Dipolar order by disorder in the classical Heisenberg antiferromagnet on the kagome lattice

NASA Astrophysics Data System (ADS)

Chern, Gia-Wei

2014-03-01

The first experiments on the ``kagome bilayer'' SCGO triggered a wave of interest in kagome antiferromagnets in particular, and frustrated systems in general. A cluster of early seminal theoretical papers established kagome magnets as model systems for novel ordering phenomena, discussing in particular spin liquidity, partial order, disorder-free glassiness and order by disorder. Despite significant recent progress in understanding the ground state for the quantum S = 1 / 2 model, the nature of the low-temperature phase for the classical kagome Heisenberg antiferromagnet has remained a mystery: the non-linear nature of the fluctuations around the exponentially numerous harmonically degenerate ground states has not permitted a controlled theory, while its complex energy landscape has precluded numerical simulations at low temperature. Here we present an efficient Monte Carlo algorithm which removes the latter obstacle. Our simulations detect a low-temperature regime in which correlations saturate at a remarkably small value. Feeding these results into an effective model and analyzing the results in the framework of an appropriate field theory implies the presence of long-range dipolar spin order with a tripled unit cell.

AlInAsSb/GaSb staircase avalanche photodiode

NASA Astrophysics Data System (ADS)

Ren, Min; Maddox, Scott; Chen, Yaojia; Woodson, Madison; Campbell, Joe C.; Bank, Seth

2016-02-01

Over 30 years ago, Capasso and co-workers [IEEE Trans. Electron Devices 30, 381 (1982)] proposed the staircase avalanche photodetector (APD) as a solid-state analog of the photomultiplier tube. In this structure, electron multiplication occurs deterministically at steps in the conduction band profile, which function as the dynodes of a photomultiplier tube, leading to low excess multiplication noise. Unlike traditional APDs, the origin of staircase gain is band engineering rather than large applied electric fields. Unfortunately, the materials available at the time, principally AlxGa1-xAs/GaAs, did not offer sufficiently large conduction band offsets and energy separations between the direct and indirect valleys to realize the full potential of the staircase gain mechanism. Here, we report a true staircase APD operation using alloys of a rather underexplored material, AlxIn1-xAsySb1-y, lattice-matched to GaSb. Single step "staircase" devices exhibited a constant gain of ˜2×, over a broad range of applied bias, operating temperature, and excitation wavelengths/intensities, consistent with Monte Carlo calculations.

Ground-state candidate for the classical dipolar kagome Ising antiferromagnet

NASA Astrophysics Data System (ADS)

Chioar, I. A.; Rougemaille, N.; Canals, B.

2016-06-01

We have investigated the low-temperature thermodynamic properties of the classical dipolar kagome Ising antiferromagnet using Monte Carlo simulations, in the quest for the ground-state manifold. In spite of the limitations of a single-spin-flip approach, we managed to identify certain ordering patterns in the low-temperature regime and we propose a candidate for this unknown state. This configuration presents some intriguing features and is fully compatible with the extrapolations of the at-equilibrium thermodynamic behavior sampled so far, making it a very likely choice for the dipolar long-range ordered state of the classical kagome Ising antiferromagnet.

Mechanical properties and cell-culture characteristics of a polycaprolactone kagome-structure scaffold fabricated by a precision extruding deposition system.

PubMed

Lee, Se-Hwan; Cho, Yong Sang; Hong, Myoung Wha; Lee, Bu-Kyu; Park, Yongdoo; Park, Sang-Hyug; Kim, Young Yul; Cho, Young-Sam

2017-09-13

To enhance the mechanical properties of three-dimensional (3D) scaffolds used for bone regeneration in tissue engineering, many researchers have studied their structure and chemistry. In the structural engineering field, the kagome structure has been known to have an excellent relative strength. In this study, to enhance the mechanical properties of a synthetic polymer scaffold used for tissue engineering, we applied the 3D kagome structure to a porous scaffold for bone regeneration. Prior to fabricating the biocompatible-polymer scaffold, the ideal kagome structure, which was manufactured by a 3D printer of the digital light processing type, was compared with a grid-structure, which was used as the control group, using a compressive experiment. A polycaprolactone (PCL) kagome-structure scaffold was successfully fabricated by additive manufacturing using a 3D printer with a precision extruding deposition head. To assess the physical characteristics of the fabricated PCL-kagome-structure scaffold, we analyzed its porosity, pore size, morphological structure, surface roughness, compressive stiffness, and mechanical bending properties. The results showed that, the mechanical properties of proposed kagome-structure scaffold were superior to those of a grid-structure scaffold. Moreover, Sarcoma osteogenic (Saos-2) cells were used to evaluate the characteristics of in vitro cell proliferation. We carried out cell counting kit-8 (CCK-8) and DNA contents assays. Consequently, the cell proliferation of the kagome-structure scaffold was increased; this could be because the surface roughness of the kagome-structure scaffold enhances initial cell attachment.

A Basin-Wide Examination of the Arctic Ocean's Double-Diffusive Staircase

NASA Astrophysics Data System (ADS)

Shibley, N.; Timmermans, M. L.; Carpenter, J. R.; Toole, J. M.

2016-02-01

The Arctic Ocean thermohaline stratification frequently exhibits a staircase structure above the Atlantic Water Layer consisting of multiple mixed layers of order 1-m in height separated by sharp interfaces. This double-diffusive staircase structure is characterized across the entire Arctic Ocean through a detailed analysis of Ice-Tethered Profiler measurements acquired between 2004 and 2013. Staircase properties (mixed layer thicknesses and temperature-salinity jumps across interfaces) are examined in relation to a bulk vertical density ratio for 50-m spanning the staircase stratification. It is shown that the Lomonosov Ridge serves as an approximate boundary between regions of low density ratio (on the Eurasian side) and higher density ratio (on the Canadian side). We find that the diffusive staircase in the Eurasian Basin is characterized by fewer, thinner mixed layers than that in the Canadian Basin, although the margins of all basins are characterized by relatively thin staircase mixed layers. Using a double-diffusive 4/3 flux law parameterization, the distribution of vertical heat fluxes through the staircase is estimated across the Arctic; it is found that heat fluxes in the Eurasian Basin [O(1) W/m^2] are generally an order of magnitude larger than those in the Canadian Basin [O(0.1) W/m^2].

Frustration and Dzyaloshinsky-Moriya anisotropy in the kagome francisites Cu3Bi (SeO3)2 O2X (X = Br , Cl )

NASA Astrophysics Data System (ADS)

Rousochatzakis, Ioannis; Richter, Johannes; Zinke, Ronald; Tsirlin, Alexander A.

2015-01-01

We investigate the antiferromagnetic canting instability of the spin-1/2 kagome ferromagnet, as realized in the layered cuprates Cu3Bi (SeO3)2 O2X (X = Br , Cl ). While the local canting can be explained in terms of competing exchange interactions, the direction of the ferrimagnetic order parameter fluctuates strongly even at short distances on account of frustration which gives rise to an infinite ground state degeneracy at the classical level. In analogy with the kagome antiferromagnet, the accidental degeneracy is fully lifted only by nonlinear 1 /S corrections, rendering the selected uniform canted phase very fragile even for spins-1/2, as shown explicitly by coupled-cluster calculations. To account for the observed ordering, we show that the minimal description of these systems must include the microscopic Dzyaloshinsky-Moriya interactions, which we obtain from density-functional band-structure calculations. The model explains all qualitative properties of the kagome francisites, including the detailed nature of the ground state and the anisotropic response under a magnetic field. The predicted magnon excitation spectrum and quantitative features of the magnetization process call for further experimental investigations of these compounds.

Quantum Spin Ice under a [111] Magnetic Field: From Pyrochlore to Kagome

NASA Astrophysics Data System (ADS)

Bojesen, Troels Arnfred; Onoda, Shigeki

2017-12-01

Quantum spin ice, modeled for magnetic rare-earth pyrochlores, has attracted great interest for hosting a U(1) quantum spin liquid, which involves spin-ice monopoles as gapped deconfined spinons, as well as gapless excitations analogous to photons. However, the global phase diagram under a [111] magnetic field remains open. Here we uncover by means of unbiased quantum Monte Carlo simulations that a supersolid of monopoles, showing both a superfluidity and a partial ionization, intervenes the kagome spin ice and a fully ionized monopole insulator, in contrast to classical spin ice where a direct discontinuous phase transition takes place. We also show that on cooling, kagome spin ice evolves towards a valence-bond solid similar to what appears in the associated kagome lattice model [S. V. Isakov et al., Phys. Rev. Lett. 97, 147202 (2006), 10.1103/PhysRevLett.97.147202]. Possible relevance to experiments is discussed.

Light propagation in gas-filled kagomé hollow core photonic crystal fibres

NASA Astrophysics Data System (ADS)

Rodrigues, Sílvia M. G.; Facão, Margarida; Ferreira, Mário F. S.

2018-04-01

We study the propagation of light in kagomé hollow core photonic crystal fibres (HC-PCFs) filled with three different noble gases, namely, helium, xenon and argon. Various properties, including the guided modes, the group-velocity dispersion, and the nonlinear parameter were determined. The zero dispersion wavelength and the nonlinear parameter vary with the gas pressure which may be used to tune the generation of new frequencies using the same pump laser and the same fibre. In the case of the kagomé HC-PCF filled with xenon, the zero dispersion wavelength shifts from 693 to 1973 nm when the pressure is increased from 1 to 150bar, while the effective Kerr nonlinearity becomes comparable to that of silica. We have simulated the propagation of femtosecond pulses launched at 790 nm in order to study the generation of supercontinuum and UV light in kagomé HC-PCFs filled with the noble gases.

Guiding properties and dispersion control of kagome lattice hollow-core photonic crystal fibers.

PubMed

Im, Song-Jin; Husakou, Anton; Herrmann, Joachim

2009-07-20

Dispersion properties, loss and optimum design of kagome lattice hollow-core photonic crystal fibers filled with argon are studied for the purpose of possible applications in ultrafast nonlinear optics. As will be shown numerically and by using an approximate analytical formula these fibers exhibit anomalous dispersion for visible or UV wavelengths both for a 1-cell-core as well for a 3-ring-core which can be controlled by the gas pressure and do not suffer from high loss. It is shown that while the loss is mainly influenced by the strut thickness of the kagome lattice the group velocity dispersion is almost independently controlled by the core size. These results demonstrate that kagome lattice hollow fibers have a promising potential in ultrashort pulse delivering of high-energy pulses and in several interesting applications in ultrafast nonlinear optics.

Probabilistic Amplitude Shaping With Hard Decision Decoding and Staircase Codes

NASA Astrophysics Data System (ADS)

Sheikh, Alireza; Amat, Alexandre Graell i.; Liva, Gianluigi; Steiner, Fabian

2018-05-01

We consider probabilistic amplitude shaping (PAS) as a means of increasing the spectral efficiency of fiber-optic communication systems. In contrast to previous works in the literature, we consider probabilistic shaping with hard decision decoding (HDD). In particular, we apply the PAS recently introduced by B\\"ocherer \\emph{et al.} to a coded modulation (CM) scheme with bit-wise HDD that uses a staircase code as the forward error correction code. We show that the CM scheme with PAS and staircase codes yields significant gains in spectral efficiency with respect to the baseline scheme using a staircase code and a standard constellation with uniformly distributed signal points. Using a single staircase code, the proposed scheme achieves performance within $0.57$--$1.44$ dB of the corresponding achievable information rate for a wide range of spectral efficiencies.

Optimal setups for forced-choice staircases with fixed step sizes.

PubMed

García-Pérez, M A

2000-01-01

Forced-choice staircases with fixed step sizes are used in a variety of formats whose relative merits have never been studied. This paper presents a comparative study aimed at determining their optimal format. Factors included in the study were the up/down rule, the length (number of reversals), and the size of the steps. The study also addressed the issue of whether a protocol involving three staircases running for N reversals each (with a subsequent average of the estimates provided by each individual staircase) has better statistical properties than an alternative protocol involving a single staircase running for 3N reversals. In all cases the size of a step up was different from that of a step down, in the appropriate ratio determined by García-Pérez (Vision Research, 1998, 38, 1861 - 1881). The results of a simulation study indicate that a) there are no conditions in which the 1-down/1-up rule is advisable; b) different combinations of up/down rule and number of reversals appear equivalent in terms of precision and cost: c) using a single long staircase with 3N reversals is more efficient than running three staircases with N reversals each: d) to avoid bias and attain sufficient accuracy, threshold estimates should be based on at least 30 reversals: and e) to avoid excessive cost and imprecision, the size of the step up should be between 2/3 and 3/3 the (known or presumed) spread of the psychometric function. An empirical study with human subjects confirmed the major characteristics revealed by the simulations.

Instabilities in a staircase stratified shear flow

NASA Astrophysics Data System (ADS)

Ponetti, G.; Balmforth, N. J.; Eaves, T. S.

2018-01-01

We study stratified shear flow instability where the density profile takes the form of a staircase of interfaces separating uniform layers. Internal gravity waves riding on density interfaces can resonantly interact due to a background shear flow, resulting in the Taylor-Caulfield instability. The many steps of the density profile permit a multitude of interactions between different interfaces, and a rich variety of Taylor-Caulfield instabilities. We analyse the linear instability of a staircase with piecewise-constant density profile embedded in a background linear shear flow, locating all the unstable modes and identifying the strongest. The interaction between nearest-neighbour interfaces leads to the most unstable modes. The nonlinear dynamics of the instabilities are explored in the long-wavelength, weakly stratified limit (the defect approximation). Unstable modes on adjacent interfaces saturate by rolling up the intervening layer into a distinctive billow. These nonlinear structures coexist when stacked vertically and are bordered by the sharp density gradients that are the remnants of the steps of the original staircase. Horizontal averages remain layer-like.

Caffeine and length dependence of staircase potentiation in skeletal muscle.

PubMed

Rassier, D E; Tubman, L A; MacIntosh, B R

1998-01-01

Skeletal muscle sensitivity to Ca2+ is greater at long lengths, and this results in an optimal length for twitch contractions that is longer than optimal length for tetanic contractions. Caffeine abolishes this length dependence of Ca2+ sensitivity. Muscle length (ML) also affects the degree of staircase potentiation. Since staircase potentiation is apparently caused by an increased Ca2+ sensitivity of the myofilaments, we tested the hypothesis that caffeine depresses the length dependence of staircase potentiation. In situ isometric twitch contractions of rat gastrocnemius muscle before and after 10 s of 10-Hz stimulation were analyzed at seven different lengths to evaluate the length dependence of staircase potentiation. In the absence of caffeine, length dependence of Ca2+ sensitivity was observed, and the degree of potentiation after 10-Hz stimulation showed a linear decrease with increased length (DT = 1.47 - 0.05 ML, r2 = 0.95, where DT is developed tension). Length dependence of Ca2+ sensitivity was decreased by caffeine when caffeine was administered in amounts estimated to result in 0.5 and 0.75 mM concentrations. Furthermore, the negative slope of the relationship between staircase potentiation and muscle length was diminished at the lower caffeine dose, and the slope was not different from zero after the higher dose (DT = 1.53 - 0.009 ML, r2 = 0.43). Our study shows that length dependence of Ca2+ sensitivity in intact skeletal muscle is diminished by caffeine. Caffeine also suppressed the length dependence of staircase potentiation, suggesting that the mechanism of this length dependence may be closely related to the mechanism for length dependence of Ca2+ sensitivity.

Fusion splice between tapered inhibited coupling hypocycloid-core Kagome fiber and SMF.

PubMed

Zheng, Ximeng; Debord, Benoît; Vincetti, Luca; Beaudou, Benoît; Gérôme, Frédéric; Benabid, Fetah

2016-06-27

We report for the first time on tapering inhibited coupling (IC) hypocycloid-core shape Kagome hollow-core photonic crystal fibers whilst maintaining their delicate core-contour negative curvature with a down-ratio as large as 2.4. The transmission loss of down-tapered sections reaches a figure as low as 0.07 dB at 1550 nm. The tapered IC fibers are also spliced to standard SMF with a total insertion loss of 0.48 dB. These results show that all-fiber photonic microcells with the ultra-low loss hypocycloid core-contour Kagome fibers is now possible.

How mesoscopic staircases condense to macroscopic barriers in confined plasma turbulence

NASA Astrophysics Data System (ADS)

Ashourvan, Arash; Diamond, P. H.

2016-11-01

This Rapid Communication sets forth the mechanism by which mesoscale staircase structures condense to form macroscopic states of enhanced confinement. Density, vorticity, and turbulent potential enstrophy are the variables for this model. Formation of the staircase structures is due to inhomogeneous mixing of (generalized) potential vorticity (PV). Such mixing results in the local sharpening of density and vorticity gradients. When PV gradients steepen, the density staircase structure develops into a lattice of mesoscale "jumps" and "steps," which are, respectively, regions of local gradient steepening and flattening. The jumps then merge and migrate in radius, leading to the emergence of a new macroscale profile structure, so indicating that profile self-organization is a global process, which may be described by a local, but nonlinear model. This work predicts and demonstrates how mesoscale condensation of staircases leads to global states of enhanced confinement.

On the emergence of macroscopic transport barriers from staircase structures

NASA Astrophysics Data System (ADS)

Ashourvan, Arash; Diamond, P. H.

2017-01-01

This paper presents a theory for the formation and evolution of coupled density staircases and zonal shear profiles in a simple model of drift-wave turbulence. Density, vorticity, and fluctuation potential enstrophy are the fields evolved in this system. Formation of staircase structures is due to inhomogeneous mixing of generalized potential vorticity (PV), resulting in the sharpening of density and vorticity gradients in some regions, and weakening them in others. When the PV gradients steepen, the density staircase structure develops into a lattice of mesoscale "jumps," and "steps," which are, respectively, the regions of local gradient steepening and flattening. The jumps merge and migrate in radius, leading to the development of macroscale profile structures from mesoscale elements. The positive feedback process, which drives the staircase formation occurs via a Rhines scale dependent mixing length. We present extensive studies of bifurcation physics of the global state, including results on the global flux-gradient relations (flux landscapes) predicted by the model. Furthermore, we demonstrate that, depending on the sources and boundary conditions, either a region of enhanced confinement, or a region with strong turbulence can form at the edge. This suggests that the profile self-organization is a global process, though one which can be described by a local, but nonlinear model. This model is the first to demonstrate how the mesoscale condensation of staircases leads to global states of enhanced confinement.

Tropical Pacific variability as a key pacemaker of the global warming staircase

NASA Astrophysics Data System (ADS)

Kosaka, Y.; Xie, S. P.

2016-12-01

Global-mean surface temperature (GMST) has increased since the 19th century with notable interdecadal accelerations and slowdowns, forming the global-warming "staircase". The last step of this staircase is the surface warming slowdown since the late 1990s, for which the transition of the Interdecadal Pacific Oscillation (IPO) from a positive to negative state has been suggested as the leading mechanism. To examine the role of IPO in the entire warming staircase, a long pacemaker experiment is performed with a coupled climate model where tropical Pacific sea surface temperatures are forced to follow the observed evolution since the late 19th century. The pacemaker experiment successfully reproduces the staircase-like global warming remarkably well since 1900. Without the tropical Pacific effect, the same model produces a continual warming from the 1900s to the 1960 followed by rapid warming. The successful reproduction identifies the tropical Pacific decadal variability as a key pacemaker of the GMST staircase. We further propose a method to remove internal variability from observed GMST changes for real-time monitoring of anthropogenic warming.

Room-temperature Coulomb staircase in semiconducting InP nanowires modulated with light illumination.

PubMed

Yamada, Toshishige; Yamada, Hidenori; Lohn, Andrew J; Kobayashi, Nobuhiko P

2011-02-04

Detailed electron transport analysis is performed for an ensemble of conical indium phosphide nanowires bridging two hydrogenated n(+)-silicon electrodes. The current-voltage (I-V) characteristics exhibit a Coulomb staircase in the dark with a period of ∼ 1 V at room temperature. The staircase is found to disappear under light illumination. This observation can be explained by assuming the presence of a tiny Coulomb island, and its existence is possible due to the large surface depletion region created within contributing nanowires. Electrons tunnel in and out of the Coulomb island, resulting in the Coulomb staircase I-V. Applying light illumination raises the electron quasi-Fermi level and the tunneling barriers are buried, causing the Coulomb staircase to disappear.

Elastic moduli of the distorted Kagome-lattice ferromagnet Nd3Ru4Al12

NASA Astrophysics Data System (ADS)

Suzuki, Takashi; Mizuno, Takuyou; Takezawa, Kohki; Kamikawa, Shuhei; Andreev, Alexander V.; Gorbunov, Denis I.; Henriques, Margarida S.; Ishii, Isao

2018-05-01

The distorted kagome-lattice compound Nd3Ru4Al12 has the hexagonal structure. This compound is reported as a ferromagnet in which spins are aligned along the c-axis with the Curie temperature TC = 39 K . The nature of localized f-electrons is expected in Nd3Ru4Al12, and magnetic anisotropy can be attributed to a crystal electric field (CEF) effect. We performed ultrasonic measurements on a Nd3Ru4Al12 single-crystalline sample in order to investigate the phase transition at TC and the CEF effect. All longitudinal and transverse elastic moduli increase monotonically with decreasing temperature, and no clear elastic softening due to a quadrupole interaction is detected under the hexagonal CEF. This result is in contrast to an isomorphic compound Dy3Ru4Al12 with a remarkable elastic softening of the transverse modulus C44. At the ferromagnetic phase transition, the moduli show obvious elastic anomalies, suggesting characteristic couplings between a strain and a magnetic order parameter.

Thermohaline Staircases in the Amundsen Basin: possible disruption by shear and mixing.

NASA Astrophysics Data System (ADS)

Guthrie, J.; Fer, I.; Morison, J.

2016-02-01

As part of the 2013 and 2014 Field Seasons of the North Pole Environmental Observatory in the Amundsen Basin of the Arctic Ocean, two temperature microstructure experiments were performed. A Rockland Scientific Microrider with FP07 fast response thermistors was attached to a Conductivity-Temperature-Depth unit (SBE 19+ in 2013, SBE 911 in 2014). From a heated hut, the instrument package was lowered through a 30" hole in the sea ice at a speed of 25 cm s-1 with a motorized winch. The 2013 data set was characterized by an extensive thermohaline staircase, indicative of the diffusive convective type of double diffusion (DDC), from 150-250 m depths. The staircase was absent in the upper part of that depth range in 2014, even though an analysis of density ratio, Rρ, still shows high susceptibility to DDC. In the depth range of interest, survey averaged Rρ = 3 in 2013 and Rρ = 3.3 in 2014, indicating that hydrographic differences might not be the cause of staircase disappearance. We propose that increased upper ocean shear and turbulent mixing, possibly associated with strong wind events, caused disruption of the staircase in 2014. Average thermal diffusivity, KT, between 70 - 120 m is elevated in 2014, 7 x 10-6 m2s-1, compared to 2013, 2 x 10-6 m2s-1. Also, finescale shear variance between 70-200 m calculated from eXpendable Current Profilers in 2014 is nearly 3 times as high when compared to 2013. Despite increased turbulence over the staircase region in 2014, heat fluxes are remarkably consistent between the surveys. Even though they have been previously reported and the basin has favorable stratification, DDC staircases are less prevalent in the Amundsen Basin when compared to the Canada Basin. Possible reasons behind the lack of an omnipresent thermohaline staircase in the Amundsen Basin will be discussed.

Unique atom hyper-kagome order in Na4Ir3O8 and in low-symmetry spinel modifications.

PubMed

Talanov, V M; Shirokov, V B; Talanov, M V

2015-05-01

Group-theoretical and thermodynamic methods of the Landau theory of phase transitions are used to investigate the hyper-kagome atomic order in structures of ordered spinels and a spinel-like Na4Ir3O8 crystal. The formation of an atom hyper-kagome sublattice in Na4Ir3O8 is described theoretically on the basis of the archetype (hypothetical parent structure/phase) concept. The archetype structure of Na4Ir3O8 has a spinel-like structure (space group Fd\\bar 3m) and composition [Na1/2Ir3/2](16d)[Na3/2](16c)O(32e)4. The critical order parameter which induces hypothetical phase transition has been stated. It is shown that the derived structure of Na4Ir3O8 is formed as a result of the displacements of Na, Ir and O atoms, and ordering of Na, Ir and O atoms, ordering dxy, dxz, dyz orbitals as well. Ordering of all atoms takes place according to the type 1:3. Ir and Na atoms form an intriguing atom order: a network of corner-shared Ir triangles called a hyper-kagome lattice. The Ir atoms form nanoclusters which are named decagons. The existence of hyper-kagome lattices in six types of ordered spinel structures is predicted theoretically. The structure mechanisms of the formation of the predicted hyper-kagome atom order in some ordered spinel phases are established. For a number of cases typical diagrams of possible crystal phase states are built in the framework of the Landau theory of phase transitions. Thermodynamical conditions of hyper-kagome order formation are discussed by means of these diagrams. The proposed theory is in accordance with experimental data.

Monte Carlo simulations of kagome lattices with magnetic dipolar interactions

NASA Astrophysics Data System (ADS)

Plumer, Martin; Holden, Mark; Way, Andrew; Saika-Voivod, Ivan; Southern, Byron

Monte Carlo simulations of classical spins on the two-dimensional kagome lattice with only dipolar interactions are presented. In addition to revealing the sixfold-degenerate ground state, the nature of the finite-temperature phase transition to long-range magnetic order is discussed. Low-temperature states consisting of mixtures of degenerate ground-state configurations separated by domain walls can be explained as a result of competing exchange-like and shape-anisotropy-like terms in the dipolar coupling. Fluctuations between pairs of degenerate spin configurations are found to persist well into the ordered state as the temperature is lowered until locking in to a low-energy state. Results suggest that the system undergoes a continuous phase transition at T ~ 0 . 43 in agreement with previous MC simulations but the nature of the ordering process differs. Preliminary results which extend this analysis to the 3D fcc ABC-stacked kagome systems will be presented.

Emergent order in the kagome Ising magnet Dy3Mg2Sb3O14

PubMed Central

Paddison, Joseph A. M.; Ong, Harapan S.; Hamp, James O.; Mukherjee, Paromita; Bai, Xiaojian; Tucker, Matthew G.; Butch, Nicholas P.; Castelnovo, Claudio; Mourigal, Martin; Dutton, S. E.

2016-01-01

The Ising model—in which degrees of freedom (spins) are binary valued (up/down)—is a cornerstone of statistical physics that shows rich behaviour when spins occupy a highly frustrated lattice such as kagome. Here we show that the layered Ising magnet Dy3Mg2Sb3O14 hosts an emergent order predicted theoretically for individual kagome layers of in-plane Ising spins. Neutron-scattering and bulk thermomagnetic measurements reveal a phase transition at ∼0.3 K from a disordered spin-ice-like regime to an emergent charge ordered state, in which emergent magnetic charge degrees of freedom exhibit three-dimensional order while spins remain partially disordered. Monte Carlo simulations show that an interplay of inter-layer interactions, spin canting and chemical disorder stabilizes this state. Our results establish Dy3Mg2Sb3O14 as a tuneable system to study interacting emergent charges arising from kagome Ising frustration. PMID:27996012

Staircase and Fractional Part Functions

ERIC Educational Resources Information Center

Amram, Meirav; Dagan, Miriam; Ioshpe, Michael; Satianov, Pavel

2016-01-01

The staircase and fractional part functions are basic examples of real functions. They can be applied in several parts of mathematics, such as analysis, number theory, formulas for primes, and so on; in computer programming, the floor and ceiling functions are provided by a significant number of programming languages--they have some basic uses in…

Thermohaline staircases in the Amundsen Basin: Possible disruption by shear and mixing

NASA Astrophysics Data System (ADS)

Guthrie, John D.; Fer, Ilker; Morison, James H.

2017-10-01

As part of the 2013 and 2014 North Pole Environmental Observatories (NPEO) in the Amundsen Basin of the Arctic Ocean, two similar temperature microstructure experiments were performed with different results. In 2013, vertical fluxes were through a thermohaline staircase, and in 2014, the thermohaline staircase was largely absent. Here we investigate the reasons for this difference. The 2013 data set was characterized by an extensive thermohaline staircase, indicative of the diffusive convective type of double diffusion (DC), from 120 to 250 m depths. The staircase was absent above 200 m in 2014, even though analysis of density ratio, Rρ, still shows high susceptibility to DDC. In the depth range of interest, survey-averaged Rρ = 3.8 in 2013 and Rρ = 3.6 in 2014, indicating that the temperature-salinity structure in the pycnocline was not the cause of the lack of a staircase in 2014. We propose that exceptionally weak turbulent mixing, even for the typically quiescent Arctic Ocean, allowed formation of the staircase in 2013. Average thermal diffusivity, KT, between 50 and 120 m is elevated in 2014, 2 × 10-5 m2 s-1, compared to 2013, 1 × 10-6 m2 s-1. However, vertical Atlantic Water (AW) DC heat fluxes in 2013 are remarkably consistent with turbulent heat fluxes in 2014. Similar data sets collected in 2007 and 2008 both resemble 2014, showing consistently higher mixing values compared to 2013. The suppression of turbulence during NPEO 2013 resulted from increased near-surface stratification, possibly caused by a different large-scale circulation pattern that year.

Seismic Oceanography in the Tyrrhenian Sea: Thermohaline Staircases, Eddies, and Internal Waves

NASA Astrophysics Data System (ADS)

Buffett, G. G.; Krahmann, G.; Klaeschen, D.; Schroeder, K.; Sallarès, V.; Papenberg, C.; Ranero, C. R.; Zitellini, N.

2017-11-01

We use seismic oceanography to document and analyze oceanic thermohaline fine structure across the Tyrrhenian Sea. Multichannel seismic (MCS) reflection data were acquired during the MEDiterranean OCcidental survey in April-May 2010. We deployed along-track expendable bathythermograph probes simultaneous with MCS acquisition. At nearby locations we gathered conductivity-temperature-depth data. An autonomous glider survey added in situ measurements of oceanic properties. The seismic reflectivity clearly delineates thermohaline fine structure in the upper 2,000 m of the water column, indicating the interfaces between Atlantic Water/Winter Intermediate Water, Levantine Intermediate Water, and Tyrrhenian Deep Water. We observe the Northern Tyrrhenian Anticyclone, a near-surface mesoscale eddy, plus laterally and vertically extensive thermohaline staircases. Using MCS, we are able to fully image the anticyclone to a depth of 800 m and to confirm the horizontal continuity of the thermohaline staircases of more than 200 km. The staircases show the clearest step-like gradients in the center of the basin while they become more diffuse toward the periphery and bottom, where impedance gradients become too small to be detected by MCS. We quantify the internal wave field and find it to be weak in the region of the eddy and in the center of the staircases, while it is stronger near the coastlines. Our results indicate this is because of the influence of the boundary currents, which disrupt the formation of staircases by preventing diffusive convection. In the interior of the basin, the staircases are clearer and the internal wave field weaker, suggesting that other mixing processes such as double diffusion prevail.

Topologically non-trivial electronic and magnetic states in doped copper Kagome lattices

NASA Astrophysics Data System (ADS)

Guterding, Daniel; Jeschke, Harald O.; Valenti, Roser

We present a theoretical investigation of doped copper kagome materials based on natural minerals Herbertsmithite [ZnCu3(OH)6Cl2] and Barlowite[Cu4(OH)6FBr]. Using ab-initio density functional theory calculations we estimate the stability of the hypothetical compounds against structural distortions and analyze their electronic and magnetic properties. We find that materials based on Herbertsmithite present an ideal playground for investigating the interplay of non-trivial band-topology and strong electronic correlation effects. In particular, we propose candidates for the Quantum Spin Hall effect at filling 4/3 and the Quantum Anomalous Hall effect at filling 2/3. For the Barlowite system we point out a route to realize a Quantum Spin Liquid. This work was supported by Deutsche Forschungsgemeinschaft under Grant No. SFB/TR 49 and the National Science Foundation under Grant No. PHY11-25915.

Spin frustration in a family of pillared kagomé layers of high-spin cobalt(II) ions.

PubMed

Wang, Long-Fei; Li, Cui-Jin; Chen, Yan-Cong; Zhang, Ze-Min; Liu, Jiang; Lin, Wei-Quan; Meng, Yan; Li, Quan-Wen; Tong, Ming-Liang

2015-02-02

Based on the analogous kagomé [Co3 (imda)2 ] layers (imda=imidazole-4,5-dicarboxylate), a family of pillar-layered frameworks with the formula of [Co3 (imda)2 (L)3 ]⋅(L)n ⋅xH2 O (1: L=pyrazine, n=0, x=8; 2: L=4,4'-bipyridine, n=1, x=8; 3: L=1,4-di(pyridin-4-yl)benzene, n=1, x=13; 4: L=4,4'-di(pyridin-4-yl)-1,1'-biphenyl, n=1, x=14) have been successfully synthesized by a hydrothermal/solvothermal method. Single-crystal structural analysis shows a significant increase in the interlayer distances synchronized with the extension of the pillar ligands, namely, 7.092(3) (1), 10.921(6) (2), 14.780(5) (3), and 19.165(4) Å (4). Despite the wrinkled kagomé layers in complexes 2-4, comprehensive magnetic characterizations revealed weakening of interlayer magnetic interactions and an increase in the degree of frustration as the pillar ligand becomes longer from 1 to 4; this leads to characteristic magnetic ground states. For compound 4, which has the longest interlayer distance, the interlayer interaction is so weak that the magnetic properties observed within the range of temperature measured would correspond to the frustrated layer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The staircase method: integrals for periodic reductions of integrable lattice equations

NASA Astrophysics Data System (ADS)

van der Kamp, Peter H.; Quispel, G. R. W.

2010-11-01

We show, in full generality, that the staircase method (Papageorgiou et al 1990 Phys. Lett. A 147 106-14, Quispel et al 1991 Physica A 173 243-66) provides integrals for mappings, and correspondences, obtained as traveling wave reductions of (systems of) integrable partial difference equations. We apply the staircase method to a variety of equations, including the Korteweg-De Vries equation, the five-point Bruschi-Calogero-Droghei equation, the quotient-difference (QD)-algorithm and the Boussinesq system. We show that, in all these cases, if the staircase method provides r integrals for an n-dimensional mapping, with 2r, then one can introduce q <= 2r variables, which reduce the dimension of the mapping from n to q. These dimension-reducing variables are obtained as joint invariants of k-symmetries of the mappings. Our results support the idea that often the staircase method provides sufficiently many integrals for the periodic reductions of integrable lattice equations to be completely integrable. We also study reductions on other quad-graphs than the regular {\\ Z}^2 lattice, and we prove linear growth of the multi-valuedness of iterates of high-dimensional correspondences obtained as reductions of the QD-algorithm.

New 3D coordination polymers constructed from pillared metal-formate Kagomé layers exhibiting spin canting only in the nickel(II) complex.

PubMed

Li, Zuo-Xi; Zhao, Jiong-Peng; Sañudo, E C; Ma, Hong; Pan, Zhong-Da; Zeng, Yong-Fei; Bu, Xian-He

2009-12-21

Sparked by the strategy of pillared-layer MOFs, three formate coordination polymers, {[Ni(2)(HCO(2))(3)(L)(2)](NO(3)).2H(2)O}(infinity) (1), {[Co(2)(HCO(2))(3)(L)(2)](HCO(2)).2H(2)O}(infinity) (2), and {[Cu(2)(HCO(2))(3)(L)(2)](HCO(2)).2H(2)O}(infinity) (3), have been synthesized by employing the rodlike ligand 4,4'-bis(imidazol-1-yl)biphenyl (L) as the pillar. Structural analysis indicates that the title complexes 1-3 are isostructural compounds, which possess metal-formate 2D layers perpendicularly pillared by the ligand L to afford a 3D open framework. This is an interesting example of a Kagome lattice based on the formate mediator. Moreover, the formate anion of this 2D Kagome layer exhibits various bridging modes: anti-anti, syn-anti, and 3.21 modes. Their magnetic measurements reveals that only complex 1 presents the spin canting phenomenon, while its isostructural Co(II) and Cu(II) complexes are simply paramagnets with antiferromagnetic coupling.

Devil's staircases and continued fractions in Josephson junctions

NASA Astrophysics Data System (ADS)

Shukrinov, Yu. M.; Medvedeva, S. Yu.; Botha, A. E.; Kolahchi, M. R.; Irie, A.

2013-12-01

Detailed numerical simulations of the IV characteristics of a Josephson junction under external electromagnetic radiation show the devil's staircase within different bias current intervals. We have found that the observed steps form very precisely continued fractions. Increase of the amplitude of the radiation shifts the devil's staircase to higher Shapiro steps. An algorithm for the appearance and detection of subharmonics with increasing radiation amplitude is proposed. We demonstrate that the subharmonic steps registered in the well-known experiments by Dayem and Wiegand [Phys. Rev. 155, 419 (1967), 10.1103/PhysRev.155.419] and Clarke [Phys. Rev. B 4, 2963 (1971), 10.1103/PhysRevB.4.2963] also form continued fractions.

High Power Spark Delivery System Using Hollow Core Kagome Lattice Fibers

PubMed Central

Dumitrache, Ciprian; Rath, Jordan; Yalin, Azer P.

2014-01-01

This study examines the use of the recently developed hollow core kagome lattice fibers for delivery of high power laser pulses. Compared to other photonic crystal fibers (PCFs), the hollow core kagome fibers have larger core diameter (~50 µm), which allows for higher energy coupling in the fiber while also maintaining high beam quality at the output (M2 = 1.25). We have conducted a study of the maximum deliverable energy versus laser pulse duration using a Nd:YAG laser at 1064 nm. Pulse energies as high as 30 mJ were transmitted for 30 ns pulse durations. This represents, to our knowledge; the highest laser pulse energy delivered using PCFs. Two fiber damage mechanisms were identified as damage at the fiber input and damage within the bulk of the fiber. Finally, we have demonstrated fiber delivered laser ignition on a single-cylinder gasoline direct injection engine. PMID:28788155

GdPtPb: A noncollinear antiferromagnet with distorted kagome lattice

DOE PAGES

Manni, S.; Bud'ko, Sergey L.; Canfield, Paul C.

2017-08-24

In the spirit of searching for Gd-based, frustrated, rare earth magnets, we have found antiferomagnetism (AF) in GdPtPb, which crystallizes in the ZrNiAl-type structure that has a distorted kagome lattice of Gd triangles. Single crystals were grown and investigated using structural, magnetic, transport, and thermodynamic measurements. GdPtPb orders antiferromagnetically at 15.5 K, arguably with a planar, noncollinear structure. The high temperature magnetic susceptibility data reveal an “anti-frustration” behavior having a frustration parameter, |f| = |Θ|/T N = 0.25, which can be explained by mean field theory within a two-sublattice model. Here, the study of the magnetic phase diagram down tomore » T = 1.8K reveals a change of magnetic structure through a metamagnetic transition at around 20 kOe and the disappearance of the AF ordering near 140 kOe. In total, our work indicates that GdPtPb can serve as an example of a planar, noncollinear AF with a distorted kagome magnetic sublattice.« less

Development of an integrated staircase lift for home access.

PubMed

Mattie, Johanne L; Borisoff, Jaimie F; Leland, Danny; Miller, William C

2015-12-01

Stairways into buildings present a significant environmental barrier for those with mobility impairments, including older adults. A number of home access solutions that allow users to safely enter and exit the home exist, however these all have some limitations. The purpose of this work was to develop a novel, inclusive home access solution that integrates a staircase and a lift into one device. The development of an integrated staircase lift followed a structured protocol with stakeholders providing feedback at various stages in the design process, consistent with rehabilitation engineering design methods. A novel home access device was developed. The integrated staircase-lift has the following features: inclusivity, by a universal design that provides an option for either use of stairs or a lift; constant availability, with a lift platform always ready for use on either level; and potential aesthetic advantages when integrating the device into an existing home. The potential also exists for emergency descent during a power outage, and self-powered versions. By engaging stakeholders in a user centred design process, insight on the limitations of existing home access solutions and specific feedback on our design guided development of a novel home access device.

Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid

DOE PAGES

Jiang, Hong -Chen; Devereaux, T.; Kivelson, S. A.

2017-08-07

We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the t–J model on a kagome lattice with a small but nonzero concentration δ of doped holes. It is now widely accepted that the undoped (δ = 0) spin-1/2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole permore » unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. In conclusion, our results may be relevant to kagome lattice herbertsmithite upon doping.« less

Staircase and fractional part functions

NASA Astrophysics Data System (ADS)

Amram, Meirav; Dagan, Miriam; Ioshpe, Michael; Satianov, Pavel

2016-10-01

The staircase and fractional part functions are basic examples of real functions. They can be applied in several parts of mathematics, such as analysis, number theory, formulas for primes, and so on; in computer programming, the floor and ceiling functions are provided by a significant number of programming languages - they have some basic uses in various programming tasks. In this paper, we view the staircase and fractional part functions as a classical example of non-continuous real functions. We introduce some of their basic properties, present some interesting constructions concerning them, and explore some intriguing interpretations of such functions. Throughout the paper, we use these functions in order to explain basic concepts in a first calculus course, such as domain of definition, discontinuity, and oddness of functions. We also explain in detail how, after researching the properties of such functions, one can draw their graph; this is a crucial part in the process of understanding their nature. In the paper, we present some subjects that the first-year student in the exact sciences may not encounter. We try to clarify those subjects and show that such ideas are important in the understanding of non-continuous functions, as a part of studying analysis in general.

22. First floor, staircase, looking east Veterans Administration Center, ...

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

22. First floor, staircase, looking east - Veterans Administration Center, Officers Duplex Quarters, 5302 East Kellogg (Legal Address); 5500 East Kellogg (Common Address), Wichita, Sedgwick County, KS

23. First floor, staircase, detail of newel post Veterans ...

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

23. First floor, staircase, detail of newel post - Veterans Administration Center, Officers Duplex Quarters, 5302 East Kellogg (Legal Address); 5500 East Kellogg (Common Address), Wichita, Sedgwick County, KS

30. Second floor, room north of staircase, looking northwest ...

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

30. Second floor, room north of staircase, looking northwest - Veterans Administration Center, Officers Duplex Quarters, 5302 East Kellogg (Legal Address); 5500 East Kellogg (Common Address), Wichita, Sedgwick County, KS

24. First floor, staircase, detail of newel post base ...

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

24. First floor, staircase, detail of newel post base - Veterans Administration Center, Officers Duplex Quarters, 5302 East Kellogg (Legal Address); 5500 East Kellogg (Common Address), Wichita, Sedgwick County, KS

31. Second floor, room north of staircase, looking southwest ...

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

31. Second floor, room north of staircase, looking southwest - Veterans Administration Center, Officers Duplex Quarters, 5302 East Kellogg (Legal Address); 5500 East Kellogg (Common Address), Wichita, Sedgwick County, KS

29. Second floor, room north of staircase, looking west ...

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

29. Second floor, room north of staircase, looking west - Veterans Administration Center, Officers Duplex Quarters, 5302 East Kellogg (Legal Address); 5500 East Kellogg (Common Address), Wichita, Sedgwick County, KS

Solutions for correlations along the coexistence curve and at the critical point of a kagomé lattice gas with three-particle interactions

NASA Astrophysics Data System (ADS)

Barry, J. H.; Muttalib, K. A.; Tanaka, T.

2008-01-01

We consider a two-dimensional (d=2) kagomé lattice gas model with attractive three-particle interactions around each triangular face of the kagomé lattice. Exact solutions are obtained for multiparticle correlations along the liquid and vapor branches of the coexistence curve and at criticality. The correlation solutions are also determined along the continuation of the curvilinear diameter of the coexistence region into the disordered fluid region. The method generates a linear algebraic system of correlation identities with coefficients dependent only upon the interaction parameter. Using a priori knowledge of pertinent solutions for the density and elementary triplet correlation, one finds a closed and linearly independent set of correlation identities defined upon a spatially compact nine-site cluster of the kagomé lattice. Resulting exact solution curves of the correlations are plotted and discussed as functions of the temperature and are compared with corresponding results in a traditional kagomé lattice gas having nearest-neighbor pair interactions. An example of application for the multiparticle correlations is demonstrated in cavitation theory.

Carbon kagome lattice and orbital-frustration-induced metal-insulator transition for optoelectronics.

PubMed

Chen, Yuanping; Sun, Y Y; Wang, H; West, D; Xie, Yuee; Zhong, J; Meunier, V; Cohen, Marvin L; Zhang, S B

2014-08-22

A three-dimensional elemental carbon kagome lattice, made of only fourfold-coordinated carbon atoms, is proposed based on first-principles calculations. Despite the existence of 60° bond angles in the triangle rings, widely perceived to be energetically unfavorable, the carbon kagome lattice is found to display exceptional stability comparable to that of C(60). The system allows us to study the effects of triangular frustration on the electronic properties of realistic solids, and it demonstrates a metal-insulator transition from that of graphene to a direct gap semiconductor in the visible blue region. By minimizing s-p orbital hybridization, which is an intrinsic property of carbon, not only the band edge states become nearly purely frustrated p states, but also the band structure is qualitatively different from any known bulk elemental semiconductors. For example, the optical properties are similar to those of direct-gap semiconductors GaN and ZnO, whereas the effective masses are comparable to or smaller than those of Si.

A training paradigm to enhance motor recovery in contused rats: effects of staircase training.

PubMed

Singh, Anita; Murray, Marion; Houle, John D

2011-01-01

Ambulating on stairs is an important aspect of daily activities for many individuals with incomplete spinal cord injury (SCI), and little is known about the effect of training for this specific task. The goal of this study was to determine whether staircase ascent training enhances motor recovery in animals with contusion injury. Rats received a midthoracic contusion lesion of moderate severity and were randomly divided into 2 groups, with one group receiving staircase ascent training for up to 8 weeks and the other receiving no training. To assess the direct effect of training, a task-specific staircase climbing test was performed. Open field test (BBB) and gait analysis (CatWalk) assessed overground recovery, and a grid test was used to assess improvement in sensorimotor tasks. Changes in muscle mass of the forelimb and hindlimb muscles were also measured, and the extent of spared white matter was determined for lesion verification and anatomical correlations. Staircase training improved the task-specific performance of ascent. Gait parameters, including base of support, stride length, regularity index (RI), and step sequence, also improved. Overground locomotion and the grid test, both showed a trend of improved performance. Finally, hindlimb muscle mass was maintained with training. Staircase ascent training after incomplete SCI has beneficial effects on task-specific as well as nonspecific motor and sensorimotor activities.

Length dependence of staircase potentiation: interactions with caffeine and dantrolene sodium.

PubMed

Rassier, D E; MacIntosh, B R

2000-04-01

In skeletal muscle, there is a length dependence of staircase potentiation for which the mechanism is unclear. In this study we tested the hypothesis that abolition of this length dependence by caffeine is effected by a mechanism independent of enhanced Ca2+ release. To test this hypothesis we have used caffeine, which abolishes length dependence of potentiation, and dantrolene sodium, which inhibits Ca2+ release. In situ isometric twitch contractions of rat gastrocnemius muscle before and after 20 s of repetitive stimulation at 5 Hz were analyzed at optimal length (Lo), Lo - 10%, and Lo + 10%. Potentiation was observed to be length dependent, with an increase in developed tension (DT) of 78 +/- 12, 51 +/- 5, and 34 +/- 9% (mean +/- SEM), at Lo - 10%, Lo, and Lo + 10%, respectively. Caffeine diminished the length dependence of activation and suppressed the length dependence of staircase potentiation, giving increases in DT of 65+/-13, 53 +/- 11, and 45 +/- 12% for Lo - 10%, Lo, and Lo + 10%, respectively. Dantrolene administered after caffeine did not reverse this effect. Dantrolene alone depressed the potentiation response, but did not affect the length dependence of staircase potentiation, with increases in DT of 58 +/- 17, 26 +/- 8, and 18 +/- 7%, respectively. This study confirms that there is a length dependence of staircase potentiation in mammalian skeletal muscle which is suppressed by caffeine. Since dantrolene did not alter this suppression of the length dependence of potentiation by caffeine, it is apparently not directly modulated by Ca2+ availability in the myoplasm.

Psychological Processes and "The Staircase to Terrorism"

ERIC Educational Resources Information Center

Moghaddam, Fathali M.

2005-01-01

This paper presents replies to the comments of Paniagua and Steiner on his original article on terrorism. The author notes that several points raised by Paniagua and Steiner are insightful and help to broaden the range of factors to be considered on the staircase to terrorism. Steiner highlights the role of incitement, and this points to the…

Phase transitions and thermodynamic properties of antiferromagnetic Ising model with next-nearest-neighbor interactions on the Kagomé lattice

NASA Astrophysics Data System (ADS)

Ramazanov, M. K.; Murtazaev, A. K.; Magomedov, M. A.; Badiev, M. K.

2018-06-01

We study phase transitions and thermodynamic properties in the two-dimensional antiferromagnetic Ising model with next-nearest-neighbor interaction on a Kagomé lattice by Monte Carlo simulations. A histogram data analysis shows that a second-order transition occurs in the model. From the analysis of obtained data, we can assume that next-nearest-neighbor ferromagnetic interactions in two-dimensional antiferromagnetic Ising model on a Kagomé lattice excite the occurrence of a second-order transition and unusual behavior of thermodynamic properties on the temperature dependence.

An adaptive staircase procedure for the E-Prime programming environment.

PubMed

Hairston, W David; Maldjian, Joseph A

2009-01-01

Many studies need to determine a subject's threshold for a given task. This can be achieved efficiently using an adaptive staircase procedure. While the logic and algorithms for staircases have been well established, the few pre-programmed routines currently available to researchers require at least moderate programming experience to integrate into new paradigms and experimental settings. Here, we describe a freely distributed routine developed for the E-Prime programming environment that can be easily integrated into any experimental protocol with only a basic understanding of E-Prime. An example experiment (visual temporal-order-judgment task) where subjects report the order of occurrence of two circles illustrates the behavior and consistency of the routine.

3. Historic American Buildings Survey, 1966, INTERIOR, DETAIL, ENCLOSED STAIRCASE ...

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

3. Historic American Buildings Survey, 1966, INTERIOR, DETAIL, ENCLOSED STAIRCASE AND TIN SHEETING. - Sig Sautelle Circus Training House, South Main Street (State Route 11), Homer, Cortland County, NY

Interior view of south central staircase, identical primary and rear ...

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

Interior view of south central staircase, identical primary and rear elevation entries, modified Dining Room entry and closet conversation - 5904 Dalecarlia Place (House), Washington, District of Columbia, DC

Tunable Quantum Spin Liquidity in the 1 /6 th-Filled Breathing Kagome Lattice

NASA Astrophysics Data System (ADS)

Akbari-Sharbaf, A.; Sinclair, R.; Verrier, A.; Ziat, D.; Zhou, H. D.; Sun, X. F.; Quilliam, J. A.

2018-06-01

We present measurements on a series of materials, Li2 In1 -xScx Mo3 O8 , that can be described as a 1 /6 th-filled breathing kagome lattice. Substituting Sc for In generates chemical pressure which alters the breathing parameter nonmonotonically. Muon spin rotation experiments show that this chemical pressure tunes the system from antiferromagnetic long range order to a quantum spin liquid phase. A strong correlation with the breathing parameter implies that it is the dominant parameter controlling the level of magnetic frustration, with increased kagome symmetry generating the quantum spin liquid phase. Magnetic susceptibility measurements suggest that this is related to distinct types of charge order induced by changes in lattice symmetry, in line with the theory of Chen et al. [Phys. Rev. B 93, 245134 (2016), 10.1103/PhysRevB.93.245134]. The specific heat for samples at intermediate Sc concentration, which have the minimum breathing parameter, show consistency with the predicted U (1 ) quantum spin liquid.

Exact ground states for the nearest neighbor quantum XXZ model on the kagome and other lattices with triangular motifs at Jz /Jxy = - 1 / 2

NASA Astrophysics Data System (ADS)

Changlani, Hitesh; Kumar, Krishna; Kochkov, Dmitrii; Fradkin, Eduardo; Clark, Bryan

We report the existence of a quantum macroscopically degenerate ground state manifold on the nearest neighbor XXZ model on the kagome lattice at the point Jz /Jxy = - 1 / 2 . On many lattices with triangular motifs (including the kagome, sawtooth, icosidodecahedron and Shastry-Sutherland lattice for a certain choice of couplings) this Hamiltonian is found to be frustration-free with exact ground states which correspond to three-colorings of these lattices. Several results also generalize to the case of variable couplings and to other motifs (albeit with possibly more complex Hamiltonians). The degenerate manifold on the kagome lattice corresponds to a ''many-body flat band'' of interacting hard-core bosons; and for the one boson case our results also explain the well-known non-interacting flat band. On adding realistic perturbations, state selection in this manifold of quantum many-body states is discussed along with the implications for the phase diagram of the kagome lattice antiferromagnet. supported by DE-FG02-12ER46875, DMR 1408713, DE-FG02-08ER46544.

Detail of concrete and stone railings on staircase leading from ...

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

Detail of concrete and stone railings on staircase leading from Shepperds Dell Bridge to trail. - Shepperds Dell Bridge, Spanning Young Creek at Columbia River Highway, Latourell, Multnomah County, OR

26. First floor, staircase, detail of newel post base near ...

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

26. First floor, staircase, detail of newel post base near ceiling - Veterans Administration Center, Officers Duplex Quarters, 5302 East Kellogg (Legal Address); 5500 East Kellogg (Common Address), Wichita, Sedgwick County, KS

Staircase Quantum Dots Configuration in Nanowires for Optimized Thermoelectric Power

PubMed Central

Li, Lijie; Jiang, Jian-Hua

2016-01-01

The performance of thermoelectric energy harvesters can be improved by nanostructures that exploit inelastic transport processes. One prototype is the three-terminal hopping thermoelectric device where electron hopping between quantum-dots are driven by hot phonons. Such three-terminal hopping thermoelectric devices have potential in achieving high efficiency or power via inelastic transport and without relying on heavy-elements or toxic compounds. We show in this work how output power of the device can be optimized via tuning the number and energy configuration of the quantum-dots embedded in parallel nanowires. We find that the staircase energy configuration with constant energy-step can improve the power factor over a serial connection of a single pair of quantum-dots. Moreover, for a fixed energy-step, there is an optimal length for the nanowire. Similarly for a fixed number of quantum-dots there is an optimal energy-step for the output power. Our results are important for future developments of high-performance nanostructured thermoelectric devices. PMID:27550093

Naturally tuned quantum critical point in the S =1 kagomé YCa3(VO) 3(BO3)4

NASA Astrophysics Data System (ADS)

Silverstein, Harlyn J.; Sinclair, Ryan; Sharma, Arzoo; Qiu, Yiming; Heinmaa, Ivo; Leitmäe, Alexander; Wiebe, Christopher R.; Stern, Raivo; Zhou, Haidong

2018-04-01

Although S =1 /2 kagomé systems have been intensely studied theoretically, and within the past decade been realized experimentally, much less is known about the S =1 analogs. While the theoretical ground state is still under debate, it has been found experimentally that S =1 kagomé systems either order at low temperatures or enter a spin glass state. In this work, YCa3(VO) 3(BO3)4 (YCVBO) is presented, with trivalent vanadium. Owing to its unusual crystal structure, the metal-metal bonding is highly connected along all three crystallographic directions, atypical of other kagomé materials. Using neutron scattering it is shown that YCVBO fails to order down to at least 50 mK and exhibits broad and dispersionless excitations. 11B NMR provides evidence of fluctuating spins at low temperatures while dc magnetization shows critical scaling that is also observed in systems near a quantum critical point such as Herbertsmithite, despite its insulating nature and S =1 magnetism. The evidence shown indicates that YCVBO is naturally tuned to be a quantum disordered magnet in the limit of T =0 K.

Staircase tableaux, the asymmetric exclusion process, and Askey-Wilson polynomials

PubMed Central

Corteel, Sylvie; Williams, Lauren K.

2010-01-01

We introduce some combinatorial objects called staircase tableaux, which have cardinality 4nn !, and connect them to both the asymmetric exclusion process (ASEP) and Askey-Wilson polynomials. The ASEP is a model from statistical mechanics introduced in the late 1960s, which describes a system of interacting particles hopping left and right on a one-dimensional lattice of n sites with open boundaries. It has been cited as a model for traffic flow and translation in protein synthesis. In its most general form, particles may enter and exit at the left with probabilities α and γ, and they may exit and enter at the right with probabilities β and δ. In the bulk, the probability of hopping left is q times the probability of hopping right. Our first result is a formula for the stationary distribution of the ASEP with all parameters general, in terms of staircase tableaux. Our second result is a formula for the moments of (the weight function of) Askey-Wilson polynomials, also in terms of staircase tableaux. Since the 1980s there has been a great deal of work giving combinatorial formulas for moments of classical orthogonal polynomials (e.g. Hermite, Charlier, Laguerre); among these polynomials, the Askey-Wilson polynomials are the most important, because they are at the top of the hierarchy of classical orthogonal polynomials. PMID:20348417

Staircase tableaux, the asymmetric exclusion process, and Askey-Wilson polynomials.

PubMed

Corteel, Sylvie; Williams, Lauren K

2010-04-13

We introduce some combinatorial objects called staircase tableaux, which have cardinality 4(n)n!, and connect them to both the asymmetric exclusion process (ASEP) and Askey-Wilson polynomials. The ASEP is a model from statistical mechanics introduced in the late 1960s, which describes a system of interacting particles hopping left and right on a one-dimensional lattice of n sites with open boundaries. It has been cited as a model for traffic flow and translation in protein synthesis. In its most general form, particles may enter and exit at the left with probabilities alpha and gamma, and they may exit and enter at the right with probabilities beta and delta. In the bulk, the probability of hopping left is q times the probability of hopping right. Our first result is a formula for the stationary distribution of the ASEP with all parameters general, in terms of staircase tableaux. Our second result is a formula for the moments of (the weight function of) Askey-Wilson polynomials, also in terms of staircase tableaux. Since the 1980s there has been a great deal of work giving combinatorial formulas for moments of classical orthogonal polynomials (e.g. Hermite, Charlier, Laguerre); among these polynomials, the Askey-Wilson polynomials are the most important, because they are at the top of the hierarchy of classical orthogonal polynomials.

