-Revised Among Undergraduate Students in China

    PubMed Central

    Sun, Li; Windle, Michael; Thompson, Nancy J.

    2016-01-01

    Background College drinking has become a significant health issue in China; the current study addressed the gap that no prior research has investigated drinking motives among Chinese undergraduate students. Objectives This study aimed to replicate the four-factor structure of the Drinking Motives Questionnaire-Revised (DMQ-R) reported for Western populations. Additionally, the relationships between drinking motives and alcohol use were investigated. Methods In 2012, 436 participants (mean age = 20.49 and SD = 1.49; 50% male) recruited from a college in China completed a self-administered survey in their classroom setting. Drinking motives were measured by the Chinese version of the DMQ-R; three indicators of alcohol use were assessed. Factor analysis was conducted to examine the factor structure of the DMQ-R, followed by regression analysis to investigate the associations between drinking motives and alcohol-related outcomes. Results Confirmatory factor analysis failed to replicate the measurement model tested, but exploratory factor analysis identified a similar four-dimensional factor structure. Reliability and convergent and discriminant validity of the four factors were acceptable. The results also showed that social motives were related to alcohol use and heavy drinking; conformity motives were related to alcohol use and alcohol-related problems. Enhancement motives were the strongest correlates of alcohol use; coping motives were the strongest correlates of heavy drinking and alcohol-related problems. Conclusions/Importance The DMQ-R was a reliable and valid scale measuring four types of drinking motives among Chinese college students. Findings suggested that the motivational model of alcohol use may apply to studying college drinking in China. PMID:26576670

  20. Sliding and Rocking of Unanchored Components and Structures: Chapter 7.6 ASCE 4 Revision 2

    SciTech Connect

    S. R. Jensen

    2011-04-01

    Chapter 7.6 of ASCE 4-Rev 2, Seismic Analysis of Safety-Related Nuclear Structures: Standard and Commentary, provides updated guidance for analysis of rocking and sliding of unanchored structures and components subjected to seismic load. This guidance includes provisions both for simplified approximate energy-based approaches, and for detailed probabilistic time history analysis using nonlinear methods. Factors to be applied to the analytical results are also provided with the intent of ensuring achievement of the 80% non-exceedence probability target of the standard. The present paper surveys the published literature supporting these provisions. The results of available testing and analysis are compared to results produced by both simplified and probabilistic approaches. In addition, adequacy of the standard's provisions for analysis methods and factors is assessed. A comparison is made between the achieved level of conservatism and the standard's non-exceedence probability target.

  1. Using the Dempster-Shafer theory of evidence with a revised lattice structure for activity recognition.

    PubMed

    Liao, Jing; Bi, Yaxin; Nugent, Chris

    2011-01-01

    This paper explores a sensor fusion method applied within smart homes used for the purposes of monitoring human activities in addition to managing uncertainty in sensor-based readings. A three-layer lattice structure has been proposed, which can be used to combine the mass functions derived from sensors along with sensor context. The proposed model can be used to infer activities. Following evaluation of the proposed methodology it has been demonstrated that the Dempster-Shafer theory of evidence can incorporate the uncertainty derived from the sensor errors and the sensor context and subsequently infer the activity using the proposed lattice structure. The results from this study show that this method can detect a toileting activity within a smart home environment with an accuracy of 88.2%. PMID:21075728

  2. Validation of the Penn Inventory of Scrupulosity (PIOS) in scrupulous and nonscrupulous patients: Revision of factor structure and psychometrics.

    PubMed

    Huppert, Jonathan D; Fradkin, Isaac

    2016-06-01

    Scrupulosity, or obsessive-compulsive symptoms related to religiosity or religion, is a common presentation of obsessive compulsive disorder (OCD), and it is important to elucidate its phenomenology and measurement. Today, the most widespread questionnaire for the assessment of scrupulosity is the Penn Inventory of Scrupulosity (PIOS). The current study examines the psychometric properties of the PIOS in outpatient, treatment-seeking patients. Results of a confirmatory factor analysis suggested an unsatisfactory fit for previously suggested factor structures. A follow-up exploratory factor analysis suggested that a bifactor model was the most suitable solution. In addition, the scores of the PIOS and its revised subscales were found to have moderate-good concurrent validity; however, its scores discriminated poorly between patients with scrupulous obsessions and patients with OCD and other repugnant obsessions. Group differences and receiver operating characteristics (ROC) analyses both indicated that the PIOS is more suitable in discriminating scrupulous obsessions in Christian patients but not in other religious groups (i.e., Jews, nonreligious patients). Additional analyses revealed that the co-occurrence of scrupulous and other repugnant obsessions is also moderated by religious affiliation. These results raise questions in terms of grouping scrupulosity with other repugnant obsessions and suggest for the need of culturally sensitive instruments of scrupulosity. (PsycINFO Database Record PMID:26372375

  3. Isolation, Structure Elucidation, Biosynthesis, and Synthesis of Antalid, a Secondary Metabolite from Polyangium species.

    PubMed

    Tautz, Thomas; Hoffmann, Judith; Hoffmann, Thomas; Steinmetz, Heinrich; Washausen, Peter; Kunze, Brigitte; Huch, Volker; Kitsche, Andreas; Reichenbach, Hans; Höfle, Gerhard; Müller, Rolf; Kalesse, Markus

    2016-06-01

    The isolation, structure elucidation, and synthesis of antalid (1), a novel secondary metabolite from Polyangium sp., is described herein. The structure elucidation of 1 was performed with the aid of mass spectrometry, high field NMR experiments, and crystal structure analysis. The absolute configuration of antalid was confirmed through the Mosher ester method and ultimately by total synthesis. In addition, the biosynthetic origin of this hybrid PKS-NRPS natural product was unraveled by the in silico analysis of its biosynthetic gene cluster. PMID:27220069

  4. Component mode synthesis and large deflection vibrations of complex structures. [beams and trusses

    NASA Technical Reports Server (NTRS)

    Mei, C.

    1984-01-01

    The accuracy of the NASTRAN modal synthesis analysis was assessed by comparing it with full structure NASTRAN and nine other modal synthesis results using a nine-bay truss. A NASTRAN component mode transient response analysis was also performed on the free-free truss structure. A finite element method was developed for nonlinear vibration of beam structures subjected to harmonic excitation. Longitudinal deformation and inertia are both included in the formula. Tables show the finite element free vibration results with and without considering the effects of longitudinal deformation and inertia as well as the frequency ratios for a simply supported and a clamped beam subjected to a uniform harmonic force.

  5. Importance of level structure in nuclear reaction cross-section calculations. Revision 1

    SciTech Connect

    Gardner, M.A.; Gardner, D.G.

    1985-11-07

    It is shown that level-density expressions cannot adequately represent or substitute for level structure information when making calculations of the Hauser-Feshbach type for cross sections or isomer-ratios for nuclei in the first few MeV above their ground state. It is stated that such discrete level information should include both experimentally confirmed and theoretically predicted levels. The utility of discrete level information to optimize level density calculations, to compute isomer ratios, in deriving dipole strength functions, and in the analysis of primary gamma ray spectra is emphasized, especially for nuclei far from the line of stability. 29 refs., 12 figs., 6 tabs. (DWL)

  6. A Rayleigh-Ritz approach to the synthesis of large structures with rotating flexible components

    NASA Technical Reports Server (NTRS)

    Meirovitch, L.; Hale, A. L.

    1976-01-01

    The equations of motion for large structures with rotating flexible components are derived by regarding the structure as an assemblage of substructures. Based on a stationarity principle for rotating structures, it is shown that each continuous or discrete substructure can be simulated by a suitable set of admissible functions or admissible vectors. This substructure synthesis approach provides a rational basis for truncating the number of degrees of freedom both of each substructure and of the assembled structure.

  7. The synthesis of nanocomposite structures on the surface of geometrically complex products

    NASA Astrophysics Data System (ADS)

    Brzhozovsky, B.; Martynov, V.; Zinina, E.; Brovkova, M.; Bochkarev, P.

    2016-07-01

    The paper presents the technology of nanocomposite structure synthesis in the surface layer of geometrically complex products under the impact of low-temperature plasma and the results of experimental study of their properties. An example is given of practical application of the nanocomposite structure product to improve the efficiency of ultrasonic dimensional processing.

  8. ACCESS-2: Approximation Concepts Code for Efficient Structural Synthesis, user's guide

    NASA Technical Reports Server (NTRS)

    Miura, H.; Schmit, L. A., Jr.

    1978-01-01

    A user's guide is presented for the ACCESS-2 computer program. ACCESS-2 is a research oriented program which implements a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and general mathematical programming algorithms are applied in the design optimization procedure.

  9. Human learning of elemental category structures: revising the classic result of Shepard, Hovland, and Jenkins (1961).

    PubMed

    Kurtz, Kenneth J; Levering, Kimery R; Stanton, Roger D; Romero, Joshua; Morris, Steven N

    2013-03-01

    The findings of Shepard, Hovland, and Jenkins (1961) on the relative ease of learning 6 elemental types of 2-way classifications have been deeply influential 2 times over: 1st, as a rebuke to pure stimulus generalization accounts, and again as the leading benchmark for evaluating formal models of human category learning. The litmus test for models is the ability to simulate an observed advantage in learning a category structure based on an exclusive-or (XOR) rule over 2 relevant dimensions (Type II) relative to category structures that have no perfectly predictive cue or cue combination (including the linearly-separable Type IV). However, a review of the literature reveals that a Type II advantage over Type IV is found only under highly specific experimental conditions. We investigate when and why a Type II advantage exists to determine the appropriate benchmark for models and the psychological theories they represent. A series of 8 experiments link particular conditions of learning to outcomes ranging from a traditional Type II advantage to compelling non-differences and reversals (i.e., Type IV advantage). Common interpretations of the Type II advantage as either a broad-based phenomenon of human learning or as strong evidence for an attention-mediated similarity-based account are called into question by our findings. Finally, a role for verbalization in the category learning process is supported. PMID:22799282

  10. Kermesite, Sb2S2O: crystal structure revision and order-disorder interpretation.

    PubMed

    Hybler, Jiří; Durovič, Slavomil

    2013-12-01

    Kermesite, Sb2S2O, is a desymmetrized order-disorder (OD) structure of layers. Two data sets were recorded using twinned crystals from Pezinok, Slovakia (named as Pz21, Pz24). The primitive unit cell is triclinic, P1, Z = 4, cell parameters are a = 8.1416 (3), b = 10.6968 (3), c = 5.7835 (2) Å, α = 102.758 (3), β = 110.657 (3), γ = 101.020 (3)°, R(obs) = 0.0243 (Pz21), and a = 8.1372 (2), b = 10.6969 (2), c = 5.7840 (1) Å, α = 102.787 (2), β = 110.606 (2), γ = 100.983 (2)°, R(obs) = 0.0321 (Pz24). The structure can also be described in the non-standard pseudo-monoclinic octuple (Z = 32), F-centered (Kupčík) cell with extra points in 1/4,1/4,0; 1/4,3/4,1/2; 3/4,1/4,1/2; 3/4,3/4,0, with parameters a = 21.6466 (9), b = 8.1416 (3), c = 20.3824 (9) Å, α = 90.079 (4), β = 101.985 (5), γ = 89.948 (4)° (Pz21), and a = 21.6558 (5), b = 8.1372 (2), c = 20.3859 (8) Å, α = 90.028 (3), β = 101.994 (3), γ = 89.986 (2)° (Pz24). The structure is built of layers parallel to the bc plane, stacked along the a vector of the octuple cell, composed of ribbons parallel to the b vector: (i) ribbon of two strips of SbO5 flattened quadrangular pyramids, sharing apical edges; (ii) ribbon of edge-sharing corrugated lozenges SbO3S. Basal S atoms of pyramids share corners of lozenges. Sb atoms are displaced out of coordination polyhedra into the inter-layer space. The OD layer comprises adjacent halves of the structure building layers. The layer group is A(1)2/m1, the protocell is defined by b, c, (a/4)sin β. The MDO1 (4A) polytype is generated by repetition of the t(1,1/4,0) [or alternatively t(1,-1/4,0)] translation. The co-existence of two kinds of domains give rise to the twinning. The twin operation is 2[010], twin index 2. The total continuation of [. a2 .] generates the MDO2 (2M) polytype, space group A12/a1. Simulated and real diffraction patterns are presented. The important values (edges, angles) and

  11. Mutational analysis of the central domain of adenovirus virus-associated RNA mandates a revision of the proposed secondary structure.

    PubMed Central

    Pe'ery, T; Mellits, K H; Mathews, M B

    1993-01-01

    Protein synthesis in adenovirus-infected cells is regulated during the late phase of infection. The rate of initiation is maintained by a small viral RNA, virus-associated (VA) RNAI, which prevents the phosphorylation of eukaryotic initiation factor eIF-2 by a double-stranded RNA-activated protein kinase, DAI. On the basis of nuclease sensitivity analysis, a secondary-structure model was proposed for VA RNA. The model predicts a complex stem-loop structure in the central part of the molecule, the central domain, joining two duplexed stems. The central domain is required for the inhibition of DAI activation and participates in the binding of VA RNA to DAI. To assess the significance of the postulated stem-loop structure in the central domain, we generated compensating, deletion, and substitution mutations. A substitution mutation which disrupts the structure in the central domain abolishes VA RNA function in vitro and in vivo. Base-compensating mutations failed to restore the function or structure of the mutant, implying that the stem-loop structure may not exist. To confirm this observation, we tested mutants with alterations in the hypothetical loop and short stem that constitute the main features of the wild-type model structure. The upper part of the hypothetical loop could be deleted without abolishing the ability of the RNA to block DAI activation in vitro, whereas other loop mutations were deleterious for function and caused major rearrangements in the molecule. Base-compensating mutations in the stem did not restore the expected base pairing, even though the mutant RNAs were still functional in vitro. Surprisingly, a mutant with a noncompensating substitution mutation in the stem was more effective than wild-type VA RNAI in DAI inhibition assays but was ineffective in vivo. The structural and functional consequences of these mutations do not support the proposed model structure for the central domain, and we therefore suggest an alternative structure in

  12. Electronic structures, vibrational spectra, and revised assignment of aniline and its radical cation: Theoretical study

    NASA Astrophysics Data System (ADS)

    Wojciechowski, Piotr M.; Zierkiewicz, Wiktor; Michalska, Danuta; Hobza, Pavel

    2003-06-01

    Comprehensive studies of the molecular and electronic structures, vibrational frequencies, and infrared and Raman intensities of the aniline radical cation, C6H5NH2+ have been performed by using the unrestricted density functional (UB3LYP) and second-order Møller-Plesset (UMP2) methods with the extended 6-311++G(df,pd) basis set. For comparison, analogous calculations were carried out for the closed-shell neutral aniline. The studies provided detailed insight into the bonding changes that take place in aniline upon ionization. The natural bond orbital (NBO) analysis has revealed that the pπ-radical conjugative interactions are of prime importance in stabilizing the planar, quinoid-type structure of the aniline radical cation. It is shown that the natural charges calculated for aniline are consistent with the chemical properties of this molecule (an ortho- and para-directing power of the NH2 group in electrophilic substitutions), whereas Mulliken charges are not reliable. The theoretical vibrational frequencies of aniline, calculated by the B3LYP method, show excellent agreement with the available experimental data. In contrast, the MP2 method is deficient in predicting the frequencies of several modes in aniline, despite the use of the extended basis set in calculations. The frequencies of aniline radical cation, calculated at the UB3LYP/6-311++G(df,pd) level, are in very good agreement with the recently reported experimental data from zero kinetic energy photoelectron and infrared depletion spectroscopic studies. The clear- cut assignment of the IR and Raman spectra of the investigated molecules has been made on the basis of the calculated potential energy distributions. Several bands in the spectra have been reassigned. It is shown that ionization of aniline can be easily identified by the appearance of the very strong band at about 1490 cm-1, in the Raman spectrum. The redshift of the N-H stretching frequencies and the blueshift of the C-H stretching

  13. Scar revision

    MedlinePlus

    ... prevention, treatment, and revision. In: Neligan PC, ed. Plastic Surgery . 3rd ed. Philadelphia, PA: Elsevier; 2013:chap ... Hebe Molmenti, MD, PhD, private practice specializing in plastic and reconstructive surgery, Baltimore, MD. Review provided by ...

  14. Structure determination of the exopolysaccharide of Lactobacillus fermentum TDS030603-a revision.

    PubMed

    Gerwig, Gerrit J; Dobruchowska, Justyna M; Shi, Tala; Urashima, Tadasu; Fukuda, Kenji; Kamerling, Johannis P

    2013-08-30

    The highly viscous neutral exopolysaccharide, produced in large amounts by Lactobacillus fermentum TDS030603 in MRS broth and in a chemically defined medium supplemented with glucose, was investigated by GLC(-EIMS) monosaccharide and methylation analysis, periodate oxidation, MALDI-TOF mass spectrometry, and 1D/2D NMR spectroscopy. The GLC(-EIMS) analyses showed that the EPS contained d-glucose and d-galactose in an averaged molar ratio of 2.6:1.0, consisting of terminal d-Glcp, 3-substituted d-Glcp, 2,3-disubstituted d-Glcp, and 6-substituted d-Galp in an averaged molar ratio of 1.3:1.0:1.1:1.1, with a trace of terminal d-Galp (0.1). Combined with the NMR data of the EPS (previously reported constituent analysis: terminal Glcp, 3-substituted Glcp, 2,3-disubstituted Glcp, and 6-substituted Galp in an averaged molar ratio of 1.2:1.1:1.0:1.1) and oligosaccharides isolated after partial acid hydrolysis, a branched tetrasaccharide repeating unit, with some heterogeneity in the side chain, having the following structure is proposed: [fromula see text]. PMID:23680670

  15. Bloch mode synthesis: Ultrafast methodology for elastic band-structure calculations

    NASA Astrophysics Data System (ADS)

    Krattiger, Dimitri; Hussein, Mahmoud I.

    2014-12-01

    We present a methodology for fast band-structure calculations that is generally applicable to problems of elastic wave propagation in periodic media. The methodology, called Bloch mode synthesis, represents an extension of component mode synthesis, a set of substructuring techniques originally developed for structural dynamics analysis. In Bloch mode synthesis, the unit cell is divided into interior and boundary degrees-of-freedom, which are described, respectively, by a set of normal modes and a set of constraint modes. A combination of these mode sets then forms a reduced basis for the band structure eigenvalue problem. The reduction is demonstrated on a phononic-crystal model and a locally resonant elastic-metamaterial model and is shown to accurately predict the frequencies and Bloch mode shapes with a dramatic decrease in computation time in excess of two orders of magnitude.

  16. The synthesis and structure of new vinylogous carbamates of sparteine

    NASA Astrophysics Data System (ADS)

    Włodarczak, Jacek; Wysocka, Waleria; Katrusiak, Andrzej

    2010-05-01

    Synthesis of new ( E)-(-)-[2-methyl ( 2), ethyl ( 3), isopropyl ( 4), benzyl ( 5) and phenyl ( 6)] carbonylmethylideno-17-oxosparteine by the Eschenmoser coupling reaction has been described. Stereochemistry of these compounds has been determined by 13C and 1H NMR and that of compound 2 additionally by X-ray analysis. The Haasnoot equation has been used to determine the HCCH dihedral angle in ( E)-(-)-2-methyl-(methylcarbonylomethylideno)-17-oxosparteine on the basis of NMR spectroscopy.

  17. Synthesis Approaches to (-)-Cytoxazone, a Novel Cytokine Modulator, and Related Structures.

    PubMed

    Miranda, Izabel L; Lopes, Ítala K B; Diaz, Marisa A N; Diaz, Gaspar

    2016-01-01

    (-)-Cytoxazone, originally isolated from cultures of a Streptomyces species has an oxazolidin-2-one 4,5-disubstituted ring. It is known that this natural product presents a cytokine modulator effect through the signaling pathway of Th2 cells (type 2 cytokines), which are involved in the process of growth and differentiation of cells. From this, the interest in the development of research aimed at the total synthesis of this molecule and its analogs has remained high, which can be confirmed by the large number of publications on the topic, more than 30 to date. This review focuses on the various creative methods for the synthesis of (-)-cytoxazone and its congeners. The assessment of the preparation of this oxazolidinone and related structures serves as a treatise on the efforts made in the synthesis of this important class of compound from its first total synthesis in 1999. PMID:27608004

  18. A Revised Parallel-Sequence Galaxy Classification: Structure and Formation of S0 and Spheroidal Galaxies

    NASA Astrophysics Data System (ADS)

    Kormendy, John; Bender, R.

    2012-01-01

    We update van den Bergh's (1976, ApJ, 206, 883) parallel sequence galaxy classification in which S0 galaxies form a sequence S0a-S0b-S0c that parallels the sequence Sa-Sb-Sc of spiral galaxies. The ratio B/T of bulge to total light defines the position of a galaxy in this tuning fork diagram. Our classification makes one main improvement. We extend the S0a-S0b-S0c sequence to spheroidal (Sph) galaxies that are positioned in parallel to irregular galaxies in a similarly extended Sa-Sb-Sc-Im sequence. This provides a natural home for spheroidals, which previously were thought to be low-surface-brightness ellipticals. To motivate our juxtaposition of spheroidals and irregulars, we present photometry and bulge-disk decompositions of late-type S0s that bridge the gap between the more common S0b and Sph galaxies. We find several S0s in the Virgo cluster that have B/T <= 0.1. They are the S0cs that were missing from van den Bergh's paper. We update the structural parameter correlations of Sph, spiral and irregular, and elliptical galaxies. We show that spheroidals of increasing luminosity form a continuous sequence with the disks (but not bulges) of S0c-S0b-S0a galaxies. Remarkably, this Sph-S0-disk sequence is almost identical to that of irregular and spiral galaxies. We suggest that spheroidal galaxies are transformed, "red and dead" Scd-Im galaxies in the same way that many S0 galaxies are transformed, red and dead Sa-Sc spiral galaxies. Plausible transformation processes include ram-pressure gas stripping, gravitational harassment, and starvation by cutting off the late infall of cold gas. We suggest that many different processes act together to engineer S0 and Sph galaxies. This work was supported by NSF grant AST-0607490.

  19. Gendered Performances during Peer Revision

    ERIC Educational Resources Information Center

    Styslinger, Mary E.

    2008-01-01

    This study explored the ways gender is accomplished in varied social contexts during the peer revision process in a secondary English classroom. Using a post-structural feminist theoretical framework, an analysis of classroom discourse provided a basis for understanding the performance of gender during peer revision, the effects of gender…

  20. Special Features of the Structure of Copper-containing Products of Plasma Dynamic Synthesis

    NASA Astrophysics Data System (ADS)

    Ivashutenko, A. S.; Nazarenko, O. B.; Sivkov, A. A.; Saigash, A. S.; Stepanov, K. I.

    2015-03-01

    Results of investigation of the dispersed, phase, and chemical compositions of products of plasma dynamic synthesis in a high-speed pulsed jet of copper-containing electroerosive plasma flowing into a closed volume with the air atmosphere are presented. Products of synthesis are investigated by the methods of x-ray phase and thermal analyses, electron microscopy, and IR spectroscopy. The structure of the synthesized powder includes metal copper, Cu2O and CuO copper oxides, and hydrated copper hydroxide Cu(OH)2·N2O. Results of investigations of structural changes of the synthesized products during heating in vacuum and air are presented.

  1. Recent developments in quasi-Newton methods for structural analysis and synthesis

    NASA Technical Reports Server (NTRS)

    Kamat, M. P.; Hayduk, R. J.

    1981-01-01

    Unlike the Newton-Raphson method, quasi-Newton methods by virture of the updates and step length control procedures are globally convergent and hence better suited for the solution of nonlinear problems of structural analysis and synthesis. Extension of quasi-Newton algorithms to large scale problems has led to the development of sparse update algorithms and to economical strategies for evaluating sparse Hessians. Ill-conditioning problems have led to the development of self-scaled variable metric and conjugate gradient algorithms, as well as the use of the singular perturbation theory. This paper emphasizes the effectiveness of such quasi-Newton algorithms for nonlinear structural analysis and synthesis.

  2. Cobalt Molybdenum Oxynitrides: Synthesis, Structural, Characterization, and Catalytic Activity for the Oxygen Reduction Reaction

    SciTech Connect

    Cao, Bingfei; Veith, Gabriel M; Diaz, Rosa; Liu, Jue; Stach, Eric; Adzic, Radoslav R.; Khalifah, P.

    2013-01-01

    Here, we report the synthesis and characterization of CoxMo1 xOyNz compounds supported on carbon black as potential cathode catalysts for ORR. They were prepared by a conventional impregnation method. Their ORR activities in both acid and alkaline electrolytes were evaluated via half-cell measurements. The synthesis temperature and sample composition both strongly impacted their physical and chemical properties. Factors influencing their crystal structures, morphologies and ORR activities will be discussed based on the results of structural and spectroscopic studies.

  3. ACCESS 1: Approximation Concepts Code for Efficient Structural Synthesis program documentation and user's guide

    NASA Technical Reports Server (NTRS)

    Miura, H.; Schmit, L. A., Jr.

    1976-01-01

    The program documentation and user's guide for the ACCESS-1 computer program is presented. ACCESS-1 is a research oriented program which implements a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and general mathematical programming algorithms are applied in the design optimization procedure. Implementation of the computer program, preparation of input data and basic program structure are described, and three illustrative examples are given.

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

    NASA Astrophysics Data System (ADS)

    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

  5. Alternative Synthesis and Structures of C-monoacetylenic Phosphaalkenes

    PubMed Central

    Orthaber, Andreas; Öberg, Elisabet; Jane, Reuben T; Ott, Sascha

    2012-01-01

    An alternative synthesis of C-monoacetylenic phosphaalkenes trans-Mes*P=C(Me)(C≡CR) (Mes* = 2, 4, 6-tBu3Ph, R = Ph, SiMe3) from C-bromophosphaalkenes cis-Mes*P=C(Me)Br using standard Sonogashira coupling conditions is described. Crystallographic studies confirm cis-trans isomerization of the P=C double bond during Pd-catalyzed cross coupling, leading exclusively to trans-acetylenic phosphaalkenes. Crystallographic studies of all synthesized compounds reveal the extend of π-conjugation over the acetylene and P=C π-systems. PMID:26063932

  6. Parent and trisubstituted triazacoronenes: synthesis, crystal structure and physicochemical properties.

    PubMed

    Tan, Qitao; Chen, Huanhuan; Xia, Huaida; Liu, Bingxin; Xu, Bin

    2016-01-11

    A four-step synthesis of the C3-symmetric parent 1,5,9-triazacoronene (TAC) and its derivatives was achieved using a three-fold Bischler-Napieralski cyclization as the key step. The single-crystal X-ray diffraction of 1b (R = n-Bu) demonstrates that the azacoronene core is perfectly co-planar and the molecules adopt a favorable 2-D "brick-wall" arrangement with strong π-π interactions. The unique stacking, tunable photophysical and electronic properties, and high thermal stability should make them promising candidates for emissive and electron-transport materials. PMID:26537285

  7. Synthesis of Aspartame by Thermolysin: An X-ray Structural Study

    PubMed Central

    2014-01-01

    Protease mediated peptide synthesis (PMPS) was first described in the 1930s but remains underexploited today. In most PMPS, the reaction equilibrium is shifted toward synthesis by the aqueous insolubility of product generated. Substrates and proteases are selected by trial and error, yields are modest, and reaction times are slow. Once implemented, however, PMPS reactions can be simple, environmentally benign, and readily scalable to a commercial level. We examined the PMPS of a precursor of the artificial sweetener aspartame, a multiton peptide synthesis catalyzed by the enzyme thermolysin. X-ray structures of thermolysin in complex with aspartame substrates separately, and after PMPS in a crystal, rationalize the reaction’s substrate preferences and reveal an unexpected form of substrate inhibition that explains its sluggishness. Structure guided optimization of this and other PMPS reactions could expand the economic viability of commercial peptides beyond current high-potency, low-volume therapeutics, with substantial green chemistry advantages. PMID:24944748

  8. Synthesis, Crystal Structure, and Elastic Properties of Novel Tungsten Nitrides

    SciTech Connect

    Wang, Shanmin; Yu, Xiaohui; Lin, Zhijun; Zhang, Ruifeng; He, Duanwei; Qin, Jiaqian; Zhu, Jinlong; Han, Jiantao; Wang, Lin; Mao, Ho-kwang; Zhang, Jianzhong; Zhao, Yusheng

    2012-12-13

    Among transition metal nitrides, tungsten nitrides possess unique and/or superior chemical, mechanical, and thermal properties. Preparation of these nitrides, however, is challenging because the incorporation of nitrogen into tungsten lattice is thermodynamically unfavorable at atmospheric pressure. To date, most materials in the W-N system are in the form of thin films produced by nonequilibrium processes and are often poorly crystallized, which severely limits their use in diverse technological applications. Here we report synthesis of tungsten nitrides through new approaches involving solid-state ion exchange and nitrogen degassing under pressure. We unveil a number of novel nitrides including hexagonal and rhombohedral W{sub 2}N{sub 3}. The final products are phase-pure and well-crystallized in bulk forms. For hexagonal W{sub 2}N{sub 3}, hexagonal WN, and cubic W3N4, they exhibit elastic properties rivaling or even exceeding cubic-BN. All four nitrides are prepared at a moderate pressure of 5 GPa, the lowest among high-pressure synthesis of transition metal nitrides, making it practically feasible for massive and industrial-scale production.

  9. Structural tailoring and feedback control synthesis - An interdisciplinary approach

    NASA Technical Reports Server (NTRS)

    Belvin, W. Keith; Park, K. C.

    1988-01-01

    Structural tailoring provides an attractive method to optimize the performance of actively controlled space structures. However, the simultaneous optimization of control gains and structural properties often becomes prohibitively expensive for large systems and physical insight is often lost in the resulting control law. This paper presents a method for optimization of the closed loop structural system using only structural tailoring. Optimal Linear Quadratic Regulator (LQR) control theory is used with weighting matrices chosen based on physical considerations. The LQR control law depends only on two scalar gains and the structural properties. Hence, the closed loop-performance can be expressed in terms of the structural parameters. Results are given for a beam and a truss-beam to show the simplicity of the method and the importance of structural tailoring to increase dynamic performance and to reduce the control effort.

  10. CTP:phosphocholine cytidylyltransferase α (CCTα) and lamins alter nuclear membrane structure without affecting phosphatidylcholine synthesis.

    PubMed

    Gehrig, Karsten; Ridgway, Neale D

    2011-06-01

    CTP:phosphocholine cytidylyltransferase α (CCTα) is a nuclear enzyme that catalyzes the rate-limiting step in the CDP-choline pathway for phosphatidylcholine (PC) synthesis. Lipid activation of CCTα results in its translocation to the nuclear envelope and expansion of an intranuclear membrane network termed the nucleoplasmic reticulum (NR) by a mechanism involving membrane deformation. Nuclear lamins are also required for stability and proliferation of the NR, but whether this unique structure, or the nuclear lamina in general, is required for PC synthesis is not known. To examine this relationship, the nuclear lamina was depleted by RNAi or disrupted by expression of the Hutchinson-Gilford progeria syndrome (HGPS) mutant lamin A (progerin), and the effect on CCTα and choline metabolism was analyzed. siRNA-mediated silencing of lamin A/C or lamin B1 in CHO cells to diminish the NR had no effect on PC synthesis, while double knockdown non-specifically inhibited the pathway. Confirming this minor role in PC synthesis, only 10% of transiently overexpressed choline/ethanolamine phosphotransferase was detected in the NR. In CHO cells, CCTα was nucleoplasmic and co-localized with GFP-progerin in nuclear folds and invaginations; however, HGPS fibroblasts displayed an abnormal distribution of CCTα in the cytoplasm and nuclear envelope that was accompanied by a 2-fold reduction in PC synthesis. In spite of its altered localization, choline-labeling experiments showed that CCT activity was unaffected, and inhibition of PC synthesis was traced to reduced activity of a hemicholinium-sensitive choline transporter. We conclude that CCTα and lamins specifically cooperate to form the NR, but the overall structure of the nuclear envelope has a minimal impact on CCT activity and PC synthesis. PMID:21504799

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

    NASA Technical Reports Server (NTRS)

    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.

  12. Gold-Catalyzed Enantioselective Synthesis, Crystal Structure, and Photophysical/Chiroptical Properties of Aza[10]helicenes.

    PubMed

    Tanaka, Maya; Shibata, Yu; Nakamura, Kyosuke; Teraoka, Kota; Uekusa, Hidehiro; Nakazono, Kazuko; Takata, Toshikazu; Tanaka, Ken

    2016-07-01

    The enantioselective synthesis of an aza[10]helicene, possessing two pyridone units, has been achieved by the gold-catalyzed intramolecular quadruple hydroarylation of a tetrayne. This aza[10]helicene was successfully converted into a fully aromatic aza[10]helicene, possessing two pyridine units. Structure-photophysical and chiroptical properties relationship in a series of azahelicene isomers has also been disclosed. PMID:27128222

  13. Total Synthesis and Structure-Activity Relationship of Glycoglycerolipids from Marine Organisms

    PubMed Central

    Zhang, Jun; Li, Chunxia; Yu, Guangli; Guan, Huashi

    2014-01-01

    Glycoglycerolipids occur widely in natural products, especially in the marine species. Glycoglycerolipids have been shown to possess a variety of bioactivities. This paper will review the different methodologies and strategies for the synthesis of biological glycoglycerolipids and their analogs for bioactivity assay. In addition, the bioactivities and structure-activity relationship of the glycoglycerolipids are also briefly outlined. PMID:24945415

  14. Rapid and Convenient Synthesis of the 1,4-Dihydropyridine Privileged Structure

    ERIC Educational Resources Information Center

    Cheung, Lawrence L. W.; Styler, Sarah A.; Dicks, Andrew P.

    2010-01-01

    A short, semi-microscale synthesis of two 1,4-dihydropyridine drug analogues via a Hantzsch reaction is described, which is appropriate for a second-year undergraduate organic laboratory. Products are specifically chosen to highlight the biological relevance of this compound type while introducing the notion of a privileged structure.…

  15. Synthesis and X-ray structures of metallocenium diamines of ironand cobalt

    SciTech Connect

    Inyushin, Sviatoslav; Shafir, Alexandr; Sheats, John E.; Minihane, Michael; Whitten Jr., Charles E.; Arnold, John

    2004-05-30

    A detailed, reproducible synthesis of 1,10-diaminocobaltocenium hexafluorophosphate is provided. The compound can be made on gram scales in several steps starting from 1,10-dimethylcobaltoceniumsalts. The X-ray structures of 1,10-diamino cobaltoceniumhexafluorophosphate and a related 1,10-diamino ferrocenium salt, are described.

  16. Revision Rhinoplasty.

    PubMed

    Loyo, Myriam; Wang, Tom D

    2016-01-01

    Revision rhinoplasty is one of the most challenging operations the facial plastic surgeon performs given the complex 3-dimensional anatomy of the nose and the psychological impact it has on patients. The intricate interplay of cartilages, bone, and soft tissue in the nose gives it its aesthetic and function. Facial harmony and attractiveness depends greatly on the nose given its central position in the face. In the following article, the authors review common motivations and anatomic findings for patients seeking revision rhinoplasty based on the senior author's 30-year experience with rhinoplasty and a review of the literature. PMID:26616705

  17. The Factorial Structure and Construct Validity of the Psychopathy Checklist-Revised (PCL-R) among Alcoholic Inpatients.

    ERIC Educational Resources Information Center

    Windle, Michael; Dumenci, Levent

    1999-01-01

    Conducted simultaneous group confirmatory factor analyses of the Psychopathy Checklist-Revised (PCL-R)(R. Hare, 1991) with 740 alcoholic inpatients. Results provide general support for the use of the PCL-R with alcoholic inpatients, although there was substantial intercorrelation for the factors of Personality and Behavioral Features. (SLD)

  18. 77 FR 74883 - Aging Management of Stainless Steel Structures and Components in Treated Borated Water; Revision 1

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-18

    ..., 2012 (77 FR 27815). Revision 1 of this document corrects the identification numbers for aging... Treated Borated Water,'' in the Federal Register on May 11, 2012 (77 FR 27815). As issued, LR-ISG-2011-01... the Standard Review Plan for Review of License Renewal Applications for Nuclear Power Plants...

  19. Synthesis Structure and Imaging of Oligodeoxyribonucleotides with Tellurium-nucleobase Derivatization

    SciTech Connect

    J Sheng; A Hassan; W Zhang; J Zhou; B Xu; A Soares; Z Huang

    2011-12-31

    We report here the first synthesis of 5-phenyl-telluride-thymidine derivatives and the Te-phosphoramidite. We also report here the synthesis, structure and STM current-imaging studies of DNA oligonucleotides containing the nucleobases (thymine) derivatized with 5-phenyl-telluride functionality (5-Te). Our results show that the 5-Te-DNA is stable, and that the Te-DNA duplex has the thermo-stability similar to the corresponding native duplex. The crystal structure indicates that the 5-Te-DNA duplex structure is virtually identical to the native one, and that the Te-modified T and native A interact similarly to the native T and A pair. Furthermore, while the corresponding native showed weak signals, the DNA duplex modified with electron-rich tellurium functionality showed strong topographic and current peaks by STM imaging, suggesting a potential strategy to directly image DNA without structural perturbation.

  20. Synthesis, structure and imaging of oligodeoxyribonucleotides with tellurium-nucleobase derivatization

    SciTech Connect

    Sheng, J.; Soares, A.; Hassan, A. E. A.; Zhang, W.; Zhou, J.; Xu, B.; Huang, Z.

    2011-05-01

    We report here the first synthesis of 5-phenyl-telluride-thymidine derivatives and the Te-phosphoramidite. We also report here the synthesis, structure and STM current-imaging studies of DNA oligonucleotides containing the nucleobases (thymine) derivatized with 5-phenyl-telluride functionality (5-Te). Our results show that the 5-Te-DNA is stable, and that the Te-DNA duplex has the thermo-stability similar to the corresponding native duplex. The crystal structure indicates that the 5-Te-DNA duplex structure is virtually identical to the native one, and that the Te-modified T and native A interact similarly to the native T and A pair. Furthermore, while the corresponding native showed weak signals, the DNA duplex modified with electron-rich tellurium functionality showed strong topographic and current peaks by STM imaging, suggesting a potential strategy to directly image DNA without structural perturbation.

  1. Synthesis, structure, and frequency-doubling effect of calcium cyanurate.

    PubMed

    Kalmutzki, Markus; Ströbele, Markus; Wackenhut, Frank; Meixner, Alfred J; Meyer, H-Jürgen

    2014-12-15

    Calcium cyanurate is synthesized by reacting calcium chloride with potassium cyanate following a solid-state reaction. The formation of the new compound Ca3(O3C3N3)2 (CCY), which occurs by the cyclotrimerization of cyanate ions, was examined thermoanalytically and the crystal structure was determined by single-crystal structure analysis. The structure of CCY is closely related to the structure of the well-known oxoborate β-BaB2O4 (BBO). Second harmonic generation (SHG) measurements on crystal powders show a higher SHG efficiency for CCY than for BBO by about one order of magnitude. PMID:25345390

  2. Synthesis of the cyanobacterial metabolite nostodione A, structural studies and potent antiparasitic activity against Toxoplasma gondii.

    PubMed

    McNulty, James; Keskar, Kunal; Jenkins, Hilary A; Werstiuk, Nick H; Bordón, Claudia; Yolken, Robert; Jones-Brando, Lorraine

    2015-10-21

    A total synthesis of the cyanobacterial natural product nostodione A is reported involving a convergent, diversity-oriented route, enabling the assembly of a mini-library of structural analogues. The first single crystal X-ray structural determination on a member of this series is reported along with SAR studies identifying potent inhibitors of invasion and replication of the parasitic protozoan Toxoplasma gondii. PMID:26291306

  3. Total Synthesis of (+)-Minfiensine: Construction of the Tetracyclic Core Structure by an Asymmetric Cascade Cyclization.

    PubMed

    Zhang, Ze-Xin; Chen, Si-Cong; Jiao, Lei

    2016-07-01

    A new method for one-step construction of the tetracyclic core structure of the indole alkaloid (+)-minfiensine was developed utilizing a palladium-catalyzed asymmetric indole dearomatization/iminium cyclization cascade. An efficient total synthesis of (+)-minfiensine was realized using this strategy. The present method enables access to the common core structure of a series of monoterpene indole alkaloids, such as vincorine, echitamine, and aspidosphylline A. PMID:27172972

  4. Polyrhythmic Tapping: Examining the Effectiveness of the Strategy of Organizing Rhythmic Structures through Synthesis

    ERIC Educational Resources Information Center

    Yokus, Hamit; Yokus, Tuba

    2015-01-01

    In this study the strategy of organizing rhythmic structures through synthesis is named, and defined, and its procedures are described. Its effectiveness for teaching the execution of 3:2, 4:3, 8:3, 5:4, and 3:5 polyrhythmic structures is examined and described. Pre-test and Post-test Control Group Design was employed to test the effectiveness of…

  5. Isolation and Structure of Kurahyne B and Total Synthesis of the Kurahynes.

    PubMed

    Okamoto, Shinichiro; Iwasaki, Arihiro; Ohno, Osamu; Suenaga, Kiyotake

    2015-11-25

    Kurahyne B (2), a new analogue of kurahyne (1), was isolated from the marine cyanobacterium Okeania sp. Its gross structure was elucidated based on spectroscopic analyses, and the absolute configuration was established by total synthesis. Kurahyne B (2) inhibited the growth of both HeLa and HL60 cells, with IC50 values of 8.1 and 9.0 μM, respectively. The growth-inhibitory activity of kurahyne B was the same as kurahyne (1). In parallel, the first total synthesis of kurahyne (1) was also achieved. PMID:26539973

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  7. Field-structured material media and methods for synthesis thereof

    DOEpatents

    Martin, James E.; Hughes, Robert C.; Anderson, Robert A.

