Anomalous giant piezoresistance in AlAs 2D electron systems with antidot lattices.
Gunawan, O; Gokmen, T; Shkolnikov, Y P; De Poortere, E P; Shayegan, M
2008-01-25
An AlAs two-dimensional electron system patterned with an antidot lattice exhibits a giant piezoresistance effect at low temperatures, with a sign opposite to the piezoresistance observed in the unpatterned region. We suggest that the origin of this anomalous giant piezoresistance is the nonuniform strain in the antidot lattice and the exclusion of electrons occupying the two conduction-band valleys from different regions of the sample. This is analogous to the well-known giant magnetoresistance effect, with valley playing the role of spin and strain the role of magnetic field. PMID:18233015
Ballistic Transport in Graphene Antidot Lattices.
Sandner, Andreas; Preis, Tobias; Schell, Christian; Giudici, Paula; Watanabe, Kenji; Taniguchi, Takashi; Weiss, Dieter; Eroms, Jonathan
2015-12-01
The bulk carrier mobility in graphene was shown to be enhanced in graphene-boron nitride heterostructures. However, nanopatterning graphene can add extra damage and drastically degrade the intrinsic properties by edge disorder. Here we show that graphene embedded into a heterostructure with hexagonal boron nitride (hBN) on both sides is protected during a nanopatterning step. In this way, we can prepare graphene-based antidot lattices where the high mobility is preserved. We report magnetotransport experiments in those antidot lattices with lattice periods down to 50 nm. We observe pronounced commensurability features stemming from ballistic orbits around one or several antidots. Due to the short lattice period in our samples, we can also explore the boundary between the classical and the quantum transport regime, as the Fermi wavelength of the electrons approaches the smallest length scale of the artificial potential. PMID:26598218
Magnetic switching of nanoscale antidot lattices
Gräfe, Joachim; Lebecki, Kristof M; Skripnik, Maxim; Haering, Felix; Schütz, Gisela; Ziemann, Paul; Goering, Eberhard; Nowak, Ulrich
2016-01-01
Summary We investigate the rich magnetic switching properties of nanoscale antidot lattices in the 200 nm regime. In-plane magnetized Fe, Co, and Permalloy (Py) as well as out-of-plane magnetized GdFe antidot films are prepared by a modified nanosphere lithography allowing for non-close packed voids in a magnetic film. We present a magnetometry protocol based on magneto-optical Kerr microscopy elucidating the switching modes using first-order reversal curves. The combination of various magnetometry and magnetic microscopy techniques as well as micromagnetic simulations delivers a thorough understanding of the switching modes. While part of the investigations has been published before, we summarize these results and add significant new insights in the magnetism of exchange-coupled antidot lattices. PMID:27335762
Critical phenomena in ferromagnetic antidot lattices
NASA Astrophysics Data System (ADS)
Zivieri, R.
2016-05-01
In this paper a quantitative theoretical formulation of the critical behavior of soft mode frequencies as a function of an applied magnetic field in two-dimensional Permalloy square antidot lattices in the nanometric range is given according to micromagnetic simulations and simple analytical calculations. The degree of softening of the two lowest-frequency modes, namely the edge mode and the fundamental mode, corresponding to the field interval around the critical magnetic field, can be expressed via numerical exponents. For the antidot lattices studied we have found that: a) the ratio between the critical magnetic field and the in-plane geometric aspect ratio and (b) the ratio between the numerical exponents of the frequency power laws of the fundamental mode and of the edge mode do not depend on the geometry. The above definitions could be extended to other types of in-plane magnetized periodic magnetic systems exhibiting soft-mode dynamics and a fourfold anisotropy.
Bandgap scaling in bilayer graphene antidot lattices.
Petersen, René; Pedersen, Thomas Garm
2015-06-10
On the basis of a tight binding model we reveal how the bandgap in bilayer graphene antidot lattices (GALs) follows a different scaling law than in monolayer GALs and we provide an explanation using the Dirac model. We show that previous findings regarding the criteria for the appearance of a bandgap in monolayer GALs are equally applicable to the bilayer case. Furthermore, we briefly investigate the optical properties of bilayer GALs and show that estimates of the bandgap using optical methods could lead to overestimates due to weak oscillator strength of the lowest transitions. Finally, we investigate the effect of imposing an electric field perpendicular to the bilayer GAL structure and find that the bandgap tunability may be extended as compared to pristine bilayer graphene. PMID:25989621
Graphene on graphene antidot lattices: Electronic and transport properties
NASA Astrophysics Data System (ADS)
Gregersen, Søren Schou; Pedersen, Jesper Goor; Power, Stephen R.; Jauho, Antti-Pekka
2015-03-01
Graphene bilayer systems are known to exhibit a band gap when the layer symmetry is broken by applying a perpendicular electric field. The resulting band structure resembles that of a conventional semiconductor with a parabolic dispersion. Here, we introduce a bilayer graphene heterostructure, where single-layer graphene is placed on top of another layer of graphene with a regular lattice of antidots. We dub this class of graphene systems GOAL: graphene on graphene antidot lattice. By varying the structure geometry, band-structure engineering can be performed to obtain linearly dispersing bands (with a high concomitant mobility), which nevertheless can be made gapped with a perpendicular field. We analyze the electronic structure and transport properties of various types of GOALs, and draw general conclusions about their properties to aid their design in experiments.
Experimental Studies of Graphene Antidot Lattices for Thermoelectric Applications
NASA Astrophysics Data System (ADS)
Hao, Qing; Xu, Dongchao; Zhao, Hongbo; Du, Xu
Pristine graphene has low thermoelectric performance due to its ultra-high thermal conductivity and zero band gap that leads to a low Seebeck coefficient (S) . Both issues can be addressed by patterning periodic nano- or sub-1-nm pores (antidots) across graphene, called graphene antidot lattices (GALs). In GALs, a geometry-dependent band gap can be opened up to dramatically increase S, with significantly reduced thermal conductivity (k) due to phonon scattering by antidots. Above will lead to a high thermoelectric figure of merit (~1.0 at 300 K by computations) in GALs to be used for device cooling. Despite numerous calculations, experimental studies of GALs are restricted to electrical conductivity (σ) measurements for GALs with ~10 nm patterns. The critical k measurements are still lacking. In this work, all three thermoelectric properties (S, k, and σ) are measured on suspended GALs with sub-10 nm pores. In comparison, electrical properties are also characterized for GALs on a substrate. The results presented here provide important guidance on how to tailor transport properties of general two-dimensional materials with ALs. Qing Hao acknowledges the support from the Young Investigator Program of U.S. Air Force Office of Scientific Research (Grant FA9550-15-1-0403).
Boron and nitrogen doping in graphene antidot lattices
NASA Astrophysics Data System (ADS)
Brun, Søren J.; Pereira, Vitor M.; Pedersen, Thomas G.
2016-06-01
Bottom-up fabrication of graphene antidot lattices (GALs) has previously yielded atomically precise structures with subnanometer periodicity. Focusing on this type of experimentally realized GAL, we perform density functional theory calculations on the pristine structure as well as GALs with edge carbon atoms substituted with boron or nitrogen. We show that p - and n -type doping levels emerge with activation energies that depend on the level of hydrogenation at the impurity. Furthermore, a tight-binding parametrization together with a Green's function method are used to describe more dilute doping. Finally, random configurations of impurities in moderately doped systems are considered to show that the doping properties are robust against disorder.
NASA Astrophysics Data System (ADS)
Gräfe, Joachim; Weigand, Markus; Träger, Nick; Schütz, Gisela; Goering, Eberhard J.; Skripnik, Maxim; Nowak, Ulrich; Haering, Felix; Ziemann, Paul; Wiedwald, Ulf
2016-03-01
While the magnetic properties of nanoscaled antidot lattices in in-plane magnetized materials have widely been investigated, much less is known about the microscopic effect of hexagonal antidot lattice patterning on materials with perpendicular magnetic anisotropy. By using a combination of first-order reversal curve measurements, magnetic x-ray microscopy, and micromagnetic simulations we elucidate the microscopic origins of the switching field distributions that arise from the introduction of antidot lattices into out-of-plane magnetized GdFe thin films. Depending on the geometric parameters of the antidot lattice we find two regimes with different magnetization reversal processes. For small antidots, the reversal process is dominated by the exchange interaction and domain wall pinning at the antidots drives up the coercivity of the system. On the other hand, for large antidots the dipolar interaction is dominating which leads to fragmentation of the system into very small domains that can be envisaged as a basis for a bit patterned media.
Influence of lattice defects on the ferromagnetic resonance behaviour of 2D magnonic crystals
NASA Astrophysics Data System (ADS)
Manzin, Alessandra; Barrera, Gabriele; Celegato, Federica; Coïsson, Marco; Tiberto, Paola
2016-02-01
This paper studies, from a modelling point of view, the influence of randomly distributed lattice defects (non-patterned areas and variable hole size) on the ferromagnetic resonance behaviour and spin wave mode profiles of 2D magnonic crystals based on Ni80Fe20 antidot arrays with hexagonal lattice. A reference sample is first defined via the comparison of experimental and simulated hysteresis loops and magnetoresistive curves of patterned films, prepared by self-assembly of polystyrene nanospheres. Second, a parametric analysis of the dynamic response is performed, investigating how edge, quasi-uniform and localized modes are affected by alterations of the lattice geometry and bias field amplitude. Finally, some results about the possible use of magnetic antidot arrays in frequency-based sensors for magnetic bead detection are presented, highlighting the need for an accurate control of microstructural features.
Influence of lattice defects on the ferromagnetic resonance behaviour of 2D magnonic crystals.
Manzin, Alessandra; Barrera, Gabriele; Celegato, Federica; Coïsson, Marco; Tiberto, Paola
2016-01-01
This paper studies, from a modelling point of view, the influence of randomly distributed lattice defects (non-patterned areas and variable hole size) on the ferromagnetic resonance behaviour and spin wave mode profiles of 2D magnonic crystals based on Ni80Fe20 antidot arrays with hexagonal lattice. A reference sample is first defined via the comparison of experimental and simulated hysteresis loops and magnetoresistive curves of patterned films, prepared by self-assembly of polystyrene nanospheres. Second, a parametric analysis of the dynamic response is performed, investigating how edge, quasi-uniform and localized modes are affected by alterations of the lattice geometry and bias field amplitude. Finally, some results about the possible use of magnetic antidot arrays in frequency-based sensors for magnetic bead detection are presented, highlighting the need for an accurate control of microstructural features. PMID:26911336
Influence of lattice defects on the ferromagnetic resonance behaviour of 2D magnonic crystals
Manzin, Alessandra; Barrera, Gabriele; Celegato, Federica; Coïsson, Marco; Tiberto, Paola
2016-01-01
This paper studies, from a modelling point of view, the influence of randomly distributed lattice defects (non-patterned areas and variable hole size) on the ferromagnetic resonance behaviour and spin wave mode profiles of 2D magnonic crystals based on Ni80Fe20 antidot arrays with hexagonal lattice. A reference sample is first defined via the comparison of experimental and simulated hysteresis loops and magnetoresistive curves of patterned films, prepared by self-assembly of polystyrene nanospheres. Second, a parametric analysis of the dynamic response is performed, investigating how edge, quasi-uniform and localized modes are affected by alterations of the lattice geometry and bias field amplitude. Finally, some results about the possible use of magnetic antidot arrays in frequency-based sensors for magnetic bead detection are presented, highlighting the need for an accurate control of microstructural features. PMID:26911336
NASA Astrophysics Data System (ADS)
Goswami, Srijit; Aamir, Mohammed Ali; Shamim, Saquib; Siegert, Christoph; Pepper, Michael; Farrer, Ian; Ritchie, David A.; Ghosh, Arindam
2013-12-01
We use a dual gated device structure to introduce a gate-tuneable periodic potential in a GaAs/AlGaAs two dimensional electron gas (2DEG). Using only a suitable choice of gate voltages we can controllably alter the potential landscape of the bare 2DEG, inducing either a periodic array of antidots or quantum dots. Antidots are artificial scattering centers, and therefore allow for a study of electron dynamics. In particular, we show that the thermovoltage of an antidot lattice is particularly sensitive to the relative positions of the Fermi level and the antidot potential. A quantum dot lattice, on the other hand, provides the opportunity to study correlated electron physics. We find that its current-voltage characteristics display a voltage threshold, as well as a power law scaling, indicative of collective Coulomb blockade in a disordered background.
Goswami, Srijit; Aamir, Mohammed Ali; Shamim, Saquib; Ghosh, Arindam; Siegert, Christoph; Farrer, Ian; Ritchie, David A.; Pepper, Michael
2013-12-04
We use a dual gated device structure to introduce a gate-tuneable periodic potential in a GaAs/AlGaAs two dimensional electron gas (2DEG). Using only a suitable choice of gate voltages we can controllably alter the potential landscape of the bare 2DEG, inducing either a periodic array of antidots or quantum dots. Antidots are artificial scattering centers, and therefore allow for a study of electron dynamics. In particular, we show that the thermovoltage of an antidot lattice is particularly sensitive to the relative positions of the Fermi level and the antidot potential. A quantum dot lattice, on the other hand, provides the opportunity to study correlated electron physics. We find that its current-voltage characteristics display a voltage threshold, as well as a power law scaling, indicative of collective Coulomb blockade in a disordered background.
NASA Astrophysics Data System (ADS)
Kozlov, D. A.; Kvon, Z. D.; Plotnikov, A. E.
2009-03-01
Commensurate peaks of magnetoresistance and Shubnikov-de Haas and Aharonov-Bohm oscillations in the two-dimensional electron gas (2DEG) in a lattice of antidots with hard potential walls have been experimentally studied. The behavior of both classical magnetoresistance peaks and quantum oscillations has been shown to fundamentally depend on the lattice period and the antidot size, as well as on the smoothness of the potential at the 2DEG-antidot interface. This result indicates the necessity of revising the interpretation of all numerous experiments with antidot lattices, since this effect has been explicitly or implicitly neglected in them.
Perpendicular magnetisation from in-plane fields in nano-scaled antidot lattices
NASA Astrophysics Data System (ADS)
Gräfe, Joachim; Haering, Felix; Tietze, Thomas; Audehm, Patrick; Weigand, Markus; Wiedwald, Ulf; Ziemann, Paul; Gawroński, Przemysław; Schütz, Gisela; Goering, Eberhard J.
2015-06-01
Investigations of geometric frustrations in magnetic antidot lattices have led to the observation of interesting phenomena like spin-ice and magnetic monopoles. By using highly focused magneto-optical Kerr effect measurements and x-ray microscopy with magnetic contrast we deduce that geometrical frustration in these nanostructured thin film systems also leads to an out-of-plane magnetization from a purely in-plane applied magnetic field. For certain orientations of the antidot lattice, formation of perpendicular magnetic domains has been found with a size of several μm that may be used for an in-plane/out-of-plane transducer.
Mandal, Ruma; Laha, Pinaki; Das, Kaustuv; Saha, Susmita; Barman, Saswati; Raychaudhuri, A. K.; Barman, Anjan
2013-12-23
We show that the optically induced spin wave spectra of nanoscale Ni{sub 80}Fe{sub 20} (permalloy) antidot lattices can be tuned by changing the antidot shape. The spin wave spectra also show an anisotropy with the variation of the in-plane bias field orientation. Analyses show this is due to various quantized and extended modes, whose nature changes with the antidot shape and bias field orientation as a result of the variation of the internal magnetic field profile. The observed variation and anisotropy in the spin waves with the internal and external parameters are important for their applications in magnonic devices.
Gubbiotti, G.; Tacchi, S.; Madami, M.; Carlotti, G.; Ding, J.; Adeyeye, A. O.
2015-06-29
The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained by dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.
NASA Astrophysics Data System (ADS)
Goswami, Srijit; Aamir, Mohammad Ali; Shamim, Saquib; Siegert, Christoph; Pepper, Michael; Farrer, Ian; Ritchie, David; Ghosh, Arindam
2012-02-01
We use a dual gated device structure to introduce a gate-tunable periodic potential in a GaAs/AlGaAs two dimensional electron gas (2DEG). Using a suitable choice of gate voltages we can controllably alter the potential landscape in the 2DEG, thereby inducing either a periodic array of antidots or quantum dots. Antidots are artificial scattering centers, and therefore allow for a study of electron dynamics. On the other hand, a quantum dot lattice provides the opportunity to study correlated electron physics. We use a variety of electrical measurements such as magneto-resistance, thermo-voltage and current-voltage characteristics to probe these two contrasting regimes.
Magnetic structure and resonance properties of a hexagonal lattice of antidots
NASA Astrophysics Data System (ADS)
Marchenko, A. I.; Krivoruchko, V. N.
2012-02-01
Static and resonance properties of ferromagnetic films with a hexagonal lattice of antidots (pores in the film) were studied. The description of the system is based on micromagnetic modeling and analytical solutions of the Landau-Lifshitz equation. The dependences of ferromagnetic resonance spectra on the in-plane direction of applied magnetic field and on the lattice parameters were investigated. The nature of the dependences of a dynamic system response on the frequency at fixed magnetic fields and on the field at fixed frequency when the field changes were explored. They cause the static magnetic order to change. It was found that the specific peculiarities of the system dynamics remain unchanged for both of these experimental conditions. Namely, for low damping the resonance spectra contain three quasi-homogeneous modes which are due to the resonance of different regions (domains) of the antidot lattice cell. It is shown that the angular field dependences of each mode are characterized by a twofold symmetry, and the related easy axes are mutually rotated by 60 °. As a result, a hexagonal symmetry of the system's static and dynamic magnetic characteristics is realized. The existence in the resonance spectrum of several quasi-homogeneous modes related to different regions of the unit cell could be fundamental for the function of the working elements of magnonics devices.
Tunable metamaterial response of a Ni80Fe20 antidot lattice for spin waves
NASA Astrophysics Data System (ADS)
Neusser, S.; Bauer, H. G.; Duerr, G.; Huber, R.; Mamica, S.; Woltersdorf, G.; Krawczyk, M.; Back, C. H.; Grundler, D.
2011-11-01
All-electrical spin-wave spectroscopy and frequency-resolved magneto-optical Kerr-effect measurements are combined to study spin waves propagating through a magnetic antidot lattice nanopatterned from a Ni80Fe20 thin film. Spin waves are injected from a plain film into the antidot lattice and the transmission across the interface is explored in detail for different wavelengths. We find that spin waves with a wavelength much greater than the lattice periodicity are not described well by recently discussed approaches. Instead the spin-wave dispersion is consistent with an effective magnetization smaller than the saturation magnetization measured on the unstructured ferromagnetic material. Consistently, we find that the transmission coefficients are modeled well by assuming an effectively continuous metamaterial for spin waves characterized by the reduced magnetization. The experimental data and interpretation are substantiated theoretically using the plane-wave method and micromagnetic modeling. The results are interesting for the development of frequency-selective mirrors in magnonics through lateral nanopatterning.
NASA Astrophysics Data System (ADS)
Gräfe, Joachim; Weigand, Markus; Stahl, Claudia; Träger, Nick; Kopp, Michael; Schütz, Gisela; Goering, Eberhard J.; Haering, Felix; Ziemann, Paul; Wiedwald, Ulf
2016-01-01
The magnetization reversal in nanoscaled antidot lattices is widely investigated to understand the tunability of the magnetic anisotropy and the coercive field through nanostructuring of thin films. By investigating highly ordered focused ion beam milled antidot lattices with a combination of first-order reversal curves and magnetic x-ray microscopy, we fully elucidate the magnetization reversal along the distinct orientations of a hexagonal antidot lattice. This combination proves especially powerful as all partial steps of this complex magnetization reversal can be identified and subsequently imaged. Through this approach we discovered several additional steps that were neglected in previous studies. Furthermore, by imaging the microscopic magnetization state during each reversal step, we were able to link the coercive and interaction fields determined by the first-order reversal curve method to true microscopic magnetization configurations and determine their origin.
Bisotto, I.; Portal, J.-C.; Brown, D.; Wieck, A. D.
2015-11-15
We present new photovoltage oscillation in a pure two dimensional electron gas (2DEG) and in the presence of circular or semicircular antidot lattices. Results were interpreted as EMPs-like photovoltage oscillations. We observed and explained the photovoltage oscillation amplitude enhancement in the presence of an antidot lattice with regard to the pure 2DEG. The microwave frequency excitation range is 139 – 350 GHz. The cyclotron and magnetoplasmon resonances take place in the magnetic field range 0.4 – 0.8 T. This original experimental condition allows edge magnetoplasmons EMPs interference like observation at low magnetic field, typically B < B{sub c} where B{sub c} is the magnetic field at which the cyclotron resonance takes place. The different oscillation periods observed and their microwave frequency dependence were discussed. For 139 and 158 GHz microwave excitation frequencies, a unique EMPs-like interference period was found in the presence of antidots whereas two periods were extracted for 295 or 350 GHz. An explanation of this effect is given taking account of strong electron interaction with antidot at low magnetic field. Indeed, electrons involved in EMPs like phenomenon interact strongly with antidots when electron cyclotron orbits are larger than or comparable to the antidot diameter.
Density functional study of graphene antidot lattices: Roles of geometrical relaxation and spin
NASA Astrophysics Data System (ADS)
Fürst, Joachim A.; Pedersen, Thomas G.; Brandbyge, Mads; Jauho, Antti-Pekka
2009-09-01
Graphene sheets with regular perforations, dubbed as antidot lattices, have theoretically been predicted to have a number of interesting properties. Their recent experimental realization with lattice constants below 100 nanometers stresses the urgency of a thorough understanding of their electronic properties. In this work, we perform calculations of the band structure for various hydrogen-passivated hole geometries using both spin-polarized density functional theory (DFT) and DFT based tight-binding (DFTB) and address the importance of relaxation of the structures using either method or a combination thereof. We find from DFT that all structures investigated have band gaps ranging from 0.2 to 1.5 eV. Band gap sizes and general trends are well captured by DFTB with band gaps agreeing within about 0.2 eV even for very small structures. A combination of the two methods is found to offer a good trade-off between computational cost and accuracy. Both methods predict nondegenerate midgap states for certain antidot hole symmetries. The inclusion of spin results in a spin-splitting of these states as well as magnetic moments obeying the Lieb theorem. The local-spin texture of both magnetic and nonmagnetic symmetries is addressed.
NASA Astrophysics Data System (ADS)
Farmer, B.; Bhat, V. S.; Sklenar, J.; Teipel, E.; Woods, J.; Ketterson, J. B.; Hastings, J. T.; De Long, L. E.
2015-05-01
The static and dynamic magnetic responses of patterned ferromagnetic thin films are uniquely altered in the case of aperiodic patterns that retain long-range order (e.g., quasicrystals). We have fabricated permalloy wire networks based on periodic square antidot lattices (ADLs) distorted according to an aperiodic Fibonacci sequence applied to two lattice translations, d1 = 1618 nm and d2 = 1000 nm. The wire segment thickness is fixed at t = 25 nm, and the width W varies from 80 to 510 nm. We measured the DC magnetization between room temperature and 5 K. Room-temperature, narrow-band (9.7 GHz) ferromagnetic resonance (FMR) spectra were acquired for various directions of applied magnetic field. The DC magnetization curves exhibited pronounced step anomalies and plateaus that signal flux closure states. Although the Fibonacci distortion breaks the fourfold symmetry of a finite periodic square ADL, the FMR data exhibit fourfold rotational symmetry with respect to the applied DC magnetic field direction.
Shi, Likun; Lou, Wenkai; Cheng, F.; Zou, Y. L.; Yang, Wen; Chang, Kai
2015-01-01
Based on the Born-Oppemheimer approximation, we divide the total electron Hamiltonian in a spin-orbit coupled system into the slow orbital motion and the fast interband transition processes. We find that the fast motion induces a gauge field on the slow orbital motion, perpendicular to the electron momentum, inducing a topological phase. From this general designing principle, we present a theory for generating artificial gauge field and topological phase in a conventional two-dimensional electron gas embedded in parabolically graded GaAs/InxGa1−xAs/GaAs quantum wells with antidot lattices. By tuning the etching depth and period of the antidot lattices, the band folding caused by the antidot potential leads to the formation of minibands and band inversions between neighboring subbands. The intersubband spin-orbit interaction opens considerably large nontrivial minigaps and leads to many pairs of helical edge states in these gaps. PMID:26471126
NASA Astrophysics Data System (ADS)
Shi, Likun; Lou, Wenkai; Cheng, F.; Zou, Y. L.; Yang, Wen; Chang, Kai
2015-10-01
Based on the Born-Oppemheimer approximation, we divide the total electron Hamiltonian in a spin-orbit coupled system into the slow orbital motion and the fast interband transition processes. We find that the fast motion induces a gauge field on the slow orbital motion, perpendicular to the electron momentum, inducing a topological phase. From this general designing principle, we present a theory for generating artificial gauge field and topological phase in a conventional two-dimensional electron gas embedded in parabolically graded GaAs/InxGa1-xAs/GaAs quantum wells with antidot lattices. By tuning the etching depth and period of the antidot lattices, the band folding caused by the antidot potential leads to the formation of minibands and band inversions between neighboring subbands. The intersubband spin-orbit interaction opens considerably large nontrivial minigaps and leads to many pairs of helical edge states in these gaps.
Beam-Plasma Instabilities in a 2D Yukawa Lattice
Kyrkos, S.; Kalman, G. J.; Rosenberg, M.
2009-06-05
We consider a 2D Yukawa lattice of grains, with a beam of other charged grains moving in the lattice plane. In contrast to Vlasov plasmas, where the electrostatic instability excited by the beam is only longitudinal, here both longitudinal and transverse instabilities of the lattice phonons can develop. We determine and compare the transverse and longitudinal growth rates. The growth rate spectrum in wave number space exhibits remarkable gaps where no instability can develop. Depending on the system parameters, the transverse instability can be selectively excited.
Unitary quantum lattice gas representation of 2D quantum turbulence
NASA Astrophysics Data System (ADS)
Zhang, Bo; Vahala, George; Vahala, Linda; Soe, Min
2011-05-01
Quantum vortex structures and energy cascades are examined for two dimensional quantum turbulence (2D QT) using a special unitary evolution algorithm. The qubit lattice gas (QLG) algorithm, is employed to simulate the weakly-coupled Bose-Einstein condensate (BEC) governed by the Gross-Pitaevskii (GP) equation. A parameter regime is uncovered in which, as in 3D QT, there is a very short Poincare recurrence time. This short recurrence time is destroyed as the nonlinear interaction energy is increased. Energy cascades for 2D QT are considered to examine whether 2D QT exhibits the inverse cascades of 2D classical turbulence. In the parameter regime considered, the spectra analysis reveals no such dual cascades---dual cascades being a hallmark of 2D classical turbulence.
Size and shape dependence study of magnetization reversal in magnetic antidot lattice arrays
NASA Astrophysics Data System (ADS)
Mallick, Sougata; Bedanta, Subhankar
2015-05-01
Magnetic Antidot Lattice (MAL) arrays of Co have been prepared in micron range using ultraviolet (UV) lithography technique with different shapes and sizes. Magnetization reversal in such MAL systems has been studied by magneto-optic Kerr effect (MOKE) based microscopy by varying the angle between the easy axis and the external magnetic field. The domain images evidence that the magnetization reversal along easy axis is highly dominated by nucleation of domains which is subsequently accompanied by domain wall motion. We have observed that with increase in active magnetic area domain size increases but on the contrary coercivity decreases. The presence of periodic holes turns the MALs magnetically hard when compared to similar thickness of continuous thin film. The magnetization relaxation along easy axis for the Co MAL at constant dc field fits very well with the exponential law of Fatuzzo-Labrune indicating domain nucleated dominant process.
Theoretical study on electronic properties of MoS{sub 2} antidot lattices
Shao, Li; Chen, Guangde; Ye, Honggang Wu, Yelong; Niu, Haibo; Zhu, Youzhang
2014-09-21
Motivated by the state of the art method for etching hexagonal array holes in molybdenum disulfide (MoS{sub 2}), the electronic properties of MoS{sub 2} antidot lattices (MoS{sub 2}ALs) with zigzag edge were studied with first-principles calculations. Monolayer MoS{sub 2}ALs are semiconducting and the band gaps converge to constant values as the supercell area increases, which can be attributed to the edge effect. Multilayer MoS{sub 2}ALs and chemical adsorbed MoS{sub 2}ALs by F atoms show metallic behavior, while the structure adsorbed with H atoms remains to be semiconducting with a tiny bandgap. Our results show that forming periodically repeating structures in MoS{sub 2} can develop a promising technique for engineering nano materials and offer new opportunities for designing MoS{sub 2}-based nanoscale electronic devices and chemical sensors.
