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.

Hessian regularization based non-negative matrix factorization for gene expression data clustering.

Science.gov (United States)

Liu, Xiao; Shi, Jun; Wang, Congzhi

2015-01-01

Since a key step in the analysis of gene expression data is to detect groups of genes that have similar expression patterns, clustering technique is then commonly used to analyze gene expression data. Data representation plays an important role in clustering analysis. The non-negative matrix factorization (NMF) is a widely used data representation method with great success in machine learning. Although the traditional manifold regularization method, Laplacian regularization (LR), can improve the performance of NMF, LR still suffers from the problem of its weak extrapolating power. Hessian regularization (HR) is a newly developed manifold regularization method, whose natural properties make it more extrapolating, especially for small sample data. In this work, we propose the HR-based NMF (HR-NMF) algorithm, and then apply it to represent gene expression data for further clustering task. The clustering experiments are conducted on five commonly used gene datasets, and the results indicate that the proposed HR-NMF outperforms LR-based NMM and original NMF, which suggests the potential application of HR-NMF for gene expression data.

Sparse subspace clustering for data with missing entries and high-rank matrix completion.

Science.gov (United States)

Fan, Jicong; Chow, Tommy W S

2017-09-01

Many methods have recently been proposed for subspace clustering, but they are often unable to handle incomplete data because of missing entries. Using matrix completion methods to recover missing entries is a common way to solve the problem. Conventional matrix completion methods require that the matrix should be of low-rank intrinsically, but most matrices are of high-rank or even full-rank in practice, especially when the number of subspaces is large. In this paper, a new method called Sparse Representation with Missing Entries and Matrix Completion is proposed to solve the problems of incomplete-data subspace clustering and high-rank matrix completion. The proposed algorithm alternately computes the matrix of sparse representation coefficients and recovers the missing entries of a data matrix. The proposed algorithm recovers missing entries through minimizing the representation coefficients, representation errors, and matrix rank. Thorough experimental study and comparative analysis based on synthetic data and natural images were conducted. The presented results demonstrate that the proposed algorithm is more effective in subspace clustering and matrix completion compared with other existing methods. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ejection of matrix-polymer clusters in matrix-assisted laser evaporation: Experimental observations

International Nuclear Information System (INIS)

Sellinger, Aaron T; Leveugle, Elodie; Gogick, Kristy; Peman, Guillaume; Zhigilei, Leonid V; Fitz-Gerald, James M

2007-01-01

The morphology of polymer films deposited with the matrix-assisted pulsed laser evaporation (MAPLE) technique is explored for various target compositions and laser fluences. Composite targets of 1 to 5 wt.% poly(methyl methacrylate), PMMA, dissolved in a volatile matrix material, toluene, were ablated using an excimer laser at fluences ranging from 0.045 J/cm 2 to 0.75 J/cm 2 . Films were deposited on Si substrates at room temperature in a dynamic 100 mTorr Ar atmosphere. Scanning electron microscopy (SEM) imaging revealed that the morphology of the deposited films varied significantly with both laser fluence and PMMA concentration. The morphologies of large deposited particles were similar to that of deflated ''balloons''. It is speculated that during ablation of the frozen target, clusters comprised of both polymer and solvent ranging from 100 nm to 10 μm in size are ejected and deposited onto the substrate. The solvent begins to evaporate from the clusters during flight from the target, but does not completely evaporate until deposited on the room temperature substrate. The dynamics of the toluene evaporation may lead to the formation of the deflated structures. This explanation is supported by the observation of stable polymer-matrix droplets ejected in molecular dynamics simulations of MAPLE

Properties of the disk system of globular clusters

International Nuclear Information System (INIS)

Armandroff, T.E.

1989-01-01

A large refined data sample is used to study the properties and origin of the disk system of globular clusters. A scale height for the disk cluster system of 800-1500 pc is found which is consistent with scale-height determinations for samples of field stars identified with the Galactic thick disk. A rotational velocity of 193 + or - 29 km/s and a line-of-sight velocity dispersion of 59 + or - 14 km/s have been found for the metal-rich clusters. 70 references

Synthesis, characterization and optical properties of hybridized CdS-PVA nanocomposites

International Nuclear Information System (INIS)

Wang Hongmei; Chen Zhe; Fang Pengfei; Wang Shaojie

2007-01-01

Hybrid nanocomposites of CdS nanoparticles embedded in poly(vinyl alcohol)(PVA) matrixes had been prepared and characterized. The -OH groups acted as the coordination sites for cadmium ion aggregations and nanosized CdS particles were successfully grown in situ at these sites with the release of S 2- ions from thioacetamide. The density and size of the nanoparticles were found to be a function of molar quantity of cadmium ion used. X-ray diffraction results showed that the obtained CdS nanoparticles were hexagonal phase. Ionic clustering within the PVA matrix occurred and had provided a confined medium for particles growth in uniform size. The optical properties of the prepared CdS-PVA hybrid nanocomposites were characterized by absorption and emission spectroscopies. The absorption spectra showed a blue shift as compared to bulk CdS band-gap. The photoluminescence studies indicated the emission peak observed in samples could be assigned to the optical transition of the first excitonic state of the CdS nanoparticles

Electronic, Magnetic, and Redox Properties of [MFe(3)S(4)] Clusters (M = Cd, Cu, Cr) in Pyrococcus furiosus Ferredoxin.

Science.gov (United States)

Staples, Christopher R.; Dhawan, Ish K.; Finnegan, Michael G.; Dwinell, Derek A.; Zhou, Zhi Hao; Huang, Heshu; Verhagen, Marc F. J. M.; Adams, Michael W. W.; Johnson, Michael K.

1997-12-03

The ground- and excited-state properties of heterometallic [CuFe(3)S(4)](2+,+), [CdFe(3)S(4)](2+,+), and [CrFe(3)S(4)](2+,+) cubane clusters assembled in Pyrococcus furiosus ferredoxin have been investigated by the combination of EPR and variable-temperature/variable-field magnetic circular dichroism (MCD) studies. The results indicate Cd(2+) incorporation into [Fe(3)S(4)](0,-) cluster fragments to yield S = 2 [CdFe(3)S(4)](2+) and S = (5)/(2) [CdFe(3)S(4)](+) clusters and Cu(+) incorporation into [Fe(3)S(4)](+,0) cluster fragments to yield S = (1)/(2) [CuFe(3)S(4)](2+) and S = 2 [CuFe(3)S(4)](+) clusters. This is the first report of the preparation of cubane type [CrFe(3)S(4)](2+,+) clusters, and the combination of EPR and MCD results indicates S = 0 and S = (3)/(2) ground states for the oxidized and reduced forms, respectively. Midpoint potentials for the [CdFe(3)S(4)](2+,+), [CrFe(3)S(4)](2+,+), and [CuFe(3)S(4)](2+,+) couples, E(m) = -470 +/- 15, -440 +/- 10, and +190 +/- 10 mV (vs NHE), respectively, were determined by EPR-monitored redox titrations or direct electrochemistry at a glassy carbon electrode. The trends in redox potential, ground-state spin, and electron delocalization of [MFe(3)S(4)](2+,+) clusters in P. furiosus ferredoxin are discussed as a function of heterometal (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Tl).

A Rank-Constrained Matrix Representation for Hypergraph-Based Subspace Clustering

Directory of Open Access Journals (Sweden)

Yubao Sun

2015-01-01

Full Text Available This paper presents a novel, rank-constrained matrix representation combined with hypergraph spectral analysis to enable the recovery of the original subspace structures of corrupted data. Real-world data are frequently corrupted with both sparse error and noise. Our matrix decomposition model separates the low-rank, sparse error, and noise components from the data in order to enhance robustness to the corruption. In order to obtain the desired rank representation of the data within a dictionary, our model directly utilizes rank constraints by restricting the upper bound of the rank range. An alternative projection algorithm is proposed to estimate the low-rank representation and separate the sparse error from the data matrix. To further capture the complex relationship between data distributed in multiple subspaces, we use hypergraph to represent the data by encapsulating multiple related samples into one hyperedge. The final clustering result is obtained by spectral decomposition of the hypergraph Laplacian matrix. Validation experiments on the Extended Yale Face Database B, AR, and Hopkins 155 datasets show that the proposed method is a promising tool for subspace clustering.

S-matrix theory of nuclear forces

International Nuclear Information System (INIS)

Vinh Mau, R.

1984-09-01

The use of the S-matrix theory for deriving the nucleon-nucleon interaction is reviewed. Fits to recent NN data are described. Applications to nuclear structure properties and nucleon-nucleus reactions are also discussed, and the results compared with data. 20 references

Anomalous properties of technetium clusters

International Nuclear Information System (INIS)

Kryuchkov, S.V.

1985-01-01

On the basis of critical evaluation of literature data in the field of chemistry of technetium cluster compounds with ligands of a weak field a conclusion is made on specific, ''anomalous'' properties of technetium cluster complexes which consist in an increased ability of the given element to the formation of a series of binuclear and multinuclear clusters, similar in composition and structure and easily transforming in each other. The majority of technetium clusters unlike similar compounds of other elements are paramagnetic with one unpaired electron on ''metallic'' MO of loosening type. All theoretical conceptions known today on the electronic structure of technetium clusters are considered. It is pointed out, that the best results in the explanation of ''anomalous'' properties of technetium clusters can be obtained in the framework of nonempirical methods of self-consistent field taking into account configuration interactions. It is also shown, that certain properties of technetium clusters can be explained on the basis of qualitative model of Coulomb repulsion of metal atoms in clusters. The conclusion is made, that technetium position in the Periodic table, as well as recently detected technetium property to the decrease of effective charge on its atoms during M-M bond formation promote a high ability of the element to cluster formation both with weak field ligands and with strong field one

Production of Au clusters by plasma gas condensation and their incorporation in oxide matrixes by sputtering

Science.gov (United States)

Figueiredo, N. M.; Serra, R.; Manninen, N. K.; Cavaleiro, A.

2018-05-01

Gold clusters were produced by plasma gas condensation method and studied in great detail for the first time. The influence of argon flow, discharge power applied to the Au target and aggregation chamber length on the size distribution and deposition rate of Au clusters was evaluated. Au clusters with sizes between 5 and 65 nm were deposited with varying deposition rates and size dispersion curves. Nanocomposite Au-TiO2 and Au-Al2O3 coatings were then deposited by alternating sputtering. These coatings were hydrophobic and showed strong colorations due to the surface plasmon resonance effect. By simulating the optical properties of the nanocomposites it was possible to identify each individual contribution to the overall surface plasmon resonance signal. These coatings show great potential to be used as high performance localized surface plasmon resonance sensors or as robust self-cleaning decorative protective layers. The hybrid method used for depositing the nanocomposites offers several advantages over co-sputtering or thermal evaporation processes, since a broader range of particle sizes can be obtained (up to tens of nanometers) without the application of any thermal annealing treatments and the properties of clusters and matrix can be controlled separately.

The properties of the disk system of globular clusters

Science.gov (United States)

Armandroff, Taft E.

1989-01-01

A large refined data sample is used to study the properties and origin of the disk system of globular clusters. A scale height for the disk cluster system of 800-1500 pc is found which is consistent with scale-height determinations for samples of field stars identified with the Galactic thick disk. A rotational velocity of 193 + or - 29 km/s and a line-of-sight velocity dispersion of 59 + or - 14 km/s have been found for the metal-rich clusters.

Statistical properties and fractals of nucleotide clusters in DNA sequences

International Nuclear Information System (INIS)

Sun Tingting; Zhang Linxi; Chen Jin; Jiang Zhouting

2004-01-01

Statistical properties of nucleotide clusters in DNA sequences and their fractals are investigated in this paper. The average size of nucleotide clusters in non-coding sequence is larger than that in coding sequence. We investigate the cluster-size distribution P(S) for human chromosomes 21 and 22, and the results are different from previous works. The cluster-size distribution P(S 1 +S 2 ) with the total size of sequential Pu-cluster and Py-cluster S 1 +S 2 is studied. We observe that P(S 1 +S 2 ) follows an exponential decay both in coding and non-coding sequences. However, we get different results for human chromosomes 21 and 22. The probability distribution P(S 1 ,S 2 ) of nucleotide clusters with the size of sequential Pu-cluster and Py-cluster S 1 and S 2 respectively, is also examined. In the meantime, some of the linear correlations are obtained in the double logarithmic plots of the fluctuation F(l) versus nucleotide cluster distance l along the DNA chain. The power spectrums of nucleotide clusters are also discussed, and it is concluded that the curves are flat and hardly changed and the 1/3 frequency is neither observed in coding sequence nor in non-coding sequence. These investigations can provide some insights into the nucleotide clusters of DNA sequences

A study of radiative properties of fractal soot aggregates using the superposition T-matrix method

International Nuclear Information System (INIS)

Li Liu; Mishchenko, Michael I.; Patrick Arnott, W.

2008-01-01

We employ the numerically exact superposition T-matrix method to perform extensive computations of scattering and absorption properties of soot aggregates with varying state of compactness and size. The fractal dimension, D f , is used to quantify the geometrical mass dispersion of the clusters. The optical properties of soot aggregates for a given fractal dimension are complex functions of the refractive index of the material m, the number of monomers N S , and the monomer radius a. It is shown that for smaller values of a, the absorption cross section tends to be relatively constant when D f f >2. However, a systematic reduction in light absorption with D f is observed for clusters with sufficiently large N S , m, and a. The scattering cross section and single-scattering albedo increase monotonically as fractals evolve from chain-like to more densely packed morphologies, which is a strong manifestation of the increasing importance of scattering interaction among spherules. Overall, the results for soot fractals differ profoundly from those calculated for the respective volume-equivalent soot spheres as well as for the respective external mixtures of soot monomers under the assumption that there are no electromagnetic interactions between the monomers. The climate-research implications of our results are discussed

Hamiltonian formalism, quantization and S matrix for supergravity. [S matrix, canonical constraints

Energy Technology Data Exchange (ETDEWEB)

Fradkin, E S; Vasiliev, M A [AN SSSR, Moscow. Fizicheskij Inst.

1977-12-05

The canonical formalism for supergravity is constructed. The algebra of canonical constraints is found. The correct expression for the S matrix is obtained. Usual 'covariant methods' lead to an incorrect S matrix in supergravity since a new four-particle interaction of ghostfields survives in the Lagrangian expression of the S matrix.

Particles as S-matrix poles: hadron democracy

International Nuclear Information System (INIS)

Chew, G.F.

1989-01-01

The connection between two theoretical ideas of the 1950s is traced in this article, namely that hadrons are nonfundamental, ''composite'' particles and that all physically observable particles correspond to singularities of an analytic scattering matrix. The S matrix theory developed by Werner Heisenberg in the early forties now incorporated the concepts of unitarity, invariance, analyticity and causality. The meson-exchange force meant that poles must be present in nucleon-nuclear and pion-nucleon scattering as predicted by dispersion relations. Experimental work in accessible regions determined pole residues. Pole residue became associated with force strength and pole position with particle mass. In 1959, the author discovered the so-called ''bootstrap'' theory the rho meson as a force generates a rho particle. By the end of the 1950s it was clear that all hadrons had equal status, each being bound states of other hadrons, sustained by hadron exchange forces and that hadrons are self-generated by an S-matrix bootstrap mechanism that determines all their properties. (UK)

Spectra of matrix isolated metal atoms and clusters

International Nuclear Information System (INIS)

Meyer, B.

1977-01-01

The matrix isolation spectra of all of the 40 presently known atomic metal species show strong matrix effects. The transition energies are increased, and the bands are broad and exhibit splitting of sublevels which are degenerate in the gas phase. Several models have been proposed for splitting of levels, but basic effects are not yet understood, and spectra cannot be predicted, yet it is possible to correlate gas phase and matrix in many of the systems. Selective production of diatomics and clusters via thermal and optical annealing of atomic species can be monitored by optical spectra, but yields spectroscopically complex systems which, however, especially in the case of transition metals, can be used as precursors in novel chemical reactions. A combination of absorption, emission, ir, Raman, ESR, and other methods is now quickly yielding data which will help correlate the increasing wealth of existing data. 55 references, 6 figures

A point mutation in the [2Fe–2S] cluster binding region of the NAF-1 protein (H114C) dramatically hinders the cluster donor properties

Energy Technology Data Exchange (ETDEWEB)

Tamir, Sagi; Eisenberg-Domovich, Yael [The Hebrew University of Jerusalem, Edmond J. Safra Campus at Givat Ram, Jerusalem 91904 (Israel); Conlan, Andrea R.; Stofleth, Jason T.; Lipper, Colin H.; Paddock, Mark L. [University of California at San Diego, La Jolla, CA 92093 (United States); Mittler, Ron [University of North Texas, Denton, TX 76203 (United States); Jennings, Patricia A. [University of California at San Diego, La Jolla, CA 92093 (United States); Livnah, Oded, E-mail: oded.livnah@huji.ac.il; Nechushtai, Rachel, E-mail: oded.livnah@huji.ac.il [The Hebrew University of Jerusalem, Edmond J. Safra Campus at Givat Ram, Jerusalem 91904 (Israel)

2014-06-01

NAF-1 has been shown to be related with human health and disease, is upregulated in epithelial breast cancer and suppression of its expression significantly suppresses tumor growth. It is shown that replacement of the single His ligand with Cys resulted in dramatic changes to the properties of its 2Fe-2S clusters without any global crystal structural changes. NAF-1 is an important [2Fe–2S] NEET protein associated with human health and disease. A mis-splicing mutation in NAF-1 results in Wolfram Syndrome type 2, a lethal childhood disease. Upregulation of NAF-1 is found in epithelial breast cancer cells, and suppression of NAF-1 expression by knockdown significantly suppresses tumor growth. Key to NAF-1 function is the NEET fold with its [2Fe–2S] cluster. In this work, the high-resolution structure of native NAF-1 was determined to 1.65 Å resolution (R factor = 13.5%) together with that of a mutant in which the single His ligand of its [2Fe–2S] cluster, His114, was replaced by Cys. The NAF-1 H114C mutant structure was determined to 1.58 Å resolution (R factor = 16.0%). All structural differences were localized to the cluster binding site. Compared with native NAF-1, the [2Fe–2S] clusters of the H114C mutant were found to (i) be 25-fold more stable, (ii) have a redox potential that is 300 mV more negative and (iii) have their cluster donation/transfer function abolished. Because no global structural differences were found between the mutant and the native (wild-type) NAF-1 proteins, yet significant functional differences exist between them, the NAF-1 H114C mutant is an excellent tool to decipher the underlying biological importance of the [2Fe–2S] cluster of NAF-1 in vivo.

A point mutation in the [2Fe–2S] cluster binding region of the NAF-1 protein (H114C) dramatically hinders the cluster donor properties

International Nuclear Information System (INIS)

Tamir, Sagi; Eisenberg-Domovich, Yael; Conlan, Andrea R.; Stofleth, Jason T.; Lipper, Colin H.; Paddock, Mark L.; Mittler, Ron; Jennings, Patricia A.; Livnah, Oded; Nechushtai, Rachel

2014-01-01

NAF-1 has been shown to be related with human health and disease, is upregulated in epithelial breast cancer and suppression of its expression significantly suppresses tumor growth. It is shown that replacement of the single His ligand with Cys resulted in dramatic changes to the properties of its 2Fe-2S clusters without any global crystal structural changes. NAF-1 is an important [2Fe–2S] NEET protein associated with human health and disease. A mis-splicing mutation in NAF-1 results in Wolfram Syndrome type 2, a lethal childhood disease. Upregulation of NAF-1 is found in epithelial breast cancer cells, and suppression of NAF-1 expression by knockdown significantly suppresses tumor growth. Key to NAF-1 function is the NEET fold with its [2Fe–2S] cluster. In this work, the high-resolution structure of native NAF-1 was determined to 1.65 Å resolution (R factor = 13.5%) together with that of a mutant in which the single His ligand of its [2Fe–2S] cluster, His114, was replaced by Cys. The NAF-1 H114C mutant structure was determined to 1.58 Å resolution (R factor = 16.0%). All structural differences were localized to the cluster binding site. Compared with native NAF-1, the [2Fe–2S] clusters of the H114C mutant were found to (i) be 25-fold more stable, (ii) have a redox potential that is 300 mV more negative and (iii) have their cluster donation/transfer function abolished. Because no global structural differences were found between the mutant and the native (wild-type) NAF-1 proteins, yet significant functional differences exist between them, the NAF-1 H114C mutant is an excellent tool to decipher the underlying biological importance of the [2Fe–2S] cluster of NAF-1 in vivo

Fe-S Clusters Emerging as Targets of Therapeutic Drugs

Directory of Open Access Journals (Sweden)

Laurence Vernis

2017-01-01

Full Text Available Fe-S centers exhibit strong electronic plasticity, which is of importance for insuring fine redox tuning of protein biological properties. In accordance, Fe-S clusters are also highly sensitive to oxidation and can be very easily altered in vivo by different drugs, either directly or indirectly due to catabolic by-products, such as nitric oxide species (NOS or reactive oxygen species (ROS. In case of metal ions, Fe-S cluster alteration might be the result of metal liganding to the coordinating sulfur atoms, as suggested for copper. Several drugs presented through this review are either capable of direct interaction with Fe-S clusters or of secondary Fe-S clusters alteration following ROS or NOS production. Reactions leading to Fe-S cluster disruption are also reported. Due to the recent interest and progress in Fe-S biology, it is very likely that an increasing number of drugs already used in clinics will emerge as molecules interfering with Fe-S centers in the near future. Targeting Fe-S centers could also become a promising strategy for drug development.

Microcausality, macrocausality and the physical region (micro)analytic S-matrix

International Nuclear Information System (INIS)

Iagolnitzer, D.

1980-01-01

Recent works on the physical region analytic structure of multiparticle collision amplitudes in relativistic quantum theory are presented. First, the structure that can be expected and which is the expression, in terms of general essential support or microanalyticity properties, of macrocausality and macrocausal factorization, is described. It is shown that, taken together, these properties are equivalent to decompositions of the S-matrix, in bounded parts of the physical region, in terms of generalized Feynman integrals. Derivations of this structure obtained recently for 3 → 3 processes below the four-particle threshold both in S-matrix theory (without recourse to the crucial ad hoc assumption of 'separation of singularities' in unitarity equations used previously) and in axiomatic field theory are then reviewed. It is finally explained how this structure applies in two-dimensional space-time and yields factorization of the multiparticle S-matrix itself for a class of models. (orig.)

Silver Matrix Composites - Structure and Properties

Directory of Open Access Journals (Sweden)

Wieczorek J.

2016-03-01

Full Text Available Phase compositions of composite materials determine their performance as well as physical and mechanical properties. Depending on the type of applied matrix and the kind, amount and morphology of the matrix reinforcement, it is possible to shape the material properties so that they meet specific operational requirements. In the paper, results of investigations on silver alloy matrix composites reinforced with ceramic particles are presented. The investigations enabled evaluation of hardness, tribological and mechanical properties as well as the structure of produced materials. The matrix of composite material was an alloy of silver and aluminium, magnesium and silicon. As the reinforcing phase, 20-60 μm ceramic particles (SiC, SiO2, Al2O3 and Cs were applied. The volume fraction of the reinforcing phase in the composites was 10%. The composites were produced using the liquid phase (casting technology, followed by plastic work (the KOBO method. The mechanical and tribological properties were analysed for plastic work-subjected composites. The mechanical properties were assessed based on a static tensile and hardness tests. The tribological properties were investigated under dry sliding conditions. The analysis of results led to determination of effects of the composite production technology on their performance. Moreover, a relationship between the type of reinforcing phase and the mechanical and tribological properties was established.

On the Equivalence of Nonnegative Matrix Factorization and K-means- Spectral Clustering

Energy Technology Data Exchange (ETDEWEB)

Ding, Chris; He, Xiaofeng; Simon, Horst D.; Jin, Rong

2005-12-04

We provide a systematic analysis of nonnegative matrix factorization (NMF) relating to data clustering. We generalize the usual X = FG{sup T} decomposition to the symmetric W = HH{sup T} and W = HSH{sup T} decompositions. We show that (1) W = HH{sup T} is equivalent to Kernel K-means clustering and the Laplacian-based spectral clustering. (2) X = FG{sup T} is equivalent to simultaneous clustering of rows and columns of a bipartite graph. We emphasizes the importance of orthogonality in NMF and soft clustering nature of NMF. These results are verified with experiments on face images and newsgroups.

Tuning the magnetic properties of GaAs:Mn/MnAs hybrids via the MnAs cluster shape

International Nuclear Information System (INIS)

Nidda, H-A Krug von; Kurz, T; Loidl, A; Hartmann, Th; Klar, P J; Heimbrodt, W; Lampalzer, M; Volz, K; Stolz, W

2006-01-01

We report a systematic study of ferromagnetic resonance in granular GaAs:Mn/MnAs hybrids grown on GaAs(001) substrates by metal-organic vapour-phase epitaxy. The ferromagnetic resonance of the MnAs clusters can be resolved at all temperatures below T c . An additional broad absorption is observed below 60 K and is ascribed to localized charge carriers of the GaAs:Mn matrix. The anisotropy of the MnAs ferromagnetic resonance field originates from the magneto-crystalline field and demagnetization effects of the ferromagnetic MnAs clusters embedded in the GaAs:Mn matrix. Its temperature dependence basically scales with magnetization. Comparison of the observed angular dependence of the resonance field with model calculations yields the preferential orientation and shape of the clusters formed in hybrid layers of different thickness (150-1000 nm) grown otherwise at the same growth conditions. The hexagonal axes of the MnAs clusters are oriented along the four cubic GaAs space diagonals. Thin layers contain lens-shaped MnAs clusters close to the surface, whereas thick layers also contain spherical clusters in the bulk of the layer. The magnetic properties of the hexagonal MnAs clusters can be tuned by a controlled variation of the cluster shape

Hessian regularization based symmetric nonnegative matrix factorization for clustering gene expression and microbiome data.

Science.gov (United States)

Ma, Yuanyuan; Hu, Xiaohua; He, Tingting; Jiang, Xingpeng

2016-12-01

Nonnegative matrix factorization (NMF) has received considerable attention due to its interpretation of observed samples as combinations of different components, and has been successfully used as a clustering method. As an extension of NMF, Symmetric NMF (SNMF) inherits the advantages of NMF. Unlike NMF, however, SNMF takes a nonnegative similarity matrix as an input, and two lower rank nonnegative matrices (H, H T ) are computed as an output to approximate the original similarity matrix. Laplacian regularization has improved the clustering performance of NMF and SNMF. However, Laplacian regularization (LR), as a classic manifold regularization method, suffers some problems because of its weak extrapolating ability. In this paper, we propose a novel variant of SNMF, called Hessian regularization based symmetric nonnegative matrix factorization (HSNMF), for this purpose. In contrast to Laplacian regularization, Hessian regularization fits the data perfectly and extrapolates nicely to unseen data. We conduct extensive experiments on several datasets including text data, gene expression data and HMP (Human Microbiome Project) data. The results show that the proposed method outperforms other methods, which suggests the potential application of HSNMF in biological data clustering. Copyright © 2016. Published by Elsevier Inc.

A theoretical study on the geometry and spectroscopic properties of ground-state and local minima isomers of (CuS)n=2-6 clusters

Science.gov (United States)

Luque-Ceballos, Jonathan C.; Posada-Borbón, Alvaro; Herrera-Urbina, Ronaldo; Aceves, R.; Juárez-Sánchez, J. Octavio; Posada-Amarillas, Alvaro

2018-03-01

Spectroscopic properties of gas-phase copper sulfide clusters (CuS)n (n = 2-6) are calculated using Density Functional Theory (DFT) and time-dependent (TD) DFT approaches. The energy landscape of the potential energy surface is explored through a basin-hopping DFT methodology. Ground-state and low-lying isomer structures are obtained. The global search was performed at the B3PW91/SDD level of theory. Normal modes are calculated to validate the existence of optimal cluster structures. Energetic properties are obtained for the ground-state and isomer clusters and their relative energies are evaluated for probing isomerization. This is a few tenths of an eV, except for (CuS)2 cluster, which presents energy differences of ∼1 eV. Notable differences in the infrared spectra exist between the ground-state and first isomer structures, even for the (CuS)5 cluster, which has in both configurations a core copper pyramid. TDDFT provides the simulated absorption spectrum, presenting a theoretical description of optical absorption bands in terms of electronic excitations in the UV and visible regions. Results exhibit a significant dependence of the calculated UV/vis spectra on clusters size and shape regarding the ground state structures. Optical absorption is strong in the UV region, and weak or forbidden in the visible region of the spectrum.

Electronic and magnetic properties of 3d-metal trioxides superhalogen cluster-doped monolayer MoS2: A first-principles study

International Nuclear Information System (INIS)

Li, Dan; Niu, Yuan; Zhao, Hongmin; Liang, Chunjun; He, Zhiqun

2014-01-01

Utilizing first-principle calculations, the structural, electronic, and magnetic properties of monolayer MoS 2 doped with 3d transition-metal (TM) atoms and 3d-metal trioxides (TMO 3 ) superhalogen clusters are investigated. 3d-metal TMO 3 superhalogen cluster-doped monolayers MoS 2 almost have negative formation energies except CoO 3 and NiO 3 doped monolayer MoS 2 , which are much lower than those of 3d TM-doped structures. 3d-metal TMO 3 superhalogen clusters are more easily embedded in monolayer MoS 2 than 3d-metal atoms. MnO 3 , FeO 3 , CoO 3 , and NiO 3 incorporated into monolayer MoS 2 are magnetic, and the total magnetic moments are approximately 1.0, 2.0, 3.0, and 4.0 μB per supercell, respectively. MnO 3 and FeO 3 incorporated into monolayer MoS 2 become semiconductors, whereas CoO 3 and NiO 3 incorporated into monolayer MoS 2 become half-metallic. Our studies demonstrate that the half-metallic ferromagnetic nature of 3d-metal TMO 3 superhalogen clusters-doped monolayer MoS 2 has a great potential for MoS 2 -based spintronic device applications. -- Highlights: •TMO 3 superhalogen clusters incorporated into monolayer MoS 2 were investigated. •TMO 3 doped structures have much lower formation energies than TM doped structures. •TMO 3 cluster-doped MoS 2 are thermodynamically favored. •Significant charge transfers between O atoms and Mo atoms in TMO 3 doped structures. •MnO 3 , FeO 3 , CoO 3 , and NiO 3 incorporated into monolayer MoS 2 are magnetic.

Single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers: Reactant- and stoichiometry-dependent syntheses, effective photocatalytic properties

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jinfang, E-mail: zjf260@jiangnan.edu.cn [China-Australia Joint Research Center for Functional Molecular Materials, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Wang, Chao [China-Australia Joint Research Center for Functional Molecular Materials, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China); Wang, Yinlin; Chen, Weitao [China-Australia Joint Research Center for Functional Molecular Materials, Scientific Research Academy, Jiangsu University, Zhenjiang 212013 (China); Cifuentes, Marie P.; Humphrey, Mark G. [Research School of Chemistry, Australian National University, Canberra ACT 0200 (Australia); Zhang, Chi, E-mail: chizhang@jiangnan.edu.cn [China-Australia Joint Research Center for Functional Molecular Materials, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122 (China)

2015-11-15

cluster-based CPs were firstly explored by monitoring the photodegradation of methylene blue (MB) under visible light irradiation, which reveals that 2 exhibits effective photocatalytic properties. - Highlights: • Reaction variables affecting Mo(W)/S/Cu cluster-based CPs is firstly explored. • Replacing central metal atom had a pronounced effect on W/S/Cu cluster-based CPs. • Photocatalytic activities of Mo(W)/S/Cu cluster-based CPs are firstly investigated.

Single cyanide-bridged Mo(W)/S/Cu cluster-based coordination polymers: Reactant- and stoichiometry-dependent syntheses, effective photocatalytic properties

International Nuclear Information System (INIS)

Zhang, Jinfang; Wang, Chao; Wang, Yinlin; Chen, Weitao; Cifuentes, Marie P.; Humphrey, Mark G.; Zhang, Chi

2015-01-01

exhibits effective photocatalytic properties. - Highlights: • Reaction variables affecting Mo(W)/S/Cu cluster-based CPs is firstly explored. • Replacing central metal atom had a pronounced effect on W/S/Cu cluster-based CPs. • Photocatalytic activities of Mo(W)/S/Cu cluster-based CPs are firstly investigated.

Nano-fillers to tune Young’s modulus of silicone matrix

International Nuclear Information System (INIS)

Xia Lijin; Xu Zhonghua; Sun Leming; Caveney, Patrick M.; Zhang Mingjun

2013-01-01

In this study, we investigated nanoparticles, nanofibers, and nanoclays for their filler effects on tuning the Young’s modulus of silicone matrix, a material with broad in vivo applications. Nano-fillers with different shapes, sizes, and surface properties were added into silicone matrix, and then their filler effects were evaluated through experimental studies. It was found that spherical nanoparticles could clearly improve Young’s modulus of the silicone matrix, while nanoclays and carbon nanofibers had limited effects. Smaller spherical nanoparticles were better in performance compared to larger nanoparticles. In addition, enhanced distribution of the nanoparticles in the matrix has been observed to improve the filler effect. In order to minimize toxicity of the nanoparticles for in vivo applications, spherical nanoparticles coated with amine, acid, or hydroxide groups were also investigated, but they were found only to diminish the filler effect of nanoparticles. This study demonstrated that spherical nanoparticles could serve as fillers to tune Young’s modulus of silicone matrix for potential applications in medicine.

Symmetric nonnegative matrix factorization: algorithms and applications to probabilistic clustering.

Science.gov (United States)

He, Zhaoshui; Xie, Shengli; Zdunek, Rafal; Zhou, Guoxu; Cichocki, Andrzej

2011-12-01

Nonnegative matrix factorization (NMF) is an unsupervised learning method useful in various applications including image processing and semantic analysis of documents. This paper focuses on symmetric NMF (SNMF), which is a special case of NMF decomposition. Three parallel multiplicative update algorithms using level 3 basic linear algebra subprograms directly are developed for this problem. First, by minimizing the Euclidean distance, a multiplicative update algorithm is proposed, and its convergence under mild conditions is proved. Based on it, we further propose another two fast parallel methods: α-SNMF and β -SNMF algorithms. All of them are easy to implement. These algorithms are applied to probabilistic clustering. We demonstrate their effectiveness for facial image clustering, document categorization, and pattern clustering in gene expression.

Mixing Matrix Estimation of Underdetermined Blind Source Separation Based on Data Field and Improved FCM Clustering

Directory of Open Access Journals (Sweden)

Qiang Guo

2018-01-01

Full Text Available In modern electronic warfare, multiple input multiple output (MIMO radar has become an important tool for electronic reconnaissance and intelligence transmission because of its anti-stealth, high resolution, low intercept and anti-destruction characteristics. As a common MIMO radar signal, discrete frequency coding waveform (DFCW has a serious overlap of both time and frequency, so it cannot be directly used in the current radar signal separation problems. The existing fuzzy clustering algorithms have problems in initial value selection, low convergence rate and local extreme values which will lead to the low accuracy of the mixing matrix estimation. Consequently, a novel mixing matrix estimation algorithm based on data field and improved fuzzy C-means (FCM clustering is proposed. First of all, the sparsity and linear clustering characteristics of the time–frequency domain MIMO radar signals are enhanced by using the single-source principal value of complex angular detection. Secondly, the data field uses the potential energy information to analyze the particle distribution, thus design a new clustering number selection scheme. Then the particle swarm optimization algorithm is introduced to improve the iterative clustering process of FCM, and finally get the estimated value of the mixing matrix. The simulation results show that the proposed algorithm improves both the estimation accuracy and the robustness of the mixing matrix.

Time-dependent--S-matrix Hartree-Fock theory of complex reactions

International Nuclear Information System (INIS)

Griffin, J.J.; Lichtner, P.C.; Dworzecka, M.

1980-01-01

Some limitations of the conventional time-dependent Hartree-Fock method for describing complex reactions are noted, and one particular ubiquitous defect is discussed in detail: the post-breakup spurious cross channel correlations which arise whenever several asymptotic reaction channels must be simultaneously described by a single determinant. A reformulated time-dependent--S-matrix Hartree-Fock theory is proposed, which obviates this difficulty. Axiomatic requirements minimal to assure that the time-dependent--S-matrix Hartree-Fock theory represents an unambiguous and physically interpretable asymptotic reaction theory are utilized to prescribe conditions upon the definition of acceptable asymptotic channels. That definition, in turn, defines the physical range of the time-dependent--S-matrix Hartree-Fock theory to encompass the collisions of mathematically well-defined ''time-dependent Hartree-Fock droplets.'' The physical properties of these objects then circumscribe the content of the Hartree-Fock single determinantal description. If their periodic vibrations occur for continuous ranges of energy then the resulting ''classical'' time-dependent Hartree-Fock droplets are seen to be intrinsically dissipative, and the single determinantal description of their collisions reduces to a ''trajectory'' theory which can describe the masses and relative motions of the fragments but can provide no information about specific asymptotic excited states beyond their constants of motion, or the average properties of the limit, if it exists, of their equilibrization process. If, on the other hand, the periodic vibrations of the time-dependent Hartree-Fock droplets are discrete in energy, then the time-dependent--S-matrix Hartree-Fock theory can describe asymptotically the time-average properties of the whole spectrum of such periodic vibrations

Kendall’s tau and agglomerative clustering for structure determination of hierarchical Archimedean copulas

Directory of Open Access Journals (Sweden)

Górecki J.

2017-01-01

Full Text Available Several successful approaches to structure determination of hierarchical Archimedean copulas (HACs proposed in the literature rely on agglomerative clustering and Kendall’s correlation coefficient. However, there has not been presented any theoretical proof justifying such approaches. This work fills this gap and introduces a theorem showing that, given the matrix of the pairwise Kendall correlation coefficients corresponding to a HAC, its structure can be recovered by an agglomerative clustering technique.

Magnetic and magneto-optical properties of CdS:Mn quantum dots in PVA matrix

International Nuclear Information System (INIS)

Fediv, V I; Savchuk, A I; Frasunyak, V M; Makoviy, V V; Savchuk, O A

2010-01-01

We have studied the magnetic and magneto-optical properties of CdS:Mn quantum dots in polyvinyl alcohol matrix synthesized by co-precipitation method. The size of quantum dots was estimated by means of absorption spectroscopy. The results of measurements of magnetic susceptibility as a function of temperature and spectral dependence of the Faraday rotation of CdS:Mn quantum dots / polyvinyl alcohol composites are presented. In this work magnetic susceptibility was investigated by Faraday's method at the temperatures of (78-300) K in magnetic fields of (0.05-0.8) T. The inverse magnetic susceptibility as a function of temperature follows a Curie Weiss law. Formation of ferromagnetic coupling between magnetic ions is supposed. Magneto-optical Faraday rotation has been investigated in the wavelength region (400-700) nm at temperature 300 K in a magnetic field up to 5 T. Sign of the Verdet constant is found to be negative.

Structure and physical properties of silicon clusters and of vacancy clusters in bulk silicon

International Nuclear Information System (INIS)

Sieck, A.

2000-01-01

In this thesis the growth-pattern of free silicon clusters and vacancy clusters in bulk silicon is investigated. The aim is to describe and to better understand the cluster to bulk transition. Silicon structures in between clusters and solids feature new interesting physical properties. The structure and physical properties of silicon clusters can be revealed by a combination of theory and experiment, only. Low-energy clusters are determined with different optimization techniques and a density-functional based tight-binding method. Additionally, infrared and Raman spectra, and polarizabilities calculated within self-consistent field density-functional theory are provided for the smaller clusters. For clusters with 25 to 35 atoms an analysis of the shape of the clusters and the related mobilities in a buffer gas is given. Finally, the clusters observed in low-temperature experiments are identified via the best match between calculated properties and experimental data. Silicon clusters with 10 to 15 atoms have a tricapped trigonal prism as a common subunit. Clusters with up to about 25 atoms follow a prolate growth-path. In the range from 24 to 30 atoms the geometry of the clusters undergoes a transition towards compact spherical structures. Low-energy clusters with up to 240 atoms feature a bonding pattern strikingly different from the tetrahedral bonding in the solid. It follows that structures with dimensions of several Angstroem have electrical and optical properties different from the solid. The calculated stabilities and positron-lifetimes of vacancy clusters in bulk silicon indicate the positron-lifetimes of about 435 ps detected in irradiated silicon to be related to clusters of 9 or 10 vacancies. The vacancies in these clusters form neighboring hexa-rings and, therefore, minimize the number of dangling bonds. (orig.)

Program package for calculating matrix elements of two-cluster structures in nuclei

International Nuclear Information System (INIS)

Krivec, R.; Mihailovic, M.V.; Kernforschungszentrum Karlsruhe G.m.b.H.

1982-01-01

Matrix elements of operators between Slater determinants of two-cluster structures must be expanded into partial waves for the purpose of angular momentum projection. The expansion coefficients contain integrals over the spherical angles theta and phi. (orig.)

Characterization of Glutaredoxin Fe-S Cluster-Binding Interactions Using Circular Dichroism Spectroscopy.

Science.gov (United States)

Albetel, Angela-Nadia; Outten, Caryn E

2018-01-01

Monothiol glutaredoxins (Grxs) with a conserved Cys-Gly-Phe-Ser (CGFS) active site are iron-sulfur (Fe-S) cluster-binding proteins that interact with a variety of partner proteins and perform crucial roles in iron metabolism including Fe-S cluster transfer, Fe-S cluster repair, and iron signaling. Various analytical and spectroscopic methods are currently being used to monitor and characterize glutaredoxin Fe-S cluster-dependent interactions at the molecular level. The electronic, magnetic, and vibrational properties of the protein-bound Fe-S cluster provide a convenient handle to probe the structure, function, and coordination chemistry of Grx complexes. However, some limitations arise from sample preparation requirements, complexity of individual techniques, or the necessity for combining multiple methods in order to achieve a complete investigation. In this chapter, we focus on the use of UV-visible circular dichroism spectroscopy as a fast and simple initial approach for investigating glutaredoxin Fe-S cluster-dependent interactions. © 2018 Elsevier Inc. All rights reserved.

Correlation effects beyond coupled cluster singles and doubles approximation through Fock matrix dressing.

Science.gov (United States)

Maitra, Rahul; Nakajima, Takahito

2017-11-28

We present an accurate single reference coupled cluster theory in which the conventional Fock operator matrix is suitably dressed to simulate the effect of triple and higher excitations within a singles and doubles framework. The dressing thus invoked originates from a second-order perturbative approximation of a similarity transformed Hamiltonian and induces higher rank excitations through local renormalization of individual occupied and unoccupied orbital lines. Such a dressing is able to recover a significant amount of correlation effects beyond singles and doubles approximation, but only with an economic n 5 additional cost. Due to the inclusion of higher rank excitations via the Fock matrix dressing, this method is a natural improvement over conventional coupled cluster theory with singles and doubles approximation, and this method would be demonstrated via applications on some challenging systems. This highly promising scheme has a conceptually simple structure which is also easily generalizable to a multi-reference coupled cluster scheme for treating strong degeneracy. We shall demonstrate that this method is a natural lowest order perturbative approximation to the recently developed iterative n-body excitation inclusive coupled cluster singles and doubles scheme [R. Maitra et al., J. Chem. Phys. 147, 074103 (2017)].

Electronic structure and properties of designer clusters and cluster-assemblies

International Nuclear Information System (INIS)

Khanna, S.N.; Jena, P.

1995-01-01

Using self-consistent calculations based on density functional theory, we demonstrate that electronic shell filling and close atomic packing criteria can be used to design ultra-stable clusters. Interaction of these clusters with each other and with gas atoms is found to be weak confirming their chemical inertness. A crystal composed of these inert clusters is expected to have electronic properties that are markedly different from crystals where atoms are the building blocks. The recent observation of ferromagnetism in potassium clusters assembled in zeolite cages is discussed. (orig.)

Tuning Properties in Silver Clusters

KAUST Repository

Joshi, Chakra Prasad

2015-07-09

The properties of Ag nanoclusters are not as well understood as those of their more precious Au cousins. However, a recent surge in the exploration of strategies to tune the physicochemical characteristics of Ag clusters addresses this imbalance, leading to new insights into their optical, luminescence, crystal habit, metal-core, ligand-shell and environmental properties. In this Perspective, we provide an overview of the latest strategies along with a brief introduction of the theoretical framework necessary to understand the properties of silver nanoclusters and the basis for their tuning. The advances in cluster research and the future prospects presented in this Perspective will eventually guide the next large systematic study of nanoclusters, resulting in a single collection of data similar to the periodic table of elements.

Tuning Properties in Silver Clusters

KAUST Repository

Joshi, Chakra Prasad; Bootharaju, Megalamane Siddaramappa; Bakr, Osman

2015-01-01

The properties of Ag nanoclusters are not as well understood as those of their more precious Au cousins. However, a recent surge in the exploration of strategies to tune the physicochemical characteristics of Ag clusters addresses this imbalance, leading to new insights into their optical, luminescence, crystal habit, metal-core, ligand-shell and environmental properties. In this Perspective, we provide an overview of the latest strategies along with a brief introduction of the theoretical framework necessary to understand the properties of silver nanoclusters and the basis for their tuning. The advances in cluster research and the future prospects presented in this Perspective will eventually guide the next large systematic study of nanoclusters, resulting in a single collection of data similar to the periodic table of elements.

Properties of the open cluster system

International Nuclear Information System (INIS)

Janes, K.A.; Tilley, C.; Lynga, G.

1988-01-01

A system of weights corresponding to the precision of open cluster data is described. Using these weights, some properties of open clusters can be studied more accurately than was possible earlier. It is clear that there are three types of objects: unbound clusters, bound clusters in the thin disk, and older bound clusters. Galactic gradients of metallicity, longevity, and linear diameter are studied. Distributions at right angles to the galactic plane are discussed in the light of the different cluster types. The clumping of clusters in complexes is studied. An estimate of the selection effects influencing the present material of open cluster data is made in order to evaluate the role played by open clusters in the history of the galactic disk. 58 references

Exploring syndrome differentiation using non-negative matrix factorization and cluster analysis in patients with atopic dermatitis.

Science.gov (United States)

Yun, Younghee; Jung, Wonmo; Kim, Hyunho; Jang, Bo-Hyoung; Kim, Min-Hee; Noh, Jiseong; Ko, Seong-Gyu; Choi, Inhwa

2017-08-01

Syndrome differentiation (SD) results in a diagnostic conclusion based on a cluster of concurrent symptoms and signs, including pulse form and tongue color. In Korea, there is a strong interest in the standardization of Traditional Medicine (TM). In order to standardize TM treatment, standardization of SD should be given priority. The aim of this study was to explore the SD, or symptom clusters, of patients with atopic dermatitis (AD) using non-negative factorization methods and k-means clustering analysis. We screened 80 patients and enrolled 73 eligible patients. One TM dermatologist evaluated the symptoms/signs using an existing clinical dataset from patients with AD. This dataset was designed to collect 15 dermatologic and 18 systemic symptoms/signs associated with AD. Non-negative matrix factorization was used to decompose the original data into a matrix with three features and a weight matrix. The point of intersection of the three coordinates from each patient was placed in three-dimensional space. With five clusters, the silhouette score reached 0.484, and this was the best silhouette score obtained from two to nine clusters. Patients were clustered according to the varying severity of concurrent symptoms/signs. Through the distribution of the null hypothesis generated by 10,000 permutation tests, we found significant cluster-specific symptoms/signs from the confidence intervals in the upper and lower 2.5% of the distribution. Patients in each cluster showed differences in symptoms/signs and severity. In a clinical situation, SD and treatment are based on the practitioners' observations and clinical experience. SD, identified through informatics, can contribute to development of standardized, objective, and consistent SD for each disease. Copyright © 2017. Published by Elsevier Ltd.

The [4Fe-4S](2+) cluster in reconstituted biotin synthase binds S-adenosyl-L-methionine.

Science.gov (United States)

Cosper, Michele Mader; Jameson, Guy N L; Davydov, Roman; Eidsness, Marly K; Hoffman, Brian M; Huynh, Boi Hanh; Johnson, Michael K

2002-11-27

The combination of resonance Raman, electron paramagnetic resonance and Mössbauer spectroscopies has been used to investigate the effect of S-adenosyl-l-methionine (SAM) on the spectroscopic properties of the [4Fe-4S]2+ cluster in biotin synthase. The results indicate that SAM interacts directly at a unique iron site of the [4Fe-4S]2+ cluster in BioB and support the hypothesis of a common inner-sphere mechanism for the reductive cleavage of SAM in the radical SAM family of Fe-S enzymes.

