Spin Chains with Dynamical Lattice Supersymmetry
NASA Astrophysics Data System (ADS)
Hagendorf, Christian
2013-02-01
Spin chains with exact supersymmetry on finite one-dimensional lattices are considered. The supercharges are nilpotent operators on the lattice of dynamical nature: they change the number of sites. A local criterion for the nilpotency on periodic lattices is formulated. Any of its solutions leads to a supersymmetric spin chain. It is shown that a class of special solutions at arbitrary spin gives the lattice equivalents of the {N}=(2,2) superconformal minimal models. The case of spin one is investigated in detail: in particular, it is shown that the Fateev-Zamolodchikov chain and its off-critical extension possess a lattice supersymmetry for all its coupling constants. Its supersymmetry singlets are thoroughly analysed, and a relation between their components and the weighted enumeration of alternating sign matrices is conjectured.
Ferrimagnetism in delta chain with anisotropic ferromagnetic and antiferromagnetic interactions.
Dmitriev, D V; Ya Krivnov, V
2016-12-21
We consider analytically and numerically an anisotropic spin-[Formula: see text] delta-chain (sawtooth chain) in which exchange interactions between apical and basal spins are ferromagnetic and those between basal spins are antiferromagnetic. In the limit of strong anisotropy of exchange interactions this model can be considered as the Ising delta chain with macroscopic degenerate ground state perturbed by transverse quantum fluctuations. These perturbations lift the ground state degeneracy and the model reduces to the basal XXZ spin chain in the magnetic field induced by static apical spins. We show that the ground state of such a model is ferrimagnetic. The excitations of the model are formed by ferrimagnetic domains separated by domain walls with a finite energy. At low temperatures the system is effectively divided into two independent subsystems, the apical subsystem described by the Ising spin-[Formula: see text] chain and the basal subsystem described by the XXZ chain with infinite zz interactions.
Ferrimagnetism in delta chain with anisotropic ferromagnetic and antiferromagnetic interactions
NASA Astrophysics Data System (ADS)
Dmitriev, D. V.; Krivnov, V. Ya
2016-12-01
We consider analytically and numerically an anisotropic spin-\\frac{1}{2} delta-chain (sawtooth chain) in which exchange interactions between apical and basal spins are ferromagnetic and those between basal spins are antiferromagnetic. In the limit of strong anisotropy of exchange interactions this model can be considered as the Ising delta chain with macroscopic degenerate ground state perturbed by transverse quantum fluctuations. These perturbations lift the ground state degeneracy and the model reduces to the basal XXZ spin chain in the magnetic field induced by static apical spins. We show that the ground state of such a model is ferrimagnetic. The excitations of the model are formed by ferrimagnetic domains separated by domain walls with a finite energy. At low temperatures the system is effectively divided into two independent subsystems, the apical subsystem described by the Ising spin-\\frac{1}{2} chain and the basal subsystem described by the XXZ chain with infinite zz interactions.
Hart, W E; Istrail, S
1997-01-01
This paper considers the protein energy minimization problem for lattice and off-lattice protein folding models that explicitly represent side chains. Lattice models of proteins have proven useful tools for reasoning about protein folding in unrestricted continuous space through analogy. This paper provides the first illustration of how rigorous algorithmic analyses of lattice models can lead to rigorous algorithmic analyses of off-lattice models. We consider two side chain models: a lattice model that generalizes the HP model (Dill, 1985) to explicitly represent side chains on the cubic lattice and a new off-lattice model, the HP Tangent Spheres Side Chain model (HP-TSSC), that generalizes this model further by representing the backbone and side chains of proteins with tangent spheres. We describe algorithms with mathematically guaranteed error bounds for both of these models. In particular, we describe a linear time performance guaranteed approximation algorithm for the HP side chain model that constructs conformations whose energy is better than 86% of optimal in a face-centered cubic lattice, and we demonstrate how this provides a better than 70% performance guarantee for the HP-TSSC model. Our analysis provides a mathematical methodology for transferring performance guarantees on lattices to off-lattice models. These results partially answer the open question of Ngo et al. (1994) concerning the complexity of protein folding models that include side chains.
Hart, W.E.; Istrail, S.
1996-08-09
This paper considers the protein structure prediction problem for lattice and off-lattice protein folding models that explicitly represent side chains. Lattice models of proteins have proven extremely useful tools for reasoning about protein folding in unrestricted continuous space through analogy. This paper provides the first illustration of how rigorous algorithmic analyses of lattice models can lead to rigorous algorithmic analyses of off-lattice models. The authors consider two side chain models: a lattice model that generalizes the HP model (Dill 85) to explicitly represent side chains on the cubic lattice, and a new off-lattice model, the HP Tangent Spheres Side Chain model (HP-TSSC), that generalizes this model further by representing the backbone and side chains of proteins with tangent spheres. They describe algorithms for both of these models with mathematically guaranteed error bounds. In particular, the authors describe a linear time performance guaranteed approximation algorithm for the HP side chain model that constructs conformations whose energy is better than 865 of optimal in a face centered cubic lattice, and they demonstrate how this provides a 70% performance guarantee for the HP-TSSC model. This is the first algorithm in the literature for off-lattice protein structure prediction that has a rigorous performance guarantee. The analysis of the HP-TSSC model builds off of the work of Dancik and Hannenhalli who have developed a 16/30 approximation algorithm for the HP model on the hexagonal close packed lattice. Further, the analysis provides a mathematical methodology for transferring performance guarantees on lattices to off-lattice models. These results partially answer the open question of Karplus et al. concerning the complexity of protein folding models that include side chains.
Nucleon, $$\\Delta$$ and $$\\Omega$$ excited states in $$N_f=2+1$$ lattice QCD
John Bulava; Edwards, Robert G.; Engelson, Eric; ...
2010-07-22
The energies of the excited states of the Nucleon,more » $$\\Delta$$ and $$\\Omega$$ are computed in lattice QCD, using two light quarks and one strange quark on anisotropic lattices. The calculation is performed at three values of the light quark mass, corresponding to pion masses $$m_{\\pi}$$ = 392(4), 438(3) and 521(3) MeV. We employ the variational method with a large basis of interpolating operators enabling six energies in each irreducible representation of the lattice to be distinguished clearly. We compare our calculation with the low-lying experimental spectrum, with which we find reasonable agreement in the pattern of states. In addition, the need to include operators that couple to the expected multi-hadron states in the spectrum is clearly identified.« less
NASA Technical Reports Server (NTRS)
Levin, D.
1981-01-01
A nonsteady vortex-lattice method is introduced for predicting the dynamic stability derivatives of a delta wing undergoing an oscillatory motion. The analysis is applied to several types of small oscillations in pitch. The angle of attack varied between + or - 1 deg, with the mean held at 0 deg when the flow was assumed to be attached and between + or - 1 deg and the mean held at 15 deg when both leading-edge separation and wake roll-up were included. The computed results for damping in pitch are compared with several other methods and with experiments, and are found to be consistent and in good agreement.
Xu, Wen-Sheng; Freed, Karl F.
2015-07-14
The lattice cluster theory (LCT) for the thermodynamics of polymer systems has recently been reformulated to treat strongly interacting self-assembling polymers composed of fully flexible linear telechelic chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)]. Here, we further extend the LCT for linear telechelic polymer melts to include a description of chain semiflexibility, which is treated by introducing a bending energy penalty whenever a pair of consecutive bonds from a single chain lies along orthogonal directions. An analytical expression for the Helmholtz free energy is derived for the model of semiflexible linear telechelic polymer melts. The extension provides a theoretical tool for investigating the influence of chain stiffness on the thermodynamics of self-assembling telechelic polymers, and for further exploring the influence of self-assembly on glass formation in such systems.
Gamma-chain heterogeneity in Greek (delta beta)zero-thalassemia.
Georgiou, I; Seferiadis, K; Lolis, D; Tsolas, O; Bourantas, K L
1995-02-01
A molecular and biochemical population study of (delta beta)zero thalassemia in central Greece is described. The molecular study was focused on the type of the deletion and the status of G gamma-XmnI polymorphism, whereas the biochemical approach was centered on the G gamma/A gamma ratio as well as the frequency of the A gamma T chain in the fetal hemoglobin of 19 delta beta-thalassemia heterozygotes and 3 homozygotes. This study includes individuals from the mountainous district of Epirus (northwestern Greece) where the trait was found to be concentrated along the river Arachthos. The Sicilian (delta beta)zero thalassemia deletion was found in all subjects tested by direct PCR. The levels for the G gamma-chain presented values ranging from 29 to 83% of the total gamma-chain content. Thirteen heterozygotes had the adult G gamma/A gamma ratio (mean G gamma: 35% +/- 10) of whom 10 were XmnI-negative (- / -), 6 had the newborn ratio (mean G gamma: 70% +/- 9) and were XmnI-positive, while homozygotes had equal amounts of G gamma and A gamma. Five of the 19 heterozygotes were A gamma T-positive with low levels of this A gamma-chain variant, suggesting an in-trans to the delta beta-thalassemia determinant production.
Kaon to Two Pions decays from Lattice QCD: Delta I = 1/2 rule and CP violation
NASA Astrophysics Data System (ADS)
Liu, Qi
We report a direct lattice calculation of the K to pipi decay matrix elements for both the DeltaI=1/2 and 3/2 amplitudes A0 and A2 on a 2+1 flavor, domain wall fermion, 163x32x16 lattice ensemble and a 243x64x16 lattice ensemble. This is a complete calculation in which all contractions for the required ten, four-quark operators are evaluated, including the disconnected graphs in which no quark line connects the initial kaon and final two-pion states. These lattice operators are non-perturbatively renormalized using the Rome-Southampton method and the quadratic divergences are studied and removed. This is an important but notoriously difficult calculation, requiring high statistics on a large volume. In this work we take a major step towards the computation of the physicalK→pipi amplitudes by performing a complete calculation at unphysical kinematics with pions of mass 422 MeV and 329 MeV at rest in the kaon rest frame. With this simplification we are able to resolve Re(A0) from zero for the first time, with a 25% statistical error on the 163 lattice and 15% on the 243 lattice. The complex amplitude A2 is calculated with small statistical errors. We obtain the DeltaI=1/2 rule with an enhancement factor of 9.1(21) and 12.0(17) on these two ensembles. From the detailed analysis of the results we gain a deeper understanding of the origin of the DeltaI=1/2 rule. We also calculate the complex amplitude A0, a calculation central to understanding and testing the standard model of CP violation in the kaon system. The final result for the measure of direct CP violation, epsilon', calculated at unphysical kinematics has an order of 100% statistical error, so this only serves as an order of magnitude check.
Triangle, square and delta-chain based cobalt tetrazolate magnets.
Yao, Ru-Xin; Qin, Ying-Lian; Ji, Fang; Zhao, Yan-Fei; Zhang, Xian-Ming
2013-05-14
Three novel tetrazole-based frustrated magnets, namely, Co3(OH)2(3-ptz)2(SO4)(H2O)4 (1), Co2(OH)(tzba)(H2O)4 (2) and [Co(OH)(tta)] (3) (3-ptz = 5-(3-pyridyl) tetrazole, H2tzba = 4-(1H-tetrazol-5-yl) benzoic acid, Htta = 1H-tetrazole) were hydrothermal synthesized and magnetically characterized. Compound 1 is a 2D (4,4) layered structure assembled by sulfate capped triangular [Co3(μ3-OH)(μ3-SO4)] clusters and in situ synthesized μ3-3-ptz ligands. Compound 2 features Co3(μ3-OH) triangle based magnetic Δ-chains linked with in situ generated μ5-tzba ligands to form a 2D layer. Compound 3 is a uninodal eight-connected body-centered-cubic (bcu) 3D network with square Co4O4 clusters as nodes and μ4-tta ligands as linkers. Interestingly, spin frustration was observed in these complexes due to inherent spin competition in triangle, Δ-chain and square. Magnetic studies show that 1 behaves as antiferromagnet, while 2 and 3 exhibits spin canting and long-range magnetic ordering.
Zhao Jianqing; Huang Jie; Chen Hui; Cui Lianxian; He Wei . E-mail: heweiimu@public.bta.net.cn
2006-01-06
Human MHC class I chain-related A (MICA) is a tumor-associated antigen that can be recognized by V{delta}1 subset of tumor-infiltrating {gamma}{delta} T cells. We previously reported that immobilized recombinant MICA protein could induce the proliferation of tumor-infiltrating V{delta}1 {gamma}{delta} T cells in vitro. But there has been no direct evidence showing the engagement of {gamma}{delta} T cell receptors (TCR) of the induced cells with MICA. In the current investigation, we show that MICA induces specific cytolytic activity of the expanded {gamma}{delta} T cells. We expressed the coupled V domains from the MICA-induced T cells as a single polypeptide chain V{delta}V{gamma} TCR ({gamma}{delta} scTCR). Such scTCR can specifically bind MICA of HeLa cells. Direct interaction of {gamma}{delta} scTCRs with in vitro expressed MICA was monitored using an IAsys biosensor. We found that the V{delta}1 scTCR can specifically bind to immobilized MICA molecule and MICA{alpha}1{alpha}2 domains are responsible for the binding reaction.
Treatment of disordered and ordered systems of polymer chains by lattice methods
Flory, Paul J.
1982-01-01
Classical lattice theories of systems of long-chain molecules provide estimates of the number Z of random configurations to the exclusion of ordered ones. The decrease of Z thus estimated to values [unk]1 with decrease in chain flexibility at high densities is genuine, but it does not take account of eligible ordered configurations; the latter are not a subset of the configurations whose numbers are estimated by classical lattice methods. Failure to recognize this fact and the fundamental distinction between disordered and ordered states has engendered misinterpretations and has cast doubt on the validity of lattice-statistical methods. In a system at equilibrium, the decline of Z (disordered) with decrease in chain flexibility must be arrested by a first order transition to an ordered state. The inference that approach of Z (disordered) to values <1 presages a thermodynamic transition of second order is tenable only if the array of ordered configurations, not comprehended by theories in which the mean field of unoccupied lattice sites is random, can be ignored. PMID:16593214
Kalyoncu, Sibel; Hyun, Jeongmin; Pai, Jennifer C; Johnson, Jennifer L; Entzminger, Kevin; Jain, Avni; Heaner, David P; Morales, Ivan A; Truskett, Thomas M; Maynard, Jennifer A; Lieberman, Raquel L
2014-09-01
Protein crystallization is dependent upon, and sensitive to, the intermolecular contacts that assist in ordering proteins into a three-dimensional lattice. Here we used protein engineering and mutagenesis to affect the crystallization of single chain antibody fragments (scFvs) that recognize the EE epitope (EYMPME) with high affinity. These hypercrystallizable scFvs are under development to assist difficult proteins, such as membrane proteins, in forming crystals, by acting as crystallization chaperones. Guided by analyses of intermolecular crystal lattice contacts, two second-generation anti-EE scFvs were produced, which bind to proteins with installed EE tags. Surprisingly, although noncomplementarity determining region (CDR) lattice residues from the parent scFv framework remained unchanged through the processes of protein engineering and rational design, crystal lattices of the derivative scFvs differ. Comparison of energy calculations and the experimentally-determined lattice interactions for this basis set provides insight into the complexity of the forces driving crystal lattice choice and demonstrates the availability of multiple well-ordered surface features in our scFvs capable of forming versatile crystal contacts.
Kalyoncu, Sibel; Hyun, Jeongmin; Pai, Jennifer C.; Johnson, Jennifer L.; Entzminger, Kevin; Jain, Avni; Heaner, David P.; Morales, Ivan A.; Truskett, Thomas M.; Maynard, Jennifer A.; Lieberman, Raquel L.
2014-01-01
Protein crystallization is dependent upon, and sensitive to, the intermolecular contacts that assist in ordering proteins into a three dimensional lattice. Here we used protein engineering and mutagenesis to affect the crystallization of single chain antibody fragments (scFvs) that recognize the EE epitope (EYMPME) with high affinity. These hypercrystallizable scFvs are under development to assist difficult proteins, such as membrane proteins, in forming crystals, by acting as crystallization chaperones. Guided by analyses of intermolecular crystal lattice contacts, two second-generation anti-EE scFvs were produced, which bind to proteins with installed EE tags. Surprisingly, although non-complementarity determining region (CDR) lattice residues from the parent scFv framework remained unchanged through the processes of protein engineering and rational design, crystal lattices of the derivative scFvs differ. Comparison of energy calculations and the experimentally-determined lattice interactions for this basis set provides insight into the complexity of the forces driving crystal lattice choice and demonstrates the availability of multiple well-ordered surface features in our scFvs capable of forming versatile crystal contacts. PMID:24615866
NASA Astrophysics Data System (ADS)
Kim, Changhoan
We report the results of a calculation of the K → pipi matrix elements of the DeltaI = 3/2 operators. Relying on the 3-flavor effective Hamiltonian, we calculate the low energy contribution to the matrix elements in quenched lattice QCD with the DBW2 action using domain wall fermions, while the high energy contribution is included in the Wilson coefficients. In order to generate interacting pipi states with non-zero relative momentum in lattice, we apply anti-periodic boundary conditions on pions. Since only the magnitude of the overlap of our interpolating operators with the initial and final state is determined, we can calculate only the magnitude of the matrix elements. From the comparison with the experimental result, however, we find some degree of discrepancy. This discrepancy might be ascribed to the unphysical kinematics we choose in this report.
Factors regulating benthic food chains in tropical river deltas and adjacent shelf areas
NASA Astrophysics Data System (ADS)
Alongi, D. M.; Robertson, A. I.
1995-09-01
Benthic food chains of the Amazon (Brazil) and Fly (Papua New Guinea) river deltas and adjacent shelves are compared. Abundance patterns of the major trophic groups (bacteria, meiofauna, and macroinfauna) are similar between regions, with very low densities, or the absence of benthos, within and near the deltas. For muds in the more quiescent areas, benthic abundance and productivity are highest, commonly coinciding with maximum pelagic primary production. Episodes of physical disturbance, erratic food supply, and dilution of river-derived, particulate organic matter foster the development of opportunistic benthic communities of variable diversity and low biomass, dominated by bacteria. These pioneering assemblages are the main food of penaeid shrimp, which dominate the demersal trawl fisheries of both fluvial-dominated regions.
Preliminary results of Delta I=1/2 and 3/2, K to pipi Decay Amplitudes from Lattice QCD
NASA Astrophysics Data System (ADS)
Liu, Q.
We report a direct lattice calculation of the $K$ to $\\pi\\pi$ decay matrix elements for both $\\Delta I=1/2$ and $3/2$ channels on 2+1 flavor, domain wall fermion, $16^3\\times32$ lattices with zero $\\pi\\pi$ relative momentum and $m_\\pi=420$ MeV. All $K^0$ to $\\pi\\pi$ contractions are carefully listed and calculated. The decay into the isospin zero $\\pi\\pi$ final state, which receives contributions from the disconnected graphs, is very difficult to calculate, but a clear signal in the similar disconnected $\\pi\\pi$ correlator can be seen. Preliminary results, some with large errors, will be presented for the various contributions to the renormalized weak matrix elements $A_0$ and $A_2$. We obtain Re$(A_0)$ with $25%$ error in the case of zero momentum on shell decay, and find a factor of 6 enhancement for the $\\Delta I=1/2$ rule in the $420$ MeV pion system.
Limited pattern of TCR delta chain gene rearrangement on the RNA level in multiple sclerosis.
Nowak, J; Januszkiewicz, D; Pernak, M; Hertmanowska, H; Nowicka-Kujawska, K; Rembowska, J; Lewandowski, K; Nowak, T; Wender, M
2001-01-01
Susceptibility to multiple sclerosis (MS) is most likely affected by a number of genes, including HLA and T-cell receptor (TCR) genes. T cells expressing gamma/delta receptors seem to contribute to autoagression in MS, as evidenced by their localization in the MS plaques in the brain. The aim of this study was to analyse the TCRdelta chain gene rearrangement at the RNA (cDNA) level and compare to the DNA pattern rearrangement. TCRdelta gene rearrangement was analysed in MS patients and healthy individuals with the use of primers specific for Vdelta1-6 and Jdelta1 genes (at the DNA level) and specific for Vdelta1-6 and Cdelta1 genes (at the cDNA level). The size of PCR products was analysed on agarose gel and by ALF-Express (Pharmacia). Additionally, the lymphocyte surface immunophenotype was studied with specific monoclonal antibodies. At the DNA level a restricted pattern of Vdelta3-Jdelta1 and Vdelta5-Jdelta1 was found only in MS patients. Contrary to DNA, mono-, oligoclonal RNA (cDNA) rearrangements were limited to Vdelta1-Cdelta1, Vdelta2-Cdelta1 and Vdelta3-Cdelta1 only in MS patients as well. Surface immunophenotype analysis revealed in MS a much higher frequency of activated gamma/delta T lymphocytes, i.e. expressing HLA-DR and CD25. An elevated level of CD56 positive cells in MS was recorded. Mono-oligoclonal pattern of TCRdelta gene rearrangement at the RNA level, along with increase in activated gamma/delta T cells, strongly argue for a significant role of gamma/delta T lymphocytes in the pathogenesis of MS.
Ward, W.C. ); Swift, G.W. )
1993-11-01
In thermoacoustic engines and refrigerators, and in many simple acoustic systems, a one dimensional wave equation determines the spatial dependence of the acoustic pressure and velocity. DELTAE numerically integrates such wave equations in the acoustic approximation, in gases or liquids, in user-defined geometries. Boundary conditions can include conventional acoustic boundary conditions of geometry and impedance, as well as temperature and thermal power in thermoacoustic systems. DELTAE can be used easily for apparatus ranging from simple duct networks and resonators to thermoacoustic engines refrigerators and combinations thereof. It can predict how a given apparatus will perform, or can allow the user to design an apparatus to achieve desired performance. DELTAE views systems as a series of segments; twenty segment types are supported. The purely acoustic segments include ducts and cones, and lumped impedances including compliances, series impedances, and endcaps. Electroacoustics tranducer segments can be defined using either frequency-independent coefficients or the conventional parameters of loudspeaker-style drivers: mass, spring constant, magnetic field strength, etc. Tranducers can be current driven, voltage driven, or connected to an electrical load impedance. Thermoacoustic segment geometries include parallel plates, circular and rectangular pores, and pin arrays. Side branches can be defined with fixed impedances, frequency-dependent radiation impedances, or as an auxiliary series of segments of any types. The user can select working fluids from among air, helium, neon, argon, hydrogen, deuterium, carbon dioxide, nitrogen, helium-argon mixtures, helium-xenon mixtures, liquid sodium, and eutectic sodium-potassium. Additional fluids and solids can be defined by the user.
NASA Astrophysics Data System (ADS)
Jesudason, Christopher G.
2017-01-01
Two aspects of conductive heat are focused here (i) the nature of conductive heat, defined as that form of energy that is transferred as a result of a temperature difference and (ii) the nature of the intermolecular potentials that induces both thermal energy flow and the temperature profile at the steady state for a 1-D lattice chain. It is found that the standard presuppositions of people like Benofy and Quay (BQ) following Joseph Fourier do not obtain for at least a certain specified regime of intermolecular potential parameters related to harmonic (quadratic) potentials for nearest neighbor interactions. For these harmonic potentials, it appears from the simulation results that steady state solutions exist utilizing non-synthetic thermostats that couple not just the two particles at the extreme ends of the lattice chain, but to a control volume of N particles located at either ends of the chain that does not accord with the unique analytical solutions that obtains for single particle thermostatting at the ends of the lattice with a different thermostatting algorithm that utilizes coupling coefficients. If the method used here is considered a more "realistic" or feasible model of the physical reality, then a re-evaluation of some aspects of the standard theoretical methodology is warranted since the standard model solution profile does not accord with the simulation temperature profile determined here for this related model. We also note that the sinusoidal temperature profile generated suggests that thermal integrated circuits with several thermal P-N junctions may be constructed, opening a way to create more complex thermal transistor circuits. A stationary principle is proposed for regions that violate the Fourier principle Jq.∇T ≤ 0, where Jq is the heat current vector and T the temperature.
NASA Astrophysics Data System (ADS)
Gorbunov, A. A.; Skvortsov, A. M.; van Male, J.; Fleer, G. J.
2001-03-01
An ideal polymer chain anchored to a planar surface is considered by using both lattice and continuum model approaches. A general equation relating the lattice and continuum model adsorption interaction parameters is derived in a consistent way by substituting the exact continuum solution for the free chain end distribution function into the lattice model boundary condition. This equation is not mathematically exact but provides excellent results. With the use of this relation the quantitative equivalence between lattice and continuum results was demonstrated for chains of both infinite and finite length and for all three regimes corresponding to attractive, repulsive and adsorption-threshold energy of polymer-surface interaction. The obtained equations are used to discuss the distribution functions describing the tail of an anchored macromolecule and its adsorbed parts. For the tail-related properties the results are independent of the microscopic details of the polymer chain and the adsorbing surface. One interesting result obtained in the vicinity of adsorption threshold point is a bimodal tail length distribution function, which manifests chain populations with either tail or loop dominance. The properties related to the number of surface contacts contain, apart from universal scaling terms, also a nonuniversal factor depending on microscopic details of polymer-surface interaction. We derived an equation for calculating this nonuniversal factor for different lattice models and demonstrated excellent agreement between the lattice results and the continuum model.
Lattice Dynamics of the Binary Aperiodic Chains of Atoms I:. Fractal Dimension of Phonon Spectra
NASA Astrophysics Data System (ADS)
Salejda, Włodzimierz
The microscopic harmonic model of lattice dynamics of the binary chains of atoms is formulated and studied numerically. The dependence of spring constants of the nearest-neighbor (NN) interactions on the average distance between atoms are taken into account. The covering fractal dimensions Df{( c ; )} of the Cantor-set-like phonon spec-tra (PS) of generalized Fibonacci and non-Fibonaccian aperiodic chains containing of 16384≤N≤33461 atoms are determined numerically. The dependence of Df{( c ; )} on the strength Q of NN interactions and on R=mH/mL, where mH and mL denotes the mass of heavy and light atoms, respectively, are calculated for a wide range of Q and R. In particular we found: (1) The fractal dimension Df{( c ; )} of the PS for the so-called goldenmean, silver-mean, bronze-mean, dodecagonal and Severin chain shows a local maximum at increasing magnitude of Q and R>1 (2) At sufficiently large Q we observe power-like diminishing of Df{( c ; )} , i.e. Df{( c ; )} ( {R > 1, Q} ; ) = a ḑot Qα , where α=-0.14±0.02 and α=-0.10±0.02 for the above specified chains and so-called octagonal, copper-mean, nickel-mean, Thue-Morse, Rudin-Shapiro chain, respectively.
Xu, Wen-Sheng; Freed, Karl F.
2015-07-14
The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in Paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction ϕ or temperature T is high, but opposes self-assembly when both ϕ and T are sufficiently low. This allows us to identify a boundary line in the ϕ-T plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts.
NASA Astrophysics Data System (ADS)
Zhang, Jinfeng; Chen, Yu; Chen, Rong; Liang, Jie
2004-07-01
Side chains of amino acid residues are the determining factor that distinguishes proteins from other unstable chain polymers. In simple models they are often represented implicitly (e.g., by spin states) or simplified as one atom. Here we study side chain effects using two-dimensional square lattice and three-dimensional tetrahedral lattice models, with explicitly constructed side chains formed by two atoms of different chirality and flexibility. We distinguish effects due to chirality and effects due to side chain flexibilities, since residues in proteins are L residues, and their side chains adopt different rotameric states. For short chains, we enumerate exhaustively all possible conformations. For long chains, we sample effectively rare events such as compact conformations and obtain complete pictures of ensemble properties of conformations of these models at all compactness region. This is made possible by using sequential Monte Carlo techniques based on chain growth method. Our results show that both chirality and reduced side chain flexibility lower the folding entropy significantly for globally compact conformations, suggesting that they are important properties of residues to ensure fast folding and stable native structure. This corresponds well with our finding that natural amino acid residues have reduced effective flexibility, as evidenced by statistical analysis of rotamer libraries and side chain rotatable bonds. We further develop a method calculating the exact side chain entropy for a given backbone structure. We show that simple rotamer counting underestimates side chain entropy significantly for both extended and near maximally compact conformations. We find that side chain entropy does not always correlate well with main chain packing. With explicit side chains, extended backbones do not have the largest side chain entropy. Among compact backbones with maximum side chain entropy, helical structures emerge as the dominating configurations. Our
Spin-lattice relaxation within a dimerized Ising chain in a magnetic field
Erdem, Rıza E-mail: rerdem29@hotmail.com; Gülpınar, Gül; Yalçın, Orhan; Pawlak, Andrzej
2014-07-21
A qualitative study of the spin-lattice relaxation within a dimerized Ising chain in a magnetic field is presented. We have first determined the time dependence of the deviation of the lattice distortion parameter δΔ from the equilibrium state within framework of a technique combining the statistical equilibrium theory based on the transfer matrix method and the linear theory of irreversible thermodynamics. We have shown that the time dependence of the lattice distortion parameter is characterized by a single time constant (τ) which diverges around the critical point in both dimerized (Δ≠0) and uniform (Δ=0) phase regions. When the temperature and magnetic field are fixed to certain values, the time τ depends only on exchange coupling between the spins. It is a characteristic time associated with the long wavelength fluctuations of distortion. We have also taken into account the effects of spatial fluctuations on the relaxation time using the full Landau-Ginzburg free energy functional. We have found an explicit expression for the relaxation time as a function of temperature, coupling constant and wave vector (q) and shown that the critical mode corresponds to the case q=0. Finally, our results are found to be in good qualitative agreement with the results obtained in recent experimental study on synchrotron x-ray scattering and muon spin relaxation in diluted material Cu{sub 1−y}Mg{sub y}GeO{sub 3} where the composition y is very close to 0.0209. These results can be considered as natural extensions of some previous works on static aspects of the problem.
Quantum Simulation of a Lattice Schwinger Model in a Chain of Trapped Ions
NASA Astrophysics Data System (ADS)
Hauke, P.; Marcos, D.; Dalmonte, M.; Zoller, P.
2013-10-01
We discuss how a lattice Schwinger model can be realized in a linear ion trap, allowing a detailed study of the physics of Abelian lattice gauge theories related to one-dimensional quantum electrodynamics. Relying on the rich quantum-simulation toolbox available in state-of-the-art trapped-ion experiments, we show how one can engineer an effectively gauge-invariant dynamics by imposing energetic constraints, provided by strong Ising-like interactions. Applying exact diagonalization to ground-state and time-dependent properties, we study the underlying microscopic model and discuss undesired interaction terms and other imperfections. As our analysis shows, the proposed scheme allows for the observation in realistic setups of spontaneous parity- and charge-symmetry breaking, as well as false-vacuum decay. Besides an implementation aimed at larger ion chains, we also discuss a minimal setting, consisting of only four ions in a simpler experimental setup, which enables us to probe basic physical phenomena related to the full many-body problem. The proposal opens a new route for analog quantum simulation of high-energy and condensed-matter models where gauge symmetries play a prominent role.
NASA Astrophysics Data System (ADS)
Maginnis, P. A.; West, M.; Dullerud, G. E.
2016-10-01
We propose an algorithm to accelerate Monte Carlo simulation for a broad class of stochastic processes. Specifically, the class of countable-state, discrete-time Markov chains driven by additive Poisson noise, or lattice discrete-time Markov chains. In particular, this class includes simulation of reaction networks via the tau-leaping algorithm. To produce the speedup, we simulate pairs of fair-draw trajectories that are negatively correlated. Thus, when averaged, these paths produce an unbiased Monte Carlo estimator that has reduced variance and, therefore, reduced error. Numerical results for three example systems included in this work demonstrate two to four orders of magnitude reduction of mean-square error. The numerical examples were chosen to illustrate different application areas and levels of system complexity. The areas are: gene expression (affine state-dependent rates), aerosol particle coagulation with emission and human immunodeficiency virus infection (both with nonlinear state-dependent rates). Our algorithm views the system dynamics as a "black-box", i.e., we only require control of pseudorandom number generator inputs. As a result, typical codes can be retrofitted with our algorithm using only minor changes. We prove several analytical results. Among these, we characterize the relationship of covariances between paths in the general nonlinear state-dependent intensity rates case, and we prove variance reduction of mean estimators in the special case of affine intensity rates.
Lin, Ming; Chen, Rong; Liang, Jie
2008-02-28
Proteins contain many voids, which are unfilled spaces enclosed in the interior. A few of them have shapes compatible to ligands and substrates and are important for protein functions. An important general question is how the need for maintaining functional voids is influenced by, and affects other aspects of proteins structures and properties (e.g., protein folding stability, kinetic accessibility, and evolution selection pressure). In this paper, we examine in detail the effects of maintaining voids of different shapes and sizes using two-dimensional lattice models. We study the propensity for conformations to form a void of specific shape, which is related to the entropic cost of void maintenance. We also study the location that voids of a specific shape and size tend to form, and the influence of compactness on the formation of such voids. As enumeration is infeasible for long chain polymer, a key development in this work is the design of a novel sequential Monte Carlo strategy for generating large number of sample conformations under very constraining restrictions. Our method is validated by comparing results obtained from sampling and from enumeration for short polymer chains. We succeeded in accurate estimation of entropic cost of void maintenance, with and without an increasing number of restrictive conditions, such as loops forming the wall of void with fixed length, with additionally fixed starting position in the sequence. Additionally, we have identified the key structural properties of voids that are important in determining the entropic cost of void formation. We have further developed a parametric model to predict quantitatively void entropy. Our model is highly effective, and these results indicate that voids representing functional sites can be used as an improved model for studying the evolution of protein functions and how protein function relates to protein stability.
NASA Astrophysics Data System (ADS)
Lin, Ming; Chen, Rong; Liang, Jie
2008-02-01
Proteins contain many voids, which are unfilled spaces enclosed in the interior. A few of them have shapes compatible to ligands and substrates and are important for protein functions. An important general question is how the need for maintaining functional voids is influenced by, and affects other aspects of proteins structures and properties (e.g., protein folding stability, kinetic accessibility, and evolution selection pressure). In this paper, we examine in detail the effects of maintaining voids of different shapes and sizes using two-dimensional lattice models. We study the propensity for conformations to form a void of specific shape, which is related to the entropic cost of void maintenance. We also study the location that voids of a specific shape and size tend to form, and the influence of compactness on the formation of such voids. As enumeration is infeasible for long chain polymer, a key development in this work is the design of a novel sequential Monte Carlo strategy for generating large number of sample conformations under very constraining restrictions. Our method is validated by comparing results obtained from sampling and from enumeration for short polymer chains. We succeeded in accurate estimation of entropic cost of void maintenance, with and without an increasing number of restrictive conditions, such as loops forming the wall of void with fixed length, with additionally fixed starting position in the sequence. Additionally, we have identified the key structural properties of voids that are important in determining the entropic cost of void formation. We have further developed a parametric model to predict quantitatively void entropy. Our model is highly effective, and these results indicate that voids representing functional sites can be used as an improved model for studying the evolution of protein functions and how protein function relates to protein stability.
Bukhanko, F. N.
2013-04-15
The structural and magnetic phase transformations that occur in the system of self-doped La{sub 1-y}Pr{sub y}MnO{sub 3+{delta}} ({delta} Almost-Equal-To 0.1, 0 {<=} y {<=} 1) manganites in the temperature range 4.2-300 K are studied by X-ray diffraction and measuring the temperature and field dependences of dc magnetization. The low-temperature magnetic phase transformations induced by the substitution of Pr for La correlate well with the structural phase transformations at T = 300 K, which indicates a strong coupling of the electronic and magnetic subsystems of La{sub 1-y}Pr{sub y}MnO{sub 3+{delta}} manganites with the crystal lattice. The anomalies of the magnetic and structural properties detected in this work in the form of peaks and inflection points in the concentration dependences of the magnetization and lattice parameters of the pseudocubic phase of La{sub 1-y}Pr{sub y}MnO{sub 3+{delta}} (0.1 {<=} y {<=} 0.7) in the temperature range 4.2-300 K are explained in terms of the existing concepts of the effect of Fermi surface nesting on the renormalization of the density of states and the hole dispersion near E{sub F} in the presence of a strong coupling of holes with low-frequency optical phonons, which results in their transformation into quasiparticles. The narrow peak in the magnetization curve M(y) of La{sub 1-y}Pr{sub y}MnO{sub 3+{delta}} that is detected near y = 0.3 at T = 4.2 K is assumed to correspond to the peak of coherence of quasiparticles with a low energy of coupling with the crystal lattice near E{sub F}, which was found earlier in the photoelectron emission spectra of manganites. The disappearance of the narrow magnetization peak with increasing Pr concentration is explained by the transition of charge carriers from the mode of 'light' holes weakly coupled to one of the soft phonons to the mode of 'heavy' holes strongly coupled to several phonons. The transition between phases with strongly different effective quasiparticle masses proceeds
Poulin, R.; Poirier, D.; Merand, Y.; Theriault, C.; Belanger, A.; Labrie, F.
1989-06-05
Estrogen-sensitive human breast cancer cells (ZR-75-1) were incubated with the 3H-labeled adrenal C19-delta 5-steroids dehydroepiandrosterone (DHEA) and its fully estrogenic derivative, androst-5-ene-3 beta,17 beta-diol (delta 5-diol) for various time intervals. When fractionated by solvent partition, Sephadex LH-20 column chromatography and silica gel TLC, the labeled cell components were largely present (40-75%) in three highly nonpolar, lipoidal fractions. Mild alkaline hydrolysis of these lipoidal derivatives yielded either free 3H-labeled DHEA or delta 5-diol. The three lipoidal fractions cochromatographed with the synthetic DHEA 3 beta-esters, delta 5-diol 3 beta (or 17 beta)-monoesters and delta 5-diol 3 beta,17 beta-diesters of long-chain fatty acids. DHEA and delta 5-diol were mainly esterified to saturated and mono-unsaturated fatty acids. For delta 5-diol, the preferred site of esterification of the fatty acids is the 3 beta-position while some esterification also takes place at the 17 beta-position. Time course studies show that ZR-75-1 cells accumulate delta 5-diol mostly (greater than 95%) as fatty acid mono- and diesters while DHEA is converted to delta 5-diol essentially as the esterified form. Furthermore, while free C19-delta 5-steroids rapidly diffuse out of the cells after removal of the precursor (3H)delta 5-diol, the fatty acid ester derivatives are progressively hydrolyzed, and DHEA and delta 5-diol thus formed are then sulfurylated prior to their release into the culture medium. The latter process however is rate-limited, since new steady-state levels of free steroids and fatty acid esters are rapidly reached and maintained for extended periods of time after removal of precursor, thus maintaining minimal concentrations of intracellular steroids.
Transitions of tethered polymer chains: a simulation study with the bond fluctuation lattice model.
Luettmer-Strathmann, Jutta; Rampf, Federica; Paul, Wolfgang; Binder, Kurt
2008-02-14
A polymer chain tethered to a surface may be compact or extended, adsorbed or desorbed, depending on interactions with the surface and the surrounding solvent. This leads to a rich phase diagram with a variety of transitions. To investigate these transitions we have performed Monte Carlo simulations of a bond fluctuation model with Wang-Landau and umbrella sampling algorithms in a two-dimensional state space. The simulations' density-of-states results have been evaluated for interaction parameters spanning the range from good- to poor-solvent conditions and from repulsive to strongly attractive surfaces. In this work, we describe the simulation method and present results for the overall phase behavior and for some of the transitions. For adsorption in good solvent, we compare with Metropolis Monte Carlo data for the same model and find good agreement between the results. For the collapse transition, which occurs when the solvent quality changes from good to poor, we consider two situations corresponding to three-dimensional (hard surface) and two-dimensional (very attractive surface) chain conformations, respectively. For the hard surface, we compare tethered chains with free chains and find very similar behavior for both types of chains. For the very attractive surface, we find the two-dimensional chain collapse to be a two-step transition with the same sequence of transitions that is observed for three-dimensional chains: a coil-globule transition that changes the overall chain size is followed by a local rearrangement of chain segments.
NASA Astrophysics Data System (ADS)
Yumak, A.; Boubaker, K.; Petkova, P.; Yahsi, U.
2015-10-01
In is known that short-chain chlorinated paraffins (SCCPs) are highly complex technical mixtures of polychlorinated n-alkanes with single chlorine content. Due to their physical properties (viscosity, flame resistance) they are used in many different applications, such as lubricant additives, metal processing, leather fat-liquoring, plastics softening, PVC plasticizing and flame retardants in paints, adhesives and sealants. SCCPs are studied here in terms of processing-linked molecular structure stability, under Simha and Somcynsky-EOS theory calculations and elements from Simha-Somcynsky-related Lattice Compatibility Theory. Analyses were carried out on 1-chloropropane, 2-chloropropane, 1-chlorobutane, 2-chlorobutane, 1-chloro 2-methylane, and 2-chloro 2-methylane as (SCCPs) universal representatives. This paper gives evidence to this stability and reviews the current state of knowledge and highlights the need for further research in order to improve future (SCCPs) monitoring efforts.
NASA Astrophysics Data System (ADS)
da Silva, L. D.; Sales, M. O.; Ranciaro Neto, A.; Lyra, M. L.; de Moura, F. A. B. F.
2016-12-01
We investigate electronic transport in a one-dimensional model with four different types of atoms and long-ranged correlated disorder. The latter was attained by choosing an adequate distribution of on-site energies. The wave-packet dynamics is followed by taking into account effects due to a static electric field and electron-phonon coupling. In the absence of electron-phonon coupling, the competition between correlated disorder and the static electric field promotes the occurrence of wave-packet oscillations in the regime of strong correlations. When the electron-lattice coupling is switched on, phonon scattering degrades the Bloch oscillations. For weak electron-phonon couplings, a coherent oscillatory-like dynamics of the wave-packet centroid persists for short periods of time. For strong couplings the wave-packet acquires a diffusive-like displacement and spreading. A slower sub-diffusive spreading takes place in the regime of weak correlations.
André, Sébastien; Kerfourn, Fabienne; Affaticati, Pierre; Guerci, Aline; Ravassard, Philippe; Fellah, Julien S
2007-06-01
Gammadelta T cells localize at mammalian epithelial surfaces to exert both protective and regulatory roles in response to infections. We have previously characterized the Mexican axolotl (Ambystoma mexicanum) T cell receptor delta (TRD) chain. In this study, TRD repertoires in spleen, liver, intestine and skin from larvae, pre-adult and adult axolotls were examined and compared to the thymic TRD repertoire. A TRDV transcript without N/D diversity, TRDV1S1-TRDJ1, dominates the TRD repertoires until sexual maturation. In adult tissues, this canonical transcript is replaced by another dominant TRDV1S1-TRDJ1 transcript. In the thymus, these two transcripts are detected early in development. Our results suggest that gammadelta T cells that express the canonical TRDV1S1-TRDJ1 transcript emerge from the thymus and colonize the peripheral tissues, where they are selectively expanded by recurrent ligands. This particular situation is probably related to the neotenic state and the slow development of the axolotl. In thymectomized axolotls, TRD repertoires appear different from those of normal axolotls, suggesting that extrathymic gammadelta T cell differentiation could occur. Gene expression analysis showed the importance of the gut in T cell development.
Snyder, Chad R. Guttman, Charles M.; Di Marzio, Edmund A.
2014-01-21
We extend the exact solutions of the Di Marzio-Rubin matrix method for the thermodynamic properties, including chain density, of a linear polymer molecule confined to walk on a lattice of finite size. Our extensions enable (a) the use of higher dimensions (explicit 2D and 3D lattices), (b) lattice boundaries of arbitrary shape, and (c) the flexibility to allow each monomer to have its own energy of attraction for each lattice site. In the case of the large chain limit, we demonstrate how periodic boundary conditions can also be employed to reduce computation time. Advantages to this method include easy definition of chemical and physical structure (or surface roughness) of the lattice and site-specific monomer-specific energetics, and straightforward relatively fast computations. We show the usefulness and ease of implementation of this extension by examining the effect of energy variation along the lattice walls of an infinite rectangular cylinder with the idea of studying the changes in properties caused by chemical inhomogeneities on the surface of the box. Herein, we look particularly at the polymer density profile as a function of temperature in the confined region for very long polymers. One particularly striking result is the shift in the critical condition for adsorption due to surface energy inhomogeneities and the length scale of the inhomogeneities; an observation that could have important implications for polymer chromatography. Our method should have applications to both copolymers and biopolymers of arbitrary molar mass.
Spin exchange dominated by charge fluctuations of the Wigner lattice in the chain cuprate Na5Cu3O6
NASA Astrophysics Data System (ADS)
Ali, Naveed Zafar; Sirker, Jesko; Nuss, Jürgen; Horsch, Peter; Jansen, Martin
2011-07-01
Na5Cu3O6, a new member of one-dimensional charge-ordered chain cuprates, was synthesized via the azide/nitrate route by reacting NaN3, NaNO3, and CuO. According to single-crystal x-ray analysis, one-dimensional ∞1CuO2n- chains built up from planar, edge-sharing CuO4 squares are a dominant feature of the crystal structure. From the analysis of the Cu-O bond lengths, we find that the system forms a Wigner lattice. The commensurate charge order allows the explicit assignment of the valence states of either +2 or +3 to each copper atom, resulting in a repetition according to Cu2+-Cu3+-Cu2+-Cu2+-Cu3+-Cu2+. Following the theoretical analysis of the previously synthesized compounds Na3Cu2O4 and Na8Cu5O10, the magnetic susceptibility was expected to show a large dimer gap. Surprisingly, this is not the case. To resolve this puzzle, we show that the magnetic couplings in this compound are strongly affected by excitations across the Wigner charge gap. By including these contributions, which are distinct from conventional superexchange in Mott-insulators, we obtain a quantitatively satisfying theoretical description of the magnetic susceptibility data.
NASA Astrophysics Data System (ADS)
Shen, Y.; Kevrekidis, P. G.; Sen, S.; Hoffman, A.
2014-08-01
Our aim in the present work is to develop approximations for the collisional dynamics of traveling waves in the context of granular chains in the presence of precompression. To that effect, we aim to quantify approximations of the relevant Hertzian FPU-type lattice through both the Korteweg-de Vries (KdV) equation and the Toda lattice. Using the availability in such settings of both one-soliton and two-soliton solutions in explicit analytical form, we initialize such coherent structures in the granular chain and observe the proximity of the resulting evolution to the underlying integrable (KdV or Toda) model. While the KdV offers the possibility to accurately capture collisions of solitary waves propagating in the same direction, the Toda lattice enables capturing both copropagating and counterpropagating soliton collisions. The error in the approximation is quantified numerically and connections to bounds established in the mathematical literature are also given.
Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains
NASA Astrophysics Data System (ADS)
Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.
2016-10-01
We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.
Nakajin, S; Takahashi, M; Shinoda, M; Hall, P F
1985-10-30
Conversion of progesterone to 17 alpha-hydroxyprogesterone plus androstenedione (17 alpha-hydroxylation) and to androstadienone (delta 16 synthetase activity) by microsomes from neonatal pig testis, were both inhibited by antibodies raised against homogeneous cytochrome P-450 C21 side-chain cleavage. Inhibition of the two activities showed the same relationship to the concentration of antibody added. Analogous results were obtained with pregnenolone as substrate. In a reconstituted enzyme system consisting of the homogeneous cytochrome P-450 C21 side-chain cleavage enzyme, P-450 reductase and NADPH, addition of cytochrome b5 resulted in the synthesis of the corresponding delta 16-C19-steroid from progesterone (androstadienone) and pregnenolone (androstadienol). The effect of cytochrome b5 was concentration-dependent and prevented by anti-cytochrome b5. It is concluded that the cytochrome P-450 C21 side-chain cleavage enzyme from pig testicular microsomes is also capable of synthesizing delta 16-C19-steroids and is, therefore, likely to be responsible for the large amounts of the pherormone androstadienone produced by male pigs.
Moumni, Imen; Zorai, Amine; Daoued, Bechir Ben; Mosbahi, Ikbel; Omar, Souheil; Kaabachi, Neziha; Dellagi, Koussay; Abbes, Salem
2007-01-01
We describe a new delta-globin variant, Hb A2-Pasteur-Tunis [delta59(E3)Lys-->Asn, AAG-->AAC]. This hemoglobin (Hb) displayed an electrophoretic mobility faster than normal Hb A2 and was expressed at 2.2 %. The molecular defect was characterized by DNA sequencing and confirmed by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-designed protocol. Hb A2-Pasteur-Tunis was found in a carrier of a codon 39 (C-->T) beta0-thalassemia (thal), presenting with a normal Hb A2 level. Phenotype and genotype investigations revealed that the total Hb A2 level of the patient was that expected for a minor beta-thal (4.8%).
Liu, Zhirong; Chan, Hue Sun
2008-04-14
We develop two classes of Monte Carlo moves for efficient sampling of wormlike DNA chains that can have significant degrees of supercoiling, a conformational feature that is key to many aspects of biological function including replication, transcription, and recombination. One class of moves entails reversing the coordinates of a segment of the chain along one, two, or three axes of an appropriately chosen local frame of reference. These transformations may be viewed as a generalization, to the continuum, of the Madras-Orlitsky-Shepp algorithm for cubic lattices. Another class of moves, termed T+/-2, allows for interconversions between chains with different lengths by adding or subtracting two beads (monomer units) to or from the chain. Length-changing moves are generally useful for conformational sampling with a given site juxtaposition, as has been shown in previous lattice studies. Here, the continuum T+/-2 moves are designed to enhance their acceptance rate in supercoiled conformations. We apply these moves to a wormlike model in which excluded volume is accounted for by a bond-bond repulsion term. The computed autocorrelation functions for the relaxation of bond length, bond angle, writhe, and branch number indicate that the new moves lead to significantly more efficient sampling than conventional bead displacements and crankshaft rotations. A close correspondence is found in the equilibrium ensemble between the map of writhe computed for pair of chain segments and the map of site juxtapositions or self-contacts. To evaluate the more coarse-grained freely jointed chain (random-flight) and cubic lattice models that are commonly used in DNA investigations, twisting (torsional) potentials are introduced into these models. Conformational properties for a given superhelical density sigma may then be sampled by computing the writhe and using White's formula to relate the degree of twisting to writhe and sigma. Extensive comparisons of contact patterns and knot
NASA Astrophysics Data System (ADS)
Streltsov, S. V.; Petrova, M. V.; Morozov, V. A.; Romanenko, G. V.; Anisimov, V. I.; Lukzen, N. N.
2013-01-01
The chain-polymer Cu(II) “breathing crystals” C21H19CuF12N4O6 were studied using the x-ray diffraction and ab initio band structure calculations. We show that the crystal structure modification at T=146 K, associated with the spin crossover transition, induces the changes of the orbital order in half of the Cu sites. This in turn results in the switch of the magnetic interaction sign in accordance with the Goodenough-Kanamori-Andersen theory of the coupling between the orbital and spin degrees of freedom.
Hiebeler, David E; Millett, Nicholas E
2011-06-21
We investigate a spatial lattice model of a population employing dispersal to nearest and second-nearest neighbors, as well as long-distance dispersal across the landscape. The model is studied via stochastic spatial simulations, ordinary pair approximation, and triplet approximation. The latter method, which uses the probabilities of state configurations of contiguous blocks of three sites as its state variables, is demonstrated to be greatly superior to pair approximations for estimating spatial correlation information at various scales. Correlations between pairs of sites separated by arbitrary distances are estimated by constructing spatial Markov processes using the information from both approximations. These correlations demonstrate why pair approximation misses basic qualitative features of the model, such as decreasing population density as a large proportion of offspring are dropped on second-nearest neighbors, and why triplet approximation is able to include them. Analytical and numerical results show that, excluding long-distance dispersal, the initial growth rate of an invading population is maximized and the equilibrium population density is also roughly maximized when the population spreads its offspring evenly over nearest and second-nearest neighboring sites.
Heikkilä, R; Ruud, E; Funderud, S; Godal, T
1985-01-01
Cytoplasmic free Ca2+ concentration and influx of 86Rb+ (K+ analogue) were determined during the first minutes after stimulation of neoplastic human B cells and B cell lines by antibodies to surface Ig. The Ca2+ concentration increased in the great majority of samples (41 of 48). All of four B cell lines also responded, providing formal evidence that accessory cells are not required for this early, surface Ig-mediated event. Antibodies to delta as well as mu, heavy chains (anti-delta and anti-mu) could induce both Ca2+ and 86Rb+ responses. 86Rb+ responders were found within the group of Ca2+ responders, but no quantitative relation was observed between the two responses. In cells expressing both sIgM and sIgD, antibodies to delta heavy chains were more potent than those to mu heavy chains in inducing Ca2+ responses, whereas the opposite pattern was seen with regard to 86Rb+ responses. These results demonstrate that sIgM and sIgD can deliver different biochemical signals to the cell. PMID:3921300
Cao, Aiqin; Li, Hai; Zhou, Yue; Wu, Minhao; Liu, Jingwen
2010-05-28
ACSL3 is a member of the long chain acyl-CoA synthetase (ACSL) family that plays key roles in fatty acid metabolism in various tissues in an isozyme-specific manner. Our previous studies showed that ACSL3 was transcriptionally up-regulated by the cytokine oncostatin M (OSM) in HepG2 cells, accompanied by reduced cellular triglyceride content and enhanced beta-oxidation. In this study, we investigated the molecular mechanism underlying the OSM-induced activation of ACSL3 gene transcription in HepG2 cells. We showed that OSM treatment resulted in a coordinated elevation of mRNA levels of ACSL3 and peroxisome proliferator-activated receptor delta (PPARdelta). The effect of OSM on ACSL3 mRNA expression was inhibited by cellular depletion of PPARdelta. By utilizing a PPARdelta agonist, L165041, we demonstrated that activation of PPARdelta led to increases in ACSL3 promoter activity, mRNA level, and protein level in HepG2 cells. Analysis of the ACSL3 promoter sequence identified two imperfect PPAR-responsive elements (PPRE) located in the ACSL3 promoter region -944 to -915, relative to the transcription start site. The up-regulation of ACSL3 promoter activity by PPARdelta was abolished by deletion of this PPRE-containing region or mutation to disrupt the binding sites. Direct interactions of PPARdelta with ACSL3-PPRE sequences were demonstrated by gel mobility shift and chromatin immunoprecipitation assays. Finally, we provided in vivo evidence showing that activation of PPARdelta by L165041 in hamsters increased ACSL3 mRNA and protein levels in the liver. These new findings define ACSL3 as a novel molecular target of PPARdelta in HepG2 cells and provide a regulatory mechanism for ACSL3 transcription in liver tissue.
