Cluster-assembled cubic zirconia films with tunable and stable nanoscale morphology against thermal annealing

KAUST Repository

Borghi, F.; Sogne, Elisa; Lenardi, C.; Podestà , A.; Merlini, M.; Ducati, C.; Milani, P.

2016-01-01

Nanostructured zirconium dioxide (zirconia) films are very promising for catalysis and biotechnological applications: a precise control of the interfacial properties of the material at different length scales and, in particular, at the nanoscale, is therefore necessary. Here, we present the characterization of cluster-assembled zirconia films produced by supersonic cluster beam deposition possessing cubic structure at room temperature and controlled nanoscale morphology. We characterized the effect of thermal annealing in reducing and oxidizing conditions on the crystalline structure, grain dimensions, and topography. We highlight the mechanisms of film growth and phase transitions, which determine the observed interfacial morphological properties and their resilience against thermal treatments. Published by AIP Publishing.

Magnetic assembly of 3D cell clusters: visualizing the formation of an engineered tissue.

Science.gov (United States)

Ghosh, S; Kumar, S R P; Puri, I K; Elankumaran, S

2016-02-01

Contactless magnetic assembly of cells into 3D clusters has been proposed as a novel means for 3D tissue culture that eliminates the need for artificial scaffolds. However, thus far its efficacy has only been studied by comparing expression levels of generic proteins. Here, it has been evaluated by visualizing the evolution of cell clusters assembled by magnetic forces, to examine their resemblance to in vivo tissues. Cells were labeled with magnetic nanoparticles, then assembled into 3D clusters using magnetic force. Scanning electron microscopy was used to image intercellular interactions and morphological features of the clusters. When cells were held together by magnetic forces for a single day, they formed intercellular contacts through extracellular fibers. These kept the clusters intact once the magnetic forces were removed, thus serving the primary function of scaffolds. The cells self-organized into constructs consistent with the corresponding tissues in vivo. Epithelial cells formed sheets while fibroblasts formed spheroids and exhibited position-dependent morphological heterogeneity. Cells on the periphery of a cluster were flattened while those within were spheroidal, a well-known characteristic of connective tissues in vivo. Cells assembled by magnetic forces presented visual features representative of their in vivo states but largely absent in monolayers. This established the efficacy of contactless assembly as a means to fabricate in vitro tissue models. © 2016 John Wiley & Sons Ltd.

Regulated Assembly of Vacuolar ATPase Is Increased during Cluster Disruption-induced Maturation of Dendritic Cells through a Phosphatidylinositol 3-Kinase/mTOR-dependent Pathway*

Science.gov (United States)

Liberman, Rachel; Bond, Sarah; Shainheit, Mara G.; Stadecker, Miguel J.; Forgac, Michael

2014-01-01

The vacuolar (H+)-ATPases (V-ATPases) are ATP-driven proton pumps composed of a peripheral V1 domain and a membrane-embedded V0 domain. Regulated assembly of V1 and V0 represents an important regulatory mechanism for controlling V-ATPase activity in vivo. Previous work has shown that V-ATPase assembly increases during maturation of bone marrow-derived dendritic cells induced by activation of Toll-like receptors. This increased assembly is essential for antigen processing, which is dependent upon an acidic lysosomal pH. Cluster disruption of dendritic cells induces a semi-mature phenotype associated with immune tolerance. Thus, semi-mature dendritic cells are able to process and present self-peptides to suppress autoimmune responses. We have investigated V-ATPase assembly in bone marrow-derived, murine dendritic cells and observed an increase in assembly following cluster disruption. This increased assembly is not dependent upon new protein synthesis and is associated with an increase in concanamycin A-sensitive proton transport in FITC-loaded lysosomes. Inhibition of phosphatidylinositol 3-kinase with wortmannin or mTORC1 with rapamycin effectively inhibits the increased assembly observed upon cluster disruption. These results suggest that the phosphatidylinositol 3-kinase/mTOR pathway is involved in controlling V-ATPase assembly during dendritic cell maturation. PMID:24273170

Calculation of drop course of control rod assembly in PWR

International Nuclear Information System (INIS)

Zhou Xiaojia; Mao Fei; Min Peng; Lin Shaoxuan

2013-01-01

The validation of control rod drop performance is an important part of safety analysis of nuclear power plant. Development of computer code for calculating control rod drop course will be useful for validating and improving the design of control rod drive line. Based on structural features of the drive line, the driving force on moving assembly was analyzed and decomposed, the transient value of each component of the driving force was calculated by choosing either theoretical method or numerical method, and the simulation code for calculating rod cluster control assembly (RCCA) drop course by time step increase was achieved. The analysis results of control rod assembly drop course calculated by theoretical model and numerical method were validated by comparing with RCCA drop test data of Qinshan Phase Ⅱ 600 MW PWR. It is shown that the developed RCCA drop course calculation code is suitable for RCCA in PWR and can correctly simulate the drop course and the stress of RCCA. (authors)

Controlled assembly of multi-segment nanowires by histidine-tagged peptides

Energy Technology Data Exchange (ETDEWEB)

Wang, Aijun A; Lee, Joun; Jenikova, Gabriela; Mulchandani, Ashok; Myung, Nosang V; Chen, Wilfred [Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521 (United States)

2006-07-28

A facile technique was demonstrated for the controlled assembly and alignment of multi-segment nanowires using bioengineered polypeptides. An elastin-like-polypeptide (ELP)-based biopolymer consisting of a hexahistine cluster at each end (His{sub 6}-ELP-His{sub 6}) was generated and purified by taking advantage of the reversible phase transition property of ELP. The affinity between the His{sub 6} domain of biopolymers and the nickel segment of multi-segment nickel/gold/nickel nanowires was exploited for the directed assembly of nanowires onto peptide-functionalized electrode surfaces. The presence of the ferromagnetic nickel segments on the nanowires allowed the control of directionality by an external magnetic field. Using this method, the directed assembly and positioning of multi-segment nanowires across two microfabricated nickel electrodes in a controlled manner was accomplished with the expected ohmic contact.

Nanomanufacturing of titania interfaces with controlled structural and functional properties by supersonic cluster beam deposition

International Nuclear Information System (INIS)

Podestà, Alessandro; Borghi, Francesca; Indrieri, Marco; Bovio, Simone; Piazzoni, Claudio; Milani, Paolo

2015-01-01

Great emphasis is placed on the development of integrated approaches for the synthesis and the characterization of ad hoc nanostructured platforms, to be used as templates with controlled morphology and chemical properties for the investigation of specific phenomena of great relevance in interdisciplinary fields such as biotechnology, medicine, and advanced materials. Here, we discuss the crucial role and the advantages of thin film deposition strategies based on cluster-assembling from supersonic cluster beams. We select cluster-assembled nanostructured titania (ns-TiO 2 ) as a case study to demonstrate that accurate control over morphological parameters can be routinely achieved, and consequently, over several relevant interfacial properties and phenomena, like surface charging in a liquid electrolyte, and proteins and nanoparticles adsorption. In particular, we show that the very good control of nanoscale morphology is obtained by taking advantage of simple scaling laws governing the ballistic deposition regime of low-energy, mass-dispersed clusters with reduced surface mobility

Nanomanufacturing of titania interfaces with controlled structural and functional properties by supersonic cluster beam deposition

Energy Technology Data Exchange (ETDEWEB)

Podestà, Alessandro, E-mail: alessandro.podesta@mi.infn.it, E-mail: pmilani@mi.infn.it; Borghi, Francesca; Indrieri, Marco; Bovio, Simone; Piazzoni, Claudio; Milani, Paolo, E-mail: alessandro.podesta@mi.infn.it, E-mail: pmilani@mi.infn.it [Centro Interdisciplinare Materiali e Interfacce Nanostrutturati (C.I.Ma.I.Na.), Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy)

2015-12-21

Great emphasis is placed on the development of integrated approaches for the synthesis and the characterization of ad hoc nanostructured platforms, to be used as templates with controlled morphology and chemical properties for the investigation of specific phenomena of great relevance in interdisciplinary fields such as biotechnology, medicine, and advanced materials. Here, we discuss the crucial role and the advantages of thin film deposition strategies based on cluster-assembling from supersonic cluster beams. We select cluster-assembled nanostructured titania (ns-TiO{sub 2}) as a case study to demonstrate that accurate control over morphological parameters can be routinely achieved, and consequently, over several relevant interfacial properties and phenomena, like surface charging in a liquid electrolyte, and proteins and nanoparticles adsorption. In particular, we show that the very good control of nanoscale morphology is obtained by taking advantage of simple scaling laws governing the ballistic deposition regime of low-energy, mass-dispersed clusters with reduced surface mobility.

Nanomanufacturing of titania interfaces with controlled structural and functional properties by supersonic cluster beam deposition

Science.gov (United States)

Podestà, Alessandro; Borghi, Francesca; Indrieri, Marco; Bovio, Simone; Piazzoni, Claudio; Milani, Paolo

2015-12-01

Great emphasis is placed on the development of integrated approaches for the synthesis and the characterization of ad hoc nanostructured platforms, to be used as templates with controlled morphology and chemical properties for the investigation of specific phenomena of great relevance in interdisciplinary fields such as biotechnology, medicine, and advanced materials. Here, we discuss the crucial role and the advantages of thin film deposition strategies based on cluster-assembling from supersonic cluster beams. We select cluster-assembled nanostructured titania (ns-TiO2) as a case study to demonstrate that accurate control over morphological parameters can be routinely achieved, and consequently, over several relevant interfacial properties and phenomena, like surface charging in a liquid electrolyte, and proteins and nanoparticles adsorption. In particular, we show that the very good control of nanoscale morphology is obtained by taking advantage of simple scaling laws governing the ballistic deposition regime of low-energy, mass-dispersed clusters with reduced surface mobility.

Correction to: Fe-S cluster assembly in the supergroup Excavata.

Science.gov (United States)

Peña-Diaz, Priscila; Lukeš, Julius

2018-05-29

The article "Fe-S cluster assembly in the supergroup Excavata", written by Priscila Peña‑Diaz, Julius Lukeš was originally published electronically on the publisher's internet portal (currently SpringerLink) without open access.

Enhanced magnetostriction derived from magnetic single domain structures in cluster-assembled SmCo films

Science.gov (United States)

Bai, Yulong; Yang, Bo; Guo, Fei; Lu, Qingshan; Zhao, Shifeng

2017-11-01

Cluster-assembled SmCo alloy films were prepared by low energy cluster beam deposition. The structure, magnetic domain, magnetization, and magnetostriction of the films were characterized. It is shown that the as-prepared films are assembled in compact and uniformly distributed spherical cluster nanoparticles, most of which, after vacuum in situ annealing at 700 K, aggregated to form cluster islands. These cluster islands result in transformations from superparamagnetic states to magnetic single domain (MSD) states in the films. Such MSD structures contribute to the enhanced magnetostrictive behaviors with a saturation magnetostrictive coefficient of 160 × 10-6 in comparison to 105 × 10-6 for the as-prepared films. This work demonstrates candidate materials that could be applied in nano-electro-mechanical systems, low power information storage, and weak magnetic detecting devices.

Defining the Architecture of the Core Machinery for the Assembly of Fe-S Clusters in Human Mitochondria.

Science.gov (United States)

Gakh, Oleksandr; Ranatunga, Wasantha; Galeano, Belinda K; Smith, Douglas S; Thompson, James R; Isaya, Grazia

2017-01-01

Although Fe-S clusters may assemble spontaneously from elemental iron and sulfur in protein-free systems, the potential toxicity of free Fe 2+ , Fe 3+ , and S 2- ions in aerobic environments underscores the requirement for specialized proteins to oversee the safe assembly of Fe-S clusters in living cells. Prokaryotes first developed multiprotein systems for Fe-S cluster assembly, from which mitochondria later derived their own system and became the main Fe-S cluster suppliers for eukaryotic cells. Early studies in yeast and human mitochondria indicated that Fe-S cluster assembly in eukaryotes is centered around highly conserved Fe-S proteins (human ISCU) that serve as scaffolds upon which new Fe-S clusters are assembled from (i) elemental sulfur, provided by a pyridoxal phosphate-dependent cysteine desulfurase (human NFS1) and its stabilizing-binding partner (human ISD11), and (ii) elemental iron, provided by an iron-binding protein of the frataxin family (human FXN). Further studies revealed that all of these proteins could form stable complexes that could reach molecular masses of megadaltons. However, the protein-protein interaction surfaces, catalytic mechanisms, and overall architecture of these macromolecular machines remained undefined for quite some time. The delay was due to difficulties inherent in reconstituting these very large multiprotein complexes in vitro or isolating them from cells in sufficient quantities to enable biochemical and structural studies. Here, we describe approaches we developed to reconstitute the human Fe-S cluster assembly machinery in Escherichia coli and to define its remarkable architecture. © 2017 Elsevier Inc. All rights reserved.

Kinetic Assembly of Near-IR Active Gold Nanoclusters using Weakly Adsorbing Polymers to Control Size

Science.gov (United States)

Tam, Jasmine M.; Murthy, Avinash K.; Ingram, Davis R.; Nguyen, Robin; Sokolov, Konstantin V.; Johnston, Keith P.

2013-01-01

Clusters of metal nanoparticles with an overall size less than 100 nm and high metal loadings for strong optical functionality, are of interest in various fields including microelectronics, sensors, optoelectronics and biomedical imaging and therapeutics. Herein we assemble ~5 nm gold particles into clusters with controlled size, as small as 30 nm and up to 100 nm, which contain only small amounts of polymeric stabilizers. The assembly is kinetically controlled with weakly adsorbing polymers, PLA(2K)-b-PEG(10K)-b-PLA(2K) or PEG (MW = 3350), by manipulating electrostatic, van der Waals (VDW), steric, and depletion forces. The cluster size and optical properties are tuned as a function of particle volume fractions and polymer/gold ratios to modulate the interparticle interactions. The close spacing between the constituent gold nanoparticles and high gold loadings (80–85% w/w gold) produce a strong absorbance cross section of ~9×10−15 m2 in the NIR at 700 nm. This morphology results from VDW and depletion attractive interactions that exclude the weakly adsorbed polymeric stabilizer from the cluster interior. The generality of this kinetic assembly platform is demonstrated for gold nanoparticles with a range of surface charges from highly negative to neutral, with the two different polymers. PMID:20361735

Architecture of the Human Mitochondrial Iron-Sulfur Cluster Assembly Machinery*

Science.gov (United States)

Gakh, Oleksandr; Ranatunga, Wasantha; Smith, Douglas Y.; Ahlgren, Eva-Christina; Al-Karadaghi, Salam; Thompson, James R.; Isaya, Grazia

2016-01-01

Fe-S clusters, essential cofactors needed for the activity of many different enzymes, are assembled by conserved protein machineries inside bacteria and mitochondria. As the architecture of the human machinery remains undefined, we co-expressed in Escherichia coli the following four proteins involved in the initial step of Fe-S cluster synthesis: FXN42–210 (iron donor); [NFS1]·[ISD11] (sulfur donor); and ISCU (scaffold upon which new clusters are assembled). We purified a stable, active complex consisting of all four proteins with 1:1:1:1 stoichiometry. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional model of the complex with ∼14 Å resolution. Molecular dynamics flexible fitting of protein structures docked into the EM map of the model revealed a [FXN42–210]24·[NFS1]24·[ISD11]24·[ISCU]24 complex, consistent with the measured 1:1:1:1 stoichiometry of its four components. The complex structure fulfills distance constraints obtained from chemical cross-linking of the complex at multiple recurring interfaces, involving hydrogen bonds, salt bridges, or hydrophobic interactions between conserved residues. The complex consists of a central roughly cubic [FXN42–210]24·[ISCU]24 sub-complex with one symmetric ISCU trimer bound on top of one symmetric FXN42–210 trimer at each of its eight vertices. Binding of 12 [NFS1]2·[ISD11]2 sub-complexes to the surface results in a globular macromolecule with a diameter of ∼15 nm and creates 24 Fe-S cluster assembly centers. The organization of each center recapitulates a previously proposed conserved mechanism for sulfur donation from NFS1 to ISCU and reveals, for the first time, a path for iron donation from FXN42–210 to ISCU. PMID:27519411

Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001.

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Puran Pandey

Full Text Available Au nano-clusters and nanoparticles (NPs have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001 by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

Concept design and cluster control of advanced space connectable intelligent microsatellite

Science.gov (United States)

Wang, Xiaohui; Li, Shuang; She, Yuchen

2017-12-01

In this note, a new type of advanced space connectable intelligent microsatellite is presented to extend the range of potential application of microsatellite and improve the efficiency of cooperation. First, the overall concept of the micro satellite cluster is described, which is characterized by autonomously connecting with each other and being able to realize relative rotation through the external interfaces. Second, the multi-satellite autonomous assembly algorithm and control algorithm of the cluster motion are developed to make the cluster system combine into a variety of configurations in order to achieve different types of functionality. Finally, the design of the satellite cluster system is proposed, and the possible applications are discussed.

Studies of cluster-assembled materials: From gas phase to condensed phase

Science.gov (United States)

Gao, Lin

. After being mass gated in a reflectron equipped time-of-flight mass spectrometer (TOF-MS) and deposited onto TEM grids, the resultant specimens can be loaded onto high-resolution TEM investigation via electron diffraction. In conclusion, soft-landing of mass selected clusters has been shown to be a successful approach to obtain structural information on Zr-Met-Car cluster-assembled materials collected from the gas phase. TEM images indicate the richness of the morphologies associated with these cluster crystals. However, passivation methods are expected to be examined further to overcome the limited stabilities of these novel clusters. From this initial study, it's shown the promising opportunity to study other Met-Cars species and more cluster-based materials. Experimental results of reactions run with a solvothermal synthesis method obtained while searching for new Zr-C cluster assembled materials, are reported. One unexpected product in single crystal form was isolated and tentatively identified by X-ray diffraction to be [Zr6i O(OH)O12·2(Bu)4], with space group P2 1/n and lattice parameters of a = 12.44 A, b = 22.06 A, c = 18.40 A, alpha = 90°, beta = 105°, gamma = 90°, V = 4875 A3 and R 1 = 3.15% for the total observed data (I ≥ 2 sigma I) and oR2 = 2.82%. This novel hexanuclear Zr(IV)-oxo-hydroxide cluster anion may be the first member in polyoxometalates class with metal atoms from the IVB group and having Oh symmetry. Alternatively, it may be the first member in {[(Zr6Z)X 12]X6}m- class with halides replaced by oxo- and hydroxyl groups and with an increased oxidation state of Zr. It is predicted to bear application potentials directed by both families. This work could suggest a direction in which the preparation of Zr-C cluster-assembled materials in a liquid environment may be eventually fulfilled. 1,3-Bis(diethylphosphino)propane (depp) protected small gold clusters are studied via multiple techniques, including Electrospray Ionization Mass Spectrometry

Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery

Science.gov (United States)

Ranatunga, Wasantha; Gakh, Oleksandr; Galeano, Belinda K.; Smith, Douglas Y.; Söderberg, Christopher A. G.; Al-Karadaghi, Salam; Thompson, James R.; Isaya, Grazia

2016-01-01

The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly. PMID:26941001

[Nitrogen oxide is involved in the regulation of the Fe-S cluster assembly in proteins and the formation of biofilms by Escherichia coli cells].

Science.gov (United States)

Vasil'eva, S V; Streltsova, D A; Starostina, I A; Sanina, N A

2013-01-01

The functions of nitrogen oxide (NO) in the regulation of the reversible processes of Fe-S cluster assembly in proteins and the formation of Escherichia coli biofilms have been investigated. S-nitrosoglutathione (GSNO) and crystalline nitrosyl complexes of iron with sulfur-containing aliphatic ligands cisaconite (CisA) and penaconite have been used as NO donors for the first time. Wild-type E. coli cells of the strain MC4100, mutants deltaiscA and deltasufA, and the double paralog mutant deltaiscA/sufA with deletions in the alternative pathways of Fe2+ supply for cluster assembly (all derived from the above-named strain) were used in this study. Plankton growth of bacterial cultures, the mass of mature biofilms, and the expression of the SoxRS[2Fe-2S] regulon have been investigated and shown to depend on strain genotype, the process of Fe-S cluster assembly in iron-sulfur proteins, NO donor structure, and the presence of Fe2+ chelator ferene in the incubation medium. The antibiotic ciprofloxacine (CF) was used as an inhibitor of E. coli biofilm formation in the positive control. NO donors regulating Fe-S cluster assembly in E. coli have been shown to control plankton growth of the cultures and the process of mature biofilm formation; toxic doses of NO caused a dramatic (3- to 4-fold) stimulation of cell entry into biofilms as a response to nitrosative stress; NO donors CisA and GSNO in physiological concentrations suppressed the formation of mature biofilms, and the activity of these compounds was comparable to that of CE Regulation of both Fe-S cluster assembly in iron-sulfur proteins and biofilm formation by NO is indicative of the connection between these processes in E. coli.

Physical controls on directed virus assembly at nanoscale chemical templates

International Nuclear Information System (INIS)

Cheung, C L; Chung, S; Chatterji, A; Lin, T; Johnson, J E; Hok, S; Perkins, J; De Yoreo, J

2006-01-01

Viruses are attractive building blocks for nanoscale heterostructures, but little is understood about the physical principles governing their directed assembly. In-situ force microscopy was used to investigate organization of Cowpea Mosaic Virus engineered to bind specifically and reversibly at nanoscale chemical templates with sub-30nm features. Morphological evolution and assembly kinetics were measured as virus flux and inter-viral potential were varied. The resulting morphologies were similar to those of atomic-scale epitaxial systems, but the underlying thermodynamics was analogous to that of colloidal systems in confined geometries. The 1D templates biased the location of initial cluster formation, introduced asymmetric sticking probabilities, and drove 1D and 2D condensation at subcritical volume fractions. The growth kinetics followed a t 1/2 law controlled by the slow diffusion of viruses. The lateral expansion of virus clusters that initially form on the 1D templates following introduction of polyethylene glycol (PEG) into the solution suggests a significant role for weak interaction

Monoatomic and cluster beam effect on ToF-SIMS spectra of self-assembled monolayers on gold

Energy Technology Data Exchange (ETDEWEB)

Tuccitto, N. [Dipartimento di Scienze Chimiche Universita degli Studi di Catania, v.le A. Doria 6, 95125, Catania (Italy)], E-mail: n.tuccitto@unict.it; Torrisi, V.; Delfanti, I.; Licciardello, A. [Dipartimento di Scienze Chimiche Universita degli Studi di Catania, v.le A. Doria 6, 95125, Catania (Italy)

2008-12-15

Self-assembled monolayers represent well-defined systems that is a good model surface to study the effect of primary ion beams used in secondary ion mass spectrometry. The effect of polyatomic primary beams on both aliphatic and aromatic self-assembled monolayers has been studied. In particular, we analysed the variation of the relative secondary ion yield of both substrate metal-cluster (Au{sub n}{sup -}) in comparison with the molecular ions (M{sup -}) and clusters (M{sub x}Au{sub y}{sup -}) by using Bi{sup +}, Bi{sub 3}{sup +}, Bi{sub 5}{sup +} beams. Moreover, the differences in the secondary ion generation efficiency are discussed. The main effect of the cluster beams is related to an increased formation of low-mass fragments and to the enhancement of the substrate related gold-clusters. The results show that, at variance of many other cases, the static SIMS of self-assembled monolayers does not benefit of the use of polyatomic primary ions.

Advanced gray rod control assembly

Science.gov (United States)

Drudy, Keith J; Carlson, William R; Conner, Michael E; Goldenfield, Mark; Hone, Michael J; Long, Jr., Carroll J; Parkinson, Jerod; Pomirleanu, Radu O

2013-09-17

An advanced gray rod control assembly (GRCA) for a nuclear reactor. The GRCA provides controlled insertion of gray rod assemblies into the reactor, thereby controlling the rate of power produced by the reactor and providing reactivity control at full power. Each gray rod assembly includes an elongated tubular member, a primary neutron-absorber disposed within the tubular member said neutron-absorber comprising an absorber material, preferably tungsten, having a 2200 m/s neutron absorption microscopic capture cross-section of from 10 to 30 barns. An internal support tube can be positioned between the primary absorber and the tubular member as a secondary absorber to enhance neutron absorption, absorber depletion, assembly weight, and assembly heat transfer characteristics.

The Effects of Halo Assembly Bias on Self-Calibration in Galaxy Cluster Surveys

Energy Technology Data Exchange (ETDEWEB)

Wu, Hao-Yi; Rozo, Eduardo; Wechsler, Risa H.

2008-08-07

Self-calibration techniques for analyzing galaxy cluster counts utilize the abundance and the clustering amplitude of dark matter halos. These properties simultaneously constrain cosmological parameters and the cluster observable-mass relation. It was recently discovered that the clustering amplitude of halos depends not only on the halo mass, but also on various secondary variables, such as the halo formation time and the concentration; these dependences are collectively termed 'assembly bias'. Applying modified Fisher matrix formalism, we explore whether these secondary variables have a significant impact on the study of dark energy properties using the self-calibration technique in current (SDSS) and the near future (DES, SPT, and LSST) cluster surveys. The impact of the secondary dependence is determined by (1) the scatter in the observable-mass relation and (2) the correlation between observable and secondary variables. We find that for optical surveys, the secondary dependence does not significantly influence an SDSS-like survey; however, it may affect a DES-like survey (given the high scatter currently expected from optical clusters) and an LSST-like survey (even for low scatter values and low correlations). For an SZ survey such as SPT, the impact of secondary dependence is insignificant if the scatter is 20% or lower but can be enhanced by the potential high scatter values introduced by a highly-correlated background. Accurate modeling of the assembly bias is necessary for cluster self-calibration in the era of precision cosmology.

Fuel assembly

International Nuclear Information System (INIS)

Gjertsen, R.K.; Bassler, E.A.; Huckestein, E.A.; Salton, R.B.; Tower, S.N.

1988-01-01

A fuel assembly adapted for use with a pressurized water nuclear reactor having capabilities for fluid moderator spectral shift control is described comprising: parallel arranged elongated nuclear fuel elements; means for providing for axial support of the fuel elements and for arranging the fuel elements in a spaced array; thimbles interspersed among the fuel elements adapted for insertion of a rod control cluster therewithin; means for structurally joining the fuel elements and the guide thimbles; fluid moderator control means for providing a volume of low neutron absorbing fluid within the fuel assembly and for removing a substantially equivalent volume of reactor coolant water therefrom, a first flow manifold at one end of the fuel assembly sealingly connected to a first end of the moderator control tubes whereby the first ends are commonly flow connected; and a second flow manifold, having an inlet passage and an outlet passage therein, sealingly connected to a second end of the moderator control tubes at a second end of the fuel assembly

Structural insights into the light-driven auto-assembly process of the water-oxidizing Mn4CaO5-cluster in photosystem II.

Science.gov (United States)

Zhang, Miao; Bommer, Martin; Chatterjee, Ruchira; Hussein, Rana; Yano, Junko; Dau, Holger; Kern, Jan; Dobbek, Holger; Zouni, Athina

2017-07-18

In plants, algae and cyanobacteria, Photosystem II (PSII) catalyzes the light-driven splitting of water at a protein-bound Mn 4 CaO 5 -cluster, the water-oxidizing complex (WOC). In the photosynthetic organisms, the light-driven formation of the WOC from dissolved metal ions is a key process because it is essential in both initial activation and continuous repair of PSII. Structural information is required for understanding of this chaperone-free metal-cluster assembly. For the first time, we obtained a structure of PSII from Thermosynechococcus elongatus without the Mn 4 CaO 5 -cluster. Surprisingly, cluster-removal leaves the positions of all coordinating amino acid residues and most nearby water molecules largely unaffected, resulting in a pre-organized ligand shell for kinetically competent and error-free photo-assembly of the Mn 4 CaO 5 -cluster. First experiments initiating (i) partial disassembly and (ii) partial re-assembly after complete depletion of the Mn 4 CaO 5 -cluster agree with a specific bi-manganese cluster, likely a di-µ-oxo bridged pair of Mn(III) ions, as an assembly intermediate.

SOS System Induction Inhibits the Assembly of Chemoreceptor Signaling Clusters in Salmonella enterica.

Science.gov (United States)

Irazoki, Oihane; Mayola, Albert; Campoy, Susana; Barbé, Jordi

2016-01-01

Swarming, a flagellar-driven multicellular form of motility, is associated with bacterial virulence and increased antibiotic resistance. In this work we demonstrate that activation of the SOS response reversibly inhibits swarming motility by preventing the assembly of chemoreceptor-signaling polar arrays. We also show that an increase in the concentration of the RecA protein, generated by SOS system activation, rather than another function of this genetic network impairs chemoreceptor polar cluster formation. Our data provide evidence that the molecular balance between RecA and CheW proteins is crucial to allow polar cluster formation in Salmonella enterica cells. Thus, activation of the SOS response by the presence of a DNA-injuring compound increases the RecA concentration, thereby disturbing the equilibrium between RecA and CheW and resulting in the cessation of swarming. Nevertheless, when the DNA-damage decreases and the SOS response is no longer activated, basal RecA levels and thus polar cluster assembly are reestablished. These results clearly show that bacterial populations moving over surfaces make use of specific mechanisms to avoid contact with DNA-damaging compounds.

CAUGHT IN THE ACT: THE ASSEMBLY OF MASSIVE CLUSTER GALAXIES AT z = 1.62

International Nuclear Information System (INIS)

Lotz, Jennifer M.; Ferguson, Henry C.; Grogin, Norman; Koekemoer, Anton M.; Papovich, Casey; Tran, Kim-Vy; Faber, S. M.; Guo Yicheng; Kocevski, Dale; Lee, Kyoung-Soo; McIntosh, Daniel; Momcheva, Ivelina; Rudnick, Gregory; Saintonge, Amelie; Van der Wel, Arjen; Willmer, Christopher

2013-01-01

We present the recent merger history of massive galaxies in a spectroscopically confirmed proto-cluster at z = 1.62. Using Hubble Space Telescope WFC3 near-infrared imaging from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we select cluster and z ∼ 1.6 field galaxies with M star ≥ 3 × 10 10 M ☉ , to determine the frequency of double nuclei or close companions within projected separations less than 20 kpc co-moving. We find that four out of five spectroscopically confirmed massive proto-cluster galaxies have double nuclei, and 57 +13 -14 % of all M star ≥ 3 × 10 10 M ☉ cluster candidates are observed in either close pair systems or have double nuclei. In contrast, only 11% ± 3% of the field galaxies are observed in close pair/double nuclei systems. After correcting for the contribution from random projections, the implied merger rate per massive galaxy in the proto-cluster is ∼3-10 times higher than the merger rate of massive field galaxies at z ∼ 1.6. Close pairs in the cluster have minor merger stellar mass ratios (M primary : M satellite ≥ 4), while the field pairs consist of both major and minor mergers. At least half of the cluster mergers are gas-poor, as indicated by their red colors and low 24 μm fluxes. Two of the double-nucleated cluster members have X-ray detected active galactic nuclei with L x > 10 43 erg s –1 , and are strong candidates for dual or offset super-massive black holes. We conclude that the massive z = 1.62 proto-cluster galaxies are undergoing accelerated assembly via minor mergers, and discuss the implications for galaxy evolution in proto-cluster environments

Variable surface composition and radial interface formation in self-assembled free, mixed Ar/Xe clusters

International Nuclear Information System (INIS)

Tchaplyguine, M.; Maartensson, N.; Lundwall, M.; Oehrwall, G.; Feifel, R.; Svensson, S.; Bjoerneholm, O.; Gisselbrecht, M.; Sorensen, S.

2004-01-01

Using photoelectron spectroscopy, we demonstrate how the self-assembling process of cluster formation in an adiabatic expansion leads to radial segregation and layering as well as to variable surface composition for binary Ar/Xe clusters. The radial structuring can be qualitatively understood from the different interatomic bonding strengths of the two components

THE XMM CLUSTER SURVEY: THE STELLAR MASS ASSEMBLY OF FOSSIL GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Harrison, Craig D.; Miller, Christopher J. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Richards, Joseph W.; Deadman, Paul-James [Center for Time Domain Informatics, University of California, Berkeley, CA 94720 (United States); Lloyd-Davies, E. J.; Kathy Romer, A.; Mehrtens, Nicola; Liddle, Andrew R. [Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Hoyle, Ben [Institute of Sciences of the Cosmos (ICCUB) and IEEC, Physics Department, University of Barcelona, Barcelona 08024 (Spain); Hilton, Matt [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000 (South Africa); Stott, John P.; Capozzi, Diego; Collins, Chris A. [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); Sahlen, Martin [Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Stanford, S. Adam [Physics Department, University of California, Davis, CA 95616 (United States); Viana, Pedro T. P., E-mail: craigha@umich.edu [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

2012-06-10

This paper presents both the result of a search for fossil systems (FSs) within the XMM Cluster Survey and the Sloan Digital Sky Survey and the results of a study of the stellar mass assembly and stellar populations of their fossil galaxies. In total, 17 groups and clusters are identified at z < 0.25 with large magnitude gaps between the first and fourth brightest galaxies. All the information necessary to classify these systems as fossils is provided. For both groups and clusters, the total and fractional luminosity of the brightest galaxy is positively correlated with the magnitude gap. The brightest galaxies in FSs (called fossil galaxies) have stellar populations and star formation histories which are similar to normal brightest cluster galaxies (BCGs). However, at fixed group/cluster mass, the stellar masses of the fossil galaxies are larger compared to normal BCGs, a fact that holds true over a wide range of group/cluster masses. Moreover, the fossil galaxies are found to contain a significant fraction of the total optical luminosity of the group/cluster within 0.5 R{sub 200}, as much as 85%, compared to the non-fossils, which can have as little as 10%. Our results suggest that FSs formed early and in the highest density regions of the universe and that fossil galaxies represent the end products of galaxy mergers in groups and clusters.

Atomically precise arrays of fluorescent silver clusters: a modular approach for metal cluster photonics on DNA nanostructures.

Science.gov (United States)

Copp, Stacy M; Schultz, Danielle E; Swasey, Steven; Gwinn, Elisabeth G

2015-03-24

The remarkable precision that DNA scaffolds provide for arraying nanoscale optical elements enables optical phenomena that arise from interactions of metal nanoparticles, dye molecules, and quantum dots placed at nanoscale separations. However, control of ensemble optical properties has been limited by the difficulty of achieving uniform particle sizes and shapes. Ligand-stabilized metal clusters offer a route to atomically precise arrays that combine desirable attributes of both metals and molecules. Exploiting the unique advantages of the cluster regime requires techniques to realize controlled nanoscale placement of select cluster structures. Here we show that atomically monodisperse arrays of fluorescent, DNA-stabilized silver clusters can be realized on a prototypical scaffold, a DNA nanotube, with attachment sites separated by <10 nm. Cluster attachment is mediated by designed DNA linkers that enable isolation of specific clusters prior to assembly on nanotubes and preserve cluster structure and spectral purity after assembly. The modularity of this approach generalizes to silver clusters of diverse sizes and DNA scaffolds of many types. Thus, these silver cluster nano-optical elements, which themselves have colors selected by their particular DNA templating oligomer, bring unique dimensions of control and flexibility to the rapidly expanding field of nano-optics.

Fluid-Mediated Stochastic Self-Assembly at Centimetric and Sub-Millimetric Scales: Design, Modeling, and Control

Directory of Open Access Journals (Sweden)

Bahar Haghighat

2016-08-01

Full Text Available Stochastic self-assembly provides promising means for building micro-/nano-structures with a variety of properties and functionalities. Numerous studies have been conducted on the control and modeling of the process in engineered self-assembling systems constituted of modules with varied capabilities ranging from completely reactive nano-/micro-particles to intelligent miniaturized robots. Depending on the capabilities of the constituting modules, different approaches have been utilized for controlling and modeling these systems. In the quest of a unifying control and modeling framework and within the broader perspective of investigating how stochastic control strategies can be adapted from the centimeter-scale down to the (sub-millimeter-scale, as well as from mechatronic to MEMS-based technology, this work presents the outcomes of our research on self-assembly during the past few years. As the first step, we leverage an experimental platform to study self-assembly of water-floating passive modules at the centimeter scale. A dedicated computational framework is developed for real-time tracking, modeling and control of the formation of specific structures. Using a similar approach, we then demonstrate controlled self-assembly of microparticles into clusters of a preset dimension in a microfluidic chamber, where the control loop is closed again through real-time tracking customized for a much faster system dynamics. Finally, with the aim of distributing the intelligence and realizing programmable self-assembly, we present a novel experimental system for fluid-mediated programmable stochastic self-assembly of active modules at the centimeter scale. The system is built around the water-floating 3-cm-sized Lily robots specifically designed to be operative in large swarms and allows for exploring the whole range of fully-centralized to fully-distributed control strategies. The outcomes of our research efforts extend the state-of-the-art methodologies

Shock buffer for nuclear control assembly

International Nuclear Information System (INIS)

Bevilacqua, F.

1977-01-01

A shock buffer is provided for the gradual deceleration of a rapidly descending control element assembly in a nuclear reactor. The interactive buffer components are associated respectively with the movable control element assembly and part of the upper guide structure independent of and spaced from the fuel assemblies of the reactor

Snubber assembly for a control rod drive

International Nuclear Information System (INIS)

Matthews, J.C.

1978-01-01

A snubber cartridge assembly is mounted to the nozzle of a control rod drive mechanism to insure that the snubber assembly will be located within the liquid filled section of a nuclear reactor vessel whenever the control rod drive is assembled thereto. The snubber assembly includes a piston mounted proximate to the control rod connecting end of the control rod drive leadscrew to allow the piston to travel within the liquid filled snubber cartridge and controllably exhaust liquid therefrom during a ''scram'' condition. The snubber cartridge provides three separate areas of increasing resistance to piston travel to insure a speedy but safe ''scram'' of the control rod into the reactor

The HST/ACS Coma Cluster Survey - VII. Structure and assembly of massive galaxies in the centre of the Coma cluster

NARCIS (Netherlands)

Weinzirl, Tim; Jogee, Shardha; Neistein, Eyal; Khochfar, Sadegh; Kormendy, John; Marinova, Irina; Hoyos, Carlos; Balcells, Marc; den Brok, Mark; Hammer, Derek; Peletier, Reynier F.; Kleijn, Gijs Verdoes; Carter, David; Goudfrooij, Paul; Lucey, John R.; Mobasher, Bahram; Trentham, Neil; Erwin, Peter; Puzia, Thomas

2014-01-01

We constrain the assembly history of galaxies in the projected central 0.5 Mpc of the Coma cluster by performing structural decomposition on 69 massive (M⋆ ≥ 109 M⊙) galaxies using high-resolution F814W images from the Hubble Space Telescope (HST) Treasury Survey of Coma. Each galaxy is modelled

THE ASSEMBLY OF GALAXY CLUSTERS

International Nuclear Information System (INIS)

Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J.; Wechsler, Risa H.

2009-01-01

We study the formation of 53 galaxy cluster-size dark matter halos (M = 10 14.0-14.76 M sun ) formed within a pair of cosmological Λ cold dark matter N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host ∼0.3 L * galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'preprocessing' in the group environment prior to their accretion into the cluster. On average, 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; less than 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past (∼<6 Gyr) than a field halo of the same mass. These results suggest that local cluster processes such as ram pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass, and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with ∼20% incorporated into the cluster halo more than 7 Gyr ago and ∼20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate timescale for late-type to early-type transformation within the cluster environment to be ∼6 Gyr.

The nanocoherer: an electrically and mechanically resettable resistive switching device based on gold clusters assembled on paper

Science.gov (United States)

Minnai, Chloé; Mirigliano, Matteo; Brown, Simon A.; Milani, Paolo

2018-03-01

We report the realization of a resettable resistive switching device based on a nanostructured film fabricated by supersonic cluster beam deposition of gold clusters on plain paper substrates. Through the application of suitable voltage ramps, we obtain, in the same device, either a complex pattern of resistive switchings, or reproducible and stable switchings between low resistance and high resistance states, with an amplitude up to five orders of magnitude. Our device retains a state of internal resistance following the history of the applied voltage similar to that reported for memristors. The two different switching regimes in the same device are both stable, the transition between them is reversible, and it can be controlled by applying voltage ramps or by mechanical deformation of the substrate. The device behavior can be related to the formation, growth and breaking of junctions between the loosely aggregated gold clusters forming the nanostructured films. The fact that our cluster-assembled device is mechanically resettable suggests that it can be considered as the analog of the coherer: a switching device based on metallic powders used for the first radio communication system.

Nuclear reactor control assembly

International Nuclear Information System (INIS)

Negron, S.B.

1991-01-01

This patent describes an assembly for providing global power control in a nuclear reactor having the core split into two halves. It comprises a disk assembly formed from at least two disks each machined with an identical surface hole pattern such that rotation of one disk relative to the other causes the hole pattern to open or close, the disk assembly being positioned substantially at the longitudinal center of and coaxial with the core halves; and means for rotating at least one of the disks relative to the other

Control rod guide tube assemblies

International Nuclear Information System (INIS)

Jabsen, F.S.

1979-01-01

A nuclear fuel assembly including sleeves telescoped over end portions of control rod guide tubes which bear against internal shoulders of the sleeves. Upper ends of the sleeves protrude beyond a control rod guide tube spider and are locked in place by means of a resilient cellular lattice or lock that is seated in mating grooves in the outer surfaces of the sleeves. A grapple is provided for disengaging the entire lock structure spider and associated washers, springs and a grill from the end of the fuel assembly in order to enable these components to be removed and subsequently replaced on the fuel assembly after inspection and repair. (UK)

Device for supporting a fuel pin cluster within a nuclear reactor fuel assembly wrapper

International Nuclear Information System (INIS)

Marmonier, P.; Mesnage, B.; Teulon, J.; Vayra, J.; Venobre, H.

1976-01-01

A supporting member for an array of parallel rails each carrying one row of slidably mounted pins of a fuel cluster is placed coaxially at the lower end of a vertical fuel assembly wrapper. Each parallel rail is provided at each end with a downward extension and terminal lug which engages in a lateral groove formed in the periphery of the supporting member in order to lock and maintain the rails and the fuel pins in uniformly spaced relation within the fuel assembly wrapper. 10 claims, 8 figures

Linked supramolecular building blocks for enhanced cluster formation

DEFF Research Database (Denmark)

McLellan, Ross; Palacios, Maria A.; Beavers, Christine M.

2015-01-01

the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]-arenes and transition metal ions or 3d-4 f combinations......(Figure Presented). Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise...

The effects of assembly bias on the inference of matter clustering from galaxy-galaxy lensing and galaxy clustering

Science.gov (United States)

McEwen, Joseph E.; Weinberg, David H.

2018-04-01

The combination of galaxy-galaxy lensing (GGL) and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modeling can extend the approach down to nonlinear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with large scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older halos affects the cutoff of the mean occupation function for central galaxies, with halos in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We introduce an extended, environment dependent HOD (EDHOD) prescription to describe these results and fit galaxy correlation measurements. Crucially, we find that the galaxy-matter cross-correlation coefficient, rgm(r) ≡ ξgm(r) . [ξmm(r)ξgg(r)]-1/2, is insensitive to assembly bias on scales r ≳ 1 h^{-1} Mpc, even though ξgm(r) and ξgg(r) are both affected individually. We can therefore recover the correct ξmm(r) from the HW13 galaxy-galaxy and galaxy-matter correlations using either a standard HOD or EDHOD fitting method. For Mr ≤ -19 or Mr ≤ -20 samples the recovery of ξmm(r) is accurate to 2% or better. For a sample of red Mr ≤ -20 galaxies we achieve 2% recovery at r ≳ 2 h^{-1} Mpc with EDHOD modeling but lower accuracy at smaller scales or with a standard HOD fit. Most of our mock galaxy samples are consistent with rgm = 1 down to r = 1h-1Mpc, to within the uncertainties set by our finite simulation volume.

The effects of assembly bias on the inference of matter clustering from galaxy-galaxy lensing and galaxy clustering

Science.gov (United States)

McEwen, Joseph E.; Weinberg, David H.

2018-07-01

The combination of galaxy-galaxy lensing and galaxy clustering is a promising route to measuring the amplitude of matter clustering and testing modified gravity theories of cosmic acceleration. Halo occupation distribution (HOD) modelling can extend the approach down to non-linear scales, but galaxy assembly bias could introduce systematic errors by causing the HOD to vary with the large-scale environment at fixed halo mass. We investigate this problem using the mock galaxy catalogs created by Hearin & Watson (2013, HW13), which exhibit significant assembly bias because galaxy luminosity is tied to halo peak circular velocity and galaxy colour is tied to halo formation time. The preferential placement of galaxies (especially red galaxies) in older haloes affects the cutoff of the mean occupation function ⟨Ncen(Mmin)⟩ for central galaxies, with haloes in overdense regions more likely to host galaxies. The effect of assembly bias on the satellite galaxy HOD is minimal. We introduce an extended, environment-dependent HOD (EDHOD) prescription to describe these results and fit galaxy correlation measurements. Crucially, we find that the galaxy-matter cross-correlation coefficient, rgm(r) ≡ ξgm(r) . [ξmm(r)ξgg(r)]-1/2, is insensitive to assembly bias on scales r ≳ 1 h-1 Mpc, even though ξgm(r) and ξgg(r) are both affected individually. We can therefore recover the correct ξmm(r) from the HW13 galaxy-galaxy and galaxy-matter correlations using either a standard HOD or EDHOD fitting method. For Mr ≤ -19 or Mr ≤ -20 samples the recovery of ξmm(r) is accurate to 2 per cent or better. For a sample of red Mr ≤ -20 galaxies, we achieve 2 per cent recovery at r ≳ 2 h-1 Mpc with EDHOD modelling but lower accuracy at smaller scales or with a standard HOD fit. Most of our mock galaxy samples are consistent with rgm = 1 down to r = 1 h-1 Mpc, to within the uncertainties set by our finite simulation volume.

Snubber assembly for a control rod drive

International Nuclear Information System (INIS)

1976-01-01

A snubber cartridge assembly is described which is mounted to the nozzle of a control rod drive mechanism to insure that it will be located within the liquid filled section of a nuclear reactor vessel whenever the control rod drive is assembled thereto. The snubber assembly includes a piston-mounted proximate to the control rod connecting end of the control rod drive leadscrew to allow the piston to travel within the liquid filled snubber cartridge and controllable exhaust the liquid during a 'scram' condition. The snubber cartridge provides three separate areas of increasing resistance to piston travel to insure a speedy but safe 'scram' of the control rod into the reactor

Shock buffer for nuclear control element assembly

International Nuclear Information System (INIS)

Bevilacqua, F.

1977-01-01

A shock buffer for a control element assembly in a nuclear reactor is described, comprising a piston and a cylinder. The piston is affixed to and extends upward from the control rod guide structure; the cylinder is supported by the upper portion of the control element assembly and is vertically oriented with open end downward for receiving the piston. Coolant liquid normally has free access to the cylinder. The piston displaces liquid from the cylinder when inserted, thereby decelerating the control element assembly near its lower extent of travel. (LL)

Deposition of metal Islands, metal clusters and metal containing single molecules on self-assembled monolayers

NARCIS (Netherlands)

Speets, Emiel Adrianus

2005-01-01

The central topic of this thesis is the deposition of metals on Self-Assembled Monolayers (SAMs). Metals are deposited in the form of submicron scale islands, nanometer scale clusters, and as supramolecular, organometallic coordination cages. Several SAMs on various substrates were prepared and

Assembling Fe/S-clusters and modifying tRNAs: ancient co-factors meet ancient adaptors.

Science.gov (United States)

Alfonzo, Juan D; Lukeš, Julius

2011-06-01

Trypanosoma brucei undergoes two clearly distinct develomental stages: in the insect vector (procyclic stage) the cells generate the bulk of their energy through respiration, whereas in the bloodstream of the mammalian host (bloodstream stage) they grow mostly glycolytically. Several mitochondrial respiratory proteins require iron-sulfur clusters for activity, and their activation coincides with developmental changes. Likewise some tRNA modification enzymes either require iron-sulfur clusters or use components of the iron-sulfur cluster assembly pathway for activity. These enzymes affect the anticodon loop of various tRNAs and can impact protein synthesis. Herein, the possibility of these pathways being integrated and exploited by T. brucei to carefully coordinate energy demands to translational rates in response to enviromental changes is examined.

Self-assembled three-dimensional chiral colloidal architecture

Science.gov (United States)

Ben Zion, Matan Yah; He, Xiaojin; Maass, Corinna C.; Sha, Ruojie; Seeman, Nadrian C.; Chaikin, Paul M.

2017-11-01

Although stereochemistry has been a central focus of the molecular sciences since Pasteur, its province has previously been restricted to the nanometric scale. We have programmed the self-assembly of micron-sized colloidal clusters with structural information stemming from a nanometric arrangement. This was done by combining DNA nanotechnology with colloidal science. Using the functional flexibility of DNA origami in conjunction with the structural rigidity of colloidal particles, we demonstrate the parallel self-assembly of three-dimensional microconstructs, evincing highly specific geometry that includes control over position, dihedral angles, and cluster chirality.

Elimination-Fusion Self-Assembly of a Nanometer-Scale 72-Nucleus Silver Cluster Caging a Pair of [EuW10 O36 ]9- Polyoxometalates.

Science.gov (United States)

Zhang, Shan-Shan; Su, Hai-Feng; Wang, Zhi; Wang, Xing-Po; Chen, Wen-Xian; Zhao, Quan-Qin; Tung, Chen-Ho; Sun, Di; Zheng, Lan-Sun

2018-02-06

The largest known polyoxometalate (POM)-templated silver-alkynyl cluster, [(EuW 10 O 36 ) 2 @Ag 72 (tBuC≡C) 48 Cl 2 ⋅4 BF 4 ] (SD/Ag20), was isolated under solvothermal conditions and structurally characterized. It was confirmed by single-crystal X-ray diffraction (SCXRD) as a {EuW 10 } 2 -in-{Ag 72 } clusters-in-cluster rod-like compound. The high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) shows that such a double anion-templated cluster is assembled from a crucial single anion-templated Ag 42 intermediate in the solution. The crystallization of Ag 42 species (SD/Ag21), followed by SCXRD, gave an important clue about the assembly route of SD/Ag20 in solution: the Ag 42 cluster eliminates six silver atoms laterally, then fuses together at the vacant face to form the final Ag 72 cluster (elimination-fusion mechanism). The characteristic emission of [EuW 10 O 36 ] 9- is well maintained in SD/Ag20. This work not only provides a new method for the synthesis of larger silver clusters as well as the functional integration of the silver cluster and POMs, but also gives deep insights about the high-nuclear silver cluster assembly mechanism. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

DNA mediated wire-like clusters of self-assembled TiO₂ nanomaterials: supercapacitor and dye sensitized solar cell applications.

Science.gov (United States)

Nithiyanantham, U; Ramadoss, Ananthakumar; Ede, Sivasankara Rao; Kundu, Subrata

2014-07-21

A new route for the formation of wire-like clusters of TiO₂ nanomaterials self-assembled in DNA scaffold within an hour of reaction time is reported. TiO₂ nanomaterials are synthesized by the reaction of titanium-isopropoxide with ethanol and water in the presence of DNA under continuous stirring and heating at 60 °C. The individual size of the TiO₂ NPs self-assembled in DNA and the diameter of the wires can be tuned by controlling the DNA to Ti-salt molar ratios and other reaction parameters. The eventual diameter of the individual particles varies between 15 ± 5 nm ranges, whereas the length of the nanowires varies in the 2-3 μm range. The synthesized wire-like DNA-TiO₂ nanomaterials are excellent materials for electrochemical supercapacitor and DSSC applications. From the electrochemical supercapacitor experiment, it was found that the TiO₂ nanomaterials showed different specific capacitance (Cs) values for the various nanowires, and the order of Cs values are as follows: wire-like clusters (small size) > wire-like clusters (large size). The highest Cs of 2.69 F g(-1) was observed for TiO₂ having wire-like structure with small sizes. The study of the long term cycling stability of wire-like clusters (small size) electrode were shown to be stable, retaining ca. 80% of the initial specific capacitance, even after 5000 cycles. The potentiality of the DNA-TiO₂ nanomaterials was also tested in photo-voltaic applications and the observed efficiency was found higher in the case of wire-like TiO₂ nanostructures with larger sizes compared to smaller sizes. In future, the described method can be extended for the synthesis of other oxide based materials on DNA scaffold and can be further used in other applications like sensors, Li-ion battery materials or treatment for environmental waste water.

Light-Controlled Swarming and Assembly of Colloidal Particles

Directory of Open Access Journals (Sweden)

Jianhua Zhang

2018-02-01

Full Text Available Swarms and assemblies are ubiquitous in nature and they can perform complex collective behaviors and cooperative functions that they cannot accomplish individually. In response to light, some colloidal particles (CPs, including light active and passive CPs, can mimic their counterparts in nature and organize into complex structures that exhibit collective functions with remote controllability and high temporospatial precision. In this review, we firstly analyze the structural characteristics of swarms and assemblies of CPs and point out that light-controlled swarming and assembly of CPs are generally achieved by constructing light-responsive interactions between CPs. Then, we summarize in detail the recent advances in light-controlled swarming and assembly of CPs based on the interactions arisen from optical forces, photochemical reactions, photothermal effects, and photoisomerizations, as well as their potential applications. In the end, we also envision some challenges and future prospects of light-controlled swarming and assembly of CPs. With the increasing innovations in mechanisms and control strategies with easy operation, low cost, and arbitrary applicability, light-controlled swarming and assembly of CPs may be employed to manufacture programmable materials and reconfigurable robots for cooperative grasping, collective cargo transportation, and micro- and nanoengineering.

Renovating process for Pressurized Water Reactor control rod assemblies and corresponding control

International Nuclear Information System (INIS)

Jahnke, S.; Ple, P.

1989-01-01

In the first PWRs the control rods are moving by the intermediary of electromagnetic mechanisms where the power fed to the electromagnets is selected by a hard wired logic circuit connected to the controldesh by another logic control. For renovating the control rod assemblies each power assembly is replaced by an electronic assembly containing an ordinator and power supply interfaces [fr

Swarm controlled emergence for ant clustering

DEFF Research Database (Denmark)

Scheidler, Alexander; Merkle, Daniel; Middendorf, Martin

2013-01-01

.g. moving robots, and clustering algorithms. Design/methodology/approach: Different types of control agents for that ant clustering model are designed by introducing slight changes to the behavioural rules of the normal agents. The clustering behaviour of the resulting swarms is investigated by extensive...... for future research to investigate the application of the method in other swarm systems. Swarm controlled emergence might be applied to control emergent effects in computing systems that consist of many autonomous components which make decentralized decisions based on local information. Practical...... simulation studies. Findings: It is shown that complex behavior can emerge in systems with two types of agents (normal agents and control agents). For a particular behavior of the control agents, an interesting swarm size dependent effect was found. The behaviour prevents clustering when the number...