Tight-binding study of the structural and magnetic properties of vanadium clusters

International Nuclear Information System (INIS)

Zhao Jijun; Lain, K.D.

1995-01-01

The structural and magnetic properties of small vanadium clusters are studied in the framework of tight-binding theory. According to parameters of the cluster dimer and bulk solid, we developed a tight-binding interatomic potential and calculated the bonding energies for the different possible structures to determine the ground state atomic configurations of the small vanadium clusters. The theoretical bonding energies for the vanadium clusters agree with the experiment much better than the simple droplet model. However, the calculated values for the clusters of odd atomic number are somewhat higher than the measured ones, corresponding to the pair occupation of delocalized 4s 1 electrons. Based on the optimized geometries, we study the magnetic properties of these clusters through a parametrized Hubbard Hamiltonian. We find the small V clusters of ground-state structures exhibit antiferromagnetic behavior while the alignment of local moments in the clusters with the unoptimized structures may show either ferromagnetic or antiferromagnetic characteristics. The average magnetic moments of the clusters decrease nonmonotonically as cluster size increases and the theoretical results are consistent with the upper limits obtained from a recent experiment. (orig.)

EMACSS: Evolve Me A Cluster of StarS

Science.gov (United States)

Alexander, Poul E. R.; Gieles, Mark

2012-03-01

The star cluster evolution code Evolve Me A Cluster of StarS (EMACSS) is a simple yet physically motivated computational model that describes the evolution of some fundamental properties of star clusters in static tidal fields. The prescription is based upon the flow of energy within the cluster, which is a constant fraction of the total energy per half-mass relaxation time. According to Henon's predictions, this flow is independent of the precise mechanisms for energy production within the core, and therefore does not require a complete description of the many-body interactions therein. Dynamical theory and analytic descriptions of escape mechanisms is used to construct a series of coupled differential equations expressing the time evolution of cluster mass and radius for a cluster of equal-mass stars. These equations are numerically solved using a fourth-order Runge-Kutta integration kernel; the results were benchmarked against a data base of direct N-body simulations. EMACSS is publicly available and reproduces the N-body results to within 10 per cent accuracy for the entire post-collapse evolution of star clusters.

Embedded Lattice and Properties of Gram Matrix

Directory of Open Access Journals (Sweden)

Futa Yuichi

2017-03-01

Full Text Available In this article, we formalize in Mizar [14] the definition of embedding of lattice and its properties. We formally define an inner product on an embedded module. We also formalize properties of Gram matrix. We formally prove that an inverse of Gram matrix for a rational lattice exists. Lattice of Z-module is necessary for lattice problems, LLL (Lenstra, Lenstra and Lov´asz base reduction algorithm [16] and cryptographic systems with lattice [17].

MARs Wars: heterogeneity and clustering of DNA-binding domains in the nuclear matrix

Directory of Open Access Journals (Sweden)

Ioudinkova E. S.

2009-12-01

Full Text Available Aim. CO326 is a chicken nuclear scaffold/matrix attachment region (MAR associated with the nuclear matrix in several types of chicken cells. It contains a binding site for a sequence-specific DNA-binding protein, F326. We have studied its interaction with the nuclear matrix. Methods. We have used an in vitro MAR assay with isolated matrices from chicken HD3 cells. Results. We have found that an oligonucleotide binding site for the F326 inhibits binding of the CO326 to the nuclear matrix. At the same time, the binding of heterologous MARs is enhanced. Conclusions. Taken together, these data suggest that there exist several classes of MARs and MAR-binding domains and that the MAR-binding proteins may be clustered in the nuclear matrix.

Causality and dispersion relations and the role of the S-matrix in the ongoing research

Energy Technology Data Exchange (ETDEWEB)

Schroer, Bert, E-mail: schroer@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Freie Univ. , Berlin (Germany). Inst. fur Theoretische Physik

2011-07-01

The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their seri- ous shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property demands the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These concepts which combine localization, vacuum polarization and thermal properties under the roof of modular theory will be explained and their use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role, but different from Heisenberg's and Mandelstam's proposals the new project is not a pure S-matrix approach. (author)

Calculations of light scattering matrices for stochastic ensembles of nanosphere clusters

International Nuclear Information System (INIS)

Bunkin, N.F.; Shkirin, A.V.; Suyazov, N.V.; Starosvetskiy, A.V.

2013-01-01

Results of the calculation of the light scattering matrices for systems of stochastic nanosphere clusters are presented. A mathematical model of spherical particle clustering with allowance for cluster–cluster aggregation is used. The fractal properties of cluster structures are explored at different values of the model parameter that governs cluster–cluster interaction. General properties of the light scattering matrices of nanosphere-cluster ensembles as dependent on their mean fractal dimension have been found. The scattering-matrix calculations were performed for finite samples of 10 3 random clusters, made up of polydisperse spherical nanoparticles, having lognormal size distribution with the effective radius 50 nm and effective variance 0.02; the mean number of monomers in a cluster and its standard deviation were set to 500 and 70, respectively. The implemented computation environment, modeling the scattering matrices for overall sequences of clusters, is based upon T-matrix program code for a given single cluster of spheres, which was developed in [1]. The ensemble-averaged results have been compared with orientation-averaged ones calculated for individual clusters. -- Highlights: ► We suggested a hierarchical model of cluster growth allowing for cluster–cluster aggregation. ► We analyzed the light scattering by whole ensembles of nanosphere clusters. ► We studied the evolution of the light scattering matrix when changing the fractal dimension

Mechanical properties study of particles reinforced aluminum matrix composites by micro-indentation experiments

Directory of Open Access Journals (Sweden)

Yuan Zhanwei

2014-04-01

Full Text Available By using instrumental micro-indentation technique, the microhardness and Young’s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro-compression-tester (MCT. The micro-indentation experiments were performed with different maximum loads, and with three loading speeds of 2.231, 4.462 and 19.368 mN/s respectively. During the investigation, matrix, particle and interface were tested by micro-indentation experiments. The results exhibit that the variations of Young’s modulus and microhardness at particle, matrix and interface were highly dependent on the loading conditions (maximum load and loading speed and the locations of indentation. Micro-indentation hardness experiments of matrix show the indentation size effects, i.e. the indentation hardness decreased with the indentation depth increasing. During the analysis, the effect of loading conditions on Young’s modulus and microhardness were explained. Besides, the elastic–plastic properties of matrix were analyzed. The validity of calculated results was identified by finite element simulation. And the simulation results had been preliminarily analyzed from statistical aspect.

OPEN CLUSTERS AS PROBES OF THE GALACTIC MAGNETIC FIELD. I. CLUSTER PROPERTIES

Energy Technology Data Exchange (ETDEWEB)

Hoq, Sadia; Clemens, D. P., E-mail: shoq@bu.edu, E-mail: clemens@bu.edu [Institute for Astrophysical Research, 725 Commonwealth Avenue, Boston University, Boston, MA 02215 (United States)

2015-10-15

Stars in open clusters are powerful probes of the intervening Galactic magnetic field via background starlight polarimetry because they provide constraints on the magnetic field distances. We use 2MASS photometric data for a sample of 31 clusters in the outer Galaxy for which near-IR polarimetric data were obtained to determine the cluster distances, ages, and reddenings via fitting theoretical isochrones to cluster color–magnitude diagrams. The fitting approach uses an objective χ{sup 2} minimization technique to derive the cluster properties and their uncertainties. We found the ages, distances, and reddenings for 24 of the clusters, and the distances and reddenings for 6 additional clusters that were either sparse or faint in the near-IR. The derived ranges of log(age), distance, and E(B−V) were 7.25–9.63, ∼670–6160 pc, and 0.02–1.46 mag, respectively. The distance uncertainties ranged from ∼8% to 20%. The derived parameters were compared to previous studies, and most cluster parameters agree within our uncertainties. To test the accuracy of the fitting technique, synthetic clusters with 50, 100, or 200 cluster members and a wide range of ages were fit. These tests recovered the input parameters within their uncertainties for more than 90% of the individual synthetic cluster parameters. These results indicate that the fitting technique likely provides reliable estimates of cluster properties. The distances derived will be used in an upcoming study of the Galactic magnetic field in the outer Galaxy.

Implementation of hierarchical clustering using k-mer sparse matrix to analyze MERS-CoV genetic relationship

Science.gov (United States)

Bustamam, A.; Ulul, E. D.; Hura, H. F. A.; Siswantining, T.

2017-07-01

Hierarchical clustering is one of effective methods in creating a phylogenetic tree based on the distance matrix between DNA (deoxyribonucleic acid) sequences. One of the well-known methods to calculate the distance matrix is k-mer method. Generally, k-mer is more efficient than some distance matrix calculation techniques. The steps of k-mer method are started from creating k-mer sparse matrix, and followed by creating k-mer singular value vectors. The last step is computing the distance amongst vectors. In this paper, we analyze the sequences of MERS-CoV (Middle East Respiratory Syndrome - Coronavirus) DNA by implementing hierarchical clustering using k-mer sparse matrix in order to perform the phylogenetic analysis. Our results show that the ancestor of our MERS-CoV is coming from Egypt. Moreover, we found that the MERS-CoV infection that occurs in one country may not necessarily come from the same country of origin. This suggests that the process of MERS-CoV mutation might not only be influenced by geographical factor.

The hybrid-cluster protein ('prismane protein') from Escherichia coli. Characterization of the hybrid-cluster protein, redox properties of the [2Fe-2S] and [4Fe-2S-2O] clusters and identification of an associated NADH oxidoreductase containing FAD and[2Fe-2S

NARCIS (Netherlands)

Berg, van den W.A.M.; Hagen, W.R.; Dongen, van W.M.A.M.

2000-01-01

Hybrid-cluster proteins ('prismane proteins') have previously been isolated and characterized from strictly anaerobic sulfate-reducing bacteria. These proteins contain two types of Fe/S clusters unique in biological systems: a [4Fe-4S] cubane cluster with spin-admixed S = 3/2 ground-state

Proximity effects on the local magnetic moments of clusters V{sub 6}-V{sub 9} embedded in a Fe matrix

Energy Technology Data Exchange (ETDEWEB)

Sosa-Hernandez, E.M. [Departamento de Matematicas Aplicadas, Facultad de Contaduria y Administration, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico); Alvarado-Leyva, P.G. [Departamento de Fisica, Facultad de Ciencias, Universidad Autonoma de San Luis Potosi Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico)]. E-mail: pal@galia.fc.uaslp.mx

2006-11-09

The magnetic behavior of clusters V{sub 6}-V{sub 9} in bulk Fe is determined by using an electronic Hamiltonian which includes s, p and d electrons. The spin density distribution is calculated self-consistenly in the unrestricted Hartree-Fock approximation. The local magnetic moments are obtained at V and Fe atoms; the magnetic coupling between Fe and V atoms is antiferromagnetic-like. We consider two cases, the first case correspond to non-interacting clusters, the distance between them is infinity, and the another case, when the clusters are interacting, the separation between them is finite; in the first case, the magnetic order in V{sub 6} is ferromagnetic-like whereas for V{sub 9} the magnetic order is antiferromagnetic-like, in the second case we have found that the magnetic order is not well stablished in V{sub 6}. We have found that the magnetic order in the matrix is not broken by the presence of the V atoms, although the local magnetic moments of Fe atoms at the interface cluster-matrix, are reduced respect to Fe bulk magnetization (2.22{mu} {sub B}) [e.g. {mu} {sub Fe}(5) = 1.98{mu} {sub B} in V{sub 6}; {mu} {sub Fe}(3) 1.89{mu} {sub B} in V{sub 9}].

Microstructure and mechanical properties of Al-Mg-Si-Cu matrix composites reinforced with AINp. processed by extrusion of powders

International Nuclear Information System (INIS)

Ortiz, J. L.; Amigo, V.; Salvador, M. D.; Perz, C. R.

2000-01-01

This article presents an experimental investigation on the structure and mechanical properties of an Al-Mg-Si-Cu P/M alloy reinforced with 5%, 10% and 15% aluminum nitride, produced by extrusion of cold compacted powders mixtures. Mechanical properties in as extruded and T6 conditions are compared. Differential Scanning Calorimetry and Dilatometric analysis were conducted to gain further insight into the precipitation process of these materials. Low cost 6061 Al/AINp composites can be produced with rate and small porosity by extrusion of cold compacted shapes without canning. The mechanical properties of the MMCs obtained by this process have limitations for high particles fractions because of clustering effects. All materials are always harder than the matrix and shows a similar behavior during aging processes but kinetics is changed. Potential applications of dilatometric techniques in the aging investigations of aluminum alloys and aluminum matrix composites have been established. (Author) 23 refs

Understanding the structural properties and thermal stabilities of Au–Pd–Pt trimetallic clusters

International Nuclear Information System (INIS)

Zhao, Zheng; Li, Mingjiang; Cheng, Daojian; Zhu, Jiqin

2014-01-01

Highlights: • Structural properties of Au–Pd–Pt clusters are studied by Monte Carlo simulation. • Melting of Au–Pd–Pt clusters is studied by molecular dynamics simulation. • Au atoms are systematically segregated on the surface of the Au–Pd–Pt clusters. • Linear decrease in cluster melting point with the inverse cluster diameter. - Abstract: In this work, surface segregation phenomena of Au–Pd–Pt trimetallic clusters are investigated by using semi-grand Monte Carlo simulations based on the Gupta potential. It is found that Au atoms are systematically segregated on the surface of the Au–Pd–Pt clusters (6–24 at.% higher than the overall Au concentration), due to the competition among the surface energies of Au, Pd, and Pt. The melting properties of Au–Pd–Pt trimetallic clusters with different composition and size are investigated by using molecular dynamics simulations, based on the same Gupta potential. It is found that the Au–Pd–Pt trimetallic cluster with the highest melting point corresponds to the one with the most stable structure. In addition, linear decrease in cluster melting point with the inverse cluster diameter is predicted for both pure and trimetallic clusters, which is well-known as the Pawlow’s law

Causality and dispersion relations and the role of the S-matrix in the ongoing research

International Nuclear Information System (INIS)

Schroer, Bert; Freie Univ. , Berlin

2011-01-01

The adaptation of the Kramers-Kronig dispersion relations to the causal localization structure of QFT led to an important project in particle physics, the only one with a successful closure. The same cannot be said about the subsequent attempts to formulate particle physics as a pure S-matrix project. The feasibility of a pure S-matrix approach are critically analyzed and their seri- ous shortcomings are highlighted. Whereas the conceptual/mathematical demands of renormalized perturbation theory are modest and misunderstandings could easily be corrected, the correct understanding about the origin of the crossing property demands the use of the mathematical theory of modular localization and its relation to the thermal KMS condition. These concepts which combine localization, vacuum polarization and thermal properties under the roof of modular theory will be explained and their use in a new constructive (nonperturbative) approach to QFT will be indicated. The S-matrix still plays a predominant role, but different from Heisenberg's and Mandelstam's proposals the new project is not a pure S-matrix approach. (author)

FORMATION OF A INNOVATION REGIONAL CLUSTER MODEL

Directory of Open Access Journals (Sweden)

G. S. Merzlikina

2015-01-01

Full Text Available Summary. As a result of investigation of science and methodical approaches related problems of building and development of innovation clusters there were some issues in functional assignments of innovation and production clusters. Because of those issues, article’s authors differ conceptions of innovation cluster and production cluster, as they explain notion of innovation-production cluster. The main goal of this article is to reveal existing organizational issues in cluster building and its successful development. Based on regional clusters building analysis carried out there was typical practical structure of cluster members interaction revealed. This structure also have its cons, as following: absence cluster orientation to marketing environment, lack of members’ prolonged relations’ building and development system, along with ineffective management of information, financial and material streams within cluster, narrow competence difference and responsibility zones between cluster members, lack of transparence of cluster’s action, low environment changes adaptivity, hard to use cluster members’ intellectual property, and commercialization of hi-tech products. When all those issues listed above come together, it reduces life activity of existing models of innovative cluster-building along with practical opportunity of cluster realization. Because of that, authors offer an upgraded innovative-productive cluster building model with more efficient business processes management system, which includes advanced innovative cluster structure, competence matrix and subcluster responsibility zone. Suggested model differs from other ones by using unified innovative product development control center, which also controls production and marketing realization.

Geometrical Structures and Electronic Properties of Ga6 and Ga5X (X = B, C, N, O, F, Al, Si, P, S, Cl Clusters

Directory of Open Access Journals (Sweden)

Yanfei Hu

2018-04-01

Full Text Available Based on the unbiased CALYPSO (Crystal structure Analysis by Particle Swarm Optimization structure searching method in combination with density functional theory (DFT, the geometrical structures and electronic properties are investigated theoretically for Ga6 and Ga5X (X = B, C, N, O, F, Al, Si, P, S, Cl clusters. The PBE0 exchange-correlation functional and the 6-311G(d basis set is carried out to determine global minima on potential energy surfaces. The relative stabilities of the clusters are examined by the binding energies and substitution reaction. Following the predictions of the Jellium model, the Ga5B cluster with the 18 valence electrons is the most stable structure. At last, with the obtained lowest energy structures, some physical properties such as electrons transfer, molecular orbitals, and total and partial densities of states are discussed, respectively.

Helium clusters as cold, liquid matrix for the laser spectroscopy of silver atoms, silver clusters and C60 fullerenes

International Nuclear Information System (INIS)

Hoffmann, K.

1999-01-01

One of the main obstacles in the study of gas phase metal clusters is their high temperature. Even cooling in a seeded beam is only of limited used, since the condensation continuously releases energy into the system. As a consequence, spectroscopic studies of free metal clusters typically yield broad structures, which are interpreted as plasma resonances of a free electron gas. An experiment on ionic sodium clusters has shown that low temperatures lead to a narrowing of the absorption bands and the appearance of additional structure, that can not be explained within the free electron model. Thus the need for cold clusters is evident. In principle the deposition of metal clusters into inert matrices eliminates the temperature problem but it can also inflict strong changes on the electronic spectra. Droplets of liquid helium serve as a much more gentle matrix that avoids many of the above problems. In this thesis the new technique of helium droplet spectroscopy is presented as a tool for the study of extremely cold metal clusters. Clusters of silver up to a mass greater than 7000 amu have been produced by pickup of single atoms by a beam of helium droplets. The droplets are formed in a supersonic expansion. The cluster's binding energy is removed by evaporative cooling and the system remains at 0.4 K. The doped droplets are probed by laser spectroscopy with a depletion technique or resonant two photon ionization. We were able to measure the first UV absorption spectrum of metal atoms (silver) inside helium droplets. Another experiment shows that a small fraction of the captured silver atoms resides on the surface of the droplet like alkali atoms. In a two photon process previously unobserved s- and d-Rydberg states of the free silver atom (20 left angle n left angle 80) were excited. The silver atoms, initially embedded in the helium droplets, are found to move to the surface and desorb when excited to the broadened 5p level. This is the first result showing laser

Entanglement property in matrix product spin systems

International Nuclear Information System (INIS)

Zhu Jingmin

2012-01-01

We study the entanglement property in matrix product spin-ring systems systemically by von Neumann entropy. We find that: (i) the Hilbert space dimension of one spin determines the upper limit of the maximal value of the entanglement entropy of one spin, while for multiparticle entanglement entropy, the upper limit of the maximal value depends on the dimension of the representation matrices. Based on the theory, we can realize the maximum of the entanglement entropy of any spin block by choosing the appropriate control parameter values. (ii) When the entanglement entropy of one spin takes its maximal value, the entanglement entropy of an asymptotically large spin block, i.e. the renormalization group fixed point, is not likely to take its maximal value, and so only the entanglement entropy S n of a spin block that varies with size n can fully characterize the spin-ring entanglement feature. Finally, we give the entanglement dynamics, i.e. the Hamiltonian of the matrix product system. (author)

Properties of porous FeAlOy/FeAlx ceramic matrix composite ...

Indian Academy of Sciences (India)

Home; Journals; Bulletin of Materials Science; Volume 36; Issue 7. Properties of porous FeAlO/FeAl ceramic matrix composite influenced by mechanical activation of FeAl powder. V Usoltsev S Tikhov A Salanov V Sadykov G Golubkova O Lomovskii. Volume 36 Issue 7 December 2013 pp 1195-1200 ...

The S-matrix of superstring field theory

International Nuclear Information System (INIS)

Konopka, Sebastian

2015-01-01

We show that the classical S-matrix calculated from the recently proposed superstring field theories give the correct perturbative S-matrix. In the proof we exploit the fact that the vertices are obtained by a field redefinition in the large Hilbert space. The result extends to include the NS-NS subsector of type II superstring field theory and the recently found equations of motions for the Ramond fields. In addition, our proof implies that the S-matrix obtained from Berkovits’ WZW-like string field theory then agrees with the perturbative S-matrix to all orders.

STAR CLUSTER PROPERTIES IN TWO LEGUS GALAXIES COMPUTED WITH STOCHASTIC STELLAR POPULATION SYNTHESIS MODELS

Energy Technology Data Exchange (ETDEWEB)

Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Adamo, Angela [Department of Astronomy, Oskar Klein Centre, Stockholm University, SE-10691 Stockholm (Sweden); Fumagalli, Michele [Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Wofford, Aida [Institut d’Astrophysique de Paris, 98bis Boulevard Arago, F-75014 Paris (France); Calzetti, Daniela; Grasha, Kathryn [Department of Astronomy, University of Massachusetts–Amherst, Amherst, MA (United States); Lee, Janice C.; Whitmore, Bradley C.; Bright, Stacey N.; Ubeda, Leonardo [Space Telescope Science Institute, Baltimore, MD (United States); Gouliermis, Dimitrios A. [Centre for Astronomy, Institute for Theoretical Astrophysics, University of Heidelberg, Heidelberg (Germany); Kim, Hwihyun [Korea Astronomy and Space Science Institute, Daejeon (Korea, Republic of); Nair, Preethi [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL (United States); Ryon, Jenna E. [Department of Astronomy, University of Wisconsin–Madison, Madison, WI (United States); Smith, Linda J. [European Space Agency/Space Telescope Science Institute, Baltimore, MD (United States); Thilker, David [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD (United States); Zackrisson, Erik, E-mail: mkrumhol@ucsc.edu, E-mail: adamo@astro.su.se [Department of Physics and Astronomy, Uppsala University, Uppsala (Sweden)

2015-10-20

We investigate a novel Bayesian analysis method, based on the Stochastically Lighting Up Galaxies (slug) code, to derive the masses, ages, and extinctions of star clusters from integrated light photometry. Unlike many analysis methods, slug correctly accounts for incomplete initial mass function (IMF) sampling, and returns full posterior probability distributions rather than simply probability maxima. We apply our technique to 621 visually confirmed clusters in two nearby galaxies, NGC 628 and NGC 7793, that are part of the Legacy Extragalactic UV Survey (LEGUS). LEGUS provides Hubble Space Telescope photometry in the NUV, U, B, V, and I bands. We analyze the sensitivity of the derived cluster properties to choices of prior probability distribution, evolutionary tracks, IMF, metallicity, treatment of nebular emission, and extinction curve. We find that slug's results for individual clusters are insensitive to most of these choices, but that the posterior probability distributions we derive are often quite broad, and sometimes multi-peaked and quite sensitive to the choice of priors. In contrast, the properties of the cluster population as a whole are relatively robust against all of these choices. We also compare our results from slug to those derived with a conventional non-stochastic fitting code, Yggdrasil. We show that slug's stochastic models are generally a better fit to the observations than the deterministic ones used by Yggdrasil. However, the overall properties of the cluster populations recovered by both codes are qualitatively similar.

Electronic and chemical properties of barium and indium clusters

International Nuclear Information System (INIS)

Onwuagba, B.N.

1992-11-01

The ground state electronic and chemical properties of divalent barium and trivalent indium are investigated in a self-consistent manner using the spin-polarized local density approximation in the framework of Density Functional Theory. A jellium model is adopted in the spirit of Gunnarsson and Lundqvist exchange and correlation energies and the calculated properties primarily associated with the s-p orbitals in barium and p orbitals in indium provide deepened insight towards the understanding of the mechanisms to the magic numbers in both clusters. (author). 21 refs, 5 figs

The revenge of the S-matrix

CERN Multimedia

CERN. Geneva

2016-01-01

In this talk I will describe recent work aiming to reinvigorate the 50 year old S-matrix program, which aims to constrain scattering of massive particles non-perturbatively. I will begin by considering quantum fields in anti-de Sitter space and show that one can extract information about the S-matrix by considering correlators in conformally invariant theories. The latter can be studied with "bootstrap" techniques, which allow us to constrain the S-matrix. In particular, in 1+1D one obtains bounds which are saturated by known integrable models. I will also show that it is also possible to directly constrain the S-matrix, without using the CFT crutch, by using crossing symmetry and unitarity. This alternative method is simpler and gives results in agreement with the previous approach. Both techniques are generalizable to higher dimensions.

Syntheses, structures and third-order non-linear optical properties of homometal clusters containing molybdenum

International Nuclear Information System (INIS)

Li Yong; Lu Jing; Cui Xiaobing; Xu Jiqing; Li Kechang; Sun Huaying; Li Guanghua; Pan Lingyun; Yang Qingxin

2005-01-01

Both the homometal cluster [P(ph 4 )] 2 [Mo 2 O 2 (μ-S) 2 (S 2 ) 2 ] (1) and [Mo 2 O 2 (μ-S) 2 (Et 2 dtc) 2 ] (2) (Et 2 dtc=diethyl-dithiocarbamate) were successfully synthesized by low-temperature solid-state reactions. X-ray single-crystal diffraction studies suggest that compound (1) is a dinuclear anion cluster, and compound (2) is a dinuclear neutral cluster. The two compounds were characterized by elemental analyses, IR spectra and UV-Vis spectra. The third-order non-linear optical (NLO) properties of the clusters were also investigated and all exhibited nice non-linear absorption and self-defocusing performance with moduli of the hyperpolarizabilities 5.145x10 -30 esu for (1) and 5.428x10 -30 esu for (2)

Integrins and extracellular matrix in mechanotransduction

Directory of Open Access Journals (Sweden)

Ramage L

2011-12-01

Full Text Available Lindsay RamageQueen’s Medical Research Institute, University of Edinburgh, Edinburgh, UKAbstract: Integrins are a family of cell surface receptors which mediate cell–matrix and cell–cell adhesions. Among other functions they provide an important mechanical link between the cells external and intracellular environments while the adhesions that they form also have critical roles in cellular signal-transduction. Cell–matrix contacts occur at zones in the cell surface where adhesion receptors cluster and when activated the receptors bind to ligands in the extracellular matrix. The extracellular matrix surrounds the cells of tissues and forms the structural support of tissue which is particularly important in connective tissues. Cells attach to the extracellular matrix through specific cell-surface receptors and molecules including integrins and transmembrane proteoglycans. Integrins work alongside other proteins such as cadherins, immunoglobulin superfamily cell adhesion molecules, selectins, and syndecans to mediate cell–cell and cell–matrix interactions and communication. Activation of adhesion receptors triggers the formation of matrix contacts in which bound matrix components, adhesion receptors, and associated intracellular cytoskeletal and signaling molecules form large functional, localized multiprotein complexes. Cell–matrix contacts are important in a variety of different cell and tissue properties including embryonic development, inflammatory responses, wound healing, and adult tissue homeostasis. This review summarizes the roles and functions of integrins and extracellular matrix proteins in mechanotransduction.Keywords: ligand binding, α subunit, ß subunit, focal adhesion, cell differentiation, mechanical loading, cell–matrix interaction

Perturbative S-matrix for massive scalar fields in global de Sitter space

International Nuclear Information System (INIS)

Marolf, Donald; Srednicki, Mark; Morrison, Ian A

2013-01-01

We construct a perturbative S-matrix for interacting massive scalar fields in global de Sitter space. Our S-matrix is formulated in terms of asymptotic particle states in the far past and future, taking appropriate care for light fields whose wavefunctions decay only very slowly near the de Sitter conformal boundaries. An alternative formulation expresses this S-matrix in terms of residues of poles in analytically-continued Euclidean correlators (computed in perturbation theory), making it clear that the standard Minkowski-space result is obtained in the flat-space limit. Our S-matrix transforms properly under CPT, is invariant under the de Sitter isometries and perturbative field redefinitions, and is unitary. This unitarity implies a de Sitter version of the optical theorem. We explicitly verify these properties to second order in the coupling for a general cubic interaction, including both tree- and loop-level contributions. Contrary to other statements in the literature, we find that a particle of any positive mass may decay at tree level to any number of particles, each of arbitrary positive masses. In particular, even very light fields (in the complementary series of de Sitter representations) are not protected from tree-level decays. (paper)

Nanostructural Characteristics and Interfacial Properties of Polymer Fibers in Cement Matrix.

Science.gov (United States)

Shalchy, Faezeh; Rahbar, Nima

2015-08-12

Concrete is the most used material in the world. It is also one of the most versatile yet complex materials that humans have used for construction. However, an important weakness of concrete (cement-based composites) is its low tensile properties. Therefore, over the past 30 years many studies were focused on improving its tensile properties using a variety of physical and chemical methods. One of the most successful attempts is to use polymer fibers in the structure of concrete to obtain a composite with high tensile strength and ductility. The advantages of polymer fiber as reinforcing material in concrete, both with regard to reducing environmental pollution and the positive effects on a country's economy, are beyond dispute. However, a thorough understanding of the mechanical behavior of fiber-reinforced concrete requires a knowledge of fiber/matrix interfaces at the nanoscale. In this study, a combination of atomistic simulations and experimental techniques has been used to study the nanostructure of fiber/matrix interfaces. A new model for calcium-silicate-hydrate (C-S-H)/fiber interfaces is also proposed on the basis of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. Finally, the adhesion energy between the C-S-H gel and three different polymeric fibers (poly(vinyl alcohol), nylon-6, and polypropylene) were numerically studied at the atomistic level because adhesion plays a key role in the design of ductile fiber-reinforced composites. The mechanisms of adhesion as a function of the nanostructure of fiber/matrix interfaces are further studied and discussed. It is observed that the functional group in the structure of polymer macromolecule affects the adhesion energy primarily by changing the C/S ratio of the C-S-H at the interface and by absorbing additional positive ions in the C-S-H structure.

Cosmological aspects and properties evolution of galaxy clusters

International Nuclear Information System (INIS)

Majerowicz, Sebastien

2003-01-01

In the standard scenario for galaxy cluster formation, galaxy clusters form by material accretion and violent merger events. Between two merger events, galaxy cluster components which are the dark matter (75 %), the intra-cluster medium (20 %) and the galaxies (5 %), reach for equilibrium. The intra-cluster medium is the main baryonic component. This is a hot optically thin gas and its temperature tells something about the gravitational potential well. This well is essentially the consequence of the dark matter distribution. The intra-cluster medium is so hot than its emission produces only x-ray photons. We studied the properties of the intra-cluster medium for some clusters by using the observations coming from the european satellite XMM-NEWTON [fr

Carbon fibre reinforced copper matrix composites: processing routes and properties

Energy Technology Data Exchange (ETDEWEB)

Le Petitcorps, Y. [Bordeaux-1 Univ., 33 - Pessac (France). ICMCB; Poueylaud, J.M. [Bordeaux-1 Univ., 33 - Pessac (France). ICMCB; Albingre, L. [Bordeaux-1 Univ., 33 - Pessac (France). ICMCB; Berdeu, B. [L`Electrolyse, 33 - Latresne (France); Lobstein, P. [L`Electrolyse, 33 - Latresne (France); Silvain, J.F. [Bordeaux-1 Univ., 33 - Pessac (France). ICMCB

1997-06-01

Copper matrix composites are of interest for applications in the electronic field which requires materials with high thermal conductivity properties. The use of carbon fibres can (1) decrease the density and the coefficient of thermal expansion of the material and (2) increase the stiffness and strength to rupture of the resulting composite. In order to produce cheap materials, chemical plating and uniaxial hot pressing processing routes were chosen. 1D-C{sub (P55Thornel)} / Cu prepregs were hot pressed in an argon atmosphere at 750 C during 30 min. The volume fraction of the fibres within the composite was in the range of 10-35%. Physical (density and thermal expansion coefficient) and thermal conductivity properties of the composite were in good agreement with the predictions. However this material exhibits very poor mechanical properties (Young`s modulus and tensile strength). Scanning electron microscopy (SEM) observations of the surfaces of ruptures have shown that (1) a very weak bonding between the graphite fibres and the copper matrix was formed and (2) the rupture of the composite was initiated in the matrix at the copper grain boundaries. In order to overcome these two difficulties, the carbon fibres were pre-coated with a thin layer (100 nm) of cobalt. The aim of the cobalt was to react with the carbon to form carbide compounds and as a consequence to increase the bonding between the metal and the fibre. The tensile properties ({sigma}{sub c}{sup R} and E{sub c}) of this composite were then increased by 50% in comparison with the former material; however the strain to rupture was still too weak ({epsilon}{sub c}{sup R} = 0.5%). In order to explain the role of each constituents, X-ray profiles and TEM analyses were done at the fibre/matrix interface and at the grain boundaries. Some modifications of the chemical plating steps were done to improve the purity of the copper. (orig.)

Defining reference sequences for Nocardia species by similarity and clustering analyses of 16S rRNA gene sequence data.

Directory of Open Access Journals (Sweden)

Manal Helal

Full Text Available BACKGROUND: The intra- and inter-species genetic diversity of bacteria and the absence of 'reference', or the most representative, sequences of individual species present a significant challenge for sequence-based identification. The aims of this study were to determine the utility, and compare the performance of several clustering and classification algorithms to identify the species of 364 sequences of 16S rRNA gene with a defined species in GenBank, and 110 sequences of 16S rRNA gene with no defined species, all within the genus Nocardia. METHODS: A total of 364 16S rRNA gene sequences of Nocardia species were studied. In addition, 110 16S rRNA gene sequences assigned only to the Nocardia genus level at the time of submission to GenBank were used for machine learning classification experiments. Different clustering algorithms were compared with a novel algorithm or the linear mapping (LM of the distance matrix. Principal Components Analysis was used for the dimensionality reduction and visualization. RESULTS: The LM algorithm achieved the highest performance and classified the set of 364 16S rRNA sequences into 80 clusters, the majority of which (83.52% corresponded with the original species. The most representative 16S rRNA sequences for individual Nocardia species have been identified as 'centroids' in respective clusters from which the distances to all other sequences were minimized; 110 16S rRNA gene sequences with identifications recorded only at the genus level were classified using machine learning methods. Simple kNN machine learning demonstrated the highest performance and classified Nocardia species sequences with an accuracy of 92.7% and a mean frequency of 0.578. CONCLUSION: The identification of centroids of 16S rRNA gene sequence clusters using novel distance matrix clustering enables the identification of the most representative sequences for each individual species of Nocardia and allows the quantitation of inter- and intra

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.

Application of Haddon’s matrix in qualitative research methodology: an experience in burns epidemiology

Directory of Open Access Journals (Sweden)

Deljavan R

2012-07-01

Full Text Available Reza Deljavan,1 Homayoun Sadeghi-Bazarganim,2,3 Nasrin Fouladim,4 Shahnam Arshi,5 Reza Mohammadi61Injury Epidemiology and Prevention Research Center, 2Neuroscience Research Center, Department of Statistics and Epidemiology, Tabriz University of Medical Sciences, Tabriz, Iran; 3Public Health Department, Karolinska Institute, Stockholm, Sweden; 4Ardabil University of Medical Sciences, Ardabil, Iran; 5Shahid Beheshti University of Medical Sciences, Tehran, Iran; 6Public Health Department, Karolinska Institute, Stockholm, SwedenBackground: Little has been done to investigate the application of injury specific qualitative research methods in the field of burn injuries. The aim of this study was to use an analytical tool (Haddon’s matrix through qualitative research methods to better understand people’s perceptions about burn injuries.Methods: This study applied Haddon’s matrix as a framework and an analytical tool for a qualitative research methodology in burn research. Both child and adult burn injury victims were enrolled into a qualitative study conducted using focus group discussion. Haddon’s matrix was used to develop an interview guide and also through the analysis phase.Results: The main analysis clusters were pre-event level/human (including risky behaviors, belief and cultural factors, and knowledge and education, pre-event level/object, pre-event phase/environment and event and post-event phase (including fire control, emergency scald and burn wound management, traditional remedies, medical consultation, and severity indicators. This research gave rise to results that are possibly useful both for future injury research and for designing burn injury prevention plans.Conclusion: Haddon’s matrix is applicable in a qualitative research methodology both at data collection and data analysis phases. The study using Haddon’s matrix through a qualitative research methodology yielded substantially rich information regarding burn injuries

On the processes of generation of particles in the extended S-matrix method

International Nuclear Information System (INIS)

Dushutin, N.K.; Mal'tsev, V.M.; Sinegovskij, S.I.

1975-01-01

In order to understand the processes of hadron multiple production very important are integral characteristics, such as the multiplicity distribution function Psub(n)=sigmasub(n)/sigmasub(inel) and correlation parameters of fsub(K). From the shape of distribution and the energy dependence of correlation parameters one may arrive at definite conclusions about the interaction dynamics. In the paper a possibility is studied of obtaining integral characteristics in the S matrix formulation of the quantum field theory. This technique is based on principles of the scattering matrix expanding beyond the energy surface (ES). This follows from the fact that the predetermination of the scattering matrix on the ES does not permit strict to determinate the condition for causality. The expansion of S matrix is performed by introducing some object described by a substantial function rho(x) and interacting with a quantum system, properties of rho(x) being such that the space of asymptotic states remains complete for the expanded matrix also, i.e., the unitarity condition is fulfilled for S(rho) too. The expansion of S-matrix over the function of the interaction insertion g(x) and the transition to the differential equations for the coupling constant allowed investigation of hadron inelastic processes at some simplifying suppositions. Experimental data do not contradict in the main the proposed picture of interactions [ru

The transformation of Spirals into S0 galaxies in the cluster environment

International Nuclear Information System (INIS)

D'Onofrio, Mauro; Marziani, Paola; Buson, Lucio

2015-01-01

We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04 < z < 0.07) and EDisCS (0.4 < z < 0.8). The most important results are: (1) the average number of S0 galaxies in clusters is almost a factor of ~ 3 − 4 larger today than at redshift z ~ 1; (2) the fraction of S0's to Spirals increases on average by a factor ~ 2 every Gyr; (3) the average rate of transformation for Spirals (not considering the infall of new galaxies from the cosmic web) is: ~ 5 Sp → S0's per Gyr and ~ 2 Sp → E's per Gyr; (4) there are evidences that the interstellar gas of Spirals is stripped by an hot intergalactic medium; (5) there are also indirect hints that major/minor merging events have played a role in the transformation of Spiral galaxies. In particular, we show that: (1) the ratio between the number of S0's and Spirals (N S0 ∕N Sp ) in the WINGS clusters is correlated with their X-ray luminosity L X ; (2) that the brightest and massive S0's are always close to the cluster center; (3) that the mean Sérsic index of S0's is always larger than that of Spirals (and lower than E's) for galaxy stellar masses above 10 9.5 M ⊙ (4) that the number of E's in clusters cannot be constant; (5) that the largest difference between the mean mass of S0's and E's with respect to Spirals is observed in clusters with low velocity dispersion. Finally, by comparing the properties of the various morphological types for galaxies in clusters and in the field, we find that the most significant effect of the environment is the stripping of the outer galaxy regions, resulting in a systematic difference in effective radius and Sérsic index.

Radio properties of central dominant galaxies in cluster cooling flows

International Nuclear Information System (INIS)

O'dea, C.P.; Baum, S.A.

1986-01-01

New VLA observations of central dominant (cd) galaxies currently thought to be in cluster cooling flows are combined with observations from the literature to examine the global properties of a heterogeneous sample of 31 cd galaxies. The radio sources tend to be of low or intermediate radio power and have small sizes (median extent about 25 kpc). The resolved sources tend to have distorted morphologies (e.g., wide-angle tails and S shapes). It is not yet clear whether the radio emission from these cd galaxies is significantly different from those not thought to be in cluster cooling flows. The result of Jones and Forman (1984), that there is a possible correlation between radio power and excess X-ray luminosity in the cluster center (above a King model fit to the X-ray surface brightness), is confirmed. 43 references

The transformation of Spirals into S0 galaxies in the cluster environment

Directory of Open Access Journals (Sweden)

Mauro eD'onofrio

2015-08-01

Full Text Available We discuss the observational evidences of the morphological transformation of Spirals into S0 galaxies in the cluster environment exploiting two big databases of galaxy clusters: WINGS (0.04S0 galaxies in clusters is almost a factor of ∼ 3 − 4 larger today than at redshift z ∼ 1; 2 the fraction of S0’s to Spirals increases on average by a factor ∼ 2 every Gyr; 3 the average rate of transformation for Spirals (not considering the infall of new galaxies from the cosmic web is: ∼ 5 Sp→S0’s per Gyr and ∼ 2 Sp→E’s per Gyr; 4 there are evidences that the interstellar gas of Spirals is stripped by an hot intergalactic medium; 5 there are also indirect hints that major/minor merging events have played a role in the transformation of Spiral galaxies. In particular, we show that: 1 the ratio between the number of S0’s and Spirals (NS0/NSp in the WINGS clusters is correlated with their X-ray luminosity LX ; 2 that the brightest and massive S0’s are always close to the cluster center; 3 that the mean Se ́rsic index of S0’s is always larger than that of Spirals (and lower than E’s for galaxy stellar masses above 10^9.5M⊙; 4 that the number of E’s in clusters cannot be constant; 5 that the largest difference between the mean mass of S0’s and E’s with respect to Spirals is observed in clusters with low velocity dispersion.Finally, by comparing the properties of the various morphological types for galaxies in clusters and in the field, we find that the most significant effect of the environment is the stripping of the outer galaxy regions, resulting in a systematic difference in effective radius and Se ́rsic index.

Baryoniums - the S-matrix approach

International Nuclear Information System (INIS)

Roy, D.P.

1979-08-01

In this series of lectures the question of how the baryoniums are related to charmoniums and strangoniums is discussed and it is pointed out that in the S-matrix framework, they all follow from the same pair of hypotheses, duality and no exotics. Invoking no underlying quark structure, except that inherent in the assumption of no exotics, it is shown that there are no mesons outside the singlet and octet representation of SU(3) and no baryons outside the singlet, octet and decaplet. In other words all mesons occur within the quantum number of a q-antiq system and all baryons within those of qqq. This seems to be an experimental fact, which has no natural explanation within the S-matrix framework except that it is the minimal non-zero solution to the duality constraints. The approach in the past has been to take it as an experimental input and build up a phenomenological S-matrix framework. Lately it has been realised that the answer may come from the colour dynamics of quarks. If true this would provide an important link between the fundamental but invisible field theory of quarks and gluons and the phenomenological but visible S-matrix theory overlying it. The subject is discussed under the headings; strangonium and charmonium, baryonium, spectroscopy, baryonium resonances, FESR constraint, baryonium exchange, phenomenological estimate of ω - baryonium mixing at t = 0, and models of ω - baryonium mixing. (UK)

Structural properties of gold clusters at different temperatures

CSIR Research Space (South Africa)

Mahladisa, MA

2005-09-01

Full Text Available A series of gold clusters consisting of aggregates of from 13 to 147 atoms was studied using the Sutton-Chen type many-body potential in molecular dynamics simulations. The properties of these clusters at temperatures from 10 K to 1000 K were...

Properties of liquid clusters in large-scale molecular dynamics nucleation simulations

International Nuclear Information System (INIS)

Angélil, Raymond; Diemand, Jürg; Tanaka, Kyoko K.; Tanaka, Hidekazu

2014-01-01

We have performed large-scale Lennard-Jones molecular dynamics simulations of homogeneous vapor-to-liquid nucleation, with 10 9 atoms. This large number allows us to resolve extremely low nucleation rates, and also provides excellent statistics for cluster properties over a wide range of cluster sizes. The nucleation rates, cluster growth rates, and size distributions are presented in Diemand et al. [J. Chem. Phys. 139, 74309 (2013)], while this paper analyses the properties of the clusters. We explore the cluster temperatures, density profiles, potential energies, and shapes. A thorough understanding of the properties of the clusters is crucial to the formulation of nucleation models. Significant latent heat is retained by stable clusters, by as much as ΔkT = 0.1ε for clusters with size i = 100. We find that the clusters deviate remarkably from spherical—with ellipsoidal axis ratios for critical cluster sizes typically within b/c = 0.7 ± 0.05 and a/c = 0.5 ± 0.05. We examine cluster spin angular momentum, and find that it plays a negligible role in the cluster dynamics. The interfaces of large, stable clusters are thinner than planar equilibrium interfaces by 10%−30%. At the critical cluster size, the cluster central densities are between 5% and 30% lower than the bulk liquid expectations. These lower densities imply larger-than-expected surface areas, which increase the energy cost to form a surface, which lowers nucleation rates

Role of Anions Associated with the Formation and Properties of Silver Clusters.

Science.gov (United States)

Wang, Quan-Ming; Lin, Yu-Mei; Liu, Kuan-Guan

2015-06-16

Metal clusters have been very attractive due to their aesthetic structures and fascinating properties. Different from nanoparticles, each cluster of a macroscopic sample has a well-defined structure with identical composition, size, and shape. As the disadvantages of polydispersity are ruled out, informative structure-property relationships of metal clusters can be established. The formation of a high-nuclearity metal cluster involves the organization of metal ions into a complex entity in an ordered way. To achieve controllable preparation of metal clusters, it is helpful to introduce a directing agent in the formation process of a cluster. To this end, anion templates have been used to direct the formation of high nuclearity clusters. In this Account, the role of anions played in the formation of a variety of silver clusters has been reviewed. Silver ions are positively charged, so anionic species could be utilized to control the formation of silver clusters on the basis of electrostatic interactions, and the size and shape of the resulted clusters can be dictated by the templating anions. In addition, since the anion is an integral component in the silver clusters described, the physical properties of the clusters can be modulated by functional anions. The templating effects of simple inorganic anions and polyoxometales are shown in silver alkynyl clusters and silver thiolate clusters. Intercluster compounds are also described regarding the importance of anions in determining the packing of the ion pairs and making contribution to electron communications between the positive and negative counterparts. The role of the anions is threefold: (a) an anion is advantageous in stabilizing a cluster via balancing local positive charges of the metal cations; (b) an anion template could help control the size and shape of a cluster product; (c) an anion can be a key factor in influencing the function of a cluster through bringing in its intrinsic properties. Properties

Mean deformation metrics for quantifying 3D cell–matrix interactions without requiring information about matrix material properties

OpenAIRE

Stout, David A.; Bar-Kochba, Eyal; Estrada, Jonathan B.; Toyjanova, Jennet; Kesari, Haneesh; Reichner, Jonathan S.; Franck, Christian

2016-01-01

Investigations in mechanobiology rely on correlation of cellular processes with mechanical signals, such as matrix stiffness and cell tractions. Almost all cell traction and force quantification methodologies require knowledge of the underlying mechanical properties of the extracellular matrix to convert displacement data into corresponding traction data, which restricts the use of these techniques to systems in which the material properties are known. To overcome this hurdle, we present a ne...

Quantification of the clustering properties of nuclear states

International Nuclear Information System (INIS)

Beck, R.; Dickmann, F.

1985-05-01

The amount of particular type of clustering in a nuclear state is defined in this paper as the norm square of the projection of the wave function onto the particular cluster model subspace. It is pointed out that, although the clusters can not be localized in space by measurement, the amount of clustering characterizes the cluster formation in close analogy with a quantum mechanical probability. The cluster model component of the wave function is proved to have a variational property. This facilitates the computation of the amount of clustering. The model dependence of the amounts of various clusterings and their relationship to the corresponding spectroscopic factors are studied via numerical examples for two models of sup(6)Li. It is concluded that, in a relative sense, the spectroscopic factor, which is more directly related to experiment, is also characteristic of the clustering contents of different states of the same nucleus, but it can not be used for comparisons between different nuclei or clusterings. (author)

Mechanical properties of aluminium matrix composites reinforced with intermetallics

International Nuclear Information System (INIS)

Torres, B.; Garcia-Escorial, A.; Ibanez, J.; Lieblich, M.