Proton spin structure from lattice QCD
Fukugita, M.; Kuramashi, Y.; Okawa, M.; Ukawa, A. ||
1995-09-11
A lattice QCD calculation of the proton matrix element of the flavor singlet axial-vector current is reported. Both the connected and disconnected contributions are calculated, for the latter employing the variant method of wall source without gauge fixing. From simulations in quenched QCD with the Wilson quark action on a 16{sup 3}{times}20 lattice at {beta}=5.7 (the lattice spacing {ital a}{approx}0.14 fm), we find {Delta}{Sigma}={Delta}{ital u}+{Delta}{ital d}+{Delta}{ital s}=+0.638(54){minus}0.347(46){minus}0.109(30)=+0.18(10) with the disconnected contribution to {Delta}{ital u} and {Delta}{ital d} equal to {minus}0.119(44), which is reasonably consistent with the experiment.
Atmospheric Science Data Center
2013-04-15
article title: The Nile River Delta View Larger Image ... of eastern Africa. At the apex of the fertile Nile River Delta is the Egyptian capital city of Cairo. To the west are the Great Pyramids ...
Atmospheric Science Data Center
2013-04-17
article title: Volga Delta and the Caspian Sea View ... appear reddish. A small cloud near the center of the delta separates into red, green, and blue components due to geometric parallax ... include several linear features located near the Volga Delta shoreline. These long, thin lines are artificially maintained shipping ...
Petrie, James R; Shrestha, Pushkar; Mansour, Maged P; Nichols, Peter D; Liu, Qing; Singh, Surinder P
2010-05-01
Long-chain (> or = C20) polyunsaturated fatty acids (LC-PUFA) EPA and DHA (20:5(Delta5,8,11,14,17) and 22:6(Delta4,7,10,13,16,19)) have well-documented health benefits against coronary heart disease, rheumatoid arthritis and other disorders. Currently, the predominant sources of these fatty acids are marine fish and algal oils, but research is being conducted to ensure that a sustainable, land-based production system can be developed. We here describe the metabolic engineering of an artificial pathway that produces 26% EPA in leaf triacylglycerol using a newly-identified Delta6-desaturase from the marine microalga Micromonas pusilla. We also demonstrate that this enzyme appears to function as an acyl-CoA desaturase that has preference for omega3 substrates both in planta and in yeast. Phylogenetic analysis indicates that this desaturase shares highly conserved motifs with previously described acyl-CoA Delta6-desaturases.
Lattices of processes in graphs with inputs
Shakhbazyan, K.V.
1995-09-01
This article is a continuation of others work, presenting a detailed analysis of finite lattices of processes in graphs with input nodes. Lattices of processes in such graphs are studied by representing the lattices in the form of an algebra of pairs. We define the algebra of pairs somewhat generalizing the definition. Let K and D be bounded distributive lattices. A sublattice {delta} {contained_in} K x D is called an algebra of pairs if for all K {element_of} K we have (K, 1{sub D}) {element_of} {delta} and for all d {element_of} D we have (O{sub K}).
Hadronic Resonances from Lattice QCD
John Bulava; Robert Edwards; George Fleming; K. Jimmy Juge; Adam C. Lichtl; Nilmani Mathur; Colin Morningstar; David Richards; Stephen J. Wallace
2007-06-16
The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.
Hadronic Resonances from Lattice QCD
Lichtl, Adam C.; Bulava, John; Morningstar, Colin; Edwards, Robert; Mathur, Nilmani; Richards, David; Fleming, George; Juge, K. Jimmy; Wallace, Stephen J.
2007-10-26
The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.
Ruiz-Ferrer, M; Barroso, N; Antiñolo, G; Aguilar-Reina, J
2004-07-01
Nowadays it is clear that chemokine-chemokine receptor interactions are important in chronic hepatitis C virus (HCV) infection. The objective of the present study was to elucidate the involvement of the CCR5-Delta 32 and CCR2-V64I polymorphisms in the response to the HCV infection, as well as in the histological damage and the outcome of the infection. A cohort of 139 patients with hepatitis C and 100 healthy blood donors were analysed for both polymorphisms using real-time polymerase chain reaction (PCR) and LightCycler technology. We have detected the CCR5-Delta 32 allele in 15 of 278 HCV chromosomes (5.4%) and 15 of 200 control chromosomes (7.5%). The CCR2-V64I allele was present in 24 of 278 HCV chromosomes (8.6%) and 19 of 200 control chromosomes (9.5%). Analysis of the histological parameters showed no statistical significance when comparing the patients carrying the variants vs the cases with the wild-type allele. Our results seem to indicate that the CCR5-Delta 32 and CCR2-V64I polymorphisms are not related to the response to HCV infection, histological damage and outcome of infection in our cohort of Spanish HCV patients.
Results and Frontiers in Lattice Baryon Spectroscopy
Bulava, John; Morningstar, Colin; Edwards, Robert; Richards, David; Fleming, George; Juge, K. Jimmy; Lichtl, Adam C.; Mathur, Nilmani; Wallace, Stephen J.
2007-10-26
The Lattice Hadron Physics Collaboration (LHPC) baryon spectroscopy effort is reviewed. To date the LHPC has performed exploratory Lattice QCD calculations of the low-lying spectrum of Nucleon and Delta baryons. These calculations demonstrate the effectiveness of our method by obtaining the masses of an unprecedented number of excited states with definite quantum numbers. Future work of the project is outlined.
Giraudat, J.; Dennis, M.; Heidmann, T.; Haumont, P.Y.; Lederer, F.; Changeux, J.P.
1987-05-05
The membrane-bound acetylcholine receptor from Torpedo marmorata was photolabeled by the noncompetitive channel blocker (/sup 3/H)chlorpromazine under equilibrium conditions in the presence of the agonist carbamoylcholine. The amount of radioactivity incorporated into all subunits was reduced by addition of phencyclidine, a specific ligand for the high-affinity site for noncompetitive blockers. The labeled ..beta.. chain was purified and digested with trypsin or CNBr, and the resulting fragments were fractionated by high-performance liquid chromatography. Sequence analysis resulted in the identification of Ser-254 and Leu-257 as residues labeled by (/sup 3/H)chlorpromazine in a phencyclidine-sensitive manner. These residues are located in the hydrophobic and potentially transmembrane segment M II of the ..beta.. chain, a region homologous to that containing the chlorpromazine-labeled Ser-262 in the delta chain. These results show that homologous regions of different receptor subunits contribute to the unique high-affinity site for noncompetitive blockers, a finding consistent with the location of this site on the axis of symmetry of the receptor molecule.
Advances in Lattice Quantum Chromodynamics
NASA Astrophysics Data System (ADS)
McGlynn, Greg
In this thesis we make four contributions to the state of the art in numerical lattice simulations of quantum chromodynamics (QCD). First, we present the most detailed investigation yet of the autocorrelations of topological observations in hybrid Monte Carlo simulations of QCD and of the effects of the boundary conditions on these autocorrelations. This results in a numerical criterion for deciding when open boundary conditions are useful for reducing these autocorrelations, which are a major barrier to reliable calculations at fine lattice spacings. Second, we develop a dislocation-enhancing determinant, and demonstrate that it reduces the autocorrelation time of the topological charge. This alleviates problems with slow topological tunneling at fine lattice spacings, enabling simulations on fine lattices to be completed with much less computational effort. Third, we show how to apply the recently developed zMobius technique to hybrid Monte Carlo evolutions with domain wall fermions, achieving nearly a factor of two speedup in the light quark determinant, the single most expensive part of the calculation. The dislocation-enhancing determinant and the zMobius technique have enabled us to begin simulations of fine ensembles with four flavors of dynamical domain wall quarks. Finally, we show how to include the previously-neglected G1 operator in nonperturbative renormalization of the DeltaS = 1 effective weak Hamiltonian on the lattice. This removes an important systematic error in lattice calculations of weak matrix elements, in particular the important K → pipi decay.
Wang, Yan; Li, Jun; Cheng, Zhineng; Li, Qilu; Pan, Xiaohui; Zhang, Ruijie; Liu, Di; Luo, Chunling; Liu, Xiang; Katsoyiannis, Athanasios; Zhang, Gan
2013-03-19
Research on the environmental fate of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in highly industrialized subtropical areas is still scarce. Air, soil, and atmospheric deposition process in the Pearl River Delta of South China were investigated, and the average SCCP and MCCP concentrations were 5.2 μg/sampler (17.69 ng/m(3)) and 4.1 μg/sampler for passive air samples, 18.3 and 59.3 ng/g for soil samples, and 5.0 and 5.3 μg/(m(2)d) for deposition samples, respectively. Influenced by primary sources and the properties of chlorinated paraffins (CPs), a gradient trend of concentrations and a fractionation of composition from more to less industrialized areas were discovered. Intense seasonal variations with high levels in summer air and winter deposition samples indicated that the air and deposition CP levels were controlled mainly by the vapor and particle phase, respectively. Complex environmental processes like volatilization and fractionation resulted in different CP profiles in different environment matrixes and sampling locations, with C(10-11) C(l6-7) and C(14) C(l6-7), C(10-12) C(l6-7) and C(14) C(l6-8), and C(11-12) C(l6-8) and C(14) C(l7-8) dominating in air, soil, and atmospheric deposition, respectively. Shorter-chain and less chlorinated congeners were enriched in air in the less industrialized areas, while longer-chain and higher chlorinated congeners were concentrated in soil in the more industrialized areas. This is suggesting that the gaseous transport of CPs is the dominant mechanism responsible for the higher concentrations of lighter and likely more mobile CPs in the rural areas.
Johnston, Steve; Monney, Claude; Bisogni, Valentina; ...
2016-02-17
Strongly correlated insulators are broadly divided into two classes: Mott–Hubbard insulators, where the insulating gap is driven by the Coulomb repulsion U on the transition-metal cation, and charge-transfer insulators, where the gap is driven by the charge-transfer energy Δ between the cation and the ligand anions. The relative magnitudes of U and Δ determine which class a material belongs to, and subsequently the nature of its low-energy excitations. These energy scales are typically understood through the local chemistry of the active ions. Here we show that the situation is more complex in the low-dimensional charge-transfer insulator Li2CuO2, where Δ hasmore » a large non-electronic component. Combining resonant inelastic X-ray scattering with detailed modelling, we determine how the elementary lattice, charge, spin and orbital excitations are entangled in this material. This results in a large lattice-driven renormalization of Δ, which significantly reshapes the fundamental electronic properties of Li2CuO2.« less
Johnston, Steve; Monney, Claude; Bisogni, Valentina; Zhou, Ke-Jin; Kraus, Roberto; Behr, Günter; Strocov, Vladimir N.; Málek, Jiři; Drechsler, Stefan-Ludwig; Geck, Jochen; Schmitt, Thorsten; van den Brink, Jeroen
2016-02-17
Strongly correlated insulators are broadly divided into two classes: Mott–Hubbard insulators, where the insulating gap is driven by the Coulomb repulsion U on the transition-metal cation, and charge-transfer insulators, where the gap is driven by the charge-transfer energy Δ between the cation and the ligand anions. The relative magnitudes of U and Δ determine which class a material belongs to, and subsequently the nature of its low-energy excitations. These energy scales are typically understood through the local chemistry of the active ions. Here we show that the situation is more complex in the low-dimensional charge-transfer insulator Li_{2}CuO_{2}, where Δ has a large non-electronic component. Combining resonant inelastic X-ray scattering with detailed modelling, we determine how the elementary lattice, charge, spin and orbital excitations are entangled in this material. This results in a large lattice-driven renormalization of Δ, which significantly reshapes the fundamental electronic properties of Li_{2}CuO_{2}.
Johnston, Steve; Monney, Claude; Bisogni, Valentina; Zhou, Ke-Jin; Kraus, Roberto; Behr, Günter; Strocov, Vladimir N.; Málek, Jiři; Drechsler, Stefan-Ludwig; Geck, Jochen; Schmitt, Thorsten; van den Brink, Jeroen
2016-01-01
Strongly correlated insulators are broadly divided into two classes: Mott–Hubbard insulators, where the insulating gap is driven by the Coulomb repulsion U on the transition-metal cation, and charge-transfer insulators, where the gap is driven by the charge-transfer energy Δ between the cation and the ligand anions. The relative magnitudes of U and Δ determine which class a material belongs to, and subsequently the nature of its low-energy excitations. These energy scales are typically understood through the local chemistry of the active ions. Here we show that the situation is more complex in the low-dimensional charge-transfer insulator Li2CuO2, where Δ has a large non-electronic component. Combining resonant inelastic X-ray scattering with detailed modelling, we determine how the elementary lattice, charge, spin and orbital excitations are entangled in this material. This results in a large lattice-driven renormalization of Δ, which significantly reshapes the fundamental electronic properties of Li2CuO2. PMID:26884151
Nonlinear dust-lattice waves: a modified Toda lattice
Cramer, N. F.
2008-09-07
Charged dust grains in a plasma interact with a Coulomb potential, but also with an exponential component to the potential, due to Debye shielding in the background plasma. Here we investigate large-amplitude oscillations and waves in dust-lattices, employing techniques used in Toda lattice analysis. The lattice consists of a linear chain of particles, or a periodic ring as occurs in experimentally observed dust particle clusters. The particle motion has a triangular waveform, and chaotic motion for large amplitude motion of a grain.
Lattice gaugefixing and other optics in lattice gauge theory
Yee, Ken.
1992-06-01
We present results from four projects. In the first, quark and gluon propagators and effective masses and {Delta}I = 1/2 Rule operator matching coefficients are computed numerically in gaugefixed lattice QCD. In the second, the same quantities are evaluated analytically in the strong coupling, N {yields} {infinity} limit. In the third project, the Schwinger model is studied in covariant gauges, where we show that the effective electron mass varies with the gauge parameter and that longitudinal gaugefixing ambiguities affect operator product expansion coefficients (analogous to {Delta}I = 1/2 Rule matching coefficients) determined by matching gauge variant matrix elements. However, we find that matching coefficients even if shifted by the unphysical modes are {xi} invariant. In the fourth project, we show that the strong coupling parallelogram lattice Schwinger model as a different thermodynamic limit than the weak coupling continuum limit. As a function of lattice skewness angle these models span the {Delta} = {minus}1 critical line of 6-vertex models which, in turn, have been identified as c = 1 conformal field theories.
NASA Technical Reports Server (NTRS)
2002-01-01
The streamers of clouds draped over the Gulf of Mexico in this true-color MODIS image from February 27, 2002, suggest that a cold, dry wind was blowing southward over the United States and began to pick up moisture over the Gulf, causing these strips of clouds. That the clouds didn't pick up until some distance from the coastline allowed MODIS to get a perfect view of the dynamic Gulf Coast environment spanning (left to right) Texas, Louisiana, Mississippi, Alabama, and Florida's Western Panhandle. The Mississippi River runs roughly down the center of the image, and is joined in Louisiana by the Red River coming in from the northwest. Over the past 7000 years, the actual delta, where the main river channel empties into the Gulf, has wandered around what we now think of as the Louisiana coast. Considering all the sediment visible in this image, it's not hard to imagine that the river carries about 2.4 billion kilograms of sediment into the Gulf each year. Deposition of some of this sediment has been building up the current delta, called the Birdfoot Delta, for obvious reasons, for about 700 years. The coastal waters are alive with microscopic organisms called phytoplankton, which contain colorful pigments, including chlorophyll, for harvesting sunlight. Beyond the sediment plume off Louisiana, the waters are very dark, which could indicate that a large amount of chlorophyll is present, absorbing lots of sunlight and causing the water to appear dark. Farther south, the waters appear bright blue, which could be a signature of coccolithophores, which use highly reflective calcium carbonate to build scaly coverings for themselves. The brighter offshore waters could also be caused by a blue-green algae called Trichodesmium, an organism that can not only harness carbon dioxide for photosynthesis, but can also take nitrogen from the air and turn it into a form that can be used by living organisms. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC
Soft Phonons in (delta)-Phase Plutonium Near the (delta)-(alpha)' Transition
Xu, R; Wong, J; Zshack, P; Hong, H; Chiang, T
2007-09-13
Plutonium and its alloys exhibit complex phase diagrams that imply anomalous lattice dynamics near phase stability boundaries. Specifically, the TA [111] phonon branch in Ga-stabilized {delta}-Pu at room temperature shows a pronounced soft mode at the zone boundary, which suggests a possible connection to the martensitic transformation from the fcc {delta}-phase to the monoclinic {alpha}{prime}-phase at low temperatures. This work is a study of the lattice dynamics of this system by x-ray thermal diffuse scattering. The results reveal little temperature dependence of the phonon frequencies, thus indicating that kinetic phonon softening is not responsible for this phase transition.
Electromagnetic excitation of the Delta(1232) resonance
V. Pascalutsa; M. Vanderhaeghen; Shin Nan Yang
2006-09-05
We review the description of the lowest-energy nucleon excitation--the Delta(1232)-resonance. Much of the recent effort has been focused on the precision measurements of the nucleon to Delta transition by means of electromagnetic probes. We review the results of those measurements and confront them with the state-of-the-art calculations based on chiral effective-field theories (EFT), lattice QCD, and QCD-inspired models. Some of the theoretical approaches are reviewed in detail. In particular, we describe the chiral EFT of QCD in the energy domain of the Delta-resonance, and its applications to the electromagnetic nucleon-to-Delta transition (gamma N Delta). We also describe the recent dynamical and unitary-isobar models of pion electroproduction which are extensively used in the extraction of the gamma* N Delta form factors from experiment. Furthermore, we discuss the link of the gamma* N Delta form factors to generalized parton distributions (GPDs), as well as the predictions of perturbative QCD for these transition form factors. The present status of understanding the Delta-resonance properties and the nature of its excitation is summarized.
Synthesis and structural chemistry of Au(III)-substituted Ba2YCu3O(7-delta)
NASA Technical Reports Server (NTRS)
Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Banerjea, A.; Hambourger, P. D.
1988-01-01
Gold-substituted superconductors, Ba2Y(Au(x)Cu(1-x))3O(7-delta) (x = 0-0.1) were synthesized. For x = 0.1, there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A) but a 0.06 A c axis expansion to 11.75 A was observed. Substituted gold is found to be trivalent by XPS. Replacing Cu(1) in the copper oxide chain with a slight reordering of oxygen is consistent with c axis expansion. The formal charge of the site remains trivalent; remaining Cu in the chains may be reduced resulting in an oxygen stoichiometry is less than or equal to 7. A small effect on T(sub c)(89 K for x = 0.10) is observed upon gold substitution.
NASA Technical Reports Server (NTRS)
2002-01-01
The Mississippi River delta teems with sediment deposited by the river as it flows into the Gulf of Mexico in this true-color image captured by MODIS on October 15, 2001. The sediment, which is marked by brown swirls in the Gulf, provides nutrients for the bloom of phytoplankton visible as blue-green swirls off the coastline. In the high-resolution image the city of Memphis can be seen in the southwest corner of Tennessee, which is just to left of center at the top of the image. The brown coloration that encompasses Memphis and either side of the river, as flows north to south along the left side of the image, is the river's flood plain. Also visible, in the upper-right hand corner of the image is the southern end of the Appalachian Mountains.
Creutz, M.
1984-01-01
After reviewing some recent developments in supercomputer access, the author discusses a few areas where perturbation theory and lattice gauge simulations make contact. The author concludes with a brief discussion of a deterministic dynamics for the Ising model. This may be useful for numerical studies of nonequilibrium phenomena. 13 references.
Assoud, Abdeljalil; Cui Yanjie; Thomas, Stephanie; Sutherland, Brodie; Kleinke, Holger
2008-08-15
The new materials BaCu{sub {delta}}Ag{sub 2-{delta}}Te{sub 2} (0{<=}{delta}{<=}2) were prepared from the elements at 800 deg. C in evacuated silica tubes. BaAg{sub 2}Te{sub 2} crystallizes in the {alpha}-BaCu{sub 2}S{sub 2} type, space group Pnma, with lattice parameters a=10.8897(3) A, b=4.6084(1) A, c=11.8134(3) A (Z=4). The structure consists of a three-dimensional network of vertex- and edge-condensed AgTe{sub 4} tetrahedra, which includes the Ba{sup 2+} cations in linear channels running along the short b-axis. Half of the Ag atoms participate in an Ag atom zigzag chain extended parallel to the channels. BaAg{sub 2}Te{sub 2} is a p-type semiconductor with large Seebeck coefficient. Within the series BaCu{sub {delta}}Ag{sub 2-{delta}}Te{sub 2}, the electrical conductivity increases and the Seebeck coefficient decreases strongly with increasing Cu content. - Graphical abstract: The tellurides BaCu{sub {delta}}Ag{sub 2-{delta}}Te{sub 2} all crystallize in the {alpha}-BaCu{sub 2}S{sub 2} type. The Ag atoms prefer the M2 sites with short M-M bonds (solid lines). The materials are (degenerate) p-type semiconductors. Higher Ag content reflects itself in higher Seebeck coefficient and lower electrical conductivity.
NASA Technical Reports Server (NTRS)
Wilczek, Frank
1987-01-01
A simple heuristic proof of the Nielsen-Ninomaya theorem is given. A method is proposed whereby the multiplication of fermion species on a lattice is reduced to the minimal doubling, in any dimension, with retention of appropriate chiral symmetries. Also, it is suggested that use of spatially thinned fermion fields is likely to be a useful and appropriate approximation in QCD - in any case, it is a self-checking one.
Manciu, M.; Sen, S.; Hurd, A.J.
1999-04-12
The authors consider a chain of elastic (Hertzian) grains that repel upon contact according to the potential V = a{delta}{sup u}, u > 2, where {delta} is the overlap between the grains. They present numerical and analytical results to show that an impulse initiated at an end of a chain of Hertzian grains in contact eventually propagates as a soliton for all n > 2 and that no solitons are possible for n {le} 2. Unlike continuous, they find that colliding solitons in discrete media initiative multiple weak solitons at the point of crossing.
NASA Astrophysics Data System (ADS)
Ousley, Gilbert W., Sr.
1991-12-01
The utilization of the Delta 2 as the vehicle for launching Aristoteles into its near Sun synchronous orbit is addressed. Delta is NASA's most reliable launch vehicle and is well suited for placing the present Aristoteles spacecraft into a 400 m circular orbit. A summary of some of the Delta 2 flight parameters is presented. Diagrams of a typical Delta 2 two stage separation are included along with statistics on delta reliability and launch plans.
Casimir effect for Dirac lattices
NASA Astrophysics Data System (ADS)
Bordag, M.; Pirozhenko, I. G.
2017-03-01
We consider polarizable sheets, which recently received some attention, especially in the context of the dispersion interaction of thin sheets like graphene. These sheets are modeled by a collection of delta function potentials and resemble zero-range potentials, which are known in quantum mechanics. We develop a theoretical description and apply the so-called TGTG formula to calculate the interaction of two such lattices. Thereby, we make use of the formulation of the scattering of waves off such sheets provided earlier. We consider all limiting cases, providing a link to earlier results. Also, we discuss the relation to the pairwise summation method.
A new approach for Delta form factors
C. Aubin, K. Orginos
2011-10-01
We discuss a new approach to reducing excited state contributions from two- and three-point correlation functions in lattice simulations. For the purposes of this talk, we focus on the Delta(1232) resonance and discuss how this new method reduces excited state contamination from two-point functions and mention how this will be applied to three-point functions to extract hadronic form factors.
delta-Hexachlorocyclohexane (delta-HCH)
Integrated Risk Information System (IRIS)
delta - Hexachlorocyclohexane ( delta - HCH ) ; CASRN 319 - 86 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Ass
... this page: //medlineplus.gov/ency/article/000216.htm Delta agent (Hepatitis D) To use the sharing features on this page, please enable JavaScript. Delta agent is a type of virus called hepatitis ...
Quantum transport in d-dimensional lattices
Manzano, Daniel; Chuang, Chern; Cao, Jianshu
2016-04-28
We show that both fermionic and bosonic uniform d-dimensional lattices can be reduced to a set of independent one-dimensional chains. This reduction leads to the expression for ballistic energy fluxes in uniform fermionic and bosonic lattices. By the use of the Jordan–Wigner transformation we can extend our analysis to spin lattices, proving the coexistence of both ballistic and non-ballistic subspaces in any dimension and for any system size. Lastly, we then relate the nature of transport to the number of excitations in the homogeneous spin lattice, indicating that a single excitation always propagates ballistically and that the non-ballistic behaviour ofmore » uniform spin lattices is a consequence of the interaction between different excitations.« less
Delta + 27 homozygosis in a Sicilian family.
Renda, M; Piazza, T; Ciaccio, C; Maggio, A
1992-01-01
During a screening program to identify at risk couples for beta-thalassemia first-trimester prenatal diagnosis, we were able to detect, by polymerase chain reaction (PCR) and direct genomic sequencing of the PCR product, a homozygosis for the G-T substitution at the first nucleotide of codon 27 of the delta-globin gene in a pregnant Sicilian woman. The possibility of showing an interaction between delta and beta thalassemia is relevant for a thalassemia prevention program because it may hide a beta-thal carrier state.
Excited state baryon spectroscopy from lattice QCD
Robert G. Edwards; Dudek, Jozef J.; Richards, David G.; ...
2011-10-31
Here, we present a calculation of the Nucleon and Delta excited state spectrum on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including $J = 7/2$, of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of $SU(6) Ⓧ O(3)$ representations and a counting ofmore » levels that is consistent with the non-relativistic $qqq$ constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the "missing resonance problem" and shows no signs of parity doubling of states.« less
Excited state baryon spectroscopy from lattice QCD
Robert G. Edwards; Dudek, Jozef J.; Richards, David G.; Wallace, Stephen J.
2011-10-31
Here, we present a calculation of the Nucleon and Delta excited state spectrum on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including $J = 7/2$, of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of $SU(6) Ⓧ O(3)$ representations and a counting of levels that is consistent with the non-relativistic $qqq$ constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the "missing resonance problem" and shows no signs of parity doubling of states.
Recombinative events of the T cell antigen receptor delta gene in peripheral T cell lymphomas.
Kanavaros, P; Farcet, J P; Gaulard, P; Haioun, C; Divine, M; Le Couedic, J P; Lefranc, M P; Reyes, F
1991-01-01
Recombinative events of the T cell antigen receptor (TCR) delta-chain gene were studied in 37 cases of peripheral T cell lymphoma (PTCL) and related to their clinical presentation and the expression of the alpha beta or gamma delta heterodimers as determined by immunostaining of frozen tissue samples. There were 22 cases of alpha beta, 5 cases of gamma delta, and 10 cases of silent TCR expressing neither the alpha beta nor gamma delta TCR. 5 different probes were used to examine the delta locus. The 22 cases of alpha beta PTCL displayed biallelic and monoallelic deletions; a monoallelic V delta 1 J delta 1 rearrangement was observed in 1 case and a monoallelic germ line configuration in 7 cases. The 5 cases of gamma delta PTCL displayed biallelic rearrangements: the productive rearrangements could be ascribed to V delta 1J delta 1 joining in 3 cases and VJ delta 1 joining in 2 cases according to the combined pattern of DNA hybridization with the appropriate probes and of cell reactivity with the TCR delta-1, delta TCS-1, and anti-V delta 2 monoclonal antibodies. In the VJ delta 1 joining, the rearranged V segments were located between V delta 1 and V delta 2. Interestingly, in the third group of 10 cases of silent PTCL, 5 cases were found to have a TCR gene configuration identical to that in the TCR alpha beta PTCL, as demonstrated by biallelic delta gene deletion. These 5 cases were CD3 positive. The 5 remaining cases showed a monoallelic delta gene rearrangement with a monoallelic germ line configuration in 4 and a monoallelic deletion in 1. Four of these cases were CD3 negative, which was consistent with an immature genotype the TCR commitent of which could not be ascertained. Finally, TCR gamma delta PTCL consisted of a distinct clinical morphological and molecular entity whereas TCR alpha beta and silent PTCL had a similar presentation. Images PMID:1991851
Nelson, E.A.; Christensen, E.J.; Mackey, H.E.; Sharitz, R.R.; Jensen, J.R.; Hodgson, M.E.
1984-02-01
Since 1954, cooling water discharges from K Reactor ({anti X} = 370 cfs {at} 59 C) to Pen Branch have altered vegetation and deposited sediment in the Savannah River Swamp forming the Pen Branch delta. Currently, the delta covers over 300 acres and continues to expand at a rate of about 16 acres/yr. Examination of delta expansion can provide important information on environmental impacts to wetlands exposed to elevated temperature and flow conditions. To assess the current status and predict future expansion of the Pen Branch delta, historic aerial photographs were analyzed using both basic photo interpretation and computer techniques to provide the following information: (1) past and current expansion rates; (2) location and changes of impacted areas; (3) total acreage presently affected. Delta acreage changes were then compared to historic reactor discharge temperature and flow data to see if expansion rate variations could be related to reactor operations.
Renormalization transformation of periodic and aperiodic lattices
Macia, Enrique; Rodriguez-Oliveros, Rogelio
2006-10-01
In this work we introduce a similarity transformation acting on transfer matrices describing the propagation of elementary excitations through either periodic or Fibonacci lattices. The proposed transformation can act at two different scale lengths. At the atomic scale the transformation allows one to express the systems' global transfer matrix in terms of an equivalent on-site model one. Correlation effects among different hopping terms are described by a series of local phase factors in that case. When acting on larger scale lengths, corresponding to short segments of the original lattice, the similarity transformation can be properly regarded as describing an effective renormalization of the chain. The nature of the resulting renormalized lattice significantly depends on the kind of order (i.e., periodic or quasiperiodic) of the original lattice, expressing a delicate balance between chemical complexity and topological order as a consequence of the renormalization process.
Palmer, R.B.
1987-05-01
This paper looks at, and compares three types of damping ring lattices: conventional, wiggler lattice with finite ..cap alpha.., wiggler lattice with ..cap alpha.. = 0, and observes the attainable equilibrium emittances for the three cases assuming a constraint on the attainable longitudinal impedance of 0.2 ohms. The emittance obtained are roughly in the ratio 4:2:1 for these cases.
Sinniah, M; Dimitrakakis, M; Tan, D S
1986-06-01
Sera from one hundred and fifty nine Malaysian individuals were screened for the prevalence of delta markers. These included 15 HBsAg positive homosexuals, 16 acute hepatitis B cases, 9 chronic hepatitis B patients, 13 healthy HBsAg carriers and 106 intravenous (i.v.) drug abusers, of whom 27 were positive for HBsAg only and the rest were anti-HBc IgG positive but HBsAg negative. The prevalence of delta markers in the homosexuals was found to be 6.7%, in the HBsAg positive drug abusers 17.8%, in acute hepatitis B cases 12.5%. No evidence of delta infection was detected in healthy HBsAg carriers, chronic hepatitis B cases and HBsAg negative i.v. drug abusers. With reference to i.v. drug abusers, the prevalence of delta markers was higher in Malays (23%) than in Chinese (7%) although the latter had a higher HBsAg carrier rate. Although the HBsAg carrier rate in the homosexuals was high, their delta prevalence rate was low as compared to drug abusers. In Malaysia, as in other non-endemic regions, hepatitis delta virus transmission appeared to occur mainly via the parenteral and sexual routes. This is the first time in Malaysia that a reservoir of delta infection has been demonstrated in certain groups of the population at high risk for hepatitis B.
NASA Technical Reports Server (NTRS)
1984-01-01
The Nile River Delta of Egypt (30.0N, 31.0E) irrigated by the Nile River and its many distributaries, is some of the richest farm land in the world and home to some 45 million people, over half of Egypt's population. The capital city of Cairo is at the apex of the delta. Just across the river from Cairo can be seen the ancient three big pyramids and sphinx at Giza and the Suez Canal is just to the right of the delta.
NASA Technical Reports Server (NTRS)
Guzik, J. A.
1998-01-01
The purpose of asteroseismology is not only to derive the internal structure of individual stars from their observed oscillation frequencies, but also to test and extend one's understanding of the physics of matter under the extremes of temperature, density, and pressure found in stellar interiors. In this review, the author hopes to point out what one can learn about the Sun by studying (delta) Scuti stars, as well as what one can learn about stars more massive or evolved than the Sun. He discusses some of the difficulties in theoretical approaches to asteroseismology for (delta) Scuti stars, using FG Vir, (delta) Scuti, and CD-24(degree) 7599 as examples.
ERIC Educational Resources Information Center
Reeder, Richard J.; Calhoun, Samuel D.
2002-01-01
The Lower Mississippi Delta region, especially the rural Delta, faces many economic challenges. The rural Delta has received much federal aid in basic income support and funding for human resource development, but less for community resource programs, which are important for economic development. Federal aid to the Delta is analyzed in terms of…
Doping of Semiconducting Atomic Chains
NASA Technical Reports Server (NTRS)
Toshishige, Yamada; Kutler, Paul (Technical Monitor)
1997-01-01
Due to the rapid progress in atom manipulation technology, atomic chain electronics would not be a dream, where foreign atoms are placed on a substrate to form a chain, and its electronic properties are designed by controlling the lattice constant d. It has been shown theoretically that a Si atomic chain is metallic regardless of d and that a Mg atomic chain is semiconducting or insulating with a band gap modified with d. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along the chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome this dilemma, we may place a dopant atom beside the chain at every N lattice periods (N > 1). Because of the periodic arrangement of dopant atoms, we can avoid the unwanted Anderson localization. Moreover, since the dopant atoms do not constitute the chain, the overlap interaction between them is minimized, and the band structure modification can be made smallest. Some tight-binding results will be discussed to demonstrate the present idea.
Structural chemistry of Au(III)-substituted Ba2YCu3O(7-delta)
NASA Technical Reports Server (NTRS)
Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Hambourger, P. D.
1988-01-01
A series of gold-substituted perovskite superconductors Ba2Y(Cu/1-x/Aux)3O(7-delta)(x = 0-0.1) was synthesized. For x = 0.1, there was no change in the a and b lattice parameters (a = 3.826 A and b = 3.889 A), but a 0.06 A c-axis expansion to 11.75 A was observed. Substituted gold was found to be trivalent by X-ray photoelectron spectroscopy. Replacing Cu(1) in the copper oxide chain with a slight reordering of oxygen is consistent with c-axis expansion. The formal charge of the site remains trivalent, while remaining Cu in the chains is reduced to Cu(I), resulting in an oxygen stoichiometry of less than 7. Finally, no large effect on Tc is observed (Tc = 89 K for x = 0.10), in contrast to the effect of a number of other metal ion dopants. These results are discussed relative to the chemistry of Au(III) and to the use of the metal in structures containing gold and ceramic superconductors.
Musumeci, S; Romeo, M A; Pizzarelli, G; Schilirò, G; Russo, G
1983-01-01
A case of double heterozygosity for A gamma delta beta-thalassaemia and A gamma G gamma delta beta-thalassaemia was found during a screening programme in Sicily. The proband, a 4-year-old girl, showed a clinical picture of thalassaemia intermedia. Hb F (85.12% by the Singer method) was G gamma A gamma type. The parents and the brother were delta beta-thalassaemia carriers. Structural analysis of Hb F showed both G gamma and A gamma chains in the father, but only A gamma chains in the mother. Images PMID:6188831
Nonlinear, unsteady aerodynamic loads on rectangular and delta wings
NASA Technical Reports Server (NTRS)
Atta, E. H.; Kandil, O. A.; Mook, D. T.; Nayfeh, A. H.
1977-01-01
Nonlinear unsteady aerodynamic loads on rectangular and delta wings in an incompressible flow are calculated by using an unsteady vortex-lattice model. Examples include flows past fixed wings in unsteady uniform streams and flows past wings undergoing unsteady motions. The unsteadiness may be due to gusty winds or pitching oscillations. The present technique establishes a reliable approach which can be utilized in the analysis of problems associated with the dynamics and aeroelasticity of wings within a wide range of angles of attack.
NASA Technical Reports Server (NTRS)
1998-01-01
Final preparations for lift off of the DELTA II Mars Pathfinder Rocket are shown. Activities include loading the liquid oxygen, completing the construction of the Rover, and placing the Rover into the Lander. After the countdown, important visual events include the launch of the Delta Rocket, burnout and separation of the three Solid Rocket Boosters, and the main engine cutoff. The cutoff of the main engine marks the beginning of the second stage engine. After the completion of the second stage, the third stage engine ignites and then cuts off. Once the third stage engine cuts off spacecraft separation occurs.
Dissipative photonic lattice solitons.
Ultanir, Erdem A; Stegeman, George I; Christodoulides, Demetrios N
2004-04-15
We show that discrete dissipative optical lattice solitons are possible in waveguide array configurations that involve periodically patterned semiconductor optical amplifiers and saturable absorbers. The characteristics of these low-power soliton states are investigated, and their propagation constant eigenvalues are mapped on Floquet-Bloch band diagrams. The prospect of observing such low-power dissipative lattice solitons is discussed in detail.
Comparison of aquatic food chains using nitrogen isotopes.
Cabana, G; Rasmussen, J B
1996-01-01
Recent studies have shown the utility of delta(15)N to model trophic structure and contaminant bioaccumulation in aquatic food webs. However, cross-system comparisons in delta(15)N can be complicated by differences in delta(15)N at the base of the food chain. Such baseline variation in delta(15)N is difficult to resolve using plankton because of the large temporal variability in the delta(15)N of small organisms that have fast nitrogen turnover. Comparisons using large primary consumers, which have stable tissue isotopic signatures because of their slower nitrogen turnover, show that delta(15)N increases markedly with the human population density in the lake watershed. This shift in delta(15)N likely reflects the high delta(15)N of human sewage. Correcting for this baseline variation in delta(15)N, we report that, contrary to expectations based on previous food-web analysis, the food chains leading up to fish varied by about only one trophic level among the 40 lakes studied. Our results also suggest that the delta(15)N signatures of nitrogen at the base of the food chain will provide a useful tool in the assessment of anthropogenic nutrient inputs. Images Fig. 4 PMID:8855268
Cramer, E.M.; Ellinger, F.H.; Land. C.C.
1960-03-22
Delta-phase plutonium alloys were developed suitable for use as reactor fuels. The alloys consist of from 1 to 4 at.% zinc and the balance plutonium. The alloys have good neutronic, corrosion, and fabrication characteristics snd possess good dimensional characteristics throughout an operating temperature range from 300 to 490 deg C.
ERIC Educational Resources Information Center
Luyben, William L.
2007-01-01
Students frequently confuse and incorrectly apply the several "deltas" that are used in chemical engineering. The deltas come in three different flavors: "out minus in", "big minus little" and "now versus then." The first applies to a change in a stream property as the stream flows through a process. For example, the "[delta]H" in an energy…
Courant, E.D.; Garren, A.A.
1985-10-01
A realistic, distributed interaction region (IR) lattice has been designed that includes new components discussed in the June 1985 lattice workshop. Unlike the test lattices, the lattice presented here includes utility straights and the mechanism for crossing the beams in the experimental straights. Moreover, both the phase trombones and the dispersion suppressors contain the same bending as the normal cells. Vertically separated beams and 6 Tesla, 1-in-1 magnets are assumed. Since the cells are 200 meters long, and have 60 degree phase advance, this lattice has been named RLD1, in analogy with the corresponding test lattice, TLD1. The quadrupole gradient is 136 tesla/meter in the cells, and has similar values in other quadrupoles except in those in the IR`s, where the maximum gradient is 245 tesla/meter. RLD1 has distributed IR`s; however, clustered realistic lattices can easily be assembled from the same components, as was recently done in a version that utilizes the same type of experimental and utility straights as those of RLD1.
Superalloy Lattice Block Structures
NASA Technical Reports Server (NTRS)
Whittenberger, J. D.; Nathal, M. V.; Hebsur, M. G.; Kraus, D. L.
2003-01-01
In their simplest form, lattice block panels are produced by direct casting and result in lightweight, fully triangulated truss-like configurations which provide strength and stiffness [2]. The earliest realizations of lattice block were made from A1 and steels, primarily under funding from the US Navy [3]. This work also showed that the mechanical efficiency (eg., specific stiffness) of lattice block structures approached that of honeycomb structures [2]. The lattice architectures are also less anisotropic, and the investment casting route should provide a large advantage in cost and temperature capability over honeycombs which are limited to alloys that can be processed into foils. Based on this early work, a program was initiated to determine the feasibility of extending the high temperature superalloy lattice block [3]. The objective of this effort was to provide an alternative to intermetallics and composites in achieving a lightweight high temperature structure without sacrificing the damage tolerance and moderate cost inherent in superalloys. To establish the feasibility of the superalloy lattice block concept, work was performed in conjunction with JAMCORP, Inc. Billerica, MA, to produce a number of lattice block panels from both IN71 8 and Mar-M247.
Quasicrystallography from Bn lattices
NASA Astrophysics Data System (ADS)
Koca, M.; Koca, N. O.; Al-Mukhaini, A.; Al-Qanabi, A.
2014-11-01
We present a group theoretical analysis of the hypercubic lattice described by the affine Coxeter-Weyl group Wa (Bn). An h-fold symmetric quasicrystal structure follows from the hyperqubic lattice whose point group is described by the Coxeter-Weyl group W (Bn) with the Coxeter number h=2n. Higher dimensional cubic lattices are explicitly constructed for n = 4,5,6 by identifying their rank-3 Coxeter subgroups and maximal dihedral subgroups. Decomposition of their Voronoi cells under the respective rank-3 subgroups W (A3), W (H2)×W (A1) and W (H3)lead to the rhombic dodecahedron, rhombic icosahedron and rhombic triacontahedron respectively. Projection of the lattice B4 describes a quasicrystal structure with 8-fold symmetry. The B5 lattice leads to quasicrystals with both 5fold and 10 fold symmetries. The lattice B6 projects on a 12-fold symmetric quasicrystal as well as a 3D icosahedral quasicrystal depending on the choice of subspace of projections. The projected sets of lattice points are compatible with the available experimental data.
Jammed lattice sphere packings
NASA Astrophysics Data System (ADS)
Kallus, Yoav; Marcotte, Étienne; Torquato, Salvatore
2013-12-01
We generate and study an ensemble of isostatic jammed hard-sphere lattices. These lattices are obtained by compression of a periodic system with an adaptive unit cell containing a single sphere until the point of mechanical stability. We present detailed numerical data about the densities, pair correlations, force distributions, and structure factors of such lattices. We show that this model retains many of the crucial structural features of the classical hard-sphere model and propose it as a model for the jamming and glass transitions that enables exploration of much higher dimensions than are usually accessible.
DELTAS: A new Global Delta Sustainability Initiative (Invited)
NASA Astrophysics Data System (ADS)
Foufoula-Georgiou, E.
2013-12-01
Deltas are economic and environmental hotspots, food baskets for many nations, home to a large part of the world population, and hosts of exceptional biodiversity and rich ecosystems. Deltas, being at the land-water interface, are international, regional, and local transport hubs, thus providing the basis for intense economic activities. Yet, deltas are deteriorating at an alarming rate as 'victims' of human actions (e.g. water and sediment reduction due to upstream basin development), climatic impacts (e.g. sea level rise and flooding from rivers and intense tropical storms), and local exploration (e.g. sand or aggregates, groundwater and hydrocarbon extraction). Although many efforts exist on individual deltas around the world, a comprehensive global delta sustainability initiative that promotes awareness, science integration, data and knowledge sharing, and development of decision support tools for an effective dialogue between scientists, managers and policy makers is lacking. Recently, the international scientific community proposed to establish the International Year of Deltas (IYD) to serve as the beginning of such a Global Delta Sustainability Initiative. The IYD was proposed as a year to: (1) increase awareness and attention to the value and vulnerability of deltas worldwide; (2) promote and enhance international and regional cooperation at the scientific, policy, and stakeholder level; and (3) serve as a launching pad for a 10-year committed effort to understand deltas as complex socio-ecological systems and ensure preparedness in protecting and restoring them in a rapidly changing environment. In this talk, the vision for such an international coordinated effort on delta sustainability will be presented as developed by a large number of international experts and recently funded through the Belmont Forum International Opportunities Fund. Participating countries include: U.S., France, Germany, U.K., India, Japan, Netherlands, Norway, Brazil, Bangladesh
Collider lattice position changes from the ``blue book`` to the 10F lattice
Ketcham, L.; Syphers, M.
1992-01-01
GREV4 was the lattice used by RTK to generate the numbers that appear in the ``blue book`` which is the basis for the present footprint. The 1000 foot wide band allows for inevitable design iterations. The first iteration, GREV5 was the lattice used for the baseline costs and descriptions. If the west utility region (at which point the Collider is tied to the injector chain) is held fixed, the coordinates of the GREV4 and GREV5 rings differ by several tens of meters in some places. This is all within the footprint defined in the ``blue book.``
Collider lattice position changes from the blue book'' to the 10F lattice
Ketcham, L.; Syphers, M.
1992-01-01
GREV4 was the lattice used by RTK to generate the numbers that appear in the blue book'' which is the basis for the present footprint. The 1000 foot wide band allows for inevitable design iterations. The first iteration, GREV5 was the lattice used for the baseline costs and descriptions. If the west utility region (at which point the Collider is tied to the injector chain) is held fixed, the coordinates of the GREV4 and GREV5 rings differ by several tens of meters in some places. This is all within the footprint defined in the blue book.''
Planar Arrays on Lattices and Their FFT Steering, a Primer
2011-04-29
by a tall B, so we cannot properly term it the inverse of B. A different terminology is called for. The Moore - Penrose pseudoinverse of any matrix B...lattice and using terminated guard elements at the array periphery. The second is multi-beam phase-shift steering of such arrays using generalized Cooley...FFT realization of the general multidimensional DFT for beam steering is developed using nested sublattice chains. The needed lattice basics are
Melting of the Abrikosov flux lattice in anisotropic superconductors
NASA Technical Reports Server (NTRS)
Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.
1992-01-01
It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.
Quantum transport in d-dimensional lattices
Manzano, Daniel; Chuang, Chern; Cao, Jianshu
2016-04-28
We show that both fermionic and bosonic uniform d-dimensional lattices can be reduced to a set of independent one-dimensional chains. This reduction leads to the expression for ballistic energy fluxes in uniform fermionic and bosonic lattices. By the use of the Jordan–Wigner transformation we can extend our analysis to spin lattices, proving the coexistence of both ballistic and non-ballistic subspaces in any dimension and for any system size. Lastly, we then relate the nature of transport to the number of excitations in the homogeneous spin lattice, indicating that a single excitation always propagates ballistically and that the non-ballistic behaviour of uniform spin lattices is a consequence of the interaction between different excitations.
A LOW GAMMA_T INJECTION LATTICE FOR POLARIZED PROTONS IN RHIC
MONTAG,C.
2007-06-25
Polarized protons are injected into the Relativistic Heavy Jon Collider (RHIC) just above transition energy. When installation of a cold partial Siberian snake in the AGS required lowering the injection energy by {Delta}{gamma} = 0.56, the transition energy in RHIC had to be lowered accordingly to ensure proper longitudinal matching. This paper presents lattice modifications implemented to lower the transition energy by {Delta}{gamma}{sub t} = 0.8.
Superalloy Lattice Block Structures
NASA Technical Reports Server (NTRS)
Nathal, M. V.; Whittenberger, J. D.; Hebsur, M. G.; Kantzos, P. T.; Krause, D. L.
2004-01-01
Initial investigations of investment cast superalloy lattice block suggest that this technology will yield a low cost approach to utilize the high temperature strength and environmental resistance of superalloys in lightweight, damage tolerant structural configurations. Work to date has demonstrated that relatively large superalloy lattice block panels can be successfully investment cast from both IN-718 and Mar-M247. These castings exhibited mechanical properties consistent with the strength of the same superalloys measured from more conventional castings. The lattice block structure also accommodates significant deformation without failure, and is defect tolerant in fatigue. The potential of lattice block structures opens new opportunities for the use of superalloys in future generations of aircraft applications that demand strength and environmental resistance at elevated temperatures along with low weight.
Root lattices and quasicrystals
NASA Astrophysics Data System (ADS)
Baake, M.; Joseph, D.; Kramer, P.; Schlottmann, M.
1990-10-01
It is shown that root lattices and their reciprocals might serve as the right pool for the construction of quasicrystalline structure models. All noncrystallographic symmetries observed so far are covered in minimal embedding with maximal symmetry.
Root lattices and quasicrystals
NASA Astrophysics Data System (ADS)
Baake, M.; Joseph, D.; Kramer, P.; Schlottmann, M.
1990-10-01
It is shown how root lattices and their reciprocals might serve as the right pool for the construction of quasicrystalline structure models. All non-periodic symmetries observed so far are covered in minimal embedding with maximal symmetry.
ORGINOS,K.
2003-01-07
I review the current status of hadronic structure computations on the lattice. I describe the basic lattice techniques and difficulties and present some of the latest lattice results; in particular recent results of the RBC group using domain wall fermions are also discussed. In conclusion, lattice computations can play an important role in understanding the hadronic structure and the fundamental properties of Quantum Chromodynamics (QCD). Although some difficulties still exist, several significant steps have been made. Advances in computer technology are expected to play a significant role in pushing these computations closer to the chiral limit and in including dynamical fermions. RBC has already begun preliminary dynamical domain wall fermion computations [49] which we expect to be pushed forward with the arrival of QCD0C. In the near future, we also expect to complete the non-perturbative renormalization of the relevant derivative operators in quenched QCD.
NASA Astrophysics Data System (ADS)
Weidner, Carrie; Yu, Hoon; Anderson, Dana
2016-05-01
In this work, we report on progress towards performing interferometry using atoms trapped in an optical lattice. That is, we start with atoms in the ground state of an optical lattice potential V(x) =V0cos [ 2 kx + ϕ(t) ] , and by a prescribed phase function ϕ(t) , transform from one atomic wavefunction to another. In this way, we implement the standard interferometric sequence of beam splitting, propagation, reflection, reverse propagation, and recombination. Through the use of optimal control techniques, we have computationally demonstrated a scalable accelerometer that provides information on the sign of the applied acceleration. Extension of this idea to a two-dimensional shaken-lattice-based gyroscope is discussed. In addition, we report on the experimental implementation of the shaken lattice system.
Understanding pesticides in California's Delta
Kuivila, Kathryn; Orlando, James L.
2012-01-01
The Sacramento-San Joaquin River Delta (Delta) is the hub of California’s water system and also an important habitat for imperiled fish and wildlife. Aquatic organisms are exposed to mixtures of pesticides that flow through the maze of Delta water channels from sources including agricultural, landscape, and urban pest-control applications. While we do not know all of the effects pesticides have on the ecosystem, there is evidence that they cause some damage to organisms in the Delta. Decades of USGS research have provided a good understanding of when, where, and how pesticides enter the Delta. However, pesticide use is continually changing. New field studies and methods are needed so that scientists can analyze which pesticides are present in the Delta, and at what concentrations, enabling them to estimate exposure and ultimate effects on organisms. Continuing research will provide resource managers and stakeholders with crucial information to manage the Delta wisely.
Martian deltas: Morphology and distribution
NASA Technical Reports Server (NTRS)
Rice, J. W., Jr.; Scott, D. H.
1993-01-01
Recent detailed mapping has revealed numerous examples of Martian deltas. The location and morphology of these deltas are described. Factors that contribute to delta morphology are river regime, coastal processes, structural stability, and climate. The largest delta systems on Mars are located near the mouths of Maja, Maumee, Vedra, Ma'adim, Kasei, and Brazos Valles. There are also several smaller-scale deltas emplaced near channel mouths situated in Ismenius Lacus, Memnonia, and Arabia. Delta morphology was used to reconstruct type, quantity, and sediment load size transported by the debouching channel systems. Methods initially developed for terrestrial systems were used to gain information on the relationships between Martian delta morphology, river regime, and coastal processes.
Automated Lattice Perturbation Theory
Monahan, Christopher
2014-11-01
I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.
Castle, Toen; Sussman, Daniel M; Tanis, Michael; Kamien, Randall D
2016-09-01
Kirigami uses bending, folding, cutting, and pasting to create complex three-dimensional (3D) structures from a flat sheet. In the case of lattice kirigami, this cutting and rejoining introduces defects into an underlying 2D lattice in the form of points of nonzero Gaussian curvature. A set of simple rules was previously used to generate a wide variety of stepped structures; we now pare back these rules to their minimum. This allows us to describe a set of techniques that unify a wide variety of cut-and-paste actions under the rubric of lattice kirigami, including adding new material and rejoining material across arbitrary cuts in the sheet. We also explore the use of more complex lattices and the different structures that consequently arise. Regardless of the choice of lattice, creating complex structures may require multiple overlapping kirigami cuts, where subsequent cuts are not performed on a locally flat lattice. Our additive kirigami method describes such cuts, providing a simple methodology and a set of techniques to build a huge variety of complex 3D shapes.
