Science.gov

Sample records for engineering structures iii

  1. Molecular beam epitaxy engineered III-V semiconductor structures for low-power optically addressed spatial light modulators

    NASA Technical Reports Server (NTRS)

    Larsson, Anders G.; Maserjian, Joseph

    1992-01-01

    Device approaches are investigated for optically addressed SLMs based on molecular-beam epitaxy (MBE) engineered III-V materials and structures. Strong photooptic effects can be achieved in periodically delta-doped multiple-quantum-well structures, but are still insufficient for high-contrast modulation with only single- or double-pass absorption through active layers of practical thickness. The asymmetric Fabry-Perot cavity approach is employed to permit extinction of light due to interference of light reflected from the front and back surfaces of the cavity. This approach is realized with an all-MBE-grown structure consisting of GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror and the GaAs surface as the low reflectance mirror. High-contrast modulation is achieved using a low-power InGaAs/GaAs quantum well laser for the control signal.

  2. Structural and dynamic properties that govern the stability of an engineered fibronectin type III domain.

    PubMed

    Porebski, Benjamin T; Nickson, Adrian A; Hoke, David E; Hunter, Morag R; Zhu, Liguang; McGowan, Sheena; Webb, Geoffrey I; Buckle, Ashley M

    2015-03-01

    Consensus protein design is a rapid and reliable technique for the improvement of protein stability, which relies on the use of homologous protein sequences. To enhance the stability of a fibronectin type III (FN3) domain, consensus design was employed using an alignment of 2123 sequences. The resulting FN3 domain, FN3con, has unprecedented stability, with a melting temperature >100°C, a ΔG(D-N) of 15.5 kcal mol(-1) and a greatly reduced unfolding rate compared with wild-type. To determine the underlying molecular basis for stability, an X-ray crystal structure of FN3con was determined to 2.0 Å and compared with other FN3 domains of varying stabilities. The structure of FN3con reveals significantly increased salt bridge interactions that are cooperatively networked, and a highly optimized hydrophobic core. Molecular dynamics simulations of FN3con and comparison structures show the cooperative power of electrostatic and hydrophobic networks in improving FN3con stability. Taken together, our data reveal that FN3con stability does not result from a single mechanism, but rather the combination of several features and the removal of non-conserved, unfavorable interactions. The large number of sequences employed in this study has most likely enhanced the robustness of the consensus design, which is now possible due to the increased sequence availability in the post-genomic era. These studies increase our knowledge of the molecular mechanisms that govern stability and demonstrate the rising potential for enhancing stability via the consensus method.

  3. Structural and dynamic properties that govern the stability of an engineered fibronectin type III domain

    PubMed Central

    Porebski, Benjamin T.; Nickson, Adrian A.; Hoke, David E.; Hunter, Morag R.; Zhu, Liguang; McGowan, Sheena; Webb, Geoffrey I.; Buckle, Ashley M.

    2015-01-01

    Consensus protein design is a rapid and reliable technique for the improvement of protein stability, which relies on the use of homologous protein sequences. To enhance the stability of a fibronectin type III (FN3) domain, consensus design was employed using an alignment of 2123 sequences. The resulting FN3 domain, FN3con, has unprecedented stability, with a melting temperature >100°C, a ΔGD−N of 15.5 kcal mol−1 and a greatly reduced unfolding rate compared with wild-type. To determine the underlying molecular basis for stability, an X-ray crystal structure of FN3con was determined to 2.0 Å and compared with other FN3 domains of varying stabilities. The structure of FN3con reveals significantly increased salt bridge interactions that are cooperatively networked, and a highly optimized hydrophobic core. Molecular dynamics simulations of FN3con and comparison structures show the cooperative power of electrostatic and hydrophobic networks in improving FN3con stability. Taken together, our data reveal that FN3con stability does not result from a single mechanism, but rather the combination of several features and the removal of non-conserved, unfavorable interactions. The large number of sequences employed in this study has most likely enhanced the robustness of the consensus design, which is now possible due to the increased sequence availability in the post-genomic era. These studies increase our knowledge of the molecular mechanisms that govern stability and demonstrate the rising potential for enhancing stability via the consensus method. PMID:25691761

  4. NIF Title III engineering plan

    SciTech Connect

    Deis, G

    1998-06-01

    The purpose of this document is to define the work that must be accomplished by the NIF Project during Title III Engineering. This definition is intended to be sufficiently detailed to provide a framework for yearly planning, to clearly identify the specific deliverables so that the Project teams can focus on them, and to provide a common set of objectives and processes across the Project. This plan has been preceded by similar documents for Title I and Title II design and complements the Site Management Plan, the Project Control Manual, the Quality Assurance Program Plan, the RM Parsons NIF Title III Configuration Control Plan, the Integrated Project Schedule, the Preliminary Safety Analysis Report, the Configuration Management Plan, and the Transition Plan.

  5. Structural Engineering: Overview

    NASA Technical Reports Server (NTRS)

    Castro, Edgar

    2011-01-01

    This slide presentation presents the work of the Structural Engineering Division of the Engineering Directorate. The work includes: providing technical expertise and leadership for the development, evaluation, and operation of structural, mechanical, and thermal spaceflight systems.

  6. Engineering design of ARIES-III

    SciTech Connect

    Sze, D.K.; Wong, C.; Cheng, E.

    1993-07-01

    An efficient organic cooled low activation ferritic steel first wall and shield has been designed for the D-{sup 3}He power reactor ARIES-III. The design allows removal of the large surface heat load without exceeding temperature and stress design limits. The structure is expected to last for the whole reactor life. The major concerns regarding using the organic coolant in fusion reactors have been greatly alleviated.

  7. VIPR III VADR SPIDER Structural Design and Analysis

    NASA Technical Reports Server (NTRS)

    Li, Wesley; Chen, Tony

    2016-01-01

    In support of the National Aeronautics and Space Administration (NASA) Vehicle Integrated Propulsion Research (VIPR) Phase III team to evaluate the volcanic ash environment effects on the Pratt & Whitney F117-PW-100 turbofan engine, NASA Armstrong Flight Research Center has successfully performed structural design and analysis on the Volcanic Ash Distribution Rig (VADR) and the Structural Particulate Integration Device for Engine Research (SPIDER) for the ash ingestion test. Static and dynamic load analyses were performed to ensure no structural failure would occur during the test. Modal analysis was conducted, and the results were used to develop engine power setting avoidance zones. These engine power setting avoidance zones were defined to minimize the dwell time when the natural frequencies of the VADR/SPIDER system coincided with the excitation frequencies of the engine which was operating at various revolutions per minute. Vortex-induced vibration due to engine suction air flow during the ingestion test was also evaluated, but was not a concern.

  8. Computer Education for Engineers, Part III.

    ERIC Educational Resources Information Center

    McCullough, Earl S.; Lofy, Frank J.

    1989-01-01

    Reports the results of the third survey of computer use in engineering education conducted in the fall of 1987 in comparing with 1981 and 1984 results. Summarizes survey data on computer course credits, languages, equipment use, CAD/CAM instruction, faculty access, and computer graphics. (YP)

  9. Computational engine structural analysis

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Johns, R. H.

    1986-01-01

    A significant research activity at the NASA Lewis Research Center is the computational simulation of complex multidisciplinary engine structural problems. This simulation is performed using computational engine structural analysis (CESA) which consists of integrated multidisciplinary computer codes in conjunction with computer post-processing for problem-specific application. A variety of the computational simulations of specific cases are described in some detail in this paper. These case studies include: (1) aeroelastic behavior of bladed rotors, (2) high velocity impact of fan blades, (3) blade-loss transient response, (4) rotor/stator/squeeze-film/bearing interaction, (5) blade-fragment/rotor-burst containment, and (6) structural behavior of advanced swept turboprops. These representative case studies are selected to demonstrate the breath of the problems analyzed and the role of the computer including post-processing and graphical display of voluminous output data.

  10. Structural characterization of Spinacia oleracea trypsin inhibitor III (SOTI-III).

    PubMed

    Glotzbach, Bernhard; Schmelz, Stefan; Reinwarth, Michael; Christmann, Andreas; Heinz, Dirk W; Kolmar, Harald

    2013-01-01

    In recent decades, several canonical serine protease inhibitor families have been classified and characterized. In contrast to most trypsin inhibitors, those from garden four o'clock (Mirabilis jalapa) and spinach (Spinacia oleracea) do not share sequence similarity and have been proposed to form the new Mirabilis serine protease inhibitor family. These 30-40-amino-acid inhibitors possess a defined disulfide-bridge topology and belong to the cystine-knot miniproteins (knottins). To date, no atomic structure of this inhibitor family has been solved. Here, the first structure of S. oleracea trypsin inhibitor III (SOTI-III), in complex with bovine pancreatic trypsin, is reported. The inhibitor was synthesized by solid-phase peptide synthesis on a multi-milligram scale and was assayed to test its inhibitory activity and binding properties. The structure confirmed the proposed cystine-bridge topology. The structural features of SOTI-III suggest that it belongs to a new canonical serine protease inhibitor family with promising properties for use in protein-engineering and medical applications.

  11. The crystal structure of methane phase III

    NASA Astrophysics Data System (ADS)

    Neumann, Marcus A.; Press, Werner; Nöldeke, Christian; Asmussen, Bernd; Prager, Michael; Ibberson, Richard M.

    2003-07-01

    Methane is the simplest organic molecule, and like many supposedly simple molecular materials it has a rich phase diagram. While crystal structures could be determined for two of the solid phases, that of the low temperature phase III remained unsolved. Using high-resolution neutron powder diffraction and a direct-space Monte Carlo simulated annealing approach, this fundamental structure has now finally been solved. It is orthorhombic with space group Cmca, and 16 molecules in the unit cell. The structure is closely related to that of phase II, yet is no subgroup of it.

  12. Computational structural mechanics for engine structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1989-01-01

    The computational structural mechanics (CSM) program at Lewis encompasses: (1) fundamental aspects for formulating and solving structural mechanics problems, and (2) development of integrated software systems to computationally simulate the performance/durability/life of engine structures. It is structured to mainly supplement, complement, and whenever possible replace, costly experimental efforts which are unavoidable during engineering research and development programs. Specific objectives include: investigate unique advantages of parallel and multiprocesses for: reformulating/solving structural mechanics and formulating/solving multidisciplinary mechanics and develop integrated structural system computational simulators for: predicting structural performances, evaluating newly developed methods, and for identifying and prioritizing improved/missing methods needed. Herein the CSM program is summarized with emphasis on the Engine Structures Computational Simulator (ESCS). Typical results obtained using ESCS are described to illustrate its versatility.

  13. Structural Characterization of Sm(III)(EDTMP).

    PubMed

    Yang, Y; Pushie, M J; Cooper, D M L; Doschak, M R

    2015-11-01

    Samarium-153 ethylenediamine-N,N,N',N'-tetrakis(methylenephosphonic acid) ((153)Sm-EDTMP, or samarium lexidronam), also known by its registered trademark name Quadramet, is an approved therapeutic radiopharmaceutical used in the palliative treatment of painful bone metastases. Typically, patients with prostate, breast, or lung cancer are most likely to go on to require bone pain palliation treatment due to bone metastases. Sm(EDTMP) is a bone-seeking drug which accumulates on rapidly growing bone, thereby delivering a highly region-specific dose of radiation, chiefly through β particle emission. Even with its widespread clinical use, the structure of Sm(EDTMP) has not yet been characterized at atomic resolution, despite attempts to crystallize the complex. Herein, we prepared a 1:1 complex of the cold (stable isotope) of Sm(EDTMP) under alkaline conditions and then isolated and characterized the complex using conventional spectroscopic techniques, as well as with extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional structure calculations, using natural abundance Sm. We present the atomic resolution structure of [Sm(III)(EDTMP)-8H](5-) for the first time, supported by the EXAFS data and complementary spectroscopic techniques, which demonstrate that the samarium coordination environment in solution is in agreement with the structure that has long been conjectured.

  14. Engine Structural Analysis Software

    NASA Technical Reports Server (NTRS)

    McKnight, R. L.; Maffeo, R. J.; Schrantz, S.; Hartle, M. S.; Bechtel, G. S.; Lewis, K.; Ridgway, M.; Chamis, Christos C. (Technical Monitor)

    2001-01-01

    The report describes the technical effort to develop: (1) geometry recipes for nozzles, inlets, disks, frames, shafts, and ducts in finite element form, (2) component design tools for nozzles, inlets, disks, frames, shafts, and ducts which utilize the recipes and (3) an integrated design tool which combines the simulations of the nozzles, inlets, disks, frames, shafts, and ducts with the previously developed combustor, turbine blade, and turbine vane models for a total engine representation. These developments will be accomplished in cooperation and in conjunction with comparable efforts of NASA Glenn Research Center.

  15. Monitoring of civil engineering structures

    NASA Astrophysics Data System (ADS)

    Tyrsa, Valentin E.; Burtseva, Larisa P.; Rivas Lopez, Moises; Tyrsa, Vera V.

    2004-07-01

    Civil engineering structures require geometrical monitoring to assure their integrity during their life time. The monitoring by geodetic devices or according to GPS technology is not always appropriate, sometimes it is unrealizable. Means for monitoring based on automatic geodetic measurements applying optical scanners are proposed. The sensor for integrity and deformation control of the structure elements and components was designed.

  16. The Structure-Mapping Engine.

    ERIC Educational Resources Information Center

    Falkenhainer, Brian; And Others

    This paper describes the Structure-Mapping Engine (SME), a cognitive simulation program for studying human analogical processing. SME is based on Gentner's Structure-Mapping theory of analogy, and provides a "tool kit" for constructing matching algorithms consistent with this theory. This flexibility enhances cognitive simulation studies by…

  17. Military engine computational structures technology

    NASA Technical Reports Server (NTRS)

    Thomson, Daniel E.

    1992-01-01

    Integrated High Performance Turbine Engine Technology Initiative (IHPTET) goals require a strong analytical base. Effective analysis of composite materials is critical to life analysis and structural optimization. Accurate life prediction for all material systems is critical. User friendly systems are also desirable. Post processing of results is very important. The IHPTET goal is to double turbine engine propulsion capability by the year 2003. Fifty percent of the goal will come from advanced materials and structures, the other 50 percent will come from increasing performance. Computer programs are listed.

  18. Structural and photophysical studies on ternary Sm(III), Nd(III), Yb(III), Er(III) complexes containing pyridyltriazole ligands

    PubMed Central

    Gusev, Alexey N.; Shul’gin, Victor F.; Meshkova, Svetlana B.; Hasegawa, Miki; Alexandrov, Grigory G.; Eremenko, Igor L.; Linert, Wolfgang

    2012-01-01

    Two bidentate pyridine-triazole ligands (3-(pyridine-2-yl)-5-phenyl-1,2,4-triazole (L1) and 5-phenyl-2-(2′-pyridyl)-7,8-benzo-6,5-dihydro-1,3,6-triazaindolizine (L2)), have been synthesized and used for Ln(Dbm)3 (Ln = Sm(III), Nd(III), Yb(III) and Er(III)) coordination. The structures of the ligands and resulting Sm(III) complex were determined in the solid state by X-ray diffraction. The title complexes were characterized by UV, fluorescent, IR-spectroscopy and thermogravimetric and elemental analyses. Photophysical studies on the Ln(III) complexes were carried out showing luminescence in the region typical for Ln(III). The effect of various factors on the enhancement luminescence of complexes is discussed. PMID:23470984

  19. High temperature turbine engine structure

    DOEpatents

    Boyd, Gary L.

    1991-01-01

    A high temperature turbine engine includes a rotor portion having axially stacked adjacent ceramic rotor parts. A ceramic/ceramic joint structure transmits torque between the rotor parts while maintaining coaxial alignment and axially spaced mutually parallel relation thereof despite thermal and centrifugal cycling.

  20. High temperature turbine engine structure

    DOEpatents

    Boyd, Gary L.

    1990-01-01

    A high temperature turbine engine includes a hybrid ceramic/metallic rotor member having ceramic/metal joint structure. The disclosed joint is able to endure higher temperatures than previously possible, and aids in controlling heat transfer in the rotor member.

  1. Fracture Control in Engineering Structures

    NASA Astrophysics Data System (ADS)

    Weatherly, G. C.

    1980-07-01

    The three-day meeting "Fracture Control in Engineering Structures" was held at the 1979 C.I.M. Annual Conference of Metallurgists in Sudbury, Ontario, August 19-21, 1979. The meeting was organized by the Materials Engineering Section of C.I.M. and the Canadian Fracture Research Committee (CFRC), a non-profit organization and the national arm of the International Congress on Fracture. The objectives of CFRC are to promote research and conferences in Canada on the Strength & Fracture of Materials. To this end, CFRC holds (sometimes jointly) conferences every year.

  2. Automotive Stirling Engine Mod I design review report. Volume III

    SciTech Connect

    Not Available

    1982-08-01

    This volume, No. 3, of the Automotive Stirling Engine Mod 1 Design Review Report contains a preliminary parts list and detailed drawings of equipment for the basic Stirling engine and for the following systems: vehicular Stirling Engine System; external heat system; hot and cold engine systems; engine drive; controls and auxiliaries; and vehicle integration. (LCL)

  3. Biochemical and Structural Properties of Mouse Kynurenine Aminotransferase III

    SciTech Connect

    Han, Q.; Robinson, H; Cai, T; Tagle, D; Li, J

    2009-01-01

    Kynurenine aminotransferase III (KAT III) has been considered to be involved in the production of mammalian brain kynurenic acid (KYNA), which plays an important role in protecting neurons from overstimulation by excitatory neurotransmitters. The enzyme was identified based on its high sequence identity with mammalian KAT I, but its activity toward kynurenine and its structural characteristics have not been established. In this study, the biochemical and structural properties of mouse KAT III (mKAT III) were determined. Specifically, mKAT III cDNA was amplified from a mouse brain cDNA library, and its recombinant protein was expressed in an insect cell protein expression system. We established that mKAT III is able to efficiently catalyze the transamination of kynurenine to KYNA and has optimum activity at relatively basic conditions of around pH 9.0 and at relatively high temperatures of 50 to 60C. In addition, mKAT III is active toward a number of other amino acids. Its activity toward kynurenine is significantly decreased in the presence of methionine, histidine, glutamine, leucine, cysteine, and 3-hydroxykynurenine. Through macromolecular crystallography, we determined the mKAT III crystal structure and its structures in complex with kynurenine and glutamine. Structural analysis revealed the overall architecture of mKAT III and its cofactor binding site and active center residues. This is the first report concerning the biochemical characteristics and crystal structures of KAT III enzymes and provides a basis toward understanding the overall physiological role of mammalian KAT III in vivo and insight into regulating the levels of endogenous KYNA through modulation of the enzyme in the mouse brain.

  4. Molecular structures of unbound and transcribing RNA polymerase III

    PubMed Central

    Hoffmann, Niklas A.; Jakobi, Arjen J.; Moreno-Morcillo, Maria; Glatt, Sebastian; Kosinski, Jan; Hagen, Wim J. H.; Sachse, Carsten; Müller, Christoph W.

    2015-01-01

    Transcription of genes encoding small structured RNAs such as tRNAs, spliceosomal U6 snRNA and ribosomal 5S RNA is carried out by RNA polymerase III (Pol III), the largest yet structurally least characterized eukaryotic RNA polymerase. The cryo-EM structures of the S. cerevisiae Pol III elongating complex at 3.9 Å resolution and the apo Pol III enzyme in two different conformations at 4.6 and 4.7 Å resolution, respectively, allow for the first time to build a 17-subunit atomic model of Pol III. The reconstructions reveal the precise orientation of the C82/C34/C31 heterotrimer in close proximity to the stalk. The C53/C37 heterodimer positions residues involved in transcription termination close to the non-template DNA strand. In the apo Pol III structures, the stalk adopts different orientations coupled with closed and open conformations of the clamp. Our results provide novel insights into Pol III-specific transcription and the adaptation of Pol III towards its small transcriptional targets. PMID:26605533

  5. Synthesis, crystal structure and magnetism of iron(III) and manganese(III) dipicolinates with pyridinemethanols

    NASA Astrophysics Data System (ADS)

    Uhrecký, Róbert; Pavlik, Ján; Růžičková, Zdeňka; Dlháň, Ľubor; Koman, Marian; Boča, Roman; Moncoľ, Ján

    2014-11-01

    Four ionic iron(III) and manganese(III) dipicolinato complexes of the formula (2-pymeH) [FeIII(dipic)2]ṡ[FeIII(H2O)2Cl(dipic)]ṡ2H2O, (3-pymeH)[MnIII(dipic)2]ṡ1.5H2O, (4-pymeH)[FeIII(dipic)2]ṡ2H2O and (4-pymeH)[MnIII(dipic)2]ṡ2H2O, where H2dipic = pyridine-2,6-dicarboxylic acid, 2-pyme = 2-pyridinemethanol, 3-pyme = 3-pyridinemethanol, 4-pyme = 4-pyridinemethanol, have been prepared and characterized by the single-crystal X-ray structure analysis, infrared spectroscopy and magnetic measurements. The magnetic data were fitted to a zero-field splitting model revealing a slight magnetic anisotropy for Mn(III) systems. The molecular field correction was consistently formulated and included in the analysis for both, magnetic susceptibility and magnetization data.

  6. Engine Structures Modeling Software System (ESMOSS)

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Engine Structures Modeling Software System (ESMOSS) is the development of a specialized software system for the construction of geometric descriptive and discrete analytical models of engine parts, components, and substructures which can be transferred to finite element analysis programs such as NASTRAN. The NASA Lewis Engine Structures Program is concerned with the development of technology for the rational structural design and analysis of advanced gas turbine engines with emphasis on advanced structural analysis, structural dynamics, structural aspects of aeroelasticity, and life prediction. Fundamental and common to all of these developments is the need for geometric and analytical model descriptions at various engine assembly levels which are generated using ESMOSS.

  7. 19-Tungstodiarsenate(III) Functionalized by Organoantimony(III) Groups: Tuning the Structure-Bioactivity Relationship.

    PubMed

    Yang, Peng; Lin, Zhengguo; Alfaro-Espinoza, Gabriela; Ullrich, Matthias S; Raţ, Ciprian I; Silvestru, Cristian; Kortz, Ulrich

    2016-01-01

    A family of three discrete organoantimony(III)-functionalized heteropolyanions-[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)](10-) (1), [{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)](8-) (2), and [{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2](14-) (3)-have been prepared by one-pot reactions of the 19-tungstodiarsenate(III) precursor [As(III)2W19O67(H2O)](14-) with 2-(Me2NCH2)C6H4SbCl2. The three novel polyanions crystallized as the hydrated mixed-alkali salts Cs3KNa6[Na{2-(Me2HN(+)CH2)C6H4Sb(III)}As(III)2W19O67(H2O)]·43H2O (CsKNa-1), Rb2.5K5.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}2As(III)2W19O67(H2O)]·18H2O·Me2NCH2C6H5 (RbK-2), and Rb2.5K11.5[{2-(Me2HN(+)CH2)C6H4Sb(III)}{WO2(H2O)}{WO(H2O)}2(B-β-As(III)W8O30)(B-α-As(III)W9O33)2]·52H2O (RbK-3), respectively. The number of incorporated {2-(Me2HN(+)CH2)C6H4Sb(III)} units could be tuned by careful control of the experimental parameters. Polyanions 1 and 2 possess a dimeric sandwich-type topology, whereas 3 features a trimeric, wheel-shaped structure, representing the largest organoantimony-containing polyanion. All three compounds were fully characterized in the solid state via single-crystal X-ray diffraction (XRD), infrared (IR) spectroscopy, and thermogravimetric analysis, and their aqueous solution stability was validated by ultraviolet-visible light (UV-vis) and multinuclear ((1)H, (13)C, and (183)W) nuclear magnetic resonance (NMR) spectroscopy. Effective inhibition against six different types of bacteria was observed for 1 and 2, and we could extract a structure-bioactivity relationship for these polyanions.

  8. Heterotrimetallic coordination polymers: {Cu(II)Ln(III)Fe(III)} chains and {Ni(II)Ln(III)Fe(III)} layers: synthesis, crystal structures, and magnetic properties.

    PubMed

    Alexandru, Maria-Gabriela; Visinescu, Diana; Andruh, Marius; Marino, Nadia; Armentano, Donatella; Cano, Joan; Lloret, Francesc; Julve, Miguel

    2015-03-27

    The use of the [Fe(III) (AA)(CN)4](-) complex anion as metalloligand towards the preformed [Cu(II) (valpn)Ln(III)](3+) or [Ni(II) (valpn)Ln(III) ](3+) heterometallic complex cations (AA=2,2'-bipyridine (bipy) and 1,10-phenathroline (phen); H2 valpn=1,3-propanediyl-bis(2-iminomethylene-6-methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu(II) (valpn)Ln(III) (H2O)3 (μ-NC)2 Fe(III) (phen)(CN)2 {(μ-NC)Fe(III) (phen)(CN)3}]NO3 ⋅7 H2O}n (Ln=Gd (1), Tb (2), and Dy (3)) and the trinuclear complex [Cu(II) (valpn)La(III) (OH2 )3 (O2 NO)(μ-NC)Fe(III) (phen)(CN)3 ]⋅NO3 ⋅H2O⋅CH3 CN (4) were obtained with the [Cu(II) (valpn)Ln(III)](3+) assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni(II) (valpn)Ln(III) (ONO2 )2 (H2 O)(μ-NC)3 Fe(III) (bipy)(CN)]⋅2 H2 O⋅2 CH3 CN}n (Ln=Gd (5), Tb (6), and Dy (7)) resulted with the related [Ni(II) (valpn)Ln(III) ](3+) precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu(II) (valpn)La(III) (OH2)3 (O2 NO)(μ-NC)Fe(III) (phen)(CN)3 ](+), nitrate counterions, and non-coordinate water and acetonitrile molecules. The heteroleptic {Fe(III) (bipy)(CN)4} moiety in 5-7 acts as a tris-monodentate ligand towards three {Ni(II) (valpn)Ln(III)} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu(II)-Ln(III) (1-3) and Ni(II)-Ln(III) (5-7) units, as well as through the single cyanide bridge between the Fe(III) and either Ni(II) (5-7) or Cu(II) (4) account for the overall ferromagnetic behavior observed in 1-7. DFT-type calculations were performed to substantiate the magnetic interactions in 1, 4, and 5. Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out-of-phase ac signals below 4.0 K in the lack of a dc field, the values of the pre

  9. Synthesis and Structural Studies of Gallium(III) and Iron(III) Hemicryptophane Complexes.

    PubMed

    Gosse, Isabelle; Robeyns, Koen; Bougault, Catherine; Martinez, Alexandre; Tinant, Bernard; Dutasta, Jean-Pierre

    2016-02-01

    New gallium(III) and iron(III) endohedral complexes were obtained from a hemicryptophane ligand bearing suitable binding sites for octahedral metal coordination. The solid-state structures of the free host and of the complexes were determined by single-crystal X-ray diffraction analysis. The metal ion is linked to the hydrazone nitrogen and the phenolate oxygen atoms, yielding a distorted octahedral geometry around the encapsulated metal. The two isomorphous structures of the metal complexes reveal the exclusive formation of PΔ/MΛ enantiomeric pairs.

  10. The Mathematical Disposition of Structural Engineers

    ERIC Educational Resources Information Center

    Gainsburg, Julie

    2007-01-01

    This ethnographic study investigated the mathematical disposition of engineers. Structural engineers in two firms were observed in everyday practice. Observation and interview data were analyzed to elucidate the role of mathematics in solving engineering problems and the engineers' perceptions of the status of mathematics relative to other…

  11. Rotation and internal structure of Population III protostars

    NASA Astrophysics Data System (ADS)

    Stacy, Athena; Greif, Thomas H.; Klessen, Ralf S.; Bromm, Volker; Loeb, Abraham

    2013-05-01

    We analyse the cosmological simulations performed in the recent work of Greif et al., which followed the early growth and merger history of Population III (Pop III) stars while resolving scales as small as 0.05 R⊙. This is the first set of cosmological simulations to self-consistently resolve the rotation and internal structure of Pop III protostars. We find that Pop III stars form under significant rotational support which is maintained for the duration of the simulations. The protostellar surfaces spin from ˜50 per cent to nearly 100 per cent of Keplerian rotational velocity. These rotation rates persist after experiencing multiple stellar merger events. In the brief time period simulated (˜10 yr), the protostars show little indication of convective instability, and their properties furthermore show little correlation with the properties of their host minihaloes. If Pop III protostars within this range of environments generally form with high degrees of rotational support, and if this rotational support is maintained for a sufficient amount of time, this has a number of crucial implications for Pop III evolution and nucleosynthesis, as well as the possibility for Pop III pair-instability supernovae, and the question of whether the first stars produced gamma-ray bursts.

  12. High temperature turbine engine structure

    DOEpatents

    Carruthers, William D.; Boyd, Gary L.

    1993-01-01

    A high temperature ceramic/metallic turbine engine includes a metallic housing which journals a rotor member of the turbine engine. A ceramic disk-like shroud portion of the engine is supported on the metallic housing portion and maintains a close running clearance with the rotor member. A ceramic spacer assembly maintains the close running clearance of the shroud portion and rotor member despite differential thermal movements between the shroud portion and metallic housing portion.

  13. High temperature turbine engine structure

    DOEpatents

    Carruthers, William D.; Boyd, Gary L.

    1994-01-01

    A high temperature ceramic/metallic turbine engine includes a metallic housing which journals a rotor member of the turbine engine. A ceramic disk-like shroud portion of the engine is supported on the metallic housing portion and maintains a close running clearance with the rotor member. A ceramic spacer assembly maintains the close running clearance of the shroud portion and rotor member despite differential thermal movements between the shroud portion and metallic housing portion.

  14. High temperature turbine engine structure

    DOEpatents

    Carruthers, William D.; Boyd, Gary L.

    1992-01-01

    A high temperature ceramic/metallic turbine engine includes a metallic housing which journals a rotor member of the turbine engine. A ceramic disk-like shroud portion of the engine is supported on the metallic housing portion and maintains a close running clearance with the rotor member. A ceramic spacer assembly maintains the close running clearance of the shroud portion and rotor member despite differential thermal movements between the shroud portion and metallic housing portion.

  15. Structure of internal combustion engine

    SciTech Connect

    Nakamura, N.; Endo, H.; Oshio, S.; Ebisudani, T.; Ito, M.; Mizukami, T.; Kishimoto, M.

    1988-09-20

    This patent describes a structure of internal combustion engine, comprising a cylinder member formed with a cylinder which demarcates a combustion chamber in cooperation with a piston connected with a crankshaft, a crankcase provided in succession with the lower end of the cylinder member to accommodate the crankshaft, a valve actuating mechanism actuating valves provided in the combustion chamber in response to rotation of the crankshaft, at least a part of the valve actuating mechanism being accommodated in a rocker case provided on the upper end of the cylinder member, an oil return passage constituting means opening at one end into the rocker case, the other end being open into the crankcase at one side which is partitioned by a plane containing the cylinder axis of the cylinder member and the axis of the crankshaft and is occupied by a crank pin of the crankshaft when the piston rises, thereby constituting a passage for leading oil in the rocker case into the crankcase, and a restraining means provided in relation to the oil return passage constituting means so that an air flow around the axis of the crankshaft within the crankcase owing to the rotation of the crankshaft is restrained from entering into the passage through the opening of the other end.

  16. Outer planet probe engineering model structural tests

    NASA Technical Reports Server (NTRS)

    Smittkamp, J. A.; Gustin, W. H.; Griffin, M. W.

    1977-01-01

    A series of proof of concept structural tests was performed on an engineering model of the Outer Planets Atmospheric Entry Probe. The tests consisted of pyrotechnic shock, dynamic and static loadings. The tests partially verified the structural concept.

  17. Double Sided Si(Ge)/Sapphire/III-Nitride Hybrid Structure

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor)

    2016-01-01

    One aspect of the present invention is a double sided hybrid crystal structure including a trigonal Sapphire wafer containing a (0001) C-plane and having front and rear sides. The Sapphire wafer is substantially transparent to light in the visible and infrared spectra, and also provides insulation with respect to electromagnetic radio frequency noise. A layer of crystalline Si material having a cubic diamond structure aligned with the cubic <111> direction on the (0001) C-plane and strained as rhombohedron to thereby enable continuous integration of a selected (SiGe) device onto the rear side of the Sapphire wafer. The double sided hybrid crystal structure further includes an integrated III-Nitride crystalline layer on the front side of the Sapphire wafer that enables continuous integration of a selected III-Nitride device on the front side of the Sapphire wafer.

  18. Engineered Magnetic Core-Shell Structures.

    PubMed

    Alavi Nikje, Mir Mohammad; Vakili, Maryam

    2015-01-01

    In recent years, engineered magnetic core-shell structures are playing an important role in the wide range of various applications. These magnetic core-shell structures have attracted considerable attention because of their unique properties and various applications. Also, the synthesis of engineered magnetic core-shell structures has attracted practical interest because of potential applications in areas such as ferrofluids, medical imaging, drug targeting and delivery, cancer therapy, separations, and catalysis. So far a large number of engineered magnetic core-shell structures have been successfully synthesized. This review article focuses on the recent progress in synthesis and characterization of engineered magnetic core-shell structures. Also, this review gives a brief description of the various application of these structures. It is hoped that this review will play some small part in helping future developments in important field. PMID:26377655

  19. Synthesis and structural characterization of new dithiocarbamate complexes from Sb(III) and Bi(III)

    NASA Astrophysics Data System (ADS)

    Jamaluddin, Nur Amirah; Baba, Ibrahim

    2013-11-01

    Twenty new antimony and bismuth dithiocarbamate complexes which employed ten different type of amines have been successfully synthesized. The synthesized complexes with metal to dithiocarbamate ratio at 1:3. Elemental analysis of the complexes gave the general formula of MCl[S2CNR'R"]2 where M = Sb(III), Bi(III); R' = methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, benzyl; R" = ethanol, methyl, ethyl, propyl, isopropyl, cyclohexyl, benzyl. The complexes were analysed by IR and NMR spectroscopy. The crystal structure of five-coordinated antimony (III) complex have been determined by X-ray single crystal diffraction. Single crystal X-ray diffraction studies on SbCl[S2CN(C4H9)(C2H5)]2 adopted a triclinic system with a space group P1 with a = 10.0141(8) Å, b = 10.1394(7) Å, c = 11.8665(9) Å, α = 67.960°, β =87.616°, γ = 80.172°.

  20. Synthesis and structural characterization of new dithiocarbamate complexes from Sb(III) and Bi(III)

    SciTech Connect

    Jamaluddin, Nur Amirah; Baba, Ibrahim

    2013-11-27

    Twenty new antimony and bismuth dithiocarbamate complexes which employed ten different type of amines have been successfully synthesized. The synthesized complexes with metal to dithiocarbamate ratio at 1:3. Elemental analysis of the complexes gave the general formula of MCl[S{sub 2}CNR’R”]{sub 2} where M = Sb(III), Bi(III); R’ = methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, benzyl; R” = ethanol, methyl, ethyl, propyl, isopropyl, cyclohexyl, benzyl. The complexes were analysed by IR and NMR spectroscopy. The crystal structure of five-coordinated antimony (III) complex have been determined by X-ray single crystal diffraction. Single crystal X-ray diffraction studies on SbCl[S{sub 2}CN(C{sub 4}H{sub 9})(C{sub 2}H{sub 5})]{sub 2} adopted a triclinic system with a space group P1 with a = 10.0141(8) Å, b = 10.1394(7) Å, c = 11.8665(9) Å, α = 67.960°, β =87.616°, γ = 80.172°.

  1. Identification of Extremely Large Scale Structures in SDSS-III

    NASA Astrophysics Data System (ADS)

    Sankhyayan, Shishir; Bagchi, J.; Sarkar, P.; Sahni, V.; Jacob, J.

    2016-10-01

    We have initiated the search and detailed study of large scale structures present in the universe using galaxy redshift surveys. In this process, we take the volume-limited sample of galaxies from Sloan Digital Sky Survey III and find very large structures even beyond the redshift of 0.2. One of the structures is even greater than 600 Mpc which raises a question on the homogeneity scale of the universe. The shapes of voids-structures (adjacent to each other) seem to be correlated, which supports the physical existence of the observed structures. The other observational supports include galaxy clusters' and QSO distribution's correlation with the density peaks of the volume limited sample of galaxies.

  2. Structural tailoring of engine blades (STAEBL)

    NASA Technical Reports Server (NTRS)

    Platt, C. E.; Pratt, T. K.; Brown, K. W.

    1982-01-01

    A mathematical optimization procedure was developed for the structural tailoring of engine blades and was used to structurally tailor two engine fan blades constructed of composite materials without midspan shrouds. The first was a solid blade made from superhybrid composites, and the second was a hollow blade with metal matrix composite inlays. Three major computerized functions were needed to complete the procedure: approximate analysis with the established input variables, optimization of an objective function, and refined analysis for design verification.

  3. Design and Development of Stress Engineering Techniques for III-Nitride Epitaxy on Si

    NASA Astrophysics Data System (ADS)

    Leathersich, Jeff

    III-Nitrides have been a heavily researched material system for decades. Their material properties are favorable for a number of applications, most commonly in the optoelectronic and power device industry. Currently a majority of commercialized devices are fabricated on sapphire and SiC substrates but these are expensive and limit the widespread commercialization of the technology. There is substantial ongoing research geared toward the development of GaN on Si substrates because of the significant cost saving that would be realized through the inexpensive, large wafer and maturity of Si fabrication. Significant challenges with the deposition of GaN on Si have, thus far, prevented its wide-spread commercialization specifically the large lattice mismatch and thermal expansion coefficient mismatch. Both of these issues can be overcome by engineering the stress levels in the films. In this thesis work close examination and exploration of the stress formation and evolution in GaN-on-Si is performed. Methods of improving stress levels are developed in addition to providing a deeper understanding of the stress evolution process. A commonly used methodology of engineering stress levels is to use an AlGaN multi-layer stack. The first layer in the stack is an AlN buffer layer. Typical deposition methods for AlN leaves the surface rough and not ideal for subsequent epitaxy. Here, two specific modifications to the conventional deposition process are made which yield dramatic improvement in material quality and stress levels of an overgrown GaN layer. Full width at half maximum measurements from HRXRD rocking curve of GaN grown on the modified buffers show a 2x reduction and ~0.45 GPa greater built-in compressive stress in the films. A semi-empirical model to predict stress evolution in III-Nitrides is established using both fundamentals and experimental data. The model will allow researchers determine the desired stress levels in the films in advance of Epitaxy. This will

  4. Interface engineering and chemistry of Hf-based high-k dielectrics on III-V substrates

    NASA Astrophysics Data System (ADS)

    He, Gang; Chen, Xiaoshuang; Sun, Zhaoqi

    2013-03-01

    Recently, III-V materials have been extensively studied as potential candidates for post-Si complementary metal-oxide-semiconductor (CMOS) channel materials. The main obstacle to implement III-V compound semiconductors for CMOS applications is the lack of high quality and thermodynamically stable insulators with low interface trap densities. Due to their excellent thermal stability and relatively high dielectric constants, Hf-based high-k gate dielectrics have been recently highlighted as the most promising high-k dielectrics for III-V-based devices. This paper provides an overview of interface engineering and chemistry of Hf-based high-k dielectrics on III-V substrates. We begin with a survey of methods developed for generating Hf-based high-k gate dielectrics. To address the impact of these hafnium based materials, their interfaces with GaAs as well as a variety of semiconductors are discussed. After that, the integration issues are highlighted, including the development of high-k deposition without Fermi level pinning, surface passivation and interface state, and integration of novel device structure with Si technology. Finally, we conclude this review with the perspectives and outlook on the future developments in this area. This review explores the possible influences of research breakthroughs of Hf-based gate dielectrics on the current and future applications for nano-MOSFET devices.

  5. 1,2,4-Diazaphospholide complexes of yttrium(iii), dysprosium(iii), erbium(iii), and europium(ii,iii): synthesis, X-ray structural characterization, and EPR analysis.

    PubMed

    Wang, Yongli; Guo, Wenzhen; Liu, Dongling; Yang, Ying; Zheng, Wenjun

    2016-01-21

    Several structurally characterized heteroleptic, charge-separated heterobimetallic, and polymeric alkali metal ate complexes of 1,2,4-diazaphospholide Y(iii), Dy(iii), Er(iii), Eu(iii), and Eu(ii) were prepared via the reaction of MCl3 and K[3,5-R2dp] in varied ratios at 200-220 °C (M = Y, Dy, Er, Eu; R = tBu, Ph). PMID:26666366

  6. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

    Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

    1987-01-01

    Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

  7. Large Hexadecametallic {Mn(III) -Ln(III) } Wheels: Synthesis, Structural, Magnetic, and Theoretical Characterization.

    PubMed

    Vignesh, Kuduva R; Langley, Stuart K; Moubaraki, Boujemaa; Murray, Keith S; Rajaraman, Gopalan

    2015-11-01

    The synthesis, gas sorption studies, magnetic properties, and theoretical studies of new molecular wheels of core type {Mn(III) 8 Ln(III) 8 } (Ln=Dy, Ho, Er, Y and Yb), using the ligand mdeaH2 , in the presence of ortho-toluic or benzoic acid are reported. From the seven wheels studied the {Mn8 Dy8 } and {Mn8 Y8 } analogues exhibit SMM behavior as determined from ac susceptibility experiments in a zero static magnetic field. From DFT calculations a S=16 ground state was determined for the {Mn8 Y8 } complex due to weak ferromagnetic Mn(III) -Mn(III) interactions. Ab initio CASSCF+RASSI-SO calculations on the {Mn8 Dy8 } wheel estimated the Mn(III) -Dy(III) exchange interaction as -0.1 cm(-1) . This weak exchange along with unfavorable single-ion anisotropy of Dy(III) /Mn(III) ions, however, led to the observation of SMM behavior with fast magnetic relaxation. The orientation of the g-anisotropy of the Dy(III) ions is found to be perpendicular to the plane of the wheel and this suggests the possibility of toroidal magnetic moments in the cluster. The {Mn8 Ln8 } clusters reported here are the largest heterometallic Mn(III) Ln(III) wheels and the largest {3d-4f} wheels to exhibit SMM behavior reported to date.

  8. Designing, engineering, and testing wood structures

    NASA Technical Reports Server (NTRS)

    Gorman, Thomas M.

    1992-01-01

    The objective of this paper is to introduce basic structural engineering concepts in a clear, simple manner while actively involving students. This project emphasizes the fact that a good design uses materials efficiently. The test structure in this experiment can easily be built and has various design options. Even when the structure is loaded to collapsing, only one or two pieces usually break, leaving the remaining pieces intact and reusable.

  9. Structure and Biophysics of Type III Secretion in Bacteria

    PubMed Central

    Chatterjee, Srirupa; Chaudhury, Sukanya; McShan, Andrew C.; Kaur, Kawaljit; De Guzman, Roberto N.

    2013-01-01

    Many plant and animal bacterial pathogens assemble a needle-like nanomachine, the type III secretion system (T3SS), to inject virulence proteins directly into eukaryotic cells to initiate infection. The ability of bacteria to inject effectors into host cells is essential for infection, survival, and pathogenesis for many Gram-negative bacteria, including Salmonella, Escherichia, Shigella, Yersinia, Pseudomonas, and Chlamydia spp. These pathogens are responsible for a wide variety of diseases, such as typhoid fever, large-scale food-borne illnesses, dysentery, bubonic plague, secondary hospital infections, and sexually transmitted diseases. The T3SS consists of structural and nonstructural proteins. The structural proteins assemble the needle apparatus, which consists of a membrane-embedded basal structure, an external needle that protrudes from the bacterial surface, and a tip complex that caps the needle. Upon host cell contact, a translocon is assembled between the needle tip complex and the host cell, serving as a gateway for translocation of effector proteins by creating a pore in the host cell membrane. Following delivery into the host cytoplasm, effectors initiate and maintain infection by manipulating host cell biology, such as cell signaling, secretory trafficking, cytoskeletal dynamics, and the inflammatory response. Finally, chaperones serve as regulators of secretion by sequestering effectors and some structural proteins within the bacterial cytoplasm. This review will focus on the latest developments and future challenges concerning the structure and biophysics of the needle apparatus. PMID:23521714

  10. 1,2,4-Diazaphospholide complexes of lanthanum(iii), cerium(iii), neodymium(iii), praseodymium(iii), and samarium(iii): synthesis, X-ray structural characterization, and magnetic susceptibility studies.

    PubMed

    Zhao, Minggang; Wang, Lixia; Li, Pangpang; Ma, Jianping; Zheng, Wenjun

    2016-07-01

    A few heteroleptic, charge-separated heterobimetallic, and polymeric alkali metalate complexes of 1,2,4-diazaphospholide lanthanum(iii), cerium(iii), neodymium(iii), praseodymium(iii), and samarium(iii) were simply prepared via the metathesis reaction of MCl3 (THF)m (m = 1-2) and K[3,5-R2dp] ([3,5-R2dp](-) = 3,5-di-substituent-1,2,4-diazaphospholide; R = tBu, Ph) in a varied ratio (1 : 3, 1 : 4, and 1 : 5, respectively) at room temperature in tetrahydrofuran. All the complexes were fully characterized by (1)H, (13)C{(1)H}, (31)P{(1)H}, IR, and X-ray single crystal diffraction analysis despite their paramagnetism (excluding La(iii) complexes). The structures of the complexes were found to feature varied coordination modes. The magnetic properties of several compounds were studied by magnetic susceptibility, and the complexes presented the magnetic moments close to or lower than the theoretical values for the free ions in the trivalent oxidation states (Pr(3+), Nd(3+)). PMID:27326667

  11. 1,2,4-Diazaphospholide complexes of lanthanum(iii), cerium(iii), neodymium(iii), praseodymium(iii), and samarium(iii): synthesis, X-ray structural characterization, and magnetic susceptibility studies.

    PubMed

    Zhao, Minggang; Wang, Lixia; Li, Pangpang; Ma, Jianping; Zheng, Wenjun

    2016-07-01

    A few heteroleptic, charge-separated heterobimetallic, and polymeric alkali metalate complexes of 1,2,4-diazaphospholide lanthanum(iii), cerium(iii), neodymium(iii), praseodymium(iii), and samarium(iii) were simply prepared via the metathesis reaction of MCl3 (THF)m (m = 1-2) and K[3,5-R2dp] ([3,5-R2dp](-) = 3,5-di-substituent-1,2,4-diazaphospholide; R = tBu, Ph) in a varied ratio (1 : 3, 1 : 4, and 1 : 5, respectively) at room temperature in tetrahydrofuran. All the complexes were fully characterized by (1)H, (13)C{(1)H}, (31)P{(1)H}, IR, and X-ray single crystal diffraction analysis despite their paramagnetism (excluding La(iii) complexes). The structures of the complexes were found to feature varied coordination modes. The magnetic properties of several compounds were studied by magnetic susceptibility, and the complexes presented the magnetic moments close to or lower than the theoretical values for the free ions in the trivalent oxidation states (Pr(3+), Nd(3+)).

  12. Teaching Structural Design in Civil Engineering Technology.

    ERIC Educational Resources Information Center

    Metwally, Ashraf

    This paper is a description of a college course in structural design, which in this case serves as the capstone of the program in Civil Engineering Technology at the College of Staten Island (New York). Fourteen weeks of class lecture topics, activities, and assignments are delineated. Coverage includes building codes, loads calculation,…

  13. 46 CFR 11.505 - Engineer officer structure.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 1 2012-10-01 2012-10-01 false Engineer officer structure. 11.505 Section 11.505... OFFICER ENDORSEMENTS Professional Requirements for Engineer Officer § 11.505 Engineer officer structure. The following diagram illustrates the engineering endorsement structure including cross over...

  14. 14 CFR 33.23 - Engine mounting attachments and structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Engine mounting attachments and structure... mounting attachments and structure. (a) The maximum allowable limit and ultimate loads for engine mounting attachments and related engine structure must be specified. (b) The engine mounting attachments and...

  15. The Structure and Function of Type III Secretion Systems

    PubMed Central

    Notti, Ryan Q.; Stebbins, C. Erec

    2015-01-01

    ARTICLE SUMMARY Type III secretion systems (T3SS) afford gram-negative bacteria a most intimate means of altering the biology of their eukaryotic hosts — the direct delivery of effector proteins from the bacterial cytoplasm to that of the eukaryote. This incredible biophysical feat is accomplished by nanosyringe “injectisomes,” which form a conduit across the three plasma membranes, peptidoglycan layer and extracellular space that form a barrier to the direct delivery of proteins from bacterium to host. The focus of this chapter is T3SS function at the structural level; we will summarize the core findings that have shaped our understanding of the structure and function of these systems and highlight recent developments in the field. In turn, we describe the T3SS secretory apparatus, consider its engagement with secretion substrates, and discuss the post-translational regulation of secretory function. Lastly, we close with a discussion of the future prospects for the interrogation of structure-function relationships in the T3SS. PMID:26999392

  16. Soy-Based, Water-Cooled, TC W-III Two Cycle Engine Oil

    SciTech Connect

    Scharf, Curtis R.; Miller, Mark E.

    2003-08-30

    The objective of this project was to achieve technical approval and commercial launch for a biodegradable soy oil-based, environmentally safe, TC W-III performance, water-cooled, two cycle engine oil. To do so would: (1) develop a new use for RBD soybean oil; (2) increase soybean utilization in North America in the range of 500 K-3.0 MM bushels; and (3) open up supply opportunities of 1.5-5.0 MM bushels worldwide. These goals have been successfully obtained.

  17. Structural and functional characterization of two unusual endonuclease III enzymes from Deinococcus radiodurans.

    PubMed

    Sarre, Aili; Ökvist, Mats; Klar, Tobias; Hall, David R; Smalås, Arne O; McSweeney, Sean; Timmins, Joanna; Moe, Elin

    2015-08-01

    While most bacteria possess a single gene encoding the bifunctional DNA glycosylase Endonuclease III (EndoIII) in their genomes, Deinococcus radiodurans possesses three: DR2438 (DrEndoIII1), DR0289 (DrEndoIII2) and DR0982 (DrEndoIII3). Here we have determined the crystal structures of DrEndoIII1 and an N-terminally truncated form of DrEndoIII3 (DrEndoIII3Δ76). We have also generated a homology model of DrEndoIII2 and measured activity of the three enzymes. All three structures consist of two all α-helical domains, one of which exhibits a [4Fe-4S] cluster and the other a HhH-motif, separated by a DNA binding cleft, similar to previously determined structures of endonuclease III from Escherichia coli and Geobacillus stearothermophilus. However, both DrEndoIII1 and DrEndoIII3 possess an extended HhH motif with extra helical features and an altered electrostatic surface potential. In addition, the DNA binding cleft of DrEndoIII3 seems to be less accessible for DNA interactions, while in DrEndoIII1 it seems to be more open. Analysis of the enzyme activities shows that DrEndoIII2 is most similar to the previously studied enzymes, while DrEndoIII1 seems to be more distant with a weaker activity towards substrate DNA containing either thymine glycol or an abasic site. DrEndoIII3 is the most distantly related enzyme and displays no detectable activity towards these substrates even though the suggested catalytic residues are conserved. Based on a comparative structural analysis, we suggest that the altered surface potential, shape of the substrate-binding pockets and specific amino acid substitutions close to the active site and in the DNA interacting loops may underlie the unexpected differences in activity. PMID:26172070

  18. Structural and functional characterization of two unusual endonuclease III enzymes from Deinococcus radiodurans.

    PubMed

    Sarre, Aili; Ökvist, Mats; Klar, Tobias; Hall, David R; Smalås, Arne O; McSweeney, Sean; Timmins, Joanna; Moe, Elin

    2015-08-01

    While most bacteria possess a single gene encoding the bifunctional DNA glycosylase Endonuclease III (EndoIII) in their genomes, Deinococcus radiodurans possesses three: DR2438 (DrEndoIII1), DR0289 (DrEndoIII2) and DR0982 (DrEndoIII3). Here we have determined the crystal structures of DrEndoIII1 and an N-terminally truncated form of DrEndoIII3 (DrEndoIII3Δ76). We have also generated a homology model of DrEndoIII2 and measured activity of the three enzymes. All three structures consist of two all α-helical domains, one of which exhibits a [4Fe-4S] cluster and the other a HhH-motif, separated by a DNA binding cleft, similar to previously determined structures of endonuclease III from Escherichia coli and Geobacillus stearothermophilus. However, both DrEndoIII1 and DrEndoIII3 possess an extended HhH motif with extra helical features and an altered electrostatic surface potential. In addition, the DNA binding cleft of DrEndoIII3 seems to be less accessible for DNA interactions, while in DrEndoIII1 it seems to be more open. Analysis of the enzyme activities shows that DrEndoIII2 is most similar to the previously studied enzymes, while DrEndoIII1 seems to be more distant with a weaker activity towards substrate DNA containing either thymine glycol or an abasic site. DrEndoIII3 is the most distantly related enzyme and displays no detectable activity towards these substrates even though the suggested catalytic residues are conserved. Based on a comparative structural analysis, we suggest that the altered surface potential, shape of the substrate-binding pockets and specific amino acid substitutions close to the active site and in the DNA interacting loops may underlie the unexpected differences in activity.

  19. Gallium(III) Tetraphenylporphyrinates Containing Hydrosulfide and Thiolate Ligands: Structural Models for Sulfur-Bound Iron(III) Hemes.

    PubMed

    Meininger, Daniel J; Chee-Garza, Max; Arman, Hadi D; Tonzetich, Zachary J

    2016-03-01

    Gallium(III) tetraphenylporphyrinates (TPP) containing anionic sulfur ligands have been prepared and characterized in the solid state and solution. The complexes serve as structural models for iron(III) heme sites containing sulfur coordination that otherwise prove challenging to synthesize due to the propensity for reduction to iron(II). The compounds prepared include the first well-characterized example of a trivalent metalloporphyrinate containing a terminal hydrosulfide ligand, [Ga(SH)(TPP)], as well as [Ga(SEt)(TPP)], [Ga(SPh)(TPP)], and [Ga(SSi(i)Pr3)(TPP)]. The stability of these compounds toward reduction has permitted an investigation of their solid-state structures and electrochemistry. The structural features and reaction chemistry of the complexes in relation to their iron(III) analogs is discussed.

  20. Electronic structure calculations of group III nitride clusters

    NASA Astrophysics Data System (ADS)

    Kandalam, Anil Kumar

    2002-04-01

    Group III nitrides have become materials of choice in the manufacturing of devices used in opto-electronic and high-temperature high-power electronic industries. Hence, these materials received wide attention and have become the focus of several theoretical and experimental studies. Though these materials are studied in bulk and thin film forms, research at the cluster level is still lacking. Hence, a first principles calculation, based on the Generalized Gradient Approximation (GGA) to Density Functional Theory (DFT) was initiated to study the structural and electronic properties of AlnN n, GanNn, and InnNn, (n = 1--6) clusters. The calculated results show that the small polyatomic nitride clusters (monomer, triatomic and dimer) have a strong tendency to form N-N multiple bonds leading to the weakening of any existent metal-N or metal-metal bonds. In the absence of the N-N bonds, the metal-nitrogen bond dominates, forming short bond-lengths and large force constants. However, the strength of these heteronuclear bonds decreases in going from Al to Ga and In, whereas the weak metal-metal bond increases its strength from Al to Ga to In in the nitride clusters. Starting from the trimers M3N3, a distinct structural difference between the lowest energy configurations of AlnNn and that of GanNn, and In nNn, clusters has been observed. For AlnNn, clusters, the metal-nitrogen bond is found to dominate the lowest energy configurations. As the cluster size is increased from Al3N3 to Al 6N6, a transition from planar ring structures towards a bulk-like three dimensional configurations is seen. However, in GanN n, and InnNn clusters, no such trend is observed and the lowest energy configurations are dominated either by N2 or (N3)- sub-units. The segregation of N atoms within the stoichiometric clusters indicates the possibility of N2 and N3 based defects in the thin-film deposition process which may affect the quality of the thin-film devices based on Group III nitrides.

  1. Balancer structure for three-cylinder engines

    SciTech Connect

    Suzuki, T.

    1986-01-21

    This patent describes a balancer structure for a three-cylinder in-line engine. The in-line engine is indicated in the patent as having a crankshaft having crank arms configured at angles of 120/sup 0/ with respect to each other and operatively connected to a piston assembly within each of the cylinders. This crankshaft and assembly, which serves as a balancer structure as one of its applications, is further characterized in the patent as consisting of a number of component parts. The first component described is a single countershaft adjacent and parallel to the crankshaft. It is specified in the patent that this countershaft must rotate at the same speed as the crankshaft but in an opposite direction in order to fulfill its role in the balancer structure. The patent also details an element of the balancer structure which consists of a means utilizing counterweights mounted on the crankshaft at the first and third cylinder positions. These weights are indicated as partially balancing the inertia forces of reciprocating masses and the entire inertia forces of rotating masses present in the described engine. The required position of these counterweights is indicated as being a location more than 90/sup 0/ from the crank arm for the corresponding cylinder and perpendicular to the second cylinder crank arm. The last component described consists of two balancers mounted on both ends of the countershaft which balance the remainder of the inertia forces of reciprocating masses and the inertia of the crankshaft about axes perpendicular to itself.

  2. Chemistry Characterization of Jet Aircraft Engine Particulate by XPS: Results from APEX III

    NASA Technical Reports Server (NTRS)

    Vander Wal, Randy L.; Bryg, Victoria M.

    2014-01-01

    This paper reports XPS analysis of jet exhaust particulate from a B737, Lear, ERJ, and A300 aircraft during the APEX III NASA led field campaign. Carbon hybridization and bonding chemistry are identified by high-resolution scans about the C1s core-shell region. Significant organic content as gauged by the sp3/sp2 ratio is found across engines and platforms. Polar oxygen functional groups include carboxylic, carbonyl and phenol with combined content of 20 percent or more. By lower resolution survey scans various elements including transition metals are identified along with lighter elements such as S, N, and O in the form of oxides. Burning additives within lubricants are probable sources of Na, Ba, Ca, Zn, P and possibly Sn. Elements present and their percentages varied significantly across all engines, not revealing any trend or identifiable cause for the differences, though the origin is likely the same for the same element when observed. This finding suggests that their presence can be used as a tracer for identifying soots from aircraft engines as well as diagnostic for monitoring engine performance and wear.

  3. Chemistry characterization of jet aircraft engine particulate matter by XPS: Results from APEX III

    NASA Astrophysics Data System (ADS)

    Vander Wal, Randy L.; Bryg, Victoria M.; Huang, Chung-Hsuan

    2016-09-01

    This paper reports X-ray photoelectron spectroscopy (XPS) analysis of jet exhaust particulate matter (PM) from a B737, Lear, ERJ and A300 aircraft during the APEX III NASA led field campaign. Carbon hybridization and bonding chemistry are identified by high-resolution scans about the C1s core-shell region. Significant organic content as gauged by the sp3/sp2 ratio is found across engines and powers. Polar oxygen functional groups include carboxylic, carbonyl and phenol with combined content of 20% or more. By survey scans various elements including transition metals are identified along with lighter elements such as S, N and O in the form of oxides. Additives within lubricants are probable sources of Na, Ba, Ca, Zn, P and possibly Sn. Elements present and their percentages varied significantly across all engines, not revealing any trend or identifiable cause for the differences, though the origin is likely the same for the same element when observed. This finding suggests that their collective presence could serve as an environmental tracer for identifying PM originating from aircraft engines and serving as a diagnostic for engine performance and wear.

  4. Bacterial nanofluidic structures for medicine and engineering.

    PubMed

    Hesse, William R; Freedman, Kevin J; Yi, Dong Kee; Ahn, Chi Won; Kim, Minjun

    2010-04-23

    Bacteria are microscopic, single-celled organisms that utilize a variety of nanofluidic structures. One of the best known and widely used nanofluidic structures that are derived from bacteria is the alpha-hemolysin pore. This pore, which self-assembles in lipid bilayers, has been used for a wide variety of sensing applications, most notably, DNA sensing. Synthetic pores drilled in a wide variety of materials, such as silicon nitride and polymers have been developed that use inspiration from the alpha-hemolysin pore. Higher-aspect-ratio nanofluidic structures, akin to nanotubes, are also synthesized by bacteria. Examples of such structures include those that are associated with bacterial transport apparatus, such as pili, and are used by bacteria to facilitate the transfer of genetic material from one bacterium to another. Flagella, and its associated structures, such as the rod and hook, are also tubular nanostructures, through which the protein, flagellin, travels to assemble the flagellum. Genetic engineering allows for the creation of modified bacterial nanopores and nanotubes that can be used for a variety of medical and engineering purposes.

  5. Solvation structure and thermodynamics for Pr(III), Nd(III) and Dy(III) complexes in ionic liquids evaluated by Raman spectroscopy and DFT calculation

    NASA Astrophysics Data System (ADS)

    Kuribara, Keita; Matsumiya, Masahiko; Tsunashima, Katsuhiko

    2016-12-01

    package. The bonding energy, ΔEb, was calculated as ΔEb = Etot(cluster) - Etot(RE3+) - nEtot([TFSA]-), and ΔEb ([Pr(III)(cis-TFSA)5]2-), ΔEb([Nd(III)(cis-TFSA)5]2-), and ΔEb([Dy(III)(cis-TFSA)5]2-) were calculated to be -4238.6 ± 6.8, -4362.3 ± 8.2, and -4284.2 ± 7.4 kJ mol-1, respectively. This series of structural results allows us to conclude that [Dy(III)(cis-TFSA)5]2- clusters are more stable state than the [Pr(III)(cis-TFSA)5]2- clusters in [P2225][TFSA]. Furthermore, the average atomic charges and the bond distances of these clusters were consistent with the thermodynamic properties.

  6. Fatigue Reliability of Gas Turbine Engine Structures

    NASA Technical Reports Server (NTRS)

    Cruse, Thomas A.; Mahadevan, Sankaran; Tryon, Robert G.

    1997-01-01

    The results of an investigation are described for fatigue reliability in engine structures. The description consists of two parts. Part 1 is for method development. Part 2 is a specific case study. In Part 1, the essential concepts and practical approaches to damage tolerance design in the gas turbine industry are summarized. These have evolved over the years in response to flight safety certification requirements. The effect of Non-Destructive Evaluation (NDE) methods on these methods is also reviewed. Assessment methods based on probabilistic fracture mechanics, with regard to both crack initiation and crack growth, are outlined. Limit state modeling techniques from structural reliability theory are shown to be appropriate for application to this problem, for both individual failure mode and system-level assessment. In Part 2, the results of a case study for the high pressure turbine of a turboprop engine are described. The response surface approach is used to construct a fatigue performance function. This performance function is used with the First Order Reliability Method (FORM) to determine the probability of failure and the sensitivity of the fatigue life to the engine parameters for the first stage disk rim of the two stage turbine. A hybrid combination of regression and Monte Carlo simulation is to use incorporate time dependent random variables. System reliability is used to determine the system probability of failure, and the sensitivity of the system fatigue life to the engine parameters of the high pressure turbine. 'ne variation in the primary hot gas and secondary cooling air, the uncertainty of the complex mission loading, and the scatter in the material data are considered.

  7. RNase III autoregulation: structure and function of rncO, the posttranscriptional "operator".

    PubMed

    Matsunaga, J; Simons, E L; Simons, R W

    1996-12-01

    Expression of the Escherichia coli rnc-era-recO operon is regulated posttranscriptionally by ribonuclease III (RNase III), encoded in the rnc gene. RNase III initiates rapid decay of the rnc operon mRNA by cleaving a double-stranded region of the rnc leader. This region, termed rncO, is portable, conferring stability and RNase III regulation to heterologous RNAs. Here, we report the detailed analysis of rncO structure and function. The first 215 nt of the rnc leader are sufficient for its function. Dimethylsulfate (DMS) modification in vivo revealed distinct structural elements in this region: a 13-nt single-stranded 5' leader, followed by a 6-bp stem-loop structure (I), a larger stem-loop structure (II) containing the RNase III site, a single-stranded region containing the rnc translation initiation site, and a small stem-loop structure (III) at the 3' terminus of rncO, wholly within the rnc coding region. Genetic analysis revealed the function of these structural elements. The single-stranded leader is not required for stability or RNase III control, stem-loop II is required only for RNase III control, and both stem-loops I and III are required for stability. Stem-loop II effectively serves only as the site at which RNase III cleaves to remove stem-loop I and thereby initiates decay, after which RNase III plays no role. Mutations at the cleavage site underscore the importance of base pairing for efficient RNase III attack. When stem-loops I and II were replaced with an artificial hairpin structure, stability was restored only partially, but was restored almost fully when a single-stranded leader was also added. PMID:8972772

  8. Engineering and building RF structures - the works

    SciTech Connect

    Schrage, D. L.

    2004-01-01

    The translation of the physics designs of linear accelerators into engineering and manufacturing requirements is discussed. The stages of conceptual design, prototyping, final design, construction, and installation are described for both superconducting (LANL {beta} = 0.175 Spoke Cavity) and normal-conducting (APT/LEDA 6.7 MeV RFQ) accelerators. An overview of codes which have linked accelerator cavity and thermal/structural analysis modules is provided. The linked RF/thermal/CFD/structural codes do work. Workers at laboratories throughout the world have been successful in predicting the thermal and structural performance of accelerator cavities using these codes. Use of these codes allows accurate prediction of resonant frequencies, Lorentz force de-tuning, tuning sensitivities and mechanical resonant frequencies. Most important, these codes allow cost-effective optimization of the cavity geometry and, for superconducting cavities, the location and shape of external stiffeners.

  9. Solution structures of europium(III) complexes of ethylenediaminetetraacetic acid

    SciTech Connect

    Latva, M.; Kankara, J.; Haapakka, K.

    1996-04-01

    Coordination of ethylenediaminetetraacetic acid (EDTA) with europium(III) has been studied at different concentrations in solution using {sup 7}F{sub 0}{yields}{sup 5}D{sub 0} excitation spectroscopy and excited-state lifetime measurements. EDTA forms with Eu(III) ion three different species in equimolar solutions at room temperature. At low pH values EuEDTAH is formed and at higher pH values than 1.5 two EuEDTA{sup -} complexes, which differ from each other with one water molecule in the first coordination sphere of the Eu(III) ion, total coordination number and coordination geometry, are also formed. When the concentration of EDTA is higher than the concentration of Eu(III), an EuEDTA(EDTAH){sup 4-} species where the second EDTA is weakly coordinated to EuEDTA{sup -}, is formed. If the concentration of Eu(III) ion is higher than EDTA, the extra Eu(III) ions associate with EuEDTA{sup -} and link to one of the carboxylate groups of EDTA thus causing a shortening of the excited-state lifetime of the EuEDTA{sup -} complex.

  10. Low-power optically addressed spatial light modulators using MBE-grown III-V structures

    NASA Astrophysics Data System (ADS)

    Maserjian, Joseph L.; Larsson, Anders G.

    1991-12-01

    Device approaches are investigated for O-SLMs based on MBE engineered III-V materials and structures. Strong photo-optic effects can be achieved in periodically (delta) -doped multiple quantum well (MQW) structures. The doping-defined barriers serve to separate and delay recombination of the photo-generated electron-hole pairs. One can use this photo-effect to change the internal field across the MQWs giving rise to quantum-confined Stark shift. Alternately, the photo-generated electrons can be used to occupy the quantum wells, which in turn causes exciton quenching and a shift of the absorption edge. Recent work has shown that both of these predicted photo-optic effects can indeed be achieved in such MBE engineered structures. However, these enhanced effects are still insufficient for high contrast modulation with only single or double pass absorption through active layers of practical thickness. We use the asymmetric Fabry-Perot cavity approach which permits extinction of light due to interference of light reflected from the front and back surfaces of the cavity. Modulation of the absorption in the active cavity layers unbalances the cavity and 'turns on' the reflected output signal, thereby allowing large contrast ratios. This approach is realized with an all-MBE- grown structure consisting of a GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror (approximately equals 0.98) and the GaAs surface as the low reflectance mirror (approximately equals 0.3). We use for our active cavities InGaAs/GaAs MQWs separated by npn (delta) -doped GaAs barriers to achieve sensitive photo-optic effect due to exciton quenching. High contrast modulation (> 60:1) is achieved with the Fabry-Perot structures using low power (< 100 mW/cm2) InGaAs/GaAS quantum well lasers for a write signal.

  11. IMPROVEMENT TO PIPELINE COMPRESSOR ENGINE RELIABILITY THROUGH RETROFIT MICRO-PILOT IGNITION SYSTEM -- PHASE III

    SciTech Connect

    Scott Chase; Daniel Olsen; Ted Bestor

    2005-03-01

    This report documents the third year's effort towards a 3-year program conducted by the Engines & Energy Conversion Laboratory (EECL) at Colorado State University (CSU) to develop micropilot ignition systems for existing pipeline compressor engines. Research activities for the overall program were conducted with the understanding that the efforts are to result in a commercial product to capture and disseminate the efficiency and environmental benefits of this new technology. Commercially-available fuel injection products were identified and applied to the program where appropriate. This approach will minimize the overall time-to-market requirements, while meeting performance and cost criteria. Two earlier phases of development precede this report. The objective for Phase I was to demonstrate the feasibility of retrofit micropilot ignition (RMI) systems for large bore, slow speed engines operating at low compression ratios under laboratory conditions at the EECL. The objective for Phase II was to further develop and optimize the micropilot ignition system at the EECL for large bore, slow speed engines operating at low compression ratios. These laboratory results were enhanced, then verified via a field demonstration project during Phase III of the Micropilot Ignition program. An Implementation Team of qualified engine retrofit service providers was assembled to install the retrofit micropilot ignition system for an engine operated by El Paso Pipeline Group at a compressor station near Window Rock, Arizona. Testing of this demonstration unit showed that the same benefits identified by laboratory testing at CSU, i.e., reduced fuel consumption and exhaust emissions (NOx, THC, CO, and CH2O). Installation efforts at Window Rock were completed towards the end of the budget period, which did not leave sufficient time to complete the durability testing. These efforts are ongoing, with funding provided by El Paso Pipeline Group, and the results will be documented in a report

  12. Band structure engineering in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Schwarze, Martin; Tress, Wolfgang; Beyer, Beatrice; Gao, Feng; Scholz, Reinhard; Poelking, Carl; Ortstein, Katrin; Günther, Alrun A.; Kasemann, Daniel; Andrienko, Denis; Leo, Karl

    2016-06-01

    A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.

