Science.gov

Sample records for aharony bergman jafferis

  1. Correlation functions of the Aharony-Bergman-Jafferis-Maldacena model

    NASA Astrophysics Data System (ADS)

    Lee, Bum-Hoon; Gwak, Bogeun; Park, Chanyong

    2013-04-01

    In the Aharony-Bergman-Jafferis-Maldacena model, we study the three-point function of two heavy operators and an (ir)relevant one. Following the AdS/CFT correspondence, the structure constant in the large ’t Hooft coupling limit can be factorized into two parts. One is the structure constant with a marginal operator, which is fully determined by the physical quantities of heavy operators and gives rise to a result that is consistent with the renormalization-group analysis. The other can be expressed as the universal form depending only on the conformal dimension of an (ir)relevant operator. We also investigate the new size effect of a circular string dual to a certain closed spin chain.

  2. Holographic entanglement entropy of mass-deformed Aharony-Bergman-Jafferis-Maldacena theory

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Kiu; Kwon, O.-Kab; Park, Chanyong; Shin, Hyeonjoon

    2014-12-01

    We investigate the effect of supersymmetry preserving mass deformation near the UV fixed point represented by the N =6 Aharony-Bergman-Jafferis-Maldacena theory. In the context of the gauge/gravity duality, we analytically calculate the leading small mass effect on the renormalized entanglement entropy (REE) for the most general Lin-Lunin-Maldacena (LLM) geometries in the cases of the strip and disk-shaped entangling surfaces. Our result shows that the properties of the REE in (2 +1 ) dimensions are consistent with those of the c function in (1 +1 ) dimensions. We also discuss the validity of our computations in terms of the curvature behavior of the LLM geometry in the large N limit and the relation between the correlation length and the mass parameter for a special LLM solution.

  3. Towards a realization of the condensed-matter-gravity correspondence in string theory via consistent Abelian truncation of the Aharony-Bergman-Jafferis-Maldacena model.

    PubMed

    Mohammed, Asadig; Murugan, Jeff; Nastase, Horatiu

    2012-11-01

    We present an embedding of the three-dimensional relativistic Landau-Ginzburg model for condensed matter systems in an N = 6, U(N) × U(N) Chern-Simons-matter theory [the Aharony-Bergman-Jafferis-Maldacena model] by consistently truncating the latter to an Abelian effective field theory encoding the collective dynamics of O(N) of the O(N(2)) modes. In fact, depending on the vacuum expectation value on one of the Aharony-Bergman-Jafferis-Maldacena scalars, a mass deformation parameter μ and the Chern-Simons level number k, our Abelianization prescription allows us to interpolate between the Abelian Higgs model with its usual multivortex solutions and a Ø(4) theory. We sketch a simple condensed matter model that reproduces all the salient features of the Abelianization. In this context, the Abelianization can be interpreted as giving a dimensional reduction from four dimensions. PMID:23215268

  4. Existence Theorems for Vortices in the Aharony-Bergman-Jaferis-Maldacena Model

    NASA Astrophysics Data System (ADS)

    Han, Xiaosen; Yang, Yisong

    2015-01-01

    A series of sharp existence and uniqueness theorems are established for the multiple vortex solutions in the supersymmetric Chern-Simons-Higgs theory formalism of Aharony, Bergman, Jaferis, and Maldacena, for which the Higgs bosons and Dirac fermions lie in the bifundamental representation of the general gauge symmetry group . The governing equations are of the BPS type and derived by Kim, Kim, Kwon, and Nakajima in the mass-deformed framework labeled by a continuous parameter.

  5. Commentary on Bergman: "yes... but".

    PubMed

    Dubler, Nancy Neveloff

    2013-01-01

    In "Surmounting Elusive Barriers: The Case for Bioethics Mediation," Bergman argues that professionals trained in bioethics, reluctant to acquire the skills of mediation, would better be replaced by a cadre of mediators with some bioethics knowledge, to which I respond, "yes ... but." PMID:23631332

  6. L2 Cohomology of the Bergman metric

    PubMed Central

    Donnelly, Harold; Fefferman, Charles

    1983-01-01

    The L2 cohomology of the Bergman metric is infinite dimensional in the middle degree and vanishes for all other degrees. Asymptotic expansions are given for the Schwartz kernels of the corresponding projections onto harmonic forms. PMID:16593319

  7. L(2) Cohomology of the Bergman metric.

    PubMed

    Donnelly, H; Fefferman, C

    1983-05-01

    The L(2) cohomology of the Bergman metric is infinite dimensional in the middle degree and vanishes for all other degrees. Asymptotic expansions are given for the Schwartz kernels of the corresponding projections onto harmonic forms. PMID:16593319

  8. Weighted Bergman Kernels and Quantization}

    NASA Astrophysics Data System (ADS)

    Engliš, Miroslav

    Let Ω be a bounded pseudoconvex domain in CN, φ, ψ two positive functions on Ω such that - log ψ, - log φ are plurisubharmonic, and z∈Ω a point at which - log φ is smooth and strictly plurisubharmonic. We show that as k-->∞, the Bergman kernels with respect to the weights φkψ have an asymptotic expansion for x,y near z, where φ(x,y) is an almost-analytic extension of &\\phi(x)=φ(x,x) and similarly for ψ. Further, . If in addition Ω is of finite type, φ,ψ behave reasonably at the boundary, and - log φ, - log ψ are strictly plurisubharmonic on Ω, we obtain also an analogous asymptotic expansion for the Berezin transform and give applications to the Berezin quantization. Finally, for Ω smoothly bounded and strictly pseudoconvex and φ a smooth strictly plurisubharmonic defining function for Ω, we also obtain results on the Berezin-Toeplitz quantization.

  9. Reversible Bergman cyclization by atomic manipulation

    NASA Astrophysics Data System (ADS)

    Schuler, Bruno; Fatayer, Shadi; Mohn, Fabian; Moll, Nikolaj; Pavliček, Niko; Meyer, Gerhard; Peña, Diego; Gross, Leo

    2016-03-01

    The Bergman cyclization is one of the most fascinating rearrangements in chemistry, with important implications in organic synthesis and pharmacology. Here we demonstrate a reversible Bergman cyclization for the first time. We induced the on-surface transformation of an individual aromatic diradical into a highly strained ten-membered diyne using atomic manipulation and verified the products by non-contact atomic force microscopy with atomic resolution. The diyne and diradical were stabilized by using an ultrathin NaCl film as the substrate, and the diyne could be transformed back into the diradical. Importantly, the diradical and the diyne exhibit different reactivity, electronic, magnetic and optical properties associated with the changes in the bond topology, and spin multiplicity. With this reversible, triggered Bergman cyclization we demonstrated switching on demand between the two reactive intermediates by means of selective C-C bond formation or cleavage, which opens up the field of radical chemistry for on-surface reactions by atomic manipulation.

  10. Ward identities and gauge flow for M-theory in N =3 superspace

    NASA Astrophysics Data System (ADS)

    Upadhyay, Sudhaker

    2015-09-01

    We derive the Becchi-Rouet-Stora-Tyutin (BRST) symmetry, Slavnov-Taylor identities, and Nielsen identities for the Aharony-Bergman-Jafferis-Maldacena theories in N =3 harmonic superspace. Further, the gauge dependence of one-particle irreducible amplitudes in this superconformal Chern-Simons theory is shown to be generated by a canonical flow with respect to the extended Slavnov-Taylor identity, induced by the extended BRST transformations (including the BRST transformations of the gauge parameters).

  11. Spin-state control of thermal and photochemical Bergman cyclization.

    PubMed

    Boerner, Leigh J K; Pink, Maren; Park, Hyunsoo; LeSueur, Amanda; Zaleski, Jeffrey M

    2013-03-14

    Thermal Bergman cyclization of Pt(II) dialkynylporphyrins reveals a marked reduction in the cyclization temperature relative to the free base and Zn(II) derivatives. In contrast, photogenerated (3)ππ* population produces no detectable Bergman photocyclization, suggesting that the photoreactivities of the related free base and Zn(II) derivatives occurs via the (1)ππ* state. PMID:23388700

  12. Bergman spaces of natural G-manifolds☆

    PubMed Central

    Della Sala, Giuseppe; Perez, Joe J.

    2013-01-01

    Let G be a unimodular Lie group, X a compact manifold with boundary, and M the total space of a principal bundle G→M→X so that M is also a strongly pseudoconvex complex manifold. In this work, we show that if there exists a point p∈bM such that TpG is contained in the complex tangent space TpcbM of bM at p, then the Bergman space of M is large. Natural examples include the gauged G-complexifications of Heinzner, Huckleberry, and Kutzschebauch. PMID:24222924

  13. Looking for a Matrix model for ABJM theory

    SciTech Connect

    Mohammed, Asadig; Murugan, Jeff; Nastase, Horatiu

    2010-10-15

    Encouraged by the recent construction of fuzzy sphere solutions in the Aharony, Bergman, Jafferis, and Maldacena (ABJM) theory, we re-analyze the latter from the perspective of a Matrix-like model. In particular, we argue that a vortex solution exhibits properties of a supergraviton, while a kink represents a 2-brane. Other solutions are also consistent with the Matrix-type interpretation. We study vortex scattering and compare with graviton scattering in the massive ABJM background, however our results are inconclusive. We speculate on how to extend our results to construct a Matrix theory of ABJM.

  14. Integrable amplitude deformations for N =4 super Yang-Mills and ABJM theory

    NASA Astrophysics Data System (ADS)

    Bargheer, Till; Huang, Yu-Tin; Loebbert, Florian; Yamazaki, Masahito

    2015-01-01

    We study Yangian-invariant deformations of scattering amplitudes in 4d N =4 super Yang-Mills theory and 3d N =6 Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. In particular, we obtain the deformed Graßmannian integral for 4d N =4 supersymmetric Yang-Mills theory, both in momentum and momentum-twistor space. For 3d ABJM theory, we initiate the study of deformed scattering amplitudes. We investigate general deformations of on-shell diagrams, and find the deformed Graßmannian integral for this theory. We furthermore introduce the algebraic R-matrix construction of deformed Yangian invariants for ABJM theory.

  15. Large N behavior of mass deformed ABJM theory

    NASA Astrophysics Data System (ADS)

    Nosaka, Tomoki; Shimizu, Kazuma; Terashima, Seiji

    2016-03-01

    In this paper, using the localization technique we analyze the large N limit of the mass deformed Aharony-Bergman-Jafferis-Maldacena (ABJM) theory on the three sphere with a finite mass parameter and finite Chern-Simons levels. We find two different solutions of the saddle point equations in the large N limit. With these solutions we compute the free energy limit and find that there is a first order phase transition. Our results may predict a phase transition in the dual gravity theory.

  16. The Weighted Super Bergman Kernels Over the Supermatrix Spaces

    NASA Astrophysics Data System (ADS)

    Feng, Zhiming

    2015-12-01

    The purpose of this paper is threefold. Firstly, using Howe duality for , we obtain integral formulas of the super Schur functions with respect to the super standard Gaussian distributions. Secondly, we give explicit expressions of the super Szegö kernels and the weighted super Bergman kernels for the Cartan superdomains of type I. Thirdly, combining these results, we obtain duality relations of integrals over the unitary groups and the Cartan superdomains, and the marginal distributions of the weighted measure.

  17. Dual instantons in antimembranes theory

    SciTech Connect

    Imaanpur, A.; Naghdi, M.

    2011-04-15

    We introduce two ansatzs for the 3-form potential of Euclidean 11d supergravity on skew-whiffed AdS{sub 4}xS{sup 7} background which results in two scalar modes with m{sup 2}=-2 on AdS{sub 4}. Being conformally coupled with a quartic interaction, it is possible to find the exact solutions of the scalar equation on this background. These modes turn out to be invariant under the SU(4) subgroup of the SO(8) isometry group, whereas there are no corresponding SU(4) singlet Bogomol'nyi-Prasad-Sommerfeld operators of dimensions one or two on the boundary theory constructed by Aharony, Bergman, Jafferis, and Maldacena. Noticing the interchange of 8{sub s} and 8{sub c} representations under skew-whiffing in the bulk, we propose the theory of antimembranes should similarly be obtained from Aharony, Bergman, Jafferis, and Maldacena's theory by swapping these representations. In particular, this enables us to identify the dual boundary operators of the two scalar modes. We deform the boundary theory by the dual operators and examine the fermionic field equations, and compare the solutions of the deformed theory with those of the bulk.

  18. Unciaphenol, an Oxygenated Analogue of the Bergman Cyclization Product of Uncialamycin Exhibits Anti-HIV Activity.

    PubMed

    Williams, David E; Bottriell, Helen; Davies, Julian; Tietjen, Ian; Brockman, Mark A; Andersen, Raymond J

    2015-11-01

    Unciaphenol (2), an oxygenated analogue of the Bergman cyclization product of the enediyne uncialamycin (1), has been isolated along with 1 from cultures of the actinomycete Streptomyces uncialis. It is proposed that the C-22 OH substituent in 2 might arise from the attack of a nucleophilic oxygen species on the p-benzyne diradical intermediate IA in the Bergman cyclization of 1. 2 shows in vitro anti-HIV activity against viral strains that are resistant to clinically utilized anti-retroviral therapies. PMID:26465962

  19. Husbands and Wives in Bergman Films: A Close Analysis Based on Empirical Need.

    ERIC Educational Resources Information Center

    Lundell, Torborg; Mulac, Anthony

    1981-01-01

    Studies viewers' impressions of husbands and wives in four Ingmar Bergman films in terms of socio-intellectual status, dynamism, and aesthetic quality. The agreement of viewer ratings indicates that viewers reacted more in tune with the underlying symbolic significance of characters than did most critics. (JMF)

  20. Martina Bergman-Osterberg (1849-1915): Creating a Professional Role for Women in Physical Training

    ERIC Educational Resources Information Center

    Bloomfield, Anne

    2005-01-01

    Martina Bergman-Osterberg came to London from Sweden versed in the theory and practice of Swedish gymnastics as taught by Per Henrik Ling (1776-1881), and introduced his system into British schools, first while working for the London School Board and subsequently by establishing the Dartford College of Physical Training. This paper examines the…

  1. BPS Wilson loops in Minkowski spacetime and Euclidean space

    NASA Astrophysics Data System (ADS)

    Ouyang, Hao; Wu, Jun-Bao; Zhang, Jia-ju

    2015-12-01

    We give evidence that spacelike BPS Wilson loops do not exist in Minkowski spacetime. We show that spacelike Wilson loops in Minkowski spacetime cannot preserve any supersymmetries, in d = 4 N = 4 super Yang-Mills theory, d = 3 N = 2 super Chern-Simons-matter theory, and d = 3 N = 6 Aharony-Bergman-Jafferis-Maldacena theory. We not only show this using infinite straight lines and circles as examples, but also we give proofs for general curves. We attribute this to the conflicts of the reality conditions of the spinors. However, spacelike Wilson loops do exist in Euclidean space. There are both BPS Wilson loops along infinite straight lines and circular BPS Wilson loops. This is because the reality conditions of the spinors are lost after Wick rotation. The result is reasonable in view of the AdS/CFT correspondence.

  2. M theory on deformed superspace

    NASA Astrophysics Data System (ADS)

    Faizal, Mir

    2011-11-01

    In this paper we will analyze a noncommutative deformation of the Aharony-Bergman-Jafferis-Maldacena (ABJM) theory in N=1 superspace formalism. We will then analyze the Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST symmetries for this deformed ABJM theory, and its linear as well as nonlinear gauges. We will show that the sum of the gauge fixing term and the ghost term for this deformed ABJM theory can be expressed as a combination of the total BRST and the total anti-BRST variation, in Landau and nonlinear gauges. We will show that in Landau and Curci-Ferrari gauges deformed ABJM theory is invariant under an additional set of symmetry transformations. We will also discuss the effect that the addition of a bare mass term has on this theory.

  3. Quantum phase transitions with dynamical flavors

    NASA Astrophysics Data System (ADS)

    Bea, Yago; Jokela, Niko; Ramallo, Alfonso V.

    2016-07-01

    We study the properties of a D6-brane probe in the Aharony-Bergman-Jafferis-Maldacena (ABJM) background with smeared massless dynamical quarks in the Veneziano limit. Working at zero temperature and nonvanishing charge density, we show that the system undergoes a quantum phase transition in which the topology of the brane embedding changes from a black hole to a Minkowski embedding. In the unflavored background the phase transition is of second order and takes place when the charge density vanishes. We determine the corresponding critical exponents and show that the scaling behavior near the quantum critical point has multiplicative logarithmic corrections. In the background with dynamical quarks the phase transition is of first order and occurs at nonzero charge density. In this case we compute the discontinuity of several physical quantities as functions of the number Nf of unquenched quarks of the background.

  4. Exact slope and interpolating functions in N=6 supersymmetric Chern-Simons theory.

    PubMed

    Gromov, Nikolay; Sizov, Grigory

    2014-09-19

    Using the quantum spectral curve approach we compute, exactly, an observable (called slope function) in the planar Aharony-Bergman-Jafferis-Maldacena theory in terms of an unknown interpolating function h(λ) which plays the role of the coupling in any integrability based calculation in this theory. We verified our results with known weak coupling expansion in the gauge theory and with the results of semiclassical string calculations. Quite surprisingly at strong coupling the result is given by an explicit rational function of h(λ) to all orders. By comparing the structure of our result with that of an exact localization based calculation for a similar observable in Marino and Putrov [J. High Energy Phys. 06 (2010) 011], we conjecture an exact expression for h(λ). PMID:25279619

  5. Exact results for Wilson loops in orbifold ABJM theory

    NASA Astrophysics Data System (ADS)

    Ouyang, Hao; Wu, Jun-Bao; Zhang, Jia-Ju

    2016-08-01

    We investigate the exact results for circular 1/4 and 1/2 BPS Wilson loops in the d = 3 mathcal = 4 super Chern-Simons-matter theory that could be obtained by orbifolding Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. The partition function of the mathcal = 4 orbifold ABJM theory has been computed previously in the literature. In this paper, we re-derive it using a slightly different method. We calculate the vacuum expectation values of the circular 1/4 BPS Wilson loops in fundamental representation and of circular 1/2 BPS Wilson loops in arbitrary representations. We use both the saddle point approach and Fermi gas approach. The results for Wilson loops are in accord with the available gravity results. Supported by NSFC (11222549, 11575202), K. C. Wong Education Foundation and Youth Innovation Promotion Association of CAS (2011016)

  6. Heavy operators in superconformal Chern-Simons theory

    NASA Astrophysics Data System (ADS)

    de Mello Koch, Robert; Kreyfelt, Rocky; Smith, Stephanie

    2014-12-01

    We study the anomalous dimensions for scalar operators in Aharony-Bergman-Jafferis-Maldacena theory in the S U (2 ) sector. The operators we consider have a classical dimension that grows as N in the large N limit. Consequently, the large N limit is not captured by summing planar diagrams—nonplanar contributions have to be included. We find that the mixing matrix at two-loop order is diagonalized using a double coset ansatz, reducing it to the Hamiltonian of a set of decoupled oscillators. The spectrum of anomalous dimensions, when interpreted in the dual gravity theory, shows that the energy of the fluctuations of the corresponding giant graviton is dependent on the size of the giant. The first subleading corrections to the large N limit are also considered. These subleading corrections to the dilatation operator do not commute with the leading terms, indicating that integrability may not survive beyond the large N limit.

  7. A note on instanton effects in ABJM theory

    NASA Astrophysics Data System (ADS)

    Wang, Xian-fu; Wang, Xin; Huang, Min-xin

    2014-11-01

    We consider the quantum spectral problem appearing the Fermi gas formulation of the ABJM (Aharony-Bergman-Jafferis-Maldacena) matrix model. This is known to related to the refined topological string on local ℙ1 × ℙ1 Calabi-Yau geometry. In the ABJM setting the problem is formulated by an integral equation, and is somewhat different from the one formulated directly in terms of the Calabi-Yau geometry and studied in our earlier paper. We use the similar method in our earlier paper to determine the non-perturbative contributions to the quantum phase volume in the ABJM case from the Bohr-Sommerfeld quantization condition. As in our earlier paper, the non-perturbative contributions contain higher order smooth corrections beyond those required by singularity cancellations with the perturbative contributions proposed by Kallen and Marino. Our results imply possible new contributions to the grand potential of the ABJM matrix model.

  8. Quantum spectral curve of the N=6 supersymmetric Chern-Simons theory.

    PubMed

    Cavaglià, Andrea; Fioravanti, Davide; Gromov, Nikolay; Tateo, Roberto

    2014-07-11

    Recently, it was shown that the spectrum of anomalous dimensions and other important observables in planar N=4 supersymmetric Yang-Mills theory are encoded into a simple nonlinear Riemann-Hilbert problem: the Pμ system or quantum spectral curve. In this Letter, we extend this formulation to the N=6 supersymmetric Chern-Simons theory introduced by Aharony, Bergman, Jafferis, and Maldacena. This may be an important step towards the exact determination of the interpolating function h(λ) characterizing the integrability of this model. We also discuss a surprising relation between the quantum spectral curves for the N=4 supersymmetric Yang-Mills theory and the N=6 supersymmetric Chern-Simons theory considered here. PMID:25062163

  9. Quantum Spectral Curve of the N =6 Supersymmetric Chern-Simons Theory

    NASA Astrophysics Data System (ADS)

    Cavaglià, Andrea; Fioravanti, Davide; Gromov, Nikolay; Tateo, Roberto

    2014-07-01

    Recently, it was shown that the spectrum of anomalous dimensions and other important observables in planar N=4 supersymmetric Yang-Mills theory are encoded into a simple nonlinear Riemann-Hilbert problem: the Pμ system or quantum spectral curve. In this Letter, we extend this formulation to the N =6 supersymmetric Chern-Simons theory introduced by Aharony, Bergman, Jafferis, and Maldacena. This may be an important step towards the exact determination of the interpolating function h(λ) characterizing the integrability of this model. We also discuss a surprising relation between the quantum spectral curves for the N=4 supersymmetric Yang-Mills theory and the N=6 supersymmetric Chern-Simons theory considered here.

  10. Exact Slope and Interpolating Functions in N=6 Supersymmetric Chern-Simons Theory

    NASA Astrophysics Data System (ADS)

    Gromov, Nikolay; Sizov, Grigory

    2014-09-01

    Using the quantum spectral curve approach we compute, exactly, an observable (called slope function) in the planar Aharony-Bergman-Jafferis-Maldacena theory in terms of an unknown interpolating function h(λ) which plays the role of the coupling in any integrability based calculation in this theory. We verified our results with known weak coupling expansion in the gauge theory and with the results of semiclassical string calculations. Quite surprisingly at strong coupling the result is given by an explicit rational function of h(λ) to all orders. By comparing the structure of our result with that of an exact localization based calculation for a similar observable in Marino and Putrov [J. High Energy Phys. 06 (2010) 011], we conjecture an exact expression for h(λ).

  11. ABJM models in Script N = 3 harmonic superspace

    NASA Astrophysics Data System (ADS)

    Buchbinder, I. L.; Ivanov, E. A.; Lechtenfeld, O.; Pletnev, N. G.; Samsonov, I. B.; Zupnik, B. M.

    2009-03-01

    We construct the classical action of the Aharony-Bergman-Jafferis-Maldacena (ABJM) model in the Script N = 3, d = 3 harmonic superspace. In such a formulation three out of six supersymmetries are realized off shell while the other three mix the superfields and close on shell. The superfield action involves two hypermultiplet superfields in the bifundamental representation of the gauge group and two Chern-Simons gauge superfields corresponding to the left and right gauge groups. The Script N = 3 superconformal invariance allows only for a minimal gauge interaction of the hypermultiplets. Amazingly, the correct sextic scalar potential of ABJM emerges after the elimination of auxiliary fields. Besides the original U(N) × U(N) ABJM model, we also construct Script N = 3 superfield formulations of some generalizations. For the SU(2) × SU(2) case we give a simple superfield proof of its enhanced Script N = 8 supersymmetry and SO(8) R-symmetry.

  12. Utilizing redox-mediated Bergman cyclization toward the development of dual-action metalloenediyne therapeutics.

    PubMed

    Lindahl, Sarah E; Park, Hyunsoo; Pink, Maren; Zaleski, Jeffrey M

    2013-03-13

    Reaction of 2 equiv of 1,2-bis((diphenylphosphino)ethynyl)benzene (dppeb, 1) with Pt(cod)Cl2 followed by treatment with N2H4 yields the reduced Pt(0) metalloenediyne, Pt(dppeb)2, 2. This complex is stable to both air oxidation and metal-mediated Bergman cyclization under ambient conditions due to the nearly idealized tetrahedral geometry. Reaction of 2 with 1 equiv of I2 in the presence of excess 1,4-cyclohexadiene (1,4-CHD) radical trap rapidly and near-quantitatively generates the cis-Bergman-cyclized, diiodo product 3 ((31)P: δ = 41 ppm, J(Pt-P) = 3346 Hz) with concomitant loss of 1 equiv of uncyclized phosphine chelate ((31)P: δ = -33 ppm). In contrast, addition of 2 equiv of I2 in the absence of additional radical trap instantaneously forms a metastable Pt(dppeb)2(2+) intermediate species, 4, that is characterized by δ = 51 ppm in the (31)P NMR (J(Pt-P) = 3171 Hz) and ν(C≡C) = 2169 cm(-1) in the Raman profile, indicating that it is an uncyclized, bis-ligated complex. Over 24 h, 4 undergoes ligand exchange to form a neutral, square planar complex that spontaneously Bergman cyclizes at ambient temperature to give the crystalline product Pt(dppnap-I2)I2 (dppnap-I2 = (1,4-diiodonaphthalene-2,3-diyl)bis(diphenylphosphine)), 5, in 52% isolated yield. Computational analysis of the oxidation reaction proposes two plausible flattened tetrahedral structures for intermediate 4: one where the phosphine core has migrated to a trans-spanning chelate geometry, and a second, higher energy structure (3.3 kcal/mol) with two cis-chelating phosphine ligands (41° dihedral angle) via a restricted alkyne-terminal starting point. While the energies are disparate, the common theme in both structures is the elongated Pt-P bond lengths (>2.4 Å), indicating that nucleophilic ligand substitution by I(-) is on the reaction trajectory to the cyclized product 5. The efficiency of the redox-mediated Bergman cyclization reaction of this stable Pt(0) metalloenediyne prodrug and

  13. Cytotoxic 1,2-dialkynylimidazole-based aza-enediynes: aza-Bergman rearrangement rates do not predict cytotoxicity.

    PubMed

    Laroche, Christophe; Li, Jing; Kerwin, Sean M

    2011-07-28

    A new class of potential antitumor agents inspired by the enediyne antitumor antibiotics has been synthesized: the 1,2-dialkynylimidazoles. The aza-Bergman rearrangement of these 1,2-dialkynylimidazoles has been investigated theoretically at the B3LYP/6-31G(d,p) level and experimentally by measuring the kinetics of rearrangement in 1,4-cyclohexadiene. There is a good correlation between the theoretical and experimental results; subtle substituent effects on the initial aza-Bergman cyclization barrier predicted by theory are confirmed by experiment. Yet, despite the ability of these 1,2-dialkynylimidazoles to undergo Bergman rearrangement to diradical/carbene intermediates under relatively mild conditions, there is no correlation between the rate of Bergman cyclization and cytotoxicity to A459 cells. In addition, cytotoxic 1,2-dialkynylimidazoles do not cause nicking of supercoiled plasmid DNA or cleavage of bovine serum albumin. An alternative mechanism for cytotoxicity involving the unexpected selective thiol addition to the N-ethynyl group of certain 1,2-dialkynylimidazoles is proposed. PMID:21667990

  14. Kahler-Einstein metrics, Bergman metrics, and higher alpha-invariants

    NASA Astrophysics Data System (ADS)

    Macbeth, Heather

    The question of the existence of Kahler-Einstein metrics on a Kahler manifold M has been a subject of study for decades. The Kahler manifolds on which this question may be studied divide naturally into three types. For two of these types the question was long ago settled by Yau and Aubin. For the third type, Fano manifolds, the question is (despite great recent progress) open for many individual manifolds. In the first part of this thesis we define algebraic invariants Bm,k(M) of a Fano manifold M, which codify certain properties of M 's Bergman metrics. We prove a criterion (Theorem 1.1.1) in terms of these invariants Bm,k( M) for the existence of a Kahler-Einstein metric on M. The proof of Theorem 1.1.1 relies on Szekelyhidi's deep recent partial C0-estimate, and on a new family of estimates for Fano manifolds. We furthermore introduce a very general hypothesis on Bergman metrics, Conjecture 6.1.2, offering some partial results (Section 6.3) in evidence. Modulo this conjecture, we prove a variation of Theorem 1.1.1, which gives a criterion for the existence of a Kahler-Einstein metric on M in terms of the well-known alpha-invariants, alpha m,k(M). This result extends a theorem of Tian. The second part of this thesis concerns Riemannian manifolds more generally. We give a characterization (Theorem 1.2.1) of conformal classes realizing a compact manifold's Yamabe invariant. This characterization is the analogue of an observation of Nadirashvili for metrics realizing the maximal first eigenvalue, and of Fraser and Schoen for metrics realizing the maximal first Steklov eigenvalue.