18. VIEW OF STAIRCASE LEADING TO SOCIAL HALL ON CABIN ...

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

18. VIEW OF STAIRCASE LEADING TO SOCIAL HALL ON CABIN (POOP) DECK, LOCATED IN CENTER OF FORWARD END OF DINING SALOON - Steam Schooner WAPAMA, Kaiser Shipyard No. 3 (Shoal Point), Richmond, Contra Costa County, CA

Intrinsic quantum anomalous Hall effect in the kagome lattice Cs 2LiMn 3F 12

DOE PAGES

Xu, Gang; Lian, Biao; Zhang, Shou -Cheng

2015-10-27

In a kagome lattice, the time reversal symmetry can be broken by a staggered magnetic flux emerging from ferromagnetic ordering and intrinsic spin-orbit coupling, leading to several well-separated nontrivial Chern bands and intrinsic quantum anomalous Hall effect. Based on this idea and ab initio calculations, we propose the realization of the intrinsic quantum anomalous Hall effect in the single layer Cs 2Mn 3F 12 kagome lattice and on the (001) surface of a Cs 2LiMn 3F 12 single crystal by modifying the carrier coverage on it, where the band gap is around 20 meV. Furthermore, a simplified tight binding modelmore » based on the in-plane ddσ antibonding states is constructed to understand the topological band structures of the system.« less

12. ENCLOSED SLEEPING PORCH INTERIOR DETAIL SHOWING PULLDOWN STAIRCASE TO ...

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

12. ENCLOSED SLEEPING PORCH INTERIOR DETAIL SHOWING PULL-DOWN STAIRCASE TO ATTIC. VIEW TO SOUTHEAST. - Big Creek Hydroelectric System, Big Creek Town, Operator House, Orchard Avenue south of Huntington Lake Road, Big Creek, Fresno County, CA

Enhancement and diminution of mechanical tension evoked by staircase and by tetanus in rat muscle

PubMed Central

Krarup, Christian

1981-01-01

1. Potentiation of the isometric twitch tension was compared during and after the staircase and after tetanic stimuli in the fast-twitch extensor digitorum longus muscle of adult Lewis rats at 37-38°C. 2. With up to 250 stimuli the potentiation rose with an increase in both the frequency and number of stimuli in the staircase (2-5/sec) and the tetanus (100-167/sec). After a tetanus of 375 stimuli (125/sec) the potentiation was smaller. The potentiation 2 sec after a tetanus of 250 stimuli (167/sec) was + 132 ± 5% (n = 21, s.e. of mean) which was greater (P < 0·001) than at the 250th stimulus at 5/sec, +92±3% (n = 21, s.e. of mean). 3. After the staircase the decay of potentiation was initially slow and later more rapid. This was taken to indicate both the recovery of a process that diminished twitch tension and the decay of a process causing potentiation. After 250 stimuli (5/sec) the rate of decay of the processes causing diminution and potentiation had time constants of 34·5 ± 3·8 sec (n = 18, s.e. of mean) and 102·2 ± 6·6 sec (n = 20, s.e. of mean) respectively. Compared with the potentiation, the process causing diminution became relatively more pronounced the greater the frequency of stimuli. 4. The decay of post-tetanic potentiation showed an initial rapid and a later slower phase of decay. After a tetanus of 250 stimuli (167/sec) the rates of decay had time constants of 5·7 ± 0·8 sec (n = 16, s.e. of mean) and 113·5 ± 8·7 sec (n = 19, s.e. of mean) respectively. 5. Compared with the unpotentiated response the time course of the twitch was shortened initially in the staircase and when the post-tetanic potentiation was low. The contraction time was then increasingly prolonged the greater the potentiation and the greater the number of stimuli in the staircase and in the tetanus. The half-relaxation time was the more prolonged the greater the number of stimuli. 6. Potentiation can be described in terms of a two-compartment model of processes

Magnetic Phase Diagrams and Magnetization Plateaus of the Spin-1/2 Antiferromagnetic Heisenberg Model on a Square-Kagome Lattice with Three Nonequivalent Exchange Interactions

NASA Astrophysics Data System (ADS)

Morita, Katsuhiro; Tohyama, Takami

2018-04-01

Magnetization plateaus in quantum spin systems emerge in two-dimensional frustrated systems such as a kagome lattice. The spin-1/2 antiferromagnetic Heisenberg model on a square-kagome lattice is also appropriate for the study of the magnetization plateau. Motivated by recent experimental findings of such a square kagome lattice with three nonequivalent bonds, we investigate the phase diagrams and magnetization plateaus of the lattice using the exact diagonalization method. In addition to the previously reported 1/3 and 2/3 plateaus in the model with two equivalent bonds, we find a new 2/3 plateau whose magnetic structure is characterized by spontaneously broken four-fold rotational symmetry. The plateau appears only in the case of three nonequivalent bonds. We propose the possibility of finding plateaus including the new one.

Actin filaments, stereocilia, and hair cells of the bird cochlea. V. How the staircase pattern of stereociliary lengths is generated.

PubMed

Tilney, L G; Tilney, M S; Cotanche, D A

1988-02-01

The stereocilia on each hair cell are arranged into rows of ascending height, resulting in what we refer to as a "staircase-like" profile. At the proximal end of the cochlea the length of the tallest row of stereocilia in the staircase is 1.5 micron, with the shortest row only 0.3 micron. As one proceeds towards the distal end of the cochlea the length of the stereocilia progressively increases so that at the extreme distal end the length of the tallest row of the staircase is 5.5 micron and the shortest row is 2 micron. During development hair cells form their staircases in four phases of growth separated from each other by developmental time. First, stereocilia sprout from the apical surfaces of the hair cells (8-10-d embryos). Second (10-12-d embryos), what will be the longest row of the staircase begins to elongate. As the embryo gets older successive rows of stereocilia initiate elongation. Thus the staircase is set up by the sequential initiation of elongation of stereociliary rows located at increased distances from the row that began elongation. Third (12-17-d embryos), all the stereocilia in the newly formed staircase elongate until those located on the first step of the staircase have reached the prescribed length. In the final phase (17-d embryos to hatchlings) there is a progressive cessation of elongation beginning with the shortest step and followed by taller and taller rows with the tallest step stopping last. Thus, to obtain a pattern of stereocilia in rows of increasing height what transpires are progressive go signals followed by a period when all the stereocilia grow and ending with progressive stop signals. We discuss how such a sequence could be controlled.

Actin filaments, stereocilia, and hair cells of the bird cochlea. V. How the staircase pattern of stereociliary lengths is generated

PubMed Central

1988-01-01

The stereocilia on each hair cell are arranged into rows of ascending height, resulting in what we refer to as a "staircase-like" profile. At the proximal end of the cochlea the length of the tallest row of stereocilia in the staircase is 1.5 micron, with the shortest row only 0.3 micron. As one proceeds towards the distal end of the cochlea the length of the stereocilia progressively increases so that at the extreme distal end the length of the tallest row of the staircase is 5.5 micron and the shortest row is 2 micron. During development hair cells form their staircases in four phases of growth separated from each other by developmental time. First, stereocilia sprout from the apical surfaces of the hair cells (8-10-d embryos). Second (10-12-d embryos), what will be the longest row of the staircase begins to elongate. As the embryo gets older successive rows of stereocilia initiate elongation. Thus the staircase is set up by the sequential initiation of elongation of stereociliary rows located at increased distances from the row that began elongation. Third (12-17-d embryos), all the stereocilia in the newly formed staircase elongate until those located on the first step of the staircase have reached the prescribed length. In the final phase (17-d embryos to hatchlings) there is a progressive cessation of elongation beginning with the shortest step and followed by taller and taller rows with the tallest step stopping last. Thus, to obtain a pattern of stereocilia in rows of increasing height what transpires are progressive go signals followed by a period when all the stereocilia grow and ending with progressive stop signals. We discuss how such a sequence could be controlled. PMID:3339095

Large-pitch kagome-structured hollow-core photonic crystal fiber

NASA Astrophysics Data System (ADS)

Couny, F.; Benabid, F.; Light, P. S.

2006-12-01

We report the fabrication and characterization of a new type of hollow-core photonic crystal fiber based on large-pitch (˜12μm) kagome lattice cladding. The optical characteristics of the 19-cell, 7-cell, and single-cell core defect fibers include broad optical transmission bands covering the visible and near-IR parts of the spectrum with relatively low loss and low chromatic dispersion, no detectable surface modes and high confinement of light in the core. Various applications of such a novel fiber are also discussed, including gas sensing, quantum optics, and high harmonic generation.

7. Staircase on south side of Building 1009, (enlisted waves' ...

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

7. Staircase on south side of Building 1009, (enlisted waves' barracks), looking southeast - Naval Air Station Chase Field, Building 1009, Essex Street, .68 mile South-southeast of intersection of Texas State Highway 202 & Independence Street, Beeville, Bee County, TX

Gapless spin excitations in the S = 1 / 2 Kagome- and triangular-lattice Heisenberg antiferromagnets

NASA Astrophysics Data System (ADS)

Sakai, Tôru; Nakano, Hiroki

2018-05-01

The S = 1 / 2 kagome- and triangular-lattice Heisenberg antiferromagnets are investigated using the numerical exact diagonalization and the finite-size scaling analysis. The behaviour of the field derivative at zero magnetization is examined for both systems. The present result indicates that the spin excitation is gapless for each system.

42. INTERIOR, FIRST FLOOR, NORTHWEST CORNER OF GRAND STAIRCASE (STAIRS ...

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

42. INTERIOR, FIRST FLOOR, NORTHWEST CORNER OF GRAND STAIRCASE (STAIRS G), SIDE AISLE, WEST WALL, THE NEGRO'S CONTRIBUTION IN THE SOCIAL AND CULTURAL DEVELOPMENT OF AMERICA: SCIENCE MURAL - U.S. Department of the Interior, Eighteenth & C Streets Northwest, Washington, District of Columbia, DC

45. INTERIOR, FIRST FLOOR, SOUTHEAST CORNER OF GRAND STAIRCASE (STAIRS ...

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

45. INTERIOR, FIRST FLOOR, SOUTHEAST CORNER OF GRAND STAIRCASE (STAIRS G), SIDE AISLE, EAST WALL, THE NEGRO'S CONTRIBUTION IN THE SOCIAL AND CULTURAL DEVELOPMENT OF AMERICA: EDUCATION MURAL - U.S. Department of the Interior, Eighteenth & C Streets Northwest, Washington, District of Columbia, DC

Susceptibility of the Ising Model on a Kagomé Lattice by Using Wang-Landau Sampling

NASA Astrophysics Data System (ADS)

Kim, Seung-Yeon; Kwak, Wooseop

2018-03-01

The susceptibility of the Ising model on a kagomé lattice has never been obtained. We investigate the properties of the kagomé-lattice Ising model by using the Wang-Landau sampling method. We estimate both the magnetic scaling exponent yh = 1.90(1) and the thermal scaling exponent yt = 1.04(2) only from the susceptibility. From the estimated values of yh and yt, we obtain all the critical exponents, the specific-heat critical exponent α = 0.08(4), the spontaneous-magnetization critical exponent β = 0.10(1), the susceptibility critical exponent γ = 1.73(5), the isothermalmagnetization critical exponent δ = 16(4), the correlation-length critical exponent ν = 0.96(2), and the correlation-function critical exponent η = 0.20(4), without using any other thermodynamic function, such as the specific heat, magnetization, correlation length, and correlation function. One should note that the evaluation of all the critical exponents only from information on the susceptibility is an innovative approach.

Detail of staircase (stepped ramp) and retaining wall at West ...

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

Detail of staircase (stepped ramp) and retaining wall at West 102nd Street, soccer field at right, looking south, with London Plane trees surrounding field. - Henry Hudson Parkway, Extending 11.2 miles from West 72nd Street to Bronx-Westchester border, New York County, NY

43. INTERIOR, FIRST FLOOR, SOUTHWEST CORNER OF GRAND STAIRCASE (STAIRS ...

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

43. INTERIOR, FIRST FLOOR, SOUTHWEST CORNER OF GRAND STAIRCASE (STAIRS G), SIDE AISLE, WEST WALL, THE NEGRO'S CONTRIBUTION IN THE SOCIAL AND CULTURAL DEVELOPMENT OF AMERICA: THE ARTS MURAL - U.S. Department of the Interior, Eighteenth & C Streets Northwest, Washington, District of Columbia, DC

Electron doping a kagome spin liquid

DOE PAGES

Kelly, Z. A.; Gallagher, M. J.; McQueen, T. M.

2016-10-13

Herbertsmithite, ZnCu 3(OH) 6Cl 2, is a two-dimensional kagome lattice realization of a spin liquid, with evidence for fractionalized excitations and a gapped ground state. Such a quantum spin liquid has been proposed to underlie high-temperature superconductivity and is predicted to produce a wealth of new states, including a Dirac metal at 1/3 electron doping. Here, we report the topochemical synthesis of electron-doped ZnLi xCu 3(OH) 6Cl 2 from x=0 to x=1.8 (3/5 per Cu 2+). Contrary to expectations, no metallicity or superconductivity is induced. Instead, we find a systematic suppression of magnetic behavior across the phase diagram. Lastly, ourmore » results demonstrate that significant theoretical work is needed to understand and predict the role of doping in magnetically frustrated narrow band insulators, particularly the interplay between local structural disorder and tendency toward electron localization, and pave the way for future studies of doped spin liquids.« less

Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators.

PubMed

Guterding, Daniel; Jeschke, Harald O; Valentí, Roser

2016-05-17

Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.

Critical frontier of the Potts and percolation models on triangular-type and kagome-type lattices. II. Numerical analysis

NASA Astrophysics Data System (ADS)

Ding, Chengxiang; Fu, Zhe; Guo, Wenan; Wu, F. Y.

2010-06-01

In the preceding paper, one of us (F. Y. Wu) considered the Potts model and bond and site percolation on two general classes of two-dimensional lattices, the triangular-type and kagome-type lattices, and obtained closed-form expressions for the critical frontier with applications to various lattice models. For the triangular-type lattices Wu’s result is exact, and for the kagome-type lattices Wu’s expression is under a homogeneity assumption. The purpose of the present paper is twofold: First, an essential step in Wu’s analysis is the derivation of lattice-dependent constants A,B,C for various lattice models, a process which can be tedious. We present here a derivation of these constants for subnet networks using a computer algorithm. Second, by means of a finite-size scaling analysis based on numerical transfer matrix calculations, we deduce critical properties and critical thresholds of various models and assess the accuracy of the homogeneity assumption. Specifically, we analyze the q -state Potts model and the bond percolation on the 3-12 and kagome-type subnet lattices (n×n):(n×n) , n≤4 , for which the exact solution is not known. Our numerical determination of critical properties such as conformal anomaly and magnetic correlation length verifies that the universality principle holds. To calibrate the accuracy of the finite-size procedure, we apply the same numerical analysis to models for which the exact critical frontiers are known. The comparison of numerical and exact results shows that our numerical values are correct within errors of our finite-size analysis, which correspond to 7 or 8 significant digits. This in turn infers that the homogeneity assumption determines critical frontiers with an accuracy of 5 decimal places or higher. Finally, we also obtained the exact percolation thresholds for site percolation on kagome-type subnet lattices (1×1):(n×n) for 1≤n≤6 .

INTERIOR SHOWING STAIRCASE TO SECOND FLOOR FROM MAIN LOBBY/RECEPTION AREA, ...

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

INTERIOR SHOWING STAIRCASE TO SECOND FLOOR FROM MAIN LOBBY/RECEPTION AREA, VIEW FACING WEST-SOUTHWEST. - Naval Air Station Barbers Point, Control Tower & Aviation Operations Building, Near intersection of runways between Hangar 110 & Building 115, Ewa, Honolulu County, HI

6. View of main interior staircase in foyer (partially freestanding ...

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

6. View of main interior staircase in foyer (partially free-standing and spiral, white pine), in foyer. Note: Back of riser with carved date "MCMXXXV" and "WE" (for Wharton Esherick, designer) - Curtis Bok House, 120 Upper Gulph Road, intersection of Route 320 & Route 76, Gulph Mills, Montgomery County, PA

Devil's staircase of odd-number charge order modulations in divalent β -vanadium bronzes under pressure

NASA Astrophysics Data System (ADS)

Yamauchi, Touru; Ueda, Hiroaki; Ohwada, Kenji; Nakao, Hironori; Ueda, Yutaka

2018-03-01

A common characteristic of quasi-one-dimensional (q1D) conductors β -A0.33V2O5 (A = Li, Na, and Ag) is that the charge ordering (CO), the ground state (GS) at ambient pressure, and the superconducting (SC) phases, the GS under high pressure, are competing with each other. We have explored high-pressure properties of divalent β -vanadium bronzes, β -A0.33V2O5 (A = Ca, Sr, and Pb), which are A -cation stoichiometry finely controlled single-crystal/powder samples, and found the absence of the SC phase. In these observations, however, we observed enormous and novel phase transitions, a kind of "devil's staircase"-type phase transitions in the charge ordering (CO) phases. The most surprising discovery in this devil's staircase, which was found mainly in β -Sr0.33V2O5 , is that all the charge modulation vectors of many kinds of CO phases can be represented as a primitive lattice translation vector along the b axis multiplied by several odd numbers. This discovery surely demonstrates interplay between the charge degree freedom and the crystallographic symmetry. We propose two possible mechanisms to explain this phenomenon: "self-charge transfer (carrier redistribution)" between the two subsystems in these compounds and "sequential symmetry reduction" that was discussed in Landau theory of phase transitions. In β -Ca0.33V2O5 we also found a P -T phase diagram similar in outlook but different in detail. The devil's staircase was also observed but it is an incomplete one. Furthermore, the charge modulation vectors in it are shorter than those in β -Sr0.33V2O5 . In β -Pb0.33V2O5 , which has no CO phase at ambient pressure, the pressure-induced antiferromagnetic ordering was observed at around 50 K above 0.5 GPa. Using these two kinds of mechanisms, we also explain the global high-pressure properties in all the stoichiometric divalent β -vanadium bronzes, which were observed as a wide variety of electromagnetic states. In addition, we also discuss a possible key for

44. INTERIOR, FIRST FLOOR, NORTHEAST CORNER OF GRAND STAIRCASE (STAIRS ...

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

44. INTERIOR, FIRST FLOOR, NORTHEAST CORNER OF GRAND STAIRCASE (STAIRS G), SIDE AISLE, EAST WALL, THE NEGRO'S CONTRIBUTION IN THE SOCIAL AND CULTURAL DEVELOPMENT OF AMERICA: RELIGION MURAL (4' x 5' negative; 8' x 10' print) - U.S. Department of the Interior, Eighteenth & C Streets Northwest, Washington, District of Columbia, DC

Tuning of magnetic frustration in S = 1 / 2 Kagomé lattices {[Cu3(CO3)2(bpe)3](CLO4)2}n and {[Cu3(CO3)2(bpy)3](CLO4)2}n through rigid and flexible ligands

NASA Astrophysics Data System (ADS)

Ajeesh, M. O.; Yogi, A.; Padmanabhan, M.; Nath, R.

2015-04-01

Single crystalline and polycrystalline samples of S = 1 / 2 Kagomé lattices { [Cu3(CO3)2(bpe)3 ](CLO4)2 } n and { [Cu3(CO3)2(bpy)3 ](CLO4)2 } n, respectively were synthesized. Their structural and magnetic properties were characterized by means of x-ray diffraction and magnetization measurements. Both compounds crystalize in a hexagonal structure (space group P-6) consisting of CuO4 Kagomé layers in the ab-plane but linked along c direction through either rigid bpy or flexible bpe ligands to form 3D frame works. Magnetic measurements reveal that both the compounds undergo ferromagnetic ordering (TC) at low temperatures and the TC and the extent of frustration could be tuned by changing the nature of the pillar ligands. {[Cu3(CO3)2(bpe)3](CLO4)2}n which is made up of flexible bpe ligands has a TC of 5.7 K and a Curie-Weiss temperature (θCW) of -39.7 K giving rise to a frustration parameter of |θCW | /TC ≃ 6.96. But the replacement of bpe by a more rigid and electronically delocalized bpy ligand leads to an enhanced TC ≃ 9.3 K and a reduced frustration parameter of |θCW | /TC ≃ 3.54.

Structured chaos in a devil's staircase of the Josephson junction.

PubMed

Shukrinov, Yu M; Botha, A E; Medvedeva, S Yu; Kolahchi, M R; Irie, A

2014-09-01

The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior. These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.

Structured chaos in a devil's staircase of the Josephson junction

NASA Astrophysics Data System (ADS)

Shukrinov, Yu. M.; Botha, A. E.; Medvedeva, S. Yu.; Kolahchi, M. R.; Irie, A.

2014-09-01

The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior. These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.

Structured chaos in a devil's staircase of the Josephson junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukrinov, Yu. M.; Botha, A. E., E-mail: bothaae@unisa.ac.za; Medvedeva, S. Yu.

2014-09-01

The phase dynamics of Josephson junctions (JJs) under external electromagnetic radiation is studied through numerical simulations. Current-voltage characteristics, Lyapunov exponents, and Poincaré sections are analyzed in detail. It is found that the subharmonic Shapiro steps at certain parameters are separated by structured chaotic windows. By performing a linear regression on the linear part of the data, a fractal dimension of D = 0.868 is obtained, with an uncertainty of ±0.012. The chaotic regions exhibit scaling similarity, and it is shown that the devil's staircase of the system can form a backbone that unifies and explains the highly correlated and structured chaotic behavior.more » These features suggest a system possessing multiple complete devil's staircases. The onset of chaos for subharmonic steps occurs through the Feigenbaum period doubling scenario. Universality in the sequence of periodic windows is also demonstrated. Finally, the influence of the radiation and JJ parameters on the structured chaos is investigated, and it is concluded that the structured chaos is a stable formation over a wide range of parameter values.« less

Numerical-Diagonalization Study of Magnetization Process of Frustrated Spin-1/2 Heisenberg Antiferromagnets in Two Dimensions: —Triangular- and Kagome-Lattice Antiferromagnets—

NASA Astrophysics Data System (ADS)

Nakano, Hiroki; Sakai, Tôru

2018-06-01

The S = 1/2 triangular- and kagome-lattice Heisenberg antiferromagnets are investigated under a magnetic field using the numerical-diagonalization method. A procedure is proposed to extract data points with very small finite-size deviations using the numerical-diagonalization results for capturing the magnetization curve. For the triangular-lattice antiferromagnet, the plateau edges at one-third the height of the saturation and the saturation field are successfully estimated. This study additionally presents results of magnetization process for a 45-site cluster of the kagome-lattice antiferromagnet; the present analysis suggests that the plateau does not open at one-ninth the height of the saturation.

Microscopic theory of the nearest-neighbor valence bond sector of the spin-1/2 kagome antiferromagnet

NASA Astrophysics Data System (ADS)

Ralko, Arnaud; Mila, Frédéric; Rousochatzakis, Ioannis

2018-03-01

The spin-1/2 Heisenberg model on the kagome lattice, which is closely realized in layered Mott insulators such as ZnCu3(OH) 6Cl2 , is one of the oldest and most enigmatic spin-1/2 lattice models. While the numerical evidence has accumulated in favor of a quantum spin liquid, the debate is still open as to whether it is a Z2 spin liquid with very short-range correlations (some kind of resonating valence bond spin liquid), or an algebraic spin liquid with power-law correlations. To address this issue, we have pushed the program started by Rokhsar and Kivelson in their derivation of the effective quantum dimer model description of Heisenberg models to unprecedented accuracy for the spin-1/2 kagome, by including all the most important virtual singlet contributions on top of the orthogonalization of the nearest-neighbor valence bond singlet basis. Quite remarkably, the resulting picture is a competition between a Z2 spin liquid and a diamond valence bond crystal with a 12-site unit cell, as in the density-matrix renormalization group simulations of Yan et al. Furthermore, we found that, on cylinders of finite diameter d , there is a transition between the Z2 spin liquid at small d and the diamond valence bond crystal at large d , the prediction of the present microscopic description for the two-dimensional lattice. These results show that, if the ground state of the spin-1/2 kagome antiferromagnet can be described by nearest-neighbor singlet dimers, it is a diamond valence bond crystal, and, a contrario, that, if the system is a quantum spin liquid, it has to involve long-range singlets, consistent with the algebraic spin liquid scenario.

Kagome fiber based ultrafast laser microsurgery probe delivering micro-Joule pulse energies

PubMed Central

Subramanian, Kaushik; Gabay, Ilan; Ferhanoğlu, Onur; Shadfan, Adam; Pawlowski, Michal; Wang, Ye; Tkaczyk, Tomasz; Ben-Yakar, Adela

2016-01-01

We present the development of a 5 mm, piezo-actuated, ultrafast laser scalpel for fast tissue microsurgery. Delivery of micro-Joules level energies to the tissue was made possible by a large, 31 μm, air-cored inhibited-coupling Kagome fiber. We overcome the fiber’s low NA by using lenses made of high refractive index ZnS, which produced an optimal focusing condition with 0.23 NA objective. The optical design achieved a focused laser spot size of 4.5 μm diameter covering a 75 × 75 μm2 scan area in a miniaturized setting. The probe could deliver the maximum available laser power, achieving an average fluence of 7.8 J/cm2 on the tissue surface at 62% transmission efficiency. Such fluences could produce uninterrupted, 40 μm deep cuts at translational speeds of up to 5 mm/s along the tissue. We predicted that the best combination of speed and coverage exists at 8 mm/s for our conditions. The onset of nonlinear absorption in ZnS, however, limited the probe’s energy delivery capabilities to 1.4 μJ for linear operation at 1.5 picosecond pulse-widths of our fiber laser. Alternatives like broadband CaF2 crystals should mitigate such nonlinear limiting behavior. Improved opto-mechanical design and appropriate material selection should allow substantially higher fluence delivery and propel such Kagome fiber-based scalpels towards clinical translation. PMID:27896003

Kagome fiber based ultrafast laser microsurgery probe delivering micro-Joule pulse energies.

PubMed

Subramanian, Kaushik; Gabay, Ilan; Ferhanoğlu, Onur; Shadfan, Adam; Pawlowski, Michal; Wang, Ye; Tkaczyk, Tomasz; Ben-Yakar, Adela

2016-11-01

We present the development of a 5 mm, piezo-actuated, ultrafast laser scalpel for fast tissue microsurgery. Delivery of micro-Joules level energies to the tissue was made possible by a large, 31 μm, air-cored inhibited-coupling Kagome fiber. We overcome the fiber's low NA by using lenses made of high refractive index ZnS, which produced an optimal focusing condition with 0.23 NA objective. The optical design achieved a focused laser spot size of 4.5 μm diameter covering a 75 × 75 μm 2 scan area in a miniaturized setting. The probe could deliver the maximum available laser power, achieving an average fluence of 7.8 J/cm 2 on the tissue surface at 62% transmission efficiency. Such fluences could produce uninterrupted, 40 μm deep cuts at translational speeds of up to 5 mm/s along the tissue. We predicted that the best combination of speed and coverage exists at 8 mm/s for our conditions. The onset of nonlinear absorption in ZnS, however, limited the probe's energy delivery capabilities to 1.4 μJ for linear operation at 1.5 picosecond pulse-widths of our fiber laser. Alternatives like broadband CaF 2 crystals should mitigate such nonlinear limiting behavior. Improved opto-mechanical design and appropriate material selection should allow substantially higher fluence delivery and propel such Kagome fiber-based scalpels towards clinical translation.

A Biophysical Model for the Staircase Geometry of Stereocilia

PubMed Central

Orly, Gilad; Manor, Uri; Gov, Nir S.

2015-01-01

Cochlear hair cell bundles, made up of 10s to 100s of individual stereocilia, are essential for hearing, and even relatively minor structural changes, due to mutations or injuries, can result in total deafness. Consistent with its specialized role, the staircase geometry (SCG) of hair cell bundles presents one of the most striking, intricate, and precise organizations of actin-based cellular shapes. Composed of rows of actin-filled stereocilia with increasing lengths, the hair cell’s staircase-shaped bundle is formed from a progenitor field of smaller, thinner, and uniformly spaced microvilli with relatively invariant lengths. While recent genetic studies have provided a significant increase in information on the multitude of stereocilia protein components, there is currently no model that integrates the basic physical forces and biochemical processes necessary to explain the emergence of the SCG. We propose such a model derived from the biophysical and biochemical characteristics of actin-based protrusions. We demonstrate that polarization of the cell’s apical surface, due to the lateral polarization of the entire epithelial layer, plays a key role in promoting SCG formation. Furthermore, our model explains many distinct features of the manifestations of SCG in different species and in the presence of various deafness-associated mutations. PMID:26207893

Exploring nonlinear topological states of matter with exciton-polaritons: Edge solitons in kagome lattice.

PubMed

Gulevich, D R; Yudin, D; Skryabin, D V; Iorsh, I V; Shelykh, I A

2017-05-11

Matter in nontrivial topological phase possesses unique properties, such as support of unidirectional edge modes on its interface. It is the existence of such modes which is responsible for the wonderful properties of a topological insulator - material which is insulating in the bulk but conducting on its surface, along with many of its recently proposed photonic and polaritonic analogues. We show that exciton-polariton fluid in a nontrivial topological phase in kagome lattice, supports nonlinear excitations in the form of solitons built up from wavepackets of topological edge modes - topological edge solitons. Our theoretical and numerical results indicate the appearance of bright, dark and grey solitons dwelling in the vicinity of the boundary of a lattice strip. In a parabolic region of the dispersion the solitons can be described by envelope functions satisfying the nonlinear Schrödinger equation. Upon collision, multiple topological edge solitons emerge undistorted, which proves them to be true solitons as opposed to solitary waves for which such requirement is waived. Importantly, kagome lattice supports topological edge mode with zero group velocity unlike other types of truncated lattices. This gives a finer control over soliton velocity which can take both positive and negative values depending on the choice of forming it topological edge modes.

Monte Carlo simulations of ABC stacked kagome lattice films

NASA Astrophysics Data System (ADS)

Yerzhakov, H. V.; Plumer, M. L.; Whitehead, J. P.

2016-05-01

Properties of films of geometrically frustrated ABC stacked antiferromagnetic kagome layers are examined using Metropolis Monte Carlo simulations. The impact of having an easy-axis anisotropy on the surface layers and cubic anisotropy in the interior layers is explored. The spin structure at the surface is shown to be different from that of the bulk 3D fcc system, where surface axial anisotropy tends to align spins along the surface [1 1 1] normal axis. This alignment then propagates only weakly to the interior layers through exchange coupling. Results are shown for the specific heat, magnetization and sub-lattice order parameters for both surface and interior spins in three and six layer films as a function of increasing axial surface anisotropy. Relevance to the exchange bias phenomenon in IrMn3 films is discussed.

The formation of thermohaline staircases for large salt concentration differences in double diffusive convection

NASA Astrophysics Data System (ADS)

Yang, Yantao; Verzicco, Roberto; Lohse, Detlef

2016-11-01

In the upper layers of the tropical and subtropical ocean, step-like mean profiles for both temperature and salinity are often observed, a phenomenon referred to as thermohaline staircase. It consists of alternatively stacked mixing layers, and finger layers with sharp gradients in both mean temperature and salinity. It is believed that thermohaline staircases are caused by double diffusive convection (DDC), i.e. the convection flow with fluid density affected by two different scalars. Here we conducted direct numerical simulations of DDC bounded by two parallel plates and aimed to realise the multi-layer state similar to the oceanic thermohaline staircase. We applied an unstable salinity difference and a stable temperature difference across the two plates. We gradually increased the salinity Rayleigh number RaS , i.e. the strength of salinity difference, and fixed the relative strength of temperature difference. When RaS is high enough the flow undergoes a transition from a single finger layer to a triple layer state, where one mixing layer emerges between two finger layers. Such triple layer state is stable up to the turbulent diffusive time scale. The finger-layer height is larger for higher RaS . The dependences of the scalar fluxes on RaS were also investigated. Supported by Dutch FOM Foundation and NWO rpogramme MCEC; Computing resources from SURFSara and PRACE project 2015133124.

Effects of exchange bias on magnetotransport in permalloy kagome artificial spin ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, B. L.; Rench, D. W.; Misra, R.

2015-02-01

We investigate the magnetotransport properties of connected kagome artificial spin ice networks composed of permalloy nanowires. Our data show clear evidence of magnetic switching among the wires, both in the longitudinal and transverse magnetoresistance. An unusual asymmetry with field sweep direction appears at temperatures below about 20 K that appears to be associated with exchange bias resulting from surface oxidation of permalloy, and which disappears in alumina-capped samples. These results demonstrate that exchange bias is a phenomenon that must be considered in understanding the physics of such artificial spin ice systems, and that opens up new possibilities for their control.

Magnetic state selected by magnetic dipole interaction in the kagome antiferromagnet NaBa2Mn3F11

NASA Astrophysics Data System (ADS)

Hayashida, Shohei; Ishikawa, Hajime; Okamoto, Yoshihiko; Okubo, Tsuyoshi; Hiroi, Zenji; Avdeev, Maxim; Manuel, Pascal; Hagihala, Masato; Soda, Minoru; Masuda, Takatsugu

2018-02-01

We haved studied the ground state of the classical kagome antiferromagnet NaBa2Mn3F11 . Strong magnetic Bragg peaks observed for d spacings shorter than 6.0 Å were indexed by the propagation vector of k0=(0 ,0 ,0 ) . Additional peaks with weak intensities in the d -spacing range above 8.0 Å were indexed by the incommensurate vector of k1=[0.3209 (2 ) ,0.3209 (2 ) ,0 ] and k2=[0.3338 (4 ) ,0.3338 (4 ) ,0 ] . Magnetic structure analysis unveils a 120∘ structure with the tail-chase geometry having k0 modulated by the incommensurate vector. A classical calculation of the Heisenberg kagome antiferromagnet with antiferromagnetic second-neighbor interaction, for which the ground state a k0120∘ degenerated structure, reveals that the magnetic dipole-dipole (MDD) interaction including up to the fourth neighbor terms selects the tail-chase structure. The observed modulation of the tail-chase structure is attributed to a small perturbation such as the long-range MDD interaction or the interlayer interaction.

76 FR 63324 - Notice of Grand Staircase-Escalante National Monument Advisory Committee Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-12

... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLUT030000-L17110000-PH0000-24-1A] Notice of Grand Staircase-Escalante National Monument Advisory Committee Meeting AGENCY: Bureau of Land Management, Interior. ACTION: Notice. SUMMARY: In accordance with the Federal Land Policy and Management Act (FLPMA...

Architectural design and physical activity: an observational study of staircase and elevator use in different buildings.

PubMed

Bassett, David R; Browning, Ray; Conger, Scott A; Wolff, Dana L; Flynn, Jennifer I

2013-05-01

The indoor built environment has the potential to influence levels of physical activity. However, the extent to which architectural design in commercial buildings can influence the percentage of people choosing to use the stairs versus elevators is unknown. The purpose of this study was to determine if buildings with centrally located, accessible, and aesthetically pleasing staircases result in a greater percentage of people taking the stairs. Direct observations of stair and elevator use were conducted in 3 buildings on a university campus. One of the buildings had a bank of 4 centrally located elevators and a fire escape stairwell behind a steel door. The other 2 buildings had centrally located staircases and out-of-the-way elevators. The percentage of people who ascended the stairs was 8.1% in the elevator-centric building, compared with 72.8% and 81.1% in the 2 stair-centric buildings (P < .001). In addition, the percentage of people who descended the stairs was 10.8% in the first building, compared with 89.5% and 93.7% in the stair-centric buildings (P < .001). The results of the current study suggest that if buildings are constructed with centrally located, accessible, and aesthetically pleasing staircases, a greater percentage of people will choose to take the stairs.

Weyl magnons in noncoplanar stacked kagome antiferromagnets

NASA Astrophysics Data System (ADS)

Owerre, S. A.

2018-03-01

Weyl nodes have been experimentally realized in photonic, electronic, and phononic crystals. However, magnonic Weyl nodes are yet to be seen experimentally. In this paper, we propose Weyl magnon nodes in noncoplanar stacked frustrated kagome antiferromagnets, naturally available in various real materials. Most crucially, the Weyl nodes in the current system occur at the lowest excitation and possess a topological thermal Hall effect, therefore they are experimentally accessible at low temperatures due to the population effect of bosonic quasiparticles. In stark contrast to other magnetic systems, the current Weyl nodes do not rely on time-reversal symmetry breaking by the magnetic order. Rather, they result from explicit macroscopically broken time reversal symmetry by the scalar spin chirality of noncoplanar spin textures and can be generalized to chiral spin liquid states. Moreover, the scalar spin chirality gives a real space Berry curvature which is not available in previously studied magnetic Weyl systems. We show the existence of magnon arc surface states connecting projected Weyl magnon nodes on the surface Brillouin zone. We also uncover the first realization of triply-degenerate nodal magnon point in the noncollinear regime with zero scalar spin chirality.

77 FR 14567 - Notice of Grand Staircase-Escalante National Monument Advisory Committee Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-12

... development of a Hole-In-The-Rock corridor management strategy, future meeting dates and other matters as may... DEPARTMENT OF THE INTERIOR Bureau of Land Management [LLUT030000-L17110000-PH0000-24-1A] Notice of Grand Staircase-Escalante National Monument Advisory Committee Meeting AGENCY: Bureau of Land Management...

Non-Abelian S =1 chiral spin liquid on the kagome lattice

NASA Astrophysics Data System (ADS)

Liu, Zheng-Xin; Tu, Hong-Hao; Wu, Ying-Hai; He, Rong-Qiang; Liu, Xiong-Jun; Zhou, Yi; Ng, Tai-Kai

2018-05-01

We study S =1 spin liquid states on the kagome lattice constructed by Gutzwiller-projected px+i py superconductors. We show that the obtained spin liquids are either non-Abelian or Abelian topological phases, depending on the topology of the fermionic mean-field state. By calculating the modular matrices S and T , we confirm that projected topological superconductors are non-Abelian chiral spin liquid (NACSL). The chiral central charge and the spin Hall conductance we obtained agree very well with the S O (3) 1 (or, equivalently, S U (2) 2 ) field-theory predictions. We propose a local Hamiltonian which may stabilize the NACSL. From a variational study, we observe a topological phase transition from the NACSL to the Z2 Abelian spin liquid.

Exterior building details of Building A; east façade: concrete staircase, ...

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

Exterior building details of Building A; east façade: concrete staircase, profiled cement, plaster door surround, recessed panel inscribed "1859", historic window opening with concrete sill above door, cement plaster dentil course and cornice truncated wood beam ends, plaster finished brick wall, granite base; westerly view - San Quentin State Prison, Building 22, Point San Quentin, San Quentin, Marin County, CA

DMRG study of the Kagome Antiferromagnetic Heisenberg Model

NASA Astrophysics Data System (ADS)

Yan, Simeng; White, Steven

2010-03-01

We have used DMRG to study the S=1/2 Heisenberg model on the Kagome lattice, using cylindrical boundary conditions and large clusters. We have focused on the spin gap and the presence or absence of the Valence Bond Crystal (VBC) order with a 36 unit cell as studied by Marston and Zeng, Singh and Huse, and others. Our results are probably the highest accuracy results for large clusters to date. Our extrapolated results find a finite spin gap with a value of about 0.05 J. To determine whether VBC order occurs, we calculated the ground states of a variety of clusters, some of which allow the 36 site VBC order, and others which do not allow it. For narrower cylinders (width < 12) , the VBC patterns are found to vanish as the number of kept states increases. For wider systems, we do observe VBC ground states, but it is not always clear that the calculations have converged. The extrapolated energies of the two types of states are very close, within about 1%.

Devil's staircases, quantum dimer models, and stripe formation in strong coupling models of quantum frustration.

NASA Astrophysics Data System (ADS)

Raman, Kumar; Papanikolaou, Stefanos; Fradkin, Eduardo

2007-03-01

We construct a two-dimensional microscopic model of interacting quantum dimers that displays an infinite number of periodic striped phases in its T=0 phase diagram. The phases form an incomplete devil's staircase and the period becomes arbitrarily large as the staircase is traversed. The Hamiltonian has purely short-range interactions, does not break any symmetries, and is generic in that it does not involve the fine tuning of a large number of parameters. Our model, a quantum mechanical analog of the Pokrovsky-Talapov model of fluctuating domain walls in two dimensional classical statistical mechanics, provides a mechanism by which striped phases with periods large compared to the lattice spacing can, in principle, form in frustrated quantum magnetic systems with only short-ranged interactions and no explicitly broken symmetries. Please see cond-mat/0611390 for more details.

Electron Doping a Kagome Spin Liquid

NASA Astrophysics Data System (ADS)

Kelly, Zachary; Gallagher, Miranda; McQueen, Tyrel

In 1987, Anderson proposed that charge doping a material with the resonating valance bond (RVB) state would yield a superconducting state. Ever since, there has been a search for these RVB containing spin liquid materials and their charge doped counterparts. Studies on the most promising spin liquid candidate, Herbertsmithite, ZnCu3(OH)6Cl2, a two dimensional kagomé lattice, show evidence of fractionalized excitations and a gapped ground state. In this work, we report the synthesis and characterization of a newly synthesized electron doped spin liquid, ZnLixCu3(OH)6Cl2 from x = 0 to x = 1.8 (3 / 5 th per Cu2+). Despite heavy doping, the series remains insulating and the magnetism is systematically suppressed. We have done extensive structural studies of the doped series to determine the effect of the intercalated atoms on the structure, and whether these structural differences induce strong localization effects that suppress the metallic and superconducting states. Other doped spin liquid candidates are also being explored to understand if this localization is system dependent or systemic to all doped spin liquid systems. NSF, Division of Materials Research (DMR), Solid State Chemistry (SSMC), CAREER Grant under Award No. DMR- 1253562, Institute for Quantum Matter under Grant No.DE-FG02- 08ER46544, and the David and Lucile Packard Foundation.

Hiatus on the upward staircase of global warming

NASA Astrophysics Data System (ADS)

Xie, S. P.; Kosaka, Y.

2016-12-01

Since the 19th century, global-mean surface temperature (GMST) has risen in staircase-like stages due to contributions from both radiative forcing and internal variability. Our earlier study showed that tropical Pacific variability, specifically the La Nina-like cooling, caused the current hiatus of global warming. We have extended the Pacific Ocean-Global Atmosphere (POGA) pacemaker experiment back to the late 19th century, by restoring tropical Pacific sea surface temperature anomalies towards the observed history. POGA reproduces annual-mean GMST variability with high correlation. We quantify relative contributions from the radiative forcing and tropical Pacific variability for various epochs of the staircase. Beyond the global mean, POGA also captures observed regional trends of surface temperature for these periods, especially over the tropical Indian Ocean, Indian subcontinent, North and South Pacific and North America. The POGA effect for the recent hiatus is comparable in magnitude with that at the beginning of the 20th century, but lasts the longest in duration over the past 150 years. The attendant strengthening of the Pacific trade winds since the 1990s is unprecedented on the instrumental record. To the extent that POGA captures much of the internal variability in GMST, we can infer radiatively forced GMST response. This method has the advantage of being independent of the model's radiative forcing and climate sensitivity. While raw data show a warming of 0.9 degree C for the recent five-year period of 2010-2014 relative to 1900, our new calculation yields a much higher anthropogenic warming of 1.2 C after correcting for the internal variability effect. This indicates that the task is more challenging than thought to implement the Paris consensus of limiting global average temperature change to below 2 C above preindustrial levels.

Investigation and hazard assessment of the 2003 and 2007 Staircase Falls rock falls, Yosemite National Park, California, USA

USGS Publications Warehouse

Wieczorek, G.F.; Stock, Gregory M.; Reichenbach, P.; Snyder, J.B.; Borchers, J.W.; Godt, J.W.

2008-01-01

Since 1857 more than 600 rock falls, rock slides, debris slides, and debris flows have been documented in Yosemite National Park, with rock falls in Yosemite Valley representing the majority of the events. On 26 December 2003, a rock fall originating from west of Glacier Point sent approximately 200 m 3 of rock debris down a series of joint-controlled ledges to the floor of Yosemite Valley. The debris impacted talus near the base of Staircase Falls, producing fragments of flying rock that struck occupied cabins in Curry Village. Several years later on 9 June 2007, and again on 26 July 2007, smaller rock falls originated from the same source area. The 26 December 2003 event coincided with a severe winter storm and was likely triggered by precipitation and/or frost wedging, but the 9 June and 26 July 2007 events lack recognizable triggering mechanisms. We investigated the geologic and hydrologic factors contributing to the Staircase Falls rock falls, including bedrock lithology, weathering, joint spacing and orientations, and hydrologic processes affecting slope stability. We improved upon previous geomorphic assessment of rock-fall hazards, based on a shadow angle approach, by using STONE, a three-dimensional rock-fall simulation computer program. STONE produced simulated rock-fall runout patterns similar to the mapped extent of the 2003 and 2007 events, allowing us to simulate potential future rock falls from the Staircase Falls detachment area. Observations of recent rock falls, mapping of rock debris, and simulations of rock fall runouts beneath the Staircase Falls detachment area suggest that rock-fall hazard zones extend farther downslope than the extent previously defined by mapped surface talus deposits.

Proof of principal for staircase auger chip removal theory

NASA Technical Reports Server (NTRS)

Barron, Jeffrey B.; Brewer, Steve; Kerns, Kenneth; Moody, Kyle; Rossi, Richard A.

1987-01-01

A proof of principal design of the staircase auger theory is provided for lunar drilling. The drill is designed to drill holes 30 meters deep and 0.1 meters in diameter. The action of the auger is 0.01 meter strokes at a varying number of strokes per second. A detailed analysis of the interaction of the auger and particle was done to optimize the parameters of the auger. This optimum design will allow for proper heat removal and reasonable drilling time. The drill bit is designed to scoop the particles into the auger while efficiently cutting through the moon's surface.

Gapless Spin-Liquid Ground State in the S =1 /2 Kagome Antiferromagnet

NASA Astrophysics Data System (ADS)

Liao, H. J.; Xie, Z. Y.; Chen, J.; Liu, Z. Y.; Xie, H. D.; Huang, R. Z.; Normand, B.; Xiang, T.

2017-03-01

The defining problem in frustrated quantum magnetism, the ground state of the nearest-neighbor S =1 /2 antiferromagnetic Heisenberg model on the kagome lattice, has defied all theoretical and numerical methods employed to date. We apply the formalism of tensor-network states, specifically the method of projected entangled simplex states, which combines infinite system size with a correct accounting for multipartite entanglement. By studying the ground-state energy, the finite magnetic order appearing at finite tensor bond dimensions, and the effects of a next-nearest-neighbor coupling, we demonstrate that the ground state is a gapless spin liquid. We discuss the comparison with other numerical studies and the physical interpretation of this result.

Gapped Spin-1/2 Spinon Excitations in a New Kagome Quantum Spin Liquid Compound Cu3Zn(OH)6FBr

NASA Astrophysics Data System (ADS)

Feng, Zili; Li, Zheng; Meng, Xin; Yi, Wei; Wei, Yuan; Zhang, Jun; Wang, Yan-Cheng; Jiang, Wei; Liu, Zheng; Li, Shiyan; Liu, Feng; Luo, Jianlin; Li, Shiliang; Zheng, Guo-qing; Meng, Zi Yang; Mei, Jia-Wei; Shi, Youguo

2017-06-01

We report a new kagome quantum spin liquid candidate Cu3Zn(OH)6FBr, which does not experience any phase transition down to 50 mK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (∼200 K). A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fractionalization in the fractional quantum Hall state. Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0300502, 2016YFA0300503, 2016YFA0300604, 2016YF0300300 and 2016YFA0300802, the National Natural Science Foundation of China under Grant Nos 11421092, 11474330, 11574359, 11674406, 11374346 and 11674375, the National Basic Research Program of China (973 Program) under Grant No 2015CB921304, the National Thousand-Young-Talents Program of China, the Strategic Priority Research Program (B) of the Chinese Academy of Sciences under Grant Nos XDB07020000, XDB07020200 and XDB07020300. The work in Utah is supported by DOE-BES under Grant No DE-FG02-04ER46148.

Helical order and multiferroicity in the S =1/2 quasi-kagome system KCu3As2O7(OD)3

NASA Astrophysics Data System (ADS)

Nilsen, G. J.; Okamoto, Y.; Ishikawa, H.; Simonet, V.; Colin, C. V.; Cano, A.; Chapon, L. C.; Hansen, T.; Mutka, H.; Hiroi, Z.

2014-04-01

Several Cu2+ hydroxide minerals have been recently identified as candidate realizations of the S=1/2 kagome Heisenberg model. In this context, we have studied the distorted system KCu3As2O7(OD)3 using neutron scattering and bulk measurements. Although the distortion favors magnetic order over a spin liquid ground state, refinement of the magnetic diffraction pattern below TN1=7.05(5) K yields a complex helical structure with k =(0.77,0,0.11). This structure, as well as the spin excitation spectrum, are well described by a classical Heisenberg model with ferromagnetic nearest neighbor couplings. Multiferroicity is observed below TN1, with an unusual crossover between improper and pseudoproper behavior occurring at TN2=5.5 K. The polarization at T =2 K is P =1.5μCm-2. The properties of KCu3As2O7(OD)3 highlight the variety of physics which arise from the interplay of spin and orbital degrees of freedom in Cu2+ kagome systems.

Assessing interconnections between wilderness and adjacent lands: the Grand Staircase-Escalante National Monument, Utah

Treesearch

Janice L. Thomson; Dawn A. Hartley; Gregory H. Aplet; Peter A. Morton

2000-01-01

Wilderness managers have traditionally managed wilderness lands based on the ecological and social content of wilderness areas. The authors propose a framework to systematically account for the biophysical, socioeconomic, and wildness characteristics of the broader landscape context. The method was applied to the proposed wilderness lands of the Grand Staircase-...

Visual Contrast Sensitivity Functions Obtained from Untrained Observers Using Tracking and Staircase Procedures. Final Report.

ERIC Educational Resources Information Center

Geri, George A.; Hubbard, David C.

Two adaptive psychophysical procedures (tracking and "yes-no" staircase) for obtaining human visual contrast sensitivity functions (CSF) were evaluated. The procedures were chosen based on their proven validity and the desire to evaluate the practical effects of stimulus transients, since tracking procedures traditionally employ gradual…

Continuous Easy-Plane Deconfined Phase Transition on the Kagome Lattice

NASA Astrophysics Data System (ADS)

Zhang, Xue-Feng; He, Yin-Chen; Eggert, Sebastian; Moessner, Roderich; Pollmann, Frank

2018-03-01

We use large scale quantum Monte Carlo simulations to study an extended Hubbard model of hard core bosons on the kagome lattice. In the limit of strong nearest-neighbor interactions at 1 /3 filling, the interplay between frustration and quantum fluctuations leads to a valence bond solid ground state. The system undergoes a quantum phase transition to a superfluid phase as the interaction strength is decreased. It is still under debate whether the transition is weakly first order or represents an unconventional continuous phase transition. We present a theory in terms of an easy plane noncompact C P1 gauge theory describing the phase transition at 1 /3 filling. Utilizing large scale quantum Monte Carlo simulations with parallel tempering in the canonical ensemble up to 15552 spins, we provide evidence that the phase transition is continuous at exactly 1 /3 filling. A careful finite size scaling analysis reveals an unconventional scaling behavior hinting at deconfined quantum criticality.

A biomechanical evaluation of staircase riser heights and tread depths during stair-climbing.

PubMed

Mital, A; Fard, H F; Khaledi, H

1987-08-01

Several different staircase riser heights and tread depths were investigated in order to determine riser height and tread depth that minimized moments acting at the ankle, knee, and hipjoints while walking upstairs. The results indicated that joint moments were minimized when the riser height was 102 mm. For the tread depth, least moments were obtained when the depth was 305 mm. Copyright © 1987. Published by Elsevier Ltd.

Tri-critical behavior of the Blume-Emery-Griffiths model on a Kagomé lattice: Effective-field theory and Rigorous bounds

NASA Astrophysics Data System (ADS)

Santos, Jander P.; Sá Barreto, F. C.

2016-01-01

Spin correlation identities for the Blume-Emery-Griffiths model on Kagomé lattice are derived and combined with rigorous correlation inequalities lead to upper bounds on the critical temperature. From the spin correlation identities the mean field approximation and the effective field approximation results for the magnetization, the critical frontiers and the tricritical points are obtained. The rigorous upper bounds on the critical temperature improve over those effective-field type theories results.

Staircase Falls Rockfall on December 26, 2003, and Geologic Hazards at Curry Village, Yosemite National Park, California

USGS Publications Warehouse

Wieczorek, Gerald F.; Snyder, James B.; Borchers, James W.; Reichenbach, Paola

2007-01-01

Since 1857, several hundred rockfalls, rockslides, and debris flows have been observed in Yosemite National Park. At 12:45 a.m. on December 26, 2003, a severe winter storm triggered a rockfall west of Glacier Point in Yosemite Valley. Rock debris moved quickly eastward down Staircase Falls toward Curry Village. As the rapidly moving rock mass reached talus at the bottom of Staircase Falls, smaller pieces of flying rock penetrated occupied cabins. Physical characterization of the rockfall site included rockfall volume, joint patterns affecting initial release of rock and the travel path of rockfall, factors affecting weathering and weakening of bedrock, and hydrology affecting slope stability within joints. Although time return intervals are not predictable, a three-dimensional rockfall model was used to assess future rockfall potential and risk. Predictive rockfall and debris-flow methods suggest that landslide hazards beneath these steep cliffs extend farther than impact ranges defined from surface talus in Yosemite Valley, leaving some park facilities vulnerable.

Staircase polymetalsilicon nanocomplexes - Polymetalphenyl siloxanes: Structure and properties

NASA Astrophysics Data System (ADS)

Shapkin, N. P.; Balanov, M. I.; Razov, V. I.; Gardionov, S. V.; Mayorov, V. Yu; Tokar, E. A.; Papynov, E. K.; Korochentsev, V. V.; Leont'ev, L. B.; Slobodyuk, A. B.; Modin, E. B.

2018-03-01

Polyphenyl siloxanes containing chromium, iron, and aluminum in the backbone chain have been synthesized. The structure of the obtained staircase nano-metal complexes has been studied by the methods of XRD analysis and IR, 29Si and 27Al NMR, and XPS spectroscopy and scanning electron microscopy. Physical-chemical characteristics of these compounds have been investigated by the positron annihilation spectroscopy (PAS) and low-temperature nitrogen adsorption. The data of X-ray diffraction analysis (XRD) enabled us to calculate the size and volume of coherent scattering regions (CSR) and the cross-section area of the polymer chains. By means of the PAS method, the specific volumes of positron (Ve+) and positronium (Vps) "traps" have been calculated. The data of 29Si NMR spectroscopy have shown the presence of T2 and T3 fragments in the structure. As was shown on the basis of the data of 27Al NMR and XPS spectroscopy, tetrahedral (66%) and octahedral surroundings of the metal atom were realized in the backbone chain. The obtained data were used to describe a spatial layered structure of phenyl siloxanes containing trivalent metals. The electron microscopy of nanocomplexes revealed the presence of spherical particles, whose size changes in cases of chromium, iron, and aluminum. Using the data of low-temperature nitrogen adsorption, it was assumed that the specific surface area was filled with a layer of compacted spherical particles, whereas the layer thickness was determined, in its turn, by the specific polarizing potential (SPP) calculated as a ratio of the polarizing potential (PP) to the volume of voids between coherent scattering regions. Similar dependence is observed between the layer thickness and the specific polarizing potential calculated as a ratio of the polarizing potential to the positronium "trap" volume. A direct dependence between the thickness of the spherical particles layer and the specific polarizing potential has been demonstrated. The assumption

Biodeterioration Risk Threatens the 3100 Year Old Staircase of Hallstatt (Austria): Possible Involvement of Halophilic Microorganisms.

PubMed

Piñar, Guadalupe; Dalnodar, Dennis; Voitl, Christian; Reschreiter, Hans; Sterflinger, Katja

2016-01-01

The prosperity of Hallstatt (Salzkammergut region, Austria) is based on the richness of salt in the surrounding mountains and salt mining, which is documented as far back as 1500 years B.C. Substantial archaeological evidence of Bronze and Iron Age salt mining has been discovered, with a wooden staircase (1108 B.C.) being one of the most impressive and well preserved finds. However, after its discovery, fungal mycelia have been observed on the surface of the staircase, most probably due to airborne contamination after its find. As a basis for the further preservation of this valuable object, the active micro-flora was examined to investigate the presence of potentially biodegradative microorganisms. Most of the strains isolated from the staircase showed to be halotolerant and halophilic microorganisms, due to the saline environment of the mine. Results derived from culture-dependent assays revealed a high fungal diversity, including both halotolerant and halophilic fungi, the most dominant strains being members of the genus Phialosimplex (synonym: Aspergillus). Additionally, some typical cellulose degraders, namely Stachybotrys sp. and Cladosporium sp. were detected. Numerous bacterial strains were isolated and identified as members of 12 different genera, most of them being moderately halophilic species. The most dominant isolates affiliated with species of the genera Halovibrio and Marinococcus. Halophilic archaea were also isolated and identified as species of the genera Halococcus and Halorubrum. Molecular analyses complemented the cultivation assays, enabling the identification of some uncultivable archaea of the genera Halolamina, Haloplanus and Halobacterium. Results derived from fungi and bacteria supported those obtained by cultivation methods, exhibiting the same dominant members in the communities. The results clearly showed the presence of some cellulose degraders that may become active if the requirements for growth and the environmental conditions

Low-loss Kagome hollow-core fibers operating from the near- to the mid-IR.

PubMed

Wheeler, N V; Bradley, T D; Hayes, J R; Gouveia, M A; Liang, S; Chen, Y; Sandoghchi, S R; Abokhamis Mousavi, S M; Poletti, F; Petrovich, M N; Richardson, D J

2017-07-01

We report the fabrication and characterization of Kagome hollow-core antiresonant fibers, which combine low attenuation (as measured at ∼30  cm bend diameter) with a wide operating bandwidth and high modal purity. Record low attenuation values are reported: 12.3 dB/km, 13.9 dB/km, and 9.6 dB/km in three different fibers optimized for operation at 1 μm, 1.55 μm, and 2.5 μm, respectively. These fibers are excellent candidates for ultra-high power delivery at key laser wavelengths including 1.064 μm and 2.94 μm, as well as for applications in gas-based sensing and nonlinear optics.