  13. Band structure engineering in organic semiconductors.

    PubMed

    Schwarze, Martin; Tress, Wolfgang; Beyer, Beatrice; Gao, Feng; Scholz, Reinhard; Poelking, Carl; Ortstein, Katrin; Günther, Alrun A; Kasemann, Daniel; Andrienko, Denis; Leo, Karl

    2016-06-17

    A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors. PMID:27313043

  14. Synthesis, structure and luminescence studies of Eu(III), Tb(III), Sm(III), Dy(III) cationic complexes with acetylacetone and bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)propane☆

    PubMed Central

    Gusev, Alexey N.; Hasegawa, Miki; Shimizu, Tomohito; Fukawa, Tomonori; Sakurai, Shoya; Nishchymenko, Galyna A.; Shul’gin, Victor F.; Meshkova, Svetlana B.; Linert, Wolfgang

    2013-01-01

    Studies concerning synthesis, structure and luminescence of eight-coordinate Eu, Tb, Sm and Dy complexes of the type [Ln(acac)2(L)]Cl (Hacac = pentanedione-2,4 and L = bis(5-(pyridine-2-yl)-1,2,4-triazol-3-yl)propane) are reported in detail. The obtained complexes were investigated by various means including elemental- and thermogravimetric analysis, IR- and electron transition spectroscopy. The structure of the Tb complex was determined by single-crystal X-ray crystallography: Tb is eight-coordinate, and L acting only as a tetradentate chelate together with two bidentate acac ligands. Photophysical studies of the complexes were carried out. The Tb(III) and Eu(III) complexes show strong emissions both in solid state and solution. The intensity of the luminescence of Dy(III) and Sm(III) are relatively weak. The factors determining the intensity of the photoluminescence are discussed. PMID:24068839

  15. Investigating the Structure of the WJ-III Cognitive at School Age

    ERIC Educational Resources Information Center

    Dombrowski, Stefan C.

    2013-01-01

    During its development, the Woodcock-Johnson, Third Edition Cognitive (WJ-III Cognitive; McGrew & Woodcock, 2001) was never subjected to structural analysis using exploratory and higher order factor analyses. Instead, confirmatory factor analyses were conducted on separate sets of WJ-III correlation matrices, yielding a seven-factor model across…

  16. Crystal structures of salicylideneguanylhydrazinium chloride and its copper(II) and cobalt(III) chloride complexes

    SciTech Connect

    Chumakov, Yu. M. Tsapkov, V. I.; Bocelli, G.; Antosyak, B. Ya.; Shova, S. G.; Gulea, A. P.

    2006-01-15

    The crystal structures of salicylideneguanylhydrazinium chloride hydrate hemiethanol solvate (I), salicylideneguanylhydrazinium trichloroaquacuprate(II) (II), and bis(salicylideneguanylhydrazino)cobalt(III) chloride trihydrate (III) are determined using X-ray diffraction. The structures of compounds I, II, and III are solved by direct methods and refined using the least-squares procedure in the anisotropic approximation for the non-hydrogen atoms to the final factors R = 0.0597, 0.0212, and 0.0283, respectively. In the structure of compound I, the monoprotonated molecules and chlorine ions linked by hydrogen bonds form layers aligned parallel to the (010) plane. In the structure of compound II, the salicylaldehyde guanylhydrazone cations and polymer chains consisting of trichloroaquacuprate(II) anions are joined by an extended three-dimensional network of hydrogen bonds. In the structure of compound III, the [Co(LH){sub 2}]{sup +} cations, chloride ions, and molecules of crystallization water are linked together by a similar network.

  17. Effect of III-V on insulator structure on quantum well intermixing

    NASA Astrophysics Data System (ADS)

    Takashima, Seiya; Ikku, Yuki; Takenaka, Mitsuru; Takagi, Shinichi

    2016-04-01

    To achieve the monolithic active/passive integration on the III-V CMOS photonics platform, quantum well intermixing (QWI) on III-V on insulator (III-V-OI) is studied for fabricating multi-bandgap III-V-OI wafers. By optimizing the QWI condition for a 250-nm-thick III-V layer, which contains a five-layer InGaAsP-based multi-quantum well (MQW) with 80-nm-thick indium phosphide (InP) cladding layers, we have successfully achieved a photoluminescence (PL) peak shift of over 100 nm on the III-V-OI wafer. We have also found that the progress of QWI on the III-V-OI wafer is slower than that on the InP bulk wafer regardless of the buried oxide (BOX) thickness, bonding interface materials, and handle wafers. We have also found that the progress of QWI on the III-V-OI wafer is slower than that on the InP bulk wafer regardless of the buried oxide (BOX) thickness, bonding interface materials, and bulk support wafers on which the III-V-OI structure is formed (handle wafers). By comparing between the measured PL shift and simulated diffusions of phosphorus vacancies and interstitials during QWI, we have found that the slow QWI progress in the III-V-OI wafer is probably attributed to the enhanced recombination of vacancies and interstitials by the diffusion blocking of vacancies and interstitials at the BOX interface.

  18. Structural Basis for Substrate Binding and the Catalytic Mechanism of Type III Pantothenate Kinase

    SciTech Connect

    Yang, Kun; Strauss, Erick; Huerta, Carlos; Zhang, Hong

    2008-07-15

    Pantothenate kinase (PanK) catalyzes the first step of the universal five-step coenzyme A (CoA) biosynthetic pathway. The recently characterized type III PanK (PanK-III, encoded by the coaX gene) is distinct in sequence, structure and enzymatic properties from both the long-known bacterial type I PanK (PanK-I, exemplified by the Escherichia coli CoaA protein) and the predominantly eukaryotic type II PanK (PanK-II). PanK-III enzymes have an unusually high K{sub m} for ATP, are resistant to feedback inhibition by CoA, and are unable to utilize the N-alkylpantothenamide family of pantothenate analogues as alternative substrates, thus making type III PanK ineffective in generating CoA analogues as antimetabolites in vivo. Previously, we reported the crystal structure of the PanK-III from Thermotoga maritima and identified it as a member of the 'acetate and sugar kinase/heat shock protein 70/actin' (ASKHA) superfamily. Here we report the crystal structures of the same PanK-III in complex with one of its substrates (pantothenate), its product (phosphopantothenate) as well as a ternary complex structure of PanK-III with pantothenate and ADP. These results are combined with isothermal titration calorimetry experiments to present a detailed structural and thermodynamic characterization of the interactions between PanK-III and its substrates ATP and pantothenate. Comparison of substrate binding and catalytic sites of PanK-III with that of eukaryotic PanK-II revealed drastic differences in the binding modes for both ATP and pantothenate substrates, and suggests that these differences may be exploited in the development of new inhibitors specifically targeting PanK-III.

  19. Effects of Humidity on Non-Hermetically Packaged III-V Structures and Devices

    NASA Technical Reports Server (NTRS)

    Leon, R.; Martin, S.; Lee, T.; Okuno, J.; Ruiz, R.; Gauldin, R.; Gaidis, M.; Smith, R.

    1999-01-01

    High humidity and temperature test (known as 85/85 tests) were performed on various III-V devices and structures to determine environmental effects in non-hermetically packaged GaAs membrane mixer diodes.

  20. Using Images To Teach the Beginnings of Structural Engineering.

    ERIC Educational Resources Information Center

    Lindenberg, Henrique; Arevalo, Luis Alberto Tello

    Aiming at turning theory of structures into a captivating subject to civil engineering students and at helping them understand the link between the mathematical models and the real structures, a new experience is underway at the Department of Structural and Foundation Engineering of Excola Politecnica da Universidada de Sao Paulo: transparencies…

  1. Balancer structure for three-cylinder engines

    SciTech Connect

    Suzuki, T.

    1986-02-11

    This patent describes a balancer structure for a three-cylinder in-line engine having aligned three cylinders, a crankshaft having crank arms disposed at angles of 120/sup 0/ with respect to each other and operatively connected to the cylinders, respectively. This structure consists of: 1.) a single countershaft adjacent and parallel to and rotated at the same speed as the crankshaft but in the opposite direction; 2.) a counterweight is securely mounted on the crankshaft only at positions corresponding to the first and third cylinders for balancing a part of inertia force of reciprocating mases and the entire inertia force of rotating masses; 3.) at least one second counterweight securely mounted on the crankshaft substantially opposite to the crank arm corresponding to the second cylinder for balancing another part of the inertia force of the reciprocating masses; 4.) at least two balancers securely mounted on the countershaft at both ends for the balancing of the remainder of the inertia force of the reciprocating masses and a couple of inertia of the crankshaft about an axis perpendicular to the crankshaft.

  2. Structure and Interactions of Fish Type III Antifreeze Protein in Solution

    PubMed Central

    Salvay, Andrés G.; Gabel, Frank; Pucci, Bernard; Santos, Javier; Howard, Eduardo I.; Ebel, Christine

    2010-01-01

    Abstract It has been suggested that above a critical protein concentration, fish Type III antifreeze protein (AFP III) self-assembles to form micelle-like structures that may play a key role in antifreeze activity. To understand the complex activity of AFP III, a comprehensive description of its association state and structural organization in solution is necessary. We used analytical ultracentrifugation, analytical size-exclusion chromatography, and dynamic light scattering to characterize the interactions and homogeneity of AFP III in solution. Small-angle neutron scattering was used to determine the low-resolution structure in solution. Our results clearly show that at concentrations up to 20 mg mL−1 and at temperatures of 20°C, 6°C, and 4°C, AFP III is monomeric in solution and adopts a structure compatible with that determined by crystallography. Surface tension measurements show a propensity of AFP III to localize at the air/water interface, but this surface activity is not correlated with any aggregation in the bulk. These results support the hypothesis that each AFP III molecule acts independently of the others, and that specific intermolecular interactions between monomers are not required for binding to ice. The lack of attractive interactions between monomers may be functionally important, allowing for more efficient binding and covering of the ice surface. PMID:20643081

  3. Structure and interactions of fish type III antifreeze protein in solution.

    PubMed

    Salvay, Andrés G; Gabel, Frank; Pucci, Bernard; Santos, Javier; Howard, Eduardo I; Ebel, Christine

    2010-07-21

    It has been suggested that above a critical protein concentration, fish Type III antifreeze protein (AFP III) self-assembles to form micelle-like structures that may play a key role in antifreeze activity. To understand the complex activity of AFP III, a comprehensive description of its association state and structural organization in solution is necessary. We used analytical ultracentrifugation, analytical size-exclusion chromatography, and dynamic light scattering to characterize the interactions and homogeneity of AFP III in solution. Small-angle neutron scattering was used to determine the low-resolution structure in solution. Our results clearly show that at concentrations up to 20 mg mL(-1) and at temperatures of 20 degrees C, 6 degrees C, and 4 degrees C, AFP III is monomeric in solution and adopts a structure compatible with that determined by crystallography. Surface tension measurements show a propensity of AFP III to localize at the air/water interface, but this surface activity is not correlated with any aggregation in the bulk. These results support the hypothesis that each AFP III molecule acts independently of the others, and that specific intermolecular interactions between monomers are not required for binding to ice. The lack of attractive interactions between monomers may be functionally important, allowing for more efficient binding and covering of the ice surface.

  4. Structure and reactivity of a mononuclear non-haem iron(III)–peroxo complex

    PubMed Central

    Cho, Jaeheung; Jeon, Sujin; Wilson, Samuel A.; Liu, Lei V.; Kang, Eun A; Braymer, Joseph J.; Lim, Mi Hee; Hedman, Britt; Hodgson, Keith O.; Valentine, Joan Selverstone; Solomon, Edward I.; Nam, Wonwoo

    2012-01-01

    Oxygen-containing mononuclear iron species—iron(III)–peroxo, iron(III)–hydroperoxo and iron(IV)–oxo—are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes1–7. It has been difficult to generate synthetic analogues of these three active iron–oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(III)–peroxo complex, [Fe(III)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(III)–peroxo complex is cleanly converted to the iron(III)–hydroperoxo complex, [Fe(III)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(III)–hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(IV)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(III)–hydroperoxo species. All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(III)–hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(IV)–oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(III)–hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes. PMID:22031443

  5. 46 CFR 11.505 - Engineer officer structure.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Engineer officer structure. 11.505 Section 11.505 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY MERCHANT MARINE OFFICERS AND SEAMEN REQUIREMENTS FOR OFFICER ENDORSEMENTS Professional Requirements for Engineer Officer § 11.505 Engineer officer...

  6. 46 CFR 11.505 - Engineer officer structure.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 1 2013-10-01 2013-10-01 false Engineer officer structure. 11.505 Section 11.505 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY MERCHANT MARINE OFFICERS AND SEAMEN REQUIREMENTS FOR OFFICER ENDORSEMENTS Professional Requirements for Engineer Officer § 11.505 Engineer officer...

  7. 46 CFR 11.505 - Engineer officer structure.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 1 2011-10-01 2011-10-01 false Engineer officer structure. 11.505 Section 11.505 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY MERCHANT MARINE OFFICERS AND SEAMEN REQUIREMENTS FOR OFFICER ENDORSEMENTS Professional Requirements for Engineer Officer § 11.505 Engineer officer...

  8. Hard magnetism in structurally engineered silica nanocomposite.

    PubMed

    Song, Hyon-Min; Zink, Jeffrey I

    2016-09-21

    Creation of structural complexity by simple experimental control will be an attractive approach for the preparation of nanomaterials, as a classical bottom-up method is supplemented by a more efficient and more direct artificial engineering method. In this study, structural manipulation of MCM-41 type mesoporous silica is investigated by generating and imbedding hard magnetic CoFe2O4 nanoparticles into mesoporous silica. Depending on the heating rate and target temperature, mesoporous silica undergoes a transformation in shape to form hollow silica, framed silica with interior voids, or melted silica with intact mesostructures. Magnetism is governed by the major CoFe2O4 phase, and it is affected by antiferromagnetic hematite (α-Fe2O3) and olivine-type cobalt silicate (Co2SiO4), as seen in its paramagnetic behavior at the annealing temperature of 430 °C. The early formation of Co2SiO4 than what is usually observed implies the effect of the partial substitution of Fe in the sites of Co. Under slow heating (2.5 °C min(-1)) mesostructures are preserved, but with significantly smaller mesopores (d100 = 1.5 nm). In addition, nonstoichiometric CoxFe1-xO with metal vacancies at 600 °C, and spinel Co3O4 at 700 °C accompany major CoFe2O4. The amorphous nature of silica matrix is thought to contribute significantly to these structurally diverse and rich phases, enabled by off-stoichiometry between Si and O, and accelerated by the diffusion of metal cations into SiO4 polyhedra at an elevated temperature. PMID:27537252

  9. Hard magnetism in structurally engineered silica nanocomposite.

    PubMed

    Song, Hyon-Min; Zink, Jeffrey I

    2016-09-21

    Creation of structural complexity by simple experimental control will be an attractive approach for the preparation of nanomaterials, as a classical bottom-up method is supplemented by a more efficient and more direct artificial engineering method. In this study, structural manipulation of MCM-41 type mesoporous silica is investigated by generating and imbedding hard magnetic CoFe2O4 nanoparticles into mesoporous silica. Depending on the heating rate and target temperature, mesoporous silica undergoes a transformation in shape to form hollow silica, framed silica with interior voids, or melted silica with intact mesostructures. Magnetism is governed by the major CoFe2O4 phase, and it is affected by antiferromagnetic hematite (α-Fe2O3) and olivine-type cobalt silicate (Co2SiO4), as seen in its paramagnetic behavior at the annealing temperature of 430 °C. The early formation of Co2SiO4 than what is usually observed implies the effect of the partial substitution of Fe in the sites of Co. Under slow heating (2.5 °C min(-1)) mesostructures are preserved, but with significantly smaller mesopores (d100 = 1.5 nm). In addition, nonstoichiometric CoxFe1-xO with metal vacancies at 600 °C, and spinel Co3O4 at 700 °C accompany major CoFe2O4. The amorphous nature of silica matrix is thought to contribute significantly to these structurally diverse and rich phases, enabled by off-stoichiometry between Si and O, and accelerated by the diffusion of metal cations into SiO4 polyhedra at an elevated temperature.

  10. Electrical properties of nanofibers and structural characterization of DNA-Au(III) complexes.

    PubMed

    Kwon, Young-Wan; Lee, Chang Hoon; Jin, Jung-Il; Hwang, Jong Seung; Hwang, Sung Woo

    2014-05-23

    In order to realize deoxyribonucleic acid (DNA)-based molecular electronics, chemical modifications of DNA are needed to improve electrical conductivity. We developed a novel method utilizing the incorporation of Au(III) ions into DNA bases to alter their electronic properties. When Au(III) ions were incorporated proportionally into DNA bases, conductance increased up to an Au(III) content of 0.42 Au(III) ion/nucleotide. Surprisingly, electron paramagnetic resonance signals of Au(II) ions were detected at g ∼1.98, and the calculated spin number of Au(II) ions ranged from ∼10(13) to ∼10(15). The structural deformation of the DNA helix occurred when complexed with Au(III); simultaneously, the conductance of DNA-Au(III) complexes decreased when the content of Au(III) was higher than 0.42 atom/nucleotide. This observation implies that the maintenance of helical structure in the Au(III) doped state of DNA molecules is very important to the enhancement of the carrier mobility of DNA. PMID:24786616

  11. Insight into the flagella type III export revealed by the complex structure of the type III ATPase and its regulator.

    PubMed

    Imada, Katsumi; Minamino, Tohru; Uchida, Yumiko; Kinoshita, Miki; Namba, Keiichi

    2016-03-29

    FliI and FliJ form the FliI6FliJ ATPase complex of the bacterial flagellar export apparatus, a member of the type III secretion system. The FliI6FliJ complex is structurally similar to the α3β3γ complex of F1-ATPase. The FliH homodimer binds to FliI to connect the ATPase complex to the flagellar base, but the details are unknown. Here we report the structure of the homodimer of a C-terminal fragment of FliH (FliHC2) in complex with FliI. FliHC2 shows an unusually asymmetric homodimeric structure that markedly resembles the peripheral stalk of the A/V-type ATPases. The FliHC2-FliI hexamer model reveals that the C-terminal domains of the FliI ATPase face the cell membrane in a way similar to the F/A/V-type ATPases. We discuss the mechanism of flagellar ATPase complex formation and a common origin shared by the type III secretion system and the F/A/V-type ATPases. PMID:26984495

  12. Advanced fabrication techniques for cooled engine structures

    NASA Technical Reports Server (NTRS)

    Buchmann, O. A.

    1978-01-01

    An improved design for regeneratively cooled engine structures was identified. This design uses photochemically machined (PCM) coolant passages. It permits the braze joint to be placed in a relatively cool area, remote from the critical hot face sheet. The geometry of the passages at the face sheet also minimizes stress concentration and, therefore, enhances the low cycle fatigue performance. The two most promising alloys identified for this application are Inconel 617 and Nickel 201. Inconel 617 was selected because it has excellent creep rupture properties, while Nickel 201 was selected because of its predicted good performance under low cycle fatigue loading. The fabrication of the PCM coolant passages in both Inconel 617 and Nickel 201 was successfully developed. During fabrication of Inconel 617, undesirable characteristics were observed in the braze joints. A development program to resolve this condition was undertaken and led to definition of an isothermal solidification process for joining Inconel 617 panels. This process produced joints which approach parent metal strength and homogeneity.

  13. Balancer structure for three-cylinder engines

    SciTech Connect

    Suzuki, T.

    1987-04-21

    This patent describes a balancer structure for a three-cylinder in-line engine having three cylinders, the latter comprising a first and third cylinder and a second cylinder disposed between the first and third cylinders, a crankshaft having crank arms disposed at angles of 120/sup 0/ with respect to each other and operatively connected to a piston assembly within each of the cylinders, respectively, consisting of: a single crankshaft adjacent and parallel to and rotated at the same speed as the crankshaft but in the opposite direction, means comprising first counterweights securely mounted on the crankshaft only at positions thereof corresponding to the first and third cylinders for balancing of a part of inertia forces of rotating masses and a part of inertia forces of reciprocating masses; means comprising at least one second counterweight securely mounted on the crankshaft substantially opposite to the crank arm corresponding to the second cylinder for balancing of the remainder of the inertia forces of rotating masses; at least two balancers respectively securely mounted on the countershaft at both ends respectively thereof for the balancing of the remainder of the inertia forces of reciprocating masses, and of the couple of inertia of the crankshaft about axes perpendicular to the crankshaft.

  14. The role of a metastable RNA secondary structure in hepatitis delta virus genotype III RNA editing

    PubMed Central

    Linnstaedt, Sarah D.; Kasprzak, Wojciech K.; Shapiro, Bruce A.; Casey, John L.

    2006-01-01

    RNA editing plays a critical role in the life cycle of hepatitis delta virus (HDV). The host editing enzyme ADAR1 recognizes specific RNA secondary structure features around the amber/W site in the HDV antigenome and deaminates the amber/W adenosine. A previous report suggested that a branched secondary structure is necessary for editing in HDV genotype III. This branched structure, which is distinct from the characteristic unbranched rod structure required for HDV replication, was only partially characterized, and knowledge concerning its formation and stability was limited. Here, we examine the secondary structures, conformational dynamics, and amber/W site editing of HDV genotype III RNA using a miniaturized HDV genotype III RNA in vitro. Computational analysis of this RNA using the MPGAfold algorithm indicated that the RNA has a tendency to form both metastable and stable unbranched secondary structures. Moreover, native polyacrylamide gel electrophoresis demonstrated that this RNA forms both branched and unbranched rod structures when transcribed in vitro. As predicted, the branched structure is a metastable structure that converts readily to the unbranched rod structure. Only branched RNA was edited at the amber/W site by ADAR1 in vitro. The structural heterogeneity of HDV genotype III RNA is significant because not only are both conformations of the RNA functionally important for viral replication, but the ratio of the two forms could modulate editing by determining the amount of substrate RNA available for modification. PMID:16790843

  15. Fatigue reliability of cracked engineering structures

    NASA Astrophysics Data System (ADS)

    Lanning, David Bruce, Jr.

    1997-12-01

    This study investigates the reliability of engineering structures containing fatigue cracks. Stress concentrations and welded joints are probable locations for the initiation and propagation of fatigue cracks. Due to the many unknowns of loading, materials properties, crack sizes and crack shapes present at these locations, a statistics-based reliability analysis is valuable in the careful consideration of these many different random factors involved in a fatigue life analysis, several of which are expanded upon in this study. The basic problem of a crack near a stress concentration is first considered. A formulation for the aspect ratio (a/c) of a propagating semi-elliptical fatigue crack located at the toe of a welded T-joint is developed using Newman and Raju's stress intensity factor for a cracked flat plate with a weld magnification factor and compared to that of a cracked flat plate, and the reliability in terms of fatigue lifetime is calculated with the aid of Paris' crack propagation equation for membrane and bending loadings. Crack closure effects are then introduced in the consideration of short crack effects, where crack growth rates typically may exceed those found using traditional linear elastic fracture mechanics solutions for long cracks. The probability of a very small, microstructurally influenced crack growing to a size influenced by local plastic conditions is calculated utilizing the probability of a crack continuing to grow past an obstacle, such as a grain boundary. The result is then combined with the probability for failure defined using the crack closure-modified Paris equation to find an overall reliability for the structure. Last, the probability of fracture is determined when a crack front encounters regions of non-uniform toughness, such as typical in the heat affected zone of a welded joint. An expression for the effective crack lengths of the dissimilar regions is derived, and used in a weakest-link fracture model in the evaluation

  16. Frequency Fine Structures of Type III Bursts Due to Localized Medium-Scale Density Structures Along Paths of Type III Beams

    NASA Astrophysics Data System (ADS)

    Li, B.; Cairns, Iver H.; Robinson, P. A.

    2012-07-01

    Predictions from large-scale kinetic simulations are presented for the effects on coronal type III bursts of localized, medium-scale, enhanced density structures superposed on the coronal background along the paths of type III beams. The simulations show that these density structures can produce pronounced frequency fine structures in type III spectra. Flux intensifications and reductions of f p and 2 f p emission relative to those for the unperturbed background corona occur at frequencies corresponding to the density structures, where f p is the local electron plasma frequency. Frequency fine structures that are intense, slowly drifting, and narrowband, and thus resemble the characteristics of stria bursts, are predicted for the 2 f p emission. The 2 f p results are consistent with the qualitative proposal of Takakura and Yousef ( Solar Phys. 40, 421, 1975) for the interpretation of stria/type IIIb bursts. However, the predicted f p emission is much weaker than the 2 f p emission and generally below observable levels, and the predicted frequency fine structures do not always show stria characteristics. The predictions are thus inconsistent with the qualitative suggestion of Takakura and Yousef and the interpretations of many observers that stria bursts occur more often in f p than in 2 f p emission. The significant discrepancies for f p emission between our numerical calculations and the qualitative proposition of Takakura and Yousef (1975) are mainly caused by: i) differences in the detailed emission processes, ii) neglect of scattering of f p emission off small-scale density fluctuations by Takakura and Yousef (1975), and iii) other simplifications made in both works. Possible improvements to the simulations are discussed, including improvements to the emission processes and the coronal and beam conditions ( e.g., beam speed), in order to produce realistic stria/type IIIb bursts in f p emission.

  17. 1. Photographic copy of engineering drawing showing structure of Test ...

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

    1. Photographic copy of engineering drawing showing structure of Test Stand 'B' (4215/E-16), also known as the 'Short Snorter.' California Institute of Technology, Jet Propulsion Laboratory, Plant Engineering 'Structural Addition - Bldg. E-12, Edwards Test Station,' drawing no. E12/1-1, 8 August 1957. - Jet Propulsion Laboratory Edwards Facility, Test Stand B, Edwards Air Force Base, Boron, Kern County, CA

  18. Tetrametallic lanthanide(III) phosphonate cages: synthetic, structural and magnetic studies.

    PubMed

    Zangana, Karzan H; Pineda, Eufemio Moreno; Winpenny, Richard E P

    2014-12-01

    The synthesis, structures and magnetic properties of a family of lanthanide complexes containing phosphonate ligands are reported. Reaction of hydrated lanthanide nitrate and (t)butylphosphonic acid under reflux conditions in iso-butanol, in the presence of pivalic acid as a co-ligand produced five new lanthanide complexes; pyridine (py) was present as a base. The compounds formed are tetrametallic, with the general formula [pyH]4[Ln4(μ3-OH)(O3P(t)Bu)3(HO3P(t)Bu)(O2C(t)Bu)2(NO3)6] where Ln = Gd(III), 1; Tb(III), 2; Dy(III), 3; Ho(III), 4 and Er(III), 5. The metal sites within the complexes lie on the vertices of a triangle-based pyramid, with phosphonate ligands on the triangular faces linking the apical Ln site to the Ln sites in the base. Each lanthanide(III) site is eight-coordinate. Magnetic studies of the compounds show a decline in the product χ(M)T with T; modelling the behaviour of 1 shows anti-ferromagnetic exchange between Gd(III) centres within the triangle with a negligible interaction to the fourth Gd(III) centre at the apex of the trigonal pyramid. PMID:25310820

  19. Engineering Property Prediction Tools for Tailored Polymer Composite Structures

    SciTech Connect

    Nguyen, Ba Nghiep; Foss, Peter; Wyzgoski, Michael; Trantina, Gerry; Kunc, Vlastimil; Schutte, Carol; Smith, Mark T.

    2009-12-23

    This report summarizes our FY 2009 research activities for the project titled:"Engineering Property Prediction Tools for Tailored Polymer Composite Structures." These activities include (i) the completion of the development of a fiber length attrition model for injection-molded long-fiber thermoplastics (LFTs), (ii) development of the a fatigue damage model for LFTs and its implementation in ABAQUS, (iii) development of an impact damage model for LFTs and its implementation in ABAQUS, (iv) development of characterization methods for fatigue testing, (v) characterization of creep and fatigue responses of glass-fiber/polyamide (PA6,6) and glass-fiber/polypropylene (PP), (vi) characterization of fiber length distribution along the flow length of glass/PA6,6 and glass-fiber/PP, and (vii) characterization of impact responses of glass-fiber/PA6,6. The fiber length attrition model accurately captures the fiber length distribution along the flow length of the studied glass-fiber/PP material. The fatigue damage model is able to predict the S-N and stiffness reduction data which are valuable to the fatigue design of LFTs. The impact damage model correctly captures damage accumulation observed in experiments of glass-fiber/PA6,6 plaques.Further work includes validations of these models for representative LFT materials and a complex LFT part.

  20. Predicted band structures of III-V semiconductors in the wurtzite phase

    SciTech Connect

    De, A.; Pryor, Craig E.

    2010-04-15

    While non-nitride III-V semiconductors typically have a zinc-blende structure, they may also form wurtzite crystals under pressure or when grown as nanowhiskers. This makes electronic structure calculation difficult since the band structures of wurtzite III-V semiconductors are poorly characterized. We have calculated the electronic band structure for nine III-V semiconductors in the wurtzite phase using transferable empirical pseudopotentials including spin-orbit coupling. We find that all the materials have direct gaps. Our results differ significantly from earlier ab initio calculations, and where experimental results are available (InP, InAs, and GaAs) our calculated band gaps are in good agreement. We tabulate energies, effective masses, and linear and cubic Dresselhaus zero-field spin-splitting coefficients for the zone-center states. The large zero-field spin-splitting coefficients we find may facilitate the development of spin-based devices.

  1. Synthesis, crystal structure, interaction with BSA and antibacterial activity of La(III) and Sm(III) complexes with enrofloxacin.

    PubMed

    Wang, Yan-Jun; Hu, Rui-Ding; Jiang, Dong-Hua; Zhang, Ping-Hua; Lin, Qiu-Yue; Wang, Yun-Yun

    2011-03-01

    Two new La(III) and Sm(III) complexes with enrofloxacin (HER, 1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid, C(19)H(21)FN(3)O(3)), [La(2)(ER)(6)(H(2)O)(2)]·14H(2)O(1) and [Sm(2)(ER)(6)(H(2)O)(2)]·14H(2)O(2) have been synthesized and characterized by elemental analysis, FT-IR, TG-DTG and X-ray single crystal diffraction. Both of the complexes are triclinic system with space group Pī. The structure of the complexes show that each rare earth atom in both complexes was nine-coordinated. Two of the enrofloxacin ions acted as tridentate chelate and bridging ligands, while the others as bidentate chelate ligands. The binding reaction between the complexes and bovine serum albumin (BSA) was studied by UV-vis absorption spectra and fluorescence spectroscopy. The results indicated that the two complexes had a quite strong ability to quench the fluorescence from BSA and the binding reaction was mainly a static quenching process. The binding constants K ( A )/(L·mol(-1)) were 1.46 × 10(5)(1) and 8.59 × 10(6)(2) and one binding site was formed. The synchronous spectroscopy suggested that tryptophan residues were placed in BSA. It was also found that the two complexes exhibited greater antimicrobial activity than enrofloxacin at given concentrations.

  2. Faculty Perceptions of Students: Structure of Faculty Characterizations, Part III.

    ERIC Educational Resources Information Center

    Davis, Junius A.

    The structure of characterizations of college students by faculty members, particularly observable and significant dimensions or trait patterns, were investigated. Student ratings by faculty members on 80 bi-polar traits, together with Scholastic Aptitude Test (SAT) scores and high school and college freshman average grades, were obtained.…

  3. Flight Investigation of the Cooling Characteristics of a Two-row Radial Engine Installation III : Engine Temperature Distribution

    NASA Technical Reports Server (NTRS)

    Rennak, Robert M; Messing, Wesley E; Morgan, James E

    1946-01-01

    The temperature distribution of a two-row radial engine in a twin-engine airplane has been investigated in a series of flight tests. The test engine was operated over a wide range of conditions at density altitudes of 5000 and 20,000 feet; quantitative results are presented showing the effects of flight and engine variables upon average engine temperature and over-all temperature spread. Discussions of the effect of the variables on the shape of the temperature patterns and on the temperature distribution of individual cylinders are also included. The results indicate that, for the tests conducted, the temperature distribution patterns were chiefly determined by the fuel-air ratio and cooling-air distributions. It was possible to calculate individual cylinder temperature, on the assumption of equal power distribution among cylinders, to within an average of plus or minus 14 degrees F. of the actual temperature. A considerable change occurred in either the spread or the thrust axis, the average engine fuel-air ratio, the engine speed, the power, or the blower ratio. Smaller effects on the temperature pattern were noticed with a change in cowl-flap opening and altitude. In most of the tests, a change in conditions affected the temperature of the barrels less than that of the heads. The variation of flight and engine variables had a negligible effect on the temperature distributions of the individual cylinders. (author)

  4. RNA structure-dependent uncoupling of substrate recognition and cleavage by Escherichia coli ribonuclease III

    PubMed Central

    Calin-Jageman, Irina; Nicholson, Allen W.

    2003-01-01

    Members of the ribonuclease III superfamily of double-strand-specific endoribonucleases participate in diverse RNA maturation and decay pathways. Ribonuclease III of the gram-negative bacterium Escherichia coli processes rRNA and mRNA precursors, and its catalytic action can regulate gene expression by controlling mRNA translation and stability. It has been proposed that E.coli RNase III can function in a non-catalytic manner, by binding RNA without cleaving phosphodiesters. However, there has been no direct evidence for this mode of action. We describe here an RNA, derived from the T7 phage R1.1 RNase III substrate, that is resistant to cleavage in vitro by E.coli RNase III but retains comparable binding affinity. R1.1[CL3B] RNA is recognized by RNase III in the same manner as R1.1 RNA, as revealed by the similar inhibitory effects of a specific mutation in both substrates. Structure-probing assays and Mfold analysis indicate that R1.1[CL3B] RNA possesses a bulge– helix–bulge motif in place of the R1.1 asymmetric internal loop. The presence of both bulges is required for uncoupling. The bulge–helix–bulge motif acts as a ‘catalytic’ antideterminant, which is distinct from recognition antideterminants, which inhibit RNase III binding. PMID:12711683

  5. Theoretical discovery of stable structures of group III-V monolayers: The materials for semiconductor devices

    SciTech Connect

    Suzuki, Tatsuo

    2015-11-23

    Group III-V compounds are very important as the materials of semiconductor devices. Stable structures of the monolayers of group III-V binary compounds have been discovered by using first-principles calculations. The primitive unit cell of the discovered structures is a rectangle, which includes four group-III atoms and four group-V atoms. A group-III atom and its three nearest-neighbor group-V atoms are placed on the same plane; however, these connections are not the sp{sup 2} hybridization. The bond angles around the group-V atoms are less than the bond angle of sp{sup 3} hybridization. The discovered structure of GaP is an indirect transition semiconductor, while the discovered structures of GaAs, InP, and InAs are direct transition semiconductors. Therefore, the discovered structures of these compounds have the potential of the materials for semiconductor devices, for example, water splitting photocatalysts. The discovered structures may become the most stable structures of monolayers which consist of other materials.

  6. High-performance computing in structural mechanics and engineering

    SciTech Connect

    Adeli, H.; Kamat, M.P.; Kulkarni, G.; Vanluchene, R.D. Georgia Inst. of Technology, Atlanta Montana State Univ., Bozeman )

    1993-07-01

    Recent advances in computer hardware and software have made multiprocessing a viable and attractive technology. This paper reviews high-performance computing methods in structural mechanics and engineering through the use of a new generation of multiprocessor computers. The paper presents an overview of vector pipelining, performance metrics for parallel and vector computers, programming languages, and general programming considerations. Recent developments in the application of concurrent processing techniques to the solution of structural mechanics and engineering problems are reviewed, with special emphasis on linear structural analysis, nonlinear structural analysis, transient structural analysis, dynamics of multibody flexible systems, and structural optimization. 64 refs.

  7. Synthesis, crystal structure and magnetic properties of a novel heterobimetallic rhenium(IV)-dysprosium(III) chain.

    PubMed

    Pejo, Carolina; Guedes, Guilherme P; Novak, Miguel A; Speziali, Nivaldo L; Chiozzone, Raúl; Julve, Miguel; Lloret, Francesc; Vaz, Maria G F; González, Ricardo

    2015-06-01

    The use of the mononuclear rhenium(IV) precursor [ReBr5 (H2 pydc)](-) (H2 pydc=3,5-pyridinedicarboxylic acid) as a metalloligand towards dysprosium(III) afforded the first heterobimetallic Re(IV) -Dy(III) complex. Crystal structures and static and dynamic magnetic properties of both rhenium-containing species are reported herein. The 5d-4f compound shows an extended 1D structure and the AC magnetic measurements reveal frequency dependence at low temperature suggesting slow relaxation of the magnetization.

  8. Type III polyketide synthase repertoire in Zingiberaceae: computational insights into the sequence, structure and evolution.

    PubMed

    Mallika, Vijayanathan; Aiswarya, Girija; Gincy, Paily Thottathil; Remakanthan, Appukuttan; Soniya, Eppurathu Vasudevan

    2016-07-01

    Zingiberaceae or 'ginger family' is the largest family in the order 'Zingiberales' with more than 1300 species in 52 genera, which are mostly distributed throughout Asia, tropical Africa and the native regions of America with their maximum diversity in Southeast Asia. Many of the members are important spice, medicinal or ornamental plants including ginger, turmeric, cardamom and kaempferia. These plants are distinguished for the highly valuable metabolic products, which are synthesised through phenylpropanoid pathway, where type III polyketide synthase is the key enzyme. In our present study, we used sequence, structural and evolutionary approaches to scrutinise the type III polyketide synthase (PKS) repertoire encoded in the Zingiberaceae family. Highly conserved amino acid residues in the sequence alignment and phylogram suggested strong relationships between the type III PKS members of Zingiberaceae. Sequence and structural level investigation of type III PKSs showed a small number of variations in the substrate binding pocket, leading to functional divergence among these PKS members. Molecular evolutionary studies indicate that type III PKSs within Zingiberaceae evolved under strong purifying selection pressure, and positive selections were rarely detected in the family. Structural modelling and protein-small molecule interaction studies on Zingiber officinale PKS 'a representative from Zingiberaceae' suggested that the protein is comparatively stable without much disorder and exhibited wide substrate acceptance.

  9. Type III polyketide synthase repertoire in Zingiberaceae: computational insights into the sequence, structure and evolution.

    PubMed

    Mallika, Vijayanathan; Aiswarya, Girija; Gincy, Paily Thottathil; Remakanthan, Appukuttan; Soniya, Eppurathu Vasudevan

    2016-07-01

    Zingiberaceae or 'ginger family' is the largest family in the order 'Zingiberales' with more than 1300 species in 52 genera, which are mostly distributed throughout Asia, tropical Africa and the native regions of America with their maximum diversity in Southeast Asia. Many of the members are important spice, medicinal or ornamental plants including ginger, turmeric, cardamom and kaempferia. These plants are distinguished for the highly valuable metabolic products, which are synthesised through phenylpropanoid pathway, where type III polyketide synthase is the key enzyme. In our present study, we used sequence, structural and evolutionary approaches to scrutinise the type III polyketide synthase (PKS) repertoire encoded in the Zingiberaceae family. Highly conserved amino acid residues in the sequence alignment and phylogram suggested strong relationships between the type III PKS members of Zingiberaceae. Sequence and structural level investigation of type III PKSs showed a small number of variations in the substrate binding pocket, leading to functional divergence among these PKS members. Molecular evolutionary studies indicate that type III PKSs within Zingiberaceae evolved under strong purifying selection pressure, and positive selections were rarely detected in the family. Structural modelling and protein-small molecule interaction studies on Zingiber officinale PKS 'a representative from Zingiberaceae' suggested that the protein is comparatively stable without much disorder and exhibited wide substrate acceptance. PMID:27138283

  10. Molecular structure and magnetic properties of acetato-bridged lanthanide(III) dimers

    SciTech Connect

    Panagiotopoulos, A.; Zafiropoulos, T.F.; Perlepes, S.P.

    1995-09-13

    Structural, magnetic, and EPR studies of diaquatetrakis({mu}-acetato)dicopper(II) have provided important insight into the magnetic interaction phenomenon in polynuclear species involving 3d ions. This compound may be considered at the archetype of the exchange-coupled copper(II) dimers. Until now, no compound of the same nature involving lanthanide(III) ions had been reported, and the factors determining the sign and the magnitude of the magnetic interaction between lanthanide(III) ions are far from being well understood. Herein the authors report on the synthesis, the structure and the magnetic properties of two lanthanide(III) dimers, namely [Ln{sub 2}(CH{sub 3}CO{sub 2}){sub 6-} (phen){sub 2}] with phen = o-phenanthroline and Ln = Ce (1) and Gd (2).

  11. 15. Photocopy of Engineering Drawing, Structural Steel Details (from City ...

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

    15. Photocopy of Engineering Drawing, Structural Steel Details (from City of Norton Shores) - William S. Antisdale Memorial State Reward Bridge, Spanning Mona Lake at Henry Street, Norton Shores, Muskegon County, MI

  12. Structure of a fibronectin type III-like module from Clostridium thermocellum

    PubMed Central

    Alahuhta, Markus; Xu, Qi; Brunecky, Roman; Adney, William S.; Ding, Shi-You; Himmel, Michael E.; Lunin, Vladimir V.

    2010-01-01

    The 1.6 Å resolution structure of a fibronectin type III-like module from Clostridium thermocellum (PDB code 3mpc) with two molecules in the asymmetric unit is reported. The crystals used for data collection belonged to space group P212121, with unit-cell parameters a = 35.43, b = 45.73, c = 107.72 Å, and the structure was refined to an R factor of 0.166. Structural comparisons found over 800 similar structures in the Protein Data Bank. The broad range of different proteins or protein domains with high structural similarity makes it especially demanding to classify these proteins. Previous studies of fibronectin type III-like modules have indicated that they might function as ligand-binding modules, as a compact form of peptide linkers or spacers between other domains, as cellulose-disrupting modules or as proteins that help large enzyme complexes remain soluble. PMID:20693658

  13. Structure and electrical characterization of gallium arsenide nanowires with different V/III ratio growth parameters

    SciTech Connect

    Muhammad, R.; Ahamad, R.; Ibrahim, Z.; Othaman, Z.

    2014-03-05

    Gallium arsenide (GaAs) nanowires were grown vertically on GaAs(111)B substrate by gold-assisted using metal-organic chemical vapour deposition. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and conductivity atomic force microscopy (CAFM) analysis were carried out to investigate the effects of V/III ratio on structural properties and current-voltage changes in the wires. Results show that GaAs NWs grow preferably in the wurtzite crystal structure than zinc blende crystal structure with increasing V/III ratio. Additionally, CAFM studies have revealed that zincblende nanowires indicate ohmic characteristic compared to oscillation current occurred for wurtzite structures. The GaAs NWs with high quality structures are needed in solar cells technology for trapping energy that directly converts of sunlight into electricity with maximum capacity.

  14. A NdIII enantiomeric pair: Synthesis, crystal structures and near-infrared luminescent properties

    NASA Astrophysics Data System (ADS)

    Li, Feng-Cai; Li, Xi-Li; Hu, Ming; Zhang, Xue-Li; Chen, Conghui; Zhu, Cancan

    2016-08-01

    Based on enantiopure bis-bidentate N-donor ligands (-)/(+)-2,5-bis(4,5-pinene- 2-pyridyl)pyrazine (LR/LS), a new pair of NdIII enantiomers with the formula Nd(dbm)3LR/S·2H2O (R-1 and S-1 being the isomers containing the LR and LS ligands, respectively, and dbm = dibenzoylmethanate) have been isolated and characterized by X-ray crystallography and spectroscopic methods. Notably, unlike our previously reported homodinuclear EuIII and DyIII complexes based on the identical ligands (LR and LS), the dinuclear NdIII congener have not been obtained by controlling the ligand-to-metal ratio as expected, the reason of which was elucidated in this work. The crystal structure analyses of R-1 and S-1 reveal that they are mononuclear NdIII complexes and crystallize in chiral space group P212121 of the orthorhombic system. Circular dichroic (CD) spectra confirmed their chiroptical activities and enantiomeric nature. The photoluminescence investigations showed that they display characteristic near-infrared (NIR) emissions of the NdIII ions with notable emitting lifetime value.

  15. A comparison of the DSM-5 Section II and Section III personality disorder structures.

    PubMed

    Anderson, Jaime; Snider, Stephen; Sellbom, Martin; Krueger, Robert; Hopwood, Christopher

    2014-05-30

    The DSM-5 Section III includes a hybrid model for the diagnosis of personality disorders, in which sets of dimensional personality trait facets are configured into personality disorder types. These PD types resemble the Section II categorical counterparts with dimensional traits descriptive of the Section II criteria to maintain continuity across the diagnostic systems. The current study sought to evaluate the continuity across the Section II and III models of personality disorders. This sample consisted of 397 undergraduate students, administered the Personality Inventory for the DSM-5 (Krueger et al., 2012) and the Structured Clinical Interview for the DSM-IV Axis II Disorders-Personality Questionnaire (First et al., 2013). We examined whether the DSM-5 Section III trait facets for the PDs would be associated with their respective Section II counterparts, as well as determining whether additional facets could augment the prediction of the Section II disorders. Results revealed that, generally, the DSM-5 Section II disorders were most strongly associated with their Section III traits. Results also showed evidence to support the addition of facets not included in the Section III diagnostic criteria in the prediction of most disorders. These results show general support for the Section III model of personality disorders, however, results also show that additional research is needed to replicate these findings.

  16. Structure of cellular ESCRT-III spirals and their relationship to HIV budding

    PubMed Central

    Cashikar, Anil G; Shim, Soomin; Roth, Robyn; Maldazys, Michael R; Heuser, John E; Hanson, Phyllis I

    2014-01-01

    The ESCRT machinery along with the AAA+ ATPase Vps4 drive membrane scission for trafficking into multivesicular bodies in the endocytic pathway and for the topologically related processes of viral budding and cytokinesis, but how they accomplish this remains unclear. Using deep-etch electron microscopy, we find that endogenous ESCRT-III filaments stabilized by depleting cells of Vps4 create uniform membrane-deforming conical spirals which are assemblies of specific ESCRT-III heteropolymers. To explore functional roles for ESCRT-III filaments, we examine HIV-1 Gag-mediated budding of virus-like particles and find that depleting Vps4 traps ESCRT-III filaments around nascent Gag assemblies. Interpolating between the observed structures suggests a new role for Vps4 in separating ESCRT-III from Gag or other cargo to allow centripetal growth of a neck constricting ESCRT-III spiral. DOI: http://dx.doi.org/10.7554/eLife.02184.001 PMID:24878737

  17. Aero/structural tailoring of engine blades (AERO/STAEBL)

    NASA Technical Reports Server (NTRS)

    Brown, K. W.

    1988-01-01

    This report describes the Aero/Structural Tailoring of Engine Blades (AERO/STAEBL) program, which is a computer code used to perform engine fan and compressor blade aero/structural numerical optimizations. These optimizations seek a blade design of minimum operating cost that satisfies realistic blade design constraints. This report documents the overall program (i.e., input, optimization procedures, approximate analyses) and also provides a detailed description of the validation test cases.

  18. Electrospun bio-composite P(LLA-CL)/collagen I/collagen III scaffolds for nerve tissue engineering.

    PubMed

    Kijeńska, Ewa; Prabhakaran, Molamma P; Swieszkowski, Wojciech; Kurzydlowski, Krzysztof J; Ramakrishna, Seeram

    2012-05-01

    One of the biggest challenges in peripheral nerve tissue engineering is to create an artificial nerve graft that could mimic the extracellular matrix (ECM) and assist in nerve regeneration. Bio-composite nanofibrous scaffolds made from synthetic and natural polymeric blends provide suitable substrate for tissue engineering and it can be used as nerve guides eliminating the need of autologous nerve grafts. Nanotopography or orientation of the fibers within the scaffolds greatly influences the nerve cell morphology and outgrowth, and the alignment of the fibers ensures better contact guidance of the cells. In this study, poly (L-lactic acid)-co-poly(ε-caprolactone) or P(LLA-CL), collagen I and collagen III are utilized for the fabrication of nanofibers of different compositions and orientations (random and aligned) by electrospinning. The morphology, mechanical, physical, and chemical properties of the electrospun scaffolds along with their biocompatibility using C17.2 nerve stem cells are studied to identify the suitable material compositions and topography of the electrospun scaffolds required for peripheral nerve regeneration. Aligned P(LLA-CL)/collagen I/collagen III nanofibrous scaffolds with average diameter of 253 ± 102 nm were fabricated and characterized with a tensile strength of 11.59 ± 1.68 MPa. Cell proliferation studies showed 22% increase in cell proliferation on aligned P(LLA-CL)/collagen I/collagen III scaffolds compared with aligned pure P(LLA-CL) scaffolds. Results of our in vitro cell proliferation, cell-scaffold interaction, and neurofilament protein expression studies demonstrated that the electrospun aligned P(LLA-CL)/collagen I/collagen III nanofibrous scaffolds mimic more closely towards the ECM of nerve and have great potential as a substrate for accelerated regeneration of the nerve.

  19. Increased procollagen type III peptide in serum of rabbits exposed to diesel engine exhaust

    SciTech Connect

    Suzuki, Takahito; Kanoh, Takako )

    1990-05-01

    Lung connective tissue is composed of collagen, elastin and proteoglycans. Collagen is the most abundant protein, comprising approximately 11% of normal adult lung and it has been provided at least five polymorphic types in lung. Collagen-producing cells such as fibroblasts and endothelial cells can synthesize procollagen within the cells. Once procollagen is secreted extracellularly, both amino- and carboxy-terminal peptides of procollagen are cleaved by endopeptidases. These peptides can move from the tissue into the blood stream. Therefore, the released peptides of type III procollagen may reflect the degree of biosynthesis of type III collagen, and increased peptide level in type III collagen, and increased peptide level in serum may suggest inflammation or the beginning of fibrosis. In this work, the authors have studied the changes of procollagen type III peptide (P-III-P) levels in sera and bronchoalveolar lavage fluid (BALF) from rabbits exposed to diesel exhaust in order to find a useful biochemical indicator of the effects of diesel exhaust exposure on human health.

  20. Speciation of iron; characterisation and structure of green rusts and Fe II-III oxyhydroxycarbonate fougerite

    NASA Astrophysics Data System (ADS)

    Génin, Jean-Marie R.; Abdelmoula, Mustapha; Ruby, Christian; Upadhyay, Chandan

    2006-06-01

    Fe II-Fe III hydroxysalt green rusts (GR) are very reactive layered double hydroxides that can be characterised mainly by XRD and Mössbauer spectroscopy. Mössbauer spectra of the main compounds presented in this article are reviewed with special emphasis on those of GRs constituted of one or two ferrous doublets and one ferric doublet. The structure of GR has a stacking sequence of alternating brucite-like layers of Fe II-III(OH) 6 octahedrons and anion interlayers as confirmed from XRD patterns. There exist two kinds of structure named green rust one (GR1) and green rust two (GR2) with R3¯m and P3¯m1 space groups, respectively. Cation and anion distributions within Fe layers and interlayers match abundances of Mössbauer spectrum components. In the view of that, it can be suggested that the fougerite mineral is partially deprotonated Fe II-III hydroxycarbonate with a general formula FeII6(1-x)FeIII6xOHCO, where x is within the range [ (1/3),(2/3)]. Cation substitution by Mg II and Al III cannot be excluded relating fougerite with other minerals like pyroaurite and hydrotalcite. To cite this article: J.-M.R. Génin et al., C. R. Geoscience 338 (2006).

  1. Crystal structure of hydrazine iron(III) phosphate, the first transition metal phosphate containing hydrazine

    PubMed Central

    David, Renald

    2015-01-01

    The title compound, poly[(μ2-hydrazine)(μ4-phosphato)iron(III)], [Fe(PO4)(N2H4)]n, was prepared under hydro­thermal conditions. Its asymmetric unit contains one FeIII atom located on an inversion centre, one P atom located on a twofold rotation axis, and two O, one N and two H atoms located on general positions. The FeIII atom is bound to four O atoms of symmetry-related PO4 tetra­hedra and to two N atoms of two symmetry-related hydrazine ligands, resulting in a slightly distorted FeO4N2 octa­hedron. The crystal structure consists of a three-dimensional hydrazine/iron phoshate framework whereby each PO4 tetra­hedron bridges four FeIII atoms and each hydrazine ligand bridges two FeIII atoms. The H atoms of the hydrazine ligands are also involved in moderate N—H⋯O hydrogen bonding with phosphate O atoms. The crystal structure is isotypic with the sulfates [Co(SO4)(N2H4)] and [Mn(SO4)(N2H4)]. PMID:26870399

  2. Molecular structure of yeast RNA polymerase III: demonstration of the tripartite transcriptive system in lower eukaryotes.

    PubMed Central

    Valenzuela, P; Hager, G L; Weinberg, F; Rutter, W J

    1976-01-01

    Homogeneous RNA polymerase III (RNA nucleotidyltransferase III) has been obtained from yeast. The subunit composition of the enzyme was examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme is composed of 12 putative subunits with molecular weights 160,000, 128,000, 82,000, 41,000, 40,500, 37,000, 34,000, 28,000, 24,000, 20,000, 14,500, and 11,000. The high-molecular-weight subunits and several of the smaller subunits of yeast RNA polymerase III are clearly different from those of enzymes I and II, indicating a distinct molecular structure. However, the molecular weights of some of the small subunits (41,000, 28,000, 24,000, and 14,500) appear to be identical to those of polymerases I and II. Thus, it is possible that the three classes of enzymes in yeast have some common subunits. As in other eukaryotes, yeast polymerase II is inhibited by relatively low concentrations of alpha-amanitin; however, contrary to what has been found in higher eukaryotes, yeast polymerase III is resistant (up to 2 mg/ml) to alpha-amanitin, while yeast polymerase I is sensitive to high concentrations of the drug (50% inhibition at 0.3 mg/ml). These results establish the existence of RNA polymerase III in yeast and provide a structural basis for the discrimination of the three functional polymerases in eukaryotes. Images PMID:772675

  3. Parameter identification of civil engineering structures

    NASA Technical Reports Server (NTRS)

    Juang, J. N.; Sun, C. T.

    1980-01-01

    This paper concerns the development of an identification method required in determining structural parameter variations for systems subjected to an extended exposure to the environment. The concept of structural identifiability of a large scale structural system in the absence of damping is presented. Three criteria are established indicating that a large number of system parameters (the coefficient parameters of the differential equations) can be identified by a few actuators and sensors. An eight-bay-fifteen-story frame structure is used as example. A simple model is employed for analyzing the dynamic response of the frame structure.

  4. Structural dynamic analysis of the Space Shuttle Main Engine

    NASA Technical Reports Server (NTRS)

    Scott, L. P.; Jamison, G. T.; Mccutcheon, W. A.; Price, J. M.

    1981-01-01

    This structural dynamic analysis supports development of the SSME by evaluating components subjected to critical dynamic loads, identifying significant parameters, and evaluating solution methods. Engine operating parameters at both rated and full power levels are considered. Detailed structural dynamic analyses of operationally critical and life limited components support the assessment of engine design modifications and environmental changes. Engine system test results are utilized to verify analytic model simulations. The SSME main chamber injector assembly is an assembly of 600 injector elements which are called LOX posts. The overall LOX post analysis procedure is shown.

  5. Amide I'-II' 2D IR spectroscopy provides enhanced protein secondary structural sensitivity.

    PubMed

    Deflores, Lauren P; Ganim, Ziad; Nicodemus, Rebecca A; Tokmakoff, Andrei

    2009-03-11

    We demonstrate how multimode 2D IR spectroscopy of the protein amide I' and II' vibrations can be used to distinguish protein secondary structure. Polarization-dependent amide I'-II' 2D IR experiments on poly-l-lysine in the beta-sheet, alpha-helix, and random coil conformations show that a combination of amide I' and II' diagonal and cross peaks can effectively distinguish between secondary structural content, where amide I' infrared spectroscopy alone cannot. The enhanced sensitivity arises from frequency and amplitude correlations between amide II' and amide I' spectra that reflect the symmetry of secondary structures. 2D IR surfaces are used to parametrize an excitonic model for the amide I'-II' manifold suitable to predict protein amide I'-II' spectra. This model reveals that the dominant vibrational interaction contributing to this sensitivity is a combination of negative amide II'-II' through-bond coupling and amide I'-II' coupling within the peptide unit. The empirically determined amide II'-II' couplings do not significantly vary with secondary structure: -8.5 cm(-1) for the beta sheet, -8.7 cm(-1) for the alpha helix, and -5 cm(-1) for the coil.

  6. Genetic analysis of bacteriophage lambda cIII gene: mRNA structural requirements for translation initiation.

    PubMed Central

    Kornitzer, D; Teff, D; Altuvia, S; Oppenheim, A B

    1989-01-01

    The bacteriophage lambda cIII gene product regulates the lysogenic pathway. The cIII gene is located in the leftward operon, which is transcribed from the pL promoter. We have previously shown (S. Altuvia and A. B. Oppenheim, J. Bacteriol. 167:415-419, 1986) that mutations that show elevated expression lie within the cIII coding sequence. We isolated mutants that show decreased CIII activity. All the mutations were found to cause a drastic reduction in the rate of initiation of cIII translation. Several mutations were found to be scattered within the first 40 nucleotides of the cIII coding region. Additional mutations affected the AUG initiation codon, the Shine-Dalgarno sequence, and the upstream RNaseIII processing site. Computer folding of the cIII mRNA suggested the presence of two alternative RNA structures. All the mutations within the coding region that reduce expression reduce the stability of one specific mRNA structure (structure B). Mutations that increase expression lie in the loops of this structure and may in fact stabilize it by interfering with the formation of the alternative structure (structure A). Thus, it appears that a specific mRNA secondary structure at the beginning of the cIII coding region is essential for efficient translation, suggesting that changes in mRNA structure regulate cIII expression. Images PMID:2523380

  7. Developing a "highway code" to steer the structural and electronic properties of Fe(III)/Dy(III) coordination clusters.

    PubMed

    Chen, Sihuai; Mereacre, Valeriu; Prodius, Denis; Kostakis, George E; Powell, Annie K

    2015-04-01

    In the recently established field of 3d/4f coordination cluster (CC) chemistry several burning questions still need to be addressed. It is clear that combining 3d and 4f metal ions within a coordination cluster core has the potential to lead to electronic structures that will be very difficult to describe but can also be extremely interesting. Furthermore, understanding why certain core topologies seem to be favored is difficult to predict. Here we show that the secondary coordination sphere provided by the ligands influences the favored product, as demonstrated for the compound [Fe4Dy2(μ3-OH)2(n-bdea)4(C6H5CO2)8]·MeCN (1), which has a 2Fe:2Dy:2Fe core and was made using [Fe(III)3O(C6H5)CO2)(L)3](+) as starting material plus Dy(NO3)3 and N-n-butyl-diethanolamine (n-bdeaH2), compared with the compound made using a methyl meta-substituent (R) on the phenyl ring of the benzoate, [Fe(III)3O(C6H4Me)CO2)(L)3](+) as starting material, which resulted in the "square-in-square" compound [Fe4Dy4(μ3-OH)4(n-bdea)4(O2CC6H4CH3)12]·MeCN (2) when using ambient conditions. Changing reaction conditions from ambient to solvothermal leads to "double-propeller" compounds [Fe4Dy4(μ4-O)3(n-bdea)3(C6H5CO2)12]·13MeCN (3) and [Fe4Dy4(μ4-O)3(n-bdea)3(O2CC6H4CH3)12]·MeCN (4) forming with this core, resulting irrespective of the substitution on the iron benzoate starting material. Furthermore, compounds 1 and 2 can be transformed into compounds 3 and 4, respectively, using a solvothermal method. Thus, compounds 3 and 4 appear to be the thermodynamically most stable species. The factors steering the reactions toward these products are discussed. The electronic structures have been investigated using magnetic and Mössbauer studies. All compounds are cooperatively coupled 3d/4f systems, with compound 1 showing single-molecule magnet behavior.

  8. Cyanide-bridged Fe(III)-Mn(III) bimetallic complexes with dimeric and chain structures constructed from a newly made mer-Fe tricyanide: structures and magnetic properties.

    PubMed

    Kim, Jae Il; Kwak, Hyun Young; Yoon, Jung Hee; Ryu, Dae Won; Yoo, In Young; Yang, Namgeun; Cho, Beong Ki; Park, Je-Geun; Lee, Hyosug; Hong, Chang Seop

    2009-04-01

    Four cyanide-linked Fe(III)-Mn(III) complexes were prepared by reacting Mn Schiff bases with a new molecular precursor (PPh(4))[Fe(qcq)(CN)(3)] [1; qcq = 8-(2-quinolinecarboxamido)quinoline anion]. They include a dimeric molecule, [Fe(qcq)(CN)(3)][Mn(3-MeOsalen)(H(2)O)] x 2 H(2)O [2 x 2 H(2)O; 3-MeOsalen = N,N'-ethylenebis(3-methoxysalicylideneiminato) dianion], and three 1D zigzag chains, [Fe(qcq)(CN)(3)][Mn(5-Clsalen)] x 3 H(2)O [3 x 2 MeOH; 5-Clsalen = N,N'-ethylenebis(5-chlorosalicylideneiminato) dianion], [Fe(qcq)(CN)(3)][Mn(5-Brsalen)] x 2 MeOH [4 x 2 MeOH; 5-Brsalen = N,N'-ethylenebis(5-bromosalicylideneiminato) dianion], and Fe(qcq)(CN)(3)][Mn(salen)].MeCN x H(2)O [5 x MeCN; salen = N,N'-ethylenebis(salicylideneiminato) dianion]. The complexes consist of extensive hydrogen bonding and pi-pi stacking interactions, generating multidimensional structures. Magnetic studies demonstrate that antiferromagnetic couplings are operative between Fe(III) and Mn(III) centers bridged by cyanide ligands. On the basis of an infinite chain model, magnetic coupling parameters of 2-5 range from -9.3 to -14.1 cm(-1). A long-range order is observed at 2.3 K for 3 and 2.2 K for 4, while compound 5 shows spin glass behavior possibly coupled with magnetic ordering.

  9. Sixty years from discovery to solution: crystal structure of bovine liver catalase form III

    SciTech Connect

    Foroughi, Leila M.; Kang, You-Na; Matzger, Adam J.

    2012-03-27

    The crystallization and structural characterization of bovine liver catalase (BLC) has been intensively studied for decades. Forms I and II of BLC have previously been fully characterized using single-crystal X-ray diffraction. Form III has previously been analyzed by electron microscopy, but owing to the thinness of this crystal form an X-ray crystal structure had not been determined. Here, the crystal structure of form III of BLC is presented in space group P212121, with unit-cell parameters a = 68.7, b = 173.7, c = 186.3 {angstrom}. The asymmetric unit is composed of the biological tetramer, which is packed in a tetrahedron motif with three other BLC tetramers. This higher resolution structure has allowed an assessment of the previously published electron-microscopy studies.

  10. Sixty years from discovery to solution: crystal structure of bovine liver catalase form III.

    PubMed

    Foroughi, Leila M; Kang, You Na; Matzger, Adam J

    2011-09-01

    The crystallization and structural characterization of bovine liver catalase (BLC) has been intensively studied for decades. Forms I and II of BLC have previously been fully characterized using single-crystal X-ray diffraction. Form III has previously been analyzed by electron microscopy, but owing to the thinness of this crystal form an X-ray crystal structure had not been determined. Here, the crystal structure of form III of BLC is presented in space group P2(1)2(1)2(1), with unit-cell parameters a = 68.7, b = 173.7, c = 186.3 Å. The asymmetric unit is composed of the biological tetramer, which is packed in a tetrahedron motif with three other BLC tetramers. This higher resolution structure has allowed an assessment of the previously published electron-microscopy studies. PMID:21904028

  11. Enhanced non-radiative energy transfer in hybrid III-nitride structures

    SciTech Connect

    Smith, R. M.; Athanasiou, M.; Bai, J.; Liu, B.; Wang, T.

    2015-09-21

    The effect of surface states has been investigated in hybrid organic/inorganic white light emitting structures that employ high efficiency, nearfield non-radiative energy transfer (NRET) coupling. The structures utilize blue emitting InGaN/GaN multiple quantum well (MQW) nanorod arrays to minimize the separation with a yellow emitting F8BT coating. Surface states due to the exposed III-nitride surfaces of the nanostructures are found to reduce the NRET coupling rate. The surface states are passivated by deposition of a silicon nitride layer on the III-nitride nanorod surface leading to reduced surface recombination. A low thickness surface passivation is shown to increase the NRET coupling rate by 4 times compared to an un-passivated hybrid structure. A model is proposed to explain the increased NRET rate for the passivated hybrid structures based on the reduction in surface electron depletion of the passivated InGaN/GaN MQW nanorods surfaces.

  12. Structural Probability Concepts Adapted to Electrical Engineering

    NASA Technical Reports Server (NTRS)

    Steinberg, Eric P.; Chamis, Christos C.

    1994-01-01

    Through the use of equivalent variable analogies, the authors demonstrate how an electrical subsystem can be modeled by an equivalent structural subsystem. This allows the electrical subsystem to be probabilistically analyzed by using available structural reliability computer codes such as NESSUS. With the ability to analyze the electrical subsystem probabilistically, we can evaluate the reliability of systems that include both structural and electrical subsystems. Common examples of such systems are a structural subsystem integrated with a health-monitoring subsystem, and smart structures. Since these systems have electrical subsystems that directly affect the operation of the overall system, probabilistically analyzing them could lead to improved reliability and reduced costs. The direct effect of the electrical subsystem on the structural subsystem is of secondary order and is not considered in the scope of this work.

  13. First structurally characterized mixed-halogen nickel(III) NCN-pincer complex

    NASA Astrophysics Data System (ADS)

    Kozhanov, Konstantin A.; Bubnov, Michael P.; Cherkasov, Vladimir K.; Fukin, Georgy K.; Vavilina, Nina N.; Efremova, Larisa Yu.; Abakumov, Gleb A.

    2009-03-01

    A square-pyramidal mixed-halogen nickel(III) NCN-pincer complex (PipeNCN)NiClBr (where PipeNCN = 2,6-bis(piperidinomethyl)phenyl) was structurally characterized. Bromine occupies apical position; pincer ligand and chlorine atom are in the basal plane. EPR detects that complex in solution exists as a mixture of two structural isomers with bromine or chlorine atoms in the top of pyramid.

  14. Crystal structure of the Yersinia type III secretion protein YscE

    SciTech Connect

    Phan, Jason; Austin, Brian P.; Waugh, David S.

    2010-12-06

    The plague-causing bacterium Yersinia pestis utilizes a contact-dependent (type III) secretion system (T3SS) to transport virulence factors from the bacterial cytosol directly into the interior of mammalian cells where they interfere with signal transduction pathways that mediate phagocytosis and the inflammatory response. The type III secretion apparatus is composed of 20-25 different Yersinia secretion (Ysc) proteins. We report here the structure of YscE, the smallest Ysc protein, which is a dimer in solution. The probable mode of oligomerization is discussed.

  15. Density functional theory studies of actinide(III) motexafins (An-Motex2+, An = Ac, Cm, Lr). Structure, stability, and comparison with lanthanide(III) motexafins.

    PubMed

    Cao, Xiaoyan; Li, Quansong; Moritz, Anna; Xie, Zhizhong; Dolg, Michael; Chen, Xuebo; Fang, Weihai

    2006-04-17

    Newly developed relativistic energy-consistent 5f-in-core actinide pseudopotentials and corresponding (7s6p5d1f)/[5s4p3d1f] basis sets in the segmented contraction scheme, combined with density functional theory methods, have been used to study the molecular structure and chemical properties of selected actinide(III) motexafins (An-Motex2+, An = Ac, Cm, Lr). Structure and stability are discussed, and a comparison to the lanthanide(III) motexafins (Ln-Motex2+, Ln = La, Gd, Lu) is made. The actinide element is found to reside above the mean N5 motexafin plane, and the larger the cation, the greater the observed out-of-plane displacement. It is concluded that the actinium(III), curium(III), and lawrencium(III) cations are tightly bound to the macrocyclic skeleton, yielding stable structures. However, the calculated metal-ligand gas-phase binding energy for An-Motex2+ is about 1-2 eV lower than that of Ln-Motex2+, implying a lower stability of An-Motex2+ compared to Ln-Motex2+. Results including solvent effects imply that Ac-Motex2+ is the most stable complex in aqueous solution and should be the best candidate for experimentalists to get stable actinide(III) motexafin complexes. PMID:16602805

  16. The joint WAIS-III and WMS-III factor structure: development and cross-validation of a six-factor model of cognitive functioning.

    PubMed

    Tulsky, David S; Price, Larry R

    2003-06-01

    During the standardization of the Wechsler Adult Intelligence Scale (3rd ed.; WAIS-III) and the Wechsler Memory Scale (3rd ed.; WMS-III) the participants in the normative study completed both scales. This "co-norming" methodology set the stage for full integration of the 2 tests and the development of an expanded structure of cognitive functioning. Until now, however, the WAIS-III and WMS-III had not been examined together in a factor analytic study. This article presents a series of confirmatory factor analyses to determine the joint WAIS-III and WMS-III factor structure. Using a structural equation modeling approach, a 6-factor model that included verbal, perceptual, processing speed, working memory, auditory memory, and visual memory constructs provided the best model fit to the data. Allowing select subtests to load simultaneously on 2 factors improved model fit and indicated that some subtests are multifaceted. The results were then replicated in a large cross-validation sample (N = 858).

  17. Iron Isotope Fractionations Reveal a Finite Bioavailable Fe Pool for Structural Fe(III) Reduction in Nontronite.

    PubMed

    Shi, Bingjie; Liu, Kai; Wu, Lingling; Li, Weiqiang; Smeaton, Christina M; Beard, Brian L; Johnson, Clark M; Roden, Eric E; Van Cappellen, Philippe

    2016-08-16

    We report on stable Fe isotope fractionation during microbial and chemical reduction of structural Fe(III) in nontronite NAu-1. (56)Fe/(54)Fe fractionation factors between aqueous Fe(II) and structural Fe(III) ranged from -1.2 to +0.8‰. Microbial (Shewanella oneidensis and Geobacter sulfurreducens) and chemical (dithionite) reduction experiments revealed a two-stage process. Stage 1 was characterized by rapid reduction of a finite Fe(III) pool along the edges of the clay particles, accompanied by a limited release to solution of Fe(II), which partially adsorbed onto basal planes. Stable Fe isotope compositions revealed that electron transfer and atom exchange (ETAE) occurred between edge-bound Fe(II) and octahedral (structural) Fe(III) within the clay lattice, as well as between aqueous Fe(II) and structural Fe(III) via a transient sorbed phase. The isotopic fractionation factors decreased with increasing extent of reduction as a result of the depletion of the finite bioavailable Fe(III) pool. During stage 2, microbial reduction was inhibited while chemical reduction continued. However, further ETAE between aqueous Fe(II) and structural Fe(III) was not observed. Our results imply that the pool of bioavailable Fe(III) is restricted to structural Fe sites located near the edges of the clay particles. Blockage of ETAE distinguishes Fe(III) reduction of layered clay minerals from that of Fe oxyhydroxides, where accumulation of structural Fe(II) is much more limited. PMID:27291525

  18. Iron Isotope Fractionations Reveal a Finite Bioavailable Fe Pool for Structural Fe(III) Reduction in Nontronite.

    PubMed

    Shi, Bingjie; Liu, Kai; Wu, Lingling; Li, Weiqiang; Smeaton, Christina M; Beard, Brian L; Johnson, Clark M; Roden, Eric E; Van Cappellen, Philippe

    2016-08-16

    We report on stable Fe isotope fractionation during microbial and chemical reduction of structural Fe(III) in nontronite NAu-1. (56)Fe/(54)Fe fractionation factors between aqueous Fe(II) and structural Fe(III) ranged from -1.2 to +0.8‰. Microbial (Shewanella oneidensis and Geobacter sulfurreducens) and chemical (dithionite) reduction experiments revealed a two-stage process. Stage 1 was characterized by rapid reduction of a finite Fe(III) pool along the edges of the clay particles, accompanied by a limited release to solution of Fe(II), which partially adsorbed onto basal planes. Stable Fe isotope compositions revealed that electron transfer and atom exchange (ETAE) occurred between edge-bound Fe(II) and octahedral (structural) Fe(III) within the clay lattice, as well as between aqueous Fe(II) and structural Fe(III) via a transient sorbed phase. The isotopic fractionation factors decreased with increasing extent of reduction as a result of the depletion of the finite bioavailable Fe(III) pool. During stage 2, microbial reduction was inhibited while chemical reduction continued. However, further ETAE between aqueous Fe(II) and structural Fe(III) was not observed. Our results imply that the pool of bioavailable Fe(III) is restricted to structural Fe sites located near the edges of the clay particles. Blockage of ETAE distinguishes Fe(III) reduction of layered clay minerals from that of Fe oxyhydroxides, where accumulation of structural Fe(II) is much more limited.