Castle, Toen; Sussman, Daniel M.; Tanis, Michael; Kamien, Randall D.
2016-01-01
Kirigami uses bending, folding, cutting, and pasting to create complex three-dimensional (3D) structures from a flat sheet. In the case of lattice kirigami, this cutting and rejoining introduces defects into an underlying 2D lattice in the form of points of nonzero Gaussian curvature. A set of simple rules was previously used to generate a wide variety of stepped structures; we now pare back these rules to their minimum. This allows us to describe a set of techniques that unify a wide variety of cut-and-paste actions under the rubric of lattice kirigami, including adding new material and rejoining material across arbitrary cuts in the sheet. We also explore the use of more complex lattices and the different structures that consequently arise. Regardless of the choice of lattice, creating complex structures may require multiple overlapping kirigami cuts, where subsequent cuts are not performed on a locally flat lattice. Our additive kirigami method describes such cuts, providing a simple methodology and a set of techniques to build a huge variety of complex 3D shapes. PMID:27679822
Delta-doping of Semiconductors
NASA Astrophysics Data System (ADS)
Schubert, E. F.
2005-08-01
Part I: 1. Introduction E. F. Schubert; Part II: 2. Electronic structure of delta-doped semiconductors C. R. Proetto; Part III: 3. Recent progress in delta-like confinement of impurities in GaAs K. H. Ploog; 4. Flow-rate modulation epitaxy (FME) of III-V semiconductors T. Makimoto and Y. Horikoshi; 5. Gas source molecular beam epitaxy (MBE) of delta-doped III-V semiconductors D. Ritter; 6. Solid phase epitaxy for delta-doping in silicon I. Eisele; 7. Low temperature MBE of silicon H.-J. Gossmann; Part IV: 8. Secondary ion mass spectrometry of delta-doped semiconductors H. S. Luftmann; 9. Capacitance-voltage profiling E. F. Schubert; 10. Redistribution of impurities in III-V semiconductors E. F. Schubert; 11. Dopant diffusion and segregation in delta-doped silicon films H.-J. Gossmann; 12. Characterisation of silicon and delta-doped structures in GaAs R. C. Newman; 13. The DX-center in silicon delta-doped GaAs and AlxGa1-xAs P. M. Koenraad; Part V: 14. Luminescence and ellipsometry spectroscopy H. Yao and E. F. Schubert; 15. Photoluminescence and Raman spectroscopy of single delta-doped III-V semiconductor heterostructures J. Wagner and D. Richards; 16. Electron transport in delta-doped quantum wells W. T. Masselink; 17. Electron mobility in delta-doped layers P. M. Koenraad; 18. Hot electrons in delta-doped GaAs M. Asche; 19. Ordered delta-doping R. L. Headrick, L. C. Feldman and B. E. Weir; Part IV: 20. Delta-doped channel III-V field effect transistors (FETs) W.-P. Hong; 21. Selectively doped heterostructure devices E. F. Schubert; 22. Silicon atomic layer doping FET K. Nakagawa and K. Yamaguchi; 23. Planar doped barrier devices R. J. Malik; 24. Silicon interband and intersubband photodetectors I. Eisele; 25. Doping superlattice devices E. F. Schubert.
Chorin, Alexandre J.
2007-12-12
A sampling method for spin systems is presented. The spin lattice is written as the union of a nested sequence of sublattices, all but the last with conditionally independent spins, which are sampled in succession using their marginals. The marginals are computed concurrently by a fast algorithm; errors in the evaluation of the marginals are offset by weights. There are no Markov chains and each sample is independent of the previous ones; the cost of a sample is proportional to the number of spins (but the number of samples needed for good statistics may grow with array size). The examples include the Edwards-Anderson spin glass in three dimensions.
Extension of a vortex-lattice method to include the effects of leading-edge separation
NASA Technical Reports Server (NTRS)
Mook, D. T.; Maddox, S. A.
1974-01-01
Vortex-lattice methods have been used successfully to obtain the aerodynamic coefficients of lifting surfaces without leading-edge separation. It is shown how an existing vortex-lattice method can be modified to include the effects of leading-edge separation. The modified version is then used to calculate the aerodynamic loads on a highly swept delta wing. The results are compared with Peckham's (1958) experimental data.
Experimental evidence for flux-lattice melting. [in high-Tc superconductors
NASA Technical Reports Server (NTRS)
Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.
1991-01-01
A low-frequency torsional oscillator has been used to search for flux-lattice melting in an untwinned single crystal of YBa2Cu3O(7-delta). The damping of the oscillator was measured as a function of temperature, for applied magnetic fields in the range H = 0.1-2.3 T. A remarkably sharp damping peak has been located. It is suggested that the temperature of the peak corresponds to the melting point of the Abrikosov flux lattice.
An improved method for extracting matrix elements from lattice three-point functions
C. Aubin, K. Orginos
2011-12-01
The extraction of matrix elements from baryon three-point functions is complicated by the fact that the signal-to-noise drops rapidly as a function of time. Using a previously discussed method to improve the signal-to-noise for lattice two-point functions, we use this technique to do so for lattice three-point functions, using electromagnetic form factors for the nucleon and Delta as an example.
Lattice Monte Carlo simulations of polymer melts
NASA Astrophysics Data System (ADS)
Hsu, Hsiao-Ping
2014-12-01
We use Monte Carlo simulations to study polymer melts consisting of fully flexible and moderately stiff chains in the bond fluctuation model at a volume fraction 0.5. In order to reduce the local density fluctuations, we test a pre-packing process for the preparation of the initial configurations of the polymer melts, before the excluded volume interaction is switched on completely. This process leads to a significantly faster decrease of the number of overlapping monomers on the lattice. This is useful for simulating very large systems, where the statistical properties of the model with a marginally incomplete elimination of excluded volume violations are the same as those of the model with strictly excluded volume. We find that the internal mean square end-to-end distance for moderately stiff chains in a melt can be very well described by a freely rotating chain model with a precise estimate of the bond-bond orientational correlation between two successive bond vectors in equilibrium. The plot of the probability distributions of the reduced end-to-end distance of chains of different stiffness also shows that the data collapse is excellent and described very well by the Gaussian distribution for ideal chains. However, while our results confirm the systematic deviations between Gaussian statistics for the chain structure factor Sc(q) [minimum in the Kratky-plot] found by Wittmer et al. [EPL 77, 56003 (2007)] for fully flexible chains in a melt, we show that for the available chain length these deviations are no longer visible, when the chain stiffness is included. The mean square bond length and the compressibility estimated from collective structure factors depend slightly on the stiffness of the chains.
Natural processes in delta restoration: application to the Mississippi Delta.
Paola, Chris; Twilley, Robert R; Edmonds, Douglas A; Kim, Wonsuck; Mohrig, David; Parker, Gary; Viparelli, Enrica; Voller, Vaughan R
2011-01-01
Restoration of river deltas involves diverting sediment and water from major channels into adjoining drowned areas, where the sediment can build new land and provide a platform for regenerating wetland ecosystems. Except for local engineered structures at the points of diversion, restoration mainly relies on natural delta-building processes. Present understanding of such processes is sufficient to provide a basis for determining the feasibility of restoration projects through quantitative estimates of land-building rates and sustainable wetland area under different scenarios of sediment supply, subsidence, and sea-level rise. We are not yet to the point of being able to predict the evolution of a restored delta in detail. Predictions of delta evolution are based on field studies of active deltas, deltas in mine-tailings ponds, experimental deltas, and countless natural experiments contained in the stratigraphic record. These studies provide input for a variety of mechanistic delta models, ranging from radially averaged formulations to more detailed models that can resolve channels, topography, and ecosystem processes. Especially exciting areas for future research include understanding the mechanisms by which deltaic channel networks self-organize, grow, and distribute sediment and nutrients over the delta surface and coupling these to ecosystem processes, especially the interplay of topography, network geometry, and ecosystem dynamics.
NASA Astrophysics Data System (ADS)
Knuth, Kevin H.
2009-12-01
Previous derivations of the sum and product rules of probability theory relied on the algebraic properties of Boolean logic. Here they are derived within a more general framework based on lattice theory. The result is a new foundation of probability theory that encompasses and generalizes both the Cox and Kolmogorov formulations. In this picture probability is a bi-valuation defined on a lattice of statements that quantifies the degree to which one statement implies another. The sum rule is a constraint equation that ensures that valuations are assigned so as to not violate associativity of the lattice join and meet. The product rule is much more interesting in that there are actually two product rules: one is a constraint equation arises from associativity of the direct products of lattices, and the other a constraint equation derived from associativity of changes of context. The generality of this formalism enables one to derive the traditionally assumed condition of additivity in measure theory, as well introduce a general notion of product. To illustrate the generic utility of this novel lattice-theoretic foundation of measure, the sum and product rules are applied to number theory. Further application of these concepts to understand the foundation of quantum mechanics is described in a joint paper in this proceedings.
NASA Technical Reports Server (NTRS)
2006-01-01
This HiRISE image covers a portion of a delta that partially fills Eberswalde crater in Margaritifer Sinus. The delta was first recognized and mapped using MOC images that revealed various features whose presence required sustained flow and deposition into a lake that once occupied the crater. The HiRISE image resolves meter-scale features that record the migration of channels and delta distributaries as the delta grew over time. Differences in grain-size of sediments within the environments on the delta enable differential erosion of the deposits. As a result, coarser channel deposits are slightly more resistant and stand in relief relative to finer-grained over-bank and more easily eroded distal delta deposits. Close examination of the relict channel deposits confirms the presence of some meter-size blocks that were likely too coarse to have been transported by water flowing within the channels. These blocks may be formed of the sand and gravel that more likely moved along the channels that was lithified and eroded. Numerous meter-scale polygonal structures are common on many surfaces, but mostly those associated with more quiescent depositional environments removed from the channels. The polygons could be the result of deposition of fine-grained sediments that were either exposed and desiccated (dried out), rich in clays that shrunk when the water was removed, turned into rock and then fractured and eroded, or some combination of these processes.
Image PSP_001336_1560 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 8, 2006. The complete image is centered at -23.8 degrees latitude, 326.4 degrees East longitude. The range to the target site was 256.3 km (160.2 miles). At this distance the image scale is 25.6 cm/pixel (with 1 x 1 binning) so objects 77 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel and north is up. The image was
Pioneer Launch on Delta Vehicle
NASA Technical Reports Server (NTRS)
1969-01-01
NASA launches the last in the series of interplanetary Pioneer spacecraft, Pioneer 10 from Cape Kennedy, Florida. The long-tank Delta launch vehicle placed the spacecraft in a solar orbit along the path of Earth's orbit. The spacecraft then passed inside and outside Earth's orbit, alternately speeding up and slowing down relative to Earth. The Delta launch vehicle family started development in 1959. The Delta was composed of parts from the Thor, an intermediate-range ballistic missile, as its first stage, and the Vanguard as its second. The first Delta was launched from Cape Canaveral on May 13, 1960 and was powerful enough to deliver a 100-pound spacecraft into geostationary transfer orbit. Delta has been used to launch civil, commercial, and military satellites into orbit. For more information about Delta, please see Chapter 3 in Roger Launius and Dennis Jenkins' book To Reach the High Frontier published by The University Press of Kentucky in 2002.
Renormalization of aperiodic model lattices: spectral properties
NASA Astrophysics Data System (ADS)
Kroon, Lars; Riklund, Rolf
2003-04-01
Many of the published results for one-dimensional deterministic aperiodic systems treat rather simplified electron models with either a constant site energy or a constant hopping integral. Here we present some rigorous results for more realistic mixed tight-binding systems with both the site energies and the hopping integrals having an aperiodic spatial variation. It is shown that the mixed Thue-Morse, period-doubling and Rudin-Shapiro lattices can be transformed to on-site models on renormalized lattices maintaining the individual order between the site energies. The character of the energy spectra for these mixed models is therefore the same as for the corresponding on-site models. Furthermore, since the study of electrons on a lattice governed by the Schrödinger tight-binding equation maps onto the study of elastic vibrations on a harmonic chain, we have proved that the vibrational spectra of aperiodic harmonic chains with distributions of masses determined by the Thue-Morse sequence and the period-doubling sequence are purely singular continuous.
Crossing on hyperbolic lattices
NASA Astrophysics Data System (ADS)
Gu, Hang; Ziff, Robert M.
2012-05-01
We divide the circular boundary of a hyperbolic lattice into four equal intervals and study the probability of a percolation crossing between an opposite pair as a function of the bond occupation probability p. We consider the {7,3} (heptagonal), enhanced or extended binary tree (EBT), the EBT-dual, and the {5,5} (pentagonal) lattices. We find that the crossing probability increases gradually from 0 to 1 as p increases from the lower pl to the upper pu critical values. We find bounds and estimates for the values of pl and pu for these lattices and identify the self-duality point p* corresponding to where the crossing probability equals 1/2. Comparison is made with recent numerical and theoretical results.
NASA Astrophysics Data System (ADS)
Weisz, Peter; Majumdar, Pushan
2012-03-01
Lattice gauge theory is a formulation of quantum field theory with gauge symmetries on a space-time lattice. This formulation is particularly suitable for describing hadronic phenomena. In this article we review the present status of lattice QCD. We outline some of the computational methods, discuss some phenomenological applications and a variety of non-perturbative topics. The list of references is severely incomplete, the ones we have included are text books or reviews and a few subjectively selected papers. Kronfeld and Quigg (2010) supply a reasonably comprehensive set of QCD references. We apologize for the fact that have not covered many important topics such as QCD at finite density and heavy quark effective theory adequately, and mention some of them only in the last section "In Brief". These topics should be considered in further Scholarpedia articles.
David Richards
2004-10-01
This talk describes progress at understanding the properties of the nucleon and its excitations from lattice QCD. I begin with a review of recent lattice results for the lowest-lying states of the excited baryon spectrum. The need to approach physical values of the light quark masses is emphasized, enabling the effects of the pion cloud to be revealed. I then outline the development of techniques that will enable the extraction of the masses of the higher resonances, and describe how such calculations provide insight into the structure of the hadrons. Finally, I discuss direct probes of the quark and gluon structure of baryons through the lattice measurement of the moments of quark distributions and of Generalized Parton Distributions.
NASA Astrophysics Data System (ADS)
Chaves Filho, V. L.; Lima, R. P. A.; Lyra, M. L.
2015-06-01
We investigate the modulational instability of uniform wavepackets governed by the discrete nonlinear Schrodinger equation in finite linear chains and square lattices. We show that, while the critical nonlinear coupling χMI above which modulational instability occurs remains finite in square lattices, it decays as 1/L in linear chains. In square lattices, there is a direct transition between the regime of stable uniform wavefunctions and the regime of asymptotically localized solutions with stationary probability distributions. On the other hand, there is an intermediate regime in linear chains for which the wavefunction dynamics develops complex breathing patterns. We analytically compute the critical nonlinear strengths for modulational instability in both lattices, as well as the characteristic time τ governing the exponential increase of perturbations in the vicinity of the transition. We unveil that the interplay between modulational instability and self-trapping phenomena is responsible for the distinct wavefunction dynamics in linear and square lattices.
Chaves Filho, V L; Lima, R P A; Lyra, M L
2015-06-01
We investigate the modulational instability of uniform wavepackets governed by the discrete nonlinear Schrodinger equation in finite linear chains and square lattices. We show that, while the critical nonlinear coupling χMI above which modulational instability occurs remains finite in square lattices, it decays as 1/L in linear chains. In square lattices, there is a direct transition between the regime of stable uniform wavefunctions and the regime of asymptotically localized solutions with stationary probability distributions. On the other hand, there is an intermediate regime in linear chains for which the wavefunction dynamics develops complex breathing patterns. We analytically compute the critical nonlinear strengths for modulational instability in both lattices, as well as the characteristic time τ governing the exponential increase of perturbations in the vicinity of the transition. We unveil that the interplay between modulational instability and self-trapping phenomena is responsible for the distinct wavefunction dynamics in linear and square lattices.
Collapsing lattice animals and lattice trees in two dimensions
NASA Astrophysics Data System (ADS)
Hsu, Hsiao-Ping; Grassberger, Peter
2005-06-01
We present high statistics simulations of weighted lattice bond animals and lattice trees on the square lattice, with fugacities for each non-bonded contact and for each bond between two neighbouring monomers. The simulations are performed using a newly developed sequential sampling method with resampling, very similar to the pruned-enriched Rosenbluth method (PERM) used for linear chain polymers. We determine with high precision the line of second-order transitions from an extended to a collapsed phase in the resulting two-dimensional phase diagram. This line includes critical bond percolation as a multicritical point, and we verify that this point divides the line into different universality classes. One of them corresponds to the collapse driven by contacts and includes the collapse of (weakly embeddable) trees. There is some evidence that the other is subdivided again into two parts with different universality classes. One of these (at the far side from collapsing trees) is bond driven and is represented by the Derrida-Herrmann model of animals having bonds only (no contacts). Between the critical percolation point and this bond-driven collapse seems to be an intermediate regime, whose other end point is a multicritical point P* where a transition line between two collapsed phases (one bond driven and the other contact driven) sparks off. This point P* seems to be attractive (in the renormalization group sense) from the side of the intermediate regime, so there are four universality classes on the transition line (collapsing trees, critical percolation, intermediate regime, and Derrida-Herrmann). We obtain very precise estimates for all critical exponents for collapsing trees. It is already harder to estimate the critical exponents for the intermediate regime. Finally, it is very difficult to obtain with our method good estimates of the critical parameters of the Derrida-Herrmann universality class. As regards the bond-driven to contact-driven transition in the
Catterall, Simon; Kaplan, David B.; Unsal, Mithat
2009-03-31
We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of N = 4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.
NASA Astrophysics Data System (ADS)
Oates, Chris
2012-06-01
Since they were first proposed in 2003 [1], optical lattice clocks have become one of the leading technologies for the next generation of atomic clocks, which will be used for advanced timing applications and in tests of fundamental physics [2]. These clocks are based on stabilized lasers whose frequency is ultimately referenced to an ultra-narrow neutral atom transition (natural linewidths << 1 Hz). To suppress the effects of atomic motion/recoil, the atoms in the sample (˜10^4 atoms) are confined tightly in the potential wells of an optical standing wave (lattice). The wavelength of the lattice light is tuned to its ``magic'' value so as to yield a vanishing net AC Stark shift for the clock transition. As a result lattice clocks have demonstrated the capability of generating high stability clock signals with small absolute uncertainties (˜ 1 part in 10^16). In this presentation I will first give an overview of the field, which now includes three different atomic species. I will then use experiments with Yb performed in our laboratory to illustrate the key features of a lattice clock. Our research has included the development of state-of-the-art optical cavities enabling ultra-high-resolution optical spectroscopy (1 Hz linewidth). Together with the large atom number in the optical lattice, we are able to achieve very low clock instability (< 0.3 Hz in 1 s) [3]. Furthermore, I will show results from some of our recent investigations of key shifts for the Yb lattice clock, including high precision measurements of ultracold atom-atom interactions in the lattice and the dc Stark effect for the Yb clock transition (necessary for the evaluation of blackbody radiation shifts). [4pt] [1] H. Katori, M. Takamoto, V. G. Pal'chikov, and V. D. Ovsiannikov, Phys. Rev. Lett. 91, 173005 (2003). [0pt] [2] Andrei Derevianko and Hidetoshi Katori, Rev. Mod. Phys. 83, 331 (2011). [0pt] [3] Y. Y. Jiang, A. D. Ludlow, N. D. Lemke, R. W. Fox, J. A. Sherman, L.-S. Ma, and C. W. Oates
NASA Astrophysics Data System (ADS)
Wong, Chun Wa; Yasui, Kosuke
2006-06-01
The one-dimensional fall of a folded chain with one end suspended from a rigid support and a chain falling from a resting heap on a table is studied. Because their Lagrangians contain no explicit time dependence, the falling chains are conservative systems. Their equations of motion are shown to contain a term that enforces energy conservation when masses are transferred between subchains. We show that Cayley's 1857 energy nonconserving solution for a chain falling from a resting heap is incorrect because it neglects the energy gained when a link leaves a subchain. The maximum chain tension measured by Calkin and March for the falling folded chain is given a simple if rough interpretation. Other aspects of the falling folded chain are briefly discussed.
[Delta-9-tetrahydrocannabinol pharmacokinetics].
Goullé, J-P; Saussereau, E; Lacroix, C
2008-08-01
Delta-9-tetrahydrocannabinol (Delta-9-THC) is the main psychoactive ingredient of cannabis. Smoking is currently most common use of cannabis. The present review focuses on the pharmacokinetics of THC. The variability of THC in plant material which has significantly increased in recent years leads to variability in tissue THC levels from smoking, which is, in itself, a highly individual process. This variability of THC content has an important impact on drug pharmacokinetics and pharmacology. After smoking THC bioavailability averages 30%. With a 3.55% THC cigarette, a peak plasma level near 160 ng/mL occurs approximately 10 min after inhalation. THC is eliminated quickly from plasma in a multiphasic manner and is widely distributed to tissues, which is responsible for its pharmacologic effects. Body fat then serves as a long-term storage site. This particular pharmacokinetics explains the noncorrelation between THC blood level and clinical effects as is observed for ethanol. A major active 11-hydroxy metabolite is formed after both inhalation and oral dosing (20 and 100% of parent, respectively). The elimination of THC and its many metabolites, mainly THC-COOH, occurs via the feces and urine for several weeks. Thus, to confirm abstinence, urine THC-COOH analysis would be a useful tool. A positive result could be checked by gas chromatography-mass spectrometry THC blood analysis, indicative of a recent cannabis exposure.
The immunoglobulin heavy chain locus in the reptile Anolis carolinensis.
Gambón Deza, Francisco; Sánchez Espinel, Christian; Magadán Mompó, Susana
2009-05-01
We describe the entire immunoglobulin heavy chain (IgH) locus from the reptile Anolis carolinensis. The heavy chain constant (C(H)) region includes C mu, C delta and C upsilon genes. This is the first description of a C upsilon gene in the reptilian class. Variable (V(H)), diversity (D(H)) and joining (J(H)) genes are located 5' from the constant (C(H)) chain complex locus. The C mu and C upsilon genes encode antibodies with four immunoglobulin domains. The C delta gene encoded an 11 domain delta heavy chain as in Eublepharis macularius. Seventy V(H) genes, belonging to 28 families, were identified, and they can be sorted into five broader groups. The similarity of the organization of the reptilian genes with those of amphibians and mammals suggests the existence of a process of heavy chain genomic reorganization before the radiation of tetrapod vertebrates.
Coupled map lattice model of jet breakup
Minich, R W; Schwartz, A J; Baker, E L
2001-01-25
An alternative approach is described to evaluate the statistical nature of the breakup of shaped charge liners. Experimental data from ductile and brittle copper jets are analyzed in terms of velocity gradient, deviation of {Delta}V from linearity, R/S analysis, and the Hurst exponent within the coupled map lattice model. One-dimensional simulations containing 600 zones of equal mass and using distinctly different force-displacement curves are generated to simulate ductile and brittle behavior. A particle separates from the stretching jet when an element of material reaches the failure criterion. A simple model of a stretching rod using brittle, semi-brittle, and ductile force-displacement curves is in agreement with the experimental results for the Hurst exponent and the phase portraits and indicates that breakup is a correlated phenomenon.
Moving embedded lattice solitons.
Malomed, B A; Fujioka, J; Espinosa-Cerón, A; Rodríguez, R F; González, S
2006-03-01
It was recently proved that solitons embedded in the spectrum of linear waves may exist in discrete systems, and explicit solutions for isolated unstable embedded lattice solitons (ELS) of a differential-difference version of a higher-order nonlinear Schrodinger equation were found [Gonzalez-Perez-Sandi, Fujioka, and Malomed, Physica D 197, 86 (2004)]. The discovery of these ELS gives rise to relevant questions such as the following: (1) Are there continuous families of ELS? (2) Can ELS be stable? (3) Is it possible for ELS to move along the lattice? (4) How do ELS interact? The present work addresses these questions by showing that a novel equation (a discrete version of a complex modified Korteweg-de Vries equation that includes next-nearest-neighbor couplings) has a two-parameter continuous family of exact ELS. These solitons can move with arbitrary velocities across the lattice, and the numerical simulations demonstrate that these ELS are completely stable. Moreover, the numerical tests show that these ELS are robust enough to withstand collisions, and the result of a collision is only a shift in the positions of the solitons. The model may apply to the description of a Bose-Einstein condensate with dipole-dipole interactions between the atoms, trapped in a deep optical-lattice potential.
Generalizing Word Lattice Translation
2008-02-01
demonstrate substantial gains for Chinese -English and Arabic -English translation. Keywords: word lattice translation, phrase-based and hierarchical...introduce in reordering models. Our experiments evaluating the approach demonstrate substantial gains for Chinese -English and Arabic -English translation. 15...Section 4 presents two applications of the noisier channel paradigm, demonstrating substantial performance gains in Arabic -English and Chinese -English
NASA Astrophysics Data System (ADS)
Schaich, David
2016-03-01
Lattice field theory provides a non-perturbative regularization of strongly interacting systems, which has proven crucial to the study of quantum chromodynamics among many other theories. Supersymmetry plays prominent roles in the study of physics beyond the standard model, both as an ingredient in model building and as a tool to improve our understanding of quantum field theory. Attempts to apply lattice techniques to supersymmetric field theories have a long history, but until recently these efforts have generally encountered insurmountable difficulties related to the interplay of supersymmetry with the lattice discretization of spacetime. In recent years these difficulties have been overcome for a class of theories that includes the particularly interesting case of maximally supersymmetric Yang-Mills (N = 4 SYM) in four dimensions, which is a cornerstone of AdS/CFT duality. In combination with computational advances this progress enables practical numerical investigations of N = 4 SYM on the lattice, which can address questions that are difficult or impossible to handle through perturbation theory, AdS/CFT duality, or the conformal bootstrap program. I will briefly review some of the new ideas underlying this recent progress, and present some results from ongoing large-scale numerical calculations, including comparisons with analytic predictions.
Feng Haidong; Siegel, Warren
2006-08-15
We propose some new simplifying ingredients for Feynman diagrams that seem necessary for random lattice formulations of superstrings. In particular, half the fermionic variables appear only in particle loops (similarly to loop momenta), reducing the supersymmetry of the constituents of the type IIB superstring to N=1, as expected from their interpretation in the 1/N expansion as super Yang-Mills.
Andreas S. Kronfeld
2002-09-30
After reviewing some of the mathematical foundations and numerical difficulties facing lattice QCD, I review the status of several calculations relevant to experimental high-energy physics. The topics considered are moments of structure functions, which may prove relevant to search for new phenomena at the LHC, and several aspects of flavor physics, which are relevant to understanding CP and flavor violation.
Phenomenology Using Lattice QCD
NASA Astrophysics Data System (ADS)
Gupta, R.
2005-08-01
This talk provides a brief summary of the status of lattice QCD calculations of the light quark masses and the kaon bag parameter BK. Precise estimates of these four fundamental parameters of the standard model, i.e., mu, md, ms and the CP violating parameter η, help constrain grand unified models and could provide a window to new physics.
Phenomenology Using Lattice QCD
NASA Astrophysics Data System (ADS)
Gupta, R.
This talk provides a brief summary of the status of lattice QCD calculations of the light quark masses and the kaon bag parameter BK. Precise estimates of these four fundamental parameters of the standard model, i.e., mu, md, ms and the CP violating parameter η, help constrain grand unified models and could provide a window to new physics.
NASA Technical Reports Server (NTRS)
Savelyev, V. A.
1979-01-01
The means of ensuring total rigidity of lattice domes, using comparison with solid shells of 1-3 layers are discussed. Irregularities of manufacture, processing, and other factors are considered, as they relate to diminution of rigidity. The discussion uses the concepts of upper and lower critical loads on the structure in question.
Thresholds of surface codes on the general lattice structures suffering biased error and loss
Tokunaga, Yuuki; Fujii, Keisuke
2014-12-04
A family of surface codes with general lattice structures is proposed. We can control the error tolerances against bit and phase errors asymmetrically by changing the underlying lattice geometries. The surface codes on various lattices are found to be efficient in the sense that their threshold values universally approach the quantum Gilbert-Varshamov bound. We find that the error tolerance of the surface codes depends on the connectivity of the underlying lattices; the error chains on a lattice of lower connectivity are easier to correct. On the other hand, the loss tolerance of the surface codes exhibits an opposite behavior; the logical information on a lattice of higher connectivity has more robustness against qubit loss. As a result, we come upon a fundamental trade-off between error and loss tolerances in the family of surface codes with different lattice geometries.
FitzGerald, D.M.; Kulp, M.; Penland, S.; Flocks, J.; Kindinger, J.
2004-01-01
grows in dimensions, the proximal and distal tidal delta facies prograde seawards. Owing to the relatively low gradient of the inner continental shelf, the ebb-tidal delta lithosome is presently no more than 5 m thick and is generally only 2-3 m in thickness. The ebb delta sediment is sourced from deepening of the inlet and the associated channels and from the longshore sediment transport system. The final stage in the model envisages erosion and segmentation of the barrier chain, leading to a decrease in tidal discharge through the former major inlets. This process ultimately results in fine-grained sedimentation seaward of the inlets and the encasement of the ebb-tidal delta lithosome in mud. The ebb-tidal deltas along the Barataria coast are distinguished from most other ebb deltas along sand-rich coasts by their muddy content and lack of large-scale stratification produced by channel cut-and-fills and bar migration. ?? 2004 International Association of Sedimentologists.
Assembling Fibonacci anyons from a Z3 parafermion lattice model
NASA Astrophysics Data System (ADS)
Stoudenmire, E. M.; Clarke, David J.; Mong, Roger S. K.; Alicea, Jason
2015-06-01
Recent concrete proposals suggest it is possible to engineer a two-dimensional bulk phase supporting non-Abelian Fibonacci anyons out of Abelian fractional quantum Hall systems. The low-energy degrees of freedom of such setups can be modeled as Z3 parafermions "hopping" on a two-dimensional lattice. We use the density matrix renormalization group to study a model of this type interpolating between the decoupled-chain, triangular-lattice, and square-lattice limits. The results show clear evidence of the Fibonacci phase over a wide region of the phase diagram, most notably including the isotropic triangular-lattice point. We also study the broader phase diagram of this model and show that elsewhere it supports an Abelian state with semionic excitations.
The Bond Fluctuation Model and Other Lattice Models
NASA Astrophysics Data System (ADS)
Müller, Marcus
Lattice models constitute a class of coarse-grained representations of polymeric materials. They have enjoyed a longstanding tradition for investigating the universal behavior of long chain molecules by computer simulations and enumeration techniques. A coarse-grained representation is often necessary to investigate properties on large time- and length scales. First, some justification for using lattice models will be given and the benefits and limitations will be discussed. Then, the bond fluctuation model by Carmesin and Kremer [1] is placed into the context of other lattice models and compared to continuum models. Some specific techniques for measuring the pressure in lattice models will be described. The bond fluctuation model has been employed in more than 100 simulation studies in the last decade and only few selected applications can be mentioned.
NASA Technical Reports Server (NTRS)
2007-01-01
The Mackenzie River in the Northwest Territories, Canada, with its headstreams the Peace and Finley, is the longest river in North America at 4241 km, and drains an area of 1,805,000 square km. The large marshy delta provides habitat for migrating Snow Geese, Tundra Swans, Brant, and other waterfowl. The estuary is a calving area for Beluga whales. The Mackenzie (previously the Disappointment River) was named after Alexander Mackenzie who travelled the river while trying to reach the Pacific in 1789.
The image was acquired on August 4, 2005, covers an area of 55.8 x 55.8 km, and is located at 68.6 degrees north latitude, 134.7 degrees west longitude.
The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.
NASA Technical Reports Server (NTRS)
2008-01-01
The Colorado River ends its 2330 km journey in the Gulf of Mexico in Baja California. The heavy use of the river as an irrigation source for the Imperial Valley has dessicated the lower course of the river in Mexico such that it no longer consistently reaches the sea. Prior to the mid 20th century, the Colorado River Delta provided a rich estuarine marshland that is now essentially desiccated, but nonetheless is an important ecological resource.
The image was acquired May 29, 2006, covers an area of 44.3 x 57.5 km, and is located at 32.1 degrees north latitude, 115.1 degrees west longitude.
The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.
Localization oscillation in antidot lattices
NASA Astrophysics Data System (ADS)
Uryu, S.; Ando, T.
1998-06-01
The Anderson localization in square and hexagonal antidot lattices is numerically studied with the use of a Thouless number method. It is revealed that localization is very sensitive to the aspect ratio between the antidot diameter and the lattice constant. In a hexagonal lattice, both the Thouless number and the localization length oscillate with the period equal to the Al’tshuler-Aronov-Spivak oscillation. The oscillation is quite weak in a square lattice.
Fluctuating pancake vortices revealed by dissipation of Josephson vortex lattice.
Koshelev, A. E.; Buzdin, A. I.; Kakeya, I.; Yamamoto, T.; Kadowaki, K.
2011-06-01
In strongly anisotropic layered superconductors in tilted magnetic fields, the Josephson vortex lattice coexists with the lattice of pancake vortices. Due to the interaction between them, the dissipation of the Josephson vortex lattice is very sensitive to the presence of the pancake vortices. If the c-axis magnetic field is smaller than the corresponding lower critical field, the pancake stacks are not formed but the individual pancakes may exist in the fluctuational regime either near the surface in large-size samples or in the central region for small-size mesas. We calculate the contribution of such fluctuating pancake vortices to the c-axis conductivity of the Josephson vortex lattice and compare the theoretical results with measurements on small mesas fabricated out of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} crystals. A fingerprint of fluctuating pancakes is a characteristic exponential dependence of the c-axis conductivity observed experimentally. Our results provide strong evidence of the existence of the fluctuating pancakes and their influence on the Josephson vortex lattice dissipation.
Kondo lattice without Nozieres exhaustion effect.
Kikoin, K.; Kiselev, M. N.; Materials Science Division; Ben-Gurion Univ. of the Negev; Ludwig-Maximilians Univ.
2006-01-01
We discuss the properties of layered Anderson/Kondo lattices with metallic electrons confined in 2D xy planes and local spins in insulating layers forming chains in the z direction. Each spin in this model possesses its own 2D Kondo cloud, so that the Nozieres exhaustion problem does not occur. The high-temperature perturbational description is matched to exact low-T Bethe-ansatz solution. The excitation spectrum of the model is gapless both in charge and spin sectors. The disordered phases and possible experimental realizations of the model are briefly discussed.
Erosion Between Two Delta Fronts, the Mekong Delta Case
NASA Astrophysics Data System (ADS)
Unverricht, D.; Heinrich, C.; Nguyen, T. C.; Szczucinski, W.; Schwarzer, K.; Stattegger, K.
2013-12-01
Human activities, like embanking, sand mining, groundwater extraction and deforestation lead to strong changes of the deltaic environment. Especially, mangrove cutting influences strongly the coastal erosion along large areas of the southern Mekong delta coast. However, all currently published data document erosion from subaerial areas excluding the subaqueous Mekong delta. Our study fills this gap along the subaqueous Mekong Delta between the Bassac River mouth and the Gulf of Thailand. Hydroacoustic profiles and sediment coring were carried out during two cruises in 2007 and 2008. Analyses of ADCP measurements provide valuable information of current direction and velocity during the inter-monsoon season. Fine sediment dynamics including SPM were analyzed applying laser in situ scattering and Transmissiometry (LISST) at vertical profiles. Two delta fronts were found more than 200 km apart, one in front of the main Mekong river distributaries and the other around Ca Mau Cape, the south-western most spit of the Mekong River Delta. Although the delta front around Ca Mau Cape is not directly supplied by the main distributaries of the Mekong River, it is the fastest prograding region of the subaqueous Mekong delta. Alongshore sediment transport takes place from the north-eastern main distributaries towards south-west (Ca Mau Cape). Between both delta fronts, a large scale alternating sand-ridge-system, at least 120 km long and 6 to 10 km wide (ridge crest distance), has developed where erosional channels separate two sand-ridge bodies. The origin of the sand-ridge system is situated at the delta slope off Ganh Hao around water depths between 10 and 18 m. Here, the delta slope consists mainly of fine sand in the upper layer (up to 20 cm thickness) and is separated by an erosional hiatus from the lower muddy layer. The mangroves and sandy beaches at the coast in this region are also under erosion. It is assumed that the eroded beach sand feeds the sand-ridge-system. The
Fractional lattice charge transport
Flach, Sergej; Khomeriki, Ramaz
2017-01-01
We consider the dynamics of noninteracting quantum particles on a square lattice in the presence of a magnetic flux α and a dc electric field E oriented along the lattice diagonal. In general, the adiabatic dynamics will be characterized by Bloch oscillations in the electrical field direction and dispersive ballistic transport in the perpendicular direction. For rational values of α and a corresponding discrete set of values of E(α) vanishing gaps in the spectrum induce a fractionalization of the charge in the perpendicular direction - while left movers are still performing dispersive ballistic transport, the complementary fraction of right movers is propagating in a dispersionless relativistic manner in the opposite direction. Generalizations and the possible probing of the effect with atomic Bose-Einstein condensates and photonic networks are discussed. Zak phase of respective band associated with gap closing regime has been computed and it is found converging to π/2 value. PMID:28102302
NASA Astrophysics Data System (ADS)
Hsu, Hsiao-Ping; Nadler, Walder; Grassberger, Peter
2005-07-01
The scaling behavior of randomly branched polymers in a good solvent is studied in two to nine dimensions, modeled by lattice animals on simple hypercubic lattices. For the simulations, we use a biased sequential sampling algorithm with re-sampling, similar to the pruned-enriched Rosenbluth method (PERM) used extensively for linear polymers. We obtain high statistics of animals with up to several thousand sites in all dimension 2⩽d⩽9. The partition sum (number of different animals) and gyration radii are estimated. In all dimensions we verify the Parisi-Sourlas prediction, and we verify all exactly known critical exponents in dimensions 2, 3, 4, and ⩾8. In addition, we present the hitherto most precise estimates for growth constants in d⩾3. For clusters with one site attached to an attractive surface, we verify the superuniversality of the cross-over exponent at the adsorption transition predicted by Janssen and Lyssy.
Jozef Dudek
2007-08-05
Charmonium is an attractive system for the application of lattice QCD methods. While the sub-threshold spectrum has been considered in some detail in previous works, it is only very recently that excited and higher-spin states and further properties such as radiative transitions and two-photon decays have come to be calculated. I report on this recent progress with reference to work done at Jefferson Lab.
Crystallographic Lattice Boltzmann Method
NASA Astrophysics Data System (ADS)
Namburi, Manjusha; Krithivasan, Siddharth; Ansumali, Santosh
2016-06-01
Current approaches to Direct Numerical Simulation (DNS) are computationally quite expensive for most realistic scientific and engineering applications of Fluid Dynamics such as automobiles or atmospheric flows. The Lattice Boltzmann Method (LBM), with its simplified kinetic descriptions, has emerged as an important tool for simulating hydrodynamics. In a heterogeneous computing environment, it is often preferred due to its flexibility and better parallel scaling. However, direct simulation of realistic applications, without the use of turbulence models, remains a distant dream even with highly efficient methods such as LBM. In LBM, a fictitious lattice with suitable isotropy in the velocity space is considered to recover Navier-Stokes hydrodynamics in macroscopic limit. The same lattice is mapped onto a cartesian grid for spatial discretization of the kinetic equation. In this paper, we present an inverted argument of the LBM, by making spatial discretization as the central theme. We argue that the optimal spatial discretization for LBM is a Body Centered Cubic (BCC) arrangement of grid points. We illustrate an order-of-magnitude gain in efficiency for LBM and thus a significant progress towards feasibility of DNS for realistic flows.
Digital lattice gauge theories
NASA Astrophysics Data System (ADS)
Zohar, Erez; Farace, Alessandro; Reznik, Benni; Cirac, J. Ignacio
2017-02-01
We propose a general scheme for a digital construction of lattice gauge theories with dynamical fermions. In this method, the four-body interactions arising in models with 2 +1 dimensions and higher are obtained stroboscopically, through a sequence of two-body interactions with ancillary degrees of freedom. This yields stronger interactions than the ones obtained through perturbative methods, as typically done in previous proposals, and removes an important bottleneck in the road towards experimental realizations. The scheme applies to generic gauge theories with Lie or finite symmetry groups, both Abelian and non-Abelian. As a concrete example, we present the construction of a digital quantum simulator for a Z3 lattice gauge theory with dynamical fermionic matter in 2 +1 dimensions, using ultracold atoms in optical lattices, involving three atomic species, representing the matter, gauge, and auxiliary degrees of freedom, that are separated in three different layers. By moving the ancilla atoms with a proper sequence of steps, we show how we can obtain the desired evolution in a clean, controlled way.
Crystallographic Lattice Boltzmann Method
Namburi, Manjusha; Krithivasan, Siddharth; Ansumali, Santosh
2016-01-01
Current approaches to Direct Numerical Simulation (DNS) are computationally quite expensive for most realistic scientific and engineering applications of Fluid Dynamics such as automobiles or atmospheric flows. The Lattice Boltzmann Method (LBM), with its simplified kinetic descriptions, has emerged as an important tool for simulating hydrodynamics. In a heterogeneous computing environment, it is often preferred due to its flexibility and better parallel scaling. However, direct simulation of realistic applications, without the use of turbulence models, remains a distant dream even with highly efficient methods such as LBM. In LBM, a fictitious lattice with suitable isotropy in the velocity space is considered to recover Navier-Stokes hydrodynamics in macroscopic limit. The same lattice is mapped onto a cartesian grid for spatial discretization of the kinetic equation. In this paper, we present an inverted argument of the LBM, by making spatial discretization as the central theme. We argue that the optimal spatial discretization for LBM is a Body Centered Cubic (BCC) arrangement of grid points. We illustrate an order-of-magnitude gain in efficiency for LBM and thus a significant progress towards feasibility of DNS for realistic flows. PMID:27251098
NASA Astrophysics Data System (ADS)
Bietenholz, W.; Gerber, U.; Pepe, M.; Wiese, U.-J.
2010-12-01
We consider lattice field theories with topological actions, which are invariant against small deformations of the fields. Some of these actions have infinite barriers separating different topological sectors. Topological actions do not have the correct classical continuum limit and they cannot be treated using perturbation theory, but they still yield the correct quantum continuum limit. To show this, we present analytic studies of the 1-d O(2) and O(3) model, as well as Monte Carlo simulations of the 2-d O(3) model using topological lattice actions. Some topological actions obey and others violate a lattice Schwarz inequality between the action and the topological charge Q. Irrespective of this, in the 2-d O(3) model the topological susceptibility {χ_t} = {{{left< {{Q^2}} rightrangle }} left/ {V} right.} is logarithmically divergent in the continuum limit. Still, at non-zero distance the correlator of the topological charge density has a finite continuum limit which is consistent with analytic predictions. Our study shows explicitly that some classically important features of an action are irrelevant for reaching the correct quantum continuum limit.
NASA Astrophysics Data System (ADS)
Mikeš, Daniel
2010-05-01
A deltaic sedimentary system has a point source; sediment is carried over the delta plain by distributary channels away from the point source and deposited at the delta front by distributary mouth bars. The established methods to describe such a sedimentary system are "bedding analysis", "facies analysis", and "basin analysis". We shall call the ambient conditions "input" and the rock record "output". There exist a number of methods to deduce input from output, e.g. "Sequence stratigraphy" (a.o. Vail et al. 1977, Catuneanu et al. 2009), "Shoreline trajectory" (a.o. Helland-Hansen & Martinsen 1996, Helland-Hansen & Hampson 2009) on the one hand and the complex use of established techniques on the other (a.o. Miall & Miall 2001, Miall & Miall 2002). None of these deductive methods seems to be sufficient. I claim that the common errors in all these attempts are the following: (1) a sedimentary system is four-dimensional (3+1) and a lesser dimensional analysis is insufficient; (2) a sedimentary system is complex and any empirical/deductive analysis is non-unique. The proper approach to the problem is therefore the theoretical/inductive analysis. To that end we performed six scenarios of a scaled version of a passive margin delta in a flume tank. The scenarios have identical stepwise tectonic subsidence and semi-cyclic sealevel, but different supply curves, i.e. supply is: constant, highly-frequent, proportional to sealevel, inversely proportional to sealevel, lagging to sealevel, ahead of sealevel. The preliminary results are indicative. Lobe-switching occurs frequently and hence locally sedimentation occurs shortly and hiatuses are substantial; therefore events in 2D (+1) cross-sections don't correlate temporally. The number of sedimentary cycles disequals the number of sealevel cycles. Lobe-switching and stepwise tectonic subsidence cause onlap/transgression. Erosional unconformities are local diachronous events, whereas maximum flooding surfaces are regional
Improved models of dense anharmonic lattices
NASA Astrophysics Data System (ADS)
Rosenau, P.; Zilburg, A.
2017-01-01
We present two improved quasi-continuous models of dense, strictly anharmonic chains. The direct expansion which includes the leading effect due to lattice dispersion, results in a Boussinesq-type PDE with a compacton as its basic solitary mode. Without increasing its complexity we improve the model by including additional terms in the expanded interparticle potential with the resulting compacton having a milder singularity at its edges. A particular care is applied to the Hertz potential due to its non-analyticity. Since, however, the PDEs of both the basic and the improved model are ill posed, they are unsuitable for a study of chains dynamics. Using the bond length as a state variable we manipulate its dispersion and derive a well posed fourth order PDE.
Crystallography of the Delta to Alpha Martensitic Transformation in Plutonium Alloys
Jin, Y; Wang, Y; Khachaturyan, A; Krenn, C; Schwartz, A
2004-07-15
A new stress-accommodating crystallographic mechanism of the {delta} {yields} {alpha} martensitic transformation in plutonium alloys is proposed. According to this mechanism, an orientation variant of the {alpha} phase is produced by a combination of a homogeneous strain and shuffling of the alternating close-packed (111){sub {delta}} planes. It is shown that the formation of stable transformation-induced twins whose twin plane orientations and twin shear directions do not depend on the small variations of the crystal lattice parameters is the preferred stress-accommodating mode. Only these stable twins have dislocation-free twin boundaries while the twin boundaries of all others are decorated by ultra-dense distribution of partial dislocations. The theory predicts a crystal lattice rearrangement mechanism involving the (205){sub {alpha}} ((01{bar 1}){sub {delta}}) stable twins. The corresponding Invariant Plane Strain solutions, with special emphasis on two simplest shuffling modes, the single and double elementary modes, are presented and compared with the existing experimental observations. It is shown that the habit plane orientation is highly sensitive to the input values of the crystal lattice parameters and especially to the accuracy of the measured volume change in the {delta}{yields}{alpha} transformation. An analysis of these effects on the habit plane orientation and orientation relations is also presented.
Molecular mobility with respect to accessible volume in Monte Carlo lattice model for polymers
NASA Astrophysics Data System (ADS)
Diani, J.; Gilormini, P.
2017-02-01
A three-dimensional cubic Monte Carlo lattice model is considered to test the impact of volume on the molecular mobility of amorphous polymers. Assuming classic polymer chain dynamics, the concept of locked volume limiting the accessible volume around the polymer chains is introduced. The polymer mobility is assessed by its ability to explore the entire lattice thanks to reptation motions. When recording the polymer mobility with respect to the lattice accessible volume, a sharp mobility transition is observed as witnessed during glass transition. The model ability to reproduce known actual trends in terms of glass transition with respect to material parameters, is also tested.
Graphene, Lattice Field Theory and Symmetries
Drissi, L. B.; Bousmina, M.; Saidi, E. H.
2011-02-15
Borrowing ideas from tight binding model, we propose a board class of lattice field models that are classified by non simply laced Lie algebras. In the case of A{sub N-1{approx_equal}}su(N) series, we show that the couplings between the quantum states living at the first nearest neighbor sites of the lattice L{sub suN} are governed by the complex fundamental representations N-bar and N of su(N) and the second nearest neighbor interactions are described by its adjoint N-bar x N. The lattice models associated with the leading su(2), su(3), and su(4) cases are explicitly studied and their fermionic field realizations are given. It is also shown that the su(2) and su(3) models describe the electronic properties of the acetylene chain and the graphene, respectively. It is established as well that the energy dispersion of the first nearest neighbor couplings is completely determined by the A{sub N} roots {alpha} through the typical dependence N/2+{Sigma}{sub roots} cos(k.{alpha} with k the wave vector.Other features such as the SO(2N) extension and other applications are also discussed.
NASA Astrophysics Data System (ADS)
Fermi, Enrico; Leverett, Miles C.
This Patent focuses mainly on the description of an automatic system for the control rods in a nuclear reactor (in the present case made of natural uranium and graphite) reporting, aside from several related theoretical points (already considered in previous Patents), a detailed description of it. Since the reproduction ratio of a lattice structure is reduced by the presence of neutron absorbing impurities, such impurities can be introduced in the lattice in the form of control rods, made of a material such as boron or cadmium, which will absorb large amounts of neutrons. The control procedure is based on the fact that the depth to which the control rod penetrates into the lattice will determine the value of the neutron density in the system. This relatively simple task faces the fact that the reproduction ratio of the structure can change due to changes in temperature and pressure in the system. So, a connection of the control rods with an ionization chamber, measuring neutron density, can give an automatic control of the stability of the chain reaction. Moreover, an emergency circuit for operating the safety rods is illustrated in this Patent, and, in case of failure of both the control and emergency circuits, a third automatic circuit is depicted which causes the dump of a portion of the lattice structure for interrupting the neutron density rise. In a system of the type considered, about 92 percent of the total heat generated originates in the uranium toward the center of the lattice, about 6 percent originates in the graphite used as slowing medium, and the remaining 2 percent is generated in the structures surrounding the pile. Accordingly, the permissible power output of the reactor is limited by the rate of heat removal, so that, to prevent the accumulation of heat in the chain reaction pile, a coolant into contact with the uranium must be employed. However, the corrosive effect on uranium of the possible coolants has to be taken into account, because the
Lattice-induced nonadiabatic frequency shifts in optical lattice clocks
Beloy, K.
2010-09-15
We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.
Supersonic aerodynamics of delta wings
NASA Technical Reports Server (NTRS)
Wood, Richard M.
1988-01-01
Through the empirical correlation of experimental data and theoretical analysis, a set of graphs has been developed which summarize the inviscid aerodynamics of delta wings at supersonic speeds. The various graphs which detail the aerodynamic performance of delta wings at both zero-lift and lifting conditions were then employed to define a preliminary wing design approach in which both the low-lift and high-lift design criteria were combined to define a feasible design space.
elSohly, M A; Little, T L; Stanford, D F
1992-01-01
GC/MS analysis of biological specimens is believed to be the most forensically accepted method for confirming the presence of abused drugs. 11-Nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (delta 9-THC-COOH) is the major metabolite of delta 9-tetrahydrocannabinol (delta 9-THC) for which testing (including GC/MS) is directed as an indication of marijuana use. The currently available internal standard for delta 9-THC-COOH is d3-delta 9-THC-COOH, which has the deuterium atoms located on the side chain. In addition to the high cost of this compound, it suffers from a limited dynamic range of analysis, especially when the methyl derivative is used. This is because of a contribution to one of the internal standard ions (m/z 316) from a fragmentation of the natural drug which involves loss of the side chain. The new internal standard, d6-11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (d6-delta 9-THC-COOH), avoids these disadvantages. The six deuterium atoms are located on the two methyl groups of Carbon 6 in the dibenzopyran structure. The dynamic range of analysis with the new internal standard was tested between 6.25 to 1,000 ng/mL with a correlation coefficient of 0.998. Analysis of several urine specimens for delta 9-THC metabolite using both d3- and d6-internal standards showed a correlation coefficient of 0.9987.
A vortex-lattice method for general, unsteady aerodynamics
NASA Technical Reports Server (NTRS)
Konstadinopoulos, P.; Thrasher, D. F.; Mook, D. T.; Nayfeh, A. H.; Watson, L.
1985-01-01
A general method of calculating unsteady, incompressible, inviscid, three-dimensional flows around arbitrary planforms has been developed. The method is an extension of the vortex-lattice technique. It is not limited by aspect ratio, camber, or angle of attack, as long as vortex breakdown does not occur above the surface of the wing and separation occurs only along sharp edges. As the wing performs arbitrary maneuvers, the position of the wake and the distribution of circulation on the wing and in the wake are obtained as functions of time. One desirable feature of the present method is its ability to treat steady lifting flows very efficiently. Several examples of steady and unsteady flows are presented. These include rectangular wings, with and without flaps, delta, and cropped delta wings.
Dynamic Matching of Vortex Lattice in Superconducting Multilayers
Gurevich, A.; Kadyrov, E.; Larbalestier, D.C.