    2001-09-18

    The present application is directed to a new class of composite materials, called field-structured composite (FSC) materials, which comprise a oriented aggregate structure made of magnetic particles suspended in a nonmagnetic medium, and to a new class of processes for their manufacture. FSC materials have much potential for application, including use in chemical, optical, environmental, and mechanical sensors.

  8. Reduced models of multi-stage cyclic structures using cyclic symmetry reduction and component mode synthesis

    NASA Astrophysics Data System (ADS)

    Tran, Duc-Minh

    2014-10-01

    Reduced models of multi-stage cyclic structures such as bladed-disk assemblies are developed by using the multi-stage cyclic symmetry reduction and/or component mode synthesis methods. The multi-stage cyclic symmetry reduction consists in writing the equations of the bladed disks, the inter-disk structures, the inter-disk constraints and the whole multi-stage coupled system in terms of the traveling wave coordinates for all the phase indexes of the reference sectors and for all the bladed disks. Several reduced coupled systems are then solved by selecting at each time only one or a few phase indexes for each bladed disk and by applying the cyclic symmetry boundary conditions. On the other hand, component mode synthesis methods are used either independently or in combination with the multi-stage cyclic symmetry reduction to obtain reduced models of the multi-stage structure. Two of them are particularly efficient, that are firstly component mode synthesis methods with interface modes applied on the bladed disks and secondly component mode synthesis methods with traveling wave coordinates applied on the reference sectors.

  9. Structure Diversity, Synthesis, and Biological Activity of Cyathane Diterpenoids in Higher Fungi.

    PubMed

    Tang, Hao-Yu; Yin, Xia; Zhang, Cheng-Chen; Jia, Qian; Gao, Jin-Ming

    2015-01-01

    Cyathane diterpenoids, occurring exclusively in higher basidiomycete (mushrooms), represent a structurally diverse class of natural products based on a characteristic 5-6-7 tricyclic carbon scaffold, including 105 members reported to date. These compounds show a diverse range of biological activities, such as antimicrobial, anti-MRSA, agonistic toward the kappa-opioid receptor, antiinflammatory, anti-proliferative and nerve growth factor (NGF)-like properties. The present review focuses on the structure diversity, structure elucidation and biological studies of these compounds, including mechanisms of actions and structure-activity relationships (SARs). In addition, new progress in chemical synthesis of cyathane diterpenoids is discussed. PMID:25994862

  10. Enantiospecific Synthesis and Biological Investigations of a Nuphar Alkaloid: Proposed Structure of a Castoreum Component

    PubMed Central

    Seki, Hajime; Georg, Gunda I.

    2014-01-01

    An enantiospecific synthesis of a Nuphar alkaloid was achieved in 9 steps from N-Boc-(L)-proline. The alkaloid is a minor component of castoreum, the dried scent glands of the beaver. During the course of our study, the stereochemistry of three synthetic intermediates was verified by X-ray analysis, which contributes to resolving existing discrepancies among the literature reports regarding the synthesis of this particular compound. Based on our synthesis, we propose the structure of the natural product. Also, intrigued by castoreum’s therapeutic effect, which was used in ancient Greece and Rome for gynecological and other purposes, biological screening was conducted. We found that the alkaloid has affinity for the oxytocin receptor. PMID:25395879

  11. Enantiospecific Synthesis and Biological Investigations of a Nuphar Alkaloid: Proposed Structure of a Castoreum Component.

    PubMed

    Seki, Hajime; Georg, Gunda I

    2014-06-01

    An enantiospecific synthesis of a Nuphar alkaloid was achieved in 9 steps from N-Boc-(L)-proline. The alkaloid is a minor component of castoreum, the dried scent glands of the beaver. During the course of our study, the stereochemistry of three synthetic intermediates was verified by X-ray analysis, which contributes to resolving existing discrepancies among the literature reports regarding the synthesis of this particular compound. Based on our synthesis, we propose the structure of the natural product. Also, intrigued by castoreum's therapeutic effect, which was used in ancient Greece and Rome for gynecological and other purposes, biological screening was conducted. We found that the alkaloid has affinity for the oxytocin receptor. PMID:25395879

  12. Structural diversity and chemical synthesis of peroxide and peroxide-derived polyketide metabolites from marine sponges.

    PubMed

    Norris, Matthew D; Perkins, Michael V

    2016-07-28

    Covering: up to early 2016Marine sponges are widely known as a rich source of natural products, especially of polyketide origin, with a wealth of chemical diversity. Within this vast collection, peroxide and peroxide-derived secondary metabolites have attracted significant interest in the fields of natural product isolation and chemical synthesis for their structural distinction and promising in vitro antimicrobial and anticancer properties. In this review, peroxide and peroxide-derived polyketide metabolites isolated from marine sponges in the past 35 years are summarised. Efforts toward their synthesis are detailed with a focus on methods that utilise or attempt to elucidate the complex biosynthetic interrelationships of these compounds beyond enzymatic polyketide synthesis. Recent isolations, advances in synthetic methodology and theories of biogenesis are highlighted and critically evaluated. PMID:27163115

  13. Structural specificity of steroids in stimulating DNA synthesis and protooncogene expression in primary rat hepatocyte cultures.

    PubMed

    Lee, C H; Edwards, A M

    2002-05-01

    Among the chemical compounds of varied structure which possess liver tumour-promoting are steroids, such as estrogens, pregnenolone derivatives and anabolic steroids. Although the mechanism(s) of tumour promotion in liver by these xenobiotics is not well understood, it is clear that growth stimulation is one important element in their action. As a basis for better defining whether steroids stimulate growth by a common mechanism or fall into sub-groups with differing actions, the effects of 46 steroids on DNA synthesis and the expression of protooncogenes c-fos and c-myc were examined in primary cultures of normal rat hepatocytes. Tentative groupings of steroids have been identified based on apparent structural requirements for stimulation of DNA synthesis, and effects of auxiliary factors in modulating this growth stimulus. For a "progestin" group, insulin appeared to be permissive for stimulation of DNA synthesis, and presence of an ester or hydroxyl group at 17alpha-position in combination with a non-polar group at C(6) appeared to be required for stimulation. For the pregnenes, dexamethasone was stimulatory. Structural requirements include a non-polar substitution at 16alpha-position and presence of a 6alpha-methyl group. Androgens were weak or ineffective stimulators of DNA synthesis. Anabolic steroids were weak to strong stimulators and alteration to A ring structure in combination with non-polar substitution at 17alpha-position appeared to be required for the activity. With the exception of the anabolic steroid, dianabol, there do not appear to be strong correlation between ability to stimulate DNA synthesis and ability to induce protooncogene expression among the steroids. This study provides a starting point for future more detailed examination of growth-stimulatory mechanism(s) of action of steroids in the liver. PMID:12127039

  14. Synthesis of gold nanoparticles with different atomistic structural characteristics

    SciTech Connect

    Esparza, R. . E-mail: roesparza@gmail.com; Rosas, G.; Lopez Fuentes, M.; Sanchez Ramirez, J.F.; Pal, U.; Ascencio, J.A.; Perez, R.

    2007-08-15

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Here, we report the preparation and characterization of two lead(II) phosphites, namely, Pb2(HPO3)2 and Pb2(HPO3)(NO3)2 through hydrothermal reaction or simple solution synthesis, respectively. A new lead phosphite, namely, Pb2(HPO3)2, crystallizes in the noncentrosymmetric space group Cmc21 (no. 36), which features 3D framework formed by the interconnection of 2D layer of lead(II) phosphites and 1D chain of [Pb(HPO3)5]∞. The nonlinear optical properties of Pb2(HPO3)(NO3)2 have been studied for the first time. The synergistic effect of the stereo-active lone-pairs on Pb2+ cations and π-conjugated NO3 units in Pb2(HPO3)(NO3)2 produces a moderate second harmonic generation (SHG) response of ∼1.8×KDP (KH2PO4), which is phase matchable (type I). IR, UV-vis spectra and thermogravimetric analysis (TGA) for the two compounds were also measured.

  16. Synthesis, physicochemical, structural and rheological characterizations of carboxymethyl xanthan derivatives.

    PubMed

    Yahoum, Madiha M; Moulai-Mostefa, Nadji; Le Cerf, Didier

    2016-12-10

    The aim of this work was to synthesize a carboxymethylated xanthan (CMXG) via an etherification reaction between different ratios (2, 4, and 6) of xanthan gum (XG) and monochloroacetic acid (MCAA) using the Williamson synthesis method. The synthetized products were characterized in terms of their physico-chemical and rheological properties. Both FTIR and proton nuclear magnetic resonance (H(1) NMR) analyses confirmed the grafting of carboxymethyl groups on xanthan hydroxyl groups. The obtained results demonstrated that the degree of substitution was proportional to the chloroacetic acid and xanthan gum ratios. The obtained carboxymethyl derivatives presented greater hydrophilicity and lower molecular weights with increasing degrees of substitution than native xanthan gum. The rheological study revealed that the viscosity of the CMXG derivatives decreased with the degree of substitution and with the conservation of the shear-thinning and weak gel behaviours. The flow curves suggested the existence of two different populations of particles consisting of CMXG particles with a smaller average size and a second population formed by the residual fractions of native XG particles. It was also found that the elastic modulus of XG was largely higher than that of the CMXG derivatives and decreased with increasing DS. For the CMXG derivatives, two regions of viscoelastic behaviour were observed, which were separated by a crossover point corresponding to the critical frequency and relaxation time, i.e., the time required for stress relaxation. PMID:27577918

  17. The Effects of Gravity on Combustion and Structure Formation During Synthesis of Advanced Materials

    NASA Technical Reports Server (NTRS)

    Varma, A.; Pelekh, A.; Mukasyan, A.

    1999-01-01

    Combustion in a variety of heterogeneous systems, leading to the synthesis of advanced materials, is characterized by high temperatures (2000-3500 K) and heating rates (up to 10(exp 6) K/s) at and ahead of the reaction front. These high temperatures generate liquids and gases which are subject to gravity-driven flow. The removal of such gravitational effects is likely to provide increased control of the reaction front, with a consequent improvement in control of the microstructure of the synthesized products. Thus, microgravity experiments can lead to major advances in the understanding of fundamental aspects of combustion and structure formation under the extreme conditions of the combustion synthesis wave. In addition, the specific features of microgravity environment allow one to produce unique materials, which cannot be obtained under terrestrial conditions. The general goals of the current research are: 1) to improve the understanding of fundamental phenomena taking place during combustion of heterogeneous systems, 2) to use low-gravity experiments for insight into the physics and chemistry of materials synthesis processes, and 3) based on the obtained knowledge, to optimize processing conditions for synthesis of advanced materials with desired microstructures and properties. This research follows logically from the results of investigations we have conducted in the framework of our previous grant on gravity influence on combustion synthesis (CS) of gasless systems. Prior work, by others and by us, has clearly demonstrated that gravity plays an important role during combustion synthesis of materials. The immediate tasks for the future are to quantitatively identify the nature of observed effects, and to create accurate local kinetic models of the processes, which can lead to a control of the microstructure and properties of the synthesized materials. In summary, this is the value of the proposed research. Based on our prior work, we focus on the fundamental

  18. Thiosaccharine disulfide: Synthesis, crystal structure, spectroscopic characterization and theoretical study

    NASA Astrophysics Data System (ADS)

    Ferullo, Ricardo M.; Granados, Alejandro; Lanterna, Anabel; Güida, Jorge A.; Piro, Oscar E.; Castellano, Eduardo E.; Dennehy, Mariana

    2013-01-01

    The title compound, (thiosaccharine disulfide), bis[1,1'dioxide-2,3-dihidro-1,2-benzoisothiazol]disulfide, (tsac)2 has been synthesized and fully characterized by UV-Visible, IR, Raman, 1H and 13C NMR spectroscopy elemental analysis and structural X-ray crystallography. A DFT theoretical study has been performed and good agreement between experimental and theoretical values of structural parameters and vibration frequencies have been achieved.

  19. Synthesis of ultra dispersed graphite-like structures doped with nitrogen in supersonic carbon plasma flow

    NASA Astrophysics Data System (ADS)

    Sivkov, A.; Pak, A.; Shanenkov, I.; Kolganova, J.; Shatrova, K.

    2014-10-01

    In this paper the synthesis of ultra dispersed graphite-like structures doped with nitrogen by using a magneto plasma accelerator is shown. The synthesis of such structures is realized during supersonic carbon plasma jet flowing into the chamber filled with the nitrogen atmosphere. Plasma jet is generated by coaxial magneto plasma accelerator (CMPA) based on graphite electrode system. The CMPA is supplied from the pulsed capacitive energy storage with the maximum value of stored energy of 360 kJ. Electrical and energy parameters of plasma flow are recorded during experiment. According to X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) methods obtained particles with well seen triangle sectors are graphite-like carbon structures doped with nitrogen atoms. This is confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses in which carbon- nitrogen bonding configurations have been identified.

  20. Revised structures of gambiriins A1, A2, B1, and B2, chalcane-flavan dimers from gambir (Uncaria gambir extract).

    PubMed

    Taniguchi, Shoko; Kuroda, Kayo; Doi, Kou-ichi; Tanabe, Masahiro; Shibata, Takashi; Yoshida, Takashi; Hatano, Tsutomu

    2007-02-01

    Gambir, the aqueous extract from Uncaria gambir (Rubiaceae), has been used as an astringent medicine in Asian countries. Investigation of the constituents in the extract led to the isolation of four chalcane-flavan dimers, gambiriin A1 (6), A2 (7), B1 (8), and B2 (9), in addition to (+)-catechin (1), (+)-epicatechin (2), and dimeric proanthocyanidins, procyanidin B1 (3), procyanidin B3 (4), and gambiriin C (5). The spectroscopic and chemical data obtained in the present study indicated that their previously proposed structures 6a, 7a, 8a, and 9a should be revised to 6, 7, 8, and 9, respectively. PMID:17268100

  1. Synthesis and characterization of a new structure of gas hydrate

    SciTech Connect

    Tulk, Christopher A; Chakoumakos, Bryan C; Ehm, Lars; Klug, Dennis D; Parise, John B; Yang, Ling; Martin, Dave; Ripmeester, John; Moudrakovski, Igor; Ratcliffe, Chris

    2009-01-01

    Atoms and molecules 0.4 0.9 nm in diameter can be incorporated in the cages formed by hydrogen-bonded water molecules making up the crystalline solid clathrate hydrates. There are three structural families of these hydrates , known as sI, sII and sH, and the structure usually depends on the largest guest molecule in the hydrate. Species such as Ar, Kr, Xe and methane form sI or sII hydrate, sH is unique in that it requires both small and large cage guests for stability. All three structures, containing methane, other hydrocarbons, H2S and CO2, O2 and N2 have been found in the geosphere, with sI methane hydrate by far the most abundant. At high pressures (P > 0.7 kbar) small guests (Ar, Kr, Xe, methane) are also known to form sH hydrate with multiple occupancy of the largest cage in the hydrate. The high-pressure methane hydrate of sH has been proposed as playing a role in the outer solar system, including formation models for Titan , and yet another high pressure phase of methane has been reported , although its structure remains unknown. In this study, we report a new and unique hydrate structure that is derived from the high pressure sH hydrate of xenon. After quench recovery at ambient pressure and 77 K it shows considerable stability at low temperatures (T < 160 K) and is compositionally similar to the sI Xe clathrate starting material. This evidence of structural complexity in compositionally similar clathrate compounds indicates that thermodynamic pressure temperature conditions may not be the only important factor in structure determination, but also the reaction path may have an important effect.

  2. Synthesis and Characterization of Elastomeric Heptablock Terpolymers Structured by Crystallization

    SciTech Connect

    Alfonzo, C.Guillermo; Fleury, Guillaume; Chaffin, Kimberly A.; Bates, Frank S.

    2010-12-07

    We report the synthesis and characterization of fully saturated hydrocarbon block copolymer thermoplastic elastomers with competitive mechanical properties and attractive processing features. Block copolymers containing glassy poly(cyclohexylethylene) (C), elastomeric poly(ethylene-alt-propylene) (P), and semicrystalline poly(ethylene) (E) were produced in a CEC-P-CEC heptablock architecture, denoted XPX, by anionic polymerization and catalytic hydrogenation. The X blocks contain equal volume fractions of C and E, totaling 40%-60% of the material overall. All the XPX polymers are disordered above the melt temperature for E (T{sub m,E} {approx_equal} 95 C) as evidenced by SAXS and dynamic mechanical spectroscopy measurements. Cooling below T{sub m,E} results in crystallization of the E blocks, which induces microphase segregation of E, C, and P into a complex morphology with a continuous rubbery domain and randomly arranged hard domains as shown by TEM. This mechanism of segregation decouples the processing temperature from the XPX molecular weight up to a limiting value. Tensile mechanical testing (simple extension and cyclic loading) demonstrates that the tensile strength (ca. 30 MPa) and strain at break (>500%) are comparable to the behavior of CPC triblock thermoplastic elastomers of similar molecular weight and glass content. However, in the CPC materials, processability is constrained by the order-disorder transition temperature, limiting the applications of these materials. Elastic recovery of the XPX materials following seven cycles of tensile deformation is correlated with the fraction of X in the heptablock copolymer, and the residual strain approaches that of CPC when the fraction of hard blocks f{sub X} {le} 0.39.

  3. Synthesis, spectroscopic and structural perspective of new ferrocenyl amides

    NASA Astrophysics Data System (ADS)

    Etter, Martin; Nigar, Asifa; Ali, Naveed Zafar; Akhter, Zareen; Dinnebier, Robert E.

    2016-05-01

    Two new ferrocene derivatives with amide linkages were synthesized by the condensation of 4-ferrocenylaniline with n-alkyl acid chloride derivatives as pristine orange solids in good yields. FTIR and 1H/13C NMR studies have confirmed the basic structure of the molecules with the involvement of intermolecular H-bonding, which together with the ferrocene-like packing ensures the stability of the crystal structure. Crystal structures for both compounds were solved by Rietveld refinements of high resolution X-ray powder diffraction data. The XRD results show that both compounds crystallize in the monoclinic space group P21/c. The primary feature of the crystal structure is a double layer of ferrocenyl groups stretched out in the b-c -plane perpendicular to the a-axis, with packing of the ferrocenyl groups occurring in a manner similar to that of pure ferrocene. Despite the close structural similarity, both compounds differ in the optimized geometry of respective Ferrocene conformers. The Cp rings are eclipsed for one Ferrocene conformer and close to staggered for the other, owing to the low energy barrier for the rotation of a cyclopentadienyl ring relative to the rest of the molecule.

  4. Stereoselectively synthesis and structural confirmation of dehydrodipeptides with dehydrobutyrine.

    PubMed

    Tian, Xia; Li, Linna; Han, Jianrong; Zhen, Xiaoli; Liu, Shouxin

    2016-01-01

    Most of polypeptides containing α,β-dehydroamino acids have important biological activity, so exploration of synthetic method has practical significance. In this paper, dipeptides were prepared from l-threonine by protecting of c-terminal allyl acetate, and condensing reaction with a series of N-Boc amino acid. Then, treatment of dipeptides obtained with DMAP, (Boc)2O and tetramethylguanidine in the acetonitrile occured β-elimination reaction to yield stereoselectively dehydrodipeptides. Structures of dehydrodipeptides were confirmed by (1)H NMR, (13)C NMR and MS. Analysis of (1)H NMR, 2D NMR and crystal structure showed that the dehydrodipeptides were Z-configuration.Graphical abstractDehydrodipeptides were prepared from l-threonine. Their structures were confirmed by (1)H NMR, (13)C NMR and MS. PMID:27047726

  5. Synthesis, Structural, Electrical and Magnetic Studies of Ni- Ferrite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Godbole, Bhavana; Badera, Nitu; Shrivastava, S. B.; Jain, Deepti; Chandra, L. S. Sharath; Ganesan, V.

    Mono-dispersed NiFe2O4 nanoparticles have been synthesized using a stable ferric salt of FeCl3 with co-precipitation technique, for study of their structural, morphological and magnetic properties. The XRD pattern conforms the formation of FCC structure with the lattice constant 8.31Ao. The crystallite size was found to increase with the bath temperature ranging from 33 nm to 55 nm. The AFM results revealed that uniform disc shaped particles were obtained. The resistivity measurements show a metal like to semiconductor transition, which depends on the size of the grains. The magnetic study reveals that saturation magnetization increases with the grain thickness.

  6. Structure/control synthesis with nonnegligible actuator mass

    NASA Technical Reports Server (NTRS)

    Zimmerman, David C.

    1990-01-01

    The simultaneous design of a structure/active control system is addressed in which the mass of the actuators required to implement the active control is considered. An algorithm for estimating the required actuator mass given the control law and the desired maneuver is presented. A nonlinear optimization algorithm is used to direct the design process. Results are given for the design of a L shaped structure where it is desired to minimize the line of sight pointing error after a worst case slew maneuver.

  7. Fischer-Tropsch Synthesis on Ceramic Monolith-Structured Catalysts

    SciTech Connect

    Wang, Yong; Liu, Wei

    2009-04-19

    This paper reports recent research results about impact of different catalyst bed configurations on FT reaction product distribution. A CoRe/γ-alumina catalyst is prepared in bulk particle form and tested in the packed bed reactor at a size of 60 to 100 mesh. The same catalyst is ball milled and coated on a ceramic monolith support structure of channel size about 1mm. The monolith catalyst module is tested in two different ways, as a whole piece and as well-defined channels. Steady-state reaction conversion is measured at various temperatures under constant H2/CO feed ratio of 2 and reactor pressure of 25 bar. Detailed product analysis is performed. Significant formation of wax is evident with the packed particle bed and with the monolith catalyst that is improperly packed. By contrast, the wax formation is not detected in the liquid product by confining the reactions inside the monolith channel. This study presents an important finding about the structured catalyst/reactor system that the product distribution highly depends on the way how the structured reactor is set up. Even if the same catalyst and same reaction conditions (T, P, H2/oil ratio) are used, hydrodynamics (or flow conditions) inside a structured channel can have a significant impact on the product distribution.

  8. Low-authority control synthesis for large space structures

    NASA Technical Reports Server (NTRS)

    Aubrun, J. N.; Margulies, G.

    1982-01-01

    The control of vibrations of large space structures by distributed sensors and actuators is studied. A procedure is developed for calculating the feedback loop gains required to achieve specified amounts of damping. For moderate damping (Low Authority Control) the procedure is purely algebraic, but it can be applied iteratively when larger amounts of damping are required and is generalized for arbitrary time invariant systems.

  9. Synthesis, structure, and properties of glasses under extreme conditions

    NASA Astrophysics Data System (ADS)

    Guerette, Michael J.

    Anomalous mechanical properties of silica glass include stiffening upon heating, initially softening under pressure, and non-linear elastic response to strains. Through understanding structural changes in silica glass under a broad range of temperature, pressure, and strain conditions and how they influence the mechanical properties, insight was gained for how to change the silica glass network to better suit specific uses in extreme conditions. In this dissertation, pressure-quenching routes were used to effectively change the glass atomic packing and to make densified glass. Applied in the non-rigid state near the glass transition temperature, quench pressures up to 8 GPa have been used to achieve density increase of 25% in silica glass. The resulting structure and properties of as-quenched samples have been investigated using XRD, Raman and Brillouin spectroscopy. In-situ Raman and Brillouin light scattering techniques were developed to study the structure, elastic and dynamic properties of silica glass under high temperature, high pressure and high strain conditions. High temperature measurements were carried out in an optical furnace up to 1500°C, a diamond anvil cell was used to carry out high pressure experiments up to 25 GPa, and a two-point bender was used for measuring glasses in excess of 6% strain in both tensile and compressive regions. Pressure-quenching from the non-rigid state near the glass transition temperature imparts structural signatures to densified silica glass that cannot be accomplished through cold compression at room temperature. The unique structures of pressure-quenched silica glass are reflected in decreased anomalous response of silica glass to external stimuli of high temperature or high pressure, and therefore greater thermo-mechanical stability. The nonlinear elastic behavior of silica glass has been directly probed from the compressive to the tensile side of silica fibers in bend by using in-situ Brillouin light scattering. This

  10. Lanthanide coordination polymers: Synthesis, diverse structure and luminescence properties

    SciTech Connect

    Song, Xue-Qin Lei, Yao-Kun; Wang, Xiao-Run; Zhao, Meng-Meng; Peng, Yun-Qiao; Cheng, Guo-Quan

    2014-10-15

    The new semirigid exo-bidentate ligand incorporating furfurysalicylamide terminal groups, namely, 1,4-bis([(2′-furfurylaminoformyl)phenoxyl]methyl)-2,5-bismethylbenzene (L) was synthesized and used as building blocks for constructing lanthanide coordination polymers with luminescent properties. The series of lanthanide nitrate complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray diffraction analysis. The semirigid ligand L, as a bridging ligand, reacts with lanthanide nitrates forming three distinct structure types: chiral noninterpenetrated two-dimensional (2D) honeycomblike (6,3) (hcb, Schläfli symbol 6{sup 3}, vertex symbol 6 6 6) topological network as type I, 1D zigzag chain as type II and 1D trapezoid ladder-like chain as type III. The structural diversities indicate that lanthanide contraction effect played significant roles in the structural self-assembled process. The luminescent properties of Eu{sup III}, Tb{sup III} and Dy{sup III} complexes are discussed in detail. Due to the good match between the lowest triplet state of the ligand and the resonant energy level of the lanthanide ion, the lanthanide ions in Eu{sup III}, Tb{sup III} and Dy{sup III} complexes can be efficiently sensitized by the ligand. - Graphical abstract: We present herein six lanthanide coordination polymers of a new semirigid exo-bidentate ligand which not only display diverse structures but also possess strong luminescence properties. - Highlights: • We present lanthanide coordination polymers of a new semirigid exo-bidentate ligand. • The lanthanide coordination polymers exhibit diverse structures. • The luminescent properties of Tb{sup III}, Eu{sup III} and Dy{sup III} complexes are discussed in detail.

  11. Computer-aided methods for analysis and synthesis of supersonic cruise aircraft structures

    NASA Technical Reports Server (NTRS)

    Giles, G. L.

    1976-01-01

    Computer-aided methods are reviewed which are being developed by Langley Research Center in-house work and by related grants and contracts. Synthesis methods to size structural members to meet strength and stiffness (flutter) requirements are emphasized and described. Because of the strong interaction among the aerodynamic loads, structural stiffness, and member sizes of supersonic cruise aircraft structures, these methods are combined into systems of computer programs to perform design studies. The approaches used in organizing these systems to provide efficiency, flexibility of use in an iterative process, and ease of system modification are discussed.

  12. Wet-chemical synthesis and applications of non-layer structured two-dimensional nanomaterials

    PubMed Central

    Tan, Chaoliang; Zhang, Hua

    2015-01-01

    Non-layer structured nanomaterials with single- or few-layer thickness have two-dimensional sheet-like structures and possess intriguing properties. Recent years have seen major advances in development of a host of non-layer structured ultrathin two-dimensional nanomaterials such as noble metals, metal oxides and metal chalcogenides. The wet-chemical synthesis has emerged as the most promising route towards high-yield and mass production of such nanomaterials. These nanomaterials are now finding increasing applications in a wide range of areas including catalysis, energy production and storage, sensor and nanotherapy, to name but a few. PMID:26303763

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

    PubMed

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

    2015-02-01

    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. PMID:25349948

  14. Lanthanide coordination polymers: Synthesis, diverse structure and luminescence properties

    NASA Astrophysics Data System (ADS)

    Song, Xue-Qin; Lei, Yao-Kun; Wang, Xiao-Run; Zhao, Meng-Meng; Peng, Yun-Qiao; Cheng, Guo-Quan

    2014-10-01

    The new semirigid exo-bidentate ligand incorporating furfurysalicylamide terminal groups, namely, 1,4-bis{[(2‧-furfurylaminoformyl)phenoxyl]methyl}-2,5-bismethylbenzene (L) was synthesized and used as building blocks for constructing lanthanide coordination polymers with luminescent properties. The series of lanthanide nitrate complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray diffraction analysis. The semirigid ligand L, as a bridging ligand, reacts with lanthanide nitrates forming three distinct structure types: chiral noninterpenetrated two-dimensional (2D) honeycomblike (6,3) (hcb, Schläfli symbol 63, vertex symbol 6 6 6) topological network as type I, 1D zigzag chain as type II and 1D trapezoid ladder-like chain as type III. The structural diversities indicate that lanthanide contraction effect played significant roles in the structural self-assembled process. The luminescent properties of EuIII, TbIII and DyIII complexes are discussed in detail. Due to the good match between the lowest triplet state of the ligand and the resonant energy level of the lanthanide ion, the lanthanide ions in EuIII, TbIII and DyIII complexes can be efficiently sensitized by the ligand.

  15. Synthesis, properties and structure of ion exchanged hydrosodalite

    NASA Astrophysics Data System (ADS)

    Kendrick, Emma; Dann, Sandra

    2004-04-01

    Alkali metal and alkali-earth metal hydrosodalites with the formula M6[AlSiO 4] 6·8H 2O ( M=Li, Na, K, Mg, Ca, Sr) have been prepared by ion exchange of Na 6[AlSiO 4] 6·8H 2O using a solution of the appropriate metal nitrate solution under reflux for a period of 24 h. The starting materials and products were characterized using a combination of techniques including IR, DSC, TGA, ICP, AA, MASNMR and X-ray diffraction. The alkali metal and alkali-earth metal hydrosodalites crystallize with the primitive cubic sodalite unit cell and an ordered AlO 4/SiO 4 framework in the space group P 4¯3n with cell parameters lying between 8.8 and 9.2 Å. The structures of these materials have been refined using powder X-ray diffraction data in order to delineate structural changes as a function of the occluded cation. Temperature-dependent powder X-ray diffraction has been used to observe changes in the structure as a function of temperature. Results from the DSC and TGA analysis show that the temperature at which water is lost from the β cages is a two-stage process. In the second stage, the temperature rises as the size of occluded cation increases, implying that the presence of a larger cation in the six-ring window blocks the path of the exiting water molecules.

  16. Synthesis of Au nanowires with controlled morphological and structural characteristics

    NASA Astrophysics Data System (ADS)

    Singh, Gurvinder; van Helvoort, Antonius T. J.; Bandyopadhyay, Sulalit; Volden, Sondre; Andreassen, Jens-Petter; Glomm, Wilhelm R.

    2014-08-01

    A growth of one-dimensional noble metal nanostructure with controlled structural characteristic has been under intense investigation as the physical properties, for example, mechanical and electrical properties highly depend on the crystallinity of the nanostructure. Herein, we report a seed-mediated growth of gold nanowires with controlled structural and morphological characteristics, which can easily be varied by selecting appropriate seed nanoparticles, either spherical or rod type in aqueous solution at room temperature. The growth of nanowires was monitored by characterizing the samples at different time period during the reaction, and our observations suggest that growth occurs from seeds rapidly growing along one-dimension followed by surfactant induced fusion or welding and surface diffusion. The aspect ratio and morphology of these NWs can be tuned by CTAB concentration, pH and temperature of the growth solution. We show that the aspect ratio and morphology of these NWs can be tuned by the surfactant concentration, pH and temperature of the growth solution. Electron microscopy and X-ray Photoelectron spectroscopic techniques were employed for investigating structural and surface characteristics of nanowires. This approach can possibly help to synthesize nanowires of other metals with controlled crystalline behaviour which is highly essential for understanding their properties and practical applications in nanoelectronics, optical devices, catalysis, and sensors.

  17. Synthesis and structure of didysprosium complexes with a tetraketone

    NASA Astrophysics Data System (ADS)

    Yang, Luqin; Yang, Rudong

    1996-06-01

    Two novel didysprosium (Dy 2) complexes of 1,5-bis(1'-phenyl-3'-methyl-5'-pyrazolone-4')-1,5-pentanedione (H 2L), Dy 2L 3·2H 2O and Dy 2L 3·5DMF (DMF = dimethylformamide), have been synthesized. The crystal structure of Dy 2L 3·5DMF was determined by X-ray diffraction. Crystals are triclinic, space group P1¯, with a = 16.99(1), b = 17.970(9), c = 18.28(1) Å, α = 110.36(4), β = 101.47(6), γ = 111.11(5)°, V = 4533(9) Å 3, Mr = 2017.91, Z = 2, D x = 1.48 g cm -3, μ = 17.22 cm -1, F(000) = 2056, R = 0.074 with 3804 reflections used in the refinement. In the complex, each L bonds two dysprosium atoms with its two β-diketone groups. Two DMF solvent molecules bond to each dysprosium ion. The coordination number of the two dysprosium ions is eight. The eight oxygen atoms around the dysprosium ion make up a distorted square antiprism coordination polyhedron. The resonance structures of coordinated β-diketonates are also discussed. Different lanthanide ions may stabilize the specific structure.

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

    SciTech Connect

    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

  19. Synthesis, structure, and magnetic characterization of Cr4US8

    NASA Astrophysics Data System (ADS)

    Ward, Matthew D.; Chan, Ian Y.; Malliakas, Christos D.; Lee, Minseong; Choi, Eun Sang; Ibers, James A.

    2016-01-01

    The compound Cr4US8 has been synthesized at 1073 K and its crystal structure has been determined at 100 K. The structure is modulated with a two-fold commensurate supercell. The subcell may be indexed in an orthorhombic cell but weak supercell reflections lead to the monoclinic superspace group P21/c(α0γ)0s with two Cr sites, one U site, and four S sites. The structure comprises a three-dimensional framework of CrS6 octahedra with channels that are partially occupied by U atoms. Each U atom in these channels is coordinated by eight S atoms in a bicapped trigonal-prismatic arrangement. The magnetic behavior of Cr4US8 is complex. At temperatures above ~120 K at all measured fields, there is little difference between field-cooled and zero field-cooled data and χ(T) decreases monotonously with temperature, which is reminiscent of the Curie-Weiss law. At lower temperatures, the temperature dependence of χ(T) is complex and strongly dependent on the magnetic field strength.

  20. New zirconium phosphate fluorides: Hydrothermal synthesis and crystal structures

    SciTech Connect

    Wloka, M.; Troyanov, S.I.; Kemnitz, E.

    1998-02-01

    A series of zirconium phosphate fluorides were synthesized and structurally characterized using different amines as templates. The compounds have the general formulas [amH{sub n}]{sub 1/n}[Zr{sub 2}(HPO{sub 4})(PO{sub 4}){sub 2}F]{center_dot}H{sub 2}O (1, am = ethylenediamine, n = 2; 2. am = N-methylethylenediamine, n = 2; 3, am = 1,3-diaminopropane, n = 2; 4, am = diethylenetriamine, n = 3) and [amH{sub 2}]{sub 0.5}[Zr{sub 2}(HPO{sub 4}){sub 2}(PO{sub 4})F{sub 2}]{center_dot}0.5H{sub 2}O (5, am = N,N,N{prime},N{prime}-tetramethylethylenediamine). In the structures of 2--4 with a Zr:F ratio of 2:1, there exists a three-dimensional arrangement of zirconium octahedra (one ZrO{sub 6} and one ZrO{sub 5}F) and phosphate tetrahedra (two PO{sub 4} and one HPO{sub 4}) connected via common oxygen atoms, whereas fluorine atoms and OH groups are terminal. These compounds crystallize in the ZrPO-1 structure type, which contains channels along the b axis formed by eight-membered rings of alternating PO{sub 4} tetrahedra and ZrO{sub 6} or ZrO{sub 5}F octahedra, respectively. The protonated disordered templates occupy the channels. Half the water molecules are situated in the positions alternatively left free by the disordered templates and the other half are bonded via hydrogen bridges to the terminal OH groups of the HPO{sub 4} tetrahedra. In contrast, the structure of 5 reveals a Zr:F ratio of 1:1, consequently forming a layer structure. The layers formed by ZrO{sub 5}F octahedra and PO{sub 4} or HPO{sub 4} tetrahedra, respectively, are linked by hydrogen bridges of type O{single_bond}H{hor_ellipsis}F and by weak H bonds over the protonated template. The similarities in connectivity pattern between Zr octahedra and P tetrahedra in all known zirconium phosphate fluorides and some zirconium phosphates are discussed.

  1. Hydrothermal Synthesis and Structural Characterization of Organically Templated Uranyl Diphosphonates

    SciTech Connect

    Adelani, Pius O.; Oliver, Allen G.; Albrecht-Schmitt, Thomas E.

    2011-03-09

    The hydrothermal treatment of uranyl nitrate and 1,4-benzenebisphosphonic acid with a variety of aliphatic amines (tetramethylammonium hydroxide, tetraethylammonium hydroxide, and diethyldimethylammonium hydroxide) and small quantities of hydrofluoric acid at 200 °C results in the crystallization of a series of layered uranyl diphosphonate compounds, [(CH3)4N][(UO2)3(O3PC6H4PO3H)2F(H2O)]·0.5H2O (Me4Ubbp), [(CH3CH2)4N](UO2)[C6H4(PO3H)(PO3H1.5)]2(H2O) (Et4Ubbp), and [(CH3CH2)2N(CH3)2][(UO2)3(O3PC6H4PO3H)2F(H2O)] (Et2Me2Ubbp). All these new compounds have layered structures, but the structures of Me4Ubbp and Et2Me2Ubbp are similar in that they both contain UO6F and UO7 pentagonal bipyramids within dimers that are bridged by the phosphonate into a three-dimensional structure. The structure of Et4Ubbp contains a single crystallographically unique UO7 unit. The edge-sharing pentagonal bipyramids are linked into chains formulated as (UO2)[C6H4(PO3H)(PO3H1.5)]2(H2O)1-. The voids in these structures are filled with the organic templates so that the overall charge balance is maintained. Intense fluorescence was observed from these compounds at room temperature.

  2. Total Synthesis of (±)-Phomactin A. Lessons Learned from Respecting a Challenging Structural Topology

    PubMed Central

    Buchanan, Grant S.; Cole, Kevin P.; Tang, Yu; Hsung, Richard P.

    2011-01-01

    Our struggles and ultimate success in achieving a total synthesis of phomactin A are described. Our strategy features an intramolecular oxa-[3 + 3] annulation to construct its unique ABD-tricyclic manifold. Although the synthesis would constitute a distinctly new approach with the 12-membered D-ring of phomactin A being assembled simultaneously with the 1-oxadecalin at an early stage, the ABD-tricycle represents a unique structural topology that would pose a number of unprecedented challenges. One challenge concerned elaborating this tricycle to have oxygenation at the proper carbon atoms. To overcome this, we would utilize a Kornblum-DeLaMare ring-opening of a peroxide bridge as well as a challenging late-stage 1,3-allylic alcohol transposition. Further, the structural intricacies of the ABD-tricycle were uncovered by a conformational analysis that would be critical for the C5a-homologation. PMID:21819039

  3. Synthesis, Structure, Properties, and Bioimaging of a Fluorescent Nitrogen-Linked Bisbenzothiadiazole.

    PubMed

    Mota, Alberto A R; Corrêa, José R; Carvalho, Pedro H P R; de Sousa, Núbia M P; de Oliveira, Heibbe C B; Gatto, Claudia C; da Silva Filho, Demétrio A; de Oliveira, Aline L; Neto, Brenno A D

    2016-04-01

    This paper describes the synthesis, structure, photophysical properties, and bioimaging application of a novel 2,1,3-benzothiadiazole (BTD)-based rationally designed fluorophore. The capability of undergoing efficient stabilizing processes from the excited state allowed the novel BTD derivative to be used as a stable probe for bioimaging applications. No notable photobleaching effect or degradation could be observed during the experimental time period. Before the synthesis, the molecular architecture of the novel BTD derivative was evaluated by means of DFT calculations to validate the chosen design. Single-crystal X-ray analysis revealed the nearly flat characteristics of the structure in a syn conformation. The fluorophore was successfully tested as a live-cell-imaging probe and efficiently stained MCF-7 breast cancer cell lineages. PMID:26930300

  4. Reverse microemulsion-mediated synthesis and structural evolution of barium hexaaluminate nanoparticles

    SciTech Connect

    Zarur, A.J.; Hwu, H.H.; Ying, J.Y.