Low loss and flat dispersion Kagome photonic crystal fiber in the terahertz regime

NASA Astrophysics Data System (ADS)

Rana, Sohel; Rakin, Adnan Siraj; Hasan, Md. Rabiul; Reza, Md. Salim; Leonhardt, Rainer; Abbott, Derek; Subbaraman, Harish

2018-03-01

A novel fiber design based on hexagonal shaped holes incorporated within the core of a Kagome lattice photonic crystal fiber (PCF) is presented. The modal properties of the proposed fiber are evaluated by using a finite element method (FEM) with a perfectly matched layer as boundary condition. Simulation results exhibit an ultra-low effective material loss (EML) of 0.029 cm-1 at an operating frequency of 1.3 THz with an optimized core diameter of 300 μm. A positive, low, and flat dispersion of 0.49 ± 0.06 ps/THz/cm is obtained within a broad frequency range from 1.00 to 1.76 THz. Other essential guiding features of the designed fiber such as power fraction and confinement loss are studied. The fabrication possibilities are also investigated to demonstrate feasibility for a wide range of terahertz applications.

Crystal-field effects in the kagome antiferromagnet Ho3Ru4Al12

NASA Astrophysics Data System (ADS)

Gorbunov, D. I.; Nomura, T.; Ishii, I.; Henriques, M. S.; Andreev, A. V.; Doerr, M.; Stöter, T.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.

2018-05-01

In Ho3Ru4Al12 , the Ho atoms form a distorted kagome lattice. We performed magnetization, magnetic-susceptibility, specific-heat, and ultrasound measurements on a single crystal. We find that the magnetic and magnetoelastic properties of Ho3Ru4Al12 result from an interplay between geometric frustration and crystal-electric-field (CEF) effects. The Ho atoms order antiferromagnetically at TN=4.5 K with reduced magnetic moments. In applied field, the magnetization shows anomalies that can be explained by CEF level crossings. We propose a CEF level scheme for which the ground-state doublet and the first two excited singlets at about 2.7 K form a quasiquartet. Indirect interlevel transitions allow for a quadrupolar interaction. This interaction explains well changes in the elastic shear modulus C44 as a function of temperature and magnetic field.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Guangmei; Valldor, Martin; Mallick, Bert

Four open-framework transition-metal phosphates; (NH4)2Co3(HPO4)2F4 (1), (NH4)Co3(HPO4)2(H2PO4)F2 (2), KCo3(HPO4)2(H2PO4)F2 (3), and KFe3(HPO4)2(H2PO4)F2 (4); are prepared by ionothermal synthesis using pyridinium hexafluorophosphate as the ionic liquid. Single-crystal X-ray diffraction analyses reveal that the four compounds contain cobalt/iron–oxygen/fluoride layers with Kagomé topology composed of interlinked face-sharing MO3F3/MO4F2 octahedra. PO3OH pseudo-tetrahedral groups augment the [M3O6F4] (1)/[M3O8F2] layers on both sides to give M3(HPO4)2F4 (1) and M3(HPO4)2F2 (2–4) layers. These layers are stacked along the a axis in a sequence AA…, resulting in the formation of a layer structure for (NH4)2Co3(HPO4)2F4(1). In NH4Co3(HPO4)2(H2PO4)F2 and KM3(HPO4)2(H2PO4)F2, the M3(HPO4)2F2 layers are stacked along the a axismore » in a sequence AAi… and are connected by [PO3(OH)] tetrahedra, giving rise to a 3-D open framework structure with 10-ring channels along the [001] direction. The negative charges of the inorganic framework are balanced by K+/NH4+ ions located within the channels. The magnetic transition metal cations themselves form layers with stair-case Kagomé topology. Magnetic susceptibility and magnetization measurements reveal that all four compounds exhibit a canted anti-ferromagnetic ground state (Tc = 10 or 13 K for Co and Tc = 27 K for Fe) with different canting angles. The full orbital moment is observed for both Co2+ and Fe2+.« less

Low-field anomalous magnetic phase in the kagome-lattice shandite C o3S n2S2

NASA Astrophysics Data System (ADS)

Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

2017-07-01

The magnetization process of single crystals of the metallic kagome ferromagnet C o3S n2S2 was carefully measured via magnetization and ac susceptibility. Field-dependent anomalous transitions observed in low fields indicate the presence of an unconventional magnetic phase just below the Curie temperature, TC. The magnetic phase diagrams in low magnetic fields along different crystallographic directions were determined for the first time. The magnetic relaxation measurements at various frequencies covering five orders of magnitude from 0.01 to 1000 Hz indicate markedly slow spin dynamics only in the anomalous phase with characteristic relaxation times longer than 10 s.

Energy and variance budgets of a diffusive staircase with implications for heat flux scaling

NASA Astrophysics Data System (ADS)

Hieronymus, M.; Carpenter, J. R.

2016-02-01

Diffusive convection, the mode of double-diffusive convection that occur when both temperature and salinity increase with increasing depth, is commonplace throughout the high latitude oceans and diffusive staircases constitute an important heat transport process in the Arctic Ocean. Heat and buoyancy fluxes through these staircases are often estimated using flux laws deduced either from laboratory experiments, or from simplified energy or variance budgets. We have done direct numerical simulations of double-diffusive convection at a range of Rayleigh numbers and quantified the energy and variance budgets in detail. This allows us to compare the fluxes in our simulations to those derived using known flux laws and to quantify how well the simplified energy and variance budgets approximate the full budgets. The fluxes are found to agree well with earlier estimates at high Rayleigh numbers, but we find large deviations at low Rayleigh numbers. The close ties between the heat and buoyancy fluxes and the budgets of thermal variance and energy have been utilized to derive heat flux scaling laws in the field of thermal convection. The result is the so called GL-theory, which has been found to give accurate heat flux scaling laws in a very wide parameter range. Diffusive convection has many similarities to thermal convection and an extension of the GL-theory to diffusive convection is also presented and its predictions are compared to the results from our numerical simulations.

Degenerate and chiral states in the extended Heisenberg model on the kagome lattice

NASA Astrophysics Data System (ADS)

Gómez Albarracín, F. A.; Pujol, P.

2018-03-01

We present a study of the low-temperature phases of the antiferromagnetic extended classical Heisenberg model on the kagome lattice, up to third-nearest neighbors. First, we focus on the degenerate lines in the boundaries of the well-known staggered chiral phases. These boundaries have either semiextensive or extensive degeneracy, and we discuss the partial selection of states by thermal fluctuations. Then, we study the model under an external magnetic field on these lines and in the staggered chiral phases. We pay particular attention to the highly frustrated point, where the three exchange couplings are equal. We show that this point can be mapped to a model with spin-liquid behavior and nonzero chirality. Finally, we explore the effect of Dzyaloshinskii-Moriya (DM) interactions in two ways: a homogeneous and a staggered DM interaction. In both cases, there is a rich low-temperature phase diagram, with different spontaneously broken symmetries and nontrivial chiral phases.

Complex magnetic order in the kagome ferromagnet Pr3Ru4Al12

NASA Astrophysics Data System (ADS)

Henriques, M. S.; Gorbunov, D. I.; Andreev, A. V.; Fabrèges, X.; Gukasov, A.; Uhlarz, M.; Petříček, V.; Ouladdiaf, B.; Wosnitza, J.

2018-01-01

In the hexagonal crystal structure of Pr3Ru4Al12 , the Pr atoms form a distorted kagome lattice, and their magnetic moments, are subject to competing exchange and anisotropy interactions. We performed magnetization, magnetic-susceptibility, specific-heat, electrical-resistivity, and neutron-scattering measurements. Pr3Ru4Al12 is a uniaxial ferromagnet with TC=39 K that displays a collinear magnetic structure (in the high-temperature range of the magnetically ordered state) for which the only crystallographic position of Pr is split into two sites carrying different magnetic moments. A spin-reorientation phase transition is found at 7 K. Below this temperature, part of the Pr moments rotate towards the basal plane, resulting in a noncollinear magnetic state with a lower magnetic symmetry. We argue that unequal RKKY exchange interactions competing with the crystal electric field lead to a moment instability and qualitatively explain the observed magnetic phases in Pr3Ru4Al12 .

Flat electronic bands in fractal-kagomé network and the effect of perturbation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nandy, Atanu, E-mail: atanunandy1989@gmail.com; Chakrabarti, Arunava, E-mail: arunava-chakrabarti@yahoo.co.in

2016-05-06

We demonstrate an analytical prescription of demonstrating the flat band [FB] states in a fractal incorporated kagomé type network that can give rise to a countable infinity of flat non-dispersive eigenstates with a multitude of localization area. The onset of localization can, in principle, be delayed in space by an appropriate choice of energy regime. The length scale, at which the onset of localization for each mode occurs, can be tuned at will following the formalism developed within the framework of real space renormalization group. This scheme leads to an exact determination of energy eigenvalue for which one can havemore » dispersionless flat electronic bands. Furthermore, we have shown the effect ofuniform magnetic field for the same non-translationally invariant network model that has ultimately led to an‘apparent invisibility’ of such staggered localized states and to generate absolutely continuous sub-bands in the energy spectrum and again an interesting re-entrant behavior of those FB states.« less

Dual-hole unit-based kagome lattice microstructure fiber for low-loss and highly birefringent terahertz guidance

NASA Astrophysics Data System (ADS)

Hasan, Md. Rabiul; Akter, Sanjida; Khatun, Tania; Rifat, Ahmmed A.; Anower, Md. Shamim

2017-04-01

A low-loss microstructure fiber is numerically investigated for convenient transmission of polarization maintaining terahertz (THz) waves. The dual-hole units (DHUs) are used inside the core of the kagome lattice microstructure to achieve high birefringence and low effective material loss (EML). It is demonstrated that by rotating the axis of orientation of the DHUs, it is possible to obtain low EML of 0.052 cm-1, low confinement loss of 0.01 cm-1, and high birefringence of 0.0354 at 0.85 THz. It is also reported that the transmission properties of the proposed microstructure fiber are varied with rotation angle, core diameter, and operating frequencies. Other guiding characteristics, such as single-mode propagation, power fraction, and dispersion, are also discussed thoroughly.

Terrorism as a process: a critical review of Moghaddam's "Staircase to Terrorism".

PubMed

Lygre, Ragnhild B; Eid, Jarle; Larsson, Gerry; Ranstorp, Magnus

2011-12-01

This study reviews empirical evidence for Moghaddam's model "Staircase to Terrorism," which portrays terrorism as a process of six consecutive steps culminating in terrorism. An extensive literature search, where 2,564 publications on terrorism were screened, resulted in 38 articles which were subject to further analysis. The results showed that while most of the theories and processes linked to Moghaddam's model are supported by empirical evidence, the proposed transitions between the different steps are not. These results may question the validity of a linear stepwise model and may suggest that a combination of mechanisms/factors could combine in different ways to produce terrorism. © 2011 The Authors. Scandinavian Journal of Psychology © 2011 The Scandinavian Psychological Associations.

Spin-1/2 kagome XXZ model in a field: Competition between lattice nematic and solid orders

NASA Astrophysics Data System (ADS)

Kshetrimayum, Augustine; Picot, Thibaut; Orús, Román; Poilblanc, Didier

2016-12-01

We study numerically the spin-1/2 XXZ model in a field on an infinite kagome lattice. We use different algorithms based on infinite projected entangled pair states (iPEPSs) for this, namely, (i) an approach with simplex tensors and a 9-site unit cell, and (ii) an approach based on coarse-graining three spins in the kagome lattice and mapping it to a square-lattice model with local and nearest-neighbor interactions, with the usual PEPS tensors, 6- and 12-site unit cells. Similarly to our previous calculation at the SU(2)-symmetric point (Heisenberg Hamiltonian), for any anisotropy from the Ising limit to the XY limit, we also observe the emergence of magnetization plateaus as a function of the magnetic field, at mz=1/3 using 6-, 9-, and 12-site PEPS unit cells, and at mz=1/9 ,5/9 , and 7/9 using a 9-site PEPS unit cell, the latter setup being able to accommodate √{3 }×√{3 } solid order. We also find that, at mz=1/3 , (lattice) nematic and √{3 }×√{3 } VBC-order states are degenerate within the accuracy of the nine-site simplex method, for all anisotropy. The 6- and 12-site coarse-grained PEPS methods produce almost-degenerate nematic and 1 ×2 VBC-solid orders. We also find that, within our accuracy, the six-site coarse-grained PEPS method gives slightly lower energies, which can be explained by the larger amount of entanglement this approach can handle, even in cases where the PEPS unit cell is not commensurate with the expected ground-state unit cell. Furthermore, we do not observe chiral spin liquid behaviors at and close to the XY point, as has been recently proposed. Our results are the first tensor network investigations of the XXZ model in a field and reveal the subtle competition between nearby magnetic orders in numerical simulations of frustrated quantum antiferromagnets, as well as the delicate interplay between energy optimization and symmetry in tensor network numerical simulations.

Thermodynamic and Neutron Scattering Study of the Spin-1/2 Kagome Antiferromagnet ZnCu3(OH)6Cl2: A Quantum Spin Liquid System

NASA Astrophysics Data System (ADS)

Han, Tianheng

New physics, such as a quantum spin liquid, can emerge in systems where quantum fluctuations are enhanced due to reduced dimensionality and strong frustration . The realization of a quantum spin liquid in two-dimensions would represent a new state of matter. It is believed that spin liquid physics plays a role in the phenomenon of high-Tc superconductivity, and the topological properties of the spin liquid state may have applications in the field of quantum information. The Zn-paratacamite family, ZnxCu4-- x(OH)6Cl2 for x > 0.33, is an ideal system to look for such an exotic state in the form of antiferromagnetic Cu 2 + kagome planes. The x = 1 end member, named herbertsmithite, has shown promising spin liquid properties from prior studies on powder samples. Here we show a new synthesis by which high-quality centimeter-sized single crystals of Znparatacamite have been produced for the first time. Neutron and synchrotron xray diffraction experiments indicate no structural transition down to T = 2 K. The magnetic susceptibility both perpendicular and parallel to the kagome plane has been measured for the x = 1 sample. A small, temperature-dependent anisotropy has been observed, where chi z / chip > 1 at high temperatures and chiz / chip < 1 at low temperatures. Fits of the high-temperature data to a Curie-Weiss model also reveal anisotropies for thetacw's and g-factors. By comparing with theoretical calculations, the presence of a small easy-axis exchange anisotropy can be deduced as a primary perturbation to the dominant Heisenberg nearest neighbor interaction. These results have great bearing on the interpretation of theoretical calculations based on the kagome Heisenberg antiferromagnet model to the experiments on ZnCu3(OH) 6Cl2. Specific heat measurements down to dilution temperatures and under strong applied magnetic fields show a superlinear temperature dependence with a finite linear term. Most importantly, we present neutron scattering measurements of the

Zero-bias offsets in I-V characteristics of the staircase type quantum well infrared photodetectors

NASA Astrophysics Data System (ADS)

Nutku, Ferhat; Erol, Ayse; Arikan, M. Cetin; Ergun, Yuksel

2014-11-01

In this work, observed zero-bias offsets in I-V characteristics and differences in J-V characteristics of staircase quantum well infrared photodetectors were investigated. Temperature and voltage sweep rate dependence of the zero-bias offsets were studied on mesa structures shaped in different diameters. Furthermore, effect of mesa diameter on J-V characteristics was investigated. The temperature, initial bias voltage and voltage sweep rate dependence of the zero-bias offsets were explained by a qualitative model, which is based on a RC equivalent circuit of the quantum well infrared photodetector.

Characteristics of pinyon-juniper woodlands in Grand Staircase-Escalante National Monument: Changes since Monument establishment and prospects for future monitoring

Treesearch

Christopher Witt; John D. Shaw

2010-01-01

Recent data from the USDA Forest Service Forest Inventory and Analysis (FIA) program have documented spatial and temporal patterns of drought-related mortality across woodlands of the Southwest (Shaw et al. 2005). In the early 1990s, FIA collected data on forested land now included in Grand Staircase-Escalante National Monument (GSENM or the Monument) as part of a...

Climatic irregular staircases: generalized acceleration of global warming.

PubMed

De Saedeleer, Bernard

2016-01-27

Global warming rates mentioned in the literature are often restricted to a couple of arbitrary periods of time, or of isolated values of the starting year, lacking a global view. In this study, we perform on the contrary an exhaustive parametric analysis of the NASA GISS LOTI data, and also of the HadCRUT4 data. The starting year systematically varies between 1880 and 2002, and the averaging period from 5 to 30 yr - not only decades; the ending year also varies . In this way, we uncover a whole unexplored space of values for the global warming rate, and access the full picture. Additionally, stairstep averaging and linear least squares fitting to determine climatic trends have been sofar exclusive. We propose here an original hybrid method which combines both approaches in order to derive a new type of climatic trend. We find that there is an overall acceleration of the global warming whatever the value of the averaging period, and that 99.9% of the 3029 Earth's climatic irregular staircases are rising. Graphical evidence is also given that choosing an El Niño year as starting year gives lower global warming rates - except if there is a volcanic cooling in parallel. Our rates agree and generalize several results mentioned in the literature.

Staircase-scene-based nonuniformity correction in aerial point target detection systems.

PubMed

Huo, Lijun; Zhou, Dabiao; Wang, Dejiang; Liu, Rang; He, Bin

2016-09-01

Focal-plane arrays (FPAs) are often interfered by heavy fixed-pattern noise, which severely degrades the detection rate and increases the false alarms in airborne point target detection systems. Thus, high-precision nonuniformity correction is an essential preprocessing step. In this paper, a new nonuniformity correction method is proposed based on a staircase scene. This correction method can compensate for the nonlinear response of the detector and calibrate the entire optical system with computational efficiency and implementation simplicity. Then, a proof-of-concept point target detection system is established with a long-wave Sofradir FPA. Finally, the local standard deviation of the corrected image and the signal-to-clutter ratio of the Airy disk of a Boeing B738 are measured to evaluate the performance of the proposed nonuniformity correction method. Our experimental results demonstrate that the proposed correction method achieves high-quality corrections.

Quantum phase transitions and decoupling of magnetic sublattices in the quasi-two-dimensional Ising magnet Co 3V 2O 8 in a transverse magnetic field

DOE PAGES

Fritsch, Katharina; Ehlers, G.; Rule, K. C.; ...

2015-11-05

We study the application of a magnetic field transverse to the easy axis, Ising direction in the quasi-two-dimensional kagome staircase magnet, Co 3V 2O 8, induces three quantum phase transitions at low temperatures, ultimately producing a novel high field polarized state, with two distinct sublattices. New time-of-flight neutron scattering techniques, accompanied by large angular access, high magnetic field infrastructure allow the mapping of a sequence of ferromagnetic and incommensurate phases and their accompanying spin excitations. Also, at least one of the transitions to incommensurate phases at μ 0H c1~6.25 T and μ 0H c2~7 T is discontinuous, while the finalmore » quantum critical point at μ 0H c3~13 T is continuous.« less

Hierarchically self-assembled hexagonal honeycomb and kagome superlattices of binary 1D colloids.

PubMed

Lim, Sung-Hwan; Lee, Taehoon; Oh, Younghoon; Narayanan, Theyencheri; Sung, Bong June; Choi, Sung-Min

2017-08-25

Synthesis of binary nanoparticle superlattices has attracted attention for a broad spectrum of potential applications. However, this has remained challenging for one-dimensional nanoparticle systems. In this study, we investigate the packing behavior of one-dimensional nanoparticles of different diameters into a hexagonally packed cylindrical micellar system and demonstrate that binary one-dimensional nanoparticle superlattices of two different symmetries can be obtained by tuning particle diameter and mixing ratios. The hexagonal arrays of one-dimensional nanoparticles are embedded in the honeycomb lattices (for AB 2 type) or kagome lattices (for AB 3 type) of micellar cylinders. The maximization of free volume entropy is considered as the main driving force for the formation of superlattices, which is well supported by our theoretical free energy calculations. Our approach provides a route for fabricating binary one-dimensional nanoparticle superlattices and may be applicable for inorganic one-dimensional nanoparticle systems.Binary mixtures of 1D particles are rarely observed to cooperatively self-assemble into binary superlattices, as the particle types separate into phases. Here, the authors design a system that avoids phase separation, obtaining binary superlattices with different symmetries by simply tuning the particle diameter and mixture composition.

Climatic irregular staircases: generalized acceleration of global warming

PubMed Central

De Saedeleer, Bernard

2016-01-01

Global warming rates mentioned in the literature are often restricted to a couple of arbitrary periods of time, or of isolated values of the starting year, lacking a global view. In this study, we perform on the contrary an exhaustive parametric analysis of the NASA GISS LOTI data, and also of the HadCRUT4 data. The starting year systematically varies between 1880 and 2002, and the averaging period from 5 to 30 yr — not only decades; the ending year also varies . In this way, we uncover a whole unexplored space of values for the global warming rate, and access the full picture. Additionally, stairstep averaging and linear least squares fitting to determine climatic trends have been sofar exclusive. We propose here an original hybrid method which combines both approaches in order to derive a new type of climatic trend. We find that there is an overall acceleration of the global warming whatever the value of the averaging period, and that 99.9% of the 3029 Earth’s climatic irregular staircases are rising. Graphical evidence is also given that choosing an El Niño year as starting year gives lower global warming rates — except if there is a volcanic cooling in parallel. Our rates agree and generalize several results mentioned in the literature. PMID:26813867

Strain-induced topological magnon phase transitions: applications to kagome-lattice ferromagnets

NASA Astrophysics Data System (ADS)

Owerre, S. A.

2018-06-01

A common feature of topological insulators is that they are characterized by topologically invariant quantity such as the Chern number and the index. This quantity distinguishes a nontrivial topological system from a trivial one. A topological phase transition may occur when there are two topologically distinct phases, and it is usually defined by a gap closing point where the topologically invariant quantity is ill-defined. In this paper, we show that the magnon bands in the strained (distorted) kagome-lattice ferromagnets realize an example of a topological magnon phase transition in the realistic parameter regime of the system. When spin–orbit coupling (SOC) is neglected (i.e. no Dzyaloshinskii–Moriya interaction), we show that all three magnon branches are dispersive with no flat band, and there exists a critical point where tilted Dirac and semi-Dirac point coexist in the magnon spectra. The critical point separates two gapless magnon phases as opposed to the usual phase transition. Upon the inclusion of SOC, we realize a topological magnon phase transition point at the critical strain , where D and J denote the perturbative SOC and the Heisenberg spin exchange interaction respectively. It separates two distinct topological magnon phases with different Chern numbers for and for . The associated anomalous thermal Hall conductivity develops an abrupt change at , due to the divergence of the Berry curvature in momentum space. The proposed topological magnon phase transition is experimentally feasible by applying external perturbations such as uniaxial strain or pressure.

Staircase and saw-tooth field emission steps from nanopatterned n-type GaSb surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kildemo, M.; Levinsen, Y. Inntjore; Le Roy, S.

2009-09-15

High resolution field emission experiments from nanopatterned GaSb surfaces consisting of densely packed nanocones prepared by low ion-beam-energy sputtering are presented. Both uncovered and metal-covered nanopatterned surfaces were studied. Surprisingly, the field emission takes place by regular steps in the field emitted current. Depending on the field, the steps are either regular, flat, plateaus, or saw-tooth shaped. To the author's knowledge, this is the first time that such results have been reported. Each discrete jump in the field emission may be understood in terms of resonant tunneling through an extended surface space charge region in an n-type, high aspect ratio,more » single GaSb nanocone. The staircase shape may be understood from the spatial distribution of the aspect ratio of the cones.« less

Low temperature and high field regimes of connected kagome artificial spin ice: the role of domain wall topology.

PubMed

Zeissler, Katharina; Chadha, Megha; Lovell, Edmund; Cohen, Lesley F; Branford, Will R

2016-07-22

Artificial spin ices are frustrated magnetic nanostructures where single domain nanobars act as macrosized spins. In connected kagome artificial spin ice arrays, reversal occurs along one-dimensional chains by propagation of ferromagnetic domain walls through Y-shaped vertices. Both the vertices and the walls are complex chiral objects with well-defined topological edge-charges. At room temperature, it is established that the topological edge-charges determine the exact switching reversal path taken. However, magnetic reversal at low temperatures has received much less attention and how these chiral objects interact at reduced temperature is unknown. In this study we use magnetic force microscopy to image the magnetic reversal process at low temperatures revealing the formation of quite remarkable high energy remanence states and a change in the dynamics of the reversal process. The implication is the breakdown of the artificial spin ice regime in these connected structures at low temperatures.

A study of photomodulated reflectance on staircase-like, n-doped GaAs/AlxGa1-xAs quantum well structures.

PubMed

Donmez, Omer; Nutku, Ferhat; Erol, Ayse; Arikan, Cetin M; Ergun, Yuksel

2012-11-12

In this study, photomodulated reflectance (PR) technique was employed on two different quantum well infrared photodetector (QWIP) structures, which consist of n-doped GaAs quantum wells (QWs) between undoped AlxGa1-xAs barriers with three different x compositions. Therefore, the barrier profile is in the form of a staircase-like barrier. The main difference between the two structures is the doping profile and the doping concentration of the QWs. PR spectra were taken at room temperature using a He-Ne laser as a modulation source and a broadband tungsten halogen lamp as a probe light. The PR spectra were analyzed using Aspnes' third derivative functional form.Since the barriers are staircase-like, the structure has different ground state energies; therefore, several optical transitions take place in the spectrum which cannot be resolved in a conventional photoluminescence technique at room temperature. To analyze the experimental results, all energy levels in the conduction and in the valance band were calculated using transfer matrix technique, taking into account the effective mass and the parabolic band approximations. A comparison of the PR results with the calculated optical transition energies showed an excellent agreement. Several optical transition energies of the QWIP structures were resolved from PR measurements. It is concluded that PR spectroscopy is a very useful experimental tool to characterize complicated structures with a high accuracy at room temperature.

Strain-induced topological magnon phase transitions: applications to kagome-lattice ferromagnets.

PubMed

Owerre, S A

2018-06-20

A common feature of topological insulators is that they are characterized by topologically invariant quantity such as the Chern number and the [Formula: see text] index. This quantity distinguishes a nontrivial topological system from a trivial one. A topological phase transition may occur when there are two topologically distinct phases, and it is usually defined by a gap closing point where the topologically invariant quantity is ill-defined. In this paper, we show that the magnon bands in the strained (distorted) kagome-lattice ferromagnets realize an example of a topological magnon phase transition in the realistic parameter regime of the system. When spin-orbit coupling (SOC) is neglected (i.e. no Dzyaloshinskii-Moriya interaction), we show that all three magnon branches are dispersive with no flat band, and there exists a critical point where tilted Dirac and semi-Dirac point coexist in the magnon spectra. The critical point separates two gapless magnon phases as opposed to the usual phase transition. Upon the inclusion of SOC, we realize a topological magnon phase transition point at the critical strain [Formula: see text], where D and J denote the perturbative SOC and the Heisenberg spin exchange interaction respectively. It separates two distinct topological magnon phases with different Chern numbers for [Formula: see text] and for [Formula: see text]. The associated anomalous thermal Hall conductivity develops an abrupt change at [Formula: see text], due to the divergence of the Berry curvature in momentum space. The proposed topological magnon phase transition is experimentally feasible by applying external perturbations such as uniaxial strain or pressure.

A mechanism for the formation and sustainment of the self-organized global profile and E   ×   B staircase in tokamak plasmas

NASA Astrophysics Data System (ADS)

Wang, W.; Kishimoto, Y.; Imadera, K.; Li, J. Q.; Wang, Z. X.

2018-05-01

The mechanism for the formation and sustainment of a self-organized global profile and the ‘ E   ×   B staircase’ are investigated through simulations of a flux-driven ion temperature gradient (ITG) turbulence based on GKNET, a 5D global gyrokinetic code. The staircase is found to be initiated from the radially extended ITG mode structures with nearly up-down symmetry during the saturation phase, and is established as it evolves into a quasi-steady turbulence, leading to a self-organized global temperature profile and to meso-scale isomorphic profiles of the radial electric field and the temperature gradient. It is found that the quasi-regular E   ×   B shear flow pattern is primarily originated from an even-symmetrical zonal flow produced by the extended ITG mode, which flow pattern exhibits an in-phase relation with the mean flow variation induced by the temperature relaxation. Consequently, the staircase is initiated through the profiles of total electric field and temperature gradient with a self-organized manner. Since the sign of E   ×   B shear flow at the central part are opposite to that at both edges, it disintegrates the ITG mode into smaller scale eddies. Meanwhile, smaller scale eddies tend to be aligned radially by spontaneous phase matching, which can provide the growth of mode amplitude and the formation of radially extended mode structures, leading to the bursty heat transport. This process is repeated quasi-periodically, sustaining self-organized structures and the E   ×   B staircase. Moreover, the equilibrium mean field is found to be of specific importance in causing the structures and dynamics from meso- to macro scales in toroidal plasmas.

Persistence of the gapless spin liquid in the breathing kagome Heisenberg antiferromagnet

NASA Astrophysics Data System (ADS)

Iqbal, Yasir; Poilblanc, Didier; Thomale, Ronny; Becca, Federico

2018-03-01

The nature of the ground state of the spin S =1 /2 Heisenberg antiferromagnet on the kagome lattice with breathing anisotropy (i.e., with different superexchange couplings J▵ and J▿ within elementary up- and down-pointing triangles) is investigated within the framework of Gutzwiller projected fermionic wave functions and Monte Carlo methods. We analyze the stability of the U(1 ) Dirac spin liquid with respect to the presence of fermionic pairing that leads to a gapped Z2 spin liquid. For several values of the ratio J▿/J▵ , the size scaling of the energy gain due to the pairing fields and the variational parameters are reported. Our results show that the energy gain of the gapped spin liquid with respect to the gapless state either vanishes for large enough system size or scales to zero in the thermodynamic limit. Similarly, the optimized pairing amplitudes (responsible for opening the spin gap) are shown to vanish in the thermodynamic limit. Our outcome is corroborated by the application of one and two Lanczos steps to the gapless and gapped wave functions, for which no energy gain of the gapped state is detected when improving the quality of the variational states. Finally, we discuss the competition with the "simplex" Z2 resonating-valence-bond spin liquid, valence-bond crystal, and nematic states in the strongly anisotropic regime, i.e., J▿≪J▵ .

Study of system-size effects on the emergent magnetic monopoles and Dirac strings in artificial kagome spin ice

NASA Astrophysics Data System (ADS)

Leon, Alejandro

2012-02-01

In this work we study the dynamical properties of a finite array of nanomagnets in artificial kagome spin ice at room temperature. The dynamic response of the array of nanomagnets is studied by implementing a ``frustrated celular aut'omata'' (FCA), based in the charge model. In this model, each dipole is replaced by a dumbbell of two opposite charges, which are situated at the neighbouring vertices of the honeycomb lattice. The FCA simulations, allow us to study in real-time and deterministic way, the dynamic of the system, with minimal computational resource. The update function is defined according to the coordination number of vertices in the system. Our results show that for a set geometric parameters of the array of nanomagnets, the system exhibits high density of Dirac strings and high density emergent magnetic monopoles. A study of the effect of disorder in the arrangement of nanomagnets is incorporated in this work.

A study of photomodulated reflectance on staircase-like, n-doped GaAs/AlxGa1−xAs quantum well structures

PubMed Central

2012-01-01

In this study, photomodulated reflectance (PR) technique was employed on two different quantum well infrared photodetector (QWIP) structures, which consist of n-doped GaAs quantum wells (QWs) between undoped AlxGa1−xAs barriers with three different x compositions. Therefore, the barrier profile is in the form of a staircase-like barrier. The main difference between the two structures is the doping profile and the doping concentration of the QWs. PR spectra were taken at room temperature using a He-Ne laser as a modulation source and a broadband tungsten halogen lamp as a probe light. The PR spectra were analyzed using Aspnes’ third derivative functional form. Since the barriers are staircase-like, the structure has different ground state energies; therefore, several optical transitions take place in the spectrum which cannot be resolved in a conventional photoluminescence technique at room temperature. To analyze the experimental results, all energy levels in the conduction and in the valance band were calculated using transfer matrix technique, taking into account the effective mass and the parabolic band approximations. A comparison of the PR results with the calculated optical transition energies showed an excellent agreement. Several optical transition energies of the QWIP structures were resolved from PR measurements. It is concluded that PR spectroscopy is a very useful experimental tool to characterize complicated structures with a high accuracy at room temperature. PMID:23146126

A study of photomodulated reflectance on staircase-like, n-doped GaAs/Al x Ga1- x As quantum well structures

NASA Astrophysics Data System (ADS)

Donmez, Omer; Nutku, Ferhat; Erol, Ayse; Arikan, Cetin M.; Ergun, Yuksel

2012-11-01

In this study, photomodulated reflectance (PR) technique was employed on two different quantum well infrared photodetector (QWIP) structures, which consist of n-doped GaAs quantum wells (QWs) between undoped Al x Ga1- x As barriers with three different x compositions. Therefore, the barrier profile is in the form of a staircase-like barrier. The main difference between the two structures is the doping profile and the doping concentration of the QWs. PR spectra were taken at room temperature using a He-Ne laser as a modulation source and a broadband tungsten halogen lamp as a probe light. The PR spectra were analyzed using Aspnes' third derivative functional form. Since the barriers are staircase-like, the structure has different ground state energies; therefore, several optical transitions take place in the spectrum which cannot be resolved in a conventional photoluminescence technique at room temperature. To analyze the experimental results, all energy levels in the conduction and in the valance band were calculated using transfer matrix technique, taking into account the effective mass and the parabolic band approximations. A comparison of the PR results with the calculated optical transition energies showed an excellent agreement. Several optical transition energies of the QWIP structures were resolved from PR measurements. It is concluded that PR spectroscopy is a very useful experimental tool to characterize complicated structures with a high accuracy at room temperature.

Structural and magnetic properties of two branches of the tripod-kagome-lattice family A2R3Sb3O14 (A = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb)

NASA Astrophysics Data System (ADS)

Dun, Z. L.; Trinh, J.; Lee, M.; Choi, E. S.; Li, K.; Hu, Y. F.; Wang, Y. X.; Blanc, N.; Ramirez, A. P.; Zhou, H. D.

2017-03-01

We present a systematic study of the structural and magnetic properties of two branches of the rare-earth tripod-kagome-lattice (TKL) family A2R3Sb3O14 (A = Mg, Zn; R = Pr, Nd, Gd, Tb, Dy, Ho, Er, Yb; here, we use abbreviation A-R, as in MgPr for Mg2Pr3Sb3O14 ), which complements our previously reported work on MgDy, MgGd, and MgEr [Z. L. Dun et al., Phys. Rev. Lett. 116, 157201 (2016), 10.1103/PhysRevLett.116.157201]. The present susceptibility (χdc, χac) and specific-heat measurements reveal various magnetic ground states, including the nonmagnetic singlet state for MgPr, ZnPr; long-range orderings (LROs) for MgGd, ZnGd, MgNd, ZnNd, and MgYb; a long-range magnetic charge ordered state for MgDy, ZnDy, and potentially for MgHo; possible spin-glass states for ZnEr, ZnHo; the absence of spin ordering down to 80 mK for MgEr, MgTb, ZnTb, and ZnYb compounds. The ground states observed here bear both similarities as well as striking differences from the states found in the parent pyrochlore systems. In particular, while the TKLs display a greater tendency towards LRO, the lack of LRO in MgHo, MgTb, and ZnTb can be viewed from the standpoint of a balance among spin-spin interactions, anisotropies, and non-Kramers nature of single-ion state. While substituting Zn for Mg changes the chemical pressure, and subtly modifies the interaction energies for compounds with larger R ions, this substitution introduces structural disorder and modifies the ground states for compounds with smaller R ions (Ho, Er, Yb).

Novel conformal technique to reduce staircasing artifacts at material boundaries for FDTD modeling of the bioheat equation.

PubMed

Neufeld, E; Chavannes, N; Samaras, T; Kuster, N

2007-08-07

The modeling of thermal effects, often based on the Pennes Bioheat Equation, is becoming increasingly popular. The FDTD technique commonly used in this context suffers considerably from staircasing errors at boundaries. A new conformal technique is proposed that can easily be integrated into existing implementations without requiring a special update scheme. It scales fluxes at interfaces with factors derived from the local surface normal. The new scheme is validated using an analytical solution, and an error analysis is performed to understand its behavior. The new scheme behaves considerably better than the standard scheme. Furthermore, in contrast to the standard scheme, it is possible to obtain with it more accurate solutions by increasing the grid resolution.

Thermodynamics of Ising spins on the triangular kagome lattice: Exact analytical method and Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Loh, Y. L.; Yao, D. X.; Carlson, E. W.

2008-04-01

A new class of two-dimensional magnetic materials Cu9X2(cpa)6ṡxH2O ( cpa=2 -carboxypentonic acid; X=F,Cl,Br ) was recently fabricated in which Cu sites form a triangular kagome lattice (TKL). As the simplest model of geometric frustration in such a system, we study the thermodynamics of Ising spins on the TKL using exact analytic method as well as Monte Carlo simulations. We present the free energy, internal energy, specific heat, entropy, sublattice magnetizations, and susceptibility. We describe the rich phase diagram of the model as a function of coupling constants, temperature, and applied magnetic field. For frustrated interactions in the absence of applied field, the ground state is a spin liquid phase with residual entropy per spin s0/kB=(1)/(9)ln72≈0.4752… . In weak applied field, the system maps to the dimer model on a honeycomb lattice, with residual entropy 0.0359 per spin and quasi-long-range order with power-law spin-spin correlations that should be detectable by neutron scattering. The power-law correlations become exponential at finite temperatures, but the correlation length may still be long.

Prediction and synthesis of a family of atomic laminate phases with Kagomé-like and in-plane chemical ordering

PubMed Central

Dahlqvist, Martin; Lu, Jun; Meshkian, Rahele; Tao, Quanzheng; Hultman, Lars; Rosen, Johanna

2017-01-01

The enigma of MAX phases and their hybrids prevails. We probe transition metal (M) alloying in MAX phases for metal size, electronegativity, and electron configuration, and discover ordering in these MAX hybrids, namely, (V2/3Zr1/3)2AlC and (Mo2/3Y1/3)2AlC. Predictive theory and verifying materials synthesis, including a judicious choice of alloying M from groups III to VI and periods 4 and 5, indicate a potentially large family of thermodynamically stable phases, with Kagomé-like and in-plane chemical ordering, and with incorporation of elements previously not known for MAX phases, including the common Y. We propose the structure to be monoclinic C2/c. As an extension of the work, we suggest a matching set of novel MXenes, from selective etching of the A-element. The demonstrated structural design on simultaneous two-dimensional (2D) and 3D atomic levels expands the property tuning potential of functional materials. PMID:28776034

Magnetic structure of the swedenborgite CaBa (Co3Fe ) O7 derived by unpolarized neutron diffraction and spherical neutron polarimetry

NASA Astrophysics Data System (ADS)

Qureshi, N.; Díaz, M. T. Fernández; Chapon, L. C.; Senyshyn, A.; Schweika, W.; Valldor, M.

2018-02-01

We present a study that combines polarized and unpolarized neutrons to derive the magnetic structure of the swedenborgite compound CaBa (Co3Fe ) O7. Integrated intensities from a standard neutron diffraction experiment and polarization matrices from spherical neutron polarimetry have been simultaneously analyzed revealing a complex order, which differs from the usual spin configurations on a kagome lattice. We find that the magnetic structure is well described by a combination of two one-dimensional representations corresponding to the magnetic superspace symmetry P 21' , and it consists of spins rotating around an axis close to the [110] direction. Due to the propagation vector q =(1/3 00 ) , this modulation has cycloidal and helicoidal character rendering this system a potential multiferroic. The resulting spin configuration can be mapped onto the classical √{3 }×√{3 } structure of a kagome lattice, and it indicates an important interplay between the kagome and the triangular layers of the crystal structure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Kuo; Hu, Yufei; Wang, Yingxia, E-mail: Wangyx@pku.edu.cn

Isostructural compounds RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} (RE=La, Pr, Nd, Sm–Ho) with an ordered pyrochlore structure were synthesized. The structure of La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} was solved ab initio based on powder XRD data, and refined by combining with high resolution neutron diffraction data. La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} crystallizes in the space group R-3m with the unit cell parameters a=7.52954(2) Å and c=17.59983(6) Å. The structures of other members in this family are confirmed by Rietveld refinement using powder X-ray diffraction data. The cations (RE, Sb and Co) in RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} are orderly distributed, presentingmore » as [RE{sub 3}Co][Sb{sub 3}Co]O{sub 14} formula, and giving rise to two distinctive Kagome lattices constructed by RE{sup 3+} and Sb{sup 5+}, respectively. Co{sup 2+} occupies 8-coordinated and 6-coordinated environments, showing low spin (S=1/2) and high spin (S=3/2) states respectively. The magnetic susceptibility and UV–visual spectroscopy supports the magnetic observation. TDDFT calculation was performed to interpret the electronic states. The compounds [RE{sub 3}Co][Sb{sub 3}Co]O{sub 14} provide a profound example in which the ideal 2D Kagome lattice is derived from the 3D pyrochlore-type structure by an ordered distribution of the metal cations. - Graphical abstract: La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} crystallizes in a pyrochlore related structure with an ordered distribution of cations, giving rise to two sets of ideal 2D Kagome lattices formed by La{sup 3+} or Sb{sup 5+} respectively. This rhombohedral pyrochlore is a tolerant structure for stable compounds composed by many light rare-earth and d-transition elements. Substituting Zn{sup 2+} or Mg{sup 2+} for Co{sup 2+} will provide a series of compounds useful for studying magnetic interactions in the rare-earth Kagome lattices. - Highlights: • Pyrochlore-type La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} shows an ordered distribution

Emergence of nontrivial magnetic excitations in a spin-liquid state of kagomé volborthite

PubMed Central

Watanabe, Daiki; Sugii, Kaori; Shimozawa, Masaaki; Suzuki, Yoshitaka; Yajima, Takeshi; Ishikawa, Hajime; Hiroi, Zenji; Shibauchi, Takasada; Matsuda, Yuji; Yamashita, Minoru

2016-01-01

When quantum fluctuations destroy underlying long-range ordered states, novel quantum states emerge. Spin-liquid (SL) states of frustrated quantum antiferromagnets, in which highly correlated spins fluctuate down to very low temperatures, are prominent examples of such quantum states. SL states often exhibit exotic physical properties, but the precise nature of the elementary excitations behind such phenomena remains entirely elusive. Here, we use thermal Hall measurements that can capture the unexplored property of the elementary excitations in SL states, and report the observation of anomalous excitations that may unveil the unique features of the SL state. Our principal finding is a negative thermal Hall conductivity κxy which the charge-neutral spin excitations in a gapless SL state of the 2D kagomé insulator volborthite Cu3V2O7(OH)2⋅2H2O exhibit, in much the same way in which charged electrons show the conventional electric Hall effect. We find that κxy is absent in the high-temperature paramagnetic state and develops upon entering the SL state in accordance with the growth of the short-range spin correlations, demonstrating that κxy is a key signature of the elementary excitation formed in the SL state. These results suggest the emergence of nontrivial elementary excitations in the gapless SL state which feel the presence of fictitious magnetic flux, whose effective Lorentz force is found to be less than 1/100 of the force experienced by free electrons. PMID:27439874

Tunable artificial vortex ice in nanostructured superconductors with a frustrated kagome lattice of paired antidots

NASA Astrophysics Data System (ADS)

Xue, C.; Ge, J.-Y.; He, A.; Zharinov, V. S.; Moshchalkov, V. V.; Zhou, Y. H.; Silhanek, A. V.; Van de Vondel, J.

2018-04-01

Theoretical proposals for spin-ice analogs based on nanostructured superconductors have suggested larger flexibility for probing the effects of fluctuations and disorder than in the magnetic systems. In this paper, we unveil the particularities of a vortex ice system by direct observation of the vortex distribution in a kagome lattice of paired antidots using scanning Hall probe microscopy. The theoretically suggested vortex ice distribution, lacking long-range order, is observed at half matching field (H1/2 ). Moreover, the vortex ice state formed by the pinned vortices is still preserved at 2 H1/3 . This unexpected result is attributed to the introduction of interstitial vortices at these magnetic-field values. Although the interstitial vortices increase the number of possible vortex configurations, it is clearly shown that the vortex ice state observed at 2 H1/3 is less prone to defects than at H1/2 . In addition, the nonmonotonic variations of the vortex ice quality on the lattice spacing indicates that a highly ordered vortex ice state cannot be attained by simply reducing the lattice spacing. The optimal design to observe defect-free vortex ice is discussed based on the experimental statistics. The direct observations of a tunable vortex ice state provides new opportunities to explore the order-disorder transition in artificial ice systems.

External controls on formation and preservation of fluvial terrace staircases in the Southern Pyrenees foreland

NASA Astrophysics Data System (ADS)

Stange, K. M.; van Balen, R. T.; Carcaillet, J.

2012-04-01

The fluvial network of the Southern Pyrenees is an example of transverse drainage systems in young (alpine) mountain belts and it features well preserved fluvial terrace records. Some of the major Southern Pyrenees tributaries, like the Cinca and the Gallego, have been studied previously and have some age controls on their fluvial terrace levels. We extend these records to the largest drainage system of the Southern Pyrenees, the Segre river system, presenting new GIS and field data, as well as exposure ages obtained from in situ produced 10Be cosmogenic nuclides. The terrace staircase of the Segre River is built up by cut and fill type terraces, ranging from 112 to 3 meter above the present-day riverbed. Gravel deposits have commonly thicknesses of 2 to 7 meter over bedrock. Locally they have extensive thicknesses of up to 20 meter and show evidence for the impact of ongoing tectonics (i.e. gypsum doming, tectonic basin) featuring faults and folds as primary features. The terrace record can be subdivided into four groups of terraces that are separated by large incisive steps of about 20 meter: I) old extensive single terrace surfaces (TQ1, ~112m), II) terraces of limited extent preserved as remnant hills (TQ2, ~80m), III) two extensive terrace levels (TQ3 and TQ4, 60-45m), and IV) a well-preserved and extensive lower terrace complex (TQ5-TQ7, 30-3m). The staircase morphology (extent and elevations) of the Segre River shows analogies with other streams of the Southern Pyrenees indicating regional scale causes for the formation of terraces. The terraces TQ1, TQ2,TQ3 and TQ4 have been sampled for in situ produced 10Be cosmogenic nuclides. Our results show preliminary minimum ages of Middle to Late Pleistocene terrace abandonment: TQ1: 274 ka (MIS 9a), TQ2: 135 ka (MIS 5e), TQ3: 106 ka (MIS 5c), and TQ4: 65 ka (MIS 3), and erosion rates of 0.3 cm/ka (TQ1, TQ4), 0.45 cm/ka (TQ3), and 0.73 cm/ka for TQ2. The obtained ages indicate a causal relationship between terrace

Commensurability effects in the critical forces of a superconducting film with Kagomé pinning array at submatching fields

NASA Astrophysics Data System (ADS)

Vizarim, Nicolas P.; Carlone, Maicon; Verga, Lucas G.; Venegas, Pablo A.

2017-09-01

Using molecular dynamics simulations, we find the commensurability force peaks in a two-dimensional superconducting thin-film with a Kagomé pinning array. A transport force is applied in two mutually perpendicular directions, and the magnetic field is increased up to the first matching field. Usually the condition to have pronounced force peaks in systems with periodic pinning is associated to the rate between the applied magnetic field and the first matching field, it must be an integer or a rational fraction. Here, we show that another condition must be satisfied, the vortex ground state must be ordered. Our calculations show that the pinning size and strength may dramatically change the vortex ground state. Small pinning radius and high values of pinning strength may lead to disordered vortex configurations, which fade the critical force peaks. The critical forces show anisotropic behavior, but the same dependence on pinning strength and radius is observed for both driven force directions. Different to cases where the applied magnetic field is higher than the first matching field, here the depinning process begins with vortices weakly trapped on top of a pinning site and not with interstitial vortices. Our results are in good agreement with recent experimental results.

A case study of energy expenditure based on walking speed reduction during walking upstairs situation at a staircase in FKAAS, UTHM, Johor building

NASA Astrophysics Data System (ADS)

Abustan, M. S.; Ali, M. F. M.; Talib, S. H. A.

2018-04-01

Walking velocity is a vector quantity that can be determined by calculating the time taken and displacement of a moving objects. In Malaysia, there are very few researches that were done to determine the walking velocity of citizens to be compared with other countries such as the study about walking upstairs during evacuation process is important when emergency case happen, if there are people in underground garages, they have to walk upstairs for exits and look for shelter and the walking velocity of pedestrian in such cases are necessary to be analysed. Therefore, the objective of this study is to determine the walking speed of pedestrian during walking upstairs situation, finding the relationship between pedestrian walking speed and the characteristics of the pedestrian as well as analysing the energy reduction by comparing the walking speed of pedestrian at the beginning and at the end of staircase. In this case study, an experiment was done to determine the average walking speed of pedestrian. The pedestrian has been selected from different gender, physical character, and age. Based on the data collected, the average normal walking speed of male pedestrian was 1.03 m/s while female was 1.08 m/s. During walking upstairs, the walking speed of pedestrian decreased as the number of floor increased. The average speed for the first stairwell was 0.90 m/s and the number decreased to 0.73 m/s for the second stairwell. From the reduction of speed, the energy used has been calculated and the average kinetic energy used was 1.69 J. Hence, the data collected can be used for further research of staircase design and plan of evacuation process.

From the S U (2 ) quantum link model on the honeycomb lattice to the quantum dimer model on the kagome lattice: Phase transition and fractionalized flux strings

NASA Astrophysics Data System (ADS)

Banerjee, D.; Jiang, F.-J.; Olesen, T. Z.; Orland, P.; Wiese, U.-J.

2018-05-01

We consider the (2 +1 ) -dimensional S U (2 ) quantum link model on the honeycomb lattice and show that it is equivalent to a quantum dimer model on the kagome lattice. The model has crystalline confined phases with spontaneously broken translation invariance associated with pinwheel order, which is investigated with either a Metropolis or an efficient cluster algorithm. External half-integer non-Abelian charges [which transform nontrivially under the Z (2 ) center of the S U (2 ) gauge group] are confined to each other by fractionalized strings with a delocalized Z (2 ) flux. The strands of the fractionalized flux strings are domain walls that separate distinct pinwheel phases. A second-order phase transition in the three-dimensional Ising universality class separates two confining phases: one with correlated pinwheel orientations, and the other with uncorrelated pinwheel orientations.

Enhanced fatigue endurance of metallic glasses through a staircase-like fracture mechanism.

PubMed

Gludovatz, Bernd; Demetriou, Marios D; Floyd, Michael; Hohenwarter, Anton; Johnson, William L; Ritchie, Robert O

2013-11-12

Bulk-metallic glasses (BMGs) are now candidate materials for structural applications due to their exceptional strength and toughness. However, their fatigue resistance can be poor and inconsistent, severely limiting their potential as reliable structural materials. As fatigue limits are invariably governed by the local arrest of microscopically small cracks at microstructural features, the lack of microstructure in monolithic glasses, often coupled with other factors, such as the ease of crack formation in shear bands or a high susceptibility to corrosion, can lead to low fatigue limits (some ~1/20 of their tensile strengths) and highly variable fatigue lives. BMG-matrix composites can provide a solution here as their duplex microstructures can arrest shear bands at a second phase to prevent cracks from exceeding critical size; under these conditions, fatigue limits become comparable with those of crystalline alloys. Here, we report on a Pd-based glass that similarly has high fatigue resistance but without a second phase. This monolithic glass displays high intrinsic toughness from extensive shear-band proliferation with cavitation and cracking effectively obstructed. We find that this property can further promote fatigue resistance through extrinsic crack-tip shielding, a mechanism well known in crystalline metals but not previously reported in BMGs, whereby cyclically loaded cracks propagate in a highly "zig-zag" manner, creating a rough "staircase-like" profile. The resulting crack-surface contact (roughness-induced crack closure) elevates fatigue properties to those comparable to crystalline alloys, and the accompanying plasticity helps to reduce flaw sensitivity in the glass, thereby promoting structural reliability.

Enhanced fatigue endurance of metallic glasses through a staircase-like fracture mechanism

PubMed Central

Gludovatz, Bernd; Demetriou, Marios D.; Floyd, Michael; Hohenwarter, Anton; Johnson, William L.; Ritchie, Robert O.

2013-01-01

Bulk-metallic glasses (BMGs) are now candidate materials for structural applications due to their exceptional strength and toughness. However, their fatigue resistance can be poor and inconsistent, severely limiting their potential as reliable structural materials. As fatigue limits are invariably governed by the local arrest of microscopically small cracks at microstructural features, the lack of microstructure in monolithic glasses, often coupled with other factors, such as the ease of crack formation in shear bands or a high susceptibility to corrosion, can lead to low fatigue limits (some ∼1/20 of their tensile strengths) and highly variable fatigue lives. BMG-matrix composites can provide a solution here as their duplex microstructures can arrest shear bands at a second phase to prevent cracks from exceeding critical size; under these conditions, fatigue limits become comparable with those of crystalline alloys. Here, we report on a Pd-based glass that similarly has high fatigue resistance but without a second phase. This monolithic glass displays high intrinsic toughness from extensive shear-band proliferation with cavitation and cracking effectively obstructed. We find that this property can further promote fatigue resistance through extrinsic crack-tip shielding, a mechanism well known in crystalline metals but not previously reported in BMGs, whereby cyclically loaded cracks propagate in a highly “zig-zag” manner, creating a rough “staircase-like” profile. The resulting crack-surface contact (roughness-induced crack closure) elevates fatigue properties to those comparable to crystalline alloys, and the accompanying plasticity helps to reduce flaw sensitivity in the glass, thereby promoting structural reliability. PMID:24167284

Devil's staircase and the absence of chaos in the dc- and ac-driven overdamped Frenkel-Kontorova model

NASA Astrophysics Data System (ADS)

Sokolović, I.; Mali, P.; Odavić, J.; Radošević, S.; Medvedeva, S. Yu.; Botha, A. E.; Shukrinov, Yu. M.; Tekić, J.

2017-08-01

The devil's staircase structure arising from the complete mode locking of an entirely nonchaotic system, the overdamped dc+ac driven Frenkel-Kontorova model with deformable substrate potential, was observed. Even though no chaos was found, a hierarchical ordering of the Shapiro steps was made possible through the use of a previously introduced continued fraction formula. The absence of chaos, deduced here from Lyapunov exponent analyses, can be attributed to the overdamped character and the Middleton no-passing rule. A comparative analysis of a one-dimensional stack of Josephson junctions confirmed the disappearance of chaos with increasing dissipation. Other common dynamic features were also identified through this comparison. A detailed analysis of the amplitude dependence of the Shapiro steps revealed that only for the case of a purely sinusoidal substrate potential did the relative sizes of the steps follow a Farey sequence. For nonsinusoidal (deformed) potentials, the symmetry of the Stern-Brocot tree, depicting all members of particular Farey sequence, was seen to be increasingly broken, with certain steps being more prominent and their relative sizes not following the Farey rule.

Tailoring Staircase-like Hysteresis Loops in Electrodeposited Trisegmented Magnetic Nanowires: a Strategy toward Minimization of Interwire Interactions.

PubMed

Zhang, Jin; Agramunt-Puig, Sebastià; Del-Valle, Núria; Navau, Carles; Baró, Maria D; Estradé, Sònia; Peiró, Francesca; Pané, Salvador; Nelson, Bradley J; Sanchez, Alvaro; Nogués, Josep; Pellicer, Eva; Sort, Jordi

2016-02-17

A new strategy to minimize magnetic interactions between nanowires (NWs) dispersed in a fluid is proposed. Such a strategy consists of preparing trisegmented NWs containing two antiparallel ferromagnetic segments with dissimilar coercivity separated by a nonmagnetic spacer. The trisegmented NWs exhibit a staircase-like hysteresis loop with tunable shape that depends on the relative length of the soft- and hard-magnetic segments and the respective values of saturation magnetization. Such NWs are prepared by electrodepositing CoPt/Cu/Ni in a polycarbonate (PC) membrane. The antiparallel alignment is set by applying suitable magnetic fields while the NWs are still embedded in the PC membrane. Analytic calculations are used to demonstrate that the interaction magnetic energy from fully compensated trisegmented NWs with antiparallel alignment is reduced compared to a single-component NW with the same length or the trisegmented NWs with the two ferromagnetic counterparts parallel to each other. The proposed approach is appealing for the use of magnetic NWs in certain biological or catalytic applications where the aggregation of NWs is detrimental for optimized performance.

Novel Eye Movement Disorders in Whipple's Disease-Staircase Horizontal Saccades, Gaze-Evoked Nystagmus, and Esotropia.

PubMed

Shaikh, Aasef G; Ghasia, Fatema F

2017-01-01

Whipple's disease, a rare systemic infectious disorder, is complicated by the involvement of the central nervous system in about 5% of cases. Oscillations of the eyes and the jaw, called oculo-masticatory myorhythmia, are pathognomonic of the central nervous system involvement but are often absent. Typical manifestations of the central nervous system Whipple's disease are cognitive impairment, parkinsonism mimicking progressive supranuclear palsy with vertical saccade slowing, and up-gaze range limitation. We describe a unique patient with the central nervous system Whipple's disease who had typical features, including parkinsonism, cognitive impairment, and up-gaze limitation; but also had diplopia, esotropia with mild horizontal (abduction more than adduction) limitation, and vertigo. The patient also had gaze-evoked nystagmus and staircase horizontal saccades. Latter were thought to be due to mal-programmed small saccades followed by a series of corrective saccades. The saccades were disconjugate due to the concurrent strabismus. Also, we noted disconjugacy in the slow phase of gaze-evoked nystagmus. The disconjugacy of the slow phase of gaze-evoked nystagmus was larger during monocular viewing condition. We propose that interaction of the strabismic drifts of the covered eyes and the nystagmus drift, putatively at the final common pathway might lead to such disconjugacy.

Myosin phosphorylation improves contractile economy of mouse fast skeletal muscle during staircase potentiation.

PubMed

Bunda, Jordan; Gittings, William; Vandenboom, Rene

2018-01-30

Phosphorylation of the myosin regulatory light chain (RLC) by skeletal myosin light chain kinase (skMLCK) potentiates rodent fast twitch muscle but is an ATP-requiring process. Our objective was to investigate the effect of skMLCK-catalyzed RLC phosphorylation on the energetic cost of contraction and the contractile economy (ratio of mechanical output to metabolic input) of mouse fast twitch muscle in vitro (25°C). To this end, extensor digitorum longus (EDL) muscles from wild-type (WT) and from skMLCK-devoid (skMLCK -/- ) mice were subjected to repetitive low-frequency stimulation (10 Hz for 15 s) to produce staircase potentiation of isometric twitch force, after which muscles were quick frozen for determination of high-energy phosphate consumption (HEPC). During stimulation, WT muscles displayed significant potentiation of isometric twitch force while skMLCK -/- muscles did not (i.e. 23% versus 5% change, respectively). Consistent with this, RLC phosphorylation was increased ∼3.5-fold from the unstimulated control value in WT but not in skMLCK -/- muscles. Despite these differences, the HEPC of WT muscles was not greater than that of skMLCK -/- muscles. As a result of the increased contractile output relative to HEPC, the calculated contractile economy of WT muscles was greater than that of skMLCK -/- muscles. Thus, our results suggest that skMLCK-catalyzed phosphorylation of the myosin RLC increases the contractile economy of WT mouse EDL muscle compared with skMLCK -/- muscles without RLC phosphorylation. © 2018. Published by The Company of Biologists Ltd.

Physics of the spin gap in the S=1/2 Heisenberg antiferromagnet on kagome

NASA Astrophysics Data System (ADS)

Tchernyshyov, Oleg

2009-03-01

A combination of low spin and strong frustration makes the S=1/2 Heisenberg antiferromagnet on kagome a likely candidate for an unusual ground state and elementary excitations. Exact-diagonalization studies [1] on finite clusters point to a lack of magnetic order in the ground state and to an energy gap of order J/20 for S=1 excitations. The exact nature of the ground state and elementary excitations remains a subject of vigorous debate. Among the proposed ground states are chiral [2] and non-chiral [3] spin liquids and a valence-bond crystal (VBC) [4-5]; spin excitations range from deconfined spinons with a Bose [6] or Fermi statistics [2-3] to magnons [7]. We show that the system behaves as a collection of spinons, quasiparticles with S=1/2 and Fermi statistics, whose motion disturbs valence-bond order. Attraction between spinons, mediated by exchange, binds them into small, massive pairs of S=0 with a binding energy of 0.06 J [8]. The pair formation strongly suppresses the motion of individual spinons and makes the survival of the Singh-Huse VBC plausible. A spin excitation amounts to breaking up a pair into two (nearly) free spinons with S=1. The survival of the VBC is expected to lead to spinon confinement; however, small energy differences between various valence-bond configurations would make the confinement length large. [4pt] [1] Ch. Waldtmann et al., Eur. Phys. J. B 2, 510 (1998).[0pt] [2] J. B. Marston and C. Zeng, J. Appl. Phys. 69, 5962 (1991).[0pt] [3] M. B. Hastings, Phys. Rev. B 63, 014413 (2000).[0pt] [4] P. Nikolic and T. Senthil, Phys. Rev. B 68, 214415 (2003).[0pt] [5] R. R. P. Singh and D. A. Huse, Phys. Rev. B 76, 180407 (2007).[0pt] [6] S. Sachdev, Phys. Rev. B 45, 12377 (1992).[0pt] [7] R. R. P. Singh and D. A. Huse, arXiv:0801.2735. [0pt] [8] Z. Hao and O. Tchernyshyov, the subsequent talk.

Topological magnons in a kagome-lattice spin system with X X Z and Dzyaloshinskii-Moriya interactions

NASA Astrophysics Data System (ADS)

Seshadri, Ranjani; Sen, Diptiman

2018-04-01

We study the phases of a spin system on the kagome lattice with nearest-neighbor X X Z interactions with anisotropy ratio Δ and Dzyaloshinskii-Moriya interactions with strength D . In the classical limit where the spin S at each site is very large, we find a rich phase diagram of the ground state as a function of Δ and D . There are five distinct phases which correspond to different ground-state spin configurations in the classical limit. We use spin-wave theory to find the bulk energy bands of the magnons in some of these phases. We also study a strip of the system which has infinite length and finite width; we find states which are localized near one of the edges of the strip with energies which lie in the gaps of the bulk states. In the ferromagnetic phase in which all the spins point along the +z ̂ or -z ̂ direction, the bulk bands are separated from each other by finite energy gaps. This makes it possible to calculate the Berry curvature at all momenta, and hence the Chern numbers for every band; the number of edge states is related to the Chern numbers. Interestingly, we find that there are four different regions in this phase where the Chern numbers are different. Hence there are four distinct topological phases even though the ground-state spin configuration is identical in all these phases. We calculate the thermal Hall conductivity of the magnons as a function of the temperature in the above ferromagnetic phase; we find that this can distinguish between the various topological phases. These results are valid for all values of S . In the other phases, there are no gaps between the different bands; hence the edge states are not topologically protected.

Soil characteristics and plant exotic species invasions in the Grand Staircase-Escalante National Monument, Utah, USA

USGS Publications Warehouse

Bashkin, Michael A.; Stohlgren, Thomas J.; Otsuki, Yuka; Lee, Michelle; Evangelista, Paul H; Belnap, Jayne

2003-01-01

The Grand Staircase - Escalante National Monument (GSENM) contains a rich diversity of native plant communities. However, many exotic plant species have become established, potentially threatening native plant diversity. We sought to quantify patterns of native and exotic plant species and cryptobiotic crusts (mats of lichens, algae, and mosses on the soil surface), and to examine soil characteristics that may indicate or predict exotic species establishment and success. We established 97 modified-Whittaker vegetation plots in 11 vegetation types over a 29,000 ha area in the Monument. Canonical correspondence analysis (CCA) and multiple linear regressions were used to quantify relationships between soil characteristics and associated native and exotic plant species richness and cover. CCA showed that exotic species richness was significantly (P<0.05) associated with soil P (r=0.84), percentage bare ground (r=0.71), and elevation (r=0.67). Soil characteristics alone were able to predict 41 and 46% of the variation in exotic species richness and cover, respectively. In general, exotic species invasions tend to occur in fertile soils relatively high in C, N and P. These areas are represented by rare mesic high-elevation habitats that are rich in native plant diversity. This suggests that management should focus on the protection of the rare but important vegetation types with fertile soils.

Compact, integrable, and long life time Raman multiline UV-Vis source based on hypocycloid core Kagome HC-PCF

NASA Astrophysics Data System (ADS)

Chafer, M.; Lekiefs, Q.; Gorse, A.; Beaudou, B.; Debord, B.; Gérôme, F.; Benabid, F.

2017-02-01

Raman-gas filled HC-PCF has proved to be an outstanding Raman-convertor, as illustrated by the generation of more than 5 octaves wide Raman comb using a hydrogen-filled Kagome HC-PCF pumped with high power picosecond-laser, or the generation of multiline Raman-source in the UV-Vis using a very compact system pumped with micro-chip laser. Whilst these demonstrations are promising, a principal challenge for the industrialization of such a Raman source is its lifetime as the H2 diffusion through silica is high enough to leak out from the fiber within only a few months. Here, we report on a HC-PCF based Raman multiline source with a very long life-span. The system consists of hydrogen filled ultra-low loss HC-PCF contained in highly sealed box, coined CombBox, and pumped with a 532 nm micro-chip laser. This combination is a turnkey multiline Raman-source with a "shoe box" size. The CombBox is a robust and compact component that can be integrated and pumped with any common pulsed laser. When pumped with a 32 mW average power and 1 ns frequency-doubled Nd:Yag microchip laser, this Raman-source generates 24 lines spanning from 355 to 745 nm, and a peak power density per line of 260 mW/nm for the strongest lines. Both the output power and the spectrum remained constant over its monitoring duration of more than six months. The spectrum of this multiline laser superimposes with no less than 17 absorption peaks of fluorescent dyes from the Alexa Fluor family used as biological markers.

The role of rock anisotropy in developing non-Andersonian faults: staircase trajectories for strike-slip faults

NASA Astrophysics Data System (ADS)

Barchi, M. R.; Collettini, C.; Lena, G.

2012-04-01

Thrust and normal faults affecting mechanically heterogeneous multilayers often show staircase trajectories, where flat segments follow less competent units. Within flat segments the initiation/reactivation angle, θ, which is the angle that the fault makes with the σ1 direction, is different from that predicted by the Andersonian theory. This suggests that fault trajectory is mainly controlled by rock anisotropy instead of frictional properties of the material. Our study areas are located in the Umbria-Marche fold-thrust belt, within the Northern Apennines of Italy. The area is characterized by a lithologically complex multilayer, about 2000 m thick, consisting of alternated competent (mainly calcareous) and less competent (marls or evaporites) units. At the outcrop scale, some units show a significant mechanical layering, consisting of alternated limestones and shales. Due to the complex tectonic evolution of the Apennines, well developed sets of conjugate normal, thrust and strike-slip faults are exposed in the region. The study outcrop, Candigliano Gourge, is characterized by steep (dip > 60°) NE dipping beds, affected by conjugate sets of strike-slip faults, exposed in the eastern limb of a NE verging anticline. The faults develop within the Marne a Fucoidi Fm., a Cretaceous sedimentary unit, about 70 m thick, made of competent calcareous beds (about 20 cm thick), separated by marly beds (1-20 cm thick). The conjugate strike-slip faults are formed after the major folding phase: in fact the strike-slip faults cut both minor folds and striated bedding surfaces, related to syn-folding flexural slip. Faults show marked staircase trajectories, with straight segments almost parallel to the marly horizons and ramps cutting through the calcareous layers. Slip along these faults induces local block rotation of the competent strata, dilational jogs (pull-aparts), extensional duplexes and boudinage of the competent layers, while marly levels are strongly laminated. In

Microstructure and Mechanical Properties of Additively Manufactured Parts with Staircase Feature

NASA Astrophysics Data System (ADS)

Keya, Tahmina

This thesis focuses on a part with staircase feature that is made of Inconel 718 and fabricated by SLM process. The objective of the study was to observe build height effect on the microstructure and mechanical properties of the part. Due to the nature of SLM, there is possibility of different microstructure and mechanical properties in different locations depending on the design of the part. The objective was to compare microstructure and mechanical properties from different location and four comparison groups were considered: 1. Effect of thermal cycle; 2. External and internal surfaces; 3. Build height effect and 4. Bottom surfaces. To achieve the goals of this research, standard metallurgical procedure has been performed to prepare samples. Etching was done to reveal the microstructure of SLM processed Inconel 718 parts. Young's modulus and hardness were measured using nanoindentation technique. FEM analysis was performed to simulate nanoindentation. The conclusions drawn from this research are: 1. The microstructure of front and side surface of SLM processed Inconel 718 consists of arc shaped cut ends of melt pools with intermetallic phase at the border of the melt pool; 2. On top surface, melted tracks and scanning patterns can be observed and the average width of melted tracks is 100-150 microm; 3. The microstructure looks similar at different build height; 4. Microstructure on the top of a stair is more defined and organized than the internal surface; 5. The mechanical properties are highest at the bottom. OM images revealed slight difference in microstructure in terms of build height for this specific part, but mechanical properties seem to be vary noticeably. This is something to be kept in mind while designing or determining build orientation. External and internal surfaces of a stair at the same height showed difference in both microstructure and mechanical properties. To minimize that effect and to make it more uniform, gradual elevation can be

Vegetation response to fire and postburn seeding treatments in juniper woodlands of the Grand Staircase-Escalante National Monument, Utah

USGS Publications Warehouse

Evangelista, P.; Stohlgren, T.J.; Guenther, D.; Stewart, S.

2004-01-01

We compared 3 naturally ignited burns with unburned sites in the Grand Staircase-Escalante National Monument. Each burn site was restored with native and nonnative seed mixes, restored with native seeds only, or regenerated naturally. In general, burned sites had significantly lower native species richness (1.8 vs. 2.9 species), native species cover (11% vs. 22.5%), and soil crust cover (4.1% vs. 15%) than unburned sites. Most burned plots, seeded or not, had significantly higher average nonnative species richness and cover and lower average native species richness and cover than unburned sites. Regression tree analyses suggest site variation was equally important to rehabilitation results as seeding treatments. Low native species richness and cover, high soil C, and low cover of biological soil crusts may facilitate increased nonnative species richness and cover. Our study also found that unburned sites in the region had equally high cover of nonnative species compared with the rest of the Monument. Cheatgrass (Bromus tectorum) dominated both burned and unburned sites. Despite the invasion of cheatgrass, unburned sites still maintain higher native species richness; however, the high cover of cheatgrass may increase fire frequency, further reduce native species richness and cover, and ultimately change vegetation composition in juniper woodlands.

Kagomé lattices as cathode: Effect of particle size and fluoride substitution on electrochemical lithium insertion in sodium- and ammonium Jarosites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sandineni, Prashanth; Yaghoobnejad Asl, Hooman; Choudhury, Amitava, E-mail: choudhurya@mst.edu

Highly crystalline sodium and ammonium Jarosites, NaFe{sub 3}(SO{sub 4}){sub 2}(OH){sub 6} and NH{sub 4}Fe{sub 3}(SO{sub 4}){sub 2}(OH){sub 6}, have been synthesized employing hydrothermal synthesis routes. The structures consist of anionic layers of vertex-sharing FeO{sub 6} octahedra and SO{sub 4} tetrahedral units with interlayer space occupied by Na and ammonium ions, respectively. The corner-sharing FeO{sub 6} octahedral units form six and three rings similar to hexagonal tungsten bronze sheets also known as kagomé lattice. These sodium and ammonium Jarosites are thermally stable up to 400 °C and undergo facile electrochemical lithium insertion through the reduction of Fe{sup 3+} to Fe{sup 2+}.more » Galvanostatic charge–discharge indicates that up to 2.25 and 2 lithium ions per formula unit can be inserted at an average voltage of 2.49 and 2.26 V to the sodium and the ammonium Jarosites, respectively, under slow discharge rate of C/50. The cycle-life and experimental achievable capacity show strong dependence on particle sizes and synthesis conditions. A small amount of fluoride substitution improves both achievable capacity and average voltage. - Graphical abstract: Discharge capacity of jarosite phases as a function of particle size and fluoride substitution. - Highlights: • Synthesis of natro- and ammonium Jarosites. • Jarosites as cathodes for lithium ion batteries. • Li-ion electrochemistry of Jarosites. • Mössbauer spectroscopy of Jarosites.« less

Topological magnon bands in ferromagnetic star lattice.

PubMed

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.

Neutron diffraction study and theoretical analysis of the antiferromagnetic order and the diffuse scattering in the layered kagome system CaBaCo2Fe2O7

NASA Astrophysics Data System (ADS)

Reim, J. D.; Rosén, E.; Zaharko, O.; Mostovoy, M.; Robert, J.; Valldor, M.; Schweika, W.

2018-04-01

The hexagonal swedenborgite, CaBaCo2Fe2O7 , is a chiral frustrated antiferromagnet, in which magnetic ions form alternating kagome and triangular layers. We observe a long-range √{3 }×√{3 } antiferromagnetic order setting in below TN=160 K by neutron diffraction on single crystals of CaBaCo2Fe2O7 . Both magnetization and polarized neutron single crystal diffraction measurements show that close to TN spins lie predominantly in the a b plane, while upon cooling the spin structure becomes increasingly canted due to Dzyaloshinskii-Moriya interactions. The ordered structure can be described and refined within the magnetic space group P 31 m' . Diffuse scattering between the magnetic peaks reveals that the spin order is partial. Monte Carlo simulations based on a Heisenberg model with two nearest-neighbor exchange interactions show a similar diffuse scattering and coexistence of the √{3 }×√{3 } order with disorder. The coexistence can be explained by the freedom to vary spins without affecting the long-range order, which gives rise to ground-state degeneracy. Polarization analysis of the magnetic peaks indicates the presence of long-period cycloidal spin correlations resulting from the broken inversion symmetry of the lattice, in agreement with our symmetry analysis.

Doped colloidal artificial spin ice

DOE PAGES

Libál, A.; Reichhardt, C. J. Olson; Reichhardt, C.

2015-10-07

We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Conversely, magnetic artificial spin ices, unlike colloidal and vortex artificial spin ice realizations, allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloidsmore » is suppressed near the doping sites. Our results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.« less

Doped colloidal artificial spin ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Libál, A.; Reichhardt, C. J. Olson; Reichhardt, C.

We examine square and kagome artificial spin ice for colloids confined in arrays of double-well traps. Conversely, magnetic artificial spin ices, unlike colloidal and vortex artificial spin ice realizations, allow creation of doping sites through double occupation of individual traps. We find that doping square and kagome ice geometries produces opposite effects. For square ice, doping creates local excitations in the ground state configuration that produce a local melting effect as the temperature is raised. In contrast, the kagome ice ground state can absorb the doping charge without generating non-ground-state excitations, while at elevated temperatures the hopping of individual colloidsmore » is suppressed near the doping sites. Our results indicate that in the square ice, doping adds degeneracy to the ordered ground state and creates local weak spots, while in the kagome ice, which has a highly degenerate ground state, doping locally decreases the degeneracy and creates local hard regions.« less

Provenance of marbles used for building the internal spiral staircase of the bell tower of St. Nicholas Church (Pisa, Italy)

NASA Astrophysics Data System (ADS)

Lezzerini, Marco; Antonelli, Fabrizio; Gallello, Gianni; Ramacciotti, Mirco; Parodi, Luca; Alberti, Antonio; Pagnotta, Stefano; Legnaioli, Stefano; Palleschi, Vincenzo

2017-05-01

The aim of this study is to investigate the provenance of marbles used as architectural elements (bases, shafts and capitals of columns) for building the internal spiral staircase of the medieval bell tower of St. Nicholas Church at Pisa, Italy. Accordingly, the 45 collected marble samples have been analysed by optical microscopy, X-ray powder diffraction and mass spectroscopy for carbon and oxygen stable isotope ratio analysis; additionally, SEM-EDS analysis have been performed to complement data about accessory minerals. By comparison with literature data on the main sources of the white Mediterranean marbles used in ancient times, the results show that the analysed samples are mainly white crystalline marbles from Carrara (Italy) and, subordinately, from other Tuscan and Eastern Mediterranean quarrying areas. In fact, Mt. Pisano and Campiglia M.ma (Tuscany, Italy) and Marmara (Turkey), Paros, Mt. Penteli, Thasos (Greece) are minor sources. The other coloured stones identified on the strength of their macroscopic features are quartzites from Mt. Pisano area and granitoids from Sardinia and Island of Elba (Italy). Occasionally, a very limited number of architectonical elements made up of Acquabona limestone from Rosignano Marittimo (Livorno, Italy), red limestone with ammonites (the so-called "Rosso Ammonitico") and black limestone belonging to the Tuscan Nappe sequence, outcropping at northwest of Pisa in the nearby Monti d'Oltre Serchio area, are present.

A quest for 2D lattice materials for actuation

NASA Astrophysics Data System (ADS)

Pronk, T. N.; Ayas, C.; Tekõglu, C.

2017-08-01

In the last two decades, most of the studies in shape morphing technology have focused on the Kagome lattice materials, which have superior properties such as in-plane isotropy, high specific stiffness and strength, and low energy requirement for actuation of its members. The Kagome lattice is a member of the family of semi-regular tessellations of the plane. Two fundamental questions naturally arise: i-) What makes a lattice material suitable for actuation? ii-) Are there other tessellations more effective than the Kagome lattice for actuation? The present paper tackles both questions, and provides a clear answer to the first one by comparing an alternative lattice material, the hexagonal cupola, with the Kagome lattice in terms of mechanical/actuation properties. The second question remains open, but, hopefully easier to challenge owing to a newly-discovered criterion: for an n-dimensional (n = 2 , 3) in-plane isotropic lattice material to be suitable for actuation, its pin-jointed equivalent must obey the generalised Maxwell's rule, and must possess M = 3(n - 1) non strain-producing finite kinematic mechanisms.

Synthesis, crystal structure and electronic structure of the binary phase Rh{sub 2}Cd{sub 5}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koley, Biplab; Chatterjee, S.; Jana, Partha P., E-mail: ppj@chem.iitkgp.ernet.in

2017-02-15

A new phase in the Rh-Cd binary system - Rh{sub 2}Cd{sub 5} has been identified and characterized by single crystal X-ray diffraction and Energy dispersive X-ray analysis. The stoichiometric compound Rh{sub 2}Cd{sub 5} crystallizes with a unit cell containing 14 atoms, in the orthorhombic space group Pbam (55). The crystal structure of Rh{sub 2}Cd{sub 5} can be described as a defect form of the In{sub 3}Pd{sub 5} structure with ordered vacancies, formed of two 2D atomic layers with the stacking sequence: ABAB. The A type layers consist of (3.6.3.6)-Kagomé nets of Cd atoms while the B type layers consist ofmore » (3{sup 5}) (3{sup 7})- nets of both Cd and Rh atoms. The stability of this line phase is investigated by first principle electronic structure calculations on the model of ordered Rh{sub 2}Cd{sub 5}. - Graphical abstract: (3.6.3.6)-Kagomé nets of cadmium atoms (top) and (3{sup 5}) (3{sup 7})- nets of both cadmium and rhodium atoms (bottom) in the structure of Rh{sub 2}Cd{sub 5}.« less

Coexistence of ferromagnetism and unconventional spin-glass freezing in the site-disordered kagome ferrite SrS n2F e4O11

NASA Astrophysics Data System (ADS)

Shlyk, L.; Strobel, S.; Farmer, B.; De Long, L. E.; Niewa, R.

2018-02-01

Single-crystal x-ray diffraction refinements indicate SrS n2F e4O11 crystallizes in the hexagonal R -type ferrite structure with noncentrosymmetric space group P 63m c and lattice parameters a =5.9541 (2 )Å , c =13.5761 (5 )Å , Z =2 (R (F )=0.034 ). Octahedrally coordinated 2 a [M (1) and M (1a)] and 6 c sites [M (2 )] have random, mixed occupation by Sn and Fe; whereas the tetrahedrally coordinated 2 b sites [Fe(3) and Fe(3a)] are exclusively occupied by Fe, whose displacement from the ideal position with trigonal-bipyramidal coordination causes the loss of inversion symmetry. Our dc and ac magnetization data indicate SrS n2F e4O11 single crystals undergo a ferro- or ferri-magnetic transition below a temperature TC=630 K with very low coercive fields μoHc ⊥=0.27 Oe and μoHc ∥=1.5 Oe at 300 K, for applied field perpendicular and parallel to the c axis, respectively. The value for TC is exceptionally high, and the coercive fields exceptionally low, among the known R-type ferrites. Time-dependent dc magnetization and frequency-dependent ac magnetization data indicate the onset of short-range, spin-glass freezing below Tf=35.8 K , which results from crystallographic disorder of magnetic F e3 + and nonmagnetic S n4 + ions on a frustrated Kagome sublattice. Anomalous ac susceptibility and thermomagnetic relaxation behavior in the short-range-ordered state differs from that of conventional spin glasses. Optical measurements in the ultraviolet to visible frequency range in a diffuse reflectance geometry indicate an overall optical band gap of 0.8 eV, consistent with observed semiconducting properties.

Juxtaposition of the changes in intracellular calcium and force during staircase potentiation at 30 and 37°C

PubMed Central

Vandenboom, Rene

2014-01-01

Ca2+ entry during the action potential stimulates muscle contraction. During repetitive low frequency stimulation, skeletal muscle undergoes staircase potentiation (SP), a progressive increase in the peak twitch force induced by each successive stimulus. Multiple mechanisms, including myosin regulatory light chain phosphorylation, likely contribute to SP, a temperature-dependent process. Here, we used the Ca2+-sensitive fluorescence indicators acetoxymethyl (AM)-furaptra and AM-fura-2 to examine the intracellular Ca2+ transient (ICT) and the baseline Ca2+ level at the onset of each ICT during SP at 30 and 37°C in mouse lumbrical muscle. The stimulation protocol, 8 Hz for 8 s, resulted in a 27 ± 3% increase in twitch force at 37°C and a 7 ± 2% decrease in twitch force at 30°C (P < 0.05). Regardless of temperature, the peak rate of force production (+df/dt) was higher in all twitches relative to the first twitch (P < 0.05). Consistent with the differential effects of stimulation on twitch force at the two temperatures, raw ICT amplitude decreased during repetitive stimulation at 30°C (P < 0.05) but not at 37°C. Cytosolic Ca2+ accumulated during SP such that baseline Ca2+ at the onset of ICTs occurring late in the train was higher (P < 0.05) than that of those occurring early in the train. ICT duration increased progressively at both temperatures. This effect was not entirely proportional to the changes in twitch duration, as twitch duration characteristically decreased before increasing late in the protocol. This is the first study identifying a changing ICT as an important, and temperature-sensitive, modulator of muscle force during repetitive stimulation. Moreover, we extend previous observations by demonstrating that contraction-induced increases in baseline Ca2+ coincide with greater +df/dt but not necessarily with higher twitch force. PMID:25422504

Mechatronic Materials and Systems. Design and Demonstration of High Aughtority Shape Morphing Structures

DTIC Science & Technology

2005-09-01

thermal expansion of these truss elements. One side of the structure is fully clamped, while the other is free to displace. As in prior assessments [6...levels, by using the finite element package ABAQUS . To simulate the complete system, the core and the Kagome face members are modeled using linear...code ABAQUS . To simulate the complete actuation system, the core and Kagome members are modeled using linear Timoshenko-type beams, while the solid

R{sub 4}Ir{sub 13}Ge{sub 9} (R=La, Ce, Pr, Nd, Sm) and RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd): Crystal structures with nets of Ir atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yarema, Maksym; Swiss Federal Laboratories for Materials Science and Technology; Zaremba, Oksana

The crystal structures of the new ternary compounds Sm{sub 4}Ir{sub 13}Ge{sub 9} and LaIr{sub 3}Ge{sub 2} were determined and refined on the basis of single-crystal X-ray diffraction data. They belong to the Ho{sub 4}Ir{sub 13}Ge{sub 9} (oP52, Pmmn) and CeCo{sub 3}B{sub 2} (hP5, P6/mmm) structure types, respectively. The formation of isotypic compounds R{sub 4}Ir{sub 13}Ge{sub 9} with R=La, Ce, Pr, Nd, and RIr{sub 3}Ge{sub 2} with R=Ce, Pr, Nd, was established by powder X-ray diffraction. The RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd) compounds exist only in as-cast samples and decompose during annealing at 800 Degree-Sign C with the formationmore » of R{sub 4}Ir{sub 13}Ge{sub 9}. The structure of Sm{sub 4}Ir{sub 13}Ge{sub 9} contains intersecting, slightly puckered nets of Ir atoms (4{sup 4})(4{sup 3}.6){sub 2}(4.6{sup 2}){sub 2} and (4{sup 4}){sub 2}(4{sup 3}.6){sub 4}(4.6{sup 2}){sub 2} that are perpendicular to [0 1 1] as well as to [0 -1 1] and [0 0 1]. The Ir atoms are surrounded by Ge atoms that form tetrahedra or square pyramids (where the layers intersect). The Sm and additional Ir atoms (in trigonal-planar coordination) are situated in channels along [1 0 0] (short translation vector). In the structure of LaIr{sub 3}Ge{sub 2} the Ir atoms form planar Kagome nets (3.6.3.6) perpendicular to [0 0 1]. These nets alternate along the short translation vector with layers of La and Ge atoms. - Graphical abstract: The crystal structures contain the nets of Ir atoms as main structural motif: R{sub 4}Ir{sub 13}Ge{sub 9} contains intersecting slightly puckered nets of Ir atoms, whereas in the structure of RIr{sub 3}Ge{sub 2} the Ir atoms form planar Kagome nets. Highlights: Black-Right-Pointing-Pointer The Ir-rich ternary germanides R{sub 4}Ir{sub 13}Ge{sub 9} (R=La, Ce, Pr, Nd, Sm) and RIr{sub 3}Ge{sub 2} (R=La, Ce, Pr, Nd) have been synthesized. Black-Right-Pointing-Pointer The RIr{sub 3}Ge{sub 2} compounds exist only in as-cast samples and decompose during annealing

Starting points for the study of non-Fermi liquid-like properties of FeCrAs

NASA Astrophysics Data System (ADS)

O'Brien, Patrick James

FeCrAs exhibits non-Fermi liquid-like behavior because of its odd combination of thermodynamic, transport, and magnetic properties. In particular, the resistivity of FeCrAs is not characteristic of a metal or an insulator and so remains a mystery. In this thesis, we seek a model to describe its properties. In FeCrAs, local moments reside on the Cr sites, and there is some conduction. We study the simplest possible model on the kagome lattice that features local moments and itinerant electrons, the kagome Kondo Lattice Model. We present the phase diagram of this model, which features a host of complex spin orders, one of which is the √3 x √3, the experimentally observed magnetic ground state in FeCrAs. The kagome Kondo Lattice Model, having one itinerant d-orbital band on the kagome lattice, does not fully capture the microscopic physics of FeCrAs. The kagome Kondo Lattice Model also will not de- scribe the mutilation of the Fermi surface. To investigate the microscopic properties, we calculated LDA and LDA+U results. These results and GGA results from another group all exhibit high d-orbital density of states at the Fermi energy as well as low p-orbital density of states at the Fermi energy. The DFT results motivated us to construct a model based on the chemistry and full geometry of the FeCrAs crystal. The model we construct is an effective hopping model consisting of only d-orbital operators that we call the Optimal Overlap Hopping Model (OOHM). We calculate the band structure that results from the OOHM, and this band structure can be compared to ARPES measurements. As an example of how one can use the OOHM, we calculate a dynamic spin structure factor from within the OOHM, and we compare it to neutron scattering data. We consider both the OOHM and the Kondo Lattice Model on the kagome lattice as starting points from which we can launch studies of FeCrAs, and we present the existing theories for FeCrAs on a metallicity spectrum to illustrate the various

Mean-Field Scaling of the Superfluid to Mott Insulator Transition in a 2D Optical Superlattice.

PubMed

Thomas, Claire K; Barter, Thomas H; Leung, Tsz-Him; Okano, Masayuki; Jo, Gyu-Boong; Guzman, Jennie; Kimchi, Itamar; Vishwanath, Ashvin; Stamper-Kurn, Dan M

2017-09-08

The mean-field treatment of the Bose-Hubbard model predicts properties of lattice-trapped gases to be insensitive to the specific lattice geometry once system energies are scaled by the lattice coordination number z. We test this scaling directly by comparing coherence properties of ^{87}Rb gases that are driven across the superfluid to Mott insulator transition within optical lattices of either the kagome (z=4) or the triangular (z=6) geometries. The coherent fraction measured for atoms in the kagome lattice is lower than for those in a triangular lattice with the same interaction and tunneling energies. A comparison of measurements from both lattices agrees quantitatively with the scaling prediction. We also study the response of the gas to a change in lattice geometry, and observe the dynamics as a strongly interacting kagome-lattice gas is suddenly "hole doped" by introducing the additional sites of the triangular lattice.

Quaternary landscape evolution of the Helmand Basin, Afghanistan: Insights from staircase terraces, deltas, and paleoshorelines using high-resolution remote sensing analysis

NASA Astrophysics Data System (ADS)

Evenstar, L. A.; Sparks, R. S. J.; Cooper, F. J.; Lawton, M. N.

2018-06-01

The Helmand Basin in southern Afghanistan is a large (310,000 km2), structurally controlled, endorheically drained basin with a hyperarid climate. The basin hosts a high elevation ( 200 m) plateau (the Dasht-i Margo), 11 fluvial staircase terraces (T11 to T1), 7 delta systems (D1 to D7), and 6 paleolake shorelines (SL1 to SL6) within the Sistan Depression on the western side of the basin. Mapping and surveying of these features by remote sensing is integrated with geological observations to reconstruct Quaternary landscape evolution of the basin. The fluvial systems, deltas, and paleolake shorelines are correlated with one another and with the younger terraces (T7 to T1). The shape of fluvial longitudinal profiles changes depending on whether they formed pre-, syn-, or post-growth of the Koh-i Khannesin volcano on the southern margin of the Helmand River. The age of the volcano ( 0.6 Ma) and correlation of the terraces with the global history of glacial-interglacial cycles constrain the age of the younger terraces to the late Pleistocene and indicates that the older terraces are middle Pleistocene (dating back to 800 ka). The Helmand Basin once hosted a large lake, called here the Sistan paleolake, which at SL6 times and before had a surface area >50,000 km2. Since that time the lake elevation and area have decreased, evolving to the present-day dried out Sistan Depression with small ephemeral playa lakes. Episodic formation of terraces, deltas, and paleolake shorelines is attributed to changes in base level modulated by climate change related to Milankovitch cycles.

Hazardous Off-Gassing of Carbon Monoxide and Oxygen Depletion during Ocean Transportation of Wood Pellets

PubMed Central

Svedberg, Urban; Samuelsson, Jerker; Melin, Staffan

2008-01-01

Five ocean vessels were investigated for the characterization and quantification of gaseous compounds emitted during ocean transportation of wood pellets in closed cargo hatches from Canada to Sweden. The study was initiated after a fatal accident with several injured during discharge in Sweden. The objective with the investigation was to better understand the off-gassing and issues related to workers' exposure. Air sampling was done during transport and immediately before discharge in the undisturbed headspace air above the wood pellets and in the staircase adjacent to each hatch. The samples were analyzed with Fourier transform infrared spectroscopy and direct reading instruments. The following compounds and ranges were detected in samples from the five ships: carbon monoxide (CO) 1460–14650 ppm, carbon dioxide (CO2) 2960–21570 ppm, methane 79.9–956 ppm, butane equivalents 63–842 ppm, ethylene 2–21.2 ppm, propylene 5.3–36 ppm, ethane 0–25 ppm and aldehydes 2.3–35 ppm. The oxygen levels were between 0.8 and 16.9%. The concentrations in the staircases were almost as high as in the cargo hatches, indicating a fairly free passage of air between the two spaces. A potentially dangerous atmosphere was reached within a week from loading. The conclusions are that ocean transportation of wood pellets in confined spaces may produce an oxygen deficient atmosphere and lethal levels of CO which may leak into adjacent access spaces. The dangerous combination of extremely high levels of CO and reduced oxygen produces a fast-acting toxic combination. Measurement of CO in combination with oxygen is essential prior to entry in spaces having air communication with cargo hatches of wood pellets. Forced ventilation of staircases prior to entry is necessary. Redesign, locking and labeling of access doors and the establishment of rigorous entry procedures and training of onboard crew as well as personnel boarding ocean vessels are also important. PMID:18397907

Hazardous off-gassing of carbon monoxide and oxygen depletion during ocean transportation of wood pellets.

PubMed

Svedberg, Urban; Samuelsson, Jerker; Melin, Staffan

2008-06-01

Five ocean vessels were investigated for the characterization and quantification of gaseous compounds emitted during ocean transportation of wood pellets in closed cargo hatches from Canada to Sweden. The study was initiated after a fatal accident with several injured during discharge in Sweden. The objective with the investigation was to better understand the off-gassing and issues related to workers' exposure. Air sampling was done during transport and immediately before discharge in the undisturbed headspace air above the wood pellets and in the staircase adjacent to each hatch. The samples were analyzed with Fourier transform infrared spectroscopy and direct reading instruments. The following compounds and ranges were detected in samples from the five ships: carbon monoxide (CO) 1460-14650 ppm, carbon dioxide (CO2) 2960-21570 ppm, methane 79.9-956 ppm, butane equivalents 63-842 ppm, ethylene 2-21.2 ppm, propylene 5.3-36 ppm, ethane 0-25 ppm and aldehydes 2.3-35 ppm. The oxygen levels were between 0.8 and 16.9%. The concentrations in the staircases were almost as high as in the cargo hatches, indicating a fairly free passage of air between the two spaces. A potentially dangerous atmosphere was reached within a week from loading. The conclusions are that ocean transportation of wood pellets in confined spaces may produce an oxygen deficient atmosphere and lethal levels of CO which may leak into adjacent access spaces. The dangerous combination of extremely high levels of CO and reduced oxygen produces a fast-acting toxic combination. Measurement of CO in combination with oxygen is essential prior to entry in spaces having air communication with cargo hatches of wood pellets. Forced ventilation of staircases prior to entry is necessary. Redesign, locking and labeling of access doors and the establishment of rigorous entry procedures and training of onboard crew as well as personnel boarding ocean vessels are also important.

Experimental and ab Initio Study of Catena(bis(μ2-iodo)-6-methylquinoline-copper(I)) under Pressure: Synthesis, Crystal Structure, Electronic, and Luminescence Properties.

PubMed

Aguirrechu-Comerón, Amagoia; Hernández-Molina, Rita; Rodríguez-Hernández, Plácida; Muñoz, Alfonso; Rodríguez-Mendoza, Ulises R; Lavín, Vı́ctor; Angel, Ross J; Gonzalez-Platas, Javier

2016-08-01

Copper(I) iodine compounds can exhibit interesting mechanochromic and thermochromic luminescent properties with important technological applications. We report the synthesis and structure determination by X-ray diffraction of a new polymeric staircase copper(I) iodine compound catena(bis(μ2-iodo)-6-methylquinoline-copper(I), [C10H9CuIN]. The structure is composed of isolated polymeric staircase chains of copper-iodine coordinated to organic ligands through Cu-N bonds. High pressure X-ray diffraction to 6.45 GPa shows that the material is soft, with a bulk modulus K0 = 10.2(2)GPa and a first derivative K'0 = 8.1(3), typical for organometallic compounds. The unit-cell compression is very anisotropic with the stiffest direction [302] arising from a combination of the stiff CuI ladders and the shear of the planar quinolone ligands over one another. Full structure refinements at elevated pressures show that pressures reduce the Cu···Cu distances in the compound. This effect is detected in luminescence spectra with the appearance of four sub-bands at 515, 600, 647, and 712 nm above 3.5 GPa. Red-shifts are observed, and they are tentatively associated with interactions between copper(I) ions due to the shortening of the Cu···Cu distances induced by pressure, below twice the van der Waals limit (2.8 Å). Additionally, ab initio simulations were performed, and they confirmed the structure and the results obtained experimentally for the equation of state. The simulation allowed the band structure and the electronic density of states of this copper(I) iodine complex to be determined. In particular, the band gap decreases slowly with pressure in a quadratic way with dEg/dP = -0.011 eV/GPa and d(2)Eg/dP(2) = 0.001 eV/GPa(2).

Magnon Spin-Momentum Locking: Various Spin Vortices and Dirac magnons in Noncollinear Antiferromagnets.

PubMed

Okuma, Nobuyuki

2017-09-08

We generalize the concept of the spin-momentum locking to magnonic systems and derive the formula to calculate the spin expectation value for one-magnon states of general two-body spin Hamiltonians. We give no-go conditions for magnon spin to be independent of momentum. As examples of the magnon spin-momentum locking, we analyze a one-dimensional antiferromagnet with the Néel order and two-dimensional kagome lattice antiferromagnets with the 120° structure. We find that the magnon spin depends on its momentum even when the Hamiltonian has the z-axis spin rotational symmetry, which can be explained in the context of a singular band point or a U(1) symmetry breaking. A spin vortex in momentum space generated in a kagome lattice antiferromagnet has the winding number Q=-2, while the typical one observed in topological insulator surface states is characterized by Q=+1. A magnonic analogue of the surface states, the Dirac magnon with Q=+1, is found in another kagome lattice antiferromagnet. We also derive the sum rule for Q by using the Poincaré-Hopf index theorem.

Magnon Spin-Momentum Locking: Various Spin Vortices and Dirac magnons in Noncollinear Antiferromagnets

NASA Astrophysics Data System (ADS)

Okuma, Nobuyuki

2017-09-01

We generalize the concept of the spin-momentum locking to magnonic systems and derive the formula to calculate the spin expectation value for one-magnon states of general two-body spin Hamiltonians. We give no-go conditions for magnon spin to be independent of momentum. As examples of the magnon spin-momentum locking, we analyze a one-dimensional antiferromagnet with the Néel order and two-dimensional kagome lattice antiferromagnets with the 120° structure. We find that the magnon spin depends on its momentum even when the Hamiltonian has the z -axis spin rotational symmetry, which can be explained in the context of a singular band point or a U (1 ) symmetry breaking. A spin vortex in momentum space generated in a kagome lattice antiferromagnet has the winding number Q =-2 , while the typical one observed in topological insulator surface states is characterized by Q =+1 . A magnonic analogue of the surface states, the Dirac magnon with Q =+1 , is found in another kagome lattice antiferromagnet. We also derive the sum rule for Q by using the Poincaré-Hopf index theorem.

Compound matrices

NASA Astrophysics Data System (ADS)

Kravvaritis, Christos; Mitrouli, Marilena

2009-02-01

This paper studies the possibility to calculate efficiently compounds of real matrices which have a special form or structure. The usefulness of such an effort lies in the fact that the computation of compound matrices, which is generally noneffective due to its high complexity, is encountered in several applications. A new approach for computing the Singular Value Decompositions (SVD's) of the compounds of a matrix is proposed by establishing the equality (up to a permutation) between the compounds of the SVD of a matrix and the SVD's of the compounds of the matrix. The superiority of the new idea over the standard method is demonstrated. Similar approaches with some limitations can be adopted for other matrix factorizations, too. Furthermore, formulas for the n - 1 compounds of Hadamard matrices are derived, which dodge the strenuous computations of the respective numerous large determinants. Finally, a combinatorial counting technique for finding the compounds of diagonal matrices is illustrated.

Origin of the enhancement of tunneling probability in the nearly integrable system

NASA Astrophysics Data System (ADS)

Hanada, Yasutaka; Shudo, Akira; Ikeda, Kensuke S.

2015-04-01

The enhancement of tunneling probability in the nearly integrable system is closely examined, focusing on tunneling splittings plotted as a function of the inverse of the Planck's constant. On the basis of the analysis using the absorber which efficiently suppresses the coupling, creating spikes in the plot, we found that the splitting curve should be viewed as the staircase-shaped skeleton accompanied by spikes. We further introduce renormalized integrable Hamiltonians and explore the origin of such a staircase structure by investigating the nature of eigenfunctions closely. It is found that the origin of the staircase structure could trace back to the anomalous structure in tunneling tail which manifests itself in the representation using renormalized action bases. This also explains the reason why the staircase does not appear in the completely integrable system.

Electrodynamics of quantum spin liquids

NASA Astrophysics Data System (ADS)

Dressel, Martin; Pustogow, Andrej

2018-05-01

Quantum spin liquids attract great interest due to their exceptional magnetic properties characterized by the absence of long-range order down to low temperatures despite the strong magnetic interaction. Commonly, these compounds are strongly correlated electron systems, and their electrodynamic response is governed by the Mott gap in the excitation spectrum. Here we summarize and discuss the optical properties of several two-dimensional quantum spin liquid candidates. First we consider the inorganic material herbertsmithite ZnCu3(OH)6Cl2 and related compounds, which crystallize in a kagome lattice. Then we turn to the organic compounds -EtMe3Sb[Pd(dmit)2]2, κ-(BEDT-TTF)2Ag2(CN)3 and κ-(BEDT-TTF)2Cu2(CN)3, where the spins are arranged in an almost perfect triangular lattice, leading to strong frustration. Due to differences in bandwidth, the effective correlation strength varies over a wide range, leading to a rather distinct behavior as far as the electrodynamic properties are concerned. We discuss the spinon contributions to the optical conductivity in comparison to metallic quantum fluctuations in the vicinity of the Mott transition.

Preparation and antibacterial activity of compound chitosan-compound Yizhihao-nanoparticles.

PubMed

Ou, Sheng; Zhang, Yang-de

2008-05-01

To prepare chitosan (CS)-compound Yizhihao-nanoparticles (NP) and to investigate its antibacterial activity. CS NPs were formed by the incorporation of CS and Na3 PO4. CS-compound Yizhihao NPs were prepared by ion-cross-linking. The particle sizes and surface charges of CS NPs were determined by Malvern Zetasizer 1000-HAS and atomic force microscope (AFM), respectively. The antibacterial activity of CS-compound Yizhihao-NPs was studied in vitro and compared with that of compound Yizhihao powder. Malvern Zetasizer 1000-HAS and AFM demonstrated that the diameter of CS-compound Yizhihao NPs was (137.00+/-14.28)nm and CS NPs had (16.90+/-1.32)mV positive surface charges. The minimal inhibitory concentrations (MIC) of CS-compound Yizhihao NPs on Staphylococcus aureus,Pneumococcus,beta-hemolytic streptococcus, and Escherichia coli were 1:32,1:32,1:16,and 1:2, respectively. The minimal bactericidal concentrations (MBC) of CS-compound Yizhihao-NPs on Staphylococcus aureus, Pneumococcus, beta-hemolytic streptococcus, and Escherichia coli were 1:16,1:16,1:8, and 1:2, respectively. The antibacterial efficacy of CS-compound Yizhihao-NPs to Staphylococcus aureus, Pneumococcus, and beta-hemolytic streptococcus had been improved significantly (P< 0.05). CS-compound Yizhihao-nanoparticles have obvious antibacterial activity to the Staphylococcus aureus,Pneumococcus,and beta-hemolytic streptococcus,which lays the experimental foundation for new preparation of traditional Chinese medicine in future research.

Compounding in Ukraine.

PubMed

Zdoryk, Oleksandr A; Georgiyants, Victoriya A; Gryzodub, Oleksandr I; Schnatz, Rick

2013-01-01

Pharmaceutical compounding in modern Ukraine has a rich history and goes back to ancient times. Today in the Ukraine, there is a revival of compounding practice, the opening of private compounding pharmacies, updating of legislative framework and requirements of the State Pharmacopeia of Ukraine for compounding preparations, and the introduction of Good Pharmaceutical Practice.

Quantum phase transition in strongly correlated systems

NASA Astrophysics Data System (ADS)

Jiang, Longhua

phase, which is the original LO state, is the most stable phase. This result may be relevant to the detection of the FFLO state in some heavy fermion compounds and the pairing lattice structure of fermions with unequal populations on the BCS side of the Feshbach resonance in ultra-cold atoms. In chapter 4, the Boson Hubbard model is studied by duality transformation. Interacting bosons at filling factor f = p/q hopping on a lattice can be mapped to interacting vortices hopping on the dual lattice subject to a fluctuating dual " magnetic field" whose average strength through a dual plaquette is equal to the boson density f = p/q. So the kinetic term of the vortices is the same as the Hofstadter problem of electrons moving in a lattice in the presence of f = p/q flux per plaquette. Motivated by this mapping, we study the Hofstadter bands of vortices hopping in the presence of magnetic flux f = p/q per plaquette on the 5 most common bipartite and frustrated lattices namely square, honeycomb, triangular, dice and kagome lattices. We count the total number of bands and determine the number of minima in the lowest band and their locations. We also numerically calculate the bandwidths of the lowest Hofstadter bands in these lattices, which directly measure the mobility of the dual vortices. The less mobile the dual vortices are, the more likely the bosons are in a superfluid state. We find that, except for the kagome lattice at odd q, they all satisfy the exponential decay law W = Ae-cq even at the smallest q. At given q, the bandwidth W decreases in the order: triangle, square and honeycomb lattice. This indicates that the domain of the superfluid state of the original bosons increases in the order of the corresponding direct lattices: honeycome, square and triangular. When q = 2, we find that the lowest Hofstadter band is completely flat for both kagome and dice lattices. There is a gap on the kagome lattice, but no gap on dice lattice. This indicates that the boson ground

Classical Magnetic Frustration

NASA Astrophysics Data System (ADS)

Tsao, Eugene; Henriksen, Erik

We report on studies of classical magnetic frustration, inspired by Mellado et al., by studying an ensemble of freely rotating magnets, made of 1'' rare-earth bar magnets press-fit into polypropylene spheres floating on air bearings. The magnets can be arranged in any configuration to study frustration in 1, 2, or 3 dimensions. For instance, arranged in a Kagome lattice the magnets show an absence of high-energy in-in-in and out-out-out states; the presence of multiple ground states is indicative of macroscopic frustration. We also observe classical ``magnon'' transport in a one-dimensional chain. We will report on progress made in exploring the behavior of these magnets in triangular, Kagome, and honeycomb lattice configurations.

Frustrated Magnetism in Low-Dimensional Lattices

NASA Astrophysics Data System (ADS)

Tovar, Mayra

2011-12-01

In this dissertation we present the results of a theoretical investigation of spin models on two-dimensional and quasi one-dimensional lattices, all unified under the concept of quantum frustrated antiferromagnetism, and all discussing various aspects of the antiferromagnetic Heisenberg model on the kagome lattice. In the Introduction (Chapter 1), we discuss at some length such concepts as frustration and superexchange, among others, which are of common relevance in the rest of the chapters. In Chapter 2, we study the effect of Dzyaloshinskii-Moriya (DM) interactions on the zero-temperature magnetic susceptibility of systems whose low energy can be described by short-range valence bond states. Our work shows that this treatment is consistent with the experimentally observed non-vanishing susceptibility---in the specified temperature limit---of the spin-1/2 kagome antiferromagnetic compound ZnCu3(OH)6Cl2, also known as herbertsmithite. Although the objective of this work is explaining the aforementioned characteristic of the experimental system, our methods are more general and we apply them to the checkerboard and Shastry-Sutherland lattices as well. In Chapter 3, we discuss our findings in the study of ghost-mediated domain wall interactions in the diamondback ladder. These domain walls are the the spin excitations---the kinks and the antikinks---separating the ground states along one chain of the ladder. While as individual entities an antikink is energy costly and a kink energy free, our study finds that both interact via the ghosts that they produce in the opposite side of the ladder from where they are located. Through the study of these ghosts, we find that domain walls proliferate in the system above a critical value of the system's coupling constants. It is this proliferation that makes their treatment as free, non-interacting particles impossible, so we study here their interactions both quantitatively and qualitatively, in a region where the latter are

Disordered artificial spin ices: Avalanches and criticality (invited)

NASA Astrophysics Data System (ADS)

Reichhardt, Cynthia J. Olson; Chern, Gia-Wei; Libál, Andras; Reichhardt, Charles

2015-05-01

We show that square and kagome artificial spin ices with disconnected islands exhibit disorder-induced nonequilibrium phase transitions. The critical point of the transition is characterized by a diverging length scale and the effective spin reconfiguration avalanche sizes are power-law distributed. For weak disorder, the magnetization reversal is dominated by system-spanning avalanche events characteristic of a supercritical regime, while at strong disorder, the avalanche distributions have subcritical behavior and are cut off above a length scale that decreases with increasing disorder. The different type of geometrical frustration in the two lattices produces distinct forms of critical avalanche behavior. Avalanches in the square ice consist of the propagation of locally stable domain walls separating the two polarized ground states, and we find a scaling collapse consistent with an interface depinning mechanism. In the fully frustrated kagome ice, however, the avalanches branch strongly in a manner reminiscent of directed percolation. We also observe an interesting crossover in the power-law scaling of the kagome ice avalanches at low disorder. Our results show that artificial spin ices are ideal systems in which to study a variety of nonequilibrium critical point phenomena as the microscopic degrees of freedom can be accessed directly in experiments.

Disordered artificial spin ices: Avalanches and criticality (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reichhardt, Cynthia J. Olson, E-mail: cjrx@lanl.gov; Chern, Gia-Wei; Reichhardt, Charles

2015-05-07

We show that square and kagome artificial spin ices with disconnected islands exhibit disorder-induced nonequilibrium phase transitions. The critical point of the transition is characterized by a diverging length scale and the effective spin reconfiguration avalanche sizes are power-law distributed. For weak disorder, the magnetization reversal is dominated by system-spanning avalanche events characteristic of a supercritical regime, while at strong disorder, the avalanche distributions have subcritical behavior and are cut off above a length scale that decreases with increasing disorder. The different type of geometrical frustration in the two lattices produces distinct forms of critical avalanche behavior. Avalanches in themore » square ice consist of the propagation of locally stable domain walls separating the two polarized ground states, and we find a scaling collapse consistent with an interface depinning mechanism. In the fully frustrated kagome ice, however, the avalanches branch strongly in a manner reminiscent of directed percolation. We also observe an interesting crossover in the power-law scaling of the kagome ice avalanches at low disorder. Our results show that artificial spin ices are ideal systems in which to study a variety of nonequilibrium critical point phenomena as the microscopic degrees of freedom can be accessed directly in experiments.« less

Effects of environmental changes in a stair climbing intervention: generalization to stair descent.

PubMed

Webb, Oliver J; Eves, Frank F

2007-01-01

Visual improvements have been shown to encourage stair use in worksites independently of written prompts. This study examined whether visual modifications alone can influence behavior in a shopping mall. Climbing one flight of stairs, however, will not confer health benefits. Therefore, this study also assessed whether exposure to the intervention encouraged subsequent stair use. Interrupted time-series design. Escalators flanked by a staircase on either side. Ascending and descending pedestrians (N = 81,948). Following baseline monitoring, a colorful design was introduced on the stair risers of one staircase (the target staircase). A health promotion message was superimposed later on top. The intervention was visible only to ascending pedestrians. Thus, any rise in descending stair use would indicate increased intention to use stairs, which endured after initial exposure to the intervention. Observers inconspicuously coded pedestrians' means of ascent/descent and demographic characteristics. The design alone had no meaningful impact. Addition of the message, however, increased stair climbing at the target and nontarget staircases by 190% and 52%, respectively. The message also produced a modest increase in stair descent at the target (25%) and nontarget (9%) staircases. In public venues, a message component is critical to the success of interventions. In addition, it appears that exposure to an intervention can encourage pedestrians to use stairs on a subsequent occasion.

Polybenzimidazole compounds

DOEpatents

Klaehn, John R [Idaho Falls, ID; Peterson, Eric S [Idaho Falls, ID; Orme, Christopher J [Shelley, ID; Jones, Michael G [Chubbuck, ID; Wertsching, Alan K [Idaho Falls, ID; Luther, Thomas A [Idaho Falls, ID; Trowbridge, Tammy L [Idaho Falls, ID

2011-11-22

A PBI compound includes imidazole nitrogens at least a portion of which are substituted with a moiety containing a carbonyl group, the substituted imidazole nitrogens being bonded to carbon of the carbonyl group. At least 85% of the nitrogens may be substituted. The carbonyl-containing moiety may include RCO--, where R is alkoxy or haloalkyl. The PBI compound may exhibit a first temperature marking an onset of weight loss corresponding to reversion of the substituted PBI that is less than a second temperature marking an onset of decomposition of an otherwise identical PBI compound without the substituted moiety. The PBI compound may be included in separatory media. A substituted PBI synthesis method may include providing a parent PBI in a less than 5 wt % solvent solution. Substituting may use more than 5 equivalents in relation to the imidazole nitrogens to be substituted.

PERFLUORINATED AROMATIC COMPOUND

DTIC Science & Technology

octafluorobiphenyl, and perfluoroaliphatic aldehydes. Synthetic routes to perfluoro cyclohexyls via reactions of phenyl and pentafluorphenyl lithium with...other perfluorinated aromatic compounds were employed in the synthesis of perfluorinated aromatic model compounds and polymers. The hydrogenic analogues...hydrazides, and imides. Synthetic routes to perfluoro aralkyl compounds are being investigated. Starting materials are tetrafluorobenzene

Polybenzimidazole compounds

DOEpatents

Klaehn, John R.; Peterson, Eric S.; Wertsching, Alan K.; Orme, Christopher J.; Luther, Thomas A.; Jones, Michael G.

2010-08-10

A PBI compound that includes imidazole nitrogens, at least a portion of which are substituted with an organic-inorganic hybrid moiety. At least 85% of the imidazole nitrogens may be substituted. The organic-inorganic hybrid moiety may be an organosilane moiety, for example, (R)Me.sub.2SiCH.sub.2--, where R is selected from among methyl, phenyl, vinyl, and allyl. The PBI compound may exhibit similar thermal properties in comparison to the unsubstituted PBI. The PBI compound may exhibit a solubility in an organic solvent greater than the solubility of the unsubstituted PBI. The PBI compound may be included in separatory media. A substituted PBI synthesis method may include providing a parent PBI in a less than 5 wt % solvent solution. Substituting may occur at about room temperature and/or at about atmospheric pressure. Substituting may use at least five equivalents in relation to the imidazole nitrogens to be substituted or, preferably, about fifteen equivalents.

Staircases, Towers, and Castles

ERIC Educational Resources Information Center

Kara, Melike; Eames, Cheryl L.; Miller, Amanda L.; Chieu, Annie

2015-01-01

The very nature of algebra concerns the generalization of patterns (Lee 1996). Patterning activities that are geometric in nature can serve as powerful contexts that engage students in algebraic thinking and visually support them in constructing a variety of generalizations and justifications (e.g., Healy and Hoyles 1999; Lannin 2005). In this…

Colloquium: Herbertsmithite and the search for the quantum spin liquid

DOE PAGES

Norman, M. R.

2016-12-02

Quantum spin liquids form a novel class of matter where, despite the existence of strong exchange interactions, spins do not order down to the lowest measured temperature. Typically, these occur in lattices that act to frustrate the appearance of magnetism. In two dimensions, the classic example is the kagome lattice composed of corner sharing triangles. There are a variety of minerals whose transition metal ions form such a lattice. Hence, a number of them have been studied and were then subsequently synthesized in order to obtain more pristine samples. Of particular note was the report in 2005 by Dan Nocera'smore » group of the synthesis of herbertsmithite, composed of a lattice of copper ions sitting on a kagome lattice, which indeed does not order down to the lowest measured temperature despite the existence of a large exchange interaction of 17 meV. Over the past decade, this material has been extensively studied, yielding a number of intriguing surprises that have in turn motivated a resurgence of interest in the theoretical study of the spin 1/2 Heisenberg model on a kagome lattice. In this paper, this Colloquium reviews these developments and then discusses potential future directions, both experimental and theoretical, as well as the challenge of doping these materials with the hope that this could lead to the discovery of novel topological and superconducting phases.« less

Phenolic Molding Compounds

NASA Astrophysics Data System (ADS)

Koizumi, Koji; Charles, Ted; de Keyser, Hendrik

Phenolic Molding Compounds continue to exhibit well balanced properties such as heat resistance, chemical resistance, dimensional stability, and creep resistance. They are widely applied in electrical, appliance, small engine, commutator, and automotive applications. As the focus of the automotive industry is weight reduction for greater fuel efficiency, phenolic molding compounds become appealing alternatives to metals. Current market volumes and trends, formulation components and its impact on properties, and a review of common manufacturing methods are presented. Molding processes as well as unique advanced techniques such as high temperature molding, live sprue, and injection/compression technique provide additional benefits in improving the performance characterisitics of phenolic molding compounds. Of special interest are descriptions of some of the latest innovations in automotive components, such as the phenolic intake manifold and valve block for dual clutch transmissions. The chapter also characterizes the most recent developments in new materials, including long glass phenolic molding compounds and carbon fiber reinforced phenolic molding compounds exhibiting a 10-20-fold increase in Charpy impact strength when compared to short fiber filled materials. The role of fatigue testing and fatigue fracture behavior presents some insight into long-term reliability and durability of glass-filled phenolic molding compounds. A section on new technology outlines the important factors to consider in modeling phenolic parts by finite element analysis and flow simulation.

PERFLUORINATED AROMATIC COMPOUNDS

DTIC Science & Technology

decafluorodiphenylamine, 3,3’,4,4’-tetra substituted- hexafluorobiphenyls, tetrafluororesorcinol, perfluoroaromatic thioethers, and dithiols. These...and other perfluorinated aromatic compounds are the intermediates employed in the synthesis of perfluorinated model compounds and polymers.

Nitrodifluoraminoterphenyl compounds and processes

DOEpatents

Lerom, M.W.; Peters, H.M.

1975-07-08

This patent relates to the nitrodifluoraminoterphenyl compounds: 3,3''-bis (difluoramino)-2,2'' 4,4', 4'',6,6',6''-octanitro-m-terphenyl (DDONT) and 3,3''-bis(difluoramino)-2,2',2''4,4',4'',6,6',6''-nonanitro-m-terphenyl (DDNONA). Procedures are described wherein diamino precursors of the indicated compounds are prepared and the final compounds are obtained by a fluorination operation. The compounds are highly energetic and suitable for use as explosives and particularly in exploding bridge wire (EBW) detonators. (auth)

Perpendicular susceptibility and geometrical frustration in two-dimensional Ising antiferromagnets: Exact solutions

NASA Astrophysics Data System (ADS)

Muttalib, K. A.; Khatun, M.; Barry, J. H.

2017-11-01

Discovery of new materials and improved experimental as well as numerical techniques have led to a renewed interest in geometrically frustrated spin systems. However, there are very few exact results available that can provide a benchmark for comparison. In this work, we calculate exactly the perpendicular susceptibility χ⊥ for an Ising antiferromagnet with (i) nearest-neighbor pair interaction on a kagome lattice where strong frustration prevents long-range ordering and (ii) elementary triplet interactions on a kagome lattice which has no frustration but the system remains disordered down to zero temperature. By comparing with other known exact results with and without frustration, we propose that an appropriately temperature-scaled χ⊥ can be used as a quantitative measure of the degree of frustration in Ising spin systems.

Antifungal and Antiaflatoxigenic Methylenedioxy-Containing Compounds and Piperine-Like Synthetic Compounds

PubMed Central

Moon, Young-Sun; Choi, Won-Sik; Park, Eun-Sil; Bae, In Kyung; Choi, Sung-Deuk; Paek, Ockjin; Kim, Sheen-Hee; Chun, Hyang Sook; Lee, Sung-Eun

2016-01-01

Twelve methylenedioxy-containing compounds including piperine and 10 piperine-like synthetic compounds were assessed to determine their antifungal and antiaflatoxigenic activities against Aspergillus flavus ATCC 22546 in terms of their structure–activity relationships. Piperonal and 1,3-benzodioxole had inhibitory effects against A. flavus mycelial growth and aflatoxin B1 production up to a concentration of 1000 μg/mL. Ten piperine-like synthetic compounds were synthesized that differed in terms of the carbon length in the hydrocarbon backbone and the presence of the methylenedioxy moiety. In particular, 1-(2-methylpiperidin-1-yl)-3-phenylprop-2-en-1-one had potent antifungal and antiaflatoxigenic effects against A. flavus up to a concentration of 1 μg/mL. This synthetic compound was remarkable because the positive control thiabendazole had no inhibitory effect at this concentration. Reverse transcription-PCR analysis showed that five genes involved in aflatoxin biosynthesis pathways were down-regulated in A. flavus, i.e., aflD, aflK, aflQ, aflR, and aflS; therefore, the synthetic compound inhibited aflatoxin production by down-regulating these genes. PMID:27537912

Bilingual reading of compound words.

PubMed

Ko, In Yeong; Wang, Min; Kim, Say Young

2011-02-01

The present study investigated whether bilingual readers activate constituents of compound words in one language while processing compound words in the other language via decomposition. Two experiments using a lexical decision task were conducted with adult Korean-English bilingual readers. In Experiment 1, the lexical decision of real English compound words was more accurate when the translated compounds (the combination of the translation equivalents of the constituents) in Korean (the nontarget language) were real words than when they were nonwords. In Experiment 2, when the frequency of the second constituents of compound words in English (the target language) was manipulated, the effect of lexical status of the translated compounds was greater on the compounds with high-frequency second constituents than on those with low-frequency second constituents in the target language. Together, these results provided evidence for morphological decomposition and cross-language activation in bilingual reading of compound words.

Reliability and validity of a brief method to assess nociceptive flexion reflex (NFR) threshold.

PubMed

Rhudy, Jamie L; France, Christopher R

2011-07-01

The nociceptive flexion reflex (NFR) is a physiological tool to study spinal nociception. However, NFR assessment can take several minutes and expose participants to repeated suprathreshold stimulations. The 4 studies reported here assessed the reliability and validity of a brief method to assess NFR threshold that uses a single ascending series of stimulations (Peak 1 NFR), by comparing it to a well-validated method that uses 3 ascending/descending staircases of stimulations (Staircase NFR). Correlations between the NFR definitions were high, were on par with test-retest correlations of Staircase NFR, and were not affected by participant sex or chronic pain status. Results also indicated the test-retest reliabilities for the 2 definitions were similar. Using larger stimulus increments (4 mAs) to assess Peak 1 NFR tended to result in higher NFR threshold estimates than using the Staircase NFR definition, whereas smaller stimulus increments (2 mAs) tended to result in lower NFR threshold estimates than the Staircase NFR definition. Neither NFR definition was correlated with anxiety, pain catastrophizing, or anxiety sensitivity. In sum, a single ascending series of electrical stimulations results in a reliable and valid estimate of NFR threshold. However, caution may be warranted when comparing NFR thresholds across studies that differ in the ascending stimulus increments. This brief method to assess NFR threshold is reliable and valid; therefore, it should be useful to clinical pain researchers interested in quickly assessing inter- and intra-individual differences in spinal nociceptive processes. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Neurobehavioural evaluation of resveratrol in murine models of anxiety and schizophrenia.

PubMed

Magaji, Mohammed Garba; Iniaghe, Loretta Oghenekome; Abolarin, Mutiat; Abdullahi, Opeyemi Isa; Magaji, Rabiu Abdusalam

2017-04-01

Resveratrol, a caloric restriction mimetic, is a naturally occurring polyphenolic compound with antioxidant and anti-inflammatory properties. Oxidative stress has been implicated in the etiology of a number of neuropsychiatric disorders including generalized anxiety and schizophrenia. This study investigated the anxiolytic and antipsychotic potentials of resveratrol in murine models of anxiety and schizophrenia. Mice were pretreated with resveratrol (200 and 400 mg/kg) in 1% carboxymethyl cellulose for 14 days and subjected to behavioural tests on the 15th day. Anxiolytic activity of resveratrol was determined using the hole board and staircase tests while its anti-psychotic property was evaluated via apormorphine induced stereotypy and swim-induced grooming tests. Although resveratrol did not significantly reduce the mean number of head dips at doses used in the hole board test, it significantly (p < 0.01) decreased the mean episodes of rearing without significantly altering the total number of upward steps climbed in the staircase test. Resveratrol significantly (p < 0.05) reduced the mean climbing scores in the first ten minutes of the apormorphine induced stereotypic climbing and significantly decreased (p < 0.01) episodes and total duration of swim induced grooming in mice. Administration of resveratrol at doses used in this study produced anxiolysis and anti-psychotic effects in mice.

Synthesis, crystal structure and electronic structure of the binary phase Rh2Cd5

NASA Astrophysics Data System (ADS)

Koley, Biplab; Chatterjee, S.; Jana, Partha P.

2017-02-01

A new phase in the Rh-Cd binary system - Rh2Cd5 has been identified and characterized by single crystal X-ray diffraction and Energy dispersive X-ray analysis. The stoichiometric compound Rh2Cd5 crystallizes with a unit cell containing 14 atoms, in the orthorhombic space group Pbam (55). The crystal structure of Rh2Cd5 can be described as a defect form of the In3Pd5 structure with ordered vacancies, formed of two 2D atomic layers with the stacking sequence: ABAB. The A type layers consist of (3.6.3.6)-Kagomé nets of Cd atoms while the B type layers consist of (35) (37)- nets of both Cd and Rh atoms. The stability of this line phase is investigated by first principle electronic structure calculations on the model of ordered Rh2Cd5.

Single crystal growth and characterization of kagomé-lattice shandites Co3Sn2-xInxS2

NASA Astrophysics Data System (ADS)

Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

2015-09-01

Single crystals of the shandite-type half metallic ferromagnet Co3Sn2S2, and its In-substituted compounds, Co3Sn2-xInxS2 (0compounds.

Biodegradation of Organofluorine Compounds

DTIC Science & Technology

2016-02-01

BIODEGRADATION OF ORGANOFLUORINE COMPOUNDS ECBC-TR-1347 Melissa M. Dixon Steve P. Harvey RESEARCH AND...2011 4. TITLE AND SUBTITLE Biodegradation of Organofluorine Compounds 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR...compounds as sole carbon sources. This work will be continued in future studies. 15. SUBJECT TERMS Organofluorine Biodegradation Defluorination

Magneto-elastic coupling across the first-order transition in the distorted kagome lattice antiferromagnet Dy3Ru4Al12

PubMed Central

Henriques, M.S.; Gorbunov, D.I.; Kriegner, D.; Vališka, M.; Andreev, A.V.; Matěj, Z.

2018-01-01

Structural changes through the first-order paramagnetic-antiferromagnetic phase transition of Dy3Ru4Al12 at 7 K have been studied by means of X-ray diffraction and thermal expansion measurements. The compound crystallizes in a hexagonal crystal structure of Gd3Ru4Al12 type (P63/mmc space group), and no structural phase transition has been found in the temperature interval between 2.5 and 300 K. Nevertheless, due to the spin-lattice coupling the crystal volume undergoes a small orthorhombic distortion of the order of 2×10-5 as the compound enters the antiferromagnetic state. We propose that the first-order phase transition is not driven by the structural changes but rather by the exchange interactions present in the system. PMID:29445250

Instrumentation and Methodology for Generation of an Electrochemical Data Base for Pattern Recognition.

DTIC Science & Technology

1982-05-01

and mercury drop hang time all produced changes in cyclic differential capacity curves and -..-- DD 0A" 1473 EDITION OF 1 NOV 6S IS OBSOLETE S/N 0102...scan rate, and mercury drop hang time all produced changes in cyclic differential capacity curves and cyclic staircase voltammograms which were unique...Faradaic measurements with staircase voltammetry have been enumerated elewhere (24, 25). -4- EXPERIMENTAL Experimental Design The seven variables which

Membrane rejection of nitrogen compounds

NASA Technical Reports Server (NTRS)

Lee, S.; Lueptow, R. M.

2001-01-01

Rejection characteristics of nitrogen compounds were examined for reverse osmosis, nanofiltration, and low-pressure reverse osmosis membranes. The rejection of nitrogen compounds is explained by integrating experimental results with calculations using the extended Nernst-Planck model coupled with a steric hindrance model. The molecular weight and chemical structure of nitrogen compounds appear to be less important in determining rejection than electrostatic properties. The rejection is greatest when the Donnan potential exceeds 0.05 V or when the ratio of the solute radius to the pore radius is greater than 0.8. The transport of solute in the pore is dominated by diffusion, although convective transport is significant for organic nitrogen compounds. Electromigration contributes negligibly to the overall solute transport in the membrane. Urea, a small organic compound, has lower rejection than ionic compounds such as ammonium, nitrate, and nitrite, indicating the critical role of electrostatic interaction in rejection. This suggests that better treatment efficiency for organic nitrogen compounds can be obtained after ammonification of urea.

Preparation of uranium compounds

DOEpatents

Kiplinger, Jaqueline L; Montreal, Marisa J; Thomson, Robert K; Cantat, Thibault; Travia, Nicholas E

2013-02-19

UI.sub.3(1,4-dioxane).sub.1.5 and UI.sub.4(1,4-dioxane).sub.2, were synthesized in high yield by reacting turnings of elemental uranium with iodine dissolved in 1,4-dioxane under mild conditions. These molecular compounds of uranium are thermally stable and excellent precursor materials for synthesizing other molecular compounds of uranium including alkoxide, amide, organometallic, and halide compounds.

[Detection of organic compounds on Mars].

PubMed

Kobayashi, K

1997-03-01

McKay et al. detected polycyclic aromatic hydrocarbons (PAHs) in Martian meteorite ALH 84001 by two-step laser mass spectrometry. From the presence of PAHs, together with other results, they concluded that there were past life of Mars. On the other hands, no organisms nor organic compounds were detected in Martian regolith in Viking experiments in 1976. In order to obtain solid evidence for organisms or bioorganic compounds compounds on Mars, further analyses of Martian samples are required. There may be four classes of organic compounds on Mars, which are (i) organic compounds abiotically formed from primitive Mars atmosphere, (ii) Organic compounds delivered out of Mars, (iii) Organic compounds biotically formed by Mars organisms, and (iv) Organic compounds abiotically formed from the present Mars atmosphere. Possible organic compounds on Mars and analytical methods for them are discussed.

Depth-estimation-enabled compound eyes

NASA Astrophysics Data System (ADS)

Lee, Woong-Bi; Lee, Heung-No

2018-04-01

Most animals that have compound eyes determine object distances by using monocular cues, especially motion parallax. In artificial compound eye imaging systems inspired by natural compound eyes, object depths are typically estimated by measuring optic flow; however, this requires mechanical movement of the compound eyes or additional acquisition time. In this paper, we propose a method for estimating object depths in a monocular compound eye imaging system based on the computational compound eye (COMPU-EYE) framework. In the COMPU-EYE system, acceptance angles are considerably larger than interommatidial angles, causing overlap between the ommatidial receptive fields. In the proposed depth estimation technique, the disparities between these receptive fields are used to determine object distances. We demonstrate that the proposed depth estimation technique can estimate the distances of multiple objects.

Monitoring the Wobbe Index of Natural Gas Using Fiber-Enhanced Raman Spectroscopy.

PubMed

Sandfort, Vincenz; Trabold, Barbara M; Abdolvand, Amir; Bolwien, Carsten; Russell, Philip St. J; Wöllenstein, Jürgen; Palzer, Stefan

2017-11-24

The fast and reliable analysis of the natural gas composition requires the simultaneous quantification of numerous gaseous components. To this end, fiber-enhanced Raman spectroscopy is a powerful tool to detect most components in a single measurement using a single laser source. However, practical issues such as detection limit, gas exchange time and background Raman signals from the fiber material still pose obstacles to utilizing the scheme in real-world settings. This paper compares the performance of two types of hollow-core photonic crystal fiber (PCF), namely photonic bandgap PCF and kagomé-style PCF, and assesses their potential for online determination of the Wobbe index. In contrast to bandgap PCF, kagomé-PCF allows for reliable detection of Raman-scattered photons even below 1200 cm -1 , which in turn enables fast and comprehensive assessment of the natural gas quality of arbitrary mixtures.

Veterinary Compounding: Regulation, Challenges, and Resources

PubMed Central

Davidson, Gigi

2017-01-01

The spectrum of therapeutic need in veterinary medicine is large, and the availability of approved drug products for all veterinary species and indications is relatively small. For this reason, extemporaneous preparation, or compounding, of drugs is commonly employed to provide veterinary medical therapies. The scope of veterinary compounding is broad and focused primarily on meeting the therapeutic needs of companion animals and not food-producing animals in order to avoid human exposure to drug residues. As beneficial as compounded medical therapies may be to animal patients, these therapies are not without risks, and serious adverse events may occur from poor quality compounds or excipients that are uniquely toxic when administered to a given species. Other challenges in extemporaneous compounding for animals include significant regulatory variation across the global veterinary community, a relative lack of validated compounding formulas for use in animals, and poor adherence by compounders to established compounding standards. The information presented in this article is intended to provide an overview of the current landscape of compounding for animals; a discussion on associated benefits, risks, and challenges; and resources to aid compounders in preparing animal compounds of the highest possible quality. PMID:28075379

SULFUR COMPOUNDS IN MORPHOGENESIS.

DTIC Science & Technology

CHICKENS, GROWTH(PHYSIOLOGY), MITOSIS, BACTERIA, ALGAE, LIPOIC ACID , THIOLS, BELGIUM...ORGANIC SULFUR COMPOUNDS, METABOLISM), (*MORPHOLOGY(BIOLOGY), ORGANIC SULFUR COMPOUNDS), (*NUCLEIC ACIDS , BIOSYNTHESIS), EGGS, EMBRYOS, AMPHIBIANS

Pressor mechanism evaluation for phytochemical compounds using in silico compound-protein interaction prediction.

PubMed

He, Min; Cao, Dong-Sheng; Liang, Yi-Zeng; Li, Ya-Ping; Liu, Ping-Le; Xu, Qing-Song; Huang, Ren-Bin

2013-10-01

In this study, a method was applied to evaluate pressor mechanisms through compound-protein interactions. Our method assumed that the compounds with different pressor mechanisms should bind to different target proteins, and thereby these mechanisms could be differentiated using compound-protein interactions. Twenty-six phytochemical components and 46 tested target proteins related to blood pressure (BP) elevation were collected. Then, in silico compound-protein interactions prediction probabilities were calculated using a random forest model, which have been implemented in a web server, and the credibility was judged using related literature and other methods. Further, a heat map was constructed, it clearly showed different prediction probabilities accompanied with hierarchical clustering analysis results. Followed by a compound-protein interaction network was depicted according to the results, we can see the connectivity layout of phytochemical components with different target proteins within the BP elevation network, which guided the hypothesis generation of poly-pharmacology. Lastly, principal components analysis (PCA) was carried out upon the prediction probabilities, and pressor targets could be divided into three large classes: neurotransmitter receptors, hormones receptors and monoamine oxidases. In addition, steroid glycosides seem to be close to the region of hormone receptors, and a weak difference existed between them. This work explored the possibility for pharmacological or toxicological mechanism classification using compound-protein interactions. Such approaches could also be used to deduce pharmacological or toxicological mechanisms for uncharacterized compounds. Copyright © 2013 Elsevier Inc. All rights reserved.

Organic Compounds in Carbonaceous Meteorites

NASA Technical Reports Server (NTRS)

Cooper, Grorge

2001-01-01

Carbonaceous meteorites are relatively enriched in soluble organic compounds. To date, these compounds provide the only record available to study a range of organic chemical processes in the early Solar System chemistry. The Murchison meteorite is the best-characterized carbonaceous meteorite with respect to organic chemistry. The study of its organic compounds has related principally to aqueous meteorite parent body chemistry and compounds of potential importance for the origin of life. Among the classes of organic compounds found in Murchison are amino acids, amides, carboxylic acids, hydroxy acids, sulfonic acids, phosphonic acids, purines and pyrimidines (Table 1). Compounds such as these were quite likely delivered to the early Earth in asteroids and comets. Until now, polyhydroxylated compounds (polyols), including sugars (polyhydroxy aldehydes or ketones), sugar alcohols, sugar acids, etc., had not been identified in Murchison. Ribose and deoxyribose, five-carbon sugars, are central to the role of contemporary nucleic acids, DNA and RNA. Glycerol, a three-carbon sugar alcohol, is a constituent of all known biological membranes. Due to the relative lability of sugars, some researchers have questioned the lifetime of sugars under the presumed conditions on the early Earth and postulated other (more stable) compounds as constituents of the first replicating molecules. The identification of potential sources and/or formation mechanisms of pre-biotic polyols would add to the understanding of what organic compounds were available, and for what length of time, on the ancient Earth.

Component Selection for Sterile Compounding.

PubMed

Dilzer, Richard H

2017-01-01

This article describes the factors to consider, as well as the process of proper component selection, for use in preparing compounded sterile preparations. Special emphasis is placed on individual chemical factors that may impact a preparation's accuracy and potency. Values reported in a typical certificate of analysis are discussed, including methods of identifying any required adjustments to a master formulation or compounding record during the compounding of sterile preparations. Proper screening of the certificate of analysis, the Safety Data Sheet, procedural documentation, and the filing of all certificates of conformance are crucial to the operation of a sterile compounding facility. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Compounding Opportunities in Urology.

PubMed

Biundo, Bruce

2017-01-01

There are a lot of options that pharmacists, including compounding pharmacists, can offer urologists to assist their patients. Compounding pharmacists are in a great position to offer unique, effective preparations for many of the conditions urologists treat on a daily basis. It would be well worth the time to learn a little about the conditions these specialists treat and become familiar with what you can offer. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Multipurpose Compound

NASA Technical Reports Server (NTRS)

1983-01-01

Specially formulated derivatives of an unusual basic compound known as Alcide may be the answer to effective treatment and prevention of the disease bovine mastitis, a bacterial inflammation of a cow's mammary gland that results in loss of milk production and in extreme cases, death. Manufactured by Alcide Corporation the Alcide compound has killed all tested bacteria, virus and fungi, shortly after contact, with minimal toxic effects on humans or animals. Alcide Corporation credits the existence of the mastitis treatment/prevention products to assistance provided the company by NERAC, Inc.

Autophagic compound database: A resource connecting autophagy-modulating compounds, their potential targets and relevant diseases.

PubMed

Deng, Yiqi; Zhu, Lingjuan; Cai, Haoyang; Wang, Guan; Liu, Bo

2018-06-01

Autophagy, a highly conserved lysosomal degradation process in eukaryotic cells, can digest long-lived proteins and damaged organelles through vesicular trafficking pathways. Nowadays, mechanisms of autophagy have been gradually elucidated and thus the discovery of small-molecule drugs targeting autophagy has always been drawing much attention. So far, some autophagy-related web servers have been available online to facilitate scientists to obtain the information relevant to autophagy conveniently, such as HADb, CTLPScanner, iLIR server and ncRDeathDB. However, to the best of our knowledge, there is not any web server available about the autophagy-modulating compounds. According to published articles, all the compounds and their relations with autophagy were anatomized. Subsequently, an online Autophagic Compound Database (ACDB) (http://www.acdbliulab.com/) was constructed, which contained information of 357 compounds with 164 corresponding signalling pathways and potential targets in different diseases. We achieved a great deal of information of autophagy-modulating compounds, including compounds, targets/pathways and diseases. ACDB is a valuable resource for users to access to more than 300 curated small-molecule compounds correlated with autophagy. Autophagic compound database will facilitate to the discovery of more novel therapeutic drugs in the near future. © 2017 John Wiley & Sons Ltd.

Bilayer Effects of Antimalarial Compounds

PubMed Central

Ramsey, Nicole B.; Andersen, Olaf S.

2015-01-01

Because of the perpetual development of resistance to current therapies for malaria, the Medicines for Malaria Venture developed the Malaria Box to facilitate the drug development process. We tested the 80 most potent compounds from the box for bilayer-mediated effects on membrane protein conformational changes (a measure of likely toxicity) in a gramicidin-based stopped flow fluorescence assay. Among the Malaria Box compounds tested, four compounds altered membrane properties (p< 0.05); MMV007384 stood out as a potent bilayer-perturbing compound that is toxic in many cell-based assays, suggesting that testing for membrane perturbation could help identify toxic compounds. In any case, MMV007384 should be approached with caution, if at all. PMID:26551613

Bilayer Effects of Antimalarial Compounds.

PubMed

Ramsey, Nicole B; Andersen, Olaf S

2015-01-01

Because of the perpetual development of resistance to current therapies for malaria, the Medicines for Malaria Venture developed the Malaria Box to facilitate the drug development process. We tested the 80 most potent compounds from the box for bilayer-mediated effects on membrane protein conformational changes (a measure of likely toxicity) in a gramicidin-based stopped flow fluorescence assay. Among the Malaria Box compounds tested, four compounds altered membrane properties (p< 0.05); MMV007384 stood out as a potent bilayer-perturbing compound that is toxic in many cell-based assays, suggesting that testing for membrane perturbation could help identify toxic compounds. In any case, MMV007384 should be approached with caution, if at all.

Compounds affecting cholesterol absorption

NASA Technical Reports Server (NTRS)

Koo, Sung I. (Inventor); Noh, Sang K. (Inventor); Hua, Duy H. (Inventor)

2004-01-01

A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.

Pharmacists' Perceptions of the Economic Value of Compounded Pharmaceuticals: A Comparison of Compounded and Commercial Pharmaceuticals in Select Disease States.

PubMed

Lobb, William B; Wilkin, Noel E; Holmes, Erin R

2015-01-01

Studies have been conducted to assess patient satisfaction with compounded pharmaceuticals and to directly compare compounded pharmaceuticals with their comparable commercial pharmaceuticals. Yet, the economic value of or potential for economic value derived from compounded pharmaceuticals relative to commercial pharmaceuticals is still not known. Therefore, the purpose of this study was to assess and compare compounding and non-compounding pharmacists' perceptions of the economic value of compounded preparations relative to commercial products. In-depth interviews with 10 compounding pharmacists and physicians who prescribe compounded prescription pharmaceutical preparations were conducted to help develop a self-administered questionnaire distributed to 50 compounding and 50 non-compounding pharmacists. Compounding and non-compounding pharmacists' perceptions differed most often in the context of compounded pharmaceuticals for pediatric patients. However, both groups responded with moderate agreement that compounded prescription treatments are more profitable for the pharmacy than commercial prescription treatments in most therapeutic areas. This research sought to understand the perception of pharmacists of areas for potential direct and indirect economic cost savings as a result of compounding. For all items whereby compounding and non-compounding pharmacists' ratings were significantly different, compounding pharmacists more strongly believed that compounding pharmaceuticals offered benefit and vice versa. The differences in ratings that were most common were those that directly compared the economic value of compounding and commercial pharmaceuticals, with compounding pharmacists more strongly agreeing with the potential cost savings associated with compounded pharmaceuticals. Based on these findings, prescription compounds are believed to have a benefit to the health system by those who provide them. Future research should proactively explore the economic

Devices for collecting chemical compounds

DOEpatents

Scott, Jill R; Groenewold, Gary S

2013-12-24

A device for sampling chemical compounds from fixed surfaces and related methods are disclosed. The device may include a vacuum source, a chamber and a sorbent material. The device may utilize vacuum extraction to volatilize the chemical compounds from a fixed surface so that they may be sorbed by the sorbent material. The sorbent material may then be analyzed using conventional thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) instrumentation to determine presence of the chemical compounds. The methods may include detecting release and presence of one or more chemical compounds and determining the efficacy of decontamination. The device may be useful in collection and analysis of a variety of chemical compounds, such as residual chemical warfare agents, chemical attribution signatures and toxic industrial chemicals.

Layered semi-convection and tides in giant planet interiors. I. Propagation of internal waves

NASA Astrophysics Data System (ADS)

André, Q.; Barker, A. J.; Mathis, S.

2017-09-01

Context. Layered semi-convection is a possible candidate to explain Saturn's luminosity excess and the abnormally large radius of some hot Jupiters. In giant planet interiors, it could lead to the creation of density staircases, which are convective layers separated by thin stably stratified interfaces. These are also observed on Earth in some lakes and in the Arctic Ocean. Aims: We aim to study the propagation of internal waves in a region of layered semi-convection, with the aim to predict energy transport by internal waves incident upon a density staircase. The goal is then to understand the resulting tidal dissipation when these waves are excited by other bodies such as moons in giant planets systems. Methods: We used a local Cartesian analytical model, taking into account the complete Coriolis acceleration at any latitude, thus generalising previous works. We used a model in which stably stratified interfaces are infinitesimally thin, before relaxing this assumption with a second model that assumes a piecewise linear stratification. Results: We find transmission of incident internal waves to be strongly affected by the presence of a density staircase, even if these waves are initially pure inertial waves (which are restored by the Coriolis acceleration). In particular, low-frequency waves of all wavelengths are perfectly transmitted near the critical latitude, defined by θc = sin-1(ω/ 2Ω), where ω is the wave's frequency and Ω is the rotation rate of the planet. Otherwise, short-wavelength waves are only efficiently transmitted if they are resonant with a free mode (interfacial gravity wave or short-wavelength inertial mode) of the staircase. In all other cases, waves are primarily reflected unless their wavelengths are longer than the vertical extent of the entire staircase (not just a single step). Conclusions: We expect incident internal waves to be strongly affected by the presence of a density staircase in a frequency-, latitude- and wavelength

Basics of Compounding: Compounding Irrigation Solutions for Sterile and Nonsterile Preparations.

PubMed

Allen, Loyd V

2017-01-01

Compounding pharmacists are sometimes called upon to prepare irrigation solutions, especially in the hospital or clinical setting. Irrigations are indicated for washing or bathing surgical incisions, wounds, and body tissues, including body cavities. Some irrigation solutions coming in contact with exposed tissue, must meet stringent requirements of sterility and bacterial endotoxins. Compounded irrigation solutions may involve wound(s), the bladder, and also may be for ophthalmic, otic, and nasal application. Some vaginal douches/instillations and rectal solutions may also be used as irrigations. As with any medication administered to the body or used on body tissues, there are requirements, and these may vary depending on the type of irrigation solution involved. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Physical realization of a quantum spin liquid based on a complex frustration mechanism

NASA Astrophysics Data System (ADS)

Reuther, Johannes; Balz, Christian; Lake, Bella

Unlike conventional magnets where the spins undergo magnetic long-range order in the ground state, in a quantum spin liquid they remain disordered down to the lowest temperatures without breaking local symmetries. Here, we investigate the novel, unexplored bilayer-kagome magnet Ca10Cr7O28, which has a complex Hamiltonian consisting of isotropic antiferromagnetic and ferromagnetic interactions where the ferromagnetic couplings are the dominant ones. We show both experimentally and theoretically that this compound displays all the features expected of a quantum spin liquid. In particular, experiments rule out static magnetic order down to 19mK and reveal a diffuse spinon-like excitation spectrum. Numerically simulating this material using the pseudo fermion functional renormalization group (PFFRG) method, we theoretically confirm the non-magnetic ground state of the system and qualitatively reproduce the measured spin correlation profile. By tuning the model parameters away from those realized in Ca10Cr7O28 we further show that the spin-liquid phase is of remarkable stability.

Reducing Memory Cost of Exact Diagonalization using Singular Value Decomposition

NASA Astrophysics Data System (ADS)

Weinstein, Marvin; Chandra, Ravi; Auerbach, Assa

2012-02-01

We present a modified Lanczos algorithm to diagonalize lattice Hamiltonians with dramatically reduced memory requirements. In contrast to variational approaches and most implementations of DMRG, Lanczos rotations towards the ground state do not involve incremental minimizations, (e.g. sweeping procedures) which may get stuck in false local minima. The lattice of size N is partitioned into two subclusters. At each iteration the rotating Lanczos vector is compressed into two sets of nsvd small subcluster vectors using singular value decomposition. For low entanglement entropy See, (satisfied by short range Hamiltonians), the truncation error is bounded by (-nsvd^1/See). Convergence is tested for the Heisenberg model on Kagom'e clusters of 24, 30 and 36 sites, with no lattice symmetries exploited, using less than 15GB of dynamical memory. Generalization of the Lanczos-SVD algorithm to multiple partitioning is discussed, and comparisons to other techniques are given. Reference: arXiv:1105.0007

Monitoring the Wobbe Index of Natural Gas Using Fiber-Enhanced Raman Spectroscopy

PubMed Central

Sandfort, Vincenz; Trabold, Barbara M.; Abdolvand, Amir; Bolwien, Carsten; Russell, Philip St. J.; Wöllenstein, Jürgen

2017-01-01

The fast and reliable analysis of the natural gas composition requires the simultaneous quantification of numerous gaseous components. To this end, fiber-enhanced Raman spectroscopy is a powerful tool to detect most components in a single measurement using a single laser source. However, practical issues such as detection limit, gas exchange time and background Raman signals from the fiber material still pose obstacles to utilizing the scheme in real-world settings. This paper compares the performance of two types of hollow-core photonic crystal fiber (PCF), namely photonic bandgap PCF and kagomé-style PCF, and assesses their potential for online determination of the Wobbe index. In contrast to bandgap PCF, kagomé-PCF allows for reliable detection of Raman-scattered photons even below 1200 cm−1, which in turn enables fast and comprehensive assessment of the natural gas quality of arbitrary mixtures. PMID:29186768

Sarcomere length-dependence of activity-dependent twitch potentiation in mouse skeletal muscle

PubMed Central

Rassier, Dilson E; MacIntosh, Brian R

2002-01-01

Background It has been reported that potentiation of a skeletal muscle twitch response is proportional to muscle length with a negative slope during staircase, and a positive slope during posttetanic potentiation. This study was done to directly compare staircase and posttetanic responses with measurement of sarcomere length to compare their length-dependence. Methods Mouse extensor digitorum longus (EDL) muscles were dissected to small bundles of fibers, which permit measurement of sarcomere length (SL), by laser diffraction. In vitro fixed-end contractions of EDL fiber bundles were elicited at 22°C and 35°C at sarcomere lengths ranging from 2.35 μm to 3.85 μm. Twitch contractions were assessed before and after 1.5 s of 75 Hz stimulation at 22°C or during 10 s of 10 Hz stimulation at 22°C or 35°C. Results Staircase potentiation was greater at 35°C than 22°C, and the relative magnitude of the twitch contraction (Pt*/Pt) was proportional to sarcomere length with a negative slope, over the range 2.3 μm – 3.7 μm. Linear regression yielded the following: Pt*/Pt = -0.59·SL+3.27 (r2 = 0.74); Pt*/Pt = -0.39·SL+2.34 (r2 = 0.48); and Pt*/Pt = -0.50·SL+2.45 (r2 = 0.80) for staircase at 35°C, and 22°C and posttetanic response respectively. Posttetanic depression rather than potentiation was present at long SL. This indicates that there may be two processes operating in these muscles to modulate the force: one that enhances and a second that depresses the force. Either or both of these processes may have a length-dependence of its mechanism. Conclusion There is no evidence that posttetanic potentiation is fundamentally different from staircase in these muscles. PMID:12475395

Volatile flavor compounds in yogurt: a review.

PubMed

Cheng, Hefa

2010-11-01

Considerable knowledge has been accumulated on the volatile compounds contributing to the aroma and flavor of yogurt. This review outlines the production of the major flavor compounds in yogurt fermentation and the analysis techniques, both instrumental and sensory, for quantifying the volatile compounds in yogurt. The volatile compounds that have been identified in plain yogurt are summarized, with the few key aroma compounds described in detail. Most flavor compounds in yogurt are produced from lipolysis of milkfat and microbiological transformations of lactose and citrate. More than 100 volatiles, including carbonyl compounds, alcohols, acids, esters, hydrocarbons, aromatic compounds, sulfur-containing compounds, and heterocyclic compounds, are found in yogurt at low to trace concentrations. Besides lactic acid, acetaldehyde, diacetyl, acetoin, acetone, and 2-butanone contribute most to the typical aroma and flavor of yogurt. Extended storage of yogurt causes off-flavor development, which is mainly attributed to the production of undesired aldehydes and fatty acids during lipid oxidation. Further work on studying the volatile flavor compounds-matrix interactions, flavor release mechanisms, and the synergistic effect of flavor compounds, and on correlating the sensory properties of yogurt with the compositions of volatile flavor compounds are needed to fully elucidate yogurt aroma and flavor.

Drugs and Drug-Like Compounds: Discriminating Approved Pharmaceuticals from Screening-Library Compounds

NASA Astrophysics Data System (ADS)

Schierz, Amanda C.; King, Ross D.

Compounds in drug screening-libraries should resemble pharmaceuticals. To operationally test this, we analysed the compounds in terms of known drug-like filters and developed a novel machine learning method to discriminate approved pharmaceuticals from “drug-like” compounds. This method uses both structural features and molecular properties for discrimination. The method has an estimated accuracy of 91% in discriminating between the Maybridge HitFinder library and approved pharmaceuticals, and 99% between the NATDiverse collection (from Analyticon Discovery) and approved pharmaceuticals. These results show that Lipinski’s Rule of 5 for oral absorption is not sufficient to describe “drug-likeness” and be the main basis of screening-library design.

Organic electronic devices using phthalimide compounds

DOEpatents

Hassan, Azad M.; Thompson, Mark E.

2010-09-07

Organic electronic devices comprising a phthalimide compound. The phthalimide compounds disclosed herein are electron transporters with large HOMO-LUMO gaps, high triplet energies, large reduction potentials, and/or thermal and chemical stability. As such, these phthalimide compounds are suitable for use in any of various organic electronic devices, such as OLEDs and solar cells. In an OLED, the phthalimide compounds may serve various functions, such as a host in the emissive layer, as a hole blocking material, or as an electron transport material. In a solar cell, the phthalimide compounds may serve various functions, such as an exciton blocking material. Various examples of phthalimide compounds which may be suitable for use in the present invention are disclosed.

Organic electronic devices using phthalimide compounds

DOEpatents

Hassan, Azad M.; Thompson, Mark E.

2012-10-23

Organic electronic devices comprising a phthalimide compound. The phthalimide compounds disclosed herein are electron transporters with large HOMO-LUMO gaps, high triplet energies, large reduction potentials, and/or thermal and chemical stability. As such, these phthalimide compounds are suitable for use in any of various organic electronic devices, such as OLEDs and solar cells. In an OLED, the phthalimide compounds may serve various functions, such as a host in the emissive layer, as a hole blocking material, or as an electron transport material. In a solar cell, the phthalimide compounds may serve various functions, such as an exciton blocking material. Various examples of phthalimide compounds which may be suitable for use in the present invention are disclosed.

Organic electronic devices using phthalimide compounds

DOEpatents

Hassan, Azad M.; Thompson, Mark E.

2013-03-19

Organic electronic devices comprising a phthalimide compound. The phthalimide compounds disclosed herein are electron transporters with large HOMO-LUMO gaps, high triplet energies, large reduction potentials, and/or thermal and chemical stability. As such, these phthalimide compounds are suitable for use in any of various organic electronic devices, such as OLEDs and solar cells. In an OLED, the phthalimide compounds may serve various functions, such as a host in the emissive layer, as a hole blocking material, or as an electron transport material. In a solar cell, the phthalimide compounds may serve various functions, such as an exciton blocking material. Various examples of phthalimide compounds which may be suitable for use in the present invention are disclosed.

Deuterium permeation through EPDM rubber compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zapp, P.E.

1988-01-01

The permeation of deuterium through a specially formulated compound of ethylene propylene diene rubber was measured in the temperature range of 26/degree/C to 120/degree/C. The results were similar to permeation through two commercial compounds of this elastomer. Permeation was reduced after gamma irradiation (in the presence of hydrogen gas to simulate a tritium exposure). However the reduction was smaller than that experienced by the two commercial compounds. Radiation damage is apparently less severe in the special compound. It is possible that mechanical properties such as compression set may be influenced less by ionizing radiation in this compound as compared withmore » the commercial compounds. 4 figs., 1 tab.« less

The Onium Compounds

NASA Astrophysics Data System (ADS)

Tsarevsky, Nicolay V.; Slaveykova, Vera; Manev, Stefan; Lazarov, Dobri

1997-06-01

The onium salts are of a big interest for theoretical and structural chemistry, and for organic synthesis. Some representatives of the group (e.g. ammonium salts) were known from the oldest times. Many onium salts are met the nature: ammonium salts (either as inorganic salts, and organic derivatives, e.g. aminoacids, salts of biogenic amines and alkaloids, etc.); oxonium salts (plant pigments as anthocyans are organic oxonium compounds), etc. In 1894 C. Hartmann and V. Meyer prepared the first iodonium salts - 4-iododiphenyliodonium hydrogensulfate and diphenyliodonium salts, and suggested the ending -onium for all compounds with properties similar to those of ammonium salts. Nowadays onium compounds of almost all nonmetals are synthesised and studied. A great variety of physical methods: diffraction (e.g. XRD) and spectral methods (IR-, NMR-, and UV-spectra), as well as the chemical properties and methods of preparation of onium salts have been used in determination of the structure of these compounds. The application of different onium salts is immense. Ammonium, phosphonium and sulfonium salts are used as phase-transfer catalysts; diazonium salts - for the preparation of dyes, metalochromic and pH-indicators. All the onium salts and especially diazonium and iodonium salts are very useful reagents in organic synthesis.

Thin films of mixed metal compounds

DOEpatents

Mickelsen, R.A.; Chen, W.S.

1985-06-11

Disclosed is a thin film heterojunction solar cell, said heterojunction comprising a p-type I-III-IV[sub 2] chalcopyrite substrate and an overlying layer of an n-type ternary mixed metal compound wherein said ternary mixed metal compound is applied to said substrate by introducing the vapor of a first metal compound to a vessel containing said substrate from a first vapor source while simultaneously introducing a vapor of a second metal compound from a second vapor source of said vessel, said first and second metals comprising the metal components of said mixed metal compound; independently controlling the vaporization rate of said first and second vapor sources; reducing the mean free path between vapor particles in said vessel, said gas being present in an amount sufficient to induce homogeneity of said vapor mixture; and depositing said mixed metal compound on said substrate in the form of a uniform composition polycrystalline mixed metal compound. 5 figs.

Staircase Methods of Sensitivity Testing,

DTIC Science & Technology

1946-03-21

Mathematical Preliminaries ............. 32 b. Outline of the Investigation ..... .......... 35 8. The Possible Adjustments ...... ............... .. 36 9...bh Ar’Lied MathematIcs Pa-nel. ZCC, uU, -. for one decermntation !f tie per centtage point and the average nmber ee exp-li.-n. required far one such...accuracy per explosion. 32. II. TECOI4ICPJJ 7. Introduction. a. Some Mathematical Preliminaries. Expressed mathematically , the problem of sensitivity

The Postmodernist Descending the Staircase.

ERIC Educational Resources Information Center

Paterson, Susan

This paper considers the artistic and literary movement called "Postmodernism." Noting that postmodernism is intellectually grounded in the premise that its discourse must expose positions of privilege and power relations in society, the paper asks of art education, How much has the postmodern condition, a thesis of cultural relativism…

Calculus Student Descending a Staircase.

ERIC Educational Resources Information Center

Mueller, William

1999-01-01

Common student attitudes toward reform methods are conveyed through the thoughts of a student leaving a multivariable calculus exam and musings range over textbooks, homework, workload, group work, writing, noncomputational problems, instructional problems, instructional styles, and classroom activities. (Author/ASK)

Therapeutic Phytogenic Compounds for Obesity and Diabetes

PubMed Central

Jung, Hee Soong; Lim, Yun; Kim, Eun-Kyoung

2014-01-01

Natural compounds have been used to develop drugs for many decades. Vast diversities and minimum side effects make natural compounds a good source for drug development. However, the composition and concentrations of natural compounds can vary. Despite this inconsistency, half of the Food and Drug Administration (FDA)-approved pharmaceuticals are natural compounds or their derivatives. Therefore, it is essential to continuously investigate natural compounds as sources of new pharmaceuticals. This review provides comprehensive information and analysis on natural compounds from plants (phytogenic compounds) that may serve as anti-obesity and/or anti-diabetes therapeutics. Our growing understanding and further exploration of the mechanisms of action of the phytogenic compounds may afford opportunities for development of therapeutic interventions in metabolic diseases. PMID:25421245

Transition Metal Compounds Towards Holography

PubMed Central

Dieckmann, Volker; Eicke, Sebastian; Springfeld, Kristin; Imlau, Mirco

2012-01-01

We have successfully proposed the application of transition metal compounds in holographic recording media. Such compounds feature an ultra-fast light-induced linkage isomerization of the transition-metal–ligand bond with switching times in the sub-picosecond regime and lifetimes from microseconds up to hours at room temperature. This article highlights the photofunctionality of two of the most promising transition metal compounds and the photophysical mechanisms that are underlying the hologram recording. We present the latest progress with respect to the key measures of holographic media assembled from transition metal compounds, the molecular embedding in a dielectric matrix and their impressive potential for modern holographic applications. PMID:28817028

Method of preparing metallocene compounds

DOEpatents

Rosenblum, Myron; Matchett, Stephen A.

1992-01-01

This invention describes a novel method of preparing metallocene compounds. The invention is based on synthesis of novel bis cyclopentadienides that, under appropriate conditions, will either encapsulate a transition metal to produce a metallocene such as ferrocene, or ferrocene derivative, or will yield a polymeric metallocene. Compounds produced by this process are useful as catalysts in propulsion systems, or as anti-knock compounds in gasolines.

STATISTICAL DATA ON CHEMICAL COMPOUNDS.

DTIC Science & Technology

DATA STORAGE SYSTEMS, FEASIBILITY STUDIES, COMPUTERS, STATISTICAL DATA , DOCUMENTS, ARMY...CHEMICAL COMPOUNDS, INFORMATION RETRIEVAL), (*INFORMATION RETRIEVAL, CHEMICAL COMPOUNDS), MOLECULAR STRUCTURE, BIBLIOGRAPHIES, DATA PROCESSING

Host compounds for red phosphorescent OLEDs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Chuanjun; Cheon, Kwang -Ohk

2015-08-25

Novel compounds containing a triphenylene moiety linked to an .alpha..beta. connected binaphthyl ring system are provided. These compounds have surprisingly good solubility in organic solvents and are useful as host compounds in red phosphorescent OLEDs.

The nature of compounds: a psychocentric perspective.

PubMed

Libben, Gary

2014-01-01

Although compound words often seem to be words that themselves contain words, this paper argues that this is not the case for the vast majority of lexicalized compounds. Rather, it is claimed that as a result of acts of lexical processing, the constituents of compound words develop into new lexical representations. These representations are bound to specific morphological roles and positions (e.g., head, modifier) within a compound word. The development of these positionally bound compound constituents creates a rich network of lexical knowledge that facilitates compound processing and also creates some of the well-documented patterns in the psycholinguistic and neurolinguistic study of compounding.

Method for purifying bidentate organophosphorus compounds

DOEpatents

Schulz, Wallace W.

1977-01-01

Bidentate organophosphorus compounds useful for extracting actinide elements from acidic nuclear waste solutions are purified of undesirable acidic impurities by contacting the compounds with ethylene glycol which preferentially extracts the impurities found in technical grade bidentate compounds.

Assimilation of Unusual Carbon Compounds

NASA Astrophysics Data System (ADS)

Middelhoven, Wouter J.

Yeast taxa traditionally are distinguished by growth tests on several sugars and organic acids. During the last decades it became apparent that many yeast species assimilate a much greater variety of naturally occurring carbon compounds as sole source of carbon and energy. These abilities are indicative of a greater role of yeasts in the carbon cycle than previously assumed. Especially in acidic soils and other habitats, yeasts may play a role in the degradation of carbon compounds. Such compounds include purines like uric acid and adenine, aliphatic amines, diamines and hydroxyamines, phenolics and other benzene compounds and polysaccharides. Assimilation of purines and amines is a feature of many ascomycetes and basidiomycetes. However, benzene compounds are degraded by only a few ascomycetous yeasts (e.g. the Stephanoascus/ Blastobotrys clade and black yeastlike fungi) but by many basidiomycetes, e.g. Filobasidiales, Trichosporonales, red yeasts producing ballistoconidia and related species, but not by Tremellales. Assimilation of polysaccharides is wide-spread among basidiomycetes

Tunable Quantum Spin Liquidity in Mo3O13 Cluster Mott Insulators

NASA Astrophysics Data System (ADS)

Akbari-Sharbaf, Arash; Ziat, Djamel; Verrier, Aime; Quilliam, Jeffrey A.; Sinclair, Ryan; Zhou, Haidong D.; Sun, Xuefeng F.

A study of a tunable quantum spin liquid (QSL) phase in the compound Li2In1- x ScxMo3O8 (x = 0.2, 0.4, 0.6, 0.8, 1) will be presented. Crystal structure of these compounds can be viewed as Mo ions arranged on an asymmetric Kagome lattice (KL), with two different Mo-Mo bond lengths, separated by nonmagnetic layers composed of Li, In, and Sc ions. Using X-ray diffraction spectroscopy, muon spin relaxation spectroscopy, bulk magnetic susceptibility and specific heat measurements we show that by changing the composition of the nonmagnetic layers we can drive the system from an ordered antiferromagnetic state to a quantum spin liquid state. The mechanism responsible for the tunability of the magnetic phase in this class of materials may be associated with the degree of asymmetry of the KL controlled by the composition of the nonmagnetic layers. For high degree of asymmetry the constraint on the electronic distribution leads to a configuration of Mo3O8 clusters with net spin-1/2 per cluster arrange on a triangular lattice and long range antiferromagnetic order. For low degree of asymmetry the electronic distribution leads to a magnetic phase with QSL character. We acknowledge support from NSERC and CFREF.

Highly sweet compounds of plant origin.

PubMed

Kim, Nam-Cheol; Kinghorn, A Douglas

2002-12-01

The demand for new alternative "low calorie" sweeteners for dietetic and diabetic purposes has increased worldwide. Although the currently developed and commercially used highly sweet sucrose substitutes are mostly synthetic compounds, the search for such compounds from natural sources is continuing. As of mid-2002, over 100 plant-derived sweet compounds of 20 major structural types had been reported, and were isolated from more than 25 different families of green plants. Several of these highly sweet natural products are marketed as sweeteners or flavoring agents in some countries as pure compounds, compound mixtures, or refined extracts. These highly sweet natural substances are reviewed herein.

When what we need influences what we see: choice of energetic replenishment is linked with perceived steepness.

PubMed

Taylor-Covill, Guy A H; Eves, Frank F

2014-06-01

The apparent steepness of the locomotor challenge presented by hills and staircases is overestimated in explicit awareness. Experimental evidence suggests the visual system may rescale our conscious experience of steepness in line with available energy resources. Skeptics of this "embodied" view argue that such findings reflect experimental demand. This article tested whether perceived steepness was related to resource choices in the built environment. Travelers in a station estimated the slant angle of a 6.45 m staircase (23.4°) either before (N = 302) or after (N = 109) choosing from a selection of consumable items containing differing levels of energetic resources. Participants unknowingly allocated themselves to a quasi-experimental group based on the energetic resources provided by the item they chose. Consistent with a resource based model, individuals that chose items with a greater energy density, or more rapidly available energy, estimated the staircase as steeper than those opting for items that provided less energetic resources. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Semantics and technologies in modern design of interior stairs

NASA Astrophysics Data System (ADS)

Kukhta, M.; Sokolov, A.; Pelevin, E.

2015-10-01

Use of metal in the design of interior stairs presents new features for shaping, and can be implemented using different technologies. The article discusses the features of design and production technologies of forged metal spiral staircase considering the image semantics based on the historical and cultural heritage. To achieve the objective was applied structural- semantic method (to identify the organization of structure and semantic features of the artistic image), engineering methods (to justify the construction of the object), anthropometry method and ergonomics (to provide usability), methods of comparative analysis (to reveale the features of the way the ladder in different periods of culture). According to the research results are as follows. Was revealed the semantics influence on the design of interior staircase that is based on the World Tree image. Also was suggested rational calculation of steps to ensure the required strength. And finally was presented technology, providing the realization of the artistic image. In the practical part of the work is presented version of forged staircase.

Polishing compound for plastic surfaces

DOEpatents

Stowell, M.S.

1991-01-01

This invention is comprised of a polishing compound for plastic materials. The compound includes approximately by approximately by weight 25 to 80 parts at least one petroleum distillate lubricant, 1 to 12 parts mineral spirits, 50 to 155 parts abrasive paste, and 15 to 60 parts water. Preferably, the compound includes approximately 37 to 42 parts at least one petroleum distillate lubricant, up to 8 parts mineral spirits, 95 to 110 parts abrasive paste, and 50 to 55 parts water. The proportions of the ingredients are varied in accordance with the particular application. The compound is used on PLEXIGLAS{trademark}, LEXAN{trademark}, LUCITE{trademark}, polyvinyl chloride (PVC), and similar plastic materials whenever a smooth, clear polished surface is desired.

A Multiplexed Assay That Monitors Effects of Multiple Compound Treatment Times Reveals Candidate Immune-Enhancing Compounds.

PubMed

Zhao, Ziyan; Henowitz, Liza; Zweifach, Adam

2018-05-01

We previously developed a flow cytometry assay that monitored lytic granule exocytosis in cytotoxic T lymphocytes stimulated by contacting beads coated with activating anti-CD3 antibodies. That assay was multiplexed in that responses of cells that did or did not receive the activating stimulus were distinguished via changes in light scatter accompanying binding of cells to beads, allowing us to discriminate compounds that activate responses on their own from compounds that enhance responses in cells that received the activating stimulus, all within a single sample. Here we add a second dimension of multiplexing by developing means to assess in a single sample the effects of treating cells with test compounds for different times. Bar-coding cells before adding them to test wells lets us determine compound treatment time while also monitoring activation status and response amplitude at the point of interrogation. This multiplexed assay is suitable for screening 96-well plates. We used it to screen compounds from the National Cancer Institute, identifying several compounds that enhance anti-LAMP1 responses. Multiple-treatment-time (MTT) screening enabled by bar-coding and read via high-throughput flow cytometry may be a generally useful method for facilitating the discovery of compounds of interest.

In situ catalytic hydrogenation of model compounds and biomass-derived phenolic compounds for bio-oil upgrading

Treesearch

Junfeng Feng; Zhongzhi Yang; Chung-yun Hse; Qiuli Su; Kui Wang; Jianchun Jiang; Junming Xu

2017-01-01

The renewable phenolic compounds produced by directional liquefaction of biomass are a mixture of complete fragments decomposed from native lignin. These compounds are unstable and difficult to use directly as biofuel. Here, we report an efficient in situ catalytic hydrogenation method that can convert phenolic compounds into saturated cyclohexanes. The process has...

Characterization of selected volatile organic compounds, polycyclic aromatic hydrocarbons and carbonyl compounds at a roadside monitoring station

NASA Astrophysics Data System (ADS)

Ho, K. F.; Lee, S. C.; Chiu, Gloria M. Y.

Volatile organic compounds (VOCs), PAHs and carbonyl compounds are the major toxic components in Hong Kong. Emissions from motor vehicles have been one of the primary pollution sources in the metropolitan areas throughout Hong Kong for a long time. A 1-yr monitoring program for VOCs, PAHs and carbonyl compounds had been performed at a roadside urban station at Hong Kong Polytechnic University in order to determine the variations and correlations of each selected species (VOCs, PAHs and carbonyl compounds). This study is aimed to analyze toxic volatile organic compounds (benzene, toluene, ethylbenzene and xylene), two carbonyl compounds (formaldehyde, acetaldehyde), and selective polycyclic aromatic hydrocarbons. The monitoring program started from 16 April 1999 to 30 March 2000. Ambient VOC concentrations, many of which originate from the same sources as particulate PAHs and carbonyls compounds, show significant quantities of benzene, toluene and xylenes. Correlations and multivariate analysis of selected gaseous and particulate phase organic pollutants were performed. Source identification by principle component analysis and hierarchical cluster analysis allowed the identification of four sources (factors) for the roadside monitoring station. Factor 1 represents the effect of diesel vehicle exhaust. Factor 2 shows the contribution of aromatic compounds. Factor 3 explains photochemical products—formaldehyde and acetaldehyde. Factor 4 explains the effect of gasoline vehicle exhaust.

Automated compound classification using a chemical ontology.

PubMed

Bobach, Claudia; Böhme, Timo; Laube, Ulf; Püschel, Anett; Weber, Lutz

2012-12-29

Classification of chemical compounds into compound classes by using structure derived descriptors is a well-established method to aid the evaluation and abstraction of compound properties in chemical compound databases. MeSH and recently ChEBI are examples of chemical ontologies that provide a hierarchical classification of compounds into general compound classes of biological interest based on their structural as well as property or use features. In these ontologies, compounds have been assigned manually to their respective classes. However, with the ever increasing possibilities to extract new compounds from text documents using name-to-structure tools and considering the large number of compounds deposited in databases, automated and comprehensive chemical classification methods are needed to avoid the error prone and time consuming manual classification of compounds. In the present work we implement principles and methods to construct a chemical ontology of classes that shall support the automated, high-quality compound classification in chemical databases or text documents. While SMARTS expressions have already been used to define chemical structure class concepts, in the present work we have extended the expressive power of such class definitions by expanding their structure-based reasoning logic. Thus, to achieve the required precision and granularity of chemical class definitions, sets of SMARTS class definitions are connected by OR and NOT logical operators. In addition, AND logic has been implemented to allow the concomitant use of flexible atom lists and stereochemistry definitions. The resulting chemical ontology is a multi-hierarchical taxonomy of concept nodes connected by directed, transitive relationships. A proposal for a rule based definition of chemical classes has been made that allows to define chemical compound classes more precisely than before. The proposed structure-based reasoning logic allows to translate chemistry expert knowledge into a

Automated compound classification using a chemical ontology

PubMed Central

2012-01-01

Background Classification of chemical compounds into compound classes by using structure derived descriptors is a well-established method to aid the evaluation and abstraction of compound properties in chemical compound databases. MeSH and recently ChEBI are examples of chemical ontologies that provide a hierarchical classification of compounds into general compound classes of biological interest based on their structural as well as property or use features. In these ontologies, compounds have been assigned manually to their respective classes. However, with the ever increasing possibilities to extract new compounds from text documents using name-to-structure tools and considering the large number of compounds deposited in databases, automated and comprehensive chemical classification methods are needed to avoid the error prone and time consuming manual classification of compounds. Results In the present work we implement principles and methods to construct a chemical ontology of classes that shall support the automated, high-quality compound classification in chemical databases or text documents. While SMARTS expressions have already been used to define chemical structure class concepts, in the present work we have extended the expressive power of such class definitions by expanding their structure-based reasoning logic. Thus, to achieve the required precision and granularity of chemical class definitions, sets of SMARTS class definitions are connected by OR and NOT logical operators. In addition, AND logic has been implemented to allow the concomitant use of flexible atom lists and stereochemistry definitions. The resulting chemical ontology is a multi-hierarchical taxonomy of concept nodes connected by directed, transitive relationships. Conclusions A proposal for a rule based definition of chemical classes has been made that allows to define chemical compound classes more precisely than before. The proposed structure-based reasoning logic allows to translate

Response of Bioluminescent Bacteria to Alkyltin Compounds.

DTIC Science & Technology

1987-12-01

found in the butyltiri series of compounds; tributyltin was (’Stimes more toxic than dibutyltin and (- 50 times more toxic than (mono)butyltin. When...correlations between compounds, tributyltin was -35 tine more Kicrotxit and fish bLoessays for pure toxic than dibutyltin end -750 times More compounds and...the compounds as a decrease in toxicity (5) tributyltin compounds ea -150 tines more and a method to study synergistic andtoxic than trinethyltia

Nitroaromatic Compounds, from Synthesis to Biodegradation

PubMed Central

Ju, Kou-San; Parales, Rebecca E.

2010-01-01

Summary: Nitroaromatic compounds are relatively rare in nature and have been introduced into the environment mainly by human activities. This important class of industrial chemicals is widely used in the synthesis of many diverse products, including dyes, polymers, pesticides, and explosives. Unfortunately, their extensive use has led to environmental contamination of soil and groundwater. The nitro group, which provides chemical and functional diversity in these molecules, also contributes to the recalcitrance of these compounds to biodegradation. The electron-withdrawing nature of the nitro group, in concert with the stability of the benzene ring, makes nitroaromatic compounds resistant to oxidative degradation. Recalcitrance is further compounded by their acute toxicity, mutagenicity, and easy reduction into carcinogenic aromatic amines. Nitroaromatic compounds are hazardous to human health and are registered on the U.S. Environmental Protection Agency's list of priority pollutants for environmental remediation. Although the majority of these compounds are synthetic in nature, microorganisms in contaminated environments have rapidly adapted to their presence by evolving new biodegradation pathways that take advantage of them as sources of carbon, nitrogen, and energy. This review provides an overview of the synthesis of both man-made and biogenic nitroaromatic compounds, the bacteria that have been identified to grow on and completely mineralize nitroaromatic compounds, and the pathways that are present in these strains. The possible evolutionary origins of the newly evolved pathways are also discussed. PMID:20508249

Symmetry-protected gapless Z2 spin liquids

NASA Astrophysics Data System (ADS)

Lu, Yuan-Ming

2018-03-01

Despite rapid progress in understanding gapped topological states, much less is known about gapless topological phases of matter, especially in strongly correlated electrons. In this work, we discuss a large class of robust gapless quantum spin liquids in frustrated magnets made of half-integer spins, which are described by gapless fermionic spinons coupled to dynamical Z2 gauge fields. Requiring U(1 ) spin conservation, time-reversal, and certain space-group symmetries, we show that certain spinon symmetry fractionalization class necessarily leads to a gapless spectrum. These gapless excitations are stable against any perturbations, as long as the required symmetries are preserved. Applying these gapless criteria to spin-1/2 systems on square, triangular, and kagome lattices, we show that all gapped symmetric Z2 spin liquids in Abrikosov-fermion representation can also be realized in Schwinger-boson representation. This leads to 64 gapped Z2 spin liquids on square lattice, and 8 gapped states on both kagome and triangular lattices.

Extemporaneous compounding of medicated ointments.

PubMed

Nagel, Karen; Ali, Fatima; Al-Khudari, Sarah; Khan, Ayesha; Patel, Khushbu; Patel, Nikunj; Desai, Archana

2010-01-01

Topical preparations represent a large percentage of compounded prescriptions, particularly in the area of dermatology. Properties of ointment bases vary greatly, and active ingredients are frequently added as aqueous or alcoholic solutions. Currently, there are no quantitative guidelines stating the various water and alcohol absorption capacity of different bases. A short experiment was designed to quantitate the amount of water or alcohol that could be absorbed by a series of ointment bases of varying types. Our findings may be used to assist compounding pharmacists in deciding what base is most suitable to use when considering the amount of water, alcohol, or any similar solvent needed to compound the preparation. A general overview of issues related to topical medication compounding is also provided in this article.

Fig volatile compounds--a first comparative study.

PubMed

Grison-Pigé, Laure; Hossaert-McKey, Martine; Greeff, Jaco M; Bessière, Jean-Marie

2002-09-01

We analysed the compounds of volatile blends released by receptive figs of twenty Ficus species to attract their specific pollinating wasps. In all, 99 different compounds were identified. The compounds are mainly terpenoids, aliphatic compounds and products from the shikimic acid pathway. In each species blend, there are few major compounds, which are generally common among floral fragrances. Most species blends also include rare compounds, but generally their proportion in the blend is low. A possible basis for species-specificity of Ficus-wasp interactions is discussed in relation to the patterns of volatiles found in this interspecies comparison. Copyright 2002 Elsevier Science Ltd.

Phenolic compounds in Ross Sea water

NASA Astrophysics Data System (ADS)

Zangrando, Roberta; Barbaro, Elena; Gambaro, Andrea; Barbante, Carlo; Corami, Fabiana; Kehrwald, Natalie; Capodaglio, Gabriele

2016-04-01

Phenolic compounds are semi-volatile organic compounds produced during biomass burning and lignin degradation in water. In atmospheric and paleoclimatic ice cores studies, these compounds are used as biomarkers of wood combustion and supply information on the type of combusted biomass. Phenolic compounds are therefore indicators of paleoclimatic interest. Recent studies of Antarctic aerosols highlighted that phenolic compounds in Antarctica are not exclusively attributable to biomass burning but also derive from marine sources. In order to study the marine contribution to aerosols we developed an analytical method to determine the concentration of vanillic acid, vanillin, p-coumaric acid, syringic acid, isovanillic acid, homovanillic acid, syringaldehyde, acetosyringone and acetovanillone present in dissolved and particle phases in Sea Ross waters using HPLC-MS/MS. The analytical method was validated and used to quantify phenolic compounds in 28 sea water samples collected during a 2012 Ross Sea R/V cruise. The observed compounds were vanillic acid, vanillin, acetovanillone and p-coumaric acid with concentrations in the ng/L range. Higher concentrations of analytes were present in the dissolved phase than in the particle phase. Sample concentrations were greatest in the coastal, surficial and less saline Ross Sea waters near Victoria Land.

Release and skin distribution of silicone-related compound(s) from a silicone gel sheet in vitro.

PubMed

Shigeki, S; Nobuoka, N; Murakami, T; Ikuta, Y

1999-01-01

The efficacy of topical silicone gel sheeting in prevention and/or reduction of keloids and hypertrophic scars is well recognized. In the present study, we reexamined the possible release of silicone-related compound(s) from a commercially available silicone gel sheet (Cica-Care, Smith and Nephew, Hull, England) in aqueous media in vitro. The silicone gel sheet was also applied on the excised skin surface to examine the possible distribution of silicone-related compounds into the skin in vitro. Silicone-related compounds were measured as silicon by an inductively coupled plasma-atomic emission spectrophotometer. When a piece of silicone gel sheet was placed in phosphate buffer solution (pH 3-9) at 37 degrees C for 7 days, the concentration of silicon in the medium increased with time, depending on the pH of the medium. This indicates that the released silicone-related compounds are water-soluble. When Cica-Care was applied on the surface of excised rat skin, human axilla skin and hypertrophic scars under hydrated conditions in vitro, silicon was detected in all skin samples. Greater distribution was observed in rat skin than in human axilla skin and hypertrophic scars. The release of silicone-related compounds from a silicone gel sheet (Cica-Care) and their distribution into the skin were demonstrated in vitro. Silicone-related compounds distributed into the skin may have pharmacological effects on the skin. Further investigation will be necessary to investigate in detail the action of silicone-related compounds on the proliferation of fibroblasts and excessive production of collagen.

Fast scan control for deflection type mass spectrometers

NASA Technical Reports Server (NTRS)

Yeager, P. R.; Gaetano, G.; Hughes, D. B. (Inventor)

1974-01-01

A high speed scan device is reported that allows most any scanning sector mass spectrometer to measure preselected gases at a very high sampling rate. The device generates a rapidly changing staircase output which is applied to the accelerator of the spectrometer and it also generates defocusing pulses that are applied to one of the deflecting plates of the spectrometer which when shorted to ground deflects the ion beam away from the collector. A defocusing pulse occurs each time there is a change in the staircase output.

Semiconducting compounds and devices incorporating same

DOEpatents

Marks, Tobin J; Facchetti, Antonio; Boudreault, Pierre-Luc; Miyauchi, Hiroyuki

2014-06-17

Disclosed are molecular and polymeric compounds having desirable properties as semiconducting materials. Such compounds can exhibit desirable electronic properties and possess processing advantages including solution-processability and/or good stability. Organic transistor and photovoltaic devices incorporating the present compounds as the active layer exhibit good device performance.

Semiconducting compounds and devices incorporating same

DOEpatents

Marks, Tobin J.; Facchetti, Antonio; Boudreault, Pierre-Luc; Miyauchi, Hiroyuki

2016-01-19

Disclosed are molecular and polymeric compounds having desirable properties as semiconducting materials. Such compounds can exhibit desirable electronic properties and possess processing advantages including solution-processability and/or good stability. Organic transistor and photovoltaic devices incorporating the present compounds as the active layer exhibit good device performance.

Practices of pharmacies that compound extemporaneous formulations.

PubMed

Treadway, Angela K; Craddock, Deeatra; Leff, Richard

2007-07-01

A survey was conducted to characterize the standard of practice for extemporaneous pharmaceutical compounding within community and institutional pharmacies. Extemporaneous compounding practices vary among pharmacies. Because of this, the survey inquired specifically about a single pharmaceutical product (caffeine citrate 20 mg/mL) to minimize variability among respondents. Survey questions were written to identify compounding practice variations with (1) policies and procedures, (2) process validation, (3) personnel education, training, and evaluation, (4) expiration dating, (5) storage and handling of compounded prescriptions within the pharmacy, (6) labeling, (7) facilities and equipment, (8) end-product evaluation, (9) handling of sterile products outside of the pharmacy, (10) aseptic technique and product preparation, and (11) documentation. A total of 522 surveys were mailed; 117 completed surveys were returned and included in the analyses. Over half of the pharmacies surveyed were large institutional pharmacies with daily prescriptions exceeding 300. Almost 71% of pharmacies reported having policies and procedures for compounding and providing compounding training for staff. Almost one third of the pharmacies that responded did not have compounding policies and procedures and did not provide staff training. For those pharmacies that provided training, the methods used were diverse (e.g., lectures and videotapes, external certificate programs). Formulations used to compound caffeine appeared to be diverse as evidenced by the varied addition of inactive ingredients. A survey of compounding pharmacies found variability in overall compounding practices and training and in practices specifically related to compounding preparations of caffeine citrate.

Literature-based compound profiling: application to toxicogenomics.

PubMed

Frijters, Raoul; Verhoeven, Stefan; Alkema, Wynand; van Schaik, René; Polman, Jan

2007-11-01

To reduce continuously increasing costs in drug development, adverse effects of drugs need to be detected as early as possible in the process. In recent years, compound-induced gene expression profiling methodologies have been developed to assess compound toxicity, including Gene Ontology term and pathway over-representation analyses. The objective of this study was to introduce an additional approach, in which literature information is used for compound profiling to evaluate compound toxicity and mode of toxicity. Gene annotations were built by text mining in Medline abstracts for retrieval of co-publications between genes, pathology terms, biological processes and pathways. This literature information was used to generate compound-specific keyword fingerprints, representing over-represented keywords calculated in a set of regulated genes after compound administration. To see whether keyword fingerprints can be used for assessment of compound toxicity, we analyzed microarray data sets of rat liver treated with 11 hepatotoxicants. Analysis of keyword fingerprints of two genotoxic carcinogens, two nongenotoxic carcinogens, two peroxisome proliferators and two randomly generated gene sets, showed that each compound produced a specific keyword fingerprint that correlated with the experimentally observed histopathological events induced by the individual compounds. By contrast, the random sets produced a flat aspecific keyword profile, indicating that the fingerprints induced by the compounds reflect biological events rather than random noise. A more detailed analysis of the keyword profiles of diethylhexylphthalate, dimethylnitrosamine and methapyrilene (MPy) showed that the differences in the keyword fingerprints of these three compounds are based upon known distinct modes of action. Visualization of MPy-linked keywords and MPy-induced genes in a literature network enabled us to construct a mode of toxicity proposal for MPy, which is in agreement with known effects

Prioritizing pesticide compounds for analytical methods development

USGS Publications Warehouse

Norman, Julia E.; Kuivila, Kathryn; Nowell, Lisa H.

2012-01-01

The U.S. Geological Survey (USGS) has a periodic need to re-evaluate pesticide compounds in terms of priorities for inclusion in monitoring and studies and, thus, must also assess the current analytical capabilities for pesticide detection. To meet this need, a strategy has been developed to prioritize pesticides and degradates for analytical methods development. Screening procedures were developed to separately prioritize pesticide compounds in water and sediment. The procedures evaluate pesticide compounds in existing USGS analytical methods for water and sediment and compounds for which recent agricultural-use information was available. Measured occurrence (detection frequency and concentrations) in water and sediment, predicted concentrations in water and predicted likelihood of occurrence in sediment, potential toxicity to aquatic life or humans, and priorities of other agencies or organizations, regulatory or otherwise, were considered. Several existing strategies for prioritizing chemicals for various purposes were reviewed, including those that identify and prioritize persistent, bioaccumulative, and toxic compounds, and those that determine candidates for future regulation of drinking-water contaminants. The systematic procedures developed and used in this study rely on concepts common to many previously established strategies. The evaluation of pesticide compounds resulted in the classification of compounds into three groups: Tier 1 for high priority compounds, Tier 2 for moderate priority compounds, and Tier 3 for low priority compounds. For water, a total of 247 pesticide compounds were classified as Tier 1 and, thus, are high priority for inclusion in analytical methods for monitoring and studies. Of these, about three-quarters are included in some USGS analytical method; however, many of these compounds are included on research methods that are expensive and for which there are few data on environmental samples. The remaining quarter of Tier 1

The Chemiluminescence of Organometallic Compounds

NASA Astrophysics Data System (ADS)

Tolstikov, Genrikh A.; Bulgakov, Ramil G.; Kazakov, Valeri P.

1985-11-01

Studies on the liquid-phase and gas-phase reactions of organometallic compounds accompanied by the emission of light are described systematically and discussed. The influence of the magnetic field on the chemiluminescence of Grignard reagents and the study of the electrochemiluminescence of solutions of organometallic compounds are examined. The ways leading to further development of the field of the chemiluminescence of organometallic compounds and certain possible applications of the phenomenon in the monitoring of industrial processes are discussed. The bibliography includes 80 references.

Microoptical compound lens

DOEpatents

Sweatt, William C.; Gill, David D.

2007-10-23

An apposition microoptical compound lens comprises a plurality of lenslets arrayed around a segment of a hollow, three-dimensional optical shell. The lenslets collect light from an object and focus the light rays onto the concentric, curved front surface of a coherent fiber bundle. The fiber bundle transports the light rays to a planar detector, forming a plurality of sub-images that can be reconstructed as a full image. The microoptical compound lens can have a small size (millimeters), wide field of view (up to 180.degree.), and adequate resolution for object recognition and tracking.

Antifouling Compounds from Marine Invertebrates.

PubMed

Qi, Shu-Hua; Ma, Xuan

2017-08-28

In this review, a comprehensive overview about the antifouling compounds from marine invertebrates is described. In total, more than 198 antifouling compounds have been obtained from marine invertebrates, specifically, sponges, gorgonian and soft corals.

Hydrodesulfurization catalysis by Chevrel phase compounds

DOEpatents

McCarty, Kevin F.; Schrader, Glenn L.

1985-12-24

A process is disclosed for the hydrodesulfurization of sulfur-containing hydrocarbon fuel with reduced ternary molybdenum sulfides, known as Chevrel phase compounds. Chevrel phase compounds of the general composition M.sub.x Mo.sub.6 S.sub.8, with M being Ho, Pb, Sn, Ag, In, Cu, Fe, Ni, or Co, were found to have hydrodesulfurization activities comparable to model unpromoted and cobalt-promoted MoS.sub.2 catalysts. The most active catalysts were the "large" cation compounds (Ho, Pb, Sn), and the least active catalysts were the "small" cation compounds (Cu, Fe, Ni, Co.).

Hydrodesulfurization catalyst by Chevrel phase compounds

DOEpatents

McCarty, K.F.; Schrader, G.L.

1985-05-20

A process is disclosed for the hydrodesulfurization of sulfur-containing hydrocarbon fuel with reduced ternary molybdenum sulfides, known as Chevrel phase compounds. Chevrel phase compounds of the general composition M/sub x/Mo/sub 6/S/sub 8/, with M being Ho, Pb, Sn, Ag, In, Cu, Fe, Ni, or Co, were found to have hydrodesulfurization activities comparable to model unpromoted and cobalt-promoted MoS/sub 2/ catalysts. The most active catalysts were the ''large'' cation compounds (Ho, Pb, Sn), and the least active catalysts were the ''small'' cation compounds (Cu, Fe, Ni, Co.).

Sulfur compounds in coal

NASA Technical Reports Server (NTRS)

Attar, A.; Corcoran, W. H.

1977-01-01

The literature on the chemical structure of the organic sulfur compounds (or functional groups) in coal is reviewed. Four methods were applied in the literature to study the sulfur compounds in coal: direct spectrometric and chemical analysis, depolymerization in drastic conditions, depolymerization in mild conditions, and studies on simulated coal. The data suggest that most of the organic sulfur in coal is in the form of thiophenic structures and aromatic and aliphatic sulfides. The relative abundance of the sulfur groups in bituminous coal is estimated as 50:30:20%, respectively. The ratio changes during processing and during the chemical analysis. The main effects are the transformation during processing of sulfides to the more stable thiophenic compounds and the elimination of hydrogen sulfide.

Learning-based 3D surface optimization from medical image reconstruction

NASA Astrophysics Data System (ADS)

Wei, Mingqiang; Wang, Jun; Guo, Xianglin; Wu, Huisi; Xie, Haoran; Wang, Fu Lee; Qin, Jing

2018-04-01

Mesh optimization has been studied from the graphical point of view: It often focuses on 3D surfaces obtained by optical and laser scanners. This is despite the fact that isosurfaced meshes of medical image reconstruction suffer from both staircases and noise: Isotropic filters lead to shape distortion, while anisotropic ones maintain pseudo-features. We present a data-driven method for automatically removing these medical artifacts while not introducing additional ones. We consider mesh optimization as a combination of vertex filtering and facet filtering in two stages: Offline training and runtime optimization. In specific, we first detect staircases based on the scanning direction of CT/MRI scanners, and design a staircase-sensitive Laplacian filter (vertex-based) to remove them; and then design a unilateral filtered facet normal descriptor (uFND) for measuring the geometry features around each facet of a given mesh, and learn the regression functions from a set of medical meshes and their high-resolution reference counterparts for mapping the uFNDs to the facet normals of the reference meshes (facet-based). At runtime, we first perform staircase-sensitive Laplacian filter on an input MC (Marching Cubes) mesh, and then filter the mesh facet normal field using the learned regression functions, and finally deform it to match the new normal field for obtaining a compact approximation of the high-resolution reference model. Tests show that our algorithm achieves higher quality results than previous approaches regarding surface smoothness and surface accuracy.

Environmental exposure to preformed nitroso compounds.

PubMed

Tricker, A R; Spiegelhalder, B; Preussmann, R

1989-01-01

In the human environment, nitrosatable amine precursors to N-nitroso compounds and nitrosating species such as nitrite and oxides of nitrogen are abundant. As a result, the formation of N-nitroso compounds and human exposure to these compounds show a rather complex pattern. The largest known human exposures to exogenous N-nitrosamines occur in the work place. This is particularly evident in the rubber and tyre manufacturing industry and in metal cutting and grinding shops. Nearly all industries which are concerned with the production and/or use of amines have a related nitrosamine problem. Outside the industrial environment, commodities such as cosmetics, pharmaceuticals, rubber and household products, which are either prepared from amines or contain high concentrations of amino compounds, may be subject to contamination by low concentrations of N-nitroso compounds. This contamination may result from the use of contaminated starting materials, in particular amines, or from the formation of N-nitroso compounds during manufacturing processes. A similar problem exists with agricultural chemicals. As our knowledge of the occurrence and formation of N-nitroso compounds in the environment increases, preventive measures can be introduced, particularly in manufacturing industries, to reduce the levels of human exposure to nitrosamines in the work place and to protect the consumer from nitrosamine exposure from household commodities.

Resistance to phenicol compounds following adaptation to quaternary ammonium compounds in Escherichia coli.

PubMed

Soumet, C; Fourreau, E; Legrandois, P; Maris, P

2012-07-06

Bacterial adaptation to quaternary ammonium compounds (QACs) is mainly documented for benzalkonium chloride (BC) and few data are available for other QACs. The aim of this study was to assess the effects of repeated exposure to different quaternary ammonium compounds (QACs) on the susceptibility and/or resistance of bacteria to other QACs and antibiotics. Escherichia coli strains (n=10) were adapted by daily exposure to increasingly sub-inhibitory concentrations of a QAC for 7 days. Three QACs were studied. Following adaptation, we found similar levels of reduction in susceptibility to QACs with a mean 3-fold increase in the minimum inhibitory concentration (MIC) compared to initial MIC values, whatever the QAC used during adaptation. No significant differences in antibiotic susceptibility were observed between the tested QACs. Antibiotic susceptibility was reduced from 3.5- to 7.5-fold for phenicol compounds, β lactams, and quinolones. Increased MIC was associated with a shift in phenotype from susceptible to resistant for phenicol compounds (florfenicol and chloramphenicol) in 90% of E. coli strains. Regardless of the QAC used for adaptation, exposure to gradually increasing concentrations of this type of disinfectant results in reduced susceptibility to QACs and antibiotics as well as cross-resistance to phenicol compounds in E. coli strains. Extensive use of QACs at sub-inhibitory concentrations may lead to the emergence of antibiotic-resistant bacteria and may represent a public health risk. Published by Elsevier B.V.

Antifouling Compounds from Marine Invertebrates

PubMed Central

Qi, Shu-Hua; Ma, Xuan

2017-01-01

In this review, a comprehensive overview about the antifouling compounds from marine invertebrates is described. In total, more than 198 antifouling compounds have been obtained from marine invertebrates, specifically, sponges, gorgonian and soft corals. PMID:28846623

Compound curvature laser window development

NASA Technical Reports Server (NTRS)

Verhoff, Vincent G.

1993-01-01

The NASA Lewis Research Center has developed and implemented a unique process for forming flawless compound curvature laser windows. These windows represent a major part of specialized, nonintrusive laser data acquisition systems used in a variety of compressor and turbine research test facilities. This report summarizes the main aspects of compound curvature laser window development. It is an overview of the methodology and the peculiarities associated with the formulation of these windows. Included in this discussion is new information regarding procedures for compound curvature laser window development.

Electromigration in Sn-Cu intermetallic compounds

NASA Astrophysics Data System (ADS)

Wei, C. C.; Chen, C. F.; Liu, P. C.; Chen, Chih

2009-01-01

As the shrinking in bump size continues, the effect of intermetallic compounds (IMCs) on electromigration becomes more pronounced. Electromigration in Sn-Cu intermetallic compounds was examined using edge displacement method. It was found that Cu6Sn5 compounds are more susceptible to electromigration than Cu3Sn compounds. The lower solidus temperature and higher resistivity of the Cu6Sn5 IMCs are responsible for its higher electromigration rate. Length-dependent electromigration behavior was found in the stripes of various lengths and the critical length was determined to be between 5 and 10 μm at 225 °C, which corresponded to a critical product between 2.5 and 5 A/cm. Furthermore, the Sn-Cu compounds were proven to have better electromigration resistance than eutectic SnAgCu solder.

Large Constituent Families Help Children Parse Compounds

ERIC Educational Resources Information Center

Krott, Andrea; Nicoladis, Elena

2005-01-01

The family size of the constituents of compound words, or the number of compounds sharing the constituents, has been shown to affect adults' access to compound words in the mental lexicon. The present study was designed to see if family size would affect children's segmentation of compounds. Twenty-five English-speaking children between 3;7 and…

Single-crystal growth of C u4(OH) 6BrF and universal behavior in quantum spin liquid candidates synthetic barlowite and herbertsmithite

NASA Astrophysics Data System (ADS)

Pasco, C. M.; Trump, B. A.; Tran, Thao T.; Kelly, Z. A.; Hoffmann, C.; Heinmaa, I.; Stern, R.; McQueen, T. M.

2018-04-01

Synthetic barlowite, C u4(OH) 6BrF , has emerged as a new quantum spin liquid (QSL) host, containing kagomé layers of S =1 /2 C u2 + ions separated by interlayer C u2 + ions. Similar to synthetic herbertsmithite, ZnC u3(OH) 6C l2 , it has been reported that Z n2 + substitution for the interlayer C u2 + induces a QSL ground state. Here we report a scalable synthesis of single crystals of C u4(OH) 6BrF . Through x-ray, neutron, and electron diffraction measurements coupled with magic angle spinning 19F and 1H NMR spectroscopy, we resolve the previously reported positional disorder of the interlayer C u2 + ions and find that the structure is best described in the orthorhombic space group, Cmcm, with lattice parameters a =6.665 (13 )Å ,b =11.521 (2 )Å ,c =9.256 (18 )Å , and an ordered arrangement of interlayer C u2 + ions. Infrared spectroscopy measurements of the O—H and F—H stretching frequencies demonstrate that the orthorhombic symmetry persists upon substitution of Z n2 + for C u2 + . Specific heat and magnetic susceptibility measurements of Zn-substituted barlowite, Z nxC u4 -x(OH) 6BrF , reveal striking similarities with the behavior of Z nxC u4 -x(OH) 6C l2 . These parallels imply universal behavior of copper kagomé lattices even in the presence of small symmetry-breaking distortions. Thus, synthetic barlowite demonstrates universality of the physics of synthetic C u2 + kagomé minerals and furthers the development of real QSL states.

One-Compound-Multi-Target: Combination Prospect of Natural Compounds with Thrombolytic Therapy in Acute Ischemic Stroke

PubMed Central

Chen, Han-Sen; Qi, Su-Hua; Shen, Jian-Gang

2017-01-01

Abstract: Tissue plasminogen activator (t-PA) is the only FDA-approved drug for acute ischemic stroke treatment, but its clinical use is limited due to the narrow therapeutic time window and severe adverse effects, including hemorrhagic transformation (HT) and neurotoxicity. One of the potential resolutions is to use adjunct therapies to reduce the side effects and extend t-PA's therapeutic time window. However, therapies modulating single target seem not to be satisfied, and a multi-target strategy is warranted to resolve such complex disease. Recently, large amount of efforts have been made to explore the active compounds from herbal supplements to treat ischemic stroke. Some natural compounds revealed both neuro- and blood-brain-barrier (BBB)-protective effects by concurrently targeting multiple cellular signaling pathways in cerebral ischemia-reperfusion injury. Thus, those compounds are potential to be one-drug-multi-target agents as combined therapy with t-PA for ischemic stroke. In this review article, we summarize current progress about molecular targets involving in t-PA-mediated HT and neurotoxicity in ischemic brain injury. Based on these targets, we select 23 promising compounds from currently available literature with the bioactivities simultaneously targeting several important molecular targets. We propose that those compounds merit further investigation as combined therapy with t-PA. Finally, we discuss the potential drawbacks of the natural compounds' studies and raise several important issues to be addressed in the future for the development of natural compound as an adjunct therapy. PMID:27334020

Miniature curved artificial compound eyes

PubMed Central

Floreano, Dario; Pericet-Camara, Ramon; Viollet, Stéphane; Ruffier, Franck; Brückner, Andreas; Leitel, Robert; Buss, Wolfgang; Menouni, Mohsine; Expert, Fabien; Juston, Raphaël; Dobrzynski, Michal Karol; L’Eplattenier, Geraud; Recktenwald, Fabian; Mallot, Hanspeter A.; Franceschini, Nicolas

2013-01-01

In most animal species, vision is mediated by compound eyes, which offer lower resolution than vertebrate single-lens eyes, but significantly larger fields of view with negligible distortion and spherical aberration, as well as high temporal resolution in a tiny package. Compound eyes are ideally suited for fast panoramic motion perception. Engineering a miniature artificial compound eye is challenging because it requires accurate alignment of photoreceptive and optical components on a curved surface. Here, we describe a unique design method for biomimetic compound eyes featuring a panoramic, undistorted field of view in a very thin package. The design consists of three planar layers of separately produced arrays, namely, a microlens array, a neuromorphic photodetector array, and a flexible printed circuit board that are stacked, cut, and curved to produce a mechanically flexible imager. Following this method, we have prototyped and characterized an artificial compound eye bearing a hemispherical field of view with embedded and programmable low-power signal processing, high temporal resolution, and local adaptation to illumination. The prototyped artificial compound eye possesses several characteristics similar to the eye of the fruit fly Drosophila and other arthropod species. This design method opens up additional vistas for a broad range of applications in which wide field motion detection is at a premium, such as collision-free navigation of terrestrial and aerospace vehicles, and for the experimental testing of insect vision theories. PMID:23690574

Cytotoxic Compounds from Brucea mollis

PubMed Central

Tung, Mai Hung Thanh; Đuc, Ho Viet; Huong, Tran Thu; Duong, Nguyen Thanh; Phuong, Do Thi; Thao, Do Thi; Tai, Bui Huu; Kim, Young Ho; Bach, Tran The; Cuong, Nguyen Manh

2013-01-01

Ten compounds, including soulameanone (1), isobruceine B (2), 9-methoxy-canthin-6-one (3), bruceolline F (4), niloticine (5), octatriacontan-1-ol (6), bombiprenone (7), α-tocopherol (8), inosine (9), and apigenin 7-O-β-D-glucopyranoside (10), were isolated from the leaves, stems, and roots of Brucea mollis Wall. ex Kurz. Their structures were determined using one-and two-dimensional NMR spectroscopy and mass spectrometry. All compounds were evaluated for their cytotoxic activity against KB (human carcinoma of the mouth), LU-1 (human lung adenocarcinoma), LNCaP (human prostate adeno-carcinoma), and HL-60 (human promyelocytic leukemia) cancer cell lines. Compound 2 showed significant cytotoxic activity against KB, LU-1, LNCaP, and HL-60 cancer cells with IC50 values of 0.39, 0.40, 0.34, and 0.23 μg/mL, respectively. In addition, compounds 3 and 5 showed significant cytotoxic activity against KB, LU-1, LNCaP, and HL-60 cancer cells with IC50 values around 1–4 μg/mL. Compounds 9-methoxycanthin-6-one (3) and niloticine (5) have been discovered for the first time from the Brucea genus. PMID:24106661

Thin films of mixed metal compounds

DOEpatents

Mickelsen, Reid A.; Chen, Wen S.

1985-01-01

A compositionally uniform thin film of a mixed metal compound is formed by simultaneously evaporating a first metal compound and a second metal compound from independent sources. The mean free path between the vapor particles is reduced by a gas and the mixed vapors are deposited uniformly. The invention finds particular utility in forming thin film heterojunction solar cells.

Compound formation and melting behavior in the AB compound and rare earth oxide systems

NASA Astrophysics Data System (ADS)

Huang, Z. K.; Yan, D. S.; Yen, T. S.; Tien, T. Y.

1990-03-01

Compound formation in the systems of the covalent compounds BeO, AlN, and SiC with R2O 3(rare earth oxides) is described. Tentative phase diagrams of the AlN sbnd Nd 2O 3 and AlN sbnd Eu 2O 3 systems are presented.

Four new compounds from Imperata cylindrica.

PubMed

Liu, Xuan; Zhang, Bin-Feng; Yang, Li; Chou, Gui-Xin; Wang, Zheng-Tao

2014-04-01

Four new compounds, impecylone (1), deacetylimpecyloside (2), seguinoside K 4-methylether (3) and impecylenolide (4), were isolated from Imperata cylindrica along with two known compounds, impecyloside (5) and seguinoside K (6). Their structures were elucidated mainly by spectroscopic analyses including 1D- and 2D-NMR techniques, and the absolute configuration of 1 was confirmed by X-ray diffraction analysis. In calcium assay, the result indicated that compounds 1, 2, 4 and 5 cannot obviously inhibit the calcium peak value compared with the negative control, and suggested that the four compounds could not have anti-inflammatory activity.

Metalloid compounds as drugs

PubMed Central

Sekhon, B. S.

2013-01-01

The six elements commonly known as metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. Metalloid containing compounds have been used as antiprotozoal drugs. Boron-based drugs, the benzoxaboroles have been exploited as potential treatments for neglected tropical diseases. Arsenic has been used as a medicinal agent and arsphenamine was the main drug used to treat syphilis. Arsenic trioxide has been approved for the treatment of acute promyelocytic leukemia. Pentavalent antimonials have been the recommended drug for visceral leishmaniasis and cutaneous leishmaniasis. Tellurium (IV) compounds may have important roles in thiol redox biological activity in the human body, and ammonium trichloro (dioxoethylene-O, O’-)tellurate (AS101) may be a promising agent for the treatment of Parkinson’s disease. Organosilicon compounds have been shown to be effective in vitro multidrug-resistance reverting agents. PMID:24019824

Use of Polyphenolic Compounds in Dermatologic Oncology

PubMed Central

Costa, Adilson; Bonner, Michael Yi

2017-01-01

Polyphenols are a widely used class of compounds in dermatology. While phenol itself, the most basic member of the phenol family, is chemically synthesized, most polyphenolic compounds are found in plants and form part of their defense mechanism against decomposition. Polyphenolic compounds, which include phenolic acids, flavonoids, stilbenes, and lignans, play an integral role in preventing the attack on plants by bacteria and fungi, as well as serving as cross-links in plant polymers. There is also mounting evidence that polyphenolic compounds play an important role in human health as well. One of the most important benefits, which puts them in the spotlight of current studies, is their antitumor profile. Some of these polyphenolic compounds have already presented promising results in either in vitro or in vivo studies for non-melanoma skin cancer and melanoma. These compounds act on several biomolecular pathways including cell division cycle arrest, autophagy, and apoptosis. Indeed, such natural compounds may be of potential for both preventive and therapeutic fields of cancer. This review evaluates the existing scientific literature in order to provide support for new research opportunities using polyphenolic compounds in oncodermatology. PMID:27164914

Enzymatic Decontamination of Environmental Organophosphorus Compounds

DTIC Science & Technology

2006-12-04

ABSTRACT (Maximum 200 words) The abstract is below since many authors do not follow the 200 word limit 14. SUBJECT TERMS organophosphorus compounds ...5404 Enzymatic decontamination of environmental organophosphorus compounds REPORT DOCUMENTATION PAGE 18. SECURITY CLASSIFICATION ON THIS PAGE...239-18 298-102 15. NUMBER OF PAGES 20. LIMITATION OF ABSTRACT UL - 4-Dec-2006 Enzymatic decontamination of environmental organophosphorus compounds

Compound cuing in free recall.

PubMed

Lohnas, Lynn J; Kahana, Michael J

2014-01-01

According to the retrieved context theory of episodic memory, the cue for recall of an item is a weighted sum of recently activated cognitive states, including previously recalled and studied items as well as their associations. We show that this theory predicts there should be compound cuing in free recall. Specifically, the temporal contiguity effect should be greater when the 2 most recently recalled items were studied in contiguous list positions. A meta-analysis of published free recall experiments demonstrates evidence for compound cuing in both conditional response probabilities and interresponse times. To help rule out a rehearsal-based account of these compound cuing effects, we conducted an experiment with immediate, delayed, and continual-distractor free recall conditions. Consistent with retrieved context theory but not with a rehearsal-based account, compound cuing was present in all conditions, and was not significantly influenced by the presence of interitem distractors.

Orodispersible Films for Compounding Pharmacies.

PubMed

Ferreira, Anderson O; Brandão, Marcos Antônio F; Raposo, Francisco José; Polonini, Hudson C; Raposo, Nádia Rezende Barbosa

2017-01-01

Orodispersible film can be defined as a solid pharmaceutical form intended for the delivery and rapid local or systemic release of active ingredients, consisting of a water-soluble polymer film that hydrates rapidly, adhering and dissolving immediately when placed on the tongue or in the oral cavity (oral, palatal, gingival, lingual, or sublingual), without the need for water administration or mastication. Due to its outstanding importance in cases of emergency, practicality of use by patients in transit, and high adherence, orodispersible film has evolved in popularity and success among consumers. It is a promising dosage form for compounding pharmacies, as simpler technologies are being developed to make the compound process easier and faster for the pharmacist. This article aims to explore some of the basics on orodispersible film and the main possible preparations to be developed in compounding pharmacies worldwide. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Compound cueing in free recall

PubMed Central

Lohnas, Lynn J.; Kahana, Michael J.

2013-01-01

According to the retrieved context theory of episodic memory, the cue for recall of an item is a weighted sum of recently activated cognitive states, including previously recalled and studied items as well as their associations. We show that this theory predicts there should be compound cueing in free recall. Specifically, the temporal contiguity effect should be greater when the two most recently recalled items were studied in contiguous list positions. A meta-analysis of published free recall experiments demonstrates evidence for compound cueing in both conditional response probabilities and inter-response times. To help rule out a rehearsal-based account of these compound cueing effects, we conducted an experiment with immediate, delayed and continual-distractor free recall conditions. Consistent with retrieved context theory but not with a rehearsal-based account, compound cueing was present in all conditions, and was not significantly influenced by the presence of interitem distractors. PMID:23957364

Biologically inspired artificial compound eyes.

PubMed

Jeong, Ki-Hun; Kim, Jaeyoun; Lee, Luke P

2006-04-28

This work presents the fabrication of biologically inspired artificial compound eyes. The artificial ommatidium, like that of an insect's compound eyes, consists of a refractive polymer microlens, a light-guiding polymer cone, and a self-aligned waveguide to collect light with a small angular acceptance. The ommatidia are omnidirectionally arranged along a hemispherical polymer dome such that they provide a wide field of view similar to that of a natural compound eye. The spherical configuration of the microlenses is accomplished by reconfigurable microtemplating, that is, polymer replication using the deformed elastomer membrane with microlens patterns. The formation of polymer waveguides self-aligned with microlenses is also realized by a self-writing process in a photosensitive polymer resin. The angular acceptance is directly measured by three-dimensional optical sectioning with a confocal microscope, and the detailed optical characteristics are studied in comparison with a natural compound eye.

Detection of chlorinated aromatic compounds

DOEpatents

Ekechukwu, Amy A.

1996-01-01

A method for making a composition for measuring the concentration of chloated aromatic compounds in aqueous fluids, and an optical probe for use with the method. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis.

Elastomer Compound Developed for High Wear Applications

NASA Technical Reports Server (NTRS)

Crawford, D.; Feuer, H.; Flanagan, D.; Rodriguez, G.; Teets, A.; Touchet, P.

1993-01-01

The U.S. Army is currently spending 300 million dollars per year replacing rubber track pads. An experimental rubber compound has been developed which exhibits 2 to 3 times greater service life than standard production pad compounds. To improve the service life of the tank track pads various aspects of rubber chemistry were explored including polymer, curing and reinforcing systems. Compounds that exhibited superior physical properties based on laboratory data were then fabricated into tank pads and field tested. This paper will discuss the compounding studies, laboratory data and field testing that led to the high wear elastomer compound.

Carbonyl compounds generated from electronic cigarettes.

PubMed

Bekki, Kanae; Uchiyama, Shigehisa; Ohta, Kazushi; Inaba, Yohei; Nakagome, Hideki; Kunugita, Naoki

2014-10-28

Electronic cigarettes (e-cigarettes) are advertised as being safer than tobacco cigarettes products as the chemical compounds inhaled from e-cigarettes are believed to be fewer and less toxic than those from tobacco cigarettes. Therefore, continuous careful monitoring and risk management of e-cigarettes should be implemented, with the aim of protecting and promoting public health worldwide. Moreover, basic scientific data are required for the regulation of e-cigarette. To date, there have been reports of many hazardous chemical compounds generated from e-cigarettes, particularly carbonyl compounds such as formaldehyde, acetaldehyde, acrolein, and glyoxal, which are often found in e-cigarette aerosols. These carbonyl compounds are incidentally generated by the oxidation of e-liquid (liquid in e-cigarette; glycerol and glycols) when the liquid comes in contact with the heated nichrome wire. The compositions and concentrations of these compounds vary depending on the type of e-liquid and the battery voltage. In some cases, extremely high concentrations of these carbonyl compounds are generated, and may contribute to various health effects. Suppliers, risk management organizations, and users of e-cigarettes should be aware of this phenomenon.

Applying Quality by Design Concepts to Pharmacy Compounding.

PubMed

Timko, Robert J

2015-01-01

Compounding of medications is an important part of the practice of the pharmacy profession. Because compounded medications do not have U.S. Food and Drug Administration approval, a pharmacist has the responsibility to ensure that compounded medications are of suitable quality, safety, and efficacy. The Federal Government and numerous states have updated their laws and regulations regarding pharmacy compounding as a result of recent quality issues. Compounding pharmacists are expected to follow good preparation prodecures in their compounding practices in much the same way pharmaceutical manufacturers are required to follow Current Good Manufacturing Procedures as detailed in the United States Code of Federal Regulations. Application of Quality by Design concepts to the preparation process for a compounded medication can help in understanding the potential pitfalls and the means to mitigate their impact. The goal is to build quality into the compounding process to ensure that the resultant compounded prescription meets the human or animal patients' requirements.

False HDAC Inhibition by Aurone Compound.

PubMed

Itoh, Yukihiro; Suzuki, Miki; Matsui, Taiji; Ota, Yosuke; Hui, Zi; Tsubaki, Kazunori; Suzuki, Takayoshi

2016-01-01

Fluorescence assays are useful tools for estimating enzymatic activity. Their simplicity and manageability make them suitable for screening enzyme inhibitors in drug discovery studies. However, researchers need to pay attention to compounds that show auto-fluorescence and quench fluorescence, because such compounds lower the accuracy of the fluorescence assay systems by producing false-positive or negative results. In this study, we found that aurone compound 7, which has been reported as a histone deacetylase (HDAC) inhibitor, gave false-positive results. Although compound 7 was identified by an in vitro HDAC fluorescence assay, it did not show HDAC inhibitory activity in a cell-based assay, leading us to suspect its in vitro HDAC inhibitory activity. As a result of verification experiments, we found that compound 7 interferes with the HDAC fluorescence assay by quenching the HDAC fluorescence signal. Our findings underscore the faults of fluorescence assays and call attention to careless interpretation.

METHOD OF REDUCING PLUTONIUM COMPOUNDS

DOEpatents

Johns, I.B.

1958-06-01

A method is described for reducing plutonium compounds in aqueous solution from a higher to a lower valence state. This reduction of valence is achieved by treating the aqueous solution of higher valence plutonium compounds with hydrogen in contact with an activated platinum catalyst.

Perfluorinated Compounds

EPA Science Inventory

Perfluorinated compounds such as the perfluoroalkyl acids (PFAAs) and their derivatives are important man-made chemicals that have wide consumer and industrial applications. They are relatively contemporary chemicals, being in use only since the 1950s, and until recently, have be...

Polishing compound for plastic surfaces

DOEpatents

Stowell, Michael S.

1995-01-01

A polishing compound for plastic surfaces. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains fine particles silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS.TM., LEXAN.TM., LUCITE.TM., polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired.

Diazo compounds in the chemistry of fullerenes

NASA Astrophysics Data System (ADS)

Tuktarov, Airat R.; Dzhemilev, Usein M.

2010-09-01

Experimental and theoretical data on the reactions of different diazo compounds (diazomethane, its derivatives, cyclic diazo compounds and diazocarbonyl compounds) with fullerenes are summarized. The structures and stereochemistry of cycloadducts formed in these reactions are considered.

Blue Photoluminescence From Silacyclobutene Compounds

NASA Astrophysics Data System (ADS)

Pernisz, Udo

1999-04-01

Organosilicon compounds in which the Si atom is bound to an aromatic moiety such as a phenyl group, exhibit strong blue photoluminescence when excited with UV light (for example at a wavelength of 337 nm). This phenomenon was investigated quantitatively at room temperature and at the temperature of liquid nitrogen (78 K) by measuring the emission and excitation spectra of the total luminescence, and of the phosphorescence, for a silacyclobutene compound in which two phenyl groups are joined across the C=C double bond of the ring. The effect of a series of organic substituents on the Si atom was investigated as well as the time dependence of the phosphorescence intensity decay for this class of materials. A tentative model of the energy levels in this compound is proposed. The observation of visible blue emission -- in contrast to photoluminescence in the UV from the aromatic groups -- is explained by the Si-C bond lowering the energy of the molecular orbitals, an effect that is currently under study for a range of Si-containing compounds. Synthesis of the silacyclobutene compounds was performed at the laboratory of Prof. N. Auner, now at J.W. Goethe Universität, Frankfurt, Germany. His contributions, and those of his collaborators, to the work reported here are gratefully acknowledged.

Extraterrestrial Organic Compounds in Meteorites

NASA Technical Reports Server (NTRS)

Botta, Oliver; Bada, Jeffrey L.; Meyer, Michael (Technical Monitor)

2003-01-01

Many organic compounds or their precursors found in meteorites originated in the interstellar or circumstellar medium and were later incorporated into planetesimals during the formation of the solar system. There they either survived intact or underwent further processing to synthesize secondary products on the meteorite parent body. The most distinct feature of CI and CM carbonaceous chondrites, two types of stony meteorites, is their high carbon content (up to 3% of weight), either in the form of carbonates or of organic compounds. The bulk of the organic carbon consists of an insoluble macromolecular material with a complex structure. Also present is a soluble organic fraction, which has been analyzed by several separation and analytical procedures. Low detection limits can be achieved by derivatization of the organic molecules with reagents that allow for analysis by gas chromatography/mass spectroscopy and high performance liquid chromatography. The CM meteorite Murchison has been found to contain more than 70 extraterrestrial amino acids and several other classes of compounds including carboxylic acids, hydroxy carboxylic acids, sulphonic and phosphonic acids, aliphatic, aromatic and polar hydrocarbons, fullerenes, heterocycles as well as carbonyl compounds, alcohols, amines and amides. The organic matter was found to be enriched in deuterium, and distinct organic compounds show isotopic enrichments of carbon and nitrogen relative to terrestrial matter.

PRELIMINARY STUDIES ON THE BEHAVIOURAL EFFECTS OF THE METHANOL EXTRACT OF LEONOTIS NEPETIFOLIA LINN STEM IN MICE

PubMed Central

Ayanwuyi, Lydia O.; Kwanashie, Helen O.; Hussaini, Isa M.; Yaro, Abdullahi H.

2016-01-01

Background: Leonotis nepetifolia Linn (Lamiaceae) is used in traditional medicine for its calming (tranquilizing) effects. The aim of this study was to determine whether there is any scientific justification for this use. To achieve this purpose, we investigated the behavioural effects of the methanol extract of Leonotis nepetifolia stem (37.5, 75 and 150 mg/kg) in mice. Methods: Acute toxicity studies were carried out on the methanol stem extract of Leonotis nepetifolia to determine the LD50. The behavioural tests employed were diazepam-induced sleep onset and duration, hole board assay for exploratory activity, mouse beam walk assay for motor coordination, and the staircase test for the detection of anxiolytic compounds. Preliminary phytochemical screening was also carried out on the extract. Results: The intraperitoneal LD50 value was found to be 3.8 g/kg. The results showed that the extract significantly prolonged the duration of diazepam-induced sleep at the highest dose (150 mg/kg). There was no observable effect on exploratory activity and motor coordination at the doses tested (37.5, 75 and 150 mg/kg). The extract, however, at 150 mg/kg elicited a significant decrease in the number of rearings in the staircase test, an effect also observed in the group of mice injected with an anxiolytic dose of diazepam. The preliminary phytochemical screening revealed the presence of alkaloids, saponins, glycosides and triterpenoids. Conclusion: The results obtained suggest that the crude methanol extract of Leonotis nepetifolia stem possesses some biologically active constituents with potential anxiolytic activity and thus may justify its traditional use as a tranquilizer. PMID:28852715

Thiophenic Sulfur Compounds Released During Coal Pyrolysis

PubMed Central

Xing, Mengwen; Kong, Jiao; Dong, Jie; Jiao, Haili; Li, Fan

2013-01-01

Abstract Thiophenic sulfur compounds are released during coal gasification, carbonization, and combustion. Previous studies indicate that thiophenic sulfur compounds degrade very slowly in the environment, and are more carcinogenic than polycyclic aromatic hydrocarbons and nitrogenous compounds. Therefore, it is very important to study the principle of thiophenic sulfur compounds during coal conversion, in order to control their emission and promote clean coal utilization. To realize this goal and understand the formation mechanism of thiophenic sulfur compounds, this study focused on the release behavior of thiophenic sulfur compounds during coal pyrolysis, which is an important phase for all coal thermal conversion processes. The pyrolyzer (CDS-5250) and gas chromatography–mass spectrometry (Focus GC-DSQII) were used to analyze thiophenic sulfur compounds in situ. Several coals with different coal ranks and sulfur contents were chosen as experimental samples, and thiophenic sulfur compounds of the gas produced during pyrolysis under different temperatures and heating rates were investigated. Levels of benzothiophene and dibenzothiophene were obtained during pyrolysis at temperatures ranging from 200°C to 1300°C, and heating rates ranging from 6°C/ms to 14°C/ms and 6°C/s to 14°C/s. Moreover, the relationship between the total amount of benzothiophene and dibenzothiophene released during coal pyrolysis and the organic sulfur content in coal was also discussed. This study is beneficial for understanding the formation and control of thiophenic sulfur compounds, since it provides a series of significant results that show the impact that operation conditions and organic sulfur content in coal have on the amount and species of thiophenic sulfur compounds produced during coal pyrolysis. PMID:23781126

X-ray targeted bond or compound destruction

DOEpatents

Pravica, Sr., Michael G.

2016-11-01

This document provides methods, systems, and devices for inducing a decomposition reaction by directing x-rays towards a location including a particular compound. The x-rays can have an irradiation energy that corresponds to a bond distance of a bond in the particular compound in order to break that bond and induce a decomposition of that particular compound. In some cases, the particular compound is a hazardous substance or part of a hazardous substance. In some cases, the particular compound is delivered to a desired location in an organism and x-rays induce a decomposition reaction that creates a therapeutic substance (e.g., a toxin that kills cancer cells) in the location of the organism. In some cases, the particular compound decomposes to produce a reactant in a reactor apparatus (e.g., fuel cell or semiconductor fabricator).

Detection of chlorinated aromatic compounds

DOEpatents

Ekechukwu, A.A.

1996-02-06

A method for making a composition for measuring the concentration of chlorinated aromatic compounds in aqueous fluids, and an optical probe for use with the method are disclosed. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis. 5 figs.

Quality Assessment of Compounded 17-hydroxyprogesterone Caproate

PubMed Central

Chang, Justine; Zhao, Yang; Zhao, WenChen; Venkataramanan, Raman; Caritis, Steve N.

2013-01-01

Objective To evaluate the quality of compounded 17-hydroxyprogesterone caproate (17-OHPC) Study Design Compounded 17-OHPC was obtained from 15 compounding pharmacies throughout the U.S. and analyzed for potency, impurities, sterility, and pyrogen status. Results Eighteen samples were supplied by 15 compounding pharmacies. The concentration of 17-OHPC in all samples was within the specification limits and all tested samples passed sterility and pyrogen testing. Only 1 of 18 samples was out of specification limits for impurities. Conclusion Compounded 17-OHPC obtained from 15 pharmacies throughout the U.S. did not raise safety concerns when assessed for potency, sterility, pyrogen status or impurities. PMID:24200163

Identification of compound-protein interactions through the analysis of gene ontology, KEGG enrichment for proteins and molecular fragments of compounds.

PubMed

Chen, Lei; Zhang, Yu-Hang; Zheng, Mingyue; Huang, Tao; Cai, Yu-Dong

2016-12-01

Compound-protein interactions play important roles in every cell via the recognition and regulation of specific functional proteins. The correct identification of compound-protein interactions can lead to a good comprehension of this complicated system and provide useful input for the investigation of various attributes of compounds and proteins. In this study, we attempted to understand this system by extracting properties from both proteins and compounds, in which proteins were represented by gene ontology and KEGG pathway enrichment scores and compounds were represented by molecular fragments. Advanced feature selection methods, including minimum redundancy maximum relevance, incremental feature selection, and the basic machine learning algorithm random forest, were used to analyze these properties and extract core factors for the determination of actual compound-protein interactions. Compound-protein interactions reported in The Binding Databases were used as positive samples. To improve the reliability of the results, the analytic procedure was executed five times using different negative samples. Simultaneously, five optimal prediction methods based on a random forest and yielding maximum MCCs of approximately 77.55 % were constructed and may be useful tools for the prediction of compound-protein interactions. This work provides new clues to understanding the system of compound-protein interactions by analyzing extracted core features. Our results indicate that compound-protein interactions are related to biological processes involving immune, developmental and hormone-associated pathways.

Should we consider steps with variable height for a safer stair negotiation in older adults?

PubMed

Kunzler, Marcos R; da Rocha, Emmanuel S; Dos Santos, Christielen S; Ceccon, Fernando G; Priario, Liver A; Carpes, Felipe P

2018-01-01

Effects of exercise on foot clearances are important. In older adults variations in foot clearances during walking may lead to a fall, but there is a lack of information concerning stair negotiation in older adults. Whether a condition of post exercise changes foot clearances between steps of a staircase in older adults still unknown. To determine differences in clearances when older adults negotiate different steps of a staircase before and after a session of aerobic exercise. Kinematics data from 30 older adults were acquired and the toe and heel clearances were determined for each step. Clearances were compared between the steps. Smaller clearances were found at the highest step during ascending and descending, which was not changed by exercise. Smaller clearances suggest higher risk of tripping at the top of the staircase, regardless of exercise. A smaller step at the top of a short flight of stairs could reduce chances of tripping in older adults. It suggests that steps with variable height could make stair negotiation safer in older adults. This hypothesis should be tested in further studies.

Bilingual Reading of Compound Words

ERIC Educational Resources Information Center

Ko, In Yeong; Wang, Min; Kim, Say Young

2011-01-01

The present study investigated whether bilingual readers activate constituents of compound words in one language while processing compound words in the other language via decomposition. Two experiments using a lexical decision task were conducted with adult Korean-English bilingual readers. In Experiment 1, the lexical decision of real English…

Method for halogenating or radiohalogenating a chemical compound

DOEpatents

Kabalka, George W.

2006-05-09

A method for obtaining a halogenated organic compound, whereby an organotrifluoroborate compound is reacted with a halide ion in the presence of an oxidizing agent to produce the corresponding halogenated organic compound. The method may be used for producing radiohalogenated organic compounds.

Peanut flavor compounds from amino acid precursors

USDA-ARS?s Scientific Manuscript database

Investigations to determine the chemical compounds responsible for peanut flavor have traditionally depended on the analysis of volatile compounds. The more recent field of the study of metabolomics provides new tools and approaches for the determination of chemical compounds that are lost, created...

Consultation for Human, Veterinary, and Compounded Medications.

PubMed

Moghadam, Gabriella; Forsythe, Lauren Eichstadt

2017-01-01

Providing consultation on medications is a daily responsibility for pharmacists. However, counseling components for veterinary or compounded medications can differ from those for manufactured medications for humans. This article lists the content that should be provided during consultation, describes differences between counseling for human and veterinary patients, and provides references that can be used. Because many veterinary medications are compounded, this article also provides information that should accompany compounded preparations. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Polishing compound for plastic surfaces

DOEpatents

Stowell, M.S.

1993-01-01

A polishing compound for plastic surfaces is disclosed. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains colloidal silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS{sup TM}, LEXAN{sup TM}, LUCITE{sup TM}, polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired.

Polishing compound for plastic surfaces

DOEpatents

Stowell, M.S.

1995-08-22

A polishing compound for plastic surfaces is disclosed. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains fine particles silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS{trademark}, LEXAN{trademark}, LUCITE{trademark}, polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired. 5 figs.

Chemistry of peroxide compounds

NASA Technical Reports Server (NTRS)

Volnov, I. I.

1981-01-01

The history of Soviet research from 1866 to 1967 on peroxide compounds is reviewed. This research dealt mainly with peroxide kinetics, reactivity and characteristics, peroxide production processes, and more recently with superoxides and ozonides and emphasis on the higher oxides of group 1 and 2 elements. Solid state fluidized bed synthesis and production of high purity products based on the relative solubilities of the initial, intermediate, and final compounds and elements in liquid ammonia are discussed.

Pharmaceutical compounding or pharmaceutical manufacturing? A regulatory perspective.

PubMed

Timko, Robert J; Crooker, Philip E M

2014-01-01

At one time, nearly all prescriptions were compounded preparations. There is an ongoing demand for compounded prescription medications because manufacturers cannot fulfill the needs of all individual patients. Compounding pharmacies are a long standing yet less frequently discussed element in the complex matrix of prescription drug manufacturing, distribution, and patient use. The drug shortage situation for many necessary and life-saving drug products is a complicating factor that has led to the numerous quality issues that currently plague large-scale compounding pharmacies. The states are the primary regulator of pharmacies, including community drug stores, large chains, and specialty pharmacies. Pharmacies making and distributing drugs in a way that is outside the bounds of traditional pharmacy compounding are of great concern to the U.S. Food and Drug Administration. The U.S. Congress has recently passed the Drug Quality and Security Act. This legislation establishes a clear boundary between traditional compounders and compounding manufacturers. It clarifies a national, uniform set of rules for compounding manufacturers while preserving the states' primary role in traditional pharmacy regulation. It clarifies the U.S. Food and Drug Administration's authority over the compounding of human drugs while requiring the Agency to engage and coordinate with states to ensure the safety of compounded drugs.

Compound management beyond efficiency.

PubMed

Burr, Ian; Winchester, Toby; Keighley, Wilma; Sewing, Andreas

2009-06-01

Codeveloping alongside chemistry and in vitro screening, compound management was one of the first areas in research recognizing the need for efficient processes and workflows. Material management groups have centralized, automated, miniaturized and, importantly, found out what not to do with compounds. While driving down cost and improving quality in storage and processing, researchers still face the challenge of interfacing optimally with changing business processes, in screening groups, and with external vendors and focusing on biologicals in many companies. Here we review our strategy to provide a seamless link between compound acquisition and screening operations and the impact of material management on quality of the downstream processes. Although this is driven in part by new technologies and improved quality control within material management, redefining team structures and roles also drives job satisfaction and motivation in our teams with a subsequent positive impact on cycle times and customer feedback.

Gallium-containing anticancer compounds.

PubMed

Chitambar, Christopher R

2012-06-01

There is an ever pressing need to develop new drugs for the treatment of cancer. Gallium nitrate, a group IIIa metal salt, inhibits the proliferation of tumor cells in vitro and in vivo and has shown activity against non-Hodgkin's lymphoma and bladder cancer in clinical trials. Gallium can function as an iron mimetic and perturb iron-dependent proliferation and other iron-related processes in tumor cells. Gallium nitrate lacks crossresistance with conventional chemotherapeutic drugs and is not myelosuppressive; it can be used when other drugs have failed or when the blood count is low. Given the therapeutic potential of gallium, newer generations of gallium compounds are now in various phases of preclinical and clinical development. These compounds hold the promise of greater anti-tumor activity against a broader spectrum of cancers. The development of gallium compounds for cancer treatment and their mechanisms of action will be discussed.

Anti-Amyloidogenic Properties of Some Phenolic Compounds

PubMed Central

Porzoor, Afsaneh; Alford, Benjamin; Hügel, Helmut M.; Grando, Danilla; Caine, Joanne; Macreadie, Ian

2015-01-01

A family of 21 polyphenolic compounds consisting of those found naturally in danshen and their analogues were synthesized and subsequently screened for their anti-amyloidogenic activity against the amyloid beta peptide (Aβ42) of Alzheimer’s disease. After 24 h incubation with Aβ42, five compounds reduced thioflavin T (ThT) fluorescence, indicative of their anti-amyloidogenic propensity (p < 0.001). TEM and immunoblotting analysis also showed that selected compounds were capable of hindering fibril formation even after prolonged incubations. These compounds were also capable of rescuing the yeast cells from toxic changes induced by the chemically synthesized Aβ42. In a second assay, a Saccharomyces cerevisiae AHP1 deletant strain transformed with GFP fused to Aβ42 was treated with these compounds and analyzed by flow cytometry. There was a significant reduction in the green fluorescence intensity associated with 14 compounds. We interpret this result to mean that the compounds had an anti-amyloid-aggregation propensity in the yeast and GFP-Aβ42 was removed by proteolysis. The position and not the number of hydroxyl groups on the aromatic ring was found to be the most important determinant for the anti-amyloidogenic properties. PMID:25898401

Morphological Dynamics in Compound Processing

ERIC Educational Resources Information Center

Kuperman, Victor; Bertram, Raymond; Baayen, R. Harald

2008-01-01

This paper explores the time-course of morphological processing of trimorphemic Finnish compounds. We find evidence for the parallel access to full-forms and morphological constituents diagnosed by the early effects of compound frequency, as well as early effects of left constituent frequency and family size. We also observe an interaction between…

Drug-likeness analysis of traditional Chinese medicines: 2. Characterization of scaffold architectures for drug-like compounds, non-drug-like compounds, and natural compounds from traditional Chinese medicines.

PubMed

Tian, Sheng; Li, Youyong; Wang, Junmei; Xu, Xiaojie; Xu, Lei; Wang, Xiaohong; Chen, Lei; Hou, Tingjun

2013-01-21

In order to better understand the structural features of natural compounds from traditional Chinese medicines, the scaffold architectures of drug-like compounds in MACCS-II Drug Data Report (MDDR), non-drug-like compounds in Available Chemical Directory (ACD), and natural compounds in Traditional Chinese Medicine Compound Database (TCMCD) were explored and compared. First, the different scaffolds were extracted from ACD, MDDR and TCMCD by using three scaffold representations, including Murcko frameworks, Scaffold Tree, and ring systems with different complexity and side chains. Then, by examining the accumulative frequency of the scaffolds in each dataset, we observed that the Level 1 scaffolds of the Scaffold Tree offer advantages over the other scaffold architectures to represent the scaffold diversity of the compound libraries. By comparing the similarity of the scaffold architectures presented in MDDR, ACD and TCMCD, structural overlaps were observed not only between MDDR and TCMCD but also between MDDR and ACD. Finally, Tree Maps were used to cluster the Level 1 scaffolds of the Scaffold Tree and visualize the scaffold space of the three datasets. The analysis of the scaffold architectures of MDDR, ACD and TCMCD shows that, on average, drug-like molecules in MDDR have the highest diversity while natural compounds in TCMCD have the highest complexity. According to the Tree Maps, it can be observed that the Level 1 scaffolds present in MDDR have higher diversity than those presented in TCMCD and ACD. However, some representative scaffolds in MDDR with high frequency show structural similarities to those in TCMCD and ACD, suggesting that some scaffolds in TCMCD and ACD may be potentially drug-like fragments for fragment-based and de novo drug design.

Using Deep Learning for Compound Selectivity Prediction.

PubMed

Zhang, Ruisheng; Li, Juan; Lu, Jingjing; Hu, Rongjing; Yuan, Yongna; Zhao, Zhili

2016-01-01

Compound selectivity prediction plays an important role in identifying potential compounds that bind to the target of interest with high affinity. However, there is still short of efficient and accurate computational approaches to analyze and predict compound selectivity. In this paper, we propose two methods to improve the compound selectivity prediction. We employ an improved multitask learning method in Neural Networks (NNs), which not only incorporates both activity and selectivity for other targets, but also uses a probabilistic classifier with a logistic regression. We further improve the compound selectivity prediction by using the multitask learning method in Deep Belief Networks (DBNs) which can build a distributed representation model and improve the generalization of the shared tasks. In addition, we assign different weights to the auxiliary tasks that are related to the primary selectivity prediction task. In contrast to other related work, our methods greatly improve the accuracy of the compound selectivity prediction, in particular, using the multitask learning in DBNs with modified weights obtains the best performance.

Child-safety Containers/Devices and Compounding.

PubMed

Allen, Loyd V

2017-01-01

The U.S. Consumer Product Safety Commission has been around since it was created in 1972 through the Consumer Product Safety Act. Its purpose is to protect "against unreasonable risks of injuries associated with consumer products." Manufactured drugs must meet the standards unless specifically exempted. Dispensing and compounding pharmacists must also meet the standards. Due to a smaller market size, compliant products to meet the U.S. Consumer Product Safety Commission's standards to aid compounding pharmacists have been slow in coming. However, now there are numerous different products, some introduced recently, which make it easier for compounding pharmacists to comply with the standards. The new technologies are innovative and serve a great need. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Magnesium compounds

USGS Publications Warehouse

Kramer, D.A.

2007-01-01

Seawater and natural brines accounted for about 52 percent of U.S. magnesium compounds production in 2006. Dead-burned magnesia was produced by Martin Marietta Magnesia Specialties from well brines in Michigan. Caustic-calcined magnesia was recovered from sea-water by Premier Chemicals in Florida; from well brines in Michigan by Martin Marietta and Rohm and Haas; and from magnesite in Nevada by Premier Chemicals. Intrepid Potash-Wendover and Great Salt Lake Minerals recovered magnesium chloride brines from the Great Salt Lake in Utah. Magnesium hydroxide was produced from brucite by Applied Chemical Magnesias in Texas, from seawater by SPI Pharma in Delaware and Premier Chemicals in Florida, and by Martin Marietta and Rohm and Haas from their operations mentioned above. About 59 percent of the magnesium compounds consumed in the United States was used for refractories that are used mainly to line steelmaking furnaces. The remaining 41 percent was consumed in agricultural, chemical, construction, environmental and industrial applications.

Compound Nouns and Category Structure in Young Children.

ERIC Educational Resources Information Center

Clark, Eve V.; And Others

1985-01-01

In two experiments 96 children and eight adults were tested for comprehension of the modifier-head relation in compounds such as apple-knife or were asked to label objects with compounds. Results show that by age three children reliably interpret novel compounds and made use of novel compounds to subcategorize. (RH)

Thermal Stability Characteristics of Nitroaromatic Compounds.

DTIC Science & Technology

1986-09-15

of a methyl ortho to the nitro group in nitroaromatic compounds introduces a new element into the decomposition behavior of such compounds. Inasmuch...thus without the aid of acid, base or photon catalysis. It is clear that the presence of a methyl ortho to the nitro group in nitroaromatic compounds...particular interest in terms of the substance of this work is the drastic change in reaction product when a methyl group is ortho to the nitro . Furthermore

40 CFR 721.9668 - Organotin lithium compound.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Organotin lithium compound. 721.9668... Substances § 721.9668 Organotin lithium compound. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as an organotin lithium compound (PMN P-93-1119...

40 CFR 721.9668 - Organotin lithium compound.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Organotin lithium compound. 721.9668... Substances § 721.9668 Organotin lithium compound. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as an organotin lithium compound (PMN P-93-1119...

40 CFR 721.9668 - Organotin lithium compound.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Organotin lithium compound. 721.9668... Substances § 721.9668 Organotin lithium compound. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as an organotin lithium compound (PMN P-93-1119...

40 CFR 721.9668 - Organotin lithium compound.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Organotin lithium compound. 721.9668... Substances § 721.9668 Organotin lithium compound. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as an organotin lithium compound (PMN P-93-1119...

40 CFR 721.9668 - Organotin lithium compound.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Organotin lithium compound. 721.9668... Substances § 721.9668 Organotin lithium compound. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance generically identified as an organotin lithium compound (PMN P-93-1119...

Fumigant toxicity of basil oil compounds and related compounds to Thrips palmi and Orius strigicollis.

PubMed

Kim, Kwang-Ho; Yi, Chang-Geun; Ahn, Young-Joon; Kim, Soon Il; Lee, Sang-Guei; Kim, Jun-Ran

2015-09-01

This study was aimed at assessing the fumigant toxicity to adult Thrips palmi (a serious insect pest) and Orius strigicollis (a beneficial predator insect) of basil (Ocimum basilicum) essential oil compounds and structurally related compounds using vapour-phase toxicity bioassays. Against adult T. palmi, linalool (LD50 0.0055 mg cm(-3) ) was the most toxic fumigant and was 15.2-fold more effective than dichlorvos (0.0837 mg cm(-3) ). Strong fumigant toxicity was also observed in pulegone (0.0095 mg cm(-3) ), (±)-camphor (0.0097 mg cm(-3) ) and 1,8-cineole (0.0167 mg cm(-3) ). Moderate toxicity was produced by camphene, 3-carene, (-)-menthone, (+)-α-pinene, (+)-β-pinene, α-terpineol and (-)-α-thujone (0.0215-0.0388 mg cm(-3) ). Against adult O. strigicollis, dichlorvos (LD50 9.0 × 10(-10) mg cm(-3) ) was the most toxic fumigant, whereas the LD50 values of these compounds ranged from 0.0127 to >0.23 mg cm(-3) . Based upon the selective toxicity ratio, the compounds described are more selective than dichlorvos. The basil oil compounds described merit further study as potential insecticides for control of T. palmi in greenhouses because of their generally lower toxicity to O. strigicollis and their greater activity as a fumigant than dichlorvos. © 2014 Society of Chemical Industry.

Possible complex organic compounds on Mars.

PubMed

Kobayashi, K; Sato, T; Kajishima, S; Kaneko, T; Ishikawa, Y; Saito, T

1997-01-01

It is suggested that primitive Mars had somehow similar environments as primitive Earth. If life was born on the primitive earth using organic compounds which were produced from the early Earth environment, the same types of organic compounds were also formed on primitive Mars. Such organic compounds might have been preserved on Mars still now. We are studying possible organic formation on primitive and present Mars. A gaseous mixture of CO2, CO, N2 and H2O with various mixing ratios were irradiated with high energy protons (major components of cosmic rays). Hydrogen cyanide and formaldehyde were detected among volatile products, and yellow-brown-colored water-soluble non-volatile substances were produced, which gave amino acids after acid-hydrolysis. Major part of "amino acid precursors" were not simple molecules like aminonitriles, but complex compounds which eluted earlier than free amino acids in cation-exchange HPLC. These organic compounds should be major targets in the future Mars mission. Strategy for the detection of the complex organics on Mars will be discussed.

Pyrolysis reaction networks for lignin model compounds: unraveling thermal deconstruction of β-O-4 and α-O-4 compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Yong S.; Singh, Rahul; Zhang, Jing

2016-01-01

Although lignin is one of the main components of biomass, its pyrolysis chemistry is not well understood due to complex heterogeneity. To gain insights into this chemistry, the pyrolysis of seven lignin model compounds (five ..beta..-O-4 and two ..alpha..-O-4 linked molecules) was investigated in a micropyrolyzer connected to GC-MS/FID. According to quantitative product mole balance for the reaction networks, concerted retro-ene fragmentation and homolytic dissociation were strongly suggested as the initial reaction step for ..beta..-O-4 compounds and ..alpha..-O-4 compounds, respectively. The difference in reaction pathway between compounds with different linkages was believed to result from thermodynamics of the radical initiation.more » The rate constants for the different reaction pathways were predicted from ab initio density functional theory calculations and pre-exponential literature values. The computational findings were consistent with the experiment results, further supporting the different pyrolysis mechanisms for the ..beta..-ether linked and ..alpha..-ether linked compounds. A combination of the two pathways from the dimeric model compounds was able to describe qualitatively the pyrolysis of a trimeric lignin model compound containing both ..beta..-O-4 and ..alpha..-O-4 linkages.« less

Gallium-containing anticancer compounds

PubMed Central

Chitambar, Christopher R

2013-01-01

There is an ever pressing need to develop new drugs for the treatment of cancer. Gallium nitrate, a group IIIa metal salt, inhibits the proliferation of tumor cells in vitro and in vivo and has shown activity against non-Hodgkin’s lymphoma and bladder cancer in clinical trials. Gallium can function as an iron mimetic and perturb iron-dependent proliferation and other iron-related processes in tumor cells. Gallium nitrate lacks cross resistance with conventional chemotherapeutic drugs and is not myelosuppressive; it can be used when other drugs have failed or when the blood count is low. Given the therapeutic potential of gallium, newer generations of gallium compounds are now in various phases of preclinical and clinical development. These compounds hold the promise of greater anti-tumor activity against a broader spectrum of cancers. The development of gallium compounds for cancer treatment and their mechanisms of action will be discussed. PMID:22800370

Compound cycle engine program

NASA Technical Reports Server (NTRS)

Bobula, G. A.; Wintucky, W. T.; Castor, J. G.

1987-01-01

The Compound Cycle Engine (CCE) is a highly turbocharged, power compounded power plant which combines the lightweight pressure rise capability of a gas turbine with the high efficiency of a diesel. When optimized for a rotorcraft, the CCE will reduce fuel burn for a typical 2 hr (plus 30 min reserve) mission by 30 to 40 percent when compared to a conventional advanced technology gas turbine. The CCE can provide a 50 percent increase in range-payload product on this mission. A program to establish the technology base for a Compound Cycle Engine is presented. The goal of this program is to research and develop those technologies which are barriers to demonstrating a multicylinder diesel core in the early 1990's. The major activity underway is a three-phased contract with the Garrett Turbine Engine Company to perform: (1) a light helicopter feasibility study, (2) component technology development, and (3) lubricant and material research and development. Other related activities are also presented.

Compound cycle engine program

NASA Technical Reports Server (NTRS)

Bobula, G. A.; Wintucky, W. T.; Castor, J. G.

1986-01-01

The Compound Cycle Engine (CCE) is a highly turbocharged, power compounded power plant which combines the lightweight pressure rise capability of a gas turbine with the high efficiency of a diesel. When optimized for a rotorcraft, the CCE will reduce fuel burned for a typical 2 hr (plus 30 min reserve) mission by 30 to 40 percent when compared to a conventional advanced technology gas turbine. The CCE can provide a 50 percent increase in range-payload product on this mission. A program to establish the technology base for a Compound Cycle Engine is presented. The goal of this program is to research and develop those technologies which are barriers to demonstrating a multicylinder diesel core in the early 1990's. The major activity underway is a three-phased contract with the Garrett Turbine Engine Company to perform: (1) a light helicopter feasibility study, (2) component technology development, and (3) lubricant and material research and development. Other related activities are also presented.

Biodegradation of coal-related model compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, J.A.; Stewart, D.L.; McCulloch, M.

1988-06-01

We have studied the reactions of model compounds having coal-related functionalities (ester linkages, ether linkages, PAH) with the intact organism, cell-free filtrate, and cell-free enzyme of C. versicolor to better understand the process of biosolubilization. Many of the degradation products have been identified by gas chromatography/mass spectroscopy (GC/MS). Results indicate that the two compounds tested with the intact fungal organism were completely degraded. Complete degradation refers to no recovery of model compound. We can probably assume that the other two would also be totally degraded, since we have not yet found a simple compound that will survive long-term exposure tomore » the intact fungus. The ease of degradation with the cell-free filtrate appears to be in the order: phenylbenzoate > benzylbenzoate > benzyl ether > methoxybenzophenone. Esters and ethers that are activated by aromatic rings appear to be susceptible to the fungal extract; however, aromatic ketones are not affected by the extract. From the limited results we have obtained from the isolated enzyme, it appears that the activity may parallel the cell-free filtrate. When the cell-free extract was tested with the model compounds indole, dibenzothiophene, and bibenzyl, no degradation with the enzyme was noted: however, exposure of these compounds to the intact organism resulted in complete degradation. Analysis of the controls indicated no degradation. 8 refs., 1 fig., 1 tab.« less

Compounds that Inhibit Insect Host-Seeking Ability

USDA-ARS?s Scientific Manuscript database

Humans release hundreds of volatile compounds from their skin. Some of these compounds are used by mosquitoes and other insects to locate the host (kairomones) while a few compounds are found in trace amounts that tend to produce anosmia in these insects. The net result of this anosmic action on th...

PLUTONIUM COMPOUNDS AND PROCESS FOR THEIR PREPARATION

DOEpatents

Wolter, F.J.; Diehl, H.C. Jr.

1958-01-01

This patent relates to certain new compounds of plutonium, and to the utilization of these compounds to effect purification or separation of the plutonium. The compounds are organic chelate compounds consisting of tetravalent plutonium together with a di(salicylal) alkylenediimine. These chelates are soluble in various organic solvents, but not in water. Use is made of this property in extracting the plutonium by contacting an aqueous solution thereof with an organic solution of the diimine. The plutonium is chelated, extracted and effectively separated from any impurities accompaying it in the aqueous phase.

Hidden symmetries of the extended Kitaev-Heisenberg model: Implications for the honeycomb-lattice iridates A2IrO3

NASA Astrophysics Data System (ADS)

Chaloupka, Jiří; Khaliullin, Giniyat

2015-07-01

We have explored the hidden symmetries of a generic four-parameter nearest-neighbor spin model, allowed in honeycomb-lattice compounds under trigonal compression. Our method utilizes a systematic algorithm to identify all dual transformations of the model that map the Hamiltonian on itself, changing the parameters and providing exact links between different points in its parameter space. We have found the complete set of points of hidden SU(2) symmetry at which a seemingly highly anisotropic model can be mapped back on the Heisenberg model and inherits therefore its properties such as the presence of gapless Goldstone modes. The procedure used to search for the hidden symmetries is quite general and may be extended to other bond-anisotropic spin models and other lattices, such as the triangular, kagome, hyperhoneycomb, or harmonic-honeycomb lattices. We apply our findings to the honeycomb-lattice iridates Na2IrO3 and Li2IrO3 , and illustrate how they help to identify plausible values of the model parameters that are compatible with the available experimental data.

Hyperpolarizable compounds and devices fabricated therefrom

DOEpatents

Therien, Michael J.; DiMagno, Stephen G.

1998-01-01

Substituted compounds having relatively large molecular first order hyperpolarizabilities are provided, along with devices and materials containing them. In general, the compounds bear electron-donating and electron-withdrawing chemical substituents on a polyheterocyclic core.

IRIS Toxicological Review of Thallium and Compounds ...

EPA Pesticide Factsheets

Thallium compounds are used in the semiconductor industry, the manufacture of optic lenses and low-melting glass, low-temperature thermometers, alloys, electronic devices, mercury lamps, fireworks, and imitation germs, and clinically as an imaging agent in the diagnosis of certain tumors. EPA's assessment of noncancer health effects and carcinogenic potential of thallium compounds was last prepared and added to the IRIS database between 1988 and 1990. The IRIS program is preparing an assessment that will incorporate current health effects information available for thallium and compounds, and current risk assessment methods. The IRIS assessment for thallium compounds will consist of a Toxicological Review and IRIS Summary. The Toxicological Review is a critical review of the physiochemical and toxicokinetic properties of a chemical, and its toxicity in humans and experimental systems. The assessment will present reference values for the noncancer effects of thallium compounds (RfD and Rfc), and a cancer assessment. The Toxicological Review and IRIS Summary have been subject to Agency review, Interagency review, and external scientific peer review. The final product will reflect the Agency opinion on the overall toxicity of thallium and compounds. EPA is undertaking an Integrated Risk Information System (IRIS) health assessment for thallium and compounds. IRIS is an EPA database containing Agency scientific positions on potential adverse human health effec

The Modification of Compounds by Attributive Adjectives

ERIC Educational Resources Information Center

Berg, Thomas

2011-01-01

This paper examines the modification of nominal compounds by attributive adjectives in English. It draws on a distinction between compound-external (i.e. syntactic) and compound-internal (i.e. morphological) modification. An analysis is presented of more than 1000 pertinent cases, which are roughly equally divided into two-, three- and four-noun…

Drug-likeness analysis of traditional Chinese medicines: 2. Characterization of scaffold architectures for drug-like compounds, non-drug-like compounds, and natural compounds from traditional Chinese medicines

PubMed Central

2013-01-01

Background In order to better understand the structural features of natural compounds from traditional Chinese medicines, the scaffold architectures of drug-like compounds in MACCS-II Drug Data Report (MDDR), non-drug-like compounds in Available Chemical Directory (ACD), and natural compounds in Traditional Chinese Medicine Compound Database (TCMCD) were explored and compared. Results First, the different scaffolds were extracted from ACD, MDDR and TCMCD by using three scaffold representations, including Murcko frameworks, Scaffold Tree, and ring systems with different complexity and side chains. Then, by examining the accumulative frequency of the scaffolds in each dataset, we observed that the Level 1 scaffolds of the Scaffold Tree offer advantages over the other scaffold architectures to represent the scaffold diversity of the compound libraries. By comparing the similarity of the scaffold architectures presented in MDDR, ACD and TCMCD, structural overlaps were observed not only between MDDR and TCMCD but also between MDDR and ACD. Finally, Tree Maps were used to cluster the Level 1 scaffolds of the Scaffold Tree and visualize the scaffold space of the three datasets. Conclusion The analysis of the scaffold architectures of MDDR, ACD and TCMCD shows that, on average, drug-like molecules in MDDR have the highest diversity while natural compounds in TCMCD have the highest complexity. According to the Tree Maps, it can be observed that the Level 1 scaffolds present in MDDR have higher diversity than those presented in TCMCD and ACD. However, some representative scaffolds in MDDR with high frequency show structural similarities to those in TCMCD and ACD, suggesting that some scaffolds in TCMCD and ACD may be potentially drug-like fragments for fragment-based and de novo drug design. PMID:23336706

Structure-based virtual screening and characterization of a novel IL-6 antagonistic compound from synthetic compound database.

PubMed

Wang, Jing; Qiao, Chunxia; Xiao, He; Lin, Zhou; Li, Yan; Zhang, Jiyan; Shen, Beifen; Fu, Tinghuan; Feng, Jiannan

2016-01-01

According to the three-dimensional (3D) complex structure of (hIL-6⋅hIL-6R⋅gp 130) 2 and the binding orientation of hIL-6, three compounds with high affinity to hIL-6R and bioactivity to block hIL-6 in vitro were screened theoretically from the chemical databases, including 3D-Available Chemicals Directory (ACD) and MDL Drug Data Report (MDDR), by means of the computer-guided virtual screening method. Using distance geometry, molecular modeling and molecular dynamics trajectory analysis methods, the binding mode and binding energy of the three compounds were evaluated theoretically. Enzyme-linked immunosorbent assay analysis demonstrated that all the three compounds could block IL-6 binding to IL-6R specifically. However, only compound 1 could effectively antagonize the function of hIL-6 and inhibit the proliferation of XG-7 cells in a dose-dependent manner, whereas it showed no cytotoxicity to SP2/0 or L929 cells. These data demonstrated that the compound 1 could be a promising candidate of hIL-6 antagonist.

Reading Compounds in Neglect Dyslexia: The Headedness Effect

ERIC Educational Resources Information Center

Semenza, Carlo; Arcara, Giorgio; Facchini, Silvia; Meneghello, Francesca; Ferraro, Marco; Passarini, Laura; Pilosio, Cristina; Vigato, Giovanna; Mondini, Sara

2011-01-01

Reading compound words was studied in neglect dyslexia in order to assess the influence of "headedness". The "head" of a compound is the component that determines the grammatical category, the syntactic (e.g., the gender) and the semantic properties of the compound as a whole. For example, in the word "blackberry" "berry" is the compound's head.…

Food applications of natural antimicrobial compounds.

PubMed

Lucera, Annalisa; Costa, Cristina; Conte, Amalia; Del Nobile, Matteo A

2012-01-01

In agreement with the current trend of giving value to natural and renewable resources, the use of natural antimicrobial compounds, particularly in food and biomedical applications, becomes very frequent. The direct addition of natural compounds to food is the most common method of application, even if numerous efforts have been made to find alternative solutions to the aim of avoiding undesirable inactivation. Dipping, spraying, and coating treatment of food with active solutions are currently applied to product prior to packaging as valid options. The aim of the current work is to give an overview on the use of natural compounds in food sector. In particular, the review will gather numerous case-studies of meat, fish, dairy products, minimally processed fruit and vegetables, and cereal-based products where these compounds found application.

Food applications of natural antimicrobial compounds

PubMed Central

Lucera, Annalisa; Costa, Cristina; Conte, Amalia; Del Nobile, Matteo A.

2012-01-01

In agreement with the current trend of giving value to natural and renewable resources, the use of natural antimicrobial compounds, particularly in food and biomedical applications, becomes very frequent. The direct addition of natural compounds to food is the most common method of application, even if numerous efforts have been made to find alternative solutions to the aim of avoiding undesirable inactivation. Dipping, spraying, and coating treatment of food with active solutions are currently applied to product prior to packaging as valid options. The aim of the current work is to give an overview on the use of natural compounds in food sector. In particular, the review will gather numerous case-studies of meat, fish, dairy products, minimally processed fruit and vegetables, and cereal-based products where these compounds found application. PMID:23060862

Two-photon absorption in diazobenzene compounds

NASA Astrophysics Data System (ADS)

Andrade, A. A.; Yamaki, S. B.; Misoguti, L.; Zilio, S. C.; Atvars, Teresa D. Z.; Oliveira, O. N.; Mendonça, C. R.

2004-12-01

An investigation is made into molecular design strategies to enhance the two-photon absorption (2PA) of organic materials by measuring the 2PA cross-section of diazoaromatic compounds with the femtosecond pulses Z-scan technique at 775 nm. These diazo dyes exhibit a moderate 2PA cross-section, of the order of 300 GM, comparable to those of regular azoaromatic compounds. The increase in the π-electron bridge in the diazoaromatic compounds does not bring, therefore, substantial increase to the measured 2PA intensities, while the main factor to enhance the 2PA cross-section is the presence of charge donor and acceptor groups. It is concluded that current molecular design strategies are unlikely to produce azoaromatic compounds that are useful for applications requiring very high 2PA coefficients.

A kinase-focused compound collection: compilation and screening strategy.

PubMed

Sun, Dongyu; Chuaqui, Claudio; Deng, Zhan; Bowes, Scott; Chin, Donovan; Singh, Juswinder; Cullen, Patrick; Hankins, Gretchen; Lee, Wen-Cherng; Donnelly, Jason; Friedman, Jessica; Josiah, Serene

2006-06-01

Lead identification by high-throughput screening of large compound libraries has been supplemented with virtual screening and focused compound libraries. To complement existing approaches for lead identification at Biogen Idec, a kinase-focused compound collection was designed, developed and validated. Two strategies were adopted to populate the compound collection: a ligand shape-based virtual screening and a receptor-based approach (structural interaction fingerprint). Compounds selected with the two approaches were cherry-picked from an existing high-throughput screening compound library, ordered from suppliers and supplemented with specific medicinal compounds from internal programs. Promising hits and leads have been generated from the kinase-focused compound collection against multiple kinase targets. The principle of the collection design and screening strategy was validated and the use of the kinase-focused compound collection for lead identification has been added to existing strategies.

Multi-Phase Equilibrium and Solubilities of Aromatic Compounds and Inorganic Compounds in Sub- and Supercritical Water: A Review.

PubMed

Liu, Qinli; Ding, Xin; Du, Bowen; Fang, Tao

2017-11-02

Supercritical water oxidation (SCWO), as a novel and efficient technology, has been applied to wastewater treatment processes. The use of phase equilibrium data to optimize process parameters can offer a theoretical guidance for designing SCWO processes and reducing the equipment and operating costs. In this work, high-pressure phase equilibrium data for aromatic compounds+water systems and inorganic compounds+water systems are given. Moreover, thermodynamic models, equations of state (EOS) and empirical and semi-empirical approaches are summarized and evaluated. This paper also lists the existing problems of multi-phase equilibria and solubility studies on aromatic compounds and inorganic compounds in sub- and supercritical water.

21 CFR 170.45 - Fluorine-containing compounds.

Code of Federal Regulations, 2010 CFR

2010-04-01

... § 170.45 Fluorine-containing compounds. The Commissioner of Food and Drugs has concluded that it is in the interest of the public health to limit the addition of fluorine compounds to foods (a) to that... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Fluorine-containing compounds. 170.45 Section 170...

When to Compound Medications for Veterinary Patients.

PubMed

Forsythe, Lauren Eichstadt

2017-01-01

This article serves as a brief discussion about some of the restrictions applicable to compounding medications for veterinary patients based on U. S. Food and Drug Administration compliance policy guidelines and provides a brief summary of when it is appropriate to compound medications for veterinary patients. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Control of ultrafast pulses in a hydrogen-filled hollow-core photonic-crystal fiber by Raman coherence

NASA Astrophysics Data System (ADS)

Belli, F.; Abdolvand, A.; Travers, J. C.; Russell, P. St. J.

2018-01-01

We present the results of an experimental and numerical investigation into temporally nonlocal coherent interactions between ultrashort pulses, mediated by Raman coherence, in a gas-filled kagome-style hollow-core photonic-crystal fiber. A pump pulse first sets up the Raman coherence, creating a refractive index spatiotemporal grating in the gas that travels at the group velocity of the pump pulse. Varying the arrival time of a second, probe, pulse allows a high degree of control over its evolution as it propagates along the fiber through the grating. Of particular interest are soliton-driven effects such as self-compression and dispersive wave (DW) emission. In the experiments reported, a DW is emitted at ˜300 nm and exhibits a wiggling effect, with its central frequency oscillating periodically with pump-probe delay. The results demonstrate that a strong Raman coherence, created in a broadband guiding gas-filled kagome photonic-crystal fiber, can be used to control the nonlinear dynamics of ultrashort probe pulses, even in difficult-to-access spectral regions such as the deep and vacuum ultraviolet.

Hyperpolarizable compounds and devices fabricated therefrom

DOEpatents

Therien, M.J.; DiMagno, S.G.

1998-07-21

Substituted compounds having relatively large molecular first order hyperpolarizabilities are provided, along with devices and materials containing them. In general, the compounds bear electron-donating and electron-withdrawing chemical substituents on a polyheterocyclic core. 13 figs.

Competition between the compound and the pre-compound emission processes in α-induced reactions at near astrophysical energy to well above it

NASA Astrophysics Data System (ADS)

Sharma, Manoj Kumar; Sharma, Vijay Raj; Yadav, Abhiskek; Singh, Pushpendra P.; Singh, B. P.; Prasad, R.

2016-04-01

The study of pre-compound emission in α-induced reactions, particularly at the low incident energies, is of considerable interest as the pre-compound emission is more likely to occur at higher energies. With a view to study the competition between the compound and the pre-compound emission processes in α-induced reactions at different energies and with different targets, a systematics for neutron emission channels in targets 51V, 55Mn, 93Nb, 121, 123Sb and 141Pr at energy ranging from astrophysical interest to well above it, has been developed. The off-line γ-ray-spectrometry based activation technique has been adopted to measure the excitation functions. The experimental excitation functions have been analysed within the framework of the compound nucleus mechanism based on the Weisskopf-Ewing model and the pre-compound emission calculations based on the geometry dependent hybrid model. The analysis of the data shows that experimental excitation functions could be reproduced only when the pre-compound emission, simulated theoretically, is taken into account. The strength of pre-compound emission process for each system has been obtained by deducing the pre-compound fraction. Analysis of data indicates that in α-induced reactions, the pre-compound emission process plays an important role, particularly at the low incident energies, where the pure compound nucleus process is likely to dominate.

Compound Walls For Vacuum Chambers

NASA Technical Reports Server (NTRS)

Frazer, Robert E.

1988-01-01

Proposed compound-wall configuration enables construction of large high-vacuum chambers without having to use thick layers of expensive material to obtain necessary strength. Walls enclose chambers more than 1 m in diameter and several kilometers long. Compound wall made of strong outer layer of structural-steel culvert pipe welded to thin layer of high-quality, low-outgassing stainless steel.

Aza compounds as anion receptors

DOEpatents

Lee, Hung Sui; Yang, Xiao-Qing; McBreen, James

1998-01-06

A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li.sup.+ ion in alkali metal batteries.

Aza compounds as anion receptors

DOEpatents

Lee, H.S.; Yang, X.Q.; McBreen, J.

1998-01-06

A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li{sup +} ion in alkali metal batteries. 3 figs.

Heart testing compound

DOEpatents

Knapp, Jr., Furn F.; Goodman, Mark M.

1985-01-01

The compound 15-(p-[.sup.125 I]-iodophenyl)-6-tellurapentadecanoic acid is disclosed as a myocardial imaging agent having rapid and pronounced uptake, prolonged myocardial retention, and low in vivo deiodination.

Heart testing compound

DOEpatents

Knapp, F.F. Jr.; Goodman, M.M.

1983-06-29

The compound 15-(p-(/sup 125/I)-iodophenyl)-6-tellurapentadecanoic acid is disclosed as a myocardial imaging agent having rapid and pronounced uptake, prolonged myocardial retention, and low in vivo deiodination.

A survey of synthetic and natural phytotoxic compounds and phytoalexins as potential antimalarial compounds.

PubMed

Bajsa, Joanna; Singh, Kshipra; Nanayakkara, Dhammika; Duke, Stephen Oscar; Rimando, Agnes Mamaril; Evidente, Antonio; Tekwani, Babu Lal

2007-09-01

The apicomplexan parasites pathogens such as Plasmodium spp. possess an apicoplast, a plastid organelle similar to those of plants. The apicoplast has some essential plant-like metabolic pathways and processes, making these parasites susceptible to inhibitors of these functions. The main objective of this paper is to determine if phytotoxins with plastid target sites are more likely to be good antiplasmodial compounds than are those with other modes of action. The antiplasmodial activities of some compounds with established phytotoxic action were determined in vitro on a chloroquine (CQ) sensitive (D6, Sierra Leone) strain of Plasmodium falciparum. In this study, we provide in vitro activities of almost 50 such compounds, as well as a few phytoalexins against P. falciparum. Endothall, anisomycin, and cerulenin had sufficient antiplasmodial action to be considered as new lead antimalarial structures. Some derivatives of fusicoccin possessed markedly improved antiplasmodial action than the parent compound. Our results suggest that phytotoxins with plastid targets may not necessarily be better antiplasmodials than those that act at other molecular sites. The herbicides, phytotoxins and the phytoalexins reported here with significant antiplasmodial activity may be useful probes for identification of new antimalarial drug targets and may also be used as new lead structures for new antiplasmodial drug discovery.

Characterization of ToxCast Phase II compounds disruption of ...

EPA Pesticide Factsheets

The development of multi-well microelectrode array (mwMEA) systems has increased in vitro screening throughput making them an effective method to screen and prioritize large sets of compounds for potential neurotoxicity. In the present experiments, a multiplexed approach was used to determine compound effects on both neural function and cell health in primary cortical networks grown on mwMEA plates following exposure to ~1100 compounds from EPA’s Phase II ToxCast libraries. On DIV 13, baseline activity (40 min) was recorded prior to exposure to each compound at 40 µM. DMSO and the GABAA antagonist bicuculline (BIC) were included as controls on each mwMEA plate. Changes in spontaneous network activity (mean firing rate; MFR) and cell viability (lactate dehydrogenase; LDH and CellTiter Blue; CTB) were assessed within the same well following compound exposure. Activity calls (“hits”) were established using the 90th and 20th percentiles of the compound-induced change in MFR (medians of triplicates) across all tested compounds; compounds above (top 10% of compounds increasing MFR), and below (bottom 20% of compounds decreasing MFR) these thresholds, respectively were considered hits. MFR was altered beyond one of these thresholds by 322 compounds. Four compound categories accounted for 66% of the hits, including: insecticides (e.g. abamectin, lindane, prallethrin), pharmaceuticals (e.g. haloperidol, reserpine), fungicides (e.g. hexaconazole, fenamidone), and h

Polyfluorinated Compounds: Past, Present, and Future

EPA Science Inventory

Interest and concern about polyfluorinated compounds (PFCs), such as perfluorooctane sulfonate (PFOS), erfluorooctanoic acid (PFOA), and an increasing number of other related compounds is growing as more is learned about these ubiquitous anthropogenic substances. Many of these co...

Antimicrobial Action of Compounds from Marine Seaweed

PubMed Central

Pérez, María José; Falqué, Elena; Domínguez, Herminia

2016-01-01

Seaweed produces metabolites aiding in the protection against different environmental stresses. These compounds show antiviral, antiprotozoal, antifungal, and antibacterial properties. Macroalgae can be cultured in high volumes and would represent an attractive source of potential compounds useful for unconventional drugs able to control new diseases or multiresistant strains of pathogenic microorganisms. The substances isolated from green, brown and red algae showing potent antimicrobial activity belong to polysaccharides, fatty acids, phlorotannins, pigments, lectins, alkaloids, terpenoids and halogenated compounds. This review presents the major compounds found in macroalga showing antimicrobial activities and their most promising applications. PMID:27005637

Diazo Compounds: Versatile Tools for Chemical Biology.

PubMed

Mix, Kalie A; Aronoff, Matthew R; Raines, Ronald T

2016-12-16

Diazo groups have broad and tunable reactivity. That and other attributes endow diazo compounds with the potential to be valuable reagents for chemical biologists. The presence of diazo groups in natural products underscores their metabolic stability and anticipates their utility in a biological context. The chemoselectivity of diazo groups, even in the presence of azido groups, presents many opportunities. Already, diazo compounds have served as chemical probes and elicited novel modifications of proteins and nucleic acids. Here, we review advances that have facilitated the chemical synthesis of diazo compounds, and we highlight applications of diazo compounds in the detection and modification of biomolecules.

Bio-inspired hemispherical compound eye camera

NASA Astrophysics Data System (ADS)

Xiao, Jianliang; Song, Young Min; Xie, Yizhu; Malyarchuk, Viktor; Jung, Inhwa; Choi, Ki-Joong; Liu, Zhuangjian; Park, Hyunsung; Lu, Chaofeng; Kim, Rak-Hwan; Li, Rui; Crozier, Kenneth B.; Huang, Yonggang; Rogers, John A.

2014-03-01

Compound eyes in arthropods demonstrate distinct imaging characteristics from human eyes, with wide angle field of view, low aberrations, high acuity to motion and infinite depth of field. Artificial imaging systems with similar geometries and properties are of great interest for many applications. However, the challenges in building such systems with hemispherical, compound apposition layouts cannot be met through established planar sensor technologies and conventional optics. We present our recent progress in combining optics, materials, mechanics and integration schemes to build fully functional artificial compound eye cameras. Nearly full hemispherical shapes (about 160 degrees) with densely packed artificial ommatidia were realized. The number of ommatidia (180) is comparable to those of the eyes of fire ants and bark beetles. The devices combine elastomeric compound optical elements with deformable arrays of thin silicon photodetectors, which were fabricated in the planar geometries and then integrated and elastically transformed to hemispherical shapes. Imaging results and quantitative ray-tracing-based simulations illustrate key features of operation. These general strategies seem to be applicable to other compound eye devices, such as those inspired by moths and lacewings (refracting superposition eyes), lobster and shrimp (reflecting superposition eyes), and houseflies (neural superposition eyes).

The Chemistry of Nitroxyl-Releasing Compounds

PubMed Central

DuMond, Jenna F.

2011-01-01

Abstract Nitroxyl (HNO) demonstrates a diverse and unique biological profile compared to nitric oxide, a redox-related compound. Although numerous studies support the use of HNO as a therapeutic agent, the inherent chemical reactivity of HNO requires the use of donor molecules. Two general chemical strategies currently exist for HNO generation from nitrogen-containing molecules: (i) the disproportionation of hydroxylamine derivatives containing good leaving groups attached to the nitrogen atom and (ii) the decomposition of nitroso compounds (X-N=O, where X represents a good leaving group). This review summarizes the synthesis and structure, the HNO-releasing mechanisms, kinetics and by-product formation, and alternative reactions of six major groups of HNO donors: Angeli's salt, Piloty's acid and its derivatives, cyanamide, diazenium diolate-derived compounds, acyl nitroso compounds, and acyloxy nitroso compounds. A large body of work exists defining these six groups of HNO donors and the overall chemistry of each donor requires consideration in light of its ability to produce HNO. The increasing interest in HNO biology and the potential of HNO-based therapeutics presents exciting opportunities to further develop HNO donors as both research tools and potential treatments. Antioxid. Redox Signal. 14, 1637–1648. PMID:21235345

Atmospheric Chemistry of Micrometeoritic Organic Compounds

NASA Technical Reports Server (NTRS)

Kress, M. E.; Belle, C. L.; Pevyhouse, A. R.; Iraci, L. T.

2011-01-01

Micrometeorites approx.100 m in diameter deliver most of the Earth s annual accumulation of extraterrestrial material. These small particles are so strongly heated upon atmospheric entry that most of their volatile content is vaporized. Here we present preliminary results from two sets of experiments to investigate the fate of the organic fraction of micrometeorites. In the first set of experiments, 300 m particles of a CM carbonaceous chondrite were subject to flash pyrolysis, simulating atmospheric entry. In addition to CO and CO2, many organic compounds were released, including functionalized benzenes, hydrocarbons, and small polycyclic aromatic hydrocarbons. In the second set of experiments, we subjected two of these compounds to conditions that simulate the heterogeneous chemistry of Earth s upper atmosphere. We find evidence that meteor-derived compounds can follow reaction pathways leading to the formation of more complex organic compounds.

Methods of making organic compounds by metathesis

DOEpatents

Abraham, Timothy W.; Kaido, Hiroki; Lee, Choon Woo; Pederson, Richard L.; Schrodi, Yann; Tupy, Michael John

2015-09-01

Described are methods of making organic compounds by metathesis chemistry. The methods of the invention are particularly useful for making industrially-important organic compounds beginning with starting compositions derived from renewable feedstocks, such as natural oils. The methods make use of a cross-metathesis step with an olefin compound to produce functionalized alkene intermediates having a pre-determined double bond position. Once isolated, the functionalized alkene intermediate can be self-metathesized or cross-metathesized (e.g., with a second functionalized alkene) to produce the desired organic compound or a precursor thereto. The method may be used to make bifunctional organic compounds, such as diacids, diesters, dicarboxylate salts, acid/esters, acid/amines, acid/alcohols, acid/aldehydes, acid/ketones, acid/halides, acid/nitriles, ester/amines, ester/alcohols, ester/aldehydes, ester/ketones, ester/halides, ester/nitriles, and the like.

Antiviral Screening of Multiple Compounds against Ebola Virus.

PubMed

Dowall, Stuart D; Bewley, Kevin; Watson, Robert J; Vasan, Seshadri S; Ghosh, Chandradhish; Konai, Mohini M; Gausdal, Gro; Lorens, James B; Long, Jason; Barclay, Wendy; Garcia-Dorival, Isabel; Hiscox, Julian; Bosworth, Andrew; Taylor, Irene; Easterbrook, Linda; Pitman, James; Summers, Sian; Chan-Pensley, Jenny; Funnell, Simon; Vipond, Julia; Charlton, Sue; Haldar, Jayanta; Hewson, Roger; Carroll, Miles W

2016-10-27

In light of the recent outbreak of Ebola virus (EBOV) disease in West Africa, there have been renewed efforts to search for effective antiviral countermeasures. A range of compounds currently available with broad antimicrobial activity have been tested for activity against EBOV. Using live EBOV, eighteen candidate compounds were screened for antiviral activity in vitro. The compounds were selected on a rational basis because their mechanisms of action suggested that they had the potential to disrupt EBOV entry, replication or exit from cells or because they had displayed some antiviral activity against EBOV in previous tests. Nine compounds caused no reduction in viral replication despite cells remaining healthy, so they were excluded from further analysis (zidovudine; didanosine; stavudine; abacavir sulphate; entecavir; JB1a; Aimspro; celgosivir; and castanospermine). A second screen of the remaining compounds and the feasibility of appropriateness for in vivo testing removed six further compounds (ouabain; omeprazole; esomeprazole; Gleevec; D-LANA-14; and Tasigna). The three most promising compounds (17-DMAG; BGB324; and NCK-8) were further screened for in vivo activity in the guinea pig model of EBOV disease. Two of the compounds, BGB324 and NCK-8, showed some effect against lethal infection in vivo at the concentrations tested, which warrants further investigation. Further, these data add to the body of knowledge on the antiviral activities of multiple compounds against EBOV and indicate that the scientific community should invest more effort into the development of novel and specific antiviral compounds to treat Ebola virus disease.

Application of bicyclic and cage compounds

NASA Technical Reports Server (NTRS)

Clark, R. D.; Archuleta, B. S.

1976-01-01

The results of a literature survey of the field of bicyclic and cage compounds were presented, with the objective of identifying those types of compounds with unusual physical and chemical stability, and determining what practical applications have been found for these compounds. Major applications have been as polymers, polymer additives, medicinals, and pesticides. Lesser applications have included fuels, fuel additives, lubricants, lubricant additives, and perfumes. Several areas where further work might be useful were also outlined; these are primarily in the areas of polymers, polymer additives, medicinals, and synthetic lubricants.

Lipid encapsulated phenolic compounds by fluidization

USDA-ARS?s Scientific Manuscript database

Phenolic compounds exhibit antioxidant and antimicrobial activities with applications as functional food and feed additives. Ferulic acid, a phenolic compound present in grain crops and lignocellulose biomass, was encapsulated with saturated triglycerides using a laboratory fluidizer. Stability of t...

Antifouling Compounds from Marine Macroalgae

PubMed Central

Dahms, Hans Uwe; Dobretsov, Sergey

2017-01-01

Marine macroalgae produce a wide variety of biologically-active metabolites that have been developed into commercial products, such as antibiotics, immunosuppressive, anti-inflammatory, cytotoxic agents, and cosmetic products. Many marine algae remain clean over longer periods of time, suggesting their strong antifouling potential. Isolation of biogenic compounds and the determination of their structure could provide leads for the development of environmentally-friendly antifouling paints. Isolated substances with potent antifouling activity belong to fatty acids, lipopeptides, amides, alkaloids, lactones, steroids, terpenoids, and pyrroles. It is unclear as yet to what extent symbiotic microorganisms are involved in the synthesis of these compounds. Algal secondary metabolites have the potential to be produced commercially using genetic and metabolic engineering techniques. This review provides an overview of publications from 2010 to February 2017 about antifouling activity of green, brown, and red algae. Some researchers were focusing on antifouling compounds of brown macroalgae, while metabolites of green algae received less attention. Several studies tested antifouling activity against bacteria, microalgae and invertebrates, but in only a few studies was the quorum sensing inhibitory activity of marine macroalgae tested. Rarely, antifouling compounds from macroalgae were isolated and tested in an ecologically-relevant way. PMID:28846625

Antifouling Compounds from Marine Macroalgae.

PubMed

Dahms, Hans Uwe; Dobretsov, Sergey

2017-08-28

Marine macroalgae produce a wide variety of biologically-active metabolites that have been developed into commercial products, such as antibiotics, immunosuppressive, anti-inflammatory, cytotoxic agents, and cosmetic products. Many marine algae remain clean over longer periods of time, suggesting their strong antifouling potential. Isolation of biogenic compounds and the determination of their structure could provide leads for the development of environmentally-friendly antifouling paints. Isolated substances with potent antifouling activity belong to fatty acids, lipopeptides, amides, alkaloids, lactones, steroids, terpenoids, and pyrroles. It is unclear as yet to what extent symbiotic microorganisms are involved in the synthesis of these compounds. Algal secondary metabolites have the potential to be produced commercially using genetic and metabolic engineering techniques. This review provides an overview of publications from 2010 to February 2017 about antifouling activity of green, brown, and red algae. Some researchers were focusing on antifouling compounds of brown macroalgae, while metabolites of green algae received less attention. Several studies tested antifouling activity against bacteria, microalgae and invertebrates, but in only a few studies was the quorum sensing inhibitory activity of marine macroalgae tested. Rarely, antifouling compounds from macroalgae were isolated and tested in an ecologically-relevant way.

The Generation of Diazo Compounds in Continuous-Flow.

PubMed

Hock, Katharina J; Koenigs, Rene M

2018-03-25

Toxic, cancerogenic and explosive - these attributes are typically associated with diazo compounds. Nonetheless, diazo compounds are nowadays a highly demanded class of reagents for organic synthesis, yet the concerns with regards to safe and scalable transformations of these compounds are still exceptionally high. Lately, the research area of the continuous-flow synthesis of diazo compounds attracted significant interest and a whole variety of protocols for their "on-demand" preparation have been realized to date. This concept article focuses on the recent developments using continuous-flow technologies to access diazo compounds; thus minimizing risks and hazards when working with this particular class of compounds. In this article we discuss these concepts and highlight different pre-requisites to access and to perform downstream functionalization reaction. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Devil's Staircase Wilderness Act of 2013

THOMAS, 113th Congress

Sen. Wyden, Ron [D-OR

2013-02-14

House - 06/21/2013 Referred to the Subcommittee on Public Lands and Environmental Regulation. (All Actions) Tracker: This bill has the status Passed SenateHere are the steps for Status of Legislation:

Devil's Staircase Wilderness Act of 2011

THOMAS, 112th Congress

Sen. Wyden, Ron [D-OR

2011-04-07

Senate - 01/13/2012 Placed on Senate Legislative Calendar under General Orders. Calendar No. 277. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Devil's Staircase Wilderness Act of 2010

THOMAS, 111th Congress

Sen. Wyden, Ron [D-OR

2009-06-16

Senate - 08/05/2010 Placed on Senate Legislative Calendar under General Orders. Calendar No. 527. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Pre-compound emission in low-energy heavy-ion interactions

NASA Astrophysics Data System (ADS)

Sharma, Manoj Kumar; Shuaib, Mohd.; Sharma, Vijay R.; Yadav, Abhishek; Singh, Pushpendra P.; Singh, Devendra P.; Unnati; Singh, B. P.; Prasad, R.

2017-11-01

Recent experimental studies have shown the presence of pre-compound emission component in heavy ion reactions at low projectile energy ranging from 4 to 7 MeV/nucleons. In earlier measurements strength of the pre-compound component has been estimated from the difference in forward-backward distributions of emitted particles. Present measurement is a part of an ongoing program on the study of reaction dynamics of heavy ion interactions at low energies aimed at investigating the effect of momentum transfer in compound, precompound, complete and incomplete fusion processes in heavy ion reactions. In the present work on the basis of momentum transfer the measurement of the recoil range distributions of heavy residues has been used to decipher the components of compound and pre-compound emission processes in the fusion of 16O projectile with 159Tb and 169Tm targets. The analysis of recoil range distribution measurements show two distinct linear momentum transfer components corresponding to pre-compound and compound nucleus processes are involved. In order to obtain the mean input angular momentum associated with compound and pre-compound emission processes, an online measurement of the spin distributions of the residues has been performed. The analysis of spin distribution indicate that the mean input angular momentum associated with pre-compound products is found to be relatively lower than that associated with compound nucleus process. The pre-compound components obtained from the present analysis are consistent with those obtained from the analysis of excitation functions.

Anti-Fog Compound

NASA Technical Reports Server (NTRS)

1985-01-01

Tracer Chemical Corporation's TRX Anti-Fog Composition is an inexpensive product which prevents condensation on plastic and glass surfaces. It was the result from a Tech Briefs article detailing a Johnson Space Center compound.

PERFLUORINATED ORGANIC COMPOUND EXPOSURE ASSESSMENT RESEARCH

EPA Science Inventory

A wide range of perfluorinated organic compounds (PFCs) has been used in a variety of industrial processes and consumer products. The most commonly studied PFCs include perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), but there are many more compounds in this c...

Herbal Compounds and Toxins Modulating TRP Channels

PubMed Central

Vriens, Joris; Nilius, Bernd; Vennekens, Rudi

2008-01-01

Although the benefits are sometimes obvious, traditional or herbal medicine is regarded with skepticism, because the mechanism through which plant compounds exert their powers are largely elusive. Recent studies have shown however that many of these plant compounds interact with specific ion channels and thereby modulate the sensing mechanism of the human body. Especially members of the Transient Receptor Potential (TRP) channels have drawn large attention lately as the receptors for plant-derived compounds such as capsaicin and menthol. TRP channels constitute a large and diverse family of channel proteins that can serve as versatile sensors that allow individual cells and entire organisms to detect changes in their environment. For this family, a striking number of empirical views have turned into mechanism-based actions of natural compounds. In this review we will give an overview of herbal compounds and toxins, which modulate TRP channels. PMID:19305789

Biodegradation of NSO-compounds under different redox-conditions

NASA Astrophysics Data System (ADS)

Dyreborg, S.; Arvin, E.; Broholm, K.

1997-03-01

Laboratory experiments were carried out to investigate the potential of groundwater microorganisms to degrade selected heterocyclic aromatic compounds containing nitrogen, sulphur, or oxygen (NSO-compounds) under four redox-conditions over a period of 846 days. Eight compounds (pyrrole, 1-methylpyrrole, quinoline, indole, carbazole, dibenzothiophene, benzofuran, and dibenzofuran) were degraded under aerobic conditions, whereas thiophene and benzothiophene were degraded only when other compounds were degraded concomitantly. Quinoline and indole were the only two NSO-compounds degraded under anaerobic conditions, even though the microorganisms present in the anaerobic microcosms were active throughout the incubation period. A high variability in the lag period among the NSO-compounds was observed under aerobic conditions. While quinoline, indole, and carbazole were degraded with a lag period of 3-25 days, the lag periods for pyrrole, dibenzothiophene, benzofuran, and dibenzofuran were significantly longer (29-278 days). Under anaerobic conditions, lag periods of 100-300 days were observed. Differences in the degradation rate among the compounds were also observed. Indole, quinoline, carbazole, and benzofuran were quickly degraded in the aerobic microcosms, whereas a slow degradation of dibenzothiophene and dibenzofuran was observed. Pyrrole and 1-methylpyrrole were slowly degraded and 1-methylpyrrole was not completely removed within the 846 days. The anaerobic degradation rate was significantly slower than the aerobic degradation rate. The degradation rate under sulphate-reducing conditions was higher than under denitrifying and methanogenic conditions, though after re-addition of a compound a quick removal was observed. The persistence of many NSO-compounds under anaerobic conditions together with the long lag periods and the low degradation rates under aerobic conditions suggest that NSO-compounds might persist in groundwater at creosote-contaminated sites.

Accuracy of testosterone concentrations in compounded testosterone products.

PubMed

Grober, Ethan D; Garbens, Alaina; Božović, Andrea; Kulasingam, Vathany; Fanipour, Majid; Diamandis, Eleftherios P

2015-06-01

This study aims to evaluate the accuracy of the testosterone concentrations within testosterone gels and creams manufactured by compounding pharmacies. Ten compounding pharmacies within Toronto area were included. Pharmacies were blinded as to the nature of the study. A standardized prescription for 50 mg of compounded testosterone gel/cream applied once daily was presented to each pharmacy. Two independently compounded batches were analyzed from each pharmacy 1 month apart. Testosterone concentrations in a 5-g sachet of Androgel® 1% (Abbott) and 5-g tube of Testim®1% (Auxilium) were evaluated as controls. Samples were analyzed independently and in a blinded fashion by the Laboratory Medicine Program at the University Health Network. Measurement of testosterone concentration was performed using a modified liquid chromatography tandem mass spectrometry validated for serum testosterone. Compounded formulations included seven gels and three creams with a volume/daily dose ranging from 0.2 mL to 1.25 mL. Product cost ranged from $57.32 to $160.71 for a 30-day supply. There was significant variability both within and between pharmacies with respect to the measured concentration of testosterone in the compounded products. In contrast, the concentration of testosterone within Androgel and Testim was consistent and accurate. Collectively, only 50% (batch 1) and 30% (batch 2) of the compounding pharmacies provided a product with a testosterone concentration within ± 20% of the prescribed dose. Two pharmacies compounded products with >20% of the prescribed dose. One pharmacy compounded a product with essentially no testosterone. Testosterone concentrations in compounded testosterone products can be variable and potentially compromise the efficacy and safety of treatment. © 2015 International Society for Sexual Medicine.

Antiviral lead compounds from marine sponges.

PubMed

Sagar, Sunil; Kaur, Mandeep; Minneman, Kenneth P

2010-10-11

Marine sponges are currently one of the richest sources of pharmacologically active compounds found in the marine environment. These bioactive molecules are often secondary metabolites, whose main function is to enable and/or modulate cellular communication and defense. They are usually produced by functional enzyme clusters in sponges and/or their associated symbiotic microorganisms. Natural product lead compounds from sponges have often been found to be promising pharmaceutical agents. Several of them have successfully been approved as antiviral agents for clinical use or have been advanced to the late stages of clinical trials. Most of these drugs are used for the treatment of human immunodeficiency virus (HIV) and herpes simplex virus (HSV). The most important antiviral lead of marine origin reported thus far is nucleoside Ara-A (vidarabine) isolated from sponge Tethya crypta. It inhibits viral DNA polymerase and DNA synthesis of herpes, vaccinica and varicella zoster viruses. However due to the discovery of new types of viruses and emergence of drug resistant strains, it is necessary to develop new antiviral lead compounds continuously. Several sponge derived antiviral lead compounds which are hoped to be developed as future drugs are discussed in this review. Supply problems are usually the major bottleneck to the development of these compounds as drugs during clinical trials. However advances in the field of metagenomics and high throughput microbial cultivation has raised the possibility that these techniques could lead to the cost-effective large scale production of such compounds. Perspectives on biotechnological methods with respect to marine drug development are also discussed.