1996-11-01
We observed oscillations of a nonlinear flux flow resistivity {ital R}({ital j},{ital H}) as a function of a parallel magnetic field 6{lt}{ital H}{lt}9 T in Nb-Ti/Cu multilayers. We show that the oscillations in {ital R}({ital H}), which have the field period {Delta}{ital H}{approx_equal}0.1 T independent of temperature and current, indicate a long-range order in the rapidly moving vortex structure. The critical current {ital I}{sub {ital c}}({ital H}) exhibits no oscillations characteristic of {ital R}({ital H}). We propose an explanation of the effect in terms of dynamic matching of the moving vortex lattice with periodic microstructure and show that both {Delta}{ital H} and the amplitude of the oscillations of {ital R}({ital H}) are inversely proportional to the sample thickness. {copyright} {ital 1996 The American Physical Society.}
Single identities for lattice theory and for weakly associative lattices
McCune, W.; Padmanabhan, R.
1995-03-13
We present a single identity for the variety of all lattices that is much simpler than those previously known to us. We also show that the variety of weakly associative lattices is one-based, and we present a generalized one-based theorem for subvarieties of weakly associative lattices that can be defined with absorption laws. The automated theorem-proving program OTTER was used in substantial way to obtain the results.
Delta-doping in diffusion studies
NASA Astrophysics Data System (ADS)
Bénière, François; Chaplain, René; Gauneau, Marcel; Reddy, Viswanatha; Régrény, André
1993-12-01
The δ-doping where the dopant is confined on the length-scale of the lattice constant provides perfectly ideal conditions to study the atomic transport processes. We have studied MBE-grown GaAs samples δ-doped with Si and Al layers. Long time diffusion anneals have been performed in the temperature range 550 800 °C. The distribution profiles are examined by SIMS-profiling. We obtain Si diffusion coefficients in good agreement with the other recent studies using different techniques (rapid thermal annealing, capacitance-voltage profiling, sandwiched diffusion source). This contrasts with the earlier measurements based on diffusion of implanted dopants which were much more widely spread. We conclude that the more accurate data allowed with the δ-doping show that the diffusion coefficient is an intrinsic parameter provided that the amount of dopant and the dislocation density are kept sufficiently small. Le dopage-delta, où le dopant est confiné à l'échelle du paramètre du réseau, fournit les conditions parfaitement idéales pour étudier les processus de transport atomique. Nous avons étudié des échantillons de GaAs obtenus par épitaxie par jet moléculaire dopés par des couches-delta de Si et Al. Des traitements de diffusion de longue durée ont été réalisés dans l'intervalle de température 550 à 800°C. Les profils de distribution sont examinés par spectrométrie d'émission d'ions secondaires. Nous obtenons des coefficients de diffusion de Si en bon accord avec les autres études récentes utilisant des techniques différentes (traitement thermique ultrarapide, profil de distribution par la méthode capacité-voltage, diffusion d'une couche “ sandwich ”). Ceci diffère des mesures antérieures qui, basées sur la diffusion de dopants implantés, étaient beaucoup plus dispersées. Nous concluons que les données plus précises rendues possibles par le dopage-delta montrent que le coefficient de diffusion est un paramètre intrinsèque
Thermodynamics of the Relationship between Lattice Energy and Lattice Enthalpy
NASA Astrophysics Data System (ADS)
Jenkins, H. Donald B.
2005-06-01
Incorporation of lattice potential energy, U POT , within a Born Fajans Haber thermochemical cycle based on enthalpy changes necessitates correction of the energy of the lattice to an enthalpy term, Δ H L . For a lattice containing p i ions of type i in the formula unit, the lattice enthalpy is given by Δ H L = U POT + ∑ s i [( c i /2) - 2] RT where R is the gas constant (= 8.314 J K -1 mol -1 ), T is the absolute temperature, and c i is defined according as to whether the ion i is monatomic ( c i = 3), linear polyatomic ( c i = 5), or polyatomic ( c i = 6), respectively.
Delta and Omega masses in a three-quark covariant Faddeev approach
Sanchis-Alepuz, Helios; Villalba-Chavez, Selym; Alkofer, Reinhard; Eichmann, Gernot
2011-11-01
We present the solution of the Poincare-covariant Faddeev equation for the {Delta}(1232) and {Omega}(1672) baryons. The covariant structure of the corresponding baryon amplitudes and their decomposition in terms of internal spin and orbital angular momentum is explicitly derived. The interaction kernel is truncated to a rainbow-ladder dressed-gluon exchange such that chiral symmetry and its dynamical breaking are correctly implemented. The resulting physical masses agree reasonably with experiment and their evolution with the pion mass compares favorably with lattice calculations. Evidence for the nonsphericity of the {Delta} resonance is discussed as well.
NASA Astrophysics Data System (ADS)
Beane, Silas
2016-09-01
Over the last several decades, theoretical nuclear physics has been evolving from a very-successful phenomenology of the properties of nuclei, to a first-principles derivation of the properties of visible matter in the Universe from the known underlying theories of Quantum Chromodynamics (QCD) and Electrodynamics. Many nuclear properties have now been calculated using lattice QCD, a method for treating QCD numerically with large computers. In this talk, some of the most recent results in this frontier area of nuclear theory will be reviewed.
LocalMove: computing on-lattice fits for biopolymers
Ponty, Y.; Istrate, R.; Porcelli, E.; Clote, P.
2008-01-01
Given an input Protein Data Bank file (PDB) for a protein or RNA molecule, LocalMove is a web server that determines an on-lattice representation for the input biomolecule. The web server implements a Markov Chain Monte-Carlo algorithm with simulated annealing to compute an approximate fit for either the coarse-grain model or backbone model on either the cubic or face-centered cubic lattice. LocalMove returns a PDB file as output, as well as dynamic movie of 3D images of intermediate conformations during the computation. The LocalMove server is publicly available at http://bioinformatics.bc.edu/clotelab/localmove/. PMID:18556754
Exponentially Fragile PT Symmetry in Lattices with Localized Eigenmodes
Bendix, Oliver; Fleischmann, Ragnar; Kottos, Tsampikos; Shapiro, Boris
2009-07-17
We study the effect of localized modes in lattices of size N with parity-time (PT) symmetry. Such modes are arranged in pairs of quasidegenerate levels with splitting deltaapproxexp{sup -N/x}i where xi is their localization length. The level 'evolution' with respect to the PT breaking parameter gamma shows a cascade of bifurcations during which a pair of real levels becomes complex. The spontaneous PT symmetry breaking occurs at gamma{sub PT}approxmin(delta), thus resulting in an exponentially narrow exact PT phase. As N/xi decreases, it becomes more robust with gamma{sub PT}approx1/N{sup 2} and the distribution P(gamma{sub PT}) changes from log-normal to semi-Gaussian. Our theory can be tested in the frame of optical lattices.
The 3-D lattice theory of Flower Constellations
NASA Astrophysics Data System (ADS)
Davis, Jeremy J.; Avendaño, Martín E.; Mortari, Daniele
2013-08-01
Flower Constellations (FCs) have been extensively studied for use in optimal constellation design. The Harmonic FCs (HFCs) subset, representing the symmetric configurations, have recently been reformulated into 2-D Lattice Flower Constellations (2D-LFCs), encompassing the complete set of HFCs. Elliptic orbits are generally avoided due to the deleterious effects of Earth's oblateness on the constellation, but here we present a novel concept for avoiding this problem and enabling more effective global coverage utilizing elliptic orbits. This new 3D Lattice Flower Constellations (3D-LFCs) framework generalizes the 2D-LFCs, Walker constellations, elliptical Walker constellations, and many of Draim's global coverage constellations. Previous studies have shown FCs can provide improved performance in global navigation over existing Global Navigation Satellite Systems (GNSS). We found a 3D-LFC design that improved the average positioning accuracy by 3.5 % while reducing launch \\varDelta v requirements when compared to the existing Galileo GNSS constellation.
Lattice harmonics expansion revisited
NASA Astrophysics Data System (ADS)
Kontrym-Sznajd, G.; Holas, A.
2017-04-01
The main subject of the work is to provide the most effective way of determining the expansion of some quantities into orthogonal polynomials, when these quantities are known only along some limited number of sampling directions. By comparing the commonly used Houston method with the method based on the orthogonality relation, some relationships, which define the applicability and correctness of these methods, are demonstrated. They are verified for various sets of sampling directions applicable for expanding quantities having the full symmetry of the Brillouin zone of cubic and non-cubic lattices. All results clearly show that the Houston method is always better than the orthogonality-relation one. For the cubic symmetry we present a few sets of special directions (SDs) showing how their construction and, next, a proper application depend on the choice of various sets of lattice harmonics. SDs are important mainly for experimentalists who want to reconstruct anisotropic quantities from their measurements, performed at a limited number of sampling directions.
Orthocomplemented complete lattices and graphs
NASA Astrophysics Data System (ADS)
Ollech, Astrid
1995-08-01
The problem I consider originates from Dörfler, who found a construction to assign an Orthocomplemented lattice H(G) to a graph G. By Dörfler it is known that for every finite Orthocomplemented lattice L there exists a graph G such that H(G)=L. Unfortunately, we can find more than one graph G with this property, i.e., orthocomplemented lattices which belong to different graphs can be isomorphic. I show some conditions under which two graphs have the same orthocomplemented lattice.
S.R. Beane; P.F.Bedaque; A. Parreno; M.J. Savage
2004-04-01
The two-nucleon sector is near an infrared fixed point of QCD and as a result the S-wave scattering lengths are unnaturally large compared to the effective ranges and shape parameters. It is usually assumed that a lattice QCD simulation of the two-nucleon sector will require a lattice that is much larger than the scattering lengths in order to extract quantitative information. In this paper we point out that this does not have to be the case: lattice QCD simulations on much smaller lattices will produce rigorous results for nuclear physics.
Electric Polarizability of Neutral Hadrons from Lattice QCD
Joe Christensen; Walter Wilcox; Frank X. Lee; Leming Zhou
2004-08-01
By simulating a uniform electric field on a lattice and measuring the change in the rest mass, we calculate the electric polarizability of neutral mesons and baryons using the methods of quenched lattice QCD. Specifically, we measure the electric polarizability coefficient from the quadratic response to the electric field for 10 particles: the vector mesons {rho}{sup 0} and K{sup *0}; the octet baryons n, {Sigma}{sup 0}, {Lambda}{sub o}{sup 0}, {Lambda}{sub s}{sup 0}, and {Xi}{sup 0}; and the decouplet baryons {Delta}{sup 0}, {Sigma}{sup 0}, and {Xi}{sup 0}. Independent calculations using two fermion actions were done for consistency and comparison purposes. One calculation uses Wilson fermions with a lattice spacing of a = 0.10 fm. The other uses tadpole improved Luesher-Weiss gauge fields and clover quark action with a lattice spacing a = 0.17 fm. Our results for neutron electric polarizability are compared to experiment.
Elimination of spurious lattice fermion solutions and noncompact lattice QCD
Lee, T.D.
1997-09-22
It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2{sup D} degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l {ne} 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in {rvec {gamma}}, and herein lies one of the essential differences.
Nucleon structure in lattice QCD with dynamical domain-wall fermions quarks
Huey-Wen Lin; Shigemi Ohta
2006-07-23
We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with about 200 gauge configurations each. The lattice cutoff is about 1.7 GeV and the spatial volume is about (1.9 fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments
NUCLEON STRUCTURE IN LATTICE QCD WITH DYNAMICAL DOMAIN--WALL FERMIONS QUARKS.
LIN H.-W.; OHTA, S.
2006-10-02
We report RBC and RBC/UKQCD lattice QCD numerical calculations of nucleon electroweak matrix elements with dynamical domain-wall fermions (DWF) quarks. The first, RBC, set of dynamical DWF ensembles employs two degenerate flavors of DWF quarks and the DBW2 gauge action. Three sea quark mass values of 0.04, 0.03 and 0.02 in lattice units are used with 220 gauge configurations each. The lattice cutoff is a{sup -1} {approx} 1.7GeV and the spatial volume is about (1.9fm){sup 3}. Despite the small volume, the ratio of the isovector vector and axial charges g{sub A}/g{sub V} and that of structure function moments
The DELTA Synchrotron Light Interferometer
Berges, U.
2004-05-12
Synchrotron radiation sources like DELTA, the Dortmund Electron Accelerator, a third generation synchrotron light source, need an optical monitoring system to measure the beam size at different points of the ring with high resolution and accuracy. These measurements also allow an investigation of the emittance of the storage ring, an important working parameter for the efficiency of working beamlines with experiments using the synchrotron radiation. The resolution limits of the different types of optical synchrotron light monitors at DELTA are investigated. The minimum measurable beamsize with the normal synchrotron light monitor using visible light at DELTA is about 80 {mu}m. Due to this a synchrotron light interferometer was built up and tested at DELTA. The interferometer uses the same beamline in the visible range. The minimum measurable beamsize is with about 8 {mu}m one order of magnitude smaller. This resolution is sufficient for the expected small vertical beamsizes at DELTA. The electron beamsize and emittance were measured with both systems at different electron beam energies of the storage ring. The theoretical values of the present optics are smaller than the measured emittance. So possible reasons for beam movements are investigated.
Optical Abelian lattice gauge theories
Tagliacozzo, L.; Celi, A.; Zamora, A.; Lewenstein, M.
2013-03-15
We discuss a general framework for the realization of a family of Abelian lattice gauge theories, i.e., link models or gauge magnets, in optical lattices. We analyze the properties of these models that make them suitable for quantum simulations. Within this class, we study in detail the phases of a U(1)-invariant lattice gauge theory in 2+1 dimensions, originally proposed by P. Orland. By using exact diagonalization, we extract the low-energy states for small lattices, up to 4 Multiplication-Sign 4. We confirm that the model has two phases, with the confined entangled one characterized by strings wrapping around the whole lattice. We explain how to study larger lattices by using either tensor network techniques or digital quantum simulations with Rydberg atoms loaded in optical lattices, where we discuss in detail a protocol for the preparation of the ground-state. We propose two key experimental tests that can be used as smoking gun of the proper implementation of a gauge theory in optical lattices. These tests consist in verifying the absence of spontaneous (gauge) symmetry breaking of the ground-state and the presence of charge confinement. We also comment on the relation between standard compact U(1) lattice gauge theory and the model considered in this paper. - Highlights: Black-Right-Pointing-Pointer We study the quantum simulation of dynamical gauge theories in optical lattices. Black-Right-Pointing-Pointer We focus on digital simulation of abelian lattice gauge theory. Black-Right-Pointing-Pointer We rediscover and discuss the puzzling phase diagram of gauge magnets. Black-Right-Pointing-Pointer We detail the protocol for time evolution and ground-state preparation in any phase. Black-Right-Pointing-Pointer We provide two experimental tests to validate gauge theory quantum simulators.
Avner, R; Laufer, N; Safran, A; Kerem, B S; Friedmann, A; Mitrani-Rosenbaum, S
1994-09-01
W1282X (W) and delta F508 (delta) are the two most common mutations of the cystic fibrosis Israeli population. Patients who are homozygotes (WW and delta delta) as well as compound heterozygotes (W delta) present a severe phenotype of the disease. In the present study, we have developed a polymerase chain reaction (PCR)-based method for the detection of both mutations simultaneously in a single blastomere. Unfertilized human oocytes and single polyspermic blastomeres were subjected to a two-round PCR amplification: a first round of multiplex PCR followed by a second round of nested PCR, done separately at each locus. Clear signals at both loci were obtained in 51% (47/65) of oocytes and 69% (24/35) of blastomeres. The genotype of the single cell analysed was determined by endonuclease digestion of the W products and by heteroduplex formation of the delta F products. This diagnostic system will allow the identification of affected embryos (WW, delta delta, W delta) as well as phenotypically normal carriers (W+, +delta), and therefore may be used for cystic fibrosis preimplantation diagnosis in families who carry either or both mutations.
Direct Tunneling Delay Time Measurement in an Optical Lattice
NASA Astrophysics Data System (ADS)
Fortun, A.; Cabrera-Gutiérrez, C.; Condon, G.; Michon, E.; Billy, J.; Guéry-Odelin, D.
2016-07-01
We report on the measurement of the time required for a wave packet to tunnel through the potential barriers of an optical lattice. The experiment is carried out by loading adiabatically a Bose-Einstein condensate into a 1D optical lattice. A sudden displacement of the lattice by a few tens of nanometers excites the micromotion of the dipole mode. We then directly observe in momentum space the splitting of the wave packet at the turning points and measure the delay between the reflected and the tunneled packets for various initial displacements. Using this atomic beam splitter twice, we realize a chain of coherent micron-size Mach-Zehnder interferometers at the exit of which we get essentially a wave packet with a negative momentum, a result opposite to the prediction of classical physics.
Variational calculation of transport coefficients in diffusive lattice gases
NASA Astrophysics Data System (ADS)
Arita, Chikashi; Krapivsky, P. L.; Mallick, Kirone
2017-03-01
A diffusive lattice gas is characterized by the diffusion coefficient depending only on the density. The Green-Kubo formula for diffusivity can be represented as a variational formula, but even when the equilibrium properties of a lattice gas are analytically known, the diffusion coefficient can be computed only in the exceptional situation when the lattice gas is gradient. In the general case, minimization over an infinite-dimensional space is required. We propose an approximation scheme based on minimizing over finite-dimensional subspaces of functions. The procedure is demonstrated for one-dimensional generalized exclusion processes in which each site can accommodate at most two particles. Our analytical predictions provide upper bounds for the diffusivity that are very close to simulation results throughout the entire density range. We also analyze nonequilibrium density profiles for finite chains coupled to reservoirs. The predictions for the profiles are in excellent agreement with simulations.
Recent progress in lattice QCD
Sharpe, S.R.
1992-12-01
A brief overview of the status of lattice QCD is given, with emphasis on topics relevant to phenomenology. The calculation of the light quark spectrum, the lattice prediction of {alpha} {sub {ovr MS}} (M {sub Z}), and the calculation of f{sub B} are discussed. 3 figs., 3 tabs., 40 refs.
Introduction to lattice gauge theory
NASA Astrophysics Data System (ADS)
Gupta, R.
The lattice formulation of Quantum Field Theory (QFT) can be exploited in many ways. We can derive the lattice Feynman rules and carry out weak coupling perturbation expansions. The lattice then serves as a manifestly gauge invariant regularization scheme, albeit one that is more complicated than standard continuum schemes. Strong coupling expansions: these give us useful qualitative information, but unfortunately no hard numbers. The lattice theory is amenable to numerical simulations by which one calculates the long distance properties of a strongly interacting theory from first principles. The observables are measured as a function of the bare coupling g and a gauge invariant cut-off approx. = 1/alpha, where alpha is the lattice spacing. The continuum (physical) behavior is recovered in the limit alpha yields 0, at which point the lattice artifacts go to zero. This is the more powerful use of lattice formulation, so in these lectures the author focuses on setting up the theory for the purpose of numerical simulations to get hard numbers. The numerical techniques used in Lattice Gauge Theories have their roots in statistical mechanics, so it is important to develop an intuition for the interconnection between quantum mechanics and statistical mechanics.
Study of lattice defect vibration
NASA Technical Reports Server (NTRS)
Elliott, R. J.
1969-01-01
Report on the vibrations of defects in crystals relates how defects, well localized in a crystal but interacting strongly with the other atoms, change the properties of a perfect crystal. The methods used to solve defect problems relate the properties of an imperfect lattice to the properties of a perfect lattice.
Branes and integrable lattice models
NASA Astrophysics Data System (ADS)
Yagi, Junya
2017-01-01
This is a brief review of my work on the correspondence between four-dimensional 𝒩 = 1 supersymmetric field theories realized by brane tilings and two-dimensional integrable lattice models. I explain how to construct integrable lattice models from extended operators in partially topological quantum field theories, and elucidate the correspondence as an application of this construction.
Buckling modes in pantographic lattices
NASA Astrophysics Data System (ADS)
Giorgio, Ivan; Della Corte, Alessandro; dell'Isola, Francesco; Steigmann, David J.
2016-07-01
We study buckling patterns in pantographic sheets, regarded as two-dimensional continua consisting of lattices of continuously distributed fibers. The fibers are modeled as beams endowed with elastic resistance to stretching, shearing, bending and twist. Included in the theory is a non-standard elasticity due to geodesic bending of the fibers relative to the lattice surface. xml:lang="fr"
1972-08-01
35609 Advanced Techniques Branch Plans and Programs Analysis Division Directorate for Product Assurance U. S. Army Missile Command Redstone Arsenal...Ray Heathcock Advanced Techniques Branch Plans and Programs Analysis Division Directorate for Product Assurance U. S. Army Missile Command...for Product Assurance has established a rather unique computer program for handling a variety of chain sampling schemes and is available for
A study of the N to Delta transition form factors in full QCD
Constantia Alexandrou; Robert Edwards; Giannis Koutsou; Theodoros Leontiou; Hartmut Neff; John W. Negele; Wolfram Schroers; Antonios Tsapalis
2005-07-01
The N to Delta transition form factors GM1, GE2 and GC2 are evaluated using dynamical MILC configurations and valence domain wall fermions at three values of quark mass corresponding to pion mass 606 MeV, 502 MeV and 364 MeV on lattices of spatial size 20{sup 3} and 28{sup 3}. The unquenched results are compared to those obtained at similar pion mass in the quenched theory.
Lattice models of ionic systems
NASA Astrophysics Data System (ADS)
Kobelev, Vladimir; Kolomeisky, Anatoly B.; Fisher, Michael E.
2002-05-01
A theoretical analysis of Coulomb systems on lattices in general dimensions is presented. The thermodynamics is developed using Debye-Hückel theory with ion-pairing and dipole-ion solvation, specific calculations being performed for three-dimensional lattices. As for continuum electrolytes, low-density results for simple cubic (sc), body-centered cubic (bcc), and face-centered cubic (fcc) lattices indicate the existence of gas-liquid phase separation. The predicted critical densities have values comparable to those of continuum ionic systems, while the critical temperatures are 60%-70% higher. However, when the possibility of sublattice ordering as well as Debye screening is taken into account systematically, order-disorder transitions and a tricritical point are found on sc and bcc lattices, and gas-liquid coexistence is suppressed. Our results agree with recent Monte Carlo simulations of lattice electrolytes.
NASA Astrophysics Data System (ADS)
Podgorski, J. E.; Kgotlhang, L.; Ngwisanyi, T.; Ploug, C.; Auken, E.; Kinzelbach, W. K.; Green, A. G.
2010-12-01
The Okavango Delta within the Kalahari Desert of northwestern Botswana is one of the world's largest inland deltas and the largest wetland in southern Africa. An annual flood originating from the Okavango River in the northwest passes through the upper panhandle region of the delta before inundating the 150 km x 150 km fan where most water is lost to evapotranspiration. The fan occupies an active graben at the southwestern end of the East Africa rift zone. The focus of faulting is along the fan’s southeastern end where the Kunyere-Thamalakane faults show 200-300 m of dip-slip offset, forming a backstop to the movement of water and sediments. An airborne TEM survey was flown over the entire delta in 2007 with 2 km line spacing. A preliminary inversion of the entire data set has been undertaken using a quasi-2D inversion scheme that includes resistivity, layer thickness, and transmitter height as parameters. Tests with a many-layer model indicate that a four-layer model explains the data. Inversion results are corroborated by limited borehole data. The TEM model includes significant lateral and vertical variations in electrical resistivity. In the central region of the fan, a near-surface high resistivity layer is underlain sequentially by a more conductive layer (about 100 m depth) and a more resistive half-space (about 160 m depth), the latter of which could be a fresh water aquifer. This resistive feature has a fan-like form. A plausible evolutionary scenario that explains the TEM data includes a proto-Okavango Delta (highly resistive half-space ) and a lake (intermediate-depth conductive layer). During a climatic episode similar to today’s, a proto-Okavango Delta sequence would have been deposited against a fault, much as the Kunyere-Thamalakane faults today delineate the southeastern margin of the present Okavango Delta. This region would have then been flooded by a Pleistocene lake system that inundated much of northern Botswana and was the source of
Defect modes of a Bose-Einstein condensate in an optical lattice with a localized impurity
Brazhnyi, Valeriy A.; Konotop, Vladimir V.; Perez-Garcia, Victor M.
2006-08-15
We study defect modes of a Bose-Einstein condensate in an optical lattice with a localized defect within the framework of the one-dimensional Gross-Pitaevskii equation. It is shown that for a significant range of parameters the defect modes can be accurately described by an expansion over Wannier functions, whose envelope is governed by the coupled nonlinear Schroedinger equations with a {delta} impurity. The stability of the defect modes is verified by direct numerical simulations of the underlying Gross-Pitaevskii equation with a periodic and defect potentials. We also discuss possibilities of driving defect modes through the lattice and suggest ideas for their experimental generation.
Side-chain entropy and packing in proteins.
Bromberg, S.; Dill, K. A.
1994-01-01
What role does side-chain packing play in protein stability and structure? To address this question, we compare a lattice model with side chains (SCM) to a linear lattice model without side chains (LCM). Self-avoiding configurations are enumerated in 2 and 3 dimensions exhaustively for short chains and by Monte Carlo sampling for chains up to 50 main-chain monomers long. This comparison shows that (1) side-chain degrees of freedom increase the entropy of open conformations, but side-chain steric exclusion decreases the entropy of compact conformations, thus producing a substantial entropy that opposes folding; (2) there is side-chain "freezing" or ordering, i.e., a sharp decrease in entropy, near maximum compactness; and (3) the different types of contacts among side chains (s) and main-chain elements (m) have different frequencies, and the frequencies have different dependencies on compactness. mm contacts contribute significantly only at high densities, suggesting that main-chain hydrogen bonding in proteins may be promoted by compactness. The distributions of mm, ms, and ss contacts in compact SCM configurations are similar to the distributions in protein structures in the Brookhaven Protein Data Bank. We propose that packing in proteins is more like the packing of nuts and bolts in a jar than like the pairwise matching of jigsaw puzzle pieces. PMID:7920265
NASA Technical Reports Server (NTRS)
2006-01-01
6 August 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a chain of clustered and battered craters. These were formed by secondary impact. That is, somewhere to the south (beyond the bottom of this image), a large impact crater formed. When this occurred, material ejected from the crater was thrown tens to hundreds of kilometers away. This material then impacted the martian surface, forming clusters and chains of smaller craters.
Location near: 15.8oN, 35.6oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Northern Spring
Delta launch vehicle inertial guidance system (DIGS)
NASA Technical Reports Server (NTRS)
Duck, K. I.
1973-01-01
The Delta inertial guidance system, part of the Delta launch vehicle improvement effort, has been flown on three launches and was found to perform as expected for a variety of mission profiles and vehicle configurations.
Revisiting double Dirac delta potential
NASA Astrophysics Data System (ADS)
Ahmed, Zafar; Kumar, Sachin; Sharma, Mayank; Sharma, Vibhu
2016-07-01
We study a general double Dirac delta potential to show that this is the simplest yet still versatile solvable potential to introduce double wells, avoided crossings, resonances and perfect transmission (T = 1). Perfect transmission energies turn out to be the critical property of symmetric and anti-symmetric cases wherein these discrete energies are found to correspond to the eigenvalues of a Dirac delta potential placed symmetrically between two rigid walls. For well(s) or barrier(s), perfect transmission (or zero reflectivity, R(E)) at energy E=0 is non-intuitive. However, this has been found earlier and called the ‘threshold anomaly’. Here we show that it is a critical phenomenon and we can have 0≤slant R(0)\\lt 1 when the parameters of the double delta potential satisfy an interesting condition. We also invoke a zero-energy and zero curvature eigenstate (\\psi (x)={Ax}+B) of the delta well between two symmetric rigid walls for R(0)=0. We resolve that the resonant energies and the perfect transmission energies are different and they arise differently.
Graczyk, Krzysztof M.
2011-11-23
A short review of the Rein-Sehgal and isobar models is presented. The attention is focused on the nucleon-{Delta}(1232) weak transition form-factors. The results of the recent re-analyses of the ANL and BNL bubble chamber neutrino-deuteron scattering data are discussed.
... increased level of urinary delta-ALA may indicate: Lead poisoning Porphyria (several types) A decreased level may occur ... A.M. Editorial team. Related MedlinePlus Health Topics Lead Poisoning Porphyria Browse the Encyclopedia A.D.A.M., ...
Spongeplant Spreading in the Delta
Technology Transfer Automated Retrieval System (TEKTRAN)
Invasive, exotic aquatic plants impact a range of important economic and ecological functions in the Sacramento-San Joaquin Delta of California, and the state now spends over $5 million to control water hyacinth and Brazilian waterweed. In 2007, a new exotic floating plant South American Spongeplan...
Phytoplankton fuels Delta food web
Jassby, Alan D.; Cloern, James E.; Muller-Solger, A. B.
2003-01-01
Populations of certain fishes and invertebrates in the Sacramento-San Joaquin Delta have declined in abundance in recent decades and there is evidence that food supply is partly responsible. While many sources of organic matter in the Delta could be supporting fish populations indirectly through the food web (including aquatic vegetation and decaying organic matter from agricultural drainage), a careful accounting shows that phytoplankton is the dominant food source. Phytoplankton, communities of microscopic free-floating algae, are the most important food source on a Delta-wide scale when both food quantity and quality are taken into account. These microscopic algae have declined since the late 1960s. Fertilizer and pesticide runoff do not appear to be playing a direct role in long-term phytoplankton changes; rather, species invasions, increasing water transparency and fluctuations in water transport are responsible. Although the potential toxicity of herbicides and pesticides to plank- ton in the Delta is well documented, the ecological significance remains speculative. Nutrient inputs from agricultural runoff at current levels, in combination with increasing transparency, could result in harmful al- gal blooms.
Maintenance of large deltas through channelization
NASA Astrophysics Data System (ADS)
Giosan, L.; Constatinescu, S.; Filip, F.
2013-12-01
A new paradigm for delta restoration is currently taking shape using primarily Mississippi delta examples. Here we propose an alternative for delta maintenance primarily envisioned for wave-influenced deltas based on Danube delta experiences. Over the last half century, while the total sediment load of the Danube dramatically decreased due to dam construction on tributaries and its mainstem, a grand experiment was inadvertently run in the Danube delta: the construction of a dense network of canals, which almost tripled the water discharge toward the interior of the delta plain. We use core-based and chart-based sedimentation rates and patterns to explore the delta transition from the natural to an anthropogenic regime, to understand the effects of far-field damming and near-field channelization, and to construct a conceptual model for delta development as a function sediment partition between the delta plain and the delta coastal fringe. We show that sediment fluxes increased to the delta plain due to channelization, counteracting sea level rise. In turn, the delta coastal fringe was most impacted by the Danube's sediment load collapse. Furthermore, we show that morphodynamic feedbacks at the river mouth are crucial in trapping sediment near the coast and constructing wave-dominated deltas or lobes or delaying their destruction. As a general conclusion, we suggest that increased channelization that mimics and enhances natural processes may provide a simple solution for keeping delta plains above sea level and that abandonment of wave-dominated lobes may be the most long term efficient solution for protecting the internal fluvial regions of deltas and provide new coastal growth downcoast.
Synthesis and oxygen content dependent properties of hexagonal DyMnO[subscript 3+delta
Remsen, S.; Dabrowski, B.; Chmaissem, O.; Mais, J.; Szewczyk, A.
2011-10-28
Oxygen deficient polycrystalline samples of hexagonal P6{sub 3}cm (space group No.185) DyMnO{sub 3+{delta}} ({delta} < 0) were synthesized in Ar by intentional decomposition of its perovskite phase obtained in air. The relative stability of these phases is in accord with our previous studies of the temperature and oxygen vacancy dependent tolerance factor. Thermogravimetric measurements have shown that hexagonal samples of DyMnO{sub 3+{delta}} (0 {le} {delta} {le} 0.4) exhibit unusually large excess oxygen content, which readily incorporates on heating near 300 C in various partial-pressures of oxygen atmospheres. Neutron and synchrotron diffraction data show the presence of two new structural phases at {delta} {approx} 0.25 (Hex{sub 2}) and {delta} {approx} 0.40 (Hex{sub 3}). Rietveld refinements of the Hex{sub 2} phase strongly suggest it is well modeled by the R3 space group (No.146). These phases were observed to transform back to P6{sub 3}cm above {approx} 350 C when material becomes stoichiometric in oxygen content ({delta} = 0). Chemical expansion of the crystal lattice corresponding to these large changes of oxygen was found to be 3.48 x 10{sup -2} mol{sup -1}. Thermal expansion of stoichiometric phases were determined to be 11.6 x 10{sup -6} and 2.1 x 10{sup -6} K{sup -1} for the P6{sub 3}cm and Hex{sub 2} phases, respectively. Our measurements also indicate that the oxygen non-stoichiometry of hexagonal RMnO{sub 3+{delta}} materials may have important influence on their multiferroic properties.
Frequency of the delta ccr5 deletion allele in the urban Brazilian population.
Passos, G A; Picanço, V P
1998-04-01
Studies on screening genes conferring resistance to HIV-1 and AIDS onset have shown a direct relationship between a 32 base pair (bp) deletion in the CCR5 beta-chemokine receptor gene (delta ccr5 mutant allele) and long survival of HIV-1 infected individuals bearing this mutation. These findings led to an interest in studies of delta ccr5 allele distribution in human populations. In the present study, polymerase chain reactions (PCR) in genomic DNA samples, using specific CCR5 oligonucleotide primers surrounding the breakpoint deletion, detected a 193-bp product from the normal CCR5 allele and a 161-bp product from the 32-bp deletion allele. In an investigation of the urban Brazilian population we detected a 93% frequency of normal CCR5/CCR5 homozygous individuals and a 7% frequency of CCR5/delta ccr5 heterozygous individuals. The frequency of the delta ccr5 mutant allele in this population is 0.035; however, no homozygous delta ccr5 individual has been detected thus far. This is the first evidence for the contribution of the delta ccr5 allele to the genetic background of the urban Brazilian population, which is characterized by intense ethnic admixture. These findings open perspectives for further studies on the relationship between delta ccr5 allele frequency and AIDS onset in high-risk HIV-1 exposures individuals.
Localized structures in Kagome lattices
Saxena, Avadh B; Bishop, Alan R; Law, K J H; Kevrekidis, P G
2009-01-01
We investigate the existence and stability of gap vortices and multi-pole gap solitons in a Kagome lattice with a defocusing nonlinearity both in a discrete case and in a continuum one with periodic external modulation. In particular, predictions are made based on expansion around a simple and analytically tractable anti-continuum (zero coupling) limit. These predictions are then confirmed for a continuum model of an optically-induced Kagome lattice in a photorefractive crystal obtained by a continuous transformation of a honeycomb lattice.
Lattice QCD: Status and Prospect
Ukawa, Akira
2006-02-08
A brief review is given of the current status and near-future prospect of lattice QCD studies of the Standard Model. After summarizing a bit of history, we describe current attempts toward inclusion of dynamical up, down and strange quarks. Recent results on the light hadron mass spectrum as well as those on the heavy quark quantities are described. Recent work on lattice pentaquark search is summarized. We touch upon the PACS-CS Project for building our next machine for lattice QCD, and conclude with a summary of computer situation and the physics possibilities over the next several years.
Limited junctional diversity of V delta 5-J delta 1 rearrangement in multiple sclerosis patients.
Nowak, J S; Michałowska-Wender, G; Januszkiewicz, D; Wender, M
1997-01-01
T-cell receptor (TCR) delta gene repertoire, as assessed by V delta-J delta rearrangements, has been analyzed in nine multiple sclerosis (MS) cases and in 30 healthy individuals by seminested PCR technique. Among the V delta-J delta junctional diversities studied, the most striking result has been observed in V delta 5-J delta 1 rearrangement. The detection of repeated V delta 5-J delta 1 nucleotide sequences in all analyzed clones from seven out of nine patients studied proved the monoclonal nature of gamma delta T-cells with V delta 5-J delta 1 rearrangement. The clonal nature of this rearrangement proved by PAGE and sequencing analysis may suggest an antigen-driven expansion of gamma delta T cells and argues for a significant role of gamma delta T-cells with V delta 5-J delta 1 rearrangement in MS pathogenesis. However, it cannot be excluded that clonal expansion of these lymphocytes may represent secondary change to central nervous system damage.
Yang, Yi-feng; Fisk, Zachary; Lee, Han-Oh; Thompson, J D; Pines, David
2008-07-31
The origin of magnetic order in metals has two extremes: an instability in a liquid of local magnetic moments interacting through conduction electrons, and a spin-density wave instability in a Fermi liquid of itinerant electrons. This dichotomy between 'local-moment' magnetism and 'itinerant-electron' magnetism is reminiscent of the valence bond/molecular orbital dichotomy present in studies of chemical bonding. The class of heavy-electron intermetallic compounds of cerium, ytterbium and various 5f elements bridges the extremes, with itinerant-electron magnetic characteristics at low temperatures that grow out of a high-temperature local-moment state. Describing this transition quantitatively has proved difficult, and one of the main unsolved problems is finding what determines the temperature scale for the evolution of this behaviour. Here we present a simple, semi-quantitative solution to this problem that provides a basic framework for interpreting the physics of heavy-electron materials and offers the prospect of a quantitative determination of the physical origin of their magnetic ordering and superconductivity. It also reveals the difference between the temperature scales that distinguish the conduction electrons' response to a single magnetic impurity and their response to a lattice of local moments, and provides an updated version of the well-known Doniach diagram.
27 CFR 9.96 - Mississippi Delta.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Mississippi Delta. 9.96... Mississippi Delta. (a) Name. The name of the viticultural area described in this section is “Mississippi Delta.” (b) Approved maps. The appropriate maps for determining the boundaries of the Mississippi...
27 CFR 9.96 - Mississippi Delta.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Mississippi Delta. 9.96... Mississippi Delta. (a) Name. The name of the viticultural area described in this section is “Mississippi Delta.” (b) Approved maps. The appropriate maps for determining the boundaries of the Mississippi...
27 CFR 9.96 - Mississippi Delta.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Mississippi Delta. 9.96... Mississippi Delta. (a) Name. The name of the viticultural area described in this section is “Mississippi Delta.” (b) Approved maps. The appropriate maps for determining the boundaries of the Mississippi...
27 CFR 9.96 - Mississippi Delta.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Mississippi Delta. 9.96... Mississippi Delta. (a) Name. The name of the viticultural area described in this section is “Mississippi Delta.” (b) Approved maps. The appropriate maps for determining the boundaries of the Mississippi...
27 CFR 9.96 - Mississippi Delta.
Code of Federal Regulations, 2012 CFR
2012-04-01
... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Mississippi Delta. 9.96... Mississippi Delta. (a) Name. The name of the viticultural area described in this section is “Mississippi Delta.” (b) Approved maps. The appropriate maps for determining the boundaries of the Mississippi...
Lattice function measurement with TBT BPM data
Yang, M.J.
1995-06-01
At Fermilab Main Ring some of the Beam Position Monitors (BPM) are instrumented with Turn-By-Turn (TBT) capability to record up to 1,024 consecutive turns of BPM data for each given trigger. For example, there are 9 horizontal plane and 8 vertical plane BPM`s in the sector D3 and D4. The BPM data, which records the betatron oscillation, is fitted to obtain beam parameters x, x{prime}, y, y{prime}, and {Delta}p/p, using the calculated beam line transfer matrix. The resulted TBT beam parameters (x, x{prime}) or (y, y{prime}) are fitted to ellipses to obtain the lattice function {beta}, {alpha}, and the emittance associated with the betatron oscillation. The tune of the machine can be calculated from the phase space angles of the successive turns, in the normalized phase space. The beam parameters can also be used to extract transfer matrix to be used for local and global coupling analysis. The process of fitting the BPM data produces information that can be used to diagnose problems such as calibration, noise level and polarity. Being available at every turn and at changing beam position the information carries a lot of statistical power. Since most of the BPM`s are located at high beta location only the x and y beam position information is not simultaneously available. The BPM data fitting processing essentially bridged the gap.
Kaon matrix elements and CP violation from quenched lattice QCD
NASA Astrophysics Data System (ADS)
Cristian, Calin-Radu
We report the results of a calculation of the K → pipi matrix elements relevant for the DeltaI = 1/2 rule and epsilon '/epsilon in quenched lattice QCD using domain wall fermions at a fixed lattice spacing of a-1 ˜ 2 GeV. Working in the three-quark effective theory, where only the u, d and s quarks enter and which is known perturbatively to next-to-leading order; we calculate the lattice K → pi and K → |0> matrix elements of dimension six, four-fermion operators. Through lowest order chiral perturbation theory these yield K → pipi matrix elements, which we then normalize to continuum values through a non-perturbative renormalization technique. For the Delta I = 1/2 rule we find a value of 25.3 +/- 1.8 (statistical error only) compared to the experimental value of 22.2, with individual isospin amplitudes 10--20% below the experimental values. For epsilon '/epsilon; using known central values for standard model parameters, we calculate (-4.0 +/- 2.3) x 10-4 (statistical error only) compared to the current experimental average of (17.2 +/- 1.8) x 10-4. Because we find a large cancellation between the I = 0 and I = 2 contributions to epsilon'/epsilon, the result may be very sensitive to the approximations employed. Among these are the use of: quenched QCD, lowest order chiral perturbation theory and continuum perturbation theory below 1.3 GeV. We have also calculated the kaon B parameter, BK and find BK(2 GeV) = 0.532(11). Although currently unable to give a reliable systematic error; we have control over statistical errors and more simulations will yield information about the effects of the approximations on this first-principles determination of these important quantities.
Lattice design for head-on beam-beam compensation at RHIC
Montag, C.
2011-03-28
Electron lenses for head-on beam-beam compensation will be installed in IP 10 at RHIC. Compensation of the beam-beam effect experienced at IP 8 requires betatron phase advances of {Delta}{psi} = k {center_dot} {pi} between the proton-proton interaction point at IP 8, and the electron lens at IP 10. This paper describes the lattice solutions for both the BLUE and the YELLOW ring to achieve this goal.
Counting Lattice-Gas Invariants
2007-11-02
Dominique d’Humières, Brosl Hasslacher, Pierre Lallemand, Yves Pomeau, and Jean-Pierre Rivet . Lattice gas hydrodynamics in two and three dimensions...177. Springer -Verlag, Februrary 1989. Proceedings of the Winter School, Les Houches, France. 6
LATTICE QCD AT FINITE TEMPERATURE.
PETRECZKY, P.
2005-03-12
I review recent progress in lattice QCD at finite temperature. Results on the transition temperature will be summarized. Recent progress in understanding in-medium modifications of interquark forces and quarkonia spectral functions at finite temperatures is discussed.
Lattice Multiplication: Old and New.
ERIC Educational Resources Information Center
Givan, Betty; Karr, Rosemary
1988-01-01
The author presents two examples of lattice multiplication followed by a computer algorithm to perform this multiplication. The algorithm is given in psuedocode but could easily be given in Pascal. (PK)
Andreas S. Kronfeld
2003-11-05
This paper is a review of heavy quarks in lattice gauge theory, focusing on methodology. It includes a status report on some of the calculations that are relevant to heavy-quark spectroscopy and to flavor physics.
Lattice Studies of Hyperon Spectroscopy
Richards, David G.
2016-04-01
I describe recent progress at studying the spectrum of hadrons containing the strange quark through lattice QCD calculations. I emphasise in particular the richness of the spectrum revealed by lattice studies, with a spectrum of states at least as rich as that of the quark model. I conclude by prospects for future calculations, including in particular the determination of the decay amplitudes for the excited states.
Lattice QCD in rotating frames.
Yamamoto, Arata; Hirono, Yuji
2013-08-23
We formulate lattice QCD in rotating frames to study the physics of QCD matter under rotation. We construct the lattice QCD action with the rotational metric and apply it to the Monte Carlo simulation. As the first application, we calculate the angular momenta of gluons and quarks in the rotating QCD vacuum. This new framework is useful to analyze various rotation-related phenomena in QCD.
Yamamoto, Arata
2016-07-29
We propose the lattice QCD calculation of the Berry phase, which is defined by the ground state of a single fermion. We perform the ground-state projection of a single-fermion propagator, construct the Berry link variable on a momentum-space lattice, and calculate the Berry phase. As the first application, the first Chern number of the (2+1)-dimensional Wilson fermion is calculated by the Monte Carlo simulation.
Lattice QCD: A Brief Introduction
NASA Astrophysics Data System (ADS)
Meyer, H. B.
A general introduction to lattice QCD is given. The reader is assumed to have some basic familiarity with the path integral representation of quantum field theory. Emphasis is placed on showing that the lattice regularization provides a robust conceptual and computational framework within quantum field theory. The goal is to provide a useful overview, with many references pointing to the following chapters and to freely available lecture series for more in-depth treatments of specifics topics.
Mello Koch, Robert de; Mashile, Grant; Park, Nicholas
2010-05-15
In this article the anomalous dimension of a class of operators with a bare dimension of O(N) is studied. The operators considered are dual to excited states of a two giant graviton system. In the Yang-Mills theory they are described by restricted Schur polynomials, labeled with Young diagrams that have at most two columns. In a certain limit the dilatation operator looks like a lattice version of a second derivative, with the lattice emerging from the Young diagram itself.
DeGrand, T.
1997-06-01
These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and {alpha}{sub s} (M{sub z}), and B-{anti B} mixing. 67 refs., 36 figs.
Maximum-likelihood approach to topological charge fluctuations in lattice gauge theory
NASA Astrophysics Data System (ADS)
Brower, R. C.; Cheng, M.; Fleming, G. T.; Lin, M. F.; Neil, E. T.; Osborn, J. C.; Rebbi, C.; Rinaldi, E.; Schaich, D.; Schroeder, C.; Voronov, G.; Vranas, P.; Weinberg, E.; Witzel, O.
2014-07-01
We present a novel technique for the determination of the topological susceptibility (related to the variance of the distribution of global topological charge) from lattice gauge theory simulations, based on maximum-likelihood analysis of the Markov-chain Monte Carlo time series. This technique is expected to be particularly useful in situations where relatively few tunneling events are observed. Restriction to a lattice subvolume on which topological charge is not quantized is explored, and may lead to further improvement when the global topology is poorly sampled. We test our proposed method on a set of lattice data, and compare it to traditional methods.
Lattice architecture effect on the cooperativity of spin transition coordination polymers
Chiruta, Daniel; Jureschi, Catalin-Maricel; Rotaru, Aurelian E-mail: rotaru@eed.usv.ro; Linares, Jorge E-mail: rotaru@eed.usv.ro; Garcia, Yann
2014-02-07
We have investigated in the framework of the Ising-like model, by means of Monte Carlo Metropolis method with open boundary condition, the architecture effect on the cooperativity of spin transition coordination polymers. We have analyzed the influence of several physical parameters (size, pressure, and edge effects) on different lattice architectures which were in good agreement with reported experimental data. We show that the cooperativity of a spin crossover system, characterized by the same number of molecules and the same short- and long-range interaction parameters, is progressively enhanced when going from a 1D chain to a 1D ladder type lattice and to a 2D square lattice.
Lattice architecture effect on the cooperativity of spin transition coordination polymers
NASA Astrophysics Data System (ADS)
Chiruta, Daniel; Jureschi, Catalin-Maricel; Linares, Jorge; Garcia, Yann; Rotaru, Aurelian
2014-02-01
We have investigated in the framework of the Ising-like model, by means of Monte Carlo Metropolis method with open boundary condition, the architecture effect on the cooperativity of spin transition coordination polymers. We have analyzed the influence of several physical parameters (size, pressure, and edge effects) on different lattice architectures which were in good agreement with reported experimental data. We show that the cooperativity of a spin crossover system, characterized by the same number of molecules and the same short- and long-range interaction parameters, is progressively enhanced when going from a 1D chain to a 1D ladder type lattice and to a 2D square lattice.
Optimal lattice-structured materials
NASA Astrophysics Data System (ADS)
Messner, Mark C.
2016-11-01
This work describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describing the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.
Optimal lattice-structured materials
Messner, Mark C.
2016-07-09
This paper describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describingmore » the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.« less
Optimal lattice-structured materials
Messner, Mark C.
2016-07-09
This paper describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describing the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.
Phyllotaxis of flux lattices in layered superconductors
Levitov, L.S. )
1991-01-14
The geometry of a flux lattice pinned by superconducting layers is studied. Under variation of magnetic field the lattice undergoes an infinite sequence of continuous transitions corresponding to different ways of selection of shortest distances. All possible lattices form a hierarchical structure identified as the hierarchy of Farey numbers. It is shown that dynamically accessible lattices are characterized by pairs of consecutive Fibonacci numbers.
Topological Charge Evolution in the Markov-Chain of QCD
Derek Leinweber; Anthony Williams; Jian-bo Zhang; Frank Lee
2004-04-01
The topological charge is studied on lattices of large physical volume and fine lattice spacing. We illustrate how a parity transformation on the SU(3) link-variables of lattice gauge configurations reverses the sign of the topological charge and leaves the action invariant. Random applications of the parity transformation are proposed to traverse from one topological charge sign to the other. The transformation provides an improved unbiased estimator of the ensemble average and is essential in improving the ergodicity of the Markov chain process.
Discharge Asymmetry in Delta Bifurcations
NASA Astrophysics Data System (ADS)
Salter, G.; Paola, C.; Voller, V. R.
2015-12-01
Distributary networks are formed by channels which bifurcate downstream in a river delta. Sediment and water fluxes are often split unequally in delta bifurcations. Understanding flux asymmetry in distributary networks is important for predicting how a delta will respond to sea-level rise. We present results of a quasi-1D model of a delta bifurcation. Consistent with previous results, in the absence of deposition, stable bifurcations may be either symmetric or asymmetric, depending on flow conditions. However, in a depositional setting, a stable asymmetric flow partitioning is no longer possible, as the dominant branch becomes less and less steep relative to the other branch. This feedback eventually causes the second branch to become favored. For the depositional case, we identify three regimes of bifurcation behavior: 1) stable symmetric bifurcation, 2) "soft" avulsions where the dominant branch switches without complete abandonment of the previous channel, and 3) complete avulsions where one branch is completely abandoned. In each case, the bifurcation is symmetric in the long-term average, but the latter two allow for short-term asymmetry. We find that keeping upstream sediment and water discharges fixed, as downstream channel length increases the regime shifts from symmetric to soft avulsions to complete avulsions. In the two avulsion regimes we examine the effect of upstream sediment and water discharges and downstream channel length on avulsion period and maximum discharge ratio. Finally, we compare numerical modeling results to a fixed-wall bifurcation experiment. As in the numerical model, the presence or absence of a downstream sink exerts a strong control on system behavior. If a sink is present, a bifurcation may be asymmetric indefinitely. Conversely, without a sink the system is depositional, and the feedback between sediment discharge asymmetry and slope causes the bifurcation to remain symmetric in the long-term average.
Deformation characteristics of {delta} phase in the delta-processed Inconel 718 alloy
Zhang, H.Y.; Zhang, S.H.; Cheng, M.; Li, Z.X.
2010-01-15
The hot working characteristics of {delta} phase in the delta-processed Inconel 718 alloy during isothermal compression deformation at temperature of 950 deg. C and strain rate of 0.005 s{sup -1}, were studied by using optical microscope, scanning electron microscope and quantitative X-ray diffraction technique. The results showed that the dissolution of plate-like {delta} phase and the precipitation of spherical {delta} phase particles coexisted during the deformation, and the content of {delta} phase decreased from 7.05 wt.% to 5.14 wt.%. As a result of deformation breakage and dissolution breakage, the plate-like {delta} phase was spheroidized and transferred to spherical {delta} phase particles. In the center with largest strain, the plate-like {delta} phase disappeared and spherical {delta} phase appeared in the interior of grains and grain boundaries.
Doping Scheme of Semiconducting Atomic Chains
NASA Technical Reports Server (NTRS)
Toshishige, Yamada; Saini, Subhash (Technical Monitor)
1998-01-01
Atomic chains, precise structures of atomic scale created on an atomically regulated substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are acceptors. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or acceptors is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br-doped (p-type) and Cs-doped (n-type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified.
Parallel Markov chain Monte Carlo simulations.
Ren, Ruichao; Orkoulas, G
2007-06-07
With strict detailed balance, parallel Monte Carlo simulation through domain decomposition cannot be validated with conventional Markov chain theory, which describes an intrinsically serial stochastic process. In this work, the parallel version of Markov chain theory and its role in accelerating Monte Carlo simulations via cluster computing is explored. It is shown that sequential updating is the key to improving efficiency in parallel simulations through domain decomposition. A parallel scheme is proposed to reduce interprocessor communication or synchronization, which slows down parallel simulation with increasing number of processors. Parallel simulation results for the two-dimensional lattice gas model show substantial reduction of simulation time for systems of moderate and large size.
Parallel Markov chain Monte Carlo simulations
NASA Astrophysics Data System (ADS)
Ren, Ruichao; Orkoulas, G.
2007-06-01
With strict detailed balance, parallel Monte Carlo simulation through domain decomposition cannot be validated with conventional Markov chain theory, which describes an intrinsically serial stochastic process. In this work, the parallel version of Markov chain theory and its role in accelerating Monte Carlo simulations via cluster computing is explored. It is shown that sequential updating is the key to improving efficiency in parallel simulations through domain decomposition. A parallel scheme is proposed to reduce interprocessor communication or synchronization, which slows down parallel simulation with increasing number of processors. Parallel simulation results for the two-dimensional lattice gas model show substantial reduction of simulation time for systems of moderate and large size.
Love, S.P.; Scott, B.; Worl, L.A.; Huckett, S.C.; Saxena, A.; Huang, X.Z.; Bishop, A.R.; Swanson, B.I.