Mallick, Sougata; Mallik, Srijani; Bedanta, Subhankar
2015-08-28
Microdimensional triangular magnetic antidot lattice arrays were prepared by varying the speed of substrate rotation. The pre-deposition patterning has been performed using photolithography technique followed by a post-deposition lift-off. Surface morphology taken by atomic force microscopy depicted that the growth mechanism of the grains changes from chain like formation to island structures due to the substrate rotation. Study of magnetization reversal via magneto optic Kerr effect based microscopy revealed reduction of uniaxial anisotropy and increase in domain size with substrate rotation. The relaxation measured under constant magnetic field becomes faster with rotation of the substrate during deposition. The nature of relaxation for the non-rotating sample can be described by a double exponential decay. However, the relaxation for the sample with substrate rotation is well described either by a double exponential or a Fatuzzo-Labrune like single exponential decay, which increases in applied field.
Jungfleisch, Matthias B.; Zhang, Wei; Jiang, Wanjun; Sklenar, Joseph; Pearson, John E.; Ketterson, John B.; Hoffmann, Axel
2016-01-01
The understanding of spin dynamics in laterally confined structures on sub-micron length scales has become a significant aspect of the development of novel magnetic storage technologies. Numerous ferromagnetic resonance measurements, optical characterization by Kerr microscopy and Brillouin light scattering spectroscopy and x-ray studies were carried out to detect the dynamics in patterned magnetic antidot lattices. Here, we investigate Oersted-field driven spin dynamics in rectangular Ni80Fe20/Pt antidot lattices with different lattice parameters by electrical means. When the system is driven to resonance, a dc voltage across the length of the sample is detected that changes its sign upon field reversal, which is in agreement with a rectification mechanism based on the inverse spin Hall effect. Furthermore, we show that the voltage output scales linearly with the applied microwave drive in the investigated range of powers. Our findings have direct implications on the development of engineered magnonics applications and devices.
Pal, S.; Das, K.; Barman, A.; Klos, J. W.; Gruszecki, P.; Krawczyk, M.; Hellwig, O.
2014-10-20
We present an all-optical time-resolved measurement of spin wave (SW) dynamics in a series of antidot lattices based on [Co(0.75 nm)/Pd(0.9 nm)]{sub 8} multilayer (ML) systems with perpendicular magnetic anisotropy. The spectra depend significantly on the areal density of the antidots. The observed SW modes are qualitatively reproduced by the plane wave method. The interesting results found in our measurements and calculations at small lattice constants can be attributed to the increase of areal density of the shells with modified magnetic properties probably due to distortion of the regular ML structure by the Ga ion bombardment and to increased coupling between localized modes. We propose and discuss the possible mechanisms for this coupling including exchange interaction, tunnelling, and dipolar interactions.
Mandal, R.; Barman, S.; Saha, S.; Barman, A.; Otani, Y.
2015-08-07
Ferromagnetic antidot lattices are important systems for magnetic data storage and magnonic devices, and understanding their magnetization dynamics by varying their structural parameters is an important problems in magnetism. Here, we investigate the variation in spin wave spectrum in two-dimensional nanoscale Ni{sub 80}Fe{sub 20} antidot lattices with lattice symmetry. By varying the bias magnetic field values in a broadband ferromagnetic resonance spectrometer, we observed a stark variation in the spin wave spectrum with the variation of lattice symmetry. The simulated mode profiles showed further difference in the spatial nature of the modes between different lattices. While for square and rectangular lattices extended modes are observed in addition to standing spin wave modes, all modes in the hexagonal, honeycomb, and octagonal lattices are either localized or standing waves. In addition, the honeycomb and octagonal lattices showed two different types of modes confined within the honeycomb (octagonal) units and between two such consecutive units. Simulated internal magnetic fields confirm the origin of such a wide variation in the frequency and spatial nature of the spin wave modes. The tunability of spin waves with the variation of lattice symmetry is important for the design of future magnetic data storage and magnonic devices.
NASA Astrophysics Data System (ADS)
Jungfleisch, Matthias B.; Zhang, Wei; Ding, Junjia; Jiang, Wanjun; Sklenar, Joseph; Pearson, John E.; Ketterson, John B.; Hoffmann, Axel
2016-02-01
The understanding of spin dynamics in laterally confined structures on sub-micron length scales has become a significant aspect of the development of novel magnetic storage technologies. Numerous ferromagnetic resonance measurements, optical characterization by Kerr microscopy and Brillouin light scattering spectroscopy, and x-ray studies were carried out to detect the dynamics in patterned magnetic antidot lattices. Here, we investigate Oersted-field driven spin dynamics in rectangular Ni80Fe20/Pt antidot lattices with different lattice parameters by electrical means and compare them to micromagnetic simulations. When the system is driven to resonance, a dc voltage across the length of the sample is detected that changes its sign upon field reversal, which is in agreement with a rectification mechanism based on the inverse spin Hall effect. Furthermore, we show that the voltage output scales linearly with the applied microwave drive in the investigated range of powers. Our findings have direct implications on the development of engineered magnonics applications and devices.
NASA Astrophysics Data System (ADS)
Abuali, Z.; Golshan, M. M.; Davatolhagh, S.
2016-09-01
The present work is concerned with a report on the effects of Pauli, Rashba and Dresselhaus spin-orbit interactions (SOI) on the energy levels of a 2D circular hydrogenic quantum anti-dot(QAD). To pursue this aim, we first present a brief review on the analytical solutions to the Schrödinger equation of electronic states in a quantum anti-dot when a hydrogenic donor is placed at the center, revealing the degeneracies involved in the ground, first and second excited states. We then proceed by adding the aforementioned spin-orbit interactions to the Hamiltonian and treat them as perturbation, thereby, calculating the energy shifts to the first three states. As we show, the Rashba spin-orbit interaction gives rise to a shift in the energies of the ground and second excited states, while it partially lifts the degeneracy of the first excited state. Our calculations also indicate that the Dresselhaus effect, while keeping the degeneracy of the ground and second excited states intact, removes the degeneracy of the first excited state in the opposite sense. The Pauli spin-orbit interaction, on the other hand, is diagonal in the appropriate bases, and thus its effect is readily calculated. The results show that degeneracy of ℓ = 0 (prevailing in the ground and second excited state) remains but the degeneracy of ℓ = 1 (prevailing in the first excited state) is again partially lifted. Moreover, we present the energy corrections due to the three spin-orbit interactions as functions of anti-dot's radius, Rashba and Dresselhaus strengths discussing how they affect the corresponding states. The material presented in the article conceives the possibility of generating spin currents in the hydrogenic circular anti-dots.
Lattice Boltzmann Equation On a 2D Rectangular Grid
NASA Technical Reports Server (NTRS)
Bouzidi, MHamed; DHumieres, Dominique; Lallemand, Pierre; Luo, Li-Shi; Bushnell, Dennis M. (Technical Monitor)
2002-01-01
We construct a multi-relaxation lattice Boltzmann model on a two-dimensional rectangular grid. The model is partly inspired by a previous work of Koelman to construct a lattice BGK model on a two-dimensional rectangular grid. The linearized dispersion equation is analyzed to obtain the constraints on the isotropy of the transport coefficients and Galilean invariance for various wave propagations in the model. The linear stability of the model is also studied. The model is numerically tested for three cases: (a) a vortex moving with a constant velocity on a mesh periodic boundary conditions; (b) Poiseuille flow with an arbitrasy inclined angle with respect to the lattice orientation: and (c) a cylinder &symmetrically placed in a channel. The numerical results of these tests are compared with either analytic solutions or the results obtained by other methods. Satisfactory results are obtained for the numerical simulations.
Lattice Formulation of 2D SQCD with exact supersymmetry
Sugino, Fumihiko
2008-11-23
We construct a lattice model for two-dimensional N = (2,2) supersymmetric QCD (SQCD), with the matter multiplets belonging to the fundamental or anti-fundamental representation of the gauge group U(N) or SU(N). The construction is based on the topological field theory (twisted supercharge) formulation and exactly preserves one supercharge. In order to avoid the species doublers of the matter multiplets, we introduce the Wilson terms and the model is defined for the case of the number of the fundamental matters (n{sub +}) equal to that of the anti-fundamental matters (n{sub -}). If some of the matter multiplets decouple from the theory by sending the corresponding anti-holomorphic twisted masses to the infinity, we can analyze the general n{sub +}{ne}n{sub -} case, although the lattice model is defined for n{sub +} = n{sub -}. By computing the anomaly of the U(1){sub A} R-symmetry in the lattice perturbation, we see that the decoupling is achieved and the anomaly for n{sub +}{ne}n{sub -} is correctly obtained.
NASA Astrophysics Data System (ADS)
Tacchi, S.; Botters, B.; Madami, M.; Kłos, J. W.; Sokolovskyy, M. L.; Krawczyk, M.; Gubbiotti, G.; Carlotti, G.; Adeyeye, A. O.; Neusser, S.; Grundler, D.
2012-07-01
We report spin wave excitations in a nanopatterned antidot lattice fabricated from a 30-nm thick Ni80Fe20 film. The 250-nm-wide circular holes are arranged in a rhombic unit cell with a lattice constant of 400 nm. By Brillouin light scattering, we find that quantized spin wave modes transform to propagating ones and vice versa by changing the in-plane orientation of the applied magnetic field H by 30∘. Spin waves of either negative or positive group velocity are found. In the latter case, they propagate in narrow channels exhibiting a width of below 100 nm. We use the plane wave method to calculate the spin wave dispersions for the two relevant orientations of H. The theory allows us to explain the wave-vector-dependent characteristics of the prominent modes. Allowed minibands are formed for selected modes only for specific orientations of H and wave vector. The results are important for applications such as spin wave filters and interconnected waveguides in the emerging field of magnonics where the control of spin wave propagation on the nanoscale is key.
Dynamical polarizability of the 2D pseudospin-1 dice lattice
NASA Astrophysics Data System (ADS)
Malcolm, John; Nicol, Elisabeth
The two-dimensional dice lattice is composed of three triangular sublattices whose low-energy excitation spectrum consists of Dirac-Weyl fermions with pseudospin-1. The energy dispersion has two Dirac cones, like the pseudospin-1/2 two-triangular-sublattice graphene, with an additional third band exactly at zero energy. We present theoretical results for the electronic dynamical polarization function in the material. This is a fundamental entity in many-body physics, renormalizing the Coulomb interaction through the dielectric function. From the polarization function we also obtain the Lindhard function, the plasmon branch, and can discuss other screening effects. These are constrasted with those of graphene.
Quantum spin Hall phase in 2D trigonal lattice.
Wang, Z F; Jin, Kyung-Hwan; Liu, Feng
2016-01-01
The quantum spin Hall (QSH) phase is an exotic phenomena in condensed-matter physics. Here we show that a minimal basis of three orbitals (s, px, py) is required to produce a QSH phase via nearest-neighbour hopping in a two-dimensional trigonal lattice. Tight-binding model analyses and calculations show that the QSH phase arises from a spin-orbit coupling (SOC)-induced s-p band inversion or p-p bandgap opening at Brillouin zone centre (Γ point), whose topological phase diagram is mapped out in the parameter space of orbital energy and SOC. Remarkably, based on first-principles calculations, this exact model of QSH phase is shown to be realizable in an experimental system of Au/GaAs(111) surface with an SOC gap of ∼73 meV, facilitating the possible room-temperature measurement. Our results will extend the search for substrate supported QSH materials to new lattice and orbital types. PMID:27599580
Resonant tunneling diode based on band gap engineered graphene antidot structures
NASA Astrophysics Data System (ADS)
Palla, Penchalaiah; Ethiraj, Anita S.; Raina, J. P.
2016-04-01
The present work demonstrates the operation and performance of double barrier Graphene Antidot Resonant Tunnel Diode (DBGA-RTD). Non-Equilibrium Green's Function (NEGF) frame work with tight-binding Hamiltonian and 2-D Poisson equations were solved self-consistently for device study. The interesting feature in this device is that it is an all graphene RTD with band gap engineered graphene antidot tunnel barriers. Another interesting new finding is that it shows negative differential resistance (NDR), which involves the resonant tunneling in the graphene quantum well through both the electron and hole bound states. The Graphene Antidot Lattice (GAL) barriers in this device efficiently improved the Peak to Valley Ratio to approximately 20 even at room temperature. A new fitting model is developed for the number of antidots and their corresponding effective barrier width, which will help in determining effective barrier width of any size of actual antidot geometry.
Grid Cell Responses in 1D Environments Assessed as Slices through a 2D Lattice.
Yoon, KiJung; Lewallen, Sam; Kinkhabwala, Amina A; Tank, David W; Fiete, Ila R
2016-03-01
Grid cells, defined by their striking periodic spatial responses in open 2D arenas, appear to respond differently on 1D tracks: the multiple response fields are not periodically arranged, peak amplitudes vary across fields, and the mean spacing between fields is larger than in 2D environments. We ask whether such 1D responses are consistent with the system's 2D dynamics. Combining analytical and numerical methods, we show that the 1D responses of grid cells with stable 1D fields are consistent with a linear slice through a 2D triangular lattice. Further, the 1D responses of comodular cells are well described by parallel slices, and the offsets in the starting points of the 1D slices can predict the measured 2D relative spatial phase between the cells. From these results, we conclude that the 2D dynamics of these cells is preserved in 1D, suggesting a common computation during both types of navigation behavior. PMID:26898777
Optimization and Design of 2d Honeycomb Lattice Photonic Crystal Modulated by Liquid Crystals
NASA Astrophysics Data System (ADS)
Guo, Caihong; Zheng, Jihong; Gui, Kun; Zhang, Menghua; Zhuang, Songlin
2013-12-01
Photonic crystals (PCs) with infiltrating liquid crystals (LCs) have many potential applications because of their ability to continuously modulate the band-gaps. Using the plane-wave expansion method (PWM), we simulate the band-gap distribution of 2D honeycomb lattice PC with different pillar structures (circle, hexagonal and square pillar) and with different filling ratios, considering both when the LC is used as filling pillar material and semiconductors (Si, Ge) are used in the substrate, and when the semiconductors (Si, Ge) are pillar material and the LC is the substrate. Results show that unlike LC-based triangle lattice PC, optimized honeycomb lattice PC has the ability to generate absolute photonic band-gaps for fabricating optical switches. We provide optimization parameters for LC infiltrating honeycomb lattice PC structure based on simulation results and analysis.
Light trapping at Dirac point in 2D triangular Archimedean-like lattice photonic crystal.
Mao, Qiuping; Xie, Kang; Hu, Lei; Li, Qian; Zhang, Wei; Jiang, Haiming; Hu, Zhijia; Wang, Erlei
2016-04-20
Optical cavities and waveguides are critical parts of modern optical devices. Traditionally, optical cavities and waveguides rely on photonic bandgaps, or total internal reflection, to achieve light trapping. It has been reported that a novel light trapping, which exists in triangular and honeycomb lattices, is attributed to the so-called Dirac point. Our analysis reveals that 2D triangular Archimedean-like lattice photonic crystals also can support this Dirac mode with similar characteristics. This is a new type of localized mode with a different algebraic field profile at a different specified Dirac frequency, which is also beyond any complete photonic bandgap. The new wave localization has different features and can be applied to the design of new optical devices. PMID:27140119
Self-Assembly of Cubes into 2D Hexagonal and Honeycomb Lattices by Hexapolar Capillary Interactions
NASA Astrophysics Data System (ADS)
Soligno, Giuseppe; Dijkstra, Marjolein; van Roij, René
2016-06-01
Particles adsorbed at a fluid-fluid interface induce capillary deformations that determine their orientations and generate mutual capillary interactions which drive them to assemble into 2D ordered structures. We numerically calculate, by energy minimization, the capillary deformations induced by adsorbed cubes for various Young's contact angles. First, we show that capillarity is crucial not only for quantitative, but also for qualitative predictions of equilibrium configurations of a single cube. For a Young's contact angle close to 90°, we show that a single-adsorbed cube generates a hexapolar interface deformation with three rises and three depressions. Thanks to the threefold symmetry of this hexapole, strongly directional capillary interactions drive the cubes to self-assemble into hexagonal or graphenelike honeycomb lattices. By a simple free-energy model, we predict a density-temperature phase diagram in which both the honeycomb and hexagonal lattice phases are present as stable states.
Self-Assembly of Cubes into 2D Hexagonal and Honeycomb Lattices by Hexapolar Capillary Interactions.
Soligno, Giuseppe; Dijkstra, Marjolein; van Roij, René
2016-06-24
Particles adsorbed at a fluid-fluid interface induce capillary deformations that determine their orientations and generate mutual capillary interactions which drive them to assemble into 2D ordered structures. We numerically calculate, by energy minimization, the capillary deformations induced by adsorbed cubes for various Young's contact angles. First, we show that capillarity is crucial not only for quantitative, but also for qualitative predictions of equilibrium configurations of a single cube. For a Young's contact angle close to 90°, we show that a single-adsorbed cube generates a hexapolar interface deformation with three rises and three depressions. Thanks to the threefold symmetry of this hexapole, strongly directional capillary interactions drive the cubes to self-assemble into hexagonal or graphenelike honeycomb lattices. By a simple free-energy model, we predict a density-temperature phase diagram in which both the honeycomb and hexagonal lattice phases are present as stable states. PMID:27391753
2D photonic crystals on the Archimedean lattices (tribute to Johannes Kepler (1571 1630))
NASA Astrophysics Data System (ADS)
Gajić, R.; class="cross-out">D. Jovanović,
2008-03-01
Results of our research on 2D Archemedean lattice photonic crystals are presented. This involves the calculations of the band structures, band-gap maps, equifrequency contours and FDTD simulations of electromagnetic propagation through the structures as well as an experimental verification of negative refraction at microwaves. The band-gap dependence on dielectric contrast is established both for dielectric rods in air and air-holes in dielectric materials. A special emphasis is placed on possibilities of negative refraction and left-handedness in these structures. Together with the familiar Archimedean lattices like square, triangular, honeycomb and Kagome' ones, we consider also, the less known, (3 2, 4, 3, 4) (ladybug) and (3, 4, 6, 4) (honeycomb-ring) structures.
Analysis of the antiferromagnetic phase transitions of the 2D Kondo lattice
NASA Astrophysics Data System (ADS)
Jones, Barbara
2010-03-01
The Kondo lattice continues to present an interesting and relevant challenge, with its interactions between Kondo, RKKY, and coherent order. We present our study[1] of the antiferromagnetic quantum phase transitions of a 2D Kondo-Heisenberg square lattice. Starting from the nonlinear sigma model as a model of antiferromagnetism, we carry out a renormalization group analysis of the competing Kondo-RKKY interaction to one-loop order in an ɛ-expansion. We find a new quantum critical point (QCP) strongly affected by Kondo fluctuations. Near this QCP, there is a breakdown of hydrodynamic behavior, and the spin waves are logarithmically frozen out. The renormalization group results allow us to propose a new phase diagram near the antiferromagnetic fixed point of this 2D Kondo lattice model. The T=0 phase diagram contains four phases separated by a tetracritical point, the new QCP. For small spin fluctuations, we find a stable local magnetic moment antiferromagnet. For stronger coupling, region II is a metallic quantum disordered paramagnet. We find in region III a paramagnetic phase driven by Kondo interactions, with possible ground states of a heavy fermion liquid or a Kondo driven spin-liquid. The fourth phase is a spiral phase, or a large-Fermi-surface antiferromagnetic phase. We will describe these phases in more detail, including possible experimental confirmation of the spiral phase. The existence of the tetracritical point found here would be expected to affect the phase diagram at finite temperatures as well. In addition, It is hoped that these results, and particularly the Kondo interaction paramagnetic phase, will serve to bridge to solutions starting from the opposite limit, of a Kondo effect leading to a heavy fermion ground state. Work in collaboration with T. Tzen Ong. [4pt] [1] T. Ong and B. A. Jones, Phys. Rev. Lett. 103, 066405 (2009).
Identifying topological edge states in 2D optical lattices using light scattering
NASA Astrophysics Data System (ADS)
Goldman, Nathan; Beugnon, Jérôme; Gerbier, Fabrice
2013-02-01
We recently proposed in a Letter [Phys. Rev. Lett. 108, 255303] a novel scheme to detect topological edge states in an optical lattice, based on a generalization of Bragg spectroscopy. The scope of the present article is to provide a more detailed and pedagogical description of the system - the Hofstadter optical lattice - and probing method. We first show the existence of topological edge states, in an ultra-cold gas trapped in a 2D optical lattice and subjected to a synthetic magnetic field. The remarkable robustness of the edge states is verified for a variety of external confining potentials. Then, we describe a specific laser probe, made from two lasers in Laguerre-Gaussian modes, which captures unambiguous signatures of these edge states. In particular, the resulting Bragg spectra provide the dispersion relation of the edge states, establishing their chiral nature. In order to make the Bragg signal experimentally detectable, we introduce a "shelving method", which simultaneously transfers angular momentum and changes the internal atomic state. This scheme allows to directly visualize the selected edge states on a dark background, offering an instructive view on topological insulating phases, not accessible in solid-state experiments.
Kiyota, Kazuya
2016-02-01
In Japan, several products of the antidote for poisoning have been authorized in clinical use from some recent years. For example, Hydroxcobalamin for cyanide poisoning was introduced in 2008. In 2009, Ministry of Health, Labour and Welfare invited suggestions of demand of pharmaceutical products which is high in the need in the medical care but yet unauthorized. Japanese Society for Clinical Toxicology and Japan Poison Information Center applied some candidates including methyleneblue (MB) and fomepizole, both of them were authorized in clinical market in 2015. MB is the medicine for methemoglobinemia, caused by variety of chemical products such as nitrogen oxide. Fomepizole is the antidote for methanol and ethyleneglycol, blocking alcohol dehydrogenase. PMID:26915245
Electronic and geometrical properties of monoatomic and diatomic 2D honeycomb lattices. A DFT study
NASA Astrophysics Data System (ADS)
Rojas, Ángela; Rey, Rafael; Fonseca, Karen; Grupo de Óptica e Información Cuántica Team
Since the discovery of graphene by Geim and Novoselov at 2004, several analogous systems have been theoretically and experimentally studied, due to their technological interest. Both monoatomic lattices, such as silicine and germanene, and diatomic lattices (h-GaAs and h-GaN) have been studied. Using Density Functional Theory we obtain and confirm the chemical stability of these hexagonal 2D systems through the total energy curves as a function of interatomic distance. Unlike graphene, silicine and germanene, gapless materials, h-GaAs and h-GaN exhibit electronic gaps, different from that of the bulk, which could be interesting for the industry. On the other hand, the ab initio band structure calculations for graphene, silicene and germanene show a non-circular cross section around K points, at variance with the prediction of usual Tight-binding models. In fact, we have found that Dirac cones display a dihedral group symmetry. This implies that Fermi speed can change up to 30 % due to the orientation of the wave vector, for both electrons and holes. Traditional analytic studies use the Dirac equation for the electron dynamics at low energies. However, this equation assumes an isotropic, homogeneous and uniform space. Authors would like to thank the División de Investigación Sede Bogotá for their financial support at Universidad Nacional de Colombia. A. M. Rojas-Cuervo would also like to thank the Colciencias, Colombia.
Lattice Boltzmann simulations of 2D laminar flows past two tandem cylinders
NASA Astrophysics Data System (ADS)
Mussa, Alberto; Asinari, Pietro; Luo, Li-Shi
2009-03-01
We apply the lattice Boltzmann equation (LBE) with multiple-relaxation-time (MRT) collision model to simulate laminar flows in two-dimensions (2D). In order to simulate flows in an unbounded domain with the LBE method, we need to address two issues: stretched non-uniform mesh and inflow and outflow boundary conditions. We use the interpolated grid stretching method to address the need of non-uniform mesh. We demonstrate that various inflow and outflow boundary conditions can be easily and consistently realized with the MRT-LBE. The MRT-LBE with non-uniform stretched grids is first validated with a number of test cases: the Poiseuille flow, the flow past a cylinder asymmetrically placed in a channel, and the flow past a cylinder in an unbounded domain. We use the LBE method to simulate the flow past two tandem cylinders in an unbounded domain with Re = 100. Our results agree well with existing ones. Through this work we demonstrate the effectiveness of the MRT-LBE method with grid stretching.
NASA Astrophysics Data System (ADS)
Guillamon, I.; Vieira, S.; Suderow, H.; Cordoba, R.; Sese, J.; de Teresa, J. M.; Ibarra, R.
In two dimensional (2D) systems, theory has proposed that random disorder destroys long range correlations driving a transition to a glassy state. Here, I will discuss new insights into this issue obtained through the direct visualization of the critical behaviour of a 2D superconducting vortex lattice formed in a thin film with a smooth 1D thickness modulation. Using scanning tunneling microscopy at 0.1K, we have tracked the modification in the 2D vortex arrangements induced by the 1D thickness modulation while increasing the vortex density by three orders of magnitude. Upon increasing the field, we observed a two-step order-disorder transition in the 2D vortex lattice mediated by the appearance of dislocations and disclinations and accompanied by an increase in the local vortex density fluctuations. Through a detailed analysis of correlation functions, we find that the transition is driven by the incommensurate 1D thickness modulation. We calculate the critical points and exponents and find that they are well above theoretical expectation for random disorder. Our results show that long range 1D correlations in random potentials enhance the stability range of the ordered phase in a 2D vortex lattice. Work supported by Spanish MINECO, CIG Marie Curie Grant, Axa Research Fund and FBBVA.
Orso, G.; Stringari, S.; Menotti, C.
2006-11-10
We use Bogoliubov theory to calculate the beyond mean field correction to the equation of state of a weakly interacting Bose gas in the presence of a tight 2D optical lattice. We show that the lattice induces a characteristic 3D to 1D crossover in the behavior of quantum fluctuations. Using the hydrodynamic theory of superfluids, we calculate the corresponding shift of the collective frequencies of a harmonically trapped gas. We find that this correction can be of the order of a few percent and hence easily measurable in current experiments. The behavior of the quantum depletion of the condensate is also discussed.
NASA Astrophysics Data System (ADS)
Volčko, Dušan; Quader, Khandker F.
2012-12-01
We consider fermions on a 2D square lattice with a finite-range pairing interaction, and obtain signatures for unconventional pair-symmetry states, dx2-y2 and extended-s (s*), in the Bardeen-Cooper-Schrieffer-Bose-Einstein Condensation crossover region. We find that the fermion momentum distribution function, vk2, the ratio of the Bogoliubov coefficients, vk/uk, and the Fourier transform of vk2 are strikingly different for d and s* symmetries in the crossover region. The chemical potential and the gap functions for both pairing symmetries show several interesting features as a function of interaction. Fermionic atoms in 2D optical lattices may provide a way to test these signatures. We discuss current generation cold atom experiments that may be utilized.
Zharova, Yu. A. Fedulova, G. V.; Astrova, E. V.; Baldycheva, A. V.; Tolmachev, V. A.; Perova, T. S.
2011-08-15
Design and fabrication technology of a microcavity structure based on a double heterojunction in macroporous silicon is suggested. The fabrication process of a strip of a 2D photonic crystal constituted by a finite number of lattice periods and the technique for defect formation by local opening of macropores on the substrate side, followed by filling of these macropores with a nematic liquid crystal, are considered.
The two-antidot system in the ballistic regime
NASA Astrophysics Data System (ADS)
Sachrajda, A. S.; Gould, C.; Kirczenow, G.; Johnson, B.; Feng, Y.; Kelly, P. J.; Delage, A.
1998-01-01
A tunable two-antidot device is studied in the cyclotron-trapping regime. Periodic quantum oscillations are found to be superimposed on the peaks reminiscent of those observed in antidot lattices. The results are compared to quantum and classical simulations and Feynman path integral analysis. Published by Elsevier Science B.V.
2D and 3D Anilato-Based Heterometallic M(I)M(III) Lattices: The Missing Link.