Assembling the Streptococcus thermophilus clustered regularly interspaced short palindromic repeats (CRISPR) array for multiplex DNA targeting.

Science.gov (United States)

Guo, Lijun; Xu, Kun; Liu, Zhiyuan; Zhang, Cunfang; Xin, Ying; Zhang, Zhiying

2015-06-01

In addition to the advantages of scalable, affordable, and easy to engineer, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) technology is superior for multiplex targeting, which is laborious and inconvenient when achieved by cloning multiple gRNA expressing cassettes. Here, we report a simple CRISPR array assembling method which will facilitate multiplex targeting usage. First, the Streptococcus thermophilus CRISPR3/Cas locus was cloned. Second, different CRISPR arrays were assembled with different crRNA spacers. Transformation assays using different Escherichia coli strains demonstrated efficient plasmid DNA targeting, and we achieved targeting efficiency up to 95% with an assembled CRISPR array with three crRNA spacers. Copyright © 2015 Elsevier Inc. All rights reserved.

Manipulating cluster size of polyanion-stabilized Fe3O4 magnetic nanoparticle clusters via electrostatic-mediated assembly for tunable magnetophoresis behavior

International Nuclear Information System (INIS)

Yeap, Swee Pin; Ahmad, Abdul Latif; Ooi, Boon Seng; Lim, JitKang

2015-01-01

We report in this article an approach for manipulating the size of magnetic nanoparticle clusters (MNCs) via electrostatic-mediated assembly technique using an electrolyte as a clustering agent. The clusters were surface-tethered with poly(sodium 4-styrenesulfonate) (PSS) through electrostatic compensation to enhance their colloidal stability. Dynamic light scattering was employed to trace the evolution of cluster size. Simultaneously, electrophoretic mobility and Fourier transform infrared spectroscopy analyses were conducted to investigate the possible schemes involved in both cluster formation and PSS grafting. Results showed that the average hydrodynamic cluster size of the PSS/MNCs and their corresponding size distributions were successfully shifted by means of manipulating the suspension pH, the ionic nature of the electrolyte, and the electrolyte concentration. More specifically, the electrokinetic behavior of the particles upon interaction with the electrolyte plays a profound role in the formation of the PSS/MNCs. Nonetheless, the solubility of the polymer in electrolyte solution and the purification of the particles from residual ions should not be omitted in determining the effectiveness of this clustering approach. The PSS adlayer makes the resultant entities highly water-dispersible and provides electrosteric stabilization to shield the PSS/MNCs from aggregation. In this study, the experimental observations were analyzed and discussed on the basis of existing fundamental colloidal theories. The strategy of cluster size manipulation proposed here is simple and convenient to implement. Furthermore, manipulating the size of the MNCs also facilitates the tuning of magnetophoresis kinetics on exposure to low magnetic field gradient, which makes this nano-entity useful for engineering applications, specifically in separation processes.

Properties of the gold-sulphur interface: from self-assembled monolayers to clusters.

Science.gov (United States)

Bürgi, Thomas

2015-10-14

The gold-sulphur interface of self-assembled monolayers (SAMs) was extensively studied some time ago. More recently tremendous progress has been made in the preparation and characterization of thiolate-protected gold clusters. In this feature article we address different properties of the two systems such as their structure, the mobility of the thiolates on the surface and other dynamical aspects, the chirality of the structures and characteristics related to it and their vibrational properties. SAMs and clusters are in the focus of different communities that typically use different experimental approaches to study the respective systems. However, it seems that the nature of the Au-S interfaces in the two cases is quite similar. Recent single crystal X-ray structures of thiolate-protected gold clusters reveal staple motifs characterized by gold ad-atoms sandwiched between two sulphur atoms. This finding contradicts older work on SAMs. However, newer studies on SAMs also reveal ad-atoms. Whether this finding can be generalized remains to be shown. In any case, more and more studies highlight the dynamic nature of the Au-S interface, both on flat surfaces and in clusters. At temperatures slightly above ambient thiolates migrate on the gold surface and on clusters. Evidence for desorption of thiolates at room temperature, at least under certain conditions, has been demonstrated for both systems. The adsorbed thiolate can lead to chirality at different lengths scales, which has been shown both on surfaces and for clusters. Chirality emerges from the organization of the thiolates as well as locally at the molecular level. Chirality can also be transferred from a chiral surface to an adsorbate, as evidenced by vibrational spectroscopy.

Properties of the gold-sulphur interface: from self-assembled monolayers to clusters

Science.gov (United States)

Bürgi, Thomas

2015-09-01

The gold-sulphur interface of self-assembled monolayers (SAMs) was extensively studied some time ago. More recently tremendous progress has been made in the preparation and characterization of thiolate-protected gold clusters. In this feature article we address different properties of the two systems such as their structure, the mobility of the thiolates on the surface and other dynamical aspects, the chirality of the structures and characteristics related to it and their vibrational properties. SAMs and clusters are in the focus of different communities that typically use different experimental approaches to study the respective systems. However, it seems that the nature of the Au-S interfaces in the two cases is quite similar. Recent single crystal X-ray structures of thiolate-protected gold clusters reveal staple motifs characterized by gold ad-atoms sandwiched between two sulphur atoms. This finding contradicts older work on SAMs. However, newer studies on SAMs also reveal ad-atoms. Whether this finding can be generalized remains to be shown. In any case, more and more studies highlight the dynamic nature of the Au-S interface, both on flat surfaces and in clusters. At temperatures slightly above ambient thiolates migrate on the gold surface and on clusters. Evidence for desorption of thiolates at room temperature, at least under certain conditions, has been demonstrated for both systems. The adsorbed thiolate can lead to chirality at different lengths scales, which has been shown both on surfaces and for clusters. Chirality emerges from the organization of the thiolates as well as locally at the molecular level. Chirality can also be transferred from a chiral surface to an adsorbate, as evidenced by vibrational spectroscopy.

THE METALLICITY BIMODALITY OF GLOBULAR CLUSTER SYSTEMS: A TEST OF GALAXY ASSEMBLY AND OF THE EVOLUTION OF THE GALAXY MASS-METALLICITY RELATION

International Nuclear Information System (INIS)

Tonini, Chiara

2013-01-01

We build a theoretical model to study the origin of the globular cluster metallicity bimodality in the hierarchical galaxy assembly scenario. The model is based on empirical relations such as the galaxy mass-metallicity relation [O/H]-M star as a function of redshift, and on the observed galaxy stellar mass function up to redshift z ∼ 4. We make use of the theoretical merger rates as a function of mass and redshift from the Millennium simulation to build galaxy merger trees. We derive a new galaxy [Fe/H]-M star relation as a function of redshift, and by assuming that globular clusters share the metallicity of their original parent galaxy at the time of their formation, we populate the merger tree with globular clusters. We perform a series of Monte Carlo simulations of the galaxy hierarchical assembly, and study the properties of the final globular cluster population as a function of galaxy mass, assembly and star formation history, and under different assumptions for the evolution of the galaxy mass-metallicity relation. The main results and predictions of the model are the following. (1) The hierarchical clustering scenario naturally predicts a metallicity bimodality in the galaxy globular cluster population, where the metal-rich subpopulation is composed of globular clusters formed in the galaxy main progenitor around redshift z ∼ 2, and the metal-poor subpopulation is composed of clusters accreted from satellites, and formed at redshifts z ∼ 3-4. (2) The model reproduces the observed relations by Peng et al. for the metallicities of the metal-rich and metal-poor globular cluster subpopulations as a function of galaxy mass; the positions of the metal-poor and metal-rich peaks depend exclusively on the evolution of the galaxy mass-metallicity relation and the [O/Fe], both of which can be constrained by this method. In particular, we find that the galaxy [O/Fe] evolves linearly with redshift from a value of ∼0.5 at redshift z ∼ 4 to a value of ∼0.1 at

The immitigable nature of assembly bias: the impact of halo definition on assembly bias

Science.gov (United States)

Villarreal, Antonio S.; Zentner, Andrew R.; Mao, Yao-Yuan; Purcell, Chris W.; van den Bosch, Frank C.; Diemer, Benedikt; Lange, Johannes U.; Wang, Kuan; Campbell, Duncan

2017-11-01

Dark matter halo clustering depends not only on halo mass, but also on other properties such as concentration and shape. This phenomenon is known broadly as assembly bias. We explore the dependence of assembly bias on halo definition, parametrized by spherical overdensity parameter, Δ. We summarize the strength of concentration-, shape-, and spin-dependent halo clustering as a function of halo mass and halo definition. Concentration-dependent clustering depends strongly on mass at all Δ. For conventional halo definitions (Δ ∼ 200 - 600 m), concentration-dependent clustering at low mass is driven by a population of haloes that is altered through interactions with neighbouring haloes. Concentration-dependent clustering can be greatly reduced through a mass-dependent halo definition with Δ ∼ 20 - 40 m for haloes with M200 m ≲ 1012 h-1M⊙. Smaller Δ implies larger radii and mitigates assembly bias at low mass by subsuming altered, so-called backsplash haloes into now larger host haloes. At higher masses (M200 m ≳ 1013 h-1M⊙) larger overdensities, Δ ≳ 600 m, are necessary. Shape- and spin-dependent clustering are significant for all halo definitions that we explore and exhibit a relatively weaker mass dependence. Generally, both the strength and the sense of assembly bias depend on halo definition, varying significantly even among common definitions. We identify no halo definition that mitigates all manifestations of assembly bias. A halo definition that mitigates assembly bias based on one halo property (e.g. concentration) must be mass dependent. The halo definitions that best mitigate concentration-dependent halo clustering do not coincide with the expected average splashback radii at fixed halo mass.

Control rod guide tube assembly

International Nuclear Information System (INIS)

Jabsen, F.S.

1982-01-01

An improved fuel assembly is described as consisting of a sleeve that engages one end of a control rod guide tube essentially fixing the guide tube to one of the fuel assembly end structures. The end of the sleeve protrudes above the surface of the end fitting. The outer surface of the sleeve has a peripheral groove that engages the resilient sides of a cellular grid or lattice shaped lock. This lock fixes the sleeve in position between the various elements that comprise the end fitting, thereby eliminating a profusion of costly and potentially troublesome nuts, threaded studs and the like that are frequently employed in the fuel assemblies that are presently in use

Magnetism, structures and stabilities of cluster assembled TM@Si nanotubes (TM = Cr, Mn and Fe): a density functional study.

Science.gov (United States)

Dhaka, Kapil; Bandyopadhyay, Debashis

2016-08-02

The present study reports transition metal (TM = Cr, Mn and Fe) doped silicon nanotubes with tunable band structures and magnetic properties by careful selection of cluster assemblies as building blocks using the first-principles density functional theory. We found that the transition metal doping and in addition, the hydrogen termination process can stabilize the pure silicon nanoclusters or cluster assemblies and then it could be extended as magnetic nanotubes with finite magnetic moments. Study of the band structures and density of states (DOS) of different empty and TM doped nanotubes (Type 1 to Type 4) show that these nanotubes are useful as metals, semiconductors, semi-metals and half-metals. These designer magnetic materials could be useful in spintronics and magnetic devices of nanoscale order.

DNA mediated wire-like clusters of self-assembled TiO2 nanomaterials: supercapacitor and dye sensitized solar cell applications

Science.gov (United States)

Nithiyanantham, U.; Ramadoss, Ananthakumar; Ede, Sivasankara Rao; Kundu, Subrata

2014-06-01

A new route for the formation of wire-like clusters of TiO2 nanomaterials self-assembled in DNA scaffold within an hour of reaction time is reported. TiO2 nanomaterials are synthesized by the reaction of titanium-isopropoxide with ethanol and water in the presence of DNA under continuous stirring and heating at 60 °C. The individual size of the TiO2 NPs self-assembled in DNA and the diameter of the wires can be tuned by controlling the DNA to Ti-salt molar ratios and other reaction parameters. The eventual diameter of the individual particles varies between 15 +/- 5 nm ranges, whereas the length of the nanowires varies in the 2-3 μm range. The synthesized wire-like DNA-TiO2 nanomaterials are excellent materials for electrochemical supercapacitor and DSSC applications. From the electrochemical supercapacitor experiment, it was found that the TiO2 nanomaterials showed different specific capacitance (Cs) values for the various nanowires, and the order of Cs values are as follows: wire-like clusters (small size) > wire-like clusters (large size). The highest Cs of 2.69 F g-1 was observed for TiO2 having wire-like structure with small sizes. The study of the long term cycling stability of wire-like clusters (small size) electrode were shown to be stable, retaining ca. 80% of the initial specific capacitance, even after 5000 cycles. The potentiality of the DNA-TiO2 nanomaterials was also tested in photo-voltaic applications and the observed efficiency was found higher in the case of wire-like TiO2 nanostructures with larger sizes compared to smaller sizes. In future, the described method can be extended for the synthesis of other oxide based materials on DNA scaffold and can be further used in other applications like sensors, Li-ion battery materials or treatment for environmental waste water.A new route for the formation of wire-like clusters of TiO2 nanomaterials self-assembled in DNA scaffold within an hour of reaction time is reported. TiO2 nanomaterials are

Reconstitutable control assembly having removable control rods with detachable split upper end plugs

International Nuclear Information System (INIS)

Gjertsen, R.K.; Knott, R.P.; Sparrow, J.A.

1989-01-01

This patent describes, in a reconstitutable control assembly for use with a nuclear fuel assembly, the control assembly including a spider structure and at least one control rod, an attachment joint for detachable fastening the control rod to the spider structure. The attachment joint comprising: a hollow connecting finger on the spider structure; and an elongated detachable split upper end plug on the control rod having a pair of separate upper and lower plug portions, the upper plug portion having integrally-connected tandemly- arranged upper, middle and lower sections. The lower plug portion having integrally-connected tandemly-arranged upper, middle and lower segments

Dimensional scale effects on surface enhanced Raman scattering efficiency of self-assembled silver nanoparticle clusters

International Nuclear Information System (INIS)

Fasolato, C.; Domenici, F.; De Angelis, L.; Luongo, F.; Postorino, P.; Sennato, S.; Mura, F.; Costantini, F.; Bordi, F.

2014-01-01

A study of the Surface Enhanced Raman Scattering (SERS) from micrometric metallic nanoparticle aggregates is presented. The sample is obtained from the self-assembly on glass slides of micro-clusters of silver nanoparticles (60 and 100 nm diameter), functionalized with the organic molecule 4-aminothiophenol in water solution. For nanoparticle clusters at the micron scale, a maximum enhancement factor of 10 9 is estimated from the SERS over the Raman intensity ratio normalized to the single molecule contribution. Atomic force microscopy, correlated to spatially resolved Raman measurements, allows highlighting the connection between morphology and efficiency of the plasmonic system. The correlation between geometric features and SERS response of the metallic structures reveals a linear trend of the cluster maximum scattered intensity as a function of the surface area of the aggregate. On given clusters, the intensity turns out to be also influenced by the number of stacking planes of the aggregate, thus suggesting a plasmonic waveguide effect. The linear dependence results weakened for the largest area clusters, suggesting 30 μm 2 as the upper limit for exploiting the coherence over large scale of the plasmonic response.

The iron-sulfur cluster assembly machineries in plants: current knowledge and open questions

Science.gov (United States)

Couturier, Jérémy; Touraine, Brigitte; Briat, Jean-François; Gaymard, Frédéric; Rouhier, Nicolas

2013-01-01

Many metabolic pathways and cellular processes occurring in most sub-cellular compartments depend on the functioning of iron-sulfur (Fe-S) proteins, whose cofactors are assembled through dedicated protein machineries. Recent advances have been made in the knowledge of the functions of individual components through a combination of genetic, biochemical and structural approaches, primarily in prokaryotes and non-plant eukaryotes. Whereas most of the components of these machineries are conserved between kingdoms, their complexity is likely increased in plants owing to the presence of additional assembly proteins and to the existence of expanded families for several assembly proteins. This review focuses on the new actors discovered in the past few years, such as glutaredoxin, BOLA and NEET proteins as well as MIP18, MMS19, TAH18, DRE2 for the cytosolic machinery, which are integrated into a model for the plant Fe-S cluster biogenesis systems. It also discusses a few issues currently subjected to an intense debate such as the role of the mitochondrial frataxin and of glutaredoxins, the functional separation between scaffold, carrier and iron-delivery proteins and the crosstalk existing between different organelles. PMID:23898337

Supersonic cluster beams: a powerful method for the deposition of nanostructured thin films with tailored properties

International Nuclear Information System (INIS)

Milani, P.

2002-01-01

By using a pulsed micro-plasma cluster source and by exploiting aero-dynamical effects typical of supersonic beams it is possible to obtain very high deposition rates with a control on neutral cluster mass distribution, allowing the deposition of thin films with controlled nanostructure. Due to high deposition rates, high lateral resolution, low temperature processing supersonic cluster beams can also be used for the micro and nano-patterning of cluster-assembled films when little or no post-growth manipulation or assembly is required. For example the nano and meso-structure of films obtained by carbon cluster beam deposition can be controlled by selecting in the beam the elemental building blocks, moreover functional properties such as field emission can be controlled and tailored. The use of supersonic cluster beams opens also new perspectives for the production of nano-structured films with novel physico-chemical and topological properties such as nano-structured carbon matrices containing carbide and transition metal particles. (Author)

Overexpression of the yeast frataxin homolog (Yfh1): contrasting effects on iron-sulfur cluster assembly, heme synthesis and resistance to oxidative stress

DEFF Research Database (Denmark)

Seguin, Alexandra; Bayot, Aurélien; Dancis, Andrew

2009-01-01

of 2muYFH1 cells compared to wild-type cells. To our knowledge, this work is the first description where major frataxin-related phenotypes ([Fe-S] cluster assembly and heme synthesis) can be split in vivo, suggesting that frataxin has independent roles in both processes, and that the optimal conditions......Friedreich's ataxia is generally associated with defects in [Fe-S] cluster assembly/stability and heme synthesis and strong susceptibility to oxidative stress. We used the yeast (Saccharomyces cerevisiae) model of Friedreich's ataxia to study the physiological consequences of modulating...... for these independent roles are different....

Side-chain-controlled self-assembly of polystyrene-polypeptide miktoarm star copolymers

KAUST Repository

Junnila, Susanna

2012-03-27

We show how the self-assembly of miktoarm star copolymers can be controlled by modifying the side chains of their polypeptide arms, using A 2B and A 2B 2 type polymer/polypeptide hybrids (macromolecular chimeras). Initially synthesized PS 2PBLL and PS 2PBLL 2 (PS, polystyrene; PBLL, poly(ε-tert-butyloxycarbonyl-l-lysine) ) miktoarms were first deprotected to PS 2PLLHCl and PS 2PLLHCl 2 miktoarms (PLLHCl, poly(l-lysine hydrochloride)) and then complexed ionically with sodium dodecyl sulfonate (DS) to give the supramolecular complexes PS 2PLL(DS) and PS 2(PLL(DS)) 2. The solid-state self-assemblies of these six miktoarm systems were studied by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and small- and wide-angle X-ray scattering (SAXS, WAXS). The side chains of the polypeptide arms were observed to have a large effect on the solubility, polypeptide conformation, and self-assembly of the miktoarms. Three main categories were observed: (i) lamellar self-assemblies at the block copolymer length scale with packed layers of α-helices in PS 2PBLL and PS 2PBLL 2; (ii) charge-clustered polypeptide micelles with less-defined conformations in a nonordered lattice within a PS matrix in PS 2PLLHCl and PS 2PLLHCl 2; (iii) lamellar polypeptide-surfactant self-assemblies with β-sheet conformation in PS 2PLL(DS) and PS 2(PLL(DS)) 2 which dominate over the formation of block copolymer scale structures. Differences between the 3- and 4-arm systems illustrate how packing frustration between the coil-like PS arms and rigid polypeptide conformations can be relieved by the right number of arms, leading to differences in the extent of order. © 2012 American Chemical Society.

Compactable control element assembly for a nuclear reactor

International Nuclear Information System (INIS)

Dupen, C.F.G.

1976-01-01

A description is given of a compactable control element assembly for a nuclear reactor in which the absorber pins of the assembly are compacted during downward movement of the pin and are returned to their uncompacted state when downward movement is stopped. The control element assembly comprises a support member longitudinally movable within a control assembly duct and a plurality of absorber pins supported laterally outward of the support member and within the duct by pairs of support arms. The absorber pins are pivotably mounted to the support arms and the support arms in turn are supported from the support member for upward pivotable movement in a longitudinal plane. As the support member is moved downward, the support arms pivot upwardly and the absorber pins move upwardly and inwardly towards the support member. When the support member is stopped the absorber pins return to their uncompacted position

ClusterControl: a web interface for distributing and monitoring bioinformatics applications on a Linux cluster.

Science.gov (United States)

Stocker, Gernot; Rieder, Dietmar; Trajanoski, Zlatko

2004-03-22

ClusterControl is a web interface to simplify distributing and monitoring bioinformatics applications on Linux cluster systems. We have developed a modular concept that enables integration of command line oriented program into the application framework of ClusterControl. The systems facilitate integration of different applications accessed through one interface and executed on a distributed cluster system. The package is based on freely available technologies like Apache as web server, PHP as server-side scripting language and OpenPBS as queuing system and is available free of charge for academic and non-profit institutions. http://genome.tugraz.at/Software/ClusterControl

Design requirement on KALIMER control rod assembly duct

International Nuclear Information System (INIS)

Hwang, W.; Kang, H. Y.; Nam, C.; Kim, J. O.; Kim, Y. J.

1998-03-01

This document establishes the design guidelines which are needs for designing the control rod assembly duct of the KALIMER as design requirements. it describes control rod assembly duct of the KALIMER and its requirements that includes functional requirements, performance requirements, interfacing systems, design limits and strength requirements, seismic requirements, structural requirements, environmental requirements, reliability and safety requirements, standard and codes, QA programs, and other requirements. The control rod system consists of three parts, which are drive mechanism, drive-line, and absorber bundle. This report deals with the absorber bundle and its outer duct only because the others are beyond the scope of fuel system design. The guidelines for design requirements intend to be used for an improved design of the control rod assembly duct of the KALIMER. (author). 19 refs

Design requirement on KALIMER control rod assembly duct

Energy Technology Data Exchange (ETDEWEB)

Hwang, W.; Kang, H. Y.; Nam, C.; Kim, J. O.; Kim, Y. J

1998-03-01

This document establishes the design guidelines which are needs for designing the control rod assembly duct of the KALIMER as design requirements. it describes control rod assembly duct of the KALIMER and its requirements that includes functional requirements, performance requirements, interfacing systems, design limits and strength requirements, seismic requirements, structural requirements, environmental requirements, reliability and safety requirements, standard and codes, QA programs, and other requirements. The control rod system consists of three parts, which are drive mechanism, drive-line, and absorber bundle. This report deals with the absorber bundle and its outer duct only because the others are beyond the scope of fuel system design. The guidelines for design requirements intend to be used for an improved design of the control rod assembly duct of the KALIMER. (author). 19 refs.

Atomically precise cluster catalysis towards quantum controlled catalysts

International Nuclear Information System (INIS)

Watanabe, Yoshihide

2014-01-01

Catalysis of atomically precise clusters supported on a substrate is reviewed in relation to the type of reactions. The catalytic activity of supported clusters has generally been discussed in terms of electronic structure. Several lines of evidence have indicated that the electronic structure of clusters and the geometry of clusters on a support, including the accompanying cluster-support interaction, are strongly correlated with catalytic activity. The electronic states of small clusters would be easily affected by cluster–support interactions. Several studies have suggested that it is possible to tune the electronic structure through atomic control of the cluster size. It is promising to tune not only the number of cluster atoms, but also the hybridization between the electronic states of the adsorbed reactant molecules and clusters in order to realize a quantum-controlled catalyst. (review)

Reactor core and control rod assembly in FBR type reactor

International Nuclear Information System (INIS)

Fujimura, Koji; Kawashima, Katsuyuki; Itooka, Satoshi.

1993-01-01

Fuel assemblies and control rod assemblies are attached respectively to reactor core support plates each in a cantilever fashion. Intermediate spacer pads are disposed to the lateral side of a wrapper tube just above the fuel rod region. Intermediate space pads are disposed to the lateral side of a control rod guide tube just above a fuel rod region. The thickness of the intermediate spacer pad for the control rod assembly is made smaller than the thickness of the intermediate spacer pad for the fuel assembly. This can prevent contact between intermediate spacer pads of the control guide tube and the fuel assembly even if the temperature of coolants is elevated to thermally expand the intermediate spacer pad, by which the radial displacement amount of the reactor core region along the direction of the height of the control guide tube is reduced substantially to zero. Accordingly, contribution of the control rod assembly to the radial expansion reactivity can be reduced to zero or negative level, by which the effect of the negative radial expansion reactivity of the reactor is increased to improve the safety upon thermal transient stage, for example, loss of coolant flow rate accident. (I.N.)

Manipulating cluster size of polyanion-stabilized Fe{sub 3}O{sub 4} magnetic nanoparticle clusters via electrostatic-mediated assembly for tunable magnetophoresis behavior

Energy Technology Data Exchange (ETDEWEB)

Yeap, Swee Pin, E-mail: sweepin0727@hotmail.com; Ahmad, Abdul Latif; Ooi, Boon Seng; Lim, JitKang, E-mail: chjitkangl@usm.my [Universiti Sains Malaysia, School of Chemical Engineering (Malaysia)

2015-10-15

We report in this article an approach for manipulating the size of magnetic nanoparticle clusters (MNCs) via electrostatic-mediated assembly technique using an electrolyte as a clustering agent. The clusters were surface-tethered with poly(sodium 4-styrenesulfonate) (PSS) through electrostatic compensation to enhance their colloidal stability. Dynamic light scattering was employed to trace the evolution of cluster size. Simultaneously, electrophoretic mobility and Fourier transform infrared spectroscopy analyses were conducted to investigate the possible schemes involved in both cluster formation and PSS grafting. Results showed that the average hydrodynamic cluster size of the PSS/MNCs and their corresponding size distributions were successfully shifted by means of manipulating the suspension pH, the ionic nature of the electrolyte, and the electrolyte concentration. More specifically, the electrokinetic behavior of the particles upon interaction with the electrolyte plays a profound role in the formation of the PSS/MNCs. Nonetheless, the solubility of the polymer in electrolyte solution and the purification of the particles from residual ions should not be omitted in determining the effectiveness of this clustering approach. The PSS adlayer makes the resultant entities highly water-dispersible and provides electrosteric stabilization to shield the PSS/MNCs from aggregation. In this study, the experimental observations were analyzed and discussed on the basis of existing fundamental colloidal theories. The strategy of cluster size manipulation proposed here is simple and convenient to implement. Furthermore, manipulating the size of the MNCs also facilitates the tuning of magnetophoresis kinetics on exposure to low magnetic field gradient, which makes this nano-entity useful for engineering applications, specifically in separation processes.

Inlet for fuel assembly having finger control rods

International Nuclear Information System (INIS)

Berglund, A.; Suvanto, A.; Tornblom, L.

1975-01-01

A nuclear reactor with vertically arranged fuel assemblies positioned on supporting members and with control rods displaceably arranged in guide tubes between the fuel rods inside the fuel assemblies is described. The supporting plate is provided with a transverse end piece with throttling means for the liquid flow which passes from below up through the supporting member and past the fuel rods in the fuel assembly. The inlets for the guide tubes for the control rods are located below the end piece and the throttling means. In this way a higher pressure prevails at the inlet to the guide tubes than above the end piece, so that a stronger flow of coolant is produced through guide tubes than through the fuel assembly. (U.S.)

System and method for controlling a combustor assembly

Science.gov (United States)

York, William David; Ziminsky, Willy Steve; Johnson, Thomas Edward; Stevenson, Christian Xavier

2013-03-05

A system and method for controlling a combustor assembly are disclosed. The system includes a combustor assembly. The combustor assembly includes a combustor and a fuel nozzle assembly. The combustor includes a casing. The fuel nozzle assembly is positioned at least partially within the casing and includes a fuel nozzle. The fuel nozzle assembly further defines a head end. The system further includes a viewing device configured for capturing an image of at least a portion of the head end, and a processor communicatively coupled to the viewing device, the processor configured to compare the image to a standard image for the head end.

Status of control assembly materials in Indian water reactors

International Nuclear Information System (INIS)

Date, V.G.; Kulkarni, P.G.

2000-01-01

India's present operating water cooled power reactors comprise boiling water reactors of Tarapur Atomic Power Station (TAPS) and pressurized heavy water reactors (PHWRs) at Kota (RAPS), Kalpakkam (MAPS), Narora (NAPS) and Kakrapara (KAPS). Boiling water reactors of TAPS use boron carbide control blades for control of power as well as for shut down (scram). PHWRs use boron steel and cobalt absorber rods for power control and Cd sandwiched shut off rods (primary shut down system) and liquid poison rods (secondary shut down system) for shut down. In TAPS, Gadolinium rods (burnable poison rods) are also incorporated in fuel assembly for flux flattening. Boron carbide control blades and Gadolinium rods for TAPS, cobalt absorber rods and shut down assemblies for PHWRs are fabricated indigenously. Considerable development work was carried out for evolving material specifications, component and assembly drawings, and fabrication processes. Details of various control and shut off assemblies being fabricated currently are highlighted in the paper. (author)

Distributed controller clustering in software defined networks.

Directory of Open Access Journals (Sweden)

Ahmed Abdelaziz

Full Text Available Software Defined Networking (SDN is an emerging promising paradigm for network management because of its centralized network intelligence. However, the centralized control architecture of the software-defined networks (SDNs brings novel challenges of reliability, scalability, fault tolerance and interoperability. In this paper, we proposed a novel clustered distributed controller architecture in the real setting of SDNs. The distributed cluster implementation comprises of multiple popular SDN controllers. The proposed mechanism is evaluated using a real world network topology running on top of an emulated SDN environment. The result shows that the proposed distributed controller clustering mechanism is able to significantly reduce the average latency from 8.1% to 1.6%, the packet loss from 5.22% to 4.15%, compared to distributed controller without clustering running on HP Virtual Application Network (VAN SDN and Open Network Operating System (ONOS controllers respectively. Moreover, proposed method also shows reasonable CPU utilization results. Furthermore, the proposed mechanism makes possible to handle unexpected load fluctuations while maintaining a continuous network operation, even when there is a controller failure. The paper is a potential contribution stepping towards addressing the issues of reliability, scalability, fault tolerance, and inter-operability.

Distributed controller clustering in software defined networks.

Science.gov (United States)

Abdelaziz, Ahmed; Fong, Ang Tan; Gani, Abdullah; Garba, Usman; Khan, Suleman; Akhunzada, Adnan; Talebian, Hamid; Choo, Kim-Kwang Raymond

2017-01-01

Software Defined Networking (SDN) is an emerging promising paradigm for network management because of its centralized network intelligence. However, the centralized control architecture of the software-defined networks (SDNs) brings novel challenges of reliability, scalability, fault tolerance and interoperability. In this paper, we proposed a novel clustered distributed controller architecture in the real setting of SDNs. The distributed cluster implementation comprises of multiple popular SDN controllers. The proposed mechanism is evaluated using a real world network topology running on top of an emulated SDN environment. The result shows that the proposed distributed controller clustering mechanism is able to significantly reduce the average latency from 8.1% to 1.6%, the packet loss from 5.22% to 4.15%, compared to distributed controller without clustering running on HP Virtual Application Network (VAN) SDN and Open Network Operating System (ONOS) controllers respectively. Moreover, proposed method also shows reasonable CPU utilization results. Furthermore, the proposed mechanism makes possible to handle unexpected load fluctuations while maintaining a continuous network operation, even when there is a controller failure. The paper is a potential contribution stepping towards addressing the issues of reliability, scalability, fault tolerance, and inter-operability.

Nuclear fuel assembly

International Nuclear Information System (INIS)

1975-01-01

The nuclear fuel assembly described includes a cluster of fuel elements supported at a distance from each other so that their axes are parallel in order to establish secondary channels between them reserved for the coolant. Several ducts for an auxiliary cooling fluid are arranged in the cluster. The wall of each duct is pierced with coolant ejection holes which are placed circumferentially to a pre-determined pattern established according to the position of the duct in the cluster and by the axial distance of the ejection hole along the duct. This assembly is intended for reactors cooled by light or heavy water [fr

Coding the Assembly of Polyoxotungstates with a Programmable Reaction System.

Science.gov (United States)

Ruiz de la Oliva, Andreu; Sans, Victor; Miras, Haralampos N; Long, De-Liang; Cronin, Leroy

2017-05-01

Chemical transformations are normally conducted in batch or flow mode, thereby allowing the chemistry to be temporally or spatially controlled, but these approaches are not normally combined dynamically. However, the investigation of the underlying chemistry masked by the self-assembly processes that often occur in one-pot reactions and exploitation of the potential of complex chemical systems requires control in both time and space. Additionally, maintaining the intermediate constituents of a self-assembled system "off equilibrium" and utilizing them dynamically at specific time intervals provide access to building blocks that cannot coexist under one-pot conditions and ultimately to the formation of new clusters. Herein, we implement the concept of a programmable networked reaction system, allowing us to connect discrete "one-pot" reactions that produce the building block{W 11 O 38 } ≡ {W 11 } under different conditions and control, in real time, the assembly of a series of polyoxometalate clusters {W 12 O 42 } ≡ {W 12 }, {W 22 O 74 } ≡ {W 22 } 1a, {W 34 O 116 } ≡ {W 34 } 2a, and {W 36 O 120 } ≡ {W 36 } 3a, using pH and ultraviolet-visible monitoring. The programmable networked reaction system reveals that is possible to assemble a range of different clusters using {W 11 }-based building blocks, demonstrating the relationship between the clusters within the family of iso-polyoxotungstates, with the final structural motif being entirely dependent on the building block libraries generated in each separate reaction space within the network. In total, this approach led to the isolation of five distinct inorganic clusters using a "fixed" set of reagents and using a fully automated sequence code, rather than five entirely different reaction protocols. As such, this approach allows us to discover, record, and implement complex one-pot reaction syntheses in a more general way, increasing the yield and reproducibility and potentially giving access to

Extension of lattice cluster theory to strongly interacting, self-assembling polymeric systems.

Science.gov (United States)

Freed, Karl F

2009-02-14

A new extension of the lattice cluster theory is developed to describe the influence of monomer structure and local correlations on the free energy of strongly interacting and self-assembling polymer systems. This extension combines a systematic high dimension (1/d) and high temperature expansion (that is appropriate for weakly interacting systems) with a direct treatment of strong interactions. The general theory is illustrated for a binary polymer blend whose two components contain "sticky" donor and acceptor groups, respectively. The free energy is determined as an explicit function of the donor-acceptor contact probabilities that depend, in turn, on the local structure and both the strong and weak interactions.

Dividing traffic cluster into parts by signal control

Science.gov (United States)

Nagatani, Takashi

2018-02-01

When a cluster of vehicles with various speeds moves through the series of signals, the cluster breaks down by stopping at signals and results in smaller groups of vehicles. We present the nonlinear-map model of the motion of vehicles controlled by the signals. We study the breakup of a cluster of vehicles through the series of signals. The cluster of vehicles is divided into various groups by controlling the cycle time of signals. The vehicles within each group move with the same mean velocity. The breakup of the traffic cluster depends highly on the signal control. The dependence of dividing on both cycle time and vehicular speed is clarified. Also, we investigate the effect of the irregular interval between signals on dividing.

Diblock-copolymer-mediated self-assembly of protein-stabilized iron oxide nanoparticle clusters for magnetic resonance imaging.

Science.gov (United States)

Tähkä, Sari; Laiho, Ari; Kostiainen, Mauri A

2014-03-03

Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (Doxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical experiment designs: study of the vibrational behaviour of the control rod cluster of a pressurized water reactor

International Nuclear Information System (INIS)

Soulier, B.; Bosselut, D.; Regnier, G.

1997-01-01

A finite element model has been performed at EDF to simulate the vibrations of control rod cluster assembly and to analyse the wear phenomenon of control rods. A parametrical study bas been performed for a given computer experiment domain with an experimental design method. The building of the computer experiment design is described. The influence of parameters on calculated mean wear power has been determined along rods and responses surfaces have been easily approximated. Systematism and closeness of experiment design technique is underlined. (authors)

Controlled assembly and single electron charging of monolayer protected Au144 clusters: an electrochemistry and scanning tunneling spectroscopy study

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Bodappa, Nataraju; Fluch, Ulrike; Fu, Yongchun; Mayor, Marcel; Moreno-García, Pavel; Siegenthaler, Hans; Wandlowski, Thomas

2014-11-01

Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups exposed by the Au-MPCs enable their immobilization on Pt(111) substrates. By varying the humidity during their deposition, samples coated by stacks of compact monolayers of Au-MPCs or decorated with individual, laterally separated Au-MPCs are obtained. DPV experiments with stacked monolayers of Au144-MPCs and EC-STS experiments with laterally separated individual Au144-MPCs are performed both in aqueous and ionic liquid electrolytes. Lower capacitance values were observed for individual clusters compared to ensemble clusters. This trend remains the same irrespective of the composition of the electrolyte surrounding the Au144-MPC. However, the resolution of the energy level spacing of the single clusters is strongly affected by the proximity of neighboring particles.Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups

Control of the interparticle spacing in superparamagnetic iron oxide nanoparticle clusters by surface ligand engineering

Science.gov (United States)

Dan, Wang; Bingbing, Lin; Taipeng, Shen; Jun, Wu; Fuhua, Hao; Chunchao, Xia; Qiyong, Gong; Huiru, Tang; Bin, Song; Hua, Ai

2016-07-01

Polymer-mediated self-assembly of superparamagnetic iron oxide (SPIO) nanoparticles allows modulation of the structure of SPIO nanocrystal cluster and their magnetic properties. In this study, dopamine-functionalized polyesters (DA-polyester) were used to directly control the magnetic nanoparticle spacing and its effect on magnetic resonance relaxation properties of these clusters was investigated. Monodisperse SPIO nanocrystals with different surface coating materials (poly(ɛ-caprolactone), poly(lactic acid)) of different molecular weights containing dopamine (DA) structure (DA-PCL2k, DA-PCL1k, DA-PLA1k)) were prepared via ligand exchange reaction, and these nanocrystals were encapsulated inside amphiphilic polymer micelles to modulate the SPIO nanocrystal interparticle spacing. Small-angle x-ray scattering (SAXS) was applied to quantify the interparticle spacing of SPIO clusters. The results demonstrated that the tailored magnetic nanoparticle clusters featured controllable interparticle spacing providing directly by the different surface coating of SPIO nanocrystals. Systematic modulation of SPIO nanocrystal interparticle spacing can regulate the saturation magnetization (M s) and T 2 relaxation of the aggregation, and lead to increased magnetic resonance (MR) relaxation properties with decreased interparticle spacing. Project supported by the National Key Basic Research Program of China (Grant No. 2013CB933903), the National Key Technology R&D Program of China (Grant No. 2012BAI23B08), and the National Natural Science Foundation of China (Grant Nos. 20974065, 51173117, and 50830107).

Zinc and the iron donor frataxin regulate oligomerization of the scaffold protein to form new Fe-S cluster assembly centers.

Science.gov (United States)

Galeano, B K; Ranatunga, W; Gakh, O; Smith, D Y; Thompson, J R; Isaya, G

2017-06-21

Early studies of the bacterial Fe-S cluster assembly system provided structural details for how the scaffold protein and the cysteine desulfurase interact. This work and additional work on the yeast and human systems elucidated a conserved mechanism for sulfur donation but did not provide any conclusive insights into the mechanism for iron delivery from the iron donor, frataxin, to the scaffold. We previously showed that oligomerization is a mechanism by which yeast frataxin (Yfh1) can promote assembly of the core machinery for Fe-S cluster synthesis both in vitro and in cells, in such a manner that the scaffold protein, Isu1, can bind to Yfh1 independent of the presence of the cysteine desulfurase, Nfs1. Here, in the absence of Yfh1, Isu1 was found to exist in two forms, one mostly monomeric with limited tendency to dimerize, and one with a strong propensity to oligomerize. Whereas the monomeric form is stabilized by zinc, the loss of zinc promotes formation of dimer and higher order oligomers. However, upon binding to oligomeric Yfh1, both forms take on a similar symmetrical trimeric configuration that places the Fe-S cluster coordinating residues of Isu1 in close proximity of iron-binding residues of Yfh1. This configuration is suitable for docking of Nfs1 in a manner that provides a structural context for coordinate iron and sulfur donation to the scaffold. Moreover, distinct structural features suggest that in physiological conditions the zinc-regulated abundance of monomeric vs. oligomeric Isu1 yields [Yfh1]·[Isu1] complexes with different Isu1 configurations that afford unique functional properties for Fe-S cluster assembly and delivery.

Giant magnetoresistance in cluster-assembled nanostructures: on the influence of inter-particle interactions

International Nuclear Information System (INIS)

Oyarzún, Simón; Domingues Tavares de Sa, Artur; Tuaillon-Combes, Juliette; Tamion, Alexandre; Hillion, Arnaud; Boisron, Olivier; Mosset, Alexis; Pellarin, Michel; Dupuis, Véronique; Hillenkamp, Matthias

2013-01-01

The giant magnetoresistance response of granular systems has since its discovery been described by a simple model based on the geometric orientation of the magnetic moments of adjacent nanoparticles. This model has been proven quite successful in many cases but its being based on decoupled neighboring grains has never been verified as all available studies rely on samples with too high concentration. Here we report on magnetic and magnetotransport measurements of cluster-assembled nanostructures with cobalt clusters around 2.3 nm diameter embedded in copper matrices at different concentrations. The thorough magnetic characterization based on the recently developed “triple fit” method allows the detection of measurable inter-particle interactions and thus assures true superparamagnetic behavior in the most dilute sample. The spintronic response is compared to theory and we show that only at low concentration (0.5 at.% Co) all experiments are consistent and the common theoretical description is appropriate. Increasing the concentration to 2.5 and 5 at.% implies deviations between magnetometry and magnetotransport

Electrodynamic tailoring of self-assembled three-dimensional electrospun constructs

Science.gov (United States)

Reis, Tiago C.; Correia, Ilídio J.; Aguiar-Ricardo, Ana

2013-07-01

The rational design of three-dimensional electrospun constructs (3DECs) can lead to striking topographies and tailored shapes of electrospun materials. This new generation of materials is suppressing some of the current limitations of the usual 2D non-woven electrospun fiber mats, such as small pore sizes or only flat shaped constructs. Herein, we pursued an explanation for the self-assembly of 3DECs based on electrodynamic simulations and experimental validation. We concluded that the self-assembly process is driven by the establishment of attractive electrostatic forces between the positively charged aerial fibers and the already collected ones, which tend to acquire a negatively charged network oriented towards the nozzle. The in situ polarization degree is strengthened by higher amounts of clustered fibers, and therefore the initial high density fibrous regions are the preliminary motifs for the self-assembly mechanism. As such regions increase their in situ polarization electrostatic repulsive forces will appear, favoring a competitive growth of these self-assembled fibrous clusters. Highly polarized regions will evidence higher distances between consecutive micro-assembled fibers (MAFs). Different processing parameters - deposition time, electric field intensity, concentration of polymer solution, environmental temperature and relative humidity - were evaluated in an attempt to control material's design.The rational design of three-dimensional electrospun constructs (3DECs) can lead to striking topographies and tailored shapes of electrospun materials. This new generation of materials is suppressing some of the current limitations of the usual 2D non-woven electrospun fiber mats, such as small pore sizes or only flat shaped constructs. Herein, we pursued an explanation for the self-assembly of 3DECs based on electrodynamic simulations and experimental validation. We concluded that the self-assembly process is driven by the establishment of attractive

Spectromicroscopy of self-assembled protein clusters

Energy Technology Data Exchange (ETDEWEB)

Schonschek, O.; Hormes, J.; Herzog, V. [Univ. of Bonn (Germany)

1997-04-01

The aim of this project is to use synchrotron radiation as a tool to study biomedical questions concerned with the thyroid glands. The biological background is outlined in a recent paper. In short, Thyroglobulin (TG), the precursor protein of the hormone thyroxine, forms large (20 - 500 microns in diameter) clusters in the extracellular lumen of thyrocytes. The process of the cluster formation is still not well understood but is thought to be a main storage mechanism of TG and therefore thyroxine inside the thyroid glands. For human thyroids, the interconnections of the proteins inside the clusters are mainly disulfide bondings. Normally, sulfur bridges are catalyzed by an enzyme called Protein Disulfide Bridge Isomerase (PDI). While this enzyme is supposed to be not present in any extracellular space, the cluster formation of TG takes place in the lumen between the thyrocytes. A possible explanation is the autocatalysis of TG.

Quality and reliability control on assemblies

International Nuclear Information System (INIS)

Mueller, H.

1976-01-01

Taking as an example electronic assemblies in printed circuit board engineering, quality control during manufacture is dealt with. After giving a survey of four phases of quality and reliability control, some specific methods of quality control are dealt with by means of a flowchart, and by some examples the necessity and the success of these measures are shown. (RW) [de

Magnetic domains in Co-cluster assembled films deposited by LECBD

International Nuclear Information System (INIS)

Dumas-Bouchiat, F.; Nagaraja, H.S.; Rossignol, F.; Champeaux, C.; Catherinot, A.

2005-01-01

Cobalt aggregates prepared using a cluster beam generator have been deposited on Si(100) substrate leading to thin films of randomly assembled Co nanoparticles which exhibit a spherical shape with a mono-dispersed diameter distribution centred around 9nm. Films with thickness ranging from 50 to 550nm are investigated using magnetic force microscopy (MFM) and results show the presence of twisted magnetic domains. An in-plane magnetic field applied during the growth of the layer leads to the formation of magnetic stripe domains but we observe a similar behaviour if an in-plane magnetic field is applied after the deposition. This indicates that probably the magnetic field applied during the film growth does not drive its magnetic structure. Finally, the measured variation of magnetic domain width D reveals a t dependence, where t is the film thickness, and is independent of the magnetic history of the films

High aspect ratio, remote controlled pumping assembly

Science.gov (United States)

Brown, Steve B.; Milanovich, Fred P.

1995-01-01

A miniature dual syringe-type pump assembly which has a high aspect ratio and which is remotely controlled, for use such as in a small diameter penetrometer cone or well packer used in water contamination applications. The pump assembly may be used to supply and remove a reagent to a water contamination sensor, for example, and includes a motor, gearhead and motor encoder assembly for turning a drive screw for an actuator which provides pushing on one syringe and pulling on the other syringe for injecting new reagent and withdrawing used reagent from an associated sensor.

The formation and assembly history of the Milky Way revealed by its globular cluster population

Science.gov (United States)

Kruijssen, J. M. Diederik; Pfeffer, Joel L.; Reina-Campos, Marta; Crain, Robert A.; Bastian, Nate

2018-06-01

We use the age-metallicity distribution of 96 Galactic globular clusters (GCs) to infer the formation and assembly history of the Milky Way (MW), culminating in the reconstruction of its merger tree. Based on a quantitative comparison of the Galactic GC population to the 25 cosmological zoom-in simulations of MW-mass galaxies in the E-MOSAICS project, which self-consistently model the formation and evolution of GC populations in a cosmological context, we find that the MW assembled quickly for its mass, reaching {25, 50}% of its present-day halo mass already at z = {3, 1.5} and half of its present-day stellar mass at z = 1.2. We reconstruct the MW's merger tree from its GC age-metallicity distribution, inferring the number of mergers as a function of mass ratio and redshift. These statistics place the MW's assembly rate among the 72th-94th percentile of the E-MOSAICS galaxies, whereas its integrated properties (e.g. number of mergers, halo concentration) match the median of the simulations. We conclude that the MW has experienced no major mergers (mass ratios >1:4) since z ˜ 4, sharpening previous limits of z ˜ 2. We identify three massive satellite progenitors and constrain their mass growth and enrichment histories. Two are proposed to correspond to Sagittarius (few 108M⊙) and Canis Major (˜109 M⊙). The third satellite has no known associated relic and was likely accreted between z = 0.6-1.3. We name this enigmatic galaxy Kraken and propose that it is the most massive satellite (M* ˜ 2 × 109 M⊙) ever accreted by the MW. We predict that ˜40% of the Galactic GCs formed ex-situ (in galaxies with masses M* = 2 × 107-2 × 109 M⊙), with 6 ± 1 being former nuclear clusters.

Interactions of iron-bound frataxin with ISCU and ferredoxin on the cysteine desulfurase complex leading to Fe-S cluster assembly.

Science.gov (United States)

Cai, Kai; Frederick, Ronnie O; Tonelli, Marco; Markley, John L

2018-06-01

Frataxin (FXN) is involved in mitochondrial iron‑sulfur (Fe-S) cluster biogenesis and serves to accelerate Fe-S cluster formation. FXN deficiency is associated with Friedreich ataxia, a neurodegenerative disease. We have used a combination of isothermal titration calorimetry and multinuclear NMR spectroscopy to investigate interactions among the components of the biological machine that carries out the assembly of iron‑sulfur clusters in human mitochondria. Our results show that FXN tightly binds a single Fe 2+ but not Fe 3+ . While FXN (with or without bound Fe 2+ ) does not bind the scaffold protein ISCU directly, the two proteins interact mutually when each is bound to the cysteine desulfurase complex ([NFS1] 2 :[ISD11] 2 :[Acp] 2 ), abbreviated as (NIA) 2 , where "N" represents the cysteine desulfurase (NFS1), "I" represents the accessory protein (ISD11), and "A" represents acyl carrier protein (Acp). FXN binds (NIA) 2 weakly in the absence of ISCU but more strongly in its presence. Fe 2+ -FXN binds to the (NIA) 2 -ISCU 2 complex without release of iron. However, upon the addition of both l-cysteine and a reductant (either reduced FDX2 or DTT), Fe 2+ is released from FXN as consistent with Fe 2+ -FXN being the proximal source of iron for Fe-S cluster assembly. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Self-assembly of Fe3O4 nanocrystal-clusters into cauliflower-like architectures: Synthesis and characterization

International Nuclear Information System (INIS)

Zhu Luping; Liao Guihong; Bing Naici; Wang Linlin; Xie Hongyong

2011-01-01

Large-scale cauliflower-like Fe 3 O 4 architectures consist of well-assembled magnetite nanocrystal clusters have been synthesized by a simple solvothermal process. The as-synthesized Fe 3 O 4 samples were characterized by XRD, XPS, FT-IR, SEM, TEM, etc. The results show that the samples exhibit cauliflower-like hierarchical microstructures. The influences of synthesis parameters on the morphology of the samples were experimentally investigated. Magnetic properties of the Fe 3 O 4 cauliflower-like hierarchical microstructures have been detected by VSM at room temperature, showing a relatively low saturation magnetization of 65 emu/g and an enhanced coercive force of 247 Oe. - Graphical Abstract: Cauliflower-like Fe 3 O 4 architectures consist of well-assembled magnetite nanocrystal clusters have been synthesized by a simple solvothermal process, using FeCl 3 .6H 2 O and EDA as the starting materials. Highlights: → Cauliflower-like Fe 3 O 4 architectures were successfully prepared by a simple solvothermal route. → The cauliflower-like Fe 3 O 4 architectures have a size in the range of 200-300 nm. → They show a low saturation magnetization of 65 emu/g and an enhanced coercive force of 247 Oe. → These Fe 3 O 4 architectures may have potential applications in catalysis and biological fields.

Morphology and Pattern Control of Diphenylalanine Self-Assembly via Evaporative Dewetting.

Science.gov (United States)

Chen, Jiarui; Qin, Shuyu; Wu, Xinglong; Chu, And Paul K

2016-01-26

Self-assembled peptide nanostructures have unique physical and biological properties and promising applications in electrical devices and functional molecular recognition. Although solution-based peptide molecules can self-assemble into different morphologies, it is challenging to control the self-assembly process. Herein, controllable self-assembly of diphenylalanine (FF) in an evaporative dewetting solution is reported. The fluid mechanical dimensionless numbers, namely Rayleigh, Marangoni, and capillary numbers, are introduced to control the interaction between the solution and FF molecules in the self-assembly process. The difference in the film thickness reflects the effects of Rayleigh and Marangoni convection, and the water vapor flow rate reveals the role of viscous fingering in the emergence of aligned FF flakes. By employing dewetting, various FF self-assembled patterns, like concentric and spokelike, and morphologies, like strips and hexagonal tubes/rods, can be produced, and there are no significant lattice structural changes in the FF nanostructures.

Satellite cluster flight using on-off cyclic control

Science.gov (United States)

Zhang, Hao; Gurfil, Pini

2015-01-01

Nano-satellite clusters and disaggregated satellites are new concepts in the realm of distributed satellite systems, which require complex cluster management - mainly regulating the maximal and minimal inter-satellite distances on time scales of years - while utilizing simple on-off propulsion systems. The simple actuators and long time scales require judicious astrodynamical modeling coupled with specialized orbit control. This paper offers a satellite cluster orbit control law which works for long time scales in a perturbed environment while utilizing fixed-magnitude thrusters. The main idea is to design a distributed controller which balances the fuel consumption among the satellites, thus mitigating the effect of differential drag perturbations. The underlying methodology utilizes a cyclic control algorithm based on a mean orbital elements feedback. Stability properties of the closed-loop cyclic control system do not adhere to the classical Lyapunov stability theory, so an effort is made to define and implement a suitable stability theory of noncompact equilibria sets. A state selection scheme is proposed for efficiently establishing a low Earth orbit cluster. Several simulations, including a real mission study, and several comparative investigations, are performed to show the strengths of the proposed control law.

Synthesis, delivery and regulation of eukaryotic heme and Fe-S cluster cofactors.

Science.gov (United States)

Barupala, Dulmini P; Dzul, Stephen P; Riggs-Gelasco, Pamela Jo; Stemmler, Timothy L

2016-02-15

In humans, the bulk of iron in the body (over 75%) is directed towards heme- or Fe-S cluster cofactor synthesis, and the complex, highly regulated pathways in place to accomplish biosynthesis have evolved to safely assemble and load these cofactors into apoprotein partners. In eukaryotes, heme biosynthesis is both initiated and finalized within the mitochondria, while cellular Fe-S cluster assembly is controlled by correlated pathways both within the mitochondria and within the cytosol. Iron plays a vital role in a wide array of metabolic processes and defects in iron cofactor assembly leads to human diseases. This review describes progress towards our molecular-level understanding of cellular heme and Fe-S cluster biosynthesis, focusing on the regulation and mechanistic details that are essential for understanding human disorders related to the breakdown in these essential pathways. Copyright © 2016 Elsevier Inc. All rights reserved.

Self-assembled metal clusters on an alumina nanomesh

International Nuclear Information System (INIS)

Buchsbaum, A.