    2000-04-04

    Nanocrystalline barium hexaaluminate has been successfully synthesized through the use of a reverse microemulsion as a medium for controlled hydrolysis and polycondensation of barium and aluminum alkoxides. The nanoparticles derived were characterized with electron microscopy, X-ray diffraction, and nitrogen adsorption analysis. This novel material possessed a well-defined particle morphology and an ultrahigh surface area, and exhibited excellent catalytic performance in methane combustion. Its structural evolution was found to be strongly dependent on synthesis parameters, such as water/alkoxide ratio and aging period. Powder recovery and drying techniques also had an important impact on particle agglomeration and structural development. Through the unique synthesis approach described, barium hexaaluminate with superb thermal stability was achieved, with surface areas in excess of 100 m{sup 2}/g retained even after calcination at 1,300 C.

  5. Synthesis of a specified, silica molecular sieve by using computationally predicted organic structure-directing agents.

    PubMed

    Schmidt, Joel E; Deem, Michael W; Davis, Mark E

    2014-08-01

    Crystalline molecular sieves are used in numerous applications, where the properties exploited for each technology are the direct consequence of structural features. New materials are typically discovered by trial and error, and in many cases, organic structure-directing agents (OSDAs) are used to direct their formation. Here, we report the first successful synthesis of a specified molecular sieve through the use of an OSDA that was predicted from a recently developed computational method that constructs chemically synthesizable OSDAs. Pentamethylimidazolium is computationally predicted to have the largest stabilization energy in the STW framework, and is experimentally shown to strongly direct the synthesis of pure-silica STW. Other OSDAs with lower stabilization energies did not form STW. The general method demonstrated here to create STW may lead to new, simpler OSDAs for existing frameworks and provide a way to predict OSDAs for desired, theoretical frameworks. PMID:24961789

  6. Synthesis, Structural Characterization, and Bioactivity of the Stable Peptide RCB-1 from Ricinus communis.

    PubMed

    Boldbaatar, Delgerbat; Gunasekera, Sunithi; El-Seedi, Hesham R; Göransson, Ulf

    2015-11-25

    The Ricinus communis biomarker peptides RCB-1 to -3 comprise homologous sequences of 19 (RCB-1) or 18 (RCB-2 and -3) amino acid residues. They all include four cysteine moieties, which form two disulfide bonds. However, neither the 3D structure nor the biological activity of any of these peptides is known. The synthesis of RCB-1, using microwave-assisted, Fmoc-based solid-phase peptide synthesis, and a method for its oxidative folding are reported. The tertiary structure of RCB-1, subsequently established using solution-state NMR, reveals a twisted loop fold with antiparallel β-sheets reinforced by the two disulfide bonds. Moreover, RCB-1 was tested for antibacterial, antifungal, and cytotoxic activity, as well as in a serum stability assay, in which it proved to be remarkably stable. PMID:26509914

  7. Fischer-Tropsch synthesis on hierarchically structured cobalt nanoparticle/carbon nanofiber/carbon felt composites.

    PubMed

    Zarubova, Sarka; Rane, Shreyas; Yang, Jia; Yu, Yingda; Zhu, Ye; Chen, De; Holmen, Anders

    2011-07-18

    The hierarchically structured carbon nanofibers (CNFs)/carbon felt composites, in which CNFs were directly grown on the surface of microfibers in carbon felt, forming a CNF layer on a micrometer range that completely covers the microfiber surfaces, were tested as a novel support material for cobalt nanoparticles in the highly exothermic Fischer-Tropsch (F-T) synthesis. A compact, fixed-bed reactor, made of disks of such composite materials, offered the advantages of improved heat and mass transfer, relatively low pressure drop, and safe handling of immobilized CNFs. An efficient 3-D thermal conductive network in the composite provided a relatively uniform temperature profile, whereas the open structure of the CNF layer afforded an almost 100 % effectiveness of Co nanoparticles in the F-T synthesis in the fixed bed. The greatly improved mass and heat transport makes the compact reactor attractive for applications in the conversion of biomass, coal, and natural gas to liquids. PMID:21563315

  8. Synthesis, structure, antimycobacterial and anticancer evaluation of new pyrrolo-phenanthroline derivatives.

    PubMed

    Al Matarneh, Cristina M; Mangalagiu, Ionel I; Shova, Sergiu; Danac, Ramona

    2016-06-01

    A study concerning design, synthesis, structure and in vitro antimycobacterial and anticancer evaluation of new fused derivatives with pyrrolo[2,1-c][4,7]phenanthroline skeleton is described. The strategy adopted for synthesis involves a [3 + 2] dipolar cycloaddition of several in situ generated 4,7-phenanthrolin-4-ium ylides to different substituted alkynes and alkenes. Stereo- and regiochemistry of cycloaddition reactions were discussed. The structure of the new compounds was proven unambiguously, single-crystal X-ray diffraction studies including. The antimycobacterial and anticancer activity of a selection of new synthesized compounds was evaluated against Mycobacterium tuberculosis H37Rv under aerobic conditions and 60 human tumour cell line panel, respectively. Five of the tested compounds possess a moderate antimycobacterial activity, while two of the compounds have a significant antitumor activity against renal cancer and breast cancer. PMID:25945747

  9. Simulating Cellulose Structure, Properties, Thermodynamics, Synthesis, and Deconstruction with Atomistic and Coarse-Grain Models

    SciTech Connect

    Crowley, M. F.; Matthews, J.; Beckham, G.; Bomble, Y.; Hynninen, A. P.; Ciesielski, P. F.

    2012-01-01

    Cellulose is still a mysterious polymer in many ways: structure of microfibrils, thermodynamics of synthesis and degradation, and interactions with other plant cell wall components. Our aim is to uncover the details and mechanisms of cellulose digestion and synthesis. We report the details of the structure of cellulose 1-beta under several temperature conditions and report here the results of these studies and connections to experimental measurements and the measurement in-silico the free energy of decrystallization of several morphologies of cellulose. In spatially large modeling, we show the most recent work of mapping atomistic and coarse-grain models into tomographic images of cellulose and extreme coarse-grain modeling of interactions of large cellulase complexes with microfibrils. We discuss the difficulties of modeling cellulose and suggest future work both experimental and theoretical to increase our understanding of cellulose and our ability to use it as a raw material for fuels and materials.

  10. Synthesis and structure of undoped and indium-doped thermoelectric lead telluride nanoparticles

    PubMed Central

    2014-01-01

    Undoped and indium (In)-doped lead telluride (PbTe) nanostructures were synthesized via solvothermal/hydrothermal route. The crystalline structure of the as-prepared undoped and In-doped PbTe samples was examined by X-ray diffraction (XRD) which indicated the formation of face-centered single-phase cubic crystal. A first principle calculation on indium doping shows that the indium atoms are more likely to replace lead (Pb) rather than to take the interstitial sites. Laser-induced breakdown spectroscopy (LIBS) analysis confirms that indium is incorporated into the PbTe matrix of the indium-doped PbTe samples. The effects of surfactant and synthesis temperature on the structure and morphology of the undoped PbTe were also investigated; it was found that PbTe nanostructures synthesized with the addition of surfactants exhibited uniform shapes and their size increased with the synthesis temperature. PMID:24872808

  11. Chemical synthesis and structure elucidation of bovine {kappa}-casein (1-44)

    SciTech Connect

    Bansal, Paramjit S.; Grieve, Paul A.; Marschke, Ronald J.; Daly, Norelle L.; McGhie, Emily; Craik, David J.; Alewood, Paul F. . E-mail: p.alewood@imb.uq.edu.au

    2006-02-24

    The caseins ({alpha}{sub s1}, {alpha}{sub s2}, {beta}, and {kappa}) 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 {kappa}-casein, the protein which maintains the micellar structure of the caseins. {kappa}-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{sup 8} to Arg{sup 34}. This is First report which demonstrates extensive secondary structure within the casein class of proteins.

  12. Studies toward the Total Synthesis of Itralamide B and Biological Evaluation of Its Structural Analogs

    PubMed Central

    Wang, Xiaoji; Lv, Chanshan; Feng, Junmin; Tang, Linjun; Wang, Zhuo; Liu, Yuqing; Meng, Yi; Ye, Tao; Xu, Zhengshuang

    2015-01-01

    Itralamides A and B were isolated from the lipophilic extract of Lyngbya majuscula collected from the eastern Caribbean. Itralamide B (1) showed cytotoxic activity towards human embryonic kidney cells (HEK293, IC50 = 6 μM). Preliminary studies disapproved the proposed stereochemistry of itralamide. In this paper, we will provide a full account of the total synthesis of four stereoisomers of itralamide B and the results derived from biological tests of these structural congeners. PMID:25871289

  13. Spiropyran salts and their neutral precursors: synthesis, crystal structure, photochromic transformations in solutions and solid state

    NASA Astrophysics Data System (ADS)

    Yurieva, E. A.; Aldoshin, S. M.

    2015-06-01

    This review covers investigations of spiropyran iodides with N-substituted indoline fragment, and with the pyran cycle being annelated to N-methylated pyridine ring. The schemes of synthesis of iodides and their neutral precursors, as well as results of X-ray analysis and photochemical study of the crystals of the obtained compounds are presented. Based on our and literature data, the relationship between the structure and photochromic properties has been discussed for a series of salts and neutral pyridospiropyrans.

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

    SciTech Connect

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

    2012-12-15

    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 Degree-Sign 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{sup 2+}, Ni{sup 2+} and Co{sup 2+} were found to follow a Freundlich isotherm. In addition, it shows higher affinity towards Cu{sup 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 Degree-Sign C through an intermediate crystalline alumino silicate phase. Highlights: Black-Right-Pointing-Pointer Egyptian kaolin was successfully used to prepare pure phase of JBW Structure. Black-Right-Pointing-Pointer JBW is stable till <300 Degree-Sign C. Black-Right-Pointing-Pointer JBW phase crystallizes as cylindrical shape but agglomerates in a Nano spherical shape. Black-Right-Pointing-Pointer The ion exchange isotherms of Cu{sup 2+}, Ni{sup 2+}, and Co{sup 2+} followed up Freundlich isotherm. Black-Right-Pointing-Pointer Selectivity towards Cu{sup 2+} is much higher than Co{sup 2+} or Ni{sup 2+}.

  15. A uranium (VI) complex: Synthesis, structural and thermal kinetic analysis

    NASA Astrophysics Data System (ADS)

    Goel, Nidhi

    2016-08-01

    A new complex [UO2(2,6-DNP)2phen] (1) (2,6-DNP = 2,6-dinitrophenol, phen = 1,10-phenanthroline) was synthesized, and identified by elemental analysis, IR, Powder XRD and single crystal X-ray crystallography. Crystal structure provides the abundant information's about the bonding and geometry around the U(VI) metal center. The thermal decomposition was studied by TG-DSC, and the kinetics of thermolysis was investigated by applying model fitting as well as isoconversional methods. Explosion delay measurement (De) was also evaluated to determine the response of this complex under the condition of rapid heating.

  16. Hydroflux synthesis and crystal structure of new lanthanide tungstate oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Latshaw, Allison M.; Smith, Mark D.; Chance, W. Michael; zur Loye, Hans-Conrad

    2015-04-01

    Single crystals of Na5Ln(OH)6WO4 where Ln = Er, Tm, and Yb were grown out of a NaOH hydroflux. The crystals were characterized by single crystal X-ray diffraction and were found to crystallize in the monoclinic space group I2/a. The lattice parameter ranges for the three structures are a = 11.2024(7) Å-11.2412(6) Å, b = 16.1850(10) Å-16.2220(10) Å, and c = 11.9913(7) Å-12.0323(7) Å while the β angle range is 101.999(2)°-102.025(2)°.

  17. Long tailed cage amines: Synthesis, metal complexation, and structure

    SciTech Connect

    Dittrich, Birger; Harrowfield, Jack M.; Koutsantonis, George A.; Nealon, Gareth L.; Skelton, Brian W.

    2011-12-09

    The generation of amphiphiles derived from macrobicyclic hexamines of the 'sarcophagine' class can be prepared through efficient and selective reactions involving the reductive alkylation, using long-chain aldehydes, of amino-functionalized sarcophagines when bound to Cu(II) or Mg(II). The Mg(II) pathway is particularly convenient for the ultimate isolation of the free ligands, which can then be used to form metalloamphiphiles with a variety of metal ions. Structural studies have been made of one of the free (protonated) ligands and some of their complexes.

  18. Synthesis, structure and properties of hierarchical nanostructured porous materials studied by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Chae, Kisung

    For applications of porous materials in many fields of technological importance, such as catalysis, filtration, separation, energy storage and conversion, the efficiency is often limited by chemical kinetics, and/or diffusion of reactants and products to and from the active sites. Hierarchical nanostructured porous materials (HNPMs) that possess both mesopores (2 nm < pore size < 50 nm) and micropores (pore size < 2 nm) have shown great potential for these applications as their bimodal porous structure can provide highly efficient mass transport through mesopores and high electrochemically accessible surface area from micropores. Despite extensive experimental studies, it remains a great challenge to quantify the synthesis-structure-properties relations in HNPMs due to the limitations of existing characterization tools and the difficulty in separating the sum of many effects in experiments. In this thesis work, we carried out a detailed study on the synthesis-structure-property relations in hierarchical nanostructured porous carbons (HNPCs) by using classical molecular dynamics (MD) simulations. We first developed a unique computational nanocasting approach in MD to mimic the synthesis of HNPCs with both mesopores from the templating and micropores from the direct quench of carbon source in MD. Mesoporous structure such as the pore size and the pore wall roughness as well as the microporous structure such as the density and the graphitic pore walls can be independently controlled by synthesis parameters, such as the size of the template, the interaction strength between the template and carbon source, the initial carbon density and the quench rate, respectively. These atomic models allowed us to quantify the structure-mechanical properties relation in aligned carbon nanotubes/amorphous porous carbon nanocomposites. Our study shows that there is an optimum balance between the crystallinity of CNTs and the number bridging bonds between CNTs and the microporous matrix

  19. Hanford Site Environmental Restoration Program 1994 fiscal year work plan. Work breakdown structure 2.0: Revision 1

    SciTech Connect

    Not Available

    1993-12-22

    Site Management System (SMS) guidance requires a Fiscal Year Work Plan (FYWP) to be prepared for the Environmental Restoration (ER) Mission Area and all related programs. This revision is a complete update to cover the FY 1994 time period. This document describes the overall ER Missions Area and provides FYWP appendices for each of the following five program areas: Remedial Action (RA); Decontamination and Decommissioning (D&D); Project Management and Support (PM&S); Surveillance and Maintenance (S&M); and Disposal Facilities (DF).

  20. STRUCTURE-ACTIVITY STUDY OF PARACETAMOL ANALOGUES: INHIBITION OF REPLICATIVE DNA SYNTHESIS IN V79 CHINESE HAMSTER CELLS

    EPA Science Inventory

    Experimental and theoretical evidence pertaining to cytotoxic and genotoxic activity of paracetamol in biological systems was used to formulate a simple mechanistic hypothesis to explain the relative inhibition of replicative DNA synthesis by a series of 19 structurally similar p...

  1. Synthesis and structural characterization of base-stabilized oligomeric heterovinylidenes.

    PubMed

    Leung, Wing-Por; Chiu, Wang-Kin; Mak, Thomas C W

    2013-08-19

    Metalation of the (iminophosphoranyl)phosphine PPh2CH2(PPh2═NSiMe3) (1) with an equimolar amount of n-BuLi afforded the monolithium salt [Li{CH(PPh2)(PPh2═NSiMe3)}(THF)2] (2). The reaction of 2 with GeCl2·1,4-dioxane has led to the formation of a germavinylene moiety, which trimerized to form a new heterocyclic cage compound, [{(PPh2═NSiMe3)(PPh2)C═Ge:}{(PPh2═NSiMe3)(PPh2)C}2Ge→Ge:] (3). A similar reaction of the lithium methanide complex 2 with SnCl2 afforded the stannavinylidene moiety, which underwent a "head-to-tail" cycloaddition to form a stable 1,3-distannacyclobutane, 4. A trapping reaction of 4 with diiron nonacarbonyl gave the novel iron stannavinylidene complex 5. The solid-state structure analysis of 5 reveals that it contains two stannavinylidene moieties bonded in a Sn-P "head-to-tail" fashion, with one of the tin(II) centers coordinating to a Fe(CO)4 moiety. The X-ray structures of 2-5 have been determined by X-ray crystallography. In addition, the dynamic behavior of 5 has been studied by means of variable-temperature (31)P and (119)Sn NMR spectroscopy. PMID:23924072

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

    NASA Technical Reports Server (NTRS)

    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.

  3. Synthesis, Structures, and Multiferroic Properties of Strontium Hexaferrite Ceramics

    NASA Astrophysics Data System (ADS)

    Tan, Guolong; Chen, Xiuna

    2013-05-01

    Simultaneous occurrence of large ferroelectricity and strong ferromagnetism has been observed in strontium hexaferrite (SrFe12O19) ceramics. Strontium hexaferrite powders with hexagonal crystal structures have been successfully synthesized through the co-precipitation precursor method using strontium nitrate and ferric nitrate as starting materials. The powders were pressed into pellets and then sintered into ceramics at a temperature range of at 1000°C to 1100°C for 1 h. The structure and morphology of the ceramics were determined using x-ray diffraction and field-emission scanning electron microscopy techniques. Clear ferroelectric hysteresis loops demonstrated large spontaneous polarization in the SrFe12O19 ceramics at room temperature. The maximum remnant polarization of the SrFe12O19 ceramic was estimated to be approximately 15 μC/cm2. The FeO6 octahedron in its perovskite-like hexagonal unit cell and the displacement of Fe3+ off the center of the octahedron are proposed to be the origin of electric polarization in SrFe12O19. In our experimental observations, the SrFe12O19 ceramic also revealed strong ferromagnetism at room temperature.

  4. Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels

    PubMed Central

    Matsui, Daisuke; Mayumi, Koichi

    2015-01-01

    Summary A significantly soft and tough nanocomposite gel was realized by a novel network formed using cyclodextrin-based polyrotaxanes. Covalent bond formation between the cyclic components of polyrotaxanes and the surface of silica nanoparticles (15 nm diameter) resulted in an infinite network structure without direct bonds between the main chain polymer and the silica. Small-angle X-ray scattering revealed that the homogeneous distribution of silica nanoparticles in solution was maintained in the gel state. Such homogeneous nanocomposite gels were obtained with at least 30 wt % silica content, and the Young’s modulus increased with silica content. Gelation did not occur without silica. This suggests that the silica nanoparticles behave as cross-linkers. Viscoelastic measurements of the nanocomposite gels showed no stress relaxation regardless of the silica content for <20% compression strain, indicating an infinite stable network without physical cross-links that have finite lifetime. On the other hand, the infinite network exhibited an abnormally low Young’s modulus, ~1 kPa, which is not explainable by traditional rubber theory. In addition, the composite gels were tough enough to completely maintain the network structure under 80% compression strain. These toughness and softness properties are attributable to both the characteristic sliding of polymer chains through the immobilized cyclodextrins on the silica nanoparticle and the entropic contribution of the cyclic components to the elasticity of the gels. PMID:26664642

  5. A novel series of thiosemicarbazone drugs: from synthesis to structure.

    PubMed

    Ebrahimi, Hossein Pasha; Hadi, Jabbar S; Alsalim, Tahseen A; Ghali, Thaer S; Bolandnazar, Zeinab

    2015-02-25

    A new series of thiosemicarbazones (TSCs) and their 1,3,4-thiadiazolines (TDZs) containing acetamide group have been synthesized from thiosemicarbazide compounds by the reaction of TSCs with cyclic ketones as well as aromatic aldehydes. The structures of newly synthesized 1,3,4-thiadiazole derivatives obtained by heterocyclization of the TSCs with acetic anhydride were experimentally characterized by spectral methods using IR, (1)H NMR, (13)C NMR and mass spectroscopic methods. Furthermore, the structural, thermodynamic, and electronic properties of the studied compounds were also studied theoretically by performing Density Functional Theory (DFT) to access reliable results to the experimental values. The molecular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and Mulliken atomic charges of the studied compounds have been calculated at the B3LYP method and standard 6-31+G(d,p) basis set starting from optimized geometry. The theoretical (13)C chemical shift results were also calculated using the gauge independent atomic orbital (GIAO) approach and their respective linear correlations were obtained. PMID:25291504

  6. A novel series of thiosemicarbazone drugs: From synthesis to structure

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Hossein Pasha; Hadi, Jabbar S.; Alsalim, Tahseen A.; Ghali, Thaer S.; Bolandnazar, Zeinab

    2015-02-01

    A new series of thiosemicarbazones (TSCs) and their 1,3,4-thiadiazolines (TDZs) containing acetamide group have been synthesized from thiosemicarbazide compounds by the reaction of TSCs with cyclic ketones as well as aromatic aldehydes. The structures of newly synthesized 1,3,4-thiadiazole derivatives obtained by heterocyclization of the TSCs with acetic anhydride were experimentally characterized by spectral methods using IR, 1H NMR, 13C NMR and mass spectroscopic methods. Furthermore, the structural, thermodynamic, and electronic properties of the studied compounds were also studied theoretically by performing Density Functional Theory (DFT) to access reliable results to the experimental values. The molecular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and Mulliken atomic charges of the studied compounds have been calculated at the B3LYP method and standard 6-31+G(d,p) basis set starting from optimized geometry. The theoretical 13C chemical shift results were also calculated using the gauge independent atomic orbital (GIAO) approach and their respective linear correlations were obtained.

  7. Synthesis and Structure of Environmentally Relevant Perfluorinated Sulfonamides

    PubMed Central

    Lehmler, Hans-Joachim; Rama Rao, V.V.V.N.S.; Nauduri, Dhananjaya; Vargo, John D.; Parkin, Sean

    2008-01-01

    Alkylated perfluorooctanesulfonamides are compounds of environmental concern. To make these compounds available for environmental and toxicological studies, a series of N-alkylated perfluorooctanesulfonamides and structurally related compounds were synthesized by reaction of the corresponding perfluoroalkanesulfonyl fluoride with a suitable primary or secondary amine. Perfluoroalkanesulfonamidoethanols were obtained from the N-alkyl perfluoroalkanesulfonamides either by direct alkylation with bromoethanol or alkylation with acetic acid 2-bromo-ethyl ester followed by hydrolysis of the acetate. N-Alkyl perfluorooctanesulfonamidoacetates were synthesized in an analogous way by alkylation of N-alkyl perfluoroalkanesulfonamides with a bromo acetic acid ester, followed by basic ester hydrolysis. Alternatively, N-alkyl perfluoroalkanesulfonamides can be alkylated with an appropriate alcohol using the Mitsunobu reaction. Perfluorooctanesulfonamide was synthesized from the perfluorooctanesulfonyl fluoride via the azide by reduction with Zn/HCl. All perfluorooctanesulfonamides contained linear as well as branched C8F17 isomers, typically in a 20:1 to 30:1 ratio. The crystal structures of N-ethyl and N,N-diethyl perfluorooctanesulfonamide show that the S-N bond has considerable double bond character. This double bond character results in a significant rotational barrier around the S-N bond (ΔG≠ = 62–71 kJ mol−1) and a preferred solid state and solution conformation in which the N-alkyl groups are oriented opposite to the perfluorooctyl group to minimize steric crowding around the S-N bond. PMID:18516235

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Hydrothermal Synthesis and Structure of Neptunium(V) Oxide

    SciTech Connect

    Forbes, Tori Z.; Burns, Peter C.; Soderholm, L. |; Skanthakumar, S.

    2007-07-01

    Single crystals of Np{sub 2}O{sub 5} have been synthesized by low-temperature hydrothermal reaction of a (NpO{sub 2}){sup +} stock solution with natural calcite crystals. The structure of Np{sub 2}O{sub 5} was solved by direct methods and refined on the basis of F{sup 2} for all unique data collected on a Bruker X-ray diffractometer equipped with an APEX II CCD detector. Np{sub 2}O{sub 5} is monoclinic, space group P2/c, with a = 8.168(2) A, b = 6.584(1) A, c = 9.3130(2) A, {beta} = 116.01(1) deg., V = 449.8(2) A{sup 3}, and Z = 1. The structure contains chains of edge-sharing neptunyl pentagonal bi-pyramids linked into sheets through cation-cation interactions with distorted neptunyl square bi-pyramids. Additional cation-cation interactions connect the sheets into a three-dimensional framework. The formation of Np{sub 2}O{sub 5} on the surface of calcite crystals has important implications for the precipitation of isolated neptunyl phases in natural aqueous systems. (authors)

  10. Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels.

    PubMed

    Kato, Kazuaki; Matsui, Daisuke; Mayumi, Koichi; Ito, Kohzo

    2015-01-01

    A significantly soft and tough nanocomposite gel was realized by a novel network formed using cyclodextrin-based polyrotaxanes. Covalent bond formation between the cyclic components of polyrotaxanes and the surface of silica nanoparticles (15 nm diameter) resulted in an infinite network structure without direct bonds between the main chain polymer and the silica. Small-angle X-ray scattering revealed that the homogeneous distribution of silica nanoparticles in solution was maintained in the gel state. Such homogeneous nanocomposite gels were obtained with at least 30 wt % silica content, and the Young's modulus increased with silica content. Gelation did not occur without silica. This suggests that the silica nanoparticles behave as cross-linkers. Viscoelastic measurements of the nanocomposite gels showed no stress relaxation regardless of the silica content for <20% compression strain, indicating an infinite stable network without physical cross-links that have finite lifetime. On the other hand, the infinite network exhibited an abnormally low Young's modulus, ~1 kPa, which is not explainable by traditional rubber theory. In addition, the composite gels were tough enough to completely maintain the network structure under 80% compression strain. These toughness and softness properties are attributable to both the characteristic sliding of polymer chains through the immobilized cyclodextrins on the silica nanoparticle and the entropic contribution of the cyclic components to the elasticity of the gels. PMID:26664642

  11. Bridged bis-BODIPYs: their synthesis, structures and properties.

    PubMed

    Kesavan, Praseetha E; Das, Sudipta; Lone, Mohsin Y; Jha, Prakash C; Mori, Shigeki; Gupta, Iti

    2015-10-21

    A series of bis-BODIPYs 1-6 bridged via thiophene, furan, N-alkylcarbazole, triphenyl-amine, para- and meta-phenylene groups have been synthesized and characterized by various spectroscopic techniques. The change in the spectroscopic properties of bis-BODIPYs upon varying the size of spacers was studied. X-ray crystal structures of three bis-BODIPYs containing triphenylamine, para- and meta-phenylene bridges were solved. Intermolecular C(H)π and ππ stacking interactions were observed in solid state structures of three bis-BODIPYs. The dihedral angles between the spacer unit and two boron-dipyrrin units were lower in all three compounds as compared to their corresponding monomers. This suggests increased interactions between the two boron-dipyrrin units in molecules which are in turn reflected in the anodic shifts in their reduction potentials. DFT studies indicated effective electronic interactions between spacers and two boron dipyrrin units in all the bis-BODIPYs. The calculated HOMO-LUMO gap was found to be lower for bis-BODIPY having bulky carbazole spacers and higher for bis-BODIPY having smaller furan spacers. Changing the spacer size clearly affected the spectroscopic properties of the bis-BODIPYs and red shifted absorption and emission maxima were observed for bis-BODIPYs with furan and thiophene spacers as compared to bis-BODIPYs with phenylene or bulky aromatic spacers. PMID:26373792

  12. Synthesis of Specifically Modified Oligonucleotides for Application in Structural and Functional Analysis of RNA

    PubMed Central

    Rublack, Nico; Nguyen, Hien; Appel, Bettina; Springstubbe, Danilo; Strohbach, Denise; Müller, Sabine

    2011-01-01

    Nowadays, RNA synthesis has become an essential tool not only in the field of molecular biology and medicine, but also in areas like molecular diagnostics and material sciences. Beyond synthetic RNAs for antisense, aptamer, ribozyme, and siRNA technologies, oligoribonucleotides carrying site-specific modifications for structure and function studies are needed. This often requires labeling of the RNA with a suitable spectroscopic reporter group. Herein, we describe the synthesis of functionalized monomer building blocks that upon incorporation in RNA allow for selective reaction with a specific reporter or functional entity. In particular, we report on the synthesis of 5′-O-dimethoxytrityl-2′-O-tert-butyldimethylsilyl protected 3′-O-phosphoramidites of nucleosides that carry amino linkers of different lengths and flexibility at the heterocyclic base, their incorporation in a variety of RNAs, and postsynthetic conjugation with fluorescent dyes and nitroxide spin labels. Further, we show the synthesis of a flavine mononucleotide-N-hydroxy-succinimidyl ester and its conjugation to amino functionalized RNA. PMID:22013508

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

    SciTech Connect

    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}}} which crystallizes in a tetragonal unit. AgFAuF{sub 4} has a triclinic unit cell and is isostructural with CuFAuF{sub 4}. AgFAuF{sub 6} has an orthorhombic unit cell and appears to be isostructural with AgFAsF{sub 6}. A second mixed valence silver fluoride, Ag{sup II}Ag{sup III}F{sub 5}, is prepared, which magnetic measurements indicate is probably an AgF{sup +} salt. Magnetic data for all of the AgF{sup +} 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 O{sub 2} to O{sub 2}{sup +}. Reactions with C{sub 6}F{sub 6} and C{sub 3}F{sub 6} suggest an electron capture mechanism for cationic AG(II) oxidations.

  14. Synthesis and applications of novel silver nanoparticle structures

    NASA Astrophysics Data System (ADS)

    Dukes, Kyle

    The field of nanotechnology is rapidly expanding across disciplines as each new development is realized. New exciting technologies are being driven by advances in the application of nanotechnology; including biochemical, optical, and semiconductors research. This thesis will focus on the use of silver nanoparticles as optical labels on cells, methods of forming different small structures of silver nanoparticles, as well as the use of silver nanoparticles in the development of a photovoltaic cell. Silver nanoparticles have been modified with self-assembled monolayers of hydroxyl-terminated long chain thiols and encapsulated with a silica shell. The resulting core-shell nanoparticles were used as optical labels for cell analysis using flow cytometry and microscopy. The excitation of plasmon resonances in nanoparticles results in strong depolarized scattering of visible light permitting detection at the single nanoparticle level. The nanoparticles were modified with neutravidin via epoxide-azide coupling chemistry and biotinylated antibodies targeting cell surface receptors were bound to the nanoparticle surface. The nanoparticle labels exhibited long-term stability under physiological conditions without aggregation or silver ion leaching. Labeled cells exhibited two orders of magnitude enhancement of the scattering intensity compared to unlabeled cells. Dimers of silver nanoparticles have been fabricated by first immobilizing a monolayer of single silver nanoparticles onto poly(4-vinylpyridine) covered glass slides. The monolayer was then exposed to adenine, which has two amines which will bind to silver. The nanoparticle monolayer, now modified with adenine, is exposed to a second suspension of nanoparticles which will bind with the amine modified monolayer. Finally, a thin silica shell is formed about the structure via solgel chemistry to prevent dissolution or aggregation upon sonication/striping. Circular arrays of silver nanoparticels are developed using a

  15. The synthesis, structure and reactivity of 4-nonafluorobiphenyl complexes.

    PubMed

    Martin, Eddy; Hughes, David L; Hursthouse, Michael B; Male, Louise; Lancaster, Simon J

    2009-03-01

    The Grignard reagent Ar(F)'MgBr (Ar(F)' = 4-(C(6)F(5))C(6)F(4)) reacts with Me(3)SiCl, Me(2)SiCl(2) and Me(3)SnCl to give the 4-nonafluorobiphenyl group 14 complexes Ar(F)'Me(3)Si, (Ar(F)')(2)Me(2)Si and Ar(F)'Me(3)Sn respectively. Ar(F)'Me(3)Sn undergoes only methyl group exchange when treated with BBr(3), yielding Ar(F)'Me(2)SnBr. The solid state structures of Ar(F)'Me(3)Sn and Ar(F)'Me(2)SnBr have been determined and exhibit the expected distorted tetrahedral geometries at tin. The reaction between three equivalents of Ar(F)'MgBr and BF(3) was not selective, while one equivalent of Ar(F)'MgBr and (Ar(F))(2)BF (Ar(F) = C(6)F(5)) reacted cleanly to give (Ar(F))(2)Ar(F)'B. Treatment of BCl(3) with three equivalents of Ar(F)'Li, prepared at low temperature from the reaction between Ar(F)'Br and n-BuLi, yielded (Ar(F)')(3)B. The molecular structures of the acetonitrile adducts of (Ar(F))(2)Ar(F)'B and (Ar(F)')(3)B closely resemble that of (Ar(F))(3)B.NCMe. During the course of the boron investigations, reaction with adventitious water led to the structural characterization of (Ar(F)')(2)BOH.OH(2) as a hydrogen-bonded dimer. The Grignard reagent reacts selectively with ZnCl(2) in diethyl ether giving first [(Ar(F)')Zn(micro-Cl)(OEt(2))](2) then (Ar(F)')(2)Zn(OEt(2))(2), both of which have been characterised by X-ray diffraction. The corresponding reaction with HgCl(2) requires the use of tetrahydrofuran as the solvent and yields (Ar(F)')(2)Hg(THF)(2). PMID:19421603

  16. Synthesis, structural and conformational study of chromane derivatives

    NASA Astrophysics Data System (ADS)

    Ciolkowski, Michal; Malecka, Magdalena; Modranka, Roman; Budzisz, Elzbieta

    2009-11-01

    2-Methyl-4-oxo-4 H-chromene-3-carboxylic acid methyl ester ( 1) and 2-phenyl-4-oxo-4 H-chromene-3-carboxylic acid ethyl ester ( 2) were reacted with NaBH 4 to give 2-R-2,3-dihydro-4-hydroxy-2 H-1-benzopyran-3-carboxylic acid esters ( 3: methyl ester, R = methyl, 4: ethyl ester, R = phenyl - respectively). The structures of resultant compounds 3 and 4 were confirmed by IR, 1H NMR spectroscopy, mass spectrometry and elemental analysis. Additionally the X-ray analysis of the compound 3 revealed that hydrogen atoms bonded to the C2 and C4 atoms are in axial positions and hydrogen atom bonded to C3 atom is in equatorial position. The main conformation in solution for both compounds is similar and was confirmed based on the 3JHH coupling constants obtained from experimental spectra and from DFT conformational analysis.

  17. Stochastic Control Synthesis of Systems with Structured Uncertainty

    NASA Technical Reports Server (NTRS)

    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.

  18. α-Cationic Arsines: Synthesis, Structure, Reactivity, and Applications.

    PubMed

    Dube, Jonathan W; Zheng, Yiying; Thiel, Walter; Alcarazo, Manuel

    2016-06-01

    A series of structurally differentiated cationic arsines containing imidazolium, cyclopropenium, formamidinium, and pyridinium substituents have been synthesized through short and scalable routes. Evaluation of the donor properties of these compounds by IR spectroscopy and DFT calculations reveals similar σ-electron-releasing abilities for all of them; however, their π-acceptor properties are strongly influenced by the nature of the positively charged group. We describe the coordination chemistry of the newly prepared α-cationic arsines toward different metal centers and their reactivity in the presence of strong oxidants to afford cationic As(V) species. Their unique electronic properties have been exploited in Pt(II) catalysis to develop a new catalyst with remarkable activity in the cycloisomerization of enynes to trisubstituted cyclopropanes. To the best of our knowledge, this is the first report on the use of α-cationic arsine ligands in catalysis. PMID:27214007

  19. Pyrenes, Peropyrenes, and Teropyrenes: Synthesis, Structures, and Photophysical Properties.

    PubMed

    Yang, Wenlong; Monteiro, Jorge H S K; de Bettencourt-Dias, Ana; Catalano, Vincent J; Chalifoux, Wesley A

    2016-08-22

    The design of a relatively simple and efficient method to extend the π-conjugation of readily available aromatics in one-dimension is of significant value. In this paper, pyrenes, peropyrenes, and teropyrenes were synthesized through a double or quadruple benzannulation reaction of alkynes promoted by Brønsted acid. This novel method does not involve cyclodehydrogenation (oxidative aryl-aryl coupling) to arrive at the newly incorporated large arene moieties. All of the target compounds were synthesized in moderate to good yields and were fully characterized with the structures unambiguously confirmed by X-ray crystallography. As expected, photophysical characterization clearly shows increasing red-shifts as a function of extended conjugation within the fused ring systems. PMID:27457893

  20. Tubular precipitation structures: materials synthesis under non-equilibrium conditions.

    PubMed

    Makki, Rabih; Roszol, László; Pagano, Jason J; Steinbock, Oliver

    2012-06-28

    Inorganic precipitation reactions are known to self-organize a variety of macroscopic structures, including hollow tubes. We discuss recent advances in this field with an emphasis on experiments similar to 'silica gardens'. These reactions involve metal salts and sodium silicate solution. Reactions triggered from reagent-loaded microbeads can produce tubes with inner radii of down to 3 μm. Distinct wall morphologies are reported. For pump-driven injection, three qualitatively different growth regimes exist. In one of these regimes, tubes assemble around a buoyant jet of reactant solution, which allows the quantitative prediction of the tube radius. Additional topics include relaxation oscillations and the templating of tube growth with pinned gas bubble and mechanical devices. The tube materials and their nano-to-micro architectures are discussed for the cases of silica/Cu(OH)(2) and silica/Zn(OH)(2)/ZnO tubes. The latter case shows photocatalytic activity and photoluminescence. PMID:22615464

  1. Approach to cis-Phlegmarine Alkaloids via Stereodivergent Reduction: Total Synthesis of (+)-Serratezomine E and Putative Structure of (-)-Huperzine N.

    PubMed

    Bosch, Caroline; Fiser, Béla; Gómez-Bengoa, Enrique; Bradshaw, Ben; Bonjoch, Josep

    2015-10-16

    A unified strategy for the synthesis of the cis-phlegmarine group of alkaloids is presented, leading to the first synthesis of serratezomine E (1) as well as the putative structure of huperzine N (2). A contrasteric hydrogenation method was developed based on the use of Wilkinson's catalyst, which allowed the facial selectivity of standard hydrogenation to be completely overturned. Calculations were performed to determine the mechanism, and structures for huperzines M and N are reassigned. PMID:26406568

  2. Synthesis and structural evaluation of freeze-cast porous alumina

    SciTech Connect

    Souza, Douglas F.; Nunes, Eduardo H.M.; Pimenta, Daiana S.; Vasconcelos, Daniela C.L.; Nascimento, Jailton F.; Grava, Wilson; Vasconcelos, Wander L.

    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.