  15. A QM/MM study of the Bergman reaction of dynemicin A in the minor groove of DNA.

    PubMed

    Tuttle, Tell; Kraka, Elfi; Thiel, Walter; Cremer, Dieter

    2007-07-19

    The Bergman cyclization of the natural enediyne dynemicin A in its triggered form (2) bound to the minor groove of DNA is compared with the corresponding reaction of its open isomer (4) utilizing QM/MM methodology. The two isomers are typical representatives of 10-membered cyclic (2) and acyclic (4) enediynes, which possess significantly different barriers for the Bergman reaction in the gas phase (2, 20.4 kcal/mol; 4, 31.3 kcal/mol). In the case of the cyclic enediyne (2) the explicit consideration of environmental factors such as the receptor DNA, the solvent water, and charge neutralization by counterions has only minor effects on the energy profile of the cyclization reaction and the corresponding optimized structures when compared with the gas phase. The energetics of the reaction is predominantly determined by QM (electronic) effects. This makes it possible to replace the explicit description of the environment by an implicit one, thus avoiding costly QM/MM calculations and using instead a decoupled QM+MM approach. A conformationally driven hinge mechanism is identified for 2 that makes it possible for the ligand to adjust to the dimensions of the minor groove without significant energy loss. In the case of the acyclic enediyne 4 a QM/MM treatment is necessary to describe the Bergman cyclization in the minor groove. QM/MM corrects the cyclization barrier from 31.3 to 23.7 kcal/mol, which makes the reaction feasible under physiological conditions. The reduction of the barrier is a result of transition-state stabilization, which is caused by an increased dipole moment and hence stronger electrostatic interactions with the environment. In both cases the anionic charge of dynemicin A is largely shielded by water solvation and ion pair formation so that it does not significantly affect the energetics of the Bergman cyclization. PMID:17585802

  16. Towards photoswitchable enediyne antibiotics: single and two-photon triggering of bergman cyclization.

    PubMed

    Polukhtine, Andrei; Karpov, Grigori; Popik, Vladimir V

    2008-01-01

    The concept of photoswitchable enediynes, which are stable in the dark but undergo efficient cycloaro-matization reaction to produce p-benzyne diradical after irradiation with light of an appropriate wavelength, is discussed. Two novel methods for the generation of reactive enediyne compounds from thermally stable precursors have been developed. In the first approach, one of the triple bonds of cyclodeca-3-ene-1,5-diynes is replaced with cyclopropenone group. Cyclopropenone-containing enediyne precursors are unable to undergo cycloaromatization because the enediyne fragment is incomplete. Photolysis of cyclopropenones results in the efficient decarbonylation and the regeneration of a triple bond thus completing the enediyne pi-system. The second method employs photo-Wolff reaction to achieve ring contraction of stable eleven-membered ring precursor enediynes. Benzannulated cyclic enediynes produced by the photodecomposition of enediyne precursor containing 2-diazo-1,3-diketones possess enolized beta-ketoester fragment and undergo remarkably facile tau(36)o = 5 min - 3 h) Bergman cyclization. The generation of reactive enediyne was also achieved with NIR light by non resonant two-photon excitation. PMID:18397169

  17. Direct and inverse theorems of rational approximation in the Bergman space

    SciTech Connect

    Mardvilko, Tat'yana S; Pekarskii, Alexandr A

    2011-09-30

    For positive numbers p and {mu} let A{sub p,{mu}} denote the Bergman space of analytic functions in the half-plane {Pi}:={l_brace}z element of C:Imz>0{r_brace}. For f element of A{sub p,{mu}} let R{sub n} (f){sub p,{mu}} be the best approximation by rational functions of degree at most n. Also let {alpha} element of R and {tau}>0 be numbers such that {alpha}+{mu}=1/{tau}-1/p and 1/p+{mu} not element of N. Then the main result of the paper claims that the set of functions f element of A{sub p,{mu}} such that {Sigma}{sub n=1}{sup {infinity}} 1/n (n{sup {alpha}}+{mu}R{sub n} (f){sub p,{mu}}){sup {tau}}<{infinity} is precisely the Besov space B{sub {tau}}{sup {alpha}} of analytic functions in {Pi}. Bibliography: 23 titles.

  18. An ONIOM study of the Bergman reaction: a computationally efficient and accurate method for modeling the enediyne anticancer antibiotics

    NASA Astrophysics Data System (ADS)

    Feldgus, Steven; Shields, George C.

    2001-10-01

    The Bergman cyclization of large polycyclic enediyne systems that mimic the cores of the enediyne anticancer antibiotics was studied using the ONIOM hybrid method. Tests on small enediynes show that ONIOM can accurately match experimental data. The effect of the triggering reaction in the natural products is investigated, and we support the argument that it is strain effects that lower the cyclization barrier. The barrier for the triggered molecule is very low, leading to a reasonable half-life at biological temperatures. No evidence is found that would suggest a concerted cyclization/H-atom abstraction mechanism is necessary for DNA cleavage.

  19. Trajectory Calculations for Bergman Cyclization Predict H/D Kinetic Isotope Effects Due to Nonstatistical Dynamics in the Product.

    PubMed

    Doubleday, Charles; Boguslav, Mayla; Howell, Caronae; Korotkin, Scott D; Shaked, David

    2016-06-22

    An unusual H/D kinetic isotope effect (KIE) is described, in which isotopic selectivity arises primarily from nonstatistical dynamics in the product. In DFT-based quasiclassical trajectories of Bergman cyclization of (Z)-3-hexen-1,5-diyne (1) at 470 K, the new CC bond retains its energy, and 28% of nascent p-benzyne recrosses back to the enediyne on a vibrational time scale. The competing process of intramolecular vibrational redistribution (IVR) in p-benzyne is too slow to prevent this. Deuteration increases the rate of IVR, which decreases the fraction of recrossing and increases the yield of statistical (trapable) p-benzyne, 2. Trapable yields for three isotopomers of 2 range from 72% to 86%. The resulting KIEs for Bergman cyclization differ substantially from KIEs predicted by transition state theory, which suggests that IVR in this reaction can be studied by conventional KIEs. Leakage of vibrational zero point energy (ZPE) into the reaction coordinate was probed by trajectories in which initial ZPE in the CH/CD stretching modes was reduced by 25%. This did not change the predicted KIEs. PMID:27281683

  20. Bergman Clusters, Multiple Bonds, and Defect Planes: Synthetic Outcomes of Chemical Frustration in Ternary Intermetallic Systems

    NASA Astrophysics Data System (ADS)

    Hadler, Amelia Beth

    Intermetallics crystallize in a variety of complex structures, many of which show unusual bonding or intriguing properties. Understanding what factors drive this structural chemistry would be a valuable step towards designing new intermetallics with specific structures or properties. One pathway towards understanding and predicting the structures of complex intermetallics is chemical frustration, a design tool which harnesses competition between incompatible bonding or packing modes to induce complexity in ternary intermetallic systems. The research outlined in this thesis focuses on developing chemical frustration through exploratory synthesis in ternary systems designed to induce frustration between the tetrahedral close packing of many intermetallics and the simple cubic packing seen for ionic salts or elemental metals. Syntheses in three systems yielded six new ternary intermetallics, four of which crystallize in novel structure types. Three were discovered in the Ca-Cu-Cd system: Ca5Cu2Cd and Ca2Cu 2Cd9, which adopt ternary variants of binary structures, and Ca10Cu2Cd27, which crystallizes in a new structure built from Bergman clusters. All three structures can be traced to electronic packing frustration induced by the similar electronegativities but different metallic radii of Cu and Cd. The Gd-Fe-C system yielded the new carbometalate Gd13Fe 10C13 and an oxycarbide derivative. These phases crystallize in structures built from Gd tricapped trigonal prisms interpenetrated by an Fe-C network. Theoretical analyses reveal that Fe-Fe and Fe-C multiple bonding is found throughout this network. A theoretical investigation of similar carbides uncovers additional metal-metal, metal-carbon, and carbon-carbon multiple bonding. This unusual bonding stabilizes the carbides by satisfying preferred electron counts for their transition metal sites. One new phase, Mg4.5Pd5Ge1.5, was found in the Mg-Pd-Ge system. Its structure is closely related to the CsCl-type structure of

  1. Further Clarification on the Hom, Mitchell, Lee, and Griffeth (2012) Model: Reply to Bergman, Payne, and Boswell (2012) and Maertz (2012)

    ERIC Educational Resources Information Center

    Griffeth, Rodger W.; Lee, Thomas W.; Mitchell, Terence R.; Hom, Peter W.

    2012-01-01

    In this article, we reply to Bergman, Payne, and Boswell (2012) and Maertz (2012), who commented on our reconceptualization of the employee turnover criterion and proximal withdrawal states (Hom, Mitchell, Lee, & Griffeth, 2012). We agree with some points (e.g., anticipated destinations) but take issue with others (e.g., turnover intentions as…

  2. Multimatrix models and tri-Sasaki Einstein spaces

    SciTech Connect

    Herzog, Christopher P.; Pufu, Silviu S.; Tesileanu, Tiberiu; Klebanov, Igor R.

    2011-02-15

    Localization methods reduce the path integrals in N{>=}2 supersymmetric Chern-Simons gauge theories on S{sup 3} to multimatrix integrals. A recent evaluation of such a two-matrix integral for the N=6 superconformal U(N)xU(N) Aharony-Bergman-Jafferis-Maldacena theory produced detailed agreement with the AdS/CFT correspondence, explaining, in particular, the N{sup 3/2} scaling of the free energy. We study a class of p-matrix integrals describing N=3 superconformal U(N){sup p} Chern-Simons gauge theories. We present a simple method that allows us to evaluate the eigenvalue densities and the free energies in the large N limit keeping the Chern-Simons levels k{sub i} fixed. The dual M-theory backgrounds are AdS{sub 4}xY, where Y are seven-dimensional tri-Sasaki Einstein spaces specified by the k{sub i}. The gravitational free energy scales inversely with the square root of the volume of Y. We find a general formula for the p-matrix free energies that agrees with the available results for volumes of the tri-Sasaki Einstein spaces Y, thus providing a thorough test of the corresponding AdS{sub 4}/CFT{sub 3} dualities. This formula is consistent with the Seiberg duality conjectured for Chern-Simons gauge theories.

  3. Construction and classification of novel BPS Wilson loops in quiver Chern-Simons-matter theories

    NASA Astrophysics Data System (ADS)

    Ouyang, Hao; Wu, Jun-Bao; Zhang, Jia-ju

    2016-09-01

    In this paper we construct and classify novel Drukker-Trancanelli (DT) type BPS Wilson loops along infinite straight lines and circles in N = 2 , 3 quiver superconformal Chern-Simons-matter theories, Aharony-Bergman-Jafferis-Maldacena (ABJM) theory, and N = 4 orbifold ABJM theory. Generally we have four classes of Wilson loops, and all of them preserve the same supersymmetries as the BPS Gaiotto-Yin (GY) type Wilson loops. There are several free complex parameters in the DT type BPS Wilson loops, and for two classes of Wilson loops in ABJM theory and N = 4 orbifold ABJM theory there are supersymmetry enhancements at special values of the parameters. We check that the differences of the DT type and GY type Wilson loops are Q-exact with Q being some supercharges preserved by both the DT type and GY type Wilson loops. The results would be useful to calculate vacuum expectation values of the DT type Wilson loops in matrix models if they are still BPS quantum mechanically.

  4. New instantons in AdS4/CFT3 from D4-branes wrapping some of CP3

    NASA Astrophysics Data System (ADS)

    Naghdi, M.

    2013-07-01

    With use of a 6-form field strength of ten-dimensional type IIA supergravity over AdS4×CP3, when S7/Zk is considered as a S1 Hopf fibration on CP3, we earn a fully localized solution in the bulk of Euclideanized AdS4. Indeed, this object appears in the external space because of wrapping a D4(M5)-brane over some parts of the respective internal spaces. Interestingly, this supersymmetry breaking SU(4)×U(1)-singlet mode exists in already known spectra when one uses the 8c gravitino representation of SO(8). To adjust the boundary theory, we should swap the original 8s and 8c representations for supercharges and fermions in the Aharony-Bergman-Jafferis-Maldacena model. The procedure could later be interpreted as adding an anti-D4(M5)-brane to the prime N=6 membrane theory, resulting in a N=0 antimembrane theory while other symmetries are preserved. Then, according to the well-known state-operator correspondence rules, we find a proper dual operator with the conformal dimension of Δ+=3 that matches to the bulk massless pseudoscalar state. After that, by making use of some fitting Ansätze for the used matter fields, we arrive at an exact boundary solution and comment on the other related issues as well.

  5. Marginal fluctuations as instantons on M2/D2-branes

    NASA Astrophysics Data System (ADS)

    Naghdi, M.

    2014-03-01

    We introduce some (anti-) M/D-branes through turning on the corresponding field strengths of the 11- and 10-dimensional supergravity theories over spaces, where we use and for the internal spaces. Indeed, when we add M2/D2-branes on the same directions with the near horizon branes of the Aharony-Bergman-Jafferis-Maldacena model, all symmetries and supersymmetries are preserved trivially. In this case, we obtain a localized object just in the horizon. This normalizable bulk massless scalar mode is a singlet of and , and it agrees with a marginal boundary operator of the conformal dimension of . However, after performing a special conformal transformation, we see that the solution is localized in the Euclideanized space and is attributable to the included anti-M2/D2-branes, which are also necessary to ensure that there is no back-reaction. The resultant theory now breaks all supersymmetries to , while the other symmetries are so preserved. The dual boundary operator is then set up from the skew-whiffing of the representations and for the supercharges and scalars, respectively, while the fermions remain fixed in of the original theory. Besides, we also address another alternate bulk to boundary matching procedure through turning on one of the gauge fields of the full gauge group along the same lines with a similar situation to the one faced in the AdS/CFT correspondence. The latter approach covers the difficulty already faced with in the bulk-boundary matching procedure for as well.

  6. Fermi surface behavior in the ABJM M2-brane theory

    NASA Astrophysics Data System (ADS)

    DeWolfe, Oliver; Henriksson, Oscar; Rosen, Christopher

    2015-06-01

    We calculate fermionic Green's functions for states of the three-dimensional Aharony-Bergman-Jafferis-Maldacena M2-brane theory at large N using the gauge-gravity correspondence. We embed extremal black brane solutions in four-dimensional maximally supersymmetric gauged supergravity, obtain the linearized Dirac equations for each spin-1 /2 mode that cannot mix with a gravitino, and solve these equations with infalling boundary conditions to calculate retarded Green's functions. For generic values of the chemical potentials, we find Fermi surfaces with universally non-Fermi liquid behavior, matching the situation for four-dimensional N =4 super-Yang-Mills. Fermi surface singularities appear and disappear discontinuously at the point where all chemical potentials are equal, reminiscent of a quantum critical point. One limit of parameter space has zero entropy at zero temperature, and fermionic fluctuations are perfectly stable inside an energy region around the Fermi surface. An ambiguity in the quantization of the fermions is resolved by supersymmetry.

  7. Superconformal Chern-Simons-matter theories in N =4 superspace

    NASA Astrophysics Data System (ADS)

    Kuzenko, Sergei M.; Samsonov, Igor B.

    2015-11-01

    In three dimensions, every known N =4 supermultiplet has an off-shell completion. However, there is no off-shell N =4 formulation for the known extended superconformal Chern-Simons (CS) theories with eight and more supercharges. To achieve a better understanding of this issue, we provide N =4 superfield realizations for the equations of motion which correspond to various N =4 and N =6 superconformal CS theories, including the Gaiotto-Witten theory and the Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. These superfield realizations demonstrate that the superconformal CS theories with N ≥4 (except for the Gaiotto-Witten theory) require a reducible long N =4 vector multiplet, from which the standard left and right N =4 vector multiplets are obtained by constraining the field strength to be either self-dual or antiself-dual. Such a long multiplet naturally originates upon reduction of any off-shell N >4 vector multiplet to N =4 superspace. For the long N =4 vector multiplet we develop a prepotential formulation. It makes use of two prepotentials being subject to the constraint which defines the so-called hybrid projective multiplets introduced in the framework of N =4 supergravity-matter systems in arXiv:1101.4013. We also couple N =4 superconformal CS theories to N =4 conformal supergravity.

  8. On three-algebra and bi-fundamental matter amplitudes and integrability of supergravity

    NASA Astrophysics Data System (ADS)

    Huang, Yu-tin; Johansson, Henrik; Lee, Sangmin

    2013-11-01

    We explore tree-level amplitude relations for SU( N) × SU( M) bi-fundamental matter theories. Embedding the group-theory structure in a Lie three-algebra, we derive Kleiss-Kuijf-like relations for bi-fundamental matter theories in general dimension. We investigate the three-algebra color-kinematics duality for these theories. Unlike the Yang-Mills two-algebra case, the three-algebra Bern-Carrasco-Johansson relations depend on the spacetime dimension and on the detailed symmetry properties of the structure constants. We find the presence of such relations in three and two dimensions, and absence in D > 3. Surprisingly, beyond six point, such relations are absent in the Aharony-Bergman-Jafferis-Maldacena theory for general gauge group, while the Bagger-Lambert-Gustavsson theory, and its supersymmetry truncations, obey the color-kinematics duality like clockwork. At four and six points the relevant partial amplitudes of the two theories are bijectively related, explaining previous results in the literature. In D = 2 the color-kinematics duality gives results consistent with integrability of two-dimensional = 16 supergravity: the four-point amplitude satisfies a Yang-Baxter equation; the six- and eight-point amplitudes vanish for certain kinematics away from factorization channels, as expected from integrability.

  9. Essential oil of Nepeta x faassenii Bergmans ex Stearn (N. mussinii Spreng. x N. nepetella L.): a comparison study.

    PubMed

    Radulović, Niko; Blagojević, Polina D; Rabbitt, Kevin; Menezes, Fabio de Sousa

    2011-07-01

    Analysis (GC and GC/MS) of an essential oil sample obtained from dry leaves of Nepeta x faassenii Bergmans ex Steam, a hybrid species produced by crossbreeding N. mussinii Spreng. with N. nepetella L., led to the identification of 109 constituents that represented 95.9% of the oil. The major constituents were 4aalpha,7alpha,7aalpha-nepetalactone (67.8%), 1,8-cineole (6.6%), germacrene D (4.8%), beta-pinene (2.7%), (E)-beta-ocimene (2.6%), 4aalpha,7beta,7aalpha-nepetalactone (2.3%) and (E)-beta-farnesene (1.0%). Chemical composition of the oil was compared, using multivariate statistical analyses (MVA) with those of the oils of other Nepeta taxa, in particular N. mussinii and N. nepetella. This was done in order to explore the mode of inheritance of the monoterpene biosynthetic apparatus of N. faassenii. Chemical composition of the volatiles of a Nepeta taxon (different populations) can be subject to variation due to environmental and geographical factors. To accommodate this fact in the MVAs, along side with N. faassenii essential oil, additional 6 oils (3 different populations of N. nuda L. and N. cataria L. from Serbia) were included in this study (isolated and analyzed (chemically and statistically)). The MVA analyses recognized N. faassenii as being closely related to both N. mussinii and N. nepetella. If the relative content of oil constituents per plant and not per chromatogram were used as variables in the MVA (this was done by simple multiplication of the yields and relative percentages of components) a higher degree of mutual similarity (in respect to the monoterpene biosynthesis) of N. faassenii to N. mussinii, than to the other parent species, was observed. PMID:21834248

  10. Conformationally gated fragmentations and rearrangements promoted by interception of the Bergman cyclization through intramolecular H-abstraction: a possible mechanism of auto-resistance to natural enediyne antibiotics?

    PubMed

    Baroudi, Abdulkader; Mauldin, Justin; Alabugin, Igor V

    2010-01-27

    A variety of fragmentations and rearrangements can follow Bergman cyclization in enediynes equipped with acetal rings mimicking the carbohydrate moiety of natural enediyne antibiotics of the esperamicine and calchiamicine families. In the first step of all these processes, intramolecular H-atom abstraction efficiently intercepts the p-benzyne product of the Bergman cyclization through a six-membered TS and transforms the p-benzyne into a new more stable radical. Depending on the substitution pattern and reaction conditions, this radical follows four alternative paths: (a) abstraction of an external hydrogen atom, (b) O-neophyl rearrangement which transposes O- and C-atoms of the substituent, (c) fragmentation of the O-C bond in the acetal ring, or (d) fragmentation with elimination of the appended acetal moiety as a whole. Experiments with varying concentrations of external H-atom donor (1,4-cyclohexadiene) were performed to gain further insight into the competition between intermolecular H-abstraction and the fragmentations. The Thorpe-Ingold effect in gem-dimethyl substituted enediynes enhances the efficiency of fragmentation to the extent where it cannot be prevented even by a large excess of external H-atom donor. These processes provide insight into a possible mechanism of unusual fragmentation of esperamicin A(1) upon its Bergman cycloaromatization and lay foundation for a new approach for the conformational control of reactivity of these natural antitumor antibiotics. Such an approach, in conjunction with supramolecular constraints, may provide a plausible mechanism for resistance to enediyne antibiotics by the enediyne-producing microorganisms. PMID:20041688

  11. Conventional and stuffed Bergman-type phases in the Na-Au-T (T = Ga, Ge, Sn) systems: syntheses, structures, coloring of cluster centers, and Fermi sphere-brillouin zone interactions.

    PubMed

    Lin, Qisheng; Smetana, Volodymyr; Miller, Gordon J; Corbett, John D

    2012-08-20

    Bergman-type phases in the Na-Au-T (T = Ga, Ge, and Sn) systems were synthesized by solid-state means and structurally characterized by single-crystal X-ray diffraction studies. Two structurally related (1/1) Bergman phases were found in the Na-Au-Ga system: (a) a conventional Bergman-type (CB) structure, Na(26)Au(x)Ga(54-x), which features empty innermost icosahedra, as refined with x = 18.1 (3), Im3, a = 14.512(2) Å, and Z = 2; (b) a stuffed Bergman-type (SB) structure, Na(26)Au(y)Ga(55-y), which contains Ga-centered innermost icosahedra, as refined with y = 36.0 (1), Im3, a = 14.597(2) Å, and Z = 2. Although these two subtypes have considerable phase widths along with respective tie lines at Na ≈ 32.5 and 32.1 atom %, they do not merge into a continuous solid solution. Rather, a quasicrystalline phase close to the Au-poor CB phase and an orthorhombic derivative near the Au-rich SB phase lie between them. In contrast, only Au-rich SB phases exist in the Ge and Sn systems, in which the innermost icosahedra are centered by Au rather than Ge or Sn. These were refined for Na(26)Au(40.93(5))Ge(14.07(5)) (Im3, a = 14.581(2) Å, and Z = 2) and Na(26)Au(39.83(6))Sn(15.17(6)) (Im3, a = 15.009(2) Å, and Z = 2), respectively. Occupations of the centers of Bergman clusters are rare. Such centering and coloring correlate with the sizes of the neighboring icosahedra, the size ratios between electropositive and electronegative components, and the values of the average valence electron count per atom (e/a). Theoretical calculations revealed that all of these phases are Hume-Rothery phases, with evident pseudogaps in the density of states curves that arise from the interactions between Fermi surface and Brillouin zone boundaries corresponding to a strong diffraction intensity. PMID:22862775

  12. Conventional and Stuffed Bergman-Type Phases in the Na-Au-T (T=Ga, Ge, Sn) Systems: Synthesis, Structures, Coloring of Cluster Centers, and Fermi Sphere - Brillouin Zone Interactions

    SciTech Connect

    Lin, Qisheng; Smetana, Volodymur; Miller, Gordon J.; Corbett, John D

    2012-08-03

    Bergman-type phases in the Na−Au−T (T = Ga, Ge, and Sn) systems were synthesized by solid-state means and structurally characterized by single-crystal X-ray diffraction studies. Two structurally related (1/1) Bergman phases were found in the Na− Au−Ga system: (a) a conventional Bergman-type (CB) structure, Na26AuxGa54−x, which features empty innermost icosahedra, as refined with x = 18.1 (3), Im3̅, a = 14.512(2) Å, and Z = 2; (b) a stuffed Bergman-type (SB) structure, Na26AuyGa55−y, which contains Gacentered innermost icosahedra, as refined with y = 36.0 (1), Im3̅, a = 14.597(2) Å, and Z = 2. Although these two subtypes have considerable phase widths along with respective tie lines at Na ≈ 32.5 and 32.1 atom %, they do not merge into a continuous solid solution. Rather, a quasicrystalline phase close to the Au-poor CB phase and an orthorhombic derivative near the Au-rich SB phase lie between them. In contrast, only Au-rich SB phases exist in the Ge and Sn systems, in which the innermost icosahedra are centered by Au rather than Ge or Sn. These were refined for Na26Au40.93(5)Ge14.07(5) (Im3̅, a = 14.581(2) Å, and Z = 2) and Na26Au39.83(6)Sn15.17(6) (Im3̅, a = 15.009(2) Å, and Z = 2), respectively. Occupations of the centers of Bergman clusters are rare. Such centering and coloring correlate with the sizes of the neighboring icosahedra, the size ratios between electropositive and electronegative components, and the values of the average valence electron count per atom (e/a). Theoretical calculations revealed that all of these phases are Hume−Rothery phases, with evident pseudogaps in the density of states curves that arise from the interactions between Fermi surface and Brillouin zone boundaries corresponding to a strong diffraction intensity.

  13. Comments on the opinions published by Bergman et al. (2015) on Critical Comments on the WHO-UNEP State of the Science of Endocrine Disrupting Chemicals (Lamb et al., 2014).

    PubMed

    Lamb, James C; Boffetta, Paolo; Foster, Warren G; Goodman, Julie E; Hentz, Karyn L; Rhomberg, Lorenz R; Staveley, Jane; Swaen, Gerard; Van Der Kraak, Glen; Williams, Amy L

    2015-12-01

    Recently Bergman et al. (2015) took issue with our comments (Lamb et al., 2014) on the WHO-UNEP(1) report entitled the "State of the Science of Endocrine Disrupting Chemicals - 2012" (WHO 2013a). We find several key differences between their view and ours regarding the selection of studies and presentation of data related to endocrine disrupting chemicals (EDCs) under the WHO-IPCS(2) definition (2002). In this response we address the factors that we think are most important: 1. the difference between hazard and risk; 2. the different approaches for hazard identification (weight of the evidence [WOE] vs. emphasizing positive findings over null results); and 3. the lack of a justification for conceptual or practical differences between EDCs and other groups of agents. PMID:26550933

  14. An Extended Ab Initio and Theoretical Thermodynamics Studies of the Bergman Reaction and the Energy Splitting of the Singlet Ortho-, Meta-, and Para-Benzynes

    NASA Technical Reports Server (NTRS)

    Lindh, Roland; Lee, Timothy J.; Bernhardsson, Anders; Persson, B. Joakim; Karlstroem, Gunnar; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    The autoaromatization of (Z)-hex-3-ene-1,5-diyne to the singlet biradical para-benzyne has been reinvestigated by state of the art ab initio methods. Previous CCSD(T)/6-31G(d,p) and CASPT2[0]/ANO[C(5s4p2d1f)/H(3s2p)] calculations estimated the the reaction heat at 298 K to be 8-10 and 4.9 plus or minus 3.2 kcal/mol, respectively. Recent NO- and oxygen-dependent trapping experiments and collision-induced dissociation threshold energy experiments estimate the heat of reaction to be 8.5 plus or minus 1.0 at 470 K (recomputed to 9.5 plus or minus 1.0 at 298 K) and 8.4 plus or minus 3.0 kcal/mol at 298 K, respectively. New theoretical estimates at 298 K predict the values at the basis set limit for the CCSD(T) and CASPT2(g1) methods to be 12.7 plus or minus 2.0 and 5.4 plus or minus 2.0 kcal/mol, respectively. The experimentally predicted electronic contribution to the heat of activation is 28.6 kcal/mol. This can be compared with 25.5 and 29.8 kcal/mol from the CASPT2[g1] and the CCSD(T) methods, respectively. The new study has in particular improved on the one-particle basis set for the CCSD(T) method as compared to earlier studies. For the CASPT2 investigation the better suited CASPT2[g1] approximation is utilized. The original CASPT2 method, CASPT2[0], systematically favors open shell systems relative to closed shell systems. This was previously corrected empirically. The study shows that the energy difference between CCSD(T) and CASPT2[g1] at the basis set limit is estimated to be 7 plus or minus 2 kcal/mol. The study also demonstrates that the estimated heat of reaction is very sensitive to the quality of the basis set.

  15. Understanding Film as Process of Change: A Metalanguage for the Study of Film Developed and Applied to Ingmar Bergman's "Persona" and Alan J. Pakula's "The Sterile Cuckoo."

    ERIC Educational Resources Information Center

    Koch, Christian Herbert

    This study develops and applies a way of talking about that transformation or change occurring in the mind of a film viewer as he views a film. This articulation is expressed in a metalanguage constructed along parameters of a game situation. The terminology employed in the articulation is derived from contemporary French structuralism and…

  16. Open Wilson lines and chiral condensates in thermal holographic QCD

    SciTech Connect

    Argyres, Philip C.; Edalati, Mohammad; Leigh, Robert G.; Vazquez-Poritz, Justin F.