2012-01-01

Template mediated growth of metals has attracted much interest due to the remarkable magnetic and catalytic properties of clusters in the nanometer range and provides the opportunity to grow clusters with narrow size distributions. When the Ni3Al(111) surface is exposed to oxygen at elevated temperature a thin oxide film with a well-defined structure and uniform thickness grows and covers the alloy surface completely. The structure of the alumina film has been solved mainly by the help of scanning tunneling microscopy (STM) combined with density functional theory (DFT) calculations. The structure of the approx. 0.5 nm thick oxide film has sixfold symmetry and exhibits holes with a diameter of approx. 400 pm reaching down to the metal substrate at the corners of the (Sqrt(67) x Sqrt(67))R12.2° unit cell. The side length of the unit cell is 4.1 nm. The driving force for the formation of the oxide nanomesh is the reduction of the metal/oxide interface energy by the formation of energetically favorable Al-Ni bonds at the interface. Due to better wetting of metal on metal surfaces than on oxide surfaces, metal atoms prefer to bind to the substrate in the hole, not to the oxide. Therefore the oxide forms a template with a hexagonal 4.1 nm lattice for the growth of well-ordered metal clusters. Nevertheless, the growth of most metal clusters on top of the corner holes is not straightforward. Fe and Co atoms cannot jump into the corner holes due to a barrier for diffusion and nucleate at their second favorable adsorption site. However, Pd atoms trapped in these corner holes reduce the barrier for diffusion and create metallic nucleation sites where Fe as well as Co clusters can nucleate and form a well-ordered hexagonal arrangement on the oxide nanomesh. We have studied these Fe and Co clusters and applied different methods like STM and surface x-ray diffraction (SXRD) to determine the morphology and crystallography of the clusters. For Fe we found cluster growth with

NIF-type iron-sulfur cluster assembly system is duplicated and distributed in the mitochondria and cytosol of Mastigamoeba balamuthi.

Science.gov (United States)

Nývltová, Eva; Šuták, Robert; Harant, Karel; Šedinová, Miroslava; Hrdy, Ivan; Paces, Jan; Vlček, Čestmír; Tachezy, Jan

2013-04-30

In most eukaryotes, the mitochondrion is the main organelle for the formation of iron-sulfur (FeS) clusters. This function is mediated through the iron-sulfur cluster assembly machinery, which was inherited from the α-proteobacterial ancestor of mitochondria. In Archamoebae, including pathogenic Entamoeba histolytica and free-living Mastigamoeba balamuthi, the complex iron-sulfur cluster machinery has been replaced by an ε-proteobacterial nitrogen fixation (NIF) system consisting of two components: NifS (cysteine desulfurase) and NifU (scaffold protein). However, the cellular localization of the NIF system and the involvement of mitochondria in archamoebal FeS assembly are controversial. Here, we show that the genes for both NIF components are duplicated within the M. balamuthi genome. One paralog of each protein contains an amino-terminal extension that targets proteins to mitochondria (NifS-M and NifU-M), and the second paralog lacks a targeting signal, thereby reflecting the cytosolic form of the NIF machinery (NifS-C and NifU-C). The dual localization of the NIF system corresponds to the presence of FeS proteins in both cellular compartments, including detectable hydrogenase activity in Mastigamoeba cytosol and mitochondria. In contrast, E. histolytica possesses only single genes encoding NifS and NifU, respectively, and there is no evidence for the presence of the NIF machinery in its reduced mitochondria. Thus, M. balamuthi is unique among eukaryotes in that its FeS cluster formation is mediated through two most likely independent NIF machineries present in two cellular compartments.

Transient Analysis of a Gas-cooled Fast Reactor for Single Control Assembly Withdrawal

International Nuclear Information System (INIS)

Choi, Hangbok

2014-01-01

The Energy Multiplier Module (EMZ) system response has been evaluated for control assembly withdrawal transients. Currently the EM2 core is equipped with six cylindrical drum-type control assemblies in the reflector zone for excess reactivity control and power maneuvering during the operating core life. This study investigates the system response to the control assembly withdrawal accident with various rotational speeds and reactivity worth to determine feasible control assembly design requirements from the physics viewpoint. The simulations have been conducted for single control assembly withdrawal transients without scram by a gas-cooled reactor plant simulator, which is based on a simplified plant nodal model, including the point reactor kinetics, single channel core thermal-fluid model, and a turbo-machinery performance model. Simulations were conducted for the middle-of- cycle core, when the excess reactivity of the core is the highest. Control assembly withdrawal times were varied from 1 (runaway) to 180 sec and reactivity worth was varied from 100 to 400 pcm. For a single control assembly withdrawal, the simulation has shown that the peak fuel temperature is expected to be ~1820°C when the assembly worth is 200 pcm and the runaway time is 1 sec per 180 degree rotation. The peak temperature could be reduced to ~1780°C if the assembly is rotated out in a moderate speed such as 1 degree/sec. These peak temperatures give a thermal margin of 22 to 24% to the melting point of uranium carbide fuel. The results also indicate that the current design with a single control assembly worth of 314 pcm may need adjustments in the future design. (author)

Brightest Cluster Galaxies in REXCESS Clusters

Science.gov (United States)

Haarsma, Deborah B.; Leisman, L.; Bruch, S.; Donahue, M.

2009-01-01

Most galaxy clusters contain a Brightest Cluster Galaxy (BCG) which is larger than the other cluster ellipticals and has a more extended profile. In the hierarchical model, the BCG forms through many galaxy mergers in the crowded center of the cluster, and thus its properties give insight into the assembly of the cluster as a whole. In this project, we are working with the Representative XMM-Newton Cluster Structure Survey (REXCESS) team (Boehringer et al 2007) to study BCGs in 33 X-ray luminous galaxy clusters, 0.055 < z < 0.183. We are imaging the BCGs in R band at the Southern Observatory for Astrophysical Research (SOAR) in Chile. In this poster, we discuss our methods and give preliminary measurements of the BCG magnitudes, morphology, and stellar mass. We compare these BCG properties with the properties of their host clusters, particularly of the X-ray emitting gas.

Rod cluster having improved vane configuration

International Nuclear Information System (INIS)

Shockling, L.A.; Francis, T.A.

1989-01-01

This patent describes a pressurized water reactor vessel, the vessel defining a predetermined axial direction of the flow of coolant therewithin and having plural spider assemblies supporting, for vertical movement within the vessel, respective clusters of rods in spaced, parallel axial relationship, parallel to the predetermined axial direction of coolant flow, and a rod guide for each spider assembly and respective cluster of rods. The rod guide having horizontally oriented support plates therewithin, each plate having an interior opening for accommodating axial movement therethrough of the spider assembly and respective cluster of rods. The opening defining plural radially extending channels and corresponding parallel interior wall surfaces of the support plate

Blind Quantum Signature with Controlled Four-Particle Cluster States

Science.gov (United States)

Li, Wei; Shi, Jinjing; Shi, Ronghua; Guo, Ying

2017-08-01

A novel blind quantum signature scheme based on cluster states is introduced. Cluster states are a type of multi-qubit entangled states and it is more immune to decoherence than other entangled states. The controlled four-particle cluster states are created by acting controlled-Z gate on particles of four-particle cluster states. The presented scheme utilizes the above entangled states and simplifies the measurement basis to generate and verify the signature. Security analysis demonstrates that the scheme is unconditional secure. It can be employed to E-commerce systems in quantum scenario.

Testing the Large-scale Environments of Cool-core and Non-cool-core Clusters with Clustering Bias

Energy Technology Data Exchange (ETDEWEB)

Medezinski, Elinor; Battaglia, Nicholas; Cen, Renyue; Gaspari, Massimo; Strauss, Michael A.; Spergel, David N. [Department of Astrophysical Sciences, 4 Ivy Lane, Princeton, NJ 08544 (United States); Coupon, Jean, E-mail: elinorm@astro.princeton.edu [Department of Astronomy, University of Geneva, ch. dEcogia 16, CH-1290 Versoix (Switzerland)

2017-02-10

There are well-observed differences between cool-core (CC) and non-cool-core (NCC) clusters, but the origin of this distinction is still largely unknown. Competing theories can be divided into internal (inside-out), in which internal physical processes transform or maintain the NCC phase, and external (outside-in), in which the cluster type is determined by its initial conditions, which in turn leads to different formation histories (i.e., assembly bias). We propose a new method that uses the relative assembly bias of CC to NCC clusters, as determined via the two-point cluster-galaxy cross-correlation function (CCF), to test whether formation history plays a role in determining their nature. We apply our method to 48 ACCEPT clusters, which have well resolved central entropies, and cross-correlate with the SDSS-III/BOSS LOWZ galaxy catalog. We find that the relative bias of NCC over CC clusters is b = 1.42 ± 0.35 (1.6 σ different from unity). Our measurement is limited by the small number of clusters with core entropy information within the BOSS footprint, 14 CC and 34 NCC clusters. Future compilations of X-ray cluster samples, combined with deep all-sky redshift surveys, will be able to better constrain the relative assembly bias of CC and NCC clusters and determine the origin of the bimodality.

Testing the Large-scale Environments of Cool-core and Non-cool-core Clusters with Clustering Bias

International Nuclear Information System (INIS)

Medezinski, Elinor; Battaglia, Nicholas; Cen, Renyue; Gaspari, Massimo; Strauss, Michael A.; Spergel, David N.; Coupon, Jean

2017-01-01

There are well-observed differences between cool-core (CC) and non-cool-core (NCC) clusters, but the origin of this distinction is still largely unknown. Competing theories can be divided into internal (inside-out), in which internal physical processes transform or maintain the NCC phase, and external (outside-in), in which the cluster type is determined by its initial conditions, which in turn leads to different formation histories (i.e., assembly bias). We propose a new method that uses the relative assembly bias of CC to NCC clusters, as determined via the two-point cluster-galaxy cross-correlation function (CCF), to test whether formation history plays a role in determining their nature. We apply our method to 48 ACCEPT clusters, which have well resolved central entropies, and cross-correlate with the SDSS-III/BOSS LOWZ galaxy catalog. We find that the relative bias of NCC over CC clusters is b = 1.42 ± 0.35 (1.6 σ different from unity). Our measurement is limited by the small number of clusters with core entropy information within the BOSS footprint, 14 CC and 34 NCC clusters. Future compilations of X-ray cluster samples, combined with deep all-sky redshift surveys, will be able to better constrain the relative assembly bias of CC and NCC clusters and determine the origin of the bimodality.

Cluster Dynamics: Laying the Foundation for Tailoring the Design of Cluster ASSE

Science.gov (United States)

2016-02-25

AFRL-AFOSR-VA-TR-2016-0081 CLUSTER DYNAMICS: LAYING THE FOUNDATION FOR TAILORING THE DESIGN OF CLUSTER ASSE Albert Castleman PENNSYLVANIA STATE...15-10-2015 4. TITLE AND SUBTITLE CLUSTER DYNAMICS: LAYING THE FOUNDATION FOR TAILORING THE DESIGN OF CLUSTER ASSEMBLED NANOSCALE MATERIALS 5a... clusters as the building blocks of new materials with tailored properties that are beneficial to the AFOSR. Our continuing program is composed of two

Gag induces the coalescence of clustered lipid rafts and tetraspanin-enriched microdomains at HIV-1 assembly sites on the plasma membrane.

Science.gov (United States)

Hogue, Ian B; Grover, Jonathan R; Soheilian, Ferri; Nagashima, Kunio; Ono, Akira

2011-10-01

The HIV-1 structural protein Gag associates with two types of plasma membrane microdomains, lipid rafts and tetraspanin-enriched microdomains (TEMs), both of which have been proposed to be platforms for HIV-1 assembly. However, a variety of studies have demonstrated that lipid rafts and TEMs are distinct microdomains in the absence of HIV-1 infection. To measure the impact of Gag on microdomain behaviors, we took advantage of two assays: an antibody-mediated copatching assay and a Förster resonance energy transfer (FRET) assay that measures the clustering of microdomain markers in live cells without antibody-mediated patching. We found that lipid rafts and TEMs copatched and clustered to a greater extent in the presence of membrane-bound Gag in both assays, suggesting that Gag induces the coalescence of lipid rafts and TEMs. Substitutions in membrane binding motifs of Gag revealed that, while Gag membrane binding is necessary to induce coalescence of lipid rafts and TEMs, either acylation of Gag or binding of phosphatidylinositol-(4,5)-bisphosphate is sufficient. Finally, a Gag derivative that is defective in inducing membrane curvature appeared less able to induce lipid raft and TEM coalescence. A higher-resolution analysis of assembly sites by correlative fluorescence and scanning electron microscopy showed that coalescence of clustered lipid rafts and TEMs occurs predominantly at completed cell surface virus-like particles, whereas a transmembrane raft marker protein appeared to associate with punctate Gag fluorescence even in the absence of cell surface particles. Together, these results suggest that different membrane microdomain components are recruited in a stepwise manner during assembly.

Changing cluster composition in cluster randomised controlled trials: design and analysis considerations

Science.gov (United States)

2014-01-01

Background There are many methodological challenges in the conduct and analysis of cluster randomised controlled trials, but one that has received little attention is that of post-randomisation changes to cluster composition. To illustrate this, we focus on the issue of cluster merging, considering the impact on the design, analysis and interpretation of trial outcomes. Methods We explored the effects of merging clusters on study power using standard methods of power calculation. We assessed the potential impacts on study findings of both homogeneous cluster merges (involving clusters randomised to the same arm of a trial) and heterogeneous merges (involving clusters randomised to different arms of a trial) by simulation. To determine the impact on bias and precision of treatment effect estimates, we applied standard methods of analysis to different populations under analysis. Results Cluster merging produced a systematic reduction in study power. This effect depended on the number of merges and was most pronounced when variability in cluster size was at its greatest. Simulations demonstrate that the impact on analysis was minimal when cluster merges were homogeneous, with impact on study power being balanced by a change in observed intracluster correlation coefficient (ICC). We found a decrease in study power when cluster merges were heterogeneous, and the estimate of treatment effect was attenuated. Conclusions Examples of cluster merges found in previously published reports of cluster randomised trials were typically homogeneous rather than heterogeneous. Simulations demonstrated that trial findings in such cases would be unbiased. However, simulations also showed that any heterogeneous cluster merges would introduce bias that would be hard to quantify, as well as having negative impacts on the precision of estimates obtained. Further methodological development is warranted to better determine how to analyse such trials appropriately. Interim recommendations

Formation of clusters composed of C60 molecules via self-assembly in critical fluids

International Nuclear Information System (INIS)

Fukuda, Takahiro; Ishii, Koji; Kurosu, Shunji; Whitby, Raymond; Maekawa, Toru

2007-01-01

Fullerenes are promising candidates for intelligent, functional nanomaterials because of their unique mechanical, electronic and chemical properties. However, it is necessary to invent some efficient but relatively simple methods of producing structures composed of fullerenes for the development of nanomechatronic, nanoelectronic and biochemical devices and sensors. In this paper, we show that various structures such as straight fibres, networks formed by fibres, wide sheets and helical structures, which are composed of C 60 molecules, are created by placing C 60 -crystals in critical ethane, carbon dioxide and xenon even though C 60 molecules do not dissolve or disperse in the above fluids. It is supposed, judging by the intermolecular potentials between C 60 and C 60 , between C 60 and ethane, and between ethane and ethane, that C 60 -clusters grow with the assistance of solvent molecules, which are trapped between C 60 molecules under critical conditions. This room-temperature self-assembly cluster growth process in critical fluids may open up a new methodology of forming structures built up with fullerenes without the need for any ultra-fine processing technologies

Performance of FFTF reference fuel and control assemblies

International Nuclear Information System (INIS)

Leggett, R.D.; Weber, E.T.

1984-11-01

This paper describes the performance of the reference fuel and control assemblies used in FFTF through the first four cycles of irradiation (446 equivalent full power days, EFPD). These assemblies performed flawlessly through the rigors of the Startup Testing Program, STP, (beginning in late 1979) with its cyclic operation and continued to do so throughout Cycles 1, 2, 3 and 4, the latter ending in April 1984

Nonleachable Imidazolium-Incorporated Composite for Disruption of Bacterial Clustering, Exopolysaccharide-Matrix Assembly, and Enhanced Biofilm Removal.

Science.gov (United States)

Hwang, Geelsu; Koltisko, Bernard; Jin, Xiaoming; Koo, Hyun

2017-11-08

Surface-grown bacteria and production of an extracellular polymeric matrix modulate the assembly of highly cohesive and firmly attached biofilms, making them difficult to remove from solid surfaces. Inhibition of cell growth and inactivation of matrix-producing bacteria can impair biofilm formation and facilitate removal. Here, we developed a novel nonleachable antibacterial composite with potent antibiofilm activity by directly incorporating polymerizable imidazolium-containing resin (antibacterial resin with carbonate linkage; ABR-C) into a methacrylate-based scaffold (ABR-modified composite; ABR-MC) using an efficient yet simplified chemistry. Low-dose inclusion of imidazolium moiety (∼2 wt %) resulted in bioactivity with minimal cytotoxicity without compromising mechanical integrity of the restorative material. The antibiofilm properties of ABR-MC were assessed using an exopolysaccharide-matrix-producing (EPS-matrix-producing) oral pathogen (Streptococcus mutans) in an experimental biofilm model. Using high-resolution confocal fluorescence imaging and biophysical methods, we observed remarkable disruption of bacterial accumulation and defective 3D matrix structure on the surface of ABR-MC. Specifically, the antibacterial composite impaired the ability of S. mutans to form organized bacterial clusters on the surface, resulting in altered biofilm architecture with sparse cell accumulation and reduced amounts of EPS matrix (versus control composite). Biofilm topology analyses on the control composite revealed a highly organized and weblike EPS structure that tethers the bacterial clusters to each other and to the surface, forming a highly cohesive unit. In contrast, such a structured matrix was absent on the surface of ABR-MC with mostly sparse and amorphous EPS, indicating disruption in the biofilm physical stability. Consistent with lack of structural organization, the defective biofilm on the surface of ABR-MC was readily detached when subjected to low shear

Multi-sensor control for precise assembly of optical components

Directory of Open Access Journals (Sweden)

Ma Li

2014-06-01

Full Text Available In order to perform an optical assembly accurately, a multi-sensor control strategy is developed which includes an attitude measurement system, a vision system, a loss measurement system and a force sensor. A 3-DOF attitude measuring method using linear variable differential transformers (LVDT is designed to adjust the relation of position and attitude between the spherical mirror and the resonator. A micro vision feedback system is set up to extract the light beam and the diaphragm, which can achieve the coarse positioning of the spherical mirror in the optical assembly process. A rapid self-correlation method is presented to analyze the spectrum signal for the fine positioning. In order to prevent the damage of the optical components and realize sealing of the resonator, a hybrid force-position control is constructed to control the contact force of the optical components. The experimental results show that the proposed multi-sensor control strategy succeeds in accomplishing the precise assembly of the optical components, which consists of parallel adjustment, macro coarse adjustment, macro approach, micro fine adjustment, micro approach and optical contact. Therefore, the results validate the multi-sensor control strategy.

The CMS online cluster: IT for a large data acquisition and control cluster

International Nuclear Information System (INIS)

Bauer, G; Beccati, B; Cano, E; Ciganek, M; Cittolin, S; Deldicque, C; Erhan, S; Gigi, D; Glege, F; Gomez-Reino, R; Gutleber, J; Behrens, U; Hatton, D; Biery, K; Brett, A; Cheung, H; Branson, J; Coarasa, J A; Dusinberre, E; Rodrigues, F Fortes

2010-01-01

The CMS online cluster consists of more than 2000 computers running about 10000 application instances. These applications implement the control of the experiment, the event building, the high level trigger, the online database and the control of the buffering and transferring of data to the Central Data Recording at CERN. In this paper the IT solutions employed to fulfil the requirements of such a large cluster are revised. Details are given on the chosen network structure, configuration management system, monitoring infrastructure and on the implementation of the high availability for the services and infrastructure.

Gag Induces the Coalescence of Clustered Lipid Rafts and Tetraspanin-Enriched Microdomains at HIV-1 Assembly Sites on the Plasma Membrane ▿

Science.gov (United States)

Hogue, Ian B.; Grover, Jonathan R.; Soheilian, Ferri; Nagashima, Kunio; Ono, Akira

2011-01-01

The HIV-1 structural protein Gag associates with two types of plasma membrane microdomains, lipid rafts and tetraspanin-enriched microdomains (TEMs), both of which have been proposed to be platforms for HIV-1 assembly. However, a variety of studies have demonstrated that lipid rafts and TEMs are distinct microdomains in the absence of HIV-1 infection. To measure the impact of Gag on microdomain behaviors, we took advantage of two assays: an antibody-mediated copatching assay and a Förster resonance energy transfer (FRET) assay that measures the clustering of microdomain markers in live cells without antibody-mediated patching. We found that lipid rafts and TEMs copatched and clustered to a greater extent in the presence of membrane-bound Gag in both assays, suggesting that Gag induces the coalescence of lipid rafts and TEMs. Substitutions in membrane binding motifs of Gag revealed that, while Gag membrane binding is necessary to induce coalescence of lipid rafts and TEMs, either acylation of Gag or binding of phosphatidylinositol-(4,5)-bisphosphate is sufficient. Finally, a Gag derivative that is defective in inducing membrane curvature appeared less able to induce lipid raft and TEM coalescence. A higher-resolution analysis of assembly sites by correlative fluorescence and scanning electron microscopy showed that coalescence of clustered lipid rafts and TEMs occurs predominately at completed cell surface virus-like particles, whereas a transmembrane raft marker protein appeared to associate with punctate Gag fluorescence even in the absence of cell surface particles. Together, these results suggest that different membrane microdomain components are recruited in a stepwise manner during assembly. PMID:21813604

Design parameters for voltage-controllable directed assembly of single nanoparticles

International Nuclear Information System (INIS)

Porter, Benjamin F; Bhaskaran, Harish; Abelmann, Leon

2013-01-01

Techniques to reliably pick-and-place single nanoparticles into functional assemblies are required to incorporate exotic nanoparticles into standard electronic circuits. In this paper we explore the use of electric fields to drive and direct the assembly process, which has the advantage of being able to control the nano-assembly process at the single nanoparticle level. To achieve this, we design an electrostatic gating system, thus enabling a voltage-controllable nanoparticle picking technique. Simulating this system with the nonlinear Poisson–Boltzmann equation, we can successfully characterize the parameters required for single particle placement, the key being single particle selectivity, in effect designing a system that can achieve this controllably. We then present the optimum design parameters required for successful single nanoparticle placement at ambient temperature, an important requirement for nanomanufacturing processes. (paper)

Transfer of sulfur from IscS to IscU during Fe/S cluster assembly.

Science.gov (United States)

Urbina, H D; Silberg, J J; Hoff, K G; Vickery, L E

2001-11-30

The cysteine desulfurase enzymes NifS and IscS provide sulfur for the biosynthesis of Fe/S proteins. NifU and IscU have been proposed to serve as template or scaffold proteins in the initial Fe/S cluster assembly events, but the mechanism of sulfur transfer from NifS or IscS to NifU or IscU has not been elucidated. We have employed [(35)S]cysteine radiotracer studies to monitor sulfur transfer between IscS and IscU from Escherichia coli and have used direct binding measurements to investigate interactions between the proteins. IscS catalyzed transfer of (35)S from [(35)S]cysteine to IscU in the absence of additional thiol reagents, suggesting that transfer can occur directly and without involvement of an intermediate carrier. Surface plasmon resonance studies and isothermal titration calorimetry measurements further revealed that IscU binds to IscS with high affinity (K(d) approximately 2 microm) in support of a direct transfer mechanism. Transfer was inhibited by treatment of IscU with iodoacetamide, and (35)S was released by reducing reagents, suggesting that transfer of persulfide sulfur occurs to cysteinyl groups of IscU. A deletion mutant of IscS lacking C-terminal residues 376-413 (IscSDelta376-413) displayed cysteine desulfurase activity similar to the full-length protein but exhibited lower binding affinity for IscU, decreased ability to transfer (35)S to IscU, and reduced activity in assays of Fe/S cluster assembly on IscU. The findings with IscSDelta376-413 provide additional support for a mechanism of sulfur transfer involving a direct interaction between IscS and IscU and suggest that the C-terminal region of IscS may be important for binding IscU.

CdTe magic-sized clusters and the use as building blocks for assembling two-dimensional nanoplatelets

Science.gov (United States)

Xu, Hu; Hou, Yumei; Zhang, Hua

2017-06-01

A facile one-pot noninjection synthesis of CdTe magic-sized clusters (MSCs) and their use as building blocks for assembling two-dimensional (2D) quantum confined nanoplatelets (NPLs) are reported. Four distinct MSC families, with the first exciton absorption peaks at 447 nm (F447), 485 nm (F485), 535 nm (F535), and 555 nm (F555), are synthesized by the reaction between cadmium oleate and trioctylphosphine tellurium (TOP-Te) in octadecene media containing primary amine and TOP at appropriate intermediate temperatures. Especially, F447 is obtained in pure form and can self-assemble in situ into 2D NPLs in the reaction solution. The formation, growth, and transformation of CdTe MSCs are monitored mainly by UV-Vis absorption spectroscopy. The pure F447 and its assembled 2D NPLs are further characterized using transmission electron microscopy. The influence of various experimental variables, including reaction temperature, the nature, and amount of capping ligands, on the stability and growth kinetics of the obtained MSC families has been systematically investigated. Experimental results indicate that the appropriate reaction temperature and the presence of long hydrocarbon chain primary amines play a crucial role in the formation of MSCs and the subsequent assembly into 2D NPLs. Primary amines can also promote ultra-small sized CdTe regular nanocrystals to transform into MSCs, and therefore, CdTe MSCs can be obtained indirectly from regularly sized nanocrystals. [Figure not available: see fulltext.

A Calculation of the radioactivity induced in PWR cluster control rods with the origin and casmo codes

International Nuclear Information System (INIS)

Ekberg, K.

1980-03-01

The radioactivity induced in PWR cluster control rods during reactor operation has been calculated using the computer programme ORIGEN. Neutron fluxes and spectrum conditions as well as the strongly shielded cross sections for the absorber materials Ag, In and Cd have been obtained by running the cell and assembly code CASMO for a couple of typical cases. The results show that Ag-110m, Fe-55 and Co-60 give the largest activity contributions in the interval 1-10 years after the end of irradiation, and Ni-63 and Cd-113m in a longer time perspective. (author)

Reconstitutable control rod spider assembly

International Nuclear Information System (INIS)

Shallenberger, J.M.; Ferian, S.J.

1990-01-01

A reconstitutable control rod/spider assembly includes a hollow connecting finger of the spider having a pair of opposing flat segments formed on the interior thereof and engaging a pair of opposing flat sectors formed on the exterior of a stem extending form the upper end of control rod. The stem also has an externally-threaded portion engaging a nut and a pilot aligning portion for the nut. The nut has a radially flexible and expandable thread-defining element captured in its bore. The segments and sectors allow the rod to be removed and reattached after turning through 180 0 to allow more even wear on the rod. (author)

Globular cluster formation and evolution in the context of cosmological galaxy assembly: open questions

Science.gov (United States)

Forbes, Duncan A.; Bastian, Nate; Gieles, Mark; Crain, Robert A.; Kruijssen, J. M. Diederik; Larsen, Søren S.; Ploeckinger, Sylvia; Agertz, Oscar; Trenti, Michele; Ferguson, Annette M. N.; Pfeffer, Joel; Gnedin, Oleg Y.

2018-02-01

We discuss some of the key open questions regarding the formation and evolution of globular clusters (GCs) during galaxy formation and assembly within a cosmological framework. The current state of the art for both observations and simulations is described, and we briefly mention directions for future research. The oldest GCs have ages greater than or equal to 12.5 Gyr and formed around the time of reionization. Resolved colour-magnitude diagrams of Milky Way GCs and direct imaging of lensed proto-GCs at z˜6 with the James Webb Space Telescope (JWST) promise further insight. GCs are known to host multiple populations of stars with variations in their chemical abundances. Recently, such multiple populations have been detected in ˜2 Gyr old compact, massive star clusters. This suggests a common, single pathway for the formation of GCs at high and low redshift. The shape of the initial mass function for GCs remains unknown; however, for massive galaxies a power-law mass function is favoured. Significant progress has been made recently modelling GC formation in the context of galaxy formation, with success in reproducing many of the observed GC-galaxy scaling relations.

Chinese mitten crab (Eriocheir sinensis) iron-sulphur cluster assembly protein 2 (EsIscA2) is differentially regulated after immune and oxidative stress challenges.

Science.gov (United States)

Zhang, Peng; Liu, Yu; Wang, Min; Dong, Miren; Liu, Zhaoqun; Jia, Zhihao; Wang, Weilin; Zhang, Anguo; Wang, Lingling; Song, Linsheng

2018-07-01

Iron-sulphur clusters (ISCs), one of the oldest and most versatile cofactors of proteins, are involved in catalysis reactions, electron transport reactions, regulation processes as well as sensing of ambient conditions. Iron-sulphur cluster assembly protein (IscA) is a scaffold protein member of ISC formation system, which plays a significant role in the assembly and maturation process of ISC proteins. In the present study, the cDNA sequence of iron-sulphur cluster assembly protein 2 (designated as EsIscA2) was cloned from Eriocheir sinensis. The open reading frame (ORF) of EsIscA2 was of 507 bp, encoding a peptide of 168 amino acids with a typically conserved Fe-S domain. A tetrameric form was predicated by the SWISS-MODEL prediction algorithm, and three conserved cysteine residues (Cys-93, Cys-158, Cys-160) from each IscA monomer were predicted to form a 'cysteine pocket'. The deduced amino acid sequence of EsIscA2 shared over 50% similarity with that of other IscAs. EsIscA2 was clustered with IscA2 proteins from invertebrates and vertebrates, indicating that the protein was highly conservative in the evolution. rEsIscA2 exhibited a high iron binding affinity in the concentration ranging from 2 to 200 μM. EsIscA2 transcripts were detected in all the tested tissues including gonad, hemocytes, gill, muscle, heart, hepatopancreas and eyestalk, and EsIscA2 protein was detected in the mitochondria of hemocytes. The highest mRNA expression level of EsIscA2 was detected in muscle and hepatopancreas, which was about 34.66-fold (p < 0.05) and 27.07-fold (p < 0.05) of that in hemocytes, respectively. After Aeromonas hydrophila and lipopolysaccharide (LPS) stimulations, the mRNA expression of EsIscA2 in hemocytes was down-regulated and reached the lowest level at 24 h (0.31-fold, p < 0.05) and 48 h (0.29-fold, p < 0.05) compared to control group, respectively. And the expression of EsIscA2 mRNA in hepatopancreas was repressed from 6 h to 48 h post

The intermembrane space protein Erv1 of Trypanosoma brucei is essential for mitochondrial Fe-S cluster assembly and operates alone

Czech Academy of Sciences Publication Activity Database

Haindrich, Alexander C.; Boudova, M.; Vancová, Marie; Peña-Diaz, Priscila; Horáková, Eva; Lukeš, Julius

2017-01-01

Roč. 214, JUN (2017), s. 47-51 ISSN 0166-6851 R&D Projects: GA ČR GA15-21974S; GA ČR(CZ) GA16-18699S Institutional support: RVO:60077344 Keywords : Trypanosoma * Erv1 * Fe-S cluster assembly * mitochondrion Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Biochemistry and molecular biology Impact factor: 2.536, year: 2016

Interaction of the iron–sulfur cluster assembly protein IscU with the Hsc66/Hsc20 molecular chaperone system of Escherichia coli

Science.gov (United States)

Hoff, Kevin G.; Silberg, Jonathan J.; Vickery, Larry E.

2000-01-01

The iscU gene in bacteria is located in a gene cluster encoding proteins implicated in iron–sulfur cluster assembly and an hsc70-type (heat shock cognate) molecular chaperone system, iscSUA-hscBA. To investigate possible interactions between these systems, we have overproduced and purified the IscU protein from Escherichia coli and have studied its interactions with the hscA and hscB gene products Hsc66 and Hsc20. IscU and its iron–sulfur complex (IscU–Fe/S) stimulated the basal steady-state ATPase activity of Hsc66 weakly in the absence of Hsc20 but, in the presence of Hsc20, increased the ATPase activity up to 480-fold. Hsc20 also decreased the apparent Km for IscU stimulation of Hsc66 ATPase activity, and surface plasmon resonance studies revealed that Hsc20 enhances binding of IscU to Hsc66. Surface plasmon resonance and isothermal titration calorimetry further showed that IscU and Hsc20 form a complex, and Hsc20 may thereby aid in the targeting of IscU to Hsc66. These results establish a direct and specific role for the Hsc66/Hsc20 chaperone system in functioning with isc gene components for the assembly of iron–sulfur cluster proteins. PMID:10869428

An approximation for kanban controlled assembly systems

NARCIS (Netherlands)

Topan, E.; Avsar, Z.M.

2011-01-01

An approximation is proposed to evaluate the steady-state performance of kanban controlled two-stage assembly systems. The development of the approximation is as follows. The considered continuous-time Markov chain is aggregated keeping the model exact, and this aggregate model is approximated

Controlling Photoconductivity in PBI Films by Supramolecular Assembly.

Science.gov (United States)

Draper, Emily R; Archibald, Lewis J; Nolan, Michael C; Schweins, Ralf; Zwijnenburg, Martijn A; Sproules, Stephen; Adams, Dave J

2018-03-15

Perylene bisimides (PBIs) self-assemble in solution. The solubility of the PBIs is commonly changed through the choice of substituents at the imide positions. It is generally assumed this substitution does not affect the electronic properties of the PBI, and that the properties of the self-assembled aggregate are essentially that of the isolated molecule. However, substituents do affect the self-assembly, resulting in potentially different packing in the formed aggregates. Here, we show that the photoconductivity of films formed from a library of substituted PBIs varies strongly with the substituent and demonstrate that this is due to the different ways in which they pack. Our results open the possibility for tuning the optoelectronic properties of self-assembled PBIs by controlling the aggregate structure through careful choice of substituent, as demonstrated by us here optimising the photoconductivity of PBI films in this way. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Hierarchical silica particles by dynamic multicomponent assembly

DEFF Research Database (Denmark)

Wu, Z. W.; Hu, Q. Y.; Pang, J. B.

2005-01-01

Abstract: Aerosol-assisted assembly of mesoporous silica particles with hierarchically controllable pore structure has been prepared using cetyltrimethylammonium bromide (CTAB) and poly(propylene oxide) (PPO, H[OCH(CH3)CH2],OH) as co-templates. Addition of the hydrophobic PPO significantly...... influences the delicate hydrophilic-hydrophobic balance in the well-studied CTAB-silicate co-assembling system, resulting in various mesostructures (such as hexagonal, lamellar, and hierarchical structure). The co-assembly of CTAB, silicate clusters, and a low-molecular-weight PPO (average M-n 425) results...... in a uniform lamellar structure, while the use of a high-molecular-weight PPO (average M-n 2000), which is more hydrophobic, leads to the formation of hierarchical pore structure that contains meso-meso or meso-macro pore structure. The role of PPO additives on the mesostructure evolution in the CTAB...

Balancing the intermolecular forces in peptide amphiphiles for controlling self-assembly transitions.

Science.gov (United States)

Buettner, C J; Wallace, A J; Ok, S; Manos, A A; Nicholl, M J; Ghosh, A; Tweedle, M F; Goldberger, J E

2017-06-21

While the influence of alkyl chain length and headgroup size on self-assembly behaviour has been well-established for simple surfactants, the rational control over the pH- and concentration-dependent self-assembly behaviour in stimuli responsive peptides remains an elusive goal. Here, we show that different amphiphilic peptides can have similar self-assembly phase diagrams, providing the relative strengths of the attractive and repulsive forces are balanced. Using palmitoyl-YYAAEEEEK(DO3A:Gd)-NH 2 and palmitoyl-YAAEEEEK(DO3A:Gd)-NH 2 as controls, we show that reducing hydrophobic attractive forces through fewer methylene groups in the alkyl chain will lead to a similar self-assembly phase diagram as increasing the electrostatic repulsive forces via the addition of a glutamic acid residue. These changes allow creation of self-assembled MRI vehicles with slightly different micelle and nanofiber diameters but with minimal changes in the spin-lattice T 1 relaxivity. These findings reveal a powerful strategy to design self-assembled vehicles with different sizes but with similar self-assembly profiles.

Hierarchical Control for Multiple DC Microgrids Clusters

DEFF Research Database (Denmark)

Shafiee, Qobad; Dragicevic, Tomislav; Vasquez, Juan Carlos

2014-01-01

This paper presents a distributed hierarchical control framework to ensure reliable operation of dc Microgrid (MG) clusters. In this hierarchy, primary control is used to regulate the common bus voltage inside each MG locally. An adaptive droop method is proposed for this level which determines...

Towards Robust Predictive Fault–Tolerant Control for a Battery Assembly System

Directory of Open Access Journals (Sweden)

Seybold Lothar

2015-12-01

Full Text Available The paper deals with the modeling and fault-tolerant control of a real battery assembly system which is under implementation at the RAFI GmbH company (one of the leading electronic manufacturing service providers in Germany. To model and control the battery assembly system, a unified max-plus algebra and model predictive control framework is introduced. Subsequently, the control strategy is enhanced with fault-tolerance features that increase the overall performance of the production system being considered. In particular, it enables tolerating (up to some degree mobile robot, processing and transportation faults. The paper discusses also robustness issues, which are inevitable in real production systems. As a result, a novel robust predictive fault-tolerant strategy is developed that is applied to the battery assembly system. The last part of the paper shows illustrative examples, which clearly exhibit the performance of the proposed approach.

Cluster Control of Offshore Wind Power Plants Connected to a Common HVDC Station

DEFF Research Database (Denmark)

Göksu, Ömer; Sakamuri, Jayachandra N.; Rapp, C. Andrea

2016-01-01

of offshore AC grid voltage control and onshore ancillary services provision, i.e. POD by the active power modulation of the cluster. The two cases are simulated using DIgSILENT PowerFactory, where the IEC 61400-27-1 wind turbine and WPP control models and a generic offshore layout with cluster of three WPPs......In this paper a coordinated control for cluster of offshore WPPs connected to the same HVDC connection is being implemented and analyzed. The study is targeting two cases as; coordination of reactive power flow between HVDC converter and the WPP cluster while providing offshore AC grid voltage...... control, and coordinated closed loop control between the HVDC and the WPPs while the cluster is providing Power Oscillation Damping ( POD) via active power modulation. It is shown that the coordinated cluster control helps to improve the steady-state and dynamic response of the offshore AC grid in case...

Controlled capillary assembly of magnetic Janus Particles at fluid-fluid interfaces

NARCIS (Netherlands)

Xie, Q.; Davies, G.B.; Harting, J.D.R.

2016-01-01

Capillary interactions can be used to direct assembly of particles adsorbed at fluid-fluid interfaces. Precisely controlling the magnitude and direction of capillary interactions to assemble particles into favoured structures for materials science purposes is desirable but challenging. In this

Quality control of FWC during assembly/commissioning on SST-1

International Nuclear Information System (INIS)

Patel, Hiteshkumar; Santra, Prosenjit; Jaiswal, Snehal

2015-01-01

First Wall components (FWC) of SST-1 tokamak, which are in the immediate vicinity of plasma comprises of limiters, divertors, baffles, passive stabilizers are designed to operate long duration (1000 s) discharges of elongated plasma. All FWC consists of a copper alloy heat sink modules with SS cooling tubes brazed onto it, graphite tiles acting as armour material facing the plasma, and are mounted to the vacuum vessels with suitable Inconel support structures at ring and port locations. The FWC are very recently assembled and commissioned successfully inside the vacuum vessel of SST-1 under going a rigorous quality control and checks at every stage of the assembly process. This paper will present the quality control and checks of FWC from commencement of assembly procedure, namely material test reports, leak testing of high temperature baked components, assembled dimensional tolerances, leak testing of all welded joints, graphite tile tightening torques, electrical continuity of passive stabilizers, and electrical isolation of passive stabilizers from vacuum vessel, baking and cooling hydraulic connections inside vacuum vessel. (author)

Further development of the Dynamic Control Assemblies Worth Measurement Method for Advanced Reactivity Computers

International Nuclear Information System (INIS)

Petenyi, V.; Strmensky, C.; Jagrik, J.; Minarcin, M.; Sarvaic, I.

2005-01-01

The dynamic control assemblies worth measurement technique is a quick method for validation of predicted control assemblies worth. The dynamic control assemblies worth measurement utilize space-time corrections for the measured out of core ionization chamber readings calculated by DYN 3D computer code. The space-time correction arising from the prompt neutron density redistribution in the measured ionization chamber reading can be directly applied in the advanced reactivity computer. The second correction concerning the difference of spatial distribution of delayed neutrons can be calculated by simulation the measurement procedure by dynamic version of the DYN 3D code. In the paper some results of dynamic control assemblies worth measurement applied for NPP Mochovce are presented (Authors)

Doping-Induced Anisotropic Self-Assembly of Silver Icosahedra in [Pt2Ag23Cl7(PPh3)10] Nanoclusters

KAUST Repository

Bootharaju, Megalamane Siddaramappa; Kozlov, Sergey M.; Cao, Zhen; Harb, Moussab; Maity, Niladri; Shkurenko, Aleksander; Parida, Manas R.; Hedhili, Mohamed N.; Eddaoudi, Mohamed; Mohammed, Omar F.; Bakr, Osman; Cavallo, Luigi; Basset, Jean-Marie

2017-01-01

Atomically precise self-assembled architectures of noble metals with unique surface structures are necessary for prospective applications. However, the synthesis of such structures based on silver is challenging because of their instability. In this work, by developing a selective and controlled doping strategy, we synthesized and characterized a rod-shaped, charge-neutral, diplatinum-doped Ag nanocluster (NC) of [Pt2Ag23Cl7(PPh3)10]. Its crystal structure revealed the self-assembly of two Pt-centered Ag icosahedra through vertex sharing. Five bridging and two terminal chlorides and 10 PPh3 ligands were found to stabilize the cluster. Electronic structure simulations corroborated structural and optical characterization of the cluster and provided insights into the effect of the Pt dopants on the optical properties and stability of the cluster. Our study will open new avenues for designing novel self-assembled NCs using different elemental dopants.

Doping-Induced Anisotropic Self-Assembly of Silver Icosahedra in [Pt2Ag23Cl7(PPh3)10] Nanoclusters

KAUST Repository

Bootharaju, Megalamane Siddaramappa

2017-01-09

Atomically precise self-assembled architectures of noble metals with unique surface structures are necessary for prospective applications. However, the synthesis of such structures based on silver is challenging because of their instability. In this work, by developing a selective and controlled doping strategy, we synthesized and characterized a rod-shaped, charge-neutral, diplatinum-doped Ag nanocluster (NC) of [Pt2Ag23Cl7(PPh3)10]. Its crystal structure revealed the self-assembly of two Pt-centered Ag icosahedra through vertex sharing. Five bridging and two terminal chlorides and 10 PPh3 ligands were found to stabilize the cluster. Electronic structure simulations corroborated structural and optical characterization of the cluster and provided insights into the effect of the Pt dopants on the optical properties and stability of the cluster. Our study will open new avenues for designing novel self-assembled NCs using different elemental dopants.

Automatic coolant flow control device for a nuclear reactor assembly

Science.gov (United States)

Hutter, Ernest

1986-01-01

A device which controls coolant flow through a nuclear reactor assembly comprises a baffle means at the exit end of said assembly having a plurality of orifices, and a bimetallic member in operative relation to the baffle means such that at increased temperatures said bimetallic member deforms to unblock some of said orifices and allow increased coolant flow therethrough.

Properties of Molecular organized assemblies at interfaces

Indian Academy of Sciences (India)

Dr.AURNA

Organized molecular assemblies. An organized molecular assembly is a group of atoms or ..... Simulations of the growth of clusters on a .... dynamics and function. ➢Actively ... Study of amphiphilic derivatives of YIGSR, mutated at hyper active ...

Rod cluster control assemblies and rod cluster control guide tubes: wear and drop time

International Nuclear Information System (INIS)

Zbinden, M.

1997-01-01

The wear of RCCAs and of RCC guide tubes is due to two quite different mechanisms and the remedies to apply for each case might lead to contradictory solutions: - the impact/sliding wear for the seldom moving RCCAs, namely the shutdown RCCAs, under flow-induced vibrations, - the axial sliding wear for the control rods subjected to the stepping movements ordered by the acting load. In this case the hydraulic sticking forces are those which produce an evolution of the surface states that may increase the drop time. The introduction, an historical survey of the encountered difficulties, is followed by short description of the components and then the paper presents contributions of EDF in the R and D field, which take place in two successive multi-annual projects. Lastly, some information is given about the recent evolutions and new problems as well for impact/sliding wear as for drop time under normal or seismic conditions. (author)

A missed Fe-S cluster handoff causes a metabolic shakeup.

Science.gov (United States)

Berteau, Olivier

2018-05-25

The general framework of pathways by which iron-sulfur (Fe-S) clusters are assembled in cells is well-known, but the cellular consequences of disruptions to that framework are not fully understood. Crooks et al. report a novel cellular system that creates an acute Fe-S cluster deficiency, using mutants of ISCU, the main scaffold protein for Fe-S cluster assembly. Surprisingly, the resultant metabolic reprogramming leads to the accumulation of lipid droplets, a situation encountered in many poorly understood pathological conditions, highlighting unanticipated links between Fe-S assembly machinery and human disease. © 2018 Berteau.

Generation of clusters in complex dynamical networks via pinning control

International Nuclear Information System (INIS)

Li Kezan; Fu Xinchu; Small, Michael

2008-01-01

Many real-world networks show community structure, i.e., groups (or clusters) of nodes that have a high density of links within them but with a lower density of links between them. In this paper, by applying feedback injections to a fraction of network nodes, various clusters are synchronized independently according to the community structure generated by the group partition of the network (cluster synchronization). This control is achieved by pinning (i.e. applying linear feedback control) to a subset of the network nodes. Those pinned nodes are selected not randomly but according to the topological structure of communities of a given network. Specifically, for a given group partition of a network, those nodes with direct connections between groups must be pinned in order to achieve cluster synchronization. Both the local stability and global stability of cluster synchronization are investigated. Taking the tree-shaped network and the most modular network as two particular examples, we illustrate in detail how the pinning strategy influences the generation of clusters. The simulations verify the efficiency of the pinning schemes used in this paper

A pH-Regulated Quality Control Cycle for Surveillance of Secretory Protein Assembly

Science.gov (United States)

Vavassori, Stefano; Cortini, Margherita; Masui, Shoji; Sannino, Sara; Anelli, Tiziana; Caserta, Imma R.; Fagioli, Claudio; Mossuto, Maria F.; Fornili, Arianna; van Anken, Eelco; Degano, Massimo; Inaba, Kenji; Sitia, Roberto

2013-01-01

Summary To warrant the quality of the secretory proteome, stringent control systems operate at the endoplasmic reticulum (ER)-Golgi interface, preventing the release of nonnative products. Incompletely assembled oligomeric proteins that are deemed correctly folded must rely on additional quality control mechanisms dedicated to proper assembly. Here we unveil how ERp44 cycles between cisGolgi and ER in a pH-regulated manner, patrolling assembly of disulfide-linked oligomers such as IgM and adiponectin. At neutral, ER-equivalent pH, the ERp44 carboxy-terminal tail occludes the substrate-binding site. At the lower pH of the cisGolgi, conformational rearrangements of this peptide, likely involving protonation of ERp44’s active cysteine, simultaneously unmask the substrate binding site and −RDEL motif, allowing capture of orphan secretory protein subunits and ER retrieval via KDEL receptors. The ERp44 assembly control cycle couples secretion fidelity and efficiency downstream of the calnexin/calreticulin and BiP-dependent quality control cycles. PMID:23685074

Stoichiometry-Controlled Inversion of Supramolecular Chirality in Nanostructures Co-assembled with Bipyridines.

Science.gov (United States)

Wang, Fang; Feng, Chuan-Liang

2018-02-01

To control supramolecular chirality of the co-assembled nanostructures, one of the remaining issues is how stoichiometry of the different molecules involved in co-assembly influence chiral transformation. Through co-assembly of achiral 1,4-bis(pyrid-4-yl)benzene and chiral phenylalanine-glycine derivative hydrogelators, stoichiometry is found to be an effective tool for controlling supramolecular chirality inversion processes. This inversion is mainly mediated by a delicate balance between intermolecular hydrogen bonding interactions and π-π stacking of the two components, which may subtly change the stacking of the molecules, in turn, the self-assembled nanostructures. This study exemplifies a simplistic way to invert the handedness of chiral nanostructures and provide fundamental understanding of the inherent principles of supramolecular chirality. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design of an integral missile shield in integrated head assembly for pressurized water reactor at commercial nuclear plants

International Nuclear Information System (INIS)

Baliga, Ravi; Watts, Tom Neal; Kamath, Harish

2015-01-01

In ICONE22, the authors presented the Integrated Head Assembly (IHA) design concept implemented at Callaway Nuclear Power Plant in Missouri, USA. The IHA concept is implemented to reduce the outage duration and the associated radiation exposure to the workers by reducing critical path time during Plant Refueling Outage. One of the head area components in the IHA is a steel missile shield designed to protect the Control Rod Drive Mechanism (CRDM) assembly from damaging other safety-related components in the vicinity in the Containment. Per Federally implemented General Design Criteria for commercial nuclear plants in the USA, the design of Nuclear Steam Supply System (NSSS) must provide protection from the damages caused by a postulated event of CRDM housing units and their associated parts disengaging from the reactor vessel assembly. This event is considered as a Loss of Coolant Accident (LOCA) and assumes that once the CRDM housing unit and their associated parts disengage from the reactor vessel internals assembly, they travel upward by the water jet with the following sequence of events: Per Reference 1, the drive shaft and control rod cluster are forced out of the reactor core by the differential pressure across the drive shaft with the assumption that the drive shaft and control rod cluster, latched together, are fully inserted when the accident occurs. After the travel, the rod cluster control spider will impact the lower side of the upper support plate inside the reactor vessel fracturing the flexure arms in the joint freeing the drive shaft from the control rod cluster. The control rod cluster is stopped by the upper support plate and will remain below the upper support plate during this accident. However, the drive shaft will continue to accelerate in the upward direction until it is stopped by a safety feature in the IHA. The integral missile shield as a safety feature in the IHA is designed to stop the CRDM drive shaft from moving further up in the

DNA-Protected Silver Clusters for Nanophotonics

Directory of Open Access Journals (Sweden)

Elisabeth Gwinn

2015-02-01

Full Text Available DNA-protected silver clusters (AgN-DNA possess unique fluorescence properties that depend on the specific DNA template that stabilizes the cluster. They exhibit peak emission wavelengths that range across the visible and near-IR spectrum. This wide color palette, combined with low toxicity, high fluorescence quantum yields of some clusters, low synthesis costs, small cluster sizes and compatibility with DNA are enabling many applications that employ AgN-DNA. Here we review what is known about the underlying composition and structure of AgN-DNA, and how these relate to the optical properties of these fascinating, hybrid biomolecule-metal cluster nanomaterials. We place AgN-DNA in the general context of ligand-stabilized metal clusters and compare their properties to those of other noble metal clusters stabilized by small molecule ligands. The methods used to isolate pure AgN-DNA for analysis of composition and for studies of solution and single-emitter optical properties are discussed. We give a brief overview of structurally sensitive chiroptical studies, both theoretical and experimental, and review experiments on bringing silver clusters of distinct size and color into nanoscale DNA assemblies. Progress towards using DNA scaffolds to assemble multi-cluster arrays is also reviewed.

Superlattices assembled through shape-induced directional binding

Science.gov (United States)

Lu, Fang; Yager, Kevin G.; Zhang, Yugang; Xin, Huolin; Gang, Oleg

2015-04-01

Organization of spherical particles into lattices is typically driven by packing considerations. Although the addition of directional binding can significantly broaden structural diversity, nanoscale implementation remains challenging. Here we investigate the assembly of clusters and lattices in which anisotropic polyhedral blocks coordinate isotropic spherical nanoparticles via shape-induced directional interactions facilitated by DNA recognition. We show that these polyhedral blocks--cubes and octahedrons--when mixed with spheres, promote the assembly of clusters with architecture determined by polyhedron symmetry. Moreover, three-dimensional binary superlattices are formed when DNA shells accommodate the shape disparity between nanoparticle interfaces. The crystallographic symmetry of assembled lattices is determined by the spatial symmetry of the block's facets, while structural order depends on DNA-tuned interactions and particle size ratio. The presented lattice assembly strategy, exploiting shape for defining the global structure and DNA-mediation locally, opens novel possibilities for by-design fabrication of binary lattices.

High-throughput shadow mask printing of passive electrical components on paper by supersonic cluster beam deposition

Energy Technology Data Exchange (ETDEWEB)

Caruso, Francesco; Bellacicca, Andrea; Milani, Paolo, E-mail: pmilani@mi.infn.it [CIMaINa and Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)

2016-04-18

We report the rapid prototyping of passive electrical components (resistors and capacitors) on plain paper by an additive and parallel technology consisting of supersonic cluster beam deposition (SCBD) coupled with shadow mask printing. Cluster-assembled films have a growth mechanism substantially different from that of atom-assembled ones providing the possibility of a fine tuning of their electrical conduction properties around the percolative conduction threshold. Exploiting the precise control on cluster beam intensity and shape typical of SCBD, we produced, in a one-step process, batches of resistors with resistance values spanning a range of two orders of magnitude. Parallel plate capacitors with paper as the dielectric medium were also produced with capacitance in the range of tens of picofarads. Compared to standard deposition technologies, SCBD allows for a very efficient use of raw materials and the rapid production of components with different shape and dimensions while controlling independently the electrical characteristics. Discrete electrical components produced by SCBD are very robust against deformation and bending, and they can be easily assembled to build circuits with desired characteristics. The availability of large batches of these components enables the rapid and cheap prototyping and integration of electrical components on paper as building blocks of more complex systems.

Boundaries Control Collective Dynamics of Inertial Self-Propelled Robots

Science.gov (United States)

Deblais, A.; Barois, T.; Guerin, T.; Delville, P. H.; Vaudaine, R.; Lintuvuori, J. S.; Boudet, J. F.; Baret, J. C.; Kellay, H.

2018-05-01

Simple ingredients, such as well-defined interactions and couplings for the velocity and orientation of self-propelled objects, are sufficient to produce complex collective behavior in assemblies of such entities. Here, we use assemblies of rodlike robots made motile through self-vibration. When confined in circular arenas, dilute assemblies of these rods act as a gas. Increasing the surface fraction leads to a collective behavior near the boundaries: polar clusters emerge while, in the bulk, gaslike behavior is retained. The coexistence between a gas and surface clusters is a direct consequence of inertial effects as shown by our simulations. A theoretical model, based on surface mediated transport accounts for this coexistence and illustrates the exact role of the boundaries. Our study paves the way towards the control of collective behavior: By using deformable but free to move arenas, we demonstrate that the surface induced clusters can lead to directed motion, while the topology of the surface states can be controlled by biasing the motility of the particles.