Benmansour, Samia; Vallés-García, Cristina; Gómez-Claramunt, Patricia; Mínguez Espallargas, Guillermo; Gómez-García, Carlos J
2015-06-01
The similar bis-bidentate coordination mode of oxalato and anilato-based ligands is exploited here to create the first examples of 2D and 3D heterometallic lattices based on anilato ligands combining M(I) and a M(III) ions, phases already observed with oxalato but unknown with anilato-type ligands. These lattices are prepared with alkaline metal ions and magnetic chiral tris(anilato)metalate molecular building blocks: [M(III)(C6O4X2)3](3-) (M(III) = Fe and Cr; X = Cl and Br; (C6O4X2)(2-) = dianion of the 3,6-disubstituted derivatives of 2,5-dihydroxy-1,4-benzoquinone, H4C6O4). The new compounds include two very similar 2D lattices formulated as (PBu3Me)2[NaCr(C6O4Br2)3] (1) and (PPh3Et)2[KFe(C6O4Cl2)3](dmf)2 (2), both presenting hexagonal [M(I)M(III)(C6O4X2)3](2-) honeycomb layers with (PBu3Me)(+) in 1 or (PPh3Et)(+) and dmf in 2 inserted between them. Minor modifications in the synthetic conditions yield the novel 3D lattice (NEt3Me)[Na(dmf)][NaFe(C6O4Cl2)3] (3), in which hexagonal layers analogous to 1 and 2 are interconnected through Na(+) cations, and (NBu3Me)2[NaCr(C6O4Br2)3] (4), the first heterometallic 3D lattice based on anilato ligands. This compound presents two interlocked chiral 3D (10,3) lattices with opposite chiralities. Attempts to prepare 4 in larger quantities result in the 2D polymorph of compound 4 (4'). Magnetic properties of compounds 1, 3, and 4' are reported, and in all cases we observe, as expected, paramagnetic behaviors that can be satisfactorily reproduced with simple monomer models including a zero field splitting (ZFS) of the corresponding S = 3/2 for Cr(III) in 1 and 4' or S = 5/2 for Fe(III) in 3. PMID:25965415
Microscopy of a Quantum Gas in a 2D Optical Lattice
NASA Astrophysics Data System (ADS)
Bakr, Waseem; Peng, Amy; Tai, Ming; Ma, Ruichao; Jotzu, Gregor; Gillen, Jonathon; Foelling, Simon; Greiner, Markus
2010-03-01
Ultracold quantum gases in optical lattices provide a rich experimental toolbox for simulating the physics of condensed matter systems. With atoms in the lattice playing the role of electrons or Cooper pairs in real materials, it is possible to experimentally realize condensed matter Hamiltonians in a controlled way. To realize the full potential of such quantum simulations, we have created a quantum gas microscope (NA = 0.8) which can spatially resolve the atoms in the optical lattice at the single site level, and project arbitrary potential landscapes onto the atoms by combining the high resolution optics with static holographic masks or a spatial light modulator. The high resolution microscope operates with the atoms trapped in a two dimensional optical lattice at a distance of 10 microns from a glass surface that is part of the microscope. We have experimentally verified a resolution of ˜ 600 nm, providing the capability to study the phase diagram of the Bose Hubbard model by measuring occupation number at individual sites.
Magnetic Property in Large Array Niobium Antidot Thin Films
NASA Astrophysics Data System (ADS)
Tinghui, Chen; Hsiang-Hsi, Kung; Wei-Li, Lee; Institute of Physics, Academia Sinica, Taipei, Taiwan Team
2014-03-01
In a superconducting ring, the total flux inside the ring is required to be an integer number of the flux quanta. Therefore, a supercurrent current can appear within the ring in order to satisfy this quantization rule, which gives rise to certain magnetic response. By using a special monolayer polymer/nanosphere hybrid we developed previously, we fabricated a series of superconducting niobium antidot thin films with different antidot diameters. The antidots form well-ordered triangular lattice with a lattice spacing about 200 nm and extend over an area larger than 1 cm2, which enables magnetic detections simply by a SQUID magnetometer. We observed magnetization oscillation with external magnetic field due to the supercurrent screening effect, where different features for large and small antidot thin films were found. Detailed size and temperature dependencies of the magnetization in niobium antidot nanostructures will be presented.
Lattice Boltzmann methods for some 2-D nonlinear diffusion equations:Computational results
Elton, B.H.; Rodrigue, G.H. . Dept. of Applied Science Lawrence Livermore National Lab., CA ); Levermore, C.D. . Dept. of Mathematics)
1990-01-01
In this paper we examine two lattice Boltzmann methods (that are a derivative of lattice gas methods) for computing solutions to two two-dimensional nonlinear diffusion equations of the form {partial derivative}/{partial derivative}t u = v ({partial derivative}/{partial derivative}x D(u){partial derivative}/{partial derivative}x u + {partial derivative}/{partial derivative}y D(u){partial derivative}/{partial derivative}y u), where u = u({rvec x},t), {rvec x} {element of} R{sup 2}, v is a constant, and D(u) is a nonlinear term that arises from a Chapman-Enskog asymptotic expansion. In particular, we provide computational evidence supporting recent results showing that the methods are second order convergent (in the L{sub 1}-norm), conservative, conditionally monotone finite difference methods. Solutions computed via the lattice Boltzmann methods are compared with those computed by other explicit, second order, conservative, monotone finite difference methods. Results are reported for both the L{sub 1}- and L{sub {infinity}}-norms.
Buckling in 2D periodic, soft and porous structures: effect of pore shape and lattice pattern
NASA Astrophysics Data System (ADS)
Shan, Sicong; Bertoldi, Katia; Shim, Jongmin; Overvelde, Johannes T. B.; Kang, Sung Hoon
2013-03-01
Adaptive structures allowing dramatic shape changes offer unique opportunities for the design of responsive and reconfigurable devices. Traditional morphing and foldable structures with stiff structural members and mechanical joints remains a challenge in manufacturing at small length scales. Soft structures where the folding mechanisms are induced by a mechanical instability represent a new class of novel adaptive materials which can be easily manufactured over a wide range of length scales. More specifically, soft porous structures with deliberately designed patterns can significantly change their architecture in response to diverse stimuli, opening avenues for reconfigurable devices that change their shapes to respond to their environment. While so far only two-dimensional periodic porous structures with circular holes arranged on a square or triangular lattice have been investigated, here we investigate both numerically and experimentally the effects of pore shape and lattice pattern on the macroscopic properties of the structures. Our results show that both the pore shape and lattice pattern can be used to effectively design desired materials and pave the way for the development of a new class of soft, active and reconfigurable devices over a wide range of length scales.
Algebraic rings of integers and some 2D lattice problems in physics
NASA Astrophysics Data System (ADS)
Nanxian, Chen; Zhaodou, Chen; Shaojun, Liu; Yanan, Shen; Xijin, Ge
1996-09-01
This paper develops the Möbius inversion formula for the Gaussian integers and Eisenstein's integers, and gives two applications. The first application is to the two-dimensional arithmetic Fourier transform (AFT), which is suitable for parallel processing. The second application is to two-dimensional inverse lattice problems, and is illustrated with the recovery of interatomic potentials from the cohesive energy for monolayer graphite. The paper demonstrates the potential application in the physical science of integral domains other than the standard integers.
Exact ground state for the four-electron problem in a 2D finite honeycomb lattice
NASA Astrophysics Data System (ADS)
Trencsényi, Réka; Glukhov, Konstantin; Gulácsi, Zsolt
2014-07-01
Working in a subspace with dimensionality much smaller than the dimension of the full Hilbert space, we deduce exact four-particle ground states in 2D samples containing hexagonal repeat units and described by Hubbard type of models. The procedure identifies first a small subspace ? in which the ground state ? is placed, than deduces ? by exact diagonalization in ?. The small subspace is obtained by the repeated application of the Hamiltonian ? on a carefully chosen starting wave vector describing the most interacting particle configuration, and the wave vectors resulting from the application of ?, till the obtained system of equations closes in itself. The procedure which can be applied in principle at fixed but arbitrary system size and number of particles is interesting on its own since it provides exact information for the numerical approximation techniques which use a similar strategy, but apply non-complete basis for ?. The diagonalization inside ? provides an incomplete image of the low lying part of the excitation spectrum, but provides the exact ?. Once the exact ground state is obtained, its properties can be easily analysed. The ? is found always as a singlet state whose energy, interestingly, saturates in the ? limit. The unapproximated results show that the emergence probabilities of different particle configurations in the ground state presents 'Zittern' (trembling) characteristics which are absent in 2D square Hubbard systems. Consequently, the manifestation of the local Coulomb repulsion in 2D square and honeycomb types of systems presents differences, which can be a real source in the differences in the many-body behaviour.
Complex zeros of the 2 d Ising model on dynamical random lattices
NASA Astrophysics Data System (ADS)
Ambjørn, J.; Anagnostopoulos, K. N.; Magnea, U.
1998-04-01
We study the zeros in the complex plane of the partition function for the Ising model coupled to 2 d quantum gravity for complex magnetic field and for complex temperature. We compute the zeros by using the exact solution coming from a two matrix model and by Monte Carlo simulations of Ising spins on dynamical triangulations. We present evidence that the zeros form simple one-dimensional patterns in the complex plane, and that the critical behaviour of the system is governed by the scaling of the distribution of singularities near the critical point.
Hubbard Model study of Off Diagonally Confined fermions in a 2D Optical Lattice
NASA Astrophysics Data System (ADS)
Cone, Dave; Chiesa, Simone; Scalettar, Richard; Batrouni, George
2010-03-01
We report Quantum Monte Carlo simulations of a Hubbard Hamiltonian which incorporates a proposed new method for confining atoms in an optical lattice employing an inhomogeneous array of hopping matrix elements which trap atoms by going to zero at the lattice edges. This has been termed ``Off Diagonal Confinement (ODC)'' [1] to distinguish it from the more conventional use of a parabolic trap coupling to (diagonal) density operators. It has the advantage of producing systems which, while still being inhomogeneous, are entirely in the Mott phase, and allow simulations which are free of the sign problem at low temperatures. We analyze the effects of using ODC traps on the local density, density fluctuation, spin, and pairing correlation functions. Finally, we will discuss the advantages and importance of this new confinement technique for modeling correlated systems. Research supported by the Department of Energy, Office of Science SCIDAC program, DOE-DE-FC0206ER25793. [1] V.G. Rousseau et al., arXiv:0909.3543
Modeling Selective Local Interactions with Memory: Motion on a 2D Lattice.
Weinberg, Daniel; Levy, Doron
2014-06-15
We consider a system of particles that simultaneously move on a two-dimensional periodic lattice at discrete times steps. Particles remember their last direction of movement and may either choose to continue moving in this direction, remain stationary, or move toward one of their neighbors. The form of motion is chosen based on predetermined stationary probabilities. Simulations of this model reveal a connection between these probabilities and the emerging patterns and size of aggregates. In addition, we develop a reaction diffusion master equation from which we derive a system of ODEs describing the dynamics of the particles on the lattice. Simulations demonstrate that solutions of the ODEs may replicate the aggregation patterns produced by the stochastic particle model. We investigate conditions on the parameters that influence the locations at which particles prefer to aggregate. This work is a two-dimensional generalization of [Galante & Levy, Physica D, http://dx.doi.org/10.1016/j.physd.2012.10.010], in which the corresponding one-dimensional problem was studied. PMID:25045193
Yang Xuefeng; Cui Jian; Zhang Yuan; Liu Yue
2012-07-15
The dispersion relations of the externally and thermally (naturally) excited dust lattice modes (both longitudinal and transverse) in two-dimensional Debye-Yukawa complex plasma crystals are investigated. The dispersion relations are calculated numerically by taking the neutral gas damping effects into account and the numerical results are in agreement with the experimental data given by Nunomura et al.[Phys. Rev. E 65, 066402 (2002)]. It is found that for the mode excited by an external disturbance with a real frequency, the dispersion properties are changed at a critical frequency near where the group velocity of the mode goes to zero. Therefore, the high frequency branch with negative dispersion cannot be reached. In contrast, for the thermally excited mode, the dispersion curve can extend all the way to the negative dispersion region, while a 'cut-off' wave number exists at the long wavelength end of the dispersion in the transverse mode.
Particulate nature of blood determines macroscopic rheology: a 2-D lattice Boltzmann analysis.
Sun, Chenghai; Munn, Lance L
2005-03-01
Historically, predicting macroscopic blood flow characteristics such as viscosity has been an empirical process due to the difficulty in rigorously including the particulate nature of blood in a mathematical representation of blood rheology. Using a two-dimensional lattice Boltzmann approach, we have simulated the flow of red blood cells in a blood vessel to estimate flow resistance at various hematocrits and vessel diameters. By including white blood cells (WBCs) in the flow, we also calculate the increase in resistance due to white cell rolling and adhesion. The model considers the blood as a suspension of particles in plasma, accounting for cell-cell and cell-wall interactions to predict macroscopic blood rheology. The model is able to reproduce the Fahraeus-Lindqvist effect, i.e., the increase in relative apparent viscosity as tube size increases, and the Fahraeus effect, i.e., tube hematocrit is lower than discharge hematocrit. In addition, the model allows direct assessment of the effect of WBCs on blood flow in the microvasculature, reproducing the dramatic increases in flow resistance as WBCs enter short capillary segments. This powerful and flexible model can be used to predict blood flow properties in any vessel geometry and with any blood composition. PMID:15613630
Adiabatic and Hamiltonian computing on a 2D lattice with simple two-qubit interactions
NASA Astrophysics Data System (ADS)
Lloyd, Seth; Terhal, Barbara M.
2016-02-01
We show how to perform universal Hamiltonian and adiabatic computing using a time-independent Hamiltonian on a 2D grid describing a system of hopping particles which string together and interact to perform the computation. In this construction, the movement of one particle is controlled by the presence or absence of other particles, an effective quantum field effect transistor that allows the construction of controlled-NOT and controlled-rotation gates. The construction translates into a model for universal quantum computation with time-independent two-qubit ZZ and XX+YY interactions on an (almost) planar grid. The effective Hamiltonian is arrived at by a single use of first-order perturbation theory avoiding the use of perturbation gadgets. The dynamics and spectral properties of the effective Hamiltonian can be fully determined as it corresponds to a particular realization of a mapping between a quantum circuit and a Hamiltonian called the space-time circuit-to-Hamiltonian construction. Because of the simple interactions required, and because no higher-order perturbation gadgets are employed, our construction is potentially realizable using superconducting or other solid-state qubits.
A hierarchical lattice spring model to simulate the mechanics of 2-D materials-based composites
NASA Astrophysics Data System (ADS)
Brely, Lucas; Bosia, Federico; Pugno, Nicola
2015-07-01
In the field of engineering materials, strength and toughness are typically two mutually exclusive properties. Structural biological materials such as bone, tendon or dentin have resolved this conflict and show unprecedented damage tolerance, toughness and strength levels. The common feature of these materials is their hierarchical heterogeneous structure, which contributes to increased energy dissipation before failure occurring at different scale levels. These structural properties are the key to exceptional bioinspired material mechanical properties, in particular for nanocomposites. Here, we develop a numerical model in order to simulate the mechanisms involved in damage progression and energy dissipation at different size scales in nano- and macro-composites, which depend both on the heterogeneity of the material and on the type of hierarchical structure. Both these aspects have been incorporated into a 2-dimensional model based on a Lattice Spring Model, accounting for geometrical nonlinearities and including statistically-based fracture phenomena. The model has been validated by comparing numerical results to continuum and fracture mechanics results as well as finite elements simulations, and then employed to study how structural aspects impact on hierarchical composite material properties. Results obtained with the numerical code highlight the dependence of stress distributions on matrix properties and reinforcement dispersion, geometry and properties, and how failure of sacrificial elements is directly involved in the damage tolerance of the material. Thanks to the rapidly developing field of nanocomposite manufacture, it is already possible to artificially create materials with multi-scale hierarchical reinforcements. The developed code could be a valuable support in the design and optimization of these advanced materials, drawing inspiration and going beyond biological materials with exceptional mechanical properties.
Beyond classical nucleation theory: A 2-D lattice-gas automata model
NASA Astrophysics Data System (ADS)
Hickey, Joseph
Nucleation is the first step in the formation of a new phase in a thermodynamic system. The Classical Nucleation Theory (CNT) is the traditional theory used to describe this phenomenon. The object of this thesis is to investigate nucleation beyond one of the most significant limitations of the CNT: the assumption that the surface tension of a nucleating cluster of the new phase is independent of the cluster's size and has the same value that it would have in the bulk of the new phase. In order to accomplish this, we consider a microscopic, two-dimensional Lattice Gas Automata (LGA) model of precipitate nucleation in a supersaturated system, with model input parameters Ess (solid particle-to-solid particle bonding energy), Esw (solid particle-to-water particle bonding energy), eta (next-to-nearest neighbour bonding coeffiicent in solid phase), and Cin (initial solute concentration). The LGA method was chosen for its advantages of easy implementation, low memory requirements, and fast computation speed. Analytical results for the system's concentration and the crystal radius as functions of time are derived and the former is fit to the simulation data in order to determine the system's equilibrium concentration. A mean first-passage time (MFPT) technique is used to obtain the nucleation rate and critical nucleus size from the simulation data. The nucleation rate and supersaturation are evaluated using a modification to the CNT that incorporates a two-dimensional, radius-dependent surface tension term. The Tolman parameter, delta, which controls the radius-dependence of the surface tension, decreases (increases) as a function of the magnitude of Ess (Esw), at fixed values of eta and Esw (Ess). On the other hand, delta increases as eta increases while E ss and Esw are held constant. The constant surface tension term of the CNT, Sigma0, increases (decreases) with increasing magnitudes of Ess (Esw) fixed values of Esw (Ess), and increases as eta is increased. Together
Ao, L; Pham, A; Xiao, H Y; Zu, X T; Li, S
2016-03-14
We have systematically investigated the effects of different vacancy defects in 2D d(0) materials SnS2 and ZrS2 using first principles calculations. The theoretical results show that the single cation vacancy and the vacancy complex like V-SnS6 can induce large magnetic moments (3-4 μB) in these single layer materials. Other defects, such as V-SnS3, V-S, V-ZrS3 and V-ZrS6, can result in n-type conductivity. In addition, the ab initio studies also reveal that the magnetic and conductive properties from the cation vacancy and the defect complex V-SnS6 can be modified using the compressive/tensile strain of the in-plane lattices. Specifically, the V-Zr doped ZrS2 monolayer can be tuned from a ferromagnetic semiconductor to a metallic/half-metallic material with decreasing/increasing magnetic moments depending on the external compressive/tensile strains. On the other hand, the semiconducting and magnetic properties of V-Sn doped SnS2 is preserved under different lattice compression and tension. For the defect complex like V-SnS6, only the lattice compression can tune the magnetic moments in SnS2. As a result, by manipulating the fabrication parameters, the magnetic and conductive properties of SnS2 and ZrS2 can be tuned without the need for chemical doping. PMID:26888010
Magnetic edge states and magnetotransport in graphene antidot barriers
NASA Astrophysics Data System (ADS)
Thomsen, M. R.; Power, S. R.; Jauho, A.-P.; Pedersen, T. G.
2016-07-01
Magnetic fields are often used for characterizing transport in nanoscale materials. Recent magnetotransport experiments have demonstrated that ballistic transport is possible in graphene antidot lattices (GALs). These experiments have inspired the present theoretical study of GALs in a perpendicular magnetic field. We calculate magnetotransport through graphene antidot barriers (GABs), which are finite rows of antidots arranged periodically in a pristine graphene sheet, using a tight-binding model and the Landauer-Büttiker formula. We show that GABs behave as ideal Dirac mass barriers for antidots smaller than the magnetic length and demonstrate the presence of magnetic edge states, which are localized states on the periphery of the antidots due to successive reflections on the antidot edge in the presence of a magnetic field. We show that these states are robust against variations in lattice configuration and antidot edge chirality. Moreover, we calculate the transmittance of disordered GABs and find that magnetic edge states survive a moderate degree of disorder. Due to the long phase-coherence length in graphene and the robustness of these states, we expect magnetic edge states to be observable in experiments as well.
Quantum Hall effect in bilayer system with array of antidots
NASA Astrophysics Data System (ADS)
Pagnossin, I. R.; Gusev, G. M.; Sotomayor, N. M.; Seabra, A. C.; Quivy, A. A.; Lamas, T. E.; Portal, J. C.
2007-04-01
We have studied the Quantum Hall effect in a bilayer system modulated by gate-controlled antidot lattice potential. The Hall resistance shows plateaus which are quantized to anomalous multiplies of h/e2. We suggest that this complex behavior is due to the nature of the edge-states in double quantum well (DQW) structures coupled to an array of antidots: these plateaus may be originated from the coexistence of normal and counter-rotating edge-states in different layers.
NASA Astrophysics Data System (ADS)
Woods, Justin; Bhat, Vinayak; Farmer, Barry; Sklenar, Joseph; Teipel, Eric; Ketterson, John; Hastings, J. Todd; de Long, Lance
2015-03-01
Artificial spin ice (ASI) systems are composed of nanoscale ferromagnetic segments whose shape anisotropy dictates they behave as mesoscopic Ising spins. Most ASI have segments patterned on periodic lattices and a single vertex topology. We have continuously distorted 2D honeycomb and square lattices such that the pattern vertex spacings follow a Fibonacci chain sequence along primitive lattice directions. The Fibonacci distortion is related to the aperiodic translational symmetry of 2D artificial quasicrystals1 that cannot be viewed as continuous distortions of periodic lattices due to their forbidden (e.g., fivefold) rotational symmetries. In contrast, Fibonacci distortions of 2D periodic lattices can be ``turned on'' by control of the ratio of two lattice parameters d1 and d2. Distortions alter film segments such that pattern vertices are no longer equivalent and traditional spin ice rules are no longer strictly valid. We have performed OOMMF simulations of magnetization reversal for samples having different levels of distortion, and found the magnetic reversal to be dramatically slowed by small distortions (d1/d2 ~ 1). Research at Kentucky is supported by U.S. DoE Grant DE-FG02-97ER45653 and NSF Grant EPS-0814194.
An exact and efficient first passage time algorithm for reaction–diffusion processes on a 2D-lattice
Bezzola, Andri; Bales, Benjamin B.; Alkire, Richard C.; Petzold, Linda R.
2014-01-01
We present an exact and efficient algorithm for reaction–diffusion–nucleation processes on a 2D-lattice. The algorithm makes use of first passage time (FPT) to replace the computationally intensive simulation of diffusion hops in KMC by larger jumps when particles are far away from step-edges or other particles. Our approach computes exact probability distributions of jump times and target locations in a closed-form formula, based on the eigenvectors and eigenvalues of the corresponding 1D transition matrix, maintaining atomic-scale resolution of resulting shapes of deposit islands. We have applied our method to three different test cases of electrodeposition: pure diffusional aggregation for large ranges of diffusivity rates and for simulation domain sizes of up to 4096×4096 sites, the effect of diffusivity on island shapes and sizes in combination with a KMC edge diffusion, and the calculation of an exclusion zone in front of a step-edge, confirming statistical equivalence to standard KMC simulations. The algorithm achieves significant speedup compared to standard KMC for cases where particles diffuse over long distances before nucleating with other particles or being captured by larger islands.
Dependence of magnetization process on thickness of Permalloy antidot arrays
Merazzo, K. J.; Real, R. P. del; Asenjo, A.; Vazquez, M.
2011-04-01
Nanohole films or antidot arrays of Permalloy have been prepared by the sputtering of Ni{sub 80}Fe{sub 20} onto anodic alumina membrane templates. The film thickness varies from 5 to 47 nm and the antidot diameters go from 42 to 61 nm, for a hexagonal lattice parameter of 105 nm. For the thinner antidot films (5 and 10 nm thick), magnetic moments locally distribute in a complex manner to reduce the magnetostatic energy, and their mostly reversible magnetization process is ascribed to spin rotations. In the case of the thicker (20 and 47 nm) antidot films, pseudodomain walls appear and the magnetization process is mostly irreversible where hysteresis denotes the effect of nanoholes pinning to wall motion.
NASA Astrophysics Data System (ADS)
Velarde, M. G.; Ebeling, W.; Chetverikov, A. P.
2013-01-01
We study the thermal excitation of intrinsic localized modes in the form of solitons in 1d and 2d anharmonic lattices at moderately high temperatures. Such finite-amplitude fluctuations form long-living dynamical structures with life-time in the pico-second range thus surviving a relatively long time in comparison to other thermal fluctuations. Further we discuss the influence of such long-living fluctuations on the dynamics of added excess free electrons. The atomic lattice units are treated as quasi-classical objects interacting by Morse forces and stochastically moving according to Langevin equations. In 2d the atoms are initially organized in a triangular lattice. The electron distributions are in a first estimate represented by equilibrium adiabatic distributions in the actual polarization fields. Computer simulations show that in 2d systems such excitations are moving with supersonic velocities along lattice rows oriented with the cristallographic axes. By following the electron distributions we have also been able to study the excitations of solectron type (electron-soliton dynamic bound states) and estimate their life times.
Magnetic vortex crystal formation in the antidot complement of square artificial spin ice
Araujo, C. I. L. de Silva, R. C.; Ribeiro, I. R. B.; Nascimento, F. S.; Felix, J. F.; Ferreira, S. O.; Moura-Melo, W. A.; Pereira, A. R.; Mól, L. A. S.
2014-03-03
We have studied ferromagnetic nickel thin films patterned with square lattices of elongated antidots that are negative analogues of square artificial spin ice. Micromagnetic simulations and direct current magnetic moment measurements reveal in-plane anisotropy of the magnetic hysteresis loops, and the formation of a dense array of magnetic vortices with random polarization and chirality. These multiply-connected antidot arrays could be superior to lattices of disconnected nanodisks for investigations of vortex switching by applied electric current.
Magnetic vortex crystal formation in the antidot complement of square artificial spin ice
NASA Astrophysics Data System (ADS)
de Araujo, C. I. L.; Silva, R. C.; Ribeiro, I. R. B.; Nascimento, F. S.; Felix, J. F.; Ferreira, S. O.; Mól, L. A. S.; Moura-Melo, W. A.; Pereira, A. R.
2014-03-01
We have studied ferromagnetic nickel thin films patterned with square lattices of elongated antidots that are negative analogues of square artificial spin ice. Micromagnetic simulations and direct current magnetic moment measurements reveal in-plane anisotropy of the magnetic hysteresis loops, and the formation of a dense array of magnetic vortices with random polarization and chirality. These multiply-connected antidot arrays could be superior to lattices of disconnected nanodisks for investigations of vortex switching by applied electric current.
NaKV4O9·2H2O: a new 2D magnetic compound with a 1/5-depleted square lattice.
Cui, Meiyan; He, Zhangzhen; Wang, Nannan; Tang, Yingying; Guo, Wenbin; Zhang, Suyun; Wang, Lin; Xiang, Hongping
2016-03-15
A new vanadate compound NaKV4O9·2H2O is successfully synthesized by a conventional hydrothermal method. This compound crystallizes in the monoclinic system with the space group C2/c, showing a typical 2D layered structure built from VO5 pyramids, in which the layers are separated by Na(+), K(+), and H2O. The topology structure of magnetic V(4+) ions shows a quite interesting 1/5-depleted square lattice, which is quite similar to that of a famous low-dimensional quantum spin system CaV4O9. A structural and magnetic comparison confirmed that the title compound may exhibit a more pronounced 2D character with a large spin gap. PMID:26892907
Magnetic properties engineering of nanopatterned cobalt antidot arrays
NASA Astrophysics Data System (ADS)
Kaidatzis, Andreas; del Real, Rafael P.; Alvaro, Raquel; Palma, Juan Luis; Anguita, José; Niarchos, Dimitrios; Vázquez, Manuel; Escrig, Juan; García-Martín, José Miguel
2016-05-01
We report on the study of arrays of 60 nm wide cobalt antidots, nanopatterned using focused ion beam milling. Square and hexagonal symmetry arrays have been studied, with varying antidot densities and lattice constant from 150 up to 300 nm. We find a strong increase of the arrays’ magnetic coercivity with respect to the unpatterned film, which is monotonic as the antidot density increases. Additionally, there is a strong influence of the array symmetry to the in-plane magnetic anisotropy: square arrays exhibit fourfold symmetry and hexagonal arrays exhibit sixfold symmetry. The above findings are corroborated by magnetic imaging and micromagnetic modeling, which show the magnetic structure of the arrays to depend strongly on the array morphology.
NASA Astrophysics Data System (ADS)
Li, Shuai; Qiu, Wen-Xuan; Gao, Jin-Hua
2016-06-01
Recently, a new kind of artificial two dimensional (2D) electron lattice on the nanoscale, i.e. molecular graphene, has drawn a lot of interest, where the metal surface electrons are transformed into a honeycomb lattice via absorbing a molecular lattice on the metal surface [Gomes et al., Nature, 2012, 438, 306; Wang et al., Phys. Rev. Lett., 2014, 113, 196803]. In this work, we theoretically demonstrate that this technique can be readily used to build other complex 2D electron lattices on a metal surface, which are of high interest in the field of condensed matter physics. The main challenge to build a complex 2D electron lattice is that this is a quantum antidot system, where the absorbed molecule normally exerts a repulsive potential on the surface electrons. Thus, there is no straightforward corresponding relation between the molecular lattice pattern and the desired 2D lattice of surface electrons. Here, we give an interesting example about the Kagome lattice, which has exotic correlated electronic states. We design a special molecular pattern and show that this molecular lattice can transform the surface electrons into a Kagome-like lattice. The numerical simulation is conducted using a Cu(111) surface and CO molecules. We first estimate the effective parameters of the Cu/CO system by fitting experimental data of the molecular graphene. Then, we calculate the corresponding energy bands and LDOS of the surface electrons in the presence of the proposed molecular lattice. Finally, we interpret the numerical results by the tight binding model of the Kagome lattice. We hope that our work can stimulate further theoretical and experimental interest in this novel artificial 2D electron lattice system.