  3. Targeted Synthesis of Two Super-Complex Zeolites with Embedded Isoreticular Structures.

    PubMed

    Shin, Jiho; Xu, Hongyi; Seo, Seungwan; Guo, Peng; Min, Jung Gi; Cho, Jung; Wright, Paul A; Zou, Xiaodong; Hong, Suk Bong

    2016-04-11

    A novel structural coding approach combining structure solution, prediction, and the targeted synthesis of new zeolites with expanding complexity and embedded isoreticular structures was recently proposed. Using this approach, the structures of two new zeolites in the RHO family, PST-20 and PST-25, were predicted and synthesized. Herein, by extending this approach, the next two higher generation members of this family, PST-26 and PST-28, have been predicted and synthesized. These two zeolites have much larger unit cell volumes (422 655 Å(3) and 614 912 Å(3) , respectively) than those of the lower generations. Their crystallization was confirmed by a combination of both powder X-ray and electron diffraction techniques. Aluminate and water concentrations in the synthetic mixture were found to be the two most critical factors influencing the structural expansion of embedded isoreticular zeolites under the synthetic conditions studied herein. PMID:26990818

  4. Synthesis of Silicate Zeolite Analogues Using Organic Sulfonium Compounds as Structure-Directing Agents.

    PubMed

    Jo, Changbum; Lee, Sungjune; Cho, Sung June; Ryoo, Ryong

    2015-10-19

    A microporous crystalline silica zeolite of the MEL structure type and three other zeolite analogues composed of germanosilicate frameworks were synthesized using tributylsulfonium, triphenylsulfonium, or tri(para-tolyl)sulfonium as the structure-directing agent. The germanosilicates thus obtained had ISV, ITT, or a new zeolite structure depending on the synthesis conditions. The structure of the new germanosilicate was solved using X-ray powder diffraction data with the aid of a charge-flipping method. The solution indicated a crystal structure belonging to the P63/mmc space group with cell parameters of a=16.2003 Å and c=21.8579 Å. After calcination, the new germanosilicate material exhibited two types of accessible micropores with diameters of 0.61 and 0.78 nm. PMID:26302889

  5. Heterometallic europium disiloxanediolates: synthesis, structural diversity, and photoluminescence properties.

    PubMed

    Rausch, Janek; Lorenz, Volker; Hrib, Cristian G; Frettlöh, Vanessa; Adlung, Matthias; Wickleder, Claudia; Hilfert, Liane; Jones, Peter G; Edelmann, Frank T

    2014-11-01

    This contribution presents a full account of a structurally diverse class of heterometallic europium disiloxanediolates. The synthetic protocol involves in situ metalation of (HO)SiPh2OSiPh2(OH) (1) with either (n)BuLi or KN(SiMe3)2 followed by treatment with EuCl3 in suitable solvents such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THF). Reaction of EuCl3 with 2 equiv of (LiO)SiPh2OSiPh2(OLi) in DME afforded the Eu(III) bis(disiloxanediolate) "ate" complex [{(Ph2SiO)2O}2{Li(DME)}3]EuCl2 (2), which upon attempted reduction with Zn gave the tris(disiloxanediolate) [{(Ph2SiO)2O}3{Li(DME)}3]Eu (3). Treatment of EuCl3 with (LiO)SiPh2OSiPh2(OLi) in a molar ratio of 1:2 yielded both the ate complex [{(Ph2SiO)2O}3Li{Li(THF)2}{Li(THF)}]EuCl·Li(THF)3 (4) and the LiCl-free europium(III) complex [{(Ph2SiO)2O}2{Li(THF)2}2]EuCl (5). Compound 5 was found to exhibit a brilliant red triboluminescence. When (KO)SiPh2OSiPh2(OK) was used as starting material in a 3:1 reaction with EuCl3, the Eu(III) tris(disiloxanediolate) [{(Ph2SiO)2O}3{K(DME)}3]Eu (6) was isolated. Attempted ligand transfer between 5 and (DAD(Dipp))2Ba(DME) (DAD(Dipp) = N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene) afforded the unique mixed-valent Eu(III)/Eu(II) disiloxanediolate cluster [(Ph2SiO)2O]6Eu(II)4Eu(III)2Li4O2Cl2 (7). All new complexes were structurally characterized by X-ray diffraction. Photoluminescence studies were carried out for complex 5 showing an excellent color quality, due to the strong (5)D0→(7)F2 transition, but a weak antenna effect. PMID:25330143

  6. Phosphine derivatives of sparfloxacin - Synthesis, structures and in vitro activity

    NASA Astrophysics Data System (ADS)

    Komarnicka, Urszula K.; Starosta, Radosław; Guz-Regner, Katarzyna; Bugla-Płoskońska, Gabriela; Kyzioł, Agnieszka; Jeżowska-Bojczuk, Małgorzata

    2015-09-01

    We synthesized two derivatives of sparfloxacin (HSf): aminomethyl(diphenyl)phosphine (PSf) and its oxide (OPSf). The compounds were characterized by NMR spectroscopy, MS and elemental analysis. In addition, the molecular structures of the compounds were determined using DFT and X-ray (OPSf) analysis. The antibacterial activity of HSf and both derivatives was tested against four reference and fifteen clinical Gram-positive and Gram-negative strains of bacteria (sensitive or resistant to fluoroquinolones). The results showed that the activity of PSf was similar to or higher than the activity of HSf, while OPSf was found significantly less active. The compounds were also tested in vitro toward the following cancer cell lines: mouse colon carcinoma (CT26) and human lung adenocarcinoma (A549). Regardless of the cancer cell line, derivatization of HSf resulted in the gradual increase of cytotoxicity. OPSf exhibited the highest one (4 h - incubation time: IC50(CT26) = 51.0 ± 1.2; IC50(A549) = 74.9 ± 1.4 and 24 h: IC50(CT26) = 109.2 ± 8.8; IC50(A549) = 52.7 ± 9.2).

  7. Crystal structure controlled synthesis and characterization of copper sulfide nanoparticles

    NASA Astrophysics Data System (ADS)

    Senthilkumar, M.; Babu, S. Moorthy

    2016-05-01

    Phase pure, controlled crystal structure of digenite (Cu9S5) copper sulfide nanoparticles were synthesized by hot injection method at the temperature of 180°C. The mixture of Oleylamine, 1-Octadecene and 1-Dodecanethiol were taken as solvent as well as capping agents. The effect of the mixture of solvents on the phase formation and morphology of the synthesized nanoparticles were analysed. The nanocrystals were characterized using X-Ray diffraction (XRD) which confirms the presence of single phase rhombohedral digenite Cu9S5 NPs, Morphological analysis clearly depicts the formation of hexagonal faceted Cu9S5 NPs, Energy dispersive X-ray absorption spectroscopy (EDS) reveals the stoichiometric ratio of 1.8:1 for synthesized NPs. From the UV-Vis absorption spectroscopy the bandgap value of Cu1.8S is found to be 1.71 eV. The presence of capping agents along the surface of the Cu9S5 NPs was confirmed from FTIR analysis.

  8. Synthesis, single crystal structure and characterization of pentanitromonoformylhexaazaisowurtzitane.

    PubMed

    Chen, Huaxiong; Chen, Shusen; Li, Lijie; Jiao, Qingze; Wei, Tianyu; Jin, Shaohua

    2010-03-15

    Pentanitromonoformylhexaazaisowurtzitane (PNMFIW) was synthesized by the nitrolysis of tetraacetyldiformylhexaazaisowurtzitane (TADFIW) in mixed nitric and sulfuric acids and structurally characterized by element analysis, FT-IR, MS and (1)H NMR. Single crystals of PNMFIW were grown from aqueous solution employing the technique of controlled evaporation. PNMFIW belongs to the orthorhombic system having four molecules in the unit cell, with space group P2(1)2(1)2(1) and the lattice parameters a=8.8000(18)A, b=12.534(2)A, and c=12.829(3)A. The calculated density reaches 1.977 g/cm(3) at 93 K, while the experimental density is 1.946 g/cm(3) at 20 degrees C. The calculated detonation velocity and pressure of PNMFIW according to the experimental density are 9195.76 m/s and 39.68G Pa, respectively. PNMFIW is insensitive compared with epsilon-HNIW through drop hammer impact sensitivity test. PMID:19913358

  9. Synthesis and textural evolution of alumina particles with mesoporous structures

    SciTech Connect

    Liu Xun; Peng Tianyou; Yao Jinchun; Lv Hongjin; Huang Cheng

    2010-06-15

    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 {gamma}-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{sup -} 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 {gamma}-Al{sub 2}O{sub 3} particles with mesostructures after further calcination at 1173 K, whereas coexisting SO{sub 4}{sup 2-} can promote above morphology evolution and then transformed into {gamma}-Al{sub 2}O{sub 3} nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m{sup 2} g{sup -1} even after calcinations at 1173 K. - Graphical abstract: Co-existing Cl{sup -} is beneficial for the formation of {gamma}-alumina nanoparticles with mesostructures during the precipitation process. Interparticle and intraparticle mesopores can be derived from acidic solution and near neutral solution, respectively.

  10. Synthesis, structural and fungicidal studies of hydrazone based coordination compounds

    NASA Astrophysics Data System (ADS)

    Sharma, Amit Kumar; Chandra, Sulekh

    2013-02-01

    The coordination compounds of the Co(II), Ni(II) and Cu(II) metal ions derived from imine based ligand, benzil bis(carbohydarzone) were structurally and pharmaceutically studied. The compounds have the general stoichiometry [M(L)]X2 and [Co(L)X2], where M = Ni(II) and Cu(II), and X=NO3- and Cl- ions. The analytical techniques like elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, UV/Visible, NMR, ESI mass and EPR were used to study the compounds. The key IR bands, i.e., amide I, amide II and amide III stretching vibrations accounts for the tetradentate metal binding nature of the ligand. The electronic and EPR spectral results suggest the square planar Ni(II) and Cu(II) complexes (giso = 2.11-2.22) and tetragonal geometry Co(II) complexes (giso = 2.10-2.17). To explore the compounds in the biological field, they were examined against the opportunistic pathogens, i.e., Alternaria brassicae, Aspergillus niger and Fusarium oxysporum. The partial covalent character of metal-ligand bond is supported by the orbital reduction factor k (0.62-0.92) and nephalauxetic parameter β (0.55-0.57).

  11. Synthesis and crystal structure of MgB{sub 12}

    SciTech Connect

    Adasch, Volker; Hess, Kai-Uwe; Vojteer, Natascha; Hillebrecht, Harald . E-mail: harald.hillebrecht@ac.uni-freiburg.de

    2006-09-15

    Single crystals of MgB{sub 12} were synthesized from the elements in a Mg/Cu melt at 1600deg. C. MgB{sub 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{sub 1}(F)=0.049, wR{sub 2}(I)=0.134) consists of a three dimensional net of B{sub 12} icosahedra and B{sub 21} units in a ratio 2:1. The B{sub 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{sub 12.35} or Mg{sub 0.97}B{sub 12} , respectively. This is in good agreement with the value of MgB{sub 11.25} as expected by electronic reasons to stabilize the boron polyhedra B{sub 12}{sup 2-} and B{sub 21}{sup 4-}.

  12. Active control synthesis for flexible space structures excited by persistent disturbances

    NASA Technical Reports Server (NTRS)

    Wie, Bong; Gonzalez, Marcelo

    1990-01-01

    Both classical and state-space synthesis methods for active control of flexible space structures in the presence of persistent disturbances are presented. The methods exploit the so-called internal model principle for asymptotic disturbance rejection. A generic example of flexible space structures is used to illustrate the simplicity of the proposed design methodologies. The concept of a disturbance rejection filter dipole is introduced from a classical control viewpoint. It is shown that the proposed design methods will invariably make use of non-minimum-phase compensation for a class of noncolocated control problems. The need for tradeoffs between performance and parameter robustness is discussed.

  13. Unsaturated platinum-rhenium cluster complexes. Synthesis, structures and reactivity.

    PubMed

    Adams, Richard D; Captain, Burjor; Smith, Mark D; Beddie, Chad; Hall, Michael B

    2007-05-01

    Two new compounds PtRe3(CO)12(PBut3)(micro-H)3, 9, and PtRe2(CO)9(PBut3)(micro-H)2, 10, were obtained from the reaction of Pt(PBut3)2 with Re3(CO)12(micro-H3), 8, at room temperature. Compound 9 contains a butterfly cluster of four metals formed by the insertion of the platinum atom from a Pt(PBut3) group into one of the hydride-bridged metal-metal bonds of 8. The three hydrido ligands are bridging ligands across each of three new Pt-Re bonds. Compound 10 contains a triangular PtRe2 cluster with two hydrido ligands; one bridges a Pt-Re bond, and the other bridges the Re-Re bond. The new compound Pt2Re2(CO)7(PBut3)2(micro-H)2, 11, was obtained from the reaction of 8 with Pt(PBut3)2 in hexane at reflux. Compound 11 was also obtained from 10 by reaction with an additional quantity of Pt(PBut3)2. Compound 11 contains a tetrahedral cluster of four metal atoms with two dynamically active hydrido ligands. A CO ligand on one of the two platinum atoms also exchanges between the two platinum atoms rapidly on the NMR time scale. Compound 11 is electronically unsaturated and was found to add hydrogen at room temperature to form the tetrahydrido cluster complex, Pt2Re2(CO)7(PBut3)2(micro-H)4, 12. Compound 12 has a structure similar to 11 but contains one triply bridging hydrido ligand, two edge bridging hydrido ligands, and one terminal hydrido ligand on one of the two platinum atoms. A kinetic isotope effect D/H of 1.5(1) was determined for the addition of H2 to 11. Hydrogen can be eliminated from 12 by heating to 97 degrees C or by the application of UV-vis irradiation at room temperature. Compound 12 adds CO at room temperature to yield the complex Pt2Re2(CO)8(PBut3)2(micro-H)4, 13, which contains a planar cluster of four metal atoms with a Pt-Pt bond and four edge bridging hydrido ligands. Compounds 11 and 12 react with Pt(PBut3)2 to yield the known five metal cluster complexes Pt3Re2(CO)6(PBut3)3(micro-H)2, 14, and Pt3Re2(CO)6(PBut3)3(micro-H)4, 15, respectively. Density

  14. Synthesis and structure of two octahedral molybdenum chloride sulfide clusters

    SciTech Connect

    Michel, J.B.

    1980-03-01

    A preparation for chloride sulfide Mo/sub 6/X/sub 8/ clusters has been devised which employs substitution by sulfide into the Mo/sub 6/Cl/sub 8//sup 4 +/ cluster. The Mo/sub 6/Cl/sub 7/S/sup 3 +/ cluster has been isolated in the two compounds (C/sub 5/H/sub 5/NH)/sub 3/((Mo/sub 6/Cl/sub 7/S)Cl/sub 6/) x 3(C/sub 5/H/sub 5/NH)Cl and (C/sub 5/H/sub 5/NH)/sub 3/((Mo/sub 6/Cl/sub 7/S)Cl/sub 6/). The structures of both compounds were determined by single crystal x-ray techniques. Despite the different site symmetries of the (Mo/sub 6/Cl/sub 7/S)Cl/sub 6//sup 3 -/ units in the two compounds (S/sub 6/ in the former, C/sub i/ in the latter), corresponding average bond distances and angles are equivalent. The infrared spectra (200 to 450 cm/sup -1/) of the two compounds are identical, and exhibit a band at 421 cm/sup -1/ assigned to a (Mo/sub 6/Cl/sub 7/S)Cl/sub 6//sup 3 -/ cluster vibration of predominant Mo-S character. Resolution of the chlorine 2p photoelectron spectra into components reveals not only that sulfide occupies a bridging ligand site of the (Mo/sub 6/Cl/sub 7/S)Cl/sub 6//sup 3 -/ cluster, but also that the difference between the chlorine 2p binding energies of the bridging and terminal chlorides is anomalously small. The Mo/sub 6/S/sub 6/Cl/sub 2/ cluster has been isolated in the novel compound (Mo/sub 6/S/sub 6/Cl/sub 2/)(NC/sub 5/H/sub 5/)/sub 6/. The structure, determined by single crystal x-ray techniques, consists of an approximately cubic Mo/sub 6/X/sub 8/ cluster with six terminal pyridine ligands. (Mo/sub 6/S/sub 6/Cl/sub 2/)(NC/sub 5/H/sub 5/)/sub 6/ is the first example of a Mo/sub 6/X/sub 8/ cluster with terminal ligands which has fewer that 24 electrons in its metal-metal bonding orbitals. X-ray powder data indicates this compound may be one composition in a molecular solid solution (Mo/sub 6/S/sub 7-x/Cl/sub 1+x/)(NC/sub 5/H/sub 5/)/sub 6/(0 less than or equal to x less than or equal to 2).

  15. (Pentamethylcyclopentadienyl)molybdenum(IV) chloride. Synthesis, structure, and properties

    SciTech Connect

    Abugideiri, F.; Desai, J.U.; Gordon, J.C.

    1994-08-17

    Three different syntheses of trichloro(pentamethylcyclopentadienyl)molybdenum(IV) are described, I.E. (1) thermal decarbonylation of Cp{sup *}MoCl{sub 3}(CO){sub 2}, (2) reduction of Cp{sup *}MoCl{sub 4}, and (3) chlorination of [Cp{sup *}MoCl{sub 2}]{sub 2}. A fourth route (conproportionation of [Cp{sup *}MoCl{sub 2}]{sub 2} and Cp{sup *}MoCl{sub 4}) has been investigated by {sup 1}H-NMR. The product has a dinuclear, dichloro-bridged structure with a four-legged piano stool geometry around each metal atom; the two piano stools have a mutual anti arrangement and the two metals are 3.888(1) {Angstrom} from each other, indicating the absence of a direct metal-metal bonding interaction. Crystal data: monoclinic, space group P2{sub 1}/n, a = 8.424(1) {Angstrom}, b = 13.323(4) {Angstrom}, c = 11.266(2) {Angstrom}, {beta} = 93.87(1){degrees}, V = 1261.6(8) {Angstrom}{sup 3}, Z = 2, R = 0.038, R{sub w} = 0.057 for 127 parameters and 1350 observed reflections with F{sub o}{sup 2} > 3{sigma}(F{sub o}{sup 2}). The temperature dependent magnetic moment of the material could be fit to the sum of two Bleany-Bowers equations. [Cp{sup *}MoCl{sub 3}]{sub 2} reacts readily with CO, Cl{sup {minus}}, and PMe{sub 3} to afford Cp{sup *}MoCl{sub 3}(CO){sub 2}, [Cp{sup *}MoCl{sub 4}]{sup {minus}}, and Cp{sup *}MoCl{sub 3}(PMe{sub 3}), respectively, while the reaction with 1,2-bis(diphenylphosphino)ethane (dppe) affords the reduction product Cp{sup *}MoCl{sub 2}(dppe).

  16. Synthesis, structure and luminescent properties of lanthanide fluoroalkoxides.

    PubMed

    Kuzyaev, D M; Balashova, T V; Burin, M E; Fukin, G K; Rumyantcev, R V; Pushkarev, A P; Ilichev, V A; Grishin, I D; Vorozhtsov, D L; Bochkarev, M N

    2016-02-28

    Alkoxides [Ln(OR)3(DME)]2 (R = CH(CF3)2, Ln = Sm (1), Yb (2)), [Ce(OR)3(Phen)]2 (3) (Phen = 1,10-phenanthroline), [Ce(OR′)3(DME)2]2 (R′ = C(CF3)3) (4), {Gd(OR′)3(DME)2} (5), {Ln2[O(CF3)2C–C(CF3)2O]3} (Ln = Ce (6), Gd (7)), {Ce2[O(CF3)2C–C(CF3)2O]3(Phen)2} (8), and {Ce[O(CF3)2C–C(CF3)2O][O(CF3)2–C(CF3)2OH](Phen)2} (9) were synthesized by the reactions of silylamides Ln[N(SiMe3)2]3 with respective fluorinated alcohols. The heterovalent trinuclear complex {Sm2(μ2-OR)3(μ3-OR)2Sm(OR)2(THF)2.5(Et2O)0.5} (10) was obtained by treatment of SmI2(THF)2 with ROK. The reaction of europium(II) and yttrium(III) silylamides with ROH afforded the heterobimetallic alkoxide {Eu2(μ2-OR)3(μ3-OR)2Y(OR)2(DME)2} (11) containing divalent europium. The molecular structures of 1, 2, 3, 9, 10 and 11 were determined by X-ray analysis. All the prepared cerium derivatives as well as the europium–yttrium isopropoxide upon UV excitation exhibited photoluminescence in the regions of 370–425 (for Ce3+) and 485 nm (for Eu2+) which was assigned to 4d→5f transitions. PMID:26795570

  17. Synthesis, Structure, and Resolution of Exceptionally Twisted Pentacenes

    SciTech Connect

    Lu,J.; Ho, D.; Vogelaar, N.; Kraml, C.; Bernhard, S.; Byme, N.; Kim, L.; Pascal, Jr., R.

    2006-01-01

    9,10,11,20,21,22-hexaphenyltetrabenzo[a,c,l,n]pentacene (2) and a dimethyl derivative (2m) were prepared by the reaction of 1,3-diphenylphenanthro[9,10-c]furan with bisaryne equivalents generated from 1,2,4,5-tetrabromo-3,6-diarylbenzenes in the presence of n-butyllithium, followed by deoxygenation of the double adducts with low-valent titanium. Both are bright red solids with a strong orange fluorescence in solution. The X-ray structures of these compounds show them to be the most highly twisted polycyclic aromatic hydrocarbons known. Compound 2 has an end-to-end twist of 144{sup o}, and the two crystallographically independent molecules of 2m have twists of 138{sup o} and 143{sup o}. Both molecules were resolved by chromatography on chiral supports, and the pure enantiomers have extremely high specific rotations (for 2, [{alpha}]{sub D} = 7400{sup o}; for 2m, 5600{sup o}), but the molecules racemize slowly at room temperature ({Delta}G{sup {double_dagger}}{sub rac} = 24 kcal/mol). Both the experimental geometry and the observed racemization barrier for 2 are in good agreement with computational studies of the molecule at a variety of levels. Attempts to prepare compound 2 by reaction of tetraphenylbenzyne with 9,10,12,13-tetraphenyl-11-oxacyclopenta[b]triphenylene (3, a twisted isobenzofuran) gave no adducts, and attempts to prepare tetradecaphenylpentacene by reaction of hexaphenylisobenzofuran (11) with bisaryne equivalents gave only monoadducts.

  18. [Cloning of structural genes involved in riboflavin synthesis of the yeast Candida famata].

    PubMed

    Dmytruk, K V; Abbas, C A; Voronovsky, A Y; Kshanovska, B V; Sybirna, K A; Sybirny, A A

    2004-01-01

    The riboflavin overproducing mutants of the flavinogenic yeast Candida famata isolated by conventional selection methods are used for the industrial production of vitamin B2. Recently, a transformation system was developed for C. famata using the leu2 mutant as a recipient strain and Saccharomyces cerevislae LEU2 gene as a selective marker. In this paper the cloning of C. famata genes for riboflavin synthesis on the basis of developed transformation system for this yeast species is described. Riboflavin autotrophic mutants were isolated from a previously selected C. famata leu2 strain. C. famata genomic DNA library was constructed and used for cloning of the corresponding structural genes for riboflavin synthesis by complementation of the growth defects on a medium without leucine and riboflavin. As a result, the DNA fragments harboring genes RIB1, RIB2, RIB5, RIB6 and RIB7 encoding GTP cyclohydrolase, reductase, dimethylribityllumazine synthase, dihydroxybutanone phosphate synthase and riboflavin synthase, were isolated and subsequently subcloned to the smallest possible fragments. The plasmids with these genes successfully complemented riboflavin auxotrophies of the corresponding mutants of another flavinogenic yeast Pichia guilliermondii. This suggested that C. famata structural genes for riboflavin synthesis and not some of the supressor genes were cloned. PMID:15909421

  19. Ionothermal synthesis, crystal structure, and magnetic study of Co2PO4OH isostructural with caminite.

    PubMed

    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. PMID:24597964

  20. Addressing a "Black Box" of Bottom-Up Synthesis: Revealing the Structures of Growing Colloidal-Nanocrystal Nuclei.

    PubMed

    Sobol, Oded; Gadot, Eyal; Wang, Yifeng; Weinstock, Ira A; Meshi, Louisa

    2015-11-16

    In bottom-up synthesis, products from reactions of structural building units rapidly pass from soluble molecular complexes to nanoscale intermediates, whose solution-state structures defy elucidation by any routine method. To address this, electron diffraction is used to reveal the structures of cryogenically "trapped" colloidal nanocrystals. PMID:26536393

  1. Insights into eukaryotic primer synthesis from structures of the p48 subunit of human DNA primase

    PubMed Central

    Vaithiyalingam, Sivaraja; Arnett, Diana R.; Aggarwal, Amit; Eichman, Brandt F.; Fanning, Ellen; Chazin, Walter J.

    2013-01-01

    DNA replication in all organisms requires polymerases to synthesize copies of the genome. DNA polymerases are unable to function on a bare template and require a primer. Primases are crucial RNA polymerases that perform the initial de novo synthesis, generating the first 8–10 nucleotides of the primer. Although structures of archaeal and bacterial primases have provided insights into general priming mechanisms, these proteins are not well conserved with heterodimeric (p48/p58) primases in eukaryotes. Here, we present X-ray crystal structures of the catalytic engine of a eukaryotic primase, which is contained in the p48 subunit. The structures of p48 reveal eukaryotic primases maintain the conserved catalytic prim fold domain, but with a unique sub-domain not found in the archaeal and bacterial primases. Calorimetry experiments reveal Mn2+ but not Mg2+ significantly enhances the binding of nucleotide to primase, which correlates with in vitro higher catalytic efficiency. The structure of p48 with bound UTP and Mn2+ provides insights into the mechanism of nucleotide synthesis by primase. Substitution of conserved residues involved in either metal or nucleotide binding altered nucleotide binding affinities, and yeast strains containing the corresponding Pri1p substitutions were not viable. Our results revealed two residues (S160 and H166) in direct contact with the nucleotide that were previously unrecognized as critical to the human primase active site. Comparing p48 structures to those of similar polymerases in different states of action suggests changes that would be required to attain a catalytically competent conformation capable of initiating dinucleotide synthesis. PMID:24239947

  2. Biologically Inspired Synthesis Route to Three-Dimensionally Structured Inorganic Thin Films

    DOE PAGESBeta

    Schwenzer, Birgit; Morse, Daniel E.

    2008-01-01

    Inorganic thin films (hydroxide, oxide, and phosphate materials) that are textured on a submicron scale have been prepared from aqueous metal salt solutions at room temperature using vapor-diffusion catalysis. This generic synthesis approach mimics the essential advantages of the catalytic and structure-directing mechanisms observed for the formation of silica skeletons of marine sponges. Chemical composition, crystallinity, and the three-dimensional morphology of films prepared by this method are extremely sensitive to changes in the synthesis conditions, such as concentrations, reaction times, and the presence and nature of substrate materials. Focusing on different materials systems, the reaction mechanism for the formation ofmore » these thin films and the influence of different reaction parameters on the product are explained.« less

  3. The Effects of Gravity on Combustion and Structure Formation During Combustion Synthesis in Gasless Systems

    NASA Technical Reports Server (NTRS)

    Varma, Arvind; Mukasyan, Alexander; Pelekh, Aleksey

    1997-01-01

    There have been relatively few publications examining the role of gravity during combustion synthesis (CS), mostly involving thermite systems. The main goal of this research was to study the influence of gravity on the combustion characteristics of heterogeneous gasless systems. In addition, some aspects of microstructure formation processes which occur during gasless CS were also studied. Four directions for experimental investigation have been explored: (1) the influence of gravity force on the characteristic features of heterogeneous combustion wave propagation (average velocity, instantaneous velocities, shape of combustion front); (2) the combustion of highly porous mixtures (with porosity greater than that for loose powders), which cannot be obtained in normal gravity; (3) the effect of gravity on sample expansion during combustion, in order to produce highly porous materials under microgravity conditions; and (4) the effect of gravity on the structure formation mechanism during the combustion synthesis of poreless composite materials.

  4. Total synthesis, stereochemical assignment, and biological activity of chamuvarinin and structural analogues.

    PubMed

    Florence, Gordon J; Morris, Joanne C; Murray, Ross G; Vanga, Raghava R; Osler, Jonathan D; Smith, Terry K

    2013-06-17

    A highly stereocontrolled synthesis of (+)-chamuvarinin has been completed in 1.5% overall yield over 20 steps. The key fragment coupling reactions were the addition of alkyne 8 to aldehyde 7 (under Felkin-Anh control), followed by the two step activation/cyclization to close the C20-C23 2,5-cis-substituted tetrahydrofuran ring and a Julia-Kocienski olefination at C8-C9 to introduce the terminal butenolide. The inherent flexibility of our coupling strategy led to a streamlined synthesis with 17 steps in the longest sequence (2.2% overall yield), in which the key bond couplings are reversed. In addition, a series of structural analogues of chamuvarinin have been prepared and screened for activity against HeLa cancer cell lines and both the bloodstream and insect forms of Trypanosoma brucei, the parasitic agent responsible for African sleeping sickness. PMID:23630031

  5. Synthesis of structural/control systems robust with respect to design variable tolerances

    NASA Technical Reports Server (NTRS)

    Thomas, H. L.; Schmit, L. A.

    1991-01-01

    A methodology is presented for the synthesis of control augmented structures which can be modeled as an assemblage of beam, truss, and nonstructural mass elements augmented by a robust noncollocated direct output feedback control system. The control system is robust in the sense that it can tolerate manufacturing and realization errors. The robust control system is synthesized using a constraint buffering technique in conjunction with the approximation concepts approach to system synthesis. All of the design constraints on the system, including the dynamic stability, are buffered by a nonlinear quantity that is a function of acceptable tolerances on the design variables and the sensitivity of the constraints to changes in these design variables. Numerical results which illustrate the effectiveness of the method presented are given.

  6. Controlled synthesis of linear and cyclic liquid crystals containing conformationally flexible structural units

    NASA Astrophysics Data System (ADS)

    Asandei, Alexandru Dragos

    This thesis decribes the design, synthesis and characterization of a large variety of molecular, macromolecular and supramolecular liquid crystalline (LC) systems with linear, cyclic, and combinations of linear and cyclic architectures. These structures are based on mesogens that display conformational isomerism. Several series of macrocyclics based on 1-(4-hydroxyphenyl)-2-(2-methyl-4-hydroxyphenyl)ethane (MBPE) and various alpha,omega-dibromoalkanes were synthesized and characterized. These macrocyclics display more stable and broader LC phases than the corresponding linear polymers. Relatively minor modifications in the structure of the mesogen, spacer or microstructure of polymeric chains have a strong effect on the phase behavior of main chain polyethers. This is demonstrated for polymers based on 1-(4-hydroxyphenyl)-2-(4-hydroxy-4'-biphenylyl)butane (TPB') and alpha,omega-dibromoalkanes containing from 4 to 19 methylenic units. A stepwise synthetic procedure is described for the synthesis of a series of LC macrocyclics based of TPB' and 1,10-dibromodecane. Large increases in the yields by comparison with the one-pot method are obtained, and the procedure is also illustrated by the synthesis of the first example of a liquid crystalline bicyclic compound. The stepwise synthesis and characterization of macrocyclic monomers and of the first examples of side chain and main chain LC polymers containing supramolecular mesogens based on collapsed macrocyclics building blocks are described and discussed. An iterative stepwise procedure that allows for an exponential 2spn growth in molecular weight after n synthetic cycles is presented and applied to the synthesis of linear polyethers based on 1-(4-hydroxy-4'-biphenylyl)-2-(4-hydroxyphenyl)butane (TPB) and 1,10-dibromodecane. A library of linear monodisperse oligomers and polymers with a degree of polymerization (DP) up to 33 and with a variety of chain ends was generated, and the dependence of the phase behavior of

  7. Antineoplastic Agents 579. Synthesis and Cancer Cell Growth Evaluation of E-Stilstatin 3: A Resveratrol Structural Modification⊥

    PubMed Central

    Pettit, George R.; Melody, Noeleen; Thornhill, Andrew; Knight, John C.; Groy, Thomas L.; Herald, Cherry L.

    2009-01-01

    As an extension of our earlier structure/activity investigation of resveratrol (1a) cancer cell growth inhibitory activity compared to the structurally related stilbene combretastatin series (e.g., 2a), an efficient synthesis of E-stilstatin 3 (3a) and its phosphate prodrug 3b was completed. The trans-stilbene 3a was obtained using a convergent synthesis employing a Wittig reaction with phosphonium bromide 9 as the key reaction step. Deprotection of the Z-silyl ether 13 gave E-stilstatin 3 (3a) as the exclusive product. The structure and stereochemistry of 3a was confirmed by X-ray crystal structure determination. PMID:19719153

  8. Synthesis and structural characterization of some trisulfide analoges of thiouracil-based antithyroid drugs

    NASA Astrophysics Data System (ADS)

    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.

  9. Carborane-containing urea-based inhibitors of glutamate carboxypeptidase II: Synthesis and structural characterization.

    PubMed

    Youn, Sihyun; Kim, Kyung Im; Ptacek, Jakub; Ok, Kiwon; Novakova, Zora; Kim, YunHye; Koo, JaeHyung; Barinka, Cyril; Byun, Youngjoo

    2015-11-15

    Glutamate carboxypeptidase II (GCPII) is a zinc metalloprotease on the surface of astrocytes which cleaves N-acetylaspartylglutamate to release N-acetylaspartate and glutamate. GCPII inhibitors can decrease glutamate concentration and play a protective role against apoptosis or degradation of brain neurons. Herein, we report the synthesis and structural analysis of novel carborane-based GCPII inhibitors. We determined the X-ray crystal structure of GCPII in complex with a carborane-containing inhibitor at 1.79Å resolution. The X-ray analysis revealed that the bulky closo-carborane cluster is located in the spacious entrance funnel region of GCPII, indicating that the carborane cluster can be further structurally modified to identify promising lead structures of novel GCPII inhibitors. PMID:26459214

  10. Structural basis of high-fidelity DNA synthesis by yeast DNA polymerase [delta

    SciTech Connect

    Swan, Michael K.; Johnson, Robert E.; Prakash, Louise; Prakash, Satya; Aggarwal, Aneel K.

    2009-09-25

    DNA polymerase {delta} (Pol {delta}) is a high-fidelity polymerase that has a central role in replication from yeast to humans. We present the crystal structure of the catalytic subunit of yeast Pol {delta} in ternary complex with a template primer and an incoming nucleotide. The structure, determined at 2.0-{angstrom} resolution, catches the enzyme in the act of replication, revealing how the polymerase and exonuclease domains are juxtaposed relative to each other and how a correct nucleotide is selected and incorporated. The structure also reveals the 'sensing' interactions near the primer terminus, which signal a switch from the polymerizing to the editing mode. Taken together, the structure provides a chemical basis for the bulk of DNA synthesis in eukaryotic cells and a framework for understanding the effects of cancer-causing mutations in Pol {delta}.

  11. Local structure of ZnO micro flowers and nanoparticles obtained by micro segmented flow synthesis

    SciTech Connect

    Li, Shuning; Roy, Amitava; Lichtenberg, Henning; Merchan, Gregory; Kumar, Challa S.S.R.; Köhler, J. Michael

    2012-03-07

    The micro-segmented flow technique was applied for continuous synthesis of ZnO micro- and nanoparticles with short residence times of 9.4 s and 21.4 s, respectively. The obtained particles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Small angle X-ray scattering (SAXS) and photoluminescence spectroscopy were used to determine the size and optical properties of ZnO nanoparticles. In addition, extended X-ray absorption fine structure (EXAFS) spectroscopy was employed to investigate local structural properties. The EXAFS measurements reveal a larger degree of structural disorder in the nanoparticles than the microparticles. These structural changes should be taken into consideration while evaluating the size-dependent visible emission of ZnO nanoparticles.

  12. Synthesis of regional crust and upper-mantle structure from seismic and gravity data

    NASA Technical Reports Server (NTRS)

    Alexander, S. S.; Lavin, P. M.

    1979-01-01

    Available seismic and ground based gravity data are combined to infer the three dimensional crust and upper mantle structure in selected regions. This synthesis and interpretation proceeds from large-scale average models suitable for early comparison with high-altitude satellite potential field data to more detailed delineation of structural boundaries and other variations that may be significant in natural resource assessment. Seismic and ground based gravity data are the primary focal point, but other relevant information (e.g. magnetic field, heat flow, Landsat imagery, geodetic leveling, and natural resources maps) is used to constrain the structure inferred and to assist in defining structural domains and boundaries. The seismic data consists of regional refraction lines, limited reflection coverage, surface wave dispersion, teleseismic P and S wave delay times, anelastic absorption, and regional seismicity patterns. The gravity data base consists of available point gravity determinations for the areas considered.

  13. Ordovician and Silurian Phi Kappa and Trail Creek formations, Pioneer Mountains, central Idaho; stratigraphic and structural revisions, and new data on graptolite faunas

    USGS Publications Warehouse

    Dover, James H.; Berry, William B.N.; Ross, Reuben James, Jr.

    1980-01-01

    Recent geologic mapping in the northern Pioneer Mountains combined with the identification of graptolites from 116 new collections indicate that the Ordovician and Silurian Phi Kappa and Trail Creek Formations occur in a series of thrust-bounded slices within a broad zone of imbricate thrust faulting. Though confirming a deformational style first reported in a 1963 study by Michael Churkin, our data suggest that the complexity and regional extent of the thrust zone were not previously recognized. Most previously published sections of the Phi Kappa and Trail Creek Formations were measured across unrecognized thrust faults and therefore include not only structural repetitions of graptolitic Ordovician and Silurian rocks but also other tectonically juxtaposed lithostratigraphic units of diverse ages as well. Because of this discovery, the need to reconsider the stratigraphic validity of these formations and their lithology, nomenclature, structural distribution, facies relations, and graptolite faunas has arisen. The Phi Kappa Formation in most thrust slices has internal stratigraphic continuity despite the intensity of deformation to which it was subjected. As revised herein, the Phi Kappa Formation is restricted to a structurally repeated succession of predominantly black, carbonaceous, graptolitic argillite and shale. Some limy, light-gray-weathering shale occurs in the middle part of the section, and fine-grained locally pebbly quartzite is present at the base. The basal quartzite is here named the Basin Gulch Quartzite Member of the Phi Kappa. The Phi Kappa redefined on a lithologic basis represents the span of Ordovician time from W. B. N. Berry's graptolite zones 2-4 through 15 and also includes approximately 17 m of lithologically identical shale of Early and Middle Silurian age at the top. The lower contact of the formation as revised is tectonic. The Phi Kappa is gradationally overlain by the Trail Creek Formation as restricted herein. Most of the coarser

  14. Synthesis and single crystal structure refinement of the one-layer hydrate of sodium brittle mica

    SciTech Connect

    Kalo, Hussein; Milius, Wolfgang; Braeu, Michael; Breu, Josef

    2013-02-15

    A sodium brittle mica with the ideal composition [Na{sub 4}]{sup inter}[Mg{sub 6}]{sup oct}[Si{sub 4}Al{sub 4}]{sup tet}O{sub 20}F{sub 4} was synthesized via melt synthesis in a gas tight crucible. This mica is unusual inasmuch as the known mica structure holds only room for two interlayer cations per unit cell and inasmuch as it readily hydrates despite the high layer charge while ordinary micas and brittle micas are non-swelling. The crystal structure of one-layer hydrate sodium brittle mica was determined and refined from single crystal X-ray data. Interlayer cations reside at the center of the distorted hexagonal cavities and are coordinated by the three inner basal oxygen atoms. The coordination of the interlayer cation is completed by three interlayer water molecules residing at the center of the interlayer region. The relative position of adjacent 2:1-layers thus is fixed by these octahedrally coordinated interlayer cations. Pseudo-symmetry leads to extensive twinning. In total five twin operations generate the same environment for the interlayer species and are energetically degenerate. - Graphical abstract: The sodium brittle mica has been successfully synthesized by melt synthesis and the crystal structure of the one-layer hydrate of sodium brittle mica was determined from single crystal X-ray diffraction data. Highlights: Black-Right-Pointing-Pointer Melt synthesis yielded coarse grained sodium brittle mica which showed little disorder. Black-Right-Pointing-Pointer Sodium brittle mica hydrated completely to the state of one-layer hydrate. Black-Right-Pointing-Pointer Structure of one-layer hydrate of sodium brittle mica could therefore be determined and refined. Black-Right-Pointing-Pointer Arrangement of upper and lower tetrahedral sheet encompassing interlayer cation were clarified.

  15. The structural synthesis of tendon-driven manipulators having a pseudotriangular structure matrix

    SciTech Connect

    Jyhjone Lee; Lungwen Tsai )

    1991-06-01

    Tendons have been widely used for power transmission in the field of anthropomorphic manipulating systems. This article deals with the identification and enumeration of the kinematic structure of tendon-driven robotic mechanisms. The structural isomorphism of tendon-driven manipulators is defined, and the structural characteristics of such mechanical systems are described. Applying these structural characteristics, a methodology for the enumeration of tendon-driven robotic mechanisms is developed. Mechanism structures with up to six degrees of freedom are enumerated.

  16. Structures and Functions of Qβ Replicase: Translation Factors beyond Protein Synthesis

    PubMed Central

    Tomita, Kozo

    2014-01-01

    Qβ replicase is a unique RNA polymerase complex, comprising Qβ virus-encoded RNA-dependent RNA polymerase (the catalytic β-subunit) and three host-derived factors: translational elongation factor (EF) -Tu, EF-Ts and ribosomal protein S1. For almost fifty years, since the isolation of Qβ replicase, there have been several unsolved, important questions about the mechanism of RNA polymerization by Qβ replicase. Especially, the detailed functions of the host factors, EF-Tu, EF-Ts, and S1, in Qβ replicase, which are all essential in the Escherichia coli (E. coli) host for protein synthesis, had remained enigmatic, due to the absence of structural information about Qβ replicase. In the last five years, the crystal structures of the core Qβ replicase, consisting of the β-subunit, EF-Tu and Ts, and those of the core Qβ replicase representing RNA polymerization, have been reported. Recently, the structure of Qβ replicase comprising the β-subunit, EF-Tu, EF-Ts and the N-terminal half of S1, which is capable of initiating Qβ RNA replication, has also been reported. In this review, based on the structures of Qβ replicase, we describe our current understanding of the alternative functions of the host translational elongation factors and ribosomal protein S1 in Qβ replicase as replication factors, beyond their established functions in protein synthesis. PMID:25184952

  17. Scar revision

    PubMed Central

    Sharma, Mohit; Wakure, Abhijeet

    2013-01-01

    Most surgical patients end up with a scar and most of these would want at least some improvement in the appearance of the scar. Using sound techniques for wound closure surgeons can, to a certain extent, prevent suboptimal scars. This article reviews the principles of prevention and treatment of suboptimal scars. Surgical techniques of scar revision, i.e., Z plasty, W plasty, and geometrical broken line closure are described. Post-operative care and other adjuvant therapies of scars are described. A short description of dermabrasion and lasers for management of scars is given. It is hoped that this review helps the surgeon to formulate a comprehensive plan for management of scars of these patients. PMID:24516292

  18. The structure of post-traumatic stress symptoms in survivors of war: confirmatory factor analyses of the Impact of Event Scale--revised.