  19. Engineering structure and function using thermoresponsive biopolymers.

    PubMed

    Pastuszka, Martha K; MacKay, J Andrew

    2016-01-01

    Self-assembly enables exquisite control at the smallest scale and generates order among macromolecular-building blocks that remain too small to be manipulated individually. Environmental cues, such as heating, can trigger the organization of these materials from individual molecules to multipartixcle assemblies with a variety of compositions and functions. Synthetic as well as biological polymers have been engineered for these purposes; however, biological strategies can offer unparalleled control over the composition of these macromolecular-building blocks. Biologic polymers are macromolecules composed of monomeric units that can be precisely tailored at the genetic level; furthermore, they can often utilize endogenous biodegradation pathways, which may enhance their potential clinical applications. DNA (nucleotides), polysaccharides (carbohydrates), and proteins (amino acids) have all been engineered to self-assemble into nanostructures in response to a change in temperature. This focus article reviews the growing body of literature exploring temperature-dependent nano-assembly of these biological macromolecules, summarizes some of their physical properties, and discusses future directions.

  20. Structure and Mechanistic Implications of a Uroporphyrinogen III Synthase−Product Complex

    SciTech Connect

    Schubert,H.; Phillips, J.; Heroux, A.; Hill, C.

    2008-01-01

    Uroporphyrinogen III synthase (U3S) catalyzes the asymmetrical cyclization of a linear tetrapyrrole to form the physiologically relevant uroporphyrinogen III (uro'gen III) isomer during heme biosynthesis. Here, we report four apoenzyme and one product complex crystal structures of the Thermus thermophilus (HB27) U3S protein. The overlay of eight crystallographically unique U3S molecules reveals a huge range of conformational flexibility, including a 'closed' product complex. The product, uro'gen III, binds between the two domains and is held in place by a network of hydrogen bonds between the product's side chain carboxylates and the protein's main chain amides. Interactions of the product A and B ring carboxylate side chains with both structural domains of U3S appear to dictate the relative orientation of the domains in the closed enzyme conformation and likely remain intact during catalysis. The product C and D rings are less constrained in the structure, consistent with the conformational changes required for the catalytic cyclization with inversion of D ring orientation. A conserved tyrosine residue is potentially positioned to facilitate loss of a hydroxyl from the substrate to initiate the catalytic reaction.

  1. Reduction of structural Fe(III) in nontronite by methanogen Methanosarcina barkeri

    USGS Publications Warehouse

    Liu, D.; Dong, Hailiang H.; Bishop, M.E.; Wang, Hongfang; Agrawal, A.; Tritschler, S.; Eberl, D.D.; Xie, S.

    2011-01-01

    Clay minerals and methanogens are ubiquitous and co-exist in anoxic environments, yet it is unclear whether methanogens are able to reduce structural Fe(III) in clay minerals. In this study, the ability of methanogen Methanosarcina barkeri to reduce structural Fe(III) in iron-rich smectite (nontronite NAu-2) and the relationship between iron reduction and methanogenesis were investigated. Bioreduction experiments were conducted in growth medium using three types of substrate: H2/CO2, methanol, and acetate. Time course methane production and hydrogen consumption were measured by gas chromatography. M. barkeri was able to reduce structural Fe(III) in NAu-2 with H2/CO2 and methanol as substrate, but not with acetate. The extent of bioreduction, as measured by the 1,10-phenanthroline method, was 7-13% with H2/CO2 as substrate, depending on nontronite concentration (5-10g/L). The extent was higher when methanol was used as a substrate, reaching 25-33%. Methanogenesis was inhibited by Fe(III) reduction in the H2/CO2 culture, but enhanced when methanol was used. High charge smectite and biogenic silica formed as a result of bioreduction. Our results suggest that methanogens may play an important role in biogeochemical cycling of iron in clay minerals and may have important implications for the global methane budget. ?? 2010 Elsevier Ltd.

  2. Geometric and Electronic Structure of a Peroxomanganese(III) Complex Supported by a Scorpionate Ligand

    PubMed Central

    Colmer, Hannah E.; Geiger, Robert A.; Leto, Domenick F.; Wijeratne, Gayan B.; Day, Victor W.; Jackson, Timothy A.

    2014-01-01

    A monomeric MnII complex has been prepared with the facially-coordinating TpPh2 ligand, (TpPh2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate). The X-ray crystal structure shows three coordinating solvent molecules resulting in a six-coordinate complex with Mn-ligand bond lengths that are consistent with a high-spin MnII ion. Treatment of this MnII complex with excess KO2 at room temperature resulted in the formation of a MnIII-O2 complex that is stable for several days at ambient conditions, allowing for the determination of the X-ray crystal structure of this intermediate. The electronic structure of this peroxomanganese(III) adduct was examined by using electronic absorption, electron paramagnetic resonance (EPR), low-temperature magnetic circular dichroism (MCD), and variable-temperature variable-field (VTVH) MCD spectroscopies. Density functional theory (DFT), time-dependent (TD)-DFT, and multireference ab initio CASSCF/NEVPT2 calculations were used to assign the electronic transitions and further investigate the electronic structure of the peroxomanganese(III) species. The lowest ligand-field transition in the electronic absorption spectrum of the MnIII-O2 complex exhibits a blue shift in energy compared to other previously characterized peroxomanganese(III) complexes that results from a large axial bond elongation, reducing the metal-ligand covalency and stabilizing the σ-antibonding Mn dz2 MO that is the donor MO for this transition. PMID:25312785

  3. Production of fine structures in type III solar radio bursts due to turbulent density profiles

    SciTech Connect

    Loi, Shyeh Tjing; Cairns, Iver H.; Li, Bo

    2014-07-20

    Magnetic reconnection events in the corona release energetic electron beams along open field lines, and the beams generate radio emission at multiples of the electron plasma frequency f{sub p} to produce type III solar radio bursts. Type III bursts often exhibit irregularities in the form of flux modulations with frequency and/or local temporal advances and delays, and a type IIIb burst represents the extreme case where a type III burst is fragmented into a chain of narrowband features called striae. Remote and in situ spacecraft measurements have shown that density turbulence is ubiquitous in the corona and solar wind, and often exhibits a Kolmogorov power spectrum. In this work, we numerically investigate the effects of one-dimensional macroscopic density turbulence (along the beam direction) on the behavior of type III bursts, and find that this turbulence produces stria-like fine structures in the dynamic spectra of both f{sub p} and 2 f{sub p} radiation. Spectral and temporal fine structures in the predicted type III emission are produced by variations in the scattering path lengths and group speeds of radio emission, and in the locations and sizes of emitting volumes. Moderate turbulence levels yield flux enhancements with much broader half-power bandwidths in f{sub p} than 2 f{sub p} emission, possibly explaining the often observed type IIIb-III harmonic pairs as being where intensifications in 2 f{sub p} radiation are not resolved observationally. Larger turbulence levels producing trough-peak regions in the plasma density profile may lead to broader, resolvable intensifications in 2 f{sub p} radiation, which may account for the type IIIb-IIIb pairs that are sometimes observed.

  4. Production of Fine Structures in Type III Solar Radio Bursts Due to Turbulent Density Profiles

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Cairns, Iver H.; Li, Bo

    2014-07-01

    Magnetic reconnection events in the corona release energetic electron beams along open field lines, and the beams generate radio emission at multiples of the electron plasma frequency fp to produce type III solar radio bursts. Type III bursts often exhibit irregularities in the form of flux modulations with frequency and/or local temporal advances and delays, and a type IIIb burst represents the extreme case where a type III burst is fragmented into a chain of narrowband features called striae. Remote and in situ spacecraft measurements have shown that density turbulence is ubiquitous in the corona and solar wind, and often exhibits a Kolmogorov power spectrum. In this work, we numerically investigate the effects of one-dimensional macroscopic density turbulence (along the beam direction) on the behavior of type III bursts, and find that this turbulence produces stria-like fine structures in the dynamic spectra of both fp and 2 fp radiation. Spectral and temporal fine structures in the predicted type III emission are produced by variations in the scattering path lengths and group speeds of radio emission, and in the locations and sizes of emitting volumes. Moderate turbulence levels yield flux enhancements with much broader half-power bandwidths in fp than 2 fp emission, possibly explaining the often observed type IIIb-III harmonic pairs as being where intensifications in 2 fp radiation are not resolved observationally. Larger turbulence levels producing trough-peak regions in the plasma density profile may lead to broader, resolvable intensifications in 2 fp radiation, which may account for the type IIIb-IIIb pairs that are sometimes observed.

  5. Simultaneous analysis and design. [in structural engineering

    NASA Technical Reports Server (NTRS)

    Haftka, R. T.

    1985-01-01

    Optimization techniques are increasingly being used for performing nonlinear structural analysis. The development of element by element (EBE) preconditioned conjugate gradient (CG) techniques is expected to extend this trend to linear analysis. Under these circumstances the structural design problem can be viewed as a nested optimization problem. There are computational benefits to treating this nested problem as a large single optimization problem. The response variables (such as displacements) and the structural parameters are all treated as design variables in a unified formulation which performs simultaneously the design and analysis. Two examples are used for demonstration. A seventy-two bar truss is optimized subject to linear stress constraints and a wing box structure is optimized subject to nonlinear collapse constraints. Both examples show substantial computational savings with the unified approach as compared to the traditional nested approach.

  6. Structural Requirements for the Space Propulsion Engine Systems

    NASA Technical Reports Server (NTRS)

    Aggarwal, Pravin K.

    2006-01-01

    In January 2004, the National Aeronautics and Space Administration (NASA) was given a vision for Space Exploration by President Bush, setting our sight on a bold new path to go back to the Moon, then to Mars and beyond. As NASA gets ready to meet the vision set by President Bush, failures are not an option. Reliability of the propulsion engine systems will play an important role in establishing an overall safe and reliable operation of these new space systems. A new standard, NASA-STD-5012, Strength and Life Assessment for Space Propulsion System Engines, has been developed to provide structural requirements for assessment of the propulsion systems engine. This standard is a complement to the current NASA-wide standard NASA-STD-5001, Structural Design and Test Factors of Safety for Spaceflight Hardware, which excluded the requirement for the engine systems (rotatory structures) along with pressure vessels. As developed, this document builds on the heritage of the multiple industrial standards related to strength and life assessment of the structures. For assuring a safe and reliable operation of a product and/or mission, establishing a set of structural assessment requirements is a key ingredient. Hence, a concentrated effort was made to improve the requirements where there are known lessons learned during the design, test, and operation phases of the Space Shuttle Main Engine (SSME) and other engine development programs. Requirements delineated in this standard are also applicable for the reusable and/or human missions. It shall be noted that "reliability of a system cannot be tested and inspected but can only be achieved if it is first designed into a system." Hence, these strength and life assessment requirements for the space propulsion system engines shall be used along with other good engineering practices, requirements, and policies.

  7. Structural Characteristics of University Engineering Students' Conceptions of Energy.

    ERIC Educational Resources Information Center

    Liu, Xiufeng; Ebenezer, Jazlin; Fraser, Duncan M.

    2002-01-01

    Examines structural characteristics of university engineering students' conceptions of energy elicited through paragraph writing and their relations with categories of their conceptions specific to energy in solution processes identified through interviews. Reports that structures of students' conceptions are characterized primarily by…

  8. Structure and membrane actions of a marine worm protein cytolysin, Cerebratulus toxin A-III.

    PubMed

    Kem, W R

    1994-02-28

    Four homologous Cerebratulus lacteus A toxins are the first and as yet only protein cytolysins to be isolated from an ancient phylum of marine worms, the nemertines. The most abundant and toxic variant, toxin A-III, has been sequenced and its mechanisms of action studied in the most detail. It consists of a single basic polypeptide chain of 95 amino acid residues cross-linked by three disulfide bonds, and possesses a predominantly alpha-helical secondary structure. The C-terminal third of the toxin sequence is postulated to be a helical 'hairpin' structure involved in pore formation. Toxin A-III permeabilizes a variety of cells as well as liposomes made from a variety of phospholipids; apparently large pores are formed, as large proteins are released almost as rapidly as small organic molecules and inorganic ions. At sublytic concentrations, the toxin also inhibits protein kinase C and endogenous voltage-gated cation selective (sodium, calcium) channels occurring in the nervous and cardiovascular systems. A curious observation, also reported for colicins and some other protein cytolysins, was the conservation of toxin secondary structure upon insertion into phospholipid liposomes, despite the strong likelihood that significant changes in tertiary structure occur to provide a hydrophobic surface for interaction with membrane lipids. Because of its small size and presumed single helical hairpin secondary structure, Cl toxin A-III is an excellent molecular subject for investigating protein insertion into biological membranes and mechanisms of pore formation.

  9. Crystal structure of class III chitinase from pomegranate provides the insight into its metal storage capacity.

    PubMed

    Masuda, Taro; Zhao, Guanghua; Mikami, Bunzo

    2015-01-01

    Chitinase hydrolyzes the β-1,4-glycosidic bond in chitin. In higher plants, this enzyme has been regarded as a pathogenesis-related protein. Recently, we identified a class III chitinase, which functions as a calcium storage protein in pomegranate (Punica granatum) seed (PSC, pomegranate seed chitinase). Here, we solved a crystal structure of PSC at 1.6 Å resolution. Although its overall structure, including the structure of catalytic site and non-proline cis-peptides, was closely similar to those of other class III chitinases, PSC had some unique structural characteristics. First, there were some metal-binding sites with coordinated water molecules on the surface of PSC. Second, many unconserved aspartate residues were present in the PSC sequence which rendered the surface of PSC negatively charged. This acidic electrostatic property is in contrast to that of hevamine, well-characterized plant class III chitinase, which has rather a positively charged surface. Thus, the crystal structure provides a clue for metal association property of PSC.

  10. Crystal structures of 3-methyladenine DNA glycosylase MagIII and the recognition of alkylated bases.

    PubMed

    Eichman, Brandt F; O'Rourke, Eyleen J; Radicella, J Pablo; Ellenberger, Tom

    2003-10-01

    DNA glycosylases catalyze the excision of chemically modified bases from DNA. Although most glycosylases are specific to a particular base, the 3-methyladenine (m3A) DNA glycosylases include both highly specific enzymes acting on a single modified base, and enzymes with broader specificity for alkylation-damaged DNA. Our structural understanding of these different enzymatic specificities is currently limited to crystal and NMR structures of the unliganded enzymes and complexes with abasic DNA inhibitors. Presented here are high-resolution crystal structures of the m3A DNA glycosylase from Helicobacter pylori (MagIII) in the unliganded form and bound to alkylated bases 3,9-dimethyladenine and 1,N6-ethenoadenine. These are the first structures of a nucleobase bound in the active site of a m3A glycosylase belonging to the helix-hairpin-helix superfamily. MagIII achieves its specificity for positively-charged m3A not by direct interactions with purine or methyl substituent atoms, but rather by stacking the base between two aromatic side chains in a pocket that excludes 7-methylguanine. We report base excision and DNA binding activities of MagIII active site mutants, together with a structural comparison of the HhH glycosylases. PMID:14517230

  11. Situated learning methodologies and assessment in civil engineering structures education

    NASA Astrophysics Data System (ADS)

    Bertz, Michael Davis

    This thesis describes an overarching study of civil engineering undergraduate structural education through student performance in recalling and applying basic structural engineering knowledge, and the viability of alternative situated learning environments for more effectively supporting the learning of this knowledge. To properly ground this study, a thorough investigation of related work in assessment, cognitive science, educational technology, and design education was completed, with connections and applications to civil engineering education highlighted. The experimental work of the thesis is organized into three parts: an assessment of civil engineering undergraduates' fundamental structural engineering knowledge and abilities; the development and testing of a software support environment for situated learning, the Civil Engineering Learning Library (CELL); and, the implementation and evaluation of the design studio, a pedagogical model for situated learning in the classroom. The results of the assessment study indicate that civil engineering seniors (and also students earlier in the curriculum) have difficulty retaining and applying basic knowledge of structural behavior, especially doing so in a flexible fashion in design situations. The survey also suggests that visualization plays an important role in understanding structural behavior. Tests with the CELL system show that a cognitively-flexible multimedia environment can support structural learning, but were inconclusive about whether the computer-based system helped the students to learn better than conventional classroom lecture. Two trial implementations of the design studio indicate that the studio model can serve as a powerful situated learning environment, and that it can be scaled up to reasonable class sizes. Significant requirements are associated with this model, however, primarily in faculty involvement, but also in physical resources and student time. In addition to these conclusions about the

  12. Structural characterization of CFA/III and Longus type IVb pili from enterotoxigenic Escherichia coli.

    PubMed

    Kolappan, Subramaniapillai; Roos, Justin; Yuen, Alex S W; Pierce, Owen M; Craig, Lisa

    2012-05-01

    The type IV pili are helical filaments found on many Gram-negative pathogenic bacteria, with multiple diverse roles in pathogenesis, including microcolony formation, adhesion, and twitching motility. Many pathogenic enterotoxigenic Escherichia coli (ETEC) isolates express one of two type IV pili belonging to the type IVb subclass: CFA/III or Longus. Here we show a direct correlation between CFA/III expression and ETEC aggregation, suggesting that these pili, like the Vibrio cholerae toxin-coregulated pili (TCP), mediate microcolony formation. We report a 1.26-Å resolution crystal structure of CofA, the major pilin subunit from CFA/III. CofA is very similar in structure to V. cholerae TcpA but possesses a 10-amino-acid insertion that replaces part of the α2-helix with an irregular loop containing a 3(10)-helix. Homology modeling suggests a very similar structure for the Longus LngA pilin. A model for the CFA/III pilus filament was generated using the TCP electron microscopy reconstruction as a template. The unique 3(10)-helix insert fits perfectly within the gap between CofA globular domains. This insert, together with differences in surface-exposed residues, produces a filament that is smoother and more negatively charged than TCP. To explore the specificity of the type IV pilus assembly apparatus, CofA was expressed heterologously in V. cholerae by replacing the tcpA gene with that of cofA within the tcp operon. Although CofA was synthesized and processed by V. cholerae, no CFA/III filaments were detected, suggesting that the components of the type IVb pilus assembly system are highly specific to their pilin substrates. PMID:22447901

  13. Structural Characterization of CFA/III and Longus Type IVb Pili from Enterotoxigenic Escherichia coli

    PubMed Central

    Kolappan, Subramaniapillai; Roos, Justin; Yuen, Alex S. W.; Pierce, Owen M.

    2012-01-01

    The type IV pili are helical filaments found on many Gram-negative pathogenic bacteria, with multiple diverse roles in pathogenesis, including microcolony formation, adhesion, and twitching motility. Many pathogenic enterotoxigenic Escherichia coli (ETEC) isolates express one of two type IV pili belonging to the type IVb subclass: CFA/III or Longus. Here we show a direct correlation between CFA/III expression and ETEC aggregation, suggesting that these pili, like the Vibrio cholerae toxin-coregulated pili (TCP), mediate microcolony formation. We report a 1.26-Å resolution crystal structure of CofA, the major pilin subunit from CFA/III. CofA is very similar in structure to V. cholerae TcpA but possesses a 10-amino-acid insertion that replaces part of the α2-helix with an irregular loop containing a 310-helix. Homology modeling suggests a very similar structure for the Longus LngA pilin. A model for the CFA/III pilus filament was generated using the TCP electron microscopy reconstruction as a template. The unique 310-helix insert fits perfectly within the gap between CofA globular domains. This insert, together with differences in surface-exposed residues, produces a filament that is smoother and more negatively charged than TCP. To explore the specificity of the type IV pilus assembly apparatus, CofA was expressed heterologously in V. cholerae by replacing the tcpA gene with that of cofA within the tcp operon. Although CofA was synthesized and processed by V. cholerae, no CFA/III filaments were detected, suggesting that the components of the type IVb pilus assembly system are highly specific to their pilin substrates. PMID:22447901

  14. Structure Analysis of Composition Modulation in Epitaxially-Grown III-V Semiconductor Alloys

    NASA Astrophysics Data System (ADS)

    Ishimaru, Manabu; Hasegawa, Shigehiko; Asahi, Hajime; Sato, Kazuhisa; Konno, Toyohiko J.

    2013-11-01

    It has been reported that composition modulation is naturally formed in some of the epitaxially-grown thin films. Structural characterization of these materials is necessary for controlling their nanostructures precisely. Here, we prepared epitaxially-grown III-V semiconductor alloys and characterized their atomistic structures by means of diffraction crystallography and electron microscopy techniques. As a consequence, we found that the following quantum well structures are spontaneously formed: (1) ultrashort period lateral composition modulation (LCM) with a modulation period of ˜1 nm; (2) complex vertical composition modulated (VCM) structures consisting of two modulated structures with a different period (˜4 and ˜25 nm). The former LCM structure is created via nanoscale phase separation at the growth surface, while the shorter-period modulation in the later VCM structure is induced by rotating a substrate through an inhomogeneous distribution of the anion flux within a chamber.

  15. Polarization engineering and approaches for high-performance III-nitride light emitters

    NASA Astrophysics Data System (ADS)

    Arif, Ronald A.

    Light emitting diodes (LEDs) have been increasingly integrated into mainstream lighting. In all applications requiring single-colored light, LEDs have outperformed filtered incandescent lamps. However, there are two major challenges. First is the issue of cost. High-performance nitride-based white LEDs cost roughly two orders of magnitude more expensive than incandescent lamps. The second challenge is color rendering---quantified by Color Rendering Index (CRI). Today's nitride white light LEDs still rely on the mixing of blue light from blue InGaN LEDs and yellow phosphor, and the CRI is relatively low. The best white LEDs to date have a CRI of 70--80, in comparison to traditional lamps, which generally have a CRI close to 100, and able to represent the true color of an object. An ideal way to improve the CRI is by mixing the luminescence of primary color LEDs. However, in order to make this approach viable, all the LEDs have to be based on a single materials platform. AlInGaN is the only materials system to date with the potential to fulfill this, since the bandgap of this nitride compound (with varying amount of Al, In, and Ga) can be varied from UV to IR range. There is still a lot of room for improvement in the efficiencies of nitride blue and green LEDs, while nitride-based active region emitting in the red wavelength (lambda ˜ 650-nm) regime is not realizable yet. In this dissertation, methods to increase internal quantum efficiency by polarization field engineering have been proposed. Two novel structures based on (1) staggered InGaN QW and (2) type-II InGaN-GaNAs QW have been investigated. Staggered InGaN QWs have shown improvement in the photoluminescence, cathodoluminescence, and LED output power, which agree well with numerical model prediction. All materials and devices in this work have been designed, grown and fabricated in-house. For the LED fabrication, a method based on selective area epitaxy---which bypasses dry-etching---has been utilized. In

  16. Asymmetric ring structure of Vps4 required for ESCRT-III disassembly

    NASA Astrophysics Data System (ADS)

    Caillat, Christophe; Macheboeuf, Pauline; Wu, Yuanfei; McCarthy, Andrew A.; Boeri-Erba, Elisabetta; Effantin, Gregory; Göttlinger, Heinrich G.; Weissenhorn, Winfried; Renesto, Patricia

    2015-12-01

    The vacuolar protein sorting 4 AAA-ATPase (Vps4) recycles endosomal sorting complexes required for transport (ESCRT-III) polymers from cellular membranes. Here we present a 3.6-Å X-ray structure of ring-shaped Vps4 from Metallosphera sedula (MsVps4), seen as an asymmetric pseudohexamer. Conserved key interface residues are shown to be important for MsVps4 assembly, ATPase activity in vitro, ESCRT-III disassembly in vitro and HIV-1 budding. ADP binding leads to conformational changes within the protomer, which might propagate within the ring structure. All ATP-binding sites are accessible and the pseudohexamer binds six ATP with micromolar affinity in vitro. In contrast, ADP occupies one high-affinity and five low-affinity binding sites in vitro, consistent with conformational asymmetry induced on ATP hydrolysis. The structure represents a snapshot of an assembled Vps4 conformation and provides insight into the molecular motions the ring structure undergoes in a concerted action to couple ATP hydrolysis to ESCRT-III substrate disassembly.

  17. Electronic Band Structures of the Highly Desirable III-V Semiconductors: TB-mBJ DFT Studies

    NASA Astrophysics Data System (ADS)

    Rehman, Gul; Shafiq, M.; Saifullah; Ahmad, Rashid; Jalali-Asadabadi, S.; Maqbool, M.; Khan, Imad; Rahnamaye-Aliabad, H.; Ahmad, Iftikhar

    2016-07-01

    The correct band gaps of semiconductors are highly desirable for their effective use in optoelectronic and other photonic devices. However, the experimental and theoretical results of the exact band gaps are quite challenging and sometimes tricky. In this article, we explore the electronic band structures of the highly desirable optical materials, III-V semiconductors. The main reason of the ineffectiveness of the theoretical band gaps of these compounds is their mixed bonding character, where large proportions of electrons reside outside atomic spheres in the intestinal regions, which are challenging for proper theoretical treatment. In this article, the band gaps of the compounds are revisited and successfully reproduced by properly treating the density of electrons using the recently developed non-regular Tran and Blaha's modified Becke-Johnson (nTB-mBJ) approach. This study additionally suggests that this theoretical scheme could also be useful for the band gap engineering of the III-V semiconductors. Furthermore, the optical properties of these compounds are also calculated and compared with the experimental results.

  18. Structures, performance, benefit, cost study. [gas turbine engines

    NASA Technical Reports Server (NTRS)

    Feder, E.

    1981-01-01

    Aircraft engine structures were studied to identify the advanced structural technologies that would provide the most benefits to future aircraft operations. A series of studies identified engine systems with the greatest potential for improvements. Based on these studies, six advanced generic structural concepts were selected and conceptually designed. The benefits of each concept were quantitatively assessed in terms of thrust specific fuel consumption, weight, cost, maintenance cost, fuel burned and direct operating cost plus interest. The probability of success of each concept was also determined. The concepts were ranked and the three most promising were selected for further study which consisted of identifying and comprehensively outlining the advanced technologies required to develop these concepts for aircraft engine application. Analytic, fabrication, and test technology developments are required. The technology programs outlined emphasize the need to provide basic, fundamental understanding of technology to obtain the benefit goals.

  19. Nontronite (NAu-1) Structure Associated with Microbial Fe(III) Reduction in Various Redox Conditions

    NASA Astrophysics Data System (ADS)

    Koo, T.; Kim, S.; Kim, J.

    2011-12-01

    Shewanella oneidensis MR-1 respires the structural Fe(III) of smectite and promotes illite formation in O2-free environment (Kostka et al., 1996, Kim et al., 2004). Since S. oneidensis is a facultative iron reducing bacterium, it is crucial to understand the structural changes induced by bio-reduction of structural Fe(III) in various redox conditions. Furthermore, the changes in cation exchange capacity (CEC) of bio-reduced nontronite upon the modification of mineral structure has not been extensively studied in terms of Fe-cycling. In this present study, we reported the evolution of nontronite structure at various time points in various redox conditions and corresponding CEC upon reduction and re-oxidation. S. oneidensis MR-1 was incubated in M1 medium with Na-lactate as the electron donor and Fe in nontronite (NAu-1) as the sole electron acceptor at pH 7 in anaerobic chamber for 3 hrs, 12 hrs, 1 day, 2 days, 4 days, 7 days, 14 days, and 21 days. O2 gas bubbling was then applied to the sample at each time point for 24 hours for re-oxidation. The triplet samples at each time point for both reduction and re-oxidation experiments were prepared. The extent of Fe(III) reduction measured by 1,10-phenanthroline method (Stucki and Anderson, 1981) indicated that the structural Fe(III) was reduced up to 8.8% of total Fe(III) within 21 days. XRD data with various treatments such as air dried, glycolated and lithium-saturated showed that K-nontronite may be formed because no discrete 10-Å illite peak was observed in Li-saturated sample upon glycolation. The CEC increased from 747 meg/kg to 1145 meg/kg during Fe(III) reduction and decreased to 954 meg/kg upon re-oxidation, supporting the possible formation of K-nontronite. The direct observation by electron microscopy verified the structural changes in nontonite in various redox conditions. The long-term experiment for 6 months, is in progress in anaerobic chamber, and results will be discussed. Kim, J. W., Dong, H., Seabaugh

  20. Structural Dissection of the Extracellular Moieties of the Type III Secretion Apparatus

    PubMed Central

    Wang, Yu; Zhang, Lingling; Picking, Wendy L.; Picking, William D.; De Guzman, Roberto N.

    2013-01-01

    Summary Many Gram-negative bacterial pathogens use type III secretion systems (TTSSs) for subverting the normal cellular functions of their target eukaryotic cells. The type III secretion apparatus (TTSA) functions like a syringe to inject proteins through an external needle and into a target cell’s membrane and cytosol. The TTSA basal body spans the bacterial inner and outer membranes, and the external needle is topped with a tip complex that controls the secretion and delivery of translocator and effector proteins. Recent structures of TTSA proteins have greatly advanced our understanding of shared themes in apparatus assembly and function. In this review, the structure-function of TTSA needle and tip complex proteins are described and common themes discussed. PMID:19396380

  1. Neurotypic cell attachment and growth on III-nitride lateral polarity structures.

    PubMed

    Bain, L E; Kirste, R; Johnson, C A; Ghashghaei, H T; Collazo, R; Ivanisevic, A

    2016-01-01

    III-nitride materials have recently received increasing levels of attention for their potential to successfully interface with, and sense biochemical interactions in biological systems. Expanding on available sensing schemes (including transistor-based devices,) a III-N lateral polarity structure capable of introducing quasi-phase matching through a periodic polarity grating presents a novel platform for second harmonic generation. This platform constitutes a non-linear optical phenomenon with exquisite sensitivity to the chemical state of a surface or interface. To characterize the response of a biological system to the nanostructured lateral polarity structures, we cultured neurotypic PC12 cells on AlGaN with varying ratios of Al:Ga - 0, 0.4, 0.6, and 1 - and on surfaces of varying pitch to the III-polar vs. N-polar grating - 5, 10, 20 and 50 μm. While some toxicity associated with increasing Al is observed, we documented and quantified trends in cell responses to the local material polarity and nanoscale roughness. The nitrogen-polar material has a significantly higher nanoscale roughness than III-polar regions, and a 80-200 nm step height difference between the III-polar and N-polar materials in the lateral polarity configuration generates adequate changes in topography to influence cell growth, improves cell adhesion and promotes cell migration along the direction of the features. As the designed material configuration is further explored for biochemical sensing, the lateral polarity scheme may provide a route in assessing the non-specific protein adsorption to this varying nano-topography that drives the subsequent cell response.

  2. Synthesis, Structure and Antitumour Properties of a New 1,2-Propylenediaminetetraacetate-Ruthenium(III) Compound

    PubMed Central

    Vilaplana, R.; Romero, M. A.; Quirós, M.; Salas, J. M.

    1995-01-01

    A novel complex formed by ruthenium (III) and the sequestering ligand 1,2-propylenediaminetetraacetic acid (PDTA) has been synthetized and characterized. The structure of the monomeric compound, studied by X-ray diffraction , shows an almost symmetric octahedral geometry around the metal ion, with two chlorine atoms in a cis conformation. The antitumour activity against a variety of murine and human cancers is reported. PMID:18472768

  3. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT III, MAINTAINING THE FUEL SYSTEM--DETROIT DIESEL ENGINE.

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE FUEL SYSTEM. TOPICS ARE (1) PURPOSE OF THE FUEL SYSTEM, (2) TRACING THE FUEL FLOW, (3) MINOR COMPONENTS OF THE FUEL SYSTEM, (4) MAINTENANCE TIPS, (5) CONSTRUCTION AND FUNCTION OF THE FUEL INJECTORS, AND (6)…

  4. Reverse engineering chemical structures from molecular descriptors : how many solutions?

    SciTech Connect

    Brown, William Michael; Martin, Shawn Bryan; Faulon, Jean-Loup Michel

    2005-06-01

    Physical, chemical and biological properties are the ultimate information of interest for chemical compounds. Molecular descriptors that map structural information to activities and properties are obvious candidates for information sharing. In this paper, we consider the feasibility of using molecular descriptors to safely exchange chemical information in such a way that the original chemical structures cannot be reverse engineered. To investigate the safety of sharing such descriptors, we compute the degeneracy (the number of structure matching a descriptor value) of several 2D descriptors, and use various methods to search for and reverse engineer structures. We examine degeneracy in the entire chemical space taking descriptors values from the alkane isomer series and the PubChem database. We further use a stochastic search to retrieve structures matching specific topological index values. Finally, we investigate the safety of exchanging of fragmental descriptors using deterministic enumeration.

  5. Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex

    NASA Astrophysics Data System (ADS)

    Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

    2016-05-01

    The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

  6. Structure and function of the ESCRT-II-III interface in multivesicular body biogenesis

    SciTech Connect

    Im, Young Jun; Wollert, Thomas; Boura, Evzen; Hurley, James H.

    2009-09-08

    The ESCRT-II-ESCRT-III interaction coordinates the sorting of ubiquitinated cargo with the budding and scission of intralumenal vesicles into multivesicular bodies. The interacting regions of these complexes were mapped to the second winged helix domain of human ESCRT-II subunit VPS25 and the first helix of ESCRT-III subunit VPS20. The crystal structure of this complex was determined at 2.0 {angstrom} resolution. Residues involved in structural interactions explain the specificity of ESCRT-II for Vps20, and are critical for cargo sorting in vivo. ESCRT-II directly activates ESCRT-III-driven vesicle budding and scission in vitro via these structural interactions. VPS20 and ESCRT-II bind membranes with nanomolar affinity, explaining why binding to ESCRT-II is dispensable for the recruitment of Vps20 to membranes. Docking of the ESCRT-II-VPS202 supercomplex reveals a convex membrane-binding surface, suggesting a hypothesis for negative membrane curvature induction in the nascent intralumenal vesicle.

  7. Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex.

    PubMed

    Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

    2016-05-28

    The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms. PMID:27250314

  8. Lutetium(iii) aqua ion: On the dynamical structure of the heaviest lanthanoid hydration complex.

    PubMed

    Sessa, Francesco; Spezia, Riccardo; D'Angelo, Paola

    2016-05-28

    The structure and dynamics of the lutetium(iii) ion in aqueous solution have been investigated by means of a polarizable force field molecular dynamics (MD). An 8-fold square antiprism (SAP) geometry has been found to be the dominant configuration of the lutetium(iii) aqua ion. Nevertheless, a low percentage of 9-fold complexes arranged in a tricapped trigonal prism (TTP) geometry has been also detected. Dynamic properties have been explored by carrying out six independent MD simulations for each of four different temperatures: 277 K, 298 K, 423 K, 632 K. The mean residence time of water molecules in the first hydration shell at room temperature has been found to increase as compared to the central elements of the lanthanoid series in agreement with previous experimental findings. Water exchange kinetic rate constants at each temperature and activation parameters of the process have been determined from the MD simulations. The obtained structural and dynamical results suggest that the water exchange process for the lutetium(iii) aqua ion proceeds with an associative mechanism, in which the SAP hydration complex undergoes temporary structural changes passing through a 9-fold TTP intermediate. Such results are consistent with the water exchange mechanism proposed for heavy lanthanoid atoms.

  9. Structure, Evolution, and Functions of Bacterial Type III Toxin-Antitoxin Systems

    PubMed Central

    Goeders, Nathalie; Chai, Ray; Chen, Bihe; Day, Andrew; Salmond, George P. C.

    2016-01-01

    Toxin-antitoxin (TA) systems are small genetic modules that encode a toxin (that targets an essential cellular process) and an antitoxin that neutralises or suppresses the deleterious effect of the toxin. Based on the molecular nature of the toxin and antitoxin components, TA systems are categorised into different types. Type III TA systems, the focus of this review, are composed of a toxic endoribonuclease neutralised by a non-coding RNA antitoxin in a pseudoknotted configuration. Bioinformatic analysis shows that the Type III systems can be classified into subtypes. These TA systems were originally discovered through a phage resistance phenotype arising due to a process akin to an altruistic suicide; the phenomenon of abortive infection. Some Type III TA systems are bifunctional and can stabilise plasmids during vegetative growth and sporulation. Features particular to Type III systems are explored here, emphasising some of the characteristics of the RNA antitoxin and how these may affect the co-evolutionary relationship between toxins and cognate antitoxins in their quaternary structures. Finally, an updated analysis of the distribution and diversity of these systems are presented and discussed. PMID:27690100

  10. Structural basis for activation, assembly and membrane binding of ESCRT-III Snf7 filaments

    PubMed Central

    Tang, Shaogeng; Henne, W Mike; Borbat, Peter P; Buchkovich, Nicholas J; Freed, Jack H; Mao, Yuxin; Fromme, J Christopher; Emr, Scott D

    2015-01-01

    The endosomal sorting complexes required for transport (ESCRTs) constitute hetero-oligomeric machines that catalyze multiple topologically similar membrane-remodeling processes. Although ESCRT-III subunits polymerize into spirals, how individual ESCRT-III subunits are activated and assembled together into a membrane-deforming filament remains unknown. Here, we determine X-ray crystal structures of the most abundant ESCRT-III subunit Snf7 in its active conformation. Using pulsed dipolar electron spin resonance spectroscopy (PDS), we show that Snf7 activation requires a prominent conformational rearrangement to expose protein-membrane and protein-protein interfaces. This promotes the assembly of Snf7 arrays with ~30 Å periodicity into a membrane-sculpting filament. Using a combination of biochemical and genetic approaches, both in vitro and in vivo, we demonstrate that mutations on these protein interfaces halt Snf7 assembly and block ESCRT function. The architecture of the activated and membrane-bound Snf7 polymer provides crucial insights into the spatially unique ESCRT-III-mediated membrane remodeling. DOI: http://dx.doi.org/10.7554/eLife.12548.001 PMID:26670543

  11. Electrical transport engineering of semiconductor superlattice structures

    NASA Astrophysics Data System (ADS)

    Shokri, Aliasghar

    2014-04-01

    We investigate the influence of doping concentration on band structures of electrons and electrical transmission in a typical aperiodic semiconductor superlattice consisting of quantum well and barrier layers, theoretically. For this purpose, we assume that each unit cell of the superlattice contains alternately two types of material GaAs (as a well) and GaAlAs (as a barrier) with six sublayers of two materials. Our calculations are based on the generalized Kronig-Penny (KP) model and the transfer matrix method within the framework of the parabolic conductance band effective mass approximation in the coherent regime. This model reduces the numerical calculation time and enables us to use the transfer matrix method to investigate transport in the superlattices. We show that by varying the doping concentration and geometrical parameters, one can easily block the transmission of the electrons. The numerical results may be useful in designing of nanoenergy filter devices.

  12. Appurtenance Influence on Type III Hanford Single-Shell Tank Structural Integrity

    SciTech Connect

    Sanborn, Scott E.; Larsen, Brian M.; Julyk, Larry J.; Johnson, Kenneth I.

    2012-02-26

    The interim stabilized Hanford Single Shell Tanks (SSTs) are currently undergoing a state of the art analysis to assess the structural integrity of the waste storage tanks, for cleanup and closure operations, considering their adverse thermal histories and an updated seismic hazard for the Hanford Site near Richland, Washington. The SSTs contain a variety of ancillary pits, piping, piping supports, risers, equipment, and penetrations known as appurtenances. These appurtenances may alter the structural response and ultimately could affect the structural integrity of the SSTs. An important challenge to the structural analysis of the SSTs is determining the impact of these appurtenances on structural integrity. To achieve this, the various appurtenances were reviewed and bounding appurtenance configurations for SST Types II and III tank designs were analyzed using finite element software. The bounding configurations for the Type II tanks considered four heavy offset pits with a central pit with and without a 36-inch diameter central post-construction penetration and four 42-inch diameter offset penetrations. The bounding configuration for the Type III tanks is a tank with two heavy offset pits and one heavy central pit. For each bounding configuration two finite element models are developed: a seismic analysis model and a thermal and operating loads analysis (TOLA) model. The TOLA models include a Type II or III thermal history, concrete cracking and thermal degradation, reinforcement yielding, and soil plasticity. Additionally, operating loads such as internal waste pressure and concentrated and distributed soil surface loads are applied to the TOLA model. The seismic model treats the tank concrete as linear elastic based on the present day degraded concrete properties. Also, in the seismic model the soil is treated as linear elastic while special techniques are used in the soil above the tank dome and along the tank wall to avoid soil arching and achieve the proper

  13. Ab initio studies on the structure of and atomic interactions in cellulose III(I) crystals.

    PubMed

    Ishikawa, Tetsuya; Hayakawa, Daichi; Miyamoto, Hitomi; Ozawa, Motoyasu; Ozawa, Tomonaga; Ueda, Kazuyoshi

    2015-11-19

    The crystal structure of cellulose III(I)was analyzed using first-principles density functional theory (DFT). The geometry was optimized using variable-cell relaxation, as implemented in Quantum ESPRESSO. The Perdew-Burke-Ernzerhof (PBE) functional with a correction term for long-range van der Waals interactions (PBE-D) reproduced the experimental structure well. By using the optimized crystal structure, the interactions existed among the cellulose chains in the crystal were precisely investigated using the NBO analysis. The results showed that the weak bonding nature of CH/O and the hydrogen bonding occur among glucose molecules in the optimized crystal structure. To investigate the strength of interaction, dimeric and trimeric glucose units were extracted from the crystal, and analyzed using MP2 ab initio counterpoise methods with BSSE correction. The results estimated the strength of the interactions. That is, the packed chains along with a-axis interacts with weak bonding nature of CH/O and dispersion interactions by -7.50 kcal/mol, and two hydrogen bonds of O2HO2…O6 and O6HO6…O2 connect the neighboring packed chains with -11.9 kcal/mol. Moreover, FMO4 calculation was also applied to the optimized crystal structure to estimate the strength of the interactions. These methods can well estimate the interactions existed in the crystal structure of cellulose III(I).

  14. Structural Optimization Methodology for Rotating Disks of Aircraft Engines

    NASA Technical Reports Server (NTRS)

    Armand, Sasan C.

    1995-01-01

    In support of the preliminary evaluation of various engine technologies, a methodology has been developed for structurally designing the rotating disks of an aircraft engine. The structural design methodology, along with a previously derived methodology for predicting low-cycle fatigue life, was implemented in a computer program. An interface computer program was also developed that gathers the required data from a flowpath analysis program (WATE) being used at NASA Lewis. The computer program developed for this study requires minimum interaction with the user, thus allowing engineers with varying backgrounds in aeropropulsion to successfully execute it. The stress analysis portion of the methodology and the computer program were verified by employing the finite element analysis method. The 10th- stage, high-pressure-compressor disk of the Energy Efficient Engine Program (E3) engine was used to verify the stress analysis; the differences between the stresses and displacements obtained from the computer program developed for this study and from the finite element analysis were all below 3 percent for the problem solved. The computer program developed for this study was employed to structurally optimize the rotating disks of the E3 high-pressure compressor. The rotating disks designed by the computer program in this study were approximately 26 percent lighter than calculated from the E3 drawings. The methodology is presented herein.

  15. Evaluation of engineering plastic for rollover protective structure (ROPS) mounting.

    PubMed

    Comer, R S; Ayers, P D; Liu, J

    2007-04-01

    Agriculture has one of the highest fatality rates of any industry in America. Tractor rollovers are a significant contributor to the high death rate. Rollover protective structures (ROPS) have helped lower these high fatality rates on full-size tractors. However, a large number of older tractors still do not use ROPS due to the difficulty of designing and creating a mounting structure. To help reduce this difficulty, engineering plastics were evaluated for use in a ROPS mounting structure on older tractors. The use of engineering plastics around axle housings could provide a uniform mounting configuration as well as lower costs for aftermarket ROPS. Various plastics were examined through shear testing, scale model testing, and compressive strength testing. Once a material was chosen based upon strength and cost, full-scale testing of the plastic's strength on axle housings was conducted. Finally, a mounting structure was tested in static ROPS tests, and field upset tests were performed in accordance with SAE Standard J2194. Initial tests revealed that the ROPS mounting structure and axle housing combination had higher torsional strength with less twisting than the axle housing alone. An engineering plastic ROPS mounting structure was easily successful in withstanding the forces applied during the static longitudinal and lateral ROPS tests. Field upset testing revealed that the mounting structure could withstand the impact loads seen during actual upsets without a failure. During both static testing and field upset testing, no permanent twisting of the mounting structure was found. Engineering plastic could therefore be a viable option for a universal ROPS mounting structure for older tractors.

  16. STAEBL: Structural tailoring of engine blades, phase 2

    NASA Technical Reports Server (NTRS)

    Hirschbein, M. S.; Brown, K. W.

    1984-01-01

    The Structural Tailoring of Engine Blades (STAEBL) program was initiated at NASA Lewis Research Center in 1980 to introduce optimal structural tailoring into the design process for aircraft gas turbine engine blades. The standard procedure for blade design is highly iterative with the engineer directly providing most of the decisions that control the design process. The goal of the STAEBL program has been to develop an automated approach to generate structurally optimal blade designs. The program has evolved as a three-phase effort with the developmental work being performed contractually by Pratt & Whitney Aircraft. Phase 1 was intended as a proof of concept in which two fan blades were structurally tailored to meet a full set of structural design constraints while minimizing DOC+I (direct operating cost plus interest) for a representative aircraft. This phase was successfully completed and was reported in reference 1 and 2. Phase 2 has recently been completed and is the basis for this discussion. During this phase, three tasks were accomplished: (1) a nonproprietary structural tailoring computer code was developed; (2) a dedicated approximate finite-element analysis was developed; and (3) an approximate large-deflection analysis was developed to assess local foreign object damage. Phase 3 is just beginning and is designed to incorporated aerodynamic analyses directly into the structural tailoring system in order to relax current geometric constraints.

  17. Synthesis, structure, luminescent, and magnetic properties of carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2] (Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato).

    PubMed

    Ehama, Kiyomi; Ohmichi, Yusuke; Sakamoto, Soichiro; Fujinami, Takeshi; Matsumoto, Naohide; Mochida, Naotaka; Ishida, Takayuki; Sunatsuki, Yukinari; Tsuchimoto, Masanobu; Re, Nazzareno

    2013-11-01

    Carbonato-bridged Zn(II)2Ln(III)2 complexes [(μ4-CO3)2{Zn(II)L(n)Ln(III)(NO3)}2]·solvent were synthesized through atmospheric CO2 fixation reaction of [Zn(II)L(n)(H2O)2]·xH2O, Ln(III)(NO3)3·6H2O, and triethylamine, where Ln(III) = Gd(III), Tb(III), Dy(III); L(1) = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L(2) = N,N'-bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato. Each Zn(II)2Ln(III)2 structure possessing an inversion center can be described as two di-μ-phenoxo-bridged {Zn(II)L(n)Ln(III)(NO3)} binuclear units bridged by two carbonato CO3(2-) ions. The Zn(II) ion has square pyramidal coordination geometry with N2O2 donor atoms of L(n) and one oxygen atom of a bridging carbonato ion at the axial site. Ln(III) ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base L(n), two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9-300 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic susceptibilities under the direct current bias fields of 0 and 1000 Oe were measured. The magnetic properties of the Zn(II)2Ln(III)2 complexes are analyzed on the basis of the dicarbonato-bridged binuclear Ln(III)-Ln(III) structure, as the Zn(II) ion with d(10) electronic configuration is diamagnetic. ZnGd1 (L(1)) and ZnGd2 (L(2)) show a ferromagnetic Gd(III)-Gd(III) interaction with J(Gd-Gd) = +0.042 and +0.028 cm(-1), respectively, on the basis of the Hamiltonian H = -2J(Gd-Gd)ŜGd1·ŜGd2. The magnetic data of the Zn(II)2Ln(III)2 complexes (Ln(III) = Tb(III), Dy(III)) were analyzed by a spin Hamiltonian including the crystal field effect on the Ln(III) ions and the Ln(III)-Ln(III) magnetic interaction. The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy. Luminescence spectra of Zn(II)2Tb(III)2 complexes were observed, while those

  18. The structure of the hydrated gallium(III), indium(III), and chromium(III) ions in aqueous solution. A large angle X-ray scattering and EXAFS study

    SciTech Connect

    Lindqvist-Reis, P.; Pattanaik, S.; Sandstroem, M.; Munoz-Paez, A.; Diaz-Moreno, S.; Persson, I.

    1998-12-28

    The structure of the hydrated gallium(III), indium(III), and chromium(III) ions has been determined in aqueous perchlorate and nitrate solutions by means of the large-angle X-ray scattering (LAXS) and extended X-ray absorption fine structure (EXAFS) techniques. The EXAFS studies have been performed over a wide concentration range, 0.005--1.0 mol/dm{sup 3} (2.6 mol/dm{sup 3} for chromium(III)), while the LAXS studies are restricted to concentrated solutions, ca. 1.5 mol/dm{sup 3}. All three metal ions were found to coordinate six water molecules, each of which are hydrogen bonded to two water molecules in a second hydration sphere. Analyses of the Ga, In, and Cr K-edge EXAFS data of the aqueous perchlorate and nitrate solutions showed no influence on the first shell M{single_bond}O distance by a change of concentration or anion. The minor contribution from the second sphere M{hor_ellipsis}O distance is obscured by multiple scattering within the tightly bonded first shell. EXAFS data for the alum salts CsM(SO{sub 4}){sub 2}{center_dot}12H{sub 2}O, M = Ga or In, showed the M-O bond length of the hexahydrated gallium(III) and indium(III) ions to be 1.957(2) and 2.122(2) {angstrom}, respectively.

  19. Appurtenance Influence on Type III Hanford Single-Shell Tank Structural Integrity - 12255

    SciTech Connect

    Sanborn, Scott E.; Johnson, Kenneth I.; Larsen, Brian M.; Julyk, Larry J.

    2012-07-01

    The interim stabilized Hanford Single-Shell Tanks (SSTs) are currently undergoing a state of the art analysis to assess the structural integrity of the waste storage tanks, for cleanup and closure operations, considering their adverse thermal histories and an updated seismic hazard for the Hanford Site near Richland, Washington. The SSTs contain a variety of ancillary pits, piping, piping supports, risers, equipment, and penetrations known as appurtenances. These appurtenances may alter the structural response and ultimately could affect the structural integrity of the SSTs. An important challenge to the structural analysis of the SSTs is to determine the impact of these appurtenances on structural integrity. To achieve this, the various appurtenances were reviewed and a bounding appurtenance configuration for the SST Type III tanks was analyzed using finite element models for both thermal and operating loads as well as seismic loads. Tank structural demands from the finite element analyses were evaluated according to American Concrete Institute (ACI-349) code requirements to determine the tank structural integrity. The appurtenances configuration is found to increase the demand to capacity ratios in local regions near the appurtenances. Away from the appurtenances the influence on structural integrity is minor. The ACI-349-06 evaluation of the Type III SST bounding appurtenance configuration shows the tank is still structurally sound under all evaluated load combinations. When the appurtenance model D/C ratios were compared to those from the baseline axisymmetric model it was found that there were significant differences in the results, particularly under seismic loading conditions. This indicates that the effect of appurtenances on tank structural integrity should at least be considered in all SST AORs. (authors)

  20. Hydrogen effects in dilute III-N-V alloys: From defect engineering to nanostructuring

    SciTech Connect

    Pettinari, G.; Felici, M.; Capizzi, M.; Polimeni, A.; Trotta, R.

    2014-01-07

    The variation of the band gap energy of III-N-V semiconductors induced by hydrogen incorporation is the most striking effect that H produces in these materials. A special emphasis is given here to the combination of N-activity passivation by hydrogen with H diffusion kinetics in dilute nitrides. Secondary ion mass spectrometry shows an extremely steep (smaller than 5 nm/decade) forefront of the H diffusion profile in Ga(AsN) under appropriate hydrogenation conditions. This discovery prompts the opportunity for an in-plane nanostructuring of hydrogen incorporation and, hence, for a modulation of the material band gap energy at the nanoscale. The properties of quantum dots fabricated by a lithographically defined hydrogenation are presented, showing the zero-dimensional character of these novel nanostructures. Applicative prospects of this nanofabrication method are finally outlined.

  1. Complex quantum networks as structured environments: engineering and probing

    PubMed Central

    Nokkala, Johannes; Galve, Fernando; Zambrini, Roberta; Maniscalco, Sabrina; Piilo, Jyrki

    2016-01-01

    We consider structured environments modeled by bosonic quantum networks and investigate the probing of their spectral density, structure, and topology. We demonstrate how to engineer a desired spectral density by changing the network structure. Our results show that the spectral density can be very accurately detected via a locally immersed quantum probe for virtually any network configuration. Moreover, we show how the entire network structure can be reconstructed by using a single quantum probe. We illustrate our findings presenting examples of spectral densities and topology probing for networks of genuine complexity. PMID:27230125

  2. Complex quantum networks as structured environments: engineering and probing

    NASA Astrophysics Data System (ADS)

    Nokkala, Johannes; Galve, Fernando; Zambrini, Roberta; Maniscalco, Sabrina; Piilo, Jyrki

    2016-05-01

    We consider structured environments modeled by bosonic quantum networks and investigate the probing of their spectral density, structure, and topology. We demonstrate how to engineer a desired spectral density by changing the network structure. Our results show that the spectral density can be very accurately detected via a locally immersed quantum probe for virtually any network configuration. Moreover, we show how the entire network structure can be reconstructed by using a single quantum probe. We illustrate our findings presenting examples of spectral densities and topology probing for networks of genuine complexity.

  3. Complex quantum networks as structured environments: engineering and probing.

    PubMed

    Nokkala, Johannes; Galve, Fernando; Zambrini, Roberta; Maniscalco, Sabrina; Piilo, Jyrki

    2016-05-27

    We consider structured environments modeled by bosonic quantum networks and investigate the probing of their spectral density, structure, and topology. We demonstrate how to engineer a desired spectral density by changing the network structure. Our results show that the spectral density can be very accurately detected via a locally immersed quantum probe for virtually any network configuration. Moreover, we show how the entire network structure can be reconstructed by using a single quantum probe. We illustrate our findings presenting examples of spectral densities and topology probing for networks of genuine complexity.

  4. Structure-function relationships within Keppler-type antitumor ruthenium(III) complexes: the case of 2-aminothiazolium[trans-tetrachlorobis(2-aminothiazole)ruthenate(III)].

    PubMed

    Mura, Pasquale; Piccioli, Francesca; Gabbiani, Chiara; Camalli, Mercedes; Messori, Luigi

    2005-07-11

    Keppler-type ruthenium(III) complexes exhibit promising antitumor properties. We report here a study of 2-aminothiazolium[trans-tetrachlorobis(2-aminothiazole)ruthenate(III)], both in the solid state and in solution. The crystal structure has been solved and found to exhibit classical features. Important solvatochromic effects were revealed. Notably, we observed that introduction of an amino group in position 2 greatly accelerates chloride hydrolysis compared to the thiazole analogue; this latter finding may be of interest for a fine-tuning of the reactivity of these novel metallodrugs.

  5. Optical Engineering for Children--A Structured Approach

    ERIC Educational Resources Information Center

    McCarthy, John; Moore, R. A.

    2006-01-01

    The present paper focuses on the application of a structured template, maximum impact flow (MIF), in order to encourage young students in the area of optics and optical engineering. MIF introduces a template in terms of individual steps and linked functionality and is shown to fuse separate learning tools together into a cohesive unit.…

  6. CAL Packages for Civil Engineering Hydraulics and Structural Design.

    ERIC Educational Resources Information Center

    Moss, W. D.; And Others

    1979-01-01

    Describes computer assisted learning (CAL) packages written in FORTRAN IV and developed for use in a degree course in civil engineering dealing with hydraulics and structures. All are used in the interactive mode through a terminal with a keyboard and visual display unit. (Author/CMV)

  7. Abstraction and Concreteness in the Everyday Mathematics of Structural Engineers.

    ERIC Educational Resources Information Center

    Gainsburg, Julie

    The everyday mathematics processes of structural engineers were studied and analyzed in terms of abstraction. A main purpose of the study was to explore the degree to which the notion of a gap between school and everyday mathematics holds when the scope of practices considered "everyday" is extended. J. Lave (1988) promoted a methodology that…

  8. A New Degree Programme in Structural Engineering and Architecture.

    ERIC Educational Resources Information Center

    Davison, J. B.; Popovic, O.; Tyas, A.

    Structural engineers and architects are educated completely independently. Although both play a major part in designing and building a nation's infrastructure, they are not encouraged to fully understand the work of each other which can result in a lack of collaboration and co-operation, often to the detriment of a project. This divide between the…

  9. Structural Role of the Vps4-Vta1 Interface in ESCRT-III Recycling

    SciTech Connect

    Yang, Dong; Hurley, James H.

    2010-09-27

    The ESCRT complexes are required for multivesicular body biogenesis, macroautophagy, cytokinesis, and the budding of HIV-1. The final step in the ESCRT cycle is the disassembly of the ESCRT-III lattice by the AAA+ ATPase Vps4. Vps4 assembles on its membrane-bound ESCRT-III substrate with its cofactor, Vta1. The crystal structure of the dimeric VSL domain of yeast Vta1 with the small ATPase and the {beta}domains of Vps4 was determined. Residues involved in structural interactions are conserved and are required for binding in vitro and for Cps1 sorting in vivo. Modeling of the Vta1 complex in complex with the lower hexameric ring of Vps4 indicates that the two-fold axis of the Vta1 VSL domain is parallel to within {approx}20 degrees of the six-fold axis of the hexamer. This suggests that Vta1 might not crosslink the two hexameric rings of Vps4, but rather stabilizes an array of Vps4-Vta1 complexes for ESCRT-III disassembly.

  10. Applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures

    NASA Astrophysics Data System (ADS)

    Zou, Tao; Kaminski, Miroslaw Lech

    2016-09-01

    In design and operation of floating offshore structures, one has to avoid fatigue failures caused by action of ocean waves. The aim of this paper is to investigate the applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures. The applicability was investigated for Bluewaters' FPSO (Floating Production, Storage and Offloading) which had been turret moored at Sable field for half a decade. The waves were predicted as sea-state time series consisting of one wind sea and one swell. The predicted waves were compared with wave data obtained from ERA-interim and buoy measurements. Furthermore, the fatigue calculations were also carried out for main deck and side shell locations. It has been concluded that predicted fatigue damages of main deck using WaveWatch-III are in a very good agreement regardless of differences in predicted wind waves and swells caused by differences in wave system partitioning. When compared to buoy measurements, the model underestimates fatigue damages of side shell by approximately 30 %. The reason for that has been found in wider directional spreading of actual waves. The WaveWatch-III wave model has been found suitable for the fatigue assessment. However, more attention should be paid on relative wave directionality, wave system partitioning and uncertainty analysis in further development.

  11. Structural basis for midbody targeting of spastin by the ESCRT-III protein CHMP1B

    SciTech Connect

    Yang, Dong; Rimanchi, Neggy; Renvoise, Benoit; Lippincott-Schwartz, Jennifer; Blackstone, Craig; Hurley, James H.

    2009-01-15

    The endosomal sorting complex required for transport (ESCRT) machinery, including ESCRT-III, localizes to the midbody and participates in the membrane-abscission step of cytokinesis. The ESCRT-III protein charged multivesicular body protein 1B (CHMP1B) is required for recruitment of the MIT domain-containing protein spastin, a microtubule-severing enzyme, to the midbody. The 2.5-{angstrom} structure of the C-terminal tail of CHMP1B with the MIT domain of spastin reveals a specific, high-affinity complex involving a noncanonical binding site between the first and third helices of the MIT domain. The structural interface is twice as large as that of the MIT domain of the VPS4-CHMP complex, consistent with the high affinity of the interaction. A series of unique hydrogen-bonding interactions and close packing of small side chains discriminate against the other ten human ESCRT-III subunits. Point mutants in the CHMP1B binding site of spastin block recruitment of spastin to the midbody and impair cytokinesis.

  12. Three-Coordinate Terminal Imidoiron(III) Complexes: Structure, Spectroscopy, and Mechanism of Formation

    PubMed Central

    Cowley, Ryan E.; DeYonker, Nathan J.; Eckert, Nathan A.; Cundari, Thomas R.; DeBeer, Serena; Bill, Eckhard; Ottenwaelder, Xavier; Flaschenriem, Christine; Holland, Patrick L.

    2010-01-01

    Reaction of 1-adamantyl azide with iron(I) diketiminate precursors gives metastable but isolable imidoiron(III) complexes LFe=NAd (L = bulky β-diketiminate ligand; Ad = 1-adamantyl). This paper addresses: (1) the spectroscopic and structural characterization of the Fe=N multiple bond in these interesting three-coordinate iron imido complexes, and (2) the mechanism through which the imido complexes form. The iron(III) imido complexes have been examined by 1H NMR and EPR spectroscopies and temperature-dependent magnetic susceptibility (SQUID), and structurally characterized by crystallography and/or X-ray absorption (EXAFS) measurements. These data show that the imido complexes have quartet ground states and short (1.68 ± 0.01 Å) iron-nitrogen bonds. The formation of the imido complexes proceeds through unobserved iron–RN3 intermediates, which are indicated by QM/MM computations to be best described as iron(II) with an RN3 radical anion. The radical character on the organoazide bends its NNN linkage to enable easy N2 loss and imido complex formation. The product distribution between imidoiron(III) products and hexazene-bridged diiron(II) products is solvent-dependent, and the solvent dependence can be explained by coordination of certain solvents to the iron(I) precursor prior to interaction with the organoazide. PMID:20524625

  13. Investigating the Structure of the WJ-III Cognitive in Early School Age through Two Exploratory Bifactor Analysis Procedures

    ERIC Educational Resources Information Center

    Dombrowski, Stefan C.

    2014-01-01

    Two exploratory bifactor methods (e.g., Schmid-Leiman [SL] and exploratory bifactor analysis [EBFA]) were used to investigate the structure of the Woodcock-Johnson III (WJ-III) Cognitive in early school age (age 6-8). The SL procedure is recognized by factor analysts as a preferred method for EBFA. Jennrich and Bentler recently developed an…

  14. Solution structure of monomeric BsaL, the type III secretion needle protein of Burkholderia pseudomallei.

    PubMed

    Zhang, Lingling; Wang, Yu; Picking, Wendy L; Picking, William D; De Guzman, Roberto N

    2006-06-01

    Many gram-negative bacteria that are important human pathogens possess type III secretion systems as part of their required virulence factor repertoire. During the establishment of infection, these pathogens coordinately assemble greater than 20 different proteins into a macromolecular structure that spans the bacterial inner and outer membranes and, in many respects, resembles and functions like a syringe. This type III secretion apparatus (TTSA) is used to inject proteins into a host cell's membrane and cytoplasm to subvert normal cellular processes. The external portion of the TTSA is a needle that is composed of a single type of protein that is polymerized in a helical fashion to form an elongated tube with a central channel of 2-3 nm in diameter. TTSA needle proteins from a variety of bacterial pathogens share sequence conservation; however, no atomic structure for any TTSA needle protein is yet available. Here, we report the structure of a TTSA needle protein called BsaL from Burkholderia pseudomallei determined by nuclear magnetic resonance (NMR) spectroscopy. The central part of the protein assumes a helix-turn-helix core domain with two well-defined alpha-helices that are joined by an ordered, four-residue linker. This forms a two-helix bundle that is stabilized by interhelix hydrophobic contacts. Residues that flank this presumably exposed core region are not completely disordered, but adopt a partial helical conformation. The atomic structure of BsaL and its sequence homology with other TTSA needle proteins suggest potentially unique structural dynamics that could be linked with a universal mechanism for control of type III secretion in diverse gram-negative bacterial pathogens.

  15. The Bacterial Flagellar Type III Export Gate Complex Is a Dual Fuel Engine That Can Use Both H+ and Na+ for Flagellar Protein Export.

    PubMed

    Minamino, Tohru; Morimoto, Yusuke V; Hara, Noritaka; Aldridge, Phillip D; Namba, Keiichi

    2016-03-01

    The bacterial flagellar type III export apparatus utilizes ATP and proton motive force (PMF) to transport flagellar proteins to the distal end of the growing flagellar structure for self-assembly. The transmembrane export gate complex is a H+-protein antiporter, of which activity is greatly augmented by an associated cytoplasmic ATPase complex. Here, we report that the export gate complex can use sodium motive force (SMF) in addition to PMF across the cytoplasmic membrane to drive protein export. Protein export was considerably reduced in the absence of the ATPase complex and a pH gradient across the membrane, but Na+ increased it dramatically. Phenamil, a blocker of Na+ translocation, inhibited protein export. Overexpression of FlhA increased the intracellular Na+ concentration in the presence of 100 mM NaCl but not in its absence, suggesting that FlhA acts as a Na+ channel. In wild-type cells, however, neither Na+ nor phenamil affected protein export, indicating that the Na+ channel activity of FlhA is suppressed by the ATPase complex. We propose that the export gate by itself is a dual fuel engine that uses both PMF and SMF for protein export and that the ATPase complex switches this dual fuel engine into a PMF-driven export machinery to become much more robust against environmental changes in external pH and Na+ concentration. PMID:26943926

  16. The Bacterial Flagellar Type III Export Gate Complex Is a Dual Fuel Engine That Can Use Both H+ and Na+ for Flagellar Protein Export

    PubMed Central

    Minamino, Tohru; Morimoto, Yusuke V.; Hara, Noritaka; Aldridge, Phillip D.; Namba, Keiichi

    2016-01-01

    The bacterial flagellar type III export apparatus utilizes ATP and proton motive force (PMF) to transport flagellar proteins to the distal end of the growing flagellar structure for self-assembly. The transmembrane export gate complex is a H+–protein antiporter, of which activity is greatly augmented by an associated cytoplasmic ATPase complex. Here, we report that the export gate complex can use sodium motive force (SMF) in addition to PMF across the cytoplasmic membrane to drive protein export. Protein export was considerably reduced in the absence of the ATPase complex and a pH gradient across the membrane, but Na+ increased it dramatically. Phenamil, a blocker of Na+ translocation, inhibited protein export. Overexpression of FlhA increased the intracellular Na+ concentration in the presence of 100 mM NaCl but not in its absence, suggesting that FlhA acts as a Na+ channel. In wild-type cells, however, neither Na+ nor phenamil affected protein export, indicating that the Na+ channel activity of FlhA is suppressed by the ATPase complex. We propose that the export gate by itself is a dual fuel engine that uses both PMF and SMF for protein export and that the ATPase complex switches this dual fuel engine into a PMF-driven export machinery to become much more robust against environmental changes in external pH and Na+ concentration. PMID:26943926

  17. The Bacterial Flagellar Type III Export Gate Complex Is a Dual Fuel Engine That Can Use Both H+ and Na+ for Flagellar Protein Export.

    PubMed

    Minamino, Tohru; Morimoto, Yusuke V; Hara, Noritaka; Aldridge, Phillip D; Namba, Keiichi

    2016-03-01

    The bacterial flagellar type III export apparatus utilizes ATP and proton motive force (PMF) to transport flagellar proteins to the distal end of the growing flagellar structure for self-assembly. The transmembrane export gate complex is a H+-protein antiporter, of which activity is greatly augmented by an associated cytoplasmic ATPase complex. Here, we report that the export gate complex can use sodium motive force (SMF) in addition to PMF across the cytoplasmic membrane to drive protein export. Protein export was considerably reduced in the absence of the ATPase complex and a pH gradient across the membrane, but Na+ increased it dramatically. Phenamil, a blocker of Na+ translocation, inhibited protein export. Overexpression of FlhA increased the intracellular Na+ concentration in the presence of 100 mM NaCl but not in its absence, suggesting that FlhA acts as a Na+ channel. In wild-type cells, however, neither Na+ nor phenamil affected protein export, indicating that the Na+ channel activity of FlhA is suppressed by the ATPase complex. We propose that the export gate by itself is a dual fuel engine that uses both PMF and SMF for protein export and that the ATPase complex switches this dual fuel engine into a PMF-driven export machinery to become much more robust against environmental changes in external pH and Na+ concentration.

  18. Electronic structure engineering of various structural phases of phosphorene.

    PubMed

    Kaur, Sumandeep; Kumar, Ashok; Srivastava, Sunita; Tankeshwar, K

    2016-07-21

    We report the tailoring of the electronic structures of various structural phases of phosphorene (α-P, β-P, γ-P and δ-P) based homo- and hetero-bilayers through in-plane mechanical strains, vertical pressure and transverse electric field by employing density functional theory. In-plane biaxial strains have considerably modified the electronic bandgap of both homo- and hetero-bilayers while vertical pressure induces metallization in the considered structures. The γ-P homo-bilayer structure showed the highest ultimate tensile strength (UTS ∼ 6.21 GPa) upon in-plane stretching. Upon application of a transverse electric field, the variation in the bandgap of hetero-bilayers was found to be strongly dependent on the polarity of the applied field which is attributed to the counterbalance between the external electric field and the internal field induced by different structural phases and heterogeneity in the arrangements of atoms of each surface of the hetero-bilayer system. Our results demonstrate that the electronic structures of the considered hetero- and homo-bilayers of phosphorene could be modified by biaxial strain, pressure and electric field to achieve the desired properties for future nano-electronic devices.

  19. Work extremum principle: structure and function of quantum heat engines.

    PubMed

    Allahverdyan, Armen E; Johal, Ramandeep S; Mahler, Guenter

    2008-04-01

    We consider a class of quantum heat engines consisting of two subsystems interacting with a work-source and coupled to two separate baths at different temperatures Th>Tc. The purpose of the engine is to extract work due to the temperature difference. Its dynamics is not restricted to the near equilibrium regime. The engine structure is determined by maximizing the extracted work under various constraints. When this maximization is carried out at finite power, the engine dynamics is described by well-defined temperatures and satisfies the local version of the second law. In addition, its efficiency is bounded from below by the Curzon-Ahlborn value 1-radical Tc/Th and from above by the Carnot value 1-(Tc/Th). The latter is reached-at finite power--for a macroscopic engine, while the former is achieved in the equilibrium limit Th-->Tc . The efficiency that maximizes the power is strictly larger than the Curzon-Ahloborn value. When the work is maximized at a zero power, even a small (few-level) engine extracts work right at the Carnot efficiency.

  20. Multiscale structural characterizations of mixed U(iv)-An(iii) oxalates (An(iii) = Pu or Am) combining XAS and XRD measurements.

