Identification of Arbitrary Zonation in Groundwater Parameters using the Level Set Method and a Parallel Genetic Algorithm

NASA Astrophysics Data System (ADS)

Lei, H.; Lu, Z.; Vesselinov, V. V.; Ye, M.

2017-12-01

Simultaneous identification of both the zonation structure of aquifer heterogeneity and the hydrogeological parameters associated with these zones is challenging, especially for complex subsurface heterogeneity fields. In this study, a new approach, based on the combination of the level set method and a parallel genetic algorithm is proposed. Starting with an initial guess for the zonation field (including both zonation structure and the hydraulic properties of each zone), the level set method ensures that material interfaces are evolved through the inverse process such that the total residual between the simulated and observed state variables (hydraulic head) always decreases, which means that the inversion result depends on the initial guess field and the minimization process might fail if it encounters a local minimum. To find the global minimum, the genetic algorithm (GA) is utilized to explore the parameters that define initial guess fields, and the minimal total residual corresponding to each initial guess field is considered as the fitness function value in the GA. Due to the expensive evaluation of the fitness function, a parallel GA is adapted in combination with a simulated annealing algorithm. The new approach has been applied to several synthetic cases in both steady-state and transient flow fields, including a case with real flow conditions at the chromium contaminant site at the Los Alamos National Laboratory. The results show that this approach is capable of identifying the arbitrary zonation structures of aquifer heterogeneity and the hydrogeological parameters associated with these zones effectively.

Studies of the g factors of the ground 4A2 and the first excited 2E state of Cr 3+ ions in emerald

NASA Astrophysics Data System (ADS)

Wei, Qun; Guo, Li-Xin; Yang, Zi-Yuan; Wei, Bing

2011-09-01

By using complete diagonalization method, the zero-field splitting and g factors of the ground 4A2 and the first excited 2E states of Cr 3+ ions in emerald are calculated. The theoretical results are in good agreement with the experimental data. The dependencies of the g factors on the crystal field parameters, including Dq, v, and v', have been studied. It is shown that, the g factors of the ground state varied with the crystal field parameters approximately in a linear way, but the g factors of the first excited state varied nonlinearly with these parameters.

Study of Far—Field Directivity Pattern for Linear Arrays

NASA Astrophysics Data System (ADS)

Ana-Maria, Chiselev; Luminita, Moraru; Laura, Onose

2011-10-01

A model to calculate directivity pattern in far field is developed in this paper. Based on this model, the three-dimensional beam pattern is introduced and analyzed in order to investigate geometric parameters of linear arrays and their influences on the directivity pattern. Simulations in azimuthal plane are made to highlight the influence of transducers parameters, including number of elements and inter-element spacing. It is true that these parameters are important factors that influence the directivity pattern and the appearance of side-lobes for linear arrays.

Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

DOEpatents

Stevens, Fred J.

1992-01-01

A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

The diagram of phase-field crystal structures: an influence of model parameters in a two-mode approximation

NASA Astrophysics Data System (ADS)

Ankudinov, V.; Galenko, P. K.

2017-04-01

Effect of phase-field crystal model (PFC-model) parameters on the structure diagram is analyzed. The PFC-model is taken in a two-mode approximation and the construction of structure diagram follows from the free energy minimization and Maxwell thermodynamic rule. The diagram of structure’s coexistence for three dimensional crystal structures [Body-Centered-Cubic (BCC), Face-Centered-Cubic (FCC) and homogeneous structures] are constructed. An influence of the model parameters, including the stability parameters, are discussed. A question about the structure diagram construction using the two-mode PFC-model with the application to real materials is established.

Correlation between Macular Thickness and Visual Field in Early Open Angle Glaucoma: A Cross-Sectional Study.

PubMed

Fallahi Motlagh, Behzad; Sadeghi, Ali

2017-01-01

The aim of this study was to correlate macular thickness and visual field parameters in early glaucoma. A total of 104 eyes affected with early glaucoma were examined in a cross-sectional, prospective study. Visual field testing using both standard automated perimetry (SAP) and shortwave automated perimetry (SWAP) was performed. Global visual field parameters, including mean deviation (MD) and pattern standard deviation (PSD), were recorded and correlated with spectral domain optical coherence tomography (SD-OCT)-measured macular thickness and asymmetry. Average macular thickness correlated significantly with all measures of visual field including MD-SWAP (r = 0.42), MD-SAP (r = 0.41), PSD-SWAP (r = -0.23), and PSD-SAP (r = -0.21), with P-values <0.001 for all correlations. The mean MD scores (using both SWAP and SAP) were significantly higher in the eyes with thin than in those with intermediate average macular thickness. Intraeye (superior macula thickness - inferior macula thickness) asymmetries correlated significantly with both PSD-SWAP (r = 0.63, P < 0.001) and PSD-SAP (r = 0.26, P = 0.01) scores. This study revealed a significant correlation between macular thickness and visual field parameters in early glaucoma. The results of this study should make macular thickness measurements even more meaningful to glaucoma specialists.

Supergravity, complex parameters and the Janis-Newman algorithm

NASA Astrophysics Data System (ADS)

Erbin, Harold; Heurtier, Lucien

2015-08-01

The Demiański-Janis-Newman (DJN) algorithm is an original solution generating technique. For a long time it has been limited to producing rotating solutions, restricted to the case of a metric and real scalar fields, despite the fact that Demiański extended it to include more parameters such as a NUT charge. Recently two independent prescriptions have been given for extending the algorithm to gauge fields and thus electrically charged configurations. In this paper we aim to end setting up the algorithm by providing a missing but important piece, which is how the transformation is applied to complex scalar fields. We illustrate our proposal through several examples taken from N = 2 supergravity, including the stationary BPS solutions from Behrndt et al and Sen's axion-dilaton rotating black hole. Moreover we discuss solutions that include pairs of complex parameters, such as the mass and the NUT charge, or the electric and magnetic charges, and we explain how to perform the algorithm in this context (with the example of Kerr-Newman-Taub-NUT and dyonic Kerr-Newman black holes). The final formulation of the DJN algorithm can possibly handle solutions with five of the six Plebański-Demiański parameters along with any type of bosonic fields with spin less than two (exemplified with the stationary Israel-Wilson-Perjes solutions). This provides all the necessary tools for applications to general matter-coupled gravity and to (gauged) supergravity.

Comments on MacDowell-Mansouri gravity and torsion

NASA Astrophysics Data System (ADS)

López-Domínguez, J. C.; Rosales-Quintero, J. E.; Sabido, M.

Starting with the MacDowell-Mansouri formulation of gravity with a SO(4, 1) gauge group, we introduce new parameters into the action to include the nondynamical Holst term, and the topological Nieh-Yan and Pontryagin classes. Then, we consider the new parameters as fields and analyze the solutions coming from their equations of motion. The new fields introduce torsional contributions to the theory that modify Einstein’s equations.

Jupiter's outer atmosphere.

NASA Technical Reports Server (NTRS)

Brice, N. M.

1973-01-01

The current state of the theory of Jupiter's outer atmosphere is briefly reviewed. The similarities and dissimilarities between the terrestrial and Jovian upper atmospheres are discussed, including the interaction of the solar wind with the planetary magnetic fields. Estimates of Jovian parameters are given, including magnetosphere and auroral zone sizes, ionospheric conductivity, energy inputs, and solar wind parameters at Jupiter. The influence of the large centrifugal force on the cold plasma distribution is considered. The Jovian Van Allen belt is attributed to solar wind particles diffused in toward the planet by dynamo electric fields from ionospheric neutral winds, and the consequences of this theory are indicated.

Polarizable atomic multipole-based force field for DOPC and POPE membrane lipids

NASA Astrophysics Data System (ADS)

Chu, Huiying; Peng, Xiangda; Li, Yan; Zhang, Yuebin; Min, Hanyi; Li, Guohui

2018-04-01

A polarizable atomic multipole-based force field for the membrane bilayer models 1,2-dioleoyl-phosphocholine (DOPC) and 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE) has been developed. The force field adopts the same framework as the Atomic Multipole Optimized Energetics for Biomolecular Applications (AMOEBA) model, in which the charge distribution of each atom is represented by the permanent atomic monopole, dipole and quadrupole moments. Many-body polarization including the inter- and intra-molecular polarization is modelled in a consistent manner with distributed atomic polarizabilities. The van der Waals parameters were first transferred from existing AMOEBA parameters for small organic molecules and then optimised by fitting to ab initio intermolecular interaction energies between models and a water molecule. Molecular dynamics simulations of the two aqueous DOPC and POPE membrane bilayer systems, consisting of 72 model molecules, were then carried out to validate the force field parameters. Membrane width, area per lipid, volume per lipid, deuterium order parameters, electron density profile, etc. were consistent with experimental values.

Simulation study of spheroidal dust gains charging: Applicable to dust grain alignment

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

Zahed, H.; Sobhanian, S.; Mahmoodi, J.

2006-09-15

The charging process of nonspherical dust grains in an unmagnetized plasma as well as in the presence of a magnetic field is studied. It is shown that unlike the spherical dust grain, due to nonhomogeneity of charge distribution on the spheroidal dust surface, the resultant electric forces on electrons and ions are different. This process produces some surface charge density gradient on the nonspherical grain surface. Effects of a magnetic field and other plasma parameters on the properties of the dust particulate are studied. It has been shown that the alignment direction could be changed or even reversed with themore » magnetic field and plasma parameters. Finally, the charge distribution on the spheroidal grain surface is studied for different ambient parameters including plasma temperature, neutral collision frequency, and the magnitude of the magnetic field.« less

Thermodynamics of anisotropic antiferromagnetic Heisenberg chain in the presence of longitudinal magnetic field

NASA Astrophysics Data System (ADS)

Rezania, H.

2018-07-01

We have addressed the specific heat and magnetization of one dimensional spin-1/2 anisotropic antiferromagnetic Heisenberg chain at finite magnetic field. We have investigated the thermodynamic properties by means of excitation spectrum in terms of a hard core Bosonic representation. The effect of in-plane anisotropy thermodynamic properties has also been studied via the Bosonic model by Green's function approach. This anisotropy is considered for exchange constants that couple spin components perpendicular to magnetic field direction. We have found the temperature dependence of the specific heat and longitudinal magnetization in the gapped field induced spin-polarized phase for various magnetic fields and anisotropy parameters. Furthermore we have studied the magnetic field dependence of specific heat and magnetization for various anisotropy parameters. Our results show temperature dependence of specific heat includes a peak so that its temperature position goes to higher temperature with increase of magnetic field. We have found the magnetic field dependence of specific heat shows a monotonic decreasing behavior for various magnetic fields due to increase of energy gap in the excitation spectrum. Also we have studied the temperature dependence of magnetization for different magnetic fields and various anisotropy parameters.

Effects of extremely low frequency magnetic field on oxidative balance in brain of rats.

PubMed

Ciejka, Elzbieta; Kleniewska, P; Skibska, B; Goraca, A

2011-12-01

Extremely low frequency magnetic field (ELF-MF) may result in oxidative DNA damage and lipid peroxidation with an ultimate effect on a number of systemic disturbances and cell death. The aim of the study is to assess the effect of ELF-MF parameters most frequently used in magnetotherapy on reactive oxygen species generation (ROS) in brain tissue of experimental animals depending on the time of exposure to this field. The research material included adult male Sprague-Dawley rats, aged 3-4 months. The animals were divided into 3 groups: I - control (shame) group; II - exposed to the following parameters of the magnetic field: 7 mT, 40 Hz, 30 min/day, 10 days; III - exposed to the ELF-MF parameters of 7 mT, 40 Hz, 60 min/day, 10 days. The selected parameters of oxidative stress: thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H(2)O(2)), total free sulphydryl groups (-SH groups) and protein in brain homogenates were measured after the exposure of rats to the magnetic field. ELF-MF parameters of 7 mT, 40 Hz, 30 min/day for 10 days caused a significant increase in lipid peroxidation and insignificant increase in H(2)O(2) and free -SH groups. The same ELF-MF parameters but applied for 60 min/day caused a significant increase in free -SH groups and protein concentration in the brain homogenates indicating the adaptive mechanism. The study has shown that ELF-MF applied for 30 min/day for 10 days can affect free radical generation in the brain. Prolongation of the exposure to ELF-MF (60/min/day) caused adaptation to this field. The effect of ELF-MF irradiation on oxidative stress parameters depends on the time of animal exposure to magnetic field.

The geometric field (gravity) as an electro-chemical potential in a Ginzburg-Landau theory of superconductivity

NASA Astrophysics Data System (ADS)

Atanasov, Victor

2017-07-01

We extend the superconductor's free energy to include an interaction of the order parameter with the curvature of space-time. This interaction leads to geometry dependent coherence length and Ginzburg-Landau parameter which suggests that the curvature of space-time can change the superconductor's type. The curvature of space-time doesn't affect the ideal diamagnetism of the superconductor but acts as chemical potential. In a particular circumstance, the geometric field becomes order-parameter dependent, therefore the superconductor's order parameter dynamics affects the curvature of space-time and electrical or internal quantum mechanical energy can be channelled into the curvature of space-time. Experimental consequences are discussed.

Light field imaging and application analysis in THz

NASA Astrophysics Data System (ADS)

Zhang, Hongfei; Su, Bo; He, Jingsuo; Zhang, Cong; Wu, Yaxiong; Zhang, Shengbo; Zhang, Cunlin

2018-01-01

The light field includes the direction information and location information. Light field imaging can capture the whole light field by single exposure. The four-dimensional light field function model represented by two-plane parameter, which is proposed by Levoy, is adopted in the light field. Acquisition of light field is based on the microlens array, camera array and the mask. We calculate the dates of light-field to synthetize light field image. The processing techniques of light field data include technology of refocusing rendering, technology of synthetic aperture and technology of microscopic imaging. Introducing the technology of light field imaging into THz, the efficiency of 3D imaging is higher than that of conventional THz 3D imaging technology. The advantages compared with visible light field imaging include large depth of field, wide dynamic range and true three-dimensional. It has broad application prospects.

FIRST ZEEMAN DOPPLER IMAGING OF A COOL STAR USING ALL FOUR STOKES PARAMETERS

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

Rosén, L.; Kochukhov, O.; Wade, G. A.

Magnetic fields are ubiquitous in active cool stars, but they are in general complex and weak. Current Zeeman Doppler imaging (ZDI) studies of cool star magnetic fields chiefly employ circular polarization observations because linear polarization is difficult to detect and requires a more sophisticated radiative transfer modeling to interpret. But it has been shown in previous theoretical studies, and in the observational analyses of magnetic Ap stars, that including linear polarization in the magnetic inversion process makes it possible to correctly recover many otherwise lost or misinterpreted magnetic features. We have obtained phase-resolved observations in all four Stokes parameters ofmore » the RS CVn star II Peg at two separate epochs. Here we present temperature and magnetic field maps reconstructed for this star using all four Stokes parameters. This is the very first such ZDI study of a cool active star. Our magnetic inversions reveal a highly structured magnetic field topology for both epochs. The strength of some surface features is doubled or even quadrupled when linear polarization is taken into account. The total magnetic energy of the reconstructed field map also becomes about 2.1–3.5 times higher. The overall complexity is also increased as the field energy is shifted toward higher harmonic modes when four Stokes parameters are used. As a consequence, the potential field extrapolation of the four Stokes parameter ZDI results indicates that magnetic field becomes weaker at a distance of several stellar radii due to a decrease of the large-scale field component.« less

Fractional blood flow in oscillatory arteries with thermal radiation and magnetic field effects

NASA Astrophysics Data System (ADS)

Bansi, C. D. K.; Tabi, C. B.; Motsumi, T. G.; Mohamadou, A.

2018-06-01

A fractional model is proposed to study the effect of heat transfer and magnetic field on the blood flowing inside oscillatory arteries. The flow is due to periodic pressure gradient and the fractional model equations include body acceleration. The proposed velocity and temperature distribution equations are solved using the Laplace and Hankel transforms. The effect of the fluid parameters such as the Reynolds number (Re), the magnetic parameter (M) and the radiation parameter (N) is studied graphically with changing the fractional-order parameter. It is found that the fractional derivative is a valuable tool to control both the temperature and velocity of blood when flow parameters change under treatment, for example. Besides, this work highlights the fact that in the presence of strong magnetic field, blood velocity and temperature reduce. A reversed effect is observed where the applied thermal radiation increase; the velocity and temperature of blood increase. However, the temperature remains high around the artery centerline, which is appropriate during treatment to avoid tissues damage.

Optical properties of the Tietz-Hua quantum well under the applied external fields

NASA Astrophysics Data System (ADS)

Kasapoglu, E.; Sakiroglu, S.; Ungan, F.; Yesilgul, U.; Duque, C. A.; Sökmen, I.

2017-12-01

In this study, the effects of the electric and magnetic fields as well as structure parameter- γ on the total absorption coefficient, including linear and third order nonlinear absorption coefficients for the optical transitions between any two subband in the Tietz-Hua quantum well have been investigated. The optical transitions were investigated by using the density matrix formalism and the perturbation expansion method. The Tietz-Hua quantum well becomes narrower (wider) when the γ - structure parameter increases (decreases) and so the energies of the bound states will be functions of this parameter. Therefore, we can provide the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric and magnetic fields as well as the structure parameters and these results can be used to adjust and control the optical properties of the Tietz-Hua quantum well.

Pulsed electric fields for pasteurization: defining processing conditions

USDA-ARS?s Scientific Manuscript database

Application of pulsed electric fields (PEF) technology in food pasteurization has been extensively studied. Optimal PEF treatment conditions for maximum microbial inactivation depend on multiple factors including PEF processing conditions, production parameters and product properties. In order for...

Mean-field models for heterogeneous networks of two-dimensional integrate and fire neurons.

PubMed

Nicola, Wilten; Campbell, Sue Ann

2013-01-01

We analytically derive mean-field models for all-to-all coupled networks of heterogeneous, adapting, two-dimensional integrate and fire neurons. The class of models we consider includes the Izhikevich, adaptive exponential and quartic integrate and fire models. The heterogeneity in the parameters leads to different moment closure assumptions that can be made in the derivation of the mean-field model from the population density equation for the large network. Three different moment closure assumptions lead to three different mean-field systems. These systems can be used for distinct purposes such as bifurcation analysis of the large networks, prediction of steady state firing rate distributions, parameter estimation for actual neurons and faster exploration of the parameter space. We use the mean-field systems to analyze adaptation induced bursting under realistic sources of heterogeneity in multiple parameters. Our analysis demonstrates that the presence of heterogeneity causes the Hopf bifurcation associated with the emergence of bursting to change from sub-critical to super-critical. This is confirmed with numerical simulations of the full network for biologically reasonable parameter values. This change decreases the plausibility of adaptation being the cause of bursting in hippocampal area CA3, an area with a sizable population of heavily coupled, strongly adapting neurons.

Mean-field models for heterogeneous networks of two-dimensional integrate and fire neurons

PubMed Central

Nicola, Wilten; Campbell, Sue Ann

2013-01-01

We analytically derive mean-field models for all-to-all coupled networks of heterogeneous, adapting, two-dimensional integrate and fire neurons. The class of models we consider includes the Izhikevich, adaptive exponential and quartic integrate and fire models. The heterogeneity in the parameters leads to different moment closure assumptions that can be made in the derivation of the mean-field model from the population density equation for the large network. Three different moment closure assumptions lead to three different mean-field systems. These systems can be used for distinct purposes such as bifurcation analysis of the large networks, prediction of steady state firing rate distributions, parameter estimation for actual neurons and faster exploration of the parameter space. We use the mean-field systems to analyze adaptation induced bursting under realistic sources of heterogeneity in multiple parameters. Our analysis demonstrates that the presence of heterogeneity causes the Hopf bifurcation associated with the emergence of bursting to change from sub-critical to super-critical. This is confirmed with numerical simulations of the full network for biologically reasonable parameter values. This change decreases the plausibility of adaptation being the cause of bursting in hippocampal area CA3, an area with a sizable population of heavily coupled, strongly adapting neurons. PMID:24416013

Sakiadis flow of Maxwell fluid considering magnetic field and convective boundary conditions

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

Mustafa, M., E-mail: meraj-mm@hotmail.com; Khan, Junaid Ahmad; Hayat, T.

2015-02-15

In this paper we address the flow of Maxwell fluid due to constantly moving flat radiative surface with convective condition. The flow is under the influence of non-uniform transverse magnetic field. The velocity and temperature distributions have been evaluated numerically by shooting approach. The solution depends on various interesting parameters including local Deborah number De, magnetic field parameter M, Prandtl number Pr and Biot number Bi. We found that variation in velocity with an increase in local Deborah number De is non-monotonic. However temperature is a decreasing function of local Deborah number De.

Binding energy of donor impurity states and optical absorption in the Tietz-Hua quantum well under an applied electric field

NASA Astrophysics Data System (ADS)

Al, E. B.; Kasapoglu, E.; Sakiroglu, S.; Duque, C. A.; Sökmen, I.

2018-04-01

For a quantum well which has the Tietz-Hua potential, the ground and some excited donor impurity binding energies and the total absorption coefficients, including linear and third order nonlinear terms for the transitions between the related impurity states with respect to the structure parameters and the impurity position as well as the electric field strength are investigated. The binding energies were obtained using the effective-mass approximation within a variational scheme and the optical transitions between any two impurity states were calculated by using the density matrix formalism and the perturbation expansion method. Our results show that the effects of the electric field and the structure parameters on the optical transitions are more pronounced. So we can adjust the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric field as well as the structure parameters.

Tikekar superdense stars in electric fields

NASA Astrophysics Data System (ADS)

Komathiraj, K.; Maharaj, S. D.

2007-04-01

We present exact solutions to the Einstein-Maxwell system of equations with a specified form of the electric field intensity by assuming that the hypersurface {t=constant} are spheroidal. The solution of the Einstein-Maxwell system is reduced to a recurrence relation with variable rational coefficients which can be solved in general using mathematical induction. New classes of solutions of linearly independent functions are obtained by restricting the spheroidal parameter K and the electric field intensity parameter α. Consequently, it is possible to find exact solutions in terms of elementary functions, namely, polynomials and algebraic functions. Our result contains models found previously including the superdense Tikekar neutron star model [J. Math. Phys. 31, 2454 (1990)] when K=-7 and α=0. Our class of charged spheroidal models generalize the uncharged isotropic Maharaj and Leach solutions [J. Math. Phys. 37, 430 (1996)]. In particular, we find an explicit relationship directly relating the spheroidal parameter K to the electromagnetic field.

Terahertz radiation generation through the nonlinear interaction of Hermite and Laguerre Gaussian laser beams with collisional plasma: Field profile optimization

NASA Astrophysics Data System (ADS)

Safari, Samaneh; Niknam, Ali Reza; Jahangiri, Fazel; Jazi, Bahram

2018-04-01

The nonlinear interaction of Hermite-Gaussian and Laguerre-Gaussian (LG) laser beams with a collisional inhomogeneous plasma is studied, and the amplitude of the emitted terahertz (THz) electric field is evaluated. The effects of laser beams and plasma parameters, including the beams width, LG modes, the plasma collision frequency, and the amplitude of density ripple on the evolution of THz electric field amplitude, are examined. It is found that the shape of the generated THz radiation pattern can be tuned by the laser parameters. In addition, the optimum values of the effective parameters for achieving the maximum THz electric field amplitude are proposed. It is shown that a significant enhancement up to 4.5% can be obtained in our scheme, which is much greater than the maximum efficiency obtained for laser beams with the same profiles.

Petermann I and II spot size: Accurate semi analytical description involving Nelder-Mead method of nonlinear unconstrained optimization and three parameter fundamental modal field

NASA Astrophysics Data System (ADS)

Roy Choudhury, Raja; Roy Choudhury, Arundhati; Kanti Ghose, Mrinal

2013-01-01

A semi-analytical model with three optimizing parameters and a novel non-Gaussian function as the fundamental modal field solution has been proposed to arrive at an accurate solution to predict various propagation parameters of graded-index fibers with less computational burden than numerical methods. In our semi analytical formulation the optimization of core parameter U which is usually uncertain, noisy or even discontinuous, is being calculated by Nelder-Mead method of nonlinear unconstrained minimizations as it is an efficient and compact direct search method and does not need any derivative information. Three optimizing parameters are included in the formulation of fundamental modal field of an optical fiber to make it more flexible and accurate than other available approximations. Employing variational technique, Petermann I and II spot sizes have been evaluated for triangular and trapezoidal-index fibers with the proposed fundamental modal field. It has been demonstrated that, the results of the proposed solution identically match with the numerical results over a wide range of normalized frequencies. This approximation can also be used in the study of doped and nonlinear fiber amplifier.

Universal relations for range corrections to Efimov features

DOE PAGES

Ji, Chen; Braaten, Eric; Phillips, Daniel R.; ...

2015-09-09

In a three-body system of identical bosons interacting through a large S-wave scattering length a, there are several sets of features related to the Efimov effect that are characterized by discrete scale invariance. Effective field theory was recently used to derive universal relations between these Efimov features that include the first-order correction due to a nonzero effective range r s. We reveal a simple pattern in these range corrections that had not been previously identified. The pattern is explained by the renormalization group for the effective field theory, which implies that the Efimov three-body parameter runs logarithmically with the momentummore » scale at a rate proportional to r s/a. The running Efimov parameter also explains the empirical observation that range corrections can be largely taken into account by shifting the Efimov parameter by an adjustable parameter divided by a. Furthermore, the accuracy of universal relations that include first-order range corrections is verified by comparing them with various theoretical calculations using models with nonzero range.« less

DRAINMOD-GIS: a lumped parameter watershed scale drainage and water quality model

Treesearch

G.P. Fernandez; G.M. Chescheir; R.W. Skaggs; D.M. Amatya

2006-01-01

A watershed scale lumped parameter hydrology and water quality model that includes an uncertainty analysis component was developed and tested on a lower coastal plain watershed in North Carolina. Uncertainty analysis was used to determine the impacts of uncertainty in field and network parameters of the model on the predicted outflows and nitrate-nitrogen loads at the...

Complete set of homogeneous isotropic analytic solutions in scalar-tensor cosmology with radiation and curvature

NASA Astrophysics Data System (ADS)

Bars, Itzhak; Chen, Shih-Hung; Steinhardt, Paul J.; Turok, Neil

2012-10-01

We study a model of a scalar field minimally coupled to gravity, with a specific potential energy for the scalar field, and include curvature and radiation as two additional parameters. Our goal is to obtain analytically the complete set of configurations of a homogeneous and isotropic universe as a function of time. This leads to a geodesically complete description of the Universe, including the passage through the cosmological singularities, at the classical level. We give all the solutions analytically without any restrictions on the parameter space of the model or initial values of the fields. We find that for generic solutions the Universe goes through a singular (zero-size) bounce by entering a period of antigravity at each big crunch and exiting from it at the following big bang. This happens cyclically again and again without violating the null-energy condition. There is a special subset of geodesically complete nongeneric solutions which perform zero-size bounces without ever entering the antigravity regime in all cycles. For these, initial values of the fields are synchronized and quantized but the parameters of the model are not restricted. There is also a subset of spatial curvature-induced solutions that have finite-size bounces in the gravity regime and never enter the antigravity phase. These exist only within a small continuous domain of parameter space without fine-tuning the initial conditions. To obtain these results, we identified 25 regions of a 6-parameter space in which the complete set of analytic solutions are explicitly obtained.

Evaluating Parametrization Protocols for Hydration Free Energy Calculations with the AMOEBA Polarizable Force Field.

PubMed

Bradshaw, Richard T; Essex, Jonathan W

2016-08-09

Hydration free energy (HFE) calculations are often used to assess the performance of biomolecular force fields and the quality of assigned parameters. The AMOEBA polarizable force field moves beyond traditional pairwise additive models of electrostatics and may be expected to improve upon predictions of thermodynamic quantities such as HFEs over and above fixed-point-charge models. The recent SAMPL4 challenge evaluated the AMOEBA polarizable force field in this regard but showed substantially worse results than those using the fixed-point-charge GAFF model. Starting with a set of automatically generated AMOEBA parameters for the SAMPL4 data set, we evaluate the cumulative effects of a series of incremental improvements in parametrization protocol, including both solute and solvent model changes. Ultimately, the optimized AMOEBA parameters give a set of results that are not statistically significantly different from those of GAFF in terms of signed and unsigned error metrics. This allows us to propose a number of guidelines for new molecule parameter derivation with AMOEBA, which we expect to have benefits for a range of biomolecular simulation applications such as protein-ligand binding studies.

Detection of co-seismic earthquake gravity field signals using GRACE-like mission simulations

NASA Astrophysics Data System (ADS)

Sharifi, Mohammad Ali; Shahamat, Abolfazl

2017-05-01

After launching the GRACE satellite mission in 2002, the earth's gravity field and its temporal variations are measured with a closer inspection. Although these variations are mainly because of the mass transfer of land water storage, they can also happen due to mass movements related to some natural phenomena including earthquakes, volcanic eruptions, melting of polar ice caps and glacial isostatic adjustment. Therefore this paper shows which parameters of an earthquake are more sensitive to GRACE-Like satellite missions. For this purpose, the parameters of the Maule earthquake that occurred in recent years and Alaska earthquake that occurred in 1964 have been chosen. Then we changed their several parameters to serve our purpose. The GRACE-Like sensitivity is observed by using the simulation of the earthquakes along with gravity changes they caused, as well as using dislocation theory under a half space earth. This observation affects the various faulting parameters which include fault length, width, depth and average slip. These changes were therefore evaluated and the result shows that the GRACE satellite missions tend to be more sensitive to Width among the Length and Width, the other parameter is Dip variations than other parameters. This article can be useful to the upcoming scenario designers and seismologists in their quest to study fault parameters.

Methods of Optimizing X-Ray Optical Prescriptions for Wide-Field Applications

NASA Technical Reports Server (NTRS)

Elsner, R. F.; O'Dell, S. L.; Ramsey, B. D.; Weisskopf, M. C.

2010-01-01

We are working on the development of a method for optimizing wide-field x-ray telescope mirror prescriptions, including polynomial coefficients, mirror shell relative displacements, and (assuming 4 focal plane detectors) detector placement and tilt that does not require a search through the multi-dimensional parameter space. Under the assumption that the parameters are small enough that second order expansions are valid, we show that the performance at the detector surface can be expressed as a quadratic function of the parameters with numerical coefficients derived from a ray trace through the underlying Wolter I optic. The best values for the parameters are found by solving the linear system of equations creating by setting derivatives of this function with respect to each parameter to zero. We describe the present status of this development effort.

Simulation of carbohydrates, from molecular docking to dynamics in water.

PubMed

Sapay, Nicolas; Nurisso, Alessandra; Imberty, Anne

2013-01-01

Modeling of carbohydrates is particularly challenging because of the variety of structures resulting for the high number of monosaccharides and possible linkages and also because of their intrinsic flexibility. The development of carbohydrate parameters for molecular modeling is still an active field. Nowadays, main carbohydrates force fields are GLYCAM06, CHARMM36, and GROMOS 45A4. GLYCAM06 includes the largest choice of compounds and is compatible with the AMBER force fields and associated. Furthermore, AMBER includes tools for the implementation of new parameters. When looking at protein-carbohydrate interaction, the choice of the starting structure is of importance. Such complex can be sometimes obtained from the Protein Data Bank-although the stereochemistry of sugars may require some corrections. When no experimental data is available, molecular docking simulation is generally used to the obtain protein-carbohydrate complex coordinates. As molecular docking parameters are not specifically dedicated to carbohydrates, inaccuracies should be expected, especially for the docking of polysaccharides. This issue can be addressed at least partially by combining molecular docking with molecular dynamics simulation in water.

Measurement of Anisotropic Particle Interactions with Nonuniform ac Electric Fields.

PubMed

Rupp, Bradley; Torres-Díaz, Isaac; Hua, Xiaoqing; Bevan, Michael A

2018-02-20

Optical microscopy measurements are reported for single anisotropic polymer particles interacting with nonuniform ac electric fields. The present study is limited to conditions where gravity confines particles with their long axis parallel to the substrate such that particles can be treated using quasi-2D analysis. Field parameters are investigated that result in particles residing at either electric field maxima or minima and with long axes oriented either parallel or perpendicular to the electric field direction. By nonintrusively observing thermally sampled positions and orientations at different field frequencies and amplitudes, a Boltzmann inversion of the time-averaged probability of states yields kT-scale energy landscapes (including dipole-field, particle-substrate, and gravitational potentials). The measured energy landscapes show agreement with theoretical potentials using particle conductivity as the sole adjustable material property. Understanding anisotropic particle-field energy landscapes vs field parameters enables quantitative control of local forces and torques on single anisotropic particles to manipulate their position and orientation within nonuniform fields.

Consistent parameter fixing in the quark-meson model with vacuum fluctuations

NASA Astrophysics Data System (ADS)

Carignano, Stefano; Buballa, Michael; Elkamhawy, Wael

2016-08-01

We revisit the renormalization prescription for the quark-meson model in an extended mean-field approximation, where vacuum quark fluctuations are included. At a given cutoff scale the model parameters are fixed by fitting vacuum quantities, typically including the sigma-meson mass mσ and the pion decay constant fπ. In most publications the latter is identified with the expectation value of the sigma field, while for mσ the curvature mass is taken. When quark loops are included, this prescription is however inconsistent, and the correct identification involves the renormalized pion decay constant and the sigma pole mass. In the present article we investigate the influence of the parameter-fixing scheme on the phase structure of the model at finite temperature and chemical potential. Despite large differences between the model parameters in the two schemes, we find that in homogeneous matter the effect on the phase diagram is relatively small. For inhomogeneous phases, on the other hand, the choice of the proper renormalization prescription is crucial. In particular, we show that if renormalization effects on the pion decay constant are not considered, the model does not even present a well-defined renormalized limit when the cutoff is sent to infinity.

WaveAR: A software tool for calculating parameters for water waves with incident and reflected components

NASA Astrophysics Data System (ADS)

Landry, Blake J.; Hancock, Matthew J.; Mei, Chiang C.; García, Marcelo H.

2012-09-01

The ability to determine wave heights and phases along a spatial domain is vital to understanding a wide range of littoral processes. The software tool presented here employs established Stokes wave theory and sampling methods to calculate parameters for the incident and reflected components of a field of weakly nonlinear waves, monochromatic at first order in wave slope and propagating in one horizontal dimension. The software calculates wave parameters over an entire wave tank and accounts for reflection, weak nonlinearity, and a free second harmonic. Currently, no publicly available program has such functionality. The included MATLAB®-based open source code has also been compiled for Windows®, Mac® and Linux® operating systems. An additional companion program, VirtualWave, is included to generate virtual wave fields for WaveAR. Together, the programs serve as ideal analysis and teaching tools for laboratory water wave systems.

The Gaia-ESO Survey Astrophysical Calibration

NASA Astrophysics Data System (ADS)

Pancino, E.; Gaia-ESO Survey Consortium

2016-05-01

The Gaia-ESO Survey is a wide field spectroscopic survey recently started with the FLAMES@VLT in Cerro Paranal, Chile. It will produce radial velocities more accurate than Gaia's for faint stars (down to V ≃ 18), and astrophysical parameters and abundances for approximately 100 000 stars, belonging to all Galactic populations. 300 nights were assigned in 5 years (with the last year subject to approval after a detailed report). In particular, to connect with other ongoing and planned spectroscopic surveys, a detailed calibration program — for the astrophysical parameters derivation — is planned, including well known clusters, Gaia benchmark stars, and special equatorial calibration fields designed for wide field/multifiber spectrographs.

Coherent Doppler lidar signal covariance including wind shear and wind turbulence

NASA Technical Reports Server (NTRS)

Frehlich, R. G.

1993-01-01

The performance of coherent Doppler lidar is determined by the statistics of the coherent Doppler signal. The derivation and calculation of the covariance of the Doppler lidar signal is presented for random atmospheric wind fields with wind shear. The random component is described by a Kolmogorov turbulence spectrum. The signal parameters are clarified for a general coherent Doppler lidar system. There are two distinct physical regimes: one where the transmitted pulse determines the signal statistics and the other where the wind field dominates the signal statistics. The Doppler shift of the signal is identified in terms of the wind field and system parameters.

LEOrbit: A program to calculate parameters relevant to modeling Low Earth Orbit spacecraft-plasma interaction

NASA Astrophysics Data System (ADS)

Marchand, R.; Purschke, D.; Samson, J.

2013-03-01

Understanding the physics of interaction between satellites and the space environment is essential in planning and exploiting space missions. Several computer models have been developed over the years to study this interaction. In all cases, simulations are carried out in the reference frame of the spacecraft and effects such as charging, the formation of electrostatic sheaths and wakes are calculated for given conditions of the space environment. In this paper we present a program used to compute magnetic fields and a number of space plasma and space environment parameters relevant to Low Earth Orbits (LEO) spacecraft-plasma interaction modeling. Magnetic fields are obtained from the International Geophysical Reference Field (IGRF) and plasma parameters are obtained from the International Reference Ionosphere (IRI) model. All parameters are computed in the spacecraft frame of reference as a function of its six Keplerian elements. They are presented in a format that can be used directly in most spacecraft-plasma interaction models. Catalogue identifier: AENY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENY_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 270308 No. of bytes in distributed program, including test data, etc.: 2323222 Distribution format: tar.gz Programming language: FORTRAN 90. Computer: Non specific. Operating system: Non specific. RAM: 7.1 MB Classification: 19, 4.14. External routines: IRI, IGRF (included in the package). Nature of problem: Compute magnetic field components, direction of the sun, sun visibility factor and approximate plasma parameters in the reference frame of a Low Earth Orbit satellite. Solution method: Orbit integration, calls to IGRF and IRI libraries and transformation of coordinates from geocentric to spacecraft frame reference. Restrictions: Low Earth orbits, altitudes between 150 and 2000 km. Running time: Approximately two seconds to parameterize a full orbit with 1000 points.

Further along the Road Less Traveled: AMBER ff15ipq, an Original Protein Force Field Built on a Self-Consistent Physical Model

PubMed Central

2016-01-01

We present the AMBER ff15ipq force field for proteins, the second-generation force field developed using the Implicitly Polarized Q (IPolQ) scheme for deriving implicitly polarized atomic charges in the presence of explicit solvent. The ff15ipq force field is a complete rederivation including more than 300 unique atomic charges, 900 unique torsion terms, 60 new angle parameters, and new atomic radii for polar hydrogens. The atomic charges were derived in the context of the SPC/Eb water model, which yields more-accurate rotational diffusion of proteins and enables direct calculation of nuclear magnetic resonance (NMR) relaxation parameters from molecular dynamics simulations. The atomic radii improve the accuracy of modeling salt bridge interactions relative to contemporary fixed-charge force fields, rectifying a limitation of ff14ipq that resulted from its use of pair-specific Lennard-Jones radii. In addition, ff15ipq reproduces penta-alanine J-coupling constants exceptionally well, gives reasonable agreement with NMR relaxation rates, and maintains the expected conformational propensities of structured proteins/peptides, as well as disordered peptides—all on the microsecond (μs) time scale, which is a critical regime for drug design applications. These encouraging results demonstrate the power and robustness of our automated methods for deriving new force fields. All parameters described here and the mdgx program used to fit them are included in the AmberTools16 distribution. PMID:27399642

Tower Illuminance Model

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

Ho, Clifford K.; Sims, Cianan

TIM is a real-time interactive concentrating solar field simulation. TIM models a concentrating tower (receiver), heliostat field, and potential reflected glare based on user-specified parameters such as field capacity, tower height and location. TIM provides a navigable 3D interface, allowing the user to “fly” around the field to determine the potential glare hazard from off-target heliostats. Various heliostat aiming strategies are available for specifying how heliostats behave when in standby mode. Strategies include annulus, point-per-group, up-aiming and single-point-focus. Additionally, TIM includes an avian path feature for approximating the irradiance and feather temperature of a bird flying through the field airspace.

Combined Uncertainty and A-Posteriori Error Bound Estimates for CFD Calculations: Theory and Implementation

NASA Technical Reports Server (NTRS)

Barth, Timothy J.

2014-01-01

Simulation codes often utilize finite-dimensional approximation resulting in numerical error. Some examples include, numerical methods utilizing grids and finite-dimensional basis functions, particle methods using a finite number of particles. These same simulation codes also often contain sources of uncertainty, for example, uncertain parameters and fields associated with the imposition of initial and boundary data,uncertain physical model parameters such as chemical reaction rates, mixture model parameters, material property parameters, etc.

Effects of high voltage transmission lines on honeybees: a feasibility study. Final report

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

Greenberg, B.

1977-07-01

Methodology is described for the investigation of the effects of electric fields generated by high-tension power lines on honeybees (Apis mellifera L.). The parameters to be measured include colony population, honey stores, amount of acoustical noise generated by the bees, in-hive temperature, incidence of queen cell production, and tendency to swarm. Accompanying dosimetric support includes in-hive electric field measurements, development of shielding to eliminate the electric field from selected colonies, analysis of the acoustical data, and periodic checks on the ambient electric field present under the line and at the control site.

Nondimensional Parameters and Equations for Nonlinear and Bifurcation Analyses of Thin Anisotropic Quasi-Shallow Shells

NASA Technical Reports Server (NTRS)

Nemeth, Michael P.

2010-01-01

A comprehensive development of nondimensional parameters and equations for nonlinear and bifurcations analyses of quasi-shallow shells, based on the Donnell-Mushtari-Vlasov theory for thin anisotropic shells, is presented. A complete set of field equations for geometrically imperfect shells is presented in terms general of lines-of-curvature coordinates. A systematic nondimensionalization of these equations is developed, several new nondimensional parameters are defined, and a comprehensive stress-function formulation is presented that includes variational principles for equilibrium and compatibility. Bifurcation analysis is applied to the nondimensional nonlinear field equations and a comprehensive set of bifurcation equations are presented. An extensive collection of tables and figures are presented that show the effects of lamina material properties and stacking sequence on the nondimensional parameters.

Parametric study of waste chicken fat catalytic chemical vapour deposition for controlled synthesis of vertically aligned carbon nanotubes

NASA Astrophysics Data System (ADS)

Suriani, A. B.; Dalila, A. R.; Mohamed, A.; Rosmi, M. S.; Mamat, M. H.; Malek, M. F.; Ahmad, M. K.; Hashim, N.; Isa, I. M.; Soga, T.; Tanemura, M.

2016-12-01

High-quality vertically aligned carbon nanotubes (VACNTs) were synthesised using ferrocene-chicken oil mixture utilising a thermal chemical vapour deposition (TCVD) method. Reaction parameters including vaporisation temperature, catalyst concentration and synthesis time were examined for the first time to investigate their influence on the growth of VACNTs. Analysis via field emission scanning electron microscopy and micro-Raman spectroscopy revealed that the growth rate, diameter and crystallinity of VACNTs depend on the varied synthesis parameters. Vaporisation temperature of 570°C, catalyst concentration of 5.33 wt% and synthesis time of 60 min were considered as optimum parameters for the production of VACNTs from waste chicken fat. These parameters are able to produce VACNTs with small diameters in the range of 15-30 nm and good quality (ID/IG 0.39 and purity 76%) which were comparable to those synthesised using conventional carbon precursor. The low turn on and threshold fields of VACNTs synthesised using optimum parameters indicated that the VACNTs synthesised using waste chicken fat are good candidate for field electron emitter. The result of this study therefore can be used to optimise the growth and production of VACNTs from waste chicken fat in a large scale for field emission application.

A Semi-analytical Line Transfer (SALT) Model. II: The Effects of a Bi-conical Geometry

NASA Astrophysics Data System (ADS)

Carr, Cody; Scarlata, Claudia; Panagia, Nino; Henry, Alaina

2018-06-01

We generalize the semi-analytical line transfer model recently introduced by Scarlata & Panagia for modeling galactic outflows, to account for bi-conical geometries of various opening angles and orientations with respect to the line of sight to the observer, as well as generalized velocity fields. We model the absorption and emission component of the line profile resulting from resonant absorption in the bi-conical outflow. We show how the outflow geometry impacts the resulting line profile. We use simulated spectra with different geometries and velocity fields to study how well the outflow parameters can be recovered. We find that geometrical parameters (including the opening angle and the orientation) are always well recovered. The density and velocity field parameters are reliably recovered when both an absorption and an emission component are visible in the spectra. This condition implies that the velocity and density fields for narrow cones oriented perpendicular to the line of sight will remain unconstrained.

Self-Consistent Drift-Diffusion Transport in Thermoelectrics and Implications for Measuring the Scattering Parameter

NASA Astrophysics Data System (ADS)

Santhanam, Parthiban; Ram, Rajeev J.

2010-09-01

We present a microscopic model of the Seebeck effect based on a generalized drift-diffusion equation and use it to predict a simple relationship between the electric field within an operating thermoelectric and the scattering parameter. Our model replicates existing theoretical results and permits an intuitive spatial picture of the Seebeck effect. A similar formalism was independently developed by Cai and Mahan, but this work includes numerical results for high dopant concentrations where the thermoelectric power factor is maximized. Based on these results, we propose that measurement of the bulk electric field should constitute a measurement of the scattering parameter, the improvement of which could lead to greater thermoelectric efficiency.

Bifurcation and Stability Analysis of the Equilibrium States in Thermodynamic Systems in a Small Vicinity of the Equilibrium Values of Parameters

NASA Astrophysics Data System (ADS)

Barsuk, Alexandr A.; Paladi, Florentin

2018-04-01

The dynamic behavior of thermodynamic system, described by one order parameter and one control parameter, in a small neighborhood of ordinary and bifurcation equilibrium values of the system parameters is studied. Using the general methods of investigating the branching (bifurcations) of solutions for nonlinear equations, we performed an exhaustive analysis of the order parameter dependences on the control parameter in a small vicinity of the equilibrium values of parameters, including the stability analysis of the equilibrium states, and the asymptotic behavior of the order parameter dependences on the control parameter (bifurcation diagrams). The peculiarities of the transition to an unstable state of the system are discussed, and the estimates of the transition time to the unstable state in the neighborhood of ordinary and bifurcation equilibrium values of parameters are given. The influence of an external field on the dynamic behavior of thermodynamic system is analyzed, and the peculiarities of the system dynamic behavior are discussed near the ordinary and bifurcation equilibrium values of parameters in the presence of external field. The dynamic process of magnetization of a ferromagnet is discussed by using the general methods of bifurcation and stability analysis presented in the paper.

Filter performance parameters for vectorial high-aperture wave fields.

PubMed

Sheppard, Colin J R; Martinez-Corral, M

2008-03-01

Performance parameters have been presented that can be used to compare the focusing performance of different optical systems, including the effect of pupil filters. These were originally given for the paraxial case and recently extended to the high-aperture scalar regime. We generalize these parameters to the full vectorial case for an aplanatic optical system illuminated by a plane-polarized wave. The behavior of different optical systems is compared.

Systems and methods for measuring a parameter of a landfill including a barrier cap and wireless sensor systems and methods

DOEpatents

Kunerth, Dennis C.; Svoboda, John M.; Johnson, James T.

2007-03-06

A method of measuring a parameter of a landfill including a cap, without passing wires through the cap, includes burying a sensor apparatus in the landfill prior to closing the landfill with the cap; providing a reader capable of communicating with the sensor apparatus via radio frequency (RF); placing an antenna above the barrier, spaced apart from the sensor apparatus; coupling the antenna to the reader either before or after placing the antenna above the barrier; providing power to the sensor apparatus, via the antenna, by generating a field using the reader; accumulating and storing power in the sensor apparatus; sensing a parameter of the landfill using the sensor apparatus while using power; and transmitting the sensed parameter to the reader via a wireless response signal. A system for measuring a parameter of a landfill is also provided.

Evaluating Glaucomatous Retinal Nerve Fiber Damage by GDx VCC Polarimetry in Taiwan Chinese Population

PubMed Central

Chen, Hsin-Yi; Huang, Mei-Ling; Huang, Wei-Cheng

2010-01-01

Purpose To study the capability of scanning laser polarimetry with variable corneal compensation (GDx VCC) to detect differences in retinal nerve fiber layer thickness between normal and glaucomatous eyes in a Taiwan Chinese population. Methods This study included 44 normal eyes and 107 glaucomatous eyes. The glaucomatous eyes were divided into three subgroups on the basis of its visual field defects (early, moderate, severe). Each subject underwent a GDx-VCC exam and visual field testing. The area under the receiver-operating characteristic curve (AROC) of each relevant parameter was used to differentiate normal from each glaucoma subgroup, respectively. The correlation between visual field index and each parameter was evaluated for the eyes in the glaucoma group. Results For normal vs. early glaucoma, the parameter with the best AROC was Nerve fiber indicator (NFI) (0.942). For normal vs. moderate glaucoma, the parameter showing the best AROC was NFI (0.985). For normal vs. severe glaucoma, the parameter that had the best AROC was NFI (1.000). For early vs. moderate glaucoma, the parameter with the best AROC was NFI (0.732). For moderate vs. severe, the parameter showing the best AROC was temporal-superior-nasal-inferior-temporal average (0.652). For early vs. severe, the parameter with the best AROC was NFI (0.852). Conclusions GDx-VCC-measured parameters may serve as a useful tool to distinguish normal from glaucomatous eyes; in particular, NFI turned out to be the best discriminating parameter.

Relativistic thermal plasmas - Effects of magnetic fields

NASA Technical Reports Server (NTRS)

Araki, S.; Lightman, A. P.

1983-01-01

Processes and equilibria in finite, relativistic, thermal plasmas are investigated, taking into account electron-positron creation and annihilation, photon production by internal processes, and photon production by a magnetic field. Inclusion of the latter extends previous work on such plasmas. The basic relations for thermal, Comptonized synchrotron emission are analyzed, including emission and absorption without Comptonization, Comptonized thermal synchrotron emission, and the Comptonized synchrotron and bremsstrahlung luminosities. Pair equilibria are calculated, including approximations and dimensionless parameters, the pair balance equation, maximum temperatures and field strengths, and individual models and cooling curves.

Immirzi parameter without Immirzi ambiguity: Conformal loop quantization of scalar-tensor gravity

NASA Astrophysics Data System (ADS)

Veraguth, Olivier J.; Wang, Charles H.-T.

2017-10-01

Conformal loop quantum gravity provides an approach to loop quantization through an underlying conformal structure i.e. conformally equivalent class of metrics. The property that general relativity itself has no conformal invariance is reinstated with a constrained scalar field setting the physical scale. Conformally equivalent metrics have recently been shown to be amenable to loop quantization including matter coupling. It has been suggested that conformal geometry may provide an extended symmetry to allow a reformulated Immirzi parameter necessary for loop quantization to behave like an arbitrary group parameter that requires no further fixing as its present standard form does. Here, we find that this can be naturally realized via conformal frame transformations in scalar-tensor gravity. Such a theory generally incorporates a dynamical scalar gravitational field and reduces to general relativity when the scalar field becomes a pure gauge. In particular, we introduce a conformal Einstein frame in which loop quantization is implemented. We then discuss how different Immirzi parameters under this description may be related by conformal frame transformations and yet share the same quantization having, for example, the same area gaps, modulated by the scalar gravitational field.

Experimental results on current-driven turbulence in plasmas - a survey

NASA Astrophysics Data System (ADS)

de Kluiver, H.; Perepelkin, N. F.; Hirose, A.

1991-01-01

The experimental consequences of plasma turbulence driven by a current parallel to a magnetic field and concurrent anomalous plasma heating are reviewed, with an attempt to deduce universalities in key parameters such as the anomalous electrical conductivities observed in diverse devices. It has been found that the nature of plasma turbulence and turbulent heating depends on several parameters including the electric field, current and magnetic fields. A classification of turbulence regimes based on these parameters has been made. Experimental observations of the anomalous electrical conductivity, plasma heating, skin effect, runaway electron braking and turbulent fluctuations are surveyed, and current theoretical understanding is briefly reviewed. Experimental results recently obtained in stellarators (SIRIUS, URAGAN at Kharkov), and in tokamaks (TORTUR at Nieuwegein, STOR-1M at Saskatoon) are presented in some detail in the light of investigating the feasibility of using turbulent heating as a means of injecting a large power into toroidal devices.

Gaugeon formalism for the second-rank antisymmetric tensor gauge fields

NASA Astrophysics Data System (ADS)

Aochi, Masataka; Endo, Ryusuke; Miura, Hikaru

2018-02-01

We present a BRST symmetric gaugeon formalism for the second-rank antisymmetric tensor gauge fields. A set of vector gaugeon fields is introduced as a quantum gauge freedom. One of the gaugeon fields satisfies a higher-derivative field equation; this property is necessary to change the gauge-fixing parameter of the antisymmetric tensor gauge field. A naive Lagrangian for the vector gaugeon fields is itself invariant under a gauge transformation for the vector gaugeon field. The Lagrangian of our theory includes the gauge-fixing terms for the gaugeon fields and corresponding Faddeev-Popov ghost terms.

A Small Disc Area Is a Risk Factor for Visual Field Loss Progression in Primary Open-Angle Glaucoma: The Glaucoma Stereo Analysis Study.

PubMed

Kitaoka, Yasushi; Tanito, Masaki; Yokoyama, Yu; Nitta, Koji; Katai, Maki; Omodaka, Kazuko; Nakazawa, Toru

2018-01-01

The Glaucoma Stereo Analysis Study, a cross-sectional multicenter collaborative study, used a stereo fundus camera (nonmyd WX) to assess various morphological parameters of the optic nerve head (ONH) in glaucoma patients. We compared the associations of each parameter between the visual field loss progression group and no-progression group. The study included 187 eyes of 187 patients with primary open-angle glaucoma or normal-tension glaucoma. We divided the mean deviation (MD) slope values of all patients into the progression group (<-0.3 dB/year) and no-progression group (≧-0.3 dB/year). ONH morphological parameters were calculated with prototype analysis software. The correlations between glaucomatous visual field progression and patient characteristics or each ONH parameter were analyzed with Spearman's rank correlation coefficient. The MD slope averages in the progression group and no-progression group were -0.58 ± 0.28 dB/year and 0.05 ± 0.26 dB/year, respectively. Among disc parameters, vertical disc width (diameter), disc area, cup area, and cup volume in the progression group were significantly less than those in the no-progression group. Logistic regression analysis revealed a significant association between the visual field progression and disc area (odds ratio 0.49/mm 2 disc area). A smaller disc area may be associated with more rapid glaucomatous visual field progression.

Field-Scale Evaluation of Infiltration Parameters From Soil Texture for Hydrologic Analysis

NASA Astrophysics Data System (ADS)

Springer, Everett P.; Cundy, Terrance W.

1987-02-01

Recent interest in predicting soil hydraulic properties from simple physical properties such as texture has major implications in the parameterization of physically based models of surface runoff. This study was undertaken to (1) compare, on a field scale, soil hydraulic parameters predicted from texture to those derived from field measurements and (2) compare simulated overland flow response using these two parameter sets. The parameters for the Green-Ampt infiltration equation were obtained from field measurements and using texture-based predictors for two agricultural fields, which were mapped as single soil units. Results of the analyses were that (1) the mean and variance of the field-based parameters were not preserved by the texture-based estimates, (2) spatial and cross correlations between parameters were induced by the texture-based estimation procedures, (3) the overland flow simulations using texture-based parameters were significantly different than those from field-based parameters, and (4) simulations using field-measured hydraulic conductivities and texture-based storage parameters were very close to simulations using only field-based parameters.

Static Magnetic Field Therapy: A Critical Review of Treatment Parameters

PubMed Central

Wahbeh, Helané; Harling, Noelle; Connelly, Erin; Schiffke, Heather C.; Forsten, Cora; Gregory, William L.; Markov, Marko S.; Souder, James J.; Elmer, Patricia; King, Valerie

2009-01-01

Static magnetic field (SMF) therapy, applied via a permanent magnet attached to the skin, is used by people worldwide for self-care. Despite a lack of established SMF dosage and treatment regimens, multiple studies are conducted to evaluate SMF therapy effectiveness. Our objectives in conducting this review are to:(i) summarize SMF research conducted in humans; (ii) critically evaluate reporting quality of SMF dosages and treatment parameters and (iii) propose a set of criteria for reporting SMF treatment parameters in future clinical trials. We searched 27 electronic databases and reference lists. Only English language human studies were included. Excluded were studies of electromagnetic fields, transcranial magnetic stimulation, magnets placed on acupuncture points, animal studies, abstracts, posters and editorials. Data were extracted on clinical indication, study design and 10 essential SMF parameters. Three reviewers assessed quality of reporting and calculated a quality assessment score for each of the 10 treatment parameters. Fifty-six studies were reviewed, 42 conducted in patient populations and 14 in healthy volunteers. The SMF treatment parameters most often and most completely described were site of application, magnet support device and frequency and duration of application. Least often and least completely described were characteristics of the SMF: magnet dimensions, measured field strength and estimated distance of the magnet from the target tissue. Thirty-four (61%) of studies failed to provide enough detail about SMF dosage to permit protocol replication by other investigators. Our findings highlight the need to optimize SMF dosing parameters for individual clinical conditions before proceeding to a full-scale clinical trial. PMID:18955243

A power-law coupled three-form dark energy model

NASA Astrophysics Data System (ADS)

Yao, Yan-Hong; Yan, Yang-Jie; Meng, Xin-He

2018-02-01

We consider a field theory model of coupled dark energy which treats dark energy as a three-form field and dark matter as a spinor field. By assuming the effective mass of dark matter as a power-law function of the three-form field and neglecting the potential term of dark energy, we obtain three solutions of the autonomous system of evolution equations, including a de Sitter attractor, a tracking solution and an approximate solution. To understand the strength of the coupling, we confront the model with the latest Type Ia Supernova, Baryon Acoustic Oscillations and Cosmic Microwave Background radiation observations, with the conclusion that the combination of these three databases marginalized over the present dark matter density parameter Ω _{m0} and the present three-form field κ X0 gives stringent constraints on the coupling constant, - 0.017< λ <0.047 (2σ confidence level), by which we present the model's applicable parameter range.

General Anisotropy Identification of Paperboard with Virtual Fields Method

Treesearch

J.M. Considine; F. Pierron; K.T. Turner; D.W. Vahey

2014-01-01

This work extends previous efforts in plate bending of Virtual Fields Method (VFM) parameter identification to include a general 2-D anisotropicmaterial. Such an extension was needed for instances in which material principal directions are unknown or when specimen orientation is not aligned with material principal directions. A new fixture with a multiaxial force...

Application of an automatic approach to calibrate the NEMURO nutrient-phytoplankton-zooplankton food web model in the Oyashio region

NASA Astrophysics Data System (ADS)

Ito, Shin-ichi; Yoshie, Naoki; Okunishi, Takeshi; Ono, Tsuneo; Okazaki, Yuji; Kuwata, Akira; Hashioka, Taketo; Rose, Kenneth A.; Megrey, Bernard A.; Kishi, Michio J.; Nakamachi, Miwa; Shimizu, Yugo; Kakehi, Shigeho; Saito, Hiroaki; Takahashi, Kazutaka; Tadokoro, Kazuaki; Kusaka, Akira; Kasai, Hiromi

2010-10-01

The Oyashio region in the western North Pacific supports high biological productivity and has been well monitored. We applied the NEMURO (North Pacific Ecosystem Model for Understanding Regional Oceanography) model to simulate the nutrients, phytoplankton, and zooplankton dynamics. Determination of parameters values is very important, yet ad hoc calibration methods are often used. We used the automatic calibration software PEST (model-independent Parameter ESTimation), which has been used previously with NEMURO but in a system without ontogenetic vertical migration of the large zooplankton functional group. Determining the performance of PEST with vertical migration, and obtaining a set of realistic parameter values for the Oyashio, will likely be useful in future applications of NEMURO. Five identical twin simulation experiments were performed with the one-box version of NEMURO. The experiments differed in whether monthly snapshot or averaged state variables were used, in whether state variables were model functional groups or were aggregated (total phytoplankton, small plus large zooplankton), and in whether vertical migration of large zooplankton was included or not. We then applied NEMURO to monthly climatological field data covering 1 year for the Oyashio, and compared model fits and parameter values between PEST-determined estimates and values used in previous applications to the Oyashio region that relied on ad hoc calibration. We substituted the PEST and ad hoc calibrated parameter values into a 3-D version of NEMURO for the western North Pacific, and compared the two sets of spatial maps of chlorophyll- a with satellite-derived data. The identical twin experiments demonstrated that PEST could recover the known model parameter values when vertical migration was included, and that over-fitting can occur as a result of slight differences in the values of the state variables. PEST recovered known parameter values when using monthly snapshots of aggregated state variables, but estimated a different set of parameters with monthly averaged values. Both sets of parameters resulted in good fits of the model to the simulated data. Disaggregating the variables provided to PEST into functional groups did not solve the over-fitting problem, and including vertical migration seemed to amplify the problem. When we used the climatological field data, simulated values with PEST-estimated parameters were closer to these field data than with the previously determined ad hoc set of parameter values. When these same PEST and ad hoc sets of parameter values were substituted into 3-D-NEMURO (without vertical migration), the PEST-estimated parameter values generated spatial maps that were similar to the satellite data for the Kuroshio Extension during January and March and for the subarctic ocean from May to November. With non-linear problems, such as vertical migration, PEST should be used with caution because parameter estimates can be sensitive to how the data are prepared and to the values used for the searching parameters of PEST. We recommend the usage of PEST, or other parameter optimization methods, to generate first-order parameter estimates for simulating specific systems and for insertion into 2-D and 3-D models. The parameter estimates that are generated are useful, and the inconsistencies between simulated values and the available field data provide valuable information on model behavior and the dynamics of the ecosystem.

Two-electrons quantum dot in plasmas under the external fields

NASA Astrophysics Data System (ADS)

Bahar, M. K.; Soylu, A.

2018-02-01

In this study, for the first time, the combined effects of the external electric field, magnetic field, and confinement frequency on energies of two-electron parabolic quantum dots in Debye and quantum plasmas modeled by more general exponential cosine screened Coulomb (MGECSC) potential are investigated by numerically solving the Schrödinger equation using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in potential. Since the plasma is an important experimental argument for quantum dots, the influence of plasmas modeled by the MGECSC potential on quantum dots is probed. The confinement frequency of quantum dots and the external fields created significant quantum restrictions on quantum dot. In this study, as well as discussion of the functionalities of the quantum restrictions for experimental applications, the parameters are also compared with each other in terms of influence and behaviour. In this manner, the motivation points of this study are summarized as follows: Which parameter can be alternative to which parameter, in terms of experimental applications? Which parameters exhibit similar behaviour? What is the role of plasmas on the corresponding behaviours? In the light of these research studies, it can be said that obtained results and performed discussions would be important in experimental and theoretical research related to plasma physics and/or quantum dots.

Inverse and forward modeling under uncertainty using MRE-based Bayesian approach

NASA Astrophysics Data System (ADS)

Hou, Z.; Rubin, Y.

2004-12-01

A stochastic inverse approach for subsurface characterization is proposed and applied to shallow vadose zone at a winery field site in north California and to a gas reservoir at the Ormen Lange field site in the North Sea. The approach is formulated in a Bayesian-stochastic framework, whereby the unknown parameters are identified in terms of their statistical moments or their probabilities. Instead of the traditional single-valued estimation /prediction provided by deterministic methods, the approach gives a probability distribution for an unknown parameter. This allows calculating the mean, the mode, and the confidence interval, which is useful for a rational treatment of uncertainty and its consequences. The approach also allows incorporating data of various types and different error levels, including measurements of state variables as well as information such as bounds on or statistical moments of the unknown parameters, which may represent prior information. To obtain minimally subjective prior probabilities required for the Bayesian approach, the principle of Minimum Relative Entropy (MRE) is employed. The approach is tested in field sites for flow parameters identification and soil moisture estimation in the vadose zone and for gas saturation estimation at great depth below the ocean floor. Results indicate the potential of coupling various types of field data within a MRE-based Bayesian formalism for improving the estimation of the parameters of interest.

Electronic and Magnetic Structures, Magnetic Hyperfine Fields and Electric Field Gradients in UX3 (X = In, Tl, Pb) Intermetallic Compounds

NASA Astrophysics Data System (ADS)

Khan, Sajid; Yazdani-Kachoei, Majid; Jalali-Asadabadi, Saeid; Farooq, Muhammad Bilal; Ahmad, Iftikhar

2018-02-01

Cubic uranium compounds such as UX3 (X is a non-transition element of groups IIIA or IVA) exhibit highly diverse magnetic properties, including Pauli paramagnetism, spin fluctuation and anti-ferromagnetism. In the present paper, we explore the structural, electronic and magnetic properties as well as the hyperfine fields (HFFs) and electric field gradients (EFGs) with quadrupole coupling constant of UX3 (X = In, Tl, Pb) compounds using local density approximation, Perdew-Burke-Ernzerhof parametrization of generalized gradient approximation (PBE-GGA) including the Hubbard U parameter (GGA + U), a revised version of PBE-GGA that improves equilibrium properties of densely packed solids and their surfaces (PBEsol-GGA), and a hybrid functional (HF-PBEsol). The spin orbit-coupling calculations have been added to investigate the relativistic effect of electrons in these materials. The comparison between the experimental parameters and our calculated structural parameters we confirm the consistency and effectiveness of our theoretical tools. The computed magnetic moments show that magnetic moment increases from indium to lead in the UX3 family, and all these compounds are antiferromagnetic in nature. The EFGs and HFFs, as well as the quadrupole coupling constant of UX3 (X = In, Tl, Pb), are discussed in detail. These properties primarily originate from f and p states of uranium and post-transition sites.

The UCSD Time-dependent Tomography and IPS use for Exploring Space Weather Events

NASA Astrophysics Data System (ADS)

Yu, H. S.; Jackson, B. V.; Buffington, A.; Hick, P. P.; Tokumaru, M.; Odstrcil, D.; Kim, J.; Yun, J.

2016-12-01

The University of California, San Diego (UCSD) time-dependent, iterative, kinematic reconstruction technique has been used and expanded upon for over two decades. It provides some of the most-accurate predictions and three-dimensional (3D) analyses of heliospheric solar-wind parameters now available using interplanetary scintillation (IPS) data. The parameters provided include reconstructions of velocity, density, and three-component magnetic fields. Precise time-dependent results are now obtained at any solar distance in the inner heliosphere using ISEE (formerly STELab), Japan, IPS data sets, and can be used to drive 3D-MHD models including ENLIL. Using IPS data, these reconstructions provide a real-time prediction of the global solar wind parameters across the whole heliosphere with a time cadence of about one day (see http://ips.ucsd.edu). Here we compare the results (such as density, velocity, and magnetic fields) from the IPS tomography with different in-situ measurements and discuss several specific space weather events that demonstrate the issues resulting from these analyses.

Study of free-piston Stirling engine driven linear alternators

NASA Technical Reports Server (NTRS)

Nasar, S. A.; Chen, C.

1987-01-01

The analysis, design and operation of single phase, single slot tubular permanent magnet linear alternator is presented. Included is the no-load and on-load magnetic field investigation, permanent magnet's leakage field analysis, parameter identification, design guidelines and an optimal design of a permanent magnet linear alternator. For analysis of the magnetic field, a simplified magnetic circuit is utilized. The analysis accounts for saturation, leakage and armature reaction.

Unified Scaling Law for flux pinning in practical superconductors: II. Parameter testing, scaling constants, and the Extrapolative Scaling Expression

NASA Astrophysics Data System (ADS)

Ekin, Jack W.; Cheggour, Najib; Goodrich, Loren; Splett, Jolene; Bordini, Bernardo; Richter, David

2016-12-01

A scaling study of several thousand Nb3Sn critical-current (I c) measurements is used to derive the Extrapolative Scaling Expression (ESE), a relation that can quickly and accurately extrapolate limited datasets to obtain full three-dimensional dependences of I c on magnetic field (B), temperature (T), and mechanical strain (ɛ). The relation has the advantage of being easy to implement, and offers significant savings in sample characterization time and a useful tool for magnet design. Thorough data-based analysis of the general parameterization of the Unified Scaling Law (USL) shows the existence of three universal scaling constants for practical Nb3Sn conductors. The study also identifies the scaling parameters that are conductor specific and need to be fitted to each conductor. This investigation includes two new, rare, and very large I c(B,T,ɛ) datasets (each with nearly a thousand I c measurements spanning magnetic fields from 1 to 16 T, temperatures from ˜2.26 to 14 K, and intrinsic strains from -1.1% to +0.3%). The results are summarized in terms of the general USL parameters given in table 3 of Part 1 (Ekin J W 2010 Supercond. Sci. Technol. 23 083001) of this series of articles. The scaling constants determined for practical Nb3Sn conductors are: the upper-critical-field temperature parameter v = 1.50 ± 0.04 the cross-link parameter w = 3.0 ± 0.3 and the strain curvature parameter u = 1.7 ± 0.1 (from equation (29) for b c2(ɛ) in Part 1). These constants and required fitting parameters result in the ESE relation, given by I c ( B , T , ɛ ) B = C [ b c 2 ( ɛ ) ] s ( 1 - t 1.5 ) η - μ ( 1 - t 2 ) μ b p ( 1 - b ) q with reduced magnetic field b ≡ B/B c2*(T,ɛ) and reduced temperature t ≡ T/T c*(ɛ), where: B c 2 * ( T , ɛ ) = B c 2 * ( 0 , 0 ) ( 1 - t 1.5 ) b c 2 ( ɛ ) T c * ( ɛ ) = T c * ( 0 ) [ b c 2 ( ɛ ) ] 1/3 and fitting parameters: C, B c2*(0,0), T c*(0), s, either η or μ (but not both), plus the parameters in the strain function b c2(ɛ). The pinning-force shape parameters p and q are also preferably fitted (simultaneously with the other parameters), but default values p = 0.5 and q = 2.0 also give high fitting accuracy when the range of relative magnetic fields is not extensive. Default values are also essential when the magnetic field data range is insufficient to determine p and q. The scaling constants are remarkably stable (changes less than ˜1%) with respect to different values of p and q, Nb3Sn conductor configurations, magnetic self-field corrections, and pinning-force trim values. The results demonstrate that the scaling of transport critical current holds down to the lowest temperatures measured ˜2.2 K, for both magnetic self-field corrected and uncorrected data. An initial comparison is also made between transport and magnetization scaling data in matched Nb3Sn samples and significant differences are found, especially for the upper critical field B c2*(T,ɛ), which may be a result of inhomogeneous shielding currents. In Part 3 of this topical review series (Ekin J W 2017 Supercond. Sci. Technol. at press), the smallest practical minimum dataset for extrapolating full I c(B,T,ɛ) datasets is derived. Application of the ESE relation is illustrated in several new areas, including full characterization of Nb3Sn conductors from as little as a single I c(B) curve when a few core parameters have been determined for similar conductors.

Higher derivative extensions of 3 d Chern-Simons models: conservation laws and stability

NASA Astrophysics Data System (ADS)

Kaparulin, D. S.; Karataeva, I. Yu.; Lyakhovich, S. L.

2015-11-01

We consider the class of higher derivative 3 d vector field models with the field equation operator being a polynomial of the Chern-Simons operator. For the nth-order theory of this type, we provide a general recipe for constructing n-parameter family of conserved second rank tensors. The family includes the canonical energy-momentum tensor, which is unbounded, while there are bounded conserved tensors that provide classical stability of the system for certain combinations of the parameters in the Lagrangian. We also demonstrate the examples of consistent interactions which are compatible with the requirement of stability.