    PubMed

    Morina, Nexhmedin; Böhme, Hendryk F; Ajdukovic, Dean; Bogic, Marija; Franciskovic, Tanja; Galeazzi, Gian M; Kucukalic, Abdulah; Lecic-Tosevski, Dusica; Popovski, Mihajlo; Schützwohl, Matthias; Stangier, Ulrich; Priebe, Stefan

    2010-08-01

    The study aimed at establishing the factor structure of the Impact of Event Scale-Revised (IES-R) in survivors of war. A total sample of 4167 participants with potentially traumatic experiences during the war in Ex-Yugoslavia was split into three samples: two independent samples of people who stayed in the area of conflict and one sample of refugees to Western European countries. Alternative models with three, four, and five factors of post-traumatic symptoms were tested in one sample. The other samples were used for cross-validation. Results indicated that the model of best fit had five factors, i.e., intrusion, avoidance, hyperarousal, numbing, and sleep disturbance. Model superiority was cross-validated in the two other samples. These findings suggest a five-factor model of post-traumatic stress symptoms in war survivors with numbing and sleep disturbance as separate factors in addition to intrusion, avoidance and hyperarousal. PMID:20430572

  19. Effect of Alcohol Structure on the Optimum Condition for Novozym 435-Catalyzed Synthesis of Adipate Esters

    PubMed Central

    Abdul Rahman, Mohd Basyaruddin; Chaibakhsh, Naz; Basri, Mahiran

    2011-01-01

    Immobilized Candida antarctica lipase B, Novozym 435, was used as the biocatalyst in the esterification of adipic acid with four different isomers of butanol (n-butanol, sec-butanol, iso-butanol, and tert-butanol). Optimum conditions for the synthesis of adipate esters were obtained using response surface methodology approach with a four-factor-five-level central composite design concerning important reaction parameters which include time, temperature, substrate molar ratio, and amount of enzyme. Reactions under optimized conditions has yielded a high percentage of esterification (>96%) for n-butanol, iso-butanol, and sec-butanol, indicating that extent of esterification is independent of the alcohol structure for primary and secondary alcohols at the optimum conditions. Minimum reaction time (135 min) for achieving maximum ester yield was obtained for iso-butanol. The required time for attaining maximum yield and also the initial rates in the synthesis of di-n-butyl and di-sec-butyl adipate were nearly the same. Immobilized Candida antarctica lipase B was also capable of esterifying tert-butanol with a maximum yield of 39.1%. The enzyme is highly efficient biocatalyst for the synthesis of adipate esters by offering a simple production process and a high esterification yield. PMID:22389769

  20. Nickel hydroxides and related materials: a review of their structures, synthesis and properties

    PubMed Central

    Hall, David S.; Lockwood, David J.; Bock, Christina; MacDougall, Barry R.

    2015-01-01

    This review article summarizes the last few decades of research on nickel hydroxide, an important material in physics and chemistry, that has many applications in engineering including, significantly, batteries. First, the structures of the two known polymorphs, denoted as α-Ni(OH)2 and β-Ni(OH)2, are described. The various types of disorder, which are frequently present in nickel hydroxide materials, are discussed including hydration, stacking fault disorder, mechanical stresses and the incorporation of ionic impurities. Several related materials are discussed, including intercalated α-derivatives and basic nickel salts. Next, a number of methods to prepare, or synthesize, nickel hydroxides are summarized, including chemical precipitation, electrochemical precipitation, sol–gel synthesis, chemical ageing, hydrothermal and solvothermal synthesis, electrochemical oxidation, microwave-assisted synthesis, and sonochemical methods. Finally, the known physical properties of the nickel hydroxides are reviewed, including their magnetic, vibrational, optical, electrical and mechanical properties. The last section in this paper is intended to serve as a summary of both the potentially useful properties of these materials and the methods for the identification and characterization of ‘unknown’ nickel hydroxide-based samples. PMID:25663812

  1. An empirical investigation of the structure of anxiety and depressive symptoms in late adolescence: cross-sectional study using the Greek version of the revised Clinical Interview Schedule.

    PubMed

    Skapinakis, Petros; Anagnostopoulos, Fotios; Bellos, Stefanos; Magklara, Konstantina; Lewis, Glyn; Mavreas, Venetsanos

    2011-04-30

    Several studies in the past have examined whether the hierarchical structure of anxiety and depressive symptoms can explain the high comorbidity between them but more studies are needed from other settings and with different methods. The present study aimed to examine the structure of common anxiety and depressive symptoms in adolescents 16-18 years old attending secondary schools using the Greek version of the revised Clinical Interview Schedule (CIS-R), a fully structured psychiatric interview. A total of 2431 adolescents were interviewed with the computerized version of the CIS-R. The hierarchical structure of 12 depressive and anxiety symptoms was examined with confirmatory factor analytical methods. Four alternative models of increasing complexity were tested. The best-fitting model included three first-order factors, representing the dimensions of anxiety, depression and non-specific distress respectively. A model with a higher-order factor representing the broader internalizing dimension was less supported by the data. The findings of this and other studies should be taken into account in future classifications of psychiatric disorders and may have clinical practical implications. PMID:20846727

  2. The Nuclear Magnetic Resonance of CCCC RNA Reveals a Right-Handed Helix, and Revised Parameters for AMBER Force Field Torsions Improve Structural Predictions from Molecular Dynamics

    PubMed Central

    2013-01-01

    The sequence dependence of RNA energetics is important for predicting RNA structure. Hairpins with Cn loops are consistently less stable than hairpins with other loops, which suggests the structure of Cn regions could be unusual in the “unfolded” state. For example, previous nuclear magnetic resonance (NMR) evidence suggested that polycytidylic acid forms a left-handed helix. In this study, UV melting experiments show that the hairpin formed by r(5′GGACCCCCGUCC) is less stable than r(5′GGACUUUUGUCC). NMR spectra for single-stranded C4 oligonucleotide, mimicking the unfolded hairpin loop, are consistent with a right-handed A-form-like helix. Comparisons between NMR spectra and molecular dynamics (MD) simulations suggest that recent reparametrizations, parm99χ_YIL and parm99TOR, of the AMBER parm99 force field improve the agreement between structural features for C4 determined by NMR and predicted by MD. Evidently, the force field revisions to parm99 improve the modeling of RNA energetics and therefore structure. PMID:23286901

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  4. An integrated approach to the synthesis of geometrically non-linear structures

    NASA Technical Reports Server (NTRS)

    Smaoui, H.; Schmit, L. A.

    1988-01-01

    An integrated approach to the minimum weight design of geometrically nonlinear three-dimensional truss structures with geometric imperfections, subject to inequality constraints on static displacements, stresses, local buckling and cross sectional areas, is investigated. The integrated structural synthesis problem involves design and response quantities as independent variables and equilibrium equations, describing the finite element model, as equality constraints. The nonlinear structural analysis and the optimization are thus merged together into a single process. A computer program developed to compute the constraint values and analytical gradients is coupled with a generalized reduced gradient algorithm to solve the integrated problem. Numerical results for a geometrically nonlinear shallow dome example problem are presented for various types of imperfections. Furthermore, it is found that the algorithm is capable of detecting and guarding against system as well as element elastic instability using equilibrium information only, that is, without imposing system and local buckling inequality constraints.

  5. Novel aldehyde and thiosemicarbazone derivatives: Synthesis, spectroscopic characterization, structural studies and molecular docking studies

    NASA Astrophysics Data System (ADS)

    Karakurt, Tuncay; Tahtaci, Hakan; Subasi, Nuriye Tuna; Er, Mustafa; Ağar, Erbil

    2016-12-01

    In this study our purpose is that, synthesis and characterization of compounds containing the aldehyde and thiosemicarbazone groups and comparison of the theoretical results with the experimental results. The structures of all synthesized compounds were elucidated by IR, 1H NMR, 13C NMR, elemental analyses techniques. The structure of compound (4) (C9H8N4O2S) was also elucidated by X-ray diffraction analysis. In addition, the theoretical IR spectrum, 1H NMR and 13C NMR chemical shift values, frontier molecular orbital values (FMO) of these molecules were analyzed by using Becke-3- Lee-Yang-Parr (B3LYP) method with LanL2DZ basis set. Finally, molecular docking studies were performed on synthesized compounds using the 4DKI beta-lactam protein structure to determine the potential binding mode of inhibitors.

  6. Application of the Probabilistic Dynamic Synthesis Method to the Analysis of a Realistic Structure

    NASA Technical Reports Server (NTRS)

    Brown, Andrew M.; Ferri, Aldo A.

    1998-01-01

    The Probabilistic Dynamic Synthesis method is a new technique for obtaining the statistics of a desired response engineering quantity for a structure with non-deterministic parameters. The method uses measured data from modal testing of the structure as the input random variables, rather than more "primitive" quantities like geometry or material variation. This modal information is much more comprehensive and easily measured than the "primitive" information. The probabilistic analysis is carried out using either response surface reliability methods or Monte Carlo simulation. A previous work verified the feasibility of the PDS method on a simple seven degree-of-freedom spring-mass system. In this paper, extensive issues involved with applying the method to a realistic three-substructure system are examined, and free and forced response analyses are performed. The results from using the method are promising, especially when the lack of alternatives for obtaining quantitative output for probabilistic structures is considered.

  7. Structural requirements of (2'-5') oligoadenylate for protein synthesis inhibition in human fibroblasts.

    PubMed Central

    Drocourt, J L; Dieffenbach, C W; Ts'o, P O; Justesen, J; Thang, M N

    1982-01-01

    The structural requirements of (2'-5')-oligoadenylic acid (pppA(2'p5'A)x, X greater than or equal to 1 or (2'-5'An) for inhibition of protein synthesis in cells were examined with a modified calcium-coprecipitation technique, using a series of trinucleotide analogs (pppA2'p5'A2'p5'N, N=rC, rG, rU, T, dC, dG, dA). In this system both the degree and the duration of the inhibition of protein synthesis were dependent on the added concentration of (2'-5')A3. Of all the heterotrimers, only the deoxy A derivative was active as an inhibitor of protein synthesis, while the other members of the analog series were found to have no inhibitory effects. In competition experiments between (2'-5')A3 and the non-active analogs, three heterotrimers were shown to reduce the activity of (2'-5')A3 in protein inhibition. In contrast, the dephosphorylated (2'-5')A3 had no inhibitory effect and was not effective in blocking (2'-5')A3. These results indicate that the 5'-terminal triphosphate is important for binding of (2'-5')A3 to the site of (2'-5')An action and the adenine base at the 2'-terminus is important for activating the machinery responsible for protein synthesis inhibition in the cells, most likely the (2'-5')An-activated nuclease. PMID:7079179

  8. Synthesis, spectroscopic characterizations, crystal structures and DFT studies of nalidixic acid carbonyl hydrazones derivatives

    NASA Astrophysics Data System (ADS)

    Bergamini, F. R. G.; Ribeiro, M. A.; Lancellotti, M.; Machado, D.; Miranda, P. C. M. L.; Cuin, A.; Formiga, A. L. B.; Corbi, P. P.

    2016-09-01

    This article describes the synthesis and characterization of the 1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-carbohydrazide (hzd) and six carbonyl hydrazones derivatives of the nalidixic with 1H-pyrrol-2-ylmethylidene (hpyrr), 1H-imidazol-2-ylmethylidene (h2imi), pyridin-2-ylmethylidene (h2py), pyridin-3-ylmethylidene (h3py), pyridin-4-ylmethylidene(h4py) and (2-hydroxyphenyl)methylidene (hsali). The carbonyl hydrazones were characterized by elemental and ESI-QTOF-MS analyses, IR and detailed NMR spectroscopic measurements. The 2D NMR experiments allowed the unambiguous assignment of the hydrogen, carbon and nitrogen atoms, which have not been reported for nalidixic acid carbonyl hydrazone derivatives so far. Crystal structures of hzd and the new carbonyl hydrazones h2imi, hpyrr and h3py were determined by X-ray diffraction studies. Although the synthesis of hzd was reported decades ago, the hzd crystal structure have not been reported yet. Geometric optimizations of all the characterized structures were performed with the aid of DFT studies. Despite the fact that the hydrazones with 2-pyridine carboxylic acid (h2py) and salicyl aldehyde (hsali) were already reported by literature, a detailed spectroscopic study followed by DFT studies are also reported for such compounds in this manuscript. Antimicrobial studies of the compounds are also presented.

  9. Synthesis of N-Doped Hollow-Structured Mesoporous Carbon Nanospheres for High-Performance Supercapacitors.

    PubMed

    Liu, Chao; Wang, Jing; Li, Jiansheng; Zeng, Mengli; Luo, Rui; Shen, Jinyou; Sun, Xiuyun; Han, Weiqing; Wang, Lianjun

    2016-03-23

    We have demonstrated a facile and controllable synthesis of monodispersed N-doped hollow mesoporous carbon nanospheres (N-HMCSs) and yolk-shell hollow mesoporous carbon nanospheres (N-YSHMCSs) by a modified "silica-assisted" route. The synthesis process can be carried out by using resorcinol-formaldehyde resin as a carbon precursor, melamine as a nitrogen source, hexadecyl trimethylammonium chloride as a template, and silicate oligomers as structure-supporter. The morphological (i.e., particle size, shell thickness, cavity size, and core diameter) and textural features of the carbon nanospheres are easily controlled by varying the amount of ammonium. The resultant carbon nanospheres possess high surface areas (up to 2464 m(2) g(-1)), large pore volumes (up to 2.36 cm(3) g(-1)), and uniform mesopore size (∼2.4 nm for N-HMCSs, ∼ 4.5 nm for N-YSHMCSs). Through combining the hollow mesoporous structure, high porosity, large surface area, and N heteroatomic functionality, the as-synthesized N-doped hollow-structured carbon nanospheres manifest excellent supercapacitor performance with high capacitance (up to 240 F/g), favorable capacitance retention (97.0% capacitive retention after 5000 cycles), and high energy density (up to 11.1 Wh kg(-1)). PMID:26942712

  10. Mechanochemical Synthesis of Hydroxyapatite and Its Modifications: Composition, Structure, and Properties

    NASA Astrophysics Data System (ADS)

    Chaikina, M. V.; Bulina, N. V.; Ishchenko, A. V.; Prosanov, I. Yu.

    2014-02-01

    The mechanochemical method is used to synthesize samples of hydroxyapatite (HA) with substitution of the phosphate ion by silicate and zirconate ions, and substitution of calcium ions by copper ions. In the process of mechanochemical synthesis, carbonate ions and water molecules are incorporated into the structure of HA due to interaction of components of the reaction mixture with air. Intrusion of carbonate into the structure of HA is a competing process with modification of apatite by silicate and zirconate anions; therefore, the composition of the product during synthesis differs from the prescribed one. After annealing of the samples, the composition of the anion-modified HA can be described by the formula Са10(РО4)6- х (АО4) х (ОН)2- х , where (АО4)4- is the modifying anion. Substitution of calcium by copper ions localized at the Са1 position has been detected. Silver ions are not incorporated into the structure of HA, but are distributed in the apatite matrix in the form of nanocrystals of metallic silver.

  11. Synthesis and characterization of high temperature curable poly(arylene ether) structural adhesive and composite matrices

    SciTech Connect

    Mecham, S.J.; Jayaraman, S.; Bobbitt, M.M.

    1996-12-31

    Crosslinked poly(arylene ether) systems are projected to display many desirable properties suitable for aerospace structural adhesive and composite matrix applications. The synthesis and characterization of a series of processable high temperature curing poly(arylene ether) oligomers incorporating terminally reactive phenylethynyl endgroups will be discussed. Characterization of the oligomers includes NMR, intrinsic viscosity, parallel plate rheological behavior, TGA, and DSC. Curing of these oligomers was conducted at or above 380{degrees}C, providing a large processing window. Thermal stability is very good and the melt viscosity of the oligomers in the processing temperature range is exceptionally low.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Choosing Sensor Configuration for a Flexible Structure Using Full Control Synthesis

    NASA Technical Reports Server (NTRS)

    Lind, Rick; Nalbantoglu, Volkan; Balas, Gary

    1997-01-01

    Optimal locations and types for feedback sensors which meet design constraints and control requirements are difficult to determine. This paper introduces an approach to choosing a sensor configuration based on Full Control synthesis. A globally optimal Full Control compensator is computed for each member of a set of sensor configurations which are feasible for the plant. The sensor configuration associated with the Full Control system achieving the best closed-loop performance is chosen for feedback measurements to an output feedback controller. A flexible structure is used as an example to demonstrate this procedure. Experimental results show sensor configurations chosen to optimize the Full Control performance are effective for output feedback controllers.

  14. Heteroatom-directed reverse Wacker oxidations. Synthesis of the reported structure of (-)-herbaric acid.

    PubMed

    Choi, Peter J; Sperry, Jonathan; Brimble, Margaret A

    2010-11-01

    A microwave-assisted chemoenzymatic resolution has been used to install the C3 stereocenter of the reported structure of the fungal metabolite herbaric acid in high enantiomeric excess. The synthesis and stereochemical assignment was accomplished using a completely regioselective anti-Markovnikov addition of water to vinylphthalide 3, achieved using a heteroatom-directed Wacker oxidation that proceeds with retention of stereochemistry. These results establish that so-called "reverse" Wacker oxidations are a viable alternative to hydroboration/oxidation procedures. PMID:20873747

  15. Synthesis, characterization, and crystal structure of 2-iodo-3,4,5-trimethoxybenzoic acid

    NASA Astrophysics Data System (ADS)

    Kolev, Iliyan N.; Petrova, Svetlana P.; Nikolova, Rositsa P.; Dimowa, Louiza T.; Shivachev, Boris L.

    2013-02-01

    This work describes the synthesis of 2-iodo-3,4,5-trimethoxybenzoic acid. The combination of iodine and silver trifluoroacetate (AgTFA) reagents was used successfully for the iodination of 3,4,5-trimetoxybenzoic acid. To improve the efficiency of the synthetic process a significant modification on the experimental design was also performed. The main structural features of the obtained aryl iodide were investigated by a single crystal X-ray diffraction analysis, FTIR, 1H and 13C NMR spectroscopy.

  16. Structural organization of films based on polyaniline/polysulfonic acid complexes depending on the synthesis method

    SciTech Connect

    Simagina, L. V. Gaynutdinov, R. V.; Stepina, N. D.; Sorokina, K. L.; Morozova, O. V.; Shumakovich, G. P.; Yaropolov, A. I.; Tolstikhina, A. L.

    2010-07-15

    The optical properties and morphology of complexes based on polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS), depending on their synthesis conditions, have been characterized by UV-visible spectroscopy and atomic force microscopy. The dependence of the electron absorption spectra of PANI/PAMPS complexes and the surface topography of their films on the initiation way of PANI formation (chemical and enzymatic) and the use of promoters of aniline polymerization has been investigated. The aniline polymerization kinetics with and without polymerization promoters has been studied. All PANI/PAMPS complexes are found to have a nanocomposite time-stable structure.

  17. Synthesis and characterization of nitroaromatic peptoids: fine tuning peptoid secondary structure through monomer position and functionality.

    PubMed

    Fowler, Sarah A; Luechapanichkul, Rinrada; Blackwell, Helen E

    2009-02-20

    N-substituted glycine oligomers, or peptoids, have emerged as an important class of foldamers for the study of biomolecular interactions and for potential use as therapeutic agents. However, the design of peptoids with well-defined conformations a priori remains a formidable challenge. New approaches are required to address this problem, and the systematic study of the role of individual monomer units in the global peptoid folding process represents one strategy. Here, we report our efforts toward this approach through the design, synthesis, and characterization of peptoids containing nitroaromatic monomer units. This work required the synthesis of a new chiral amine building block, (S)-1-(2-nitrophenyl)ethanamine (s2ne), which could be readily installed into peptoids using standard solid-phase peptoid synthesis techniques. We designed a series of peptoid nonamers that allowed us to probe the effects of this relatively electron-deficient and sterically encumbered alpha-chiral side chain on peptoid structure, namely, the peptoid threaded loop and helix. Circular dichroism spectroscopy of the peptoids revealed that the nitroaromatic monomer has a significant effect on peptoid secondary structure. Specifically, the threaded loop structure was disrupted in a nonamer containing alternating N-(S)-1-phenylethylglycine (Nspe) and Ns2ne monomers, and the major conformation was helical instead. Indeed, placement of a single Ns2ne at the N-terminal position of (Nspe)(9) resulted in a destabilized form of the threaded loop structure relative to the homononamer (Nspe)(9). Conversely, we observed that incorporation of N-(S)-1-(4-nitrophenyl)ethylglycine (Nsnp, a p-nitro monomer) at the N-terminal position stabilized the threaded loop structure relative to (Nspe)(9). Additional experiments revealed that nitroaromatic side chains can influence peptoid nonamer folding by modulating the strength of key intramolecular hydrogen bonds in the peptoid threaded loop structure. Steric

  18. A Rayleigh-Ritz approach to the synthesis of large gyroscopic structures. [spinning spacecraft and helicopter rotors

    NASA Technical Reports Server (NTRS)

    Meirovitch, L.; Hale, A. L.

    1977-01-01

    The equations of motion for large structures with rotating flexible components are derived by regarding the structure as an assemblage of substructures. Based on a stationarity principle for rotating structures, it is shown that each continuous or discrete substructure can be simulated by a suitable set of admissible functions or admissible vectors. This substructure synthesis approach provides a rational basis for truncating the number of degrees of freedom both of each substructure and of the assembled structure.

  19. Direct synthesis of a {Co₆(III)Fe₆(III)} dodecanuclear complex, revealing an unprecedented molecular structure type.

    PubMed

    Chygorin, Eduard N; Kokozay, Vladimir N; Omelchenko, Irina V; Shishkin, Oleg V; Titiš, Ján; Boča, Roman; Nesterov, Dmytro S

    2015-06-28

    A novel heterometallic Co6Fe6 Schiff base complex, possessing an unprecedented {M12(μ-X)22} branched structure (according to the search via the Cambridge Structural Database), has been prepared using the "direct synthesis" approach and characterized by single crystal X-ray diffraction and magnetometry. PMID:25992842

  20. Revision sphenoidethmoidectomy.

    PubMed

    Eichel, B S

    1985-03-01

    In 1981, a series of 236 intranasal ethmoidectomy (INE) procedures was reported with a complication rate of 1.8%. Special attention has subsequently been directed to the surgical failures; namely, recurrent nasal polyposis which accounted for approximately 17%. The reason for recurrence in most instances was felt due to failure to do a more thorough posterior ethmoidectomy and enter and clean out the sphenoid sinuses. Subsequently, in all revision cases where a more thorough sphenoidethmoidectomy (RSE) was performed, the overall long-term success rate raised to better than 90%. Attention to skeletonizing the middle turbinate by stripping mucosa and leaving a thin bony shell is an important technical factor. An attempt is made to leave some of this bony skeletonized medial wall of the middle turbinate as it represents the most crucial landmark in doing the surgery via the intranasal route. There still remains approximately 8% to 10% of this patient population with nasal polyposis and sinusitis of such severity that surgery has offered only a temporary measure of relief. In dealing with this group it may be necessary to see these patients postoperatively at four to six-week intervals, carefully suctioning the ethmoid labyrinth and occasionally doing minor office "touch-up" ethmoidectomy-polypectomy procedures to clean off redundant mucosa or early polyposis. This paper is written to offer a compromise to the two schools of intranasal ethmoidectomy surgery as to the necessity of removing the middle turbinate in its entirety. PMID:3974381

  1. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

    DOE PAGESBeta

    Caskey, Christopher M.; Holder, Aaron; Shulda, Sarah; Christensen, Steven T.; Diercks, David; Schwartz, Craig P.; Biagioni, David; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; et al

    2016-04-12

    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 filmmore » 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 Sn3N4 spinel compound, which provides a fresh scientific insight into the reasons for growth of polymorphs of the metastable material. In addition to reporting on the discovery of the simple binary SnN compound, this study 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.« less

  2. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures.

    PubMed

    Caskey, Christopher M; Holder, Aaron; Shulda, Sarah; Christensen, Steven T; Diercks, David; Schwartz, Craig P; Biagioni, David; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; Prendergast, David; Orvananos, Bernardo; Sun, Wenhao; Zhang, Xiuwen; Ceder, Gerbrand; Ginley, David S; Tumas, William; Perkins, John D; Stevanovic, Vladan; Pylypenko, Svitlana; Lany, Stephan; Richards, Ryan M; Zakutayev, Andriy

    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 Sn3N4 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. PMID:27083713

  3. Structure of the Basin and Ridge System West of New Caledonia (Southwest Pacific): A Synthesis

    NASA Astrophysics Data System (ADS)

    Lafoy, Y.; Brodien, I.; Vially, R.; Exon, N. F.

    2005-03-01

    Complementary to previous work mainly based on seismic interpretation, our compilation of geophysical data (multibeam bathymetry, gravity, magnetic and seismic) acquired within the framework of the ZoNéCo (ongoing since 1993) and FAUST (1998 2001) programs enables us to improve the knowledge of the New Caledonia Basin, Fairway Basin and Fairway Ridge, located within the Southwest Pacific region. The structural synthesis map obtained from geophysical data interpretation allows definition of the deep structure, nature and formation of the Fairway and New Caledonia Basins. Development of the Fairway Basin took place during the Late Cretaceous (95 65 Ma) by continental stretching. This perched basin forms the western margin of the New Caledonia Basin. A newly identified major SW NE boundary fault zone separates northern NW SE trending segments of the two basins from southern N S trending segments. This crustal-scale fault lineament, that we interpret to be related to Cretaceous-early Cainozoic Tasman Sea spreading, separates the NW SE thinned-continental and N S oceanic segments of the New Caledonia Basin. We can thus propose the following pattern for the formation of the study area. The end of continental stretching within the Fairway and West Caledonia Basins ( 65 62 Ma) is interpreted as contemporaneous with the onset of emplacement of oceanic crust within the New Caledonia Basin’s central segment. Spreading occurred during the Paleocene (62 56 Ma), and isolated the Gondwanaland block to the west from the Norfolk block to the east. Finally, our geophysical synthesis enables us to extend the structural Fairway Basin down to the structural Taranaki Basin, with the structural New Caledonia Basin lying east of the Fairway Basin and ending further north than previously thought, within the Reinga Basin northwest of New Zealand.

  4. Synthesis of a mixed-valent tin nitride and considerations of its possible crystal structures

    NASA Astrophysics Data System (ADS)

    Caskey, Christopher M.; Holder, Aaron; Shulda, Sarah; Christensen, Steven T.; Diercks, David; Schwartz, Craig P.; Biagioni, David; Nordlund, Dennis; Kukliansky, Alon; Natan, Amir; Prendergast, David; Orvananos, Bernardo; Sun, Wenhao; Zhang, Xiuwen; Ceder, Gerbrand; Ginley, David S.; Tumas, William; Perkins, John D.; Stevanovic, Vladan; Pylypenko, Svitlana; Lany, Stephan; Richards, Ryan M.; Zakutayev, Andriy

    2016-04-01

    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 Sn3N4 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.

  5. Controllable synthesis of branched ZnO/Si nanowire arrays with hierarchical structure

    PubMed Central

    2014-01-01

    A rational approach for creating branched ZnO/Si nanowire arrays with hierarchical structure was developed based on a combination of three simple and cost-effective synthesis pathways. The crucial procedure included growth of crystalline Si nanowire arrays as backbones by chemical etching of Si substrates, deposition of ZnO thin film as a seed layer by magnetron sputtering, and fabrication of ZnO nanowire arrays as branches by hydrothermal growth. The successful synthesis of ZnO/Si heterogeneous nanostructures was confirmed by morphologic, structural, and optical characterizations. The roles of key experimental parameters, such as the etchant solution, the substrate direction, and the seed layer on the hierarchical nanostructure formation, were systematically investigated. It was demonstrated that an etchant solution with an appropriate redox potential of the oxidant was crucial for a moderate etching speed to achieve a well-aligned Si nanowire array with solid and round surface. Meanwhile, the presence of gravity gradient was a key issue for the growth of branched ZnO nanowire arrays. The substrate should be placed vertically or facedown in contrast to the solution surface during the hydrothermal growth. Otherwise, only the condensation of the ZnO nanoparticles took place in a form of film on the substrate surface. The seed layer played another important role in the growth of ZnO nanowire arrays, as it provided nucleation sites and determined the growing direction and density of the nanowire arrays for reducing the thermodynamic barrier. The results of this study might provide insight on the synthesis of hierarchical three-dimensional nanostructure materials and offer an approach for the development of complex devices and advanced applications. PMID:25024688

  6. High Pressure Synthesis of Rhombohedral Delafossite Structured α-AgGaO2

    NASA Astrophysics Data System (ADS)

    Akhtar, Meysam; Menon, Madhu; Sunkara, Mahendra; Sumanasekera, Gamini; Durygin, Andriy; Jasinski, Jacek

    In this work, we demonstrate for the first time the high pressure synthesis of α-AgGaO2 via a solid state reaction of Ag2O and Ga2O3. Synthesis experiments were carried out at pressures and temperatures up to 10 GPa and 600 °C, respectively, using a resistively-heated diamond anvil cell. Electron diffraction confirmed the rhombohedral delafossite crystal structure of the synthesized AgGaO2 and its corresponding lattice parameters of a = 2.99 Å and c = 18.43 Å. The vibrational modes analysis was also conducted using a combination of ab initio density functional theory (DFT) and Raman spectroscopy. This analysis yielded good agreement between the calculated Raman-active modes and experimental Raman data. Finally, the application of the GGA + U formalism-based on DFT to calculate the electronic band structure of α-AgGaO2 provided a more realistic theoretical band gap value than those reported previously.

  7. A synthesis of predictions and correlation studies of the Lotung soil- structure interaction experiment

    SciTech Connect

    Hadjian, A.H. )

    1991-10-01

    Unnecessary conservatism is seismic design and licensing acceptance criteria is largely due to the lack of field data to validate the analytical methods used. EPRI and the Taiwan Power Company (TPC) constructed the Lotung large-scale seismic test (LSST) facility in Taiwan to collect forced-vibration and seismic response data for soil-structure interaction (SSI) methods evaluation. To date, more than 30 earthquakes have been recorded. EPRI, TPC, and NRC cosponsored a round-robin evaluation program to test the response prediction capability of the existing SSI models and analysis practices. The results were reported at a workshop in December 1987. Since then, EPRI has conducted additional post-earthquake studies to further evaluate, understand, and correlate SSI responses. The LSST results synthesis has yielded significant insights and findings with respect to the validity of SSI analysis methodologies for earthquake responses. The differences in response predictions among the commonly used SSI methodologies are due more to the modeling of the soil-structure systems than the calculation techniques. The more advanced methodologies, such as SASSI and CLASSI, generally yield better correlation results. The simple soil-spring approach and the two-dimensional FLUSH method should be used with care, considering their limitations. The synthesis of results also confirms the adequacy of the vertical wave-propagation assumption and the significance of strain-dependent soil property variations for the SSI analysis. 19 refs., 26 figs., 12 tabs.

  8. Synthesis of magnesium- and manganese-doped hydroxyapatite structures assisted by the simultaneous incorporation of strontium.

    PubMed

    Moreira, Mirna Pereira; de Almeida Soares, Gloria Dulce; Dentzer, Joseph; Anselme, Karine; de Sena, Lídia Ágata; Kuznetsov, Alexei; dos Santos, Euler Araujo

    2016-04-01

    Samples of crystalline hydroxyapatite (HA) with and without the addition of individual Mg(2+), Mn(2+) and Sr(2+) ions and samples with the addition of all three ions simultaneously were prepared using the precipitation method in an aqueous medium. Chemical, structural, spectroscopic and thermophysical analyses of the synthesized samples were conducted. The obtained results indicate that Sr(2+) ions were easily incorporated into the HA crystal structure, whereas it was difficult to incorporate Mg(2+) and Mn(2+) ions into the HA lattice when these ions were individually introduced into the samples. The synthesis of HA with Mg(2+) or Mn(2+) ions is characterized by the formation of HA with a low concentration of doping elements that is outweighed by the amount of these atoms present in less biocompatible phases that formed simultaneously. However, the incorporation of Sr(2+) along with Mg(2+) and Mn(2+) ions into the samples allowed for the synthesis of HA with considerably higher concentrations of Mg(2+) and Mn(2+) in the crystal lattice. PMID:26838904

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Controversies in Revision Rhinoplasty.

    PubMed

    Rosenberger, Eric S; Toriumi, Dean M

    2016-08-01

    Revision rhinoplasty is a complex operation with many variables that may influence the final esthetic and functional outcome of the procedure. Cartilage forms the structural framework of the lower two-thirds of nose and is essential for long-term support and maintenance of a patent nasal airway. The use of autologous cartilage grafting is the primary source of this material, limited by donor site quantity, quality, and harvest morbidity. Alloplastic materials, solid and injectable, are often used for augmentation purposes and may have devastating consequences. This article discusses past and current treatment concepts for various nasal deformities using available autologous grafting techniques. PMID:27400847

  11. Multiscale Theoretical and Computational Modeling of the Synthesis, Structure and Performance of Functional Carbon Materials

    NASA Astrophysics Data System (ADS)

    Mushrif, Samir Hemant

    2010-09-01

    Functional carbon-based/supported materials, including those doped with transition metal, are widely applied in hydrogen mediated catalysis and are currently being designed for hydrogen storage applications. This thesis focuses on acquiring a fundamental understanding and quantitative characterization of: (i) the chemistry of their synthesis procedure, (ii) their microstructure and chemical composition and (iii) their functionality, using multiscale modeling and simulation methodologies. Palladium and palladium(II) acetylacetonate are the transition metal and its precursor of interest, respectively. A first-principles modeling approach consisting of the planewave-pseudopotential implementation of the Kohn-Sham density functional theory, combined with the Car-Parrinello molecular dynamics, is implemented to model the palladium doping step in the synthesis of carbon-based/supported material and its interaction with hydrogen. The electronic structure is analyzed using the electron localization function and, when required, the hydrogen interaction dynamics are accelerated and the energetics are computed using the metadynamics technique. Palladium pseudopotentials are tested and validated for their use in a hydrocarbon environment by successfully computing the experimentally observed crystal structure of palladium(II) acetylacetonate. Long-standing hypotheses related to the palladium doping process are confirmed and new fundamental insights about its molecular chemistry are revealed. The dynamics, mechanism and energy landscape and barriers of hydrogen adsorption and migration on and desorption from the carbon-based/supported palladium clusters are reported for the first time. The effects of palladium doping and of the synthesis procedure on the pore structure of palladium-doped activated carbon fibers are quantified by applying novel statistical mechanical based methods to the experimental physisorption isotherms. The drawbacks of the conventional adsorption-based pore

  12. Heteroaryl chalcones: design, synthesis, X-ray crystal structures and biological evaluation.

    PubMed

    Kumar, C S Chidan; Loh, Wan-Sin; Ooi, Chin Wei; Quah, Ching Kheng; Fun, Hoong-Kun

    2013-01-01

    Chalcone derivatives have attracted increasing attention due to their numerous pharmacological activities. Changes in their structures have displayed high degree of diversity that has proven to result in a broad spectrum of biological activities. The present study highlights the synthesis of some halogen substituted chalcones 3(a-i) containing the 5-chlorothiophene moiety, their X-ray crystal structures and the evaluation of possible biological activities such as antibacterial, antifungal and reducing power abilities. The results indicate the tested compounds show a varied range of inhibition values against all the tested microbial strains. Compound 3c with a p-fluoro substituent on the phenyl ring exhibits elevated antimicrobial activity, whereas the compounds 3e and 3f displayed the least antimicrobial activities. The compounds 3d, 3e, 3f and 3i showed good ferric and cupric reducing abilities, and the compounds 3b and 3c showed the weakest reducing power in the series. PMID:24132195

  13. Synthesis and structure of high-valent organouranium complexes containing terminal monooxo functional groups

    SciTech Connect

    Arney, D.S.J.; Burns, C.J. )

    1993-10-20

    We describe the synthesis by oxidative atom-transfer chemistry and structure of organouranium(V) and -(VI)complexes containing terminal oxo functional groups of the general formula (C[sub 5]Me[sub 5])[sub 2]U-(EAr)(O) (E = O (3) and N (4); Ar=2,6-diisopropylphenyl). In effect, we have extended the synthetic utility of oxidative atom-transfer chemistry to the preparation of the first complexes of uranium(V) and-(VI)containing terminal nonooxo functional groups. The structural characterization of these compounds reveals uranium oxo bond lengths longer than those typical for the uranyl ion (UO[sub 2])[sup 2+], which may reflect a reduced relative bond order. 18 refs., 1 fig.

  14. Synthesis and structure design of new bio-based elastomers via Thiol-ene-Click Reactions.

    PubMed

    Khan, Shafiullah; Wang, Zhao; Wang, Runguo; Zhang, Liqun

    2016-10-01

    The additions of 2-mercaptoethanol to (S)-(-)-limonene via click reaction is described as an adaptable and efficient way to obtain alcohol functionalized renewable monomer for the synthesis of new cross-linkable bio-based elastomers. Thiol first reacted with the limonene endocyclic double bond and then reacted with the exocyclics double bond to form the difunctional monomer. The structure of the monomer was determined by using FTIR, (1)H NMR and mass spectrometry. Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetrys (DSC) characterization exposed that this monomer could be used to synthesize elastomers with excellent and adaptable thermal properties. The molecular weight of the synthesized elastomer could reach 186kDaa via melting polycondensation route and the structure-properties relationship was deliberated. Finally, these elastomers were mixed with dicumyl peroxide (DCP) to form cross-linked elastomers with certain mechanical property, and the gel contents of the elastomers were confirmed by using Soxhlet extraction method. PMID:27287154

  15. Synthesis, crystal structures and spectroscopic properties of cobalt(II) complexes with chelating sulfonylamidophosphate ligands

    NASA Astrophysics Data System (ADS)

    Znovjyak, Kateryna O.; Seredyuk, Maksym; Kusz, Joachim; Nowak, Maria; Moroz, Olesia V.; Sliva, Tetiana Yu; Amirkhanov, Vladimir M.

    2015-11-01

    Two new cobalt(II) complexes with general formula Co(L1)2Phen (1) and Co(L2)2Phen (2), in which HL1 = dimethyl phenylsulfonylphosphoramidate and HL2 = dimethyl tosylphosphoramidate, were prepared in one-step synthesis and characterized by IR, UV-VIS spectroscopy, TGA-DTA and elemental analysis. Moreover, the single crystal structures of 1 and 2 were determined by single crystal X-ray diffractometry. Complexes consist of mononuclear units comprising two L1-(or L2-) and phenanthroline ligands bidentatly linked to metal ion. The UV-VIS spectra of complexes in the solid state show broad asymmetric band at 530 nm attributed to the d-d transition of the metal ion. Comparing of these spectra with the absorption spectra in acetone, octahedral environment of the cobalt(II) ion in solution were considered. The structural similarity of 1 and 2 leads to a similar thermal decomposition profile.

  16. The structure and in situ synthesis investigation of isomorphic mononuclear molecular metal phenylphosphonates.

    PubMed

    Wilke, Manuel; Buzanich, Ana Guilherme; Reinholz, Uwe; Rademann, Klaus; Emmerling, Franziska

    2016-06-21

    We describe a fast and effective synthesis for molecular metal phosphonates. Isomorphic compounds [M(ii)(HO3PPh)2(H2O3PPh)2(H2O)2] (M = Mn (1), Co (2), Ni (3); Ph = C6H5) were obtained by grinding. The complexes are mononuclear compounds containing neutral and monodeprotonated phenylphosphonic acid and water as ligands. The crystal structures were determined using powder X-ray diffraction (PXRD) data and validated by extended X-ray absorption fine structure (EXAFS) data. Combined synchrotron XRD measurements and Raman spectroscopy were conducted for investigating the reactions in situ. Based on these data, the intermediates were characterized and the formation mechanism was derived. PMID:27188480

  17. Controllable synthesis of CuS-P(AM-co-MAA) composite microspheres with patterned surface structures.

    PubMed

    Zhang, Ying; Liu, Huijin; Zhao, Ya; Fang, Yu

    2008-09-15

    Copper sulfide-poly(acrylamide-co-methacrylic acid) (CuS-P(AM-co-MAA)) composite microspheres with patterned surface structures have been synthesized in a controllable manner by means of the polymer microgel template method. The formation of CuS particles can be regulated by controlling the decomposition of thioacetamide (TAA) in acidic solution. Compared with the microgel template, the surface morphologies of the composite microspheres are characterized by compact and creased textures. The surface morphology of the composite microspheres has been found to be mainly influenced by the amount of copper sulfide precipitated and hence by the rate of H(2)S gas generation. This study might provide a potential route for controlling the synthesis of various metal sulfide-polymer composites with patterned surface structures. PMID:18649893

  18. ACCESS 3. Approximation concepts code for efficient structural synthesis: User's guide

    NASA Technical Reports Server (NTRS)

    Fleury, C.; Schmit, L. A., Jr.