Li, Shuai; Qiu, Wen-Xuan; Gao, Jin-Hua
2016-07-01
Recently, a new kind of artificial two dimensional (2D) electron lattice on the nanoscale, i.e. molecular graphene, has drawn a lot of interest, where the metal surface electrons are transformed into a honeycomb lattice via absorbing a molecular lattice on the metal surface [Gomes et al., Nature, 2012, 438, 306; Wang et al., Phys. Rev. Lett., 2014, 113, 196803]. In this work, we theoretically demonstrate that this technique can be readily used to build other complex 2D electron lattices on a metal surface, which are of high interest in the field of condensed matter physics. The main challenge to build a complex 2D electron lattice is that this is a quantum antidot system, where the absorbed molecule normally exerts a repulsive potential on the surface electrons. Thus, there is no straightforward corresponding relation between the molecular lattice pattern and the desired 2D lattice of surface electrons. Here, we give an interesting example about the Kagome lattice, which has exotic correlated electronic states. We design a special molecular pattern and show that this molecular lattice can transform the surface electrons into a Kagome-like lattice. The numerical simulation is conducted using a Cu(111) surface and CO molecules. We first estimate the effective parameters of the Cu/CO system by fitting experimental data of the molecular graphene. Then, we calculate the corresponding energy bands and LDOS of the surface electrons in the presence of the proposed molecular lattice. Finally, we interpret the numerical results by the tight binding model of the Kagome lattice. We hope that our work can stimulate further theoretical and experimental interest in this novel artificial 2D electron lattice system. PMID:27279292
NASA Astrophysics Data System (ADS)
Yang, PeiPei; Wen, Zhi; Dou, RuiFeng; Liu, Xunliang
2016-08-01
Flow and heat transfer through a 2D random porous medium are studied by using the lattice Boltzmann method (LBM). For the random porous medium, the influence of disordered cylinder arrangement on permeability and Nusselt number are investigated. Results indicate that the permeability and Nusselt number for different cylinder locations are unequal even with the same number and size of cylinders. New correlations for the permeability and coefficient b‧Den of the Forchheimer equation are proposed for random porous medium composed of Gaussian distributed circular cylinders. Furthermore, a general set of heat transfer correlations is proposed and compared with existing experimental data and empirical correlations. Our results show that the Nu number increases with the increase of the porosity, hence heat transfer is found to be accurate considering the effect of porosity.
Ashley, Carlee E; Dunphy, Darren R; Jiang, Zhang; Carnes, Eric C; Yuan, Zhen; Petsev, Dimiter N; Atanassov, Plamen B; Velev, Orlin D; Sprung, Michael; Wang, Jin; Peabody, David S; Brinker, C Jeffrey
2011-04-18
The rapid assembly of icosohedral virus-like particles (VLPs) into highly ordered (domain size > 600 nm), oriented 2D superlattices directly onto a solid substrate using convective coating is demonstrated. In-situ grazing-incidence small-angle X-ray scattering (GISAXS) is used to follow the self-assembly process in real time to characterize the mechanism of superlattice formation, with the ultimate goal of tailoring film deposition conditions to optimize long-range order. From water, GISAXS data are consistent with a transport-limited assembly process where convective flow directs assembly of VLPs into a lattice oriented with respect to the water drying line. Addition of a nonvolatile solvent (glycerol) modified this assembly pathway, resulting in non-oriented superlattices with improved long-range order. Modification of electrostatic conditions (solution ionic strength, substrate charge) also alters assembly behavior; however, a comparison of in-situ assembly data between VLPs derived from the bacteriophages MS2 and Qβ show that this assembly process is not fully described by a simple Derjaguin-Landau-Verwey-Overbeek model alone. PMID:21425464
The dilemma of approving antidotes.
Steffen, Christian
2007-04-20
Clinical trials with antidotes are difficult to perform for a variety of practical, ethical, and financial reasons. As acute poisoning is a rare event, the commercial interest in basic and clinical research is low. Poisoned patients are usually not available for normal clinical trial procedures and, if they are, they cannot give informed consent. This situation results in a dilemma: antidotes are essential drugs. A resolution of the Council of Europe requests to guarantee the optimal availability of antidotes and the improvement of their use. As comprehensive data on the efficacy of antidotes are often missing, a marketing authorisation under exceptional circumstances according to Article 14(8) of Regulation (EC) No. 276/2004, will often be the only way to get an approval, as: (1) the indications for which the product in question is intended are encountered so rarely that the applicant cannot reasonably be expected to provide comprehensive evidence ("orphan drug"), (2) in the present state of scientific knowledge, comprehensive information cannot be provided, or (3) it would be contrary to generally accepted principles of medical ethics to collect such data. Typically, data on antidotes are obtained from a patchwork of studies with animals, human tissue and a few observations from human poisoning corroborated with data from clinical observations and biochemistry. Generalisations from chemical and mechanistic similarities between groups of poisons are usual, but often lack scientific evidence. Current standards of good clinical practice can rarely be observed. Therefore, public funding and other financial support are necessary incentives to initiate trials in this important area. PMID:17207900
Pérez-Montoto, Lázaro G; Santana, Lourdes; González-Díaz, Humberto
2009-11-01
We introduce here a new class of invariants for MD trajectories based on the spectral moments pi(k)(L) of the Markov matrix associated to lattice network-like (LN) graph representations of Molecular Dynamics (MD) trajectories. The procedure embeds the MD energy profiles on a 2D Cartesian coordinates system using simple heuristic rules. At the same time, we associate the LN with a Markov matrix that describes the probabilities of passing from one state to other in the new 2D space. We construct this type of LNs for 422 MD trajectories obtained in DNA-drug docking experiments of 57 furocoumarins. The combined use of psoralens+ultraviolet light (UVA) radiation is known as PUVA therapy. PUVA is effective in the treatment of skin diseases such as psoriasis and mycosis fungoides. PUVA is also useful to treat human platelet (PTL) concentrates in order to eliminate Leishmania spp. and Trypanosoma cruzi. Both are parasites that cause Leishmaniosis (a dangerous skin and visceral disease) and Chagas disease, respectively; and may circulate in blood products collected from infected donors. We included in this study both lineal (psoralens) and angular (angelicins) furocoumarins. In the study, we grouped the LNs on two sets; set1: DNA-drug complex MD trajectories for active compounds and set2: MD trajectories of non-active compounds or no-optimal MD trajectories of active compounds. We calculated the respective pi(k)(L) values for all these LNs and used them as inputs to train a new classifier that discriminate set1 from set2 cases. In training series the model correctly classifies 79 out of 80 (specificity=98.75%) set1 and 226 out of 238 (Sensitivity=94.96%) set2 trajectories. In independent validation series the model correctly classifies 26 out of 26 (specificity=100%) set1 and 75 out of 78 (sensitivity=96.15%) set2 trajectories. We propose this new model as a scoring function to guide DNA-docking studies in the drug design of new coumarins for anticancer or antiparasitic
Dea-Ayuela, María Auxiliadora; Pérez-Castillo, Yunierkis; Meneses-Marcel, Alfredo; Ubeira, Florencio M; Bolas-Fernández, Francisco; Chou, Kuo-Chen; González-Díaz, Humberto
2008-08-15
The toxicity and inefficacy of actual organic drugs against Leishmaniosis justify research projects to find new molecular targets in Leishmania species including Leishmania infantum (L. infantum) and Leishmaniamajor (L. major), both important pathogens. In this sense, quantitative structure-activity relationship (QSAR) methods, which are very useful in Bioorganic and Medicinal Chemistry to discover small-sized drugs, may help to identify not only new drugs but also new drug targets, if we apply them to proteins. Dyneins are important proteins of these parasites governing fundamental processes such as cilia and flagella motion, nuclear migration, organization of the mitotic splinde, and chromosome separation during mitosis. However, despite the interest for them as potential drug targets, so far there has been no report whatsoever on dyneins with QSAR techniques. To the best of our knowledge, we report here the first QSAR for dynein proteins. We used as input the Spectral Moments of a Markov matrix associated to the HP-Lattice Network of the protein sequence. The data contain 411 protein sequences of different species selected by ClustalX to develop a QSAR that correctly discriminates on average between 92.75% and 92.51% of dyneins and other proteins in four different train and cross-validation datasets. We also report a combined experimental and theoretic study of a new dynein sequence in order to illustrate the utility of the model to search for potential drug targets with a practical example. First, we carried out a 2D-electrophoresis analysis of L. infantum biological samples. Next, we excised from 2D-E gels one spot of interest belonging to an unknown protein or protein fragment in the region M<20,200 and pI<4. We used MASCOT search engine to find proteins in the L. major data base with the highest similarity score to the MS of the protein isolated from L. infantum. We used the QSAR model to predict the new sequence as dynein with probability of 99.99% without
2011-01-01
Insects carry out essential ecological functions, such as pollination, but also cause extensive damage to agricultural crops and transmit human diseases such as malaria and dengue fever. Advances in insect transgenesis are making it increasingly feasible to engineer genes conferring desirable phenotypes, and gene drive systems are required to spread these genes into wild populations. Medea provides one solution, being able to spread into a population from very low initial frequencies through the action of a maternally-expressed toxin linked to a zygotically-expressed antidote. Several other toxin-antidote combinations are imaginable that distort the offspring ratio in favor of a desired transgene, or drive the population towards an all-male crash. We explore two such systems—Semele, which is capable of spreading a desired transgene into an isolated population in a confined manner; and Merea, which is capable of inducing a local population crash when located on the Z chromosome of a Lepidopteron pest. PMID:21876382
NASA Astrophysics Data System (ADS)
Kumar, Ajit; Verma, Sanjay K.; Alvi, P. A.; Jasrotia, Dinesh
2016-04-01
The nanospatial morphological features of [ZnCl]- [C5H4NCH3]+ hybrid derivative depicts 28 nm granular size and 3D spreader shape packing pattern as analyzed by FESEM and single crystal XRD structural studies. The organic moiety connect the inorganic components through N-H+…Cl- hydrogen bond to form a hybrid composite, the replacement of organic derivatives from 2-methylpyridine to 2-Amino-5-choloropyridine results the increase in granular size from 28nm to 60nm and unit cell packing pattern from 3D-2D lattice dimensionality along ac plane. The change in optical energy direct band gap value from 3.01eV for [ZnCl]- [C5H4NCH3]+ (HM1) to 3.42eV for [ZnCl]- [C5H5ClN2]+ (HM2) indicates the role of organic moiety in optical properties of hybrid materials. The photoluminescence emission spectra is observed in the wavelength range of 370 to 600 nm with maximum peak intensity of 9.66a.u. at 438 nm for (HM1) and 370 to 600 nm with max peak intensity of 9.91 a.u. at 442 nm for (HM2), indicating that the emission spectra lies in visible range. PL excitation spectra depicts the maximum excitation intensity [9.8] at 245.5 nm for (HM1) and its value of 9.9 a.u. at 294 nm, specify the excitation spectra lies in UV range. Photoluminescence excitation spectra is observed in the wavelength range of 280 to 350 nm with maximum peak intensity of 9.4 a.u. at 285.5 nm and 9.9 a.u. at 294 and 297 nm, indicating excitation in the UV spectrum. Single crystal growth process and detailed physiochemical characterization such as XRD, FESEM image analysis photoluminescence property reveals the structure stability with non-covalent interactions, lattice dimensionality (3D-2D) correlations interweaving into the design of inorganic-organic hybrid materials.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 5 2014-10-01 2014-10-01 false Antidotes. 154.1440 Section 154.1440 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Safety Equipment § 154.1440 Antidotes. Each vessel must...
Code of Federal Regulations, 2010 CFR
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Antidotes. 154.1440 Section 154.1440 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Safety Equipment § 154.1440 Antidotes. Each vessel must...
46 CFR 153.930 - Cargo antidotes.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Cargo antidotes. 153.930 Section 153.930 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Operations General Vessel Safety § 153.930 Cargo antidotes. No person may operate...
46 CFR 153.930 - Cargo antidotes.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 5 2014-10-01 2014-10-01 false Cargo antidotes. 153.930 Section 153.930 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Operations General Vessel Safety § 153.930 Cargo antidotes. No person may operate...
Who gets antidotes? choosing the chosen few.
Buckley, Nicholas A; Dawson, Andrew H; Juurlink, David N; Isbister, Geoffrey K
2016-03-01
An understanding of mechanisms, potential benefits and risks of antidotes is essential for clinicians who manage poisoned patients. Of the dozens of antidotes currently available, only a few are regularly used. These include activated charcoal, acetylcysteine, naloxone, sodium bicarbonate, atropine, flumazenil, therapeutic antibodies and various vitamins. Even then, most are used in a minority of poisonings. There is little randomized trial evidence to support the use of most antidotes. Consequently, decisions about when to use them are often based on a mechanistic understanding of the poisoning and the expected influence of the antidote on the patient's clinical course. For some antidotes, such as atropine and insulin, the doses employed can be orders of magnitude higher than standard dosing. Importantly, most poisoned patients who reach hospital can recover with supportive care alone. In low risk patients, the routine use of even low risk antidotes such as activated charcoal is unwarranted. In more serious poisonings, decisions regarding antidote use are generally guided by a risk/benefit assessment based on low quality evidence. PMID:26816206
Regular Exercise: Antidote for Deadly Diseases?
... https://medlineplus.gov/news/fullstory_160326.html Regular Exercise: Antidote for Deadly Diseases? High levels of physical ... Aug. 9, 2016 (HealthDay News) -- Getting lots of exercise may reduce your risk for five common diseases, ...
NASA Astrophysics Data System (ADS)
Mishra, M. K.; Sharma, R. K.; Tyagi, R.; Manchanda, R.; Pandey, A. K.; Thakur, O. P.; Muralidharan, R.
2016-04-01
Large low temperature negative magnetoresistance (NMR) experimentally observed in AlGaN/GaN high electron mobility transistors (HEMT) structures grown by metalorganic chemical vapour deposition on sapphire substrate has been reported. A linear B ‑1 ln B dependence of magnetoresistance observed in our samples indicates the presence of random antidot array together with smooth disorder. It is proposed that the antidots are linked with high bandgap AlN rich regions formed due to possible Al–Ga segregation at the interface during growth and the smooth random disorder is due to interface roughness. The antidot density is estimated to be of ∼7 to 8 × 1010 cm‑2 in our samples. The magnitude of NMR is also correlated with the extent of interface roughness indicated by x-ray reflectivity. It is also proposed that the formation of antidots is related with the lattice mismatch between substrate and epitaxial heterostructures. The NMR in AlGaN/GaN HEMT structures grown on SiC substrates having relatively lower lattice mismatch has been shown to have a usual B 2 and ln T dependences indicating only electron–electron interaction and absence of antidot-like scatterers.
Magnetic modulation of the tunnelling between defect states in antidot superlattices.
Movilla, J L; Planelles, J
2012-07-11
We show theoretically that the tunnelling between properly designed defects in periodic antidot lattices can be strongly modulated by applied magnetic fields. Further, transport channels made up of linear arrangements of tunnel-coupled defects can accommodate Aharonov-Bohm cages, suggesting a magnetic control of the transport through the system. Evidence supporting an unusual robustness of the caging effect against electron-electron interactions is also provided. PMID:22713775
Switching modes in easy and hard axis magnetic reversal in a self-assembled antidot array
NASA Astrophysics Data System (ADS)
Haering, Felix; Wiedwald, Ulf; Nothelfer, Steffen; Koslowski, Berndt; Ziemann, Paul; Lechner, Lorenz; Wallucks, Andreas; Lebecki, Kristof; Nowak, Ulrich; Gräfe, Joachim; Goering, Eberhard; Schütz, Gisela
2013-11-01
We study the reversal mechanisms in a self-assembled, hexagonally ordered Fe antidot array with a period of 200 nm and an antidot diameter of 100 nm which was prepared by polystyrene nanosphere lithography. Direction-dependent information in such a self-assembled sample is obtained by measuring the anisotropic magnetoresistance (AMR) through constrictions processed by focused ion beam milling in nearest neighbor and next nearest neighbor directions. We show that such an originally integral method can be used to investigate the strong in-plane anisotropy introduced by the antidot lattice. The easy and hard axis reversal mechanisms and corresponding AMR signals are modeled by micromagnetic simulations. Additional in-field magnetic force microscopy studies allow the correlation of microscopic switching to features in the integral AMR. We find that the easy axis of magnetization is connected to a distinct periodic magnetic domain pattern, which can be observed during the whole magnetization reversal. While this process is driven by nucleation and propagation of reversed domains, the hard axis reversal is characterized by a (stepwise) rotation of the magnetization via the antidot lattice’ easy axes.
NASA Astrophysics Data System (ADS)
Bouchiat, Marie-Anne; Bouchiat, Claude
2012-10-01
We have constructed the geometric phases emerging from the non-trivial topology of a space-dependent magnetic field B(r), interacting with the spin magnetic moment of a neutral particle. Our basic tool, adapted from a previous work on Berry’s phases, is the space-dependent unitary transformation {U}({\\mathbf {r}}), which leads to the identity, {U}({\\mathbf {r}})^{\\dag }\\, {\\mathbf {S}}\\,{\\bm \\cdot}\\, {\\mathbf {B}}({\\mathbf {r}}) \\, {U}({\\mathbf {r}}) = \\vert {\\mathbf {B}}({\\mathbf {r}}) \\vert \\, S_z, at each point r. In the ‘rotated’ Hamiltonian \\widehat{ H}, \\frac{ \\partial }{\\partial {\\mathbf {r}}} is replaced by the non-Abelian covariant derivative \\frac{ \\partial }{\\partial {\\mathbf {r}}}- \\frac{i}{\\hbar } {A}({\\mathbf {r}}) where {A}({\\mathbf {r}}) = i \\hbar \\, {U}^{\\dag }\\,{\\bm\\cdot}\\, \\frac{ \\partial }{\\partial {\\mathbf {r}}} {U} can be written as A1(r)Sx + A2(r)Sy + A3(r)Sz. The Abelian differentials Ak(r)·dr are given in terms of the Euler angles defining the orientation of B(r). The non-Abelian field {A}({\\mathbf {r}}) transforms as a Yang-Mills field; however, its vanishing ‘curvature’ reveals its purely geometric character. We have defined a perturbation scheme based upon the assumption that in \\widehat{ H} the longitudinal field A3(r) dominates the transverse field A1, 2(r) contributions, evaluated to second order. The geometry embedded in both the vector field A3(r) and the geometric magnetic field \\mathbf { B}_3 ({\\mathbf {r}}) = \\frac{ \\partial }{\\partial {\\mathbf {r}}}\\wedge {{\\mathbf {A}}}_3({\\mathbf {r}}) is described by their associated Aharonov-Bohm phase. As an illustration we study the physics of cold 171Yb atoms dressed by overlaying two circularly polarized stationary waves with orthogonal directions, which form a 2D square optical lattice. The frequency is tuned midway between the two hyperfine levels of the (6s6p)3P1 states to protect the optical B(r) field generated by the
Gao, Song; Fan, Rui Qing; Wang, Xin Ming; Wei, Li Guo; Song, Yang; Du, Xi; Xing, Kai; Wang, Ping; Yang, Yu Lin
2016-07-28
In this work, a rare 2D → 3D single-crystal-to-single-crystal transformation (SCSC) is observed in metal-organic coordination complexes, which is triggered by thermal treatment. The 2D two-fold interpenetrating square lattice layer [Cd(IBA)2]n (1) is irreversibly converted into a 3D four-fold interpenetrating diamond framework {[Cd(IBA)2(H2O)]·2.5H2O}n (2) (HIBA = 4-(1H-imidazol-1-yl)benzoic acid). Consideration is given to these two complexes with different interpenetrating structures and dimensionality, and their influence on photovoltaic properties are studied. Encouraged by the UV-visible absorption and HOMO-LUMO energy states matched for sensitizing TiO2, the two complexes are employed in combination with N719 in dye-sensitized solar cells (DSSCs) to compensate absorption in the ultraviolet and blue-violet region, offset competitive visible light absorption of I3(-) and reducing charge the recombination of injected electrons. After co-sensitization with 1 and 2, the device co-sensitized by 1/N719 and 2/N719 to yield overall efficiencies of 7.82% and 8.39%, which are 19.94% and 28.68% higher than that of the device sensitized only by N719 (6.52%). Consequently, high dimensional interpenetrating complexes could serve as excellent co-sensitizers and have application in DSSCs. PMID:27356177
Spectral properties of a charged particle in antidot array: A limiting case of quantum billiard
Geyler, V.A.; Pavlov, B.S.; Popov, I.Y.
1996-10-01
A model of the periodic array of quantum antidots in the presence of a uniform magnetic field is suggested. The model can be conceived as a periodic lattice of resonators (curvilinear triangles) connected through {open_quote}{open_quote}infinitely small{close_quote}{close_quote} openings at the vertices of the triangles. The model Hamiltonian is obtained by means of operator extension theory in indefinite metric spaces. In the case of rational magnetic flux through an elementary cell of the lattice, the dispersion equation is found in an explicit form with the help of harmonic analysis on the magnetic translation group. It is proved, at least in the case of integer flux, that the spectrum of the model Hamiltonian consists of three parts: (1) Landau levels (they correspond to the classical orbits lying between antidots); (2) extended states that correspond to the classical propagation trajectories; and (3) bound states satisfying the dispersion equation; they correspond to the classical chaotic orbits rotating around single antidots. Among other things, methods of finding the Green{close_quote}s function for some planar domains with curvilinear boundaries are derived. {copyright} {ital 1996 American Institute of Physics.}
Zhang, Kai; Du, Kai; Liu, Hao; Zhang, X.-G.; Lan, Fanli; Lin, Hanxuan; Wei, Wengang; Zhu, Yinyan; Kou, Yunfang; Shao, Jian; Niu, Jiebin; Wang, Wenbin; Wu, Ruqian; Yin, Lifeng; Plummer, E. W.; Shen, Jian
2015-01-01
The interesting transport and magnetic properties in manganites depend sensitively on the nucleation and growth of electronic phase-separated domains. By fabricating antidot arrays in La0.325Pr0.3Ca0.375MnO3 (LPCMO) epitaxial thin films, we create ordered arrays of micrometer-sized ferromagnetic metallic (FMM) rings in the LPCMO films that lead to dramatically increased metal–insulator transition temperatures and reduced resistances. The FMM rings emerge from the edges of the antidots where the lattice symmetry is broken. Based on our Monte Carlo simulation, these FMM rings assist the nucleation and growth of FMM phase domains increasing the metal–insulator transition with decreasing temperature or increasing magnetic field. This study points to a way in which electronic phase separation in manganites can be artificially controlled without changing chemical composition or applying external field. PMID:26195791
Self-assembled Metallic Dots and Antidots: Epitaxial Co on Ru(0001)
NASA Astrophysics Data System (ADS)
Yu, Chengtao; Li, Dongqi; Pearson, J.; Bader, S. D.
2001-03-01
We have grown 1-420 nm thick epitaxial Co wedge on Ru(0001) with molecular beam epitaxy at 350^oC to investigate self-assembly in metals utilizing ex-situ atomic force microscopy. A novel growth mode was observed whereby three-dimensional islands (dots) or a flat film network with deep holes (antidots) in truncated pyramidal shapes exist below or above 20 nm, respectively. The tops of the islands and the rims of the holes are flat with a root mean square roughness values of 0.3 nm. The lateral sizes of these dots/antidots, 10^2 nm, tend to be uniform. We postulate that this growth mode, similar to that of self-assembled quantum dots in semiconductors, is mainly driven by strain as a result of an 8% lateral mismatch between the basil plane lattice constants of bulk Co and Ru.
[Antidotes--often expensive and not always available].
Hoppu, Kalle; Pajarre-Sorsa, Suvi
2012-01-01
While there is seldom need for most anti-poisoning agents and antidotes, they should be quickly available, when needed. Local worst-case scenarios, regional staggering of the treatment, and distances must be taken into account at the health care unit level. Hospitals are fairly well equipped with the recommended antidotes. Replenishment of the stocks is complicated by continual disruptions in supply of antidotes. New antidotes in the updated recommendation include calcium folinate (leucovorin) for methanol poisoning and octreotide for the treatment of hypoglycemia caused by intoxications resulting from antidiabetics of the sulfonyl urea group. PMID:23167174
Newer clinically available antithrombotics and their antidotes.
Lévy, Samuel
2014-09-01
New oral anticoagulants (NOACs) have emerged as an alternative therapy to warfarin in the treatment of arterial and venous thromboembolism and in stroke prevention in patients with non-valvular atrial fibrillation (AF). Three of them, i.e., dabigatran, rivaroxaban, and apixaban, have been approved for clinical use in North America and in a number of European countries. In non-valvular AF, their approval was based on large randomized trials showing that they are non-inferior or even, in some instances, superior to warfarin. Dabigatran is a direct thrombin (factor IIa) inhibitor; rivaroxaban and apixaban are direct factor Xa inhibitors. Before using NOACs, it is recommended to become familiar with their pharmacological characteristics and their metabolism. The absence of specific antidotes is often cited as part of the possible weaknesses of NOACs. Antidotes are perceived to be useful in emergency situations such as life-threatening bleeding or non-elective major surgery. NOACs do not require blood monitoring, and therefore, patient compliance to the treatment is essential. For the present time, there are no specific antidotes available for the three NOACs approved for clinical use. However, phase I or phase II research studies in this area are ongoing. For dabigatran, a specific antidote has been tested in a rat model of anticoagulation, and a study in healthy male volunteers has been recently reported. For rivaroxaban, prothrombin complex concentrates (PCCs) have been found to completely reverse the prolongation of the prothrombin time induced by this NOAC. For apixaban, recombinant factor VII was found in an experimental study using human blood to be superior to activated PCC (aPCC) and PCC. More specific antidotes for rivaroxaban and apixaban are in phases I and II evaluation. The management of patients suffering from a major bleeding or requiring a non-elective major surgery includes non-specific reversal agents and is discussed in the light of a recent position
ANTIDotE: anti-tick vaccines to prevent tick-borne diseases in Europe
2014-01-01
Ixodes ricinus transmits bacterial, protozoal and viral pathogens, causing disease and forming an increasing health concern in Europe. ANTIDotE is an European Commission funded consortium of seven institutes, which aims to identify and characterize tick proteins involved in feeding and pathogen transmission. The knowledge gained will be used to develop and evaluate anti-tick vaccines that may prevent multiple human tick-borne diseases. Strategies encompassing anti-tick vaccines to prevent transmission of pathogens to humans, animals or wildlife will be developed with relevant stakeholders with the ultimate aim of reducing the incidence of tick-borne diseases in humans. PMID:24559082
Thermodynamic properties of a quantum Hall anti-dot interferometer
NASA Astrophysics Data System (ADS)
Levy Schreier, Sarah; Stern, Ady; Rosenow, Bernd; Halperin, Bertrand I.
2016-02-01
We study quantum Hall interferometers in which the interference loop encircles a quantum anti-dot. We base our study on thermodynamic considerations, which we believe reflect the essential aspects of interference transport phenomena. We find that similar to the more conventional Fabry-Perot quantum Hall interferometers, in which the interference loop forms a quantum dot, the anti-dot interferometer is affected by the electro-static Coulomb interaction between the edge modes defining the loop. We show that in the Aharonov-Bohm regime, in which effects of fractional statistics should be visible, is easier to access in interferometers based on anti-dots than in those based on dots. We discuss the relevance of our results to recent measurements on anti-dots interferometers.
Antidot effects on micromagnetic behavior of Py ferromagnetic samples
NASA Astrophysics Data System (ADS)
Yetis, Hakan; Denizli, Haluk
2016-09-01
The coercivity and magnetic hysteresis behavior of permalloy (Py) samples have been studied in the presence of square arrays of the circular antidots. The open source OOMMF micromagnetic software is used to numerically solve the Landau-Lifshitz-Gilbert (LLG) equation. In calculations, Py samples are designed in such a way that they include a different number of antidot in an array which possess the same total surface area. In this way, the total Py region stayed unchanged despite the growing number of antidots in a fixed sample size. We found significant increase in the coercive field for the sample with the smallest antidot spacing. The results are discussed within the framework of superdomain (SD) and superdomain wall (SDW) formation.