3D Forest: An application for descriptions of three-dimensional forest structures using terrestrial LiDAR

PubMed Central

Krůček, Martin; Vrška, Tomáš; Král, Kamil

2017-01-01

Terrestrial laser scanning is a powerful technology for capturing the three-dimensional structure of forests with a high level of detail and accuracy. Over the last decade, many algorithms have been developed to extract various tree parameters from terrestrial laser scanning data. Here we present 3D Forest, an open-source non-platform-specific software application with an easy-to-use graphical user interface with the compilation of algorithms focused on the forest environment and extraction of tree parameters. The current version (0.42) extracts important parameters of forest structure from the terrestrial laser scanning data, such as stem positions (X, Y, Z), tree heights, diameters at breast height (DBH), as well as more advanced parameters such as tree planar projections, stem profiles or detailed crown parameters including convex and concave crown surface and volume. Moreover, 3D Forest provides quantitative measures of between-crown interactions and their real arrangement in 3D space. 3D Forest also includes an original algorithm of automatic tree segmentation and crown segmentation. Comparison with field data measurements showed no significant difference in measuring DBH or tree height using 3D Forest, although for DBH only the Randomized Hough Transform algorithm proved to be sufficiently resistant to noise and provided results comparable to traditional field measurements. PMID:28472167

PP/PS anisotropic stereotomography

NASA Astrophysics Data System (ADS)

Nag, Steinar; Alerini, Mathias; Ursin, Bjørn

2010-04-01

Stereotomography is a slope tomographic method which gives good results for background velocity model estimation in 2-D isotropic media. We develop here the extension of the method to 3-D general anisotropic media for PP and PS events. We do not take into account the issue of shear wave degeneracy. As in isotropic media, the sensitivity matrix of the inversion can be computed by paraxial ray tracing. We introduce a `constant Z stereotomography' approach, which can reduce the size of the sensitivity matrix. Based on ray perturbation theory, we give all the derivatives of stereotomography data parameters with respect to model parameters in a 3-D general anisotropic medium. These general formulas for the derivatives can also be used in other applications that rely on anisotropic ray perturbation theory. In particular, we obtain derivatives of the phase velocity with respect to position, phase angle and elastic medium parameters, all for general anisotropic media. The derivatives are expressed using the Voigt notation for the elastic medium parameters. We include a Jacobian that allows to change the model parametrization from Voigt to Thomsen parameters. Explicit expressions for the derivatives of the data are given for the case of 2-D tilted transversely isotropic (TTI) media. We validate the method by single-parameter estimation of each Thomsen parameter field of a 2-D TTI synthetic model, where data are modelled by ray tracing. For each Thomsen parameter, the estimated velocity field fits well with the true velocity field.

New measurements of photospheric magnetic fields in late-type stars and emerging trends

NASA Technical Reports Server (NTRS)

Saar, S. H.; Linsky, J. L.

1986-01-01

The magnetic fields of late-type stars are measured using the method of Saar et al. (1986). The method includes radiative transfer effects and compensation for line blending; the photospheric magnetic field parameters are derived by comparing observed and theoretical line profiles using an LTE code that includes line saturation and full Zeeman pattern. The preliminary mean active region magnetic field strengths (B) and surface area coverages for 20 stars are discussed. It is observed that there is a trend of increasing B towards the cooler dwarfs stars, and the linear correlation between B and the equipartition value of the magnetic field strength suggests that the photospheric gas pressure determines the photospheric magnetic field strengths. A tendency toward larger filling factors at larger stellar angular velocities is also detected.

Contribution functions for Zeeman-split lines, and line formation in photospheric faculae

NASA Technical Reports Server (NTRS)

Vanballegooijen, A. A.

1985-01-01

The transfer of polarized light in an inhomogeneous stellar atmosphere, and the formation of magnetically sensitive spectral lines, are discussed. A new method for the solution of the transfer equations is proposed. The method gives a natural definition of the contribution functions for Stokes' parameters, i.e., functions describing the contributions from different parts along the line-of-sight (LOS). The formalism includes all magneto-optical effects, and allows for an arbitrary variation of magnetic field, velocity field, temperature, density, etc., along the LOS. The formation of FeI lambda 5250.2 in photospheric faculae is described. A potential-field model of a facular element is presented, and spectra profiles and contribution functions are computed for the Stokes parameters I, Q, and V.

Predictive simulations and optimization of nanowire field-effect PSA sensors including screening

NASA Astrophysics Data System (ADS)

Baumgartner, Stefan; Heitzinger, Clemens; Vacic, Aleksandar; Reed, Mark A.

2013-06-01

We apply our self-consistent PDE model for the electrical response of field-effect sensors to the 3D simulation of nanowire PSA (prostate-specific antigen) sensors. The charge concentration in the biofunctionalized boundary layer at the semiconductor-electrolyte interface is calculated using the propka algorithm, and the screening of the biomolecules by the free ions in the liquid is modeled by a sensitivity factor. This comprehensive approach yields excellent agreement with experimental current-voltage characteristics without any fitting parameters. Having verified the numerical model in this manner, we study the sensitivity of nanowire PSA sensors by changing device parameters, making it possible to optimize the devices and revealing the attributes of the optimal field-effect sensor.

Systems and methods for locating and imaging proppant in an induced fracture

DOEpatents

Aldridge, David F.; Bartel, Lewis C.

2016-02-02

Born Scattering Inversion (BSI) systems and methods are disclosed. A BSI system may be incorporated in a well system for accessing natural gas, oil and geothermal reserves in a geologic formation beneath the surface of the Earth. The BSI system may be used to generate a three-dimensional image of a proppant-filled hydraulically-induced fracture in the geologic formation. The BSI system may include computing equipment and sensors for measuring electromagnetic fields in the vicinity of the fracture before and after the fracture is generated, adjusting the parameters of a first Born approximation model of a scattered component of the surface electromagnetic fields using the measured electromagnetic fields, and generating the image of the proppant-filled fracture using the adjusted parameters.

Magnetic moment of solar plasma and the Kelvin force: -The driving force of plasma up-flow -

NASA Astrophysics Data System (ADS)

Shibasaki, Kiyoto

2017-04-01

Thermal plasma in the solar atmosphere is magnetized (diamagnetic). The magnetic moment does not disappear by collisions because complete gyration is not a necessary condition to have magnetic moment. Magnetized fluid is subjected to Kelvin force in non-uniform magnetic field. Generally, magnetic field strength decreases upwards in the solar atmosphere, hence the Kelvin force is directed upwards along the field. This force is not included in the fluid treatment of MHD. By adding the Kelvin force to the MHD equation of motion, we can expect temperature dependent plasma flows along the field which are reported by many observations. The temperature dependence of the flow speed is explained by temperature dependence of magnetic moment. From the observed parameters, we can infer physical parameters in the solar atmosphere such as scale length of the magnetic field strength and the friction force acting on the flowing plasma. In case of closed magnetic field lines, loop-top concentration of hot plasma is expected which is frequently observed.

Voltage current characteristics of type III superconductors

NASA Astrophysics Data System (ADS)

Dorofejev, G. L.; Imenitov, A. B.; Klimenko, E. Yu.

1980-06-01

An adequate description of voltage-current characteristics is important in order to understand the nature of high critical current for the electrodynamic construction of type-III superconductors and for commercial superconductor specification. Homogenious monofilament and multifilament Nb-Ti, Nb-Zr, Nb 3Sn wires were investigated in different ranges of magnetic field, temperature and current. The longitudinal electric field for homogenious wires may be described by E=J ρnexp- T c/T 0+ T/T 0+ B/B 0+ J/J 0, where To, Bo, Jo are the increasing parameters, which depend weakly on B and T, of the electric field. The shape of the voltage-current characteristics of multifilament wires, and the parameter's dependence on temperature and magnetic field may be explained qualitatively by the longitudinal heterogeneous nature of the filaments. A method of attaining the complete specification of the wire's electro-physical properties is proposed. It includes the traditional description of a critical surface (ie the surface corresponding to a certain conventional effective resistivity in T, B, J - space) and a description of any increasing parameter that depends on B and T.

Orbitally limited pair-density-wave phase of multilayer superconductors

NASA Astrophysics Data System (ADS)

Möckli, David; Yanase, Youichi; Sigrist, Manfred

2018-04-01

We investigate the magnetic field dependence of an ideal superconducting vortex lattice in the parity-mixed pair-density-wave phase of multilayer superconductors within a circular cell Ginzburg-Landau approach. In multilayer systems, due to local inversion symmetry breaking, a Rashba spin-orbit coupling is induced at the outer layers. This combined with a perpendicular paramagnetic (Pauli) limiting magnetic field stabilizes a staggered layer dependent pair-density-wave phase in the superconducting singlet channel. The high-field pair-density-wave phase is separated from the low-field BCS phase by a first-order phase transition. The motivating guiding question in this paper is: What is the minimal necessary Maki parameter αM for the appearance of the pair-density-wave phase of a superconducting trilayer system? To address this problem we generalize the circular cell method for the regular flux-line lattice of a type-II superconductor to include paramagnetic depairing effects. Then, we apply the model to the trilayer system, where each of the layers are characterized by Ginzburg-Landau parameter κ0 and a Maki parameter αM. We find that when the spin-orbit Rashba interaction compares to the superconducting condensation energy, the orbitally limited pair-density-wave phase stabilizes for Maki parameters αM>10 .

Vacuum Microelectronic Field Emission Array Devices for Microwave Amplification.

NASA Astrophysics Data System (ADS)

Mancusi, Joseph Edward

This dissertation presents the design, analysis, and measurement of vacuum microelectronic devices which use field emission to extract an electron current from arrays of silicon cones. The arrays of regularly-spaced silicon cones, the field emission cathodes or emitters, are fabricated with an integrated gate electrode which controls the electric field at the tip of the cone, and thus the electron current. An anode or collector electrode is placed above the array to collect the emission current. These arrays, which are fabricated in a standard silicon processing facility, are developed for use as high power microwave amplifiers. Field emission has been studied extensively since it was first characterized in 1928, however due to the large electric fields required practical field emission devices are difficult to make. With the development of the semiconductor industry came the development of fabrication equipment and techniques which allow for the manufacture of the precision micron-scale structures necessary for practical field emission devices. The active region of a field emission device is a vacuum, therefore the electron travel is ballistic. This analysis of field emission devices includes electric field and electron emission modeling, development of a device equivalent circuit, analysis of the parameters in the equivalent circuit, and device testing. Variations in device structure are taken into account using a statistical model based upon device measurements. Measurements of silicon field emitter arrays at DC and RF are presented and analyzed. In this dissertation, the equivalent circuit is developed from the analysis of the device structure. The circuit parameters are calculated from geometrical considerations and material properties, or are determined from device measurements. It is necessary to include the emitter resistance in the equivalent circuit model since relatively high resistivity silicon wafers are used. As is demonstrated, the circuit model accurately predicts the magnitude of the emission current at a number of typical bias current levels when the device is operating at frequencies within the range of 10 MHz to 1 GHz. At low frequencies and at high frequencies within this range, certain parameters are negligible, and simplifications may be made in the equivalent circuit model.

Characteristic parameters of superconductor-coolant interaction including high Tc current density limits

NASA Technical Reports Server (NTRS)

Frederking, T. H. K.

1989-01-01

In the area of basic mechanisms of helium heat transfer and related influence on super-conducting magnet stability, thermal boundary conditions are important constraints. Characteristic lengths are considered along with other parameters of the superconducting composite-coolant system. Based on helium temperature range developments, limiting critical current densities are assessed at low fields for high transition temperature superconductors.

On the effect of model parameters on forecast objects

NASA Astrophysics Data System (ADS)

Marzban, Caren; Jones, Corinne; Li, Ning; Sandgathe, Scott

2018-04-01

Many physics-based numerical models produce a gridded, spatial field of forecasts, e.g., a temperature map. The field for some quantities generally consists of spatially coherent and disconnected objects. Such objects arise in many problems, including precipitation forecasts in atmospheric models, eddy currents in ocean models, and models of forest fires. Certain features of these objects (e.g., location, size, intensity, and shape) are generally of interest. Here, a methodology is developed for assessing the impact of model parameters on the features of forecast objects. The main ingredients of the methodology include the use of (1) Latin hypercube sampling for varying the values of the model parameters, (2) statistical clustering algorithms for identifying objects, (3) multivariate multiple regression for assessing the impact of multiple model parameters on the distribution (across the forecast domain) of object features, and (4) methods for reducing the number of hypothesis tests and controlling the resulting errors. The final output of the methodology is a series of box plots and confidence intervals that visually display the sensitivities. The methodology is demonstrated on precipitation forecasts from a mesoscale numerical weather prediction model.

Recent Developments and Applications of the CHARMM force fields

PubMed Central

Zhu, Xiao; Lopes, Pedro E.M.; MacKerell, Alexander D.

2011-01-01

Empirical force fields commonly used to describe the condensed phase properties of complex systems such as biological macromolecules are continuously being updated. Improvements in quantum mechanical (QM) methods used to generate target data, availability of new experimental target data, incorporation of new classes of compounds and new theoretical developments (eg. polarizable methods) make force-field development a dynamic domain of research. Accordingly, a number of improvements and extensions of the CHARMM force fields have occurred over the years. The objective of the present review is to provide an up-to-date overview of the CHARMM force fields. A limited presentation on the historical aspects of force fields will be given, including underlying methodologies and principles, along with a brief description of the strategies used for parameter development. This is followed by information on the CHARMM additive and polarizable force fields, including examples of recent applications of those force fields. PMID:23066428

Ligandbook: an online repository for small and drug-like molecule force field parameters.

PubMed

Domanski, Jan; Beckstein, Oliver; Iorga, Bogdan I

2017-06-01

Ligandbook is a public database and archive for force field parameters of small and drug-like molecules. It is a repository for parameter sets that are part of published work but are not easily available to the community otherwise. Parameter sets can be downloaded and immediately used in molecular dynamics simulations. The sets of parameters are versioned with full histories and carry unique identifiers to facilitate reproducible research. Text-based search on rich metadata and chemical substructure search allow precise identification of desired compounds or functional groups. Ligandbook enables the rapid set up of reproducible molecular dynamics simulations of ligands and protein-ligand complexes. Ligandbook is available online at https://ligandbook.org and supports all modern browsers. Parameters can be searched and downloaded without registration, including access through a programmatic RESTful API. Deposition of files requires free user registration. Ligandbook is implemented in the PHP Symfony2 framework with TCL scripts using the CACTVS toolkit. oliver.beckstein@asu.edu or bogdan.iorga@cnrs.fr ; contact@ligandbook.org . Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press.

Developing Si(Li) nuclear radiation detectors by pulsed electric field treatment

NASA Astrophysics Data System (ADS)

Muminov, R. A.; Radzhapov, S. A.; Saimbetov, A. K.

2009-08-01

Fabrication of Si(Li) nuclear radiation detectors using lithium ion drift under the action of a pulsed electric field is considered. Optimum treatment regime parameters are determined, including the pulse amplitude, duration, and repetition rate. Experimental data are presented, which show that the ion drift in a pulsed electric field decreases the semiconductor bulk compensation time by a factor of two to four and significantly increases the efficiency of detectors.

Evaluation of GIS Technology in Assessing and Modeling Land Management Practices

NASA Technical Reports Server (NTRS)

Archer, F.; Coleman, T. L.; Manu, A.; Tadesse, W.; Liu, G.

1997-01-01

There is an increasing concern of land owners to protect and maintain healthy and sustainable agroecosystems through the implementation of best management practices (BMP). The objectives of this study were: (1) To develop and evaluate the use of a Geographic Information System (GIS) technology for enhancing field-scale management practices; (2) evaluate the use of 2-dimensional displays of the landscape and (3) define spatial classes of variables from interpretation of geostatistical parameters. Soil samples were collected to a depth of 2 m at 15 cm increments. Existing data from topographic, land use, and soil survey maps of the Winfred Thomas Agricultural Research Station were converted to digital format. Additional soils data which included texture, pH, and organic matter were also generated. The digitized parameters were used to create a multilayered field-scale GIS. Two dimensional (2-D) displays of the parameters were generated using the ARC/INFO software. The spatial distribution of the parameters evaluated in both fields were similar which could be attributed to the similarity in vegetation and surface elevation. The ratio of the nugget to total semivariance, expressed as a percentage, was used to assess the degree of spatial variability. The results indicated that most of the parameters were moderate spatially dependent Biophysical constraint maps were generated from the database layers, and used in multiple combination to visualize results of the BMP. Understanding the spatial relationships of physical and chemical parameters that exists within a field should enable land managers to more effectively implement BMP to ensure a safe and sustainable environment.

Comparing performances of logistic regression and neural networks for predicting melatonin excretion patterns in the rat exposed to ELF magnetic fields.

PubMed

Jahandideh, Samad; Abdolmaleki, Parviz; Movahedi, Mohammad Mehdi

2010-02-01

Various studies have been reported on the bioeffects of magnetic field exposure; however, no consensus or guideline is available for experimental designs relating to exposure conditions as yet. In this study, logistic regression (LR) and artificial neural networks (ANNs) were used in order to analyze and predict the melatonin excretion patterns in the rat exposed to extremely low frequency magnetic fields (ELF-MF). Subsequently, on a database containing 33 experiments, performances of LR and ANNs were compared through resubstitution and jackknife tests. Predictor variables were more effective parameters and included frequency, polarization, exposure duration, and strength of magnetic fields. Also, five performance measures including accuracy, sensitivity, specificity, Matthew's Correlation Coefficient (MCC) and normalized percentage, better than random (S) were used to evaluate the performance of models. The LR as a conventional model obtained poor prediction performance. Nonetheless, LR distinguished the duration of magnetic fields as a statistically significant parameter. Also, horizontal polarization of magnetic fields with the highest logit coefficient (or parameter estimate) with negative sign was found to be the strongest indicator for experimental designs relating to exposure conditions. This means that each experiment with horizontal polarization of magnetic fields has a higher probability to result in "not changed melatonin level" pattern. On the other hand, ANNs, a more powerful model which has not been introduced in predicting melatonin excretion patterns in the rat exposed to ELF-MF, showed high performance measure values and higher reliability, especially obtaining 0.55 value of MCC through jackknife tests. Obtained results showed that such predictor models are promising and may play a useful role in defining guidelines for experimental designs relating to exposure conditions. In conclusion, analysis of the bioelectromagnetic data could result in finding a relationship between electromagnetic fields and different biological processes. (c) 2009 Wiley-Liss, Inc.

Gravitational effects from a series of IVS R&D VLBI-sessions with observations close to the Sun

NASA Astrophysics Data System (ADS)

Heinkelmann, R.; Soja, B.; Schuh, H.

2015-08-01

In 2011 and 2012 the IVS observed twelve VLBI research and development (R&D) sessions that include successful observations as angularly close as 3.9° from the heliocenter. Among others, one purpose of these IVS-R&D sessions was to achieve an improvement in the determination of the PPN parameter γ . Besides, by analyzing this specific set of IVS sessions, it was for the first time possible to measure the dispersive effect of the Solar corona with VLBI (Soja et al., 2014). In this work we assess the formal error of the γ-parameter and the contributions of the various terms to the partial derivative of the γ-parameter. Furthermore, we investigate the size of the gravitational delays caused by: (i) Solar monopole field at rest and with approximately linear translation, (ii) rotation of the Solar monopole field, (iii) Solar gravitational field quadrupole expansion, and (iv) Solar higher order term.

Heat and momentum transfer for magnetoconvection in a vertical external magnetic field

NASA Astrophysics Data System (ADS)

Zürner, Till; Liu, Wenjun; Krasnov, Dmitry; Schumacher, Jörg

2016-11-01

The scaling theory of Grossmann and Lohse for the turbulent heat and momentum transfer is extended to the magnetoconvection case in the presence of a (strong) vertical magnetic field. The comparison with existing laboratory experiments and direct numerical simulations in the quasistatic limit allows to restrict the parameter space to very low Prandtl and magnetic Prandtl numbers and thus to reduce the number of unknown parameters in the model. Also included is the Chandrasekhar limit for which the outer magnetic induction field B is large enough such that convective motion is suppressed and heat is transported by diffusion. Our theory identifies four distinct regimes of magnetoconvection which are distinguished by the strength of the outer magnetic field and the level of turbulence in the flow, respectively. LIMTECH Research Alliance and Research Training Group GK 1567 on Lorentz Force Velocimetry, funded by the Deutsche Forschungsgemeinschaft.

New force field for molecular simulation of guanidinium-based ionic liquids.

PubMed

Liu, Xiaomin; Zhang, Suojiang; Zhou, Guohui; Wu, Guangwen; Yuan, Xiaoliang; Yao, Xiaoqian

2006-06-22

An all-atom force field was proposed for a new class of room temperature ionic liquids (RTILs), N,N,N',N'-tetramethylguanidinium (TMG) RTILs. The model is based on the AMBER force field with modifications on several parameters. The refinements include (1) fitting the vibration frequencies for obtaining force coefficients of bonds and angles against the data obtained by ab initio calculations and/or by experiments and (2) fitting the torsion energy profiles of dihedral angles for obtaining torsion parameters against the data obtained by ab initio calculations. To validate the force field, molecular dynamics (MD) simulations at different temperatures were performed for five kinds of RTILs, where TMG acts as a cation and formate, lactate, perchlorate, trifluoroacetate, and trifluoromethylsulfonate act as anions. The predicted densities were in good agreement with the experimental data. Radial distribution functions (RDFs) and spatial distribution functions (SDFs) were investigated to depict the microscopic structures of the RTILs.

Parametrization of Stillinger-Weber potential based on valence force field model: application to single-layer MoS2 and black phosphorus

NASA Astrophysics Data System (ADS)

Jiang, Jin-Wu

2015-08-01

We propose parametrizing the Stillinger-Weber potential for covalent materials starting from the valence force-field model. All geometrical parameters in the Stillinger-Weber potential are determined analytically according to the equilibrium condition for each individual potential term, while the energy parameters are derived from the valence force-field model. This parametrization approach transfers the accuracy of the valence force field model to the Stillinger-Weber potential. Furthermore, the resulting Stilliinger-Weber potential supports stable molecular dynamics simulations, as each potential term is at an energy-minimum state separately at the equilibrium configuration. We employ this procedure to parametrize Stillinger-Weber potentials for single-layer MoS2 and black phosphorous. The obtained Stillinger-Weber potentials predict an accurate phonon spectrum and mechanical behaviors. We also provide input scripts of these Stillinger-Weber potentials used by publicly available simulation packages including GULP and LAMMPS.

Parametrization of Stillinger-Weber potential based on valence force field model: application to single-layer MoS2 and black phosphorus.

PubMed

Jiang, Jin-Wu

2015-08-07

We propose parametrizing the Stillinger-Weber potential for covalent materials starting from the valence force-field model. All geometrical parameters in the Stillinger-Weber potential are determined analytically according to the equilibrium condition for each individual potential term, while the energy parameters are derived from the valence force-field model. This parametrization approach transfers the accuracy of the valence force field model to the Stillinger-Weber potential. Furthermore, the resulting Stilliinger-Weber potential supports stable molecular dynamics simulations, as each potential term is at an energy-minimum state separately at the equilibrium configuration. We employ this procedure to parametrize Stillinger-Weber potentials for single-layer MoS2 and black phosphorous. The obtained Stillinger-Weber potentials predict an accurate phonon spectrum and mechanical behaviors. We also provide input scripts of these Stillinger-Weber potentials used by publicly available simulation packages including GULP and LAMMPS.

Delineation and Prediction Uncertainty of Areas Contributing Recharge to Selected Well Fields in Wetland and Coastal Settings, Southern Rhode Island

USGS Publications Warehouse

Friesz, Paul J.

2010-01-01

Areas contributing recharge to four well fields in two study sites in southern Rhode Island were delineated on the basis of steady-state groundwater-flow models representing average hydrologic conditions. The wells are screened in sand and gravel deposits in wetland and coastal settings. The groundwater-flow models were calibrated by inverse modeling using nonlinear regression. Summary statistics from nonlinear regression were used to evaluate the uncertainty associated with the predicted areas contributing recharge to the well fields. In South Kingstown, two United Water Rhode Island well fields are in Mink Brook watershed and near Worden Pond and extensive wetlands. Wetland deposits of peat near the well fields generally range in thickness from 5 to 8 feet. Analysis of water-level drawdowns in a piezometer screened beneath the peat during a 20-day pumping period indicated vertical leakage and a vertical hydraulic conductivity for the peat of roughly 0.01 ft/d. The simulated area contributing recharge for average withdrawals of 2,138 gallons per minute during 2003-07 extended to groundwater divides in mostly till and morainal deposits, and it encompassed 2.30 square miles. Most of a sand and gravel mining operation between the well fields was in the simulated contributing area. For the maximum pumping capacity (5,100 gallons per minute), the simulated area contributing recharge expanded to 5.54 square miles. The well fields intercepted most of the precipitation recharge in Mink Brook watershed and in an adjacent small watershed, and simulated streams ceased to flow. The simulated contributing area to the well fields included an area beneath Worden Pond and a remote, isolated area in upland till on the opposite side of Worden Pond from the well fields. About 12 percent of the pumped water was derived from Worden Pond. In Charlestown, the Central Beach Fire District and the East Beach Water Association well fields are on a small (0.85 square mile) peninsula in a coastal setting. The wells are screened in a coarse-grained, ice-proximal part of a morphosequence with saturated thicknesses generally less than 30 feet on the peninsula. The simulated area contributing recharge for the average withdrawal (16 gallons per minute) during 2003-07 was 0.018 square mile. The contributing area extended southwestward from the well fields to a simulated groundwater mound; it underlay part of a small nearby wetland, and it included isolated areas on the side of the wetland opposite the well fields. For the maximum pumping rate (230 gallons per minute), the simulated area contributing recharge (0.26 square mile) expanded in all directions; it included a till area on the peninsula, and it underlay part of a nearby pond. Because the well fields are screened in a thin aquifer, simulated groundwater traveltimes from recharge locations to the discharging wells were short: 94 percent of the traveltimes were 10 years or less, and the median traveltime was 1.3 years. Model-prediction uncertainty was evaluated using a Monte Carlo analysis; the parameter variance-covariance matrix from nonlinear regression was used to create parameter sets for the analysis. Important parameters for model prediction that could not be estimated by nonlinear regression were incorporated into the variance-covariance matrix. For the South Kingstown study site, observations provided enough information to constrain the uncertainty of these parameters within realistic ranges, but for the Charlestown study site, prior information on parameters was required. Thus, the uncertainty analysis for the South Kingstown study site was an outcome of calibrating the model to available observations, but the Charlestown study site was also dependent on information provided by the modeler. A water budget and model-fit statistical criteria were used to assess parameter sets so that prediction uncertainty was not overestimated. For the scenarios using maximum pumping rates at both study

A Biologically Constrained, Mathematical Model of Cortical Wave Propagation Preceding Seizure Termination

PubMed Central

González-Ramírez, Laura R.; Ahmed, Omar J.; Cash, Sydney S.; Wayne, C. Eugene; Kramer, Mark A.

2015-01-01

Epilepsy—the condition of recurrent, unprovoked seizures—manifests in brain voltage activity with characteristic spatiotemporal patterns. These patterns include stereotyped semi-rhythmic activity produced by aggregate neuronal populations, and organized spatiotemporal phenomena, including waves. To assess these spatiotemporal patterns, we develop a mathematical model consistent with the observed neuronal population activity and determine analytically the parameter configurations that support traveling wave solutions. We then utilize high-density local field potential data recorded in vivo from human cortex preceding seizure termination from three patients to constrain the model parameters, and propose basic mechanisms that contribute to the observed traveling waves. We conclude that a relatively simple and abstract mathematical model consisting of localized interactions between excitatory cells with slow adaptation captures the quantitative features of wave propagation observed in the human local field potential preceding seizure termination. PMID:25689136

A variational approach to parameter estimation in ordinary differential equations.

PubMed

Kaschek, Daniel; Timmer, Jens

2012-08-14

Ordinary differential equations are widely-used in the field of systems biology and chemical engineering to model chemical reaction networks. Numerous techniques have been developed to estimate parameters like rate constants, initial conditions or steady state concentrations from time-resolved data. In contrast to this countable set of parameters, the estimation of entire courses of network components corresponds to an innumerable set of parameters. The approach presented in this work is able to deal with course estimation for extrinsic system inputs or intrinsic reactants, both not being constrained by the reaction network itself. Our method is based on variational calculus which is carried out analytically to derive an augmented system of differential equations including the unconstrained components as ordinary state variables. Finally, conventional parameter estimation is applied to the augmented system resulting in a combined estimation of courses and parameters. The combined estimation approach takes the uncertainty in input courses correctly into account. This leads to precise parameter estimates and correct confidence intervals. In particular this implies that small motifs of large reaction networks can be analysed independently of the rest. By the use of variational methods, elements from control theory and statistics are combined allowing for future transfer of methods between the two fields.

Impact of toroidal and poloidal mode spectra on the control of non-axisymmetric fields in tokamaks

NASA Astrophysics Data System (ADS)

Lanctot, Matthew J.

2016-10-01

In several tokamaks, non-axisymmetric magnetic field studies show applied n=2 fields can lead to disruptive n=1 locked modes, suggesting nonlinear mode coupling. A multimode plasma response to n=2 fields can be observed in H-mode plasmas, in contrast to the single-mode response found in Ohmic plasmas. These effects highlight a role for n >1 error field correction in disruption avoidance, and identify additional degrees of freedom for 3D field optimization at high plasma pressure. In COMPASS, EAST, and DIII-D Ohmic plasmas, n=2 magnetic reconnection thresholds in otherwise stable discharges are readily accessed at edge safety factors q 3 and low density. Similar to previous studies, the thresholds are correlated with the ``overlap'' field for the dominant linear ideal MHD plasma mode calculated with the IPEC code. The overlap field measures the plasma-mediated coupling of the external field to the resonant field. Remarkably, the critical overlap fields are similar for n=1 and 2 fields with m >nq fields dominating the drive for resonant fields. Complementary experiments in RFX-Mod show fields with m 1 control, including the need for multiple rows of coils to control selected plasma parameters for specific functions (e.g., rotation control or ELM suppression). Optimal multi-harmonic (n=1 and n=2) error field control may be achieved using control algorithms that continuously respond to time-varying 3D field sources and plasma parameters. Supported by the US DOE under DE-FC02-04ER54698.

Passive Fully Polarimetric W-Band Millimeter-Wave Imaging

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

Bernacki, Bruce E.; Kelly, James F.; Sheen, David M.

2012-04-01

We present the theory, design, and experimental results obtained from a scanning passive W-band fully polarimetric imager. Passive millimeter-wave imaging offers persistent day/nighttime imaging and the ability to penetrate dust, clouds and other obscurants, including clothing and dry soil. The single-pixel scanning imager includes both far-field and near-field fore-optics for investigation of polarization phenomena. Using both fore-optics, a variety of scenes including natural and man-made objects was imaged and these results are presented showing the utility of polarimetric imaging for anomaly detection. Analysis includes conventional Stokes-parameter based approaches as well as multivariate image analysis methods.

The reduced basis method for the electric field integral equation

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

Fares, M., E-mail: fares@cerfacs.f; Hesthaven, J.S., E-mail: Jan_Hesthaven@Brown.ed; Maday, Y., E-mail: maday@ann.jussieu.f

We introduce the reduced basis method (RBM) as an efficient tool for parametrized scattering problems in computational electromagnetics for problems where field solutions are computed using a standard Boundary Element Method (BEM) for the parametrized electric field integral equation (EFIE). This combination enables an algorithmic cooperation which results in a two step procedure. The first step consists of a computationally intense assembling of the reduced basis, that needs to be effected only once. In the second step, we compute output functionals of the solution, such as the Radar Cross Section (RCS), independently of the dimension of the discretization space, formore » many different parameter values in a many-query context at very little cost. Parameters include the wavenumber, the angle of the incident plane wave and its polarization.« less

Relationship between the global electric circuit and electrified cloud parameters at diurnal, seasonal, and interannual timescales

NASA Astrophysics Data System (ADS)

Lavigne, Thomas; Liu, Chuntao; Deierling, Wiebke; Mach, Douglas

2017-08-01

In the early 1900s, J. W. Whipple began to validate C. T. R. Wilson's global electric circuit (GEC) hypothesis by correlating the diurnal variation of global thunder days with the diurnal variation of the fair weather electric field measured by the Carnegie Cruise. This study applies 16+ years of precipitation feature (PF) data from the Tropical Rainfall Measuring Mission, including lightning data from the Lightning Imaging Sensor, alongside 12 years of electric field measurements from Vostok, Antarctica, to further examine this relationship. Joint diurnal-seasonal variations of the electric field are introduced and compared with a variety of PF parameters that are potentially related to the GEC. All tested PF parameters showed significant correlations to the electric field on the joint seasonal-diurnal timescale, with the flash rate and volume of 30 dBZ between the -5°C and -35°C isotherms showing the best linear correlations with R2 values of 0.67 and 0.62, respectively. Furthermore, these relationships are analyzed during the two different phases of the El Niño-Southern Oscillation. Results show different seasonal-diurnal variations of the electric field during El Niño and La Niña periods, with enhancements in the electric field between the months of January through April at 16-24 UTC in La Niña years. A similar trend is shown in global PF parameters, indicating relationships between the variations seen in the fair weather electric field and the variations of global PFs at diurnal, seasonal, and interannual timescales. This provides further evidence that PFs around the globe have a direct connection to the GEC.

Understanding controls of hydrologic processes across two monolithological catchments using model-data integration

NASA Astrophysics Data System (ADS)

Xiao, D.; Shi, Y.; Li, L.

2016-12-01

Field measurements are important to understand the fluxes of water, energy, sediment, and solute in the Critical Zone however are expensive in time, money, and labor. This study aims to assess the model predictability of hydrological processes in a watershed using information from another intensively-measured watershed. We compare two watersheds of different lithology using national datasets, field measurements, and physics-based model, Flux-PIHM. We focus on two monolithological, forested watersheds under the same climate in the Shale Hills Susquehanna CZO in central Pennsylvania: the Shale-based Shale Hills (SSH, 0.08 km2) and the sandstone-based Garner Run (GR, 1.34 km2). We firstly tested the transferability of calibration coefficients from SSH to GR. We found that without any calibration the model can successfully predict seasonal average soil moisture and discharge which shows the advantage of a physics-based model, however, cannot precisely capture some peaks or the runoff in summer. The model reproduces the GR field data better after calibrating the soil hydrology parameters. In particular, the percentage of sand turns out to be a critical parameter in reproducing data. With sandstone being the dominant lithology, GR has much higher sand percentage than SSH (48.02% vs. 29.01%), leading to higher hydraulic conductivity, lower overall water storage capacity, and in general lower soil moisture. This is consistent with area averaged soil moisture observations using the cosmic-ray soil moisture observing system (COSMOS) at the two sites. This work indicates that some parameters, including evapotranspiration parameters, are transferrable due to similar climatic and land cover conditions. However, the key parameters that control soil moisture, including the sand percentage, need to be recalibrated, reflecting the key role of soil hydrological properties.

Force Field Development and Molecular Dynamics of [NiFe] Hydrogenase

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

Smith, Dayle MA; Xiong, Yijia; Straatsma, TP

2012-05-09

Classical molecular force-field parameters describing the structure and motion of metal clusters in [NiFe] hydrogenase enzymes can be used to compare the dynamics and thermodynamics of [NiFe] under different oxidation, protonation, and ligation circumstances. Using density functional theory (DFT) calculations of small model clusters representative of the active site and the proximal, medial, and distal Fe/S metal centers and their attached protein side chains, we have calculated classical force-field parameters for [NiFe] in reduced and oxidized states, including internal coordinates, force constants, and atom-centered charges. Derived force constants revealed that cysteinate ligands bound to the metal ions are more flexiblemore » in the Ni-B active site, which has a bridging hydroxide ligand, than in the Ni-C active site, which has a bridging hydride. Ten nanosecond all-atom, explicit-solvent MD simulations of [NiFe] hydrogenase in oxidized and reduced catalytic states established the stability of the derived force-field parameters in terms of C{alpha} and metal cluster fluctuations. Average active site structures from the protein MD simulations are consistent with [NiFe] structures from the Protein Data Bank, suggesting that the derived force-field parameters are transferrable to other hydrogenases beyond the structure used for testing. A comparison of experimental H{sub 2}-production rates demonstrated a relationship between cysteinate side chain rotation and activity, justifying the use of a fully dynamic model of [NiFe] metal cluster motion.« less

Study of relation between Pc 3 micropulsations and magnetosheath fluctuations, and multisatellite investigation of earth's bow shock

NASA Technical Reports Server (NTRS)

Greenstadt, E. W.

1975-01-01

The validity is investigated of a suggested model according to which Pc 3 and/or Pc 4 micropulsations are excited by magnetosheath field (and plasma) fluctuations arising in the quasi-parallel structure of the subsolar bow shock. The influence of solar wind plasma parameters on local shock structure and on the configuration of the entire bow shock system is included. Simultaneous data from two or more spacecraft and from multiple diagnostics is used to evaluate the geometrical factor, field-to-shock normal angle, or its B-X equivalent, and the principal plasma parameters. Results are presented and discussed.

Phenomenological analysis of thermal hysteresis in Ni-Mn-Ga Heusler alloys

NASA Astrophysics Data System (ADS)

Zagrebin, M. A.; Sokolovskiy, V. V.; Buchelnikov, V. D.

2018-05-01

The manipulation of thermal hysteresis in Ni-Mn-Ga Heusler alloys with coupled magnetostructural phase transition is studied theoretically using the Landau theory, including magnetic, elastic and crystal lattice modulation order parameters as well as an external magnetic field. It is shown that for the assigned combination of phenomenological parameters, in the phase diagrams, the Austenite-Martensite first-order phase transition has a finite (critical) point in which the thermal hysteresis is disappeared. Moreover, this point depends on the relation between modulation and elastic constants as well as on the magnetic field. Obtained results have been compared with other theoretical end experimental data.

Tunable far infrared studies of molecular parameters in support of stratospheric measurements

NASA Technical Reports Server (NTRS)

Chance, K. V.; Nolt, Ira G.; Radostitz, J. V.; Park, K.

1990-01-01

The purpose of this research is to make precise, fully line-resolved measurements of molecular parameters that are necessary for the analysis of spectra obtained in far infrared field measurement programs. These measurements make it possible to accurately analyze the data from field measurements to obtain atmospheric concentration profiles of key trace gases involved in the ozone chemistry. The research objectives include: measurements of pressure broadening of molecular lines of OH, O2, O3, HCl, and H2O, their temperature dependence, and, when possible, the pressure-induced frequency shifts of the lines; measurements of line positions of radical species, such as HO2.

Response of Velocity Anisotropy of Shale Under Isotropic and Anisotropic Stress Fields

NASA Astrophysics Data System (ADS)

Li, Xiaying; Lei, Xinglin; Li, Qi

2018-03-01

We investigated the responses of P-wave velocity and associated anisotropy in terms of Thomsen's parameters to isotropic and anisotropic stress fields on Longmaxi shales cored along different directions. An array of piezoelectric ceramic transducers allows us to measure P-wave velocities along numerous different propagation directions. Anisotropic parameters, including the P-wave velocity α along a symmetry axis, Thomsen's parameters ɛ and δ, and the orientation of the symmetry axis, could then be extracted by fitting Thomsen's weak anisotropy model to the experimental data. The results indicate that Longmaxi shale displays weakly intrinsic velocity anisotropy with Thomsen's parameters ɛ and δ being approximately 0.05 and 0.15, respectively. The isotropic stress field has only a slight effect on velocity and associated anisotropy in terms of Thomsen's parameters. In contrast, both the magnitude and orientation of the anisotropic stress field with respect to the shale fabric are important in controlling the evolution of velocity and associated anisotropy in a changing stress field. For shale with bedding-parallel loading, velocity anisotropy is enhanced because velocities with smaller angles relative to the maximum stress increase significantly during the entire loading process, whereas those with larger angles increase slightly before the yield stress and afterwards decrease with the increasing differential stress. For shale with bedding-normal loading, anisotropy reversal is observed, and the anisotropy is progressively modified by the applied differential stress. Before reaching the yield stress, velocities with smaller angles relative to the maximum stress increase more significantly and even exceed the level of those with larger angles. After reaching the yield stress, velocities with larger angles decrease more significantly. Microstructural features such as the closure and generation of microcracks can explain the modification of the velocity anisotropy due to the applied stress anisotropy.

Rotor Wake Vortex Definition: Initial Evaluation of 3-C PIV Results of the Hart-II Study

NASA Technical Reports Server (NTRS)

Burley, Casey L.; Brooks, Thomas F.; vanderWall, Berend; Richard, Hughes; Raffel, Markus; Beaumier, Philippe; Delrieux, Yves; Lim, Joon W.; Yu, Yung H.; Tung, Chee

2002-01-01

An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.

Trans-dimensional matched-field geoacoustic inversion with hierarchical error models and interacting Markov chains.

PubMed

Dettmer, Jan; Dosso, Stan E

2012-10-01

This paper develops a trans-dimensional approach to matched-field geoacoustic inversion, including interacting Markov chains to improve efficiency and an autoregressive model to account for correlated errors. The trans-dimensional approach and hierarchical seabed model allows inversion without assuming any particular parametrization by relaxing model specification to a range of plausible seabed models (e.g., in this case, the number of sediment layers is an unknown parameter). Data errors are addressed by sampling statistical error-distribution parameters, including correlated errors (covariance), by applying a hierarchical autoregressive error model. The well-known difficulty of low acceptance rates for trans-dimensional jumps is addressed with interacting Markov chains, resulting in a substantial increase in efficiency. The trans-dimensional seabed model and the hierarchical error model relax the degree of prior assumptions required in the inversion, resulting in substantially improved (more realistic) uncertainty estimates and a more automated algorithm. In particular, the approach gives seabed parameter uncertainty estimates that account for uncertainty due to prior model choice (layering and data error statistics). The approach is applied to data measured on a vertical array in the Mediterranean Sea.

Wireless sensor systems and methods, and methods of monitoring structures

DOEpatents

Kunerth, Dennis C.; Svoboda, John M.; Johnson, James T.; Harding, L. Dean; Klingler, Kerry M.

2007-02-20

A wireless sensor system includes a passive sensor apparatus configured to be embedded within a concrete structure to monitor infiltration of contaminants into the structure. The sensor apparatus includes charging circuitry and a plurality of sensors respectively configured to measure environmental parameters of the structure which include information related to the infiltration of contaminants into the structure. A reader apparatus is communicatively coupled to the sensor apparatus, the reader apparatus being configured to provide power to the charging circuitry during measurements of the environmental parameters by the sensors. The reader apparatus is configured to independently interrogate individual ones of the sensors to obtain information measured by the individual sensors. The reader apparatus is configured to generate an induction field to energize the sensor apparatus. Information measured by the sensor apparatus is transmitted to the reader apparatus via a response signal that is superimposed on a return induction field generated by the sensor apparatus. Methods of monitoring structural integrity of the structure are also provided.

Bernese advances towards a global analysis of Lunar geodesy

NASA Astrophysics Data System (ADS)

Bertone, S.; Girardin, V.; Bourgoin, A.; Arnold, D.; Jaeggi, A.

2017-12-01

In this presentation we discuss our latest GRAIL-based lunar gravity fields generated with the Celestial Mechanics Approach using the planetary extension of the Bernese GNSS Software (BSW) developed at the Astronomical Institute of the University of Bern (AIUB).Based on one-way X band and two-way S-band Doppler data, we perform orbit determination by solving six initial orbital elements, dynamical parameters, and stochastic parameters in daily arcs using a least-squares adjustment. Significative improvements to our solutions come from the recent implementation of an accurate modeling of non-gravitational forces, including accelerations due to solar and planetary (albedo and IR) radiation pressure, based on the 28-plate macromodel to represent the GRAIL satellites. Also, as suggested in previous works, we deal with imperfections in the modeling of solar eclipses by both an accurate data screening at mid-latitudes and by taking into account solar panel voltage data in our processing. Empirical and pseudo-stochastic parameters are estimated on top of our dynamical modeling to absorb its deficiencies. We analyze the impact of different parametrizations using either pulses (i.e., instantaneous velocity changes) and piecewise constant accelerations (PCA) on our orbits.Based on these improved orbits, one- and two-way Doppler and KBRR data are then used together with an appropriate weighting for a combined orbit and gravity field determination process.We present our latest solutions of the lunar gravity field, based on the recent GRAIL GRGM900C gravity field (as validation of our modeling and parametrization) and on iterations from the SELENE SGM150J gravity field (to check the independence of our solution). We detail our procedure to gradually enlarge the parameter space while adding new data to our gravity field solution. In addition, we present our latest solution for the Moon tidal Love number k_2.Moreover, some important lunar geophysical parameters are best obtained by processing data from Lunar Laser Ranging (LLR) stations. We analyze the impact of a combined processing on the recovery of a set of parameters and we provide some preliminary results.Finally, we compare all of our results with the most recent solutions of the lunar gravity field and of other geodetic parameters released by other groups.

Statistics of partially-polarized fields: beyond the Stokes vector and coherence matrix

NASA Astrophysics Data System (ADS)

Charnotskii, Mikhail

2017-08-01

Traditionally, the partially-polarized light is characterized by the four Stokes parameters. Equivalent description is also provided by correlation tensor of the optical field. These statistics specify only the second moments of the complex amplitudes of the narrow-band two-dimensional electric field of the optical wave. Electric field vector of the random quasi monochromatic wave is a nonstationary oscillating two-dimensional real random variable. We introduce a novel statistical description of these partially polarized waves: the Period-Averaged Probability Density Function (PA-PDF) of the field. PA-PDF contains more information on the polarization state of the field than the Stokes vector. In particular, in addition to the conventional distinction between the polarized and depolarized components of the field PA-PDF allows to separate the coherent and fluctuating components of the field. We present several model examples of the fields with identical Stokes vectors and very distinct shapes of PA-PDF. In the simplest case of the nonstationary, oscillating normal 2-D probability distribution of the real electrical field and stationary 4-D probability distribution of the complex amplitudes, the newly-introduced PA-PDF is determined by 13 parameters that include the first moments and covariance matrix of the quadrature components of the oscillating vector field.

Do lab-derived distribution coefficient values of pesticides match distribution coefficient values determined from column and field-scale experiments? A critical analysis of relevant literature.

PubMed

Vereecken, H; Vanderborght, J; Kasteel, R; Spiteller, M; Schäffer, A; Close, M

2011-01-01

In this study, we analyzed sorption parameters for pesticides that were derived from batch and column or batch and field experiments. The batch experiments analyzed in this study were run with the same pesticide and soil as in the column and field experiments. We analyzed the relationship between the pore water velocity of the column and field experiments, solute residence times, and sorption parameters, such as the organic carbon normalized distribution coefficient ( ) and the mass exchange coefficient in kinetic models, as well as the predictability of sorption parameters from basic soil properties. The batch/column analysis included 38 studies with a total of 139 observations. The batch/field analysis included five studies, resulting in a dataset of 24 observations. For the batch/column data, power law relationships between pore water velocity, residence time, and sorption constants were derived. The unexplained variability in these equations was reduced, taking into account the saturation status and the packing status (disturbed-undisturbed) of the soil sample. A new regression equation was derived that allows estimating the values derived from column experiments using organic matter and bulk density with an value of 0.56. Regression analysis of the batch/column data showed that the relationship between batch- and column-derived values depends on the saturation status and packing of the soil column. Analysis of the batch/field data showed that as the batch-derived value becomes larger, field-derived values tend to be lower than the corresponding batch-derived values, and vice versa. The present dataset also showed that the variability in the ratio of batch- to column-derived value increases with increasing pore water velocity, with a maximum value approaching 3.5. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

The multiscale coarse-graining method. II. Numerical implementation for coarse-grained molecular models

PubMed Central

Noid, W. G.; Liu, Pu; Wang, Yanting; Chu, Jhih-Wei; Ayton, Gary S.; Izvekov, Sergei; Andersen, Hans C.; Voth, Gregory A.

2008-01-01

The multiscale coarse-graining (MS-CG) method [S. Izvekov and G. A. Voth, J. Phys. Chem. B 109, 2469 (2005);J. Chem. Phys. 123, 134105 (2005)] employs a variational principle to determine an interaction potential for a CG model from simulations of an atomically detailed model of the same system. The companion paper proved that, if no restrictions regarding the form of the CG interaction potential are introduced and if the equilibrium distribution of the atomistic model has been adequately sampled, then the MS-CG variational principle determines the exact many-body potential of mean force (PMF) governing the equilibrium distribution of CG sites generated by the atomistic model. In practice, though, CG force fields are not completely flexible, but only include particular types of interactions between CG sites, e.g., nonbonded forces between pairs of sites. If the CG force field depends linearly on the force field parameters, then the vector valued functions that relate the CG forces to these parameters determine a set of basis vectors that span a vector subspace of CG force fields. The companion paper introduced a distance metric for the vector space of CG force fields and proved that the MS-CG variational principle determines the CG force force field that is within that vector subspace and that is closest to the force field determined by the many-body PMF. The present paper applies the MS-CG variational principle for parametrizing molecular CG force fields and derives a linear least squares problem for the parameter set determining the optimal approximation to this many-body PMF. Linear systems of equations for these CG force field parameters are derived and analyzed in terms of equilibrium structural correlation functions. Numerical calculations for a one-site CG model of methanol and a molecular CG model of the EMIM+∕NO3− ionic liquid are provided to illustrate the method. PMID:18601325

Determination of structure parameters in strong-field tunneling ionization theory of molecules

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

Zhao Songfeng; Jin Cheng; College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou, Gansu 730070

2010-03-15

In the strong field molecular tunneling ionization theory of Tong et al. [Phys. Rev. A 66, 033402 (2002)], the ionization rate depends on the asymptotic wave function of the molecular orbital from which the electron is removed. The orbital wave functions obtained from standard quantum chemistry packages in general are not good enough in the asymptotic region. Here we construct a one-electron model potential for several linear molecules using density functional theory. We show that the asymptotic wave function can be improved with an iteration method and after one iteration accurate asymptotic wave functions and structure parameters are determined. Withmore » the new parameters we examine the alignment-dependent tunneling ionization probabilities for several molecules and compare with other calculations and with recent measurements, including ionization from inner molecular orbitals.« less

Neutron stars in a perturbative f(R) gravity model with strong magnetic fields

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

Cheoun, Myung-Ki; Deliduman, Cemsinan; Güngör, Can

2013-10-01

In Kaluza-Klein electromagnetism it is natural to associate modified gravity with strong electromagnetic fields. Hence, in this paper we investigate the combined effects of a strong magnetic field and perturbative f(R) gravity on the structure of neutron stars. The effect of an interior strong magnetic field of about 10{sup 17−18} G on the equation of state is derived in the context of a quantum hadrodynamics (QHD) equation of state (EoS) including effects of the magnetic pressure and energy along with occupied Landau levels. Adopting a random orientation of interior field domains, we solve the modified spherically symmetric hydrostatic equilibrium equationsmore » derived for a gravity model with f(R) = R+αR{sup 2}. Effects of both the finite magnetic field and the modified gravity are detailed for various values of the magnetic field and the perturbation parameter α along with a discussion of their physical implications. We show that there exists a parameter space of the modified gravity and the magnetic field strength, in which even a soft equation of state can accommodate a large ( > 2 M{sub s}un) maximum neutron star mass.« less

Modeling of microstructure evolution in direct metal laser sintering: A phase field approach

NASA Astrophysics Data System (ADS)

Nandy, Jyotirmoy; Sarangi, Hrushikesh; Sahoo, Seshadev

2017-02-01

Direct Metal Laser Sintering (DMLS) is a new technology in the field of additive manufacturing, which builds metal parts in a layer by layer fashion directly from the powder bed. The process occurs within a very short time period with rapid solidification rate. Slight variations in the process parameters may cause enormous change in the final build parts. The physical and mechanical properties of the final build parts are dependent on the solidification rate which directly affects the microstructure of the material. Thus, the evolving of microstructure plays a vital role in the process parameters optimization. Nowadays, the increase in computational power allows for direct simulations of microstructures during materials processing for specific manufacturing conditions. In this study, modeling of microstructure evolution of Al-Si-10Mg powder in DMLS process was carried out by using a phase field approach. A MATLAB code was developed to solve the set of phase field equations, where simulation parameters include temperature gradient, laser scan speed and laser power. The effects of temperature gradient on microstructure evolution were studied and found that with increase in temperature gradient, the dendritic tip grows at a faster rate.

Force-field parameters from the SAFT-γ equation of state for use in coarse-grained molecular simulations.

PubMed

Müller, Erich A; Jackson, George

2014-01-01

A description of fluid systems with molecular-based algebraic equations of state (EoSs) and by direct molecular simulation is common practice in chemical engineering and the physical sciences, but the two approaches are rarely closely coupled. The key for an integrated representation is through a well-defined force field and Hamiltonian at the molecular level. In developing coarse-grained intermolecular potential functions for the fluid state, one typically starts with a detailed, bottom-up quantum-mechanical or atomic-level description and then integrates out the unwanted degrees of freedom using a variety of techniques; an iterative heuristic simulation procedure is then used to refine the parameters of the model. By contrast, with a top-down technique, one can use an accurate EoS to link the macroscopic properties of the fluid and the force-field parameters. We discuss the latest developments in a top-down representation of fluids, with a particular focus on a group-contribution formulation of the statistical associating fluid theory (SAFT-γ). The accurate SAFT-γ EoS is used to estimate the parameters of the Mie force field, which can then be used with confidence in direct molecular simulations to obtain thermodynamic, structural, interfacial, and dynamical properties that are otherwise inaccessible from the EoS. This is exemplified for several prototypical fluids and mixtures, including carbon dioxide, hydrocarbons, perfluorohydrocarbons, and aqueous surfactants.

Dynamics of entanglement of a three-level atom in motion interacting with two coupled modes including parametric down conversion

NASA Astrophysics Data System (ADS)

Faghihi, M. J.; Tavassoly, M. K.; Hatami, M.

In this paper, a model by which we study the interaction between a motional three-level atom and two-mode field injected simultaneously in a bichromatic cavity is considered; the three-level atom is assumed to be in a Λ-type configuration. As a result, the atom-field and the field-field interaction (parametric down conversion) will be appeared. It is shown that, by applying a canonical transformation, the introduced model can be reduced to a well-known form of the generalized Jaynes-Cummings model. Under particular initial conditions, which may be prepared for the atom and the field, the time evolution of state vector of the entire system is analytically evaluated. Then, the dynamics of atom by considering ‘atomic population inversion’ and two different measures of entanglement, i.e., ‘von Neumann entropy’ and ‘idempotency defect’ is discussed, in detail. It is deduced from the numerical results that, the duration and the maximum amount of the considered physical quantities can be suitably tuned by selecting the proper field-mode structure parameter p and the detuning parameters.

Analysis of Acoustic Emission Parameters from Corrosion of AST Bottom Plate in Field Testing

NASA Astrophysics Data System (ADS)

Jomdecha, C.; Jirarungsatian, C.; Suwansin, W.

Field testing of aboveground storage tank (AST) to monitor corrosion of the bottom plate is presented in this chapter. AE testing data of the ten AST with different sizes, materials, and products were employed to monitor the bottom plate condition. AE sensors of 30 and 150 kHz were used to monitor the corrosion activity of up to 24 channels including guard sensors. Acoustic emission (AE) parameters were analyzed to explore the AE parameter patterns of occurring corrosion compared to the laboratory results. Amplitude, count, duration, and energy were main parameters of analysis. Pattern recognition technique with statistical was implemented to eliminate the electrical and environmental noises. The results showed the specific AE patterns of corrosion activities related to the empirical results. In addition, plane algorithm was utilized to locate the significant AE events from corrosion. Both results of parameter patterns and AE event locations can be used to interpret and locate the corrosion activities. Finally, basic statistical grading technique was used to evaluate the bottom plate condition of the AST.

Accounting for the fringe magnetic field from the bending magnet in a Monte Carlo accelerator treatment head simulation.

PubMed

O'Shea, Tuathan P; Foley, Mark J; Faddegon, Bruce A

2011-06-01

Monte Carlo (MC) simulation can be used for accurate electron beam treatment planning and modeling. Measurement of large electron fields, with the applicator removed and secondary collimator wide open, has been shown to provide accurate simulation parameters, including asymmetry in the measured dose, for the full range of clinical field sizes and patient positions. Recently, disassembly of the treatment head of a linear accelerator has been used to refine the simulation of the electron beam, setting tightly measured constraints on source and geometry parameters used in simulation. The simulation did not explicitly include the known deflection of the electron beam by a fringe magnetic field from the bending magnet, which extended into the treatment head. Instead, the secondary scattering foil and monitor chamber were unrealistically laterally offset to account for the beam deflection. This work is focused on accounting for this fringe magnetic field in treatment head simulation. The magnetic field below the exit window of a Siemens Oncor linear accelerator was measured with a Tesla-meter from 0 to 12 cm from the exit window and 1-3 cm off-axis. Treatment head simulation was performed with the EGSnrc/BEAMnrc code, modified to incorporate the effect of the magnetic field on charged particle transport. Simulations were used to analyze the sensitivity of dose profiles to various sources of asymmetry in the treatment head. This included the lateral spot offset and beam angle at the exit window, the fringe magnetic field and independent lateral offsets of the secondary scattering foil and electron monitor chamber. Simulation parameters were selected within the limits imposed by measurement uncertainties. Calculated dose distributions were then compared with those measured in water. The magnetic field was a maximum at the exit window, increasing from 0.006 T at 6 MeV to 0.020 T at 21 MeV and dropping to approximately 5% of the maximum at the secondary scattering foil. It was up to three times higher in the bending plane, away from the electron gun, and symmetric within measurement uncertainty in the transverse plane. Simulations showed the magnetic field resulted in an offset of the electron beam of 0.80 cm (mean) at the machine isocenter for the exit window only configuration. The fringe field resulted in a 3.5%-7.6% symmetry and 0.25-0.35 cm offset of the clinical beam R(max) profiles. With the magnetic field included in simulations, a single (realistic) position of the secondary scattering foil and monitor chamber was selected. Measured and simulated dose profiles showed agreement to an average of 2.5%/0.16 cm (maximum: 3%/0.2 cm), which is a better match than previously achieved without incorporating the magnetic field in the simulation. The undulations from the 3 stepped layers of the secondary scattering foil, evident in the measured profiles of the higher energy beams, are now aligned with those in the simulated beam. The simulated fringe magnetic field had negligible effect on the central axis depth dose curves and cross-plane dose profiles. The fringe magnetic field is a significant contributor to the electron beam in-plane asymmetry. With the magnetic field included explicitly in the simulation, realistic monitor chamber and secondary scattering foil positions have been achieved, and the calculated fluence and dose distributions are more accurate.

EOS Terra Validation Program

NASA Technical Reports Server (NTRS)

Starr, David

2000-01-01

The EOS Terra mission will be launched in July 1999. This mission has great relevance to the atmospheric radiation community and global change issues. Terra instruments include Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Clouds and Earth's Radiant Energy System (CERES), Multi-Angle Imaging Spectroradiometer (MISR), Moderate Resolution Imaging Spectroradiometer (MODIS) and Measurements of Pollution in the Troposphere (MOPITT). In addition to the fundamental radiance data sets, numerous global science data products will be generated, including various Earth radiation budget, cloud and aerosol parameters, as well as land surface, terrestrial ecology, ocean color, and atmospheric chemistry parameters. Significant investments have been made in on-board calibration to ensure the quality of the radiance observations. A key component of the Terra mission is the validation of the science data products. This is essential for a mission focused on global change issues and the underlying processes. The Terra algorithms have been subject to extensive pre-launch testing with field data whenever possible. Intensive efforts will be made to validate the Terra data products after launch. These include validation of instrument calibration (vicarious calibration) experiments, instrument and cross-platform comparisons, routine collection of high quality correlative data from ground-based networks, such as AERONET, and intensive sites, such as the SGP ARM site, as well as a variety field experiments, cruises, etc. Airborne simulator instruments have been developed for the field experiment and underflight activities including the MODIS Airborne Simulator (MAS) AirMISR, MASTER (MODIS-ASTER), and MOPITT-A. All are integrated on the NASA ER-2 though low altitude platforms are more typically used for MASTER. MATR is an additional sensor used for MOPITT algorithm development and validation. The intensive validation activities planned for the first year of the Terra mission will be described with emphasis on derived geophysical parameters of most relevance to the atmospheric radiation community.

EOS Terra Validation Program

NASA Technical Reports Server (NTRS)

Starr, David

1999-01-01

The EOS Terra mission will be launched in July 1999. This mission has great relevance to the atmospheric radiation community and global change issues. Terra instruments include ASTER, CERES, MISR, MODIS and MOPITT. In addition to the fundamental radiance data sets, numerous global science data products will be generated, including various Earth radiation budget, cloud and aerosol parameters, as well as land surface, terrestrial ecology, ocean color, and atmospheric chemistry parameters. Significant investments have been made in on-board calibration to ensure the quality of the radiance observations. A key component of the Terra mission is the validation of the science data products. This is essential for a mission focused on global change issues and the underlying processes. The Terra algorithms have been subject to extensive pre-launch testing with field data whenever possible. Intensive efforts will be made to validate the Terra data products after launch. These include validation of instrument calibration (vicarious calibration) experiments, instrument and cross-platform comparisons, routine collection of high quality correlative data from ground-based networks, such as AERONET, and intensive sites, such as the SGP ARM site, as well as a variety field experiments, cruises, etc. Airborne simulator instruments have been developed for the field experiment and underflight activities including the MODIS Airborne Simulator (MAS), AirMISR, MASTER (MODIS-ASTER), and MOPITT-A. All are integrated on the NASA ER-2, though low altitude platforms are more typically used for MASTER. MATR is an additional sensor used for MOPITT algorithm development and validation. The intensive validation activities planned for the first year of the Terra mission will be described with emphasis on derived geophysical parameters of most relevance to the atmospheric radiation community. Detailed information about the EOS Terra validation Program can be found on the EOS Validation program homepage i/e.: http://ospso.gsfc.nasa.gov/validation/valpage.html).

Atomistic modelling of magnetic nano-granular thin films

NASA Astrophysics Data System (ADS)

Agudelo-Giraldo, J. D.; Arbeláez-Echeverry, O. D.; Restrepo-Parra, E.

2018-03-01

In this work, a complete model for studying the magnetic behaviour of polycrystalline thin films at nanoscale was processed. This model includes terms as exchange interaction, dipolar interaction and various types of anisotropies. For the first term, exchange interaction dependence of the distance n was used with purpose of quantify the interaction, mainly in grain boundaries. The third term includes crystalline, surface and boundary anisotropies. Special attention was paid to the disorder vector that determines the loss of cubic symmetry in the crystalline structure. For the case of the dipolar interaction, a similar implementation of the fast multiple method (FMM) was performed. Using these tools, modelling and simulations were developed varying the number of grains, and the results obtained presented a great dependence of the magnetic properties on this parameter. Comparisons between critical temperature and magnetization of saturation depending on the number of grains were performed for samples with and without factors as the surface and boundary anisotropies, and the dipolar interaction. It was observed that the inclusion of these parameters produced a decrease in the critical temperature and the magnetization of saturation; furthermore, in both cases, including and not including the disorder parameters, not only the critical temperature, but also the magnetization of saturation exhibited a range of values that also depend on the number of grains. This presence of a critical interval is due to each grain can transit toward the ferromagnetic state at different values of critical temperature. The processes of Zero field cooling (ZFC), Field cooling (FCC) and field cooling in warming mode (FCW) were necessary for understanding the mono-domain regime around of transition temperature, due to the high probabilities of a Super-paramagnetic (SPM) state.

Variation of Supergranule Parameters with Solar Cycles: Results from Century-long Kodaikanal Digitized Ca ii K Data

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

Chatterjee, Subhamoy; Mandal, Sudip; Banerjee, Dipankar, E-mail: dipu@iiap.res.in

The Ca ii K spectroheliograms spanning over a century (1907–2007) from Kodaikanal Solar Observatory, India, have recently been digitized and calibrated. Applying a fully automated algorithm (which includes contrast enhancement and the “Watershed method”) to these data, we have identified the supergranules and calculated the associated parameters, such as scale, circularity, and fractal dimension. We have segregated the quiet and active regions and obtained the supergranule parameters separately for these two domains. In this way, we have isolated the effect of large-scale and small-scale magnetic fields on these structures and find a significantly different behavior of the supergranule parameters overmore » solar cycles. These differences indicate intrinsic changes in the physical mechanism behind the generation and evolution of supergranules in the presence of small-scale and large-scale magnetic fields. This also highlights the need for further studies using solar dynamo theory along with magneto-convection models.« less

Generalisation of Gilbert damping and magnetic inertia parameter as a series of higher-order relativistic terms

NASA Astrophysics Data System (ADS)

Mondal, Ritwik; Berritta, Marco; Oppeneer, Peter M.

2018-07-01

The phenomenological Landau–Lifshitz–Gilbert (LLG) equation of motion remains as the cornerstone of contemporary magnetisation dynamics studies, wherein the Gilbert damping parameter has been attributed to first-order relativistic effects. To include magnetic inertial effects the LLG equation has previously been extended with a supplemental inertia term; the arising inertial dynamics has been related to second-order relativistic effects. Here we start from the relativistic Dirac equation and, performing a Foldy–Wouthuysen transformation, derive a generalised Pauli spin Hamiltonian that contains relativistic correction terms to any higher order. Using the Heisenberg equation of spin motion we derive general relativistic expressions for the tensorial Gilbert damping and magnetic inertia parameters, and show that these tensors can be expressed as series of higher-order relativistic correction terms. We further show that, in the case of a harmonic external driving field, these series can be summed and we provide closed analytical expressions for the Gilbert and inertial parameters that are functions of the frequency of the driving field.

Generalisation of Gilbert damping and magnetic inertia parameter as a series of higher-order relativistic terms.

PubMed

Mondal, Ritwik; Berritta, Marco; Oppeneer, Peter M

2018-05-17

The phenomenological Landau-Lifshitz-Gilbert (LLG) equation of motion remains as the cornerstone of contemporary magnetisation dynamics studies, wherein the Gilbert damping parameter has been attributed to first-order relativistic effects. To include magnetic inertial effects the LLG equation has previously been extended with a supplemental inertia term; the arising inertial dynamics has been related to second-order relativistic effects. Here we start from the relativistic Dirac equation and, performing a Foldy-Wouthuysen transformation, derive a generalised Pauli spin Hamiltonian that contains relativistic correction terms to any higher order. Using the Heisenberg equation of spin motion we derive general relativistic expressions for the tensorial Gilbert damping and magnetic inertia parameters, and show that these tensors can be expressed as series of higher-order relativistic correction terms. We further show that, in the case of a harmonic external driving field, these series can be summed and we provide closed analytical expressions for the Gilbert and inertial parameters that are functions of the frequency of the driving field.

Effect of Cuscuta campestris parasitism on the physiological and anatomical changes in untreated and herbicide-treated sugar beet.

PubMed

Saric-Krsmanovic, Marija M; Bozic, Dragana M; Radivojevic, Ljiljana M; Umiljendic, Jelena S Gajic; Vrbnicanin, Sava P

2017-11-02

The effects of field dodder on physiological and anatomical processes in untreated sugar beet plants and the effects of propyzamide on field dodder were examined under controlled conditions. The experiment included the following variants: N-noninfested sugar beet plants (control); I - infested sugar beet plants (untreated), and infested plants treated with propyzamide (1500 g a.i. ha -1 (T 1 ) and 2000 g a.i. ha -1 (T 2 )). The following parameters were checked: physiological-pigment contents (chlorophyll a, chlorophyll b, total carotenoids); anatomical -leaf parameters: thickness of epidermis, parenchyma and spongy tissue, mesophyll and underside leaf epidermis, and diameter of bundle sheath cells; petiole parameters: diameter of tracheid, petiole hydraulic conductance, xylem surface, phloem cell diameter and phloem area in sugar beet plants. A conventional paraffin wax method was used to prepare the samples for microscopy. Pigment contents were measured spectrophotometrically after methanol extraction. All parameters were measured: prior to herbicide application (0 assessment), then 7, 14, 21, 28 and 35 days after application (DAA). Field dodder was found to affect the pigment contents in untreated sugar beet plants, causing significant reductions. Conversely, reduction in the treated plants decreased 27% to 4% for chlorophyll a, from 21% to 5% for chlorophyll b, and from 28% to 5% for carotenoids (T 1 ). Also, in treatment T 2, reduction decreased in infested and treated plants from 19% to 2% for chlorophyll a, from 21% to 2% for chlorophyll b, from 23% to 3% for carotenoids and stimulation of 1% and 2% was observed 28 and 35 DAA, respectively. Plants infested (untreated) by field dodder had lower values of most anatomical parameters, compared to noninfested plants. The measured anatomical parameters of sugar beet leaves and petiole had significantly higher values in noninfested plants and plants treated with propyzamide than in untreated plants. Also, the results showed that propyzamide is an adequate herbicide for control of field dodder at the stage of early infestation.

The effect of air flow, panel curvature, and internal pressurization on field-incidence transmission loss. [acoustic propagation through aircraft fuselage

NASA Technical Reports Server (NTRS)

Koval, L. R.

1975-01-01

In the context of sound transmission through aircraft fuselage panels, equations for the field-incidence transmission loss (TL) of a single-walled panel are derived that include the effects of external air flow, panel curvature, and internal fuselage pressurization. These effects are incorporated into the classical equations for the TL of single panels, and the resulting double integral for field-incidence TL is numerically evaluated for a specific set of parameters.

A dissipative random velocity field for fully developed fluid turbulence

NASA Astrophysics Data System (ADS)

Chevillard, Laurent; Pereira, Rodrigo; Garban, Christophe

2016-11-01

We investigate the statistical properties, based on numerical simulations and analytical calculations, of a recently proposed stochastic model for the velocity field of an incompressible, homogeneous, isotropic and fully developed turbulent flow. A key step in the construction of this model is the introduction of some aspects of the vorticity stretching mechanism that governs the dynamics of fluid particles along their trajectory. An additional further phenomenological step aimed at including the long range correlated nature of turbulence makes this model depending on a single free parameter that can be estimated from experimental measurements. We confirm the realism of the model regarding the geometry of the velocity gradient tensor, the power-law behaviour of the moments of velocity increments, including the intermittent corrections, and the existence of energy transfers across scales. We quantify the dependence of these basic properties of turbulent flows on the free parameter and derive analytically the spectrum of exponents of the structure functions in a simplified non dissipative case. A perturbative expansion shows that energy transfers indeed take place, justifying the dissipative nature of this random field.

Constitutive models for the Etchegoin Sands, Belridge Diatomite, and overburden formations at the Lost Hills oil field, California

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

FOSSUM,ARLO F.; FREDRICH,JOANNE T.

2000-04-01

This report documents the development of constitutive material models for the overburden formations, reservoir formations, and underlying strata at the Lost Hills oil field located about 45 miles northwest of Bakersfield in Kern County, California. Triaxial rock mechanics tests were performed on specimens prepared from cores recovered from the Lost Hills field, and included measurements of axial and radial stresses and strains under different load paths. The tested intervals comprise diatomaceous sands of the Etchegoin Formation and several diatomite types of the Belridge Diatomite Member of the Monterey Formation, including cycles both above and below the diagenetic phase boundary betweenmore » opal-A and opal-CT. The laboratory data are used to drive constitutive parameters for the Extended Sandler-Rubin (ESR) cap model that is implemented in Sandia's structural mechanics finite element code JAS3D. Available data in the literature are also used to derive ESR shear failure parameters for overburden formations. The material models are being used in large-scale three-dimensional geomechanical simulations of the reservoir behavior during primary and secondary recovery.« less

Interplanetary magnetic field over two solar cycles and out to 20 AU

NASA Technical Reports Server (NTRS)

Smith, J. E.

1989-01-01

Interplanetary field measurements are now available from Pioneer and Voyager at large distances and from various spacecraft in the inner solar system. These multiple observations at different locations have proven indispensable in separating temporal from spatial dependences. The data set has revealed a number of characteristic solar cycle variations including changes in field strength and the inclination of the heliospheric current sheet responsible for magnetic sectors. Spatial gradients in the field parameters out to 20 AU have been compared with the Parker Model including the spiral angle, the north-south field component and the magnitude. As a result of planetary encounters, Pioneer and the Voyagers are traveling outward at significantly different latitudes making it possible to investigate latitudinal, as well as radial, dependences. Effects associated with the pick-up of interstellar ions are being sought.

Charge control microcomputer device for vehicle

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

Morishita, M.; Kouge, S.

1986-08-26

A charge control microcomputer device is described for a vehicle, comprising: an AC generator driven by an engine for generating an output current, the generator having armature coils and a field coil; a battery charged by a rectified output of the generator and generating a terminal voltage; a voltage regulator for controlling a current flowing in the field coil, to control an output voltage of the generator to a predetermined value; an engine controlling microcomputer for receiving engine parameter data from the engine, to control the operation of the engine; a charge control microcomputer for processing input data including datamore » on at least one engine parameter output from the engine controlling microcomputer, and charge system data including at least one of battery terminal voltage data, generator voltage data and generator output current data, to provide a reference voltage for the voltage regulator.« less

Numerical modeling and characterization of blast waves for application in blast-induced mild traumatic brain injury research

NASA Astrophysics Data System (ADS)

Phillips, Michael G.

Human exposure to blast waves, including blast-induced traumatic brain injury, is a developing field in medical research. Experiments with explosives have many disadvantages including safety, cost, and required area for trials. Shock tubes provide an alternative method to produce free field blast wave profiles. A compressed nitrogen shock tube experiment instrumented with static and reflective pressure taps is modeled using a numerical simulation. The geometry of the numerical model is simplified and blast wave characteristics are derived based upon static and pressure profiles. The pressure profiles are analyzed along the shock tube centerline and radially away from the tube axis. The blast wave parameters found from the pressure profiles provide guidelines for spatial location of a specimen. The location could be based on multiple parameters and provides a distribution of anticipated pressure profiles experience by the specimen.

Modeling Electric Field Influences on Plasmaspheric Refilling

NASA Technical Reports Server (NTRS)

Liemohn, M. W.; Kozyra, J. U.; Khazanov, G. V.; Craven, Paul D.

1998-01-01

We have a new model of ion transport that we have applied to the problem of plasmaspheric flux tube refilling after a geomagnetic disturbance. This model solves the Fokker-Planck kinetic equation by applying discrete difference numerical schemes to the various operators. Features of the model include a time-varying ionospheric source, self-consistent Coulomb collisions, field-aligned electric field, hot plasma interactions, and ion cyclotron wave heating. We see refilling rates similar to those of earlier observations and models, except when the electric field is included. In this case, the refilling rates can be quite different that previously predicted. Depending on the populations included and the values of relevant parameters, trap zone densities can increase or decrease. In particular, the inclusion of hot populations near the equatorial region (specifically warm pancake distributions and ring current ions) can dramatically alter the refilling rate. Results are compared with observations as well as previous hydrodynamic and kinetic particle model simulations.

Methods for using groundwater model predictions to guide hydrogeologic data collection, with application to the Death Valley regional groundwater flow system

USGS Publications Warehouse

Tiedeman, C.R.; Hill, M.C.; D'Agnese, F. A.; Faunt, C.C.

2003-01-01

Calibrated models of groundwater systems can provide substantial information for guiding data collection. This work considers using such models to guide hydrogeologic data collection for improving model predictions by identifying model parameters that are most important to the predictions. Identification of these important parameters can help guide collection of field data about parameter values and associated flow system features and can lead to improved predictions. Methods for identifying parameters important to predictions include prediction scaled sensitivities (PSS), which account for uncertainty on individual parameters as well as prediction sensitivity to parameters, and a new "value of improved information" (VOII) method presented here, which includes the effects of parameter correlation in addition to individual parameter uncertainty and prediction sensitivity. In this work, the PSS and VOII methods are demonstrated and evaluated using a model of the Death Valley regional groundwater flow system. The predictions of interest are advective transport paths originating at sites of past underground nuclear testing. Results show that for two paths evaluated the most important parameters include a subset of five or six of the 23 defined model parameters. Some of the parameters identified as most important are associated with flow system attributes that do not lie in the immediate vicinity of the paths. Results also indicate that the PSS and VOII methods can identify different important parameters. Because the methods emphasize somewhat different criteria for parameter importance, it is suggested that parameters identified by both methods be carefully considered in subsequent data collection efforts aimed at improving model predictions.

Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer

USGS Publications Warehouse

Green, Christopher T.; Böhlke, John Karl; Bekins, Barbara A.; Phillips, Steven P.

2010-01-01

Gradients in contaminant concentrations and isotopic compositions commonly are used to derive reaction parameters for natural attenuation in aquifers. Differences between field‐scale (apparent) estimated reaction rates and isotopic fractionations and local‐scale (intrinsic) effects are poorly understood for complex natural systems. For a heterogeneous alluvial fan aquifer, numerical models and field observations were used to study the effects of physical heterogeneity on reaction parameter estimates. Field measurements included major ions, age tracers, stable isotopes, and dissolved gases. Parameters were estimated for the O2 reduction rate, denitrification rate, O2 threshold for denitrification, and stable N isotope fractionation during denitrification. For multiple geostatistical realizations of the aquifer, inverse modeling was used to establish reactive transport simulations that were consistent with field observations and served as a basis for numerical experiments to compare sample‐based estimates of “apparent” parameters with “true“ (intrinsic) values. For this aquifer, non‐Gaussian dispersion reduced the magnitudes of apparent reaction rates and isotope fractionations to a greater extent than Gaussian mixing alone. Apparent and true rate constants and fractionation parameters can differ by an order of magnitude or more, especially for samples subject to slow transport, long travel times, or rapid reactions. The effect of mixing on apparent N isotope fractionation potentially explains differences between previous laboratory and field estimates. Similarly, predicted effects on apparent O2threshold values for denitrification are consistent with previous reports of higher values in aquifers than in the laboratory. These results show that hydrogeological complexity substantially influences the interpretation and prediction of reactive transport.

Quantitative vs. subjective portal verification using digital portal images.

PubMed

Bissett, R; Leszczynski, K; Loose, S; Boyko, S; Dunscombe, P

1996-01-15

Off-line, computer-aided prescription (simulator) and treatment (portal) image registration using chamfer matching has been implemented on PC based viewing station. The purposes of this study were (a) to evaluate the performance of interactive anatomy and field edge extraction and subsequent registration, and (b) to compare observer's perceptions of field accuracy with measured discrepancies following anatomical registration. Prescription-treatment image pairs for 48 different patients were examined in this study. Digital prescription images were produced with the aid of a television camera and a digital frame grabber, while the treatment images were obtained directly from an on-line portal imaging system. To facilitate perception of low contrast anatomical detail, on-line portal images were enhanced with selective adaptive histogram equalization prior to extraction of anatomical edges. Following interactive extraction of anatomical and field border information by an experienced observer, the identified anatomy was registered using chamfer matching. The degree of conformity between the prescription and treatment fields was quantified using several parameters, which included relative prescription field coverage and overcoverage, as well as the translational and rotational displacements as measured by chamfer matching applied to the boundaries of the two fields. These quantitative measures were compared with subjective evaluations made by four radiation oncologists. All the images in this series that included a range of the most commonly seen treatment sites were registered and the conformity parameters were found. The mean treatment/prescription field coverage and overcoverage were approximately 95 and 7%, respectively before registration. The mean translational displacement in the transverse and cranio-caudal directions were 2.9 and 3.4 mm, respectively. The mean rotational displacement was approximately 2 degrees. For all four oncologists, the portals classified as unacceptable, in terms of the field placement, exhibited significantly higher (p < 0.03) translational errors in the transverse direction. The field coverages were significantly lower (p < 0.05) and the translational errors in the cranio-caudal direction were significantly higher (p < 0.05) for the portals rated as unacceptable by two of the oncologists. From the parameters that were used to quantify the degree of conformity between the prescription and treatment fields, the translational error in the transverse direction correlated best with the oncologists' assessments on the field placement. Field coverage and translational error in the cranio-caudal direction correlated well with assessments of only two out of the four participating oncologists. This can be explained by the fact that for the majority of treatment sites included in the study the positioning of field borders was more critical for the transverse direction. A conclusion for the design of future quantitative and automated on-line portal verification systems is that they will have to model different perceived significances of different types of localization errors intrinsic to oncologist evaluation of portal images.

An update of Leighton's solar dynamo model

NASA Astrophysics Data System (ADS)

Cameron, R. H.; Schüssler, M.

2017-03-01

In 1969, Leighton developed a quasi-1D mathematical model of the solar dynamo, building upon the phenomenological scenario of Babcock published in 1961. Here we present a modification and extension of Leighton's model. Using the axisymmetric component (longitudinal average) of the magnetic field, we consider the radial field component at the solar surface and the radially integrated toroidal magnetic flux in the convection zone, both as functions of latitude. No assumptions are made with regard to the radial location of the toroidal flux. The model includes the effects of (I) turbulent diffusion at the surface and in the convection zone; (II) poleward meridional flow at the surface and an equatorward return flow affecting the toroidal flux; (III) latitudinal differential rotation and the near-surface layer of radial rotational shear; (iv) downward convective pumping of magnetic flux in the shear layer; and (v) flux emergence in the form of tilted bipolar magnetic regions treated as a source term for the radial surface field. While the parameters relevant for the transport of the surface field are taken from observations, the model condenses the unknown properties of magnetic field and flow in the convection zone into a few free parameters (turbulent diffusivity, effective return flow, amplitude of the source term, and a parameter describing the effective radial shear). Comparison with the results of 2D flux transport dynamo codes shows that the model captures the essential features of these simulations. We make use of the computational efficiency of the model to carry out an extended parameter study. We cover an extended domain of the 4D parameter space and identify the parameter ranges that provide solar-like solutions. Dipole parity is always preferred and solutions with periods around 22 yr and a correct phase difference between flux emergence in low latitudes and the strength of the polar fields are found for a return flow speed around 2 m s-1, turbulent diffusivity below about 80 km2s-1, and dynamo excitation not too far above the threshold (linear growth rate less than 0.1 yr-1).

Visualizing the deep end of sound: plotting multi-parameter results from infrasound data analysis

NASA Astrophysics Data System (ADS)

Perttu, A. B.; Taisne, B.

2016-12-01

Infrasound is sound below the threshold of human hearing: approximately 20 Hz. The field of infrasound research, like other waveform based fields relies on several standard processing methods and data visualizations, including waveform plots and spectrograms. The installation of the International Monitoring System (IMS) global network of infrasound arrays, contributed to the resurgence of infrasound research. Array processing is an important method used in infrasound research, however, this method produces data sets with a large number of parameters, and requires innovative plotting techniques. The goal in designing new figures is to be able to present easily comprehendible, and information-rich plots by careful selection of data density and plotting methods.

Decorrelation Times of Photospheric Fields and Flows

NASA Technical Reports Server (NTRS)

Welsch, B. T.; Kusano, K.; Yamamoto, T. T.; Muglach, K.

2012-01-01

We use autocorrelation to investigate evolution in flow fields inferred by applying Fourier Local Correlation Tracking (FLCT) to a sequence of high-resolution (0.3 "), high-cadence (approx = 2 min) line-of-sight magnetograms of NOAA active region (AR) 10930 recorded by the Narrowband Filter Imager (NFI) of the Solar Optical Telescope (SOT) aboard the Hinode satellite over 12 - 13 December 2006. To baseline the timescales of flow evolution, we also autocorrelated the magnetograms, at several spatial binnings, to characterize the lifetimes of active region magnetic structures versus spatial scale. Autocorrelation of flow maps can be used to optimize tracking parameters, to understand tracking algorithms f susceptibility to noise, and to estimate flow lifetimes. Tracking parameters varied include: time interval Delta t between magnetogram pairs tracked, spatial binning applied to the magnetograms, and windowing parameter sigma used in FLCT. Flow structures vary over a range of spatial and temporal scales (including unresolved scales), so tracked flows represent a local average of the flow over a particular range of space and time. We define flow lifetime to be the flow decorrelation time, tau . For Delta t > tau, tracking results represent the average velocity over one or more flow lifetimes. We analyze lifetimes of flow components, divergences, and curls as functions of magnetic field strength and spatial scale. We find a significant trend of increasing lifetimes of flow components, divergences, and curls with field strength, consistent with Lorentz forces partially governing flows in the active photosphere, as well as strong trends of increasing flow lifetime and decreasing magnitudes with increases in both spatial scale and Delta t.

Ultrasonic bubbles in medicine: influence of the shell.

PubMed

Postema, Michiel; Schmitz, Georg

2007-04-01

Ultrasound contrast agents consist of microscopically small bubbles encapsulated by an elastic shell. These microbubbles oscillate upon ultrasound insonification, and demonstrate highly nonlinear behavior, ameliorating their detectability. (Potential) medical applications involving the ultrasonic disruption of contrast agent microbubble shells include release-burst imaging, localized drug delivery, and noninvasive blood pressure measurement. To develop and enhance these techniques, predicting the cracking behavior of ultrasound-insonified encapsulated microbubbles has been of importance. In this paper, we explore microbubble behavior in an ultrasound field, with special attention to the influence of the bubble shell. A bubble in a sound field can be considered a forced damped harmonic oscillator. For encapsulated microbubbles, the presence of a shell has to be taken into account. In models, an extra damping parameter and a shell stiffness parameter have been included, assuming that Hooke's Law holds for the bubble shell. At high acoustic amplitudes, disruptive phenomena have been observed, such as microbubble fragmentation and ultrasonic cracking. We analyzed the occurrence of ultrasound contrast agent fragmentation, by simulating the oscillating behavior of encapsulated microbubbles with various sizes in a harmonic acoustic field. Fragmentation occurs exclusively during the collapse phase and occurs if the kinetic energy of the collapsing microbubble is greater than the instantaneous bubble surface energy, provided that surface instabilities have grown big enough to allow for break-up. From our simulations it follows that the Blake critical radius is not a good approximation for a fragmentation threshold. We demonstrated how the phase angle differences between a damped radially oscillating bubble and an incident sound field depend on shell parameters.

A simple model of hysteresis behavior using spreadsheet analysis

NASA Astrophysics Data System (ADS)

Ehrmann, A.; Blachowicz, T.

2015-01-01

Hysteresis loops occur in many scientific and technical problems, especially as field dependent magnetization of ferromagnetic materials, but also as stress-strain-curves of materials measured by tensile tests including thermal effects, liquid-solid phase transitions, in cell biology or economics. While several mathematical models exist which aim to calculate hysteresis energies and other parameters, here we offer a simple model for a general hysteretic system, showing different hysteresis loops depending on the defined parameters. The calculation which is based on basic spreadsheet analysis plus an easy macro code can be used by students to understand how these systems work and how the parameters influence the reactions of the system on an external field. Importantly, in the step-by-step mode, each change of the system state, compared to the last step, becomes visible. The simple program can be developed further by several changes and additions, enabling the building of a tool which is capable of answering real physical questions in the broad field of magnetism as well as in other scientific areas, in which similar hysteresis loops occur.

Electric field enhancement due to a saw-tooth asperity in a channel and implications on microscale gas breakdown

NASA Astrophysics Data System (ADS)

Venkattraman, Ayyaswamy

2014-10-01

The electric field enhancement due to an isolated saw-tooth asperity in an infinite channel is considered with the goal of providing some inputs to the choice of field enhancement factors used to describe microscale gas breakdown. The Schwarz-Christoffel transformation is used to map the interior of the channel to the upper half of the transformed plane. The expression for the electric field in the transformed plane is then used to determine the electric field distribution in the channel as well as field enhancement near the asperity. The effective field enhancement factor is determined and its dependence on operating and geometrical parameters is studied. While the effective field enhancement factor depends only weakly on the height of the asperity in comparison to the channel, it is influenced significantly by the base angles of the asperity. Due to the strong dependence of field emission current density on electric field, the effective field enhancement factor (βeff) is shown to vary rapidly with the applied electric field irrespective of the geometrical parameters. This variation is included in the analysis of microscale gas breakdown and compared with results obtained using a constant βeff as is done traditionally. Even though results for a varying βeff may be approximately reproduced using an equivalent constant βeff independent of E-field, it might be important for a range of operating conditions. This is confirmed by extracting βeff from experimental data for breakdown in argon microgaps with plane-parallel cathodes and comparing its dependence on the E-field. While the use of two-dimensional asperities is shown to be a minor disadvantage of the proposed approach in its current form, it can potentially help in developing predictive capabilities as opposed to treating βeff as a curve-fitting parameter.

Diagnostic Ability of Wide-field Retinal Nerve Fiber Layer Maps Using Swept-Source Optical Coherence Tomography for Detection of Preperimetric and Early Perimetric Glaucoma.

PubMed

Lee, Won June; Na, Kyeong Ik; Kim, Young Kook; Jeoung, Jin Wook; Park, Ki Ho

2017-06-01

To evaluate the diagnostic ability of wide-field retinal nerve fiber layer (RNFL) maps with swept-source optical coherence tomography (SS-OCT) for detection of preperimetric (PPG) and early perimetric glaucoma (EG). One hundred eighty-four eyes, including 67 healthy eyes, 43 eyes with PPG, and 74 eyes with EG, were analyzed. Patients underwent a comprehensive ocular examination including red-free RNFL photography, visual field testing and wide-field SS-OCT scanning (DRI-OCT-1 Atlantis; Topcon, Tokyo, Japan). SS-OCT provides a wide-field RNFL thickness map and a SuperPixel map, which are composed of the RNFL deviation map of the peripapillary area and the deviation map of the composition of the ganglion cell layer with the inner plexiform layer and RNFL (GC-IPL+RNFL) in the macular area. The ability to discriminate PPG and EG from healthy eyes was assessed using sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) for all parameters and criteria provided by the wide-field SS-OCT scan. The wide-field RNFL thickness map using SS-OCT showed the highest sensitivity of PPG-diagnostic and EG-diagnostic performance compared with the other SS-OCT criteria based on the internal normative base (93.0 and 97.3%, respectively). Among the SS-OCT continuous parameters, the RFNL thickness of the 7 clock-hour, inferior and inferotemporal macular ganglion cell analyses showed the largest AUC of PPG-diagnostic and EG-diagnostic performance (AUC=0.809 to 0.865). The wide-field RNFL thickness map using SS-OCT performed well in distinguishing eyes with PPG and EG from healthy eyes. In the clinical setting, wide-field RNFL maps of SS-OCT can be useful tools for detection of early-stage glaucoma.

Apparatus and method for radioactive waste screening

DOEpatents

Akers, Douglas W.; Roybal, Lyle G.; Salomon, Hopi; Williams, Charles Leroy

2012-09-04

An apparatus and method relating to screening radioactive waste are disclosed for ensuring that at least one calculated parameter for the measurement data of a sample falls within a range between an upper limit and a lower limit prior to the sample being packaged for disposal. The apparatus includes a radiation detector configured for detecting radioactivity and radionuclide content of the of the sample of radioactive waste and generating measurement data in response thereto, and a collimator including at least one aperture to direct a field of view of the radiation detector. The method includes measuring a radioactive content of a sample, and calculating one or more parameters from the radioactive content of the sample.

Calculation of the Initial Magnetic Field for Mercury's Magnetosphere Hybrid Model

NASA Astrophysics Data System (ADS)

Alexeev, Igor; Parunakian, David; Dyadechkin, Sergey; Belenkaya, Elena; Khodachenko, Maxim; Kallio, Esa; Alho, Markku

2018-03-01

Several types of numerical models are used to analyze the interactions of the solar wind flow with Mercury's magnetosphere, including kinetic models that determine magnetic and electric fields based on the spatial distribution of charges and currents, magnetohydrodynamic models that describe plasma as a conductive liquid, and hybrid models that describe ions kinetically in collisionless mode and represent electrons as a massless neutralizing liquid. The structure of resulting solutions is determined not only by the chosen set of equations that govern the behavior of plasma, but also by the initial and boundary conditions; i.e., their effects are not limited to the amount of computational work required to achieve a quasi-stationary solution. In this work, we have proposed using the magnetic field computed by the paraboloid model of Mercury's magnetosphere as the initial condition for subsequent hybrid modeling. The results of the model have been compared to measurements performed by the Messenger spacecraft during a single crossing of the magnetosheath and the magnetosphere. The selected orbit lies in the terminator plane, which allows us to observe two crossings of the bow shock and the magnetopause. In our calculations, we have defined the initial parameters of the global magnetospheric current systems in a way that allows us to minimize paraboloid magnetic field deviation along the trajectory of the Messenger from the experimental data. We have shown that the optimal initial field parameters include setting the penetration of a partial interplanetary magnetic field into the magnetosphere with a penetration coefficient of 0.2.

Magnetised winds and their influence in the escaping upper atmosphere of HD 209458b

NASA Astrophysics Data System (ADS)

D'Angelo, Carolina Villarreal; Esquivel, Alejandro; Schneiter, Matías; Sgró, Mario Agustín

2018-06-01

Lyman α observations during an exoplanet transit have proved to be very useful to study the interaction between the stellar wind and the planetary atmosphere. They have been extensively used to constrain planetary system parameters that are not directly observed, such as the planetary mass loss rate. In this way, Ly α observations can be a powerful tool to infer the existence of a planetary magnetic field, since it is expected that the latter will affect the escaping planetary material. To explore the effect that magnetic fields have on the Ly α absorption of HD 209458b, we run a set of 3D MHD simulations including dipolar magnetic fields for the planet and the star. We assume values for the surface magnetic field at the poles of the planet in the range of [0-5] G, and from 1 to 5 G at the poles of the star. Our models also include collisional and photo-ionisation, radiative recombination, and an approximation for the radiation pressure. Our results show that the magnetic field of the planet and the star change the shape of the Ly α absorption profile, since it controls the extent of the planetary magnetosphere and the amount of neutral material inside it. The model that best reproduces the absorption observed in HD 209458b (with canonical values for the stellar wind parameters) corresponds to a dipole planetary field of ≲ 1 gauss at the poles.

Bayesian parameter estimation for chiral effective field theory

NASA Astrophysics Data System (ADS)

Wesolowski, Sarah; Furnstahl, Richard; Phillips, Daniel; Klco, Natalie

2016-09-01

The low-energy constants (LECs) of a chiral effective field theory (EFT) interaction in the two-body sector are fit to observable data using a Bayesian parameter estimation framework. By using Bayesian prior probability distributions (pdfs), we quantify relevant physical expectations such as LEC naturalness and include them in the parameter estimation procedure. The final result is a posterior pdf for the LECs, which can be used to propagate uncertainty resulting from the fit to data to the final observable predictions. The posterior pdf also allows an empirical test of operator redundancy and other features of the potential. We compare results of our framework with other fitting procedures, interpreting the underlying assumptions in Bayesian probabilistic language. We also compare results from fitting all partial waves of the interaction simultaneously to cross section data compared to fitting to extracted phase shifts, appropriately accounting for correlations in the data. Supported in part by the NSF and DOE.

Evaluation of parameters of Black Hole, stellar cluster and dark matter distribution from bright star orbits in the Galactic Center

NASA Astrophysics Data System (ADS)

Zakharov, Alexander

It is well-known that one can evaluate black hole (BH) parameters (including spin) analyz-ing trajectories of stars around BH. A bulk distribution of matter (dark matter (DM)+stellar cluster) inside stellar orbits modifies trajectories of stars, namely, generally there is a apoas-tron shift in direction which opposite to GR one, even now one could put constraints on DM distribution and BH parameters and constraints will more stringent in the future. Therefore, an analyze of bright star trajectories provides a relativistic test in a weak gravitational field approximation, but in the future one can test a strong gravitational field near the BH at the Galactic Center with the same technique due to a rapid progress in observational facilities. References A. Zakharov et al., Phys. Rev. D76, 062001 (2007). A.F. Zakharov et al., Space Sci. Rev. 148, 301313(2009).

Characteristics of buoyancy force on stagnation point flow with magneto-nanoparticles and zero mass flux condition

NASA Astrophysics Data System (ADS)

Uddin, Iftikhar; Khan, Muhammad Altaf; Ullah, Saif; Islam, Saeed; Israr, Muhammad; Hussain, Fawad

2018-03-01

This attempt dedicated to the solution of buoyancy effect over a stretching sheet in existence of MHD stagnation point flow with convective boundary conditions. Thermophoresis and Brownian motion aspects are included. Incompressible fluid is electrically conducted in the presence of varying magnetic field. Boundary layer analysis is used to develop the mathematical formulation. Zero mass flux condition is considered at the boundary. Non-linear ordinary differential system of equations is constructed by means of proper transformations. Interval of convergence via numerical data and plots are developed. Characteristics of involved variables on the velocity, temperature and concentration distributions are sketched and discussed. Features of correlated parameters on Cf and Nu are examined by means of tables. It is found that buoyancy ratio and magnetic parameters increase and reduce the velocity field. Further opposite feature is noticed for higher values of thermophoresis and Brownian motion parameters on concentration distribution.

Quantum Space Charge Waves in a Waveguide Filled with Fermi-Dirac Plasmas Including Relativistic Wake Field and Quantum Statistical Pressure Effects

NASA Astrophysics Data System (ADS)

Hong, Woo-Pyo; Jung, Young-Dae

2018-03-01

The effects of quantum statistical degeneracy pressure on the propagation of the quantum space charge wave are investigated in a cylindrically bounded plasma waveguide filled with relativistically degenerate quantum Fermi-Dirac plasmas and the relativistic ion wake field. The results show that the domain of the degenerate parameter for the resonant beam instability significantly increases with an increase of the scaled beam velocity. It is found that the instability domain of the wave number increases with an increase of the degenerate parameter. It is also found that the growth rate for the resonant beam instability decreases with an increase of the degenerate parameter. In addition, it is shown that the lowest harmonic mode provides the maximum value of the growth rates. Moreover, it is shown that the instability domain of the wave number decreases with an increase of the beam velocity.

Gravitational effective action at second order in curvature and gravitational waves

NASA Astrophysics Data System (ADS)

Calmet, Xavier; Capozziello, Salvatore; Pryer, Daniel

2017-09-01

We consider the full effective theory for quantum gravity at second order in curvature including non-local terms. We show that the theory contains two new degrees of freedom beyond the massless graviton: namely a massive spin-2 ghost and a massive scalar field. Furthermore, we show that it is impossible to fine-tune the parameters of the effective action to eliminate completely the classical spin-2 ghost because of the non-local terms in the effective action. Being a classical field, it is not clear anyway that this ghost is problematic. It simply implies a repulsive contribution to Newton's potential. We then consider how to extract the parameters of the effective action and show that it is possible to measure, at least in principle, the parameters of the local terms independently of each other using a combination of observations of gravitational waves and measurements performed by pendulum type experiments searching for deviations of Newton's potential.

Tuning magnetofluidic spreading in microchannels

NASA Astrophysics Data System (ADS)

Wang, Zhaomeng; Varma, V. B.; Wang, Z. P.; Ramanujan, R. V.

2015-12-01

Magnetofluidic spreading (MFS) is a phenomenon in which a uniform magnetic field is used to induce spreading of a ferrofluid core cladded by diamagnetic fluidic streams in a three-stream channel. Applications of MFS include micromixing, cell sorting and novel microfluidic lab-on-a-chip design. However, the relative importance of the parameters which govern MFS is still unclear, leading to non-optimal control of MFS. Hence, in this work, the effect of various key parameters on MFS was experimentally and numerically studied. Our multi-physics model, which combines magnetic and fluidic analysis, showed excellent agreement between theory and experiment. It was found that spreading was mainly due to cross-sectional convection induced by magnetic forces, and can be enhanced by tuning various parameters. Smaller flow rate ratio, higher magnetic field, higher core stream or lower cladding stream dynamic viscosity, and larger magnetic particle size can increase MFS. These results can be used to tune magnetofluidic spreading in microchannels.

Constraining the String Gauge Field by Galaxy Rotation Curves and Perihelion Precession of Planets

NASA Astrophysics Data System (ADS)

Cheung, Yeuk-Kwan E.; Xu, Feng

2013-09-01

We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have observable signatures on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of 22 spiral galaxies of varied luminosities and sizes and perihelion precessions of planets in the solar system. The rotation curves of the same group of galaxies are independently fit using a dark matter model with the generalized Navarro-Frenk-White (NFW) profile and the string model. A remarkable fit of galaxy rotation curves is achieved using the one-parameter string model as compared to the three-parameter dark matter model with the NFW profile. The average χ2 value of the NFW fit is 9% better than that of the string model at a price of two more free parameters. Furthermore, from the string model, we can give a dynamical explanation for the phenomenological Tully-Fisher relation. We are able to derive a relation between field strength, galaxy size, and luminosity, which can be verified with data from the 22 galaxies. To further test the hypothesis of the universal existence of the string gauge field, we apply our string model to the solar system. Constraint on the magnitude of the string field in the solar system is deduced from the current ranges for any anomalous perihelion precession of planets allowed by the latest observations. The field distribution resembles a dipole field originating from the Sun. The string field strength deduced from the solar system observations is of a similar magnitude as the field strength needed to sustain the rotational speed of the Sun inside the Milky Way. This hypothesis can be tested further by future observations with higher precision.

High-resolution empirical geomagnetic field model TS07D: Investigating run-on-request and forecasting modes of operation

NASA Astrophysics Data System (ADS)

Stephens, G. K.; Sitnov, M. I.; Ukhorskiy, A. Y.; Vandegriff, J. D.; Tsyganenko, N. A.

2010-12-01

The dramatic increase of the geomagnetic field data volume available due to many recent missions, including GOES, Polar, Geotail, Cluster, and THEMIS, required at some point the appropriate qualitative transition in the empirical modeling tools. Classical empirical models, such as T96 and T02, used few custom-tailored modules to represent major magnetospheric current systems and simple data binning or loading-unloading inputs for their fitting with data and the subsequent applications. They have been replaced by more systematic expansions of the equatorial and field-aligned current contributions as well as by the advanced data-mining algorithms searching for events with the global activity parameters, such as the Sym-H index, similar to those at the time of interest, as is done in the model TS07D (Tsyganenko and Sitnov, 2007; Sitnov et al., 2008). The necessity to mine and fit data dynamically, with the individual subset of the database being used to reproduce the geomagnetic field pattern at every new moment in time, requires the corresponding transition in the use of the new empirical geomagnetic field models. It becomes more similar to runs-on-request offered by the Community Coordinated Modeling Center for many first principles MHD and kinetic codes. To provide this mode of operation for the TS07D model a new web-based modeling tool has been created and tested at the JHU/APL (http://geomag_field.jhuapl.edu/model/), and we discuss the first results of its performance testing and validation, including in-sample and out-of-sample modeling of a number of CME- and CIR-driven magnetic storms. We also report on the first tests of the forecasting version of the TS07D model, where the magnetospheric part of the macro-parameters involved in the data-binning process (Sym-H index and its trend parameter) are replaced by their solar wind-based analogs obtained using the Burton-McPherron-Russell approach.

Two dimensional model for coherent synchrotron radiation

NASA Astrophysics Data System (ADS)

Huang, Chengkun; Kwan, Thomas J. T.; Carlsten, Bruce E.

2013-01-01

Understanding coherent synchrotron radiation (CSR) effects in a bunch compressor requires an accurate model accounting for the realistic beam shape and parameters. We extend the well-known 1D CSR analytic model into two dimensions and develop a simple numerical model based on the Liénard-Wiechert formula for the CSR field of a coasting beam. This CSR numerical model includes the 2D spatial dependence of the field in the bending plane and is accurate for arbitrary beam energy. It also removes the singularity in the space charge field calculation present in a 1D model. Good agreement is obtained with 1D CSR analytic result for free electron laser (FEL) related beam parameters but it can also give a more accurate result for low-energy/large spot size beams and off-axis/transient fields. This 2D CSR model can be used for understanding the limitation of various 1D models and for benchmarking fully electromagnetic multidimensional particle-in-cell simulations for self-consistent CSR modeling.

Spatio-temporal modelling of wind speed variations and extremes in the Caribbean and the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Rychlik, Igor; Mao, Wengang

2018-02-01

The wind speed variability in the North Atlantic has been successfully modelled using a spatio-temporal transformed Gaussian field. However, this type of model does not correctly describe the extreme wind speeds attributed to tropical storms and hurricanes. In this study, the transformed Gaussian model is further developed to include the occurrence of severe storms. In this new model, random components are added to the transformed Gaussian field to model rare events with extreme wind speeds. The resulting random field is locally stationary and homogeneous. The localized dependence structure is described by time- and space-dependent parameters. The parameters have a natural physical interpretation. To exemplify its application, the model is fitted to the ECMWF ERA-Interim reanalysis data set. The model is applied to compute long-term wind speed distributions and return values, e.g., 100- or 1000-year extreme wind speeds, and to simulate random wind speed time series at a fixed location or spatio-temporal wind fields around that location.

Finite element method (FEM) model of the mechanical stress on phospholipid membranes from shock waves produced in nanosecond electric pulses (nsEP)

NASA Astrophysics Data System (ADS)

Barnes, Ronald; Roth, Caleb C.; Shadaram, Mehdi; Beier, Hope; Ibey, Bennett L.

2015-03-01

The underlying mechanism(s) responsible for nanoporation of phospholipid membranes by nanosecond pulsed electric fields (nsEP) remains unknown. The passage of a high electric field through a conductive medium creates two primary contributing factors that may induce poration: the electric field interaction at the membrane and the shockwave produced from electrostriction of a polar submersion medium exposed to an electric field. Previous work has focused on the electric field interaction at the cell membrane, through such models as the transport lattice method. Our objective is to model the shock wave cell membrane interaction induced from the density perturbation formed at the rising edge of a high voltage pulse in a polar liquid resulting in a shock wave propagating away from the electrode toward the cell membrane. Utilizing previous data from cell membrane mechanical parameters, and nsEP generated shockwave parameters, an acoustic shock wave model based on the Helmholtz equation for sound pressure was developed and coupled to a cell membrane model with finite-element modeling in COMSOL. The acoustic structure interaction model was developed to illustrate the harmonic membrane displacements and stresses resulting from shockwave and membrane interaction based on Hooke's law. Poration is predicted by utilizing membrane mechanical breakdown parameters including cortical stress limits and hydrostatic pressure gradients.

Balancing the Interactions of Ions, Water, and DNA in the Drude Polarizable Force Field

PubMed Central

2015-01-01

Recently we presented a first-generation all-atom Drude polarizable force field for DNA based on the classical Drude oscillator model, focusing on optimization of key dihedral angles followed by extensive validation of the force field parameters. Presently, we describe the procedure for balancing the electrostatic interactions between ions, water, and DNA as required for development of the Drude force field for DNA. The proper balance of these interactions is shown to impact DNA stability and subtler conformational properties, including the conformational equilibrium between the BI and BII states, and the A and B forms of DNA. The parametrization efforts were simultaneously guided by gas-phase quantum mechanics (QM) data on small model compounds and condensed-phase experimental data on the hydration and osmotic properties of biologically relevant ions and their solutions, as well as theoretical predictions for ionic distribution around DNA oligomer. In addition, fine-tuning of the internal base parameters was performed to obtain the final DNA model. Notably, the Drude model is shown to more accurately reproduce counterion condensation theory predictions of DNA charge neutralization by the condensed ions as compared to the CHARMM36 additive DNA force field, indicating an improved physical description of the forces dictating the ionic solvation of DNA due to the explicit treatment of electronic polarizability. In combination with the polarizable DNA force field, the availability of Drude polarizable parameters for proteins, lipids, and carbohydrates will allow for simulation studies of heterogeneous biological systems. PMID:24874104

Observatory geoelectric fields induced in a two-layer lithosphere during magnetic storms

USGS Publications Warehouse

Love, Jeffrey J.; Swidinsky, Andrei

2015-01-01

We report on the development and validation of an algorithm for estimating geoelectric fields induced in the lithosphere beneath an observatory during a magnetic storm. To accommodate induction in three-dimensional lithospheric electrical conductivity, we analyze a simple nine-parameter model: two horizontal layers, each with uniform electrical conductivity properties given by independent distortion tensors. With Laplace transformation of the induction equations into the complex frequency domain, we obtain a transfer function describing induction of observatory geoelectric fields having frequency-dependent polarization. Upon inverse transformation back to the time domain, the convolution of the corresponding impulse-response function with a geomagnetic time series yields an estimated geoelectric time series. We obtain an optimized set of conductivity parameters using 1-s resolution geomagnetic and geoelectric field data collected at the Kakioka, Japan, observatory for five different intense magnetic storms, including the October 2003 Halloween storm; our estimated geoelectric field accounts for 93% of that measured during the Halloween storm. This work demonstrates the need for detailed modeling of the Earth’s lithospheric conductivity structure and the utility of co-located geomagnetic and geoelectric monitoring.

SU-D-304-06: Measurement of LET in Patient-Specific Proton Therapy Treatment Fields Using Optically Stimulated Luminescence Detectors

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

Granville, DA; Sahoo, N; Sawakuchi, GO

Purpose: To investigate the use of optically stimulated luminescence (OSL) detectors (OSLDs) for measurements of dose-averaged linear energy transfer (LET) in patient-specific proton therapy treatment fields. Methods: We used Al{sub 2}O{sub 3}:C OSLDs made from the same material as commercially available nanoDot OSLDs from Landauer, Inc. We calibrated two parameters of the OSL signal as functions of LET in therapeutic proton beams: the ratio of the ultraviolet and blue emission intensities (UV/blue ratio) and the OSL curve shape. These calibration curves were created by irradiating OSLDs in passively scattered beams of known LET (0.96 to 3.91 keV/µm). The LET valuesmore » were determined using a validated Monte Carlo model of the beamline. We then irradiated new OSLDs with the prescription dose (16 to 74 cGy absorbed dose to water) at the center of the spread-out Bragg peak (SOBP) of four patient-specific treatment fields. From readouts of these OSLDs, we determined both the UV/blue ratio and OSL curve shape parameters. Combining these parameters with the calibration curves, we were able to measure LET using the OSLDs. The measurements were compared to the theoretical LET values obtained from Monte Carlo simulations of the patient-specific treatments fields. Results: Using the UV/blue ratio parameter, we were able to measure LET within 3.8%, 6.2%, 5.6% and 8.6% of the Monte Carlo value for each of the patient fields. Similarly, using the OSL curve shape parameter, LET measurements agreed within 0.5%, 11.0%, 2.5% and 7.6% for each of the four fields. Conclusion: We have demonstrated a method to verify LET in patient-specific proton therapy treatment fields using OSLDs. The possibility of enhancing biological effectiveness of proton therapy treatment plans by including LET in the optimization has been previously shown. The LET verification method we have demonstrated will be useful in the quality assurance of such LET optimized treatment plans. DA Granville received financial support from the Natural Sciences and Engineering Research Council of Canada.« less

SU-E-T-176: Clinical Experience of Brass Mesh Bolus: Patient-Specific Parameters as Predictors of Measured Dosimetric Effect

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

Yock, A; Manger, R; Einck, J

2015-06-15

Purpose: Increasingly, brass mesh bolus is used to insure dosimetric coverage of the skin for patients treated post-mastectomy for breast cancer. Contribution of photoelectrons from interactions between the bolus and the primary beam increases dose superficially without affecting dose at greater depths. We present our experience using brass mesh bolus – including patients for whom the bolus was dosimetrically inadequate – along with analysis of relevant patient-specific parameters. Methods: Optically-stimulated luminescent dosimeters (OSLDs) were used to determine the effect of the bolus for 15 patients. They were positioned beneath the bolus within the tangent fields at three positions: 1.5–3cm insidemore » the medial and lateral field edges, and midway between the two. All OSLDs were midfield in the cranial-caudal direction. The measurements were compared with patient-specific parameters including separation, chest wall/breast tissue thickness, beam angle incidence, and planned surface dose. Results: The average OSLD measurement at the medial field edge, midfield, and lateral field edge position was 86.8%, 101.8%, and 92.8% of the prescription dose, respectively. A measurement for one patient was low enough (77.0%) to warrant a switch to an alternative type of bolus. Anatomic parameters were analyzed to investigate the low dose in this case, not observed in the planning system. The patient was observed to have a thin chest wall and very oblique beam angles. A second patient was also switched to an alternative type of bolus due to her being high risk and treated with an electron patch that extended onto the breast. Conclusion: Brass mesh bolus increases dose superficially while leaving dose at greater depths unaffected. However, our results suggest that this effect may be insufficient in patients with a thin chest wall or very oblique beam angles. More data and analysis is necessary to proactively identify patients for whom brass mesh bolus is effective.« less

The use of laboratory-determined ion exchange parameters in the predictive modelling of field-scale major cation migration in groundwater over a 40-year period.

PubMed

Carlyle, Harriet F; Tellam, John H; Parker, Karen E

2004-01-01

An attempt has been made to estimate quantitatively cation concentration changes as estuary water invades a Triassic Sandstone aquifer in northwest England. Cation exchange capacities and selectivity coefficients for Na(+), K(+), Ca(2+), and Mg(2+) were measured in the laboratory using standard techniques. Selectivity coefficients were also determined using a method involving optimized back-calculation from flushing experiments, thus permitting better representation of field conditions; in all cases, the Gaines-Thomas/constant cation exchange capacity (CEC) model was found to be a reasonable, though not perfect, first description. The exchange parameters interpreted from the laboratory experiments were used in a one-dimensional reactive transport mixing cell model, and predictions compared with field pumping well data (Cl and hardness spanning a period of around 40 years, and full major ion analyses in approximately 1980). The concentration patterns predicted using Gaines-Thomas exchange with calcite equilibrium were similar to the observed patterns, but the concentrations of the divalent ions were significantly overestimated, as were 1980 sulphate concentrations, and 1980 alkalinity concentrations were underestimated. Including representation of sulphate reduction in the estuarine alluvium failed to replicate 1980 HCO(3) and pH values. However, by including partial CO(2) degassing following sulphate reduction, a process for which there is 34S and 18O evidence from a previous study, a good match for SO(4), HCO(3), and pH was attained. Using this modified estuary water and averaged values from the laboratory ion exchange parameter determinations, good predictions for the field cation data were obtained. It is concluded that the Gaines-Thomas/constant exchange capacity model with averaged parameter values can be used successfully in ion exchange predictions in this aquifer at a regional scale and over extended time scales, despite the numerous assumptions inherent in the approach; this has also been found to be the case in the few other published studies of regional ion exchanging flow.

The use of laboratory-determined ion exchange parameters in the predictive modelling of field-scale major cation migration in groundwater over a 40-year period

NASA Astrophysics Data System (ADS)

Carlyle, Harriet F.; Tellam, John H.; Parker, Karen E.

2004-01-01

An attempt has been made to estimate quantitatively cation concentration changes as estuary water invades a Triassic Sandstone aquifer in northwest England. Cation exchange capacities and selectivity coefficients for Na +, K +, Ca 2+, and Mg 2+ were measured in the laboratory using standard techniques. Selectivity coefficients were also determined using a method involving optimized back-calculation from flushing experiments, thus permitting better representation of field conditions; in all cases, the Gaines-Thomas/constant cation exchange capacity (CEC) model was found to be a reasonable, though not perfect, first description. The exchange parameters interpreted from the laboratory experiments were used in a one-dimensional reactive transport mixing cell model, and predictions compared with field pumping well data (Cl and hardness spanning a period of around 40 years, and full major ion analyses in ˜1980). The concentration patterns predicted using Gaines-Thomas exchange with calcite equilibrium were similar to the observed patterns, but the concentrations of the divalent ions were significantly overestimated, as were 1980 sulphate concentrations, and 1980 alkalinity concentrations were underestimated. Including representation of sulphate reduction in the estuarine alluvium failed to replicate 1980 HCO 3 and pH values. However, by including partial CO 2 degassing following sulphate reduction, a process for which there is 34S and 18O evidence from a previous study, a good match for SO 4, HCO 3, and pH was attained. Using this modified estuary water and averaged values from the laboratory ion exchange parameter determinations, good predictions for the field cation data were obtained. It is concluded that the Gaines-Thomas/constant exchange capacity model with averaged parameter values can be used successfully in ion exchange predictions in this aquifer at a regional scale and over extended time scales, despite the numerous assumptions inherent in the approach; this has also been found to be the case in the few other published studies of regional ion exchanging flow.

Revised Planning Methodology For Signalized Intersections And Operational Analysis Of Exclusive Left-Turn Lanes, Part-II: Models And Procedures (Final Report)

DOT National Transportation Integrated Search

1996-04-01

THIS REPORT ALSO DESCRIBES THE PROCEDURES FOR DIRECT ESTIMATION OF INTERSECTION CAPACITY WITH SIMULATION, INCLUDING A SET OF RIGOROUS STATISTICAL TESTS FOR SIMULATION PARAMETER CALIBRATION FROM FIELD DATA.

Modelling biological invasions: species traits, species interactions, and habitat heterogeneity.

PubMed

Cannas, Sergio A; Marco, Diana E; Páez, Sergio A

2003-05-01

In this paper we explore the integration of different factors to understand, predict and control ecological invasions, through a general cellular automaton model especially developed. The model includes life history traits of several species in a modular structure interacting multiple cellular automata. We performed simulations using field values corresponding to the exotic Gleditsia triacanthos and native co-dominant trees in a montane area. Presence of G. triacanthos juvenile bank was a determinant condition for invasion success. Main parameters influencing invasion velocity were mean seed dispersal distance and minimum reproductive age. Seed production had a small influence on the invasion velocity. Velocities predicted by the model agreed well with estimations from field data. Values of population density predicted matched field values closely. The modular structure of the model, the explicit interaction between the invader and the native species, and the simplicity of parameters and transition rules are novel features of the model.

Black holes in a cubic Galileon universe

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

Babichev, E.; Charmousis, C.; Lehébel, A.

2016-09-01

We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches according to their effective cosmological constant. For two ofmore » these branches, we find families of black hole solutions, parametrized by the velocity of the scalar field. These spherically symmetric solutions, obtained numerically, are different from GR solutions close to the black hole event horizon, while they have the same de-Sitter asymptotic behavior. The velocity parameter represents black hole primary hair.« less

Ab Initio Crystal Field for Lanthanides.

PubMed

Ungur, Liviu; Chibotaru, Liviu F

2017-03-13

An ab initio methodology for the first-principle derivation of crystal-field (CF) parameters for lanthanides is described. The methodology is applied to the analysis of CF parameters in [Tb(Pc) 2 ] - (Pc=phthalocyanine) and Dy 4 K 2 ([Dy 4 K 2 O(OtBu) 12 ]) complexes, and compared with often used approximate and model descriptions. It is found that the application of geometry symmetrization, and the use of electrostatic point-charge and phenomenological CF models, lead to unacceptably large deviations from predictions based on ab initio calculations for experimental geometry. It is shown how the predictions of standard CASSCF (Complete Active Space Self-Consistent Field) calculations (with 4f orbitals in the active space) can be systematically improved by including effects of dynamical electronic correlation (CASPT2 step) and by admixing electronic configurations of the 5d shell. This is exemplified for the well-studied Er-trensal complex (H 3 trensal=2,2',2"-tris(salicylideneimido)trimethylamine). The electrostatic contributions to CF parameters in this complex, calculated with true charge distributions in the ligands, yield less than half of the total CF splitting, thus pointing to the dominant role of covalent effects. This analysis allows the conclusion that ab initio crystal field is an essential tool for the decent description of lanthanides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum model of a hysteresis in a single-domain magnetically soft ferromagnetic

NASA Astrophysics Data System (ADS)

Ignatiev, V. K.; Lebedev, N. G.; Orlov, A. A.

2018-01-01

A quantum model of a single-domain magnetically soft ferromagnetic is proposed. The α-Fe crystal in a state of the saturation magnetization and a variable magnetic field is considered as a sample. The method of an effective Hamiltonian, including the operators of the Zeeman energy, the spin-orbit interaction and the interaction with the crystal field, is used in the model. An expansion of trial single-electron wave function in a series in small parameter of the spin-orbit interaction is suggested to account for the magnetic anisotropy. Within the framework of the Heisenberg representation, the nonlinear equations of motion for the magnetization and the orbital moment of single domain are obtained. Parameters of the modelling Hamiltonian are found from a comparison with experimental data on the magnetic anisotropy of iron. A phenomenological term of the magnetic friction is introduced into equation of the magnetization motion. Nonlinear equations are solved numerically by the Runge-Kutta method. A dependence of the single domain magnetization on magnetic field intensity has a characteristic form of a hysteresis loop which parameters are quantitatively coordinated with experimental data of researches of magnetic properties of nanoparticles of iron and iron oxide. The method is extended for modelling the magnetization dynamics of multi-domain ferromagnetic in the approximation of a strong crystal field.

Protein labeling reactions in electrochemical microchannel flow: Numerical simulation and uncertainty propagation

NASA Astrophysics Data System (ADS)

Debusschere, Bert J.; Najm, Habib N.; Matta, Alain; Knio, Omar M.; Ghanem, Roger G.; Le Maître, Olivier P.

2003-08-01

This paper presents a model for two-dimensional electrochemical microchannel flow including the propagation of uncertainty from model parameters to the simulation results. For a detailed representation of electroosmotic and pressure-driven microchannel flow, the model considers the coupled momentum, species transport, and electrostatic field equations, including variable zeta potential. The chemistry model accounts for pH-dependent protein labeling reactions as well as detailed buffer electrochemistry in a mixed finite-rate/equilibrium formulation. Uncertainty from the model parameters and boundary conditions is propagated to the model predictions using a pseudo-spectral stochastic formulation with polynomial chaos (PC) representations for parameters and field quantities. Using a Galerkin approach, the governing equations are reformulated into equations for the coefficients in the PC expansion. The implementation of the physical model with the stochastic uncertainty propagation is applied to protein-labeling in a homogeneous buffer, as well as in two-dimensional electrochemical microchannel flow. The results for the two-dimensional channel show strong distortion of sample profiles due to ion movement and consequent buffer disturbances. The uncertainty in these results is dominated by the uncertainty in the applied voltage across the channel.

Application of the precipitation-runoff model in the Warrior coal field, Alabama

USGS Publications Warehouse

Kidd, Robert E.; Bossong, C.R.

1987-01-01

A deterministic precipitation-runoff model, the Precipitation-Runoff Modeling System, was applied in two small basins located in the Warrior coal field, Alabama. Each basin has distinct geologic, hydrologic, and land-use characteristics. Bear Creek basin (15.03 square miles) is undisturbed, is underlain almost entirely by consolidated coal-bearing rocks of Pennsylvanian age (Pottsville Formation), and is drained by an intermittent stream. Turkey Creek basin (6.08 square miles) contains a surface coal mine and is underlain by both the Pottsville Formation and unconsolidated clay, sand, and gravel deposits of Cretaceous age (Coker Formation). Aquifers in the Coker Formation sustain flow through extended rainless periods. Preliminary daily and storm calibrations were developed for each basin. Initial parameter and variable values were determined according to techniques recommended in the user's manual for the modeling system and through field reconnaissance. Parameters with meaningful sensitivity were identified and adjusted to match hydrograph shapes and to compute realistic water year budgets. When the developed calibrations were applied to data exclusive of the calibration period as a verification exercise, results were comparable to those for the calibration period. The model calibrations included preliminary parameter values for the various categories of geology and land use in each basin. The parameter values for areas underlain by the Pottsville Formation in the Bear Creek basin were transferred directly to similar areas in the Turkey Creek basin, and these parameter values were held constant throughout the model calibration. Parameter values for all geologic and land-use categories addressed in the two calibrations can probably be used in ungaged basins where similar conditions exist. The parameter transfer worked well, as a good calibration was obtained for Turkey Creek basin.

Application of parametric equations of motion to study the laser induced multiphoton dissociation of H2+ in intense laser field.

PubMed

Kalita, Dhruba J; Rao, Akshay; Rajvanshi, Ishir; Gupta, Ashish K

2011-06-14

We have applied parametric equations of motion (PEM) to study photodissociation dynamics of H(2)(+). The resonances are extracted using smooth exterior scaling method. This is the first application of PEM to non-Hermitian Hamiltonian that includes resonances and the continuum. Here, we have studied how the different resonance states behave with respect to the change in field amplitude. The advantage of this method is that one can easily trace the different states that are changing as the field parameter changes.

A new test statistic for climate models that includes field and spatial dependencies using Gaussian Markov random fields

DOE PAGES

Nosedal-Sanchez, Alvaro; Jackson, Charles S.; Huerta, Gabriel

2016-07-20

A new test statistic for climate model evaluation has been developed that potentially mitigates some of the limitations that exist for observing and representing field and space dependencies of climate phenomena. Traditionally such dependencies have been ignored when climate models have been evaluated against observational data, which makes it difficult to assess whether any given model is simulating observed climate for the right reasons. The new statistic uses Gaussian Markov random fields for estimating field and space dependencies within a first-order grid point neighborhood structure. We illustrate the ability of Gaussian Markov random fields to represent empirical estimates of fieldmore » and space covariances using "witch hat" graphs. We further use the new statistic to evaluate the tropical response of a climate model (CAM3.1) to changes in two parameters important to its representation of cloud and precipitation physics. Overall, the inclusion of dependency information did not alter significantly the recognition of those regions of parameter space that best approximated observations. However, there were some qualitative differences in the shape of the response surface that suggest how such a measure could affect estimates of model uncertainty.« less

A new test statistic for climate models that includes field and spatial dependencies using Gaussian Markov random fields

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

Nosedal-Sanchez, Alvaro; Jackson, Charles S.; Huerta, Gabriel

A new test statistic for climate model evaluation has been developed that potentially mitigates some of the limitations that exist for observing and representing field and space dependencies of climate phenomena. Traditionally such dependencies have been ignored when climate models have been evaluated against observational data, which makes it difficult to assess whether any given model is simulating observed climate for the right reasons. The new statistic uses Gaussian Markov random fields for estimating field and space dependencies within a first-order grid point neighborhood structure. We illustrate the ability of Gaussian Markov random fields to represent empirical estimates of fieldmore » and space covariances using "witch hat" graphs. We further use the new statistic to evaluate the tropical response of a climate model (CAM3.1) to changes in two parameters important to its representation of cloud and precipitation physics. Overall, the inclusion of dependency information did not alter significantly the recognition of those regions of parameter space that best approximated observations. However, there were some qualitative differences in the shape of the response surface that suggest how such a measure could affect estimates of model uncertainty.« less

Non-extensive entropy and properties of polaron in RbCl delta quantum dot under an applied electric field and Coulombic impurity

NASA Astrophysics Data System (ADS)

Tiotsop, M.; Fotue, A. J.; Fotsin, H. B.; Fai, L. C.

2017-08-01

Bound polaron in RbCl delta quantum dot under electric field and Coulombic impurity were considered. The ground and first excited state energy were derived by employing Pekar variational and unitary transformation methods. Applying Fermi golden rule, the expression of temperature and polaron lifetime were derived. The decoherence was studied trough the Tsallis entropy. Results shows that decreasing (or increasing) the lifetime increases (or decreases) the temperature and delta parameter (electric field strength and hydrogenic impurity). This suggests that to accelerate quantum transition in nanostructure, temperature and delta have to be enhanced. The improvement of electric field and coulomb parameter, increases the lifetime of the delta quantum dot qubit. Energy spectrum of polaron increases with increase in temperature, electric field strength, Coulomb parameter, delta parameter, and polaronic radius. The control of the delta quantum dot energies can be done via the electric field, coulomb impurity, and delta parameter. Results also show that the non-extensive entropy is an oscillatory function of time. With the enhancement of delta parameter, non-extensive parameter, Coulombic parameter, and electric field strength, the entropy has a sinusoidal increase behavior with time. With the study of decoherence through the Tsallis entropy, it may be advised that to have a quantum system with efficient transmission of information, the non-extensive and delta parameters need to be significant. The study of the probability density showed an increase from the boundary to the center of the dot where it has its maximum value and oscillates with period T0 = ℏ / ΔE with the tunneling of the delta parameter, electric field strength, and Coulombic parameter. The results may be very helpful in the transmission of information in nanostructures and control of decoherence

Refractive and relativistic effects on ITER low field side reflectometer design.

PubMed

Wang, G; Rhodes, T L; Peebles, W A; Harvey, R W; Budny, R V

2010-10-01

The ITER low field side reflectometer faces some unique design challenges, among which are included the effect of relativistic electron temperatures and refraction of probing waves. This paper utilizes GENRAY, a 3D ray tracing code, to investigate these effects. Using a simulated ITER operating scenario, characteristics of the reflected millimeter waves after return to the launch plane are quantified as a function of a range of design parameters, including antenna height, antenna diameter, and antenna radial position. Results for edge/SOL measurement with both O- and X-mode polarizations using proposed antennas are reported.

The effect of the hot oxygen corona on the interaction of the solar wind with Venus

NASA Technical Reports Server (NTRS)

Belotserkovskii, O. M.; Mitnitskii, V. IA.; Breus, T. K.; Krymskii, A. M.; Nagy, A. F.

1987-01-01

A numerical gasdynamic model, which includes the effects of mass loading of the shocked solar wind, was used to calculate the density and magnetic field variations in the magnetosheath of Venus. These calculations were carried out for conditions corresponding to a specific orbit of the Pioneer Venus Orbiter (PVO orbit 582). A comparison of the model predictions and the measured shock position, density and magnetic field values showed a reasonable agreement, indicating that a gasdynamic model that includes the effects of mass loading can be used to predict these parameters.

The effect of the hot oxygen corona on the interaction of the solar wind with Venus

NASA Astrophysics Data System (ADS)

Belotserkovskii, O. M.; Breus, T. K.; Krymskii, A. M.; Mitnitskii, V. Ya.; Nagey, A. F.; Gombosi, T. I.

1987-05-01

A numerical gas dynamic model, which includes the effects of mass loading of the shocked solar wind, was used to calculate the density and magnetic field variations in the magnetosheath of Venus. These calculations were carried out for conditions corresponding to a specific orbit of the Pioneer Venus Orbiter (PVO orbit 582). A comparison of the model predictions and the measured shock position, density and magnetic field values showed a reasonable agreement, indicating that a gas dynamic model that includes the effects of mass loading can be used to predict these parameters.

Comparison of resistive MHD simulations and experimental CHI discharges in NSTX

NASA Astrophysics Data System (ADS)

Hooper, E. B.; Sovinec, C. R.; Raman, R.; Fatima, F.

2013-10-01

Resistive MHD simulations using NIMROD simulate CHI discharges for NSTX startup plasmas. Quantitative comparison with experiment ensures that the simulation physics includes a minimal physics set needed to extend the simulations to new experiments, e.g. NSTX-U. Important are time-varying vacuum magnetic field, ohmic heating, thermal transport, impurity radiation, and spatially-varying plasma parameters including density. Equilibria are compared with experimental injector currents, voltages and parameters including toroidal current, photographs of emitted light and measurements of midplane temperature profiles, radiation and surface heating. Initial results demonstrate that adjusting impurity radiation and cross-field transport yields temperatures and injected-current channel widths similar to experiment. These determine the plasma resistance, feeding back to the impedance on the injector power supply. Work performed under the auspices of the U.S. Department of Energy under contracts DE-AC52-07NA27344 at LLNL and DE-AC02-09CH11466 at PPPL, and grants DE-FC02-05ER54813 at PSI Center (U. Wisc.) and DOE-FG02-12ER55115 (at Princeton U.).

Magnetohydrodynamic peristaltic motion of a Newtonian fluid through porous walls through suction and injection

NASA Astrophysics Data System (ADS)

Sivaiah, R.; Hemadri Reddy, R.

2017-11-01

In this paper, we investigate the peristaltic transport of a conducting Newtonian fluid bounded by permeable walls with suction and injection moving with constant velocity of the wave in the wave frame of reference under the consideration of long wavelength and low Reynolds number. The analytical solution for the velocity field, pressure gradient and the frictional force are obtained. The effect of suction/injection parameter, amplitude ratio and the permeability parameter including slip on the flow quantities are discussed graphically. It is found that the greater the suction/injection parameter, the smaller the pressure rise against the pump works. Further, the pressure rise increases with increasing Magnetic parameter.

Assessing performance of feedlot operations using epidemiology.

PubMed

Corbin, Marilyn J; Griffin, Dee

2006-03-01

The progressive feedlot veterinarian must be well versed not only in individual production animal medicine, but also in population-based medicine. Feedlot health programs must be goal oriented, and evaluation of these goals is accomplished through diligent use of record systems and analytic evaluation of these record systems. Basic feedlot monitoring parameters include health and economic parameters in addition to the use of bench marking parameters between and among feed yards. When these parameters have significant changes, steps should be initiated to begin field investigations. Feedlot epidemiology uses several novel applications such as partial budgeting, risk assessment, and packing plant audits to provide scientifically sound and economically feasible solutions for the feeding industry.

An analysis of sensitivity of CLIMEX parameters in mapping species potential distribution and the broad-scale changes observed with minor variations in parameters values: an investigation using open-field Solanum lycopersicum and Neoleucinodes elegantalis as an example

NASA Astrophysics Data System (ADS)

da Silva, Ricardo Siqueira; Kumar, Lalit; Shabani, Farzin; Picanço, Marcelo Coutinho

2018-04-01

A sensitivity analysis can categorize levels of parameter influence on a model's output. Identifying parameters having the most influence facilitates establishing the best values for parameters of models, providing useful implications in species modelling of crops and associated insect pests. The aim of this study was to quantify the response of species models through a CLIMEX sensitivity analysis. Using open-field Solanum lycopersicum and Neoleucinodes elegantalis distribution records, and 17 fitting parameters, including growth and stress parameters, comparisons were made in model performance by altering one parameter value at a time, in comparison to the best-fit parameter values. Parameters that were found to have a greater effect on the model results are termed "sensitive". Through the use of two species, we show that even when the Ecoclimatic Index has a major change through upward or downward parameter value alterations, the effect on the species is dependent on the selection of suitability categories and regions of modelling. Two parameters were shown to have the greatest sensitivity, dependent on the suitability categories of each species in the study. Results enhance user understanding of which climatic factors had a greater impact on both species distributions in our model, in terms of suitability categories and areas, when parameter values were perturbed by higher or lower values, compared to the best-fit parameter values. Thus, the sensitivity analyses have the potential to provide additional information for end users, in terms of improving management, by identifying the climatic variables that are most sensitive.

Including gauge-group parameters into the theory of interactions: an alternative mass-generating mechanism for gauge fields

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

Aldaya, V.; Lopez-Ruiz, F. F.; Sanchez-Sastre, E.

2006-11-03

We reformulate the gauge theory of interactions by introducing the gauge group parameters into the model. The dynamics of the new 'Goldstone-like' bosons is accomplished through a non-linear {sigma}-model Lagrangian. They are minimally coupled according to a proper prescription which provides mass terms to the intermediate vector bosons without spoiling gauge invariance. The present formalism is explicitly applied to the Standard Model of electroweak interactions.

Structure-Function Correlation Using Confocal Laser Ophthalmoscope in Primary Open-Angle Glaucoma and Pseudoexfoliative Glaucoma.

PubMed

Pappas, Theofanis; Founti, Panayiota; Yin, Xiang Jun; Koskosas, Archimidis; Anastasopoulos, Eleftherios; Salonikiou, Angeliki; Kilintzis, Vasilios; Antoniadis, Antonios; Ziakas, Nikolaos; Topouzis, Fotis

2016-04-01

To compare Heidelberg Retina Tomograph (HRT) optic disc parameters and structure-function correlation between primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEXG). Prospective, observation case series. A total of 54 POAG and 33 PEXG cases, consecutively recruited from a University Glaucoma Service, underwent a comprehensive ophthalmic examination, including HRT optic disc imaging. Glaucoma definition required the presence of both structural and functional damage. One eye per subject was included in the analysis. T test, Mann-Whitney U test, and analysis of covariance were used to compare HRT parameters between POAG and PEXG, adjusting for age, mean deviation (MD) in the visual field, intraocular pressure, and disc area. The correlation between HRT and MD was assessed in each group. Cup area (P=0.048), height variation contour (P=0.016), and cup/disc area ratio (P=0.023) were higher in POAG, whereas the mean retinal nerve fiber layer thickness (P=0.048), retinal nerve fiber layer cross-section area (P=0.044), and rim area (P=0.048) were lower in POAG, compared with PEXG. The correlation of HRT parameters with MD was significant only in the POAG group. At a similar level of functional damage, POAG subjects presented with more pronounced structural damage than PEXG subjects. The correlation between HRT and visual field parameters was more evident in POAG, compared with PEXG.

Nano-optical scan probes: Opening doors to previously-inaccessible parameter spaces

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

Schuck, James

2014-06-08

I will discuss recent progress on new near-field probe geometries, including the “campanile” geometry, which has been used in recent hyperspectral imaging experiments, providing nanoscale spectral information distinct from what is obtained with other methods. Article not available.

Multisite EPR oximetry from multiple quadrature harmonics.

PubMed

Ahmad, R; Som, S; Johnson, D H; Zweier, J L; Kuppusamy, P; Potter, L C

2012-01-01

Multisite continuous wave (CW) electron paramagnetic resonance (EPR) oximetry using multiple quadrature field modulation harmonics is presented. First, a recently developed digital receiver is used to extract multiple harmonics of field modulated projection data. Second, a forward model is presented that relates the projection data to unknown parameters, including linewidth at each site. Third, a maximum likelihood estimator of unknown parameters is reported using an iterative algorithm capable of jointly processing multiple quadrature harmonics. The data modeling and processing are applicable for parametric lineshapes under nonsaturating conditions. Joint processing of multiple harmonics leads to 2-3-fold acceleration of EPR data acquisition. For demonstration in two spatial dimensions, both simulations and phantom studies on an L-band system are reported. Copyright © 2011 Elsevier Inc. All rights reserved.

Experimental and Numerical Study of Drift Alfv'en Waves in LAPD

NASA Astrophysics Data System (ADS)

Friedman, Brett; Popovich, P.; Carter, T. A.; Auerbach, D.; Schaffner, D.

2009-11-01

We present a study of drift Alfv'en waves in linear geometry using experiments in the Large Plasma Device (LAPD) at UCLA and simulations from the Boundary Turbulence code (BOUT). BOUT solves the 3D time evolution of plasma parameters and turbulence using Braginskii fluid equations. First, we present a verification study of linear drift Alfven wave physics in BOUT, which has been modified to simulate the cylindrical geometry of LAPD. Second, we present measurements of density and magnetic field fluctuations in the LAPD plasma and the correlation of these fluctuations as a function of plasma parameters, including strength of the background field and discharge current. We also compare the measurements to nonlinear BOUT calculations using experimental LAPD profiles.

SU-E-T-473: A Patient-Specific QC Paradigm Based On Trajectory Log Files and DICOM Plan Files

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

DeMarco, J; McCloskey, S; Low, D

Purpose: To evaluate a remote QC tool for monitoring treatment machine parameters and treatment workflow. Methods: The Varian TrueBeamTM linear accelerator is a digital machine that records machine axis parameters and MLC leaf positions as a function of delivered monitor unit or control point. This information is saved to a binary trajectory log file for every treatment or imaging field in the patient treatment session. A MATLAB analysis routine was developed to parse the trajectory log files for a given patient, compare the expected versus actual machine and MLC positions as well as perform a cross-comparison with the DICOM-RT planmore » file exported from the treatment planning system. The parsing routine sorts the trajectory log files based on the time and date stamp and generates a sequential report file listing treatment parameters and provides a match relative to the DICOM-RT plan file. Results: The trajectory log parsing-routine was compared against a standard record and verify listing for patients undergoing initial IMRT dosimetry verification and weekly and final chart QC. The complete treatment course was independently verified for 10 patients of varying treatment site and a total of 1267 treatment fields were evaluated including pre-treatment imaging fields where applicable. In the context of IMRT plan verification, eight prostate SBRT plans with 4-arcs per plan were evaluated based on expected versus actual machine axis parameters. The average value for the maximum RMS MLC error was 0.067±0.001mm and 0.066±0.002mm for leaf bank A and B respectively. Conclusion: A real-time QC analysis program was tested using trajectory log files and DICOM-RT plan files. The parsing routine is efficient and able to evaluate all relevant machine axis parameters during a patient treatment course including MLC leaf positions and table positions at time of image acquisition and during treatment.« less

All-Atom Internal Coordinate Mechanics (ICM) Force Field for Hexopyranoses and Glycoproteins.

PubMed

Arnautova, Yelena A; Abagyan, Ruben; Totrov, Maxim

2015-05-12

We present an extension of the all-atom internal-coordinate force field, ICMFF, that allows for simulation of heterogeneous systems including hexopyranose saccharides and glycan chains in addition to proteins. A library of standard glycan geometries containing α- and β-anomers of the most common hexapyranoses, i.e., d-galactose, d-glucose, d-mannose, d-xylose, l-fucose, N -acetylglucosamine, N -acetylgalactosamine, sialic, and glucuronic acids, is created based on the analysis of the saccharide structures reported in the Cambridge Structural Database. The new force field parameters include molecular electrostatic potential-derived partial atomic charges and the torsional parameters derived from quantum mechanical data for a collection of minimal molecular fragments and related molecules. The ϕ/ψ torsional parameters for different types of glycosidic linkages are developed using model compounds containing the key atoms in the full carbohydrates, i.e., glycosidic-linked tetrahydropyran-cyclohexane dimers. Target data for parameter optimization include two-dimensional energy surfaces corresponding to the ϕ/ψ glycosidic dihedral angles in the disaccharide analogues, as determined by quantum mechanical MP2/6-31G** single-point energies on HF/6-31G** optimized structures. To achieve better agreement with the observed geometries of glycosidic linkages, the bond angles at the O-linkage atoms are added to the internal variable set and the corresponding bond bending energy term is parametrized using quantum mechanical data. The resulting force field is validated on glycan chains of 1-12 residues from a set of high-resolution X-ray glycoprotein structures based on heavy atom root-mean-square deviations of the lowest-energy glycan conformations generated by the biased probability Monte Carlo (BPMC) molecular mechanics simulations from the native structures. The appropriate BPMC distributions for monosaccharide-monosaccharide and protein-glycan linkages are derived from the extensive analysis of conformational properties of glycoprotein structures reported in the Protein Data Bank. Use of the BPMC search leads to significant improvements in sampling efficiency for glycan simulations. Moreover, good agreement with the X-ray glycoprotein structures is achieved for all glycan chain lengths. Thus, average/median RMSDs are 0.81/0.68 Å for one-residue glycans and 1.32/1.47 Å for three-residue glycans. RMSD from the native structure for the lowest-energy conformation of the 12-residue glycan chain (PDB ID 3og2) is 1.53 Å. Additionally, results obtained for free short oligosaccharides using the new force field are in line with the available experimental data, i.e., the most populated conformations in solution are predicted to be the lowest energy ones. The newly developed parameters allow for the accurate modeling of linear and branched hexopyranose glycosides in heterogeneous systems.

In-field experiment of electro-hydraulic tillage depth draft-position mixed control on tractor

NASA Astrophysics Data System (ADS)

Han, Jiangyi; Xia, Changgao; Shang, Gaogao; Gao, Xiang

2017-12-01

The soil condition and condition of the plow affect the tillage resistance and the maximum traction of tractor. In order to improve the adaptability of tractor tillage depth control, a multi-parameter control strategy is proposed that included tillage depth target, draft force aim and draft-position mixed ratio. In the strategy, the resistance coefficient was used to adjust the draft force target. Then, based on a JINMA1204 tractor, the electro-hydraulic hitch prototype is constructed that could set control parameters.. The fuzzy controller of draft-position mixed control is designed. After that, in-field experiments of position control was carried on, and the result of experiment shows the error of tillage depth was less than ±20mm. The experiment of draft-position control shown that the draft force and the tillage depth could be adjust by multi-parameter such as tillage depth, resistance coefficient and draft-position mixed coefficient. So that, the multi-parameter control strategy could improve the adaptability of tillage depth control in various soils and plow condition.

Mixed convection and heat generation/absorption aspects in MHD flow of tangent-hyperbolic nanoliquid with Newtonian heat/mass transfer

NASA Astrophysics Data System (ADS)

Qayyum, Sajid; Hayat, Tasawar; Shehzad, Sabir Ali; Alsaedi, Ahmed

2018-03-01

This article concentrates on the magnetohydrodynamic (MHD) stagnation point flow of tangent hyperbolic nanofluid in the presence of buoyancy forces. Flow analysis caused due to stretching surface. Characteristics of heat transfer are examined under the influence of thermal radiation and heat generation/absorption. Newtonian conditions for heat and mass transfer are employed. Nanofluid model includes Brownian motion and thermophoresis. The governing nonlinear partial differential systems of the problem are transformed into a systems of nonlinear ordinary differential equations through appropriate variables. Impact of embedded parameters on the velocity, temperature and nanoparticle concentration fields are presented graphically. Numerical computations are made to obtain the values of skin friction coefficient, local Nusselt and Sherwood numbers. It is concluded that velocity field enhances in the frame of mixed convection parameter while reverse situation is observed due to power law index. Effect of Brownian motion parameter on the temperature and heat transfer rate is quite reverse. Moreover impact of solutal conjugate parameter on the concentration and local Sherwood number is quite similar.

Optimization Design of Bipolar Plate Flow Field in PEM Stack

NASA Astrophysics Data System (ADS)

Wen, Ming; He, Kanghao; Li, Peilong; Yang, Lei; Deng, Li; Jiang, Fei; Yao, Yong

2017-12-01

A new design of bipolar plate flow field in proton exchange membrane (PEM) stack was presented to develop a high-performance transfer efficiency of the two-phase flow. Two different flow fields were studied by using numerical simulations and the performance of the flow fields was presented. the hydrodynamic properties include pressure gap between inlet and outlet, the Reynold’s number of the two types were compared based on the Navier-Stokes equations. Computer aided optimization software was implemented in the design of experiments of the preferable flow field. The design of experiments (DOE) for the favorable concept was carried out to study the hydrodynamic properties when changing the design parameters of the bipolar plate.

Phenotypic Intratumoral Heterogeneity of Endometrial Carcinomas.

PubMed

Silva, Cátia; Pires-Luís, Ana S; Rocha, Eduardo; Bartosch, Carla; Lopes, José M

2018-03-01

Intratumoral heterogeneity has been shown to play an important role in diagnostic accuracy, development of treatment resistance, and prognosis of cancer patients. Recent studies have proposed quantitative measurement of phenotypic intratumoral heterogeneity, but no study is yet available in endometrial carcinomas. In our study we evaluated the phenotypic intratumoral heterogeneity of a consecutive series of 10 endometrial carcinomas using measures of dispersion and diversity. Morphometric architectural (%tumor cells, %solid tumor, %differentiated tumor, and %lumens) and nuclear [volume-weighted mean nuclear volume ((Equation is included in full-text article.))] parameters, as well as estrogen receptor, progesterone receptor, p53, vimentin, and beta-catenin immunoexpression (H-score) were digitally analyzed in 20 microscopic fields per carcinoma. Quantitative measures of intratumoral heterogeneity included coefficient of variation (CV) and relative quadratic entropy (rQE). In each endometrial carcinoma there was slight variation of architecture from field to field, resulting in globally low levels of heterogeneity measures (mean CV %tumor cells: 0.10, %solid tumor: 0.73, %differentiated tumor: 0.19, %lumens: 0.61 and mean rQE %tumor cells: 18.5, %solid tumor: 20.3, %differentiated tumor: 25.6, %lumens: 21.8). Nuclear intratumoral heterogeneity was also globally low (mean (Equation is included in full-text article.)CV: 0.23 and rQE: 27.3), but significantly higher than the heterogeneity of architectural parameters within most carcinomas. In general, there was low to moderate variability of immunoexpression markers within each carcinoma, but estrogen receptor (mean CV: 0.56 and rQE: 46.2) and progesterone receptor (mean CV: 0.60 and rQE: 39.3) displayed the highest values of heterogeneity measures. Intratumoral heterogeneity of immunoexpression was significantly higher than that observed for morphometric parameters. In conclusion, our study indicates that endometrial carcinomas present a variable but predominantly low degree of phenotypic intratumoral heterogeneity.

Topological nature of nonlinear optical effects in solids.

PubMed

Morimoto, Takahiro; Nagaosa, Naoto

2016-05-01

There are a variety of nonlinear optical effects including higher harmonic generations, photovoltaic effects, and nonlinear Kerr rotations. They are realized by strong light irradiation to materials that results in nonlinear polarizations in the electric field. These are of great importance in studying the physics of excited states of the system as well as for applications to optical devices and solar cells. Nonlinear properties of materials are usually described by nonlinear susceptibilities, which have complex expressions including many matrix elements and energy denominators. On the other hand, a nonequilibrium steady state under an electric field periodic in time has a concise description in terms of the Floquet bands of electrons dressed by photons. We show theoretically, using the Floquet formalism, that various nonlinear optical effects, such as the shift current in noncentrosymmetric materials, photovoltaic Hall response, and photo-induced change of order parameters under the continuous irradiation of monochromatic light, can be described in a unified fashion by topological quantities involving the Berry connection and Berry curvature. We found that vector fields defined with the Berry connections in the space of momentum and/or parameters govern the nonlinear responses. This topological view offers a route to designing nonlinear optical materials.

Theory and in vivo application of electroporative gene delivery.

PubMed

Somiari, S; Glasspool-Malone, J; Drabick, J J; Gilbert, R A; Heller, R; Jaroszeski, M J; Malone, R W

2000-09-01

Efficient and safe methods for delivering exogenous genetic material into tissues must be developed before the clinical potential of gene therapy will be realized. Recently, in vivo electroporation has emerged as a leading technology for developing nonviral gene therapies and nucleic acid vaccines (NAV). Electroporation (EP) involves the application of pulsed electric fields to cells to enhance cell permeability, resulting in exogenous polynucleotide transit across the cytoplasmic membrane. Similar pulsed electrical field treatments are employed in a wide range of biotechnological processes including in vitro EP, hybridoma production, development of transgenic animals, and clinical electrochemotherapy. Electroporative gene delivery studies benefit from well-developed literature that may be used to guide experimental design and interpretation. Both theory and experimental analysis predict that the critical parameters governing EP efficacy include cell size and field strength, duration, frequency, and total number of applied pulses. These parameters must be optimized for each tissue in order to maximize gene delivery while minimizing irreversible cell damage. By providing an overview of the theory and practice of electroporative gene transfer, this review intends to aid researchers that wish to employ the method for preclinical and translational gene therapy, NAV, and functional genomic research.

Topological nature of nonlinear optical effects in solids

PubMed Central

Morimoto, Takahiro; Nagaosa, Naoto

2016-01-01

There are a variety of nonlinear optical effects including higher harmonic generations, photovoltaic effects, and nonlinear Kerr rotations. They are realized by strong light irradiation to materials that results in nonlinear polarizations in the electric field. These are of great importance in studying the physics of excited states of the system as well as for applications to optical devices and solar cells. Nonlinear properties of materials are usually described by nonlinear susceptibilities, which have complex expressions including many matrix elements and energy denominators. On the other hand, a nonequilibrium steady state under an electric field periodic in time has a concise description in terms of the Floquet bands of electrons dressed by photons. We show theoretically, using the Floquet formalism, that various nonlinear optical effects, such as the shift current in noncentrosymmetric materials, photovoltaic Hall response, and photo-induced change of order parameters under the continuous irradiation of monochromatic light, can be described in a unified fashion by topological quantities involving the Berry connection and Berry curvature. We found that vector fields defined with the Berry connections in the space of momentum and/or parameters govern the nonlinear responses. This topological view offers a route to designing nonlinear optical materials. PMID:27386523

Attitude-Independent Magnetometer Calibration for Spin-Stabilized Spacecraft

NASA Technical Reports Server (NTRS)

Natanson, Gregory

2005-01-01

The paper describes a three-step estimator to calibrate a Three-Axis Magnetometer (TAM) using TAM and slit Sun or star sensor measurements. In the first step, the Calibration Utility forms a loss function from the residuals of the magnitude of the geomagnetic field. This loss function is minimized with respect to biases, scale factors, and nonorthogonality corrections. The second step minimizes residuals of the projection of the geomagnetic field onto the spin axis under the assumption that spacecraft nutation has been suppressed by a nutation damper. Minimization is done with respect to various directions of the body spin axis in the TAM frame. The direction of the spin axis in the inertial coordinate system required for the residual computation is assumed to be unchanged with time. It is either determined independently using other sensors or included in the estimation parameters. In both cases all estimation parameters can be found using simple analytical formulas derived in the paper. The last step is to minimize a third loss function formed by residuals of the dot product between the geomagnetic field and Sun or star vector with respect to the misalignment angle about the body spin axis. The method is illustrated by calibrating TAM for the Fast Auroral Snapshot Explorer (FAST) using in-flight TAM and Sun sensor data. The estimated parameters include magnetic biases, scale factors, and misalignment angles of the spin axis in the TAM frame. Estimation of the misalignment angle about the spin axis was inconclusive since (at least for the selected time interval) the Sun vector was about 15 degrees from the direction of the spin axis; as a result residuals of the dot product between the geomagnetic field and Sun vectors were to a large extent minimized as a by-product of the second step.

Dynamic diagnostics of the error fields in tokamaks

NASA Astrophysics Data System (ADS)

Pustovitov, V. D.

2007-07-01

The error field diagnostics based on magnetic measurements outside the plasma is discussed. The analysed methods rely on measuring the plasma dynamic response to the finite-amplitude external magnetic perturbations, which are the error fields and the pre-programmed probing pulses. Such pulses can be created by the coils designed for static error field correction and for stabilization of the resistive wall modes, the technique developed and applied in several tokamaks, including DIII-D and JET. Here analysis is based on the theory predictions for the resonant field amplification (RFA). To achieve the desired level of the error field correction in tokamaks, the diagnostics must be sensitive to signals of several Gauss. Therefore, part of the measurements should be performed near the plasma stability boundary, where the RFA effect is stronger. While the proximity to the marginal stability is important, the absolute values of plasma parameters are not. This means that the necessary measurements can be done in the diagnostic discharges with parameters below the nominal operating regimes, with the stability boundary intentionally lowered. The estimates for ITER are presented. The discussed diagnostics can be tested in dedicated experiments in existing tokamaks. The diagnostics can be considered as an extension of the 'active MHD spectroscopy' used recently in the DIII-D tokamak and the EXTRAP T2R reversed field pinch.

Estimating thermal performance curves from repeated field observations

USGS Publications Warehouse

Childress, Evan; Letcher, Benjamin H.

2017-01-01

Estimating thermal performance of organisms is critical for understanding population distributions and dynamics and predicting responses to climate change. Typically, performance curves are estimated using laboratory studies to isolate temperature effects, but other abiotic and biotic factors influence temperature-performance relationships in nature reducing these models' predictive ability. We present a model for estimating thermal performance curves from repeated field observations that includes environmental and individual variation. We fit the model in a Bayesian framework using MCMC sampling, which allowed for estimation of unobserved latent growth while propagating uncertainty. Fitting the model to simulated data varying in sampling design and parameter values demonstrated that the parameter estimates were accurate, precise, and unbiased. Fitting the model to individual growth data from wild trout revealed high out-of-sample predictive ability relative to laboratory-derived models, which produced more biased predictions for field performance. The field-based estimates of thermal maxima were lower than those based on laboratory studies. Under warming temperature scenarios, field-derived performance models predicted stronger declines in body size than laboratory-derived models, suggesting that laboratory-based models may underestimate climate change effects. The presented model estimates true, realized field performance, avoiding assumptions required for applying laboratory-based models to field performance, which should improve estimates of performance under climate change and advance thermal ecology.

Magnetic properties of the synthetically charged neutral bosons

NASA Astrophysics Data System (ADS)

Hassan, Ahmed S.; Abbas, Abbas H.; El-Sherbini, Tharwat M.; Seif, Walaa M.

2018-07-01

In this paper, we conclude that BEC of synthetically charged bosons is possible and leads to several new and interesting phenomena. Thermal and magnetic properties of the system are investigated. The temperature dependence of the magnetic parameters, including the magnetization, magnetic susceptibility and the heat capacity at constant synthetic magnetic field are calculated. These properties are investigated for finite atoms number and synthetic magnetic field strength. We show that those properties, in particular Bose- Einstein transition temperature, depends upon the strength of the synthetic magnetic field. A diffuse condensation of the synthetically charged bosons appears for changing the synthetic field. The obtained results provide important magnetic properties.

Identification of corn fields using multidate radar data

NASA Technical Reports Server (NTRS)

Shanmugan, K. S.; Ulaby, F. T.; Narayanan, V.; Dobson, C.

1983-01-01

Airborne C- and L-band radar data acquired over a test site in western kansas were analyzed to determine corn-field identification accuracies obtainable using single-channel, multichannel, and multidate radar data. An automated pattern-recognition procedure was used to classify 144 fields into three categories: corn, pasture land, and bare soil (including wheat stubble and fallow). Corn fields were identified with accuracies ranging from 85 percent for single channel, single-date data to 100 percent for single-channel, multidate data. The effects of radar parameters such as frequency, polarization, and look angle as well as the effects of soil moisture on the classification accuracy are also presented.

Modeling of mid-infrared quantum cascade lasers: The role of temperature and operating field strength on the laser performance

NASA Astrophysics Data System (ADS)

Yousefvand, Hossein Reza

2017-07-01

In this paper a self-consistent numerical approach to study the temperature and bias dependent characteristics of mid-infrared (mid-IR) quantum cascade lasers (QCLs) is presented which integrates a number of quantum mechanical models. The field-dependent laser parameters including the nonradiative scattering times, the detuning and energy levels, the escape activation energy, the backfilling excitation energy and dipole moment of the optical transition are calculated for a wide range of applied electric fields by a self-consistent solution of Schrodinger-Poisson equations. A detailed analysis of performance of the obtained structure is carried out within a self-consistent solution of the subband population rate equations coupled with carrier coherent transport equations through the sequential resonant tunneling, by taking into account the temperature and bias dependency of the relevant parameters. Furthermore, the heat transfer equation is included in order to calculate the carrier temperature inside the active region levels. This leads to a compact predictive model to analyze the temperature and electric field dependent characteristics of the mid-IR QCLs such as the light-current (L-I), electric field-current (F-I) and core temperature-electric field (T-F) curves. For a typical mid-IR QCL, a good agreement was found between the simulated temperature-dependent L-I characteristic and experimental data, which confirms validity of the model. It is found that the main characteristics of the device such as output power and turn-on delay time are degraded by interplay between the temperature and Stark effects.

Links between the charge model and bonded parameter force constants in biomolecular force fields

NASA Astrophysics Data System (ADS)

Cerutti, David S.; Debiec, Karl T.; Case, David A.; Chong, Lillian T.

2017-10-01

The ff15ipq protein force field is a fixed charge model built by automated tools based on the two charge sets of the implicitly polarized charge method: one set (appropriate for vacuum) for deriving bonded parameters and the other (appropriate for aqueous solution) for running simulations. The duality is intended to treat water-induced electronic polarization with an understanding that fitting data for bonded parameters will come from quantum mechanical calculations in the gas phase. In this study, we compare ff15ipq to two alternatives produced with the same fitting software and a further expanded data set but following more conventional methods for tailoring bonded parameters (harmonic angle terms and torsion potentials) to the charge model. First, ff15ipq-Qsolv derives bonded parameters in the context of the ff15ipq solution phase charge set. Second, ff15ipq-Vac takes ff15ipq's bonded parameters and runs simulations with the vacuum phase charge set used to derive those parameters. The IPolQ charge model and associated protocol for deriving bonded parameters are shown to be an incremental improvement over protocols that do not account for the material phases of each source of their fitting data. Both force fields incorporating the polarized charge set depict stable globular proteins and have varying degrees of success modeling the metastability of short (5-19 residues) peptides. In this particular case, ff15ipq-Qsolv increases stability in a number of α -helices, correctly obtaining 70% helical character in the K19 system at 275 K and showing appropriately diminishing content up to 325 K, but overestimating the helical fraction of AAQAA3 by 50% or more, forming long-lived α -helices in simulations of a β -hairpin, and increasing the likelihood that the disordered p53 N-terminal peptide will also form a helix. This may indicate a systematic bias imparted by the ff15ipq-Qsolv parameter development strategy, which has the hallmarks of strategies used to develop other popular force fields, and may explain some of the need for manual corrections in this force fields' evolution. In contrast, ff15ipq-Vac incorrectly depicts globular protein unfolding in numerous systems tested, including Trp cage, villin, lysozyme, and GB3, and does not perform any better than ff15ipq or ff15ipq-Qsolv in tests on short peptides. We analyze the free energy surfaces of individual amino acid dipeptides and the electrostatic potential energy surfaces of each charge model to explain the differences.

Development of a field test method for total suspended solids analysis.

DOT National Transportation Integrated Search

2013-11-01

Total suspended solids (TSS) are all particles in water that will not pass through a glass fiber filter with a pore size less : than 2 m, including sediments, algae, nutrients, and metals. TSS is an important water quality parameter because of its ...

Generation of dynamo waves by spatially separated sources in the Earth and other celestial bodies

NASA Astrophysics Data System (ADS)

Popova, E.

2017-12-01

The amplitude and the spatial configuration of the planetary and stellar magnetic field can changing over the years. Celestial bodies can have cyclic, chaotic or unchanging in time magnetic activity which is connected with a dynamo mechanism. This mechanism is based on the consideration of the joint influence of the alpha-effect and differential rotation. Dynamo sources can be located at different depths (active layers) of the celestial body and can have different intensities. Application of this concept allows us to get different forms of solutions and some of which can include wave propagating inside the celestial body. We analytically showed that in the case of spatially separated sources of magnetic field each source generates a wave whose frequency depends on the physical parameters of its source. We estimated parameters of sources required for the generation nondecaying waves. We discus structure of such sources and matter motion (including meridional circulation) in the liquid outer core of the Earth and active layers of other celestial bodies.

Observability of ionospheric space-time structure with ISR: A simulation study

NASA Astrophysics Data System (ADS)

Swoboda, John; Semeter, Joshua; Zettergren, Matthew; Erickson, Philip J.

2017-02-01

The sources of error from electronically steerable array (ESA) incoherent scatter radar (ISR) systems are investigated both theoretically and with use of an open-source ISR simulator, developed by the authors, called Simulator for ISR (SimISR). The main sources of error incorporated in the simulator include statistical uncertainty, which arises due to nature of the measurement mechanism and the inherent space-time ambiguity from the sensor. SimISR can take a field of plasma parameters, parameterized by time and space, and create simulated ISR data at the scattered electric field (i.e., complex receiver voltage) level, subsequently processing these data to show possible reconstructions of the original parameter field. To demonstrate general utility, we show a number of simulation examples, with two cases using data from a self-consistent multifluid transport model. Results highlight the significant influence of the forward model of the ISR process and the resulting statistical uncertainty on plasma parameter measurements and the core experiment design trade-offs that must be made when planning observations. These conclusions further underscore the utility of this class of measurement simulator as a design tool for more optimal experiment design efforts using flexible ESA class ISR systems.

Drifting oscillations in axion monodromy

DOE PAGES

Flauger, Raphael; McAllister, Liam; Silverstein, Eva; ...

2017-10-31

In this paper, we study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effectsmore » of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. Finally, we use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.« less

Physical, Hydraulic, and Transport Properties of Sediments and Engineered Materials Associated with Hanford Immobilized Low-Activity Waste

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

Rockhold, Mark L.; Zhang, Z. F.; Meyer, Philip D.

2015-02-28

Current plans for treatment and disposal of immobilized low-activity waste (ILAW) from Hanford’s underground waste storage tanks include vitrification and storage of the glass waste form in a nearsurface disposal facility. This Integrated Disposal Facility (IDF) is located in the 200 East Area of the Hanford Central Plateau. Performance assessment (PA) of the IDF requires numerical modeling of subsurface flow and reactive transport processes over very long periods (thousands of years). The models used to predict facility performance require parameters describing various physical, hydraulic, and transport properties. This report provides updated estimates of physical, hydraulic, and transport properties and parametersmore » for both near- and far-field materials, intended for use in future IDF PA modeling efforts. Previous work on physical and hydraulic property characterization for earlier IDF PA analyses is reviewed and summarized. For near-field materials, portions of this document and parameter estimates are taken from an earlier data package. For far-field materials, a critical review is provided of methodologies used in previous data packages. Alternative methods are described and associated parameters are provided.« less

Simplified contaminant source depletion models as analogs of multiphase simulators

NASA Astrophysics Data System (ADS)

Basu, Nandita B.; Fure, Adrian D.; Jawitz, James W.

2008-04-01

Four simplified dense non-aqueous phase liquid (DNAPL) source depletion models recently introduced in the literature are evaluated for the prediction of long-term effects of source depletion under natural gradient flow. These models are simple in form (a power function equation is an example) but are shown here to serve as mathematical analogs to complex multiphase flow and transport simulators. The spill and subsequent dissolution of DNAPLs was simulated in domains having different hydrologic characteristics (variance of the log conductivity field = 0.2, 1 and 3) using the multiphase flow and transport simulator UTCHEM. The dissolution profiles were fitted using four analytical models: the equilibrium streamtube model (ESM), the advection dispersion model (ADM), the power law model (PLM) and the Damkohler number model (DaM). All four models, though very different in their conceptualization, include two basic parameters that describe the mean DNAPL mass and the joint variability in the velocity and DNAPL distributions. The variability parameter was observed to be strongly correlated with the variance of the log conductivity field in the ESM and ADM but weakly correlated in the PLM and DaM. The DaM also includes a third parameter that describes the effect of rate-limited dissolution, but here this parameter was held constant as the numerical simulations were found to be insensitive to local-scale mass transfer. All four models were able to emulate the characteristics of the dissolution profiles generated from the complex numerical simulator, but the one-parameter PLM fits were the poorest, especially for the low heterogeneity case.

Simplified contaminant source depletion models as analogs of multiphase simulators.

PubMed

Basu, Nandita B; Fure, Adrian D; Jawitz, James W

2008-04-28

Four simplified dense non-aqueous phase liquid (DNAPL) source depletion models recently introduced in the literature are evaluated for the prediction of long-term effects of source depletion under natural gradient flow. These models are simple in form (a power function equation is an example) but are shown here to serve as mathematical analogs to complex multiphase flow and transport simulators. The spill and subsequent dissolution of DNAPLs was simulated in domains having different hydrologic characteristics (variance of the log conductivity field=0.2, 1 and 3) using the multiphase flow and transport simulator UTCHEM. The dissolution profiles were fitted using four analytical models: the equilibrium streamtube model (ESM), the advection dispersion model (ADM), the power law model (PLM) and the Damkohler number model (DaM). All four models, though very different in their conceptualization, include two basic parameters that describe the mean DNAPL mass and the joint variability in the velocity and DNAPL distributions. The variability parameter was observed to be strongly correlated with the variance of the log conductivity field in the ESM and ADM but weakly correlated in the PLM and DaM. The DaM also includes a third parameter that describes the effect of rate-limited dissolution, but here this parameter was held constant as the numerical simulations were found to be insensitive to local-scale mass transfer. All four models were able to emulate the characteristics of the dissolution profiles generated from the complex numerical simulator, but the one-parameter PLM fits were the poorest, especially for the low heterogeneity case.

Three-dimensional time domain model of lightning including corona effects

NASA Technical Reports Server (NTRS)

Podgorski, Andrew S.

1991-01-01

A new 3-D lightning model that incorporates the effect of corona is described for the first time. The new model is based on a Thin Wire Time Domain Lightning (TWTDL) Code developed previously. The TWTDL Code was verified during the 1985 and 1986 lightning seasons by the measurements conducted at the 553 m CN Tower in Toronto, Ontario. The inclusion of corona in the TWTDL code allowed study of the corona effects on the lightning current parameters and the associated electric field parameters.

Phase diagram of the Shastry-Sutherland Kondo lattice model with classical localized spins: a variational calculation study

NASA Astrophysics Data System (ADS)

Shahzad, Munir; Sengupta, Pinaki

2017-08-01

We study the Shastry-Sutherland Kondo lattice model with additional Dzyaloshinskii-Moriya (DM) interactions, exploring the possible magnetic phases in its multi-dimensional parameter space. Treating the local moments as classical spins and using a variational ansatz, we identify the parameter ranges over which various common magnetic orderings are potentially stabilized. Our results reveal that the competing interactions result in a heightened susceptibility towards a wide range of spin configurations including longitudinal ferromagnetic and antiferromagnetic order, coplanar flux configurations and most interestingly, multiple non-coplanar configurations including a novel canted-flux state as the different Hamiltonian parameters like electron density, interaction strengths and degree of frustration are varied. The non-coplanar and non-collinear magnetic ordering of localized spins behave like emergent electromagnetic fields and drive unusual transport and electronic phenomena.

Joining direct and indirect inverse calibration methods to characterize karst, coastal aquifers

NASA Astrophysics Data System (ADS)

De Filippis, Giovanna; Foglia, Laura; Giudici, Mauro; Mehl, Steffen; Margiotta, Stefano; Negri, Sergio

2016-04-01

Parameter estimation is extremely relevant for accurate simulation of groundwater flow. Parameter values for models of large-scale catchments are usually derived from a limited set of field observations, which can rarely be obtained in a straightforward way from field tests or laboratory measurements on samples, due to a number of factors, including measurement errors and inadequate sampling density. Indeed, a wide gap exists between the local scale, at which most of the observations are taken, and the regional or basin scale, at which the planning and management decisions are usually made. For this reason, the use of geologic information and field data is generally made by zoning the parameter fields. However, pure zoning does not perform well in the case of fairly complex aquifers and this is particularly true for karst aquifers. In fact, the support of the hydraulic conductivity measured in the field is normally much smaller than the cell size of the numerical model, so it should be upscaled to a scale consistent with that of the numerical model discretization. Automatic inverse calibration is a valuable procedure to identify model parameter values by conditioning on observed, available data, limiting the subjective evaluations introduced with the trial-and-error technique. Many approaches have been proposed to solve the inverse problem. Generally speaking, inverse methods fall into two groups: direct and indirect methods. Direct methods allow determination of hydraulic conductivities from the groundwater flow equations which relate the conductivity and head fields. Indirect methods, instead, can handle any type of parameters, independently from the mathematical equations that govern the process, and condition parameter values and model construction on measurements of model output quantities, compared with the available observation data, through the minimization of an objective function. Both approaches have pros and cons, depending also on model complexity. For this reason, a joint procedure is proposed by merging both direct and indirect approaches, thus taking advantage of their strengths, first among them the possibility to get a hydraulic head distribution all over the domain, instead of a zonation. Pros and cons of such an integrated methodology, so far unexplored to the authors' knowledge, are derived after application to a highly heterogeneous karst, coastal aquifer located in southern Italy.

The Evolution of the Solar Magnetic Field: A Comparative Analysis of Two Models

NASA Astrophysics Data System (ADS)

McMichael, K. D.; Karak, B. B.; Upton, L.; Miesch, M. S.; Vierkens, O.

2017-12-01

Understanding the complexity of the solar magnetic cycle is a task that has plagued scientists for decades. However, with the help of computer simulations, we have begun to gain more insight into possible solutions to the plethora of questions inside the Sun. STABLE (Surface Transport and Babcock Leighton) is a newly developed 3D dynamo model that can reproduce features of the solar cycle. In this model, the tilted bipolar sunspots are formed on the surface (based on the toroidal field at the bottom of the convection zone) and then decay and disperse, producing the poloidal field. Since STABLE is a 3D model, it is able to solve the full induction equation in the entirety of the solar convection zone as well as incorporate many free parameters (such as spot depth and turbulent diffusion) which are difficult to observe. In an attempt to constrain some of these free parameters, we compare STABLE to a surface flux transport model called AFT (Advective Flux Transport) which solves the radial component of the magnetic field on the solar surface. AFT is a state-of-the-art surface flux transport model that has a proven record of being able to reproduce solar observations with great accuracy. In this project, we implement synthetic bipolar sunspots into both models, using identical surface parameters, and run the models for comparison. We demonstrate that the 3D structure of the sunspots in the interior and the vertical diffusion of the sunspot magnetic field play an important role in establishing the surface magnetic field in STABLE. We found that when a sufficient amount of downward magnetic pumping is included in STABLE, the surface magnetic field from this model becomes insensitive to the internal structure of the sunspot and more consistent with that of AFT.

FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME

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

Filippazzo, Joseph C.; Rice, Emily L.; Faherty, Jacqueline

We combine optical, near-infrared, and mid-infrared spectra and photometry to construct expanded spectral energy distributions for 145 field age (>500 Myr) and 53 young (lower age estimate <500 Myr) ultracool dwarfs (M6-T9). This range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. A subsample of 29 objects have well constrained ages as probable members of a nearby young moving group. We use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities (L{sub bol})more » and radius estimates from evolutionary models give semi-empirical effective temperatures (T{sub eff}) for the full range of young and field age late-M, L, and T dwarfs. We construct age-sensitive relationships of luminosity, temperature, and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as T{sub eff}, surface gravity, and clouds on spectral morphology. We report bolometric corrections in J for both field age and young objects and find differences of up to a magnitude for late-L dwarfs. Our correction in Ks shows a larger dispersion but not necessarily a different relationship for young and field age sequences. We also characterize the NIR–MIR reddening of low gravity L dwarfs and identify a systematically cooler T{sub eff} of up to 300 K from field age objects of the same spectral type and 400 K cooler from field age objects of the same M{sub H} magnitude.« less

Fundamentals of Transcranial Electric and Magnetic Stimulation Dose: Definition, Selection, and Reporting Practices

PubMed Central

Peterchev, Angel V.; Wagner, Timothy A.; Miranda, Pedro C.; Nitsche, Michael A.; Paulus, Walter; Lisanby, Sarah H.; Pascual-Leone, Alvaro; Bikson, Marom

2011-01-01

The growing use of transcranial electric and magnetic (EM) brain stimulation in basic research and in clinical applications necessitates a clear understanding of what constitutes the dose of EM stimulation and how it should be reported. The biological effects of EM stimulation are mediated through an electromagnetic field injected (via electric stimulation) or induced (via magnetic stimulation) in the body. Therefore, transcranial EM stimulation dose ought to be defined by all parameters of the stimulation device that affect the electromagnetic field generated in the body, including the stimulation electrode or coil configuration parameters: shape, size, position, and electrical properties, as well as the electrode or coil current (or voltage) waveform parameters: pulse shape, amplitude, width, polarity, and repetition frequency; duration of and interval between bursts or trains of pulses; total number of pulses; and interval between stimulation sessions and total number of sessions. Knowledge of the electromagnetic field generated in the body may not be sufficient but is necessary to understand the biological effects of EM stimulation. We believe that reporting of EM stimulation dose should be guided by the principle of reproducibility: sufficient information about the stimulation parameters should be provided so that the dose can be replicated. This paper provides fundamental definition and principles for reporting of dose that encompass any transcranial EM brain stimulation protocol. PMID:22305345

Fundamentals of transcranial electric and magnetic stimulation dose: definition, selection, and reporting practices.

PubMed

Peterchev, Angel V; Wagner, Timothy A; Miranda, Pedro C; Nitsche, Michael A; Paulus, Walter; Lisanby, Sarah H; Pascual-Leone, Alvaro; Bikson, Marom

2012-10-01

The growing use of transcranial electric and magnetic (EM) brain stimulation in basic research and in clinical applications necessitates a clear understanding of what constitutes the dose of EM stimulation and how it should be reported. This paper provides fundamental definitions and principles for reporting of dose that encompass any transcranial EM brain stimulation protocol. The biologic effects of EM stimulation are mediated through an electromagnetic field injected (via electric stimulation) or induced (via magnetic stimulation) in the body. Therefore, transcranial EM stimulation dose ought to be defined by all parameters of the stimulation device that affect the electromagnetic field generated in the body, including the stimulation electrode or coil configuration parameters: shape, size, position, and electrical properties, as well as the electrode or coil current (or voltage) waveform parameters: pulse shape, amplitude, width, polarity, and repetition frequency; duration of and interval between bursts or trains of pulses; total number of pulses; and interval between stimulation sessions and total number of sessions. Knowledge of the electromagnetic field generated in the body may not be sufficient but is necessary to understand the biologic effects of EM stimulation. We believe that reporting of EM stimulation dose should be guided by the principle of reproducibility: sufficient information about the stimulation parameters should be provided so that the dose can be replicated. Copyright © 2012 Elsevier Inc. All rights reserved.

Distorted neutrino oscillations from time varying cosmic fields

NASA Astrophysics Data System (ADS)

Krnjaic, Gordan; Machado, Pedro A. N.; Necib, Lina

2018-04-01

Cold, ultralight (≪eV ) bosonic fields can induce fast temporal variation in neutrino couplings, thereby distorting neutrino oscillations. In this paper, we exploit this effect to introduce a novel probe of neutrino time variation and dark matter at long-baseline experiments. We study several representative observables and find that current and future experiments, including DUNE and JUNO, are sensitive to a wide range of model parameters over many decades in mass reach and time-variation periodicity.

Study on superconducting state parameters of Cu1-xZrx metallic glasses using model potentials

NASA Astrophysics Data System (ADS)

Jambusarwala, Tasneem S.; Gajjar, P. N.

2018-05-01

The superconducting state parameters (SSP) of Cu1-xZrx metallic glasses over the full range of concentration x of Zr have been investigated to study influence of various local pseudopotentials. The study includes the computation of electron-phonon coupling strength (λ), transition temperature (TC), isotope effect exponent (α) and effective interaction strength (N0V) using fourteen different forms of local model potentials. The local field correction function proposed by Taylor (T) is used. The influence of model potential on various parameters is ranging from 6% to 83% for pure Zr and 28% to 84% for pure Cu. The present study confirms that the identification of model potential is vital in studying Superconducting State Parameters.

Magnetic field control of microstructural development in melt-spun Pr2Co14 B

NASA Astrophysics Data System (ADS)

McGuire, Michael A.; Rios, Orlando; Conner, Ben S.; Carter, William G.; Huang, Mianliang; Sun, Kewei; Palasyuk, Olena; Jensen, Brandt; Zhou, Lin; Dennis, Kevin; Nlebedim, Ikenna C.; Kramer, Matthew J.

2017-05-01

In the processing of commercial rare earth permanent magnets, use of external magnetic fields is limited mainly to the alignment of anisotropic particles and the polarization of the finished magnets. Here we explore the effects of high magnetic fields on earlier stages of magnet synthesis, including the crystallization and chemical phase transformations that produce the 2:14:1 phase in the Pr-Co-B system. Pr2Co14 B alloys produced by melt-spinning were annealed in the presence of strong applied magnetic fields (H=90 kOe). The resulting materials were characterized by x-ray diffraction, electron microscopy, and magnetization measurements. We find that magnetic fields suppress the nucleation and growth of crystalline phases, resulting in significantly smaller particle sizes. In addition, magnetic fields applied during processing strongly affects chemical phase selection, suppressing the formation of Pr2Co14 B and α-Co in favor of Pr2Co17 . The results demonstrate that increased control over key microstructural properties is achievable by including a strong magnetic field as a processing parameter for rare-earth magnet materials.

Design parameters for toroidal and bobbin magnetics. [conversion from English to metric units

NASA Technical Reports Server (NTRS)

Mclyman, W. T.

1974-01-01

The adoption by NASA of the metric system for dimensioning to replace long-used English units imposes a requirement on the U.S. transformer designer to convert from the familiar units to the less familiar metric equivalents. Material is presented to assist in that transition in the field of transformer design and fabrication. The conversion data makes it possible for the designer to obtain a fast and close approximation of significant parameters such as size, weight, and temperature rise. Nomographs are included to provide a close approximation for breadboarding purposes. For greater convenience, derivations of some of the parameters are also presented.

MODELED MESOSCALE METEOROLOGICAL FIELDS WITH FOUR-DIMENSIONAL DATA ASSIMILATION IN REGIONAL SCALE AIR QUALITY MODELS

EPA Science Inventory

This paper addresses the need to increase the temporal and spatial resolution of meteorological data currently used in air quality simulation models, AQSMs. ransport and diffusion parameters including mixing heights and stability used in regulatory air quality dispersion models a...

A coastal three-dimensional water quality model of nitrogen in Jiaozhou Bay linking field experiments with modelling.

PubMed

Lu, Dongliang; Li, Keqiang; Liang, Shengkang; Lin, Guohong; Wang, Xiulin

2017-01-15

With anthropogenic changes, the structure and quantity of nitrogen nutrients have changed in coastal ocean, which has dramatically influenced the water quality. Water quality modeling can contribute to the necessary scientific grounding of coastal management. In this paper, some of the dynamic functions and parameters of nitrogen were calibrated based on coastal field experiments covering the dynamic nitrogen processes in Jiaozhou Bay (JZB), including phytoplankton growth, respiration, and mortality; particulate nitrogen degradation; and dissolved organic nitrogen remineralization. The results of the field experiments and box model simulations showed good agreement (RSD=20%±2% and SI=0.77±0.04). A three-dimensional water quality model of nitrogen (3DWQMN) in JZB was improved and the dynamic parameters were updated according to field experiments. The 3DWQMN was validated based on observed data from 2012 to 2013, with good agreement (RSD=27±4%, SI=0.68±0.06, and K=0.48±0.04), which testifies to the model's credibility. Copyright © 2016 Elsevier Ltd. All rights reserved.

Assessing the performance of community-available global MHD models using key system parameters and empirical relationships

NASA Astrophysics Data System (ADS)

Gordeev, E.; Sergeev, V.; Honkonen, I.; Kuznetsova, M.; Rastätter, L.; Palmroth, M.; Janhunen, P.; Tóth, G.; Lyon, J.; Wiltberger, M.

2015-12-01

Global magnetohydrodynamic (MHD) modeling is a powerful tool in space weather research and predictions. There are several advanced and still developing global MHD (GMHD) models that are publicly available via Community Coordinated Modeling Center's (CCMC) Run on Request system, which allows the users to simulate the magnetospheric response to different solar wind conditions including extraordinary events, like geomagnetic storms. Systematic validation of GMHD models against observations still continues to be a challenge, as well as comparative benchmarking of different models against each other. In this paper we describe and test a new approach in which (i) a set of critical large-scale system parameters is explored/tested, which are produced by (ii) specially designed set of computer runs to simulate realistic statistical distributions of critical solar wind parameters and are compared to (iii) observation-based empirical relationships for these parameters. Being tested in approximately similar conditions (similar inputs, comparable grid resolution, etc.), the four models publicly available at the CCMC predict rather well the absolute values and variations of those key parameters (magnetospheric size, magnetic field, and pressure) which are directly related to the large-scale magnetospheric equilibrium in the outer magnetosphere, for which the MHD is supposed to be a valid approach. At the same time, the models have systematic differences in other parameters, being especially different in predicting the global convection rate, total field-aligned current, and magnetic flux loading into the magnetotail after the north-south interplanetary magnetic field turning. According to validation results, none of the models emerges as an absolute leader. The new approach suggested for the evaluation of the models performance against reality may be used by model users while planning their investigations, as well as by model developers and those interesting to quantitatively evaluate progress in magnetospheric modeling.

A modified hybrid uncertain analysis method for dynamic response field of the LSOAAC with random and interval parameters

NASA Astrophysics Data System (ADS)

Zi, Bin; Zhou, Bin

2016-07-01

For the prediction of dynamic response field of the luffing system of an automobile crane (LSOAAC) with random and interval parameters, a hybrid uncertain model is introduced. In the hybrid uncertain model, the parameters with certain probability distribution are modeled as random variables, whereas, the parameters with lower and upper bounds are modeled as interval variables instead of given precise values. Based on the hybrid uncertain model, the hybrid uncertain dynamic response equilibrium equation, in which different random and interval parameters are simultaneously included in input and output terms, is constructed. Then a modified hybrid uncertain analysis method (MHUAM) is proposed. In the MHUAM, based on random interval perturbation method, the first-order Taylor series expansion and the first-order Neumann series, the dynamic response expression of the LSOAAC is developed. Moreover, the mathematical characteristics of extrema of bounds of dynamic response are determined by random interval moment method and monotonic analysis technique. Compared with the hybrid Monte Carlo method (HMCM) and interval perturbation method (IPM), numerical results show the feasibility and efficiency of the MHUAM for solving the hybrid LSOAAC problems. The effects of different uncertain models and parameters on the LSOAAC response field are also investigated deeply, and numerical results indicate that the impact made by the randomness in the thrust of the luffing cylinder F is larger than that made by the gravity of the weight in suspension Q . In addition, the impact made by the uncertainty in the displacement between the lower end of the lifting arm and the luffing cylinder a is larger than that made by the length of the lifting arm L .

BIOTEX--biosensing textiles for personalised healthcare management.

PubMed

Coyle, Shirley; Lau, King-Tong; Moyna, Niall; O'Gorman, Donal; Diamond, Dermot; Di Francesco, Fabio; Costanzo, Daniele; Salvo, Pietro; Trivella, Maria Giovanna; De Rossi, Danilo Emilio; Taccini, Nicola; Paradiso, Rita; Porchet, Jacque-André; Ridolfi, Andrea; Luprano, Jean; Chuzel, Cyril; Lanier, Thierry; Revol-Cavalier, Frdéric; Schoumacker, Sébastien; Mourier, Véronique; Chartier, Isabelle; Convert, Reynald; De-Moncuit, Henri; Bini, Christina

2010-03-01

Textile-based sensors offer an unobtrusive method of continually monitoring physiological parameters during daily activities. Chemical analysis of body fluids, noninvasively, is a novel and exciting area of personalized wearable healthcare systems. BIOTEX was an EU-funded project that aimed to develop textile sensors to measure physiological parameters and the chemical composition of body fluids, with a particular interest in sweat. A wearable sensing system has been developed that integrates a textile-based fluid handling system for sample collection and transport with a number of sensors including sodium, conductivity, and pH sensors. Sensors for sweat rate, ECG, respiration, and blood oxygenation were also developed. For the first time, it has been possible to monitor a number of physiological parameters together with sweat composition in real time. This has been carried out via a network of wearable sensors distributed around the body of a subject user. This has huge implications for the field of sports and human performance and opens a whole new field of research in the clinical setting.

Effects of Various Parameters on Structural and Optical Properties of CBD-Grown ZnS Thin Films: A Review

NASA Astrophysics Data System (ADS)

Sinha, Tarkeshwar; Lilhare, Devjyoti; Khare, Ayush

2018-02-01

Zinc sulfide (ZnS) thin films deposited by chemical bath deposition (CBD) technique have proved their capability in a wide area of applications including electroluminescent and display devices, solar cells, sensors, and field emitters. These semiconducting thin films have attracted a much attention from the scientific community for industrial and research purposes. In this article, we provide a comprehensive review on the effect of various parameters on various properties of CBD-grown ZnS films. In the first part, we discuss the historical background of ZnS, its basic properties, and the advantages of the CBD technique. Detailed discussions on the film growth, structural and optical properties of ZnS thin films affected by various parameters, such as bath temperature and concentration, deposition time, stirring speed, complexing agents, pH value, humidity in the environment, and annealing conditions, are also presented. In later sections, brief information about the recent studies and findings is also added to explore the scope of research work in this field.

Use of optimization to predict the effect of selected parameters on commuter aircraft performance

NASA Technical Reports Server (NTRS)

Wells, V. L.; Shevell, R. S.

1982-01-01

An optimizing computer program determined the turboprop aircraft with lowest direct operating cost for various sets of cruise speed and field length constraints. External variables included wing area, wing aspect ratio and engine sea level static horsepower; tail sizes, climb speed and cruise altitude were varied within the function evaluation program. Direct operating cost was minimized for a 150 n.mi typical mission. Generally, DOC increased with increasing speed and decreasing field length but not by a large amount. Ride roughness, however, increased considerably as speed became higher and field length became shorter.

Determining fundamental properties of matter created in ultrarelativistic heavy-ion collisions

NASA Astrophysics Data System (ADS)

Novak, J.; Novak, K.; Pratt, S.; Vredevoogd, J.; Coleman-Smith, C. E.; Wolpert, R. L.

2014-03-01

Posterior distributions for physical parameters describing relativistic heavy-ion collisions, such as the viscosity of the quark-gluon plasma, are extracted through a comparison of hydrodynamic-based transport models to experimental results from 100AGeV+100AGeV Au +Au collisions at the Relativistic Heavy Ion Collider. By simultaneously varying six parameters and by evaluating several classes of observables, we are able to explore the complex intertwined dependencies of observables on model parameters. The methods provide a full multidimensional posterior distribution for the model output, including a range of acceptable values for each parameter, and reveal correlations between them. The breadth of observables and the number of parameters considered here go beyond previous studies in this field. The statistical tools, which are based upon Gaussian process emulators, are tested in detail and should be extendable to larger data sets and a higher number of parameters.

Electron paramagnetic resonance field-modulation eddy-current analysis of silver-plated graphite resonators

NASA Astrophysics Data System (ADS)

Mett, Richard R.; Anderson, James R.; Sidabras, Jason W.; Hyde, James S.

2005-09-01

Magnetic field modulation is often introduced into a cylindrical TE011 electron paramagnetic resonance (EPR) cavity through silver plating over a nonconductive substrate. The plating thickness must be many times the skin depth of the rf and smaller than the skin depth of the modulation. We derive a parameter that quantifies the modulation field penetration and find that it also depends on resonator dimensions. Design criteria based on this parameter are presented graphically. This parameter is then used to predict the behavior of eddy currents in substrates of moderate conductivity, such as graphite. The conductivity of the graphite permits improved plating uniformity and permits use of electric discharge machining (EDM) techniques to make the resonator. EDM offers precision tolerances of 0.005 mm and is suitable for small, complicated shapes that are difficult to machine by other methods. Analytic predictions of the modulation penetration are compared with the results of finite-element simulations. Simulated magnetic field modulation uniformity and penetration are shown for several elemental coils and structures including the plated graphite TE011 cavity. Fabrication and experimental testing of the structure are discussed. Spatial inhomogeneity of the modulation phase is also investigated by computer simulation. We find that the modulation phase is uniform to within 1% over the TE011 cavity. Structures of lower symmetry have increased phase nonuniformity.

Comparative Performance of Multivariable Agro-Physiological Parameters for Detecting Salt Tolerance of Wheat Cultivars under Simulated Saline Field Growing Conditions

PubMed Central

El-Hendawy, Salah E.; Hassan, Wael M.; Al-Suhaibani, Nasser A.; Refay, Yahya; Abdella, Kamel A.

2017-01-01

Field-based trials are crucial for successfully achieving the goals of plant breeding programs aiming to screen and improve the salt tolerance of crop genotypes. In this study, simulated saline field growing conditions were designed using the subsurface water retention technique (SWRT) and three saline irrigation levels (control, 60, and 120 mM NaCl) to accurately appraise the suitability of a set of agro-physiological parameters including shoot biomass, grain yield, leaf water relations, gas exchange, chlorophyll fluorescence, and ion accumulation as screening criteria to establish the salt tolerance of the salt-tolerant (Sakha 93) and salt-sensitive (Sakha 61) wheat cultivars. Shoot dry weight and grain yield per hectare were substantially reduced by salinity, but the reduction was more pronounced in Sakha 61 than in Sakha 93. Increasing salinity stress caused a significant decrease in the net photosynthesis rate and stomatal conductance of both cultivars, although their leaf turgor pressure increased. The accumulation of toxic ions (Na+ and Cl-) was higher in Sakha 61, but the accumulation of essential cations (K+ and Ca2+) was higher in Sakha 93, which could be the reason for the observed maintenance of the higher leaf turgor of both cultivars in the salt treatments. The maximum quantum PSII photochemical efficiency (Fv/Fm) and the PSII quantum yield (ΦPSII) decreased with increasing salinity levels in Sakha 61, but they only started to decline at the moderate salinity condition in Sakha 93. The principle component analysis successfully identified the interrelationships between all parameters. The parameters of leaf water relations and toxic ion concentrations were significantly related to each other and could identify Sakha 61 at mild and moderate salinity levels, and, to a lesser extent, Sakha 93 at the moderate salinity level. Both cultivars under the control treatment and Sakha 93 at the mild salinity level were identified by most of the other parameters. The variability in the angle between the vectors of parameters explained which parameters could be used as individual, interchangeable, or supplementary screening criteria for evaluating wheat salt tolerance under simulated field conditions. PMID:28424718

Knowledge transmission model with differing initial transmission and retransmission process

NASA Astrophysics Data System (ADS)

Wang, Haiying; Wang, Jun; Small, Michael

2018-10-01

Knowledge transmission is a cyclic dynamic diffusion process. The rate of acceptance of knowledge differs upon whether or not the recipient has previously held the knowledge. In this paper, the knowledge transmission process is divided into an initial and a retransmission procedure, each with its own transmission and self-learning parameters. Based on epidemic spreading model, we propose a naive-evangelical-agnostic (VEA) knowledge transmission model and derive mean-field equations to describe the dynamics of knowledge transmission in homogeneous networks. Theoretical analysis identifies a criterion for the persistence of knowledge, i.e., the reproduction number R0 depends on the minor effective parameters between the initial and retransmission process. Moreover, the final size of evangelical individuals is only related to retransmission process parameters. Numerical simulations validate the theoretical analysis. Furthermore, the simulations indicate that increasing the initial transmission parameters, including first transmission and self-learning rates of naive individuals, can accelerate the velocity of knowledge transmission efficiently but have no effect on the final size of evangelical individuals. In contrast, the retransmission parameters, including retransmission and self-learning rates of agnostic individuals, have a significant effect on the rate of knowledge transmission, i.e., the larger parameters the greater final density of evangelical individuals.

Lunar and Planetary Science XXXV: Mars Geophysics

NASA Technical Reports Server (NTRS)

2004-01-01

The titles in this section include: 1) Distribution of Large Visible and Buried Impact Basins on Mars: Comparison with Free-Air Gravity, Crustal Thickness, and Magnetization Models; 2) The Early Thermal and Magnetic State of Terra Cimmeria, Southern Highlands of Mars; 3) Compatible Vector Components of the Magnetic Field of the Martian Crust; 4) Vertical Extrapolation of Mars Magnetic Potentials; 5) Rock Magnetic Fields Shield the Surface of Mars from Harmful Radiation; 6) Loading-induced Stresses near the Martian Hemispheric Dichotomy Boundary; 7) Growth of the Hemispheric Dichotomy and the Cessation of Plate Tectonics on Mars; 8) A Look at the Interior of Mars; 9) Uncertainties on Mars Interior Parameters Deduced from Orientation Parameters Using Different Radio-Links: Analytical Simulations; 10) Refinement of Phobos Ephemeris Using Mars Orbiter Laser Altimetry Radiometry.

Quantal diffusion description of multinucleon transfers in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Ayik, S.; Yilmaz, B.; Yilmaz, O.; Umar, A. S.

2018-05-01

Employing the stochastic mean-field (SMF) approach, we develop a quantal diffusion description of the multi-nucleon transfer in heavy-ion collisions at finite impact parameters. The quantal transport coefficients are determined by the occupied single-particle wave functions of the time-dependent Hartree-Fock equations. As a result, the primary fragment mass and charge distribution functions are determined entirely in terms of the mean-field properties. This powerful description does not involve any adjustable parameter, includes the effects of shell structure, and is consistent with the fluctuation-dissipation theorem of the nonequilibrium statistical mechanics. As a first application of the approach, we analyze the fragment mass distribution in 48Ca+ 238U collisions at the center-of-mass energy Ec.m.=193 MeV and compare the calculations with the experimental data.

The Landau-de Gennes approach revisited: A minimal self-consistent microscopic theory for spatially inhomogeneous nematic liquid crystals

NASA Astrophysics Data System (ADS)

Gârlea, Ioana C.; Mulder, Bela M.

2017-12-01

We design a novel microscopic mean-field theory of inhomogeneous nematic liquid crystals formulated entirely in terms of the tensor order parameter field. It combines the virtues of the Landau-de Gennes approach in allowing both the direction and magnitude of the local order to vary, with a self-consistent treatment of the local free-energy valid beyond the small order parameter limit. As a proof of principle, we apply this theory to the well-studied problem of a colloid dispersed in a nematic liquid crystal by including a tunable wall coupling term. For the two-dimensional case, we investigate the organization of the liquid crystal and the position of the point defects as a function of the strength of the coupling constant.

Validation conform ISO-15189 of assays in the field of autoimmunity: Joint efforts in The Netherlands.

PubMed

Mulder, Leontine; van der Molen, Renate; Koelman, Carin; van Leeuwen, Ester; Roos, Anja; Damoiseaux, Jan

2018-05-01

ISO 15189:2012 requires validation of methods used in the medical laboratory, and lists a series of performance parameters for consideration to include. Although these performance parameters are feasible for clinical chemistry analytes, application in the validation of autoimmunity tests is a challenge. Lack of gold standards or reference methods in combination with the scarcity of well-defined diagnostic samples of patients with rare diseases make validation of new assays difficult. The present manuscript describes the initiative of Dutch medical immunology laboratory specialists to combine efforts and perform multi-center validation studies of new assays in the field of autoimmunity. Validation data and reports are made available to interested Dutch laboratory specialists. Copyright © 2018 Elsevier B.V. All rights reserved.

A study of the origin of large magnetic field coupled electric polarization in HoAl(BO3)4

NASA Astrophysics Data System (ADS)

Yu, Tian; Zhang, Han; Tyson, Trevor; Chen, Zhiqiang; Abeykoon, Milinda; Nelson, Christie; Bezmaternykh, Leonard

2015-03-01

The multiferroic system RAl(BO3)4 is known to exhibit a strong coupling of magnetic field to the electrical polarization. Recently a giant magnetoelectric effect was found in HoAl3(BO3)4 system. This phenomenon is considered quite interesting because the value discovered is significantly higher than reported values of linear magnetoelectric or even multiferroic compounds. We are conducting detailed structural measurements to understand the coupling. We are exploring the local and long range structure in these systems using x-ray PDF, XAFS and single crystal diffraction measurement between 10 K and 400 K. Structural parameters including lattice parameters and ADPs are being determined over the full temperature range. This work is supported by DOE Grant DE-FG02-07ER46402.

Surface roughness scattering of electrons in bulk mosfets

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

Zuverink, Amanda Renee

2015-11-01

Surface-roughness scattering of electrons at the Si-SiO 2 interface is a very important consideration when analyzing Si metal-oxide-semiconductor field-effect transistors (MOSFETs). Scattering reduces the mobility of the electrons and degrades the device performance. 250-nm and 50-nm bulk MOSFETs were simulated with varying device parameters and mesh sizes in order to compare the effects of surface-roughness scattering in multiple devices. The simulation framework includes the ensemble Monte Carlo method used to solve the Boltzmann transport equation coupled with a successive over-relaxation method used to solve the two-dimensional Poisson's equation. Four methods for simulating the surface-roughness scattering of electrons were implemented onmore » both devices and compared: the constant specularity parameter, the momentum-dependent specularity parameter, and the real-space-roughness method with both uniform and varying electric fields. The specularity parameter is the probability of an electron scattering speculariy from a rough surface. It can be chosen as a constant, characterizing partially diffuse scattering of all electrons from the surface the same way, or it can be momentum dependent, where the size of rms roughness and the normal component of the electron wave number determine the probability of electron-momentum randomization. The real-space rough surface method uses the rms roughness height and correlation length of an actual MOSFET to simulate a rough interface. Due to their charge, electrons scatter from the electric field and not directly from the surface. If the electric field is kept uniform, the electrons do not perceive the roughness and scatter as if from a at surface. However, if the field is allowed to vary, the electrons scatter from the varying electric field as they would in a MOSFET. These methods were implemented for both the 50-nm and 250-nm MOSFETs, and using the rms roughness heights and correlation lengths for real devices. The current-voltage and mobility-electric field curves were plotted for each method on the two devices and compared. The conclusion is that the specularity-parameter methods are valuable as simple models for relatively smooth interfaces. However, they have limitations, as they cannot accurately describe the drastic reduction in the current and the electron mobility that occur in MOSFETs with very rough Si-SiO 2 interfaces.« less

Microwave remote sensing and radar polarization signatures of natural fields

NASA Technical Reports Server (NTRS)

Mo, Tsan

1989-01-01

Theoretical models developed for simulation of microwave remote sensing of the Earth surface from airborne/spaceborne sensors are described. Theoretical model calculations were performed and the results were compared with data of field measurements. Data studied included polarimetric images at the frequencies of P band, L band, and C band, acquired with airborne polarimeters over a agricultural field test site. Radar polarization signatures from bare soil surfaces and from tree covered fields were obtained from the data. The models developed in this report include: (1) Small perturbation model of wave scatterings from randomly rough surfaces, (2) Physical optics model, (3) Geometrical optics model, and (4) Electromagnetic wave scattering from dielectric cylinders of finite lengths, which replace the trees and branches in the modeling of tree covered field. Additionally, a three-layer emissivity model for passive sensing of a vegetation covered soil surface is also developed. The effects of surface roughness, soil moisture contents, and tree parameters on the polarization signatures were investigated.

The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs - Space-Weather HMI Active Region Patches

NASA Astrophysics Data System (ADS)

Bobra, M. G.; Sun, X.; Hoeksema, J. T.; Turmon, M.; Liu, Y.; Hayashi, K.; Barnes, G.; Leka, K. D.

2014-09-01

A new data product from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) called Space-weather HMI Active Region Patches ( SHARPs) is now available. SDO/HMI is the first space-based instrument to map the full-disk photospheric vector magnetic field with high cadence and continuity. The SHARP data series provide maps in patches that encompass automatically tracked magnetic concentrations for their entire lifetime; map quantities include the photospheric vector magnetic field and its uncertainty, along with Doppler velocity, continuum intensity, and line-of-sight magnetic field. Furthermore, keywords in the SHARP data series provide several parameters that concisely characterize the magnetic-field distribution and its deviation from a potential-field configuration. These indices may be useful for active-region event forecasting and for identifying regions of interest. The indices are calculated per patch and are available on a twelve-minute cadence. Quick-look data are available within approximately three hours of observation; definitive science products are produced approximately five weeks later. SHARP data are available at jsoc.stanford.edu and maps are available in either of two different coordinate systems. This article describes the SHARP data products and presents examples of SHARP data and parameters.

CONSTRAINING THE STRING GAUGE FIELD BY GALAXY ROTATION CURVES AND PERIHELION PRECESSION OF PLANETS

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

Cheung, Yeuk-Kwan E.; Xu Feng, E-mail: cheung@nju.edu.cn

2013-09-01

We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have observable signatures on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of 22 spiral galaxies of varied luminosities and sizes and perihelion precessions of planets in the solar system. The rotation curves of the same group of galaxies are independently fit using a dark matter model with the generalized Navarro-Frenk-White (NFW) profile and the string model. A remarkable fit of galaxy rotation curves is achieved using the one-parameter stringmore » model as compared to the three-parameter dark matter model with the NFW profile. The average {chi}{sup 2} value of the NFW fit is 9% better than that of the string model at a price of two more free parameters. Furthermore, from the string model, we can give a dynamical explanation for the phenomenological Tully-Fisher relation. We are able to derive a relation between field strength, galaxy size, and luminosity, which can be verified with data from the 22 galaxies. To further test the hypothesis of the universal existence of the string gauge field, we apply our string model to the solar system. Constraint on the magnitude of the string field in the solar system is deduced from the current ranges for any anomalous perihelion precession of planets allowed by the latest observations. The field distribution resembles a dipole field originating from the Sun. The string field strength deduced from the solar system observations is of a similar magnitude as the field strength needed to sustain the rotational speed of the Sun inside the Milky Way. This hypothesis can be tested further by future observations with higher precision.« less

Macroscopic electromagnetic properties of the Irvine Field-Reversed Configuration: Equilibrium, power balance and fluctuations

NASA Astrophysics Data System (ADS)

Trask, Erik Harold

The plasma parameters and characteristics of the Irvine Field-Reversed Configuration (IFRC) are summarized in this thesis. Particular emphasis is placed on the development of the different diagnostics used to make measurements in the experiment, as well as the measurements themselves. Whenever possible, actual measurements are used in lieu of theoretical or analytical fits to data. Analysis of magnetic probes (B-dots) comprises the bulk of what is known about the IFRC. From these B-dot probes, the magnetic field structure in a two dimensional plane at constant toroidal position has been determined, and has been found to be consistent with a field-reversed configuration. Peak reversed fields of approximately 250 Gauss have been observed. Further analyses have been developed to extract information from the magnetic field structure, including components of the electric field, the current density, and plasma pressure in the same two dimensional plane. Electric field magnitudes reach 600 V/m, concurrent with current densities greater than 105 Amps/m2 and thermal pressures over 200 Pa. Spectroscopic analysis of hydrogen lines has been done to make estimates of the electron temperature, while spectroscopic measurements of the Doppler broadening of the Halpha line31 have allowed an estimate of the ion temperature. Particle losses out one axial end plane measured by an array of Faraday cups quantify the how well the configuration traps particles. Spectral information derived from B-dot probes indicates that there is substantial power present at frequencies lying between the hydrogen cyclotron and mean gyrofrequency. These various measurements are used to find the following parameters that characterize the Irvine FRC: (1) Electromagnetic and thermal stored energies as functions of time. (2) Power balance, including input power from the field coils, resistive heating, power lost by particle transport and radiation, and particle and energy confinement times. (3) Strong correlations between magnetic fluctuations and particle loss.

Actuator model of electrostrictive polymers (EPs) for microactuators

NASA Astrophysics Data System (ADS)

Kim, Hunmo; Oh, Sinjong; Hwang, Kyoil; Choi, Hyoukryeol; Jeon, Jaewook; Nam, Jaedo

2001-07-01

Recently, Electrostrictive polymers (EPs) are studied for micro-actuator, because of similarity of body tissue. Electrostrictive polymers (EPs) are based on the deformation of dielectric elastomer polymer in the presence of an electric field. Modeling of electrostrictive polymer has been studied, which is about voltage and displacement. And there are many parameters such as Young's modulus, voltage, thickness of EPs, pre-strain, dielectric, frequency and temperature which effect to movement of EPs. To do exact modeling, all parameters are included. In order to use as actuator, we accurately understood about the parameter that we refer above. And we have to execute modeling which parameters are considered. We used FEM in order to understand effects of parameters. Specially, because of pre-strain effects are very important, we derive the relations of stress and strain by using elastic strain energy.

The Kormendy relation of galaxies in the Frontier Fields clusters: Abell S1063 and MACS J1149.5+2223

NASA Astrophysics Data System (ADS)

Tortorelli, Luca; Mercurio, Amata; Paolillo, Maurizio; Rosati, Piero; Gargiulo, Adriana; Gobat, Raphael; Balestra, Italo; Caminha, G. B.; Annunziatella, Marianna; Grillo, Claudio; Lombardi, Marco; Nonino, Mario; Rettura, Alessandro; Sartoris, Barbara; Strazzullo, Veronica

2018-06-01

We analyse the Kormendy relations (KRs) of the two Frontier Fields clusters, Abell S1063, at z = 0.348, and MACS J1149.5+2223, at z = 0.542, exploiting very deep Hubble Space Telescope photometry and Very Large Telescope (VLT)/Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy. With this novel data set, we are able to investigate how the KR parameters depend on the cluster galaxy sample selection and how this affects studies of galaxy evolution based on the KR. We define and compare four different galaxy samples according to (a) Sérsic indices: early-type (`ETG'), (b) visual inspection: `ellipticals', (c) colours: `red', (d) spectral properties: `passive'. The classification is performed for a complete sample of galaxies with mF814W ≤ 22.5 ABmag (M* ≳ 1010.0 M⊙). To derive robust galaxy structural parameters, we use two methods: (1) an iterative estimate of structural parameters using images of increasing size, in order to deal with closely separated galaxies and (2) different background estimations, to deal with the intracluster light contamination. The comparison between the KRs obtained from the different samples suggests that the sample selection could affect the estimate of the best-fitting KR parameters. The KR built with ETGs is fully consistent with the one obtained for ellipticals and passive. On the other hand, the KR slope built on the red sample is only marginally consistent with those obtained with the other samples. We also release the photometric catalogue with structural parameters for the galaxies included in the present analysis.

Inverse models: A necessary next step in ground-water modeling

USGS Publications Warehouse

Poeter, E.P.; Hill, M.C.

1997-01-01

Inverse models using, for example, nonlinear least-squares regression, provide capabilities that help modelers take full advantage of the insight available from ground-water models. However, lack of information about the requirements and benefits of inverse models is an obstacle to their widespread use. This paper presents a simple ground-water flow problem to illustrate the requirements and benefits of the nonlinear least-squares repression method of inverse modeling and discusses how these attributes apply to field problems. The benefits of inverse modeling include: (1) expedited determination of best fit parameter values; (2) quantification of the (a) quality of calibration, (b) data shortcomings and needs, and (c) confidence limits on parameter estimates and predictions; and (3) identification of issues that are easily overlooked during nonautomated calibration.Inverse models using, for example, nonlinear least-squares regression, provide capabilities that help modelers take full advantage of the insight available from ground-water models. However, lack of information about the requirements and benefits of inverse models is an obstacle to their widespread use. This paper presents a simple ground-water flow problem to illustrate the requirements and benefits of the nonlinear least-squares regression method of inverse modeling and discusses how these attributes apply to field problems. The benefits of inverse modeling include: (1) expedited determination of best fit parameter values; (2) quantification of the (a) quality of calibration, (b) data shortcomings and needs, and (c) confidence limits on parameter estimates and predictions; and (3) identification of issues that are easily overlooked during nonautomated calibration.

High throughput nanoimprint lithography for semiconductor memory applications

NASA Astrophysics Data System (ADS)

Ye, Zhengmao; Zhang, Wei; Khusnatdinov, Niyaz; Stachowiak, Tim; Irving, J. W.; Longsine, Whitney; Traub, Matthew; Fletcher, Brian; Liu, Weijun

2017-03-01

Imprint lithography is a promising technology for replication of nano-scale features. For semiconductor device applications, Canon deposits a low viscosity resist on a field by field basis using jetting technology. A patterned mask is lowered into the resist fluid which then quickly flows into the relief patterns in the mask by capillary action. Following this filling step, the resist is crosslinked under UV radiation, and then the mask is removed, leaving a patterned resist on the substrate. There are two critical components to meeting throughput requirements for imprint lithography. Using a similar approach to what is already done for many deposition and etch processes, imprint stations can be clustered to enhance throughput. The FPA-1200NZ2C is a four station cluster system designed for high volume manufacturing. For a single station, throughput includes overhead, resist dispense, resist fill time (or spread time), exposure and separation. Resist exposure time and mask/wafer separation are well understood processing steps with typical durations on the order of 0.10 to 0.20 seconds. To achieve a total process throughput of 17 wafers per hour (wph) for a single station, it is necessary to complete the fluid fill step in 1.2 seconds. For a throughput of 20 wph, fill time must be reduced to only one 1.1 seconds. There are several parameters that can impact resist filling. Key parameters include resist drop volume (smaller is better), system controls (which address drop spreading after jetting), Design for Imprint or DFI (to accelerate drop spreading) and material engineering (to promote wetting between the resist and underlying adhesion layer). In addition, it is mandatory to maintain fast filling, even for edge field imprinting. In this paper, we address the improvements made in all of these parameters to first enable a 1.20 second filling process for a device like pattern and have demonstrated this capability for both full fields and edge fields. Non-fill defectivity is well under 1.0 defects/cm2 for both field types. Next, by further reducing drop volume and optimizing drop patterns, a fill time of 1.1 seconds was demonstrated.

University of Maryland MRSEC - Research: Seed 3

Science.gov Websites

MRSEC Templates Opportunities Search Home » Research » Seed 3 Seed 3: Modeling Elastic Effects on controlling parameters and variables include temperature, deposition flux, external electric field and elastic simulating the effects of these controlling factors often lead to predictions that guide future experiments

REGIONAL-SCALE (1000 KM) MODEL OF PHOTOCHEMICAL AIR POLLUTION. PART 2. INPUT PROCESSOR NETWORK DESIGN

EPA Science Inventory

Detailed specifications are given for a network of data processors and submodels that can generate the parameter fields required by the regional oxidant model formulated in Part 1 of this report. Operations performed by the processor network include simulation of the motion and d...

Experiments on Adaptive Self-Tuning of Seismic Signal Detector Parameters

NASA Astrophysics Data System (ADS)

Knox, H. A.; Draelos, T.; Young, C. J.; Chael, E. P.; Peterson, M. G.; Lawry, B.; Phillips-Alonge, K. E.; Balch, R. S.; Ziegler, A.

2016-12-01

Scientific applications, including underground nuclear test monitoring and microseismic monitoring can benefit enormously from data-driven dynamic algorithms for tuning seismic and infrasound signal detection parameters since continuous streams are producing waveform archives on the order of 1TB per month. Tuning is a challenge because there are a large number of data processing parameters that interact in complex ways, and because the underlying populating of true signal detections is generally unknown. The largely manual process of identifying effective parameters, often performed only over a subset of stations over a short time period, is painstaking and does not guarantee that the resulting controls are the optimal configuration settings. We present improvements to an Adaptive Self-Tuning algorithm for continuously adjusting detection parameters based on consistency with neighboring sensors. Results are shown for 1) data from a very dense network ( 120 stations, 10 km radius) deployed during 2008 on Erebus Volcano, Antarctica, and 2) data from a continuous downhole seismic array in the Farnsworth Field, an oil field in Northern Texas that hosts an ongoing carbon capture, utilization, and storage project. Performance is assessed in terms of missed detections and false detections relative to human analyst detections, simulated waveforms where ground-truth detections exist and visual inspection.

Parameterization of an interfacial force field for accurate representation of peptide adsorption free energy on high-density polyethylene

PubMed Central

Abramyan, Tigran M.; Snyder, James A.; Yancey, Jeremy A.; Thyparambil, Aby A.; Wei, Yang; Stuart, Steven J.; Latour, Robert A.

2015-01-01

Interfacial force field (IFF) parameters for use with the CHARMM force field have been developed for interactions between peptides and high-density polyethylene (HDPE). Parameterization of the IFF was performed to achieve agreement between experimental and calculated adsorption free energies of small TGTG–X–GTGT host–guest peptides (T = threonine, G = glycine, and X = variable amino-acid residue) on HDPE, with ±0.5 kcal/mol agreement. This IFF parameter set consists of tuned nonbonded parameters (i.e., partial charges and Lennard–Jones parameters) for use with an in-house-modified CHARMM molecular dynamic program that enables the use of an independent set of force field parameters to control molecular behavior at a solid–liquid interface. The R correlation coefficient between the simulated and experimental peptide adsorption free energies increased from 0.00 for the standard CHARMM force field parameters to 0.88 for the tuned IFF parameters. Subsequent studies are planned to apply the tuned IFF parameter set for the simulation of protein adsorption behavior on an HDPE surface for comparison with experimental values of adsorbed protein orientation and conformation. PMID:25818122

FAST TRACK COMMUNICATION: The origin of Bohm diffusion, investigated by a comparison of different modelling methods

NASA Astrophysics Data System (ADS)

Bultinck, E.; Mahieu, S.; Depla, D.; Bogaerts, A.

2010-07-01

'Bohm diffusion' causes the electrons to diffuse perpendicularly to the magnetic field lines. However, its origin is not yet completely understood: low and high frequency electric field fluctuations are both named to cause Bohm diffusion. The importance of including this process in a Monte Carlo (MC) model is demonstrated by comparing calculated ionization rates with particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations. A good agreement is found with a Bohm diffusion parameter of 0.05, which corresponds well to experiments. Since the PIC/MCC method accounts for fast electric field fluctuations, we conclude that Bohm diffusion is caused by fast electric field phenomena.

A method of evaluating quantitative magnetospheric field models by an angular parameter alpha

NASA Technical Reports Server (NTRS)

Sugiura, M.; Poros, D. J.

1979-01-01

The paper introduces an angular parameter, termed alpha, which represents the angular difference between the observed, or model, field and the internal model field. The study discusses why this parameter is chosen and demonstrates its usefulness by applying it to both observations and models. In certain areas alpha is more sensitive than delta-B (the difference between the magnitude of the observed magnetic field and that of the earth's internal field calculated from a spherical harmonic expansion) in expressing magnetospheric field distortions. It is recommended to use both alpha and delta-B in comparing models with observations.

A method for approximating acoustic-field-amplitude uncertainty caused by environmental uncertainties.

PubMed

James, Kevin R; Dowling, David R

2008-09-01

In underwater acoustics, the accuracy of computational field predictions is commonly limited by uncertainty in environmental parameters. An approximate technique for determining the probability density function (PDF) of computed field amplitude, A, from known environmental uncertainties is presented here. The technique can be applied to several, N, uncertain parameters simultaneously, requires N+1 field calculations, and can be used with any acoustic field model. The technique implicitly assumes independent input parameters and is based on finding the optimum spatial shift between field calculations completed at two different values of each uncertain parameter. This shift information is used to convert uncertain-environmental-parameter distributions into PDF(A). The technique's accuracy is good when the shifted fields match well. Its accuracy is evaluated in range-independent underwater sound channels via an L(1) error-norm defined between approximate and numerically converged results for PDF(A). In 50-m- and 100-m-deep sound channels with 0.5% uncertainty in depth (N=1) at frequencies between 100 and 800 Hz, and for ranges from 1 to 8 km, 95% of the approximate field-amplitude distributions generated L(1) values less than 0.52 using only two field calculations. Obtaining comparable accuracy from traditional methods requires of order 10 field calculations and up to 10(N) when N>1.

Astrophysical particle acceleration mechanisms in colliding magnetized laser-produced plasmas

DOE PAGES

Fox, W.; Park, J.; Deng, W.; ...