    1980-01-01

    A user's guide is presented for ACCESS-3, a research oriented program which combines dual methods and a collection of approximation concepts to achieve excellent efficiency in structural synthesis. The finite element method is used for structural analysis and dual algorithms of mathematical programming are applied in the design optimization procedure. This program retains all of the ACCESS-2 capabilities and the data preparation formats are fully compatible. Four distinct optimizer options were added: interior point penalty function method (NEWSUMT); second order primal projection method (PRIMAL2); second order Newton-type dual method (DUAL2); and first order gradient projection-type dual method (DUAL1). A pure discrete and mixed continuous-discrete design variable capability, and zero order approximation of the stress constraints are also included.

  19. Synthesis, biological evaluation and structural analysis of novel peripherally active morphiceptin analogs.

    PubMed

    Adamska, Anna; Kluczyk, Alicja; Cerlesi, Maria Camilla; Calo, Girolamo; Janecka, Anna; Borics, Attila

    2016-04-01

    Morphiceptin (Tyr-Pro-Phe-Pro-NH2), a tetrapeptide amide, is a selective ligand of the μ-opioid receptor (MOR). This study reports the synthesis and biological evaluation of a series of novel morphiceptin analogs modified in positions 2 or/and 4 by introduction of 4,4-difluoroproline (F2Pro) in l or d configuration. Depending on the fluorinated amino acid configuration and its position in the sequence, new analogs behaved as selective full MOR agonists showing high, moderate, or relatively low potency. The most potent analog, Tyr-F2Pro-Phe-d-F2Pro-NH2, was also able to activate the κ-opioid receptor (KOR), although with low potency. Docking studies and the comparison of results with the high resolution crystallographic structure of a MOR-agonist complex revealed possible structure-activity relationships of this compound family. PMID:26944625

  20. Synthesis and crystal structure determination of yttrium ultraphosphate YP{sub 5}O{sub 14}

    SciTech Connect

    Mbarek, A.; Graia, M. Chadeyron, G.; Zambon, D.; Bouaziz, J.; Fourati, M.

    2009-03-15

    The crystal structure of monoclinic YP{sub 5}O{sub 14} (space group C2/c, a=12.919(2) A, b=12.796(4) A, c=12.457(2) A, {beta}=91.30(1){sup o}, Z=8) has been refined from single-crystal X-ray diffraction data. Full-matrix least-squares refinement on F{sup 2} using 2249 independent reflections for 183 refinable parameters results in a final R value of 0.027 ({omega}R=0.069). The structure is isotypic with HoP{sub 5}O{sub 14}. This structure is built up from infinite layers of PO{sub 4} tetrahedra linked through isolated YO{sub 8} polyhedra. The three-dimensional cohesion of the framework results from Y-O-P bridges. This crystal structure refinement leads to the calculated X-ray diffraction powder pattern of this monoclinic polymorph, which has been the starting point of a thorough study of the solid-state synthesis of this ultraphosphate. This investigation further leads to a better outstanding of features observed during the synthesis of powdered samples. The thermal behavior of this ultraphosphate has been studied by DTA and TGA analyses. The infrared and Raman spectroscopic characterizations have been carried out on polycrystalline samples. The luminescence properties of the Eu{sup 3+} ion incorporated in the monoclinic C2/c polymorph of YP{sub 5}O{sub 14} as local structural probe show that in YP{sub 5}O{sub 14}: 5% Eu{sup 3+} sample, the Eu{sup 3+} ions are distributed over the two Y{sup 3+} crystallographic sites of C{sub 2} symmetry of this structure. - Graphical Abstract: The crystal structure of the monoclinic C2/c polymorph of YP{sub 5}O{sub 14} has been refined from single-crystal X-ray diffraction data. The luminescence properties of the Eu{sup 3+} ion incorporated in this matrix as local structural probe show that the Eu{sup 3+} ions are distributed over the two Y{sup 3+} crystallographic sites of C{sub 2} symmetry of this structure.

  1. sp(2)-sp(3) diboranes: astounding structural variability and mild sources of nucleophilic boron for organic synthesis.

    PubMed

    Dewhurst, Rian D; Neeve, Emily C; Braunschweig, Holger; Marder, Todd B

    2015-06-14

    Despite the widespread use of organoborane reagents in organic synthesis and catalysis, a major challenge still remains: very few boron-centered nucleophiles exist for the direct construction of B-C bonds. Perhaps the most promising emerging solution to this problem is the use of sp(2)-sp(3) diboranes, in which one boron atom of a conventional diborane(4) is quaternised by either a neutral or anionic nucleophile. These compounds, either isolated or generated in situ, serve as relatively mild and convenient sources of the boryl anion [BR2](-) for use in organic synthesis and have already proven their efficacy in metal-free as well as metal-catalysed borylation reactions. This Feature article documents the history of sp(2)-sp(3) diborane synthesis, their properties and surprising structural variability, and their burgeoning utility in organic synthesis. PMID:25912808

  2. Medicinal properties of mangiferin, structural features, derivative synthesis, pharmacokinetics and biological activities.

    PubMed

    Benard, Outhiriaradjou; Chi, Yuling

    2015-01-01

    The identification of biologically active and potentially therapeutically useful pharmacophores from natural products has been a long-term focus in the pharmaceutical industry. The recent emergence of a worldwide obesity and Type II diabetes epidemic has increased focus upon small molecules that can modulate energy metabolism, insulin sensitivity and fat biology. Interesting preliminary work done on mangiferin (MGF), the predominant constituent of extracts of the mango plant Mangifera indica L., portends potential for this pharmacophore as a novel parent compound for treating metabolic disorders. MGF is comprised of a C-glucosylated xanthone. Owing to the xanthone chemical structure, MGF has a redox active aromatic system and has antioxidant properties. MGF exerts varied and impressive metabolic effects in animals, improving metabolic disorders. For example we have discovered that MGF is a novel activator of the mammalian pyruvate dehydrogenase complex, leading to enhancement of carbohydrate utilization in oxidative metabolism, and leading to increased insulin sensitivity in animal models of obesity and insulin resistance. In addition, recent unbiased proteomics studies revealed that MGF upregulates proteins pivotal for mitochondrial bioenergetics and downregulates proteins controlling de novo lipogenesis in liver, helping to explain protective effects of MGF in prevention of liver steatosis. Several chemical studies have achieved synthesis of MGF, suggesting possible synthetic strategies to alter its chemical structure for development of structure-activity relationship (SAR) information. Ultimately, chemical derivatization studies could lead to the eventual development of novel therapeutics based upon the parent pharmacophore structure. Here we provide comprehensive review on chemical features of MGF, synthesis of its derivatives, its pharmacokinetics and biological activities. PMID:25827900

  3. Mechanistic Studies of Combustion and Structure Formation During Synthesis of Advanced Materials

    NASA Technical Reports Server (NTRS)

    Varma, A.; Lau, C.; Mukasyan, A. S.

    2001-01-01

    Combustion in a variety of heterogeneous systems, leading to the synthesis of advanced materials, is characterized by high temperatures (2000-3500 K) and heating rates (up to 10(exp 6) K/s) at and ahead of the reaction front. These high temperatures generate liquids and gases which are subject to gravity-driven flow. The removal of such gravitational effects is likely to provide increased control of the reaction front, with a consequent improvement in control of the microstructure of the synthesized products. Thus, microgravity (mu-g) experiments lead to major advances in the understanding of fundamental aspects of combustion and structure formation under the extreme conditions of the combustion synthesis (CS) wave. In addition, the specific features of microgravity environment allow one to produce unique materials, which cannot be obtained under terrestrial conditions. The current research is a logic continuation of our previous work on investigations of the fundamental phenomena of combustion and structure formation that occur at the high temperatures achieved in a CS wave. Our research is being conducted in three main directions: 1) Microstructural Transformations during Combustion Synthesis of Metal-Ceramic Composites. The studies are devoted to the investigation of particle growth during CS of intermetallic-ceramic composites, synthesized from nickel, aluminum, titanium, and boron metal reactants. To determine the mechanisms of particle growth, the investigation varies the relative amount of components in the initial mixture to yield combustion wave products with different ratios of solid and liquid phases, under 1g and mu-g conditions; 2) Mechanisms of Heat Transfer during Reactions in Heterogeneous Media. Specifically, new phenomena of gasless combustion wave propagation in heterogeneous media with porosity higher than that achievable in normal gravity conditions, are being studied. Two types of mixtures are investigated: clad powders, where contact between

  4. Investigating the Synthesis, Structure, and Catalytic Properties of Versatile Gold-Based Nanocatalvsts

    NASA Astrophysics Data System (ADS)

    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

  5. Synthesis of a 2'-Se-thymidine Phosphoramidite and Its Incorporation into Oligonucleotides for Crystal Structure Study

    SciTech Connect

    Sheng,J.; Jian, J.; Salon, J.; Huang, Z.

    2007-01-01

    To investigate nucleic acids with selenium derivatization for crystallography, we report the first synthesis of 2'-methylseleno-thymidine phosphoramidite and its incorporation into DNAs and RNAs by solid-phase synthesis with over 99% coupling yield. The d(GT{sub Se}GTACAC){sub 2} crystal structure was also determined at 1.40 {angstrom} resolution using Se phasing, revealing that this Se derivatization did not cause significant structure perturbation, consistent with our UV melting study. In addition, we observed that the Se modification largely facilitated the crystallization.

  6. Effects of particle size and synthesis temperature on the structural properties of the Ni nanoparticles: Insights about the formation of the fcc-Ni structure

    NASA Astrophysics Data System (ADS)

    de Souza, Edvaldo Alves; Winnischofer, Hebert; Haddad, Paula; Costa, Tulio C. R.; Zanchet, Daniela

    2009-01-01

    Nickel nanoparticles (NPs) have been studied due to their superparamagnetic features and potential applications in magnetic devices. Nickel NPs are also interesting because they can be synthesized in three different structures, amorphous, hcp-Ni and fcc-Ni. This work presents the structural studies of Nickel NPs. The results are based on the analysis of the oxidation state and the structural local order around Ni atoms of NPs synthesized at different particle sizes and synthesis temperatures.

  7. Human Milk Oligosaccharides (HMOS): Structure, Function, and Enzyme-Catalyzed Synthesis.

    PubMed

    Chen, Xi

    2015-01-01

    The important roles played by human milk oligosaccharides (HMOS), the third major component of human milk, in the health of breast-fed infants have been increasingly recognized, as the structures of more than 100 different HMOS have now been elucidated. Despite the recognition of the various functions of HMOS as prebiotics, antiadhesive antimicrobials, and immunomodulators, the roles and the applications of individual HMOS species are less clear. This is mainly due to the limited accessibility to large amounts of individual HMOS in their pure forms. Current advances in the development of enzymatic, chemoenzymatic, whole-cell, and living-cell systems allow for the production of a growing number of HMOS in increasing amounts. This effort will greatly facilitate the elucidation of the important roles of HMOS and allow exploration into the applications of HMOS both as individual compounds and as mixtures of defined structures with desired functions. The structures, functions, and enzyme-catalyzed synthesis of HMOS are briefly surveyed to provide a general picture about the current progress on these aspects. Future efforts should be devoted to elucidating the structures of more complex HMOS, synthesizing more complex HMOS including those with branched structures, and developing HMOS-based or HMOS-inspired prebiotics, additives, and therapeutics. PMID:26613816

  8. Synthesis of adsorbents with dendronic structures for protein hydrophobic interaction chromatography.

    PubMed

    Mata-Gómez, Marco A; Yaman, Sena; Valencia-Gallegos, Jesus A; Tari, Canan; Rito-Palomares, Marco; González-Valdez, José

    2016-04-22

    Here, we introduced a new technology based on the incorporation of dendrons-branched chemical structures-onto supports for synthesis of HIC adsorbents. In doing so we studied the synthesis and performance of these novel HIC dendron-based adsorbents. The adsorbents were synthesized in a facile two-step reaction. First, Sepharose 4FF (R) was chemically modified with polyester dendrons of different branching degrees i.e. third (G3) or fifth (G5) generations. Then, butyl-end valeric acid ligands were coupled to dendrons via ester bond formation. UV-vis spectrophotometry and FTIR analyses of the modified resins confirmed the presence of the dendrons and their ligands on them. Inclusion of dendrons allowed the increment of ligand density, 82.5 ± 11 and 175.6 ± 5.7 μmol ligand/mL resin for RG3 and RG5, respectively. Static adsorption capacity of modified resins was found to be ∼ 60 mg BSA/mL resin. Interestingly, dynamic binding capacity was higher at high flow rates, 62.5 ± 0.8 and 58.0 ± 0.5mg/mL for RG3 and RG5, respectively. RG3 was able to separate lipase, β-lactoglobulin and α-chymotrypsin selectively as well as fractionating of a whole proteome from yeast. This innovative technology will improve the existing HIC resin synthesis methods. It will also allow the reduction of the amount of adsorbent used in a chromatographic procedure and thus permit the use of smaller columns resulting in faster processes. Furthermore, this method could potentially be considered as a green technology since both, dendrons and ligands, are formed by ester bonds that are more biodegradable allowing the disposal of used resin waste in a more ecofriendly manner when compared to other exiting resins. PMID:27018188

  9. Hydrothermal synthesis, structural determination, and property characterization of transition metal sulfosalts and phosphates

    NASA Astrophysics Data System (ADS)

    Korzenski, Michael Burt

    Supercritical fluids are fascinating media for the synthesis of inorganic compounds. This is due in part to the tremendous versatility of these fluids, especially in providing access to unusual and kinetically stabilized solid phases. It is well understood that the ideal critical point of a solvent in a real solution has little meaning, and a gradual onset of critical properties with increasing temperature is normally observed, rather than a dramatic change in behavior at the magic critical point. In aqueous phases, the term hydrothermal is used for any reaction done in water above it sea level boiling point of 100°C while any reactions done above the critical point of 374°C are said to be supercritical. Hydrothermal synthesis has been used extensively over the past 150 years for the growth of large, high quality, single crystals of many known compounds, and has attained considerable significance over the last 50 years in industry for the growth of electronically important materials such as alpha-quartz and potassium titanyl phosphate (KTP). However, over the past two decades, many chemists have exploited the extraordinary solvating power of hydrothermal fluids for preparative inorganic synthesis, particularly for the preparation of zeolite-type materials. Much of this work was undertaken in the temperature range of 115 to 250°C, and thus work near the supercritical parameters of water (Tc = 374°C Pc = 221 bar) has been largely ignored due to the technological demands of aqueous systems at elevated temperatures and pressures. Therefore, we have decided to explore hydrothermal routes to both novel and known solid-state compounds which possess interesting physical properties. We have chosen to investigate a class of chalcopnictides and phosphates because of their structural diversity which promotes the preparation of chains, sheets and three-dimensional networks.

  10. Synthesis, structure, and spectroscopic characterization of three uranyl phosphates with unique structural units

    NASA Astrophysics Data System (ADS)

    Wylie, Ernest M.; Dawes, Colleen M.; Burns, Peter C.

    2012-12-01

    Single crystals of Zn4(OH)2[(UO2)(PO4)2(OH)2(H2O)] (UZnP), Cs[(UO2)(HPO4)NO3] (UCsP), and In3[(UO2)2(PO4)4OH(H2O)6].2H2O (UInP) were obtained from hydrothermal reactions and have been structurally and chemically characterized. UZnP crystallizes in space group Pbcn, a=8.8817(7), b=6.6109(5), c=19.569(1) Å; UCsP crystallizes in P-1, a=7.015(2), b=7.441(1), c=9.393(2) Å, α=72.974(2), β=74.261(2), γ=79.498(2); and UInP crystallizes in P-1, a=7.9856(5), b=9.159(1), c=9.2398(6) Å α=101.289(1), β=114.642(1), γ=99.203(2). The U6+ cations are present as (UO2)2+ uranyl ions coordinated by five O atoms to give pentagonal bipyramids. The structural unit in UZnP is a finite cluster containing a uranyl pentagonal bipyramid that shares corners with two phosphate tetrahedra. The structural unit in UCsP is composed of uranyl pentagonal bipyramids with one chelating nitrate group that are linked into chains by three bridging hydrogen phosphate tetrahedra. In UInP, the structural unit contains pairs of edge-sharing uranyl pentagonal bipyramids with two chelating phosphate tetrahedra that are linked into chains through two bridging phosphate tetrahedra. Indium octahedra link these uranyl phosphate chains into a 3-dimensional framework. All three compounds exhibit unique structural units that deviate from the typical layered structures observed in uranyl phosphate solid-state chemistry.

  11. 3-D structural analysis of the crucial intermediate of skeletal muscle myosin and its role in revised actomyosin cross-bridge cycle

    PubMed Central

    Katayama, Eisaku

    2014-01-01

    Skeletal myosin S1 consists of two functional segments, a catalytic-domain and a lever-arm. Since the crystal structure of ADP/Vi-bound S1 exhibits a strong intramolecular flexure between two segments, inter-conversion between bent and extended forms; i.e. “tilting of the lever-arm” has been accepted as the established molecular mechanism of skeletal muscle contraction. We utilized quick-freeze deep-etch replica electron microscopy to directly visualize the structure of in vitro actin-sliding myosin, and found the existence of a novel oppositely-bent configuration, instead of the expected ADP/Vi-bound form. We also noticed that SH1–SH2 cross-linked myosin gives an aberrant appearance similar to the above structure. Since SH1–SH2-cross-linked myosin is a well-studied analogue of the transient intermediate of the actomyosin cross-bridge cycle, we devised a new image-processing procedure to define the relative view-angles between the catalytic-domain and the lever-arm from those averaged images, and built a 3-D model of the new conformer. The lever-arm in that model was bent oppositely to the ADP/Vi-bound form, in accordance with observed actin-sliding cross-bridge structure. Introducing this conformer as the crucial intermediate that transiently appears during sliding, we propose a revised scheme of the cross-bridge cycle. In the scenario, the novel conformer keeps actin-binding in two different modes until it forms a primed configuration. The final extension of the lever-arm back to the original rigor-state constitutes the “power-stroke”. Various images observed during sliding could be easily interpreted by the new conformer. Even the enigmatic behavior of the cross-bridges reported as “loose chemo-mechanical coupling” might be adequately explained under some assumptions. PMID:27493503

  12. Synthesis and structural characterization of raffinosyl-oligofructosides upon transfructosylation by Lactobacillus gasseri DSM 20604 inulosucrase.

    PubMed

    Díez-Municio, Marina; Herrero, Miguel; de Las Rivas, Blanca; Muñoz, Rosario; Jimeno, M Luisa; Moreno, F Javier

    2016-07-01

    A new process based on enzymatic synthesis of a series of raffinose-derived oligosaccharides or raffinosyl-oligofructosides (RFOS) with degree of polymerization (DP) from 4 to 8 was developed in the presence of raffinose. This process involves a transfructosylation reaction catalyzed by an inulosucrase from Lactobacillus gasseri DSM 20604 (IS). The main synthesized RFOS were structurally characterized by nuclear magnetic resonance (NMR). According to the elucidated structures, RFOS consist of β-2,1-linked fructose unit(s) to raffinose: α-D-galactopyranosyl-(1 → 6)-α-D-glucopyranosyl-(1↔2)-β-D-fructofuranosyl-((1 ← 2)-β-D-fructofuranoside)n (where n refers to the number of transferred fructose moieties). The maximum yield of RFOS was 33.4 % (in weight respect to the initial amount of raffinose) and was obtained at the time interval of 8-24 h of transfructosylation reaction initiated with 50 % (w/v) of raffinose. Results revealed the high acceptor and donor affinity of IS towards raffinose, being fairly comparable with that of sucrose for the production of fructooligosaccharides (FOS), including when both carbohydrates coexisted (sucrose/raffinose mixture, 250 g L(-1) each). The production of RFOS was also attempted in the presence of sucrose/melibiose mixtures; in this case, the predominant acceptor-product formed was raffinose followed by a minor production of a series of oligosaccharides with varying DP. The easiness of RFOS synthesis and the structural similarities with both raffinose and fructan series of oligosaccharides warrant the further study of the potential bioactive properties of these unexplored oligosaccharides. PMID:26940051

  13. Antimicrobial profile of some novel keto esters: Synthesis, crystal structures and structure-activity relationship studies.

    PubMed

    Khan, Imtiaz; Saeed, Aamer; Arshad, Mohammad Ifzan; White, Jonathan Michael

    2016-01-01

    Rapid increase in bacterial resistance has become a major public concern by escalating alongside a lack of development of new anti-infective drugs. Novel remedies in the battle against multidrug-resistant bacterial strains are urgently needed. So, in this context, the present work is towards the investigation of antimicrobial efficacy of some novel keto ester derivatives, which are prepared by the condensation of substituted benzoic acids with various substituted phenacyl bromides in dimethylformamide at room temperature using triethylamine as a catalyst. The structural build-up of the target compounds was accomplished by spectroscopic techniques including FTIR, (1)H and (13)C NMR spectroscopy and mass spectrometry. The purity of the synthesized compounds was ascertained by elemental analysis. The molecular structures of compounds (4b) and (4l) were established by X-ray crystallographic analysis. The prepared analogues were evaluated for their antimicrobial activity against Gram-positive (Staphylococcus aureus, Micrococcus leuteus) and Gram-negative (Pseudomonas picketti, Salmonella setuball) bacteria and two fungal pathogenic strains (Aspergillus niger, Aspergillus flavus), respectively. Among the screened derivatives, several compounds were found to possess significant activity but (4b) and (4l) turned out to be lead molecules with remarkable antimicrobial efficacy. The structure-activity relationship analysis of this study also revealed that structural modifications on the basic skeleton affected the antimicrobial activity of the synthesized compounds. PMID:26826838

  14. KBiMS{sub 4} (M=Si, Ge): Synthesis, structure, and electronic structure

    SciTech Connect

    Mei Dajiang; Lin Zheshuai; Bai Lei; Yao Jiyong; Fu Peizhen; Wu Yicheng

    2010-07-15

    Two new bismuth sulfides KBiSiS{sub 4} and KBiGeS{sub 4} have been synthesized by means of the reactive flux method. They adopt the RbBiSiS{sub 4} structure type and crystallize in space group P2{sub 1}/c of the monoclinic system. The structure consists of {sup {infinity}}{sub 2}[BiMS{sub 4}{sup -}] (M=Si, Ge) layers separated by bicapped trigonal-prismatically coordinated K atoms. The M atom is tetrahedrally coordinated to four S atoms and the Bi atom is coordinated to a distorted monocapped trigonal prism of seven S atoms. The optical band gap of 2.25(2) eV for KBiSiS{sub 4} was deduced from the diffuse reflectance spectrum. From a band structure calculation, the optical absorption for KBiSiS{sub 4} originates from the {sup {infinity}}{sub 2}[BiSiS{sub 4}{sup -}] layer. The Si 3p orbitals, Bi 6p orbitals, and S 3p orbitals are highly hybridized near the Fermi level. The orbitals of K have no contributions on both the upper of valence band and the bottom of conduction band. - Graphical abstract: Two new bismuth sulfides KBiSiS{sub 4} and KBiGeS{sub 4} have been synthesized and characterized. The figure is the view down [0 1 0] of the crystal structure of KBiSiS{sub 4}.

  15. Topotactic synthesis of strontium cobalt oxyhydride thin film with perovskite structure

    SciTech Connect

    Katayama, Tsukasa; Chikamatsu, Akira Kamisaka, Hideyuki; Yokoyama, Yuichi; Hirata, Yasuyuki; Wadati, Hiroki; Fukumura, Tomoteru; Hasegawa, Tetsuya

    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.

  16. Synthesis and structural studies of lanthanide substituted bismuth-titanium pyrochlores

    SciTech Connect

    Ting, Jimmy; Kennedy, Brendan J.; Withers, Ray L.; Avdeev, Maxim

    2009-04-15

    The identity of the pyrochlore phase seen during the synthesis of ferroelectric Bi{sub 4-x}Ln{sub x}Ti{sub 3}O{sub 12} Aurivillius oxides is shown to be Bi{sub 2/3}Ln{sub 4/3}Ti{sub 2}O{sub 7}. This pyrochlore is only stable for Ln{sup 3+}=Sm{sup 3+} or smaller. For larger lanthanides the layered Aurivillius oxide is favoured. The presence of six-fold disorder, associated with the Bi 6s{sup 2} lone pair electrons, is believed to stabilise the unexpected stoichiometry of this oxide. Precise structures, obtained by Rietveld refinement from synchrotron X-ray diffraction data, of three examples Ln{sup 3+}=Eu, Ho and Yb are presented. - Graphical Abstract: The pyrochlore phase formed during the synthesis of the ferroelectric oxides Bi{sub 4-x}Ln{sub x}Ti{sub 3}O{sub 12} is shown to be Bi{sub 2/3}Ln{sub 4/3}Ti{sub 2}O{sub 7}. This is found to be stable only for Ln{sup 3+}cations smaller than Sm{sup 3+}. Displacive disorder of the Bi and Ln cations is observed.

  17. Design, synthesis, and characterization of novel nanowire structures for photovoltaics and intracellular probes.

    PubMed

    Tian, Bozhi; Lieber, Charles M

    2011-01-01

    Semiconductor nanowires (NWs) represent a unique system for exploring phenomena at the nanoscale and are expected to play a critical role in future electronic, optoelectronic, and miniaturized biomedical devices. Modulation of the composition and geometry of nanostructures during growth could encode information or function, and realize novel applications beyond the conventional lithographical limits. This review focuses on the fundamental science aspects of the bottom-up paradigm, which are synthesis and physical property characterization of semiconductor NWs and NW heterostructures, as well as proof-of-concept device concept demonstrations, including solar energy conversion and intracellular probes. A new NW materials synthesis is discussed and, in particular, a new "nanotectonic" approach is introduced that provides iterative control over the NW nucleation and growth for constructing 2D kinked NW superstructures. The use of radial and axial p-type/intrinsic/n-type (p-i-n) silicon NW (Si-NW) building blocks for solar cells and nanoscale power source applications is then discussed. The critical benefits of such structures and recent results are described and critically analyzed, together with some of the diverse challenges and opportunities in the near future. Finally, results are presented on several new directions, which have recently been exploited in interfacing biological systems with NW devices. PMID:22707797

  18. Structural synthesis of a class of 2R2T hybrid mechanisms

    NASA Astrophysics Data System (ADS)

    Tian, Chunxu; Fang, Yuefa; Guo, Sheng

    2016-01-01

    Conventional overconstrained parallel manipulators have been widely studied both in industry and academia, however the structural synthesis of hybrid mechanisms with additional constraints is seldom studied, especially for the four degrees of freedom(DOF) hybrid mechanisms. In order to develop a manipulator with additional constraints, a class of important spatial mechanisms with coupling chains(CCs) whose motion type is two rotations and two translations(2R2T) is presented. Based on screw theory, the combination of different types of limbs which are used to construct parallel mechanisms and coupling chains is proposed. The basic types of the general parallel mechanisms and geometric conditions of the kinematic chains are given using constraint synthesis method. Moreover, the 2R2T motion pattern hybrid mechanisms which are derived by adding coupling chains between different serial kinematic chains(SKCs) of the corresponding parallel mechanisms are presented. According to the constraint analysis of the mechanisms, the movement relationship of the moving platform and the kinematic chains is derived by disassembling the coupling chains. At last, fourteen novel hybrid mechanisms with two or three serial kinematic chains are presented. The proposed novel hybrid mechanisms and construction method enrich the family of the spatial mechanisms and provide an instruction to design more complex hybrid mechanisms.

  19. Synthesis, molecular structure, and properties of a neutral Schiff base phenolic complex of magnesium

    SciTech Connect

    Polyakov, V.R.; Sharma, V.; Crankshaw, C.L.; Piwnica-Worms, D.

    1998-09-07

    Multidrug resistance (MDR) in cancer mediated by the MDR1 P-glycoprotein (Pgp), a 140--180 kDa plasma membrane protein, renders chemotherapeutic treatment ineffective by pumping a variety of natural product cytotoxic agents and xenobiotic compounds out of cancer cells. Pgp has been a major target for synthesis and development of both therapeutic antagonists that block its transport function and diagnostic radiopharmaceuticals that are transported by the protein for use in functional imaging of Pgp transport activity in tumors in vivo. Most, but not all, compounds that interact with Pgp are hydrophobic and cationic at physiological pH. To further understand the Pgp targeting properties, the authors sought to directly evaluate the effect of charge of the complex on Pgp interactions. This could be done by comparing the cytotoxicity profile of a neutral complex to that of an identical, but positively charged, complex in both drug-sensitive and multidrug-resistant cancer cells. Thus, a neutral analogue of the Ga(III) and Fe(III) complexes was desired. Herein the authors describe the synthesis and structure of a novel neutral Schiff base Mg complex and evaluate its cytotoxic potency in human drug-sensitive KB-3-1 and multi-drug-resistant KB-8-5 tumor cells.

  20. Design, synthesis, and characterization of novel nanowire structures for photovoltaics and intracellular probes*

    PubMed Central

    Lieber, Charles M.

    2012-01-01

    Semiconductor nanowires (NWs) represent a unique system for exploring phenomena at the nanoscale and are expected to play a critical role in future electronic, optoelectronic, and miniaturized biomedical devices. Modulation of the composition and geometry of nanostructures during growth could encode information or function, and realize novel applications beyond the conventional lithographical limits. This review focuses on the fundamental science aspects of the bottom-up paradigm, which are synthesis and physical property characterization of semiconductor NWs and NW heterostructures, as well as proof-of-concept device concept demonstrations, including solar energy conversion and intracellular probes. A new NW materials synthesis is discussed and, in particular, a new “nanotectonic” approach is introduced that provides iterative control over the NW nucleation and growth for constructing 2D kinked NW superstructures. The use of radial and axial p-type/intrinsic/n-type (p-i-n) silicon NW (Si-NW) building blocks for solar cells and nanoscale power source applications is then discussed. The critical benefits of such structures and recent results are described and critically analyzed, together with some of the diverse challenges and opportunities in the near future. Finally, results are presented on several new directions, which have recently been exploited in interfacing biological systems with NW devices. PMID:22707797

  1. Synthesis, reaction and structure of a series of chromium(III) complexes containing oxalate ligand

    NASA Astrophysics Data System (ADS)

    Chen, Xu-Fang; Liu, Li; Ma, Jian-Gong; Yi, Long; Cheng, Peng; Liao, Dai-Zheng; Yan, Shi-Ping; Jiang, Zong-Hui

    2005-08-01

    A series of chromium(III) complexes [Cr(bipy)(HC2O4)2]Cl·3H2O (1), [Cr(phen)(HC2O4)2]Cl·3H2O (2), [Cr(phen)2(C2O4)]ClO4 (3), [Cr2(bipy)4(C2O4)](SO4)·(bipy)0.5·H2O (4) and [Mn(phen)2(H2O)2]2[Cr(phen)(C2O4)2]3ClO4·14H2O (5) were synthesized (bipy=4,4‧-bipyridine, phen=1,10-phenanthroline), while the crystal structures of 1 and 3-5 have been determined by X-ray analysis. 1 and 3 are mononuclear complexes, 4 contains binuclear chromium(III) ions and 5 is a 3D supromolecule formed by complicated hydrogen bonding. 1-3 are potential molecular bricks of chromium(III) building blocks for synthesis heterometallic complexes. When we use these molecular bricks as ligands to react with other metal salts, unexpected complexes 4 and 5 are isolated in water solution. The synthesis conditions and reaction results are also discussed.

  2. Electrospray synthesis and properties of hierarchically structured PLGA TIPS microspheres for use as controlled release technologies.

    PubMed

    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. PMID:26803601

  3. New and Improved? A Comparison of the Original and Revised Versions of the Structured Interview of Reported Symptoms

    ERIC Educational Resources Information Center

    Green, Debbie; Rosenfeld, Barry; Belfi, Brian

    2013-01-01

    The current study evaluated the accuracy of the Structured Interview of Reported Symptoms, Second Edition (SIRS-2) in a criterion-group study using a sample of forensic psychiatric patients and a community simulation sample, comparing it to the original SIRS and to results published in the SIRS-2 manual. The SIRS-2 yielded an impressive…

  4. WWC Quick Review of the Article "Culture and the Interaction of Student Ethnicity with Reward Structure in Group Learning" Revised

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2010

    2010-01-01

    This paper presents an updated WWC (What Works Clearinghouse) Review of the Article "Culture and the Interaction of Student Ethnicity with Reward Structure in Group Learning". The study examined the effects of different reward systems used in group learning situations on the math skills of African-American and White students. The research…

  5. Effects of Written Feedback and Revision on Learners' Accuracy in Using Two English Grammatical Structures

    ERIC Educational Resources Information Center

    Shintani, Natsuko; Ellis, Rod; Suzuki, Wataru

    2014-01-01

    The study compared the effects of two types of form-focused written feedback--direct corrective feedback (DCF) and metalinguistic explanation (ME) given to the whole class--on Japanese university students' accuracy of use of two grammatical structures: indefinite article and the hypothetical conditional. Both types of feedback were given with…

  6. Facile Synthesis of Yolk-Shell-Structured Triple-Hybridized Periodic Mesoporous Organosilica Nanoparticles for Biomedicine.

    PubMed

    Teng, Zhaogang; Zhang, Junjie; Li, Wei; Zheng, Yuanyi; Su, Xiaodan; Tang, Yuxia; Dang, Meng; Tian, Ying; Yuwen, Lihui; Weng, Lixing; Lu, Guangming; Wang, Lianhui

    2016-07-01

    The synthesis of mesoporous nanoparticles with controllable structure and organic groups is important for their applications. In this work, yolk-shell-structured periodic mesoporous organosilica (PMO) nanoparticles simultaneously incorporated with ethane-, thioether-, and benzene-bridged moieties are successfully synthesized. The preparation of the triple-hybridized PMOs is via a cetyltrimethylammonium bromide-directed sol-gel process using mixed bridged silsesquioxanes as precursors and a following hydrothermal treatment. The yolk-shell-structured triple-hybridized PMO nanoparticles have large surface area (320 m(2) g(-1) ), ordered mesochannels (2.5 nm), large pore volume (0.59 cm(3) g(-1) ), uniform and controllable diameter (88-380 nm), core size (22-110 nm), and shell thickness (13-45 nm). In vitro cytotoxicity, hemolysis assay, and histological studies demonstrate that the yolk-shell-structured triple-hybridized PMO nanoparticles have excellent biocompatibility. Moreover, the organic groups in the triple-hybridized PMOs endow them with an ability for covalent connection of near-infrared fluorescence dyes, a high hydrophobic drug loading capacity, and a glutathione-responsive drug release property, which make them promising candidates for applications in bioimaging and drug delivery. PMID:27183872

  7. Synthesis, structural characterization and quantum chemical studies of silicon-containing benzoic acid derivatives

    NASA Astrophysics Data System (ADS)

    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.

  8. Modular Synthesis of Heparan Sulfate Oligosaccharides for Structure-Activity Relationship Studies

    PubMed Central

    Arungundram, Sailaja; Al-Mafraji, Kanar; Asong, Jinkeng; Leach, Franklin E.; Amster, I. Jonathan; Venot, Andre; Turnbull, Jeremy E.; Boons, Geert-Jan

    2010-01-01

    Although hundreds of heparan sulfate binding proteins have been identified, and implicated in a myriad of physiological and pathological processes, very little information is known about ligand requirements for binding and mediating biological activities by these proteins. This difficulty results from a lack of technology for establishing structure-activity-relationships, which in turn is due to the structural complexity of natural heparan sulfate (HS) and difficulties of preparing well-defined HS-oligosaccharides. To address this deficiency, we have developed a modular approach for the parallel combinatorial synthesis of HS oligosaccharides that utilizes a relatively small number of selectively protected disaccharide building blocks, which can easily be converted into glycosyl donors and acceptors. The utility of the modular building blocks has been demonstrated by the preparation of a library of twelve oligosaccharides, which has been employed to probe structural features of HS for inhibiting the protease, BACE-1. The complex variations in activity with structural changes support the view that important functional information is embedded in HS sequences. Furthermore, the most active derivative provides an attractive lead compound for the preparation of more potent compounds, which may find use as a therapeutic agent for Alzheimer's disease. PMID:19904943

  9. Structural Studies of Silver Nanoparticles Obtained Through Single-Step Green Synthesis

    NASA Astrophysics Data System (ADS)

    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.

  10. A structural-stochastic model for the analysis and synthesis of cloud images

    NASA Technical Reports Server (NTRS)

    Garand, L.; Weinman, J. A.

    1986-01-01

    A structural-stochastic image model is developed for the analysis and synthesis of cloud images. The ability of the model to characterize the visual appearance of cloud fields observed by satellite with a limited number of parameters is demonstrated. The model merges structural and stochastic information, the stochastic model acting as a local statistical operator applied to the output of the structural model. The structural or large-scale organization of the scene is retrieved from the two-dimensional Fourier representation of the digital image. The pattern generated by the major Fourier components provides a first guess of the scene. The stochastic aspect is described by a Markov model of texture that assumes a binomial probability distribution for the local grey-level variability. This Markov model provides four parameters that represent the clustering strength in the horizontal, vertical and diagonal directions. These parameters are estimated by a standard maximum-likelihood technique. The image can be reproduced with a fair degree of verisimilitude from these parameters. The data compression factor is of the order of one hundred to several hundreds.

  11. Synthesis, structure, and electronic structure of CsAgGa{sub 2}Se{sub 4}

    SciTech Connect

    Mei Dajiang; Yin Wenlong; Feng Kai; Bai Lei; Lin Zheshuai; Yao Jiyong; Wu Yicheng

    2012-02-15

    The new metal chalcogenide CsAgGa{sub 2}Se{sub 4} has been synthesized by means of the reactive flux method. It crystallizes in the space group P2{sub 1}/c of the monoclinic system with cell dimensions of a=11.225(2) A, b=7.9443(16) A, c=21.303(4) A, {beta}=103.10(3), V=1850.3(6), and Z=8. The structure contains two-dimensional {sub {infinity}}{sup 2}[AgGa{sub 2}Se{sub 4}]{sup -} layers separated by Cs{sup +} cations. The {sub {infinity}}{sup 2}[AgGa{sub 2}Se{sub 4}]{sup -} superlayer possesses a novel chain-sublayer-chain structure: a {sub {infinity}}{sup 2}[Ag{sub 2}GaSe{sub 6}]{sup 7-} sublayer, composed of {sub {infinity}}{sup 1}[AgGaSe{sub 4}]{sup 4-} chains that are further connected by Ag{sup +} ions, is sandwiched by parallel {sub {infinity}}{sup 1}[Ga{sub 3}Se{sub 8}]{sup 7-} chains to generate the {sub {infinity}}{sup 2}[AgGa{sub 2}Se{sub 4}]{sup -} superlayer. From a band structure calculation, the orbitals of all atoms have contributions to the bottoms of conduction bands, but the band gap is mainly determined by the 4s, 4p orbitals of Ga and Se. - Graphical Abstract: CsAgGa{sub 2}Se{sub 4} contains two-dimensional {sub {infinity}}{sup 2}[AgGa{sub 2}Se{sub 4}]{sup -} layers with a novel chain-sublayer-chain structure. Highlights: Black-Right-Pointing-Pointer New chalcogenide CsAgGa{sub 2}Se{sub 4} has been synthesized. Black-Right-Pointing-Pointer It possesses a new structure type with {sub {infinity}}{sup 2}[AgGa{sub 2}Se{sub 4}]{sup -} layers separated by Cs{sup +} cations. Black-Right-Pointing-Pointer {sub {infinity}}{sup 2}[AgGa{sub 2}Se{sub 4}]{sup -} consists of a {sub {infinity}}{sup 2}[Ag{sub 2}GaSe{sub 6}]{sup 7-} sublayer sandwiched by {sub {infinity}}{sup 1}[Ga{sub 3}Se{sub 8}]{sup 7-} chains. Black-Right-Pointing-Pointer Band gap of CsAgGa{sub 2}Se{sub 4} is mainly determined by the 4s, 4p orbitals of Ga and Se.

  12. The Mount Evans batholith in the Colorado Front Range: revision of its age and reinterpretation of its structure

    USGS Publications Warehouse

    Aleinikoff, J.N.; Reed, J.C., Jr.; Dewitt, E.

    1993-01-01

    The Mount Evans batholith is composed of a main phase of massive to conspicuously foliated monzogranite and granodiorite and undeformed aplite and pegmatite. The Mount Evans batholith was previously considered to be part of the 1.7 Ga Routt Plutonic Suite. New U-Pb zircon ages on four samples (granodiorite, monzogranite, and granite), however, indicate that the batholith was emplaced at 1442 ?? 2 Ma and belongs to the Berthoud Plutonic Suite. Most of the batholith has igneous textures and structures, except in the vicinity of the Idaho Springs-Ralston shear zone where those features are tectonically recrystallized and foliated. The Mount Evans batholith is anomalous in composition and structure compared to most other 1.4 Ga plutons of the southwestern US. The differences probably reflect different sources of partial melting; the specific tectonic setting where rocks of such disparate origin are temporally and spatially juxtaposed is not understood. -from Authors

  13. Copyright Revision in Canada

    ERIC Educational Resources Information Center

    Keyes, A. A.