    PubMed

    Arab-Chapelet, B; Martin, P M; Costenoble, S; Delahaye, T; Scheinost, A C; Grandjean, S; Abraham, F

    2016-04-28

    Mixed actinide(III,IV) oxalates of the general formula M2.2UAn(C2O4)5·nH2O (An = Pu or Am and M = H3O(+) and N2H5(+)) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield >99%). Thorough multiscale structural characterization using XRD and XAS measurements confirmed the existence of mixed actinide oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium, are maintained during the precipitation step. EXAFS measurements show that the local environments around U(+IV), Pu(+III) and Am(+III) are comparable, and the actinides are surrounded by ten oxygen atoms from five bidentate oxalate anions. The mean metal-oxygen distances obtained by XAS measurements are in agreement with those calculated from XRD lattice parameters. PMID:26979820

  1. Interaction of curcumin with Al(III) and its complex structures based on experiments and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Jiang, Teng; Wang, Long; Zhang, Sui; Sun, Ping-Chuan; Ding, Chuan-Fan; Chu, Yan-Qiu; Zhou, Ping

    2011-10-01

    Curcumin has been recognized as a potential natural drug to treat the Alzheimer's disease (AD) by chelating baleful metal ions, scavenging radicals and preventing the amyloid β (Aβ) peptides from the aggregation. In this paper, Al(III)-curcumin complexes with Al(III) were synthesized and characterized by liquid-state 1H, 13C and 27Al nuclear magnetic resonance (NMR), mass spectroscopy (MS), ultraviolet spectroscopy (UV) and generalized 2D UV-UV correlation spectroscopy. In addition, the density functional theory (DFT)-based UV and chemical shift calculations were also performed to view insight into the structures and properties of curcumin and its complexes. It was revealed that curcumin could interact strongly with Al(III) ion, and form three types of complexes under different molar ratios of [Al(III)]/[curcumin], which would restrain the interaction of Al(III) with the Aβ peptide, reducing the toxicity effect of Al(III) on the peptide.

  2. Performance of J33 turbojet engine with shaft-power extraction III : turbine performance

    NASA Technical Reports Server (NTRS)

    Huppert, M C; Nettles, J C

    1949-01-01

    The performance of the turbine component of a J33 turbojet engine was determined over a range of turbine speeds from 8000 to 11,500 rpm.Turbine-inlet temperature was varied from the minimum required to drive the compressor to a maximum of approximately 2000 degrees R at each of several intermediate turbine speeds. Data are presented that show the horsepower developed by the turbine per pound of gas flow. The relation between turbine-inlet stagnation pressure, turbine-outlet stagnation pressure, and turbine-outlet static pressure was established. The turbine-weight-flow parameter varied from 39.2 to 43.6. The maximum turbine efficiency measured was 0.86 at a pressure ratio of 3.5 and a ratio of blade speed to theoretical nozzle velocity of 0.39. A generalized performance map of the turbine-horsepower parameter plotted against the turbine-speed parameter indicated that the best turbine efficiency is obtained when the turbine power is 10 percent greater than the compressor horsepower. The variation of efficiency with the ratio of blade speed to nozzle velocity indicated that the turbine operates at a speed above that for maximum efficiency when the engine is operated normally with the 19-inch-diameter jet nozzle.

  3. Structural tailoring of engine blades (STAEBL) theoretical manual

    NASA Technical Reports Server (NTRS)

    Brown, K. W.

    1985-01-01

    This Theoretical Manual includes the theories included in the Structural Tailoring of Engine Blades (STAEBL) computer program which was developed to perform engine fan and compressor blade numerical optimizations. These blade optimizations seek a minimum weight or cost design that satisfies practical blade design constraints, by controlling one to twenty design variables. The STAEBL constraint analyses include blade stresses, vibratory response, flutter, and foreign object damage. Blade design variables include airfoil thickness at several locations, blade chord, and construction variables: hole size for hollow blades, and composite material layup for composite blades.

  4. Structural tailoring of engine blades (STAEBL) user's manual

    NASA Technical Reports Server (NTRS)

    Brown, K. W.

    1985-01-01

    This User's Manual contains instructions and demonstration case to prepare input data, run, and modify the Structural Tailoring of Engine Blades (STAEBL) computer code. STAEBL was developed to perform engine fan and compressor blade numerical optimizations. This blade optimization seeks a minimum weight or cost design that satisfies realistic blade design constraints, by tuning one to twenty design variables. The STAEBL constraint analyses include blade stresses, vibratory response, flutter, and foreign object damage. Blade design variables include airfoil thickness at several locations, blade chord, and construction variables: hole size for hollow blades, and composite material layup for composite blades.

  5. Interdisciplinary and multilevel optimum design. [in aerospace structural engineering

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, Jaroslaw; Haftka, Raphael T.

    1987-01-01

    Interactions among engineering disciplines and subsystems in engineering system design are surveyed and specific instances of such interactions are described. Examination of the interactions that a traditional design process in which the numerical values of major design variables are decided consecutively is likely to lead to a suboptimal design. Supporting numerical examples are a glider and a space antenna. Under an alternative approach introduced, the design and its sensitivity data from the subsystems and disciplines are generated concurrently and then made available to the system designer enabling him to modify the system design so as to improve its performance. Examples of a framework structure and an airliner wing illustrate that approach.

  6. Remodeling of tissue-engineered bone structures in vivo.

    PubMed

    Hofmann, Sandra; Hilbe, Monika; Fajardo, Robert J; Hagenmüller, Henri; Nuss, Katja; Arras, Margarete; Müller, Ralph; von Rechenberg, Brigitte; Kaplan, David L; Merkle, Hans P; Meinel, Lorenz

    2013-09-01

    Implant design for bone regeneration is expected to be optimized when implant structures resemble the anatomical situation of the defect site. We tested the validity of this hypothesis by exploring the feasibility of generating different in vitro engineered bone-like structures originating from porous silk fibroin scaffolds decorated with RGD sequences (SF-RGD), seeded with human mesenchymal stem cells (hMSC). Scaffolds with small (106-212 μm), medium (212-300 μm), and large pore diameter ranges (300-425 μm) were seeded with hMSC and subsequently differentiated in vitro into bone-like tissue resembling initial scaffold geometries and featuring bone-like structures. Eight weeks after implantation into calvarial defects in mice, the in vitro engineered bone-like tissues had remodeled into bone featuring different proportions of woven/lamellar bone bridging the defects. Regardless of pore diameter, all implants integrated well, vascularization was advanced, and bone marrow ingrowth had started. Ultimately, in this defect model, the geometry of the in vitro generated tissue-engineered bone structure, trabecular- or plate-like, had no significant impact on the healing of the defect, owing to an efficient remodeling of its structure after implantation. PMID:23958323

  7. Engineering the Salmonella type III secretion system to export spider silk monomers.

    PubMed

    Widmaier, Daniel M; Tullman-Ercek, Danielle; Mirsky, Ethan A; Hill, Rena; Govindarajan, Sridhar; Minshull, Jeremy; Voigt, Christopher A

    2009-01-01

    The type III secretion system (T3SS) exports proteins from the cytoplasm, through both the inner and outer membranes, to the external environment. Here, a system is constructed to harness the T3SS encoded within Salmonella Pathogeneity Island 1 to export proteins of biotechnological interest. The system is composed of an operon containing the target protein fused to an N-terminal secretion tag and its cognate chaperone. Transcription is controlled by a genetic circuit that only turns on when the cell is actively secreting protein. The system is refined using a small human protein (DH domain) and demonstrated by exporting three silk monomers (ADF-1, -2, and -3), representative of different types of spider silk. Synthetic genes encoding silk monomers were designed to enhance genetic stability and codon usage, constructed by automated DNA synthesis, and cloned into the secretion control system. Secretion rates up to 1.8 mg l(-1) h(-1) are demonstrated with up to 14% of expressed protein secreted. This work introduces new parts to control protein secretion in Gram-negative bacteria, which will be broadly applicable to problems in biotechnology. PMID:19756048

  8. III-V strain layer superlattice based band engineered avalanche photodiodes (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ghosh, Sid

    2015-08-01

    Laser detection and ranging (LADAR)-based systems operating in the Near Infrared (NIR) and Short Wave Infrared (SWIR) have become popular optical sensors for remote sensing, medical, and environmental applications. Sophisticated laser-based radar and weapon systems used for long-range military and astronomical applications need to detect, recognize, and track a variety of targets under a wide spectrum of atmospheric conditions. Infrared APDs play an important role in LADAR systems by integrating the detection and gain stages in a single device. Robust silicon-APDs are limited to visible and very near infrared region (< 1 um), while InGaAs works well up to wavelengths of about 1.5um. Si APDs have low multiplication or excess noise but are limited to below 1um due very poor quantum efficiency above 0.8um. InGaAs and Ge APDs operate up to wavelengths of 1.5um but have poor multiplication or excess noise due to a low impact ionization coefficient ratio between electrons and holes. For the past several decades HgCdTe has been traditionally used in longer wavelength (> 3um) infrared photon detection applications. Recently, various research groups (including Ghosh et. al.) have reported SWIR and MWIR HgCdTe APDs on CdZnTe and Si substrates. However, HgCdTe APDs suffer from low breakdown fields due to material defects, and excess noise increases significantly at high electric fields. During the past decade, InAs/GaSb Strain Layer Superlattice (SLS) material system has emerged as a potential material for the entire infrared spectrum because of relatively easier growth, comparable absorption coefficients, lower tunneling currents and longer Auger lifetimes resulting in enhanced detectivities (D*). Band engineering in type II SLS allows us to engineer avalanche properties of electrons and holes. This is a great advantage over bulk InGaAs and HgCdTe APDs where engineering avalanche properties is not possible. The talk will discuss the evolution of superlattice based avalanche

  9. Engineering the Electronic Band Structure for Multiband Solar Cells

    SciTech Connect

    Lopez, N.; Reichertz, L.A.; Yu, K.M.; Campman, K.; Walukiewicz, W.

    2010-07-12

    Using the unique features of the electronic band structure of GaNxAs1-x alloys, we have designed, fabricated and tested a multiband photovoltaic device. The device demonstrates an optical activity of three energy bands that absorb, and convert into electrical current, the crucial part of the solar spectrum. The performance of the device and measurements of electroluminescence, quantum efficiency and photomodulated reflectivity are analyzed in terms of the Band Anticrossing model of the electronic structure of highly mismatched alloys. The results demonstrate the feasibility of using highly mismatched alloys to engineer the semiconductor energy band structure for specific device applications.

  10. Structurally compliant rocket engine combustion chamber: Experimental and analytical validation

    NASA Technical Reports Server (NTRS)

    Jankovsky, Robert S.; Arya, Vinod K.; Kazaroff, John M.; Halford, Gary R.

    1994-01-01

    A new, structurally compliant rocket engine combustion chamber design has been validated through analysis and experiment. Subscale, tubular channel chambers have been cyclically tested and analytically evaluated. Cyclic lives were determined to have a potential for 1000 percent increase over those of rectangular channel designs, the current state of the art. Greater structural compliance in the circumferential direction gave rise to lower thermal strains during hot firing, resulting in lower thermal strain ratcheting and longer predicted fatigue lives. Thermal, structural, and durability analyses of the combustion chamber design, involving cyclic temperatures, strains, and low-cycle fatigue lives, have corroborated the experimental observations.

  11. Cabin-fuselage-wing structural design concept with engine installation

    NASA Technical Reports Server (NTRS)

    Ariotti, Scott; Garner, M.; Cepeda, A.; Vieira, J.; Bolton, D.

    1993-01-01

    The purpose of this project is to provide a fuselage structural assembly and wing structural design that will be able to withstand the given operational parameters and loads provided by Federal Aviation Regulation Part 23 (FAR 23) and the Statement of Work (SOW). The goal is to provide a durable lightweight structure that will transfer the applied loads through the most efficient load path. Areas of producibility and maintainability of the structure will also be addressed. All of the structural members will also meet or exceed the desired loading criteria, along with providing adequate stiffness, reliability, and fatigue life as stated in the SOW. Considerations need to be made for control system routing and cabin heating/ventilation. The goal of the wing structure and carry through structure is also to provide a simple, lightweight structure that will transfer the aerodynamic forces produced by the wing, tailboom, and landing gear. These forces will be channeled through various internal structures sized for the pre-determined loading criteria. Other considerations were to include space for flaps, ailerons, fuel tanks, and electrical and control system routing. The difficulties encountered in the fuselage design include expanding the fuselage cabin to accept a third occupant in a staggered configuration and providing ample volume for their safety. By adding a third person the CG of aircraft will move forward so the engine needs to be moved aft to compensate for the difference in the moment. This required the provisions of a ring frame structure for the new position of the engine mount. The difficulties encountered in the wing structural design include resizing the wing for the increased capacity and weight, and compensating for a large torsion produced by the tail boom by placing a great number of stiffeners inside the boom, which will result in the relocation of the fuel tank. Finally, an adequate carry through structure for the wing and fuselage interface will be

  12. Fourier Analysis and Structure Determination--Part III: X-ray Crystal Structure Analysis.

    ERIC Educational Resources Information Center

    Chesick, John P.

    1989-01-01

    Discussed is single crystal X-ray crystal structure analysis. A common link between the NMR imaging and the traditional X-ray crystal structure analysis is reported. Claims that comparisons aid in the understanding of both techniques. (MVL)

  13. Structure, function, and engineering of enzymes in isoflavonoid biosynthesis.

    PubMed

    Wang, Xiaoqiang

    2011-03-01

    Isoflavonoids are a large group of plant natural products and play important roles in plant defense. They also possess valuable health-promoting activities with significant health benefits for animals and humans. The isoflavonoids are identified primarily in leguminous plants and are synthesized through the central phenylpropanoid pathway and the specific isoflavonoid branch pathways in legumes. Structural studies of some key enzymes in the central phenylpropanoid pathway shed light on the early stages of the (iso)flavonoid biosynthetic process. Significant impact has also been made on structural studies of enzymes in the isoflavonoid branch pathways. Structures of isoflavonoid-specific NADPH-dependent reductases revealed how the (iso)flavonoid backbones are modified by reduction reactions and how enzymes specifically recognize isoflavonoids and catalyze stereo-specific reductions. Structural studies of isoflavonoid methyltransferases and glycosyltransferases revealed how isoflavonoids are further decorated with methyl group and sugars in different methylation and glycosylation patterns that determine their bioactivities and functions. In combination with mutagenesis and biochemical studies, the detailed structural information of these enzymes provides a basis for understanding the complex biosynthetic process, enzyme catalytic mechanisms, and substrate specificities. Structure-based homology modeling facilitates the functional characterization of these large groups of biosynthetic enzymes and their homologs. Structure-based enzyme engineering is becoming a new strategy for synthesis of bioactive isoflavonoids and also facilitates plant metabolic engineering towards improvement of quality and production of crop plants.

  14. Nitroxylcob(III)Alamin: Synthesis And X-Ray Structural Characterization

    SciTech Connect

    Hannibal, L.; Smith, C.A.; Jacobsen, D.W.; Brasch, N.E.

    2009-06-01

    The long-elusive crystal structure of nitrosylcobalamin (NOCbl) reveals that the Co-N-O angle is 117.4-121.4{sup o}; hence, NOCbl is best described as nitroxylcob(III)alamin in the solid state (see picture: Co purple, N blue, O red, P orange, C gray, H white). The length of the Co-N bond trans to the NO ligand is typical of those seen when strong {beta}-axial ligands are positioned trans to the 5,6-dimethylbenzimidazole group.

  15. Engineering development of coal-fired high performance power systems, Phase II and III

    SciTech Connect

    1999-04-01

    The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: thermal efficiency (HHV) {ge} 47%, NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) coal providing {ge} 65% of heat input, all solid wastes benign, and cost of electricity {le} 90% of present plants. Phase 1, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase 1 also included preliminary R and D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. This phase, Phase 2, involves the development and testing of plant subsystems, refinement and updating of the HIPPS commercial plant design, and the site selection and engineering design of a HIPPS prototype plant. Work reported herein is from: Task 2.1 HITAC Combustors; Task 2.2 HITAF Air Heaters; Task 6 HIPPS Commercial Plant Design Update.

  16. Engineering development of coal-fired high performance power systems, Phase II and III

    SciTech Connect

    1998-07-01

    The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: thermal efficiency (HHV) {ge} 47%, NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard), coal providing {ge} 65% of heat input, all solid wastes benign cost of electricity {le} 90% of present plants. Phase 1, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase 1 also included preliminary R and D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. This phase, Phase 2, involves the development and testing of plant subsystems, refinement and updating of the HIPPS commercial plant design, and the site selection and engineering design of a HIPPS prototype plant. Work reported herein is from: Task 2.1 HITAF Combustor; Task 2.2 HITAF Air Heaters; Task 6 HIPPS Commercial Plant Design Update.

  17. Engineering development of coal-fired high performance power systems, Phase II and III

    SciTech Connect

    1999-01-01

    The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: thermal efficiency (HHV) {ge} 47%; NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) coal providing {ge} 65% of heat input; all solid wastes benign; cost of electricity {le} 90% of present plants. Phase 1, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase 1 also included preliminary R and D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. This phase, Phase 2, involves the development and testing of plant subsystems, refinement and updating of the HIPPS commercial plant design, and the site selection and engineering design of a HIPPS prototype plant. Work reported herein is from: Task 2.1 HITAC Combustors; Task 2.2 HITAF Air Heaters; Task 6 HIPPS Commercial Plant Design Update.

  18. Note: Comparison of grazing incidence small angle x-ray scattering of a titania sponge structure at the beamlines BW4 (DORIS III) and P03 (PETRA III)

    SciTech Connect

    Rawolle, M.; Koerstgens, V.; Ruderer, M. A.; Metwalli, E.; Guo, S.; Mueller-Buschbaum, P.; Herzog, G.; Benecke, G.; Schwartzkopf, M.; Buffet, A.; Perlich, J.; Roth, S. V.

    2012-10-15

    Grazing incidence small angle x-ray scattering (GISAXS) is a powerful technique for morphology investigation of nanostructured thin films. GISAXS measurements at the newly installed P03 beamline at the storage ring PETRA III in Hamburg, Germany, are compared to the GISAXS data from the beamline BW4 at the storage ring DORIS III, which had been used extensively for GISAXS investigations in the past. As an example, a titania thin film sponge structure is investigated. Compared to BW4, at beamline P03 the resolution of larger structures is slightly improved and a higher incident flux leads to a factor of 750 in scattered intensity. Therefore, the acquisition time in GISAXS geometry is reduced significantly at beamline P03.

  19. Fatty Acid Biosynthesis Revisited: Structure Elucidation and Metabolic Engineering

    PubMed Central

    Beld, Joris; Lee, D. John

    2014-01-01

    Fatty acids are primary metabolites synthesized by complex, elegant, and essential biosynthetic machinery. Fatty acid synthases resemble an iterative assembly line, with an acyl carrier protein conveying the growing fatty acid to necessary enzymatic domains for modification. Each catalytic domain is a unique enzyme spanning a wide range of folds and structures. Although they harbor the same enzymatic activities, two different types of fatty acid synthase architectures are observed in nature. During recent years, strained petroleum supplies have driven interest in engineering organisms to either produce more fatty acids or specific high value products. Such efforts require a fundamental understanding of the enzymatic activities and regulation of fatty acid synthases. Despite more than one hundred years of research, we continue to learn new lessons about fatty acid synthases’ many intricate structural and regulatory elements. In this review, we summarize each enzymatic domain and discuss efforts to engineer fatty acid synthases, providing some clues to important challenges and opportunities in the field. PMID:25360565

  20. Fatty acid biosynthesis revisited: structure elucidation and metabolic engineering.

    PubMed

    Beld, Joris; Lee, D John; Burkart, Michael D

    2015-01-01

    Fatty acids are primary metabolites synthesized by complex, elegant, and essential biosynthetic machinery. Fatty acid synthases resemble an iterative assembly line, with an acyl carrier protein conveying the growing fatty acid to necessary enzymatic domains for modification. Each catalytic domain is a unique enzyme spanning a wide range of folds and structures. Although they harbor the same enzymatic activities, two different types of fatty acid synthase architectures are observed in nature. During recent years, strained petroleum supplies have driven interest in engineering organisms to either produce more fatty acids or specific high value products. Such efforts require a fundamental understanding of the enzymatic activities and regulation of fatty acid synthases. Despite more than one hundred years of research, we continue to learn new lessons about fatty acid synthases' many intricate structural and regulatory elements. In this review, we summarize each enzymatic domain and discuss efforts to engineer fatty acid synthases, providing some clues to important challenges and opportunities in the field. PMID:25360565

  1. Advanced stress analysis methods applicable to turbine engine structures

    NASA Technical Reports Server (NTRS)

    Pian, T. H. H.

    1985-01-01

    Advanced stress analysis methods applicable to turbine engine structures are investigated. Constructions of special elements which containing traction-free circular boundaries are investigated. New versions of mixed variational principle and version of hybrid stress elements are formulated. A method is established for suppression of kinematic deformation modes. semiLoof plate and shell elements are constructed by assumed stress hybrid method. An elastic-plastic analysis is conducted by viscoplasticity theory using the mechanical subelement model.

  2. Intrinsic acidity of aluminum, chromium (III) and iron (III) μ 3-hydroxo functional groups from ab initio electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Dixon, David A.; Felmy, Andrew R.

    2000-05-01

    Density functional calculations are performed on M 3(OH) 7(H 2O) 62+ and M 3O(OH) 6(H 2O) 6+ clusters for MAl, Cr(III), and Fe(III), allowing determination of the relative acidities of the μ 3-hydroxo and aquo functional groups. Contrary to previous predictions and rationalizations, Fe 3OH and Al 3OH groups have nearly the same intrinsic acidity, while Cr 3OH groups are significantly more acidic. The gas-phase acidity of the Fe 3OH site is in good agreement with the value predicted by the molecular mechanics model previously used to estimate the relative acidities of surface sites on iron oxides. [ J. R. Rustad et al. (1996)Geochim. Cosmochim. Acta 60, 1563]. Acidities of aquo functional groups were also computed for Al and Cr. The AlOH 2 site is more acidic than the Al 3OH site, whereas the Cr 3OH site is more acidic than the CrOH 2 site. These findings predict that the surface charging behavior of chromium oxides/oxyhydroxides should be distinguishable from their Fe, Al counterparts. The calculations also provide insight into why the lepidocrocite/boehmite polymorph is not observed for CrOOH.

  3. Equilibrium Phase Diagrams for Stranski-Krastanov Structure Mode of III V Ternary Quantum Dots

    NASA Astrophysics Data System (ADS)

    Nakajima, Kazuo

    1999-04-01

    The strain, surface and interfacial energies of III V ternary systems were calculated for three kinds of structure modes: the Frank-van der Merwe (FM) mode, the Stranski-Krastanov (SK) mode and the Volmer-Weber (VW) mode. The free energy for each mode was estimated as functions of the thickness and composition or lattice misfit. Through comparison of the free energy of each mode, it was found that the thickness-composition phase diagrams of III V ternary systems can be determined only by considering the balance of the free energy and three kinds of structure modes appear in the phase diagrams. The SK mode appears only when the lattice misfit is large and/or the lattice layer is thick. The VW mode appears when the lattice misfit is large and the lattice layer is thin and only in the InPSb/InP and GaPSb/GaP systems which have the largest lattice misfit of III V ternary systems. The stable region of the SK mode in the GaPSb/GaP and InPSb/InP phase diagrams is largest of all because the composition dependence of the strain energy of these systems is stronger than that of the other systems. The critical number of lattice layers below which two-dimensional (2D) layers precede the three-dimensional (3D) nucleation in the SK mode at x=1.0 depends on the lattice misfit. In the InPSb/InP system, the smallest number of 2D layers precede the 3D nucleation in the SK mode.

  4. Synthesis, structural characterization and photoluminescence properties of a novel La(III) complex

    NASA Astrophysics Data System (ADS)

    Köse, Muhammet; Ceyhan, Gökhan; Atcı, Emine; McKee, Vickie; Tümer, Mehmet

    2015-05-01

    In this study, a novel La(III) complex [La(H2L)2(NO3)3(MeOH)] of a Schiff base ligand was synthesized and characterized by spectroscopic and analytical methods. Single crystals of the complex suitable for X-ray diffraction study were obtained by slow diffusion of diethyl ether into a MeOH solution of the complex which was found to crystallise as [La(H2L)2(NO3)3(MeOH)]ṡ2MeOHṡH2O. The structure was solved in monoclinic crystal system, P21/n space group with unit cell parameters a = 10.5641(11), b = 12.6661(16), c = 16.0022(17) Å, α = 67.364(2), β = 83.794(2)°, γ = 70.541(2)°, V = 1862.9(4) Å3 and Z = 2 with R final value of 0.526. In the complex, the La(III) ion is ten-coordinated by O atoms, five of which come from three nitrate ions, four from the two Schiff base ligands and one from MeOH oxygen atom. The Schiff base ligands in the structure are in a zwitter ion form with the phenolic H transferred to the imine N atom. Thermal properties of the La(III) complex were examined by thermogravimetric analysis and the complex was found to be thermally stable up to 310 °C. The Schiff base ligand and its La(II) complex were screened for their in vitro antimicrobial activity against Bacillus megaterium, Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus (Gram positive bacteria), Klebsiella pneumonia, Escherichia coli, Enterobacter aerogenes, Pseudomonas aeruginosa (Gram negative bacteria), Candida albicans,Yarrowia lipolytica (fungus) and Saccharomyces cerevisiae (yeast). The complex shows more antimicrobial activity than the free ligand.

  5. Syntheses and structural characterization of two new nanostructured Bi(III) supramolecular polymers via sonochemical method.

    PubMed

    Yan, Xiao-Wei; Haji-Hasani, Ensieh; Morsali, Ali

    2016-07-01

    Two new bismuth(III) coordination supramolecular polymers, {[Bi2(Hbpp)(bpp)(μ-I)2I6](Hbpp)·MeOH}n (1) and [Bi(Hbpp)(Br4)] (2), (bpp=1,3-di(pyridin-4-yl)propane) were prepared and were structurally characterized by single crystal X-ray diffraction. Single crystalline one-dimensional materials were prepared using a heat gradient applied a solution of the reagents using the branched tube method. The structural determination by single crystal X-ray crystallography shows that compounds 1 and 2 form monoclinic polymers with symmetry space group P21 in the solid state. These new nanostructured Bi(III) supramolecular compounds, {[Bi2(Hbpp)(bpp)(μ-I)2I6](Hbpp)·MeOH} (1) and [Bi(Hbpp)(Br4)] (2), were also synthesized by sonochemical method. The nanostructures were characterized by Field Emission-scanning electron microscopy (FE-SEM), powder X-ray diffraction (PXRD) and IR spectroscopy. PMID:26964932

  6. Structure of the dsRNA binding domain of E. coli RNase III.

    PubMed Central

    Kharrat, A; Macias, M J; Gibson, T J; Nilges, M; Pastore, A

    1995-01-01

    The double-stranded RNA binding domain (dsRBD) is a approximately 70 residue motif found in a variety of modular proteins exhibiting diverse functions, yet always in association with dsRNA. We report here the structure of the dsRBD from RNase III, an enzyme present in most, perhaps all, living cells. It is involved in processing transcripts, such as rRNA precursors, by cleavage at short hairpin sequences. The RNase III protein consists of two modules, a approximately 150 residue N-terminal catalytic domain and a approximately 70 residue C-terminal recognition module, homologous with other dsRBDs. The structure of the dsRBD expressed in Escherichia coli has been investigated by homonuclear NMR techniques and solved with the aid of a novel calculation strategy. It was found to have an alpha-beta-beta-beta-alpha topology in which a three-stranded anti-parallel beta-sheet packs on one side against the two helices. Examination of 44 aligned dsRBD sequences reveals several conserved, positively charged residues. These residues map to the N-terminus of the second helix and a nearby loop, leading to a model for the possible contacts between the domain and dsRNA. Images PMID:7628457

  7. Effects of strain on the band structure of group-III nitrides

    NASA Astrophysics Data System (ADS)

    Yan, Qimin; Rinke, Patrick; Janotti, Anderson; Scheffler, Matthias; Van de Walle, Chris G.

    2014-09-01

    We present a systematic study of strain effects on the electronic band structure of the group-III-nitrides (AlN, GaN and InN) in the wurtzite phase. The calculations are based on density functional theory with band-gap-corrected approaches including the Heyd-Scuseria-Ernzerhof hybrid functional (HSE) and quasiparticle G0W0 methods. We study strain effects under realistic strain conditions, hydrostatic pressure, and biaxial stress. The strain-induced modification of the band structures is found to be nonlinear; transition energies and crystal-field splittings show a strong nonlinear behavior under biaxial stress. For the linear regime around the experimental lattice parameters, we present a complete set of deformation potentials (acz, act, D1, D2, D3, D4, D5, D6) that allows us to predict the band positions of group-III nitrides and their alloys (InGaN and AlGaN) under realistic strain conditions. The benchmarking G0W0 results for GaN agree well with the HSE data and indicate that HSE provides an appropriate description for the band structures of nitrides. We present a systematic study of strain effects on the electronic band structure of the group-III nitrides (AlN, GaN, and InN). We quantify the nonlinearity of strain effects by introducing a set of bowing parameters. We apply the calculated deformation potentials to the prediction of strain effects on transition energies and valence-band structures of InGaN alloys and quantum wells (QWs) grown on GaN, in various orientations (including c-plane, m-plane, and semipolar). The calculated band gap bowing parameters, including the strain effect for c-plane InGaN, agree well with the results obtained by hybrid functional alloy calculations. For semipolar InGaN QWs grown in (202¯1), (303¯1), and (303¯1¯) orientations, our calculated deformation potentials have provided results for polarization ratios in good agreement with the experimental observations, providing further confidence in the accuracy of our values.

  8. Engineered Biosynthesis of Plant Polyketides: Structure-Based and Precursor-Directed Approach

    NASA Astrophysics Data System (ADS)

    Abe, Ikuro

    Pentaketide chromone synthase (PCS) and octaketide synthase (OKS) are novel plant-specific type III polyketide synthases (PKSs) obtained from Aloe arborescens. Recombinant PCS expressed in Escherichia coli catalyzes iterative condensations of five molecules of malonyl-CoA to produce a pentaketide 5,7-dihydroxy-2-methylchromone, while recombinant OKS carries out sequential condensations of eight molecules of malonyl-CoA to yield octaketides SEK4 and SEK4b, the longest polyketides produced by the structurally simple type III PKS. The amino acid sequences of PCS and OKS are 91% identical, sharing 50-60% identity with those of other chalcone synthase (CHS) superfamily type III PKSs of plant origin. One of the most characteristic features is that the conserved active-site Thr197 of CHS (numbering in Medicago sativa CHS) is uniquely replaced with Met207 in PCS and with Gly207 in OKS, respectively. Site-directed mutagenesis and X-ray crystallographic analyses demonstrated that the chemically inert single residue lining the active-site cavity controls the polyketide chain length and the product specificity depending on the steric bulk of the side chain. On the basis of the crystal structures, an F80A/Y82A/M207G triple mutant of the pentaketide-producing PCS was constructed and shown to catalyze condensations of nine molecules of malonyl-CoA to produce an unnatural novel nonaketide naphthopyrone, whereas an N222G mutant of the octaketides-producing OKS yielded a decaketide benzophenone SEK15 from ten molecules of malonyl-CoA. On the other hand, the type III PKSs exhibited broad substrate specificities and catalytic potential. OKS accepted p-coumaroyl-CoA as a starter substrate to produce an unnatural novel C19 hexaketide stilbene and a C21 heptaketide chalcone. Remarkably, the C21 chalcone-forming activity was dramatically increased in the structure-guided OKS N222G mutant. In addition, OKS N222G mutant also yielded unnatural novel polyketides from phenylacetyl-CoA and

  9. Distinct Structural Elements Dictate the Specificity of the Type III Pentaketide Synthase from Neurospora crassa

    SciTech Connect

    Rubin-Pitel, Sheryl B.; Zhang, Houjin; Vu, Trang; Brunzelle, Joseph S.; Zhao, Huimin; Nair, Satish K.

    2009-01-15

    The fungal type III polyketide synthase 2'-oxoalkylresorcyclic acid synthase (ORAS) primes with a range of acyl-Coenzyme A thioesters (C{sub 4}--C{sub 20}) and extends using malonyl-Coenzyme A to produce pyrones, resorcinols, and resorcylic acids. To gain insight into this unusual substrate specificity and product profile, we have determined the crystal structures of ORAS to 1.75 {angstrom} resolution, the Phe-252{yields}Gly site-directed mutant to 2.1 {angstrom} resolution, and a binary conplex of ORAS with eicosanoic acid to 2.0 {angstrom} resolution. The structures reveal a distinct rearrangement of structural elements near the active site that allows accomodation of long-chain fatty acid esters and a reorientation of the gating mechanism that controls cyclization and polyketide chain length. The roles of these structural elements are further elucidated by characterization of various structure-based site-directed variants. These studies establish an unexpected plasticity to the PKS fold, unanticipated from structural studies of other members of this enzyme family.

  10. Structural integrity of engineering composite materials: a cracking good yarn.

    PubMed

    Beaumont, Peter W R; Soutis, Costas

    2016-07-13

    Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a 'fracture safe design' is immense. Fitness considerations for long-life implementation of large composite structures include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, life expectancy and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined, and takes service duty into account. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242293

  11. Structural integrity of engineering composite materials: a cracking good yarn

    PubMed Central

    Beaumont, Peter W. R.

    2016-01-01

    Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a ‘fracture safe design’ is immense. Fitness considerations for long-life implementation of large composite structures include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, life expectancy and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined, and takes service duty into account. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242293

  12. Structural integrity of engineering composite materials: a cracking good yarn.

    PubMed

    Beaumont, Peter W R; Soutis, Costas

    2016-07-13

    Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a 'fracture safe design' is immense. Fitness considerations for long-life implementation of large composite structures include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, life expectancy and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined, and takes service duty into account. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

  13. Microfabrication of hierarchical structures for engineered mechanical materials

    NASA Astrophysics Data System (ADS)

    Vera Canudas, Marc

    Materials found in nature present, in some cases, unique properties from their constituents that are of great interest in engineered materials for applications ranging from structural materials for the construction of bridges, canals and buildings to the fabrication of new lightweight composites for airplane and automotive bodies, to protective thin film coatings, amongst other fields. Research in the growing field of biomimetic materials indicates that the micro-architectures present in natural materials are critical to their macroscopic mechanical properties. A better understanding of the effect that structure and hierarchy across scales have on the material properties will enable engineered materials with enhanced properties. At the moment, very few theoretical models predict mechanical properties of simple materials based on their microstructures. Moreover these models are based on observations from complex biological systems. One way to overcome this challenge is through the use of microfabrication techniques to design and fabricate simple materials, more appropriate for the study of hierarchical organizations and microstructured materials. Arrays of structures with controlled geometry and dimension can be designed and fabricated at different length scales, ranging from a few hundred nanometers to centimeters, in order to mimic similar systems found in nature. In this thesis, materials have been fabricated in order to gain fundamental insight into the complex hierarchical materials found in nature and to engineer novel materials with enhanced mechanical properties. The materials fabricated here were mechanically characterized and compared to simple mechanics models to describe their behavior with the goal of applying the knowledge acquired to the design and synthesis of future engineered materials with novel properties.

  14. Structure and Management of an Engineering Senior Design Course.

    PubMed

    Tanaka, Martin L; Fischer, Kenneth J

    2016-07-01

    The design of products and processes is an important area in engineering. Students in engineering schools learn fundamental principles in their courses but often lack an opportunity to apply these methods to real-world problems until their senior year. This article describes important elements that should be incorporated into a senior capstone design course. It includes a description of the general principles used in engineering design and a discussion of why students often have difficulty with application and revert to trial and error methods. The structure of a properly designed capstone course is dissected and its individual components are evaluated. Major components include assessing resources, identifying projects, establishing teams, understanding requirements, developing conceptual designs, creating detailed designs, building prototypes, testing performance, and final presentations. In addition to the course design, team management and effective mentoring are critical to success. This article includes suggested guidelines and tips for effective design team leadership, attention to detail, investment of time, and managing project scope. Furthermore, the importance of understanding business culture, displaying professionalism, and considerations of different types of senior projects is discussed. Through a well-designed course and proper mentoring, students will learn to apply their engineering skills and gain basic business knowledge that will prepare them for entry-level positions in industry.

  15. Controlling the Structural and Functional Anisotropy of Engineered Cardiac Tissues

    PubMed Central

    Bursac, N

    2014-01-01

    The ability to control the degree of structural and functional anisotropy in 3D engineered cardiac tissues would have high utility for both in vitro studies of cardiac muscle physiology and pathology as well as potential tissue engineering therapies for myocardial infarction. Here, we applied a high aspect ratio soft lithography technique to generate network-like tissue patches seeded with neonatal rat cardiomyocytes. Fabricating longer elliptical pores within the patch networks increased the overall cardiomyocyte and extracellular matrix (ECM) alignment within the patch. Improved uniformity of cell and matrix alignment yielded an increase in anisotropy of action potential propagation and faster longitudinal conduction velocity (LCV). Cardiac tissue patches with a higher degree of cardiomyocyte alignment and electrical anisotropy also demonstrated greater isometric twitch forces. After two weeks of culture, specific measures of electrical and contractile function (LCV = 26.8 ± 0.8 cm/s, specific twitch force = 8.9 ± 1.1 mN/mm2 for the longest pores studied) were comparable to those of neonatal rat myocardium. We have thus described methodology for engineering of highly functional 3D engineered cardiac tissues with controllable degree of anisotropy. PMID:24717534

  16. Crystal Structures and Coordination Behavior of Aqua- and Cyano-Co(III) Tetradehydrocorrins in the Heme Pocket of Myoglobin.

    PubMed

    Morita, Yoshitsugu; Oohora, Koji; Mizohata, Eiichi; Sawada, Akiyoshi; Kamachi, Takashi; Yoshizawa, Kazunari; Inoue, Tsuyoshi; Hayashi, Takashi

    2016-02-01

    Myoglobins reconstituted with aqua- and cyano-Co(III) tetradehydrocorrins, rMb(Co(III)(OH2)(TDHC)) and rMb(Co(III)(CN)(TDHC)), respectively, were prepared and investigated as models of a cobalamin-dependent enzyme. The former protein was obtained by oxidation of rMb(Co(II)(TDHC)) with K3[Fe(CN)6]. The cyanide-coordinated Co(III) species in the latter protein was prepared by ligand exchange of rMb(Co(III)(OH2)(TDHC)) with exogenous cyanide upon addition of KCN. The X-ray crystallographic study reveals the hexacoordinated structures of rMb(Co(III)(OH)(TDHC)) and rMb(Co(III)(CN)(TDHC)) at 1.20 and 1.40 Å resolution, respectively. The (13)C NMR chemical shifts of the cyanide in rMb(Co(III)(CN)(TDHC)) were determined to be 108.6 and 110.6 ppm. IR measurements show that the cyanide of rMb(Co(III)(CN)(TDHC)) has a stretching frequency peak at 2151 cm(-1) which is higher than that of cyanocobalamin. The (13)C NMR and IR measurements indicate weaker coordination of the cyanide to Co(III)(TDHC) relative to cobalamin, a vitamin B12 derivative. Thus, the extent of π-back-donation from the cobalt ion to the cyanide ion is lower in rMb(Co(III)(CN)(TDHC)). Furthermore, the pK(1/2) values of rMb(Co(III)(OH2)(TDHC)) and rMb(Co(III)(CN)(TDHC)) were determined by a pH titration experiment to be 3.2 and 5.5, respectively, indicating that the cyanide ligation weakens the Co-N(His93) bond. Theoretical calculations also demonstrate that the axial ligand exchange from water to cyanide elongates the Co-N(axial) bond with a decrease in the bond dissociation energy. Taken together, the cyano-Co(III) tetradehydrocorrin in myoglobin is appropriate for investigation as a structural analogue of methylcobalamin, a key intermediate in methionine synthase reaction.

  17. Crystal Structures and Coordination Behavior of Aqua- and Cyano-Co(III) Tetradehydrocorrins in the Heme Pocket of Myoglobin.

    PubMed

    Morita, Yoshitsugu; Oohora, Koji; Mizohata, Eiichi; Sawada, Akiyoshi; Kamachi, Takashi; Yoshizawa, Kazunari; Inoue, Tsuyoshi; Hayashi, Takashi

    2016-02-01

    Myoglobins reconstituted with aqua- and cyano-Co(III) tetradehydrocorrins, rMb(Co(III)(OH2)(TDHC)) and rMb(Co(III)(CN)(TDHC)), respectively, were prepared and investigated as models of a cobalamin-dependent enzyme. The former protein was obtained by oxidation of rMb(Co(II)(TDHC)) with K3[Fe(CN)6]. The cyanide-coordinated Co(III) species in the latter protein was prepared by ligand exchange of rMb(Co(III)(OH2)(TDHC)) with exogenous cyanide upon addition of KCN. The X-ray crystallographic study reveals the hexacoordinated structures of rMb(Co(III)(OH)(TDHC)) and rMb(Co(III)(CN)(TDHC)) at 1.20 and 1.40 Å resolution, respectively. The (13)C NMR chemical shifts of the cyanide in rMb(Co(III)(CN)(TDHC)) were determined to be 108.6 and 110.6 ppm. IR measurements show that the cyanide of rMb(Co(III)(CN)(TDHC)) has a stretching frequency peak at 2151 cm(-1) which is higher than that of cyanocobalamin. The (13)C NMR and IR measurements indicate weaker coordination of the cyanide to Co(III)(TDHC) relative to cobalamin, a vitamin B12 derivative. Thus, the extent of π-back-donation from the cobalt ion to the cyanide ion is lower in rMb(Co(III)(CN)(TDHC)). Furthermore, the pK(1/2) values of rMb(Co(III)(OH2)(TDHC)) and rMb(Co(III)(CN)(TDHC)) were determined by a pH titration experiment to be 3.2 and 5.5, respectively, indicating that the cyanide ligation weakens the Co-N(His93) bond. Theoretical calculations also demonstrate that the axial ligand exchange from water to cyanide elongates the Co-N(axial) bond with a decrease in the bond dissociation energy. Taken together, the cyano-Co(III) tetradehydrocorrin in myoglobin is appropriate for investigation as a structural analogue of methylcobalamin, a key intermediate in methionine synthase reaction. PMID:26760442

  18. Engineering the cell-semiconductor interface: a materials modification approach using II-VI and III-V semiconductor materials.

    PubMed

    Bain, Lauren E; Ivanisevic, Albena

    2015-02-18

    Developing functional biomedical devices based on semiconductor materials requires an understanding of interactions taking place at the material-biosystem interface. Cell behavior is dependent on the local physicochemical environment. While standard routes of material preparation involve chemical functionalization of the active surface, this review emphasizes both biocompatibility of unmodified surfaces as well as use of topographic features in manipulating cell-material interactions. Initially, the review discusses experiments involving unmodified II-VI and III-V semiconductors - a starting point for assessing cytotoxicity and biocompatibility - followed by specific surface modification, including the generation of submicron roughness or the potential effect of quantum dot structures. Finally, the discussion turns to more recent work in coupling topography and specific chemistry, enhancing the tunability of the cell-semiconductor interface. With this broadened materials approach, researchers' ability to tune the interactions between semiconductors and biological environments continues to improve, reaching new heights in device function.

  19. Dynamical structure of solar radio burst type III as evidence of energy of solar flares

    NASA Astrophysics Data System (ADS)

    Hamidi, Zety Sharizat Binti

    2013-11-01

    Observations of low frequency solar type III radio bursts associated with the ejection of plasma oscillations localized disturbance is due to excitation atoms in the plasma frequency incoherent radiations play a dominant role at the meter and decimeter wavelengths. Here, we report the results of the dynamical structure of solar flare type III that occurred on 9th March 2012 at National Space Centre, Sg Lang, Selangor, Malaysia by using the CALLISTO system. These bursts are associated with solar flare type M6 which suddenly ejected in the active region AR 1429 starting at 03:32 UT and ending at 05:00 UT with the peak at 04:12 UT. The observation showed an initial strong burst occurred due to strong signal at the beginning of the phase. We also found that both solar burst and flares tend to be a numerous on the same day and probability of chance coincidence is high. It is clearly seen that an impulsive lace burst was detected at 4:24 UT and it is more plausible that the energies are confined to the top of the loop when we compared with X-ray results. Associated with this event was type II with velocities 1285 km/s and type IV radio sweeps along with a full halo Coronal Mass Ejections (CMEs) first seen in SOHO/LASCO C2 imagery at 09/0426 Z. We concluded that the significance of study solar burst type III lies in the fact that the emission at decimetric wavelength comes from the role of magnetic field in active region that may provide the key to the energy release mechanism in a flare.

  20. Perturbing the Copper(III)-Hydroxide Unit through Ligand Structural Variation.

    PubMed

    Dhar, Debanjan; Yee, Gereon M; Spaeth, Andrew D; Boyce, David W; Zhang, Hongtu; Dereli, Büsra; Cramer, Christopher J; Tolman, William B

    2016-01-13

    Two new ligand sets, (pipMe)LH2 and (NO2)LH2 ((pipMe)L = N,N'-bis(2,6-diisopropylphenyl)-1-methylpiperidine-2,6-dicarboxamide, (NO2)L = N,N'-bis(2,6-diisopropyl-4-nitrophenyl)pyridine-2,6-dicarboxamide), are reported which are designed to perturb the overall electronics of the copper(III)-hydroxide core and the resulting effects on the thermodynamics and kinetics of its hydrogen-atom abstraction (HAT) reactions. Bond dissociation energies (BDEs) for the O-H bonds of the corresponding Cu(II)-OH2 complexes were measured that reveal that changes in the redox potential for the Cu(III)/Cu(II) couple are only partially offset by opposite changes in the pKa, leading to modest differences in BDE among the three compounds. The effects of these changes were further probed by evaluating the rates of HAT by the corresponding Cu(III)-hydroxide complexes from substrates with C-H bonds of variable strength. These studies revealed an overarching linear trend in the relationship between the log k (where k is the second-order rate constant) and the ΔH of reaction. Additional subtleties in measured rates arise, however, that are associated with variations in hydrogen-atom abstraction barrier heights and tunneling efficiencies over the temperature range from -80 to -20 °C, as inferred from measured kinetic isotope effects and corresponding electronic-structure-based transition-state theory calculations. PMID:26693733

  1. Structural engineering of three-dimensional phononic crystals

    NASA Astrophysics Data System (ADS)

    Delpero, Tommaso; Schoenwald, Stefan; Zemp, Armin; Bergamini, Andrea

    2016-02-01

    Artificially-structured materials are attracting the research interest of a growing community of scientists for the possibility to develop novel materials with advantageous properties that arise from the ability to tailor the propagation of elastic waves, and thus energy, through them. In this work, we propose a three-dimensional phononic crystal whose unit cell has been engineered to obtain a strong wave-attenuation band in the middle of the acoustic frequency range. The combination of its acoustic properties with the dimensions of the unit cell and its static mechanical properties makes it an interesting material for possibly several applications in civil and mechanical engineering, for instance as the core of an acoustically insulating sandwich panel. A sample of this crystal has been manufactured and experimentally tested with respect to its acoustic transmissibility. The performance of the phononic crystal core is remarkable both in terms of amplitude reduction in the transmissibility and width of the attenuation band. A parametric study has been finally conducted on selected geometrical parameters of the unit cell and on their effect on the macroscopic properties of the crystal. This work represents an application-oriented example of how the macroscopic properties of an artificially-structured material can be designed, according to specific needs, by a conventional engineering of its unit cell.

  2. Structural and phase transformation of A{sup III}B{sup V}(100) semiconductor surface in interaction with selenium

    SciTech Connect

    Bezryadin, N. N.; Kotov, G. I. Kuzubov, S. V.

    2015-03-15

    Surfaces of GaAs(100), InAs(100), and GaP(100) substrates thermally treated in selenium vapor have been investigated by transmission electron microscopy and electron probe X-ray microanalysis. Some specific features and regularities of the formation of A{sub 3}{sup III}B{sub 4}{sup VI} (100)c(2 × 2) surface phases and thin layers of gallium or indium selenides A{sub 2}{sup III}B{sub 3}{sup VI} (100) on surfaces of different A{sup III}B{sup V}(100) semiconductors are discussed within the vacancy model of surface atomic structure.

  3. Simulation of Aircraft Engine Blade-Out Structural Dynamics

    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.

  4. 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.

  5. Extracellular matrix, mechanotransduction and structural hierarchies in heart tissue engineering.

    PubMed

    Parker, Kevin K; Ingber, Donald E

    2007-08-29

    The spatial and temporal scales of cardiac organogenesis and pathogenesis make engineering of artificial heart tissue a daunting challenge. The temporal scales range from nanosecond conformational changes responsible for ion channel opening to fibrillation which occurs over seconds and can lead to death. Spatial scales range from nanometre pore sizes in membrane channels and gap junctions to the metre length scale of the whole cardiovascular system in a living patient. Synchrony over these scales requires a hierarchy of control mechanisms that are governed by a single common principle: integration of structure and function. To ensure that the function of ion channels and contraction of muscle cells lead to changes in heart chamber volume, an elegant choreography of metabolic, electrical and mechanical events are executed by protein networks composed of extracellular matrix, transmembrane integrin receptors and cytoskeleton which are functionally connected across all size scales. These structural control networks are mechanoresponsive, and they process mechanical and chemical signals in a massively parallel fashion, while also serving as a bidirectional circuit for information flow. This review explores how these hierarchical structural networks regulate the form and function of living cells and tissues, as well as how microfabrication techniques can be used to probe this structural control mechanism that maintains metabolic supply, electrical activation and mechanical pumping of heart muscle. Through this process, we delineate various design principles that may be useful for engineering artificial heart tissue in the future.

  6. Structural diversity and transcription of class III peroxidases from Arabidopsis thaliana.

    PubMed

    Welinder, Karen G; Justesen, Annemarie F; Kjaersgård, Inger V H; Jensen, Rikke B; Rasmussen, Søren K; Jespersen, Hans M; Duroux, Laurent

    2002-12-01

    Understanding peroxidase function in plants is complicated by the lack of substrate specificity, the high number of genes, their diversity in structure and our limited knowledge of peroxidase gene transcription and translation. In the present study we sequenced expressed sequence tags (ESTs) encoding novel heme-containing class III peroxidases from Arabidopsis thaliana and annotated 73 full-length genes identified in the genome. In total, transcripts of 58 of these genes have now been observed. The expression of individual peroxidase genes was assessed in organ-specific EST libraries and compared to the expression of 33 peroxidase genes which we analyzed in whole plants 3, 6, 15, 35 and 59 days after sowing. Expression was assessed in root, rosette leaf, stem, cauline leaf, flower bud and cell culture tissues using the gene-specific and highly sensitive reverse transcriptase-polymerase chain reaction (RT-PCR). We predicted that 71 genes could yield stable proteins folded similarly to horseradish peroxidase (HRP). The putative mature peroxidases derived from these genes showed 28-94% amino acid sequence identity and were all targeted to the endoplasmic reticulum by N-terminal signal peptides. In 20 peroxidases these signal peptides were followed by various N-terminal extensions of unknown function which are not present in HRP. Ten peroxidases showed a C-terminal extension indicating vacuolar targeting. We found that the majority of peroxidase genes were expressed in root. In total, class III peroxidases accounted for an impressive 2.2% of root ESTs. Rather few peroxidases showed organ specificity. Most importantly, genes expressed constitutively in all organs and genes with a preference for root represented structurally diverse peroxidases (< 70% sequence identity). Furthermore, genes appearing in tandem showed distinct expression profiles. The alignment of 73 Arabidopsis peroxidase sequences provides an easy access to the identification of orthologous peroxidases

  7. STRUCTURE OF THE TYPE III PANTOTHENATE KINASE FROM Bacillus anthracis AT 2.0 Å RESOLUTION

    PubMed Central

    Nicely, Nathan I.; Parsonage, Derek; Paige, Carleitta; Newton, Gerald L.; Fahey, Robert C.; Leonardi, Roberta; Jackowski, Suzanne; Mallett, T. Conn; Claiborne, Al

    2008-01-01

    Coenzyme A (CoASH) is the major low-molecular weight thiol in Staphylococcus aureus and a number of other bacteria; the crystal structure of the S. aureus coenzyme A-disulfide reductase (CoADR), which maintains the reduced intracellular state of CoASH, has recently been reported [Mallett, T.C., Wallen, J.R., Karplus, P.A., Sakai, H., Tsukihara, T., and Claiborne, A. (2006) Biochemistry 45, 11278-11289]. In this report we demonstrate that CoASH is the major thiol in Bacillus anthracis; a bioinformatics analysis indicates that three of the four proteins responsible for the conversion of pantothenate (Pan) to CoASH in Escherichia coli are conserved in B. anthracis. In contrast, a novel type III pantothenate kinase (PanK) catalyzes the first committed step in the biosynthetic pathway in B. anthracis; unlike the E. coli type I PanK, this enzyme is not subject to feedback inhibition by CoASH. The crystal structure of B. anthracis PanK (BaPanK), solved using multiwavelength anomalous dispersion data and refined at a resolution of 2.0 Å, demonstrates that BaPanK is a new member of the Acetate and Sugar Kinase/Hsc70/Actin (ASKHA) superfamily. The Pan and ATP substrates have been modeled into the active-site cleft; in addition to providing a clear rationale for the absence of CoASH inhibition, analysis of the Pan-binding pocket has led to the development of two new structure-based motifs (the PAN and INTERFACE motifs). Our analyses also suggest that the type III PanK in the spore-forming B. anthracis plays an essential role in the novel thiol/disulfide redox biology of this category A biodefense pathogen. PMID:17323930

  8. Recent progress in III-V based ferromagnetic semiconductors: Band structure, Fermi level, and tunneling transport

    SciTech Connect

    Tanaka, Masaaki; Ohya, Shinobu Nam Hai, Pham

    2014-03-15

    Spin-based electronics or spintronics is an emerging field, in which we try to utilize spin degrees of freedom as well as charge transport in materials and devices. While metal-based spin-devices, such as magnetic-field sensors and magnetoresistive random access memory using giant magnetoresistance and tunneling magnetoresistance, are already put to practical use, semiconductor-based spintronics has greater potential for expansion because of good compatibility with existing semiconductor technology. Many semiconductor-based spintronics devices with useful functionalities have been proposed and explored so far. To realize those devices and functionalities, we definitely need appropriate materials which have both the properties of semiconductors and ferromagnets. Ferromagnetic semiconductors (FMSs), which are alloy semiconductors containing magnetic atoms such as Mn and Fe, are one of the most promising classes of materials for this purpose and thus have been intensively studied for the past two decades. Here, we review the recent progress in the studies of the most prototypical III-V based FMS, p-type (GaMn)As and its heterostructures with focus on tunneling transport, Fermi level, and bandstructure. Furthermore, we cover the properties of a new n-type FMS, (In,Fe)As, which shows electron-induced ferromagnetism. These FMS materials having zinc-blende crystal structure show excellent compatibility with well-developed III-V heterostructures and devices.

  9. The synthesis, structure, magnetic and luminescent properties of a new tetranuclear dysprosium (III) cluster

    SciTech Connect

    Chen, Yen-Han; Tsai, Yun-Fan; Lee, Gene-Hsian; Yang, En-Che

    2012-01-15

    The synthesis and characterization of [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} (1), a new tetranuclear dysprosium (III) complex, is described. The compound was characterized by its X-ray structure, magnetic properties as well as the luminescent spectra. The compound crystallizes in a P1-bar space group with a zig-zag linear form of geometry. The ac magnetic susceptibilities of the molecule indicate that it is a magnetic molecule with a slow magnetization relaxation. The molecule also exhibits an emission spectrum that was confirmed to be ligand based. These results indicate that this molecule has both a slow magnetization relaxation (that could be potentially a SMM) and luminescent properties. - Graphical Abstract: A new tetranuclear dysprosium (III) complex [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} is synthesized and reported in this paper. This molecule has luminescence and can potentially act as a SMM. Highlights: Black-Right-Pointing-Pointer A new designed ligand (dhampH{sub 5}) was syntheisized. Black-Right-Pointing-Pointer A new tetra-dysprosium cluster [Dy{sub 4}(dhampH{sub 3}){sub 4}(NO{sub 3}){sub 2}](NO{sub 3}){sub 2} was made. Black-Right-Pointing-Pointer Slow magnetization relaxation phenomenon was observed. Black-Right-Pointing-Pointer Ligand-based luminescence was observed.

  10. Structure-function analysis of hRPC62 provides insights into RNA polymerase III transcription initiation.

    PubMed

    Lefèvre, Stéphane; Dumay-Odelot, Hélène; El-Ayoubi, Leyla; Budd, Aidan; Legrand, Pierre; Pinaud, Noël; Teichmann, Martin; Fribourg, Sébastien

    2011-03-01

    The 17-subunit human RNA polymerase III (hPol III) transcribes small, untranslated RNA genes that are involved in the regulation of transcription, splicing and translation. hPol III subunits hRPC62, hRPC39 and hRPC32 form a stable ternary subcomplex required for promoter-specific transcription initiation by hPol III. Here, we report the crystal structure of hRPC62. This subunit folds as a four-tandem extended winged helix (eWH) protein that is structurally related to the transcription factor TFIIEα N terminus. Through biochemical analyses, we mapped the protein-protein interactions of hRPC62, hRPC32 and hRPC39. In addition, we demonstrated that hRPC62 and hRPC39 bind single-stranded and duplex DNA, respectively, in a sequence-independent manner. Overall, we shed light on structural similarities between the hPol III-specific subunit hRPC62 and TFIIEα and propose specific functions for hRPC39 and hRPC62 in transcription initiation by hPol III. PMID:21358628

  11. Cr(III) exerts stronger structural effects than Cr(VI) on the human erythrocyte membrane and molecular models.

    PubMed

    Suwalsky, M; Castro, R; Villena, F; Sotomayor, C P

    2008-04-01

    Chromium exists in many oxidation states, of which only the hexavalent Cr(VI) and the trivalent Cr(III) ions are stable under environmental conditions. It is generally reported that Cr(VI) is highly toxic while Cr(III) is relatively innocuous, although others have reported just the opposite. On the other hand, despite the many studies on chromium toxicity, and particularly after the knowledge that Cr(VI) anions readily enter the erythrocytes where they are reduced to Cr(III), there are practically no reports on the structural effects induced by chromium compounds on the erythrocyte membrane. With the aim to better understand the molecular mechanisms of the interaction of Cr(III) and Cr(VI) with cell membranes, CrCl(3), and K(2)CrO(4) were incubated with intact erythrocytes, isolated unsealed human erythrocyte membranes (IUM), and molecular models of the erythrocyte membrane. These consisted in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylcholine (DMPE), phospholipid classes present in the outer and inner monolayers of the erythrocyte membrane, respectively. The capacity of Cr(III) and Cr(VI) to perturb the bilayer structures of DMPC and DMPE was evaluated by X-ray diffraction, DMPC large unilamellar vesicles (LUV) and IUM were studied by fluorescence spectroscopy, and intact human erythrocytes were observed with scanning electron microscopy (SEM). In all these systems, it was found that Cr(III) induced considerably higher structural perturbations than Cr(VI). PMID:18234343

  12. Structural Evaluation of Exo-Skeletal Engine Fan Blades

    NASA Technical Reports Server (NTRS)

    Kuguoglu, Latife; Abumeri, Galib; Chamis, Christos C.

    2003-01-01

    The available computational simulation capability is used to demonstrate the structural viability of composite fan blades of innovative Exo-Skeletal Engine (ESE) developed at NASA Glenn Research Center for a subsonic mission. Full structural analysis and progressive damage evaluation of ESE composite fan blade is conducted through the NASA in-house computational simulation software system EST/BEST. The results of structural assessment indicate that longitudinal stresses acting on the blade are in compression. At a design speed of 2000 rpm, pressure and suction surface outer most ply stresses in longitudinal, transverse and shear direction are much lower than the corresponding composite ply strengths. Damage is initiated at 4870 rpm and blade fracture takes place at rotor speed of 7735 rpm. Damage volume is 51 percent. The progressive damage, buckling, stress and strength results indicate that the design at hand is very sound because of the factor of safety, damage tolerance, and buckling load of 6811 rpm.

  13. Proton NMR investigation of the heme active site structure of an engineered cytochrome c peroxidase that mimics manganese peroxidase.

    PubMed

    Wang, X; Lu, Y

    1999-07-13

    The heme active site structure of an engineered cytochrome c peroxidase [MnCcP; see Yeung, B. K., et al. (1997) Chem. Biol. 4, 215-221] that closely mimics manganese peroxidase (MnP) has been characterized by both one- and two-dimensional NMR spectroscopy. All hyperfine-shifted resonances from the heme pocket as well as resonances from catalytically relevant amino acid residues in the congested diamagnetic envelope have been assigned. From the NMR spectral assignment and the line broadening pattern of specific protons in NOESY spectra of MnCcP, the location of the engineered Mn(II) center is firmly identified. Furthermore, we found that the creation of the Mn(II)-binding site in CcP resulted in no detectable structural changes on the distal heme pocket of the protein. However, notable structural changes are observed at the proximal side of the heme cavity. Both CepsilonH shift of the proximal histidine and (15)N shift of the bound C(15)N(-) suggest a weaker heme Fe(III)-N(His) bond in MnCcP compared to WtCcP. Our results indicate that the engineered Mn(II)-binding site in CcP resulted in not only a similar Mn(II)-binding affinity and improved MnP activity, but also weakened the Fe(III)-N(His) bond strength of the template protein CcP so that its bond strength is similar to that of the target protein MnP. The results presented here help elucidate the impact of designing a metal-binding site on both the local and global structure of the enzyme, and provide a structural basis for engineering the next generation of MnCcP that mimics MnP more closely. PMID:10413489

  14. Structural, energetic, and electronic properties of La(III)-dimethyl sulfoxide clusters.

    PubMed

    Bodo, Enrico; Chiricotto, Mara; Spezia, Riccardo

    2014-12-11

    By using accurate density functional theory calculations, we have studied the cluster complexes of a La(3+) ion interacting with a small number of dimethyl sulfoxide (DMSO) molecules of growing size (from 1 to 12). Extended structural, energetic, and electronic structure analyses have been performed to provide a complete picture of the physical properties that are the basis of the interaction of La(III) with DMSO. Recent experimental data in the solid and liquid phase have suggested a coordination number of 8 DMSO molecules with a square antiprism geometry arranged similarly in the liquid and crystalline phases. By using a cluster approach on the La(3+)(DMSO)n gas phase isolated structures, we have found that the 8-fold geometry, albeit less regular than in the crystal, is probably the most stable cluster. Furthermore, we provide new evidence of a 9-fold complexation geometric arrangement that is competitive (at least energetically) with the 8-fold one and that might suggest the existence of transient structures with higher coordination numbers in the liquid phase.

  15. Crystal structure of Spa40, the specificity switch for the Shigella flexneri type III secretion system

    PubMed Central

    Deane, Janet E; Graham, Stephen C; Mitchell, Edward P; Flot, David; Johnson, Steven; Lea, Susan M

    2008-01-01

    The pathogenic bacterium Shigella flexneri uses a type III secretion system to inject virulence factors from the bacterial cytosol directly into host cells. The machinery that identifies secretion substrates and controls the export of extracellular components and effector proteins consists of several inner-membrane and cytoplasmic proteins. One of the inner membrane components, Spa40, belongs to a family of proteins proposed to regulate the switching of substrate specificity of the export apparatus. We show that Spa40 is cleaved within the strictly conserved amino acid sequence NPTH and substitution of the proposed autocatalytic residue abolishes cleavage. Here we also report the crystal structure of the cytoplasmic complex Spa40C and compare it with the recent structures of the homologues from Escherichia coli and Salmonella typhimurium. These structures reveal the tight association of the cleaved fragments and show that the conserved NPTH sequence lies on a loop which, when cleaved, swings away from the catalytic N257 residue, resulting in different surface features in this region. This structural rearrangement suggests a mechanism by which non-cleaving forms of these proteins interfere with correct substrate switching of the apparatus. PMID:18485071

  16. Crystal structure of new complexes of praseodymium(III) nitrate and ytterbium(III) nitrate with 2,2': 6,2''-terpyridine

    SciTech Connect

    Charushnikova, I. A. Auwer, C. Den

    2006-12-15

    The crystal structure of new complexes of praseodymium(III) and ytterbium(III) (elements from the initial and final parts of the lanthanide series), namely, [Pr(NO{sub 3}){sub 3} (Terpy)((CH{sub 3}){sub 2}CO)] (I) and [Yb(NO{sub 3}){sub 2}(Terpy)(H{sub 2}O){sub 2}]NO{sub 3} . 2H{sub 2}O (II), is investigated. The structure of compound I consists of [Pr(NO{sub 3}){sub 3}(Terpy)((CH{sub 3}){sub 2}CO)] neutral complexes. The coordination number of the praseodymium atom is 10. The coordination polyhedron of the praseodymium atom can be described as a distorted bicapped tetragonal antiprism. The structure of compound II is composed of [Yb(NO{sub 3}){sub 2}(Terpy)(H{sub 2}O){sub 2}]{sup +} cationic complexes, nitrate anions, and molecules of crystallization water. The structural components are joined together via a three-dimensional system of hydrogen bonds. The coordination polyhedron of the ytterbium atom can be represented as a distorted tricapped trigonal prism. The coordination number of the ytterbium atom is 9.

  17. Nebraska School Facilities: Educational Adequacy of Class III School District Structures

    ERIC Educational Resources Information Center

    Weidner, John M., Sr.

    2009-01-01

    In 2009, a replication of the Pool study was conducted. This study, however, focused on the school systems classified as Class III districts. Nebraska has 252 Class III districts. Compared with Class II (21), Class IV (1), and Class V(1) districts, the Class III districts offer a wide array of school settings, from urban to extremely rural, and…

  18. Structural and Machine Design Using Piezoceramic Materials: A Guide for Structural Design Engineers

    NASA Technical Reports Server (NTRS)

    Inman, Daniel J.; Cudney, Harley H.

    2000-01-01

    Using piezoceramic materials is one way the design engineer can create structures which have an ability to both sense and respond to their environment. Piezoceramic materials can be used to create structural sensors and structural actuators. Because piezoceramic materials have transduction as a material property, their sensing or actuation functions are a result of what happens to the material. This is different than discrete devices we might attach to the structure. For example, attaching an accelerometer to a structure will yield an electrical signal proportional to the acceleration at the attachment point on the structure. Using a electromagnetic shaker as an actuator will create an applied force at the attachment point. Active material elements in a structural design are not easily modeled as providing transduction at a point, but rather they change the physics of the structure in the areas where they are used. Hence, a designer must not think of adding discrete devices to a structure to obtain an effect, but rather must design a structural system which accounts for the physical principles of all the elements in the structure. The purpose of this manual is to provide practicing engineers the information necessary to incorporate piezoelectric materials in structural design and machine design. First, we will review the solid-state physics of piezoelectric materials. Then we will discuss the physical characteristics of the electrical-active material-structural system. We will present the elements of this system which must be considered as part of the design task for a structural engineer. We will cover simple modeling techniques and review the features and capabilities of commercial design tools that are available. We will then cover practical how-to elements of working with piezoceramic materials. We will review sources of piezoceramic materials and built-up devices, and their characteristics. Finally, we will provide two design examples using piezoceramic

  19. Structural studies of the antigen III cell wall polysaccharide of Trichosporon domesticum.

    PubMed

    Ichikawa, T; Nishikawa, A; Wada, H; Ikeda, R; Shinoda, T

    2001-02-28

    Cell wall and soluble polysaccharides that reacted with Trichosporon domesticum factor III serum were isolated from the type strain of T. domesticum. The fractions contained O-acetyl groups, which contributed to the serological reactivity. The antigenic structure was characterized by chromatographic and spectroscopic methods. The polysaccharide has an alpha-(1-->3)-D-mannan backbone with hetero-oligosaccharide side chains consisting of a 2-O-substituted beta-D-glucuronic acid residue bound to O-2 of the mannose residue, beta-D-xylopyranosyl residues located in the middle of the side chain, and a nonreducing terminal alpha-L-arabinopyranosyl residue bound to 0-4 of xylose. The mannan backbone is O-acetylated at O-6 of the mannose residues.

  20. Crystal structure of tris-(ethyl-enedi-ammonium) hexasulfatopraseodymium(III) hexa-hydrate.

    PubMed

    Held, Peter

    2014-10-01

    In the title salt, (C2H10N2)3[Pr2(SO4)6]·6H2O, the Pr(III) cation is surrounded ninefold by five sulfate groups (two monodentate and three chelating) and by one water mol-ecule [range of Pr-O bond lengths 2.383 (3) to 2.582 (3) Å]. The [Pr(SO4)5(H2O)] groups are arranged in sheets parallel to (010). Two crystal water mol-ecules and two ethyl-enedi-ammonium cations (one with point group symmetry -1) connect the sheets via O-H⋯O and N-H⋯O hydrogen bonds from weak up to medium strength into a three-dimensional framework structure. PMID:25484661

  1. Advanced stress analysis methods applicable to turbine engine structures

    NASA Technical Reports Server (NTRS)

    Pian, Theodore H. H.

    1991-01-01

    The following tasks on the study of advanced stress analysis methods applicable to turbine engine structures are described: (1) constructions of special elements which contain traction-free circular boundaries; (2) formulation of new version of mixed variational principles and new version of hybrid stress elements; (3) establishment of methods for suppression of kinematic deformation modes; (4) construction of semiLoof plate and shell elements by assumed stress hybrid method; and (5) elastic-plastic analysis by viscoplasticity theory using the mechanical subelement model.

  2. Grain boundary engineering for structure materials of nuclear reactors

    NASA Astrophysics Data System (ADS)

    Tan, L.; Allen, T. R.; Busby, J. T.

    2013-10-01

    Grain boundary engineering (GBE), primarily implemented by thermomechanical processing, is an effective and economical method of enhancing the properties of polycrystalline materials. Among the factors affecting grain boundary character distribution, literature data showed definitive effect of grain size and texture. GBE is more effective for austenitic stainless steels and Ni-base alloys compared to other structural materials of nuclear reactors, such as refractory metals, ferritic and ferritic-martensitic steels, and Zr alloys. GBE has shown beneficial effects on improving the strength, creep strength, and resistance to stress corrosion cracking and oxidation of austenitic stainless steels and Ni-base alloys.

  3. Overview of Lightweight Structures for Rotorcraft Engines and Drivetrains

    NASA Technical Reports Server (NTRS)

    Roberts, Gary D.

    2011-01-01

    This is an overview presentation of research being performed in the Advanced Materials Task within the NASA Subsonic Rotary Wing Project. This research is focused on technology areas that address both national goals and project goals for advanced rotorcraft. Specific technology areas discussed are: (1) high temperature materials for advanced turbines in turboshaft engines; (2) polymer matrix composites for lightweight drive system components; (3) lightweight structure approaches for noise and vibration control; and (4) an advanced metal alloy for lighter weight bearings and more reliable mechanical components. An overview of the technology in each area is discussed, and recent accomplishments are presented.

  4. The formation of Population III stars and their effect on cosmological structure in the early universe

    NASA Astrophysics Data System (ADS)

    O'Shea, Brian William

    2005-11-01

    The first generation of stars to form in the universe have a profound impact on their environment. These stars are responsible for beginning the universe's transition from a "cosmic dark age" where no sources of visible light existed; to the bright universe seen today. Additionally, these stars were believed to be the first sources of all elements heavier than lithium, which strongly affected the ability of gas to cool and permanently changed how star formation occurred. In this dissertation I present results from numerical simulations of the formation of the first generation of stars to form in the universe ("Population III" stars) and their effects on later structure formation. I compare Enzo, the adaptive mesh refinement cosmology code used to perform all of the simulations in this work, to GADGET, a smoothed particle hydrodynamics cosmology code. Nearly identical results can be obtained when using two extremely different numerical methods, which helps to verify the correctness of both codes and strengthen the confidence of predictions made with these tools. I perform high dynamical range calculations of the formation of an ensemble of Population III stars, varying multiple simulation parameters, in a standard cold dark matter cosmology as well as with a soft ultraviolet background and in a generic warm dark matter cosmology. I find that the accretion rates of primordial protostars have been systematically overestimated by previously published work, which has profound implications for later structure formation and the reionization of the universe. Additionally, the presence of a soft ultraviolet background and warm dark matter serves to delay the onset of star formation. I propose limits on the possible mass of a warm dark matter particle. I also present results of simulations which demonstrate the effects of the HII regions and metal enrichment from Population III stars. It appears that HII regions from these stars may hasten the formation of later generations

  5. New Insights into Structure and Luminescence of EuIII and SmIII Complexes of the 3,4,3-LI(1,2-HOPO) Ligand

    PubMed Central

    2016-01-01

    We report the preparation and new insight into photophysical properties of luminescent hydroxypyridonate complexes [MIIIL]− (M = Eu or Sm) of the versatile 3,4,3-LI(1,2-HOPO) ligand (L). We report the crystal structure of this ligand with EuIII as well as insights into the coordination behavior and geometry in solution by using magnetic circular dichroism. In addition TD-DFT calculations were used to examine the excited states of the two different chromophores present in the 3,4,3-LI(1,2-HOPO) ligand. We find that the EuIII and SmIII complexes of this ligand undergo a transformation after in situ preparation to yield complexes with higher quantum yield (QY) over time. It is proposed that the lower QY in the in situ complexes is not only due to water quenching but could also be due to a lower degree of f-orbital overlap (in a kinetic isomer) as indicated by magnetic circular dichroism measurements. PMID:25607882

  6. Engineering NK Cells Modified With an EGFRvIII-specific Chimeric Antigen Receptor to Overexpress CXCR4 Improves Immunotherapy of CXCL12/SDF-1α-secreting Glioblastoma.

    PubMed

    Müller, Nadja; Michen, Susanne; Tietze, Stefanie; Töpfer, Katrin; Schulte, Alexander; Lamszus, Katrin; Schmitz, Marc; Schackert, Gabriele; Pastan, Ira; Temme, Achim

    2015-06-01

    Natural killer (NK) cells are promising effector cells for adjuvant immunotherapy of cancer. So far, several preclinical studies have shown the feasibility of gene-engineered NK cells, which upon expression of chimeric antigen receptors (CARs) are redirected to otherwise NK cell-resistant tumors. Yet, we reasoned that the efficiency of an immunotherapy using CAR-modified NK cells critically relies on efficient migration to the tumor site and might be improved by the engraftment of a receptor specific for a chemokine released by the tumor. On the basis of the DNAX-activation protein 12 (DAP12), a signaling adapter molecule involved in signal transduction of activating NK cell receptors, we constructed an epidermal growth factor variant III (EGFRvIII)-CAR, designated MR1.1-DAP12 which confers specific cytotoxicity of NK cell towards EGFRvIII glioblastoma cells in vitro and to established subcutaneous U87-MG tumor xenografts. So far, infusion of NK cells with expression of MR1.1-DAP12 caused a moderate but significantly delayed tumor growth and increased median survival time when compared with NK cells transduced with an ITAM-defective CAR. Notably, the further genetic engineering of these EGFRvIII-specific NK cells with the chemokine receptor CXCR4 conferred a specific chemotaxis to CXCL12/SDF-1α secreting U87-MG glioblastoma cells. Moreover, the administration of such NK cells resulted in complete tumor remission in a number of mice and a significantly increased survival when compared with the treatment of xenografts with NK cells expressing only the EGFRvIII-specific CAR or mock control. We conclude that chemokine receptor-engineered NK cells with concomitant expression of a tumor-specific CAR are a promising tool to improve adoptive tumor immunotherapy.

  7. Engineering NK cells modified with an EGFRvIII-specific chimeric antigen receptor to overexpress CXCR4 improves immunotherapy of CXCL12/SDF-1α-secreting glioblastoma

    PubMed Central

    Müller, Nadja; Michen, Susanne; Tietze, Stefanie; Töpfer, Katrin; Schulte, Alexander; Lamszus, Katrin; Schmitz, Marc; Schackert, Gabriele; Pastan, Ira; Temme, Achim

    2015-01-01

    NK cells are promising effector cells for adjuvant immunotherapy of cancer. So far, several preclinical studies have shown the feasibility of gene-engineered NK cells, which upon expression of chimeric antigen receptors (CARs) are redirected to otherwise NK-cell resistant tumors. Yet, we reasoned that the efficiency of an immunotherapy using CAR-modified NK cells critically relies on efficient migration to the tumor site and might be improved by the engraftment of a receptor specific for a chemokine released by the tumor. Based on the DNAX-activation protein 12 (DAP12), a signaling adapter molecule involved in signal transduction of activating NK cell receptors, we constructed an EGFRvIII-CAR, designated MR1.1-DAP12 which confers specific cytotoxicity of NK cell towards EGFRvIII+ glioblastoma cells in vitro and to established subcutaneous U87-MGEGFRvIII tumor xenografts. So far, infusion of NK cells with expression of MR1.1-DAP12 caused a moderate but significantly delayed tumor growth and increased median survival time when compared to NK cells transduced with an ITAM-defective CAR. Notably, the further genetic engineering of these EGFRvIII-specific NK cells with the chemokine receptor CXCR4 conferred a specific chemotaxis to CXCL12/SDF-1α secreting U87-MG glioblastoma cells. Moreover, the administration of such NK cells resulted in complete tumor remission in a number of mice and a significantly increased survival when compared to the treatment of xenografts with NK cells expressing only the EGFRvIII-specific CAR or mock control. We conclude that chemokine receptor engineered NK cells with concomitant expression of a tumor-specific CAR are a promising tool to improve adoptive tumor immunotherapy. PMID:25962108

  8. Characterization of capture cross sections of interface states in dielectric/III-nitride heterojunction structures

    NASA Astrophysics Data System (ADS)

    Matys, M.; Stoklas, R.; Kuzmik, J.; Adamowicz, B.; Yatabe, Z.; Hashizume, T.

    2016-05-01

    We performed, for the first time, quantitative characterization of electron capture cross sections σ of the interface states at dielectric/III-N heterojunction interfaces. We developed a new method, which is based on the photo-assisted capacitance-voltage measurements using photon energies below the semiconductor band gap. The analysis was carried out for AlGaN/GaN metal-insulator-semiconductor heterojunction (MISH) structures with Al2O3, SiO2, or SiN films as insulator deposited on the AlGaN layers with Al content (x) varying over a wide range of values. Additionally, we also investigated an Al2O3/InAlN/GaN MISH structure. Prior to insulator deposition, the AlGaN and InAlN surfaces were subjected to different treatments. We found that σ for all these structures lies in the range between 5 × 10 - 19 and 10 - 16 cm2. Furthermore, we revealed that σ for dielectric/AlxGa1-xN interfaces increases with increasing x. We showed that both the multiphonon-emission and cascade processes can explain the obtained results.

  9. Structure-activity relationship for Fe(III)-salen-like complexes as potent anticancer agents.

    PubMed

    Ghanbari, Zahra; Housaindokht, Mohammad R; Izadyar, Mohammad; Bozorgmehr, Mohammad R; Eshtiagh-Hosseini, Hossein; Bahrami, Ahmad R; Matin, Maryam M; Khoshkholgh, Maliheh Javan

    2014-01-01

    Quantitative structure activity relationship (QSAR) for the anticancer activity of Fe(III)-salen and salen-like complexes was studied. The methods of density function theory (B3LYP/LANL2DZ) were used to optimize the structures. A pool of descriptors was calculated: 1497 theoretical descriptors and quantum-chemical parameters, shielding NMR, and electronic descriptors. The study of structure and activity relationship was performed with multiple linear regression (MLR) and artificial neural network (ANN). In nonlinear method, the adaptive neuro-fuzzy inference system (ANFIS) was applied in order to choose the most effective descriptors. The ANN-ANFIS model with high statistical significance (R (2) train = 0.99, RMSE = 0.138, and Q (2) LOO = 0.82) has better capability to predict the anticancer activity of the new compounds series of this family. Based on this study, anticancer activity of this compound is mainly dependent on the geometrical parameters, position, and the nature of the substituent of salen ligand. PMID:24955417

  10. Structure-Activity Relationship for Fe(III)-Salen-Like Complexes as Potent Anticancer Agents

    PubMed Central

    Ghanbari, Zahra; Housaindokht, Mohammad R.; Izadyar, Mohammad; Bozorgmehr, Mohammad R.; Eshtiagh-Hosseini, Hossein; Bahrami, Ahmad R.; Matin, Maryam M.; Khoshkholgh, Maliheh Javan

    2014-01-01

    Quantitative structure activity relationship (QSAR) for the anticancer activity of Fe(III)-salen and salen-like complexes was studied. The methods of density function theory (B3LYP/LANL2DZ) were used to optimize the structures. A pool of descriptors was calculated: 1497 theoretical descriptors and quantum-chemical parameters, shielding NMR, and electronic descriptors. The study of structure and activity relationship was performed with multiple linear regression (MLR) and artificial neural network (ANN). In nonlinear method, the adaptive neuro-fuzzy inference system (ANFIS) was applied in order to choose the most effective descriptors. The ANN-ANFIS model with high statistical significance (R2train = 0.99, RMSE = 0.138, and Q2LOO = 0.82) has better capability to predict the anticancer activity of the new compounds series of this family. Based on this study, anticancer activity of this compound is mainly dependent on the geometrical parameters, position, and the nature of the substituent of salen ligand. PMID:24955417

  11. Structure of a bacterial type III secretion system in contact with a host membrane in situ

    PubMed Central

    Nans, Andrea; Kudryashev, Mikhail; Saibil, Helen R.; Hayward, Richard D.

    2015-01-01

    Many bacterial pathogens of animals and plants use a conserved type III secretion system (T3SS) to inject virulence effector proteins directly into eukaryotic cells to subvert host functions. Contact with host membranes is critical for T3SS activation, yet little is known about T3SS architecture in this state or the conformational changes that drive effector translocation. Here we use cryo-electron tomography and sub-tomogram averaging to derive the intact structure of the primordial Chlamydia trachomatis T3SS in the presence and absence of host membrane contact. Comparison of the averaged structures demonstrates a marked compaction of the basal body (4 nm) occurs when the needle tip contacts the host cell membrane. This compaction is coupled to a stabilization of the cytosolic sorting platform–ATPase. Our findings reveal the first structure of a bacterial T3SS from a major human pathogen engaged with a eukaryotic host, and reveal striking ‘pump-action' conformational changes that underpin effector injection. PMID:26656452

  12. Structure of a bacterial type III secretion system in contact with a host membrane in situ

    NASA Astrophysics Data System (ADS)

    Nans, Andrea; Kudryashev, Mikhail; Saibil, Helen R.; Hayward, Richard D.

    2015-12-01

    Many bacterial pathogens of animals and plants use a conserved type III secretion system (T3SS) to inject virulence effector proteins directly into eukaryotic cells to subvert host functions. Contact with host membranes is critical for T3SS activation, yet little is known about T3SS architecture in this state or the conformational changes that drive effector translocation. Here we use cryo-electron tomography and sub-tomogram averaging to derive the intact structure of the primordial Chlamydia trachomatis T3SS in the presence and absence of host membrane contact. Comparison of the averaged structures demonstrates a marked compaction of the basal body (4 nm) occurs when the needle tip contacts the host cell membrane. This compaction is coupled to a stabilization of the cytosolic sorting platform-ATPase. Our findings reveal the first structure of a bacterial T3SS from a major human pathogen engaged with a eukaryotic host, and reveal striking `pump-action' conformational changes that underpin effector injection.

  13. Structural, Hirshfeld surface and spectroscopic studies of the noncentrosymmetric 1-ethylpiperazinediium pentachloroantimonate (III) monohydrate

    NASA Astrophysics Data System (ADS)

    Soudani, S.; Zeller, M.; Jelsch, C.; Lefebvre, F.; Ben Nasr, Cherif

    2016-08-01

    1-Ethylpiperazinediium pentachloroantimonate (III) monohydrate, C6H16N2SbCl5·H2O, has been synthesized by the reaction of antimony trioxide (Sb2O3) and 1-ethylpiperazine in an aqueous solution of hydrochloric acid. The structure crystallizes in orthorhombic system, in the non-centrosymmetric space group Pca21 and consists of isolated [C6H16N2]2+ cations, square pyramidal [SbCl5]2- anions and lattice water molecules. Osbnd H⋯Cl hydrogen bonds link the [SbCl5]2- anions and water molecules to form double chains stretching along the [101] direction. The chains in turn are linked to the organic cations via Nsbnd H⋯Cl, Csbnd H⋯Cl, Csbnd H⋯O and Nsbnd H⋯O hydrogen bonds to form a three-dimensional network. This structure presents an example of a general square pyramidal complex ion containing a stereo-chemically active lone pair of electrons. Solid state 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure, and vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the NMR peaks and IR absorption bands. The interactions variability of the two independent cations and ten chloride atoms is analyzed via Hirshfeld surface analysis.

  14. CAR-Engineered NK Cells Targeting Wild-Type EGFR and EGFRvIII Enhance Killing of Glioblastoma and Patient-Derived Glioblastoma Stem Cells

    PubMed Central

    Han, Jianfeng; Chu, Jianhong; Keung Chan, Wing; Zhang, Jianying; Wang, Youwei; Cohen, Justus B.; Victor, Aaron; Meisen, Walter H.; Kim, Sung-hak; Grandi, Paola; Wang, Qi-En; He, Xiaoming; Nakano, Ichiro; Chiocca, E. Antonio; Glorioso III, Joseph C.; Kaur, Balveen; Caligiuri, Michael A.; Yu, Jianhua

    2015-01-01

    Glioblastoma (GB) remains the most aggressive primary brain malignancy. Adoptive transfer of chimeric antigen receptor (CAR)-modified immune cells has emerged as a promising anti-cancer approach, yet the potential utility of CAR-engineered natural killer (NK) cells to treat GB has not been explored. Tumors from approximately 50% of GB patients express wild-type EGFR (wtEGFR) and in fewer cases express both wtEGFR and the mutant form EGFRvIII; however, previously reported CAR T cell studies only focus on targeting EGFRvIII. Here we explore whether both wtEGFR and EGFRvIII can be effectively targeted by CAR-redirected NK cells to treat GB. We transduced human NK cell lines NK-92 and NKL, and primary NK cells with a lentiviral construct harboring a second generation CAR targeting both wtEGFR and EGFRvIII and evaluated the anti-GB efficacy of EGFR-CAR-modified NK cells. EGFR-CAR-engineered NK cells displayed enhanced cytolytic capability and IFN-γ production when co-cultured with GB cells or patient-derived GB stem cells in an EGFR-dependent manner. In two orthotopic GB xenograft mouse models, intracranial administration of NK-92-EGFR-CAR cells resulted in efficient suppression of tumor growth and significantly prolonged the tumor-bearing mice survival. These findings support intracranial administration of NK-92-EGFR-CAR cells represents a promising clinical strategy to treat GB. PMID:26155832

  15. Time-resolved pump and probe x-ray absorption fine structure spectroscopy at beamline P11 at PETRA III.

    PubMed

    Göries, D; Dicke, B; Roedig, P; Stübe, N; Meyer, J; Galler, A; Gawelda, W; Britz, A; Geßler, P; Sotoudi Namin, H; Beckmann, A; Schlie, M; Warmer, M; Naumova, M; Bressler, C; Rübhausen, M; Weckert, E; Meents, A

    2016-05-01

    We report about the development and implementation of a new setup for time-resolved X-ray absorption fine structure spectroscopy at beamline P11 utilizing the outstanding source properties of the low-emittance PETRA III synchrotron storage ring in Hamburg. Using a high intensity micrometer-sized X-ray beam in combination with two positional feedback systems, measurements were performed on the transition metal complex fac-Tris[2-phenylpyridinato-C2,N]iridium(III) also referred to as fac-Ir(ppy)3. This compound is a representative of the phosphorescent iridium(III) complexes, which play an important role in organic light emitting diode (OLED) technology. The experiment could directly prove the anticipated photoinduced charge transfer reaction. Our results further reveal that the temporal resolution of the experiment is limited by the PETRA III X-ray bunch length of ∼103 ps full width at half maximum (FWHM). PMID:27250401

  16. Time-resolved pump and probe x-ray absorption fine structure spectroscopy at beamline P11 at PETRA III.

    PubMed

    Göries, D; Dicke, B; Roedig, P; Stübe, N; Meyer, J; Galler, A; Gawelda, W; Britz, A; Geßler, P; Sotoudi Namin, H; Beckmann, A; Schlie, M; Warmer, M; Naumova, M; Bressler, C; Rübhausen, M; Weckert, E; Meents, A

    2016-05-01

    We report about the development and implementation of a new setup for time-resolved X-ray absorption fine structure spectroscopy at beamline P11 utilizing the outstanding source properties of the low-emittance PETRA III synchrotron storage ring in Hamburg. Using a high intensity micrometer-sized X-ray beam in combination with two positional feedback systems, measurements were performed on the transition metal complex fac-Tris[2-phenylpyridinato-C2,N]iridium(III) also referred to as fac-Ir(ppy)3. This compound is a representative of the phosphorescent iridium(III) complexes, which play an important role in organic light emitting diode (OLED) technology. The experiment could directly prove the anticipated photoinduced charge transfer reaction. Our results further reveal that the temporal resolution of the experiment is limited by the PETRA III X-ray bunch length of ∼103 ps full width at half maximum (FWHM).

  17. Biochemical and Structural Characterization of Germicidin Synthase: Analysis of a Type III Polyketide Synthase That Employs Acyl-ACP as a Starter Unit Donor

    SciTech Connect

    Chemler, Joseph A.; Buchholz, Tonia J.; Geders, Todd W.; Akey, David L.; Rath, Christopher M.; Chlipala, George E.; Smith, Janet L.; Sherman, David H.

    2012-08-10

    Germicidin synthase (Gcs) from Streptomyces coelicolor is a type III polyketide synthase (PKS) with broad substrate flexibility for acyl groups linked through a thioester bond to either coenzyme A (CoA) or acyl carrier protein (ACP). Germicidin synthesis was reconstituted in vitro by coupling Gcs with fatty acid biosynthesis. Since Gcs has broad substrate flexibility, we directly compared the kinetic properties of Gcs with both acyl-ACP and acyl-CoA. The catalytic efficiency of Gcs for acyl-ACP was 10-fold higher than for acyl-CoA, suggesting a strong preference toward carrier protein starter unit transfer. The 2.9 {angstrom} germicidin synthase crystal structure revealed canonical type III PKS architecture along with an unusual helical bundle of unknown function that appears to extend the dimerization interface. A pair of arginine residues adjacent to the active site affect catalytic activity but not ACP binding. This investigation provides new and surprising information about the interactions between type III PKSs and ACPs that will facilitate the construction of engineered systems for production of novel polyketides.

  18. Advanced fabrication techniques for hydrogen-cooled engine structures

    NASA Technical Reports Server (NTRS)

    Buchmann, O. A.; Arefian, V. V.; Warren, H. A.; Vuigner, A. A.; Pohlman, M. J.

    1985-01-01

    Described is a program for development of coolant passage geometries, material systems, and joining processes that will produce long-life hydrogen-cooled structures for scramjet applications. Tests were performed to establish basic material properties, and samples constructed and evaluated to substantiate fabrication processes and inspection techniques. Results of the study show that the basic goal of increasing the life of hydrogen-cooled structures two orders of magnitude relative to that of the Hypersonic Research Engine can be reached with available means. Estimated life is 19000 cycles for the channels and 16000 cycles for pin-fin coolant passage configurations using Nickel 201. Additional research is required to establish the fatigue characteristics of dissimilar-metal coolant passages (Nickel 201/Inconel 718) and to investigate the embrittling effects of the hydrogen coolant.

  19. Structural insight into the evolutionary and pharmacologic homology of glutamate carboxypeptidases II and III

    SciTech Connect

    Hlouchova, Klara; Barinka, Cyril; Konvalinka, Jan; Lubkowski, Jacek

    2009-10-23

    Glutamate carboxypeptidase III (GCPIII) is a metalloenzyme that belongs to the transferrin receptor/glutamate carboxypeptidase II (GCPII; EC 3.4.17.21) superfamily. GCPIII has been studied mainly because of its evolutionary relationship to GCPII, an enzyme involved in a variety of neuropathologies and malignancies, such as glutamatergic neurotoxicity and prostate cancer. Given the potential functional and pharmacological overlap between GCPIII and GCPII, studies addressing the structural and physiological properties of GCPIII are crucial for obtaining a deeper understanding of the GCPII/GCPIII system. In the present study, we report high-resolution crystal structures of the human GCPIII ectodomain in a 'pseudo-unliganded' state and in a complex with: (a) L-glutamate (a product of hydrolysis); (b) a phosphapeptide transition state mimetic, namely (2S,3'S)-{l_brace}[(3'-amino-3'-carboxy-propyl)-hydroxyphosphinoyl]methyl{r_brace}-pentanedioic acid; and (c) quisqualic acid, a glutamate biostere. Our data reveal the overall fold and quaternary arrangement of the GCPIII molecule, define the architecture of the GCPIII substrate-binding cavity, and offer an experimental evidence for the presence of Zn{sup 2+} ions in the bimetallic active site. Furthermore, the structures allow us to detail interactions between the enzyme and its ligands and to characterize the functional flexibility of GCPIII, which is essential for substrate recognition. A comparison of these GCPIII structures with the equivalent GCPII complexes reveals differences in the organization of specificity pockets, in surface charge distribution, and in the occupancy of the co-catalytic zinc sites. The data presented here provide information that should prove to be essential for the structurally-aided design of GCPIII-specific inhibitors and might comprise guidelines for future comparative GCPII/GCPIII studies.

  20. Spectroscopic Survey Telescope design. III - Optical support structure and overall configuration

    NASA Astrophysics Data System (ADS)

    Ray, F. B.

    1990-07-01

    The Universities of Texas and Penn State are working together on an Arecibo-type optical telescope to be utilized in a semitransit mode for spectroscopic survey work. Its optics include a spherical primary mirror, a 2-element all-reflecting Gregorian spherical aberration corrector, and a series of optical fibers that will transmit light to a family of spectrographs. An optical support structure is being developed to permit position adjustment in azimuth only. During an azimuth position change, the instrument's entire weight is borne by steel rollers bearing on a circular crane rail of standard section, with support loads transmitted to the telescope base through pneumatic springs. Extensive application of various analytical procedures and computer-aided engineering tools has effectively allowed the detailed examination of several design iterations, thereby increasing the probability of success in the realized structure.

  1. Cabin fuselage structural design with engine installation and control system

    NASA Technical Reports Server (NTRS)

    Balakrishnan, Tanapaal; Bishop, Mike; Gumus, Ilker; Gussy, Joel; Triggs, Mike

    1994-01-01

    Design requirements for the cabin, cabin system, flight controls, engine installation, and wing-fuselage interface that provide adequate interior volume for occupant seating, cabin ingress and egress, and safety are presented. The fuselage structure must be sufficient to meet the loadings specified in the appropriate sections of Federal Aviation Regulation Part 23. The critical structure must provide a safe life of 10(exp 6) load cycles and 10,000 operational mission cycles. The cabin seating and controls must provide adjustment to account for various pilot physiques and to aid in maintenance and operation of the aircraft. Seats and doors shall not bind or lockup under normal operation. Cabin systems such as heating and ventilation, electrical, lighting, intercom, and avionics must be included in the design. The control system will consist of ailerons, elevator, and rudders. The system must provide required deflections with a combination of push rods, bell cranks, pulleys, and linkages. The system will be free from slack and provide smooth operation without binding. Environmental considerations include variations in temperature and atmospheric pressure, protection against sand, dust, rain, humidity, ice, snow, salt/fog atmosphere, wind and gusts, and shock and vibration. The following design goals were set to meet the requirements of the statement of work: safety, performance, manufacturing and cost. To prevent the engine from penetrating the passenger area in the event of a crash was the primary safety concern. Weight and the fuselage aerodynamics were the primary performance concerns. Commonality and ease of manufacturing were major considerations to reduce cost.

  2. Assessment and economic analysis of the MOD III Stirling-engine driven chiller system. Final report, October 1989-July 1990

    SciTech Connect

    Moryl, J.

    1990-07-01

    The Stirling engine is an inherently clean and efficient engine. With the requirements for environmentally benign emissions and high energy efficiency, the Stirling engine is an attractive alternative to both internal combustion (IC) engines and electric motors. The study evaluated a Stirling-engine-driven chiller package. Technically, the Stirling engine is a good selection as a compressor drive, with inherently low vibrations, quiet operation, long life, and low maintenance. Exhaust emissions are below the projected 1995 stringent California standards. Economically, the Stirling-engine-driven chiller is a viable alternative to both IV-engine and electric-driven chillers, trading off slightly higher installed cost against lower total operating expenses. The penetration of a small portion of the projected near-term stationary engine market opportunity will provide the volume production basis to achieve competitively priced engines.

  3. Lanthanide(III) complexes of bis-semicarbazone and bis-imine-substituted phenanthroline ligands: solid-state structures, photophysical properties, and anion sensing.

    PubMed

    Nadella, Sandeep; Selvakumar, Paulraj M; Suresh, Eringathodi; Subramanian, Palani S; Albrecht, Markus; Giese, Michael; Fröhlich, Roland

    2012-12-21

    Phenanthroline-based hexadentate ligands L(1) and L(2) bearing two achiral semicarbazone or two chiral imine moieties as well as the respective mononuclear complexes incorporating various lanthanide ions, such as La(III), Eu(III), Tb(III), Lu(III), and Y(III) metal ions, were synthesized, and the crystal structures of [ML(1)Cl(3)] (M=La(III), Eu(III), Tb(III), Lu(III), or Y(III)) complexes were determined. Solvent or water molecules act as coligands for the rare-earth metals in addition to halide anions. The big Ln(III) ion exhibits a coordination number (CN) of 10, whereas the corresponding Eu(III), Tb(III), Lu(III), and Y(III) centers with smaller ionic radii show CN=9. Complexes of L(2), namely [ML(2)Cl(3)] (M=Eu(III), Tb(III), Lu(III), or Y(III)) ions could also be prepared. Only the complex of Eu(III) showed red luminescence, whereas all the others were nonluminescent. The emission properties of the Eu derivative can be applied as a photophysical signal for sensing various anions. The addition of phosphate anions leads to a unique change in the luminescence behavior. As a case study, the quenching behavior of adenosine-5'-triphosphate (ATP) was investigated at physiological pH value in an aqueous solvent. A specificity of the sensor for ATP relative to adenosine-5'-diphosphate (ADP) and adenosine-5'-monophosphate (AMP) was found. (31)P NMR spectroscopic studies revealed the formation of a [EuL(2)(ATP)] coordination species.

  4. Structural Analysis of a Specialized Type III Secretion System Peptidoglycan-cleaving Enzyme*

    PubMed Central

    Burkinshaw, Brianne J.; Deng, Wanyin; Lameignère, Emilie; Wasney, Gregory A.; Zhu, Haizhong; Worrall, Liam J.; Finlay, B. Brett; Strynadka, Natalie C.J.

    2015-01-01

    The Gram-negative bacterium enteropathogenic Escherichia coli uses a syringe-like type III secretion system (T3SS) to inject virulence or “effector” proteins into the cytoplasm of host intestinal epithelial cells. To assemble, the T3SS must traverse both bacterial membranes, as well as the peptidoglycan layer. Peptidoglycan is made of repeating N-acetylmuramic acid and N-acetylglucosamine disaccharides cross-linked by pentapeptides to form a tight mesh barrier. Assembly of many macromolecular machines requires a dedicated peptidoglycan lytic enzyme (PG-lytic enzyme) to locally clear peptidoglycan. Here we have solved the first structure of a T3SS-associated PG-lytic enzyme, EtgA from enteropathogenic E. coli. Unexpectedly, the active site of EtgA has features in common with both lytic transglycosylases and hen egg white lysozyme. Most notably, the β-hairpin region resembles that of lysozyme and contains an aspartate that aligns with lysozyme Asp-52 (a residue critical for catalysis), a conservation not observed in other previously characterized lytic transglycosylase families to which the conserved T3SS enzymes had been presumed to belong. Mutation of the EtgA catalytic glutamate, Glu-42, conserved across lytic transglycosylases and hen egg white lysozyme, and this differentiating aspartate diminishes type III secretion in vivo, supporting its essential role in clearing the peptidoglycan for T3SS assembly. Finally, we show that EtgA forms a 1:1 complex with the building block of the polymerized T3SS inner rod component, EscI, and that this interaction enhances PG-lytic activity of EtgA in vitro, collectively providing the necessary strict localization and regulation of the lytic activity to prevent overall cell lysis. PMID:25678709

  5. Blue light emission from cyclometallated iridium (III) cyano complexes: Syntheses, crystal structures, and photophysical properties

    SciTech Connect

    Sanner, Robert D.; Cherepy, Nerine J.; Young, Jr., Victor G.

    2015-11-02

    In this study, we describe the synthesis and crystal structures of four iridium compounds containing the 2-(4,6-difluorophenyl)pyridyl ligand. Cleavage of dichloro-bridged iridium(III) dimers with phosphorus ligands leads to (46dfppy)2Ir(L)(Cl) where L = PPh3 or P(OPh)3. Treatment of the chloro compounds with cyanide forms the cyano complexes (46dfppy)2Ir(L)(CN). All complexes exhibit a trans effect in their molecular structures due to the phosphorus ligands, with the phosphite having a greater effect than the phosphine. With L = PPh3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.24), quantum yield of 0.66 ± 0.15 and 4.5 ± 0.5 μs decay time is measured. For L = P(OPh)3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.21), quantum yield of 0.65 ± 0.15 and 2.9 ± 0.3 μs decay time is measured.

  6. Blue light emission from cyclometallated iridium (III) cyano complexes: Syntheses, crystal structures, and photophysical properties

    DOE PAGES

    Sanner, Robert D.; Cherepy, Nerine J.; Young, Jr., Victor G.

    2015-11-02

    In this study, we describe the synthesis and crystal structures of four iridium compounds containing the 2-(4,6-difluorophenyl)pyridyl ligand. Cleavage of dichloro-bridged iridium(III) dimers with phosphorus ligands leads to (46dfppy)2Ir(L)(Cl) where L = PPh3 or P(OPh)3. Treatment of the chloro compounds with cyanide forms the cyano complexes (46dfppy)2Ir(L)(CN). All complexes exhibit a trans effect in their molecular structures due to the phosphorus ligands, with the phosphite having a greater effect than the phosphine. With L = PPh3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.24), quantum yield of 0.66 ± 0.15 and 4.5 ± 0.5 μs decay timemore » is measured. For L = P(OPh)3, blue photoluminescence with CIE coordinates (x = 0.16, y = 0.21), quantum yield of 0.65 ± 0.15 and 2.9 ± 0.3 μs decay time is measured.« less

  7. The first 3-D LaIII-SrII heterometallic complex: Synthesis, structure and luminescent properties

    NASA Astrophysics Data System (ADS)

    Hong, Zhiwei; Ran, Jingwen; Li, Tao; Chen, Yanmei

    2016-10-01

    The first 3-D LaIII-SrII heterometallic complex, namely [La2Sr(pda)4(H2O)4]n·6nH2O (1, H2pda = pyridine-2,6-dicarboxylic acid), has been successfully synthesized under solvothermal conditions. Single crystal X-ray diffraction analysis reveals that complex 1 features a 3-D porous framework and displays a new topology. The crystal structure can be simplified to a 4,6-connected 3-D network with Schläfli symbol of {34·42·88·9}2{34·42}. The crystals also have been characterized by X-ray powder diffraction, elemental analysis, thermal analysis, and IR spectroscopy. The infrared spectral analysis indicates that complex 1 is a carboxylate coordinated compound, several water molecules exist in the compound. The thermal study shows that there are ten water molecules in the crystal structure. The luminescent property has also been investigated. It shows a blue-purple fluorescence emission.

  8. Passive and active structural monitoring experience: Civil engineering applications

    NASA Astrophysics Data System (ADS)

    Thompson, L. D.; Westermo, B. D.; Crum, D. B.; Law, W. R.; Trombi, R. G.

    2000-05-01

    State Departments of Transportation and regional city government officials are beginning to view the long-term monitoring of infrastructure as being beneficial for structural damage accumulation assessment, condition based maintenance, life extension, and post-earthquake or -hurricane (-tornado, -typhoon, etc.) damage assessment. Active and passive structural monitoring systems were installed over the last few years to monitor concerns in a wide range of civil infrastructure applications. This paper describes the monitoring technologies and systems employed for such applications. Bridge system applications were directed at monitoring corrosion damage accumulation, composite reinforcements for life extension, general service cracking damage related to fatigue and overloads, and post-earthquake damage. Residential system applications were directed primarily at identifying damage accumulation and post-earthquake damage assessment. A professional sports stadium was monitored for isolated ground instability problems and for post-earthquake damage assessment. Internet-based, remote, data acquisition system experience is discussed with examples of long-term passive and active system data collected from many of the individual sites to illustrate the potential for both passive and active structural health monitoring. A summary of system-based operating characteristics and key engineering recommendations are provided to achieve specific structural monitoring objectives for a wide range of civil infrastructure applications.

  9. Additive manufacturing of ceramic structures by laser engineered net shaping

    NASA Astrophysics Data System (ADS)

    Niu, Fangyong; Wu, Dongjiang; Ma, Guangyi; Zhang, Bi

    2015-11-01

    Ceramic is an important material with outstanding physical properties whereas impurities and porosities generated by traditional manufacturing methods limits its further industrial applications. In order to solve this problem, direct fabrication of Al2O3 ceramic structures is conducted by laser engineered net shaping system and pure ceramic powders. Grain refinement strengthening method by doping ZrO2 and dispersion strengthening method by doping SiC are proposed to suppress cracks in fabricating Al2O3 structure. Phase compositions, microstructures as well as mechanical properties of fabricated specimens are then analyzed. The results show that the proposed two methods are effective in suppressing cracks and structures of single-bead wall, arc and cylinder ring are successfully deposited. Stable phase of α-Al2O3 and t-ZrO2 are obtained in the fabricated specimens. Micro-hardness higher than 1700 HV are also achieved for both Al2O3 and Al2O3/ZrO2, which are resulted from fine directional crystals generated by the melting-solidification process. Results presented indicate that additive manufacturing is a very attractive technique for the production of high-performance ceramic structures in a single step.

  10. Acoustic-Structure Interaction in Rocket Engines: Validation Testing

    NASA Technical Reports Server (NTRS)

    Davis, R. Benjamin; Joji, Scott S.; Parks, Russel A.; Brown, Andrew M.

    2009-01-01

    While analyzing a rocket engine component, it is often necessary to account for any effects that adjacent fluids (e.g., liquid fuels or oxidizers) might have on the structural dynamics of the component. To better characterize the fully coupled fluid-structure system responses, an analytical approach that models the system as a coupled expansion of rigid wall acoustic modes and in vacuo structural modes has been proposed. The present work seeks to experimentally validate this approach. To experimentally observe well-coupled system modes, the test article and fluid cavities are designed such that the uncoupled structural frequencies are comparable to the uncoupled acoustic frequencies. The test measures the natural frequencies, mode shapes, and forced response of cylindrical test articles in contact with fluid-filled cylindrical and/or annular cavities. The test article is excited with a stinger and the fluid-loaded response is acquired using a laser-doppler vibrometer. The experimentally determined fluid-loaded natural frequencies are compared directly to the results of the analytical model. Due to the geometric configuration of the test article, the analytical model is found to be valid for natural modes with circumferential wave numbers greater than four. In the case of these modes, the natural frequencies predicted by the analytical model demonstrate excellent agreement with the experimentally determined natural frequencies.

  11. Syntheses, crystal structures, and properties of three new lanthanum(III) vanadium iodates.

    PubMed

    Sun, Chuan-Fu; Hu, Ting; Xu, Xiang; Mao, Jiang-Gao

    2010-09-14

    Systematic explorations of new compounds in the La(3+)-V(4+)/V(5+)-iodate system led to three new lanthanum(III) vanadium iodates, namely, LaVO(IO(3))(5), LaV(2)O(6)(IO(3)), and LaVO(2)(IO(3))(4).H(2)O. LaVO(IO(3))(5) is isostructural with LaTiO(IO(3))(5) and its structure contains a 0D [VO(IO(3))(5)](3-) anionic unit composed of one VO(6) octahedron linked to five IO(3)(-) groups. Such 0D anionic units are separated by La(3+) ions. LaV(2)O(6)(IO(3)) exhibits a unique 3D framework composed of 1D [V(2)O(6)](2-) ladder like chains and 2D [La(IO(3))](2+) layers. LaVO(2)(IO(3))(4).H(2)O is isostructural with LnMoO(2)(IO(3))(4)(OH) (Ln = La, Nd, Sm, Eu) with a polar space group P2(1), its structure contains a novel 0D [VO(2)(IO(3))(4)](3-) anionic unit composed of one VO(6) octahedron linked with four IO(3)(-) groups and two terminal O(2-) anions. Such 0D anionic units are separated by La(3+) ions. The structure of LaVO(2)(IO(3))(4).H(2)O can also be described as the 8-MR channels of the 3D [La(IO(3))(4)](-) anion being filled by the VO(6) octahedra and lattice water molecules. LaVO(2)(IO(3))(4).H(2)O displays a weak SHG response of about 0.2 times that of KDP. Optical, thermal stability and magnetic susceptibility measurements as well as theoretical calculations have also been performed.

  12. MoSi2-Base Structural Composite Passed Engine Test

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V.; Hebsur, Mohan G.

    1999-01-01

    The intermetallic compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity; and it is easily machined. Past research at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus.

  13. Evidence for alternative quaternary structure in a bacterial Type III secretion system chaperone

    SciTech Connect

    Barta, Michael L.; Zhang, Lingling; Picking, Wendy L.; Geisbrecht, Brian V.

    2010-10-05

    Type III secretion systems are a common virulence mechanism in many Gram-negative bacterial pathogens. These systems use a nanomachine resembling a molecular needle and syringe to provide an energized conduit for the translocation of effector proteins from the bacterial cytoplasm to the host cell cytoplasm for the benefit of the pathogen. Prior to translocation specialized chaperones maintain proper effector protein conformation. The class II chaperone, Invasion plasmid gene (Ipg) C, stabilizes two pore forming translocator proteins. IpgC exists as a functional dimer to facilitate the mutually exclusive binding of both translocators. In this study, we present the 3.3 {angstrom} crystal structure of an amino-terminally truncated form (residues 10-155, denoted IpgC10-155) of the class II chaperone IpgC from Shigella flexneri. Our structure demonstrates an alternative quaternary arrangement to that previously described for a carboxy-terminally truncated variant of IpgC (IpgC{sup 1-151}). Specifically, we observe a rotationally-symmetric 'head-to-head' dimerization interface that is far more similar to that previously described for SycD from Yersinia enterocolitica than to IpgC1-151. The IpgC structure presented here displays major differences in the amino terminal region, where extended coil-like structures are seen, as opposed to the short, ordered alpha helices and asymmetric dimerization interface seen within IpgC{sup 1-151}. Despite these differences, however, both modes of dimerization support chaperone activity, as judged by a copurification assay with a recombinant form of the translocator protein, IpaB. Conclusions: From primary to quaternary structure, these results presented here suggest that a symmetric dimerization interface is conserved across bacterial class II chaperones. In light of previous data which have described the structure and function of asymmetric dimerization, our results raise the possibility that class II chaperones may transition between

  14. Band structure engineering in topological insulator based heterostructures.

    PubMed

    Menshchikova, T V; Otrokov, M M; Tsirkin, S S; Samorokov, D A; Bebneva, V V; Ernst, A; Kuznetsov, V M; Chulkov, E V

    2013-01-01

    The ability to engineer an electronic band structure of topological insulators would allow the production of topological materials with tailor-made properties. Using ab initio calculations, we show a promising way to control the conducting surface state in topological insulator based heterostructures representing an insulator ultrathin films on the topological insulator substrates. Because of a specific relation between work functions and band gaps of the topological insulator substrate and the insulator ultrathin film overlayer, a sizable shift of the Dirac point occurs resulting in a significant increase in the number of the topological surface state charge carriers as compared to that of the substrate itself. Such an effect can also be realized by applying the external electric field that allows a gradual tuning of the topological surface state. A simultaneous use of both approaches makes it possible to obtain a topological insulator based heterostructure with a highly tunable topological surface state.

  15. Engineering the shape and structure of materials by fractal cut

    PubMed Central

    Cho, Yigil; Shin, Joong-Ho; Costa, Avelino; Kim, Tae Ann; Kunin, Valentin; Li, Ju; Lee, Su Yeon; Yang, Shu; Han, Heung Nam; Choi, In-Suk; Srolovitz, David J.

    2014-01-01

    In this paper we discuss the transformation of a sheet of material into a wide range of desired shapes and patterns by introducing a set of simple cuts in a multilevel hierarchy with different motifs. Each choice of hierarchical cut motif and cut level allows the material to expand into a unique structure with a unique set of properties. We can reverse-engineer the desired expanded geometries to find the requisite cut pattern to produce it without changing the physical properties of the initial material. The concept was experimentally realized and applied to create an electrode that expands to >800% the original area with only very minor stretching of the underlying material. The generality of our approach greatly expands the design space for materials so that they can be tuned for diverse applications. PMID:25422433

  16. Engineering the shape and structure of materials by fractal cut.

    PubMed

    Cho, Yigil; Shin, Joong-Ho; Costa, Avelino; Kim, Tae Ann; Kunin, Valentin; Li, Ju; Lee, Su Yeon; Yang, Shu; Han, Heung Nam; Choi, In-Suk; Srolovitz, David J

    2014-12-01

    In this paper we discuss the transformation of a sheet of material into a wide range of desired shapes and patterns by introducing a set of simple cuts in a multilevel hierarchy with different motifs. Each choice of hierarchical cut motif and cut level allows the material to expand into a unique structure with a unique set of properties. We can reverse-engineer the desired expanded geometries to find the requisite cut pattern to produce it without changing the physical properties of the initial material. The concept was experimentally realized and applied to create an electrode that expands to >800% the original area with only very minor stretching of the underlying material. The generality of our approach greatly expands the design space for materials so that they can be tuned for diverse applications. PMID:25422433

  17. Crankshaft structure of two-cycle internal combustion engine

    SciTech Connect

    Oyama, K.

    1986-11-18

    This patent describes a crankshaft structure in a two-cycle internal combustion engine comprising a crank web and a crank journal rotatably supported in a crank case by a bearing means. The crank web includes a supporting part having a central bore for receiving the crank journal press-fit therein. The supporting part has a reduced outer diameter portion disposed adjacent the bearing means supporting the crank journal and at an axial position overlying a press-fit part of the crank journal in the central bore of the crank web supporting part. The reduced outer diameter portion of the supporting part has a sealing member disposed on the outer periphery thereof.

  18. Crankshaft supporting structure for multicylinder internal combustion engines

    SciTech Connect

    Fukuo, K.; Ito, T.; Ichida, K.

    1988-03-08

    A crankshaft supporting structure in a multicylinder internal combustion engine is described including a bearing caps secured respectively to journal walls integral with a crankcase of a cylinder block, a crankshaft rotatably supported between the journal walls and the bearing caps, at least one counterweight on the crankshaft, and a bridge interconnecting the bearing caps. The bridge includes integral baffle plates extending between locations of the bearing caps and curved along a path of outer peripheral surfaces of each counterweight on the crankshaft. The bridge includes an oil supply gallery which extends substantially along a length of the bridge and generally parallel to the crankshaft and branch passages are provided in the bridge and the bearing caps extending from the gallery to a bearing hole defined by each journal wall and bearing cap.

  19. Crankshaft supporting structure for multicylinder internal combustion combustion engines

    SciTech Connect

    Fukuo, K.; Chosa, M.; Kazama, A.; Anno, N.; Kusakabe, Y.

    1988-06-28

    A crankshaft support structure is described for a multicylinder engine, comprising, a cylinder block of a lightweight material having a first coefficient of thermal expansion, the cylinder block extending longitudinally along the crankshaft and having a plurality of lateral extending and longitudinally spaced journal walls. Bearing caps of heavyweight material have a second coefficient of thermal expansion different from the first coefficient, a bearing cap mounted on each journal wall, the bearing caps and journal walls define bearing holes therebetween for supporting the crankshaft, a bridge of a lightweight material having a coefficient of thermal expansion which is substantially equal to the first coefficient, the bridge extending longitudinally over the bearing caps, and means mounting the bridge and bearing caps of the journal walls whereby the cylinder block and bridge undergo a substantially equal amount of thermal expansion and the bearing caps undergo a different amount of thermal expansion which is accommodated by the cylinder block and bridge.

  20. Engineering metal oxide structures for efficient photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Concina, Isabella; Selopal, Gurpreet S.; Milan, Riccardo; Vomiero, Alberto; Sberveglieri, Giorgio

    2014-03-01

    Metal oxide-based photoanodes are critical components of dye sensitized solar cells (DSSCs), which are photoelectrochemical cells for the conversion of solar energy, promising to have several benefits as compared with their traditional counterparts. A careful engineering of the wide band gap metal oxide composing the photoanode, as well as their process design, is strategic for improving device performances and for planning a near future production scale up, especially devoted to reducing the environmental impact of the device fabrication. Herein, we present the application of ZnO hierarchical structures as efficient materials to be applied as photoanodes in DSSC, in the perspective of looking for alternative to TiO2 nanoparticles, currently the most exploited metal oxide in these devices.

  1. Novel preparation of graded porous structures for medical engineering.

    PubMed

    Muthutantri, Anushini; Huang, Jie; Edirisinghe, Mohan

    2008-12-01

    The gradation of porosity in a biomaterial can be very useful for a variety of medical engineering applications such as filtration, bone replacement and implant development. However, the preparation of such structures is not a technologically trivial task and replication methods do not offer an easy solution. In this work, we elucidate the preparation of structures having a graded porosity by electrohydrodynamic spraying, using zirconia (ZrO2), which is widely used in biomedical and other applications. The processes are generic and can be achieved using other bioactive ceramics with similar particle characteristics. The pores on the sprayed surface, the innermost surface and lengthwise cross sections have been analysed in addition to the change in depth of penetration as a function of spraying time. Control of porosity, pore size and depth of penetration has been obtained by varying parameters such as the spraying time, sintering temperature and the sacrificial template. It has been possible to obtain structures with interconnected pore networks of pore size greater than 100microm as well as scattered pores smaller than 10microm in size.

  2. Structurally embedded fiber Bragg gratings: civil engineering applications

    NASA Astrophysics Data System (ADS)

    Nellen, Philipp M.; Broennimann, Rolf; Frank, Andreas; Mauron, Pascal; Sennhauser, Urs J.

    1999-12-01

    In civil engineering it is of interest to monitor long-term performance of structures made of new lightweight materials like glass or carbon fiber reinforced polymers (GFRP/CFRP). In contrast to surface applied optical fiber sensors, embedded sensors are expected to be better protected against rough handling and harsh environmental conditions. We report on two recently done fiber optical sensor applications in civil engineering. Both include structurally embedded fiber Bragg grating (BG) arrays but have different demands with respect to their operation. For the first application fiber BGs were embedded in GFRP rockbolts of 3 - 5 m in length either of 3, 8, or 22 mm diameter. The sensor equipped rockbolts are made for distributed measurements of boulder motion during tunnel construction and operation and should withstand strain up to 1.6%. Rockbolt sensors were field tested in a tunnel near Sargans in Switzerland. For a second application fiber BGs were embedded in CFRP wires of 5 mm diameter used for the pre- stressing cables of a 56 m long bridge near Lucerne in Switzerland. The permanent load on the cable corresponds to 0.8% strain. Due to the embedded sensors, strain decay inside the cable anchoring heads could be measured for the first time during loading and operation of the cables. For both applications mechanical and thermal loading tests were performed to assess the function of these new elements. Also, temperature and strain sensitivity were calibrated. Reliability studies with respect to stress transfer, fiber mechanical failure, and wavelength shift caused by thermal BG decay as well as monitoring results of both applications are presented.

  3. Nd(III) and Dy(III) coordination compounds based on 1H-tetrazolate-5-acetic acid ligands: Synthesis, crystal structures and catalytic properties

    SciTech Connect

    Li Qiaoyun; Chen Dianyu; He Minghua; Yang Gaowen; Shen Lei; Zhai Chun; Shen Wei; Gu Kun; Zhao Jingjing

    2012-06-15

    Reactions of 1H-tetrazolate-5-acetic acid(H{sub 2}tza) with Nd(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O or Dy(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O with the presence of KOH under solvothermal conditions, produced two new coordination compounds, [M{sub 2}(tza){sub 3}(H{sub 2}O){sub 6}]{center_dot}2H{sub 2}O [M=Nd(1), Dy(2)]. Both compounds were structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Compounds 1 and 2 reveal 1D structures via bridging tza as linker. Furthermore, the compounds 1 and 2 showed a specific and good catalytic behavior for the polymerization of styrene, and the polymerization showed controlled characteristics. - Graphical Abstract: Two new coordination compounds, [M{sub 2}(tza){sub 3}(H{sub 2}O){sub 6}]{center_dot}2H{sub 2}O [M=Nd(1), Dy(2)] have been synthesis. 1 and 2 reveal 1D structures via bridging tza as linker, and showed a specific and good catalytic behavior for the polymerization of styrene. Highlights: Black-Right-Pointing-Pointer we have reported two novel compounds formed by H{sub 2}tza and Nd(III) or Dy(III). Black-Right-Pointing-Pointer Compounds 1 and 2 were found to have catalysis property for the photo-polymerization of styrene. Black-Right-Pointing-Pointer The high molecular weight polymers with narrow molecular weight distributions were obtained.

  4. Resonance assignments and secondary structure prediction of the As(III) metallochaperone ArsD in solution

    PubMed Central

    Ye, Jun; He, Yanan; Skalicky, Jack; Rosen, Barry P.; Stemmler, Timothy L.

    2012-01-01

    ArsD is a metallochaperone that delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump encoded by the arsRDABC operon of Escherichia coli plasmid R773. Conserved ArsD cysteine residues (Cys12, Cys13 and Cys18) construct the As(III) binding site of the protein, however a global structural understanding of this arsenic binding remains unclear. We have obtained NMR assignments for ArsD as a starting point for probing structural changes on the protein that occur in response to metalloid binding and upon formation of a complex with ArsA. The predicted solution structure of ArsD is in agreement with recently published crystallographic structural results. PMID:21063813

  5. Volatilization of arsenic from polluted soil by Pseudomonas putida engineered for expression of the arsM Arsenic(III) S-adenosine methyltransferase gene.

    PubMed

    Chen, Jian; Sun, Guo-Xin; Wang, Xiao-Xue; Lorenzo, Víctor de; Rosen, Barry P; Zhu, Yong-Guan

    2014-09-01

    Even though arsenic is one of the most widespread environmental carcinogens, methods of remediation are still limited. In this report we demonstrate that a strain of Pseudomonas putida KT2440 endowed with chromosomal expression of the arsM gene encoding the As(III) S-adenosylmethionine (SAM) methyltransfase from Rhodopseudomonas palustris to remove arsenic from contaminated soil. We genetically engineered the P. putida KT2440 with stable expression of an arsM-gfp fusion gene (GE P. putida), which was inserted into the bacterial chromosome. GE P. putida showed high arsenic methylation and volatilization activity. When exposed to 25 μM arsenite or arsenate overnight, most inorganic arsenic was methylated to the less toxic methylated arsenicals methylarsenate (MAs(V)), dimethylarsenate (DMAs(V)) and trimethylarsine oxide (TMAs(V)O). Of total added arsenic, the species were about 62 ± 2.2% DMAs(V), 25 ± 1.4% MAs(V) and 10 ± 1.2% TMAs(V)O. Volatilized arsenicals were trapped, and the predominant species were dimethylarsine (Me2AsH) (21 ± 1.0%) and trimethylarsine (TMAs(III)) (10 ± 1.2%). At later times, more DMAs(V) and volatile species were produced. Volatilization of Me2AsH and TMAs(III) from contaminated soil is thus possible with this genetically engineered bacterium and could be instrumental as an agent for reducing the inorganic arsenic content of soil and agricultural products. PMID:25122054

  6. Volatilization of Arsenic from Polluted Soil by Pseudomonas putida Engineered for Expression of the arsM Arsenic(III) S-Adenosine Methyltransferase Gene

    PubMed Central

    2015-01-01

    Even though arsenic is one of the most widespread environmental carcinogens, methods of remediation are still limited. In this report we demonstrate that a strain of Pseudomonas putida KT2440 endowed with chromosomal expression of the arsM gene encoding the As(III) S-adenosylmethionine (SAM) methyltransfase from Rhodopseudomonas palustris to remove arsenic from contaminated soil. We genetically engineered the P. putida KT2440 with stable expression of an arsM-gfp fusion gene (GE P. putida), which was inserted into the bacterial chromosome. GE P. putida showed high arsenic methylation and volatilization activity. When exposed to 25 μM arsenite or arsenate overnight, most inorganic arsenic was methylated to the less toxic methylated arsenicals methylarsenate (MAs(V)), dimethylarsenate (DMAs(V)) and trimethylarsine oxide (TMAs(V)O). Of total added arsenic, the species were about 62 ± 2.2% DMAs(V), 25 ± 1.4% MAs(V) and 10 ± 1.2% TMAs(V)O. Volatilized arsenicals were trapped, and the predominant species were dimethylarsine (Me2AsH) (21 ± 1.0%) and trimethylarsine (TMAs(III)) (10 ± 1.2%). At later times, more DMAs(V) and volatile species were produced. Volatilization of Me2AsH and TMAs(III) from contaminated soil is thus possible with this genetically engineered bacterium and could be instrumental as an agent for reducing the inorganic arsenic content of soil and agricultural products. PMID:25122054

  7. The structural and optical properties of type III human collagen biosynthetic corneal substitutes

    PubMed Central

    Hayes, Sally; Lewis, Phillip; Islam, M. Mirazul; Doutch, James; Sorensen, Thomas; White, Tomas; Griffith, May; Meek, Keith M.

    2015-01-01

    The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout. This arrangement differs from the predominantly biaxial alignment of collagen fibrils that exists in the human cornea. By virtue of their high water content (90%), very fine collagen filaments (2–9 nm) and lack of cells, the collagen hydrogels were found to transmit almost all incident light in the visible spectrum. They also transmitted a large proportion of UV light compared to the cornea which acts as an effective UV filter. Patients implanted with these hydrogels should be cautious about UV exposure prior to regrowth of the epithelium and in-growth of corneal cells into the implants. PMID:26159106

  8. The structural and optical properties of type III human collagen biosynthetic corneal substitutes.

    PubMed

    Hayes, Sally; Lewis, Phillip; Islam, M Mirazul; Doutch, James; Sorensen, Thomas; White, Tomas; Griffith, May; Meek, Keith M

    2015-10-01

    The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout. This arrangement differs from the predominantly biaxial alignment of collagen fibrils that exists in the human cornea. By virtue of their high water content (90%), very fine collagen filaments (2-9 nm) and lack of cells, the collagen hydrogels were found to transmit almost all incident light in the visible spectrum. They also transmitted a large proportion of UV light compared to the cornea which acts as an effective UV filter. Patients implanted with these hydrogels should be cautious about UV exposure prior to regrowth of the epithelium and in-growth of corneal cells into the implants. PMID:26159106

  9. Spectroscopic and quantum chemical study of the structure of a new paramagnetic dimeric palladium(II,III) complex with creatine

    NASA Astrophysics Data System (ADS)

    Mitewa, Mariana; Enchev, Venelin; Bakalova, Tatyana

    2002-05-01

    The structure and coordination mode of the newly synthesized dimeric paramagnetic Pd(II,III) complex are studied using magneto-chemical, EPR and IR spectroscopic methods. In order to perform reliable assignment of the IR bands, the structure and IR spectrum of the free creatine were calculated using ab initio method. For calculation of the configuration of its deprotonated and doubly deprotonated forms the semiempirical AM1 method was used.

  10. Structural investigations of PuIII phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    NASA Astrophysics Data System (ADS)

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Prieur, Damien; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J. M.; Somers, Joseph

    2015-10-01

    PuPO4 was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β- decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state 31P NMR agrees with the XANES results and the presence of a solid-solution.

  11. Solution structure and behavior of dimeric uranium(III) metallocene halides

    SciTech Connect

    Lukens, W.W. Jr.; Beshouri, S.M.; Stuart, A.L.; Andersen, R.A.

    1999-03-29

    The variable-temperature {sup 1}H NMR behavior of the uranium(III) dimers [Cp{double_prime}{sub 2}UX]{sub 2} and [Cp{sup {double_dagger}}{sub 2}UX]{sub 2}, where X is F, Cl, Br, or I, Cp{double_prime} is 1,3-(Me{sub 3}Si){sub 2}C{sub 5}H{sub 3}, and Cp{sup {double_dagger}} is 1,3-(Me{sub 3}C){sub 2}C{sub 5}H{sub 3}, has been examined. At low temperature, the number of inequivalent CMe{sub 3} or SiMe{sub 3} groups implies that the solution structure is the same as the solid-state structure in all of these complexes. The barriers to ring rotation in the Cp{double_prime} series are strongly dependent upon the U-X distance, but all of the barriers to ring rotation in the Cp{sup {double_dagger}} series are the same. The trends in ring rotation barriers are explained by the different conformations of the Cp ligands in the dimers. In addition to the homo-halide dimers, the variable-temperature NMR behavior of the hetero-halide dimers Cp{prime}{sub 4}({mu}-X)({mu}-Y), where Cp{prime} is Cp{double_prime} or Cp{sup {double_dagger}} and X and Y are halides where X {ne} Y, was examined. Above room temperature, the halide atoms exchange sites rapidly on the NMR time scale.

  12. Synthesis, structure, and properties of low-spin manganese(III)-poly(pyrazolyl)borate complexes.

    PubMed

    Hossain, Ferdaus; Rigsby, Matthew A; Duncan, Cole T; Milligan, Paul L; Lord, Richard L; Baik, Mu-Hyun; Schultz, Franklin A

    2007-04-01

    The manganese(III)-bis[poly(pyrazolyl)borate] complexes, Mn(pzb)2SbF6, where pzb- = tetrakis(pyrazolyl)borate (pzTp) (1), hydrotris(pyrazolyl)borate (Tp) (2), or hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) (3), have been synthesized by oxidation of the corresponding Mn(pzb)2 compounds with NOSbF6. The Mn(III) complexes are low-spin in solution and the solid state (microeff = 2.9-3.8 microB). X-ray crystallography confirms their uncommon low-spin character. The close conformity of mean Mn-N distances of 1.974(4), 1.984(5), and 1.996(4) A in 1, 2, and 3, respectively, indicates absence of the characteristic Jahn-Teller distortion of a high-spin d4 center. N-Mn-N bite angles of slightly less than 90 degrees within the facially coordinated pzb- ligands produce a small trigonal distortion and effective D3d symmetry in 1 and 2. These angles increase to 90.0(4)degrees in 3, yielding an almost perfectly octahedral disposition of N donors in Mn(Tp*)2+. Examination of structural data from 23 metal-bis(pzb) complexes reveals systematic changes within the metal-(pyrazolyl)borate framework as the ligand is changed from pzTp to Tp to Tp*. These deformations consist of significant increases in M-N-N, N-B-N, and N-N-B angles and a minimal increase in Mn-N distance as a consequence of the steric demands of the 3-methyl groups. Less effective overlap of pyrazole lone pairs with metal atom orbitals resulting from the M-N-N angular displacement is suggested to contribute to the lower ligand field strength of Tp* complexes. Mn(pzb)2+ complexes undergo electrochemical reduction and oxidation in CH3CN. The electrochemical rate constant (ks,h) for reduction of t2g4 Mn(pzb)2+ to t2g3eg2 Mn(pzb)2 (a coupled electron-transfer and spin-crossover reaction) is 1-2 orders of magnitude smaller than that for oxidation of t2g4 Mn(pzb)2+ to t2g3 Mn(pzb)22+. ks,h values decrease as Tp* > pzTp > Tp for the Mn(pzb)2+/0 electrode reactions, which contrasts with the behavior of the comparable Fe(pzb)2

  13. Structural design of Stirling engine with free pistons

    NASA Astrophysics Data System (ADS)

    Matusov, Jozef; Gavlas, Stanislav; Malcho, Milan

    2014-08-01

    Stirling engine is a device that converts thermal energy to mechanical work, which is mostly used to drive a generator of electricity. Advantage of Stirling engine is that it works with closed-cycle, where working medium is regularly cooled and heated, which acts on the working piston. This engine can be made in three modifications - alpha, beta, gamma. This paper discusses the design of the gamma Stirling engine with free pistons.

  14. Structure and stability of hexa-aqua V(III) cations in vanadium redox flow battery electrolytes.

    PubMed

    Vijayakumar, M; Li, Liyu; Nie, Zimin; Yang, Zhenguo; Hu, JianZhi

    2012-08-01

    The vanadium(III) cation structure in mixed acid based electrolyte solution from vanadium redox flow batteries is studied by (17)O and (35/37)Cl nuclear magnetic resonance (NMR) spectroscopy, electronic spectroscopy and density functional theory (DFT) based computational modelling. Both computational and experimental results reveal that the V(III) species can complex with counter anions (sulfate/chlorine) depending on the composition of its solvation sphere. By analyzing the powder precipitate it was found that the formation of sulfate complexed V(III) species is the crucial process in the precipitation reaction. The precipitation occurs through nucleation of neutral species formed through deprotonation and ion-pair formation process. However, the powder precipitate shows a multiphase nature which warrants multiple reaction pathways for precipitation reaction. PMID:22735894

  15. Structure and Stability of Hexa-Aqua V(III) Cations in Vanadium Redox Flow Battery Electrolytes

    SciTech Connect

    Vijayakumar, M.; Li, Liyu; Nie, Zimin; Yang, Zhenguo; Hu, Jian Z.

    2012-05-09

    The Vanadium (III) cation structure in mixed acid based electrolyte solution from vanadium redox flow batteries were studied by 17O and 35/37Cl Nuclear Magnetic Resonance (NMR) spectroscopy, electronic spectroscopy and density functional theory (DFT) based computational modeling. Both computational and experimental results reveals that the V(III) species can complex with counter anions (sulfate/chlorine) 10 depend on the composition of its solvation sphere. By analyzing the powder precipitate it was found that the formation of sulfate complexed V(III) species is the crucial process in the precipitation reaction. The precipitation occurs through nucleation of neutral species formed through deprotonation and ion-pair formation process. However, the powder precipitate shows a multiphase nature which warrants multiple reaction pathways for precipitation reaction.

  16. Structure and stability of hexa-aqua V(III) cations in vanadium redox flow battery electrolytes.

    PubMed

    Vijayakumar, M; Li, Liyu; Nie, Zimin; Yang, Zhenguo; Hu, JianZhi

    2012-08-01

    The vanadium(III) cation structure in mixed acid based electrolyte solution from vanadium redox flow batteries is studied by (17)O and (35/37)Cl nuclear magnetic resonance (NMR) spectroscopy, electronic spectroscopy and density functional theory (DFT) based computational modelling. Both computational and experimental results reveal that the V(III) species can complex with counter anions (sulfate/chlorine) depending on the composition of its solvation sphere. By analyzing the powder precipitate it was found that the formation of sulfate complexed V(III) species is the crucial process in the precipitation reaction. The precipitation occurs through nucleation of neutral species formed through deprotonation and ion-pair formation process. However, the powder precipitate shows a multiphase nature which warrants multiple reaction pathways for precipitation reaction.

  17. Development and fabrication of structural components for a scramjet engine

    NASA Technical Reports Server (NTRS)

    Buchmann, O. A.

    1990-01-01

    A program broadly directed toward design and development of long-life (100 hours and 1,000 cycles with a goal of 1,000 hours and 10,000 cycles) hydrogen-cooled structures for application to scramjets is presented. Previous phases of the program resulted in an overall engine design and analytical and experimental characterization of selected candidate materials and concepts. The latter efforts indicated that the basic life goals for the program can be reached with available means. The main objective of this effort was an integrated, experimental evaluation of the results of the previous program phases. The fuel injection strut was selected for this purpose, including fabrication development and fabrication of a full-scale strut. Testing of the completed strut was to be performed in a NASA-Langley wind tunnel. In addition, conceptual designs were formulated for a heat transfer test unit and a flat panel structural test unit. Tooling and fabrication procedures required to fabricate the strut were developed, and fabrication and delivery to NASA of all strut components, including major subassemblies, were completed.

  18. Structure of the cytoplasmic domain of Yersinia pestis YscD, an essential component of the type III secretion system

    PubMed Central

    Lountos, George T.; Tropea, Joseph E.; Waugh, David S.

    2012-01-01

    The Yersinia pestis YscD protein is an essential component of the type III secretion system. YscD consists of an N-terminal cytoplasmic domain (residues 1–121), a transmembrane linker (122–142) and a large periplasmic domain (143–419). Both the cytoplasmic and the periplasmic domains are required for the assembly of the type III secretion system. Here, the structure of the YscD cytoplasmic domain solved by SAD phasing is presented. Although the three-dimensional structure is similar to those of forkhead-associated (FHA) domains, comparison with the structures of canonical FHA domains revealed that the cytoplasmic domain of YscD lacks the conserved residues that are required for binding phosphothreonine and is therefore unlikely to function as a true FHA domain. PMID:22349221

  19. Structure of the cytoplasmic domain of Yersinia pestis YscD, an essential component of the type III secretion system

    SciTech Connect

    Lountos, George T.; Tropea, Joseph E.; Waugh, David S.

    2012-09-17

    The Yersinia pestis YscD protein is an essential component of the type III secretion system. YscD consists of an N-terminal cytoplasmic domain (residues 1-121), a transmembrane linker (122-142) and a large periplasmic domain (143-419). Both the cytoplasmic and the periplasmic domains are required for the assembly of the type III secretion system. Here, the structure of the YscD cytoplasmic domain solved by SAD phasing is presented. Although the three-dimensional structure is similar to those of forkhead-associated (FHA) domains, comparison with the structures of canonical FHA domains revealed that the cytoplasmic domain of YscD lacks the conserved residues that are required for binding phosphothreonine and is therefore unlikely to function as a true FHA domain.

  20. The structural basis for partitioning of the XRCC1/DNA ligase III-[alpha] BRCT-mediated dimer complexes

    SciTech Connect

    Cuneo, Matthew J.; Gabel, Scott A.; Krahn, Joseph M.; Ricker, Melissa A.; London, Robert E.

    2011-11-17

    The ultimate step common to almost all DNA repair pathways is the ligation of the nicked intermediate to form contiguous double-stranded DNA. In the mammalian nucleotide and base excision repair pathways, the ligation step is carried out by ligase III-{alpha}. For efficient ligation, ligase III-{alpha} is constitutively bound to the scaffolding protein XRCC1 through interactions between the C-terminal BRCT domains of each protein. Although structural data for the individual domains has been available, no structure of the complex has been determined and several alternative proposals for this interaction have been advanced. Interpretation of the models is complicated by the formation of homodimers that, depending on the model, may either contribute to, or compete with heterodimer formation. We report here the structures of both homodimer complexes as well as the heterodimer complex. Structural characterization of the heterodimer formed from a longer XRCC1 BRCT domain construct, including residues comprising the interdomain linker region, revealed an expanded heterodimer interface with the ligase III-{alpha} BRCT domain. This enhanced linker-mediated binding interface plays a significant role in the determination of heterodimer/homodimer selectivity. These data provide fundamental insights into the structural basis of BRCT-mediated dimerization, and resolve questions related to the organization of this important repair complex.

  1. The Structural Basis for Partitioning of the XRCC1/DNA Ligase III-alpha BRCT-mediated Dimer Complexes

    SciTech Connect

    M Cuneo; S Gabel; J Krahn; M Ricker; R London

    2011-12-31

    The ultimate step common to almost all DNA repair pathways is the ligation of the nicked intermediate to form contiguous double-stranded DNA. In the mammalian nucleotide and base excision repair pathways, the ligation step is carried out by ligase III-{alpha}. For efficient ligation, ligase III-{alpha} is constitutively bound to the scaffolding protein XRCC1 through interactions between the C-terminal BRCT domains of each protein. Although structural data for the individual domains has been available, no structure of the complex has been determined and several alternative proposals for this interaction have been advanced. Interpretation of the models is complicated by the formation of homodimers that, depending on the model, may either contribute to, or compete with heterodimer formation. We report here the structures of both homodimer complexes as well as the heterodimer complex. Structural characterization of the heterodimer formed from a longer XRCC1 BRCT domain construct, including residues comprising the interdomain linker region, revealed an expanded heterodimer interface with the ligase III-{alpha} BRCT domain. This enhanced linker-mediated binding interface plays a significant role in the determination of heterodimer/homodimer selectivity. These data provide fundamental insights into the structural basis of BRCT-mediated dimerization, and resolve questions related to the organization of this important repair complex.

  2. Forensic engineering of advanced polymeric materials. Part III - Biodegradation of thermoformed rigid PLA packaging under industrial composting conditions.

    PubMed

    Musioł, Marta; Sikorska, Wanda; Adamus, Grazyna; Janeczek, Henryk; Richert, Jozef; Malinowski, Rafal; Jiang, Guozhan; Kowalczuk, Marek

    2016-06-01

    This paper presents a forensic engineering study on the biodegradation behaviour of prototype packaging thermoformed from PLA-extruded film and plain PLA film under industrial composting conditions. Hydrolytic degradation in water was conducted for reference. The effects of composting duration on changes in molar mass, glass transition temperature and degree of crystallinity of the polymeric material were monitored using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The chemical structure of water soluble degradation products of the polymeric material was determined using nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). The results show that the biodegradation process is less dependent on the thermoforming process of PLA and more dependent on the composting/degradation conditions that are applied. The increase in the dispersity index, leading to the bimodal molar mass distribution profile, suggests an autocatalytic hydrolysis effect at the early stage of the composting process, during which the bulk hydrolysis mechanism dominantly operates. Both the prototype PLA-packaging and PLA rigid film samples were shown to have a gradual increase in opacity due to an increase in the degree of crystallinity. PMID:27103398

  3. Forensic engineering of advanced polymeric materials. Part III - Biodegradation of thermoformed rigid PLA packaging under industrial composting conditions.