2001-01-01

In this work 2124 aluminium matrix composites reinforced with Ni 3 Al, NiAl, MoSi 2 and Cr 3 Si intermetallic powder particles have been investigated. For comparison purposes, un reinforced 2124 and reinforced with SiC have also been studied. In all cases, the same powder metallurgy route was used, i. e. the 2124 alloy was obtained by rapid solidification and the intermetallic particles by self-propagating high-temperature synthesis (SHS). The matrix and the intermetallics were mechanically blended, cold compacted and finally hot extruded. Tensile tests were carried out in T1 and T4 treatments. Results indicate that mechanical properties depend strongly on the tendency to form new phases at the matrix-intermetallic interface during processing and/or further thermal treatments. The materials which present better properties are those that present less reaction between matrix and intermetallic reinforcement, i. e. MoSi 2 and SiC reinforced composites. (Author) 9 refs

Structural properties of small rhodium clusters

Energy Technology Data Exchange (ETDEWEB)

Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

2015-04-24

We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

Role of the [2Fe-2S] cluster in recombinant Escherichia coli biotin synthase.

Science.gov (United States)

Jameson, Guy N L; Cosper, Michele Mader; Hernández, Heather L; Johnson, Michael K; Huynh, Boi Hanh

2004-02-24

Biotin synthase (BioB) converts dethiobiotin into biotin by inserting a sulfur atom between C6 and C9 of dethiobiotin in an S-adenosylmethionine (SAM)-dependent reaction. The as-purified recombinant BioB from Escherichia coli is a homodimeric molecule containing one [2Fe-2S](2+) cluster per monomer. It is inactive in vitro without the addition of exogenous Fe. Anaerobic reconstitution of the as-purified [2Fe-2S]-containing BioB with Fe(2+) and S(2)(-) produces a form of BioB that contains approximately one [2Fe-2S](2+) and one [4Fe-4S](2+) cluster per monomer ([2Fe-2S]/[4Fe-4S] BioB). In the absence of added Fe, the [2Fe-2S]/[4Fe-4S] BioB is active and can produce up to approximately 0.7 equiv of biotin per monomer. To better define the roles of the Fe-S clusters in the BioB reaction, Mössbauer and electron paramagnetic resonance (EPR) spectroscopy have been used to monitor the states of the Fe-S clusters during the conversion of dethiobiotin to biotin. The results show that the [4Fe-4S](2+) cluster is stable during the reaction and present in the SAM-bound form, supporting the current consensus that the functional role of the [4Fe-4S] cluster is to bind SAM and facilitate the reductive cleavage of SAM to generate the catalytically essential 5'-deoxyadenosyl radical. The results also demonstrate that approximately (2)/(3) of the [2Fe-2S] clusters are degraded by the end of the turnover experiment (24 h at 25 degrees C). A transient species with spectroscopic properties consistent with a [2Fe-2S](+) cluster is observed during turnover, suggesting that the degradation of the [2Fe-2S](2+) cluster is initiated by reduction of the cluster. This observed degradation of the [2Fe-2S] cluster during biotin formation is consistent with the proposed sacrificial S-donating function of the [2Fe-2S] cluster put forth by Jarrett and co-workers (Ugulava et al. (2001) Biochemistry 40, 8352-8358). Interestingly, degradation of the [2Fe-2S](2+) cluster was found not to parallel

Synthesis and crystalline properties of CdS incorporated polyvinylidene fluoride (PVDF) composite film

Science.gov (United States)

Patel, Arunendra Kumar; Sunder, Aishwarya; Mishra, Shweta; Bajpai, Rakesh

2018-05-01

This paper gives an insight on the synthesis and crystalline properties of Polyvinylidene Fluoride (PVDF) (host matrix) composites impregnated with Cadmium Sulphide (CdS) using Dimethyl formamide (DMF) as the base, prepared by the well known solvent casting technique. The effect of doping concentration of CdS in to the PVDF matrix was studied using X-ray diffraction technique. The structural properties like crystallinity Cr, interplanar distance d, average size of the crystalline region (D), and average inter crystalline separation (R) have been estimated for the developed composite. The crystallinity index, crystallite size and inter crystalline separation is increasing with increase in the concentration of CdS in to the PVDF matrix while the interplanar distance d is decreasing.

Development of a Genetic Algorithm to Automate Clustering of a Dependency Structure Matrix

Science.gov (United States)

Rogers, James L.; Korte, John J.; Bilardo, Vincent J.

2006-01-01

Much technology assessment and organization design data exists in Microsoft Excel spreadsheets. Tools are needed to put this data into a form that can be used by design managers to make design decisions. One need is to cluster data that is highly coupled. Tools such as the Dependency Structure Matrix (DSM) and a Genetic Algorithm (GA) can be of great benefit. However, no tool currently combines the DSM and a GA to solve the clustering problem. This paper describes a new software tool that interfaces a GA written as an Excel macro with a DSM in spreadsheet format. The results of several test cases are included to demonstrate how well this new tool works.

The influence of matrix properties on growth and morphogenesis of human pancreatic ductal epithelial cells in 3D

Science.gov (United States)

Raza, Asad; Ki, Chang Seok; Lin, Chien-Chi

2013-01-01

A highly tunable synthetic biomimetic hydrogel platform was developed to study the growth and morphogenesis of pancreatic ductal epithelial cells (PDEC) under the influence of a myriad of instructive cues. A PDEC line, PANC-1, was used as a model system to illustrate the importance of matrix compositions on cell fate determination. PANC-1 is an immortalized ductal epithelial cell line widely used in the study of pancreatic tumor cell behaviors. PANC-1 cells are also increasingly explored as a potential cell source for endocrine differentiation. Thus far, most studies related to PANC-1, among other PDEC lines, are performed on 2D culture surfaces. Here, we evaluated the effect of matrix compositions on PANC-1 cell growth and morphogenesis in 3D. Specifically, PANC-1 cells were encapsulated in PEG-based hydrogels prepared by step-growth thiol-ene photopolymerization. It was found that thiol-ene hydrogels provided a cytocompatible environment for encapsulation and 3D culture of PANC-1 cells. In contrast to a monolayer morphology on 2D culture surfaces, PANC-1 cells formed clusters in 3D thiol-ene hydrogels within 4 days of culture. After culturing for 10 days, however, the growth and structures of these clusters were significantly impacted by gel matrix properties, including sensitivity of the matrix to proteases, stiffness of the matrix, and ECM-mimetic motifs. The use of matrix metalloproteinase (MMP) sensitive linker or the immobilization of fibronectin-derived RGDS ligand in the matrix promoted PANC-1 cell growth and encouraged them to adopt ductal cyst-like structures. On the other hand, the encapsulated cells formed smaller and more compact aggregates in non-MMP responsive gels. The incorporation of laminin-derived YIGSR peptide did not enhance cell growth and caused the cells to form compact aggregates. Immobilized YIGSR also enhanced the expression of epithelial cell markers including β-catenin and E-cadherin. These studies have established PEG

S-Matrix to potential inversion of low-energy α-12C phase shifts

Science.gov (United States)

Cooper, S. G.; Mackintosh, R. S.

1990-10-01

The IP S-matrix to potential inversion procedure is applied to phase shifts for selected partial waves over a range of energies below the inelastic threshold for α-12C scattering. The phase shifts were determined by Plaga et al. Potentials found by Buck and Rubio to fit the low-energy alpha cluster resonances need only an increased attraction in the surface to accurately reproduce the phase-shift behaviour. Substantial differences between the potentials for odd and even partial waves are necessary. The surface tail of the potential is postulated to be a threshold effect.

NMR of proteins (4Fe-4S): structural properties and intramolecular electron transfer

International Nuclear Information System (INIS)

Huber, J.G.

1996-01-01

NMR started to be applied to Fe-S proteins in the seventies. Its use has recently been enlarged as the problems arising from the paramagnetic polymetallic clusters ware overcome. Applications to [4Fe-4S] are presented herein. The information derived thereof deepens the understanding of the redox properties of these proteins which play a central role in the metabolism of bacterial cells. The secondary structure elements and the overall folding of Chromatium vinosum ferredoxin (Cv Fd) in solution have been established by NMR. The unique features of this sequence have been shown to fold as an α helix at the C-terminus and as a loop between two cysteines ligand of one cluster: these two parts localize in close proximity from one another. The interaction between nuclear and electronic spins is a source of additional structural information for (4Fe-AS] proteins. The conformation of the cysteine-ligands, as revealed by the Fe-(S γ -C β -H β )Cys dihedral angles, is related to the chemical shifts of the signals associated with the protons of these residues. The longitudinal relaxation times of the protons depend on their distance to the cluster. A quantitative relationship has been established and used to show that the solution structure of the high-potential ferredoxin from Cv differs significantly from the crystal structure around Phe-48. Both parameters (chemical shifts and longitudinal relaxation times) give also insight into the electronic and magnetic properties of the [4Fe-4S] clusters. The rate of intramolecular electron transfer between the two [4FE-4S] clusters of ferredoxins has been measured by NMR. It is far slower in the case of Cv Fd than for shorter ferredoxins. The difference may be associated with changes in the magnetic and/or electronic properties of one cluster. The strong paramagnetism of the [4Fe-4S] clusters, which originally limited the applicability of NMR to proteins containing these cofactors, has been proven instrumental in affording new

Biochemical and biomechanical properties of the pacemaking sinoatrial node extracellular matrix are distinct from contractile left ventricular matrix.

Directory of Open Access Journals (Sweden)

Jessica M Gluck

Full Text Available Extracellular matrix plays a role in differentiation and phenotype development of its resident cells. Although cardiac extracellular matrix from the contractile tissues has been studied and utilized in tissue engineering, extracellular matrix properties of the pacemaking sinoatrial node are largely unknown. In this study, the biomechanical properties and biochemical composition and distribution of extracellular matrix in the sinoatrial node were investigated relative to the left ventricle. Extracellular matrix of the sinoatrial node was found to be overall stiffer than that of the left ventricle and highly heterogeneous with interstitial regions composed of predominantly fibrillar collagens and rich in elastin. The extracellular matrix protein distribution suggests that resident pacemaking cardiomyocytes are enclosed in fibrillar collagens that can withstand greater tensile strength while the surrounding elastin-rich regions may undergo deformation to reduce the mechanical strain in these cells. Moreover, basement membrane-associated adhesion proteins that are ligands for integrins were of low abundance in the sinoatrial node, which may decrease force transduction in the pacemaking cardiomyocytes. In contrast to extracellular matrix of the left ventricle, extracellular matrix of the sinoatrial node may reduce mechanical strain and force transduction in pacemaking cardiomyocytes. These findings provide the criteria for a suitable matrix scaffold for engineering biopacemakers.

First principles results of structural and electronic properties of ZnS

Indian Academy of Sciences (India)

We present results of the study of ZnS (1 ≤ ≤ 9) clusters, using the density functional formalism and projector augmented wave method within the generalized gradient approximation. Along with the structural and electronic properties, nature of bonding and overall stability of clusters has been studied.

Structure–property relationships of iron–hydroxyapatite ceramic matrix nanocomposite fabricated using mechanosynthesis method

Energy Technology Data Exchange (ETDEWEB)

Nordin, Jamillah Amer [Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Prajitno, Djoko Hadi [Nuclear Technology Center for Materials and Radiometry, National Nuclear Energy, Bandung 40132 (Indonesia); Saidin, Syafiqah [Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Nur, Hadi, E-mail: hadi@kimia.fs.utm.my [Centre for Sustainable Nanomaterials, Ibnu Sina Institute for Scientific and Industrial Research, Universiti Teknologi Malaysia, Johor Bahru 81310 (Malaysia); Department of Physics, Institut Sains dan Teknologi Nasional, Jl. Moh. Kahfi II, Jagakarsa, Jakarta Selatan 12640 (Indonesia); Hermawan, Hendra, E-mail: hendra.hermawan@gmn.ulaval.ca [Department of Mining, Metallurgical and Materials Engineering & CHU de Québec Research Center, Laval University, Québec City G1V 0A6 (Canada)

2015-06-01

Hydroxyapatite (HAp) is an attractive bioceramics due to its similar composition to bone mineral and its ability to promote bone–implant interaction. However, its low strength has limited its application as load bearing implants. This paper presented a work focusing on the improvement of HAp mechanical property by synthesizing iron (Fe)-reinforced bovine HAp nanocomposite powders via mechanosynthesis method. The synthesis process was performed using high energy milling at varied milling time (3, 6, 9, and 12 h). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM). Its mechanical properties were investigated by micro-Vicker's hardness and compression tests. Results showed that milling time directly influenced the characteristics of the nanocomposite powders. Amorphous BHAp was formed after 9 and 12 h milling in the presence of HPO{sub 4}{sup 2−} ions. Continuous milling has improved the crystallinity of Fe without changing the HAp lattice structure. The nanocomposite powders were found in spherical shape, agglomerated and dense after longer milling time. The hardness and Young's modulus of the nanocomposites were also increased at 69% and 66%, respectively, as the milling time was prolonged from 3 to 12 h. Therefore, the improvement of the mechanical properties of nanocomposite was attributed to high Fe crystallinity and homogenous, dense structure produced by mechanosynthesis - Highlights: • Improvement of mechanical properties of HAp bioceramics by mechanosynthesis method • Structure–property relationship of iron–hydroxyapatite ceramic matrix nanocomposite • Milling time influenced the properties of iron–hydroxyapatite ceramic matrix nanocomposite.

Structure–property relationships of iron–hydroxyapatite ceramic matrix nanocomposite fabricated using mechanosynthesis method

International Nuclear Information System (INIS)

Nordin, Jamillah Amer; Prajitno, Djoko Hadi; Saidin, Syafiqah; Nur, Hadi; Hermawan, Hendra

2015-01-01

Hydroxyapatite (HAp) is an attractive bioceramics due to its similar composition to bone mineral and its ability to promote bone–implant interaction. However, its low strength has limited its application as load bearing implants. This paper presented a work focusing on the improvement of HAp mechanical property by synthesizing iron (Fe)-reinforced bovine HAp nanocomposite powders via mechanosynthesis method. The synthesis process was performed using high energy milling at varied milling time (3, 6, 9, and 12 h). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM). Its mechanical properties were investigated by micro-Vicker's hardness and compression tests. Results showed that milling time directly influenced the characteristics of the nanocomposite powders. Amorphous BHAp was formed after 9 and 12 h milling in the presence of HPO 4 2− ions. Continuous milling has improved the crystallinity of Fe without changing the HAp lattice structure. The nanocomposite powders were found in spherical shape, agglomerated and dense after longer milling time. The hardness and Young's modulus of the nanocomposites were also increased at 69% and 66%, respectively, as the milling time was prolonged from 3 to 12 h. Therefore, the improvement of the mechanical properties of nanocomposite was attributed to high Fe crystallinity and homogenous, dense structure produced by mechanosynthesis - Highlights: • Improvement of mechanical properties of HAp bioceramics by mechanosynthesis method • Structure–property relationship of iron–hydroxyapatite ceramic matrix nanocomposite • Milling time influenced the properties of iron–hydroxyapatite ceramic matrix nanocomposite

Structural properties of matrix metalloproteinases.

Science.gov (United States)

Bode, W; Fernandez-Catalan, C; Tschesche, H; Grams, F; Nagase, H; Maskos, K

1999-04-01

Matrix metalloproteinases (MMPs) are involved in extracellular matrix degradation. Their proteolytic activity must be precisely regulated by their endogenous protein inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Disruption of this balance results in serious diseases such as arthritis, tumour growth and metastasis. Knowledge of the tertiary structures of the proteins involved is crucial for understanding their functional properties and interference with associated dysfunctions. Within the last few years, several three-dimensional MMP and MMP-TIMP structures became available, showing the domain organization, polypeptide fold and main specificity determinants. Complexes of the catalytic MMP domains with various synthetic inhibitors enabled the structure-based design and improvement of high-affinity ligands, which might be elaborated into drugs. A multitude of reviews surveying work done on all aspects of MMPs have appeared in recent years, but none of them has focused on the three-dimensional structures. This review was written to close the gap.

Synthetic properties of models of globular clusters

Energy Technology Data Exchange (ETDEWEB)

Angeletti, L; Dolcetta, R; Giannone, P. (Rome Univ. (Italy). Osservatorio Astronomico)

1980-05-01

Synthetic and projected properties of models of globular clusters have been computed on the basis of stellar evolution and time changes of the dynamical cluster structure. Clusters with five and eight stellar groups (each group consisting of stars with the same mass) were studied. Mass loss from evolved stars was taken into account. Observational features were obtained at ages of 10-19 x 10/sup 9/ yr. The basic importance of the horizontal- and asymptotic-branch stars was pointed out. A comparison of the results with observed data of M3 is discussed with the purpose of obtaining general indications rather than a specific fit.

Synthetic properties of models of globular clusters

International Nuclear Information System (INIS)

Angeletti, L.; Dolcetta, R.; Giannone, P.

1980-01-01

Synthetic and projected properties of models of globular clusters have been computed on the basis of stellar evolution and time changes of the dynamical cluster structure. Clusters with five and eight stellar groups (each group consisting of stars with the same mass) were studied. Mass loss from evolved stars was taken into account. Observational features were obtained at ages of 10-19 x 10 9 yr. The basic importance of the horizontal- and asymptotic-branch stars was pointed out. A comparison of the results with observed data of M3 is discussed with the purpose of obtaining general indications rather than a specific fit. (orig.)

The optical properties of galaxies in the Ophiuchus cluster

Science.gov (United States)

Durret, F.; Wakamatsu, K.; Adami, C.; Nagayama, T.; Omega Muleka Mwewa Mwaba, J. M.

2018-05-01

Context. Ophiuchus is one of the most massive clusters known, but due to its low Galactic latitude its optical properties remain poorly known. Aims: We investigate the optical properties of Ophiuchus to obtain clues on the formation epoch of this cluster, and compare them to those of the Coma cluster, which is comparable in mass to Ophiuchus but much more dynamically disturbed. Methods: Based on a deep image of the Ophiuchus cluster in the r' band obtained at the Canada France Hawaii Telescope with the MegaCam camera, we have applied an iterative process to subtract the contribution of the numerous stars that, due to the low Galactic latitude of the cluster, pollute the image, and have obtained a photometric catalogue of 2818 galaxies fully complete at r' = 20.5 mag and still 91% complete at r' = 21.5 mag. We use this catalogue to derive the cluster Galaxy Luminosity Function (GLF) for the overall image and for a region (hereafter the "rectangle" region) covering exactly the same physical size as the region in which the GLF of the Coma cluster was previously studied. We then compute density maps based on an adaptive kernel technique, for different magnitude limits, and define three circular regions covering 0.08, 0.08, and 0.06 deg2, respectively, centred on the cluster (C), on northwest (NW) of the cluster, and southeast (SE) of the cluster, in which we compute the GLFs. Results: The GLF fits are much better when a Gaussian is added to the usual Schechter function, to account for the excess of very bright galaxies. Compared to Coma, Ophiuchus shows a strong excess of bright galaxies. Conclusions: The properties of the two nearby very massive clusters Ophiuchus and Coma are quite comparable, though they seem embedded in different large-scale environments. Our interpretation is that Ophiuchus was built up long ago, as confirmed by its relaxed state (see paper I) while Coma is still in the process of forming. The photometric catalogue of Ophiuchus (full Table B.1) is

Density functional study of structural and electronic properties of bimetallic silver-gold clusters: Comparison with pure gold and silver clusters

Science.gov (United States)

Bonacic-Koutecky, Vlasta; Burda, Jaroslav; Mitric, Roland; Ge, Maofa; Zampella, Giuseppe; Fantucci, Piercarlo

2002-08-01

Bimetallic silver-gold clusters offer an excellent opportunity to study changes in metallic versus "ionic" properties involving charge transfer as a function of the size and the composition, particularly when compared to pure silver and gold clusters. We have determined structures, ionization potentials, and vertical detachment energies for neutral and charged bimetallic AgmAun 3[less-than-or-equal](m+n)[less-than-or-equal]5 clusters. Calculated VDE values compare well with available experimental data. In the stable structures of these clusters Au atoms assume positions which favor the charge transfer from Ag atoms. Heteronuclear bonding is usually preferred to homonuclear bonding in clusters with equal numbers of hetero atoms. In fact, stable structures of neutral Ag2Au2, Ag3Au3, and Ag4Au4 clusters are characterized by the maximum number of hetero bonds and peripheral positions of Au atoms. Bimetallic tetramer as well as hexamer are planar and have common structural properties with corresponding one-component systems, while Ag4Au4 and Ag8 have 3D forms in contrast to Au8 which assumes planar structure. At the density functional level of theory we have shown that this is due to participation of d electrons in bonding of pure Aun clusters while s electrons dominate bonding in pure Agm as well as in bimetallic clusters. In fact, Aun clusters remain planar for larger sizes than Agm and AgnAun clusters. Segregation between two components in bimetallic systems is not favorable, as shown in the example of Ag5Au5 cluster. We have found that the structures of bimetallic clusters with 20 atoms Ag10Au10 and Ag12Au8 are characterized by negatively charged Au subunits embedded in Ag environment. In the latter case, the shape of Au8 is related to a pentagonal bipyramid capped by one atom and contains three exposed negatively charged Au atoms. They might be suitable for activating reactions relevant to catalysis. According to our findings the charge transfer in bimetallic

Energy properties of deuterium cluster impacts on TiD targets

International Nuclear Information System (INIS)

Yamamura, Yasunori

1992-01-01

In order to know the energy properties of deuterium atoms in the cluster impact region, the deuterium cluster impact phenomena have been simulated by using the time-evolution Monte Carlo simulation code DYACAT, where the (D) n (n being 100 to 500 ) with energy 500eV/atom are bombarded on TiD targets. For comparison, the energy properties of 500 eV/atom (Al) 500 cluster impacts on amorphous Au targets have also been simulated. In the case of the deuterium cluster impacts on TiD targets, the high energy tail of the energy distribution of deuterium atoms drops so fast. The temperature of the deuterium cluster impact region is less than 100 ev, and it decreases slightly as the cluster size increases due to the enhanced energy removal with reflected deuterium atoms and sputtered deuterium atoms. While in the case of 500 eV/atom (Al) 500 cluster impacts on Au the high-energy tail of the energy distribution of Al atoms due to the big cluster impact can be well described in terms of the Maxwell-Boltzmann function whose temperature is 270 ev. (author)

The AdS5xS5 superstring worldsheet S matrix and crossing symmetry

International Nuclear Information System (INIS)

Janik, Romuald A.

2006-01-01

An S matrix satisfying the Yang-Baxter equation with symmetries relevant to the AdS 5 xS 5 superstring recently has been determined up to an unknown scalar factor. Such scalar factors are typically fixed using crossing relations; however, due to the lack of conventional relativistic invariance, in this case its determination remained an open problem. In this paper we propose an algebraic way to implement crossing relations for the AdS 5 xS 5 superstring worldsheet S matrix. We base our construction on a Hopf-algebraic formulation of crossing in terms of the antipode and introduce generalized rapidities living on the universal cover of the parameter space which is constructed through an auxillary, coupling-constant dependent, elliptic curve. We determine the crossing transformation and write functional equations for the scalar factor of the S matrix in the generalized rapidity plane

Large Magnetovolume Effect Induced by Embedding Ferromagnetic Clusters into Antiferromagnetic Matrix of Cobaltite Perovskite.

Science.gov (United States)

Miao, Ping; Lin, Xiaohuan; Koda, Akihiro; Lee, Sanghyun; Ishikawa, Yoshihisa; Torii, Shuki; Yonemura, Masao; Mochiku, Takashi; Sagayama, Hajime; Itoh, Shinichi; Ikeda, Kazutaka; Otomo, Toshiya; Wang, Yinxia; Kadono, Ryosuke; Kamiyama, Takashi

2017-07-01

Materials that show negative thermal expansion (NTE) have significant industrial merit because they can be used to fabricate composites whose dimensions remain invariant upon heating. In some materials, NTE is concomitant with the spontaneous magnetization due to the magnetovolume effect (MVE). Here the authors report a new class of MVE material; namely, a layered perovskite PrBaCo 2 O 5.5+ x (0 ≤ x ≤ 0.41), in which strong NTE [β ≈ -3.6 × 10 -5 K -1 (90-110 K) at x = 0.24] is triggered by embedding ferromagnetic (F) clusters into the antiferromagnetic (AF) matrix. The strongest MVE is found near the boundary between F and AF phases in the phase diagram, indicating the essential role of competition between the F-clusters and the AF-matrix. Furthermore, the MVE is not limited to the PrBaCo 2 O 5.5+ x but is also observed in the NdBaCo 2 O 5.5+ x . The present study provides a new approach to obtaining MVE and offers a path to the design of NTE materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electromagnetic properties of 6Li in a cluster model with breathing clusters

International Nuclear Information System (INIS)

Kruppa, A.T.; Beck, R.; Dickmann, F.

1987-01-01

Electromagnetic properties of 6 Li are studied using a microscopic (α+δ) cluster model. In addition to the ground state of the clusters, their breathing excited states are included in the wave function in order to take into account the distortion of the clusters. The elastic charge form factor is in good agreement with experiment up to a momentum transfer of 8 fm -2 . The ground state magnetic form factor and the inelastic charge form factor are also well described. The effect of the breathing states of α on the form factors proves to be negligible except at high momentum transfer. The ground-state charge density, rms charge radius, the magnetic dipole moment and a reduced transition strength are also obtained in fair agreement with experiment. (author)

Structural Characteristics and Magnetic Properties of Al2O3 Matrix-Based Co-Cermet Nanogranular Films

Directory of Open Access Journals (Sweden)

Giap Van Cuong

2015-01-01

Full Text Available Magnetic micro- and nanogranular materials prepared by different methods have been used widely in studies of magnetooptical response. However, among them there seems to be nothing about magnetic nanogranular thin films prepared by a rf cosputtering technique for both metals and insulators till now. This paper presented and discussed preparation, structural characteristics, and magnetic properties of alumina (Al2O3 matrix-based granular Co-cermet thin films deposited by means of the cosputtering technique for both Co and Al2O3. By varying the ferromagnetic (Co atomic fraction, x, from 0.04 to 0.63, several dominant features of deposition for these thin films were shown. Structural characteristics by X-ray diffraction confirmed a cermet-type structure for these films. Furthermore, magnetic behaviours presented a transition from paramagnetic- to superparamagnetic- and then to ferromagnetic-like properties, indicating agglomeration and growth following Co components of Co clusters or nanoparticles. These results show a typical granular Co-cermet feature for the Co-Al2O3 thin films prepared, in which Co magnetic nanogranules are dispersed in a ceramic matrix. Such nanomaterials can be applied suitably for our investigations in future on the magnetooptical responses of spinplasmonics.

Fe-S Cluster Biogenesis in Isolated Mammalian Mitochondria

Science.gov (United States)

Pandey, Alok; Pain, Jayashree; Ghosh, Arnab K.; Dancis, Andrew; Pain, Debkumar

2015-01-01

Iron-sulfur (Fe-S) clusters are essential cofactors, and mitochondria contain several Fe-S proteins, including the [4Fe-4S] protein aconitase and the [2Fe-2S] protein ferredoxin. Fe-S cluster assembly of these proteins occurs within mitochondria. Although considerable data exist for yeast mitochondria, this biosynthetic process has never been directly demonstrated in mammalian mitochondria. Using [35S]cysteine as the source of sulfur, here we show that mitochondria isolated from Cath.A-derived cells, a murine neuronal cell line, can synthesize and insert new Fe-35S clusters into aconitase and ferredoxins. The process requires GTP, NADH, ATP, and iron, and hydrolysis of both GTP and ATP is necessary. Importantly, we have identified the 35S-labeled persulfide on the NFS1 cysteine desulfurase as a genuine intermediate en route to Fe-S cluster synthesis. In physiological settings, the persulfide sulfur is released from NFS1 and transferred to a scaffold protein, where it combines with iron to form an Fe-S cluster intermediate. We found that the release of persulfide sulfur from NFS1 requires iron, showing that the use of iron and sulfur for the synthesis of Fe-S cluster intermediates is a highly coordinated process. The release of persulfide sulfur also requires GTP and NADH, probably mediated by a GTPase and a reductase, respectively. ATP, a cofactor for a multifunctional Hsp70 chaperone, is not required at this step. The experimental system described here may help to define the biochemical basis of diseases that are associated with impaired Fe-S cluster biogenesis in mitochondria, such as Friedreich ataxia. PMID:25398879

Structural and optical properties of Si-doped Ag clusters

KAUST Repository

Mokkath, Junais Habeeb

2014-03-06

The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

Structural and optical properties of Si-doped Ag clusters

KAUST Repository

Mokkath, Junais Habeeb; Schwingenschlö gl, Udo

2014-01-01

The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

S-matrix elements from T-duality

International Nuclear Information System (INIS)

Babaei Velni, Komeil; Garousi, Mohammad R.

2013-01-01

Recently it has been speculated that the S-matrix elements satisfy the Ward identity associated with the T-duality. This indicates that a group of S-matrix elements is invariant under the linear T-duality transformations on the external states. If one evaluates one component of such T-dual multiplet, then all other components may be found by the simple use of the linear T-duality. The assumption that fields must be independent of the Killing coordinate, however, may cause, in some cases, the T-dual multiplet not to be gauge invariant. In those cases, the S-matrix elements contain more than one T-dual multiplet which are intertwined by the gauge symmetry. In this paper, we apply the T-dual Ward identity on the S-matrix element of one RR (p−3)-form and two NSNS states on the world volume of a D p -brane to find its corresponding T-dual multiplet. In the case that the RR potential has two transverse indices, the T-dual multiplet is gauge invariant, however, in the case that it has one transverse index the multiplet is not gauge invariant. We find a new T-dual multiplet in this case by imposing the gauge symmetry. We show that the multiplets are reproduced by explicit calculation, and their low energy contact terms at order α ′2 are consistent with the existing couplings in the literature

Graphene-Reinforced Aluminum Matrix Composites: A Review of Synthesis Methods and Properties

Science.gov (United States)

Chen, Fei; Gupta, Nikhil; Behera, Rakesh K.; Rohatgi, Pradeep K.

2018-03-01

Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent + inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application.

Graphene-Reinforced Aluminum Matrix Composites: A Review of Synthesis Methods and Properties

Science.gov (United States)

Chen, Fei; Gupta, Nikhil; Behera, Rakesh K.; Rohatgi, Pradeep K.

2018-06-01

Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent + inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application.

D2O clusters isolated in rare-gas solids: Dependence of infrared spectrum on concentration, deposition rate, heating temperature, and matrix material

Science.gov (United States)

Shimazaki, Yoichi; Arakawa, Ichiro; Yamakawa, Koichiro

2018-04-01

The infrared absorption spectra of D2O monomers and clusters isolated in rare-gas matrices were systematically reinvestigated under the control of the following factors: the D2O concentration, deposition rate, heating temperature, and rare-gas species. We clearly show that the cluster-size distribution is dependent on not only the D2O concentration but also the deposition rate of a sample; as the rate got higher, smaller clusters were preferentially formed. Under the heating procedures at different temperatures, the cluster-size growth was successfully observed. Since the monomer diffusion was not enough to balance the changes in the column densities of the clusters, the dimer diffusion was likely to contribute the cluster growth. The frequencies of the bonded-OD stretches of (D2O)k with k = 2-6 were almost linearly correlated with the square root of the critical temperature of the matrix material. Additional absorption peaks of (D2O)2 and (D2O)3 in a Xe matrix were assigned to the species trapped in tight accommodation sites.

Dynamics of Strong Interactions and the S-Matrix

Energy Technology Data Exchange (ETDEWEB)

Omnes, R. [Laboratoire de Physique Theorique et Hautes Energies, Universite de Paris, Orsay (France)

1969-08-15

The physical principles underlying the S-matrix theory of strong interactions are reviewed. In particular, the problem of whether these principles are sufficient to completely determine the S-matrix, i.e. to yield a dynamical theory of strong interactions, is discussed. (author)

Tailoring the properties of magnetite nanoparticles clusters by coating with double inorganic layers

Energy Technology Data Exchange (ETDEWEB)

Petran, Anca [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Str., 400293 Cluj-Napoca (Romania); Radu, Teodora, E-mail: teodora.radu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Str., 400293 Cluj-Napoca (Romania); Culic, Bogdan [Faculty of Dental Medicine,Iuliu Hatieganu University of Medicine and Pharmacy, 32 Clinicilor Str., 400006 Cluj-Napoca (Romania); Turcu, Rodica, E-mail: rodica.turcu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Str., 400293 Cluj-Napoca (Romania)

2016-12-30

Highlights: • New magnetite clusters covered with inorganic oxides double layers. • Coating layers influence on the surface properties of the magnetic clusters. • Color parameters assessment for the inorganic oxides coated magnetic clusters. • High magnetization clusters with appropiate color for magnetic security paper. - Abstract: New magnetic nanoparticles based on Fe{sub 3}O{sub 4} clusters covered with a double layer of inorganic salts/oxides with high magnetization for incorporation in security materials such as security paper were synthesized. For the inorganic layers ZnO, SiO{sub 2} and BaSO{sub 4} were used. The microstructure and composition of the products were determined by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). Magnetization measurements on the obtained samples show a straightforward correlation between the saturation magnetization (M{sub s}) and morphology of the samples. The results obtained from color parameter assessment are discussed in relation with the morphology and microstructure of the prepared samples.

Photoelectron spectroscopy and density functional theory studies of (FeS)mH- (m = 2-4) cluster anions: effects of the single hydrogen.

Science.gov (United States)

Yin, Shi; Bernstein, Elliot R

2017-12-20

Single hydrogen containing iron hydrosulfide cluster anions (FeS) m H - (m = 2-4) are studied by photoelectron spectroscopy (PES) at 3.492 eV (355 nm) and 4.661 eV (266 nm) photon energies, and by Density Functional Theory (DFT) calculations. The structural properties, relative energies of different spin states and isomers, and the first calculated vertical detachment energies (VDEs) of different spin states for these (FeS) m H - (m = 2-4) cluster anions are investigated at various reasonable theory levels. Two types of structural isomers are found for these (FeS) m H - (m = 2-4) clusters: (1) the single hydrogen atom bonds to a sulfur site (SH-type); and (2) the single hydrogen atom bonds to an iron site (FeH-type). Experimental and theoretical results suggest such available different SH- and FeH-type structural isomers should be considered when evaluating the properties and behavior of these single hydrogen containing iron sulfide clusters in real chemical and biological systems. Compared to their related, respective pure iron sulfur (FeS) m - clusters, the first VDE trend of the diverse type (FeS) m H 0,1 - (m = 1-4) clusters can be understood through (1) the different electron distribution properties of their highest singly occupied molecular orbital employing natural bond orbital analysis (NBO/HSOMO), and (2) the partial charge distribution on the NBO/HSOMO localized sites of each cluster anion. Generally, the properties of the NBO/HSOMOs play the principal role with regard to the physical and chemical properties of all the anions. The change of cluster VDE from low to high is associated with the change in nature of their NBO/HSOMO from a dipole bound and valence electron mixed character, to a valence p orbital on S, to a valence d orbital on Fe, and to a valence p orbital on Fe or an Fe-Fe delocalized valence bonding orbital. For clusters having the same properties for NBO/HSOMOs, the partial charge distributions at the NBO/HSOMO localized sites additionally

Tuning the magnetic properties of deposited transition metal clusters by decoration

Energy Technology Data Exchange (ETDEWEB)

Minar, Jan; Bornemann, S.; Ebert, H. [Dept. Chemie, LMU, Butenandtstr. 5-13, 81377 Muenchen (Germany); Staunton, J.B. [Department of Physics, University of Warwick (United Kingdom); Rusponi, S.; Brunne, H. [EPF Lausanne (Switzerland)

2008-07-01

Using the fully relativistic version of the KKR-method for electronic structure calculations within local spin density functional theory (LSDA) the magnetic properties of Fe, Co and Ni clusters deposited on the Pt(111) surface have been investigated. Of central interest are the role of spin-orbit coupling as it influences the spontaneous formation and orientation of magnetic moments and gives rise amongst others to the occurrence of orbital magnetic moments, the magnetic anisotropy energy (MAE) and magnetic circular dichroism in X-ray absorption (XMCD). Our systematic investigations of different clusters and nanostructures aim to reveal the mutual relationship among their spin-orbit induced properties. In addition they show how their various magnetic properties depend on the structural properties and chemical composition of the studied system. For large two-dimensional clusters we focussed especially on the dependency of the MAE on decoration with another transition metal. Our results are in qualitative agreement with recent experimental findings. We resolved the MAE contributions for inequivalent cluster atoms and will discuss the effect of the induced MAE within the Pt substrate.

Universality and clustering in 1 + 1 dimensional superstring-bit models

International Nuclear Information System (INIS)

Bergman, O.; Thorn, C.B.

1996-01-01

We construct a 1+1 dimensional superstring-bit model for D=3 Type IIB superstring. This low dimension model escapes the problem encountered in higher dimension models: (1) It possesses full Galilean supersymmetry; (2) For noninteracting Polymers of bits, the exactly soluble linear superpotential describing bit interactions is in a large universality class of superpotentials which includes ones bounded at spatial infinity; (3) The latter are used to construct a superstring-bit model with the clustering properties needed to define an S-matrix for closed polymers of superstring-bits

Computational Chemistry of Modified [MFe3S4] and [M2Fe2S4] Clusters: Assessment of Trends in Electronic Structure and Properties

DEFF Research Database (Denmark)

Kepp, Kasper Planeta; Ooi, Bee Lean; Christensen, Hans Erik Mølager

2008-01-01

The aim of this work is to understand the molecular evolution of iron−sulfur clusters in terms of electronic structure and function. Metal-substituted models of biological [Fe4S4] clusters in oxidation states [MxFe4−xS4]3+/2+/1+ have been studied by density functional theory (M = Cr, Mn, Fe, Co, ...

Investigations of the thermal treatment effect on the generation of cadmium sulfide clusters in polymeric films

International Nuclear Information System (INIS)

Stanculescu, Anca; Socol, M.; Stanculescu, F.

2002-01-01

In the last years a special interest has been paid to the field of nanometer-sized semiconductor compound crystalline clusters synthesized in different matrix (inorganic or organic), due to their special physical and chemical properties intermediate between the molecular and bulk limits. To obtain the thin film samples of CdS particles embedded in a polymeric transparent matrix, as bisphenol A polycarbonate, we followed a process containing three important steps: preparation of the so-called 'mother solution', film deposition and thermal treatment. The samples obtained after the first two steps were heat treated at different temperatures (90 deg. C and 150 deg. C) for 0.5 h, 1 h and 1.5 h, and we have analyzed the influence of these parameters on the film quality using UV-VIS spectrophotometric methods. This paper presents a study of the influence of the thermal treatment on the CdS clusters' generation process and film quality and homogeneity. The parameters of the processing procedure of the polymeric film, as the cooling rate, have a great influence on the rate of germination and development of the crystalline phase. A slow cooling rate is a more favorable process for CdS clusters' formation, indicated .by structured features of the fundamental absorption situated between 350-450 nm. When the temperature for thermal treatment increases to 90 deg. C a sharp rise and a shift to shorter wavelengths of the absorption onset edge was observed. This shift proves the existence of a weak quantum confinement effects. We concluded that these two parameters have some equivalent effects on the CdS clusters' generation in polymeric matrix. Varying the treatment duration with a fixed temperature produces similar results as the fixed duration, varied temperature treatment. (authors)

Geometric, stable and electronic properties of Aun–2Y2 (n = 3–8) clusters

International Nuclear Information System (INIS)

Kai-Tian, Qi; Yong, Sheng; Hua-Ping, Mao; Hong-Yan, Wang

2010-01-01

Employing first-principles methods, based on the density function theory, and using the LANL2DZ basis sets, the ground-state geometric, the stable and the electronic properties of Au n–2 Y 2 clusters are investigated in this paper. Meanwhile, the differences in property among pure gold clusters, pure yttrium clusters, gold clusters doped with one yttrium atom, and gold clusters doped with two yttrium atoms are studied. We find that when gold clusters are doped by two yttrium atoms, the odd-even oscillatory behaviours of Au n–1 Y and Au n disappear. The properties of Au n–2 Y 2 clusters are close to those of pure yttrium clusters

a Moessbauer Effect and Fenske-Hall Molecular Orbital Study of the Electronic Properties of Organoiron Clusters.

Science.gov (United States)

Buhl, Margaret Linn

The electronic properties of trinuclear iron, tetranuclear iron butterfly, iron-cobalt, and iron-copper clusters have been studied experimentally at 78K by the Mossbauer effect and theoretically by Fenske-Hall molecular orbital calculations. The Mossbauer effect isomer shift is very sensitive to the differences in the iron s-electron densities in these clusters and, as expected, decreases as the sum of the iron 4s Mulliken population and the Clementi and Raimondi effective nuclear charge increases. The molecular orbital wave functions and the Mulliken atomic charges are used to calculate the electric field gradient at the metal nuclei and the iron Mossbauer effect quadrupole splittings. The valence contribution was found to be the major component of the electric field gradient in all the clusters studied. In general the calculated value of Delta E_ {Q} is larger than the observed value, as a result of neglect of the valence Sternheimer factor, R. The metal charge depends upon its electronegativity and upon the nature of its Lewis base ligands. The carbonyl ligand carbon charge becomes more positive as the metal electronegativity increases. The oxygen charge becomes more negative as the anionic cluster charge increases, and in so doing, yields the maximum anionic charge separation. The electronic properties of the terminal carbonyl ligands are similar to those of carbon monoxide, whereas the electronic properties of the bridging carbonyl ligands are similar to those of the carbonyl group found in aldehydes and ketones.

The X-ray spectra of clusters of galaxies and their relationship to other cluster properties

International Nuclear Information System (INIS)

Mitchell, R.J.; Dickens, R.J.; Burnell, S.J.B.; Culhane, J.L.

1979-01-01

New observations with the MSSL proportional counter spectrometer on the Ariel V satellite of the X-ray spectra of 20 candidate clusters of galaxies are reported. The data are compared with the results from the OSO-8 satellite and the combined sample of some 30 cluster X-ray spectra are analysed. The present study finds generally larger values of Lsub(X) than do Uhuru or the SSI, which, because of the larger field of view, may indicate significant amounts of hot gas away from the cluster centres. The validity of all X-ray cluster identifications has been examined, and sources have been classified according to certainty of identification. The incidence of X-ray line emission from the clusters has been investigated and temperatures, kTsub(X), have been derived on the basis of an isothermal model. Relationships between X-ray, optical and radio properties of the clusters have been studied. The more massive, centrally condensed clusters generally contain higher temperature gas and have a greater luminosity than the less massive, more irregular clusters. (author)

Fluctuation, stationarity, and ergodic properties of random-matrix ensembles

International Nuclear Information System (INIS)

Pandey, A.

1979-01-01

The properties of random-matrix ensembles and the application of such ensembles to energy-level fluctuations and strength fluctuations are discussed. The two-point correlation function for complex spectra described by the three standard Gaussian ensembles is calculated, and its essential simplicity, displayed by an elementary procedure that derives from the dominance of binary correlations. The resultant function is exact for the unitary case and a very good approximation to the orthogonal and symplectic cases. The same procedure yields the spectrum for a Gaussian orthogonal ensemble (GOE) deformed by a pairing interaction. Several extensions are given and relationships to other problems of current interest are discussed. The standard fluctuation measures are rederived for the GOE, and their extensions to the unitary and symplectic cases are given. The measures are shown to derive, for the most part, from the two-point function, and new relationships between them are established, answering some long-standing questions. Some comparisons with experimental values are also made. All the cluster functions, and therefore the fluctuation measures, are shown to be stationary and strongly ergodic, thus justifying the use of random matrices for individual spectra. Strength fluctuations in the orthogonal ensemble are also considered. The Porter-Thomas distribution in its various forms is rederived and its ergodicity is established

S-matrix to potential inversion of low-energy. alpha. - sup 12 C phase shifts

Energy Technology Data Exchange (ETDEWEB)

Cooper, S.G.; Mackintosh, R.S. (Open Univ., Milton Keynes (UK). Dept. of Physics)

1990-10-22

The IP S-matrix to potential inversion procedure is applied to phase shifts for selected partial waves over a range of energies below the inelastic threshold for {alpha}-{sup 12}C scattering. The phase shifts were determined by Plaga et al. Potentials found by Buck and Rubio to fit the low-energy alpha cluster resonances need only an increased attraction in the surface to accurately reproduce the phase-shift behaviour. Substantial differences between the potentials for odd and even partial waves are necessary. The surface tail of the potential is postulated to be a threshold effect. (orig.).

Time dependent mean field approximation to the many-body S-matrix

International Nuclear Information System (INIS)

Alhassid, Y.; Koonin, S.E.

1980-01-01

Time-dependent Hartree-Fock (TDHF) calculations are a good description of some inclusive properties of deep inelastic heavy-ion collisions. The first steps toward a mean-field theory that approximates specific elements of the many-body S matrix are presented. A many-body system with pairwise interactions excited by an external, time-dependent one-body field is considered. The methods are used to solve the forced Lipkin model. The moduli of elastic and excitation amplitudes are plotted. 3 figures

Physicochemical properties of different corn varieties by principal components analysis and cluster analysis

International Nuclear Information System (INIS)

Zeng, J.; Li, G.; Sun, J.

2013-01-01

Principal components analysis and cluster analysis were used to investigate the properties of different corn varieties. The chemical compositions and some properties of corn flour which processed by drying milling were determined. The results showed that the chemical compositions and physicochemical properties were significantly different among twenty six corn varieties. The quality of corn flour was concerned with five principal components from principal component analysis and the contribution rate of starch pasting properties was important, which could account for 48.90%. Twenty six corn varieties could be classified into four groups by cluster analysis. The consistency between principal components analysis and cluster analysis indicated that multivariate analyses were feasible in the study of corn variety properties. (author)

Investigation of the alpha cluster model and the density matrix expansion in ion-ion collision

International Nuclear Information System (INIS)

Rashdan, M.B.M.

1986-01-01

This thesis deals with the investigation of the alpha cluster model (ACM) of brink and studies of the accuracy of the density matrix expansion (DME) approximation in deriving the real part of the ion-ion optical potential. the ACM is applied to calculate the inelastic 0 1 + →2 1 + charge form factor for electron scattering by 12 C to investigate the validity of this model for 12 C nucleus. it is found that the experimental curve can be fitted over the entire range of the momentum transfer by a generator - coordinate state for the 2 1 + state that consist of a superposition of two triangular ACM states with two different cluster separations and the same oscillator parameter

Physical, Spatial, and Molecular Aspects of Extracellular Matrix of In Vivo Niches and Artificial Scaffolds Relevant to Stem Cells Research

Directory of Open Access Journals (Sweden)

Maria Akhmanova

2015-01-01

Full Text Available Extracellular matrix can influence stem cell choices, such as self-renewal, quiescence, migration, proliferation, phenotype maintenance, differentiation, or apoptosis. Three aspects of extracellular matrix were extensively studied during the last decade: physical properties, spatial presentation of adhesive epitopes, and molecular complexity. Over 15 different parameters have been shown to influence stem cell choices. Physical aspects include stiffness (or elasticity, viscoelasticity, pore size, porosity, amplitude and frequency of static and dynamic deformations applied to the matrix. Spatial aspects include scaffold dimensionality (2D or 3D and thickness; cell polarity; area, shape, and microscale topography of cell adhesion surface; epitope concentration, epitope clustering characteristics (number of epitopes per cluster, spacing between epitopes within cluster, spacing between separate clusters, cluster patterns, and level of disorder in epitope arrangement, and nanotopography. Biochemical characteristics of natural extracellular matrix molecules regard diversity and structural complexity of matrix molecules, affinity and specificity of epitope interaction with cell receptors, role of non-affinity domains, complexity of supramolecular organization, and co-signaling by growth factors or matrix epitopes. Synergy between several matrix aspects enables stem cells to retain their function in vivo and may be a key to generation of long-term, robust, and effective in vitro stem cell culture systems.

[Electronic and structural properties of individual nanometer-size supported metallic clusters

International Nuclear Information System (INIS)

Reifenberger, R.