48 CFR 225.7005 - Restriction on certain chemical weapons antidote.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false Restriction on certain chemical weapons antidote. 225.7005 Section 225.7005 Federal Acquisition Regulations System DEFENSE... on certain chemical weapons antidote....
48 CFR 225.7005 - Restriction on certain chemical weapons antidote.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Restriction on certain chemical weapons antidote. 225.7005 Section 225.7005 Federal Acquisition Regulations System DEFENSE... on certain chemical weapons antidote....
48 CFR 225.7005 - Restriction on certain chemical weapons antidote.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Restriction on certain chemical weapons antidote. 225.7005 Section 225.7005 Federal Acquisition Regulations System DEFENSE... on certain chemical weapons antidote....
48 CFR 225.7005 - Restriction on certain chemical weapons antidote.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Restriction on certain chemical weapons antidote. 225.7005 Section 225.7005 Federal Acquisition Regulations System DEFENSE... on certain chemical weapons antidote....
48 CFR 225.7005 - Restriction on certain chemical weapons antidote.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Restriction on certain chemical weapons antidote. 225.7005 Section 225.7005 Federal Acquisition Regulations System DEFENSE... on certain chemical weapons antidote....
Magneto Transport of Graphene Monolayer with Antidot Arrays
NASA Astrophysics Data System (ADS)
Wang, Lei; Yin, Ming; Datta, Timir; Mbamalu, Godwin; Alameri, Dheyaa
Graphene has a significant potential for electronics application as well as in high precision resistive metrological standard. Here we report magneto transport studies of monolayer graphene with antidot in hexagonal arrays on SiO2/Si substrate. The choice of antidot array was motivated by the potential to enhance quantum interference effect amongst charge carriers. The graphene-antidot arrays were fabricated by electron beam lithography followed by reactive ion etching. In our samples the dc magnetic field (B) was applied continuously up to 18 Tesla while the measurement temperature (T) was held steady at desired set points, ranging from 200 mK to 20 K. The effect of nanoarrays on the temperature and field dependence of the electrical properties (MR) and quantum hall effect with particular attention to Aharonov-Bohm oscillations will be reported.
Magnetoconductance of a hybrid quantum ring: Effects of antidot potentials
NASA Astrophysics Data System (ADS)
Kim, Nammee; Park, Dae-Han; Kim, Heesang
2016-05-01
The electronic structures and two-terminal magnetoconductance of a hybrid quantum ring are studied. The backscattering due to energy-resonance is considered in the conductance calculation. The hybrid magnetic-electric quantum ring is fabricated by applying an antidot electrostatic potential in the middle of a magnetic quantum dot. Electrons are both magnetically and electrically confined in the plane. The antidot potential repelling electrons from the center of the dot plays a critical role in the energy spectra and magnetoconductance. The angular momentum transition in the energy dispersion and the magnetoconductance behavior are investigated in consideration of the antidot potential variation. Results are shown using a comparison of the results of the conventional magnetic quantum dot.
Si, Haibin; Lian, Gang; Wang, Aizhu; Cui, Deliang; Zhao, Mingwen; Wang, Qilong; Wong, Ching-Ping
2015-12-01
Investigation of light-element magnetism system is essential in fundamental and practical fields. Here, few-layer (∼3 nm) fluorinated hexagonal boron nitride (F-BN) nanocages with zigzag-edge triangular antidot defects were synthesized via a facile one-step solid-state reaction. They are free of metallic impurities confirmed by X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and inductively coupled plasma atomic emission spectroscopy. Ferromagnetism is obviously observed in the BN nanocages. Saturation magnetization values of them differed by less than 7% between 5 and 300 K, indicating that the Curie temperature (Tc) was much higher than 300 K. By adjusting the concentration of triangular antidot defects and fluorine dopants, the ferromagnetic performance of BN nanocages could be effectively varied, indicating that the observed magnetism originates from triangular antidot defects and fluorination. The corresponding theoretical calculation shows that antidot defects and fluorine doping in BN lattice both favor spontaneous spin polarization and the formation of local magnetic moment, which should be responsible for long-range magnetic ordering in the sp material. PMID:26599763
CoCrPt antidot arrays with perpendicular magnetic anisotropy made on anodic alumina templates
NASA Astrophysics Data System (ADS)
Navas, D.; Ilievski, F.; Ross, C. A.
2009-06-01
Ti(5 nm)/CoCrPt(5-20 nm) bilayers with perpendicular magnetic anisotropy were deposited by rf sputtering onto porous alumina films to form antidot arrays with period 105 nm and pore diameters ranging from 18 to 56 nm. The coercivities of the antidot arrays are greater than those of unpatterned films and show only a weak dependence on antidot diameter. Magnetic force microscopy of ac-demagnetized samples shows that the antidot arrays have domain sizes larger than the 105 nm period. The magnetic behavior is discussed in terms of domain wall pinning by the antidots.
Energy Science and Technology Software Center (ESTSC)
2005-07-01
Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.
Creativity: Performativity's Poison or Its Antidote?
ERIC Educational Resources Information Center
Munday, Ian
2014-01-01
A common move in the study of creativity and performativity is to present the former as an antidote to the latter. Might we, therefore, see work on creativity in education as heralding an era of post-performativity? In this paper I argue that the portrayal of performativity in the literature on creativity presents an overly simplistic (vulgar?)…
Writing as a Neighborly Act: An Antidote for Academentia.
ERIC Educational Resources Information Center
Savage, Mary C.
1989-01-01
Describes "academentia," the delusion that disciplines are intellectually powerful as a result of their specialization. Prescribes "neighborliness"--intellectual and practical work done from the perspective of critical consciousness--as the antidote to academentia. Suggests that writing projects have great potential as "neighborly" activities. (MM)
Greg Flach, Frank Smith
2011-12-31
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.
Energy Science and Technology Software Center (ESTSC)
2011-12-31
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less
NASA Astrophysics Data System (ADS)
Lotsch, Bettina V.
2015-07-01
Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chemistry perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major—yet largely disjunct—developments in 2D heterostructures, which are firmly rooted in solid-state chemistry or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.
Observation of Novel Low-Field FMR modes in Permalloy Antidot Arrays
NASA Astrophysics Data System (ADS)
de Long, Lance; Bhat, Vinayak; Farmer, Barry; Woods, Justin; Hastings, Todd; Sklenar, Joseph; Ketterson, John
2013-03-01
Permalloy films of thickness 23 nm were patterned with square arrays of square antidots (AD) with feature size D = 120 nm, and lattice constants d = 200, 300, 500 and 700 nm (total sample area = 2 mm x 2mm), using electron beam lithography. Our broad-band (frequencies f = 10 MHz-15 GHz) and narrow-band (9.7 GHz) FMR measurements of even dilute (D/d <<1) AD lattices (ADL) reveal remarkably reproducible absorption spectra in the low-frequency, hysteretic regime in which disordered domain wall (DW) patterns and unsaturated magnetization textures are expected for unpatterned films, but in the present case are strongly affected by the periodic ADL. Other modes in the saturated regime exhibit strong dependence on the angle between the applied DC field H and the ADL axes, as confirmed by our micromagnetic simulations. Novel modes are observed at DC fields above that of the uniform mode, which simulations indicate are localized at AD edges. Other novel modes are observed for DC fields below that of the uniform mode, which simulated power and phase maps indicate are confined to ADL interstices oriented parallel to H. These results show even dilute AD concentrations can effect strong control of DW evolution. Research at Kentucky is supported by U.S. DoE Grant DE-FG02-97ER45653 and NSF Grant EPS-0814194.
Simonenko, V E; Sarmanaev, S Kh; Kovalev, E V; Sarmanaeva, R R; Kukhanov, A V
2014-11-01
This article analyses the approaches to the formation of specific treatment of acute poisoning in the various countries. The authors present a systematic review of scientific publications about the formation of reserves of antidote agents at medical institutions of the Russian Federation, the US, Canada, France, Spain, Greece, Norway, Czech Republic, Taiwan and Poland. A search for a variety of databases, as well as by reviewing reference lists of publications on the subject of "stockpiling antidote means". It is concluded that the antidote provision at health care institutions in different countries is insufficient. State of affairs with the formation of antidote stocks is better at hospitals of Czech Republic, France and Spain. To determine the range and volume of the stock of fixed assets necessary antidote coordination and approval of the list and the number of mandatory for every medical institution antidotes. PMID:25816678
Nanometer Scale Hard/Soft Bilayer Magnetic Antidots.
Béron, Fanny; Kaidatzis, Andreas; Velo, Murilo F; Arzuza, Luis C C; Palmero, Ester M; Del Real, Rafael P; Niarchos, Dimitrios; Pirota, Kleber R; García-Martín, José Miguel
2016-12-01
The effect of arrays of nanometer scale pores on the magnetic properties of thin films has been analyzed. Particularly, we investigated the influence of the out-of-plane magnetization component created by the nanopores on the in-plane magnetic behavior of patterned hard/soft magnetic thin films in antidot morphology. Its influence on the coupling in Co/Py bilayers of few tens of nanometer thick is compared for disordered and ordered antidots of 35-nm diameter. The combination of magneto-optical Kerr effect (MOKE) and first-order reversal curve (FORC) technique allows probing the effects of the induced perpendicular magnetization component on the bilayer magnetic behavior, while magnetic force microscopy (MFM) is used to image it. We found that ordered antidots yield a stronger out-of-plane component than disordered ones, influencing in a similar manner the hard layer global in-plane magnetic behavior if with a thin or without soft layer. However, its influence changes with a thicker soft layer, which may be an indication of a weaker coupling. PMID:26873261
Photostability of antidotal oxime HI-6, impact on drug development.
Bogan, Reinhard; Worek, Franz; Koller, Marianne; Klaubert, Bernd
2012-01-01
HI-6 exhibits superior efficacy in the therapy of intoxication by different highly toxic organophosphorus nerve agents. Therefore HI-6 is a promising candidate for the development of new antidotes against nerve agents. For ethical and safety reasons antidotes containing HI-6 should get marketing authorization. Active pharmaceutical ingredients of medicinal products have to fulfil regulatory conditions in terms of purity and stability. Photostability is an essential parameter in this testing strategy. HI-6 was tested under conditions of ICH Q1B 'Photostability testing of new drug substances and products'. The data showed a marked degradation of HI-6 after exposure to daylight. The mechanism of degradation could be detected as photoisomerism. The light burden dependent rate of photoisomerism was followed quantitatively. Based on these quantitative results on the amount of light induced isomeric product a pharmacological qualification was made. A standardized in vitro test showed a decreased ability of light exposed HI-6 to reactivate sarin- and paraoxon-inhibited human acetylcholinesterase. These results have an impact on the further development of antidotes containing HI-6, as light protection will probably be necessary during handling, packaging, storage and application. PMID:22359386
Performance effects of chemical warfare antidotes: A perspective
Caldwell, J.A.
1992-07-01
The threat that enemy forces may use chemical warfare against United States military troops has caused the medical research and development community to find effective antidotes. Particularly in the case of nerve agent poisoning, the timely use of antidote therapies represents the key to survival in contaminated environments. Current training doctrine instructs soldiers how to recognize the symptoms of nerve agent exposure, and then how to counteract the life-threatening effects with the administration of atropine sulfate and pralidoxime chloride. However, these compounds can produce performance degrading effects on their own even when no chemical agent is present. Particularly in the case of the aviator, who is expected to exercise very precise control over an inherently complex vehicle such as a helicopter, the impact of self-administered antidotes should be fully appreciated. The present review briefly summarizes what is known about the actions and performance effects of both atropine and pralidoxime chloride, and recommendations are made concerning the need for additional research.
Fang, H.; Akinoglu, E. M.; Fumagalli, P.; Caballero, B.; García-Martín, A.; Papaioannou, E. Th.; Cuevas, J. C.; Giersig, M.
2015-04-13
A combined experimental and theoretical study of the magneto-optic properties of a series of nickel antidot thin films is presented. The hole diameter varies from 869 down to 636 nm, while the lattice periodicity is fixed at 920 nm. This results in an overall increase of the polar Kerr rotation with decreasing hole diameter due to the increasing surface coverage with nickel. In addition, at photon energies of 2.7 and 3.3 eV, where surface-plasmon excitations are expected, we observe distinct features in the polar Kerr rotation not present in continuous nickel films. The spectral position of the peaks exhibits a red shift with decreasing hole size. This is explained within the context of an effective medium theory by a change in the effective dielectric function of the Ni thin films.
Emergence of bound states in ballistic magnetotransport of graphene antidots
NASA Astrophysics Data System (ADS)
Rakyta, P.; Tóvári, E.; Csontos, M.; Csonka, Sz.; Csordás, A.; Cserti, J.
2014-09-01
An experimental method for detection of bound states around an antidot formed by a hole in a graphene sheet is proposed via measuring the ballistic two-terminal conductance. In particular, we consider the effect of bound states formed by a magnetic field on the two-terminal conductance and show that one can observe Breit-Wigner-like resonances in the conductance as a function of the Fermi level close to the energies of the bound states. In addition, we develop a numerical method utilizing a reduced computational effort compared to the existing numerical recursive Green's function methods.
NASA Astrophysics Data System (ADS)
Wang, Jin; Ma, Jianyong; Zhou, Changhe
2014-11-01
A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.
Quaternary heteroaromatic salts with prophylactic and antidotal activity towards soman
Sundberg, R.J.; Dalvie, D.; Cordero, J.; Sabat, M.
1993-05-13
A series of quaternary heteroaromatic salts has been prepared and evaluated for prophylactic and antidotal activity towards the lethal toxicity of soman. One series of compounds contains 2-, 3-, or 4-(dimethylaminocarbonyloxy)phenoxymethyl substituents at the 2 position of the following rings: 1,3-dimethylimidazolium, 1-methylpyridinium, 1-methylquinolinium, 1,3-dimethylbenzimidazolium and 1-methylimidazo1,2-Apyridinium. The compounds were evaluated both in vitro, by determining the IC50 for electric eel acetylcholinesterase, and in vivo, using both antidotal and prophylactic assays in mice. Compound 2b was most active in the in vitro assay (IC50 = 0.01 M). However, its toxicity is high and compound la is more effective in vivo with 80-100% protective activity against 2 LD50 of soman at 6.2 to 62.5 mg/kg. A second series of compounds consisted of 6-substituted 2'-, 3'-, and 4'-(dimethylaminocarbonyloxy) phenylimidazo (1,2-a) pyridinium salts (8).
Energy Science and Technology Software Center (ESTSC)
2004-08-01
AnisWave2D is a 2D finite-difference code for a simulating seismic wave propagation in fully anisotropic materials. The code is implemented to run in parallel over multiple processors and is fully portable. A mesh refinement algorithm has been utilized to allow the grid-spacing to be tailored to the velocity model, avoiding the over-sampling of high-velocity materials that usually occurs in fixed-grid schemes.
That's a Phat Antidote: Intravenous Fat Emulsions and Toxicological Emergencies.
Schultz, Amy E; Lewis, Temeka; Reed, Brittany S; Weant, Kyle A; Justice, Stephanie Baker
2015-01-01
Health care providers in the emergency department (ED) frequently find themselves caring for patients who may have overdosed on a medication(s) or other toxic substance. These patients can prove to be a challenge, as providers must try to determine the substance(s) involved so that the appropriate treatment can be initiated. For those patients who are hemodynamically unstable upon presentation, it is important to note that supportive care is of the utmost importance, as there are few substances that have antidotes available. In these situations, lipid emulsion can be considered. This is especially true in the setting of the following toxicities: local anesthetics, β-blockers, calcium channel blockers, and the tricyclic antidepressants. Even though lipid emulsion may not be used that frequently in the ED, it is important to be aware of its role in the setting of toxicological emergencies, how it should be dosed and administered, and the necessary safety precautions. PMID:26218483
Reprint of : Thermodynamic properties of a quantum Hall anti-dot interferometer
NASA Astrophysics Data System (ADS)
Levy Schreier, Sarah; Stern, Ady; Rosenow, Bernd; Halperin, Bertrand I.
2016-08-01
We study quantum Hall interferometers in which the interference loop encircles a quantum anti-dot. We base our study on thermodynamic considerations, which we believe reflect the essential aspects of interference transport phenomena. We find that similar to the more conventional Fabry-Perot quantum Hall interferometers, in which the interference loop forms a quantum dot, the anti-dot interferometer is affected by the electro-static Coulomb interaction between the edge modes defining the loop. We show that in the Aharonov-Bohm regime, in which effects of fractional statistics should be visible, is easier to access in interferometers based on anti-dots than in those based on dots. We discuss the relevance of our results to recent measurements on anti-dots interferometers.
Specific antidotes in development for reversal of novel anticoagulants: a review.
Gomez-Outes, Antonio; Suarez-Gea, M L; Lecumberri, Ramon; Terleira-Fernandez, Ana I; Vargas-Castrillon, Emilio
2014-01-01
In the last decade, several direct oral anticoagulants (DOAC; dabigatran, rivaroxaban, apixaban, edoxaban) have been marketed for prophylaxis and/or treatment of thromboembolism without having specific antidotes available for their reversal. Current management of bleeding associated to DOAC includes the removal of all antithrombotic medications and supportive care. Non-specific procoagulant agents (prothrombin complex concentrates and activated factor VIIa) have been used in case of serious bleeding. Currently, some specific antidotes for the DOAC are under development. Idarucizumab (BI 655075; Boehringer Ingelheim) is a fragment of an antibody (Fab), which is a specific antidote to the oral direct thrombin inhibitor dabigatran. Andexanet alfa (r-Antidote, PRT064445; Portola Pharmaceuticals) is a truncated form of enzymatically inactive factor Xa, which binds and reverses the anticoagulant action of the factor Xa inhibitors (e.g.: rivaroxaban, apixaban and edoxaban). Aripazine (PER-977, ciraparantag; Perosphere Inc.) is a synthetic small molecule (~500 Da) that reverses oral dabigatran, apixaban, rivaroxaban, as well as subcutaneous fondaparinux and LMWH in vivo. These antidotes could provide an alternative for management of life-threatening bleeding events occurring with the above-mentioned anticoagulants. In addition, the specific antidote anivamersen (RB007; Regado Biosciences Inc.) is an RNA aptamer in clinical development to reverse the anticoagulant effect of the parenteral factor IXa inhibitor pegnivacogin, which is also in development. This anticoagulant-antidote pair may provide an alternative in situations in which a fast onset and offset of anticoagulation is needed, like in patients undergoing cardiac surgery with extracorporeal circulation, as an alternative to the heparin/protamine pair. This patent review includes a description of the pharmacological characteristics of the novel specific antidotes, the available results from completed non
Temperature-dependent nonlinear Hall effect in macroscopic Si-MOS antidot array
NASA Astrophysics Data System (ADS)
Kuntsevich, A. Yu.; Shupletsov, A. V.; Nunuparov, M. S.
2016-05-01
By measuring magnetoresistance and the Hall effect in a classically moderate perpendicular magnetic field in a Si-MOSFET-type macroscopic antidot array, we found a nonlinear with field, temperature- and density-dependent Hall resistivity. We argue that this nonlinearity originates from low mobility shells of the antidots with a strong temperature dependence of the resistivity and suggest a qualitative explanation of the phenomenon.
Magnetic characteristics of CoPd and FePd antidot arrays on nanoperforated Al2O3 templates
NASA Astrophysics Data System (ADS)
Maximenko, A.; Fedotova, J.; Marszałek, M.; Zarzycki, A.; Zabila, Y.
2016-02-01
Hard magnetic antidot arrays show promising results in context of designing of percolated perpendicular media. In this work the technology of magnetic FePd and CoPd antidot arrays fabrication is presented and correlation between surface morphology, structure and magnetic properties is discussed. CoPd and FePd antidot arrays were fabricated by deposition of Co/Pd and Fe/Pd multilayers (MLs) on porous anodic aluminum oxide templates with bowl-shape cell structure with inclined intercellular regions. FePd ordered L10 structure was obtained by successive vacuum annealing at elevated temperatures (530 °C) and confirmed by XRD analysis. Systematic analysis of magnetization curves evidenced perpendicular magnetic anisotropy of CoPd antidot arrays, while FePd antidot arrays revealed isotropic magnetic anisotropy with increased out-of-plane magnetic contribution. MFM images of antidots showed more complicated contrast, with alternating magnetic dots oriented parallel and antiparallel to tip magnetization moment.
NASA Astrophysics Data System (ADS)
Mayor, Louise
2016-05-01
Graphene might be the most famous example, but there are other 2D materials and compounds too. Louise Mayor explains how these atomically thin sheets can be layered together to create flexible “van der Waals heterostructures”, which could lead to a range of novel applications.
Thermal conductivity measurements in a 2D Yukawa system
NASA Astrophysics Data System (ADS)
Nosenko, V.; Ivlev, A.; Zhdanov, S.; Morfill, G.; Goree, J.; Piel, A.
2007-03-01
Thermal conductivity was measured for a 2D Yukawa system. First, we formed a monolayer suspension of microspheres in a plasma, i.e., a dusty plasma, which is like a colloidal suspension, but with an extremely low volume fraction and a partially-ionized rarefied gas instead of solvent. In the absence of manipulation, the suspension forms a 2D triangular lattice. To melt this lattice and form a liquid, we used a laser-heating method. Two focused laser beams were moved rapidly around in the monolayer. The kinetic temperature of the particles increased with the laser power applied, and above a threshold a melting transition occurred. We used digital video microscopy for direct imaging and particle tracking. The spatial profiles of the particle kinetic temperature were calculated. Using the heat transport equation with an additional term to account for the energy dissipation due to the gas drag, we analyzed the temperature distribution to derive the thermal conductivity.
Pride and Purpose as Antidotes to Black Homicidal Violence
Thomas, Charles W.
1987-01-01
The incidence of black male homicide is a major public menace. The lowest incidence of black male homicide was when the black power movement was visible and flourishing. Psychohistorical data support the contention that racial pride is an effective means for regulating intragroup tensions. In the absence of an Afrocentric orientation that promotes community power and self-determination, the need for self-reliance is eroded by value illnesses. The value orientation of the black movement supplied the pride used to obtain academic success, to reduce juvenile delinquency, and to help Afro-Americans to structure their lives for personal satisfactions. Blackness has always been about personal power and social control, but society does not allow much access to either for Afro-Americans. As a consequence, stress from racism is severe, asymptomatic, and multi-faceted. The best antidote to black homicidal violence comes from a pro-social effort based upon a self-image that gives a feeling of positive accomplishment and appreciation. Afrocentric pride promotes or enhances pro-social behavior. PMID:3560242
Antidotes for poisoning by alcohols that form toxic metabolites.
McMartin, Kenneth; Jacobsen, Dag; Hovda, Knut Erik
2016-03-01
The alcohols, methanol, ethylene glycol and diethylene glycol, have many features in common, the most important of which is the fact that the compounds themselves are relatively non-toxic but are metabolized, initially by alcohol dehydrogenase, to various toxic intermediates. These compounds are readily available worldwide in commercial products as well as in homemade alcoholic beverages, both of which lead to most of the poisoning cases, from either unintentional or intentional ingestion. Although relatively infrequent in overall occurrence, poisonings by metabolically-toxic alcohols do unfortunately occur in outbreaks and can result in severe morbidity and mortality. These poisonings have traditionally been treated with ethanol since it competes for the active site of alcohol dehydrogenase and decreases the formation of toxic metabolites. Although ethanol can be effective in these poisonings, there are substantial practical problems with its use and so fomepizole, a potent competitive inhibitor of alcohol dehydrogenase, was developed for a hopefully better treatment for metabolically-toxic alcohol poisonings. Fomepizole has few side effects and is easy to use in practice and it may obviate the need for haemodialysis in some, but not all, patients. Hence, fomepizole has largely replaced ethanol as the toxic alcohol antidote in many countries. Nevertheless, ethanol remains an important alternative because access to fomepizole can be limited, the cost may appear excessive, or the physician may prefer ethanol due to experience. PMID:26551875
Pride and purpose as antidotes to black homicidal violence.
Thomas, C W
1987-02-01
The incidence of black male homicide is a major public menace. The lowest incidence of black male homicide was when the black power movement was visible and flourishing. Psychohistorical data support the contention that racial pride is an effective means for regulating intragroup tensions. In the absence of an Afrocentric orientation that promotes community power and self-determination, the need for self-reliance is eroded by value illnesses.The value orientation of the black movement supplied the pride used to obtain academic success, to reduce juvenile delinquency, and to help Afro-Americans to structure their lives for personal satisfactions. Blackness has always been about personal power and social control, but society does not allow much access to either for Afro-Americans. As a consequence, stress from racism is severe, asymptomatic, and multi-faceted. The best antidote to black homicidal violence comes from a pro-social effort based upon a self-image that gives a feeling of positive accomplishment and appreciation. Afrocentric pride promotes or enhances pro-social behavior. PMID:3560242
Nitrite as an antidote for acute hydrogen sulfide intoxication
Beck, J.F.; Bradbury, C.M.; Connors, A.J.; Donini, J.C.
1981-11-01
The detoxification of hydrogen sulfide (H/sub 2/S) by a heme catalyzed oxidation was examined as part of an on-going study of H/sub 2/S toxicity. Interlocking O/sub 2/ absorption and sulfide depletion data indicate that both oxyhemoglobin and methemoglobin are effective catalytic agents. Although the latter is more efficacious, the life time of excess sulfide in the presence of oxygen and either of the above is of the order of minutes. It has also been established that the formation of methemoglobin following nitrite administration occurs preferentially under oxygen poor conditions. Under an atmospheric or oxygen enriched environment, which favors sulfide depletion, the nitrite retards sulfide oxidation. Thus nitrite as an antidote for acute H/sub 2/S intoxication can only be effective within the first few minutes after the exposure, at which time resuscitation and/or ventilation of the victim is likely to produce conditions in which the nitrite actually slows sulfide removal.
Energy Science and Technology Software Center (ESTSC)
2001-01-31
This software reduces the data from two-dimensional kSA MOS program, k-Space Associates, Ann Arbor, MI. Initial MOS data is recorded without headers in 38 columns, with one row of data per acquisition per lase beam tracked. The final MOSS 2d data file is reduced, graphed, and saved in a tab-delimited column format with headers that can be plotted in any graphing software.
Metrology for graphene and 2D materials
NASA Astrophysics Data System (ADS)
Pollard, Andrew J.
2016-09-01
The application of graphene, a one atom-thick honeycomb lattice of carbon atoms with superlative properties, such as electrical conductivity, thermal conductivity and strength, has already shown that it can be used to benefit metrology itself as a new quantum standard for resistance. However, there are many application areas where graphene and other 2D materials, such as molybdenum disulphide (MoS2) and hexagonal boron nitride (h-BN), may be disruptive, areas such as flexible electronics, nanocomposites, sensing and energy storage. Applying metrology to the area of graphene is now critical to enable the new, emerging global graphene commercial world and bridge the gap between academia and industry. Measurement capabilities and expertise in a wide range of scientific areas are required to address this challenge. The combined and complementary approach of varied characterisation methods for structural, chemical, electrical and other properties, will allow the real-world issues of commercialising graphene and other 2D materials to be addressed. Here, examples of metrology challenges that have been overcome through a multi-technique or new approach are discussed. Firstly, the structural characterisation of defects in both graphene and MoS2 via Raman spectroscopy is described, and how nanoscale mapping of vacancy defects in graphene is also possible using tip-enhanced Raman spectroscopy (TERS). Furthermore, the chemical characterisation and removal of polymer residue on chemical vapour deposition (CVD) grown graphene via secondary ion mass spectrometry (SIMS) is detailed, as well as the chemical characterisation of iron films used to grow large domain single-layer h-BN through CVD growth, revealing how contamination of the substrate itself plays a role in the resulting h-BN layer. In addition, the role of international standardisation in this area is described, outlining the current work ongoing in both the International Organization of Standardization (ISO) and the
An in vivo zebrafish screen identifies organophosphate antidotes with diverse mechanisms of action.