1993-01-01
Resonance Raman techniques, together with lattice-dynamics and Peierls-Hubbard modelling, are used to explore the electronic and vibrational dynamics of the quasi-one-dimensional metal-halogen chain solids [Pt(en)[sub 2
Shocks, Rarefaction Waves, and Current Fluctuations for Anharmonic Chains
NASA Astrophysics Data System (ADS)
Mendl, Christian B.; Spohn, Herbert
2017-02-01
The nonequilibrium dynamics of anharmonic chains is studied by imposing an initial domain-wall state, in which the two half lattices are prepared in equilibrium with distinct parameters. We analyse the Riemann problem for the corresponding Euler equations and, in specific cases, compare with molecular dynamics. Additionally, the fluctuations of time-integrated currents are investigated. In analogy with the KPZ equation, their typical fluctuations should be of size t^{1/3} and have a Tracy-Widom GUE distributed amplitude. The proper extension to anharmonic chains is explained and tested through molecular dynamics. Our results are calibrated against the stochastic LeRoux lattice gas.
Shocks, Rarefaction Waves, and Current Fluctuations for Anharmonic Chains
NASA Astrophysics Data System (ADS)
Mendl, Christian B.; Spohn, Herbert
2016-10-01
The nonequilibrium dynamics of anharmonic chains is studied by imposing an initial domain-wall state, in which the two half lattices are prepared in equilibrium with distinct parameters. We analyse the Riemann problem for the corresponding Euler equations and, in specific cases, compare with molecular dynamics. Additionally, the fluctuations of time-integrated currents are investigated. In analogy with the KPZ equation, their typical fluctuations should be of size t^{1/3} and have a Tracy-Widom GUE distributed amplitude. The proper extension to anharmonic chains is explained and tested through molecular dynamics. Our results are calibrated against the stochastic LeRoux lattice gas.
The kaon B-parameter from unquenched mixed action lattice QCD
Aubin, Christopher A.; Laiho, Jack; Van de Water, Ruth S.
2007-10-01
We present a preliminary calculation of B{sub K} using domain-wall valence quarks and 2+1 flavors of improved staggered sea quarks. Both the size of the residual quark mass, which measures the amount of chiral symmetry breaking, and of the mixed meson splitting Delta{sub mix}, a measure of taste-symmetry breaking, show that discretization effects are under control in our mixed action lattice simulations. We show preliminary data for pseudoscalar meson masses, decay constants and B{sub K}. We discuss general issues associated with the chiral extrapolation of lattice data, and, as an example, present a preliminary chiral and continuum extrapolation of f{sub pi}. The quality of our data shows that the good chiral properties of domain-wall quarks, in combination with the light sea quark masses and multiple lattice spacings available with the MILC staggered configurations, will allow for a precise determination of B{sub K}.
Delta deposition influenced by diapiric uplifts
Kindinger, J.L.
1988-01-01
The continental shelf in the northern Gulf of Mexico is overlain by many superimposed deltas. One late Wisconsinan delta, here informally named the lagniappe, is located east of the Mississippi River bird-foot delta and extends from mid-shelf to the continental slope. The lagniappe delta is adjacent to, but not genetically associated with, the Mississippi River delta complex. The lagniappe delta is a shelf-margin delta formed in part by stream erosion of the exposed inner and outer shelf during the late Wisconsinan lowstand. On the basis of its overall pattern and direction of accretion, the delta's fluvial source was most probably the ancient Pearl or Mobile River farther east. The progradational deposits, as seen in the high-resolution seismic reflection profile, are characterized by foreset and bottomset bedding. Areal distribution and sediment thickness were partially controlled by two diapirs active before and during deltaic sedimentation. The diapirs were a barrier to seaward progradation. As the delta prograded seaward, sediment ponded in an area between and shoreward of both uplifted diapirs. The basic geometry of the lagniappe delta was effectively changed during deposition by the presence of these diapirs.
Warczok, Piotr; Chumak, Igor
2009-04-15
The title compound Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As was characterized by means of single crystal X-ray diffraction. It represents a new structure type of intermetallic compounds (space group Pnma; lattice parameters a=7.142(2) A, b=3.583(2) A, c=11.640(2) A) and shows a small homogeneity range corresponding to (0.1<delta<0.25) at 1400 deg. C. The crystal structure may be visualized by a combination of As-centred trigonal prisms of the metal atoms and bcc-like fragments formed by metal atoms. Structural relations with various binary arsenides are discussed. The structure of Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As shows significant preferred site occupation of Hf and Nb at the three independent metal positions (differential fractional site occupancy). Structure-composition relations in the section Hf{sub 3}As-Nb{sub 3}As which also contains the new phase Hf{sub 2+{delta}}Nb{sub 1-{delta}}As with Ti{sub 3}P-type structure (space group P4{sub 2}/n) are discussed. Ground state energies of various ordered compounds with Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As-, Ti{sub 3}P- and Ta{sub 3}As-type structures were calculated from ab initio density functional theory. These energies were used for thermodynamic calculations employing the compound energy formalism (CEF) with the aim to model the experimentally observed site fraction data for both ternary compounds as well as Gibbs energies at the temperature of equilibration (1400 deg. C). - Graphical abstract: Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As with a new structure type (space group Pnma; lattice parameters a=7.142(2) A, b=3.583(2) A, c=11.640(2)A) was synthesized. Phase relations, energies and partial ordering in the section Hf{sub 3}As-Nb{sub 3}As were studied by first principle DFT calculations and thermodynamic modelling.
NASA Astrophysics Data System (ADS)
Stouthamer, E.; van Asselen, S.
2015-11-01
Deltas are increasingly under pressure from human impact and climate change. To deal with these pressures that threat future delta functioning, we need to understand interactions between physical, biological, chemical and social processes in deltas. This requires an integrated approach, in which knowledge on natural system functioning is combined with knowledge on spatial planning, land and water governance and legislative frameworks. In the research focus area Future Deltas of Utrecht University an interdisciplinary team from different research groups therefore works together. This allows developing integrated sustainable and resilient delta management strategies, which is urgently needed to prevent loss of vital delta services.
T (sub c)-delta relations in YBa2Cu3O(7-delta) thin films: Effects of oxygen pressure during growth
NASA Astrophysics Data System (ADS)
Feenstra, R.; Norton, D. P.; Budai, J. D.; Christen, D. K.; Lowndes, D. H.; Matijasevic, V. C.; Eom, C. B.; Geballe, T. H.; Hellman, E. S.; Hartford, E. H.
1992-04-01
The (Tc) dependence on oxygen content was measured for YBa2Cu3O(7-delta) films grown with a variety of techniques (solid phase epitaxy, laser ablation, off-axis sputtering, co-evaporation) at oxygen pressures p(O2) ranging from 1.0 atm to 0.1 mTorr. Dissimilar dependences resulted for each film type, with (Tc) either increasing or decreasing for small increments in delta from maximum oxygen occupancy. Varying systematically with p(O2) during growth, the deviations are attributed to competing effects from hole-doping lattice defects (most likely on the Y-site) on the carrier density of the CuO2 planes and basal plane oxygen capacity, respectively, giving rise to overdoping or underdoping after low temperature oxidation in 1.0 atm of oxygen.
Discrete vortices on anisotropic lattices
NASA Astrophysics Data System (ADS)
Chen, Gui-Hua; Wang, Hong-Cheng; Chen, Zi-Fa
2015-08-01
We consider the effects of anisotropy on two types of localized states with topological charges equal to 1 in two-dimensional nonlinear lattices, using the discrete nonlinear Schrödinger equation as a paradigm model. We find that on-site-centered vortices with different propagation constants are not globally stable, and that upper and lower boundaries of the propagation constant exist. The region between these two boundaries is the domain outside of which the on-site-centered vortices are unstable. This region decreases in size as the anisotropy parameter is gradually increased. We also consider off-site-centered vortices on anisotropic lattices, which are unstable on this lattice type and either transform into stable quadrupoles or collapse. We find that the transformation of off-sitecentered vortices into quadrupoles, which occurs on anisotropic lattices, cannot occur on isotropic lattices. In the quadrupole case, a propagation-constant region also exists, outside of which the localized states cannot stably exist. The influence of anisotropy on this region is almost identical to its effects on the on-site-centered vortex case.
Quantum state control and characterization in an optical lattice
NASA Astrophysics Data System (ADS)
Myrskog, Stefan Henrik
In this dissertation I present experimental work on the measurement and manipulation of the center-of-mass motion of laser-cooled atoms. The first experiment described demonstrates cooling of an atom cloud by 'delta-kick cooling'. A thermal cloud of atoms in a vacuum expands ballistically, generating correlations between position and momentum. An appropriate momentum kick, proportional to position, results in slowing down all the atoms in the cloud. Through this technique a cloud of atoms can be cooled by greater than a factor of 10, preserving phase-space density, but decreasing the number density of atoms. By using laser-cooled atoms, it is also possible to confine atoms in potentials created by the AC-Stark shift of the atomic energy levels. Using interfering lasers to create the Stark shift, atoms are confined in a sinusoidal potential called an optical lattice. After preparing atoms in the lowest-energy band of the lattice, a spatial displacement can create coherent superpositions of many states of the potential. A combination of time delays and secondary displacements allows the measurement of the Q (Husimi) and W (Wigner) quasi-probability distributions, each of which completely characterizes the motional state of the atoms. Alternatively, a shallow lattice that only support two long-lived states can be used. The two-state system may be characterized with far fewer measurements, and furthermore, can be used as a model system for a qubit, a quantum representation of a single bit of information, useful for quantum computation. We demonstrate reconstruction of the density matrix in the 2-state system. The two-state system has be further used to characterize the physical action of an operation. By preparing a complete set of input density matrices we perform quantum process tomography for the intrinsic decoherence of the lattice, and two operations that correspond to single qubit rotations.
Framework for improved lattice calculations of epsilion'/epsilon
NASA Astrophysics Data System (ADS)
Laiho, Jack
In this thesis we show that it is possible to construct epsilon '/epsilon to NLO using both full and partially quenched chiral perturbation theory (PQChPT) from amplitudes that are computable using numerical lattice gauge theory. We find that the electro-weak penguin (Delta I = 3/2 and 1/2) contributions to epsilon'/epsilon in PQChPT can be determined to NLO using only degenerate (mK = mpi) K → pi computations without momentum insertion. All one-loop formulas needed to extract the necessary NLO constants from the lattice are presented in this work. Issues pertaining to power divergent contributions, originating from mixing with lower dimensional operators in a lattice regularization, are addressed. In embedding the QCD penguin left-right operator onto PQChPT an ambiguity arises when the number of light sea quarks is not the physical value of three, as first emphasized by Golterman and Pallante. In the quenched theory they have pointed out that there are additional effective operators that appear in the quenched chiral perturbation theory needed to make contact with K → pipi amplitudes at physical kinematics. They have also proposed a method for determining the leading order low-energy constant, aNSq , associated with the new operators. We show that their method has difficulties due to power divergent contributions and propose a new method to obtain this constant from the lattice which does not suffer from this problem. Using this alternative method, we obtain aNSq , and show that our value implies a large ambiguity in the quenched contribution of Q6 to epsilon'/epsilon.
Alarcón, B; Ley, S C; Sánchez-Madrid, F; Blumberg, R S; Ju, S T; Fresno, M; Terhorst, C
1991-01-01
The T cell receptor for antigen (TCR) consists of two glycoproteins containing variable regions (TCR-alpha/beta or TCR-gamma/delta) which are expressed on the cell surface in association with at least four invariant proteins (CD3-gamma, -delta, -epsilon and -zeta). CD3-gamma and CD3-delta chains are highly homologous, especially in the cytoplasmic domain. The similarity observed in their genomic organization and their proximity in the chromosome indicate that both genes arose from duplication of a single gene. Here, we provide several lines of evidence which indicate that in human and murine T cells which expressed both the CD3-gamma and CD3-delta chains on their surface, the TCR/CD3 complex consisted of a mixture of alpha beta gamma epsilon zeta and alpha beta delta epsilon zeta complexes rather than a single alpha beta gamma delta epsilon zeta complex. First, a CD3-gamma specific antibody failed to co-immunoprecipitate CD3-delta and conversely, several CD3-delta specific antibodies did not coprecipitate CD3-gamma. Secondly, analysis of a panel of human and murine T cell lines demonstrated that CD3-gamma and CD3-delta were expressed at highly variable ratios on their surface. This suggested that these chains were not expressed as a single complex. Thirdly, CD3-gamma and CD3-delta competed for binding to CD3-epsilon in transfected COS cells, suggesting that CD3-gamma and CD3-delta formed mutually exclusive complexes. The existence of these two forms of TCR/CD3 complexes could have important implications in the understanding of T cell receptor function and its role in T cell development. Images PMID:1826255
Clathrin heavy chain, light chain interactions.
Winkler, F K; Stanley, K K
1983-01-01
Purified pig brain clathrin can be reversibly dissociated and separated into heavy chain trimers and light chains in the presence of non-denaturing concentrations of the chaotrope thiocyanate. The isolated heavy chain trimers reassemble into regular polygonal cage structures in the absence of light chains. The light chain fraction can be further resolved into its two components L alpha and L beta which give different one-dimensional peptide maps. Radiolabelled light chains bind with high affinity (KD < 10(-10) M) to heavy chain trimers, to heavy chain cages and to a 110,000 mol. wt. tryptic fragment of the heavy chain. Both light chains compete with each other and with light chains from other sources for the same binding sites on heavy chains and c.d. spectroscopy shows that the two pig brain light chains possess very similar structures. We conclude that light chains from different sources, despite some heterogeneity, have a highly conserved, high affinity binding site on the heavy chain but are not essential for the formation of regular cage structures. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 8. PMID:10872336
Chang, Tina; Ke, Ying; Ly, Kevin; McDonald, Fiona J.
2011-08-05
Highlights: {yields} The COMM domain of COMMD1 mediates binding to {delta}ENaC. {yields} COMMD1 reduces the cell surface population of {delta}ENaC. {yields} COMMD1 increases the population of {delta}ENaC-ubiquitin. {yields} Both endogenous and transfected {delta}ENaC localize with COMMD1 and transferrin suggesting they are located in early/recycling endosomes. -- Abstract: The delta subunit of the epithelial sodium channel ({delta}ENaC) is a member of the ENaC/degenerin family of ion channels. {delta}ENaC is distinct from the related {alpha}-, {beta}- and {gamma}ENaC subunits, known for their role in sodium homeostasis and blood pressure control, as {delta}ENaC is expressed in brain neurons and activated by external protons. COMMD1 (copper metabolism Murr1 domain 1) was previously found to associate with and downregulate {delta}ENaC activity. Here, we show that COMMD1 interacts with {delta}ENaC through its COMM domain. Co-expression of {delta}ENaC with COMMD1 significantly reduced {delta}ENaC surface expression, and led to an increase in {delta}ENaC ubiquitination. Immunocytochemical and confocal microscopy studies show that COMMD1 promoted localization of {delta}ENaC to the early/recycling endosomal pool where the two proteins were localized together. These results suggest that COMMD1 downregulates {delta}ENaC activity by reducing {delta}ENaC surface expression through promoting internalization of surface {delta}ENaC to an intracellular recycling pool, possibly via enhanced ubiquitination.
Lattice Structures For Aerospace Applications
NASA Astrophysics Data System (ADS)
Del Olmo, E.; Grande, E.; Samartin, C. R.; Bezdenejnykh, M.; Torres, J.; Blanco, N.; Frovel, M.; Canas, J.
2012-07-01
The way of mass reduction improving performances in the aerospace structures is a constant and relevant challenge in the space business. The designs, materials and manufacturing processes are permanently in evolution to explore and get mass optimization solutions at low cost. In the framework of ICARO project, EADS CASA ESPACIO (ECE) has designed, manufactured and tested a technology demonstrator which shows that lattice type of grid structures is a promising weight saving solution for replacing some traditional metallic and composite structures for space applications. A virtual testing methodology was used in order to support the design of a high modulus CFRP cylindrical lattice technology demonstrator. The manufacturing process, based on composite Automatic Fiber Placement (AFP) technology developed by ECE, allows obtaining high quality low weight lattice structures potentially applicable to a wide range of aerospace structures. Launcher payload adaptors, satellite platforms, antenna towers or instrument supports are some promising candidates.
Algebraic Lattices in QFT Renormalization
NASA Astrophysics Data System (ADS)
Borinsky, Michael
2016-07-01
The structure of overlapping subdivergences, which appear in the perturbative expansions of quantum field theory, is analyzed using algebraic lattice theory. It is shown that for specific QFTs the sets of subdivergences of Feynman diagrams form algebraic lattices. This class of QFTs includes the standard model. In kinematic renormalization schemes, in which tadpole diagrams vanish, these lattices are semimodular. This implies that the Hopf algebra of Feynman diagrams is graded by the coradical degree or equivalently that every maximal forest has the same length in the scope of BPHZ renormalization. As an application of this framework, a formula for the counter terms in zero-dimensional QFT is given together with some examples of the enumeration of primitive or skeleton diagrams.
Donoghue, J.F. . Geology Dept.); White, N.M. . Dept. of Anthropology)
1993-03-01
Late Holocene environmental changes in the lower Apalachicola River region of the northwest Florida appear to be related to deltaic lobe-shifting and sea level change. Sedimentologic, archaeologic and seismic evidence all indicate a major shift in deltaic deposition approximately 2,000 years ago. The effect is observed in the mid-region of the modern Apalachicola Delta as a pronounced change from estuarine to freshwater conditions. On the barrier island chain flanking the delta the result was a change in depositional patterns with a shift in the sediment supply.
Nucleon Structure from Lattice QCD
Haegler, Philipp
2011-10-24
Hadron structure calculations in lattice QCD have seen substantial progress during recent years. We illustrate the achievements that have been made by discussing latest lattice results for a limited number of important observables related to nucleon form factors and generalized parton distributions. A particular focus is placed on the decomposition of the nucleon spin 1/2 in terms of quark spin and orbital angular momentum contributions. Results and limitations of the necessary chiral extrapolations based on ChPT will be briefly discussed.
Tetraquark states from lattice QCD
Mathur, Nilmani
2011-10-24
Recently there have been considerable interests in studying hadronic states beyond the usual two and three quark configurations. With the renewed experimental interests in {sigma}(600) and the inability of quark model to incorporate too many light scalar mesons, it is quite appropriate to study hadronic states with four quark configurations. Moreover, some of the newly observed charmed hadrons may well be described by four quark configurations. Lattice QCD is perhaps the most desirable tool to adjudicate the theoretical controversy of the scalar mesons and to interpret the structures of the newly observed charmed states. Here we briefly reviewed the lattice studies of four-quark hadrons.
Negative-viscosity lattice gases
Rothman, D.H. )
1989-08-01
A new irreversible collision rule is introduced for lattice-gas automata. The rule maximizes the flux of momentum in the direction of the local momentum gradient, yielding a negative shear viscosity. Numerically results in 2D show that the negative viscosity leads to the spontaneous ordering of the velocity field, with vorticity resolvable down to one lattice-link length. The new rule may be used in conjunction with previously proposed collision rules to yield a positive shear viscosity lower than the previous rules provide. In particular, Poiseuille flow tests demonstrate a decrease in viscosity by more than a factor of 2.
Lattice QCD and Nuclear Physics
Konstantinos Orginos
2007-03-01
A steady stream of developments in Lattice QCD have made it possible today to begin to address the question of how nuclear physics emerges from the underlying theory of strong interactions. Central role in this understanding play both the effective field theory description of nuclear forces and the ability to perform accurate non-perturbative calculations in lo w energy QCD. Here I present some recent results that attempt to extract important low energy constants of the effective field theory of nuclear forces from lattice QCD.
Nuclear Physics from Lattice QCD
William Detmold, Silas Beane, Konstantinos Orginos, Martin Savage
2011-01-01
We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.
Chiral symmetry on the lattice
Creutz, M.
1994-11-01
The author reviews some of the difficulties associated with chiral symmetry in the context of a lattice regulator. The author discusses the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. The author briefly discusses the surface mode approach, the use of mirror Fermions to cancel anomalies, and finally speculates on the problems with lattice versions of the standard model.
Mission Stream Analysis - Delta Analytic Model. Revision
2014-09-01
demonstrating mission effectiveness. The second tool is the ( Delta ) Analytic Model, which provides an approach for identifying disparate...requirements into a system’s technical performance and operator workload requirements; and help minimize the “ delta ” between domains across the system’s...mission and system capability requirements into a system’s technical performance and operator workload requirements; and help minimize the “ delta
Delta Clipper vehicle design for supportability
NASA Astrophysics Data System (ADS)
Smiljanic, Ray R.; Klevatt, Paul L.; Steinmeyer, Donald A.
1993-02-01
The paper describes the Single Stage Rocket Technology (SSRT) Delta Clipper vehicle design. As a means of reducing vehicle processing and turnaround times, the SSRT Delta Clipper design, contrary to past practices, incorporates support ability engineering features into its initial set of design requirements. The engineering process used to 'design-in' supportability into the Delta Clipper vehicle is described in detail and is illustrated using diagrams.
Delta Clipper - Design for supportability
NASA Astrophysics Data System (ADS)
Smiljanic, Ray R.; Conrad, Charles; Spaulding, Ed; Gisburne, Don
1993-07-01
The 'Delta Clipper' Single Stage Rocket Technology (SSRT) currently under development in the DC-X program will implement reliability-centered maintenance and support, involving on-equipment/off-equipment two-level maintenance, a logistics and spares pipeline, and a minimization of 'blue suit' skill-level personnel. Attention is given to the range of SSRT features that are to be validated via the DC-X test program; these prominently involve LRUs replaceability and accessibility, standardization and interchangeability, and 'aircraft-like' automated data collection.
Dettinger, Michael; Anderson, Jamie; Anderson, Michael L.; Brown, Larry R.; Cayan, Daniel; Maurer, Edwin P.
2016-01-01
Anthropogenic climate change amounts to a rapidly approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to challenge these management and ecological systems in different ways that are characterized by different levels of uncertainty. For example, there is high certainty that climate will warm by about 2°C more (than late-20th-century averages) by mid-century and about 4°C by end of century, if greenhouse-gas emissions continue their current rates of acceleration. Future precipitation changes are much less certain, with as many climate models projecting wetter conditions as drier. However, the same projections agree that precipitation will be more intense when storms do arrive, even as more dry days will separate storms. Warmer temperatures will likely enhance evaporative demands and raise water temperatures. Consequently, climate change is projected to yield both more extreme flood risks and greater drought risks. Sea level rise (SLR) during the 20th century was about 22cm, and is projected to increase by at least 3-fold this century. SLR together with land subsidence threatens the Delta with greater vulnerabilities to inundation and salinity intrusion. Effects on the Delta ecosystem that are traceable to warming include SLR, reduced snowpack, earlier snowmelt and larger storm-driven streamflows, warmer and longer summers, warmer summer water temperatures, and water-quality changes. These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas. Although the effects of climate change on Delta ecosystems may be profound, the end results are difficult to predict, except that native species will fare worse than invaders. Successful
Lattice Green's Function for the Body-Centered Cubic Lattice
NASA Astrophysics Data System (ADS)
Sakaji, A. J.
2002-05-01
An expression for the Green's function (GF) of Body-Centered Cubic (BCC) lat tice is evaluated analytically and numerically for a single impurity lattice. Th e density of states (DOS), phase shift, and scattering cross section are express ed in terms of complete elliptic integrals of the first kind.
Navigational Use of Cassini Delta V Telemetry
NASA Technical Reports Server (NTRS)
Roth, Duane C.; Antreasian, Peter G.; Ardalan, Shadan M.; Criddle, Kevin E.; Goodson, Troy; Ionasescu, Rodica; Jones, Jeremy B.; Parcher, Daniel W.; Pelletier, Frederic J.; Thompson, Paul F.; Vaughan, Andrew T.
2008-01-01
Telemetry data are used to improve navigation of the Saturn orbiting Cassini spacecraft. Thrust induced delta V's are computed on-board the spacecraft, recorded in telemetry, and downlinked to Earth. This paper discusses how and why the Cassini Navigation team utilizes spacecraft delta V telemetry. Operational changes making this information attractive to the Navigation Team will be briefly discussed, as will spacecraft hardware and software algorithms responsible for the on-board computation. An analysis of past delta V telemetry, providing calibrations and accuracies that can be applied to the estimation of future delta V activity, is described.
From Natural to Design River Deltas
NASA Astrophysics Data System (ADS)
Giosan, Liviu
2016-04-01
Productive and biologically diverse, deltaic lowlands attracted humans since prehistory and may have spurred the emergence of the first urban civilizations. Deltas continued to be an important nexus for economic development across the world and are currently home for over half a billion people. But recently, under the double whammy of sea level rise and inland sediment capture behind dams, they have become the most threatened coastal landscape. Here I will address several deceptively simple questions to sketch some unexpected answers using example deltas from across the world from the Arctic to the Tropics, from the Danube to the Indus, Mississippi to Godavari and Krishna, Mackenzie to Yukon. What is a river delta? What is natural and what is not in a river delta? Are the geological and human histories of a delta important for its current management? Is maintaining a delta the same to building a new one? Can we design better deltas than Nature? These answers help us see clearly that survival of deltas in the next century depends on human intervention and is neither assured nor simple to address or universally applicable. Empirical observations on the hydrology, geology, biology and biochemistry of deltas are significantly lagging behind modeling capabilities endangering the applicability of numerical-based reconstruction solutions and need to be ramped up significantly and rapidly across the world.
{Delta} isobars and (p,p') reactions
Sammarruca, F.; Stephenson, E. J.
2001-09-01
We explore the role of coupling to {Delta} isobars (in both the N{Delta} and {Delta}{Delta} channels) in medium modifications of the effective NN interaction that drives 200-MeV proton inelastic scattering. A comparison of the predictions to natural-parity (p,p') cross section and analyzing power data show that isobar degrees of freedom in the medium generate overly repulsive effective interactions. Furthermore, this model extension is unable to resolve difficulties observed earlier describing polarization transfer measurements in some high-spin, unnatural-parity (p,p') transitions.
K-->pipi amplitudes from lattice QCD with a light charm quark.
Giusti, L; Hernández, P; Laine, M; Pena, C; Wennekers, J; Wittig, H
2007-02-23
We compute the leading-order low-energy constants of the DeltaS=1 effective weak Hamiltonian in the quenched approximation of QCD with up, down, strange, and charm quarks degenerate and light. They are extracted by comparing the predictions of finite-volume chiral perturbation theory with lattice QCD computations of suitable correlation functions carried out with quark masses ranging from a few MeV up to half of the physical strange mass. We observe a DeltaI=1/2 enhancement in this corner of the parameter space of the theory. Although matching with the experimental result is not observed for the DeltaI=1/2 amplitude, our computation suggests large QCD contributions to the physical DeltaI=1/2 rule in the GIM limit, and represents the first step to quantify the role of the charm-quark mass in K-->pipi amplitudes. The use of fermions with an exact chiral symmetry is an essential ingredient in our computation.
Comments on the slip factor and the relation Delta phi = -h Delta theta
Ng, K.Y.; /Fermilab
2009-09-01
The definition of the slip factor can be obtained from the phase equation. However, a derivation using the relation {Delta}{phi} = -h{Delta}{theta} leads to a different slip-factor definition. This apparent paradox is examined in detail and resolved. Here {Delta}{phi} is the rf phase difference and {Delta}{theta} is the azimuthal phase difference around the accelerator ring between an off-momentum particle and the synchronous particle, while h is the rf harmonic.
Developing a Truly Global Delta Database to Assess Delta Morphology and Morphodynamics
NASA Astrophysics Data System (ADS)
Caldwell, R. L.; Edmonds, D. A.; Baumgardner, S. E.; Whaling, A.
2015-12-01
Delta morphology reflects the interplay of various environmental parameters, though these relationships have only been tested on small datasets with 30-50 deltas. These datasets are biased toward the largest deltas, which typically have compound morphologies, form on passive margins, and may not be representative of the full breadth in delta morphology. With the goal of building more robust predictions of delta morphology to enhance hazard mitigation and resiliency planning, we have developed a truly global delta database including every delta on the world's marine coastlines. Using Google Earth imagery, we first identified all fluvial river mouths (≥ 50 m wide) connected to an upstream catchment. Deltas are defined geomorphically as river mouths that split into two or more active or relict distributary channels, end in a depositional protrusion from the shoreline, or do both. In our database we identified 5,801 river mouths, and 1,426 of those coastal rivers (~25%) have a geomorphic delta. ~75% of deltas exhibit an active or relict distributary network, while the remaining ~25% are single channel deltas with a basinward protrusion. Preliminary morphometric analysis (ratio of shore-parallel width, W, to shore-perpendicular length, L) on a subset of 159 deltas suggests W:L values range from 0.52 (elongate) to 23.6 (broad/cuspate). The median W:L value is 2.68, suggesting the majority of deltas are roughly semi-circular (W:L = 2), and the distribution is heavily skewed to the broad/cuspate deltas (~28% are >4 times wider than they are long). Preliminary comparison to downstream significant wave height data shows that the 'wider' deltas relate to higher wave heights (R2 = 0.42), though the data are scattered. Ultimately, the database will include additional measured morphometrics, including number of channel mouths and delta area, and morphodynamic data derived from serial Landsat imagery.
The Atchafalaya River Delta. Report 1. A Plan for Predicting Delta Evolution
1991-05-01
Report HL-85-1, US Army Engineer Waterways Experi- ment Station, Vicksburg, MS. Thomas, W. A., Heath, R. E., Stewart, J. P., and Clark , D G., 1988...the Brazilian Continental Margin, Belem City. Para, Brazil, 29 October- 4 November 1972. pp 145-155. WAVES, DISCHARGE, DELTAS. Coleman, J. M., and...and Clark , D. G. 1988 (Dec). "The Atchafalaya River Delta Report 5, The Atchafalaya River Delta Quasi-Two- Dimensional Model of Delta Growth and
gamma/delta and other unconventional T lymphocytes: what do they see and what do they do?
Kaufmann, S H
1996-01-01
T lymphocytes recognize specific ligands by clonally distributed T-cell receptors (TCR). In humans and most animals, the vast majority of T cells express a TCR composed of an alpha chain and a beta chain, whereas a minor T-cell population is characterized by the TCR gamma/delta. Almost all of our knowledge about T cells stems from alpha/beta T cells and only now are we beginning to understand gamma/delta T cells. In contrast to conventional alpha/beta T cells, which are specific for antigenic peptides presented by gene products of the major histocompatibility complex, gamma/delta T cells directly recognize proteins and even nonproteinacious phospholigands. These findings reveal that gamma/delta T cells and alpha/beta T cells recognize antigen in a fundamentally different way and hence mitigate the dogma of exclusive peptide-major histocompatibility complex recognition by T cells. A role for gamma/delta T cells in antimicrobial immunity has been firmly established. Although some gamma/delta T cells perform effector functions, regulation of the professional and the nonprofessional immune system seems to be of at least equal importance. The prominent residence of gamma/delta T cells in epithelial tissues and the rapid mobilization of gamma/delta T cells in response to infection are consistent with such regulatory activities under physiological and pathologic conditions. Thus, although gamma/delta T cells are a minor fraction of all T cells, they are not just uninfluential kin of alpha/beta T cells but have their unique raison d'être. Images Fig. 1 Fig. 2 PMID:8637862
Stress Wave Propagation in Two-dimensional Buckyball Lattice
NASA Astrophysics Data System (ADS)
Xu, Jun; Zheng, Bowen
2016-11-01
Orderly arrayed granular crystals exhibit extraordinary capability to tune stress wave propagation. Granular system of higher dimension renders many more stress wave patterns, showing its great potential for physical and engineering applications. At nanoscale, one-dimensionally arranged buckyball (C60) system has shown the ability to support solitary wave. In this paper, stress wave behaviors of two-dimensional buckyball (C60) lattice are investigated based on square close packing and hexagonal close packing. We show that the square close packed system supports highly directional Nesterenko solitary waves along initially excited chains and hexagonal close packed system tends to distribute the impulse and dissipates impact exponentially. Results of numerical calculations based on a two-dimensional nonlinear spring model are in a good agreement with the results of molecular dynamics simulations. This work enhances the understanding of wave properties and allows manipulations of nanoscale lattice and novel design of shock mitigation and nanoscale energy harvesting devices.
Many-body lattice wave functions from conformal blocks
NASA Astrophysics Data System (ADS)
Montes, Sebastián; Rodríguez-Laguna, Javier; Tu, Hong-Hao; Sierra, Germán
2017-02-01
We introduce a general framework to construct many-body lattice wave functions starting from the conformal blocks (CBs) of rational conformal field theories (RCFTs). We discuss the different ways of encoding the physical degrees of freedom of the lattice system using both the internal symmetries of the theory and the fusion channels of the CBs. We illustrate this construction both by revisiting the known Haldane-Shastry model and by providing a novel implementation for the Ising RCFT. In the latter case, we find a connection to the Ising transverse field (ITF) spin chain via the Kramers-Wannier duality and the Temperley-Lieb-Jones algebra. We also find evidence that the ground state of the finite-size critical ITF Hamiltonian corresponds exactly to the wave function obtained from CBs of spin fields.
Stress Wave Propagation in Two-dimensional Buckyball Lattice
Xu, Jun; Zheng, Bowen
2016-01-01
Orderly arrayed granular crystals exhibit extraordinary capability to tune stress wave propagation. Granular system of higher dimension renders many more stress wave patterns, showing its great potential for physical and engineering applications. At nanoscale, one-dimensionally arranged buckyball (C60) system has shown the ability to support solitary wave. In this paper, stress wave behaviors of two-dimensional buckyball (C60) lattice are investigated based on square close packing and hexagonal close packing. We show that the square close packed system supports highly directional Nesterenko solitary waves along initially excited chains and hexagonal close packed system tends to distribute the impulse and dissipates impact exponentially. Results of numerical calculations based on a two-dimensional nonlinear spring model are in a good agreement with the results of molecular dynamics simulations. This work enhances the understanding of wave properties and allows manipulations of nanoscale lattice and novel design of shock mitigation and nanoscale energy harvesting devices. PMID:27892963
Exact and numerical results for a dimerized coupled spin- 1/2 chain
Martins; Nienhuis
2000-12-04
We establish exact results for coupled spin-1/2 chains for special values of the four-spin interaction V and dimerization parameter delta. The first exact result is at delta = 1/2 and V = -2. Because we find a very small but finite gap in this dimerized chain, this can serve as a very strong test case for numerical and approximate analytical techniques. The second result is for the homogeneous chain with V = -4 and gives evidence that the system has a spontaneously dimerized ground state. Numerical diagonalization and bosonization techniques indicate that the interplay between dimerization and interaction could result in gapless phases in the regime 0
Vikingstad, E.; Saetersdal, H.
1980-10-01
The change in partial molal volume (DELTA VM) and compressibility (DELTA KSM) during micelle formation was determined at 25 C for the homologous series of sodium alkylmalonates. CH/sub 3/(CH/sub 2/) 7 CH CH - (CoO-Na+)2 to CH/sub 3/(CH/sub 2/) 11CH(COD-Na/sub +/)/sub 2/. DELTA VM and DELTA KSM were determined from density measurements and ultrasound measurements, respectively. Both these quantities increase with increasing surfactant chain length. The fraction of associated counterions to the micelles was determined by EMF measurements, and it was found that this quantity increases slightly with increasing surfactant chain length.
Moments of Isovector Quark Distributions in Lattice QCD
W. Detmold; Wally Melnitchouk; A.W. Thomas
2002-06-01
We investigate the connection of lattice calculations of moments of isovector parton distributions to the physical regime through extrapolations in the quark mass. We consider the one pion loop renormalization of the nucleon matrix elements of the corresponding operators and thereby develop formulae with which to extrapolate the moments of the unpolarized, helicity and transversity distributions. There formulae are consistent with chiral perturbation theory in the chiral limit and incorporate the correct heavy quark limits. In the polarized cases, the inclusion of intermediate states involving the Delta isobar is found to be very important. The results of our extrapolations are in general agreement with the phenomenological values of these moments where they are known, and for the first time we perform an extrapolation of the low moments of the isovector transversity distribution which is consistent with chiral symmetry.
Event-chain Monte Carlo for classical continuous spin models
NASA Astrophysics Data System (ADS)
Michel, Manon; Mayer, Johannes; Krauth, Werner
2015-10-01
We apply the event-chain Monte Carlo algorithm to classical continuum spin models on a lattice and clarify the condition for its validity. In the two-dimensional XY model, it outperforms the local Monte Carlo algorithm by two orders of magnitude, although it remains slower than the Wolff cluster algorithm. In the three-dimensional XY spin glass model at low temperature, the event-chain algorithm is far superior to the other algorithms.
Lattice continuum and diffusional creep
NASA Astrophysics Data System (ADS)
Mesarovic, Sinisa Dj.
2016-04-01
Diffusional creep is characterized by growth/disappearance of lattice planes at the crystal boundaries that serve as sources/sinks of vacancies, and by diffusion of vacancies. The lattice continuum theory developed here represents a natural and intuitive framework for the analysis of diffusion in crystals and lattice growth/loss at the boundaries. The formulation includes the definition of the Lagrangian reference configuration for the newly created lattice, the transport theorem and the definition of the creep rate tensor for a polycrystal as a piecewise uniform, discontinuous field. The values associated with each crystalline grain are related to the normal diffusional flux at grain boundaries. The governing equations for Nabarro-Herring creep are derived with coupled diffusion and elasticity with compositional eigenstrain. Both, bulk diffusional dissipation and boundary dissipation accompanying vacancy nucleation and absorption, are considered, but the latter is found to be negligible. For periodic arrangements of grains, diffusion formally decouples from elasticity but at the cost of a complicated boundary condition. The equilibrium of deviatorically stressed polycrystals is impossible without inclusion of interface energies. The secondary creep rate estimates correspond to the standard Nabarro-Herring model, and the volumetric creep is small. The initial (primary) creep rate is estimated to be much larger than the secondary creep rate.
Lattice continuum and diffusional creep
2016-01-01
Diffusional creep is characterized by growth/disappearance of lattice planes at the crystal boundaries that serve as sources/sinks of vacancies, and by diffusion of vacancies. The lattice continuum theory developed here represents a natural and intuitive framework for the analysis of diffusion in crystals and lattice growth/loss at the boundaries. The formulation includes the definition of the Lagrangian reference configuration for the newly created lattice, the transport theorem and the definition of the creep rate tensor for a polycrystal as a piecewise uniform, discontinuous field. The values associated with each crystalline grain are related to the normal diffusional flux at grain boundaries. The governing equations for Nabarro–Herring creep are derived with coupled diffusion and elasticity with compositional eigenstrain. Both, bulk diffusional dissipation and boundary dissipation accompanying vacancy nucleation and absorption, are considered, but the latter is found to be negligible. For periodic arrangements of grains, diffusion formally decouples from elasticity but at the cost of a complicated boundary condition. The equilibrium of deviatorically stressed polycrystals is impossible without inclusion of interface energies. The secondary creep rate estimates correspond to the standard Nabarro–Herring model, and the volumetric creep is small. The initial (primary) creep rate is estimated to be much larger than the secondary creep rate. PMID:27274696
Lattice QCD in Background Fields
William Detmold, Brian Tiburzi, Andre Walker-Loud
2009-06-01
Electromagnetic properties of hadrons can be computed by lattice simulations of QCD in background fields. We demonstrate new techniques for the investigation of charged hadron properties in electric fields. Our current calculations employ large electric fields, motivating us to analyze chiral dynamics in strong QED backgrounds, and subsequently uncover surprising non-perturbative effects present at finite volume.
Confinement and lattice gauge theory
Creutz, M
1980-06-01
The motivation for formulating gauge theories on a lattice to study non-perturbative phenomena is reviewed, and recent progress supporting the compatibility of asymptotic freedom and quark confinement in the standard SU(3) Yang-Mills theory of the strong interaction is discussed.
Hadronic Interactions from Lattice QCD
Konstantinos Orginos
2006-03-19
In this talk I discuss a few recent results on lattice calculations of scattering lengths in hadronic processes. In particular, I present the scattering length of the pion-pion scattering in the I=2 channel and the nucleon-nucleon {sup 1}S{sub 0} channel and {sup 3}S{sub 1}-{sup 3}D{sub 1} coupled channels.
Studies of iron impurities in YxPr1-xBa2Cu3O7-delta
NASA Technical Reports Server (NTRS)
Swartzendruber, L. J.; Bennett, L. H.; Ritter, J.; Rubinstein, M.; Harford, M. Z.
1990-01-01
Pr is the only rare earth which, when substituted for Y in YBa2Cu3O7, significantly alters the superconducting transition temperature T(sub c) without changing the crystal structure. For YxPr1-xBa2Cu3O7-delta with delta approx. equal to 0, T(sub c) is reduced rapidly as x is increased, reaching zero for x about 0.5. For x above 0.5 the compound is antiferromagnetic with a Neel temperature that increases with increasing x, rising to above room temperature for x near 1. A similar behavior is observed when the oxygen deficit delta is increased from zero to 1 with x=0. For the case of Pr substitution, the drop in T(sub c) is believed due to magnetic interactions. For the case of varying delta with x=0, the drop can be attributed to a combination of magnetic interactions, band filling, and changes in crystal structure. To study these effects, the Mossbauer effect of 57 Fe atoms substituted for the Cu atoms has been observed as a function of delta, x, and temperature. The observed spectra are all well described by a two quadrupole-split pairs, a central singlet, and a six-line magnetic hyperfine field pattern. For several Pr compositions both delta and temperature were varied, and the results support the hypothesis that a magnetic interaction exists between the Fe in the Cu lattice and the substitutional Pr atoms.
NASA Astrophysics Data System (ADS)
Ossandon, Jorge G.
Magnetically aligned samples of sintered YBa _2Cu_3O_ {7-delta} were used to test the effects of oxygen-deficiency delta (with 0<=qdelta<=q 0.2) on the superconductive magnetization M, critical current density J_{c}, irreversibility field B_{irr }, upper critical field H_{ rm c2}, coherence length xi , condensation energy F_{c}, London penetration depth lambda and related properties as functions of temperature T and applied magnetic field H | c. In selected cases, studies were also made with H | ab. The open porosity and granularity of the material allowed rapid and homogeneous oxygenation. The oxygen content was monitored in situ by Thermo-Gravimetric Analysis. We found no significant enhancement of intragrain J_{c} with chain -site O-defects. With few exceptions, maximum J _{c} occurred at full oxygenation. This implies that chain-site O-defects are not strong or effective pinning centers over most of the field-temperature regime investigated. Except for T _{c}, which was practically independent of delta within the interval 0<=qdelta<=q 0.11 (so called "T_{c} -plateau"), most properties such as J_{ c}, F_{c}, H_{c2} , B_{irr}(T), lambda and xi were strongly and continuously influenced by the oxygen deficiency. The observed abnormal magnetization ("fishtail" or "bowtie" effect) with H | c was weak at low T but became more pronounced as T and delta increased. No abnormal magnetization was detected with H | ab. As oxygen was removed, B_{irr }(T) and H_{c2}(T) separated and both lines shifted to lower T and lower H. Moreover, B_{irr} was strongly correlated with J _{c} at low temperature. Determination of the thermodynamic critical field H_{ c} yielded condensation energies F _{c}(delta) that suffered a strong reduction with increasing delta. As predicted by a simple, single-site pinning model, a good correlation was found between J _{c}(delta) and the product F_{c}xi _{ab} (where xi_{ab} is the coherence length in the a-b plane). This correlation was corroborated by
Chiral four-dimensional heterotic covariant lattices
NASA Astrophysics Data System (ADS)
Beye, Florian
2014-11-01
In the covariant lattice formalism, chiral four-dimensional heterotic string vacua are obtained from certain even self-dual lattices which completely decompose into a left-mover and a right-mover lattice. The main purpose of this work is to classify all right-mover lattices that can appear in such a chiral model, and to study the corresponding left-mover lattices using the theory of lattice genera. In particular, the Smith-Minkowski-Siegel mass formula is employed to calculate a lower bound on the number of left-mover lattices. Also, the known relationship between asymmetric orbifolds and covariant lattices is considered in the context of our classification.
NASA Astrophysics Data System (ADS)
Cecile, D. J.
In Quantum Chromodynamics (QCD), the pions are the lightest bound states. Current lattice QCD calculations are not able to study pions at realistic masses due to algorithmic difficulties. Instead, lattice studies are limited to unphysically large pion masses, and Chiral Perturbation Theory (ChPT) is often relied upon to extrapolate lattice results to the phenomenological regime and to the chiral limit, where quarks are massless. One of the outstanding problems in the field is to determine the range of quark masses where ChPT is valid and to understand the nonperturbative physics that may cause ChPT to break down. Given the difficulty of studying QCD, it is interesting and useful to construct a lattice field theory model of pions, which would allow a direct lattice calculation without the need for chiral extrapolations. This model can be used to evaluate the reliability of chiral extrapolations as applied to lattice data in the context of a lattice field theory that is exactly solvable numerically even at small quark masses and in the chiral limit. In this light, to create a model of pions of two-flavor Quantum Chromodynamics (QCD), a lattice field theory involving two flavors of staggered quarks interacting strongly with Abelian gauge fields is constructed. In the chiral limit, this theory exhibits a SUL(2) x SU R(2) x UA(1) symmetry. The UA(1) symmetry can be broken by introducing a four-fermion term into the action, thereby incorporating the physics of the QCD anomaly. To qualify as a meaningful model of QCD, this lattice model must exhibit spontaneous chiral symmetry breaking and confinement and must have a continuum limit. An interesting mechanism is introduced to address the continuum limit. In particular, an extra dimension allows one to tune a fictitious temperature in order to access a phase of broken symmetry and to find a range where the pion decay constant is much smaller than the lattice cutoff, i.e. Fpi ≪1a . Unlike lattice QCD, a major advantage of
a Matrix Model Representation of the Integrable Xxz Heisenberg Chain on Random Surfaces
NASA Astrophysics Data System (ADS)
Ambjørn, J.; Sedrakyan, A.
2013-11-01
We consider integrable models, i.e. models defined by R-matrices, on random Manhattan lattices (RML). The set of random Manhattan lattices is defined as the set dual to the lattice random surfaces embedded on a regular d-dimensional lattice. As an example we formulate a random matrix model where the partition function reproduces annealed average of the XXZ Heisenberg chain over all RML. A technique is presented which reduces the random matrix integration in partition function to an integration over their eigenvalues.
Doping Scheme in Atomic Chain Electronics
NASA Technical Reports Server (NTRS)
Toshishige, Yamada
1997-01-01
Due to the dramatic reduction in MOS size, there appear many unwanted effects. In these small devices, the number of dopant atoms in the channel is not macroscopic and electrons may suffer significantly different scattering from device to device since the spatial distribution of dopant atoms is no longer regarded as continuous. This prohibits integration, while it is impossible to control such dopant positions within atomic scale. A fundamental solution is to create electronics with simple but atomically precise structures, which could be fabricated with recent atom manipulation technology. All the constituent atoms are placed as planned, and then the device characteristics are deviation-free, which is mandatory for integration. Atomic chain electronics belongs to this category. Foreign atom chains or arrays form devices, and they are placed on the atomically flat substrate surface. We can design the band structure and the resultant Fermi energy of these structures by manipulating the lattice constant. Using the tight-binding theory with universal parameters, it has been predicted that isolated Si chains and arrays are metallic, Mg chains are insulating, and Mg arrays have metallic and insulating phases [1]. The transport properties along a metallic chain have been studied, emphasizing the role of the contact to electrodes [2]. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along die chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome
Zank, T K; Zähringer, U; Lerchl, J; Heinz, E
2000-12-01
In order to elucidate the biosynthesis of long-chain polyunsaturated fatty acids (PUFAs) in plants we searched for a cDNA encoding a Delta(6)-specific PUFA elongase from Physcomitrella patens, which is known to contain high proportions of arachidonic acid (20:4 Delta(5,8,11,14)). An EST clone from P. patens was identified by its low homology to the yeast gene ELO1, which is required for the elongation of medium-chain fatty acids. We functionally characterized this cDNA by heterologous expression in Saccharomyces cerevisiae grown in the presence of several fatty acids. Analysis of the fatty acid profile of the transgenic yeast revealed that the cDNA encodes a protein that leads to the elongation of the C(18) Delta(6)-polyunsaturated fatty acids gamma-linolenic acid (18:3 Delta(6,9,12)) and stearidonic acid (18:4 Delta(6,9,12,15)), which were recovered to 45-51% as their elongation products. In contrast, linoleic and alpha-linolenic acids were hardly elongated and we could not measure any elongation of saturated and mono-unsaturated fatty acids (including 18:1 Delta(6)), indicating that the elongase is highly specific for the polyunsaturated nature of the fatty acid acting as substrate.
The delta opioid receptor tool box.
Vicente-Sanchez, Ana; Segura, Laura; Pradhan, Amynah A
2016-12-03
In recent years, the delta opioid receptor has attracted increasing interest as a target for the treatment of chronic pain and emotional disorders. Due to their therapeutic potential, numerous tools have been developed to study the delta opioid receptor from both a molecular and a functional perspective. This review summarizes the most commonly available tools, with an emphasis on their use and limitations. Here, we describe (1) the cell-based assays used to study the delta opioid receptor. (2) The features of several delta opioid receptor ligands, including peptide and non-peptide drugs. (3) The existing approaches to detect delta opioid receptors in fixed tissue, and debates that surround these techniques. (4) Behavioral assays used to study the in vivo effects of delta opioid receptor agonists; including locomotor stimulation and convulsions that are induced by some ligands, but not others. (5) The characterization of genetically modified mice used specifically to study the delta opioid receptor. Overall, this review aims to provide a guideline for the use of these tools with the final goal of increasing our understanding of delta opioid receptor physiology.
Revision of the Delta Nursing Scales.
ERIC Educational Resources Information Center
Wilson, Barry J.; Packwood, Gene
An item analysis was performed on two rating scales, the Delta Survey of Nurses and the Delta Nursing Survey, developed for evaluating the preparation and job performance of nursing graduates. Resulting data supported the basic design of the instruments. The revised instruments consist of seven fewer items; two subtests were deleted, and a number…
Delta Blues Scholarship and Imperialist Nostalgia.
ERIC Educational Resources Information Center
Nye, William P.
When Delta blues are considered to be "folk music," the genre is inextricably tied to the neocolonial, sharecropping system of cotton production characteristic of the Mississippi Delta region between the Civil War and World War II. "Imperialist nostalgia," then, arises in accounts which pay primary and positive tribute to blues…
Wave-angle control of delta evolution
NASA Astrophysics Data System (ADS)
Ashton, Andrew D.; Giosan, Liviu
2011-07-01
Wave-influenced deltas, with large-scale arcuate shapes and demarcated beach ridge complexes, often display an asymmetrical form about their river channel. Here, we use a numerical model to demonstrate that the angles from which waves approach a delta can have a first-order influence upon its plan-view morphologic evolution and sedimentary architecture. The directional spread of incoming waves plays a dominant role over fluvial sediment discharge in controlling the width of an active delta lobe, which in turn affects the characteristic rates of delta progradation. Oblique wave approach (and a consequent net alongshore sediment transport) can lead to the development of morphologic asymmetry about the river in a delta's plan-view form. This plan-form asymmetry can include the development of discrete breaks in shoreline orientation and the appearance of self-organized features arising from shoreline instability along the downdrift delta flank, such as spits and migrating shoreline sand waves—features observed on natural deltas. Somewhat surprisingly, waves approaching preferentially from one direction tend to increase sediment deposition updrift of the river. This ‘morphodynamic groin effect’ occurs when the delta's plan-form aspect ratio is sufficiently large such that the orientation of the shoreline on the downdrift flank is rotated past the angle of maximum alongshore sediment transport, resulting in preferential redirection of fluvial sediment updrift of the river mouth.
SF Bay Delta TMDL Progress Assessment
EPA assessed the progress 14 TMDLs in the SF Bay Delta Estuary (SF Bay Delta) to determine if the actions called for in the TMDL were being accomplished and water quality was improving. Status and water quality reports can be found here.
Lattice dynamics and lattice thermal conductivity of thorium dicarbide
NASA Astrophysics Data System (ADS)
Liao, Zongmeng; Huai, Ping; Qiu, Wujie; Ke, Xuezhi; Zhang, Wenqing; Zhu, Zhiyuan
2014-11-01
The elastic and thermodynamic properties of ThC2 with a monoclinic symmetry have been studied by means of density functional theory and direct force-constant method. The calculated properties including the thermal expansion, the heat capacity and the elastic constants are in a good agreement with experiment. Our results show that the vibrational property of the C2 dimer in ThC2 is similar to that of a free standing C2 dimer. This indicates that the C2 dimer in ThC2 is not strongly bonded to Th atoms. The lattice thermal conductivity for ThC2 was calculated by means of the Debye-Callaway model. As a comparison, the conductivity of ThC was also calculated. Our results show that the ThC and ThC2 contributions of the lattice thermal conductivity to the total conductivity are 29% and 17%, respectively.
Marriage of exact enumeration and 1/d expansion methods: Lattice model of dilute polymers
NASA Astrophysics Data System (ADS)
Nemirovsky, A. M.; Freed, Karl F.; Ishinabe, Takao; Douglas, Jack F.
1992-06-01
We consider the properties of a self-avoiding polymer chain with nearestneighbor contact energy ɛ on a d-dimensional hypercubic lattice. General theoretical arguments enable us to prescribe the exact analytic form of the n-segment chain partition function C n ,and unknown coefficients for chains of up to 11 segments are determined using exact enumeration data in d=2-6. This exact form provides the main ingredient to produce a large- n expansion in d -1of the chain free energy through fifth order with the full dependence on the contact energy retained. The ɛ-dependent chain connectivity constant and free energy amplitude are evaluated within the d -1expansion to O(d -5). Our general formulation includes for the first time self-avoiding walks, neighboravoiding walks, theta, and collapsed chains as particular limiting cases.
The CKM Matrix from Lattice QCD
Mackenzie, Paul B.; /Fermilab
2009-07-01
Lattice QCD plays an essential role in testing and determining the parameters of the CKM theory of flavor mixing and CP violation. Very high precisions are required for lattice calculations analyzing CKM data; I discuss the prospects for achieving them. Lattice calculations will also play a role in investigating flavor mixing and CP violation beyond the Standard Model.
Long-Range Lattice-Gas Algorithm
2007-11-02
lattice-gases, and therefore inherits exact computabil- ity on a discrete spacetime lattice. Our contribution is the use of nonlocal interactions that...gases, and therefore inherits exact computability on a discrete spacetime lattice. Our contribution is the use of nonlocal interactions that allow us to
Lattice Boltzmann solver of Rossler equation
NASA Astrophysics Data System (ADS)
Yan, Guangwu; Ruan, Li
2000-06-01
We proposed a lattice Boltzmann model for the Rossler equation. Using a method of multiscales in the lattice Boltzmann model, we get the diffusion reaction as a special case. If the diffusion effect disappeared, we can obtain the lattice Boltzmann solution of the Rossler equation on the mesescopic scale. The numerical results show the method can be used to simulate Rossler equation.
Belopolski, Ilya; Xu, Su-Yang; Koirala, Nikesh; Liu, Chang; Bian, Guang; Strocov, Vladimir N.; Chang, Guoqing; Neupane, Madhab; Alidoust, Nasser; Sanchez, Daniel; Zheng, Hao; Brahlek, Matthew; Rogalev, Victor; Kim, Timur; Plumb, Nicholas C.; Chen, Chaoyu; Bertran, François; Le Fèvre, Patrick; Taleb-Ibrahimi, Amina; Asensio, Maria-Carmen; Shi, Ming; Lin, Hsin; Hoesch, Moritz; Oh, Seongshik; Hasan, M. Zahid
2017-01-01
Engineered lattices in condensed matter physics, such as cold-atom optical lattices or photonic crystals, can have properties that are fundamentally different from those of naturally occurring electronic crystals. We report a novel type of artificial quantum matter lattice. Our lattice is a multilayer heterostructure built from alternating thin films of topological and trivial insulators. Each interface within the heterostructure hosts a set of topologically protected interface states, and by making the layers sufficiently thin, we demonstrate for the first time a hybridization of interface states across layers. In this way, our heterostructure forms an emergent atomic chain, where the interfaces act as lattice sites and the interface states act as atomic orbitals, as seen from our measurements by angle-resolved photoemission spectroscopy. By changing the composition of the heterostructure, we can directly control hopping between lattice sites. We realize a topological and a trivial phase in our superlattice band structure. We argue that the superlattice may be characterized in a significant way by a one-dimensional topological invariant, closely related to the invariant of the Su-Schrieffer-Heeger model. Our topological insulator heterostructure demonstrates a novel experimental platform where we can engineer band structures by directly controlling how electrons hop between lattice sites. PMID:28378013
Compounds of paired electrons and lattice solitons moving with supersonic velocity
NASA Astrophysics Data System (ADS)
Hennig, D.; Velarde, M. G.; Ebeling, W.; Chetverikov, A.
2008-12-01
We study the time evolution of two correlated electrons of opposite spin in an anharmonic lattice chain. The electrons are described quantum mechanically by the Hubbard model while the lattice is treated classically. The lattice units are coupled via Morse-Toda potentials. Interaction between the lattice and the electrons arises due to the dependence of the electron transfer-matrix element on the distance between neighboring lattice units. Localized configurations comprising a paired electron and a pair of lattice deformation solitons are constructed such that an associated energy functional is minimized. We investigate long-lived, stable pairing features. It is demonstrated that traveling pairs of lattice solitons serve as carriers for the paired electrons realizing coherent transport of the two correlated electrons. We also observe dynamical narrowing of the states, that is, starting from an initial double-peak profile of the electron probability distribution, a single-peak profile is adopted going along with enhancement of localization of the paired electrons. Interestingly, a parameter regime is identified for which supersonic transport of paired electrons is achieved.
Oxygen-disorder effects on the electronic structure of YBa sub 2 Cu sub 3 O sub 6+. delta
Modak, S. ); Moran-Lopez, J.L. )
1989-11-01
The electronic structure of YBa{sub 2}Cu{sub 3}O{sub 6+{delta}} is calculated in the framework of the tight-binding Hamiltonian. The effects of the oxygen concentration {delta} and its spatial ordering in the basal plane are studied by means of the Bethe-lattice method. The local density of states at the various Cu and O sites are calculated as a function of {delta} and of the degree of oxygen ordering. Special attention is given to the number of holes {ital h} in both the ordered and disordered systems for various concentrations. We find that the electronic structure at the CuO{sub 2} planes is almost insensitive to the degree of order, in contrast to the local density of states of sites located in the basal plane.
Immunogenicity of Staphylococcus aureus delta-toxin.
Nolte, F S; Kapral, F A
1981-01-01
Studies were conducted to determine the immunogenicity of purified Staphylococcus aureus delta-toxin. Rabbits and guinea pigs immunized with delta-toxin incorporated into a multiple antibody, whereas animals given toxin in saline or toxin in saline with Tween 80 did not produce antibody. The immunoglobulin G (IgG) fraction isolated by chromatography on protein A-Sepharose was examined for the presence of anti-delta-toxin antibody by immunoelectrophoresis, immunodiffusion, quantitative precipitation tests, affinity chromatography, and toxin neutralization tests. Although delta-toxin-specific IgG precipitated the toxin in agar gels, the antibody did not neutralize the toxin's hemolytic activity. Delta-toxin binding to human erythrocyte membranes was demonstrated by indirect immunofluorescent staining of toxin-treated erythrocytes. Images PMID:7014461
Iida, T; Tamura, T; Matsumoto, T
1980-03-01
Proton nuclear magnetic resonance (1H-NMR) spectra at 90 MHz were measured for a number of side chain isomers of phytosterols (sterols with a C8H17 side chain, and delta 24-, 24-methylene, delta 22-, 24-ethylidene, 24-methly, 24-ethyl, 24-methyl-delta 22-, 24-ethyl delta 22-, and 24-ethyl-delta 22,25(27)-sterols) with or without a lanthanide shift reagent, tris[1,1,1,2,2,3,3 - heptafluoro - 7,7 - dimethyloctane - 4,6 - dionato]ytterbium, Yb(fod)3, and the effect of Yb(fod)3 on the side chain methyl protons is discussed. The change of the chemical shifts induced Yb(fod)3 for the side chain methyls was expressed in terms of the induced shift ratios (ISR values), i.e., the ratios of the induced chemical shifts of the respective side chain methyls to that of the fastest moving side chain methyl. The ISR values were sentitive to minor structural and stereochemical differences, but almost independent of ring structures and of substrate concentrations, thus providing confirmatory evidence for the side chain structures. Also, the Yb(fod)3-induced spectral patterns observed in the high-field methyl region bore the fingerprints of the side chain structures. Several isomeric pairs of sterols, which differ only in the geometry of double bonds or the absolute configuration at C-24 in the side chain, i.e., cis- and trans-isomers of delta 22-and 24-ethylidene sterols, 24R/alpha- and 24S/beta-methyl sterols, 24R/alpha- and 24S/beta-ethyl sterols, and 24S/alpha- and 24R/beta-ethyl-delta 22-sterols, could be differentiated from each other under the influence of Yb(fod)3, even though they were measured at 90 MHz.
Heuristic algorithm for off-lattice protein folding problem*
Chen, Mao; Huang, Wen-qi
2006-01-01
Enlightened by the law of interactions among objects in the physical world, we propose a heuristic algorithm for solving the three-dimensional (3D) off-lattice protein folding problem. Based on a physical model, the problem is converted from a nonlinear constraint-satisfied problem to an unconstrained optimization problem which can be solved by the well-known gradient method. To improve the efficiency of our algorithm, a strategy was introduced to generate initial configuration. Computational results showed that this algorithm could find states with lower energy than previously proposed ground states obtained by nPERM algorithm for all chains with length ranging from 13 to 55. PMID:16365919
Delta connected resonant snubber circuit
Lai, J.S.; Peng, F.Z.; Young, R.W. Sr.; Ott, G.W. Jr.
1998-01-20
A delta connected, resonant snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the dc supply voltage through the main inverter switches and the auxiliary switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter. 36 figs.
Delta connected resonant snubber circuit
Lai, Jih-Sheng; Peng, Fang Zheng; Young, Sr., Robert W.; Ott, Jr., George W.
1998-01-01
A delta connected, resonant snubber-based, soft switching, inverter circuit achieves lossless switching during dc-to-ac power conversion and power conditioning with minimum component count and size. Current is supplied to the resonant snubber branches solely by the dc supply voltage through the main inverter switches and the auxiliary switches. Component count and size are reduced by use of a single semiconductor switch in the resonant snubber branches. Component count is also reduced by maximizing the use of stray capacitances of the main switches as parallel resonant capacitors. Resonance charging and discharging of the parallel capacitances allows lossless, zero voltage switching. In one embodiment, circuit component size and count are minimized while achieving lossless, zero voltage switching within a three-phase inverter.
Neutron total scattering study of the delta and beta phases of Bi2O3.
Hull, Stephen; Norberg, Stefan T; Tucker, Matthew G; Eriksson, Sten G; Mohn, Chris E; Stølen, Svein
2009-10-28
The highly disordered structure of the delta phase of Bi2O3, which possesses the highest known oxide-ion conductivity, has been studied using neutron powder diffraction. A detailed analysis of data collected at 1033(3) K using Rietveld refinement indicates that the time-averaged structure of delta-Bi2O3 can be described using the accepted model of a disordered, anion-deficient fluorite structure in space group Fm3m. However, reverse Monte Carlo modelling of the total (Bragg plus diffuse) scattering demonstrates that the local anion environment around the Bi3+ resembles the distorted square pyramidal arrangement found within the stable alpha and metastable beta phases at ambient temperature, which is characteristic of the cation's 6s2 lone-pair configuration. Similarities between the structures of the highly disordered delta phase and the ambient temperature metastable beta phase are used to support this assignment and assess the validity of previous structural models based on short-range ordering of vacancies within the cubic lattice of delta-Bi2O3.
Magnetic Moments of Delta and Omega- baryons with dynamical clover fermions
Aubin, Christopher; Orginos, Konstantinos; Pascalutsa, Vladimir; Vanderhaeghen, Marc
2009-01-01
We calculate the magnetic dipole moment of the Delta(1232) and Omega- baryons with 2+1-flavors of clover fermions on anisotropic lattices using a background magnetic field. This is the first dynamical calculation of these magnetic moments using a background field technique. The calculation for Omega- is done at the physical strange quark mass, with the result in units of the physical nuclear magneton Âµ_(Omega-) = -1.93(8)(12) (where the first error is statistical and the second is systematic) compared to the experimental number: -2.02(5). The Delta has been studied at three unphysical quark masses, corresponding to pion mass 366, 438, and 548 MeV. The pion-mass dependence is compared with the behavior obtained from chiral effective-field theory.
Geomorphologic model for Mississippi delta evolution
Boyd, R.; Penland, S.
1988-09-01
The Holocene Mississippi delta is over 9000 years old. During this time, the Mississippi River has established six delta complexes. Sediments are currently supplied only to two of these complexes, neither of which is more than 500 years old. Deltaic sedimentation during most of the Holocene has occurred in shoal-water deltas, unlike the modern Balize lobe, which is located at the shelf break. Mississippi delta sedimentation is cyclic and consists of a regressive and a transgressive phase. Each delta complex first experiences progradation until overextension leads to abandonment and reworking. Mississippi deltas undergoing transgression are dominated by subsidence and marine basin processes leading to the formation of sandy barriers and lagoons. Each of the six delta complexes followed a common pattern of development. Current delta geomorphology reflects the variation in age of each delta complex and can be summarizes in a three-stage model beginning with stage 1: erosional headland and flanking barriers. Here, distributary sands are reworked by the retreating shoreface and dispersed laterally by longshore transport into flanking barriers which enclose interdistributary bays. In stage 2, transgressive barrier island arc, submergence of the erosional headland generates an intradeltaic lagoon that separates the barrier island arc from the retreating mainland. The model ends with stage 3, inner shelf shoals, where the retreating barrier-island arc is unable to keep pace with relative sea level rise or the more rapidly retreating mainland. This stage results in submergence of the barrier-island arc, which continues to be reworked as a sandy shoal on the inner continental shelf. This model of delta evolution illustrates mechanisms for generation of both barrier islands (in stages 1 and 2) and continental shelf sand bodies (in stage 3).
Januszkiewicz, D A; Nowak, J S
1994-09-01
DNA-based PCR with various sets of primers for TCR gamma/delta, and Ig heavy chain (IgH) genes were used to study clonality in childhood B-lineage acute lymphoblastic leukemia. Amplification of the IgH CDR-III was observed in 75 of 120 analyzed cases (62.5%). From all analyzed groups, the IgH gene rearrangement was most often observed in pre-B ALL (85.7%) and was rather rare in null-ALL (34.5%). TCR delta gene rearrangement was the most common, and was observed in 77 patients (64.2%). The typical pattern of rearrangements was defined as an incomplete V delta 2 to D delta 3, V delta 2 to D delta 2, or D delta 3 to D delta 2 recombination product. Rearrangements of TCR gamma gene we observed in 61 cases (50.8%). TCR gamma gene rearrangements were detected predominantly in null-ALL and early B-ALL (55.2% and 60%, respectively) and were rather rare in other groups. Of all eight V segments of V gamma I group, the most frequent gene usage concerns regions V gamma 2, V gamma 4, and psi V gamma 7. We have confirmed that IgH gene amplification, together with TCR gamma and delta gene amplification, provides a rapid, sensitive approach to assessing clonality in ALL almost in 100% of cases.
LATTICE QCD AT FINITE DENSITY.
SCHMIDT, C.
2006-07-23
I discuss different approaches to finite density lattice QCD. In particular, I focus on the structure of the phase diagram and discuss attempts to determine the location of the critical end-point. Recent results on the transition line as function of the chemical potential (T{sub c}({mu}{sub q})) are reviewed. Along the transition line, hadronic fluctuations have been calculated; which can be used to characterize properties of the Quark Gluon plasma and eventually can also help to identify the location of the critical end-point in the QCD phase diagram on the lattice and in heavy ion experiments. Furthermore, I comment on the structure of the phase diagram at large {mu}{sub q}.
Lattice Simulations and Infrared Conformality
Appelquist, Thomas; Fleming, George T.; Lin, Meifeng; ...
2011-09-01
We examine several recent lattice-simulation data sets, asking whether they are consistent with infrared conformality. We observe, in particular, that for an SU(3) gauge theory with 12 Dirac fermions in the fundamental representation, recent simulation data can be described assuming infrared conformality. Lattice simulations include a fermion mass m which is then extrapolated to zero, and we note that this data can be fit by a small-m expansion, allowing a controlled extrapolation. We also note that the conformal hypothesis does not work well for two theories that are known or expected to be confining and chirally broken, and that itmore » does work well for another theory expected to be infrared conformal.« less
The Fermilab lattice supercomputer project
NASA Astrophysics Data System (ADS)
Fischler, Mark; Atac, R.; Cook, A.; Deppe, J.; Gaines, I.; Husby, D.; Nash, T.; Pham, T.; Zmuda, T.; Hockney, George; Eichten, E.; Mackenzie, P.; Thacker, H. B.; Toussaint, D.
1989-06-01
The ACPMAPS system is a highly cost effective, local memory MIMD computer targeted at algorithm development and production running for gauge theory on the lattice. The machine consists of a compound hypercube of crates, each of which is a full crossbar switch containing several processors. The processing nodes are single board array processors based on the Weitek XL chip set, each with a peak power of 20 MFLOPS and supported by 8MBytes of data memory. The system currently being assembled has a peak power of 5 GFLOPS, delivering performance at approximately $250/MFLOP. The system is programmable in C and Fortran. An underpinning of software routines (CANOPY) provides an easy and natural way of coding lattice problems, such that the details of parallelism, and communication and system architecture are transparent to the user. CANOPY can easily be ported to any single CPU or MIMD system which supports C, and allows the coding of typical applications with very little effort.
Dru Renner
2012-04-01
Precision computation of hadronic physics with lattice QCD is becoming feasible. The last decade has seen precent-level calculations of many simple properties of mesons, and the last few years have seen calculations of baryon masses, including the nucleon mass, accurate to a few percent. As computational power increases and algorithms advance, the precise calculation of a variety of more demanding hadronic properties will become realistic. With this in mind, I discuss the current lattice QCD calculations of generalized parton distributions with an emphasis on the prospects for well-controlled calculations for these observables as well. I will do this by way of several examples: the pion and nucleon form factors and moments of the nucleon parton and generalized-parton distributions.
Tracking the SSC test lattices
Leemann, B.T.; Douglas, D.R.; Forest, E.
1990-01-01
The dynamic aperture and its determination emerged from the SSC reference design study as the single most important accelerator physics issue pertinent to the SSC. Beside the fundamental need of a finite dynamic aperture for any accelerator, it was considered to be a useful criterion for the magnet selection. An aperture workshop organized in November 1984 at LBL served the purpose to identify the various aspects of the aperture question and to organize the aperture task force accordingly. It was recognized that numerical models had to play an important role and the qualifications of several tracking codes were investigated. None of the existing codes could meet all of the criteria for an ideal tracking code and substantial program development became unavoidable. It was therefore decided to begin tracking SSC test lattices, which were provided by the aperture task force's lattice group and are described in an other paper to this conference, with existing tracking programs. 6 refs., 5 figs., 2 tabs.
Innovations in Lattice QCD Algorithms
Konstantinos Orginos
2006-06-25
Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today.
78 FR 53127 - Delta-Bienville Resource Advisory Committee
Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-28
...; ] DEPARTMENT OF AGRICULTURE Forest Service Delta-Bienville Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. Date change. SUMMARY: The Delta-Bienville Resource Advisory...
Spectral Properties of Unimodular Lattice Triangulations
NASA Astrophysics Data System (ADS)
Krüger, Benedikt; Schmidt, Ella M.; Mecke, Klaus
2016-05-01
Random unimodular lattice triangulations have been recently used as an embedded random graph model, which exhibit a crossover behavior between an ordered, large-world and a disordered, small-world behavior. Using the ergodic Pachner flips that transform such triangulations into another and an energy functional that corresponds to the degree distribution variance, Markov chain Monte Carlo simulations can be applied to study these graphs. Here, we consider the spectra of the adjacency and the Laplacian matrix as well as the algebraic connectivity and the spectral radius. Power law dependencies on the system size can clearly be identified and compared to analytical solutions for periodic ground states. For random triangulations we find a qualitative agreement of the spectral properties with well-known random graph models. In the microcanonical ensemble analytical approximations agree with numerical simulations. In the canonical ensemble a crossover behavior can be found for the algebraic connectivity and the spectral radius, thus combining large-world and small-world behavior in one model. The considered spectral properties can be applied to transport problems on triangulation graphs and the crossover behavior allows a tuning of important transport quantities.
Flutter analysis and testing of pairs of aerodynamically interfering delta wings
NASA Technical Reports Server (NTRS)
Chipman, R. R.; Rauch, F. J.
1973-01-01
To examine the effect on flutter of the aerodynamic interference between pairs of closely spaced delta wings, several structurally uncoupled 1/80th-scale models were studied by experiment and analysis. Flutter test boundaries run in a 26-in transonic blowdown wind tunnel were compared with subsonic analytical results generated using the doublet lattice method. Trends for several combinations of vertical and longitudinal wing separation showed that flutter speeds can be significantly lowered in closely spaced configurations. For some configurations, a new flutter mechanism, characterized by coupling of the flexible modes from both surfaces at a distinctive flutter frequency, was predicted and observed.
Pressure measurements on a thick cambered and twisted 58 deg delta wing at high subsonic speeds
NASA Technical Reports Server (NTRS)
Chu, Julio; Lamar, John E.
1987-01-01
A pressure experiment at high subsonic speeds was conducted by a cambered and twisted thick delta wing at the design condition (Mach number 0.80), as well as at nearby Mach numbers (0.75 and 0.83) and over an angle-of-attack range. Effects of twin vertical tails on the wing pressure measurements were also assessed. Comparisons of detailed theoretical and experimental surface pressures and sectional characteristics for the wing alone are presented. The theoretical codes employed are FLO-57, FLO-28, PAN AIR, and the Vortex Lattice Method-Suction Analogy.
Delta and Omega electromagnetic form factors in a Dyson-Schwinger/Bethe-Salpeter approach
Diana Nicmorus, Gernot Eichmann, Reinhard Alkofer
2010-12-01
We investigate the electromagnetic form factors of the Delta and the Omega baryons within the Poincare-covariant framework of Dyson-Schwinger and Bethe-Salpeter equations. The three-quark core contributions of the form factors are evaluated by employing a quark-diquark approximation. We use a consistent setup for the quark-gluon dressing, the quark-quark bound-state kernel and the quark-photon interaction. Our predictions for the multipole form factors are compatible with available experimental data and quark-model estimates. The current-quark mass evolution of the static electromagnetic properties agrees with results provided by lattice calculations.
Enhancing the Electron Mobility via Delta-Doping in SrTiO3
Kozuka, Y.
2011-08-11
We fabricated high-mobility {delta}-doped structures in SrTiO{sub 3} thin films in order to investigate the low temperature electronic transport properties of confined carriers in this system. An enhancement of the electron mobility above the bulk value was observed as the doped layer thickness decreased. High-field Hall measurements revealed that this mobility enhancement originates from higher-mobility electrons in the undoped clean regions, which have quantum-mechanically broadened from the doped layer. Because of the absence of apparent lattice misfit between the layers, this structure is highly suitable for investigating two-dimensional electron gases in SrTiO{sub 3}
Scanning phononic lattices with ultrasound
Vines, R.E.; Wolfe, J.P.; Every, A.V.
1999-11-01
A method for probing the elastic properties of newly developed periodic structures using acoustic waves is introduced. Highly anisotropic transmission of surface acoustic waves is observed by continuously scanning the wave vector angle. Preliminary models of wave propagation through multilayers and two-dimensional lattices explain some of the experimental features, while other features can be attributed to the resonant excitation of interface waves. {copyright} {ital 1999} {ital The American Physical Society}
Hadron physics from lattice QCD
NASA Astrophysics Data System (ADS)
Bietenholz, Wolfgang
2016-07-01
We sketch the basic ideas of the lattice regularization in Quantum Field Theory, the corresponding Monte Carlo simulations, and applications to Quantum Chromodynamics (QCD). This approach enables the numerical measurement of observables at the non-perturbative level. We comment on selected results, with a focus on hadron masses and the link to Chiral Perturbation Theory. At last, we address two outstanding issues: topological freezing and the sign problem.
Apiary B Factory Lattice Design
Donald, M.H.R.; Garren, A.A.
1991-05-03
The Apiary B Factory is a proposed high-intensity electron-positron collider. This paper presents the lattice design for this facility, which envisions two rings with unequal energies in the PEP tunnel. The design has many interesting optical and geometrical features due to the needs to conform to the existing tunnel, and to achieve the necessary emittances, damping times and vacuum. Existing hardware is used to a maximum extent.
Apiary B Factory lattice design
Donald, M.H.R. ); Garren, A.A. )
1991-04-01
The Apiary B Factory is a proposed high-intensity electron-positron collider. This paper will present the lattice design for this facility, which envisions two rings with unequal energies in the PEP tunnel. The design has many interesting optical and geometrical features due to the needs to conform to the existing tunnel, and to achieve the necessary emittances, damping times and vacuum. Existing hardware is used to a maximum extent. 8 figs. 1 tab.
Newsome, Seth D; Bentall, Gena B; Tinker, M Tim; Oftedal, Olav T; Ralls, Katherine; Estes, James A; Fogel, Marilyn L
2010-09-01
The ability to quantify dietary inputs using stable isotope data depends on accurate estimates of isotopic differences between a consumer (c) and its diet (d), commonly referred to as trophic discrimination factors (TDFs) and denoted by delta(c-d). At present, TDFs are available for only a few mammals and are usually derived in captive settings. The magnitude of TDFs and the degree to which they vary in wild populations is unknown. We determined delta13C and delta15N TDFs for vibrissae (i.e., whiskers), a tissue that is rapidly becoming an informative isotopic substrate for ecologists, of a wild population of sea otters for which individual diet has been quantified through extensive observational study. This is one of the very few studies that report TDFs for free-living wild animals feeding on natural diets. Trophic discrimination factors of 2.2 per thousand +/- 0.7 per thousand for delta13C and 3.5 per thousand +/- 0.6 per thousand for delta15N (mean +/- SD) were similar to those reported for captive carnivores, and variation in individual delta13C TDFs was negatively but significantly related to sea urchin consumption. This pattern may relate to the lipid-rich diet consumed by most sea otters in this population and suggests that it may not be appropriate to lipid-extract prey samples when using the isotopic composition of keratinaceous tissues to examine diet in consumers that frequently consume lipid-rich foods, such as many marine mammals and seabirds. We suggest that inherent variation in TDFs should be included in isotopically based estimates of trophic level, food chain length, and mixing models used to quantify dietary inputs in wild populations; this practice will further define the capabilities and limitations of isotopic approaches in ecological studies.
Rapisarda, Paolo; Camin, Federica; Fabroni, Simona; Perini, Matteo; Torrisi, Biagio; Intrigliolo, Francesco
2010-03-24
To investigate the influence of different types of fertilizers on quality parameters, N-containing compounds, and the delta(15)N, delta(13)C, delta(2)H, delta (34)S, and delta(18)O values of citrus fruit, a study was performed on the orange fruit cv. 'Valencia late' (Citrus sinensis L. Osbeck), which was harvested in four plots (three organic and one conventional) located on the same farm. The results demonstrated that different types of organic fertilizers containing the same amount of nitrogen did not effect important changes in orange fruit quality parameters. The levels of total N and N-containing compounds such as synephrine in fruit juice were not statistically different among the different treatments. The delta(15)N values of orange fruit grown under fertilizer derived from animal origin as well as from vegetable compost were statistically higher than those grown with mineral fertilizer. Therefore, delta(15)N values can be used as an indicator of citrus fertilization management (organic or conventional), because even when applied organic fertilizers are of different origins, the natural abundance of (15)N in organic citrus fruit remains higher than in conventional ones. These treatments also did not effect differences in the delta(13)C, delta(2)H, delta(34)S, and delta(18)O values of fruit.
Nuclear reactions from lattice QCD
Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.
2015-01-13
In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculationsmore » of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.« less
Nuclear reactions from lattice QCD
Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.
2015-01-13
In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.
Brownlee, B G; Hall, R H; Whitty, C D
1975-01-01
An enzyme preparation from immature corn kernels catalyzed cleavage of N-6-(delta-2-isopentenyl)adenine to give the aldehyde, 3-methyl-2-butenal, as the major side-chain derived product. This product, in the form of the semicarbazone, was identical with an authentic product by several criteria: chromatographic behavior, mass and ultraviolet spectra.
Ectopic A-lattice seams destabilize microtubules.
Katsuki, Miho; Drummond, Douglas R; Cross, Robert A
2014-01-01
Natural microtubules typically include one A-lattice seam within an otherwise helically symmetric B-lattice tube. It is currently unclear how A-lattice seams influence microtubule dynamic instability. Here we find that including extra A-lattice seams in GMPCPP microtubules, structural analogues of the GTP caps of dynamic microtubules, destabilizes them, enhancing their median shrinkage rate by >20-fold. Dynamic microtubules nucleated by seeds containing extra A-lattice seams have growth rates similar to microtubules nucleated by B-lattice seeds, yet have increased catastrophe frequencies at both ends. Furthermore, binding B-lattice GDP microtubules to a rigor kinesin surface stabilizes them against shrinkage, whereas microtubules with extra A-lattice seams are stabilized only slightly. Our data suggest that introducing extra A-lattice seams into dynamic microtubules destabilizes them by destabilizing their GTP caps. On this basis, we propose that the single A-lattice seam of natural B-lattice MTs may act as a trigger point, and potentially a regulation point, for catastrophe.
Ising models on the 2 x 2 x {infinity} lattices
Yurishchev, M. A.
2007-03-15
Exact analytic solutions are presented for two 2 x 2 x {infinity} Ising etageres. The first model has a simple cubic lattice with fully anisotropic interactions. The second model consists of two different types of linear chains and includes noncrossing diagonal bonds on the side faces of the 2 x 2 x {infinity} parallelepiped. In both cases, the solutions are expressed through square radicals and obtained by using the obvious symmetry of the Hamiltonians, Z{sub 2} x C{sub 2v}, and the hidden algebraic {lambda}{lambda} symmetry of the transfer matrix secular equations. The solution found for the second model is used to analyze the behavior of specific heat in a frustrated many-chain system.
Monte Carlo lattice models for adsorbed polymer conformation
NASA Technical Reports Server (NTRS)
Good, B. S.
1985-01-01
The adhesion between a polymer film and a metal surface is of great technological interest. However, the prediction of adhesion and wear properties of polymer coated metals is quite difficult because a fundamental understanding of the polymer surface interaction does not yet exist. A computer model for the conformation of a polymer molecule adsorbed on a surface is discussed. The chain conformation is assumed to be described by a partially directed random walk on a three dimensional simple cubic lattice. An attractive surface potential is incorporated into the model through the use of a random walk step probability distribution that is anisotropic in the direction normal to the attractive surface. The effects of variations in potential characteristics are qualitatively included by varying both the degree of anisotropy of the step distribution and the range of the anisotropy. Polymer conformation is characterized by the average end to end distance, average radius of gyration, and average number of chain segments adsorbed on the surface.
NASA Astrophysics Data System (ADS)
Sun, He Bi.
The physical properties of oxygen deficient polycrystalline rm YBa_2Cu_3O_{7 -delta} superconducting materials have been systematically investigated. These properties include magnetic susceptibility, electrical transport, thermoelectric power and infrared reflectivity. A great deal of this study has concentrated on the magnetic and transport properties of these materials when they are in the mixed state. The polycrystalline specimens used in this work were prepared through a solid state reaction. The oxygen content of the specimens was controlled using several annealing methods and the oxygen deficiency delta was determined by X-ray diffraction, gas evolution, iodometric titration and neutron diffraction techniques. A new method has been developed for the investigation of magnetic relaxation in these materials using the conventional a.c. susceptibility technique after modification. This thesis represents the first detailed and systematic study of the thermal activation energy for high Tc superconductors using many different methods, including a.c. susceptibility, magnetic relaxation, electric resistivity and thermoelectric power. All the results obtained, including their numerical values and field dependence are consistent with and comparable to previously reported data. A modified critical state model has been successfully used to interpret the magnetic field dependence of the isothermal a.c. susceptibility data, including field dependent a.c. losses and the chi^' -chi^{'' } interrelationship. This study highlights the strong influence that delta exerts on the superconducting and normal state properties of polycrystalline rm YBa_2Cu_3O_{7-delta } material. In particular, for transport properties, delta affects the carrier doping in the CuO_2 planes, which determines the carrier concentration. Therefore increasing delta reduces the superconducting transition temperature. For the magnetic property, delta has a negative influence on the pinning energy in
Lattice Truss Structural Response Using Energy Methods
NASA Technical Reports Server (NTRS)
Kenner, Winfred Scottson
1996-01-01
A deterministic methodology is presented for developing closed-form deflection equations for two-dimensional and three-dimensional lattice structures. Four types of lattice structures are studied: beams, plates, shells and soft lattices. Castigliano's second theorem, which entails the total strain energy of a structure, is utilized to generate highly accurate results. Derived deflection equations provide new insight into the bending and shear behavior of the four types of lattices, in contrast to classic solutions of similar structures. Lattice derivations utilizing kinetic energy are also presented, and used to examine the free vibration response of simple lattice structures. Derivations utilizing finite element theory for unique lattice behavior are also presented and validated using the finite element analysis code EAL.
Alegret, M; Cerqueda, E; Ferrando, R; Vázquez, M; Sánchez, R M; Adzet, T; Merlos, M; Laguna, J C
1995-01-01
1. The time-course of the effect of clofibrate (CFB), bezafibrate (BFB) and gemfibrozil (GFB) on lipid plasma levels and palmitoyl-, palmitoleoyl- and gamma-linolenoyl-CoA elongase, delta-9, delta-6 and delta-5 desaturase activities, and microsomal electron transport chains, as well as the correlation with the peroxisomal proliferation phenomenon have been studied in male Sprague-Dawley rats. 2. As reported in our previous work, the three drugs behave as peroxisomal proliferators (the order of potency was BFB > CFB > or = GFB) and induced a clear reduction in both plasma cholesterol and triglyceride levels. 3. Palmitoyl-CoA elongation activity was increased by the three drugs (BFB = GFB > CFB), whereas palmitoleoyl-CoA elongation activity was only enhanced by GFB. Elongation activity was not modified by fibrates when gamma-linolenoyl-CoA was used as substrate. These results are in accordance with the existence of three different elongation systems for saturated, mono- and polyunsaturated fatty acids. 4. delta-9, delta-6 and delta-5 desaturase activities were increased by the three fibrates, with an order of potency BFB > CFB = GFB for delta-9 and delta-5, and GFB > BFB = CFB for delta-6. 5. Of the enzyme activities integrated in the microsomal electron transport chains, NADH cytochrome b5 reductase was not affected by fibrate treatment, NADPH cytochrome c reductase activity was enhanced (BFB = GFB > CFB), whereas NADH cytochrome c reductase activity was reduced by CFB and BFB.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7606338
Identifying hazards associated with lava deltas
Poland, Michael P.; Orr, Tim R.
2014-01-01
Lava deltas, formed where lava enters the ocean and builds a shelf of new land extending from the coastline, represent a significant local hazard, especially on populated ocean island volcanoes. Such structures are unstable and prone to collapse—events that are often accompanied by small explosions that can deposit boulders and cobbles hundreds of meters inland. Explosions that coincide with collapses of the East Lae ‘Apuki lava delta at Kīlauea Volcano, Hawai‘i, during 2005–2007 followed an evolutionary progression mirroring that of the delta itself. A collapse that occurred when the lava–ocean entry was active was associated with a blast of lithic blocks and dispersal of spatter and fine, glassy tephra. Shortly after delta growth ceased, a collapse exposed hot rock to cold ocean water, resulting in an explosion composed entirely of lithic blocks and lapilli. Further collapse of the delta after several months of inactivity, by which time it had cooled significantly, resulted in no recognizable explosion deposit. Seaward displacement and subsidence of the coastline immediately inland of the delta was measured by both satellite and ground-based sensors and occurred at rates of several centimeters per month even after the lava–ocean entry had ceased. The anomalous deformation ended only after complete collapse of the delta. Monitoring of ground deformation may therefore provide an indication of the potential for delta collapse, while the hazard associated with collapse can be inferred from the level of activity, or the time since the last activity, on the delta.
Health supply chain management.
Zimmerman, Rolf; Gallagher, Pat
2010-01-01
This chapter gives an educational overview of: * The actual application of supply chain practice and disciplines required for service delivery improvement within the current health environment. * A rationale for the application of Supply Chain Management (SCM) approaches to the Health sector. * The tools and methods available for supply chain analysis and benchmarking. * Key supply chain success factors.
Fractional scaling of quantum walks on percolation lattices
NASA Astrophysics Data System (ADS)
Kendon, Viv; Leung, Godfrey; Bailey, Joe; Knott, Paul
2011-03-01
Quantum walks can be used to model processes such as transport in spin chains and bio-molecules. The enhanced spreading and mixing properties of quantum walks compared with their classical counterparts have been well-studied on regular structures and also shown to be sensitive to defects and imperfections. Using numerical simulation, we study the spreading properties of quantum walks on percolation lattices for both bond and site percolation. The randomly missing edges or sites provide a controlled amount of disorder in the regular Cartesian lattice. In one dimension (the line) we introduce a simple model of quantum tunneling to allow the walk to proceed past the missing edges or sites. This allows the quantum walk to spread faster than a classical random walk for short times, but at longer times the disorder localises the quantum walk. In two dimensions, we observe fractional scaling of the spreading with the number of steps of the walk. For percolation above the 85% level, we obtain faster spreading than classical random walks on the full lattice.
Counting in Lattices: Combinatorial Problems from Statistical Mechanics.
NASA Astrophysics Data System (ADS)
Randall, Dana Jill
In this thesis we consider two classical combinatorial problems arising in statistical mechanics: counting matchings and self-avoiding walks in lattice graphs. The first problem arises in the study of the thermodynamical properties of monomers and dimers (diatomic molecules) in crystals. Fisher, Kasteleyn and Temperley discovered an elegant technique to exactly count the number of perfect matchings in two dimensional lattices, but it is not applicable for matchings of arbitrary size, or in higher dimensional lattices. We present the first efficient approximation algorithm for computing the number of matchings of any size in any periodic lattice in arbitrary dimension. The algorithm is based on Monte Carlo simulation of a suitable Markov chain and has rigorously derived performance guarantees that do not rely on any assumptions. In addition, we show that these results generalize to counting matchings in any graph which is the Cayley graph of a finite group. The second problem is counting self-avoiding walks in lattices. This problem arises in the study of the thermodynamics of long polymer chains in dilute solution. While there are a number of Monte Carlo algorithms used to count self -avoiding walks in practice, these are heuristic and their correctness relies on unproven conjectures. In contrast, we present an efficient algorithm which relies on a single, widely-believed conjecture that is simpler than preceding assumptions and, more importantly, is one which the algorithm itself can test. Thus our algorithm is reliable, in the sense that it either outputs answers that are guaranteed, with high probability, to be correct, or finds a counterexample to the conjecture. In either case we know we can trust our results and the algorithm is guaranteed to run in polynomial time. This is the first algorithm for counting self-avoiding walks in which the error bounds are rigorously controlled. This work was supported in part by an AT&T graduate fellowship, a University of
ERIC Educational Resources Information Center
Caglayan, Günhan
2016-01-01
A Steiner chain is defined as the sequence of n circles that are all tangent to two given non-intersecting circles. A closed chain, in particular, is one in which every circle in the sequence is tangent to the previous and next circles of the chain. In a closed Steiner chain the first and the "n"th circles of the chain are also tangent…
The heme precursor delta-aminolevulinate blocks peripheral myelin formation
Felitsyn, Natalia; McLeod, Colin; Shroads, Albert L.; Stacpoole, Peter W.; Notterpek, Lucia
2008-01-01
Delta-aminolevulinic acid (δ-ALA) is a heme precursor implicated in neurological complications associated with porphyria and tyrosinemia type I. Delta-ALA is also elevated in the urine of animals and patients treated with the investigational drug dichloroacetate (DCA). We postulated that δ-ALA may be responsible, in part, for the peripheral neuropathy observed in subjects receiving DCA. To test this hypothesis, myelinating cocultures of Schwann cells and sensory neurons were exposed to δ-ALA (0.1–1 mM) and analyzed for the expression of neural proteins and lipids and markers of oxidative stress. Exposure of myelinating samples to δ-ALA is associated with a pronounced reduction in the levels of myelin-associated lipids and proteins, including myelin protein zero and peripheral myelin protein 22. We also observed an increase in protein carbonylation and the formation of hydroxynonenal and malondialdehyde after treatment with δ-ALA. Studies of isolated Schwann cells and neurons indicate that glial cells are more vulnerable to this pro-oxidant than neurons, based on a selective decrease in the expression of mitochondrial respiratory chain proteins in glial, but not in neuronal, cells. These results suggest that the neuropathic effects of δ-ALA are attributable, at least in part, to its pro-oxidant properties which damage myelinating Schwann cells. PMID:18665889
Novel diazabicycloalkane delta opioid agonists.
Loriga, Giovanni; Lazzari, Paolo; Manca, Ilaria; Ruiu, Stefania; Falzoi, Matteo; Murineddu, Gabriele; Bottazzi, Mirko Emilio Heiner; Pinna, Giovanni; Pinna, Gérard Aimè
2015-09-01
Here we report the investigation of diazabicycloalkane cores as potential new scaffolds for the development of novel analogues of the previously reported diazatricyclodecane selective delta (δ) opioid agonists, as conformationally constrained homologues of the reference δ agonist (+)-4-[(αR)-α((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC80). In particular, we have simplified the diazatricyclodecane motif of δ opioid agonist prototype 1a with bridged bicyclic cores. 3,6-diazabicyclo[3.1.1]heptane, 3,8-diazabicyclo[3.2.1]octane, 3,9-diazabicyclo[3.3.1]nonane, 3,9-diazabicyclo[4.2.1]nonane, and 3,10-diazabicyclo[4.3.1]decane were adopted as core motifs of the novel derivatives. The compounds were synthesized and biologically assayed as racemic (3-5) or diastereoisomeric (6,7) mixtures. All the novel compounds 3-7 showed δ agonism behaviour and remarkable affinity to δ receptors. Amongst the novel derivatives, 3,8-diazabicyclo[3.2.1]octane based compound 4 evidenced improved δ affinity and selectivity relative to SNC80.
Delta Electroproduction in 12-C
McLauchlan, Steven
2003-01-01
The Δ-nucleus potential is a crucial element in the understanding of the nuclear system. Previous electroexcitation measurements in the delta region reported a Q^{2} dependence of the Δ mass indicating that this potential is dependent on the momentum of the Δ. Such a dependence is not observed for protons and neutrons in the nuclear medium. This thesis presents the experimental study of the electroexcitation of the Δ resonance in ^{12}C, performed using the high energy electron beam at the Thomas Jefferson National Accelerator Facility, and the near 4π acceptance detector CLAS that enables the detection of the full reaction final state. Inclusive, semi inclusive, and exclusive cross sections were measured with an incident electron beam energy of 1.162GeV over the Q^{2} range 0.175-0.475 (GeV/c)^{2}. A Q^{2} dependence of the Δ mass was only observed in the exclusive measurements indicating that the Δ-nucleus potential is affected by the momentum of the Δ.
Unbiased sampling of lattice Hamilton path ensembles
NASA Astrophysics Data System (ADS)
Mansfield, Marc L.
2006-10-01
Hamilton paths, or Hamiltonian paths, are walks on a lattice which visit each site exactly once. They have been proposed as models of globular proteins and of compact polymers. A previously published algorithm [Mansfield, Macromolecules 27, 5924 (1994)] for sampling Hamilton paths on simple square and simple cubic lattices is tested for bias and for efficiency. Because the algorithm is a Metropolis Monte Carlo technique obviously satisfying detailed balance, we need only demonstrate ergodicity to ensure unbiased sampling. Two different tests for ergodicity (exact enumeration on small lattices, nonexhaustive enumeration on larger lattices) demonstrate ergodicity unequivocally for small lattices and provide strong support for ergodicity on larger lattices. Two other sampling algorithms [Ramakrishnan et al., J. Chem. Phys. 103, 7592 (1995); Lua et al., Polymer 45, 717 (2004)] are both known to produce biases on both 2×2×2 and 3×3×3 lattices, but it is shown here that the current algorithm gives unbiased sampling on these same lattices. Successive Hamilton paths are strongly correlated, so that many iterations are required between statistically independent samples. Rules for estimating the number of iterations needed to dissipate these correlations are given. However, the iteration time is so fast that the efficiency is still very good except on extremely large lattices. For example, even on lattices of total size 10×10×10 we are able to generate tens of thousands of uncorrelated Hamilton paths per hour of CPU time.
Topological magnon bands in ferromagnetic star lattice.
Owerre, S A
2017-05-10
The experimental observation of topological magnon bands and thermal Hall effect in a kagomé lattice ferromagnet Cu(1-3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii-Moriya (DM) spin-orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnet is an ideal candidate for this purpose because it is a variant of the kagomé lattice with additional links that connect the up-pointing and down-pointing triangles. This gives rise to twice the unit cell of the kagomé lattice, and hence more interesting topological magnon effects. In particular, the triangular bridges on the star lattice can be coupled either ferromagnetically or antiferromagnetically which is not possible on the kagomé lattice ferromagnets. Here, we study DM-induced topological magnon bands, chiral edge modes, and thermal magnon Hall effect on the star lattice ferromagnet in different parameter regimes. The star lattice can also be visualized as the parent material from which topological magnon bands can be realized for the kagomé and honeycomb lattices in some limiting cases.
NASA Astrophysics Data System (ADS)
Xia, Chunxin
Lymphatic drug transport can confer bioavailability advantage by avoiding the first-pass metabolism normally observed in the portal vein hepatic route. It was reported that long chain lipid-based delivery systems can stimulate the formation of chylomicron and thus promote the lymphatic transport of drugs. In this study, a novel delta-tocopherol (delta-T) loaded Solid Lipid Nanoparticle (SLN) system was developed to investigate its effect on promoting the lymphatic transport of delta-T. The delta-T SLN was prepared with hot melt emulsification method by using glyceryl behenate (compritol RTM888) as the lipid phase and lecithin (PC75) as the emulsifier. Formula configuration, processing condition and loading capacity were carefully optimized. Physicochemical properties (particle size, surface charge, morphology) were also characterized. Moreover, excellent stability of the developed delta-T SLN in the gastrointestinal environment was observed by using an in vitro digestion model. Further investigations of the SLN in stimulating delta-T lymphatic transport were performed on mice without cannulation. Compared with the control group (delta-T corn oil dispersion), much lower delta-T levels in both blood and liver indicated reduced portal vein and hepatic transport of delta-T in the form of SLN. On the other hand, significantly higher concentrations of delta-T were observed in thymus, a major lymphatic tissue, indicating improved lymphatic transport of delta-T with the SLN delivery system. Finally, the far less excreted delta-T level in feces further confirmed improved lymphatic transport and overall bioavailability of delta-T by using SLN system. Nobiletin (NOB), one of most abundant polymethoxyflavones (PMFs) found in Citrus genus, has a low solubility in both water and oil at ambient temperatures. Thus it tends to form crystals when the loading exceeds its saturation level in the carrier system. This character greatly impaired its bioavailability and application. To
Delta-nucleus dynamics: proceedings of symposium
Lee, T.S.H.; Geesaman, D.F.; Schiffer, J.P.
1983-10-01
The appreciation of the role in nuclear physics of the first excited state of the nucleon, the delta ..delta..(1232), has grown rapidly in the past decade. The delta resonance dominates nuclear reactions induced by intermediate energy pions, nucleons, and electromagnetic probes. It is also the most important non-nucleonic degree of freedom needed to resolve many fundamental problems encountered in the study of low-energy nuclear phenomena. Clearly, a new phase of nuclear physics has emerged and conventional thinking must be extended to account for this new dimension of nuclear dynamics. The most challenging problem we are facing is how a unified theory can be developed to describe ..delta..-nucleus dynamics at all energies. In exploring this new direction, it is important to have direct discussions among researchers with different viewpoints. Separate entries were prepared for the 49 papers presented. (WHK)
Damped Oscillator with Delta-Kicked Frequency
NASA Technical Reports Server (NTRS)
Manko, O. V.
1996-01-01
Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.
Contemporary depositional environments of the Omo delta.
Butzer, K W
1970-05-02
Geomorphological and sedimentological studies of depositional environments of the modern Omo River delta and floodplain are essential to an understanding of the Pliocene to Pleistocene Mursi, Nkalabong and Kibish Formations of the Lower Omo Basin (southwestern Ethiopia).
Thermodynamics of folding and association of lattice-model proteins
NASA Astrophysics Data System (ADS)
Cellmer, Troy; Bratko, Dusan; Prausnitz, John M.; Blanch, Harvey
2005-05-01
Closely related to the "protein folding problem" is the issue of protein misfolding and aggregation. Protein aggregation has been associated with the pathologies of nearly 20 human diseases and presents serious difficulties during the manufacture of pharmaceutical proteins. Computational studies of multiprotein systems have recently emerged as a powerful complement to experimental efforts aimed at understanding the mechanisms of protein aggregation. We describe the thermodynamics of systems containing two lattice-model 64-mers. A parallel tempering algorithm abates problems associated with glassy systems and the weighted histogram analysis method improves statistical quality. The presence of a second chain has a substantial effect on single-chain conformational preferences. The melting temperature is substantially reduced, and the increase in the population of unfolded states is correlated with an increase in interactions between chains. The transition from two native chains to a non-native aggregate is entropically favorable. Non-native aggregates receive ˜25% of their stabilizing energy from intraprotein contacts not found in the lowest-energy structure. Contact maps show that for non-native dimers, nearly 50% of the most probable interprotein contacts involve pairs of residues that form native contacts, suggesting that a domain-swapping mechanism is involved in self-association.
Lattice cluster theory for dense, thin polymer films.
Freed, Karl F
2015-04-07
While the application of the lattice cluster theory (LCT) to study the miscibility of polymer blends has greatly expanded our understanding of the monomer scale molecular details influencing miscibility, the corresponding theory for inhomogeneous systems has not yet emerged because of considerable technical difficulties and much greater complexity. Here, we present a general formulation enabling the extension of the LCT to describe the thermodynamic properties of dense, thin polymer films using a high dimension, high temperature expansion. Whereas the leading order of the LCT for bulk polymer systems is essentially simple Flory-Huggins theory, the highly non-trivial leading order inhomogeneous LCT (ILCT) for a film with L layers already involves the numerical solution of 3(L - 1) coupled, highly nonlinear equations for the various density profiles in the film. The new theory incorporates the essential "transport" constraints of Helfand and focuses on the strict imposition of excluded volume constraints, appropriate to dense polymer systems, rather than the maintenance of chain connectivity as appropriate for lower densities and as implemented in self-consistent theories of polymer adsorption at interfaces. The ILCT is illustrated by presenting examples of the computed profiles of the density, the parallel and perpendicular bonds, and the chain ends for free standing and supported films as a function of average film density, chain length, temperature, interaction with support, and chain stiffness. The results generally agree with expected general trends.
Lattice cluster theory for dense, thin polymer films
Freed, Karl F.
2015-04-07
While the application of the lattice cluster theory (LCT) to study the miscibility of polymer blends has greatly expanded our understanding of the monomer scale molecular details influencing miscibility, the corresponding theory for inhomogeneous systems has not yet emerged because of considerable technical difficulties and much greater complexity. Here, we present a general formulation enabling the extension of the LCT to describe the thermodynamic properties of dense, thin polymer films using a high dimension, high temperature expansion. Whereas the leading order of the LCT for bulk polymer systems is essentially simple Flory-Huggins theory, the highly non-trivial leading order inhomogeneous LCT (ILCT) for a film with L layers already involves the numerical solution of 3(L − 1) coupled, highly nonlinear equations for the various density profiles in the film. The new theory incorporates the essential “transport” constraints of Helfand and focuses on the strict imposition of excluded volume constraints, appropriate to dense polymer systems, rather than the maintenance of chain connectivity as appropriate for lower densities and as implemented in self-consistent theories of polymer adsorption at interfaces. The ILCT is illustrated by presenting examples of the computed profiles of the density, the parallel and perpendicular bonds, and the chain ends for free standing and supported films as a function of average film density, chain length, temperature, interaction with support, and chain stiffness. The results generally agree with expected general trends.
Transitions of tethered chain molecules under tension.
Luettmer-Strathmann, Jutta; Binder, Kurt
2014-09-21
An applied tension force changes the equilibrium conformations of a polymer chain tethered to a planar substrate and thus affects the adsorption transition as well as the coil-globule and crystallization transitions. Conversely, solvent quality and surface attraction are reflected in equilibrium force-extension curves that can be measured in experiments. To investigate these effects theoretically, we study tethered chains under tension with Wang-Landau simulations of a bond-fluctuation lattice model. Applying our model to pulling experiments on biological molecules we obtain a good description of experimental data in the intermediate force range, where universal features dominate and finite size effects are small. For tethered chains in poor solvent, we observe the predicted two-phase coexistence at transitions from the globule to stretched conformations and also discover direct transitions from crystalline to stretched conformations. A phase portrait for finite chains constructed by evaluating the density of states for a broad range of solvent conditions and tensions shows how increasing tension leads to a disappearance of the globular phase. For chains in good solvents tethered to hard and attractive surfaces we find the predicted scaling with the chain length in the low-force regime and show that our results are well described by an analytical, independent-bond approximation for the bond-fluctuation model for the highest tensions. Finally, for a hard or slightly attractive surface the stretching of a tethered chain is a conformational change that does not correspond to a phase transition. However, when the surface attraction is sufficient to adsorb a chain it will undergo a desorption transition at a critical value of the applied force. Our results for force-induced desorption show the transition to be discontinuous with partially desorbed conformations in the coexistence region.
Fractional random walk lattice dynamics
NASA Astrophysics Data System (ADS)
Michelitsch, T. M.; Collet, B. A.; Riascos, A. P.; Nowakowski, A. F.; Nicolleau, F. C. G. A.