Nuclear reactor fuel assembly

International Nuclear Information System (INIS)

1975-01-01

A description is given of a nuclear reactor fuel assembly comprising a cluster of fuel elements supported by transversal grids so that their axes are parallel to and at a distance from each other, in order to establish interstices for the axial flow of a coolant. At least one of the interstices is occupied by an axial duct reserved for an auxiliary cooling fluid and is fitted with side holes through which the auxiliary cooling fluid is sprayed into the cluster. Deflectors extend as from a transversal grid in a position opposite the holes to deflect the cooling fluid jet towards those parts of the fuel elements that are not accessible to the auxiliary coolant. This assembly is intended for reactors cooled by light or heavy water [fr

Self-Assembled Colloidal Particle Clusters from In Situ Pickering-Like Emulsion Polymerization via Single Electron Transfer Mechanism.

Science.gov (United States)

Yuan, Jinfeng; Zhao, Weiting; Pan, Mingwang; Zhu, Lei

2016-08-01

A simple route is reported to synthesize colloidal particle clusters (CPCs) from self-assembly of in situ poly(vinylidene fluoride)/poly(styrene-co-tert-butyl acrylate) [PVDF/P(St-co-tBA)] Janus particles through one-pot seeded emulsion single electron transfer radical polymerization. In the in situ Pickering-like emulsion polymerization, the tBA/St/PVDF feed ratio and polymerization temperature are important for the formation of well-defined CPCs. When the tBA/St/PVDF feed ratio is 0.75 g/2.5 g/0.5 g and the reaction temperature is 35 °C, relatively uniform raspberry-like CPCs are obtained. The hydrophobicity of the P(St-co-tBA) domains and the affinity of PVDF to the aqueous environment are considered to be the driving force for the self-assembly of the in situ formed PVDF/P(St-co-tBA) Janus particles. The resultant raspberry-like CPCs with PVDF particles protruding outward may be promising for superhydrophobic smart coatings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PLC based control system for RAM assembly test facility

International Nuclear Information System (INIS)

Kulkarni, S.S.; Kumar, Vinaya; Chandra, Umesh

1994-01-01

The flexibility, expandability, ease of programming and diagnostic features makes the programmable logic controller (PLC) suitable for a variety of control applications in engineering system test facilities. A PLC based control system for RAM assembly test facility (RATF) and for testing the related hydraulic components is being developed and installed at BARC. This paper describes the approach taken for meeting the control requirements and illustrates the PLC software that has been developed. (author). 1 fig

Molecular Clusters: Nanoscale Building Blocks for Solid-State Materials.

Science.gov (United States)

Pinkard, Andrew; Champsaur, Anouck M; Roy, Xavier

2018-04-17

The programmed assembly of nanoscale building blocks into multicomponent hierarchical structures is a powerful strategy for the bottom-up construction of functional materials. To develop this concept, our team has explored the use of molecular clusters as superatomic building blocks to fabricate new classes of materials. The library of molecular clusters is rich with exciting properties, including diverse functionalization, redox activity, and magnetic ordering, so the resulting cluster-assembled solids, which we term superatomic crystals (SACs), hold the promise of high tunability, atomic precision, and robust architectures among a diverse range of other material properties. Molecular clusters have only seldom been used as precursors for functional materials. Our team has been at the forefront of new developments in this exciting research area, and this Account focuses on our progress toward designing materials from cluster-based precursors. In particular, this Account discusses (1) the design and synthesis of molecular cluster superatomic building blocks, (2) their self-assembly into SACs, and (3) their resulting collective properties. The set of molecular clusters discussed herein is diverse, with different cluster cores and ligand arrangements to create an impressive array of solids. The cluster cores include octahedral M 6 E 8 and cubane M 4 E 4 (M = metal; E = chalcogen), which are typically passivated by a shell of supporting ligands, a feature upon which we have expanded upon by designing and synthesizing more exotic ligands that can be used to direct solid-state assembly. Building from this library, we have designed whole families of binary SACs where the building blocks are held together through electrostatic, covalent, or van der Waals interactions. Using single-crystal X-ray diffraction (SCXRD) to determine the atomic structure, a remarkable range of compositional variability is accessible. We can also use this technique, in tandem with vibrational

The role of cladding material for performance of LWR control assemblies

International Nuclear Information System (INIS)

Dewes, P.; Roppelt, A.

2000-01-01

The lifetime of control assemblies in LWRs can be limited presently by mechanical failure of the absorber cladding. The major cause of failure is mechanical interaction of the absorber with the cladding due to irradiation induced dimensional changes such as absorber swelling and cladding creep, resulting in cracking of the clad. Such failures occurred in both BWRs and PWRs. Experience and in-reactor tests revealed that cracking can be avoided principally by two ways: First, if strain rates and hence, stresses in the cladding are kept low (well below the yield strength), significant strains can be tolerated. This is the case for the cladding of PWR control assemblies with slowly swelling Ag-In-Cd absorber. Recent examinations of highly exposed PWR control assemblies confirmed the design correlation up to the presently used strain limit. Second, in such cases where strongly swelling absorber material like boron carbide is still preferred, materials which are resistant against irradiation assisted stress corrosion cracking (IASCC) can be used. The influence of material composition and condition on IASCC was studied in-reactor using tubular samples of various stainless steels and Ni-base alloys stressed by swelling mandrels. In several programme steps high purity materials with special features had been identified as resistant to IASCC. Another process of cladding damage which may occur in PWRs is wear caused by friction of the control rods in the surrounding guide structure. For replacement control assemblies this problem is solved by coating of the cladding. There exists meanwhile excellent experience of up to 18 operation cycles with coated claddings. (author)

Missing Links in Antibody Assembly Control

Directory of Open Access Journals (Sweden)

Tiziana Anelli

2013-01-01

Full Text Available Fidelity of the humoral immune response requires that quiescent B lymphocytes display membrane bound immunoglobulin M (IgM on B lymphocytes surface as part of the B cell receptor, whose function is to recognize an antigen. At the same time B lymphocytes should not secrete IgM until recognition of the antigen has occurred. The heavy chains of the secretory IgM have a C-terminal tail with a cysteine instead of a membrane anchor, which serves to covalently link the IgM subunits by disulfide bonds to form “pentamers” or “hexamers.” By virtue of the same cysteine, unassembled secretory IgM subunits are recognized and retained (via mixed disulfide bonds by members of the protein disulfide isomerase family, in particular ERp44. This so-called “thiol-mediated retention” bars assembly intermediates from prematurely leaving the cell and thereby exerts quality control on the humoral immune response. In this essay we discuss recent findings on how ERp44 governs such assembly control in a pH-dependent manner, shuttling between the cisGolgi and endoplasmic reticulum, and finally on how pERp1/MZB1, possibly as a co-chaperone of GRP94, may help to overrule the thiol-mediated retention in the activated B cell to give way to antibody secretion.

Supervisory Control Technique For An Assembly Workstation As A Dynamic Discrete Event System

Directory of Open Access Journals (Sweden)

Daniela Cristina CERNEGA

2001-12-01

Full Text Available This paper proposes a control problem statement in the framework of supervisory control technique for the assembly workstations. A desired behaviour of an assembly workstation is analysed. The behaviour of such a workstation is cyclic and some linguistic properties are established. In this paper, it is proposed an algorithm for the computation of the supremal controllable language of the closed system desired language. Copyright © 2001 IFAC.

Consensus of satellite cluster flight using an energy-matching optimal control method

Science.gov (United States)

Luo, Jianjun; Zhou, Liang; Zhang, Bo

2017-11-01

This paper presents an optimal control method for consensus of satellite cluster flight under a kind of energy matching condition. Firstly, the relation between energy matching and satellite periodically bounded relative motion is analyzed, and the satellite energy matching principle is applied to configure the initial conditions. Then, period-delayed errors are adopted as state variables to establish the period-delayed errors dynamics models of a single satellite and the cluster. Next a novel satellite cluster feedback control protocol with coupling gain is designed, so that the satellite cluster periodically bounded relative motion consensus problem (period-delayed errors state consensus problem) is transformed to the stability of a set of matrices with the same low dimension. Based on the consensus region theory in the research of multi-agent system consensus issues, the coupling gain can be obtained to satisfy the requirement of consensus region and decouple the satellite cluster information topology and the feedback control gain matrix, which can be determined by Linear quadratic regulator (LQR) optimal method. This method can realize the consensus of satellite cluster period-delayed errors, leading to the consistency of semi-major axes (SMA) and the energy-matching of satellite cluster. Then satellites can emerge the global coordinative cluster behavior. Finally the feasibility and effectiveness of the present energy-matching optimal consensus for satellite cluster flight is verified through numerical simulations.

Controlled clustering of carboxylated SPIONs through polyethylenimine

Energy Technology Data Exchange (ETDEWEB)

Nesztor, Dániel; Bali, Krisztina; Tóth, Ildikó Y.; Szekeres, Márta; Tombácz, Etelka, E-mail: tombacz@chem.u-szeged.hu

2015-04-15

Clusters of magnetite nanoparticles (MNPs) were synthesized using poly(acrylic acid-co-maleic acid) coated MNPs (PAM@MNP) and branched polyethylenimine (PEI). Materials were characterized by potentiometric titration, zeta potential and dynamic light scattering (DLS) measurements. PEI and PAM@MNP are oppositely charged as characterized by zeta potential measurements (+8, −34 mV respectively) and titration (10.30 mmol −NH{sub 3}{sup +}/g PEI; 0.175 mmol −COO{sup −}/g PAM@MNP) at pH 6.5±0.2; therefore magnetic clusters are formed by electrostatic adhesion. Two different preparation methods and the effect of PEI and electrolyte (NaCl) concentration on the cluster formation was studied. Choosing an optimal concentration of PEI (charge ratio of PEI to PAM@MNP: 0.17) and electrolyte (10 mM), a concentrated (10 g MNP/L) product containing PEI–PAM@MNP nanoclusters with size of 165±10 nm was prepared. Its specific absorption rate (SAR) measured in AC magnetic field (110 kHz, 25 mT) is 12 W/g Fe. The clustered product is expected to have enhanced contrast efficiency in MRI. - Highlights: • SPION clusters of controlled size were prepared by means of electrostatic adhesion. • Nanocluster formation optimum was at 0.17 charge ratio of PEI to PAM@MNP. • Huge aggregates form at higher PEI to PAM@MNP charge ratio. • Higher ionic strength promotes the formation of clusters at lower PEI concentrations.

Real-time analysis of self-assembled nucleobases by Venturi easy ambient sonic-spray ionization mass spectrometry.

Science.gov (United States)

Na, Na; Shi, Ruixia; Long, Zi; Lu, Xin; Jiang, Fubin; Ouyang, Jin

2014-10-01

In this study, the real-time analysis of self-assembled nucleobases was employed by Venturi easy ambient sonic-spray ionization mass spectrometry (V-EASI-MS). With the analysis of three nucleobases including 6-methyluracil (6MU), uracil (U) and thymine (T) as examples, different orders of clusters centered with different metal ions were recorded in both positive and negative modes. Compared with the results obtained by traditional electrospray ionization mass spectrometry (ESI-MS) under the same condition, more clusters with high orders, such as [6MU7+Na](+), [6MU15+2NH4](2+), [6MU10+Na](+), [T7+Na](+), and [T15+2NH4](2+) were detected by V-EASI-MS, which demonstrated the soft ionization ability of V-EASI for studying the non-covalent interaction in a self-assembly process. Furthermore, with the injection of K(+) to the system by a syringe pumping, the real-time monitoring of the formation of nucleobases clusters was achieved by the direct extraction of samples from the system under the Venturi effect. Therefore, the effect of cations on the formation of clusters during self-assembly of nucleobases was demonstrated, which was in accordance with the reports. Free of high voltage, heating or radiation during the ionization, this technique is much soft and suitable for obtaining the real-time information of the self-assembly system, which also makes it quite convenient for extraction samples from the reaction system. This "easy and soft" ionization technique has provided a potential pathway for monitoring and controlling the self-assembly processes. Copyright © 2014 Elsevier B.V. All rights reserved.

Power peak in vicinity of WWER-440 control assembly

International Nuclear Information System (INIS)

Mikus, J.

2002-01-01

This paper presents information concerning the WWER-440 local power peaking problem induced by a control assembly and corresponding investigation possibilities on the light-water zero-power reactor LR-O at the Nuclear Research Institute Rez plc. Brief description of the disposable CA model, experimental arrangement and conditions on the LR-O reactor, preparation of the relevant measurements in the WWER-440 type cores with CA model, as well as some preliminary results of the fission density distribution obtained in a core without boron and with fuel assemblies having profiled enrichment are mentioned too (Author)

Exponential cluster synchronization in directed community networks via adaptive nonperiodically intermittent pinning control

Science.gov (United States)

Zhou, Peipei; Cai, Shuiming; Jiang, Shengqin; Liu, Zengrong

2018-02-01

In this paper, the problem of exponential cluster synchronization for a class of directed community networks is investigated via adaptive nonperiodically intermittent pinning control. By constructing a novel piecewise continuous Lyapunov function, some sufficient conditions to guarantee globally exponential cluster synchronization are derived. It is noted that the derived cluster synchronization criteria rely on the control rates, but not the control widths or the control periods, which facilitates the choice of the control periods in practical applications. A numerical example is finally presented to show the effectiveness of the obtained theoretical results.

Collagen attachment to the substrate controls cell clustering through migration

International Nuclear Information System (INIS)

Hou, Yue; Rodriguez, Laura Lara; Wang, Juan; Schneider, Ian C

2014-01-01

Cell clustering and scattering play important roles in cancer progression and tissue engineering. While the extracellular matrix (ECM) is known to control cell clustering, much of the quantitative work has focused on the analysis of clustering between cells with strong cell–cell junctions. Much less is known about how the ECM regulates cells with weak cell–cell contact. Clustering characteristics were quantified in rat adenocarcinoma cells, which form clusters on physically adsorbed collagen substrates, but not on covalently attached collagen substrates. Covalently attaching collagen inhibited desorption of collagen from the surface. While changes in proliferation rate could not explain differences seen in the clustering, changes in cell motility could. Cells plated under conditions that resulted in more clustering had a lower persistence time and slower migration rate than those under conditions that resulted in less clustering. Understanding how the ECM regulates clustering will not only impact the fundamental understanding of cancer progression, but also will guide the design of tissue engineered constructs that allow for the clustering or dissemination of cells throughout the construct. (paper)

Force-controlled robotic assembly processes of rigid and flexible objects methodologies and applications

CERN Document Server

Ghalyan, Ibrahim Fahad Jasim

2016-01-01

This book provides comprehensive and integrated approaches for rigid and flexible object assembly. It presents comparison studies with the available force-guided robotic processes and covers contact-state modeling, scheme control strategies, and position searching algorithms. Further, it includes experimental validations for different assembly situations, including those for the assembly of industrial parts taken from the automotive industry. .

Control of entanglement transitions in quantum spin clusters

Science.gov (United States)

Irons, Hannah R.; Quintanilla, Jorge; Perring, Toby G.; Amico, Luigi; Aeppli, Gabriel

2017-12-01

Quantum spin clusters provide a platform for the experimental study of many-body entanglement. Here we address a simple model of a single-molecule nanomagnet featuring N interacting spins in a transverse field. The field can control an entanglement transition (ET). We calculate the magnetization, low-energy gap, and neutron-scattering cross section and find that the ET has distinct signatures, detectable at temperatures as high as 5% of the interaction strength. The signatures are stronger for smaller clusters.

Two applications of airtightness control techniques on big assemblies

CERN Document Server

Devallan, C; Marcellin, J

1973-01-01

Deals with two airtightness control techniques respectively applied on intersecting storage rings (ISR) at CERN in Geneva and on a liquid methane storage tank. These two big assemblies called for two different control techniques which use helium and ammonia respectively as tracer gas. Existing practical leakage detection techniques to meet industrial needs are discussed at the end of the article. (2 refs).

Achieving 3-D Nanoparticle Assembly in Nanocomposite Thin Films via Kinetic Control

Energy Technology Data Exchange (ETDEWEB)

Huang, Jingyu; Xiao, Yihan; Xu, Ting [UCB

2017-02-20

Nanocomposite thin films containing well-ordered nanoparticle (NP) assemblies are ideal candidates for the fabrication of metamaterials. Achieving 3-D assembly of NPs in nanocomposite thin films is thermodynamically challenging as the particle size gets similar to that of a single polymer chain. The entropic penalties of polymeric matrix upon NP incorporation leads to NP aggregation on the film surface or within the defects in the film. Controlling the kinetic pathways of assembly process provides an alternative path forward by arresting the system in nonequilibrium states. Here, we report the thin film 3-D hierarchical assembly of 20 nm NPs in supramolecules with a 30 nm periodicity. By mediating the NP diffusion kinetics in the supramolecular matrix, surface aggregation of NPs was suppressed and NPs coassemble with supramolecules to form new 3-D morphologies in thin films. The present studies opened a viable route to achieve designer functional composite thin films via kinetic control.

Search for a transport method for the calculation of the PWR control and safety clusters

International Nuclear Information System (INIS)

Bruna, G.B.; Van Frank, C.; Vergain, M.L.; Chauvin, J.P.; Palmiotti, G.; Nobile, M.

1990-01-01

The project studies of power reactors rely mainly on diffusion calculations, but transport ones are often needed for assessing fine effects, intimately linked to geometry and spectrum heterogeneities. Accurate transport computations are necessary, in particular, for shielded cross section generation, and when homogenization and dishomogenization processes are involved. The transport codes, generally, offer the user a variety of computational options, related to different approximation levels. In every case, it is obviously desirable to be able to choose the reliable degree of approximation to be accepted in any particular computational circumstance of the project. The search for such adapted procedures is to be made on the basis of critical experiments. In our studies, this task was made possible by the availability of suitable results of the CAMELEON critical experiment, carried on in the EOLE facility at CEA's Center of Cadarache. In this paper, we summarize some of the work in progress at FRAMATOME on the definition of an assembly based transport calculation scheme to be used for PWR control and safety cluster computations. Two main items, devoted to the search of the optimum computational procedures, are presented here: - a parametrical study on computational options, made in an infinite medium assembly geometry, - a series of comparisons between calculated and experimental values of pin power distribution

Thermal hydraulic performance of naturally aspirated control rod housing assemblies

International Nuclear Information System (INIS)

Geiger, G.T.; Randolph, H.W.; Paik, I.K.; Foti, D.J.

1992-01-01

Savannah River Site reactors are comprised of heat generating fuel/target assemblies, control rods which regulate reactor power, and heavy water which acts as the coolant and as a moderator. The fuel/target assemblies are cooled by the downflow of heavy water while the control rods are cooled via upflow. Five control rods are grouped with two safety rods in seven-channel assemblies called septifoils. Under normal operating conditions, the reactor power level, radial shape flux and axial power flux are regulated by the positioning of the control rods. The control rods are solid rods of a lithium-aluminum alloy with an thin aluminum outer sheath. Lithium is a good absorber of neutrons and, thus control rod temperatures rise with reactor power. At conditions of sufficiently high reactor power and degraded coolant flow, the control rods could heat sufficiently to cause a metallurigical failure of the sheath leading to molten material coming in contact with water and the possibility of a steam explosion. An accident has been postulated as part of the analysis involving the safety upgrade of Savannah River Site reactors in which the housing is not seated on the pin. Coolant from the upflow pin would not be directed into the housing but, into the moderator space surrounding the housing. Only naturally aspirated cooling due to buoyancy effects would be available to cool the control rods and the coolant mass flow rate would drop significantly from its nominal value. In this study, the mechanisms and limits of cooling heated rods housed in an unseated septifoil are addressed. Experiments were conducted on a shortened, prototypic housing with electrically heated rods to gain an understanding of the phenomena governing the cooling in such a case and develop data which can be used to evaluate predictive models. These experiments are described, their results discussed, and the predictions of current models is presented

Reconstitutable control assembly having removable control rods with detachable split upper end plugs

International Nuclear Information System (INIS)

Gjertsen, R.K.; Knott, R.P.; Sparrow, J.A.

1991-01-01

This patent describes, for use in facilitating replacement of a neutron absorber control rod on a control assembly spider structure, an end plug. It comprises a pair of separate upper and lower plug portions; the upper section of the upper plug portion being configured for rigid attachment; the middle section of the upper plug portion having angularly displaced flat surfaces formed on the exterior

Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery: THE SUB-COMPLEX FORMED BY THE IRON DONOR, Yfh1 PROTEIN, AND THE SCAFFOLD, Isu1 PROTEIN.

Science.gov (United States)

Ranatunga, Wasantha; Gakh, Oleksandr; Galeano, Belinda K; Smith, Douglas Y; Söderberg, Christopher A G; Al-Karadaghi, Salam; Thompson, James R; Isaya, Grazia

2016-05-06

The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24 Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

WWER-440 control assembly local power peaking investigation on LR-0 reactor

International Nuclear Information System (INIS)

Mikus, J.

2002-01-01

This paper presents information concerning the local power peaking problem induced by the WWER-440 control assembly and the investigation possibilities on the light water, zero power reactor LR-0 at the Nuclear Research Institute (NRI) Rez plc. A brief description is given about the disposable control assembly model, experimental arrangement and conditions on the LR-0 reactor with regard to the earlier performed investigations as well as to the relevant measurements to be realized in the near future.(abstract)

Orientation-controlled parallel assembly at the air–water interface

International Nuclear Information System (INIS)

Park, Kwang Soon; Hoo, Ji Hao; Baskaran, Rajashree; Böhringer, Karl F

2012-01-01

This paper presents an experimental and theoretical study with statistical analysis of a high-yield, orientation-specific fluidic self-assembly process on a preprogrammed template. We demonstrate self-assembly of thin (less than few hundred microns in thickness) parts, which is vital for many applications in miniaturized platforms but problematic for today's pick-and-place robots. The assembly proceeds row-by-row as the substrate is pulled up through an air–water interface. Experiments and analysis are presented with an emphasis on the combined effect of controlled surface waves and magnetic force. For various gap values between a magnet and Ni-patterned parts, magnetic force distributions are generated using Monte Carlo simulation and employed to predict assembly yield. An analysis of these distributions shows that a gradual decline in yield following the probability density function can be expected with degrading conditions. The experimentally determined critical magnetic force is in good agreement with a derived value from a model of competing forces acting on a part. A general set of design guidelines is also presented from the developed model and experimental data. (paper)

Synthesis and Molecular Structure of a Novel Compound Containing a Carbonate-Bridged Hexacalcium Cluster Cation Assembled on a Trimeric Trititanium(IV)-Substituted Wells-Dawson Polyoxometalate.

Science.gov (United States)

Hoshino, Takahiro; Isobe, Rina; Kaneko, Takuya; Matsuki, Yusuke; Nomiya, Kenji

2017-08-21

A novel compound containing a hexacalcium cluster cation, one carbonate anion, and one calcium cation assembled on a trimeric trititanium(IV)-substituted Wells-Dawson polyoxometalate (POM), [{Ca 6 (CO 3 )(μ 3 -OH)(OH 2 ) 18 }(P 2 W 15 Ti 3 O 61 ) 3 Ca(OH 2 ) 3 ] 19- (Ca 7 Ti 9 Trimer), was obtained as the Na 7 Ca 6 salt (NaCa-Ca 7 Ti 9 Trimer) by the reaction of calcium chloride with the monomeric trititanium(IV)-substituted Wells-Dawson POM species "[P 2 W 15 Ti 3 O 59 (OH) 3 ] 9- " (Ti 3 Monomer). Ti 3 Monomer was generated in situ under basic conditions from the separately prepared tetrameric species with bridging Ti(OH 2 ) 3 groups and an encapsulated Cl - ion, [{P 2 W 15 Ti 3 O 59 (OH) 3 } 4 {μ 3 -Ti(H 2 O) 3 } 4 Cl] 21- (Ti 16 Tetramer). The Na 7 Ca 6 salt of Ca 7 Ti 9 Trimer was characterized by complete elemental analysis, thermogravimetric (TG) and differential thermal analyses (DTA), FTIR, single-crystal X-ray structure analysis, and solution 183 W and 31 P NMR spectroscopy. X-ray crystallography revealed that the [Ca 6 (CO 3 )(μ 3 -OH)(OH 2 ) 18 ] 9+ cluster cation was composed of six calcium cations linked by one μ 6 -carbonato anion and one μ 3 -OH - anion. The cluster cation was assembled, together with one calcium ion, on a trimeric species composed of three tri-Ti(IV)-substituted Wells-Dawson subunits linked by Ti-O-Ti bonds. Ca 7 Ti 9 Trimer is an unprecedented POM species containing an alkaline-earth-metal cluster cation and is the first example of alkaline-earth-metal ions clustered around a titanium(IV)-substituted POM.

The OGCleaner: filtering false-positive homology clusters.

Science.gov (United States)

Fujimoto, M Stanley; Suvorov, Anton; Jensen, Nicholas O; Clement, Mark J; Snell, Quinn; Bybee, Seth M

2017-01-01

Detecting homologous sequences in organisms is an essential step in protein structure and function prediction, gene annotation and phylogenetic tree construction. Heuristic methods are often employed for quality control of putative homology clusters. These heuristics, however, usually only apply to pairwise sequence comparison and do not examine clusters as a whole. We present the Orthology Group Cleaner (the OGCleaner), a tool designed for filtering putative orthology groups as homology or non-homology clusters by considering all sequences in a cluster. The OGCleaner relies on high-quality orthologous groups identified in OrthoDB to train machine learning algorithms that are able to distinguish between true-positive and false-positive homology groups. This package aims to improve the quality of phylogenetic tree construction especially in instances of lower-quality transcriptome assemblies. https://github.com/byucsl/ogcleaner CONTACT: sfujimoto@gmail.comSupplementary information: Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Case-control geographic clustering for residential histories accounting for risk factors and covariates

Science.gov (United States)

2006-01-01

Background Methods for analyzing space-time variation in risk in case-control studies typically ignore residential mobility. We develop an approach for analyzing case-control data for mobile individuals and apply it to study bladder cancer in 11 counties in southeastern Michigan. At this time data collection is incomplete and no inferences should be drawn – we analyze these data to demonstrate the novel methods. Global, local and focused clustering of residential histories for 219 cases and 437 controls is quantified using time-dependent nearest neighbor relationships. Business address histories for 268 industries that release known or suspected bladder cancer carcinogens are analyzed. A logistic model accounting for smoking, gender, age, race and education specifies the probability of being a case, and is incorporated into the cluster randomization procedures. Sensitivity of clustering to definition of the proximity metric is assessed for 1 to 75 k nearest neighbors. Results Global clustering is partly explained by the covariates but remains statistically significant at 12 of the 14 levels of k considered. After accounting for the covariates 26 Local clusters are found in Lapeer, Ingham, Oakland and Jackson counties, with the clusters in Ingham and Oakland counties appearing in 1950 and persisting to the present. Statistically significant focused clusters are found about the business address histories of 22 industries located in Oakland (19 clusters), Ingham (2) and Jackson (1) counties. Clusters in central and southeastern Oakland County appear in the 1930's and persist to the present day. Conclusion These methods provide a systematic approach for evaluating a series of increasingly realistic alternative hypotheses regarding the sources of excess risk. So long as selection of cases and controls is population-based and not geographically biased, these tools can provide insights into geographic risk factors that were not specifically assessed in the case-control

Case-control geographic clustering for residential histories accounting for risk factors and covariates

Directory of Open Access Journals (Sweden)

Goovaerts Pierre

2006-08-01

Full Text Available Abstract Background Methods for analyzing space-time variation in risk in case-control studies typically ignore residential mobility. We develop an approach for analyzing case-control data for mobile individuals and apply it to study bladder cancer in 11 counties in southeastern Michigan. At this time data collection is incomplete and no inferences should be drawn – we analyze these data to demonstrate the novel methods. Global, local and focused clustering of residential histories for 219 cases and 437 controls is quantified using time-dependent nearest neighbor relationships. Business address histories for 268 industries that release known or suspected bladder cancer carcinogens are analyzed. A logistic model accounting for smoking, gender, age, race and education specifies the probability of being a case, and is incorporated into the cluster randomization procedures. Sensitivity of clustering to definition of the proximity metric is assessed for 1 to 75 k nearest neighbors. Results Global clustering is partly explained by the covariates but remains statistically significant at 12 of the 14 levels of k considered. After accounting for the covariates 26 Local clusters are found in Lapeer, Ingham, Oakland and Jackson counties, with the clusters in Ingham and Oakland counties appearing in 1950 and persisting to the present. Statistically significant focused clusters are found about the business address histories of 22 industries located in Oakland (19 clusters, Ingham (2 and Jackson (1 counties. Clusters in central and southeastern Oakland County appear in the 1930's and persist to the present day. Conclusion These methods provide a systematic approach for evaluating a series of increasingly realistic alternative hypotheses regarding the sources of excess risk. So long as selection of cases and controls is population-based and not geographically biased, these tools can provide insights into geographic risk factors that were not specifically

Controlling the amplification of chirality in hydrogen-bonded assemblies

NARCIS (Netherlands)

Mateos timoneda, Miguel; Crego Calama, Mercedes; Reinhoudt, David

2005-01-01

The amplification of chirality (a high enantiomeric or diastereomeric excess induced by a small initial amount of chiral bias) on hydrogen-bonded assemblies has been studied using “sergeants-and-soldiers” experiments under thermodynamically controlled conditions. Here it is shown that different

The Molecular Bases of the Dual Regulation of Bacterial Iron Sulfur Cluster Biogenesis by CyaY and IscX

Directory of Open Access Journals (Sweden)

Salvatore Adinolfi

2018-02-01

Full Text Available IscX (or YfhJ is a protein of unknown function which takes part in the iron-sulfur cluster assembly machinery, a highly specialized and essential metabolic pathway. IscX binds to iron with low affinity and interacts with IscS, the desulfurase central to cluster assembly. Previous studies have suggested a competition between IscX and CyaY, the bacterial ortholog of frataxin, for the same binding surface of IscS. This competition could suggest a link between the two proteins with a functional significance. Using a hybrid approach based on nuclear magnetic resonance, small angle scattering and biochemical methods, we show here that IscX is a modulator of the inhibitory properties of CyaY: by competing for the same site on IscS, the presence of IscX rescues the rates of enzymatic cluster formation which are inhibited by CyaY. The effect is stronger at low iron concentrations, whereas it becomes negligible at high iron concentrations. These results strongly suggest the mechanism of the dual regulation of iron sulfur cluster assembly under the control of iron as the effector.

Origin and distribution of epipolythiodioxopiperazine (ETP gene clusters in filamentous ascomycetes

Directory of Open Access Journals (Sweden)

Gardiner Donald M

2007-09-01

Full Text Available Abstract Background Genes responsible for biosynthesis of fungal secondary metabolites are usually tightly clustered in the genome and co-regulated with metabolite production. Epipolythiodioxopiperazines (ETPs are a class of secondary metabolite toxins produced by disparate ascomycete fungi and implicated in several animal and plant diseases. Gene clusters responsible for their production have previously been defined in only two fungi. Fungal genome sequence data have been surveyed for the presence of putative ETP clusters and cluster data have been generated from several fungal taxa where genome sequences are not available. Phylogenetic analysis of cluster genes has been used to investigate the assembly and heredity of these gene clusters. Results Putative ETP gene clusters are present in 14 ascomycete taxa, but absent in numerous other ascomycetes examined. These clusters are discontinuously distributed in ascomycete lineages. Gene content is not absolutely fixed, however, common genes are identified and phylogenies of six of these are separately inferred. In each phylogeny almost all cluster genes form monophyletic clades with non-cluster fungal paralogues being the nearest outgroups. This relatedness of cluster genes suggests that a progenitor ETP gene cluster assembled within an ancestral taxon. Within each of the cluster clades, the cluster genes group together in consistent subclades, however, these relationships do not always reflect the phylogeny of ascomycetes. Micro-synteny of several of the genes within the clusters provides further support for these subclades. Conclusion ETP gene clusters appear to have a single origin and have been inherited relatively intact rather than assembling independently in the different ascomycete lineages. This progenitor cluster has given rise to a small number of distinct phylogenetic classes of clusters that are represented in a discontinuous pattern throughout ascomycetes. The disjunct heredity of

Light-activated control of protein channel assembly mediated by membrane mechanics

Science.gov (United States)

Miller, David M.; Findlay, Heather E.; Ces, Oscar; Templer, Richard H.; Booth, Paula J.

2016-12-01

Photochemical processes provide versatile triggers of chemical reactions. Here, we use a photoactivated lipid switch to modulate the folding and assembly of a protein channel within a model biological membrane. In contrast to the information rich field of water-soluble protein folding, there is only a limited understanding of the assembly of proteins that are integral to biological membranes. It is however possible to exploit the foreboding hydrophobic lipid environment and control membrane protein folding via lipid bilayer mechanics. Mechanical properties such as lipid chain lateral pressure influence the insertion and folding of proteins in membranes, with different stages of folding having contrasting sensitivities to the bilayer properties. Studies to date have relied on altering bilayer properties through lipid compositional changes made at equilibrium, and thus can only be made before or after folding. We show that light-activation of photoisomerisable di-(5-[[4-(4-butylphenyl)azo]phenoxy]pentyl)phosphate (4-Azo-5P) lipids influences the folding and assembly of the pentameric bacterial mechanosensitive channel MscL. The use of a photochemical reaction enables the bilayer properties to be altered during folding, which is unprecedented. This mechanical manipulation during folding, allows for optimisation of different stages of the component insertion, folding and assembly steps within the same lipid system. The photochemical approach offers the potential to control channel assembly when generating synthetic devices that exploit the mechanosensitive protein as a nanovalve.

A microgrid cluster structure and its autonomous coordination control strategy

DEFF Research Database (Denmark)

Zhou, Xiaoping; Zhou, Leming; Chen, Yandong

2018-01-01

This paper proposes a microgrid cluster structure and its autonomous coordination control strategy. Unlike existing microgrids that are purely AC or DC, the microgrid cluster studied here is an interconnected system with multiple AC and DC microgrids, which enables mutual power support among...... control method combining the normalized droop-based control and adaptive control is proposed for PEU, which can effectively realize mutual power support among microgrids and reduce the bus voltage or frequency deviation in microgrids. In addition, the adaptive control strategy of PEU can ensure...... that the bigger the normalized index of microgrid is, the larger the active power exchange coefficient is, which can make all of microgrids operate around the rated state as much as possible. Besides, EP is mainly used to balance the system power, and the hierarchical coordinated control method of EP is proposed...

Integrated Quality Control of Precision Assemblies using Computed Tomography

DEFF Research Database (Denmark)

Stolfi, Alessandro

coor-dinate measuring machines (CMMs) when working with complex and fragile parts. This Ph.D. project at DTU Mechanical Engineering concerns the applicability of CT for quality control of precision assem-blies. Investigations to quantify the accuracy of CT measurements, reference artefacts to correct...

Quality control of FWC during assembly and commissioning in SST-1 Tokamak

Science.gov (United States)

Patel, Hitesh; Santra, Prosenjit; Parekh, Tejas; Biswas, Prabal; Jayswal, Snehal; Chauhan, Pradeep; Paravastu, Yuvakiran; George, Siju; Semwal, Pratibha; Thankey, Prashant; Ramesh, Gattu; Prakash, Arun; Dhanani, Kalpesh; Raval, D. C.; Khan, Ziauddin; Pradhan, Subrata

2017-04-01

First Wall Components (FWC) of SST-1 tokamak, which are in the immediate vicinity of plasma, comprises of limiters, divertors, baffles, passive stabilizers designed to operate long duration (∼1000 s) discharges of elongated plasma. All FWC consist of copper alloy heat sink modules with SS cooling tubes brazed onto it, graphite tiles acting as armour material facing the plasma, and are mounted to the vacuum vessels with suitable Inconel support structures at inter-connected ring & port locations. The FWC are very recently assembled and commissioned successfully inside the vacuum vessel of SST-1 undergoing a rigorous quality control and checks at every stage of the assembly process. This paper will present the quality control aspects and checks of FWC from commencement of assembly procedure, namely material test reports, leak testing of high temperature baked components, assembled dimensional tolerances, leak testing of all welded joints, graphite tile tightening torques, electrical continuity and electrical isolation of passive stabilizers from vacuum vessel, baking and cooling hydraulic connections inside vacuum vessel.

Programming Cells for Dynamic Assembly of Inorganic Nano-Objects with Spatiotemporal Control.

Science.gov (United States)

Wang, Xinyu; Pu, Jiahua; An, Bolin; Li, Yingfeng; Shang, Yuequn; Ning, Zhijun; Liu, Yi; Ba, Fang; Zhang, Jiaming; Zhong, Chao

2018-04-01

Programming living cells to organize inorganic nano-objects (NOs) in a spatiotemporally precise fashion would advance new techniques for creating ordered ensembles of NOs and new bio-abiotic hybrid materials with emerging functionalities. Bacterial cells often grow in cellular communities called biofilms. Here, a strategy is reported for programming dynamic biofilm formation for the synchronized assembly of discrete NOs or hetero-nanostructures on diverse interfaces in a dynamic, scalable, and hierarchical fashion. By engineering Escherichia coli to sense blue light and respond by producing biofilm curli fibers, biofilm formation is spatially controlled and the patterned NOs' assembly is simultaneously achieved. Diverse and complex fluorescent quantum dot patterns with a minimum patterning resolution of 100 µm are demonstrated. By temporally controlling the sequential addition of NOs into the culture, multilayered heterostructured thin films are fabricated through autonomous layer-by-layer assembly. It is demonstrated that biologically dynamic self-assembly can be used to advance a new repertoire of nanotechnologies and materials with increasing complexity that would be otherwise challenging to produce. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interaction between Nbp35 and Cfd1 proteins of cytosolic Fe-S cluster assembly reveals a stable complex formation in Entamoeba histolytica.

Directory of Open Access Journals (Sweden)

Shadab Anwar

Full Text Available Iron-Sulfur (Fe-S proteins are involved in many biological functions such as electron transport, photosynthesis, regulation of gene expression and enzymatic activities. Biosynthesis and transfer of Fe-S clusters depend on Fe-S clusters assembly processes such as ISC, SUF, NIF, and CIA systems. Unlike other eukaryotes which possess ISC and CIA systems, amitochondriate Entamoeba histolytica has retained NIF & CIA systems for Fe-S cluster assembly in the cytosol. In the present study, we have elucidated interaction between two proteins of E. histolytica CIA system, Cytosolic Fe-S cluster deficient 1 (Cfd1 protein and Nucleotide binding protein 35 (Nbp35. In-silico analysis showed that structural regions ranging from amino acid residues (P33-K35, G131-V135 and I147-E151 of Nbp35 and (G5-V6, M34-D39 and G46-A52 of Cfd1 are involved in the formation of protein-protein complex. Furthermore, Molecular dynamic (MD simulations study suggested that hydrophobic forces surpass over hydrophilic forces between Nbp35 and Cfd1 and Van-der-Waal interaction plays crucial role in the formation of stable complex. Both proteins were separately cloned, expressed as recombinant fusion proteins in E. coli and purified to homogeneity by affinity column chromatography. Physical interaction between Nbp35 and Cfd1 proteins was confirmed in vitro by co-purification of recombinant Nbp35 with thrombin digested Cfd1 and in vivo by pull down assay and immunoprecipitation. The insilico, in vitro as well as in vivo results prove a stable interaction between these two proteins, supporting the possibility of its involvement in Fe-S cluster transfer to target apo-proteins through CIA machinery in E. histolytica. Our study indicates that initial synthesis of a Fe-S precursor in mitochondria is not necessary for the formation of Cfd1-Nbp35 complex. Thus, Cfd1 and Nbp35 with the help of cytosolic NifS and NifU proteins can participate in the maturation of non-mitosomal Fe-S proteins

Morphology-controlled synthesis of self-assembled LiFePO4/C/RGO for high-performance Li-ion batteries.

Science.gov (United States)

Lin, Mei; Chen, Yuming; Chen, Bolei; Wu, Xiao; Kam, Kifung; Lu, Wei; Chan, Helen Lai Wa; Yuan, Jikang

2014-10-22

Novel architectured LiFePO4 (LFP) that consisted of ordered LFP nanocubes was prepared through a facile hydrothermal method using polyethylene glycol (PEG) as a surfactant. The micro/nanostructured LFP with various morphologies ranging from cube cluster to rugby-like structure was synthesized via controlling the pH values of the precursor. A reasonable assembly process elucidating the formation of the hierarchical structure is also provided based on the experimental results. After a combination of carbon (C) coating and reduced graphene oxide (RGO) wrapping, the obtained LFP/C/RGO composites exhibit enhanced electrochemical performance compared to that of blank LFP synthesized under the same condition. Among as-synthesized cube-cluster-like, dumbbell-like, rod-like, and rugby-like composites, the rugby-like LFP/C/RGO reveal the best electrochemical properties with the discharge specific capacity of ∼150 mA h g(-1) after 100 cycles and a high reversible specific capacity of 152 mA h g(-1) at 0.1 C. The prepared LFP/C/RGO composite can be a promising cathode material for high energy, low cost, and environmentally friendly lithium-ion batteries.

Controlled assembly of jammed colloidal shells on fluid droplets

Science.gov (United States)

Subramaniam, Anand Bala; Abkarian, Manouk; Stone, Howard A.

2005-07-01

Assembly of colloidal particles on fluid interfaces is a promising technique for synthesizing two-dimensional microcrystalline materials useful in fields as diverse as biomedicine, materials science, mineral flotation and food processing. Current approaches rely on bulk emulsification methods, require further chemical and thermal treatments, and are restrictive with respect to the materials used. The development of methods that exploit the great potential of interfacial assembly for producing tailored materials have been hampered by the lack of understanding of the assembly process. Here we report a microfluidic method that allows direct visualization and understanding of the dynamics of colloidal crystal growth on curved interfaces. The crystals are periodically ejected to form stable jammed shells, which we refer to as colloidal armour. We propose that the energetic barriers to interfacial crystal growth and organization can be overcome by targeted delivery of colloidal particles through hydrodynamic flows. Our method allows an unprecedented degree of control over armour composition, size and stability.

Self-assembly of a tetrahedral 58-nuclear barium vanadium oxide cluster.

Science.gov (United States)

Kastner, Katharina; Puscher, Bianka; Streb, Carsten

2013-01-07

We report the synthesis and characterization of a molecular barium vanadium oxide cluster featuring high nuclearity and high symmetry. The tetrameric, 2.3 nm cluster H(5)[Ba(10)(NMP)(14)(H(2)O)(8)[V(12)O(33)](4)Br] is based on a bromide-centred, octahedral barium scaffold which is capped by four previously unknown [V(12)O(33)](6-) clusters in a tetrahedral fashion. The compound represents the largest polyoxovanadate-based heterometallic cluster known to date. The cluster is formed in organic solution and it is suggested that the bulky N-methyl-2-pyrrolidone (NMP) solvent ligands allow the isolation of this giant molecule and prevent further condensation to a solid-state metal oxide. The cluster is fully characterized using single-crystal XRD, elemental analysis, ESI mass spectrometry and other spectroscopic techniques.

Numerical Analysis on the Free Fall Motion of the Control Rod Assembly for the Sodium Cooled Fast Reactor

Energy Technology Data Exchange (ETDEWEB)

Oh, Se-Hong; Choi, Choengryul; Son, Sung-Man [ELSOLTEC, Yongin (Korea, Republic of); Kim, Jae-Yong; Yoon, Kyung-Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

On receiving the scram signal, the control rod assemblies are released to fall into the reactor core by its weight. Thus drop time and falling velocity of the control rod assembly must be estimated for the safety evaluation. However, because of its complex shape, it is difficult to estimate the drop time by theoretical method. In this study, numerical analysis has been carried out in order to estimate drop time and falling velocity of the control rod assembly to provide the underlying data for the design optimization. Numerical analysis has been carried out to estimate the drop time and falling velocity of the control rod assembly for sodium-cooled fast reactor. Before performing the numerical analysis for the control rod assembly, sphere dropping experiment has been carried out for verification of the CFD methodology. The result of the numerical analysis for the method verification is almost same as the result of the experiment. Falling velocity and drag force increase rapidly in the beginning. And then it goes to the stable state. When the piston head of the control rod assembly is inserted into the damper, the drag force increases instantaneously and the falling velocity decreases quickly. The falling velocity is reduced about 14 % by damper. The total drop time of the control rod assembly is about 1.47s. In the next study, the experiment for the control rod assembly will be carried out, and its result is going to be compared with the CFD analysis result.

Drop performance test of conceptually designed control rod assembly for prototype generation IV sodium-cooled fast reactor

Energy Technology Data Exchange (ETDEWEB)

Lee, Young Kyu; Lee, Jae Han; Kim, Hoe Woong; KIm, Sung Kyun; Kim, Jong Bum [Sodium-cooled Fast Reactor NSSS Design Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-06-15

The control rod assembly controls reactor power by adjusting its position during normal operation and shuts down chain reactions by its free drop under scram conditions. Therefore, the drop performance of the control rod assembly is important for the safety of a nuclear reactor. In this study, the drop performance of the conceptually designed control rod assembly for the prototype generation IV sodium-cooled fast reactor that is being developed at the Korea Atomic Energy Research Institute as a next-generation nuclear reactor was experimentally investigated. For the performance test, the test facility and test procedure were established first, and several free drop performance tests of the control rod assembly under different flow rate conditions were then carried out. Moreover, performance tests under several types and magnitudes of seismic loading conditions were also conducted to investigate the effects of seismic loading on the drop performance of the control rod assembly. The drop time of the conceptually designed control rod assembly for 0% of the tentatively designed flow rate was measured to be 1.527 seconds, and this agrees well with the analytically calculated drop time. It was also observed that the effect of seismic loading on the drop time was not significant.

A GMBCG GALAXY CLUSTER CATALOG OF 55,424 RICH CLUSTERS FROM SDSS DR7

International Nuclear Information System (INIS)

Hao Jiangang; Annis, James; Johnston, David E.; McKay, Timothy A.; Evrard, August; Siegel, Seth R.; Gerdes, David; Koester, Benjamin P.; Rykoff, Eli S.; Rozo, Eduardo; Wechsler, Risa H.; Busha, Michael; Becker, Matthew; Sheldon, Erin

2010-01-01

We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red-sequence plus brightest cluster galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red-sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 deg 2 of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.

A GMBCG galaxy cluster catalog of 55,880 rich clusters from SDSS DR7

Energy Technology Data Exchange (ETDEWEB)

Hao, Jiangang; McKay, Timothy A.; Koester, Benjamin P.; Rykoff, Eli S.; Rozo, Eduardo; Annis, James; Wechsler, Risa H.; Evrard, August; Siegel, Seth R.; Becker, Matthew; Busha, Michael; /Fermilab /Michigan U. /Chicago U., Astron. Astrophys. Ctr. /UC, Santa Barbara /KICP, Chicago /KIPAC, Menlo Park /SLAC /Caltech /Brookhaven

2010-08-01

We present a large catalog of optically selected galaxy clusters from the application of a new Gaussian Mixture Brightest Cluster Galaxy (GMBCG) algorithm to SDSS Data Release 7 data. The algorithm detects clusters by identifying the red sequence plus Brightest Cluster Galaxy (BCG) feature, which is unique for galaxy clusters and does not exist among field galaxies. Red sequence clustering in color space is detected using an Error Corrected Gaussian Mixture Model. We run GMBCG on 8240 square degrees of photometric data from SDSS DR7 to assemble the largest ever optical galaxy cluster catalog, consisting of over 55,000 rich clusters across the redshift range from 0.1 < z < 0.55. We present Monte Carlo tests of completeness and purity and perform cross-matching with X-ray clusters and with the maxBCG sample at low redshift. These tests indicate high completeness and purity across the full redshift range for clusters with 15 or more members.

Simulating control rod and fuel assembly motion using moving meshes

Energy Technology Data Exchange (ETDEWEB)

Gilbert, D. [Department of Electrical and Computer Engineering, McMaster University, 1280 Main Street West, Hamilton Ontario, L8S 4K1 (Canada)], E-mail: gilbertdw1@gmail.com; Roman, J.E. [Departamento de Sistemas Informaticos y Computacion, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Garland, Wm. J. [Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton Ontario, L8S 4K1 (Canada); Poehlman, W.F.S. [Department of Computing and Software, McMaster University, 1280 Main Street West, Hamilton Ontario, L8S 4K1 (Canada)

2008-02-15

A prerequisite for designing a transient simulation experiment which includes the motion of control and fuel assemblies is the careful verification of a steady state model which computes k{sub eff} versus assembly insertion distance. Previous studies in nuclear engineering have usually approached the problem of the motion of control rods with the use of nonlinear nodal models. Nodal methods employ special approximations for the leading and trailing cells of the moving assemblies to avoid the rod cusping problem which results from the naive volume weighted cell cross-section approximation. A prototype framework called the MOOSE has been developed for modeling moving components in the presence of diffusion phenomena. A linear finite difference model is constructed, solutions for which are computed by SLEPc, a high performance parallel eigenvalue solver. Design techniques for the implementation of a patched non-conformal mesh which links groups of sub-meshes that can move relative to one another are presented. The generation of matrices which represent moving meshes which conserve neutron current at their boundaries, and the performance of the framework when applied to model reactivity insertion experiments is also discussed.

Key Performance Indicators for the Impact of Cognitive Assembly Planning on Ramp-Up Process

Directory of Open Access Journals (Sweden)

Christian Buescher

2012-01-01

Full Text Available Within the ramp-up phase of highly automated assembly systems, the planning effort forms a large part of production costs. Due to shortening product lifecycles, changing customer demands, and therefore an increasing number of ramp-up processes, these costs even rise. So assembly systems should reduce these efforts and simultaneously be flexible for quick adaption to changes in products and their variants. A cognitive interaction system in the field of assembly planning systems is developed within the Cluster of Excellence “Integrative production technology for high-wage countries” at RWTH Aachen University which integrates several cognitive capabilities according to human cognition. This approach combines the advantages of automation with the flexibility of humans. In this paper the main principles of the system's core component—the cognitive control unit—are presented to underline its advantages with respect to traditional assembly systems. Based on this, the actual innovation of this paper is the development of key performance indicators. These refer to the ramp-up process as a main objective of such a system is to minimize the planning effort during ramp-up. The KPIs are also designed to show the impact on the main idea of the Cluster of Excellence in resolving the so-called Polylemma of Production.

Tritium system test assembly control system cost estimate

International Nuclear Information System (INIS)

Stutz, R.A.

1979-01-01

The principal objectives of the Tritium Systems Test Assembly (TSTA), which includes the development, demonstration and interfacing of technologies related to the deuterium--tritium fuel cycle for fusion reactor systems, are concisely stated. The various integrated subsystems comprising TSTA and their functions are discussed. Each of the four major subdivisions of TSTA, including the main process system, the environmental and safety systems, supporting systems and the physical plant are briefly discussed. An overview of the Master Data Acquisition and Control System, which will control all functional operation of TSTA, is provided

Distinct functional domains within the acidic cluster of tegument protein pp28 required for trafficking and cytoplasmic envelopment of human cytomegalovirus.

Science.gov (United States)

Seo, Jun-Young; Jeon, Hyejin; Hong, Sookyung; Britt, William J

2016-10-01

Human cytomegalovirus UL99-encoded tegument protein pp28 contains a 16 aa acidic cluster that is required for pp28 trafficking to the assembly compartment (AC) and the virus assembly. However, functional signals within the acidic cluster of pp28 remain undefined. Here, we demonstrated that an acidic cluster rather than specific sorting signals was required for trafficking to the AC. Recombinant viruses with chimeric pp28 proteins expressing non-native acidic clusters exhibited delayed viral growth kinetics and decreased production of infectious virus, indicating that the native acidic cluster of pp28 was essential for wild-type virus assembly. These results suggested that the acidic cluster of pp28 has distinct functional domains required for trafficking and for efficient virus assembly. The first half (aa 44-50) of the acidic cluster was sufficient for pp28 trafficking, whereas the native acidic cluster consisting of aa 51-59 was required for the assembly of wild-type levels of infectious virus.

Towards Cluster-Assembled Materials of True Monodispersity in Size and Chemical Environment: Synthesis, Dynamics and Activity

Science.gov (United States)

2016-10-27

thermodynamic and kinetic cluster size control on periodically wet - table surfaces, new questions came up concerning the link between diffusivity and...from ring-hollow (H,F) to ring-bridge (B). Left: STM annealing series (50×50 nm2), Moiré cell scheme and cluster position evaluation. Pd clus- ters...growth at T>700 K. Below: Measured and theoretically simulated (insets) STM images of various stages in the dehydrogenation process upon annealing

Self-Controlling Rig for Jaw Crusher Assembly

OpenAIRE

Saurabh Jadhav; Anup Pawar

2017-01-01

The aim of the work is to develop a method for easy assembly of the bearing in the housing by standardized way. The assembly of bearing should take place on the atomized set up. Based on this method a assembly setup was constructed which enables to assembly of the shaft with bearing of different models of jaw crusher. First tests were done with manual alignment and it shows that with proper alignment shaft assembly is very easy operation and also safe. Results of those tests show that the dev...

A Carbon Dioxide Bubble-Induced Vortex Triggers Co-Assembly of Nanotubes with Controlled Chirality.

Science.gov (United States)

Zhang, Ling; Zhou, Laicheng; Xu, Na; Ouyang, Zhenjie

2017-07-03

It is challenging to prepare co-organized nanotube systems with controlled nanoscale chirality in an aqueous liquid flow field. Such systems are responsive to a bubbled external gas. A liquid vortex induced by bubbling carbon dioxide (CO 2 ) gas was used to stimulate the formation of nanotubes with controlled chirality; two kinds of achiral cationic building blocks were co-assembled in aqueous solution. CO 2 -triggered nanotube formation occurs by formation of metastable intermediate structures (short helical ribbons and short tubules) and by transition from short tubules to long tubules in response to chirality matching self-assembly. Interestingly, the chirality sign of these assemblies can be selected for by the circulation direction of the CO 2 bubble-induced vortex during the co-assembly process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cluster-based control of a separating flow over a smoothly contoured ramp

Science.gov (United States)

Kaiser, Eurika; Noack, Bernd R.; Spohn, Andreas; Cattafesta, Louis N.; Morzyński, Marek

2017-12-01

The ability to manipulate and control fluid flows is of great importance in many scientific and engineering applications. The proposed closed-loop control framework addresses a key issue of model-based control: The actuation effect often results from slow dynamics of strongly nonlinear interactions which the flow reveals at timescales much longer than the prediction horizon of any model. Hence, we employ a probabilistic approach based on a cluster-based discretization of the Liouville equation for the evolution of the probability distribution. The proposed methodology frames high-dimensional, nonlinear dynamics into low-dimensional, probabilistic, linear dynamics which considerably simplifies the optimal control problem while preserving nonlinear actuation mechanisms. The data-driven approach builds upon a state space discretization using a clustering algorithm which groups kinematically similar flow states into a low number of clusters. The temporal evolution of the probability distribution on this set of clusters is then described by a control-dependent Markov model. This Markov model can be used as predictor for the ergodic probability distribution for a particular control law. This probability distribution approximates the long-term behavior of the original system on which basis the optimal control law is determined. We examine how the approach can be used to improve the open-loop actuation in a separating flow dominated by Kelvin-Helmholtz shedding. For this purpose, the feature space, in which the model is learned, and the admissible control inputs are tailored to strongly oscillatory flows.