Jin, Shan; Sarkar, Kumar S; Jin, Youngnam N; Liu, Yan; Kokel, David; Van Ham, Tjakko J; Roberts, Lee D; Gerszten, Robert E; Macrae, Calum A; Peterson, Randall T
2013-01-01
Organophosphates are a class of highly toxic chemicals that includes many pesticides and chemical weapons. Exposure to organophosphates, either through accidents or acts of terrorism, poses a significant risk to human health and safety. Existing antidotes, in use for over 50 years, have modest efficacy and undesirable toxicities. Therefore, discovering new organophosphate antidotes is a high priority. Early life stage zebrafish exposed to organophosphates exhibit several phenotypes that parallel the human response to organophosphates, including behavioral deficits, paralysis, and eventual death. Here, we have developed a high-throughput zebrafish screen in a 96-well plate format to find new antidotes that counteract organophosphate-induced lethality. In a pilot screen of 1200 known drugs, we identified 16 compounds that suppress organophosphate toxicity in zebrafish. Several in vitro assays coupled with liquid chromatography/tandem mass spectrometry-based metabolite profiling enabled determination of mechanisms of action for several of the antidotes, including reversible acetylcholinesterase inhibition, cholinergic receptor antagonism, and inhibition of bioactivation. Therefore, the in vivo screen is capable of discovering organophosphate antidotes that intervene in distinct pathways. These findings suggest that zebrafish screens might be a broadly applicable approach for discovering compounds that counteract the toxic effects of accidental or malicious poisonous exposures. PMID:22960781
Nanoimprint lithography: 2D or not 2D? A review
NASA Astrophysics Data System (ADS)
Schift, Helmut
2015-11-01
Nanoimprint lithography (NIL) is more than a planar high-end technology for the patterning of wafer-like substrates. It is essentially a 3D process, because it replicates various stamp topographies by 3D displacement of material and takes advantage of the bending of stamps while the mold cavities are filled. But at the same time, it keeps all assets of a 2D technique being able to pattern thin masking layers like in photon- and electron-based traditional lithography. This review reports about 20 years of development of replication techniques at Paul Scherrer Institut, with a focus on 3D aspects of molding, which enable NIL to stay 2D, but at the same time enable 3D applications which are "more than Moore." As an example, the manufacturing of a demonstrator for backlighting applications based on thermally activated selective topography equilibration will be presented. This technique allows generating almost arbitrary sloped, convex and concave profiles in the same polymer film with dimensions in micro- and nanometer scale.
Mechanics of advanced fiber reinforced lattice composites
NASA Astrophysics Data System (ADS)
Fan, Hua-Lin; Zeng, Tao; Fang, Dai-Ning; Yang, Wei
2010-12-01
Fiber reinforced lattice composites are light-weight attractive due to their high specific strength and specific stiffness. In the past 10 years, researchers developed three-dimensional (3D) lattice trusses and two-dimensional (2D) lattice grids by various methods including interlacing, weaving, interlocking, filament winding and molding hot-press. The lattice composites have been applied in the fields of radar cross-section reduction, explosive absorption and heat-resistance. In this paper, topologies of the lattice composites, their manufacturing routes, as well as their mechanical and multifunctional applications, were surveyed.
N-acetylcysteine amide, a promising antidote for acetaminophen toxicity.
Khayyat, Ahdab; Tobwala, Shakila; Hart, Marcia; Ercal, Nuran
2016-01-22
Acetaminophen (N-acetyl-p-aminophenol, APAP) is one of the most widely used over the counter antipyretic and analgesic medications. It is safe at therapeutic doses, but its overdose can result in severe hepatotoxicity, a leading cause of drug-induced acute liver failure in the USA. Depletion of glutathione (GSH) is one of the initiating steps in APAP-induced hepatotoxicity; therefore, one strategy for restricting organ damage is to restore GSH levels by using GSH prodrugs. N-acetylcysteine (NAC), a GSH precursor, is the only currently approved antidote for an acetaminophen overdose. Unfortunately, fairly high doses and longer treatment times are required due to its poor bioavailability. In addition, oral and I.V. administration of NAC in a hospital setting are laborious and costly. Therefore, we studied the protective effects of N-acetylcysteine amide (NACA), a novel antioxidant with higher bioavailability, and compared it with NAC in APAP-induced hepatotoxicity in C57BL/6 mice. Our results showed that NACA is better than NAC at a low dose (106mg/kg) in preventing oxidative stress and protecting against APAP-induced damage. NACA significantly increased GSH levels and the GSH/GSSG ratio in the liver to 66.5% and 60.5% of the control, respectively; and it reduced the level of ALT by 30%. However, at the dose used, NAC was not effective in combating the oxidative stress induced by APAP. Thus, NACA appears to be better than NAC in reducing the oxidative stress induced by APAP. It would be of great value in the health care field to develop drugs like NACA as more effective and safer options for the prevention and therapeutic intervention in APAP-induced toxicity. PMID:26602168
The Copernican Revolution as Story: an Antidote for Scientific Illiteracy
NASA Astrophysics Data System (ADS)
Wallace, P. M.
2005-08-01
``When a white-robed scientist, momentarily looking away from his microscope or cyclotron [or telescope], makes some pronouncement for the general public, he may not be understood but at least he is certain to be believed.'' The truth of this opening sentence of Anthony Standen's 1950 book Science is a Sacred Cow, as clear today as it was then, is the motivation for a new astronomy course at Berry College near Atlanta, GA, USA. To non-scientists, science is known by its products, not by what it is: a human progress. For this illiteracy an antidote is offered: the history of astronomy. In this course the story of the Copernican Revolution is told, for within this story the true nature of science can be found in its fullness. For example, Aristotle's uniform circular motion is used to emphasize the role of assumptions, and the occasional value of wrong ideas is evident in Tycho's theory and in Kepler's universe of perfect solids. Tycho's observations of Mars and Kepler's analysis illustrate the interplay of observation, theory, and technology. As a final example, the indirectness and often-unintentional nature of scientific advance can be seen in the work of Copernicus. The roles of personality and the intersections of science and society are themes throughout the course, as are the merging of disparate fields and the power of strong theories. There are other themes (e.g., coherence, the role of mathematics), but the emphasis is on the science and much of the work is quantitative. There is a laboratory component that features observations and experiments, and in order to bring the narrative to life the class spends two weeks in Poland, the Czech Republic, and Italy, touring sites that are relevant to the story of the Copernican Revolution.
Davies, C. S. Kruglyak, V. V.; Sadovnikov, A. V.; Nikitov, S. A.; Grishin, S. V.; Sharaevskii, Yu. P.
2015-10-19
We have used Brillouin Light Scattering and micromagnetic simulations to demonstrate a point-like source of spin waves created by the inherently nonuniform internal magnetic field in the vicinity of an isolated antidot formed in a continuous film of yttrium-iron-garnet. The field nonuniformity ensures that only well-defined regions near the antidot respond in resonance to a continuous excitation of the entire sample with a harmonic microwave field. The resonantly excited parts of the sample then served as reconfigurable sources of spin waves propagating (across the considered sample) in the form of caustic beams. Our findings are relevant to further development of magnonic circuits, in which point-like spin wave stimuli could be required, and as a building block for interpretation of spin wave behavior in magnonic crystals formed by antidot arrays.
Monitoring the Effects and Antidotes of the Non-vitamin K Oral Anticoagulants
Rahmat, Nur A; Lip, Gregory Y H
2015-01-01
In the last decade, we have witnessed the emergence of the oral non-vitamin K oral anticoagulants (NOACs), which have numerous advantages compared with the vitamin K antagonists, particularly their lack of need for monitoring; as a result their use is increasing. Nonetheless, the NOACs face two major challenges: the need for reliable laboratory assays to assess their anticoagulation effect, and the lack of approved antidotes to reverse their action. This article provides an overview of monitoring the anticoagulant effect of NOACs and their potential specific antidotes in development. PMID:26835107
dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots.
Tsindlekht, M I; Genkin, V M; Felner, I; Zeides, F; Katz, N; Gazi, Š; Chromik, Š; Dobrovolskiy, O V; Sachser, R; Huth, M
2016-06-01
dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above H c1, but in fields lower than H c1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures above [Formula: see text] and [Formula: see text] the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near H c3. This similarity does not exist at low fields in a swept mode. PMID:27143621
Bornyakov, V.G.
2005-06-01
Possibilities that are provided by a lattice regularization of QCD for studying nonperturbative properties of QCD are discussed. A review of some recent results obtained from computer calculations in lattice QCD is given. In particular, the results for the QCD vacuum structure, the hadron mass spectrum, and the strong coupling constant are considered.
NASA Astrophysics Data System (ADS)
Singh, Kevin; Geiger, Zachary; Senaratne, Ruwan; Rajagopal, Shankari; Fujiwara, Kurt; Weld, David; Weld Group Team
2015-05-01
Quasiperiodicity is intimately involved in quantum phenomena from localization to the quantum Hall effect. Recent experimental investigation of quasiperiodic quantum effects in photonic and electronic systems have revealed intriguing connections to topological phenomena. However, such experiments have been limited by the absence of techniques for creating tunable quasiperiodic structures. We propose a new type of quasiperiodic optical lattice, constructed by intersecting a Gaussian beam with a 2D square lattice at an angle with an irrational tangent. The resulting potential, a generalization of the Fibonacci lattice, is a physical realization of the mathematical ``cut-and-project'' construction which underlies all quasiperiodic structures. Calculation of the energies and wavefunctions of atoms loaded into the proposed quasiperiodic lattice demonstrate a fractal energy spectrum and the existence of edge states. We acknowledge support from the ONR (award N00014-14-1-0805), the ARO and the PECASE program (award W911NF-14-1-0154), the AFOSR (award FA9550-12-1-0305), and the Alfred P. Sloan foundation (grant BR2013-110).
Graphene based dots and antidots: a comparative study from first principles.
Cui, X Y; Li, L; Zheng, R K; Liu, Z W; Stampfl, C; Ringer, S P
2013-02-01
Graphene based quantum dots and antidots are two nanostructures of primary importance for their fundamental physics and technological applications, particularly in the emerging field of graphene-based nanoelectronics and nanospintronics. Herein, based on first principles density functional theory calculations, we report a comparative study on the electronic structure of these two structurally complementary entities, where the bandgap opening, edge magnetism and the role of hydrogenation are investigated. Our results show the diversity of electronic structures of various dots and antidots, whose properties are sensitive to the edge detailed geometry (including size and shape and edge type). Hydrogen passivation plays an essential roal in affecting the related properties, in particular, it leads to larger bandgap values and suppress the edge magnetism. The frontier orbital analysis is employed to rationalize and compare the complicated nature of dots and antidots. Based on the specific geometrical consideration and the total energy competition of the ground antiferromagnetic and the ferromagnetic states, some magnetic structures (the unpassivated 42-atom-antidot and 54-atom-dot) are proposed to be useful as magnetic switches. PMID:23646613
Isom, G.E.
1996-02-01
Work for this contract involved both cyanide (Part 1) and sulfur mustard vesicants (Part 2). Part (1) To develop an in vitro screen for cyanide antidotes, compounds were tested empirically for ability to block the biochemical effects of cyanide in isolated rat pheochromocytoma (PC 12) cells. Effects in vitro were then compared to ability to block cyanide toxicity in mice. Of the five biochemical actions of cyanide tested, blockade of catalase activity was the one most correlated with in vivo protection. Overall, significant correlations were found between catalase protection in vitro and cyanide antidotal effects in vivo. Data involving 40 different chemical compounds showed that approximately 75% of the time, the in vitro assay was predictive of effectiveness in vivo. The results indicate that the ability of a compound to protect catalase in cultured PC 12 cells against cyanide is a useful screen for cyanide antidotal action in mice. Part (2) To develop an in vitro screen for antivesicant compounds. Mechanisms by which sulfur mustards cause cell death were studied in differentiated PC 12 cells. Both the `Apotag` method and electron microscopy indicated that apoptosis occurred after sulfur mustard exposure. A necrotic mechanism was also evident at higher concentrations (>10-4M). It may be possible to identify sulfur mustard antidotes by their ability to block each of these mechanisms in differentiated PC12 cells.
Prehospital diagnosis of massive ethylene glycol poisoning and use of an early antidote.
Amathieu, Roland; Merouani, Medhi; Borron, Stephen W; Lapostolle, Frédéric; Smail, Nadia; Adnet, Frédéric
2006-08-01
We report the case of a patient suspected of voluntary massive poisoning by ethylene glycol. Prehospital diagnosis was established by portable blood analyser and an early antidote with 4 MP treatment initiated in out-of-hospital setting. Use of portable blood analyser in prehospital care should be considered in case of suspected massive poisoning by ethylene glycol. PMID:16808995
Lattice Green's functions in all dimensions
NASA Astrophysics Data System (ADS)
Guttmann, Anthony J.
2010-07-01
We give a systematic treatment of lattice Green's functions (LGF) on the d-dimensional diamond, simple cubic, body-centred cubic and face-centred cubic lattices for arbitrary dimensionality d >= 2 for the first three lattices, and for 2 <= d <= 5 for the hyper-fcc lattice. We show that there is a close connection between the LGF of the d-dimensional hyper-cubic lattice and that of the (d - 1)-dimensional diamond lattice. We give constant-term formulations of LGFs for each of these lattices in all dimensions. Through a still under-developed connection with Mahler measures, we point out an unexpected connection between the coefficients of the sc, bcc and diamond LGFs and some Ramanujan-type formulae for 1/π.
Thermodynamic modeling using BINGO-ANTIDOTE: A new strategy to investigate metamorphic rocks
NASA Astrophysics Data System (ADS)
Lanari, Pierre; Duesterhoeft, Erik
2016-04-01
BINGO-ANTIDOTE is a new program, combing the achievements of the two petrological software packages XMAPTOOLS[1] and THERIAK-DOMINO[2]. XMAPTOOLS affords information about compositional zoning in mineral and local bulk composition of domains at the thin sections scale. THERIAK-DOMINO calculates equilibrium phase assemblages from given bulk rock composition, temperature T and pressure P. Primarily BINGO-ANTIDOTE can be described as an inverse THERIAK-DOMINO, because it uses the information provided by XMAPTOOLS to calculate the probable P-T equilibrium conditions of metamorphic rocks. Consequently, the introduced program combines the strengths of forward Gibbs free energy minimization models with the intuitive output of inverse thermobarometry models. In order to get "best" P-T equilibrium conditions of a metamorphic rock sample and thus estimating the degree of agreement between the observed and calculated mineral assemblage, it is critical to define a reliable scoring strategy. BINGO uses the THERIAKD ADD-ON[3] (Duesterhoeft and de Capitani, 2013) and is a flexible model scorer with 3+1 evaluation criteria. These criteria are the statistical agreement between the observed and calculated mineral-assemblage, -proportions (vol%) and -composition (mol). Additionally, a total likelihood, consisting of the first three criteria, allows the user an evaluation of the most probable equilibrium P-T condition. ANTIDOTE is an interactive user interface, displaying the 3+1 evaluation criteria as probability P-T-maps. It can be used with and without XMAPTOOLS. As a stand-alone program, the user is able to give the program macroscopic observations (i.e., mineral names and proportions), which ANTIDOTE converts to a readable BINGO input. In this manner, the use of BINGO-ANTIDOTE opens up thermodynamics to students and people with only a basic knowledge of phase diagrams and thermodynamic modeling techniques. This presentation introduces BINGO-ANTIDOTE and includes typical examples
Quaternary and tertiary aldoxime antidotes for organophosphate exposure in a zebrafish model system
Schmidt, Hayden R.; Radić, Zoran; Taylor, Palmer; Fradinger, Erica A.
2015-04-15
The zebrafish is rapidly becoming an important model system for screening of new therapeutics. Here we evaluated the zebrafish as a potential pharmacological model for screening novel oxime antidotes to organophosphate (OP)-inhibited acetylcholinesterase (AChE). The k{sub i} values determined for chlorpyrifos oxon (CPO) and dichlorvos (DDVP) showed that CPO was a more potent inhibitor of both human and zebrafish AChE, but overall zebrafish AChE was less sensitive to OP inhibition. In contrast, aldoxime antidotes, the quaternary ammonium 2-PAM and tertiary amine RS-194B, showed generally similar overall reactivation kinetics, k{sub r}, in both zebrafish and human AChE. However, differences between the K{sub ox} and k{sub 2} constants suggest that zebrafish AChE associates more tightly with oximes, but has a slower maximal reactivation rate than human AChE. Homology modeling suggests that these kinetic differences result from divergences in the amino acids lining the entrance to the active site gorge. Although 2-PAM had the more favorable in vitro reactivation kinetics, RS-194B was more effective antidote in vivo. In intact zebrafish embryos, antidotal treatment with RS-194B rescued embryos from OP toxicity, whereas 2-PAM had no effect. Dechorionation of the embryos prior to antidotal treatment allowed both 2-PAM and RS-194B to rescue zebrafish embryos from OP toxicity. Interestingly, RS-194B and 2-PAM alone increased cholinergic motor activity in dechorionated embryos possibly due to the reversible inhibition kinetics, K{sub i} and αK{sub i}, of the oximes. Together these results demonstrate that the zebrafish at various developmental stages provides an excellent model for investigating membrane penetrant antidotes to OP exposure. - Highlights: • Zebrafish AChE shares significant structural similarities with human AChE. • OP-inhibited zebrafish and human AChE exhibit similar reactivation kinetics. • The zebrafish chorion is permeable to BBB penetrant and not
Lattice kinetic simulation of nonisothermal magnetohydrodynamics.
Chatterjee, Dipankar; Amiroudine, Sakir
2010-06-01
In this paper, a lattice kinetic algorithm is presented to simulate nonisothermal magnetohydrodynamics in the low-Mach number incompressible limit. The flow and thermal fields are described by two separate distribution functions through respective scalar kinetic equations and the magnetic field is governed by a vector distribution function through a vector kinetic equation. The distribution functions are only coupled via the macroscopic density, momentum, magnetic field, and temperature computed at the lattice points. The novelty of the work is the computation of the thermal field in conjunction with the hydromagnetic fields in the lattice Boltzmann framework. A 9-bit two-dimensional (2D) lattice scheme is used for the numerical computation of the hydrodynamic and thermal fields, whereas the magnetic field is simulated in a 5-bit 2D lattice. Simulation of Hartmann flow in a channel provides excellent agreement with corresponding analytical results. PMID:20866540
2012-01-01
Background Acute paracetamol poisoning is a rapidly increasing problem in Sri Lanka. The antidotes are expensive and yet no health economic evaluation has been done on the therapy for acute paracetamol poisoning in the developing world. The aim of this study is to determine the cost effectiveness of using N-acetylcysteine over methionine in the management of acute paracetamol poisoning in Sri Lanka. Methods Economic analysis was applied using public healthcare system payer perspective. Costs were obtained from a series of patients admitted to the National Hospital of Sri Lanka with a history of acute paracetamol overdose. Evidence on effectiveness was obtained from a systematic review of the literature. Death due to hepatotoxicity was used as the primary outcome of interest. Analysis and development of decision tree models was done using Tree Age Pro 2008. Results An affordable treatment threshold of Sri Lankan rupees 1,537,120/death prevented was set from the expected years of productive life gained and the average contribution to GDP. A cost-minimisation analysis was appropriate for patients presenting within 10 hours and methionine was the least costly antidote. For patients presenting 10-24 hours after poisoning, n-acetylcysteine was more effective and the incremental cost effectiveness ratio of Sri Lankan rupees 316,182/life saved was well under the threshold. One-way and multi-way sensitivity analysis also supported methionine for patients treated within 10 hours and n-acetylcysteine for patients treated within 10-24 hours as preferred antidotes. Conclusions Post ingestion time is an important determinant of preferred antidotal therapy for acute paracetamol poisoning patients in Sri Lanka. Using n-acetylcysteine in all patients is not cost effective. On economic grounds, methionine should become the preferred antidote for Sri Lankan patients treated within 10 hours of the acute ingestion and n-acetylcysteine should continue to be given to patients treated
An antidot array as an edge for total non-reflection of spin waves in yttrium iron garnet films
Gieniusz, R. Guzowska, U.; Maziewski, A.; Bessonov, V. D.; Stognii, A. I.
2014-02-24
An array of antidots has been used as an edge to create the phenomenon of total non-reflection of spin waves in yttrium iron garnet films. At the critical angle between the line of antidots and the magnetic field, we observe a high-intensity beam of spin waves moving along the line of antidots. The properties of these waves are investigated experimentally by Brillouin light scattering spectroscopy. The conditions required for the occurrence of this phenomenon based on an analysis of the properties of the isofrequency dependencies are presented. The numerical simulations are in good agreement with those of the experimental measurements.
ERIC Educational Resources Information Center
Parris, Richard
2011-01-01
Given a segment that joins two lattice points in R[superscript 3], when is it possible to form a lattice cube that uses this segment as one of its twelve edges? A necessary and sufficient condition is that the length of the segment be an integer. This paper presents an algorithm for finding such a cube when the prime factors of the length are…
NKG2D ligands as therapeutic targets
Spear, Paul; Wu, Ming-Ru; Sentman, Marie-Louise; Sentman, Charles L.
2013-01-01
The Natural Killer Group 2D (NKG2D) receptor plays an important role in protecting the host from infections and cancer. By recognizing ligands induced on infected or tumor cells, NKG2D modulates lymphocyte activation and promotes immunity to eliminate ligand-expressing cells. Because these ligands are not widely expressed on healthy adult tissue, NKG2D ligands may present a useful target for immunotherapeutic approaches in cancer. Novel therapies targeting NKG2D ligands for the treatment of cancer have shown preclinical success and are poised to enter into clinical trials. In this review, the NKG2D receptor and its ligands are discussed in the context of cancer, infection, and autoimmunity. In addition, therapies targeting NKG2D ligands in cancer are also reviewed. PMID:23833565
Subwavelength Lattice Optics by Evolutionary Design
2015-01-01
This paper describes a new class of structured optical materials—lattice opto-materials—that can manipulate the flow of visible light into a wide range of three-dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm that includes and optimizes contributions from every element in the lattice. Lattice opto-materials can exhibit simple properties, such as on- and off-axis focusing, and can also concentrate light into multiple, discrete spots. We expanded the unit cell shapes of the lattice to achieve distinct, polarization-dependent optical responses from the same 2D patterned substrate. Finally, these lattice opto-materials can also be combined into architectures that resemble a new type of compound flat lens. PMID:25380062
Subwavelength lattice optics by evolutionary design.
Huntington, Mark D; Lauhon, Lincoln J; Odom, Teri W
2014-12-10
This paper describes a new class of structured optical materials--lattice opto-materials--that can manipulate the flow of visible light into a wide range of three-dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm that includes and optimizes contributions from every element in the lattice. Lattice opto-materials can exhibit simple properties, such as on- and off-axis focusing, and can also concentrate light into multiple, discrete spots. We expanded the unit cell shapes of the lattice to achieve distinct, polarization-dependent optical responses from the same 2D patterned substrate. Finally, these lattice opto-materials can also be combined into architectures that resemble a new type of compound flat lens. PMID:25380062
Gong, W. J.; Liu, W. Feng, J. N.; Zhang, Z. D.; Kim, D. S.; Choi, C. J.
2014-04-07
The effect of antiferromagnetic (AFM) layer on exchange bias (EB), training effect, and magnetotransport properties in ferromagnetic (FM) /AFM nanoscale antidot arrays and sheet films Ag(10 nm)/Co(8 nm)/NiO(t{sub NiO})/Ag(5 nm) at 10 K is studied. The AFM layer thickness dependence of the EB field shows a peak at t{sub NiO} = 2 nm that is explained by using the random field model. The misalignment of magnetic moments in the three-dimensional antidot arrays causes smaller decrease of EB field compared with that in the sheet films for training effect. The anomalous magnetotransport properties, in particular positive magnetoresistance (MR) for antidot arrays but negative MR for sheet films are found. The training effect and magnetotransport properties are strongly affected by the three-dimensional spin-alignment effects in the antidot arrays.
Lentz, J.M.; Reams, G.G.; DeJohn, C.A.
1986-04-01
The bibliographic abstracts in this report are part of a project to assess biomedical effects of chemical-warfare antidote agents and related pre-treatment drugs. Specific attention is focused on the biomedical effects in the following general areas: vision, auditory, spatial orientation, musculoskeletal, cardipulmonary, cognitive performance, pharmacology, cutaneous stimuli, and cortical effects. In some cases, the bibliography addresses other therapeutic drugs that may be used simultaneously with chemical-warfare antidotes.
Parametric analysis of 2D guided-wave photonic band gap structures
NASA Astrophysics Data System (ADS)
Ciminelli, C.; Peluso, F.; Armenise, M. N.
2005-11-01
The parametric analysis of the electromagnetic properties of 2D guided wave photonic band gap structures is reported with the aim of providing a valid tool for the optimal design. The modelling approach is based on the Bloch-Floquet method. Different lattice configurations and geometrical parameters are considered. An optimum value for the ratio between the hole (or rod) radius and the lattice constant does exist and the calculation demonstrated that it is almost independent from the etching depth, only depending on the lattice type. The results are suitable for the design optimisation of photonic crystal reflectors to be used in integrated optical devices.
Parametric analysis of 2D guided-wave photonic band gap structures.
Ciminelli, C; Peluso, F; Armenise, M
2005-11-28
The parametric analysis of the electromagnetic properties of 2D guided wave photonic band gap structures is reported with the aim of providing a valid tool for the optimal design. The modelling approach is based on the Bloch-Floquet method. Different lattice configurations and geometrical parameters are considered. An optimum value for the ratio between the hole (or rod) radius and the lattice constant does exist and the calculation demonstrated that it is almost independent from the etching depth, only depending on the lattice type. The results are suitable for the design optimisation of photonic crystal reflectors to be used in integrated optical devices. PMID:19503180
Perspectives for spintronics in 2D materials
NASA Astrophysics Data System (ADS)
Han, Wei
2016-03-01
The past decade has been especially creative for spintronics since the (re)discovery of various two dimensional (2D) materials. Due to the unusual physical characteristics, 2D materials have provided new platforms to probe the spin interaction with other degrees of freedom for electrons, as well as to be used for novel spintronics applications. This review briefly presents the most important recent and ongoing research for spintronics in 2D materials.
dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots
NASA Astrophysics Data System (ADS)
Tsindlekht, M. I.; Genkin, V. M.; Felner, I.; Zeides, F.; Katz, N.; Gazi, Š.; Chromik, Š.; Dobrovolskiy, O. V.; Sachser, R.; Huth, M.
2016-06-01
dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above H c1, but in fields lower than H c1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures above 0.66{{T}\\text{c}} and 0.78{{T}\\text{c}} the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near H c3. This similarity does not exist at low fields in a swept mode.
Agrawal, Vijay Kumar; Bansal, Abhishek; Singh, Ranjeet Kumar; Kumawat, Bhanwar Lal; Mahajan, Parul
2015-02-01
Aluminum phosphide (ALP) poisoning is one of the major causes of suicidal deaths. Toxicity by ALP is caused by the liberation of phosphine gas, which rapidly causes cell hypoxia due to inhibition of oxidative phosphorylation, leading to circulatory failure. Treatment of ALP toxicity is mainly supportive as there is no specific antidote. We recently managed 7 cases of ALP poisoning with severe hemodynamic effects. Patients were treated with supportive measures including gastric lavage with diluted potassium permanganate, coconut oil and sodium-bicarbonate first person account should be avoided in a scientific paper. Intravenous magnesium sulfate, proper hemodynamic monitoring and vasopressors. Four out of 7 survived thus suggesting a role of such supportive measures in the absence of specific antidote for ALP poisoning. PMID:25722553
Mashkova, D; Kolchev, Kh; Kotev, G
1977-01-01
The authors carried out studies on 18 nonanesthetised and anesthetised cats under the conditions of complete imobilization with tricuran and under artificial respiration and examined the temporary consequence of the effects on the spontaneous and induced cerebral activity after poisoning with lethal doses of phosdrine and treatment with Doline, which is the therapeutic antidote of phosphorganic pesticides. The authors established that after lethal poisoning with phosdrin the secondary induced cerebral hypoxia enhanced deepening of the disintegration in the intercerebral interrelationships, which caused the appearence of epileptiform activity. The antidote Doline within 1-2 minutes, after its muscular administration abolished effectively the generalized epileptic seizure and repaired quickly the electrophysiological indices-peculiar for the normal EEG. PMID:590179
Marshall, John M
2011-01-01
Insects carry out essential ecological functions, such as pollination, but also cause extensive damage to agricultural crops, and transmit human diseases such as malaria and dengue fever. Advances in insect transgenesis are making it increasingly feasible to engineer genes conferring desirable phenotypes, and gene drive systems are required to spread these genes into wild populations. Medea provides one solution, being able to spread into a population from very low initial frequencies through the action of a maternally-expressed toxin linked to a zygotically-expressed antidote. Several other toxin-antidote combinations are imaginable that distort the offspring ratio in favor of a desired transgene, or drive the population towards an all-male crash. We explore two such systems--Semele, which is capable of spreading a desired transgene into an isolated population in a confined manner; and Merea, which is capable of inducing a local population crash when located on the Z chromosome of a Lepidopteron pest. PMID:21876382
NASA Astrophysics Data System (ADS)
Zhou, Peiheng; Zhang, Nan; Liu, Tao; Xie, Jianliang; Deng, Longjiang
2014-08-01
Magnetic domain structure of FeCoBSi antidot array thin films of varying thickness were characterized using surface magneto-optic Kerr effect. Vibrating sample magnetometry and microstrip transmission line measurements helped to associate the microwave magnetic analysis of the antidot arrays with hysteresis studies. The domain structure evolution from quasi-continuous domains to strip domains induced by the competing exchange and dipolar interaction resulted in the change of ferromagnetic resonance from multi-band to single-band. Hence, the mechanisms of multi-resonance are proposed to be related to domain wall motion, natural resonance and spin wave modes. This phenomenon can be used to control the magnetization dynamics in spin wave devices.