Organic compounds in radiation fogs in Davis (California)

NASA Astrophysics Data System (ADS)

Herckes, Pierre; Hannigan, Michael P.; Trenary, Laurie; Lee, Taehyoung; Collett, Jeffrey L.

New stainless steel active fogwater collectors were designed and used in Davis (CA, USA) to collect fogwater for the speciation of organic matter. Organic compounds in fog samples were extracted by liquid-liquid extraction and analyzed by gas chromatography coupled to mass spectrometry. Numerous organic compounds, including various alkanes, polycyclic aromatic hydrocarbons (PAH) and alkanoic acids, have been identified in the fogwater samples. Higher molecular weight (MW) compounds are preferentially associated with an insoluble phase inside the fog drops, whereas lower molecular weight and more polar compounds are found predominantly in the dissolved phase. Concentrations in the dissolved phase were sometimes much higher than estimated by the compounds' aqueous solubilities.

VOLATILE ORGANIC COMPOUNDS (VOCS) CHAPTER 31.

EPA Science Inventory

The term "volatile organic compounds' (VOCs) was originally coined to refer, as a class, to carbon-containing chemicals that participate in photochemical reactions in the ambient (outdoor) are. The regulatory definition of VOCs used by the U.S. EPA is: Any compound of carbon, ex...

Ambient Air Monitoring for Sulfur Compounds

ERIC Educational Resources Information Center

Forrest, Joseph; Newman, Leonard

1973-01-01

A literature review of analytical techniques available for the study of compounds at low concentrations points up some of the areas where further research is needed. Compounds reviewed are sulfur dioxide, sulfuric acid, ammonium sulfate and bisulfate, metal sulfates, hydrogen sulfide, and organic sulfides. (BL)

Biodegradable compounds: Rheological, mechanical and thermal properties

NASA Astrophysics Data System (ADS)

Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.

2015-12-01

Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

Basics of Compounding: Hot Melt Extrusion.

PubMed

DePasquale, Seth

2017-01-01

Hot Melt Extrusion, a production process that has been around for quite some time, has the ability to produce innovative compounds not previously achievable with conventional methods. However, many variables need to be considered prior to production. The use of small-scale extruders and 3D printers provides compounders a pathway for developing new dosage forms at a minimal cost while initial research is being completed. This article discusses the uses of Hot Melt Extrusion, the equipment used, the current and future applications, and the challenges with the technology. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Independent Community Pharmacists' Perspectives on Compounding in Contemporary Pharmacy Education

PubMed Central

McPherson, Timothy B.; Fontane, Patrick E.; Berry, Tricia; Chereson, Rasma; Bilger, Rhonda

2009-01-01

Objectives To identify compounding practices of independent community pharmacy practitioners in order to make recommendations for the development of curricular objectives for doctor of pharmacy (PharmD) programs. Methods Independent community practitioners were asked about compounding regarding their motivations, common activities, educational exposures, and recommendations for PharmD education. Results Most respondents (69%) accepted compounding as a component of pharmaceutical care and compounded dermatological preparations for local effects, oral solutions, and suspensions at least once a week. Ninety-five percent were exposed to compounding in required pharmacy school courses and most (98%) who identified compounding as a professional service offered in their pharmacy sought additional postgraduate compounding education. Regardless of the extent of compounding emphasis in the practices surveyed, 84% stated that PharmD curricula should include compounding. Conclusions Pharmacy schools should define compounding curricular objectives and develop compounding abilities in a required laboratory course to prepare graduates for pharmaceutical care practice. PMID:19564997

COMPLEX RUTHENIUM ACIDO-NITROS COMPOUNDS (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zvyagintsev, O.E.; Starostin, S.M.

1961-06-01

The chemical nature of the water in the complex ruthenium acidonitroso compounds is studied by measuring certain acid properties, reactions, and behaviors of the compounds in aqueous solution. The dependence of molecular electrical conductivity on time and dilution, variations of specific electroconductivity, the optical density, and the light absorption of the compounds at 200 to 800 m mu wave range were investigated and the dissociation constants were calculated. (R.V.J.)

A Database for Compounding Stress Intensity Factors.

DTIC Science & Technology

1985-04-01

8217"’.’’" . ." ’" " " " "".. .... .... .... . .. .... . : ,.’. .. MICROCOP RE O UT O ," EST CHART...8217 - .. . , ., . . ,. . .,\\ .- . , , . -, . .- . . . , * TR 85046 o UNLIMITED __ ROYAL AIRCRAFT ESTABLISHMENT O Technical Report 85046 April 1985 A DATABASE FOR COMPOUNDING STRESS INTENSITY FACTORS L W by...DATABASE FOR COMPOUNDING STRESS INTENSITY FACTORS by A. M. Prior . ..- - . .. _ D. P. Rooke D. J. Cartwright* SUMMARY . The compounding method enables

Two new compounds from Ganoderma lucidum.

PubMed

Wang, Xin-Fang; Yan, Yong-Ming; Wang, Xin-Long; Ma, Xiu-Jing; Fu, Xue-Yan; Cheng, Yong-Xian

2015-01-01

Two pairs of new enantiomers, lucidulactones A and B (1 and 2), and two known compounds were isolated from Ganoderma lucidum. Their structures were determined by means of spectroscopic methods. The chiral HPLC was used to separate the ( - )- and (+)-antipodes of the new compounds.

High-Temperature Syntheses of New, Thermally-Stable Chemical Compounds.

DTIC Science & Technology

SYNTHESIS(CHEMISTRY), HEAT RESISTANT PLASTICS, NITRILES, FLUORINE COMPOUNDS, COMPLEX COMPOUNDS, NITROGEN, SULFIDES, ORGANOMETALLIC COMPOUNDS, ORGANOBORANES, BORIDES, SPINEL, CARBIDES, NITRIDES, SILICIDES .

Halogenated compounds from marine algae.

PubMed

Cabrita, Maria Teresa; Vale, Carlos; Rauter, Amélia Pilar

2010-08-09

Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds.

Halogenated Compounds from Marine Algae

PubMed Central

Cabrita, Maria Teresa; Vale, Carlos; Rauter, Amélia Pilar

2010-01-01

Marine algae produce a cocktail of halogenated metabolites with potential commercial value. Structures exhibited by these compounds go from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for a few decades, however other properties, such as antifouling, are not to be discarded. Many compounds were discovered in the last years, although the need for new drugs keeps this field open as many algal species are poorly screened. The ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to comprehending biodiversity. Furthermore, understanding interactions between halogenated compound production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research of halogenated metabolites has been more focused on macroalgae than on phytoplankton. However, phytoplankton could be a very promising material since it is the base of the marine food chain with quick adaptation to environmental changes, which undoubtedly has consequences on secondary metabolism. This paper reviews recent progress on this field and presents trends on the role of marine algae as producers of halogenated compounds. PMID:20948909

Bioactive compounds from Peperomia pellucida.

PubMed

Xu, Su; Li, Na; Ning, Meng-Meng; Zhou, Cai-Hong; Yang, Qiao-Rong; Wang, Ming-Wei

2006-02-01

Five new compounds (1-5), including two secolignans, two tetrahydrofuran lignans, and one highly methoxylated dihydronaphthalenone, were isolated from the whole plant of Peperomia pellucida. These compounds were accompanied by the known peperomins A, B, C, and E, 7,8-trans-8,8'-trans-7',8'-cis-7,7'-bis(5-methoxy-3,4-methylenedioxyphenyl)-8-acetoxymethyl-8'-hydroxymethyltetrahydrofuran, 7,8-trans-8,8'-trans-7',8'-cis-7-(5-methoxy-3,4-methylenedioxyphenyl)-7'-(4-hydroxy-3,5-dimethoxyphenyl)-8,8'-diacetoxymethyltetrahydrofuran, sesamin, and isoswertisin. New structures were elucidated mainly by NMR and MS techniques, and anticancer activities evaluated in HL-60, MCF-7, and HeLa cell lines. Compound 1 and peperomin E show growth inhibitory effects on the three cancer cell lines with IC(50) values ranging between 1.4 and 9.1 and between 1.8 and 11.1 microM, respectively. Compound 2 has a weak suppressive activity on HL-60 cells (IC(50) = 10.8 microM), while 7,8-trans-8,8'-trans-7',8'-cis-7,7'-bis(5-methoxy-3,4-methylenedioxyphenyl)-8-acetoxymethyl-8'-hydroxymethyltetrahydrofuran exhibits estrogen-like properties (EC(50) = 3.1 microM) in CV-1 cells transfected with human estrogen receptor (ERalpha).

Production method for making rare earth compounds

DOEpatents

McCallum, R.W.; Ellis, T.W.; Dennis, K.W.; Hofer, R.J.; Branagan, D.J.

1997-11-25

A method of making a rare earth compound, such as a earth-transition metal permanent magnet compound, without the need for producing rare earth metal as a process step, comprises carbothermically reacting a rare earth oxide to form a rare earth carbide and heating the rare earth carbide, a compound-forming reactant (e.g., a transition metal and optional boron), and a carbide-forming element (e.g., a refractory metal) that forms a carbide that is more thermodynamically favorable than the rare earth carbide whereby the rare earth compound (e.g., Nd{sub 2}Fe{sub 14}B or LaNi{sub 5}) and a carbide of the carbide-forming element are formed.

Production method for making rare earth compounds

DOEpatents

McCallum, R. William; Ellis, Timothy W.; Dennis, Kevin W.; Hofer, Robert J.; Branagan, Daniel J.

1997-11-25

A method of making a rare earth compound, such as a earth-transition metal permanent magnet compound, without the need for producing rare earth metal as a process step, comprises carbothermically reacting a rare earth oxide to form a rare earth carbide and heating the rare earth carbide, a compound-forming reactant (e.g. a transition metal and optional boron), and a carbide-forming element (e.g. a refractory metal) that forms a carbide that is more thermodynamically favorable than the rare earth carbide whereby the rare earth compound (e.g. Nd.sub.2 Fe.sub.14 B or LaNi.sub.5) and a carbide of the carbide-forming element are formed.

Site preferences of actinide cations in [NZP] compounds

NASA Astrophysics Data System (ADS)

Hawkins, H. T.; Spearing, D. R.; Smith, D. M.; Hampel, F. G.; Veirs, D. K.; Scheetz, B. E.

2000-07-01

Compounds adopting the sodium dizirconium tris(phosphate) (NaZr2(PO4)3) structure type belong to the [NZP] structural family of compounds. [NZP] compounds possess desirable properties that would permit their application as hosts for the actinides. These properties include compositional flexibility (i.e., three structural sites that can accommodate a variety of different cations), high thermal stability, negligible thermal expansion, and resistance to radiation damage. Experimental data indicate that [NZP] compounds resist dissolution and release of constituents over a wide range of experimental conditions. Moreover, [NZP] compounds may be synthesized by both conventional and novel methods and may be heat treated or sintered at modest temperatures (800 °C-1350 °C) in open or restricted systems.

Phyllosphere Methylobacterium bacteria contain UVA-absorbing compounds.

PubMed

Yoshida, Shigenobu; Hiradate, Syuntaro; Koitabashi, Motoo; Kamo, Tsunashi; Tsushima, Seiya

2017-02-01

Microbes inhabiting the phyllosphere encounter harmful ultraviolet rays, and must develop adaptive strategies against this irradiation. In this study, we screened bacterial isolates originating from the phyllosphere of various plants which harbored absorbers of ultraviolet A (UVA), a wavelength range which is recognized as harmful to human skin. Of the 200 phyllosphere bacterial isolates we screened, methanol extracts from bacterial cells of seventeen isolates absorbed wavelengths in the range of 315-400nm. All of the UVA-absorbing strains belonged to Methylobacterium species based on 16S ribosomal RNA gene sequences, suggesting that cells of this bacterial genus contain specific UVA-absorbing compounds. When cells of a representative Methylobacterium strain were extracted using various solvents, UVA absorption was observed in the extracts obtained using several aqueous solvents, indicating that the UVA-absorbing compounds were highly polar. A compound was purified using solid columns and HPLC separation, and comparative analysis revealed that the absorption strength and spectrum of the compound were similar to those of the known UVA filter, avobenzone. The compound was also verified to be stable under UVA exposure for at least 480min. Based on these results, the UVA-absorbing compound harbored by Methylobacterium has potential to be used as a novel sunscreen ingredient. Copyright © 2016 Elsevier B.V. All rights reserved.

BitterDB: a database of bitter compounds

PubMed Central

Wiener, Ayana; Shudler, Marina; Levit, Anat; Niv, Masha Y.

2012-01-01

Basic taste qualities like sour, salty, sweet, bitter and umami serve specific functions in identifying food components found in the diet of humans and animals, and are recognized by proteins in the oral cavity. Recognition of bitter taste and aversion to it are thought to protect the organism against the ingestion of poisonous food compounds, which are often bitter. Interestingly, bitter taste receptors are expressed not only in the mouth but also in extraoral tissues, such as the gastrointestinal tract, indicating that they may play a role in digestive and metabolic processes. BitterDB database, available at http://bitterdb.agri.huji.ac.il/bitterdb/, includes over 550 compounds that were reported to taste bitter to humans. The compounds can be searched by name, chemical structure, similarity to other bitter compounds, association with a particular human bitter taste receptor, and so on. The database also contains information on mutations in bitter taste receptors that were shown to influence receptor activation by bitter compounds. The aim of BitterDB is to facilitate studying the chemical features associated with bitterness. These studies may contribute to predicting bitterness of unknown compounds, predicting ligands for bitter receptors from different species and rational design of bitterness modulators. PMID:21940398

Extemporaneous compounding in veterinary practice: a New Zealand perspective.

PubMed

Gargiulo, D A; Chemal, C; Joda, L; Lee, Y J; Pilkington, M; Haywood, A; Garg, S

2013-11-01

The aims of this study were to explore the extent of extemporaneous compounding in veterinary centres throughout New Zealand and to determine whether pharmacists could collaborate with veterinarians to improve this service in New Zealand. Questionnaires were sent to 200 randomly selected veterinarians in New Zealand. Semi-structured interviews were also conducted with selected participants from four animal facilities (zoos, research facilities and animal shelters) and two compounding pharmacies. Of the 200 veterinarian questionnaire recipients, 99 responded. Ten replies were withdrawn from the study giving a response rate of 44.5%. Of these 89, 33 (37%) compounded in their practice. Of the 33 compounding professionals, 3 (9%) compounded daily for animals under their care; 11 (34%) weekly, 18 (54%) monthly and 1 (3%) compounded yearly. Compounding was done by 29/33 (88%) veterinarians, 16/33 (48%) veterinary nurses or 6/33 (18%) others. It was carried out due to the unavailability of commercial products, or the need for dose adjustment to ease administration or improve compliance. The animals most commonly requiring veterinary compounding were dogs (21/33; 64%), cats (19/33; 58%) or cattle (15/33; 46%). Products which were commonly compounded included cyclosporin eye drops, methimazole gels and potassium bromide solutions. Issues commonly faced when compounding included unavailability of dosage forms (18/33; 55%) or appropriate ingredients (14/33; 42%), stability (12/33; 36%), time constraints (10/33; 30%) or unavailability of equipment (9/33; 27%). Reasons given for not compounding included medicines being commercially available (38/56; 68%), pharmacy compounding for those particular practices (24/56; 43%), lack of training (21/56; 38%), ingredients (16/56; 29%) or equipment (15/56; 11%). All participants who worked with a pharmacist (11/33; 33%) described this relationship as beneficial and indicated they would continue to do so in the future. Veterinary

Electronic properties of hybrid Cu2S/Ru semiconductor/metallic-cage nanoparticles.

PubMed

Bekenstein, Yehonadav; Vinokurov, Kathy; Banin, Uri; Millo, Oded

2012-12-21

Hybrid inorganic nanoparticles, comprising a semiconducting Cu(2)S quantum-dot (QD) core encapsulated by a metallic Ru cage-like shell, and each of their individual components, are studied via scanning tunneling spectroscopy. Bare Cu(2)S QDs show nearly identical semiconducting-like I-V characteristics while the empty Ru cages exhibit single electron tunneling effects-the Coulomb blockade and staircase. Surprisingly, in some cases negative differential conductance features, with periodicity that correlates to the Coulomb staircase, were observed. The tunneling spectra measured on the hybrid QDs varies greatly along a single particle, manifesting synergetic electrical properties that originate from this unique semiconducting-metallic interface.

Magnesium compounds

USGS Publications Warehouse

Kramer, D.A.

2003-01-01

Seawater and natural brines accounted for about 60 percent of U.S. magnesium compounds production during 2002. Dead-burned and caustic-calcined magnesias were recovered from seawater by Premier Chemicals in Florida. They were also recovered from well brines in Michigan by Dow Chemical, Martin Marietta Magnesia Specialties and Rohm & Haas. And they were recovered from magnesite in Nevada by Premier Chemicals.

Reading compounds in neglect dyslexia: the headedness effect.

PubMed

Semenza, Carlo; Arcara, Giorgio; Facchini, Silvia; Meneghello, Francesca; Ferraro, Marco; Passarini, Laura; Pilosio, Cristina; Vigato, Giovanna; Mondini, Sara

2011-09-01

Reading compound words was studied in neglect dyslexia in order to assess the influence of 'headedness'. The 'head' of a compound is the component that determines the grammatical category, the syntactic (e.g., the gender) and the semantic properties of the compound as a whole. For example, in the word 'blackberry'berry is the compound's head. The question was addressed of whether or not the privileged status of the head constituent influences processing and determines behavioural patterns in the breakdown of spatial attention in neglect. Italian right-headed (e.g. capobanda, band leader) and left-headed compounds (e.g. astronave, spaceship) were administered to 18 participants affected by neglect dyslexia. Left-headed compounds were read better than right-headed compounds. This result was not due to factors such as frequency, familiarity, age of acquisition or imageability, since these effects were controlled. It is suggested that attention is captured by the head component after implicit reading of the whole word. The head would require a relatively lighter processing load than the modifier and benefit from top-down facilitation. Copyright © 2011 Elsevier Ltd. All rights reserved.

Human biological monitoring of suspected endocrine-disrupting compounds

PubMed Central

Faniband, Moosa; Lindh, Christian H; Jönsson, Bo AG

2014-01-01

Endocrine-disrupting compounds are exogenous agents that interfere with the natural hormones of the body. Human biological monitoring is a powerful method for monitoring exposure to endocrine disrupting compounds. In this review, we describe human biological monitoring systems for different groups of endocrine disrupting compounds, polychlorinated biphenyls, brominated flame retardants, phthalates, alkylphenols, pesticides, metals, perfluronated compounds, parabens, ultraviolet filters, and organic solvents. The aspects discussed are origin to exposure, metabolism, matrices to analyse, analytical determination methods, determinants, and time trends. PMID:24369128

Antibacterial and Antifungal Compounds from Marine Fungi

PubMed Central

Xu, Lijian; Meng, Wei; Cao, Cong; Wang, Jian; Shan, Wenjun; Wang, Qinggui

2015-01-01

This paper reviews 116 new compounds with antifungal or antibacterial activities as well as 169 other known antimicrobial compounds, with a specific focus on January 2010 through March 2015. Furthermore, the phylogeny of the fungi producing these antibacterial or antifungal compounds was analyzed. The new methods used to isolate marine fungi that possess antibacterial or antifungal activities as well as the relationship between structure and activity are shown in this review. PMID:26042616

Why Become Pharmacy Compounding Accreditation Board Accredited?

PubMed

Dillon, L Rad

2016-01-01

The Pharmacy Compounding Accreditation Board's goal is to assist pharmacies to obtain formal recognition of their status as a high-quality and fully compliant provider of pharmaceuticals and patient services. This article provides a brief outline of the application process, the survey preparation, points of information about the actual survey, and suggestions on how to remain in compliance with Pharmacy Compounding Accreditation Board's standards. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Method for conversion of .beta.-hydroxy carbonyl compounds

DOEpatents

Lilga, Michael A.; White, James F.; Holladay, Johnathan E.; Zacher, Alan H.; Muzatko, Danielle S.; Orth, Rick J.

2010-03-30

A process is disclosed for conversion of salts of .beta.-hydroxy carbonyl compounds forming useful conversion products including, e.g., .alpha.,.beta.-unsaturated carbonyl compounds and/or salts of .alpha.,.beta.-unsaturated carbonyl compounds. Conversion products find use, e.g., as feedstock and/or end-use chemicals.

Hexavalent Chromium Compounds

Cancer.gov

Learn about chromium, exposure to which can increase your risk of lung cancer and cancer of the paranasal sinuses and nasal cavity. Hexavalent chromium compounds have been used as corrosion inhibitors in a wide variety of products and processes.

Experience with compound words influences their processing: An eye movement investigation with English compound words.

PubMed

Juhasz, Barbara J

2016-11-14

Recording eye movements provides information on the time-course of word recognition during reading. Juhasz and Rayner [Juhasz, B. J., & Rayner, K. (2003). Investigating the effects of a set of intercorrelated variables on eye fixation durations in reading. Journal of Experimental Psychology: Learning, Memory and Cognition, 29, 1312-1318] examined the impact of five word recognition variables, including familiarity and age-of-acquisition (AoA), on fixation durations. All variables impacted fixation durations, but the time-course differed. However, the study focused on relatively short, morphologically simple words. Eye movements are also informative for examining the processing of morphologically complex words such as compound words. The present study further examined the time-course of lexical and semantic variables during morphological processing. A total of 120 English compound words that varied in familiarity, AoA, semantic transparency, lexeme meaning dominance, sensory experience rating (SER), and imageability were selected. The impact of these variables on fixation durations was examined when length, word frequency, and lexeme frequencies were controlled in a regression model. The most robust effects were found for familiarity and AoA, indicating that a reader's experience with compound words significantly impacts compound recognition. These results provide insight into semantic processing of morphologically complex words during reading.

Boron-containing amino carboxylic acid compounds and uses thereof

DOEpatents

Kabalka, George W.; Srivastava, Rajiv R.

2000-03-14

Novel compounds which are useful for boron neutron capture therapy (BNCT) are disclosed. The compounds comprise a stable boron-containing group and an aminocycloalkane carboxylic acid group or a boronated acyclic hydrocarbon-linked amino carboxylic acid. Methods for synthesis of the compounds and for use of the compounds in BNCT are disclosed.

Device for collecting chemical compounds and related methods

DOEpatents

Scott, Jill R.; Groenewold, Gary S.; Rae, Catherine

2013-01-01

A device for sampling chemical compounds from fixed surfaces and related methods are disclosed. The device may include a vacuum source, a chamber and a sorbent material. The device may utilize vacuum extraction to volatilize the chemical compounds from the fixed surfaces so that they may be sorbed by the sorbent material. The sorbent material may then be analyzed using conventional thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) instrumentation to determine presence of the chemical compounds. The methods may include detecting release and presence of one or more chemical compounds and determining the efficacy of decontamination. The device may be useful in collection and analysis of a variety of chemical compounds, such as residual chemical warfare agents, chemical attribution signatures and toxic industrial chemicals.

Chemical effect on diffusion in intermetallic compounds

NASA Astrophysics Data System (ADS)

Chen, Yi-Ting

With the trend of big data and the Internet of things, we live in a world full of personal electronic devices and small electronic devices. In order to make the devices more powerful, advanced electronic packaging such as wafer level packaging or 3D IC packaging play an important role. Furthermore, ?-bumps, which connect silicon dies together with dimension less than 10 ?m, are crucial parts in advanced packaging. Owing to the dimension of ?-bumps, they transform into intermetallic compound from tin based solder after the liquid state bonding process. Moreover, many new reliability issues will occur in electronic packaging when the bonding materials change; in this case, we no longer have tin based solder joint, instead, we have intermetallic compound ?-bumps. Most of the potential reliability issues in intermetallic compounds are caused by the chemical reactions driven by atomic diffusion in the material; thus, to know the diffusivities of atoms inside a material is significant and can help us to further analyze the reliability issues. However, we are lacking these kinds of data in intermetallic compound because there are some problems if used traditional Darken's analysis. Therefore, we considered Wagner diffusivity in our system to solve the problems and applied the concept of chemical effect on diffusion by taking the advantage that large amount of energy will release when compounds formed. Moreover, by inventing the holes markers made by Focus ion beam (FIB), we can conduct the diffusion experiment and obtain the tracer diffusivities of atoms inside the intermetallic compound. We applied the technique on Ni3Sn4 and Cu3Sn, which are two of the most common materials in electronic packaging, and the tracer diffusivities are measured under several different temperatures; moreover, microstructure of the intermetallic compounds are investigated to ensure the diffusion environment. Additionally, the detail diffusion mechanism was also discussed in aspect of diffusion

A first principles study on newly proposed (Ca/Sr/Ba)Fe2Bi2 compounds with their parent compounds

NASA Astrophysics Data System (ADS)

Sundareswari, M.; Jayalakshmi, D. S.; Viswanathan, E.

2016-02-01

The structural, electronic, bonding and magnetic properties of newly proposed iron-based compounds viz., CaFe2Bi2, SrFe2Bi2, BaFe2Bi2 with their Fermi surface topology are reported here for the first time by means of first principles calculation. All these properties of newly proposed compounds are compared and analysed along with their respective parent compounds namely (Ca,Sr,Ba)Fe2As2.

Toxicity prediction of compounds from turmeric (Curcuma longa L).

PubMed

Balaji, S; Chempakam, B

2010-10-01

Turmeric belongs to the ginger family Zingiberaceae. Currently, cheminformatics approaches are not employed in any of the spices to study the medicinal properties traditionally attributed to them. The aim of this study is to find the most efficacious molecule which does not have any toxic effects. In the present study, toxicity of 200 chemical compounds from turmeric were predicted (includes bacterial mutagenicity, rodent carcinogenicity and human hepatotoxicity). The study shows out of 200 compounds, 184 compounds were predicted as toxigenic, 136 compounds are mutagenic, 153 compounds are carcinogenic and 64 compounds are hepatotoxic. To cross validate our results, we have chosen the popular curcumin and found that curcumin and its derivatives may cause dose dependent hepatotoxicity. The results of these studies indicate that, in contrast to curcumin, few other compounds in turmeric which are non-mutagenic, non-carcinogenic, non-hepatotoxic, and do not have any side-effects. Hence, the cost-effective approach presented in this paper could be used to filter toxic compounds from the drug discovery lifecycle. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Micro-optical artificial compound eyes.

PubMed

Duparré, J W; Wippermann, F C

2006-03-01

Natural compound eyes combine small eye volumes with a large field of view at the cost of comparatively low spatial resolution. For small invertebrates such as flies or moths, compound eyes are the perfectly adapted solution to obtaining sufficient visual information about their environment without overloading their brains with the necessary image processing. However, to date little effort has been made to adopt this principle in optics. Classical imaging always had its archetype in natural single aperture eyes which, for example, human vision is based on. But a high-resolution image is not always required. Often the focus is on very compact, robust and cheap vision systems. The main question is consequently: what is the better approach for extremely miniaturized imaging systems-just scaling of classical lens designs or being inspired by alternative imaging principles evolved by nature in the case of small insects? In this paper, it is shown that such optical systems can be achieved using state-of-the-art micro-optics technology. This enables the generation of highly precise and uniform microlens arrays and their accurate alignment to the subsequent optics-, spacing- and optoelectronics structures. The results are thin, simple and monolithic imaging devices with a high accuracy of photolithography. Two different artificial compound eye concepts for compact vision systems have been investigated in detail: the artificial apposition compound eye and the cluster eye. Novel optical design methods and characterization tools were developed to allow the layout and experimental testing of the planar micro-optical imaging systems, which were fabricated for the first time by micro-optics technology. The artificial apposition compound eye can be considered as a simple imaging optical sensor while the cluster eye is capable of becoming a valid alternative to classical bulk objectives but is much more complex than the first system.

46 CFR 153.1025 - Motor fuel antiknock compounds.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Motor fuel antiknock compounds. 153.1025 Section 153... Cargo Procedures § 153.1025 Motor fuel antiknock compounds. (a) No person may load or carry any other cargo in a containment system approved for motor fuel antiknock compounds containing lead alkyls except...

46 CFR 153.1025 - Motor fuel antiknock compounds.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Motor fuel antiknock compounds. 153.1025 Section 153... Cargo Procedures § 153.1025 Motor fuel antiknock compounds. (a) No person may load or carry any other cargo in a containment system approved for motor fuel antiknock compounds containing lead alkyls except...

46 CFR 153.1025 - Motor fuel antiknock compounds.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Motor fuel antiknock compounds. 153.1025 Section 153... Cargo Procedures § 153.1025 Motor fuel antiknock compounds. (a) No person may load or carry any other cargo in a containment system approved for motor fuel antiknock compounds containing lead alkyls except...

Cannabinoid-like anti-inflammatory compounds from flax fiber.

PubMed

Styrczewska, Monika; Kulma, Anna; Ratajczak, Katarzyna; Amarowicz, Ryszard; Szopa, Jan

2012-09-01

Flax is a valuable source of fibers, linseed and oil. The compounds of the latter two products have already been widely examined and have been proven to possess many health-beneficial properties. In the course of analysis of fibers extract from previously generated transgenic plants overproducing phenylpropanoids a new terpenoid compound was discovered.The UV spectra and the retention time in UPLC analysis of this new compound reveal similarity to a cannabinoid-like compound, probably cannabidiol (CBD). This was confirmed by finding two ions at m/z 174.1 and 231.2 in mass spectra analysis. Further confirmation of the nature of the compound was based on a biological activity assay. It was found that the compound affects the expression of genes involved in inflammatory processes in mouse and human fibroblasts and likely the CBD from Cannabis sativa activates the specific peripheral cannabinoid receptor 2 (CB2) gene expression. Besides fibers, the compound was also found in all other flax tissues. It should be pointed out that the industrial process of fabric production does not affect CBD activity.The presented data suggest for the first time that flax products can be a source of biologically active cannabinoid-like compounds that are able to influence the cell immunological response. These findings might open up many new applications for medical flax products, especially for the fabric as a material for wound dressing with anti-inflammatory properties.

Organometallic compounds: an opportunity for chemical biology?

PubMed

Patra, Malay; Gasser, Gilles

2012-06-18

Organometallic compounds are renowned for their remarkable applications in the field of catalysis, but much less is known about their potential in chemical biology. Indeed, such compounds have long been considered to be either unstable under physiological conditions or cytotoxic. As a consequence, little attention has been paid to their possible utilisation for biological purposes. Because of their outstanding physicochemical properties, which include chemical stability, structural diversity and unique photo- and electrochemical properties, however, organometallic compounds have the ability to play a leading role in the field of chemical biology. Indeed, remarkable examples of the use of such compounds-notably as enzyme inhibitors and as luminescent agents-have recently been reported. Here we summarise recent advances in the use of organometallic compounds for chemical biology purposes, an area that we define as "organometallic chemical biology". We also demonstrate that these recent discoveries are only a beginning and that many other organometallic complexes are likely to be found useful in this field of research in the near future. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for production of a borohydride compound

DOEpatents

Allen, Nathan Tait; Butterick, III, Robert; Chin, Arthur Achhing; Millar, Dean Michael; Molzahn, David Craig

2014-08-19

A process for production of a borohydride compound M(BH.sub.4).sub.y. The process has three steps. The first step combines a compound of formula (R.sup.1O).sub.yM with aluminum, hydrogen and a metallic catalyst containing at least one metal selected from the group consisting of titanium, zirconium, hafnium, niobium, vanadium, tantalum and iron to produce a compound of formula M(AlH.sub.3OR.sup.1).sub.y, wherein R.sup.1 is phenyl or phenyl substituted by at least one alkyl or alkoxy group; M is an alkali metal, Be or Mg; and y is one or two; wherein the catalyst is present at a level of at least 200 ppm based on weight of aluminum. The second step combines the compound of formula M(AlH.sub.3OR.sup.1).sub.y with a borate, boroxine or borazine compound to produce M(BH.sub.4).sub.y and a byproduct mixture containing alkali metal and aluminum aryloxides. The third step separates M(BH.sub.4).sub.y from the byproduct mixture.

Nonaminoglycoside compounds induce readthrough of nonsense mutations

PubMed Central

Damoiseaux, Robert; Nahas, Shareef; Gao, Kun; Hu, Hailiang; Pollard, Julianne M.; Goldstine, Jimena; Jung, Michael E.; Henning, Susanne M.; Bertoni, Carmen

2009-01-01

Large numbers of genetic disorders are caused by nonsense mutations for which compound-induced readthrough of premature termination codons (PTCs) might be exploited as a potential treatment strategy. We have successfully developed a sensitive and quantitative high-throughput screening (HTS) assay, protein transcription/translation (PTT)–enzyme-linked immunosorbent assay (ELISA), for identifying novel PTC-readthrough compounds using ataxia-telangiectasia (A-T) as a genetic disease model. This HTS PTT-ELISA assay is based on a coupled PTT that uses plasmid templates containing prototypic A-T mutated (ATM) mutations for HTS. The assay is luciferase independent. We screened ∼34,000 compounds and identified 12 low-molecular-mass nonaminoglycosides with potential PTC-readthrough activity. From these, two leading compounds consistently induced functional ATM protein in ATM-deficient cells containing disease-causing nonsense mutations, as demonstrated by direct measurement of ATM protein, restored ATM kinase activity, and colony survival assays for cellular radiosensitivity. The two compounds also demonstrated readthrough activity in mdx mouse myotube cells carrying a nonsense mutation and induced significant amounts of dystrophin protein. PMID:19770270

Tritium labeling of organic compounds deposited on porous structures

DOEpatents

Ehrenkaufer, Richard L. E.; Wolf, Alfred P.; Hembree, Wylie C.

1979-01-01

An improved process for labeling organic compounds with tritium is carried out by depositing the selected compound on the extensive surface of a porous structure such as a membrane filter and exposing the membrane containing the compound to tritium gas activated by the microwave discharge technique. The labeled compound is then recovered from the porous structure.

Magnesium compounds

USGS Publications Warehouse

Kramer, D.A.

2006-01-01

In 2005, seawater and natural brines accounted for 51% of US magnesium compounds production. World magnesia production was estimated to be 14.5 Mt. Most of the production came from China, North Korea, Russia and Turkey. Although no specific production figures are available, Japan and the United States are estimated to account for almost one-half of the world's capacity from seawater and brines.

Antimalarial compounds in Phase II clinical development.

PubMed

Held, Jana; Jeyaraj, Sankarganesh; Kreidenweiss, Andrea

2015-03-01

Malaria is a major health problem in endemic countries and chemotherapy remains the most important tool in combating it. Treatment options are limited and essentially rely on a single drug class - the artemisinins. Efforts are ongoing to restrict the evolving threat of artemisinin resistance but declining sensitivity has been reported. Fueled by the ambitious aim of malaria eradication, novel antimalarial compounds, with improved properties, are now in the progressive phase of drug development. Herein, the authors describe antimalarial compounds currently in Phase II clinical development and present the results of these investigations. Thanks to recent efforts, a number of promising antimalarial compounds are now in the pipeline. First safety data have been generated for all of these candidates, although their efficacy as antimalarials is still unclear for most of them. Of particular note are KAE609, KAF156 and DSM265, which are of chemical scaffolds new to malaria chemotherapy and would truly diversify antimalarial options. Apart from SAR97276, which also has a novel chemical scaffold that has had its development stopped, all other compounds in the pipeline belong to already known substance classes, which have been chemically modified. At this moment in time, there is not one standout compound that will revolutionize malaria treatment but several compounds that will add to its control in the future.

The use of compound topical anesthetics: a review.

PubMed

Kravitz, Neal D

2007-10-01

The author reviewed the history of, federal regulations regarding, risks of and adverse drug reactions of five compound topical anesthetics: tetracaine, adrenaline/epinephrine and cocaine (TAC); lidocaine, adrenaline/epinephrine and tetracaine (LET); lidocaine, tetracaine and phenylephrine (TAC 20 percent Alternate); lidocaine, prilocaine and tetracaine (Profound); and lidocaine, prilocaine, tetracaine and phenylephrine with thickeners (Profound PET). The author reviewed clinical trials, case reports, descriptive articles, and U.S. Food and Drug Administration (FDA) regulations and recent public advisory warnings regarding the federal approval of and risks associated with the use of compound topical anesthetics. Compound topical anesthetics are neither FDA-regulated nor -unregulated. Some compounding pharmacies bypass the new FDA drug approval process, which is based on reliable scientific data and ensures that a marketed drug is safe, effective, properly manufactured and accurately labeled. Two deaths have been attributed to the lay use of compound topical anesthetics. In response, the FDA has announced the strengthening of its efforts against unapproved drug products. Compound topical anesthetics may be an effective alternative to local infiltration for some minimally invasive dental procedures; however, legitimate concerns exist in regard to their safety. Until they become federally regulated, compound topical anesthetics remain unapproved drug products whose benefits may not outweigh their risks for dental patients.

Polymers containing borane or carborane cage compounds and related applications

DOEpatents

Bowen, III, Daniel E; Eastwood, Eric A

2013-04-23

Polymers comprising residues of cage compound monomers having at least one polyalkoxy silyl substituent are provided. The cage compound monomers are selected from borane cage compound monomers comprising at least 7 cage atoms and/or carborane cage compound monomers comprising 7 to 11 cage compound monomers. Such polymers can further comprise one or more reactive matrices and/or co-monomers covalently bound with the cage compound monomer residues. Articles of manufacture comprising such polymers are also disclosed.

Biodegradation of Aromatic Compounds by Escherichia coli

PubMed Central

Díaz, Eduardo; Ferrández, Abel; Prieto, María A.; García, José L.

2001-01-01

Although Escherichia coli has long been recognized as the best-understood living organism, little was known about its abilities to use aromatic compounds as sole carbon and energy sources. This review gives an extensive overview of the current knowledge of the catabolism of aromatic compounds by E. coli. After giving a general overview of the aromatic compounds that E. coli strains encounter and mineralize in the different habitats that they colonize, we provide an up-to-date status report on the genes and proteins involved in the catabolism of such compounds, namely, several aromatic acids (phenylacetic acid, 3- and 4-hydroxyphenylacetic acid, phenylpropionic acid, 3-hydroxyphenylpropionic acid, and 3-hydroxycinnamic acid) and amines (phenylethylamine, tyramine, and dopamine). Other enzymatic activities acting on aromatic compounds in E. coli are also reviewed and evaluated. The review also reflects the present impact of genomic research and how the analysis of the whole E. coli genome reveals novel aromatic catabolic functions. Moreover, evolutionary considerations derived from sequence comparisons between the aromatic catabolic clusters of E. coli and homologous clusters from an increasing number of bacteria are also discussed. The recent progress in the understanding of the fundamentals that govern the degradation of aromatic compounds in E. coli makes this bacterium a very useful model system to decipher biochemical, genetic, evolutionary, and ecological aspects of the catabolism of such compounds. In the last part of the review, we discuss strategies and concepts to metabolically engineer E. coli to suit specific needs for biodegradation and biotransformation of aromatics and we provide several examples based on selected studies. Finally, conclusions derived from this review may serve as a lead for future research and applications. PMID:11729263

Formation of Stoichiometric CsFn Compounds

PubMed Central

Zhu, Qiang; Oganov, Artem R.; Zeng, Qingfeng

2015-01-01

Alkali halides MX, have been viewed as typical ionic compounds, characterized by 1:1 ratio necessary for charge balance between M+ and X−. It was proposed that group I elements like Cs can be oxidized further under high pressure. Here we perform a comprehensive study for the CsF-F system at pressures up to 100 GPa, and find extremely versatile chemistry. A series of CsFn (n ≥ 1) compounds are predicted to be stable already at ambient pressure. Under pressure, 5p electrons of Cs atoms become active, with growing tendency to form Cs (III) and (V) valence states at fluorine-rich conditions. Although Cs (II) and (IV) are not energetically favoured, the interplay between two mechanisms (polyfluoride anions and polyvalent Cs cations) allows CsF2 and CsF4 compounds to be stable under pressure. The estimated defluorination temperatures of CsFn (n = 2,3,5) compounds at atmospheric pressure (218°C, 150°C, -15°C, respectively), are attractive for fluorine storage applications. PMID:25608669

MICROBIAL METABOLISM OF AROMATIC COMPOUNDS I.

PubMed Central

Tabak, Henry H.; Chambers, Cecil W.; Kabler, Paul W.

1964-01-01

Tabak, Henry H. (Robert A. Taft Sanitary Engineering Center, Cincinnati, Ohio), Cecil W. Chambers, and Paul W. Kabler. Microbial metabolism of aromatic carbon compounds. I. Decomposition of phenolic compounds and aromatic hydrocarbons by phenol-adapted bacteria. J. Bacteriol. 87:910–919. 1964.—Bacteria from soil and related environments were selected or adapted to metabolize phenol, hydroxy phenols, nitrophenols, chlorophenols, methylphenols, alkylphenols, and arylphenols when cultured in mineral salts media with the specific substrate as the sole source of carbon. A phenol-adapted culture (substrate-induced enzyme synthesis proven) was challenged in respirometric tests with 104 related compounds; probable significant oxidative activity occurred with 65. Dihydric phenols were generally oxidized; trihydric phenols were not. Cresols and dimethylphenols were oxidized; adding a chloro group increased resistance. Benzoic and hydroxybenzoic acids were oxidized; sulfonated, methoxylated, nitro, and chlorobenzoic acids were not; m-toluic acid was utilized but not the o- and p-isomers. Benzaldehyde and p-hydroxybenzaldehyde were oxidized. In general, nitro- and chloro-substituted compounds and the benzenes were difficult to oxidize. PMID:14137630

Volatile sulphur compounds in UHT milk.

PubMed

Al-Attabi, Z; D'Arcy, B R; Deeth, H C

2009-01-01

Several volatile sulphur compounds have been detected in raw and processed milk. These are hydrogen sulphide, methanethiol, carbonyl sulphide, dimethyl sulphide, carbon disulphide, dimethyl disulphide, dimethyl trisulphide, dimethyl sulphoxide, and dimethyl sulphone. Many of these increase in milk during heat processing and are associated with the cooked flavor of heat-treated milks, particularly UHT and sterilized milk. Several researchers have attempted to explain the origin of these volatiles in both raw and processed milk, and how to reduce the associated cooked flavor that has a negative impact on consumer acceptability of processed milk. These compounds are difficult to detect and analyze due to their high volatility, sensitivity to oxidation and heat, and in some cases, their very low concentrations. However, methods of detection and quantification have improved in recent years. Pre-concentration methods such as solid phase microextraction (SPME) together with gas chromatography equipped with sulphur-selective detectors now enable low concentrations of these compounds to be analyzed. In this review, methods of extraction and analyzes of these volatile sulphur compounds are compared, and their occurrence in milk is reviewed.

Ab initio Thermal Transport in Compound Semiconductors

DTIC Science & Technology

2013-04-02

upper bound to the thermal conductivities of cubic aluminum-V, gallium -V, and indium-V compounds as limited by anharmonic phonon scattering. The effects...and GaP [red circles (Ref. 51) and red triangles (Ref. 52)]. B. Gallium -V compounds We previously presented results for κL and P for wurtzite GaN and...data was found. We used this approach to examine κL in aluminum-V, gallium -V, and indium-V compounds as well as the technologically important materials

Antiosteoporotic compounds from seeds of Cuscuta chinensis.

PubMed

Yang, Lijuan; Chen, Qianfeng; Wang, Fei; Zhang, Guolin

2011-05-17

The seeds of Cuscuta chinensis (Tu-Si-Zi, TSZ) have long been used for the treatment of osteoporosis in China and some Asian countries. The compounds in TSZ responsible for the antiosteoporotic activity are still poorly understood. The present study was designed to investigate the osteogenic compounds in TSZ, and to evaluate their antiosteoporotic effects in osteoblastic cells. Osteoblast-like UMR-106 cells were used for bioactivity-guided isolation of the active compounds. The activity of alkaline phosphatase (ALP) in UMR-106 cells was measured by p-nitrophenyl sodium phosphate assay. The proliferation of UMR-106 cells was assayed by Alamar-Blue method. Estrogenic activity of the extracts and isolated compounds was evaluated by activation of estrogen response element (ERE) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 5×ERE luciferase reporter plasmid. Antiestrogenic activity of the extracts and isolated compounds were evaluated by activation of activator protein-1 (AP-1) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 6×AP-1 luciferase reporter plasmid. ALP-guided fractionation led to the isolation of five known flavonoids, quercetin, kaempferol, isorhamnetin, hyperoside and astragalin from the crude ethanolic extract of TSZ. Further study showed that kaempferol and hyperoside significantly increased the ALP activity in UMR-106 cells. Astragalin promoted the proliferation of UMR-106 cells whereas other compounds had no such effect. The isolated compounds showed estrogenic activity but quercetin, kaempferol and isorhamnetin showed more potent ERβ agonist activity. However, compared with their ER agonist activity, only quercetin and kaempferol showed potent ER antagonist activity by activating ERα/β-mediated AP-1 reporter expression. Our findings validated the clinical use of TSZ in

Thin film Heusler compounds manganese nickel gallium

NASA Astrophysics Data System (ADS)

Jenkins, Catherine Ann

Multiferroic Heusler compounds Mn3--xNi xGa (x=0,1,2) have a tetragonal unit cell that can variously be used for magneto-mechanically coupled shape memory ( x=1,2) and spin-mechanical applications (x=0). The first fabrication of fully epitaxial thin films of these and electronically related compounds by sputtering is discussed. Traditional and custom lab characterization of the magnetic and temperature driven multiferroic behavior is augmented by more detailed synchrotron-based high energy photoemission spectroscopic techniques to describe the atomic and electronic structure. Integration of the MnNi2Ga magnetic shape memory compound in microwave patch antennas and active free-standing structures represents a fraction of the available and promising applications for these compounds. Prototype magnetic tunnel junctions are demonstrated by Mn3Ga electrodes with perpendicular anisotropy for spin torque transfer memory structures. The main body of the work concentrates on the definition and exploration of the material series Mn3--xNi xGa (x=0,1,2) and the relevant multiferroic phenomena exhibited as a function of preparation and external stimuli. Engineering results on each x=0,1,2 are presented with device prototypes where relevant. In the appendices the process of the materials design undertaken with the goal of developing new ternary intermetallics with enhanced properties is presented with a full exploration of the road from band structure calculations to device implementation. Cobalt based compounds in single crystal and nanoparticle form are fabricated with an eye to developing the production methods for new cobalt- and iron-based magnetic shape memory compounds for device applications in different forms. Mn2CoSn, a compound isolectronic and with similar atomic ordering to Mn2NiGa is experimentally determined to be a nearly half-metallic ferromagnet in contrast to the metallic ferrimagnetism in the parent compound. High energy photoemission spectroscopy is shown to

An Inhibitory Within-Compound Association Attenuates Overshadowing

PubMed Central

Amundson, Jeffrey C.; Pineño, Oskar; Witnauer, James E.; Miller, Ralph R.

2008-01-01

According to the comparator hypothesis (Miller & Matzel, 1988), cue competition depends on the association between a target stimulus (X) and a competing cue (e.g., an overshadowing cue [A]). Thus, it was expected that overshadowing would be reduced by establishing an inhibitory-like relationship between X and A before compound conditioning. In three lever press suppression experiments with rats, this expectation was supported. Experiment 1 showed that establishing an inhibitory X-A relationship reduced overshadowing. In Experiment 2, degrading the inhibitory-like relationship before conditioning allowed reinforced AX compound trials to result in overshadowing. Experiment 3 replicated the results of Experiment 2 when the inhibitory relationship was degraded after compound conditioning. The results support the view that within-compound associations are necessary not only for retrospective revaluation, but also for conventional cue competition. PMID:18248120

One Way to Design a Valence-Skip Compound.

PubMed

Hase, I; Yanagisawa, T; Kawashima, K

2017-12-01

Valence-skip compound is a good candidate with high T c and low anisotropy because it has a large attractive interaction at the site of valence-skip atom. However, it is not easy to synthesize such compound because of (i) the instability of the skipping valence state, (ii) the competing charge order, and (iii) that formal valence may not be true in some compounds. In the present study, we show several examples of the valence-skip compounds and discuss how we can design them by first principles calculations. Furthermore, we calculated the electronic structure of a promising candidate of valence skipping compound RbTlCl 3 from first principles. We confirmed that the charge-density wave (CDW) is formed in this compound, and the Tl atoms in two crystallographic different sites take the valence Tl 1+ and Tl 3+ . Structure optimization study reveals that this CDW is stable at the ambient pressure, while this CDW gap can be collapsed when we apply pressure with several gigapascals. In this metallic phase, we can expect a large charge fluctuation and a large electron-phonon interaction.

Boron and Compounds

Integrated Risk Information System (IRIS)

Boron and Compounds ; CASRN 7440 - 42 - 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 Assessments for Noncarcinoge

Zinc and Compounds

Integrated Risk Information System (IRIS)

Zinc and Compounds ; CASRN 7440 - 66 - 6 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 Assessments for Noncarcinogen

Beryllium and compounds

Integrated Risk Information System (IRIS)

EPA / 635 / R - 98 / 008 TOXICOLOGICAL REVIEW OF BERYLLIUM AND COMPOUNDS ( CAS No . 7440 - 41 - 7 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) April 1998 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed in ac

Selenium and Compounds

Integrated Risk Information System (IRIS)

Selenium and Compounds ; CASRN 7782 - 49 - 2 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 Assessments for Noncarcin

Indole compounds may be promising medicines for ulcerative colitis.

PubMed

Sugimoto, Shinya; Naganuma, Makoto; Kanai, Takanori

2016-09-01

Indole compounds are extracted from indigo plants and have been used as blue or purple dyes for hundreds of years. In traditional Chinese medicine, herbal agents in combination with Qing-Dai (also known as indigo naturalis) have been used to treat patients with ulcerative colitis (UC) and to remedy inflammatory conditions. Recent studies have noted that indole compounds can be biosynthesized from tryptophan metabolites produced by various enzymes derived from intestinal microbiota. In addition to their action on indole compounds, the intestinal microbiota produce various tryptophan metabolites that mediate critical functions through distinct pathways and enzymes. Furthermore, some indole compounds, such as indigo and indirubin, act as ligands for the aryl hydrocarbon receptor. This signaling pathway stimulates mucosal type 3 innate lymphoid cells to produce interleukin-22, which induces antimicrobial peptide and tight junction molecule production, suggesting a role for indole compounds during the mucosal healing process. Thus, indole compounds may represent a novel treatment strategy for UC patients. In this review, we describe the origin and function of this indole compound-containing Chinese herb, as well as the drug development of indole compounds.

Feasibility of Active Machine Learning for Multiclass Compound Classification.

PubMed

Lang, Tobias; Flachsenberg, Florian; von Luxburg, Ulrike; Rarey, Matthias

2016-01-25

A common task in the hit-to-lead process is classifying sets of compounds into multiple, usually structural classes, which build the groundwork for subsequent SAR studies. Machine learning techniques can be used to automate this process by learning classification models from training compounds of each class. Gathering class information for compounds can be cost-intensive as the required data needs to be provided by human experts or experiments. This paper studies whether active machine learning can be used to reduce the required number of training compounds. Active learning is a machine learning method which processes class label data in an iterative fashion. It has gained much attention in a broad range of application areas. In this paper, an active learning method for multiclass compound classification is proposed. This method selects informative training compounds so as to optimally support the learning progress. The combination with human feedback leads to a semiautomated interactive multiclass classification procedure. This method was investigated empirically on 15 compound classification tasks containing 86-2870 compounds in 3-38 classes. The empirical results show that active learning can solve these classification tasks using 10-80% of the data which would be necessary for standard learning techniques.

Neuroprotective compounds of Tilia amurensis

PubMed Central

Lee, Bohyung; Weon, Jin Bae; Eom, Min Rye; Jung, Youn Sik; Ma, Choong Je

2015-01-01

Background: Tilia amurensis (Tiliacese) has been used for anti-tumor and anti-inflammatory in Korea, China, and Japan. Objective: In this study, we isolated five compounds from T. amurensis and determined whether protected neuronal cells against glutamate-induced oxidative stress in HT22 cells. Materials and Methods: Compounds were isolated using chromatographic techniques including silica gel, Sephadex LH-20 open column and high performance liquid chromatography analysis, and evaluated neuroprotective effect in HT22 cells by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Results: β-D-fructofuranosyl α-D-glucopyranoside (1), (-)-epicatechin (2), nudiposide (3), lyoniside (4), and scopoletin (5) were isolated by bioactivity-guided fractionation from the ethyl acetate fraction of T. amurensis. Among them, (-)-epicatechin, nudiposide, lyoniside, and scopoletin had significant neuroprotective activities against glutamate-injured neurotoxicity in HT22 cells. Conclusion: These results demonstrated that compound two, three, four, and five have a pronounced protective effect against glutamate-induced neurotoxicity in HT22 cells. PMID:26664019

Separation of Biologically Active Compounds by Membrane Operations.

PubMed

Zhu, Xiaoying; Bai, Renbi

2017-01-01

Bioactive compounds from various natural sources have been attracting more and more attention, owing to their broad diversity of functionalities and availabilities. However, many of the bioactive compounds often exist at an extremely low concentration in a mixture so that massive harvesting is needed to obtain sufficient amounts for their practical usage. Thus, effective fractionation or separation technologies are essential for the screening and production of the bioactive compound products. The applicatons of conventional processes such as extraction, distillation and lyophilisation, etc. may be tedious, have high energy consumption or cause denature or degradation of the bioactive compounds. Membrane separation processes operate at ambient temperature, without the need for heating and therefore with less energy consumption. The "cold" separation technology also prevents the possible degradation of the bioactive compounds. The separation process is mainly physical and both fractions (permeate and retentate) of the membrane processes may be recovered. Thus, using membrane separation technology is a promising approach to concentrate and separate bioactive compounds. A comprehensive survey of membrane operations used for the separation of bioactive compounds is conducted. The available and established membrane separation processes are introduced and reviewed. The most frequently used membrane processes are the pressure driven ones, including microfiltration (MF), ultrafiltration (UF) and nanofiltration (NF). They are applied either individually as a single sieve or in combination as an integrated membrane array to meet the different requirements in the separation of bioactive compounds. Other new membrane processes with multiple functions have also been developed and employed for the separation or fractionation of bioactive compounds. The hybrid electrodialysis (ED)-UF membrane process, for example has been used to provide a solution for the separation of

Exploring monovalent copper compounds with oxygen and hydrogen

PubMed Central

Korzhavyi, Pavel A.; Soroka, Inna L.; Isaev, Eyvaz I.; Lilja, Christina; Johansson, Börje

2012-01-01

New important applications of copper metal, e.g., in the areas of hydrogen production, fuel cell operation, and spent nuclear fuel disposal, require accurate knowledge of the physical and chemical properties of stable and metastable copper compounds. Among the copper(I) compounds with oxygen and hydrogen, cuprous oxide Cu2O is the only one stable and the best studied. Other such compounds are less known (CuH) or totally unknown (CuOH) due to their instability relative to the oxide. Here we combine quantum-mechanical calculations with experimental studies to search for possible compounds of monovalent copper. Cuprous hydride (CuH) and cuprous hydroxide (CuOH) are proved to exist in solid form. We establish the chemical and physical properties of these compounds, thereby filling the existing gaps in our understanding of hydrogen- and oxygen-related phenomena in Cu metal. PMID:22219370

English Compound and Non-Compound Processing in Bilingual and Multilingual Speakers: Effects of Dominance and Sequential Multilingualism

ERIC Educational Resources Information Center

González Alonso, Jorge; Villegas, Julián; García Mayo, María del Pilar

2016-01-01

This article reports on a study investigating the relative influence of the first language and dominant language (L1) on second language (L2) and third language (L3) morpho-lexical processing. A lexical decision task compared the responses to English NV-er compounds (e.g. "taxi driver") and non-compounds provided by a group of native…

Barium and Compounds

Integrated Risk Information System (IRIS)

EPA / 635 / R - 05 / 001 www.epa.gov / iris TOXICOLOGICAL REVIEW OF BARIUM AND COMPOUNDS ( CAS No . 7440 - 39 - 3 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) March 1998 Minor revisions January 1999 Reference dose revised June 2005 U.S . Environmental Protec

Aminopropyl thiophene compounds

DOEpatents

Goodman, Mark M.; Knapp, Jr., Furn F.

1990-01-01

Radiopharmaceuticals useful in brain imaging comprising radiohalogenated thienylethylamine derivatives. The compounds are 5-halo-thiophene-2-isopropyl amines able to cross the blood-brain barrier and be retained for a sufficient length of time to allow the evaluation of regional blood flow by radioimaging of the brain.

Bioprospecting Sponge-Associated Microbes for Antimicrobial Compounds

PubMed Central

Indraningrat, Anak Agung Gede; Smidt, Hauke; Sipkema, Detmer

2016-01-01

Sponges are the most prolific marine organisms with respect to their arsenal of bioactive compounds including antimicrobials. However, the majority of these substances are probably not produced by the sponge itself, but rather by bacteria or fungi that are associated with their host. This review for the first time provides a comprehensive overview of antimicrobial compounds that are known to be produced by sponge-associated microbes. We discuss the current state-of-the-art by grouping the bioactive compounds produced by sponge-associated microorganisms in four categories: antiviral, antibacterial, antifungal and antiprotozoal compounds. Based on in vitro activity tests, identified targets of potent antimicrobial substances derived from sponge-associated microbes include: human immunodeficiency virus 1 (HIV-1) (2-undecyl-4-quinolone, sorbicillactone A and chartarutine B); influenza A (H1N1) virus (truncateol M); nosocomial Gram positive bacteria (thiopeptide YM-266183, YM-266184, mayamycin and kocurin); Escherichia coli (sydonic acid), Chlamydia trachomatis (naphthacene glycoside SF2446A2); Plasmodium spp. (manzamine A and quinolone 1); Leishmania donovani (manzamine A and valinomycin); Trypanosoma brucei (valinomycin and staurosporine); Candida albicans and dermatophytic fungi (saadamycin, 5,7-dimethoxy-4-p-methoxylphenylcoumarin and YM-202204). Thirty-five bacterial and 12 fungal genera associated with sponges that produce antimicrobials were identified, with Streptomyces, Pseudovibrio, Bacillus, Aspergillus and Penicillium as the prominent producers of antimicrobial compounds. Furthemore culture-independent approaches to more comprehensively exploit the genetic richness of antimicrobial compound-producing pathways from sponge-associated bacteria are addressed. PMID:27144573