Spectroscopic and functional characterization of iron-sulfur cluster-bound forms of Azotobacter vinelandii (Nif)IscA.

Science.gov (United States)

Mapolelo, Daphne T; Zhang, Bo; Naik, Sunil G; Huynh, Boi Hanh; Johnson, Michael K

2012-10-16

The mechanism of [4Fe-4S] cluster assembly on A-type Fe-S cluster assembly proteins, in general, and the specific role of (Nif)IscA in the maturation of nitrogen fixation proteins are currently unknown. To address these questions, in vitro spectroscopic studies (UV-visible absorption/CD, resonance Raman and Mössbauer) have been used to investigate the mechanism of [4Fe-4S] cluster assembly on Azotobacter vinelandii(Nif)IscA, and the ability of (Nif)IscA to accept clusters from NifU and to donate clusters to the apo form of the nitrogenase Fe-protein. The results show that (Nif)IscA can rapidly and reversibly cycle between forms containing one [2Fe-2S](2+) and one [4Fe-4S](2+) cluster per homodimer via DTT-induced two-electron reductive coupling of two [2Fe-2S](2+) clusters and O(2)-induced [4Fe-4S](2+) oxidative cleavage. This unique type of cluster interconversion in response to cellular redox status and oxygen levels is likely to be important for the specific role of A-type proteins in the maturation of [4Fe-4S] cluster-containing proteins under aerobic growth or oxidative stress conditions. Only the [4Fe-4S](2+)-(Nif)IscA was competent for rapid activation of apo-nitrogenase Fe protein under anaerobic conditions. Apo-(Nif)IscA was shown to accept clusters from [4Fe-4S] cluster-bound NifU via rapid intact cluster transfer, indicating a potential role as a cluster carrier for delivery of clusters assembled on NifU. Overall the results support the proposal that A-type proteins can function as carrier proteins for clusters assembled on U-type proteins and suggest that they are likely to supply [2Fe-2S] clusters rather than [4Fe-4S] for the maturation of [4Fe-4S] cluster-containing proteins under aerobic or oxidative stress growth conditions.

Controlled short-linkage assembly of functional nano-objects

Energy Technology Data Exchange (ETDEWEB)

Chaudhary, Shilpi; Kamra, Tripta [Division of Pure and Applied Biochemistry, Lund University, Box 124, 221 00 Lund (Sweden); ENI AB, Malmö (Sweden); Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Uddin, Khan Mohammad Ahsan [Division of Pure and Applied Biochemistry, Lund University, Box 124, 221 00 Lund (Sweden); Snezhkova, Olesia [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Jayawardena, H. Surangi N. [Department of Chemistry, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854 (United States); Yan, Mingdi [Department of Chemistry, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854 (United States); Department of Chemistry, KTH – Royal Institute of Technology, Teknikringen 30, S-10044 Stockholm (Sweden); Montelius, Lars [ENI AB, Malmö (Sweden); Schnadt, Joachim, E-mail: joachim.schnadt@sljus.lu.se [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Ye, Lei, E-mail: lei.ye@tbiokem.lth.se [Division of Pure and Applied Biochemistry, Lund University, Box 124, 221 00 Lund (Sweden)

2014-05-01

Graphical abstract: - Highlights: • Fast photoconjugation of nanoparticles on surface. • Non-destructive feature guarantees intact function of nanoparticles. • Direct contact between nano-objects allows efficient photon and electron transfer. • Possibility of generating patterned nanoparticle assemblies on surface. • Open new opportunities for assembling chemical sensors. - Abstract: In this work, we report a method that allows the deterministic, photo-controlled covalent assembly of nanoparticles directly on surface. As a model system, we study the conjugation of molecularly imprinted polymer (MIP) nanoparticles on a glass surface and confirm that the immobilized nanoparticles maintain their molecular recognition functionality. The glass slide was first modified with perfluorophenylazide and then used to bind MIP nanoparticles under UV irradiation. After each step the surface was analyzed by water contact angle measurement, fluorescence microscopy, scanning electron microscopy, and/or synchrotron-based X-ray photoelectron spectroscopy. The MIP nanoparticles immobilized on the glass surface remained stable and maintained specific binding for the template molecule, propranolol. The method developed in this work allows MIP nanoparticles to be directly coupled to a flat surface, offering a straightforward means to construct robust chemical sensors. Using the reported photo conjugation method, it is possible to generate patterned assembly of nanoparticles using a photomask. Since perfluorophenylazide-based photochemistry works with all kinds of organic material, the method developed in this work is expected to enable immobilization of not only MIPs but also other kinds of organic and inorganic–organic core–shell particles for various applications involving photon or electron transfer.

Controlled short-linkage assembly of functional nano-objects

International Nuclear Information System (INIS)

Chaudhary, Shilpi; Kamra, Tripta; Uddin, Khan Mohammad Ahsan; Snezhkova, Olesia; Jayawardena, H. Surangi N.; Yan, Mingdi; Montelius, Lars; Schnadt, Joachim; Ye, Lei

2014-01-01

Graphical abstract: - Highlights: • Fast photoconjugation of nanoparticles on surface. • Non-destructive feature guarantees intact function of nanoparticles. • Direct contact between nano-objects allows efficient photon and electron transfer. • Possibility of generating patterned nanoparticle assemblies on surface. • Open new opportunities for assembling chemical sensors. - Abstract: In this work, we report a method that allows the deterministic, photo-controlled covalent assembly of nanoparticles directly on surface. As a model system, we study the conjugation of molecularly imprinted polymer (MIP) nanoparticles on a glass surface and confirm that the immobilized nanoparticles maintain their molecular recognition functionality. The glass slide was first modified with perfluorophenylazide and then used to bind MIP nanoparticles under UV irradiation. After each step the surface was analyzed by water contact angle measurement, fluorescence microscopy, scanning electron microscopy, and/or synchrotron-based X-ray photoelectron spectroscopy. The MIP nanoparticles immobilized on the glass surface remained stable and maintained specific binding for the template molecule, propranolol. The method developed in this work allows MIP nanoparticles to be directly coupled to a flat surface, offering a straightforward means to construct robust chemical sensors. Using the reported photo conjugation method, it is possible to generate patterned assembly of nanoparticles using a photomask. Since perfluorophenylazide-based photochemistry works with all kinds of organic material, the method developed in this work is expected to enable immobilization of not only MIPs but also other kinds of organic and inorganic–organic core–shell particles for various applications involving photon or electron transfer

DNA controlled assembly of liposomes

DEFF Research Database (Denmark)

Vogel, Stefan; Jakobsen, Ulla; Simonsen, Adam Cohen

2009-01-01

DNA-encoding of solid nanoparticles requires surfacechemistry, which is often tedious and not generally applicable. In the present study non-covalently attached DNA are used to assemble soft nanoparticles (liposomes) in solution. This process displays remarkably sharp thermal transitions from...... assembled to disassembled state for which reason this method allows easy and fast detection of polynucleotides (e.g. DNA or RNA), including single nucleotide polymorphisms as well as insertions and deletions....

Density control of dodecamanganese clusters anchored on silicon(100).

Science.gov (United States)

Condorelli, Guglielmo G; Motta, Alessandro; Favazza, Maria; Nativo, Paola; Fragalà, Ignazio L; Gatteschi, Dante

2006-04-24

A synthetic strategy to control the density of Mn12 clusters anchored on silicon(100) was investigated. Diluted monolayers suitable for Mn12 anchoring were prepared by Si-grafting mixtures of the methyl 10-undecylenoate precursor ligand with 1-decene spectator spacers. Different ratios of these mixtures were tested. The grafted surfaces were hydrolyzed to reveal the carboxylic groups available for the subsequent exchange with the [Mn12O12(OAc)16(H2O)4]4 H2O2 AcOH cluster. Modified surfaces were analyzed by attenuated total reflection (ATR)-FTIR spectroscopy, X-ray photoemission spectroscopy (XPS), and AFM imaging. Results of XPS and ATR-FTIR spectroscopy show that the surface mole ratio between grafted ester and decene is higher than in the source solution. The surface density of the Mn12 cluster is, in turn, strictly proportional to the ester mole fraction. Well-resolved and isolated clusters were observed by AFM, using a diluted ester/decene 1:1 solution.

Reuse-oriented common structure discovery in assembly models

Energy Technology Data Exchange (ETDEWEB)

Wang, Pan; Zhang Jie; Li, Yuan; Yu, Jian Feng [The Ministry of Education Key Lab of Contemporary Design and Integrated Manufacturing Technology, Northwestern Polytechnical University, Xian (China)

2017-01-15

Discovering the common structures in assembly models provides designers with the commonalities that carry significant design knowledge across multiple products, which helps to improve design efficiency and accelerate the design process. In this paper, a discovery method has been developed to obtain the common structure in assembly models. First, this work proposes a graph descriptor that captures both the geometrical and topological information of the assembly model, in which shape vectors and link vectors quantitatively describe the part models and mating relationships, respectively. Then, a clustering step is introduced into the discovery, which clusters the similar parts by comparing the similarities between them. In addition, some rules are also provided to filter the frequent subgraphs in order to obtain the expected results. Compared with the existing method, the proposed approach could overcome the disadvantages by providing an independent description of the part model and taking into consideration the similar parts in assemblies, which leads to a more reasonable result. Finally, some experiments have been carried out and the experimental results demonstrate the effectiveness of the proposed approach.

Reuse-oriented common structure discovery in assembly models

International Nuclear Information System (INIS)

Wang, Pan; Zhang Jie; Li, Yuan; Yu, Jian Feng

2017-01-01

Discovering the common structures in assembly models provides designers with the commonalities that carry significant design knowledge across multiple products, which helps to improve design efficiency and accelerate the design process. In this paper, a discovery method has been developed to obtain the common structure in assembly models. First, this work proposes a graph descriptor that captures both the geometrical and topological information of the assembly model, in which shape vectors and link vectors quantitatively describe the part models and mating relationships, respectively. Then, a clustering step is introduced into the discovery, which clusters the similar parts by comparing the similarities between them. In addition, some rules are also provided to filter the frequent subgraphs in order to obtain the expected results. Compared with the existing method, the proposed approach could overcome the disadvantages by providing an independent description of the part model and taking into consideration the similar parts in assemblies, which leads to a more reasonable result. Finally, some experiments have been carried out and the experimental results demonstrate the effectiveness of the proposed approach

Controllable assembly of silver nanoparticles induced by femtosecond laser direct writing

International Nuclear Information System (INIS)

Wang, Huan; Liu, Sen; Zhang, Yong-Lai; Wang, Jian-Nan; Wang, Lei; Xia, Hong; Chen, Qi-Dai; Sun, Hong-Bo; Ding, Hong

2015-01-01

We report controllable assembly of silver nanoparticles (Ag NPs) for patterning of silver microstructures. The assembly is induced by femtosecond laser direct writing (FsLDW). A tightly focused femtosecond laser beam is capable of trapping and driving Ag NPs to form desired micropatterns with a high resolution of ∼190 nm. Taking advantage of the ‘direct writing’ feature, three microelectrodes have been integrated with a microfluidic chip; two silver-based microdevices including a microheater and a catalytic reactor have been fabricated inside a microfluidic channel for chip functionalization. The FsLDW-induced programmable assembly of Ag NPs may open up a new way to the designable patterning of silver microstructures toward flexible fabrication and integration of functional devices. (focus issue paper)

Mesoscale Simulation and Machine Learning of Asphaltene Aggregation Phase Behavior and Molecular Assembly Landscapes.

Science.gov (United States)

Wang, Jiang; Gayatri, Mohit A; Ferguson, Andrew L

2017-05-11

Asphaltenes constitute the heaviest fraction of the aromatic group in crude oil. Aggregation and precipitation of asphaltenes during petroleum processing costs the petroleum industry billions of dollars each year due to downtime and production inefficiencies. Asphaltene aggregation proceeds via a hierarchical self-assembly process that is well-described by the Yen-Mullins model. Nevertheless, the microscopic details of the emergent cluster morphologies and their relative stability under different processing conditions remain poorly understood. We perform coarse-grained molecular dynamics simulations of a prototypical asphaltene molecule to establish a phase diagram mapping the self-assembled morphologies as a function of temperature, pressure, and n-heptane:toluene solvent ratio informing how to control asphaltene aggregation by regulating external processing conditions. We then combine our simulations with graph matching and nonlinear manifold learning to determine low-dimensional free energy surfaces governing asphaltene self-assembly. In doing so, we introduce a variant of diffusion maps designed to handle data sets with large local density variations, and report the first application of many-body diffusion maps to molecular self-assembly to recover a pseudo-1D free energy landscape. Increasing pressure only weakly affects the landscape, serving only to destabilize the largest aggregates. Increasing temperature and toluene solvent fraction stabilizes small cluster sizes and loose bonding arrangements. Although the underlying molecular mechanisms differ, the strikingly similar effect of these variables on the free energy landscape suggests that toluene acts upon asphaltene self-assembly as an effective temperature.

Assembly of Liposomes Controlled by Triple Helix Formation

DEFF Research Database (Denmark)

Vogel, Stefan; Jakobsen, Ulla

2013-01-01

Attachment of DNA to the surface of different solid nanoparticles (e.g. gold- and silica nanoparticles) is well established and a number of DNA-modified solid nanoparticle systems have been applied to thermal denaturation analysis of oligonucleotides. We report herein the non-covalent immobilizat...... analysis (NTA) and dynamic light scattering (DLS) show independently from ultraviolet spectroscopy experiments the formation of liposome aggregates.......-covalent immobilization of oligonucleotides on the surface of soft nanoparticles (e.g. liposomes) and the subsequent controlled assembly by DNA triple helix formation. The non-covalent approach avoids tedious surface chemistry and necessary purification procedures and can simplify and extend the available methodology...... sequences (G or C-rich) to explore the applicability of the method for different triple helical assembly modes. We demonstrate advantages and limitations of the approach and proof the reversible and reproducible formation of liposome aggregates during thermal denaturation cycles. Nanoparticle tracking...

Controllable self-assembly of sodium caseinate with a zwitterionic vitamin-derived bolaamphiphile.

Science.gov (United States)

Sun, Li-Hui; Sun, Yu-Long; Yang, Li-Jun; Zhang, Jian; Chen, Zhong-Xiu

2013-11-06

The control of self-assembly of sodium caseinate (SC) including the formation of mixed layers, microspheres, or nanoparticles is highly relevant to the microstructure of food and the design of promising drug delivery systems. In this paper, we designed a structure-switchable zwitterionic bolaamphiphile, 1,12-diaminododecanediorotate (DDO), from orotic acid, which has special binding sites and can guide the self-assembly of SC. Complexation between SC and DDO was investigated using dynamic light scattering, transmission electron microscopy, differential scanning calorimetry, and fluorescence spectra measurements. Monomeric DDO was bound to the negatively charged sites on the SC micelle and made the structure of SC more compact with decreased electrostatic repulsion between the head groups. Vesicular DDO led to reassociation of vesicles with enlarged size via preferable hydrophobic interactions. Moreover, the aggregation between SC and DDO was found to be temperature-dependent and reversible. This research provides an effective way to control the reversible self-assembly of SC by the zwitterionic vitamin-derived bolaamphiphile.

Defect- and dopant-controlled carbon nanotubes fabricated by self-assembly of graphene nanoribbons

Institute of Scientific and Technical Information of China (English)

Cun Zhang and Shaohua Chen

2015-01-01

Molecular dynamics simulations showed that a basal carbon nanotube can activate and guide the fabrication of single-walled carbon nanotubes （CNTs） on its internal surface by self-assembly of edge-unpassivated graphene nanoribbons with defects. Furthermore, the distribution of defects on self-assembled CNTs is controllable. The system temperature and defect fraction are two main factors that influence the success of self-assembly. Due to possible joint flaws formed at the boundaries under a relatively high constant temperature, a technique based on increasing the temperature is adopted. Self-assembly is always successful for graphene nanoribbons with relatively small defect fractions, while it will fail in cases with relatively large ones. Similar to the self-assembly of graphene nanoribbons with defects, graphene nanoribbons with different types of dopants can also be self-assembled into carbon nanotubes. The finding provides a possible fabrication technique not only for carbon nanotubes with metallic or semi-con- ductive properties but also for carbon nanotubes with electromagnetic induction characteristics.

Non-fuel assembly components: 10 CFR 61.55 classification for waste disposal

International Nuclear Information System (INIS)

Migliore, R.J.; Reid, B.D.; Fadeff, S.K.; Pauley, K.A.; Jenquin, U.P.

1994-09-01

This document reports the results of laboratory radionuclide measurements on a representative group of non-fuel assembly (NFA) components for the purposes of waste classification. This document also provides a methodology to estimate the radionuclide inventory of NFA components, including those located outside the fueled region of a nuclear reactor. These radionuclide estimates can then be used to determine the waste classification of NFA components for which there are no physical measurements. Previously, few radionuclide inventory measurements had been performed on NFA components. For this project, recommended scaling factors were selected for the ORIGEN2 computer code that result in conservative estimates of radionuclide concentrations in NFA components. These scaling factors were based upon experimental data obtained from the following NFA components: (1) a pressurized water reactor (PWR) burnable poison rod assembly, (2) a PVM rod cluster control assembly, and (3) a boiling water reactor cruciform control rod blade. As a whole, these components were found to be within Class C limits. Laboratory radionuclide measurements for these components are provided in detail

Ligand Bridging-Angle-Driven Assembly of Molecular Architectures Based on Quadruply Bonded Mo-Mo Dimers

Energy Technology Data Exchange (ETDEWEB)

Li, Jian-Rong; Yakovenko, Andrey A; Lu, Weigang; Timmons, Daren J; Zhuang, Wenjuan; Yuan, Daqiang; Zhou, Hong-Cai

2010-12-15

A systematic exploration of the assembly of Mo₂(O₂C-)₄-based metal–organic molecular architectures structurally controlled by the bridging angles of rigid organic linkers has been performed. Twelve bridging dicarboxylate ligands were designed to be of different sizes with bridging angles of 0, 60, 90, and 120° while incorporating a variety of nonbridging functional groups, and these ligands were used as linkers. These dicarboxylate linkers assemble with quadruply bonded Mo–Mo clusters acting as nodes to give 13 molecular architectures, termed metal–organic polygons/polyhedra with metal cluster node arrangements of a linear shape, triangle, octahedron, and cuboctahedron/anti-cuboctahedron. The syntheses of these complexes have been optimized and their structures determined by single-crystal X-ray diffraction. The results have shown that the shape and size of the resulting molecular architecture can be controlled by tuning the bridging angle and size of the linker, respectively. Functionalization of the linker can adjust the solubility of the ensuing molecular assembly but has little or no effect on the geometry of the product. Preliminary gas adsorption, spectroscopic, and electrochemical properties of selected members were also studied. The present work is trying to enrich metal-containing supramolecular chemistry through the inclusion of well-characterized quadruply bonded Mo–Mo units into the structures, which can widen the prospect of additional electronic functionality, thereby leading to novel properties.

Ligand bridging-angle-driven assembly of molecular architectures based on quadruply bonded Mo-Mo dimers.

Science.gov (United States)

Li, Jian-Rong; Yakovenko, Andrey A; Lu, Weigang; Timmons, Daren J; Zhuang, Wenjuan; Yuan, Daqiang; Zhou, Hong-Cai

2010-12-15

A systematic exploration of the assembly of Mo2(O2C-)4-based metal-organic molecular architectures structurally controlled by the bridging angles of rigid organic linkers has been performed. Twelve bridging dicarboxylate ligands were designed to be of different sizes with bridging angles of 0, 60, 90, and 120° while incorporating a variety of nonbridging functional groups, and these ligands were used as linkers. These dicarboxylate linkers assemble with quadruply bonded Mo-Mo clusters acting as nodes to give 13 molecular architectures, termed metal-organic polygons/polyhedra with metal cluster node arrangements of a linear shape, triangle, octahedron, and cuboctahedron/anti-cuboctahedron. The syntheses of these complexes have been optimized and their structures determined by single-crystal X-ray diffraction. The results have shown that the shape and size of the resulting molecular architecture can be controlled by tuning the bridging angle and size of the linker, respectively. Functionalization of the linker can adjust the solubility of the ensuing molecular assembly but has little or no effect on the geometry of the product. Preliminary gas adsorption, spectroscopic, and electrochemical properties of selected members were also studied. The present work is trying to enrich metal-containing supramolecular chemistry through the inclusion of well-characterized quadruply bonded Mo-Mo units into the structures, which can widen the prospect of additional electronic functionality, thereby leading to novel properties.

Selection bias and subject refusal in a cluster-randomized controlled trial

Directory of Open Access Journals (Sweden)

Rochelle Yang

2017-07-01

Full Text Available Abstract Background Selection bias and non-participation bias are major methodological concerns which impact external validity. Cluster-randomized controlled trials are especially prone to selection bias as it is impractical to blind clusters to their allocation into intervention or control. This study assessed the impact of selection bias in a large cluster-randomized controlled trial. Methods The Improved Cardiovascular Risk Reduction to Enhance Rural Primary Care (ICARE study examined the impact of a remote pharmacist-led intervention in twelve medical offices. To assess eligibility, a standardized form containing patient demographics and medical information was completed for each screened patient. Eligible patients were approached by the study coordinator for recruitment. Both the study coordinator and the patient were aware of the site’s allocation prior to consent. Patients who consented or declined to participate were compared across control and intervention arms for differing characteristics. Statistical significance was determined using a two-tailed, equal variance t-test and a chi-square test with adjusted Bonferroni p-values. Results were adjusted for random cluster variation. Results There were 2749 completed screening forms returned to research staff with 461 subjects who had either consented or declined participation. Patients with poorly controlled diabetes were found to be significantly more likely to decline participation in intervention sites compared to those in control sites. A higher mean diastolic blood pressure was seen in patients with uncontrolled hypertension who declined in the control sites compared to those who declined in the intervention sites. However, these findings were no longer significant after adjustment for random variation among the sites. After this adjustment, females were now found to be significantly more likely to consent than males (odds ratio = 1.41; 95% confidence interval = 1.03, 1

Hierarchical self-assembly of magnetic nanoclusters for theranostics: Tunable size, enhanced magnetic resonance imagability, and controlled and targeted drug delivery.

Science.gov (United States)

Nguyen, Dai Hai; Lee, Jung Seok; Choi, Jong Hoon; Park, Kyung Min; Lee, Yunki; Park, Ki Dong

2016-04-15

Nanoparticle-based imaging and therapy are of interest for theranostic nanomedicine. In particular, superparamagnetic iron oxide (SPIO) nanoparticles (NPs) have attracted much attention in cancer imaging, diagnostics, and treatment because of their superior imagability and biocompatibility (approved by the Food and Drug Administration). Here, we developed SPIO nanoparticles (NPs) that self-assembled into magnetic nanoclusters (SAMNs) in aqueous environments as a theranostic nano-system. To generate multi-functional SPIO NPs, we covalently conjugated β-cyclodextrin (β-CD) to SPIO NPs using metal-adhesive dopamine groups. Polyethylene glycol (PEG) and paclitaxel (PTX) were hosted in the β-CD cavity through high affinity complexation. The core-shell structure of the magnetic nanoclusters was elucidated based on the condensed SPIO core and a PEG shell using electron microscopy and the composition was analyzed by thermogravimetric analysis (TGA). Our results indicate that nanocluster size could be readily controlled by changing the SPIO/PEG ratio in the assemblies. Interestingly, we observed a significant enhancement in magnetic resonance contrast due to the large cluster size and dense iron oxide core. In addition, tethering a tumor-targeting peptide to the SAMNs enhanced their uptake into tumor cells. PTX was efficiently loaded into β-CDs and released in a controlled manner when exposed to competitive guest molecules. These results strongly indicate that the SAMNs developed in this study possess great potential for application in image-guided cancer chemotherapy. In this study, we developed multi-functional SPIO NPs that self-assembled into magnetic nanoclusters (SAMNs) in aqueous conditions as a theranostic nano-system. The beta-cyclodextrin (β-CD) was immobilized on the surfaces of SPIO NPs and RGD-conjugated polyethylene glycol (PEG) and paclitaxel (PTX) were hosted in the β-CD cavity through high affinity complexation. We found that nanocluster size could be

Design of polymetallic uranium assemblies for the development of single molecule magnets

International Nuclear Information System (INIS)

Chatelain, Lucile

2016-01-01

The study of actinide chemistry is not only essential for the development of nuclear fuel, nuclear fuel reprocessing or environmental clean up, but also for the understanding of fundamental actinide/ligand interactions and multiple bounding. The magnetic properties of polynuclear actinide molecules are of significant interest to investigate the magnetic communication between the metallic centres. Furthermore, they are highly promising for the design of molecular magnets. Uranium undergoes redox reactions due to a wide range of available oxidation states and easily forms polynuclear assemblies. However, only a few controlled synthetic routes towards these polynuclear uranium assemblies are described in the literature. In this context, the first part of this work was dedicated to the synthesis of oxo/hydroxo uranium clusters from the controlled hydrolysis of tetravalent uranium in the presence of an environmentally relevant ligand. This led to the synthesis of clusters with novel topologies, for which size could be varied as a function of the reaction conditions employed. However, the obtained clusters do not behave as SMM. In order to gain a stronger interaction between metallic centres, the cation-cation interaction was used to rationally design polynuclear uranyl(V) complexes. The isolation of uranyl(V) complexes had been limited in the past by its disproportionation, however, a fine tuning of the organic ligand and reaction conditions finally allowed to stabilise uranyl(V). We used stable uranyl(V) units as building block to form heteronuclear complexes with 3d and 4f metals with polymeric or discrete structures. The study of the magnetic properties of the uranium polynuclear assemblies was carried out and revealed single molecule or chain magnet behaviours with high energy barriers. The uranyl(V) unit was also used as a structural model for the more radioactive neptunium element, allowing the isolation of an isostructural trinuclear neptunyl(V) assembly in

Polymorphic Ring-Shaped Molecular Clusters Made of Shape-Variable Building Blocks

Directory of Open Access Journals (Sweden)

Keitel Cervantes-Salguero

2015-02-01

Full Text Available Self-assembling molecular building blocks able to dynamically change their shapes, is a concept that would offer a route to reconfigurable systems. Although simulation studies predict novel properties useful for applications in diverse fields, such kinds of building blocks, have not been implemented thus far with molecules. Here, we report shape-variable building blocks fabricated by DNA self-assembly. Blocks are movable enough to undergo shape transitions along geometrical ranges. Blocks connect to each other and assemble into polymorphic ring-shaped clusters via the stacking of DNA blunt-ends. Reconfiguration of the polymorphic clusters is achieved by the surface diffusion on mica substrate in response to a monovalent salt concentration. This work could inspire novel reconfigurable self-assembling systems for applications in molecular robotics.

On the Analysis of Case-Control Studies in Cluster-correlated Data Settings.

Science.gov (United States)

Haneuse, Sebastien; Rivera-Rodriguez, Claudia

2018-01-01

In resource-limited settings, long-term evaluation of national antiretroviral treatment (ART) programs often relies on aggregated data, the analysis of which may be subject to ecological bias. As researchers and policy makers consider evaluating individual-level outcomes such as treatment adherence or mortality, the well-known case-control design is appealing in that it provides efficiency gains over random sampling. In the context that motivates this article, valid estimation and inference requires acknowledging any clustering, although, to our knowledge, no statistical methods have been published for the analysis of case-control data for which the underlying population exhibits clustering. Furthermore, in the specific context of an ongoing collaboration in Malawi, rather than performing case-control sampling across all clinics, case-control sampling within clinics has been suggested as a more practical strategy. To our knowledge, although similar outcome-dependent sampling schemes have been described in the literature, a case-control design specific to correlated data settings is new. In this article, we describe this design, discuss balanced versus unbalanced sampling techniques, and provide a general approach to analyzing case-control studies in cluster-correlated settings based on inverse probability-weighted generalized estimating equations. Inference is based on a robust sandwich estimator with correlation parameters estimated to ensure appropriate accounting of the outcome-dependent sampling scheme. We conduct comprehensive simulations, based in part on real data on a sample of N = 78,155 program registrants in Malawi between 2005 and 2007, to evaluate small-sample operating characteristics and potential trade-offs associated with standard case-control sampling or when case-control sampling is performed within clusters.

A Cluster-Based Dual-Adaptive Topology Control Approach in Wireless Sensor Networks.

Science.gov (United States)

Gui, Jinsong; Zhou, Kai; Xiong, Naixue

2016-09-25

Multi-Input Multi-Output (MIMO) can improve wireless network performance. Sensors are usually single-antenna devices due to the high hardware complexity and cost, so several sensors are used to form virtual MIMO array, which is a desirable approach to efficiently take advantage of MIMO gains. Also, in large Wireless Sensor Networks (WSNs), clustering can improve the network scalability, which is an effective topology control approach. The existing virtual MIMO-based clustering schemes do not either fully explore the benefits of MIMO or adaptively determine the clustering ranges. Also, clustering mechanism needs to be further improved to enhance the cluster structure life. In this paper, we propose an improved clustering scheme for virtual MIMO-based topology construction (ICV-MIMO), which can determine adaptively not only the inter-cluster transmission modes but also the clustering ranges. Through the rational division of cluster head function and the optimization of cluster head selection criteria and information exchange process, the ICV-MIMO scheme effectively reduces the network energy consumption and improves the lifetime of the cluster structure when compared with the existing typical virtual MIMO-based scheme. Moreover, the message overhead and time complexity are still in the same order of magnitude.

Multigeometry Nanoparticle Engineering via Kinetic Control through Multistep assembly

Science.gov (United States)

Chen, Yingchao; Wang, Xiaojun; Zhang, Ke; Zhang, Fuwu; Mays, Jimmy; Wooley, Karen; Pochan, Darrin

2014-03-01

Organization of block copolymers into complicated multicompartment (MCM) and multigeometry (MGM) nanostructures is of increasing interest. Multistep, co-assembly methods resulting in kinetic control processing was used to produce complex nanoparticles that are not obtained via other assembly methods. Vesicle-cylinder, separate vesicle and cylinder, disk-cylinder, and mixed vesicle nanoparticles were constructed by binary blends of distinct diblock copolymers. Initially, the vesicle former polyacrylic acid-polyisoprene and cylinder former polyacrylic acid-polystyrene which share the same hydrophilic domain but immiscible hydrophobic domain were blended in THF. Secondly, dimaine molecules are added to associate with the common hydrophilic PAA. Importantly, and lastly, by tuning the kinetic addition rate of selective, miscible solvent water, the unlike hydrophobic blocks are kinetically trapped into one particle and eventually nanophase separate to form multiple compartments and multigeometries. The effective bottom-up multistep assembly strategies can be applied in other binary/ternary blends, in which new vesicle-sphere, disk-disk and cylinder-cylinder MCM/MGM nanoparticles were programed. We are grateful for the financial support from the National Science Funding DMR-0906815 (D.J.P. and K.L.W.) and NIST METROLOGY POCHAN 2012.

Lithographic stress control for the self-assembly of polymer MEMS structures

International Nuclear Information System (INIS)

Lee, S-W; Sameoto, D; Parameswaran, M; Mahanfar, A

2008-01-01

We present a novel self-assembly mechanism to produce an assortment of predetermined three-dimensional micromechanical structures in polymer MEMS technology using lithographically defined areas of stress and mechanical reinforcement within a single structural material. This self-assembly technology is based on the tensile stress that arises during the cross-linking of the negative tone, epoxy-based photoresist SU-8. Two different thicknesses of SU-8 are used in a single compliant structure. The first SU-8 layer forms the main structural element and the second SU-8 layer determines the aspects of self-assembly. The second SU-8 layer thickness acts to both to create a stress differential within the structure as well as define the direction in which the induced stress will cause the structure to deform. In this manner, both the magnitude and direction of self-assembled structures can be controlled using a single lithographic step. Although this technique uses a single structural material, the basic concept may be adapted for other processes, with different material choices, for a wide variety of applications

Star clusters in evolving galaxies

Science.gov (United States)

Renaud, Florent

2018-04-01

Their ubiquity and extreme densities make star clusters probes of prime importance of galaxy evolution. Old globular clusters keep imprints of the physical conditions of their assembly in the early Universe, and younger stellar objects, observationally resolved, tell us about the mechanisms at stake in their formation. Yet, we still do not understand the diversity involved: why is star cluster formation limited to 105M⊙ objects in the Milky Way, while some dwarf galaxies like NGC 1705 are able to produce clusters 10 times more massive? Why do dwarfs generally host a higher specific frequency of clusters than larger galaxies? How to connect the present-day, often resolved, stellar systems to the formation of globular clusters at high redshift? And how do these links depend on the galactic and cosmological environments of these clusters? In this review, I present recent advances on star cluster formation and evolution, in galactic and cosmological context. The emphasis is put on the theory, formation scenarios and the effects of the environment on the evolution of the global properties of clusters. A few open questions are identified.

Orthology Guided Assembly in highly heterozygous crops

DEFF Research Database (Denmark)

Ruttink, Tom; Sterck, Lieven; Rohde, Antje

2013-01-01

to outbreeding crop species hamper De Bruijn Graph-based de novo assembly algorithms, causing transcript fragmentation and the redundant assembly of allelic contigs. If multiple genotypes are sequenced to study genetic diversity, primary de novo assembly is best performed per genotype to limit the level......Despite current advances in next-generation sequencing data analysis procedures, de novo assembly of a reference sequence required for SNP discovery and expression analysis is still a major challenge in genetically uncharacterized, highly heterozygous species. High levels of polymorphism inherent...... of polymorphism and avoid transcript fragmentation. Here, we propose an Orthology Guided Assembly procedure that first uses sequence similarity (tBLASTn) to proteins of a model species to select allelic and fragmented contigs from all genotypes and then performs CAP3 clustering on a gene-by-gene basis. Thus, we...

Development and characterization of the control assembly system for the large 2400 MWth Generation IV gas-cooled fast reactor

International Nuclear Information System (INIS)

Girardin, G.; Rimpault, G.; Morin, F.; Bosq, J.C.; Coddington, P.; Mikityuk, K.; Chawla, R.

2008-01-01

The present paper is related to the design and neutronic characterization of the principal control assembly system for the reference large (2400 MWth) Generation IV gas-cooled fast reactor (GFR), which makes use of ceramic-ceramic (CERCER) plate-type fuel-elements with (U-Pu) carbide fuel contained within a SiC inert matrix. For the neutronic calculations, the deterministic code system ERANOS-2.0 has been used, in association with a full core model including a European fast reactor (EFR)-type pattern for the control assemblies as a starting point. More specifically, the core contains a total of 33 control (control system device: CSD) and safety (diverse safety device: DSD) assemblies implemented in three banks. In the design of the new control assembly system, particular attention was given to the heat generation within the assemblies, so that both neutronic and thermal-hydraulic constraints could be appropriately accounted for. The thermal-hydraulic calculations have been performed with the code COPERNIC, significant coolant mass flow rates being found necessary to maintain acceptable cladding temperatures of the absorber pins. Complementary to the design study, neutronic investigations have been performed to assess the impact of the control assemblies in the GFR core in greater detail (rod interactions, shift of the flux, peaking factors, etc.). Thus, considerable shadowing effects have been observed between the first bank and the safety bank, as also between individual assemblies within the first bank. Large anti-shadowing effects also occur, the most prominent being that between the two CSD banks, where the total assembly worth is almost doubled in comparison to the sum of the individual values. Additional investigations have been performed and, in this context, it has been found that computation of the first-order eigenvalue and the eigenvalue separation is a robust tool to anticipate control assembly interactions in a large fast-spectrum core. One interesting

De Novo Assembly and Genome Analyses of the Marine-Derived Scopulariopsis brevicaulis Strain LF580 Unravels Life-Style Traits and Anticancerous Scopularide Biosynthetic Gene Cluster.

Science.gov (United States)

Kumar, Abhishek; Henrissat, Bernard; Arvas, Mikko; Syed, Muhammad Fahad; Thieme, Nils; Benz, J Philipp; Sørensen, Jens Laurids; Record, Eric; Pöggeler, Stefanie; Kempken, Frank

2015-01-01

The marine-derived Scopulariopsis brevicaulis strain LF580 produces scopularides A and B, which have anticancerous properties. We carried out genome sequencing using three next-generation DNA sequencing methods. De novo hybrid assembly yielded 621 scaffolds with a total size of 32.2 Mb and 16298 putative gene models. We identified a large non-ribosomal peptide synthetase gene (nrps1) and supporting pks2 gene in the same biosynthetic gene cluster. This cluster and the genes within the cluster are functionally active as confirmed by RNA-Seq. Characterization of carbohydrate-active enzymes and major facilitator superfamily (MFS)-type transporters lead to postulate S. brevicaulis originated from a soil fungus, which came into contact with the marine sponge Tethya aurantium. This marine sponge seems to provide shelter to this fungus and micro-environment suitable for its survival in the ocean. This study also builds the platform for further investigations of the role of life-style and secondary metabolites from S. brevicaulis.

Nuclear reactor fuel assembly

International Nuclear Information System (INIS)

Vikhorev, Yu.V.; Biryukov, G.I.; Kirilyuk, N.A.; Lobanov, V.N.

1977-01-01

A fuel assembly is proposed for nuclear reactors allowing remote replacement of control rod bundles or their shifting from one assembly to another, i.e., their multipurpose use. This leads to a significant increase in fuel assembly usability. In the fuel assembly the control rod bundle is placed in guide tube channels to which baffles are attached for fuel element spacing. The remote handling of control rods is provided by a hollow cylinder with openings in its lower bottom through which the control rods pass. All control rods in a bundle are mounted to a cross beam which in turn is mounted in the cylinder and is designed for grasping the whole rod bundle by a remotely controlled telescopic mechanism in bundle replacement or shifting. (Z.M.)

Coordinated voltage control in offshore HVDC connected cluster of wind power plants

DEFF Research Database (Denmark)

Sakamuri, Jayachandra Naidu; Rather, Zakir Hussain; Rimez, Johan

This paper presents a coordinated voltage control scheme (CVCS) for a cluster of offshore wind power plants connected to a voltage-source converter-based high-voltage direct current system. The primary control point of the proposed voltage control scheme is the introduced Pilot bus, which is having...... by dispatching reactive power references to each wind turbine (WT) in the wind power plant cluster based on their available reactive power margin and network sensitivity-based participation factors, which are derived from the dV/dQ sensitivity of a WT bus w.r.t. the Pilot bus. This method leads...

Calculation of the local power peaking near WWER-440 control assemblies with Hf plates

International Nuclear Information System (INIS)

Hegyi, Gy.; Hordosy, G.; Kereszturi, A.; Maraszy, Cs.; Temesvari, E.

2003-01-01

The original coupler design of the WWER-440 assemblies had the following well known deficiency: The relatively large amount of water in the coupler between the absorber and fuel port of the control assembly can cause undesirably sharp power peaking in the fuel rods next to the coupler. The power peaking can be especially high after control rod withdrawal when the coupler reached low burnup level region of the adjacent assembly. The modernized coupler design overcomes the original problem by applying a thin Hf plate in the critical region. The very complicated structure of the coupler requires the verification of the core design methods by high precision 3D Monte Carlo calculations. The paper presents an MCNP reference calculation on the control rod coupler benchmark with Hf absorber plates. The benchmark solution with the KARATE-440 code system is also presented. The need for treating the Hf burnout in the reflector region is investigated (Authors)

Finite-Time and Fixed-Time Cluster Synchronization With or Without Pinning Control.

Science.gov (United States)

Liu, Xiwei; Chen, Tianping

2018-01-01

In this paper, the finite-time and fixed-time cluster synchronization problem for complex networks with or without pinning control are discussed. Finite-time (or fixed-time) synchronization has been a hot topic in recent years, which means that the network can achieve synchronization in finite-time, and the settling time depends on the initial values for finite-time synchronization (or the settling time is bounded by a constant for any initial values for fixed-time synchronization). To realize the finite-time and fixed-time cluster synchronization, some simple distributed protocols with or without pinning control are designed and the effectiveness is rigorously proved. Several sufficient criteria are also obtained to clarify the effects of coupling terms for finite-time and fixed-time cluster synchronization. Especially, when the cluster number is one, the cluster synchronization becomes the complete synchronization problem; when the network has only one node, the coupling term between nodes will disappear, and the synchronization problem becomes the simplest master-slave case, which also includes the stability problem for nonlinear systems like neural networks. All these cases are also discussed. Finally, numerical simulations are presented to demonstrate the correctness of obtained theoretical results.

A Cluster-Based Dual-Adaptive Topology Control Approach in Wireless Sensor Networks

Science.gov (United States)

Gui, Jinsong; Zhou, Kai; Xiong, Naixue

2016-01-01

Multi-Input Multi-Output (MIMO) can improve wireless network performance. Sensors are usually single-antenna devices due to the high hardware complexity and cost, so several sensors are used to form virtual MIMO array, which is a desirable approach to efficiently take advantage of MIMO gains. Also, in large Wireless Sensor Networks (WSNs), clustering can improve the network scalability, which is an effective topology control approach. The existing virtual MIMO-based clustering schemes do not either fully explore the benefits of MIMO or adaptively determine the clustering ranges. Also, clustering mechanism needs to be further improved to enhance the cluster structure life. In this paper, we propose an improved clustering scheme for virtual MIMO-based topology construction (ICV-MIMO), which can determine adaptively not only the inter-cluster transmission modes but also the clustering ranges. Through the rational division of cluster head function and the optimization of cluster head selection criteria and information exchange process, the ICV-MIMO scheme effectively reduces the network energy consumption and improves the lifetime of the cluster structure when compared with the existing typical virtual MIMO-based scheme. Moreover, the message overhead and time complexity are still in the same order of magnitude. PMID:27681731

A Cluster-Based Dual-Adaptive Topology Control Approach in Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Jinsong Gui

2016-09-01

Full Text Available Multi-Input Multi-Output (MIMO can improve wireless network performance. Sensors are usually single-antenna devices due to the high hardware complexity and cost, so several sensors are used to form virtual MIMO array, which is a desirable approach to efficiently take advantage of MIMO gains. Also, in large Wireless Sensor Networks (WSNs, clustering can improve the network scalability, which is an effective topology control approach. The existing virtual MIMO-based clustering schemes do not either fully explore the benefits of MIMO or adaptively determine the clustering ranges. Also, clustering mechanism needs to be further improved to enhance the cluster structure life. In this paper, we propose an improved clustering scheme for virtual MIMO-based topology construction (ICV-MIMO, which can determine adaptively not only the inter-cluster transmission modes but also the clustering ranges. Through the rational division of cluster head function and the optimization of cluster head selection criteria and information exchange process, the ICV-MIMO scheme effectively reduces the network energy consumption and improves the lifetime of the cluster structure when compared with the existing typical virtual MIMO-based scheme. Moreover, the message overhead and time complexity are still in the same order of magnitude.

Nanophase materials assembled from atomic clusters

International Nuclear Information System (INIS)

Siegel, R.W.

1989-09-01

The preparation of atomic clusters of metals and ceramics by means of the gas-condensation method, followed by their in situ consolidation under high-vacuum conditions, has recently led to the synthesis of a new class of ultrafine-grained materials for which their physics is intimately coupled with their application. These nanophase materials, with 2 to 20 nm grain sizes, appear to have properties that are often rather different from conventional materials, and also processing characteristics that are greatly improved. The nanophase synthesis method described here should enable the design of materials heretofore unavailable, with improved or unique properties, based upon an understanding of the physics of these new materials. 23 refs., 8 figs

Nanophase materials assembled from atomic clusters

Energy Technology Data Exchange (ETDEWEB)

Siegel, R.W.

1989-09-01

The preparation of atomic clusters of metals and ceramics by means of the gas-condensation method, followed by their in situ consolidation under high-vacuum conditions, has recently led to the synthesis of a new class of ultrafine-grained materials for which their physics is intimately coupled with their application. These nanophase materials, with 2 to 20 nm grain sizes, appear to have properties that are often rather different from conventional materials, and also processing characteristics that are greatly improved. The nanophase synthesis method described here should enable the design of materials heretofore unavailable, with improved or unique properties, based upon an understanding of the physics of these new materials. 23 refs., 8 figs.

Twenty five years of clusters -- from Bochum to Strasbourg

International Nuclear Information System (INIS)

Betts, R.R.; Chicago Univ., IL

1994-01-01

Developments in the area of clustering aspects of nuclear structure and reactions over the past twenty-five years are reviewed. The viewpoint is that the nucleus is an assembly of clusters. The question is whether clusters actually exist in the nucleus. Although there is abundant evidence for this in light nuclei, the situation for more complex clusters in heavier nuclei is much worse. Differential cross sections for scattering of alpha particles and heavy ions are shown

Effects of hyperthermal proton bombardment on alkanethiol self-assembled monolayer on Au(1 1 1)

Energy Technology Data Exchange (ETDEWEB)

Xi Luan [Surface Science Western, University of Western Ontario, London, Ontario N6A 5B7 (Canada); Zheng Zhi; Lam, N.-S. [Department of Physics, Chinese University of Hong Kong, Shatin, Hong Kong (China); Grizzi, Oscar [Centro Atomico Bariloche, 8400 San Carlos de Bariloche, Rio Negro (Argentina); Lau, W.-M. [Surface Science Western, University of Western Ontario, London, Ontario N6A 5B7 (Canada)], E-mail: llau22@uwo.ca

2007-10-31

The effects of hyperthermal proton bombardment on alkanethiol self-assembled monolayer (SAM) on Au(1 1 1) are studied with scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS). The STM and XPS results show that proton bombardment with proton energy as low as 2 eV can induce cross-linking of the adsorbed alkanethiols and transform the original ordered SAM lattice to an array of nanoclusters of the cross-linked alkanethiols. For a bombardment at 3 eV with a fluence of 3x10{sup 15} cm{sup -2}, the typical cluster size is about 5 nm. In addition, the cluster size distribution is narrow, with no cluster larger than 8 nm. The cluster growth can be promoted by increasing the fluence at a fixed bombardment energy or increasing the energy at a fixed fluence. This indicates that surface diffusion of alkanethiols and cluster growth can be harnessed by the control of the bombardment energy and fluence.

Effects of hyperthermal proton bombardment on alkanethiol self-assembled monolayer on Au(1 1 1)

International Nuclear Information System (INIS)

Xi Luan; Zheng Zhi; Lam, N.-S.; Grizzi, Oscar; Lau, W.-M.

2007-01-01

The effects of hyperthermal proton bombardment on alkanethiol self-assembled monolayer (SAM) on Au(1 1 1) are studied with scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS). The STM and XPS results show that proton bombardment with proton energy as low as 2 eV can induce cross-linking of the adsorbed alkanethiols and transform the original ordered SAM lattice to an array of nanoclusters of the cross-linked alkanethiols. For a bombardment at 3 eV with a fluence of 3x10 15 cm -2 , the typical cluster size is about 5 nm. In addition, the cluster size distribution is narrow, with no cluster larger than 8 nm. The cluster growth can be promoted by increasing the fluence at a fixed bombardment energy or increasing the energy at a fixed fluence. This indicates that surface diffusion of alkanethiols and cluster growth can be harnessed by the control of the bombardment energy and fluence

Spitzer Imaging of Planck-Herschel Dusty Proto-Clusters at z=2-3

Science.gov (United States)

Cooray, Asantha; Ma, Jingzhe; Greenslade, Joshua; Kubo, Mariko; Nayyeri, Hooshang; Clements, David; Cheng, Tai-An

2018-05-01

We have recently introduced a new proto-cluster selection technique by combing Herschel/SPIRE imaging data and Planck/HFIk all-sky survey point source catalog. These sources are identified as Planck point sources with clumps of Herschel source over-densities with far-IR colors comparable to z=0 ULIRGS redshifted to z=2 to 3. The selection is sensitive to dusty starbursts and obscured QSOs and we have recovered couple of the known proto-clusters and close to 30 new proto-clusters. The candidate proto-clusters selected from this technique have far-IR flux densities several times higher than those that are optically selected, such as using LBG selection, implying that the member galaxies are in a special phase of heightened dusty starburst and dusty QSO activity. This far-IR luminous phase may be short but likely to be necessary piece to understand the whole stellar mass assembly history of clusters. Moreover, our photo-clusters are missed in optical selections, suggesting that optically selected proto-clusters alone do not provide adequate statistics and a comparison of the far-IR and optical selected clusters may reveal the importance of the dusty stellar mass assembly. Here, we propose IRAC observations of six of the highest priority new proto-clusters, to establish the validity of the technique and to determine the total stellar mass through SED models. For a modest observing time the science program will have a substantial impact on an upcoming science topic in cosmology with implications for observations with JWST and WFIRST to understand the mass assembly in the universe.

Cluster synchronization of community network with distributed time delays via impulsive control

International Nuclear Information System (INIS)

Leng Hui; Wu Zhao-Yan

2016-01-01

Cluster synchronization is an important dynamical behavior in community networks and deserves further investigations. A community network with distributed time delays is investigated in this paper. For achieving cluster synchronization, an impulsive control scheme is introduced to design proper controllers and an adaptive strategy is adopted to make the impulsive controllers unified for different networks. Through taking advantage of the linear matrix inequality technique and constructing Lyapunov functions, some synchronization criteria with respect to the impulsive gains, instants, and system parameters without adaptive strategy are obtained and generalized to the adaptive case. Finally, numerical examples are presented to demonstrate the effectiveness of the theoretical results. (paper)

Core-control assembly with a fixed fuel support

International Nuclear Information System (INIS)

Challberg, R.C.

1993-01-01

A core-control assembly is described comprising: a control rod having a plurality of blades; a control-rod guide tube for guiding vertical motion of said control rod; a fuel support for supporting fuel bundles separated by said blades, said fuel support having an aperture conforming to a cross section of said control rod through said blades for preventing rotational movement of said control rod to a decoupling orientation when said control rod is between a maximum power position and a minimum power position, said minimum power position being above said maximum power position, said fuel support being supported by said control-rod guide tube; control-rod drive means for controlling vertical motion of said control rod, said control-rod drive means providing for vertical motion between said maximum power position and said minimum power position, said control-rod drive means providing for vertical movement to a decoupling position, said decoupling position being no lower than said minimum power position, said decoupling position being at a level sufficient to permit said control rod to rotate to a decoupling orientation relative to said fuel support; and coupling means for coupling said control rod to said control rod drive means, said coupling means being releasable by rotational movement of said control rod to said decoupling orientation relative to said control-rod drive means

Review on Control of DC Microgrids and Multiple Microgrid Clusters

DEFF Research Database (Denmark)

Meng, Lexuan; Shafiee, Qobad; Ferrari-Trecate, Giancarlo

2017-01-01

This paper performs an extensive review on control schemes and architectures applied to DC microgrids. It covers multi-layer hierarchical control schemes, coordinated control strategies, plug-and-play operations, stability and active damping aspects as well as nonlinear control algorithms....... Islanding detection, protection and microgrid clusters control are also briefly summarized. All the mentioned issues are discussed with the goal of providing control design guidelines for DC microgrids. The future research challenges, from the authors’ point of view, are also provided in the final...

Sparsity enabled cluster reduced-order models for control

Science.gov (United States)

Kaiser, Eurika; Morzyński, Marek; Daviller, Guillaume; Kutz, J. Nathan; Brunton, Bingni W.; Brunton, Steven L.

2018-01-01

Characterizing and controlling nonlinear, multi-scale phenomena are central goals in science and engineering. Cluster-based reduced-order modeling (CROM) was introduced to exploit the underlying low-dimensional dynamics of complex systems. CROM builds a data-driven discretization of the Perron-Frobenius operator, resulting in a probabilistic model for ensembles of trajectories. A key advantage of CROM is that it embeds nonlinear dynamics in a linear framework, which enables the application of standard linear techniques to the nonlinear system. CROM is typically computed on high-dimensional data; however, access to and computations on this full-state data limit the online implementation of CROM for prediction and control. Here, we address this key challenge by identifying a small subset of critical measurements to learn an efficient CROM, referred to as sparsity-enabled CROM. In particular, we leverage compressive measurements to faithfully embed the cluster geometry and preserve the probabilistic dynamics. Further, we show how to identify fewer optimized sensor locations tailored to a specific problem that outperform random measurements. Both of these sparsity-enabled sensing strategies significantly reduce the burden of data acquisition and processing for low-latency in-time estimation and control. We illustrate this unsupervised learning approach on three different high-dimensional nonlinear dynamical systems from fluids with increasing complexity, with one application in flow control. Sparsity-enabled CROM is a critical facilitator for real-time implementation on high-dimensional systems where full-state information may be inaccessible.

Sm cluster superlattice on graphene/Ir(111)

Science.gov (United States)

Mousadakos, Dimitris; Pivetta, Marina; Brune, Harald; Rusponi, Stefano

2017-12-01

We report on the first example of a self-assembled rare earth cluster superlattice. As a template, we use the moiré pattern formed by graphene on Ir(111); its lattice constant of 2.52 nm defines the interparticle distance. The samarium cluster superlattice forms for substrate temperatures during deposition ranging from 80 to 110 K, and it is stable upon annealing to 140 K. By varying the samarium coverage, the mean cluster size can be increased up to 50 atoms, without affecting the long-range order. The spatial order and the width of the cluster size distribution match the best examples of metal cluster superlattices grown by atomic beam epitaxy on template surfaces.

Control assembly ejection accident analysis for WWER-440 (Armenian NPP)

International Nuclear Information System (INIS)

Bznuni, S.; Malakyan, Ts.; Amirjanyan, A.; Ghasabyan, L.