Nitrocobinamide, a New Cyanide Antidote That Can Be Administered by Intramuscular Injection
Chan, Adriano; Jiang, Jingjing; Fridman, Alla; Guo, Ling T.; Shelton, G. Diane; Liu, Ming-Tao; Green, Carol; Haushalter, Kristofer J.; Patel, Hemal H.; Lee, Jangwoen; Yoon, David; Burney, Tanya; Mukai, David; Mahon, Sari B.; Brenner, Matthew; Pilz, Renate B.; Boss, Gerry R.
2015-01-01
Currently available cyanide antidotes must be given by intravenous injection over 5–10 min, making them illsuited for treating many people in the field, as could occur in a major fire, an industrial accident, or a terrorist attack. These scenarios call for a drug that can be given quickly, e.g., by intramuscular injection. We have shown that aquohydroxocobinamide is a potent cyanide antidote in animal models of cyanide poisoning, but it is unstable in solution and poorly absorbed after intramuscular injection. Here we show that adding sodium nitrite to cobinamide yields a stable derivative (referred to as nitrocobinamide) that rescues cyanide-poisoned mice and rabbits when given by intramuscular injection. We also show that the efficacy of nitrocobinamide is markedly enhanced by coadministering sodium thiosulfate (reducing the total injected volume), and we calculate that ∼1.4 mL each of nitrocobinamide and sodium thiosulfate should rescue a human from a lethal cyanide exposure. PMID:25650735
Quantum Hall effect in semiconductor systems with quantum dots and antidots
Beltukov, Ya. M.; Greshnov, A. A.
2015-04-15
The integer quantum Hall effect in systems of semiconductor quantum dots and antidots is studied theoretically as a factor of temperature. It is established that the conditions for carrier localization in quantum-dot systems favor the observation of the quantum Hall effect at higher temperatures than in quantum-well systems. The obtained numerical results show that the fundamental plateau corresponding to the transition between the ground and first excited Landau levels can be retained up to a temperature of T ∼ 50 K, which is an order of magnitude higher than in the case of quantum wells. Implementation of the quantum Hall effect at such temperatures requires quantum-dot systems with controllable characteristics, including the optimal size and concentration and moderate geometrical and composition fluctuations. In addition, ordered arrangement is desirable, hence quantum antidots are preferable.
The bezoar stone: a princely antidote, the Távora Sequeira Pinto Collection-Oporto.
Do Sameiro Barroso, Maria
2014-01-01
Bezoar stones, once used as universal antidotes and panaceas, but currently regarded as costly and useless medicines of the past, are a major milestone in the history of toxicology. Arabic physicians had been using bezoars in medicine from the 8th century onwards. In the 16th century, the Portuguese controlled bezoar trade from India, and the Portuguese doctors Garcia de Orta, Amatus Lusitanus, and Cristobal Acosta introduced the medicinal use of Oriental bezoars to European medical literature. Some criticism aside, leading European doctors prescribed bezoars mainly as powerful antidotes. Five bezoars that now adorn the Távora Sequeira Pinto Collection in Oporto testify to the allure and glory of bezoars at the height of their golden age, when they equalled the splendour of gems and noble minerals that dominated the Eastern and Western lithotherapy.The end of the 18th century marked the end of ancient panaceas. This article focuses on the therapeutic and apotropaic use of bezoars. PMID:25310610
Agrawal, Vijay Kumar; Bansal, Abhishek; Singh, Ranjeet Kumar; Kumawat, Bhanwar Lal; Mahajan, Parul
2015-01-01
Aluminum phosphide (ALP) poisoning is one of the major causes of suicidal deaths. Toxicity by ALP is caused by the liberation of phosphine gas, which rapidly causes cell hypoxia due to inhibition of oxidative phosphorylation, leading to circulatory failure. Treatment of ALP toxicity is mainly supportive as there is no specific antidote. We recently managed 7 cases of ALP poisoning with severe hemodynamic effects. Patients were treated with supportive measures including gastric lavage with diluted potassium permanganate, coconut oil and sodium-bicarbonate first person account should be avoided in a scientific paper. Intravenous magnesium sulfate, proper hemodynamic monitoring and vasopressors. Four out of 7 survived thus suggesting a role of such supportive measures in the absence of specific antidote for ALP poisoning. PMID:25722553
Collective spin excitations in 2D paramagnet with dipole interaction
NASA Astrophysics Data System (ADS)
Tsiberkin, Kirill
2016-02-01
The collective spin excitations in the unbounded 2D paramagnetic system with dipole interactions are studied. The model Hamiltonian includes Zeeman energy and dipole interaction energy, while the exchange vanishes. The system is placed into a constant uniform magnetic field which is orthogonal to the lattice plane. It provides the equilibrium state with spin ordering along the field direction, and the saturation is reached at zero temperature. We consider the deviations of spin magnetic moments from its equilibrium position along the external field. The Holstein-Primakoff representation is applied to spin operators in low-temperature approximation. When the interaction between the spin waves is negligible and only two-magnon terms are taken into account, the Hamiltonian diagonalisation is possible. We obtain the dispersion relation for spin waves in the square and hexagonal honeycomb lattice. Bose-Einstein statistics determine the average number of spin deviations, and total system magnetization. The lattice structure does not influence on magnetization at the long-wavelength limit. The dependencies of the relative magnetization and longitudinal susceptibility on temperature and external field intensity are found. The internal energy and specific heat of the Bose gas of spin waves are calculated. The collective spin excitations play a significant role in the properties of the paramagnetic system at low temperature and strong external magnetic field.
Kalaska, Bartlomiej; Kaminski, Kamil; Sokolowska, Emilia; Czaplicki, Dominik; Kujdowicz, Monika; Stalinska, Krystyna; Bereta, Joanna; Szczubialka, Krzysztof; Pawlak, Dariusz; Nowakowska, Maria; Mogielnicki, Andrzej
2015-01-01
Protamine, the only registered antidote of unfractionated heparin (UFH), may produce a number of adverse effects, such as anaphylactic shock or serious hypotension. We aimed to develop an alternative UFH antidote as efficient as protamine, but safer and easier to produce. As a starting material, we have chosen generally non-toxic, biocompatible, widely available, inexpensive, and easy to functionalize polysaccharides. Our approach was to synthesize, purify and characterize cationic derivatives of dextran, hydroxypropylcellulose, pullulan and γ-cyclodextrin, then to screen them for potential heparin-reversal activity using an in vitro assay and finally examine efficacy and safety of the most active polymers in Wistar rat and BALB/c mouse models of experimentally induced arterial and venous thrombosis. Efficacy studies included the measurement of thrombus formation, activated partial thromboplastin time, bleeding time, and anti-factor Xa activity; safety studies included the measurement of hemodynamic, hematologic and immunologic parameters. Linear, high molecular weight dextran substituted with glycidyltrimethylammonium chloride groups at a ratio of 0.65 per glucose unit (Dex40-GTMAC3) is the most potent and the safest UFH inhibitor showing activity comparable to that of protamine while possessing lower immunogenicity. Cationic polysaccharides of various structures neutralize UFH. Dex40-GTMAC3 is a promising and potentially better UFH antidote than protamine. PMID:25781030
Antidotes, antibody-mediated immunity and the future of pharmaceutical product development
Caoili, Salvador Eugenio C.
2013-01-01
If new scientific knowledge is to be more efficiently generated and applied toward the advancement of health, human safety must be more effectively addressed in the conduct of research. Given the present difficulties of accurately predicting biological outcomes of novel interventions in vivo, the imperative of human safety suggests the development of novel pharmaceutical products in tandem with their prospective antidotes in anticipation of possible adverse events, to render the risks of initial clinical trials more acceptable from a regulatory standpoint. Antibody-mediated immunity provides a generally applicable mechanistic basis for developing antidotes to both biologicals and small-molecule drugs (such that antibodies may serve as antidotes to pharmaceutical agents as a class including other antibodies) and also for the control and prevention of both infectious and noninfectious diseases via passive or active immunization. Accordingly, the development of prophylactic or therapeutic passive-immunization strategies using antipeptide antibodies is a plausible prelude to the development of corresponding active-immunization strategies using peptide-based vaccines. In line with this scheme, global proliferation of antibody- and vaccine-production technologies, especially those that obviate dependence on the cold chain for storage and transport of finished products, could provide geographically distributed breakout capability against emerging and future health challenges. PMID:23291934
Jones, S.G.; Jones, M.M.
1984-03-01
Eight sodium dithiocarbamates (NaS/sub 2/CNR/sub 1/R/sub 2/) have been examined as antidotes for acute cadmium intoxication. While all of them possess an ability to increase survival when given to mice 2 hr after a lethal (>99%) intraperitoneal injection of 10 mg/kg of CdCl/sub 2/. 2.5H/sub 2/O, their effects on the organ distribution of cadmium vary considerably. It has been possible to show that the accumulation of cadmium in the brain and kidney as well as the survival rates can be correlated with a numerical measure of the polarity of the groups R/sub 1/ and R/sub 2/. Each factor has a different dependence on the polarity, but it is possible to construct a composite factor for antidotal efficacy which incorporates survival rate, brain cadmium levels and kidney cadmium levels. The factor constructed here exhibits an optimal value approximately in the middle of the polarity range studied. Compounds which have R/sub 1/ = -CH/sub 2/CH/sub 1/OH and R/sub 2/ = -CH/sub 2/CH/sub 2/OH, OR -CH/sub 3/ or -C/sub 2/H/sub 5/ appear to be the most effective antidotes of the compounds examined. 22 references, 4 figures 3 tables.
Antidotes, antibody-mediated immunity and the future of pharmaceutical product development.
Caoili, Salvador Eugenio C
2013-02-01
If new scientific knowledge is to be more efficiently generated and applied toward the advancement of health, human safety must be more effectively addressed in the conduct of research. Given the present difficulties of accurately predicting biological outcomes of novel interventions in vivo, the imperative of human safety suggests the development of novel pharmaceutical products in tandem with their prospective antidotes in anticipation of possible adverse events, to render the risks of initial clinical trials more acceptable from a regulatory standpoint. Antibody-mediated immunity provides a generally applicable mechanistic basis for developing antidotes to both biologicals and small-molecule drugs (such that antibodies may serve as antidotes to pharmaceutical agents as a class including other antibodies) and also for the control and prevention of both infectious and noninfectious diseases via passive or active immunization. Accordingly, the development of prophylactic or therapeutic passive-immunization strategies using antipeptide antibodies is a plausible prelude to the development of corresponding active-immunization strategies using peptide-based vaccines. In line with this scheme, global proliferation of antibody- and vaccine-production technologies, especially those that obviate dependence on the cold chain for storage and transport of finished products, could provide geographically distributed breakout capability against emerging and future health challenges. PMID:23291934
Kalaska, Bartlomiej; Kaminski, Kamil; Sokolowska, Emilia; Czaplicki, Dominik; Kujdowicz, Monika; Stalinska, Krystyna; Bereta, Joanna; Szczubialka, Krzysztof; Pawlak, Dariusz; Nowakowska, Maria; Mogielnicki, Andrzej
2015-01-01
Protamine, the only registered antidote of unfractionated heparin (UFH), may produce a number of adverse effects, such as anaphylactic shock or serious hypotension. We aimed to develop an alternative UFH antidote as efficient as protamine, but safer and easier to produce. As a starting material, we have chosen generally non-toxic, biocompatible, widely available, inexpensive, and easy to functionalize polysaccharides. Our approach was to synthesize, purify and characterize cationic derivatives of dextran, hydroxypropylcellulose, pullulan and γ-cyclodextrin, then to screen them for potential heparin-reversal activity using an in vitro assay and finally examine efficacy and safety of the most active polymers in Wistar rat and BALB/c mouse models of experimentally induced arterial and venous thrombosis. Efficacy studies included the measurement of thrombus formation, activated partial thromboplastin time, bleeding time, and anti-factor Xa activity; safety studies included the measurement of hemodynamic, hematologic and immunologic parameters. Linear, high molecular weight dextran substituted with glycidyltrimethylammonium chloride groups at a ratio of 0.65 per glucose unit (Dex40-GTMAC3) is the most potent and the safest UFH inhibitor showing activity comparable to that of protamine while possessing lower immunogenicity. Cationic polysaccharides of various structures neutralize UFH. Dex40-GTMAC3 is a promising and potentially better UFH antidote than protamine. PMID:25781030
Exchange bias and magnetization reversal in ferromagnet/antiferromagnet antidot arrays
NASA Astrophysics Data System (ADS)
Luo, An; Ma, Fenghua; Hu, Yong
2016-09-01
Exchange bias and coercivity in ferromagnet/antiferromagnet antidot arrays magnetized perpendicularly are simulated to demonstrate the mechanism of their variations in specific nanostructures, using a modified Monte Carlo Metropolis algorithm. Three kinds of antidot array models characterized by different morphologies in the vicinity of pore are established and their magnetization behaviors are compared with that in the continuous film. An increase in the exchange bias field with a suppressed coercivity is obtained if the antiferromagnet covers the wall of pore entirely. By means of the results of the spin configurations, it is found that only the heterostructure component, e.g., the antiferromagnet can cut off the domain in the ferromagnet layer into small sizes effectively, and thus increases the pinning effect to the ferromagnet and changes the nucleation field. Moreover, the thermal stability of exchange bias in the antidot arrays is not enhanced and the coercivity is nonmonotonic with increasing temperature probably due to the magnetic field applied perpendicular to the film plane. We suggest that our numerical findings are also suitable for other nanostructures.
Annotated Bibliography of EDGE2D Use
J.D. Strachan and G. Corrigan
2005-06-24
This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables.
Staring 2-D hadamard transform spectral imager
Gentry, Stephen M.; Wehlburg, Christine M.; Wehlburg, Joseph C.; Smith, Mark W.; Smith, Jody L.
2006-02-07
A staring imaging system inputs a 2D spatial image containing multi-frequency spectral information. This image is encoded in one dimension of the image with a cyclic Hadamarid S-matrix. The resulting image is detecting with a spatial 2D detector; and a computer applies a Hadamard transform to recover the encoded image.
NASA Astrophysics Data System (ADS)
Buchheim, Jakob; Wyss, Roman M.; Shorubalko, Ivan; Park, Hyung Gyu
2016-04-01
We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He+ and Ga+ irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He+ at high energies (10-30 keV) allowing the passage of >97% He+ particles without creating destructive lattice vacancy. Large Ga+ ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ~50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He+ ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration.We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of
Mirror effects and optical meta-surfaces in 2d atomic arrays
NASA Astrophysics Data System (ADS)
Shahmoon, Ephraim; Wild, Dominik; Lukin, Mikhail; Yelin, Susanne
2016-05-01
Strong optical response of natural and artificial (meta-) materials typically relies on the fact that the lattice constant that separates their constituent particles (atoms or electromagnetic resonators, respectively) is much smaller than the optical wavelength. Here we consider a single layer of a 2d atom array with a lattice constant on the order of an optical wavelength, which can be thought of as a highly dilute 2d metamaterial (meta-surface). Our theoretical analysis shows how strong scattering of resonant incoming light off the array can be controlled by choosing its lattice constant, e.g. allowing the array to operate as a perfect mirror or a retro-reflector for most incident angles of the incoming light. We discuss the prospects for quantum metasurfaces, i.e. the ability to shape the output quantum state of light by controlling the atomic states, and the possible generality of our results as a universal wave phenomena.
Buchheim, Jakob; Wyss, Roman M; Shorubalko, Ivan; Park, Hyung Gyu
2016-04-21
We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He(+) and Ga(+) irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He(+) at high energies (10-30 keV) allowing the passage of >97% He(+) particles without creating destructive lattice vacancy. Large Ga(+) ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ∼50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He(+) ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration. PMID:27043304
Cold atoms in a rotating optical lattice
NASA Astrophysics Data System (ADS)
Foot, Christopher J.
2009-05-01
We have demonstrated a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz. Our arrangement also allows the periodicity of the optical lattice to be varied dynamically, producing a 2D ``accordion lattice'' [1]. The angles of the laser beams are controlled by acousto-optic deflectors and this allows smooth changes with little heating of the trapped cold (rubidium) atoms. We have loaded a BEC into lattices with periodicities ranging from 1.8μm to 18μm, observing the collapse and revival of the diffraction orders of the condensate over a large range of lattice parameters as recently reported by a group in NIST [2]. We have also imaged atoms in situ in a 2D lattice over a range of lattice periodicities. Ultracold atoms in a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, i.e. the Hamiltonian of the atoms in the rotating frame resembles that of a charged particle in a strong magnetic field. In the future, we plan to use this to investigate a range of phenomena such as the analogue of the fractional quantum Hall effect. [4pt] [1] R. A. Williams, J. D. Pillet, S. Al-Assam, B. Fletcher, M. Shotter, and C. J. Foot, ``Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms,'' Opt. Express 16, 16977-16983 (2008) [0pt] [2] J. H. Huckans, I. B. Spielman, B. Laburthe Tolra, W. D. Phillips, and J. V. Porto, Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice, arXiv:0901.1386v1
Inertial solvation in femtosecond 2D spectra
NASA Astrophysics Data System (ADS)
Hybl, John; Albrecht Ferro, Allison; Farrow, Darcie; Jonas, David
2001-03-01
We have used 2D Fourier transform spectroscopy to investigate polar solvation. 2D spectroscopy can reveal molecular lineshapes beneath ensemble averaged spectra and freeze molecular motions to give an undistorted picture of the microscopic dynamics of polar solvation. The transition from "inhomogeneous" to "homogeneous" 2D spectra is governed by both vibrational relaxation and solvent motion. Therefore, the time dependence of the 2D spectrum directly reflects the total response of the solvent-solute system. IR144, a cyanine dye with a dipole moment change upon electronic excitation, was used to probe inertial solvation in methanol and propylene carbonate. Since the static Stokes' shift of IR144 in each of these solvents is similar, differences in the 2D spectra result from solvation dynamics. Initial results indicate that the larger propylene carbonate responds more slowly than methanol, but appear to be inconsistent with rotational estimates of the inertial response. To disentangle intra-molecular vibrations from solvent motion, the 2D spectra of IR144 will be compared to the time-dependent 2D spectra of the structurally related nonpolar cyanine dye HDITCP.
Light field morphing using 2D features.
Wang, Lifeng; Lin, Stephen; Lee, Seungyong; Guo, Baining; Shum, Heung-Yeung
2005-01-01
We present a 2D feature-based technique for morphing 3D objects represented by light fields. Existing light field morphing methods require the user to specify corresponding 3D feature elements to guide morph computation. Since slight errors in 3D specification can lead to significant morphing artifacts, we propose a scheme based on 2D feature elements that is less sensitive to imprecise marking of features. First, 2D features are specified by the user in a number of key views in the source and target light fields. Then the two light fields are warped view by view as guided by the corresponding 2D features. Finally, the two warped light fields are blended together to yield the desired light field morph. Two key issues in light field morphing are feature specification and warping of light field rays. For feature specification, we introduce a user interface for delineating 2D features in key views of a light field, which are automatically interpolated to other views. For ray warping, we describe a 2D technique that accounts for visibility changes and present a comparison to the ideal morphing of light fields. Light field morphing based on 2D features makes it simple to incorporate previous image morphing techniques such as nonuniform blending, as well as to morph between an image and a light field. PMID:15631126
Internal Photoemission Spectroscopy of 2-D Materials
NASA Astrophysics Data System (ADS)
Nguyen, Nhan; Li, Mingda; Vishwanath, Suresh; Yan, Rusen; Xiao, Shudong; Xing, Huili; Cheng, Guangjun; Hight Walker, Angela; Zhang, Qin
Recent research has shown the great benefits of using 2-D materials in the tunnel field-effect transistor (TFET), which is considered a promising candidate for the beyond-CMOS technology. The on-state current of TFET can be enhanced by engineering the band alignment of different 2D-2D or 2D-3D heterostructures. Here we present the internal photoemission spectroscopy (IPE) approach to determine the band alignments of various 2-D materials, in particular SnSe2 and WSe2, which have been proposed for new TFET designs. The metal-oxide-2-D semiconductor test structures are fabricated and characterized by IPE, where the band offsets from the 2-D semiconductor to the oxide conduction band minimum are determined by the threshold of the cube root of IPE yields as a function of photon energy. In particular, we find that SnSe2 has a larger electron affinity than most semiconductors and can be combined with other semiconductors to form near broken-gap heterojunctions with low barrier heights which can produce a higher on-state current. The details of data analysis of IPE and the results from Raman spectroscopy and spectroscopic ellipsometry measurements will also be presented and discussed.
2D materials for nanophotonic devices
NASA Astrophysics Data System (ADS)
Xu, Renjing; Yang, Jiong; Zhang, Shuang; Pei, Jiajie; Lu, Yuerui
2015-12-01
Two-dimensional (2D) materials have become very important building blocks for electronic, photonic, and phononic devices. The 2D material family has four key members, including the metallic graphene, transition metal dichalcogenide (TMD) layered semiconductors, semiconducting black phosphorous, and the insulating h-BN. Owing to the strong quantum confinements and defect-free surfaces, these atomically thin layers have offered us perfect platforms to investigate the interactions among photons, electrons and phonons. The unique interactions in these 2D materials are very important for both scientific research and application engineering. In this talk, I would like to briefly summarize and highlight the key findings, opportunities and challenges in this field. Next, I will introduce/highlight our recent achievements. We demonstrated atomically thin micro-lens and gratings using 2D MoS2, which is the thinnest optical component around the world. These devices are based on our discovery that the elastic light-matter interactions in highindex 2D materials is very strong. Also, I would like to introduce a new two-dimensional material phosphorene. Phosphorene has strongly anisotropic optical response, which creates 1D excitons in a 2D system. The strong confinement in phosphorene also enables the ultra-high trion (charged exciton) binding energies, which have been successfully measured in our experiments. Finally, I will briefly talk about the potential applications of 2D materials in energy harvesting.
Unusual dimensionality effects and surface charge density in 2D Mg(OH)2
Suslu, Aslihan; Wu, Kedi; Sahin, Hasan; Chen, Bin; Yang, Sijie; Cai, Hui; Aoki, Toshihiro; Horzum, Seyda; Kang, Jun; Peeters, Francois M.; Tongay, Sefaattin
2016-01-01
We present two-dimensional Mg(OH)2 sheets and their vertical heterojunctions with CVD-MoS2 for the first time as flexible 2D insulators with anomalous lattice vibration and chemical and physical properties. New hydrothermal crystal growth technique enabled isolation of environmentally stable monolayer Mg(OH)2 sheets. Raman spectroscopy and vibrational calculations reveal that the lattice vibrations of Mg(OH)2 have fundamentally different signature peaks and dimensionality effects compared to other 2D material systems known to date. Sub-wavelength electron energy-loss spectroscopy measurements and theoretical calculations show that Mg(OH)2 is a 6 eV direct-gap insulator in 2D, and its optical band gap displays strong band renormalization effects from monolayer to bulk, marking the first experimental confirmation of confinement effects in 2D insulators. Interestingly, 2D-Mg(OH)2 sheets possess rather strong surface polarization (charge) effects which is in contrast to electrically neutral h-BN materials. Using 2D-Mg(OH)2 sheets together with CVD-MoS2 in the vertical stacking shows that a strong change transfer occurs from n-doped CVD-MoS2 sheets to Mg(OH)2, naturally depleting the semiconductor, pushing towards intrinsic doping limit and enhancing overall optical performance of 2D semiconductors. Results not only establish unusual confinement effects in 2D-Mg(OH)2, but also offer novel 2D-insulating material with unique physical, vibrational, and chemical properties for potential applications in flexible optoelectronics. PMID:26846617
Unusual dimensionality effects and surface charge density in 2D Mg(OH)2
NASA Astrophysics Data System (ADS)
Suslu, Aslihan; Wu, Kedi; Sahin, Hasan; Chen, Bin; Yang, Sijie; Cai, Hui; Aoki, Toshihiro; Horzum, Seyda; Kang, Jun; Peeters, Francois M.; Tongay, Sefaattin
2016-02-01
We present two-dimensional Mg(OH)2 sheets and their vertical heterojunctions with CVD-MoS2 for the first time as flexible 2D insulators with anomalous lattice vibration and chemical and physical properties. New hydrothermal crystal growth technique enabled isolation of environmentally stable monolayer Mg(OH)2 sheets. Raman spectroscopy and vibrational calculations reveal that the lattice vibrations of Mg(OH)2 have fundamentally different signature peaks and dimensionality effects compared to other 2D material systems known to date. Sub-wavelength electron energy-loss spectroscopy measurements and theoretical calculations show that Mg(OH)2 is a 6 eV direct-gap insulator in 2D, and its optical band gap displays strong band renormalization effects from monolayer to bulk, marking the first experimental confirmation of confinement effects in 2D insulators. Interestingly, 2D-Mg(OH)2 sheets possess rather strong surface polarization (charge) effects which is in contrast to electrically neutral h-BN materials. Using 2D-Mg(OH)2 sheets together with CVD-MoS2 in the vertical stacking shows that a strong change transfer occurs from n-doped CVD-MoS2 sheets to Mg(OH)2, naturally depleting the semiconductor, pushing towards intrinsic doping limit and enhancing overall optical performance of 2D semiconductors. Results not only establish unusual confinement effects in 2D-Mg(OH)2, but also offer novel 2D-insulating material with unique physical, vibrational, and chemical properties for potential applications in flexible optoelectronics.
Unusual dimensionality effects and surface charge density in 2D Mg(OH)2.
Suslu, Aslihan; Wu, Kedi; Sahin, Hasan; Chen, Bin; Yang, Sijie; Cai, Hui; Aoki, Toshihiro; Horzum, Seyda; Kang, Jun; Peeters, Francois M; Tongay, Sefaattin
2016-01-01
We present two-dimensional Mg(OH)2 sheets and their vertical heterojunctions with CVD-MoS2 for the first time as flexible 2D insulators with anomalous lattice vibration and chemical and physical properties. New hydrothermal crystal growth technique enabled isolation of environmentally stable monolayer Mg(OH)2 sheets. Raman spectroscopy and vibrational calculations reveal that the lattice vibrations of Mg(OH)2 have fundamentally different signature peaks and dimensionality effects compared to other 2D material systems known to date. Sub-wavelength electron energy-loss spectroscopy measurements and theoretical calculations show that Mg(OH)2 is a 6 eV direct-gap insulator in 2D, and its optical band gap displays strong band renormalization effects from monolayer to bulk, marking the first experimental confirmation of confinement effects in 2D insulators. Interestingly, 2D-Mg(OH)2 sheets possess rather strong surface polarization (charge) effects which is in contrast to electrically neutral h-BN materials. Using 2D-Mg(OH)2 sheets together with CVD-MoS2 in the vertical stacking shows that a strong change transfer occurs from n-doped CVD-MoS2 sheets to Mg(OH)2, naturally depleting the semiconductor, pushing towards intrinsic doping limit and enhancing overall optical performance of 2D semiconductors. Results not only establish unusual confinement effects in 2D-Mg(OH)2, but also offer novel 2D-insulating material with unique physical, vibrational, and chemical properties for potential applications in flexible optoelectronics. PMID:26846617
Ginsparg, P.
1991-01-01
These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.
Ginsparg, P.
1991-12-31
These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.
Brittle damage models in DYNA2D
Faux, D.R.
1997-09-01
DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.
2-d Finite Element Code Postprocessor
Energy Science and Technology Software Center (ESTSC)
1996-07-15
ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forcesmore » along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.« less
2D electronic materials for army applications
NASA Astrophysics Data System (ADS)
O'Regan, Terrance; Perconti, Philip
2015-05-01
The record electronic properties achieved in monolayer graphene and related 2D materials such as molybdenum disulfide and hexagonal boron nitride show promise for revolutionary high-speed and low-power electronic devices. Heterogeneous 2D-stacked materials may create enabling technology for future communication and computation applications to meet soldier requirements. For instance, transparent, flexible and even wearable systems may become feasible. With soldier and squad level electronic power demands increasing, the Army is committed to developing and harnessing graphene-like 2D materials for compact low size-weight-and-power-cost (SWAP-C) systems. This paper will review developments in 2D electronic materials at the Army Research Laboratory over the last five years and discuss directions for future army applications.