2017-02-01
We analyze time-discrete and time-continuous ‘fractional’ random walks on undirected regular networks with special focus on cubic periodic lattices in n = 1, 2, 3,.. dimensions. The fractional random walk dynamics is governed by a master equation involving fractional powers of Laplacian matrices {{L}\\fracα{2}}} where α =2 recovers the normal walk. First we demonstrate that the interval 0<α ≤slant 2 is admissible for the fractional random walk. We derive analytical expressions for the transition matrix of the fractional random walk and closely related the average return probabilities. We further obtain the fundamental matrix {{Z}(α )} , and the mean relaxation time (Kemeny constant) for the fractional random walk. The representation for the fundamental matrix {{Z}(α )} relates fractional random walks with normal random walks. We show that the matrix elements of the transition matrix of the fractional random walk exihibit for large cubic n-dimensional lattices a power law decay of an n-dimensional infinite space Riesz fractional derivative type indicating emergence of Lévy flights. As a further footprint of Lévy flights in the n-dimensional space, the transition matrix and return probabilities of the fractional random walk are dominated for large times t by slowly relaxing long-wave modes leading to a characteristic {{t}-\\frac{n{α}} -decay. It can be concluded that, due to long range moves of fractional random walk, a small world property is emerging increasing the efficiency to explore the lattice when instead of a normal random walk a fractional random walk is chosen.
Migration in Vulnerable Deltas: A Research Strategy
NASA Astrophysics Data System (ADS)
Hutton, C.; Nicholls, R. J.; Allan, A.
2015-12-01
C. Hutton1, & R. J. Nicholls1, , 1 University of Southampton, University Road, Southampton, Hampshire, United Kingdom, SO17 1BJ. cwh@geodata. soton.ac.ukAbstractGlobally, deltas contain 500 million people and with rising sea levels often linked to large number of forced migrants are expected in the coming century. However, migration is already a major process in deltas, such as the growth of major cities such as Dhaka and Kolkata. Climate and environmental change interacts with a range of catchment and delta level drivers, which encompass a nexus of sea-level rise, storms, freshwater and sediment supply from the catchment, land degradation, subsidence, agricultural loss and socio-economic stresses. DECCMA (Deltas, Vulnerability and Climate Change: Migration and Adaptation/CARRIA) is investigating migration in the Ganges-Brahmaputra-Meghna (GBM), Mahanadi and Volta Deltas, including the influence of climate change. The research will explore migration from a range of perspectives including governance and stakeholder analysis, demographic analysis, household surveys of sending and receiving areas, macro-economic analysis, and hazards and hotspot analysis both historically and into the future. Migration under climate change will depend on other adaptation in the deltas and this will be examined. Collectively, integrated analysis will be developed to examine migration, other adaptation and development pathways with a particular focus on the implications for the poorest. This will require the development of input scenarios, including expert-derived exogenous scenarios (e.g., climate change) and endogenous scenarios of the delta developed in a participatory manner. This applied research will facilitate decision support methods for the development of deltas under climate change, with a focus on migration and other adaptation strategies.
Percolation in finite matching lattices
NASA Astrophysics Data System (ADS)
Mertens, Stephan; Ziff, Robert M.
2016-12-01
We derive an exact, simple relation between the average number of clusters and the wrapping probabilities for two-dimensional percolation. The relation holds for periodic lattices of any size. It generalizes a classical result of Sykes and Essam, and it can be used to find exact or very accurate approximations of the critical density. The criterion that follows is related to the criterion used by Scullard and Jacobsen to find precise approximate thresholds, and our work provides a different perspective on their approach.
Fractal lattice of gelatin nanoglobules
NASA Astrophysics Data System (ADS)
Novikov, D. V.; Krasovskii, A. N.
2012-11-01
The globular structure of polymer coatings on a glass, which were obtained from micellar solutions of gelatin in the isooctane-water-sodium (bis-2-ethylhexyl) sulfosuccinate system, has been studied using electron microscopy. It has been shown that an increase in the average globule size is accompanied by the formation of a fractal lattice of nanoglobules and a periodic physical network of macromolecules in the coating. The stability of such system of the "liquid-in-a-solid" type is limited by the destruction of globules and the formation of a homogeneous network structure of the coating.
Lattice models of biological growth
Young, D.A.; Corey, E.M. )
1990-06-15
We show that very simple iterative rules for the growth of cells on a two-dimensional lattice can simulate biological-growth phenomena realistically. We discuss random cellular automata models for the growth of fern gametophytes, branching fungi, and leaves, and for shape transformations useful in the study of biological variation and evolution. Although there are interesting analogies between biological and physical growth processes, we stress the uniqueness of biological automata behavior. The computer growth algorithms that successfully mimic observed growth behavior may be helpful in determining the underlying biochemical mechanisms of growth regulation.
Lena River delta formation during the Holocene
NASA Astrophysics Data System (ADS)
Bolshiyanov, D.; Makarov, A.; Savelieva, L.
2015-01-01
The Lena River delta, the largest delta of the Arctic Ocean, differs from other deltas because it consists mainly of organomineral sediments, commonly called peat, that contain a huge organic carbon reservoir. The analysis of delta sediment radiocarbon ages showed that they could not have formed as peat during floodplain bogging; rather, they accumulated when Laptev Sea water level was high and green mosses and sedges grew and were deposited on the surface of flooded marshes. The Lena River delta formed as organomineral masses and layered sediments accumulated during transgressive phases when sea level rose. In regressive phases, the islands composed of these sediments and other, more ancient islands were eroded. Each new sea transgression led to further accumulation of layered sediments. As a result of alternating transgressive and regressive phases, the first alluvial-marine terrace formed, consisting of geological bodies of different ages. Determining the formation age of different areas of the first terrace and other marine terraces on the coast allowed the periods of increasing (8000-6000 BP (years before present), 4500-4000, 2500-1500, and 400-200 BP) and decreasing (5000, 3000, and 500 BP) Laptev Sea levels to be distinguished in the Lena Delta area.
Preparing Nimbus E on Delta Vehicle
NASA Technical Reports Server (NTRS)
1972-01-01
Nimbus E, the sixth spacecraft in the Nimbus series, is shown preparing for launch on December 12, 1972 from the Western Test Range (WTR), Space Launch Complex SLC-2, West, by the Thrust- Augmented Delta vehicle. The satellite was placed in an 1100-kilometer run-synchronous nearly circular polar orbit. The spacecraft was designated Nimbus 5 upon confirmation that it had achieved successful orbit. The Delta launch vehicle family started development in 1959. The Delta is composed of parts from the Thor, an intermediate-range ballistic missile, as its first stage, and the Vanguard as its second. The first Delta was launched from Cape Canaveral on May 13, 1960 and was powerful enough to deliver a 100-pound spacecraft into geostationary transfer orbit. Delta has been used to launch civil, commercial, and military satellites into orbit. For more information about Delta, please see Chapter 3 in Roger Launius and Dennis Jenkins' book To Reach the High Frontier published by The University Press of Kentucky in 2002.
I=2 pi-pi Scattering from Fully-Dynamical Mixed-Action Lattice QCD
Silas R. Beane; Paulo F. Bedaque; Kostas Orginos; Martin J. Savage
2005-06-11
We compute the I=2 {pi}{pi} scattering length at pion masses of m{sub {pi}} = 294, 348 and 484 MeV in fully-dynamical lattice QCD using Luescher's finite-volume method. The calculation is performed with domain-wall valence-quark propagators on asqtad-improved MILC configurations with staggered sea quarks. Chiral perturbation theory is used to perform the extrapolation of the scattering length from lattice quark masses down to the physical value, and we find m{sub {pi}}a{sub 2} = -0.0426 {+-} 0.0006 {+-} 0.0003 {+-} 0.0018, in good agreement with experiment. The I = 2 {pi}{pi} scattering phase shift is calculated to be {delta} = -43 {+-} 10 {+-} 5 degrees at |p| {approx} 544 MeV for m{pi} {approx} 484 MeV.
Localization of Waves in Merged Lattices
Alagappan, G.; Png, C. E.
2016-01-01
This article describes a new two–dimensional physical topology–merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two–dimensional scattering “beats” which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its’ quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications. PMID:27535096
Localization of Waves in Merged Lattices
NASA Astrophysics Data System (ADS)
Alagappan, G.; Png, C. E.
2016-08-01
This article describes a new two–dimensional physical topology–merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two–dimensional scattering “beats” which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its’ quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications.
Working Group Report: Lattice Field Theory
Blum, T.; et al.,
2013-10-22
This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) lattice-QCD effort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCD Collaboration, and describe a broad program of lattice-QCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.
Dynamics of Polymer Chains Confined in Slit-Like Pores
NASA Astrophysics Data System (ADS)
Milchev, Andrey; Binder, Kurt
1996-01-01
Monte Carlo simulations of an off-lattice bead sping model of polymer chains are presented, confining the chains between two repulsive parallel planes a distance D apart. Varying the chain length N from N=16 to N=128, we show that under good solvent conditions the chains behave like two-dimensional self-avoiding walks, their mean square gyration radius scales as <~ngle R_g^2ranglepropto N^{2ν} with ν =3/4. The density profile across the slit is independent of N and maximal in the center of the slit. The dynamical properties of the chains are found to be in full agreement with the Rouse model with excluded volume in d=2 dimensions, the relaxation times vary like taupropto N^z with z=2ν+1=5/2, the diffusion constant still being given by D_Npropto 1/N. The dynamical behavior of various mean square displacements is analyzed in detail.
Observing dynamical SUSY breaking with lattice simulation
Kanamori, Issaku
2008-11-23
On the basis of the recently developed lattice formulation of supersymmetric theories which keeps a part of the supersymmetry, we propose a method of observing dynamical SUSY breaking with lattice simulation. We use Hamiltonian as an order parameter and measure the ground state energy as a zero temperature limit of the finite temperature simulation. Our method provides a way of obtaining a physical result from the lattice simulation for supersymmetric theories.
Bose-Einstein condensates in rotating lattices.
Bhat, Rajiv; Holland, M J; Carr, L D
2006-02-17
Strongly interacting bosons in a two-dimensional rotating square lattice are investigated via a modified Bose-Hubbard Hamiltonian. Such a system corresponds to a rotating lattice potential imprinted on a trapped Bose-Einstein condensate. Second-order quantum phase transitions between states of different symmetries are observed at discrete rotation rates. For the square lattice we study, there are four possible ground-state symmetries.
Hackel, Richard P.
1992-01-01
A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain.
Hackel, R.P.
1992-10-20
A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain. 6 figs.
A novel mouse PKC{delta} splice variant, PKC{delta}IX, inhibits etoposide-induced apoptosis
Kim, Jung D.; Seo, Kwang W.; Lee, Eun A.; Quang, Nguyen N.; Cho, Hong R.; Kwon, Byungsuk
2011-07-01
Highlights: {yields} A novel PKC{delta} isoform, named PKC{delta}IX, that lacks the C1 domain and the ATP-binding site is ubiquitously expressed. {yields} PKC{delta}IX inhibits etoposide-induced apoptosis. {yields} PKC{delta}IX may function as an endogenous dominant negative isoform for PKC{delta}. -- Abstract: Protein kinase C (PKC) {delta} plays an important role in cellular proliferation and apoptosis. The catalytic fragment of PKC{delta} generated by caspase-dependent cleavage is essential for the initiation of etoposide-induced apoptosis. In this study, we identified a novel mouse PKC{delta} isoform named PKC{delta}IX (Genebank Accession No. (HQ840432)). PKC{delta}IX is generated by alternative splicing and is ubiquitously expressed, as seen in its full-length PKC{delta}. PKC{delta}IX lacks the C1 domain, the caspase 3 cleavage site, and the ATP binding site but preserves an almost intact c-terminal catalytic domain and a nuclear localization signal (NLS). The structural characteristics of PKC{delta}IX provided a possibility that this PKC{delta} isozyme functions as a novel dominant-negative form for PKC{delta} due to its lack of the ATP-binding domain that is required for the kinase activity of PKC{delta}. Indeed, overexpression of PKC{delta}IX significantly inhibited etoposide-induced apoptosis in NIH3T3 cells. In addition, an in vitro kinase assay showed that recombinant PKC{delta}IX protein could competitively inhibit the kinase activity of PKC{delta}. We conclude that PKC{delta}IX can function as a natural dominant-negative inhibitor of PKC{delta}in vivo.
Effects of alcohols on the phase transition temperatures of mixed-chain phosphatidylcholines.
Li, S; Lin, H N; Wang, G; Huang, C
1996-01-01
The biphasic effect of ethanol on the main phase transition temperature (Tm) of identical-chain phosphatidyl-cholines (PCs) in excess H2O is now well known. This biphasic effect can be attributed to the transformation of the lipid bilayer, induced by high concentrations of ethanol, from the partially interdigitated L beta, phase to the fully interdigitated L beta I phase at T < Tm. The basic packing unit of the L beta I phase has been identified recently as a binary mixture of PC/ethanol at the molar ratio of 1:2. The ethanol effect on mixed-chain PCs, however, is not known. We have thus in this study investigated the alcohol effects on the Tm of mixed-chain PCs with different delta C values, where delta C is the effective acyl chain length difference between the sn-1 and sn-2 acyl chains. Initially, molecular mechanics (MM) simulations are employed to calculate the steric energies associated with a homologous series of mixed-chain PCs packed in the partially and the fully interdigitated L beta I motifs. Based on the energetics, the preference of each mixed-chain PC for packing between these two different motifs can be estimated. Guided by MM results, high-resolution differential scanning calorimetry is subsequently employed to determine the Tm values for aqueous lipid dispersions prepared individually from a series of mixed-chain PCs (delta C = 0.5-6.5 C-C bond lengths) in the presence of various concentrations of ethanol. Results indicate that aqueous dispersions prepared from mixed-chain PCs with a delta C value of less than 4 exhibit a biphasic profile in the plot of Tm versus ethanol concentration. In contrast, highly asymmetric PCs (delta C > 4) do not exhibit such biphasic behavior. In the presence of a longer chain n-alcohol, however, aqueous dispersions of highly asymmetric C(12):C(20)PC (delta C = 6.5) do show such biphasic behavior against ethanol. Our results suggest that the delta C region in a highly asymmetric PC packed in the L beta I phase is most
The Fermilab lattice supercomputer project
Fischler, M.; Atac, R.; Cook, A.; Deppe, J.; Gaines, I.; Husby, D.; Nash, T.; Pham, T.; Zmuda, T.; Hockney, G.
1989-02-01
The ACPMAPS system is a highly cost effective, local memory MIMD computer targeted at algorithm development and production running for gauge theory on the lattice. The machine consists of a compound hypercube of crates, each of which is a full crossbar switch containing several processors. The processing nodes are single board array processors based on the Weitek XL chip set, each with a peak power of 20 MFLOPS and supported by 8 MBytes of data memory. The system currently being assembled has a peak power of 5 GFLOPS, delivering performance at approximately $250/MFLOP. The system is programmable in C and Fortran. An underpinning of software routines (CANOPY) provides an easy and natural way of coding lattice problems, such that the details of parallelism, and communication and system architecture are transparent to the user. CANOPY can easily be ported to any single CPU or MIMD system which supports C, and allows the coding of typical applications with very little effort. 3 refs., 1 fig.
QCD thermodynamics on a lattice
NASA Astrophysics Data System (ADS)
Levkova, Ludmila A.
Numerical simulations of full QCD on anisotropic lattices provide a convenient way to study QCD thermodynamics with fixed physics scales and reduced lattice spacing errors. We report results from calculations with two flavors of dynamical staggered fermions, where all bare parameters and the renormalized anisotropy are kept constant and the temperature is changed in small steps by varying only the number of time slices. Including results from zero-temperature scale setting simulations, which determine the Karsch coefficients, allows for the calculation of the Equation of State at finite temperatures. We also report on studies of the chiral properties of dynamical domain-wall fermions combined with the DBW2 gauge action for different gauge couplings and fermion masses. For quenched theories, the DBW2 action gives a residual chiral symmetry breaking much smaller than what was found with more traditional choices for the gauge action. Our goal is to investigate the possibilities which this and further improvements provide for the study of QCD thermodynamics and other simulations at stronger couplings.
Computational study of lattice models
NASA Astrophysics Data System (ADS)
Zujev, Aleksander
This dissertation is composed of the descriptions of a few projects undertook to complete my doctorate at the University of California, Davis. Different as they are, the common feature of them is that they all deal with simulations of lattice models, and physics which results from interparticle interactions. As an example, both the Feynman-Kikuchi model (Chapter 3) and Bose-Fermi mixture (Chapter 4) deal with the conditions under which superfluid transitions occur. The dissertation is divided into two parts. Part I (Chapters 1-2) is theoretical. It describes the systems we study - superfluidity and particularly superfluid helium, and optical lattices. The numerical methods of working with them are described. The use of Monte Carlo methods is another unifying theme of the different projects in this thesis. Part II (Chapters 3-6) deals with applications. It consists of 4 chapters describing different projects. Two of them, Feynman-Kikuchi model, and Bose-Fermi mixture are finished and published. The work done on t - J model, described in Chapter 5, is more preliminary, and the project is far from complete. A preliminary report on it was given on 2009 APS March meeting. The Isentropic project, described in the last chapter, is finished. A report on it was given on 2010 APS March meeting, and a paper is in preparation. The quantum simulation program used for Bose-Fermi mixture project was written by our collaborators Valery Rousseau and Peter Denteneer. I had written my own code for the other projects.
Transmission Electron Microscope Measures Lattice Parameters
NASA Technical Reports Server (NTRS)
Pike, William T.
1996-01-01
Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.
Commissioning Simulations for the APS Upgrade Lattice
Sajaev, V.; Borland, M.
2015-01-01
A hybrid seven-bend-achromat lattice that features very strong focusing elements and a relatively small vacuum chamber has been proposed for the APS upgrade. Achieving design lattice parameters during commissioning will need to be accomplished quickly in order to minimize dark time for APS users. The paper will describe start-to-end simulation of the machine commissioning beginning from first-turn trajectory correction, progressing to orbit and lattice correction, and culminating in evaluation of the nonlinear performance of the corrected lattice
NASA Astrophysics Data System (ADS)
Costanza, E. F.; Costanza, G.
2017-02-01
Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a hexagonal lattice which has the particular feature that need four types of dynamical variables. This example shows additional features to the general procedure and some extensions are also suggested in order to provide a wider insight in the present approach.
NASA Astrophysics Data System (ADS)
Costanza, E. F.; Costanza, G.
2016-12-01
Continuum partial differential equations are obtained from a set of discrete stochastic evolution equations of both non-Markovian and Markovian processes and applied to the diffusion within the context of the lattice gas model. A procedure allowing to construct one-dimensional lattices that are topologically equivalent to two-dimensional lattices is described in detail in the case of a triangular lattice. This example shows the general features that possess the procedure and extensions are also suggested in order to provide a wider insight in the present approach.
Polarization response of RHIC electron lens lattices
NASA Astrophysics Data System (ADS)
Ranjbar, V. H.; Méot, F.; Bai, M.; Abell, D. T.; Meiser, D.
2016-10-01
Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. In particular we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. These results are benchmarked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. Finally we consider the effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.
Subwavelength Lattice Optics by Evolutionary Design
2015-01-01
This paper describes a new class of structured optical materials—lattice opto-materials—that can manipulate the flow of visible light into a wide range of three-dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm that includes and optimizes contributions from every element in the lattice. Lattice opto-materials can exhibit simple properties, such as on- and off-axis focusing, and can also concentrate light into multiple, discrete spots. We expanded the unit cell shapes of the lattice to achieve distinct, polarization-dependent optical responses from the same 2D patterned substrate. Finally, these lattice opto-materials can also be combined into architectures that resemble a new type of compound flat lens. PMID:25380062
Dark periodic lattices in nonlinear liquid media
NASA Astrophysics Data System (ADS)
Alvarado-Méndez, Edgar; Trejo-Durán, Mónica; Cano-Lara, Miroslava; Huerta-Mascotte, Eduardo; Castaňo, Víctor M.
2007-11-01
Experimental evidence of the formation of one- and two-dimensional dark periodic lattices in a negative Kerr-type nonlinear liquid media is presented. Bright periodic lattices propagate throughout two nonlinear liquids [alcohol with rhodamine (R6G), and acetone with R6G] as the negative nonlinear refractive index forms a dark periodic lattice. Our experiments demonstrate that the nonlinearity increases with the optical power and that a proper selection of the period leads to self-phase modulation of the lattice.
Elastic lattice in an incommensurate background
Dickman, R.; Chudnovsky, E.M. )
1995-01-01
We study a harmonic triangular lattice, which relaxes in the presence of an incommensurate short-wavelength potential. Monte Carlo simulations reveal that the elastic lattice exhibits only short-ranged translational correlations, despite the absence of defects in either lattice. Extended orientational order, however, persists in the presence of the background. Translational correlation lengths exhibit approximate power-law dependence upon cooling rate and background strength. Our results may be relevant to Wigner crystals, atomic monolayers on crystals surfaces, and flux-line and magnetic bubble lattices.
The Okavango: Whose Delta is it?
NASA Astrophysics Data System (ADS)
Magole, Lapologang; Magole, Lefatshe Innocent
The Okavango Delta is amongst the largest Ramsar sites ( http://www.ramsar.org/sitelist.pdf) in the world and an important wetland for community livelihoods, conservation and tourism in Botswana. Over the years, the utilization of the delta has shifted from communal use to state control, with an increased use for conservation and tourism. This increased use for conservation and tourism has manifested in the physical expansion of the conservation area - Moremi Game Reserve and the formation of Wildlife Management Areas (WMAs) around the reserve, whose primary land use is wildlife utilization. The expansion of the conservation area has translated into several practical matters, including expansion of the area for non-hunting activities or photographic areas. The livelihoods of local communities of the Okavango delta who depended on fishing, hunter-gathering, livestock rearing, rain-fed agriculture and flood recession farming have been negatively affected by the expansion of conservation and tourism in the delta. The livelihoods alternatives in the form of Community Based Natural Resource Management (CBNRM) and tourism have not provided substitutes for the people as the communities are still reliant on the same old livelihood sources as in the past, albeit within smaller and restricted areas. This paper explores the ownership of the natural resources within the Okavango Delta. It asks and attempts to answer the following questions: Who owns and controls the use of the land? Who has access to other resources there in? Who makes the decisions on how the delta resources should be managed and used? Who benefits from the delta resources? We argue firstly that ownership of the delta as defined by legal parameters and demonstrated in natural resource management practice is vested on government. Secondly, government, after assuming ownership of the delta continues to sell its stake to the international community, at the expense of local ownership and access to resources. We
Tanner, Bertrand C.W.; Miller, Mark S.; Miller, Becky M.; Lekkas, Panagiotis; Irving, Thomas C.; Maughan, David W.; Vigoreaux, Jim O.
2011-08-26
The indirect flight muscle (IFM) of insects is characterized by a near crystalline myofilament lattice structure that likely evolved to achieve high power output. In Drosophila IFM, the myosin rod binding protein flightin plays a crucial role in thick filament organization and sarcomere integrity. Here we investigate the extent to which the COOH terminus of flightin contributes to IFM structure and mechanical performance using transgenic Drosophila expressing a truncated flightin lacking the 44 COOH-terminal amino acids (fln{sup {Delta}C44}). Electron microscopy and X-ray diffraction measurements show decreased myofilament lattice order in the fln{sup {Delta}C44} line compared with control, a transgenic flightin-null rescued line (fln{sup +}). fln{sup {Delta}C44} fibers produced roughly 1/3 the oscillatory work and power of fln{sup +}, with reduced frequencies of maximum work (123 Hz vs. 154 Hz) and power (139 Hz vs. 187 Hz) output, indicating slower myosin cycling kinetics. These reductions in work and power stem from a slower rate of cross-bridge recruitment and decreased cross-bridge binding in fln{sup {Delta}C44} fibers, although the mean duration of cross-bridge attachment was not different between both lines. The decreases in lattice order and myosin kinetics resulted in fln{sup {Delta}C44} flies being unable to beat their wings. These results indicate that the COOH terminus of flightin is necessary for normal myofilament lattice organization, thereby facilitating the cross-bridge binding required to achieve high power output for flight.
Effect of impurities on the vortex lattice in Bose-Einstein condensates on optical lattice
NASA Astrophysics Data System (ADS)
Mithun, T.; Porsezian, K.; Dey, Bishwajyoti
2015-06-01
We numerically solve the Gross-Pitaeveskii equation to study the Bose-Einstein condensate in the rotating harmonical tarp and co-rotating optical lattice. The effect of a pinning site or impurity shows that it is able to move the vortex lattice center to either left or right depending on the position of the impurity. Also, it is observed that the impurity at the random positions can destroy the vortex lattice and the resulting disordered lattice has more energy.
Díaz, F J; Vega, J A; Patiño, P J; Bedoya, G; Nagles, J; Villegas, C; Vesga, R; Rugeles, M T
2000-01-01
Repeated exposure to human immunodeficiency virus (HIV) does not always result in seroconversion. Modifications in coreceptors for HIV entrance to target cells are one of the factors that block the infection. We studied the frequency of Delta-32 mutation in ccr5 gene in Medellin, Colombia. Two hundred and eighteen individuals distributed in three different groups were analyzed for Delta-32 mutation in ccr5 gene by polymerase chain reaction (PCR): 29 HIV seropositive (SP), 39 exposed seronegative (ESN) and 150 individuals as a general population sample (GPS). The frequency of the Delta-32 mutant allele was 3.8% for ESN, 2.7% for GPS and 1.7% for SP. Only one homozygous mutant genotype (Delta-32/Delta-32) was found among the ESN (2.6%). The heterozygous genotype (ccr5/Delta-32) was found in eight GPS (5.3%), in one SP (3.4%) and in one ESN (2.6%). The differences in the allelic and genotypic frequencies among the three groups were not statistically significant. A comparison between the expected and the observed genotypic frequencies showed that these frequencies were significantly different for the ESN group, which indirectly suggests a protective effect of the mutant genotype (Delta-32/Delta-32). Since this mutant genotype explained the resistance of infection in only one of our ESN persons, different mechanisms of protection must be playing a more important role in this population.
Parallel algorithms for simulating continuous time Markov chains
NASA Technical Reports Server (NTRS)
Nicol, David M.; Heidelberger, Philip
1992-01-01
We have previously shown that the mathematical technique of uniformization can serve as the basis of synchronization for the parallel simulation of continuous-time Markov chains. This paper reviews the basic method and compares five different methods based on uniformization, evaluating their strengths and weaknesses as a function of problem characteristics. The methods vary in their use of optimism, logical aggregation, communication management, and adaptivity. Performance evaluation is conducted on the Intel Touchstone Delta multiprocessor, using up to 256 processors.
Model for the {Delta}(1600) resonance and {gamma}N{yields}{Delta}(1600) transition
Ramalho, G.; Tsushima, K.
2010-10-01
A covariant spectator constituent quark model is applied to study the {gamma}N{yields}{Delta}(1600) transition. Two processes are important in the transition: a photon couples to the individual quarks of the {Delta}(1600) core (quark core), and a photon couples to the intermediate pion-baryon states (pion cloud). While the quark core contributions are estimated assuming {Delta}(1600) as the first radial excitation of {Delta}(1232), the pion cloud contributions are estimated based on an analogy with the {gamma}N{yields}{Delta}(1232) transition. To estimate the pion cloud contributions in the {gamma}N{yields}{Delta}(1600) transition, we include the relevant intermediate states, {pi}N, {pi}{Delta}, {pi}N(1440) and {pi}{Delta}(1600). Dependence on the four-momentum transfer squared, Q{sup 2}, is predicted for the magnetic dipole transition form factor, G{sub M}*(Q{sup 2}), as well as the helicity amplitudes, A{sub 1/2}(Q{sup 2}) and A{sub 3/2}(Q{sup 2}). The results at Q{sup 2}=0 are compared with the existing data.
A model for the Delta(1600) resonance and gamma N -> Delta(1600) transition
G. Ramalho, K. Tsushima
2010-10-01
A covariant spectator constituent quark model is applied to study the gamma N -> Delta(1600) transition. Two processes are important in the transition: a photon couples to the individual quarks of the Delta(1600) core (quark core), and a photon couples to the intermediate pion-baryon states (pion cloud). While the quark core contributions are estimated assuming Delta(1600) as the first radial excitation of Delta(1232), the pion cloud contributions are estimated based on an analogy with the gamma N -> Delta(1232) transition. To estimate the pion cloud contributions in the gamma N -> Delta(1600) transition, we include the relevant intermediate states, pi-N, pi-Delta, pi-N(1440) and pi-Delta(1600). Dependence on the four-momentum transfer squared, Q2, is predicted for the magnetic dipole transition form factor, GM*(Q2), as well as the helicity amplitudes, A_1/2(Q2) and A_3/2(Q2). The results at Q2=0 are compared with the existing data.
Interdisciplinary and Distance Education in the Delta: The Delta Health Education Partnership.
ERIC Educational Resources Information Center
Skorga, Phyllis
2002-01-01
Describes the Delta Health Education Partnership, an interdisciplinary distance education program intended to recruit, educate, and retain interdisciplinary groups of primary care health practitioners to increase access to health care in medically underserved and health professional shortage areas of the lower Mississippi Delta. It spans six…
Cold atoms in a rotating optical lattice
NASA Astrophysics Data System (ADS)
Foot, Christopher J.
2009-05-01
We have demonstrated a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz. Our arrangement also allows the periodicity of the optical lattice to be varied dynamically, producing a 2D ``accordion lattice'' [1]. The angles of the laser beams are controlled by acousto-optic deflectors and this allows smooth changes with little heating of the trapped cold (rubidium) atoms. We have loaded a BEC into lattices with periodicities ranging from 1.8μm to 18μm, observing the collapse and revival of the diffraction orders of the condensate over a large range of lattice parameters as recently reported by a group in NIST [2]. We have also imaged atoms in situ in a 2D lattice over a range of lattice periodicities. Ultracold atoms in a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, i.e. the Hamiltonian of the atoms in the rotating frame resembles that of a charged particle in a strong magnetic field. In the future, we plan to use this to investigate a range of phenomena such as the analogue of the fractional quantum Hall effect. [4pt] [1] R. A. Williams, J. D. Pillet, S. Al-Assam, B. Fletcher, M. Shotter, and C. J. Foot, ``Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms,'' Opt. Express 16, 16977-16983 (2008) [0pt] [2] J. H. Huckans, I. B. Spielman, B. Laburthe Tolra, W. D. Phillips, and J. V. Porto, Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice, arXiv:0901.1386v1
Bimaterial lattices as thermal adapters and actuators
NASA Astrophysics Data System (ADS)
Toropova, Marina M.; Steeves, Craig A.
2016-11-01
The goal of this paper is to demonstrate how anisotropic biomaterial lattices can be used in thermal actuation. Compared to other lattices with tailored thermal expansion, the anisotropy of these bimaterial lattices makes them uniquely suitable for use as thermal actuators. Each individual cell, and hence lattices consisting of such cells, can be designed with widely different predetermined coefficients of thermal expansion (CTE) in different directions, enabling complex shape changes appropriate for actuation with either passive or active control. The lattices are composed of planar non-identical cells that each consist of a skewed hexagon surrounding an irregular triangle. The cells and all members of any cell are connected to each other by pins so that they have no rotational constraints and are able to expand or contract freely. In this case, the skew angles of the hexagon and the ratio of the CTEs of the two component materials determine the overall performance of the lattice. At its boundaries, the lattice is connected to substrates by pins and configured such that the CTE between two neighboring lattice vertices coincides with the CTE of the adjacent substrate. Provided the boundary behavior of the lattice is matched to the thermal properties of the substrates, temperature changes in the structure produce thermal strains without producing any corresponding stresses. Such lattices can be used in three different ways: as adaptive elements for stress-free connection of components with different CTEs; for fine tuning of structures; and as thermally driven actuators. In this paper, we demonstrate some concepts for lattice configurations that produce thermally-driven displacements that enable several actuators: a switch, a valve and tweezers.
The DELTA MONSTER: An RPV designed to investigate the aerodynamics of a delta wing platform
NASA Technical Reports Server (NTRS)
Connolly, Kristen; Flynn, Mike; Gallagher, Randy; Greek, Chris; Kozlowski, Marc; Mcdonald, Brian; Mckenna, Matt; Sellar, Rich; Shearon, Andy
1989-01-01
The mission requirements for the performance of aerodynamic tests on a delta wind planform posed some problems, these include aerodynamic interference; structural support; data acquisition and transmission instrumentation; aircraft stability and control; and propulsion implementation. To eliminate the problems of wall interference, free stream turbulence, and the difficulty of achieving dynamic similarity between the test and actual flight aircraft that are associated with aerodynamic testing in wind tunnels, the concept of the remotely piloted vehicle which can perform a basic aerodynamic study on a delta wing was the main objective for the Green Mission - the Delta Monster. The basic aerodynamic studies were performed on a delta wing with a sweep angle greater than 45 degrees. These tests were performed at various angles of attack and Reynolds numbers. The delta wing was instrumented to determine the primary leading edge vortex formation and location, using pressure measurements and/or flow visualization. A data acquisition system was provided to collect all necessary data.
Broman, D.; Axelman, J.; Bergqvist, P.A.; Naef, C.; Rolff, C.; Zebuehr, Y.
1995-12-31
Ratios of naturally occurring stable isotopes of nitrogen ({delta}{sup 15}N) can be used to numerically classify trophic levels of organisms in food chains. By combining analyses results of various HOCs (e.g. PCDD/Fs, PCBs, DDTs, HCHs and some other pesticides) the biomagnification of these substances can be quantitatively estimated. In this paper different pelagic and benthic northern Baltic food chains were studied. The {delta}{sup 15}N-data gave food chain descriptions qualitatively consistent with previous conceptions of trophic arrangements in the food chains. The different HOCs concentrations were plotted versus the {delta}{sup 15}N-values for the different trophic levels and an exponential model of the form e{sup (A+B*{delta}N)} was fitted to the data. The estimates of the constant B in the model allows for an estimation of a biomagnification power (B) of different singular, or groups of, contaminants. A B-value around zero indicates that a substance is flowing through the food chain without being magnified, whereas a value > 0 indicates that a substance is biomagnified. Negative B-values indicate that a substance is not taken up or is metabolized. The A-term of the expression is only a scaling factor depending on the background level of the contaminant.
Tracking Nile Delta vulnerability to Holocene change.
Marriner, Nick; Flaux, Clément; Morhange, Christophe; Stanley, Jean-Daniel
2013-01-01
Understanding deltaic resilience in the face of Holocene climate change and human impacts is an important challenge for the earth sciences in characterizing the full range of present and future wetland responses to global warming. Here, we report an 8000-year mass balance record from the Nile Delta to reconstruct when and how this sedimentary basin has responded to past hydrological shifts. In a global Holocene context, the long-term decrease in Nile Delta accretion rates is consistent with insolation-driven changes in the 'monsoon pacemaker', attested throughout the mid-latitude tropics. Following the early to mid-Holocene growth of the Nile's deltaic plain, sediment losses and pronounced erosion are first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. Against the backcloth of the Saharan 'depeopling', reduced river flow underpinned by a weakening of monsoonal precipitation appears to have been particularly conducive to the expansion of human activities on the delta by exposing productive floodplain lands for occupation and irrigation agriculture. The reconstruction suggests that the Nile Delta has a particularly long history of vulnerability to extreme events (e.g. floods and storms) and sea-level rise, although the present sediment-starved system does not have a direct Holocene analogue. This study highlights the importance of the world's deltas as sensitive archives to investigate Holocene geosystem responses to climate change, risks and hazards, and societal interaction.
{delta}-mediated pion production in nuclei
Praet, C.; Lalakulich, O.; Jachowicz, N.; Ryckebusch, J.
2009-04-15
We present a fully relativistic formalism for describing neutrino-induced {delta}-mediated single-pion production in nuclei. We assess the ambiguities stemming from the {delta} interactions and quantify the uncertainties in the axial form-factor parameters by comparing with the available bubble-chamber neutrino-scattering data. To include nuclear effects, we turn to a relativistic plane-wave impulse approximation (RPWIA) using realistic bound-state wave functions derived in the Hartree approximation to the {sigma}-{omega} Walecka model. For neutrino energies larger than 1 GeV, we show that a relativistic Fermi-gas model with appropriate binding-energy correction produces results that are comparable to the RPWIA that naturally includes Fermi motion, nuclear-binding effects, and the Pauli exclusion principle. Including {delta} medium modifications roughly halves the RPWIA cross section. Calculations for primary (prior to undergoing final-state interactions) pion production are presented for both electron- and neutrino-induced processes, and a comparison with electron-scattering data and other theoretical approaches is included. We infer that the total {delta}-production strength is underestimated by about 20 to 25%, a fraction that is due to the pionless decay modes of the {delta} in a medium. The model presented in this work can be naturally extended to include the effect of final-state interactions in a relativistic and quantum-mechanical way.
FFAG lattice without opposite bends
NASA Astrophysics Data System (ADS)
Trbojevic, Dejan; Courant, Ernest D.; Garren, Al
2000-08-01
A future "neutrino factory" or Muon Collider requires fast muon acceleration before the storage ring. Several alternatives for fast muon acceleration have previously been considered. One of them is the FFAG (Fixed Field Alternating Gradient) synchrotron. The FFAG concept was developed in 1952 by K. R. Symon (ref. 1). The advantages of this design are the fixed magnetic field, large range of particle energy, simple RF; power supplies are simple, and there is no transition energy. But a drawback is that reverse bending magnets are included in the configuration; this increases the size and cost of the ring. Recently some modified FFAG lattice designs have been described where the amount of opposite bending was significantly reduced (ref. 2, ref. 3).
Realizing Parafermions in Optical Lattices
NASA Astrophysics Data System (ADS)
Liu, Fangli; Gorshkov, Alexey
2016-05-01
Parafermions, which are the fractional versions of Majorana fermions, possess more exotic braiding statistics than Majorana fermions and are therefore more powerful from the point of view of topological quantum computing. We propose a scheme to realize parafermionic zero modes in optical lattices, without the use of superconductive paring. With the help of laser assisted tunneling and on-site interactions, two layers of ultracold atoms in distinct hyperfine states can be engineered to host +/- 1 / m fractional quantum Hall states. We then introduce a finite-extent potential barrier that pierces both layers - this gives rise to two counter-propagating edge states that sit on top of each other. Finally, laser induced coupling is used to introduce backscattering between the two edge states and to gap them out. We show that the resulting defects give rise to the topological degeneracy associated with parafermions. We also discuss methods for preparation and detection.
Lattice mechanics of origami tessellations.
Evans, Arthur A; Silverberg, Jesse L; Santangelo, Christian D
2015-07-01
Origami-based design holds promise for developing materials whose mechanical properties are tuned by crease patterns introduced to thin sheets. Although there have been heuristic developments in constructing patterns with desirable qualities, the bridge between origami and physics has yet to be fully developed. To truly consider origami structures as a class of materials, methods akin to solid mechanics need to be developed to understand their long-wavelength behavior. We introduce here a lattice theory for examining the mechanics of origami tessellations in terms of the topology of their crease pattern and the relationship between the folds at each vertex. This formulation provides a general method for associating mechanical properties with periodic folded structures and allows for a concrete connection between more conventional materials and the mechanical metamaterials constructed using origami-based design.
Lattice mechanics of origami tessellations
NASA Astrophysics Data System (ADS)
Evans, Arthur A.; Silverberg, Jesse L.; Santangelo, Christian D.
2015-07-01
Origami-based design holds promise for developing materials whose mechanical properties are tuned by crease patterns introduced to thin sheets. Although there have been heuristic developments in constructing patterns with desirable qualities, the bridge between origami and physics has yet to be fully developed. To truly consider origami structures as a class of materials, methods akin to solid mechanics need to be developed to understand their long-wavelength behavior. We introduce here a lattice theory for examining the mechanics of origami tessellations in terms of the topology of their crease pattern and the relationship between the folds at each vertex. This formulation provides a general method for associating mechanical properties with periodic folded structures and allows for a concrete connection between more conventional materials and the mechanical metamaterials constructed using origami-based design.
Nuclear forces from lattice QCD
Ishii, Noriyoshi
2011-05-06
Lattice QCD construction of nuclear forces is reviewed. In this method, the nuclear potentials are constructed by solving the Schroedinger equation, where equal-time Nambu-Bethe-Salpeter (NBS) wave functions are regarded as quantum mechanical wave functions. Since the long distance behavior of equal-time NBS wave functions is controlled by the scattering phase, which is in exactly the same way as scattering wave functions in quantum mechanics, the resulting potentials are faithful to the NN scattering data. The derivative expansion of this potential leads to the central and the tensor potentials at the leading order. Some of numerical results of these two potentials are shown based on the quenched QCD.
On lattice chiral gauge theories
NASA Technical Reports Server (NTRS)
Maiani, L.; Rossi, G. C.; Testa, M.
1991-01-01
The Smit-Swift-Aoki formulation of a lattice chiral gauge theory is presented. In this formulation the Wilson and other non invariant terms in the action are made gauge invariant by the coupling with a nonlinear auxilary scalar field, omega. It is shown that omega decouples from the physical states only if appropriate parameters are tuned so as to satisfy a set of BRST identities. In addition, explicit ghost fields are necessary to ensure decoupling. These theories can give rise to the correct continuum limit. Similar considerations apply to schemes with mirror fermions. Simpler cases with a global chiral symmetry are discussed and it is shown that the theory becomes free at decoupling. Recent numerical simulations agree with those considerations.
Reflooding of tight lattice bundles
Veteau, J.M.; Digonnet, A.; Deruaz, R. . Centre d'Etudes Nucleaires de Grenoble)
1994-07-01
Results regarding analytical bottom reflooding experiments in a 37- and a 127-heater rod bundle are presented for two different tight lattices. A comparison between these two geometries and with the standard pressurized water reactor (PWR) array shows a degradation of cooling efficiency when the cross section of the subchannels is decreased. The core heat sinks (guide thimbles and water tubes'') are seen to have a noticeable influence on the overall cooling of the bundle, and it is confirmed that a combined top/bottom injection does not significantly improve cooling efficiency. Calculations with CATHARE 1.3 code adjusted for the standard PWR array are presented (zero heat sinks), but results have to be confirmed over a wider range of parameters.
Tracking the SSC test lattices
Leemann, B.T.; Douglas, D.R.; Forest, E.
1985-10-01
The dynamic aperture and its determination emerged from the SSC reference design study as the single most important accelerator physics issue pertinent to the SSC. Beside the fundamental need of a finite dynamic aperture for any accelerator, it was considered to be a useful criterion for the magnet selection. An aperture workshop organized in November 1984 at LBL served the purpose to identify the various aspects of the aperture question and to organize the aperture task force accordingly. It was recognized that numerical models had to play an important role and the qualifications of several tracking codes were investigated. None of the existing codes could meet all of the criteria for an ideal tracking code and substantial program development became unavoidable. It was therefore decided to begin tracking SSC test lattices.
Entropy of Open Lattice Systems
NASA Astrophysics Data System (ADS)
Derrida, B.; Lebowitz, J. L.; Speer, E. R.
2007-03-01
We investigate the behavior of the Gibbs-Shannon entropy of the stationary nonequilibrium measure describing a one-dimensional lattice gas, of L sites, with symmetric exclusion dynamics and in contact with particle reservoirs at different densities. In the hydrodynamic scaling limit, L → ∞, the leading order ( O( L)) behavior of this entropy has been shown by Bahadoran to be that of a product measure corresponding to strict local equilibrium; we compute the first correction, which is O(1). The computation uses a formal expansion of the entropy in terms of truncated correlation functions; for this system the k th such correlation is shown to be O( L - k+1). This entropy correction depends only on the scaled truncated pair correlation, which describes the covariance of the density field. It coincides, in the large L limit, with the corresponding correction obtained from a Gaussian measure with the same covariance.
NASA Astrophysics Data System (ADS)
Chen, Zhaopin; Malomed, Boris A.
2017-03-01
We introduce a two-component one-dimensional system, which is based on two nonlinear Schrödinger or Gross-Pitaevskii equations (GPEs) with spatially periodic modulation of linear coupling ("Rabi lattice") and self-repulsive nonlinearity. The system may be realized in a binary Bose-Einstein condensate, whose components are resonantly coupled by a standing optical wave, as well as in terms of the bimodal light propagation in periodically twisted waveguides. The system supports various types of gap solitons (GSs), which are constructed, and their stability is investigated, in the first two finite bandgaps of the underlying spectrum. These include on- and off-site-centered solitons (the GSs of the off-site type are additionally categorized as spatially even and odd ones), which may be symmetric or antisymmetric, with respect to the coupled components. The GSs are chiefly stable in the first finite bandgap and unstable in the second one. In addition to that, there are narrow regions near the right edge of the first bandgap, and in the second one, which feature intricate alternation of stability and instability. Unstable solitons evolve into robust breathers or spatially confined turbulent modes. On-site-centered GSs are also considered in a version of the system that is made asymmetric by the Zeeman effect, or by birefringence of the optical waveguide. A region of alternate stability is found in the latter case too. In the limit of strong asymmetry, GSs are obtained in a semianalytical approximation, which reduces two coupled GPEs to a single one with an effective lattice potential.
Lattice studies of hadrons with heavy flavors
Christopher Aubin
2009-07-01
I will discuss recent developments in lattice studies of hadrons composed of heavy quarks. I will mostly cover topics which are at a state of direct comparison with experiment, but will also discuss new ideas and promising techniques to aid future studies of lattice heavy quark physics.
Disorder solutions of lattice spin models
NASA Astrophysics Data System (ADS)
Batchelor, M. T.; van Leeuwen, J. M. J.
1989-01-01
It is shown that disorder solutions, which have been obtained by different methods, follow from a simple decimation method. The method is put in general form and new disorder solutions are constructed for the Blume-Emery-Griffiths model on a triangular lattice and for Potts and Ising models on square and fcc lattices.
Recent advances in lattice Boltzmann methods
Chen, S.; Doolen, G.D.; He, X.; Nie, X.; Zhang, R.
1998-12-31
In this paper, the authors briefly present the basic principles of lattice Boltzmann method and summarize recent advances of the method, including the application of the lattice Boltzmann method for fluid flows in MEMS and simulation of the multiphase mixing and turbulence.
The Chroma Software System for Lattice QCD
Robert Edwards; Balint Joo
2004-06-01
We describe aspects of the Chroma software system for lattice QCD calculations. Chroma is an open source C++ based software system developed using the software infrastructure of the US SciDAC initiative. Chroma interfaces with output from the BAGEL assembly generator for optimized lattice fermion kernels on some architectures. It can be run on workstations, clusters and the QCDOC supercomputer.
The mystery of the fifteenth Bravais lattice
NASA Astrophysics Data System (ADS)
Nussbaum, Allen
2000-10-01
An understanding of the principles of crystal structure is necessary for the study of solids. There are contradictions in the literature dealing with the nature of crystal lattices, and there is also a miscounting of the number of possible lattices. This paper clarifies the situation in a systematic and simple way.
Numerical study of localization in antidot lattices
NASA Astrophysics Data System (ADS)
Uryu, Seiji; Ando, Tsuneya
1998-10-01
Localization effects in antidot lattices in weak magnetic fields are numerically studied with the use of a Thouless-number method. In hexagonal antidot lattices, both conductance and inverse localization length oscillate as a function of a magnetic flux with the same period as an Al'tshuler-Aronov-Spivak oscillation, in qualitative agreement with recent experiments.
The ecology of the Sacramento-San Joaquin Delta
Herbold, B.; Moyle, P.B. . Dept. of Wildlife and Fisheries Biology)
1989-09-01
This report describes an ecosystem significantly different from other delta ecosystems in North America. The Sacramento-San Joaquin Delta is one of the 60 largest river deltas in the world and is the largest river delta on the west coast. As the hub of California's water system, the delta is of immense municipal, agricultural, and industrial importance. The amount of freshwater that flows through the delta controls the delta's productivity and regulates the life cycles of many of its organisms. The vast estuary of the Sacramento and San Joaquin Rivers is one of the most highly modified and intensively managed estuaries in the world. Biological processes in the delta are obscured by the temporal dynamics of the system. Many of the most significant alterations, such as leveeing, diking, and agricultural practices, are not now recognized as such by most citizens, making conservation and protection of the delta difficult. 308 refs., 43 figs., 11 tabs.
Carroll, A.M.; Slack, J.K.; Mu, Xiaochun )
1993-03-15
The standard products of V(D)J recombination are coding junctions, which encode Ag receptor polypeptide, and their commonly excised reciprocal products, signal junctions. Additional nonstandard products also have been detected, mostly in artificial recombination substrate studies. The occurrence of nonstandard products, including pseudonormal, hybrid, and open/shut junctions, indicates significant indeterminacy of the V(D)J recombinase. However, the incidence of nonstandard products of endogenous Ag receptor genes in vivo has not been specifically addressed. The data presented here show that for the TCR-[delta] locus, D element-associated recombination in mouse thymocytes results in a high incidence of nonstandard recombination products. D[delta]1-D[delta]2 rearrangements, both chromosome retained and excised episomal products, were studied by polymerase chain reaction amplification, cloning, and sequence analysis. The proximity of D[delta]1 and D[delta]2 elements, and the fact that both are flanked by 5[prime] and 3[prime] recombination signal sequences with 12-bp and 23-bp spacers, respectively, results in frequent pseudonormal joining. The resulting products are signal junctions retained on the chromosome. Excised episomal products include coding junctions, hybrid junctions formed in apparent violation of the 12/23 spacer rule, and standard signal junctions; some signal junctions show evidence of imprecise cleavage. Evidence for open/shut and/or oligonucleotide capture events was also seen. Similar rearrangements were detectable in thymocytes of mutant scid mice. These findings indicate a high degree of indeterminancy of V(D)J recombinase-mediated D[delta]1-D[delta]2 rearrangement in both wild-type and scid thymocytes. This indeterminacy affects the productive potential of TCR-[delta] loci. 45 refs., 4 figs.
Observation of Aubry-type transition in finite atom chains via friction.
Bylinskii, Alexei; Gangloff, Dorian; Counts, Ian; Vuletić, Vladan
2016-07-01
The highly nonlinear many-body physics of a chain of mutually interacting atoms in contact with a periodic substrate gives rise to complex static and dynamical phenomena, such as structural phase transitions and friction. In the limit of an infinite chain incommensurate with the substrate, Aubry predicted a transition with increasing substrate potential, from the chain's intrinsic arrangement free to slide on the substrate, to a pinned arrangement favouring the substrate pattern. So far, the Aubry transition has not been observed. Here, using spatially resolved position and friction measurements of cold trapped ions in an optical lattice, we observed a finite version of the Aubry transition and the onset of its hallmark fractal atomic arrangement. Notably, the observed critical lattice depth for few-ion chains agrees well with the infinite-chain prediction. Our results elucidate the connection between competing ordering patterns and superlubricity in nanocontacts-the elementary building blocks of friction.
Synthetic magnetic fluxes on the honeycomb lattice
Gorecka, Agnieszka; Gremaud, Benoit; Miniatura, Christian
2011-08-15
We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter's butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.
Marin, E.; Tomas, R.; Bambade, P.; Okugi, T.; Tauchi, T.; Terunuma, N.; Urakawa, J.; Seryi, A.; White, G.; Woodley, M.; /SLAC
2011-12-09
The current status for the ATF2 Nominal and Ultra-low {beta}* lattices are presented in this paper. New lattice designs have been obtained in order to minimise the impact of the last interpretation of multipole measurements that have been included into the model. However, the new ATF2 Ultra-low design is not able to recover the expected vertical beam size at the IP with the current magnet distribution. Therefore, different quadrupole sorting have been studied. A significant gain is evident for the ATF2 Ultra-low lattice when sorting the magnets according to the skew-sextupolar components. The ATF2 Nominal lattice is also expected to benefit from the new sorting. Tuning results of the new ATF2 Ultra-low lattice under realistic imperfections are also reported.
Lattice Boltzmann modeling of phonon transport
NASA Astrophysics Data System (ADS)
Guo, Yangyu; Wang, Moran
2016-06-01
A novel lattice Boltzmann scheme is proposed for phonon transport based on the phonon Boltzmann equation. Through the Chapman-Enskog expansion, the phonon lattice Boltzmann equation under the gray relaxation time approximation recovers the classical Fourier's law in the diffusive limit. The numerical parameters in the lattice Boltzmann model are therefore rigorously correlated to the bulk material properties. The new scheme does not only eliminate the fictitious phonon speed in the diagonal direction of a square lattice system in the previous lattice Boltzmann models, but also displays very robust performances in predicting both temperature and heat flux distributions consistent with analytical solutions for diverse numerical cases, including steady-state and transient, macroscale and microscale, one-dimensional and multi-dimensional phonon heat transport. This method may provide a powerful numerical tool for deep studies of nonlinear and nonlocal heat transports in nanosystems.
Synthetic magnetic fluxes on the honeycomb lattice
NASA Astrophysics Data System (ADS)
Górecka, Agnieszka; Grémaud, Benoît; Miniatura, Christian
2011-08-01
We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter’s butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.
Counting lattice animals in high dimensions
NASA Astrophysics Data System (ADS)
Luther, Sebastian; Mertens, Stephan
2011-09-01
We present an implementation of Redelemeier's algorithm for the enumeration of lattice animals in high-dimensional lattices. The implementation is lean and fast enough to allow us to extend the existing tables of animal counts, perimeter polynomials and series expansion coefficients in d-dimensional hypercubic lattices for 3 <= d <= 10. From the data we compute formulae for perimeter polynomials for lattice animals of size n <= 11 in arbitrary dimension d. When amended by combinatorial arguments, the new data suffice to yield explicit formulae for the number of lattice animals of size n <= 14 and arbitrary d. We also use the enumeration data to compute numerical estimates for growth rates and exponents in high dimensions that agree very well with Monte Carlo simulations and recent predictions from field theory.
Ising antiferromagnet on the Archimedean lattices
NASA Astrophysics Data System (ADS)
Yu, Unjong
2015-06-01
Geometric frustration effects were studied systematically with the Ising antiferromagnet on the 11 Archimedean lattices using the Monte Carlo methods. The Wang-Landau algorithm for static properties (specific heat and residual entropy) and the Metropolis algorithm for a freezing order parameter were adopted. The exact residual entropy was also found. Based on the degree of frustration and dynamic properties, ground states of them were determined. The Shastry-Sutherland lattice and the trellis lattice are weakly frustrated and have two- and one-dimensional long-range-ordered ground states, respectively. The bounce, maple-leaf, and star lattices have the spin ice phase. The spin liquid phase appears in the triangular and kagome lattices.
A lattice approach to spinorial quantum gravity
NASA Technical Reports Server (NTRS)
Renteln, Paul; Smolin, Lee
1989-01-01
A new lattice regularization of quantum general relativity based on Ashtekar's reformulation of Hamiltonian general relativity is presented. In this form, quantum states of the gravitational field are represented within the physical Hilbert space of a Kogut-Susskind lattice gauge theory. The gauge field of the theory is a complexified SU(2) connection which is the gravitational connection for left-handed spinor fields. The physical states of the gravitational field are those which are annihilated by additional constraints which correspond to the four constraints of general relativity. Lattice versions of these constraints are constructed. Those corresponding to the three-dimensional diffeomorphism generators move states associated with Wilson loops around on the lattice. The lattice Hamiltonian constraint has a simple form, and a correspondingly simple interpretation: it is an operator which cuts and joins Wilson loops at points of intersection.
Extended applications of the vortex lattice method
NASA Technical Reports Server (NTRS)
Miranda, L. R.
1976-01-01
The application of the vortex lattice method to problems not usually dealt with by this technique is considered. It is shown that if the discrete vortex lattice is considered as an approximation to surface-distributed vorticity, then the concept of the generalized principal part of an integral yields a residual term to the vortex-induced velocity that renders the vortex lattice method valid for supersonic flow. Special schemes for simulating non-zero thickness lifting surfaces and fusiform bodies with vortex lattice elements are presented. Thickness effects of wing-like components are simulated by a double vortex lattice layer, and fusiform bodies are represented by a vortex grid arranged on a series of concentric cylindrical surfaces. Numerical considerations peculiar to the application of these techniques are briefly discussed.
de Kroon, A.I.P.M.; Killian, J.A.; de Gier, J.; de Kruijff, B. )
1991-01-29
Deuterium nuclear magnetic resonance ({sup 2}H NMR) was used to study the interaction of amphiphilic model peptides with model membranes consisting of 1,2-dioleoyl-sn-glycero-3-phospho-L-serine deuterated either at the {beta}-position of the serine moiety ((2-{sup 2}H)DOPS) or at the 11-position of the acyl chains ((11,11-{sup 2}H{sub 2})DOPS). The peptides are derived from the sequences H-Ala-Met-Leu-Trp-Ala-OH and H-Arg-Met-Leu-Trp-Ala-OH and contain a positive charge of +1 or +2 at the amino terminus or one positive charge at each end of the molecule. Upon titration of dispersions of DOPS with the peptides, the divalent peptides show a similar extent of binding to the DOPS bilyers, which is larger than that of the single charged peptide. Under these conditions the values of the quadrupolar splitting of both (2-{sup 2}H)DOPS and (11,11-{sup 2}H{sub 2})DOPS are decreased, indicating that the peptides reduce the order of both the DOPS headgroup and the acyl chains. The extent of the decrease depends on the amount of peptide bound and on the position of the charged moieties in the peptide molecule. Titrations of DOPS with poly(L-lysine){sub 100}, which were included for reasons of comparison, reveal increased {Delta}v{sub q} values. When the peptide-lipid titrations are carried out without applying a freeze-thaw procedure to achieve full equilibration, two-component {sup 2}H NMR spectra occur. The apparently limited accessibility of the lipid to the peptides under these circumstances is discussed in relation to the ability of the peptides to exhibit transbilayer movement. {sup 2}H spin-lattice relaxation time T1 measurements demonstrate a decrease of the rates of motion of both headgroup and acyl chains of DOPS in the presence of the peptides.
NASA Astrophysics Data System (ADS)
Belyaev, Alexander; Sukhanov, Alexander; Tsvetkov, Alexander
2016-03-01
This article addresses the problem in which a chain falls from a glass from some height. This phenomenon demonstrates a paradoxical rise of the chain over the glass. To explain this effect, an initial hypothesis and an appropriate theory are proposed for calculating the steady fall parameters of the chain. For this purpose, the modified Cayley's problem of falling chain given its rise due to the centrifugal force of upward inertia is solved. Results show that the lift caused by an increase in linear density at the part of chain where it is being bent (the upper part) is due to the convergence of the chain balls to one another. The experiments confirm the obtained estimates of the lifting chain.
Telesat-G/Delta post launch report
NASA Technical Reports Server (NTRS)
Mahon, J. B.; Abrahamson, J. A.
1983-01-01
The Canadiari Telesat-G (ANIK-D1) commercial communications satellite was launched successfully from the Eastern space and Missile Center (ESMC) at 7:10 p.m., EDT, on August 25, 1982, by a Delta 3920 Vehicle, Mission Number 164. Performance of the two stage Delta launch vehicle was nominal and placed the payload in a low circular orbit as planned. The Payload Assist Module (PAM-D), which is part of the payload, also performed nominally. The synchronous transfer orbital elements achieved by Delta/PAM, compared with the nominal expected, are provided. The satellite performed satisfactorily during the transfer orbit, and the ABM was fired successfully at 5:29 p.m., EDT, on August 29, 1982. The satellite was maneuvered to a position 104 degrees West Longitude above the equator. Satellite status is satisfactory and it has entered service.
NASA Technical Reports Server (NTRS)
1978-01-01
NATO-3C, the third in a series of NATO defense-related communication satellites, is scheduled to be launched on a delta vehicle from the Eastern Test Range no earlier than November 15, 1978. NATO-3A and -3B were successfully launched by Delta vehicles in April 1976 and January 1977, respectively. The NATO-3C spacecraft will be capable of transmitting voice, data, facsimile, and telex messages among military ground stations. The launch vehicle for the NATO-3C mission will be the Delta 2914 configuration. The launch vehicle is to place the spacecraft in a synchronous transfer orbit. The spacecraft Apogee Kick motor is to be fired at fifth transfer orbit apogee to circularize its orbit at geosynchronous altitude of 35,900 km(22,260 miles) above the equator over the Atlantic Ocean somewhere between 45 and 50 degrees W longitude.
DNA polymerase III accessory proteins. I. holA and holB encoding delta and delta'.
Dong, Z; Onrust, R; Skangalis, M; O'Donnell, M
1993-06-05
The genes encoding the delta and delta' subunits of the 10-subunit Escherichia coli replicase, DNA polymerase III holoenzyme, have been identified and sequenced. The holA gene encoding delta is located downstream of rlpB at 15.2 min and predicts a 38.7 kda protein. The holB gene encoding delta' is located at 24.3 min and predicts a 36.9-kDa protein. Hence the delta and delta' subunits are unrelated proteins encoded by separate genes. The genes have been used to express and purify delta and delta' in quantity. The predicted amino acid sequence of delta' is homologous to the sequences of the tau and gamma subunits revealing a large amount of structural redundancy within the holoenzyme.
Toward a realistic low-field SSC lattice
Heifets, S.
1985-10-01
Three six-fold lattices for 3 T superferric SSC have been generated at TAC. The program based on the first order canonical transformation was used to compare lattices. On this basis the realistic race-track lattices were generated.
Lefèvre, A; Rogier, E; Astraudo, C; Duquenne, C; Finaz, C
1994-12-01
Vitamin A is a potent regulator of testicular function. We have reported that retinol (R) and retinoic acid (RA) induced a down regulation of luteinizing hormone/human chorionic gonadotropin (LH/CG) binding sites in K9 Leydig cells. In the present study we evaluated the effect of R and RA on LH/CG receptors, cholesterol side-chain cleavage cytochrome P-450 (P-450 scc), 17 alpha-hydroxylase/C17-20 lyase (P-450 17 alpha) and 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) mRNA levels in K9 mouse Leydig cells. To validate K9 cells as a model for studying Leydig cell steroidogenesis at the molecular level, we first investigated the effect of hCG on mRNA levels of the steroidogenic enzymes. P-450 scc, 3 beta HSD and P-450 17 alpha were expressed constitutively. The addition of 10 ng/ml hCG enhanced mRNA levels for the three genes within 2 h. Maximal accumulation of P-450 scc, P-450 17 alpha and 3 beta HSD mRNA in treated cells represents a 2.5-, 8.5- and 4-fold increase over control values, respectively. P-450 17 alpha expression reached a maximum by 4 h and then declined rapidly to return to control value by 24 h. The pattern of LH/CG receptor mRNAs in K9 cells was very similar to that of MA10 Leydig cells and showed six transcripts of 1.1, 1.6, 1.9, 2.6, 4.2 and 7.0 kb. Treatment of cells with R or RA resulted in a time- and dose-dependent decrease in all six species.(ABSTRACT TRUNCATED AT 250 WORDS)
NASA Astrophysics Data System (ADS)
Khoo, Andy; Iwaki, Takafumi; Shew, Chwen-Yang; Yoshikawa, Kenichi
2009-09-01
A lattice chain model is extended to investigate the preferential position of a sticky sphere bound to a polymer chain, motivated by wrapping one nanosize core-histone with DNA to form a nucleosome structure. It was shown that the single bound histone is populated in DNA chain ends from the experiment by T. Sakaue et al. [Phys. Rev. Lett. 87, 078105 (2001)]. Here, the possible mechanisms are examined to elucidate such behavior. For neutral chains or ionic chains in high salt concentrations, spheres bound on the middle of chain may trigger conformational constraints to reduce conformational entropy. For ionic chains, the bound sphere can be driven to chain ends if its effective charge and the charge of chain monomers are of like charge. The two-dimensional chain is further studied to mimic the chromosome strongly adsorbed onto surfaces, of which behavior is similar to the three-dimensional case with minor difference due to surface confinement.
Sigma Delta Dac Using Vhdl-Ams
NASA Astrophysics Data System (ADS)
Utage, S. A.; Dube, R. R.
2010-11-01
Sigma Delta Digital to analog converters (DACs) convert a binary number into a voltage directly proportional to the value of the binary number. A variety of applications use DACs including waveform generators and programmable voltage sources. This paper describes a Delta-Sigma DAC implemented in a FPGA. The only external circuitry required is a low pass filter comprised of just one resistor and one capacitor. Internal resource requirements are also minimal. The speed and flexible output structure of the FPGAs make them ideal for this application.
Delta Clipper-Experimental (DC-X)
NASA Technical Reports Server (NTRS)
1995-01-01
Pictured here is a DC-XA Reusable Launch Vehicle (RLV) prototype concept with an RLV logo. The Delta Clipper-Experimental (DC-X) was originally developed by McDornell Douglas for the Department of Defense (DOD). The DC-XA is a single-stage-to-orbit, vertical takeoff/vertical landing, launch vehicle concept, whose development is geared to significantly reduce launch costs and will provide a test bed for NASA Reusable Launch Vehicle (RLV) technology as the Delta Clipper-Experimental Advanced (DC-XA).
The Delta Launch Vehicle Model 2914 Series
NASA Technical Reports Server (NTRS)
Gunn, C. R.
1973-01-01
The newest Delta launch vehicle configuration, Model 2914 is described for potential users together with recent flight results. A functional description of the vehicle, its performance, flight profile, flight environment, injection accuracy, spacecraft integration requirements, user organizational interfaces, launch operations, costs and reimbursable users payment plan are provided. The versatile, relatively low cost Delta has a flight demonstrated reliability record of 92 percent that has been established in 96 launches over twelve years while concurrently undergoing ten major upratings to keep pace with the ever increasing performance and reliability requirements of its users. At least 40 more launches are scheduled over the next three years from the Eastern and Western Test Ranges.
All optical binary delta-sigma modulator
NASA Astrophysics Data System (ADS)
Sayeh, Mohammad R.; Siahmakoun, Azad
2005-09-01
This paper describes a novel A/D converter called "Binary Delta-Sigma Modulator" (BDSM) which operates only with nonnegative signal with positive feedback and binary threshold. This important modification to the conventional delta-sigma modulator makes the high-speed (>100GHz) all-optical implementation possible. It has also the capability to modify its own sampling frequency as well as its input dynamic range. This adaptive feature helps designers to optimize the system performance under highly noisy environment and also manage the power consumption of the A/D converters.
Calderon, Silvia N
2011-01-01
The discovery of the selective delta (delta) opioid agonists SNC 80 and BW373U86, which possess a diarylmethylpiperazine structure unique among opioids, represented a major advance in the field of delta-opioid ligands. Extensive research has recently been performed to uncover the structure-activity relationships (SAR) of this class of ligands, thereby providing valuable tools for the pharmacological characterization of the delta opioid receptor. This review focuses on the SAR of this unique series of ligands, and provides an overview of the various chemical routes that have been developed and optimized through the years to allow the syntheses of these ligands on a multigram scale. The search for selective delta opioid agonists and antagonists, as well as for those with mixed opioid agonist properties with potential therapeutic value, continues. Several questions regarding the interaction at the molecular level of diphenylmethylpiperazine derivatives and related analogs with opioid receptors and in particular with the delta opioid system still remain unanswered. Indeed, the development and pharmacological characterization of novel nonpeptidic delta opioid ligands remains an active area of research, as it may provide a better understanding of the role of this receptor in multiple disease states and disorders.
Critical Casimir force and its fluctuations in lattice spin models: exact and Monte Carlo results.
Dantchev, Daniel; Krech, Michael
2004-04-01
We present general arguments and construct a stress tensor operator for finite lattice spin models. The average value of this operator gives the Casimir force of the system close to the bulk critical temperature T(c). We verify our arguments via exact results for the force in the two-dimensional Ising model, d -dimensional Gaussian, and mean spherical model with 2
Bayro, Marvin J; Tycko, Robert
2016-07-13
The HIV-1 capsid protein (CA) forms the capsid shell that encloses RNA within a mature HIV-1 virion. Previous studies by electron microscopy have shown that the capsid shell is primarily a triangular lattice of CA hexamers, with variable curvature that destroys the ideal symmetry of a planar lattice. The mature CA lattice depends on CA dimerization, which occurs through interactions between helix 9 segments of the C-terminal domain (CTD) of CA. Several high-resolution structures of the CTD-CTD dimerization interface have been reported, based on X-ray crystallography and multidimensional solution nuclear magnetic resonance (NMR), with significant differences in amino acid side chain conformations and helix 9-helix 9 orientations. In a structural model for tubular CA assemblies based on cryogenic electron microscopy (cryoEM) [Zhao et al. Nature, 2013, 497, 643-646], the dimerization interface is substantially disordered. The dimerization interface structure in noncrystalline CA assemblies and the extent to which this interface is structurally ordered within a curved lattice have therefore been unclear. Here we describe solid state NMR measurements on the dimerization interface in tubular CA assemblies, which contain the curved triangular lattice of a mature virion, including quantitative measurements of intermolecular and intramolecular distances using dipolar recoupling techniques, solid state NMR chemical shifts, and long-range side chain-side chain contacts. When combined with restraints on the distance and orientation between helix 9 segments from the cryoEM study, the solid state NMR data lead to a unique high-resolution structure for the dimerization interface in the noncrystalline lattice of CA tubes. These results demonstrate that CA lattice curvature is not dependent on disorder or variability in the dimerization interface. This work also demonstrates the feasibility of local structure determination within large noncrystalline assemblies formed by high
Perlovich, German L; Volkova, Tatyana V; Bauer-Brandl, Annette
2006-10-01
Temperature dependencies of saturated vapor pressure for the monoclinic modification of paracetamol (acetaminophen), acetanilide, and phenacetin (acetophenetidin) were measured and thermodynamic functions of sublimation calculated (paracetamol: DeltaGsub298=60.0 kJ/mol; DeltaHsub298=117.9+/-0.7 kJ/mol; DeltaSsub298=190+/-2 J/mol.K; acetanilide: DeltaGsub298=40.5 kJ/mol; DeltaHsub298=99.8+/-0.8 kJ/mol; DeltaSsub298=197+/-2 J/mol.K; phenacetin: DeltaGsub298=52.3 kJ/mol; DeltaHsub298=121.8+/-0.7 kJ/mol; DeltaSsub298=226+/-2 J/mol.K). Analysis of packing energies based on geometry optimization of molecules in the crystal lattices using diffraction data and the program Dmol3 was carried out. Parameters analyzed were: (a) energetic contribution of van der Waals forces and hydrogen bonding to the total packing energy; (b) contributions of fragments of the molecules to the packing energy. The fraction of hydrogen bond energy in the packing energy increases as: phenacetin (17.5%)
Chiral spin liquids in arrays of spin chains
NASA Astrophysics Data System (ADS)
Gorohovsky, Gregory; Pereira, Rodrigo G.; Sela, Eran
2015-06-01
We describe a coupled-chain construction for chiral spin liquids in two-dimensional spin systems. Starting from a one-dimensional zigzag spin chain and imposing SU(2) symmetry in the framework of non-Abelian bosonization, we first show that our approach faithfully describes the low-energy physics of an exactly solvable model with a three-spin interaction. Generalizing the construction to the two-dimensional case, we obtain a theory that incorporates the universal properties of the chiral spin liquid predicted by Kalmeyer and Laughlin: charge-neutral edge states, gapped spin-1/2 bulk excitations, and ground-state degeneracy on the torus signaling the topological order of this quantum state. In addition, we show that the chiral spin liquid phase is more easily stabilized in frustrated lattices containing corner-sharing triangles, such as the extended kagome lattice, than in the triangular lattice. Our field-theoretical approach invites generalizations to more exotic chiral spin liquids and may be used to assess the existence of the chiral spin liquid as the ground state of specific lattice systems.
How Deltas Die - a Case Study of the End of Sedimentation in Two Giant Deltas
NASA Astrophysics Data System (ADS)
Macdonald, D.; Robinson, P.; Nicholson, U.
2013-12-01
Most well-studied deltas are on passive margins (e.g. Mississippi, Rhone, Ebro), where the main tectonic control on accommodation space is thermal subsidence. As long as the main river in the sediment routing system keeps flowing, there is no particular reason for sedimentation to end, and some deltas have a history extending more than 100 Ma (e.g. Niger at 130 Ma). However, some very large deltas can build out over active margins. For example, the Amur, Orinoco, and Colorado (US) deltas all straddle strike-slip plate boundaries and are much less long-lived than their passive margin counterparts. This paper looks in detail at the end of the deltaic sedimentation in the Pliocene deltas of the Amur River on the island of Sakhalin, and the Colorado River in the Fish Creek-Vallecito Basin of southern California. In both cases the deltas are sand-rich with distant provenances in East Asia and the Colorado Plateau respectively; also they both coexist with locally derived clastic sedimentation. Despite these similarities, there are significant differences between the two deltas as a direct result of the differences in plate boundary movement rates and tectonic state. On Sakhalin, the plate boundary has moved at about 1.95 mm a-1 during the Pliocene and has been in a transpressional state. Primary deltaic sedimentation ended by a three main mechanisms: uplift of the island along the transpressional plate boundary detached the delta from the trunk stream; growth of anticlines over strands of the plate boundary disrupted the consequent delta-top drainage; and late sedimentation involved reworking of the far-travelled deltaic material. In California, where the plate boundary has moved at about 50 mm a-1 in the Pliocene, deltaic sedimentation ceased by translation of the receiving basin from the river mouth. New field and mineralogical data suggest that Colorado River sedimentation waned over a period of about 1 Ma in the Late Pliocene, and was gradually overwhelmed by locally
Modeling delta growth and channel geometry on Wax Lake Delta, Louisiana. Preliminary results
NASA Astrophysics Data System (ADS)
Viparelli, E.; Czapiga, M. J.; Li, C.; Shaw, J. B.; Parker, G.
2013-12-01
A numerical model of delta growth, in which the distributary channels are assumed to have self-constructed their cross sections, is validated on Wax Lake Delta, Louisiana. As in previous laterally averaged models of delta growth, the delta is divided in a low slope delta top, a steep delta front and a low slope basement. The flow on the delta top is assumed steady, and a backwater formulation is implemented. Since one or more channels can actively transport water and sediment on the delta top during floods, we simplify the problem by assuming that the bed material is transported in one rectangular channel, with width and depth roughly equal to the sum of the active channel widths, and to the average depth of the active channels. The problem is characterized by one equation (i.e. the backwater equation) in two unknowns, the channel width and depth. Another equation is thus needed to close the problem. Under the assumptions that 1) the system is at bankfull flow, and 2) the Shields number in the channels is equal to its channel formative value, our closure relation is a channel-formative criterion. In particular, a recently derived relation to estimate the formative (bankfull) Shields number as a function of the friction slope is implemented. Recent field work on Wax Lake Delta shows that the distributary channels are incising into a relatively stiff basement. In our model we do not attempt to directly model channel incision, but we implicitly account for it with a modified formulation to compute the shoreline migration rate. In this formulation the bed material at the shoreline is trapped in the non-channelized portion of the delta front only. Measured and numerical shoreline migration rates, longitudinal profiles of delta elevation, and channel geometry, i.e. width and depth, are compared. In the relatively near future we plan to 1) use our model to estimate land-building potential of engineered diversions of the Mississippi River, and 2) couple the present model
Vortex Breakdown over Slender Delta Wings (Eclatement tourbillonnaire sur les ailes delta effil es)
2009-11-01
Figure A-2: Effect of helix pitch on binormal and tangential induced velocity coefficients ‘ENGINEERING’ MODELS OF DELTA WING VORTEX BREAKDOWN AND... pitch rig in SARL wind tunnel 5-22 Fig. 9 OPLEC Coning rig in IAR water tunnel 5-23 Fig. 10 Skin friction topologies on 65° delta wing in roll 5-23...Cross-Flow Plane as a Function of Angle 6-17 of Attack for a Periodically Pitching Delta Wing Figure 23 Flow Visualization of Vortex Breakdown for
Dynamic Behavior of Engineered Lattice Materials
Hawreliak, J. A.; Lind, J.; Maddox, B.; Barham, M.; Messner, M.; Barton, N.; Jensen, B. J.; Kumar, M.
2016-01-01
Additive manufacturing (AM) is enabling the fabrication of materials with engineered lattice structures at the micron scale. These mesoscopic structures fall between the length scale associated with the organization of atoms and the scale at which macroscopic structures are constructed. Dynamic compression experiments were performed to study the emergence of behavior owing to the lattice periodicity in AM materials on length scales that approach a single unit cell. For the lattice structures, both bend and stretch dominated, elastic deflection of the structure was observed ahead of the compaction of the lattice, while no elastic deformation was observed to precede the compaction in a stochastic, random structure. The material showed lattice characteristics in the elastic response of the material, while the compaction was consistent with a model for compression of porous media. The experimental observations made on arrays of 4 × 4 × 6 lattice unit cells show excellent agreement with elastic wave velocity calculations for an infinite periodic lattice, as determined by Bloch wave analysis, and finite element simulations. PMID:27321697
Agarwala, R.; Batzoglou, S.; Dancik, V.
1997-06-01
We consider the problem of determining the three-dimensional folding of a protein given its one-dimensional amino acid sequence. We use the HP model for protein folding proposed by Dill, which models protein as a chain of amino acid residues that are either hydrophobic or polar, and hydrophobic interactions are the dominant initial driving force for the protein folding. Hart and Istrail gave approximation algorithms for folding proteins on the cubic lattice under HP model. In this paper, we examine the choice of a lattice by considering its algorithmic and geometric implications and argue that triangular lattice is a more reasonable choice. We present a set of folding rules for a triangular lattice and analyze the approximation ratio which they achieve. In addition, we introduce a generalization of the HP model to account for residues having different levels of hydrophobicity. After describing the biological foundation for this generalization, we show that in the new model we are able to achieve similar constant factor approximation guarantees on the triangular lattice as were achieved in the standard HP model. While the structures derived from our folding rules are probably still far from biological reality, we hope that having a set of folding rules with different properties will yield more interesting folds when combined.
Tailoring the plasmonic modes of metal nanoparticle arrays with lattice anisotropy
NASA Astrophysics Data System (ADS)
Lai, King Chun; Lee, Sze Fung; Yu, Kin Wah
2014-03-01
We have studied the plasmonic band structure of three-dimensional lattices of nanoparticles under external electromagnetic waves. The long-range dipolar forces among polarized nanoparticles lead to the collective motion of the dipole moments to form plasmon. The resulting plasmonic dispersion thus depends on the polarizability of individual particle and the lattice structure of the whole system. We tailor sets of desirable plasmonic modes through varying the polarizability of nanoparticles or lattice anisotropy which can be tuned by incident GHz ultrasonic waves. Similar work of one-dimensional particle chain was contributed by Maier (2003), but we further extend the system into three-dimensional cases. In order to deal with the long-range interactions, we adopt the Ewald method to develop a viable means for calculating the plasmonic dispersion relation. Furthermore, we consider the formalism for diatomic basis of nanoshell. The plasmonic modes of each particle may couple and form hybridized plasmonic band attributed to level repulsion effect. This method provides a flexible way to manipulate plasmonic wave in a lattice by tuning the characteristic parameters of particle shape or lattice structure.
Colson, Brett A.; Locher, Matthew R.; Bekyarova, Tanya; Patel, Jitandrakumar R.; Fitzsimons, Daniel P.; Irving, Thomas C.; Moss, Richard L.
2010-05-25
Phosphorylation of myosin regulatory light chain (RLC) by myosin light chain kinase (MLCK) and myosin binding protein-C (cMyBP-C) by protein kinase A (PKA) independently accelerate the kinetics of force development in ventricular myocardium. However, while MLCK treatment has been shown to increase the Ca{sup 2+} sensitivity of force (pCa{sub 50}), PKA treatment has been shown to decrease pCa{sub 50}, presumably due to cardiac troponin I phosphorylation. Further, MLCK treatment increases Ca{sup 2+}-independent force and maximum Ca{sup 2+}-activated force, whereas PKA treatment has no effect on either force. To investigate the structural basis underlying the kinase-specific differential effects on steady-state force, we used synchrotron low-angle X-ray diffraction to compare equatorial intensity ratios (I{sub 1,1}/I{sub 1,0}) to assess the proximity of myosin cross-bridge mass relative to actin and to compare lattice spacings (d{sub 1,0}) to assess the inter-thick filament spacing in skinned myocardium following treatment with either MLCK or PKA. As we showed previously, PKA phosphorylation of cMyBP-C increases I{sub 1,1}/I{sub 1,0} and, as hypothesized, treatment with MLCK also increased I{sub 1,1}/I{sub 1,0}, which can explain the accelerated rates of force development during activation. Importantly, interfilament spacing was reduced by {approx}2 nm ({Delta} 3.5%) with MLCK treatment, but did not change with PKA treatment. Thus, RLC or cMyBP-C phosphorylation increases the proximity of cross-bridges to actin, but only RLC phosphorylation affects lattice spacing, which suggests that RLC and cMyBP-C modulate the kinetics of force development by similar structural mechanisms; however, the effect of RLC phosphorylation to increase the Ca{sup 2+} sensitivity of force is mediated by a distinct mechanism, most probably involving changes in interfilament spacing.
Crystal structure of delta-chymotrypsin bound to a peptidyl chloromethyl ketone inhibitor.
Mac Sweeney, A; Birrane, G; Walsh, M A; O'Connell, T; Malthouse, J P; Higgins, T M
2000-03-01
Chymotrypsin is a member of the trypsin family of serine proteases and is one of the first proteins successfully studied by X-ray crystallography. It is secreted into the intestine as the inactive precursor chymotrypsinogen; four sequential cleavages of the peptide bonds following residues 13, 15, 146 and 148 occur to generate the active pi, delta, kappa and alpha forms of chymotrypsin. (13)C NMR has shown [O'Connell & Malthouse (1995). Biochem. J. 307, 353-359] that when the delta form of chymotrypsin is inhibited by 2-(13)C-enriched benzyloxycarbonylglycylglycylphenylalanyl chloromethane, a tetrahedral adduct is formed which is thought to be analogous to the tetrahedral intermediate formed during catalysis. This inhibitor complex has been crystallized as a dimer in space group P4(1)2(1)2. The structure has been refined at 2.14 A resolution to an R value of 21.2% (free R = 25.2%). Conformational differences between delta-chymotrypsin and chymotrypsinogen in the region of the flexible autolysis loop (residues 145-150) were observed. This is the first crystal structure of delta-chymotrypsin and includes two residues which are disordered in previous crystal structures of active chymotrypsin. A difference of 11.3 A(2) between the average B values of the monomers within the asymmetric unit is caused by lattice-disordering effects approximating to rotation of the molecules about a crystallographic screw axis. The substrate-binding mode of the inhibitor was similar to other chymotrypsin peptidyl inhibitor complexes, but this is the first published chymotrypsin structure in which the tetrahedral chloromethyl ketone transition-state analogue is observed. This structure is compared with that of a similar tetrahedral transition-state analogue which does not alkylate the active-site histidine residue.
Discretization effects and the scalar meson correlator in mixed-action lattice simulations
Aubin, C.; Laiho, Jack; Van de Water, Ruth S.
2008-06-01
We study discretization effects in a mixed-action lattice theory with domain-wall valence quarks and Asqtad-improved staggered sea quarks. At the level of the chiral effective Lagrangian, discretization effects in the mixed-action theory give rise to two new parameters as compared to the lowest order Lagrangian for rooted-staggered fermions - the residual quark mass m{sub res} and the mixed valence-sea meson mass splitting {delta}{sub mix}. We find that m{sub res}, which parametrizes explicit chiral symmetry breaking in the mixed-action theory, is approximately one-quarter the size of our lightest valence quark mass on our coarser lattice spacing and of comparable size to that of simulations by the RBC and UKQCD Collaborations. We also find that the size of {delta}{sub mix} is comparable to the size of the smallest of the staggered meson taste splittings measured by the MILC Collaboration. Because lattice artifacts are different in the valence and sea sectors of the mixed-action theory, they give rise to unitarity-violating effects that disappear in the continuum limit, some of which should be described by mixed-action chiral perturbation theory (MA{chi}PT). Such effects are expected to be mild for many quantities of interest but are expected to be significant in the case of the isovector scalar (a{sub 0}) correlator. Specifically, once the parameters m{sub res}, {delta}{sub mix}, and two others that can be determined from the light pseudoscalar meson spectrum are known, the two-particle intermediate state 'bubble' contribution to the scalar correlator is completely predicted within MA{chi}PT. We find that the behavior of the scalar meson correlator is quantitatively consistent with the MA{chi}PT prediction; this supports the claim that MA{chi}PT describes the dominant unitarity-violating effects in the mixed-action theory and can therefore be used to remove lattice artifacts and recover physical quantities.
Quantum signatures of breathers in a finite Heisenberg spin chain.
Djoufack, Z I; Kenfack-Jiotsa, A; Nguenang, J P; Domngang, S
2010-05-26
A map of a quantum Heisenberg spin chain into an extended Bose-Hubbard-like Hamiltonian is set up. Within this framework, the spectrum of the corresponding Bose-Hubbard chain, on a periodic one-dimensional lattice containing two, four, and six bosons shows interesting detailed band structures. These fine structures are studied using numerical diagonalization, and nondegenerate and degenerate perturbation theory. We also focus our attention on the effect of the anisotropy and Heisenberg exchange energy on the detailed band structures. The signature of the quantum breather is also set up by the square of the amplitudes of the corresponding eigenvectors in real space.
A parity breaking Ising chain Hamiltonian as a Brownian motor
NASA Astrophysics Data System (ADS)
Cornu, F.; Hilhorst, H. J.
2014-10-01
We consider the translationally invariant but parity (left-right symmetry) breaking Ising chain Hamiltonian {\\cal H} =-{U_2}\\sumk sksk+1 - {U_3}\\sumk sksk+1sk+3 and let this system evolve by Kawasaki spin exchange dynamics. Monte Carlo simulations show that perturbations forcing this system off equilibrium make it act as a Brownian molecular motor which, in the lattice gas interpretation, transports particles along the chain. We determine the particle current under various different circumstances, in particular as a function of the ratio {U_3}/{U_2} and of the conserved magnetization M=\\sum_ksk . The symmetry of the U3 term in the Hamiltonian is discussed.
Cloning and characterization of a delta-6 desaturase encoding gene from Nannochloropsis oculata
NASA Astrophysics Data System (ADS)
Ma, Xiaolei; Yu, Jianzhong; Zhu, Baohua; Pan, Kehou; Pan, Jin; Yang, Guanpin
2011-03-01
A gene ( NANOC-D6D) encoding a desaturase that removes two hydrogen atoms from fatty acids at delta 6 position was isolated from a cDNA library of Nannochloropsis oculata (Droop) D. J. Hibberd (Eustigmatophyceae). The unicellular marine microalga N. oculata synthesizes rich long chain polyunsaturated fatty acids (LCPUFAs), including eicosapentaenoic acid (20:5n-3, EPA). The deduced protein contains 474 amino acids that fold into 4 trans-membrane domains. The neighbor-joining phylogenetic tree indicates that NANOC-D6D is phylogenetically close to the delta-6 fatty acid desaturase of marine microalgae such as Glossomastix chrysoplasta, Thalassiosira pseudonana, and Phaeodactylum tricornutum. The gene was expressed in Saccharomyces cerevisiae INVScl to verify the substrate specificity of NANOC-D6D. Our results suggest that the recombinant NANOC-D6D simultaneously desaturates linoleic acid (LA) and α-linolenic acid (ALA).
Validation of WIMS-IST for CANDU R-type lattices
Bromley, B. P.; Davis, R.
2006-07-01
Prior validation studies of 28-element natural uranium (28-NU) CANDU R-type fuel bundles using the WIMS-IST lattice physics code had demonstrated a bias in the calculation of the coolant void reactivity (CVR) of approximately +0.5 to +0.6 mk (1 mk =100 pcm = 0.001 {Delta}k/k). However, these validation studies were performed using experimental data for 28-element bundles with pressure tubes that were smaller than standard CANDU-type pressure tubes, giving a smaller coolant volume, and a modified neutron energy spectrum. Validation studies performed with 37-element and 43-element fuel bundles with a CANDU-type lattice pitch and pressure tube had shown a CVR bias of {approx} 1.7 to 1.9 mk. It was believed that the CVR bias for a 28-element bundle would be closer to this range of values if a standard CANDU pressure tube diameter were used The objective of this study was to confirm this hypothesis, that using a larger CANDU-standard pressure tube would give a larger CVR bias for a 28-NU fuel bundle, as computed by WIMS-IST in comparison to experimental measurements of critical buckling. Thus, new critical-height and flux-map measurements were performed in substitution experiments in the ZED-2 research reactor to determine the pure critical lattice buckling for 28-element fuel with standard-size CANDU pressure tubes. The derived buckling from these experiments were used in WIMS-IST transport calculations to determine the effective multiplication factors for cooled and voided lattices and hence the bias in the CVR. Calculation results demonstrated that the CVR bias for the 28-NU was {approx} 1.7 mk {+-} 0.42 mk, which is consistent with the results for 37-element and 43-element CANDU-type lattices. (authors)
Growth algorithms for lattice heteropolymers at low temperatures
NASA Astrophysics Data System (ADS)
Hsu, Hsiao-Ping; Mehra, Vishal; Nadler, Walter; Grassberger, Peter
2003-01-01
Two improved versions of the pruned-enriched-Rosenbluth method (PERM) are proposed and tested on simple models of lattice heteropolymers. Both are found to outperform not only the previous version of PERM, but also all other stochastic algorithms which have been employed on this problem, except for the core directed chain growth method (CG) of Beutler and Dill. In nearly all test cases they are faster in finding low-energy states, and in many cases they found new lowest energy states missed in previous papers. The CG method is superior to our method in some cases, but less efficient in others. On the other hand, the CG method uses heavily heuristics based on presumptions about the hydrophobic core and does not give thermodynamic properties, while the present method is a fully blind general purpose algorithm giving correct Boltzmann-Gibbs weights, and can be applied in principle to any stochastic sampling problem.
Monte Carlo Study of Real Time Dynamics on the Lattice
NASA Astrophysics Data System (ADS)
Alexandru, Andrei; Başar, Gökçe; Bedaque, Paulo F.; Vartak, Sohan; Warrington, Neill C.
2016-08-01
Monte Carlo studies involving real time dynamics are severely restricted by the sign problem that emerges from a highly oscillatory phase of the path integral. In this Letter, we present a new method to compute real time quantities on the lattice using the Schwinger-Keldysh formalism via Monte Carlo simulations. The key idea is to deform the path integration domain to a complex manifold where the phase oscillations are mild and the sign problem is manageable. We use the previously introduced "contraction algorithm" to create a Markov chain on this alternative manifold. We substantiate our approach by analyzing the quantum mechanical anharmonic oscillator. Our results are in agreement with the exact ones obtained by diagonalization of the Hamiltonian. The method we introduce is generic and, in principle, applicable to quantum field theory albeit very slow. We discuss some possible improvements that should speed up the algorithm.
Characterization of Si volume- and delta-doped InGaAs grown by molecular beam epitaxy
Fedoryshyn, Y.; Kaspar, P.; Jaeckel, H.; Beck, M.
2010-05-15
Bulk InGaAs layers were grown at 400 deg. C lattice-matched to InP semi-insulating substrates by molecular beam epitaxy. Si doping of the layers was performed by applying volume- and delta-doping techniques. The samples were characterized by capacitance-voltage, van der Pauw-Hall, secondary ion mass spectroscopy and photoluminescence measurements. Good agreement in terms of dependence of mobility and Burstein-Moss shift shift on doping concentration in samples doped by the two different techniques was obtained. Amphoteric behavior of Si was observed at doping concentrations higher than {approx}2.9x10{sup 19} cm{sup -3} in both delta- and volume-doped samples. Degradation of InGaAs crystalline quality occurred in samples with Si concentrations higher than {approx}4x10{sup 19} cm{sup -3}.
Making the cut: lattice kirigami rules.
Castle, Toen; Cho, Yigil; Gong, Xingting; Jung, Euiyeon; Sussman, Daniel M; Yang, Shu; Kamien, Randall D
2014-12-12
In this Letter we explore and develop a simple set of rules that apply to cutting, pasting, and folding honeycomb lattices. We consider origami-like structures that are extrinsically flat away from zero-dimensional sources of Gaussian curvature and one-dimensional sources of mean curvature, and our cutting and pasting rules maintain the intrinsic bond lengths on both the lattice and its dual lattice. We find that a small set of rules is allowed providing a framework for exploring and building kirigami—folding, cutting, and pasting the edges of paper.
Making the Cut: Lattice Kirigami Rules
NASA Astrophysics Data System (ADS)
Castle, Toen; Cho, Yigil; Gong, Xingting; Jung, Euiyeon; Sussman, Daniel M.; Yang, Shu; Kamien, Randall D.
2014-12-01
In this Letter we explore and develop a simple set of rules that apply to cutting, pasting, and folding honeycomb lattices. We consider origami-like structures that are extrinsically flat away from zero-dimensional sources of Gaussian curvature and one-dimensional sources of mean curvature, and our cutting and pasting rules maintain the intrinsic bond lengths on both the lattice and its dual lattice. We find that a small set of rules is allowed providing a framework for exploring and building kirigami—folding, cutting, and pasting the edges of paper.
Coincidence lattices in the hyperbolic plane.
Rodríguez-Andrade, M A; Aragón-González, G; Aragón, J L; Gómez-Rodríguez, A
2011-01-01
The problem of coincidences of lattices in the space R(p,q), with p + q = 2, is analyzed using Clifford algebra. We show that, as in R(n), any coincidence isometry can be decomposed as a product of at most two reflections by vectors of the lattice. Bases and coincidence indices are constructed explicitly for several interesting lattices. Our procedure is metric-independent and, in particular, the hyperbolic plane is obtained when p = q = 1. Additionally, we provide a proof of the Cartan-Dieudonné theorem for R(p,q), with p + q = 2, that includes an algorithm to decompose an orthogonal transformation into a product of reflections.
Continuum methods in lattice perturbation theory
Becher, Thomas G
2002-11-15
We show how methods of continuum perturbation theory can be used to simplify perturbative lattice calculations. We use the technique of asymptotic expansions to expand lattice loop integrals around the continuum limit. After the expansion, all nontrivial dependence on momenta and masses is encoded in continuum loop integrals and the only genuine lattice integrals left are tadpole integrals. Using integration-by-parts relations all of these can be expressed in terms of a small number of master integrals. Four master integrals are needed for bosonic one loop integrals, sixteen in QCD with Wilson or staggered fermions.
Lattice surgery translation for quantum computation
NASA Astrophysics Data System (ADS)
Herr, Daniel; Nori, Franco; Devitt, Simon J.
2017-01-01
In this paper we outline a method for a compiler to translate any non fault tolerant quantum circuit to the geometric representation of the lattice surgery error-correcting code using inherent merge and split operations. Since the efficiency of state distillation procedures has not yet been investigated in the lattice surgery model, their translation is given as an example using the proposed method. The resource requirements seem comparable or better to the defect-based state distillation process, but modularity and eventual implementability allow the lattice surgery model to be an interesting alternative to braiding.
Charmonium excited state spectrum in lattice QCD
Jozef Dudek; Robert Edwards; Nilmani Mathur; David Richards
2008-02-01
Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.
Reactive Orthotropic Lattice Diffuser for Noise Reduction
NASA Technical Reports Server (NTRS)
Khorrami, Mehdi R. (Inventor)
2016-01-01
An orthotropic lattice structure interconnects porous surfaces of the flap with internal lattice-structured perforations to equalize the steady pressure field on the flap surfaces adjacent to the end and to reduce the amplitude of the fluctuations in the flow field near the flap end. The global communication that exists within all of the perforations provides the mechanism to lessen the pressure gradients experienced by the end portion of the flap. In addition to having diffusive effects (diffusing the incoming flow), the three-dimensional orthogonal lattice structure is also reactive (acoustic wave phase distortion) due to the interconnection of the perforations.
Shock wave structure in a lattice gas
NASA Astrophysics Data System (ADS)
Broadwell, James E.; Han, Donghee
2007-05-01
The motion and structure of shock and expansion waves in a simple particle system, a lattice gas and cellular automaton, are determined in an exact computation. Shock wave solutions, also exact, of a continuum description, a model Boltzmann equation, are compared with the lattice results. The comparison demonstrates that, as proved by Caprino et al. ["A derivation of the Broadwell equation," Commun. Math. Phys. 135, 443 (1991)] only when the lattice processes are stochastic is the model Boltzmann description accurate. In the strongest shock wave, the velocity distribution function is the bimodal function proposed by Mott-Smith.
Lee, Y.Y.; Barton, D.S.; Claus, J.; Cottingham, J.G.; Courant, E.D.; Danby, G.T.; Dell, G.F.; Forsyth, E.B.; Gupta, R.C.; Kats, J.
1987-01-01
The AGS Booster has three objectives. They are to increase the space charge limit of the AGS, to increase the intensity of the polarized proton beam by accumulating many linac pulses (since the intensity is limited by the polarized ion source), and to reaccelerate heavy ions from the BNL Tandem Van de Graaff before injection into the AGS. The machine is capable of accelerating protons at 7.5 Hertz from 200 MeV to 1.5 GeV or to lower final energies at faster repetition rates. The machine will also be able to accelerate heavy ions from as low as 1 MeV/nucleon to a magnetic rigidity as high as 17.6 Tesla-meters with a one second repetition rate. As an accumulator for polarized protons, the Booster should be able to store the protons at 200 MeV for several seconds. We expect that the Booster will increase the AGS proton intensity by a factor of four, polarized proton intensity by a factor of twenty to thirty, and will also enable the AGS to accelerate all species of heavy ions (at present the AGS heavy ion program is limited to the elements lighter than sulfur because it can only accelerate fully stripped ions). The construction project started in FY 1985 and is expected to be completed in 1989. The purpose of this paper is to provide a future reference for the AGS Booster lattice.
Nuclear reactions from lattice QCD
NASA Astrophysics Data System (ADS)
Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.
2015-02-01
One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, quantum chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three-nucleon (and higher) interactions in a consistent manner. Currently, lattice quantum chromodynamics (LQCD) provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between LQCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from LQCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.
Anyonic braiding in optical lattices
Zhang, Chuanwei; Scarola, V. W.; Tewari, Sumanta; Das Sarma, S.
2007-01-01
Topological quantum states of matter, both Abelian and non-Abelian, are characterized by excitations whose wavefunctions undergo nontrivial statistical transformations as one excitation is moved (braided) around another. Topological quantum computation proposes to use the topological protection and the braiding statistics of a non-Abelian topological state to perform quantum computation. The enormous technological prospect of topological quantum computation provides new motivation for experimentally observing a topological state. Here, we explicitly work out a realistic experimental scheme to create and braid the Abelian topological excitations in the Kitaev model built on a tunable robust system, a cold atom optical lattice. We also demonstrate how to detect the key feature of these excitations: their braiding statistics. Observation of this statistics would directly establish the existence of anyons, quantum particles that are neither fermions nor bosons. In addition to establishing topological matter, the experimental scheme we develop here can also be adapted to a non-Abelian topological state, supported by the same Kitaev model but in a different parameter regime, to eventually build topologically protected quantum gates. PMID:18000038
Lattice Universe: examples and problems.
Brilenkov, Maxim; Eingorn, Maxim; Zhuk, Alexander
We consider lattice Universes with spatial topologies [Formula: see text], [Formula: see text], and [Formula: see text]. In the Newtonian limit of General Relativity, we solve the Poisson equation for the gravitational potential in the enumerated models. In the case of point-like massive sources in the [Formula: see text] model, we demonstrate that the gravitational potential has no definite values on the straight lines joining identical masses in neighboring cells, i.e. at points where masses are absent. Clearly, this is a nonphysical result, since the dynamics of cosmic bodies is not determined in such a case. The only way to avoid this problem and get a regular solution at any point of the cell is the smearing of these masses over some region. Therefore, the smearing of gravitating bodies in [Formula: see text]-body simulations is not only a technical method but also a physically substantiated procedure. In the cases of [Formula: see text] and [Formula: see text] topologies, there is no way to get any physically reasonable and nontrivial solution. The only solutions we can get here are the ones which reduce these topologies to the [Formula: see text] one.
Sequence design in lattice models by graph theoretical methods
NASA Astrophysics Data System (ADS)
Sanjeev, B. S.; Patra, S. M.; Vishveshwara, S.
2001-01-01
A general strategy has been developed based on graph theoretical methods, for finding amino acid sequences that take up a desired conformation as the native state. This problem of inverse design has been addressed by assigning topological indices for the monomer sites (vertices) of the polymer on a 3×3×3 cubic lattice. This is a simple design strategy, which takes into account only the topology of the target protein and identifies the best sequence for a given composition. The procedure allows the design of a good sequence for a target native state by assigning weights for the vertices on a lattice site in a given conformation. It is seen across a variety of conformations that the predicted sequences perform well both in sequence and in conformation space, in identifying the target conformation as native state for a fixed composition of amino acids. Although the method is tested in the framework of the HP model [K. F. Lau and K. A. Dill, Macromolecules 22, 3986 (1989)] it can be used in any context if proper potential functions are available, since the procedure derives unique weights for all the sites (vertices, nodes) of the polymer chain of a chosen conformation (graph).
Group theoretic reduction of Laplacian dynamical problems on fractal lattices
Schwalm, W.A.; Schwalm, M.K.; Giona, M.
1997-06-01
Discrete forms of the Schr{umlt o}dinger equation, the diffusion equation, the linearized Landau-Ginzburg equation, and discrete models for vibrations and spin dynamics belong to a class of Laplacian-based finite difference models. Real-space renormalization of such models on finitely ramified regular fractals is known to give exact recursion relations. It is shown that these recursions commute with Lie groups representing continuous symmetries of the discrete models. Each such symmetry reduces the order of the renormalization recursions by one, resulting in a system of recursions with one fewer variable. Group trajectories are obtained from inverse images of fixed and invariant sets of the recursions. A subset of the Laplacian finite difference models can be mapped by change of boundary conditions and time dependence to a diffusion problem with closed boundaries. In such cases conservation of mass simplifies the group flow and obtaining the groups becomes easier. To illustrate this, the renormalization recursions for Green functions on four standard examples are decoupled. The examples are (1) the linear chain, (2) an anisotropic version of Dhar{close_quote}s 3-simplex, similar to a model dealt with by Hood and Southern, (3) the fourfold coordinated Sierpi{acute n}ski lattice of Rammal and of Domany {ital et al.}, and (4) a form of the Vicsek lattice. Prospects for applying the group theoretic method to more general dynamical systems are discussed. {copyright} {ital 1997} {ital The American Physical Society}
Susceptibility of Naegleria fowleri to delta 9-tetrahydrocannabinol.
Pringle, H L; Bradley, S G; Harris, L S
1979-01-01
Growth of the pathogenic amoeboflagellate Naegleria fowleri is inhibited by delta 9-tetrahydrocannabinol (delta 9-THC). delta 9-THC is amoebostatic at 5 to 50 micrograms/ml. delta 9-THC prevents enflagellation and encystment, but does not impair amoeboid movement. Calf serum at 10 and 20% (vol/vol) reduces the antiamoeba activity of delta 9-THC. Only 1-methoxy delta 8-tetrahydrocannabinol, of 17 cannabinoids tested, failed to inhibit growth of N. fowleri. Antinaeglerial activity was not markedly altered by opening the pyran ring, by converting the cyclohexyl ring to an aromatic ring, or by reversing the hydroxyl and pentyl groups on the benzene ring. delta 9-THC prevented the cytopathic effect of N. fowleri on African green monkey (Vero) cells and human epithelioma (HEp-2) cells in culture. delta 9-THC afforded modest protection to mice infected with N. fowleri. Images PMID:526010
The Mississippi Delta. Reading for Young People.
ERIC Educational Resources Information Center
Dorsett, Cora Matheny, Ed.
As part of a series of regional bibliographies of reading materials, this book presents an annotated list of materials focusing on state and regional history for Arkansas, Louisiana, and Mississippi. Following a brief history about the lower Mississippi Delta region, the book annotates approximately three hundred books, arranged by state and then…
A delta configured auxiliary resonant snubber inverter
Lai, J.S.; Young, R.W.; Ott, G.W. Jr.; McKeever, J.W.; Peng, F.Z. |
1995-09-01
A delta ({Delta}) configured auxiliary resonant snubber inverter is developed to overcome the voltage floating problem in a wye (Y) configured resonant snubber inverter. The proposed inverter is to connect auxiliary resonant branches between phase outputs to avoid a floating point voltage which may cause over-voltage failure of the auxiliary switches. Each auxiliary branch consists of a resonant inductor and a reverse blocking auxiliary switch. Instead of using an anti-paralleled diode to allow resonant current to flow in the reverse direction, as in the Y-configured version, the resonant branch in the {Delta}-configured version must block the negative voltage, typically done by a series diode. This paper shows single-phase and three-phase versions of {Delta}-configured resonant snubber inverters and describes in detail the operating principle of a single-phase version. The extended three-phase version is proposed with non-adjacent state space vector modulation. For hardware implementation, a single-phase 1-kW unit and a three-phase 100-kW unit were built to prove the concept. Experimental results show the superiority of the proposed topology.
Spectroscopic Survey Of Delta Scuti Stars
NASA Astrophysics Data System (ADS)
Kahraman Alicavus, Filiz; Niemczura, Ewa; Polinska, Magdalena; Helminiak, Krzysztof G.; Lampens, Patricia; Molenda-Zakowicz, Joanna; Ukita, Nobuharu; Kambe, Eiji
2016-07-01
We present the results of a spectroscopic study of pulsating stars of Delta Scuti type. The spectral types and luminosity classes, fundamental atmospheric parameters (the effective temperature, surface gravity, microturbulent velocity), detailed chemical composition and projected rotational velocities of a significant number of Delta Scuti-type stars were derived. The spectral classification was performed by comparing the spectra of our targets with the spectra of standard stars. The atmospheric parameters were determined by using different methods. The initial atmospheric parameters were derived from the analysis of photometric indices, the spectral energy distribution and the hydrogen lines, while the final atmospheric parameters were obtained from the analysis of iron lines. The spectrum synthesis method was used to determine chemical compositions of the investigated stars. As a result, we derived accurate atmospheric parameters, the projected rotational velocities and the abundance patterns of analysed sample. These results allow us to examine the position of Delta Scuti-type stars in the H-R diagram, and to investigate the effect of the rotational velocity on pulsation properties and a chemical difference between the Delta Scuti-type stars and the Gamma Doradus and A-F type hybrid stars.
Phi Delta Kappa at the Threshold
ERIC Educational Resources Information Center
Walling, Donovan R.
2006-01-01
Since its fraternal origins a century ago, Phi Delta Kappa (PDK) International has been foremost a society of individuals joined together in professional collegiality and dedicated to tenets of leadership, service, and research in education. As PDK crosses the threshold into its second century, that early spirit of association lit in 1906, like…
Applications of Dirac's Delta Function in Statistics
ERIC Educational Resources Information Center
Khuri, Andre
2004-01-01
The Dirac delta function has been used successfully in mathematical physics for many years. The purpose of this article is to bring attention to several useful applications of this function in mathematical statistics. Some of these applications include a unified representation of the distribution of a function (or functions) of one or several…