2007-01-01

Control Assembly ejection in WWER-440 initiated by the loss of integrity of the Control Assemblies drive housing has been analyzed. This event causes a very rapid reactivity insertion to the core and small break LOCA which potentially could lead to rapid power increase and redistribution of heat release in the core resulting in a fuel, cladding and coolant temperature rise; primary pressure increase, radiological consequences due to loss of primary coolant and potential loss of cladding integrity and fuel disintegration (if applicable). Methodology of the analysis is based on conservative assumptions as well as on deterministic approach for selection of functioning logic of systems and equipment's to maximize reactor core power and minimize power decreasing reactivity feedback. Computational analyses were performed by 3D kinetics PARCS-RELAP coupled code. WWER-440 fuel cross-section libraries, diffusion coefficients and kinetics parameters were calculated by HELOS code. In this paper analysis of accident for Hot Full Power was presented. Results of analysis show that ANPP WWER-440 reactor design meets acceptance criteria prescribed for RIA type design based accidents (Authors)

Assembly and control of large microtubule complexes

Science.gov (United States)

Korolev, Kirill; Ishihara, Keisuke; Mitchison, Timothy

Motility, division, and other cellular processes require rapid assembly and disassembly of microtubule structures. We report a new mechanism for the formation of asters, radial microtubule complexes found in very large cells. The standard model of aster growth assumes elongation of a fixed number of microtubules originating from the centrosomes. However, aster morphology in this model does not scale with cell size, and we found evidence for microtubule nucleation away from centrosomes. By combining polymerization dynamics and auto-catalytic nucleation of microtubules, we developed a new biophysical model of aster growth. The model predicts an explosive transition from an aster with a steady-state radius to one that expands as a travelling wave. At the transition, microtubule density increases continuously, but aster growth rate discontinuously jumps to a nonzero value. We tested our model with biochemical perturbations in egg extract and confirmed main theoretical predictions including the jump in the growth rate. Our results show that asters can grow even though individual microtubules are short and unstable. The dynamic balance between microtubule collapse and nucleation could be a general framework for the assembly and control of large microtubule complexes. NIH GM39565; Simons Foundation 409704; Honjo International 486 Scholarship Foundation.

Control assembly materials for water reactors: Experience, performance and perspectives. Proceedings of a technical committee meeting

Energy Technology Data Exchange (ETDEWEB)

NONE

2000-02-01

The safe, reliable and economic operation of water cooled nuclear power reactors depends to a large extent upon the reliable operation of control assemblies for the regulation and shutdown of the reactors. These consist of neutron absorbing materials clad in stainless steel or zirconium based alloys, guide tubes and guide cards, and other structural components. Current designs have worked extremely well in normal conditions, but less than ideal behaviour limits the lifetimes of control materials, imposing an economic penalty which acts as a strong incentive to produce improved materials and designs that are more reliable. Neutron absorbing materials currently in use include the ceramic boron carbide, the high melting point metal hafnium and the low melting point complex alloy Ag-In-Cd. Other promising neutron absorbing materials, such as dysprosium titanate, are being evaluated in the Russian Federation. These control materials exhibit widely differing mechanical, physical and chemical properties, which must be understood in order to be able to predict the behaviour of control rod assemblies. Identification of existing failure mechanisms, end of life criteria and the implications of the gradual introduction of extended burnup, mixed oxide (MOX) fuels and more complex fuel cycles constitutes the first step in a search for improved materials and designs. In the early part of this decade, it was recognized by the International Working Group on Fuel Performance and Technology (IWGFPT) that international conferences, symposia and published reviews on the materials science aspects of control assemblies were few and far between. Consequently, the IWGFPT recommended that the IAEA should rectify this situation with a series of Technical Committee meetings (TCMs) devoted entirely to the materials aspects of reactor control assemblies. The first was held in 1993 and in the intervening five years considerable progress has been made. In bringing together experts in the

Control assembly materials for water reactors: Experience, performance and perspectives. Proceedings of a technical committee meeting

International Nuclear Information System (INIS)

2000-02-01

The safe, reliable and economic operation of water cooled nuclear power reactors depends to a large extent upon the reliable operation of control assemblies for the regulation and shutdown of the reactors. These consist of neutron absorbing materials clad in stainless steel or zirconium based alloys, guide tubes and guide cards, and other structural components. Current designs have worked extremely well in normal conditions, but less than ideal behaviour limits the lifetimes of control materials, imposing an economic penalty which acts as a strong incentive to produce improved materials and designs that are more reliable. Neutron absorbing materials currently in use include the ceramic boron carbide, the high melting point metal hafnium and the low melting point complex alloy Ag-In-Cd. Other promising neutron absorbing materials, such as dysprosium titanate, are being evaluated in the Russian Federation. These control materials exhibit widely differing mechanical, physical and chemical properties, which must be understood in order to be able to predict the behaviour of control rod assemblies. Identification of existing failure mechanisms, end of life criteria and the implications of the gradual introduction of extended burnup, mixed oxide (MOX) fuels and more complex fuel cycles constitutes the first step in a search for improved materials and designs. In the early part of this decade, it was recognized by the International Working Group on Fuel Performance and Technology (IWGFPT) that international conferences, symposia and published reviews on the materials science aspects of control assemblies were few and far between. Consequently, the IWGFPT recommended that the IAEA should rectify this situation with a series of Technical Committee meetings (TCMs) devoted entirely to the materials aspects of reactor control assemblies. The first was held in 1993 and in the intervening five years considerable progress has been made. In bringing together experts in the

Control rod cluster with removable rods for nuclear fuel assembly

International Nuclear Information System (INIS)

Denizou, J.P.

1989-01-01

For each removable control rod, the open end section of the sleeve has a certain length of reduced diameter with openings in its wall. The top end of the rod is joined to an extension tube that surrounds the shaft over part of its lenght. This extension tube fits over the reduced part of the sleeve when the shaft is screwed into the bore of the sleeve. Rotation of the rod in the sleeve is prevented by deforming the extension tube locally in the openings of the end part of the sleeve. The rod is dismantled by exerting a torque on it using a gripping area near the end of the rod [fr

Assembly of Collagen Matrices as a Phase Transition Revealed by Structural and Rheologic Studies

OpenAIRE

Forgacs, Gabor; Newman, Stuart A.; Hinner, Bernhard; Maier, Christian W.; Sackmann, Erich

2003-01-01

We have studied the structural and viscoelastic properties of assembling networks of the extracellular matrix protein type-I collagen by means of phase contrast microscopy and rotating disk rheometry. The initial stage of the assembly is a nucleation process of collagen monomers associating to randomly distributed branched clusters with extensions of several microns. Eventually a sol-gel transition takes place, which is due to the interconnection of these clusters. We analyzed this transition...

Experience feedback of operational events of the control rod assembly and its drive mechanism in nuclear power plants

International Nuclear Information System (INIS)

Zhou Hong; Xiao Zhi; Tao Shusheng; Zheng Lixin; Chen Zhaolin

2013-01-01

Seventeen operational events of the control rod assembly and its drive mechanism are collected from 1992 to 2012 important nuclear operational events and feedback in referred nuclear power plants. After investigated and classified, several important issues, such as the impact of control rod swell and fuel assembly distortion, control rod drive mechanism leakage, and the control system reliability of control rod, are emphatically analyzed. Some suggestions of experience feedback are proposed. (authors)

A study of the friction and wear processes of the structural components of fuel assemblies for water-cooled and water moderated power reactors

International Nuclear Information System (INIS)

Makarov, V.; Afanasiev, A.; Matvienko, I.; Drozdov, Y.; Puchkov, V.

2011-01-01

The friction forces affect the fuel assembly (FA) strength at all the stages of its lifecycle. The paper covers the methods and the results of the pre-irradiation experimental studies of the static and dynamic processes the friction forces are involved in. These comprise the FA assembling at the manufacturer, fuel rod flow-induced vibration and fretting-wear in the fuel rod-to-cell friction pairs, rod cluster control assembly (RCCA) movement in the FA guide tubes, FA bowing, FA loading-unloading into the core, irradiation-induced growth and thermal-mechanical fuel rod-to-spacer grid interaction. (authors)

Bi-Level Decentralized Active Power Control for Large-Scale Wind Farm Cluster

DEFF Research Database (Denmark)

Huang, Shengli; Wu, Qiuwei; Guo, Yifei

2018-01-01

This paper presents a bi-level decentralized active power control (DAPC) for a large-scale wind farm cluster, consisting of several wind farms for better active power dispatch. In the upper level, a distributed active power control scheme based on the distributed consensus is designed to achieve...... fair active power sharing among multiple wind farms, which generates the power reference for each wind farm. A distributed estimator is used to estimate the total available power of all wind farms. In the lower level, a centralized control scheme based on the Model Predictive Control (MPC) is proposed...... to regulate active power outputs of all wind turbines (WTs) within a wind farm, which reduces the fatigue loads of WTs while tracking the power reference obtained from the upper level control. A wind farm cluster with 8 wind farms and totally 160 WTs, was used to test the control performance of the proposed...

Colloidal polymers with controlled sequence and branching constructed from magnetic field assembled nanoparticles.

Science.gov (United States)

Bannwarth, Markus B; Utech, Stefanie; Ebert, Sandro; Weitz, David A; Crespy, Daniel; Landfester, Katharina

2015-03-24

The assembly of nanoparticles into polymer-like architectures is challenging and usually requires highly defined colloidal building blocks. Here, we show that the broad size-distribution of a simple dispersion of magnetic nanocolloids can be exploited to obtain various polymer-like architectures. The particles are assembled under an external magnetic field and permanently linked by thermal sintering. The remarkable variety of polymer-analogue architectures that arises from this simple process ranges from statistical and block copolymer-like sequencing to branched chains and networks. This library of architectures can be realized by controlling the sequencing of the particles and the junction points via a size-dependent self-assembly of the single building blocks.

Phytosterol-based oleogels self-assembled with monoglyceride for controlled volatile release.

Science.gov (United States)

Yang, Dan-Xia; Chen, Xiao-Wei; Yang, Xiao-Quan

2018-01-01

Oleogels have recently emerged as a subject of growing interest among industrial and academic researchers as an alternative to saturated/trans-fat and delivery of functional ingredients. Phytosterols, comprising plant-derived natural steroid compounds, are preferred for oleogel production because they are both natural and healthy. In the present study, phytosterol-based oleogels self-assembled with monoglyceride were studied with respect to tuning volatile release. Microscopy images of the bicomponent oleogels of β-sitosterol and monoglyceride showed the formation of a new three-dimensional network of entangled crystals and a controllable microstructure. Our analysis from differential scanning calorimetry and small angle X-ray scattering results suggests the self-assembly of β-sitosterol and monoglyceride via intermolecular hydrogen bonds into spherulitic microstructures. The results showed that the release rate (v 0 ), maximum headspace concentrations (C max ) and partition coefficients (k a/o ) for oleogels showed a significantly controlled release and were tunable via the microstructure of phytosterol-based oleogels under both dynamic and static conditions. In addition, the solid-like oleogels had interesting thixotropic and thermoresponsive behaviors, probably as a result of intermolecular hydrogen bonding. The self-assembly of phytosterol-based oleogels with monoglyceride was attributed to intermolecular hydrogen and is demonstrated to be a promising tunable and functional strategy for delivering flavor compounds. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

CFD Analysis of Hot Spot Fuel Temperature in the Control Fuel Block Assembly of a VHTR core

International Nuclear Information System (INIS)

Kim, Min Hwan; Tak, Nam Il; Noh, Jae Man

2010-01-01

The Very High Temperature Reactor (VHTR) dedicated for efficient hydrogen production requires core outlet temperatures of more than 950 .deg. C. As the outlet temperature increases, the thermal margin of the core decreases, which highlights the need for a detailed analysis to reduce its uncertainty. Tak et al. performed CFD analysis for a 1/12 fuel assembly model and compared the result with a simple unit-cell model in order to emphasize the need of a detailed CFD analysis for the prediction of hot spot fuel temperatures. Their CFD model, however, was focused on the standard fuel assembly but not on the control fuel assembly in which a considerable amount of bypass flow is expected to occur through the control rod passages. In this study, a CFD model for the control fuel block assembly is developed and applied for the hot spot analyses of PMR200 core. Not only the bypass flow but also the cross flow is considered in the analyses

Symmetry and topology code of the cluster self-assembly of framework MT structures of alumophosphates AlPO4(H2O)2 (metavariscite and variscite) and Al2(PO4)2(H2O)3 (APC)

Science.gov (United States)

Ilyushin, G. D.; Blatov, V. A.

2017-03-01

The supramolecular chemistry of alumophosphates, which form framework 3D MT structures from polyhedral AlO4(H2O)2 clusters with octahedral O coordination (of M polyhedra) and PO4 and AlO4 with tetrahedral O coordination (of T polyhedra), is considered. A combinatorial-topological modeling of the formation of possible types of linear (six types) and ring (two types) tetrapolyhedral cluster precursors M2T2 from MT monomers is carried out. Different versions of chain formation from linked (MT)2 rings (six types) are considered. The model, which has a universal character, has been used to simulate the cluster selfassembly of the crystal structure of AlPO4(H2O)2 minerals (metavariscite, m-VAR, and variscite, VAR) and zeolite [Al2(PO4)2(H2O)2] · H2O (APC). A tetrapolyhedral linear precursor is established for m-VAR and a ring precursor (MT)2 is established for VAR and APC. The symmetry and topology code of the processes of crystal structure self-assembly from cluster precursors is completely reconstructed. The functional role of the O-H···O hydrogen bonds is considered for the first time. The cluster self-assembly model explains the specific features of the morphogenesis of single crystals: m-VAR prisms, flattened VAR octahedra, and needleshaped APC square-base prisms.

THE REST-FRAME OPTICAL LUMINOSITY FUNCTION OF CLUSTER GALAXIES AT z < 0.8 AND THE ASSEMBLY OF THE CLUSTER RED SEQUENCE

International Nuclear Information System (INIS)

Rudnick, Gregory; Von der Linden, Anja; De Lucia, Gabriella; White, Simon; Pello, Roser; Aragon-Salamanca, Alfonso; Marchesini, Danilo; Clowe, Douglas; Halliday, Claire; Jablonka, Pascale; Milvang-Jensen, Bo; Poggianti, Bianca; Saglia, Roberto; Simard, Luc; Zaritsky, Dennis

2009-01-01

We present the rest-frame optical luminosity function (LF) of red-sequence galaxies in 16 clusters at 0.4 < z < 0.8 drawn from the ESO Distant Cluster Survey (EDisCS). We compare our clusters to an analogous sample from the Sloan Digital Sky Survey (SDSS) and match the EDisCS clusters to their most likely descendants. We measure all LFs down to M ∼ M * + (2.5-3.5). At z < 0.8, the bright end of the LF is consistent with passive evolution but there is a significant buildup of the faint end of the red sequence toward lower redshift. There is a weak dependence of the LF on cluster velocity dispersion for EDisCS but no such dependence for the SDSS clusters. We find tentative evidence that red-sequence galaxies brighter than a threshold magnitude are already in place, and that this threshold evolves to fainter magnitudes toward lower redshifts. We compare the EDisCS LFs with the LF of coeval red-sequence galaxies in the field and find that the bright end of the LFs agree. However, relative to the number of bright red galaxies, the field has more faint red galaxies than clusters at 0.6 < z < 0.8 but fewer at 0.4 < z < 0.6, implying differential evolution. We compare the total light in the EDisCS cluster red sequences to the total red-sequence light in our SDSS cluster sample. Clusters at 0.4 < z < 0.8 must increase their luminosity on the red sequence (and therefore stellar mass in red galaxies) by a factor of 1-3 by z = 0. The necessary processes that add mass to the red sequence in clusters predict local clusters that are overluminous as compared to those observed in the SDSS. The predicted cluster luminosities can be reconciled with observed local cluster luminosities by combining multiple previously known effects.

A 'quick-look' report on the THETIS 80% blocked cluster forced reflood experiments

International Nuclear Information System (INIS)

Cooper, C.A.; Pearson, K.G.

1984-01-01

A brief selection of results of forced reflooding experiments with the THETIS 80 percent blocked cluster is presented. A description of the THETIS blocked cluster test assemblies, and details of the test conditions, are given. The two forced reflooding experiments have been the subject of a blind calculation exercise with the BART code, and the results of these experiments are compared with the results from corresponding experiments with the 90 percent blocked cluster test assembly. Some general observations are made, arising from the comparison of these two series of experiments, and a qualitative explanation for the relatively complex variation of the heat transfer within the THETIS blockages is advanced. A full report on the 80 percent blocked cluster forced reflooding experiments will be available later. (U.K.)

Interactions within the yeast t-SNARE Sso1p that control SNARE complex assembly.

Science.gov (United States)

Munson, M; Chen, X; Cocina, A E; Schultz, S M; Hughson, F M

2000-10-01

In the eukaryotic secretory and endocytic pathways, transport vesicles shuttle cargo among intracellular organelles and to and from the plasma membrane. Cargo delivery entails fusion of the transport vesicle with its target, a process thought to be mediated by membrane bridging SNARE protein complexes. Temporal and spatial control of intracellular trafficking depends in part on regulating the assembly of these complexes. In vitro, SNARE assembly is inhibited by the closed conformation adopted by the syntaxin family of SNAREs. To visualize this closed conformation directly, the X-ray crystal structure of a yeast syntaxin, Sso1p, has been determined and refined to 2.1 A resolution. Mutants designed to destabilize the closed conformation exhibit accelerated rates of SNARE assembly. Our results provide insight into the mechanism of SNARE assembly and its intramolecular and intermolecular regulation.

Supramolecular Nanocomposites Under Confinement: Chiral Optically Active Nanoparticle Assemblies and Beyond

Science.gov (United States)

Bai, Peter; Yang, Sui; Bao, Wei; Salmeron, Miquel; Zhang, Xiang; Xu, Ting

2015-03-01

Block copolymer-based supramolecules provide a versatile platform to direct the self-assembly of nanoparticles (NPs) into precisely controlled nanostructures in bulk and thin film geometries. A supramolecule, PS-b-P4VP(PDP), composed of the small molecule 3-pentadecylphenol (PDP) hydrogen bonded to a diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), was subjected to 2-D volume confinement in cylindrical anodic aluminum oxide (AAO) membrane pores. TEM and 3-D TEM tomography reveal that the morphologies accessible by the supramolecule and supramolecule/NP composites, such as NP clusters, arrays, stacked rings, and single and double helical ribbons, are significantly different from those in the bulk or thin film. Furthermore, single molecule dark field scattering measurements demonstrate strong chiral optical response of single helical Au NP ribbon nanostructures in the near infrared wavelength regime. These studies demonstrate 2-D confinement to be an effective means to tailor self-assembled NP structure within supramolecule nanocomposites and pave the way for this assembly approach to be applied towards next generation chiral metamaterials and optoelectronic devices.

Assembly and Breakup of Supercontinents -42 ...

Indian Academy of Sciences (India)

ABRoy. The history of earth is replete with the story of assembly and break up of continental blocks. More than 180 million years ago, all the continental blocks were clustered into one supercontinental framework, called the Pangea, surrounded by a single ocean. New evidence cropped up recently which indicated existence ...

Toward demonstrating controlled-X operation based on continuous-variable four-partite cluster states and quantum teleporters

International Nuclear Information System (INIS)

Wang Yu; Su Xiaolong; Shen Heng; Tan Aihong; Xie Changde; Peng Kunchi

2010-01-01

One-way quantum computation based on measurement and multipartite cluster entanglement offers the ability to perform a variety of unitary operations only through different choices of measurement bases. Here we present an experimental study toward demonstrating the controlled-X operation, a two-mode gate in which continuous variable (CV) four-partite cluster states of optical modes are utilized. Two quantum teleportation elements are used for achieving the gate operation of the quantum state transformation from input target and control states to output states. By means of the optical cluster state prepared off-line, the homodyne detection and electronic feeding forward, the information carried by the input control state is transformed to the output target state. The presented scheme of the controlled-X operation based on teleportation can be implemented nonlocally and deterministically. The distortion of the quantum information resulting from the imperfect cluster entanglement is estimated with the fidelity.

Controllable Self-Assembly of Amphiphilic Zwitterionic PBI Towards Tunable Surface Wettability of the Nanostructures.

Science.gov (United States)

Ye, Yong; Lü, Baozhong; Cheng, Wenyu; Wu, Zhen; Wei, Jie; Yin, Meizhen

2017-05-04

Amphiphilic molecules have received wide attention as they possess both hydrophobic and hydrophilic properties, and can form diverse nanostructures in selective solvents. Herein, we report an asymmetric amphiphilic zwitterionic perylene bisimide (AZP) with an octyl chain and a zwitterionic group on the opposite imide positions of perylene tetracarboxylic dianhydride. The controllable nanostructures of AZP with tunable hydrophilic/hydrophobic surface have been investigated through solvent-dependent amphiphilic self-assembly as confirmed by SEM, TEM, and contact angle measurements. The planar perylene core of AZP contributes to strong π-π stacking, while the amphiphilic balance of asymmetric AZP adjusts the self-assembly property. Additionally, due to intermolecular π-π stacking and solvent-solute interactions, AZP could self-assemble into hydrophilic microtubes in a polar solvent (acetone) and hydrophobic nanofibers in an apolar solvent (hexane). This facile method provides a new pathway for controlling the surface properties based on an asymmetric amphiphilic zwitterionic perylene bisimide. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical tests of the bolt of the gripper latch on the control rod cluster

International Nuclear Information System (INIS)

Lemaire, E.; Couet, D.; Molinie, D.; Grandjean, Y.; Radat, M.P.; Guttmann, D.

1998-01-01

Failure analysis and mechanical testing indicate that control rod drive mechanisms malfunctioning by 1995-96 is due to rupture by fatigue of a bolt inside the stationary gripper assembly. Fatigue is enhanced by free working following surface adaptation and unscrewing of the assembly. These results are taken into account for the choice of a new anti-rotation device. (authors)

Controlling Self-Assembly in Al(110) Homoepitaxy

Science.gov (United States)

Tiwary, Yogesh; Fichthorn, Kristen

2010-03-01

Homoepitaxial growth on Al(110) exhibits nanoscale self-assembly into huts with well-defined (100) and (111) facets [1]. Although some of the diffusion mechanisms underlying this kinetic self-assembly were identified and incorporated into a two-dimensional model [2], we used density-functional theory (DFT) to identify many other mechanisms that are needed to describe the three-dimensional assembly seen experimentally [3]. We developed a three-dimensional kinetic Monte Carlo (KMC) model of Al(110) homoepitaxy. The inputs to the model were obtained from DFT [3,4]. Our model is in agreement with experimentally observed trends for this system. We used KMC to predict self-assembly under various growth conditions. To achieve precise placement of Al nanohuts, we simulated thermal-field-directed assembly [5]. Our results indicate that this technique can be used to create uniform arrays of nanostructures. [1] F. Buatier de Mongeot, W. Zhu, A. Molle, R. Buzio, C. Boragno, U. Valbusa, E. Wang, and Z. Zhang, Phys. Rev. Lett. 91, 016102 (2003). [2] W. Zhu, F. Buatier de Mongeot, U. Valbusa, E. G. Wang, and Z. Y. Zhang, Phys. Rev. Lett. 92, 106102 (2004). [3] Y. Tiwary and K. A. Fichthorn, submitted to Phys. Rev. B. [4] Y. Tiwary and K. A. Fichthorn, Phys. Rev. B 78, 205418 (2008). [5] C. Zhang and R. Kalyanaraman, Appl. Phys. Lett. 83, 4827 (2003).

Systems and methods for creation of conducting networks of magnetic particles through dynamic self-assembly process

Science.gov (United States)

Snezhko, Oleksiy [Woodridge, IL; Aronson, Igor [Darien, IL; Kwok, Wai-Kwong [Downers Grove, IL

2011-01-25

Self-assembly of magnetic microparticles in AC magnetic fields. Excitation of the system by an AC magnetic field provides a variety of patterns that can be controlled by adjusting the frequency and the amplitude of the field. At low particle densities the low-frequency magnetic excitation favors cluster phase formation, while high frequency excitation favors chains and netlike structures. For denser configurations, an abrupt transition to the network phase was obtained.

CRAB-II: a computer program to predict hydraulics and scram dynamics of LMFBR control assemblies and its validation

International Nuclear Information System (INIS)

Carelli, M.D.; Baker, L.A.; Willis, J.M.; Engel, F.C.; Nee, D.Y.

1982-01-01

This paper presents an analytical method, the computer code CRAB-II, which calculates the hydraulics and scram dynamics of LMFBR control assemblies of the rod bundle type and its validation against prototypic data obtained for the Clinch River Breeder Reactor (CRBR) primary control assemblies. The physical-mathematical model of the code is presented, followed by a description of the testing of prototypic CRBR control assemblies in water and sodium to characterize, respectively, their hydraulic and scram dynamics behavior. Comparison of code predictions against the experimental data are presened in detail; excellent agreement was found. Also reported are experimental data and empirical correlations for the friction factor of the absorber bundle in the entire flow range (laminar to turbulent) which represent an extension of the state-of-the-art, since only fuel and blanket assemblies friction factor correlations were previously reported in the open literature

Cysteine 295 indirectly affects Ni coordination of carbon monoxide dehydrogenase-II C-cluster

Energy Technology Data Exchange (ETDEWEB)

Inoue, Takahiro; Takao, Kyosuke; Yoshida, Takashi [Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502 (Japan); Wada, Kei [Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-1692 (Japan); Daifuku, Takashi; Yoneda, Yasuko [Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502 (Japan); Fukuyama, Keiichi [Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Sako, Yoshihiko, E-mail: sako@kais.kyoto-u.ac.jp [Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502 (Japan)

2013-11-08

Highlights: •CODH-II harbors a unique [Ni-Fe-S] cluster. •We substituted the ligand residues of Cys{sup 295} and His{sup 261}. •Dramatic decreases in Ni content upon substitutions were observed. •All substitutions did not affect Fe-S clusters assembly. •CO oxidation activity was decreased by the substitutions. -- Abstract: A unique [Ni–Fe–S] cluster (C-cluster) constitutes the active center of Ni-containing carbon monoxide dehydrogenases (CODHs). His{sup 261}, which coordinates one of the Fe atoms with Cys{sup 295}, is suggested to be the only residue required for Ni coordination in the C-cluster. To evaluate the role of Cys{sup 295}, we constructed CODH-II variants. Ala substitution for the Cys{sup 295} substitution resulted in the decrease of Ni content and didn’t result in major change of Fe content. In addition, the substitution had no effect on the ability to assemble a full complement of [Fe–S] clusters. This strongly suggests Cys{sup 295} indirectly and His{sup 261} together affect Ni-coordination in the C-cluster.

Cysteine 295 indirectly affects Ni coordination of carbon monoxide dehydrogenase-II C-cluster

International Nuclear Information System (INIS)

Inoue, Takahiro; Takao, Kyosuke; Yoshida, Takashi; Wada, Kei; Daifuku, Takashi; Yoneda, Yasuko; Fukuyama, Keiichi; Sako, Yoshihiko

2013-01-01

Highlights: •CODH-II harbors a unique [Ni-Fe-S] cluster. •We substituted the ligand residues of Cys 295 and His 261 . •Dramatic decreases in Ni content upon substitutions were observed. •All substitutions did not affect Fe-S clusters assembly. •CO oxidation activity was decreased by the substitutions. -- Abstract: A unique [Ni–Fe–S] cluster (C-cluster) constitutes the active center of Ni-containing carbon monoxide dehydrogenases (CODHs). His 261 , which coordinates one of the Fe atoms with Cys 295 , is suggested to be the only residue required for Ni coordination in the C-cluster. To evaluate the role of Cys 295 , we constructed CODH-II variants. Ala substitution for the Cys 295 substitution resulted in the decrease of Ni content and didn’t result in major change of Fe content. In addition, the substitution had no effect on the ability to assemble a full complement of [Fe–S] clusters. This strongly suggests Cys 295 indirectly and His 261 together affect Ni-coordination in the C-cluster

Large-scale parallel genome assembler over cloud computing environment.

Science.gov (United States)

Das, Arghya Kusum; Koppa, Praveen Kumar; Goswami, Sayan; Platania, Richard; Park, Seung-Jong

2017-06-01

The size of high throughput DNA sequencing data has already reached the terabyte scale. To manage this huge volume of data, many downstream sequencing applications started using locality-based computing over different cloud infrastructures to take advantage of elastic (pay as you go) resources at a lower cost. However, the locality-based programming model (e.g. MapReduce) is relatively new. Consequently, developing scalable data-intensive bioinformatics applications using this model and understanding the hardware environment that these applications require for good performance, both require further research. In this paper, we present a de Bruijn graph oriented Parallel Giraph-based Genome Assembler (GiGA), as well as the hardware platform required for its optimal performance. GiGA uses the power of Hadoop (MapReduce) and Giraph (large-scale graph analysis) to achieve high scalability over hundreds of compute nodes by collocating the computation and data. GiGA achieves significantly higher scalability with competitive assembly quality compared to contemporary parallel assemblers (e.g. ABySS and Contrail) over traditional HPC cluster. Moreover, we show that the performance of GiGA is significantly improved by using an SSD-based private cloud infrastructure over traditional HPC cluster. We observe that the performance of GiGA on 256 cores of this SSD-based cloud infrastructure closely matches that of 512 cores of traditional HPC cluster.

Simultaneous gains tuning in boiler/turbine PID-based controller clusters using iterative feedback tuning methodology.

Science.gov (United States)

Zhang, Shu; Taft, Cyrus W; Bentsman, Joseph; Hussey, Aaron; Petrus, Bryan

2012-09-01

Tuning a complex multi-loop PID based control system requires considerable experience. In today's power industry the number of available qualified tuners is dwindling and there is a great need for better tuning tools to maintain and improve the performance of complex multivariable processes. Multi-loop PID tuning is the procedure for the online tuning of a cluster of PID controllers operating in a closed loop with a multivariable process. This paper presents the first application of the simultaneous tuning technique to the multi-input-multi-output (MIMO) PID based nonlinear controller in the power plant control context, with the closed-loop system consisting of a MIMO nonlinear boiler/turbine model and a nonlinear cluster of six PID-type controllers. Although simplified, the dynamics and cross-coupling of the process and the PID cluster are similar to those used in a real power plant. The particular technique selected, iterative feedback tuning (IFT), utilizes the linearized version of the PID cluster for signal conditioning, but the data collection and tuning is carried out on the full nonlinear closed-loop system. Based on the figure of merit for the control system performance, the IFT is shown to deliver performance favorably comparable to that attained through the empirical tuning carried out by an experienced control engineer. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Optically controlled three-dimensional assembly of microfabricated building blocks

DEFF Research Database (Denmark)

Rodrigo, Peter John; Kelemen, Lorand; Palima, Darwin

2009-01-01

We demonstrate a system for constructing reconfigurable microstructures using multiple, real-time configurable counterpropagating-beam traps. We optically assemble geometrically complementary microstructures with complex three-dimensional (3D) topologies produced by two-photon polymerization....... This demonstrates utilization of controllable 3D optical traps for building hierarchical structures from microfabricated building blocks. Optical microassembly with translational and tip-tilt control in 3D achieved by dynamic multiple CB traps can potentially facilitate the construction of functional microdevices...... and may also lead to the future realization of optically actuated micromachines. Fabricating morphologically complex microstructures and then optically manipulating these archetypal building blocks can also be used to construct reconfigurable microenvironments that can aid in understanding cellular...

Coordinated Voltage Control in Offshore HVDC Connected Cluster of Wind Power Plants

DEFF Research Database (Denmark)

Sakamuri, Jayachandra N.; Rather, Zakir Hussain; Rimez, Johan

2016-01-01

This paper presents a coordinated voltage control scheme (CVCS) for a cluster of offshore wind power plants (OWPPs) connected to a VSC HVDC system. The primary control point of the proposed voltage control scheme is the introduced Pilot bus, which is having the highest short circuit capacity...... in the offshore AC grid. The developed CVCS comprehends an optimization algorithm, aiming for minimum active power losses in the offshore grid, to generate voltage reference to the Pilot bus. During steady state operation, the Pilot bus voltage is controlled by dispatching reactive power references to each wind...... turbine (WT) in the WPP cluster based on their available reactive power margin and network sensitivity based participation factors, which are derived from the dV/dQ sensitivity of a WT bus w.r.t the Pilot bus. This method leads to minimization of the risk of undesired effects, particularly overvoltage...

Controlled AFM manipulation of small nanoparticles and assembly of hybrid nanostructures

International Nuclear Information System (INIS)

Kim, Suenne; Shafiei, Farbod; Ratchford, Daniel; Li Xiaoqin

2011-01-01

We demonstrate controlled manipulation of semiconductor and metallic nanoparticles (NPs) with 5-15 nm diameters and assemble these NPs into hybrid structures. The manipulation is accomplished under ambient environment using a commercial atomic force microscope (AFM). There are particular difficulties associated with manipulating NPs this small. In addition to spatial drift, the shape of an asymmetric AFM tip has to be taken into account in order to understand the intended and actual manipulation results. Furthermore, small NPs often attach to the tip via electrostatic interaction and modify the effective tip shape. We suggest a method for detaching the NPs by performing a pseudo-manipulation step. Finally, we show by example the ability to assemble these small NPs into prototypical hybrid nanostructures with well-defined composition and geometry.

Analysis of subcritical control rod worth measurements in assembly BZB/3

International Nuclear Information System (INIS)

Giese, H.

1981-07-01

A series of subcritical absorber array measurements was performed in version three of the BIZET assembly BZB in order to check the ability of standard reactor computational codes used by the BIZET participants in predicting control rod worths in large fast reactors. Assembly BZB/3 was a two-zone core with a diameter of about 2.5 m and a core height of 0.89 m, fuelled with plutonium. Fifteen control rod positions and twelve secondary shutdown rod positions were simulated in the core. The measurements comprised the insertion of single absorbers as well as various groups of absorbers and were based on the modified source multiplication method. The KfK analysis was confined to the calculation of eigenvalues for different absorber arrays, also with a view to a comparison with the results of a former BZA evaluation with calculation-to-experiment values of up to C/E ∼ 1.10. The C/E-values found for BZB/3 ranged from 1.02 to 1.10 and did not show a systematic variation at different radial positions or different degrees of absorber asymmetry

Self-Assembled Gold Nano-Ripple Formation by Gas Cluster Ion Beam Bombardment.

Science.gov (United States)

Tilakaratne, Buddhi P; Chen, Quark Y; Chu, Wei-Kan

2017-09-08

In this study, we used a 30 keV argon cluster ion beam bombardment to investigate the dynamic processes during nano-ripple formation on gold surfaces. Atomic force microscope analysis shows that the gold surface has maximum roughness at an incident angle of 60° from the surface normal; moreover, at this angle, and for an applied fluence of 3 × 10 16 clusters/cm², the aspect ratio of the nano-ripple pattern is in the range of ~50%. Rutherford backscattering spectrometry analysis reveals a formation of a surface gradient due to prolonged gas cluster ion bombardment, although the surface roughness remains consistent throughout the bombarded surface area. As a result, significant mass redistribution is triggered by gas cluster ion beam bombardment at room temperature. Where mass redistribution is responsible for nano-ripple formation, the surface erosion process refines the formed nano-ripple structures.

Photo-crosslinking induced geometric restriction controls the self-assembly of diphenylalanine based peptides

International Nuclear Information System (INIS)

Tie Zuoxiu; Qin Meng; Zou Dawei; Cao Yi; Wang Wei

2011-01-01

The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π-π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive 'smart' materials. (authors)

Role of the HSPA9/HSC20 chaperone pair in promoting directional human iron-sulfur cluster exchange involving monothiol glutaredoxin 5.

Science.gov (United States)

Olive, Joshua A; Cowan, J A

2018-07-01

Iron‑sulfur clusters are essential cofactors found across all domains of life. Their assembly and transfer are accomplished by highly conserved protein complexes and partners. In eukaryotes a [2Fe-2S] cluster is first assembled in the mitochondria on the iron‑sulfur cluster scaffold protein ISCU in tandem with iron, sulfide, and electron donors. Current models suggest that a chaperone pair interacts with a cluster-bound ISCU to facilitate cluster transfer to a monothiol glutaredoxin. In humans this protein is glutaredoxin 5 (GLRX5) and the cluster can then be exchanged with a variety of target apo proteins. By use of circular dichroism spectroscopy, the kinetics of cluster exchange reactivity has been evaluated for human GLRX5 with a variety of cluster donor and acceptor partners, and the role of chaperones determined for several of these. In contrast to the prokaryotic model, where heat-shock type chaperone proteins HscA and HscB are required for successful and efficient transfer of a [2Fe-2S] cluster from the ISCU scaffold to a monothiol glutaredoxin. However, in the human system the chaperone homologs, HSPA9 and HSC20, are not necessary for human ISCU to promote cluster transfer to GLRX5, and appear to promote the reverse transfer. Cluster exchange with the human iron‑sulfur cluster carrier protein NFU1 and ferredoxins (FDX's), and the role of chaperones, has also been evaluated, demonstrating in certain cases control over the directionality of cluster transfer. In contrast to other prokaryotic and eukaryotic organisms, NFU1 is identified as a more likely physiological donor of [2Fe-2S] cluster to human GLRX5 than ISCU. Copyright © 2018 Elsevier Inc. All rights reserved.

Programming Hierarchical Self-Assembly of Patchy Particles into Colloidal Crystals via Colloidal Molecules.

Science.gov (United States)

Morphew, Daniel; Shaw, James; Avins, Christopher; Chakrabarti, Dwaipayan

2018-03-27

Colloidal self-assembly is a promising bottom-up route to a wide variety of three-dimensional structures, from clusters to crystals. Programming hierarchical self-assembly of colloidal building blocks, which can give rise to structures ordered at multiple levels to rival biological complexity, poses a multiscale design problem. Here we explore a generic design principle that exploits a hierarchy of interaction strengths and employ this design principle in computer simulations to demonstrate the hierarchical self-assembly of triblock patchy colloidal particles into two distinct colloidal crystals. We obtain cubic diamond and body-centered cubic crystals via distinct clusters of uniform size and shape, namely, tetrahedra and octahedra, respectively. Such a conceptual design framework has the potential to reliably encode hierarchical self-assembly of colloidal particles into a high level of sophistication. Moreover, the design framework underpins a bottom-up route to cubic diamond colloidal crystals, which have remained elusive despite being much sought after for their attractive photonic applications.

Wave propagation visualization in an experimental model for a control rod drive mechanism assembly

International Nuclear Information System (INIS)

Lee, Jung-Ryul; Jeong, Hyomi; Kong, Churl-Won

2011-01-01

Highlights: → We fabricate a full-scale mock-up of the control rod drive mechanism (CRDM) assembly in the upper reactor head of the nuclear power plant. → An ultrasonic propagation imaging method using a scanning laser ultrasonic generator is proposed to visualize and simulate ultrasonic wave propagation around the CRDM assembly. → The ultrasonic source location and frequency are simulated by changing the sensor location and the band pass-filtering zone. → The ultrasonic propagation patterns before and after cracks in the weld and nozzle of the CRDM assembly are analyzed. - Abstract: Nondestructive inspection techniques such as ultrasonic testing, eddy current testing, and visual testing are being developed to detect primary water stress corrosion cracks in control rod drive mechanism (CRDM) assemblies of nuclear power plants. A unit CRDM assembly consists of a reactor upper head including cladding, a penetration nozzle, and J-groove dissimilar metal welds with buttering. In this study, we fabricated a full-scale CRDM assembly mock-up. An ultrasonic propagation imaging (UPI) method using a scanning laser ultrasonic generator is proposed to visualize and simulate ultrasonic wave propagation around the thick and complex CRDM assembly. First, the proposed laser UPI system was validated for a simple aluminium plate by comparing the ultrasonic wave propagation movie (UWPM) obtained using the system with numerical simulation results reported in the literature. Lamb wave mode identification and damage detectability, depending on the ultrasonic frequency, were also included in the UWPM analysis. A CRDM assembly mock-up was fabricated in full-size and its vertical cross section was scanned using the laser UPI system to investigate the propagation characteristics of the longitudinal and Rayleigh waves in the complex structure. The ultrasonic source location and frequency were easily simulated by changing the sensor location and the band pass filtering zone

Fibroblast Cluster Formation on 3D Collagen Matrices Requires Cell Contraction-Dependent Fibronectin Matrix Organization

Science.gov (United States)

da Rocha-Azevedo, Bruno; Ho, Chin-Han; Grinnell, Frederick

2012-01-01

Fibroblasts incubated on 3D collagen matrices in serum or lysophosphatidic acid (LPA)-containing medium self-organize into clusters through a mechanism that requires cell contraction. However, in platelet-derived growth factor (PDGF)-containing medium, cells migrate as individuals and do not form clusters even though they constantly encounter each other. Here, we present evidence that a required function of cell contraction in clustering is formation of fibronectin fibrillar matrix. We found that in serum or LPA but not in PDGF or basal medium, cells organized FN (both serum and cellular) into a fibrillar, detergent-insoluble matrix. Cell clusters developed concomitant with FN matrix formation. FN fibrils accumulated beneath cells and along the borders of cell clusters in regions of cell-matrix tension. Blocking Rho kinase or myosin II activity prevented FN matrix assembly and cell clustering. Using siRNA silencing and function-blocking antibodies and peptides, we found that cell clustering and FN matrix assembly required α5β1 integrins and fibronectin. Cells were still able to exert contractile force and compact the collagen matrix under the latter conditions, which showed that contraction was not sufficient for cell clustering to occur. Our findings provide new insights into how procontractile (serum/LPA) and promigratory (PDGF) growth factor environments can differentially regulate FN matrix assembly by fibroblasts interacting with collagen matrices and thereby influence mesenchymal cell morphogenetic behavior under physiologic circumstances such as wound repair, morphogenesis and malignancy. PMID:23117111

Fibroblast cluster formation on 3D collagen matrices requires cell contraction dependent fibronectin matrix organization.

Science.gov (United States)

da Rocha-Azevedo, Bruno; Ho, Chin-Han; Grinnell, Frederick

2013-02-15

Fibroblasts incubated on 3D collagen matrices in serum or lysophosphatidic acid (LPA)-containing medium self-organize into clusters through a mechanism that requires cell contraction. However, in platelet-derived growth factor (PDGF)-containing medium, cells migrate as individuals and do not form clusters even though they constantly encounter each other. Here, we present evidence that a required function of cell contraction in clustering is formation of fibronectin (FN) fibrillar matrix. We found that in serum or LPA but not in PDGF or basal medium, cells organized FN (both serum and cellular) into a fibrillar, detergent-insoluble matrix. Cell clusters developed concomitant with FN matrix formation. FN fibrils accumulated beneath cells and along the borders of cell clusters in regions of cell-matrix tension. Blocking Rho kinase or myosin II activity prevented FN matrix assembly and cell clustering. Using siRNA silencing and function-blocking antibodies and peptides, we found that cell clustering and FN matrix assembly required α5β1 integrins and fibronectin. Cells were still able to exert contractile force and compact the collagen matrix under the latter conditions, which showed that contraction was not sufficient for cell clustering to occur. Our findings provide new insights into how procontractile (serum/LPA) and promigratory (PDGF) growth factor environments can differentially regulate FN matrix assembly by fibroblasts interacting with collagen matrices and thereby influence mesenchymal cell morphogenetic behavior under physiologic circumstances such as wound repair, morphogenesis and malignancy. Copyright © 2012 Elsevier Inc. All rights reserved.

Rigid Biopolymer Nanocrystal Systems for Controlling Multicomponent Nanoparticle Assembly and Orientation in Thin Film Solar Cells

Energy Technology Data Exchange (ETDEWEB)

Cha, Jennifer [Univ. of Colorado, Boulder, CO (United States)

2016-10-31

We have discovered techniques to synthesize well-defined DN conjugated nanostructures that are stable in a wide variety of conditions needed for DNA mediated assembly. Starting from this, we have shown that DNA can be used to control the assembly and integration of semiconductor nanocrystals into thin film devices that show photovoltaic effects.

FPGA cluster for high-performance AO real-time control system

Science.gov (United States)

Geng, Deli; Goodsell, Stephen J.; Basden, Alastair G.; Dipper, Nigel A.; Myers, Richard M.; Saunter, Chris D.

2006-06-01

Whilst the high throughput and low latency requirements for the next generation AO real-time control systems have posed a significant challenge to von Neumann architecture processor systems, the Field Programmable Gate Array (FPGA) has emerged as a long term solution with high performance on throughput and excellent predictability on latency. Moreover, FPGA devices have highly capable programmable interfacing, which lead to more highly integrated system. Nevertheless, a single FPGA is still not enough: multiple FPGA devices need to be clustered to perform the required subaperture processing and the reconstruction computation. In an AO real-time control system, the memory bandwidth is often the bottleneck of the system, simply because a vast amount of supporting data, e.g. pixel calibration maps and the reconstruction matrix, need to be accessed within a short period. The cluster, as a general computing architecture, has excellent scalability in processing throughput, memory bandwidth, memory capacity, and communication bandwidth. Problems, such as task distribution, node communication, system verification, are discussed.

Development of Mathematical Model and Analysis Code for Estimating Drop Behavior of the Control Rod Assembly in the Sodium Cooled Fast Reactor

International Nuclear Information System (INIS)

Oh, Se-Hong; Kang, SeungHoon; Choi, Choengryul; Yoon, Kyung Ho; Cheon, Jin Sik

2016-01-01

On receiving the scram signal, the control rod assemblies are released to fall into the reactor core by its weight. Thus drop time and falling velocity of the control rod assembly must be estimated for the safety evaluation. There are three typical ways to estimate the drop behavior of the control rod assembly in scram action: Experimental, numerical and theoretical methods. But experimental and numerical(CFD) method require a lot of cost and time. Thus, these methods are difficult to apply to the initial design process. In this study, mathematical model and theoretical analysis code have been developed in order to estimate drop behavior of the control rod assembly to provide the underlying data for the design optimization. Mathematical model and theoretical analysis code have been developed in order to estimate drop behavior of the control rod assembly to provide the underlying data for the design optimization. A simplified control rod assembly model is considered to minimize the uncertainty in the development process. And the hydraulic circuit analysis technique is adopted to evaluate the internal/external flow distribution of the control rod assembly. Finally, the theoretical analysis code(named as HEXCON) has been developed based on the mathematical model. To verify the reliability of the developed code, CFD analysis has been conducted. And a calculation using the developed analysis code was carried out under the same condition, and both results were compared

Height control of self-assembled quantum dots by strain engineering during capping

NARCIS (Netherlands)

Grossi, D.; Smereka, P.; Keizer, J.G.; Ulloa, J.M.; Koenraad, P.M.

2014-01-01

Strain engineering during the capping of III-V quantum dots has been explored as a means to control the height of strained self-assembled quantum dots. Results of Kinetic Monte Carlo simulations are confronted with cross-sectional Scanning Tunnel Microscopy (STM) measurements performed on InAs

The nature of assembly bias - III. Observational properties

Science.gov (United States)

Lacerna, Ivan; Padilla, Nelson; Stasyszyn, Federico

2014-10-01

We analyse galaxies in groups in the Sloan Digital Sky Survey (SDSS) and find a weak but significant assembly-type bias, where old central galaxies have a higher clustering amplitude (61 ± 9 per cent) at scales >1 h-1 Mpc than young central galaxies of equal host halo mass (Mh ˜ 1011.8 h- 1 M⊙). The observational sample is volume limited out to z = 0.1 with Mr - 5 log (h) ≤ -19.6. We construct a mock catalogue of galaxies that shows a similar signal of assembly bias (46 ± 9 per cent) at the same halo mass. We then adapt the model presented by Lacerna & Padilla (Paper I) to redefine the overdensity peak height, which traces the assembly bias such that galaxies in equal density peaks show the same clustering regardless of their stellar age, but this time using observational features such as a flux limit. The proxy for peak height, which is proposed as a better alternative than the virial mass, consists in the total mass given by the mass of neighbour host haloes in cylinders centred at each central galaxy. The radius of the cylinder is parameterized as a function of stellar age and virial mass. The best-fitting sets of parameters that make the assembly bias signal lower than 5-15 per cent for both SDSS and mock central galaxies are similar. The idea behind the parameterization is not to minimize the bias, but it is to use this method to understand the physical features that produce the assembly bias effect. Even though the tracers of the density field used here differ significantly from those used in Paper I, our analysis of the simulated catalogue indicates that the different tracers produce correlated proxies, and therefore the reason behind assembly bias is the crowding of peaks in both simulations and the SDSS.

Self-assembly and speed distributions of active granular particles

Science.gov (United States)

Sánchez, R.; Díaz-Leyva, P.

2018-06-01

The relationship between the dynamics of self-propelled systems and the self-assembly of structured clusters are studied via the experimental speed distributions of submonolayers of self-propelled granular particles. A distribution developed for non-self-propelled granular particles describes the speed distributions remarkably well, despite some of the assumptions behind its original derivation not being applicable. This is explained in terms of clustering and dissipation being the key phenomena governing this regime.

Bottom-up strategies for the assembling of magnetic systems using nanoclusters

Science.gov (United States)

Dupuis, V.; Hillion, A.; Robert, A.; Loiselet, O.; Khadra, G.; Capiod, P.; Albin, C.; Boisron, O.; Le Roy, D.; Bardotti, L.; Tournus, F.; Tamion, A.

2018-05-01

In the frame of the 20th Anniversary of the Journal of Nanoparticle Research (JNR), our aim is to start from the historical context 20 years ago and to give some recent results and perspectives concerning nanomagnets prepared from clusters preformed in the gas phase using the low-energy cluster beam deposition (LECBD) technique. In this paper, we focus our attention on the typical case of Co clusters embedded in various matrices to study interface magnetic anisotropy and magnetic interactions as a function of volume concentrations, and on still current and perspectives through two examples of binary metallic 3d-5d TM (namely CoPt and FeAu) cluster assemblies to illustrate size-related and nanoalloy phenomena on magnetic properties in well-defined mass-selected clusters. The structural and magnetic properties of these cluster assemblies were investigated using various experimental techniques that include high-resolution transmission electron microscopy (HRTEM), superconducting quantum interference device (SQUID) magnetometry, and synchrotron techniques such as extended X-ray absorption fine structure (EXAFS) and X-ray magnetic circular dichroism (XMCD). Depending on the chemical nature of both NPs and matrix, we observe different magnetic responses compared to their bulk counterparts. In particular, we show how finite size effects (size reduction) enhance their magnetic moment and how specific relaxation in nanoalloys can impact their magnetic anisotropy.

Controllable irregular melting induced by atomic segregation in bimetallic clusters with fabricating different initial configurations

International Nuclear Information System (INIS)

Li Guojian; Liu Tie; Wang Qiang; Lue Xiao; Wang Kai; He Jicheng

2010-01-01

The melting process of Co, Co-Cu and Co-Ni clusters with different initial configurations is studied in molecular dynamics by a general embedded atom method. An irregular melting, at which energy decreases as the temperature increase near the melting point, is found in the onion-like Co-Cu-Co clusters, but not in the mixed Co-Cu and onion-like Co-Ni-Co clusters. From the analysis of atomic distributions and energy variation, the results indicate the irregular melting is induced by Cu atomic segregation. Furthermore, this melting can be controlled by doping hetero atoms with different surface energies and controlling their distributions.

COMPACT STELLAR BINARY ASSEMBLY IN THE FIRST NUCLEAR STAR CLUSTERS AND r-PROCESS SYNTHESIS IN THE EARLY UNIVERSE

International Nuclear Information System (INIS)

Ramirez-Ruiz, Enrico; MacLeod, Morgan; Trenti, Michele; Roberts, Luke F.; Lee, William H.; Saladino-Rosas, Martha I.

2015-01-01

Investigations of elemental abundances in the ancient and most metal deficient stars are extremely important because they serve as tests of variable nucleosynthesis pathways and can provide critical inferences of the type of stars that lived and died before them. The presence of r-process elements in a handful of carbon-enhanced metal-poor (CEMP-r) stars, which are assumed to be closely connected to the chemical yield from the first stars, is hard to reconcile with standard neutron star mergers. Here we show that the production rate of dynamically assembled compact binaries in high-z nuclear star clusters can attain a sufficient high value to be a potential viable source of heavy r-process material in CEMP-r stars. The predicted frequency of such events in the early Galaxy, much lower than the frequency of Type II supernovae but with significantly higher mass ejected per event, can naturally lead to a high level of scatter of Eu as observed in CEMP-r stars

COMPACT STELLAR BINARY ASSEMBLY IN THE FIRST NUCLEAR STAR CLUSTERS AND r-PROCESS SYNTHESIS IN THE EARLY UNIVERSE

Energy Technology Data Exchange (ETDEWEB)

Ramirez-Ruiz, Enrico; MacLeod, Morgan [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Trenti, Michele [Kavli Institute for Cosmology and Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Roberts, Luke F. [TAPIR, California Institute of Technology, Pasadena, California 91125 (United States); Lee, William H.; Saladino-Rosas, Martha I. [Instituto de Astronomía, Universidad Nacional Autónoma de México, México DF 04510, México (Mexico)

2015-04-01

Investigations of elemental abundances in the ancient and most metal deficient stars are extremely important because they serve as tests of variable nucleosynthesis pathways and can provide critical inferences of the type of stars that lived and died before them. The presence of r-process elements in a handful of carbon-enhanced metal-poor (CEMP-r) stars, which are assumed to be closely connected to the chemical yield from the first stars, is hard to reconcile with standard neutron star mergers. Here we show that the production rate of dynamically assembled compact binaries in high-z nuclear star clusters can attain a sufficient high value to be a potential viable source of heavy r-process material in CEMP-r stars. The predicted frequency of such events in the early Galaxy, much lower than the frequency of Type II supernovae but with significantly higher mass ejected per event, can naturally lead to a high level of scatter of Eu as observed in CEMP-r stars.

Control of Phlebotomus argentipes (Diptera: Psychodidae sand fly in Bangladesh: A cluster randomized controlled trial.