    2009-02-15

    We investigate various aspects of a proposal by Aharony and Kutasov [O. Aharony and D. Kutasov, Phys. Rev. D 78, 026005 (2008).] for the gravity dual of an open Wilson line in the Sakai-Sugimoto model or its noncompact version. In particular, we use their proposal to determine the effect of finite temperature, as well as background electric and magnetic fields, on the chiral symmetry breaking order parameter. We also generalize their prescription to more complicated worldsheets and identify the operators dual to such worldsheets.

  17. The Use of Descriptors with Exemplar and Model Answers to Improve Quality of Students' Narrative Writing in English French and Arabic

    ERIC Educational Resources Information Center

    Somba, Anne W.; Obura, Ger; Njuguna, Margaret; Itevete, Boniface; Mulwa, Jones; Wandera, Nooh

    2015-01-01

    The importance of writing skills in enhancing student performance in language exams and even other subject areas is widely acknowledged. At Jaffery secondary, the approach to the teaching of writing has generally been to use three approaches: product-based approach with focus on what the students composed; process-based approach that is focused on…

  18. Proceedings of the Conference of the International Group for the Psychology of Mathematics Education (21st, Lahti, Finland, July 14-19, 1997). Volume 2.

    ERIC Educational Resources Information Center

    Pehkonen, Erkki, Ed.

    The second volume of the proceedings of 21st annual meeting of the International Group for the Psychology of Mathematics Education contains the following papers: (1) "The Dilemma of Transparency: Seeing and Seeing through Talk in the Mathematics Classroom" (J. Adler); (2) "Abstraction is Hard in Computer-Science Too" (D. Aharoni and U. Leron); (3)…

  19. Proceedings of the Conference of the International Group for the Psychology of Mathematics Education (PME) (24th, Hiroshima, Japan, July 23-27, 2000), Volume 2.

    ERIC Educational Resources Information Center

    Nakahara, Tadao, Ed.; Koyama, Masataka, Ed.

    The second volume of the 24th annual conference of the International Group for the Psychology of Mathematics Education contains full research report papers. Papers include: (1) "What you see is what you get: The influence of visualization on the perception of data structures" (Dan Aharoni); (2) "Exploring the transparency of graphs and graphing"…

  20. Three Literary Sources for "Through a Glass Darkly"

    ERIC Educational Resources Information Center

    Holden, David F.

    1974-01-01

    Analyzes the three literary sources of Ingmar Bergman's film, "Through a Glass Darkly," in an attempt to account for some of the film's technical weaknesses and shed light on the film's interpretation. (TO)

  1. Medium-range icosahedral order in quasicrystal-forming Zr{sub 2}Pd binary metallic glass

    SciTech Connect

    Huang Li; Fang, X. W.; Wang, C. Z.; Ho, K. M.; Kramer, M. J.; Ding, Z. J.

    2011-06-06

    Medium-range order in Zr{sub 2}Pd metallic glass was studied using a combination of x-ray diffraction experiment and atomistic simulations. We show that, in contrast to earlier experimental interpretations, the icosahedral-like polyhedron is centered around Pd, rather than Zr. Furthermore, we find that the ordered icosahedral packing around Pd extends to the third shell in the way similar to that in the Bergman-type clusters. The existence of Bergman-type clusters sheds interesting light into the formation of nanoquasicrystal phase during crystallization process of Zr{sub 2}Pd metallic glass.

  2. Reconstruction of Bulk Operators within the Entanglement Wedge in Gauge-Gravity Duality

    NASA Astrophysics Data System (ADS)

    Dong, Xi; Harlow, Daniel; Wall, Aron C.

    2016-07-01

    In this Letter we prove a simple theorem in quantum information theory, which implies that bulk operators in the anti-de Sitter/conformal field theory (AdS/CFT) correspondence can be reconstructed as CFT operators in a spatial subregion A , provided that they lie in its entanglement wedge. This is an improvement on existing reconstruction methods, which have at most succeeded in the smaller causal wedge. The proof is a combination of the recent work of Jafferis, Lewkowycz, Maldacena, and Suh on the quantum relative entropy of a CFT subregion with earlier ideas interpreting the correspondence as a quantum error correcting code.

  3. Reconstruction of Bulk Operators within the Entanglement Wedge in Gauge-Gravity Duality.

    PubMed

    Dong, Xi; Harlow, Daniel; Wall, Aron C

    2016-07-01

    In this Letter we prove a simple theorem in quantum information theory, which implies that bulk operators in the anti-de Sitter/conformal field theory (AdS/CFT) correspondence can be reconstructed as CFT operators in a spatial subregion A, provided that they lie in its entanglement wedge. This is an improvement on existing reconstruction methods, which have at most succeeded in the smaller causal wedge. The proof is a combination of the recent work of Jafferis, Lewkowycz, Maldacena, and Suh on the quantum relative entropy of a CFT subregion with earlier ideas interpreting the correspondence as a quantum error correcting code. PMID:27447499

  4. Home on the Wide-Open Range of Gender

    ERIC Educational Resources Information Center

    Beemyn, Genny

    2011-01-01

    Kate Bornstein and S. Bear Bergman's "Gender Outlaws: The Next Generation" is a collection of narratives written by individuals with a wide range of gender identities and expressions from around the world. The text shows how gender-nonconforming people are changing how society looks at gender. As many of the individuals who are challenging gender…

  5. Exemplary Institute. Proceedings of the Annual Conference (3rd, Albuquerque, New Mexico, February 22-24, 1998).

    ERIC Educational Resources Information Center

    Native American Scholarship Fund, Inc., Albuquerque, NM.

    This proceedings contains presentations and workshop summaries from the 3rd Annual Exemplary Institute for educators of Native American students. Presentations include: "Quality in Learning: Romancing the Journey" (quality management at Mount Edgecumbe High School, Alaska) (Todd Bergman); "Creating a School-wide Literacy Climate" (Sig Boloz); "How…

  6. Developmental Stages in the Conceptualization of Marriage

    ERIC Educational Resources Information Center

    Tamashiro, Roy T.

    1978-01-01

    "Marriage" is treated as a mental concept that evolves in a developmental sequence of four qualitatively distinct stages: Magical, Idealized Conventional, Individualistic, and Affirmational. Each stage is illustrated with excerpts from Ingmar Bergman's Scenes From a Marriage. Some applications for marriage counselors are suggested. (Author)

  7. Multi-Age Caregiving. Beginnings Workshop.

    ERIC Educational Resources Information Center

    Katz, Lilian G.; Allison, Jeanette; Clark, Marty; Bergman, Roberta; Gainer, Sue

    1998-01-01

    Presents four articles on the benefits of multi-age child care settings as being similar to a natural family setting. The workshop titles are: "The Benefits of the Mix" (Katz); "Dealing with Staff and Parent Concerns" (Allison); "Multi-Age at Riverfield Country Day School" (Clark); and "Making Multi-Age Groups Work" (Bergman and Gainer). (LBT)

  8. The Rigors of Predictive Validation: Some Comments on "A Job Learning Approach to Performance Prediction"

    ERIC Educational Resources Information Center

    Cohen, Stephen L.; Penner, Louis A.

    1976-01-01

    In a recent article in this journal (EJ 130 391) Siegel and Bergman described a "miniature job training and evaluation" approach to performance prediction. This research highlights their methodology's strengths and weaknesses in light of standard procedures recommended in developing any set of predictors. (Author/RK)

  9. "The Seventh Seal."

    ERIC Educational Resources Information Center

    Palmer, Peter M.

    1969-01-01

    The significance of Bergman's "Seventh Seal" lies not in the speeches nor in the actions of the central characters but rather in the film's form, its totality created by the emotive elements of imagery and sound together with the intellectual elements of actions and words. The scene-units are related to a central motif (the opening of the seventh…

  10. Updating the Trainability Tests Literature on Black-White Subgroup Differences and Reconsidering Criterion-Related Validity

    ERIC Educational Resources Information Center

    Roth, Philip L.; Buster, Maury A.; Bobko, Philip

    2011-01-01

    A number of applied psychologists have suggested that trainability test Black-White ethnic group differences are low or relatively low (e.g., Siegel & Bergman, 1975), though data are scarce. Likewise, there are relatively few estimates of criterion-related validity for trainability tests predicting job performance (cf. Robertson & Downs, 1989). We…

  11. Proceedings of the Annual Conference of the International Association of School LIbrarianship (19th, Umea, Sweden, July 8-12, 1990).

    ERIC Educational Resources Information Center

    International Association of School Librarianship, Kalamazoo, MI.

    This conference report contains 32 presented papers: "Talking Books for Children in Sweden in Libraries and Schools" (L. Bergman); "At-Risk Students: How Do School (Library) Systems Respond?" (G. R. Brown); "Providing School Library Services to Immigrant Populations" (K. W. Craver); "Bibliographic Aids for School Libraries" (K. Darling); "The…

  12. Do Students Learn More from a Flip? An Exploration of the Efficacy of Flipped and Traditional Lessons

    ERIC Educational Resources Information Center

    DeSantis, Joshua; Van Curen, Rebecca; Putsch, Jake; Metzger, Justin

    2015-01-01

    Flipped lesson planning, as popularized by Bergman & Sams (2012a), has been viewed by many as a revolutionary pedagogy, tailor-made for the twenty-first century classroom. Enthusiasm for flipped lesson planning has out-paced the collection of data that might determine its effectiveness. This paper presents the results of a study that compared…

  13. 76 FR 16821 - Gregory F. Saric, M.D.; Decision and Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-25

    ... similar to that of Respondent's.'' Exceptions at 1 (citing Stuart A. Bergman, M.D., 70 FR 33193 (2005... Health Servs., 72 FR 42126 (2007) (quoting Bourne Pharmacy, Inc., 72 FR 18273, 18274 (2007) (quoting 21 U... * * * controlled substances under the laws of the State in which he practices.''); Bourne Pharmacy, 72 FR at...

  14. New roles for icosahedral clusters in intermetallic phases: micelle-like segregation of Ca-Cd and Cu-Cd interactions in Ca10Cd27Cu2.

    PubMed

    Hadler, Amelia B; Harris, Nicholas A; Fredrickson, Daniel C

    2013-11-20

    Despite significant progress in the structural characterization of the quasicrystalline state, the chemical origins of long- and short-range icosahedral order remain mysterious and a subject of debate. In this Article, we present the crystal structure of a new complex intermetallic phase, Ca10Cd27Cu2 (mC234.24), whose geometrical features offer clues to the driving forces underlying the icosahedral clusters that occur in Bergman-type quasicrystals. Ca10Cd27Cu2 adopts a C-centered monoclinic superstructure of the 1/1 Bergman approximant structure, in which [110] layers of Bergman clusters in the 1/1 structure are separated through the insertion of additional atoms (accompanied by substantial positional disorder). An examination of the coordination environments of Ca and Cu (in the ordered regions) reveals that the structure can be viewed as a combination of coordination polyhedra present in the nearest binary phases in the Ca-Cd-Cu compositional space. A notable feature is the separation of Ca-Cd and Cu-Cd interactions, with Bergman clusters emerging as Ca-Cd Friauf polyhedra (derived from the MgZn2-type CaCd2 phase) encapsulate a Cu-Cd icosahedron similar to those appearing in Cu2Cd5. DFT chemical pressure calculations on nearby binary phases point to the importance of this segregation of Ca-Cd and Cu-Cd interactions. The mismatch in atomic size between Cu and Cd leads to an inability to satisfy Ca-Cu and Ca-Cd interactions simultaneously in the Friauf polyhedra of the nearby Laves phase CaCd2. The relegation of the Cu atoms to icosahedra prevents this frustration while nucleating the formation of Bergman clusters. PMID:24147875

  15. Multimodal imaging measures predict rearrest

    PubMed Central

    Steele, Vaughn R.; Claus, Eric D.; Aharoni, Eyal; Vincent, Gina M.; Calhoun, Vince D.; Kiehl, Kent A.

    2015-01-01

    Rearrest has been predicted by hemodynamic activity in the anterior cingulate cortex (ACC) during error-processing (Aharoni et al., 2013). Here, we evaluate the predictive power after adding an additional imaging modality in a subsample of 45 incarcerated males from Aharoni et al. (2013). Event-related potentials (ERPs) and hemodynamic activity were collected during a Go/NoGo response inhibition task. Neural measures of error-processing were obtained from the ACC and two ERP components, the error-related negativity (ERN/Ne) and the error positivity (Pe). Measures from the Pe and ACC differentiated individuals who were and were not subsequently rearrested. Cox regression, logistic regression, and support vector machine (SVM) neuroprediction models were calculated. Each of these models proved successful in predicting rearrest and SVM provided the strongest results. Multimodal neuroprediction SVM models with out of sample cross-validating accurately predicted rearrest (83.33%). Offenders with increased Pe amplitude and decreased ACC activation, suggesting abnormal error-processing, were at greatest risk of rearrest. PMID:26283947

  16. Spatially resolved distribution function and the medium-range order in metallic liquid and glass

    SciTech Connect

    Fang, Xiaowei; Wang, Cai-Zhuang; Hao, Shaogang; Kramer, Matthew; Yao, Yongxin; Mendelev, Mikhail; Napolitano, Ralph; Ho, Kai-Ming

    2011-12-23

    The structural description of disordered systems has been a longstanding challenge in physical science. We propose an atomic cluster alignment method to reveal the development of three-dimensional topological ordering in a metallic liquid as it undercools to form a glass. By analyzing molecular dynamic (MD) simulation trajectories of a Cu{sub 64.5}Zr{sub 35.5} alloy, we show that medium-range order (MRO) develops in the liquid as it approaches the glass transition. Specifically, around Cu sites, we observe 'Bergman triacontahedron' packing (icosahedron, dodecahedron and icosahedron) that extends out to the fourth shell, forming an interpenetrating backbone network in the glass. The discovery of Bergman-type MRO from our order-mining technique provides unique insights into the topological ordering near the glass transition and the relationship between metallic glasses and quasicrystals.

  17. Spontaneous poisoning by Solanum subinerme Jack as a cause of cerebellar cortical degeneration in cattle.

    PubMed

    Lima, Everton Ferreira; Riet-Correa, Franklin; de Medeiros, Rosane Maria Trindade

    2014-05-01

    The present work reports cerebellar degeneration in cattle associated with the ingestion of Solanum subinerme in northern Brazil. The main clinical signs were periodic crises with loss of balance, falls, opisthotonus, and nystagmus. The histological lesions consisted of diffuse vacuolation of the perikaryon of the Purkinje neurons, followed by the loss of these cells and their substitution by Bergman glia. It is concluded that S. subinerme is another species of Solanum that causes cerebellar degeneration in cattle. PMID:24561122

  18. [The work of Carl Wilhelm Scheele].

    PubMed

    Cassebaum, H

    1986-12-01

    On the occasion of C. W. Scheele's 200th anniversary of death corrections and complements to some of his important investigations and theories including discussions of priorities, are given to elucidate his works and to avoid misunderstanding (element term; tartaric, oxalic and benzoic acid; pyrolusit; earths/spar/Bologneese luminous stone/barite; Scheele/Bergman/Lavoisier; fire theory/discovery of oxygen; graphite/Wolfram; Scheele/Wenzel). PMID:3554272

  19. A Sodium-Containing Quasicrystal: Using Gold To Enhance Sodium's Covalency in Intermetallic Compounds

    SciTech Connect

    Smetana, Volodymyr; Lin, Qisheng; Pratt, Daniel K.; Kreyssig, Andreas; Ramazanoglu, Mehmet; Corbett, John D.; Goldman, Alan I.; Miller, Gordon J.

    2013-09-26

    Gold macht stabil: Na13Au12Ga15, ein natriumhaltiges thermodynamisch stabiles quasikristallines Material, wurde bei einer systematischen Studie des polaren Na-Au-Ga-Intermetallsystems entdeckt. Sein Elektron/Atom-Verhältnis von 1.75 ist für Bergman-Ikosaederphasen extrem klein, doch der substanzielle Au-Anteil sorgt für eine Hume-Rothery-Stabilisierung und neuartige polar-kovalente Na-Au-Wechselwirkungen.

  20. Berezin Transform in Clifford Analysis

    SciTech Connect

    Ren Guangbin; Liu Liang

    2008-09-01

    In the weighted monogenic Bergman spaces A{sup 2}(B{sub n},Ll{sub 0,n},dV{sub {alpha}}), the Berezin transform of a bounded continuous function f tends to itself pointwise as the parameter {alpha} tends to infinity. As a consequence, the norm of the Toeplitz operator parallel T{sub f}{sup ({alpha})} parallel tends to parallel f parallel {sub {infinity}} as {alpha} tends to infinity.

  1. A study of the structure and energy of the Néel domain wall by the numerical method

    NASA Astrophysics Data System (ADS)

    Semenov, V. S.

    2016-02-01

    The Brown-LaBonte variation numerical method has been used to investigate the structure and energy of the Néel domain wall (DW) in a thin magnetic film of the Permalloy type. The equilibrium structure of the DW corresponds to the minimum of the total energy and to the Aharoni criterion close to unity. It has been shown that, when moving from the center of the DW, variations in the magnetization occur in an oscillating manner with a period that increases upon approaching the edge of the DW. At the edge of the DW, the period reaches a maximum value and, in this region, a sharp decrease occurs in the magnetization. In the region of the extended side tails of the DW, a larger gradient of the change in the magnetization is obtained, compared to the model of a logarithmic variation.

  2. Scaling relations and multicritical phenomena from functional renormalization.

    PubMed

    Boettcher, Igor

    2015-06-01

    We investigate multicritical phenomena in O(N)+O(M) models by means of nonperturbative renormalization group equations. This constitutes an elementary building block for the study of competing orders in a variety of physical systems. To identify possible multicritical points in phase diagrams with two ordered phases, we compute the stability of isotropic and decoupled fixed point solutions from scaling potentials of single-field models. We verify the validity of Aharony's scaling relation within the scale-dependent derivative expansion of the effective average action. We discuss implications for the analysis of multicritical phenomena with truncated flow equations. These findings are an important step towards studies of competing orders and multicritical quantum phase transitions within the framework of functional renormalization. PMID:26172666

  3. Asymptotic dependence of the relaxation time of the magnetization of a ferromagnetic particle on the anisotropy of the particle

    NASA Astrophysics Data System (ADS)

    Scully, C. N.; Cregg, P. J.; Crothers, D. S. F.

    1992-01-01

    It is known that the direction of the magnetization vector of very fine single-domain ferromagnetic particles fluctuates under the influence of thermal agitation. Perturbation theory is applied rigorously to a singular integral equation to derive an asymptotic formula for the relaxation time of the magnetization, for the case of uniaxial anisotropy and an applied magnetic field. The result agrees with that of Brown [Phys. Rev. 130, 1677 (1963)] as described succinctly by Aharoni [Phys. Rev. 177, 793 (1969)]. It should be emphasized that both Gilbert's equation and the earlier Landau-Lifshitz equation are merely phenomenological equations, which are used to explain the time decay of the average magnetization. Brown suggested that the Gilbert equation should be augmented by a white-noise driving term in order to explain the effect of thermal fluctuations of the surroundings on the magnetization.

  4. Blood glucose regulation in diabetics. A flatness based nonlinear control simulation study

    NASA Astrophysics Data System (ADS)

    Cocha, Guillermo; Podestá, Melina; Mazzadi, Alejandro; Amorena, Carlos; D’Atellis, Carlos

    2016-04-01

    Flat systems are a generalization of linear systems, but the techniques used for controlling flat systems are much different than many of the existing techniques for linear systems. In this paper we present the flatness-based control of blood glucose regulation in human system. A non-near model, he Bergman Minimal Model, is used o represent he dynamics of blood regulation in humans and because of the flatness property, he system variables can be expressed as functions of he at output and heir time derivatives and a control aw developed.

  5. Development of ideas on renovascular hypertension.

    PubMed

    Peart, S

    2000-09-01

    Stephen Hales was the first to measure blood pressure directly in the horse (1733), and the definitive studies on human nephrins by Richard Bright followed much later (1836). The relation between high blood pressure and renal disease was established by Mahomed (1872). The discovery of renin and its possible link with Bright's disease was made by Tigerstedt and Bergman (1898), but only the experimental production of renal hypertension by Goldblatt and his colleagues (1934) led to the delineation of the role of the kidney in human hypertension by a wide variety of methods. PMID:11022890

  6. Bounds on Transport Coefficients of Porous Media

    SciTech Connect

    Berryman, J G

    2005-03-21

    An analytical formulation of conductivity bounds by Bergman and Milton is used in a different way to obtain rigorous bounds on the real transport coefficients (electrical conductivity, thermal conductivity, and/or fluid permeability) of a fluid-saturated porous medium. These bounds do not depend explicitly on the porosity, but rather on two formation factors--one associated with the pore space and the other with the solid frame. Hashin-Shtrikman bounds for transport in random polycrystals of porous-material laminates will also be discussed.

  7. Two-Photon Photochemical Generation of Reactive Enediyne

    PubMed Central

    Poloukhtine, Andrei; Popik, Vladimir V.

    2008-01-01

    p-Quinoid cyclopropenone-containing enediyne precursor (1) has been synthesized by mono-cyclopropanation of one of the triple bonds in p-dimethoxy substituted 3,4-benzocyclodeca-1,5-diyne followed by oxidative demethylation. Cyclopropenone 1 is stable up to 90°C but readily produces reactive enediyne 2 upon single-photon (Φ300nm = 0.46) or two-photon (σ800 nm = 0.5 GM) photolysis. The photo-product 2 undergoes Bergman cyclization at 40°C with the life time of 88 h. PMID:16958537

  8. Students Share Their Research at Student Poster Day | Poster

    Cancer.gov

    Students Share Their Research at Student Poster Day  By Ashley DeVine, Staff Writer More than 50 Werner H. Kirsten student interns and college interns presented their research at Summer Student Poster Day on August 6 in the Building 549 lobby.  Joseph Bergman, a high school intern in the Center for Cancer Research Nanobiology Laboratory, participated in the event “for the opportunity to present my summer research. It allowed me to meet people and get the experience of sharing and explaining my work.”

  9. Listings of model values for the simulation of ground-water flow in the Cimarron River alluvium and terrace deposits from Freedom to Guthrie, Oklahoma

    USGS Publications Warehouse

    Adams, G.P.

    1995-01-01

    This report contains MODFLOW input and output listings for the simulation of ground-water flow in alluvium and terrace deposits associated with the Cimarron River from Freedom to Guthrie, Oklahoma. These values are to be used in conjuction with the report, 'Geohydrology of alluvium and terrace deposits of the Cimarron River from Freedom to Guthrie, Oklahoma,' by G.P. Adams and D.L. Bergman, published as U.S. Geological Survey Water-Resources Investigatons Report 95-4066. The simulation used a digital ground-water flow model and was evaluated by a management and statistical program.

  10. Strong correlations of dynamical and structural heterogeneities with localized soft modes in a Cu-Zr metallic glass

    SciTech Connect

    Zhang, Ying; Wang, Cai-Zhuang; Zhang, Feng; Mendelev, Mikhail I; Kramer, Matthew J; Ho, Kai-Ming

    2014-10-13

    Structural and dynamical heterogeneities in metallic glasses, while intensely studied, remain an enigma. For instance, whether and how the dynamical and structural heterogeneities are correlated is still an outstanding question. Meanwhile, the nature of the impact of medium-range order (MRO) on the dynamical heterogeneity remains elusive. In this paper, we analyzed the structural and dynamical heterogeneities in both as-quenched and relaxed Cu 64.5Zr35.5 metallic glasses based on the atomistic trajectories collected from molecular dynamics simulations. We found that the majority of the mobile atoms are not involved in icosahedral clusters or Bergman superclusters, indicating that dynamical heterogeneities are strongly correlated with structural heterogeneities. The Bergman-type MRO has an even stronger correlation with the dynamical heterogeneity than the icosahedral short range order. Moreover, we found that the localized soft vibration modes below 1.0 THz are mostly concentrated on the mobile atoms. These results suggest that the vibrational properties can be conveniently utilized to predict the atomic mobility in metallic glasses, which can bridge the studies of dynamical heterogeneity by experiments and simulations.

  11. Correlations between dynamics and atomic structures in Cu64.5Zr35.5 metallic glass

    NASA Astrophysics Data System (ADS)

    Wang, C. Z.; Zhang, Y.; Zhang, F.; Mendelev, M. I.; Kramer, M. J.; Ho, K. M.

    2015-03-01

    The atomic structure of Cu-Zr metallic glasses (MGs) has been widely accepted to be heterogeneous and dominated by icosahedral short range order (ISRO). However, the correlations between dynamics and atomic structures in Cu-Zr MGs remain an enigma. Using molecular dynamics (MD) simulations, we investigated the correlations between dynamics and atomic structures in Cu64.5Zr35.5 MG. The atomic structures are characterized using ISRO and the Bergman-type medium range order (BMRO). The simulation and analysis results show that the majority of the mobile atoms are not involved in ISRO or BMRO, indicating that the dynamical heterogeneity has a strong correlation to structural heterogeneity. Moreover, we found that the localized soft vibration modes below 1.0 THz are mostly concentrated on the mobile atoms. The diffusion was studied using the atomic trajectory collected in an extended time interval of 1.2 μs at 700 K in MD simulations. It was found that the long range diffusion in MGs is highly heterogeneous, which is confined to the liquid-like regions and strongly avoids the ISRO and the Bergman-type MRO. All These results clearly demonstrate strong correlations between dynamics (in terms of dynamical heterogeneity and diffusion) and atomic structures in Cu64.5Zr35.5 MGs. This work was supported by the U.S. Department of Energy, Basic Energy Sciences, Division of Materials Science and Engineering under the Contract No. DE-AC02-07CH11358.

  12. Stereological studies of the effects of sodium benzoate or ascorbic acid on rats’ cerebellum

    PubMed Central

    Noorafshan, Ali; Erfanizadeh, Mahboobeh; Karbalay-Doust, Saied

    2014-01-01

    Objectives: To evaluate the cerebellar structure in sodium benzoate (NaB) or ascorbic acid (AA) treated rats. Methods: This experimental study was conducted between May and September 2013 in the Laboratory Animal Center of Shiraz University of Medical Sciences, Shiraz, Iran. The rats received distilled either water, NaB (200mg/kg/day), AA (100mg/kg/day), or NaB+AA. The hemispheres were removed after 28 days and underwent quantitative study. Results: The total volume of the cerebellar hemisphere, its cortex, intracerebellar nuclei; the total number of the Purkinje, Bergman, granule, neurons, and glial cells of the molecular layer; and neurons and glial cells of the intracerebellar nuclei reduced by 21-52% in the NaB-treated rats compared with the distilled water group (p=0.004). The total number of the Purkinje, Bergman, Golgi, and granule cells was 29-45% higher in the AA-treated rats compared with the distilled water group (p=0.05). However, these measures reduced by 17-50% in the NaB+AA-treated rats compared with the distilled water group (p=0.004). The NaB+AA group did not induce any significant structural changes in comparison with the NaB group (p>0.05). Conclusions: The NaB exposure with or without AA treatment could alter the cerebellum. Yet, AA could prevent the loss of some cells in the cerebellum. PMID:25491215

  13. Strong correlations of dynamical and structural heterogeneities with localized soft modes in a Cu-Zr metallic glass

    SciTech Connect

    Zhang, Y.; Zhang, F.; Mendelev, M. I.; Wang, C. Z. Ho, K. M.; Kramer, M. J.

    2014-10-13

    Structural and dynamical heterogeneities in metallic glasses, while intensely studied, remain an enigma. For instance, whether and how the dynamical and structural heterogeneities are correlated is still an outstanding question. Meanwhile, the nature of the impact of medium-range order (MRO) on the dynamical heterogeneity remains elusive. In this paper, we analyzed the structural and dynamical heterogeneities in both as-quenched and relaxed Cu{sub 64.5}Zr{sub 35.5} metallic glasses based on the atomistic trajectories collected from molecular dynamics simulations. We found that the majority of the mobile atoms are not involved in icosahedral clusters or Bergman superclusters, indicating that dynamical heterogeneities are strongly correlated with structural heterogeneities. The Bergman-type MRO has an even stronger correlation with the dynamical heterogeneity than the icosahedral short range order. Moreover, we found that the localized soft vibration modes below 1.0 THz are mostly concentrated on the mobile atoms. These results suggest that the vibrational properties can be conveniently utilized to predict the atomic mobility in metallic glasses, which can bridge the studies of dynamical heterogeneity by experiments and simulations.

  14. Design of a new warhead for the natural enediyne dynemicin A. An increase of biological activity.

    PubMed

    Kraka, Elfi; Tuttle, Tell; Cremer, Dieter

    2008-03-01

    A concept for designing nontoxic enediyne-based antitumor drugs that was previously suggested (J. Am. Chem. Soc. 2000, 122, 8245) is converted into reality by merging amidines with the natural enediyne dynemicin A. The dynemicin-amidines (DADs) resulting from this combination are biologically not active because they form extremely labile singlet biradicals that can no longer abstract H from DNA. However, if protonated in the acidic environment of the tumor cell, they possess increased biological activity, as is reflected by a lowering of the activation enthalpy for the Bergman cyclization from 16.7 (dynemicin A) to 11-12 kcal/mol (DADs), kinetic stability of the singlet biradicals formed in the cyclization reaction, increased H abstraction ability of the singlet biradicals, and improved docking properties in the minor groove of the duplex 10-mer B-DNA sequence d(CTACTACTGG).d(CCAGTAGTAG) throughout the triggering and Bergman reactions. The implications and the consequences of using DADs to exploit the differences between normal and tumor cells and to design a nontoxic antitumor drugs are discussed. PMID:18269275

  15. Strong correlations of dynamical and structural heterogeneities with localized soft modes in a Cu-Zr metallic glass

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Wang, C. Z.; Zhang, F.; Mendelev, M. I.; Kramer, M. J.; Ho, K. M.