1993-01-01

This report summarizes the work performed under contract DOE-FCO2-84ER45162. During the past ten years, our study of electron emission from laser-illuminated field emission tips has taken on a broader scope by addressing problems of direct interest to those concerned with the unique physical and chemical properties of nanometer-size clusters. The work performed has demonstrated that much needed data can be obtained on individual nanometer-size clusters supported on a wide-variety of different substrates. The work was performed in collaboration with R.P. Andres in the School of Chemical Engineering at Purdue University. The Multiple Expansion Cluster Source developed by Andres and his students was essential for producing the nanometer-size clusters studied. The following report features a discussion of these results. This report provides a motivation for studying the properties of nanometer-size clusters and summarizes the results obtained

Cluster-enriched Yang-Baxter equation from SUSY gauge theories

Science.gov (United States)

Yamazaki, Masahito

2018-04-01

We propose a new generalization of the Yang-Baxter equation, where the R-matrix depends on cluster y-variables in addition to the spectral parameters. We point out that we can construct solutions to this new equation from the recently found correspondence between Yang-Baxter equations and supersymmetric gauge theories. The S^2 partition function of a certain 2d N=(2,2) quiver gauge theory gives an R-matrix, whereas its FI parameters can be identified with the cluster y-variables.

Interfacial (Fiber-matrix) Properties of High-strength Mortar (150 MPa) from Fiber Pullout

DEFF Research Database (Denmark)

Shannag, M.J.; Brincker, Rune; Hansen, Will

1996-01-01

 The steel fiber-matrix properties of high-strength mortar (150 MPa), such as DSP (densified small particle), are obtained and compared to an ordinary strength mortar (40 MPa) using a specially designed fiber pullout apparatus. A new method for estimating the debonding energy of the interfacial z......-strength DSP mortar has significantly improved interfacial properties compared to ordinary strength mortar. These results are important in the understanding of the role of steel fibers in improving the tensile properties of high-strength, brittle, cement-matrix composites....... The steel fiber-matrix properties of high-strength mortar (150 MPa), such as DSP (densified small particle), are obtained and compared to an ordinary strength mortar (40 MPa) using a specially designed fiber pullout apparatus. A new method for estimating the debonding energy of the interfacial...

Influence of short range ordering and clustering on transport properties

International Nuclear Information System (INIS)

Vigier, G.; Pelletier, J.M.

1982-01-01

The influence of short range ordering and clustering phenomena on the electrical resistivity p and the thermopower S is investigated both theoretically and experimentally. According to the considered alloys either increases or decreases of transport properties may be observed when deviations from a random distribution of solute atoms occur. These observations are explained with a model based on free electrons and Born approximations the importance of the potential choice is underlined; two kinds of description of the structure factor are investigated. A good semiquantitative agreement is obtained between computed results and experimental observations

Matrix density effects on the mechanical properties of SiC fiber-reinforced silicon nitride matrix properties

Science.gov (United States)

Bhatt, Ramakrishna T.; Kiser, Lames D.

1990-01-01

The room temperature mechanical properties were measured for SiC fiber reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 microns and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus were approx. 15 and 50 percent higher, respectively, and ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIPed composites appears to be related to a degradation in fiber strength at the HIP temperature. However, the density effect on matrix fracture strength was much less than would be expected based on typical monolithic Si3N4 behavior, suggesting that composite theory is indeed operating. Possible practical implications of these observations are discussed.

Mutation of the His ligand in mitoNEET stabilizes the 2Fe–2S cluster despite conformational heterogeneity in the ligand environment

Energy Technology Data Exchange (ETDEWEB)

Conlan, Andrea R.; Paddock, Mark L.; Homer, Christina [University of California at San Diego, La Jolla, CA 92093 (United States); Axelrod, Herbert L.; Cohen, Aina E. [Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Abresch, Edward C.; Zuris, John A. [University of California at San Diego, La Jolla, CA 92093 (United States); Nechushtai, Rachel [Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel); Jennings, Patricia A., E-mail: pajennin@ucsd.edu [University of California at San Diego, La Jolla, CA 92093 (United States)

2011-06-01

The spectroscopic and stability properties and X-ray crystal structure of the H87C mutant of the 2Fe–2S ligand mitoNEET are reported. Strikingly, the single point mutation leads to changes in its absorbance and CD spectra and an increase of around sixfold in the stability of the 2Fe–2S clusters over the pH range 5–7. However, the crystal structure of the H87C mutant displays heterogeneity in a few key residues, including the introduced cysteine ligand. Nonetheless, the cluster is highly stabilized from release. MitoNEET is the only identified Fe–S protein localized to the outer mitochondrial membrane and a 1.5 Å resolution X-ray analysis has revealed a unique structure [Paddock et al. (2007 ▶), Proc. Natl Acad. Sci. USA, 104, 14342–14347]. The 2Fe–2S cluster is bound with a 3Cys–1His coordination which defines a new class of 2Fe–2S proteins. The hallmark feature of this class is the single noncysteine ligand His87, which when replaced by Cys decreases the redox potential (E{sub m}) by ∼300 mV and increases the stability of the cluster by around sixfold. Unexpectedly, the pH dependence of the lifetime of the 2Fe–2S cluster remains the same as in the wild-type protein. Here, the crystal structure of H87C mitoNEET was determined to 1.7 Å resolution (R factor = 18%) to investigate the structural basis of the changes in the properties of the 2Fe–2S cluster. In comparison to the wild type, structural changes are localized to the immediate vicinity of the cluster-binding region. Despite the increased stability, Cys87 displays two distinct conformations, with distances of 2.3 and 3.2 Å between the S{sup γ} and the outer Fe of the 2Fe–2S cluster. In addition, Lys55 exhibits multiple conformations in the H87C mutant protein. The structure and distinct characteristics of the H87C mutant provide a framework for further studies investigating the effects of mutation on the properties of the 2Fe–2S cluster in this new class of proteins.

Analysis of Fiber Clustering in Composite Materials Using High-Fidelity Multiscale Micromechanics

Science.gov (United States)

Bednarcyk, Brett A.; Aboudi, Jacob; Arnold, Steven M.

2015-01-01

A new multiscale micromechanical approach is developed for the prediction of the behavior of fiber reinforced composites in presence of fiber clustering. The developed method is based on a coupled two-scale implementation of the High-Fidelity Generalized Method of Cells theory, wherein both the local and global scales are represented using this micromechanical method. Concentration tensors and effective constitutive equations are established on both scales and linked to establish the required coupling, thus providing the local fields throughout the composite as well as the global properties and effective nonlinear response. Two nondimensional parameters, in conjunction with actual composite micrographs, are used to characterize the clustering of fibers in the composite. Based on the predicted local fields, initial yield and damage envelopes are generated for various clustering parameters for a polymer matrix composite with both carbon and glass fibers. Nonlinear epoxy matrix behavior is also considered, with results in the form of effective nonlinear response curves, with varying fiber clustering and for two sets of nonlinear matrix parameters.

Photoelectron Spectroscopy and Density Functional Theory Studies of Iron Sulfur (FeS)m- (m = 2-8) Cluster Anions: Coexisting Multiple Spin States.

Science.gov (United States)

Yin, Shi; Bernstein, Elliot R

2017-10-05

Iron sulfur cluster anions (FeS) m - (m = 2-8) are studied by photoelectron spectroscopy (PES) at 3.492 eV (355 nm) and 4.661 eV (266 nm) photon energies, and by density functional theory (DFT) calculations. The most probable structures and ground state spin multiplicities for (FeS) m - (m = 2-8) clusters are tentatively assigned through a comparison of their theoretical and experiment first vertical detachment energy (VDE) values. Many spin states lie within 0.5 eV of the ground spin state for the larger (FeS) m - (m ≥ 4) clusters. Theoretical VDEs of these low lying spin states are in good agreement with the experimental VDE values. Therefore, multiple spin states of each of these iron sulfur cluster anions probably coexist under the current experimental conditions. Such available multiple spin states must be considered when evaluating the properties and behavior of these iron sulfur clusters in real chemical and biological systems. The experimental first VDEs of (FeS) m - (m = 1-8) clusters are observed to change with the cluster size (number m). The first VDE trends noted can be related to the different properties of the highest singly occupied molecular orbitals (NBO, HSOMOs) of each cluster anion. The changing nature of the NBO/HSOMO of these (FeS) m - (m = 1-8) clusters from a p orbital on S, to a d orbital on Fe, and to an Fe-Fe bonding orbital is probably responsible for the observed increasing trend for their first VDEs with respect to m.

Scattering of neutral metal clusters: Long-range interactions and response properties

International Nuclear Information System (INIS)

Kresin, V.V.; Scheidemann, A.

1993-01-01

The absolute integral cross sections for low-energy collisions of neutral sodium clusters Na n (n=2--40) with atoms and molecules (Ar, N 2 , O 2 , and halogens) have been measured. The cross sections are found to be exceptionally large (up to thousands of square angstroms), showing the dominant role of long-range intermolecular interactions. Elastic scattering proceeding under the influence of the van der Waals force, and a reaction channel involving electron transfer can successfully describe the measurements. The strength of the van der Waals potential is defined by such cluster response properties as the electric polarizability and the frequency of the giant dipole resonance. The reactive electron-jump channel, in turn, is described by the ''harpooning'' mechanism which is sensitive to the cluster ionization potential. Employing parameters taken from spectroscopic studies of alkali clusters, we obtain good agreement with the observed cross sections. This provides a direct connection between beam scattering experiments and studies of cluster electromagnetic response properties

The black hole S-Matrix from quantum mechanics

International Nuclear Information System (INIS)

Betzios, Panagiotis; Gaddam, Nava; Papadoulaki, Olga

2016-01-01

We revisit the old black hole S-Matrix construction and its new partial wave expansion of ’t Hooft. Inspired by old ideas from non-critical string theory & c=1 Matrix Quantum Mechanics, we reformulate the scattering in terms of a quantum mechanical model — of waves scattering off inverted harmonic oscillator potentials — that exactly reproduces the unitary black hole S-Matrix for all spherical harmonics; each partial wave corresponds to an inverted harmonic oscillator with ground state energy that is shifted relative to the s-wave oscillator. Identifying a connection to 2d string theory allows us to show that there is an exponential degeneracy in how a given total initial energy may be distributed among many partial waves of the 4d black hole.

The black hole S-Matrix from quantum mechanics

Energy Technology Data Exchange (ETDEWEB)

Betzios, Panagiotis; Gaddam, Nava; Papadoulaki, Olga [Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena,Utrecht University, Princetonplein 5, Utrecht, 3508 TD The (Netherlands)

2016-11-22

We revisit the old black hole S-Matrix construction and its new partial wave expansion of ’t Hooft. Inspired by old ideas from non-critical string theory & c=1 Matrix Quantum Mechanics, we reformulate the scattering in terms of a quantum mechanical model — of waves scattering off inverted harmonic oscillator potentials — that exactly reproduces the unitary black hole S-Matrix for all spherical harmonics; each partial wave corresponds to an inverted harmonic oscillator with ground state energy that is shifted relative to the s-wave oscillator. Identifying a connection to 2d string theory allows us to show that there is an exponential degeneracy in how a given total initial energy may be distributed among many partial waves of the 4d black hole.

Microlocal study of S-matrix singularity structure

International Nuclear Information System (INIS)

Kawai, Takahiro; Kyoto Univ.; Stapp, H.P.

1975-01-01

Support is adduced for two related conjectures of simplicity of the analytic structure of the S-matrix and related function; namely, Sato's conjecture that the S-matrix is a solution of a maximally over-determined system of pseudo-differential equations, and our conjecture that the singularity spectrum of any bubble diagram function has the conormal structure with respect to a canonical decomposition of the solutions of the relevant Landau equations. This latter conjecture eliminates the open sets of allowed singularities that existing procedures permit. (orig.) [de

Cluster implementation for parallel computation within MATLAB software environment

International Nuclear Information System (INIS)

Santana, Antonio O. de; Dantas, Carlos C.; Charamba, Luiz G. da R.; Souza Neto, Wilson F. de; Melo, Silvio B. Melo; Lima, Emerson A. de O.

2013-01-01

A cluster for parallel computation with MATLAB software the COCGT - Cluster for Optimizing Computing in Gamma ray Transmission methods, is implemented. The implementation correspond to creation of a local net of computers, facilities and configurations of software, as well as the accomplishment of cluster tests for determine and optimizing of performance in the data processing. The COCGT implementation was required by data computation from gamma transmission measurements applied to fluid dynamic and tomography reconstruction in a FCC-Fluid Catalytic Cracking cold pilot unity, and simulation data as well. As an initial test the determination of SVD - Singular Values Decomposition - of random matrix with dimension (n , n), n=1000, using the Girco's law modified, revealed that COCGT was faster in comparison to the literature [1] cluster, which is similar and operates at the same conditions. Solution of a system of linear equations provided a new test for the COCGT performance by processing a square matrix with n=10000, computing time was 27 s and for square matrix with n=12000, computation time was 45 s. For determination of the cluster behavior in relation to 'parfor' (parallel for-loop) and 'spmd' (single program multiple data), two codes were used containing those two commands and the same problem: determination of SVD of a square matrix with n= 1000. The execution of codes by means of COCGT proved: 1) for the code with 'parfor', the performance improved with the labs number from 1 to 8 labs; 2) for the code 'spmd', just 1 lab (core) was enough to process and give results in less than 1 s. In similar situation, with the difference that now the SVD will be determined from square matrix with n1500, for code with 'parfor', and n=7000, for code with 'spmd'. That results take to conclusions: 1) for the code with 'parfor', the behavior was the same already described above; 2) for code with 'spmd', the same besides having produced a larger performance, it supports a

The MUSIC of galaxy clusters - II. X-ray global properties and scaling relations

Science.gov (United States)

Biffi, V.; Sembolini, F.; De Petris, M.; Valdarnini, R.; Yepes, G.; Gottlöber, S.

2014-03-01

We present the X-ray properties and scaling relations of a large sample of clusters extracted from the Marenostrum MUltidark SImulations of galaxy Clusters (MUSIC) data set. We focus on a sub-sample of 179 clusters at redshift z ˜ 0.11, with 3.2 × 1014 h-1 M⊙ mass. We employed the X-ray photon simulator PHOX to obtain synthetic Chandra observations and derive observable-like global properties of the intracluster medium (ICM), as X-ray temperature (TX) and luminosity (LX). TX is found to slightly underestimate the true mass-weighted temperature, although tracing fairly well the cluster total mass. We also study the effects of TX on scaling relations with cluster intrinsic properties: total (M500 and gas Mg,500 mass; integrated Compton parameter (YSZ) of the Sunyaev-Zel'dovich (SZ) thermal effect; YX = Mg,500 TX. We confirm that YX is a very good mass proxy, with a scatter on M500-YX and YSZ-YX lower than 5 per cent. The study of scaling relations among X-ray, intrinsic and SZ properties indicates that simulated MUSIC clusters reasonably resemble the self-similar prediction, especially for correlations involving TX. The observational approach also allows for a more direct comparison with real clusters, from which we find deviations mainly due to the physical description of the ICM, affecting TX and, particularly, LX.

Influence of tissue- and cell-scale extracellular matrix distribution on the mechanical properties of tissue engineered cartilage

NARCIS (Netherlands)

Khoshgoftar, M.; Wilson, W.; Ito, K.; Donkelaar, van C.C.

2013-01-01

The insufficient load-bearing capacity of today’s tissue- engineered (TE) cartilage limits its clinical application. Generally, cartilage TE studies aim to increase the extracellular matrix (ECM) content, as this is thought to determine the load-bearing properties of the cartilage. However, there

Electronic and magnetic properties of small rhodium clusters

Energy Technology Data Exchange (ETDEWEB)

Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

2015-04-24

We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

S-matrix description of anomalous large-angle heavy-ion scattering

Energy Technology Data Exchange (ETDEWEB)

Frahn, W E; Hussein, M S [Sao Paulo Univ. (Brazil). Inst. de Fisica; Canto, L F; Donangelo, R [Rio de Janeiro Univ. (Brazil). Inst. de Fisica

1981-10-12

We present a quantitative description of the well-known anomalous features observed in the large-angle scattering of n..cap alpha.. type heavy ions, in particular of the pronounced structures in the backangle excitation function for /sup 16/O + /sup 28/Si. Our treatment is based on the close connection between these anomalies and particular structural deviations of the partial-wave S-matrix from normal strong-absorption behaviour. The properties of these deviations are found to be rather well specified by the data: they are localized within a narrow 'l-window' centered at a critical angular momentum significantly smaller than the grazing value, and have a parity-dependent as well as a parity-independent part. These properties provide important clues as to the physical processes causing the large-angle enhancement.

S-matrix description of anomalus large-angle heavy-ion scattering

International Nuclear Information System (INIS)

Frahn, W.E.; Hussein, M.S.; Canto, L.F.; Donangelo, R.J.

1981-01-01

A quantitative description of the well-known anomalous features observed in the large-angle scattering of n.α type heavy ions, in particular of the pronounced structures in the backangle excitation function or 16 O + 28 Si is presented. This treatment is based on the close connection between these anomalies and particular structural deviations of the partial-wave S-matrix from normal strong-absorption behaviour. The properties of these deviations are found to be rather well specified by the data: they are localized within a narrow 'l-window' centered at a critical angular momentum significantly smaller than the grazing value, and have a parity-dependent as well as a parity-independent part. These properties provide important clues as to the physical processes causing the large-angle enhancement. (Author) [pt

NATO Advanced Research Workshop on Physics and Chemistry of Finite Systems : from Clusters to Crystals

CERN Document Server

Khanna, S; Rao, B

1992-01-01

Recent innovations in experimental techniques such as molecular and cluster beam epitaxy, supersonic jet expansion, matrix isolation and chemical synthesis are increasingly enabling researchers to produce materials by design and with atomic dimension. These materials constrained by sire, shape, and symmetry range from clusters containing as few as two atoms to nanoscale materials consisting of thousands of atoms. They possess unique structuraI, electronic, magnetic and optical properties that depend strongly on their size and geometry. The availability of these materials raises many fundamental questions as weIl as technological possibilities. From the academic viewpoint, the most pertinent question concerns the evolution of the atomic and electronic structure of the system as it grows from micro clusters to crystals. At what stage, for example, does the cluster look as if it is a fragment of the corresponding crystal. How do electrons forming bonds in micro-clusters transform to bands in solids? How do the s...

Short and long carbon fibre reinforced Cu-matrix composites: microstructural results and structural origin of properties

International Nuclear Information System (INIS)

Buchgraber, W.

1997-01-01

Carbon fibre reinforced copper matrix composites possess properties of copper, i.e. excellent thermal and electrical conductivities, and properties of carbon fibre, i.e. a small thermal expansion coefficient. Since the desirable properties of the composite can be obtained by selecting the amount, type and orientation of the carbon fibres, it is considered to be suitable for use as electric and electronic materials. This lecture focuses on two-dimensional isotropic carbon fibre reinforced copper matrix composites with long or short carbon fibres. Short carbon fibre reinforced copper matrix composites have been produced by hot-pressing of copper coated short carbon fibres. During hot-pressing, the carbon fibres take on a preferred orientation in a plane perpendicular to the hot pressing direction. Within this plane the fibre orientation is random. Long carbon fibre reinforced copper matrix composites have been made by hot pressing of monolayers consisting of copper coated long carbon fibres. Different orientations of the monolayers will be compared. Both the physical and mechanical properties of the discussed composites are strongly influenced not only by the properties of its individual constituents, but also by the microstructure and properties of the fibre matrix interface. The problem of poor wettability of the carbon fibre by the copper matrix will be discussed. The microstructure of several types of carbon fibre reinforced copper matrix composites will be discussed. Their thermophysical properties will be compared with microstructural results. (author)

q-Virasoro constraints in matrix models

Energy Technology Data Exchange (ETDEWEB)

Nedelin, Anton [Dipartimento di Fisica, Università di Milano-Bicocca and INFN, sezione di Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Department of Physics and Astronomy, Uppsala university,Box 516, SE-75120 Uppsala (Sweden); Zabzine, Maxim [Department of Physics and Astronomy, Uppsala university,Box 516, SE-75120 Uppsala (Sweden)

2017-03-20

The Virasoro constraints play the important role in the study of matrix models and in understanding of the relation between matrix models and CFTs. Recently the localization calculations in supersymmetric gauge theories produced new families of matrix models and we have very limited knowledge about these matrix models. We concentrate on elliptic generalization of hermitian matrix model which corresponds to calculation of partition function on S{sup 3}×S{sup 1} for vector multiplet. We derive the q-Virasoro constraints for this matrix model. We also observe some interesting algebraic properties of the q-Virasoro algebra.

Pharmacokinetic properties and tolerability of low-dose SoluMatrix diclofenac.

Science.gov (United States)

Desjardins, Paul J; Olugemo, Kemi; Solorio, Daniel; Young, Clarence L

2015-02-01

This study compared the pharmacokinetic properties and safety profile of low-dose (18- and 35-mg) diclofenac capsules manufactured using SoluMatrix Fine Particle Technology (Trademark of iCeutica Inc. (Philadelphia, Pennsylvania), and the technology is licensed to Iroko Pharmaceuticals, LLC (Philadelphia, Pennsylvania) for exclusive use in NSAIDs), which produces submicron-sized drug particles with enhanced dissolution properties, to those of diclofenac potassium immediate-release (IR) 50-mg tablets. This Phase 1, single-center, randomized, open-label, single-dose crossover study was conducted in 40 healthy volunteers. Subjects received, in randomized order, SoluMatrix diclofenac 18- or 35-mg capsules in the fasting condition, SoluMatrix diclofenac 35-mg capsules under fed conditions, and diclofenac potassium IR 50-mg tablets under fasting and fed conditions. Pharmacokinetic parameters (T(max), C(max), AUC(0-t), AUC(0-∞)) were calculated from the concentrations of diclofenac in the plasma. Absorption, food effect, and dose proportionality were determined using a mixed-model ANOVA for C(max), AUC(0-t), AUC(0-∞). Tolerability was assessed by recording adverse events, physical examination findings, vital sign measurements: clinical laboratory test results. Overall, 35 healthy volunteers aged 18 to 52 years completed the study. The mean age of the subjects was 33.4 years, and approximately half were men (47.5%). Median T(max) values were similar between the low-dose SoluMatrix diclofenac 35-mg capsules and the diclofenac potassium IR 50-mg tablets (both, ~1.0 hour). The mean maximum plasma concentration (C(max)) after the administration of low-dose SoluMatrix diclofenac 35-mg capsules was 26% lower than that with diclofenac potassium IR 50-mg tablets under fasting conditions (868.72 vs 1194.21 ng/mL). The administration of low-dose SoluMatrix diclofenac 35-mg capsules was associated with a 23% lower overall systemic exposure compared with that of diclofenac

Absence of particle production and factorization of the s-matrix in 1 + 1 dimensional models

International Nuclear Information System (INIS)

Parke, S.

1980-01-01

In massive, 1 + 1 dimensional, local, quantum field theories the existence of two conserved charges is shown to be a sufficient condition for the absence of particle production and factorization of the s-matrix. These charges must commute and be integrals of local current densities. Their transformation properties under the Lorentz group must be different and also different from the transformation properties under the Lorentz group must be different and also different from the transformation properties pf a vector or a scalar. Also, they must not annihilate any single-particle momentum eigenstate. (orig.)

Towards an S-matrix Description of Gravitational Collapse

CERN Document Server

Amati, D; Veneziano, Gabriele

2008-01-01

Extending our previous results on trans-Planckian ($Gs \\gg \\hbar$) scattering of light particles in quantum string-gravity we present a calculation of the corresponding S-matrix from the region of large impact parameters ($b \\gg G\\sqrt{s}>\\lambda_s$) down to the regime where classical gravitational collapse is expected to occur. By solving the semiclassical equations of a previously introduced effective-action approximation, we find that the perturbative expansion around the leading eikonal result diverges at a critical value $b = b_c = O(G\\sqrt{s})$, signalling the onset of a new (black-hole related?) regime. We then discuss the main features of our explicitly unitary S-matrix -- and of the associated effective metric -- down to (and in the vicinity of) $b = b_c$, and present some ideas and results on its extension all the way to the $ b \\to 0$ region. We find that for $bS-matrix shows additional absorption, related to a new production mechanis...

Microscopic cluster model analysis of 14O+p elastic scattering

International Nuclear Information System (INIS)

Baye, D.; Descouvemont, P.; Leo, F.

2005-01-01

The 14 O+p elastic scattering is discussed in detail in a fully microscopic cluster model. The 14 O cluster is described by a closed p shell for protons and a closed p3/2 subshell for neutrons in the translation-invariant harmonic-oscillator model. The exchange and spin-orbit parameters of the effective forces are tuned on the energy levels of the 15 C mirror system. With the generator-coordinate and microscopic R-matrix methods, phase shifts and cross sections are calculated for the 14 O+p elastic scattering. An excellent agreement is found with recent experimental data. A comparison is performed with phenomenological R-matrix fits. Resonances properties in 15 F are discussed

CEMCAN Software Enhanced for Predicting the Properties of Woven Ceramic Matrix Composites

Science.gov (United States)

Murthy, Pappu L. N.; Mital, Subodh K.; DiCarlo, James A.

2000-01-01

Major advancements are needed in current high-temperature materials to meet the requirements of future space and aeropropulsion structural components. Ceramic matrix composites (CMC's) are one class of materials that are being evaluated as candidate materials for many high-temperature applications. Past efforts to improve the performance of CMC's focused primarily on improving the properties of the fiber, interfacial coatings, and matrix constituents as individual phases. Design and analysis tools must take into consideration the complex geometries, microstructures, and fabrication processes involved in these composites and must allow the composite properties to be tailored for optimum performance. Major accomplishments during the past year include the development and inclusion of woven CMC micromechanics methodology into the CEMCAN (Ceramic Matrix Composites Analyzer) computer code. The code enables one to calibrate a consistent set of constituent properties as a function of temperature with the aid of experimentally measured data.

Consumers' Kansei Needs Clustering Method for Product Emotional Design Based on Numerical Design Structure Matrix and Genetic Algorithms.

Science.gov (United States)

Yang, Yan-Pu; Chen, Deng-Kai; Gu, Rong; Gu, Yu-Feng; Yu, Sui-Huai

2016-01-01

Consumers' Kansei needs reflect their perception about a product and always consist of a large number of adjectives. Reducing the dimension complexity of these needs to extract primary words not only enables the target product to be explicitly positioned, but also provides a convenient design basis for designers engaging in design work. Accordingly, this study employs a numerical design structure matrix (NDSM) by parameterizing a conventional DSM and integrating genetic algorithms to find optimum Kansei clusters. A four-point scale method is applied to assign link weights of every two Kansei adjectives as values of cells when constructing an NDSM. Genetic algorithms are used to cluster the Kansei NDSM and find optimum clusters. Furthermore, the process of the proposed method is presented. The details of the proposed approach are illustrated using an example of electronic scooter for Kansei needs clustering. The case study reveals that the proposed method is promising for clustering Kansei needs adjectives in product emotional design.

Quantitative properties of clustering within modern microscopic nuclear models

International Nuclear Information System (INIS)

Volya, A.; Tchuvil’sky, Yu. M.

2016-01-01

A method for studying cluster spectroscopic properties of nuclear fragmentation, such as spectroscopic amplitudes, cluster form factors, and spectroscopic factors, is developed on the basis of modern precision nuclear models that take into account the mixing of large-scale shell-model configurations. Alpha-cluster channels are considered as an example. A mathematical proof of the need for taking into account the channel-wave-function renormalization generated by exchange terms of the antisymmetrization operator (Fliessbach effect) is given. Examples where this effect is confirmed by a high quality of the description of experimental data are presented. By and large, the method in question extends substantially the possibilities for studying clustering phenomena in nuclei and for improving the quality of their description.

Structural properties of silicon clusters: An empirical potential study

International Nuclear Information System (INIS)

Gong, X.G.; Zheng, Q.Q.; He Yizhen

1993-09-01

By using our newly proposed empirical interatomic potential for silicon, the structure and some dynamical properties of silicon cluster Si n (10 ≤ n ≤ 24) have been studied. It is found that the obtained results are close to those from ab-initio methods. From present results, we can gain a new insight into the understanding of the experimental data on the Si n clusters. (author). 20 refs, 6 figs

Dielectric properties of isolated clusters beam deflection studies

CERN Document Server

Heiles, Sven

2013-01-01

A broad range of state-of-the-art methods to determine properties of clusters are presented. The experimental setup and underlying physical concepts of these experiments are described. Furthermore, existing theoretical models to explain the experimental observations are introduced and the possibility to deduce structural information from measurements of dielectric properties is discussed. Additional case studies are presented in the book to emphasize the possibilities but also drawbacks of the methods.

Generation of CsI cluster ions for mass calibration in matrix-assisted laser desorption/ionization mass spectrometry

NARCIS (Netherlands)

Lou, X.; Dongen, van J.L.J.; Meijer, E.W.

2010-01-01

A simple method was developed for the generation of cesium iodide (CsI) cluster ions up to m/z over 20,000 in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Calibration ions in both positive and negative ion modes can readily be generated from a single MALDI spot of CsI(3)

Z4-symmetric factorized S-matrix in two space-time dimensions

International Nuclear Information System (INIS)

Zamolodchikov, A.B.

1979-01-01

The factorized S-matrix with internal symmetry Z 4 is constructed in two space-time dimensions. The two-particle amplitudes are obtained by means of solving the factorization, unitarity and analyticity equations. The solution of factorization equations can be expressed in terms of elliptic functions. The S-matrix cotains the resonance poles naturally. The simple formal relation between the general factorized S-matrices and the Baxter-type lattice transfer matrices is found. In the sense of this relation the Z 4 -symmetric S-matrix corresponds to the Baxter transfer matrix itself. (orig.)

The Cluster Enterprise of Real Property Business

DEFF Research Database (Denmark)

Stubkjær, Erik

2008-01-01

others. The paper regards the domain of real property transactions. Drawing on research of European scope, it analyzes the framework of business processes in order to facilitate adoption of service oriented architectures. The paper motivates the notion of a ‘cluster enterprise' and identifies further......In order to apply the potential of available web technology, business processes must be described in a coherent way across organizational boundaries. Business processes include geographical data in the context of constructions, as well as environmental affairs and real property transactions, among...... steps towards a standardization of real estate business....

On modular properties of the AdS3 CFT

International Nuclear Information System (INIS)

Baron, Walter H.; Nunez, Carmen A.

2011-01-01

We study modular properties of the AdS 3 Wess-Zumino-Novikov-Witten model. Although the Euclidean partition function is modular invariant, the characters on the Euclidean torus diverge and the regularization proposed in the literature removes information on the spectrum and the usual one to one map between characters and representations of rational models is lost. Reconsidering the characters defined on the Lorentzian torus and focusing on their structure as distributions, we obtain expressions that recover those properties. We study their modular transformations and find a generalized S matrix, depending on the sign of the real modular parameters, which has two diagonal blocks and one off-diagonal block, mixing discrete and continuous representations, that we fully determine. We then explore the relations among the modular transformations, the fusion algebra and the boundary states. We explicitly construct Ishibashi states for the maximally symmetric D-branes and show that the generalized S matrix defines the one-point functions associated to pointlike and H 2 -branes as well as the fusion rules of the degenerate representations of sl(2,R) appearing in the open string spectrum of the pointlike D-branes, through a generalized Verlinde theorem.

Irradiation-Induced Solute Clustering in a Low Nickel FeMnNi Ferritic Alloy

International Nuclear Information System (INIS)

Meslin, E.; Barbu, A.; Radiguet, B.; Pareige, P.; Toffolon, C.

2011-01-01

Understanding the radiation embrittlement of reactor pressure vessel (RPV) steels is required to be able to operate safely a nuclear power plant or to extend its lifetime. The mechanical properties degradation is partly due to the clustering of solute under irradiation. To gain knowledge about the clustering process, a Fe-1.1 Mn-0.7 Ni (at.%) alloy was irradiated in a test reactor at two fluxes of 0.15 and 9 *10 17 n E≥1MeV . m -2 .s -1 and at increasing doses from 0.18 to 1.3 *10 24 n E≥1MeV ) . m -2 at 300 degrees C. Atom probe tomography (APT) experiments revealed that the irradiation promotes the formation in the α iron matrix of Mn/Mn and/or Ni/Ni pair correlations at low dose and Mn-Ni enriched clusters at high dose. These clusters dissolve partially after a thermal treatment at 400 degrees C. Based on a comparison with thermodynamic calculations, we show that the solute clustering under irradiation can just result from an induced mechanism. (authors)

Prediction of the creep properties of discontinuous fibre composites from the matrix creep law

International Nuclear Information System (INIS)

Bilde-Soerensen, J.B.; Boecker Pedersen, O.; Lilholt, H.

1975-02-01

Existing theories for predicting the creep properties of discontinuous fibre composites with non-creeping fibres from matrix creep properties, originally based on a power law, are extended to include an exponential law, and in principle a general matrixlaw. An analysis shows that the composite creep curve can be obtained by a simple displacement of the matrix creep curve in a log sigma vs. log epsilon diagram. This principle, that each point on the matrix curve has a corresponding point on the composite curve,is given a physical interpretation. The direction of displacement is such that the transition from a power law toan exponential law occurs at a lower strain rate for the composite than for the unreinforced matrix. This emphasizes the importance of the exponential creep range in the creep of fibre composites. The combined use of matrix and composite data may allow the creep phenomenon to be studied over a larger range of strain rates than otherwise possible. A method for constructing generalized composite creep diagrams is suggested. Creep properties predicted from matrix data by the present analysis are compared with experimental data from the literature. (author)

NMR of proteins (4Fe-4S): structural properties and intramolecular electron transfer; RMN de proteines (4Fe-4S): proprietes structurales et transfert electronique intramoleculaire

Energy Technology Data Exchange (ETDEWEB)

Huber, J G

1996-10-17

NMR started to be applied to Fe-S proteins in the seventies. Its use has recently been enlarged as the problems arising from the paramagnetic polymetallic clusters ware overcome. Applications to [4Fe-4S] are presented herein. The information derived thereof deepens the understanding of the redox properties of these proteins which play a central role in the metabolism of bacterial cells. The secondary structure elements and the overall folding of Chromatium vinosum ferredoxin (Cv Fd) in solution have been established by NMR. The unique features of this sequence have been shown to fold as an {alpha} helix at the C-terminus and as a loop between two cysteines ligand of one cluster: these two parts localize in close proximity from one another. The interaction between nuclear and electronic spins is a source of additional structural information for (4Fe-AS] proteins. The conformation of the cysteine-ligands, as revealed by the Fe-(S{sub {gamma}}-C{sub {beta}}-H{sub {beta}})Cys dihedral angles, is related to the chemical shifts of the signals associated with the protons of these residues. The longitudinal relaxation times of the protons depend on their distance to the cluster. A quantitative relationship has been established and used to show that the solution structure of the high-potential ferredoxin from Cv differs significantly from the crystal structure around Phe-48. Both parameters (chemical shifts and longitudinal relaxation times) give also insight into the electronic and magnetic properties of the [4Fe-4S] clusters. The rate of intramolecular electron transfer between the two [4FE-4S] clusters of ferredoxins has been measured by NMR. It is far slower in the case of Cv Fd than for shorter ferredoxins. The difference may be associated with changes in the magnetic and/or electronic properties of one cluster. The strong paramagnetism of the [4Fe-4S] clusters, which originally limited the applicability of NMR to proteins containing these cofactors, has been proven

Physicochemical properties of discontinuous S2-glass fiber reinforced resin composite.

Science.gov (United States)

Huang, Qiting; Qin, Wei; Garoushi, Sufyan; He, Jingwei; Lin, Zhengmei; Liu, Fang; Vallittu, Pekka K; Lassila, Lippo V J

2018-01-30

The objective of this study was to investigate several physicochemical properties of an experimental discontinuous S2-glass fiber-reinforced resin composite. The experimental composite was prepared by mixing 10 wt% of discontinuous S2-glass fibers with 27.5 wt% of resin matrix and 62.5 wt% of particulate fillers. Flexural strength (FS) and modulus (FM), fracture toughness (FT), work of fracture (WOF), double bond conversion (DC), Vickers hardness, volume shrinkage (VS) and fiber length distribution were determined. These were compared with two commercial resin composites. The experimental composite showed the highest FS, WOF and FT compared with two control composites. The DC of the experimental composite was comparable with controls. No significant difference was observed in VS between the three tested composites. The use of discontinuous glass fiber fillers with polymer matrix and particulate fillers yielded improved physical properties and substantial improvement was associated with the use of S2-glass fiber.

Structure and properties of nanocrystalline soft magnetic composite materials with silicon polymer matrix

International Nuclear Information System (INIS)

Dobrzanski, L.A.; Nowosielski, R.; Konieczny, J.; PrzybyI, A.; WysIocki, J.

2005-01-01

The paper concerns investigation of nanocrystalline composites technology preparation. The composites in the form of rings with rectangular transverse section, and with polymer matrix and nanocrystalline metallic powders fulfillment were made, for obtaining good ferromagnetic properties. The nanocrystalline ferromagnetic powders were manufactured by high-energy ball milling of metallic glasses strips in an as-quenched state. Generally for investigation, Co matrix alloys with the silicon polymer were used. Magnetic properties in the form of hysteresis loop by rings method were measured. Generally composite cores showed lower soft ferromagnetic properties than winded cores of nanocrystalline strips, but composite cores showed interesting mechanical properties. Furthermore, the structure of strips and powders on properties of composites were investigated

Clustering via Kernel Decomposition

DEFF Research Database (Denmark)

Have, Anna Szynkowiak; Girolami, Mark A.; Larsen, Jan

2006-01-01

Methods for spectral clustering have been proposed recently which rely on the eigenvalue decomposition of an affinity matrix. In this work it is proposed that the affinity matrix is created based on the elements of a non-parametric density estimator. This matrix is then decomposed to obtain...... posterior probabilities of class membership using an appropriate form of nonnegative matrix factorization. The troublesome selection of hyperparameters such as kernel width and number of clusters can be obtained using standard cross-validation methods as is demonstrated on a number of diverse data sets....

The role of extended Fe4S4 cluster ligands in mediating sulfite reductase hemoprotein activity.

Science.gov (United States)

Cepeda, Marisa R; McGarry, Lauren; Pennington, Joseph M; Krzystek, J; Elizabeth Stroupe, M

2018-05-28

The siroheme-containing subunit from the multimeric hemoflavoprotein NADPH-dependent sulfite reductase (SiR/SiRHP) catalyzes the six electron-reduction of SO 3 2- to S 2- . Siroheme is an iron-containing isobacteriochlorin that is found in sulfite and homologous siroheme-containing nitrite reductases. Siroheme does not work alone but is covalently coupled to a Fe 4 S 4 cluster through one of the cluster's ligands. One long-standing hypothesis predicted from this observation is that the environment of one iron-containing cofactor influences the properties of the other. We tested this hypothesis by identifying three amino acids (F437, M444, and T477) that interact with the Fe 4 S 4 cluster and probing the effect of altering them to alanine on the function and structure of the resulting enzymes by use of activity assays, X-ray crystallographic analysis, and EPR spectroscopy. We showed that F437 and M444 gate access for electron transfer to the siroheme-cluster assembly and the direct hydrogen bond between T477 and one of the cluster sulfides is important for determining the geometry of the siroheme active site. Copyright © 2018. Published by Elsevier B.V.

A matrix S for all simple current extensions

International Nuclear Information System (INIS)

Fuchs, J.; Schellekens, A.N.; Schweigert, C.

1996-01-01

A formula is presented for the modular transformation matrix S for any simple current extension of the chiral algebra of a conformal field theory. This provides in particular an algorithm for resolving arbitrary simple current fixed points, in such a way that the matrix S we obtain is unitary and symmetric and furnishes a modular group representation. The formalism works in principle for any conformal field theory. A crucial ingredient is a set of matrices S ab J , where J is a simple current and a and b are fixed points of J. We expect that these input matrices realize the modular group for the torus one-point functions of the simple currents. In the case of WZW-models these matrices can be identified with the S-matrices of the orbit Lie algebras that were introduced recently. As a special case of our conjecture we obtain the modular matrix S for WZW-theories based on group manifolds that are not simply connected, as well as for most coset models. (orig.)

Nanoindentation measurements of the mechanical properties of zirconium matrix and hydrides in unirradiated pre-hydrided nuclear fuel cladding

International Nuclear Information System (INIS)

Rico, A.; Martin-Rengel, M.A.; Ruiz-Hervias, J.; Rodriguez, J.; Gomez-Sanchez, F.J.

2014-01-01

It is well known that the mechanical properties of the nuclear fuel cladding may be affected by the presence of hydrides. The average mechanical properties of hydrided cladding have been extensively investigated from a macroscopic point of view. In addition, the mechanical and fracture properties of bulk hydride samples fabricated from zirconium plates have also been reported. In this paper, Young’s modulus, hardness and yield stress are measured for each phase, namely zirconium hydrides and matrix, of pre-hydrided nuclear fuel cladding. To this end, nanoindentation tests were performed on ZIRLO samples in as-received state, on a hydride blister and in samples with 150 and 1200 ppm of hydrogen homogeneously distributed along the hoop direction of the cladding. The results show that the measured mechanical properties of the zirconium hydrides and ZIRLO matrix (Young’s modulus, hardness and yield stress) are rather similar. From the experimental data, the hydride volume fraction in the cladding samples with 150 and 1200 ppm was estimated and the average mechanical properties were calculated by means of the rule of mixtures. These values were compared with those obtained from ring compression tests. Good agreement between the results obtained by both methods was found

Relationship Between Filler-Matrix Interface and Macroscopical Properties of Polymer Nanocomposites

KAUST Repository

Aguilar Ventura, Isaac Enrique

2017-11-01

The macroscopic properties of Multiwall Carbon Nanotube (MWCNT) polymer nano-composites and multiscale composites have been studied from a multifunctional standpoint. The objective is to understand and correlate the mechanisms in which the addition of a small content of MWCNTs can affect the mechanical, thermal and electrical properties of thermoplastic and thermoset polymer nanocomposites. While CNTs are well-known to possess extraordinary properties in the nanoscale, it has been shown that, the CNT/polymer matrix and CNT/CNT interactions are mainly responsible for the modification of properties in the nanocomposites. Observation of the mechanical properties revealed that the addition of CNTs can increase the stiffness of the material, but the increment of interfacial regions can accelerate the damage process under cyclic loading conditions. Additionally, CNTs can interact with polymer chains in the matrix affecting thermomechanical properties such as the glass transition temperature and the storage modulus. A low content of well-dispersed CNTs can form percolated networks within the matrix, which, due to the nature of the electrical conduction mechanism, have demonstrated potential in increasing the electrical conductivity of the nanocomposites. In contrast, high phonon scattering at the interconnections along the CNT network are responsible for marginal increases in thermal conductivity. In this study, a special focus was placed in modifying the CNT interconnections with a conductive polymer "bridge" to increase the efficiency of the electrical carrier transport. Additional experimental observations such as piezoresistivity and electrical conductivity/temperature dependency, demonstrated the major role of the interfacial regions with respect to the observed material properties in the macroscale. Controlling the interactions that occur in these regions is key to achieve tailorable, multifunctional nanocomposites.

Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites.

Science.gov (United States)

Li, Feng; Jiang, Xiaosong; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

2018-04-16

Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca₃(PO₄)₂, Ti x P y , and Ti₃O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed.

Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites

Directory of Open Access Journals (Sweden)

Feng Li

2018-04-01

Full Text Available Biomaterial composites made of titanium and hydroxyapatite (HA powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD, back scattered electron imaging (BSE, scanning electron microscope (SEM equipped with energy dispersive spectrometer (EDS, electron probe microanalyzer (EPMA, and transmission electron microscope (TEM. The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca3(PO42, TixPy, and Ti3O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed.

Semiclassical S-matrix for black holes

CERN Document Server

Bezrukov, Fedor; Sibiryakov, Sergey

2015-01-01

We propose a semiclassical method to calculate S-matrix elements for two-stage gravitational transitions involving matter collapse into a black hole and evaporation of the latter. The method consistently incorporates back-reaction of the collapsing and emitted quanta on the metric. We illustrate the method in several toy models describing spherical self-gravitating shells in asymptotically flat and AdS space-times. We find that electrically neutral shells reflect via the above collapse-evaporation process with probability exp(-B), where B is the Bekenstein-Hawking entropy of the intermediate black hole. This is consistent with interpretation of exp(B) as the number of black hole states. The same expression for the probability is obtained in the case of charged shells if one takes into account instability of the Cauchy horizon of the intermediate Reissner-Nordstrom black hole. Our semiclassical method opens a new systematic approach to the gravitational S-matrix in the non-perturbative regime.

Catalytic activity of Cu4-cluster to adsorb H2S gas: h-BN nanosheet

Science.gov (United States)

Kansara, Shivam; Gupta, Sanjeev K.; Sonvane, Yogesh

2018-05-01

We have investigated the electronic properties, adsorptions strength and charge transfer using first principles calculations using density functional theory (DFT). The hexagonal boron nitride (h-BN) substrate shows metallic behavior, which helps to enhance the absorption process. The adsorption of three different orientations (S, D and T) of the H2S gas molecules to analyze the maximum adsorption strength from them onto a copper cluster (Cu4) based on h-BN nanosheet. The maximum adsorption energy of the H2S gas molecule is -1.50 eV for the S orientation and for D and U, it is -0.71 eV and -0.78 eV, respectively. The results show that Cu4 cluster helps to capture H2S gas from the environment and results are useful for the cleaning environment from the toxic gases.

Effect Of Neutron Activation Factor On The Physico-Chemical Properties Of Hydrophilic And Hydrophobic Polymer Formulation Of Matrix Tablets

International Nuclear Information System (INIS)

Ibrahim Ijang; Bohari Yaacob; Nordiana, N.R.

2011-01-01

This study was to investigate effect of neutron activation on the physicochemical properties and in vitro dissolution of sustained-release matrix tablets. The tablets incorporation of Samarium oxide (Sm 2 O 3 ) and were compared before and after irradiation with thermal neutron for 5 minutes at 1.2 x 10 12 neutron cm -2 s -1 . The neutron activation factor did not influence the compression properties of the tablets. The dissolution tests showed that irradiation increased the release of the model drug ketoprofen from the tablets. This effect might be explained by polymer degradation. Incorporation of Sm 2 O 3 in the matrix tablets did not influence the release. (author)

POLLA-NESC, Resonance Parameter R-Matrix to S-Matrix Conversion by Reich-Moore Method

International Nuclear Information System (INIS)

Saussure, G. de; Perez, R.B.

1975-01-01

1 - Description of problem or function: The program transforms a set of r-matrix nuclear resonance parameters into a set of equivalent s-matrix (or Kapur-Peierls) resonance parameters. 2 - Method of solution: The program utilizes the multilevel formalism of Reich and Moore and avoids diagonalization of the level matrix. The parameters are obtained by a direct partial fraction expansion of the Reich-Moore expression of the collision matrix. This approach appears simpler and faster when the number of fission channels is known and small. The method is particularly useful when a large number of levels must be considered because it does not require diagonalization of a large level matrix. 3 - Restrictions on the complexity of the problem: By DIMENSION statements, the program is limited to maxima of 100 levels and 5 channels

The S-matrix for abstract scattering systems

International Nuclear Information System (INIS)

Amrein, W.O.; Pearson, D.B.

1979-01-01

Let S(lambda) be the S-matrix at energy lambda for an abstract scattering system. A bound is derived in terms of the interaction, on integrals of the form ∫ h(lambda)/S(lambda) - I/ 2 sub(HS) dlambda, where /./sub(HS) denotes the Hilbert-Schmidt norm. (Auth.)

Bipartite entanglement in continuous variable cluster states

Energy Technology Data Exchange (ETDEWEB)

Cable, Hugo; Browne, Daniel E, E-mail: cqthvc@nus.edu.s, E-mail: d.browne@ucl.ac.u [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore)

2010-11-15

A study of the entanglement properties of Gaussian cluster states, proposed as a universal resource for continuous variable (CV) quantum computing is presented in this paper. The central aim is to compare mathematically idealized cluster states defined using quadrature eigenstates, which have infinite squeezing and cannot exist in nature, with Gaussian approximations that are experimentally accessible. Adopting widely used definitions, we first review the key concepts, by analysing a process of teleportation along a CV quantum wire in the language of matrix product states. Next we consider the bipartite entanglement properties of the wire, providing analytic results. We proceed to grid cluster states, which are universal for the qubit case. To extend our analysis of the bipartite entanglement, we adopt the entropic-entanglement width, a specialized entanglement measure introduced recently by Van den Nest et al (2006 Phys. Rev. Lett. 97 150504), adapting their definition to the CV context. Finally, we consider the effects of photonic loss, extending our arguments to mixed states. Cumulatively our results point to key differences in the properties of idealized and Gaussian cluster states. Even modest loss rates are found to strongly limit the amount of entanglement. We discuss the implications for the potential of CV analogues for measurement-based quantum computation.

The black hole S-Matrix from quantum mechanics

NARCIS (Netherlands)

Betzios, Panagiotis; Gaddam, Nava; Papadoulaki, Olga

2016-01-01

We revisit the old black hole S-Matrix construction and its new partial wave expansion of 't Hooft. Inspired by old ideas from non-critical string theory \\& $c=1$ Matrix Quantum Mechanics, we reformulate the scattering in terms of a quantum mechanical model\\textemdash of waves scattering off

Finite-size modifications of the magnetic properties of clusters

DEFF Research Database (Denmark)

Hendriksen, Peter Vang; Linderoth, Søren; Lindgård, Per-Anker

1993-01-01

relative to the bulk, and the consequent neutron-scattering cross section exhibits discretely spaced wave-vector-broadened eigenstates. The implications of the finite size on thermodynamic properties, like the temperature dependence of the magnetization and the critical temperature, are also elucidated. We...... find the temperature dependence of the cluster magnetization to be well described by an effective power law, M(mean) is-proportional-to 1 - BT(alpha), with a size-dependent, but structure-independent, exponent larger than the bulk value. The critical temperature of the clusters is calculated from...... the spin-wave spectrum by a method based on the correlation theory and the spherical approximation generalized to the case of finite systems. A size-dependent reduction of the critical temperature by up to 50% for the smallest clusters is found. The trends found for the model clusters are extrapolated...

Born series for (2 cluster) → (2 cluster) scattering of two, three, and four particle Schroedinger operators

International Nuclear Information System (INIS)

Hagedorn, G.A.

1979-01-01

We investigate elastic and inelastic (2 cluster)→(2 cluster)scattering for classes of two, three, and four body Schroedinger operators H=H 0 +ΣVij. Formulas are derived for those generalized eigenfunctions of H which correspond asymptotically in the past to two freely moving clusters. With these eigenfunctions, we establish a formula for the (2 cluster)→(2 cluster) T-matrix and prove the convergence of a Born series for the T-matrix at high energy. (orig.) [de

Anisotropic properties of the enamel organic extracellular matrix.

Science.gov (United States)

do Espírito Santo, Alexandre R; Novaes, Pedro D; Line, Sérgio R P

2006-05-01

Enamel biosynthesis is initiated by the secretion, processing, and self-assembly of a complex mixture of proteins. This supramolecular ensemble controls the nucleation of the crystalline mineral phase. The detection of anisotropic properties by polarizing microscopy has been extensively used to detect macromolecular organizations in ordinary histological sections. The aim of this work was to study the birefringence of enamel organic matrix during the development of rat molar and incisor teeth. Incisor and molar teeth of rats were fixed in 2% paraformaldehyde/0.5% glutaraldehyde in 0.2 M phosphate-buffered saline (PBS), pH 7.2, and decalcified in 5% nitric acid/4% formaldehyde. After paraffin embedding, 5-microm-thick sections were obtained, treated with xylene, and hydrated. Form birefringence curves were obtained after measuring optical retardations in imbibing media, with different refractive indices. Our observations showed that enamel organic matrix of rat incisor and molar teeth is strongly birefringent, presenting an ordered supramolecular structure. The birefringence starts during the early secretion phase and disappears at the maturation phase. The analysis of enamel organic matrix birefringence may be used to detect the effects of genetic and environmental factors on the supramolecular orientation of enamel matrix and their effects on the structure of mature enamel.

Metal matrix composites. Part 1. Types, properties, applications

International Nuclear Information System (INIS)

Edil da Costa, C.; Velasco Lopez, F.; Torralba Castello, M.

2000-01-01

An overview on the state of the art of metal matrix composites used in the automotive and aerospace industries is made. These materials usually are based on light alloys (Al, Ti and Mg) and reinforced with fibres or particles. In this review, it is presented a general scope on the different MMCs families, about their properties and their main applications. (Author) 61 refs

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...

The use of Ixaru's method in locating the poles of the S-matrix in strictly finite-range potentials

Energy Technology Data Exchange (ETDEWEB)

Vertse, Tamas; Lovas, R. G.; Racz, A.; Salamon, P. [University of Debrecen, Faculty of Informatics, Chair of Applied Mathematics and Probability, Debrecen, Hungary and Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen (Hungary); Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen (Hungary); University of Debrecen, Faculty of Informatics, Chair of Applied Mathematics and Probability, Debrecen (Hungary); Institute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen (Hungary)

2012-09-26

Energies of the S-matrix poles are calculated by solving the radial Schroedinger equation numerically by using Ixaru's CPM(2) method. The trajectories of the poles in the complex wave number plane are determined for two nuclear potentials that are zero beyond finite distances. These are the Woods-Saxon form with cutoff and the Salamon-Vertse potential, which goes to zero smoothly at a finite distance. Properties of the trajectories are analyzed for real and complex values of the depths of the corresponding potentials.

Determination of Matrix Diffusion Properties of Granite

International Nuclear Information System (INIS)

Holtta, Pirkko; Siitari-Kauppi, Marja; Huittinen, Nina; Poteri, Antti

2007-01-01

Rock-core column experiments were introduced to estimate the diffusion and sorption properties of Kuru Grey granite used in block-scale experiments. The objective was to examine the processes causing retention in solute transport through rock fractures, especially matrix diffusion. The objective was also to estimate the importance of retention processes during transport in different scales and flow conditions. Rock-core columns were constructed from cores drilled into the fracture and were placed inside tubes to form flow channels in the 0.5 mm gap between the cores and the tube walls. Tracer experiments were performed using uranin, HTO, 36 Cl, 131 I, 22 Na and 85 Sr at flow rates of 1-50 μL.min -1 . Rock matrix was characterized using 14 C-PMMA method, scanning electron microscopy (SEM), energy dispersive X-ray micro analysis (EDX) and the B.E.T. method. Solute mass flux through a column was modelled by applying the assumption of a linear velocity profile and molecular diffusion. Coupling of the advection and diffusion processes was based on the model of generalised Taylor dispersion in the linear velocity profile. Experiments could be modelled applying a consistent parameterization and transport processes. The results provide evidence that it is possible to investigate matrix diffusion at the laboratory scale. The effects of matrix diffusion were demonstrated on the slightly-sorbing tracer breakthrough curves. Based on scoping calculations matrix diffusion begins to be clearly observable for non-sorbing tracer when the flow rate is 0.1 μL.min -1 . The experimental results presented here cannot be transferred directly to the spatial and temporal scales that prevail in an underground repository. However, the knowledge and understanding of transport and retention processes gained from this study is transferable to different scales from laboratory to in-situ conditions. (authors)

Clustering of near clusters versus cluster compactness

International Nuclear Information System (INIS)

Yu Gao; Yipeng Jing

1989-01-01

The clustering properties of near Zwicky clusters are studied by using the two-point angular correlation function. The angular correlation functions for compact and medium compact clusters, for open clusters, and for all near Zwicky clusters are estimated. The results show much stronger clustering for compact and medium compact clusters than for open clusters, and that open clusters have nearly the same clustering strength as galaxies. A detailed study of the compactness-dependence of correlation function strength is worth investigating. (author)

Transformations of the FeS Clusters of the Methylthiotransferases MiaB and RimO, Detected by Direct Electrochemistry

Science.gov (United States)

2016-01-01

The methylthiotransferases (MTTases) represent a subfamily of the S-adenosylmethionine (AdoMet) radical superfamily of enzymes that catalyze the attachment of a methylthioether (-SCH3) moiety on unactivated carbon centers. These enzymes contain two [4Fe-4S] clusters, one of which participates in the reductive fragmentation of AdoMet to generate a 5′-deoxyadenosyl 5′-radical and the other of which, termed the auxiliary cluster, is believed to play a central role in constructing the methylthio group and attaching it to the substrate. Because the redox properties of the bound cofactors within the AdoMet radical superfamily are so poorly understood, we have examined two MTTases in parallel, MiaB and RimO, using protein electrochemistry. We resolve the redox potentials of each [4Fe-4S] cluster, show that the auxiliary cluster has a potential higher than that of the AdoMet-binding cluster, and demonstrate that upon incubation of either enzyme with AdoMet, a unique low-potential state of the enzyme emerges. Our results are consistent with a mechanism whereby the auxiliary cluster is transiently methylated during substrate methylthiolation. PMID:27598886

Formation and vibrational structure of Si nano-clusters in ZnO matrix

Energy Technology Data Exchange (ETDEWEB)

Garcia-Serrano, J. [Universidad Autonoma del Estado de Hidalgo, Hidalgo (Mexico); Pal, U. [Universidad Autonoma de Puebla, Puebla (Mexico); Koshizaki, N.; Sasaki, T. [National Institute of Materials and Chemical Research, Ibaraki (Japan)

2001-02-01

We have studied the formation and vibrational structure of Si nano-clusters in ZnO matrix prepared by radio-frequency (r.f.) co-sputtering, and characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and Infrared (IR) spectroscopy techniques. The composite films of Si/ZnO were grown o quartz substrates by co-sputtering of Si and ZnO targets. TEM images show a homogeneous distribution of clusters in the matrix with average size varied from 3.7 nm to 34 nm depending on the temperature of annealing. IR absorption measurements revealed the bands correspond to the modes of vibrations of Si{sub 3} in its triangular geometrical structure. By analysing the IR absorption and XPS spectra we found that the nano-clusters consist of a Si{sub 3} core and a SiO{sub x} cap layer. With the increase of annealing temperature, the vibrational states of Si changed from the triplet {sup 3}B1(C2{sub v}) and {sup 3}A'{sub 2}(D{sub 3h}) states to its singlet ground state {sup 1}A{sub 1}(C2{sub v}) and the oxidation state of Si in SiO{sub x} increased. The evolution of the local atomic structure of the Si nano-clusters with the variation of Si content in the film and with the variation of the temperature of annealing are discussed. [Spanish] Se estudia la formacion y estructura vibracional de nano-cumulos de Si en matriz de ZnO preparados por la tecnica de radio-frecuencia (r.f.) co-sputtering, y caracterizados por Microscopia Electronica de Transmision (TEM), Espectroscopia Fotoelectronica de rayos X (XPS) y Espectroscopia de Infrarrojo (IR). Las peliculas compositas de Si/ZnO fueron crecidas sobre sustratos de cuarzo mediante el co-sputtering de blancos de Si y ZnO. Las imagenes de TEM mostraron una distribucion homogenea de cumulos en la matriz con un tamano promedio de 3.7 nm a 34 nm dependiendo de la temperatura de tratamiento. Las mediciones de IR relevaron las bandas correspondientes a los modos de vibracion de Si{sub 3} en su estructura

Structure, reactivity and electronic properties of Mn doped Ni13 clusters

International Nuclear Information System (INIS)

Banerjee, Radhashyam; Datta, Soumendu; Mookerjee, Abhijit

2013-01-01

In this work we have studied the structural and magnetic properties of Ni 13 cluster mono- and bi-doped with Mn atoms. We have noted their tendency of being reactive toward the H 2 molecule. We have found unusually enhanced stability in the mono-doped cluster (i.e. of the Ni 12 Mn) and the diminished stability of the corresponding chemisorbed cluster, Ni 12 MnH 2 . Our analysis of the stability and HOMO–LUMO gap explains this unusual behavior. Interestingly, we have also seen the quenching in the net magnetic moment upon H 2 absorption in the doped Ni 13−m Mn m alloy clusters. This has been reported earlier for smaller Ni n clusters [1

Structure, reactivity and electronic properties of Mn doped Ni13 clusters

Science.gov (United States)

Banerjee, Radhashyam; Datta, Soumendu; Mookerjee, Abhijit

2013-06-01

In this work we have studied the structural and magnetic properties of Ni13 cluster mono- and bi-doped with Mn atoms. We have noted their tendency of being reactive toward the H2 molecule. We have found unusually enhanced stability in the mono-doped cluster (i.e. of the Ni12Mn) and the diminished stability of the corresponding chemisorbed cluster, Ni12MnH2. Our analysis of the stability and HOMO-LUMO gap explains this unusual behavior. Interestingly, we have also seen the quenching in the net magnetic moment upon H2 absorption in the doped NiMnm alloy clusters. This has been reported earlier for smaller Nin clusters [1].

S-AMP: Approximate Message Passing for General Matrix Ensembles

DEFF Research Database (Denmark)

Cakmak, Burak; Winther, Ole; Fleury, Bernard H.

2014-01-01

the approximate message-passing (AMP) algorithm to general matrix ensembles with a well-defined large system size limit. The generalization is based on the S-transform (in free probability) of the spectrum of the measurement matrix. Furthermore, we show that the optimality of S-AMP follows directly from its......We propose a novel iterative estimation algorithm for linear observation models called S-AMP. The fixed points of S-AMP are the stationary points of the exact Gibbs free energy under a set of (first- and second-) moment consistency constraints in the large system limit. S-AMP extends...

Properties of Merger Shocks in Merging Galaxy Clusters

Science.gov (United States)

Ha, Ji-Hoon; Ryu, Dongsu; Kang, Hyesung

2018-04-01

X-ray shocks and radio relics detected in the cluster outskirts are commonly interpreted as shocks induced by mergers of subclumps. We study the properties of merger shocks in merging galaxy clusters, using a set of cosmological simulations for the large-scale structure formation of the universe. As a representative case, we focus on the simulated clusters that undergo almost head-on collisions with mass ratio ∼2. Due to the turbulent nature of the intracluster medium, shock surfaces are not smooth, but composed of shocks with different Mach numbers. As the merger shocks expand outward from the core to the outskirts, the average Mach number, , increases in time. We suggest that the shocks propagating along the merger axis could be manifested as X-ray shocks and/or radio relics. The kinetic energy through the shocks, F ϕ , peaks at ∼1 Gyr after their initial launching, or at ∼1–2 Mpc from the core. Because of the Mach number dependent model adopted here for the cosmic-ray (CR) acceleration efficiency, their CR-energy-weighted Mach number is higher with }CR}∼ 3{--}4, compared to the kinetic-energy-weighted Mach number, }φ ∼ 2{--}3. Most energetic shocks are to be found ahead of the lighter dark matter (DM) clump, while the heavier DM clump is located on the opposite side of clusters. Although our study is limited to the merger case considered, the results such as the means and variations of shock properties and their time evolution could be compared with the observed characteristics of merger shocks, constraining interpretations of relevant observations.

Effect of mitochondrial complex I inhibition on Fe-S cluster protein activity

Energy Technology Data Exchange (ETDEWEB)

Mena, Natalia P. [Department of Biology, Faculty of Sciences, Universidad de Chile, Las Palmeras 3425, Santiago (Chile); Millennium Institute of Cell Dynamics and Biotechnology, Santiago (Chile); Bulteau, Anne Laure [UPMC Univ Paris 06, UMRS 975 - UMR 7725, Centre de Recherche en Neurosciences, ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, F-75005 Paris (France); Inserm, U 975, Centre de Recherche en Neurosciences, ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, F-75005 Paris (France); CNRS, UMR 7225, Centre de Recherche en Neurosciences, ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, F-75005 Paris (France); ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, Paris 75013 (France); Salazar, Julio [Millennium Institute of Cell Dynamics and Biotechnology, Santiago (Chile); Hirsch, Etienne C. [UPMC Univ Paris 06, UMRS 975 - UMR 7725, Centre de Recherche en Neurosciences, ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, F-75005 Paris (France); Inserm, U 975, Centre de Recherche en Neurosciences, ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, F-75005 Paris (France); CNRS, UMR 7225, Centre de Recherche en Neurosciences, ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, F-75005 Paris (France); ICM, Therapeutique Experimentale de la Neurodegenerescence, Hopital de la Salpetriere, Paris 75013 (France); Nunez, Marco T., E-mail: mnunez@uchile.cl [Department of Biology, Faculty of Sciences, Universidad de Chile, Las Palmeras 3425, Santiago (Chile); Millennium Institute of Cell Dynamics and Biotechnology, Santiago (Chile)

2011-06-03

Highlights: {yields} Mitochondrial complex I inhibition resulted in decreased activity of Fe-S containing enzymes mitochondrial aconitase and cytoplasmic aconitase and xanthine oxidase. {yields} Complex I inhibition resulted in the loss of Fe-S clusters in cytoplasmic aconitase and of glutamine phosphoribosyl pyrophosphate amidotransferase. {yields} Consistent with loss of cytoplasmic aconitase activity, an increase in iron regulatory protein 1 activity was found. {yields} Complex I inhibition resulted in an increase in the labile cytoplasmic iron pool. -- Abstract: Iron-sulfur (Fe-S) clusters are small inorganic cofactors formed by tetrahedral coordination of iron atoms with sulfur groups. Present in numerous proteins, these clusters are involved in key biological processes such as electron transfer, metabolic and regulatory processes, DNA synthesis and repair and protein structure stabilization. Fe-S clusters are synthesized mainly in the mitochondrion, where they are directly incorporated into mitochondrial Fe-S cluster-containing proteins or exported for cytoplasmic and nuclear cluster-protein assembly. In this study, we tested the hypothesis that inhibition of mitochondrial complex I by rotenone decreases Fe-S cluster synthesis and cluster content and activity of Fe-S cluster-containing enzymes. Inhibition of complex I resulted in decreased activity of three Fe-S cluster-containing enzymes: mitochondrial and cytosolic aconitases and xanthine oxidase. In addition, the Fe-S cluster content of glutamine phosphoribosyl pyrophosphate amidotransferase and mitochondrial aconitase was dramatically decreased. The reduction in cytosolic aconitase activity was associated with an increase in iron regulatory protein (IRP) mRNA binding activity and with an increase in the cytoplasmic labile iron pool. Since IRP activity post-transcriptionally regulates the expression of iron import proteins, Fe-S cluster inhibition may result in a false iron deficiency signal. Given that

Statistical Properties of Kawai-Kerman-McVoy T-matrix

International Nuclear Information System (INIS)

Arbanas, Goran; Bertulani, Carlos A.; Dean, David Jarvis; Kerman, Arthur K.

2008-01-01

Kawai, Kerman and McVoy (KKM) derived an optical background-plus-fluctuations representation of T-matrix, T = T opt + T fluct , so that an energy average of T fluct over a single-particle resonance width is expected to be negligibly small (Ann. of Phys. 75, 156 (1973)). We investigate this property numerically in a simple model with 1,600 compound nuclear levels and 40 channels, coupled via a random interaction. We find that the energy average of the fluctuating term is much smaller than the optical background, T opt , in support of the KKM result. A self-contained derivation of KKM T-matrix is presented.

Rates of proton transfer to Fe-S-based clusters: comparison of clusters containing {MFe(mu(2)-S)(2)}n+ and {MFe(3)(mu(3)-S)(4)}n+ (M = Fe, Mo, or W) cores.

Science.gov (United States)

Bates, Katie; Garrett, Brendan; Henderson, Richard A

2007-12-24

The rates of proton transfer from [pyrH]+ (pyr = pyrrolidine) to the binuclear complexes [Fe2S2Cl4]2- and [S2MS2FeCl2]2- (M = Mo or W) are reported. The reactions were studied using stopped-flow spectrophotometry, and the rate constants for proton transfer were determined from analysis of the kinetics of the substitution reactions of these clusters with the nucleophiles Br- or PhS- in the presence of [pyrH]+. In general, Br- is a poor nucleophile for these clusters, and proton transfer occurs before Br- binds, allowing direct measure of the rate of proton transfer from [pyrH]+ to the cluster. In contrast, PhS- is a better nucleophile, and a pathway in which PhS- binds preferentially to the cluster prior to proton transfer from [pyrH]+ usually operates. For the reaction of [Fe2S2Cl4]2- with PhS- in the presence of [pyrH]+ both pathways are observed. Comparison of the results presented in this paper with analogous studies reported earlier on cuboidal Fe-S-based clusters allows discussion of the factors which affect the rates of proton transfer in synthetic clusters including the nuclearity of the cluster core, the metal composition, and the nature of the terminal ligands. The possible relevance of these findings to the protonation sites of natural Fe-S-based clusters, including FeMo-cofactor from nitrogenase, are presented.

Effect of mitochondrial complex I inhibition on Fe-S cluster protein activity

International Nuclear Information System (INIS)

Mena, Natalia P.; Bulteau, Anne Laure; Salazar, Julio; Hirsch, Etienne C.; Nunez, Marco T.

2011-01-01

Highlights: → Mitochondrial complex I inhibition resulted in decreased activity of Fe-S containing enzymes mitochondrial aconitase and cytoplasmic aconitase and xanthine oxidase. → Complex I inhibition resulted in the loss of Fe-S clusters in cytoplasmic aconitase and of glutamine phosphoribosyl pyrophosphate amidotransferase. → Consistent with loss of cytoplasmic aconitase activity, an increase in iron regulatory protein 1 activity was found. → Complex I inhibition resulted in an increase in the labile cytoplasmic iron pool. -- Abstract: Iron-sulfur (Fe-S) clusters are small inorganic cofactors formed by tetrahedral coordination of iron atoms with sulfur groups. Present in numerous proteins, these clusters are involved in key biological processes such as electron transfer, metabolic and regulatory processes, DNA synthesis and repair and protein structure stabilization. Fe-S clusters are synthesized mainly in the mitochondrion, where they are directly incorporated into mitochondrial Fe-S cluster-containing proteins or exported for cytoplasmic and nuclear cluster-protein assembly. In this study, we tested the hypothesis that inhibition of mitochondrial complex I by rotenone decreases Fe-S cluster synthesis and cluster content and activity of Fe-S cluster-containing enzymes. Inhibition of complex I resulted in decreased activity of three Fe-S cluster-containing enzymes: mitochondrial and cytosolic aconitases and xanthine oxidase. In addition, the Fe-S cluster content of glutamine phosphoribosyl pyrophosphate amidotransferase and mitochondrial aconitase was dramatically decreased. The reduction in cytosolic aconitase activity was associated with an increase in iron regulatory protein (IRP) mRNA binding activity and with an increase in the cytoplasmic labile iron pool. Since IRP activity post-transcriptionally regulates the expression of iron import proteins, Fe-S cluster inhibition may result in a false iron deficiency signal. Given that inhibition of complex

Structural, electronic and magnetic properties of small bimetallic zirconium–palladium clusters: Ab initio study

International Nuclear Information System (INIS)

Bezi Javan, Masoud

2015-01-01

Highlights: • Electronic and magnetic properties of small Zr n Pd m (n + m ⩽ 5) have been investigated. • Binding energies of the Zr n clusters are significantly higher than Pd n clusters. • Binding energy of the Pd n clusters increase with substituting one or more Zr atom. • HOMO–LUMO gap of the Zr n Pd m clusters increase in comparison with pure states. - Abstract: Structural, electronic and magnetic properties of small bimetallic zirconium–palladium clusters, Zr n Pd m (n + m ⩽ 5), have been investigated using density functional theory with considering generalized gradient approximation and PBE functional. We have determined the ground state conformations of the bimetallic zirconium–palladium clusters by substitution of Zr and Pd atoms in the optimized lowest energy structures of pure zirconium and palladium clusters. Results reveal that binding energies of the pure Zr n clusters are significantly higher than Pd n clusters with the same number of atoms. Also it is found that binding energy of the Zr n and Pd n clusters increase with growth of the number of consisting atoms in the clusters. Results indicate that, for both Zr n and Pd n clusters the binding energy of planar forms is lower than three-dimensional structures. We have also found that the binding energy of the Pd n clusters increase with substituting one or more Zr atoms in these clusters. We have also studied the HOMO–LUMO energy gap and magnetic moment of the pure and combined Zr and Pd clusters. The energy gap analysis of the pure and combined Pd and Zr clusters show that in generally the HOMO–LUMO gap of the bimetallic Zr n Pd m clusters increase in comparison with their corresponding pure clusters with the same number of atoms. According to the spin polarization DFT calculations all of the Zr n Pd m (n + m ⩽ 5) have net magnetic moments as instance the Zr 2 , Pd 2 and ZrPd clusters show a total magnetic moment value of 2 μ B . Some more discussions around charge population

Investigation into Korean EFL Learners’ Acquisition of English /s/ + Consonant Onset Clusters

Directory of Open Access Journals (Sweden)

Jungyoun Choi

2016-04-01

Full Text Available This paper investigated the phonological acquisition of English /s/ + consonant onset clusters by Korean learners of English as a Foreign Language (EFL who varied in their levels of proficiency. The data were collected from twenty eighth-graders in a Korean secondary school, who were divided into two groups according to their proficiency: low- and high-achievement. The major findings were: 1 the high-achievement group did not use a vowel epenthesis strategy in the articulation of the /s/ + consonant onset cluster, unlike the low-achievement group; 2 the duration of /s/ pronunciation was longer in the high-achievement group, as follows: /s/ + stop + liquid, /s/ + stop, /s/ + liquid; 3 the low-achievement group’s duration of oral closure was longer than was that of the high-achievement group, as follows: /s/ + stop + liquid, s/ + stop, and 4 with regard to how /s/ + consonant onset clusters are perceived by native English speakers, /s/ + stop + liquid was related more significantly to the learners’ level of proficiency than were the biliteral consonant onset clusters. Among biliteral onsets, /s/ + stop and /s/ + liquid clusters differed significantly between the groups, while the /s/ + nasal cluster did not. Keywords: English /s/ + consonant onset clusters, L1 transfer, the sonority sequencing principle, syllable structure, L2 phonological acquisition

The impact of yeast fermentation on dough matrix properties.

Science.gov (United States)

Rezaei, Mohammad N; Jayaram, Vinay B; Verstrepen, Kevin J; Courtin, Christophe M

2016-08-01

Most studies on dough properties are performed on yeastless dough to exclude the complicating, time-dependent effect of yeast. Baker's yeast, however, impacts dough matrix properties during fermentation, probably through the production of primary (CO2 and ethanol) and secondary (glycerol, acetic acid and succinic acid) metabolites. The aim of this study is to obtain a better understanding of the changes in yeasted dough behavior introduced by fermentation, by investigating the impact of yeast fermentation on Farinograph dough consistency, dough spread, Kieffer rig dough extensibility and gluten agglomeration behavior in a fermented dough-batter gluten starch separation system. Results show that fermentation leads to a dough with less flow and lower extensibility that breaks more easily under stress and strain. The dough showed less elastic and more plastic deformation behavior. Gluten agglomerates were smaller for yeasted dough than for the unyeasted control. These changes probably have to be attributed to metabolites generated during fermentation. Indeed, organic acids and also ethanol in concentrations produced by yeast were previously shown to have similar effects in yeastless dough. These findings imply the high importance of yeast fermentation metabolites on dough matrix properties in industrial bread production. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

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.

Properties and origin of the old, metal rich, star cluster, NGC 6791

OpenAIRE

Carraro, Giovanni

2013-01-01

In this contribution I summarize the unique properties of the old, metal rich, star cluster NGC 6791, with particular emphasis on its population of extreme blue horizontal branch stars. I then conclude providing my personal view on the origin of this fascinating star cluster.

Reactive fillers based on SWCNTs functionalized with matrix-based moieties for the production of epoxy composites with superior and tunable properties

International Nuclear Information System (INIS)

González-Domínguez, Jose M; Ansón-Casaos, A; Martínez, M Teresa; Martínez-Rubí, Yadienka; Simard, Benoit; Díez-Pascual, Ana M; Gómez-Fatou, Marian

2012-01-01

Composite materials based on epoxy matrix and single-walled carbon nanotubes (SWCNTs) are able to exhibit outstanding improvements in physical properties when using a tailored covalent functionalization with matrix-based moieties containing terminal amines or epoxide rings. The proper choice of grafted moiety and integration protocol makes it feasible to tune the composite physical properties. At 0.5 wt% SWCNT loading, these composites exhibit up to 65% improvement in storage modulus, 91% improvement in tensile strength, and 65% improvement in toughness. A 15 °C increase in the glass transition temperature relative to the parent matrix was also achieved. This suggests that a highly improved interfacial bonding between matrix and filler, coupled to improved dispersion, are achieved. The degradation temperatures show an upshift in the range of 40–60 °C, which indicates superior thermal performance. Electrical conductivity ranges from ∼10 −13 to ∼10 −3 S cm −1 , which also shows the possibility of tuning the insulating or conductive behaviour of the composites. The chemical affinity of the functionalization moieties with the matrix and the unchanged molecular structure at the SWCNT/matrix interface are responsible for such improvements. (paper)

Investigation of Electrochemical and Morphological Properties of Mixed Matrix Polysulfone-Silica Anion Exchange Membrane

Directory of Open Access Journals (Sweden)

Khoiruddin

2016-02-01

Full Text Available Mixed matrix anion exchange membranes (AEMs were synthesized using dry-wet phase inversion. The casting solutions were prepared by dispersing finely ground anion-exchange resin particles in N,N-dimethylacetamide (DMAc solutions of polysulfone (PSf. Subsequently, nanosilica particles were introduced into the membranes. The results show that evaporation time (tev and solution composition contributed to membrane properties formation. A longer tev produces membranes with reduced void fraction inside the membranes, thus the amount of water adsorbed and membrane conductivity are reduced. Meanwhile, the permselectivity was improved by increasing tev, since a longer tev produces membranes with a narrower channel for ion migration and more effective Donnan exclusion. The incorporation of 0.5 %-wt nanosilica particles into the polymer matrix led to conductivity improvement (from 2.27 to 3.41 mS.cm-1. This may be associated with additional pathway formation by hydroxyl groups on the silica surface that entraps water and assists ion migration. However, at further silica loading (1.0 and 1.5 %-wt, these properties decreased (to 1.9 and 1.4 mS.cm-1 respectively, which attributed to inaccessibility of ion-exchange functional groups due to membrane compactness. It was found from the results that nanosilica contributes to membrane formation (increases casting solution viscosity then reduces void fraction and membrane functional group addition (provides hydroxyl groups.

Formation, spectroscopic characterization, and solution stability of an [Fe4S4]2+ cluster derived from β-cyclodextrin dithiolate.

Science.gov (United States)

Lo, Wayne; Zhang, Ping; Ling, Chang-Chun; Huang, Shaw; Holm, R H

2012-09-17

The formation and solution properties, including stability in mixed aqueous-Me(2)SO media, have been investigated for an [Fe(4)S(4)](2+) cluster derived from β-cyclodextrin (CD) dithiolate. Clusters of the type [Fe(4)S(4)(SAr)(4)](2-) (Ar = Ph, C(6)H(4)-3-F) are generated in Me(2)SO by redox reactions of [Fe(4)S(4)(SEt)(4)](2-) with 2 equiv of ArSSAr. An analogous reaction with the intramolecular disulfide of 6(A),6(D)-(3-NHCOC(6)H(4)-1-SH)(2)-6(A),6(D)-dideoxy-β-cyclodextrin (14), whose synthesis is described, affords a completely substituted cluster formulated as [Fe(4)S(4){β-CD-(1,3-NHCOC(6)H(4)S)(2)}(2)](2-) (15). Ligand binding is indicated by a circular dichroism spectrum and also by UV-visible and isotropically shifted (1)H NMR spectra and redox behavior convincingly similar to [Fe(4)S(4)(SPh)(4)](2-). One formulation of 15 is a single cluster to which two dithiolates are bound, each in bidentate coordination. With there being no proven precedent for this binding mode, we show that the cluster [Fe(4)S(4)(S(2)-m-xyl)(2)](2-) is a single cubane whose m-xylyldithiolate ligands are bound in a bidentate arrangement. This same structure type was proposed for a cluster formulated as [Fe(4)S(4){β-CD-(1,3-SC(6)H(4)S)(2)}(2)](2-) (16; Kuroda et al. J. Am. Chem. Soc.1988, 110, 4049-4050) and reported to be water-stable. Clusters 15 and 16 are derived from similar ligands differing only in the spacer group between the thiolate binding site and the CD platform. In our search for clusters stable in aqueous or organic-aqueous mixed solvents that are potential candidates for the reconstitution of scaffold proteins implicated in cluster biogenesis, 15 is the most stable cluster that we have thus far encountered under anaerobic conditions in the absence of added ligand.

Robustness of cluster synchronous patterns in small-world networks with inter-cluster co-competition balance

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jianbao [School of Science, Hangzhou Dianzi University, Hangzhou 310018 (China); Ma, Zhongjun, E-mail: mzj1234402@163.com [School of Mathematics and Computing Science, Guilin University of Electronic Technology, Guilin 541004 (China); Chen, Guanrong [Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong (China)

2014-06-15

All edges in the classical Watts and Strogatz's small-world network model are unweighted and cooperative (positive). By introducing competitive (negative) inter-cluster edges and assigning edge weights to mimic more realistic networks, this paper develops a modified model which possesses co-competitive weighted couplings and cluster structures while maintaining the common small-world network properties of small average shortest path lengths and large clustering coefficients. Based on theoretical analysis, it is proved that the new model with inter-cluster co-competition balance has an important dynamical property of robust cluster synchronous pattern formation. More precisely, clusters will neither merge nor split regardless of adding or deleting nodes and edges, under the condition of inter-cluster co-competition balance. Numerical simulations demonstrate the robustness of the model against the increase of the coupling strength and several topological variations.

Direct integration of the S-matrix applied to rigorous diffraction

International Nuclear Information System (INIS)

Iff, W; Lindlein, N; Tishchenko, A V

2014-01-01

A novel Fourier method for rigorous diffraction computation at periodic structures is presented. The procedure is based on a differential equation for the S-matrix, which allows direct integration of the S-matrix blocks. This results in a new method in Fourier space, which can be considered as a numerically stable and well-parallelizable alternative to the conventional differential method based on T-matrix integration and subsequent conversions from the T-matrices to S-matrix blocks. Integration of the novel differential equation in implicit manner is expounded. The applicability of the new method is shown on the basis of 1D periodic structures. It is clear however, that the new technique can also be applied to arbitrary 2D periodic or periodized structures. The complexity of the new method is O(N 3 ) similar to the conventional differential method with N being the number of diffraction orders. (fast track communication)

Star formation properties of galaxy cluster A1767

International Nuclear Information System (INIS)

Yan, Peng-Fei; Li, Feng; Yuan, Qi-Rong

2015-01-01

Abell 1767 is a dynamically relaxed, cD cluster of galaxies with a redshift of 0.0703. Among 250 spectroscopically confirmed member galaxies within a projected radius of 2.5r 200 , 243 galaxies (∼ 97%) are spectroscopically covered by the Sloan Digital Sky Survey. Based on this homogeneous spectral sample, the stellar evolutionary synthesis code STARLIGHT is applied to investigate the stellar populations and star formation histories of galaxies in this cluster. The star formation properties of galaxies, such as mean stellar ages, metallicities, stellar masses, and star formation rates, are presented as functions of local galaxy density. A strong environmental effect is found such that massive galaxies in the high-density core region of the cluster tend to have higher metallicities, older mean stellar ages, and lower specific star formation rates (SSFRs), and their recent star formation activities have been remarkably suppressed. In addition, the correlations of the metallicity and SSFR with stellar mass are confirmed. (paper)

X-RAY DETECTION OF THE CLUSTER CONTAINING THE CEPHEID S MUS

Energy Technology Data Exchange (ETDEWEB)

Evans, Nancy Remage; Pillitteri, Ignazio; Wolk, Scott; Karovska, Margarita; DePasquale, Joseph; Tingle, Evan [Smithsonian Astrophysical Observatory, MS 4, 60 Garden Street, Cambridge, MA 02138 (United States); Guinan, Edward; Engle, Scott [Department of Astronomy and Astrophysics, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085 (United States); Bond, Howard E. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Schaefer, Gail H., E-mail: nevans@cfa.harvard.edu [The CHARA Array of Georgia State University, Mount Wilson, CA 91023 (United States)

2014-04-20

The galactic Cepheid S Muscae has recently been added to the important list of Cepheids linked to open clusters, in this case the sparse young cluster ASCC 69. Low-mass members of a young cluster are expected to have rapid rotation and X-ray activity, making X-ray emission an excellent way to discriminate them from old field stars. We have made an XMM-Newton observation centered on S Mus and identified a population of X-ray sources whose near-IR Two Micron All Sky Survey counterparts lie at locations in the J, (J – K) color-magnitude diagram consistent with cluster membership at the distance of S Mus. Their median energy and X-ray luminosity are consistent with young cluster members as distinct from field stars. These strengthen the association of S Mus with the young cluster, making it a potential Leavitt law (period-luminosity relation) calibrator.

X-Ray Detection of the Cluster Containing the Cepheid S Mus

Science.gov (United States)

Evans, Nancy Remage; Pillitteri, Ignazio; Wolk, Scott; Guinan, Edward; Engle, Scott; Bond, Howard E.; Schaefer, Gail H.; Karovska, Margarita; DePasquale, Joseph; Tingle, Evan

2014-04-01

The galactic Cepheid S Muscae has recently been added to the important list of Cepheids linked to open clusters, in this case the sparse young cluster ASCC 69. Low-mass members of a young cluster are expected to have rapid rotation and X-ray activity, making X-ray emission an excellent way to discriminate them from old field stars. We have made an XMM-Newton observation centered on S Mus and identified a population of X-ray sources whose near-IR Two Micron All Sky Survey counterparts lie at locations in the J, (J - K) color-magnitude diagram consistent with cluster membership at the distance of S Mus. Their median energy and X-ray luminosity are consistent with young cluster members as distinct from field stars. These strengthen the association of S Mus with the young cluster, making it a potential Leavitt law (period-luminosity relation) calibrator.

X-RAY DETECTION OF THE CLUSTER CONTAINING THE CEPHEID S MUS

International Nuclear Information System (INIS)

Evans, Nancy Remage; Pillitteri, Ignazio; Wolk, Scott; Karovska, Margarita; DePasquale, Joseph; Tingle, Evan; Guinan, Edward; Engle, Scott; Bond, Howard E.; Schaefer, Gail H.

2014-01-01

The galactic Cepheid S Muscae has recently been added to the important list of Cepheids linked to open clusters, in this case the sparse young cluster ASCC 69. Low-mass members of a young cluster are expected to have rapid rotation and X-ray activity, making X-ray emission an excellent way to discriminate them from old field stars. We have made an XMM-Newton observation centered on S Mus and identified a population of X-ray sources whose near-IR Two Micron All Sky Survey counterparts lie at locations in the J, (J – K) color-magnitude diagram consistent with cluster membership at the distance of S Mus. Their median energy and X-ray luminosity are consistent with young cluster members as distinct from field stars. These strengthen the association of S Mus with the young cluster, making it a potential Leavitt law (period-luminosity relation) calibrator

Symplectic Maps from Cluster Algebras

Directory of Open Access Journals (Sweden)

Allan P. Fordy

2011-09-01

Full Text Available We consider nonlinear recurrences generated from the iteration of maps that arise from cluster algebras. More precisely, starting from a skew-symmetric integer matrix, or its corresponding quiver, one can define a set of mutation operations, as well as a set of associated cluster mutations that are applied to a set of affine coordinates (the cluster variables. Fordy and Marsh recently provided a complete classification of all such quivers that have a certain periodicity property under sequences of mutations. This periodicity implies that a suitable sequence of cluster mutations is precisely equivalent to iteration of a nonlinear recurrence relation. Here we explain briefly how to introduce a symplectic structure in this setting, which is preserved by a corresponding birational map (possibly on a space of lower dimension. We give examples of both integrable and non-integrable maps that arise from this construction. We use algebraic entropy as an approach to classifying integrable cases. The degrees of the iterates satisfy a tropical version of the map.

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.

Analysis of X-ray structures of matrix metalloproteinases via chaotic map clustering.

Science.gov (United States)

Giangreco, Ilenia; Nicolotti, Orazio; Carotti, Angelo; De Carlo, Francesco; Gargano, Gianfranco; Bellotti, Roberto

2010-10-08

Matrix metalloproteinases (MMPs) are well-known biological targets implicated in tumour progression, homeostatic regulation, innate immunity, impaired delivery of pro-apoptotic ligands, and the release and cleavage of cell-surface receptors. With this in mind, the perception of the intimate relationships among diverse MMPs could be a solid basis for accelerated learning in designing new selective MMP inhibitors. In this regard, decrypting the latent molecular reasons in order to elucidate similarity among MMPs is a key challenge. We describe a pairwise variant of the non-parametric chaotic map clustering (CMC) algorithm and its application to 104 X-ray MMP structures. In this analysis electrostatic potentials are computed and used as input for the CMC algorithm. It was shown that differences between proteins reflect genuine variation of their electrostatic potentials. In addition, the analysis has been also extended to analyze the protein primary structures and the molecular shapes of the MMP co-crystallised ligands. The CMC algorithm was shown to be a valuable tool in knowledge acquisition and transfer from MMP structures. Based on the variation of electrostatic potentials, CMC was successful in analysing the MMP target family landscape and different subsites. The first investigation resulted in rational figure interpretation of both domain organization as well as of substrate specificity classifications. The second made it possible to distinguish the MMP classes, demonstrating the high specificity of the S1' pocket, to detect both the occurrence of punctual mutations of ionisable residues and different side-chain conformations that likely account for induced-fit phenomena. In addition, CMC demonstrated a potential comparable to the most popular UPGMA (Unweighted Pair Group Method with Arithmetic mean) method that, at present, represents a standard clustering bioinformatics approach. Interestingly, CMC and UPGMA resulted in closely comparable outcomes, but often

Effects of substrate temperature on structural and electrical properties of SiO2-matrix boron-doped silicon nanocrystal thin films

International Nuclear Information System (INIS)

Huang, Junjun; Zeng, Yuheng; Tan, Ruiqin; Wang, Weiyan; Yang, Ye; Dai, Ning; Song, Weijie

2013-01-01

In this work, silicon-rich SiO 2 (SRSO) thin films were deposited at different substrate temperatures (T s ) and then annealed by rapid thermal annealing to form SiO 2 -matrix boron-doped silicon-nanocrystals (Si-NCs). The effects of T s on the micro-structure and electrical properties of the SiO 2 -matrix boron-doped Si-NC thin films were investigated using Raman spectroscopy and Hall measurements. Results showed that the crystalline fraction and dark conductivity of the SiO 2 -matrix boron-doped Si-NC thin films both increased significantly when the T s was increased from room temperature to 373 K. When the T s was further increased from 373 K to 676 K, the crystalline fraction of 1373 K-annealed thin films decreased from 52.2% to 38.1%, and the dark conductivity reduced from 8 × 10 −3 S/cm to 5.5 × 10 −5 S/cm. The changes in micro-structure and dark conductivity of the SiO 2 -matrix boron-doped Si-NC thin films were most possibly due to the different amount of Si-O 4 bond in the as-deposited SRSO thin films. Our work indicated that there was an optimal T s , which could significantly increase the crystallization and conductivity of Si-NC thin films. Also, it was illumined that the low-resistivity SiO 2 -matrix boron-doped Si-NC thin films can be achieved under the optimal substrate temperatures, T s .

Evaluation of Mechanical Properties of Nonsteroidal Anti-Inflammatory Matrix Type Transdermal Therapeutic Systems

Directory of Open Access Journals (Sweden)

Antonoaea Paula

2017-06-01

Full Text Available Objective: Transdermal therapeutic systems (TTSs represent an intensely studied alternative to oral delivery of non-steroid anti-inflammatory drugs (NSAIDs in the treatment of rheumatic diseases due to its ability of avoiding the side effects of the oral route. This study aims to present the evaluation of the mechanical properties of three NSAIDs (meloxicam, tenoxicam and indomethacin individually included in four type of polymeric matrixes, as part of new formulations development process. Methods: 12 products in form of TTS matrixes were prepared by solvent casting evaporation technique, using hydroxypropyl methylcellulose (HPMC 15000, HPMC E5 and/or ethylcellulose as matrix-forming polymers. Each of the resulted products was evaluated by determining the water vapor absorption, desorption or transmission in controlled atmosphere humidity (evaluation of porosity; the elongation capacity, tensile strength and bioadhesiveness (evaluation of mechanical properties. Results: The analysis of three groups of the experimental data expressed as averages on each group was necessary, in order to identify the parameters which statistically are critically influenced by the ingredients associated in the TTSs matrix compositions. Analysis by normality tests, variance and correlation tests (Anova, Pearson enabled evaluation of the effect of NSAID type vs. the effect of polymer matrix type on the parameters of the NSAID TTS matrix. Conclusions: Meloxicam incorporated in the structure of HPMC 15000 polymeric matrix favors its viscoelastic structure. Ethylcellulose functions as plasticizer and supports the matrix bioadhesiveness. HPMC E5 does not meet the requirements for TTS preparation in the used experimental conditions.

First principles prediction of the magnetic properties of Fe-X6 (X = S, C, N, O, F) doped monolayer MoS2

KAUST Repository

Feng, Nan; Mi, Wenbo; Cheng, Yingchun; Guo, Zaibing; Schwingenschlö gl, Udo; Bai, Haili

2014-01-01

Using first-principles calculations, we have investigated the electronic structure and magnetic properties of Fe-X 6 clusters (X = S, C, N, O, and F) incorporated in 4 4 monolayer MoS 2, where a Mo atom is substituted by Fe and its nearest S atoms are substituted by C, N, O, and F. Single Fe and Fe-F 6 substituions make the system display half-metallic properties, Fe-C 6 and Fe-N 6 substitutions lead to a spin gapless semiconducting behavior, and Fe-O 6 doped monolayer MoS 2 is semiconducting. Magnetic moments of 1.93, 1.45, 3.18, 2.08, and 2.21...? B are obtained for X = S, C, N, O, and F, respectively. The different electronic and magnetic characters originate from hybridization between the X and Fe/Mo atoms. Our results suggest that cluster doping can be an efficient strategy for exploring two-dimensional diluted magnetic semiconductors.

First principles prediction of the magnetic properties of Fe-X6 (X = S, C, N, O, F) doped monolayer MoS2

KAUST Repository

Feng, Nan

2014-02-05

Using first-principles calculations, we have investigated the electronic structure and magnetic properties of Fe-X 6 clusters (X = S, C, N, O, and F) incorporated in 4 4 monolayer MoS 2, where a Mo atom is substituted by Fe and its nearest S atoms are substituted by C, N, O, and F. Single Fe and Fe-F 6 substituions make the system display half-metallic properties, Fe-C 6 and Fe-N 6 substitutions lead to a spin gapless semiconducting behavior, and Fe-O 6 doped monolayer MoS 2 is semiconducting. Magnetic moments of 1.93, 1.45, 3.18, 2.08, and 2.21...? B are obtained for X = S, C, N, O, and F, respectively. The different electronic and magnetic characters originate from hybridization between the X and Fe/Mo atoms. Our results suggest that cluster doping can be an efficient strategy for exploring two-dimensional diluted magnetic semiconductors.

MANOVA, LDA, and FA criteria in clusters parameter estimation

Directory of Open Access Journals (Sweden)

Stan Lipovetsky

2015-12-01

Full Text Available Multivariate analysis of variance (MANOVA and linear discriminant analysis (LDA apply such well-known criteria as the Wilks’ lambda, Lawley–Hotelling trace, and Pillai’s trace test for checking quality of the solutions. The current paper suggests using these criteria for building objectives for finding clusters parameters because optimizing such objectives corresponds to the best distinguishing between the clusters. Relation to Joreskog’s classification for factor analysis (FA techniques is also considered. The problem can be reduced to the multinomial parameterization, and solution can be found in a nonlinear optimization procedure which yields the estimates for the cluster centers and sizes. This approach for clustering works with data compressed into covariance matrix so can be especially useful for big data.

The E. coli monothiol glutaredoxin GrxD forms homodimeric and heterodimeric FeS cluster containing complexes.

Science.gov (United States)

Yeung, N; Gold, B; Liu, N L; Prathapam, R; Sterling, H J; Willams, E R; Butland, G

2011-10-18

Monothiol glutaredoxins (mono-Grx) represent a highly evolutionarily conserved class of proteins present in organisms ranging from prokaryotes to humans. Mono-Grxs have been implicated in iron sulfur (FeS) cluster biosynthesis as potential scaffold proteins and in iron homeostasis via an FeS-containing complex with Fra2p (homologue of E. coli BolA) in yeast and are linked to signal transduction in mammalian systems. However, the function of the mono-Grx in prokaryotes and the nature of an interaction with BolA-like proteins have not been established. Recent genome-wide screens for E. coli genetic interactions reported the synthetic lethality (combination of mutations leading to cell death; mutation of only one of these genes does not) of a grxD mutation when combined with strains defective in FeS cluster biosynthesis (isc operon) functions [Butland, G., et al. (2008) Nature Methods 5, 789-795]. These data connected the only E. coli mono-Grx, GrxD to a potential role in FeS cluster biosynthesis. We investigated GrxD to uncover the molecular basis of this synthetic lethality and observed that GrxD can form FeS-bound homodimeric and BolA containing heterodimeric complexes. These complexes display substantially different spectroscopic and functional properties, including the ability to act as scaffold proteins for intact FeS cluster transfer to the model [2Fe-2S] acceptor protein E. coli apo-ferredoxin (Fdx), with the homodimer being significantly more efficient. In this work, we functionally dissect the potential cellular roles of GrxD as a component of both homodimeric and heterodimeric complexes to ultimately uncover if either of these complexes performs functions linked to FeS cluster biosynthesis. © 2011 American Chemical Society

Weighted similarity-based clustering of chemical structures and bioactivity data in early drug discovery.

Science.gov (United States)

Perualila-Tan, Nolen Joy; Shkedy, Ziv; Talloen, Willem; Göhlmann, Hinrich W H; Moerbeke, Marijke Van; Kasim, Adetayo

2016-08-01

The modern process of discovering candidate molecules in early drug discovery phase includes a wide range of approaches to extract vital information from the intersection of biology and chemistry. A typical strategy in compound selection involves compound clustering based on chemical similarity to obtain representative chemically diverse compounds (not incorporating potency information). In this paper, we propose an integrative clustering approach that makes use of both biological (compound efficacy) and chemical (structural features) data sources for the purpose of discovering a subset of compounds with aligned structural and biological properties. The datasets are integrated at the similarity level by assigning complementary weights to produce a weighted similarity matrix, serving as a generic input in any clustering algorithm. This new analysis work flow is semi-supervised method since, after the determination of clusters, a secondary analysis is performed wherein it finds differentially expressed genes associated to the derived integrated cluster(s) to further explain the compound-induced biological effects inside the cell. In this paper, datasets from two drug development oncology projects are used to illustrate the usefulness of the weighted similarity-based clustering approach to integrate multi-source high-dimensional information to aid drug discovery. Compounds that are structurally and biologically similar to the reference compounds are discovered using this proposed integrative approach.

Sparse matrix-vector multiplication on GPGPU clusters: A new storage format and a scalable implementation

OpenAIRE

Kreutzer, Moritz; Hager, Georg; Wellein, Gerhard; Fehske, Holger; Basermann, Achim; Bishop, Alan R.

2011-01-01

Sparse matrix-vector multiplication (spMVM) is the dominant operation in many sparse solvers. We investigate performance properties of spMVM with matrices of various sparsity patterns on the nVidia “Fermi” class of GPGPUs. A new “padded jagged diagonals storage” (pJDS) format is proposed which may substantially reduce the memory overhead intrinsic to the widespread ELLPACK-R scheme while making no assumptions about the matrix structure. In our test scenarios the pJDS format cuts the ...

Computational study of the Rayleigh light scattering properties of atmospheric pre-nucleation clusters

DEFF Research Database (Denmark)

Elm, Jonas; Norman, Patrick; Bilde, Merete

2014-01-01

The Rayleigh and hyper Rayleigh scattering properties of the binary (H 2SO4)(H2O)n and ternary (H 2SO4)(NH3)(H2O)n clusters are investigated using a quantum mechanical response theory approach. The molecular Rayleigh scattering intensities are expressed using the dipole polarizability α...... and hyperpolarizability β tensors. Using density functional theory, we elucidate the effect of cluster morphology on the scattering properties using a combinatorial sampling approach. We find that the Rayleigh scattering intensity depends quadratically on the number of water molecules in the cluster and that a single...... ammonia molecule is able to induce a high anisotropy, which further increases the scattering intensity. The hyper Rayleigh scattering activities are found to be extremely low. This study presents the first attempt to map the scattering of atmospheric molecular clusters using a bottom-up approach...

*K-means and Cluster Models for Cancer Signatures

OpenAIRE

Kakushadze, Zura; Yu, Willie

2017-01-01

We present *K-means clustering algorithm and source code by expanding statistical clustering methods applied in https://ssrn.com/abstract=2802753 to quantitative finance. *K-means is statistically deterministic without specifying initial centers, etc. We apply *K-means to extracting cancer signatures from genome data without using nonnegative matrix factorization (NMF). *K-means’ computational cost is a fraction of NMF’s. Using 1389 published samples for 14 cancer types, we find that 3 cancer...

EVALUATION OF EFFECTIVE PROPERTIES OF BASALT TEXTILE REINFORCED CERAMIC MATRIX COMPOSITES

Directory of Open Access Journals (Sweden)

Soňa Valentová

2017-11-01

Full Text Available The present paper is concerned with the analysis of a ceramic matrix composite, more specifically the plain weave textile fabric composite made of basalt fibers embedded into the pyrolyzed polysiloxane matrix. Attention is paid to the determination of effective elastic properties of the yarn via homogenization based on the Mori-Tanaka averaging scheme and the 1st order numerical homogenization method adopting a suitable representative computational model. The latter approach is then employed to simulate the response of the yarn when loaded beyond the elastic limits. The required mechanical properties of individual material phases are directly measured using nanoindentation with in-build scanning probe microscopy. Applicability of the proposed computational methodology is supported by the analysis of a unidirectional fibrous composite, representing the yarn, subjected to a macroscopically uniform strain.

The function and properties of the iron-sulfur center in spinach ferredoxin: Thioredoxin reductase: A new biological role for iron-sulfur clusters

Energy Technology Data Exchange (ETDEWEB)

Staples, C.R.; Ameyibor, E.; Fu, Weiguang; Johnson, M.K. [Univ. of Georgia, Athens, GA (United States)] [and others

1996-09-03

Thioredoxin reduction in chloroplasts in catalyzed by a unique class of disulfide reductases which use a [2Fe-2S]{sup 2+/+} ferredoxin as the electron donor and contain an Fe-S cluster as the sole prosthetic group in addition to the active-site disulfide. The nature, properties, and function of the Fe-S cluster in spinach ferredoxin: thioredoxin reductase (FTR) have been investigated by the combination of UV/visible absorption, variable-temperature magnetic circular dichroism (MCD), EPR, and resonance Raman (RR) spectroscopies. 66 refs., 5 figs., 1 tab.

Three-body forces for electrons by the S-matrix method

International Nuclear Information System (INIS)

Margaritelli, R.

1989-01-01

A electromagnetic three-body potential between eletrons is derived by the S-matrix method. This potential can be compared up to a certain point with other electromagnetic potentials (obtained by other methods) encountered in the literature. However, since the potential derived here is far more complete than others, this turns direct comparison with the potentials found in the literature somewhat difficult. These calculations allow a better understanding of the S-matrix method as applied to problems which involve the calculations of three-body nuclear forces (these calculations are performed in order to understand the 3 He form factor). Furthermore, these results enable us to decide between two discrepant works which derive the two-pion exchange three-body potential, both by the S-matrix method. (author) [pt

Computational study of textured ferroelectric polycrystals: Dielectric and piezoelectric properties of template-matrix composites

Science.gov (United States)

Zhou, Jie E.; Yan, Yongke; Priya, Shashank; Wang, Yu U.

2017-01-01

Quantitative relationships between processing, microstructure, and properties in textured ferroelectric polycrystals and the underlying responsible mechanisms are investigated by phase field modeling and computer simulation. This study focuses on three important aspects of textured ferroelectric ceramics: (i) grain microstructure evolution during templated grain growth processing, (ii) crystallographic texture development as a function of volume fraction and seed size of the templates, and (iii) dielectric and piezoelectric properties of the obtained template-matrix composites of textured polycrystals. Findings on the third aspect are presented here, while an accompanying paper of this work reports findings on the first two aspects. In this paper, the competing effects of crystallographic texture and template seed volume fraction on the dielectric and piezoelectric properties of ferroelectric polycrystals are investigated. The phase field model of ferroelectric composites consisting of template seeds embedded in matrix grains is developed to simulate domain evolution, polarization-electric field (P-E), and strain-electric field (ɛ-E) hysteresis loops. The coercive field, remnant polarization, dielectric permittivity, piezoelectric coefficient, and dissipation factor are studied as a function of grain texture and template seed volume fraction. It is found that, while crystallographic texture significantly improves the polycrystal properties towards those of single crystals, a higher volume fraction of template seeds tends to decrease the electromechanical properties, thus canceling the advantage of ferroelectric polycrystals textured by templated grain growth processing. This competing detrimental effect is shown to arise from the composite effect, where the template phase possesses material properties inferior to the matrix phase, causing mechanical clamping and charge accumulation at inter-phase interfaces between matrix and template inclusions. The computational

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.

Response matrix properties and convergence implications for an interface-current nodal formulation

International Nuclear Information System (INIS)

Yang, W.S.

1995-01-01

An analytic study was performed of the properties and the associated convergence implications of the response matrix equations derived via the widely used nodal expansion method. By using the DIF3D nodal formulation in hexagonal-z geometry as a concrete example, an analytic expression for the response matrix is first derived by using the hexagonal prism symmetry transformations. The spectral radius of the local response matrix is shown to be always 2 -norm of the response matrix is shown to be ∞ -norm is not always 2 - and l ∞ -norms of the response matrix are found to increase as the removal cross section decreases. On the other hand, for a given removal cross section, each of these matrix norms takes its minimum at a certain diffusion coefficient and increases as the diffusion coefficient deviates from this value. Based on these matrix norms, sufficient conditions for the convergence of the iteration schemes for solving the response matrix equations are discussed. The range of node-height-to-hexagon-pitch ratios that guarantees a positive solution is derived as a function of the diffusion coefficient and the removal cross section

Two Ti13-oxo-clusters showing non-compact structures, film electrode preparation and photocurrent properties.

Science.gov (United States)

Hou, Jin-Le; Luo, Wen; Wu, Yin-Yin; Su, Hu-Chao; Zhang, Guang-Lin; Zhu, Qin-Yu; Dai, Jie

2015-12-14

Two benzene dicarboxylate (BDC) and salicylate (SAL) substituted titanium-oxo-clusters, Ti13O10(o-BDC)4(SAL)4(O(i)Pr)16 (1) and Ti13O10(o-BDC)4(SAL-Cl)4(O(i)Pr)16 (2), are prepared by one step in situ solvothermal synthesis. Single crystal analysis shows that the two Ti13 clusters take a paddle arrangement with an S4 symmetry. The non-compact (non-sphere) structure is stabilized by the coordination of BDC and SAL. Film photoelectrodes are prepared by the wet coating process using the solution of the clusters and the photocurrent response properties of the electrodes are studied. It is found that the photocurrent density and photoresponsiveness of the electrodes are related to the number of coating layers and the annealing temperature. Using ligand coordinated titanium-oxo-clusters as the molecular precursors of TiO2 anatase films is found to be effective due to their high solubility, appropriate stability in solution and hence the easy controllability.

Co-clustering directed graphs to discover asymmetries and directional communities.

Science.gov (United States)

Rohe, Karl; Qin, Tai; Yu, Bin

2016-10-21

In directed graphs, relationships are asymmetric and these asymmetries contain essential structural information about the graph. Directed relationships lead to a new type of clustering that is not feasible in undirected graphs. We propose a spectral co-clustering algorithm called di-sim for asymmetry discovery and directional clustering. A Stochastic co-Blockmodel is introduced to show favorable properties of di-sim To account for the sparse and highly heterogeneous nature of directed networks, di-sim uses the regularized graph Laplacian and projects the rows of the eigenvector matrix onto the sphere. A nodewise asymmetry score and di-sim are used to analyze the clustering asymmetries in the networks of Enron emails, political blogs, and the Caenorhabditis elegans chemical connectome. In each example, a subset of nodes have clustering asymmetries; these nodes send edges to one cluster, but receive edges from another cluster. Such nodes yield insightful information (e.g., communication bottlenecks) about directed networks, but are missed if the analysis ignores edge direction.

Class Restricted Clustering and Micro-Perturbation for Data Privacy.

Science.gov (United States)

Li, Xiao-Bai; Sarkar, Sumit

2013-04-01

The extensive use of information technologies by organizations to collect and share personal data has raised strong privacy concerns. To respond to the public's demand for data privacy, a class of clustering-based data masking techniques is increasingly being used for privacy-preserving data sharing and analytics. Traditional clustering-based approaches for masking numeric attributes, while addressing re-identification risks, typically do not consider the disclosure risk of categorical confidential attributes. We propose a new approach to deal with this problem. The proposed method clusters data such that the data points within a group are similar in the non-confidential attribute values whereas the confidential attribute values within a group are well distributed . To accomplish this, the clustering method, which is based on a minimum spanning tree (MST) technique, uses two risk-utility tradeoff measures in the growing and pruning stages of the MST technique respectively. As part of our approach we also propose a novel cluster-level micro-perturbation method for masking data that overcomes a common problem of traditional clustering-based methods for data masking, which is their inability to preserve important statistical properties such as the variance of attributes and the covariance across attributes. We show that the mean vector and the covariance matrix of the masked data generated using the micro-perturbation method are unbiased estimates of the original mean vector and covariance matrix. An experimental study on several real-world datasets demonstrates the effectiveness of the proposed approach.

Residual stresses and mechanical properties of metal matrix composites

International Nuclear Information System (INIS)

Persson, Christer.

1993-01-01

The large difference in coefficient of thermal expansion of the matrix and particles in a metal matrix composite will introduce residual stresses during cooling from process temperature. These stresses are locally very high, and are known to influence the mechanical behaviour of the material. Changes in the stress state will occur during heat treatments and when the material is loaded due to different elastic, plastic, and creep properties of the constituents. The change of residual stresses in an Al-SiC particulate composite after different degree of plastic straining has been studied. The effect of plastic straining was modelled by an Eshelby model. The model and the measurements both show that the stress in the loading direction decreases for a tensile plastic strain and increases for a compressive plastic strain. By x-ray diffraction the stress response in the matrix and particles can be measured independently. This has been used to determine the stress state under and after heat treatments and under mechanical loading in two Al 15% SiC metal matrix composites. By analysing the line width from x-ray experiment the changes in the microstrains in the material were studied. A finite element model was used to model the generation of thermal residual stresses, stress relaxation during heat treatments, and load sharing during the first load cycle. Calculated stresses and microstrains were found to be in good agreement with the measured values. The elastic behaviour of the composite can be understood largely in terms of elastic load transfer between matrix and particles. However, at higher loads when the matrix becomes plastic residual stresses also become important. 21 refs

[Electronic and structural properties of individual nanometer-size supported metallic clusters]. Final performance report

Energy Technology Data Exchange (ETDEWEB)

Reifenberger, R.

1993-09-01

This report summarizes the work performed under contract DOE-FCO2-84ER45162. During the past ten years, our study of electron emission from laser-illuminated field emission tips has taken on a broader scope by addressing problems of direct interest to those concerned with the unique physical and chemical properties of nanometer-size clusters. The work performed has demonstrated that much needed data can be obtained on individual nanometer-size clusters supported on a wide-variety of different substrates. The work was performed in collaboration with R.P. Andres in the School of Chemical Engineering at Purdue University. The Multiple Expansion Cluster Source developed by Andres and his students was essential for producing the nanometer-size clusters studied. The following report features a discussion of these results. This report provides a motivation for studying the properties of nanometer-size clusters and summarizes the results obtained.

Young Cluster Berkeley 59: Properties, Evolution, and Star Formation

Science.gov (United States)

Panwar, Neelam; Pandey, A. K.; Samal, Manash R.; Battinelli, Paolo; Ogura, K.; Ojha, D. K.; Chen, W. P.; Singh, H. P.

2018-01-01

Berkeley 59 is a nearby (∼1 kpc) young cluster associated with the Sh2-171 H II region. We present deep optical observations of the central ∼2.5 × 2.5 pc2 area of the cluster, obtained with the 3.58 m Telescopio Nazionale Galileo. The V/(V–I) color–magnitude diagram manifests a clear pre-main-sequence (PMS) population down to ∼0.2 M ⊙. Using the near-infrared and optical colors of the low-mass PMS members, we derive a global extinction of A V = 4 mag and a mean age of ∼1.8 Myr, respectively, for the cluster. We constructed the initial mass function and found that its global slopes in the mass ranges of 0.2–28 M ⊙ and 0.2–1.5 M ⊙ are ‑1.33 and ‑1.23, respectively, in good agreement with the Salpeter value in the solar neighborhood. We looked for the radial variation of the mass function and found that the slope is flatter in the inner region than in the outer region, indicating mass segregation. The dynamical status of the cluster suggests that the mass segregation is likely primordial. The age distribution of the PMS sources reveals that the younger sources appear to concentrate close to the inner region compared to the outer region of the cluster, a phenomenon possibly linked to the time evolution of star-forming clouds. Within the observed area, we derive a total mass of ∼103 M ⊙ for the cluster. Comparing the properties of Berkeley 59 with other young clusters, we suggest it resembles more closely the Trapezium cluster.

Overall mechanical properties of fiber-reinforced metal matrix composites for fusion applications

International Nuclear Information System (INIS)

You, J.H.; Bolt, H.

2002-01-01

The high-temperature strength and creep properties are among the crucial criteria for the structural materials of plasma facing components (PFC) of fusion reactors, as they will be subjected to severe thermal stresses. The fiber-reinforced metal matrix composites are a potential heat sink material for the PFC application, since the combination of different material properties can lead to versatile performances. In this article, the overall mechanical properties of two model composites based on theoretical predictions are presented. The matrix materials considered were a precipitation hardened CuCrZr alloy and reduced activation martensitic steel 'Eurofer'. Continuous SiC fibers were used for the reinforcement. The results demonstrate that yield stress, ultimate tensile strength, work hardening rate and creep resistance could be extensively improved by the fiber reinforcement up to fiber content of 40 vol.%. The influence of the residual stresses on the plastic behavior of the composites is also discussed

Prediction of Solvent Physical Properties using the Hierarchical Clustering Method

Science.gov (United States)

Recently a QSAR (Quantitative Structure Activity Relationship) method, the hierarchical clustering method, was developed to estimate acute toxicity values for large, diverse datasets. This methodology has now been applied to the estimate solvent physical properties including sur...

Electronic and structural properties of B i2S e3:Cu

Science.gov (United States)

Sobczak, Kamil; Strak, Pawel; Kempisty, Pawel; Wolos, Agnieszka; Hruban, Andrzej; Materna, Andrzej; Borysiuk, Jolanta

2018-04-01

Electronic and structural properties of B i2S e3 and its extension to copper doped B i2S e3:Cu were studied using combined ab initio simulations and transmission electron microscopy based techniques, including electron energy loss spectroscopy, energy filtered transmission electron microscopy, and energy dispersive x-ray spectroscopy. The stability of the mixed phases was investigated for substitutional and intercalation changes of basic B i2S e3 structure. Four systems were compared: B i2S e3 , structures obtaining by Cu intercalation of the van der Waals gap, by substitution of Bi by Cu in quintuple layers, and C u2Se . The structures were identified and their electronic properties were obtained. Transmission electron microscopy measurements of B i2S e3 and the B i2S e3:Cu system identified the first structure as uniform and the second as composite, consisting of a nonuniform lower-Cu-content matrix and randomly distributed high-Cu-concentration precipitates. Critical comparison of the ab initio and experimental data identified the matrix as having a B i2S e3 dominant part with randomly distributed Cu-intercalated regions having 1Cu-B i2S e3 structure. The precipitates were determined to have 3Cu-B i2S e3 structure.

Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

Directory of Open Access Journals (Sweden)

M. H. Denton

2008-03-01

Full Text Available Moments calculated from the ion distributions (~0–40 keV measured by the Cluster Ion Spectrometry (CIS instrument are combined with data from the Cluster Flux Gate Magnetometer (FGM instrument and used to characterise the bulk properties of the plasma in the near-Earth magnetosphere over five years (2001–2005. Results are presented in the form of 2-D xy, xz and yz GSM cuts through the magnetosphere using data obtained from the Cluster Science Data System (CSDS and the Cluster Active Archive (CAA. Analysis reveals the distribution of ~0–40 keV ions in the inner magnetosphere is highly ordered and highly responsive to changes in solar wind velocity. Specifically, elevations in temperature are found to occur across the entire nightside plasma sheet region during times of fast solar wind. We demonstrate that the nightside plasma sheet ion temperature at a downtail distance of ~12 to 19 Earth radii increases by a factor of ~2 during periods of fast solar wind (500–1000 km s⁻¹ compared to periods of slow solar wind (100–400 km s⁻¹. The spatial extent of these increases are shown in the xy, xz and yz GSM planes. The results from the study have implications for modelling studies and simulations of solar-wind/magnetosphere coupling, which ultimately rely on in situ observations of the plasma sheet properties for input/boundary conditions.

Formation and properties of selected quantum dots in maize amylopectin matrix

Energy Technology Data Exchange (ETDEWEB)

Khachatryan, Karen, E-mail: rrchacza@cyf-kr.edu.pl [Department of Chemistry and Physics, Agricultural University, Balicka Street 122, 30 149 Krakow (Poland); Khachatryan, Gohar; Fiedorowicz, Maciej [Department of Chemistry and Physics, Agricultural University, Balicka Street 122, 30 149 Krakow (Poland); Tomasik, Piotr [Krakow College of Health Promotion, Krowoderska Street 73, 31 158 Krakow (Poland)

2014-09-01

Highlights: • Synthesis of quantum dots in aqueous gel of amylopectin. • Generation of quantum dots in non-ionic polysaccharide. • Preparation of CdS, Ga{sub 2}S{sub 3} and ZnS quantum dots of the size below 10 nm. • The amylopectin matrix is not suitable for generation of CaS and Cs{sub 2}S quantum dots. - Abstract: CdS, ZnS, Ga{sub 2}S{sub 3}, CaS and Cs{sub 2}S quantum dots (QDs) were generated in the amylopectin (Ap) matrix. They all emitted a light between 460 (ZnS) and 475 (CdS) nm. Sizes of Ga{sub 2}S{sub 3} and CdS QDs were 7–9 nm and 5–7 nm, respectively. Single ZnS QDs had 6–7 nm but they readily aggregated. The CaS and Cs{sub 2}S appeared mainly as 30–100 nm aggregates. There were no significant interactions between QDs and the Ap matrix. Presented method appeared unsuitable for the generation of CaS and Cs{sub 2}S QDs as they as well as their substrates [Ca(NO{sub 3}){sub 2}] hydrolyzed. Calcium compounds formed complexes with Ap and alkaline solution from CsOH could produce cesium salts of Ap as well as cause oxidation of Ap.

The sorption and mechanical properties of the modified cement matrix used for conditioning of radioactive waste

International Nuclear Information System (INIS)

Dogaru, Daniela; Nuculae, Ortenzia; Jinescu, Gheorghita; Duliu, Octavian; Dogaru, Gheorghe

2008-01-01

Full text: Radioactive contaminant sorption onto concrete represents one of the most important retardation mechanisms in engineered barriers such as the conditioning matrix itself, concrete walls and concrete floors. During the life of a disposal facility for radioactive waste, the sorption properties as well as the mechanical properties of the cement are affected by both external and internal processes. The most important sorbing material present in concrete is the hydrated cement. The sorption data obtained for specific cement or cement mixes in general may be used to characterize a given cement type. In order to improve the mechanical and sorption properties of the cement matrix, different additives were used in the laboratory tests. The used additives are known to have good sorption properties. The paper describes the influence of the concentration of additives on the mechanical and sorption properties of the cement matrix. As radioactive contaminants 134 Cs, 60 Co, 3 H, 241 Am were used. (authors)

Structure, reactivity and electronic properties of Mn doped Ni{sub 13} clusters

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Radhashyam; Datta, Soumendu; Mookerjee, Abhijit, E-mail: abhijit.mookerjee61@gmail.com

2013-06-15

In this work we have studied the structural and magnetic properties of Ni{sub 13} cluster mono- and bi-doped with Mn atoms. We have noted their tendency of being reactive toward the H{sub 2} molecule. We have found unusually enhanced stability in the mono-doped cluster (i.e. of the Ni{sub 12}Mn) and the diminished stability of the corresponding chemisorbed cluster, Ni{sub 12}MnH{sub 2}. Our analysis of the stability and HOMO–LUMO gap explains this unusual behavior. Interestingly, we have also seen the quenching in the net magnetic moment upon H{sub 2} absorption in the doped Ni{sub 13−m}Mn{sub m} alloy clusters. This has been reported earlier for smaller Ni{sub n} clusters [1].

Positive semidefinite matrix completion, universal rigidity and the Strong Arnold Property

NARCIS (Netherlands)

M. Laurent (Monique); A. Varvitsiotis (Antonios)

2014-01-01

htmlabstractThis paper addresses the following three topics: positive semidefinite (psd) matrix completions, universal rigidity of frameworks, and the Strong Arnold Property (SAP). We show some strong connections among these topics, using semidefinite programming as unifying theme. Our main

A density functional theory study on structures, stabilities, and electronic and magnetic properties of Au{sub n}C (n = 1–9) clusters

Energy Technology Data Exchange (ETDEWEB)

Hou, Xiao-Fei; Yan, Li-Li; Huang, Teng; Hong, Yu; Miao, Shou-Kui [Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Peng, Xiu-Qiu [School of Environmental Science & Optoelectronic Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Liu, Yi-Rong, E-mail: liuyirong@aiofm.ac.cn [Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Wei, E-mail: huangwei6@ustc.edu.cn [Laboratory of Atmospheric Physico-Chemistry, Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); School of Environmental Science & Optoelectronic Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2016-06-15

The equilibrium geometric structures, relative stabilities, electronic stabilities, and electronic and magnetic properties of the Au{sub n}C and Au{sub n+1} (n = 1–9) clusters are systematically investigated using density functional theory (DFT) with hyper-generalized gradient approximation (GGA). The optimized geometries show that one Au atom added to the Au{sub n−1}C cluster is the dominant growth pattern for the Au{sub n}C clusters. In contrast to the pure gold clusters, the Au{sub n}C clusters are most stable in a quasi-planar or three-dimensional (3D) structure because the C dopant induces the local non-planarity, with exceptions of the Au{sub 6,8}C clusters who have 2D structures. The analysis of the relative and electronic stabilities reveals that the Au{sub 4}C and Au{sub 6} clusters are the most stable in the series of studied clusters, respectively. In addition, a natural bond orbital (NBO) analysis shows that the charges in the Au{sub n}C clusters transfer from the Au{sub n} host to the C atom. Moreover, the Au and C atoms interact with each other mostly via covalent bond rather than ionic bond, which can be confirmed through the average ionic character of the Au–C bond. Meanwhile, the charges mainly transfer between 2s and 2p orbitals within the C atom, and among 5d, 6s, and 6p orbitals within the Au atom for the Au{sub n}C clusters. As for the magnetic properties of the Au{sub n}C clusters, the total magnetic moments are 1 μ{sub B} for n = odd clusters, with the total magnetic moments mainly locating on the C atoms for Au{sub 1,3,9}C and on the Au{sub n} host for Au{sub 5,7}C clusters. However, the total magnetic moments of the Au{sub n}C clusters are zero for n = even clusters. Simultaneously, the magnetic moments mainly locate on the 2p orbital within the C atom and on the 5d, 6s orbitals within the Au atom.

Spectral properties in supersymmetric matrix models

International Nuclear Information System (INIS)

Boulton, Lyonell; Garcia del Moral, Maria Pilar; Restuccia, Alvaro

2012-01-01

We formulate a general sufficiency criterion for discreteness of the spectrum of both supersymmmetric and non-supersymmetric theories with a fermionic contribution. This criterion allows an analysis of Hamiltonians in complete form rather than just their semiclassical limits. In such a framework we examine spectral properties of various (1+0) matrix models. We consider the BMN model of M-theory compactified on a maximally supersymmetric pp-wave background, different regularizations of the supermembrane with central charges and a non-supersymmetric model comprising a bound state of N D2 with m D0. While the first two examples have a purely discrete spectrum, the latter has a continuous spectrum with a lower end given in terms of the monopole charge.

Positive semidefinite matrix completion, universal rigidity and the Strong Arnold Property

NARCIS (Netherlands)

Laurent, Monique; Varvitsiotis, A.

This paper addresses the following three topics: positive semidefinite (psd) matrix completions, universal rigidity of frameworks, and the Strong Arnold Property (SAP). We show some strong connections among these topics, using semidefinite programming as unifying theme. Our main contribution is a

Magnetic and electrical properties in BaNiS2-type solid solutions

International Nuclear Information System (INIS)

Irizawa, Akinori; Yoshimura, Kazuyoshi; Kosuge, Koji

2000-01-01

The magnetic and electrical properties are reported in the new solid solutions BaCo 1-x Cu x S 2 and BaNi 1-x Fe x S 2 . Both compounds show spin-glass-like behavior, although the type of spin frustrations is different with each other. BaCo 1-x Cu x S 2 shows a competition type spin-glass behavior with reentrant phenomenon from antiferromagnetic to spin-glass at low temperatures. BaNi 1-x Fe x S 2 shows a dilute type spin-glass behavior together with super-paramagnetic properties. The temperature variation of 57 Fe Moessbauer spectra in BaNi 0.8 Fe 0.2 S 2 is explicable in a framework of cluster-glass. (author)

Porcine bladder acellular matrix (ACM): protein expression, mechanical properties

International Nuclear Information System (INIS)

Farhat, Walid A; Chen Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Yeger, Herman; Sherman, Christopher; Derwin, Kathleen

2008-01-01

Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization

Porcine bladder acellular matrix (ACM): protein expression, mechanical properties.

Science.gov (United States)

Farhat, Walid A; Chen, Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Sherman, Christopher; Derwin, Kathleen; Yeger, Herman

2008-06-01

Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization.

Porcine bladder acellular matrix (ACM): protein expression, mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Farhat, Walid A [Department of Surgery, Division of Urology, University of Toronto and Hospital for Sick Children, Toronto, ON M5G 1X8 (Canada); Chen Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Yeger, Herman [Department of Developmental and Stem Cell Biology, Research Institute, Hospital for Sick Children, Toronto, ON M5G 1X8 (Canada); Sherman, Christopher [Department of Anatomic Pathology, Sunnybrook and Women' s College Health Sciences Centre, Toronto, ON (Canada); Derwin, Kathleen [Department of Biomedical Engineering, Lerner Research Institute and Orthopaedic Research Center, Cleveland Clinic Foundation, Cleveland, OH (United States)], E-mail: walid.farhat@sickkids.ca

2008-06-01

Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization.

Ferromagnetism and suppression of metallic clusters in Fe implanted ZnO -- a phenomenon related to defects?

International Nuclear Information System (INIS)

Arenholz, Elke; Zhou, S.; Potzger, K.; Talut, G.; Reuther, H.; Kuepper, K.; Grenzer, J.; Xu, Q.; Mucklich, A.; Helm, M.; Fassbender, J.; Arenholz, E.

2008-01-01

We investigated ZnO(0001) single crystals annealed in high vacuum with respect to their magnetic properties and cluster formation tendency after implant-doping with Fe. While metallic Fe cluster formation is suppressed, no evidence for the relevance of the Fe magnetic moment to the observed ferromagnetism was found. The latter along with the cluster suppression is discussed with respect to defects in the ZnO host matrix, since the crystalline quality of the substrates was lowered due to the preparation as observed by x-ray diffraction

Constraining omega from X-ray properties of clusters of galaxies at high redshifts

DEFF Research Database (Denmark)

Sadat, R.; Blanchard, A.; Oukbir, J.

1997-01-01

Properties of high redshift clusters are a fundamental source of information for cosmology. It has been shown by Oukbir and Blanchard (1997) that the combined knowledge of the redshift distribution of X-ray clusters of galaxies and the luminosity-temperature correlation, L-X - T-X, provides a pow...

In-situ experiments to investigate rock matrix retention properties in ONKALO, Olkiluoto, Finland

Energy Technology Data Exchange (ETDEWEB)

Voutilainen, Mikko; Helariutta, Kerttuli [Helsinki Univ. (Finland). Dept. of Chemistry; Poteri, Antti [Technical Research Centre of Finland VTT (Finland); and others

2015-07-01

Spent nuclear fuel from nuclear power plants, owned by TVO (Teollisuuden Voima Oy) and Fortum, is planned to be disposed to a repository at a depth of more than 400 meters in the bedrock of Olkiluoto (Eurajoki, Finland). The repository system of multiple release barriers consists of both manmade and natural barriers. The surrounding rock acts as the last barrier if other barriers fail during passage of the millennia. Therefore, safe disposal of spent nuclear fuel requires information on the radionuclide transport and retention properties within the porous and water-containing rock matrix along the water conducting flow paths. To this end, various types of experiments are being performed and planned within ONKALO, the underground rock characterization facility in Olkiluoto, as part of the project @''rock matrix REtention PROperties'' (REPRO). The research site is located at a depth of 420 meters close to the repository site. The aim is to study the diffusion and sorption properties of nuclear compounds in the rock matrix under real in-situ conditions. The first in-situ experiment was performed during 2012 using HTO, Na-22, Cl-36 and I-125 as tracer nuclides. Breakthrough curves show retention and asymptotic behavior that are in-line with those caused by matrix diffusion and sorption were observed in their breakthrough curves. Weak sorption was also observed in the breakthrough curves of Na-22 and I-125.

Petrophysics at the rock matrix scale: hydraulic properties and petrographic interpretation

International Nuclear Information System (INIS)

Montoto, M.

2003-01-01

The main objective of this publication is to review, summarize and make comprehensive the hydraulic properties of rocks, at the rock matrix or in tact rock scale. Also to describe how to petrographically interpret those properties. For this purpose, the procedures for the characterization and visualisation of the rock-forming components and in special the water path-ways at that scale are explained. Further more, to establish a methodological approach for an appropriate petrographic interpretation of all the mentioned properties is intended. This Technical Report is applied to the geological solution for the final disposal of high level radioactive wastes. In any case, most of the aspects covered here are of scientific and technical interest for any researcher interested in the behaviour of water in rocks and vice versa, also in the potential fluid- rock interactions. The document is divided into six Chapters, mainly theoretical and methodological, and six Appen - dixes, more focussed to practical tests and procedures for rock characterization. Two significant rock types in high level radioactive waste, HLW, granites and clays, have been used for illustrating most of the examples here included. Under a wide geological perspective, it must be stated that in any geological scenario two different systems or scales coexist; the rock massif (with fractures of about m to km) and the rock matrix (with internal discontinuities such as fissures and cracks to the order of Fm to dm). Their different behaviour is considered in Chapter 1 as well as the specific role played by the rock matrix in the long- and short-term period. General considerations about physical properties of rocks and comparative advantages and disadvantages of the main candidate rocks for radioactive repositories are also included. (Author)

Dwarf galaxies in the coma cluster: Star formation properties and evolution

Science.gov (United States)

Hammer, Derek M.

The infall regions of galaxy clusters are unique laboratories for studying the impact of environment on galaxy evolution. This intermediate region links the low-density field environment and the dense core of the cluster, and is thought to host recently accreted galaxies whose star formation is being quenched by external processes associated with the cluster. In this dissertation, we measure the star formation properties of galaxies at the infall region of the nearby rich cluster of galaxies, Coma. We rely primarily on Ultraviolet (UV) data owing to its sensitivity to recent star formation and we place more emphasis on the properties of dwarf galaxies. Dwarf galaxies are good tracers of external processes in clusters but their evolution is poorly constrained as they are intrinsically faint and hence more challenging to detect. We make use of deep GALEX far-UV and near-UV observations at the infall region of the Coma cluster. This area of the cluster has supporting photometric coverage at optical and IR wavelengths in addition to optical spectroscopic data that includes deep redshift coverage of dwarf galaxies in Coma. Our GALEX observations were the deepest exposures taken for a local galaxy cluster. The depth of these images required alternative data analysis techniques to overcome systematic effects that limit the default GALEX pipeline analysis. Specifically, we used a deblending method that improved detection efficiency by a factor of ˜2 and allowed reliable photometry a few magnitudes deeper than the pipeline catalog. We performed deep measurements of the total UV galaxy counts in our field that were used to measure the source confusion limit for crowded GALEX fields. The star formation properties of Coma members were studied for galaxies that span from starbursts to passive galaxies. Star-forming galaxies in Coma tend to have lower specific star formation rates, on average, as compared to field galaxies. We show that the majority of these galaxies are likely

Ionothermal synthesis of discrete supertetrahedral Tn (n = 4, 5) clusters with tunable components, band gaps, and fluorescence properties.

Science.gov (United States)

Yang, Dan-Dan; Li, Wei; Xiong, Wei-Wei; Li, Jian-Rong; Huang, Xiao-Ying

2018-05-01

The preparation of crystalline molecularly supertetrahedral Tn clusters with variable sizes and components is of vital importance for the fundamental study of their physicochemical properties. However, setting up an efficient method to stabilize large discrete Tn clusters is a challenge due to their high negative charges and polymerization nature. In this work, we report on the ionothermal synthesis of three discrete T4 cluster compounds, namely [Bmmim]5[(CH3)2NH2]4[NH4][M4In16S31(SH)4]·6H2O (M = Mn (1), Zn (2), Cd (3), Bmmim = 1-buty-2,3-dimethyl-imidazolium), and four discrete T5 cluster compounds, namely [Bmmim]10[NH4]3[Cu5Ga30-xInxS52(SH)4] (x = 6.6 (5), 14.5 (6), 23.8 (7), and 30 (8)). The compound [Bmmim]10[NH4]3[Cu5Ga30S52(SH)4] (4) previously reported by us features a discrete T5 cluster. The steep UV-Vis absorption edges indicate band gaps of 2.20 eV for 1, 2.64 eV for 2, 2.69 eV for 3, 3.04 eV for 4, 2.65 eV for 5, 2.48 eV for 6, 2.32 eV for 7, and 2.30 eV for 8. The compositions of T5 clusters could be varied with the ratios of Ga : In in the starting reagents, providing an opportunity to systematically control the band gaps and fluorescence performances of T5 cluster-based compounds. This research might advance the understanding of the ionothermal preparation and functionality tuning of crystalline chalcogenides.

Luminescent properties of fluorophosphate glasses with lead chalcogenides molecular clusters

International Nuclear Information System (INIS)

Kolobkova, E.V.; Kukushkin, D.S.; Nikonorov, N.V.; Shakhverdov, T.A.; Sidorov, A.I.; Vasiliev, V.N.

2015-01-01

Fluorophosphate glasses containing lead, selenium, and sulfur exhibit an intense luminescence in the 400–620 nm spectral region when excited by the 240–420 nm radiation. This luminescence is due to the presence of (PbSe) n and/or (PbS) n molecular clusters in the glasses, which appear in the as-prepared glasses before quantum dots formation. The thermal treatment at temperatures less than the glass transition temperature results in the red-shift of the luminescence bands and in an increase in the luminescence intensity. Heating the thermally treated glass samples leads to the reversible thermal quenching of the luminescence. - Highlights: • Fluorophosphate glasses with Pb, Se, and S ions contain (PbSe) n or (PbS) n molecular clusters. • (PbSe) n and (PbS) n molecular clusters possess luminescence in the visible with UV excitation. • Heating the glass leads to the reversible thermal quenching of the luminescence

Asymptotic Bethe ansatz S-matrix and Landau-Lifshitz-type effective 2d actions

International Nuclear Information System (INIS)

Roiban, R; Tirziu, A; Tseytlin, A A

2006-01-01

Motivated by the desire to relate Bethe ansatz equations for anomalous dimensions found on the gauge-theory side of the AdS/CFT correspondence to superstring theory on AdS 5 x S 5 we explore a connection between the asymptotic S-matrix that enters the Bethe ansatz and an effective two-dimensional quantum field theory. The latter generalizes the standard 'non-relativistic' Landau-Lifshitz (LL) model describing low-energy modes of ferromagnetic Heisenberg spin chain and should be related to a limit of superstring effective action. We find the exact form of the quartic interaction terms in the generalized LL-type action whose quantum S-matrix matches the low-energy limit of the asymptotic S-matrix of the spin chain of Beisert, Dippel and Staudacher (BDS). This generalizes to all orders in the 't Hooft coupling λ an earlier computation of Klose and Zarembo of the S-matrix of the standard LL model. We also consider a generalization to the case when the spin-chain S-matrix contains an extra 'string' phase and determine the exact form of the LL 4-vertex corresponding to the low-energy limit of the ansatz of Arutyunov, Frolov and Staudacher (AFS). We explain the relation between the resulting 'non-relativistic' non-local action and the second-derivative string sigma model. We comment on modifications introduced by strong-coupling corrections to the AFS phase. We mostly discuss the SU(2) sector but also present generalizations to the SL(2) and SU(1|1) sectors, confirming universality of the dressing phase contribution by matching the low-energy limit of the AFS-type spin-chain S-matrix with tree-level string-theory S-matrix

Impact of foamed matrix components on foamed concrete properties

Science.gov (United States)

Tarasenko, V. N.

2018-03-01

The improvement of the matrix foam structure by means of foam stabilizing additives is aimed at solving the technology-oriented problems as well as at the further improvement of physical and mechanical properties of cellular-concrete composites. The dry foam mineralization is the mainstream of this research. Adding the concrete densifiers, foam stabilizers and mineral powders reduces the drying shrinkage, which makes the foam concrete products technologically effective.

Mechanical, spectral, and luminescence properties of ZnS:Mn doped PDMS

Energy Technology Data Exchange (ETDEWEB)

Fontenot, Ross S. [University of Louisiana at Lafayette, Department of Physics, PO Box 44210, Lafayette, LA 70504 (United States); Allison, Stephen W., E-mail: steve.allison@emergingmeasurements.com [Emerging Measurements, Collierville, TN 38017 (United States); Lynch, Kyle J, E-mail: kjlynch@memphis.edu [Department of Physics, University of Memphis, Memphis, TN 38152 (United States); Hollerman, William A. [University of Louisiana at Lafayette, Department of Physics, PO Box 44210, Lafayette, LA 70504 (United States); Sabri, Firouzeh, E-mail: fsabri@memphis.edu [Department of Physics, University of Memphis, Memphis, TN 38152 (United States)

2016-02-15

Zinc sulfide doped with manganese (ZnS:Mn) is one of the brightest triboluminescent materials known and has been studied for a variety of applications. The powder form of this material restricts its safe handling and utilization, which limits the range of applications that can take advantage of its unique properties. In this study, the tribo- and photo-luminescent properties as well as the mechanical properties of ZnS:Mn encapsulated in an inert and optically transparent elastomer – Sylgard 184, have been investigated and fully characterized. ZnS:Mn particles of 8.5 µm diameter were incorporated into the Sylgard 184 polymer matrix prior to the curing stage with increasing amounts targeting a final (mass) concentration of 5%, 15%, and 50%. Additionally, the effect of the ZnS:Mn particles on the overall surface properties of the encapsulating elastomer was investigated and reported here. It was observed that the triboluminescent emission from impact scales with phosphor concentration and was not affected by the encapsulating medium. - Highlights: • Polymer encapsulation effects on the luminescent properties of ZnS:Mn was investigated. • Sylgard 184 encapsulated with ZnS:Mn (5, 15, 50 wt%) were characterized. • The triboluminescent emission from impact, scales with phosphor concentration. • Effect of the elastomeric medium on luminescent properties of ZnS:Mn was determined. • The work presented here demonstrates the feasibility of ZnS:Mn-based flexible sensors.

Theoretical study of electronic and dynamic properties of simple metal clusters in jellium model

International Nuclear Information System (INIS)

El-Amine Madjet, M.

1994-01-01

We have studied the electronic properties of alkali-metal clusters in various theoretical approximations and in the framework of the spherical jellium model. We have investigated the ground state properties of alkali clusters both in the LDA (local density approximation) and in HF (Hartree-Fock) theory. We have compared the LDA predictions of the ground state properties to predictions obtained within the HF theory. Such a comparison permitted us to check the validity of the local density functional theory in describing the ground state of a finite fermion system. For the study of collective dipolar excitations in clusters, we have considered an electromagnetic excitation. We have investigated the collective modes in the following approximations: random phase approximation (RPA), time-dependent local-density approximation (TDLDA) and the sum-rules approach. An assessment of the approximation for the continuum state within the RPA is made by comparing with TDLDA calculations for the static and dynamic electronic properties. The comparative study that we have done on the exchange-correlation effects on the electronic and optical properties have shown that the discrepancies with measured data are due mostly to the jellium approximation for the ionic background. (author). 69 refs., 30 figs., 18 tabs

A random matrix model of relaxation

International Nuclear Information System (INIS)

Lebowitz, J L; Pastur, L

2004-01-01

We consider a two-level system, S 2 , coupled to a general n level system, S n , via a random matrix. We derive an integral representation for the mean reduced density matrix ρ(t) of S 2 in the limit n → ∞, and we identify a model of S n which possesses some of the properties expected for macroscopic thermal reservoirs. In particular, it yields the Gibbs form for ρ(∞). We also consider an analog of the van Hove limit and obtain a master equation (Markov dynamics) for the evolution of ρ(t) on an appropriate time scale

Site-directed mutagenesis of Azotobacter vinelandii ferredoxin I: [Fe-S] cluster-driven protein rearrangement

International Nuclear Information System (INIS)

Martin, A.E.; Burgess, B.K.; Stout, C.D.; Cash, V.L.; Dean, D.R.; Jensen, G.M.; Stephens, P.J.

1990-01-01

Azotobacter vinelandii ferredoxin I is a small protein that contains one [4Fe-4S] cluster and one [3Fe-4S] cluster. Recently the x-ray crystal structure has been redetermined and the fdxA gene, which encodes the protein, has been cloned and sequenced. Here the authors report the site-directed mutation of Cys-20, which is a ligand of the [4Fe-4S] cluster in the native protein, to alanine and the characterization of the protein product by x-ray crystallographic and spectroscopic methods. The data show that the mutant protein again contains one [4Fe-4S] cluster and one [3Fe-4S] cluster. The new [4Fe-4S] cluster obtains its fourth ligand from Cys-24, a free cysteine in the native structure. The formation of this [4Fe-4S] cluster drives rearrangement of the protein structure

Interplay of electronic and geometry shell effects in properties of neutral and charged Sr clusters

DEFF Research Database (Denmark)

Lyalin, Andrey; Solov'yov, Ilia; Solov'yov, Andrey V.

2007-01-01

that the size evolution of structural and electronic properties of strontium clusters is governed by an interplay of the electronic and geometry shell closures. Influence of the electronic shell effects on structural rearrangements can lead to violation of the icosahedral growth motif of strontium clusters......The optimized structure and electronic properties of neutral, singly, and doubly charged strontium clusters have been investigated using ab initio theoretical methods based on density-functional theory. We have systematically calculated the optimized geometries of neutral, singly, and doubly...... charged strontium clusters consisting of up to 14 atoms, average bonding distances, electronic shell closures, binding energies per atom, the gap between the highest occupied and the lowest unoccupied molecular orbitals, and spectra of the density of electronic states (DOS). It is demonstrated...

Highly stable polymer coated nano-clustered silver plates: a multimodal optical contrast agent for biomedical imaging

International Nuclear Information System (INIS)

Ray, Aniruddha; Mukundan, Ananya; Karamchand, Leshern; Kopelman, Raoul; Xie, Zhixing; Wang, Xueding

2014-01-01

Here, we present a new optical contrast agent based on silver nanoplate clusters embedded inside of a polymer nano matrix. Unlike nanosphere clusters, which have been well studied, nanoplate clusters have unique properties due to the different possible orientations of interaction between the individual plates, resulting in a significant broadening of the absorption spectra. These nanoclusters were immobilized inside of a polymer cladding so as to maintain their stability and optical properties under in vivo conditions. The polymer-coated silver nanoplate clusters show a lower toxicity compared to the uncoated nanoparticles. At high nanoparticle concentrations, cell death occurs mostly due to apoptosis. These nanoparticles were used for targeted fluorescence imaging in a rat glioma cell line by incorporating a fluorescent dye into the matrix, followed by conjugation of a tumor targeting an F3 peptide. We further used these nanoparticles as photoacoustic contrast agents in vivo to enhance the contrast of the vasculature structures in a rat ear model. We observed a contrast enhancement of over 90% following the nanoparticle injection. It is also shown that these NPs can serve as efficient contrast agents, with specific targeting abilities for broadband multimodal imaging that are usable for diagnostic applications and that extend into use as therapeutic agents as well. (paper)

Action of an ionizing radiation and hydrodynamic effect on matrix properties of DNA during extracellular synthesis of RNA, and thiophosphate protection of matrix properties of T2-DNA against. gamma. -radiation. [gamma radiation

Energy Technology Data Exchange (ETDEWEB)

Shekhtman, Ya L; Domashenko, A D; Kamzolova, S G; Medvedkov, A A [AN SSSR, Pushchino-na-Oke. Inst. Biologicheskoj Fiziki

1976-05-01

Action of an ionizing radiation and the hydrodynamic effect of the matrix activity of thymus DNA and T2 phase DNA have been studied in vitro in the RNA: polymerase system of E.coli B. Also studied have been the thiophosphate protection of matrix properties of T2-DNA against ..gamma..-radiation.

Transformation Matrix for Time Discretization Based on Tustin’s Method

Directory of Open Access Journals (Sweden)

Yiming Jiang

2014-01-01

Full Text Available This paper studies rules in transformation of transfer function through time discretization. A method of using transformation matrix to realize bilinear transform (also known as Tustin’s method is presented. This method can be described as the conversion between the coefficients of transfer functions, which are expressed as transform by certain matrix. For a polynomial of degree n, the corresponding transformation matrix of order n exists and is unique. Furthermore, the transformation matrix can be decomposed into an upper triangular matrix multiplied with another lower triangular matrix. And both have obvious regularity. The proposed method can achieve rapid bilinear transform used in automatic design of digital filter. The result of numerical simulation verifies the correctness of the theoretical results. Moreover, it also can be extended to other similar problems. Example in the last throws light on this point.

A transfer-matrix method for spatially modulated structures

International Nuclear Information System (INIS)

Surda, A.

1991-03-01

A cluster transfer-matrix method convenient for calculation of spatially modulated structures of a wide class of lattice-gas models is developed. The method formulates the problem of calculation of the partition function in terms of non-linear mapping of effective multi-site fields. It is applied to a lattice-gas model qualitatively describing the system of oxygen atoms in the basal planes of high-temperature superconductors. The properties of an incommensurate structure occurring at intermediate temperatures are discussed in detail. (author). 21 refs, 15 figs

Reactivity of Cubane-Type [(OC)(3)MFe(3)S(4)(SR)(3)](3-) Clusters (M = Mo, W): Interconversion with Cuboidal [Fe(3)S(4)](0) Clusters and Electron Transfer.

Science.gov (United States)

Raebiger, James W.; Crawford, Charles A.; Zhou, Jian; Holm, R. H.

1997-03-12

The title clusters, several examples of which have been reported earlier, have been prepared by two different methods and subjected to structural and reactivity studies. The compounds (Et(4)N)(3)[(OC)(3)MFe(3)S(4)(Smes)(3)].MeCN (M = Mo/W) are isomorphous and crystallize in monoclinic space group P2(1)/n with a = 13.412(1)/13.297(1) Å, b = 19.0380(1)/18.9376(3) Å, c = 26.4210(1)/26.2949(1) Å, beta = 97.87(1)/97.549(1) degrees, and Z = 4. The clusters contain long M-S (2.62/2.59 Å) and M-Fe (3.22/3.19 Å) bonds, consistent with the reported structure of [(OC)(3)MoFe(3)S(4)(SEt)(3)](3-) (3). Reaction of [(OC)(3)MoFe(3)S(4)(LS(3))](3-) (7) with CO in the presence of NaPF(6) affords cuboidal [Fe(3)S(4)(LS(3))](3-) (9), also prepared in this laboratory by another route as a synthetic analogue of protein-bound [Fe(3)S(4)](0) clusters. The clusters [Fe(3)S(4)(SR)(3)](3-) (R = mes, Et), of limited stability, were generated by the same reaction. Treatment of 9 with [M(CO)(3)(MeCN)(3)] affords 7 and its M = W analogue. The clusters [(OC)(3)MFe(3)S(4)(SR)(3)](3-) form a four-member electron transfer series in which the 3- cluster can be once reduced (4-) and twice oxidized (2-, 1-) to afford clusters of the indicated charges. The correct assignment of redox couple to potential in the redox series of six clusters is presented, correcting an earlier misassignment of the redox series of 3. Carbonyl stretching frequencies are shown to be sensitive to cluster oxidation state, showing that the M sites and Fe(3)S(4) fragments are electronically coupled despite the long bond distances. (LS(3) = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzenate(3-); mes = mesityl.)

Analysis of X-ray Structures of Matrix Metalloproteinases via Chaotic Map Clustering

Directory of Open Access Journals (Sweden)

Gargano Gianfranco

2010-10-01

Full Text Available Abstract Background Matrix metalloproteinases (MMPs are well-known biological targets implicated in tumour progression, homeostatic regulation, innate immunity, impaired delivery of pro-apoptotic ligands, and the release and cleavage of cell-surface receptors. With this in mind, the perception of the intimate relationships among diverse MMPs could be a solid basis for accelerated learning in designing new selective MMP inhibitors. In this regard, decrypting the latent molecular reasons in order to elucidate similarity among MMPs is a key challenge. Results We describe a pairwise variant of the non-parametric chaotic map clustering (CMC algorithm and its application to 104 X-ray MMP structures. In this analysis electrostatic potentials are computed and used as input for the CMC algorithm. It was shown that differences between proteins reflect genuine variation of their electrostatic potentials. In addition, the analysis has been also extended to analyze the protein primary structures and the molecular shapes of the MMP co-crystallised ligands. Conclusions The CMC algorithm was shown to be a valuable tool in knowledge acquisition and transfer from MMP structures. Based on the variation of electrostatic potentials, CMC was successful in analysing the MMP target family landscape and different subsites. The first investigation resulted in rational figure interpretation of both domain organization as well as of substrate specificity classifications. The second made it possible to distinguish the MMP classes, demonstrating the high specificity of the S1' pocket, to detect both the occurrence of punctual mutations of ionisable residues and different side-chain conformations that likely account for induced-fit phenomena. In addition, CMC demonstrated a potential comparable to the most popular UPGMA (Unweighted Pair Group Method with Arithmetic mean method that, at present, represents a standard clustering bioinformatics approach. Interestingly, CMC and

A-centres build-up kinetics in the conductive matrix of pulled n-type silicon with calculation of their recharges at defect clusters

International Nuclear Information System (INIS)

Dolgolenko, A.P.; Fishchuk, I.I.

1981-01-01

Pulled n-Si samples with rho approximately 40 Ωcm are investigated after irradiation with different doses of fast-pile neutrons. It is known that the simple defects are created not only in the conductive matrix but also in the region of the space charge of defect clusters. Then the charge state, for example, of A-centres in the region of the space charge is defined by both, the temperature and the value of the electrostatical potential. If this circumstance is not taken into account the calculation of the conductive volume is not precise enough. In the present paper the temperature dependence of the volume fraction is calculated, in which the space charge of defect clusters occurs, taking into account the recharges of A-centres in the region of the space charge. Using the expression obtained the A-centres build-up kinetics in the conductive matrix of pulled n-type silicon is calculated. (author)

Classical-limit S-matrix for heavy ion scattering

International Nuclear Information System (INIS)

Donangelo, R.J.

1977-01-01

An integral representation for the classical limit of the quantum mechanical S-matrix is developed and applied to heavy-ion Coulomb excitation and Coulomb-nuclear interference. The method combines the quantum principle of superposition with exact classical dynamics to describe the projectile-target system. A detailed consideration of the classical trajectories and of the dimensionless parameters that characterize the system is carried out. The results are compared, where possible, to exact quantum mechanical calculations and to conventional semiclassical calculations. It is found that in the case of backscattering the classical limit S-matrix method is able to almost exactly reproduce the quantum-mechanical S-matrix elements, and therefore the transition probabilities, even for projectiles as light as protons. The results also suggest that this approach should be a better approximation for heavy-ion multiple Coulomb excitation than earlier semiclassical methods, due to a more accurate description of the classical orbits in the electromagnetic field of the target nucleus. Calculations using this method indicate that the rotational excitation probabilities in the Coulomb-nuclear interference region should be very sensitive to the details of the potential at the surface of the nucleus, suggesting that heavy-ion rotational excitation could constitute a sensitive probe of the nuclear potential in this region. The application to other problems as well as the present limits of applicability of the formalism are also discussed

1/2-BPS correlators as c = 1 S-matrix

International Nuclear Information System (INIS)

Jevicki, Antal; Yoneya, Tamiaki

2007-01-01

We argue from two complementary viewpoints of Holography that the 2-point correlation functions of 1/2-BPS multi-trace operators in the large-N (planar) limit are nothing but the (Wick-rotated) S-matrix elements of c = 1 matrix model. On the bulk side, we consider an Euclideanized version of the so-called bubbling geometries and show that the corresponding droplets reach the conformal boundary. Then the scattering matrix of fluctuations of the droplets gives directly the two-point correlators through the GKPW prescription. On the Yang-Mills side, we show that the two-point correlators of holomorphic and anti-holomorphic operators are essentially equivalent with the transformation functions between asymptotic in- and out-states of c = 1 matrix model. Extension to non-planar case is also discussed

Ferromagnetism and suppression of metallic clusters in Fe implanted ZnO: a phenomenon related to defects?

International Nuclear Information System (INIS)

Zhou Shengqiang; Potzger, K; Talut, G; Reuther, H; Kuepper, K; Grenzer, J; Xu Qingyu; Muecklich, A; Helm, M; Fassbender, J; Arenholz, E

2008-01-01

We investigated ZnO(0 0 0 1) single crystals annealed in high vacuum with respect to their magnetic properties and cluster formation tendency after implant-doping with Fe. While metallic Fe cluster formation is suppressed, no evidence for the relevance of the Fe magnetic moment to the observed ferromagnetism was found. The latter along with the cluster suppression is discussed with respect to defects in the ZnO host matrix, since the crystalline quality of the substrates was lowered due to the preparation as observed by x-ray diffraction

Spectral properties of the Google matrix of the World Wide Web and other directed networks.

Science.gov (United States)

Georgeot, Bertrand; Giraud, Olivier; Shepelyansky, Dima L

2010-05-01

We study numerically the spectrum and eigenstate properties of the Google matrix of various examples of directed networks such as vocabulary networks of dictionaries and university World Wide Web networks. The spectra have gapless structure in the vicinity of the maximal eigenvalue for Google damping parameter α equal to unity. The vocabulary networks have relatively homogeneous spectral density, while university networks have pronounced spectral structures which change from one university to another, reflecting specific properties of the networks. We also determine specific properties of eigenstates of the Google matrix, including the PageRank. The fidelity of the PageRank is proposed as a characterization of its stability.

Structures, stabilities, and electronic properties for rare-earth lanthanum doped gold clusters

International Nuclear Information System (INIS)

Zhao, Ya-Ru

2015-01-01

The structures, stabilities, and electronic properties of rare-earth lanthanum doped gold La 2 Au n (n = 1-9) and pure gold Au n (n ≤ 11) clusters have been investigated by using density functional theory. The optimized geometries show that the lowest energy structures of La 2 Au n clusters favour the 3D structure at n ≥ 3. The lanthanum atoms can strongly enhance the stabilities of gold clusters and tend to occupy the most highly coordinated position. By analysing the gap, vertical ionization potential, and chemical hardness, it is found that the La 2 Au 6 isomer possesses higher stability for small-sized La 2 Au n clusters (n = 1-9). The charges in the La 2 Au n clusters transfer from La atoms to the Au n host. In addition, Wiberg bond indices analysis reveals that the intensity of different bonds of La 2 Au n clusters exhibits a sequence of La-La bond > La-Au bond > Au-Au bond.

Towards Tuning the Mechanical Properties of Three-Dimensional Collagen Scaffolds Using a Coupled Fiber-Matrix Model

Directory of Open Access Journals (Sweden)

Shengmao Lin

2015-08-01

Full Text Available Scaffold mechanical properties are essential in regulating the microenvironment of three-dimensional cell culture. A coupled fiber-matrix numerical model was developed in this work for predicting the mechanical response of collagen scaffolds subjected to various levels of non-enzymatic glycation and collagen concentrations. The scaffold was simulated by a Voronoi network embedded in a matrix. The computational model was validated using published experimental data. Results indicate that both non-enzymatic glycation-induced matrix stiffening and fiber network density, as regulated by collagen concentration, influence scaffold behavior. The heterogeneous stress patterns of the scaffold were induced by the interfacial mechanics between the collagen fiber network and the matrix. The knowledge obtained in this work could help to fine-tune the mechanical properties of collagen scaffolds for improved tissue regeneration applications.

Mechanical Properties of TC4 Matrix Composites Prepared by Laser Cladding

Directory of Open Access Journals (Sweden)

WANG Lin

2017-06-01

Full Text Available In order to improve the penetration performance of TC4, the direct laser deposition technology was used to prepare TC4 composite material. TA15+30% TiC powder, TA15+20%Cr3C2 powder and TA15+15%B4C powder were used as deposited materials for TC4 matrix. The micromorphology, change of hardness of the deposited coating and mechanical properties of the three composites were studied. The experimental results demonstrate that the TC4 matrix with the three kinds of materials can form a complete metallurgical bonding, and the strength of TC4-(TA15+TiC, TC4-(TA15+Cr3C2 and TC4-(TA15+B4C are higher than that of TC4 matrix materials, while the plasticity is slightly worse.

Complex Masses in the S-Matrix

International Nuclear Information System (INIS)

Rupp, G.; Coito, S.; Beveren, E. van

2010-01-01

Most excited hadrons have multiparticle strong decay modes, which can often be described as resulting from intermediate states containing one or two resonances. In a theoretical approach, such a description in terms of quasi-two-particle initial and final states leads to unitarity violations, because of the complex masses of the involved resonances. In the present paper, an empirical algebraic procedure is presented to restore unitarity of the S-matrix while preserving its symmetry. Preliminary results are presented in a first application to S-wave ππ scattering, in the framework of the Resonance-Spectrum Expansion. (author)

Optical properties of cluster plasma

Energy Technology Data Exchange (ETDEWEB)

Kishimoto, Yasuaki; Tajima, Toshiki [Japan Atomic Energy Research Inst., Neyagawa, Osaka (Japan). Kansai Research Establishment; Downer, M C

1998-03-01

It is shown that unlike a gas plasma or an electron plasma in a metal, an ionized clustered material (`cluster plasma`) permits propagation below the plasma cut-off of electromagnetic (EM) waves whose phase velocity is close to but below the speed of light. This results from the excitation of a plasma oscillation mode (and/or polarization mode) through the cluster surface which does not exist in usual gaseous plasma. The existence of this new optical mode, cluster mode, is confirmed via numerical simulation. (author)

Cluster analysis of midlatitude oceanic cloud regimes: mean properties and temperature sensitivity

Directory of Open Access Journals (Sweden)

N. D. Gordon

2010-07-01

Full Text Available Clouds play an important role in the climate system by reducing the amount of shortwave radiation reaching the surface and the amount of longwave radiation escaping to space. Accurate simulation of clouds in computer models remains elusive, however, pointing to a lack of understanding of the connection between large-scale dynamics and cloud properties. This study uses a k-means clustering algorithm to group 21 years of satellite cloud data over midlatitude oceans into seven clusters, and demonstrates that the cloud clusters are associated with distinct large-scale dynamical conditions. Three clusters correspond to low-level cloud regimes with different cloud fraction and cumuliform or stratiform characteristics, but all occur under large-scale descent and a relatively dry free troposphere. Three clusters correspond to vertically extensive cloud regimes with tops in the middle or upper troposphere, and they differ according to the strength of large-scale ascent and enhancement of tropospheric temperature and humidity. The final cluster is associated with a lower troposphere that is dry and an upper troposphere that is moist and experiencing weak ascent and horizontal moist advection.

Since the present balance of reflection of shortwave and absorption of longwave radiation by clouds could change as the atmosphere warms from increasing anthropogenic greenhouse gases, we must also better understand how increasing temperature modifies cloud and radiative properties. We therefore undertake an observational analysis of how midlatitude oceanic clouds change with temperature when dynamical processes are held constant (i.e., partial derivative with respect to temperature. For each of the seven cloud regimes, we examine the difference in cloud and radiative properties between warm and cold subsets. To avoid misinterpreting a cloud response to large-scale dynamical forcing as a cloud response to temperature, we require horizontal and vertical

Delineation of Stenotrophomonas maltophilia isolates from cystic fibrosis patients by fatty acid methyl ester profiles and matrix-assisted laser desorption/ionization time-of-flight mass spectra using hierarchical cluster analysis and principal component analysis.

Science.gov (United States)

Vidigal, Pedrina Gonçalves; Mosel, Frank; Koehling, Hedda Luise; Mueller, Karl Dieter; Buer, Jan; Rath, Peter Michael; Steinmann, Joerg

2014-12-01

Stenotrophomonas maltophilia is an opportunist multidrug-resistant pathogen that causes a wide range of nosocomial infections. Various cystic fibrosis (CF) centres have reported an increasing prevalence of S. maltophilia colonization/infection among patients with this disease. The purpose of this study was to assess specific fingerprints of S. maltophilia isolates from CF patients (n = 71) by investigating fatty acid methyl esters (FAMEs) through gas chromatography (GC) and highly abundant proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and to compare them with isolates obtained from intensive care unit (ICU) patients (n = 20) and the environment (n = 11). Principal component analysis (PCA) of GC-FAME patterns did not reveal a clustering corresponding to distinct CF, ICU or environmental types. Based on the peak area index, it was observed that S. maltophilia isolates from CF patients produced significantly higher amounts of fatty acids in comparison with ICU patients and the environmental isolates. Hierarchical cluster analysis (HCA) based on the MALDI-TOF MS peak profiles of S. maltophilia revealed the presence of five large clusters, suggesting a high phenotypic diversity. Although HCA of MALDI-TOF mass spectra did not result in distinct clusters predominantly composed of CF isolates, PCA revealed the presence of a distinct cluster composed of S. maltophilia isolates from CF patients. Our data suggest that S. maltophilia colonizing CF patients tend to modify not only their fatty acid patterns but also their protein patterns as a response to adaptation in the unfavourable environment of the CF lung. © 2014 The Authors.

Cluster-cluster correlations in the two-dimensional stationary Ising-model

International Nuclear Information System (INIS)

Klassmann, A.

1997-01-01

In numerical integration of the Cahn-Hillard equation, which describes Oswald rising in a two-phase matrix, N. Masbaum showed that spatial correlations between clusters scale with respect to the mean cluster size (itself a function of time). T. B. Liverpool showed by Monte Carlo simulations for the Ising model that the analogous correlations have a similar form. Both demonstrated that immediately around each cluster there is some depletion area followed by something like a ring of clusters of the same size as the original one. More precisely, it has been shown that the distribution of clusters around a given cluster looks like a sinus-curve decaying exponentially with respect to the distance to a constant value

Glycolthermal synthesis and characterization of hexagonal CdS round microparticles in flower-like clusters

International Nuclear Information System (INIS)

Phuruangrat, Anukorn; Ekthammathat, Nuengruethai; Thongtem, Titipun; Thongtem, Somchai

2011-01-01

Highlights: → CdS as one of II-VI semiconducting materials. → Lab-made Teflon-lined stainless steel autoclaves enable us to form hexagonal CdS. → By 100-200 deg. C processing, round microparticles in flower clusters were synthesized. → A promising material for multiple potential applications. - Abstract: Hexagonal CdS round microparticles in flower-like clusters were synthesized by glycolthermal reactions of CdCl 2 and thiourea as cadmium and sulphur sources in 1,2-propylene glycol (PG) at 100-200 deg. C for 10-30 h. Phase and morphology were detected using X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM, TEM). The products were pure phase of hexagonal wurtzite CdS. The quantitative elemental analysis of Cd:S ratio was detected using energy dispersive X-ray (EDX) analyzer. Raman spectrometer revealed the presence of fundamental and overtone modes at 296 and 595 cm -1 , corresponding to the strong 1LO and weak 2LO modes, respectively. Photonic properties were investigated using UV-visible and photoluminescence (PL) spectroscopy. They showed the same absorption at 493-498 nm, and emission at 431 nm due to the excitonic recombination process. A possible formation mechanism was also proposed, according to experimental results.

Glycolthermal synthesis and characterization of hexagonal CdS round microparticles in flower-like clusters

Energy Technology Data Exchange (ETDEWEB)

Phuruangrat, Anukorn, E-mail: phuruangrat@hotmail.com [Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112 (Thailand); Ekthammathat, Nuengruethai [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thongtem, Titipun, E-mail: ttpthongtem@yahoo.com [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thongtem, Somchai [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

2011-10-13

Highlights: > CdS as one of II-VI semiconducting materials. > Lab-made Teflon-lined stainless steel autoclaves enable us to form hexagonal CdS. > By 100-200 deg. C processing, round microparticles in flower clusters were synthesized. > A promising material for multiple potential applications. - Abstract: Hexagonal CdS round microparticles in flower-like clusters were synthesized by glycolthermal reactions of CdCl{sub 2} and thiourea as cadmium and sulphur sources in 1,2-propylene glycol (PG) at 100-200 deg. C for 10-30 h. Phase and morphology were detected using X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM, TEM). The products were pure phase of hexagonal wurtzite CdS. The quantitative elemental analysis of Cd:S ratio was detected using energy dispersive X-ray (EDX) analyzer. Raman spectrometer revealed the presence of fundamental and overtone modes at 296 and 595 cm{sup -1}, corresponding to the strong 1LO and weak 2LO modes, respectively. Photonic properties were investigated using UV-visible and photoluminescence (PL) spectroscopy. They showed the same absorption at 493-498 nm, and emission at 431 nm due to the excitonic recombination process. A possible formation mechanism was also proposed, according to experimental results.

Electronic properties of large metal clusters in Jellium and pseudo-jellium models

International Nuclear Information System (INIS)

Catara, F.; Van Giai, N.; Chomaz, P.

1994-08-01

The energy-density functional approach and jellium-like models are used to examine two important electronic properties of metal (Li, Na, K) clusters: their shell and supershell structures, and the behaviour of plasmon energies with increasing cluster sizes. A comparative study is made between predictions of the usual jellium model and those of the pseudo-jellium model where pseudo-Hamiltonians are used. (authors) 10 figs., 5 tabs., 16 refs

Transport properties of dilute α -Fe (X ) solid solutions (X = C, N, O)

Science.gov (United States)

Schuler, Thomas; Nastar, Maylise

2016-06-01

We extend the self-consistent mean field (SCMF) method to the calculation of the Onsager matrix of Fe-based interstitial solid solutions. Both interstitial jumps and substitutional atom-vacancy exchanges are accounted for. A general procedure is introduced to split the Onsager matrix of a dilute solid solution into intrinsic cluster Onsager matrices, and extract from them flux-coupling ratios, mobilities, and association-dissociation rates for each cluster. The formalism is applied to vacancy-interstitial solute pairs in α -Fe (V X pairs, X = C, N, O), with ab initio based thermodynamic and kinetic parameters. Convergence of the cluster mobility contribution gives a controlled estimation of the cluster definition distance, taking into account both its thermodynamic and kinetic properties. Then, the flux-coupling behavior of each V X pair is discussed, and qualitative understanding is achieved from the comparison between various contributions to the Onsager matrix. Also, the effect of low-activation energy second-nearest-neighbor interstitial solute jumps around a vacancy on these results is addressed.

S-matrix analysis of the baryon electric charge correlation

Science.gov (United States)

Lo, Pok Man; Friman, Bengt; Redlich, Krzysztof; Sasaki, Chihiro

2018-03-01

We compute the correlation of the net baryon number with the electric charge (χBQ) for an interacting hadron gas using the S-matrix formulation of statistical mechanics. The observable χBQ is particularly sensitive to the details of the pion-nucleon interaction, which are consistently incorporated in the current scheme via the empirical scattering phase shifts. Comparing to the recent lattice QCD studies in the (2 + 1)-flavor system, we find that the natural implementation of interactions and the proper treatment of resonances in the S-matrix approach lead to an improved description of the lattice data over that obtained in the hadron resonance gas model.

S-matrix formulation of thermodynamics with N-body scatterings

Energy Technology Data Exchange (ETDEWEB)

Lo, Pok Man [University of Wroclaw, Institute of Theoretical Physics, Wroclaw (Poland); Extreme Matter Institute EMMI, GSI, Darmstadt (Germany)

2017-08-15

We apply a phase space expansion scheme to incorporate the N-body scattering processes in the S-matrix formulation of statistical mechanics. A generalized phase shift function suitable for studying the thermal contribution of N → N processes is motivated and examined in various models. Using the expansion scheme, we revisit how the hadron resonance gas model emerges from the S-matrix framework, and consider an example of structureless scattering in which the phase shift function can be exactly worked out. Finally we analyze the influence of dynamics on the phase shift function in a simple example of 3- and 4-body scattering. (orig.)

The double galaxy cluster Abell 2465 - I. Basic properties: optical imaging and spectroscopy

Science.gov (United States)

Wegner, Gary A.

2011-05-01

Optical imaging and spectroscopic observations of the z= 0.245 double galaxy cluster Abell 2465 are described. This object appears to be undergoing a major merger. It is a double X-ray source and is detected in the radio at 1.4 GHz. The purpose of this paper is to investigate signatures of the interaction of the two components. Redshifts were measured to determine velocity dispersions and virial radii of each component. The technique of fuzzy clustering was used to assign membership weights to the galaxies in each clump. Using redshifts of 93 cluster members within 1.4 Mpc of the subcluster centres, the virial masses of the north-east (NE) and south-west (SW) components are Mv= 4.1 ± 0.8 × 1014 and 3.8 ± 0.8 × 1014 M⊙, respectively. These agree within the errors with masses from X-ray scaling relations. The projected velocity difference between the two subclusters is 205 ± 149 km s-1. The anisotropy parameter, β, is found to be low for both components. Spectra of 37 per cent of the spectroscopically observed galaxies show emission lines and are predominantly star forming in the diagnostic diagram. No strong active galactic nucleus sources were found. The emission-line galaxies tend to lie between the two cluster centres with more near the SW clump. The luminosity functions of the two subclusters differ. The NE component is similar to many rich clusters, while the SW component has more faint galaxies. The NE clump’s light profile follows a single Navarro-Frenk-White profile with c= 10 while the SW is better fitted with an extended outer region and a compact inner core, consistent with available X-ray data indicating that the SW clump has a cooling core. The observed differences and properties of the two components of Abell 2465 are interpreted to have been caused by a collision 2-4 Gyr ago, after which they have moved apart and are now near their apocentres, although the start of a merger remains a possibility. The number of emission-line galaxies gives

Intercomparison of the GOS approach, superposition T-matrix method, and laboratory measurements for black carbon optical properties during aging

International Nuclear Information System (INIS)

He, Cenlin; Takano, Yoshi; Liou, Kuo-Nan; Yang, Ping; Li, Qinbin; Mackowski, Daniel W.

2016-01-01

We perform a comprehensive intercomparison of the geometric-optics surface-wave (GOS) approach, the superposition T-matrix method, and laboratory measurements for optical properties of fresh and coated/aged black carbon (BC) particles with complex structures. GOS and T-matrix calculations capture the measured optical (i.e., extinction, absorption, and scattering) cross sections of fresh BC aggregates, with 5–20% differences depending on particle size. We find that the T-matrix results tend to be lower than the measurements, due to uncertainty in theoretical approximations of realistic BC structures, particle property measurements, and numerical computations in the method. On the contrary, the GOS results are higher than the measurements (hence the T-matrix results) for BC radii 100 nm. We find good agreement (differences 100 nm. We find small deviations (≤10%) in asymmetry factors computed from the two methods for most BC coating structures and sizes, but several complex structures have 10–30% differences. This study provides the foundation for downstream application of the GOS approach in radiative transfer and climate studies. - Highlights: • The GOS and T-matrix methods capture laboratory measurements of BC optical properties. • The GOS results are consistent with the T-matrix results for BC optical properties. • BC optical properties vary remarkably with coating structures and sizes during aging.

Fabrication and properties of CNTs reinforced polymeric matrix nanocomposites for sports applications

International Nuclear Information System (INIS)

Rasheed, A; Khalid, F A

2014-01-01

The polymeric matrix composites have found extensive applications in sports because of high strength to weight ratio, ease of processing, and longer life. This work was carried out to study the properties of different sections of composite field hockey sticks and the influence of carbon nanotubes on their properties. The samples were fabricated by compression molding process. The increase in mechanical properties by the incorporation of carbon nanotubes is correlated with the process parameters to consider enhancement in the overall performance of the stick sections

Fabrication and properties of CNTs reinforced polymeric matrix nanocomposites for sports applications

International Nuclear Information System (INIS)

Rasheed, A.; Khalid, F. A.

2013-01-01

The polymeric matrix composites have found extensive applications in sports because of high strength to weight ratio, ease of processing, and longer life. This work was carried out to study the properties of different sections of composite field hockey sticks and the influence of carbon nanotubes on their properties. The samples were fabricated by compression molding process. The increase in mechanical properties by the incorporation of carbon nanotubes is correlated with the process parameters to consider enhancement in the overall performance of the stick sections. (author)

Enhanced magnetocrystalline anisotropy in deposited cobalt clusters

Energy Technology Data Exchange (ETDEWEB)

Eastham, D.A.; Denby, P.M.; Kirkman, I.W. [Daresbury Laboratory, Daresbury, Warrington (United Kingdom); Harrison, A.; Whittaker, A.G. [Department of Chemistry, University of Edinburgh, Edinburgh (United Kingdom)

2002-01-28

The magnetic properties of nanomaterials made by embedding cobalt nanocrystals in a copper matrix have been studied using a SQUID magnetometer. The remanent magnetization at temperatures down to 1.8 K and the RT (room temperature) field-dependent magnetization of 1000- and 8000-atom (average-size) cobalt cluster samples have been measured. In all cases it has been possible to relate the morphology of the material to the magnetic properties. However, it is found that the deposited cluster samples contain a majority of sintered clusters even at cobalt concentrations as low as 5% by volume. The remanent magnetization of the 8000-atom samples was found to be bimodal, consisting of one contribution from spherical particles and one from touching (sintered) clusters. Using a Monte Carlo calculation to simulate the sintering it has been possible to calculate a size distribution which fits the RT superparamagnetic behaviour of the 1000-atom samples. The remanent magnetization for this average size of clusters could then be fitted to a simple model assuming that all the nanoparticles are spherical and have a size distribution which fits the superparamagnetic behaviour. This gives a value for the potential energy barrier height (for reversing the spin direction) of 2.0 {mu}eV/atom which is almost four times the accepted value for face-centred-cubic bulk cobalt. The remanent magnetization for the spherical component of the large-cluster sample could not be fitted with a single barrier height and it is conjectured that this is because the barriers change as a function of cluster size. The average value is 1.5 {mu}eV/atom but presumably this value tends toward the bulk value (0.5 {mu}eV/atom) for the largest clusters in this sample. (author)

MOLECULAR CLUMPS AND INFRARED CLUSTERS IN THE S247, S252, AND BFS52 REGIONS

Energy Technology Data Exchange (ETDEWEB)

Shimoikura, Tomomi; Dobashi, Kazuhito [Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501 (Japan); Saito, Hiro; Nakamura, Fumitaka [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Matsumoto, Tomoaki [Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160 (Japan); Nishimura, Atsushi; Kimura, Kimihiro; Onishi, Toshikazu; Ogawa, Hideo, E-mail: ikura@u-gakugei.ac.jp [Department of Physical Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan)

2013-05-01

We present results of the observations carried out toward the S247, S252, and BFS52 H II regions with various molecular lines using the 1.85 m radio telescope and the 45 m telescope at Nobeyama Radio Observatory. There are at least 11 young infrared clusters (IR clusters) within the observed region. We found that there are two velocity components in {sup 12}CO (J = 2-1), and also that their spatial distributions show an anti-correlation. The IR clusters are located at their interfaces, suggesting that two distinct clouds with different velocities are colliding with each other, which may have induced the cluster formation. Based on {sup 13}CO (J = 1-0) and C{sup 18}O (J = 1-0) observations, we identified 16 clumps in and around the three H II regions. Eleven of the clumps are associated with the IR clusters and the other five clumps are not associated with any known young stellar objects. We investigated variations in the velocity dispersions of the 16 clumps as a function of the distance from the center of the clusters or the clumps. Clumps with clusters tend to have velocity dispersions that increase with distance from the cluster center, while clumps without clusters show a flat velocity dispersion over the clump extents. A {sup 12}CO outflow has been found in some of the clumps with IR clusters but not in the other clumps, supporting a strong relation of these clumps to the broader velocity dispersion region. We also estimated a mean star formation efficiency of {approx}30% for the clumps with IR clusters in the three H II regions.

Structure of the nucleotide-binding domain of a dipeptide ABC transporter reveals a novel iron-sulfur cluster-binding domain.

Science.gov (United States)

Li, Xiaolu; Zhuo, Wei; Yu, Jie; Ge, Jingpeng; Gu, Jinke; Feng, Yue; Yang, Maojun; Wang, Linfang; Wang, Na

2013-02-01

Dipeptide permease (Dpp), which belongs to an ABC transport system, imports peptides consisting of two or three L-amino acids from the matrix to the cytoplasm in microbes. Previous studies have indicated that haem competes with dipeptides to bind DppA in vitro and in vivo and that the Dpp system can also translocate haem. Here, the crystal structure of DppD, the nucleotide-binding domain (NBD) of the ABC-type dipeptide/oligopeptide/nickel-transport system from Thermoanaerobacter tengcongensis, bound with ATP, Mg(2+) and a [4Fe-4S] iron-sulfur cluster is reported. The N-terminal domain of DppD shares a similar structural fold with the NBDs of other ABC transporters. Interestingly, the C-terminal domain of DppD contains a [4Fe-4S] cluster. The UV-visible absorbance spectrum of DppD was consistent with the presence of a [4Fe-4S] cluster. A search with DALI revealed that the [4Fe-4S] cluster-binding domain is a novel structural fold. Structural analysis and comparisons with other ABC transporters revealed that this iron-sulfur cluster may act as a mediator in substrate (dipeptide or haem) binding by electron transfer and may regulate the transport process in Dpp ABC transport systems. The crystal structure provides a basis for understanding the properties of ABC transporters and will be helpful in investigating the functions of NBDs in the regulation of ABC transporter activity.

14O+p elastic scattering in a microscopic cluster model

International Nuclear Information System (INIS)

Descouvemont, P.; Baye, D.; Leo, F.

2006-01-01

The 14O+p elastic scattering is analyzed in a fully microscopic cluster model. With the Resonating Group Method associated with the microscopic R-matrix theory, phase shifts and cross sections are calculated. Data on 16O+p are used to test the precision of the model. For the 14O+p elastic scattering, an excellent agreement is found with recent experimental data. Resonances properties in 15F are discussed

Combining cluster number counts and galaxy clustering

Energy Technology Data Exchange (ETDEWEB)

Lacasa, Fabien; Rosenfeld, Rogerio, E-mail: fabien@ift.unesp.br, E-mail: rosenfel@ift.unesp.br [ICTP South American Institute for Fundamental Research, Instituto de Física Teórica, Universidade Estadual Paulista, São Paulo (Brazil)

2016-08-01

The abundance of clusters and the clustering of galaxies are two of the important cosmological probes for current and future large scale surveys of galaxies, such as the Dark Energy Survey. In order to combine them one has to account for the fact that they are not independent quantities, since they probe the same density field. It is important to develop a good understanding of their correlation in order to extract parameter constraints. We present a detailed modelling of the joint covariance matrix between cluster number counts and the galaxy angular power spectrum. We employ the framework of the halo model complemented by a Halo Occupation Distribution model (HOD). We demonstrate the importance of accounting for non-Gaussianity to produce accurate covariance predictions. Indeed, we show that the non-Gaussian covariance becomes dominant at small scales, low redshifts or high cluster masses. We discuss in particular the case of the super-sample covariance (SSC), including the effects of galaxy shot-noise, halo second order bias and non-local bias. We demonstrate that the SSC obeys mathematical inequalities and positivity. Using the joint covariance matrix and a Fisher matrix methodology, we examine the prospects of combining these two probes to constrain cosmological and HOD parameters. We find that the combination indeed results in noticeably better constraints, with improvements of order 20% on cosmological parameters compared to the best single probe, and even greater improvement on HOD parameters, with reduction of error bars by a factor 1.4-4.8. This happens in particular because the cross-covariance introduces a synergy between the probes on small scales. We conclude that accounting for non-Gaussian effects is required for the joint analysis of these observables in galaxy surveys.

Extracellular matrix organization in developing muscle: correlation with acetylcholine receptor aggregates.

Science.gov (United States)

Bayne, E K; Anderson, M J; Fambrough, D M

1984-10-01

Monoclonal antibodies recognizing laminin, heparan sulfate proteoglycan, fibronectin, and two apparently novel connective tissue components have been used to examine the organization of extracellular matrix of skeletal muscle in vivo and in vitro. Four of the five monoclonal antibodies are described for the first time here. Immunocytochemical experiments with frozen-sectioned muscle demonstrated that both the heparan sulfate proteoglycan and laminin exhibited staining patterns identical to that expected for components of the basal lamina. In contrast, the remaining matrix constituents were detected in all regions of muscle connective tissue: the endomysium, perimysium, and epimysium. Embryonic muscle cells developing in culture elaborated an extracellular matrix, each antigen exhibiting a unique distribution. Of particular interest was the organization of extracellular matrix on myotubes: the build-up of matrix components was most apparent in plaques overlying clusters of an integral membrane protein, the acetylcholine receptor (AChR). The heparan sulfate proteoglycan was concentrated at virtually all AChR clusters and showed a remarkable level of congruence with receptor organization; laminin was detected at 70-95% of AChR clusters but often was not completely co-distributed with AChR within the cluster; fibronectin and the two other extracellular matrix antigens occurred at approximately 20, 8, and 2% of the AChR clusters, respectively, and showed little or no congruence with AChR. From observations on the distribution of extracellular matrix components in tissue cultured fibroblasts and myogenic cells, several ideas about the organization of extracellular matrix are suggested. (a) Congruence between AChR clusters and heparan sulfate proteoglycan suggests the existence of some linkage between the two molecules, possibly important for regulation of AChR distribution within the muscle membrane. (b) The qualitatively different patterns of extracellular matrix

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)

Highly stabilized and photoluminescence enhancement of ZnS:Mn2+ nanoparticles in biotin matrix

International Nuclear Information System (INIS)

Keshari, Ashish K.; Pandey, Avinash C.

2009-01-01

We synthesized the ZnS:Mn 2+ nanoparticles passivated by biocompatible layer, namely, biotin by chemical precipitation route and studied their temporal evolution for size, structure, optical, and photoluminescence stability. To monitor the structural and optoelectronic properties of the nanoparticles with time, we have characterized the grown product by x-ray diffraction, small angle x-ray scattering, UV visible, and photoluminescence spectroscopic techniques at a regular interval for a period of three months. Results showed that the properties of nanophosphors capped with biotin are remaining the same even after 3 months. Energy dispersive x-ray analysis of 3 month aged sample shows long time compatibility between ZnS:Mn 2+ nanoparticles and the biotin. This is also confirmed by electron microscopy that the growth of the nanoparticles is strongly arrested by the biotin. X-ray photoelectron spectra were also recorded to show the chemical state of the elements. Enhanced ratio of Zn 2p to Mn 2p peaks in the x-ray photoelectron spectra of ZnS:Mn 2+ nanoparticles shows that the Mn 2+ ions are incorporated within ZnS host matrix. We found that biotin capping will enhance the luminescence from ZnS:Mn 2+ nanoparticles as compared to without capped particles. Absence of biotin will gradually degrade the luminescence upon aging while drastic degradation in luminescence intensity was observed after annealing. Properties show that biotin also protected the nanoparticles from any environmental attack

Physical–chemical properties, separation performance, and fouling resistance of mixed-matrix ultrafiltration membranes

KAUST Repository

Hoek, Eric M.V.; Ghosh, Asim K.; Huang, Xiaofei; Liong, Monty; Zink, Jeffrey I.

2011-01-01

Herein we report on the formation and characterization of mixed-matrix ultrafiltration (UF) membranes hand-cast by nonsolvent induced phase inversion. We evaluated nanometer-to-micrometer sized inorganic fillers (silver, copper, silica, zeolite, and silver-zeolite) materials with polysulfone (PSf) as the polymeric dispersing matrix. In general, mixed-matrix membranes were rougher, more hydrophilic, and more mechanically robust. Only sub-micron zeolite-PSf mixed-matrix membranes exhibited simultaneous improvements in water permeability and solute selectivity; all other mixed-matrix membranes were more permeable, but less selective due to defects associated with poor polymer-filler binding. Protein and bacterial fouling resistance of mixed-matrix membranes containing silver, zeolite, and silver-zeolite nanoparticles were compared to a low-fouling, poly(acrylonitrile) (PAN) UF membrane. Zeolite and silver containing membranes exhibited better protein fouling resistance (due to higher hydrophilicity), whereas silver and silver-zeolite based membranes produce better bacterial fouling resistance due to antimicrobial properties. Overall, zeolite-PSf and silver exchanged zeolite-PSf membranes offered the best combination of improved permeability, selectivity, and fouling resistance - superior to the commercial PAN membrane. © 2011 Elsevier B.V.

Physical–chemical properties, separation performance, and fouling resistance of mixed-matrix ultrafiltration membranes

KAUST Repository

Hoek, Eric M.V.

2011-12-01

Herein we report on the formation and characterization of mixed-matrix ultrafiltration (UF) membranes hand-cast by nonsolvent induced phase inversion. We evaluated nanometer-to-micrometer sized inorganic fillers (silver, copper, silica, zeolite, and silver-zeolite) materials with polysulfone (PSf) as the polymeric dispersing matrix. In general, mixed-matrix membranes were rougher, more hydrophilic, and more mechanically robust. Only sub-micron zeolite-PSf mixed-matrix membranes exhibited simultaneous improvements in water permeability and solute selectivity; all other mixed-matrix membranes were more permeable, but less selective due to defects associated with poor polymer-filler binding. Protein and bacterial fouling resistance of mixed-matrix membranes containing silver, zeolite, and silver-zeolite nanoparticles were compared to a low-fouling, poly(acrylonitrile) (PAN) UF membrane. Zeolite and silver containing membranes exhibited better protein fouling resistance (due to higher hydrophilicity), whereas silver and silver-zeolite based membranes produce better bacterial fouling resistance due to antimicrobial properties. Overall, zeolite-PSf and silver exchanged zeolite-PSf membranes offered the best combination of improved permeability, selectivity, and fouling resistance - superior to the commercial PAN membrane. © 2011 Elsevier B.V.

A Random Walk Approach to Query Informative Constraints for Clustering.

Science.gov (United States)

Abin, Ahmad Ali

2017-08-09

This paper presents a random walk approach to the problem of querying informative constraints for clustering. The proposed method is based on the properties of the commute time, that is the expected time taken for a random walk to travel between two nodes and return, on the adjacency graph of data. Commute time has the nice property of that, the more short paths connect two given nodes in a graph, the more similar those nodes are. Since computing the commute time takes the Laplacian eigenspectrum into account, we use this property in a recursive fashion to query informative constraints for clustering. At each recursion, the proposed method constructs the adjacency graph of data and utilizes the spectral properties of the commute time matrix to bipartition the adjacency graph. Thereafter, the proposed method benefits from the commute times distance on graph to query informative constraints between partitions. This process iterates for each partition until the stop condition becomes true. Experiments on real-world data show the efficiency of the proposed method for constraints selection.

Preparation and properties of DLC/MoS2 multilayer coatings for high humidity tribology

Science.gov (United States)

Zhao, Xiaoyu; Lu, Zhibin; Wu, Guizhi; Zhang, Guangan; Wang, Liping; Xue, Qunji

2016-06-01

The DLC/MoS2 multilayer coatings with different modulus ratios were deposited by magnetron sputtering in this study. The morphology, structure, composition, mechanical properties and tribological properties were investigated using several analytical techniques (FESEM, AFM, TEM, AES, XPS, nanoindentation and high humidity tribological test). The results showed that the well-defined multilayer coatings were composed of densely packed particles in which many nanocrystallines with some kinds of defects were distributed in matrix. The incorporation of oxygen into the lattice led to the degraded chemical stability. The coating’s hardness and elastic modulus were almost in the same range. Moderate improvement on the high humidity tribological properties were obtained, which was important for the extension of the service life of MoS2 in humid air.

Various Extraction Methods Influence the Adhesive Properties of Dried Distiller’s Grains and Solubles, and Press Cakes of Pennycress (Thlaspi arvense L. and Lesquerella [Lesquerella fendleri (A. Gary S. Watson], in the Fabrication of Lignocellulosic Composites

Directory of Open Access Journals (Sweden)

Brent Tisserat

2018-04-01

Full Text Available Lignocellulosic composite (LC panels were fabricated using an adhesive matrix prepared from three different agricultural by-products: dried distillers grains with solubles (DDGS, pennycress (Thlaspi arvense L. press cake (PPC, or lesquerella [Lesquerella fendleri (A. Gary S. Watson] press cake (LPC reinforced with Paulownia elongata L. wood (PW particles. The goal in this study was to assess the mechanical properties of composites utilizing these low-cost matrix materials, which were subjected to various oil extraction methods. Three types of oil extraction methods were utilized: ethanol, supercritical CO2, and hexane, in order to generate matrix materials. These matrix materials were mixed with equal proportions of PW and hot pressed to generate panels. Overall, hexane extraction was the best method to enhance the mechanical properties of the matrices used to fabricate lignocellulosic composites. LPC’s produced a matrix that gave the resulting composite superior flexural properties compared to composites generated from DDGS and PPC matrices. The mechanical properties of composites generated from soy products (soybean meal flour or soy protein isolate were similar to those derived from DDGS, PPC, or LPC. The dimensional stability properties of LCs were improved when the hexane extraction method was employed, unlike with the other extraction methods that were used to generate matrices.

Tetrahedron equations and the relativistic S-matrix of straight-strings in 2+1-dimensions

International Nuclear Information System (INIS)

Zamolodchikov, A.B.

1981-01-01

The quantum S-matrix theory of straight-strings (infinite one-dimensioanl objects like straight domain walls) in 2 + 1-dimensions is considered. The S-matrix is supposed to be purely elastic and factorized. The tetrahedron equations (which are the factorization conditions) are investigated for the special two-colour model. The relativistic three-string S-matrix, which apparently satisfies this tetrahedron equation, is proposed. (orig.)

Effects of interface formation kinetics on the microstructural properties of wear-resistant metal-matrix composites

International Nuclear Information System (INIS)

Ilo, S.; Just, Ch.; Badisch, E.; Wosik, J.; Danninger, H.

2010-01-01

Research highlights: The dissolution reaction kinetics and the formation of intermediate layers of tungsten carbides in Ni-(Cr)-B-Si matrices were studied in liquid-phase sintering with well-defined temperature/time relationship. → The internal intermediate layer formation, close to the original primary tungsten carbide showed diffusion-controlled kinetic (∼t 0.5 ), whereas the outside layer thickness formation, proportional to the processing time (∼t), was formed by the subsequent eutectic reaction of the Ni-(Cr)-B-Si matrix with the WC/W 2 C component. → Cr-addition in the matrix highly influences the inner layer thickness caused probably by increasing the C-diffusion rate, whereas the outer layer thickness was not dependent on the initial Cr-content in the matrix. Generally, the Cr-addition in the Ni-based matrix increased the hardness and elastic modulus of the intermediate phases along the carbide/matrix interface. → The different microstructure gradients are depended mainly on the interface growth kinetics. → The intermediate layers are hard phases (carbides, borides or carbo-borides). → The hardness of the carbide/matrix interface area is significantly lower as the hardness of the original primary tungsten carbides. - Abstract: Hard-particle metal-matrix composites (MMC) are generally used to increase the lifetime of machinery equipment exposed to severe wear conditions. Depending on the manufacturing technology, dissolution reactions of hard phases undergo different temperature/time profiles during processing affecting the microstructure and mechanical properties of the MMCs. Therefore, quantification of the carbide dissolution effects on the microstructure and micro-mechanical properties is the key to success in the development and optimisation of MMCs. Dissolution kinetics of WC/W 2 C in Ni-based matrices were determined in the liquid-sintering with a well-defined temperature/time profile. Microscopic evaluation of the samples showed two

Evaluation of mechanical properties of aluminium alloy–alumina–boron carbide metal matrix composites

International Nuclear Information System (INIS)

Vijaya Ramnath, B.; Elanchezhian, C.; Jaivignesh, M.; Rajesh, S.; Parswajinan, C.; Siddique Ahmed Ghias, A.

2014-01-01

Highlights: • Fabrication of MMC with aluminium alloy–alumina–boron carbide is done. • Different proportions of reinforcements are added. • The effects of varying proportions are studied. • Investigation on mechanical properties above composites is performed. • Failure morphology analysis is done using SEM. - Abstract: This paper deals with the fabrication and mechanical investigation of aluminium alloy, alumina (Al 2 O 3 ) and boron carbide metal matrix composites. Aluminium is the matrix metal having properties like light weight, high strength and ease of machinability. Alumina which has better wear resistance, high strength, hardness and boron carbide which has excellent hardness and fracture toughness are added as reinforcements. Here, the fabrication is done by stir casting which involves mixing the required quantities of additives into stirred molten aluminium. After solidification, the samples are prepared and tested to find the various mechanical properties like tensile, flexural, impact and hardness. The internal structure of the composite is observed using Scanning Electron Microscope (SEM)

Nanostructure of aluminium alloy 2024: Segregation, clustering and precipitation processes

International Nuclear Information System (INIS)

Sha, G.; Marceau, R.K.W.; Gao, X.; Muddle, B.C.; Ringer, S.P.

2011-01-01

Variations in solute element distribution occurring in a commercial 2024 aluminium alloy during isothermal ageing treatments at 170 deg. C for up to 120 h have been characterized using atom probe tomography. An early (0.5 h at 170 deg. C) rapid increase in hardness was correlated with the formation of fine scale (average 24 atom) solute clusters, comprising principally Mg and Cu, but with minor concentrations of Si and Zn. There was, in addition, evidence of significant segregation of Mg, Cu and Si to at least some fraction of grain boundaries and existing matrix dislocations. At peak hardness (80 h at 170 deg. C) the microstructure comprised coarse precipitates of S phase, with a composition approaching stoichiometric Al 2 CuMg, a dense distribution of Guinier-Preston-Bagaryatsky zones elongated parallel to in a matrix of α-Al and a residual distribution of smaller equiaxed solute clusters. Both the clusters and zones contained predominantly Mg and Cu, with minor concentrations of Si and Zn. The S phase contained small but significant (0.5-1.8 at.%) concentrations of Si, which was non-uniformly distributed in elongated domains within the laths of the S phase. In overaged samples (114 h at 170 deg. C) the microstructure comprised almost exclusively coarse S phase, Al 2 Mg(Cu,Si), in assemblies suggestive of a combination of precipitate coarsening and coalescence.

Comparison of FeS, FeS + S and solid superacid catalytic properties for coal hydro-liquefaction

Energy Technology Data Exchange (ETDEWEB)

Zhicai Wang; Hengfu Shui; Dexiang Zhang; Jinsheng Gao [East China University of Science and Technology, Shanghai (China). College of Resource and Environment Engineering

2007-03-15

Catalyst plays an important role in direct coal liquefaction. This paper focuses on the catalytic behavior of a novel SO{sub 4}{sup 2-}/ZrO{sub 2} superacid catalyst in coal hydro-liquefaction. A series of hydro-liquefaction experiments were conducted under mild conditions - 400{sup o}C, 30 min and H{sub 2} initial pressure 4 MPa in a batch autoclave with a volume of 100 ml. The catalytic property of SO{sub 4}{sup 2-}/ZrO{sub 2} was compared with FeS and FeS + S by Shenhua coal. The liquefaction products catalyzed by different catalysts were analyzed by FTIR spectrum, {sup 1}H NMR spectrum and element analysis. In addition, the SO{sub 4}{sup 2-}/ZrO{sub 2} solid superacid was characterized. The results indicated that the SO{sub 4}{sup 2-}/ZrO{sub 2} solid superacid shows outstanding catalytic property for direct liquefaction of coal and gives the highest coal conversion and gas + oil yield compared to other two catalysts. The THF conversion and the extraction yield of CS{sub 2}/NMP mixed solvent of liquefied coal catalyzed with SO{sub 4}{sup 2-}/ZrO{sub 2} are 76.3%, daf and 81.2%, daf respectively, and the yield of gas + oil is 62.5%, daf under the condition used in this study. The pyrolysis of coal macromolecular clusters can be promoted by catalysts such as FeS, FeS + S and SO{sub 4}{sup 2-}/ZrO{sub 2}. There may be only the pyrolysis of volatile matter and the relaxation of the structure of coal macromolecular clusters in non-catalytic liquefaction at 400{sup o}C. Added sulfur in FeS can improve the catalytic activity of hydrogenation. SO{sub 4}{sup 2-}/ZrO{sub 2} is a notable catalyst in the study of coal direct liquefaction because it shows excellent catalytic activities for the pyrolysis and the hydrogenation. In addition, it has been found that the C-O bond is the most stable group in coal liquefaction reaction except for the covalent bond between carbon and carbon. 34 refs., 6 figs., 6 tabs.

Mechanical Properties Analysis Of Composite Magnetic Base On hexa ferrite And Polyester Or Epoxy Matrix With Silane Additive Addition

International Nuclear Information System (INIS)

Sudirman; Ridwan; Mujamilah; K K, Aloma; Rembulan, Marisa; Fitriyanti

2003-01-01

Application of composite magnetic especially hexa ferrite magnet for industry and home industry in Indonesia has been used. Research purposes were making composite magnetic by mixing hexa ferrite powder with polyester or epoxy and studying the effect of coupling agent 3-aminopropyltriethoxysilane (3-APE) addition on mechanical properties of composite magnetic. The coupling agent may increase bonding properties between magnetic powder and matrix polymer, so that tensile strength of magnetic composite will increase without decreasing the magnetic properties. Magnetic powder (SrM or BaM) wich be coated by coupling agent were added to matrix polyester and mekpo or epoxy and versamid, mixed until homogen then pressing into to the dumbbell form molding. For epoxy matrix, pressing was done in hot press at 70 deg. C and 150 kg/cm 2 following by cooling in cold press, while for polyester matrix pressing was done in hydraulic press and following by curing at 70 deg. C in an oven for 1 hour. The composition of magnetic powder were varied to 30, 40 and 50% volume fraction and coupling agent were varied to 5, 10 and 15 ml for every volume fraction. The result showed that 10 ml added of coupling agent was give best mechanical properties both polyester and epoxy matrix. However generally, increasing of magnetic powder content decreased the tensile strength of magnetic composite. The properties of magnetic composite SrM was better than BaM either in polyester or epoxy matrix

Theoretical approach to embed nanocrystallites into a bulk crystalline matrix and the embedding influence on the electronic band structure and optical properties of the resulting heterostructures

Science.gov (United States)

Balagan, Semyon A.; Nazarov, Vladimir U.; Shevlyagin, Alexander V.; Goroshko, Dmitrii L.; Galkin, Nikolay G.

2018-06-01

We develop an approach and present results of the combined molecular dynamics and density functional theory calculations of the structural and optical properties of the nanometer-sized crystallites embedded in a bulk crystalline matrix. The method is designed and implemented for both compatible and incompatible lattices of the nanocrystallite (NC) and the host matrix, when determining the NC optimal orientation relative to the matrix constitutes a challenging problem. We suggest and substantiate an expression for the cost function of the search algorithm, which is the energy per supercell generalized for varying number of atoms in the latter. The epitaxial relationships at the Si/NC interfaces and the optical properties are obtained and found to be in a reasonable agreement with experimental data. Dielectric functions show significant sensitivity to the NC’s orientation relative to the matrix at energies below 0.5 eV.

Properties of an ionised-cluster beam from a vaporised-cluster ion source

International Nuclear Information System (INIS)

Takagi, T.; Yamada, I.; Sasaki, A.

1978-01-01

A new type of ion source vaporised-metal cluster ion source, has been developed for deposition and epitaxy. A cluster consisting of 10 2 to 10 3 atoms coupled loosely together is formed by adiabatic expansion ejecting the vapour of materials into a high-vacuum region through the nozzle of a heated crucible. The clusters are ionised by electron bombardment and accelerated with neutral clusters toward a substrate. In this paper, mechanisms of cluster formation experimental results of the cluster size (atoms/cluster) and its distribution, and characteristics of the cluster ion beams are reported. The size is calculated from the kinetic equation E = (1/2)mNVsub(ej) 2 , where E is the cluster beam energy, Vsub(ej) is the ejection velocity, m is the mass of atom and N is the cluster size. The energy and the velocity of the cluster are measured by an electrostatic 127 0 energy analyser and a rotating disc system, respectively. The cluster size obtained for Ag is about 5 x 10 2 to 2 x 10 3 atoms. The retarding potential method is used to confirm the results for Ag. The same dependence on cluster size for metals such as Ag, Cu and Pb has been obtained in previous experiments. In the cluster state the cluster ion beam is easily produced by electron bombardment. About 50% of ionised clusters are obtained under typical operation conditions, because of the large ionisation cross sections of the clusters. To obtain a uniform spatial distribution, the ionising electrode system is also discussed. The new techniques are termed ionised-cluster beam deposition (ICBD) and epitaxy (ICBE). (author)

Structural stabilities and electronic properties of Mg28-nAln clusters: A first-principles study

Directory of Open Access Journals (Sweden)

Bao-Juan Lu

2017-09-01

Full Text Available In this paper, we have constructed the alloy configurations of Mg28-nAln by replacing atoms at various possible positions, starting from the stable structures of Mg28 and Al28 clusters. According to the symmetry of the cluster structure, the isomers of these initial structures have been screened with the congruence check, which would reduce computational hours and improve efficiency. Using the first-principles method, the structural evolution, mixing behavior and electronic properties of Mg28-nAln clusters are investigated for all compositions. We conclude that Al atoms prefer to reside in the central positions of Mg−Al clusters and Mg atoms tend to occupy the peripheral location. The negative mixing enthalpies imply the stabilities of these Mg-Al clusters and thus possible applications in catalysis and hydrogen storage materials. Among Mg28-nAln clusters, Mg24Al4, Mg21Al7, Mg14Al14, Mg26Al2 and Mg27Al1 present relatively high thermodynamic stabilities, and the electronic properties of these stable structures are discussed with the charge distributions around the Fermi level.

Cu 4s → 4p atomic like excitations in the Ne matrix.

Science.gov (United States)

Hatano, Yasuyo; Tatewaki, Hiroshi; Yamamoto, Shigeyoshi

2013-06-07

The lowest three or four excited states (the triplet or quartet states) of the Cu atom in a neon (Ne) matrix have been studied experimentally, and have been presumed to have the electronic configuration of Cu 4p(1). The origins of the triplet and the quartet are not yet fully clear, although many models have been proposed. It has been argued, for example, that the existence of different trapping sites would give rise to two partly overlapping triplets, leading to spectra having three or four lines or more. Below, the electronic structures of the ground state and lowest excited states of the Cu atom in the neon matrix are clarified by means of ab initio molecular orbital calculations, using the cluster model. It was found that a rather large vacancy (hollow) with residual Ne atoms is vital for explaining the observed spectra having three or more lines; the Cu atom occupies the center of the substitutional site of a face-centered cubic (fcc)-like cluster comprising 66 Ne atoms, in which the first shell composed of 12 Ne atoms is empty. The presence of the residual Ne atoms in the first shell gives rise to more than three excited states, explaining the experimental spectra. Electron-electron interaction (including the crystal field) and spin-orbit interaction are both important in explaining the experimental spectra.

The early S-matrix theory and its propagation (1942-1952)

International Nuclear Information System (INIS)

Rechenberg, H.

1989-01-01

This paper describes the development of S-matrix theory in the 1940s and 1950s, which described the scattering and emission problems in elementary particle theory. Its chief architect, Werner Heisenberg, worked in Germany all through the Second World War. Communication problems were intense and made discussion of this useful tool very difficult. Werner Heisenberg's collaborative efforts with Hendrik Kramers in Holland and Christian Moeller are noted. The theory had its opponents and their objections are described. As other scientists took up the theory it was used in new ways such as in quantum electrodynamics, and to predict the creation of massive particles by analyzing S-matrix threshold behaviour. Although the theory fell into disfavour in the early 1950s, it was later readopted when ideas such as crossed channels and analytic behaviour in the complex angular-momentum plane needed explanations. (UK)

Vacuum states and the S matrix in dS/CFT

International Nuclear Information System (INIS)

Spradlin, Marcus; Volovich, Anastasia

2002-01-01

We propose a definition of dS/CFT correlation functions by equating them to S-matrix elements for scattering particles from I - to I + . In planar coordinates, which cover half of de Sitter space, we consider instead the S vector obtained by specifying a fixed state on the horizon. We construct the one-parameter family of de Sitter invariant vacuum states for a massive scalar field in these coordinates, and show that the vacuum obtained by analytic continuation from the sphere has no particles on the past horizon. We use this formalism to provide evidence that the one-parameter family of vacua corresponds to marginal deformations of the CFT by computing a three-point function

Extended biorthogonal matrix polynomials

Directory of Open Access Journals (Sweden)

Ayman Shehata

2017-01-01

Full Text Available The pair of biorthogonal matrix polynomials for commutative matrices were first introduced by Varma and Tasdelen in [22]. The main aim of this paper is to extend the properties of the pair of biorthogonal matrix polynomials of Varma and Tasdelen and certain generating matrix functions, finite series, some matrix recurrence relations, several important properties of matrix differential recurrence relations, biorthogonality relations and matrix differential equation for the pair of biorthogonal matrix polynomials J(A,B n (x, k and K(A,B n (x, k are discussed. For the matrix polynomials J(A,B n (x, k, various families of bilinear and bilateral generating matrix functions are constructed in the sequel.

MoS_2/Ag nanohybrid: A novel matrix with synergistic effect for small molecule drugs analysis by negative-ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

International Nuclear Information System (INIS)

Zhao, Yaju; Deng, Guoqing; Liu, Xiaohui; Sun, Liang; Li, Hui; Cheng, Quan; Xi, Kai; Xu, Danke

2016-01-01

This paper reports a facile synthesis of molybdenum disulfide nanosheets/silver nanoparticles (MoS_2/Ag) hybrid and its use as an effective matrix in negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The nanohybrid exerts a strong synergistic effect, leading to high performance detection of small molecule analytes including amino acids, peptides, fatty acids and drugs. The enhancement of laser desorption/ionization (LDI) efficiency is largely attributed to the high surface roughness and large surface area for analyte adsorption, better dispersibility, increased thermal conductivity and enhanced UV energy absorption as compared to pure MoS_2. Moreover, both Ag nanoparticles and the edge of the MoS_2 layers function as deprotonation sites for proton capture, facilitating the charging process in negative ion mode and promoting formation of negative ions. As a result, the MoS_2/Ag nanohybrid proves to be a highly attractive matrix in MALDI-TOF MS, with desired features such as high desorption/ionization efficiency, low fragmentation interference, high salt tolerance, and no sweet-spots for mass signal. These characteristic properties allowed for simultaneous analysis of eight different drugs and quantification of acetylsalicylic acid in the spiked human serum. This work demonstrates for the first time the fabrication and application of a novel MoS_2/Ag hybrid, and provides a new platform for use in the rapid and high throughput analysis of small molecules by mass spectrometry. - Highlights: • MoS_2/Ag nanohybrid was applied as a novel matrix in negative-ion MALDI-TOF MS. • The MoS_2/Ag nanohybrid exerted synergistic effect on the detection of small molecules. • The MoS_2/Ag nanohybrid showed good signal reproducibility and low background interferences comparing to organic matrices. • MoS_2/Ag allows simultaneous analysis of multiple drugs and quantification of acetylsalicylic acid in spiked serum samples.

Ground state structures and properties of Si3Hn (n= 1–6) clusters

Indian Academy of Sciences (India)

The ground state structures and properties of Si3H (1 ≤ ≤ 6) clusters have been calculated using Car–Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. We have studied cohesive energy per particle and first excited electronic level gap of the clusters as a function of ...

Breathing Raman modes in Ag{sub 2}S nanoparticles obtained from F9 zeolite matrix

Energy Technology Data Exchange (ETDEWEB)

Delgado-Beleño, Y. [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190 Hermosillo, Son. (Mexico); Cortez-Valadez, M., E-mail: jose.cortez@unison.mx [CONACYT Research Fellow, Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190 Hermosillo, Son. (Mexico); Martinez-Nuñez, C.E.; Britto Hurtado, R.; Alvarez, Ramón A.B.; Rocha-Rocha, O.; Arizpe-Chávez, H.; Perez-Rodríguez, A.; Flores-Acosta, M. [Departamento de Investigación en Física, Universidad de Sonora, Apdo. Postal 5-88, 83190 Hermosillo, Son. (Mexico)

2015-12-16

Highlights: • Raman breathing modes in small silver sulfide nanoparticles. • Low energy (AgS){sub n} clusters. • Vibrational spectra predicted by DFT. • Zeolite synthesis for small nanoparticles. - Abstract: Ag{sub 2}S nanoparticles were synthesized with a combination of synthetic F9, silver nitrate (AgNO{sub 3}) and monohydrated sodium sulfide (Na{sub 2}S{sub 9}H{sub 2}O). An ionic exchange was achieved via hydrothermal reaction. Nanoparticles with a predominant size ranging from 2 to 3 nm were obtained through Transmission Electron Microscopy (TEM). The nanoparticles feature a phase P21/n (14) monoclinic structure. A Raman band can be observed at around 250 cm{sup −1} in the nanoparticles. Furthermore, the vibrational properties and stability parameters of the clusters (AgS){sub n}, (with n = 2–9) were studied by the Density Functional Theory (DFT). The approximation levels used with DFT were: Local Spin Density Approximation (LSDA) and Becke’s three-parameter and the gradient corrected functional of Lee, Yang and Puar (B3LYP) in combination with the basis set LANL2DZ (the effective core potentials and associated double-zeta valence). The Radial Breathing Mode (RBM) for B3LYP was found between 227 and 295 cm{sup −1} as well as in longer wavelengths for LSDA.

Exploring the Optical and Morphological Properties of Ag and Ag/TiO2 Nanocomposites Grown by Supersonic Cluster Beam Deposition

Directory of Open Access Journals (Sweden)

Emanuele Cavaliere

2017-12-01

Full Text Available Nanocomposite systems and nanoparticle (NP films are crucial for many applications and research fields. The structure-properties correlation raises complex questions due to the collective structure of these systems, often granular and porous, a crucial factor impacting their effectiveness and performance. In this framework, we investigate the optical and morphological properties of Ag nanoparticles (NPs films and of Ag NPs/TiO2 porous matrix films, one-step grown by supersonic cluster beam deposition. Morphology and structure of the Ag NPs film and of the Ag/TiO2 (Ag/Ti 50-50 nanocomposite are related to the optical properties of the film employing spectroscopic ellipsometry (SE. We employ a simple Bruggeman effective medium approximation model, corrected by finite size effects of the nano-objects in the film structure to gather information on the structure and morphology of the nanocomposites, in particular porosity and average NPs size for the Ag/TiO2 NP film. Our results suggest that SE is a simple, quick and effective method to measure porosity of nanoscale films and systems, where standard methods for measuring pore sizes might not be applicable.

Electronic and magnetic properties of 3d transition metal-doped strontium clusters: Prospective magnetic superatoms

International Nuclear Information System (INIS)

Chauhan, Vikas; Sen, Prasenjit

2013-01-01

Highlights: • Structural, electronic and magnetic properties of TM-Sr clusters are studied using DFT methods. • CrSr 9 and MnSr 10 have enhanced stability in the CrSr n and MnSrn series. • These two clusters behave as magnetic superatoms. • A qualitative understanding of the magnetic coupling between two superatom units is offered. • Reactivity of these superatoms to molecular oxygen also studied. - Abstract: Structural, electronic and magnetic properties of 3d transition metal doped strontium clusters are studied using first-principles electronic structure methods based on density functional theory. Clusters with enhanced kinetic and thermodynamic stability are identified by studying their hardness, second order energy difference and adiabatic spin excitation energy. CrSr 9 and MnSr 10 are found to have enhanced stability. They retain their structural identities in assemblies, and are classified as magnetic superatoms. A qualitative understanding of the magnetic coupling between two cluster units is arrived at. Reactivity of these superatoms with O 2 molecule is also studied. Prospects for using these magnetic superatoms in applications are discussed

Properties of coupled-cluster equations originating in excitation sub-algebras

Science.gov (United States)

Kowalski, Karol

2018-03-01

In this paper, we discuss properties of single-reference coupled cluster (CC) equations associated with the existence of sub-algebras of excitations that allow one to represent CC equations in a hybrid fashion where the cluster amplitudes associated with these sub-algebras can be obtained by solving the corresponding eigenvalue problem. For closed-shell formulations analyzed in this paper, the hybrid representation of CC equations provides a natural way for extending active-space and seniority number concepts to provide an accurate description of electron correlation effects. Moreover, a new representation can be utilized to re-define iterative algorithms used to solve CC equations, especially for tough cases defined by the presence of strong static and dynamical correlation effects. We will also explore invariance properties associated with excitation sub-algebras to define a new class of CC approximations referred to in this paper as the sub-algebra-flow-based CC methods. We illustrate the performance of these methods on the example of ground- and excited-state calculations for commonly used small benchmark systems.

Emerging critical roles of Fe-S clusters in DNA replication and repair

Science.gov (United States)

Fuss, Jill O.; Tsai, Chi-Lin; Ishida, Justin P.; Tainer, John A.

2015-01-01

Fe-S clusters are partners in the origin of life that predate cells, acetyl-CoA metabolism, DNA, and the RNA world. The double helix solved the mystery of DNA replication by base pairing for accurate copying. Yet, for genome stability necessary to life, the double helix has equally important implications for damage repair. Here we examine striking advances that uncover Fe-S cluster roles both in copying the genetic sequence by DNA polymerases and in crucial repair processes for genome maintenance, as mutational defects cause cancer and degenerative disease. Moreover, we examine an exciting, controversial role for Fe-S clusters in a third element required for life – the long-range coordination and regulation of replication and repair events. By their ability to delocalize electrons over both Fe and S centers, Fe-S clusters have unbeatable features for protein conformational control and charge transfer via double-stranded DNA that may fundamentally transform our understanding of life, replication, and repair. PMID:25655665

Clustering of scientific citations in Wikipedia

DEFF Research Database (Denmark)

Nielsen, Finn Årup

The instances of templates in Wikipedia form an interesting data set of structured information. Here I focus on the cite journal template that is primarily used for citation to articles in scientific journals. These citations can be extracted and analyzed: Non-negative matrix factorization...... is performed on a (article x journal) matrix resulting in a soft clustering of Wikipedia articles and scientific journals, each cluster more or less representing a scientific topic....

Note on dual superconformal symmetry of the N=4 super Yang-Mills S matrix

International Nuclear Information System (INIS)

Brandhuber, Andreas; Heslop, Paul; Travaglini, Gabriele

2008-01-01

We present a supersymmetric recursion relation for tree-level scattering amplitudes in N=4 super Yang-Mills. Using this recursion relation, we prove that the tree-level S matrix of the maximally supersymmetric theory is covariant under dual superconformal transformations. We further analyze the consequences that the transformation properties of the trees under this symmetry have on those of the loops. In particular, we show that the coefficients of the expansion of generic one-loop amplitudes in a basis of pseudoconformally invariant scalar box functions transform covariantly under dual superconformal symmetry, and in exactly the same way as the corresponding tree-level amplitudes.

The thermodynamic and kinetic interactions of He interstitial clusters with bubbles in W

Energy Technology Data Exchange (ETDEWEB)

Perez, Danny, E-mail: danny-perez@lanl.gov; Sandoval, Luis; Voter, Arthur F. [Theoretical Division T-1, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Uberuaga, Blas P. [Materials Science and Technology MST-8, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2016-05-28

Due to its enviable properties, tungsten is a leading candidate plasma facing material in nuclear fusion reactors. However, like many other metals, tungsten is known to be affected by the high doses of helium atoms incoming from the plasma. Indeed, the implanted interstitial helium atoms cluster together and, upon reaching a critical cluster size, convert into substitutional nanoscale He bubbles. These bubbles then grow by absorbing further interstitial clusters from the matrix. This process can lead to deleterious changes in microstructure, degradation of mechanical properties, and contamination of the plasma. In order to better understand the growth process, we use traditional and accelerated molecular dynamics simulations to investigate the interactions between interstitial He clusters and pre-existing bubbles. These interactions are characterized in terms of thermodynamics and kinetics. We show that the proximity of the bubble leads to an enhancement of the trap mutation rate and, consequently, to the nucleation of satellite bubbles in the neighborhood of existing ones. We also uncover a number of mechanisms that can lead to the subsequent annihilation of such satellite nanobubbles.

Nuclear reaction matrix and nuclear forces

International Nuclear Information System (INIS)

Nagata, Sinobu; Bando, Hiroharu; Akaishi, Yoshinori.

1979-01-01

An essentially exact method of solution is presented for the reaction- matrix (G-matrix) equation defined with the orthogonalized plane-wave intermediate spectrum for high-lying two-particle states. The accuracy is examined for introduced truncations and also in comparison with the Tsai-Kuo and Sauer methods. Properties of the G-matrix are discussed with emphasis on the relation with the saturation mechanism, especially overall saturation from light to heavy nuclei. Density and starting-energy dependences of the G-matrix are separately extracted and discussed. It is demonstrated that the triplet-even tensor component of the nuclear force is principally responsible for these dependences and hence for the saturation mechanism. In this context different nuclear potentials are used in the renormalized Brueckner calculation for energies of closed-shell nuclei in the harmonic oscillator basis. A semi-phenomenological ''two-body potential'' is devised so that it can reproduce the saturation energies and densities of nuclear matter and finite nuclei in the lowest-order Brueckner treatment. It is composed of a realistic N-N potential and two additional parts; one incorporates the three-body force effect and the other is assumed to embody higher-cluster correlations in G. The tensor component in the triplet-even state of this potential is enhanced by the three-body force effect. The G-matrix is represented in the effective local form and decomposed into central, LS and tensor components. (author)

Clustering of Health Behaviors and Cardiorespiratory Fitness Among U.S. Adolescents.

Science.gov (United States)

Hartz, Jacob; Yingling, Leah; Ayers, Colby; Adu-Brimpong, Joel; Rivers, Joshua; Ahuja, Chaarushi; Powell-Wiley, Tiffany M

2018-05-01

Decreased cardiorespiratory fitness (CRF) is associated with an increased risk of cardiovascular disease. However, little is known how the interaction of diet, physical activity (PA), and sedentary time (ST) affects CRF among adolescents. By using a nationally representative sample of U.S. adolescents, we used cluster analysis to investigate the interactions of these behaviors with CRF. We hypothesized that distinct clustering patterns exist and that less healthy clusters are associated with lower CRF. We used 2003-2004 National Health and Nutrition Examination Survey data for persons aged 12-19 years (N = 1,225). PA and ST were measured objectively by an accelerometer, and the American Heart Association Healthy Diet Score quantified diet quality. Maximal oxygen consumption (V˙O 2 ​max) was measured by submaximal treadmill exercise test. We performed cluster analysis to identify sex-specific clustering of diet, PA, and ST. Adjusting for accelerometer wear time, age, body mass index, race/ethnicity, and the poverty-to-income ratio, we performed sex-stratified linear regression analysis to evaluate the association of cluster with V˙O 2 ​max. Three clusters were identified for girls and boys. For girls, there was no difference across clusters for age (p = .1), weight (p = .3), and BMI (p = .5), and no relationship between clusters and V˙O 2 ​max. For boys, the youngest cluster (p < .01) had three healthy behaviors, weighed less, and was associated with a higher V˙O 2 ​max compared with the two older clusters. We observed clustering of diet, PA, and ST in U.S. adolescents. Specific patterns were associated with lower V˙O 2 ​max for boys, suggesting that our clusters may help identify adolescent boys most in need of interventions. Published by Elsevier Inc.

Chondrogenic properties of collagen type XI, a component of cartilage extracellular matrix.

Science.gov (United States)

Li, Ang; Wei, Yiyong; Hung, Clark; Vunjak-Novakovic, Gordana

2018-08-01

Cartilage extracellular matrix (ECM) has been used for promoting tissue engineering. However, the exact effects of ECM on chondrogenesis and the acting mechanisms are not well understood. In this study, we investigated the chondrogenic effects of cartilage ECM on human mesenchymal stem cells (MSCs) and identified the contributing molecular components. To this end, a preparation of articular cartilage ECM was supplemented to pellets of chondrogenically differentiating MSCs, pellets of human chondrocytes, and bovine articular cartilage explants to evaluate the effects on cell proliferation and the production of cartilaginous matrix. Selective enzymatic digestion and screening of ECM components were conducted to identify matrix molecules with chondrogenic properties. Cartilage ECM promoted MSC proliferation, production of cartilaginous matrix, and maturity of chondrogenic differentiation, and inhibited the hypertrophic differentiation of MSC-derived chondrocytes. Selective digestion of ECM components revealed a contributory role of collagens in promoting chondrogenesis. The screening of various collagen subtypes revealed strong chondrogenic effect of collagen type XI. Finally, collagen XI was found to promote production and inhibit degradation of cartilage matrix in human articular chondrocyte pellets and bovine articular cartilage explants. Our results indicate that cartilage ECM promotes chondrogenesis and inhibits hypertrophic differentiation in MSCs. Collagen type XI is the ECM component that has the strongest effects on enhancing the production and inhibiting the degradation of cartilage matrix. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cosensitization Properties of Glutathione-Protected Au25 Cluster on Ruthenium Dye-Sensitized TiO2 Photoelectrode

Directory of Open Access Journals (Sweden)

Kazuya Nakata

2013-01-01

Full Text Available Cosensitization by glutathione-protected Au25 clusters on Ru complex, N719-sensitized TiO2 photoelectrodes is demonstrated. Glutathione-protected Au25 clusters showed no significant changes in properties after adsorption onto TiO2 particles, as confirmed by optical absorption spectroscopy, transmission electron microscopy, and laser desorption/ionization mass spectrometry. Adsorption property of the glutathione-protected Au25 clusters depends on the pH, which affects the incident photon-to-current conversion efficiency (IPCE of the TiO2 photoelectrode containing Au25 clusters. When pH 7. The IPCE of a TiO2 photoelectrode sensitized by both glutathione-protected Au25 clusters and N719 was increased compared with photoelectrodes containing either glutathione-protected Au25 clusters or N719, which suggests that glutathione-protected Au25 clusters act as a coadsorbent for N719 on TiO2 photoelectrodes. This is also supported by the results that the IPCE of N719-sensitized TiO2 photoelectrodes increased upon addition of glutathione. Furthermore, cosensitization by glutathione-protected Au25 clusters on N719-sensitized TiO2 photoelectrodes allows that wavelength of photoelectric conversion was extended to the near infrared (NIR region. These results suggest that glutathione-protected Au25 clusters act not only as a coadsorbent to increase IPCE but also as an NIR-active sensitizer.

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.

Clustering properties of dynamical dark energy models

International Nuclear Information System (INIS)

Avelino, P. P.; Beca, L. M. G.; Martins, C. J. A. P.

2008-01-01

We provide a generic but physically clear discussion of the clustering properties of dark energy models. We explicitly show that in quintessence-type models the dark energy fluctuations, on scales smaller than the Hubble radius, are of the order of the perturbations to the Newtonian gravitational potential, hence necessarily small on cosmological scales. Moreover, comparable fluctuations are associated with different gauge choices. We also demonstrate that the often used homogeneous approximation is unrealistic, and that the so-called dark energy mutation is a trivial artifact of an effective, single fluid description. Finally, we discuss the particular case where the dark energy fluid is nonminimally coupled to dark matter

SPATIAL CLUSTER AND OUTLIER IDENTIFICATION OF GEOCHEMICAL ASSOCIATION OF ELEMENTS: A CASE STUDY IN JUIRUI COPPER MINING AREA

Directory of Open Access Journals (Sweden)

Tien Thanh NGUYEN

2016-12-01

Full Text Available Spatial clusters and spatial outliers play an important role in the study of the spatial distribution patterns of geochemical data. They characterize the fundamental properties of mineralization processes, the spatial distribution of mineral deposits, and ore element concentrations in mineral districts. In this study, a new method for the study of spatial distribution patterns of multivariate data is proposed based on a combination of robust Mahalanobis distance and local Moran’s Ii. In order to construct the spatial matrix, the Moran's I spatial correlogram was first used to determine the range. The robust Mahalanobis distances were then computed for an association of elements. Finally, local Moran’s Ii statistics was used to measure the degree of spatial association and discover the spatial distribution patterns of associations of Cu, Au, Mo, Ag, Pb, Zn, As, and Sb elements including spatial clusters and spatial outliers. Spatial patterns were analyzed at six different spatial scales (2km, 4 km, 6 km, 8 km, 10 km and 12 km for both the raw data and Box-Cox transformed data. The results show that identified spatial cluster and spatial outlier areas using local Moran’s Ii and the robust Mahalanobis accord the objective reality and have a good conformity with known deposits in the study area.

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.

MoS{sub 2}/Ag nanohybrid: A novel matrix with synergistic effect for small molecule drugs analysis by negative-ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yaju, E-mail: daisy19900911@hotmail.com [State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023 (China); Deng, Guoqing, E-mail: denggqq@sina.com [Department of Polymer Science and Engineering, Nanjing University, Nanjing, 210023 (China); Liu, Xiaohui, E-mail: lcswyh@126.com [State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023 (China); Sun, Liang, E-mail: sunliang@nju.edu.cn [State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023 (China); Li, Hui, E-mail: lihui@nju.edu.cn [State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023 (China); Cheng, Quan, E-mail: quan.cheng@ucr.edu [Department of Chemistry, University of California, Riverside, CA, 92521 (United States); Xi, Kai, E-mail: xikai@nju.edu.cn [Department of Polymer Science and Engineering, Nanjing University, Nanjing, 210023 (China); Xu, Danke, E-mail: xudanke@nju.edu.cn [State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023 (China)

2016-09-21

This paper reports a facile synthesis of molybdenum disulfide nanosheets/silver nanoparticles (MoS{sub 2}/Ag) hybrid and its use as an effective matrix in negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The nanohybrid exerts a strong synergistic effect, leading to high performance detection of small molecule analytes including amino acids, peptides, fatty acids and drugs. The enhancement of laser desorption/ionization (LDI) efficiency is largely attributed to the high surface roughness and large surface area for analyte adsorption, better dispersibility, increased thermal conductivity and enhanced UV energy absorption as compared to pure MoS{sub 2}. Moreover, both Ag nanoparticles and the edge of the MoS{sub 2} layers function as deprotonation sites for proton capture, facilitating the charging process in negative ion mode and promoting formation of negative ions. As a result, the MoS{sub 2}/Ag nanohybrid proves to be a highly attractive matrix in MALDI-TOF MS, with desired features such as high desorption/ionization efficiency, low fragmentation interference, high salt tolerance, and no sweet-spots for mass signal. These characteristic properties allowed for simultaneous analysis of eight different drugs and quantification of acetylsalicylic acid in the spiked human serum. This work demonstrates for the first time the fabrication and application of a novel MoS{sub 2}/Ag hybrid, and provides a new platform for use in the rapid and high throughput analysis of small molecules by mass spectrometry. - Highlights: • MoS{sub 2}/Ag nanohybrid was applied as a novel matrix in negative-ion MALDI-TOF MS. • The MoS{sub 2}/Ag nanohybrid exerted synergistic effect on the detection of small molecules. • The MoS{sub 2}/Ag nanohybrid showed good signal reproducibility and low background interferences comparing to organic matrices. • MoS{sub 2}/Ag allows simultaneous analysis of multiple drugs and quantification of

THE GEMINI/HST CLUSTER PROJECT: STRUCTURAL AND PHOTOMETRIC PROPERTIES OF GALAXIES IN THREE z = 0.28-0.89 CLUSTERS

International Nuclear Information System (INIS)

Chiboucas, Kristin; Joergensen, Inger; Barr, Jordi; Collobert, Maela; Davies, Roger; Flint, Kathleen

2009-01-01

We present the data processing and analysis techniques we are using to determine the structural and photometric properties of galaxies in our Gemini/HST Galaxy Cluster Project sample. The goal of this study is to understand cluster galaxy evolution in terms of scaling relations and structural properties of cluster galaxies at redshifts 0.15 1/4 law and Sersic function two-dimensional surface brightness profiles to each of the galaxies in our sample. Using simulated galaxies, we test how the assumed profile affects the derived parameters and how the uncertainties affect our Fundamental Plane results. We find that while fitting galaxies that have Sersic index n 1/4 law profiles systematically overestimates the galaxy radius and flux, the combination of profile parameters that enter the Fundamental Plane has uncertainties that are small. Average systematic offsets and associated random uncertainties in magnitude and log r e for n>2 galaxies fitted with r 1/4 law profiles are -0.1 ± 0.3 and 0.1 ± 0.2, respectively. The combination of effective radius and surface brightness, log r e - βlog (I) e , that enters the Fundamental Plane produces offsets smaller than -0.02 ± 0.10. This systematic error is insignificant and independent of galaxy magnitude or size. A catalog of photometry and surface brightness profile parameters is presented for three of the clusters in our sample, RX J0142.0+2131, RX J0152.7-1357, and RX J1226.9+3332 at redshifts 0.28, 0.83, and 0.89, respectively.

Iterative approach as alternative to S-matrix in modal methods

Science.gov (United States)

Semenikhin, Igor; Zanuccoli, Mauro

2014-12-01

The continuously increasing complexity of opto-electronic devices and the rising demands of simulation accuracy lead to the need of solving very large systems of linear equations making iterative methods promising and attractive from the computational point of view with respect to direct methods. In particular, iterative approach potentially enables the reduction of required computational time to solve Maxwell's equations by Eigenmode Expansion algorithms. Regardless of the particular eigenmodes finding method used, the expansion coefficients are computed as a rule by scattering matrix (S-matrix) approach or similar techniques requiring order of M3 operations. In this work we consider alternatives to the S-matrix technique which are based on pure iterative or mixed direct-iterative approaches. The possibility to diminish the impact of M3 -order calculations to overall time and in some cases even to reduce the number of arithmetic operations to M2 by applying iterative techniques are discussed. Numerical results are illustrated to discuss validity and potentiality of the proposed approaches.

Determination of local constitutive properties of titanium alloy matrix in boron-modified titanium alloys using spherical indentation

International Nuclear Information System (INIS)

Sreeranganathan, A.; Gokhale, A.; Tamirisakandala, S.

2008-01-01

The constitutive properties of the titanium alloy matrix in boron-modified titanium alloys are different from those of the corresponding unreinforced alloy due to the microstructural changes resulting from the addition of boron. Experimental and finite-element analyses of spherical indentation with a large penetration depth to indenter radius ratio are used to compute the local constitutive properties of the matrix alloy. The results are compared with that of the corresponding alloy without boron, processed in the same manner

Methods for simultaneously identifying coherent local clusters with smooth global patterns in gene expression profiles

Directory of Open Access Journals (Sweden)

Lee Yun-Shien

2008-03-01

Full Text Available Abstract Background The hierarchical clustering tree (HCT with a dendrogram 1 and the singular value decomposition (SVD with a dimension-reduced representative map 2 are popular methods for two-way sorting the gene-by-array matrix map employed in gene expression profiling. While HCT dendrograms tend to optimize local coherent clustering patterns, SVD leading eigenvectors usually identify better global grouping and transitional structures. Results This study proposes a flipping mechanism for a conventional agglomerative HCT using a rank-two ellipse (R2E, an improved SVD algorithm for sorting purpose seriation by Chen 3 as an external reference. While HCTs always produce permutations with good local behaviour, the rank-two ellipse seriation gives the best global grouping patterns and smooth transitional trends. The resulting algorithm automatically integrates the desirable properties of each method so that users have access to a clustering and visualization environment for gene expression profiles that preserves coherent local clusters and identifies global grouping trends. Conclusion We demonstrate, through four examples, that the proposed method not only possesses better numerical and statistical properties, it also provides more meaningful biomedical insights than other sorting algorithms. We suggest that sorted proximity matrices for genes and arrays, in addition to the gene-by-array expression matrix, can greatly aid in the search for comprehensive understanding of gene expression structures. Software for the proposed methods can be obtained at http://gap.stat.sinica.edu.tw/Software/GAP.

Calculation of the electronic and magnetic structures of 3d impurities in the Hcp Fe matrix

International Nuclear Information System (INIS)

Franca, Fernando

1995-01-01

In this work we investigate the local magnetic properties and the electronic structure of HCP Fe, as well introducing transition metals atoms 3d (Cs, Ti, Cr, Mn, Co, Ni, Cu, Zn) in HCP iron matrix. We employed the discrete variational method (DVM), which is an orbital molecular method which incorporate the Hartree-Fock-Slater theory and the linear combination of atomic orbitals (LCAO), in the self-consistent charge approximation and the local density approximation of Von Barth and Hedin to the exchange-correlation potential. We used the embedded cluster model to investigate the electronic structure and the local magnetic properties for the central atom of a cluster of 27 atoms immersed in the microcrystal representing the HCP Fe. (author)

A DFT study of the effects of Sc doping on electronic and optical properties of CdS nanoparticles

Directory of Open Access Journals (Sweden)

Ur Rehman Shafiq

2015-12-01

Full Text Available In the present work a systematic study was carried out to understand the influence of Sc doping on electronic and optical properties of CdS nanoparticles. The geometry optimization and symmetry computation for CdS and Sc doped CdS nanoparticles using Density Functional Theory (DFT on B3LYP level with the QZ4P for Cd and DZ2P for sulphur and Sc were performed by Amsterdam Density Functional (ADF. The results show that HOMO-LUMO gap as well as electronic and optical properties of CdS clusters vary with Sc doping. The HOMO-LUMO gap is affected by the dopant and its value decreases to 0.6 eV. Through considering the numerical integration scheme in the ADF package, we investigated different vibrational modes and our calculated Raman and IR spectra are consistent with the reported result. The calculated IR and Raman peaks of CdS and Sc doped CdS clusters were in the range of 100 to 289 cm−1, 60 cm−1 to 350 cm−1 and 99 cm−1 to 282 cm−1, 60 cm−1 to 350 cm−1, respectively, which was also confirmed by experiment as well as a blue shift occurrence. Subsequently, for deeper research of pure and doped CdS clusters, their absorption spectra were calculated using time-dependent DFT method.

High-accuracy coupled cluster calculations of atomic properties

Energy Technology Data Exchange (ETDEWEB)

Borschevsky, A. [School of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel and Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, Private Bag 102904, 0745 Auckland (New Zealand); Yakobi, H.; Eliav, E.; Kaldor, U. [School of Chemistry, Tel Aviv University, 69978 Tel Aviv (Israel)

2015-01-22

The four-component Fock-space coupled cluster and intermediate Hamiltonian methods are implemented to evaluate atomic properties. The latter include the spectra of nobelium and lawrencium (elements 102 and 103) in the range 20000-30000 cm{sup −1}, the polarizabilities of elements 112-114 and 118, required for estimating their adsorption enthalpies on surfaces used to separate them in accelerators, and the nuclear quadrupole moments of some heavy atoms. The calculations on superheavy elements are supported by the very good agreement with experiment obtained for the lighter homologues.

High-accuracy coupled cluster calculations of atomic properties

International Nuclear Information System (INIS)

Borschevsky, A.; Yakobi, H.; Eliav, E.; Kaldor, U.

2015-01-01

The four-component Fock-space coupled cluster and intermediate Hamiltonian methods are implemented to evaluate atomic properties. The latter include the spectra of nobelium and lawrencium (elements 102 and 103) in the range 20000-30000 cm −1 , the polarizabilities of elements 112-114 and 118, required for estimating their adsorption enthalpies on surfaces used to separate them in accelerators, and the nuclear quadrupole moments of some heavy atoms. The calculations on superheavy elements are supported by the very good agreement with experiment obtained for the lighter homologues

Progress on matrix SiC processing and properties for fully ceramic microencapsulated fuel form

International Nuclear Information System (INIS)

Terrani, K.A.; Kiggans, J.O.; Silva, C.M.; Shih, C.; Katoh, Y.; Snead, L.L.

2015-01-01

The consolidation mechanism and resulting properties of the silicon carbide (SiC) matrix of fully ceramic microencapsulated (FCM) fuel form are discussed. The matrix is produced via the nano-infiltration transient eutectic-forming (NITE) process. Coefficient of thermal expansion, thermal conductivity, and strength characteristics of this SiC matrix have been characterized in the unirradiated state. An ad hoc methodology for estimation of thermal conductivity of the neutron-irradiated NITE–SiC matrix is also provided to aid fuel performance modeling efforts specific to this concept. Finally, specific processing methods developed for production of an optimal and reliable fuel form using this process are summarized. These various sections collectively report the progress made to date on production of optimal FCM fuel form to enable its application in light water and advanced reactors

In vivo fluorescent detection of Fe-S clusters coordinated by human GRX2.

Science.gov (United States)

Hoff, Kevin G; Culler, Stephanie J; Nguyen, Peter Q; McGuire, Ryan M; Silberg, Jonathan J; Smolke, Christina D

2009-12-24

A major challenge to studying Fe-S cluster biosynthesis in higher eukaryotes is the lack of simple tools for imaging metallocluster binding to proteins. We describe the first fluorescent approach for in vivo detection of 2Fe2S clusters that is based upon the complementation of Venus fluorescent protein fragments via human glutaredoxin 2 (GRX2) coordination of a 2Fe2S cluster. We show that Escherichia coli and mammalian cells expressing Venus fragments fused to GRX2 exhibit greater fluorescence than cells expressing fragments fused to a C37A mutant that cannot coordinate a metallocluster. In addition, we find that maximal fluorescence in the cytosol of mammalian cells requires the iron-sulfur cluster assembly proteins ISCU and NFS1. These findings provide evidence that glutaredoxins can dimerize within mammalian cells through coordination of a 2Fe2S cluster as observed with purified recombinant proteins. Copyright 2009 Elsevier Ltd. All rights reserved.

S matrix theory of the massive Thirring model

International Nuclear Information System (INIS)

Berg, B.

1980-01-01

The S matrix theory of the massive Thirring model, describing the exact quantum scattering of solitons and their boundstates, is reviewed. Treated are: Factorization equations and their solution, boundstates, generalized Jost functions and Levinson's theorem, scattering of boundstates, 'virtual' and anomalous thresholds. (orig.) 891 HSI/orig. 892 MKO

Interplay between experiments and calculations for organometallic clusters and caged clusters

International Nuclear Information System (INIS)

Nakajima, Atsushi

2015-01-01

Clusters consisting of 10-1000 atoms exhibit size-dependent electronic and geometric properties. In particular, composite clusters consisting of several elements and/or components provide a promising way for a bottom-up approach for designing functional advanced materials, because the functionality of the composite clusters can be optimized not only by the cluster size but also by their compositions. In the formation of composite clusters, their geometric symmetry and dimensionality are emphasized to control the physical and chemical properties, because selective and anisotropic enhancements for optical, chemical, and magnetic properties can be expected. Organometallic clusters and caged clusters are demonstrated as a representative example of designing the functionality of the composite clusters. Organometallic vanadium-benzene forms a one dimensional sandwich structure showing ferromagnetic behaviors and anomalously large HOMO-LUMO gap differences of two spin orbitals, which can be regarded as spin-filter components for cluster-based spintronic devices. Caged clusters of aluminum (Al) are well stabilized both geometrically and electronically at Al 12 X, behaving as a “superatom”