Directory of Open Access Journals (Sweden)

Rajib Chowdhury

2017-09-01

Full Text Available A number of studies on visceral leishmaniasis (VL vector control have been conducted during the past decade, sometimes came to very different conclusion. The present study on a large sample investigated different options which are partially unexplored including: (1 indoor residual spraying (IRS with alpha cypermethrin 5WP; (2 long lasting insecticide impregnated bed-net (LLIN; (3 impregnation of local bed-nets with slow release insecticide K-O TAB 1-2-3 (KOTAB; (4 insecticide spraying in potential breeding sites outside of house using chlorpyrifos 20EC (OUT and different combinations of the above.The study was a cluster randomized controlled trial where 3089 houses from 11 villages were divided into 10 sections, each section with 6 clusters and each cluster having approximately 50 houses. Based on vector density (males plus females during baseline survey, the 60 clusters were categorized into 3 groups: (1 high, (2 medium and (3 low. Each group had 20 clusters. From these three groups, 6 clusters (about 300 households were randomly selected for each type of intervention and control arms. Vector density was measured before and 2, 4, 5, 7, 11, 14, 15, 18 and 22 months after intervention using CDC light traps. The impact of interventions was measured by using the difference-in-differences regression model.A total of 17,434 sand flies were collected at baseline and during the surveys conducted over 9 months following the baseline measurements. At baseline, the average P. argentipes density per household was 10.6 (SD = 11.5 in the control arm and 7.3 (SD = 8.46 to 11.5 (SD = 20.2 in intervention arms. The intervention results presented as the range of percent reductions of sand flies (males plus females and rate ratios in 9 measurements over 22 months. Among single type interventions, the effect of IRS with 2 rounds of spraying (applied by the research team ranged from 13% to 75% reduction of P. argentipes density compared to the control arm (rate

Self-assembled superparamagnetic nanoparticles as MRI contrast agents— A review

International Nuclear Information System (INIS)

Su Hong-Ying; Wu Chang-Qiang; Ai Hua; Li Dan-Yang

2015-01-01

Recent progress of the preparation and applications of superparamagnetic iron oxide (SPIO) clusters as magnetic resonance imaging (MRI) probes is reviewed with regard to their applications in labeling and tracking cells in vivo, in diagnosis of cardiovascular diseases and tumors, and in drug delivery systems. Magnetic nanoparticles (NPs), especially SPIO nanoparticles, have long been used as MRI contrast agents and as an advantageous nanoplatform for drug delivery, taking advantage of their unique magnetic properties and ability to function at the molecular and cellular levels. Due to advances in nanotechnology, various means to control SPIO NPs’ size, composition, magnetization and relaxivity have been developed, as well as ways to usefully modify their surface. Recently, self-assembly of SPIO NP clusters in particulate carriers—such as polymeric micelles, vesicles, liposomes, and layer-by-layer (LbL) capsules—have been widely studied for application as ultrasensitive MRI probes, owing to their remarkably high spin–spin (T 2 ) relaxivity and convenience for further functionalization. (topical review)

Energy Efficient Medium Access Control Protocol for Clustered Wireless Sensor Networks with Adaptive Cross-Layer Scheduling.

Science.gov (United States)

Sefuba, Maria; Walingo, Tom; Takawira, Fambirai

2015-09-18

This paper presents an Energy Efficient Medium Access Control (MAC) protocol for clustered wireless sensor networks that aims to improve energy efficiency and delay performance. The proposed protocol employs an adaptive cross-layer intra-cluster scheduling and an inter-cluster relay selection diversity. The scheduling is based on available data packets and remaining energy level of the source node (SN). This helps to minimize idle listening on nodes without data to transmit as well as reducing control packet overhead. The relay selection diversity is carried out between clusters, by the cluster head (CH), and the base station (BS). The diversity helps to improve network reliability and prolong the network lifetime. Relay selection is determined based on the communication distance, the remaining energy and the channel quality indicator (CQI) for the relay cluster head (RCH). An analytical framework for energy consumption and transmission delay for the proposed MAC protocol is presented in this work. The performance of the proposed MAC protocol is evaluated based on transmission delay, energy consumption, and network lifetime. The results obtained indicate that the proposed MAC protocol provides improved performance than traditional cluster based MAC protocols.

Cluster-based adaptive power control protocol using Hidden Markov Model for Wireless Sensor Networks

Science.gov (United States)

Vinutha, C. B.; Nalini, N.; Nagaraja, M.

2017-06-01

This paper presents strategies for an efficient and dynamic transmission power control technique, in order to reduce packet drop and hence energy consumption of power-hungry sensor nodes operated in highly non-linear channel conditions of Wireless Sensor Networks. Besides, we also focus to prolong network lifetime and scalability by designing cluster-based network structure. Specifically we consider weight-based clustering approach wherein, minimum significant node is chosen as Cluster Head (CH) which is computed stemmed from the factors distance, remaining residual battery power and received signal strength (RSS). Further, transmission power control schemes to fit into dynamic channel conditions are meticulously implemented using Hidden Markov Model (HMM) where probability transition matrix is formulated based on the observed RSS measurements. Typically, CH estimates initial transmission power of its cluster members (CMs) from RSS using HMM and broadcast this value to its CMs for initialising their power value. Further, if CH finds that there are variations in link quality and RSS of the CMs, it again re-computes and optimises the transmission power level of the nodes using HMM to avoid packet loss due noise interference. We have demonstrated our simulation results to prove that our technique efficiently controls the power levels of sensing nodes to save significant quantity of energy for different sized network.

Photo-Crosslinking Induced Geometric Restriction Controls the Self-Assembly of Diphenylalanine Based Peptides

International Nuclear Information System (INIS)

Tie Zuo-Xiu; Qin Meng; Zou Da-Wei; Cao Yi; Wang Wei

2011-01-01

The diphenylalanine (FF) motif has been widely used in the design of peptides that are capable of forming various ordered structures, such as nanotubes, nanospheres and hydrogels. In these assemblies, FF based peptides adopt an antiparallel structure and are stabilized by π — π stacking among the phenyl groups. Here we show that assembly of FF-based peptides can be controlled by their geometric restrictions. Using tripeptide FFY (L-Phe-L-Phe-L-Tyr) as an example, we demonstrate that photo-crosslinking of C-terminal tyrosine can impose a geometric restriction to the formation of an antiparallel structure, leading to a structural change of the assemblies from nanosphere to amorphous. This finding is confirmed using far-UV circular dichroism, Fourier transform infrared spectroscopy and atomic force microscopy. Based on such a mechanism, we are able to control the gel-sol transition of Fmoc-FFY using the geometric restriction induced by photo-crosslinking of C-terminal tyrosine groups. We believe that geometric restriction should be considered as an important factor in the design of peptide-based materials. It can also be implemented as a useful strategy for the construction of environment-responsive 'smart' materials. (cross-disciplinary physics and related areas of science and technology)

Integrity Evaluation of Control Rod Assembly for Sodium-Cooled Fast Reactor due to Drop Impact

Energy Technology Data Exchange (ETDEWEB)

Lee, Hyun Seung; Yoon, Kyung Ho; Kim, Hyung Kyu; Cheon, Jin Sik; Lee, Chan Bock [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-03-15

The CA (Control Assembly) of an SFR has a CRA(Control Rod Assembly) with an inner duct and control rod. During an emergency situation, the CRA falls into the duct of the CA for a rapid shut-down. The drop time and impact velocity of the CRA are important parameters with respect to the reactivity insertion time and the structural integrity of the CRA. The objective of this study was to investigate the dynamic behavior and integrity of the CRA owing to a drop impact. The impact analysis of the CRA under normal/abnormal drop conditions was carried out using the commercial FEM code LS-DYNA. Results of the drop impact analysis demonstrated that the CRA maintained structural integrity, and could be safely inserted into the flow hole of the damper under abnormal conditions.

Integrity Evaluation of Control Rod Assembly for Sodium-Cooled Fast Reactor due to Drop Impact

International Nuclear Information System (INIS)

Lee, Hyun Seung; Yoon, Kyung Ho; Kim, Hyung Kyu; Cheon, Jin Sik; Lee, Chan Bock

2017-01-01

The CA (Control Assembly) of an SFR has a CRA(Control Rod Assembly) with an inner duct and control rod. During an emergency situation, the CRA falls into the duct of the CA for a rapid shut-down. The drop time and impact velocity of the CRA are important parameters with respect to the reactivity insertion time and the structural integrity of the CRA. The objective of this study was to investigate the dynamic behavior and integrity of the CRA owing to a drop impact. The impact analysis of the CRA under normal/abnormal drop conditions was carried out using the commercial FEM code LS-DYNA. Results of the drop impact analysis demonstrated that the CRA maintained structural integrity, and could be safely inserted into the flow hole of the damper under abnormal conditions.

Space-Time Analysis of Testicular Cancer Clusters Using Residential Histories: A Case-Control Study in Denmark

Science.gov (United States)

Sloan, Chantel D.; Nordsborg, Rikke B.; Jacquez, Geoffrey M.; Raaschou-Nielsen, Ole; Meliker, Jaymie R.

2015-01-01

Though the etiology is largely unknown, testicular cancer incidence has seen recent significant increases in northern Europe and throughout many Western regions. The most common cancer in males under age 40, age period cohort models have posited exposures in the in utero environment or in early childhood as possible causes of increased risk of testicular cancer. Some of these factors may be tied to geography through being associated with behavioral, cultural, sociodemographic or built environment characteristics. If so, this could result in detectable geographic clusters of cases that could lead to hypotheses regarding environmental targets for intervention. Given a latency period between exposure to an environmental carcinogen and testicular cancer diagnosis, mobility histories are beneficial for spatial cluster analyses. Nearest-neighbor based Q-statistics allow for the incorporation of changes in residency in spatial disease cluster detection. Using these methods, a space-time cluster analysis was conducted on a population-wide case-control population selected from the Danish Cancer Registry with mobility histories since 1971 extracted from the Danish Civil Registration System. Cases (N=3297) were diagnosed between 1991 and 2003, and two sets of controls (N=3297 for each set) matched on sex and date of birth were included in the study. We also examined spatial patterns in maternal residential history for those cases and controls born in 1971 or later (N= 589 case-control pairs). Several small clusters were detected when aligning individuals by year prior to diagnosis, age at diagnosis and calendar year of diagnosis. However, the largest of these clusters contained only 2 statistically significant individuals at their center, and were not replicated in SaTScan spatial-only analyses which are less susceptible to multiple testing bias. We found little evidence of local clusters in residential histories of testicular cancer cases in this Danish population. PMID

Space-time analysis of testicular cancer clusters using residential histories: a case-control study in Denmark.

Directory of Open Access Journals (Sweden)

Chantel D Sloan

Full Text Available Though the etiology is largely unknown, testicular cancer incidence has seen recent significant increases in northern Europe and throughout many Western regions. The most common cancer in males under age 40, age period cohort models have posited exposures in the in utero environment or in early childhood as possible causes of increased risk of testicular cancer. Some of these factors may be tied to geography through being associated with behavioral, cultural, sociodemographic or built environment characteristics. If so, this could result in detectable geographic clusters of cases that could lead to hypotheses regarding environmental targets for intervention. Given a latency period between exposure to an environmental carcinogen and testicular cancer diagnosis, mobility histories are beneficial for spatial cluster analyses. Nearest-neighbor based Q-statistics allow for the incorporation of changes in residency in spatial disease cluster detection. Using these methods, a space-time cluster analysis was conducted on a population-wide case-control population selected from the Danish Cancer Registry with mobility histories since 1971 extracted from the Danish Civil Registration System. Cases (N=3297 were diagnosed between 1991 and 2003, and two sets of controls (N=3297 for each set matched on sex and date of birth were included in the study. We also examined spatial patterns in maternal residential history for those cases and controls born in 1971 or later (N= 589 case-control pairs. Several small clusters were detected when aligning individuals by year prior to diagnosis, age at diagnosis and calendar year of diagnosis. However, the largest of these clusters contained only 2 statistically significant individuals at their center, and were not replicated in SaTScan spatial-only analyses which are less susceptible to multiple testing bias. We found little evidence of local clusters in residential histories of testicular cancer cases in this Danish

Space-time analysis of testicular cancer clusters using residential histories: a case-control study in Denmark.

Science.gov (United States)

Sloan, Chantel D; Nordsborg, Rikke B; Jacquez, Geoffrey M; Raaschou-Nielsen, Ole; Meliker, Jaymie R

2015-01-01

Though the etiology is largely unknown, testicular cancer incidence has seen recent significant increases in northern Europe and throughout many Western regions. The most common cancer in males under age 40, age period cohort models have posited exposures in the in utero environment or in early childhood as possible causes of increased risk of testicular cancer. Some of these factors may be tied to geography through being associated with behavioral, cultural, sociodemographic or built environment characteristics. If so, this could result in detectable geographic clusters of cases that could lead to hypotheses regarding environmental targets for intervention. Given a latency period between exposure to an environmental carcinogen and testicular cancer diagnosis, mobility histories are beneficial for spatial cluster analyses. Nearest-neighbor based Q-statistics allow for the incorporation of changes in residency in spatial disease cluster detection. Using these methods, a space-time cluster analysis was conducted on a population-wide case-control population selected from the Danish Cancer Registry with mobility histories since 1971 extracted from the Danish Civil Registration System. Cases (N=3297) were diagnosed between 1991 and 2003, and two sets of controls (N=3297 for each set) matched on sex and date of birth were included in the study. We also examined spatial patterns in maternal residential history for those cases and controls born in 1971 or later (N= 589 case-control pairs). Several small clusters were detected when aligning individuals by year prior to diagnosis, age at diagnosis and calendar year of diagnosis. However, the largest of these clusters contained only 2 statistically significant individuals at their center, and were not replicated in SaTScan spatial-only analyses which are less susceptible to multiple testing bias. We found little evidence of local clusters in residential histories of testicular cancer cases in this Danish population.

SP-100 nuclear assembly test: Test assembly functional requirements and system arrangement

International Nuclear Information System (INIS)

Fallas, T.T.; Gluck, R.; Motwani, K.; Clay, H.; O'Neill, G.

1991-01-01

This paper describes the functional requirements and the system that will be tested to validate the reactor, flight shield, and flight controller of the SP-100 Generic Flight System (GFS). The Nuclear Assembly Test (NAT) consists of the test article (SP-100 reactor with control devices and the flight shield) and its supporting systems. The NAT test assembly is being designed by GE. Westinghouse Hanford Company (WHC) is designing the test cell and vacuum vessel system that will contain the NAT test assembly (Renkey et al. 1989). Preliminary design reviews have been completed and the final design is under way

Architectural design for a topological cluster state quantum computer

International Nuclear Information System (INIS)

Devitt, Simon J; Munro, William J; Nemoto, Kae; Fowler, Austin G; Stephens, Ashley M; Greentree, Andrew D; Hollenberg, Lloyd C L

2009-01-01

The development of a large scale quantum computer is a highly sought after goal of fundamental research and consequently a highly non-trivial problem. Scalability in quantum information processing is not just a problem of qubit manufacturing and control but it crucially depends on the ability to adapt advanced techniques in quantum information theory, such as error correction, to the experimental restrictions of assembling qubit arrays into the millions. In this paper, we introduce a feasible architectural design for large scale quantum computation in optical systems. We combine the recent developments in topological cluster state computation with the photonic module, a simple chip-based device that can be used as a fundamental building block for a large-scale computer. The integration of the topological cluster model with this comparatively simple operational element addresses many significant issues in scalable computing and leads to a promising modular architecture with complete integration of active error correction, exhibiting high fault-tolerant thresholds.

Surface mediated assembly of small, metastable gold nanoclusters

Science.gov (United States)

Pettibone, John M.; Osborn, William A.; Rykaczewski, Konrad; Talin, A. Alec; Bonevich, John E.; Hudgens, Jeffrey W.; Allendorf, Mark D.

2013-06-01

The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The films exhibit distinct structure from Au nanoparticles observed by X-ray diffraction, and film dissolution data support the preservation of small nanoclusters. UV-Vis spectroscopy, electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and electron microscopy are used to elucidate information regarding the nanocluster formation and assembly mechanism. Preferential deposition of nanocluster assemblies can be achieved on multiple substrates, including polymer, Cr, Si, SiO2, SiNx, and metal-organic frameworks (MOFs). Unlike other vapor phase coating processes, nanocluster assembly on the MIL-68(In) MOF crystal is capable of preferentially coating the external surface and stabilizing the crystal structure in hydrothermal conditions, which should enhance their storage, separation and delivery capabilities.The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The

Communication: Programmable self-assembly of thin-shell mesostructures

Science.gov (United States)

Halverson, Jonathan D.; Tkachenko, Alexei V.

2017-10-01

We study numerically the possibility of programmable self-assembly of various thin-shell architectures. They include clusters isomorphic to fullerenes C20 and C60, finite and infinite sheets, tube-shaped and toroidal mesostructures. Our approach is based on the recently introduced directionally functionalized nanoparticle platform, for which we employ a hybrid technique of Brownian dynamics with stochastic bond formation. By combining a number of strategies, we were able to achieve a near-perfect yield of the desired structures with a reduced "alphabet" of building blocks. Among those strategies are the following: the use of bending rigidity of the interparticle bond as a control parameter, programming the morphology with a seed architecture, use of chirality-preserving symmetries for reduction of the particle alphabet, and the hierarchic approach.

Design strategies for self-assembly of discrete targets

International Nuclear Information System (INIS)

Madge, Jim; Miller, Mark A.

2015-01-01

Both biological and artificial self-assembly processes can take place by a range of different schemes, from the successive addition of identical building blocks to hierarchical sequences of intermediates, all the way to the fully addressable limit in which each component is unique. In this paper, we introduce an idealized model of cubic particles with patterned faces that allows self-assembly strategies to be compared and tested. We consider a simple octameric target, starting with the minimal requirements for successful self-assembly and comparing the benefits and limitations of more sophisticated hierarchical and addressable schemes. Simulations are performed using a hybrid dynamical Monte Carlo protocol that allows self-assembling clusters to rearrange internally while still providing Stokes-Einstein-like diffusion of aggregates of different sizes. Our simulations explicitly capture the thermodynamic, dynamic, and steric challenges typically faced by self-assembly processes, including competition between multiple partially completed structures. Self-assembly pathways are extracted from the simulation trajectories by a fully extendable scheme for identifying structural fragments, which are then assembled into history diagrams for successfully completed target structures. For the simple target, a one-component assembly scheme is most efficient and robust overall, but hierarchical and addressable strategies can have an advantage under some conditions if high yield is a priority

Structure formation of lipid membranes: Membrane self-assembly and vesicle opening-up to octopus-like micelles

Science.gov (United States)

Noguchi, Hiroshi

2013-02-01

We briefly review our recent studies on self-assembly and vesicle rupture of lipid membranes using coarse-grained molecular simulations. For single component membranes, lipid molecules self-assemble from random gas states to vesicles via disk-shaped clusters. Clusters aggregate into larger clusters, and subsequently the large disks close into vesicles. The size of vesicles are determined by kinetics than by thermodynamics. When a vesicle composed of lipid and detergent types of molecules is ruptured, a disk-shaped micelle called bicelle can be formed. When both surfactants have negligibly low critical micelle concentration, it is found that bicelles connected with worm-like micelles are also formed depending on the surfactant ratio and spontaneous curvature of the membrane monolayer.

Cluster synchronization induced by one-node clusters in networks with asymmetric negative couplings

International Nuclear Information System (INIS)

Zhang, Jianbao; Ma, Zhongjun; Zhang, Gang

2013-01-01

This paper deals with the problem of cluster synchronization in networks with asymmetric negative couplings. By decomposing the coupling matrix into three matrices, and employing Lyapunov function method, sufficient conditions are derived for cluster synchronization. The conditions show that the couplings of multi-node clusters from one-node clusters have beneficial effects on cluster synchronization. Based on the effects of the one-node clusters, an effective and universal control scheme is put forward for the first time. The obtained results may help us better understand the relation between cluster synchronization and cluster structures of the networks. The validity of the control scheme is confirmed through two numerical simulations, in a network with no cluster structure and in a scale-free network

Cluster synchronization induced by one-node clusters in networks with asymmetric negative couplings

Science.gov (United States)

Zhang, Jianbao; Ma, Zhongjun; Zhang, Gang

2013-12-01

This paper deals with the problem of cluster synchronization in networks with asymmetric negative couplings. By decomposing the coupling matrix into three matrices, and employing Lyapunov function method, sufficient conditions are derived for cluster synchronization. The conditions show that the couplings of multi-node clusters from one-node clusters have beneficial effects on cluster synchronization. Based on the effects of the one-node clusters, an effective and universal control scheme is put forward for the first time. The obtained results may help us better understand the relation between cluster synchronization and cluster structures of the networks. The validity of the control scheme is confirmed through two numerical simulations, in a network with no cluster structure and in a scale-free network.

Electrical transport properties in Fe-Cr nanocluster-assembled granular films

Science.gov (United States)

Wang, Xiong-Zhi; Wang, Lai-Sen; Zhang, Qin-Fu; Liu, Xiang; Xie, Jia; Su, A.-Mei; Zheng, Hong-Fei; Peng, Dong-Liang

2017-09-01

The Fe100-xCrx nanocluster-assembled granular films with Cr atomic fraction (x) ranging from 0 to 100 were fabricated by using a plasma-gas-condensation cluster deposition system. The TEM characterization revealed that the uniform Fe clusters were coated with a Cr layer to form a Fe-Cr core-shell structure. Then, the as-prepared Fe100-xCrx nanoclusters were randomly assembled into a granular film in vacuum environments with increasing the deposition time. Because of the competition between interfacial resistance and shunting effect of Cr layer, the room temperature resistivity of the Fe100-xCrx nanocluster-assembled granular films first increased and then decreased with increasing the Cr atomic fraction (x), and revealed a maximum of 2 × 104 μΩ cm at x = 26 at.%. The temperature-dependent longitudinal resistivity (ρxx), magnetoresistance (MR) effect and anomalous Hall effect (AHE) of these Fe100-xCrx nanocluster-assembled granular films were also studied systematically. As the x increased from 0 to 100, the ρxx of all samples firstly decreased and then increased with increasing the measuring temperature. The dependence of ρxx on temperature could be well addressed by a mechanism incorporated for the fluctuation-induced-tunneling (FIT) conduction process and temperature-dependent scattering effect. It was found that the anomalous Hall effect (AHE) had no legible scaling relation in Fe100-xCrx nanocluster-assembled granular films. However, after deducting the contribution of tunneling effect, the scaling relation was unambiguous. Additionally, the Fe100-xCrx nanocluster-assembled granular films revealed a small negative magnetoresistance (MR), which decreased with the increase of x. The detailed physical mechanism of the electrical transport properties in these Fe100-xCrx nanocluster-assembled granular films was also studied.

Intra Cluster Light properties in the CLASH-VLT cluster MACS J1206.2-0847

CERN Document Server

Presotto, V; Nonino, M; Mercurio, A; Grillo, C; Rosati, P; Biviano, A; Annunziatella, M; Balestra, I; Cui, W; Sartoris, B; Lemze, D; Ascaso, B; Moustakas, J; Ford, H; Fritz, A; Czoske, O; Ettori, S; Kuchner, U; Lombardi, M; Maier, C; Medezinski, E; Molino, A; Scodeggio, M; Strazzullo, V; Tozzi, P; Ziegler, B; Bartelmann, M; Benitez, N; Bradley, L; Brescia, M; Broadhurst, T; Coe, D; Donahue, M; Gobat, R; Graves, G; Kelson, D; Koekemoer, A; Melchior, P; Meneghetti, M; Merten, J; Moustakas, L; Munari, E; Postman, M; Regős, E; Seitz, S; Umetsu, K; Zheng, W; Zitrin, A

2014-01-01

We aim at constraining the assembly history of clusters by studying the intra cluster light (ICL) properties, estimating its contribution to the fraction of baryons in stars, f*, and understanding possible systematics/bias using different ICL detection techniques. We developed an automated method, GALtoICL, based on the software GALAPAGOS to obtain a refined version of typical BCG+ICL maps. We applied this method to our test case MACS J1206.2-0847, a massive cluster located at z=0.44, that is part of the CLASH sample. Using deep multi-band SUBARU images, we extracted the surface brightness (SB) profile of the BCG+ICL and we studied the ICL morphology, color, and contribution to f* out to R500. We repeated the same analysis using a different definition of the ICL, SBlimit method, i.e. a SB cut-off level, to compare the results. The most peculiar feature of the ICL in MACS1206 is its asymmetric radial distribution, with an excess in the SE direction and extending towards the 2nd brightest cluster galaxy which i...

Self-assembly of coiled coil peptides into nanoparticles vs 2-d plates: effects of assembly pathway

Science.gov (United States)

Kim, Kyunghee; Pochan, Darrin

Molecular solution assembly, or self-assembly, is a process by which ordered nanostructures or patterns are formed by non-covalent interactions during assembly. Biomimicry, the use of bioinspired molecules or biologically relevant materials, is an important area of self-assembly research with peptides serving a critical role as molecular tools. The morphology of peptide assemblies can be controlled by adjusting solution conditions such as the concentration of peptides, the temperature, and pH. Herein, spherical nanostructures, which have potential for creating an encapsulation system, are formed by self-assembly when coiled coil peptides are combined in solution. These peptides are homotrimeric and heterodimeric coiled-coil bundles and the homotrimer is connected with each of heterodimer through their external surfaces via disulfide bonds. The resultant covalent constructs could co-assemble into complementary trimeric hubs, respectively. The two peptide constructs are directly mixed and assembled in solution in order to produce either spherical particles or 2-d plates depending on the solution conditions and kinetic pathway of assembly. In particular, structural changes of the self-assembled peptides are explored by control of the thermal history of the assembly solution.

Stoichiometric control of multiple different tectons in coordination-driven self-assembly: preparation of fused metallacyclic polygons.

Science.gov (United States)

Lee, Junseong; Ghosh, Koushik; Stang, Peter J

2009-09-02

We present a general strategy for the synthesis of stable, multicomponent fused polygon complexes in which coordination-driven self-assembly allows for single supramolecular species to be formed from multicomponent self-assembly and the shape of the obtained polygons can be controlled simply by changing the ratio of individual components. The compounds have been characterized by multinuclear NMR spectroscopy and electrospray ionization mass spectrometry.

Water ordering controls the dynamic equilibrium of micelle-fibre formation in self-assembly of peptide amphiphiles.

Science.gov (United States)

Deshmukh, Sanket A; Solomon, Lee A; Kamath, Ganesh; Fry, H Christopher; Sankaranarayanan, Subramanian K R S

2016-08-24

Understanding the role of water in governing the kinetics of the self-assembly processes of amphiphilic peptides remains elusive. Here, we use a multistage atomistic-coarse-grained approach, complemented by circular dichroism/infrared spectroscopy and dynamic light scattering experiments to highlight the dual nature of water in driving the self-assembly of peptide amphiphiles (PAs). We show computationally that water cage formation and breakage near the hydrophobic groups control the fusion dynamics and aggregation of PAs in the micellar stage. Simulations also suggest that enhanced structural ordering of vicinal water near the hydrophilic amino acids shifts the equilibrium towards the fibre phase and stimulates structure and order during the PA assembly into nanofibres. Experiments validate our simulation findings; the measured infrared O-H bond stretching frequency is reminiscent of an ice-like bond which suggests that the solvated water becomes increasingly ordered with time in the assembled peptide network, thus shedding light on the role of water in a self-assembly process.

PAVE: Program for assembling and viewing ESTs

Directory of Open Access Journals (Sweden)

Bomhoff Matthew

2009-08-01

Full Text Available Abstract Background New sequencing technologies are rapidly emerging. Many laboratories are simultaneously working with the traditional Sanger ESTs and experimenting with ESTs generated by the 454 Life Science sequencers. Though Sanger ESTs have been used to generate contigs for many years, no program takes full advantage of the 5' and 3' mate-pair information, hence, many tentative transcripts are assembled into two separate contigs. The new 454 technology has the benefit of high-throughput expression profiling, but introduces time and space problems for assembling large contigs. Results The PAVE (Program for Assembling and Viewing ESTs assembler takes advantage of the 5' and 3' mate-pair information by requiring that the mate-pairs be assembled into the same contig and joined by n's if the two sub-contigs do not overlap. It handles the depth of 454 data sets by "burying" similar ESTs during assembly, which retains the expression level information while circumventing time and space problems. PAVE uses MegaBLAST for the clustering step and CAP3 for assembly, however it assembles incrementally to enforce the mate-pair constraint, bury ESTs, and reduce incorrect joins and splits. The PAVE data management system uses a MySQL database to store multiple libraries of ESTs along with their metadata; the management system allows multiple assemblies with variations on libraries and parameters. Analysis routines provide standard annotation for the contigs including a measure of differentially expressed genes across the libraries. A Java viewer program is provided for display and analysis of the results. Our results clearly show the benefit of using the PAVE assembler to explicitly use mate-pair information and bury ESTs for large contigs. Conclusion The PAVE assembler provides a software package for assembling Sanger and/or 454 ESTs. The assembly software, data management software, Java viewer and user's guide are freely available.

PAVE: program for assembling and viewing ESTs.

Science.gov (United States)

Soderlund, Carol; Johnson, Eric; Bomhoff, Matthew; Descour, Anne

2009-08-26

New sequencing technologies are rapidly emerging. Many laboratories are simultaneously working with the traditional Sanger ESTs and experimenting with ESTs generated by the 454 Life Science sequencers. Though Sanger ESTs have been used to generate contigs for many years, no program takes full advantage of the 5' and 3' mate-pair information, hence, many tentative transcripts are assembled into two separate contigs. The new 454 technology has the benefit of high-throughput expression profiling, but introduces time and space problems for assembling large contigs. The PAVE (Program for Assembling and Viewing ESTs) assembler takes advantage of the 5' and 3' mate-pair information by requiring that the mate-pairs be assembled into the same contig and joined by n's if the two sub-contigs do not overlap. It handles the depth of 454 data sets by "burying" similar ESTs during assembly, which retains the expression level information while circumventing time and space problems. PAVE uses MegaBLAST for the clustering step and CAP3 for assembly, however it assembles incrementally to enforce the mate-pair constraint, bury ESTs, and reduce incorrect joins and splits. The PAVE data management system uses a MySQL database to store multiple libraries of ESTs along with their metadata; the management system allows multiple assemblies with variations on libraries and parameters. Analysis routines provide standard annotation for the contigs including a measure of differentially expressed genes across the libraries. A Java viewer program is provided for display and analysis of the results. Our results clearly show the benefit of using the PAVE assembler to explicitly use mate-pair information and bury ESTs for large contigs. The PAVE assembler provides a software package for assembling Sanger and/or 454 ESTs. The assembly software, data management software, Java viewer and user's guide are freely available.

Study of pressure losses in the EL 4 cluster

International Nuclear Information System (INIS)

Berriaud, Ch.

1964-01-01

The evolution of research on the EL-4 cluster is examined here from the pressure losses point of view. These may be split up into separate pressure losses along the rode and in pressure losses corresponding to various particularities of the cluster. Tests have been carried out on series of three or four clusters placed in a channel. Water was first used, and then carbon dioxide at 60 bars. In all cases the following two parameters were varied: the Reynolds' number, and the rotation of a cluster around its axis with respect to the surrounding clusters. The influence of the gap between to successive clusters has also been studied. The first tests were carried out on clusters without jackets, the subsequent ones on clusters fitted with jackets. It was thus possible to study various types of element assemblies. The results are given in the form of curves representing: the evolution of the independent pressure loss coefficients as a function of the Reynolds number. (author) [fr

On the solution self-assembly of nanocolloidal brushes: insights from simulations

International Nuclear Information System (INIS)

Striolo, Alberto

2008-01-01

The synthesis of novel nanoparticles with exceptional properties continues to stimulate the search for advanced applications in fields as diverse as solar energy harvesting and polymer reinforcement. It is widely recognized that to practically exploit the promised benefits it is necessary to guide the assembly of the various nanoparticles into well-defined supra-molecular structures. Towards this goal, we report Monte Carlo simulation results for the self-assembly of spherical nanoparticles in implicit solvent. The nanoparticles interact solely via dispersive interactions, modeled as square-well potentials. To control the morphology of the self-assembled aggregates, side chains are grafted on specific locations on the nanoparticle surface (i.e., on the equator, on the tropics, on the entire tropical region, or uniformly on the nanoparticle surface). The results are discussed in terms of average cluster size, probability of observing aggregates of given size, and aggregate radius of gyration and asphericity as a function of the aggregate size. The parameters of interest are the solution conditions and the nanoparticle volume fraction (always in the dilute regime). As shown in previous reports (e.g., Striolo 2007 Small 3 628), the nanoparticles form insoluble agglomerates in the absence of the side chains. When the side chains are long and uniformly distributed on the nanoparticles, these remain individually dispersed in solution. More importantly, when the side chains are grafted on selected locations on the nanoparticles, these self-assemble, yielding structures composed of up to 7-10 nanoparticles. The number of grafted side chains is the parameter that predominantly determines the average aggregate size, while the aggregate morphology can be tuned by appropriately controlling the distribution and length of the grafted side chains.

SEEDisCs: How Clusters Form and Galaxies Transform in the Cosmic Web

Science.gov (United States)

Jablonka, P.

2017-08-01

This presentation introduces a new survey, the Spatial Extended EDisCS Survey (SEEDisCS), which aims at understanding how clusters assemble and the level at which galaxies are preprocessed before falling on the cluster cores. I focus on the changes in galaxy properties in the cluster large scale environments, and how we can get constraints on the timescale of star formation quenching. I also discuss new ALMA CO observations, which trace the fate of the galaxy cold gas content along the infalling paths towards the cluster cores.

Trace Contaminant Control During the International Space Station's On-Orbit Assembly and Outfitting

Science.gov (United States)

Perry, J. L.

2017-01-01

Achieving acceptable cabin air quality must balance competing elements during spacecraft design, assembly, ground processing, and flight operations. Among the elements that contribute to the trace chemical contaminant load and, therefore, the cabin air quality aboard crewed spacecraft are the vehicle configuration, crew size and activities, mission duration and objectives, materials selection, and vehicle manufacturing and preflight ground processing methods. Trace chemical contaminants produced from pervasive sources such as equipment offgassing, human metabolism, and cleaning fluids during preflight ground processing present challenges to maintaining acceptable cabin air quality. To address these challenges, both passive and active contamination control techniques are used during a spacecraft's design, manufacturing, preflight preparation, and operational phases. Passive contamination control methods seek to minimize the equipment offgassing load by selecting materials, manufacturing processes, preflight preparation processes, and in-flight operations that have low chemical offgassing characteristics. Passive methods can be employed across the spacecraft's entire life cycle from conceptual design through flight operations. However, because the passive contamination control techniques cannot fully eliminate the contaminant load, active contamination control equipment must be deployed aboard the spacecraft to purify and revitalize the cabin atmosphere during in-flight operations. Verifying that the passive contamination control techniques have successfully maintained the total trace contaminant load within the active contamination control equipment's capabilities occurs late in the preflight preparation stages. This verification consists of subjecting the spacecraft to an offgassing test to determine the trace contaminant load. This load is then assessed versus the active contamination control equipment's capabilities via trace contaminant control (TCC) engineering

TreeCluster: Massively scalable transmission clustering using phylogenetic trees

OpenAIRE

Moshiri, Alexander

2018-01-01

Background: The ability to infer transmission clusters from molecular data is critical to designing and evaluating viral control strategies. Viral sequencing datasets are growing rapidly, but standard methods of transmission cluster inference do not scale well beyond thousands of sequences. Results: I present TreeCluster, a cross-platform tool that performs transmission cluster inference on a given phylogenetic tree orders of magnitude faster than existing inference methods and supports multi...

Hematite Thin Films with Various Nanoscopic Morphologies Through Control of Self-Assembly Structures

Science.gov (United States)

Liu, Jingling; Kim, Yong-Tae; Kwon, Young-Uk

2015-05-01

Hematite (α-Fe2O3) thin films with various nanostructures were synthesized through self-assembly between iron oxide hydroxide particles, generated by hydrolysis and condensation of Fe(NO3)3 · 6H2O, and a Pluronic triblock copolymer (F127, (EO)106(PO)70(EO)106, EO = ethylene oxide, PO = propylene oxide), followed by calcination. The self-assembly structure can be tuned by introducing water in a controlled manner through the control of the humidity level in the surrounding of the as-cast films during aging stage. For the given Fe(NO3)3 · 6H2O:F127 ratio, there appear to be three different thermodynamically stable self-assembly structures depending on the water content in the film material, which correspond to mesoporous, spherical micellar, and rod-like micellar structures after removal of F127. Coupled with the thermodynamic driving forces, the kinetics of the irreversible reactions of coalescence of iron oxide hydroxide particles into larger ones induce diverse nanostructures of the resultant films. The length scale of so-obtained nanostructures ranges from 6 nm to a few hundred nanometers. In addition to water content, the effects of other experimental parameters such as aging temperature, spin rate during spin coating, type of substrate, and type of iron reagent were investigated.

Self-assembly and flux closure studies of magnetic nanoparticle rings

DEFF Research Database (Denmark)

Wei, Alexander; Kasama, Takeshi; Dunin-Borkowski, Rafal E.

2011-01-01

Thermoremanent magnetic nanoparticles (MNPs) can self-assemble into rings through dipolar interactions, when dispersed under appropriate conditions. Analysis of individual MNP rings and clusters by off-axis electron holography reveals bistable flux closure (FC) states at ambient temperatures...

The Yeast Nbp35-Cfd1 Cytosolic Iron-Sulfur Cluster Scaffold Is an ATPase.

Science.gov (United States)

Camire, Eric J; Grossman, John D; Thole, Grace J; Fleischman, Nicholas M; Perlstein, Deborah L

2015-09-25

Nbp35 and Cfd1 are prototypical members of the MRP/Nbp35 class of iron-sulfur (FeS) cluster scaffolds that function to assemble nascent FeS clusters for transfer to FeS-requiring enzymes. Both proteins contain a conserved NTPase domain that genetic studies have demonstrated is essential for their cluster assembly activity inside the cell. It was recently reported that these proteins possess no or very low nucleotide hydrolysis activity in vitro, and thus the role of the NTPase domain in cluster biogenesis has remained uncertain. We have reexamined the NTPase activity of Nbp35, Cfd1, and their complex. Using in vitro assays and site-directed mutagenesis, we demonstrate that the Nbp35 homodimer and the Nbp35-Cfd1 heterodimer are ATPases, whereas the Cfd1 homodimer exhibited no or very low ATPase activity. We ruled out the possibility that the observed ATP hydrolysis activity might result from a contaminating ATPase by showing that mutation of key active site residues reduced activity to background levels. Finally, we demonstrate that the fluorescent ATP analog 2'/3'-O-(N'-methylanthraniloyl)-ATP (mantATP) binds stoichiometrically to Nbp35 with a KD = 15.6 μM and that an Nbp35 mutant deficient in ATP hydrolysis activity also displays an increased KD for mantATP. Together, our results demonstrate that the cytosolic iron-sulfur cluster assembly scaffold is an ATPase and pave the way for interrogating the role of nucleotide hydrolysis in cluster biogenesis by this large family of cluster scaffolding proteins found across all domains of life. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

A protein interaction map of the kalimantacin biosynthesis assembly line

Directory of Open Access Journals (Sweden)

Birgit Uytterhoeven

2016-11-01

Full Text Available The antimicrobial secondary metabolite kalimantacin is produced by a hybrid polyketide/ non-ribosomal peptide system in Pseudomonas fluorescens BCCM_ID9359. In this study, the kalimantacin biosynthesis gene cluster is analyzed by yeast two-hybrid analysis, creating a protein-protein interaction map of the entire assembly line. In total, 28 potential interactions were identified, of which 13 could be confirmed further. These interactions include the dimerization of ketosynthase domains, a link between assembly line modules 9 and 10, and a specific interaction between the trans-acting enoyl reductase BatK and the carrier proteins of modules 8 and 10. These interactions reveal fundamental insight into the biosynthesis of secondary metabolites.This study is the first to reveal interactions in a complete biosynthetic pathway. Similar future studies could build a strong basis for engineering strategies in such clusters.

Management system of ELHEP cluster machine for FEL photonics design

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Zysik, Jacek; Poźniak, Krzysztof; Romaniuk, Ryszard

2006-10-01

A multipurpose, distributed MatLab calculations oriented, cluster machine was assembled in PERG/ELHEP laboratory at ISE/WUT. It is predicted mainly for advanced photonics and FPGA/DSP based systems design for Free Electron Laser. It will be used also for student projects for superconducting accelerator and FEL. Here we present one specific side of cluster design. For an intense, distributed daily work with the cluster, it is important to have a good interface and practical access to all machine resources. A complex management system was implemented in PERG laboratory. It helps all registered users to work using all necessary applications, communicate with other logged in people, check all the news and gather all necessary information about what is going on in the system, how it is utilized, etc. The system is also very practical for administrator purposes, it helps to keep controlling who is using the resources and for how long. It provides different privileges for different applications and many more. The system is introduced as a freeware, using open source code and can be modified by system operators or super-users who are interested in nonstandard system configuration.

Scaffold Architecture Controls Insulinoma Clustering, Viability, and Insulin Production

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Blackstone, Britani N.; Palmer, Andre F.; Rilo, Horacio R.

2014-01-01

Recently, in vitro diagnostic tools have shifted focus toward personalized medicine by incorporating patient cells into traditional test beds. These cell-based platforms commonly utilize two-dimensional substrates that lack the ability to support three-dimensional cell structures seen in vivo. As monolayer cell cultures have previously been shown to function differently than cells in vivo, the results of such in vitro tests may not accurately reflect cell response in vivo. It is therefore of interest to determine the relationships between substrate architecture, cell structure, and cell function in 3D cell-based platforms. To investigate the effect of substrate architecture on insulinoma organization and function, insulinomas were seeded onto 2D gelatin substrates and 3D fibrous gelatin scaffolds with three distinct fiber diameters and fiber densities. Cell viability and clustering was assessed at culture days 3, 5, and 7 with baseline insulin secretion and glucose-stimulated insulin production measured at day 7. Small, closely spaced gelatin fibers promoted the formation of large, rounded insulinoma clusters, whereas monolayer organization and large fibers prevented cell clustering and reduced glucose-stimulated insulin production. Taken together, these data show that scaffold properties can be used to control the organization and function of insulin-producing cells and may be useful as a 3D test bed for diabetes drug development. PMID:24410263

Identifying Patient Attitudinal Clusters Associated with Asthma Control: The European REALISE Survey.

Science.gov (United States)

van der Molen, Thys; Fletcher, Monica; Price, David

Asthma is a highly heterogeneous disease that can be classified into different clinical phenotypes, and treatment may be tailored accordingly. However, factors beyond purely clinical traits, such as patient attitudes and behaviors, can also have a marked impact on treatment outcomes. The objective of this study was to further analyze data from the REcognise Asthma and LInk to Symptoms and Experience (REALISE) Europe survey, to identify distinct patient groups sharing common attitudes toward asthma and its management. Factor analysis of respondent data (N = 7,930) from the REALISE Europe survey consolidated the 34 attitudinal variables provided by the study population into a set of 8 summary factors. Cluster analyses were used to identify patient clusters that showed similar attitudes and behaviors toward each of the 8 summary factors. Five distinct patient clusters were identified and named according to the key characteristics comprising that cluster: "Confident and self-managing," "Confident and accepting of their asthma," "Confident but dependent on others," "Concerned but confident in their health care professional (HCP)," and "Not confident in themselves or their HCP." Clusters showed clear variability in attributes such as degree of confidence in managing their asthma, use of reliever and preventer medication, and level of asthma control. The 5 patient clusters identified in this analysis displayed distinctly different personal attitudes that would require different approaches in the consultation room certainly for asthma but probably also for other chronic diseases. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods.

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Chakraborty, Amrita; Fernandez, Ann Candice; Som, Anirban; Mondal, Biswajit; Natarajan, Ganapati; Paramasivam, Ganesan; Lahtinen, Tanja; Häkkinen, Hannu; Nonappa, Nonappa; Pradeep, Thalappil

2018-04-01

We present the self-assembled structures of atomically precise, ligand-protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs). Unlike highly sophisticated DNA nanotechnology, our approach demonstrates a strategically simple hydrogen bonding-directed self-assembly of nanoclusters leading to octahedral nanocrystals encapsulating GNRs. Specifically, we use the p-mercaptobenzoic acid (pMBA) protected atomically precise nanocluster, Na4[Ag44(pMBA)30] and pMBA functionalized GNRs. High resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H-bonding leading to octahedral symmetry. Further, use of water dispersible gold nanoclusters, Au~250(pMBA)n and Au102(pMBA)44 also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles present a new category of precision hybrids with diverse possibilities. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamic simulations of many-body electrostatic self-assembly

Science.gov (United States)

Lindgren, Eric B.; Stamm, Benjamin; Maday, Yvon; Besley, Elena; Stace, A. J.

2018-03-01

Two experimental studies relating to electrostatic self-assembly have been the subject of dynamic computer simulations, where the consequences of changing the charge and the dielectric constant of the materials concerned have been explored. One series of calculations relates to experiments on the assembly of polymer particles that have been subjected to tribocharging and the simulations successfully reproduce many of the observed patterns of behaviour. A second study explores events observed following collisions between single particles and small clusters composed of charged particles derived from a metal oxide composite. As before, observations recorded during the course of the experiments are reproduced by the calculations. One study in particular reveals how particle polarizability can influence the assembly process. This article is part of the theme issue `Modern theoretical chemistry'.

α-synuclein assemblies sequester neuronal α3-Na+/K+-ATPase and impair Na+ gradient

Science.gov (United States)

Shrivastava, Amulya Nidhi; Redeker, Virginie; Fritz, Nicolas; Pieri, Laura; Almeida, Leandro G; Spolidoro, Maria; Liebmann, Thomas; Bousset, Luc; Renner, Marianne; Léna, Clément; Aperia, Anita; Melki, Ronald; Triller, Antoine

2015-01-01

Extracellular α-synuclein (α-syn) assemblies can be up-taken by neurons; however, their interaction with the plasma membrane and proteins has not been studied specifically. Here we demonstrate that α-syn assemblies form clusters within the plasma membrane of neurons. Using a proteomic-based approach, we identify the α3-subunit of Na+/K+-ATPase (NKA) as a cell surface partner of α-syn assemblies. The interaction strength depended on the state of α-syn, fibrils being the strongest, oligomers weak, and monomers none. Mutations within the neuron-specific α3-subunit are linked to rapid-onset dystonia Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). We show that freely diffusing α3-NKA are trapped within α-syn clusters resulting in α3-NKA redistribution and formation of larger nanoclusters. This creates regions within the plasma membrane with reduced local densities of α3-NKA, thereby decreasing the efficiency of Na+ extrusion following stimulus. Thus, interactions of α3-NKA with extracellular α-syn assemblies reduce its pumping activity as its mutations in RDP/AHC. PMID:26323479

Cerium chloride stimulated controlled conversion of B-to-Z DNA in self-assembled nanostructures

International Nuclear Information System (INIS)

Bhanjadeo, Madhabi M.; Nayak, Ashok K.; Subudhi, Umakanta

2017-01-01

DNA adopts different conformation not only because of novel base pairs but also while interacting with inorganic or organic compounds. Self-assembled branched DNA (bDNA) structures or DNA origami that change conformation in response to environmental cues hold great promises in sensing and actuation at the nanoscale. Recently, the B-Z transition in DNA is being explored to design various nanomechanical devices. In this communication we have demonstrated that Cerium chloride binds to the phosphate backbone of self-assembled bDNA structure and induce B-to-Z transition at physiological concentration. The mechanism of controlled conversion from right-handed to left-handed has been assayed by various dye binding studies using CD and fluorescence spectroscopy. Three different bDNA structures have been identified to display B-Z transition. This approach provides a rapid and reversible means to change bDNA conformation, which can be used for dynamic and progressive control at the nanoscale. - Highlights: • Cerium-induced B-to-Z DNA transition in self-assembled nanostructures. • Lower melting temperature of Z-DNA than B-DNA confirmed by CD spectroscopy. • Binding mechanism of cerium chloride is explained using fluorescence spectroscopy. • Right-handed to left-handed DNA conformation is also noticed in modified bDNA structure.

A VTVH MCD and EPR Spectroscopic Study of the Maturation of the "Second" Nitrogenase P-Cluster.

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Rupnik, Kresimir; Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W; Hales, Brian J

2018-04-16

The P-cluster of the nitrogenase MoFe protein is a [ Fe 8 S 7 ] cluster that mediates efficient transfer of electrons to the active site for substrate reduction. Arguably the most complex homometallic FeS cluster found in nature, the biosynthetic mechanism of the P-cluster is of considerable theoretical and synthetic interest to chemists and biochemists alike. Previous studies have revealed a biphasic assembly mechanism of the two P-clusters in the MoFe protein upon incubation with Fe protein and ATP, in which the first P-cluster is formed through fast fusion of a pair of [ Fe 4 S 4 ] + clusters within 5 min and the second P-cluster is formed through slow fusion of the second pair of [ Fe 4 S 4 ] + clusters in a period of 2 h. Here we report a VTVH MCD and EPR spectroscopic study of the biosynthesis of the slow-forming, second P-cluster within the MoFe protein. Our results show that the first major step in the formation of the second P-cluster is the conversion of one of the precursor [ Fe 4 S 4 ] + clusters into the integer spin cluster [ Fe 4 S 3-4 ] α , a process aided by the assembly protein NifZ, whereas the second major biosynthetic step appears to be the formation of a diamagnetic cluster with a possible structure of [ Fe 8 S 7-8 ] β , which is eventually converted into the P-cluster.

Cluster analysis in systems of magnetic spheres and cubes

Energy Technology Data Exchange (ETDEWEB)

Pyanzina, E.S., E-mail: elena.pyanzina@urfu.ru [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Gudkova, A.V. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Donaldson, J.G. [University of Vienna, Sensengasse 8, Vienna (Austria); Kantorovich, S.S. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); University of Vienna, Sensengasse 8, Vienna (Austria)

2017-06-01

In the present work we use molecular dynamics simulations and graph-theory based cluster analysis to compare self-assembly in systems of magnetic spheres, and cubes where the dipole moment is oriented along the side of the cube in the [001] crystallographic direction. We show that under the same conditions cubes aggregate far less than their spherical counterparts. This difference can be explained in terms of the volume of phase space in which the formation of the bond is thermodynamically advantageous. It follows that this volume is much larger for a dipolar sphere than for a dipolar cube. - Highlights: • A comparison of the degree of self-assembly in systems of magnetic spheres and cubes. • Spheres are more likely to form larger clusters than cubes. • Differences in microstructure will manifest in the magnetic response of each system.

Cationic and neutral copper(I) iodide cluster MOFs derived from ...

Indian Academy of Sciences (India)

Ashok Yadav

These reactions yielded two new cluster-MOFs 2 and 3. While the ..... (a) Ortep plots at 50% ellipsoid probabilities for the cationic segments of 2; (b) View of the. 3D-MOF assembly of 2 ... identical emission colour of 2 at 298 K and 77 K under the. UV-lamp. .... C 2013 A multi-metal-cluster MOF with Cu4I4 and. Cu6S6 as ...

The fidelity of synaptonemal complex assembly is regulated by a signaling mechanism that controls early meiotic progression.

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Silva, Nicola; Ferrandiz, Nuria; Barroso, Consuelo; Tognetti, Silvia; Lightfoot, James; Telecan, Oana; Encheva, Vesela; Faull, Peter; Hanni, Simon; Furger, Andre; Snijders, Ambrosius P; Speck, Christian; Martinez-Perez, Enrique

2014-11-24

Proper chromosome segregation during meiosis requires the assembly of the synaptonemal complex (SC) between homologous chromosomes. However, the SC structure itself is indifferent to homology, and poorly understood mechanisms that depend on conserved HORMA-domain proteins prevent ectopic SC assembly. Although HORMA-domain proteins are thought to regulate SC assembly as intrinsic components of meiotic chromosomes, here we uncover a key role for nuclear soluble HORMA-domain protein HTP-1 in the quality control of SC assembly. We show that a mutant form of HTP-1 impaired in chromosome loading provides functionality of an HTP-1-dependent checkpoint that delays exit from homology search-competent stages until all homolog pairs are linked by the SC. Bypassing of this regulatory mechanism results in premature meiotic progression and licensing of homology-independent SC assembly. These findings identify nuclear soluble HTP-1 as a regulator of early meiotic progression, suggesting parallels with the mode of action of Mad2 in the spindle assembly checkpoint. Copyright © 2014 Elsevier Inc. All rights reserved.

THE HST/ACS COMA CLUSTER SURVEY. IV. INTERGALACTIC GLOBULAR CLUSTERS AND THE MASSIVE GLOBULAR CLUSTER SYSTEM AT THE CORE OF THE COMA GALAXY CLUSTER

International Nuclear Information System (INIS)

Peng, Eric W.; Ferguson, Henry C.; Goudfrooij, Paul; Hammer, Derek; Lucey, John R.; Marzke, Ronald O.; Puzia, Thomas H.; Carter, David; Balcells, Marc; Bridges, Terry; Chiboucas, Kristin; Del Burgo, Carlos; Graham, Alister W.; Guzman, Rafael; Hudson, Michael J.; Matkovic, Ana

2011-01-01

Intracluster stellar populations are a natural result of tidal interactions in galaxy clusters. Measuring these populations is difficult, but important for understanding the assembly of the most massive galaxies. The Coma cluster of galaxies is one of the nearest truly massive galaxy clusters and is host to a correspondingly large system of globular clusters (GCs). We use imaging from the HST/ACS Coma Cluster Survey to present the first definitive detection of a large population of intracluster GCs (IGCs) that fills the Coma cluster core and is not associated with individual galaxies. The GC surface density profile around the central massive elliptical galaxy, NGC 4874, is dominated at large radii by a population of IGCs that extend to the limit of our data (R +4000 -5000 (systematic) IGCs out to this radius, and that they make up ∼70% of the central GC system, making this the largest GC system in the nearby universe. Even including the GC systems of other cluster galaxies, the IGCs still make up ∼30%-45% of the GCs in the cluster core. Observational limits from previous studies of the intracluster light (ICL) suggest that the IGC population has a high specific frequency. If the IGC population has a specific frequency similar to high-S N dwarf galaxies, then the ICL has a mean surface brightness of μ V ∼ 27 mag arcsec -2 and a total stellar mass of roughly 10 12 M sun within the cluster core. The ICL makes up approximately half of the stellar luminosity and one-third of the stellar mass of the central (NGC 4874+ICL) system. The color distribution of the IGC population is bimodal, with blue, metal-poor GCs outnumbering red, metal-rich GCs by a ratio of 4:1. The inner GCs associated with NGC 4874 also have a bimodal distribution in color, but with a redder metal-poor population. The fraction of red IGCs (20%), and the red color of those GCs, implies that IGCs can originate from the halos of relatively massive, L* galaxies, and not solely from the disruption of

Self-assembly of silk-elastinlike protein polymers into three-dimensional scaffolds for biomedical applications

Science.gov (United States)

Zeng, Like

Production of brand new protein-based materials with precise control over the amino acid sequences at single residue level has been made possible by genetic engineering, through which artificial genes can be developed that encode protein-based materials with desired features. As an example, silk-elastinlike protein polymers (SELPs), composed of tandem repeats of amino acid sequence motifs from Bombyx mori (silkworm) silk and mammalian elastin, have been produced in this approach. SELPs have been studied extensively in the past two decades, however, the fundamental mechanism governing the self-assembly process to date still remains largely unresolved. Further, regardless of the unprecedented success when exploited in areas including drug delivery, gene therapy, and tissue augmentation, SELPs scaffolds as a three-dimensional cell culture model system are complicated by the inability of SELPs to provide the embedded tissue cells with appropriate biochemical stimuli essential for cell survival and function. In this dissertation, it is reported that the self-assembly of silk-elastinlike protein polymers (SELPs) into nanofibers in aqueous solutions can be modulated by tuning the curing temperature, the size of the silk blocks, and the charge of the elastin blocks. A core-sheath model was proposed for nanofiber formation, with the silk blocks in the cores and the hydrated elastin blocks in the sheaths. The folding of the silk blocks into stable cores -- affected by the size of the silk blocks and the charge of the elastin blocks -- plays a critical role in the assembly of silk-elastin nanofibers. The assembled nanofibers further form nanofiber clusters on the microscale, and the nanofiber clusters then coalesce into nanofiber micro-assemblies, interconnection of which eventually leads to the formation of three-dimensional scaffolds with distinct nanoscale and microscale features. SELP-Collagen hybrid scaffolds were also fabricated to enable independent control over the

Electrical Programming of Soft Matter: Using Temporally Varying Electrical Inputs To Spatially Control Self Assembly.

Science.gov (United States)

Yan, Kun; Liu, Yi; Zhang, Jitao; Correa, Santiago O; Shang, Wu; Tsai, Cheng-Chieh; Bentley, William E; Shen, Jana; Scarcelli, Giuliano; Raub, Christopher B; Shi, Xiao-Wen; Payne, Gregory F

2018-02-12

The growing importance of hydrogels in translational medicine has stimulated the development of top-down fabrication methods, yet often these methods lack the capabilities to generate the complex matrix architectures observed in biology. Here we show that temporally varying electrical signals can cue a self-assembling polysaccharide to controllably form a hydrogel with complex internal patterns. Evidence from theory and experiment indicate that internal structure emerges through a subtle interplay between the electrical current that triggers self-assembly and the electrical potential (or electric field) that recruits and appears to orient the polysaccharide chains at the growing gel front. These studies demonstrate that short sequences (minutes) of low-power (∼1 V) electrical inputs can provide the program to guide self-assembly that yields hydrogels with stable, complex, and spatially varying structure and properties.

Redox-Active Carbohydrate-Coated Nanoparticles: Self-Assembly of a Cyclodextrin-Polystyrene Glycopolymer with Tetrazine-Naphthalimide.

Science.gov (United States)

Gross, Andrew J; Haddad, Raoudha; Travelet, Christophe; Reynaud, Eric; Audebert, Pierre; Borsali, Redouane; Cosnier, Serge

2016-11-15

The controlled self-assembly of precise and well-defined photochemically and electrochemically active carbohydrate-coated nanoparticles offers the exciting prospect of biocompatible catalysts for energy storage/conversion and biolabeling applications. Here an aqueous nanoparticle system has been developed with a versatile outer layer for host-guest molecule encapsulation via β-cyclodextrin inclusion complexes. A β-cyclodextrin-modified polystyrene polymer was first obtained by copper nanopowder click chemistry. The glycopolymer enables self-assembly and controlled encapsulation of tetrazine-naphthalimide, as a model redox-active agent, into nanoparticles via nanoprecipitation. Cyclodextrin host-guest interactions permit encapsulation and internanoparticle cross-linking for the formation of fluorescent compound and clustered self-assemblies with chemically reversible electroactivity in aqueous solution. Light scattering experiments revealed stable particles with hydrodynamic diameters of 138 and 654 nm for nanoparticles prepared with tetrazine, of which 95% of the nanoparticles represent the smaller objects by number. Dynamic light scattering revealed differences as a function of preparation method in terms of size, 3-month stability, polydispersity, radius of gyration, and shape factor. Individual self-assemblies were visualized by atomic force microscopy and fluorescence microscopy and monitored in real-time by nanoparticle tracking analysis. UV-vis and fluorescence spectra provided insight into the optical properties and critical evidence for host-guest encapsulation as evidenced by solvachromatism and enhanced tetrazine uptake. Cyclic voltammetry was used to investigate the electrochemical properties and provided further support for encapsulation and an estimate of the tetrazine loading capacity in tandem with light scattering data.

Binding branched and linear DNA structures: From isolated clusters to fully bonded gels

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Fernandez-Castanon, J.; Bomboi, F.; Sciortino, F.

2018-01-01

The proper design of DNA sequences allows for the formation of well-defined supramolecular units with controlled interactions via a consecution of self-assembling processes. Here, we benefit from the controlled DNA self-assembly to experimentally realize particles with well-defined valence, namely, tetravalent nanostars (A) and bivalent chains (B). We specifically focus on the case in which A particles can only bind to B particles, via appropriately designed sticky-end sequences. Hence AA and BB bonds are not allowed. Such a binary mixture system reproduces with DNA-based particles the physics of poly-functional condensation, with an exquisite control over the bonding process, tuned by the ratio, r, between B and A units and by the temperature, T. We report dynamic light scattering experiments in a window of Ts ranging from 10 °C to 55 °C and an interval of r around the percolation transition to quantify the decay of the density correlation for the different cases. At low T, when all possible bonds are formed, the system behaves as a fully bonded network, as a percolating gel, and as a cluster fluid depending on the selected r.

Calix[4]arene supported clusters: a dimer of [Mn(III)Mn(II)] dimers

DEFF Research Database (Denmark)

Taylor, Stephanie M; McIntosh, Ruaraidh D; Beavers, Christine M

2011-01-01

Phosphinate ligands allow for the transformation of a calix[4]arene supported [Mn(III)(2)Mn(II)(2)] tetramer cluster motif into an unusual [Mn(III)Mn(II)](2) dimer of dimers; the clusters self-assemble in the crystal to form bi-layer arrays reminiscent of the typical packing of calixarene solvates....

Construction of a controllable β-carotene biosynthetic pathway by decentralized assembly strategy in Saccharomyces cerevisiae.

Science.gov (United States)

Xie, Wenping; Liu, Min; Lv, Xiaomei; Lu, Wenqiang; Gu, Jiali; Yu, Hongwei

2014-01-01

Saccharomyces cerevisiae is an important platform organism for the synthesis of a great number of natural products. However, the assembly of controllable and genetically stable heterogeneous biosynthetic pathways in S. cerevisiae still remains a significant challenge. Here, we present a strategy for reconstructing controllable multi-gene pathways by employing the GAL regulatory system. A set of marker recyclable integrative plasmids (pMRI) was designed for decentralized assembly of pathways. As proof-of-principle, a controllable β-carotene biosynthesis pathway (∼16 kb) was reconstructed and optimized by repeatedly using GAL10-GAL1 bidirectional promoters with high efficiency (80-100%). By controling the switch time of the pathway, production of 11 mg/g DCW of total carotenoids (72.57 mg/L) and 7.41 mg/g DCW of β-carotene was achieved in shake-flask culture. In addition, the engineered yeast strain exhibited high genetic stability after 20 generations of subculture. The results demonstrated a controllable and genetically stable biosynthetic pathway capable of increasing the yield of target products. Furthermore, the strategy presented in this study could be extended to construct other pathways in S. cerevisisae. © 2013 Wiley Periodicals, Inc.

Nuclear reactor shutdown control rod assembly

International Nuclear Information System (INIS)

Bilibin, K.

1988-01-01

This patent describes a nuclear reactor having a reactor core and a reactor coolant flowing therethrough, a temperature responsive, self-actuated nuclear reactor shutdown control rod assembly, comprising: an upper drive line terminating at its lower end with a substantially cylindrical wall member having inner and outer surfaces; a lower drive line having a lower end adapted to be attached to a neutron absorber; a ring movable disposed about the outer surface of the wall member of the upper drive line; thermal actuation means adapted to be in heat exchange relationship with coolant in an associated reactor core and in contact with the ring, and balls located within the openings in the upper drive line. When reactor coolant approaches a predetermined design temperature the actuation means moves the ring sufficiently so that the balls move radially out from the recess and into the space formed by the second portion of the ring thereby removing the vertical support for the lower drive line such that the lower drive line moves downwardly and inserts an associated neutron absorber into an associated reactor core resulting in automatic reduction of reactor power

Super-resolution imaging of ESCRT-proteins at HIV-1 assembly sites.

Directory of Open Access Journals (Sweden)

Jens Prescher

2015-02-01

Full Text Available The cellular endosomal sorting complex required for transport (ESCRT machinery is involved in membrane budding processes, such as multivesicular biogenesis and cytokinesis. In HIV-infected cells, HIV-1 hijacks the ESCRT machinery to drive HIV release. Early in the HIV-1 assembly process, the ESCRT-I protein Tsg101 and the ESCRT-related protein ALIX are recruited to the assembly site. Further downstream, components such as the ESCRT-III proteins CHMP4 and CHMP2 form transient membrane associated lattices, which are involved in virus-host membrane fission. Although various geometries of ESCRT-III assemblies could be observed, the actual membrane constriction and fission mechanism is not fully understood. Fission might be driven from inside the HIV-1 budding neck by narrowing the membranes from the outside by larger lattices surrounding the neck, or from within the bud. Here, we use super-resolution fluorescence microscopy to elucidate the size and structure of the ESCRT components Tsg101, ALIX, CHMP4B and CHMP2A during HIV-1 budding below the diffraction limit. To avoid the deleterious effects of using fusion proteins attached to ESCRT components, we performed measurements on the endogenous protein or, in the case of CHMP4B, constructs modified with the small HA tag. Due to the transient nature of the ESCRT interactions, the fraction of HIV-1 assembly sites with colocalizing ESCRT complexes was low (1.5%-3.4%. All colocalizing ESCRT clusters exhibited closed, circular structures with an average size (full-width at half-maximum between 45 and 60 nm or a diameter (determined using a Ripley's L-function analysis of roughly 60 to 100 nm. The size distributions for colocalizing clusters were narrower than for non-colocalizing clusters, and significantly smaller than the HIV-1 bud. Hence, our results support a membrane scission process driven by ESCRT protein assemblies inside a confined structure, such as the bud neck, rather than by large lattices

A pilot cluster randomized controlled trial of structured goal-setting following stroke.

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Taylor, William J; Brown, Melanie; William, Levack; McPherson, Kathryn M; Reed, Kirk; Dean, Sarah G; Weatherall, Mark

2012-04-01

To determine the feasibility, the cluster design effect and the variance and minimal clinical importance difference in the primary outcome in a pilot study of a structured approach to goal-setting. A cluster randomized controlled trial. Inpatient rehabilitation facilities. People who were admitted to inpatient rehabilitation following stroke who had sufficient cognition to engage in structured goal-setting and complete the primary outcome measure. Structured goal elicitation using the Canadian Occupational Performance Measure. Quality of life at 12 weeks using the Schedule for Individualised Quality of Life (SEIQOL-DW), Functional Independence Measure, Short Form 36 and Patient Perception of Rehabilitation (measuring satisfaction with rehabilitation). Assessors were blinded to the intervention. Four rehabilitation services and 41 patients were randomized. We found high values of the intraclass correlation for the outcome measures (ranging from 0.03 to 0.40) and high variance of the SEIQOL-DW (SD 19.6) in relation to the minimally importance difference of 2.1, leading to impractically large sample size requirements for a cluster randomized design. A cluster randomized design is not a practical means of avoiding contamination effects in studies of inpatient rehabilitation goal-setting. Other techniques for coping with contamination effects are necessary.

Controlled synthesis of pompon-like self-assemblies of Pd nanoparticles under microwave irradiation

International Nuclear Information System (INIS)

Tong Xia; Zhao Yanxi; Huang Tao; Liu Hanfan; Liew, Kong Yong

2009-01-01

Pd nanoparticles with uniform, self-assembled pompon-like nanostructure were synthesized by thermal decomposition of palladium acetate under microwave irradiation with methyl isobutyl ketone (MIBK) as a solvent in the presence of a little amount of ethylene glycol (EG) and KOH without using any special stabilizers. The as-synthesized Pd nano-pompons were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction. The results show that the as-prepared Pd nano-pompons with the average diameters in the range of 28-81 nm were self-assemblies organized by hundreds of smaller primary nanoparticles with an average dimension of about 2.4 nm. The sizes of Pd nano-pompons can be well controlled by adjusting the concentration of palladium acetate. A little amount of EG and KOH also plays an important role in controlling the size, uniformity and dispersion of Pd nano-pompons. The Pd nano-pompons can be easily supported on γ-Al 2 O 3 and their catalytic activity was examined preliminarily.

Theoretical realization of cluster-assembled hydrogen storage materials based on terminated carbon atomic chains.

Science.gov (United States)

Liu, Chun-Sheng; An, Hui; Guo, Ling-Ju; Zeng, Zhi; Ju, Xin

2011-01-14

The capacity of carbon atomic chains with different terminations for hydrogen storage is studied using first-principles density functional theory calculations. Unlike the physisorption of H(2) on the H-terminated chain, we show that two Li (Na) atoms each capping one end of the odd- or even-numbered carbon chain can hold ten H(2) molecules with optimal binding energies for room temperature storage. The hybridization of the Li 2p states with the H(2)σ orbitals contributes to the H(2) adsorption. However, the binding mechanism of the H(2) molecules on Na arises only from the polarization interaction between the charged Na atom and the H(2). Interestingly, additional H(2) molecules can be bound to the carbon atoms at the chain ends due to the charge transfer between Li 2s2p (Na 3s) and C 2p states. More importantly, dimerization of these isolated metal-capped chains does not affect the hydrogen binding energy significantly. In addition, a single chain can be stabilized effectively by the C(60) fullerenes termination. With a hydrogen uptake of ∼10 wt.% on Li-coated C(60)-C(n)-C(60) (n = 5, 8), the Li(12)C(60)-C(n)-Li(12)C(60) complex, keeping the number of adsorbed H(2) molecules per Li and stabilizing the dispersion of individual Li atoms, can serve as better building blocks of polymers than the (Li(12)C(60))(2) dimer. These findings suggest a new route to design cluster-assembled hydrogen storage materials based on terminated sp carbon chains.

Coordinated control of active and reactive power of distribution network with distributed PV cluster via model predictive control

Science.gov (United States)

Ji, Yu; Sheng, Wanxing; Jin, Wei; Wu, Ming; Liu, Haitao; Chen, Feng

2018-02-01

A coordinated optimal control method of active and reactive power of distribution network with distributed PV cluster based on model predictive control is proposed in this paper. The method divides the control process into long-time scale optimal control and short-time scale optimal control with multi-step optimization. The models are transformed into a second-order cone programming problem due to the non-convex and nonlinear of the optimal models which are hard to be solved. An improved IEEE 33-bus distribution network system is used to analyse the feasibility and the effectiveness of the proposed control method

Silver Clusters in Zeolites: From Self-Assembly to Ground-Breaking Luminescent Properties.

Science.gov (United States)

Coutiño-Gonzalez, Eduardo; Baekelant, Wouter; Steele, Julian A; Kim, Cheol Woong; Roeffaers, Maarten B J; Hofkens, Johan

2017-09-19

Interest for functional silver clusters (Ag-CLs) has rapidly grown over years due to large advances in the field of nanoscale fabrication and materials science. The continuous development of strategies to fabricate small-scale silver clusters, together with their interesting physicochemical properties (molecule-like discrete energy levels, for example), make them very attractive for a wide variety of applied research fields, from biotechnology and the environmental sciences to fundamental chemistry and physics. Apart from useful catalytic properties, silver clusters (Ag n , n counterbalancing ions, silver loading, and zeolite topology, and cannot be overlooked. This Account is intended to shed light on the current state-of-the-art of luminescent Ag-CLs confined in zeolitic matrices, emphasizing the use of combinatorial approaches to overcome problems associated with the correct characterization and correlation of their structural, electronic, and photoluminescence properties, all to establish the important design principles for developing functional silver-zeolite-based materials. Additionally, examples of emerging applications and future perspectives for functional luminescent Ag-zeolite materials are addressed in this Account.

Environmental filtering of eudicot lineages underlies phylogenetic clustering in tropical South American flooded forests.

Science.gov (United States)

Aldana, Ana M; Carlucci, Marcos B; Fine, Paul V A; Stevenson, Pablo R

2017-02-01

The phylogenetic community assembly approach has been used to elucidate the role of ecological and historical processes in shaping tropical tree communities. Recent studies have shown that stressful environments, such as seasonally dry, white-sand and flooded forests tend to be phylogenetically clustered, arguing for niche conservatism as the main driver for this pattern. Very few studies have attempted to identify the lineages that contribute to such assembly patterns. We aimed to improve our understanding of the assembly of flooded forest tree communities in Northern South America by asking the following questions: are seasonally flooded forests phylogenetically clustered? If so, which angiosperm lineages are over-represented in seasonally flooded forests? To assess our hypotheses, we investigated seasonally flooded and terra firme forests from the Magdalena, Orinoco and Amazon Basins, in Colombia. Our results show that, regardless of the river basin in which they are located, seasonally flooded forests of Northern South America tend to be phylogenetically clustered, which means that the more abundant taxa in these forests are more closely related to each other than expected by chance. Based on our alpha and beta phylodiversity analyses we interpret that eudicots are more likely to adapt to extreme environments such as seasonally flooded forests, which indicates the importance of environmental filtering in the assembly of the Neotropical flora.

Control rod effects on reaction rate distributions in tight pitched PuO2-UO2 fuel assembly

International Nuclear Information System (INIS)

Gil, Choong-Sup; Okumura, Keisuke; Ishiguro, Yukio

1991-11-01

Investigations were made for the heterogeneity effects caused by insertion or withdrawal of a B 4 C control rod on fine structure of reaction rates distributions in a tight pitched PuO 2 -UO 2 fuel assembly. Analysis was carried out by using the VIM and SRAC codes with the libraries based on JENDL-2 for the hexagonal fuel assembly basically corresponding to the PROTEUS-LWHCR experimental core. The reaction rates are affected more remarkably by the withdrawal of the control rod rather than its insertion. The changes of the reaction rates were decomposed into three terms of spectrum shifts, the changes of effective cross sections with fine groups, and their higher order components. From the analysis, it is concluded that most changes of reaction rates are caused by spectral shifts. The SRAC code with fine group constants can predict the distribution of reaction rates and their ratios with the accuracy of about 5 % except for the values related to Pu-242 capture rate, as compared with the VIM results. To increase the accuracy, it is necessary to generate the effective cross sections of the fuel near control rods with consideration of the heterogeneities in the fuel assembly. (author)

Power semiconductor device adaptive cooling assembly

NARCIS (Netherlands)

2011-01-01

The invention relates to a power semiconductor device (100) cooling assembly for cooling a power semiconductor device (100), wherein the assembly comprises an actively cooled heat sink (102) and a controller (208; 300), wherein the controller (208; 300) is adapted for adjusting the cooling

Reconstitutable fuel assembly for a nuclear reactor

International Nuclear Information System (INIS)

Ferlan, S.J.; Kmonk, S.; Schallenberger, J.M.

1982-01-01

A reconstitutable fuel assembly for a nuclear reactor which includes a mechanical, rather than metallurgical, arrangement for connecting control rod guide thimbles to the top and bottom nozzles of a fuel assembly. Multiple sleeves enclosing control rod guide thimbles interconnect the top nozzle to the fuel assembly upper grid. Each sleeve is secured to the top nozzle by retaining rings disposed on opposite sides of the nozzle. Similar sleeves enclose the lower end of control rod guide thimbles and interconnect the bottom nozzle with the lowermost grid on the assembly. An end plug fitted in the bottom end of each sleeve extends through the bottom nozzle and is secured thereto by a retaining ring. Should it be necessary to remove a fuel rod from the assembly, the retaining rings in either the top or bottom nozzles may be removed to release the nozzle from the control rod guide thimbles and thus expose either the top or bottom ends of the fuel rods to fuel rod removing mechanisms

Order from the disorder: hierarchical nanostructures self-assembled from the gas phase (Conference Presentation)

Science.gov (United States)

Di Fonzo, Fabio

2017-02-01

The assembly of nanoscale building blocks in engineered mesostructures is one of the fundamental goals of nanotechnology. Among the various processes developed to date, self-assembly emerges as one of the most promising, since it relays solely on basic physico-chemical forces. Our research is focused on a new type of self-assembly strategy from the gas-phase: Scattered Ballistic Deposition (SBD). SBD arises from the interaction of a supersonic molecular beam with a static gas and enables the growth of quasi-1D hierarchical mesostructures. Overall, they resemble a forest composed of individual, high aspect-ratio, tree-like structures, assembled from amorphous or crystalline nanoparticles. SBD is a general occurring phenomenon and can be obtained with different vapour or cluster sources. In particular, SBD by Pulsed Laser Deposition is a convenient physical vapor technique that allows the generation of supersonic plasma jets from any inorganic material irrespective of melting temperature, preserving even the most complex stoichiometries. One of the advantages of PLD over other vapour deposition techniques is extremely wide operational pressure range, from UHV to ambient pressure. These characteristics allowed us to develop quasi-1D hierarchical nanostructures from different transition metal oxides, semiconductors and metals. The precise control offered by the SBD-PLD technique over material properties at the nanoscale allowed us to fabricate ultra-thin, high efficiency hierarchical porous photonic crystals with Bragg reflectivity up to 85%. In this communication we will discuss the application of these materials to solar energy harvesting and storage, stimuli responsive photonic crystals and smart surfaces with digital control of their wettability behaviour.

Telerobotic control of a dextrous manipulator using master and six-DOF hand-controllers for space assembly and servicing tasks

Science.gov (United States)

O'Hara, John M.

1987-01-01

Two studies were conducted evaluating methods of controlling a telerobot; bilateral force reflecting master controllers and proportional rate six degrees of freedom (DOF) hand controllers. The first study compared the controllers on performance of single manipulator arm tasks, a peg-in-the-hole task, and simulated satellite orbital replacement unit changeout. The second study, a Space Station truss assembly task, required simultaneous operation of both manipulator arms (all 12 DOFs) and complex multiaxis slave arm movements. Task times were significantly longer and fewer errors were committed with the hand controllers. The hand controllers were also rated significantly higher in cognitive and manual control workload on the two-arm task. The master controllers were rated significantly higher in physical workload. There were no significant differences in ratings of manipulator control quality.

Startup physics tests at Temelin NPP, Unit 1

International Nuclear Information System (INIS)

Sedlacek, M.; Minarcin, M.; Toth, L.; Elko, M.; Hascik, R.

2002-01-01

The objective, scope and proceedings of the physics tests of Temelin NPP, Unit 1 physical commissioning are given in this paper. Furthermore, some results of selected physics tests are presented: reactor initial criticality test, determination of reactor power range for physics testing, measurement of control rod cluster assembly group no. 10 reactivity worth in case of limitation system LS(a) actuation, control rod cluster assembly system reactivity worth measurement with single rod cluster assembly of greatest reactivity worth stuck in fully withdrawn position, measurement of differential reactivity worth of control rod cluster assembly group no. 9, boron 'endpoint' determination and measurement of power reactivity coefficient (Authors)

Effectiveness of job rotation for preventing work-related musculoskeletal diseases: a cluster randomised controlled trial.

Science.gov (United States)

Comper, Maria Luiza Caires; Dennerlein, Jack Tigh; Evangelista, Gabriela Dos Santos; Rodrigues da Silva, Patricia; Padula, Rosimeire Simprini

2017-08-01

Job rotation is an organisational strategy widely used on assembly lines in manufacturing industries to mitigate workers' exposure so as to prevent musculoskeletal disorders. This study aimed to evaluate the effectiveness of job rotation for reducing working hours lost due to sick leave resulting from musculoskeletal diseases. The design consisted of a 1-year cluster randomised controlled trial with a blinded assessor. Production sectors of the textile industry were randomised to intervention and control groups. Both groups received ergonomic training. The intervention group performed a job rotation programme. The primary outcome measure was number of working hours lost due to sick leave as a result of musculoskeletal disease (ICD-10). The secondary outcome measures were musculoskeletal symptoms (Yes/No), risk factors for musculoskeletal diseases (0-10), psychosocial factors and fatigue (0-100), general health (0-100), and productivity (0-10). All secondary outcomes were measured at baseline and 12-month follow-up. At the 12-month follow-up, both groups showed an increase in the number of working hours lost due to sick leave for musculoskeletal disease. There was no significant difference between the job rotation intervention group (mean deviation -5.6 hours, 95% CI -25.0 to 13.8) at the 12-month follow-up and the control group. There were no significant differences between groups for the secondary outcomes (p>0.05). The job rotation programme was not effective in reducing the number of working hours lost due to sick leave, decreasing the prevalence of musculoskeletal symptoms, or improving perception of musculoskeletal pain and workplace risk factors, psychosocial risk factors and productivity. NCT01979731. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Development and Qualification of ATV Propulsion Assemblies

Science.gov (United States)

Riehle, M.; Jost, R.

2002-01-01

qualification will be presented starting from components and assemblies up to sub- system. Exemplarily, the path of the 200N shall be described in more detail since requirements of various kinds are to be applied here. This thruster is used in a total of 28 engines located on 4 thruster cluster assemblies on the bottom and 4 on the front of the space craft delivering steady state thrust as well as impulse bit to the ATV and can be used also as backup for the main thrusters. Safety and thus redundancy is one of the major driver for the design. As a first step i.e. the thrusters are equipped with measures to detect malfunctions and problems by continuous measuring chamber temperature and combustion pressure. The layout of the thruster clusters arrangement in combination with control electronics are such are such that multiple independent branches are controlling the system by which each of them could to fulfil the whole operational objectives. The thruster clusters are also affected by most of the environmental constraints that require careful thermal or mechanical design. For example severe shock loads induced by the stage separation nearby as well as meteorites and debris have to be taken into account for mechanical design. Or large transient pressure spikes and water hammer caused by simultaneous operation of thrusters have to be considered for hydraulic design. As well as extreme conditions for thermal design facing high thermal loads both radiation and conductive during thruster firing and sun exposure of the externally mounted assembly as well as low heater budget and I/F flux limitations when exposed to deep space during long phases. Intensive test programs have been carried out or are under preparation as well as complementary numerical analysis are completing and supporting each step of the development. The paper will describe those design and qualification activities as well as the results as far as available to that time in order to give an overview of the status of

Star Cluster Structure from Hierarchical Star Formation

Science.gov (United States)

Grudic, Michael; Hopkins, Philip; Murray, Norman; Lamberts, Astrid; Guszejnov, David; Schmitz, Denise; Boylan-Kolchin, Michael

2018-01-01

Young massive star clusters (YMCs) spanning 104-108 M⊙ in mass generally have similar radial surface density profiles, with an outer power-law index typically between -2 and -3. This similarity suggests that they are shaped by scale-free physics at formation. Recent multi-physics MHD simulations of YMC formation have also produced populations of YMCs with this type of surface density profile, allowing us to narrow down the physics necessary to form a YMC with properties as observed. We show that the shallow density profiles of YMCs are a natural result of phase-space mixing that occurs as they assemble from the clumpy, hierarchically-clustered configuration imprinted by the star formation process. We develop physical intuition for this process via analytic arguments and collisionless N-body experiments, elucidating the connection between star formation physics and star cluster structure. This has implications for the early-time structure and evolution of proto-globular clusters, and prospects for simulating their formation in the FIRE cosmological zoom-in simulations.

Net-zero Building Cluster Simulations and On-line Energy Forecasting for Adaptive and Real-Time Control and Decisions

Science.gov (United States)

Li, Xiwang

Buildings consume about 41.1% of primary energy and 74% of the electricity in the U.S. Moreover, it is estimated by the National Energy Technology Laboratory that more than 1/4 of the 713 GW of U.S. electricity demand in 2010 could be dispatchable if only buildings could respond to that dispatch through advanced building energy control and operation strategies and smart grid infrastructure. In this study, it is envisioned that neighboring buildings will have the tendency to form a cluster, an open cyber-physical system to exploit the economic opportunities provided by a smart grid, distributed power generation, and storage devices. Through optimized demand management, these building clusters will then reduce overall primary energy consumption and peak time electricity consumption, and be more resilient to power disruptions. Therefore, this project seeks to develop a Net-zero building cluster simulation testbed and high fidelity energy forecasting models for adaptive and real-time control and decision making strategy development that can be used in a Net-zero building cluster. The following research activities are summarized in this thesis: 1) Development of a building cluster emulator for building cluster control and operation strategy assessment. 2) Development of a novel building energy forecasting methodology using active system identification and data fusion techniques. In this methodology, a systematic approach for building energy system characteristic evaluation, system excitation and model adaptation is included. The developed methodology is compared with other literature-reported building energy forecasting methods; 3) Development of the high fidelity on-line building cluster energy forecasting models, which includes energy forecasting models for buildings, PV panels, batteries and ice tank thermal storage systems 4) Small scale real building validation study to verify the performance of the developed building energy forecasting methodology. The outcomes of

The Stormy Life of Galaxy Clusters

Science.gov (United States)

Rudnick, Lawrence

2018-01-01

Galaxy clusters, the largest gravitationally bound structures, hold the full history of their baryonic evolution, serve as important cosmological tools and allow us to probe unique physical regimes in their diffuse plasmas. With characteristic dynamical timescales of 107-109 years, these diffuse thermal and relativistic media continue to evolve, as dark matter drives major mergers and more gentle continuing accretion. The history of this assembly is encoded in the plasmas, and a wide range of observational and theoretical investigations are aimed at decoding their signatures. X-ray temperature and density variations, low Mach number shocks, and "cold front" discontinuities all illuminate clusters' continued evolution. Radio structures and spectra are passive indicators of merger shocks, while radio galaxy distortions reveal the complex motions in the intracluster medium. Deep in cluster cores, AGNs associated with brightest cluster galaxies provide ongoing energy, and perhaps even stabilize the intracluster medium. In this talk, we will recount this evolving picture of the stormy ICM, and suggest areas of likely advance in the coming years.

Controlled AFM detachments and movement of nanoparticles: gold clusters on HOPG at different temperatures.

Science.gov (United States)

Tripathi, Manoj; Paolicelli, Guido; D'Addato, Sergio; Valeri, Sergio

2012-06-22

The effect of temperature on the onset of movement of gold nanoclusters (diameter 27 nm) deposited on highly oriented pyrolytic graphite (HOPG) has been studied by atomic force microscopy (AFM) techniques. Using the AFM with amplitude modulation (tapping mode AFM) we have stimulated and controlled the movement of individual clusters. We show how, at room temperature, controlled detachments and smooth movements can be obtained for clusters having dimensions comparable to or smaller than the tip radius. Displacement is practically visible in real time and it can be started and stopped easily by adjusting only one parameter, the tip amplitude oscillation. Analysing the energy dissipation signal at the onset of nanocluster sliding we evaluated a detachment threshold energy as a function of temperature in the range 300-413 K. We also analysed single cluster thermal induced displacement and combining this delicate procedure with AFM forced movement behaviour we conclude that detachment threshold energy is directly related to the activation energy of nanocluster diffusion and it scales linearly with temperature as expected for a single-particle thermally activated process.

Energy transfer and clustering of photosynthetic light-harvesting complexes in reconstituted lipid membranes

International Nuclear Information System (INIS)

Dewa, Takehisa; Sumino, Ayumi; Watanabe, Natsuko; Noji, Tomoyasu; Nango, Mamoru

2013-01-01

Highlights: ► Photosynthetic light-harvesting complexes were reconstituted into lipid membranes. ► Energy transfers between light-harvesting complexes were examined. ► Atomic force microscopy indicated cluster formation of light-harvesting complexes. ► Efficient energy transfer was observed for the clustered complexes in the membranes. - Abstract: In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency

Energy transfer and clustering of photosynthetic light-harvesting complexes in reconstituted lipid membranes

Energy Technology Data Exchange (ETDEWEB)

Dewa, Takehisa, E-mail: takedewa@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Japan Science and Technology, PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan); Sumino, Ayumi; Watanabe, Natsuko; Noji, Tomoyasu [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nango, Mamoru, E-mail: nango@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2013-06-20

Highlights: ► Photosynthetic light-harvesting complexes were reconstituted into lipid membranes. ► Energy transfers between light-harvesting complexes were examined. ► Atomic force microscopy indicated cluster formation of light-harvesting complexes. ► Efficient energy transfer was observed for the clustered complexes in the membranes. - Abstract: In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency.

Vibration control of a cluster of buildings through the Vibrating Barrier

Science.gov (United States)

Tombari, A.; Garcia Espinosa, M.; Alexander, N. A.; Cacciola, P.

2018-02-01

A novel device, called Vibrating Barrier (ViBa), that aims to reduce the vibrations of adjacent structures subjected to ground motion waves has been recently proposed. The ViBa is a structure buried in the soil and detached from surrounding buildings that is able to absorb a significant portion of the dynamic energy arising from the ground motion. The working principle exploits the dynamic interaction among vibrating structures due to the propagation of waves through the soil, namely the structure-soil-structure interaction. In this paper the efficiency of the ViBa is investigated to control the vibrations of a cluster of buildings. To this aim, a discrete model of structures-site interaction involving multiple buildings and the ViBa is developed where the effects of the soil on the structures, i.e. the soil-structure interaction (SSI), the structure-soil-structure interaction (SSSI) as well as the ViBa-soil-structures interaction are taken into account by means of linear elastic springs. Closed-form solutions are derived to design the ViBa in the case of harmonic excitation from the analysis of the discrete model. Advanced finite element numerical simulations are performed in order to assess the efficiency of the ViBa for protecting more than a single building. Parametric studies are also conducted to identify beneficial/adverse effects in the use of the proposed vibration control strategy to protect cluster of buildings. Finally, experimental shake table tests are performed to a prototype of a cluster of two buildings protected by the ViBa device for validating the proposed numerical models.

A kinetic model for impact/sliding wear of pressurized water reactor internal components. Application to rod cluster control assemblies

International Nuclear Information System (INIS)

Zbinden, M.; Durbec, V.

1996-12-01

A new concept of industrial wear model adapted to components of nuclear plants is proposed. Its originality is to be supported, on one hand, by experimental results obtained via wear machines of relatively short operational times, and, on the other hand, by the information obtained from the operating feedback over real wear kinetics of the reactors components. The proposed model is illustrated by an example which corresponds to a specific real situation. The determination of the coefficients permitting to cover all assembly of configurations and the validation of the model in these configurations have been the object of the most recent work. (author)

The effect on cross sections for Quad Cities by introducing control rod history in the assembly program LEWARD

International Nuclear Information System (INIS)

Nonboel, E.

1989-08-01

This paper shows the effect on the 2-group neutron cross sections for the BWR reactor Quad Cities by introducing control rod ''history'' in the assembly program LEWARD. Control rod ''history'' is a concept which accounts for the movement of control rods during operation. (author)

Modelling of Control Bars in Calculations of Boiling Water Reactors

International Nuclear Information System (INIS)

Khlaifi, A.; Buiron, L.

2004-01-01

The core of a nuclear reactor is generally composed of a neat assemblies of fissile material from where neutrons were descended. In general, the energy of fission is extracted by a fluid serving to cool clusters. A reflector is arranged around the assemblies to reduce escaping of neutrons. This is made outside the reactor core. Different mechanisms of reactivity are generally necessary to control the chain reaction. Manoeuvring of Boiling Water Reactor takes place by controlling insertion of absorbent rods to various places of the core. If no blocked assembly calculations are known and mastered, blocked assembly neutronic calculation are delicate and often treated by case to case in present studies [1]. Answering the question how to model crossbar for the control of a boiling water reactor ? requires the choice of a representation level for every chain of variables, the physical model, and its representing equations, etc. The aim of this study is to select the best applicable parameter serving to calculate blocked assembly of a Boiling Water Reactor. This will be made through a range of representative configurations of these reactors and used absorbing environment, in order to illustrate strategies of modelling in the case of an industrial calculation. (authors)

Iron-sulfur cluster biogenesis in mammalian cells: new insights into the molecular mechanisms of cluster delivery

Science.gov (United States)

Maio, Nunziata; Rouault, Tracey. A.

2014-01-01

Iron-sulfur (Fe-S) clusters are ancient, ubiquitous cofactors composed of iron and inorganic sulfur. The combination of the chemical reactivity of iron and sulfur, together with many variations of cluster composition, oxidation states and protein environments, enables Fe-S clusters to participate in numerous biological processes. Fe-S clusters are essential to redox catalysis in nitrogen fixation, mitochondrial respiration and photosynthesis, to regulatory sensing in key metabolic pathways (i. e. cellular iron homeostasis and oxidative stress response), and to the replication and maintenance of the nuclear genome. Fe-S cluster biogenesis is a multistep process that involves a complex sequence of catalyzed protein- protein interactions and coupled conformational changes between the components of several dedicated multimeric complexes. Intensive studies of the assembly process have clarified key points in the biogenesis of Fe-S proteins. However several critical questions still remain, such as: what is the role of frataxin? Why do some defects of Fe-S cluster biogenesis cause mitochondrial iron overload? How are specific Fe-S recipient proteins recognized in the process of Fe-S transfer? This review focuses on the basic steps of Fe-S cluster biogenesis, drawing attention to recent advances achieved on the identification of molecular features that guide selection of specific subsets of nascent Fe-S recipients by the cochaperone HSC20. Additionally, it outlines the distinctive phenotypes of human diseases due to mutations in the components of the basic pathway. PMID:25245479

Experimental investigation of control absorber blade effects in a modern 10x10 BWR assembly

Energy Technology Data Exchange (ETDEWEB)

Jatuff, F.; Grimm, P.; Murphy, M.; Luethi, A.; Seiler, R.; Joneja, O.; Meister, A.; Geemert, R. van; Brogli, R.; Chawla, R. [Paul Scherrer Inst., CH-5232 Villigen PSI (Switzerland); Williams, T. [EGL Laufenburg (Switzerland); Helmersson, S. [Westinghouse Atom (Sweden)

2001-03-01

The accurate estimation of reactor physics parameters related to the presence of cruciform absorber blades. In Boiling Water Reactors (BWR) is important for safety assessment, and for achieving a flexible operation during the cycle. Characteristics which are affected strongly include the power distribution for controlled core regions and its impact on linear heat generation rate margins, as well as the build-up of plutonium, and its influence on core excess reactivity and the reactivity worth of the shutdown system. PSI and the Swiss Nuclear Utilities (UAK) are conducting an experimental reactor physics programme related to modern Light Water Reactor (LWR) fuel assemblies, as employed in the Swiss nuclear power plants: the so-called. LWR-PROTEUS Phase I project. A significant part of this project has been devoted to the characterization of highly heterogeneous BWR fuel elements in the presence of absorber blades. The paper presents typical results for the performance of modern lattice codes in the estimation of controlled assembly reaction rate distributions, the sensitivity to the geometrical and material characterization, and a preliminary comparison of reflected-test-zone calculations with experimental reaction rate distributions measured in a Westinghouse SVEA-96+ assembly under full-density water moderation conditions in the presence of Westinghouse boron-carbide absorber blades. (author)

Experimental investigation of control absorber blade effects in a modern 10x10 BWR assembly

International Nuclear Information System (INIS)

Jatuff, F.; Grimm, P.; Murphy, M.; Luethi, A.; Seiler, R.; Joneja, O.; Meister, A.; Geemert, R. van; Brogli, R.; Chawla, R.; Williams, T.; Helmersson, S.

2001-01-01

The accurate estimation of reactor physics parameters related to the presence of cruciform absorber blades. In Boiling Water Reactors (BWR) is important for safety assessment, and for achieving a flexible operation during the cycle. Characteristics which are affected strongly include the power distribution for controlled core regions and its impact on linear heat generation rate margins, as well as the build-up of plutonium, and its influence on core excess reactivity and the reactivity worth of the shutdown system. PSI and the Swiss Nuclear Utilities (UAK) are conducting an experimental reactor physics programme related to modern Light Water Reactor (LWR) fuel assemblies, as employed in the Swiss nuclear power plants: the so-called. LWR-PROTEUS Phase I project. A significant part of this project has been devoted to the characterization of highly heterogeneous BWR fuel elements in the presence of absorber blades. The paper presents typical results for the performance of modern lattice codes in the estimation of controlled assembly reaction rate distributions, the sensitivity to the geometrical and material characterization, and a preliminary comparison of reflected-test-zone calculations with experimental reaction rate distributions measured in a Westinghouse SVEA-96+ assembly under full-density water moderation conditions in the presence of Westinghouse boron-carbide absorber blades. (author)

Controlled interface between carbon fiber and epoxy by molecular self-assembly method

International Nuclear Information System (INIS)

He Jinmei; Huang Yudong; Liu Li; Cao Hailin

2006-01-01

In this paper, a new treatment method based on molecular self-assembly on carbon fiber surface was proposed for obtaining a controlled interface between carbon fiber and epoxy matrix in composite system. To form the controlled interfacial region, the surfaces of carbon fibers were first metallized by electroless Ag plating, then were reacted with a series of thiols (different chain lengths and terminally functional groups) to form self-assembly monolayers (SAMs), which further reacted with epoxy resin to generate a strong adhesion interface. The morphology, structure and composition of untreated and treated carbon fiber surface were investigated by atomic force microscope (AFM), surface-enhanced Raman scattering spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS), respectively. SERS study showed that thiols chemisorbed on Ag/carbon fiber in the form of thiolate species via the strong S-Ag coordinative bond. XPS study further confirmed the chemisorption by an S 2p 3/2 component observed at 162.2 eV. The binding energy was characteristic of silver thiolate. The interfacial shear strength of the carbon fiber/epoxy microcomposites was evaluated by the microbond technique. The results showed that there was a direct effect of the interfacial parameters changes such as chain lengths and surface functional groups on the fiber/matrix adhesion

Control of cluster ion sizes for efficient injection heating

International Nuclear Information System (INIS)

Enjoji, Hiroshi; Be, S.H.; Yano, Katsuki; Okamoto, Kosuke

1976-01-01

For heating of plasmas by injection of hydrogen cluster ions, the specific size (N/Z) approximately 10 2 molecules/charge is believed to be most desirable. A fundamental research to develop a practical method for tailoring large cluster ions into small suitable sizes has been carried out by using nitrogen cluster ions of the initial mean specific size (N/Z) 0 approximately 10 5 . The beam of neutral large clusters of total intensity 20 mAsub(eq) was led to an ionizer and then the large cluster ions are accelerated to 8.9 keV before entering the divider which disintegrates them into small fragments by multiple ionization. The mean specific size of disintegrated cluster ions (N/Z)' becomes smaller with increase in ionizing electron current of the divider. (N/Z)' becomes 10 3 approximately 10 4 at an electron current of 140 mA and an accelerating voltage of 680 V of the divider with its efficiency of 20 approximately 60%. Thus, the original large cluster ions are divided into small fragments of which the mean specific size is 1/20 approximately 1/100 of the initial value without much decrease in total intensity of the cluster ion beam

Gene cluster statistics with gene families.

Science.gov (United States)

Raghupathy, Narayanan; Durand, Dannie

2009-05-01

Identifying genomic regions that descended from a common ancestor is important for understanding the function and evolution of genomes. In distantly related genomes, clusters of homologous gene pairs are evidence of candidate homologous regions. Demonstrating the statistical significance of such "gene clusters" is an essential component of comparative genomic analyses. However, currently there are no practical statistical tests for gene clusters that model the influence of the number of homologs in each gene family on cluster significance. In this work, we demonstrate empirically that failure to incorporate gene family size in gene cluster statistics results in overestimation of significance, leading to incorrect conclusions. We further present novel analytical methods for estimating gene cluster significance that take gene family size into account. Our methods do not require complete genome data and are suitable for testing individual clusters found in local regions, such as contigs in an unfinished assembly. We consider pairs of regions drawn from the same genome (paralogous clusters), as well as regions drawn from two different genomes (orthologous clusters). Determining cluster significance under general models of gene family size is computationally intractable. By assuming that all gene families are of equal size, we obtain analytical expressions that allow fast approximation of cluster probabilities. We evaluate the accuracy of this approximation by comparing the resulting gene cluster probabilities with cluster probabilities obtained by simulating a realistic, power-law distributed model of gene family size, with parameters inferred from genomic data. Surprisingly, despite the simplicity of the underlying assumption, our method accurately approximates the true cluster probabilities. It slightly overestimates these probabilities, yielding a conservative test. We present additional simulation results indicating the best choice of parameter values for data

Design of a versatile chemical assembly method for patterning colloidal nanoparticles

International Nuclear Information System (INIS)

Choi, J H; Adams, S M; Ragan, R

2009-01-01

Poly(methyl methacrylate) (PMMA) domains in phase-separated polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer thin films were chemically modified for controlled placement of solution synthesized Au nanoparticles having a mean diameter of 24 nm. Colloidal Au nanoparticles functionalized with thioctic acid were immobilized on amine functionalized PMMA domains on the PS-b-PMMA template using 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride linking chemistry and N-hydroxy sulfosuccinimide stabilizer. Atomic force microscopy and scanning electron microscopy images demonstrated immobilization of Au nanoparticles commensurate with PMMA domains. Nanoparticles form into clusters of single particles, dimers, and linear chains as directed by the PMMA domain size and shape. Capillary forces influence the spacing between Au nanoparticles on PMMA domains. Inter-particle spacings below 3 nm were achieved and these assemblies of closely spaced nanoparticle clusters are expected to exhibit strong localized electromagnetic fields. Thus, these processes and material systems provide an experimental platform for studying resonantly enhanced excitations of surface plasmons as a function of material and geometric structure as well as utilization in catalytic applications.

Self-assembling hybrid diamond–biological quantum devices

International Nuclear Information System (INIS)

Albrecht, A; B Plenio, M; Koplovitz, G; Yochelis, S; Paltiel, Y; Retzker, A; Nevo, Y; Shoseyov, O; Jelezko, F; Porath, D

2014-01-01

The realization of scalable arrangements of nitrogen vacancy (NV) centers in diamond remains a key challenge on the way towards efficient quantum information processing, quantum simulation and quantum sensing applications. Although technologies based on implanting NV-centers in bulk diamond crystals or hybrid device approaches have been developed, they are limited by the achievable spatial resolution and by the intricate technological complexities involved in achieving scalability. We propose and demonstrate a novel approach for creating an arrangement of NV-centers, based on the self-assembling capabilities of biological systems and their beneficial nanometer spatial resolution. Here, a self-assembled protein structure serves as a structural scaffold for surface functionalized nanodiamonds, in this way allowing for the controlled creation of NV-structures on the nanoscale and providing a new avenue towards bridging the bio–nano interface. One-, two- as well as three-dimensional structures are within the scope of biological structural assembling techniques. We realized experimentally the formation of regular structures by interconnecting nanodiamonds using biological protein scaffolds. Based on the achievable NV-center distances of 11 nm, we evaluate the expected dipolar coupling interaction with neighboring NV-centers as well as the expected decoherence time. Moreover, by exploiting these couplings, we provide a detailed theoretical analysis on the viability of multiqubit quantum operations, suggest the possibility of individual addressing based on the random distribution of the NV intrinsic symmetry axes and address the challenges posed by decoherence and imperfect couplings. We then demonstrate in the last part that our scheme allows for the high-fidelity creation of entanglement, cluster states and quantum simulation applications. (papers)

Self-assembling hybrid diamond-biological quantum devices

Science.gov (United States)

Albrecht, A.; Koplovitz, G.; Retzker, A.; Jelezko, F.; Yochelis, S.; Porath, D.; Nevo, Y.; Shoseyov, O.; Paltiel, Y.; Plenio, M. B.

2014-09-01

The realization of scalable arrangements of nitrogen vacancy (NV) centers in diamond remains a key challenge on the way towards efficient quantum information processing, quantum simulation and quantum sensing applications. Although technologies based on implanting NV-centers in bulk diamond crystals or hybrid device approaches have been developed, they are limited by the achievable spatial resolution and by the intricate technological complexities involved in achieving scalability. We propose and demonstrate a novel approach for creating an arrangement of NV-centers, based on the self-assembling capabilities of biological systems and their beneficial nanometer spatial resolution. Here, a self-assembled protein structure serves as a structural scaffold for surface functionalized nanodiamonds, in this way allowing for the controlled creation of NV-structures on the nanoscale and providing a new avenue towards bridging the bio-nano interface. One-, two- as well as three-dimensional structures are within the scope of biological structural assembling techniques. We realized experimentally the formation of regular structures by interconnecting nanodiamonds using biological protein scaffolds. Based on the achievable NV-center distances of 11 nm, we evaluate the expected dipolar coupling interaction with neighboring NV-centers as well as the expected decoherence time. Moreover, by exploiting these couplings, we provide a detailed theoretical analysis on the viability of multiqubit quantum operations, suggest the possibility of individual addressing based on the random distribution of the NV intrinsic symmetry axes and address the challenges posed by decoherence and imperfect couplings. We then demonstrate in the last part that our scheme allows for the high-fidelity creation of entanglement, cluster states and quantum simulation applications.

Mechanism of acetylcholine receptor cluster formation induced by DC electric field.

Directory of Open Access Journals (Sweden)

Hailong Luke Zhang

Full Text Available BACKGROUND: The formation of acetylcholine receptor (AChR cluster is a key event during the development of the neuromuscular junction. It is induced through the activation of muscle-specific kinase (MuSK by the heparan-sulfate proteoglycan agrin released from the motor axon. On the other hand, DC electric field, a non-neuronal stimulus, is also highly effective in causing AChRs to cluster along the cathode-facing edge of muscle cells. METHODOLOGY/PRINCIPAL FINDINGS: To understand its molecular mechanism, quantum dots (QDs were used to follow the movement of AChRs as they became clustered under the influence of electric field. From analyses of trajectories of AChR movement in the membrane, it was concluded that diffuse receptors underwent Brownian motion until they were immobilized at sites of cluster formation. This supports the diffusion-mediated trapping model in explaining AChR clustering under the influence of this stimulus. Disrupting F-actin cytoskeleton assembly and interfering with rapsyn-AChR interaction suppressed this phenomenon, suggesting that these are integral components of the trapping mechanism induced by the electric field. Consistent with the idea that signaling pathways are activated by this stimulus, the localization of tyrosine-phosphorylated forms of AChR β-subunit and Src was observed at cathodal AChR clusters. Furthermore, disrupting MuSK activity through the expression of a kinase-dead form of this enzyme abolished electric field-induced AChR clustering. CONCLUSIONS: These results suggest that DC electric field as a physical stimulus elicits molecular reactions in muscle cells in the form of cathodal MuSK activation in a ligand-free manner to trigger a signaling pathway that leads to cytoskeletal assembly and AChR clustering.

Cranial vasculature in zebrafish forms by angioblast cluster-derived angiogenesis.

Science.gov (United States)

Proulx, Kira; Lu, Annie; Sumanas, Saulius

2010-12-01

Formation of embryonic vasculature involves vasculogenesis as endothelial cells differentiate and aggregate into vascular cords and angiogenesis which includes branching from the existing vessels. In the zebrafish which has emerged as an advantageous model to study vasculogenesis, cranial vasculature is thought to originate by a combination of vasculogenesis and angiogenesis, but how these processes are coordinated is not well understood. To determine how angioblasts assemble into cranial vasculature, we generated an etsrp:GFP transgenic line in which GFP reporter is expressed under the promoter control of an early regulator of vascular and myeloid development, etsrp/etv2. By utilizing time-lapse imaging we show that cranial vessels originate by angiogenesis from angioblast clusters, which themselves form by the mechanism of vasculogenesis. The two major pairs of bilateral clusters include the rostral organizing center (ROC) which gives rise to the most rostral cranial vessels and the midbrain organizing center (MOC) which gives rise to the posterior cranial vessels and to the myeloid and endocardial lineages. In Etsrp knockdown embryos initial cranial vasculogenesis proceeds normally but endothelial and myeloid progenitors fail to initiate differentiation, migration and angiogenesis. Such angioblast cluster-derived angiogenesis is likely to be involved during vasculature formation in other vertebrate systems as well. Copyright © 2010 Elsevier Inc. All rights reserved.

Tower Shielding Reactor II design and operation report. Vol. 3. Assembling and testing of the control mechanism assembly

International Nuclear Information System (INIS)

Ward, D.R.; Holland, L.B.

1979-09-01

The mechanisms that are operated to control the reactivity of the Tower Shielding Reactor II(TSR-II) are mounted on a Control Mechanism Housing (CMH) that is centered inside the reactor core. The information required to procure, fabricate, inspect, and assemble a CMH is contained in the ORNL engineering drawings listed in the appropriate sections. The components are fabricated and inspected from these drawings in accordance with a Quality Assurance Plan and a Manufacturing Plan. The material in this report describes the acceptance and performance tests of CMH subassemblies used ty the Tower Shielding Facility (TSF) staff but it can also be used by personnel fabricating the components. This information which was developed and used before the advent of the formalized QA Program and Manufacturing Plans evolved during the fabrication and testing of the first five CMHs

Assembly factors for the membrane arm of human complex I.

Science.gov (United States)

Andrews, Byron; Carroll, Joe; Ding, Shujing; Fearnley, Ian M; Walker, John E

2013-11-19

Mitochondrial respiratory complex I is a product of both the nuclear and mitochondrial genomes. The integration of seven subunits encoded in mitochondrial DNA into the inner membrane, their association with 14 nuclear-encoded membrane subunits, the construction of the extrinsic arm from 23 additional nuclear-encoded proteins, iron-sulfur clusters, and flavin mononucleotide cofactor require the participation of assembly factors. Some are intrinsic to the complex, whereas others participate transiently. The suppression of the expression of the NDUFA11 subunit of complex I disrupted the assembly of the complex, and subcomplexes with masses of 550 and 815 kDa accumulated. Eight of the known extrinsic assembly factors plus a hydrophobic protein, C3orf1, were associated with the subcomplexes. The characteristics of C3orf1, of another assembly factor, TMEM126B, and of NDUFA11 suggest that they all participate in constructing the membrane arm of complex I.

Performance Analysis of Quality-of-Service Controls in a Cell-Cluster-Based Wireless ATM Network

Energy Technology Data Exchange (ETDEWEB)

Cho, Young Jong [Ajou University, Suwon (Korea, Republic of)

1997-04-01

In this paper, an efficient cell-cluster-based call control scheme with guaranteed quality-of-service(QoS) provision ing is presented for next generation wireless ATM networks and its performance is mathematically analyzed using the open queuing network. With the cell-cluster-based call control, at the time a mobile connection is admitted to the network, a virtual cell is constructed by choosing a group of neighboring base stations to which the call may probabilistic ally hand over and by assigning to the call a collection of virtual paths between the base stations. Within a micro cell/pico cell environment, it is seen that the cell-cluster-based call control can support effectively a very high rate of handovers, provides very high system capacity, and guarantees a high degree of frequency reuse over the same geographical region without requiring the intervention of the network call control processor each time a handover occurs. But since mobiles, once admitted, are free to roam within the virtual cell, congestion condition occurs in which the number of calls to be handled by one base station exceeds the cell sites` capacity of radio channel and consequently a predefined QoS provision cannot be guaranteed. So, there must be a call admission control function to limit the number of calls existing in a cell-cluster such that required QoS objectives are met. As call acceptance criteria for constant-bit-rate or realtime variable-bit-rate ATM connections, we define four mobile QoS metrics: new-call blocking probability, wireless channel utilization efficiency, congestion probability and normalized average congestion duration. In addition, for QoS provision ing to available-bit-rate, unspecified-bit-rate or non-realtime variable-bit-rate connections, we further define another QoS metric, the minimum threshold breaking probability. By using the open network queuing model, we derive closed form expressions for the five QoS metrics defined above and show that they can be