2017-08-11

Significant particle energization is observed to occur in numerous astrophysical environments, and in the standard models, this acceleration occurs alongside energy conversion processes including collisionless shocks or magnetic reconnection. Recent platforms for laboratory experiments using magnetized laser-produced plasmas have opened opportunities to study these particle acceleration processes in the laboratory. Through fully kinetic particle-in-cell simulations, we investigate acceleration mechanisms in experiments with colliding magnetized laser-produced plasmas, with geometry and parameters matched to recent high-Mach number reconnection experiments with externally controlled magnetic fields. 2-D simulations demonstrate significant particle acceleration with three phases of energization: first, a “direct” Fermi acceleration driven bymore » approaching magnetized plumes; second, x-line acceleration during magnetic reconnection of anti-parallel fields; and finally, an additional Fermi energization of particles trapped in contracting and relaxing magnetic islands produced by reconnection. Furthermore, the relative effectiveness of these mechanisms depends on plasma and magnetic field parameters of the experiments.« less

Analytic quantum-interference conditions in Coulomb corrected photoelectron holography

NASA Astrophysics Data System (ADS)

Maxwell, A. S.; Al-Jawahiry, A.; Lai, X. Y.; Figueira de Morisson Faria, C.

2018-02-01

We provide approximate analytic expressions for above-threshold ionization (ATI) transition probabilities and photoelectron angular distributions. These analytic expressions are more general than those existing in the literature and include the residual binding potential in the electron continuum propagation. They successfully reproduce the ATI side lobes and specific holographic structures such as the near-threshold fan-shaped pattern and the spider-like structure that extends up to relatively high photoelectron energies. We compare such expressions with the Coulomb quantum orbit strong-field approximation (CQSFA) and the full solution of the time-dependent Schrödinger equation for different driving-field frequencies and intensities, and provide an in-depth analysis of the physical mechanisms behind specific holographic structures. Our results shed additional light on what aspects of the CQSFA must be prioritized in order to obtain the key holographic features, and highlight the importance of forward scattered trajectories. Furthermore, we find that the holographic patterns change considerably for different field parameters, even if the Keldysh parameter is kept roughly the same.

Kinklike structures in models of the Dirac-Born-Infeld type

NASA Astrophysics Data System (ADS)

Bazeia, D.; Lima, Elisama E. M.; Losano, L.

2018-01-01

The present work investigates several models of a single real scalar field, engendering kinetic term of the Dirac-Born- Infeld type. Such theories introduce nonlinearities to the kinetic part of the Lagrangian, which presents a square root restricting the field evolution and including additional powers in derivatives of the scalar field, controlled by a real parameter. In order to obtain topological solutions analytically, we propose a first-order framework that simplifies the equation of motion ensuring solutions that are linearly stable. This is implemented using the deformation method, and we introduce examples presenting two categories of potentials, one having polynomial interactions and the other with nonpolynomial interactions. We also explore how the Dirac-Born-Infeld kinetic term affects the properties of the solutions. In particular, we note that the kinklike solutions are similar to the ones obtained through models with standard kinetic term and canonical potential, but their energy densities and stability potentials vary according to the parameter introduced to control the new models.

Distorted neutrino oscillations from time varying cosmic fields

DOE PAGES

Krnjaic, Gordan; Machado, Pedro A. N.; Necib, Lina

2018-04-16

Cold, ultralight (more » $$\\ll$$ eV) bosonic fields can induce fast temporal variation in neutrino couplings, thereby distorting neutrino oscillations. In this paper, we exploit this effect to introduce a novel probe of neutrino time variation and dark matter at long-baseline experiments. We study several representative observables and find that current and future experiments, including DUNE and JUNO, are sensitive to a wide range of model parameters over many decades in mass reach and time-variation periodicity.« less

Distorted neutrino oscillations from time varying cosmic fields

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

Krnjaic, Gordan; Machado, Pedro A. N.; Necib, Lina

Cold, ultralight (more » $$\\ll$$ eV) bosonic fields can induce fast temporal variation in neutrino couplings, thereby distorting neutrino oscillations. In this paper, we exploit this effect to introduce a novel probe of neutrino time variation and dark matter at long-baseline experiments. We study several representative observables and find that current and future experiments, including DUNE and JUNO, are sensitive to a wide range of model parameters over many decades in mass reach and time-variation periodicity.« less

Modelling the water balance of irrigated fields in tropical floodplain soils using Hydrus-1D

NASA Astrophysics Data System (ADS)

Beyene, Abebech; Frankl, Amaury; Verhoest, Niko E. C.; Tilahun, Seifu; Alamirew, Tena; Adgo, Enyew; Nyssen, Jan

2017-04-01

Accurate estimation of evaporation, transpiration and deep percolation is crucial in irrigated agriculture and the sustainable management of water resources. Here, the Hydrus-1D process-based numerical model was used to estimate the actual transpiration, soil evaporation and deep percolation from irrigated fields of floodplain soils. Field experiments were conducted from Dec 2015 to May 2016 in a small irrigation scheme (50 ha) called 'Shina' located in the Lake Tana floodplains of Ethiopia. Six experimental plots (three for onion and three for maize) were selected along a topographic transect to account for soil and groundwater variability. Irrigation amount (400 to 550 mm during the growing period) was measured using V-notches installed at each plot boundary and daily groundwater levels were measured manually from piezometers. There was no surface runoff observed in the growing period and rainfall was measured using a manual rain gauge. All daily weather data required for the evapotranspiration calculation using Pen Man Monteith equation were collected from a nearby metrological station. The soil profiles were described for each field to include the vertical soil heterogeneity in the soil water balance simulations. The soil texture, organic matter, bulk density, field capacity, wilting point and saturated moisture content were measured for all the soil horizons. Soil moisture monitoring at 30 and 60 cm depths was performed. The soil hydraulic parameters for each horizon was estimated using KNN pedotransfer functions for tropical soils and were effectively fitted using the RETC program (R2= 0.98±0.011) for initial prediction. A local sensitivity analysis was performed to select and optimize the most important hydraulic parameters for soil water flow in the unsaturated zone. The most sensitive parameters were saturated hydraulic conductivity (Ks), saturated moisture content (θs) and pore size distribution (n). Inverse modelling using Hydrus-1D further optimized these parameters (R2 =0.74±0.13). Using the optimized hydraulic parameters, the soil water dynamics were simulated using Hydrus-1D. The atmospheric boundary conditions with surface runoff was used as upper boundary condition with measured rainfall and irrigation input data. The variable pressure head was selected as lower boundary conditions with daily records of groundwater level as time-variable input data. The Hydrus-1D model was successfully applied and calibrated in the study area. The average seasonal actual transpiration values are 310±13 mm for onion and 429±24.7 mm for maize fields. The seasonal average soil evaporation ranges from 12±2.05 mm for maize fields to 38±2.85 mm for onion fields. The seasonal deep percolation from irrigation appeared to be 12 to 40% of applied irrigation. The Hydrus-1D model was able to simulate the temporal and the spatial variations of soil water dynamics in the unsaturated zone of tropical floodplain soils. Key words: floodplains, hydraulic parameters, parameter optimization, small-scale irrigation

Sensitivity-based virtual fields for the non-linear virtual fields method

NASA Astrophysics Data System (ADS)

Marek, Aleksander; Davis, Frances M.; Pierron, Fabrice

2017-09-01

The virtual fields method is an approach to inversely identify material parameters using full-field deformation data. In this manuscript, a new set of automatically-defined virtual fields for non-linear constitutive models has been proposed. These new sensitivity-based virtual fields reduce the influence of noise on the parameter identification. The sensitivity-based virtual fields were applied to a numerical example involving small strain plasticity; however, the general formulation derived for these virtual fields is applicable to any non-linear constitutive model. To quantify the improvement offered by these new virtual fields, they were compared with stiffness-based and manually defined virtual fields. The proposed sensitivity-based virtual fields were consistently able to identify plastic model parameters and outperform the stiffness-based and manually defined virtual fields when the data was corrupted by noise.

Application of lab derived kinetic biodegradation parameters at the field scale

NASA Astrophysics Data System (ADS)

Schirmer, M.; Barker, J. F.; Butler, B. J.; Frind, E. O.

2003-04-01

Estimating the intrinsic remediation potential of an aquifer typically requires the accurate assessment of the biodegradation kinetics, the level of available electron acceptors and the flow field. Zero- and first-order degradation rates derived at the laboratory scale generally overpredict the rate of biodegradation when applied to the field scale, because limited electron acceptor availability and microbial growth are typically not considered. On the other hand, field estimated zero- and first-order rates are often not suitable to forecast plume development because they may be an oversimplification of the processes at the field scale and ignore several key processes, phenomena and characteristics of the aquifer. This study uses the numerical model BIO3D to link the laboratory and field scale by applying laboratory derived Monod kinetic degradation parameters to simulate a dissolved gasoline field experiment at Canadian Forces Base (CFB) Borden. All additional input parameters were derived from laboratory and field measurements or taken from the literature. The simulated results match the experimental results reasonably well without having to calibrate the model. An extensive sensitivity analysis was performed to estimate the influence of the most uncertain input parameters and to define the key controlling factors at the field scale. It is shown that the most uncertain input parameters have only a minor influence on the simulation results. Furthermore it is shown that the flow field, the amount of electron acceptor (oxygen) available and the Monod kinetic parameters have a significant influence on the simulated results. Under the field conditions modelled and the assumptions made for the simulations, it can be concluded that laboratory derived Monod kinetic parameters can adequately describe field scale degradation processes, if all controlling factors are incorporated in the field scale modelling that are not necessarily observed at the lab scale. In this way, there are no scale relationships to be found that link the laboratory and the field scale, accurately incorporating the additional processes, phenomena and characteristics, such as a) advective and dispersive transport of one or more contaminants, b) advective and dispersive transport and availability of electron acceptors, c) mass transfer limitations and d) spatial heterogeneities, at the larger scale and applying well defined lab scale parameters should accurately describe field scale processes.

Seasonal soybean crop reflectance

NASA Technical Reports Server (NTRS)

Lemaster, E. W. (Principal Investigator); Chance, J. E.

1983-01-01

Data are presented from field measurements of 1980 including 5 acquisitions of handheld radiometer reflectance measurements, 7 complete sets of parameters for implementing the Suits mode, and other biophysical parameters to characterize the soybean canopy. LANDSAT calculations on the simulated Brazilian soybean reflectance are included along with data collected during the summer and fall on 1981 on soybean single leaf optical parameters for three irrigation treatments. Tests of the Suits vegetative canopy reflectance model for the full hemisphere of observer directions as well as the nadir direction show moderate agreement for the visible channels of the MSS and poor agreement in the near infrared channel. Temporal changes in the spectral characteristics of the single leaves were seen to occur as a function of maturity which demonstrates that the absorptance of a soybean single leaf is more a function of thetransmittancee characteristics than the seasonally consistent single leaf reflectance.

MAGNETOROTATIONAL TURBULENCE TRANSPORTS ANGULAR MOMENTUM IN STRATIFIED DISKS WITH LOW MAGNETIC PRANDTL NUMBER BUT MAGNETIC REYNOLDS NUMBER ABOVE A CRITICAL VALUE

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

Oishi, Jeffrey S.; Mac Low, Mordecai-Mark, E-mail: jsoishi@stanford.edu, E-mail: mordecai@amnh.org

2011-10-10

The magnetorotational instability (MRI) may dominate outward transport of angular momentum in accretion disks, allowing material to fall onto the central object. Previous work has established that the MRI can drive a mean-field dynamo, possibly leading to a self-sustaining accretion system. Recently, however, simulations of the scaling of the angular momentum transport parameter {alpha}{sub SS} with the magnetic Prandtl number Pm have cast doubt on the ability of the MRI to transport astrophysically relevant amounts of angular momentum in real disk systems. Here, we use simulations including explicit physical viscosity and resistivity to show that when vertical stratification is included,more » mean-field dynamo action operates, driving the system to a configuration in which the magnetic field is not fully helical. This relaxes the constraints on the generated field provided by magnetic helicity conservation, allowing the generation of a mean field on timescales independent of the resistivity. Our models demonstrate the existence of a critical magnetic Reynolds number Rm{sub crit}, below which transport becomes strongly Pm-dependent and chaotic, but above which the transport is steady and Pm-independent. Prior simulations showing Pm dependence had Rm < Rm{sub crit}. We conjecture that this steady regime is possible because the mean-field dynamo is not helicity-limited and thus does not depend on the details of the helicity ejection process. Scaling to realistic astrophysical parameters suggests that disks around both protostars and stellar mass black holes have Rm >> Rm{sub crit}. Thus, we suggest that the strong Pm dependence seen in recent simulations does not occur in real systems.« less

Magnetorotational Turbulence Transports Angular Momentum in Stratified Disks with Low Magnetic Prandtl Number but Magnetic Reynolds Number above a Critical Value

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

Oishi, Jeffrey S.; /KIPAC, Menlo Park; Low, Mordecai-Mark Mac

2012-02-14

The magnetorotational instability (MRI) may dominate outward transport of angular momentum in accretion disks, allowing material to fall onto the central object. Previous work has established that the MRI can drive a mean-field dynamo, possibly leading to a self-sustaining accretion system. Recently, however, simulations of the scaling of the angular momentum transport parameter {alpha}{sub SS} with the magnetic Prandtl number Pm have cast doubt on the ability of the MRI to transport astrophysically relevant amounts of angular momentum in real disk systems. Here, we use simulations including explicit physical viscosity and resistivity to show that when vertical stratification is included,more » mean field dynamo action operates, driving the system to a configuration in which the magnetic field is not fully helical. This relaxes the constraints on the generated field provided by magnetic helicity conservation, allowing the generation of a mean field on timescales independent of the resistivity. Our models demonstrate the existence of a critical magnetic Reynolds number Rm{sub crit}, below which transport becomes strongly Pm-dependent and chaotic, but above which the transport is steady and Pm-independent. Prior simulations showing Pm-dependence had Rm < Rm{sub crit}. We conjecture that this steady regime is possible because the mean field dynamo is not helicity-limited and thus does not depend on the details of the helicity ejection process. Scaling to realistic astrophysical parameters suggests that disks around both protostars and stellar mass black holes have Rm >> Rm{sub crit}. Thus, we suggest that the strong Pm dependence seen in recent simulations does not occur in real systems.« less

Force Field for Peptides and Proteins based on the Classical Drude Oscillator

PubMed Central

Lopes, Pedro E.M.; Huang, Jing; Shim, Jihyun; Luo, Yun; Li, Hui; Roux, Benoît; MacKerell, Alexander D.

2013-01-01

Presented is a polarizable force field based on a classical Drude oscillator framework, currently implemented in the programs CHARMM and NAMD, for modeling and molecular dynamics (MD) simulation studies of peptides and proteins. Building upon parameters for model compounds representative of the functional groups in proteins, the development of the force field focused on the optimization of the parameters for the polypeptide backbone and the connectivity between the backbone and side chains. Optimization of the backbone electrostatic parameters targeted quantum mechanical conformational energies, interactions with water, molecular dipole moments and polarizabilities and experimental condensed phase data for short polypeptides such as (Ala)5. Additional optimization of the backbone φ, ψ conformational preferences included adjustments of the tabulated two-dimensional spline function through the CMAP term. Validation of the model included simulations of a collection of peptides and proteins. This 1st generation polarizable model is shown to maintain the folded state of the studied systems on the 100 ns timescale in explicit solvent MD simulations. The Drude model typically yields larger RMS differences as compared to the additive CHARMM36 force field (C36) and shows additional flexibility as compared to the additive model. Comparison with NMR chemical shift data shows a small degradation of the polarizable model with respect to the additive, though the level of agreement may be considered satisfactory, while for residues shown to have significantly underestimated S2 order parameters in the additive model, improvements are calculated with the polarizable model. Analysis of dipole moments associated with the peptide backbone and tryptophan side chains show the Drude model to have significantly larger values than those present in C36, with the dipole moments of the peptide backbone enhanced to a greater extent in sheets versus helices and the dipoles of individual moieties observed to undergo significant variations during the MD simulations. Although there are still some limitations, the presented model, termed Drude-2013, is anticipated to yield a molecular picture of peptide and protein structure and function that will be of increased physical validity and internal consistency in a computationally accessible fashion. PMID:24459460

Constraining cosmologies with fundamental constants - I. Quintessence and K-essence

NASA Astrophysics Data System (ADS)

Thompson, Rodger I.; Martins, C. J. A. P.; Vielzeuf, P. E.

2013-01-01

Many cosmological models invoke rolling scalar fields to account for the observed acceleration of the expansion of the Universe. These theories generally include a potential V(φ) which is a function of the scalar field φ. Although V(φ) can be represented by a very diverse set of functions, recent work has shown that under some conditions, such as the slow-roll conditions, the equation of state parameter w is either independent of the form of V(φ) or part of family of solutions with only a few parameters. In realistic models of this type the scalar field couples to other sectors of the model leading to possibly observable changes in the fundamental constants such as the fine structure constant α and the proton to electron mass ratio μ. Although the current situation on a possible variance of α is complicated, there are firm limitations on the variance of μ in the early universe. This paper explores the limits this puts on the validity of various cosmologies that invoke rolling scalar fields. We find that the limit on the variation of μ puts significant constraints on the product of a cosmological parameter w + 1 and a new physics parameter ζ2μ, the coupling constant between μ and the rolling scalar field. Even when the cosmologies are restricted to very slow roll conditions either the value of ζμ must be at the lower end of or less than its expected values or the value of w + 1 must be restricted to values vanishingly close to 0. This implies that either the rolling scalar field is very weakly coupled to the electromagnetic field, small ζμ, very weakly coupled to gravity, (w + 1) ≈ 0 or both. These results stress that adherence to the measured invariance in μ is a very significant test of the validity of any proposed cosmology and any new physics it requires. The limits on the variation of μ also produces a significant tension with the reported changes in the value of α.

POSSIBLE EVIDENCE FOR A FISK-TYPE HELIOSPHERIC MAGNETIC FIELD. I. ANALYZING ULYSSES/KET ELECTRON OBSERVATIONS

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

Sternal, O.; Heber, B.; Kopp, A.

The propagation of energetic charged particles in the heliospheric magnetic field is one of the fundamental problems in heliophysics. In particular, the structure of the heliospheric magnetic field remains an unsolved problem and is discussed as a controversial topic. The first successful analytic approach to the structure of the heliospheric magnetic field was the Parker field. However, the measurements of the Ulysses spacecraft at high latitudes revealed the possible need for refinements of the existing magnetic field model during solar minimum. Among other reasons, this led to the development of the Fisk field. This approach is highly debated and couldmore » not be ruled out with magnetic field measurements so far. A promising method to trace this magnetic field structure is to model the propagation of electrons in the energy range of a few MeV. Employing three-dimensional and time-dependent simulations of the propagation of energetic electrons, this work shows that the influence of a Fisk-type field on the particle transport in the heliosphere leads to characteristic variations of the electron intensities on the timescale of a solar rotation. For the first time it is shown that the Ulysses count rates of 2.5-7 MeV electrons contain the imprint of a Fisk-type heliospheric magnetic field structure. From a comparison of simulation results and the Ulysses count rates, realistic parameters for the Fisk theory are derived. Furthermore, these parameters are used to investigate the modeled relative amplitudes of protons and electrons, including the effects of drifts.« less

A model of the FAD redox cycle describes the dynamics of the effect of the geomagnetic field on the human visual system.

PubMed

Thoss, Franz; Bartsch, Bengt

2017-12-01

In experimental studies, we could show that the visual threshold of man is influenced by the geomagnetic field. One of the results was that the threshold shows periodic fluctuations when the vertical component of the field is reversed periodically. The maximum of these oscillations occurred at a period duration of 110 s. To explain this phenomenon, we chose the process that likely underlies the navigation of birds in the geomagnetic field: the light reaction of the FAD component of cryptochrome in the retina. The human retina contains cryptpochrome like the bird retina. Based on the investigations of Müller and Ahmad (J Biol Chem 286:21033-21040, 2011) and Solov'yov and Schulten (J Phys Chem B 116:1089-1099, 2012), we designed a model of the light-induced reduction and subsequent reoxidation of FAD. This model contains a radical pair, whose interconversion dynamics are affected by the geomagnetic field. The parameters of the model were partly calculated from the data of our experimental investigation and partly taken from the results of other authors. These parameters were then optimized by adjusting the model behaviour to the experimental results. The simulation of the finished model shows that the concentrations of all substances included show really oscillations with the frequency of the modelled magnetic field. After optimization of the parameters, the oscillations of FAD and FADH* show maximal amplitude at a period duration of 110 s, as was observed in the experiment. This makes it most likely that the signal, which influences the visual system, originates from FADH* (signalling state).

Study of potential health effects of electromagnetic fields of telephony and Wi-Fi, using chicken embryo development as animal model.

PubMed

Woelders, Henri; de Wit, Agnes; Lourens, Alexander; Stockhofe, Norbert; Engel, Bas; Hulsegge, Ina; Schokker, Dirkjan; van Heijningen, Paula; Vossen, Stefan; Bekers, Dave; Zwamborn, Peter

2017-04-01

The objective of this study is to investigate possible biological effects of radiofrequency electromagnetic fields (RF-EMF) as used in modern wireless telecommunication in a well-controlled experimental environment using chicken embryo development as animal model. Chicken eggs were incubated under continuous experimental exposure to GSM (1.8 GHz), DECT (1.88 GHz), UMTS (2.1 GHz), and WLAN (5.6 GHz) radiation, with the appropriate modulation protocol, using a homogeneous field distribution at a field strength of approximately 3 V/m, representing the maximum field level in a normal living environment. Radiation-shielded exposure units/egg incubators were operating in parallel for exposed and control eggs in a climatized homogeneous environment, using 450 eggs per treatment in three successive rounds per treatment. Dosimetry of the exposure (field characteristics and specific absorption rate) were studied. Biological parameters studied included embryo death during incubation, hatching percentage, and various morphological and histological parameters of embryos and chicks and their organs, and gene expression profiles of embryos on day 7 and day 18 of incubation by microarray and qPCR. No conclusive evidence was found for induced embryonic mortality or malformations by exposure to the used EMFs, or for effects on the other measured parameters. Estimated differences between treatment groups were always small and the effect of treatment was not significant. In a statistical model that ignored possible interaction between rounds and exposure units, some of the many pairwise comparisons of exposed versus control had P-values lower than 0.05, but were not significant after correction for multiple testing. Bioelectromagnetics. 38:186-203, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

A point-charge force field for molecular mechanics simulations of proteins based on condensed-phase quantum mechanical calculations.

PubMed

Duan, Yong; Wu, Chun; Chowdhury, Shibasish; Lee, Mathew C; Xiong, Guoming; Zhang, Wei; Yang, Rong; Cieplak, Piotr; Luo, Ray; Lee, Taisung; Caldwell, James; Wang, Junmei; Kollman, Peter

2003-12-01

Molecular mechanics models have been applied extensively to study the dynamics of proteins and nucleic acids. Here we report the development of a third-generation point-charge all-atom force field for proteins. Following the earlier approach of Cornell et al., the charge set was obtained by fitting to the electrostatic potentials of dipeptides calculated using B3LYP/cc-pVTZ//HF/6-31G** quantum mechanical methods. The main-chain torsion parameters were obtained by fitting to the energy profiles of Ace-Ala-Nme and Ace-Gly-Nme di-peptides calculated using MP2/cc-pVTZ//HF/6-31G** quantum mechanical methods. All other parameters were taken from the existing AMBER data base. The major departure from previous force fields is that all quantum mechanical calculations were done in the condensed phase with continuum solvent models and an effective dielectric constant of epsilon = 4. We anticipate that this force field parameter set will address certain critical short comings of previous force fields in condensed-phase simulations of proteins. Initial tests on peptides demonstrated a high-degree of similarity between the calculated and the statistically measured Ramanchandran maps for both Ace-Gly-Nme and Ace-Ala-Nme di-peptides. Some highlights of our results include (1) well-preserved balance between the extended and helical region distributions, and (2) favorable type-II poly-proline helical region in agreement with recent experiments. Backward compatibility between the new and Cornell et al. charge sets, as judged by overall agreement between dipole moments, allows a smooth transition to the new force field in the area of ligand-binding calculations. Test simulations on a large set of proteins are also discussed. Copyright 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1999-2012, 2003

Molecular Dynamics Simulations, Challenges and Opportunities: A Biologist's Prospective.

PubMed

Kumari, Indu; Sandhu, Padmani; Ahmed, Mushtaq; Akhter, Yusuf

2017-08-30

Molecular dynamics (MD) is a computational technique which is used to study biomolecules in virtual environment. Each of the constituent atoms represents a particle and hence the biomolecule embodies a multi-particle mechanical system analyzed within a simulation box during MD analysis. The potential energies of the atoms are explained by a mathematical expression consisting of different forces and space parameters. There are various software and force fields that have been developed for MD studies of the biomolecules. MD analysis has unravelled the various biological mechanisms (protein folding/unfolding, protein-small molecule interactions, protein-protein interactions, DNA/RNA-protein interactions, proteins embedded in membrane, lipid-lipid interactions, drug transport etc.) operating at the atomic and molecular levels. However, there are still some parameters including torsions in amino acids, carbohydrates (whose structure is extended and not well defined like that of proteins) and single stranded nucleic acids for which the force fields need further improvement, although there are several workers putting in constant efforts in these directions. The existing force fields are not efficient for studying the crowded environment inside the cells, since these interactions involve multiple factors in real time. Therefore, the improved force fields may provide the opportunities for their wider applications on the complex biosystems in diverse cellular conditions. In conclusion, the intervention of MD in the basic sciences involving interdisciplinary approaches will be helpful for understanding many fundamental biological and physiological processes at the molecular levels that may be further applied in various fields including biotechnology, fisheries, sustainable agriculture and biomedical research. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Using sensitivity analysis in model calibration efforts

USGS Publications Warehouse

Tiedeman, Claire; Hill, Mary C.

2003-01-01

In models of natural and engineered systems, sensitivity analysis can be used to assess relations among system state observations, model parameters, and model predictions. The model itself links these three entities, and model sensitivities can be used to quantify the links. Sensitivities are defined as the derivatives of simulated quantities (such as simulated equivalents of observations, or model predictions) with respect to model parameters. We present four measures calculated from model sensitivities that quantify the observation-parameter-prediction links and that are especially useful during the calibration and prediction phases of modeling. These four measures are composite scaled sensitivities (CSS), prediction scaled sensitivities (PSS), the value of improved information (VOII) statistic, and the observation prediction (OPR) statistic. These measures can be used to help guide initial calibration of models, collection of field data beneficial to model predictions, and recalibration of models updated with new field information. Once model sensitivities have been calculated, each of the four measures requires minimal computational effort. We apply the four measures to a three-layer MODFLOW-2000 (Harbaugh et al., 2000; Hill et al., 2000) model of the Death Valley regional ground-water flow system (DVRFS), located in southern Nevada and California. D’Agnese et al. (1997, 1999) developed and calibrated the model using nonlinear regression methods. Figure 1 shows some of the observations, parameters, and predictions for the DVRFS model. Observed quantities include hydraulic heads and spring flows. The 23 defined model parameters include hydraulic conductivities, vertical anisotropies, recharge rates, evapotranspiration rates, and pumpage. Predictions of interest for this regional-scale model are advective transport paths from potential contamination sites underlying the Nevada Test Site and Yucca Mountain.

Approaches to highly parameterized inversion-A guide to using PEST for groundwater-model calibration

USGS Publications Warehouse

Doherty, John E.; Hunt, Randall J.

2010-01-01

Highly parameterized groundwater models can create calibration difficulties. Regularized inversion-the combined use of large numbers of parameters with mathematical approaches for stable parameter estimation-is becoming a common approach to address these difficulties and enhance the transfer of information contained in field measurements to parameters used to model that system. Though commonly used in other industries, regularized inversion is somewhat imperfectly understood in the groundwater field. There is concern that this unfamiliarity can lead to underuse, and misuse, of the methodology. This document is constructed to facilitate the appropriate use of regularized inversion for calibrating highly parameterized groundwater models. The presentation is directed at an intermediate- to advanced-level modeler, and it focuses on the PEST software suite-a frequently used tool for highly parameterized model calibration and one that is widely supported by commercial graphical user interfaces. A brief overview of the regularized inversion approach is provided, and techniques for mathematical regularization offered by PEST are outlined, including Tikhonov, subspace, and hybrid schemes. Guidelines for applying regularized inversion techniques are presented after a logical progression of steps for building suitable PEST input. The discussion starts with use of pilot points as a parameterization device and processing/grouping observations to form multicomponent objective functions. A description of potential parameter solution methodologies and resources available through the PEST software and its supporting utility programs follows. Directing the parameter-estimation process through PEST control variables is then discussed, including guidance for monitoring and optimizing the performance of PEST. Comprehensive listings of PEST control variables, and of the roles performed by PEST utility support programs, are presented in the appendixes.

Fitness costs associated with field-evolved resistance to Bt maize in Spodoptera frugiperda (Lepidoptera: Noctuidae).

PubMed

Jakka, S R K; Knight, V R; Jurat-Fuentes, J L

2014-02-01

Increasing adoption of transgenic crops expressing cry toxin genes from Bacillus thuringiensis (Bt crops) represents an augmented risk for development of insect resistance. While fitness costs can greatly influence the rate of resistance evolution, most available data related to Bt resistance have been obtained from laboratory-selected insect strains. In this article, we test the existence of fitness costs associated with high levels of field-evolved resistance to Bt maize event TC1507 in a strain of Spodoptera frugiperda (JE Smith) originated from maize fields in Puerto Rico. Fitness costs in resistant S. frugiperda were evaluated by comparing biological performance to susceptible insects when reared on meridic diet, maize or soybean leaf tissue, or cotton reproductive tissues. Parameters monitored included larval survival, larval and pupal weights, developmental time (larval and pupal), adult longevity, reproductive traits (fecundity and fertility), and sex ratio. We found that all monitored parameters were influenced to a similar extent by the host, independently of susceptibility to Bt maize. The only parameter that significantly differed between strains for all hosts was a longer larval developmental period in resistant S. frugiperda, which resulted in emergence asynchrony between susceptible and resistant adults. To test the relevance of fitness costs in resistant S. frugiperda, we performed a selection experiment to monitor the stability of resistance in a heterogeneous strain through 12 generations of rearing on meridic diet. Our data demonstrate lack of fitness costs relevant to stability of field-evolved resistance to Bt maize and help explain reported stability of field-evolved resistance in Puerto Rican populations of S. frugiperda.

Studies of the Impact of Magnetic Field Uncertainties on Physics Parameters of the Mu2e Experiment

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

Bradascio, Federica

The Mu2e experiment at Fermilab will search for a signature of charged lepton flavor violation, an effect prohibitively too small to be observed within the Standard Model of particle physics. Therefore, its observation is a signal of new physics. The signature that Mu2e will search for is the ratio of the rate of neutrinoless coherent conversion of muons into electrons in the field of a nucleus, relative to the muon capture rate by the nucleus. The conversion process is an example of charged lepton flavor violation. This experiment aims at a sensitivity of four orders of magnitude higher than previousmore » related experiments. The desired sensitivity implies highly demanding requirements of accuracy in the design and conduct of the experiment. It is therefore important to investigate the tolerance of the experiment to instrumental uncertainties and provide specifications that the design and construction must meet. This is the core of the work reported in this thesis. The design of the experiment is based on three superconducting solenoid magnets. The most important uncertainties in the magnetic field of the solenoids can arise from misalignments of the Transport Solenoid, which transfers the beam from the muon production area to the detector area and eliminates beam-originating backgrounds. In this thesis, the field uncertainties induced by possible misalignments and their impact on the physics parameters of the experiment are examined. The physics parameters include the muon and pion stopping rates and the scattering of beam electrons off the capture target, which determine the signal, intrinsic background and late-arriving background yields, respectively. Additionally, a possible test of the Transport Solenoid alignment with low momentum electrons is examined, as an alternative option to measure its field with conventional probes, which is technically difficult due to mechanical interference. Misalignments of the Transport Solenoid were simulated using standard magnetic field cal- culation tools. Particle transport was simulated using the Mu2e Offline software, which includes realistic models of particle interactions with materials in the full Mu2e geometry. The physics parameters were found tolerant within the precision requirements of the experiment for rigid-body type of misalignments, which are the most dangerous, up to a maximum coil displacement of nearly 10 mm. With the appropriate choice of low momentum electron detector, the proposed Transport Solenoid test is found to be sensitive to such misalignments.« less

Cardiac magnetic field map topology quantified by Kullback-Leibler entropy identifies patients with hypertrophic cardiomyopathy

NASA Astrophysics Data System (ADS)

Schirdewan, A.; Gapelyuk, A.; Fischer, R.; Koch, L.; Schütt, H.; Zacharzowsky, U.; Dietz, R.; Thierfelder, L.; Wessel, N.

2007-03-01

Hypertrophic cardiomyopathy (HCM) is a common primary inherited cardiac muscle disorder, defined clinically by the presence of unexplained left ventricular hypertrophy. The detection of affected patients remains challenging. Genetic testing is limited because only in 50%-60% of all HCM diagnoses an underlying mutation can be found. Furthermore, the disease has a varied clinical course and outcome, with many patients having little or no discernible cardiovascular symptoms, whereas others develop profound exercise limitation and recurrent arrhythmias or sudden cardiac death. Therefore prospective screening of HCM family members is strongly recommended. According to the current guidelines this includes serial echocardiographic and electrocardiographic examinations. In this study we investigated the capability of cardiac magnetic field mapping (CMFM) to detect patients suffering from HCM. We introduce for the first time a combined diagnostic approach based on map topology quantification using Kullback-Leibler (KL) entropy and regional magnetic field strength parameters. The cardiac magnetic field was recorded over the anterior chest wall using a multichannel-LT-SQUID system. CMFM was calculated based on a regular 36 point grid. We analyzed CMFM in patients with confirmed diagnosis of HCM (HCM, n =33, 43.8±13 years, 13 women, 20 men), a control group of healthy subjects (NORMAL, n =57, 39.6±8.9 years; 22 women and 35 men), and patients with confirmed cardiac hypertrophy due to arterial hypertension (HYP, n =42, 49.7±7.9 years, 15 women and 27 men). A subgroup analysis was performed between HCM patients suffering from the obstructive (HOCM, n =19) and nonobstructive (HNCM, n =14) form of the disease. KL entropy based map topology quantification alone identified HCM patients with a sensitivity of 78.8% and specificity of 86.9% (overall classification rate 84.8%). The combination of the KL parameters with a regional field strength parameter improved the overall classification rate to 87.9% (sensitivity: 84.8%, specificity: 88.9%, area under ROC curve: 0.94). KL measures applied to discriminate between HOCM and HNCM patients showed a correct classification of 78.8%. The combination of one KL and one regional parameter again improved the overall classification rate to 97%. A preliminary prospective analysis in two HCM families showed the feasibility of this diagnostic approach with a correct diagnosis of all 22 screened family members (1 HOCM, 4 HNCM, 17 normal). In conclusion, Cardiac Magnetic Field Mapping including KL entropy based topology quantifications is a suitable tool for HCM screening.

Well-Production Data and Gas-Reservoir Heterogeneity -- Reserve Growth Applications

USGS Publications Warehouse

Dyman, Thaddeus S.; Schmoker, James W.

2003-01-01

Oil and gas well production parameters, including peakmonthly production (PMP), peak-consecutive-twelve month production (PYP), and cumulative production (CP), are tested as tools to quantify and understand the heterogeneity of reservoirs in fields where current monthly production is 10 percent or less of PMP. Variation coefficients, defined as VC= (F5-F95)/F50, where F5, F95, and F50 are the 5th, 95th, and 50th (median) fractiles of a probability distribution, are calculated for peak and cumulative production and examined with respect to internal consistency, type of production parameter, conventional versus unconventional accumulations, and reservoir depth. Well-production data for this study were compiled for 69 oil and gas fields in the Lower Pennsylvanian Morrow Formation of the Anadarko Basin, Oklahoma. Of these, 47 fields represent production from marine clastic facies. The Morrow data were supplemented by data from the Upper Cambrian and Lower Ordovician Arbuckle Group, Middle Ordovician Simpson Group, Middle Pennsylvanian Atoka Formation, and Silurian and Lower Devonian Hunton Group of the Anadarko Basin, one large gas field in Upper Cretaceous reservoirs of north-central Montana (Bowdoin field), and three areas of the Upper Devonian and Lower Mississippian Bakken Formation continuous-type (unconventional) oil accumulation in the Williston Basin, North Dakota and Montana. Production parameters (PMP, PYP, and CP) measure the net result of complex geologic, engineering, and economic processes. Our fundamental hypothesis is that well-production data provide information about subsurface heterogeneity in older fields that would be impossible to obtain using geologic techniques with smaller measurement scales such as petrographic, core, and well-log analysis. Results such as these indicate that quantitative measures of production rates and production volumes of wells, expressed as dimensionless variation coefficients, are potentially valuable tools for documenting reservoir heterogeneity in older fields for field redevelopment and risk analysis.

Gravitation theory - Empirical status from solar system experiments.

NASA Technical Reports Server (NTRS)

Nordtvedt, K. L., Jr.

1972-01-01

Review of historical and recent experiments which speak in favor of a post-Newtonian relativistic gravitational theory. The topics include the foundational experiments, metric theories of gravity, experiments designed to differentiate among the metric theories, and tests of Machian concepts of gravity. It is shown that the metric field for any metric theory can be specified by a series of potential terms with several parameters. It is pointed out that empirical results available up to date yield values of the parameters which are consistent with the prediction of Einstein's general relativity.

TH-CD-BRA-07: MRI-Linac Dosimetry: Parameters That Change in a Magnetic Field

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

O’Brien, D. J.; Sawakuchi, G. O.

Purpose: In MRI-linac integrated systems, the presence of the magnetic (B-)field has a large impact of the dose-distribution and the dose-responses of detectors; yet established protocols and previous experience may lead to assumptions about the commissioning process that are no longer valid. This study quantifies parameters that change when performing dosimetry with an MRI-linac including beam quality specifiers and the effective-point-of-measurement (EPOM) of ionization chambers. Methods: We used the Geant4 Monte Carlo code for this work with physics parameters that pass the Fano cavity test to within 0.1% for the simulated conditions with and without a 1.5 T B-field. Amore » point source model with the energy distribution of an MRI-linac beam was used with and without the B-field to calculate the beam quality specifiers %dd(10)× and TPR{sup 20}{sub 10}, the variation of chamber response with orientation and the how the B-field affects the EPOM of ionization chambers by comparing depth-dose curves calculated in water to those generated by a model PTW30013 Farmer chamber. Results: The %dd(10)× changes by over 2% in the presence of the B-field while the TPR{sup 20}{sub 10} is unaffected. Ionization chamber dose-response is known to depend on the orientation w.r.t. the B-field, but two alternative perpendicular orientations (anti-parallel to each other) also differ in dose-response by over 1%. The B-field shifts the EPOM downstream (closer to the chamber center) but it is also shifted laterally by 0.27 times the chamber’s cavity radius. Conclusion: The EPOM is affected by the B-field and it even shifts laterally. The relationship between %dd(10)× and the Spencer-Attix stopping powers is also changed. Care must be taken when using chambers perpendicular to the field as the dose-response changes depending on which perpendicular orientation is used. All of these effects must be considered when performing dosimetry in B-fields and should be accounted for in future dosimetry protocols. This project was partially funded by Elekta Ltd.« less

Static shape control for flexible structures

NASA Technical Reports Server (NTRS)

Rodriguez, G.; Scheid, R. E., Jr.

1986-01-01

An integrated methodology is described for defining static shape control laws for large flexible structures. The techniques include modeling, identifying and estimating the control laws of distributed systems characterized in terms of infinite dimensional state and parameter spaces. The models are expressed as interconnected elliptic partial differential equations governing a range of static loads, with the capability of analyzing electromagnetic fields around antenna systems. A second-order analysis is carried out for statistical errors, and model parameters are determined by maximizing an appropriate defined likelihood functional which adjusts the model to observational data. The parameter estimates are derived from the conditional mean of the observational data, resulting in a least squares superposition of shape functions obtained from the structural model.

Least-Squares Self-Calibration of Imaging Array Data

NASA Technical Reports Server (NTRS)

Arendt, R. G.; Moseley, S. H.; Fixsen, D. J.

2004-01-01

When arrays are used to collect multiple appropriately-dithered images of the same region of sky, the resulting data set can be calibrated using a least-squares minimization procedure that determines the optimal fit between the data and a model of that data. The model parameters include the desired sky intensities as well as instrument parameters such as pixel-to-pixel gains and offsets. The least-squares solution simultaneously provides the formal error estimates for the model parameters. With a suitable observing strategy, the need for separate calibration observations is reduced or eliminated. We show examples of this calibration technique applied to HST NICMOS observations of the Hubble Deep Fields and simulated SIRTF IRAC observations.

Effect of textiles structural parameters on surgical healing; a case study

NASA Astrophysics Data System (ADS)

Marwa, A. Ali

2017-10-01

Medical Textiles is one of the most rapidly expanding sectors in the technical textile market. The huge growth of medical textiles applications was over the last 12 years. “Biomedical Textiles” is a subcategory of medical textiles that narrows the field down to those applications that are intended for active tissue contact, tissue regeneration or surgical implantation. Since the mid-1960s, the current wave of usage is coming as a result of new fibers and new technologies for textile materials construction. “Biotextiles” term include structures composed of textile fibers designed for use in specific biological environments. Medical Textile field was utilizing different materials, textile techniques and structures to provide new medical products with high functionality in the markets. There are other processes that are associated with textiles in terms of the various treatments and finishing. The aim of this article is to draw attention to the medical field in each of Vitro and Vivo trend, and its relation with textile structural parameters, with regard to the fiber material, production techniques, and fabric structures. Also, it is focusing on some cases studies which were applied in our research which produced with different textile parameters. Finally; an overview is presented about modern and innovative applications of the medical textiles.

Langmuir probe diagnostic suite in the C-2 field-reversed configuration

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

Roche, T., E-mail: troche@trialphaenergy.com; Armstrong, S.; Knapp, K.

2014-11-15

Several in situ probes have been designed and implemented into the diagnostic array of the C-2 field-reversed configuration (FRC) at Tri Alpha Energy [M. Tuszewski et al. (the TAE Team), Phys. Rev. Lett. 108, 255008 (2012)]. The probes are all variations on the traditional Langmuir probe. They include linear arrays of triple probes, linear arrays of single-tipped swept probes, a multi-faced Gundestrup probe, and an ion-sensitive probe. The probes vary from 5 to 7 mm diameter in size to minimize plasma perturbations. They also have boron nitride outer casings that prevent unwanted electrical breakdown and reduce the introduction of impurities.more » The probes are mounted on motorized linear-actuators allowing for programmatic scans of the various plasma parameters over the course of several shots. Each probe has a custom set of electronics that allows for measurement of the desired signals. High frequency ( > 5MHz) analog optical-isolators ensure that plasma parameters can be measured at sub-microsecond time scales while providing electrical isolation between machine and data acquisition systems. With these probes time-resolved plasma parameters (temperature, density, spatial potential, flow, and electric field) can be directly/locally measured in the FRC jet and edge/scrape-off layer.« less

Optimizing the operating parameters of corona electrostatic separation for recycling waste scraped printed circuit boards by computer simulation of electric field.

PubMed

Li, Jia; Lu, Hongzhou; Liu, Shushu; Xu, Zhenming

2008-05-01

The printed circuit board (PCB) has a metal content of nearly 28% metal, including an abundance of nonferrous metals such as copper, lead, and tin. The purity of precious metals in PCBs is more than 10 times that of rich-content minerals. Therefore, the recycling of PCBs is an important subject, not only from the viewpoint of waste treatment, but also with respect to the recovery of valuable materials. Compared with traditional process the corona electrostatic separation (CES) had no waste water or gas during the process and it had high productivity with a low-energy cost. In this paper, the roll-type corona electrostatic separator was used to separate metals and nonmetals from scraped waste PCBs. The software MATLAB was used to simulate the distribution of electric field in separating space. It was found that, the variations of parameters of electrodes and applied voltages directly influenced the distribution of electric field. Through the correlation of simulated and experimental results, the good separation results were got under the optimized operating parameter: U=20-30 kV, L=L(1)=L(2)=0.21 m, R(1)=0.114, R(2)=0.019 m, theta(1)=20 degrees and theta(2)=60 degrees .

A new linear plasma device for the study of plasma waves in the electron magnetohydrodynamics regime

NASA Astrophysics Data System (ADS)

Joshi, Garima; Ravi, G.; Mukherjee, S.

2018-06-01

A new, user-friendly, linear plasma device has been developed in our laboratory where a quiescent (Δ n/n ≈ 1%), low temperature (1-10 eV), pulsed (3-10 ms) plasma can be produced over a large uniform region of 30-40 cm diameter and 40 cm length. Salient features of the device include the flexibility of tuning the plasma density in the range of 10^{10} to 10^{12} cm^{-3} and capability of scanning the plasma and field parameters in two dimensions with a precision of < 1 mm. The plasma is produced by a multifilamentary cathode and external magnetic field by Helmholtz coils, both designed and constructed in-house. The plasma parameters can be measured by Langmuir probes and electromagnetic field parameters by miniature magnetic probes and Rogowski coils. The plasma produced is uniform and essentially unbounded for performing experiments on waves and turbulence. The whole device can be operated single-handedly by undergraduate or graduate students. The device can be opened, serviced, new antennas/probes installed and ready for operation in a matter of hours. Some results on the excitation of electromagnetic structures in the context of electron magnetohydrodynamics (EMHD) are also presented to demonstrate the suitability of the device for carrying out such experiments.

Influence of Weak External Magnetic Field on Amorphous and Nanocrystalline Fe-based Alloys

NASA Astrophysics Data System (ADS)

Degmová, J.; Sitek, J.

2010-07-01

Nanoperm, Hitperm and Finamet amorphous and nanocrystalline alloys were measured by Mössbauer spectrometry in a weak external magnetic field of 0.5 T. It was shown that the most sensitive parameters of Mössbauer spectra are the intensities of the 2nd and the 5th lines. Rather small changes were observed also in the case of internal magnetic field values. The spectrum of nanocrystalline Nanoperm showed the increase in A23 parameter (ratio of line intensities) from 2.4 to 3.7 and decrease of internal magnetic field from 20 to 19 T for amorphous subspectrum under the influence of magnetic field. Spectrum of nanocrystalline Finemet shown decrease in A23 parameter from 3.5 to 2.6 almost without a change in the internal magnetic field value. In the case of amorphous Nanoperm and Finemet samples, the changes are almost negligible. Hitperm alloy showed the highest sensitivity to the weak magnetic field, when the A23 parameter increased from 0.4 to 2.5 in the external magnetic fields. The A23 parameter of crystalline subspectrum increased from 2.7 to 3.8 and the value of internal magnetic field corresponding to amorphous subspectrum increased from 22 to 24 T. The behavior of nanocrystalline alloys under weak external magnetic field was analyzed within the three-level relaxation model of magnetic dynamics in an assembly of single-domain particles.

Feasibility study of a procedure to detect and warn of low level wind shear

NASA Technical Reports Server (NTRS)

Turkel, B. S.; Kessel, P. A.; Frost, W.

1981-01-01

A Doppler radar system which provides an aircraft with advanced warning of longitudinal wind shear is described. This system uses a Doppler radar beamed along the glide slope linked with an on line microprocessor containing a two dimensional, three degree of freedom model of the motion of an aircraft including pilot/autopilot control. The Doppler measured longitudinal glide slope winds are entered into the aircraft motion model, and a simulated controlled aircraft trajectory is calculated. Several flight path deterioration parameters are calculated from the computed aircraft trajectory information. The aircraft trajectory program, pilot control models, and the flight path deterioration parameters are discussed. The performance of the computer model and a test pilot in a flight simulator through longitudinal and vertical wind fields characteristic of a thunderstorm wind field are compared.

An Optimization-based Framework to Learn Conditional Random Fields for Multi-label Classification

PubMed Central

Naeini, Mahdi Pakdaman; Batal, Iyad; Liu, Zitao; Hong, CharmGil; Hauskrecht, Milos

2015-01-01

This paper studies multi-label classification problem in which data instances are associated with multiple, possibly high-dimensional, label vectors. This problem is especially challenging when labels are dependent and one cannot decompose the problem into a set of independent classification problems. To address the problem and properly represent label dependencies we propose and study a pairwise conditional random Field (CRF) model. We develop a new approach for learning the structure and parameters of the CRF from data. The approach maximizes the pseudo likelihood of observed labels and relies on the fast proximal gradient descend for learning the structure and limited memory BFGS for learning the parameters of the model. Empirical results on several datasets show that our approach outperforms several multi-label classification baselines, including recently published state-of-the-art methods. PMID:25927015

Studying Solar Wind Properties Around CIRs and Their Effects on GCR Modulation

NASA Astrophysics Data System (ADS)

Ghanbari, K.; Florinski, V. A.

2017-12-01

Corotating interaction region (CIR) events occur when a fast solar wind stream overtakes slow solar wind, forming a compression region ahead and a rarefaction region behind in the fast solar wind. Usually this phenomena occurs along with a crossing of heliospheric current sheet which is the surface separating solar magnetic fields of opposing polarities. In this work, the solar plasma data provided by the ACE science center are utilized to do a superposed epoch analysis on solar parameters including proton density, proton temperature, solar wind speed and solar magnetic field in order to study how the variations of these parameters affect the modulation of galactic cosmic rays. Magnetic fluctuation variances in different parts a of CIR are computed and analyzed using similar techniques in order to understand the cosmic-ray diffusive transport in these regions.

Determination of nuclear quadrupolar parameters using singularities in field-swept NMR patterns.

PubMed

Ichijo, Naoki; Takeda, Kazuyuki; Yamada, Kazuhiko; Takegoshi, K

2016-10-07

We propose a simple data-analysis scheme to determine the coupling constant and the asymmetry parameter of nuclear quadrupolar interactions in field-swept nuclear magnetic resonance (NMR) for static powder samples. This approach correlates the quadrupolar parameters to the positions of the singularities, which can readily be found out as sharp peaks in the field-swept pattern. Moreover, the parameters can be determined without quantitative acquisition and elaborate calculation of the overall profile of the pattern. Since both experimental and computational efforts are significantly reduced, the approach presented in this work will enhance the power of the field-swept NMR for yet unexplored quadrupolar nuclei. We demonstrate this approach in 33 S in α-S 8 and 35 Cl in chloranil. The accuracy of the obtained quadrupolar parameters is also discussed.

Review and perspectives of electrostatic turbulence and transport studies in the basic plasma physics device TORPEX

NASA Astrophysics Data System (ADS)

Avino, Fabio; Bovet, Alexandre; Fasoli, Ambrogio; Furno, Ivo; Gustafson, Kyle; Loizu, Joaquim; Ricci, Paolo; Theiler, Christian

2012-10-01

TORPEX is a basic plasma physics toroidal device located at the CRPP-EPFL in Lausanne. In TORPEX, a vertical magnetic field superposed on a toroidal field creates helicoidal field lines with both ends terminating on the torus vessel. We review recent advances in the understanding and control of electrostatic interchange turbulence, associated structures and their effect on suprathermal ions. These advances are obtained using high-resolution diagnostics of plasma parameters and wave fields throughout the whole device cross-section, fluid models and numerical simulations. Furthermore, we discuss future developments including the possibility of generating closed field line configurations with rotational transform using an internal toroidal wire carrying a current. This system will also allow the study of innovative fusion-relevant configurations, such as the snowflake divertor.

Proton Radiography of Spontaneous Fields, Plasma Flows and Dynamics in X-Ray Driven Inertial-Confinement Fusion Implosions

NASA Astrophysics Data System (ADS)

Li, C. K.; Seguin, F. H.; Frenje, J. A.; Rosenberg, M.; Zylstra, A. B.; Rinderknecht, H. G.; Petrasso, R. D.; Amendt, P. A.; Landen, O. L.; Town, R. P. J.; Betti, R.; Knauer, J. P.; Meyerhofer, D. D.; Back, C. A.; Kilkenny, J. D.; Nikroo, A.

2010-11-01

Backlighting of x-ray-driven implosions in empty hohlraums with mono-energetic protons on the OMEGA laser facility has allowed a number of important phenomena to be observed. Several critical parameters were determined, including plasma flow, three types of spontaneous electric fields and megaGauss magnetic fields. These results provide insight into important issues in indirect-drive ICF. Even though the cavity is effectively a Faraday cage, the strong, local fields inside the hohlraum can affect laser-plasma instabilities, electron distributions and implosion symmetry. They are of fundamental scientific importance for a range of new experiments at the frontiers of high-energy-density physics. Future experiments designed to characterize the field formation and evolution in low-Z gas fill hohlraums will be discussed.

Vacuum Magnetic Field Mapping of the Compact Toroidal Hybrid (CTH)

NASA Astrophysics Data System (ADS)

Peterson, J. T.; Hanson, J.; Hartwell, G. J.; Knowlton, S. F.; Montgomery, C.; Munoz, J.

2007-11-01

Vacuum magnetic field mapping experiments are performed on the CTH torsatron with a movable electron gun and phosphor-coated screen or movable wand at two different toroidal locations. These experiments compare the experimentally measured magnetic configuration produced by the as-built coil set, to the magnetic configuration simulated with the IFT Biot-Savart code using the measured coil set parameters. Efforts to minimize differences between the experimentally measured location of the magnetic axis and its predicted value utilizing a Singular Value Decomposition (SVD) process result in small modifications of the helical coil winding law used to model the vacuum magnetic field geometry of CTH. Because these studies are performed at relatively low fields B = 0.01 - 0.05 T, a uniform ambient magnetic field is included in the minimization procedure.

Modeling local structure using crystal field and spin Hamiltonian parameters: the tetragonal FeK3+-OI2- defect center in KTaO3 crystal

NASA Astrophysics Data System (ADS)

Gnutek, P.; Y Yang, Z.; Rudowicz, C.

2009-11-01

The local structure and the spin Hamiltonian (SH) parameters, including the zero-field-splitting (ZFS) parameters D and (a+2F/3), and the Zeeman g factors g_{\\parallel } and g_{\\perp } , are theoretically investigated for the FeK3+-OI2- center in KTaO3 crystal. The microscopic SH (MSH) parameters are modeled within the framework of the crystal field (CF) theory employing the CF analysis (CFA) package, which also incorporates the MSH modules. Our approach takes into account the spin-orbit interaction as well as the spin-spin and spin-other-orbit interactions omitted in previous studies. The superposition model (SPM) calculations are carried out to provide input CF parameters for the CFA/MSH package. The combined SPM-CFA/MSH approach is used to consider various structural models for the FeK3+-OI2- defect center in KTaO3. This modeling reveals that the off-center displacement of the Fe3+ ions, Δ1(Fe3+), combined with an inward relaxation of the nearest oxygen ligands, Δ2(O2-), and the existence of the interstitial oxygen OI2- give rise to a strong tetragonal crystal field. This finding may explain the large ZFS experimentally observed for the FeK3+-OI2- center in KTaO3. Matching the theoretical MSH predictions with the available structural data as well as electron magnetic resonance (EMR) and optical spectroscopy data enables predicting reasonable ranges of values of Δ1(Fe3+) and Δ2(O2-) as well as the possible location of OI2- ligands around Fe3+ ions in KTaO3. The defect structure model obtained using the SPM-CFA/MSH approach reproduces very well the ranges of the experimental SH parameters D, g_{\\parallel } and g_{\\perp } and importantly yields not only the correct magnitude of D but also the sign, unlike previous studies. More reliable predictions may be achieved when experimental data on (a+2F/3) and/or crystal field energy levels become available. Comparison of our results with those arising from alternative models existing in the literature indicates considerable advantages of our method and presumably higher reliability of our predictions.

Correlation of Electric Field and Critical Design Parameters for Ferroelectric Tunable Microwave Filters

NASA Technical Reports Server (NTRS)

Subramanyam, Guru; VanKeuls, Fred W.; Miranda, Felix A.; Canedy, Chadwick L.; Aggarwal, Sanjeev; Venkatesan, Thirumalai; Ramesh, Ramamoorthy

2000-01-01

The correlation of electric field and critical design parameters such as the insertion loss, frequency ability return loss, and bandwidth of conductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work. This work is based primarily on barium strontium titanate (BSTO) ferroelectric thin film based tunable microstrip filters for room temperature applications. Two new parameters which we believe will simplify the evaluation of ferroelectric thin films for tunable microwave filters, are defined. The first of these, called the sensitivity parameter, is defined as the incremental change in center frequency with incremental change in maximum applied electric field (EPEAK) in the filter. The other, the loss parameter, is defined as the incremental or decremental change in insertion loss of the filter with incremental change in maximum applied electric field. At room temperature, the Au/BSTO/LAO microstrip filters exhibited a sensitivity parameter value between 15 and 5 MHz/cm/kV. The loss parameter varied for different bias configurations used for electrically tuning the filter. The loss parameter varied from 0.05 to 0.01 dB/cm/kV at room temperature.

Photospheric Magnetic Field Properties of Flaring versus Flare-quiet Active Regions. II. Discriminant Analysis

NASA Astrophysics Data System (ADS)

Leka, K. D.; Barnes, G.

2003-10-01

We apply statistical tests based on discriminant analysis to the wide range of photospheric magnetic parameters described in a companion paper by Leka & Barnes, with the goal of identifying those properties that are important for the production of energetic events such as solar flares. The photospheric vector magnetic field data from the University of Hawai'i Imaging Vector Magnetograph are well sampled both temporally and spatially, and we include here data covering 24 flare-event and flare-quiet epochs taken from seven active regions. The mean value and rate of change of each magnetic parameter are treated as separate variables, thus evaluating both the parameter's state and its evolution, to determine which properties are associated with flaring. Considering single variables first, Hotelling's T2-tests show small statistical differences between flare-producing and flare-quiet epochs. Even pairs of variables considered simultaneously, which do show a statistical difference for a number of properties, have high error rates, implying a large degree of overlap of the samples. To better distinguish between flare-producing and flare-quiet populations, larger numbers of variables are simultaneously considered; lower error rates result, but no unique combination of variables is clearly the best discriminator. The sample size is too small to directly compare the predictive power of large numbers of variables simultaneously. Instead, we rank all possible four-variable permutations based on Hotelling's T2-test and look for the most frequently appearing variables in the best permutations, with the interpretation that they are most likely to be associated with flaring. These variables include an increasing kurtosis of the twist parameter and a larger standard deviation of the twist parameter, but a smaller standard deviation of the distribution of the horizontal shear angle and a horizontal field that has a smaller standard deviation but a larger kurtosis. To support the ``sorting all permutations'' method of selecting the most frequently occurring variables, we show that the results of a single 10-variable discriminant analysis are consistent with the ranking. We demonstrate that individually, the variables considered here have little ability to differentiate between flaring and flare-quiet populations, but with multivariable combinations, the populations may be distinguished.

Reference Ellipsoid and Geoid in Chronometric Geodesy

NASA Astrophysics Data System (ADS)

Kopeikin, Sergei M.

2016-02-01

Chronometric geodesy applies general relativity to study the problem of the shape of celestial bodies including the earth, and their gravitational field. The present paper discusses the relativistic problem of construction of a background geometric manifold that is used for describing a reference ellipsoid, geoid, the normal gravity field of the earth and for calculating geoid's undulation (height). We choose the perfect fluid with an ellipsoidal mass distribution uniformly rotating around a fixed axis as a source of matter generating the geometry of the background manifold through the Einstein equations. We formulate the post-Newtonian hydrodynamic equations of the rotating fluid to find out the set of algebraic equations defining the equipotential surface of the gravity field. In order to solve these equations we explicitly perform all integrals characterizing the interior gravitational potentials in terms of elementary functions depending on the parameters defining the shape of the body and the mass distribution. We employ the coordinate freedom of the equations to choose these parameters to make the shape of the rotating fluid configuration to be an ellipsoid of rotation. We derive expressions of the post-Newtonian mass and angular momentum of the rotating fluid as functions of the rotational velocity and the parameters of the ellipsoid including its bare density, eccentricity and semi-major axes. We formulate the post-Newtonian Pizzetti and Clairaut theorems that are used in geodesy to connect the parameters of the reference ellipsoid to the polar and equatorial values of force of gravity. We expand the post-Newtonian geodetic equations characterizing the reference ellipsoid into the Taylor series with respect to the eccentricity of the ellipsoid, and discuss the small-eccentricity approximation. Finally, we introduce the concept of relativistic geoid and its undulation with respect to the reference ellipsoid, and discuss how to calculate it in chronometric geodesy by making use of the anomalous gravity potential.

The Impact of Rainfall on Soil Moisture Dynamics in a Foggy Desert.

PubMed

Li, Bonan; Wang, Lixin; Kaseke, Kudzai F; Li, Lin; Seely, Mary K

2016-01-01

Soil moisture is a key variable in dryland ecosystems since it determines the occurrence and duration of vegetation water stress and affects the development of weather patterns including rainfall. However, the lack of ground observations of soil moisture and rainfall dynamics in many drylands has long been a major obstacle in understanding ecohydrological processes in these ecosystems. It is also uncertain to what extent rainfall controls soil moisture dynamics in fog dominated dryland systems. To this end, in this study, twelve to nineteen months' continuous daily records of rainfall and soil moisture (from January 2014 to August 2015) obtained from three sites (one sand dune site and two gravel plain sites) in the Namib Desert are reported. A process-based model simulating the stochastic soil moisture dynamics in water-limited systems was used to study the relationships between soil moisture and rainfall dynamics. Model sensitivity in response to different soil and vegetation parameters under diverse soil textures was also investigated. Our field observations showed that surface soil moisture dynamics generally follow rainfall patterns at the two gravel plain sites, whereas soil moisture dynamics in the sand dune site did not show a significant relationship with rainfall pattern. The modeling results suggested that most of the soil moisture dynamics can be simulated except the daily fluctuations, which may require a modification of the model structure to include non-rainfall components. Sensitivity analyses suggested that soil hygroscopic point (sh) and field capacity (sfc) were two main parameters controlling soil moisture output, though permanent wilting point (sw) was also very sensitive under the parameter setting of sand dune (Gobabeb) and gravel plain (Kleinberg). Overall, the modeling results were not sensitive to the parameters in non-bounded group (e.g., soil hydraulic conductivity (Ks) and soil porosity (n)). Field observations, stochastic modeling results as well as sensitivity analyses provide soil moisture baseline information for future monitoring and the prediction of soil moisture patterns in the Namib Desert.

The Impact of Rainfall on Soil Moisture Dynamics in a Foggy Desert

PubMed Central

Li, Bonan; Wang, Lixin; Kaseke, Kudzai F.; Li, Lin; Seely, Mary K.

2016-01-01

Soil moisture is a key variable in dryland ecosystems since it determines the occurrence and duration of vegetation water stress and affects the development of weather patterns including rainfall. However, the lack of ground observations of soil moisture and rainfall dynamics in many drylands has long been a major obstacle in understanding ecohydrological processes in these ecosystems. It is also uncertain to what extent rainfall controls soil moisture dynamics in fog dominated dryland systems. To this end, in this study, twelve to nineteen months’ continuous daily records of rainfall and soil moisture (from January 2014 to August 2015) obtained from three sites (one sand dune site and two gravel plain sites) in the Namib Desert are reported. A process-based model simulating the stochastic soil moisture dynamics in water-limited systems was used to study the relationships between soil moisture and rainfall dynamics. Model sensitivity in response to different soil and vegetation parameters under diverse soil textures was also investigated. Our field observations showed that surface soil moisture dynamics generally follow rainfall patterns at the two gravel plain sites, whereas soil moisture dynamics in the sand dune site did not show a significant relationship with rainfall pattern. The modeling results suggested that most of the soil moisture dynamics can be simulated except the daily fluctuations, which may require a modification of the model structure to include non-rainfall components. Sensitivity analyses suggested that soil hygroscopic point (sh) and field capacity (sfc) were two main parameters controlling soil moisture output, though permanent wilting point (sw) was also very sensitive under the parameter setting of sand dune (Gobabeb) and gravel plain (Kleinberg). Overall, the modeling results were not sensitive to the parameters in non-bounded group (e.g., soil hydraulic conductivity (Ks) and soil porosity (n)). Field observations, stochastic modeling results as well as sensitivity analyses provide soil moisture baseline information for future monitoring and the prediction of soil moisture patterns in the Namib Desert. PMID:27764203

Numerical Study of Plasmonic Efficiency of Gold Nanostripes for Molecule Detection

PubMed Central

2015-01-01

In plasmonics, the accurate computation of the electromagnetic field enhancement is necessary in determining the amplitude and the spatial extension of the field around nanostructures. Here, the problem of the interaction between an electromagnetic excitation and gold nanostripes is solved. An optimization scheme, including an adaptive remeshing process with error estimator, is used to solve the problem through a finite element method. The variations of the electromagnetic field amplitude and the plasmonic active zones around nanostructures for molecule detection are studied in this paper taking into account the physical and geometrical parameters of the nanostripes. The evolution between the sizes and number of nanostripes is shown. PMID:25734184

Cascades and dissipation ratio in rotating magnetohydrodynamic turbulence at low magnetic Prandtl number.

PubMed

Plunian, Franck; Stepanov, Rodion

2010-10-01

A phenomenology of isotropic magnetohydrodynamic (MHD) turbulence subject to both rotation and applied magnetic field is presented. It is assumed that the triple correlation decay time is the shortest between the eddy turn-over time and the ones associated to the rotating frequency and the Alfvén wave period. For Pm=1 it leads to four kinds of piecewise spectra, depending on four parameters: injection rate of energy, magnetic diffusivity, rotation rate, and applied field. With a shell model of MHD turbulence (including rotation and applied magnetic field), spectra for Pm ≤ 1 are presented, together with the ratio between magnetic and viscous dissipations.

Characterizing Weak-Link Effects in Mo/Au Transition-Edge Sensors

NASA Technical Reports Server (NTRS)

Smith, Stephen

2011-01-01

We are developing Mo/Au bilayer transition-edge sensors (TESs) for applications in X-ray astronomy. Critical current measurements on these TESs show they act as weak superconducting links exhibiting oscillatory, Fraunhofer-like, behavior with applied magnetic field. In this contribution we investigate the implications of this behavior for TES detectors, under operational bias conditions. This includes characterizing the logarithmic resistance sensitivity with temperature, (alpha, and current, beta, as a function of applied magnetic field and bias point within the resistive transition. Results show that these important device parameters exhibit similar oscillatory behavior with applied magnetic field, which in turn affects the signal responsivity, noise and energy resolution.

Developing a methodology for the inverse estimation of root architectural parameters from field based sampling schemes

NASA Astrophysics Data System (ADS)

Morandage, Shehan; Schnepf, Andrea; Vanderborght, Jan; Javaux, Mathieu; Leitner, Daniel; Laloy, Eric; Vereecken, Harry

2017-04-01

Root traits are increasingly important in breading of new crop varieties. E.g., longer and fewer lateral roots are suggested to improve drought resistance of wheat. Thus, detailed root architectural parameters are important. However, classical field sampling of roots only provides more aggregated information such as root length density (coring), root counts per area (trenches) or root arrival curves at certain depths (rhizotubes). We investigate the possibility of obtaining the information about root system architecture of plants using field based classical root sampling schemes, based on sensitivity analysis and inverse parameter estimation. This methodology was developed based on a virtual experiment where a root architectural model was used to simulate root system development in a field, parameterized for winter wheat. This information provided the ground truth which is normally unknown in a real field experiment. The three sampling schemes coring, trenching, and rhizotubes where virtually applied to and aggregated information computed. Morris OAT global sensitivity analysis method was then performed to determine the most sensitive parameters of root architecture model for the three different sampling methods. The estimated means and the standard deviation of elementary effects of a total number of 37 parameters were evaluated. Upper and lower bounds of the parameters were obtained based on literature and published data of winter wheat root architectural parameters. Root length density profiles of coring, arrival curve characteristics observed in rhizotubes, and root counts in grids of trench profile method were evaluated statistically to investigate the influence of each parameter using five different error functions. Number of branches, insertion angle inter-nodal distance, and elongation rates are the most sensitive parameters and the parameter sensitivity varies slightly with the depth. Most parameters and their interaction with the other parameters show highly nonlinear effect to the model output. The most sensitive parameters will be subject to inverse estimation from the virtual field sampling data using DREAMzs algorithm. The estimated parameters can then be compared with the ground truth in order to determine the suitability of the sampling schemes to identify specific traits or parameters of the root growth model.

Sample Size Estimation in Cluster Randomized Educational Trials: An Empirical Bayes Approach

ERIC Educational Resources Information Center

Rotondi, Michael A.; Donner, Allan

2009-01-01

The educational field has now accumulated an extensive literature reporting on values of the intraclass correlation coefficient, a parameter essential to determining the required size of a planned cluster randomized trial. We propose here a simple simulation-based approach including all relevant information that can facilitate this task. An…

Considerations for site-specific implementation of active downforce and seeding depth technologies on row-crop planters

USDA-ARS?s Scientific Manuscript database

Planter technology continues to rapidly advance including row-by-row control of parameters such as applied downforce and seeding depth that permit real-time adjustment to varying field conditions. The objective of this research was to investigate the relationship of seeding depth and applied downfo...

Effects of a wavy neutral sheet on cosmic ray anisotropies

NASA Technical Reports Server (NTRS)

Kota, J.; Jokipii, J. R.

1985-01-01

The first results of a three-dimensional numerical code calculating cosmic ray anisotropies is presented. The code includes diffusion, convection, adiabatic cooling, and drift in an interplanetary magnetic field model containing a wavy neutral sheet. The 3-D model can reproduce all the principal observations for a reasonable set of parameters.

Improved Methodology for Developing Cost Uncertainty Models for Naval Vessels

DTIC Science & Technology

2009-04-22

Deegan , 2007). Risk cannot be assessed with a point estimate, as it represents a single value that serves as a best guess for the parameter to be...or stakeholders ( Deegan & Fields, 2007). This paper analyzes the current NAVSEA 05C Cruiser (CG(X)) probabilistic cost model including data...provided by Mr. Chris Deegan and his CG(X) analysts. The CG(X) model encompasses all factors considered for cost of the entire program, including

Determination of crustal motions using satellite laser ranging

NASA Technical Reports Server (NTRS)

1991-01-01

Satellite laser ranging has matured over the last decade into one of the essential space geodesy techniques. It has demonstrated centimeter site positioning and millimeter per year velocity determinations in a frame tied dynamically to the mass center of the solid Earth hydrosphere atmosphere system. Such a coordinate system is a requirement for studying long term eustatic sea level rise and other global change phenomena. Earth orientation parameters determined with the coordinate system have been produced in near real time operationally since 1983, at a relatively modest cost. The SLR ranging to Lageos has also provided a rich spectrum of results based upon the analysis of Lageos orbital dynamics. These include significant improvements in the knowledge of the mean and variable components of the Earth's gravity field and the Earth's gravitational parameter. The ability to measure the time variations of the Earth's gravity field has opened as exciting area of study in relating global processes, including meteorologically derived mass transport through changes in the satellite dynamics. New confirmation of general relativity was obtained using the Lageos SLR data.

A fortran program for Monte Carlo simulation of oil-field discovery sequences

USGS Publications Warehouse

Bohling, Geoffrey C.; Davis, J.C.

1993-01-01

We have developed a program for performing Monte Carlo simulation of oil-field discovery histories. A synthetic parent population of fields is generated as a finite sample from a distribution of specified form. The discovery sequence then is simulated by sampling without replacement from this parent population in accordance with a probabilistic discovery process model. The program computes a chi-squared deviation between synthetic and actual discovery sequences as a function of the parameters of the discovery process model, the number of fields in the parent population, and the distributional parameters of the parent population. The program employs the three-parameter log gamma model for the distribution of field sizes and employs a two-parameter discovery process model, allowing the simulation of a wide range of scenarios. ?? 1993.

Magnetic field control of microstructural development in melt-spun Pr 2 Co 14 B

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

McGuire, Michael A.; Rios, Orlando; Conner, Ben S.

In the processing of commercial rare earth permanent magnets, use of external magnetic fields is limited mainly to the alignment of anisotropic particles and the polarization of the finished magnets. Here we explore the effects of high magnetic fields on earlier stages of magnet synthesis, including the crystallization and chemical phase transformations that produce the 2:14:1 phase in the Pr-Co-B system. Pr 2Co 14B alloys produced by melt-spinning were annealed in the presence of strong applied magnetic fields (H=90 kOe). The resulting materials were characterized by x-ray diffraction, electron microscopy, and magnetization measurements. We find that magnetic fields suppress themore » nucleation and growth of crystalline phases, resulting in significantly smaller particle sizes. In addition, magnetic fields applied during processing strongly affects chemical phase selection, suppressing the formation of Pr 2Co 14B and α-Co in favor of Pr 2Co 17. Here, the results demonstrate that increased control over key microstructural properties is achievable by including a strong magnetic field as a processing parameter for rare-earth magnet materials.« less

Magnetic field control of microstructural development in melt-spun Pr 2 Co 14 B

DOE PAGES

McGuire, Michael A.; Rios, Orlando; Conner, Ben S.; ...

2017-01-27

In the processing of commercial rare earth permanent magnets, use of external magnetic fields is limited mainly to the alignment of anisotropic particles and the polarization of the finished magnets. Here we explore the effects of high magnetic fields on earlier stages of magnet synthesis, including the crystallization and chemical phase transformations that produce the 2:14:1 phase in the Pr-Co-B system. Pr 2Co 14B alloys produced by melt-spinning were annealed in the presence of strong applied magnetic fields (H=90 kOe). The resulting materials were characterized by x-ray diffraction, electron microscopy, and magnetization measurements. We find that magnetic fields suppress themore » nucleation and growth of crystalline phases, resulting in significantly smaller particle sizes. In addition, magnetic fields applied during processing strongly affects chemical phase selection, suppressing the formation of Pr 2Co 14B and α-Co in favor of Pr 2Co 17. Here, the results demonstrate that increased control over key microstructural properties is achievable by including a strong magnetic field as a processing parameter for rare-earth magnet materials.« less

The importance of flow history in mixed shear and extensional flows

NASA Astrophysics Data System (ADS)

Wagner, Caroline; McKinley, Gareth

2015-11-01

Many complex fluid flows of experimental and academic interest exhibit mixed kinematics with regions of shear and elongation. Examples include flows through planar hyperbolic contractions in microfluidic devices and through porous media or geometric arrays. Through the introduction of a ``flow-type parameter'' α which varies between 0 in pure shear and 1 in pure elongation, the local velocity fields of all such mixed flows can be concisely characterized. It is tempting to then consider the local stress field and interpret the local state of stress in a complex fluid in terms of shearing or extensional material functions. However, the material response of such fluids exhibit a fading memory of the entire deformation history. We consider a dilute solution of Hookean dumbbells and solve the Oldroyd-B model to obtain analytic expressions for the entire stress field in any arbitrary mixed flow of constant strain rate and flow-type parameter α. We then consider a more complex flow for which the shear rate is constant but the flow-type parameter α varies periodically in time (reminiscent of flow through a periodic array or through repeated contractions and expansions). We show that the flow history and kinematic sequencing (in terms of whether the flow was initialized as shearing or extensional) is extremely important in determining the ensuing stress field and rate of dissipated energy in the flow, and can only be ignored in the limit of infinitely slow flow variations.

Effects of long-term fluid injection on induced seismicity parameters and maximum magnitude in northwestern part of The Geysers geothermal field

NASA Astrophysics Data System (ADS)

Kwiatek, Grzegorz; Martínez-Garzón, Patricia; Dresen, Georg; Bohnhoff, Marco; Sone, Hiroki; Hartline, Craig

2015-10-01

The long-term temporal and spatial changes in statistical, source, and stress characteristics of one cluster of induced seismicity recorded at The Geysers geothermal field (U.S.) are analyzed in relation to the field operations, fluid migration, and constraints on the maximum likely magnitude. Two injection wells, Prati-9 and Prati-29, located in the northwestern part of the field and their associated seismicity composed of 1776 events recorded throughout a 7 year period were analyzed. The seismicity catalog was relocated, and the source characteristics including focal mechanisms and static source parameters were refined using first-motion polarity, spectral fitting, and mesh spectral ratio analysis techniques. The source characteristics together with statistical parameters (b value) and cluster dynamics were used to investigate and understand the details of fluid migration scheme in the vicinity of injection wells. The observed temporal, spatial, and source characteristics were clearly attributed to fluid injection and fluid migration toward greater depths, involving increasing pore pressure in the reservoir. The seasonal changes of injection rates were found to directly impact the shape and spatial extent of the seismic cloud. A tendency of larger seismic events to occur closer to injection wells and a correlation between the spatial extent of the seismic cloud and source sizes of the largest events was observed suggesting geometrical constraints on the maximum likely magnitude and its correlation to the average injection rate and volume of fluids present in the reservoir.

Reparameterization of RNA chi Torsion Parameters for the AMBER Force Field and Comparison to NMR Spectra for Cytidine and Uridine.

PubMed

Yildirim, Ilyas; Stern, Harry A; Kennedy, Scott D; Tubbs, Jason D; Turner, Douglas H

2010-05-11

A reparameterization of the torsional parameters for the glycosidic dihedral angle, chi, for the AMBER99 force field in RNA nucleosides is used to provide a modified force field, AMBER99chi. Molecular dynamics simulations of cytidine, uridine, adenosine, and guanosine in aqueous solution using the AMBER99 and AMBER99chi force fields are compared with NMR results. For each nucleoside and force field, 10 individual molecular dynamics simulations of 30 ns each were run. For cytidine with AMBER99chi force field, each molecular dynamics simulation time was extended to 120 ns for convergence purposes. Nuclear magnetic resonance (NMR) spectroscopy, including one-dimensional (1D) (1)H, steady-state 1D (1)H nuclear Overhauser effect (NOE), and transient 1D (1)H NOE, was used to determine the sugar puckering and preferred base orientation with respect to the ribose of cytidine and uridine. The AMBER99 force field overestimates the population of syn conformations of the base orientation and of C2'-endo sugar puckering of the pyrimidines, while the AMBER99chi force field's predictions are more consistent with NMR results. Moreover, the AMBER99 force field prefers high anti conformations with glycosidic dihedral angles around 310 degrees for the base orientation of purines. The AMBER99chi force field prefers anti conformations around 185 degrees , which is more consistent with the quantum mechanical calculations and known 3D structures of folded ribonucleic acids (RNAs). Evidently, the AMBER99chi force field predicts the structural characteristics of ribonucleosides better than the AMBER99 force field and should improve structural and thermodynamic predictions of RNA structures.

Functional identification of spike-processing neural circuits.

PubMed

Lazar, Aurel A; Slutskiy, Yevgeniy B

2014-02-01

We introduce a novel approach for a complete functional identification of biophysical spike-processing neural circuits. The circuits considered accept multidimensional spike trains as their input and comprise a multitude of temporal receptive fields and conductance-based models of action potential generation. Each temporal receptive field describes the spatiotemporal contribution of all synapses between any two neurons and incorporates the (passive) processing carried out by the dendritic tree. The aggregate dendritic current produced by a multitude of temporal receptive fields is encoded into a sequence of action potentials by a spike generator modeled as a nonlinear dynamical system. Our approach builds on the observation that during any experiment, an entire neural circuit, including its receptive fields and biophysical spike generators, is projected onto the space of stimuli used to identify the circuit. Employing the reproducing kernel Hilbert space (RKHS) of trigonometric polynomials to describe input stimuli, we quantitatively describe the relationship between underlying circuit parameters and their projections. We also derive experimental conditions under which these projections converge to the true parameters. In doing so, we achieve the mathematical tractability needed to characterize the biophysical spike generator and identify the multitude of receptive fields. The algorithms obviate the need to repeat experiments in order to compute the neurons' rate of response, rendering our methodology of interest to both experimental and theoretical neuroscientists.

Extracting physical quantities from BES data

NASA Astrophysics Data System (ADS)

Fox, Michael; Field, Anthony; Schekochihin, Alexander; van Wyk, Ferdinand; MAST Team

2015-11-01

We propose a method to extract the underlying physical properties of turbulence from measurements, thereby facilitating quantitative comparisons between theory and experiment. Beam Emission Spectroscopy (BES) diagnostics record fluctuating intensity time series, which are related to the density field in the plasma through Point-Spread Functions (PSFs). Assuming a suitable form for the correlation function of the underlying turbulence, analytical expressions are derived that relate the correlation parameters of the intensity field: the radial and poloidal correlation lengths and wavenumbers, the correlation time and the fluctuation amplitude, to the equivalent correlation properties of the density field. In many cases, the modification caused by the PSFs is substantial enough to change conclusions about physics. Our method is tested by applying PSFs to the ``real'' density field, generated by non-linear gyrokinetic simulations of MAST, to create synthetic turbulence data, from which the method successfully recovers the correlation function of the ``real'' density field. This method is applied to BES data from MAST to determine the scaling of the 2D structure of the ion-scale turbulence with equilibrium parameters, including the ExB flow shear. Work funded by the Euratom research and training programme 2014-2018 under grant agreement No 633053 and from the RCUK Energy Programme [grant number EP/I501045].

Physical characteristics and resistance parameters of typical urban cyclists.

PubMed

Tengattini, Simone; Bigazzi, Alexander York

2018-03-30

This study investigates the rolling and drag resistance parameters and bicycle and cargo masses of typical urban cyclists. These factors are important for modelling of cyclist speed, power and energy expenditure, with applications including exercise performance, health and safety assessments and transportation network analysis. However, representative values for diverse urban travellers have not been established. Resistance parameters were measured utilizing a field coast-down test for 557 intercepted cyclists in Vancouver, Canada. Masses were also measured, along with other bicycle attributes such as tire pressure and size. The average (standard deviation) of coefficient of rolling resistance, effective frontal area, bicycle plus cargo mass, and bicycle-only mass were 0.0077 (0.0036), 0.559 (0.170) m 2 , 18.3 (4.1) kg, and 13.7 (3.3) kg, respectively. The range of measured values is wider and higher than suggested in existing literature, which focusses on sport cyclists. Significant correlations are identified between resistance parameters and rider and bicycle attributes, indicating higher resistance parameters for less sport-oriented cyclists. The findings of this study are important for appropriately characterising the full range of urban cyclists, including commuters and casual riders.

High-Resolution Source Parameter and Site Characteristics Using Near-Field Recordings - Decoding the Trade-off Problems Between Site and Source

NASA Astrophysics Data System (ADS)

Chen, X.; Abercrombie, R. E.; Pennington, C.

2017-12-01

Recorded seismic waveforms include contributions from earthquake source properties and propagation effects, leading to long-standing trade-off problems between site/path effects and source effects. With near-field recordings, the path effect is relatively small, so the trade-off problem can be simplified to between source and site effects (commonly referred as "kappa value"). This problem is especially significant for small earthquakes where the corner frequencies are within similar ranges of kappa values, so direct spectrum fitting often leads to systematic biases due to corner frequency and magnitude. In response to the significantly increased seismicity rate in Oklahoma, several local networks have been deployed following major earthquakes: the Prague, Pawnee and Fairview earthquakes. Each network provides dense observations within 20 km surrounding the fault zone, recording tens of thousands of aftershocks between M1 to M3. Using near-field recordings in the Prague area, we apply a stacking approach to separate path/site and source effects. The resulting source parameters are consistent with parameters derived from ground motion and spectral ratio methods from other studies; they exhibit spatial coherence within the fault zone for different fault patches. We apply these source parameter constraints in an analysis of kappa values for stations within 20 km of the fault zone. The resulting kappa values show significantly reduced variability compared to those from direct spectral fitting without constraints on the source spectrum; they are not biased by earthquake magnitudes. With these improvements, we plan to apply the stacking analysis to other local arrays to analyze source properties and site characteristics. For selected individual earthquakes, we will also use individual-pair empirical Green's function (EGF) analysis to validate the source parameter estimations.

Developing Dynamic Field Theory Architectures for Embodied Cognitive Systems with cedar.

PubMed

Lomp, Oliver; Richter, Mathis; Zibner, Stephan K U; Schöner, Gregor

2016-01-01

Embodied artificial cognitive systems, such as autonomous robots or intelligent observers, connect cognitive processes to sensory and effector systems in real time. Prime candidates for such embodied intelligence are neurally inspired architectures. While components such as forward neural networks are well established, designing pervasively autonomous neural architectures remains a challenge. This includes the problem of tuning the parameters of such architectures so that they deliver specified functionality under variable environmental conditions and retain these functions as the architectures are expanded. The scaling and autonomy problems are solved, in part, by dynamic field theory (DFT), a theoretical framework for the neural grounding of sensorimotor and cognitive processes. In this paper, we address how to efficiently build DFT architectures that control embodied agents and how to tune their parameters so that the desired cognitive functions emerge while such agents are situated in real environments. In DFT architectures, dynamic neural fields or nodes are assigned dynamic regimes, that is, attractor states and their instabilities, from which cognitive function emerges. Tuning thus amounts to determining values of the dynamic parameters for which the components of a DFT architecture are in the specified dynamic regime under the appropriate environmental conditions. The process of tuning is facilitated by the software framework cedar , which provides a graphical interface to build and execute DFT architectures. It enables to change dynamic parameters online and visualize the activation states of any component while the agent is receiving sensory inputs in real time. Using a simple example, we take the reader through the workflow of conceiving of DFT architectures, implementing them on embodied agents, tuning their parameters, and assessing performance while the system is coupled to real sensory inputs.

Fixation parameter test-retest repeatability of the worse eye in central field loss.

PubMed

Samet, Saba; Tarita-Nistor, Luminita; González, Esther G; Mandelcorn, Mark S; Mandelcorn, Efrem D; Steinbach, Martin J

2018-06-01

Patients with bilateral central field loss develop peripheral retinal loci (PRLs) in the functional eccentric retina. PRL characteristics and visual performance in the better-seeing eye (BE) of these patients have previously been reported. In this study, we determined the test-retest repeatability of fixation parameters, including fixation stability, PRL eccentricity, and PRL span in the worse-seeing eye (WE). Retrospective consecutive case series. Thirty-six patients with bilateral central field loss referred from the Toronto Western Hospital Retina Clinic, who had completed 2 consecutive fixation examinations on the same day. Fixation stability was recorded using the Nidek MP-1 microperimeter (Nidek Technologies Srl., Padova, Italy). For each fixation recording, the following parameters were retrieved: (i) 68.2% bivariate contour ellipse area (BCEA), (ii) PRL span (major and minor axes of the BCEA), (iii) PRL meridian (polar angle), and (iv) PRL eccentricity. Test-retest repeatability for each parameter was assessed using Bland-Altman plots to determine 95% limits of agreement. The mean difference between the fixation trial pairs and the 95% limits of agreement for fixation stability, PRL major axis, PRL minor axis, PRL meridian, and PRL eccentricity were 0.06 ± 0.47 log deg 2 , 0.05° ± 1.42°, 0.07° ± 0.63°, -0.44° ± 66.0°, and -0.23° ±1.56°, respectively. The fixation parameters in the WE showed robust repeatability, comparable to that of the BE as determined from previous studies. The WE's fixation repeatability should be considered in the interpretation of fixation outcome measures subsequent to treatment interventions. Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.

Developing Dynamic Field Theory Architectures for Embodied Cognitive Systems with cedar

PubMed Central

Lomp, Oliver; Richter, Mathis; Zibner, Stephan K. U.; Schöner, Gregor

2016-01-01

Embodied artificial cognitive systems, such as autonomous robots or intelligent observers, connect cognitive processes to sensory and effector systems in real time. Prime candidates for such embodied intelligence are neurally inspired architectures. While components such as forward neural networks are well established, designing pervasively autonomous neural architectures remains a challenge. This includes the problem of tuning the parameters of such architectures so that they deliver specified functionality under variable environmental conditions and retain these functions as the architectures are expanded. The scaling and autonomy problems are solved, in part, by dynamic field theory (DFT), a theoretical framework for the neural grounding of sensorimotor and cognitive processes. In this paper, we address how to efficiently build DFT architectures that control embodied agents and how to tune their parameters so that the desired cognitive functions emerge while such agents are situated in real environments. In DFT architectures, dynamic neural fields or nodes are assigned dynamic regimes, that is, attractor states and their instabilities, from which cognitive function emerges. Tuning thus amounts to determining values of the dynamic parameters for which the components of a DFT architecture are in the specified dynamic regime under the appropriate environmental conditions. The process of tuning is facilitated by the software framework cedar, which provides a graphical interface to build and execute DFT architectures. It enables to change dynamic parameters online and visualize the activation states of any component while the agent is receiving sensory inputs in real time. Using a simple example, we take the reader through the workflow of conceiving of DFT architectures, implementing them on embodied agents, tuning their parameters, and assessing performance while the system is coupled to real sensory inputs. PMID:27853431

Thermal microwave emission from vegetated fields - A comparison between theory and experiment

NASA Technical Reports Server (NTRS)

Wang, J. R.; Shiue, J. C.; Dombrowski, M.; Chuang, S. L.; Shin, R. T.

1984-01-01

The radiometric measurements over bare field and fields covered with grass, soybean, corn, and alfalfa were made with 1.4- and 5-GHz microwave radiometers during August-October 1978. The measured results are compared with radiative transfer theory treating the vegetated fields as a two-layer random medium. It is found that the presence of a vegetation cover generally gives a higher brightness temperature T sub B than that expected from a bare soil. The amount of this T sub B excess increases with increase in the vegetation biomass and in the frequency of the observed radiation. The results of radiative transfer calculations, which include a parameter characterizing ground surface roughness, generally match well with the experimental data.

Determination of Quantum Chemistry Based Force Fields for Molecular Dynamics Simulations of Aromatic Polymers

NASA Technical Reports Server (NTRS)

Jaffe, Richard; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

Ab initio quantum chemistry calculations for model molecules can be used to parameterize force fields for molecular dynamics simulations of polymers. Emphasis in our research group is on using quantum chemistry-based force fields for molecular dynamics simulations of organic polymers in the melt and glassy states, but the methodology is applicable to simulations of small molecules, multicomponent systems and solutions. Special attention is paid to deriving reliable descriptions of the non-bonded and electrostatic interactions. Several procedures have been developed for deriving and calibrating these parameters. Our force fields for aromatic polyimide simulations will be described. In this application, the intermolecular interactions are the critical factor in determining many properties of the polymer (including its color).

Simulation of Temperature Field Distribution for Cutting the Temperated Glass by Ultraviolet Laser

NASA Astrophysics Data System (ADS)

Yang, B. J.; He, Y. C.; Dai, F.; Lin, X. C.

2017-03-01

The finite element software ANSYS was adopted to simulate the temperature field distribution for laser cutting tempered glass, and the influence of different process parameters, including laser power, glass thickness and cutting speed, on temperature field distribution was studied in detail. The results show that the laser power has a greater influence on temperature field distribution than other paremeters, and when the laser power gets to 60W, the highest temperature reaches 749°C, which is higher than the glass softening temperature. It reflects the material near the laser spot is melted and the molten slag is removed by the high-energy water beam quickly. Finally, through the water guided laser cutting tempered glass experiment the FEM theoretical analysis was verified.

Adaptive imaging through far-field turbulence

NASA Astrophysics Data System (ADS)

Troxel, Steven E.; Welsh, Byron M.; Roggemann, Michael C.

1993-11-01

This paper presents a new method for calculating the field angle dependent average OTF of an adaptive optic system and compares this method to calculations based on geometric optics. Geometric optics calculations are shown to be inaccurate due to the diffraction effects created by far-field turbulence and the approximations made in the atmospheric parameters. Our analysis includes diffraction effects and properly accounts for the effect of the atmospheric turbulence scale sizes. We show that for any atmospheric C(superscript 2)(subscript n) profile, the actual OTF is always better than the OTF calculated using geometric optics. The magnitude of the difference between the calculation methods is shown to be dependent on the amount of far- field turbulence and the values of the outer scale dimension.

Particle model of full-size ITER-relevant negative ion source.

PubMed

Taccogna, F; Minelli, P; Ippolito, N

2016-02-01

This work represents the first attempt to model the full-size ITER-relevant negative ion source including the expansion, extraction, and part of the acceleration regions keeping the mesh size fine enough to resolve every single aperture. The model consists of a 2.5D particle-in-cell Monte Carlo collision representation of the plane perpendicular to the filter field lines. Magnetic filter and electron deflection field have been included and a negative ion current density of j(H(-)) = 660 A/m(2) from the plasma grid (PG) is used as parameter for the neutral conversion. The driver is not yet included and a fixed ambipolar flux is emitted from the driver exit plane. Results show the strong asymmetry along the PG driven by the electron Hall (E × B and diamagnetic) drift perpendicular to the filter field. Such asymmetry creates an important dis-homogeneity in the electron current extracted from the different apertures. A steady state is not yet reached after 15 μs.

Towards adjoint-based inversion for rheological parameters in nonlinear viscous mantle flow

NASA Astrophysics Data System (ADS)

Worthen, Jennifer; Stadler, Georg; Petra, Noemi; Gurnis, Michael; Ghattas, Omar

2014-09-01

We address the problem of inferring mantle rheological parameter fields from surface velocity observations and instantaneous nonlinear mantle flow models. We formulate this inverse problem as an infinite-dimensional nonlinear least squares optimization problem governed by nonlinear Stokes equations. We provide expressions for the gradient of the cost functional of this optimization problem with respect to two spatially-varying rheological parameter fields: the viscosity prefactor and the exponent of the second invariant of the strain rate tensor. Adjoint (linearized) Stokes equations, which are characterized by a 4th order anisotropic viscosity tensor, facilitates efficient computation of the gradient. A quasi-Newton method for the solution of this optimization problem is presented, which requires the repeated solution of both nonlinear forward Stokes and linearized adjoint Stokes equations. For the solution of the nonlinear Stokes equations, we find that Newton’s method is significantly more efficient than a Picard fixed point method. Spectral analysis of the inverse operator given by the Hessian of the optimization problem reveals that the numerical eigenvalues collapse rapidly to zero, suggesting a high degree of ill-posedness of the inverse problem. To overcome this ill-posedness, we employ Tikhonov regularization (favoring smooth parameter fields) or total variation (TV) regularization (favoring piecewise-smooth parameter fields). Solution of two- and three-dimensional finite element-based model inverse problems show that a constant parameter in the constitutive law can be recovered well from surface velocity observations. Inverting for a spatially-varying parameter field leads to its reasonable recovery, in particular close to the surface. When inferring two spatially varying parameter fields, only an effective viscosity field and the total viscous dissipation are recoverable. Finally, a model of a subducting plate shows that a localized weak zone at the plate boundary can be partially recovered, especially with TV regularization.

Physiologic noise regression, motion regression, and TOAST dynamic field correction in complex-valued fMRI time series.

PubMed

Hahn, Andrew D; Rowe, Daniel B

2012-02-01

As more evidence is presented suggesting that the phase, as well as the magnitude, of functional MRI (fMRI) time series may contain important information and that there are theoretical drawbacks to modeling functional response in the magnitude alone, removing noise in the phase is becoming more important. Previous studies have shown that retrospective correction of noise from physiologic sources can remove significant phase variance and that dynamic main magnetic field correction and regression of estimated motion parameters also remove significant phase fluctuations. In this work, we investigate the performance of physiologic noise regression in a framework along with correction for dynamic main field fluctuations and motion regression. Our findings suggest that including physiologic regressors provides some benefit in terms of reduction in phase noise power, but it is small compared to the benefit of dynamic field corrections and use of estimated motion parameters as nuisance regressors. Additionally, we show that the use of all three techniques reduces phase variance substantially, removes undesirable spatial phase correlations and improves detection of the functional response in magnitude and phase. Copyright © 2011 Elsevier Inc. All rights reserved.

Effects of magnetic-fluid flow on structural instability of a carbon nanotube conveying nanoflow under a longitudinal magnetic field

NASA Astrophysics Data System (ADS)

Sadeghi-Goughari, Moslem; Jeon, Soo; Kwon, Hyock-Ju

2017-09-01

In drug delivery systems, carbon nanotubes (CNTs) can be used to deliver anticancer drugs into target site to kill metastatic cancer cells under the magnetic field guidance. Deep understanding of dynamic behavior of CNTs in drug delivery systems may enable more efficient use of the drugs while reducing systemic side effects. In this paper, we study the effect of magnetic-fluid flow on the structural instability of a CNT conveying nanoflow under a longitudinal magnetic field. The Navier-Stokes equation of magnetic-fluid flow is coupled with Euler-Bernoulli beam theory for modeling fluid structure interaction (FSI). Size effects of the magnetic fluid and the CNT are addressed through small-scale parameters including the Knudsen number (Kn) and the nonlocal parameter. Results show the positive role of magnetic properties of fluid flow on the structural stability of CNT. Specifically, magnetic force applied to the fluid flow has an effect of decreasing the structural stiffness of system while increasing the critical flow velocity. Furthermore, we discover that the nanoscale effects of CNT and fluid flow tend to amplify the influence of magnetic field on the vibrational behavior of the system.

A Public Ks -selected Catalog in the COSMOS/ULTRAVISTA Field: Photometry, Photometric Redshifts, and Stellar Population Parameters

NASA Astrophysics Data System (ADS)

Muzzin, Adam; Marchesini, Danilo; Stefanon, Mauro; Franx, Marijn; Milvang-Jensen, Bo; Dunlop, James S.; Fynbo, J. P. U.; Brammer, Gabriel; Labbé, Ivo; van Dokkum, Pieter

2013-05-01

We present a catalog covering 1.62 deg2 of the COSMOS/UltraVISTA field with point-spread function (PSF) matched photometry in 30 photometric bands. The catalog covers the wavelength range 0.15-24 μm including the available GALEX, Subaru, Canada-France-Hawaii Telescope, VISTA, and Spitzer data. Catalog sources have been selected from the DR1 UltraVISTA Ks band imaging that reaches a depth of K s, tot = 23.4 AB (90% completeness). The PSF-matched catalog is generated using position-dependent PSFs ensuring accurate colors across the entire field. Also included is a catalog of photometric redshifts (z phot) for all galaxies computed with the EAZY code. Comparison with spectroscopy from the zCOSMOS 10k bright sample shows that up to z ~ 1.5 the z phot are accurate to Δz/(1 + z) = 0.013, with a catastrophic outlier fraction of only 1.6%. The z phot also show good agreement with the z phot from the NEWFIRM Medium Band Survey out to z ~ 3. A catalog of stellar masses and stellar population parameters for galaxies determined using the FAST spectral energy distribution fitting code is provided for all galaxies. Also included are rest-frame U - V and V - J colors, L 2800 and L IR. The UVJ color-color diagram confirms that the galaxy bi-modality is well-established out to z ~ 2. Star-forming galaxies also obey a star-forming "main sequence" out to z ~ 2.5, and this sequence evolves in a manner consistent with previous measurements. The COSMOS/UltraVISTA Ks -selected catalog covers a unique parameter space in both depth, area, and multi-wavelength coverage and promises to be a useful tool for studying the growth of the galaxy population out to z ~ 3-4. .

A PUBLIC K{sub s} -SELECTED CATALOG IN THE COSMOS/ULTRAVISTA FIELD: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR POPULATION PARAMETERS {sup ,}

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

Muzzin, Adam; Franx, Marijn; Labbe, Ivo

2013-05-01

We present a catalog covering 1.62 deg{sup 2} of the COSMOS/UltraVISTA field with point-spread function (PSF) matched photometry in 30 photometric bands. The catalog covers the wavelength range 0.15-24 {mu}m including the available GALEX, Subaru, Canada-France-Hawaii Telescope, VISTA, and Spitzer data. Catalog sources have been selected from the DR1 UltraVISTA K{sub s} band imaging that reaches a depth of K {sub s,tot} = 23.4 AB (90% completeness). The PSF-matched catalog is generated using position-dependent PSFs ensuring accurate colors across the entire field. Also included is a catalog of photometric redshifts (z {sub phot}) for all galaxies computed with the EAZYmore » code. Comparison with spectroscopy from the zCOSMOS 10k bright sample shows that up to z {approx} 1.5 the z {sub phot} are accurate to {Delta}z/(1 + z) = 0.013, with a catastrophic outlier fraction of only 1.6%. The z {sub phot} also show good agreement with the z {sub phot} from the NEWFIRM Medium Band Survey out to z {approx} 3. A catalog of stellar masses and stellar population parameters for galaxies determined using the FAST spectral energy distribution fitting code is provided for all galaxies. Also included are rest-frame U - V and V - J colors, L {sub 2800} and L {sub IR}. The UVJ color-color diagram confirms that the galaxy bi-modality is well-established out to z {approx} 2. Star-forming galaxies also obey a star-forming 'main sequence' out to z {approx} 2.5, and this sequence evolves in a manner consistent with previous measurements. The COSMOS/UltraVISTA K{sub s} -selected catalog covers a unique parameter space in both depth, area, and multi-wavelength coverage and promises to be a useful tool for studying the growth of the galaxy population out to z {approx} 3-4.« less

Direct formulation of a 4-node hybrid shell element with rotational degrees of freedom

NASA Technical Reports Server (NTRS)

Aminpour, Mohammad A.

1990-01-01

A simple 4-node assumed-stress hybrid quadrilateral shell element with rotational or drilling degrees of freedom is formulated. The element formulation is based directly on a 4-node element. This direct formulation requires fewer computations than a similar element that is derived from an internal 8-node isoparametric element in which the midside degrees of freedom are eliminated in favor of rotational degree of freedom at the corner nodes. The formulation is based on the principle of minimum complementary energy. The membrane part of the element has 12 degrees of freedom including rotational degrees of freedom. The bending part of the element also has 12 degrees of freedom. The bending part of the quadratic variations for both in-plane and out-of-plane displacement fields and linear variations for both in-plane and out-of-plane rotation fields are assumed along the edges of the element. The element Cartesian-coordinate system is chosen such as to make the stress field invariant with respect to node numbering. The membrane part of the stress field is based on a 9-parameter equilibrating stress field, while the bending part is based on a 13-parameter equilibrating stress field. The element passes the patch test, is nearly insensitive to mesh distortion, does not lock, possesses the desirable invariance properties, has no spurious modes, and produces accurate and reliable results.

Model Parameter Variability for Enhanced Anaerobic Bioremediation of DNAPL Source Zones

NASA Astrophysics Data System (ADS)

Mao, X.; Gerhard, J. I.; Barry, D. A.

2005-12-01

The objective of the Source Area Bioremediation (SABRE) project, an international collaboration of twelve companies, two government agencies and three research institutions, is to evaluate the performance of enhanced anaerobic bioremediation for the treatment of chlorinated ethene source areas containing dense, non-aqueous phase liquids (DNAPL). This 4-year, 5.7 million dollars research effort focuses on a pilot-scale demonstration of enhanced bioremediation at a trichloroethene (TCE) DNAPL field site in the United Kingdom, and includes a significant program of laboratory and modelling studies. Prior to field implementation, a large-scale, multi-laboratory microcosm study was performed to determine the optimal system properties to support dehalogenation of TCE in site soil and groundwater. This statistically-based suite of experiments measured the influence of key variables (electron donor, nutrient addition, bioaugmentation, TCE concentration and sulphate concentration) in promoting the reductive dechlorination of TCE to ethene. As well, a comprehensive biogeochemical numerical model was developed for simulating the anaerobic dehalogenation of chlorinated ethenes. An appropriate (reduced) version of this model was combined with a parameter estimation method based on fitting of the experimental results. Each of over 150 individual microcosm calibrations involved matching predicted and observed time-varying concentrations of all chlorinated compounds. This study focuses on an analysis of this suite of fitted model parameter values. This includes determining the statistical correlation between parameters typically employed in standard Michaelis-Menten type rate descriptions (e.g., maximum dechlorination rates, half-saturation constants) and the key experimental variables. The analysis provides insight into the degree to which aqueous phase TCE and cis-DCE inhibit dechlorination of less-chlorinated compounds. Overall, this work provides a database of the numerical modelling parameters typically employed for simulating TCE dechlorination relevant for a range of system conditions (e.g, bioaugmented, high TCE concentrations, etc.). The significance of the obtained variability of parameters is illustrated with one-dimensional simulations of enhanced anaerobic bioremediation of residual TCE DNAPL.

JMOSFET: A MOSFET parameter extractor with geometry-dependent terms

NASA Technical Reports Server (NTRS)

Buehler, M. G.; Moore, B. T.

1985-01-01

The parameters from metal-oxide-silicon field-effect transistors (MOSFETs) that are included on the Combined Release and Radiation Effects Satellite (CRRES) test chips need to be extracted to have a simple but comprehensive method that can be used in wafer acceptance, and to have a method that is sufficiently accurate that it can be used in integrated circuits. A set of MOSFET parameter extraction procedures that are directly linked to the MOSFET model equations and that facilitate the use of simple, direct curve-fitting techniques are developed. In addition, the major physical effects that affect MOSFET operation in the linear and saturation regions of operation for devices fabricated in 1.2 to 3.0 mm CMOS technology are included. The fitting procedures were designed to establish single values for such parameters as threshold voltage and transconductance and to provide for slope matching between the linear and saturation regions of the MOSFET output current-voltage curves. Four different sizes of transistors that cover a rectangular-shaped region of the channel length-width plane are analyzed.

a Study of High Transition Temperature Superconductors: Mercury-Copper Oxide Systems

NASA Astrophysics Data System (ADS)

Kirven, Paul Douglas

1995-01-01

The Hg-based copper-oxides viz., HgBa _2Ca_{n-1}Cu_ nO _{2n+2+delta}, were discovered in 1993. A system consisting of many different, but related, compounds can be synthesized by including or substituting one or more elements in the original compound (e.g. Hg _{1-x}Pb_ x). In this thesis, the superconducting and normal state properties of several of these compounds were investigated. In the normal state electrical resistivity rho(T) is a linear function of temperature (T) and the magnetic susceptibility, X(T), is weakly paramagnetic. Many were observed to superconduct at very high temperatures. At 5 K up to 80% perfect diamagnetic X(T) was measured. The onset transition temperature (T_ c), where a specimen starts to superconduct, is observed to be as high as 135 K. Although T_ c is about 10 K higher than that of any previously known material, in many respects the properties of this new system are similar to that of other type II superconductors. Flux flow behavior and the nature of these type II superconductors was investigated via SQUID measurements and high field longitudinal magneto-resistance R(T,H) as a function of field and temperature. The study of flux motion allows one to observe Anderson-Kim type logarithimic flux creep at low temperature and field (T < 80K and B < 2T) and giant -flux flow at high temperature and field (80 < T < 130; B < 17T). Key parameters were determined. Some of which include reversibility temperature T*(H), critical field Hc, and pinning potential, Uo. Normal state properties which were also measured include the following: Curie constant, Curie-Weiss temperature (15-25 K), temperature independent susceptibility, and Sommerfeld constant (10-25 mJ/mol.Cu K^2). The values of these parameters of the Hg-based superconductors were compared to those of other superconductors. The results of this investigation are expected to yield a better understanding of this newest family of high temperature superconductors.

Temperature, stress, and corrosive sensing apparatus utilizing harmonic response of magnetically soft sensor element (s)

NASA Technical Reports Server (NTRS)

Grimes, Craig A. (Inventor); Ong, Keat Ghee (Inventor)

2003-01-01

A temperature sensing apparatus including a sensor element made of a magnetically soft material operatively arranged within a first and second time-varying interrogation magnetic field, the first time-varying magnetic field being generated at a frequency higher than that for the second magnetic field. A receiver, remote from the sensor element, is engaged to measure intensity of electromagnetic emissions from the sensor element to identify a relative maximum amplitude value for each of a plurality of higher-order harmonic frequency amplitudes so measured. A unit then determines a value for temperature (or other parameter of interst) using the relative maximum harmonic amplitude values identified. In other aspects of the invention, the focus is on an apparatus and technique for determining a value for of stress condition of a solid analyte and for determining a value for corrosion, using the relative maximum harmonic amplitude values identified. A magnetically hard element supporting a biasing field adjacent the magnetically soft sensor element can be included.

Crystal field parameters and energy levels scheme of trivalent chromium doped BSO

NASA Astrophysics Data System (ADS)

Petkova, P.; Andreici, E.-L.; Avram, N. M.

2014-11-01

The aim of this paper is to give an analysis of crystal field parameters and energy levels schemes for the above doped material, in order to give a reliable explanation for experimental data. The crystal field parameters have been modeled in the frame of Exchange Charge Model (ECM) of the crystal field theory, taken into account the geometry of systems, with actually site symmetry of the impurity ions. The effect of the charges of the ligands and covalence bonding between chromium cation and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of the crystal field parameters we simulated the scheme of energy levels of chromium ions by diagonalizing the matrix of the Hamiltonian of the doped crystal. The obtained energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison with experiment shows that the results are quite satisfactory which justify the model and simulation scheme used for the title system.

Crystal field parameters and energy levels scheme of trivalent chromium doped BSO

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

Petkova, P.; Andreici, E.-L.; Avram, N. M., E-mail: n1m2marva@yahoo.com

The aim of this paper is to give an analysis of crystal field parameters and energy levels schemes for the above doped material, in order to give a reliable explanation for experimental data. The crystal field parameters have been modeled in the frame of Exchange Charge Model (ECM) of the crystal field theory, taken into account the geometry of systems, with actually site symmetry of the impurity ions. The effect of the charges of the ligands and covalence bonding between chromium cation and oxygen anions, in the cluster approach, also were taken into account. With the obtained values of themore » crystal field parameters we simulated the scheme of energy levels of chromium ions by diagonalizing the matrix of the Hamiltonian of the doped crystal. The obtained energy levels and estimated Racah parameters B and C were compared with the experimental spectroscopic data and discussed. Comparison with experiment shows that the results are quite satisfactory which justify the model and simulation scheme used for the title system.« less

Simulation of aerobic and anaerobic biodegradation processes at a crude oil spill site

USGS Publications Warehouse

Essaid, Hedeff I.; Bekins, Barbara A.; Godsy, E. Michael; Warren, Ean; Baedecker, Mary Jo; Cozzarelli, Isabelle M.

1995-01-01

A two-dimensional, multispecies reactive solute transport model with sequential aerobic and anaerobic degradation processes was developed and tested. The model was used to study the field-scale solute transport and degradation processes at the Bemidji, Minnesota, crude oil spill site. The simulations included the biodegradation of volatile and nonvolatile fractions of dissolved organic carbon by aerobic processes, manganese and iron reduction, and methanogenesis. Model parameter estimates were constrained by published Monod kinetic parameters, theoretical yield estimates, and field biomass measurements. Despite the considerable uncertainty in the model parameter estimates, results of simulations reproduced the general features of the observed groundwater plume and the measured bacterial concentrations. In the simulation, 46% of the total dissolved organic carbon (TDOC) introduced into the aquifer was degraded. Aerobic degradation accounted for 40% of the TDOC degraded. Anaerobic processes accounted for the remaining 60% of degradation of TDOC: 5% by Mn reduction, 19% by Fe reduction, and 36% by methanogenesis. Thus anaerobic processes account for more than half of the removal of DOC at this site.

Coupling Network Computing Applications in Air-cooled Turbine Blades Optimization

NASA Astrophysics Data System (ADS)

Shi, Liang; Yan, Peigang; Xie, Ming; Han, Wanjin

2018-05-01

Through establishing control parameters from blade outside to inside, the parametric design of air-cooled turbine blade based on airfoil has been implemented. On the basis of fast updating structure features and generating solid model, a complex cooling system has been created. Different flow units are modeled into a complex network topology with parallel and serial connection. Applying one-dimensional flow theory, programs have been composed to get pipeline network physical quantities along flow path, including flow rate, pressure, temperature and other parameters. These inner units parameters set as inner boundary conditions for external flow field calculation program HIT-3D by interpolation, thus to achieve full field thermal coupling simulation. Referring the studies in literatures to verify the effectiveness of pipeline network program and coupling algorithm. After that, on the basis of a modified design, and with the help of iSIGHT-FD, an optimization platform had been established. Through MIGA mechanism, the target of enhancing cooling efficiency has been reached, and the thermal stress has been effectively reduced. Research work in this paper has significance for rapid deploying the cooling structure design.

Orbital Motions and the Conservation-Law/Preferred-Frame α_3 Parameter

NASA Astrophysics Data System (ADS)

Iorio, Lorenzo

2014-09-01

We analytically calculate some orbital effects induced by the Lorentz-invariance/ momentum-conservation parameterized post-Newtonian (PPN) parameter α_3 in a gravitationally bound binary system made of a primary orbited by a test particle. We neither restrict ourselves to any particular orbital configuration nor to specific orientations of the primary's spin axis ψ. We use our results to put preliminary upper bounds on α_3 in the weak-field regime by using the latest data from Solar System's planetary dynamics. By linearly combining the supplementary perihelion precessions Δw of the Earth, Mars and Saturn, determined by astronomers with the Ephemerides of Planets and the Moon (EPM) 2011 ephemerides for the general relativistic values of the PPN parameters β = γ = 1, we infer |α_3| ;5 6 × 10^-10. Our result is about three orders of magnitude better than the previous weak-field constraints existing in the literature and of the same order of magnitude of the constraint expected from the future BepiColombo mission to Mercury. It is, by construction, independent of the other preferred-frame PPN parameters α1, α2, both preliminarily constrained down to a ≈ 10^-6 level. Future analyses should be performed by explicitly including α3 and a selection of other PPN parameters in the models fitted by the astronomers to the observations and estimating them in dedicated covariance analyses.

Neural network evaluation of tokamak current profiles for real time control

NASA Astrophysics Data System (ADS)

Wróblewski, Dariusz

1997-02-01

Active feedback control of the current profile, requiring real-time determination of the current profile parameters, is envisioned for tokamaks operating in enhanced confinement regimes. The distribution of toroidal current in a tokamak is now routinely evaluated based on external (magnetic probes, flux loops) and internal (motional Stark effect) measurements of the poloidal magnetic field. However, the analysis involves reconstruction of magnetohydrodynamic equilibrium and is too intensive computationally to be performed in real time. In the present study, a neural network is used to provide a mapping from the magnetic measurements (internal and external) to selected parameters of the safety factor profile. The single-pass, feedforward calculation of output of a trained neural network is very fast, making this approach particularly suitable for real-time applications. The network was trained on a large set of simulated equilibrium data for the DIII-D tokamak. The database encompasses a large variety of current profiles including the hollow current profiles important for reversed central shear operation. The parameters of safety factor profile (a quantity related to the current profile through the magnetic field tilt angle) estimated by the neural network include central safety factor, q0, minimum value of q, qmin, and the location of qmin. Very good performance of the trained neural network both for simulated test data and for experimental datais demonstrated.

Neural network evaluation of tokamak current profiles for real time control (abstract)

NASA Astrophysics Data System (ADS)

Wróblewski, Dariusz

1997-01-01

Active feedback control of the current profile, requiring real-time determination of the current profile parameters, is envisioned for tokamaks operating in enhanced confinement regimes. The distribution of toroidal current in a tokamak is now routinely evaluated based on external (magnetic probes, flux loops) and internal (motional Stark effect) measurements of the poloidal magnetic field. However, the analysis involves reconstruction of magnetohydrodynamic equilibrium and is too intensive computationally to be performed in real time. In the present study, a neural network is used to provide a mapping from the magnetic measurements (internal and external) to selected parameters of the safety factor profile. The single-pass, feedforward calculation of output of a trained neural network is very fast, making this approach particularly suitable for real-time applications. The network was trained on a large set of simulated equilibrium data for the DIII-D tokamak. The database encompasses a large variety of current profiles including the hollow current profiles important for reversed central shear operation. The parameters of safety factor profile (a quantity related to the current profile through the magnetic field tilt angle) estimated by the neural network include central safety factor, q0, minimum value of q, qmin, and the location of qmin. Very good performance of the trained neural network both for simulated test data and for experimental data is demonstrated.

Earth's magnetic field effect on MUF calculation and consequences for hmF2 trend estimates

NASA Astrophysics Data System (ADS)

Elias, Ana G.; Zossi, Bruno S.; Yiğit, Erdal; Saavedra, Zenon; de Haro Barbas, Blas F.

2017-10-01

Knowledge of the state of the upper atmosphere, and in particular of the ionosphere, is essential in several applications such as systems used in radio frequency communications, satellite positioning and navigation. In general, these systems depend on the state and evolution of the ionosphere. In all applications involving the ionosphere an essential task is to determine the path and modifications of ray propagation through the ionospheric plasma. The ionospheric refractive index and the maximum usable frequency (MUF) that can be received over a given distance are some key parameters that are crucial for such technological applications. However, currently the representation of these parameters are in general simplified, neglecting the effects of Earth's magnetic field. The value of M(3000)F2, related to the MUF that can be received over 3000 km is routinely scaled from ionograms using a technique which also neglects the geomagnetic field effects assuming a standard simplified propagation model. M(3000)F2 is expected to be affected by a systematic trend linked to the secular variations of Earth's magnetic field. On the other hand, among the upper atmospheric effects expected from increasing greenhouse gases concentration is the lowering of the F2-layer peak density height, hmF2. This ionospheric parameter is usually estimated using the M(3000)F2 factor, so it would also carry this ;systematic trend;. In this study, the geomagnetic field effect on MUF estimations is analyzed as well as its impact on hmF2 long-term trend estimations. We find that M(3000)F2 increases when the geomagnetic field is included in its calculation, and hence hmF2, estimated using existing methods involving no magnetic field for M(3000)F2 scaling, would present a weak but steady trend linked to these variations which would increase or compensate the few kilometers decrease ( 2 km per decade) expected from greenhouse gases effect.

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

Zhou, S; Fan, Q; Lei, Y

Purpose: In-Water-Output-Ratio (IWOR) plays a significant role in linac-based radiotherapy treatment planning, linking MUs to delivered radiation dose. For an open rectangular field, IWOR depends on both its width and length, and changes rapidly when one of them becomes small. In this study, a universal functional form is proposed to fit the open field IWOR tables in Varian TrueBeam representative datasets for all photon energies. Methods: A novel Generalized Mean formula is first used to estimate the Equivalent Square (ES) for a rectangular field. The formula’s weighting factor and power index are determined by collapsing all data points as muchmore » as possible onto a single curve in IWOR vs. ES plot. The result is then fitted with a novel universal function IWOR=1+b*Log(ES/10cm)/(ES/10cm)^c via a least-square procedure to determine the optimal values for parameters b and c. The maximum relative residual error in IWOR over the entire two-dimensional measurement table with field sizes between 3cm and 40cm is used to evaluate the quality of fit for the function. Results: The two-step fitting strategy works very well in determining the optimal parameter values for open field IWOR of each photon energies in the Varian data-set. Relative residual error ≤0.71% is achieved for all photon energies (including Flattening-Filter-Free modes) with field sizes between 3cm and 40cm. The optimal parameter values change smoothly with regular photon beam quality. Conclusion: The universal functional form fits the Varian TrueBeam open field IWOR measurement tables accurately with small relative residual errors for all photon energies. Therefore, it can be an excellent choice to represent IWOR in absolute dose and MU calculations. The functional form can also be used as a QA/commissioning tool to verify the measured data quality and consistency by checking the IWOR data behavior against the function for new photon energies with arbitrary beam quality.« less

Sensitivity Analysis Reveals Critical Factors that Affect Wetland Methane Emissions using Soil Biogeochemistry Model

NASA Astrophysics Data System (ADS)

Alonso-Contes, C.; Gerber, S.; Bliznyuk, N.; Duerr, I.

2017-12-01

Wetlands contribute approximately 20 to 40 % to global sources of methane emissions. We build a Methane model for tropical and subtropical forests, that allows inundated conditions, following the approaches used in more complex global biogeochemical emission models (LPJWhyMe and CLM4Me). The model was designed to replace model formulations with field and remotely sensed collected data for 2 essential drivers: plant productivity and hydrology. This allows us to directly focus on the central processes of methane production, consumption and transport. One of our long term goals is to make the model available to a scientists interested in including methane modeling in their location of study. Sensitivity analysis results help in focusing field data collection efforts. Here, we present results from a pilot global sensitivity analysis of the model order to determine which parameters and processes contribute most to the model's uncertainty of methane emissions. Results show that parameters related to water table behavior, carbon input (in form of plant productivity) and rooting depth affect simulated methane emissions the most. Current efforts include to perform the sensitivity analysis again on methane emissions outputs from an updated model that incorporates a soil heat flux routine and to determine the extent by which the soil temperature parameters affect CH4 emissions. Currently we are conducting field collection of data during Summer 2017 for comparison among 3 different landscapes located in the Ordway-Swisher Biological Station in Melrose, FL. We are collecting soil moisture and CH4 emission data from 4 different wetland types. Having data from 4 wetland types allows for calibration of the model to diverse soil, water and vegetation characteristics.

Extreme storm surge modelling in the North Sea. The role of the sea state, forcing frequency and spatial forcing resolution

NASA Astrophysics Data System (ADS)

Ridder, Nina; de Vries, Hylke; Drijfhout, Sybren; van den Brink, Henk; van Meijgaard, Erik; de Vries, Hans

2018-02-01

This study shows that storm surge model performance in the North Sea is mostly unaffected by the application of temporal variations of surface drag due to changes in sea state provided the choice of a suitable constant Charnock parameter in the sea-state-independent case. Including essential meteorological features on smaller scales and minimising interpolation errors by increasing forcing data resolution are shown to be more important for the improvement of model performance particularly at the high tail of the probability distribution. This is found in a modelling study using WAQUA/DCSMv5 by evaluating the influence of a realistic air-sea momentum transfer parameterization and comparing it to the influence of changes in the spatial and temporal resolution of the applied forcing fields in an effort to support the improvement of impact and climate analysis studies. Particular attention is given to the representation of extreme water levels over the past decades based on the example of the Netherlands. For this, WAQUA/DCSMv5 is forced with ERA-Interim reanalysis data. Model results are obtained from a set of different forcing fields, which either (i) include a wave-state-dependent Charnock parameter or (ii) apply a constant Charnock parameter ( α C h = 0.032) tuned for young sea states in the North Sea, but differ in their spatial and/or temporal resolution. Increasing forcing field resolution from roughly 79 to 12 km through dynamically downscaling can reduce the modelled low bias, depending on coastal station, by up to 0.25 m for the modelled extreme water levels with a 1-year return period and between 0.1 m and 0.5 m for extreme surge heights.

Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution

NASA Astrophysics Data System (ADS)

Meyer, H.; Eich, T.; Beurskens, M.; Coda, S.; Hakola, A.; Martin, P.; Adamek, J.; Agostini, M.; Aguiam, D.; Ahn, J.; Aho-Mantila, L.; Akers, R.; Albanese, R.; Aledda, R.; Alessi, E.; Allan, S.; Alves, D.; Ambrosino, R.; Amicucci, L.; Anand, H.; Anastassiou, G.; Andrèbe, Y.; Angioni, C.; Apruzzese, G.; Ariola, M.; Arnichand, H.; Arter, W.; Baciero, A.; Barnes, M.; Barrera, L.; Behn, R.; Bencze, A.; Bernardo, J.; Bernert, M.; Bettini, P.; Bilková, P.; Bin, W.; Birkenmeier, G.; Bizarro, J. P. S.; Blanchard, P.; Blanken, T.; Bluteau, M.; Bobkov, V.; Bogar, O.; Böhm, P.; Bolzonella, T.; Boncagni, L.; Botrugno, A.; Bottereau, C.; Bouquey, F.; Bourdelle, C.; Brémond, S.; Brezinsek, S.; Brida, D.; Brochard, F.; Buchanan, J.; Bufferand, H.; Buratti, P.; Cahyna, P.; Calabrò, G.; Camenen, Y.; Caniello, R.; Cannas, B.; Canton, A.; Cardinali, A.; Carnevale, D.; Carr, M.; Carralero, D.; Carvalho, P.; Casali, L.; Castaldo, C.; Castejón, F.; Castro, R.; Causa, F.; Cavazzana, R.; Cavedon, M.; Cecconello, M.; Ceccuzzi, S.; Cesario, R.; Challis, C. D.; Chapman, I. T.; Chapman, S.; Chernyshova, M.; Choi, D.; Cianfarani, C.; Ciraolo, G.; Citrin, J.; Clairet, F.; Classen, I.; Coelho, R.; Coenen, J. W.; Colas, L.; Conway, G.; Corre, Y.; Costea, S.; Crisanti, F.; Cruz, N.; Cseh, G.; Czarnecka, A.; D'Arcangelo, O.; De Angeli, M.; De Masi, G.; De Temmerman, G.; De Tommasi, G.; Decker, J.; Delogu, R. S.; Dendy, R.; Denner, P.; Di Troia, C.; Dimitrova, M.; D'Inca, R.; Dorić, V.; Douai, D.; Drenik, A.; Dudson, B.; Dunai, D.; Dunne, M.; Duval, B. P.; Easy, L.; Elmore, S.; Erdös, B.; Esposito, B.; Fable, E.; Faitsch, M.; Fanni, A.; Fedorczak, N.; Felici, F.; Ferreira, J.; Février, O.; Ficker, O.; Fietz, S.; Figini, L.; Figueiredo, A.; Fil, A.; Fishpool, G.; Fitzgerald, M.; Fontana, M.; Ford, O.; Frassinetti, L.; Fridström, R.; Frigione, D.; Fuchert, G.; Fuchs, C.; Furno Palumbo, M.; Futatani, S.; Gabellieri, L.; Gałązka, K.; Galdon-Quiroga, J.; Galeani, S.; Gallart, D.; Gallo, A.; Galperti, C.; Gao, Y.; Garavaglia, S.; Garcia, J.; Garcia-Carrasco, A.; Garcia-Lopez, J.; Garcia-Munoz, M.; Gardarein, J.-L.; Garzotti, L.; Gaspar, J.; Gauthier, E.; Geelen, P.; Geiger, B.; Ghendrih, P.; Ghezzi, F.; Giacomelli, L.; Giannone, L.; Giovannozzi, E.; Giroud, C.; Gleason González, C.; Gobbin, M.; Goodman, T. P.; Gorini, G.; Gospodarczyk, M.; Granucci, G.; Gruber, M.; Gude, A.; Guimarais, L.; Guirlet, R.; Gunn, J.; Hacek, P.; Hacquin, S.; Hall, S.; Ham, C.; Happel, T.; Harrison, J.; Harting, D.; Hauer, V.; Havlickova, E.; Hellsten, T.; Helou, W.; Henderson, S.; Hennequin, P.; Heyn, M.; Hnat, B.; Hölzl, M.; Hogeweij, D.; Honoré, C.; Hopf, C.; Horáček, J.; Hornung, G.; Horváth, L.; Huang, Z.; Huber, A.; Igitkhanov, J.; Igochine, V.; Imrisek, M.; Innocente, P.; Ionita-Schrittwieser, C.; Isliker, H.; Ivanova-Stanik, I.; Jacobsen, A. S.; Jacquet, P.; Jakubowski, M.; Jardin, A.; Jaulmes, F.; Jenko, F.; Jensen, T.; Jeppe Miki Busk, O.; Jessen, M.; Joffrin, E.; Jones, O.; Jonsson, T.; Kallenbach, A.; Kallinikos, N.; Kálvin, S.; Kappatou, A.; Karhunen, J.; Karpushov, A.; Kasilov, S.; Kasprowicz, G.; Kendl, A.; Kernbichler, W.; Kim, D.; Kirk, A.; Kjer, S.; Klimek, I.; Kocsis, G.; Kogut, D.; Komm, M.; Korsholm, S. B.; Koslowski, H. R.; Koubiti, M.; Kovacic, J.; Kovarik, K.; Krawczyk, N.; Krbec, J.; Krieger, K.; Krivska, A.; Kube, R.; Kudlacek, O.; Kurki-Suonio, T.; Labit, B.; Laggner, F. M.; Laguardia, L.; Lahtinen, A.; Lalousis, P.; Lang, P.; Lauber, P.; Lazányi, N.; Lazaros, A.; Le, H. B.; Lebschy, A.; Leddy, J.; Lefévre, L.; Lehnen, M.; Leipold, F.; Lessig, A.; Leyland, M.; Li, L.; Liang, Y.; Lipschultz, B.; Liu, Y. Q.; Loarer, T.; Loarte, A.; Loewenhoff, T.; Lomanowski, B.; Loschiavo, V. P.; Lunt, T.; Lupelli, I.; Lux, H.; Lyssoivan, A.; Madsen, J.; Maget, P.; Maggi, C.; Maggiora, R.; Magnussen, M. L.; Mailloux, J.; Maljaars, B.; Malygin, A.; Mantica, P.; Mantsinen, M.; Maraschek, M.; Marchand, B.; Marconato, N.; Marini, C.; Marinucci, M.; Markovic, T.; Marocco, D.; Marrelli, L.; Martin, Y.; Solis, J. R. Martin; Martitsch, A.; Mastrostefano, S.; Mattei, M.; Matthews, G.; Mavridis, M.; Mayoral, M.-L.; Mazon, D.; McCarthy, P.; McAdams, R.; McArdle, G.; McCarthy, P.; McClements, K.; McDermott, R.; McMillan, B.; Meisl, G.; Merle, A.; Meyer, O.; Milanesio, D.; Militello, F.; Miron, I. G.; Mitosinkova, K.; Mlynar, J.; Mlynek, A.; Molina, D.; Molina, P.; Monakhov, I.; Morales, J.; Moreau, D.; Morel, P.; Moret, J.-M.; Moro, A.; Moulton, D.; Müller, H. W.; Nabais, F.; Nardon, E.; Naulin, V.; Nemes-Czopf, A.; Nespoli, F.; Neu, R.; Nielsen, A. H.; Nielsen, S. K.; Nikolaeva, V.; Nimb, S.; Nocente, M.; Nouailletas, R.; Nowak, S.; Oberkofler, M.; Oberparleiter, M.; Ochoukov, R.; Odstrčil, T.; Olsen, J.; Omotani, J.; O'Mullane, M. G.; Orain, F.; Osterman, N.; Paccagnella, R.; Pamela, S.; Pangione, L.; Panjan, M.; Papp, G.; Papřok, R.; Parail, V.; Parra, F. I.; Pau, A.; Pautasso, G.; Pehkonen, S.-P.; Pereira, A.; Perelli Cippo, E.; Pericoli Ridolfini, V.; Peterka, M.; Petersson, P.; Petrzilka, V.; Piovesan, P.; Piron, C.; Pironti, A.; Pisano, F.; Pisokas, T.; Pitts, R.; Ploumistakis, I.; Plyusnin, V.; Pokol, G.; Poljak, D.; Pölöskei, P.; Popovic, Z.; Pór, G.; Porte, L.; Potzel, S.; Predebon, I.; Preynas, M.; Primc, G.; Pucella, G.; Puiatti, M. E.; Pütterich, T.; Rack, M.; Ramogida, G.; Rapson, C.; Rasmussen, J. Juul; Rasmussen, J.; Rattá, G. A.; Ratynskaia, S.; Ravera, G.; Réfy, D.; Reich, M.; Reimerdes, H.; Reimold, F.; Reinke, M.; Reiser, D.; Resnik, M.; Reux, C.; Ripamonti, D.; Rittich, D.; Riva, G.; Rodriguez-Ramos, M.; Rohde, V.; Rosato, J.; Ryter, F.; Saarelma, S.; Sabot, R.; Saint-Laurent, F.; Salewski, M.; Salmi, A.; Samaddar, D.; Sanchis-Sanchez, L.; Santos, J.; Sauter, O.; Scannell, R.; Scheffer, M.; Schneider, M.; Schneider, B.; Schneider, P.; Schneller, M.; Schrittwieser, R.; Schubert, M.; Schweinzer, J.; Seidl, J.; Sertoli, M.; Šesnić, S.; Shabbir, A.; Shalpegin, A.; Shanahan, B.; Sharapov, S.; Sheikh, U.; Sias, G.; Sieglin, B.; Silva, C.; Silva, A.; Silva Fuglister, M.; Simpson, J.; Snicker, A.; Sommariva, C.; Sozzi, C.; Spagnolo, S.; Spizzo, G.; Spolaore, M.; Stange, T.; Stejner Pedersen, M.; Stepanov, I.; Stober, J.; Strand, P.; Šušnjara, A.; Suttrop, W.; Szepesi, T.; Tál, B.; Tala, T.; Tamain, P.; Tardini, G.; Tardocchi, M.; Teplukhina, A.; Terranova, D.; Testa, D.; Theiler, C.; Thornton, A.; Tolias, P.; Tophøj, L.; Treutterer, W.; Trevisan, G. L.; Tripsky, M.; Tsironis, C.; Tsui, C.; Tudisco, O.; Uccello, A.; Urban, J.; Valisa, M.; Vallejos, P.; Valovic, M.; Van den Brand, H.; Vanovac, B.; Varoutis, S.; Vartanian, S.; Vega, J.; Verdoolaege, G.; Verhaegh, K.; Vermare, L.; Vianello, N.; Vicente, J.; Viezzer, E.; Vignitchouk, L.; Vijvers, W. A. J.; Villone, F.; Viola, B.; Vlahos, L.; Voitsekhovitch, I.; Vondráček, P.; Vu, N. M. T.; Wagner, D.; Walkden, N.; Wang, N.; Wauters, T.; Weiland, M.; Weinzettl, V.; Westerhof, E.; Wiesenberger, M.; Willensdorfer, M.; Wischmeier, M.; Wodniak, I.; Wolfrum, E.; Yadykin, D.; Zagórski, R.; Zammuto, I.; Zanca, P.; Zaplotnik, R.; Zestanakis, P.; Zhang, W.; Zoletnik, S.; Zuin, M.; ASDEX Upgrade, the; MAST; TCV Teams

2017-10-01

Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n  =  2 RMP maintaining good confinement {{H}\\text{H≤ft(98,\\text{y}2\\right)}}≈ 0.95 . Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes. In the future we will refer to the author list of the paper as the EUROfusion MST1 Team.

Erosion in radial inflow turbines. Volume 3: Trajectories of erosive particles in radial inflow turbines

NASA Technical Reports Server (NTRS)

Clevenger, W. B., Jr.; Tabakoff, W.

1974-01-01

The theoretical trajectories that erosive particles follow in the gas flow fields of a typical radial inflow turbine were investigated. A discussion of the theoretical trajectories that the particles follow in the scroll, in the nozzles, in the vortex between the nozzles and the rotor, and in the rotor passages is included. The results are presented in terms of the characteristic length, a similarity parameter which relates the particles that follow the same trajectory in equivalent flow fields. For Vol, 1, see N74-19395.

Diffraction radiation generators

NASA Astrophysics Data System (ADS)

Shestopalov, Viktor P.; Vertii, Aleksei A.; Ermak, Gennadii P.; Skrynnik, Boris K.; Khlopov, Grigorii I.; Tsvyk, Aleksei I.

Research in the field of diffraction radiation generators (DRG) conducted at the Radio Physics and electronics Institute of the Ukranian Academy of Sciences over the past 25 years is reviewed. The effect of diffraction radiation is analyzed in detail, and various operating regimes of DRGs are discussed. The discussion then focuses on the principal requirements for the design of packaged DRGs and their principal parameters. Finally, applications of DRGs in various fields of science and technology are reviewed, including such applications as DRG spectroscopy, diagnostics of plasma, biological specimens, and vibration, and DRG radar systems.

A test of the 'one-point method' for estimating maximum carboxylation capacity from field-measured, light-saturated photosynthesis

DOE PAGES

Martin G. De Kauwe; Serbin, Shawn P.; Lin, Yan -Shih; ...

2015-12-31

Here, simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate (V cmax). Estimating this parameter using A–C i curves (net photosynthesis, A, vs intercellular CO 2 concentration, C i) is laborious, which limits availability of V cmax data. However, many multispecies field datasets include net photosynthetic rate at saturating irradiance and at ambient atmospheric CO 2 concentration (A sat) measurements, from which V cmax can be extracted using a ‘one-point method’.

Measurement of Antenna Bore-Sight Gain

NASA Technical Reports Server (NTRS)

Fortinberry, Jarrod; Shumpert, Thomas

2016-01-01

The absolute or free-field gain of a simple antenna can be approximated using standard antenna theory formulae or for a more accurate prediction, numerical methods may be employed to solve for antenna parameters including gain. Both of these methods will result in relatively reasonable estimates but in practice antenna gain is usually verified and documented via measurements and calibration. In this paper, a relatively simple and low-cost, yet effective means of determining the bore-sight free-field gain of a VHF/UHF antenna is proposed by using the Brewster angle relationship.

Current distribution on a cylindrical antenna with parallel orientation in a lossy magnetoplasma

NASA Technical Reports Server (NTRS)

Klein, C. A.; Klock, P. W.; Deschamps, G. A.

1972-01-01

The current distribution and impedance of a thin cylindrical antenna with parallel orientation to the static magnetic field of a lossy magnetoplasma is calculated with the method of moments. The electric field produced by an infinitesimal current source is first derived. Results are presented for a wide range of plasma parameters. Reasonable answers are obtained for all cases except for the overdense hyperbolic case. A discussion of the numerical stability is included which not only applies to this problem but other applications of the method of moments.

Electron Plasmas Cooled by Cyclotron-Cavity Resonance

DOE PAGES

Povilus, A. P.; DeTal, N. D.; Evans, L. T.; ...

2016-10-21

We observe that high-Q electromagnetic cavity resonances increase the cyclotron cooling rate of pure electron plasmas held in a Penning-Malmberg trap when the electron cyclotron frequency, controlled by tuning the magnetic field, matches the frequency of standing wave modes in the cavity. For certain modes and trapping configurations, this can increase the cooling rate by factors of 10 or more. In this paper, we investigate the variation of the cooling rate and equilibrium plasma temperatures over a wide range of parameters, including the plasma density, plasma position, electron number, and magnetic field.

Three-dimensional analytic model of the magnetic field for the Chalk River Superconducting Cyclotron

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

Davies, W.G.; Lee-Whiting, G.E.; Douglas, S.R.

1994-07-01

A three-dimensional analytic model of the magnetic field for the TASCC cyclotron that satisfies Maxwell`s equations exactly has been constructed for use with the new differential-algebra orbit-dynamics code. The model includes: (1) the superconducting coils; (2) the saturated iron poles; (3) the partially saturated yoke; (4) the saturated-iron trim rods. Lines of dipole density along the edges of the hills account for the non-uniformities and edge effects and along with three yoke constants constitute the only free parameters.

Opportunities for increasing natural gas production in the near term. Volume VI. The East Cameron Block 271 Field. Final report

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

Not Available

1978-02-01

This report examines the potential for increasing the rate of production of natural gas from the East Cameron Block 271 Field in the Gulf of Mexico Outer Continental Shelf. Proved reserves are estimated using all available reservoir data, including well logs and pressure tests, and cost parameters typical in the area. Alternative schedules for future production are devised, and net present values calculated from which the maximum production rate that also maximizes net present value is determined.

Estimating the hydraulic parameters of a confined aquifer based on the response of groundwater levels to seismic Rayleigh waves

NASA Astrophysics Data System (ADS)

Sun, Xiaolong; Xiang, Yang; Shi, Zheming

2018-05-01

Groundwater flow models implemented to manage regional water resources require aquifer hydraulic parameters. Traditional methods for obtaining these parameters include laboratory experiments, field tests and model inversions, and each are potentially hindered by their unique limitations. Here, we propose a methodology for estimating hydraulic conductivity and storage coefficients using the spectral characteristics of the coseismic groundwater-level oscillations and seismic Rayleigh waves. The results from Well X10 are consistent with the variations and spectral characteristics of the water-level oscillations and seismic waves and present an estimated hydraulic conductivity of approximately 1 × 10-3 m s-1 and storativity of 15 × 10-6. The proposed methodology for estimating hydraulic parameters in confined aquifers is a practical and novel approach for groundwater management and seismic precursor anomaly analyses.

Uncertainty quantification and risk analyses of CO2 leakage in heterogeneous geological formations

NASA Astrophysics Data System (ADS)

Hou, Z.; Murray, C. J.; Rockhold, M. L.

2012-12-01

A stochastic sensitivity analysis framework is adopted to evaluate the impact of spatial heterogeneity in permeability on CO2 leakage risk. The leakage is defined as the total mass of CO2 moving into the overburden through the caprock-overburden interface, in both gaseous and liquid (dissolved) phases. The entropy-based framework has the ability to quantify the uncertainty associated with the input parameters in the form of prior pdfs (probability density functions). Effective sampling of the prior pdfs enables us to fully explore the parameter space and systematically evaluate the individual and combined effects of the parameters of interest on CO2 leakage risk. The parameters that are considered in the study include: mean, variance, and horizontal to vertical spatial anisotropy ratio for caprock permeability, and those same parameters for reservoir permeability. Given the sampled spatial variogram parameters, multiple realizations of permeability fields were generated using GSLIB subroutines. For each permeability field, a numerical simulator, STOMP, (in the water-salt-CO2-energy operational mode) is used to simulate the CO2 migration within the reservoir and caprock up to 50 years after injection. Due to intensive computational demand, we run both a scalable version simulator eSTOMP and serial STOMP on various supercomputers. We then perform statistical analyses and summarize the relationships between the parameters of interest (mean/variance/anisotropy ratio of caprock and reservoir permeability) and CO2 leakage ratio. We also present the effects of those parameters on CO2 plume radius and reservoir injectivity. The statistical analysis provides a reduced order model that can be used to estimate the impact of heterogeneity on caprock leakage.

EPR, optical and superposition model study of Mn2+ doped L+ glutamic acid

NASA Astrophysics Data System (ADS)

Kripal, Ram; Singh, Manju

2015-12-01

Electron paramagnetic resonance (EPR) study of Mn2+ doped L+ glutamic acid single crystal is done at room temperature. Four interstitial sites are observed and the spin Hamiltonian parameters are calculated with the help of large number of resonant lines for various angular positions of external magnetic field. The optical absorption study is also done at room temperature. The energy values for different orbital levels are calculated, and observed bands are assigned as transitions from 6A1g(s) ground state to various excited states. With the help of these assigned bands, Racah inter-electronic repulsion parameters B = 869 cm-1, C = 2080 cm-1 and cubic crystal field splitting parameter Dq = 730 cm-1 are calculated. Zero field splitting (ZFS) parameters D and E are calculated by the perturbation formulae and crystal field parameters obtained using superposition model. The calculated values of ZFS parameters are in good agreement with the experimental values obtained by EPR.

Cosmic velocity-gravity relation in redshift space

NASA Astrophysics Data System (ADS)

Colombi, Stéphane; Chodorowski, Michał J.; Teyssier, Romain

2007-02-01

We propose a simple way to estimate the parameter β ~= Ω0.6/b from 3D galaxy surveys, where Ω is the non-relativistic matter-density parameter of the Universe and b is the bias between the galaxy distribution and the total matter distribution. Our method consists in measuring the relation between the cosmological velocity and gravity fields, and thus requires peculiar velocity measurements. The relation is measured directly in redshift space, so there is no need to reconstruct the density field in real space. In linear theory, the radial components of the gravity and velocity fields in redshift space are expected to be tightly correlated, with a slope given, in the distant observer approximation, by We test extensively this relation using controlled numerical experiments based on a cosmological N-body simulation. To perform the measurements, we propose a new and rather simple adaptive interpolation scheme to estimate the velocity and the gravity field on a grid. One of the most striking results is that non-linear effects, including `fingers of God', affect mainly the tails of the joint probability distribution function (PDF) of the velocity and gravity field: the 1-1.5 σ region around the maximum of the PDF is dominated by the linear theory regime, both in real and redshift space. This is understood explicitly by using the spherical collapse model as a proxy of non-linear dynamics. Applications of the method to real galaxy catalogues are discussed, including a preliminary investigation on homogeneous (volume-limited) `galaxy' samples extracted from the simulation with simple prescriptions based on halo and substructure identification, to quantify the effects of the bias between the galaxy distribution and the total matter distribution, as well as the effects of shot noise.

Topological properties of microwave magnetoelectric fields.

PubMed

Berezin, M; Kamenetskii, E O; Shavit, R

2014-02-01

Collective excitations of electron spins in a ferromagnetic sample dominated by the magnetic dipole-dipole interaction strongly influence the field structure of microwave radiation. A small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillation spectra can behave as a source of specific fields in vacuum, termed magnetoelectric (ME) fields. A coupling between the time-varying electric and magnetic fields in the ME-field structures is different from such a coupling in regular electromagnetic fields. The ME fields are characterized by strong energy confinement at a subwavelength region of microwave radiation, topologically distinctive power-flow vortices, and helicity parameters [E. O. Kamenetskii, R. Joffe, and R. Shavit, Phys. Rev. E 87, 023201 (2013)]. We study topological properties of microwave ME fields by loading a MDM ferrite particle with different dielectric samples. We establish a close connection between the permittivity parameters of dielectric environment and the topology of ME fields. We show that the topology of ME fields is strongly correlated with the Fano-resonance spectra observed at terminals of a microwave structure. We reveal specific thresholds in the Fano-resonance spectra appearing at certain permittivity parameters of dielectric samples. We show that ME fields originated from MDM ferrite disks can be distinguished by topological portraits of the helicity parameters and can have a torsion degree of freedom. Importantly, the ME-field phenomena can be viewed as implementations of space-time coordinate transformations on waves.

Gravity Field and Internal Structure of Mercury from MESSENGER

NASA Technical Reports Server (NTRS)

Smith, David E.; Zuber, Maria T.; Phillips, Roger J.; Solomon, Sean C.; Hauck, Steven A., II; Lemoine, Frank G.; Mazarico, Erwan; Neumann, Gregory A.; Peale, Stanton J.; Margot, Jean-Luc;

Gravity field and internal structure of Mercury from MESSENGER.

PubMed

Smith, David E; Zuber, Maria T; Phillips, Roger J; Solomon, Sean C; Hauck, Steven A; Lemoine, Frank G; Mazarico, Erwan; Neumann, Gregory A; Peale, Stanton J; Margot, Jean-Luc; Johnson, Catherine L; Torrence, Mark H; Perry, Mark E; Rowlands, David D; Goossens, Sander; Head, James W; Taylor, Anthony H

2012-04-13

Radio tracking of the MESSENGER spacecraft has provided a model of Mercury's gravity field. In the northern hemisphere, several large gravity anomalies, including candidate mass concentrations (mascons), exceed 100 milli-Galileos (mgal). Mercury's northern hemisphere crust is thicker at low latitudes and thinner in the polar region and shows evidence for thinning beneath some impact basins. The low-degree gravity field, combined with planetary spin parameters, yields the moment of inertia C/MR(2) = 0.353 ± 0.017, where M and R are Mercury's mass and radius, and a ratio of the moment of inertia of Mercury's solid outer shell to that of the planet of C(m)/C = 0.452 ± 0.035. A model for Mercury's radial density distribution consistent with these results includes a solid silicate crust and mantle overlying a solid iron-sulfide layer and an iron-rich liquid outer core and perhaps a solid inner core.

Compilation of selected hydrologic data, through water year 1992, Black Hills Hydrology Study, western South Dakota

USGS Publications Warehouse

Driscoll, Daniel G.; Bradford, Wendell

1994-01-01

This report presents water-level, water-quailty, and springflow data that have been collected or compiled, through water year 1992, for the Black Hills Hydrology Study. This study is a long-term cooperative effort between the U.S. Geological Survey, the South Dakota Department of Environmental and Natural Resources, and the West Dakota Water Development District (which represents various local and county cooperators). Water-level data are presented for 32 observation wells and 2 cave sites in the Black Hills area of western South Dakota. The wells are part of a network of observation wells maintained by the South Dakota Department of Environment and Natural Resources and are completed in various bedrock formations that are utilized as aquifers in the Black Hills area. Both cave sites are located within outcrops of the Madison Limestone. Data presented include site descriptions, hydrographs, and tabular data. Water- quality data are presented for 12 surface-water sites and 5 ground-water sites. Data presented include field parameters, bacteria counts, and concentrations of common ions, solids, nutrients, trace elements, radiometrics, cyanide, phenols, dissolved organic carbon, and suspended sediment. Spring data are presented for 83 springs and 21 stream reaches with significant springflow components. Data presented include site information, discharge, and field water-quality parameters including temperature, specific conductance, dissolved oxygen, and pH.

Dielectrophoresis of Cells

PubMed Central

Pohl, Herbert A.; Crane, Joe S.

1971-01-01

Dielectrophoresis, the motion produced by the action of nonuniform electric field upon a neutral object, is shown to be a simple and useful technique for the study of cellular organisms. In the present study of yeast (Saccharomyces cerevisiae) using a simple pin-pin electrode system of platinum and high-frequency alternating fields, one observes that the collectability of cells at the electrode tip, i.e. at the region of highest field strength, depends upon physical parameters such as field strength, field uniformity, frequency, cell concentration, suspension conductivity, and time of collection. The yield of cells collected is also observed to depend upon biological factors such as colony age, thermal treatment of the cells, and chemical poisons, but not upon irradiation with ultraviolet light. Several interesting side effect phenomena coincident with nonuniform electric field conditions were observed, including stirring (related to “jet” effects at localized electrode sites), discontinuous repulsions, and cellular rotation which was found to be frequency dependent. ImagesFIGURE 2 PMID:5132497

Vegetation and substrate properties of aeolian dune fields in the Colorado River corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Draut, Amy E.

2011-01-01

This report summarizes vegetation and substrate properties of aeolian landscapes in the Colorado River corridor through Grand Canyon, Arizona, in Grand Canyon National Park. Characterizing these parameters provides a basis from which to assess future changes in this ecosystem, including the spread of nonnative plant species. Differences are apparent between aeolian dune fields that are downwind of where modern controlled flooding deposits new sandbars (modern-fluvial-sourced dune fields) and those that have received little or no new windblown sand since river regulation began in the 1960s (relict-fluvial-sourced dune fields). The most substantial difference between modern- and relict-fluvial-sourced aeolian dune fields is the greater abundance of biologic soil crust in relict dune fields. These findings can be used with similar investigations in other geomorphic settings in Grand Canyon and elsewhere in the Colorado River corridor to evaluate the health of the Colorado River ecosystem over time.

Random walk study of electron motion in helium in crossed electromagnetic fields

NASA Technical Reports Server (NTRS)

Englert, G. W.

1972-01-01

Random walk theory, previously adapted to electron motion in the presence of an electric field, is extended to include a transverse magnetic field. In principle, the random walk approach avoids mathematical complexity and concomitant simplifying assumptions and permits determination of energy distributions and transport coefficients within the accuracy of available collisional cross section data. Application is made to a weakly ionized helium gas. Time of relaxation of electron energy distribution, determined by the random walk, is described by simple expressions based on energy exchange between the electron and an effective electric field. The restrictive effect of the magnetic field on electron motion, which increases the required number of collisions per walk to reach a terminal steady state condition, as well as the effect of the magnetic field on electron transport coefficients and mean energy can be quite adequately described by expressions involving only the Hall parameter.

Communication: Multiple atomistic force fields in a single enhanced sampling simulation

NASA Astrophysics Data System (ADS)

Hoang Viet, Man; Derreumaux, Philippe; Nguyen, Phuong H.

2015-07-01

The main concerns of biomolecular dynamics simulations are the convergence of the conformational sampling and the dependence of the results on the force fields. While the first issue can be addressed by employing enhanced sampling techniques such as simulated tempering or replica exchange molecular dynamics, repeating these simulations with different force fields is very time consuming. Here, we propose an automatic method that includes different force fields into a single advanced sampling simulation. Conformational sampling using three all-atom force fields is enhanced by simulated tempering and by formulating the weight parameters of the simulated tempering method in terms of the energy fluctuations, the system is able to perform random walk in both temperature and force field spaces. The method is first demonstrated on a 1D system and then validated by the folding of the 10-residue chignolin peptide in explicit water.

Remediation of antimony-rich mine waters: Assessment of antimony removal and shifts in the microbial community of an onsite field-scale bioreactor.

PubMed

Sun, Weimin; Xiao, Enzong; Kalin, Margarete; Krumins, Valdis; Dong, Yiran; Ning, Zengping; Liu, Tong; Sun, Min; Zhao, Yanlong; Wu, Shiliang; Mao, Jianzhong; Xiao, Tangfu

2016-08-01

An on-site field-scale bioreactor for passive treatment of antimony (Sb) contamination was installed downstream of an active Sb mine in Southwest China, and operated for one year (including a six month monitoring period). This bioreactor consisted of five treatment units, including one pre-aerobic cell, two aerobic cells, and two microaerobic cells. With the aerobic cells inoculated with indigenous mine water microflora, the bioreactor removed more than 90% of total soluble Sb and 80% of soluble antimonite (Sb(III)). An increase in pH and decrease of oxidation-reduction potential (Eh) was also observed along the flow direction. High-throughput sequencing of the small subunit ribosomal RNA (SSU rRNA) gene variable (V4) region revealed that taxonomically diverse microbial communities developed in the bioreactor. Metal (loid)-oxidizing bacteria including Ferrovum, Thiomonas, Gallionella, and Leptospirillum, were highly enriched in the bioreactor cells where the highest total Sb and Sb(III) removal occurred. Canonical correspondence analysis (CCA) indicated that a suite of in situ physicochemical parameters including pH and Eh were substantially correlated with the overall microbial communities. Based on an UPGMA (Unweighted Pair Group Method with Arithmetic Mean) tree and PCoA (Principal Coordinates Analysis), the microbial composition of each cell was distinct, indicating these in situ physicochemical parameters had an effect in shaping the indigenous microbial communities. Overall, this study was the first to employ a field-scale bioreactor to treat Sb-rich mine water onsite and, moreover, the findings suggest the feasibility of the bioreactor in removing elevated Sb from mine waters. Copyright © 2016 Elsevier Ltd. All rights reserved.

Systematic effects in LOD from SLR observations

NASA Astrophysics Data System (ADS)

Bloßfeld, Mathis; Gerstl, Michael; Hugentobler, Urs; Angermann, Detlef; Müller, Horst

2014-09-01

Beside the estimation of station coordinates and the Earth’s gravity field, laser ranging observations to near-Earth satellites can be used to determine the rotation of the Earth. One parameter of this rotation is ΔLOD (excess Length Of Day) which describes the excess revolution time of the Earth w.r.t. 86,400 s. Due to correlations among the different parameter groups, it is difficult to obtain reliable estimates for all parameters. In the official ΔLOD products of the International Earth Rotation and Reference Systems Service (IERS), the ΔLOD information determined from laser ranging observations is excluded from the processing. In this paper, we study the existing correlations between ΔLOD, the orbital node Ω, the even zonal gravity field coefficients, cross-track empirical accelerations and relativistic accelerations caused by the Lense-Thirring and deSitter effect in detail using first order Gaussian perturbation equations. We found discrepancies due to different a priories by using different gravity field models of up to 1.0 ms for polar orbits at an altitude of 500 km and up to 40.0 ms, if the gravity field coefficients are estimated using only observations to LAGEOS 1. If observations to LAGEOS 2 are included, reliable ΔLOD estimates can be achieved. Nevertheless, an impact of the a priori gravity field even on the multi-satellite ΔLOD estimates can be clearly identified. Furthermore, we investigate the effect of empirical cross-track accelerations and the effect of relativistic accelerations of near-Earth satellites on ΔLOD. A total effect of 0.0088 ms is caused by not modeled Lense-Thirring and deSitter terms. The partial derivatives of these accelerations w.r.t. the position and velocity of the satellite cause very small variations (0.1 μs) on ΔLOD.

In-duct identification of fluid-borne source with high spatial resolution

NASA Astrophysics Data System (ADS)

Heo, Yong-Ho; Ih, Jeong-Guon; Bodén, Hans

2014-11-01

Source identification of acoustic characteristics of in-duct fluid machinery is required for coping with the fluid-borne noise. By knowing the acoustic pressure and particle velocity field at the source plane in detail, the sound generation mechanism of a fluid machine can be understood. The identified spatial distribution of the strength of major radiators would be useful for the low noise design. Conventional methods for measuring the source in a wide duct have not been very helpful in investigating the source properties in detail because their spatial resolution is improper for the design purpose. In this work, an inverse method to estimate the source parameters with a high spatial resolution is studied. The theoretical formulation including the evanescent modes and near-field measurement data is given for a wide duct. After validating the proposed method to a duct excited by an acoustic driver, an experiment on a duct system driven by an air blower is conducted in the presence of flow. A convergence test for the evanescent modes is performed to find the necessary number of modes to regenerate the measured pressure field precisely. By using the converged modal amplitudes, very-close near-field pressure to the source is regenerated and compared with the measured pressure, and the maximum error was -16.3 dB. The source parameters are restored from the converged modal amplitudes. Then, the distribution of source parameters on the driver and the blower is clearly revealed with a high spatial resolution for kR<1.84 in which range only plane waves can propagate to far field in a duct. Measurement using a flush mounted sensor array is discussed, and the removal of pure radial modes in the modeling is suggested.

Relativistic effects in local inertial frames including parametrized-post-Newtonian effects

NASA Astrophysics Data System (ADS)

Shahid-Saless, Bahman; Ashby, Neil

1988-09-01

We use the concept of a generalized Fermi frame to describe relativistic effects, due to local and distant sources of gravitation, on a body placed in a local inertial frame of reference. In particular we have considered a model of two spherically symmetric gravitating point sources, moving in circular orbits around a common barycenter where one of the bodies is chosen to be the local and the other the distant one. This has been done using the slow-motion, weak-field approximation and including four of the parametrized-post-Newtonian (PPN) parameters. The position of the classical center of mass must be modified when the PPN parameter ζ2 is included. We show that the main relativistic effect on a local satellite is described by the Schwarzschild field of the local body and the nonlinear term corresponding to the self-interaction of the local source with itself. There are also much smaller terms that are proportional, respectively, to the product of the potentials of local and distant bodies and to the distant body's self-interactions. The spatial axes of the local frame undergo geodetic precession. In addition we have an acceleration of the order of 10-11 cm sec-2 that vanish in the case of general relativity, which is discussed in detail.

A review of optimization and quantification techniques for chemical exchange saturation transfer (CEST) MRI toward sensitive in vivo imaging

PubMed Central

Guo, Yingkun; Zheng, Hairong; Sun, Phillip Zhe

2015-01-01

Chemical exchange saturation transfer (CEST) MRI is a versatile imaging method that probes the chemical exchange between bulk water and exchangeable protons. CEST imaging indirectly detects dilute labile protons via bulk water signal changes following selective saturation of exchangeable protons, which offers substantial sensitivity enhancement and has sparked numerous biomedical applications. Over the past decade, CEST imaging techniques have rapidly evolved due to contributions from multiple domains, including the development of CEST mathematical models, innovative contrast agent designs, sensitive data acquisition schemes, efficient field inhomogeneity correction algorithms, and quantitative CEST (qCEST) analysis. The CEST system that underlies the apparent CEST-weighted effect, however, is complex. The experimentally measurable CEST effect depends not only on parameters such as CEST agent concentration, pH and temperature, but also on relaxation rate, magnetic field strength and more importantly, experimental parameters including repetition time, RF irradiation amplitude and scheme, and image readout. Thorough understanding of the underlying CEST system using qCEST analysis may augment the diagnostic capability of conventional imaging. In this review, we provide a concise explanation of CEST acquisition methods and processing algorithms, including their advantages and limitations, for optimization and quantification of CEST MRI experiments. PMID:25641791

Quantitative analysis of beam delivery parameters and treatment process time for proton beam therapy.

PubMed

Suzuki, Kazumichi; Gillin, Michael T; Sahoo, Narayan; Zhu, X Ronald; Lee, Andrew K; Lippy, Denise

2011-07-01

To evaluate patient census, equipment clinical availability, maximum daily treatment capacity, use factor for major beam delivery parameters, and treatment process time for actual treatments delivered by proton therapy systems. The authors have been recording all beam delivery parameters, including delivered dose, energy, range, spread-out Bragg peak widths, gantry angles, and couch angles for every treatment field in an electronic medical record system. We analyzed delivery system downtimes that had been recorded for every equipment failure and associated incidents. These data were used to evaluate the use factor of beam delivery parameters, the size of the patient census, and the equipment clinical availability of the facility. The duration of each treatment session from patient walk-in and to patient walk-out of the treatment room was measured for 82 patients with cancers at various sites. The yearly average equipment clinical availability in the last 3 yrs (June 2007-August 2010) was 97%, which exceeded the target of 95%. Approximately 2200 patients had been treated as of August 2010. The major disease sites were genitourinary (49%), thoracic (25%), central nervous system (22%), and gastrointestinal (2%). Beams have been delivered in approximately 8300 treatment fields. The use factor for six beam delivery parameters was also evaluated. Analysis of the treatment process times indicated that approximately 80% of this time was spent for patient and equipment setup. The other 20% was spent waiting for beam delivery and beam on. The total treatment process time can be expressed by a quadratic polynomial of the number of fields per session. The maximum daily treatment capacity of our facility using the current treatment processes was estimated to be 133 +/- 35 patients. This analysis shows that the facility has operated at a high performance level and has treated a large number of patients with a variety of diseases. The use factor of beam delivery parameters varies by disease site. Further improvements in efficiency may be realized in the equipment- and patient-related processes of treatment.

The effects of gentamicin and penicillin/streptomycin on the electrophysiology of human induced pluripotent stem cell-derived cardiomyocytes in manual patch clamp and multi-electrode array system.

PubMed

Hyun, Soo-Wang; Kim, Bo-Ram; Lin, Dan; Hyun, Sung-Ae; Yoon, Seong Shoon; Seo, Joung-Wook

Cell culture media usually contains antibiotics including gentamicin or penicillin/streptomycin (PS) to protect cells from bacterial contamination. However, little is known about the effects of antibiotics on action potential and field potential parameters in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The present study examined the effects of gentamicin (10, 25, and 50μg/ml) and PS (50, 100, and 200U/μg/ml) on electrophysiological activity in spontaneously beating hiPSC-CMs using manual patch clamp and multi-electrode array. We also measured mRNA expression of cardiac ion channels in hiPSC-CMs grown in media with or without gentamicin (25μg/ml) using reverse transcription-polymerase chain reaction. We recorded action potential and field potential of hiPSC-CMs grown in the presence or absence of gentamicin or PS. We also observed action potential parameters in hiPSC-CMs after short-term treatment with these antibiotics. Changes in action potential and field potential parameters were observed in hiPSC-CMs grown in media containing gentamicin or PS. Treatment with PS also affected action potential parameters in hiPSC-CMs. In addition, the mRNA expression of cardiac sodium and potassium ion channels was significantly attenuated in hiPSC-CMs grown in the presence of gentamicin (25μg/ml). The present findings suggested that gentamicin should not be used in the culture media of hiPSC-CMs used for the measurement of electrophysiological parameters. Our findings also suggest that 100U/100μg/ml of PS are the maximum appropriate concentrations of these antibiotics for recording action potential waveform, because they did not influence action potential parameters in these cells. Copyright © 2017. Published by Elsevier Inc.

String-inspired supergravity model at one loop

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

Gaillard, M.K.; Papadopoulos, A.; Pierce, D.M.

1992-03-15

We study a prototype supergravity model from superstrings, with three generations of matter fields in the untwisted sector, nonperturbatively induced supersymmetry breaking and including threshold corrections in conformity with modular invariance. The scale degeneracy of the vacuum is lifted at the one-loop level, allowing a determination of the fundamental parameters of the effective low-energy theory.

Weatherization and Indoor Air Quality: Measured Impacts in Single Family Homes Under the Weatherization Assistance Program

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

Pigg, Scott; Cautley, Dan; Francisco, Paul

2014-09-01

This report summarizes findings from a national field study of indoor air quality parameters in homes treated under the Weatherization Assistance Program (WAP). The study involved testing and monitoring in 514 single-family homes (including mobile homes) located in 35 states and served by 88 local weatherization agencies.

Time-ordered product expansions for computational stochastic system biology.

PubMed

Mjolsness, Eric

2013-06-01

The time-ordered product framework of quantum field theory can also be used to understand salient phenomena in stochastic biochemical networks. It is used here to derive Gillespie's stochastic simulation algorithm (SSA) for chemical reaction networks; consequently, the SSA can be interpreted in terms of Feynman diagrams. It is also used here to derive other, more general simulation and parameter-learning algorithms including simulation algorithms for networks of stochastic reaction-like processes operating on parameterized objects, and also hybrid stochastic reaction/differential equation models in which systems of ordinary differential equations evolve the parameters of objects that can also undergo stochastic reactions. Thus, the time-ordered product expansion can be used systematically to derive simulation and parameter-fitting algorithms for stochastic systems.

Stability analysis of automobile driver steering control

NASA Technical Reports Server (NTRS)

Allen, R. W.

1981-01-01

In steering an automobile, the driver must basically control the direction of the car's trajectory (heading angle) and the lateral deviation of the car relative to a delineated pathway. A previously published linear control model of driver steering behavior which is analyzed from a stability point of view is considered. A simple approximate expression for a stability parameter, phase margin, is derived in terms of various driver and vehicle control parameters, and boundaries for stability are discussed. A field test study is reviewed that includes the measurement of driver steering control parameters. Phase margins derived for a range of vehicle characteristics are found to be generally consistent with known adaptive properties of the human operator. The implications of these results are discussed in terms of driver adaptive behavior.

The 6dFGS Peculiar Velocity Field

NASA Astrophysics Data System (ADS)

Springob, Chris M.; Magoulas, C.; Colless, M.; Mould, J.; Erdogdu, P.; Jones, D. H.; Lucey, J.; Campbell, L.; Merson, A.; Jarrett, T.

2012-01-01

The 6dF Galaxy Survey (6dFGS) is an all southern sky galaxy survey, including 125,000 redshifts and a Fundamental Plane (FP) subsample of 10,000 peculiar velocities, making it the largest peculiar velocity sample to date. We have fit the FP using a maximum likelihood fit to a tri-variate Gaussian. We subsequently compute a Bayesian probability distribution for every possible peculiar velocity for each of the 10,000 galaxies, derived from the tri-variate Gaussian probability density distribution, accounting for our selection effects and measurement errors. We construct a predicted peculiar velocity field from the 2MASS redshift survey, and compare our observed 6dFGS velocity field to the predicted field. We discuss the resulting agreement between the observed and predicted fields, and the implications for measurements of the bias parameter and bulk flow.

REGIONAL-SCALE WIND FIELD CLASSIFICATION EMPLOYING CLUSTER ANALYSIS

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

Glascoe, L G; Glaser, R E; Chin, H S

2004-06-17

The classification of time-varying multivariate regional-scale wind fields at a specific location can assist event planning as well as consequence and risk analysis. Further, wind field classification involves data transformation and inference techniques that effectively characterize stochastic wind field variation. Such a classification scheme is potentially useful for addressing overall atmospheric transport uncertainty and meteorological parameter sensitivity issues. Different methods to classify wind fields over a location include the principal component analysis of wind data (e.g., Hardy and Walton, 1978) and the use of cluster analysis for wind data (e.g., Green et al., 1992; Kaufmann and Weber, 1996). The goalmore » of this study is to use a clustering method to classify the winds of a gridded data set, i.e, from meteorological simulations generated by a forecast model.« less

Synthetic Jet Flow Field Database for CFD Validation

NASA Technical Reports Server (NTRS)

Yao, Chung-Sheng; Chen, Fang Jenq; Neuhart, Dan; Harris, Jerome

2004-01-01

An oscillatory zero net mass flow jet was generated by a cavity-pumping device, namely a synthetic jet actuator. This basic oscillating jet flow field was selected as the first of the three test cases for the Langley workshop on CFD Validation of Synthetic Jets and Turbulent Separation Control. The purpose of this workshop was to assess the current CFD capabilities to predict unsteady flow fields of synthetic jets and separation control. This paper describes the characteristics and flow field database of a synthetic jet in a quiescent fluid. In this experiment, Particle Image Velocimetry (PIV), Laser Doppler Velocimetry (LDV), and hot-wire anemometry were used to measure the jet velocity field. In addition, the actuator operating parameters including diaphragm displacement, internal cavity pressure, and internal cavity temperature were also documented to provide boundary conditions for CFD modeling.

[Modeling and analysis of volume conduction based on field-circuit coupling].

PubMed

Tang, Zhide; Liu, Hailong; Xie, Xiaohui; Chen, Xiufa; Hou, Deming

2012-08-01

Numerical simulations of volume conduction can be used to analyze the process of energy transfer and explore the effects of some physical factors on energy transfer efficiency. We analyzed the 3D quasi-static electric field by the finite element method, and developed A 3D coupled field-circuit model of volume conduction basing on the coupling between the circuit and the electric field. The model includes a circuit simulation of the volume conduction to provide direct theoretical guidance for energy transfer optimization design. A field-circuit coupling model with circular cylinder electrodes was established on the platform of the software FEM3.5. Based on this, the effects of electrode cross section area, electrode distance and circuit parameters on the performance of volume conduction system were obtained, which provided a basis for optimized design of energy transfer efficiency.

Fractional properties of geophysical field variability on the example of hydrochemical parameters

NASA Astrophysics Data System (ADS)

Shevtsov, Boris; Shevtsova, Olga

2017-10-01

Using the properties of compound Poisson process and its fractional generalizations, statistical models of geophysical fields variability are considered on an example of hydrochemical parameters system. These models are universal to describe objects of different nature and allow us to explain various pulsing regime. Manifestations of non-conservatism in hydrochemical parameters system and the advantages of the system approach in the description of geophysical fields variability are discussed.

Intelligent printing system with AMPAC: boot program for printing machine with AMPAC

NASA Astrophysics Data System (ADS)

Yuasa, Tomonori; Mishina, Hiromichi

2000-12-01

The database AMPAC proposes the simple and unified format to describe single parameter of whole field of design, production and management. The database described by the format can be used commonly in any field connected by the network production system, since the description accepts any parameter in any fields and is field independent definition.

Very low scale Coleman-Weinberg inflation with nonminimal coupling

NASA Astrophysics Data System (ADS)

Kaneta, Kunio; Seto, Osamu; Takahashi, Ryo

2018-03-01

We study viable small-field Coleman-Weinberg (CW) inflation models with the help of nonminimal coupling to gravity. The simplest small-field CW inflation model (with a low-scale potential minimum) is incompatible with the cosmological constraint on the scalar spectral index. However, there are possibilities to make the model realistic. First, we revisit the CW inflation model supplemented with a linear potential term. We next consider the CW inflation model with a logarithmic nonminimal coupling and illustrate that the model can open a new viable parameter space that includes the model with a linear potential term. We also show parameter spaces where the Hubble scale during the inflation can be as small as 10-4 GeV , 1 GeV, 1 04 GeV , and 1 08 GeV for the number of e -folds of 40, 45, 50, and 55, respectively, with other cosmological constraints being satisfied.

Elements of an algorithm for optimizing a parameter-structural neural network

NASA Astrophysics Data System (ADS)

Mrówczyńska, Maria

2016-06-01

The field of processing information provided by measurement results is one of the most important components of geodetic technologies. The dynamic development of this field improves classic algorithms for numerical calculations in the aspect of analytical solutions that are difficult to achieve. Algorithms based on artificial intelligence in the form of artificial neural networks, including the topology of connections between neurons have become an important instrument connected to the problem of processing and modelling processes. This concept results from the integration of neural networks and parameter optimization methods and makes it possible to avoid the necessity to arbitrarily define the structure of a network. This kind of extension of the training process is exemplified by the algorithm called the Group Method of Data Handling (GMDH), which belongs to the class of evolutionary algorithms. The article presents a GMDH type network, used for modelling deformations of the geometrical axis of a steel chimney during its operation.

Atomic quantum simulation of the lattice gauge-Higgs model: Higgs couplings and emergence of exact local gauge symmetry.

PubMed

Kasamatsu, Kenichi; Ichinose, Ikuo; Matsui, Tetsuo

2013-09-13

Recently, the possibility of quantum simulation of dynamical gauge fields was pointed out by using a system of cold atoms trapped on each link in an optical lattice. However, to implement exact local gauge invariance, fine-tuning the interaction parameters among atoms is necessary. In the present Letter, we study the effect of violation of the U(1) local gauge invariance by relaxing the fine-tuning of the parameters and showing that a wide variety of cold atoms is still a faithful quantum simulator for a U(1) gauge-Higgs model containing a Higgs field sitting on sites. The clarification of the dynamics of this gauge-Higgs model sheds some light upon various unsolved problems, including the inflation process of the early Universe. We study the phase structure of this model by Monte Carlo simulation and also discuss the atomic characteristics of the Higgs phase in each simulator.

Amplification of a high-frequency electromagnetic wave by a relativistic plasma

NASA Technical Reports Server (NTRS)

Yoon, Peter H.

1990-01-01

The amplification of a high-frequency transverse electromagnetic wave by a relativistic plasma component, via the synchrotron maser process, is studied. The background plasma that supports the transverse wave is considered to be cold, and the energetic component whose density is much smaller than that of the background component has a loss-cone feature in the perpendicular momentum space and a finite field-aligned drift speed. The ratio of the background plasma frequency squared to the electron gyrofrequency squared is taken to be sufficiently larger than unity. Such a parameter regime is relevant to many space and astrophysical situations. A detailed study of the amplification process is carried out over a wide range of physical parameters including the loss-cone index, the ratio of the electron mass energy to the temperature of the energetic component, the field-aligned drift speed, the normalized density, and the wave propagation angle.

Perimetric progression using the Visual Field Index and the Advanced Glaucoma Intervention Study score and its clinical correlations.

PubMed

Gros-Otero, Juan; Castejón, Miguel; Paz-Moreno, Javier; Mikropoulos, Dimitrios; Teus, Miguel

2015-01-01

To evaluate the association between clinical parameters and the diagnosis of progression using VFI (Visual Field Index) and AGIS (Advanced Glaucoma Intervention Study) score in primary open angle glaucoma. Retrospective study of 517 visual fields of 78 eyes with primary open angle glaucoma analyzed with VFI and AGIS score. Clinical data registered included: age, sphere, pachimetry, basal intraocular pressure (IOP), and IOP during the follow up. Only the AGIS score diagnosis of progression was associated with the clinical parameters registered. Among the analyzed data, the mean IOP during follow up (p = 0.0005) and IOP at the third month of follow up (p = 0.004) were statistically associated with progression using the AGIS criteria. The diagnosis of perimetric progression using the AGIS score in the current study was closer to the real functional progression than the diagnosis using the VFI, as the former was associated with known risk factors for progression in glaucoma. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

A Robust and Fast Method to Compute Shallow States without Adjustable Parameters: Simulations for a Silicon-Based Qubit

NASA Astrophysics Data System (ADS)

Debernardi, Alberto; Fanciulli, Marco

Within the framework of the envelope function approximation we have computed - without adjustable parameters and with a reduced computational effort due to analytical expression of relevant Hamiltonian terms - the energy levels of the shallow P impurity in silicon and the hyperfine and superhyperfine splitting of the ground state. We have studied the dependence of these quantities on the applied external electric field along the [001] direction. Our results reproduce correctly the experimental splitting of the impurity ground states detected at zero electric field and provide reliable predictions for values of the field where experimental data are lacking. Further, we have studied the effect of confinement of a shallow state of a P atom at the center of a spherical Si-nanocrystal embedded in a SiO2 matrix. In our simulations the valley-orbit interaction of a realistically screened Coulomb potential and of the core potential are included exactly, within the numerical accuracy due to the use of a finite basis set, while band-anisotropy effects are taken into account within the effective-mass approximation.

Optical properties of truncated Au nanocages with different size and shape

NASA Astrophysics Data System (ADS)

Chen, Qin; Qi, Hong; Ren, Ya-Tao; Sun, Jian-Ping; Ruan, Li-Ming

2017-06-01

The hollow nanostructures are conducive to applications including drug delivery, energy storage and conversion, and catalysis. In the present work, a versatile type of Au nanoparticles, i.e. nanocage with hollow interior, was studied thoroughly. Simulation of the optical properties of nanocages with different sizes and shapes was presented, which is essential for tuning the localized surface plasmon resonance peak. The edge length, side length of triangle, and wall thickness were used as structural parameters of truncated Au nanocage. The dependence of absorption efficiency, resonant wavelength, and absorption quantum yield on the structural parameters were discussed. Meanwhile, the applications of absorption quantum yield in biomedical imaging and laser induced thermal therapy were investigated. It was found that the phenomenon of multipolar plasmon resonances exists on truncated Au nanocage. Furthermore, the electric field distribution at different resonant wavelengths was also investigated. It is found that the electromagnetic field corresponds to the dipolar mode in an individual nanocage is largely distributed at the corners. Whereas, the electromagnetic field corresponds to the multipolar region is mainly located in the internal corners and edges.

Nuclear magnetic resonance signal dynamics of liquids in the presence of distant dipolar fields, revisited

PubMed Central

Barros, Wilson; Gochberg, Daniel F.; Gore, John C.

2009-01-01

The description of the nuclear magnetic resonance magnetization dynamics in the presence of long-range dipolar interactions, which is based upon approximate solutions of Bloch–Torrey equations including the effect of a distant dipolar field, has been revisited. New experiments show that approximate analytic solutions have a broader regime of validity as well as dependencies on pulse-sequence parameters that seem to have been overlooked. In order to explain these experimental results, we developed a new method consisting of calculating the magnetization via an iterative formalism where both diffusion and distant dipolar field contributions are treated as integral operators incorporated into the Bloch–Torrey equations. The solution can be organized as a perturbative series, whereby access to higher order terms allows one to set better boundaries on validity regimes for analytic first-order approximations. Finally, the method legitimizes the use of simple analytic first-order approximations under less demanding experimental conditions, it predicts new pulse-sequence parameter dependencies for the range of validity, and clarifies weak points in previous calculations. PMID:19425789

NUMERICAL SIMULATIONS OF KELVIN–HELMHOLTZ INSTABILITY: A TWO-DIMENSIONAL PARAMETRIC STUDY

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

Tian, Chunlin; Chen, Yao, E-mail: chunlin.tian@sdu.edu.cn

2016-06-10

Using two-dimensional simulations, we numerically explore the dependences of Kelvin–Helmholtz (KH) instability upon various physical parameters, including viscosity, the width of the sheared layer, flow speed, and magnetic field strength. In most cases, a multi-vortex phase exists between the initial growth phase and the final single-vortex phase. The parametric study shows that the evolutionary properties, such as phase duration and vortex dynamics, are generally sensitive to these parameters, except in certain regimes. An interesting result is that for supersonic flows, the phase durations and saturation of velocity growth approach constant values asymptotically as the sonic Mach number increases. We confirmmore » that the linear coupling between magnetic field and KH modes is negligible if the magnetic field is weak enough. The morphological behavior suggests that the multi-vortex coalescence might be driven by the underlying wave–wave interaction. Based on these results, we present a preliminary discussion of several events observed in the solar corona. The numerical models need to be further improved to perform a practical diagnostic of the coronal plasma properties.« less

Effect of scrape-off-layer current on reconstructed tokamak equilibrium

DOE PAGES

King, J. R.; Kruger, S. E.; Groebner, R. J.; ...

2017-01-13

Methods are described that extend fields from reconstructed equilibria to include scrape-off-layer current through extrapolated parametrized and experimental fits. The extrapolation includes both the effects of the toroidal-field and pressure gradients which produce scrape-off-layer current after recomputation of the Grad-Shafranov solution. To quantify the degree that inclusion of scrape-off-layer current modifies the equilibrium, the χ-squared goodness-of-fit parameter is calculated for cases with and without scrape-off-layer current. The change in χ-squared is found to be minor when scrape-off-layer current is included however flux surfaces are shifted by up to 3 cm. Here the impact on edge modes of these scrape-off-layer modificationsmore » is also found to be small and the importance of these methods to nonlinear computation is discussed.« less

Do mobile phones pose a potential risk to autonomic modulation of the heart?

PubMed

Barutcu, Irfan; Esen, Ali Metin; Kaya, Dayimi; Turkmen, Muhsin; Karakaya, Osman; Saglam, Mustafa; Melek, Mehmet; Çelik, Ataç; Kilit, Celal; Onrat, Ersel; Kirma, Cevat

2011-11-01

It has long been speculated that mobile phones may interact with the cardiac devices and thereby cardiovascular system may be a potential target for the electromagnetic fields emitted by the mobile phones. Therefore, the present study was designed to test possible effects of radiofrequency waves emitted by digital mobile phones on cardiac autonomic modulation by short-time heart rate variability (HRV) analysis. A total of 20 healthy young subjects were included to the study. All participants were rested in supine position at least for 15 minutes on a comfortable bed, and then time and frequency domain HRV parameters were recorded at baseline in supine position for 5 minutes. After completion of baseline records, by using a mobile GSM (Global System for Mobile Communication) phone, HRV parameters were recorded at turned off mode, at turned on mode, and at calling mode over 5 minutes periods for each stage. Neither time nor frequency domain HRV parameters altered significantly during off mode compare to their baseline values. Also, neither time nor frequency domain HRV parameters altered significantly during turned on and calling mode compared to their baseline values. Short-time exposure to electromagnetic fields emitted by mobile phone does not affect cardiac autonomic modulation in healthy subjects.

Dynamical structure of magnetized dissipative accretion flow around black holes

NASA Astrophysics Data System (ADS)

Sarkar, Biplob; Das, Santabrata

2016-09-01

We study the global structure of optically thin, advection dominated, magnetized accretion flow around black holes. We consider the magnetic field to be turbulent in nature and dominated by the toroidal component. With this, we obtain the complete set of accretion solutions for dissipative flows where bremsstrahlung process is regarded as the dominant cooling mechanism. We show that rotating magnetized accretion flow experiences virtual barrier around black hole due to centrifugal repulsion that can trigger the discontinuous transition of the flow variables in the form of shock waves. We examine the properties of the shock waves and find that the dynamics of the post-shock corona (PSC) is controlled by the flow parameters, namely viscosity, cooling rate and strength of the magnetic field, respectively. We separate the effective region of the parameter space for standing shock and observe that shock can form for wide range of flow parameters. We obtain the critical viscosity parameter that allows global accretion solutions including shocks. We estimate the energy dissipation at the PSC from where a part of the accreting matter can deflect as outflows and jets. We compare the maximum energy that could be extracted from the PSC and the observed radio luminosity values for several supermassive black hole sources and the observational implications of our present analysis are discussed.

Multipolar electromagnetic fields around neutron stars: general-relativistic vacuum solutions

NASA Astrophysics Data System (ADS)

Pétri, J.

2017-12-01

Magnetic fields inside and around neutron stars are at the heart of pulsar magnetospheric activity. Strong magnetic fields are responsible for quantum effects, an essential ingredient to produce leptonic pairs and the subsequent broad-band radiation. The variety of electromagnetic field topologies could lead to the observed diversity of neutron star classes. Thus, it is important to include multipolar components to a presumably dominant dipolar magnetic field. Exact analytical solutions for these multipoles in Newtonian gravity have been computed in recent literature. However, flat space-time is not adequate to describe physics in the immediate surroundings of neutron stars. We generalize the multipole expressions to the strong gravity regime by using a slowly rotating metric approximation such as the one expected around neutron stars. Approximate formulae for the electromagnetic field including frame dragging are computed from which we estimate the Poynting flux and the braking index. Corrections to leading order in compactness and spin parameter are presented. As far as spin-down luminosity is concerned, it is shown that frame dragging remains irrelevant. For high-order multipoles starting from the quadrupole, the electric part can radiate more efficiently than the magnetic part. Both analytical and numerical tools are employed.

Self-Consistent Superthermal Electron Effects on Plasmaspheric Refilling

NASA Technical Reports Server (NTRS)

Liemohn, M. W.; Khazanov, G. V.; Moore, T. E.; Guiter, S. M.

1997-01-01

The effects of self-consistently including superthermal electrons in the definition of the ambipolar electric field are investigated for the case of plasmaspheric refilling after a geomagnetic storm. By using the total electron population in the hydrodynamic equations, a method for incorporating superthermal electron parameters in the electric field and electron temperature calculation is developed. Also, the ambipolar electric field is included in the kinetic equation for the superthermal electrons through a change of variables using the total energy and the first adiabatic invariant. Calculations based on these changes are performed by coupling time-dependent models of the thermal plasma and superthermal electrons. Results from this treatment of the electric field and the self-consistent development of the solution are discussed in detail. Specifically, there is a decreased thermal electron density in the plasmasphere during the first few minutes of refilling, a slightly accelerated proton shock front, and a decreased superthermal electron flux due to the deceleration by the electric field. The timescales of plasmaspheric refilling are discussed and determined to be somewhat shorter than previously calculated for the thermal plasma and superthermal electron population due to the effects of the field-aligned potential.

Modeling electron emission and surface effects from diamond cathodes

NASA Astrophysics Data System (ADS)

Dimitrov, D. A.; Smithe, D.; Cary, J. R.; Ben-Zvi, I.; Rao, T.; Smedley, J.; Wang, E.

2015-02-01

We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass, and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transverse electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. Using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.

First principles crystal engineering of nonlinear optical materials. I. Prototypical case of urea

NASA Astrophysics Data System (ADS)

Masunov, Artëm E.; Tannu, Arman; Dyakov, Alexander A.; Matveeva, Anastasia D.; Freidzon, Alexandra Ya.; Odinokov, Alexey V.; Bagaturyants, Alexander A.

2017-06-01

The crystalline materials with nonlinear optical (NLO) properties are critically important for several technological applications, including nanophotonic and second harmonic generation devices. Urea is often considered to be a standard NLO material, due to the combination of non-centrosymmetric crystal packing and capacity for intramolecular charge transfer. Various approaches to crystal engineering of non-centrosymmetric molecular materials were reported in the literature. Here we propose using global lattice energy minimization to predict the crystal packing from the first principles. We developed a methodology that includes the following: (1) parameter derivation for polarizable force field AMOEBA; (2) local minimizations of crystal structures with these parameters, combined with the evolutionary algorithm for a global minimum search, implemented in program USPEX; (3) filtering out duplicate polymorphs produced; (4) reoptimization and final ranking based on density functional theory (DFT) with many-body dispersion (MBD) correction; and (5) prediction of the second-order susceptibility tensor by finite field approach. This methodology was applied to predict virtual urea polymorphs. After filtering based on packing similarity, only two distinct packing modes were predicted: one experimental and one hypothetical. DFT + MBD ranking established non-centrosymmetric crystal packing as the global minimum, in agreement with the experiment. Finite field approach was used to predict nonlinear susceptibility, and H-bonding was found to account for a 2.5-fold increase in molecular hyperpolarizability to the bulk value.

Geomorphological mapping of ice-free areas using polarimetric RADARSAT-2 data on Fildes Peninsula and Ardley Island, Antarctica

NASA Astrophysics Data System (ADS)

Schmid, T.; López-Martínez, J.; Guillaso, S.; Serrano, E.; D'Hondt, O.; Koch, M.; Nieto, A.; O'Neill, T.; Mink, S.; Durán, J. J.; Maestro, A.

2017-09-01

Satellite-borne Synthetic Aperture Radar (SAR) has been used for characterizing and mapping in two relevant ice-free areas in the South Shetland Islands. The objective has been to identify and characterize land surface covers that mainly include periglacial and glacial landforms, using fully polarimetric SAR C band RADARSAT-2 data, on Fildes Peninsula that forms part of King George Island, and Ardley Island. Polarimetric parameters obtained from the SAR data, a selection of field based training and validation sites and a supervised classification approach, using the support vector machine were chosen to determine the spatial distribution of the different landforms. Eight periglacial and glacial landforms were characterized according to their scattering mechanisms using a set of 48 polarimetric parameters. The mapping of the most representative surface covers included colluvial deposits, stone fields and pavements, patterned ground, glacial till and rock outcrops, lakes and glacier ice. The overall accuracy of the results was estimated at 81%, a significant value when mapping areas that are within isolated regions where access is limited. Periglacial surface covers such as stone fields and pavements occupy 25% and patterned ground over 20% of the ice-free areas. These are results that form the basis for an extensive monitoring of the ice-free areas throughout the northern Antarctic Peninsula region.

Holographic Lifshitz superconductors: Analytic solution

NASA Astrophysics Data System (ADS)

Natsuume, Makoto; Okamura, Takashi

2018-03-01

We construct an analytic solution for a one-parameter family of holographic superconductors in asymptotically Lifshitz spacetimes. We utilize this solution to explore various properties of the systems such as (1) the superfluid phase background and the grand canonical potential, (2) the order parameter response function or the susceptibility, (3) the London equation, and (4) the background with a superfluid flow or a magnetic field. From these results, we identify the dual Ginzburg-Landau theory including numerical coefficients. Also, the dynamic critical exponent zD associated with the critical point is given by zD=2 irrespective of the value of the Lifshitz exponent z .

Collaborative Study for Analysis of High Resolution Infrared Atmospheric Spectra Between NASA Langley Research Center and the University of Denver

NASA Technical Reports Server (NTRS)

Goldman, A.

2002-01-01

The Langley-D.U. collaboration on the analysis of high resolultion infrared atmospheric spectra covered a number of important studies of trace gases identification and quantification from field spectra, and spectral line parameters analysis. The collaborative work included: 1) Quantification and monitoring of trace gases from ground-based spectra available from various locations and seasons and from balloon flights; 2) Identification and preliminary quantification of several isotopic species, including oxygen and Sulfur isotopes; 3) Search for new species on the available spectra, including the use of selective coadding of ground-based spectra for high signal to noise; 4) Update of spectroscopic line parameters, by combining laboratory and atmospheric spectra with theoretical spectroscopy methods; 5) Study of trends and correlations of atmosphere trace constituents; and 6) Algorithms developments, retrievals intercomparisons and automatization of the analysis of NDSC spectra, for both column amounts and vertical profiles.

3-D ballistic transport of ellipsoidal volcanic projectiles considering horizontal wind field and variable shape-dependent drag coefficients

NASA Astrophysics Data System (ADS)

Bertin, Daniel

2017-02-01

An innovative 3-D numerical model for the dynamics of volcanic ballistic projectiles is presented here. The model focuses on ellipsoidal particles and improves previous approaches by considering horizontal wind field, virtual mass forces, and drag forces subjected to variable shape-dependent drag coefficients. Modeling suggests that the projectile's launch velocity and ejection angle are first-order parameters influencing ballistic trajectories. The projectile's density and minor radius are second-order factors, whereas both intermediate and major radii of the projectile are of third order. Comparing output parameters, assuming different input data, highlights the importance of considering a horizontal wind field and variable shape-dependent drag coefficients in ballistic modeling, which suggests that they should be included in every ballistic model. On the other hand, virtual mass forces should be discarded since they almost do not contribute to ballistic trajectories. Simulation results were used to constrain some crucial input parameters (launch velocity, ejection angle, wind speed, and wind azimuth) of the block that formed the biggest and most distal ballistic impact crater during the 1984-1993 eruptive cycle of Lascar volcano, Northern Chile. Subsequently, up to 106 simulations were performed, whereas nine ejection parameters were defined by a Latin-hypercube sampling approach. Simulation results were summarized as a quantitative probabilistic hazard map for ballistic projectiles. Transects were also done in order to depict aerial hazard zones based on the same probabilistic procedure. Both maps combined can be used as a hazard prevention tool for ground and aerial transits nearby unresting volcanoes.

Electrically Guided Assembly of Colloidal Particles

NASA Astrophysics Data System (ADS)

Ristenpart, W. D.; Aksay, I. A.; Saville, D. A.

2002-11-01

In earlier work it was shown that the strength and frequency of an applied electric field alters the dynamic arrangement of particles on an electrode. Two-dimensional 'gas,' 'liquid' and 'solid' arrangements were formed, depending on the field strength and frequency. Since the particles are similarly charged, yet migrate over large distances under the influence of steady or oscillatory fields, it is clear that both hydrodynamic and electrical processes are involved. Here we report on an extensive study of electrically induced ordering in a parallel electrode cell. First, we discuss the kinetics of aggregation in a DC field as measured using video microscopy and digital image analysis. Rate constants were determined as a function of applied electric field strength and particle zeta potential. The kinetic parameters are compared to models based on electrohydrodynamic and electroosmotic fluid flow mechanisms Second, using monodisperse micron-sized particles, we examined the average interparticle spacing over a wide range of applied frequencies and field strengths. Variation of these parameters allows formation of closely-spaced arrangements and ordered arrays of widely separated particles. We find that there is a strong dependence on frequency, but there is surprisingly little influence of the electric field strength past a small threshold. Last, we present experiments with binary suspensions of similarly sized particles with negative but unequal surface potentials. A long-range lateral attraction is observed in an AC field. Depending on the frequency, this attractive interaction results in a diverse set of aggregate morphologies, including superstructured hexagonal lattices. These results are discussed in terms of induced dipole-dipole interactions and electrohydrodynamic flow. Finally, we explore the implications for practical applications.

Pulsed electromagnetic field with or without exercise therapy in the treatment of benign prostatic hyperplasia

PubMed Central

Elgohary, Hany M; Tantawy, Sayed A

2017-01-01

[Purpose] To investigate the effect of pulsed electromagnetic field with or without exercise therapy in the treatment of benign prostatic hyperplasia. [Subjects and Methods] Sixty male patients aged 55–65 years with benign prostatic hyperplasia were invited to participate in this study. Patients were randomly assigned to Group A (n=20; patients who received pulsed electromagnetic field in addition to pelvic floor and aerobic exercises), Group B (n=20; patients who received pulsed electromagnetic field), and Group C (n=20; patients who received placebo electromagnetic field). The assessments included post-void residual urine, urine flow rate, prostate specific antigen, white blood cells count, and International Prostate Symptom Score were weighed, before and after a 4-week intervention. [Results] There were significant differences in Group A and B in all parameters. Group C showed non-significant differences in all measured variables except for International Prostate Symptom Score. Among groups, all parameters showed highly significant differences in favor of Group A. There were non-significant differences between Group A and B and significant difference between Groups A and C and between Groups B and C. [Conclusion] The present study demonstrated that electromagnetic field had a significant impact on the treatment of benign prostatic hyperplasia. Accordingly, electromagnetic field can be utilized alone or in combination with other physiotherapy modalities. Moreover, clinicians should have the capacity to perceive the advantages accomplished using extra treatment alternatives. Electromagnetic field is a safe, noninvasive method and can be used for the treatment of benign prostatic hyperplasia. PMID:28878453

A field-validated model for in situ transport of polymer-stabilized nZVI and implications for subsurface injection.

PubMed

Krol, Magdalena M; Oleniuk, Andrew J; Kocur, Chris M; Sleep, Brent E; Bennett, Peter; Xiong, Zhong; O'Carroll, Denis M

2013-07-02

Nanoscale zerovalent iron (nZVI) particles have significant potential to remediate contaminated source zones. However, the transport of these particles through porous media is not well understood, especially at the field scale. This paper describes the simulation of a field injection of carboxylmethyl cellulose (CMC) stabilized nZVI using a 3D compositional simulator, modified to include colloidal filtration theory (CFT). The model includes composition dependent viscosity and spatially and temporally variable velocity, appropriate for the simulation of push-pull tests (PPTs) with CMC stabilized nZVI. Using only attachment efficiency as a fitting parameter, model results were in good agreement with field observations when spatially variable viscosity effects on collision efficiency were included in the transport modeling. This implies that CFT-modified transport equations can be used to simulate stabilized nZVI field transport. Model results show that an increase in solution viscosity, resulting from injection of CMC stabilized nZVI suspension, affects nZVI mobility by decreasing attachment as well as changing the hydraulics of the system. This effect is especially noticeable with intermittent pumping during PPTs. Results from this study suggest that careful consideration of nZVI suspension formulation is important for optimal delivery of nZVI which can be facilitated with the use of a compositional simulator.

Application of multigrid methods to the solution of liquid crystal equations on a SIMD computer

NASA Technical Reports Server (NTRS)

Farrell, Paul A.; Ruttan, Arden; Zeller, Reinhardt R.

1993-01-01

We will describe a finite difference code for computing the equilibrium configurations of the order-parameter tensor field for nematic liquid crystals in rectangular regions by minimization of the Landau-de Gennes Free Energy functional. The implementation of the free energy functional described here includes magnetic fields, quadratic gradient terms, and scalar bulk terms through the fourth order. Boundary conditions include the effects of strong surface anchoring. The target architectures for our implementation are SIMD machines, with interconnection networks which can be configured as 2 or 3 dimensional grids, such as the Wavetracer DTC. We also discuss the relative efficiency of a number of iterative methods for the solution of the linear systems arising from this discretization on such architectures.

Three site Higgsless model at one loop

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

Chivukula, R. Sekhar; Simmons, Elizabeth H.; Matsuzaki, Shinya

2007-04-01

In this paper we compute the one loop chiral-logarithmic corrections to all O(p{sup 4}) counterterms in the three site Higgsless model. The calculation is performed using the background field method for both the chiral and gauge fields, and using Landau gauge for the quantum fluctuations of the gauge fields. The results agree with our previous calculations of the chiral-logarithmic corrections to the S and T parameters in 't Hooft-Feynman gauge. The work reported here includes a complete evaluation of all one loop divergences in an SU(2)xU(1) nonlinear sigma model, corresponding to an electroweak effective Lagrangian in the absence of custodialmore » symmetry.« less

Squids in the Study of Cerebral Magnetic Field

NASA Astrophysics Data System (ADS)

Romani, G. L.; Narici, L.

The following sections are included: * INTRODUCTION * HISTORICAL OVERVIEW * NEUROMAGNETIC FIELDS AND AMBIENT NOISE * DETECTORS * Room temperature sensors * SQUIDs * DETECTION COILS * Magnetometers * Gradiometers * Balancing * Planar gradiometers * Choice of the gradiometer parameters * MODELING * Current pattern due to neural excitations * Action potentials and postsynaptic currents * The current dipole model * Neural population and detected fields * Spherically bounded medium * SPATIAL CONFIGURATION OF THE SENSORS * SOURCE LOCALIZATION * Localization procedure * Experimental accuracy and reproducibility * SIGNAL PROCESSING * Analog Filtering * Bandpass filters * Line rejection filters * DATA ANALYSIS * Analysis of evoked/event-related responses * Simple average * Selected average * Recursive techniques * Similarity analysis * Analysis of spontaneous activity * Mapping and localization * EXAMPLES OF NEUROMAGNETIC STUDIES * Neuromagnetic measurements * Studies on the normal brain * Clinical applications * Epilepsy * Tinnitus * CONCLUSIONS * ACKNOWLEDGEMENTS * REFERENCES

Recommendations for field measurements of aircraft noise

NASA Technical Reports Server (NTRS)

Marsh, A. H.

1982-01-01

Specific recommendations for environmental test criteria, data acquisition procedures, and instrument performance requirements for measurement of noise levels produced by aircraft in flight are provided. Recommendations are also given for measurement of associated airplane and engine parameters and atmospheric conditions. Recommendations are based on capabilities which were available commercially in 1981; they are applicable to field tests of aircraft flying subsonically past microphones located near the surface of the ground either directly under or to the side of a flight path. Aircraft types covered by the recommendations include fixed-wing airplanes powered by turbojet or turbofan engines or by propellers. The recommended field-measurement procedures are consistent with assumed requirements for data processing and analysis.

Donor impurity-related photoionization cross section in GaAs cone-like quantum dots under applied electric field

NASA Astrophysics Data System (ADS)

Iqraoun, E.; Sali, A.; Rezzouk, A.; Feddi, E.; Dujardin, F.; Mora-Ramos, M. E.; Duque, C. A.

2017-06-01

The donor impurity-related electron states in GaAs cone-like quantum dots under the influence of an externally applied static electric field are theoretically investigated. Calculations are performed within the effective mass and parabolic band approximations, using the variational procedure to include the electron-impurity correlation effects. The uncorrelated Schrödinger-like electron states are obtained in quasi-analytical form and the entire electron-impurity correlated states are used to calculate the photoionisation cross section. Results for the electron state energies and the photoionisation cross section are reported as functions of the main geometrical parameters of the cone-like structures as well as of the electric field strength.

Theoretical aspects of femtosecond double-pump single-molecule spectroscopy. I. Weak-field regime.

PubMed

Palacino-González, Elisa; Gelin, Maxim F; Domcke, Wolfgang

2017-12-13

We present a theoretical description of double-pump femtosecond single-molecule signals with fluorescence detection. We simulate these signals in the weak-field regime for a model mimicking a chromophore with a Franck-Condon-active vibrational mode. We establish several signatures of these signals which are characteristic for the weak-field regime. The signatures include the quenching of vibrational beatings by electronic dephasing and a pronounced tilt of the phase-time profiles in the two-dimensional (2D) maps. We study how environment-induced slow modulations of the electronic dephasing and relevant chromophore parameters (electronic energy, orientation, vibrational frequency and relative shift of the potential energy surfaces) affect the signals.

Simulation analysis of temperature control on RCC arch dam of hydropower station

NASA Astrophysics Data System (ADS)

XIA, Shi-fa

2017-12-01

The temperature analysis of roller compacted concrete (RCC) dam plays an important role in their design and construction. Based on three-dimensional finite element method, in the computation of temperature field, many cases are included, such as air temperature, elevated temperature by cement hydration heat, concrete temperature during placing, the influence of water in the reservoir, and boundary temperature. According to the corresponding parameters of RCC arch dam, the analysis of temperature field and stress field during the period of construction and operation is performed. The study demonstrates that detailed thermal stress analysis should be performed for RCC dams to provide a basis to minimize and control the occurrence of thermal cracking.

Issues in Turbulence Simulation for Experimental Comparison

NASA Astrophysics Data System (ADS)

Ross, D. W.; Bravenec, R. V.; Dorland, W.; Beer, M. A.; Hammett, G. W.

1999-11-01

Studies of the sensitivity of fluctuation spectra and transport fluxes to local plasma parameters and gradients(D. W. Ross et al.), Bull. Am. Phys. Soc. 43, 1760 (1998); D. W. Ross et al., Transport Task Force Workshop, Portland, Oregon, (1999). are continued using nonlinear gyrofluid simulation(M. A. Beer et al.), Phys. Plasmas 2, 2687 (1995). on the T3E at NERSC. Parameters that are characteristic of discharges in DIII-D and Alcator C-Mod are employed. In the previous work, the gradients of Z_eff, n_e, and Te were varied within the experimental uncertainty. Amplitudes and fluxes are quite sensitive to dZ_eff/dr. Here, these studies are continued and extended to variation of other parameters, including T_e/T_i, and dT_i/dr, which are important for ion temperature gradient modes. The role of electric field shear is discussed. Implications for comparison with experiment, including transient perturbations, are discussed, with the goal of quantifying the accuracy of profile data needed to verify the turbulence theory.

Quantum gravity fluctuations flatten the Planck-scale Higgs potential

NASA Astrophysics Data System (ADS)

Eichhorn, Astrid; Hamada, Yuta; Lumma, Johannes; Yamada, Masatoshi

2018-04-01

We investigate asymptotic safety of a toy model of a singlet-scalar extension of the Higgs sector including two real scalar fields under the impact of quantum-gravity fluctuations. Employing functional renormalization group techniques, we search for fixed points of the system which provide a tentative ultraviolet completion of the system. We find that in a particular regime of the gravitational parameter space the canonically marginal and relevant couplings in the scalar sector—including the mass parameters—become irrelevant at the ultraviolet fixed point. The infrared potential for the two scalars that can be reached from that fixed point is fully predicted and features no free parameters. In the remainder of the gravitational parameter space, the values of the quartic couplings in our model are predicted. In light of these results, we discuss whether the singlet-scalar could be a dark-matter candidate. Furthermore, we highlight how "classical scale invariance" in the sense of a flat potential of the scalar sector at the Planck scale could arise as a consequence of asymptotic safety.

MODFLOW-2000 : the U.S. Geological Survey modular ground-water model--documentation of the Advective-Transport Observation (ADV2) Package

USGS Publications Warehouse

Anderman, Evan R.; Hill, Mary Catherine

2001-01-01

Observations of the advective component of contaminant transport in steady-state flow fields can provide important information for the calibration of ground-water flow models. This report documents the Advective-Transport Observation (ADV2) Package, version 2, which allows advective-transport observations to be used in the three-dimensional ground-water flow parameter-estimation model MODFLOW-2000. The ADV2 Package is compatible with some of the features in the Layer-Property Flow and Hydrogeologic-Unit Flow Packages, but is not compatible with the Block-Centered Flow or Generalized Finite-Difference Packages. The particle-tracking routine used in the ADV2 Package duplicates the semi-analytical method of MODPATH, as shown in a sample problem. Particles can be tracked in a forward or backward direction, and effects such as retardation can be simulated through manipulation of the effective-porosity value used to calculate velocity. Particles can be discharged at cells that are considered to be weak sinks, in which the sink applied does not capture all the water flowing into the cell, using one of two criteria: (1) if there is any outflow to a boundary condition such as a well or surface-water feature, or (2) if the outflow exceeds a user specified fraction of the cell budget. Although effective porosity could be included as a parameter in the regression, this capability is not included in this package. The weighted sum-of-squares objective function, which is minimized in the Parameter-Estimation Process, was augmented to include the square of the weighted x-, y-, and z-components of the differences between the simulated and observed advective-front locations at defined times, thereby including the direction of travel as well as the overall travel distance in the calibration process. The sensitivities of the particle movement to the parameters needed to minimize the objective function are calculated for any particle location using the exact sensitivity-equation approach; the equations are derived by taking the partial derivatives of the semi-analytical particle-tracking equation with respect to the parameters. The ADV2 Package is verified by showing that parameter estimation using advective-transport observations produces the true parameter values in a small but complicated test case when exact observations are used. To demonstrate how the ADV2 Package can be used in practice, a field application is presented. In this application, the ADV2 Package is used first in the Sensitivity-Analysis mode of MODFLOW-2000 to calculate measures of the importance of advective-transport observations relative to head-dependent flow observations when either or both are used in conjunction with hydraulic-head observations in a simulation of the sewage-discharge plume at Cape Cod, Massachusetts. The ADV2 Package is then used in the Parameter-Estimation mode of MODFLOW-2000 to determine best-fit parameter values. It is concluded that, for this problem, advective-transport observations improved the calibration of the model and the estimation of ground-water flow parameters, and the use of formal parameter-estimation methods and related techniques produced significant insight into the physical system.

Water-quality data for selected stations in the East Everglades, Florida

USGS Publications Warehouse

Waller, Bradley G.

1981-01-01

The results of water-quality samples collected from April 1978 through April 1980 from three canal stations, four marsh stations, and two ground-water stations within the East Everglades, Dade County, Florida, are tabulated in 37 tables. The major categories of parameters analyzed are field measurements, physical characteristics, macronutrients (carbon, nitrogen, and phosphorus), major ions, trace elements, and algae. Chemical data for bulk-precipitation stations within and adjacent to the East Everglades are also given. The parameters analyzed include macronutrients, major ions, and trace elements. The period of record for these stations is October 1977 through April 1980. Bottom material at the canal and marsh stations was collected twice during the investigation. These data include analyses for macronutrients, trace elements, and chlorinated-hydrocarbon insecticides. (USGS)

Hairy AdS black holes with a toroidal horizon in 4D Einstein-nonlinear σ-model system

NASA Astrophysics Data System (ADS)

Astorino, Marco; Canfora, Fabrizio; Giacomini, Alex; Ortaggio, Marcello

2018-01-01

An exact hairy asymptotically locally AdS black hole solution with a flat horizon in the Einstein-nonlinear sigma model system in (3+1) dimensions is constructed. The ansatz for the nonlinear SU (2) field is regular everywhere and depends explicitly on Killing coordinates, but in such a way that its energy-momentum tensor is compatible with a metric with Killing fields. The solution is characterized by a discrete parameter which has neither topological nor Noether charge associated with it and therefore represents a hair. A U (1) gauge field interacting with Einstein gravity can also be included. The thermodynamics is analyzed. Interestingly, the hairy black hole is always thermodynamically favoured with respect to the corresponding black hole with vanishing Pionic field.

Nonequilibrium response of an electron-mediated charge density wave ordered material to a large dc electric field

NASA Astrophysics Data System (ADS)

Matveev, O. P.; Shvaika, A. M.; Devereaux, T. P.; Freericks, J. K.

2016-01-01

Using the Kadanoff-Baym-Keldysh formalism, we employ nonequilibrium dynamical mean-field theory to exactly solve for the nonlinear response of an electron-mediated charge-density-wave-ordered material. We examine both the dc current and the order parameter of the conduction electrons as the ordered system is driven by the electric field. Although the formalism we develop applies to all models, for concreteness, we examine the charge-density-wave phase of the Falicov-Kimball model, which displays a number of anomalous behaviors including the appearance of subgap density of states as the temperature increases. These subgap states should have a significant impact on transport properties, particularly the nonlinear response of the system to a large dc electric field.

Selected, annotated bibliography of studies relevant to the isolation of nuclear wastes. [705 references

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

Hyder, L.K.; Fore, C.S.; Vaughan, N.D.

This annotated bibliography of 705 references represents the first in a series to be published by the Ecological Sciences Information Center containing scientific, technical, economic, and regulatory information relevant to nuclear waste isolation. Most references discuss deep geologic disposal, with fewer studies of deep seabed disposal; space disposal is also included. The publication covers both domestic and foreign literature for the period 1954 to 1980. Major chapters selected are Chemical and Physical Aspects; Container Design and Performance; Disposal Site; Envirnmental Transport; General Studies and Reviews; Geology, Hydrology and Site Resources; Regulatory and Economic Aspects; Repository Design and Engineering; Transportation Technology;more » Waste Production; and Waste Treatment. Specialized data fields have been incorporated to improve the ease and accuracy of locating pertinent references. Specific radionuclides for which data are presented are listed in the Measured Radionuclides field, and specific parameters which affect the migration of these radionuclides are presented in the Measured Parameters field. The references within each chapter are arranged alphabetically by leading author, corporate affiliation, or title of the document. When the author is not given, the corporate affiliation appears first. If these two levels of authorship are not given, the title of the document is used as the identifying level. Indexes are provided for author(s), keywords, subject category, title, geographic location, measured parameters, measured radionuclides, and publication description.« less

pynoddy 1.0: an experimental platform for automated 3-D kinematic and potential field modelling

NASA Astrophysics Data System (ADS)

Florian Wellmann, J.; Thiele, Sam T.; Lindsay, Mark D.; Jessell, Mark W.

2016-03-01

We present a novel methodology for performing experiments with subsurface structural models using a set of flexible and extensible Python modules. We utilize the ability of kinematic modelling techniques to describe major deformational, tectonic, and magmatic events at low computational cost to develop experiments testing the interactions between multiple kinematic events, effect of uncertainty regarding event timing, and kinematic properties. These tests are simple to implement and perform, as they are automated within the Python scripting language, allowing the encapsulation of entire kinematic experiments within high-level class definitions and fully reproducible results. In addition, we provide a link to geophysical potential-field simulations to evaluate the effect of parameter uncertainties on maps of gravity and magnetics. We provide relevant fundamental information on kinematic modelling and our implementation, and showcase the application of our novel methods to investigate the interaction of multiple tectonic events on a pre-defined stratigraphy, the effect of changing kinematic parameters on simulated geophysical potential fields, and the distribution of uncertain areas in a full 3-D kinematic model, based on estimated uncertainties in kinematic input parameters. Additional possibilities for linking kinematic modelling to subsequent process simulations are discussed, as well as additional aspects of future research. Our modules are freely available on github, including documentation and tutorial examples, and we encourage the contribution to this project.

pynoddy 1.0: an experimental platform for automated 3-D kinematic and potential field modelling

NASA Astrophysics Data System (ADS)

Wellmann, J. F.; Thiele, S. T.; Lindsay, M. D.; Jessell, M. W.

2015-11-01

We present a novel methodology for performing experiments with subsurface structural models using a set of flexible and extensible Python modules. We utilise the ability of kinematic modelling techniques to describe major deformational, tectonic, and magmatic events at low computational cost to develop experiments testing the interactions between multiple kinematic events, effect of uncertainty regarding event timing, and kinematic properties. These tests are simple to implement and perform, as they are automated within the Python scripting language, allowing the encapsulation of entire kinematic experiments within high-level class definitions and fully reproducible results. In addition, we provide a~link to geophysical potential-field simulations to evaluate the effect of parameter uncertainties on maps of gravity and magnetics. We provide relevant fundamental information on kinematic modelling and our implementation, and showcase the application of our novel methods to investigate the interaction of multiple tectonic events on a pre-defined stratigraphy, the effect of changing kinematic parameters on simulated geophysical potential-fields, and the distribution of uncertain areas in a full 3-D kinematic model, based on estimated uncertainties in kinematic input parameters. Additional possibilities for linking kinematic modelling to subsequent process simulations are discussed, as well as additional aspects of future research. Our modules are freely available on github, including documentation and tutorial examples, and we encourage the contribution to this project.

Comparison of organic electroluminescence and liquid crystal displays for clinical utility in orthopedic endoscopic surgery.

PubMed

Dezawa, Akira; Sairyo, Koichi

2014-05-01

Organic electroluminescence displays (OELD) use organic materials that self-emit light with the passage of an electric current. OELD provide high contrast, excellent color reproducibility at low brightness, excellent video images, and less restricted viewing angles. OELD are thus promising for medical use. This study compared the utility of an OELD with conventional liquid crystal displays (LCD) for imaging in orthopedic endoscopic surgery. One OELD and two conventional LCD that were indistinguishable in external appearance were used in this study. Images from 18 patients were displayed simultaneously on three monitors and evaluated by six orthopedic surgeons with extensive surgical experience. Images were shown for 2 min, repeated twice, and viewed from the front and side (diagonally). Surgeon rated both clinical utility (12 parameters) and image quality (11 parameters) for each image on a 5-point scale: 1, very good; 2, good; 3, average; 4, poor; and 5, very poor. For clinical utility in 16 percutaneous endoscopic discectomy cases, mean scores for all 12 parameters were significantly better on the OELD than on the LCD, including organ distinguishability (2.1 vs 3.2, respectively), lesion identification (2.2 vs 3.1), and overall viewing impression (2.1 vs 3.1). For image quality, all 11 parameters were better on the OELD than on LCD. Significant differences were identified in six parameters, including contrast (1.8 vs 2.9), color reproducibility in dark areas (1.8 vs 2.9), and viewing angle (2.2 vs 2.9). The high contrast and excellent color reproducibility of the OELD reduced the constraints of imaging under endoscopy, in which securing a field of view may be difficult. Distinguishability of organs was good, including ligaments, dura mater, nerves, and adipose tissue, contributing to good stereoscopic images of the surgical field. These findings suggest the utility of OELD for excellent display of surgical images and for enabling safe and highly accurate endoscopic surgery. © 2014 Japan Society for Endoscopic Surgery, Asia Endosurgery Task Force and Wiley Publishing Asia Pty Ltd.

TAIR- TRANSONIC AIRFOIL ANALYSIS COMPUTER CODE

NASA Technical Reports Server (NTRS)

Dougherty, F. C.

1994-01-01

The Transonic Airfoil analysis computer code, TAIR, was developed to employ a fast, fully implicit algorithm to solve the conservative full-potential equation for the steady transonic flow field about an arbitrary airfoil immersed in a subsonic free stream. The full-potential formulation is considered exact under the assumptions of irrotational, isentropic, and inviscid flow. These assumptions are valid for a wide range of practical transonic flows typical of modern aircraft cruise conditions. The primary features of TAIR include: a new fully implicit iteration scheme which is typically many times faster than classical successive line overrelaxation algorithms; a new, reliable artifical density spatial differencing scheme treating the conservative form of the full-potential equation; and a numerical mapping procedure capable of generating curvilinear, body-fitted finite-difference grids about arbitrary airfoil geometries. Three aspects emphasized during the development of the TAIR code were reliability, simplicity, and speed. The reliability of TAIR comes from two sources: the new algorithm employed and the implementation of effective convergence monitoring logic. TAIR achieves ease of use by employing a "default mode" that greatly simplifies code operation, especially by inexperienced users, and many useful options including: several airfoil-geometry input options, flexible user controls over program output, and a multiple solution capability. The speed of the TAIR code is attributed to the new algorithm and the manner in which it has been implemented. Input to the TAIR program consists of airfoil coordinates, aerodynamic and flow-field convergence parameters, and geometric and grid convergence parameters. The airfoil coordinates for many airfoil shapes can be generated in TAIR from just a few input parameters. Most of the other input parameters have default values which allow the user to run an analysis in the default mode by specifing only a few input parameters. Output from TAIR may include aerodynamic coefficients, the airfoil surface solution, convergence histories, and printer plots of Mach number and density contour maps. The TAIR program is written in FORTRAN IV for batch execution and has been implemented on a CDC 7600 computer with a central memory requirement of approximately 155K (octal) of 60 bit words. The TAIR program was developed in 1981.

Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding.

PubMed

Xie, Weifeng; Fan, Chenglei; Yang, Chunli; Lin, Sanbao

2016-03-01

As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius. Copyright © 2015 Elsevier B.V. All rights reserved.

Magneto-Structural Correlations in Pseudotetrahedral Forms of the [Co(SPh)4]2- Complex Probed by Magnetometry, MCD Spectroscopy, Advanced EPR Techniques, and ab Initio Electronic Structure Calculations.

PubMed

Suturina, Elizaveta A; Nehrkorn, Joscha; Zadrozny, Joseph M; Liu, Junjie; Atanasov, Mihail; Weyhermüller, Thomas; Maganas, Dimitrios; Hill, Stephen; Schnegg, Alexander; Bill, Eckhard; Long, Jeffrey R; Neese, Frank

2017-03-06

The magnetic properties of pseudotetrahedral Co(II) complexes spawned intense interest after (PPh 4 ) 2 [Co(SPh) 4 ] was shown to be the first mononuclear transition-metal complex displaying slow relaxation of the magnetization in the absence of a direct current magnetic field. However, there are differing reports on its fundamental magnetic spin Hamiltonian (SH) parameters, which arise from inherent experimental challenges in detecting large zero-field splittings. There are also remarkable changes in the SH parameters of [Co(SPh) 4 ] 2- upon structural variations, depending on the counterion and crystallization conditions. In this work, four complementary experimental techniques are utilized to unambiguously determine the SH parameters for two different salts of [Co(SPh) 4 ] 2- : (PPh 4 ) 2 [Co(SPh) 4 ] (1) and (NEt 4 ) 2 [Co(SPh) 4 ] (2). The characterization methods employed include multifield SQUID magnetometry, high-field/high-frequency electron paramagnetic resonance (HF-EPR), variable-field variable-temperature magnetic circular dichroism (VTVH-MCD), and frequency domain Fourier transform THz-EPR (FD-FT THz-EPR). Notably, the paramagnetic Co(II) complex [Co(SPh) 4 ] 2- shows strong axial magnetic anisotropy in 1, with D = -55(1) cm -1 and E/D = 0.00(3), but rhombic anisotropy is seen for 2, with D = +11(1) cm -1 and E/D = 0.18(3). Multireference ab initio CASSCF/NEVPT2 calculations enable interpretation of the remarkable variation of D and its dependence on the electronic structure and geometry.

Introduction to the problem

NASA Technical Reports Server (NTRS)

Ramohalli, Kumar

1989-01-01

Solid propellant rockets were used extensively in space missions ranging from large boosters to orbit-raising upper stages. The smaller motors find exclusive use in various earth-based applications. The advantage of the solids include simplicity, readiness, volumetric efficiency, and storability. Important recent progress in related fields (combustion, rheology, micro-instrumentation/diagnostics, and chaos theory) can be applied to solid rockets to derive maximum advantage and avoid waste. Main objectives of research in solid propellants include: to identify critical parameters, to establish specification rules, and to develop quantitative criteria.

Ice Accretion and Performance Degradation Calculations with LEWICE/NS

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.; Al-Khalil, Kamel M.; Velazquez, Matthew T.

1993-01-01

The LEWICE ice accretion computer code has been extended to include the solution of the two-dimensional Navier-Stokes equations. The code is modular and contains separate stand-alone program elements that create a grid, calculate the flow field parameters, calculate the droplet trajectory paths, determine the amount of ice growth, calculate aeroperformance changes, and plot results. The new elements of the code are described. Calculated results are compared to experiment for several cases, including both ice shape and drag rise.

Effects of temperature and electric field on order parameters in ferroelectric hexagonal manganites

NASA Astrophysics Data System (ADS)

Zhang, C. X.; Yang, K. L.; Jia, P.; Lin, H. L.; Li, C. F.; Lin, L.; Yan, Z. B.; Liu, J.-M.

2018-03-01

In Landau-Devonshire phase transition theory, the order parameter represents a unique property for a disorder-order transition at the critical temperature. Nevertheless, for a phase transition with more than one order parameter, such behaviors can be quite different and system-dependent in many cases. In this work, we investigate the temperature (T) and electric field (E) dependence of the two order parameters in improper ferroelectric hexagonal manganites, addressing the phase transition from the high-symmetry P63/mmc structure to the polar P63cm structure. It is revealed that the trimerization as the primary order parameter with two components: the trimerization amplitude Q and phase Φ, and the spontaneous polarization P emerging as the secondary order parameter exhibit quite different stability behaviors against various T and E. The critical exponents for the two parameters Q and P are 1/2 and 3/2, respectively. As temperature increases, the window for the electric field E enduring the trimerization state will shrink. An electric field will break the Z2 part of the Z2×Z3 symmetry. The present work may shed light on the complexity of the vortex-antivortex domain structure evolution near the phase transition temperature.

Parameter estimation using meta-heuristics in systems biology: a comprehensive review.

PubMed

Sun, Jianyong; Garibaldi, Jonathan M; Hodgman, Charlie

2012-01-01

This paper gives a comprehensive review of the application of meta-heuristics to optimization problems in systems biology, mainly focussing on the parameter estimation problem (also called the inverse problem or model calibration). It is intended for either the system biologist who wishes to learn more about the various optimization techniques available and/or the meta-heuristic optimizer who is interested in applying such techniques to problems in systems biology. First, the parameter estimation problems emerging from different areas of systems biology are described from the point of view of machine learning. Brief descriptions of various meta-heuristics developed for these problems follow, along with outlines of their advantages and disadvantages. Several important issues in applying meta-heuristics to the systems biology modelling problem are addressed, including the reliability and identifiability of model parameters, optimal design of experiments, and so on. Finally, we highlight some possible future research directions in this field.

Robust Online Hamiltonian Learning

NASA Astrophysics Data System (ADS)

Granade, Christopher; Ferrie, Christopher; Wiebe, Nathan; Cory, David

2013-05-01

In this talk, we introduce a machine-learning algorithm for the problem of inferring the dynamical parameters of a quantum system, and discuss this algorithm in the example of estimating the precession frequency of a single qubit in a static field. Our algorithm is designed with practicality in mind by including parameters that control trade-offs between the requirements on computational and experimental resources. The algorithm can be implemented online, during experimental data collection, or can be used as a tool for post-processing. Most importantly, our algorithm is capable of learning Hamiltonian parameters even when the parameters change from experiment-to-experiment, and also when additional noise processes are present and unknown. Finally, we discuss the performance of the our algorithm by appeal to the Cramer-Rao bound. This work was financially supported by the Canadian government through NSERC and CERC and by the United States government through DARPA. NW would like to acknowledge funding from USARO-DTO.

Relationship Between the Global Electric Circuit and Electrified Cloud Parameters at Diurnal, Seasonal and Interannual Timescales

NASA Astrophysics Data System (ADS)

Lavigne, Thomas

In the early 1900's, J.W. Whipple began validating C.R. Wilson's Global Electric Circuit (GEC) hypothesis by correlating diurnal variations of global thunder days with diurnal variations of the fair weather electric field. This study applies 16+ years of Precipitation Feature (PF) data from the Tropical Rainfall Measuring Mission (TRMM), including lightning data from the Lightning Imaging Sensor (LIS), alongside 12-years of electric field measurements from Vostok, Antarctica to further examine this relationship. Joint diurnal-seasonal variations of the electric field are compared with PF parameters that are potentially related to the GEC. The flash rate and volume of 30 dBZ between -5°C and -35°C variables are shown to have the best direct relationship to the electric field, with r2 values of 0.67 and 0.62, respectively. However, the Coefficient of Variation (COV) of the flash rate (28%) and the electric field (12%), display relatively large differences in the spread of the variables. The volume of 30 dBZ between -5°C and -35°C shows a closer amplitude agreement to the variance of the electric field (COV=17%). Furthermore, these relationships are analyzed during two different phases of the El Nino Southern Oscillation (ENSO). Results show different seasonal-diurnal variations of the electric field during ENSO phases, with enhancements in the electric field between January through April at 16-24 UTC in La Nina years. In all, similar variations have been found in the fair weather electric field, and the variation of properties of global PFs with high potential of electrification at diurnal, seasonal, and interannual timescales. These confirm the dominant role of the global thunderclouds and electrified clouds in the global electric circuit.

Active optics and the axisymmetric case: MINITRUST wide-field three-reflection telescopes with mirrors aspherized from tulip and vase forms

NASA Astrophysics Data System (ADS)

Lemaitre, Gerard R.; Montiel, Pierre; Joulie, Patrice; Dohlen, Kjetil; Lanzoni, Patrick

2004-09-01

Wide-field astronomy requires larger size telescopes. Compared to the catadioptric Schmidt, the optical properties of a three mirror telescope provides significant advantages. (1) The flat field design is anastigmatic at any wavelength, (2) the system is extremely compact -- four times shorter than a Schmidt -- and, (3) compared to a Schmidt with refractive corrector -- requiring the polishing of three optical surfaces --, the presently proposed Modified-Rumsey design uses all of eight available free parameters of a flat fielded anastigmatic three mirror telescope for mirrors generated by active optics methods. Compared to a Rumsey design, these parameters include the additional slope continuity condition at the primary-tertiary link for in-situ stressing and aspherization from a common sphere. Then, active optics allows the polishing of only two spherical surfaces: the combined primary-tertiary mirror and the secondary mirror. All mirrors are spheroids of the hyperboloid type. This compact system is of interest for space and ground-based astronomy and allows to built larger wide-field telescopes such as demonstrated by the design and construction of identical telescopes MINITRUST-1 and -2, f/5 - 2° FOV, consisting of an in-situ stressed double vase form primary-tertiary and of a stress polished tulip form secondary. Optical tests of these telescopes, showing diffraction limited images, are presented.

Reverberation index: a novel metric by which to quantify the impact of a scientific entity on a given field.

PubMed

Kathleen Bandt, S; Dacey, Ralph G

2017-09-01

The authors propose a novel bibilometric index, the reverberation index (r-index), as a comparative assessment tool for use in determining differential reverberation between scientific fields for a given scientific entity. Conversely, this may allow comparison of 2 similar scientific entities within a single scientific field. This index is calculated using a relatively simple 3-step process. Briefly, Thompson Reuters' Web of Science is used to produce a citation report for a unique search parameter (this may be an author, journal article, or topical key word). From this citation report, a list of citing journals is retrieved from which a weighted ratio of citation patterns across journals can be calculated. This r-index is then used to compare the reverberation of the original search parameter across different fields of study or wherever a comparison is required. The advantage of this novel tool is its ability to transcend a specific component of the scientific process. This affords application to a diverse range of entities, including an author, a journal article, or a topical key word, for effective comparison of that entity's reverberation within a scientific arena. The authors introduce the context for and applications of the r-index, emphasizing neurosurgical topics and journals for illustration purposes. It should be kept in mind, however, that the r-index is readily applicable across all fields of study.

Resonances in the Field-Angle-Resolved Thermal Conductivity of CeCoIn 5

DOE PAGES

Kim, Duk Y.; Lin, Shi -Zeng; Weickert, Franziska; ...

2017-05-12

Here, the thermal conductivity measurement in a rotating magnetic field is a powerful probe of the structure of the superconducting energy gap. We present high-precision measurements of the low-temperature thermal conductivity in the unconventional heavy-fermion superconductor CeCoIn 5, with the heat current J along the nodal [110] direction of its d x2–y2 order parameter and the magnetic field up to 7 T rotating in the ab plane. In contrast to the smooth oscillations found previously for J∥[100], we observe a sharp resonancelike peak in the thermal conductivity when the magnetic field is also in the [110] direction, parallel to themore » heat current. We explain this peak qualitatively via a model of the heat transport in a d-wave superconductor. In addition, we observe two smaller but also very sharp peaks in the thermal conductivity for the field directions at angles Θ≈±33° with respect to J. The origin of the observed resonances at Θ≈±33° at present defies theoretical explanation. The challenge of uncovering their source will dictate exploring theoretically more complex models, which might include, e.g., fine details of the Fermi surface, Andreev bound vortex core states, a secondary superconducting order parameter, and the existence of gaps in spin and charge excitations.« less

Resonances in the Field-Angle-Resolved Thermal Conductivity of CeCoIn 5

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

Kim, Duk Y.; Lin, Shi -Zeng; Weickert, Franziska

Here, the thermal conductivity measurement in a rotating magnetic field is a powerful probe of the structure of the superconducting energy gap. We present high-precision measurements of the low-temperature thermal conductivity in the unconventional heavy-fermion superconductor CeCoIn 5, with the heat current J along the nodal [110] direction of its d x2–y2 order parameter and the magnetic field up to 7 T rotating in the ab plane. In contrast to the smooth oscillations found previously for J∥[100], we observe a sharp resonancelike peak in the thermal conductivity when the magnetic field is also in the [110] direction, parallel to themore » heat current. We explain this peak qualitatively via a model of the heat transport in a d-wave superconductor. In addition, we observe two smaller but also very sharp peaks in the thermal conductivity for the field directions at angles Θ≈±33° with respect to J. The origin of the observed resonances at Θ≈±33° at present defies theoretical explanation. The challenge of uncovering their source will dictate exploring theoretically more complex models, which might include, e.g., fine details of the Fermi surface, Andreev bound vortex core states, a secondary superconducting order parameter, and the existence of gaps in spin and charge excitations.« less

Strong variable linear polarization in the cool active star II Peg

NASA Astrophysics Data System (ADS)

Rosén, Lisa; Kochukhov, Oleg; Wade, Gregg A.

2014-08-01

Magnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. This provides limited information about the magnetic field geometry since circular polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy when only circular polarization is used. On the other hand, linear polarization is sensitive to the transverse component of the magnetic field. By including linear polarization in the reconstruction the quality of the reconstructed magnetic map is dramatically improved. For that reason, we wanted to identify cool stars for which linear polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and σ Gem were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. Mean polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Not only was linear polarization successfully detected in all four stars in at least one observation, but also, II Peg showed an extraordinarily strong linear polarization signature throughout all observations. This qualifies II Peg as the first promising target for magnetic Doppler imaging in all four Stokes parameters and, at the same time, suggests that other such targets can possibly be identified.

Optical Coherence Tomography Machine Learning Classifiers for Glaucoma Detection: A Preliminary Study

PubMed Central

Burgansky-Eliash, Zvia; Wollstein, Gadi; Chu, Tianjiao; Ramsey, Joseph D.; Glymour, Clark; Noecker, Robert J.; Ishikawa, Hiroshi; Schuman, Joel S.

2007-01-01

Purpose Machine-learning classifiers are trained computerized systems with the ability to detect the relationship between multiple input parameters and a diagnosis. The present study investigated whether the use of machine-learning classifiers improves optical coherence tomography (OCT) glaucoma detection. Methods Forty-seven patients with glaucoma (47 eyes) and 42 healthy subjects (42 eyes) were included in this cross-sectional study. Of the glaucoma patients, 27 had early disease (visual field mean deviation [MD] ≥ −6 dB) and 20 had advanced glaucoma (MD < −6 dB). Machine-learning classifiers were trained to discriminate between glaucomatous and healthy eyes using parameters derived from OCT output. The classifiers were trained with all 38 parameters as well as with only 8 parameters that correlated best with the visual field MD. Five classifiers were tested: linear discriminant analysis, support vector machine, recursive partitioning and regression tree, generalized linear model, and generalized additive model. For the last two classifiers, a backward feature selection was used to find the minimal number of parameters that resulted in the best and most simple prediction. The cross-validated receiver operating characteristic (ROC) curve and accuracies were calculated. Results The largest area under the ROC curve (AROC) for glaucoma detection was achieved with the support vector machine using eight parameters (0.981). The sensitivity at 80% and 95% specificity was 97.9% and 92.5%, respectively. This classifier also performed best when judged by cross-validated accuracy (0.966). The best classification between early glaucoma and advanced glaucoma was obtained with the generalized additive model using only three parameters (AROC = 0.854). Conclusions Automated machine classifiers of OCT data might be useful for enhancing the utility of this technology for detecting glaucomatous abnormality. PMID:16249492

Local sensitivity analysis for inverse problems solved by singular value decomposition

USGS Publications Warehouse

Hill, M.C.; Nolan, B.T.

2010-01-01

Local sensitivity analysis provides computationally frugal ways to evaluate models commonly used for resource management, risk assessment, and so on. This includes diagnosing inverse model convergence problems caused by parameter insensitivity and(or) parameter interdependence (correlation), understanding what aspects of the model and data contribute to measures of uncertainty, and identifying new data likely to reduce model uncertainty. Here, we consider sensitivity statistics relevant to models in which the process model parameters are transformed using singular value decomposition (SVD) to create SVD parameters for model calibration. The statistics considered include the PEST identifiability statistic, and combined use of the process-model parameter statistics composite scaled sensitivities and parameter correlation coefficients (CSS and PCC). The statistics are complimentary in that the identifiability statistic integrates the effects of parameter sensitivity and interdependence, while CSS and PCC provide individual measures of sensitivity and interdependence. PCC quantifies correlations between pairs or larger sets of parameters; when a set of parameters is intercorrelated, the absolute value of PCC is close to 1.00 for all pairs in the set. The number of singular vectors to include in the calculation of the identifiability statistic is somewhat subjective and influences the statistic. To demonstrate the statistics, we use the USDA’s Root Zone Water Quality Model to simulate nitrogen fate and transport in the unsaturated zone of the Merced River Basin, CA. There are 16 log-transformed process-model parameters, including water content at field capacity (WFC) and bulk density (BD) for each of five soil layers. Calibration data consisted of 1,670 observations comprising soil moisture, soil water tension, aqueous nitrate and bromide concentrations, soil nitrate concentration, and organic matter content. All 16 of the SVD parameters could be estimated by regression based on the range of singular values. Identifiability statistic results varied based on the number of SVD parameters included. Identifiability statistics calculated for four SVD parameters indicate the same three most important process-model parameters as CSS/PCC (WFC1, WFC2, and BD2), but the order differed. Additionally, the identifiability statistic showed that BD1 was almost as dominant as WFC1. The CSS/PCC analysis showed that this results from its high correlation with WCF1 (-0.94), and not its individual sensitivity. Such distinctions, combined with analysis of how high correlations and(or) sensitivities result from the constructed model, can produce important insights into, for example, the use of sensitivity analysis to design monitoring networks. In conclusion, the statistics considered identified similar important parameters. They differ because (1) with CSS/PCC can be more awkward because sensitivity and interdependence are considered separately and (2) identifiability requires consideration of how many SVD parameters to include. A continuing challenge is to understand how these computationally efficient methods compare with computationally demanding global methods like Markov-Chain Monte Carlo given common nonlinear processes and the often even more nonlinear models.

Higgs field and cosmological parameters in the fractal quantum system

NASA Astrophysics Data System (ADS)

Abramov, Valeriy

2017-10-01

For the fractal model of the Universe the relations of cosmological parameters and the Higgs field are established. Estimates of the critical density, the expansion and speed-up parameters of the Universe (the Hubble constant and the cosmological redshift); temperature and anisotropy of the cosmic microwave background radiation were performed.

Maximally localized Wannier functions in LaMnO3 within PBE + U, hybrid functionals and partially self-consistent GW: an efficient route to construct ab initio tight-binding parameters for eg perovskites.

PubMed

Franchini, C; Kováčik, R; Marsman, M; Murthy, S Sathyanarayana; He, J; Ederer, C; Kresse, G

2012-06-13

Using the newly developed VASP2WANNIER90 interface we have constructed maximally localized Wannier functions (MLWFs) for the e(g) states of the prototypical Jahn-Teller magnetic perovskite LaMnO(3) at different levels of approximation for the exchange-correlation kernel. These include conventional density functional theory (DFT) with and without the additional on-site Hubbard U term, hybrid DFT and partially self-consistent GW. By suitably mapping the MLWFs onto an effective e(g) tight-binding (TB) Hamiltonian we have computed a complete set of TB parameters which should serve as guidance for more elaborate treatments of correlation effects in effective Hamiltonian-based approaches. The method-dependent changes of the calculated TB parameters and their interplay with the electron-electron (el-el) interaction term are discussed and interpreted. We discuss two alternative model parameterizations: one in which the effects of the el-el interaction are implicitly incorporated in the otherwise 'noninteracting' TB parameters and a second where we include an explicit mean-field el-el interaction term in the TB Hamiltonian. Both models yield a set of tabulated TB parameters which provide the band dispersion in excellent agreement with the underlying ab initio and MLWF bands.

Comparison between the four-field box and field-in-field techniques for conformal radiotherapy of the esophagus using dose-volume histograms and normal tissue complication probabilities.

PubMed

Allaveisi, Farzaneh; Moghadam, Amir Nami

2017-06-01

We evaluated and compared the performance of the field-in-field (FIF) to that of the four-field box (4FB) technique regarding dosimetric and radiobiological parameters for radiotherapy of esophageal carcinoma. Twenty patients with esophageal cancer were selected. For each patient, two treatment plans were created: 4FB and FIF. The parameters compared included the conformity index (CI), homogeneity index (HI), D mean , D max , tumor control probability (TCP), V 20Gy and V 30Gy of the heart and lungs, normal tissue complication probability (NTCP), and monitor units per fraction (MU/fr). A paired t-test analysis did not show any significant differences (p > 0.05) between the two techniques in terms of the CI and TCP. However, the HI significantly improved when the FIF was applied. D max of the PTV, lung, and spinal cord were also significantly better with the FIF. Moreover, the lung V 20Gy as well as the NTCPs of the lung and spinal cord significantly reduced when the FIF was used, and the MU/fr was significantly decreased. The FIF showed evident advantages over 4FB: a more homogeneous dose distribution, lower D max values, and fewer required MUs, while it also retained PTV dose conformality. FIF should be considered as a simple technique to use clinically in cases with esophageal malignancies, especially in clinics with no IMRT.

Numerical Investigation of Plasma Detachment in Magnetic Nozzle Experiments

NASA Technical Reports Server (NTRS)

Sankaran, Kamesh; Polzin, Kurt A.

2008-01-01

At present there exists no generally accepted theoretical model that provides a consistent physical explanation of plasma detachment from an externally-imposed magnetic nozzle. To make progress towards that end, simulation of plasma flow in the magnetic nozzle of an arcjet experiment is performed using a multidimensional numerical simulation tool that includes theoretical models of the various dispersive and dissipative processes present in the plasma. This is an extension of the simulation tool employed in previous work by Sankaran et al. The aim is to compare the computational results with various proposed magnetic nozzle detachment theories to develop an understanding of the physical mechanisms that cause detachment. An applied magnetic field topology is obtained using a magnetostatic field solver (see Fig. I), and this field is superimposed on the time-dependent magnetic field induced in the plasma to provide a self-consistent field description. The applied magnetic field and model geometry match those found in experiments by Kuriki and Okada. This geometry is modeled because there is a substantial amount of experimental data that can be compared to the computational results, allowing for validation of the model. In addition, comparison of the simulation results with the experimentally obtained plasma parameters will provide insight into the mechanisms that lead to plasma detachment, revealing how they scale with different input parameters. Further studies will focus on modeling literature experiments both for the purpose of additional code validation and to extract physical insight regarding the mechanisms driving detachment.

Effect of low frequency magnetic fields on the growth of MNP-treated HT29 colon cancer cells

NASA Astrophysics Data System (ADS)

Spyridopoulou, K.; Makridis, A.; Maniotis, N.; Karypidou, N.; Myrovali, E.; Samaras, T.; Angelakeris, M.; Chlichlia, K.; Kalogirou, O.

2018-04-01

Recent investigations have attempted to understand and exploit the impact of magnetic field-actuated internalized magnetic nanoparticles (MNPs) on the proliferation rate of cancer cells. Due to the complexity of the parameters governing magnetic field-exposure though, individual studies to date have raised contradictory results. In our approach we performed a comparative analysis of key parameters related to the cell exposure of cancer cells to magnetic field-actuated MNPs, and to the magnetic field, in order to better understand the factors affecting cellular responses to magnetic field-stimulated MNPs. We used magnetite MNPs with a hydrodynamic diameter of 100 nm and studied the proliferation rate of MNPs-treated versus untreated HT29 human colon cancer cells, exposed to either static or alternating low frequency magnetic fields with varying intensity (40-200 mT), frequency (0-8 Hz) and field gradient. All three parameters, field intensity, frequency, and field gradient affected the growth rate of cells, with or without internalized MNPs, as compared to control MNPs-untreated and magnetic field-untreated cells. We observed that the growth inhibitory effects induced by static and rotating magnetic fields were enhanced by pre-treating the cells with MNPs, while the growth promoting effects observed in alternating field-treated cells were weakened by MNPs. Compared to static, rotating magnetic fields of the same intensity induced a similar extend of cell growth inhibition, while alternating fields of varying intensity (70 or 100 mT) and frequency (0, 4 or 8 Hz) induced cell proliferation in a frequency-dependent manner. These results, highlighting the diverse effects of mode, intensity, and frequency of the magnetic field on cell growth, indicate that consistent and reproducible results can be achieved by controlling the complexity of the exposure of biological samples to MNPs and external magnetic fields, through monitoring crucial experimental parameters. We demonstrate that further research focusing on the accurate manipulation of the aforementioned magnetic field exposure parameters could lead to the development of successful non-invasive therapeutic anticancer approaches.

A Fast and Scalable Method for A-Optimal Design of Experiments for Infinite-dimensional Bayesian Nonlinear Inverse Problems with Application to Porous Medium Flow

NASA Astrophysics Data System (ADS)

Petra, N.; Alexanderian, A.; Stadler, G.; Ghattas, O.

2015-12-01

We address the problem of optimal experimental design (OED) for Bayesian nonlinear inverse problems governed by partial differential equations (PDEs). The inverse problem seeks to infer a parameter field (e.g., the log permeability field in a porous medium flow model problem) from synthetic observations at a set of sensor locations and from the governing PDEs. The goal of the OED problem is to find an optimal placement of sensors so as to minimize the uncertainty in the inferred parameter field. We formulate the OED objective function by generalizing the classical A-optimal experimental design criterion using the expected value of the trace of the posterior covariance. This expected value is computed through sample averaging over the set of likely experimental data. Due to the infinite-dimensional character of the parameter field, we seek an optimization method that solves the OED problem at a cost (measured in the number of forward PDE solves) that is independent of both the parameter and the sensor dimension. To facilitate this goal, we construct a Gaussian approximation to the posterior at the maximum a posteriori probability (MAP) point, and use the resulting covariance operator to define the OED objective function. We use randomized trace estimation to compute the trace of this covariance operator. The resulting OED problem includes as constraints the system of PDEs characterizing the MAP point, and the PDEs describing the action of the covariance (of the Gaussian approximation to the posterior) to vectors. We control the sparsity of the sensor configurations using sparsifying penalty functions, and solve the resulting penalized bilevel optimization problem via an interior-point quasi-Newton method, where gradient information is computed via adjoints. We elaborate our OED method for the problem of determining the optimal sensor configuration to best infer the log permeability field in a porous medium flow problem. Numerical results show that the number of PDE solves required for the evaluation of the OED objective function and its gradient is essentially independent of both the parameter dimension and the sensor dimension (i.e., the number of candidate sensor locations). The number of quasi-Newton iterations for computing an OED also exhibits the same dimension invariance properties.

Validation of SMAP Radar Vegetation Data Cubes from Agricultural Field Measurements

NASA Astrophysics Data System (ADS)

Tsang, L.; Xu, X.; Liao, T.; Kim, S.; Njoku, E. G.

2012-12-01

The NASA Soil Moisture Active/Passive (SMAP) Mission will be launched in October 2014. The objective of the SMAP mission is to provide global measurements of soil moisture and its freeze/thaw state. These measurements will be used to enhance understanding of processes that link the water, energy and carbon cycles, and to extend the capabilities of weather and climate prediction models. In the active algorithm, the retrieval is performed based on the backscattering data cube, which are characterized by two surface parameters, which are soil moisture and soil surface rms height, and one vegetation parameter, the vegetation water content. We have developed a physical-based forward scattering model to generate the data cube for agricultural fields. To represent the agricultural crops, we include a layer of cylinders and disks on top of the rough surface. The scattering cross section of the vegetation layer and its interaction with the underground soil surface were calculated by the distorted Born approximation, which give explicitly three scattering mechanisms. A) The direct volume scattering B) The double bounce effect as, and C) The double bouncing effects. The direct volume scattering is calculated by using the Body of Revolution code. The double bounce effects, exhibited by the interaction of rough surface with the vegetation layer is considered by modifying the rough surface reflectivity using the coherent wave as computed by Numerical solution of Maxwell equations of 3 Dimensional simulations (NMM3D) of bare soil scattering. The rough surface scattering of the soil was calculated by NMM3D. We have compared the physical scattering models with field measurements. In the field campaign, the measurements were made on soil moisture, rough surface rms heights and vegetation water content as well as geometric parameters of vegetation. The three main crops lands are grassland, cornfield and soybean fields. The corresponding data cubes are validated using SGP99, SMEX02 and SMEX 08 field experiments.

Systematic Improvement of Potential-Derived Atomic Multipoles and Redundancy of the Electrostatic Parameter Space.

PubMed

Jakobsen, Sofie; Jensen, Frank

2014-12-09

We assess the accuracy of force field (FF) electrostatics at several levels of approximation from the standard model using fixed partial charges to conformational specific multipole fits including up to quadrupole moments. Potential-derived point charges and multipoles are calculated using least-squares methods for a total of ∼1000 different conformations of the 20 natural amino acids. Opposed to standard charge fitting schemes the procedure presented in the current work employs fitting points placed on a single isodensity surface, since the electrostatic potential (ESP) on such a surface determines the ESP at all points outside this surface. We find that the effect of multipoles beyond partial atomic charges is of the same magnitude as the effect due to neglecting conformational dependency (i.e., polarizability), suggesting that the two effects should be included at the same level in FF development. The redundancy at both the partial charge and multipole levels of approximation is quantified. We present an algorithm which stepwise reduces or increases the dimensionality of the charge or multipole parameter space and provides an upper limit of the ESP error that can be obtained at a given truncation level. Thereby, we can identify a reduced set of multipole moments corresponding to ∼40% of the total number of multipoles. This subset of parameters provides a significant improvement in the representation of the ESP compared to the simple point charge model and close to the accuracy obtained using the complete multipole parameter space. The selection of the ∼40% most important multipole sites is highly transferable among different conformations, and we find that quadrupoles are of high importance for atoms involved in π-bonding, since the anisotropic electric field generated in such regions requires a large degree of flexibility.

Impact of a primordial magnetic field on cosmic microwave background B modes with weak lensing

NASA Astrophysics Data System (ADS)

Yamazaki, Dai G.

2018-05-01

We discuss the manner in which the primordial magnetic field (PMF) suppresses the cosmic microwave background (CMB) B mode due to the weak-lensing (WL) effect. The WL effect depends on the lensing potential (LP) caused by matter perturbations, the distribution of which at cosmological scales is given by the matter power spectrum (MPS). Therefore, the WL effect on the CMB B mode is affected by the MPS. Considering the effect of the ensemble average energy density of the PMF, which we call "the background PMF," on the MPS, the amplitude of MPS is suppressed in the wave number range of k >0.01 h Mpc-1 . The MPS affects the LP and the WL effect in the CMB B mode; however, the PMF can damp this effect. Previous studies of the CMB B mode with the PMF have only considered the vector and tensor modes. These modes boost the CMB B mode in the multipole range of ℓ>1000 , whereas the background PMF damps the CMB B mode owing to the WL effect in the entire multipole range. The matter density in the Universe controls the WL effect. Therefore, when we constrain the PMF and the matter density parameters from cosmological observational data sets, including the CMB B mode, we expect degeneracy between these parameters. The CMB B mode also provides important information on the background gravitational waves, inflation theory, matter density fluctuations, and the structure formations at the cosmological scale through the cosmological parameter search. If we study these topics and correctly constrain the cosmological parameters from cosmological observations, including the CMB B mode, we need to correctly consider the background PMF.

CosmoSIS: A system for MC parameter estimation

DOE PAGES

Bridle, S.; Dodelson, S.; Jennings, E.; ...

2015-12-23

CosmoSIS is a modular system for cosmological parameter estimation, based on Markov Chain Monte Carlo and related techniques. It provides a series of samplers, which drive the exploration of the parameter space, and a series of modules, which calculate the likelihood of the observed data for a given physical model, determined by the location of a sample in the parameter space. While CosmoSIS ships with a set of modules that calculate quantities of interest to cosmologists, there is nothing about the framework itself, nor in the Markov Chain Monte Carlo technique, that is specific to cosmology. Thus CosmoSIS could bemore » used for parameter estimation problems in other fields, including HEP. This paper describes the features of CosmoSIS and show an example of its use outside of cosmology. Furthermore, it also discusses how collaborative development strategies differ between two different communities: that of HEP physicists, accustomed to working in large collaborations, and that of cosmologists, who have traditionally not worked in large groups.« less

Considering Apical Scotomas, Confusion, and Diplopia When Prescribing Prisms for Homonymous Hemianopia

PubMed Central

Apfelbaum, Henry L.; Ross, Nicole C.; Bowers, Alex R.; Peli, Eli

2013-01-01

Purpose: While prisms are commonly prescribed for homonymous hemianopia to extend or expand the visual field, they cause potentially troubling visual side effects, including nonveridical location of perceived images, diplopia, and visual confusion. In addition, the field behind a prism at its apex is lost to an apical scotoma equal in magnitude to the amount of prism shift. The perceptual consequences of apical scotomas and the other effects of various designs were examined to consider parameters and designs that can mitigate the impact of these effects. Methods: Various configurations of sector and peripheral prisms were analyzed, in various directions of gaze, and their visual effects were illustrated using simulated perimetry. A novel “percept” diagram was developed that yielded insights into the patient's view through the prisms. The predictions were verified perimetrically with patients. Results: The diagrams distinguish between potentially beneficial field expansion via visual confusion and the pericentrally disturbing and useless effect of diplopia, and their relationship to prism power and gaze direction. They also illustrate the nonexpanding substitution of field segments of some popular prism designs. Conclusions: Yoked sector prisms have no effect at primary gaze or when gaze is directed toward the seeing hemifield, and they introduce pericentral field loss when gaze is shifted into them. When fitted unilaterally, sector prisms also have an effect only when the gaze is directed into the prism and may cause a pericentral scotoma and/or central diplopia. Peripheral prisms are effective at essentially all gaze angles. Since gaze is not directed into them, they avoid problematic pericentral effects. We derive useful recommendations for prism power and position parameters, including novel ways of fitting prisms asymmetrically. Translational Relevance: Clinicians will find these novel diagrams, diagramming techniques, and analyses valuable when prescribing prismatic aids for hemianopia and when designing new prism devices for patients with various types of field loss. PMID:24049719

Comparison of Two Methods Used to Model Shape Parameters of Pareto Distributions

USGS Publications Warehouse

Liu, C.; Charpentier, R.R.; Su, J.

2011-01-01

Two methods are compared for estimating the shape parameters of Pareto field-size (or pool-size) distributions for petroleum resource assessment. Both methods assume mature exploration in which most of the larger fields have been discovered. Both methods use the sizes of larger discovered fields to estimate the numbers and sizes of smaller fields: (1) the tail-truncated method uses a plot of field size versus size rank, and (2) the log-geometric method uses data binned in field-size classes and the ratios of adjacent bin counts. Simulation experiments were conducted using discovered oil and gas pool-size distributions from four petroleum systems in Alberta, Canada and using Pareto distributions generated by Monte Carlo simulation. The estimates of the shape parameters of the Pareto distributions, calculated by both the tail-truncated and log-geometric methods, generally stabilize where discovered pool numbers are greater than 100. However, with fewer than 100 discoveries, these estimates can vary greatly with each new discovery. The estimated shape parameters of the tail-truncated method are more stable and larger than those of the log-geometric method where the number of discovered pools is more than 100. Both methods, however, tend to underestimate the shape parameter. Monte Carlo simulation was also used to create sequences of discovered pool sizes by sampling from a Pareto distribution with a discovery process model using a defined exploration efficiency (in order to show how biased the sampling was in favor of larger fields being discovered first). A higher (more biased) exploration efficiency gives better estimates of the Pareto shape parameters. ?? 2011 International Association for Mathematical Geosciences.

Hydrology of Poorly Drained Coastal Watersheds in Eastern North Carolina

Treesearch

Devendra M. Amatya; George M. Chescheir; R. Wayne Skaggs; Glenn P. Fernandez

2002-01-01

A 10,000 ha lower coastal plain land near Plymouth in eastern North Carolina has been intensively monitored since 1996 to measure hydro-meteorological parameters including outflows and quality of water drained from fields and subwatersheds with varying land management practices. This study summarized the data for a six-year period (1996-2001) for a 2950 ha forested, a...

BOREAS Level-0 NS001 TMS Imagery: Digital Counts in BIL Format

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Newcomer, Jeffrey A.; Dominguez, Roseanne

2000-01-01

For BOREAS, the NS001 TMS imagery, along with the other remotely sensed images, was collected in order to provide spatially extensive information over the primary study areas. This information includes detailed land cover and biophysical parameter maps such as fPAR and LAI. Data collections occurred over the study areas during the 1994 field campaigns.

Modeling and risk assessment of a 30-Year-old subsurface radioactive-liquid drain field

NASA Astrophysics Data System (ADS)

Dawson, Lon A.; Pohl, Phillip I.

1997-11-01

The contamination from a 30-year-old radioactive liquid drain field was assessed for movement in the subsurface and potential risks to humans. This assessment included determining field concentrations of cesium 137 (137Cs) and other inorganic contaminants and modeling of the flow and transport of the liquid waste that was sent to the drain field. The field investigation detected no contamination deeper than 15 feet (4.6 m) from the bottom of the drain field. Prediction of the water content of the vadose zone showed no saturated conditions for times greater than 10 years after the known infiltration. Sensitivity analysis of the modeling parameters showed the equilibrium sorption coefficient to be the most important factor in predicting the contaminant plumes. Calibration of modeling results with field data gave a 137Cs sorption coefficient that is within the range of values found in the literature. The risk assessment for the site showed that the contamination poses no significant risk to human health.

Quantitative theory of driven nonlinear brain dynamics.

PubMed

Roberts, J A; Robinson, P A

2012-09-01

Strong periodic stimuli such as bright flashing lights evoke nonlinear responses in the brain and interact nonlinearly with ongoing cortical activity, but the underlying mechanisms for these phenomena are poorly understood at present. The dominant features of these experimentally observed dynamics are reproduced by the dynamics of a quantitative neural field model subject to periodic drive. Model power spectra over a range of drive frequencies show agreement with multiple features of experimental measurements, exhibiting nonlinear effects including entrainment over a range of frequencies around the natural alpha frequency f(α), subharmonic entrainment near 2f(α), and harmonic generation. Further analysis of the driven dynamics as a function of the drive parameters reveals rich nonlinear dynamics that is predicted to be observable in future experiments at high drive amplitude, including period doubling, bistable phase-locking, hysteresis, wave mixing, and chaos indicated by positive Lyapunov exponents. Moreover, photosensitive seizures are predicted for physiologically realistic model parameters yielding bistability between healthy and seizure dynamics. These results demonstrate the applicability of neural field models to the new regime of periodically driven nonlinear dynamics, enabling interpretation of experimental data in terms of specific generating mechanisms and providing new tests of the theory. Copyright © 2012 Elsevier Inc. All rights reserved.

Body MR Imaging: Artifacts, k-Space, and Solutions

PubMed Central

Seethamraju, Ravi T.; Patel, Pritesh; Hahn, Peter F.; Kirsch, John E.; Guimaraes, Alexander R.

2015-01-01

Body magnetic resonance (MR) imaging is challenging because of the complex interaction of multiple factors, including motion arising from respiration and bowel peristalsis, susceptibility effects secondary to bowel gas, and the need to cover a large field of view. The combination of these factors makes body MR imaging more prone to artifacts, compared with imaging of other anatomic regions. Understanding the basic MR physics underlying artifacts is crucial to recognizing the trade-offs involved in mitigating artifacts and improving image quality. Artifacts can be classified into three main groups: (a) artifacts related to magnetic field imperfections, including the static magnetic field, the radiofrequency (RF) field, and gradient fields; (b) artifacts related to motion; and (c) artifacts arising from methods used to sample the MR signal. Static magnetic field homogeneity is essential for many MR techniques, such as fat saturation and balanced steady-state free precession. Susceptibility effects become more pronounced at higher field strengths and can be ameliorated by using spin-echo sequences when possible, increasing the receiver bandwidth, and aligning the phase-encoding gradient with the strongest susceptibility gradients, among other strategies. Nonuniformities in the RF transmit field, including dielectric effects, can be minimized by applying dielectric pads or imaging at lower field strength. Motion artifacts can be overcome through respiratory synchronization, alternative k-space sampling schemes, and parallel imaging. Aliasing and truncation artifacts derive from limitations in digital sampling of the MR signal and can be rectified by adjusting the sampling parameters. Understanding the causes of artifacts and their possible solutions will enable practitioners of body MR imaging to meet the challenges of novel pulse sequence design, parallel imaging, and increasing field strength. ©RSNA, 2015 PMID:26207581

Morphometric Parameters of Pyramidal Cells in CA1-CA4 Fields in the Hippocampus of Arctic Fox (Vulpes lagopus).

PubMed

Łuszczewska-Sierakowska, Iwona; Wawrzyniak-Gacek, Agata; Guz, Tomasz; Tatara, Marcin R; Charuta, Anna

2015-01-01

The aim of the study was a quantitative examination of neurons of hippocampal subfields (CA1-CA4) in mature male Arctic fox (Vulpes lagopus; syn. Alopex lagopus). The preparations were dyed using cresyl violet. Histological preparations were used to morphometricaly analyze the neurons of hippocampus. This analysis included the following parameters: average size of cells in μm, periphery of cells in μm, average cell area in μm2, percentage of cells in area and size of the largest and smallest cells in μm in CA1-CA4 fields. Morphometric observations show that the cells involved in hippocampal formation in polar fox in all layers CA1 -CA4 differ in size, shape, cell area and nucleus area. The size of the cell area in CA3 is the largest and fluctuates around 249.4 μm2, whereas in CA2 the cell area is 184.1 μm2. The cells of the CA2 field are densely arranged, pyramidal and contain a small amount of cytoplasm; their size fluctuates. Cells of CA2 and CA4 had the largest diameter of about 23.6 μm, whereas cells of the CA3 field had the smallest diameter of about 8.3 μm.

Derivation of a hydrodynamic theory for mesoscale dynamics in microswimmer suspensions

NASA Astrophysics Data System (ADS)

Reinken, Henning; Klapp, Sabine H. L.; Bär, Markus; Heidenreich, Sebastian

2018-02-01

In this paper, we systematically derive a fourth-order continuum theory capable of reproducing mesoscale turbulence in a three-dimensional suspension of microswimmers. We start from overdamped Langevin equations for a generic microscopic model (pushers or pullers), which include hydrodynamic interactions on both small length scales (polar alignment of neighboring swimmers) and large length scales, where the solvent flow interacts with the order parameter field. The flow field is determined via the Stokes equation supplemented by an ansatz for the stress tensor. In addition to hydrodynamic interactions, we allow for nematic pair interactions stemming from excluded-volume effects. The results here substantially extend and generalize earlier findings [S. Heidenreich et al., Phys. Rev. E 94, 020601 (2016), 10.1103/PhysRevE.94.020601], in which we derived a two-dimensional hydrodynamic theory. From the corresponding mean-field Fokker-Planck equation combined with a self-consistent closure scheme, we derive nonlinear field equations for the polar and the nematic order parameter, involving gradient terms of up to fourth order. We find that the effective microswimmer dynamics depends on the coupling between solvent flow and orientational order. For very weak coupling corresponding to a high viscosity of the suspension, the dynamics of mesoscale turbulence can be described by a simplified model containing only an effective microswimmer velocity.

Specific heats and thermodynamic critical fields in Zn-doped YBa2Cu3O(7-x) according to an induced-pairing model

NASA Technical Reports Server (NTRS)

Eagles, D. M.

1993-01-01

Electronic specific heats and thermodynamic critical fields are calculated in a mean-field version of an induced-pairing model for superconductivity, and compared with results of Loram et al. (1990) on YBa2(Cu(1-y)Zn(y))3O(7-x). This model involves induction of pairing of holes in a wideband by strongly bound electronlike pairs. It is assumed that the planar hole concentration for no Zn addition is close to, but slightly higher than, that for the maximum Tc, and that it increases by 0.015 per planar Cu ion for each increase of y by 0.01. Parameters of the model are taken to be the same as in a previous publication in which energy gaps were discussed, except that an effective hybridization parameter is adjusted for each Zn concentration to give agreement with the observed Tc. Results are presented for y = 0.0, 0.01, and 0.03. The agreement with experiment is good for thermodynamic critical fields, and is fair for specific heats. For specimens with larger y, with relatively low T(c)s, it is argued that the model should be supplemented to include effects of a BCS-type interaction amongst the wideband carriers.

Skin Rejuvenation with Non-Invasive Pulsed Electric Fields

NASA Astrophysics Data System (ADS)

Golberg, Alexander; Khan, Saiqa; Belov, Vasily; Quinn, Kyle P.; Albadawi, Hassan; Felix Broelsch, G.; Watkins, Michael T.; Georgakoudi, Irene; Papisov, Mikhail; Mihm, Martin C., Jr.; Austen, William G., Jr.; Yarmush, Martin L.

2015-05-01

Degenerative skin diseases affect one third of individuals over the age of sixty. Current therapies use various physical and chemical methods to rejuvenate skin; but since the therapies affect many tissue components including cells and extracellular matrix, they may also induce significant side effects, such as scarring. Here we report on a new, non-invasive, non-thermal technique to rejuvenate skin with pulsed electric fields. The fields destroy cells while simultaneously completely preserving the extracellular matrix architecture and releasing multiple growth factors locally that induce new cells and tissue growth. We have identified the specific pulsed electric field parameters in rats that lead to prominent proliferation of the epidermis, formation of microvasculature, and secretion of new collagen at treated areas without scarring. Our results suggest that pulsed electric fields can improve skin function and thus can potentially serve as a novel non-invasive skin therapy for multiple degenerative skin diseases.

Toward the Experimental Characterization of an Unmanned Air System Flow Field

NASA Astrophysics Data System (ADS)

Velarde, John-Michael; Connors, Jacob; Glauser, Mark

2017-11-01

The velocity flow field around a small unmanned air system (sUAS) is investigated in a series of experiments at Syracuse University. Experiments are conducted in the 2'x2' sub-sonic wind tunnel at Syracuse University and the Indoor Flow Lab. The goal of these experiments is to gain a better understanding of the rich, turbulent flow field that a sUAS creates. Comparison to large, multi-rotor manned vehicles is done to gain a better understanding of the flow physics that could be occurring with the sUAS. Regions of investigation include the downwash, above the vehicle, and far downstream. Characterization of the flow is performed using hotwire anemometry. Investigation of several locations around the sUAS show that dominant frequencies exist within the flow field. Analysis of the flow field using power spectral density will be presented as well as looking at which parameters have an effect on these dominant frequencies.

Aircraft measurements of electrified clouds at Kennedy Space Center. Part 2: Case study: 4 November 1988 (88309)

NASA Technical Reports Server (NTRS)

Jones, J. J.; Winn, W. P.; Hunyady, S. J.; Moore, C. B.; Bullock, J. W.

1990-01-01

During the fall of 1988, a Schweizer airplane equipped to measure electric field and other meteorological parameters flew over Kennedy Space Center (KSC) in a program to study clouds defined in the existing launch restriction criteria. A case study is presented of a single flight over KSC on November 4, 1988. This flight was chosen for two reasons: (1) the clouds were weakly electrified, and no lightning was reported during the flight; and (2) electric field mills in the surface array at KSC indicated field strengths greater than 3 kV/m, yet the aircraft flying directly over them at an altitude of 3.4 km above sea level measured field strengths of less than 1.6 kV/m. A weather summary, sounding description, record of cloud types, and an account of electric field measurements are included.

Statistical approach to Higgs boson couplings in the standard model effective field theory

NASA Astrophysics Data System (ADS)

Murphy, Christopher W.

2018-01-01

We perform a parameter fit in the standard model effective field theory (SMEFT) with an emphasis on using regularized linear regression to tackle the issue of the large number of parameters in the SMEFT. In regularized linear regression, a positive definite function of the parameters of interest is added to the usual cost function. A cross-validation is performed to try to determine the optimal value of the regularization parameter to use, but it selects the standard model (SM) as the best model to explain the measurements. Nevertheless as proof of principle of this technique we apply it to fitting Higgs boson signal strengths in SMEFT, including the latest Run-2 results. Results are presented in terms of the eigensystem of the covariance matrix of the least squares estimators as it has a degree model-independent to it. We find several results in this initial work: the SMEFT predicts the total width of the Higgs boson to be consistent with the SM prediction; the ATLAS and CMS experiments at the LHC are currently sensitive to non-resonant double Higgs boson production. Constraints are derived on the viable parameter space for electroweak baryogenesis in the SMEFT, reinforcing the notion that a first order phase transition requires fairly low-scale beyond the SM physics. Finally, we study which future experimental measurements would give the most improvement on the global constraints on the Higgs sector of the SMEFT.

Rapid parameterization of small molecules using the Force Field Toolkit.

PubMed

Mayne, Christopher G; Saam, Jan; Schulten, Klaus; Tajkhorshid, Emad; Gumbart, James C

2013-12-15

The inability to rapidly generate accurate and robust parameters for novel chemical matter continues to severely limit the application of molecular dynamics simulations to many biological systems of interest, especially in fields such as drug discovery. Although the release of generalized versions of common classical force fields, for example, General Amber Force Field and CHARMM General Force Field, have posited guidelines for parameterization of small molecules, many technical challenges remain that have hampered their wide-scale extension. The Force Field Toolkit (ffTK), described herein, minimizes common barriers to ligand parameterization through algorithm and method development, automation of tedious and error-prone tasks, and graphical user interface design. Distributed as a VMD plugin, ffTK facilitates the traversal of a clear and organized workflow resulting in a complete set of CHARMM-compatible parameters. A variety of tools are provided to generate quantum mechanical target data, setup multidimensional optimization routines, and analyze parameter performance. Parameters developed for a small test set of molecules using ffTK were comparable to existing CGenFF parameters in their ability to reproduce experimentally measured values for pure-solvent properties (<15% error from experiment) and free energy of solvation (±0.5 kcal/mol from experiment). Copyright © 2013 Wiley Periodicals, Inc.

Evolution of Kelvin-Helmholtz instability at Venus in the presence of the parallel magnetic field

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

Lu, H. Y.; Key Laboratory of Planetary Sciences, Chinese Academy of Sciences, Nanjing 210008; Cao, J. B.

2015-06-15

Two-dimensional MHD simulations were performed to study the evolution of the Kelvin-Helmholtz (KH) instability at the Venusian ionopause in response to the strong flow shear in presence of the in-plane magnetic field parallel to the flow direction. The physical behavior of the KH instability as well as the triggering and occurrence conditions for highly rolled-up vortices are characterized through several physical parameters, including Alfvén Mach number on the upper side of the layer, the density ratio, and the ratio of parallel magnetic fields between two sides of the layer. Using these parameters, the simulations show that both the high densitymore » ratio and the parallel magnetic field component across the boundary layer play a role of stabilizing the instability. In the high density ratio case, the amount of total magnetic energy in the final quasi-steady status is much more than that in the initial status, which is clearly different from the case with low density ratio. We particularly investigate the nonlinear development of the case that has a high density ratio and uniform magnetic field. Before the instability saturation, a single magnetic island is formed and evolves into two quasi-steady islands in the non-linear phase. A quasi-steady pattern eventually forms and is embedded within a uniform magnetic field and a broadened boundary layer. The estimation of loss rates of ions from Venus indicates that the stabilizing effect of the parallel magnetic field component on the KH instability becomes strong in the case of high density ratio.« less

Spin and orbital exchange interactions from Dynamical Mean Field Theory

NASA Astrophysics Data System (ADS)

Secchi, A.; Lichtenstein, A. I.; Katsnelson, M. I.

2016-02-01

We derive a set of equations expressing the parameters of the magnetic interactions characterizing a strongly correlated electronic system in terms of single-electron Green's functions and self-energies. This allows to establish a mapping between the initial electronic system and a spin model including up to quadratic interactions between the effective spins, with a general interaction (exchange) tensor that accounts for anisotropic exchange, Dzyaloshinskii-Moriya interaction and other symmetric terms such as dipole-dipole interaction. We present the formulas in a format that can be used for computations via Dynamical Mean Field Theory algorithms.

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

Tien, C; Brewer, M; Studenski, M

Purpose: Dynamic-jaw tracking maximizes the area blocked by both jaw and MLC in RapidArc. We developed a method to quantify jaw tracking. Methods: An Eclipse Scripting API (ESAPI) was used to export beam parameters for each arc’s control points. The specific beam parameters extracted were: gantry angle, control point number, meterset, x-jaw positions, y-jaw positions, MLC bank-number, MLC leaf-number, and MLC leaf-position. Each arc contained 178 control points with 120 MLC positions. MATLAB routines were written to process these parameters in order to calculate both the beam aperture (unblocked) size for each control point. An average aperture size was weightedmore » by meterset. Jaw factor was defined as the ratio between dynamic-jaw to static-jaw aperture size. Jaw factor was determined for forty retrospectively replanned patients treated with static-jaw delivery sites including lung, brain, prostate, H&N, rectum, and bladder. Results: Most patients had multiple arcs and reduced-field boosts, resulting in 151 fields. Of these, the lowest (0.4722) and highest (0.9622) jaw factor was observed in prostate and rectal cases, respectively. The median jaw factor was 0.7917 meaning there is the potential unincreased blocking by 20%. Clinically, the dynamic-jaw tracking represents an area surrounding the target which would receive MLC-only leakage transmission of 1.68% versus 0.1% with jaws. Jaw-tracking was more pronounced at areas farther from the target. In prostate patients, the rectum and bladder had 5.5% and 6.3% lower mean dose, respectively; the structures closer to the prostate such as the rectum and bladder both had 1.4% lower mean dose. Conclusion: A custom ESAPI script was coupled with a MATLAB routine in order to extract beam parameters from static-jaw plans and their replanned dynamic-jaw deliveries. The effects were quantified using jaw factor which is the ratio between the meterset weighted aperture size for dynamic-jaw fields versus static-jaw fields.« less

Assessment of municipal solid waste settlement models based on field-scale data analysis.

PubMed

Bareither, Christopher A; Kwak, Seungbok

2015-08-01

An evaluation of municipal solid waste (MSW) settlement model performance and applicability was conducted based on analysis of two field-scale datasets: (1) Yolo and (2) Deer Track Bioreactor Experiment (DTBE). Twelve MSW settlement models were considered that included a range of compression behavior (i.e., immediate compression, mechanical creep, and biocompression) and range of total (2-22) and optimized (2-7) model parameters. A multi-layer immediate settlement analysis developed for Yolo provides a framework to estimate initial waste thickness and waste thickness at the end-of-immediate compression. Model application to the Yolo test cells (conventional and bioreactor landfills) via least squares optimization yielded high coefficient of determinations for all settlement models (R(2)>0.83). However, empirical models (i.e., power creep, logarithmic, and hyperbolic models) are not recommended for use in MSW settlement modeling due to potential non-representative long-term MSW behavior, limited physical significance of model parameters, and required settlement data for model parameterization. Settlement models that combine mechanical creep and biocompression into a single mathematical function constrain time-dependent settlement to a single process with finite magnitude, which limits model applicability. Overall, all models evaluated that couple multiple compression processes (immediate, creep, and biocompression) provided accurate representations of both Yolo and DTBE datasets. A model presented in Gourc et al. (2010) included the lowest number of total and optimized model parameters and yielded high statistical performance for all model applications (R(2)⩾0.97). Copyright © 2015 Elsevier Ltd. All rights reserved.

Forecasts of non-Gaussian parameter spaces using Box-Cox transformations

NASA Astrophysics Data System (ADS)

Joachimi, B.; Taylor, A. N.

2011-09-01

Forecasts of statistical constraints on model parameters using the Fisher matrix abound in many fields of astrophysics. The Fisher matrix formalism involves the assumption of Gaussianity in parameter space and hence fails to predict complex features of posterior probability distributions. Combining the standard Fisher matrix with Box-Cox transformations, we propose a novel method that accurately predicts arbitrary posterior shapes. The Box-Cox transformations are applied to parameter space to render it approximately multivariate Gaussian, performing the Fisher matrix calculation on the transformed parameters. We demonstrate that, after the Box-Cox parameters have been determined from an initial likelihood evaluation, the method correctly predicts changes in the posterior when varying various parameters of the experimental setup and the data analysis, with marginally higher computational cost than a standard Fisher matrix calculation. We apply the Box-Cox-Fisher formalism to forecast cosmological parameter constraints by future weak gravitational lensing surveys. The characteristic non-linear degeneracy between matter density parameter and normalization of matter density fluctuations is reproduced for several cases, and the capabilities of breaking this degeneracy by weak-lensing three-point statistics is investigated. Possible applications of Box-Cox transformations of posterior distributions are discussed, including the prospects for performing statistical data analysis steps in the transformed Gaussianized parameter space.

Coupling heat and chemical tracer experiments for estimating heat transfer parameters in shallow alluvial aquifers.

PubMed

Wildemeersch, S; Jamin, P; Orban, P; Hermans, T; Klepikova, M; Nguyen, F; Brouyère, S; Dassargues, A

2014-11-15

Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54MJ/m(3)/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for estimating the entire set of heat transfer parameters and their spatial distribution by inverse modeling. Copyright © 2014 Elsevier B.V. All rights reserved.

Theoretical and experimental studies of the molecular orbital bonding coefficients for Cu{sup 2+} ion in cesium hydrogen oxalate single crystals

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

Kalfaoğlu, Emel, E-mail: emelkalfaoglu@mynet.com; Karabulut, Bünyamin

2016-03-25

Electron paramagnetic resonance (EPR) and optical absorption spectra of Cu{sup 2+} ions in cesium hydrogen oxalate single crystals have been investigated at room temperature. The spin-Hamiltonian parameters (g and A), have been determined. Crystalline field around the Cu{sup 2+} ion is almost axially symmetric. The results show a single paramagnetic site which confirms the triclinic crystal symmetry. Molecular orbital bonding coefficients are studied from the EPR and optical data. Theoretical octahedral field parameter and the tetragonal field parameters have been evaluated from the superposition model. Using these parameters, various bonding parameters are analyzed and the nature of bonding in themore » complex is discussed. The theoretical results are supported by experimental results.« less

Fabrication and Performance of Large Format Transition Edge Sensor Microcalorimeter Arrays

NASA Technical Reports Server (NTRS)

Chervenak, James A.; Adams, James S.; Bandler, Simon R.; Busch, Sara E.; Eckart, M. E.; Ewin, A. E.; Finkbeiner, F. M.; Kilbourne, C. A.; Kelley, R. L.; Porst, Jan-Patrick;

Monodomain dynamics for rigid rod and platelet suspensions in strongly coupled coplanar linear flow and magnetic fields. II. Kinetic theory

NASA Astrophysics Data System (ADS)

Forest, M. Gregory; Sircar, Sarthok; Wang, Qi; Zhou, Ruhai

2006-10-01

We establish reciprocity relations of the Doi-Hess kinetic theory for rigid rod macromolecular suspensions governed by the strong coupling among an excluded volume potential, linear flow, and a magnetic field. The relation provides a reduction of the flow and field driven Smoluchowski equation: from five parameters for coplanar linear flows and magnetic field, to two field parameters. The reduced model distinguishes flows with a rotational component, which map to simple shear (with rate parameter) subject to a transverse magnetic field (with strength parameter), and irrotational flows, for which the reduced model consists of a triaxial extensional flow (with two extensional rate parameters). We solve the Smoluchowski equation of the reduced model to explore: (i) the effect of introducing a coplanar magnetic field on each sheared monodomain attractor of the Doi-Hess kinetic theory and (ii) the coupling of coplanar extensional flow and magnetic fields. For (i), we show each sheared attractor (steady and unsteady, with peak axis in and out of the shearing plane, periodic and chaotic orbits) undergoes its own transition sequence versus magnetic field strength. Nonetheless, robust predictions emerge: out-of-plane degrees of freedom are arrested with increasing field strength, and a unique flow-aligning or tumbling/wagging limit cycle emerges above a threshold magnetic field strength or modified geometry parameter value. For (ii), irrotational flows coupled with a coplanar magnetic field yield only steady states. We characterize all (generically biaxial) equilibria in terms of an explicit Boltzmann distribution, providing a natural generalization of analytical results on pure nematic equilibria [P. Constantin, I. Kevrekidis, and E. S. Titi, Arch. Rat. Mech. Anal. 174, 365 (2004); P. Constantin, I. Kevrekidis, and E. S. Titi, Discrete and Continuous Dynamical Systems 11, 101 (2004); P. Constantin and J. Vukadinovic, Nonlinearity 18, 441 (2005); H. Liu, H. Zhang, and P. Zhang, Comm. Math. Sci. 3, 201 (2005); C. Luo, H. Zhang, and P. Zhang, Nonlinearity 18, 379 (2005); I. Fatkullin and V. Slastikov, Nonlinearity 18, 2565 (2005); H. Zhou, H. Wang, Q. Wang, and M. G. Forest, Nonlinearity 18, 2815 (2005)] and extensional flow-induced equilibria [Q. Wang, S. Sircar, and H. Zhou, Comm. Math. Sci. 4, 605 (2005)]. We predict large parameter regions of bi-stable equilibria; the lowest energy state always has principal axis aligned in the flow plane, while another minimum energy state often exists, with primary alignment transverse to the coplanar field.

LETTER TO THE EDITOR: On the relations between the zero-field splitting parameters in the extended Stevens operator notation and the conventional ones used in EMR for orthorhombic and lower symmetry

NASA Astrophysics Data System (ADS)

Rudowicz, C.

2000-06-01

Electron magnetic resonance (EMR) studies of paramagnetic species with the spin S ≥ 1 at orthorhombic symmetry sites require an axial zero-field splitting (ZFS) parameter and a rhombic one of the second order (k = 2), whereas at triclinic sites all five ZFS (k = 2) parameters are expressed in the crystallographic axis system. For the spin S ≥ 2 also the higher-order ZFS terms must be considered. In the principal axis system, instead of the five ZFS (k = 2) parameters, the two principal ZFS values can be used, as for orthorhombic symmetry; however, then the orientation of the principal axes with respect to the crystallographic axis system must be provided. Recently three serious cases of incorrect relations between the extended Stevens ZFS parameters and the conventional ones have been identified in the literature. The first case concerns a controversy concerning the second-order rhombic ZFS parameters and was found to have lead to misinterpretation, in a review article, of several values of either E or b22 published earlier. The second case concerns the set of five relations between the extended Stevens ZFS parameters bkq and the conventional ones Dij for triclinic symmetry, four of which turn out to be incorrect. The third case concerns the omission of the scaling factors fk for the extended Stevens ZFS parameters bkq. In all cases the incorrect relations in question have been published in spite of the earlier existence of the correct relations in the literature. The incorrect relations are likely to lead to further misinterpretation of the published values of the ZFS parameters for orthorhombic and lower symmetry. The purpose of this paper is to make the spectroscopists working in the area of EMR (including EPR and ESR) and related spectroscopies aware of the problem and to reduce proliferation of the incorrect relations.

Statistical analysis of electric field parameters for negative lightning in Malaysia

NASA Astrophysics Data System (ADS)

Wooi, Chin-Leong; Abdul-Malek, Zulkurnain; Ahmad, Noor-Azlinda; El Gayar, Ali I.

2016-08-01

This paper presents a comparative study on the electric field and its derivative parameters of negative lightning in Malaysia and other regions. This study is the first in Malaysia where the parameters of negative electric field and its derivative are thoroughly analyzed. 104 negative lightning flashes containing 277 negative return strokes occurring within 10-100 km from the measuring station and recorded during monsoon period in the state of Johor, Malaysia had been analyzed. It was found that 73% of the recorded flashes are multiple strokes with an average multiplicity of 2.6 strokes per flash. For first return strokes, the arithmetic mean (AM) of initial peak electric field and the AM of initial peak electric field derivative are 21.8 V/m and 11.3 V/m/μs, respectively. The initial peaks of electric field and its derivative for first return strokes are larger than those for the subsequent return strokes. Comparison of overall results with those obtained earlier in Sri Lanka, Germany, Sweden, Japan, Florida indicates that several electric field and its derivative parameters are affected by propagation media and geographical region. Similarity of results with other countries having the same climatic condition is also observed.

Inverse modeling of geochemical and mechanical compaction in sedimentary basins

NASA Astrophysics Data System (ADS)

Colombo, Ivo; Porta, Giovanni Michele; Guadagnini, Alberto

2015-04-01

We study key phenomena driving the feedback between sediment compaction processes and fluid flow in stratified sedimentary basins formed through lithification of sand and clay sediments after deposition. Processes we consider are mechanic compaction of the host rock and the geochemical compaction due to quartz cementation in sandstones. Key objectives of our study include (i) the quantification of the influence of the uncertainty of the model input parameters on the model output and (ii) the application of an inverse modeling technique to field scale data. Proper accounting of the feedback between sediment compaction processes and fluid flow in the subsurface is key to quantify a wide set of environmentally and industrially relevant phenomena. These include, e.g., compaction-driven brine and/or saltwater flow at deep locations and its influence on (a) tracer concentrations observed in shallow sediments, (b) build up of fluid overpressure, (c) hydrocarbon generation and migration, (d) subsidence due to groundwater and/or hydrocarbons withdrawal, and (e) formation of ore deposits. Main processes driving the diagenesis of sediments after deposition are mechanical compaction due to overburden and precipitation/dissolution associated with reactive transport. The natural evolution of sedimentary basins is characterized by geological time scales, thus preventing direct and exhaustive measurement of the system dynamical changes. The outputs of compaction models are plagued by uncertainty because of the incomplete knowledge of the models and parameters governing diagenesis. Development of robust methodologies for inverse modeling and parameter estimation under uncertainty is therefore crucial to the quantification of natural compaction phenomena. We employ a numerical methodology based on three building blocks: (i) space-time discretization of the compaction process; (ii) representation of target output variables through a Polynomial Chaos Expansion (PCE); and (iii) model inversion (parameter estimation) within a maximum likelihood framework. In this context, the PCE-based surrogate model enables one to (i) minimize the computational cost associated with the (forward and inverse) modeling procedures leading to uncertainty quantification and parameter estimation, and (ii) compute the full set of Sobol indices quantifying the contribution of each uncertain parameter to the variability of target state variables. Results are illustrated through the simulation of one-dimensional test cases. The analyses focuses on the calibration of model parameters through literature field cases. The quality of parameter estimates is then analyzed as a function of number, type and location of data.

Evaluation of Two Soil Water Redistribution Models (Finite Difference and Hourly Cascade Approach) Through The Comparison of Continuous field Sensor-Based Measurements

NASA Astrophysics Data System (ADS)

Ferreyra, R.; Stockle, C. O.; Huggins, D. R.

2014-12-01

Soil water storage and dynamics are of critical importance for a variety of processes in terrestrial ecosystems, including agriculture. Many of those systems are under significant pressure in terms of water availability and use. Therefore, assessing alternative scenarios through hydrological models is an increasingly valuable exercise. Soil water holding capacity is defined by the concepts of soil field capacity and plant available water, which are directly related to soil physical properties. Both concepts define the energy status of water in the root system and closely interact with plant physiological processes. Furthermore, these concepts play a key role in the environmental transport of nutrients and pollutants. Soil physical parameters (e.g. saturated hydraulic conductivity, total porosity and water release curve) are required as input for field-scale soil water redistribution models. These parameters are normally not easy to measure or monitor, and estimation through pedotransfer functions is often inadequate. Our objectives are to improve field-scale hydrological modeling by: (1) assessing new undisturbed methodologies for determining important soil physical parameters necessary for model inputs; and (2) evaluating model outputs, making a detailed specification of soil parameters and the particular boundary condition that are driving water movement under two contrasting environments. Soil physical properties (saturated hydraulic conductivity and determination of water release curves) were quantified using undisturbed laboratory methodologies for two different soil textural classes (silt loam and sandy loam) and used to evaluate two soil water redistribution models (finite difference solution and hourly cascade approach). We will report on model corroboration results performed using in situ, continuous, field measurements with soil water content capacitance probes and digital tensiometers. Here, natural drainage and water redistribution were monitored following a controlled water application where the study areas were isolated from other water inputs and outputs. We will also report on the assessment of two soil water sensors (Decagon Devices 5TM capacitance probe and UMS T4 tensiometers) for the two soil textural classes in terms of consistency and replicability.

On approaches to analyze the sensitivity of simulated hydrologic fluxes to model parameters in the community land model

DOE PAGES

Bao, Jie; Hou, Zhangshuan; Huang, Maoyi; ...

2015-12-04

Here, effective sensitivity analysis approaches are needed to identify important parameters or factors and their uncertainties in complex Earth system models composed of multi-phase multi-component phenomena and multiple biogeophysical-biogeochemical processes. In this study, the impacts of 10 hydrologic parameters in the Community Land Model on simulations of runoff and latent heat flux are evaluated using data from a watershed. Different metrics, including residual statistics, the Nash-Sutcliffe coefficient, and log mean square error, are used as alternative measures of the deviations between the simulated and field observed values. Four sensitivity analysis (SA) approaches, including analysis of variance based on the generalizedmore » linear model, generalized cross validation based on the multivariate adaptive regression splines model, standardized regression coefficients based on a linear regression model, and analysis of variance based on support vector machine, are investigated. Results suggest that these approaches show consistent measurement of the impacts of major hydrologic parameters on response variables, but with differences in the relative contributions, particularly for the secondary parameters. The convergence behaviors of the SA with respect to the number of sampling points are also examined with different combinations of input parameter sets and output response variables and their alternative metrics. This study helps identify the optimal SA approach, provides guidance for the calibration of the Community Land Model parameters to improve the model simulations of land surface fluxes, and approximates the magnitudes to be adjusted in the parameter values during parametric model optimization.« less

Screening of willow species for resistance to heavy metals: comparison of performance in a hydroponics system and field trials.

PubMed

Watson, C; Pulford, I D; Riddell-Black, D

2003-01-01

The aim of this study was to ascertain whether metal resistance in willow (Salix) clones grown in a hydroponics screening test correlated with data from the same clones grown independently in a field trial. If so, results from a short-term, glasshouse-based system could be extrapolated to the field, allowing rapid identification of willows suitable for planting in metal-contaminated substrates without necessitating longterm field trials. Principal Components Analysis was used to show groups of clones and to assess the relative importance of the parameters measured in both the hydroponics system and the field; including plant response factors such as increase in stem height, as well as metal concentrations in plant tissues. The clones tested fell into two distinct groups. Salix viminalis clones and the basket willow Black Maul (S. triandra) were less resistant to elevated concentrations of heavy metals than a group of hardier clones, including S. burjatica 'Germany,' S.x dasyclados, S. candida and S. spaethii. The more resistant clones produced more biomass in the glasshouse and field, and had higher metal concentrations in the wood. The less resistant clones had greater concentrations of Cu and Ni in the bark, and produced less biomass in the glasshouse and field. Significant relationships were found between the response of the same clones grown the in short-term glasshouse hydroponics system and in the field.

Vector network analyzer ferromagnetic resonance spectrometer with field differential detection

NASA Astrophysics Data System (ADS)

Tamaru, S.; Tsunegi, S.; Kubota, H.; Yuasa, S.

2018-05-01

This work presents a vector network analyzer ferromagnetic resonance (VNA-FMR) spectrometer with field differential detection. This technique differentiates the S-parameter by applying a small binary modulation field in addition to the DC bias field to the sample. By setting the modulation frequency sufficiently high, slow sensitivity fluctuations of the VNA, i.e., low-frequency components of the trace noise, which limit the signal-to-noise ratio of the conventional VNA-FMR spectrometer, can be effectively removed, resulting in a very clean FMR signal. This paper presents the details of the hardware implementation and measurement sequence as well as the data processing and analysis algorithms tailored for the FMR spectrum obtained with this technique. Because the VNA measures a complex S-parameter, it is possible to estimate the Gilbert damping parameter from the slope of the phase variation of the S-parameter with respect to the bias field. We show that this algorithm is more robust against noise than the conventional algorithm based on the linewidth.

Improved Peptide and Protein Torsional Energetics with the OPLSAA Force Field.

PubMed

Robertson, Michael J; Tirado-Rives, Julian; Jorgensen, William L

2015-07-14

The development and validation of new peptide dihedral parameters are reported for the OPLS-AA force field. High accuracy quantum chemical methods were used to scan φ, ψ, χ1, and χ2 potential energy surfaces for blocked dipeptides. New Fourier coefficients for the dihedral angle terms of the OPLS-AA force field were fit to these surfaces, utilizing a Boltzmann-weighted error function and systematically examining the effects of weighting temperature. To prevent overfitting to the available data, a minimal number of new residue-specific and peptide-specific torsion terms were developed. Extensive experimental solution-phase and quantum chemical gas-phase benchmarks were used to assess the quality of the new parameters, named OPLS-AA/M, demonstrating significant improvement over previous OPLS-AA force fields. A Boltzmann weighting temperature of 2000 K was determined to be optimal for fitting the new Fourier coefficients for dihedral angle parameters. Conclusions are drawn from the results for best practices for developing new torsion parameters for protein force fields.