    1977-01-01

    The article discusses the history of copyright laws, the directions which copyright revision can take, and the rationale behind revision. Regulations for protecting various media such as sound recordings, performances, and cable television are discussed. (JAB)

  14. Trends in computerized structural analysis and synthesis; Proceedings of the Symposium, Washington, D.C., October 30-November 1, 1978

    NASA Technical Reports Server (NTRS)

    Noor, A. K. (Editor); Mccomb, H. G., Jr.

    1978-01-01

    The subjects considered are related to future directions of structural applications and potential of new computing systems, advances and trends in data management and engineering software development, advances in applied mathematics and symbolic computing, computer-aided instruction and interactive computer graphics, nonlinear analysis, dynamic analysis and transient response, structural synthesis, structural analysis and design systems, advanced structural applications, supercomputers, numerical analysis, and trends in software systems. Attention is given to the reliability and optimality of the finite element method, computerized symbolic manipulation in structural mechanics, a standard computer graphics subroutine package, and a drag method as a finite element mesh generation scheme.

  15. Structure and synthesis of polyisoprenoids used in N-glycosylation across the three domains of life

    PubMed Central

    Jones, Meredith B.; Rosenberg, Julian N.; Betenbaugh, Michael J.; Krag, Sharon S.

    2009-01-01

    N-linked protein glycosylation was originally thought to be specific to eukaryotes, but evidence of this post-translational modification has now been discovered across all domains of life: Eucarya, Bacteria, and Archaea. In all cases, the glycans are first assembled in a step-wise manner on a polyisoprenoid carrier lipid. At some stage of lipid-linked oligosaccharide synthesis, the glycan is flipped across a membrane. Subsequently, the completed glycan is transferred to specific asparagine residues on the protein of interest. Interestingly, though the N-glycosylation pathway seems to be conserved, the biosynthetic pathways of the polyisoprenoid carriers, the specific structures of the carriers, and the glycan residues added to the carriers vary widely. In this review we will elucidate how organisms in each basic domain of life synthesize the polyisoprenoids that they utilize for N-linked glycosylation and briefly discuss the subsequent modifications of the lipid to generate a lipid-linked oligosaccharide. PMID:19348869

  16. Further developments in the controlled growth approach for optimal structural synthesis

    NASA Technical Reports Server (NTRS)

    Hajela, P.

    1982-01-01

    It is pointed out that the use of nonlinear programming methods in conjunction with finite element and other discrete analysis techniques have provided a powerful tool in the domain of optimal structural synthesis. The present investigation is concerned with new strategies which comprise an extension to the controlled growth method considered by Hajela and Sobieski-Sobieszczanski (1981). This method proposed an approach wherein the standard nonlinear programming (NLP) methodology of working with a very large number of design variables was replaced by a sequence of smaller optimization cycles, each involving a single 'dominant' variable. The current investigation outlines some new features. Attention is given to a modified cumulative constraint representation which is defined in both the feasible and infeasible domain of the design space. Other new features are related to the evaluation of the 'effectiveness measure' on which the choice of the dominant variable and the linking strategy is based.

  17. Design, synthesis, and characterization of new phosphazene related materials, and study the structure property correlations

    NASA Astrophysics Data System (ADS)

    Tian, Zhicheng

    The work described in this thesis is divided into three major parts, and all of which involve the exploration of the chemistry of polyphosphazenes. The first part (chapters 2 and 3) of my research is synthesis and study polyphoshazenes for biomedical applications, including polymer drug conjugates and injectable hydrogels for drug or biomolecule delivery. The second part (chapters 4 and 5) focuses on the synthesis of several organic/inorganic hybrid polymeric structures, such as diblock, star, brush and palm tree copolymers using living cationic polymerization and atom transfer radical polymerization techniques. The last part (chapters 6 and 7) is about exploratory synthesis of new polymeric structures with fluorinated side groups or cycloaliphatic side groups, and the study of new structure property relationships. Chapter 1 is an outline of the fundamental concepts for polymeric materials, as such the history, important definitions, and some introductory material for to polymer chemistry and physics. The chemistry and applications of phopshazenes is also briefly described. Chapter 2 is a description of the design, synthesis, and characterization of development of a new class of polymer drug conjugate materials based on biodegradable polyphosphazenes and antibiotics. Poly(dichlorophosphazene), synthesized by a thermal ring opening polymerization, was reacted with up to 25 mol% of ciprofloxacin or norfloxacin and three different amino acid esters (glycine, alanine, or phenylalanine) as cosubstituents via macromolecular substitutions. Nano/microfibers of several selected polymers were prepared by an electrospinning technique. Chapter 3 is concerned with the development of a class of injectable and biodegradable hydrogels based on water-soluble poly(organophosphazenes) containing oligo(ethylene glycol) methyl ethers and glycine ethyl esters. The hydrogels can be obtained by mixing alpha-cyclodextrin aqueous solution and poly(organophosphazenes) aqueous solution in

  18. Synthesis of azetidin-3-ones. Structure of n-tosyl-2-ethylazetidin-3-one

    SciTech Connect

    Aliev, Z.G.; Atovmyan, L.O.; Sipyagin, A.M.; Kartsev, V.G.; Dobrokhotova, O.V.

    1987-10-01

    A one-step synthesis of azetidin-3-ones by intramolecular cyclization of 1-diazo-3-arenesulfamoylalkan-2-ones was developed. The yield of cyclic product increases to 70% in the presence of an alkyl or benzyl substituent in the hydrocarbon chain of the diazoketone. The structure of N-tosyl-2-ethylazetidin-3-one was studied by x-ray diffraction analysis and it was shown that the four-membered ring has 15/sup 0/ inflection. IR spectra were recorded with a Specord 75 IR instrument in mineral oil. PMR spectra were recorded with Bruker WH-360 (360 MHz) and Jeol HL-60 (60 MHz) instruments in CDCl/sub 3/ solution, with TMS internal standard. UV spectra were obtained with a Specord UV-VIS instrument in methanol.

  19. Isolation, Structure Elucidation and Total Synthesis of Lajollamide A from the Marine Fungus Asteromyces cruciatus

    PubMed Central

    Gulder, Tobias A. M.; Hong, Hanna; Correa, Jhonny; Egereva, Ekaterina; Wiese, Jutta; Imhoff, Johannes F.; Gross, Harald

    2012-01-01

    The marine-derived filamentous fungus Asteromyces cruciatus 763, obtained off the coast of La Jolla, San Diego, USA, yielded the new pentapeptide lajollamide A (1), along with the known compounds regiolone (2), hyalodendrin (3), gliovictin (4), 1N-norgliovicitin (5), and bis-N-norgliovictin (6). The planar structure of lajollamide A (1) was determined by Nuclear Magnetic Resonance (NMR) spectroscopy in combination with mass spectrometry. The absolute configuration of lajollamide A (1) was unambiguously solved by total synthesis which provided three additional diastereomers of 1 and also revealed that an unexpected acid-mediated partial racemization (2:1) of the L-leucine and L-N-Me-leucine residues occurred during the chemical degradation process. The biological activities of the isolated metabolites, in particular their antimicrobial properties, were investigated in a series of assay systems. PMID:23342379

  20. In silico structure-based design and synthesis of novel anti-RSV compounds.

    PubMed

    Cancellieri, Michela; Bassetto, Marcella; Widjaja, Ivy; van Kuppeveld, Frank; de Haan, Cornelis A M; Brancale, Andrea

    2015-10-01

    Respiratory syncytial virus (RSV) is the major cause for respiratory tract disease in infants and young children. Currently, no licensed vaccine or a selective antiviral drug against RSV infections are available. Here, we describe a structure-based drug design approach that led to the synthesis of a novel series of zinc-ejecting compounds active against RSV replication. 30 compounds, sharing a common dithiocarbamate moiety, were designed and prepared to target the zinc finger motif of the M2-1 protein. A library of ∼ 12,000 small fragments was docked to explore the area surrounding the zinc ion. Among these, seven ligands were selected and used for the preparation of the new derivatives. The results reported here may help the development of a lead compound for the treatment of RSV infections. PMID:26259810

  1. Synthesis and structural characterization of three unique Helicobacter pylori α-cholesteryl phosphatidyl glucosides.

    PubMed

    Nguyen, Huy Q; Davis, Ryan A; Gervay-Hague, Jacquelyn

    2014-12-01

    Steryl glycosides produced by bacteria play important biological roles in the evasion and modulation of host immunity. Step-economical syntheses of three cholesteryl-6-O-phosphatidyl-α-D-glucopyranosides (αCPG) unique to Helicobacter pylori have been achieved. The approach relies upon regioselective deprotection of per-O-trimethylsilyl-α-D-cholesterylglucoside at C6 followed by phosphoramidite coupling. Global TMS ether deprotection in the presence of oxygen and subsequent deprotection of the cyano ethyl phosphoester afforded the target compounds in 16-21 % overall yield starting from D-glucose. The structures of these natural products were determined using a combination of 2D NMR methods and mass spectrometry. These robust synthesis and characterization protocols provide analogues to facilitate glycolipidomic profiling and biological studies. PMID:25195783

  2. [Synthesis of acyclic 1,3-polyols and its application to structural study of natural products].

    PubMed

    Mori, Y

    1993-06-01

    A 1,3-polyhydroxylated chain is often found on the backbone of biologically important natural products. The acyclic nature and the regular array of many hydroxyl groups are main obstacles to structural and synthetic studies, and many efforts have been made to this end. We have developed a new general synthetic method of 1,3-polyols based on the coupling of a chiral dithiane, a four-carbon unit, and an epoxide, followed by 1,3-diastereoselective reduction. We applied the method to the synthesis of polymethoxy-1-alkenes isolated from blue-green algae to establish their absolute stereochemistry. Moreover, a general procedure for assigning the absolute stereochemistry of acyclic 1,3-polyols by the difference circular dichroism (CD) method have been established. Combination of the method and a reiterative degradation enables one to determine the absolute configuration of 1,3-polyols, even if the relative stereochemistry is unknown. PMID:8355146

  3. Functionalized O6-Corona[6]arenes: Synthesis, Structure, and Fullerene Complexation Property.

    PubMed

    Ren, Wen-Sheng; Zhao, Liang; Wang, Mei-Xiang

    2016-07-01

    The synthesis, structure, and fullerene complexation property of novel and functionalized On-corona[n]arenes were reported. Based on the fragment coupling strategy, ester-containing On-corona[n]arenes (n = 6, 8) were obtained readily starting from 1,4-hydroquinone and diethyl 2,5-difluoroterephthalate. Reduction of esters with LiAlH4 produced almost quantitatively hydroxymethylated On-corona[n]arenes, which underwent etherification with MeI to afford methoxymethyl-substituted On-corona[n]arenes (n = 6, 8) in good yields. The macrocycles adopt unique corona-type conformation with a large cylindroid cavity. They are strong macrocyclic host molecules to form 1:1 complexes with fullerenes C60 and C70 in toluene with an associate constant up to (1.59 ± 0.04) × 10(5) M(-1). PMID:27324274

  4. Synthesis, growth, structure determination and optical properties of chalcone derivative single crystal

    SciTech Connect

    Karthi, S. Girija, E. K.

    2014-04-24

    Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - Π - acceptor - Π - donor (D-Π-A-Π-D) type conjugated molecule with appreciable hyperpolarizability of potential interest in NLO applications. The addition of vinyl and electron donor groups in the chalcone molecule may enhance the second harmonic generation (SHG) efficiency. Here we report the synthesis, crystal growth and characterization of a chalcone derivative 1-(4-methylphenyl)-5-(4-methoxyphenyl)-penta-2,4-dien-1-one (MPMPP). The MPMPP crystal was grown by slow evaporation solution growth technique from acetone. The grown crystal structure was studied by single crystal X-ray diffraction. The SHG efficiency of the grown crystal was determined by Kurtz and Perry method.

  5. Isolation, Structural Elucidation, and Synthesis of Lepteridine From Ma̅nuka (Leptospermum scoparium) Honey.

    PubMed

    Daniels, Benjamin J; Prijic, Gordana; Meidinger, Sarah; Loomes, Kerry M; Stephens, Jonathan M; Schlothauer, Ralf C; Furkert, Daniel P; Brimble, Margaret A

    2016-06-22

    Ma̅nuka honey, made from the nectar of Leptospermum scoparium, has garnered scientific and economical interest due to its nonperoxide antibacterial activity. Biomarkers for genuine ma̅nuka honey are increasingly in demand due to the presence of counterfeit ma̅nuka honey. This work reports the identification of a compound previously unreported in ma̅nuka honey by HPLC, and determination of the structure of the as 3,6,7-trimethyllumazine using NMR, MS, IR, and UV/vis spectroscopy. This assignment was confirmed by total synthesis. The natural product, renamed lepteridine, was only observed in ma̅nuka honeys and could potentially serve as a biomarker for genuine ma̅nuka honey. PMID:27210444

  6. SrF{sub 2} hierarchical flowerlike structures: Solvothermal synthesis, formation mechanism, and optical properties

    SciTech Connect

    Quan Zewei; Yang Dongmei; Li Chunxia; Yang Piaoping; Cheng, Ziyong; Yang Jun; Kong Deyan; Lin Jun

    2009-05-06

    We present a solvothermal route to the synthesis of SrF{sub 2} hierarchical flowerlike structures based on thermal decomposition of single source precursor (SSP) of strontium trifluoroacetate in benzylamine solvent. These flowerlike superstructures are actually composed of numerous aggregated nanoplates, and the growth process involves the initial formation of spherical nanoparticles and subsequent transformation into nanoplates, which aggregated together to form microdisks and finally flowerlike superstructures. The results demonstrate the important role of benzylamine in the formation of well-defined SrF{sub 2} superstructures, not only providing size and shape control to form nanoplates but also contributing to the self-assembly behavior of nanoplates to build into flower-like superstructures. Additionally, the photoluminescence properties of the obtained SrF{sub 2} superstructures are studied.

  7. Synthesis, growth, structure determination and optical properties of chalcone derivative single crystal

    NASA Astrophysics Data System (ADS)

    Karthi, S.; Girija, E. K.

    2014-04-01

    Acquiring large nonlinear optical (NLO) efficient organic material is essential for the development of optoelectronics and photonic devices. Chalcone is the donor - Π - acceptor - Π - donor (D-Π-A-Π-D) type conjugated molecule with appreciable hyperpolarizability of potential interest in NLO applications. The addition of vinyl and electron donor groups in the chalcone molecule may enhance the second harmonic generation (SHG) efficiency. Here we report the synthesis, crystal growth and characterization of a chalcone derivative 1-(4-methylphenyl)-5-(4-methoxyphenyl)-penta-2,4-dien-1-one (MPMPP). The MPMPP crystal was grown by slow evaporation solution growth technique from acetone. The grown crystal structure was studied by single crystal X-ray diffraction. The SHG efficiency of the grown crystal was determined by Kurtz and Perry method.

  8. Synthesis and crystal structures of gold nanowires with Gemini surfactants as directing agents.

    PubMed

    Xu, Feng; Hou, Hao; Gao, Zhinong

    2014-12-15

    The preparation of crystalline gold nanowires (NWs) by using gemini surfactants as directing agents through a three-step seed-mediated method is reported. Unlike the nanorods with relatively low aspect ratios (typically below 20) obtained by using cetyltrimethylammonium bromide as a directing agent, the NWs obtained in this investigation can reach up to 4.4 μm, and the largest aspect ratio is calculated to be 210. For this, each of seven different gemini surfactants are utilized as directing agents, and the length and/or aspect ratio of the NWs can be tuned by varying the hydrocarbon chain lengths of the gemini surfactants. Both single and twinned crystalline structures are elucidated by selected-area electron diffraction and high-resolution transmission electron microscopy studies. The use of gemini surfactants not only advances the synthesis of gold nanostructures, but improves the understanding of the growth mechanism for seed-mediated growth. PMID:25257473

  9. Fused 1,2,3-Dithiazoles: Convenient Synthesis, Structural Characterization, and Electrochemical Properties.

    PubMed

    Konstantinova, Lidia S; Baranovsky, Ilia V; Irtegova, Irina G; Bagryanskaya, Irina Y; Shundrin, Leonid A; Zibarev, Andrey V; Rakitin, Oleg A

    2016-01-01

    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. PMID:27164072

  10. Synthesis of onion-peel nanodendritic structures with sequential functional phosphorus diversity.

    PubMed

    Katir, Nadia; El Brahmi, Nabil; El Kadib, Abdelkrim; Mignani, Serge; Caminade, Anne-Marie; Bousmina, Mosto; Majoral, Jean Pierre

    2015-04-20

    The preparation of novel families of phosphorus-based macromolecular architectures called "onion peel" phosphorus nanodendritic systems is reported. This construct is based on the versatility of methods of synthesis using several building blocks and on the capability of these systems to undergo regioselective reactions within the cascade structure. Sustainable metal-free routes such as the Staudinger reaction or Schiff-base condensation, involving only water and nitrogen as byproducts, allow access to several dendritic macromolecules bearing up to seven different phosphorus units in their backbone, each of them featuring specific reactivity. The presence of the highly aurophilic P=N-P=S fragment enables selective ligation of Au(I) within the dendritic framework. PMID:25754619

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Synthesis of 2-monoacylglycerols and structured triacylglycerols rich in polyunsaturated fatty acids by enzyme catalyzed reactions.

    PubMed

    Rodríguez, Alicia; Esteban, Luis; Martín, Lorena; Jiménez, María José; Hita, Estrella; Castillo, Beatriz; González, Pedro A; Robles, Alfonso

    2012-08-10

    This paper studies the synthesis of structured triacylglycerols (STAGs) by a four-step process: (i) obtaining 2-monoacylglycerols (2-MAGs) by alcoholysis of cod liver oil with several alcohols, catalyzed by lipases Novozym 435, from Candida antartica and DF, from Rhizopus oryzae, (ii) purification of 2-MAGs, (iii) formation of STAGs by esterification of 2-MAGs with caprylic acid catalyzed by lipase DF, from R. oryzae, and (iv) purification of these STAGs. For the alcoholysis of cod liver oil, absolute ethanol, ethanol 96% (v/v) and 1-butanol were compared; the conditions with ethanol 96% were then optimized and 2-MAG yields of around 54-57% were attained using Novozym 435. In these 2-MAGs, DHA accounted for 24-31% of total fatty acids. In the operational conditions this lipase maintained a stable level of activity over at least 11 uses. These results were compared with those obtained with lipase DF, which deactivated after only three uses. The alcoholysis of cod liver oil and ethanol 96% catalyzed by Novozym 435 was scaled up by multiplying the reactant amounts 100-fold and maintaining the intensity of treatment constant (IOT=3g lipase h/g oil). In these conditions, the 2-MAG yield attained was about 67%; these 2-MAGs contained 36.6% DHA. The synthesized 2-MAGs were separated and purified from the alcoholysis reaction products by solvent extraction using solvents of low toxicity (ethanol and hexane); 2-MAG recovery yield and purity of the target product were approximately 96.4% and 83.9%, respectively. These 2-MAGs were transformed to STAGs using the optimal conditions obtained in a previous work. After synthesis and purification, 93% pure STAGs were obtained, containing 38% DHA at sn-2 position and 60% caprylic acid (CA) at sn-1,3 positions (of total fatty acids at these positions), i.e. the major TAG is the STAG with the structure CA-DHA-CA. PMID:22759534

  13. Deuterated detergents for structural and functional studies of membrane proteins: Properties, chemical synthesis and applications.

    PubMed

    Hiruma-Shimizu, Kazumi; Shimizu, Hiroki; Thompson, Gary S; Kalverda, Arnout P; Patching, Simon G

    2015-01-01

    Detergents are amphiphilic compounds that have crucial roles in the extraction, purification and stabilization of integral membrane proteins and in experimental studies of their structure and function. One technique that is highly dependent on detergents for solubilization of membrane proteins is solution-state NMR spectroscopy, where detergent micelles often serve as the best membrane mimetic for achieving particle sizes that tumble fast enough to produce high-resolution and high-sensitivity spectra, although not necessarily the best mimetic for a biomembrane. For achieving the best quality NMR spectra, detergents with partial or complete deuteration can be used, which eliminate interfering proton signals coming from the detergent itself and also eliminate potential proton relaxation pathways and strong dipole-dipole interactions that contribute line broadening effects. Deuterated detergents have also been used to solubilize membrane proteins for other experimental techniques including small angle neutron scattering and single-crystal neutron diffraction and for studying membrane proteins immobilized on gold electrodes. This is a review of the properties, chemical synthesis and applications of detergents that are currently commercially available and/or that have been synthesized with partial or complete deuteration. Specifically, the detergents are sodium dodecyl sulphate (SDS), lauryldimethylamine-oxide (LDAO), n-octyl-β-D-glucoside (β-OG), n-dodecyl-β-D-maltoside (DDM) and fos-cholines including dodecylphosphocholine (DPC). The review also considers effects of deuteration, detergent screening and guidelines for detergent selection. Although deuterated detergents are relatively expensive and not always commercially available due to challenges associated with their chemical synthesis, they will continue to play important roles in structural and functional studies of membrane proteins, especially using solution-state NMR. PMID:26906947

  14. Structural and qualitative evaluation of microscopy and directly observed treatment centers under revised national tuberculosis control programme in Nanded city of Maharashtra.

    PubMed

    Bhagat, Vijay Manohar; Gattani, Prakash Laxminarayan

    2011-01-01

    Structural and qualitative evaluation of Revised National Tuberculosis Control Programme (RNTCP) is important to determine actual status of the programme in the field settings and to uncover the concealed gaps. The present cross-sectional study assessed the infrastructural facilities and quality of services provided through microscopy and directly observed treatment (DOT) centers at Nanded city of Maharashtra. The investigator made on spot observation on the activities at microscopy and DOT centers and assessed the infrastructural facilities using an observational checklist. Expert microbiologist cross checked the microscopy report done by the laboratory technicians. It revealed that retrieval mechanism was not functioning in more than half of the DOT centers. Only 5 DOT providers were trained in RNTCP. Stock of sputum containers, methylene blue, and carbol fuchsin was found to be inadequate at some microscopy centers. Half of the laboratory technicians reported high false positive result in spite of being trained. Improvement of infrastructural and logistic support along with the refreshing training for the workers are needed for effective implementation of RNTCP. PMID:21727682

  15. Unveiling the first indole-fused thiazepine: structure, synthesis and biosynthesis of cyclonasturlexin, a remarkable cruciferous phytoalexin.

    PubMed

    Pedras, M S C; To, Q H

    2016-04-30

    As a mechanism of defense against pathogens and other types of stress, watercress plants produce a variety of elicited chemical defenses generally known as phytoalexins. Herein the chemical structure, synthesis, biosynthesis and antifungal activity of cyclonasturlexin, the most intriguing indolyl phytoalexin isolated to date, are reported. PMID:27052411

  16. Total synthesis and structural confirmation of the marine natural product Dysinosin A: a novel inhibitor of thrombin and Factor VIIa.

    PubMed

    Hanessian, Stephen; Margarita, Roberto; Hall, Adrian; Johnstone, Shawn; Tremblay, Martin; Parlanti, Luca

    2002-11-13

    The structure and absolute configuration of the marine antithrombotic product dysinosin A was confirmed by total synthesis. The strategy involved disconnections to three subunits, of which two were synthesized from the readily available l-glutamic acid, d-leucine, and d-mannitol. The Grubbs olefin metathesis carbocyclization reaction was utilized to prepare two intermediates. PMID:12418860

  17. Synthesis and structure-activity relationships of novel furazan-3,4-diamide analogs as potent anti-cancer agents.

    PubMed

    Li, Wen-Shan; More, Shivaji V; Wang, Chie-Hong; Jen, Ya Ching; Yao, Ching-Fa; Wang, Tein-Fu; Hung, Chin-Chun; Jao, Shu-Chuan

    2010-02-01

    This study describes the synthesis and structure-activity relationships of a series of furazan-3,4-diamide analogs. 1,2,5-Oxadiazole ring and electron-withdrawing substituent on the phenyl ring are proposed to be the important elements which contribute to a significant extent maximal potency of anti-proliferation effect. PMID:20022505

  18. Dopamine as a Carbon Source: The Controlled Synthesis of Hollow Carbon Spheres and Yolk-Structured Carbon Nanocomposites

    SciTech Connect

    Dai, Sheng; Liu, Rui; Mahurin, Shannon Mark; Li, Chen; Unocic, Raymond R; Idrobo Tapia, Juan C; Gao, Hongjun; Pennycook, Stephen J

    2011-01-01

    A facile and versatile synthesis using dopamine as a carbon source gives hollow carbon spheres and yolk-shell Au{at}Carbon nanocomposites. The uniform nature of dopamine coatings and their high carbon yield endow the products with high structural integrity. The Au{at}C nanocomposites are catalytically active.

  19. Thermal annealing synthesis of titanium-dioxide nanowire-nanoparticle hetero-structures

    SciTech Connect

    Yu, Choongho; Park, Jongbok

    2010-10-15

    Crystalline TiO{sub 2} nanowire-nanoparticle hetero-structures were successfully synthesized from titanium foils by using a simple thermal annealing method with the aid of CuCl{sub 2} at the atmospheric pressure. Nanowires were grown from Ti foils by simply annealing Ti foils at 850 {sup o}C. Then, TiCl{sub 4} was delivered to TiO{sub 2} nanowires so as to precipitate TiO{sub 2} nanoparticles on nanowire surfaces. At 750 {sup o}C reaction temperature, nanoparticles of tens of nanometers in diameter were well distributed on pre-grown nanowire forests. Nanoparticles were likely to be precipitated by TiCl{sub 4} decomposition or oxidation and that require high temperatures above {approx}650 {sup o}C. Electron microscopy, X-ray diffraction, and UV-vis spectroscopy analyses show they have the rutile polycrystalline structure with a slightly enlarged bandgap compared to that of bulk TiO{sub 2}. The influence of key synthesis parameters including reaction temperature, reaction time, and quantity of supplied materials on the incorporating nanoparticles was also systematically studied. The optimum reaction condition in the present paper was identified to be 750 {sup o}C annealing with repetitive 20 min reactions. A higher reaction temperature yielded larger diameter particles, and higher loading of Ti produced dense particles without changing the particle size. Finally, this method could be utilized for synthesizing other metal oxide nanowires-nanoparticle hetero-structures. - Graphical abstract: Schematic of proposed reaction mechanisms for synthesizing the hetero-structures: (a) TiO{sub 2} nanowires were grown as base structures for capturing TiCl{sub 4} gas. (b) TiCl{sub 4} gas was oxidized, precipitating crystalline TiO{sub 2} nanoparticles. (c) Repeated particle-incorporation process created tree-like hetero-structures.

  20. Structural considerations on acridine/acridinium derivatives: Synthesis, crystal structure, Hirshfeld surface analysis and computational studies

    NASA Astrophysics Data System (ADS)

    Wera, Michał; Storoniak, Piotr; Serdiuk, Illia E.; Zadykowicz, Beata

    2016-02-01

    This article describes a detailed study of the molecular packing and intermolecular interactions in crystals of four derivatives of acridine, i.e. 9-methyl-, 9-ethyl, 9-bromomethyl- and 9-piperidineacridine (1, 2, 3 and 4, respectively) and three 10-methylacridinium salts containing the trifluoromethanesulphonate anion and 9-vinyl-, 9-bromomethyl, and 9-phenyl-10-methylacridinium cations (5, 6 and 7, respectively). The crystal structures of all of the compounds are stabilized by long-range electrostatic interactions, as well as by a network of short-range C-HṡṡṡO (in hydrates and salts 3 and 5-7, respectively), C-Hṡṡṡπ, π-π, C-Fṡṡṡπ and S-Oṡṡṡπ (in salts 5-7) interactions. Hirshfeld surface analysis shows that various intermolecular contacts play an important role in the crystal packing, graphically exhibiting the differences in spatial arrangements of the acridine/acridinium derivatives under scrutiny here. Additionally, computational methods have been used to compare the intermolecular interactions in the crystal structures of the investigated compounds. Computations have confirmed the great contribution of dispersive interactions for crystal lattice stability in the case of 9-substituted acridine and electrostatic interactions for the crystal lattice stability in the case of 9-substituted 10-methylacridinium trifluoromethanesulphonates. The value of crystal lattice energy and the electrostatic contribution in the crystal lattice energy of monohydrated acridine derivatives have confirmed that these compounds have behave as acridinium derivatives.

  1. Synthesis, structure, physical properties, and electronic structure of KGaSe2

    NASA Astrophysics Data System (ADS)

    Feng, Kai; Mei, Dajiang; Bai, Lei; Lin, Zheshuai; Yao, Jiyong; Wu, Yicheng

    2012-08-01

    The ternary gallium selenide KGaSe2 has been synthesized by solid-state reactions and good quality crystal has been obtained. KGaSe2 crystallizes in the monoclinic space group C2/c with cell dimensions of a = 10.878(2) Å, b = 10.872(2) Å, c = 15.380(3) Å, and β = 100.18(3)°. In the structure, adamantane like [Ga4Se10]8- units are connected by common corners forming two-dimensional [GaSe2]- layers which are separated by K+ cations. KGaSe2 exhibits congruent-melting behavior at around 965 °C. It is transparent in the range of 0.47-20.0 μm and has a band gap of 2.60(2) eV. From a band structure calculation, KGaSe2 is a direct-gap semiconductor. The band gap is mainly determined by the [GaSe2]- layer.

  2. Synthesis, structure, and properties of a novel family of layered transition nitride compounds

    NASA Astrophysics Data System (ADS)

    Weil, Kenneth Scott

    The chemical properties of nitrogen present a number of difficulties in the synthesis of nitride compounds. Most of these compounds have small free energies of formation due in part to the strong triple bond of N2. Thus the standard solid state approach of synthesizing compounds from a mixture of their constituents at high reaction temperatures is generally precluded. A general alternative to solid state synthesis is the molecularly mixed precursor route. The primary advantage of this approach is the control of composition. This concept has been demonstrated in this study through the use of a nonaqueous, complexed co-precipitation technique to synthesize a number of new ternary nitride compounds, including the a new nitride phase, CrWN2, and four series of substitutional variations of this compound, as wen as twelve additional new compounds crystallizing in the layered dinitride, eta-nitride, and pi-nitride crystal structures. The layered nitride, CrWN2, is the focal point of this thesis. The details of its crystal and defect structure, synthesis, properties, and substitutional chemistry have been examined and discussed within. Briefly, this compound crystallizes in a trigonal structure and consists of alternating layers of chromium in octahedral coordination with nitrogen and tungsten in trigonal prismatic coordination with nitrogen. Microstructurally, the nitride frequently displays twinning and the formation of coherent rock salt structured intergrowth defects. As mentioned above, the layered nitride evolves from a co-precipitated precursor; a fine mixture of [Cr(NH3)6]Cl 2 and WOCl2·3NH3. Upon heat treatment in an ammonia atmosphere, the two transition metal complexes separately decompose into their non-complexed chloride state, i.e. CrCl2 and WOCl 2, before reacting with each other and the ambient ammonia atmosphere between 420°C and 570°C to form a glassy oxynitrochloride phase, CrWO 1.01N0.36Cl2.45. Around 600°C, this compound undergoes ammonolysis

  3. Synthesis of Pt Nanoparticles in Water-in-Oil Microemulsion: Effect of HCl on Their Surface Structure.

    PubMed

    Martínez-Rodríguez, Roberto A; Vidal-Iglesias, Francisco J; Solla-Gullón, José; Cabrera, Carlos R; Feliu, Juan M

    2014-01-29

    The synthesis of shape-controlled nanoparticles is currently a hot research topic. However, from an applied point of view, there is still a lack of easy, cheap, and scalable methodologies. In this communication we report, for the first time, the synthesis of cubic platinum nanoparticles with a very high yield using a water-in-oil microemulsion method, which unlike others, such as the colloidal method, fulfills the previous requirements. This shape/surface structure control is determined by the concentration of HCl in the water phase of the microemulsion. The results reported here show that the optimal HCl percentage in the water phase is about 25% to obtain the highest amount of cubic nanostructures. Ammonia electro-oxidation is used as a surface structure sensitive reaction to illustrate HCl surface structure effects. Moreover, in situ electrochemical characterization has been performed to study the nanoparticle surface structure. PMID:24422507

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

    SciTech Connect

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

    2004-10-01

    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.

  5. Synthesis, crystal structure, and valence states of Mn-substituted La2RuO5

    NASA Astrophysics Data System (ADS)

    Riegg, S.; Garcia-Garcia, F. J.; Reller, A.; Loidl, A.; Ebbinghaus, S. G.

    2014-07-01

    Polycrystalline samples of layered perovskite-related La2Ru1-yMnyO5 (0≤y≤0.25) were prepared by a soft-chemistry synthesis based on the thermal decomposition of a citrate precursor. The crystal structures of the compounds were determined by Rietveld analysis of x-ray diffraction patterns recorded at different temperatures. Additional neutron diffraction patterns for La2Ru0.75Mn0.25O5 were recorded between 1.5 K and 300 K. A structural phase transition from a monoclinic room-temperature to a triclinic low-temperature phase was observed for y ≤0.20, while for y =0.25 a phase separation at low temperatures was identified. The structural phase-transition temperatures decrease with increasing Mn concentration. Selected area electron diffraction of La2Ru0.75Mn0.25O5 documented the absence of cationic ordering of Ru and Mn. The Mn and Ru oxidation states were determined using x-ray absorption spectroscopy and showed a stable +4 valence for both elements in all samples investigated, at room temperature as well as at 110 K.

  6. Synthesis and structure of high-quality films of copper polyphthalocyanine – 2D conductive polymer

    SciTech Connect

    Sedlovets, Darya M.; Shuvalov, Maksim V.; Vishnevskiy, Yury V.; Volkov, Vladimir T.; Khodos, Igor I.; Trofimov, Oleg V.; Korepanov, Vitaly I.

    2013-10-15

    Graphical abstract: - Highlights: • 2D polymers show a big promise for science and technology. • We develop a new procedure for the direct synthesis of copper polyphthalocyanine. • We obtain reliable experimental data on the CuPPC structure. • With the support of quantum chemical calculations we describe electronic structure of CuPPC. - Abstract: Copper polyphthalocyanine (CuPPC), a 2D conjugated polymer, is a promising material for electronics and photovoltaics, but its applications were hindered by a poor processability. We propose an experimental approach, by which thin films of CuPPC, can be directly synthesized in a chemical vapor deposition (CVD) set-up at mild temperature (420 °C). High polymerization degree and high crystallinity of the films were confirmed by TEM, FTIR and UV–vis studies. From XRD and TEM electron diffraction, we conclude that the polymer has AA layer stacking with the inter-layer distance of 0.32 nm. The assignment of X-ray and TEM diffraction patterns was based on quantum-chemical calculations. Based on the latter, we also discuss electronic structure and conclude that CuPPC is rather a semi-metal than semi-conductor.

  7. Synthesis, Optical Properties, and Electronic Structures of Tetrakis(pentafluorophenyl)tetrathiaisophlorin Dioxide.

    PubMed

    Mishra, Vijay Lakshmi; Furuyama, Taniyuki; Kobayashi, Nagao; Goto, Kenta; Miyazaki, Takaaki; Yang, Jye-Shane; Shinmyozu, Teruo

    2016-06-27

    The synthesis, structure, optical and redox properties, and electronic structure of tetrakis(pentafluorophenyl)tetrathiaisophlorin dioxide (12) are reported. Oxidation of tetrakis(pentafluorophenyl)tetrathiaisophlorin (11) with dimethyldioxirane afforded the oxidized product, which was the tetrathiaisophlorin with two thiophene 1-oxide moieties (12). More significant nonplanarity and greater bond length alternation in 12 than those of 11 were observed by X-ray structural analysis. The absorption spectrum of 12 contains two bands at λ=348 and 276 nm, with a weak tail that extends to λ≈650 nm. Analysis of the magnetic circular dichroism spectrum of 12, based on Michl's 4N-perimeter model and molecular orbital calculations, indicate that the broad band at λ=348 nm appears to contain N2 and P2 bands, and 12 is classified as a 4nπ system, similar to 11. The nuclear-independent chemical shift values and (1) H NMR spectroscopy data indicate that 12 has more antiaromatic character than 11. PMID:27247252

  8. Radio Frequency Plasma Synthesis of Boron Nitride Nanotubes (BNNTs) for Structural Applications: Part I

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Alexa, Joel A.; Jensen, Brian J.; Thomsen, Donald L.

    2016-01-01

    It is evident that nanotubes, such as carbon, boron nitride and even silicon, offer great potential for many aerospace applications. The opportunity exists to harness the extremely high strength and stiffness exhibited by high-purity, low-defect nanotubes in structural materials. Even though the technology associated with carbon nanotube (CNT) development is mature, the mechanical property benefits have yet to be fully realized. Boron nitride nanotubes (BNNTs) offer similar structural benefits, but exhibit superior chemical and thermal stability. A broader range of potential structural applications results, particularly as reinforcing agents for metal- and ceramic- based composites. However, synthesis of BNNTs is more challenging than CNTs mainly because of the higher processing temperatures required, and mass production techniques have yet to emerge. A promising technique is radio frequency plasma spray (RFPS), which is an inductively coupled, very high temperature process. The lack of electrodes and the self- contained, inert gas environment lend themselves to an ultraclean product. It is the aim of this White Paper to survey the state of the art with regard to nano-material production by analyzing the pros and cons of existing methods. The intention is to combine the best concepts and apply the NASA Langley Research Center (LaRC) RFPS facility to reliably synthesize large quantities of consistent, high-purity BNNTs.

  9. Structural basis for the RING catalyzed synthesis of K63 linked ubiquitin chains

    PubMed Central

    Branigan, Emma; Plechanovová, Anna; Jaffray, Ellis; Naismith, James H.; Hay, Ronald T.

    2015-01-01

    The RING E3 ligase catalysed formation of lysine 63 linked ubiquitin chains by the Ube2V2–Ubc13 E2 complex is required for many important biological processes. Here we report the structure of the RING domain dimer of rat RNF4 in complex with a human Ubc13~Ub conjugate and Ube2V2. The structure has captured Ube2V2 bound to the acceptor (priming) ubiquitin with Lys63 in a position that could lead to attack on the linkage between the donor (second) ubiquitin and Ubc13 that is held in the active “folded back” conformation by the RING domain of RNF4. The interfaces identified in the structure were verified by in vitro ubiquitination assays of site directed mutants. This represents the first view of the synthesis of Lys63 linked ubiquitin chains in which both substrate ubiquitin and ubiquitin-loaded E2 are juxtaposed to allow E3 ligase mediated catalysis. PMID:26148049

  10. Structural basis for the RING-catalyzed synthesis of K63-linked ubiquitin chains.

    PubMed

    Branigan, Emma; Plechanovová, Anna; Jaffray, Ellis G; Naismith, James H; Hay, Ronald T

    2015-08-01

    RING E3 ligase-catalyzed formation of K63-linked ubiquitin chains by the Ube2V2-Ubc13 E2 complex is required in many important biological processes. Here we report the structure of the RING-domain dimer of rat RNF4 in complex with a human Ubc13∼Ub conjugate and Ube2V2. The structure has captured Ube2V2 bound to the acceptor (priming) ubiquitin with K63 in a position favorable for attack on the linkage between Ubc13 and the donor (second) ubiquitin held in the active 'folded back' conformation by the RING domain of RNF4. We verified the interfaces identified in the structure by in vitro ubiquitination assays of site-directed mutants. To our knowledge, this represents the first view of synthesis of K63-linked ubiquitin chains in which both substrate ubiquitin and ubiquitin-loaded E2 are juxtaposed to allow E3 ligase-mediated catalysis. PMID:26148049

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

    SciTech Connect

    Arslan, Ilke; Dixon, David A.; Gates, Bruce C.; Katz, Alexander

    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

  12. CO2 hydrate: Synthesis, composition, structure, dissociation behavior, and a comparison to structure I CH4 hydrate

    USGS Publications Warehouse

    Circone, S.; Stern, L.A.; Kirby, S.H.; Durham, W.B.; Chakoumakos, B.C.; Rawn, C.J.; Rondinone, A.J.; Ishii, Y.