    2014-10-01

    Structural and dynamical heterogeneities in metallic glasses, while intensely studied, remain an enigma. For instance, whether and how the dynamical and structural heterogeneities are correlated is still an outstanding question. Meanwhile, the nature of the impact of medium-range order (MRO) on the dynamical heterogeneity remains elusive. In this paper, we analyzed the structural and dynamical heterogeneities in both as-quenched and relaxed Cu64.5Zr35.5 metallic glasses based on the atomistic trajectories collected from molecular dynamics simulations. We found that the majority of the mobile atoms are not involved in icosahedral clusters or Bergman superclusters, indicating that dynamical heterogeneities are strongly correlated with structural heterogeneities. The Bergman-type MRO has an even stronger correlation with the dynamical heterogeneity than the icosahedral short range order. Moreover, we found that the localized soft vibration modes below 1.0 THz are mostly concentrated on the mobile atoms. These results suggest that the vibrational properties can be conveniently utilized to predict the atomic mobility in metallic glasses, which can bridge the studies of dynamical heterogeneity by experiments and simulations.

  16. Response to ``Comment on `Slow Debye-type peak observed in the dielectric response of polyalcohols' '' [J. Chem. Phys. 134, 037101 (2011)

    NASA Astrophysics Data System (ADS)

    Bergman, R.; Jansson, H.; Swenson, J.

    2011-01-01

    In our recent article [R. Bergman et al., J. Chem. Phys. 132, 044504 (2010)] we investigated some polyalcohols, i.e., glycerol, xylitol, and sorbitol by dielectric spectroscopy. In the study, a low-frequency peak of Debye character that normally is hidden by the large low-frequency dispersion due to conductivity was revealed by analyzing the real part of the permittivity and by using a thin Teflon film to suppress the low-frequency dispersion. We agree with the comment by Paluch et al. [J. Chem. Phys. 134, 037101 (2011)] that the Teflon film setup will indeed create a peak due to the dc conductivity. However, due to the fact that the location of the peak was almost identical in measurement with and without Teflon, we unfortunately mainly showed the data measured with Teflon, despite that it could also be observed in the real part of the permittivity without using the Teflon setup, as shown in our original article [R. Bergman et al., J. Chem. Phys. 132, 044504 (2010)]. Here, we show that the low-frequency peak of Debye character can also be observed by subtracting the dc conductivity. Furthermore, we show that the modulus representation used in Paluch et al. [J. Chem. Phys. 134, 037101 (2011).] is also not suitable for detecting processes hidden by the conductivity.

  17. Quasinormal modes in de Sitter space: Plane wave method

    NASA Astrophysics Data System (ADS)

    Tanhayi, M. Reza

    2014-09-01

    Recently, in the context of dS/CFT correspondence, quasinormal modes have been put forward to address certain features of this conjecture. In particular, it is argued that the dual states of quasinormal modes are in fact the states of CFT3 which are created by operator insertions. For a scalar field in dS4, quasinormal modes which are singular on the past horizon of the south pole and decay exponentially towards the future have been considered in [G. S. Ng and A. Strominger, Classical Quantum Gravity 30, 104002 (2013); D. L. Jafferis et al., arXiv:1305.5523]; these modes lie in two complex highest-weight representations of the dS4 isometry group. In this work, we present a simple group representation analysis of these modes so that the de Sitter invariance is obviously manifest. By making use of the so-called plane wave method, we will show that the quasinormal modes correspond to one class of the unitary irreducible representation of the de Sitter group. This consideration could be generalized straightforwardly for higher-spin fields and higher dimensions; in particular, we will study the quasinormal modes for gauge and spinor fields, and, in the case of a scalar field, the generalization to higher dimensions is also obtained.

  18. Gauging and decoupling in 3d mathcal{N} = 2 dualities

    NASA Astrophysics Data System (ADS)

    Lee, Jeongseog; Yamazaki, Masahito

    2016-06-01

    One interesting feature of 3d mathcal{N} = 2 theories is that gauge-invariant operators can decouple by strong-coupling effects, leading to emergent flavor symmetries in the IR. The details of such decoupling, however, depends very delicately on the gauge group and matter content of the theory. We here systematically study the IR behavior of 3d mathcal{N} = 2 SQCD with N f flavors, for gauge groups SU( N c ) , USp(2 N c ) and SO( N c ). We apply a combination of analytical and numerical methods, both to small values of N c , N f and also to the Veneziano limit, where N c and N f are taken to be large with their ratio N f /N c fixed. We highlight the role of monopole operators and their interplay with Aharony-type dualities. We also discuss the effect of gauging continuous and discrete flavor symmetries, and the implications of our analysis to the classification of 1 /4-BPS co-dimension 2 defects of 6d (2 , 0) theories.

  19. Calculations of the first- and second-correction-to-scaling amplitudes to order 6-d in the percolation problem

    NASA Astrophysics Data System (ADS)

    Chang, Mau-Chung

    1985-07-01

    The correction to scaling in the bond percolation problem near the percolation threshold is studied. One can write & [1+a+/-i||t||ων+b+/-i||t|| 2ων+O(||t||3ων)], where t=(pc-p)/pc, p is the percolation concentration, + (-) stands for ppc), and a+/-i,b+/-i are the first- and second-correction-to-scaling amplitudes, respectively; fi(t) can be the probability of a site being in the infinite cluster, the clusters' mean-square size, the mean number of clusters, or the pair-connected correlation length. It is shown that a+/-i/a+/-j, b+/-i/b+/-j, and b+/-i/a+/-2j are universal quantities. The detailed calculations are carried out to order ɛ (ɛ=6-d) using the two-loop renormalization results by Amit adopting the minimal subtraction procedures. The results for a+/-i/a+/-j to the zeroth order in ɛ are in agreement with those of Aharony using the recursion-relation approach. Some implications due to the second-correction-to-scaling term in the theory of critical phenomena are discussed.

  20. Na{sub 8}Au{sub 9.8(4)}Ga{sub 7.2} and Na{sub 17}Au{sub 5.87(2)}Ga{sub 46.63}: The diversity of pseudo 5-fold symmetries in the Na–Au–Ga system

    SciTech Connect

    Smetana, Volodymyr; Corbett, John D. Miller, Gordon J.

    2013-11-15

    The Na-rich part (∼30% Na) of the Na–Au–Ga system between NaAu{sub 2}, NaGa{sub 4}, and Na{sub 22}Ga{sub 39} has been found to contain the ternary phases Na{sub 8}Au{sub 9.8(4)}Ga{sub 7.2} (I) and Na{sub 17}Au{sub 5.87(2)}Ga{sub 46.63} (II), according to the results of single crystal X-ray diffraction measurements. I is orthorhombic, Cmcm, a=5.3040(1), b=24.519(5), c=14.573(3) Å, and contains a network of clusters with local 5-fold symmetry along the a-axis. Such clusters are frequent building units in decagonal quasicrystals and their approximants. II is rhombohedral, R3{sup ¯}m, a=16.325(2), c=35.242(7) Å, and contains building blocks that are structurally identical to the Bergman-type clusters as well as fused icosahedral units known with active metals, triels and late transition elements. II also contains a polycationic network with elements of the clathrate V type structure. Tight-binding electronic structure calculations using linear muffin–tin-orbital (LMTO) methods on idealized models of I and II indicate that both compounds are metallic with evident pseudogaps at the corresponding Fermi levels. The overall Hamilton bond populations are generally dominated by Au–Ga and Au–Au bonds in I and by Ga–Ga bonds in II; moreover, the Na–Au and Na–Ga contributions in I are unexpectedly large, ∼20% of the total. A similar involvement of sodium in covalent bonding has also been found in the electron-richer i-Na{sub 13}Au{sub 12}Ga{sub 15} quasicrystal approximant. - Graphical abstract: Multiply-endohedral Bergman-related clusters in the structure of Na{sub 17}Au{sub 5.9(1)}Ga{sub 46.6.} Display Omitted - Highlights: • Two new compounds with the local 5-fold symmetry have been investigated. • Na{sub 8}Au{sub 9.8(4)}Ga{sub 7.2} is an orthorhombic approximant of the Na{sub 13}Au{sub 12}Ga{sub 15} quasicrystal. • Na{sub 17}Au{sub 5.87(2)}Ga{sub 46.63} represents a rhombohedral distortion of the Bergman-type phases.

  1. Ab initio Ti-Zr-Ni phase diagram predicts stability of icosahedral TiZrNi quasicrystals

    NASA Astrophysics Data System (ADS)

    Hennig, R. G.; Carlsson, A. E.; Kelton, K. F.; Henley, C. L.

    2005-04-01

    The ab initio phase diagram determines the energetic stability of the icosahedral TiZrNi quasicrystal. The complete ab initio zero-temperature ternary phase diagram is constructed from the calculated energies of the elemental, binary and ternary Ti-Zr-Ni phases. For this, the icosahedral i -TiZrNi quasicrystal is approximated by periodic structures of up to 123 atoms/unit cell, based on a decorated-tiling model [R. G. Hennig, K. F. Kelton, A. E. Carlsson, and C. L. Henley, Phys. Rev. B 67, 134202 (2003)]. The approximant structures containing the 45-atom Bergman cluster are nearly degenerate in energy, and are all energetically stable against the competing phases. It is concluded that i -TiZrNi is a ground-state quasicrystal, as it is experimentally the low-temperature phase for its composition.

  2. Erratum; A Three-Position Spectral Line Survey of Sagittarius B2 between 218 and 263 GHz. II. Data Analysis

    NASA Astrophysics Data System (ADS)

    Nummelin, A.; Bergman, P.; Hjalmarson, Å.; Friberg, P.; Irvine, W. M.; Millar, T. J.; Ohishi, M.; Saito, S.

    2001-01-01

    In the paper ``A Three-Position Spectral Line Survey of Sagittarius B2 between 218 and 263 GHz. II. Data Analysis'' by A. Nummelin, P. Bergman, Å. Hjalmarson, P. Friberg, W. M. Irvine, T. J. Millar, M. Ohishi, and S. Saito (ApJS, 128, 213 [2000]), the affiliations for M. Ohishi and S. Saito were set incorrectly. The correct affiliation for M. Ohishi is National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; ohishi@nao.ac.jp. The correct affiliation for S. Saito is Research Center for Development of Far-Infrared Region, Fukui University, 3-9-1 Bunkyo, Fukui 901-8507, Japan; saito@maxwell.apphy.fukui-u.ac.jp. The Press sincerely regrets this error.

  3. Experimental Investigation of the Kinetics of a Ruthenium-Catalyzed Deconstruction of Lignin Model Compounds

    SciTech Connect

    Bu, L.; Nimlos, M. R.; Shirts, M. R.; Himmel, M. E.; Crowley, M. F.; Beckham, G. T.

    2012-01-01

    Lignin is a major component of plant cell walls that is typically underutilized in selective conversion strategies for renewable fuels and chemicals. The mechanisms by which thermal and catalytic treatments deconstruct lignin remain elusive. In this work, we have investigated the kinetics of the catalytic deconstruction of lignin model compounds using a ruthenium catalyst reported by Bergman et al. in 2010. A series of investigations using NMR spectroscopy and GC/MS will be presented. In addition, we propose detailed mechanisms for lignin depolymerization with ruthenium catalysts. We have also used DFT to compute transition state geometries of catalytic cycle intermediates and compare the values determined computationally with those observed experimentally. Ultimately, our objective is to apply our methods to the design of new homogeneous and heterogeneous catalysts for the effective deconstruction and valorization of lignin.

  4. Meal Detection in Patients With Type 1 Diabetes: A New Module for the Multivariable Adaptive Artificial Pancreas Control System.

    PubMed

    Turksoy, Kamuran; Samadi, Sediqeh; Feng, Jianyuan; Littlejohn, Elizabeth; Quinn, Laurie; Cinar, Ali

    2016-01-01

    A novel meal-detection algorithm is developed based on continuous glucose measurements. Bergman's minimal model is modified and used in an unscented Kalman filter for state estimations. The estimated rate of appearance of glucose is used for meal detection. Data from nine subjects are used to assess the performance of the algorithm. The results indicate that the proposed algorithm works successfully with high accuracy. The average change in glucose levels between the meals and the detection points is 16(±9.42) [mg/dl] for 61 successfully detected meals and snacks. The algorithm is developed as a new module of an integrated multivariable adaptive artificial pancreas control system. Meal detection with the proposed method is used to administer insulin boluses and prevent most of postprandial hyperglycemia without any manual meal announcements. A novel meal bolus calculation method is proposed and tested with the UVA/Padova simulator. The results indicate significant reduction in hyperglycemia. PMID:26087510

  5. The knight as patient of the squire.

    PubMed

    Chipman, Abram

    2005-01-01

    Many types of non-professional, non-credentialed relationships are seen by laypersons as analogous to those occuring in psychotherapy. This paper takes a leap backwards several centuries and describes two examples of one such type of interaction as portrayed in artistic masterpieces. In Miguel de Cervantes' novel, "Don Quixote," an elderly, depressed man pursues a restitutive and grandiose delusion of being a heroic knight errant. In Ingmar Bergman's film, "The Seventh Seal," a disillusioned knight returns from the Crusades to face the lethal bubonic plague, and he uses obsessional means in an attempt to outwit death. Both men are accompanied by squires who try, with varying degrees of success, to help their masters relinquish their infantile needs for omniscience and omnipotence, accept their human limitations, and deal more appropriately with their surrounding realities. The powerful and inspiring insights of both works have much to teach contemporary therapists whose patients wear more metaphorical suits of armor. PMID:16555464

  6. Diffusion in a Cu-Zr metallic glass studied by microsecond-scale molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Wang, C. Z.; Mendelev, M. I.; Zhang, F.; Kramer, M. J.; Ho, K. M.

    2015-05-01

    Icosahedral short-range order (ISRO) has been widely accepted to be dominant in Cu-Zr metallic glasses (MGs). However, the diffusion mechanism and correlation of ISRO and medium-range order (MRO) to diffusion in MGs remain largely unexplored. Here, we perform a long time annealing up to 1.8 μs in molecular dynamics simulations to study the diffusion mechanism and the relationship between atomic structures and the diffusion path in a C u64.5Z r35.5 MG. It is found that most of the diffusing events performed by the diffusing atoms are outside ISRO and the Bergman-type MRO. The long-range diffusion in MGs is highly heterogeneous, via collective diffusing events through the liquidlike channels in the glass. Our results clearly demonstrate a strong correlation between the atomic structures and transport in MGs.

  7. Inorganic nanoparticles for the spatial and temporal control of organic reactions: Applications to radical degradation of biopolymer networks

    NASA Astrophysics Data System (ADS)

    Walker, Joan Marie

    Nanoparticles of gold and iron oxide not only possess remarkable optical and magnetic properties, respectively, but are also capable of influencing their local environment with an astounding degree of precision. Using nanoparticles to direct the reactivity of organic molecules near their surface provides a unique method of spatial and temporal control. Enediynes represent an exceptional class of compounds that are thermally reactive to produce a diradical intermediate via Bergman cycloaromatization. While natural product enediynes are famously cytotoxic, a rich chemistry of synthetic enediynes has developed utilizing creative means to control this reactivity through structure, electronics, metal chelation, and external triggering mechanisms. In a heretofore unexplored arena for Bergman cyclization, we have investigated the reactivity of enediynes in connection with inorganic nanoparticles in which the physical properties of the nanomaterial are directly excited to thermally promote aromatization. As the first example of this methodology, gold nanoparticles conjugated with (Z)-octa-4-en-2,6-diyne-1,8-dithiol were excited with 514 nm laser irradiation. The formation of aromatic and polymeric products was confirmed through Raman spectroscopy and electron microscopy. Water soluble analogues Au-PEG-EDDA and Fe3O4-PEG-EDDA (EDDA = (Z)-octa-4-en-2,6-diyne-1,8-diamine) show similar reactivity under laser irradiation or alternating magnetic field excitation, respectively. Furthermore, we have used these functionalized nanoparticles to attack proteinaceous substrates including fibrin and extracellular matrix proteins, capitalizing on the ability of diradicals to disrupt peptidic bonds. By delivering a locally high payload of reactive molecules and thermal energy to the large biopolymer, network restructuring and collapse is achieved. As a synthetic extension towards multifunctional nanoparticles, noble metal seed-decorated iron oxides have also been prepared and assessed for

  8. Iron Mineral Catalyzed C-H Activation As a Potential Pathway for Halogenation Processes

    NASA Astrophysics Data System (ADS)

    Tubbesing, C.; Schoeler, H. F.; Benzing, K.; Krause, T.; Lippe, S.; Rudloff, M.

    2014-12-01

    Due to increasing drinking water demand of mankind and an expected climate change the impact of salt lakes and salt deserts will increase within the next decades. Furthermore, a rising sea level influences coastal areas like salt marshes and abets processes which will lead to elevated organohalogen formation. An additional increase of the global warming potential, of particle formation and stratospheric ozone depletion is expected. Understanding these multifaceted processes is essential for mankind to be prepared for these alterations of the atmosphere. For example, Keppler et al. (2000) described the production of volatile halogenated organic compounds via oxidation of organic matter driven by ferric iron. However, the formation of long-chained alkyl halides in salt lakes is yet undisclosed. Despite the relative "inertness" of alkanes a direct halogenation of these compounds might be envisaged. In 2005 Vaillancourt et al. discovered a nonheme iron enzyme which is able to halogenate organic compounds via generating the high valent ferryl cation as reaction center. Based on various publications about C-H activation (Bergman, 2007) we postulate a halogenation process in which an iron containing minerals catalyse the C-H bond cleavage of organic compounds in soils. The generated organic radicals are highly reactive towards halides connected to the iron complex. We suggest that next to diagenetically altered iron containing enzymes, minerals such as oxides, hydroxides and sulfides are involved in abiotic halogenation processes. We applied the amino acid methionine as organic model compound and soluble iron species as reactants. All samples were incubated in aqueous phases containing various NaCl concentrations. As a result various halogenated ethanes and ethenes were identified as reaction products. References Bergman, R. G. (2007) Nature, 446(7134) 391-393 Keppler, F., et al. (2000) Nature, 403(6767) 298-301 Vaillancourt, F. H., et al. (2005) Nature, 436(7054) 1191-1194

  9. Comparison of optimal design methods in inverse problems

    NASA Astrophysics Data System (ADS)

    Banks, H. T.; Holm, K.; Kappel, F.

    2011-07-01

    Typical optimal design methods for inverse or parameter estimation problems are designed to choose optimal sampling distributions through minimization of a specific cost function related to the resulting error in parameter estimates. It is hoped that the inverse problem will produce parameter estimates with increased accuracy using data collected according to the optimal sampling distribution. Here we formulate the classical optimal design problem in the context of general optimization problems over distributions of sampling times. We present a new Prohorov metric-based theoretical framework that permits one to treat succinctly and rigorously any optimal design criteria based on the Fisher information matrix. A fundamental approximation theory is also included in this framework. A new optimal design, SE-optimal design (standard error optimal design), is then introduced in the context of this framework. We compare this new design criterion with the more traditional D-optimal and E-optimal designs. The optimal sampling distributions from each design are used to compute and compare standard errors; the standard errors for parameters are computed using asymptotic theory or bootstrapping and the optimal mesh. We use three examples to illustrate ideas: the Verhulst-Pearl logistic population model (Banks H T and Tran H T 2009 Mathematical and Experimental Modeling of Physical and Biological Processes (Boca Raton, FL: Chapman and Hall/CRC)), the standard harmonic oscillator model (Banks H T and Tran H T 2009) and a popular glucose regulation model (Bergman R N, Ider Y Z, Bowden C R and Cobelli C 1979 Am. J. Physiol. 236 E667-77 De Gaetano A and Arino O 2000 J. Math. Biol. 40 136-68 Toffolo G, Bergman R N, Finegood D T, Bowden C R and Cobelli C 1980 Diabetes 29 979-90).

  10. Non-self-averaging in Ising spin glasses and hyperuniversality

    NASA Astrophysics Data System (ADS)

    Lundow, P. H.; Campbell, I. A.

    2016-01-01

    Ising spin glasses with bimodal and Gaussian near-neighbor interaction distributions are studied through numerical simulations. The non-self-averaging (normalized intersample variance) parameter U22(T ,L ) for the spin glass susceptibility [and for higher moments Un n(T ,L ) ] is reported for dimensions 2 ,3 ,4 ,5 , and 7. In each dimension d the non-self-averaging parameters in the paramagnetic regime vary with the sample size L and the correlation length ξ (T ,L ) as Un n(β ,L ) =[Kdξ (T ,L ) /L ] d and so follow a renormalization group law due to Aharony and Harris [Phys. Rev. Lett. 77, 3700 (1996), 10.1103/PhysRevLett.77.3700]. Empirically, it is found that the Kd values are independent of d to within the statistics. The maximum values [Unn(T,L ) ] max are almost independent of L in each dimension, and remarkably the estimated thermodynamic limit critical [Unn(T,L ) ] max peak values are also practically dimension-independent to within the statistics and so are "hyperuniversal." These results show that the form of the spin-spin correlation function distribution at criticality in the large L limit is independent of dimension within the ISG family. Inspection of published non-self-averaging data for three-dimensional Heisenberg and X Y spin glasses the light of the Ising spin glass non-self-averaging results show behavior which appears to be compatible with that expected on a chiral-driven ordering interpretation but incompatible with a spin-driven ordering scenario.

  11. Modular invariant regularization of string determinants and the Serre GAGA principle

    NASA Astrophysics Data System (ADS)

    Matone, Marco

    2014-01-01

    Since any string theory involves a path integration on the world-sheet metric, their partition functions are volume forms on the moduli space of genus g Riemann surfaces Mg, or on its super analog. It is well known that modular invariance fixes strong constraints that in some cases appear only at higher genus. Here we classify all the Weyl and modular invariant partition functions given by the path integral on the world-sheet metric, together with space-time coordinates, b-c and/or β-γ systems, that correspond to volume forms on Mg. This was a long standing question, advocated by Belavin and Knizhnik, inspired by the Serre GAGA principle and based on the properties of the Mumford forms. The key observation is that the Bergman reproducing kernel provides a Weyl and modular invariant way to remove the point dependence that appears in the above string determinants, a property that should have its superanalog based on the super Bergman reproducing kernel. This is strictly related to the properties of the propagator associated to the space-time coordinates. Such partition functions Z[J] have well-defined asymptotic behavior and can be considered as a basis to represent a wide class of string theories. In particular, since noncritical bosonic string partition functions ZD are volume forms on Mg, we suggest that there is a mapping, based on bosonization and degeneration techniques, from the Liouville sector to first order systems that may identify ZD as a subclass of the Z[J]. The appearance of b-c and β-γ systems of any conformal weight shows that such theories are related to W algebras. The fact that in a large N 't Hooft-like limit two-dimensional WN minimal models conformal field theories are related to higher spin gravitational theories on AdS3, suggests that the string partition functions introduced here may lead to a formulation of higher spin theories in a string context.

  12. GT Merge Process: Version 2.0

    SciTech Connect

    Flanagan, M P; Dodge, D; Myers, S C

    2008-06-10

    This document summarizes the process used to merge GT25 and better data between LANL and LLNL. The merge also includes OUO arrivals provided by AFTAC for events in the merge. The merge process is mostly automated and includes extensive quality control operations at each step. Events in common between the labs are identified and resolved using GT level criteria. Arrivals in common between the labs are also resolved through the use of agreed upon arrival author rankings. Finally, baselined origin times are computed for all crustal events using either teleseismic P-arrivals and the iasp91 model or, in certain regions, regional P-arrivals and regional velocity models that are known to be consistent with teleseismic iasp91 P-wave predictions. We combine the core tables from each contributor and resolve unique and common GT events between contributors. Next, we merge at the pick level so that each distinct EVENT-STATION-PHASE tuple has a unique arrival. All BMEB (Bondar-Myers-Engdahl-Bergman) GT are recalculated and evaluated for adherence to their criteria. Finally, new origin times are computed (baselining) for the merged GT events. In addition to the reconciliation of events and picks between contributors, the merge process involves several quality control steps that are intended to remove outlier and irrelevant data from the final results. The process is described in the section entitled 'Merge Steps'.

  13. American Academy of Clinical Neuropsychology Consensus Conference Statement on the neuropsychological assessment of effort, response bias, and malingering.

    PubMed

    Heilbronner, Robert L; Sweet, Jerry J; Morgan, Joel E; Larrabee, Glenn J; Millis, Scott R

    2009-09-01

    During the past two decades clinical and research efforts have led to increasingly sophisticated and effective methods and instruments designed to detect exaggeration or fabrication of neuropsychological dysfunction, as well as somatic and psychological symptom complaints. A vast literature based on relevant research has emerged and substantial portions of professional meetings attended by clinical neuropsychologists have addressed topics related to malingering (Sweet, King, Malina, Bergman, & Simmons, 2002). Yet, despite these extensive activities, understanding the need for methods of detecting problematic effort and response bias and addressing the presence or absence of malingering has proven challenging for practitioners. A consensus conference, comprised of national and international experts in clinical neuropsychology, was held at the 2008 Annual Meeting of the American Academy of Clinical Neuropsychology (AACN) for the purposes of refinement of critical issues in this area. This consensus statement documents the current state of knowledge and recommendations of expert clinical neuropsychologists and is intended to assist clinicians and researchers with regard to the neuropsychological assessment of effort, response bias, and malingering. PMID:19735055

  14. Soft Tissue Esthetic Norms for Mahabubnagar Population of Southern India

    PubMed Central

    Sinojiya, Jay; Aileni, Kaladhar Reddy; Rachala, Madhukar Reddy; Pyata, Jaipal Reddy; Mallikarjun, Vankre; Reddy, C. Manjunatha

    2014-01-01

    Aims: The Aim of the study was to establish Soft Tissue Cephalometric Norms for skeletal and dental relationships amongst the Mahabubnagar adult population. Materials and Methods: Sixty subjects (30 Males & 30 Females) subjects from different part of Mahabubnagar in the age group 18-25 Years (Mean age 21.3 Years) were selected at random for the study and lateral cephalograms were taken. All the cephalograms were traced by two operators using conventional hand tracing. The parameters used in the study were taken from Arnett and Bergman soft tissue cephalometric analysis (STCA). Overall 46 measurements including 40 linear, 6 angular parameters were used. Mean and standard deviation values were calculated. The difference between males and females were evaluated using student t-test. Results: The values obtained from the study showed significant difference in most of the parameters from that of Arnett et al., norms and between males and females within Mahabubnagar population. Conclusion: Males had thicker soft tissue structures, acute nasolabial angle, increased facial lengths and heights, increased midface deficiency, recessive lower face, more convex profile and less upright mandibular incisors than females within Mahabubnagar population. PMID:24596789

  15. Impact of deformation on the atomic structures and dynamics of a Cu-Zr metallic glass: A molecular dynamics study

    SciTech Connect

    Zhang, Y.; Mendelev, M. I.; Wang, C. Z.; Ott, R.; Zhang, F.; Besser, M. F.; Ho, K. M.; Kramer, M. J.

    2014-11-03

    Despite numerous studies on the atomic structures of Cu-Zr metallic glasses (MGs), their inherent structural ordering, e.g., medium-range order (MRO), remains difficult to describe. Specifically lacking is an understanding of how the MRO responds to deformation and the associated changes in atomic mobility. In this paper, we focus on the impact of deformation on MRO and associated effect on diffusion in a well-relaxed Cu64.5Zr35.5 MG by molecular dynamics simulations. The Cu-Zr MG exhibits a larger elastic limit of 0.035 and a yield stress of 3.5 GPa. The cluster alignment method was employed to characterize the icosahedral short-range order (ISRO) and Bergman-type medium-range order (BMRO) in the models upon loading and unloading. From this analysis, we find the disruption of both ISRO and BMRO occurs as the strain reaches about 0.02, well below the elastic limit. Within the elastic limit, the total fractions of ISRO or BMRO can be fully recovered upon unloading. The diffusivity increases six to eight times in regions undergoing plastic deformation, which is due to the dramatic disruption of the ISRO and BMRO. As a result, by mapping the spatial distributions of the mobile atoms, we demonstrate the increase in atomic mobility is due to the extended regions of disrupted ISRO and more importantly BMRO.

  16. Impact of deformation on the atomic structures and dynamics of a Cu-Zr metallic glass: A molecular dynamics study

    DOE PAGESBeta

    Zhang, Y.; Mendelev, M. I.; Wang, C. Z.; Ott, R.; Zhang, F.; Besser, M. F.; Ho, K. M.; Kramer, M. J.