    PubMed

    Musioł, Marta; Sikorska, Wanda; Adamus, Grazyna; Janeczek, Henryk; Richert, Jozef; Malinowski, Rafal; Jiang, Guozhan; Kowalczuk, Marek

    2016-06-01

    This paper presents a forensic engineering study on the biodegradation behaviour of prototype packaging thermoformed from PLA-extruded film and plain PLA film under industrial composting conditions. Hydrolytic degradation in water was conducted for reference. The effects of composting duration on changes in molar mass, glass transition temperature and degree of crystallinity of the polymeric material were monitored using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The chemical structure of water soluble degradation products of the polymeric material was determined using nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). The results show that the biodegradation process is less dependent on the thermoforming process of PLA and more dependent on the composting/degradation conditions that are applied. The increase in the dispersity index, leading to the bimodal molar mass distribution profile, suggests an autocatalytic hydrolysis effect at the early stage of the composting process, during which the bulk hydrolysis mechanism dominantly operates. Both the prototype PLA-packaging and PLA rigid film samples were shown to have a gradual increase in opacity due to an increase in the degree of crystallinity.

  4. Structural and optical characterization of group III-nitride compound semiconductors

    NASA Astrophysics Data System (ADS)

    Senawiratne, Jayantha

    The structural properties of the group III-nitrides including AlN, Ga 1-xMnxN, GaN:Cu, and InN were investigated by Raman spectroscopy. Absorption and photoluminescence spectroscopy were utilized to study the optical properties in these materials. The analysis of physical vapor transport grown AlN single crystals showed that oxygen, carbon, silicon, and boron are the major impurities in the bulk AlN. The Raman analysis revealed high crystalline quality and well oriented AlN single crystals. The absorption coefficient of AlN single crystals were assessed in the spectral range from deep UV to the FIR. The absorption and photoluminescence analysis indicate that, in addition to oxygen, carbon, boron, and silicon, contribute to the optical properties of bulk AlN crystals. In situ Cu-doped GaN epilayers with Cu concentrations in the range of 2x1016 cm-3 - 5x10 17 cm-3, grown on sapphire substrate by metal organic chemical vapor deposition, were investigated by Raman and photoluminescence (PL) spectroscopy. The Raman study revealed high crystalline GaN:Cu layers with minimal damage to the hexagonal lattice structure due to the Cu incorporation. A strong Cu related emission band at 2.4 eV was assigned to Cu induced optical transitions between deep Cu states and shallow residual donor states. Compensation of Cu states by residual donors and poor activation probability of deep Cu states are responsible for semi-insulating electrical conductivity. Ferromagnetic Ga1-xMnxN epilayers, grown by MOCVD with Mn concentration from x = 0 to x = 1.5, were optically investigated by Raman, PL, and transmission spectroscopy. The Raman studies revealed Mn-related Raman peaks at 300 cm-1, 609 cm-1, and 669 cm -1. Mn-related absorption and emission bands in Ga1-xMn xN were observed at 1.5 eV and 3.0 eV, respectively. The structural properties of InN layers, grown by high pressure-CVD with different free carrier concentrations, were analyzed by Raman spectroscopy. The Raman results show that

  5. Engine-induced structural-borne noise in a general aviation aircraft

    NASA Technical Reports Server (NTRS)

    Unruh, J. F.; Scheidt, D. C.; Pomerening, D. J.

    1979-01-01

    Structural borne interior noise in a single engine general aviation aircraft was studied to determine the importance of engine induced structural borne noise and to determine the necessary modeling requirements for the prediction of structural borne interior noise. Engine attached/detached ground test data show that engine induced structural borne noise is a primary interior noise source for the single engine test aircraft, cabin noise is highly influenced by responses at the propeller tone, and cabin acoustic resonances can influence overall noise levels. Results from structural and acoustic finite element coupled models of the test aircraft show that wall flexibility has a strong influence on fundamental cabin acoustic resonances, the lightweight fuselage structure has a high modal density, and finite element analysis procedures are appropriate for the prediction of structural borne noise.

  6. A one-dimensional azido-bridged manganese(III) complex with bidentate Schiff base: Crystal structure and magnetic properties

    SciTech Connect

    Li Wei; Li Zongwei; Li Licun Liao Daizheng; Jiang Zonghui

    2007-10-15

    The synthesis, structural characterization, and magnetic behavior of a novel one-dimensional azido-bridged manganese(III) complex of formula [Mn(L){sub 2}N{sub 3}] (1) is reported, where HL is the bidentate Schiff base obtained from the condensation of salicylaldehyde with 4-methoxy aniline. Complex 1 crystallizes in the monoclinic system, space group P2{sub 1}/n, with a=11.743(4) A, b=24.986(9) A, c=13.081(5) A, {beta}=95.387(7){sup o} and Z=2. The complex is of one-dimensional chain structure with single end-to-end azido bridges and the manganese(III) ion has an elongated octahedral geometry. Magnetic studies show that the weak antiferromagnetic interaction is mediated by the single end-to-end azido bridge with the exchange parameter J=-5.84 cm{sup -1}. - Graphical abstract: A novel azido-bridged manganese(III) complex with bidentate Schiff base ligands has been prepared and characterized structurally and magnetically. The complex is of one-dimensional chain structure with single end-to-end azido bridges in axial positions. Two bidentate Schiff base ligands coordinate in the equatorial mode. The magnetic measurements show that the complex exhibits weak antiferromagnetic interaction.

  7. Structure of Fe(III) precipitates generated by the electrolytic dissolution of Fe(0) in the presence of groundwater ions

    NASA Astrophysics Data System (ADS)

    van Genuchten, Case M.; Peña, Jasquelin; Amrose, Susan E.; Gadgil, Ashok J.

    2014-02-01

    We apply Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and pair distribution function (PDF) analysis of high-energy X-ray scattering to investigate the effects of bivalent cation-oxyanion pairs on the structure of Fe(III) precipitates formed from the oxidation of Fe(II) generated by the electrolytic dissolution of Fe(0) electrodes. We found that Fe(II) oxidation in the presence of weakly adsorbing electrolytes (NaCl, CaCl2, MgCl2) leads to pseudo-lepidocrocite (Lp; γ-FeOOH), a poorly crystalline version of Lp with low sheet-stacking coherence. In the absence of bivalent cations, P and As(V) have similar uptake behavior, but different effects on the average Fe(III) precipitate structure: pseudo-Lp dominates in the presence of P, whereas a disordered ferrihydrite-like precipitate akin to hydrous ferric oxide (HFO) is the dominant phase that forms in the presence of As(V). Despite its lower affinity for Fe(III) precipitates, Si leads to Si-HFO in all conditions tested. The presence of 1 mM Ca2+ or Mg2+ enhances oxyanion uptake, destabilizes the colloidally stable oxyanion-bearing particle suspensions and, in some P and As(V) electrolytes, results in more crystalline precipitates. The trends in oxyanion uptake and Fe(III) precipitate structure in the presence of Ca2+/Mg2+ suggest a systematic decrease in the strength of bivalent cation:oxyanion interaction in the order of Ca2+ > Mg2+ and P > As(V) ≫ Si. Using the PDF technique, we identify the polyhedral linkages that contribute to the intermediate structures (>6 Å) of disordered, nanoscale oxyanion-bearing Fe(III) precipitate samples. Our results suggest that oxyanions present during Fe(III) polymerization bind to corner-sharing Fe surface sites leading to a precipitate surface deficient in corner-sharing Fe, whereas the edge- and corner-sharing Fe sites in the precipitate core likely remain intact.

  8. Innovative tissue engineering structures through advanced manufacturing technologies.

    PubMed

    Ciardelli, Gianluca; Chiono, Valeria; Cristallini, Caterina; Barbani, Niccoletta; Ahluwalia, Arti; Vozzi, Giovanni; Previti, Antonino; Tantussi, Giovanni; Giusti, Paolo

    2004-04-01

    Awide range of rapid prototyping (RP) techniques for the construction of three-dimensional (3-D) scaffolds for tissue engineering has been recently developed. In this study, we report and compare two methods for the fabrication of poly-(epsilon-caprolactone) and poly-(epsilon-caprolactone)-poly-(oxyethylene)-poly-(epsilon-caprolactone) copolymer scaffolds. The first technique is based on the use of a microsyringe and a computer-controlled three-axis micropositioner, which regulates motor speed and position. Polymer solutions are extruded through the needle of the microsyringe by the application of a constant pressure of 10-300 mm Hg, resulting in controlled polymer deposition of 5-600 microm lateral dimensions. The second method utilises the heating energy of a laser beam to sinter polymer microparticles according to computer-guided geometries. Materials may be fed either as dry powder or slurry of microparticles. Both powder granulometry and laser working parameters influence resolution (generally 300 microm x 700 microm), accuracy of sintering and surface and bulk properties of the final structures. The two RP methods allow the fabrication of 3-D scaffolds with a controlled architecture, providing a powerful means to study cell response to an environment similar to that found

  9. Crankshaft supporting structure for multicylinder internal combustion engines

    SciTech Connect

    Fukuo, K.; Chosa, M.

    1988-01-26

    A crankshaft supporting structure for a cylinder block of an internal combustion engine is described, comprising, journal walls extending laterally across the cylinder block and being longitudinally spaced along the crankshaft, a recess formed in each journal wall with inwardly and downwardly facing first mating surfaces at an upper extremity of the recess. The cylinder block has skirt portions extending downwardly from the recesses on each lateral end of the journal walls, a bearing cap mounted in the recess in each journal wall and having means cooperating with the journal wall for rotatably supporting the crankshaft, each bearing cap having outwardly and upwardly facing first mating surfaces for engaging the journal wall first mating surfaces, mating inwardly facing vertical surfaces on each skirt portion and outwardly facing vertical surfaces on each bearing cap, a longitudinally extending bridge, a pair of vertical bolts extending through the bridge and each bearing cap and threadedly engaging the journal wall, horizontal bolts extending through the skirt portions and threadedly engaging each lateral side of each bearing cap, and the bridge having a main oil gallery defined therein for passage of lubricating oil therethrough and communicating with lubricating oil passages formed through the bridge and the bearing caps for communicating oil to the crankshaft.

  10. Optical coherent sensor for monitoring and measurement of engineering structures

    NASA Astrophysics Data System (ADS)

    Łukaszewski, Dariusz; Sałbut, Leszek; Dziuban, Jan A.

    2010-05-01

    Among many coherent optical methods one should distinguished Grating Interferometry (GI) which allows accurate in-plane displacement measurements and Digital Speckle Pattern Interferometry (DSPI) used for in-plane and out-of-plane measurements. Development of sensors based on both methods mentioned above as complementary ones will provide user universal group of sensors from which depending on measurement requirements such as measuring range, object surface profile and measurement conditions the most appropriate can be chosen. In-plane displacement measurements are of interested of different branches of industry - from micro (i.e.: characterization of MEMS or MOEMS) to civil engineering (i.e.: Structural Health Monitoring systems). In the paper the new optical coherent sensor for in-plane displacement and strain measurements is presented. The sensor combines GI and DSPI methods in one device which can be used for testing of objects with different types of surfaces. GI requires the specimen grating attached at the surface but provides very good measurement accuracy however DSPI can be applied for testing of objects with rough surfaces but due to higher noise gives lower accuracy. The sensor can work in three modes: as GI only, DSPI only and both GI and DSPI simultaneously. The third mode can by useful when the specimen grating is attached on the part of object under test only. In the paper the theoretical background of the sensor is presented. For confirmation of GI/DSPI sensor possibilities the specially designed demonstrator is described and the exemplary results obtained during its laboratory tests are shown. Successful application of proposed sensor is possible due to its miniaturization, simplicity of operation by user (compact structure and automation of measurement procedure) and low cost. The last mentioned condition will be possible due to low cost replication techniques with usage of silicon technology.

  11. Terbium(III) and yttrium(III) complexes with pyridine-substituted nitronyl nitroxide radical and different β-diketonate ligands. Crystal structures and magnetic and luminescence properties.

    PubMed

    Lannes, Anthony; Intissar, Mourad; Suffren, Yan; Reber, Christian; Luneau, Dominique

    2014-09-15

    A terbium(III) complex of nitronyl nitroxide free radical 2-(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro1H-imidazolyl-1-oxy-3-oxide (NIT2Py), [Tb(acac)3NIT2Py]·0.5H2O (3) (acac = acetylacetonate), was synthesized for comparison with the previously reported [Tb(hfac)3NIT2Py]·0.5C7H16 (1) (hfac = hexafluoroacetylacetonate), together with their yttrium analogues [Y(hfac)3NIT2Py]·0.5C7H16 (2) and [Y(acac)3NIT2Py]·0.5H2O (4). The crystal structures show that in all complexes the nitronyl nitroxide radical acts as a chelating ligand. Magnetic studies show that 3 like 1 exhibits slow relaxation of magnetization at low temperature, suggesting single-molecule magnet behavior. The luminescence spectra show resolved vibronic structure with the main interval decreasing from 1600 cm(-1) to 1400 cm(-1) between 80 and 300 K. This effect is analyzed quantitatively using experimental Raman frequencies.

  12. Structural analysis and modeling reveals new mechanisms governing ESCRT-III spiral filament assembly.

    PubMed

    Shen, Qing-Tao; Schuh, Amber L; Zheng, Yuqing; Quinney, Kyle; Wang, Lei; Hanna, Michael; Mitchell, Julie C; Otegui, Marisa S; Ahlquist, Paul; Cui, Qiang; Audhya, Anjon

    2014-09-15

    The scission of biological membranes is facilitated by a variety of protein complexes that bind and manipulate lipid bilayers. ESCRT-III (endosomal sorting complex required for transport III) filaments mediate membrane scission during the ostensibly disparate processes of multivesicular endosome biogenesis, cytokinesis, and retroviral budding. However, mechanisms by which ESCRT-III subunits assemble into a polymer remain unknown. Using cryogenic electron microscopy (cryo-EM), we found that the full-length ESCRT-III subunit Vps32/CHMP4B spontaneously forms single-stranded spiral filaments. The resolution afforded by two-dimensional cryo-EM combined with molecular dynamics simulations revealed that individual Vps32/CHMP4B monomers within a filament are flexible and able to accommodate a range of bending angles. In contrast, the interface between monomers is stable and refractory to changes in conformation. We additionally found that the carboxyl terminus of Vps32/CHMP4B plays a key role in restricting the lateral association of filaments. Our findings highlight new mechanisms by which ESCRT-III filaments assemble to generate a unique polymer capable of membrane remodeling in multiple cellular contexts. PMID:25202029

  13. Synthesis, spectroscopic, structural and theoretical characterization of hydrogensquarate and mononuclear Au(III)-complex of dipeptide phenylalanyltyrosine

    NASA Astrophysics Data System (ADS)

    Koleva, Bojidarka B.; Kolev, Tsonko; Zareva, Sonya Y.; Spiteller, Michael

    2008-08-01

    The mononuclear Au(III)-complex ([Au(C 18H 18N 2O 4)Cl]) and hydrogensquarate ([C 22H 21N 2O 8]) of dipeptide phenylalanyltyrosine ( H-Phe-Tyr-OH) have been synthezised, characterized spectroscopically and structurally by means of solid-state linear-polarized IR-spectroscopy, 1H- and 13C-NMR, ESI-MS, HPLC-MS-MS, FAB-MS, TGS and DSC methods. The structure of the Au(III)-complex has been predicted theoretically by DFT calculations. The dipeptide coordinated in a tridentate manner via -NH 2, -COO - and N --groups. One Cl - ion is attached to the metal centre as a terminal ligand, yielding a planar AuN 2OCl chromophor. The hydrogensquarate consists in positive charged dipeptide moiety and negative one hydrogensquarate (HSq -) anion stabilizing by strong intermolecular hydrogen bonds.

  14. Reverse osmosis membrane composition, structure and performance modification by bisulphite, iron(III), bromide and chlorite exposure.

    PubMed

    Ferrer, O; Gibert, O; Cortina, J L

    2016-10-15

    Reverse osmosis (RO) membrane exposure to bisulphite, chlorite, bromide and iron(III) was assessed in terms of membrane composition, structure and performance. Membrane composition was determined by Rutherford backscattering spectrometry (RBS) and membrane performance was assessed by water and chloride permeation, using a modified version of the solution-diffusion model. Iron(III) dosage in presence of bisulphite led to an autooxidation of the latter, probably generating free radicals which damaged the membrane. It comprised a significant raise in chloride passage (chloride permeation coefficient increased 5.3-5.1 fold compared to the virgin membrane under the conditions studied) rapidly. No major differences in terms of water permeability and membrane composition were observed. Nevertheless, an increase in the size of the network pores, and a raise in the fraction of aggregate pores of the polyamide (PA) layer were identified, but no amide bond cleavage was observed. These structural changes were therefore, in accordance with the transport properties observed. PMID:27470468

  15. Synthesis, structural characterization, luminescent properties and theoretical study of three novel lanthanide metal-organic frameworks of Ho(III), Gd(III) and Eu(III) with 2,5-thiophenedicarboxylate anion

    SciTech Connect

    Marques, Lippy F.; Correa, Charlane C.; Ribeiro, Sidney J.L.; Santos, Molíria V. dos; Dutra, José Diogo L.; Freire, Ricardo O.; Machado, Flávia C.

    2015-07-15

    In this paper, the synthesis of three new metal-organic frameworks of lanthanides (LnMOFs) ([Ln{sub 2}(2,5-tdc){sub 3}(dmso){sub 2}]·H{sub 2}O){sub n} (Ln=Ho (1); Gd (2); Eu (3); 2,5-tdc=2,5-thiophenedicarboxylate anion; dmso=dimethylsulfoxide), and their complete characterization, including single crystal X-ray diffraction, FTIR spectroscopy and thermogravimetric analysis are reported. In especial, photophysical properties of Eu(III) complex have been studied in detail via both theoretical and experimental approaches. Crystal structure of (1) reveals that each lanthanide ion is seven-coordinated by oxygen atoms in an overall distorted capped trigonal – prismatic geometry. The 2,5-tdc{sup 2−} ligands connect four Ln(III) centers, adopting (κ{sup 1}–κ{sup 1})–(κ{sup 1}–κ{sup 1})–μ{sub 4} coordination mode, generating an 8-connected uninodal 3D network. In addition, theoretical studies for Eu(III) complex were performed using the Sparkle model for lanthanide complexes. - Graphical abstract: Three new metal-organic frameworks of lanthanides (LnMOFs) ([Ln{sub 2}(2,5-tdc){sub 3}(dmso){sub 2}]·H{sub 2}O){sub n} (Ln=Ho (1); Gd (2); Eu (3); 2,5-tdc=2,5-thiophenedicarboxylate anion; dmso=dimethylsulfoxide), were synthesized and their complete characterization, including single crystal X-ray diffraction, FTIR spectroscopy and thermogravimetric analysis are reported. In especial, photophysical properties of Eu(III) complex have been studied in detail via both theoretical and experimental approaches. - Highlights: • Three new LnMOFs were synthesized and fully characterized. • Ho{sup 3+}, Gd{sup 3+} and Eu{sup 3+} complexes photoluminescence properties were investigated. • Theoretical approaches for Eu{sup 3+} complex luminescence has been performed. • An energy level diagram is used to establish the ligand-to-metal energy transfer. • These metal−organic frameworks can act as light conversion molecular devices.

  16. Crystal structures of type III{sub H} NAD-dependent D-3-phosphoglycerate dehydrogenase from two thermophiles

    SciTech Connect

    Kumar, S.M.; Pampa, K.J.; Manjula, M.; Hemantha Kumar, G.; Kunishima, Naoki; Lokanath, N.K.

    2014-08-15

    Highlights: • Determined the crystal structures of PGDH from two thermophiles. • Monomer is composed of nucleotide binding domain and substrate binding domain. • Crystal structures of type III{sub H} PGDH. - Abstract: In the L-Serine biosynthesis, D-3-phosphoglycerate dehydrogenase (PGDH) catalyzes the inter-conversion of D-3-phosphoglycerate to phosphohydroxypyruvate. PGDH belongs to 2-hydroxyacid dehydrogenases family. We have determined the crystal structures of PGDH from Sulfolobus tokodaii (StPGDH) and Pyrococcus horikoshii (PhPGDH) using X-ray diffraction to resolution of 1.77 Å and 1.95 Å, respectively. The PGDH protomer from both species exhibits identical structures, consisting of substrate binding domain and nucleotide binding domain. The residues and water molecules interacting with the NAD are identified. The catalytic triad residues Glu-His-Arg are highly conserved. The residues involved in the dimer interface and the structural features responsible for thermostability are evaluated. Overall, structures of PGDHs with two domains and histidine at the active site are categorized as type III{sub H} and such PGDHs structures having this type are reported for the first time.

  17. Influence of the group V element on the chemical potential and crystal structure of Au-catalyzed III-V nanowires

    SciTech Connect

    Dubrovskii, V. G.

    2014-02-03

    We present a kinetic growth model having a particular emphasis on the influence of the group V element on the preferred crystal structure of Au-catalyzed III-V nanowires. The model circumvents the uncertainty in the group V contribution into the overall liquid chemical potential. We show why the nanowire elongation rate is limited by the group III transport, while the crystal structure depends on the effective group V to III imbalance. Within the model, we are able to explain some important structural trends in Au-catalyzed III-V nanowires. In particular, we show that high group V flux always favors wurtzite structure in molecular-beam epitaxy. This tendency could be inverted in vapor deposition techniques due to suppression of the group III diffusion at high group V flux.

  18. Complexation of Eu(III) with cucurbit[n]uril, n = 5 and 7: a thermodynamic and structural study.

    PubMed

    Rawat, Neetika; Kar, Aishwarya; Bhattacharyya, A; Rao, Ankita; Nayak, S K; Nayak, C; Jha, S N; Bhattacharyya, D; Tomar, B S

    2015-03-01

    Cucurbit[n]urils (CBn) are a new class of macrocyclic cage compounds capable of binding organic and inorganic species, owing to their unique pumpkin like structure comprising of both a hydrophobic cavity and a hydrophilic portal. The thermodynamics of the complexation of Eu(III) with CBn of a different cavity size viz. cucurbit[5]uril (CB5) and cucurbit[7]uril (CB7) has been studied by UV-Vis spectroscopy and calorimetry at 25 °C whereas the structure of the complexes was investigated using time resolved fluorescence spectroscopy (TRFS) and extended X-ray absorption fine structure spectroscopy (EXAFS) in a formic acid-water mixture (50 wt%). This is the first report on the structural investigation of Eu-CBn complexes in solution. The thermodynamic data (ΔG, ΔH and ΔS) for Eu(III) complexation with CBn reveal the formation of a 1 : 1 complex with CB5, while both 1 : 1 and 1 : 2 complexes are observed with CB7. The signatures of these species are observed in ESI-MS measurements, which corroborates with the species postulated in thermodynamic studies. The complexation reactions are found to be driven by ΔS as ΔH is either small negative or positive indicating the formation of inner sphere complexes, which is in line with TRFS and EXAFS results. These studies show that Eu(III) caps one of the CB5 portals by binding with all the carbonyl groups in the 1 : 1 Eu-CB5 complex, whereas in the 1 : 1 Eu-CB7 complex, Eu(III) interacts with only a few of the carbonyl groups of CB7. The computational studies (DFT calculations) on Eu-CB5 and Eu-CB7 complexes further support the experimental data.

  19. 14 CFR 25.865 - Fire protection of flight controls, engine mounts, and other flight structure.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Design and Construction Fire Protection § 25.865 Fire protection of flight controls, engine mounts, and other flight structure. Essential flight controls, engine mounts, and other flight structures located in... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Fire protection of flight controls,...

  20. 14 CFR 25.865 - Fire protection of flight controls, engine mounts, and other flight structure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Design and Construction Fire Protection § 25.865 Fire protection of flight controls, engine mounts, and other flight structure. Essential flight controls, engine mounts, and other flight structures located in... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Fire protection of flight controls,...

  1. 14 CFR 25.865 - Fire protection of flight controls, engine mounts, and other flight structure.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Design and Construction Fire Protection § 25.865 Fire protection of flight controls, engine mounts, and other flight structure. Essential flight controls, engine mounts, and other flight structures located in... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Fire protection of flight controls,...

  2. 14 CFR 25.865 - Fire protection of flight controls, engine mounts, and other flight structure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Design and Construction Fire Protection § 25.865 Fire protection of flight controls, engine mounts, and other flight structure. Essential flight controls, engine mounts, and other flight structures located in... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Fire protection of flight controls,...

  3. 14 CFR 25.865 - Fire protection of flight controls, engine mounts, and other flight structure.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Design and Construction Fire Protection § 25.865 Fire protection of flight controls, engine mounts, and other flight structure. Essential flight controls, engine mounts, and other flight structures located in... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Fire protection of flight controls,...

  4. Structural and thermochemical Aspects of (III-V)IV3 Material Assembly from First Principles

    NASA Astrophysics Data System (ADS)

    Chizmeshya, Andrew; Kouvetakis, John

    2014-03-01

    Alloys with (III-V)-(IV) compositions, including Si3(AlP), Si5-2y(AlP)y, Si3Al(As1-xNx), Si5-2yAl(P1-xNx)y and Ge5-2y(InP)y and have recently been synthesized as mono-crystalline films on Si substrates, using a synthesis route specifically designed to avoid phase separation between the III-V and IV constituents. Molecular ``building blocks'' containing group-V-centered III-V-IV3 cores, formed via interactions of group-III atoms and reactive silyly/germyl hydride precursors of desired composition (e.g, P(SiH3)3 , P(GeH3)3 , etc), assemble to form stable, covalent, diamond-like materials with the inherent tetrahedral symmetry and composition of the III-V-IV3 units. The resulting systems may provide access to a broad range of new semiconductor systems with extended optoelectronic properties, provided that the required molecular sources are available, the thermodynamic processes are viable, and the resulting alloy composition can be tuned to lattice-match the growth substrate. Molecular/solid-state simulations are used to identify promising synthetic pathways and guide the epitaxial creation of new (III-V)-(IV) materials. The thermodynamics of gas phase synthesis reactions, energetic stability of the alloys, and their epitaxial/chemical compatibility with the substrate are combined to form a global figure of merit. The latter corroborates the synthesis of known systems and predicts that formation of GaPSi3/Si(100), GaAsSi3/SiGe(100), AlPGe3/Ge(100) and InAsSi3/Ge(100) may also be favorable. Supported by NSF-DMR under SusChEM award #1309090.

  5. Weibull-Based Design Methodology for Rotating Aircraft Engine Structures

    NASA Technical Reports Server (NTRS)

    Zaretsky, Erwin; Hendricks, Robert C.; Soditus, Sherry

    2002-01-01

    The NASA Energy Efficient Engine (E(sup 3)-Engine) is used as the basis of a Weibull-based life and reliability analysis. Each component's life and thus the engine's life is defined by high-cycle fatigue (HCF) or low-cycle fatigue (LCF). Knowing the cumulative life distribution of each of the components making up the engine as represented by a Weibull slope is a prerequisite to predicting the life and reliability of the entire engine. As the engine Weibull slope increases, the predicted lives decrease. The predicted engine lives L(sub 5) (95 % probability of survival) of approximately 17,000 and 32,000 hr do correlate with current engine maintenance practices without and with refurbishment. respectively. The individual high pressure turbine (HPT) blade lives necessary to obtain a blade system life L(sub 0.1) (99.9 % probability of survival) of 9000 hr for Weibull slopes of 3, 6 and 9, are 47,391 and 20,652 and 15,658 hr, respectively. For a design life of the HPT disks having probable points of failure equal to or greater than 36,000 hr at a probability of survival of 99.9 %, the predicted disk system life L(sub 0.1) can vary from 9,408 to 24,911 hr.

  6. Structural investigations of Pu{sup III} phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    SciTech Connect

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J.M.; Somers, Joseph

    2015-10-15

    PuPO{sub 4} was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β{sup −} decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state {sup 31}P NMR agrees with the XANES results and the presence of a solid-solution. - Graphical abstract: A full structural analysis of PuPO{sub 4} based on Rietveld analysis of room temperature X-ray diffraction data, XANES and MAS NMR measurements was performed. - Highlights: • The crystal structure of PuPO{sub 4} monazite is solved. • In PuPO{sub 4} plutonium is strictly trivalent. • The presence of a minute amount of Am{sup III} is highlighted. • We propose PuPO{sub 4} as a potential reference material for spectroscopic and microscopic studies.

  7. Band structure effects on resonant tunneling in III-V quantum wells versus two-dimensional vertical heterostructures

    NASA Astrophysics Data System (ADS)

    Campbell, Philip M.; Tarasov, Alexey; Joiner, Corey A.; Ready, W. Jud; Vogel, Eric M.

    2016-01-01

    Since the invention of the Esaki diode, resonant tunneling devices have been of interest for applications including multi-valued logic and communication systems. These devices are characterized by the presence of negative differential resistance in the current-voltage characteristic, resulting from lateral momentum conservation during the tunneling process. While a large amount of research has focused on III-V material systems, such as the GaAs/AlGaAs system, for resonant tunneling devices, poor device performance and device-to-device variability have limited widespread adoption. Recently, the symmetric field-effect transistor (symFET) was proposed as a resonant tunneling device incorporating symmetric 2-D materials, such as transition metal dichalcogenides (TMDs), separated by an interlayer barrier, such as hexagonal boron-nitride. The achievable peak-to-valley ratio for TMD symFETs has been predicted to be higher than has been observed for III-V resonant tunneling devices. This work examines the effect that band structure differences between III-V devices and TMDs has on device performance. It is shown that tunneling between the quantized subbands in III-V devices increases the valley current and decreases device performance, while the interlayer barrier height has a negligible impact on performance for barrier heights greater than approximately 0.5 eV.

  8. Crystal structure and investigation of phase transitions in hexa (2 amino-indolinium) dodécachlorobithallate(III) and quinolinium tetrachlorothallate(III)

    NASA Astrophysics Data System (ADS)

    Chaari, Najla; Hamdi, Besma; Chaabouni, Slaheddine; Chniba-Boudjada, Nassira; Bordet, Pierre

    2007-12-01

    Two new thallium containing salts with different aryl ammonium cations have been prepared and characterized by X-ray crystallography, infrared spectroscopy and dielectric measurements. The salt [C 8N 2H 8] 6Tl 2Cl 12 (1) crystallizes in the monoclinic system with space group Pn. The unit cell dimensions are: a = 15.120(5), b = 11.825(5), c = 17.167(5) Å, β = 104.460(5)° with Z = 2, Dcalcd = 1.818 g cm -3, R = 0.0369. The structure consists of 2 amino-indolinium cations and monomeric TlCl63- anions. The TlCl63- has a strongly octahedral geometry presenting five short and one long (Tl1-Cl13 = 2.739(5) and Tl2-Cl26 = 2.684(5) Å) Tl-Cl bonds. The presence of multiple hydrogen bonds is considered to be responsible for the octahedral distortion. However, the second compound [C 9H 8N]TlCl 4 (2) crystallizes in the Pna2 1 orthorhombic space group, with a = 9.253(1), b = 9.799(1), c = 14.558(2) Å, Z = 4, Dcalcd = 2.397 g cm -3, R = 0.0608. The structure of the quinolinium tetrachlorothallate(III) is characterized by tetracoordinate thallium, forming a regular tetrahedral TlCl 4 with Tl-Cl distances between 2.366(2) and 2.451(3) Å. The structure consists of quinolinium cations separating chains of TlCl4- tetrahedra, these chains being perpendicular to the c axis. Infrared spectra confirm the presence of the organic cations. Differential scanning calorimetry study was carried out. Electrical measurements were performed to discuss the mechanism of the phase transition.

  9. Partitioning the effects of an ecosystem engineer: kangaroo rats control community structure via multiple pathways.

    PubMed

    Prugh, Laura R; Brashares, Justin S

    2012-05-01

    1. Ecosystem engineers impact communities by altering habitat conditions, but they can also have strong effects through consumptive, competitive and other non-engineering pathways. 2. Engineering effects can lead to fundamentally different community dynamics than non-engineering effects, but the relative strengths of these interactions are seldom quantified. 3. We combined structural equation modelling and exclosure experiments to partition the effects of a keystone engineer, the giant kangaroo rat (Dipodomys ingens), on plants, invertebrates and vertebrates in a semi-arid California grassland. 4. We separated the effects of burrow creation from kangaroo rat density and found that kangaroo rats increased the diversity and abundance of other species via both engineering and non-engineering pathways. 5. Engineering was the primary factor structuring plant and small mammal communities, whereas non-engineering effects structured invertebrate communities and increased lizard abundance. 6. These results highlight the importance of the non-engineering effects of ecosystem engineers and shed new light on the multiple pathways by which strong-interactors shape communities.

  10. Composition and structure of Fe(III)-precipitates formed by Fe(II) oxidation in water at near-neutral pH: Interdependent effects of phosphate, silicate and Ca

    NASA Astrophysics Data System (ADS)

    Senn, Anna-Caterina; Kaegi, Ralf; Hug, Stephan J.; Hering, Janet G.; Mangold, Stefan; Voegelin, Andreas

    2015-08-01

    We studied the interdependent effects of phosphate, silicate and Ca on the formation of Fe(III)-precipitates by oxidation of 0.5 mM Fe(II) in near-neutral bicarbonate-buffered aqueous solutions at concentrations relevant for natural water resources. Complementary results obtained by a suite of analytical techniques including X-ray absorption spectroscopy and transmission electron microscopy showed that the ratio of initially dissolved phosphate over Fe(II) ((P/Fe)init) had a major impact on precipitate formation. At (P/Fe)init above a critical ratio ((P/Fe)crit) of ∼0.5 in 8 mM NaHCO3 and ∼0.8 in 4 mM Ca(HCO3)2 electrolyte, Fe(II) oxidation led to exclusive formation of amorphous basic Fe(III)-phosphate or Ca-Fe(III)-phosphate ((Ca-)Fe(III)-phosphate) with maximum precipitate P/Fe ratios ((P/Fe)ppt) of ∼0.7 in Na and ∼1.1 in Ca electrolyte. Enhanced phosphate uptake in the presence of Ca was due to phosphate-Ca interactions coupled to Fe precipitation, mainly formation of mitridatite-like Ca-Fe(III)-phosphate polymers and Ca-phosphate polymers. At (P/Fe)init < (P/Fe)crit, in the absence of silicate, (Ca-)Fe(III)-phosphate precipitation was followed by the formation of poorly crystalline lepidocrocite and concomitant transformation of the (Ca-)Fe(III)-phosphate into a phosphate-rich ferrihydrite-type precipitate with a (P/Fe)ppt of ∼0.25. In the presence of 0.5 mM silicate, initially formed (Ca-)Fe(III)-phosphate nanoparticles became coated with silicate-rich ferrihydrite during continuing Fe(II) oxidation and only limited transformation of the (Ca-)Fe(III)-phosphate occurred. The results from this study indicate the complexity of Fe(III)-precipitate formation in the presence of interfering solutes and its consequences for precipitate structure and phosphate sequestration. The findings provide a solid basis for further studies of the reactivity of different Fe(III)-precipitate types and for the systematic assessment of their impact on Fe, phosphate and

  11. River valley construction as hazard for engineering structure

    NASA Astrophysics Data System (ADS)

    Postolenko, Galina

    2010-05-01

    It is common knowledge that for designing of engineering structure at river valleys it is necessary to investigate base of dam rock with a view to find out the structure disposition and nature of bottom rocks. It is important with relation to structural and economic calculation. One object of that investigation is alluvium. At present due to achievement of large success in geomorphology it is known that river valleys are constructed very complex. They have buried alluvium. Buried alluvium one can find both in plain and mountain valleys. It differs by thickness, composition and age. Since the Quaternary geological body is local, it is very important to know its chronological successive rise and the regularity of its spatial disposal. The investigative base consists in the stratigraphic and genetic research of the mellow deposit. Earlier the chronological determination depended on the hypsometric criteria . Complex of geomorphologic, biostratigraphic, lithologic, and physical data established the history of relief development and the spatial distribution of different age and genetic homogeneous relief fragments and sediment. These data show that relief and correlative sediment are formed as a result of the complex cyclical, non-one-trend geomorphologic processes at the Quaternary period. The several stages of relief and sediment development are established at the Quaternary period. They differed in process intensity, character and duration. This is the cause that the morpholithogenetic results of these stages are different. These are different sizes of valleys deepening and increasing of the relief height amplitude at the instructive stage, the different correlative sediment capacity at the constructive stage of relief development. These indexes are so significant, that river terraces of something stages turned out buried by the alluvium those stages that have the smaller alluvium capacity. Consequences of such valleys development lie in

  12. Two-dimensional NMR studies of squash family inhibitors. Sequence-specific proton assignments and secondary structure of reactive-site hydrolyzed Cucurbita maxima trypsin inhibitor III

    SciTech Connect

    Krisnamoorthi, R.; Yuxi Gong; Chanlan Sun Lin ); VanderVelde, D. )

    1992-01-28

    The solution structure of reactive-site hydrolyzed Cucurbita maxima trypsin inhibitor III (CMTI-III*) was investigated by two-dimensional proton nuclear magnetic resonance (2D NMR) spectroscopy. CMTI-III*, prepared by reacting CMTI-III with trypsin which cleaved the Arg5-Ile6 peptide bond, had the two fragments held together by a disulfide linkage. Sequence-specific {sup 1}H NMR resonance assignments were made for all the 29 amino acid residues of the protein. The secondary structure of CMTI-III*, as deduced from NOESY cross peaks and identification of slowly exchanging hydrogens, contains two turns, a 3{sub 10}-helix, and a triple-stranded {beta}-sheet. Sequential proton assignments were also made for the virgin inhibitor, CMTI-III, at pH 4.71, 30C. Comparison of backbone hydrogen chemical shifts of CMTI-III and CMTI-III* revealed significant changes for residues located far away from the reactive-site region as well as for those located near it, indicating tertiary structural changes that are transmitted through most of the 29 residues of the inhibitor protein. These chemical shift changes were relatively small compared to changes that occurred upon hydrolysis of the reactive-site peptide bond between Arg 5 and Ile6 in CMTI-III.

  13. Status of ASME Section III Task Group on Graphite Support Core Structures

    SciTech Connect

    Robert L. Bratton; Tim D. Burchell

    2005-08-01

    This report outlines the roadmap that the ASME Project Team on Graphite Core Supports is pursuing to establish design codes for unirradiated and irradiated graphite core components during its first year of operation. It discusses the deficiencies in the proposed Section III, Division 2, Subsection CE graphite design code and the different approaches the Project Team has taken to address those deficiencies.

  14. Monolithic III-V on Silicon Plasmonic Nanolaser Structure for Optical Interconnects

    NASA Astrophysics Data System (ADS)

    Li, Ning; Liu, Ke; Sorger, Volker J.; Sadana, Devendra K.

    2015-09-01

    Monolithic integration of III-V semiconductor lasers with Si circuits can reduce cost and enhance performance for optical interconnects dramatically. We propose and investigate plasmonic III-V nanolasers as monolithically integrated light source on Si chips due to many advantages. First, these III-V plasmonic light sources can be directly grown on Si substrates free of crystallographic defects due to the submicron cavity footprint (250 nm × 250 nm) being smaller than the average defect free region size of the heteroepitaxial III-V material on Si. Secondly, the small lateral and vertical dimensions facilitate process co-integration with Si complementary metal-oxide-semiconductor (CMOS) in the front end of the line. Thirdly, combining with monolithically integrated CMOS circuits with low device capacitance and parasitic capacitance, the nano-cavity optoelectronic devices consume orders of magnitude less power than the conventional lasers and reduce the energy consumption. Fourthly, the modulation bandwidth of the plasmonic light-sources is enhanced to significantly higher than conventional lasers due to enhanced photon state density and transition rate. In addition, we show that these device performance are very robust after taking into account the surface recombination and variations in device fabrication processes.

  15. Structure and membrane remodeling activity of ESCRT-III helical polymers

    PubMed Central

    McCullough, John; Clippinger, Amy K.; Talledge, Nathaniel; Skowyra, Michael L.; Saunders, Marissa G.; Naismith, Teresa V.; Colf, Leremy A.; Afonine, Pavel; Arthur, Christopher; Sundquist, Wesley I.; Hanson, Phyllis I.; Frost, Adam

    2015-01-01

    The Endosomal Sorting Complexes Required for Transport (ESCRT) proteins mediate fundamental membrane remodeling events that require stabilizing negative membrane curvature. These include endosomal intralumenal vesicle formation, HIV budding, nuclear envelope closure and cytokinetic abscission. ESCRT-III subunits perform key roles in these processes by changing conformation and polymerizing into membrane-remodeling filaments. Here, we report the 4 Å resolution cryo-EM reconstruction of a one-start, double-stranded helical copolymer composed of two different human ESCRT-III subunits, CHMP1B and IST1. The inner strand comprises “open” CHMP1B subunits that interlock in an elaborate domain-swapped architecture, and is encircled by an outer strand of “closed” IST1 subunits. Unlike other ESCRT-III proteins, CHMP1B and IST1 polymers form external coats on positively-curved membranes in vitro and in vivo. Our analysis suggests how common ESCRT-III filament architectures could stabilize different degrees and directions of membrane curvature. PMID:26634441

  16. Structure and membrane remodeling activity of ESCRT-III helical polymers.

    PubMed

    McCullough, John; Clippinger, Amy K; Talledge, Nathaniel; Skowyra, Michael L; Saunders, Marissa G; Naismith, Teresa V; Colf, Leremy A; Afonine, Pavel; Arthur, Christopher; Sundquist, Wesley I; Hanson, Phyllis I; Frost, Adam

    2015-12-18

    The endosomal sorting complexes required for transport (ESCRT) proteins mediate fundamental membrane remodeling events that require stabilizing negative membrane curvature. These include endosomal intralumenal vesicle formation, HIV budding, nuclear envelope closure, and cytokinetic abscission. ESCRT-III subunits perform key roles in these processes by changing conformation and polymerizing into membrane-remodeling filaments. Here, we report the 4 angstrom resolution cryogenic electron microscopy reconstruction of a one-start, double-stranded helical copolymer composed of two different human ESCRT-III subunits, charged multivesicular body protein 1B (CHMP1B) and increased sodium tolerance 1 (IST1). The inner strand comprises "open" CHMP1B subunits that interlock in an elaborate domain-swapped architecture and is encircled by an outer strand of "closed" IST1 subunits. Unlike other ESCRT-III proteins, CHMP1B and IST1 polymers form external coats on positively curved membranes in vitro and in vivo. Our analysis suggests how common ESCRT-III filament architectures could stabilize different degrees and directions of membrane curvature.

  17. Structure and membrane remodeling activity of ESCRT-III helical polymers

    DOE PAGES

    McCullough, John; Clippinger, Amy K.; Talledge, Nathaniel; Skowyra, Michael L.; Saunders, Marissa G.; Naismith, Teresa V.; Colf, Leremy A.; Afonine, Pavel; Arthur, Christopher; Sundquist, Wesley I.; et al

    2015-12-18

    The endosomal sorting complexes required for transport (ESCRT) proteins mediate fundamental membrane remodeling events that require stabilizing negative membrane curvature. These include endosomal intralumenal vesicle formation, HIV budding, nuclear envelope closure, and cytokinetic abscission. ESCRT-III subunits perform key roles in these processes by changing conformation and polymerizing into membrane-remodeling filaments. Here, we report the 4 angstrom resolution cryogenic electron microscopy reconstruction of a one-start, double-stranded helical copolymer composed of two different human ESCRT-III subunits, charged multivesicular body protein 1B (CHMP1B) and increased sodium tolerance 1 (IST1). The inner strand comprises “open” CHMP1B subunits that interlock in an elaborate domain-swapped architecturemore » and is encircled by an outer strand of “closed” IST1 subunits. Unlike other ESCRT-III proteins, CHMP1B and IST1 polymers form external coats on positively curved membranes in vitro and in vivo. In conclusion, our analysis suggests how common ESCRT-III filament architectures could stabilize different degrees and directions of membrane curvature.« less

  18. Structure and membrane remodeling activity of ESCRT-III helical polymers

    SciTech Connect

    McCullough, John; Clippinger, Amy K.; Talledge, Nathaniel; Skowyra, Michael L.; Saunders, Marissa G.; Naismith, Teresa V.; Colf, Leremy A.; Afonine, Pavel; Arthur, Christopher; Sundquist, Wesley I.; Hanson, Phyllis I.; Frost, Adam

    2015-12-18

    The endosomal sorting complexes required for transport (ESCRT) proteins mediate fundamental membrane remodeling events that require stabilizing negative membrane curvature. These include endosomal intralumenal vesicle formation, HIV budding, nuclear envelope closure, and cytokinetic abscission. ESCRT-III subunits perform key roles in these processes by changing conformation and polymerizing into membrane-remodeling filaments. Here, we report the 4 angstrom resolution cryogenic electron microscopy reconstruction of a one-start, double-stranded helical copolymer composed of two different human ESCRT-III subunits, charged multivesicular body protein 1B (CHMP1B) and increased sodium tolerance 1 (IST1). The inner strand comprises “open” CHMP1B subunits that interlock in an elaborate domain-swapped architecture and is encircled by an outer strand of “closed” IST1 subunits. Unlike other ESCRT-III proteins, CHMP1B and IST1 polymers form external coats on positively curved membranes in vitro and in vivo. In conclusion, our analysis suggests how common ESCRT-III filament architectures could stabilize different degrees and directions of membrane curvature.

  19. [NH2(C2H4)2O]MX5: a new family of morpholinium nonlinear optical materials among halogenoantimonate(III) and halogenobismuthate(III) compounds. Structural characterization, dielectric and piezoelectric properties.

    PubMed

    Owczarek, Magdalena; Szklarz, Przemysław; Jakubas, Ryszard; Miniewicz, Andrzej

    2012-06-28

    This paper presents the structural features of ionic complexes formed by morpholine and metal ions which belong to group VA, namely Sb(III) and Bi(III). A series of target inorganic-organic hybrid compounds of the general formula [NH(2)(C(2)H(4))(2)O](2)MX(5) (where M = Sb, Bi; X = Cl, Br) has been synthesized by incorporating the organic component (morpholine) into the highly polarizable one-dimensional halogenoantimonate(III)/halogenobismuthate(III) chain network. Among the studied compounds, four were found to crystallize in the room temperature phase in the piezoelectric, orthorhombic space group P2(1)2(1)2(1), Z = 4, the feature being confirmed by the powder second harmonic generation of light and piezoelectric measurements. Dielectric dispersion studies between 200 Hz and 2 MHz disclosed a relaxation process below room temperature well described by the Cole-Cole equation. Based on crystal structures available in Cambridge Structural Database (version 5.32, November 2010) we attempt to show a relationship between the acentric symmetry of compounds and the type of anionic network within the R(2)MX(5)-subgroup (where R denotes organic cation) of halogenoantimonates(III) and halogenobismuthates(III).

  20. Engineering, construction, and operations in space - III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vols. 1 & 2

    NASA Technical Reports Server (NTRS)

    Sadeh, Willy Z. (Editor); Sture, Stein (Editor); Miller, Russell J. (Editor)

    1992-01-01

    The present volume on engineering, construction, and operations in space discusses surface structures on the moon and Mars, surface equipment, construction, and transportation on the moon and Mars, in situ materials use and processing, and space energy. Attention is given to such orbital structures as LEO and the space station, space mining and excavation, space materials, space automation and robotics, and space life support systems. Topics addressed include lunar-based astronomy, space systems integration, terrestrial support for space functions, and space education. Also discussed are space plans, policy, and history, space science and engineering, geoengineering and space exploration, and the construction and development of a human habitat on Mars.

  1. Defect-free zinc-blende structured InAs nanowires realized by in situ two V/III ratio growth in molecular beam epitaxy.

    PubMed

    Zhang, Zhi; Lu, Zhen-Yu; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2015-08-01

    In this study, we devised a two-V/III-ratio procedure to control the Au-assisted growth of defect-free InAs nanowires in molecular beam epitaxy. The demonstrated two V/III ratio procedure consists of a first high V/III ratio growth step to prepare the nanowire foundation on the substrate surface, followed by a low V/III ratio step to induce the nanowire growth. By manipulating the V/III ratios in different steps, we have achieved the controlled growth of pure defect-free zinc-blende structured InAs nanowires on the GaAs {1̄1̄1̄} substrates. This study provides an approach to control not only the crystal structure of semiconductor nanowires, but also their structural qualities.

  2. Main group bismuth(III), gallium(III) and diorganotin(IV) complexes derived from bis(2-acetylpyrazine)thiocarbonohydrazone: synthesis, crystal structures and biological evaluation.

    PubMed

    Zhang, Nan; Tai, Yanxue; Li, Mingxue; Ma, Pengtao; Zhao, Junwei; Niu, Jingyang

    2014-04-01

    Up to now, the metal complexes with thiocarbonohydrazones have been comparatively rare. Herein, three main group monometallic complexes formulated as [Bi(HL)(NO3)2(H2O)] (1), [Ga(HL)2]OAc·EtOH (2) and [(Ph)2Sn(HL)(OAc)]·DMF (3), where H2L = bis(2-acetylpyrazine)thiocarbonohydrazone, have been synthesized and characterized. The crystal structures of complexes 2 and 3 have been determined by single-crystal X-ray diffraction. Growth inhibition assays have indicated that both the free ligand and the title complexes are capable of inhibiting cell proliferation growth and could slightly distinguish the human hepatocellular carcinoma HepG2 cells from normal hepatocyte QSG7701 cells. Of particular note is the fact that the bismuth(III) complex 1 is the most active compound of this study and is 14-fold more cytotoxic than H2L with an IC50 value of 2.96 ± 0.25 μM. Its possible apoptotic mechanism has been evaluated in HepG2 cells. Complex 1 promotes a dose-dependent apoptosis in HepG2 cells and the apoptosis is associated with an increase in intracellular reactive oxygen species (ROS) production and reduction of mitochondrial membrane potential (MMP).

  3. Structural basis for the endoribonuclease activity of the type III-A CRISPR-associated protein Csm6

    PubMed Central

    Niewoehner, Ole; Jinek, Martin

    2016-01-01

    Prokaryotic CRISPR–Cas systems provide an RNA-guided mechanism for genome defense against mobile genetic elements such as viruses and plasmids. In type III-A CRISPR–Cas systems, the RNA-guided multisubunit Csm effector complex targets both single-stranded RNAs and double-stranded DNAs. In addition to the Csm complex, efficient anti-plasmid immunity mediated by type III-A systems also requires the CRISPR-associated protein Csm6. Here we report the crystal structure of Csm6 from Thermus thermophilus and show that the protein is a ssRNA-specific endoribonuclease. The structure reveals a dimeric architecture generated by interactions involving the N-terminal CARF and C-terminal HEPN domains. HEPN domain dimerization leads to the formation of a composite ribonuclease active site. Consistently, mutations of invariant active site residues impair catalytic activity in vitro. We further show that the ribonuclease activity of Csm6 is conserved across orthologs, suggesting that it plays an important functional role in CRISPR–Cas systems. The dimer interface of the CARF domains features a conserved electropositive pocket that may function as a ligand-binding site for allosteric control of ribonuclease activity. Altogether, our work suggests that Csm6 proteins provide an auxiliary RNA-targeting interference mechanism in type III-A CRISPR–Cas systems that operates in conjunction with the RNA- and DNA-targeting endonuclease activities of the Csm effector complex. PMID:26763118

  4. Structural Studies of E. coli Topoisomerase III-DNA Complexes Reveal a Novel Type IA Topoisomerase-DNA Conformational Intermediate

    SciTech Connect

    Changela, Anita; DiGate, Russell J.; Mondragon, Alfonso

    2010-03-05

    Escherichia coli DNA topoisomerase III belongs to the type IA family of DNA topoisomerases, which transiently cleave single-stranded DNA (ssDNA) via a 5{prime} phosphotyrosine intermediate. We have solved crystal structures of wild-type E. coli topoisomerase III bound to an eight-base ssDNA molecule in three different pH environments. The structures reveal the enzyme in three distinct conformational states while bound to DNA. One conformation resembles the one observed previously with a DNA-bound, catalytically inactive mutant of topoisomerase III where DNA binding realigns catalytic residues to form a functional active site. Another conformation represents a novel intermediate in which DNA is bound along the ssDNA-binding groove but does not enter the active site, which remains in a catalytically inactive, closed state. A third conformation shows an intermediate state where the enzyme is still in a closed state, but the ssDNA is starting to invade the active site. For the first time, the active site region in the presence of both the catalytic tyrosine and ssDNA substrate is revealed for a type IA DNA topoisomerase, although there is no evidence of ssDNA cleavage. Comparative analysis of the various conformational states suggests a sequence of domain movements undertaken by the enzyme upon substrate binding.

  5. Crystal structure of [(1,2,3,4,11,12-η)-anthracene]tris-(tri-methyl-stann-yl)cobalt(III).

    PubMed

    Brennessel, William W; Ellis, John E

    2014-11-01

    The asymmetric unit of the title structure, [Co(η(6)-C14H10){Sn(CH3)3}3], contains two independent mol-ecules. Each anthracene ligand is η(6)-coordinating to a Co(III) cation and is nearly planar [fold angles of 5.4 (3) and 9.7 (3)°], as would be expected for its behaving almost entirely as a donor to a high-oxidation-state metal center. The slight fold in each anthracene ligand gives rise to slightly longer Co-C bond lengths to the ring junction carbon atoms than to the other four. Each Co(III) cation is further coordinated by three Sn(CH3)3 ligands, giving each mol-ecule a three-legged piano-stool geometry. In each of the two independent mol-ecules, the trio of SnMe3 ligands are modeled as disordered over two positions, rotated by approximately 30%, such that the C atoms nearly overlap. In one mol-ecule, the disorder ratio refined to 0.9365 (8):0.0635 (8), while that for the other refined to 0.9686 (8):0.0314 (8). The mol-ecules are well separated, and thus no significant inter-molecular inter-actions are observed. The compound is of inter-est as the first structure report of an η(6)-anthracene cobalt(III) complex. PMID:25484731

  6. Structural and photophysical studies on gallium(III) 8-hydroxyquinoline-5-sulfonates. Does excited state decay involve ligand photolabilisation?

    PubMed

    Ramos, M Luísa; de Sousa, Andreia R E; Justino, Licínia L G; Fonseca, Sofia M; Geraldes, Carlos F G C; Burrows, Hugh D

    2013-03-14

    Multinuclear ((1)H, (13)C and (71)Ga) magnetic resonance spectroscopy (1D and 2D), DFT calculations and luminescence techniques have been used to study 8-hydroxyquinoline-5-sulfonate (8-HQS) and its complexes with Ga(III) in aqueous solutions. The study combines the high sensitivity of luminescence techniques and the selectivity of multinuclear NMR spectroscopy with the structural details accessible through DFT calculations, and aims to obtain a complete understanding of the complexation between the Ga(3+) ion and 8-HQS, and how this influences the luminescence behaviour. A full speciation study has been performed on this system and three complexes detected, with (metal : ligand) 1 : 1, 1 : 2 and 1 : 3 stoichiometries, the results being consistent with those previously found for the system Al(III)-8-HQS. Complexation in these systems is relevant to their potential biomedical, sensing and optoelectronic applications. On binding to Ga(III), a marked increase is seen in the intensity of the 8-HQS fluorescence band, which is accompanied by changes in the absorption spectra. These support the use of 8-HQS as a sensitive fluorescent sensor to detect Ga(3+) metal ions in surface waters, biological fluids, etc., and its metal complexes as an emitting or charge transport layer in light emitting devices. However, the fluorescence quantum yield of the Ga(III)-8-HQS 1 : 3 complex is about 35% of that of the corresponding system with Al(III). Although this may be due in part to a heavy atom effect favouring S(1)→ T(1) intersystem crossing with Ga(3+), this does not agree with transient absorption measurements on the triplet state yield, which is lower with the Ga(III) system than with Al(III). Instead, it is suggested that photolabilisation of ligand exchange plays a major role in nonradiative decay of the excited state and that this is more efficient with the Ga(3+) complex. Based on these results, suggestions are made of ways of enhancing fluorescence

  7. Structural and photophysical studies on gallium(III) 8-hydroxyquinoline-5-sulfonates. Does excited state decay involve ligand photolabilisation?

    PubMed

    Ramos, M Luísa; de Sousa, Andreia R E; Justino, Licínia L G; Fonseca, Sofia M; Geraldes, Carlos F G C; Burrows, Hugh D

    2013-03-14

    Multinuclear ((1)H, (13)C and (71)Ga) magnetic resonance spectroscopy (1D and 2D), DFT calculations and luminescence techniques have been used to study 8-hydroxyquinoline-5-sulfonate (8-HQS) and its complexes with Ga(III) in aqueous solutions. The study combines the high sensitivity of luminescence techniques and the selectivity of multinuclear NMR spectroscopy with the structural details accessible through DFT calculations, and aims to obtain a complete understanding of the complexation between the Ga(3+) ion and 8-HQS, and how this influences the luminescence behaviour. A full speciation study has been performed on this system and three complexes detected, with (metal : ligand) 1 : 1, 1 : 2 and 1 : 3 stoichiometries, the results being consistent with those previously found for the system Al(III)-8-HQS. Complexation in these systems is relevant to their potential biomedical, sensing and optoelectronic applications. On binding to Ga(III), a marked increase is seen in the intensity of the 8-HQS fluorescence band, which is accompanied by changes in the absorption spectra. These support the use of 8-HQS as a sensitive fluorescent sensor to detect Ga(3+) metal ions in surface waters, biological fluids, etc., and its metal complexes as an emitting or charge transport layer in light emitting devices. However, the fluorescence quantum yield of the Ga(III)-8-HQS 1 : 3 complex is about 35% of that of the corresponding system with Al(III). Although this may be due in part to a heavy atom effect favouring S(1)→ T(1) intersystem crossing with Ga(3+), this does not agree with transient absorption measurements on the triplet state yield, which is lower with the Ga(III) system than with Al(III). Instead, it is suggested that photolabilisation of ligand exchange plays a major role in nonradiative decay of the excited state and that this is more efficient with the Ga(3+) complex. Based on these results, suggestions are made of ways of enhancing fluorescence

  8. Two- and three-dimensional networks of gadolinium(III) with dicarboxylate ligands: synthesis, crystal structure, and magnetic properties.

    PubMed

    Cañadillas-Delgado, Laura; Pasan, Jorge; Fabelo, Oscar; Hernandez-Molina, María; Lloret, Francesc; Julve, Miguel; Ruiz-Pérez, Catalina

    2006-12-25

    Four gadolinium(III) complexes with dicarboxylate ligands of formulas [Gd2(mal)3(H2O)5]n.2nH2O (1), [Gd2(mal)3(H2O)6]n (2), [NaGd(mal)(ox)(H2O)3]n (3), and [Gd2(ox)3(H2O)6]n.2.5nH2O (4) (mal = malonate; ox = oxalate) have been prepared, and their magnetic properties have been investigated as a function of the temperature. The structures of 1-3 have been determined by X-ray diffraction methods. The crystal structure of 4 was already known, and it is made of hexagonal layers of Gd atoms that are bridged by bis-bidentate oxalate. Compound 1 is isostructural with the europium(III) malonate complex [Eu2(mal)3(H2O)5]n.2nH2O,1 whose structure was reported elsewhere. The Gd atoms in 1 define a two-dimensional network where a terminal bidentate and bridging bidentate/bis-monodentate and tris-bidentate coordination modes of malonate occur. Compound 2 has a three-dimensional structure with a structural phase transition at 226 K, which involves a change of the space group from I2/a to Ia. Although its structure at room temperature was already known, that below 226 K was not. Pairs of Gd atoms with a double oxo-carboxylate bridge occur in both phases, and the main differences between both structures deal with the Gd environment and the H-bond pattern. 3 is also a three-dimensional compound, and it was obtained by reacting Gd(III) ions with malonic acid in a silica gel medium. Oxalic acid results as an oxidized product of the malonic acid, and single crystals of the heteroleptic complex were produced. The Gd atoms in 3 are connected through bis-bidentate oxalate and carboxylate-malonate bridges in the anti-anti and anti-syn coordination modes. Compounds 1 and 2 exhibit weak but significant ferromagnetic couplings between the Gd(III) ions through the single (1) and double (2) oxo-carboxylate bridges, whereas antiferromagnetic interactions across the bis-bidentate oxalate account for the overall antiferromagnetic behavior observed in 3 and 4.

  9. Structured system engineering methodologies used to develop a nuclear thermal propulsion engine

    NASA Technical Reports Server (NTRS)

    Corban, R.; Wagner, R.

    1993-01-01

    To facilitate the development of a space nuclear thermal propulsion engine for manned flights to Mars, requirements must be established early in the technology development cycle. The long lead times for the acquisition of the engine system and nuclear test facilities demands that the engine system size, performance and safety goals be defined at the earliest possible time. These systems are highly complex and require a large multidisciplinary systems engineering team to develop and track requirements, and to ensure that the as-built system reflects the intent of the mission. A methodology has been devised which uses sophisticated computer tools to effectively develop and interpret functional requirements, and furnish these to the specification level for implementation.

  10. Fundamentals of the Control of Gas-Turbine Power Plants for Aircraft. Part III Control of Jet Engines. Part 3; Control of Jet Engines

    NASA Technical Reports Server (NTRS)

    Kuehl, H.

    1947-01-01

    The basic principles of the control of TL ongincs are developed on .the basis of a quantitative investigation of the behavior of these behavior under various operating conditions with particular consideration of the simplifications pormissible in each case. Various possible means of control of jet engines are suggested and are illustrated by schematic designs.

  11. Structure and dynamics of La(III) in aqueous solution An ab initio QM/MM MD approach

    NASA Astrophysics Data System (ADS)

    Hofer, Thomas S.; Scharnagl, Harald; Randolf, Bernhard R.; Rode, Bernd M.

    2006-08-01

    Ab initio QM/MM MD simulations have allowed to clarify some of the ambiguities arising from various studies on the hydrated La(III) ion. Both nine- and ten-coordinated hydrates co-exist and interchange in a dissociative process on the nano- or even subnanosecond scale, and thus much faster than any other trivalent main group or transition metal ions. The weak ion-ligand bond (53 N/m) supplies a reasonable explanation for it. The simulation results for La(III) are also compared to those for the isoelectronic ions Cs(I) and Ba(II) obtained by the same ab initio MD procedure, leading to conclusions on the influence of central ion charge on structural and dynamic properties of hydrate complexes.

  12. Synthesis, structure and electrochemistry behavior of a cobalt(III) compound with azide and methyl 2-pyridyl ketone semicarbazone ligands

    NASA Astrophysics Data System (ADS)

    Shaabani, Behrouz; Khandar, Ali Akbar; Mahmoudi, Farzaneh; Balula, Salete S.; Cunha-Silva, Luís

    2013-08-01

    An unprecedented cobalt(III) compound with methyl 2-pyridyl ketone semicarbazone (HL) and the auxiliary azide ligand, [Co(L)2] [Co(L)(N3)3] (1) was synthesized and further characterized crystallographically and spectroscopically. Compound 1 crystallizes in the triclinic system and space group of P-1 and its structure consists of two mononuclear crystallographic units with metal chromophore comprising two cobalt(III) centers revealing distorted octahedral geometries and formed by distinct ligands in the inner coordination spheres. Interestingly, compound 1 represents the first complex formed by two distinct mononuclear units involving this ligand. As consequence of various donor and acceptor groups in both crystallographic units, there are several strong Nsbnd H⋯N and Nsbnd H⋯O hydrogen bonding interactions interconnecting adjacent moieties, ultimately leading to a three-dimensional supramolecular network. Furthermore, the electrochemical behavior of the HL and compound 1 were investigated.

  13. Advanced methods for 3-D inelastic structural analysis for hot engine structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1989-01-01

    Three-dimensional Inelastic Analysis Methods are described. These methods were incorporated into a series of new computer codes embodying a progression of mathematical models (mechanics of materials, specialty finite element, boundary element) for streamlined analysis of hot engine structures such as: (1) combustor liners, (2) turbine blades, and (3) turbine vanes. These models address the effects of high temperatures and thermal/mechanical loadings on the local (stress/strain) and global (displacements, frequencies, amplitudes, buckling) structural behavior of the three respective components. The methods and the three computer codes, referred to as MOMM (Mechanics Of Materials Model), MHOST (MARC-Hot Section Technology), and BEST3D (Boundary Element Stress Technology), have been developed and are briefly described.

  14. Molecular structure and biological studies on Cr(III), Mn(II) and Fe(III) complexes of heterocyclic carbohydrazone ligand

    NASA Astrophysics Data System (ADS)

    Abu El-Reash, G. M.; El-Gammal, O. A.; Radwan, A. H.

    2014-03-01

    The chelating behavior of the ligand (H2APC) based on carbohydrazone core modified with pyridine end towards Cr(III), Mn(II) and Fe(III) ions have been examined. The 1H NMR and IR data for H2APC revealed the presence of two stereoisomers syn and anti in both solid state and in solution in addition to the tautomeric versatility based on the flexible nature of the hydrazone linkage leading to varied coordination modes. The spectroscopic data confirmed that the ligand behaves as a monobasic tridentate in Cr(III) and Fe(III) complexes and as neutral tetradentate in Mn(II) complex. The electronic spectra as well as the magnetic measurements confirmed the octahedral geometry for all complexes. The bond length and angles were evaluated by DFT method using material studio program for all complexes. The thermal behavior and the kinetic parameters of degradation were determined using Coats-Redfern and Horowitz-Metzger methods. The antioxidant (DDPH and ABTS methods), anti-hemolytic and cytotoxic activities of the compounds have been screened. Cr(III) complex and H2APC showed the highest antioxidant activity using ABTS and DPPH methods. With respect to in vitro Ehrlich ascites assay, H2APC exhibited the potent activity followed by Fe(III) and Cr(III)complexes.

  15. Structural insights into the counterion effects on the manganese(III) spin crossover system with hexadentate Schiff-base ligands.

    PubMed

    Wang, Shi; Xu, Wu-Tan; He, Wen-Rui; Takaishi, Shinya; Li, Yong-Hua; Yamashita, Masahiro; Huang, Wei

    2016-04-01

    A series of new salts [Mn(5-MeO-sal-N-1,5,8,12)]Y (Y = ClO4 for 1, Y = BF4 for 2, Y = NO3 for 3 and Y = CF3SO3 for 4) based on the six-coordinated mononuclear manganese(iii) Schiff-base complex cation [Mn(5-MeO-sal-N-1,5,8,12)](+), has been investigated to determine the impact of counter anion effects, intramolecular ligand distortion and intermolecular supramolecular structures on the spin crossover (SCO) behavior. The SCO in salt 1 has resulted in a crystallographic observation of the coexistence of high-spin (HS, S = 2) and low-spin (LS, S = 1) manganese(iii) complex cations in equal proportions around 100 K. At room temperature, the two crystallographically distinct manganese centers are both close to the complete HS state. Only one of the two slightly different units undergoes SCO in the temperature range 300-180 K, whereas the other remains in the HS state down to 20 K. For salts 2 and 3, crystal structural analysis indicates change in the anion from ClO4(-) to BF4(-) and NO3(-) was led to the close arrangement of the cations and the stacking between phenyl groups from the ligands. With CF3SO3(-) as the counterion, although the cations and the anions separate clearly in one direction, the close arrangement of cations in other directions precludes the spin transformation of the Mn(iii) cations. Magnetic measurements on 2-4 indicate that the manganese(iii) complex cations remain in the HS state in the temperature range 2-300 K. PMID:26927027

  16. A novel Schiff base bearing dopamine groups with tripodal structure. Synthesis and its salen/salophen-bridged Fe/Cr(III) capped complexes

    NASA Astrophysics Data System (ADS)

    Kocyigit, Ozcan

    2013-02-01

    This work presents the synthesis of a novel Schiff base and its complexation properties with Fe(III) and Cr(III). A Schiff base bearing dopamine (TRDPA) was synthesized using dopamine hydrochloride and 1,3,5-tris (formylphenoxymethyl)benzene in methanol media. The prepared TRDPA was then reacted with four new trinuclear Fe(III) and Cr(III) complexes involving tetradenta Schiff bases N,N-bis(salicylidene)ethylenediamine-(salenH2) or bis(salicylidene)-o-phenylenediamine-(salophenH2). The structures of these compounds were characterized through 1H NMR, 13C NMR, FT-IR, thermal analysis (TG), elemental analysis, and magnetic susceptibility measurements. The complexes were also characterized as low-spin distorted octahedral Fe(III) and Cr(III) bridged by a catechol group.

  17. Complexation of Al(III) with gluconate in alkaline to hyperalkaline solutions: formation, stability and structure.

    PubMed

    Pallagi, Attila; Tasi, Ágost Gyula; Peintler, Gábor; Forgo, Péter; Pálinkó, István; Sipos, Pál

    2013-10-01

    Contrary to suggestions in the literature, it has been proven that Al(III) forms a 1 : 1 complex with gluconate (hereafter Gluc(-)) in strongly alkaline (pH > 12) aqueous solutions. The complex formation was proven via(27)Al and (1)H NMR, freezing-point depression, polarimetric measurements as well as potentiometric and conductometric titrations. This complexation is a pH independent process, i.e., a condensation reaction takes place. The stability constant of the complex formed was derived from (1)H NMR and polarimetric measurements, and was found to be log K = 2.4 ± 0.4. In the complex formed, Al(III) has a tetrahedral geometry, and the Al(OH)4(-) is most probably statistically distributed between the alcoholate groups of the Gluc(-). PMID:23897548

  18. Harmonic structure of decametric Type III emission and radio wave group delay in the solar corona

    NASA Astrophysics Data System (ADS)

    Abranin, Eh. P.; Bazelyan, L. L.; Tsybko, Ya. G.; Abranin, Eh. P.; Bazelyan, L. L.; Tsybko, Ya. G.

    1993-08-01

    Solar observations with the UTR-2 decameter-wave radio telescope antenna, performed continuously at fixed frequencies from 25 to 10 MHz during Type III, IIIb-III noise storms from 1979 to 1984, have yielded new data on the frequency drift rates Delta(f)/Delta(tf) of numerous type IIIF, IIIFb, and IIIH(b) decameter radio bursts in several narrow bands Delta(f). The data confirm that the burst drift rates are virtually independent of the phase of the 11-yr solar activity cycle. Measurements of the drift time intervals for bursts drifting over narow bands (25-20 and 12.5-10 MHZ) separated by an octave prove the reliability of the radio burst harmonic classification in which there is a clear differentiation between the emission components coinciding with the fundamental and the second harmonic of the local plasma frequency.

  19. Electron impact excitation of the Ne II and Ne III fine structure levels

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Loch, S. D.; Pindzola, M. S.; Cumbee, R.; Stancil, P. C.; Ballance, C. P.; McLaughlin, B. M.

    2016-05-01

    Electron impact excitation cross sections and rate coefficients of the low lying levels of the Ne II and Ne III ions are of great interest in cool molecular environments including young stellar objects, photodissociation regions, active galactic nuclei, and X-ray dominated regions. We have carried out details computations for cross sections and rate coefficients using the Dirac R-matrix codes (DARC), the Breit-Pauli R-matrix codes (BP) and the Intermediate Coupling Frame Transformation (ICFT) codes, for both Ne II and Ne III. We also compare our results with previous calculations. We are primarily interested in rate coefficients in the temperature range below 1000 K, and the focus is on obtaining the most accurate rate coefficients for those temperatures. We present both a recommended set of effective collision strengths and an indication of the uncertainties on these values. Work at Auburn University and UGA partly supported by NASA Grant NNX15AE47G.

  20. Investigating the growth, structural and electrical properties of III-V semiconductor nanopillars for the next-generation electronic and optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Lin, Andrew

    Extensive research efforts have been devoted to the study and development of III-V compound semiconductor nanowires (NWs) and nanopillars (NPs) because of their unique physical properties and ability to form high quality, highly lattice-mismatched axial and radial heterostructures. These advantages lead to precise nano-bandgap engineering to achieve new device functionalities. One unique and powerful approach to realize these NPs is by catalyst-free, selective-area epitaxy (SAE) via metal-organic chemical vapor deposition, in which the NP location and diameter can be precisely controlled lithographically. Early demonstrations of electronic and optoelectronic devices based on these NPs, however, are often inferior compared to their planar counterparts due to a few factors: (1) interface/surface states, (2) inaccurate doping calibration, and (3) increased carrier scattering and trapping from stacking fault formation in the NPs. In this study, the detailed growth mechanisms of different III-As, III-Sb and III-P NPs and their heterostructures are investigated. These NPs are then fabricated into single-NP field-effect transistors (FETs) to probe their electrical properties. It is shown that these devices are highly diameter-dependent, mainly because of the effects of surface states. By growing a high band-gap shell around the NP cores to passivate the surface, the device performance can be significantly improved. Further fabrication and characterization of vertical surround-gate FETs using a high-mobility InAs/InP NP channel is also discussed. Aside from the radial NP heterostructures, different approaches to achieve purely axial heterostructures in InAs/In(As)P materials are also presented with excellent interface quality. Both single barrier and double barrier structures are realized and fabricated into devices that show carrier transport characteristics over a barrier and even resonant tunneling behavior. Antimonide-based NPs are also studied for their immense

  1. Synthesis, structure and spectroscopic study of Rh III polypyridine complexes with phenylcyanamide derivative ligands

    NASA Astrophysics Data System (ADS)

    Hadadzadeh, Hassan; Rezvani, Ali R.; Belanger-Gariepy, Francine

    2005-04-01

    Several new Rh III complexes, [Rh(tpy)(bpy)L](PF 6) 2 (tpy=2,2':6',2″-terpyridine, bpy=2,2'-bipyridine, and L=monoanions of phenylcyanamide(pcyd)), 4-methylphenylcyanamide (4-MePcyd), 2,4-dimethylphenylcyanamide (2,4-Me 2pcyd), 4-methoxyphenylcyanamide (4-MeOPcyd), 2-chlorophenylcyanamide (2-Clpcyd) and 2,5-dichlorophenylcyanamide (2,5-Cl 2pcyd) have been synthesized and characterized by elemental analysis, IR, 1H NMR and electronic absorption spectroscopies. ORTEP drawing of [Rh(tpy)(bpy)(2,5-Cl 2pcyd)](PF 6) 2·1/2CH 3CN shows three pyridyl rings of the tpy ligand that are nearly coplanar, as are the two rings of bpy. The anionic cyanamide group is coordinated end-on by the nitrile nitrogen to the Rh III. The Rh III-NCN bond is bent, having an angle of 125.4°. This bent bond is largely determined by the σ-bonding interaction of a cyanamide non-bonding electron pair in a sp 2 hybrid orbital.

  2. III/V nano ridge structures for optical applications on patterned 300 mm silicon substrate

    NASA Astrophysics Data System (ADS)

    Kunert, B.; Guo, W.; Mols, Y.; Tian, B.; Wang, Z.; Shi, Y.; Van Thourhout, D.; Pantouvaki, M.; Van Campenhout, J.; Langer, R.; Barla, K.

    2016-08-01

    We report on an integration approach of III/V nano ridges on patterned silicon (Si) wafers by metal organic vapor phase epitaxy (MOVPE). Trenches of different widths (≤500 nm) were processed in a silicon oxide (SiO2) layer on top of a 300 mm (001) Si substrate. The MOVPE growth conditions were chosen in a way to guarantee an efficient defect trapping within narrow trenches and to form a box shaped ridge with increased III/V volume when growing out of the trench. Compressively strained InGaAs/GaAs multi-quantum wells with 19% indium were deposited on top of the fully relaxed GaAs ridges as an active material for optical applications. Transmission electron microcopy investigation shows that very flat quantum well (QW) interfaces were realized. A clear defect trapping inside the trenches is observed whereas the ridge material is free of threading dislocations with only a very low density of planar defects. Pronounced QW photoluminescence (PL) is detected from different ridge sizes at room temperature. The potential of these III/V nano ridges for laser integration on Si substrates is emphasized by the achieved ridge volume which could enable wave guidance and by the high crystal quality in line with the distinct PL.

  3. Equatorially connected diruthenium(II,III) units toward paramagnetic supramolecular structures with singular magnetic properties.

    PubMed

    Barral, M Carmen; Gallo, Teresa; Herrero, Santiago; Jiménez-Aparicio, Reyes; Torres, M Rosario; Urbanos, Francisco A

    2006-05-01

    The reaction of Ru2Cl(O2CMe)(DPhF)3 (DPhF = N,N'-diphenylformamidinate) with mono- and polycarboxylic acids gives a clean substitution of the acetate ligand, leading to the formation of complexes Ru2Cl(O2CC6H5)(DPhF)3 (1), Ru2Cl(O2CC6H4-p-CN)(DPhF)3 (2), [Ru2Cl(DPhF)3(H2O)]2(O2C)2 (3), [Ru2Cl(DPhF)3]2[C6H4-p-(CO2)2] (4), and [Ru2Cl(DPhF)3]3[C6H3-1,3,5-(CO2)3] (5). The preparation of [Ru2(NCS)(DPhF)3]3[C6H3-1,3,5-(CO2)3] (6) and {[Ru2(DPhF)3(H2O)]3[C6H3-1,3,5-(CO2)3]}(SO3CF3)3 (7) from 5 is also described. All complexes are characterized by elemental analysis, IR and electronic spectroscopy, mass spectrometry, cyclic voltammetry, and variable-temperature magnetic measurements. The crystal structure determinations of complexes 2.0.5THF and 3.THF.4H2O (THF = tetrahydrofuran) are reported. The reactions carried out demonstrate the high chemical stability of the fragment [Ru2(DPhF)3]2+, which is preserved in all tested experimental conditions. The stability of this fragment is also corroborated by the mass spectra. Electrochemical measurements reveal in all complexes one redox process due to the equilibrium Ru2(5+) <--> Ru2(6+). In the polynuclear complex 7, some additional oxidation processes are also observed that have been ascribed to the presence of two types of dimetallic units rather than two consecutive reversible oxidations. The magnetic behavior toward temperature for complexes 1-7 from 300 to 2 K is analyzed. Complexes 1-7 show low values of antiferromagnetic coupling in accordance with the molecular nature in 1 and 2 and the absence of important antiferromagnetic interaction through the carboxylate bridging ligands in 3-7, respectively. In addition, the magnetic properties of complex 7 do not correspond to any magnetic behavior described for diruthenium(II,III) complexes. The experimental data of compound 7 are simulated considering a physical mixture of S = 1/2 and 3/2 spin states. This magnetic study demonstrates the high sensitivity of the electronic

  4. Crystal structure of the Csm3-Csm4 subcomplex in the type III-A CRISPR-Cas interference complex.

    PubMed

    Numata, Tomoyuki; Inanaga, Hideko; Sato, Chikara; Osawa, Takuo

    2015-01-30

    Clustered, regularly interspaced, short palindromic repeat (CRISPR) loci play a pivotal role in the prokaryotic host defense system against invading genetic materials. The CRISPR loci are transcribed to produce CRISPR RNAs (crRNAs), which form interference complexes with CRISPR-associated (Cas) proteins to target the invading nucleic acid for degradation. The interference complex of the type III-A CRISPR-Cas system is composed of five Cas proteins (Csm1-Csm5) and a crRNA, and targets invading DNA. Here, we show that the Csm1, Csm3, and Csm4 proteins from Methanocaldococcus jannaschii form a stable subcomplex. We also report the crystal structure of the M. jannaschii Csm3-Csm4 subcomplex at 3.1Å resolution. The complex structure revealed the presence of a basic concave surface around their interface, suggesting the RNA and/or DNA binding ability of the complex. A gel retardation analysis showed that the Csm3-Csm4 complex binds single-stranded RNA in a non-sequence-specific manner. Csm4 structurally resembles Cmr3, a component of the type III-B CRISPR-Cas interference complex. Based on bioinformatics, we constructed a model structure of the Csm1-Csm4-Csm3 ternary complex, which provides insights into its role in the Csm interference complex.

  5. The class III cyclobutane pyrimidine dimer photolyase structure reveals a new antenna chromophore binding site and alternative photoreduction pathways.

    PubMed

    Scheerer, Patrick; Zhang, Fan; Kalms, Jacqueline; von Stetten, David; Krauß, Norbert; Oberpichler, Inga; Lamparter, Tilman

    2015-05-01

    Photolyases are proteins with an FAD chromophore that repair UV-induced pyrimidine dimers on the DNA in a light-dependent manner. The cyclobutane pyrimidine dimer class III photolyases are structurally unknown but closely related to plant cryptochromes, which serve as blue-light photoreceptors. Here we present the crystal structure of a class III photolyase termed photolyase-related protein A (PhrA) of Agrobacterium tumefaciens at 1.67-Å resolution. PhrA contains 5,10-methenyltetrahydrofolate (MTHF) as an antenna chromophore with a unique binding site and mode. Two Trp residues play pivotal roles for stabilizing MTHF by a double π-stacking sandwich. Plant cryptochrome I forms a pocket at the same site that could accommodate MTHF or a similar molecule. The PhrA structure and mutant studies showed that electrons flow during FAD photoreduction proceeds via two Trp triads. The structural studies on PhrA give a clearer picture on the evolutionary transition from photolyase to photoreceptor.

  6. Materials and structural aspects of advanced gas-turbine helicopter engines

    NASA Technical Reports Server (NTRS)

    Freche, J. C.; Acurio, J.

    1979-01-01

    The key to improved helicopter gas turbine engine performance lies in the development of advanced materials and advanced structural and design concepts. The modification of the low temperature components of helicopter engines (such as the inlet particle separator), the introduction of composites for use in the engine front frame, the development of advanced materials with increased use-temperature capability for the engine hot section, can result in improved performance and/or decreased engine maintenance cost. A major emphasis in helicopter engine design is the ability to design to meet a required lifetime. This, in turn, requires that the interrelated aspects of higher operating temperatures and pressures, cooling concepts, and environmental protection schemes be integrated into component design. The major material advances, coatings, and design life-prediction techniques pertinent to helicopter engines are reviewed; the current state-of-the-art is identified; and when appropriate, progress, problems, and future directions are assessed.

  7. Decommissioning of the SPERT-III large leach pond at the Idaho National Engineering Laboratory. Final report

    SciTech Connect

    Bradford, J.D.

    1984-04-01

    This report describes the decontamination and decommissioning of the SPERT-III large leach pond. Prior to decontamination and decommissioning the pond basin was enclosed by a mesh and barbed wire fence. An 8-in. carbon steel discharge pipe ran from the SPERT-III reactor building to the pond basin. The outlet of the discharge pipe rested on a concrete apron in the pond basin. The soil in the pond basin contained low-level radioactive contamination. The fence and apron were removed, radiologically surveyed, found to be uncontaminated, and sent to the sanitary landfill for disposal. The discharge pipe was left buried in place. The pond basin was backfilled with radiologically clean soil to reduce the surface activity to background. The area was then seeded with crested wheatgrass. A permanent marker was erected at the center of the pond basin to indicate the presence of subsurface radioactive contamination and the location of the buried discharge pipe. 5 references, 32 figures, 2 tables.

  8. Role of structural noise in aircraft pressure cockpit from vibration action of new-generation engines

    NASA Astrophysics Data System (ADS)

    Baklanov, V. S.

    2016-07-01

    The evolution of new-generation aircraft engines is transitioning from a bypass ratio of 4-6 to an increased ratio of 8-12. This is leading to substantial broadening of the vibration spectrum of engines with a shift to the low-frequency range due to decreased rotation speed of the fan rotor, in turn requiring new solutions to decrease structural noise from engine vibrations to ensure comfort in the cockpits and cabins of aircraft.

  9. Enhanced fluorescence and structural characteristics of carboxymethyl cellulose/Eu(III) nano-complex: Influence of reaction time.

    PubMed

    Ye, Jun; Wang, Ben; Xiong, Jian; Sun, Runcang

    2016-01-01

    CMC/Eu(III) nano-complexes were synthesized by reacting Eu(3+) with carboxymethyl cellulose (CMC). The SEM and EDS showed that particle size was less than 100nm and evenly distributed. FTIR and XPS indicated that the oxygen atoms in COO (-), OH, and COC were involved in the complexation with Eu(3+), yet, the O atoms were involved in different positions on anhydroglucose rings depending on reaction time. It was found that there were good energy matches between energy levels on ground state of CMC and (5)D0 Eu(III). Moreover, the intensities of (5)D0→(7)F2 of the nano-complexes were stronger than that of (5)D0→(7)F1, which indicated that the Eu(III) was not in the center of symmetry. The optimized reaction time was 35min, at this reaction time the smallest particle size and uniform distribution was obtained, the coordination structure was advantageous for the energy absorption transfer and emission.

  10. Effect of structural flexibility on the design of vibration-isolating mounts for aircraft engines

    NASA Technical Reports Server (NTRS)

    Phillips, W. H.

    1984-01-01

    Previous analyses of the design of vibration-isolating mounts for a rear-mounted engine to decouple linear and rotational oscillations are extended to take into account flexibility of the engine-mount structure. Equations and curves are presented to allow the design of mount systems and to illustrate the results for a range of design conditions.

  11. Pre-Service Science Teachers' Cognitive Structures Regarding Science, Technology, Engineering, Mathematics (STEM) and Science Education

    ERIC Educational Resources Information Center

    Hacioglu, Yasemin; Yamak, Havva; Kavak, Nusret

    2016-01-01

    The aim of this study is to reveal pre-service science teachers' cognitive structures regarding Science, Technology, Engineering, Mathematics (STEM) and science education. The study group of the study consisted of 192 pre-service science teachers. A Free Word Association Test (WAT) consisting of science, technology, engineering, mathematics and…

  12. Copper(II)-lanthanide(III) coordination polymers constructed from pyridine-2,5-dicarboxylic acid: Preparation, crystal structure and photoluminescence

    NASA Astrophysics Data System (ADS)

    Xia, Zheng-Qiang; Wei, Qing; Chen, San-Ping; Feng, Xin-Ming; Xie, Gang; Qiao, Cheng-Fang; Zhang, Guo-Chun; Gao, Sheng-Li

    2013-01-01

    A series of 3d-4f heterometallic coordination polymers, formulated as {[Cu3Ln2(pydc)6(H2O)12]·4H2O}n [Ln=Tb (1), Eu (2), Dy (3), Ho (4), Lu (5)], {[CuNd2(pydc)4(H2O)3]·H2O}n (6) and {[Cu3Pr2(pydc)6(H2O)13]·4H2O}n (7) (where H2pydc=pyridine-2,5-dicarboxylic acid), have been hydrothermally prepared by reactions of H2pydc ligand with lanthanide ions in the presence of Cu(II) ion. X-ray crystal structure analysis reveals that these compounds exhibit rich structural chemistry. 1-5 are isomorphous and present a two-dimensional network constructed from Ln2Cu2L2(H2O)2 SBU rings and CuL2(H2O) building blocks. In 6, two-dimensional ladder-like layers based on Nd(III) belts and CuL2O2 units are assembled by H2pydc ligands into a three-dimensional open framework. Polymer 7 displays a two-dimensional wave-like layer structure containing two distinct ring units, in which a new coordination mode of the pydc2- ligand is observed. The results indicate that the coordination flexibility of the pydc2- ligand and lanthanide contraction effect play cooperative roles in the formation of coordination polymers with different polymeric architectures. Compounds 1-2 exhibit intense green and red luminescence emission characteristics of Tb(III) and Eu(III), respectively. Furthermore, elemental analyses (EA), infrared spectra (IR) and thermogravimetric analyses (TGA) of these compounds were also studied.

  13. Combination of X-ray crystallography, SAXS and DEER to obtain the structure of the FnIII-3, 4 domains of integrin α6β4

    SciTech Connect

    Alonso-García, Noelia; García-Rubio, Inés; Buey, Rubén M.; Urien, Hector; Sonnenberg, Arnoud; Jeschke, Gunnar; Pereda, José M. de

    2015-04-01

    The structure of the FnIII-3, 4 region of integrin β4 was solved using a hybrid approach that combines crystallographic structures, SAXS, DEER and molecular modelling. The structure helps in understanding how integrin β4 might bind to other hemidesmosomal proteins and mediate signalling. Integrin α6β4 is a major component of hemidesmosomes that mediate the stable anchorage of epithelial cells to the underlying basement membrane. Integrin α6β4 has also been implicated in cell proliferation and migration and in carcinoma progression. The third and fourth fibronectin type III domains (FnIII-3, 4) of integrin β4 mediate binding to the hemidesmosomal proteins BPAG1e and BPAG2, and participate in signalling. Here, it is demonstrated that X-ray crystallography, small-angle X-ray scattering and double electron–electron resonance (DEER) complement each other to solve the structure of the FnIII-3, 4 region. The crystal structures of the individual FnIII-3 and FnIII-4 domains were solved and the relative arrangement of the FnIII domains was elucidated by combining DEER with site-directed spin labelling. Multiple structures of the interdomain linker were modelled by Monte Carlo methods complying with DEER constraints, and the final structures were selected against experimental scattering data. FnIII-3, 4 has a compact and cambered flat structure with an evolutionary conserved surface that is likely to correspond to a protein-interaction site. Finally, this hybrid method is of general application for the study of other macromolecules and complexes.

  14. Cobalt(III) complexes as potential anticancer agents: Physicochemical, structural, cytotoxic activity and DNA/protein interactions.

    PubMed

    Thamilarasan, V; Sengottuvelan, N; Sudha, A; Srinivasan, P; Chakkaravarthi, G

    2016-09-01

    Cobalt(III) complexes (1-3) such as [Co(acac)(bpy)(N3)2·H2O] 1, [Co(acac)(en)(N3)2] 2, and [Co(acac)(2-pic)(N3)2] 3 (where, acac=acetylacetone, bpy=2.2'-bipyridine, en=ethylenediamine, 2-pic=2-picolylamine and NaN3=sodium azide) were synthesized and characterized. The structure of complexes (1-3) has been determined by single crystal X-ray diffraction studies and the configuration around cobalt(III) ion was distorted octahedral coordination geometry. Density functional theory calculations were performed to examine the molecular geometry and frontier molecular orbital properties of complexes (1-3). DNA binding properties of the cobalt(III) complexes with calf thymus DNA (CT-DNA) were investigated by UV-visible absorption, fluorescence, circular dichroism spectroscopy and viscosity measurements. The docking studies showed the preferred orientation of sterically acceptable Co(III) complexes (1, 2) inside the DNA through the mode of intercalation, whereas complex 3 exhibited minor groove binding modes. The intrinsic binding constants Kb of complexes (1-3) with CT-DNA were in the following order 1>3>2. Complexes (1-3) exhibit a good binding propensity to bovine serum albumin (BSA) and gel electrophoresis assay demonstrated that the complexes (1-3) promote the cleavage of the pBR322 DNA in the presence of 3-mercaptopropionic acid (MPA) and cleavage process was found to proceed by singlet oxygen cleavage mechanism. Further, the in vitro cytotoxicity studies of complexes (1-3) were tested on human breast cancer cell line (MCF-7). PMID:27475779

  15. Crystal structure of bromido-bis-(naph-thal-en-1-yl)anti-mony(III).

    PubMed

    Shawkataly, Omar Bin; Hussien Abdelnasir, Hafiz Malik; Rosli, Mohd Mustaqim

    2014-10-01

    In the title compound, [SbBr(C10H7)2], the Sb(III) atom has a distorted trigonal-pyramidal coordination geometry and the planes of the two naphthalene ring systems make a dihedral angle of 80.26 (18)°. An intra-molecular C-H⋯Br hydrogen bond forms an S(5) ring motif. In the crystal, weak C-H⋯Br inter-actions link the mol-ecules into helical chains along the b-axis direction.

  16. Electronic Structure and Valence of Mn impurities in III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Schulthess, Thomas C.

    2003-11-01

    Mn doped III-V semiconductors have recently become very popular materials since they are ferromagnetic at reasonably high temperatures and in some cases show carrier induced magnetism, where the Curie temperature can be altered by changes in the carrier concentration. It is expected that these materials will play an important role in Spintronics devices. Substitutional Mn impurities in III-V semiconductors can acquire either a divalent or a trivalent configuration. For example, it is generally accepted that Mn in GaAs is in a (d^5+h) configuration with five occupied Mn d-orbitals and a delocalized hole in the valence band. In contrast, Mn in GaN is believed to be in a d^4 configuration with a deep impurity state that has d-character. But there have recently been some discussions about the possibility of having some Mn ion in GaN assuming a divalent (d^5+h) type configuration. In order to achieve carrier induced ferromagnetism, the desired state of the Mn ions in III-V semiconductors is the (d^5+h) configuration. We have therefore performed ab-initio calculations of the Mn valence when it substitutes Ga in various III-V semiconductor hosts. We use the self-interaction corrected local spin density (SIC-LSD) method which is able to treat localized impurity orbitals properly. In particular we find that the method is capable of predicting the (d^5+h) state of Mn in GaAs. For Mn in GaP and GaN the calculations predict a trivalent d^4 state in the idealized system. The energy differences between d^4 and (d^5+h) configurations in GaP are, however, very small. Introduction of defects or donors does change the valence of Mn in GaP, favoring the divalent state under certain circumstances. Work done in collaboration with W. Temmerman and S. Szotek, Daresbury Laboratory, G. M. Stocks, ORNL, and W. H. Butler, MINT Center University of Alabama. This work supported by the Defense Advanced Research Agency and by DOE Office of Science trough ASCR/MICS and BES/DMSE under Contract No

  17. Hydration structures of U(III) and U(IV) ions from ab initio molecular dynamics simulations

    SciTech Connect

    Leung, Kevin; Nenoff, Tina M.

    2012-08-21

    We apply DFT+U-based ab initio molecular dynamics simulations to study the hydration structures of U(III) and U(IV) ions, pertinent to redox reactions associated with uranium salts in aqueous media. U(III) is predicted to be coordinated to 8 water molecules, while U(IV) has a hydration number between 7 and 8. At least one of the innershell water molecules of the hydrated U(IV) complex becomes spontaneously deprotonated. As a result, the U(IV)-O pair correlation function exhibits a satellite peak at 2.15 A associated with the shorter U(IV)-(OH{sup -}) bond. This feature is not accounted for in analysis of extended x-ray absorption fine structure and x-ray adsorption near edge structure measurements, which yield higher estimates of U(IV) hydration numbers. This suggests that it may be useful to include the effect of possible hydrolysis in future interpretation of experiments, especially when the experimental pH is close to the reported hydrolysis equilibrium constant value.

  18. The Structured Clinical Interview for DSM-III-R Dissociative Disorders: preliminary report on a new diagnostic instrument.

    PubMed

    Steinberg, M; Rounsaville, B; Cicchetti, D V

    1990-01-01

    The authors describe the Structured Clinical Interview for DSM-III-R Dissociative Disorders (SCID-D), which investigates five groups of dissociative symptoms (amnesia, depersonalization, derealization, identity confusion, and identity alteration) and systematically rates both the severity of individual symptoms and the evaluation of overall diagnosis of dissociative disorder. Preliminary findings from a study of 48 subjects with and without psychiatric diagnoses indicate good to excellent reliability and discriminant validity for the SCID-D as a diagnostic instrument for the five dissociative disorders and as a tool for the evaluation of dissociative symptoms encountered within nondissociative syndromes.

  19. Slave finite elements for nonlinear analysis of engine structures, volume 1

    NASA Technical Reports Server (NTRS)

    Gellin, S.

    1991-01-01

    A 336 degrees of freedom slave finite element processing capability to analyze engine structures under severe thermomechanical loading is presented. Description of the theoretical development and demonstration of that element is presented in this volume.

  20. NASA Lewis Research Center/University Graduate Research Program on Engine Structures

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1985-01-01

    NASA Lewis Research Center established a graduate research program in support of the Engine Structures Research activities. This graduate research program focuses mainly on structural and dynamics analyses, computational mechanics, mechanics of composites and structural optimization. The broad objectives of the program, the specific program, the participating universities and the program status are briefly described.

  1. Enhancement of Tb(III) -Cu(II) Single-Molecule Magnet Performance through Structural Modification.

    PubMed

    Heras Ojea, María José; Milway, Victoria A; Velmurugan, Gunasekaran; Thomas, Lynne H; Coles, Simon J; Wilson, Claire; Wernsdorfer, Wolfgang; Rajaraman, Gopalan; Murrie, Mark

    2016-08-26

    We report a series of 3d-4f complexes {Ln2 Cu3 (H3 L)2 Xn } (X=OAc(-) , Ln=Gd, Tb or X=NO3 (-) , Ln=Gd, Tb, Dy, Ho, Er) using the 2,2'-(propane-1,3-diyldiimino)bis[2-(hydroxylmethyl)propane-1,3-diol] (H6 L) pro-ligand. All complexes, except that in which Ln=Gd, show slow magnetic relaxation in zero applied dc field. A remarkable improvement of the energy barrier to reorientation of the magnetisation in the {Tb2 Cu3 (H3 L)2 Xn } complexes is seen by changing the auxiliary ligands (X=OAc(-) for NO3 (-) ). This leads to the largest reported relaxation barrier in zero applied dc field for a Tb/Cu-based single-molecule magnet. Ab initio CASSCF calculations performed on mononuclear Tb(III) models are employed to understand the increase in energy barrier and the calculations suggest that the difference stems from a change in the Tb(III) coordination environment (C4v versus Cs ). PMID:27484259

  2. Synthesis, crystal structure, thermal and dielectric properties of tetrapropylammonium tetrachloroantimonate(III)

    NASA Astrophysics Data System (ADS)

    Weslati, N.; Chaabane, I.; Bulou, A.; Hlel, F.

    2014-05-01

    The new organic-inorganic compound, tetrapropylammonium tetrachloroantimonate(III), [N(C3H7)4][SbCl4], crystallizes at room temperature in the monoclinic system (P21/c space group) with the following unit cell parameters: a=18.1973(5) Å, b=15.7225(4) Å, c=15.7225 (3) Å, β=91.65(1)° and Z=4. The atomic arrangement can be described by a stacking of organic-inorganic layers along a direction. Each layer is made up by two types of tetrapropylammonium cations and two types of distorted tetrachloroantimonate(III) anions. Differential scanning calorimetry studies indicate a presence of two order-disorder phase transitions located at 343 K and 363 K. Besides, an analysis of the dielectric constants ɛ', ɛ″ and loss tangent (tan(δ)) versus temperature, at several frequencies, shows a distribution of relaxation times. This relaxation is probably due to the reorientational dynamics of alkyl chains.

  3. The structures of CyMe4-BTBP complexes of americium(iii) and europium(iii) in solvents used in solvent extraction, explaining their separation properties.

    PubMed

    Ekberg, Christian; Löfström-Engdahl, Elin; Aneheim, Emma; Foreman, Mark R StJ; Geist, Andreas; Lundberg, Daniel; Denecke, Melissa; Persson, Ingmar

    2015-11-14

    Separation of trivalent actinoid (An(iii)) and lanthanoid (Ln(iii)) ions is extremely challenging due to their similar ionic radii and chemical properties. Poly-aromatic nitrogen compounds acting as tetradentate chelating ligands to the metal ions in the extraction, have the ability to sufficiently separate An(iii) from Ln(iii). One of these compounds, 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzol[1,2,4]triazin-3-yl)[2,2]bipyridine, CyMe4-BTBP, has proven to be resistant towards acidic environments and strong radiation from radioactive decomposition. EXAFS studies of the dicomplexes of CyMe4-BTBP with americium(iii) and europium(iii) in nitrobenzene, cyclohexanone, 1-hexanol, 1-octanol and malonamide (DMDOHEMA) in 1-octanol have been carried out to get a deeper understanding of the parameters responsible for the separation. The predominating complexes independent of solvent used are [Am(CyMe4-BTBP)2(NO3)](2+) and [Eu(CyMe4-BTBP)2](3+), respectively, which are present as outer-sphere ion-pairs with nitrate ions in the studied solvents with low relative permittivity. The presence of a nitrate ion in the first coordination sphere of the americium(iii) complex compensates the charge density of the complex considerably in comparison when only outer-sphere ion-pairs are formed as for the [Eu(CyMe4-BTBP)2](3+) complex. The stability and solubility of a complex in a solvent with low relative permittivity increase with decreasing charge density. The [Am(CyMe4-BTBP)2(NO3)](2+) complex will therefore be increasingly soluble and stabilized over the [Eu(CyMe4-BTBP)2](3+) complex in solvents with decreasing relative permittivity of the solvent. The separation of americium(iii) from europium(iii) with CyMe4-BTBP as extraction agent will increase with decreasing relative permittivity of the solvent, and thereby also with decreasing solubility of CyMe4-BTBP. The choice of solvent is therefore a balance of a high separation factor and sufficient solubility of the CyMe4-BTBP

  4. The structures of CyMe4-BTBP complexes of americium(iii) and europium(iii) in solvents used in solvent extraction, explaining their separation properties.

    PubMed

    Ekberg, Christian; Löfström-Engdahl, Elin; Aneheim, Emma; Foreman, Mark R StJ; Geist, Andreas; Lundberg, Daniel; Denecke, Melissa; Persson, Ingmar

    2015-11-14

    Separation of trivalent actinoid (An(iii)) and lanthanoid (Ln(iii)) ions is extremely challenging due to their similar ionic radii and chemical properties. Poly-aromatic nitrogen compounds acting as tetradentate chelating ligands to the metal ions in the extraction, have the ability to sufficiently separate An(iii) from Ln(iii). One of these compounds, 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzol[1,2,4]triazin-3-yl)[2,2]bipyridine, CyMe4-BTBP, has proven to be resistant towards acidic environments and strong radiation from radioactive decomposition. EXAFS studies of the dicomplexes of CyMe4-BTBP with americium(iii) and europium(iii) in nitrobenzene, cyclohexanone, 1-hexanol, 1-octanol and malonamide (DMDOHEMA) in 1-octanol have been carried out to get a deeper understanding of the parameters responsible for the separation. The predominating complexes independent of solvent used are [Am(CyMe4-BTBP)2(NO3)](2+) and [Eu(CyMe4-BTBP)2](3+), respectively, which are present as outer-sphere ion-pairs with nitrate ions in the studied solvents with low relative permittivity. The presence of a nitrate ion in the first coordination sphere of the americium(iii) complex compensates the charge density of the complex considerably in comparison when only outer-sphere ion-pairs are formed as for the [Eu(CyMe4-BTBP)2](3+) complex. The stability and solubility of a complex in a solvent with low relative permittivity increase with decreasing charge density. The [Am(CyMe4-BTBP)2(NO3)](2+) complex will therefore be increasingly soluble and stabilized over the [Eu(CyMe4-BTBP)2](3+) complex in solvents with decreasing relative permittivity of the solvent. The separation of americium(iii) from europium(iii) with CyMe4-BTBP as extraction agent will increase with decreasing relative permittivity of the solvent, and thereby also with decreasing solubility of CyMe4-BTBP. The choice of solvent is therefore a balance of a high separation factor and sufficient solubility of the CyMe4-BTBP

  5. Stress Engineering of Multi-pass Welds of Structural Steel to Enhance Structural Integrity

    NASA Astrophysics Data System (ADS)

    Ganguly, Supriyo; Sule, Jibrin; Yakubu, Mustapha Y.

    2016-08-01

    In multi-pass welding, the weld metal and the associated heat-affected zone are subjected to repeated thermal cycling from successive deposition of filler metals. The thermal straining results into multi-mode deformation of the weld metal which causes a variably distributed residual stress field through the thickness and across the weld of a multi-pass weldment. In addition to this, the as-welded fusion zone microstructure shows dendritic formation of grains and segregation of alloying element. This may result in formation of micro-corrosion cells and the problem would aggravate in case of highly alloyed materials. Local mechanical tensioning is an effective way of elimination of the weld tensile residual stress. It has been shown that application of cold rolling is capable not only of removing the residual stress, but depending on its magnitude it may also form beneficial compressive stress state. Multi-pass structural steel welds used as structural alloy in general engineering and structural applications. Such alloys are subjected to severe in-service degradation mechanisms e.g., corrosion and stress corrosion cracking. Welds and the locked-in residual stress in the welded area often initiate the defect which finally results in failure. In the present study, a multi-pass structural steel weld metal was first subjected to post-weld cold rolling which was followed by controlled heating by a fiber laser. Cold straining resulted in redistribution of the internal stress through the thickness and controlled laser processing helps in reforming of the grain structure. However, even with controlled laser, processing the residual stress is reinstated. Therefore, a strategy has been adopted to roll the metal post-laser processing so as to obtain a complete stress-free and recrystallized microstructure.

  6. Stress Engineering of Multi-pass Welds of Structural Steel to Enhance Structural Integrity

    NASA Astrophysics Data System (ADS)

    Ganguly, Supriyo; Sule, Jibrin; Yakubu, Mustapha Y.

    2016-05-01

    In multi-pass welding, the weld metal and the associated heat-affected zone are subjected to repeated thermal cycling from successive deposition of filler metals. The thermal straining results into multi-mode deformation of the weld metal which causes a variably distributed residual stress field through the thickness and across the weld of a multi-pass weldment. In addition to this, the as-welded fusion zone microstructure shows dendritic formation of grains and segregation of alloying element. This may result in formation of micro-corrosion cells and the problem would aggravate in case of highly alloyed materials. Local mechanical tensioning is an effective way of elimination of the weld tensile residual stress. It has been shown that application of cold rolling is capable not only of removing the residual stress, but depending on its magnitude it may also form beneficial compressive stress state. Multi-pass structural steel welds used as structural alloy in general engineering and structural applications. Such alloys are subjected to severe in-service degradation mechanisms e.g., corrosion and stress corrosion cracking. Welds and the locked-in residual stress in the welded area often initiate the defect which finally results in failure. In the present study, a multi-pass structural steel weld metal was first subjected to post-weld cold rolling which was followed by controlled heating by a fiber laser. Cold straining resulted in redistribution of the internal stress through the thickness and controlled laser processing helps in reforming of the grain structure. However, even with controlled laser, processing the residual stress is reinstated. Therefore, a strategy has been adopted to roll the metal post-laser processing so as to obtain a complete stress-free and recrystallized microstructure.

  7. IgE and IgG cross-reactivity among Lol p I and Lol p II/III. Identification of the C-termini of Lol p I, II, and III as cross-reactive structures.

    PubMed

    van Ree, R; van Leeuwen, W A; van den Berg, M; Weller, H H; Aalberse, R C

    1994-04-01

    In this study, the homologous C-termini of Lol p I, Lol p II, and Lol p III were shown to contain cross-reactive B-cell epitopes. This was demonstrated by inhibition studies with purified Lol p I, II, and III and synthetic peptides of their C-termini. It was ruled out that the observed cross-reactivity was caused by cross-contamination of the purified allergens. Both human IgE and IgG bound to the C-terminus of Lol p I. These antibodies were cross-reactive with Lol p II and, more specifically, with its C-terminus. Within a small panel of allergic patients, no cross-reactivity with Lol p III was found. A hyperimmune polyclonal rabbit antiserum against Lol p I also recognized the Lol p I C-terminus. As for human antibodies, cross-reactivity with Lol p II and its C-terminus was demonstrated. Cross-reactivity with Lol p III was demonstrated with C-terminal peptides, but not with native Lol p III. A polyclonal rabbit antiserum against Lol p II bound to the C-terminal peptides of both Lol p II and III. This binding was inhibited with Lol p I, confirming that cross-reactive structures exist not only on the C-termini of Lol p II and Lol p I, but also of Lol p III and Lol p I. The existence of cross-reactivity between Lol p I and Lol p II and III possibly contributes to the frequently observed cosensitization for these allergens in grass-pollen-allergic patients.

  8. Structural Engineering of Microwave Antennas, Chapters 1-4

    NASA Technical Reports Server (NTRS)

    Levy, R.

    1994-01-01

    This paper discusses computer-aided design procedures for antenna reflector structures and related components. Examples in the paper illustrate effective design improvement for structures with several thousand degrees of freedom and within reasonable computing times.

  9. Influence of manganese incorporation on structure, surface and As(III)/As(V) removal capacity of iron oxy-hydroxides

    NASA Astrophysics Data System (ADS)

    Tresintsi, Sofia; Simeonidis, Konstantinos; Mitrakas, Manassis

    2013-04-01

    Iron oxy-hydroxides are well defined As(V) adsorbents dominating in water treatment market. The main drawback of these adsorbents, as well as of all commercial one, is their significantly low adsorption capacity for As(III). A breakthrough for improving As(III) adsorption of iron oxy-hydroxides may come by the MnO2incorporation. However, MnO2 decreases the total arsenic capacity proportionally to its percentage since its efficiency for As(V) is much lower than that of an iron oxy-hydroxide. It is concluded that an ideal adsorbent capable for high and simultaneous As(III) and As(V) removal should be consisted of a binary Fe(III)-Mn(IV) oxy-hydroxide both efficient for As(III) oxidation, due to Mn(IV) presence, and capture of As(V) due to a high positively surface charge density. This work studies the optimum parameters at the synthesis of single Fe and binary Fe/Mn oxy-hydroxides in a continuous flow kilogram-scale production reactor through the precipitation of FeSO4 in the pH range 3-12, under intense oxidative conditions using H2O2/KMnO4, that maximize arsenic adsorption. The evaluation of their efficiency was based on its As(III) and As(V) adsorption capacity (Q10-index) at equilibrium concentration equal to drinking water regulation limit (Ce= 10 μg/L) in NSF challenge water. The pH of synthesis was found to decisively affect, the structure, surface configuration and Q10-index. As a result, both single Fe and binary Fe/Mn oxy-hydroxides prepared at pH 4, which consist of schwertmannite and Mn(IV)-feroxyhyte respectively, were qualified according to their highest Q10-index of 13±0.5 μg As(V)/ mg for a residual arsenic concentration of 10 μg/L at an equilibrium pH 7. The high surface charge and the activation of an ion-exchange mechanism between SO42- adsorbed in the Stern layer and arsenate ions were found to significantly contribute to the increased adsorption capacity. The Q10-index for As(III) of Fe/Mn adsorbent at equilibrium pH 7 was 6.7 μg/mg, which

  10. Engineering approaches to illuminating brain structure and dynamics.

    PubMed

    Deisseroth, Karl; Schnitzer, Mark J

    2013-10-30

    Historical milestones in neuroscience have come in diverse forms, ranging from the resolution of specific biological mysteries via creative experimentation to broad technological advances allowing neuroscientists to ask new kinds of questions. The continuous development of tools is driven with a special necessity by the complexity, fragility, and inaccessibility of intact nervous systems, such that inventive technique development and application drawing upon engineering and the applied sciences has long been essential to neuroscience. Here we highlight recent technological directions in neuroscience spurred by progress in optical, electrical, mechanical, chemical, and biological engineering. These research areas are poised for rapid growth and will likely be central to the practice of neuroscience well into the future.

  11. Engineered Minichromosomes in Plants: Structure, Function, and Applications.

    PubMed

    Graham, Nathaniel D; Cody, Jon P; Swyers, Nathan C; McCaw, Morgan E; Zhao, Changzeng; Birchler, James A

    2015-01-01

    Engineered minichromosomes are small chromosomes that contain a transgene and selectable marker, as well as all of the necessary components required for maintenance in an organism separately from the standard chromosome set. The separation from endogenous chromosomes makes engineered minichromosomes useful in the production of transgenic plants. Introducing transgenes to minichromosomes does not have the risk of insertion within a native gene; additionally, transgenes on minichromosomes can be transferred between lines without the movement of linked genes. Of the two methods proposed for creating engineered minichromosomes, telomere-mediated truncation is more reliable in plant systems. Additionally, many plants contain a supernumerary, or B chromosome, which is an excellent starting material for minichromosome creation. The use of site-specific recombination systems in minichromosomes can increase their utility, allowing for the addition or subtraction of transgenes in vivo. The creation of minichromosomes with binary bacterial artificial chromosome vectors provides the ability to introduce many transgenes at one time. Furthermore, coupling minichromosomes with haploid induction systems can facilitate transfer between lines. Minichromosomes can be introduced to a haploid-inducing line and crossed to target lines. Haploids of the target line that then contain a minichromosome can then be doubled. These homozygous lines will contain the transgene without the need for repeated introgressions. PMID:26315884

  12. The Structures of Coiled-Coil Domains from Type III Secretion System Translocators Reveal Homology to Pore-Forming Toxins

    SciTech Connect

    Barta, Michael L.; Dickenson, Nicholas E.; Patil, Mrinalini; Keightley, Andrew; Wyckoff, Gerald J.; Picking, William D.; Picking, Wendy L.; Geisbrecht, Brian V.

    2012-03-26

    Many pathogenic Gram-negative bacteria utilize type III secretion systems (T3SSs) to alter the normal functions of target cells. Shigella flexneri uses its T3SS to invade human intestinal cells to cause bacillary dysentery (shigellosis) that is responsible for over one million deaths per year. The Shigella type III secretion apparatus is composed of a basal body spanning both bacterial membranes and an exposed oligomeric needle. Host altering effectors are secreted through this energized unidirectional conduit to promote bacterial invasion. The active needle tip complex of S. flexneri is composed of a tip protein, IpaD, and two pore-forming translocators, IpaB and IpaC. While the atomic structure of IpaD has been elucidated and studied, structural data on the hydrophobic translocators from the T3SS family remain elusive. We present here the crystal structures of a protease-stable fragment identified within the N-terminal regions of IpaB from S. flexneri and SipB from Salmonella enterica serovar Typhimurium determined at 2.1 {angstrom} and 2.8 {angstrom} limiting resolution, respectively. These newly identified domains are composed of extended-length (114 {angstrom} in IpaB and 71 {angstrom} in SipB) coiled-coil motifs that display a high degree of structural homology to one another despite the fact that they share only 21% sequence identity. Further structural comparisons also reveal substantial similarity to the coiled-coil regions of pore-forming proteins from other Gram-negative pathogens, notably, colicin Ia. This suggests that these mechanistically separate and functionally distinct membrane-targeting proteins may have diverged from a common ancestor during the course of pathogen-specific evolutionary events.

  13. A structurally rigid bis(amido) ligand framework in low-coordinate Ni(I), Ni(II), and Ni(III) analogues provides access to a Ni(III) methyl complex via oxidative addition.

    PubMed

    Lipschutz, Michael I; Yang, Xinzheng; Chatterjee, Ruchira; Tilley, T Don

    2013-10-16

    A structurally persistent bis-amido ligand framework capable of supporting nickel compounds in three different oxidation states has been identified. A highly unusual, isolable Ni(III) alkyl species has been prepared and characterized via a rare example of a two-electron oxidative addition of MeI to Ni(I).

  14. The Effect of the Secondary Structure on Dissociation of Peptide Radical Cations: Fragmentation of Angiotensin III and Its Analogues

    SciTech Connect

    Yang, Zhibo; Lam, Corey; Chu, Ivan K.; Laskin, Julia

    2008-09-28

    Fragmentation of protonated RVYIHPF and RVYIHPF-OMe and the corresponding radical cations was studied using time- and collision energy-resolved surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) specially equipped to perform SID experiments. Peptide radical cations were produced by gas-phase fragmentation of CoIII(salen)-peptide complexes. Both the energetics and mechanisms of dissociation of even-electron and odd-electron angiotensin III ions are quite different. Protonated molecules are much more stable towards fragmentation than the corresponding radical cations. RRKM modeling of the experimental data suggests that this stability is largely attributed to differences in threshold energies for dissociation while activation entropies are very similar. Detailed analysis of the experimental data obtained for radical cations demonstrated the presence of two distinct structures separated by a high free-energy barrier. The two families of structures were ascribed to the canonical and zwitterionic forms of the radical cations produced in our experiments.

  15. Heterogeneity in iota-carrageenan molecular structure: insights for polymorph II→III transition in the presence of calcium ions

    SciTech Connect

    Janaswamy, Srinivas; Chandrasekaran, Rengaswami

    2008-06-24

    Iota-carrageenan is used in pharmaceutical and food applications due to its ability to complex with other hydrocolloids and proteins. Six distinct cation dependent allomorphs, consistent with its versatile functionality, have so far been observed in the solid state. In this contribution, X-ray structural details of calcium iota-carrageenan (form III) are reported. The polysaccharide retains the half-staggered, parallel, 3-fold, right-handed double helix stabilized by interchain hydrogen bonds from O-2H and O-6H in the Galp units. Results show that there are four helices, rather than one in I or three in II, organized in a larger pseudo-trigonal unit cell of dimensions a=27.44, c=13.01 A, and gamma=120 degrees . The four helices have similar core structures, but their sulfate group orientations are quite different. Fifteen calcium ions and 64 water molecules hold the helices together and promote helix-helix interactions. The results portray how the helices would shuffle around in an orchestrated manner to yield calcium iota-carrageenan III from II.

  16. Structural basis for stem cell factor–KIT signaling and activation of class III receptor tyrosine kinases

    PubMed Central

    Liu, Heli; Chen, Xiaoyan; Focia, Pamela J; He, Xiaolin

    2007-01-01

    Stem cell factor (SCF) binds to and activates the KIT receptor, a class III receptor tyrosine kinase (RTK), to stimulate diverse processes including melanogenesis, gametogenesis and hematopoeisis. Dysregulation of KIT activation is associated with many cancers. We report a 2.5 Å crystal structure of the functional core of SCF bound to the extracellular ligand-binding domains of KIT. The structure reveals a ‘wrapping' SCF-recognition mode by KIT, in which KIT adopts a bent conformation to facilitate each of its first three immunoglobulin (Ig)-like domains to interact with SCF. Three surface epitopes on SCF, an extended loop, the B and C helices, and the N-terminal segment, contact distinct KIT domains, with two of the epitopes undergoing large conformational changes upon receptor binding. The SCF/KIT complex reveals a unique RTK dimerization assembly, and a novel recognition mode between four-helix bundle cytokines and Ig-family receptors. It serves as a framework for understanding the activation mechanisms of class III RTKs. PMID:17255936

  17. Crystal structure of the coordination polymer [FeIII 2{PtII(CN)4}3

    PubMed Central

    Seredyuk, Maksym; Muñoz, M. Carmen; Real, José A.; Iskenderov, Turganbay S.

    2015-01-01

    The title complex, poly[dodeca-μ-cyanido-diiron(III)triplat­inum(II)], [FeIII 2{PtII(CN)4}3], has a three-dimensional polymeric structure. It is built-up from square-planar [PtII(CN)4]2− anions (point group symmetry 2/m) bridging cationic [FeIIIPtII(CN)4]+ ∞ layers extending in the bc plane. The FeII atoms of the layers are located on inversion centres and exhibit an octa­hedral coordination sphere defined by six N atoms of cyanide ligands, while the PtII atoms are located on twofold rotation axes and are surrounded by four C atoms of the cyanide ligands in a square-planar coordination. The geometrical preferences of the two cations for octa­hedral and square-planar coordination, respectively, lead to a corrugated organisation of the layers. The distance between neighbouring [FeIIIPtII(CN)4]+ ∞ layers corresponds to the length a/2 = 8.0070 (3) Å, and the separation between two neighbouring PtII atoms of the bridging [PtII(CN)4]2− groups corresponds to the length of the c axis [7.5720 (2) Å]. The structure is porous with accessible voids of 390 Å3 per unit cell. PMID:25705468

  18. Covalent Attachment to GaP(110) - Engineering the Chemical Functionalization of a III-V Semiconductor

    NASA Astrophysics Data System (ADS)

    Bradley, A. J.; Ugeda, M. M.; Liu, Wenjun; Yu, Min; Tilley, T. Don; Pérez, Rubén; Neaton, Jeffrey B.; Crommie, M. F.

    2014-03-01

    With its 2.3 eV bulk bandgap, relatively high conduction band edge, and low chemical reactivity, the (110) surface of GaP is an excellent candidate for many UV and visible light applications, such as photo-catalysis and light-induced chemical reduction. However, the reconstruction and resulting charge transfer of the surface makes it difficult to covalently attach the required molecules. Indeed, very little work has been done to understand either covalent functionalization or passivation of this surface. Here we report on a Staudinger-type, thermally-driven covalent attachment of perfluorophenyl azide (pfpa) to GaP(110). We have studied the adsorption of pfpa molecules by means of high-resolution scanning tunneling microscopy and spectroscopy in combination with first principles calculations. We show a progression from a physisorbed state at room temperature to a covalently attached state after exposure to slightly higher temperatures (~ 50°C). The developed approach is expected to be valid for various other functional groups attached to the azide, as well as other III-V semiconductors.

  19. Strain properties analysis and wireless collection system of PVDF for structural local health monitoring of civil engineering structures

    NASA Astrophysics Data System (ADS)

    Yu, Yan; Wang, Yang; Dong, Weijie; Jin, Yajing; Ou, Jinping

    2009-07-01

    For large civil engineering structures and base establishments, for example, bridges, super-high buildings, long-span space structures, offshore platforms and pipe systems of water & gas supply, their lives are up to a few decades or centuries. Damaged by environmental loads, fatigue effects, corrosion effects and material aging, these structures experience inevitably such side effects as damage accumulation, resistance reduction and even accidents. The traditional civil structure is a kind of passive one, whose performance and status are unpredictable to a great extent, but the informatics' introduction breaks a new path to obtain the status of the structure, thus it is an important research direction to evaluate and improve reliability of civil structures by the use of monitoring and health diagnosis technique, and this also assures the security of service for civil engineering structures. Smart material structure, originated from the aerospace sector, has been a research hotspot in civil engineering, medicine, shipping, and so on. For structural health monitoring of civil engineering, the research about high-performance sensing unit of smart material structure is very important, and this will possibly push further the development and application of monitoring and health diagnosis techniques. At present, piezoelectric materials are one of the most widely used sensing materials among the research of smart material structures. As one of the piezoelectric materials, PVDF(Polyvinylidene Fluoride)film is widely considered for the advantages of low cost, good mechanical ability, high sensibility, the ability of being easily placed and resistance of corrosion. However, only a few studies exit about building a mature monitoring system using PVDF. In this paper, for the sake of using PVDF for sensing unit for structural local monitoring of civil engineering, the strain sensing properties of PVDF are studied in detail. Firstly, the operating mechanism of PVDF is analyzed

  20. Immobilization of cobalt(III) Schiff base complexes onto Montmorillonite-K10: Synthesis, experimental and theoretical structural determination

    NASA Astrophysics Data System (ADS)

    Kianfar, Ali Hossein; Kamil Mahmood, Wan Ahmad; Dinari, Mohammad; Farrokhpour, Hossein; Enteshari, Majid; Azarian, Mohammad Hossein

    2015-02-01

    The [Co(naphophen)(PPh3)(OH2)]ClO4 and [Co(naphophen)(PBu3)(OH2)]BF4 (where naphophen = bis(naphthaldehyde)1,2-phenylenediimine) complexes were synthesized and chracterized by FT-IR, UV-Vis, 1H NMR, 13C NMR spectroscopy and elemental analysis techniques. The coordination geometry of the synthesized complexes were determined by X-ray crystallography. Cobalt (III) complexes have six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base forms the equatorial plane. These complexes showed a dimeric structure via hydrogen bonding between the phenolate oxygen and the hydrogens of the coordinated H2O molecule. The theoretical calculations were also performed to optimize the structure of the complexes in the gas phase to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification. The synthesized complexes were incorporated onto the Montmorillonite-K10 nanoclay via simple ion-exchange reaction. The structure and morphology of the obtained nanohybrids were identified by FT-IR, XRD, TGA/DTA, SEM and TEM techniques. Based on the XRD results of the new nanohybrid materials, the Schiff base complexes were intercalated in the interlayer spaces of clay. SEM and TEM micrographs of the clay/complex shows that the resulting hybrid nanomaterials has layer structures.

  1. Immobilization of cobalt(III) Schiff base complexes onto Montmorillonite-K10: Synthesis, experimental and theoretical structural determination.

    PubMed

    Kianfar, Ali Hossein; Kamil Mahmood, Wan Ahmad; Dinari, Mohammad; Farrokhpour, Hossein; Enteshari, Majid; Azarian, Mohammad Hossein

    2015-02-01

    The [Co(naphophen)(PPh3)(OH2)]ClO4 and [Co(naphophen)(PBu3)(OH2)]BF4 (where naphophen=bis(naphthaldehyde)1,2-phenylenediimine) complexes were synthesized and chracterized by FT-IR, UV-Vis, (1)H NMR, (13)C NMR spectroscopy and elemental analysis techniques. The coordination geometry of the synthesized complexes were determined by X-ray crystallography. Cobalt (III) complexes have six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base forms the equatorial plane. These complexes showed a dimeric structure via hydrogen bonding between the phenolate oxygen and the hydrogens of the coordinated H2O molecule. The theoretical calculations were also performed to optimize the structure of the complexes in the gas phase to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification. The synthesized complexes were incorporated onto the Montmorillonite-K10 nanoclay via simple ion-exchange reaction. The structure and morphology of the obtained nanohybrids were identified by FT-IR, XRD, TGA/DTA, SEM and TEM techniques. Based on the XRD results of the new nanohybrid materials, the Schiff base complexes were intercalated in the interlayer spaces of clay. SEM and TEM micrographs of the clay/complex shows that the resulting hybrid nanomaterials has layer structures.

  2. Cryogenic magneto-caloric effect and magneto-structural correlations in carboxylate-bridged Gd(III) compounds.

    PubMed

    Roubeau, O; Lorusso, G; Teat, S J; Evangelisti, M

    2014-08-14

    Two new infinite coordination chain compounds [Gd(CH3CO2)3(dmf)]∞ (1) and {[Gd(HO(CH2)3CO2)3(H2O)]·H2O}∞ (2) have been obtained attempting to modify a prototype molecular cooler. The structures of both compounds as determined by single-crystal X-ray diffraction are reported, together with a detailed study of their magnetic and thermal properties, describing for both compounds a large magneto-caloric effect. The dominant ferromagnetic interaction present in 2 clearly favours this material at low applied magnetic fields, with respect to 1 that exhibits antiferromagnetic interactions. Magneto-structural correlations of the sign and strength of the magnetic interactions are derived for carboxylato-bridged Gd(III) systems.

  3. Thermal decomposition of crystalline Ni(II)-Cr(III) layered double hydroxide: a structural study of the segregation process.

    PubMed

    Sileo, Elsa E; Jobbagy, Matías; Paiva-Santos, Carlos O; Regazzoni, Alberto E

    2005-05-26

    A structural study of the thermal evolution of Ni(0.69)Cr(0.31)(OH)(2)(CO(3))(0.155) x nH(2)O into NiO and tetragonal NiCr(2)O(4) is reported. The characteristic structural parameters of the two coexisting crystalline phases, as well as their relative abundance, were determined by Rietveld refinement of powder x-ray diffraction (PXRD) patterns. The results of the simulations allowed us to elucidate the mechanism of the demixing process of the oxides. It is demonstrated that nucleation of a metastable nickel chromite within the common oxygen framework of the parent Cr(III)-doped bunsenite is the initial step of the cationic redistribution. The role that trivalent cations play in the segregation of crystalline spinels is also discussed. PMID:16852228

  4. III-V semiconductor Quantum Well systems: Physics of Gallium Arsenide two-dimensional hole systems and engineering of mid-infrared Quantum Cascade lasers

    NASA Astrophysics Data System (ADS)

    Chiu, YenTing

    This dissertation examines two types of III-V semiconductor quantum well systems: two-dimensional holes in GaAs, and mid-infrared Quantum Cascade lasers. GaAs holes have a much reduced hyperfine interaction with the nuclei due to the p-like orbital, resulting in a longer hole spin coherence time comparing to the electron spin coherence time. Therefore, holes' spins are promising candidates for quantum computing qubits, but the effective mass and the Lande g-factor, whose product determines the spin-susceptibility of holes, are not well known. In this thesis, we measure the effective hole mass through analyzing the temperature dependence of Shubnikov-de Haas oscillations in a relatively strong interacting two-dimensional hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose effective mass we measure to be ˜ 0.2 me. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and the spin susceptibility of the two-dimensional hole system is deduced from the depopulation field. We also confine holes in closely spaced bilayer GaAs quantum wells to study the interlayer tunneling spectrum as a function of interlayer bias and in-plane magnetic field, in hope of probing the hole's Fermi contour. Quantum Cascade lasers are one of the major mid-infrared light sources well suited for applications in health and environmental sensing. One of the important factors that affect Quantum Cascade laser performance is the quality of the interfaces between the epitaxial layers. What has long been neglected is that interface roughness causes intersubband scattering, and thus affecting the relation between the lifetimes of the upper and lower laser states, which determines if population inversion is possible. We first utilize strategically added interface roughness in the laser design to engineer the intersubband scattering lifetimes. We further

  5. Fluorescent naphthalene diols as bridging ligands in Ln(III) cluster chemistry: synthetic, structural, magnetic, and photophysical characterization of Ln(III)8 "Christmas stars".

    PubMed

    Alexandropoulos, Dimitris I; Fournet, Adeline; Cunha-Silva, Luís; Mowson, Andrew M; Bekiari, Vlasoula; Christou, George; Stamatatos, Theocharis C

    2014-06-01

    The initial employment of the fluorescent bridging ligand naphthalene-2,3-diol in 4f-metal coordination chemistry has provided access to a new family of Ln(III)8 clusters with a "Christmas-star" topology, single-molecule magnetism behavior, and ligand-centered emissions.

  6. Fluorescent naphthalene diols as bridging ligands in Ln(III) cluster chemistry: synthetic, structural, magnetic, and photophysical characterization of Ln(III)8 "Christmas stars".

    PubMed

    Alexandropoulos, Dimitris I; Fournet, Adeline; Cunha-Silva, Luís; Mowson, Andrew M; Bekiari, Vlasoula; Christou, George; Stamatatos, Theocharis C

    2014-06-01

    The initial employment of the fluorescent bridging ligand naphthalene-2,3-diol in 4f-metal coordination chemistry has provided access to a new family of Ln(III)8 clusters with a "Christmas-star" topology, single-molecule magnetism behavior, and ligand-centered emissions. PMID:24828892

  7. Ca2+ and membrane binding to annexin 3 modulate the structure and dynamics of its N terminus and domain III

    PubMed Central

    Sopkova, Jana; Raguenes-Nicol, Céline; Vincent, Michel; Chevalier, Anne; Lewit-Bentley, Anita; Russo-Marie, Françoise; Gallay, Jacques

    2002-01-01

    Annexin 3 (ANX A3) represents ∼1% of the total protein of human neutrophils and promotes tight contact between membranes of isolated specific granules in vitro leading to their aggregation. Like for other annexins, the primary molecular events of the action of this protein is likely its binding to negatively charged phospholipid membranes in a Ca2+-dependent manner, via Ca2+-binding sites located on the convex side of the highly conserved core of the molecule. The conformation and dynamics of domain III can be affected by this process, as it was shown for other members of the family. The 20 amino-acid, N-terminal segment of the protein also could be affected and also might play a role in the modulation of its binding to the membranes. The structure and dynamics of these two regions were investigated by fluorescence of the two tryptophan residues of the protein (respectively, W190 in domain III and W5 in the N-terminal segment) in the wild type and in single-tryptophan mutants. By contrast to ANX A5, which shows a closed conformation and a buried W187 residue in the absence of Ca2+, domain III of ANX A3 exhibits an open conformation and a widely solvent-accessible W190 residue in the same conditions. This is in agreement with the three-dimensional structure of the ANX A3-E231A mutant lacking the bidentate Ca2+ ligand in domain III. Ca2+ in the millimolar concentration range provokes nevertheless a large mobility increase of the W190 residue, while interaction with the membranes reduces it slightly. In the N-terminal region, the W5 residue, inserted in the central pore of the protein, is weakly accessible to the solvent and less mobile than W190. Its amplitude of rotation increases upon binding of Ca2+ and returns to its original value when interacting with membranes. Ca2+ concentration for half binding of the W5A mutant to negatively charged membranes is ∼0.5 mM while it increases to ∼1 mM for the ANX A3 wild type and to ∼3 mM for the W190 ANX A3 mutant. In

  8. A Study on Aircraft Structure and Jet Engine

    NASA Astrophysics Data System (ADS)

    Park, Gil Moon; Park, Hwan Kyu; Kim, Jong Il; Kim, Jin Won; Kim, Jin Heung; Lee, Moo Seok; Chung, Nak Kyu

    1985-12-01

    The one of critical factor in gas turbine engine performance is high turbine inlet gas temperature. Therefore, the turbine rotor has so many problems which must be considered such as the turbine blade cooling, thermal stress of turbine disk due to severe temperature gradient, turbine rotor tip clearance, under the high operation temperature. The purpose of this study is to provide the temperature distribution and heat flux in turbine disk which is required to considered premensioned problem by the Finite Difference Method and the Finite Element Methods on the steady state condition.

  9. Two-dimensional 3d-4f heterometallic coordination polymers: syntheses, crystal structures, and magnetic properties of six new Co(II)-Ln(III) compounds.

    PubMed

    Díaz-Gallifa, Pau; Fabelo, Oscar; Pasán, Jorge; Cañadillas-Delgado, Laura; Lloret, Francesc; Julve, Miguel; Ruiz-Pérez, Catalina

    2014-06-16

    Six new heterometallic cobalt(II)-lanthanide(III) complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O)6]·10H2O [Ln = Nd(III) (1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8]n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized via single-crystal X-ray diffraction. 1 and 2 are isostructural compounds with a structure composed of anionic layers of [Ln(bta)(H2O)2]n(n-) sandwiching mononuclear [Co(H2O)6](2+) cations plus crystallization water molecules, which are interlinked by electrostatic forces and hydrogen bonds, leading to a supramolecular three-dimensional network. 3-6 are also isostructural compounds, and their structure consists of neutral layers of formula [Ln2Co(bta)2(H2O)8]n and crystallization water molecules, which are connected through hydrogen bonds to afford a supramolecular three-dimensional network. Heterometallic chains formed by the regular alternation of two nine-coordinate lanthanide(III) polyhedra [Ln(III)O9] and one compressed cobalt(II) octahedron [Co(II)O6] along the crystallographic c-axis are cross-linked by bta ligands within each layer of 3-6. Magnetic susceptibility measurements on polycrystalline samples for 3-6 have been carried out in the temperature range of 2.0-300 K. The magnetic behavior of these types of Ln(III)-Co(II) complexes, which have been modeled by using matrix dagonalization techniques, reveals the lack of magnetic coupling for 3 and 4, and the occurrence of weak antiferromagnetic interactions within the Gd(III)-Gd(III) (5) and Tb(III)-Tb(III) (6) dinuclear units through the exchange pathway provided by the double oxo(carboxylate) and double syn-syn carboxylate bridges. PMID:24901707

  10. Two-dimensional 3d-4f heterometallic coordination polymers: syntheses, crystal structures, and magnetic properties of six new Co(II)-Ln(III) compounds.

    PubMed

    Díaz-Gallifa, Pau; Fabelo, Oscar; Pasán, Jorge; Cañadillas-Delgado, Laura; Lloret, Francesc; Julve, Miguel; Ruiz-Pérez, Catalina

    2014-06-16

    Six new heterometallic cobalt(II)-lanthanide(III) complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O)6]·10H2O [Ln = Nd(III) (1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8]n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized via single-crystal X-ray diffraction. 1 and 2 are isostructural compounds with a structure composed of anionic layers of [Ln(bta)(H2O)2]n(n-) sandwiching mononuclear [Co(H2O)6](2+) cations plus crystallization water molecules, which are interlinked by electrostatic forces and hydrogen bonds, leading to a supramolecular three-dimensional network. 3-6 are also isostructural compounds, and their structure consists of neutral layers of formula [Ln2Co(bta)2(H2O)8]n and crystallization water molecules, which are connected through hydrogen bonds to afford a supramolecular three-dimensional network. Heterometallic chains formed by the regular alternation of two nine-coordinate lanthanide(III) polyhedra [Ln(III)O9] and one compressed cobalt(II) octahedron [Co(II)O6] along the crystallographic c-axis are cross-linked by bta ligands within each layer of 3-6. Magnetic susceptibility measurements on polycrystalline samples for 3-6 have been carried out in the temperature range of 2.0-300 K. The magnetic behavior of these types of Ln(III)-Co(II) complexes, which have been modeled by using matrix dagonalization techniques, reveals the lack of magnetic coupling for 3 and 4, and the occurrence of weak antiferromagnetic interactions within the Gd(III)-Gd(III) (5) and Tb(III)-Tb(III) (6) dinuclear units through the exchange pathway provided by the double oxo(carboxylate) and double syn-syn carboxylate bridges.

  11. Introducing Students to Structural Dynamics and Earthquake Engineering

    ERIC Educational Resources Information Center

    Anthoine, Armelle; Marazzi, Francesco; Tirelli, Daniel

    2010-01-01

    The European Laboratory for Structural Assessment (ELSA) is one of the world's main laboratories for seismic studies. Besides its research activities, it also aims to bring applied science closer to the public. This article describes teaching activities based on a demonstration shaking table which is used to introduce the structural dynamics of…

  12. 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.

  13. Detailed Post-Soft Impact Progressive Damage Assessment for Hybrid Structure Jet Engines

    NASA Technical Reports Server (NTRS)

    Siddens, Aaron; Bayandor, Javid; Celestina, Mark L.

    2014-01-01

    Currently, certification of engine designs for resistance to bird strike is reliant on physical tests. Predictive modeling of engine structural damage has mostly been limited to evaluation of individual forward section components, such as fan blades within a fixed frame of reference, to direct impact with a bird. Such models must be extended to include interactions among engine components under operating conditions to evaluate the full extent of engine damage. This paper presents the results of a study aim to develop a methodology for evaluating bird strike damage in advanced propulsion systems incorporating hybrid composite/metal structures. The initial degradation and failure of individual fan blades struck by a bird were investigated. Subsequent damage to other fan blades and engine components due to resultant violent fan assembly vibrations and fragmentation was further evaluated. Various modeling parameters for the bird and engine components were investigated to determine guidelines for accurately capturing initial damage and progressive failure of engine components. Then, a novel hybrid structure modeling approach was investigated and incorporated into the crashworthiness methodology. Such a tool is invaluable to the process of design, development, and certification of future advanced propulsion systems.

  14. Engineering Virus Capsids Into Biomedical Delivery Vehicles: Structural Engineering Problems in Nanoscale.

    PubMed

    Bajaj, Saumya; Banerjee, Manidipa

    2015-01-01

    Virus capsids have evolved to protect the genome sequestered in their interior from harsh environmental conditions, and to deliver it safely and precisely to the host cell of choice. This characteristic makes them naturally perfect containers for delivering therapeutic molecules to specific locations. Development of an ideal virus-based nano-container for medical usage requires that the capsid be converted into a targetable protein cage which retains the original stability, flexibility and host cell penetrating properties of the native particles, without the associated immunogenicity, and is able to encapsulate large quantities of therapeutic or diagnostic material. In the last few years, several icosahedral, non-enveloped viruses, with a diameter of 25-90 nm-a size which conveniently falls within the 10-100 nm range desirable for biomedical nanoparticles-have been chemically or genetically engineered towards partial fulfilment of the above criteria. This review summarizes the approaches taken towards engineering viruses into biomedical delivery devices and discusses the challenges involved in achieving this goal. PMID:26301300

  15. Engineering Virus Capsids Into Biomedical Delivery Vehicles: Structural Engineering Problems in Nanoscale.

    PubMed

    Bajaj, Saumya; Banerjee, Manidipa

    2015-01-01

    Virus capsids have evolved to protect the genome sequestered in their interior from harsh environmental conditions, and to deliver it safely and precisely to the host cell of choice. This characteristic makes them naturally perfect containers for delivering therapeutic molecules to specific locations. Development of an ideal virus-based nano-container for medical usage requires that the capsid be converted into a targetable protein cage which retains the original stability, flexibility and host cell penetrating properties of the native particles, without the associated immunogenicity, and is able to encapsulate large quantities of therapeutic or diagnostic material. In the last few years, several icosahedral, non-enveloped viruses, with a diameter of 25-90 nm-a size which conveniently falls within the 10-100 nm range desirable for biomedical nanoparticles-have been chemically or genetically engineered towards partial fulfilment of the above criteria. This review summarizes the approaches taken towards engineering viruses into biomedical delivery devices and discusses the challenges involved in achieving this goal.

  16. Synthesis, structures and urease inhibitory activity of cobalt(III) complexes with Schiff bases.

    PubMed

    Jing, Changling; Wang, Cunfang; Yan, Kai; Zhao, Kedong; Sheng, Guihua; Qu, Dan; Niu, Fang; Zhu, Hailiang; You, Zhonglu

    2016-01-15

    A series of new cobalt(III) complexes were prepared. They are [CoL(1)(py)3]·NO3 (1), [CoL(2)(bipy)(N3)]·CH3OH (2), [CoL(3)(HL(3))(N3)]·NO3 (3), and [CoL(4)(MeOH)(N3)] (4), where L(1), L(2), L(3) and L(4) are the deprotonated form of N'-(2-hydroxy-5-methoxybenzylidene)-3-methylbenzohydrazide, N'-(2-hydroxybenzylidene)-3-hydroxylbenzohydrazide, 2-[(2-dimethylaminoethylimino)methyl]-4-methylphenol, and N,N'-bis(5-methylsalicylidene)-o-phenylenediamine, respectively, py is pyridine, and bipy is 2,2'-bipyridine. The complexes were characterized by infrared and UV-Vis spectra, and single crystal X-ray diffraction. The Co atoms in the complexes are in octahedral coordination. Complexes 1 and 4 show effective urease inhibitory activities, with IC50 values of 4.27 and 0.35 μmol L(-1), respectively. Complex 2 has medium activity against urease, with IC50 value of 68.7 μmol L(-1). While complex 3 has no activity against urease. Molecular docking study of the complexes with Helicobacter pylori urease was performed.

  17. Structure and sequence of the gene for the largest subunit of trypanosomal RNA polymerase III.

    PubMed Central

    Köck, J; Evers, R; Cornelissen, A W

    1988-01-01

    As the first step in the analysis of the transcription process in the African trypanosome, Trypanosoma brucei, we have started to characterise the trypanosomal RNA polymerases. We have previously described the gene encoding the largest subunit of RNA polymerase II and found that two almost identical RNA polymerase II genes are encoded within the genome of T. brucei. Here we present the identification, cloning and sequence analysis of the gene encoding the largest subunit of RNA polymerase III. This gene contains a single open reading frame encoding a polypeptide with a Mr of 170 kD. In total, eight encoding a polypeptide with a Mr of 170 kD. In total, eight highly conserved regions with significant homology to those previously reported in other eukaryotic RNA polymerase largest subunits were identified. Some of these domains contain functional sites, which are conserved among all eukaryotic largest subunit genes analysed thus far. Since these domains make up a large part of each polypeptide, independent of the RNA polymerase class, these data strongly support the hypothesis that these domains provide a major part of the transcription machinery of the RNA polymerase complex. The additional domains which are uniquely present in the largest subunit of RNA polymerase I and II, respectively, two large hydrophylic insertions and a C-terminal extension, might be a determining factor in specific transcription of the gene classes. Images PMID:3174432

  18. Structure of the SSB-DNA polymerase III interface and its role in DNA replication

    SciTech Connect

    Marceau, Aimee H; Bahng, Soon; Massoni, Shawn C; George, Nicholas P; Sandler, Steven J; Marians, Kenneth J; Keck, James L

    2012-05-22

    Interactions between single-stranded DNA-binding proteins (SSBs) and the DNA replication machinery are found in all organisms, but the roles of these contacts remain poorly defined. In Escherichia coli, SSB's association with the χ subunit of the DNA polymerase III holoenzyme has been proposed to confer stability to the replisome and to aid delivery of primers to the lagging-strand DNA polymerase. Here, the SSB-binding site on χ is identified crystallographically and biochemical and cellular studies delineate the consequences of destabilizing the χ/SSB interface. An essential role for the χ/SSB interaction in lagging-strand primer utilization is not supported. However, sequence changes in χ that block complex formation with SSB lead to salt-dependent uncoupling of leading- and lagging-strand DNA synthesis and to a surprising obstruction of the leading-strand DNA polymerase in vitro, pointing to roles for the χ/SSB complex in replisome establishment and maintenance. Destabilization of the χ/SSB complex in vivo produces cells with temperature-dependent cell cycle defects that appear to arise from replisome instability.

  19. Uranium dioxide in Fe(III)-containing ionic liquids with DMSO: Dissolution, separation, and structural characterization

    NASA Astrophysics Data System (ADS)

    Yao, Aining; Chu, Taiwei

    2016-11-01

    UO2 can be successfully dissolved in imidazolium-based Fe(III)-containing ionic liquids (ILs) with the help of DMSO. Spectroscopic studies and X-ray diffraction show that UO2Cl42- is the principal product. The dissolved uranyl species can be easily separated from the ILs via a combination of crystallization and solvent extraction. Moreover, even if 15.2 wt% of the rare-earth elements of Sm, Eu, and Gd, compared with the total amount of uranium and the rare-earth elements, exist in the IL, only uranium-containing crystals would be selectively formed and separated from the system. The solvents of acetone and acetonitrile could be used to separate the rare-earth elements from uranium in the IL with the help of imidazolium chloride. Considering the complete process from the dissolution of UO2 and some rare-earth oxides to the separation of uranium and rare-earth elements in the IL, the facile approach is promising for the spent nuclear fuel reprocessing.

  20. Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

    SciTech Connect

    Zheng, Qiye; Kim, Honggyu; Zhang, Runyu; Zuo, Jianmin; Braun, Paul V.; Sardela, Mauro; Balaji, Manavaimaran; Lourdudoss, Sebastian; Sun, Yan-Ting

    2015-12-14

    Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured Ga{sub x}In{sub 1−x}P (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.

  1. Upgrading of existing structures. Phase III. Shelter design options. Final report

    SciTech Connect

    Tansley, R.S.; Gabrielsen, B.L.; Cuzner, G.J.

    1981-05-01

    This report presents the results of an investigation of blast upgrading of existing structures, which consisted of developing failure prediction methodologies for various structure types, both in as built and in upgraded configurations, and verifying these prediction techniques with full-scale load tests. These upgrading schemes were developed for use as shelters in support of Civil Defense crisis relocation planning. Structure types investigated included wood, steel, and concrete floor and roof systems. The results of this study are being used in the development of a shelter manual presenting the various upgrading concepts in an illustrative workbook form for use in the field.

  2. Using structural modularity in cocrystals to engineer properties: elasticity.

    PubMed

    Saha, Subhankar; Desiraju, Gautam R

    2016-06-01

    Cocrystal formation of heterocyclic bases with halogenated aromatic acids increases the tendency for stacking and with this, an increase in structural isotropy occurs that leads to crystal elasticity. PMID:27228952

  3. Engine structures modeling software system: Computer code. User's manual

    NASA Technical Reports Server (NTRS)

    1992-01-01

    ESMOSS is a specialized software system for the construction of geometric descriptive and discrete analytical models of engine parts, components and substructures which can be transferred to finite element analysis programs such as NASTRAN. The software architecture of ESMOSS is designed in modular form with a central executive module through which the user controls and directs the development of the analytical model. Modules consist of a geometric shape generator, a library of discretization procedures, interfacing modules to join both geometric and discrete models, a deck generator to produce input for NASTRAN and a 'recipe' processor which generates geometric models from parametric definitions. ESMOSS can be executed both in interactive and batch modes. Interactive mode is considered to be the default mode and that mode will be assumed in the discussion in this document unless stated otherwise.

  4. Crankshaft supporting and lubricating structure for multicylinder internal combustion engines

    SciTech Connect

    Anno, N.

    1987-04-14

    This patent describes a crankshaft supporting and lubricating device in a multicylinder internal combustion engine having bearing caps secured to journal walls of a cylinder block rotatably supporting a crankshaft between the bearing caps and the journal walls with a bridge interconnecting the bearing caps. The improvement described here comprises: the bearing caps and the bridge having branch oil passages defined therein for supplying lubricating oil to bearings of the crankshaft; the branch oil passages being deviated to one side from a cylinder axis passing through the center of the crankshaft; the bridge having a main gallery defined therein in communication with the branch oil passages and also deviated to the one side; and the bridge and one of the bearing caps having an oil passage defined therein on the one side and providing communication between the main gallery and a pressurized oil source.

  5. Engineered/tailored nanoporous gold structures for infrared plasmonics

    NASA Astrophysics Data System (ADS)

    Garoli, Denis; Calandrini, Eugenio; Cattarin, Sandro; Barison, Simona; Zilio, Pierfrancesco; Bozzola, Angelo; Toma, Andrea; De Angelis, Francesco

    2015-08-01

    Nanoporous gold is a very promising and novel material platform for mid-infrared and THz plasmonics. Nanoporous gold can be formed by dealloying of Au-Ag alloys, previously grown by means of Ag-Au co-sputtering. The optical response is completely determined by the nanostructural film features, that depends on the initial alloy composition and on the preparation procedure. The behavior of the material in mid-infrared and its peculiar morphology with a very high surface/volume ratio can be applied for nanostructure fabrication, such for example nanoantennas. Here we report the design and fabrication of nanoporous antennas engineered to support resonances in the 1500-1700 cm-1 range where them can be exploited, for example, in the detection of protein conformational states. This novel paradigm points toward the development of a new class of efficient and high-selective biosensors.

  6. New anthracycline antibiotics produced by interspecific recombinants of streptomycetes. III. Isolation and structure of iremycin.

    PubMed

    Ihn, W; Schlegel, B; Fleck, W F; Sedmera, P

    1980-12-01

    The structure of the anthracycline antibiotic iremycin isolated from Streptomyces violaceus subspecies iremyceticus has been elucidated as 10-(alpha-L-rhodosaminyl)-gamma-rhodomycinone (I) on the basis of spectroscopic analyses and chemical reactions. PMID:7251489

  7. ORTEP-III: Oak Ridge Thermal Ellipsoid Plot Program for crystal structure illustrations

    SciTech Connect

    Burnett, M.N.; Johnson, C.K.

    1996-07-01

    This report describes a computer program for drawing crystal structure illustrations. Ball-and-stick type illustrations of a quality suitable for publication are produced with either spheres or thermal-motion probability ellipsoids on the atomic sites. The program can also produce stereoscopic pairs of illustrations which aid in the visualization of complex packing arrangements of atoms and thermal motion patterns. Interatomic distances, bond angles, and principal axes of thermal motion are also calculated to aid the structural study.

  8. The effect of ligand substituent on crystal packing: Structural and theoretical studies of two Ga(III) supramolecular compounds

    NASA Astrophysics Data System (ADS)

    Soleimannejad, Janet; Nazarnia, Esfandiar

    2016-07-01

    A new Ga(III) supramolecular compound (4,4‧-bipyH2)[Ga(hpydc)2]2·7H2O (2) (where H2hpydc = 4-hydroxy-pyridine-2,6-dicarboxylic acid and 4,4‧-bipy = 4,4‧-bipyridine) was synthesized using the proton transfer reaction. Compound 2 was structurally characterized using single crystal X-ray diffraction, and it was shown that its asymmetric unit consists of two independent anionic Ga(III) complexes, one fully protonated 4,4‧-bipyridine and seven uncoordinated water molecules. In order to understand the effect of pyridine OH substituent on supramolecular interactions and crystal packing, compound 2 was compared with (bipyH2)[Ga(pydc)2]·(H2pydc)·4H2O (1) (where H2pydc = pyridine-2,6-dicarboxylic acid), that does not have an OH group on the pyridine ligand. The Density Functional Theory (DFT) and Natural Bond Orbital (NBO) calculations and also Atoms in Molecules (AIM) analysis were used to analyze the non-covalent interactions in both complexes. The calculation of non-covalent interactions' energy provides a useful means to investigate their effects in the crystal packing.

  9. Synthesis, characterization and crystal structure of diaquadi(2,2`-bipyridine)di(dichloroacetato)lanthanide (III) monodichloroacetato

    SciTech Connect

    Lu Weimin, Cheng Yiqiang, Dong Nan

    1995-05-01

    The title complexes, Diaquadi(2,2`-bipyridine)Di(Dichloroacetato)Lanthanide (III) Monodichloroacetato [Ln(CHCI{sub 2}COO){sub 2}(2,2`-bipy){sub 2}(H{sub 2}O){sub 2}]{sup +}(CHCI{sub 2}COO){sup -}(Ln=Dy, Ho, Tm, Er, Yb) were obtained and characterized. [Er(CHCI{sub 2}COOO){sub 2}(2,2`-bipy){sub 2} (H{sub 2}O){sub 2}]+(CHCI{sub 2}COO){sup -} crystallizes in the monoclinic space group P2{sub 1}/n with Z=4. Cell dimensions are a=15.886 (9), b=13.758(2), c=16.343(4) {angstrom}, {Beta}=113.31(3){degrees}, and the structure was refined to an R of 0.049 for 3415 observed reflections. The Er(III) ion exhibits a distorted, square antiprismatic configuration. Four N atoms of 2,2`-bipy and four O atoms from two dichloroacetato and two water ligands are coordinated. One dichloroacetato group lies outside the polyhedron and is connected with water ligands by hydrogen bonds.

  10. Synthesis, molecular structure, theoretical calculation, DNA/protein interaction and cytotoxic activity of manganese(III) complex with 8-hydroxyquinoline.

    PubMed

    Thamilarasan, V; Sengottuvelan, N; Sudha, A; Srinivasan, P; Siva, A

    2015-01-01

    Manganese(III) complex (1) [Mn(8-hq)3] (where 8-hq=8-hydroxyquinoline) has been synthesized and characterized by elemental, spectral (UV-vis, FT-IR) and thermal analysis. The structure of complex (1) has been determined by single crystal X-ray diffraction studies and the configuration around manganese(III) ion was elongated octahedral coordination geometry. Density functional theory calculations were performed for ligand and its complex. Binding studies of ligand and complex 1 with calf thymus DNA (CT-DNA) was investigated by absorption, fluorescence, circular dichroic (CD) spectroscopy and viscosity measurements. Absorption spectral studies revealed that ligand and complex 1 binds to DNA groove and its intrinsic binding strength has been found to be 2.57×10(4) and 2.91×10(4)M(-1). A molecular docking study confirm that the complex 1 is a minor groove binder and was stabilized through hydrogen bonding interactions. Complex 1 exhibits a good binding propensity to bovine serum albumin (BSA) protein. The in vitro cytotoxicity study of complex 1 on breast cancer cell line (MCF-7) indicate that it has the potential to act as effective anticancer drug, with IC50 values of 3.25μM. The ligand and its complex have been screened for antimicrobial activities and the complex showed better antimicrobial activity than the free ligand.

  11. Enantiopure tetranuclear iron(III) complexes using chiral reduced Schiff base ligands: synthesis, structure, spectroscopy, magnetic properties, and DFT studies.

    PubMed

    Singh, Reena; Banerjee, Atanu; Colacio, Enrique; Rajak, Kajal Krishna

    2009-06-01

    Four new tetranuclear iron(III) complexes of formula [{Fe(L)(2)}(3)Fe], 1-4, have been prepared by reacting [Fe(ClO(4))(3)].6H(2)O with H(2)L in methanol. Here, L(2-) is the deprotonated form of N-(2-hyrdoxybenzyl)-l-valinol (H(2)L(1)), N-(2-hyrdoxybenzyl)-l-leucinol (H(2)L(2)), N-(5-chloro-2-hyrdoxybenzyl)-l-leucinol (H(2)L(3)), and N-(2-hyrdoxybenzyl)-l-phenylalaninol (H(2)L(4)). The complexes are prepared in an enantiomeric pure form. The complexes have been characterized with the help of IR, UV-vis, circular dichroism (CD), (1)H, and elemental analyses. The complex [{Fe(L(2))(2)}(3)Fe].CH(3)OH.2H(2)O, 2.CH(3)OH.2H(2)O, crystallizes in enantiomeric pure form containing a propeller-like Fe(4)O(6) core. (1)H and CD spectral studies of the four species are consistent with the structural similarities of the complexes in solution. Variable-temperature magnetic susceptibility of one case shows an intramolecular antiferromagnetic coupling between the Fe(III) ions. Magnetic measurements are in accord with the S = 5 ground state and suggest single molecular magnet behavior. The magnetic exchange coupling constant between the iron centers within the molecule is interpreted using broken-symmetry density functional theory calculation. PMID:19466801

  12. Self-Interaction Corrections to the Electronic Structure of II-VI and III-V Nitride Semiconductors

    NASA Astrophysics Data System (ADS)

    Pollmann, J.

    1998-03-01

    II-VI and group-III nitride semiconductors have paramount technological potential for applications in micro- and optoelectronics. A most accurate description of their bulk electronic structure as a basis for studying defect properties, band-edge properties in respective ternary or quaternary alloys and electronic properties of their surfaces and interfaces is of major importance, therefore. Standard LDA band-structure calculations for these wide-band-gap compounds using nonlocal normconserving pseudopotentials yield gap energies and semicore d-band positions that are largely at variance with experimental data. Actually, InN even turns out to be a semimetal with a negative gap of about --0.4 eV in standard LDA, in contrast to the experimental gap of 1.9 eV. To improve the theoretical basis for the above mentioned studies, we have developed self-interaction- and relaxation-corrected pseudopotentials (SIRC-PPs) which are very efficient and physically well-founded. The properties of the constituent atoms are incorporated in these SIRC-PPs as accurately as possible from the start by taking atomic SIC contributions and electronic relaxation in the atoms fully into account. By this construction, we arrive at very useful pseudopotentials and effective one-particle Hamiltonians for the solids that can readily be employed in ab-initio LDA codes. This approach is computationally not more involved than any LDA calculation and, nevertheless, overcomes to a large extent the above mentioned shortcomings of standard LDA calculations employing 'state-of-the-art' pseudopotentials. Applications of our approach to II-VI and group-III nitride semiconductors have shown very gratifying results. The approach has also proven very useful for Hg-chalcogenides, as well as, for Ag- and Cu-halides. The calculations yield band structures, d-band positions, gap energies, densities of states, lattice constants, bulk moduli and effective masses in very good agreement with experiment. Due to the

  13. Isoform-specific monobody inhibitors of small ubiquitin-related modifiers engineered using structure-guided library design

    PubMed Central

    Gilbreth, Ryan N.; Truong, Khue; Madu, Ikenna; Koide, Akiko; Wojcik, John B.; Li, Nan-Sheng; Piccirilli, Joseph A.; Chen, Yuan; Koide, Shohei

    2011-01-01

    Discriminating closely related molecules remains a major challenge in the engineering of binding proteins and inhibitors. Here we report the development of highly selective inhibitors of small ubiquitin-related modifier (SUMO) family proteins. SUMOylation is involved in the regulation of diverse cellular processes. Functional differences between two major SUMO isoforms in humans, SUMO1 and SUMO2/3, are thought to arise from distinct interactions mediated by each isoform with other proteins containing SUMO-interacting motifs (SIMs). However, the roles of such isoform-specific interactions are largely uncharacterized due in part to the difficulty in generating high-affinity, isoform-specific inhibitors of SUMO/SIM interactions. We first determined the crystal structure of a “monobody,” a designed binding protein based on the fibronectin type III scaffold, bound to the yeast homolog of SUMO. This structure illustrated a mechanism by which monobodies bind to the highly conserved SIM-binding site while discriminating individual SUMO isoforms. Based on this structure, we designed a SUMO-targeted library from which we obtained monobodies that bound to the SIM-binding site of human SUMO1 with Kd values of approximately 100 nM but bound to SUMO2 400 times more weakly. The monobodies inhibited SUMO1/SIM interactions and, unexpectedly, also inhibited SUMO1 conjugation. These high-affinity and isoform-specific inhibitors will enhance mechanistic and cellular investigations of SUMO biology. PMID:21518904

  14. Isoform-specific monobody inhibitors of small ubiquitin-related modifiers engineered using structure-guided library design.

    PubMed

    Gilbreth, Ryan N; Truong, Khue; Madu, Ikenna; Koide, Akiko; Wojcik, John B; Li, Nan-Sheng; Piccirilli, Joseph A; Chen, Yuan; Koide, Shohei

    2011-05-10

    Discriminating closely related molecules remains a major challenge in the engineering of binding proteins and inhibitors. Here we report the development of highly selective inhibitors of small ubiquitin-related modifier (SUMO) family proteins. SUMOylation is involved in the regulation of diverse cellular processes. Functional differences between two major SUMO isoforms in humans, SUMO1 and SUMO2/3, are thought to arise from distinct interactions mediated by each isoform with other proteins containing SUMO-interacting motifs (SIMs). However, the roles of such isoform-specific interactions are largely uncharacterized due in part to the difficulty in generating high-affinity, isoform-specific inhibitors of SUMO/SIM interactions. We first determined the crystal structure of a "monobody," a designed binding protein based on the fibronectin type III scaffold, bound to the yeast homolog of SUMO. This structure illustrated a mechanism by which monobodies bind to the highly conserved SIM-binding site while discriminating individual SUMO isoforms. Based on this structure, we designed a SUMO-targeted library from which we obtained monobodies that bound to the SIM-binding site of human SUMO1 with K(d) values of approximately 100 nM but bound to SUMO2 400 times more weakly. The monobodies inhibited SUMO1/SIM interactions and, unexpectedly, also inhibited SUMO1 conjugation. These high-affinity and isoform-specific inhibitors will enhance mechanistic and cellular investigations of SUMO biology.

  15. Metal binding properties and structure of a type III metallothionein from the metal hyperaccumulator plant Noccaea caerulescens.

    PubMed

    Fernandez, Lucia Rubio; Vandenbussche, Guy; Roosens, Nancy; Govaerts, Cédric; Goormaghtigh, Erik; Verbruggen, Nathalie

    2012-09-01

    Metallothioneins (MT) are low molecular weight proteins with cysteine-rich sequences that bind heavy metals with remarkably high affinities. Plant MTs differ from animal ones by a peculiar amino acid sequence organization consisting of two short Cys-rich terminal domains (containing from 4 to 8 Cys each) linked by a Cys free region of about 30 residues. In contrast with the current knowledge on the 3D structure of animal MTs, there is a striking lack of structural data on plant MTs. We have expressed and purified a type III MT from Noccaea caerulescens (previously Thlaspi caerulescens). This protein is able to bind a variety of cations including Cd(2+), Cu(2+), Zn(2+) and Pb(2+), with different stoichiometries as shown by mass spectrometry. The protein displays a complete absence of periodic secondary structures as measured by far-UV circular dichroism, infrared spectroscopy and hydrogen/deuterium exchange kinetics. When attached onto a BIA-ATR biosensor, no significant structural change was observed upon removing the metal ions. PMID:22668884

  16. Two-generation analysis of pollen flow across a landscape. III. Impact of adult population structure.

    PubMed

    Austerlitz, F; Smouse, P E

    2001-12-01

    The rate and distance of instantaneous pollen flow in a population are parameters of considerable current interest for plant population geneticists and conservation biologists. We have recently developed an estimator (phi ft) of differentiation between the inferred pollen clouds that fertilize several females, sampled within a single population. We have shown that there is a simple relation between phi ft and the average pollen dispersal distance (delta) for the case of a population with no geographic structure. Though forest trees usually show considerable pollen flow, assuming an absence of spatially distributed genetic structure is not always wise. Here, we develop analytical theory for the relation between phi ft and delta, for the case where the probability of Identity by Descent (IBD) for two individuals decreases with the physical distance between them. This analytical theory allows us to provide an effective method for estimating pollen dispersal distance in a population with adult genetic structure. Using real examples, we show that estimation errors can be large if genetic structure is not taken into account, so it is wise to evaluate adult genetic structure simultaneously with estimation of phi ft for the pollen clouds. We show that the results are only moderately affected by changes in the decay function, a result of some importance since no completely established theory is available for this function.

  17. Multiple piece turbine engine airfoil with a structural spar

    DOEpatents

    Vance, Steven J.

    2011-10-11

    A multiple piece turbine airfoil having an outer shell with an airfoil tip that is attached to a root with an internal structural spar is disclosed. The root may be formed from first and second sections that include an internal cavity configured to receive and secure the one or more components forming the generally elongated airfoil. The internal structural spar may be attached to an airfoil tip and place the generally elongated airfoil in compression. The configuration enables each component to be formed from different materials to reduce the cost of the materials and to optimize the choice of material for each component.

  18. Structural characterization of poorly-crystalline scorodite, iron(III)-arsenate co-precipitates and uranium mill neutralized raffinate solids using X-ray absorption fine structure spectroscopy

    SciTech Connect

    Chen, N; Jiang, D T; Cutler, J; Kotzer, T; Jia, Y F; Demopoulos, G P; Rowson, J W

    2009-12-01

    X-ray absorption fine structure (XAFS) is used to characterize the mineralogy of the iron(III)-arsenate(V) precipitates produced during the raffinate (aqueous effluent) neutralization process at the McClean Lake uranium mill in northern Saskatchewan, Canada. To facilitate the structural characterization of the precipitated solids derived from the neutralized raffinate, a set of reference compounds were synthesized and analyzed. The reference compounds include crystalline scorodite, poorly-crystalline scorodite, iron(III)-arsenate co-precipitates obtained under different pH conditions, and arsenate-adsorbed on goethite. The poorly-crystalline scorodite (prepared at pH 4 with Fe/As = 1) has similar As local structure as that of crystalline scorodite. Both As and Fe K-edge XAFS of poorly-crystalline scorodite yield consistent results on As-Fe (or Fe-As) shell. From As K-edge analysis the As-Fe shell has an inter-atomic distance of 3.33 ± 0.02 Å and coordination number of 3.2; while from Fe K-edge analysis the Fe-As distance and coordination number are 3.31 ± 0.02 Å and 3.8, respectively. These are in contrast with the typical arsenate adsorption on bidentate binuclear sites on goethite surfaces, where the As-Fe distance is 3.26 ± 0.03 Å and coordination number is close to 2. A similar local structure identified in the poorly-crystalline scorodite is also found in co-precipitation solids (Fe(III)/As(V) = 3) when precipitated at the same pH (pH = 4): As-Fe distance 3.30 ± 0.03 Å and coordination number 3.9; while at pH = 8 the co-precipitate has As-Fe distance of 3.27 ± 0.03 Å and coordination number about 2, resembling more closely the adsorption case. The As local structure in the two neutralized raffinate solid series (precipitated at pH values up to 7) closely resembles that in the poorly-crystalline scorodite. All of the raffinate solids have the same As-Fe inter-atomic distance as that in the poorly-crystalline scorodite, and a systematic decrease in the

  19. New Tools Being Developed for Engine- Airframe Blade-Out Structural Simulations

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles

    2003-01-01

    One of the primary concerns of aircraft structure designers is the accurate simulation of the blade-out event. This is required for the aircraft to pass Federal Aviation Administration (FAA) certification and to ensure that the aircraft is safe for operation. Typically, the most severe blade-out occurs when a first-stage fan blade in a high-bypass gas turbine engine is released. Structural loading results from both the impact of the blade onto the containment ring and the subsequent instantaneous unbalance of the rotating components. Reliable simulations of blade-out are required to ensure structural integrity during flight as well as to guarantee successful blade-out certification testing. The loads generated by these analyses are critical to the design teams for several components of the airplane structures including the engine, nacelle, strut, and wing, as well as the aircraft fuselage. Currently, a collection of simulation tools is used for aircraft structural design. Detailed high-fidelity simulation tools are used to capture the structural loads resulting from blade loss, and then these loads are used as input into an overall system model that includes complete structural models of both the engines and the airframe. The detailed simulation (shown in the figure) includes the time-dependent trajectory of the lost blade and its interactions with the containment structure, and 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 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. To develop and validate these new tools with test data, the NASA Glenn Research Center has teamed with GE Aircraft Engines, Pratt & Whitney, Boeing Commercial Aircraft, Rolls-Royce, and MSC.Software.

  20. Factor Structure of the Norwegian Version of the WAIS-III in a Clinical Sample: The Arithmetic Problem

    ERIC Educational Resources Information Center

    Egeland, Jens; Bosnes, Ole; Johansen, Hans

    2009-01-01

    Confirmatory Factor Analyses (CFA) of the Wechsler Adult Intelligence Scale-III (WAIS-III) lend partial support to the four-factor model proposed in the test manual. However, the Arithmetic subtest has been especially difficult to allocate to one factor. Using the new Norwegian WAIS-III version, we tested factor models differing in the number of…

  1. MOVPE of III-N LED structures with short technological process

    NASA Astrophysics Data System (ADS)

    Lundin, W. V.; Davydov, D. V.; Zavarin, E. E.; Popov, M. G.; Sakharov, A. V.; Yakovlev, E. V.; Bazarevskii, D. S.; Talalaev, R. A.; Tsatsulnikov, A. F.; Mizerov, M. N.; Ustinov, V. M.

    2015-03-01

    The paper presents results on optimizing the MOVPE technology of light-emitting diode (LED) structures in a Dragon-125 system to accelerate the technological cycle. Due to the high growth rate of GaN layers and optimization of the initial GaN growth phase, the total duration of the epitaxial process is reduced from 4 h 45 min to 2 h 44 min. The LED diode structures grown by this technique compare well in quality with LEDs grown by the standard method in the commercially available AIX2000HT system.

  2. Ellipsometric study of metal-organic chemically vapor deposited III-V semiconductor structures

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Sekula-Moise, Patricia A.; Sieg, Robert M.; Drotos, Mark N.; Bogner, Nancy A.

    1992-01-01

    An ellipsometric study of MOCVD-grown layers of AlGaAs and InGaAs in thick films and strained layer complex structures is presented. It is concluded that the ternary composition of thick nonstrained layers can be accurately determined to within experimental errors using numerical algorithms. In the case of complex structures, thickness of all layers and the alloy composition of nonstrained layers can be determined simultaneously, provided that the correlations between parameters is no higher than 0.9.

  3. Bacteriophage SPO1 structure and morphogenesis. III. SPO1 proteins and synthesis.

    PubMed Central

    Parker, M L; Eiserling, F A

    1983-01-01

    The virion proteins of SPO1 have been determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis methods on purified phage components and on phage lysates. The phage head contains 16 proteins, and the connector or neck structure has an additional 3 proteins not found in the head. The proximal part of the tail, composed of sheath, tube and connecting components, contains six proteins. The distal baseplate is the most complex structure, with 28 proteins identifiable on sodium dodecyl sulfate gels. The maximum number of proteins found in phage subassemblies is 53, which would account for nearly half the coding capacity of the SPO1 genome. Images PMID:6827651

  4. Crystal structure of tris­(ethyl­enedi­ammonium) hexasulfatopraseodymium(III) hexa­hydrate

    PubMed Central

    Held, Peter

    2014-01-01

    In the title salt, (C2H10N2)3[Pr2(SO4)6]·6H2O, the PrIII cation is surrounded ninefold by five sulfate groups (two monodentate and three chelating) and by one water mol­ecule [range of Pr—O bond lengths 2.383 (3) to 2.582 (3) Å]. The [Pr(SO4)5(H2O)] groups are arranged in sheets parallel to (010). Two crystal water mol­ecules and two ethyl­enedi­ammonium cations (one with point group symmetry -1) connect the sheets via O—H⋯O and N—H⋯O hydrogen bonds from weak up to medium strength into a three-dimensional framework structure. PMID:25484661

  5. Structural health monitoring on turbine engines using microwave blade tip clearance sensors

    NASA Astrophysics Data System (ADS)

    Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle

    2014-04-01

    The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to the aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA) has taken a lead role in the investigation of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. As part of this effort, microwave sensor technology has been investigated as a means of making high temperature non-contact blade tip clearance, blade tip timing, and blade vibration measurements for use in gas turbine engines. This paper presents a summary of key results and findings obtained from the evaluation of two different types of microwave sensors that have been investigated for possible use in structural health monitoring applications. The first is a microwave blade tip clearance sensor that has been evaluated on a large scale Axial Vane Fan, a subscale Turbofan, and more recently on sub-scale turbine engine like disks. The second is a novel microwave based blade vibration sensor that was also used in parallel with the microwave blade tip clearance sensors on the same experiments with the sub-scale turbine engine disks.

  6. Structural Health Monitoring on Turbine Engines Using Microwave Blade Tip Clearance Sensors

    NASA Technical Reports Server (NTRS)

    Woike, Mark; Abdul-Aziz, Ali; Clem, Michelle

    2014-01-01

    The ability to monitor the structural health of the rotating components, especially in the hot sections of turbine engines, is of major interest to aero community in improving engine safety and reliability. The use of instrumentation for these applications remains very challenging. It requires sensors and techniques that are highly accurate, are able to operate in a high temperature environment, and can detect minute changes and hidden flaws before catastrophic events occur. The National Aeronautics and Space Administration (NASA) has taken a lead role in the investigation of new sensor technologies and techniques for the in situ structural health monitoring of gas turbine engines. As part of this effort, microwave sensor technology has been investigated as a means of making high temperature non-contact blade tip clearance, blade tip timing, and blade vibration measurements for use in gas turbine engines. This paper presents a summary of key results and findings obtained from the evaluation of two different types of microwave sensors that have been investigated for use possible in structural health monitoring applications. The first is a microwave blade tip clearance sensor that has been evaluated on a large scale Axial Vane Fan, a subscale Turbofan, and more recently on sub-scale turbine engine like disks. The second is a novel microwave based blade vibration sensor that was also used in parallel with the microwave blade tip clearance sensors on the experiments with the sub-scale turbine engine disks.

  7. Electronic Structure of Pi Systems: Part III--Applications in Spectroscopy and Chemical Reactivity.

    ERIC Educational Resources Information Center

    Fox, Marye Anne; Matsen, F. A.

    1985-01-01

    Shows that electronic structure diagrams make more accurate predictions of spectral properties and chemical reactivity for simple pi systems than do either Huckel molecular orbital or valence bond theory alone. Topics addressed include absorption and photoelectron spectra, spin density distribution in radicals, and several problems regarding…

  8. Immobilization of cobalt(III) Schiff base complexes onto Montmorillonite-K10: Synthesis, experimental and theoretical structural determination.

    PubMed

    Kianfar, Ali Hossein; Kamil Mahmood, Wan Ahmad; Dinari, Mohammad; Farrokhpour, Hossein; Enteshari, Majid; Azarian, Mohammad Hossein

    2015-02-01

    The [Co(naphophen)(PPh3)(OH2)]ClO4 and [Co(naphophen)(PBu3)(OH2)]BF4 (where naphophen=bis(naphthaldehyde)1,2-phenylenediimine) complexes were synthesized and chracterized by FT-IR, UV-Vis, (1)H NMR, (13)C NMR spectroscopy and elemental analysis techniques. The coordination geometry of the synthesized complexes were determined by X-ray crystallography. Cobalt (III) complexes have six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base forms the equatorial plane. These complexes showed a dimeric structure via hydrogen bonding between the phenolate oxygen and the hydrogens of the coordinated H2O molecule. The theoretical calculations were also performed to optimize the structure of the complexes in the gas phase to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification. The synthesized complexes were incorporated onto the Montmorillonite-K10 nanoclay via simple ion-exchange reaction. The structure and morphology of the obtained nanohybrids were identified by FT-IR, XRD, TGA/DTA, SEM and TEM techniques. Based on the XRD results of the new nanohybrid materials, the Schiff base complexes were intercalated in the interlayer spaces of clay. SEM and TEM micrographs of the clay/complex shows that the resulting hybrid nanomaterials has layer structures. PMID:25459719

  9. Recent advances in convectively cooled engine and airframe structures for hypersonic flight

    NASA Technical Reports Server (NTRS)

    Kelly, H. N.; Wieting, A. R.; Shore, C. P.; Nowak, R. J.

    1978-01-01

    A hydrogen-cooled structure for a fixed-geometry, airframe-integrated scramjet is described. The thermal/structural problems, concepts, design features, and technological advances are applicable to a broad range of engines. Convectively cooled airframe structural concepts that have evolved from an extensive series of investigations, the technology developments that have led to these concepts, and the benefits that accrue from their use are discussed.

  10. Remote sensing in investigation of engineered underground structures

    SciTech Connect

    Kane, W.F. |; Peters, D.C.; Speirer, R.A.

    1996-08-01

    Lineaments, linear features visible on remotely sensed imagery, can be used to predict ground control problems in underground structures. Lineaments were used to backpredict hazardous ground conditions in an underground constructed facility, a coal mine in Alabama. The mine property was mapped above and below the surface for fractures and other geologic structural features. Both parametric and nonparametric statistics were employed in correlating field data with information derived from lineament maps. Results showed that fractures observed on the surface dipped vertically and extended to the mine level. Direct correlation of fracture trends with lineament trends was not apparent. However, lineaments were correlated with a change in the local fracture trend from the regional geologic structural trend. This deviation between lineament trend and fracture trend was consistent and statistically significant. Forty-two percent of all roof failures could be directly correlated with lineaments. It was found that the number of roof failures decreased exponentially with distance from a lineament. However, no relationships were found between roof fall occurrences and lineament intersections or lengths.

  11. Coherent nanocavity structures for enhancement in internal quantum efficiency of III-nitride multiple quantum wells

    SciTech Connect

    Kim, T.; Liu, B.; Smith, R.; Athanasiou, M.; Gong, Y.; Wang, T.

    2014-04-21

    A “coherent” nanocavity structure has been designed on two-dimensional well-ordered InGaN/GaN nanodisk arrays with an emission wavelength in the green spectral region, leading to a massive enhancement in resonance mode in the green spectra region. By means of a cost-effective nanosphere lithography technique, we have fabricated such a structure on an InGaN/GaN multiple quantum well epiwafer and have observed the “coherent” nanocavity effect, which leads to an enhanced spontaneous emission (SE) rate. The enhanced SE rate has been confirmed by time resolved photoluminescence measurements. Due to the coherent nanocavity effect, we have achieved a massive improvement in internal quantum efficiency with a factor of 88, compared with the as-grown sample, which could be significant to bridge the “green gap” in solid-state lighting.

  12. Non-local exchange correlation functionals impact on the structural, electronic and optical properties of III-V arsenides

    NASA Astrophysics Data System (ADS)

    Najwa Anua, N.; Ahmed, R.; Shaari, A.; Saeed, M. A.; Haq, Bakhtiar Ul; Goumri-Said, Souraya

    2013-10-01

    Exchange correlation (XC) energy functionals play a vital role in the efficiency of density functional theory (DFT) calculations, more soundly in the calculation of fundamental electronic energy bandgap. In the present DFT study of III-arsenides, we investigate the implications of XC-energy functional and corresponding potential on the structural, electronic and optical properties of XAs (X = B, Al, Ga, In). Firstly we report and discuss the optimized structural lattice parameters and the band gap calculations performed within different non-local XC functionals as implemented in the DFT-packages: WIEN2k, CASTEP and SIESTA. These packages are representative of the available code in ab initio studies. We employed the LDA, GGA-PBE, GGA-WC and mBJ-LDA using WIEN2k. In CASTEP, we employed the hybrid functional, sX-LDA. Furthermore LDA, GGA-PBE and meta-GGA were employed using SIESTA code. Our results point to GGA-WC as a more appropriate approximation for the calculations of structural parameters. However our electronic bandstructure calculations at the level of mBJ-LDA potential show considerable improvements over the other XC functionals, even the sX-LDA hybrid functional. We report also the optical properties within mBJ potential, which show a nice agreement with the experimental measurements in addition to other theoretical results.

  13. [How to measure structures, or new stereology: III. Stereology and electron microscopy].

    PubMed

    Mironov, A A; Beznusenko, G V; Sesorova, I S; Banin, V V

    2006-01-01

    This review describes modern stereological approaches and methods for estimation of subcellular structures dimensions. These estimators could be used for determination of number- and volume-weighted parameters of particle size. Very often they do not require the application of the disector at the first stage of sampling of images. Additionally, the modified version of the rotator for point counting is demonstrated, which significantly accelerates the morphometric procedure. PMID:17111667

  14. Hydrothermal synthesis and structural characterization of ammonium ion-templated lanthanide(III) carboxylate-phosphonates

    PubMed Central

    Ayi, Ayi A.; Kinnibrugh, Tiffany L.; Clearfield, Abraham

    2014-01-01

    Using N-(phosphonomethyl) iminodiacetic acid (H4PMIDA), as a complexing agent, two new complexes, (NH4)La(PMIDA)(H2O)•H2O, 1 and (NH4)Yb(PMIDA), 2 have been synthesized hydrothermally. In both compounds, the metal ions are trapped by a three five-membered chelate rings by the chelating PMIDA anions giving a tricapped trigonal prismatic LaO8N and monocapped trigonal prismatic YbO6N geometries for 1 and 2, respectively. The structure of 1 consists of La(PMIDA)(H2O) chelating units, linked together by the phosphonate oxygen atoms O1 and O3 to form a chain along the c-axis. The chains are then connected together by the bridging phosphonate oxygen O2 to form a 2D layered structure with alternating 4- and 8-membered apertures. The structure of 2 consists Yb(PMIDA) chelating units, which are connected by alternating bridging carboxylate and phosphonate groups along the [010] direction forming chains with a corrugated pattern. The third phosphonate oxygen bridges the chains together along the [001] direction to build the two-dimensional layer with 4- and 6-membered apertures in the bc-plane. Under excitation of 330 nm, compound 2 shows a broad emission band at λmax = 460 nm. This emission is essentially in the blue luminescent region, which corresponds to ligand centered fluorescence. PMID:25414845

  15. Transformations of galaxies - III. Encounter dynamics and tidal response as functions of galaxy structure

    NASA Astrophysics Data System (ADS)

    Barnes, Joshua E.

    2016-01-01

    Tidal interactions between disc galaxies depend on galaxy structure, but the details of this relationship are incompletely understood. I have constructed a three-parameter grid of bulge/disc/halo models broadly consistent with Λ cold dark matter, and simulated an extensive series of encounters using these models. Halo mass and extent strongly influence the dynamics of orbit evolution. In close encounters, the transfer of angular momentum mediated by the dynamical response of massive, extended haloes can reverse the direction of orbital motion of the central galaxies after their first passage. Tidal response is strongly correlated with the ratio ve/vc of escape to circular velocity within the participating discs. Moreover, the same ratio also correlates with the rate at which tidal tails are reaccreted by their galaxies of origin; consequently, merger remnants with `twin tails', such as NGC 7252, may prove hard to reproduce unless (ve/vc)2 ≲ 5.5. The tidal morphology of an interacting system can provide useful constraints on progenitor structure. In particular, encounters in which halo dynamics reverses orbital motion exhibit a distinctive morphology which may be recognized observationally. Detailed models attempting to reproduce observations of interacting galaxies should explore the likely range of progenitor structures along with other encounter parameters.

  16. A series of Ti(IV)/Ti(III) coordination polymers: Structures and surface photoelectric properties

    NASA Astrophysics Data System (ADS)

    Li, Lei; Zhang, Li; Liu, Dong-Wei; Jin, Jing; Chi, Yu-Xian; Niu, Shu-Yun

    2012-02-01

    Three titanium coordination polymers, {[Ti(SO 4) 2(H 2O)]·0.5bipy·2H 2O} n1, {[Ti1(SO 4) 2(H 2O)]·[Ti2(SO 4) 2(H 2O)]·bipy·5H 2O} n2 and [Ti(tea)] n3 (bipy = 4,4'-bipyridine, H 3tea = triethanolamine) were synthesized and characterized by IR, UV-Vis absorption spectra, TG analysis, X-ray single crystal diffraction and surface photovoltage spectroscopy (SPS). The surface photoelectric properties of titanium coordination polymers were discussed emphatically by the SPS. The results of single crystal diffraction indicate that polymers 1 and 2 possess 1D infinite structure bridged by SO 42- groups and coordinated water molecules and further connected into supramolecular structures by hydrogen bonds. Polymer 3 possesses 2D infinite structure bridged by weak sub-coordinated Ti-O bonds. The results of SPS show that there are obvious photovoltage responses in the range of 300-500 nm, which indicates that they possess photoelectric conversion ability. The SPS of three titanium polymers were analyzed comparatively. It is found that the valence of central metal ions, coordination micro-environment and kinds of coordination atoms influence the results of the SPS. The SPS is associated with UV-Vis absorption spectra.

  17. A series of Ti(IV)/Ti(III) coordination polymers: structures and surface photoelectric properties.

    PubMed

    Li, Lei; Zhang, Li; Liu, Dong-Wei; Jin, Jing; Chi, Yu-Xian; Niu, Shu-Yun

    2012-02-01

    Three titanium coordination polymers, {[Ti(SO(4))(2)(H(2)O)]·0.5bipy·2H(2)O}(n)1, {[Ti1(SO(4))(2)(H(2)O)]·[Ti2(SO(4))(2)(H(2)O)]·bipy·5H(2)O}(n)2 and [Ti(tea)](n)3 (bipy=4,4'-bipyridine, H(3)tea=triethanolamine) were synthesized and characterized by IR, UV-Vis absorption spectra, TG analysis, X-ray single crystal diffraction and surface photovoltage spectroscopy (SPS). The surface photoelectric properties of titanium coordination polymers were discussed emphatically by the SPS. The results of single crystal diffraction indicate that polymers 1 and 2 possess 1D infinite structure bridged by SO(4)(2-) groups and coordinated water molecules and further connected into supramolecular structures by hydrogen bonds. Polymer 3 possesses 2D infinite structure bridged by weak sub-coordinated Ti-O bonds. The results of SPS show that there are obvious photovoltage responses in the range of 300-500 nm, which indicates that they possess photoelectric conversion ability. The SPS of three titanium polymers were analyzed comparatively. It is found that the valence of central metal ions, coordination micro-environment and kinds of coordination atoms influence the results of the SPS. The SPS is associated with UV-Vis absorption spectra.

  18. Syntheses, structures, and magnetic properties of acetato- and diphenolato-bridged 3d-4f binuclear complexes [M(3-MeOsaltn)(MeOH)x(ac)Ln(hfac)2] (M = Zn(II), Cu(II), Ni(II), Co(II); Ln = La(III), Gd(III), Tb(III), Dy(III); 3-MeOsaltn = N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato; ac = acetato; hfac = hexafluoroacetylacetonato; x = 0 or 1).

    PubMed

    Towatari, Masaaki; Nishi, Koshiro; Fujinami, Takeshi; Matsumoto, Naohide; Sunatsuki, Yukinari; Kojima, Masaaki; Mochida, Naotaka; Ishida, Takayuki; Re, Nazzareno; Mrozinski, Jerzy

    2013-05-20

    A series of 3d-4f binuclear complexes, [M(3-MeOsaltn)(MeOH)x(ac)Ln(hfac)2] (x = 0 for M = Cu(II), Zn(II); x = 1 for M = Co(II), Ni(II); Ln = Gd(III), Tb(III), Dy(III), La(III)), have been synthesized and characterized, where 3-MeOsaltn, ac, and hfac denote N,N'-bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, acetato, and hexafluoroacetylacetonato, respectively. The X-ray analyses demonstrated that all the complexes have an acetato- and diphenolato-bridged M(II)-Ln(III) binuclear structure. The Cu(II)-Ln(III) and Zn(II)-Ln(III) complexes are crystallized in an isomorphous triclinic space group P1, where the Cu(II) or Zn(II) ion has square pyramidal coordination geometry with N2O2 donor atoms of 3-MeOsaltn at the equatorial coordination sites and one oxygen atom of the bridging acetato ion at the axial site. The Co(II)-Ln(III) and Ni(II)-Ln(III) complexes are crystallized in an isomorphous monoclinic space group P2(1)/c, where the Co(II) or Ni(II) ion at the high-spin state has an octahedral coordination environment with N2O2 donor atoms of 3-MeOsaltn at the equatorial sites, and one oxygen atom of the bridged acetato and a methanol oxygen atom at the two axial sites. Each Ln(III) ion for all the complexes is coordinated by four oxygen atoms of two phenolato and two methoxy oxygen atoms of "ligand-complex" M(3-MeOsaltn), four oxygen atoms of two hfac(-), and one oxygen atom of the bridging acetato ion; thus, the coordination number is nine. The temperature dependent magnetic susceptibilities from 1.9 to 300 K and the field-dependent magnetization up to 5 T at 1.9 K were measured. Due to the important orbital contributions of the Ln(III) (Tb(III), Dy(III)) and to a lesser extent the M(II) (Ni(II), Co(II)) components, the magnetic interaction between M(II) and Ln(III) ions were investigated by an empirical approach based on a comparison of the magnetic properties of the M(II)-Ln(III), Zn(II)-Ln(III), and M(II)-La(III) complexes. The differences of χ(M)T and M

  19. Conserving intertidal habitats: What is the potential of ecological engineering to mitigate impacts of coastal structures?

    NASA Astrophysics Data System (ADS)

    Perkins, Matthew J.; Ng, Terence P. T.; Dudgeon, David; Bonebrake, Timothy C.; Leung, Kenneth M. Y.

    2015-12-01

    Globally, coastlines are under pressure as coastal human population growth and urbanization continues, while climatic change leads to stormier seas and rising tides. These trends create a strong and sustained demand for land reclamation and infrastructure protection in coastal areas, requiring engineered coastal defence structures such as sea walls. Here, we review the nature of ecological impacts of coastal structures on intertidal ecosystems, seek to understand the extent to which ecological engineering can mitigate these impacts, and evaluate the effectiveness of mitigation as a tool to contribute to conservation of intertidal habitats. By so doing, we identify critical knowledge gaps to inform future research. Coastal structures alter important physical, chemical and biological processes of intertidal habitats, and strongly impact community structure, inter-habitat linkages and ecosystem services while also driving habitat loss. Such impacts occur diffusely across localised sites but scale to significant regional and global levels. Recent advances in ecological engineering have focused on developing habitat complexity on coastal structures to increase biodiversity. 'Soft' engineering options maximise habitat complexity through inclusion of natural materials, species and processes, while simultaneously delivering engineering objectives such as coastal protection. Soft options additionally sustain multiple services, providing greater economic benefits for society, and resilience to climatic change. Currently however, a lack of inclusion and economic undervaluation of intertidal ecosystem services may undermine best practice in coastline management. Importantly, reviewed evidence shows mitigation and even restoration do not support intertidal communities or processes equivalent to pre-disturbance conditions. Crucially, an absence of comprehensive empirical baseline biodiversity data, or data comprising additional ecological parameters such as ecosystem functions

  20. Engine structures analysis software: Component Specific Modeling (COSMO)

    NASA Astrophysics Data System (ADS)

    McKnight, R. L.; Maffeo, R. J.; Schwartz, S.

    1994-08-01

    A component specific modeling software program has been developed for propulsion systems. This expert program is capable of formulating the component geometry as finite element meshes for structural analysis which, in the future, can be spun off as NURB geometry for manufacturing. COSMO currently has geometry recipes for combustors, turbine blades, vanes, and disks. Component geometry recipes for nozzles, inlets, frames, shafts, and ducts are being added. COSMO uses component recipes that work through neutral files with the Technology Benefit Estimator (T/BEST) program which provides the necessary base parameters and loadings. This report contains the users manual for combustors, turbine blades, vanes, and disks.

  1. Engine Structures Analysis Software: Component Specific Modeling (COSMO)

    NASA Technical Reports Server (NTRS)

    Mcknight, R. L.; Maffeo, R. J.; Schwartz, S.

    1994-01-01

    A component specific modeling software program has been developed for propulsion systems. This expert program is capable of formulating the component geometry as finite element meshes for structural analysis which, in the future, can be spun off as NURB geometry for manufacturing. COSMO currently has geometry recipes for combustors, turbine blades, vanes, and disks. Component geometry recipes for nozzles, inlets, frames, shafts, and ducts are being added. COSMO uses component recipes that work through neutral files with the Technology Benefit Estimator (T/BEST) program which provides the necessary base parameters and loadings. This report contains the users manual for combustors, turbine blades, vanes, and disks.

  2. FIBER-TEX 1992: The Sixth Conference on Advanced Engineering Fibers and Textile Structures for Composites

    NASA Technical Reports Server (NTRS)

    Buckley, John D. (Editor)

    1993-01-01

    The FIBER-TEX 1992 proceedings contain the papers presented at the conference held on 27-29 Oct. 1992 at Drexel University. The conference was held to create a forum to encourage an interrelationship of the various disciplines involved in the fabrication of materials, the types of equipment, and the processes used in the production of advanced composite structures. Topics discussed were advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, and the latest requirements for the use of textiles in the production of composite materials and structures as related to global activities focused on textile structural composites.

  3. Characterization of the Photophysical, Thermodynamic, and Structural Properties of the Terbium(III)-DREAM Complex.

    PubMed

    Gonzalez, Walter G; Ramos, Victoria; Diaz, Maurizio; Garabedian, Alyssa; Molano-Arevalo, Juan Camilo; Fernandez-Lima, Francisco; Miksovska, Jaroslava

    2016-03-29

    DREAM (also known as K(+) channel interacting protein 3 and calsenilin) is a calcium binding protein and an active modulator of KV4 channels in neuronal cells as well as a novel Ca(2+)-regulated transcriptional modulator. DREAM has also been associated with the regulation of Alzheimer's disease through the prevention of presenilin-2 fragmentation. Many interactions of DREAM with its binding partners (Kv4, calmodulin, DNA, and drugs) have been shown to be dependent on calcium. Therefore, understanding the structural changes induced by binding of metals to DREAM is essential for elucidating the mechanism of signal transduction and biological activity of this protein. Here, we show that the fluorescence emission and excitation spectra of the calcium luminescent analogue, Tb(3+), are enhanced upon binding to the EF-hands of DREAM due to a mechanism of energy transfer between Trp and Tb(3+). We also observe that unlike Tb(3+)-bound calmodulin, the luminescence lifetime of terbium bound to DREAM decays as a complex multiexponential (τaverage ∼ 1.8 ms) that is sensitive to perturbation of the protein structure and drug (NS5806) binding. Using isothermal calorimetry, we have determined that Tb(3+) binds to at least three sites with high affinity (Kd = 1.8 μM in the presence of Ca(2+)) and displaces bound Ca(2+) through an entropically driven mechanism (ΔH ∼ 12 kcal mol(-1), and TΔS ∼ 22 kcal mol(-1)). Furthermore, the hydrophobic probe 1,8-ANS shows that Tb(3+), like Ca(2+), triggers the exposure of a hydrophobic surface on DREAM, which modulates ligand binding. Analogous to Ca(2+) binding, Tb(3+) binding also induces the dimerization of DREAM. Secondary structural analyses using far-UV circular dichroism and trapped ion mobility spectrometry-mass spectrometry reveal that replacement of Ca(2+) with Tb(3+) preserves the folding state with minimal changes to the overall structure of DREAM. These findings pave the way for further investigation of the metal binding

  4. Syntheses, crystal structures and characterizations of two new bismuth(III) arsenites

    SciTech Connect

    Liu Junhui; Kong Fang; Gai Yanli; Mao Jianggao

    2013-01-15

    Two new bismuth arsenites with two different structural types, namely, Bi{sub 2}O(AsO{sub 3})Cl (1), Bi{sub 8}O{sub 6}(AsO{sub 3}){sub 2}(AsO{sub 4}){sub 2} (2), have been synthesized by the solid-state reactions. Compound 1 exhibits novel 2D bismuth arsenite layers with Bi{sub 4}O{sub 4} rings capped by oxide anions, which are further interconnected by Bi-Cl-Bi bridges into a 3D network. Compound 2 contains both arsenite and arsenate anions, its 3D structures are based on 1D bismuth arsenite and 1D bismuth arsenate chains both along b-axis, which are interconnected by oxide anions via Bi-O-Bi bridges, forming 1D tunnels of Bi{sub 4}As{sub 4} 8-membered rings (MRs) along b-axis, the lone pairs of the arsenite groups are orientated toward the centers of the above tunnels. Thermogravimetric analysis indicated that both compounds display high thermal stability. Optical property measurements revealed that they are wide band-gap semiconductors. Both compounds display broad green-light emission bands centered at 506 nm under excitation at 380 and 388 nm. - Graphical abstract: Solid state reactions of Bi{sub 2}O{sub 3} (BiCl{sub 3}) and As{sub 2}O{sub 3} yielded two new compounds with two different structural types, namely, Bi{sub 2}O(AsO{sub 3})Cl (1), Bi{sub 8}O{sub 6}(AsO{sub 3}){sub 2}(AsO{sub 4}){sub 2} (2). They represent the first examples of bismuth arsenates. Highlights: Black-Right-Pointing-Pointer Solid state reactions of Bi{sub 2}O{sub 3} (BiCl{sub 3}) and As{sub 2}O{sub 3} yielded two new phases. Black-Right-Pointing-Pointer They represent the first examples of bismuth arsenites. Black-Right-Pointing-Pointer The two compounds exhibit two different structural types.

  5. Characterization of the Photophysical, Thermodynamic, and Structural Properties of the Terbium(III)-DREAM Complex.

    PubMed

    Gonzalez, Walter G; Ramos, Victoria; Diaz, Maurizio; Garabedian, Alyssa; Molano-Arevalo, Juan Camilo; Fernandez-Lima, Francisco; Miksovska, Jaroslava

    2016-03-29

    DREAM (also known as K(+) channel interacting protein 3 and calsenilin) is a calcium binding protein and an active modulator of KV4 channels in neuronal cells as well as a novel Ca(2+)-regulated transcriptional modulator. DREAM has also been associated with the regulation of Alzheimer's disease through the prevention of presenilin-2 fragmentation. Many interactions of DREAM with its binding partners (Kv4, calmodulin, DNA, and drugs) have been shown to be dependent on calcium. Therefore, understanding the structural changes induced by binding of metals to DREAM is essential for elucidating the mechanism of signal transduction and biological activity of this protein. Here, we show that the fluorescence emission and excitation spectra of the calcium luminescent analogue, Tb(3+), are enhanced upon binding to the EF-hands of DREAM due to a mechanism of energy transfer between Trp and Tb(3+). We also observe that unlike Tb(3+)-bound calmodulin, the luminescence lifetime of terbium bound to DREAM decays as a complex multiexponential (τaverage ∼ 1.8 ms) that is sensitive to perturbation of the protein structure and drug (NS5806) binding. Using isothermal calorimetry, we have determined that Tb(3+) binds to at least three sites with high affinity (Kd = 1.8 μM in the presence of Ca(2+)) and displaces bound Ca(2+) through an entropically driven mechanism (ΔH ∼ 12 kcal mol(-1), and TΔS ∼ 22 kcal mol(-1)). Furthermore, the hydrophobic probe 1,8-ANS shows that Tb(3+), like Ca(2+), triggers the exposure of a hydrophobic surface on DREAM, which modulates ligand binding. Analogous to Ca(2+) binding, Tb(3+) binding also induces the dimerization of DREAM. Secondary structural analyses using far-UV circular dichroism and trapped ion mobility spectrometry-mass spectrometry reveal that replacement of Ca(2+) with Tb(3+) preserves the folding state with minimal changes to the overall structure of DREAM. These findings pave the way for further investigation of the metal binding

  6. Pyripyropenes, Novel ACAT inhibitors produced by Aspergillus fumigatus. III. Structure elucidation of pyripyropenes E to L.

    PubMed

    Tomoda, H; Tabata, N; Yang, D J; Takayanagi, H; Nishida, H; Omura, S; Kaneko, T

    1995-06-01

    Eight new pyripyropenes, E to L, were isolated from the culture broth of Aspergillus fumigatus FO-1289-2501 selected as a higher producer by NTG mutation. Structural elucidation indicated that all the pyripyropenes have the same pyridino-alpha-pyrone sesquiterpene core as pyripyropenes A to D. Among them, pyripyropene L showed the most potent inhibition against acyl-CoA: cholesterol acyltransferase (ACAT) activity with an IC50 value of 0.27 microM in rat liver microsomes. PMID:7622436

  7. Structure of dimeric dysprosium (III) d-tartrate of 2:2 composition in aqueous solution

    SciTech Connect

    Chevela, V.V.; Vul`fson, S.G.; Sal`nikov, Yu.I.

    1994-12-20

    The molar constant of paramagnetic birefringence of dimeric dysprosium d-tartrate Dy{sub 2}(d-L){sup 2{minus}}{sub 2} (d-L{sup 4{minus}} is a deprotonated molecule of tartaric acid) was determined experimentally and by mathematical simulation. The structures of the ligand and hydrate environment in Dy{sub 2}(d-L){sup 2{minus}}{sub 2} were simulated by the molecular mechanics method (Dashevskii-Plyamovatyi model). Results consistent with the experimental data can be obtained only when coordination of Na{sup +} is taken into account. 6 refs., 4 figs., 8 tabs.

  8. Large-scale production and protein engineering of G protein-coupled receptors for structural studies

    PubMed Central

    Milić, Dalibor; Veprintsev, Dmitry B.

    2015-01-01

    Structural studies of G protein-coupled receptors (GPCRs) gave insights into molecular mechanisms of their action and contributed significantly to molecular pharmacology. This is primarily due to technical advances in protein engineering, production and crystallization of these important receptor targets. On the other hand, NMR spectroscopy of GPCRs, which can provide information about their dynamics, still remains challenging due to difficulties in preparation of isotopically labeled receptors and their low long-term stabilities. In this review, we discuss methods used for expression and purification of GPCRs for crystallographic and NMR studies. We also summarize protein engineering methods that played a crucial role in obtaining GPCR crystal structures. PMID:25873898

  9. Stress analysis of gas turbine engine structures using the boundary element method

    NASA Technical Reports Server (NTRS)

    Wilson, R. B.; Snow, D. W.; Banerjee, P. K.

    1985-01-01

    The theory of the boundary element method is briefly reviewed with particular reference to the feasibility of elastic and inelastic three-dimensional stress analysis of complex structures characteristic of gas turbine engine components. Particular requirements of gas turbine analysis are defined, and examples of the use of a boundary element code designed for the three-dimensional stress analysis of turbine components are presented. It is shown that the general-purpose boundary element code can accurately and efficiently analyze many of the gas turbine engine structures.

  10. Large-scale production and protein engineering of G protein-coupled receptors for structural studies.

    PubMed

    Milić, Dalibor; Veprintsev, Dmitry B

    2015-01-01

    Structural studies of G protein-coupled receptors (GPCRs) gave insights into molecular mechanisms of their action and contributed significantly to molecular pharmacology. This is primarily due to technical advances in protein engineering, production and crystallization of these important receptor targets. On the other hand, NMR spectroscopy of GPCRs, which can provide information about their dynamics, still remains challenging due to difficulties in preparation of isotopically labeled receptors and their low long-term stabilities. In this review, we discuss methods used for expression and purification of GPCRs for crystallographic and NMR studies. We also summarize protein engineering methods that played a crucial role in obtaining GPCR crystal structures.

  11. Electrical detachment of cells for engineering capillary-like structures in a photocrosslinkable hydrogel.

    PubMed

    Osaki, Tatsuya; Kakegawa, Takahiro; Suzuki, Hiroaki; Fukuda, Junji

    2011-01-01

    A major challenge in tissue engineering is the fabrication of vascular networks capable of delivering oxygen and nutrients throughout tissue constructs. Because cells located more than a few hundred micrometers away from the nearest capillaries are susceptible to oxygen shortages, it is crucial to develop microscale technologies for engineering a vascular structure in three-dimensionally thick tissues. This study describes an electrochemical approach for fabricating capillary-like structures precisely aligned within micrometer distances, the internal surfaces of which are covered with vascular endothelial cells in a photocrosslinkable hydrogel.

  12. Defect engineering in the MOSLED structure by ion implantation

    NASA Astrophysics Data System (ADS)

    Prucnal, S.; Wójtowicz, A.; Pyszniak, K.; Drozdziel, A.; Zuk, J.; Turek, M.; Rebohle, L.; Skorupa, W.

    2009-05-01

    When amorphous SiO2 films are bombarded with energetic ions, various types of defects are created as a consequence of ion-solid interaction (peroxy radicals POR, oxygen deficient centres (ODC), non-bridging oxygen hole centres (NBOHC), E‧ centres, etc.). The intensity of the electroluminescence (EL) from oxygen deficiency centres at 2.7 eV, non-bridging oxygen hole centres at 1.9 eV and defect centres with emission at 2.07 eV can be easily modified by the ion implantation of the different elements (H, N, O) into the completely processed MOSLED structure. Nitrogen implanted into the SiO2:Gd layer reduces the concentration of the ODC and NBOHC while the doping of the oxygen increases the EL intensity observed from POR defect and NBOHC. Moreover, after oxygen or hydrogen implantation into the SiO2:Ge structure fourfold or fifth fold increase of the germanium related EL intensity was observed.

  13. Nanoscale Engineering of Structures and Devices on Surfaces

    NASA Astrophysics Data System (ADS)

    Yitamben, Esmeralda

    2014-03-01

    The relentless increase in both density and speed that has characterized microelectronics, and now nanoelectronics, will require a new paradigm to continue beyond current technologies. One proposed such paradigm shift demands the ultimate control over the number and position of dopants in a device, which includes quantum information processing and variety of semiconductor device materials and architectures aimed at solving end-of-Moore's law issues. Such a work requires the development of a tool for the design of atomically precise devices on silicon and other surfaces, in hope of studying the effect of local interactions between atomic-scale structures, their microscopic behavior, and how quantum mechanical effects might influence nano-device behavior in very small structures. Demonstrations of remarkable 2D nanostructures down to single atom devices are reported here thanks to the development of scanning tunneling microscopy (STM) as an imaging and patterning tool. These include the formation of molecular chiral superstructures on metallic surfaces, as well as the atomic-scale depassivation of a hydrogen terminated surface with an STM, toward the incorporation of dopants in silicon. I will spend some time at the end, talking about my experience working at a national laboratory.

  14. Structural and thermodynamic properties of the CmIII ion solvated by water and methanol

    DOE PAGES

    Kelley, Morgan P.; Yang, Ping; Clark, Sue B.; Clark, Aurora E.

    2016-04-27

    The geometric and electronic structures of the 9-coordinate Cm3+ ion solvated with both water and methanol are systematically investigated in the gas phase at each possible solvent-shell composition and configuration using density functional theory and second-order Møller–Plesset perturbation theory. Ab initio molecular dynamics simulations are employed to assess the effects of second and third solvent shells on the gas-phase structure. The ion–solvent dissociation energy for methanol is greater than that of water, potentially because of increased charge donation to the ion made possible by the electron-rich methyl group. Further, the ion–solvent dissociation energy and the ion–solvent distance are shown tomore » be dependent on the solvent-shell composition. Furthermore, this has implications for solvent exchange, which is generally the rate-limiting step in complexation reactions utilized in the separation of curium from complex metal mixtures that derive from the advanced nuclear fuel cycle.« less

  15. Novel nanohybrids of cobalt(III) Schiff base complexes and clay: Synthesis and structural determinations

    NASA Astrophysics Data System (ADS)

    Kianfar, Ali Hossein; Mahmood, Wan Ahmad Kamil; Dinari, Mohammad; Azarian, Mohammad Hossein; Khafri, Fatemeh Zare

    2014-06-01

    The [Co(Me2Salen)(PBu3)(OH2)]BF4 and [Co(Me2Salen)(PPh3)(Solv)]BF4, complexes were synthesized and characterized by FT-IR, UV-Vis, 1H NMR spectroscopy and elemental analysis techniques. The coordination geometry of [Co(Me2Salen)(PPh3)(H2O)]BF4 was determined by X-ray crystallography. It has been found that the complex is containing [Co(Me2Salen)(PPh3)(H2O)]BF4 and [Co(Me2Salen)(PPh3)(EtOH)]BF4 hexacoordinate species in the solid state. Cobalt atom exhibits a distorted octahedral geometry and the Me2Salen ligand has the N2O2 coordinated environment in the equatorial plane. The [Co(Me2Salen)(PPh3)(H2O)]BF4 complex shows a dimeric structure via hydrogen bonding between the phenolate oxygen and hydrogens of coordinated H2O molecule. These complexes were incorporated into Montmorillonite-K10 nanoclay. The modified clays were identified by FT-IR, XRD, EDX, TGA/DTA, SEM and TEM techniques. According to the XRD results of the new nanohybrid materials, the Schiff base complexes are intercalated in the interlayer spaces of the clay. SEM and TEM micrographs show that the resulting hybrid nanomaterials have layer structures. Also, TGA/DTG results show that the intercalation reaction was taken place successfully.

  16. Synthesis, crystal structure, spectroscopic, thermal and dielectric properties of a novel semi-organic pentachloroantimonate (III)

    NASA Astrophysics Data System (ADS)

    Lahbib, Ikram; Rzaigui, Mohamed; Smirani, Wajda

    2016-09-01

    A new organic-inorganic hybrid material of formula (C10H15N2F)5(SbCl5)5.2H2O was synthesized and characterized by X-Ray diffraction analysis. It crystallizes in the monoclinic space group P21/c with the following unit cell parameters a = 15.819(4) Å, b = 17.685(3) Å, c = 30.529(4) Å, Z = 4 and V = 8540(3) Å3. The examination of the structure shows that the three-dimensional frameworks are produced by Nsbnd H⋯Cl, Nsbnd H⋯O, Csbnd H⋯Cl and Nsbnd H⋯F, Csbnd H⋯F hydrogen bonding and Cl⋯Cl interactions. IR, Raman and UV-Visible spectroscopies were also used to characterize this compound. In addition, the fluorescent properties of this compound have been investigated in the liquid state at room temperature. Differential scanning calorimetry (DSC) has revealed a structural phase transition of the order-disorder type around 370 K. Dielectric investigations revealed a step-wise change of the electric permittivity at Ttr characteristic of the crystal in the high-temperature phase. The evolution of dielectric constant as a function of temperature of the sample has been investigated in order to determine some related parameters. Measurements of AC conductivity as a function of frequency at different temperatures indicated a hopping conduction mechanism and/or reorientational motion.

  17. Vibration-based health monitoring and model refinement of civil engineering structures

    SciTech Connect

    Farrar, C.R.; Doebling, S.W.

    1997-10-01

    Damage or fault detection, as determined by changes in the dynamic properties of structures, is a subject that has received considerable attention in the technical literature beginning approximately 30 years ago. The basic idea is that changes in the structure`s properties, primarily stiffness, will alter the dynamic properties of the structure such as resonant frequencies and mode shapes, and properties derived from these quantities such as modal-based flexibility. Recently, this technology has been investigated for applications to health monitoring of large civil engineering structures. This presentation will discuss such a study undertaken by engineers from New Mexico Sate University, Sandia National Laboratory and Los Alamos National Laboratory. Experimental modal analyses were performed in an undamaged interstate highway bridge and immediately after four successively more severe damage cases were inflicted in the main girder of the structure. Results of these tests provide insight into the abilities of modal-based damage ID methods to identify damage and the current limitations of this technology. Closely related topics that will be discussed are the use of modal properties to validate computer models of the structure, the use of these computer models in the damage detection process, and the general lack of experimental investigation of large civil engineering structures.

  18. Chapter D. The Loma Prieta, California, Earthquake of October 17, 1989 - Earth Structures and Engineering Characterization of Ground Motion

    USGS Publications Warehouse

    Holzer, Thomas L.

    1998-01-01

    This chapter contains two papers that summarize the performance of engineered earth structures, dams and stabilized excavations in soil, and two papers that characterize for engineering purposes the attenuation of ground motion with distance during the Loma Prieta earthquake. Documenting the field performance of engineered structures and confirming empirically based predictions of ground motion are critical for safe and cost effective seismic design of future structures as well as the retrofitting of existing ones.

  19. Engineering plasmonic metal colloids through composition and structural design.

    PubMed

    Motl, N E; Smith, A F; DeSantis, C J; Skrabalak, S E

    2014-06-01

    The optical properties of metal nanomaterials are determined by a set of parameters that include composition, particle size and shape, overall architecture, and local environment. This Tutorial Review examines the influence of each of these factors on the localized surface plasmon resonance of colloidal metal nanoparticles. This examination is paralleled with a discussion of the advances which have enabled the synthesis of structurally defined metal nanomaterials, as these samples serve as the best platforms for elucidating the fundamental properties of plasmonic colloids. Based on the analysis of such samples, five guidelines are presented to aid the rational design and synthesis of new metal nanostructures for advanced applications in nanomedicine, energy, chemical sensing, and colloidal plasmonics in general.

  20. Electronic structure and luminescence of antimony (III) halide complexes with N,N‧-diphenylguanidine

    NASA Astrophysics Data System (ADS)

    Vovna, V. I.; Dotsenko, A. A.; Korochentsev, V. V.; Shcheka, O. L.; Os'mushko, I. S.; Mirochnik, A. G.; Sedakova, T. V.; Sergienko, V. I.

    2015-07-01

    To determine the orbital nature of the excitation for the luminescence of the SbX63-(HDphg)+3 complexes, where X = Cl, Br and HDphg+ is diphenylguanidine, the structure of the valence and core levels was investigated using X-ray photoelectron spectroscopy and density functional theory. The results indicated that the valence bands of the compounds fall into two level systems localised on the anion and cations. HOMO 3a1g2 and LUMO 4t1u on the SbX63- anion, which is responsible for the lower excited state, are antibonding combinations of the Xnpσ group orbitals with Sb 5s and 5p AOs, respectively.