    2003-01-01

    Structure I (sI) carbon dioxide (CO2) hydrate exhibits markedly different dissociation behavior from sI methane (CH4) hydrate in experiments in which equilibrated samples at 0.1 MPa are heated isobarically at 13 K/h from 210 K through the H2O melting point (273.15 K). The CO2 hydrate samples release only about 3% of their gas content up to temperatures of 240 K, which is 22 K above the hydrate phase boundary. Up to 20% is released by 270 K, and the remaining CO2 is released at 271.0 plusmn; 0.5 K, where the sample temperature is buffered until hydrate dissociation ceases. This reproducible buffering temperature for the dissociation reaction CO2??nH2O = CO2(g) + nH2O(1 to s) is measurably distinct from the pure H2O melting point at 273.15 K, which is reached as gas evolution ceases. In contrast, when si CH4 hydrate is heated at the same rate at 0.1 MPa, >95% of the gas is released within 25 K of the equilibrium temperature (193 K at 0.1 MPa). In conjunction with the dissociation study, a method for efficient and reproducible synthesis of pure polycrystalline CO2 hydrate with suitable characteristics for material properties testing was developed, and the material was characterized. CO2 hydrate was synthesized from CO2 liquid and H2O solid and liquid reactants at pressures between 5 and 25 MPa and temperatures between 250 and 281 K. Scanning electron microscopy (SEM) examination indicates that the samples consist of dense crystalline hydrate and 50-300 ??m diameter pores that are lined with euhedral cubic hydrate crystals. Deuterated hydrate samples made by this same procedure were analyzed by neutron diffraction at temperatures between 4 and 215 K; results confirm that complete conversion of water to hydrate has occurred and that the measured unit cell parameter and thermal expansion are consistent with previously reported values. On the basis of measured weight gain after synthesis and gas yields from the dissociation experiments, approximately all cages in the

  13. One-pot hydrazide-based native chemical ligation for efficient chemical synthesis and structure determination of toxin Mambalgin-1.

    PubMed

    Pan, Man; He, Yao; Wen, Ming; Wu, Fangming; Sun, Demeng; Li, Sijian; Zhang, Longhua; Li, Yiming; Tian, Changlin

    2014-06-01

    An efficient one-pot chemical synthesis of snake venom toxin Mambalgin-1 was achieved using an azide-switch strategy combined with hydrazide-based native chemical ligation. Synthetic Mambalgin-1 exhibited a well-defined structure after sequential folding in vitro. NMR spectroscopy revealed a three-finger toxin family structure, and the synthetic toxin inhibited human acid-sensing ion channel 1a. PMID:24619065

  14. Component mode synthesis and large deflection vibration of complex structures. Volume 1: Examples of NASTRAN modal synthesis capability

    NASA Technical Reports Server (NTRS)

    Mei, Chuh; Shen, Mo-How

    1987-01-01

    The use of NASTRAN model synthesis capability is illustrated. A classical truss problem is examined and the results are compared to results from other methods to test for accuracy. The problem is examined using both fixed interface modes and free interface modes. The solution is carried out for an applied dynamic load as far as recovery of forces in individual members as a function of time. Another small beam problem is used to compare different means of combining substructures.

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

    NASA Technical Reports Server (NTRS)

    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

  16. Synthesis, structure, and emission spectroscopy of luminescent Pt(COD)(dithiolate) complexes

    SciTech Connect

    Bevilacqua, J.M.; Zuleta, J.A.; Eisenberg, R.

    1993-08-18

    The synthesis, characterization, X-ray structure determination and emission spectroscopy of two Pt(COD)(S-S) complexes are reported where COD = 1,5-cycloctadiene (COD) and S-S is maleonitriledithiolate (mnt) for complex 1 and 1-(ethoxycarbonyl)-1-cyanoethylene-2,2-dithiolate (ecda) for complex 2. Both complexes are isolated in high yield from the reaction of Pt(COD)Cl{sub 2} and the corresponding dianionic dithiolate salt. Orange crystals of 1 (C{sub 12}H{sub 12}N{sub 2}PtS{sub 2}) are monoclinic, space group P2{sub 1}/n (No. 14). Each complex possess a square planar structure with chelating diolefin and dithiolate ligands. Proton NMR spectroscopy shows that the solid-state structures are maintained in solution. The complexes are luminescent at low temperature in the solid state and in frozen glasses. In the solid state at 77 K, Pt(COD)(mnt) exhibits a highly structured emission ({lambda}{sub max} = 560 nm, 17.9 kcm{sup {minus}1}) with a vibronic progression of {approximately}1400 cm{sup {minus}1}, whereas for Pt(COD)(ecda), the emission is broad and featureless ({lambda}{sub max} = 525 nm, 19.0 kcm{sup {minus}1}). The emissive state for both complexes is assigned as a metal-to-dithiolate charge transfer with differences in the structure and energy of the emissions resulting from differences in the {pi}*{sub dithiolate} orbital of the mnt and ecda ligands.

  17. Controllable synthesis of a novel hedgehog-like core/shell structure

    SciTech Connect

    Wang Shumin; Tian Hongwei; Pei Yanhui; Meng Qingnan; Chen Jianli; Wang Huan; Zeng Yi; Zheng Weitao; Liu Yichun

    2012-02-15

    A novel hedgehog-like core/shell structure, consisting of a high density of vertically aligned graphene sheets and a thin graphene shell/a copper core (VGs-GS/CC), has been synthesized via a simple one-step synthesis route using radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). Scanning and transmission electron microscopy investigations show that the morphology of this core/shell material could be controlled by deposition time. For a short deposition time, only multilayer graphene shell tightly surrounds the copper particle, while as the deposition time is relative long, graphene sheets extend from the surface of GS/CC. The GS can protect CC particles from oxidation. The growth mechanism for the obtained GS/CC and VGs-GS/CC has been revealed. Compared to VGs, VGs-GS/CC material exhibits a better electron field emission property. This investigation opens a possibility for designing a core/shell structure of different carbon-metal hybrid materials for a wide variety of practical applications. - Graphical abstract: With increasing deposition time, graphene sheets extend from the surface of GS/CC, causing the multilayer graphene encapsulated copper to be converted into vertically aligned graphene sheets-graphene shell/copper core structure. Highlights: Black-Right-Pointing-Pointer A novel hedgehog-like core/shell structure has been synthesized. Black-Right-Pointing-Pointer The structure consists of vertical graphene sheets-graphene shell and copper core. Black-Right-Pointing-Pointer The morphology of VGs-GS/CC can be controlled by choosing a proper deposition time. Black-Right-Pointing-Pointer With increasing deposition time, graphene sheets extend from the surface of GS/CC. Black-Right-Pointing-Pointer VGs-GS/CC exhibits a better electron field emission property as compared with VGs.

  18. Synthesis, crystal structure, electronic structure, and photoelectric response properties of KCu2SbS3.

    PubMed

    Wang, Ruiqi; Zhang, Xian; He, Jianqiao; Zheng, Chong; Lin, Jianhua; Huang, Fuqiang

    2016-02-28

    Copper thioantimonates have received enormous attention due to their potential for applications in photovoltaic devices. In this work, a new layered compound KCu2SbS3 was synthesized via a reactive flux method using thiourea as a reactive flux. The compound crystallizes in the triclinic space group P1[combining macron]. The structure features two-dimensional [Cu2SbS3](-) layers stacking along the c axis with K(+) ions intercalated between the layers. Each [Cu2SbS3](-) layer is composed of two single graphene-like layers connected via interlayer Cu-S bonds and CuSb contacts. The optical measurements indicate that the compound has a band gap of 1.7 eV. The Hall effect measurement shows that KCu2SbS3 is a p-type semiconductor with a carrier concentration of 7 × 10(16) cm(-3). First-principles calculations reveal that the direct transition occurs between Cu-3d-S-3p orbitals (VBM) to Sb-5p-S-3p orbitals (CBM). The photoelectric response properties of KCu2SbS3 under visible light irradiation were analyzed. The photocurrent is 3.7 μA cm(-2) at 10 V bias, demonstrating its potential for applications in photoelectric devices. PMID:26794832

  19. Microwave-assisted synthesis and characterization of hierarchically structured calcium fluoride

    SciTech Connect

    Yang, Zhenxing; Wang, Guangjian; Guo, Yajie; Kang, Fangfang; Huang, Yanhong; Bo, Dongsheng

    2012-12-15

    Graphical abstract: CaF{sub 2} with different morphologies and hierarchical structure such as dendrites, spherical and cube was prepared under microwave-assisted condition by a simple solvothermal synthesis route using CaCl{sub 2} and [BMIM]BF{sub 4} as initial reagents, respectively. It was found that the species of precursor was of vital importance for the formation of CaF{sub 2} crystals. That is, precursors itself also acted as structure directing agent. The outstanding features of the approach to obtain hierarchical structure CaF{sub 2} were its simplicity, effectiveness and ease of assembly. On the basis of the experimental results, a possible growth mechanism of the CaF{sub 2} crystals was proposed. Display Omitted Highlights: ► CaF{sub 2} with hierarchical structure was synthesized under microwave-assisted conditions. ► Characteristic morphologies with cube, dendrite, hierarchical sphere, etc. were observed. ► Thin cubes assembled into a spherical structure. ► Ionic liquid of [BMIM]BF{sub 4} was fluorine source. ► Possible growth mechanisms of CaF{sub 2} crystals were discussed. -- Abstract: CaF{sub 2} with different morphologies and hierarchical structures was prepared under microwave-assisted condition by a simple hydrothermal route using CaCl{sub 2} and ionic liquid [BMIM]BF{sub 4} as initial reagents, respectively. It was found that both the precursor and pH values played an important role in the formation of CaF{sub 2} crystals with different morphologies. The results suggested that the CaF{sub 2} with cube and spherical structures was obtained at different pH values (4, 8, 11), while the CaF{sub 2} with dendrite shape was formed through an oriented self-assembly growth using (NH{sub 4}){sub 2}HPO{sub 4} as a structure directing agent. Scanning electron microscope observation showed that the as-prepared CaF{sub 2} was of three-dimensional eight-horn-shaped dendritic structure. The influence of the pH values for the reaction solution and

  20. The revised HSE fatigue guidance

    SciTech Connect

    Stacey, A.; Sharp, J.V.

    1995-12-31

    Fatigue cracking has been a principal cause of damage to North Sea structures and consequently considerable attention has been given to the development of guidance for the prediction of fatigue performance. The fatigue guidance of the Offshore Safety Division of the Health and Safety Executive (HSE) was recently revised and published, following a significant offshore industry review in the period 1987 to 1990, and is based on the results of a considerable amount of research and development work on the fatigue behavior of welded tubular and plated joints. As a result of this review, the revised fatigue guidance incorporates several new clauses and recommendations. The revised recommendations apply to joint classification, basic design S-N curves for welded joints and cast or forged steel components, the thickness effect, the effects of environment and the treatment of low and high stress ranges. Additionally, a new appendix on the derivation of stress concentration factors is included. The new clauses cover high strength steels, bolts and threaded connectors, moorings, repaired joints and the use of fracture mechanics analysis. This paper presents an overview of the revisions to the fatigue guidance, the associated background technical information and aspects of the fatigue behavior of offshore structures which are considered to require further investigation. 67 refs., 7 figs., 8 tabs.

  1. Aerosol-assisted controlled packing of silica nanocolloids: templateless synthesis of mesoporous silicates with structural tunability and complexity.

    PubMed

    Min, Kyungmin; Choi, Chang Hyuck; Kim, Myoung Yeob; Choi, Minkee

    2015-01-01

    A template-free synthesis method for mesoporous and macro-/mesoporous hierarchically porous silicates with remarkable structural tunability and complexity is presented. SiO2 nanocolloids having diameters of 3.0-29 nm were prepared as a primary building block by using extended Stöber synthesis, and they were subsequently assembled by an aerosol-assisted drying. The silica pore structure can be rationally controlled depending on the initial diameter of SiO2 colloids and the aerosol-assembly temperature that determines the packing density of SiO2 colloids (i.e., amounts of packing defects) in the resultant materials. The present method could produce mesoporous silica spheres with remarkable pore-structural tunability (291 < BET surface area <807 m(2) g(-1), 0.42 < pore volume <0.92 cm(3) g(-1), 3.1 < pore size <26 nm). Hierarchically porous materials can also be synthesized by the evaporation-induced phase separation of solvent medium during the aerosol-assisted assembly of SiO2 colloids. By adding aluminum and Pt precursors into the SiO2 colloid suspensions before the aerosol-assisted assembly, mesoporous aluminosilicates supporting uniform Pt nanoclusters (∼2 nm) can also be synthesized. This indicates that the synthesis strategy can be used for the direct synthesis of functional silicate materials. PMID:25517201

  2. Inverse Load Calculation of Wind Turbine Support Structures - A Numerical Verification Using the Comprehensive Simulation Code FAST: Preprint (Revised)

    SciTech Connect

    Pahn, T.; Jonkman, J.; Rolges, R.; Robertson, A.

    2012-11-01

    Physically measuring the dynamic responses of wind turbine support structures enables the calculation of the applied loads using an inverse procedure. In this process, inverse means deriving the inputs/forces from the outputs/responses. This paper presents results of a numerical verification of such an inverse load calculation. For this verification, the comprehensive simulation code FAST is used. FAST accounts for the coupled dynamics of wind inflow, aerodynamics, elasticity and turbine controls. Simulations are run using a 5-MW onshore wind turbine model with a tubular tower. Both the applied loads due to the instantaneous wind field and the resulting system responses are known from the simulations. Using the system responses as inputs to the inverse calculation, the applied loads are calculated, which in this case are the rotor thrust forces. These forces are compared to the rotor thrust forces known from the FAST simulations. The results of these comparisons are presented to assess the accuracy of the inverse calculation. To study the influences of turbine controls, load cases in normal operation between cut-in and rated wind speed, near rated wind speed and between rated and cut-out wind speed are chosen. The presented study shows that the inverse load calculation is capable of computing very good estimates of the rotor thrust. The accuracy of the inverse calculation does not depend on the control activity of the wind turbine.

  3. Total synthesis, structural, and biological evaluation of stylissatin A and related analogs.

    PubMed

    Shaheen, Farzana; Jabeen, Almas; Ashraf, Samreen; Nadeem-Ul-Haque, Muhammad; Shah, Zafar Ali; Ziaee, Muhammad Asad; Dastagir, Nida; Ganesan, A

    2016-09-01

    The natural product cyclic peptide stylissatin A (1a) was reported to inhibit nitric oxide production in LPS-stimulated murine macrophage RAW 264.7 cells. In the current study, solid-phase total synthesis of stylissatin A was performed by using a safety-catch linker and yielded the peptide with a trans-Phe(7) -Pro(6) linkage, whereas the natural product is the cis rotamer at this position as evidenced by a marked difference in NMR chemical shifts. In order to preclude the possibility of 1b being an epimer of the natural product, we repeated the synthesis using d-allo-Ile in place of l-Ile and a different site for macrocyclization. The resulting product (d-allo-Ile(2) )-stylissatin A (1c) was also found to have the trans-Phe(7) -Pro(6) peptide conformations like rotamer 1b. Applying the second route to the synthesis of stylissatin A itself, we obtained stylissatin A natural rotamer 1a accompanied by rotamer 1b as the major product. Rotamers 1a, 1b, and the epimer 1c were separable by HPLC, and 1a was found to match the natural product in structure and biological activity. Six related analogs 2-7 of stylissatin A were synthesized on Wang resin and characterized by spectral analysis. The natural product (1a), the rotamer (1b), and (d-allo-Ile(2) )-stylissatin A (1c) exhibited significant inhibition of NO(.) . Further investigations were focused on 1b, which also inhibited proliferation of T-cells and inflammatory cytokine IL-2 production. The analogs 2-7 weakly inhibited NO(.) production, but strongly inhibited IL-2 cytokine production compared with synthetic peptide 1b. All analogs inhibited the proliferation of T-cells, with analog 7 having the strongest effect. In the analogs, the Pro(6) residue was replaced by Glu/Ala, and the SAR indicates that the nature of this residue plays a role in the biological function of these peptides. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd. PMID:27526945

  4. Antithyroid drugs and their analogues: synthesis, structure, and mechanism of action.

    PubMed

    Manna, Debasish; Roy, Gouriprasanna; Mugesh, Govindasamy

    2013-11-19

    Thyroid hormones are essential for the development and differentiation of all cells of the human body. They regulate protein, fat, and carbohydrate metabolism. In this Account, we discuss the synthesis, structure, and mechanism of action of thyroid hormones and their analogues. The prohormone thyroxine (T4) is synthesized on thyroglobulin by thyroid peroxidase (TPO), a heme enzyme that uses iodide and hydrogen peroxide to perform iodination and phenolic coupling reactions. The monodeiodination of T4 to 3,3',5-triiodothyronine (T3) by selenium-containing deiodinases (ID-1, ID-2) is a key step in the activation of thyroid hormones. The type 3 deiodinase (ID-3) catalyzes the deactivation of thyroid hormone in a process that removes iodine selectively from the tyrosyl ring of T4 to produce 3,3',5'-triiodothyronine (rT3). Several physiological and pathological stimuli influence thyroid hormone synthesis. The overproduction of thyroid hormones leads to hyperthyroidism, which is treated by antithyroid drugs that either inhibit the thyroid hormone biosynthesis and/or decrease the conversion of T4 to T3. Antithyroid drugs are thiourea-based compounds, which include propylthiouracil (PTU), methimazole (MMI), and carbimazole (CBZ). The thyroid gland actively concentrates these heterocyclic compounds against a concentration gradient. Recently, the selenium analogues of PTU, MMI, and CBZ attracted significant attention because the selenium moiety in these compounds has a higher nucleophilicity than that of the sulfur moiety. Researchers have developed new methods for the synthesis of the selenium compounds. Several experimental and theoretical investigations revealed that the selone (C═Se) in the selenium analogues is more polarized than the thione (C═S) in the sulfur compounds, and the selones exist predominantly in their zwitterionic forms. Although the thionamide-based antithyroid drugs have been used for almost 70 years, the mechanism of their action is not completely

  5. Methanol synthesis on ZnO(0001{sup ¯}). IV. Reaction mechanisms and electronic structure

    SciTech Connect

    Frenzel, Johannes Marx, Dominik

    2014-09-28

    Methanol synthesis from CO and H{sub 2} over ZnO, which requires high temperatures and high pressures giving rise to a complex interplay of physical and chemical processes over this heterogeneous catalyst surface, is investigated using ab initio simulations. The redox properties of the surrounding gas phase are known to directly impact on the catalyst properties and thus, set the overall catalytic reactivity of this easily reducible oxide material. In Paper III of our series [J. Kiss, J. Frenzel, N. N. Nair, B. Meyer, and D. Marx, J. Chem. Phys. 134, 064710 (2011)] we have qualitatively shown that for the partially hydroxylated and defective ZnO(0001{sup ¯}) surface there exists an intricate network of surface chemical reactions. In the present study, we employ advanced molecular dynamics techniques to resolve in detail this reaction network in terms of elementary steps on the defective surface, which is in stepwise equilibrium with the gas phase. The two individual reduction steps were investigated by ab initio metadynamics sampling of free energy landscapes in three-dimensional reaction subspaces. By also sampling adsorption and desorption processes and thus molecular species that are in the gas phase but close to the surface, our approach successfully generated several alternative pathways of methanol synthesis. The obtained results suggest an Eley-Rideal mechanism for both reduction steps, thus involving “near-surface” molecules from the gas phase, to give methanol preferentially over a strongly reduced catalyst surface, while important side reactions are of Langmuir-Hinshelwood type. Catalyst re-reduction by H{sub 2} stemming from the gas phase is a crucial process after each reduction step in order to maintain the catalyst's activity toward methanol formation and to close the catalytic cycle in some reaction channels. Furthermore, the role of oxygen vacancies, side reactions, and spectator species is investigated and mechanistic details are discussed

  6. Methanol synthesis on ZnO(000overline{1}). IV. Reaction mechanisms and electronic structure

    NASA Astrophysics Data System (ADS)

    Frenzel, Johannes; Marx, Dominik

    2014-09-01

    Methanol synthesis from CO and H2 over ZnO, which requires high temperatures and high pressures giving rise to a complex interplay of physical and chemical processes over this heterogeneous catalyst surface, is investigated using ab initio simulations. The redox properties of the surrounding gas phase are known to directly impact on the catalyst properties and thus, set the overall catalytic reactivity of this easily reducible oxide material. In Paper III of our series [J. Kiss, J. Frenzel, N. N. Nair, B. Meyer, and D. Marx, J. Chem. Phys. 134, 064710 (2011)] we have qualitatively shown that for the partially hydroxylated and defective ZnO(000overline{1}) surface there exists an intricate network of surface chemical reactions. In the present study, we employ advanced molecular dynamics techniques to resolve in detail this reaction network in terms of elementary steps on the defective surface, which is in stepwise equilibrium with the gas phase. The two individual reduction steps were investigated by ab initio metadynamics sampling of free energy landscapes in three-dimensional reaction subspaces. By also sampling adsorption and desorption processes and thus molecular species that are in the gas phase but close to the surface, our approach successfully generated several alternative pathways of methanol synthesis. The obtained results suggest an Eley-Rideal mechanism for both reduction steps, thus involving "near-surface" molecules from the gas phase, to give methanol preferentially over a strongly reduced catalyst surface, while important side reactions are of Langmuir-Hinshelwood type. Catalyst re-reduction by H2 stemming from the gas phase is a crucial process after each reduction step in order to maintain the catalyst's activity toward methanol formation and to close the catalytic cycle in some reaction channels. Furthermore, the role of oxygen vacancies, side reactions, and spectator species is investigated and mechanistic details are discussed based on

  7. Coronavirus JHM: Cell-Free Synthesis of Structural Protein p60

    PubMed Central

    Siddell, Stuart G.; Wege, Helmut; Barthel, Andrea; ter Meulen, Volker

    1980-01-01

    Sac(-) cells infected with murine coronavirus strain JHM shut off host cell protein synthesis and synthesized polypeptides with molecular weights of 150,000, 60,000, and 23,000. The 60,000- and 23,000-molecular-weight polypeptides comigrated with virion structural proteins p60 and p23, and the 60,000-molecular-weight protein was identified as p60 by tryptic peptide fingerprinting. Polyadenylate-containing RNA [poly(A) RNA] extracted from the cytoplasm of infected cells directed the synthesis of both 60,000- and 23,000-molecular-weight polypeptides in messenger-dependent cell-free systems derived from mouse L-cells and rabbit reticulocytes. The reticulocyte system also synthesized a 120,000-molecular-weight polypeptide that was specifically immunoprecipitated by antiserum raised against JHM virions. The identity of the 60,000- and 23,000-molecular-weight in vitro products was established by comigration with virion proteins, immunoprecipitation, and in the case of p60, tryptic peptide fingerprinting. The cytoplasmic poly(A) RNAs which encoded p60 and p23 sedimented in sucroseformamide gradients at 17S and 19S, respectively, and were clearly separable. These RNAs were among the major poly(A) RNA species synthesized in the cytoplasm of actinomycin D-treated cells late in infection, and the in vitro translation of size-fractionated RNA released from polysomes confirmed that they represent physiological mRNA's. These results suggest that the expression of the coronavirus JHM genome involves more than one subgenomic mRNA. Images PMID:7365865

  8. Synthesis and structure-activity relationships of potent antitumor active quinoline and naphthyridine derivatives.

    PubMed

    Srivastava, Sanjay K; Jha, Amrita; Agarwal, Shiv K; Mukherjee, Rama; Burman, Anand C

    2007-11-01

    The disease of cancer has been ranked second after cardiovascular diseases and plant-derived molecules have played an important role for the treatment of cancer. Nine cytotoxic plant-derived molecules such as vinblastine, vincristine, navelbine, etoposide, teniposide, taxol, taxotere, topotecan and irinotecan have been approved as anticancer drugs. Recently, epothilones are being emerging as future potential anti-tumor agents. However, targeted cancer therapy has now been rapidly expanding and small organic molecules are being exploited for this purpose. Amongst target specific small organic molecules, quinazoline was found as one of the most successful chemical class in cancer chemotherapy as three drugs namely Gefitinib, Erlotinib and Canertinib belong to this series. Now, quinazoline related chemical classes such as quinolines and naphthyridines are being exploited in cancer chemotherapy and a number of molecules such as compounds EKB-569 (52), HKI-272 (78) and SNS-595 (127a) are in different phases of clinical trials. This review presents the synthesis of quinolines and naphthyridines derivatives, screened for anticancer activity since year 2000. The synthesis of most potent derivatives in each prototype has been delineated. A brief structure activity relationship for each prototype has also been discussed. It has been observed that aniline group at C-4, aminoacrylamide substituents at C-6, cyano group at C-3 and alkoxy groups at C-7 in the quinoline ring play an important role for optimal activity. While aminopyrrolidine functionality at C-7, 2'-thiazolyl at N-1 and carboxy group at C-3 in 1,8-naphthyridine ring are essential for eliciting the cytotoxicity. This review would help the medicinal chemist to design and synthesize molecules for targeted cancer chemotherapy. PMID:18045063

  9. Synthesis, structure, and bonding of two lanthanum indium germanides with novel structures and properties

    SciTech Connect

    Guloy, A.M.; Corbett, J.D.

    1996-04-24

    The new tetragonal phases La{sub 3}In{sub 4}Ge and La{sub 3}InGe are obtained from high-temperature reactions of the elements in welded Ta followed by annealing. The structures of both were established by single-crystal X-ray diffraction in tetragonal space group I4/mcm (Z = 4 and 16, {alpha} = 8.5165(3) and 12.3083(2) {Angstrom}, c = 11.9024(4) and 16.0776(4) {Angstrom}, respectively). La{sub 3}In{sub 4}Ge contains layers or slabs of three-connected indium built of puckered 8-rings and 4-rings, or of squashed tetrahedra ({open_quotes}butterflies{close_quotes}) interlinked at all vertices, and these are separated by layers of La and isolated Ge. The phase is deficient of being a Zintl phase by three electrons per formula unit and is better described in terms of an alternate optimized and delocalized bonding picture and an open-shell metallic better described in terms of an alternate optimized and delocalized bonding picture and an open-shell metallic behavior for the In slabs. The more complex La{sub 3}InGe, isostructural with Gd{sub 3}Ga{sub 2}, is also layered. This phase contains pairs of mixed-occupancy (0.75 In, 0.25 Ge) sites separated by 3.020 {Angstrom}, as well as isolated In and Ge atoms. The former appear to be fully reduced closed-shell atoms (relative to the bonded Ga dimers in Gd{sub 3}Ga{sub 2}) that are held in somewhat close proximity by cation matrix effects. The compound appears to be semiconducting and thus is a classical Zintl phase, (La{sup +3}){sub 3}In{sup {minus}5}Ge{sup {minus}4} in the simplest oxidation state notation. High Coulomb energies are presumably important for the nature of the bonding and the stabilities of both compounds.

  10. The 1946 Unimak Tsunami Earthquake Area: revised tectonic structure in reprocessed seismic images and a suspect near field tsunami source

    USGS Publications Warehouse

    Miller, John J.; von Huene, Roland; Ryan, Holly F.

    2014-01-01

    In 1946 at Unimak Pass, Alaska, a tsunami destroyed the lighthouse at Scotch Cap, Unimak Island, took 159 lives on the Hawaiian Islands, damaged island coastal facilities across the south Pacific, and destroyed a hut in Antarctica. The tsunami magnitude of 9.3 is comparable to the magnitude 9.1 tsunami that devastated the Tohoku coast of Japan in 2011. Both causative earthquake epicenters occurred in shallow reaches of the subduction zone. Contractile tectonism along the Alaska margin presumably generated the far-field tsunami by producing a seafloor elevation change. However, the Scotch Cap lighthouse was destroyed by a near-field tsunami that was probably generated by a coeval large undersea landslide, yet bathymetric surveys showed no fresh large landslide scar. We investigated this problem by reprocessing five seismic lines, presented here as high-resolution graphic images, both uninterpreted and interpreted, and available for the reader to download. In addition, the processed seismic data for each line are available for download as seismic industry-standard SEG-Y files. One line, processed through prestack depth migration, crosses a 10 × 15 kilometer and 800-meter-high hill presumed previously to be basement, but that instead is composed of stratified rock superimposed on the slope sediment. This image and multibeam bathymetry illustrate a slide block that could have sourced the 1946 near-field tsunami because it is positioned within a distance determined by the time between earthquake shaking and the tsunami arrival at Scotch Cap and is consistent with the local extent of high runup of 42 meters along the adjacent Alaskan coast. The Unimak/Scotch Cap margin is structurally similar to the 2011 Tohoku tsunamigenic margin where a large landslide at the trench, coeval with the Tohoku earthquake, has been documented. Further study can improve our understanding of tsunami sources along Alaska’s erosional margins.

  11. Synthesis and Characterization of Ru Cubic Nanocages with a Face-Centered Cubic Structure by Templating with Pd Nanocubes.

    PubMed

    Zhao, Ming; Figueroa-Cosme, Legna; Elnabawy, Ahmed O; Vara, Madeline; Yang, Xuan; Roling, Luke T; Chi, Miaofang; Mavrikakis, Manos; Xia, Younan

    2016-08-10

    Nanocages have received considerable attention in recent years for catalytic applications owing to their high utilization efficiency of atoms and well-defined facets. Here we report, for the first time, the synthesis of Ru cubic nanocages with ultrathin walls, in which the atoms are crystallized in a face-centered cubic (fcc) rather than hexagonal close-packed (hcp) structure. The key to the success of this synthesis is to ensure layer-by-layer deposition of Ru atoms on the surface of Pd cubic seeds by controlling the reaction temperature and the injection rate of a Ru(III) precursor. By selectively etching away the Pd from the Pd@Ru core-shell nanocubes, we obtain Ru nanocages with an average wall thickness of 1.1 nm or about six atomic layers. Most importantly, the Ru nanocages adopt an fcc crystal structure rather than the hcp structure observed in bulk Ru. The synthesis has been successfully applied to Pd cubic seeds with different edge lengths in the range of 6-18 nm, with smaller seeds being more favorable for the formation of Ru shells with a flat, smooth surface due to shorter distance for the surface diffusion of the Ru adatoms. Self-consistent density functional theory calculations indicate that these unique fcc-structured Ru nanocages might possess promising catalytic properties for ammonia synthesis compared to hcp Ru(0001), on the basis of strengthened binding of atomic N and substantially reduced activation energies for N2 dissociation, which is the rate-determining step for ammonia synthesis on hcp Ru catalysts. PMID:27458871

  12. Silent cries, dancing tears: the metapsychology of art revisited/revised.

    PubMed

    Aragno, Anna

    2011-04-01

    Against the backdrop of a broad survey of the literature on applied psychoanalysis, a number of concepts underpinning the metapsychology of art are revisited and revised: sublimation; interrelationships between primary and secondary processes; symbolization; "fantasy"; and "cathexis." Concepts embedded in dichotomous or drive/energic contexts are examined and reformulated in terms of a continuum of semiotic processes. Freudian dream structure is viewed as a biological/natural template for nonrepressive artistic forms of sublimation. The synthesis presented proposes a model of continuous rather than discontinuous processes, in a nonenergic, biosemiotic metatheoretical framework. PMID:21653915

  13. Synthesis and atomic and electronic structure of new Si-Ge-C alloys and compounds

    SciTech Connect

    Kouvetakis, J.; Nesting, D.; Smith, D.J.

    1998-10-01

    The synthesis and characterization of completely novel binary and ternary alloy semiconductors and ordered phases based on C, Si, and Ge are discussed in this review. Metastable compound semiconductors with ordered structures, which include stoichiometric SiGe, Si{sub 4}C, Si{sub 3}GeC{sub 4} (sphalerite), Ge{sub 4}C, (Si{sub 2}Ge)C{sub x}, and (Ge{sub 2}Si)C{sub x} (x = 5%), are described. Materials systems include diamond-structured silicon-germanium solid solutions with dissolved carbon (Si{sub 1{minus}x{minus}y}Ge{sub x}C{sub y}), monocrystalline Ge{sub 1{minus}x}C{sub x} hybrids of Ge, and C-diamond and related Si-containing random alloy systems. The Si{sub 4}C and Ge{sub 4}C materials incorporate the corresponding tetrahedra that are linked together to form a diamond-cubic structure related to Si. The Si{sub 3}GeC{sub 4} phase is related to sphalerite and (Si{sub 2}Ge)C{sub x} had a new P{anti 3}m1 structure formed by Ge-Si-Si ordering along the diamond {l_angle}111{r_angle} direction. These compounds offer the prospect of band gaps wider than that of Si; in some cases, the band gaps are expected to become direct. This report emphasizes an approach that combines novel precursor chemistries and modern deposition techniques (ultrahigh-vacuum chemical-vapor deposition) to develop heteroepitaxial, device-quality inorganic materials. Important highlights of recent research based on conventional deposition methods are also summarized.

  14. Synthesis and structure-activity study of myxoma virus growth factor

    SciTech Connect

    Lin, Yao-Zhong; Ke, Xiao-Hong; Tam, J.P. )

    1991-04-02

    Myxoma virus growth factor (MGF) is an 85-residue peptide derived from the gene product of a DNA tumor virus that infects rabbits. The carboxyl domain of MGF possesses about 40% sequence homology with the epidermal growth factor (EGF). This EGF-like domain covering residues 30-83 was synthesized and found to possess putative activities of EGF. It was, however, about 200-fold less active than EGF in the competitive binding of human EGF receptor in A431 cells and the stimulation of ({sup 3}H)thymidine uptake in NRK 49F cells. MGF(30-83) is a basic and a hydrophobic peptide rich in {beta}-sheet structure. These features in MGF tend to promote aggregation, leading to precipitation even in strongly denaturing solutions. Thus, the refolding of MGF was achieved with difficulty and resulted in low yield. To increase the synthetic yield of MGF(30-83), a cluster of acidic amino acids was added to the NH{sub 2}-terminus of MGF(30-83). This approach was found to be effective in minimizing the refolding difficulties and allowed accessibility to the synthesis of analogues in this class of compounds. The relationships of structure and function of MGF were studied by using analogues with point substitution by the corresponding D-amino acid or by Ala at position 44 or 52 and analogues with deletion of basic residues from the amino terminus. Modifications of both the receptor contact and the structural residues greatly reduced the potency of MGF(30-83), and the overall result correlated well with the known structure-activity of the EGF family.

  15. Synthesis, structural characterization and catalytic activity of a multifunctional enzyme mimetic oxoperoxovanadium(V) complex.

    PubMed

    Si, Tapan K; Paul, Shiv S; Drew, Michael G B; Mukherjea, Kalyan K

    2012-05-21

    The synthesis and structural characterization of a novel oxoperoxovanadium(V) complex [VO(O(2))(PAH)(phen)] containing the ligands 2-phenylacetohydroxamic acid (PAHH) and 1,10-phenanthroline (phen) has been accomplished. The oxoperoxovanadium(V) complex was found to mimic both vanadate-dependent haloperoxidase (VHPO) activity as well as nuclease activity through effective interaction with DNA. The complex is the first example of a structurally characterized stable oxoperoxovanadium(V) complex with a coordinated bi-dentate hydroximate moiety (-CONHO(-)) from 2-phenylacetohydroximate (PAH). The oxoperoxovanadium(V) complex has been used as catalyst for the peroxidative bromination reaction of some unsaturated alcohols (e.g. 4-pentene-1-ol, 1-octene-3-ol and 9-decene-1-ol) in the presence of H(2)O(2) and KBr. The catalytic products have been characterized by GC-MS analysis and spectrophotometric methods. The DNA binding of this complex has been established with CT DNA whereas the DNA cleavage was demonstrated with plasmid DNA. The interactions of the complex with DNA have been monitored by electronic absorption and fluorescence emission spectroscopy. Viscometric measurements suggest that the compound is a DNA intercalator. The nuclease activity of this complex was confirmed by gel electrophoresis studies. PMID:22441646

  16. Yttrium-succinates coordination polymers: Hydrothermal synthesis, crystal structure and thermal decomposition

    SciTech Connect

    Amghouz, Zakariae; Roces, Laura; Garcia-Granda, Santiago; Garcia, Jose R.; Souhail, Badredine; Mafra, Luis; Shi, Fa-nian; Rocha, Joao

    2009-12-15

    New polymeric yttrium-succinates, Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 4}.6H{sub 2}O and Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 2}, have been synthesized, and their structures (solved by single crystal XRD) are compared with that of Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 2}.H{sub 2}O. Three compounds were obtained as single phases, and their thermal behaviour is described. - Graphical abstract: In the field of coordination polymers or MOF's, few studies report on the polymorphs of Ln(III)-succinic acid. Here, we describe the hydrothermal synthesis and structural characterization of two novel yttrium-succinates coordination polymers, respectively 2D and 3D, Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 4}.6H{sub 2}O and Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 2}.

  17. Discrete polynuclear manganese(ii) complexes with thiacalixarene ligands: synthesis, structures and photophysical properties.

    PubMed

    Suffren, Yan; O'Toole, Niall; Hauser, Andreas; Jeanneau, Erwann; Brioude, Arnaud; Desroches, Cédric

    2015-05-01

    The synthesis, crystal structure and photophysical properties of the new compound [Mn4(ThiaSO2)2F][K(18-crown-6)], ThiaSO2 = p-tert-butylsulphonylcalix[4]arene, are presented and compared to the ones of [Mn4(ThiaSO2)2F]K. The strong orange luminescence is attributed to the Mn(2+) centred (4)T1→(6)A1 transition. Its temperature and pressure dependence and quenching by molecular dioxygen are reported. The latter is attributed to energy transfer from the (4)T1 state exciting dioxygen to its (1)∑(+)g state. In the solid state, the quenching is much more efficient in [Mn4(ThiaSO2)2F][K(18-crown-6)] than in [Mn4(ThiaSO2)2F]K. This is attributed to the open pore structure of the former allowing fast diffusion of dioxygen into the crystal lattice. PMID:25825820

  18. Facile synthesis of diverse graphene nanomeshes based on simultaneous regulation of pore size and surface structure

    PubMed Central

    Zhang, Jia; Song, Huaibing; Zeng, Dawen; Wang, Hao; Qin, Ziyu; Xu, Keng; Pang, Aimin; Xie, Changsheng

    2016-01-01

    Recently, graphene nanomesh (GNM) has attracted great attentions due to its unique porous structure, abundant active sites, finite band gap and possesses potential applications in the fields of electronics, gas sensor/storage, catalysis, etc. Therefore, diverse GNMs with different physical and chemical properties are required urgently to meet different applications. Herein we demonstrate a facile synthetic method based on the famous Fenton reaction to prepare GNM, by using economically fabricated graphene oxide (GO) as a starting material. By precisely controlling the reaction time, simultaneous regulation of pore size from 2.9 to 11.1 nm and surface structure can be realized. Ultimately, diverse GNMs with tunable band gap and work function can be obtained. Specially, the band gap decreases from 4.5–2.3 eV for GO, which is an insulator, to 3.9–1.24 eV for GNM-5 h, which approaches to a semiconductor. The dual nature of electrophilic addition and oxidizability of HO• is responsible for this controllable synthesis. This efficient, low-cost, inherently scalable synthetic method is suitable for provide diverse and optional GNMs, and may be generalized to a universal technique. PMID:27561350

  19. Microfluidic synthesis of monodisperse nanoporous oxide particles and control of hierarchical pore structure.

    PubMed

    Carroll, Nick J; Crowder, Peter F; Pylypenko, Svitlana; Patterson, Wendy; Ratnaweera, Dilru R; Perahia, Dvora; Atanassov, Plamen; Petsev, Dimiter N

    2013-05-01

    Particles with hierarchical porosity can be formed by templating silica microparticles with a specially designed surfactant micelle/oil nanoemulsion mixture. The nanoemulsion oil droplet and micellar dimensions determine the pore size distribution: one set of pores with diameters of tens of nanometers coexisting with a second subset of pores with diameters of single nanometers. Further practical utility of these nanoporous particles requires precise tailoring of the hierarchical pore structure. In this synthesis study, the particle nanostructure is tuned by adjusting the oil, water, and surfactant mixture composition for the controlled design of nanoemulsion-templated features. We also demonstrate control of the size distribution and surface area of the smaller micelle-templated pores as a consequence of altering the hydrophobic chain length of the molecular surfactant template. Moreover, a microfluidic system is designed to process the low interfacial system for fabrication of monodisperse porous particles. The ability to direct the assembly of template nanoemulsion and micelle structures creates new opportunities to engineer hierarchically porous particles for utility as electrocatalysts for fuel cells, chromatography separations, drug delivery vehicles, and other applications. PMID:23387998

  20. Sequential structural and optical evolution of MoS2 by chemical synthesis and exfoliation

    NASA Astrophysics Data System (ADS)

    Kim, Ju Hwan; Kim, Jungkil; Oh, Si Duck; Kim, Sung; Choi, Suk-Ho

    2015-06-01

    Various types of MoS2 structures are successfully obtained by using economical and facile sequential synthesis and exfoliation methods. Spherically-shaped lumps of multilayer (ML) MoS2 are prepared by using a conventional hydrothermal method and were subsequently 1st-exfoliated in hydrazine while being kept in autoclave to be unrolled and separated into five-to-six-layer MoS2 pieces of several-hundred nm in size. The MoS2 MLs are 2nd-exfoliated in sodium naphthalenide under an Ar ambient to finally produce bilayer MoS2 crystals of ~100 nm. The sequential exfoliation processes downsize MoS2 laterally and reduce its number of layers. The three types of MoS2 allotropes exhibit particular optical properties corresponding to their structural differences. These results suggest that two-dimensional MoS2 crystals can be prepared by employing only chemical techniques without starting from high-pressure-synthesized bulk MoS2 crystals.