    2014-11-03

    Despite numerous studies on the atomic structures of Cu-Zr metallic glasses (MGs), their inherent structural ordering, e.g., medium-range order (MRO), remains difficult to describe. Specifically lacking is an understanding of how the MRO responds to deformation and the associated changes in atomic mobility. In this paper, we focus on the impact of deformation on MRO and associated effect on diffusion in a well-relaxed Cu64.5Zr35.5 MG by molecular dynamics simulations. The Cu-Zr MG exhibits a larger elastic limit of 0.035 and a yield stress of 3.5 GPa. The cluster alignment method was employed to characterize the icosahedral short-range order (ISRO) andmore » Bergman-type medium-range order (BMRO) in the models upon loading and unloading. From this analysis, we find the disruption of both ISRO and BMRO occurs as the strain reaches about 0.02, well below the elastic limit. Within the elastic limit, the total fractions of ISRO or BMRO can be fully recovered upon unloading. The diffusivity increases six to eight times in regions undergoing plastic deformation, which is due to the dramatic disruption of the ISRO and BMRO. As a result, by mapping the spatial distributions of the mobile atoms, we demonstrate the increase in atomic mobility is due to the extended regions of disrupted ISRO and more importantly BMRO.« less

  17. Noncommutative Involutive Bases

    NASA Astrophysics Data System (ADS)

    Alun Evans, Gareth

    2006-02-01

    The theory of Groebner Bases originated in the work of Buchberger and is now considered to be one of the most important and useful areas of symbolic computation. A great deal of effort has been put into improving Buchberger's algorithm for computing a Groebner Basis, and indeed in finding alternative methods of computing Groebner Bases. Two of these methods include the Groebner Walk method and the computation of Involutive Bases. By the mid 1980's, Buchberger's work had been generalised for noncommutative polynomial rings by Bergman and Mora. This thesis provides the corresponding generalisation for Involutive Bases and (to a lesser extent) the Groebner Walk, with the main results being as follows. (1) Algorithms for several new noncommutative involutive divisions are given, including strong; weak; global and local divisions. (2) An algorithm for computing a noncommutative Involutive Basis is given. When used with one of the aforementioned involutive divisions, it is shown that this algorithm returns a noncommutative Groebner Basis on termination. (3) An algorithm for a noncommutative Groebner Walk is given, in the case of conversion between two harmonious monomial orderings. It is shown that this algorithm generalises to give an algorithm for performing a noncommutative Involutive Walk, again in the case of conversion between two harmonious monomial orderings. (4) Two new properties of commutative involutive divisions are introduced (stability and extendibility), respectively ensuring the termination of the Involutive Basis algorithm and the applicability (under certain conditions) of homogeneous methods of computing Involutive Bases.

  18. Cerebellar Alterations and Gait Defects as Therapeutic Outcome Measures for Enzyme Replacement Therapy in α-Mannosidosis

    PubMed Central

    Damme, Markus; Stroobants, Stijn; Walkley, Steven U.; Lüllmann-Rauch, Renate; D`Hooge, Rudi; Fogh, Jens; Saftig, Paul; Lübke, Torben; Blanz, Judith

    2011-01-01

    α-Mannosidosis is a rare lysosomal storage disease with accumulation of undegraded mannosyl-linked oligosaccharides in cells throughout the body, most notably in the CNS. This leads to a broad spectrum of neurological manifestations, including progressive intellectual impairment, disturbed motor functions and cerebellar atrophy. To develop therapeutic outcome measures for enzyme replacement therapy (ERT) that could be used for human patients, a gene knockout model of α-mannosidosis in mice was analyzed for CNS pathology and motor deficits. In the cerebellar molecular layer, α-mannosidosis mice display clusters of activated Bergman glia, infiltration of phagocytic macrophages and accumulation of free cholesterol and gangliosides (GM1), notably in regions lacking Purkinje cells. α-mannosidosis brain lysates also displayed increased expression of Lamp1 and hyperglycosylation of the cholesterol binding protein NPC2. Detailed assessment of motor function revealed age-dependent gait defects in the mice that resemble the disturbed motor function in human patients. Short-term ERT partially reversed the observed cerebellar pathology with fewer activated macrophages and astrocytes but unchanged levels of hyperglycosylated NPC2, gangliosides and cholesterol. The present study demonstrates cerebellar alterations in α-mannosidosis mice that relate to the motor deficits and pathological changes seen in human patients and can be used as therapeutic outcome measures. PMID:21157375

  19. Epochs in the depressor/pressor balance of the renin-angiotensin system.

    PubMed

    Colafella, Katrina M Mirabito; Hilliard, Lucinda M; Denton, Kate M

    2016-05-01

    The renin-angiotensin system (RAS) plays a commanding role in the regulation of extracellular fluid homoeostasis. Tigerstadt and Bergman first identified the RAS more than two centuries ago. By the 1980s a voyage of research and discovery into the mechanisms and actions of this system led to the development of drugs that block the RAS, which have become the mainstay for the treatment of cardiovascular and renal disease. In the last 25 years new components of the RAS have come to light, including the angiotensin type 2 receptor (AT2R) and the angiotensin-converting enzyme 2 (ACE2)/angiotensin-(1-7) [Ang(1-7)]/Mas receptor (MasR) axis. These have been shown to counter the classical actions of angiotensin II (AngII) at the predominant angiotensin type 1 receptor (AT1R). Our studies, and those of others, have demonstrated that targeting these depressor RAS pathways may be therapeutically beneficial. It is apparent that the evolution of both the pressor and depressor RAS pathways is distinct throughout life and that the depressor/pressor balance of the RAS vary between the sexes. These temporal patterns of expression suggest that therapies targeting the RAS could be optimized for discrete epochs in life. PMID:27128801

  20. Effective medium based optical analysis with finite element method simulations to study photochromic transitions in Ag-TiO2 nanocomposite films

    NASA Astrophysics Data System (ADS)

    Abhilash, T.; Balasubrahmaniyam, M.; Kasiviswanathan, S.

    2016-03-01

    Photochromic transitions in silver nanoparticles (AgNPs) embedded titanium dioxide (TiO2) films under green light illumination are marked by reduction in strength and blue shift in the position of the localized surface plasmon resonance (LSPR) associated with AgNPs. These transitions, which happen in the sub-nanometer length scale, have been analysed using the variations observed in the effective dielectric properties of the Ag-TiO2 nanocomposite films in response to the size reduction of AgNPs and subsequent changes in the surrounding medium due to photo-oxidation. Bergman-Milton formulation based on spectral density approach is used to extract dielectric properties and information about the geometrical distribution of the effective medium. Combined with finite element method simulations, we isolate the effects due to the change in average size of the nanoparticles and those due to the change in the dielectric function of the surrounding medium. By analysing the dynamics of photochromic transitions in the effective medium, we conclude that the observed blue shift in LSPR is mainly because of the change in the dielectric function of surrounding medium, while a shape-preserving effective size reduction of the AgNPs causes decrease in the strength of LSPR.

  1. Selective Organic and Organometallic Reactions in Water-Soluble Host-Guest Supramolecular Systems

    SciTech Connect

    Pluth, Michael D.; Raymond, Kenneth N.; Bergman, Robert G.

    2008-02-16

    Inspired by the efficiency and selectivity of enzymes, synthetic chemists have designed and prepared a wide range of host molecules that can bind smaller molecules with their cavities; this area has become known as 'supramolecular' or 'host-guest' chemistry. Pioneered by Lehn, Cram, Pedersen, and Breslow, and followed up by a large number of more recent investigators, it has been found that the chemical environment in each assembly - defined by the size, shape, charge, and functional group availability - greatly influences the guest-binding characteristics of these compounds. In contrast to the large number of binding studies that have been carried out in this area, the exploration of chemistry - especially catalytic chemistry - that can take place inside supramolecular host cavities is still in its infancy. For example, until the work described here was carried out, very few examples of organometallic reactivity inside supramolecular hosts were known, especially in water solution. For that reason, our group and the group directed by Kenneth Raymond decided to take advantage of our complementary expertise and attempt to carry out metal-mediated C-H bond activation reactions in water-soluble supramolecular systems. This article begins by providing background from the Raymond group in supramolecular coordination chemistry and the Bergman group in C-H bond activation. It goes on to report the results of our combined efforts in supramolecular C-H activation reactions, followed by extensions of this work into a wider range of intracavity transformations.

  2. Theoretical analyses of cellular transmembrane voltage in suspensions induced by high-frequency fields.

    PubMed

    Zou, Yong; Wang, Changzhen; Peng, Ruiyun; Wang, Lifeng; Hu, Xiangjun

    2015-04-01

    A change of the transmembrane voltage is considered to cause biophysical and biochemical responses in cells. The present study focuses on the cellular transmembrane voltage (Δφ) induced by external fields. We detail analytical equations for the transmembrane voltage induced by external high-frequency (above the relaxation frequency of the cell membrane) fields on cells of a spherical shape in suspensions and layers. At direct current (DC) and low frequencies, the cell membrane was assumed to be non-conductive under physiologic conditions. However, with increasing frequency, the permittivity of the cytoplasm/extracellular medium and conductivity of the membrane must be accounted for. Our main work is to extend application of the analytical solution of Δφ to the high-frequency range. We first introduce the transmembrane voltage generated by DC and low-frequency exposures on a single cell. Then, we focus on cell suspensions exposed to high-frequency fields. Using the effective medium theory and the reasonable assumption, the approximate analytical solution of Δφ on cells in suspensions and layers can be derived. Phenomenological effective medium theory equations cannot be used to calculate the local electric field of cell suspensions, so we raised a possible solution based on the Bergman theory. PMID:25528063

  3. Metrics for diagnosing negative mass and stiffness when uncoupling experimental and analytical substructures.

    SciTech Connect

    Allen, Matthew S.; Kammer, Daniel C.; Mayes, Randall Lee

    2010-10-01

    Recently, a new substructure coupling/uncoupling approach has been introduced, called Modal Constraints for Fixture and Subsystem (MCFS) [Allen, Mayes, & Bergman, Journal of Sound and Vibration, vol. 329, 2010]. This method reduces ill-conditioning by imposing constraints on substructure modal coordinates instead of the physical interface coordinates. The experimental substructure is tested in a free-free configuration, and the interface is exercised by attaching a flexible fixture. An analytical representation of the fixture is then used to subtract its effects in order to create an experimental model for the subcomponent of interest. However, it has been observed that indefinite mass and stiffness matrices can be obtained for the experimental substructure in some situations. This paper presents two simple metrics that can be used by the analyst to determine the cause of indefinite mass or stiffness matrices after substructure uncoupling. The metrics rank the experimental and fixture modes based upon their contribution to offending negative eigenvalues. Once the troublesome modes have been identified, they can be inspected and often reveal why the mass has become negative. Two examples are presented to demonstrate the metrics and to illustrate the physical phenomena that they reveal.

  4. About the atomic structures of icosahedral quasicrystals

    NASA Astrophysics Data System (ADS)

    Quiquandon, Marianne; Gratias, Denis

    2014-01-01

    This paper is a survey of the crystallographic methods that have been developed these last twenty five years to decipher the atomic structures of the icosahedral stable quasicrystals since their discovery in 1982 by D. Shechtman. After a brief recall of the notion of quasiperiodicity and the natural description of Z-modules in 3-dim as projection of regular lattices in N>3-dim spaces, we give the basic geometrical ingredients useful to describe icosahedral quasicrystals as irrational 3-dim cuts of ordinary crystals in 6-dim space. Atoms are described by atomic surfaces (ASs) that are bounded volumes in the internal (or perpendicular) 3-dim space and the intersections of which with the physical space are the actual atomic positions. The main part of the paper is devoted to finding the major properties of quasicrystalline icosahedral structures. As experimentally demonstrated, they can be described with a surprisingly few high symmetry ASs located at high symmetry special points in 6-dim space. The atomic structures are best described by aggregations and intersections of high symmetry compact interpenetrating atomic clusters. We show here that the experimentally relevant clusters are derived from one generic cluster made of two concentric triacontahedra scaled by τ and an external icosidodecahedron. Depending on which ones of the orbits of this cluster are eventually occupied by atoms, the actual atomic clusters are of type Bergman, Mackay, Tsai and others….

  5. Preliminary Results from a Search for a Nebula in the Vicinity of Sirius

    NASA Astrophysics Data System (ADS)

    Mutz, Steven B.; Wyckoff, Susan

    1992-12-01

    Ptolemy, Seneca, and several Babylonian and mediaeval texts have described Sirius (now A1V for the visible component) as a red star (Gry and Bonnet-Bidaud 1990, Schlosser and Bergman 1985). If true, then the present color of Sirius would be very difficult to explain in terms of current theories of stellar evolution. A possible explanation is that Sirius was eclipsed by a small, dark nebula such as a Bok globule (see Gry and Bonnet-Bidaud 1990). To search for such an object J, H, K, and CO (near 2.4 mu ) imaging of the stellar field near Sirius' apparent postion of 2000 years ago was performed using the University of Arizona's 256x256 IR array on their 61-inch Mt Bigelow telescope. Preliminary (J-H) vs. (H-K) diagrams indicate the presence of color excesses in the area of study (following the methods of Jones et al. 1980, 1984). Examination of the Palomar Sky Survey plates for the region of interest shows several areas where the stellar number density is more than 3 sigma smaller than the average stellar density for that area of the sky. Also, the stellar density for these depleted regions is higher on the red Palomar plate than the number density of the regions on the blue plate, suggesting a redder stellar population in these regions, which may be due to the presence of intervening material.

  6. On Convergence Aspects of Spheroidal Monogenics

    NASA Astrophysics Data System (ADS)

    Georgiev, S.; Morais, J.

    2011-09-01

    Orthogonal polynomials have found wide applications in mathematical physics, numerical analysis, and other fields. Accordingly there is an enormous amount of variety of such polynomials and relations that describe their properties. The paper's main results are the discussion of approximation properties for monogenic functions over prolate spheroids in R3 in terms of orthogonal monogenic polynomials and their interdependences. Certain results are stated without proof for now. The motivation for the present study stems from the fact that these polynomials play an important role in the calculation of the Bergman kernel and Green's monogenic functions in a spheroid. Once these functions are known, it is possible to solve both basic boundary value and conformal mapping problems. Interestingly, most of the used methods have a n-dimensional counterpart and can be extended to arbitrary ellipsoids. But such a procedure would make the further study of the underlying ellipsoidal monogenics somewhat laborious, and for this reason we shall not discuss these general cases here. To the best of our knowledge, this does not appear to have been done in literature before.

  7. Dynamics of glass-forming liquids. XIV. A search for ultraslow dielectric relaxation in glycerol

    NASA Astrophysics Data System (ADS)

    Richert, Ranko

    2010-08-01

    A recent dielectric study of various polyalcohols reported on the general occurrence of an ultraslow process with Debye type character in hydrogen bonded liquids [R. Bergman, H. Jansson, and J. Swenson, J. Chem. Phys. 132, 044504 (2010)], whereas previous work suggested that such behavior is specific to monoalcohols only. Clarifying this issue is highly relevant for assessing models aimed at rationalizing these modes that are slower than the primary structural relaxation and associated with a single time constant. To this end, the dielectric relaxation of glycerol is measured at different electrode distances with high accuracy. In this manner, electrode polarization can be separated from the dielectric signals intrinsic in the supercooled liquid. In the frequency range below the loss peak frequency ωmax of the α-process, only dc-conductivity is required to understand the dielectric properties of supercooled glycerol within a margin of ɛ″≈±0.1 and thus no indication of an ultraslow peak is found. More quantitatively, any dielectric Debye like mode located around 10-5ωmax would need to have an amplitude smaller than 0.4% of that of the primary dielectric process to be consistent with the present findings, in contrast to previous claims of >50%.

  8. A Numerical Model for Magnetohydrodynamic Waves in a Stably-Stratified Layer in Earth's Core

    NASA Astrophysics Data System (ADS)

    Knezek, N. R.; Buffett, B. A.

    2015-12-01

    A numerical model for magnetohydrodynamic waves in a thin shell is developed and applied to study the effect of a stably-stratified layer in Earth's core on geomagnetic secular variation. The model employs a spherical coordinate system with finite differences in r and θ and Fourier decomposition in Φ. The model is linearized assuming a background azimuthal velocity field UΦ(r,θ) and an arbitrary background magnetic field Br,θ,Φ(r,θ). The Boussinesq approximation is employed and the buoyancy forces are prescribed in terms of a spatially variable Brunt-Vaisala frequency N(r,θ). The equations are cast into a sparse generalized eigenvalue problem by assuming solutions of the form uj,bj,p=CjeimΦ+λt and eigenmodes are found. Good agreement is obtained with previous approximate analytical solutions for zonal (m=0) magnetic-Archimedes-Coriolis (MAC) waves (e.g. Braginsky, 1993), global magnetic-Rossby (m>0) waves (e.g. Braginsky, 1998), and equatorially-trapped magnetic-Rossby waves (e.g. Bergman, 1993). This model is employed to study the origins of the fast equatorial waves observed by Chulliat et al. (2015) in recent high-resolution magnetic field models to constrain plausible properties of the stably-stratified layer and core-surface magnetic field.

  9. ALTERNATIVE REMEDIATION TECHNOLOGY STUDY FOR GROUNDWATER TREATMENT AT 200-PO-1 OPERABLE UNIT AT HANFORD SITE

    SciTech Connect

    DADO MA

    2008-07-31

    This study focuses on the remediation methods and technologies applicable for use at 200-PO-I Groundwater Operable Unit (OU) at the Hanford Site. The 200-PO-I Groundwater au requires groundwater remediation because of the existence of contaminants of potential concern (COPC). A screening was conducted on alternative technologies and methods of remediation to determine which show the most potential for remediation of groundwater contaminants. The possible technologies were screened to determine which would be suggested for further study and which were not applicable for groundwater remediation. COPCs determined by the Hanford Site groundwater monitoring were grouped into categories based on properties linking them by remediation methods applicable to each COPC group. The screening considered the following criteria. (1) Determine if the suggested method or technology can be used for the specific contaminants found in groundwater and if the technology can be applied at the 200-PO-I Groundwater au, based on physical characteristics such as geology and depth to groundwater. (2) Evaluate screened technologies based on testing and development stages, effectiveness, implementability, cost, and time. This report documents the results of an intern research project conducted by Mathew Dado for Central Plateau Remediation in the Soil and Groundwater Remediation Project. The study was conducted under the technical supervision of Gloria Cummins and management supervision of Theresa Bergman and Becky Austin.

  10. Multiple roles of the pilus biogenesis protein pilD: involvement of pilD in excretion of enzymes from Pseudomonas aeruginosa.

    PubMed Central

    Strom, M S; Nunn, D; Lory, S

    1991-01-01

    In Pseudomonas aeruginosa, the genes pilB, pilC, and pilD encode proteins necessary for posttranslational modification and assembly of pilin monomers into pilus organelles (D. Nunn, S. Bergman, and S. Lory, J. Bacteriol. 172:2911-2919, 1990). We show that PilD, encoding a putative pilin-specific leader peptidase, also controls export of alkaline phosphatase, phospholipase C, elastase, and exotoxin A. pilD mutants accumulate these proteins in the periplasmic space, while secretion of periplasmic and outer membrane proteins appears to be normal. The periplasmic form of exotoxin A was fully mature in size, contained all cysteines in disulfide bonds, and was toxic in a tissue culture cytotoxicity assay, suggesting that in pilD mutants, exotoxin A was folded into its native conformation. The function of the other two accessory proteins, PilB and PilC, appears to be restricted to pilus biogenesis, and strains carrying mutations in their respective genes do not show an export defect. These studies show that in addition to cleaving the leader sequence from prepilin, PilD has an additional role in secretion of proteins that are released from P. aeruginosa into the surrounding media. PilD most likely functions as a protease that is involved in processing and assembly of one or more components of the membrane machinery necessary for the later stages of protein extracellular localization. Images PMID:1671384

  11. 2-Alkynyl-N-propargyl pyridinium salts: pyridinium-based heterocyclic skipped aza-enediynes that cleave DNA by deoxyribosyl hydrogen-atom abstraction and guanine oxidation.

    PubMed

    Tuesuwan, Bodin; Kerwin, Sean M

    2006-06-13

    Diradical-generating cyclizations such as the enediyne Bergman cyclization and the enyne allene Myers-Saito cyclization have been exploited by nature in the mechanism of DNA cleavage by a series of potent antitumor antibiotics. Alternative diradical-generating cyclizations have been proposed in the design of selective antitumor agents; however, little information is available concerning the utility of these alternative cyclizations in radical-based DNA cleavage chemistry. One such alternative diradical-generating cyclization, the aza-Myers-Saito cyclization of aza-enyne allenes that are derived from base-promoted isomerization of skipped aza-enediynes, has been recently reported. Here, we report the synthesis and DNA cleavage chemistry of a series of pyridinium skipped aza-enediynes (2-alkynyl-N-propargyl pyridinium salts). Efficient DNA cleavage requires the presence of the skipped aza-enediyne functionality, and optimal DNA cleavage occurs at basic pH. Within this series of compounds, the analogue bearing a p-methoxyphenyl group on the pyridinium 2-alkyne substituents was found to be the most effective DNA cleavage agent, displaying significant supercoiled DNA-nicking activity at concentrations as low as 1 microM. Detailed studies of this analogue show that DNA cleavage occurs through 4'-hydrogen-atom abstraction from the DNA backbone and oxidation of guanine bases. This is the first report of enediyne-like radical-based DNA cleavage by an agent designed to undergo an alternative diradical-generating cyclization. PMID:16752915

  12. Enediyne compounds - new promises in anticancer therapy.

    PubMed

    Gredicak, Matija; Jerić, Ivanka

    2007-06-01

    Scientists of all kinds have long been intrigued by the nature, action and potential of natural toxins that possess exceptional antibacterial and anticancer activities. These compounds, named enediynes, are among the most effective chemotherapeutic agents known. Often compared with intelligent weapons, due to the unique structure and sophisticated mechanism by which they destroy double-helical DNA, enediyne antibiotics are nowadays the most promising leaders in the anticancer therapy. Apart from their diversity, enediyne compounds share some structural and functional similarities. One fragment of a structure is responsible for the recognition and transport, another part acts as molecular trigger while the third, reactive enediyne unit, undergoes Bergman cycloaromatization and causes DNA breakage. Members of the enediyne family are already in clinical use to treat various cancers, but more general use is limited by their complex structure, which makes them formidable targets for synthetic chemists. There are three main approaches in the design of new enediyne-related compounds: improvement of enediyne >warheads<, increasing the selectivity and control of chemical or photo-induced activation. This paper gives an overview of naturally occurring enediynes, their mode of action and efforts undertaken to design artificial enediyne-related DNA cleaving agents. PMID:17507311

  13. A differential evolution based approach for estimating minimal model parameters from IVGTT data.

    PubMed

    Ghosh, Subhojit

    2014-03-01

    Estimation of insulin sensitivity plays a crucial role in the diagnosis and clinical investigation of glucose related diseases. The Bergman minimal model provides a non-invasive approach for estimating insulin sensitivity from the glucose insulin time series data of intravenous glucose tolerance test (IVGTT). However, quite often in the traditional gradient based techniques for deriving insulin sensitivity from the minimal model, improper initialization leads to convergence problems and results in final solution, which are either incorrect or physiologically not feasible. This paper deals with a differential evolution-based approach for the determination of insulin sensitivity from the minimal model using clinical test data. Being a direct search based technique, the proposed approach enables the determination of the global solution irrespective of the initial parameter values. The fitting performance of the model with parameters estimated from the proposed approach is found to be higher than the corresponding model estimated from the widely used gradient based approach. A high correlation coefficient of 0.964 (95% confidence interval of [0.897,0.988]) is acheived between the estimated insulin sensitivity and the one obtained from the population based approach for 16 subjects. The high correlation signifies the relative similarity between the two estimated indices in representing the same physiological phenomena. The simulation results and statistical analysis reveal that the proposed technique provides a reliable estimate of insulin sensitivity with minimum prior knowledge. PMID:24529205

  14. Lung dust and lung iron contents of coal workers in different coalfields in Great Britain

    PubMed Central

    Bergman, I.; Casswell, C.

    1972-01-01

    Bergman, I., and Casswell, C. (1972).Brit. J. industr. Med.,29, 160-168. Lung dust and lung iron contents of coal workers in different coalfields in Great Britain. Lung dust analyses from seven coalfields are studied and it is found that the average dust composition varies significantly with the rank of coal. The higher the rank, the higher the coal percentage and the lower the quartz percentage of the lung dust. This holds for all coalfields except in Scotland, where the lung dust contains mainly soot instead of coal. Samples of airborne dust collected at the coalface in different coalfields show a similar but small variability of composition with rank of coal, and the results from Scotland are in good agreement with the results from other coalfields. The amount of iron in simple pneumoconiosis lungs is related to their mineral and coal contents and to the factor `years underground'. The strongest relationship is with coal and mineral for coalface workers from England. For pit accident cases (all simple pneumoconiosis) mineral is important as well as years underground, while for simple pneumoconiosis cases from Scotland, years underground is the most important factor. PMID:4336667

  15. Mathematical analysis of a model for glucose regulation.

    PubMed

    Fessel, Kimberly; Gaither, Jeffrey B; Bower, Julie K; Gaillard, Trudy; Osei, Kwame; Rempala, Grzegorz A

    2016-02-01

    Diabetes affects millions of Americans, and the correct identification of individuals afflicted with this disease, especially of those in early stages or in progression towards diabetes, remains an active area of research. The minimal model is a simplified mathematical construct for understanding glucose-insulin interactions. Developed by Bergman, Cobelli, and colleagues over three decades ago, this system of coupled ordinary differential equations prevails as an important tool for interpreting data collected during an intravenous glucose tolerance test (IVGTT). In this study we present an explicit solution to the minimal model which allows for separating the glucose and insulin dynamics of the minimal model and for identifying patient-specific parameters of glucose trajectories from IVGTT. As illustrated with patient data, our approach seems to have an edge over more complicated methods currently used. Additionally, we also present an application of our method to prediction of the time to baseline recovery and calculation of insulin sensitivity and glucose effectiveness, two quantities regarded as significant in diabetes diagnostics. PMID:26776262

  16. Transits of Venus, 1761 and 1769.

    NASA Astrophysics Data System (ADS)

    Abrahams, P.

    2003-12-01

    The Transits of Venus of 1761 and 1769 were widely anticipated, due to the efforts of Edmond Halley and Joseph-Nicolas Delisle in promoting observations to determine solar parallax. Extensive planning resulted in widespread participation; with at least 110 different observing stations stations worldwide for one or both of the events. Results from the 1761 expeditions derived solar parallax measurements between 8.28 and 10.60 arc seconds. The 1769 results were much better, 8.43 to 8.80 arc seconds, as compared with the accurate value of 8.79 arc seconds. This presentation will note the efforts of Halley, Delisle, and James Ferguson in promoting scientific observation of the transit. The poster will include the observations of Thorbern Bergman at Uppsala, Sweden; Samuel Dunn at the Royal Observatory, Greenwich; Charles Green at King George's Island; Samuel Horsley at Oxford; and William Smith at Norriton. These observers are distinguished from their contemporaries by the interesting graphic aids they used to present their studies.

  17. Digital-map grids of mean-annual precipitation for 1961-90, and generalized skew coefficients of annual maximum streamflow for Oklahoma

    USGS Publications Warehouse

    Rea, A.H.; Tortorelli, R.L.

    1997-01-01

    This digital report contains two digital-map grids of data that were used to develop peak-flow regression equations in Tortorelli, 1997, 'Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 97-4202. One data set is a grid of mean annual precipitation, in inches, based on the period 1961-90, for Oklahoma. The data set was derived from the PRISM (Parameter-elevation Regressions on Independent Slopes Model) mean annual precipitation grid for the United States, developed by Daly, Neilson, and Phillips (1994, 'A statistical-topographic model for mapping climatological precipitation over mountainous terrain:' Journal of Applied Meteorology, v. 33, no. 2, p. 140-158). The second data set is a grid of generalized skew coefficients of logarithms of annual maximum streamflow for Oklahoma streams less than or equal to 2,510 square miles in drainage area. This grid of skew coefficients is taken from figure 11 of Tortorelli and Bergman, 1985, 'Techniques for estimating flood peak discharges for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 84-4358. To save disk space, the skew coefficient values have been multiplied by 100 and rounded to integers with two significant digits. The data sets are provided in an ASCII grid format.

  18. Mackay icosahedron explaining orientation relationship of dispersoids in aluminium alloys.

    PubMed

    Muggerud, Astrid Marie F; Li, Yanjun; Holmestad, Randi; Andersen, Sigmund J

    2014-10-01

    The orientation relations (ORs) of the cubic icosahedral quasicrystal approximant phase α-Al(Fe,Mn)Si have been studied after low temperature annealing of a 3xxx wrought aluminium alloy by transmission electron microscopy. From diffraction studies it was verified that the most commonly observed OR for the α-Al(Fe,Mn)Si dispersoids is [1\\bar 11]α // [1\\bar 11]Al, (5\\bar 2\\bar 7)α // (011)Al. This orientation could be explained by assuming that the internal Mackay icosahedron (MI) in the α-phase has a fixed orientation in relation to Al, similar to that of the icosahedral quasi-crystals existing in this alloy system. It is shown that mirroring of the normal-to-high-symmetry icosahedral directions of the MI explains the alternative orientations, which are therefore likely to be caused by twinning of the fixed MI. Only one exception was found, which was related to the Bergman icosahedron internal to the T-phase of the Al-Mg-Zn system. PMID:25274523

  19. GT Merge Process: Version 1.0

    SciTech Connect

    Flanagan, M P; Dodge, D; Myers, S C

    2008-06-10

    This document summarizes the process used to merge GT25 and better data between LANL and LLNL for use in a tomographic inversion for Pn velocity of Eurasia. The merge process is automated and includes extensive quality control operations at each step. Events in common between the labs are identified and resolved using GT level criteria. Arrivals in common between the labs are also resolved through the use of agreed upon arrival author rankings. Finally, baselined origin times are computed for all crustal events using either teleseismic P-arrivals and the iasp91 model or, in certain regions, regional P-arrivals and regional velocity models that are known to be consistent with teleseismic iasp91 P-wave predictions. We combine the core tables from each lab and first resolve unique and common GT events between LANL and LLNL. Phase names are then checked and possibly adjusted for consistency. Next, we merge at the pick level so that each distinct EVENT-STATION-PHASE tuple has a unique arrival. All BMEB (Bondar-Myers-Engdahl-Bergman) GT are evaluated for adherence to their criteria, and possibly re-calculated. Finally, new origin times are computed (baselining) for the merged GT events. In addition to the reconciliation of events and picks between LANL and LLNL, the merge process involves several quality control steps that are intended to remove outlier and irrelevant data from the final results.

  20. Composition-dependent stability of the medium-range order responsible for metallic glass formation

    SciTech Connect

    Zhang, Feng; Ji, Min; Fang, Xiao-Wei; Sun, Yang; Wang, Cai-Zhuang; Mendelev, Mikhail I.; Kramer, M. J.; Napolitano, Ralph E.; Ho, Kai-Ming

    2014-09-18

    The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. Furthermore, we focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. These results show that a Bergman-type motif with crystallization-resisting icosahedral symmetry is energetically most favorable in the composition range 0.63 < xCu < 0.68, and is the underlying motif for one of the three optimal glass-forming ranges observed experimentally for this binary system (Li et al., 2008). This work establishes an energy-based methodology to evaluate specific medium-range structural motifs which compete with stable crystalline nuclei in deeply undercooled liquids.

  1. Composition-dependent stability of the medium-range order responsible for metallic glass formation

    DOE PAGESBeta

    Zhang, Feng; Ji, Min; Fang, Xiao-Wei; Sun, Yang; Wang, Cai-Zhuang; Mendelev, Mikhail I.; Kramer, M. J.; Napolitano, Ralph E.; Ho, Kai-Ming

    2014-09-18

    The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. Furthermore, we focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. These results show that a Bergman-type motifmore » with crystallization-resisting icosahedral symmetry is energetically most favorable in the composition range 0.63 < xCu < 0.68, and is the underlying motif for one of the three optimal glass-forming ranges observed experimentally for this binary system (Li et al., 2008). This work establishes an energy-based methodology to evaluate specific medium-range structural motifs which compete with stable crystalline nuclei in deeply undercooled liquids.« less

  2. PFAS - A threat for groundwater and drinking water supply in Sweden?

    NASA Astrophysics Data System (ADS)

    Lewis, Jeffrey; Banzhaf, Stefan; Ahlkrona, Malva; Arnheimer, Berit; Barthel, Roland; Bergvall, Martin; Blomquist, Niklas; Jacks, Gunnar; Jansson, Cecilia; Lissel, Patrik; Marklund, Lars; Olofsson, Bo; Persson, Kenneth M.; Sjöström, Jan; Sparrenbom, Charlotte

    2015-04-01

    Perfluoroalkyl substances (PFAS) are a group of anthropogenic environmental pollutants that are widely distributed in the global environment. They have multiple industrial uses, including water repellents in clothing, paper coatings and firefighting foam. According to a study released by the Environmental Directorate of the OECD, they are persistent, bioaccumulative and toxic to mammalian species (OECD, 2002). In some municipal drinking water wells in Sweden, measured concentrations of PFAS found to be several hundred times higher than the allowed threshold values. This has created a huge public concern and has recently attracted much media attention in Sweden (e.g. Afzelius et al., 2014; Bergman et al., 2014; Lewis et al., 2014). PFAS findings raised questions such as "What can we do to solve the problem?" When it comes to drinking water, there are a number of techniques that can ensure that PFAS levels are reduced to acceptable levels. This may be a costly challenge, but from a technical point of view it is possible. To ensure the safety of drinking water from a public health perspective is obviously a top priority. However, international experience shows that the cost of cleaning up PFAS in groundwater may be significantly higher than continuously treat drinking water in water works. Approximately fifty percent of Sweden's drinking water comes from groundwater. As a result, there are several ongoing and planned PFAS-related environmental and drinking-water investigations in Sweden. Many aquifers that supply municipal water plants are located in areas of sand and gravel deposits. Such soils have relatively high permeabilities, which permits extraction of large volumes of water. However, the downside to high permeabilities is that they also allow dissolved contaminants as PFAS to spread over large areas. If one disregards the health risks linked to its presence in drinking water, PFAS have an impact on three of Sweden's national environmental quality objectives

  3. Cost and waste volume reduction in HEPA filter trains by effective pre-filtration

    SciTech Connect

    Chadwick, Chris

    2007-07-01

    Data published elsewhere (Moore, et al., 1992; Bergman et al., 1997) suggests that the then costs of disposable type Glass Fibre HEPA filtration trains to the DOE was $55 million per year (based on an average usage of HEPA panels of 11,748 pieces per year between 1987 and 1990), $50 million of which was attributable to installation, testing, removal and disposal. The same authors suggest that by 1995 the number of HEPA panels being used had dropped to an estimated 4000 pieces per year due to the ending of the Cold War. The yearly cost to the DOE of 4000 units per year was estimated to be $29.5 million using the same parameters that previously suggested the $55 million figure. Within that cost estimate, $300 each was the value given to the filter and $4,450 was given to peripheral activity per filter. Clearly, if the $4,450 component could be reduced, tremendous saving could result, in addition to a significant reduction in the legacy burden of waste volumes. This same cost is applied to both the 11,748 and 4000 usage figures. The work up to now has focussed on the development of a low cost, long life (cleanable), direct replacement of the traditional filter train. This paper will review an alternative strategy, that of preventing the contaminating dust from reaching and blinding the HEPA filters, and thereby removing the need to replace them. What has become clear is that 'low cost' and 'Metallic HEPA' are not compatible terms. The original Bergman et al., 1997 work suggested that 1000 cfm (cubic feet per minute) (1690 m{sup 3}/hr) stainless HEPAs could be commercially available for $5000 each after development (although the $70,000 development unit may be somewhat exaggerated - the authors own company have estimated development units able to be retrofitted into strengthened standard housings would be available for perhaps $30,000). The likely true cost of such an item produced industrially in significant numbers may be closer to $15,000 each. That being the case

  4. PREFACE: Continuum Models and Discrete Systems Symposia (CMDS-12)

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Bikas K.

    2011-09-01

    The 12th International Symposium on Continuum Models and Discrete Systems (CMDS-12) (http://www.saha.ac.in/cmp/cmds.12/) took place at the Saha Institute of Nuclear Physics in Kolkata from 21-25 February 2011. Previous CMDS symposia were held in Kielce (Poland, 1975), Mont Gabriel (Canada, 1977), Freudenstadt (Federal Republic of Germany, 1979), Stockholm (Sweden, 1981), Nottingham (United Kingdom, 1985), Dijon (France, 1989), Paderborn (Germany, 1992), Varna (Bulgaria, 1995), Istanbul (Turkey, 1998), Shoresh (Israel, 2003) and Paris (France, 2007). The broad interdisciplinary character, limited number of participants (not exceeding 100) and informal and friendly atmosphere of these meetings has made them a well-acknowledged place to make highly fruitful contacts and exchange ideas, methods and results. The purpose of CMDS is to bring together scientists with different backgrounds who work on continuum theories of discrete mechanical and thermodynamical systems in the fields of mathematics, theoretical and applied mechanics, physics, material science, and engineering. The spirit of the CMDS meetings is to stimulate extensive and active interdisciplinary research. The International Scientific Committee members of this conference were: David J Bergman (Chairman CMDS 10), Tel Aviv University, Israel; Bikas K Chakrabarti (Chairman CMDS 12), Saha Institute of Nuclear Physics, India; Alex Hansen, Norwegian University of Science and Technology, Norway; Hans Jürgen Herrmann, Institute for Building Materials, ETH, Switzerland; Esin Inan (Chairman CMDS 9), Istanbul Technical University, Turkey; Dominique Jeulin (Chairman CMDS 11), Ecole des Mines de Paris, France; Frank Juelicher, Max-Planck-Institute for the Physics of Complex Systems, Germany; Hikaru Kawamura, University of Osaka, Japan; Graeme Milton, University of Utah, USA; Natalia Movchan, University of Liverpool, UK; and Ping Sheng, The Hong Kong University of Science and Technology, Hong Kong. At CMDS-12 the topics

  5. Investigations of the Electronic Properties and Surface Structures of Aluminium-Rich Quasicrystalline Alloys

    SciTech Connect

    Jason A. Barrow

    2003-08-05

    The work presented in this dissertation has investigated three distinct areas of interest in the field of quasicrystals: bulk structure, transport properties, and electronic structure. First, they have described the results of a study which explored the fundamental interactions between the atomic species of the icosahedral Al-Pd-Mn quasicrystal. The goal of this work was to determine whether the pseudo-MacKay or Bergman type clusters have a special stability or are merely a geometric coincidence. This was carried out by using laser vaporization to produce gas-phase metal clusters, which were analyzed using time-of-flight mass spectrometry. Both the kinetic and thermodynamic stabilities of the clusters were probed. The data indicated no special stability for either pseudo-MacKay or Bergman type clusters as isolated units. This, however, is not proof that these clusters are simply a geometric coincidence. It is possible that such clusters only have stability in the framework of the bulk matrix and do not exist as isolated units. Next, they have reported their investigations of the bulk thermal transport properties of a decagonal Al-Ni-Co two dimensional quasicrystal in the temperature range 373K-873K. The properties of a sample oriented along the periodic axis and another oriented along the aperiodic axis were measured. A high degree of anisotropy was observed between the aperiodic and periodic directions. Additionally, the properties were measured for a sample miscut to an orientation 45{sup o} off-axis. The properties of the miscut sample were shown to have good agreement with a theoretical model used to describe thermal transport in metallic single crystals. This model only considers thermal transport by a free-electron gas; therefore, agreement with experimental data suggests the validity of the Drude free-electron model for the decagonal Al-Ni-Co at these temperatures. Consequently, the observed anisotropy may be adequately described using classical transport

  6. Lomonosov, the discovery of Venus's atmosphere, and the eighteenth-century transits of Venus

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Sheehan, William

    2012-03-01

    The discovery of Venus's atmosphere has been widely attributed to the Russian academician M.V. Lomonosov from his observations of the 1761 transit of Venus from St. Petersburg. Other observers at the time also made observations that have been ascribed to the effects of the atmosphere of Venus. Though Venus does have an atmosphere one hundred times denser than the Earth's and refracts sunlight so as to produce an 'aureole' around the planet's disk when it is ingressing and egressing the solar limb, many eighteenth century observers also upheld the doctrine of cosmic pluralism: believing that the planets were inhabited, they had a preconceived bias for believing that the other planets must have atmospheres. A careful re-examination of several of the most important accounts of eighteenth century observers and comparisons with the observations of the nineteenth century and 2004 transits shows that Lomonosov inferred the existence of Venus's atmosphere from observations related to the 'black drop', which has nothing to do with the atmosphere of Venus. Several observers of the eighteenth-century transits, includ-ing Chappe d'Auteroche, Bergman, and Wargentin in 1761 and Wales, Dymond, and Rittenhouse in 1769, may have made bona fide observations of the aureole produced by the atmosphere of Venus. Therefore, it appears that several observers-but not Lomonosov-should receive credit for first detecting the aureole due to refraction of sunlight by the atmosphere of Venus during a transit. This crucial observation occurred almost three decades before Johann Schroeter independently demonstrated the existence of the atmosphere of Venus from his analysis of extensions of the semicircle of light of the planet near inferior conjunction, which are produced by back-scattering of light by aerosol-sized particles.

  7. Limited Diversity among Human Isolates of Bartonella henselae

    PubMed Central

    Dillon, B.; Valenzuela, J.; Don, R.; Blanckenberg, D.; Wigney, D. I.; Malik, R.; Morris, A. J.; Robson, J. M.; Iredell, J.

    2002-01-01

    A study of 59 isolates of Bartonella henselae reveals relatively limited diversity among those of human origin (n = 28). Either of two distinct alleles of both gltA and 16S ribosomal DNA (rDNA) was found in all isolates, with a high level of congruity between 16S and gltA inheritance among proven human pathogens. Human isolates from all over Eastern Australia were most commonly 16S rDNA (Bergmans) type I, with the same gltA allele as the type strain (Houston-1). Comparable feline isolates were more commonly 16S type II, with less congruity of inheritance between 16S and gltA alleles. Previously described arbitrarily primed PCR and EagI-HhaI infrequent restriction site PCR fingerprinting techniques separated Bartonella species effectively but lacked discriminating power within B. henselae. Examination of the 16-23S intergenic spacer region revealed for several strains several point mutations as well as a repeat sequence of unknown significance which is readily detected by HaeIII restriction fragment length polymorphism analysis. The bacteriophage-associated papA gene was present in all isolates. Enterobacterial repetitive intergenic consensus PCR proved to be a useful and robust typing tool and clearly separated human isolates (including imported strains) from the majority of feline isolates. Our data are consistent with published evidence and with previous suggestions of intragenomic rearrangements in the type strain and suggest that human isolates come from a limited subset of B. henselae strains. They strengthen arguments for careful exploration of genotype-phenotype relationships and for the development of a multilocus enzyme electrophoresis and multilocus sequence typing-based approach to the phylogeny of B. henselae. PMID:12454174

  8. Closed-Loop Control and Advisory Mode Evaluation of an Artificial Pancreatic β Cell: Use of Proportional–Integral–Derivative Equivalent Model-Based Controllers

    PubMed Central

    Percival, Matthew W.; Zisser, Howard; Jovanovič, Lois; Doyle, Francis J.

    2008-01-01

    Background Using currently available technology, it is possible to apply modern control theory to produce a closed-loop artificial β cell. Novel use of established control techniques would improve glycemic control, thereby reducing the complications of diabetes. Two popular controller structures, proportional–integral–derivative (PID) and model predictive control (MPC), are compared first in a theoretical sense and then in two applications. Methods The Bergman model is transformed for use in a PID equivalent model-based controller. The internal model control (IMC) structure, which makes explicit use of the model, is compared with the PID controller structure in the transfer function domain. An MPC controller is then developed as an optimization problem with restrictions on its tuning parameters and is shown to be equivalent to an IMC controller. The controllers are tuned for equivalent performance and evaluated in a simulation study as a closed-loop controller and in an advisory mode scenario on retrospective clinical data. Results Theoretical development shows conditions under which PID and MPC controllers produce equivalent output via IMC. The simulation study showed that the single tuning parameter for the equivalent controllers relates directly to the closed-loop speed of response and robustness, an important result considering system uncertainty. The risk metric allowed easy identification of instances of inadequate control. Results of the advisory mode simulation showed that suitable tuning produces consistently appropriate delivery recommendations. Conclusion The conditions under which PID and MPC are equivalent have been derived. The MPC framework is more suitable given the extensions necessary for a fully closed-loop artificial β cell, such as consideration of controller constraints. Formulation of the control problem in risk space is attractive, as it explicitly addresses the asymmetry of the problem; this is done easily with MPC. PMID:19885240

  9. Experimental design in chemistry: A tutorial.

    PubMed

    Leardi, Riccardo

    2009-10-12

    In this tutorial the main concepts and applications of experimental design in chemistry will be explained. Unfortunately, nowadays experimental design is not as known and applied as it should be, and many papers can be found in which the "optimization" of a procedure is performed one variable at a time. Goal of this paper is to show the real advantages in terms of reduced experimental effort and of increased quality of information that can be obtained if this approach is followed. To do that, three real examples will be shown. Rather than on the mathematical aspects, this paper will focus on the mental attitude required by experimental design. The readers being interested to deepen their knowledge of the mathematical and algorithmical part can find very good books and tutorials in the references [G.E.P. Box, W.G. Hunter, J.S. Hunter, Statistics for Experimenters: An Introduction to Design, Data Analysis, and Model Building, John Wiley & Sons, New York, 1978; R. Brereton, Chemometrics: Data Analysis for the Laboratory and Chemical Plant, John Wiley & Sons, New York, 1978; R. Carlson, J.E. Carlson, Design and Optimization in Organic Synthesis: Second Revised and Enlarged Edition, in: Data Handling in Science and Technology, vol. 24, Elsevier, Amsterdam, 2005; J.A. Cornell, Experiments with Mixtures: Designs, Models and the Analysis of Mixture Data, in: Series in Probability and Statistics, John Wiley & Sons, New York, 1991; R.E. Bruns, I.S. Scarminio, B. de Barros Neto, Statistical Design-Chemometrics, in: Data Handling in Science and Technology, vol. 25, Elsevier, Amsterdam, 2006; D.C. Montgomery, Design and Analysis of Experiments, 7th edition, John Wiley & Sons, Inc., 2009; T. Lundstedt, E. Seifert, L. Abramo, B. Thelin, A. Nyström, J. Pettersen, R. Bergman, Chemolab 42 (1998) 3; Y. Vander Heyden, LC-GC Europe 19 (9) (2006) 469]. PMID:19786177

  10. Three-dimensional topological insulator based nanospaser

    NASA Astrophysics Data System (ADS)

    Paudel, Hari P.; Apalkov, Vadym; Stockman, Mark I.

    2016-04-01

    After the discovery of the spaser (surface plasmon amplification by stimulated emission of radiation), first proposed by Bergman and Stockman in 2003, it has become possible to deliver optical energy beyond the diffraction limit and generate an intense source of an optical field. The spaser is a nanoplasmonic counterpart of a laser. One of the major advantages of the spaser is its size: A spaser is a truly nanoscopic device whose size can be made smaller than the skin depth of a material to a size as small as the nonlocality radius (˜1 nm). Recently, an electrically pumped graphene based nanospaser has been proposed that operates in the midinfrared region and utilizes a nanopatch of graphene as a source of plasmons and a quantum-well cascade as its gain medium. Here we propose an optically pumped nanospaser based on three-dimensional topological insulator (3D TI) materials, such as Bi2Se3 , that operates at an energy close to the bulk band-gap energy ˜0.3 eV and uses the surface as a source for plasmons and its bulk as a gain medium. Population inversion is obtained in the bulk and the radiative energy of the exciton recombination is transferred to the surface plasmons of the same material to stimulate spasing action. This is truly a nanoscale spaser as it utilizes the same material for dual purposes. We show theoretically the possibility of achieving spasing with a 3D TI. As the spaser operates in the midinfrared spectral region, it can be a useful device for a number of applications, such as nanoscopy, nanolithography, nanospectroscopy, and semiclassical information processing.

  11. Localization of metallothionein-I and -III expression in the CNS of transgenic mice with astrocyte-targeted expression of interleukin 6.

    PubMed

    Carrasco, J; Hernandez, J; Gonzalez, B; Campbell, I L; Hidalgo, J

    1998-10-01

    The effect of interleukin-6 (IL-6) on metallothionein-I (MT-I) and MT-III expression in the brain has been studied in transgenic mice expressing IL-6 under the regulatory control of the glial fibrillary acidic protein gene promoter (GFAP-IL6 mice), which develop chronic progressive neurodegenerative disease. In situ hybridization analysis revealed that GFAP-IL6 (G16-low expressor line, and G36-high expressor line) mice had strongly increased MT-I mRNA levels in the cerebellum (Purkinje and granular layers of the cerebellar cortex and basal nuclei) and, to a lesser degree, in thalamus (only G36 line) and hypothalamus, whereas no significant alterations were observed in other brain areas studied. Microautoradiography and immunocytochemistry studies suggest that the MT-I expression is predominantly localized to astrocytes throughout the cerebrum and especially in Bergman glia in the cerebellum. However, a significant expression was also observed in microglia of the GFAP-IL6 mice. MT-III expression was significantly increased in the Purkinje cell layer and basal nuclei of the cerebellum, which was confirmed by Northern blot analysis of poly(A)+ mRNA and by ELISA of the MT-III protein. In contrast, in the G36 but not G16 mice, transgene expression of IL-6 was associated with significantly decreased MT-III RNA levels in the dentate gyrus and CA3 pyramidal neuron layer of the hippocampus and, in both G36 and G16 mice, in the occipital but not frontal cortex and in ependymal cells. Thus, both the widely expressed MT-I isoform and the CNS specific MT-III isoform are significantly affected in a MT isoform- and CNS area-specific manner in the GFAP-IL6 mice, a chronic model of brain damage. PMID:9784278

  12. Effects of chronic buspirone treatment on cocaine self-administration.

    PubMed

    Mello, Nancy K; Fivel, Peter A; Kohut, Stephen J; Bergman, Jack

    2013-02-01

    Cocaine abuse and dependence is a major public health problem that continues to challenge medication-based treatment. Buspirone (Buspar) is a clinically available, non-benzodiazepine anxiolytic medication that acts on both serotonin and dopamine systems. In recent preclinical studies, acute buspirone treatment reduced cocaine self-administration at doses that did not also decrease food-reinforced behavior in rhesus monkeys (Bergman et al, 2012). The present study evaluated the effectiveness of chronic buspirone treatment on self-administration of cocaine and food. Five adult rhesus monkeys (Macaca mulatta) were trained to self-administer cocaine and food during four 1-h daily sessions under a second-order schedule of reinforcement (FR2 [VR 16:S]). Buspirone (0.32 and 0.56 mg/kg/h) was administered intravenously through one lumen of a double-lumen catheter every 20 min for 23 h each day for 7-10 consecutive days. Each buspirone treatment period was followed by saline control treatment until drug- and food-maintained responding returned to baseline levels. Buspirone significantly reduced responding maintained by cocaine, and shifted the dose-effect curve downwards. Buspirone had minimal effects on food-maintained responding. In cocaine discrimination studies, buspirone (0.1-0.32 mg/kg, IM) did not antagonize the discriminative stimulus and rate-altering effects of cocaine in four of six monkeys. These findings indicate that buspirone selectively attenuates the reinforcing effects of cocaine in a nonhuman primate model of cocaine self-administration, and has variable effects on cocaine discrimination. PMID:23072835

  13. Development of an icosahedral quasicrystal and two approximants in the Ca-Au-Sn system: syntheses and structural analyses.

    PubMed

    Lin, Qisheng; Corbett, John D

    2010-11-15

    The realm of Tsai-type (YCd(6)-type) quasicrystals (QCs) and their approximants (ACs) continues to expand to the east in the periodic table. The heavy tetrel Sn is now one of the major components in the new Ca(15.0(5))Au(60.0(4))Sn(25.0(2)) (atom %) icosahedral QC and in the corresponding 1/1 and 2/1 ACs. (The 2/1 AC with Yb is also established.) Single-crystal X-ray diffraction on a 1/1 AC gives the refined formula of Ca(3)Au(14.36(3))Sn(4.38(5)) in space group Im3, a = 15.131(1) Å, whereas a representative 2/1 AC gives Ca(13)Au(47.2(1))Sn(28.1(1)), Pa3 and a = 24.444(1) Å. Both ACs contain five-shell multiply endohedral triacontahedral clusters as the common building blocks, as in the parent structure of YCd(6). The 2/1 AC also contains four Ca(2)-dimer-centered prolate rhombohedra (PRs) in the unit cell. The long-range order between triacontahedra and PRs in the 2/1 AC is the same as those in Bergman-type 2/1 ACs. A TB-LMTO-ASA calculation on an ideal 1/1 AC model reveals a shallow pseudogap in the total densities-of-states data around the Fermi energy, as expected. The depth of the pseudogap is considerably enhanced through interactions between the Ca 3d states and s and p states of Au and Sn. PMID:20939550

  14. On the oscillator realization of conformal U(2, 2) quantum particles and their particle-hole coherent states

    SciTech Connect

    Calixto, M. Pérez-Romero, E.

    2014-08-01

    We revise the unireps. of U(2, 2) describing conformal particles with continuous mass spectrum from a many-body perspective, which shows massive conformal particles as compounds of two correlated massless particles. The statistics of the compound (boson/fermion) depends on the helicity h of the massless components (integer/half-integer). Coherent states (CS) of particle-hole pairs (“excitons”) are also explicitly constructed as the exponential action of exciton (non-canonical) creation operators on the ground state of unpaired particles. These CS are labeled by points Z (2×2 complex matrices) on the Cartan-Bergman domain D₄=U(2,2)/U(2)², and constitute a generalized (matrix) version of Perelomov U(1, 1) coherent states labeled by points z on the unit disk D₁=U(1,1)/U(1)². First, we follow a geometric approach to the construction of CS, orthonormal basis, U(2, 2) generators and their matrix elements and symbols in the reproducing kernel Hilbert space H{sub λ}(D₄) of analytic square-integrable holomorphic functions on D₄, which carries a unitary irreducible representation of U(2, 2) with index λϵN (the conformal or scale dimension). Then we introduce a many-body representation of the previous construction through an oscillator realization of the U(2, 2) Lie algebra generators in terms of eight boson operators with constraints. This particle picture allows us for a physical interpretation of our abstract mathematical construction in the many-body jargon. In particular, the index λ is related to the number 2(λ – 2) of unpaired quanta and to the helicity h = (λ – 2)/2 of each massless particle forming the massive compound.

  15. On the oscillator realization of conformal U(2, 2) quantum particles and their particle-hole coherent states

    NASA Astrophysics Data System (ADS)

    Calixto, M.; Pérez-Romero, E.

    2014-08-01

    We revise the unireps. of U(2, 2) describing conformal particles with continuous mass spectrum from a many-body perspective, which shows massive conformal particles as compounds of two correlated massless particles. The statistics of the compound (boson/fermion) depends on the helicity h of the massless components (integer/half-integer). Coherent states (CS) of particle-hole pairs ("excitons") are also explicitly constructed as the exponential action of exciton (non-canonical) creation operators on the ground state of unpaired particles. These CS are labeled by points Z (2 × 2 complex matrices) on the Cartan-Bergman domain {D}_4=U(2,2)/U(2)^2, and constitute a generalized (matrix) version of Perelomov U(1, 1) coherent states labeled by points z on the unit disk {D}_1=U(1,1)/U(1)^2. First, we follow a geometric approach to the construction of CS, orthonormal basis, U(2, 2) generators and their matrix elements and symbols in the reproducing kernel Hilbert space H_λ ({D}_4) of analytic square-integrable holomorphic functions on {D}_4, which carries a unitary irreducible representation of U(2, 2) with index λ in {N} (the conformal or scale dimension). Then we introduce a many-body representation of the previous construction through an oscillator realization of the U(2, 2) Lie algebra generators in terms of eight boson operators with constraints. This particle picture allows us for a physical interpretation of our abstract mathematical construction in the many-body jargon. In particular, the index λ is related to the number 2(λ - 2) of unpaired quanta and to the helicity h = (λ - 2)/2 of each massless particle forming the massive compound.

  16. Na8Au9.8(4)Ga7.2 and Na17Au15.87(2)Ga46.63: The diversity of pseudo 5-fold 0 Cross Mark symmetries in the Na-Au-Ga system

    SciTech Connect

    Smetana, Volodymyr; Corbett, John D.; Miller, Gordon J.

    2013-08-29

    The Na-rich part (similar to 30% Na) of the Na-Au-Ga system between NaAu2, NaGa4, and Na(22)Ga39 has been found to contain the ternary phases NasAug(8)(4)Ga-7.2 (I) and NavAu(5.87(2))Ga46.63 (II), according to the results of single crystal X-ray diffraction measurements. I is orthorhombic, Cmcm, a= 5.3040(1), b=24.519(5), c=14.573(3) A, and contains a network of clusters with local 5-fold symmetry along the a-axis. Such clusters are frequent building units in decagonal quasicrystals and their approximants. II is rhombohedral, a =16.325(2), c=35.242(7) A, and contains building blocks that are structurally. identical to the Bergman-type clusters as well as fused icosahedral units known with active metals, triels and late transition elements. II also contains a polycationic network with elements of the clathrate V type structure. Tight-binding electronic structure calculations using linear muffin-tin-orbital (LMTO) methods on idealized models of I and II indicate that both compounds are metallic with evident pseudogaps at the corresponding Fermi levels. The overall Hamilton bond populations are generally dominated by Au-Ga and Au-Au bonds in I and by Ga-Ga bonds in II; moreover, the Na-Au and Na-Ga contributions in I are unexpectedly large, 20% of the total. A similar involvement of sodium in covalent bonding has also been found in the electron-richer i-Nai(3)Aui(2)Gai(5) quasicrystal approximant. (C) 2013 Elsevier Inc. All rights reserved.

  17. The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1991-01-01

    During our participation in the NASA Crustal Dynamics Project under NASA contract NAS-27339 and grant NAG5-814 for the period 1982-1991, we published or submitted for publication 30 research papers and 52 abstracts of presentations at scientific meetings. In addition, five M.I.T. Ph.D. students (Eric Bergman, Steven Bratt, Dan Davis, Jeanne Sauber, Anne Sheehan) were supported wholly or in part by this project during their thesis research. Highlights of our research progress during this period include the following: application of geodetic data to determine rates of strain in the Mojave block and in central California and to clarify the relation of such strain to the San Andreas fault and Pacific-North American plate motions; application of geodetic data to infer post seismic deformation associated with large earthquakes in the Imperial Valley, Hebgen Lake, Argentina, and Chile; determination of the state of stress in oceanic lithosphere from a systematic study of the centroid depths and source mechanisms of oceanic intraplate earthquakes; development of models for the state of stress in young oceanic regions arising from the differential cooling of the lithosphere; determination of the depth extent and rupture characteristics of oceanic transform earthquakes; improved determination of earthquake slip vectors in the Gulf of California, an important data set for the estimation of Pacific-North American plate motions; development of models for the state of stress and mechanics of fold-and-thrust belts and accretionary wedges; development of procedures to invert geoid height, residual bathymetry, and differential body wave travel time residuals for lateral variations in the characteristic temperature and bulk composition of the oceanic upper mantle; and initial GPS measurements of crustal deformation associated with the Imperial-Cerro Prieto fault system in southern California and northern Mexico. Full descriptions of the research conducted on these topics may be

  18. Endomorphisms of spaces of virtual vectors fixed by a discrete group

    NASA Astrophysics Data System (ADS)

    Rădulescu, F.

    2016-04-01

    A study is made of unitary representations π of a discrete group G that are of type II when restricted to an almost-normal subgroup Γ\\subseteq G. The associated unitary representation \\overlineπ {p} of G on the Hilbert space of `virtual' Γ_0-invariant vectors is investigated, where Γ_0 runs over a suitable class of finite-index subgroups of Γ. The unitary representation \\overlineπ {p} of G is uniquely determined by the requirement that the Hecke operators for all Γ_0 are the `block-matrix coefficients' of \\overlineπ {p}. If π\\vert_Γ is an integer multiple of the regular representation, then there is a subspace L of the Hilbert space of π that acts as a fundamental domain for Γ. In this case the space of Γ-invariant vectors is identified with L. When π\\vert_Γ is not an integer multiple of the regular representation (for example, if G=\\operatorname{PGL}(2, Z \\lbrack 1/p \\rbrack ), Γ is the modular group, π belongs to the discrete series of representations of \\operatorname{PSL}(2, R), and the Γ-invariant vectors are cusp forms), π is assumed to be the restriction to a subspace H_0 of a larger unitary representation having a subspace L as above. The operator angle between the projection P_L onto L (typically, the characteristic function of the fundamental domain) and the projection P_0 onto the subspace H_0 (typically, a Bergman projection onto a space of analytic functions) is the analogue of the space of Γ-invariant vectors. It is proved that the character of the unitary representation \\overlineπ {p} is uniquely determined by the character of the representation π. Bibliography: 53 titles.

  19. Annealing of directionally solidified alloys revisited: No loss of solidification texture in Earth’s inner core

    NASA Astrophysics Data System (ADS)

    Al-Khatatbeh, Yahya; Bergman, Michael I.; Lewis, Daniel J.; Mason, Zachary; Zhu, Laura; Rosenstock, Sarita

    2013-10-01

    Bergman et al. (2010) found experimental evidence for recrystallization and loss of solidification texture during annealing of directionally solidified hexagonal close-packed (hcp) Zn-rich Sn alloys. They suggested that this could support the model of Alboussiere et al. (2010) and Monnereau et al. (2010), in which the Earth’s inner core translates convectively eastwards with enhanced solidification in the western hemisphere and melting in the eastern, because as inner core material translates eastwards and anneals it might lose texture, as inferred seismically. The 2010 study hypothesized that the alloys recrystallized rather than coarsened via diffusion due to the very low solubility of Sn in the Zn-rich phase. This study tests this hypothesis by annealing directionally solidified hcp Zn-rich Al alloys, in which there is greater solubility. Indeed, we find the Zn-rich Al alloys coarsen without recrystallization or fundamental change in texture. However, in contrast to the 2010 study the current study also did not find recrystallization in Zn-rich Sn alloys. This might tend to support models such as those by Cormier (2007) and Aubert et al. (2008) where long term mantle control over fluid flow near the base of the outer core might result in a weaker solidification texture in the eastern hemisphere. Although we do believe the results of the previous study are valid because they were repeatable at that time, it shows that there is something subtle that we cannot yet account for, and it remains unclear whether there is loss of solidification texture due to annealing of Earth’s inner core.

  20. Complex Airy analysis of photoreflectance spectra for III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Estrera, J. P.; Duncan, W. M.; Glosser, R.

    1994-03-01

    We present a detailed analysis of photoreflectance (PR) spectra of semiconductors using complex Airy functions and their derivatives. We demonstrate that photoreflectance spectra can be treated in terms of a single complex Airy function with an energy-dependent broadening parameter. We show analytically and numerically that this complex Airy PR treatment is functionally equivalent within field conditions appropriate for PR to the model of R. N. Bhattacharya, H. Shen, P. Parayanthal, F. H. Pollak, T. Coutts, and A. Aharoni [Phys. Rev. B 37, 4044 (1988)], where the effects of gradient electric field and non-flat-band modulation are treated explicitly. The equivalence occurs because the field gradient and non-flat-band modulation effects are included in our model in the energy dependence of the phenomenological broadening parameter Γ*=(Γ0/ħθ)exp[δ(ħω-Eg)], where ħω is the photon energy, Eg is the band-gap energy, Γ0 is the nominal broadening at the band-gap energy, and δ is a parameter directly proportional to the electric-field gradient and modulation between two finite fields. The major utility of our model is that a single effective layer can be treated instead of a more computationally intensive laminar model. We apply our complex Airy model to bulk semiconductors such as GaAs, InP, and InxGa1-xAs. In the photoreflectance spectra of these semiconductors, our model considers three distinct but convolved features at E0 which represent the light- and heavy-hole valence bands and an exciton-impurity feature below E0. At E0+Δ0 our model considers two features which are related to the spin-orbit-split valence band and a second state just below this critical point. For GaAs, we determined from our PR modeling that the band-gap energy for these films was 1.422+/-0.003 eV, which agreed, within experimental error, with the band-gap energy measured by room-temperature photoluminescence. A feature was found below the E0 gap in the GaAs samples with energies

  1. A Global Record of Surface Earth Oxygenation from Sedimentary V/Sc

    NASA Astrophysics Data System (ADS)

    Keller, C. B.; Schoene, B.; Johnston, D. T.

    2015-12-01

    One of the simplest methods to investigate changes in oxidation potential in geologic environments is to examine a pair of otherwise similar elements with dramatically different redox chemistry. The first-row transition metals Sc and V represent one such pair, with generally similar mass, radius, and ionization energies up to the trivalent redox state. However, as a d3 transition metal, Sc is limited to a maximum oxidation state of 3+, while d5 vanadium may be further oxidized to form tetravalent and pentavalent ions. Due to the greater incompatibility of pentavalent (relative to trivalent) metal cations in silicate melts, V/Sc ratio has been applied to the silicate rock record as a tracer of magma redox - indicating roughly constant mantle oxygen fugacity over Earth history1,2. As a result, the solid earth represents a boundary condition with constant V/Sc observed over geologic time1. However, oxidation state also affects the weathering, solubility, and coordination behaviour of V and Sc, resulting in a potential redox signal in the sedimentary V/Sc record. We apply the weighted bootstrap resampling approach of [2] to a geochemical dataset of ~87,000 sedimentary whole-rock analyses from the EarthChem portal3. The resulting trends reveal a 4 Gyr record of V/Sc redox chemistry, with the great oxidation event represented as an upward step ca. 2.5 Ga, and Phanerozoic variation suggestive of low oxygen in the early Paleozoic, increasing to twin maxima circa 270 Ma and 130 Ma, remarkably similar to that predicted by the COPSE model4, and broadly congruent with the Phanerozoic biochar record5. Li, Z.-X. A. & Lee, C.-T. A. EPSL 228, 483-493 (2004). Keller, C. B. & Schoene, B. Nature 485, 490-493 (2012). EarthChem Bergman, N. M. Am. J. Science 304, 397-437 (2004). Glasspool, I. J. & Scott, A. C. Nat. Geosci. 3, 627-630 (2010).

  2. E-Waste and Harm to Vulnerable Populations: A Growing Global Problem

    PubMed Central

    Heacock, Michelle; Kelly, Carol Bain; Asante, Kwadwo Ansong; Birnbaum, Linda S.; Bergman, Åke Lennart; Bruné, Marie-Noel; Buka, Irena; Carpenter, David O.; Chen, Aimin; Huo, Xia; Kamel, Mostafa; Landrigan, Philip J.; Magalini, Federico; Diaz-Barriga, Fernando; Neira, Maria; Omar, Magdy; Pascale, Antonio; Ruchirawat, Mathuros; Sly, Leith; Sly, Peter D.; Van den Berg, Martin; Suk, William A.

    2015-01-01

    Background: Electronic waste (e-waste) is produced in staggering quantities, estimated globally to be 41.8 million tonnes in 2014. Informal e-waste recycling is a source of much-needed income in many low- to middle-income countries. However, its handling and disposal in underdeveloped countries is often unsafe and leads to contaminated environments. Rudimentary and uncontrolled processing methods often result in substantial harmful chemical exposures among vulnerable populations, including women and children. E-waste hazards have not yet received the attention they deserve in research and public health agendas. Objectives: We provide an overview of the scale and health risks. We review international efforts concerned with environmental hazards, especially affecting children, as a preface to presenting next steps in addressing health issues stemming from the global e-waste problem. Discussion: The e-waste problem has been building for decades. Increased observation of adverse health effects from e-waste sites calls for protecting human health and the environment from e-waste contamination. Even if e-waste exposure intervention and prevention efforts are implemented, legacy contamination will remain, necessitating increased awareness of e-waste as a major environmental health threat. Conclusion: Global, national, and local levels efforts must aim to create safe recycling operations that consider broad security issues for people who rely on e-waste processing for survival. Paramount to these efforts is reducing pregnant women and children’s e-waste exposures to mitigate harmful health effects. With human environmental health in mind, novel dismantling methods and remediation technologies and intervention practices are needed to protect communities. Citation: Heacock M, Kelly CB, Asante KA, Birnbaum LS, Bergman AL, Bruné MN, Buka I, Carpenter DO, Chen A, Huo X, Kamel M, Landrigan PJ, Magalini F, Diaz-Barriga F, Neira M, Omar M, Pascale A, Ruchirawat M, Sly L, Sly PD

  3. Venus

    NASA Astrophysics Data System (ADS)

    Fegley, B., Jr.

    2003-12-01

    Venus is Earth's nearest planetary neighbor, and has fascinated mankind since the dawn of history. Venus' clouds reflect most of the sunlight shining on the planet and make it the brightest object in the sky after the Sun and Moon. Venus is visible with the naked eye as an evening star until a few hours after sunset, or as a morning star shortly before sunrise. Many ancient civilizations observed and worshipped Venus, which had a different name in each society, e.g., Ishtar to the Babylonians, Aphrodite to the Greeks, Tai'pei to the Chinese, and Venus to the Romans (Hunt and Moore, 1982). Venus has continued to play an important role in myth, literature, and science throughout history. In the early seventeenth century, Galileo's observations of the phases of Venus showed that the geocentric (Ptolemaic) model of the solar system was wrong and that the heliocentric (Copernican) model was correct. About a century later, Edmund Halley proposed that the distance from the Earth to the Sun (which was then unknown and is defined as one astronomical unit, AU) could be measured by observing transits of Venus across the Sun. These transits occur in pairs separated by eight years at intervals of 105.5 yr and 121.5 yr in an overall cycle of 243 yr, e.g., June 6, 1761, June 3, 1769; December 9, 1874, December 6, 1882, June 8, 2004, June 6, 2012, December 11, 2117, and December 8, 2125. The first attempted measurements of the astronomical unit during the 1761 transit were unsuccessful. However, several observers reported a halo around Venus as it entered and exited the Sun's disk. Thomas Bergman in Uppsala and Mikhail Lomonosov in St. Petersburg, independently speculated that the halo was due to an atmosphere on Venus. Eight years later observations of the 1769 solar transit (including those made by Captain Cook's expedition to Tahiti) gave a value of 1 AU=153 million kilometers, ~2.3% larger than the actual size (149.6 million kilometers) of the astronomical unit (Woolf, 1959

  4. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay.

    PubMed

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mårtensson, Lena; Swenson, Jan

    2014-07-21

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the

  5. Panoscopically optimized thermoelectric performance of a half-Heusler/full-Heusler based in situ bulk composite Zr(0.7)Hf(0.3)Ni(1+x)Sn: an energy and time efficient way.

    PubMed

    Bhardwaj, A; Chauhan, N S; Sancheti, Bhagyashree; Pandey, G N; Senguttuvan, T D; Misra, D K

    2015-11-28

    All scale hierarchical architecturing, matrix/inclusion band alignment and intra-matrix electronic structure engineering, the so called panoscopic approach for thermoelectric materials has been demonstrated to be an effective paradigm for optimizing high ZT. To achieve such hierarchically organized microstructures, composition engineering has been considered to be an efficient strategy. In this work, such a panoscopic concept has been extended to demonstrate for the first time in the case of half-Heusler based thermoelectric materials via a composition engineering route. A series of new off-stoichiometric n-type Zr0.7Hf0.3Ni1+xSn (0 ≤x≤ 0.10) HH compositions have been modified to derive HH(1 -x)/full-Heusler (FH)(x) composite with an all scale hierarchically modified microstructure with FH inclusions within the matrix to study the temperature dependent thermoelectric properties. The structural analysis employing XRD, FE-SEM and HR-TEM of these materials reveal a composite of HH and FH, with hierarchically organized microstructures. In such a submicron/nano-composite, the electronic properties are observed to be well optimized yielding a large power factor; α(2)σ (∼30.7 × 10(-4) W m(-1) K(-2) for Zr0.7Hf0.3Ni1.03Sn) and reduced thermal conductivity (∼2.4 W m(-1) K(-1) for Zr0.7Hf0.3Ni1.03Sn) yielding a high ZT∼ 0.96 at 773 K for composition Zr0.7Hf0.3Ni1.03Sn which is ∼250% larger than the normal HH Zr0.7Hf0.3NiSn (ZT∼ 0.27 at 773 K). The enhancement in ZT of these composites has been discussed in terms of primary electron filtering, electron injection and several phonon scattering mechanisms such as alloy scattering, point defect scattering, and grain boundary scattering. The Bergman and Fel model is used to calculate effective thermoelectric parameters of these composites for comparing the experimental results. PMID:26499748

  6. Biogeographic variation in the baboon: dissecting the cline

    PubMed Central

    Dunn, Jason; Cardini, Andrea; Elton, Sarah

    2013-01-01

    All species demonstrate intraspecific anatomical variation. While generalisations such as Bergman's and Allen's rules have attempted to explain the geographic structuring of variation with some success, recent work has demonstrated limited support for these in certain Old World monkeys. This study extends this research to the baboon: a species that is widely distributed across sub-Saharan Africa and exhibits clinal variation across an environmentally disparate range. This study uses trend surface analysis to map the pattern of skull variation in size and shape in order to visualise the main axes of morphological variation. Patterns of shape and size-controlled shape are compared to highlight morphological variation that is underpinned by allometry alone. Partial regression is used to dissociate the effects of environmental terms, such as rainfall, temperature and spatial position. The diminutive Kinda baboon is outlying in size, so analyses were carried out with and without this taxon. Skull size variation demonstrates an east–west pattern, with small animals at the two extremes and large animals in Central and Southern Africa. Shape variation demonstrates the same geographical pattern as skull size, with small-sized animals exhibiting classic paedomorphic morphology. However, an additional north–south axis of variation emerges. After controlling for skull size, the diminutive Kinda baboon is no longer an outlier for size and shape. Also, the east–west component is no longer evident and discriminant function analysis shows an increased misclassification of adjacent taxa previously differentiated by size. This demonstrates the east–west component of shape variation is underpinned by skull size, while the north–south axis is not. The latter axis is explicable in phylogenetic terms: baboons arose in Southern Africa and colonised East and West Africa to the north, diverging in the process, aided by climate-mediated isolating mechanisms. Environmental terms

  7. Iron diffusion from first principles calculations

    NASA Astrophysics Data System (ADS)

    Wann, E.; Ammann, M. W.; Vocadlo, L.; Wood, I. G.; Lord, O. T.; Brodholt, J. P.; Dobson, D. P.

    2013-12-01

    Research 116, B04307 (2011). 3. Buffett, B. A. Onset and orientation of convection in the inner core. Geophysical Journal International 179, 711-719 (2009). 4. Bergman, M. Measurements of electric anisotropy due to solidification texturing and the implications for the Earth's inner core. Nature 389, 60-63 (1997). 5. Deguen, R. & Cardin, P. Thermochemical convection in Earth's inner core. Geophysical Journal International 187, 1101-1118 (2011). 6. Reaman, D. M., Daehn, G. S. & Panero, W. R. Predictive mechanism for anisotropy development in the Earth's inner core. Earth and Planetary Science Letters 312, 437-442 (2011). 7. Ammann, M. W., Brodholt, J. P., Wookey, J. & Dobson, D. P. First-principles constraints on diffusion in lower-mantle minerals and a weak D'' layer. Nature 465, 462-5 (2010).

  8. Towards a coherent interpretation of the seismic inner core

    NASA Astrophysics Data System (ADS)

    Alboussiere, T.; Deguen, R.

    2012-12-01

    Research, 101, 1996 [4] M. Bergman et al., Geophysical Research Letters, 37, 2010

  9. Polyclusters and substitution effects in the Na-Au-Ga system: remarkable sodium bonding characteristics in polar intermetallics.

    PubMed

    Smetana, Volodymyr; Miller, Gordon J; Corbett, John D

    2013-11-01

    A systematic exploration of Na- and Au-poor parts of the Na-Au-Ga system (less than 15 at. % Na or Au) uncovered several compounds with novel structural features that are unusual for the rest of the system. Four ternary compounds Na1.00(3)Au0.18Ga1.82(1) (I), NaAu2Ga4 (II), Na5Au10Ga16 (III), and NaAu4Ga2 (IV) have been synthesized and structurally characterized by single crystal X-ray diffraction: Na1.00(3)Au0.18Ga1.82(1)(I, P6/mmm, a = 15.181(2), c =9.129(2)Å, Z = 30); NaAu2Ga4 (II, Pnma, a = 16.733(3), b = 4.3330(9), c =7.358(3) Å, Z = 4); Na5Au10Ga16 (III, P6(3)/m, a = 10.754(2), c =11.457(2) Å, Z = 2); and NaAu4Ga2 (IV, P2(1)/c, a = 8.292(2), b = 7.361(1), c =9.220(2)Å, β = 116.15(3), Z = 4). Compound I lies between the large family of Bergman-related compounds and Na-poor Zintl-type compounds and exhibits a clathrate-like structure containing icosahedral clusters similar to those in cubic 1/1 approximants, as well as tunnels with highly disordered cation positions and fused Na-centered clusters. Structures II, III, and IV are built of polyanionic networks and clusters that generate novel tunnels in each that contain isolated, ordered Na atoms. Tight-binding electronic structure calculations using linear muffin-tin-orbital (LMTO) methods on II, III, IV and an idealized model of I show that all are metallic with evident pseudogaps at the Fermi levels. The integrated crystal orbital Hamilton populations for II-IV are typically dominated by Au-Ga, Ga-Ga, and Au-Au bonding, although Na-Au and Na-Ga contributions are also significant. Sodium's involvement into such covalency is consistent with that recently reported in Na-Au-M (M = Ga, Ge, Sn, Zn, and Cd) phases. PMID:24138102

  10. Co-evolution of Eukaryotes and Ocean and Atmosphere Oxygenation in the Neoproterozoic and Paleozoic Eras

    NASA Astrophysics Data System (ADS)

    Lenton, T. M.; Daines, S. J.; Mills, B.; Boyle, R. A.

    2014-12-01

    producing a persistent, global oxygenation of the deep ocean [3]. Thus, the Earth's protracted second oxygenation event culminated in the Paleozoic not the Neoproterozoic. [1] Lenton et al. (2014) Nature Geoscience 7, 257-265 [2] Boyle et al. (2014) Nature Geoscience 7, 10.1038/NGEO2213 [3] Bergman et al. (2004) Am. J. Sci. 304, 397-437

  11. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

    NASA Astrophysics Data System (ADS)

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

    2014-07-01

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the

  12. Polyclusters and Substitution Effects in the Na–Au–Ga System: Remarkable Sodium Bonding Characteristics in Polar Intermetallics

    SciTech Connect

    Smetana, Volodymyr; Miller, Gordon J.; Corbett, John D.

    2013-10-18

    A systematic exploration of Na- and Au-poor parts of the Na–Au–Ga system (less than 15 at. % Na or Au) uncovered several compounds with novel structural features that are unusual for the rest of the system. Four ternary compounds Na1.00(3)Au0.18Ga1.82(1) (I), NaAu2Ga4 (II), Na5Au10Ga16 (III), and NaAu4Ga2 (IV) have been synthesized and structurally characterized by single crystal X-ray diffraction: Na1.00(3)Au0.18Ga1.82(1)(I, P6/mmm, a = 15.181(2), c =9.129(2)Å, Z = 30); NaAu2Ga4 (II, Pnma, a = 16.733(3), b = 4.3330(9), c =7.358(3) Å, Z = 4); Na5Au10Ga16 (III, P63/m, a = 10.754(2), c =11.457(2) Å, Z = 2); and NaAu4Ga2 (IV, P21/c, a = 8.292(2), b = 7.361(1), c =9.220(2)Å, β = 116.15(3), Z = 4). Compound I lies between the large family of Bergman-related compounds and Na-poor Zintl-type compounds and exhibits a clathrate-like structure containing icosahedral clusters similar to those in cubic 1/1 approximants, as well as tunnels with highly disordered cation positions and fused Na-centered clusters. Structures II, III, and IV are built of polyanionic networks and clusters that generate novel tunnels in each that contain isolated, ordered Na atoms. Tight-binding electronic structure calculations using linear muffin-tin-orbital (LMTO) methods on II, III, IV and an idealized model of I show that all are metallic with evident pseudogaps at the Fermi levels. The integrated crystal orbital Hamilton populations for II–IV are typically dominated by Au–Ga, Ga–Ga, and Au–Au bonding, although Na–Au and Na–Ga contributions are also significant. Sodium’s involvement into such covalency is consistent with that recently reported in Na–Au–M (M = Ga, Ge, Sn, Zn, and Cd) phases.

  13. PREFACE: Continuum Models and Discrete Systems Symposia (CMDS-12)

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Bikas K.

    2011-09-01

    The 12th International Symposium on Continuum Models and Discrete Systems (CMDS-12) (http://www.saha.ac.in/cmp/cmds.12/) took place at the Saha Institute of Nuclear Physics in Kolkata from 21-25 February 2011. Previous CMDS symposia were held in Kielce (Poland, 1975), Mont Gabriel (Canada, 1977), Freudenstadt (Federal Republic of Germany, 1979), Stockholm (Sweden, 1981), Nottingham (United Kingdom, 1985), Dijon (France, 1989), Paderborn (Germany, 1992), Varna (Bulgaria, 1995), Istanbul (Turkey, 1998), Shoresh (Israel, 2003) and Paris (France, 2007). The broad interdisciplinary character, limited number of participants (not exceeding 100) and informal and friendly atmosphere of these meetings has made them a well-acknowledged place to make highly fruitful contacts and exchange ideas, methods and results. The purpose of CMDS is to bring together scientists with different backgrounds who work on continuum theories of discrete mechanical and thermodynamical systems in the fields of mathematics, theoretical and applied mechanics, physics, material science, and engineering. The spirit of the CMDS meetings is to stimulate extensive and active interdisciplinary research. The International Scientific Committee members of this conference were: David J Bergman (Chairman CMDS 10), Tel Aviv University, Israel; Bikas K Chakrabarti (Chairman CMDS 12), Saha Institute of Nuclear Physics, India; Alex Hansen, Norwegian University of Science and Technology, Norway; Hans Jürgen Herrmann, Institute for Building Materials, ETH, Switzerland; Esin Inan (Chairman CMDS 9), Istanbul Technical University, Turkey; Dominique Jeulin (Chairman CMDS 11), Ecole des Mines de Paris, France; Frank Juelicher, Max-Planck-Institute for the Physics of Complex Systems, Germany; Hikaru Kawamura, University of Osaka, Japan; Graeme Milton, University of Utah, USA; Natalia Movchan, University of Liverpool, UK; and Ping Sheng, The Hong Kong University of Science and Technology, Hong Kong. At CMDS-12 the topics

  14. PREFACE: Multiferroics Multiferroics

    NASA Astrophysics Data System (ADS)

    Loidl, Alois; von Loehneysen, Hilbert; Kalvius, G. Michael

    2008-10-01

    stimulate and trigger further important contributions in experimental exploration and theoretical concepts. References [1] Hill N A 2000 J. Phys. Chem. B 104 6694-709 [2] Khomskii D I and Bull A 2001 Phys. Soc. C 21 2 Khomskii D I 2006 J. Magn. Magn. Mater. 306 1 [3] Smoleskii G A, Agranovskaia A I, Popov S N and Isupov V A 1958 Sov. Phys. Tech. Phys. 3 1981 [4] Smolenskii G A and Chupis I E 1974 Sov. Phys. Usp. 25 475 [5] Wood V E and Austin A E 1974 Int. J. Magnetism 5 303 [6] Kimura T, Goto T, Shintani H, Ishizaka K, Arima T and Tokura Y 2003 Nature 426 55 [7] Hur N, Park S, Sharma P A, Ahn J S, Guha S, Cheong S-W 2004 Nature 429 392 [8] Lawes G, Harris A B, Kimura T, Rogado N, Cava R J, Aharony A, Entin-Wohlmann O, Yildirim T, Kenzelmann M, Broholm C and Ramirez A P 2005 Phys. Rev. Lett. 95 087205

  15. Proton Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host

    SciTech Connect

    Pluth, Michael; Bergman, Robert; Raymond, Kenneth

    2009-04-10

    Synthetic supramolecular host assemblies can impart unique reactivity to encapsulated guest molecules. Synthetic host molecules have been developed to carry out complex reactions within their cavities, despite the fact that they lack the type of specifically tailored functional groups normally located in the analogous active sites of enzymes. Over the past decade, the Raymond group has developed a series of self-assembled supramolecules and the Bergman group has developed and studied a number of catalytic transformations. In this Account, we detail recent collaborative work between these two groups, focusing on chemical catalysis stemming from the encapsulation of protonated guests and expanding to acid catalysis in basic solution. We initially investigated the ability of a water-soluble, self-assembled supramolecular host molecule to encapsulate protonated guests in its hydrophobic core. Our study of encapsulated protonated amines revealed rich host-guest chemistry. We established that self-exchange (that is, in-out guest movement) rates of protonated amines were dependent on the steric bulk of the amine rather than its basicity. The host molecule has purely rotational tetrahedral (T) symmetry, so guests with geminal N-methyl groups (and their attendant mirror plane) were effectively desymmetrized; this allowed for the observation and quantification of the barriers for nitrogen inversion followed by bond rotation. Furthermore, small nitrogen heterocycles, such as N-alkylaziridines, N-alkylazetidines, and N-alkylpyrrolidines, were found to be encapsulated as proton-bound homodimers or homotrimers. We further investigated the thermodynamic stabilization of protonated amines, showing that encapsulation makes the amines more basic in the cavity. Encapsulation raises the effective basicity of protonated amines by up to 4.5 pK{sub a} units, a difference almost as large as that between the moderate and strong bases carbonate and hydroxide. The thermodynamic stabilization

  16. The triple risk hypotheses in sudden infant death syndrome.

    PubMed

    Guntheroth, Warren G; Spiers, Philip S

    2002-11-01

    Sudden infant death syndrome (SIDS) victims were regarded as normal as a matter of definition (Beckwith 1970) until 1952 when Kinney and colleagues argued for elimination of the clause, "unexpected by history." They argued that "not all SIDS victims were normal," and referred to their hypothesis that SIDS results from brain abnormalities, which they postulated "to originate in utero and lead to sudden death during a vulnerable postnatal period." Bergman (1970) argued that SIDS did not depend on any "single characteristic that ordains a infant for death," but on an interaction of risk factors with variable probabilities. Wedgwood (1972) agreed and grouped risk factors into the first "triple risk hypothesis" consisting of general vulnerability, age-specific risks, and precipitating factors. Raring (1975), based on a bell-shaped curve of age of death (log-transformed), concluded that SIDS was a random process with multifactorial causation. Rognum and Saugstad (1993) developed a "fatal triangle" in 1993, with groupings similar to those of Wedgwood, but included mucosal immunity under a vulnerable developmental stage of the infant. Filiano and Kinney (1994) presented the best known triple risk hypothesis and emphasized prenatal injury of the brainstem. They added a qualifier, "in at least a subset of SIDS," but, the National Institute of Child Health and Development SIDS Strategic Plan 2000, quoting Kinney's work, states unequivocally that "SIDS is a developmental disorder. Its origins are during fetal development." Except for the emphasis on prenatal origin, all 3 triple risk hypotheses are similar. Interest in the brainstem of SIDS victims began with Naeye's 1976 report of astrogliosis in 50% of all victims. He concluded that these changes were caused by hypoxia and were not the cause of SIDS. He noted an absence of astrogliosis in some older SIDS victims, compatible with a single, terminal episode of hypoxia without previous hypoxic episodes, prenatal or postnatal

  17. Efficiency of preventive actions for landslides and flooding - evaluation of Scandinavian practices

    NASA Astrophysics Data System (ADS)

    Bergman, R.; Andersson-sköld, Y. B.; Nyberg, L.; Johansson, M.; Persson, E.

    2011-12-01

    Author: Ramona Bergman, Yvonne Andersson-Sköld, Lars Nyberg, Magnus Johansson, Erik Persson Preventive actions can be, and are frequently, taken to reduce accidents and their consequences in different ways. The MSB funded research programme "Effects of Society's Security actions" (ESS, 2009-2013) aims to study the relationship between such actions and their effects. The program is divided into three subgroups: Frequent accidents Natural hazards (such as flooding, erosion and landslide) Chemical and landfill accidents The results presented here covers natural hazards with focus on land slides and flooding. The results are based on Swedish/Scandinavian contexts. Natural events such as erosion, flooding and land slides are common, but the number of accidents (events causing severe negative impact) is rare. Therefore, in such analysis there is limited data and other information available which can be used for example in statistical analysis of actions and their effects. Instead, the analysis must be based on other information. Therefore, the analysis may have to include aspects that only can be assessed by scenario and "what-if" analyses. In this project the main method has been interviews with officials in Swedish municipalities and national agencies in Sweden and Norway. The two levels are chosen since policies are taken on national (or international) level, while the key actions and actors are on the municipal level. The interviews cover experiences and potential scenarios. In all municipalities, one politician and officials working with planning and rescue service have been interviewed. The study covers hazard and risk mapping, follow up of such maps, physical planning and lessons learned from previous events and activities. The final outcome of the research will be a review of what is found to be well functioning, identification of weak points and recommendations for the management of landslides, erosion and flooding. The present results indicate that hazard

  18. Operational earthquake forecasting in the South Iceland Seismic Zone: improving the earthquake catalogue

    NASA Astrophysics Data System (ADS)

    Panzera, Francesco; Vogfjörd, Kristin; Zechar, J. Douglas; Eberhard, David

    2014-05-01

    attenuation relations derived for earthquakes in Iceland (Pétursson and Vogfjörd, 2010) and use this relationship to address the problem of underestimating seismic moment for larger earthquakes (>3.0). Finally, to solve the problem related with the overestimation of aftershock magnitude of large earthquakes about 150 earthquakes were checked. All such passages demonstrate the importance of carefully checking the catalogue before proceeding with the operational earthquake forecasting. References Bondar, I., S.C. Myers, E.R. Engdahl, and E.A. Bergman (2004). Epicentre accuracy based on seismicnetwork criteria, Geophys. J. Int., 156, 483-496. Gomberg, J.S., K.M. Shedlock, and S.W. Roecker (1990). The effect of S-Wave arrival times on the accuracy of hypocenter estimation, Bull. Seism. Soc. Am., 80, 1605-1628. Pétursson and Vogfjörd (2010). Attenuation relations for near- and far field peak ground motion (PGV, PGA)and new magnitude estimatesfor large earthquakes in SW-Iceland. Report n° VI 2009-012, pp. 43, ISSN 1670-8261. Slunga, R., P. Norrman and A. Glans (1984). Seismicity of Southern Sweden - Stockholm: Försvarets Forskningsanstalt, July 1984. FOA Report, C2 C20543-T1, 106 p.

  19. Systems biology of aging.

    PubMed

    Bolt, Kendra; Bergman, Aviv

    2015-01-01

    Human aging occurs at rates that vary widely between organisms and cell types. We hypothesize that in both cases, variation is due to differences in heat production, heat management and molecular susceptibility to heat-induced change. Metabolic rates have long been implored for their contributions to the aging process, with a negative correlation observed between basal metabolic rate and lifespan (Savage et al., Proc Natl Acad Sci U S A 104:4718–4723, 2007, Economos, Exp Gerontol 17:145–152, 1982, Keys et al., Metabolism 22:579–587, 1973, O’Connor et al., Comp Biochem Physiol Part A, Molr & Integr Physiol 133:835–842, 2002, Speakman, J Exp Biol 208:1717–1730, 2005, Poehlman, J Am Geriatrics Soc 41:552–559, 1993). Small amounts of heat are the well-known byproduct of metabolism and other biological processes, and despite their magnitude, are sufficient to elicit alterations in biomolecular characteristics (Somero, Ann Rev Physiol 57:43–68, 1995). Existing theories of aging suggest that damage occurs to the conformations or sequences of molecules, which only shifts focus onto the implied failure of repair mechanisms. Contrarily, heat-induced changes affect the behavioral characteristics of molecules and are thus able to persist “under the radar” of heat shock proteins and other canalizing mechanisms, which recognize only physical aberrancies (Rutherford and Lindquist, Nature 396:336–342, 1998, Siegal and Bergman, Proc Natl Acad Sci U S A 99:10528–10532, 2002, Waddington, Nature 150:563–565, 1942). According to our hypothesis, behavioral changes to the binding affinities, kinetics, motilities, and functionalities are dependent on minute energetic fields within and between molecules. Exposure to the thermal byproducts of metabolism cause heritable shifts in molecular interaction schemes and diminish the integrity of genetic and epigenetic networks. Restructured topologies alter the emergent properties of networks and are observed as the

  20. Deep-level magma ascent rates at Mt. Etna (Italy)

    NASA Astrophysics Data System (ADS)

    Armienti, P.; Perinelli, C.; Putirka, K. D.

    2012-12-01

    Deep-level ascent rates are related to the triggering mechanisms of volcanic eruptions. Recent models and experimental studies have focused on the very shallow parts of magma plumbing systems, mostly the upper few km, and have thus far emphasized that volatile contents and volatile exsolution, are key to understanding eruption dynamics and its fingerprint in the rock texture. Massive volatile loss induces a dramatic change in the liquidus temperature, thus producing observable effects on the rates of nucleation and growth of minerals . Volatile saturation, however, may well occur at greater depths, which means that initial stages of magma ascent may be triggered by events taking place at much greater depths than those recorded by melt inclusions, likely captured at shallow levels. We present a method to evaluate ascent rates deep in a volcano plumbing system, discussing the implications for magma dehydration and using Mt. Etna as case a study. We investigate the deeper levels of magma transport by presenting detailed P-T paths for Etnean magmas, and combining these with Crystal Size Distribution (CSD)-derived cooling rates. The key to this analysis is the recognition that the slope of a P-T path, as determined from mineral-melt thermobarometry, is a result of magma cooling rate, which is in turn a function of magma ascent via the effect of pressure on volatile solubility. We also rely on a thermodynamic treatment of exsolution of non-ideal H2O-CO2 mixtures, based on the Kerric & Jacobs (1981) model, and the simplified solubility model of CO2 (Spera & Bergman, 1980) and H2O (Nicholls, 1980), recalibrated with experimental and melt inclusions data from Mt. Etna. Our modeling is able to decipher magma ascent velocity, v (dH/dt; H = depth, t = time), from ascent rate (dP/dt), and rate of cooling (dT/dt), where ρ is magma density, P is pressure, T is temperature and g is the acceleration of gravity. This equation for v provides a key to investigating the relationships

  1. Caries management pathways preserve dental tissues and promote oral health.

    PubMed

    Ismail, Amid I; Tellez, Marisol; Pitts, Nigel B; Ekstrand, Kim R; Ricketts, David; Longbottom, Christopher; Eggertsson, Hafsteinn; Deery, Christopher; Fisher, Julian; Young, Douglas A; Featherstone, John D B; Evans, Wendell; Zeller, Gregory G; Zero, Domenick; Martignon, Stefania; Fontana, Margherita; Zandona, Andrea

    2013-02-01

    In May 2012, cariologists, dentists, representatives of dental organizations, manufacturers, and third party payers from several countries, met in Philadelphia, Pennsylvania, to define a common mission; goals and strategic approaches for caries management in the 21th century. The workshop started with an address by Mr. Stanley Bergman, CEO of Henry Schein Inc. which focused on the imperative for change in academia, clinical practice, and public health. For decades, new scientific evidence on caries and how it should be managed have been discussed among experts in the field. However, there has been some limited change, except in some Scandinavian countries, in the models of caries management and reimbursement which have been heavily skewed toward 'drilling and filling'. There is no overall agreement on a caries' case definition or on when to surgically intervene. The participants in the workshop defined a new mission for all caries management approaches, both conventional and new. The mission of each system should be to preserve the tooth structure, and restore only when necessary. This mission marks a pivotal line for judging when to surgically intervene and when to arrest or remineralize early noncavitated lesions. Even when restorative care is necessary, the removal of hard tissues should be lesion-focused and aim to preserve, as much as possible, sound tooth structure. Continuing management of the etiological factors of caries and the use of science-based preventive regimens also will be required to prevent recurrence and re-restoration. These changes have been debated for over a decade. The Caries Management Pathways includes all systems and philosophies, conventional and new, of caries management that can be used or modified to achieve the new mission. The choice of which system to use to achieve the mission of caries management is left to the users and should be based on the science supporting each approach or philosophy, experience, utility, and ease of use

  2. Scanning tuneeling microscopy studies of fivefold surfaces of icosahedral Al-Pd-Mn quasicrystals and of thin silver films on those surfaces

    SciTech Connect

    Unal, Baris

    2008-01-01

    their top planes. Hence, we name them as Pd+(with Pd) and Pd-(without Pd). Based on their planer structure and the step height, it can be said that these two families can be viable surface terminations. However, besides the Pd content, these two sets differ in terms of relative densities of their top planes as well as the gap separating the layer from the nearest atomic plane. The experimental data and other arguments lead to the conclusion that the Pd- family is favored over the Pd+. This has an important implication on the interpretation of local motifs seen in the high resolution STM images. In other words, the dark stars are not formed by cut-Bergmans rather they are formed by cut-Mackays.

  3. Cat herding on a global scale - the challenge of building a vocabulary for the geology of Europe with compatibility to a global ontology

    NASA Astrophysics Data System (ADS)

    Asch, Kristine

    2010-05-01

    to another question - Which classification should be adopted for the definition of "grain size": Wentworth (1922), Folk (1962), ISO 14688-1 (2003) or even another one? However, the quotation of F. J. Pettijohn (1975): "The classification of the sedimentary rocks is a problem on which much thought has been expended and one for which no mutually satisfactory or complete solution has yet been found" does not only apply to sedimentary rock types; there are numerous "bones of classication contentions" also for igneous and metamorphic rock types. Based on the vocabulary specification OneG-E will identify the generic and specific geometric and semantic harmonisation issues and will then "rework" these existing national datasets to make significant progress towards a harmonised dataset - a crucial step towards INSPIRE goals. The standards, architecture and framework developed here can then be "up-scaled" to more detailed levels and progressively deployed for higher resolution geological data. The work on the OneG-E data vocabulary is contributing to enrich and improve the global CGI vocabulary and ontology and will provide a solid base for the description of geology of each EC country when the EC INSPIRE Directive's specification is defined. References Asch, K., Bavec, M., Bergman, S., Perez Cerdan, F., Declercq, P.Y., Janjou, D., Kacer, S., Klicker, M., Nironen, M., Pantaloni, M., Schubert, C. (in preparation): OneGeology-Europe Scientific/Semantic Data Specification and - Generic Specification for Spatial Geological Data in Europe. ECP-2007-GEO-317001 Folk, R.L. (1962): Spectral subdivision of limestone types. In Ham, W.E., ed.: Classification of Carbonate Rocks - A Symposium. American Association of Petroleum Geologists Memoir 1: 62-84 ISO 14688-1 (2002): Geotechnical investigation and testing - Identification and classification of soil - Part 1: Identification and description Pettijohn, F.J. (1975): Sedimentary Rocks.- 3rd ed.; Harper & Row Publishers (New York, Evanston

  4. Cat herding on a global scale - the challenge of building a vocabulary for the geology of Europe with compatibility to a global ontology

    NASA Astrophysics Data System (ADS)

    Asch, Kristine

    2010-05-01

    to another question - Which classification should be adopted for the definition of "grain size": Wentworth (1922), Folk (1962), ISO 14688-1 (2003) or even another one? However, the quotation of F. J. Pettijohn (1975): "The classification of the sedimentary rocks is a problem on which much thought has been expended and one for which no mutually satisfactory or complete solution has yet been found" does not only apply to sedimentary rock types; there are numerous "bones of classication contentions" also for igneous and metamorphic rock types. Based on the vocabulary specification OneG-E will identify the generic and specific geometric and semantic harmonisation issues and will then "rework" these existing national datasets to make significant progress towards a harmonised dataset - a crucial step towards INSPIRE goals. The standards, architecture and framework developed here can then be "up-scaled" to more detailed levels and progressively deployed for higher resolution geological data. The work on the OneG-E data vocabulary is contributing to enrich and improve the global CGI vocabulary and ontology and will provide a solid base for the description of geology of each EC country when the EC INSPIRE Directive's specification is defined. References Asch, K., Bavec, M., Bergman, S., Perez Cerdan, F., Declercq, P.Y., Janjou, D., Kacer, S., Klicker, M., Nironen, M., Pantaloni, M., Schubert, C. (in preparation): OneGeology-Europe Scientific/Semantic Data Specification and - Generic Specification for Spatial Geological Data in Europe. ECP-2007-GEO-317001 Folk, R.L. (1962): Spectral subdivision of limestone types. In Ham, W.E., ed.: Classification of Carbonate Rocks - A Symposium. American Association of Petroleum Geologists Memoir 1: 62-84 ISO 14688-1 (2002): Geotechnical investigation and testing - Identification and classification of soil - Part 1: Identification and description Pettijohn, F.J. (1975): Sedimentary Rocks.- 3rd ed.; Harper & Row Publishers (New York, Evanston

  5. Pollen-inferred quantitative reconstructions of Holocene land-cover in NW Europe for the evaluation of past climate-vegetation feedbacks - The Swedish LANDCLIM project and the NordForsk LANDCLIM network

    NASA Astrophysics Data System (ADS)

    Gaillard, Marie-Jose; Sugita, Shinya; Rundgren, Mats; Smith, Benjamin; Mazier, Florence; Trondman, Anna-Kari; Fyfe, Ralph; Kokfelt, Ulla; Nielsen, Anne-Birgitte; Strandberg, Gustav

    2010-05-01

    Biology, University of Bergen); Pim van der Knaap (Institute of Plant Sciences, University of Bern); Malgorzata Latalowa (University of Gdansk); Michelle Leydet (IMEP CNRS 6116, University of Marseille III); Teija Alenius (Finnish Geological Survey, Espoo), Heather Almquist-Jacobson (Univ. Montana, USA), Jonas Bergman (Univ. Stockholm), Rixt de Jong (Univ. Bern), Jutta Lechterbeck (Hemmenhofen, Germany), Ann-Marie Robertsson (Univ. Stockholm), Ulf Segerström and Henrik von Stedingk (Univ. Umeå), Heikki Seppä (Univ. Helsinki). Sugita 2007. The Holocene, 17, 229-241.

  6. Screening of perfluorinated compounds in water, sediment and biota of the Llobregat River basin (NE Spain)

    NASA Astrophysics Data System (ADS)

    Campo, Julian; Perez, Francisca; Pico, Yolanda; Farre, Marinella; Barcelo, Damia; Andreu, Vicente

    2014-05-01

    compounds, 13 were identified in water samples (PFBA, PFDA, PFHpA, PFHxA, PFHxDA, PFNA, PFOA, PFPeA, PFTrDA, PFUdA, L-PFBS, L-PFHxS and L-PFOS), and their concentrations ranged between 0. 1 ng L-1 (PFNA) and 2709 ng L-1 (L-PFOS). Similarly, PFBA, PFDA, PFDoA, PFHpA, PFNA, PFOA, PFPeA, PFTrDA, PFUdA, L-PFBS, L-PFHxS, L-PFOS and PFOSA were identified in sediments samples, with concentrations ranging from 0.147 ng g-1 dw (L-PFOS) to 13 ng g-1 dw (PFBA). In biota similar PFC were detected, with values between 0.03 and 1738.06 ng g-1. According to this study, PFCs were detected in different compartments of the ecosystem where they are bio-accumulating and, potentially, would produce adverse effects on humans. Acknowledgements This work has been supported by the Spanish Ministry of Economy and Competitiveness through the projects Consolider-Ingenio 2010 CSD2009-00065 and CGL2011-29703-C02-02. We also thank the persons of IDAEA for taking the samples. References Llorca, M., Farre, M., Pico, Y., Muller, J., Knepper, T. P., Barcelo, D., 2012. Analysis of perfluoroalkyl substances in waters from Germany and Spain. Sci. Total Environ. 431, 139-150. Llorca, M., Pérez, F., Farre, M., Agramunt, S., Kogevinas, M., Barceló, D., 2012. Analysis of perfluoroalkyl substances in cord blood by turbulent flow chromatography coupled to tandem mass spectrometry. Sci. Total Environ. 433, 151-160. Pico, Y., Blasco, C., Farre, M., Barcelo, D., 2012. Occurrence of perfluorinated compounds in water and sediment of L'Albufera Natural Park (Valencia, Spain). Environ.Sci.Pollut.Res. 19, 946-957. Sundstrom, M., Ehresman, D. J., Bignert, A., Butenhoff, J. L., Olsen, G. W., Chang, S. C., Bergman, A., 2011. A temporal trend study (1972-2008) of perfluorooctanesulfonate, perfluorohexanesulfonate, and perfluorooctanoate in pooled human milk samples from Stockholm, Sweden. Environ. Inter. 37, 178-183.

  7. Sensing at the nanoscale

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Hierold, Christofer

    2013-11-01

    Stampfer C 2013 Graphene-based charge sensors Nanotechnology 24 444001 [6] Nagelli E, Naik R, Xu Y, Gao Y, Zhang M and Dai L 2013 Sensor arrays from multicomponent micropatterned nanoparticles and graphene Nanotechnology 24 444010 [7] Zhang J, Strelcov E and Kolmakov A 2013 Heat dissipation from suspended self-heated nanowires: gas sensor prospective Nanotechnology 24 444009 [8] Morante J R 2013 Chemical to electrical transduction mechanisms from single metal oxide nanowires measurements: response time constant analysis Nanotechnology 24 444004 [9] Stuart E J E, Tschulik K, Omanovi D, Cullen J T, Jurkschat K, Crossley A and Compton R G 2013 Electrochemical detection of commercial silver nanoparticles: identification, sizing and detection in environmental media Nanotechnology 24 444002 [10] Cho H, Felts J R, Yu M-F, Bergman L A, Vakakis A F and King W P 2013 Improved atomic force microscope infrared spectroscopy for rapid nanometer-scale chemical identification Nanotechnology 24 444007 [11] Yoon J-W, Kim H-J, Kim I-D and Lee J-H 2013 Electronic sensitization of C2H5OH response in p-type NiO nanofibers by Fe doping Nanotechnology 24 444005 [12] Guo Y, Su S, Wei X, Zhong Y, Su Y, Huang Q, Fan C and He Y A 2013 Silicon-based electrochemical sensor for highly sensitive, specific, label-free, and real-time DNA detection Nanotechnology 24 444012 [13] Liao Y-J, Shiang Y-C, Chen L-Y, Hsu C-L, Huang C-C and Chang H-T 2013 Detection of adenosine triphosphate through polymerization-induced aggregation of actinconjugated gold/silver nanorods Nanotechnology 24 444003 [14] Korzeniowska B, Nooney R, Wencel D and McDonagh C 2013 Silica nanoparticles for cell imaging and intracellular sensing Nanotechnology 24 442002

  8. Solid State Ionics Advanced Materials for Emerging Technologies

    NASA Astrophysics Data System (ADS)

    Chowdari, B. V. R.; Careem, M. A.; Dissanayake, M. A. K. L.; Rajapakse, R. M. G.; Seneviratne, V. A.

    2006-06-01

    . Invited papers. Cathodic properties of Al-doped LiCoO[symbol] prepared by molten salt method Li-Ion batteries / M. V. Reddy, G. V. Subba Rao, B. V. R. Chowdari. Layered ion-electron conducting materials / M. A. Santa Ana, E. Benavente, G. González. LiNi[symbol]Co[symbol]O[symbol] cathode thin-film prepared by RF sputtering for all-solid-state rechargeable microbatteries / X. J. Zhu ... [et al.] -- Contributed papers. Contributed papers. Nanocomposite cathode for SOFCs prepared by electrostatic spray deposition / A. Princivalle, E. Djurado. Effect of the addition of nanoporous carbon black on the cycling characteristics of Li[symbol]Co[symbol](MoO[symbol])[symbol] for lithium batteries / K. M. Begam, S. R. S. Prabaharan. Protonic conduction in TiP[symbol]O[symbol] / V. Nalini, T. Norby, A. M. Anuradha. Preparation and electrochemical LiMn[symbol]O[symbol] thin film by a solution deposition method / X. Y. Gan ... [et al.]. Synthesis and characterization LiMPO[symbol] (M = Ni, Co) / T. Savitha, S. Selvasekarapandian, C. S. Ramya. Synthesis and electrical characterization of LiCoO[symbol] LiFeO[symbol] and NiO compositions / A. Wijayasinghe, B. Bergman. Natural Sri Lanka graphite as conducting enhancer in manganese dioxide (Emd type) cathode of alkaline batteries / N. W. B. Balasooriya ... [et al.]. Electrochemical properties of LiNi[symbol]Al[symbol]Zn[symbol]O[symbol] cathode material synthesized by emulsion method / B.-H. Kim ... [et al.]. LiNi[symbol]Co[symbol]O[symbol] cathode materials synthesized by particulate sol-gel method for lithium ion batteries / X. J. Zhu ... [et al.]. Pulsed laser deposition of highly oriented LiCoO[symbol] and LiMn[symbol]O[symbol] thin films for microbattery applications / O. M. Hussain ... [et al.]. Preparation of LiNi[symbol]Co[symbol]O[symbol] thin films by a sol-gel method / X. J. Zhu ... [et al.]. Electrochemical lithium insertion into a manganese dioxide electrode in aqueous solutions / M. Minakshi ... [et al.]. AC impedance

  9. High energy neutrinos from astrophysical accelerators of cosmic ray nuclei

    NASA Astrophysics Data System (ADS)

    Anchordoqui, Luis A.; Hooper, Dan; Sarkar, Subir; Taylor, Andrew M.

    2008-02-01

    .1181983223S.P.LaiJ.M.GirartR.CrutcherAstrophys. J.5982003392W.BednarekMon. Not. R. Astron. Soc.3452003847W.BednarekR.J.ProtheroeAstropart. Phys.162002397P.BlasiA.V.OlintoPhys. Rev. D591999023001F.W.SteckerAstropart. Phys.262007398F.W. Stecker, arXiv:astro-ph/0610208.A γ-ray signal from the nearby starburst galaxy NGC253 was reported by the CANGAROO-II Collaboration but their subsequent re-analysis of the data is consistent with the expectation from backgrounds:C.ItohCANGAROO-II CollaborationAstron. Astrophys.3962002L1(Erratum-ibid. 462 (2007) 67)T.A. Thompson, E. Quataert, E. Waxman, A. Loeb, arXiv:astro-ph/0608699.D.J.BirdFly’s Eye CollaborationPhys. Rev. Lett.7119933401D.R.BergmanHiRes CollaborationNucl. Phys. Proc. Suppl.136200440T.Abu-ZayyadHiRes-MIA CollaborationAstrophys. J.5572001686M.NaganoJ. Phys. G181992423V.BerezinskyA.Z.GazizovS.I.GrigorievaPhys. Rev. D742006043005R.U.AbbasiHiRes CollaborationPhys. Rev. Lett.922004151101V.BerezinskyA.Z.GazizovS.I.GrigorievaPhys. Lett. B6122005147V.S.BerezinskyS.I.GrigorievaB.I.HnatykAstropart. Phys.212004617See Fig. 21 in:L.AnchordoquiM.T.DovaA.MariazziT.McCauleyT.PaulS.ReucroftJ.SwainAnn. Phys.3142004145D.AllardE.ParizotE.KhanS.GorielyA.V.OlintoAstron. Astrophys.4432005L29D.AllardE.ParizotA.V.OlintoAstropart. Phys.27200761T.Abu-ZayyadHigh Resolution Fly’s Eye CollaborationAstropart. Phys.232005157P. Sommers, et al., Pierre Auger Collaboration, arXiv:astro-ph/0507150.R.U.AbbasiHiRes CollaborationAstrophys. J.6222005910B.N. Afanasiev, et al., Yakutsk Collaboration, in: M. Nagano (Ed.), Proceedings of the Tokyo Workshop on Techniques for the Study of the Extremely High Energy Cosmic Rays, 1993.J. Knapp, private communication.J.RanftPhys. Rev. D51199564R.S.FletcherT.K.GaisserP.LipariT.StanevPhys. Rev. D5019945710J.EngelT.K.GaisserT.StanevP.LipariPhys. Rev. D4619925013N.N.KalmykovS.S.OstapchenkoA.I.PavlovNucl. Phys. Proc. Suppl.52B19977It is important to stress that the Auger data are still at a preliminary stage and the

  10. New Observations of Comet Hale-Bopp from La Silla

    NASA Astrophysics Data System (ADS)

    1998-10-01

    to the large size of the nucleus, probably 40 - 60 km in diameter, it will be possible to observe this comet with large optical telescopes for many years to come. Information about Hale-Bopp on the web Additional information about Comet Hale-Bopp is available on the web at many sites. Some of the most comprehensive websites may be accessed via the ESO Hale-Bopp site. Notes: [1] Other scientists involved in the long-term radio monitoring of Comet Hale-Bopp are Nicolas Biver (Institute for Astronomy, University of Hawaii, USA), Pierre Colom, Jacques Crovisier, Eric Gérard, Benoit Germain, Emmanuel Lellouch (Observatoire de Paris, France), Didier Despois (Observatoire de Bordeaux, France), Gabriel Paubert (IRAM, Granada, Spain), Raphael Moreno, Joern E. Wink (IRAM, Grenoble, France), John K. Davies (JAC, Hawaii, USA), William R.F. Dent (Royal Observatory, Edinburgh, UK), Hans Rickman, Marcus Gunnarsson (Uppsala Astronomiska Observatorium, Sweden), Per Bergman, Lars E.B. Johansson (OSO, Sweden), Fredrik Rantakyroe (SEST, La Silla), Darek C. Lis, David Mehringer, Dominic Benford, Martin Gardner, Tom G. Phillips (CSO, USA), Heike Rauer (DLR, Berlin, Germany). [2] The figure appears in N. Biver et al. : "Long-term Monitoring of the Outgassing of C/1995 O1 (Hale-Bopp) at Radio Wavelengths", a poster paper presented at the DPS meeting on October 11-16, 1998 (Madison, Wisconsin, USA) and to be published in Vol. 30 of the Bulletin of the American Astronomical Society . How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

  11. EDITORIAL: Special issue on applied neurodynamics: from neural dynamics to neural engineering Special issue on applied neurodynamics: from neural dynamics to neural engineering

    NASA Astrophysics Data System (ADS)

    Chiel, Hillel J.; Thomas, Peter J.

    2011-12-01

    -LXIII (London: Royal Society) Ralph T C and Pryde G J 2010 Progress in Optics vol 54, ed E Wolf (New York: Elsevier) pp 209-79 (arXiv:1103.6071) Rashevsky N 1960 Mathematical Biophysics: Physico-Mathematical Foundations of Biology vol 1 3rd edn (New York: Dover) pp 375-462 (first edition 1938) Rinzel J and Ermentrout G B 1989 Analysis of neuronal excitability and oscillations Methods in Neuronal Modeling ed C Koch and I Segev (Cambridge, MA: MIT Press) pp 135-69 Rosin B, Nevet A, Elias S, Rivlin-Etzion M, Israel Z and Bergman H 2007 Physiology and pathophysiology of the basal ganglia-thalamo-cortical networks Parkinsonism Relat. Disord. 13 S437-9 Spardy L E, Markin S N, Shevtsova N A, Prilutsky B I, Rybak I A and Rubin J E 2011a A dynamical systems analysis of afferent control in a neuromechanical model of locomotion: I. Rhythm generation J. Neural Eng. 8 065003 Spardy L E, Markin S N, Shevtsova N A, Prilutsky B I, Rybak I A and Rubin J E 2011b A dynamical systems analysis of afferent control in a neuromechanical model of locomotion: II. Phase asymmetry J. Neural Eng. 8 065004 Steane A 1998 Quantum computing Rep. Prog. Phys. 61 117-73 Strogatz S H 1994 Nonlinear Dynamics and Chaos: with Applications to Physics, Biology, Chemistry, and Engineering (Cambridge, MA: Perseus) Thomas P J 2011 A lower bound for the first passage time density of the suprathreshold Ornstein-Uhlenbeck process J. Appl. Probab. 48 420-34 White J A, Rubinstein J T and Kay A R 2000 Channel noise in neurons Trends Neurosci. 23 131-7 Wilson H R and Cowan J D 1972 Excitatory and inhibitory interactions in localized populations of model neurons Biophys. J. 12 1-24 Wilson H R and Cowan J D 1973 A mathematical theory of the functional dynamics of cortical and thalamic nervous tissue Biol. Cybern. 13 55-80