Khan, Lateef M.; Al-Harthi, Sameer E.; Alkreathy, Huda M.; Osman, Abdel-Moneim M.; Ali, Ahmed S.
2014-01-01
Objective To determine the PPVs of selected ten medication antidote signals in recognizing potential ADRs and comparison of their sensitivity with manual chart analysis, and voluntary reporting recognizing the same ADRs. Method The inpatient EMR database of internal medicine department was utilized for a period of one year, adult patients prescribed at least one of the ten signals, were included in the study, recipient patients of antidote signals were assessed for the occurrence of an ADR by Naranjo’s tool of ADR evaluation. PPVs of each antidote signal were verified. Result PPV of Methylprednisolone and Phytonadione was 0.28, Metoclopramide and Potassium Chloride – 0.29, Dextrose 50%, Promethazine, Sodium Polystyrene and Loperamide – 0.30, Protamine and Acetylcysteine – 0.33. In comparison of confirmed ADRs of antidote signals with other methods, Dextrose 50%, Metoclopramide, Sodium Polystyrene, Potassium Chloride, Methylprednisolone and Promethazine seem to be extremely significant (P value > 0.0001), while ADRs of Phytonadione, Protamine, Acetylcysteine and Loperamide were insignificant. Conclusion Antidote medication signals have definitive discerning evaluation value of ADRs over routine methods of ADR detection with a high detection rate with a minimum cost; Their integration with hospital EMR database and routine patient safety surveillance enhances transparency, time-saving and facilitates ADR detection. PMID:26594117
Chemical Approaches to 2D Materials.
Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang
2016-08-01
Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology. PMID:27478083
Extended 2D generalized dilaton gravity theories
NASA Astrophysics Data System (ADS)
de Mello, R. O.
2008-09-01
We show that an anomaly-free description of matter in (1+1) dimensions requires a deformation of the 2D relativity principle, which introduces a non-trivial centre in the 2D Poincaré algebra. Then we work out the reduced phase space of the anomaly-free 2D relativistic particle, in order to show that it lives in a noncommutative 2D Minkowski space. Moreover, we build a Gaussian wave packet to show that a Planck length is well defined in two dimensions. In order to provide a gravitational interpretation for this noncommutativity, we propose to extend the usual 2D generalized dilaton gravity models by a specific Maxwell component, which guages the extra symmetry associated with the centre of the 2D Poincaré algebra. In addition, we show that this extension is a high energy correction to the unextended dilaton theories that can affect the topology of spacetime. Further, we couple a test particle to the general extended dilaton models with the purpose of showing that they predict a noncommutativity in curved spacetime, which is locally described by a Moyal star product in the low energy limit. We also conjecture a probable generalization of this result, which provides strong evidence that the noncommutativity is described by a certain star product which is not of the Moyal type at high energies. Finally, we prove that the extended dilaton theories can be formulated as Poisson Sigma models based on a nonlinear deformation of the extended Poincaré algebra.
Tummala, Ramyashree; Kavtaradze, Ana; Gupta, Anjan; Ghosh, Raktim Kumar
2016-07-01
The Vitamin K antagonist warfarin was the only oral anticoagulant available for decades for the treatment of thrombosis and prevention of thromboembolism until Direct Oral Anticoagulants (DOACs); a group of new oral anticoagulants got approved in the last few years. Direct thrombin inhibitor: dabigatran and factor Xa inhibitors: apixaban, rivaroxaban, and edoxaban directly inhibit the coagulation cascade. DOACs have many advantages over warfarin. However, the biggest drawback of DOACs has been the lack of specific antidotes to reverse the anticoagulant effect in emergency situations. Activated charcoal, hemodialysis, and activated Prothrombin Complex Concentrate (PCC) were amongst the nonspecific agents used in a DOAC associated bleeding but with limited success. Idarucizumab, the first novel antidote against direct thrombin inhibitor dabigatran was approved by US FDA in October 2015. It comprehensively reversed dabigatran-induced anticoagulation in a phase I study. A phase III trial on Idarucizumab also complete reversal of anticoagulant effect of dabigatran. Andexanet alfa (PRT064445), a specific reversal agent against factor Xa inhibitors, showed a complete reversal of anticoagulant activity of apixaban and rivaroxaban within minutes after administration without adverse effects in two recently completed parallel phase III trials ANNEXA-A and ANNEXA-R respectively. It is currently being studied in ANNEXA-4, a phase IV study. Aripazine (PER-977), the third reversal agent, has shown promising activity against dabigatran, apixaban, rivaroxaban, as well as subcutaneous fondaparinux and LMWH. This review article summarizes pharmacological characteristics of these novel antidotes, coagulation's tests affected, available clinical and preclinical data, and the need for phase III and IV studies. PMID:27082776
Vorticity Generation by Rough Walls in 2D Decaying Turbulence
NASA Astrophysics Data System (ADS)
Tóth, Gábor; Jánosi, Imre M.
2015-12-01
In this work we present Lattice Boltzmann simulations of a decaying vortex array in a 2D rectangular domain, which is bounded by a random rough wall from one side. In order to separate the effects of the collisions with the rough wall, the opposite (smooth) rigid wall is placed at a larger distance from the center of the vortex array. Periodic boundary condition is imposed in the perpendicular direction. Well defined random roughness is generated by the widely studied Wolf-Villain surface growth algorithm. The main finding is that collisions with a rough wall generate excess vorticity compared with a smooth boundary, while the kinetic energy decreases monotonously. A proper measure is the integrated excess enstrophy, which exhibits an apparent maximum at an "optimal" roughness range. Numerical values of the excess enstrophy are very sensitive to a particular configuration (wall shape and vortex lattice randomization), however the "optimal" roughness exhibits surface features of similar characteristic sizes than that of the decaying vortices.
Lattice gas and lattice Boltzmann computational physics
Chen, S.
1993-05-01
Recent developments of the lattice gas automata method and its extension to the lattice Boltzmann method have provided new computational schemes for solving a variety of partial differential equations and modeling different physics systems. The lattice gas method, regarded as the simplest microscopic and kinetic approach which generates meaningful macroscopic dynamics, is fully parallel and can be easily programmed on parallel machines. In this talk, the author will review basic principles of the lattice gas and lattice Boltzmann method, its mathematical foundation and its numerical implementation. A detailed comparison of the lattice Boltzmann method with the lattice gas technique and other traditional numerical schemes, including the finite-difference scheme and the pseudo-spectral method, for solving the Navier-Stokes hydrodynamic fluid flows, will be discussed. Recent achievements of the lattice gas and the the lattice Boltzmann method and their applications in surface phenomena, spinodal decomposition and pattern formation in chemical reaction-diffusion systems will be presented.
Beam-Plasma Interaction and Instabilities in a 2D Yukawa Plasma
NASA Astrophysics Data System (ADS)
Kyrkos, S.; Kalman, G.; Rosenberg, M.
2008-11-01
In a complex plasma, penetrating charged particle beams may lead to beam-plasma instabilities. When either the plasma, the beam, or both, are strongly interacting [1], the features of the instability are different from those in a weakly coupled plasma. We consider the case when a 2D dusty plasma forms a lattice, and the beam is moving in the lattice plane. Both the grains and the beam particles interact through a Yukawa potential; the beam particles are weakly coupled to each other and to the lattice. The system develops both a longitudinal and a transverse instability. Based on the phonon spectrum of a 2D hexagonal Yukawa lattice [2], we determine and compare the transverse and longitudinal growth rates. As a function of the wavenumber, the growth rates exhibit remarkable gaps, where no instability is excited. The gap locations are governed by the ratio of the lattice and the beam plasma frequencies. The behavior of the growth rates also depends on the direction of the beam and on the relationship between the beam speed and the longitudinal and transverse sound speeds. [1] GJ Kalman, M Rosenberg, JPA 36, 5963 (2003). [2] T Sullivan, GJ Kalman, S Kyrkos, P Bakshi, M Rosenberg, Z Donko, JPA 39, 4607 (2006).
ERIC Educational Resources Information Center
Scott, Paul
2006-01-01
A lattice is a (rectangular) grid of points, usually pictured as occurring at the intersections of two orthogonal sets of parallel, equally spaced lines. Polygons that have lattice points as vertices are called lattice polygons. It is clear that lattice polygons come in various shapes and sizes. A very small lattice triangle may cover just 3…
2D-Crystal-Based Functional Inks.
Bonaccorso, Francesco; Bartolotta, Antonino; Coleman, Jonathan N; Backes, Claudia
2016-08-01
The possibility to produce and process graphene, related 2D crystals, and heterostructures in the liquid phase makes them promising materials for an ever-growing class of applications as composite materials, sensors, in flexible optoelectronics, and energy storage and conversion. In particular, the ability to formulate functional inks with on-demand rheological and morphological properties, i.e., lateral size and thickness of the dispersed 2D crystals, is a step forward toward the development of industrial-scale, reliable, inexpensive printing/coating processes, a boost for the full exploitation of such nanomaterials. Here, the exfoliation strategies of graphite and other layered crystals are reviewed, along with the advances in the sorting of lateral size and thickness of the exfoliated sheets together with the formulation of functional inks and the current development of printing/coating processes of interest for the realization of 2D-crystal-based devices. PMID:27273554
2D microwave imaging reflectometer electronics
Spear, A. G.; Domier, C. W. Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C.; Tobias, B. J.
2014-11-15
A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.
2D microwave imaging reflectometer electronics
NASA Astrophysics Data System (ADS)
Spear, A. G.; Domier, C. W.; Hu, X.; Muscatello, C. M.; Ren, X.; Tobias, B. J.; Luhmann, N. C.
2014-11-01
A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.
Optical modulators with 2D layered materials
NASA Astrophysics Data System (ADS)
Sun, Zhipei; Martinez, Amos; Wang, Feng
2016-04-01
Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that 2D layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this Review, we cover the state of the art of optical modulators based on 2D materials, including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as 2D heterostructures, plasmonic structures, and silicon and fibre integrated structures. We also take a look at the future perspectives and discuss the potential of yet relatively unexplored mechanisms, such as magneto-optic and acousto-optic modulation.
Large Area Synthesis of 2D Materials
NASA Astrophysics Data System (ADS)
Vogel, Eric
Transition metal dichalcogenides (TMDs) have generated significant interest for numerous applications including sensors, flexible electronics, heterostructures and optoelectronics due to their interesting, thickness-dependent properties. Despite recent progress, the synthesis of high-quality and highly uniform TMDs on a large scale is still a challenge. In this talk, synthesis routes for WSe2 and MoS2 that achieve monolayer thickness uniformity across large area substrates with electrical properties equivalent to geological crystals will be described. Controlled doping of 2D semiconductors is also critically required. However, methods established for conventional semiconductors, such as ion implantation, are not easily applicable to 2D materials because of their atomically thin structure. Redox-active molecular dopants will be demonstrated which provide large changes in carrier density and workfunction through the choice of dopant, treatment time, and the solution concentration. Finally, several applications of these large-area, uniform 2D materials will be described including heterostructures, biosensors and strain sensors.
2D microwave imaging reflectometer electronics.
Spear, A G; Domier, C W; Hu, X; Muscatello, C M; Ren, X; Tobias, B J; Luhmann, N C
2014-11-01
A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program. PMID:25430247
Zuhail, K P; Dhara, Surajit
2016-08-10
We report experimental studies on 2D colloidal crystals of dimers stabilized by vortex-like defects in planar nematic and π/2 twisted nematic cells. The dimers are prepared and self-assembled using a laser tweezer. We study the effect of temperature and electric field on the lattice parameters of the colloidal crystals. The lattice parameters vary with the temperature in the nematic phase and a discontinuous structural change is observed at the nematic to smectic-A phase transition. In the nematic phase, we observed a large change in the lattice parameters (≃30%) by applying an external electric field perpendicular to the plane of the 2D crystals. The idea and the active control of the lattice parameters could be useful for designing tunable colloidal crystals. PMID:27445255
Inkjet printing of 2D layered materials.
Li, Jiantong; Lemme, Max C; Östling, Mikael
2014-11-10
Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials. PMID:25169938
Measurement of 2D birefringence distribution
NASA Astrophysics Data System (ADS)
Noguchi, Masato; Ishikawa, Tsuyoshi; Ohno, Masahiro; Tachihara, Satoru
1992-10-01
A new measuring method of 2-D birefringence distribution has been developed. It has not been an easy job to get a birefringence distribution in an optical element with conventional ellipsometry because of its lack of scanning means. Finding an analogy between the rotating analyzer method in ellipsometry and the phase-shifting method in recently developed digital interferometry, we have applied the phase-shifting algorithm to ellipsometry, and have developed a new method that makes the measurement of 2-D birefringence distribution easy and possible. The system contains few moving parts, assuring reliability, and measures a large area of a sample at one time, making the measuring time very short.
The 2D lingual appliance system.
Cacciafesta, Vittorio
2013-09-01
The two-dimensional (2D) lingual bracket system represents a valuable treatment option for adult patients seeking a completely invisible orthodontic appliance. The ease of direct or simplified indirect bonding of 2D lingual brackets in combination with low friction mechanics makes it possible to achieve a good functional and aesthetic occlusion, even in the presence of a severe malocclusion. The use of a self-ligating bracket significantly reduces chair-side time for the orthodontist, and the low-profile bracket design greatly improves patient comfort. PMID:24005953
Knight shift and spin relaxation in the single band 2D Hubbard model
NASA Astrophysics Data System (ADS)
Leblanc, James; Chen, Xi; Gull, Emanuel
We study in detail the roles of spin and charge fluctuations in the single band 2D Hubbard model. Using dynamical mean field theory and cluster extensions such as the dynamical cluster approximation (DCA), we compute the full two particle susceptibilities in the spin and charge representations. By performing analytic continuations we obtain the temperature and doping dependence of the spin-lattice relaxation (T1- 1) and knight shift in the 2D Hubbard model relevant to NMR results on doped cuprates and connect these to RPA results in weak coupling limits.
Critical behavior of the q = 3 , 4-Potts model on quasiperiodic decagonal lattices
NASA Astrophysics Data System (ADS)
Ferraz, Carlos Handrey Araujo
2015-12-01
In this study, we performed Monte Carlo simulations of the q = 3 , 4-Potts model on quasiperiodic decagonal lattices (QDL) to assess the critical behavior of these systems. Using the single histogram technique in conjunction with the finite-size scaling analysis, we estimate the infinite lattice critical temperatures and the leading critical exponents for q = 3 and q = 4 states. Our estimates for the critical exponents on QDL are in good agreement with the exact values on 2D periodic lattices, supporting the claim that both the q = 3 and q = 4 Potts model on quasiperiodic lattices belong to the same universality class as those on 2D periodic lattices.
X , Y , and Z waves: Extended structures in nonlinear lattices
NASA Astrophysics Data System (ADS)
Kevrekidis, P. G.; Gagnon, J.; Frantzeskakis, D. J.; Malomed, B. A.
2007-01-01
We propose a new type of waveforms in two-dimensional (2D) and three-dimensional (3D) discrete media-multilegged extended nonlinear structures (ENSs), built as arrays of lattice solitons (tiles and stones, in the 2D and 3D cases, respectively). We study the stability of the tiles and stones analytically, and then extend them numerically to complete ENS forms for both 2D and 3D lattices, aiming to single out stable ENSs. The predicted patterns can be realized in Bose-Einstein condensates trapped in deep optical lattices, crystals built of microresonators, and 2D photonic crystals. In the latter case, the patterns provide for a technique for writing reconfigurable virtual partitions in multipurpose photonic devices.
X , Y , and Z waves: extended structures in nonlinear lattices.
Kevrekidis, P G; Gagnon, J; Frantzeskakis, D J; Malomed, B A
2007-01-01
We propose a new type of waveforms in two-dimensional (2D) and three-dimensional (3D) discrete media-multilegged extended nonlinear structures (ENSs), built as arrays of lattice solitons (tiles and stones, in the 2D and 3D cases, respectively). We study the stability of the tiles and stones analytically, and then extend them numerically to complete ENS forms for both 2D and 3D lattices, aiming to single out stable ENSs. The predicted patterns can be realized in Bose-Einstein condensates trapped in deep optical lattices, crystals built of microresonators, and 2D photonic crystals. In the latter case, the patterns provide for a technique for writing reconfigurable virtual partitions in multipurpose photonic devices. PMID:17358275
Vick, J.A.; Von Bredow, J.D.
1993-05-13
Successful first aid therapy for cyanide intoxication is dependent upon the immediate administration of antidotes which directly or indirectly interact with the cyanide ion to remove it from circulation. Exceptionally rapid methemoglobin formers (hydroxylamine hydrochloride 'HA) and Dimethylaminophenol (DMAP) are usually able to prevent the lethal effect of cyanide following intramuscular injections in doses sufficient to induce 20% methemoglobin (HA = 20 mg/kg and DMAP= 2 mg/kg). Sodium nitrite, the methemoglobin inducer approved by the FDA and is available for military use, must be administered by intravenous infusion since it is not an effective cyanide antidote by the intramuscular route. In the normal un-intoxicated animal an intramuscular injection of 20 mg/kg sodium nitrite will form 20% methemoglobin at a rapid rate; however, in the presence of acute cyanide intoxication the associated severe bradycardia appears to limit the rate of absorption of sodium nitrite from the intramuscular site which prevents the rapid formation of sufficient methemoglobin to counteract cyanide intoxication.
Saffron as an antidote or a protective agent against natural or chemical toxicities.
Razavi, Bibi Marjan; Hosseinzadeh, Hossein
2015-01-01
Saffron (Crocus sativus) is an extensively used food additive for its color and taste. Since ancient times this plant has been introduced as a marvelous medicine throughout the world. The wide spectrum of saffron pharmacological activities is related to its major constituents including crocin, crocetin and safranal. Based on several studies, saffron and its active ingredients have been used as an antioxidant, antiinflammatory and antinociceptive, antidepressant, antitussive, anticonvulsant, memory enhancer, hypotensive and anticancer. According to the literatures, saffron has remarkable therapeutic effects. The protective effects of saffron and its main constituents in different tissues including brain, heart, liver, kidney and lung have been reported against some toxic materials either natural or chemical toxins in animal studies.In this review article, we have summarized different in vitro and animal studies in scientific databases which investigate the antidotal and protective effects of saffron and its major components against natural toxins and chemical-induced toxicities. Due to the lake of human studies, further investigations are required to ascertain the efficacy of saffron as an antidote or a protective agent in human intoxication. PMID:25928729
Reddy, Sandesh D.; Reddy, Doodipala Samba
2015-01-01
SUMMARY Objective This review summarizes the therapeutic potential of midazolam as an anticonvulsant antidote for organophosphate (OP) intoxication. Methods Benzodiazepines are widely used for acute seizures and status epilepticus (SE), a neurological emergency of persistent seizures that can lead to severe neuronal damage or death. Midazolam is a benzodiazepine hypnotic with a rapid onset and short duration of action. Results Midazolam is considered the new drug of choice for persistent acute seizures and SE, including those caused by neurotoxic OPs and nerve agents. Midazolam is a positive allosteric modulator of synaptic GABA-A receptors in the brain. It potentiates GABAergic inhibition and thereby controls hyperexcitability and seizures. Midazolam is administered intravenously or intramuscularly to control acute seizures and SE. Due to its favorable pharmacokinetic features, midazolam is being considered as a replacement anticonvulsant for diazepam in the antidote kit for nerve agents. Clinical studies such as the recent RAMPART trial have confirmed the anticonvulsant efficacy of midazolam in SE in prehospital settings. Significance In experimental models, midazolam is effective when given at the onset of seizures caused by nerve agents. However, benzodiazepines are less effective at terminating seizures when given 30 min or later after OP exposure or seizure onset likely because of internalization or down-regulation of synaptic, but not extrasynaptic, GABA-A receptors, which can lead to diminished potency and seizure recurrence. PMID:26032507
Antidotal efficacy of bisquaternary oximes against soman and tabun poisoning in various species
Amitai, G.; Rabinovitz, I.; Chen, R.; Cohen, G.; Zomber, G.
1993-05-13
The introduction of Hagedorn oximes, e.g. HI-6 and HLo-7, was an important milestone in the development of antidotal treatment against soman poisoning. We have developed a series of 'cholinergic receptor-directed' AB-oximes which combine in their molecular structure both AChE reactivation potency and anti-cholinergic properties. Marked antidotal efficacy against soman and tabun poisoning was obtained for AB-8, AB-13, toxogonin, HLo-7 and HI-6 in conjunction with atropine and benactyzine in pyridostigmine (PYR) pretreated mice and guinea pigs. In the absence of PYR, all oximes except for HI-6 in mice or HI-6 and HLo-7 in guinea pigs provided poor protection (PR=1-2) against soman. In tabun poisoning, AB-13, toxogonin and HLO-7 conferred high PR values: 8.6, 21.3 and 21.7, respectively, even without PYR pretreatment. These data are consistent with reactivation potency of these oximes (kr = 12.5, 157 and 18.7 m(1) min(1), respectively) for tabun-inhibited FBS-AChE. Elimination of benactyzine significantly decreased the PR values obtained against soman in guinea pigs.
NASA Astrophysics Data System (ADS)
Yumak, Mehmet; Ture, Kerim; Aktas, Gulen; Vega, Victor; Prida, Victor; Garcia, Carlos
2012-02-01
Porous anodic alumina is a particularly attractive self-ordered system used as template to fabricate nanostructures. The anodic film contains a self-ordered hexagonal array of parallel pores with tunable pore size and interpore distance, and whose pore locations can be templated. Deposition of magnetic films onto porous alumina leads to the formation of porous magnetic films, whose properties differ significantly from those of unpatterned films. The study of antidot arrays has both technological and fundamental importance. Although porous alumina films are typically synthesized in a planar geometry, in this work we deposited NiFe and Ti/CoCrPt magnetic films with in-plane and out-of-plane anisotropy onto cylindrical-geometry porous anodic alumina substrates to achieve cylindrical antidot arrays. The effect of both, the magnitude of the AC current and the circular magnetic field on the magnetization reversal has been studied for in-plane and perpendicular anisotropies. The level of reduction in the switching field was found to be dependent on the power, the frequency of the microwave pulses and the circular applied magnetic field. Such a reduction is associate with the competition between pumping and damping processes.
Bajgar, Jirí
2010-01-01
The studies dealing with mechanism of organophosphates (OP)/nerve agent action, prophylaxis and treatment of intoxications is a very hot topic at present. Though the research is very intensive, unfortunately, up to now, there is not universal or significantly better reactivator sufficiently effective against all nerve agents/OP when compared with presently available oximes (pralidoxime, methoxime, obidoxime, trimedoxime, HI-6). The use of the most effective reactivator (HI-6) using simple type of autoinjector (e.g. ComboPen) is strictly limited because of decomposition of HI-6 in solution. Thanks to better solubility it is clear that another salt of HI-6 (dimethanesulfonate, HI-6 DMS) is more convenient for the use as antidote against nerve agents in the autoinjector than HI-6 chloride (Cl). It was clearly demonstrated that reactivation potency of HI-6 DMS in comparison with HI-6 Cl in vivo was the same and bioavailability of HI-6 DMS is better than that of HI-6 Cl. Three chambered autoinjector allows administration of all three antidotes (atropine, reactivator, diazepam) simultaneously. Moreover, the content of chambers can be changed according to proposed requirements. Possible way to solve the problem of universal reactivator could be the use of two reactivators. Three chambered autoinjector is an ideal device for this purpose. PMID:21400978
Microparticle manipulation in optical lattices
NASA Astrophysics Data System (ADS)
Mu, Weiqiang
With the interference of several coherent beams, a periodical potential is produced for the particles trapped inside. The theoretical calculations show that the optical force applied on the particle in such optical lattice is in sinusoidal form. The force amplitudes vary greatly depending on the ratio of the particle size to the spacing of the optical lattice. A setup is constructed to demonstrate this dependence with two different methods: equipartition theorem and hydrodynamic-drag method. Based on this size dependence we develop an approach that allows tunable, size-dependent force selection of a subset of particles from an ensemble containing mixed particles. Combining a universal constant force with the sinusoidal optical force, a tilted washboard potential can be formed for the trapped particle. The diffusion of a particle over the barrier in this tilted washboard potential is briefly discussed. When the washboard potential oscillates, some interesting phenomena will happen: at high oscillation frequency, the particle's movement depends only on the oscillating amplitude; at low frequency, there are some combinations of the oscillation frequency and amplitude that induce the enhanced movement of the particle. This enhancement is first experimentally demonstrated with our setup. By implanting a single laser tweezers into the interferometric optical tweezers, we succeed in dynamically assembling designer colloidal lattices on the background of the interferometric optical tweezers. This new technique provides a flexible tool to design 2-d colloidal lattices.
Parallel stitching of 2D materials
Ling, Xi; Wu, Lijun; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; et al
2016-01-27
Diverse parallel stitched 2D heterostructures, including metal–semiconductor, semiconductor–semiconductor, and insulator–semiconductor, are synthesized directly through selective “sowing” of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. Lastly, the methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.
Parallel Stitching of 2D Materials.
Ling, Xi; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; Hsu, Allen L; Bie, Yaqing; Lee, Yi-Hsien; Zhu, Yimei; Wu, Lijun; Li, Ju; Jarillo-Herrero, Pablo; Dresselhaus, Mildred; Palacios, Tomás; Kong, Jing
2016-03-01
Diverse parallel stitched 2D heterostructures, including metal-semiconductor, semiconductor-semiconductor, and insulator-semiconductor, are synthesized directly through selective "sowing" of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. The methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits. PMID:26813882
Baby universes in 2d quantum gravity
NASA Astrophysics Data System (ADS)
Ambjørn, Jan; Jain, Sanjay; Thorleifsson, Gudmar
1993-06-01
We investigate the fractal structure of 2d quantum gravity, both for pure gravity and for gravity coupled to multiple gaussian fields and for gravity coupled to Ising spins. The roughness of the surfaces is described in terms of baby universes and using numerical simulations we measure their distribution which is related to the string susceptibility exponent γstring.
Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology
Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr
2016-01-01
The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct “beyond graphene” domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials. PMID:26861346
Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology.
Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr
2016-01-01
The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials. PMID:26861346
Hamad, Eike; Babu, Kavita; Bebarta, Vikhyat S
2016-06-01
Cyanide toxicity is common after significant smoke inhalation. Two cases are presented that provide framework for the discussion of epidemiology, pathogenesis, presenting signs and symptoms, and treatment options of inhalational cyanide poisoning. An evidence-based algorithm is proposed that utilizes point-of-care testing to help physicians identify patients who benefit most from antidotal therapy. PMID:26831054
2D to 3D transition of polymeric carbon nitride nanosheets
Chamorro-Posada, Pedro; Vázquez-Cabo, José; Martín-Ramos, Pablo; Martín-Gil, Jesús; Navas-Gracia, Luis M.; Dante, Roberto C.
2014-11-15
The transition from a prevalent turbostratic arrangement with low planar interactions (2D) to an array of polymeric carbon nitride nanosheets with stronger interplanar interactions (3D), occurring for samples treated above 650 °C, was detected by terahertz-time domain spectroscopy (THz-TDS). The simulated 3D material made of stacks of shifted quasi planar sheets composed of zigzagged polymer ribbons, delivered a XRD simulated pattern in relatively good agreement with the experimental one. The 2D to 3D transition was also supported by the simulation of THz-TDS spectra obtained from quantum chemistry calculations, in which the same broad bands around 2 THz and 1.5 THz were found for 2D and 3D arrays, respectively. This transition was also in accordance with the tightening of the interplanar distance probably due to an interplanar π bond contribution, as evidenced also by a broad absorption around 2.6 eV in the UV–vis spectrum, which appeared in the sample treated at 650 °C, and increased in the sample treated at 700 °C. The band gap was calculated for 1D and 2D cases. The value of 3.374 eV for the 2D case is, within the model accuracy and precision, in a relative good agreement with the value of 3.055 eV obtained from the experimental results. - Graphical abstract: 2D lattice mode vibrations and structural changes correlated with the so called “2D to 3D transition”. - Highlights: • A 2D to 3D transition has been detected for polymeric carbon nitride. • THz-TDS allowed us to discover and detect the 2D to 3D transition of polymeric carbon nitride. • We propose a structure for polymeric carbon nitride confirming it with THz-TDS.
Stochastic Inversion of 2D Magnetotelluric Data
Chen, Jinsong
2010-07-01
The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function is explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows