Repulsion Between Finite Charged Plates with Strongly Overlapped Electric Double Layers.

PubMed

Ghosal, Sandip; Sherwood, John D

2016-09-20

Screened Coulomb interactions between uniformly charged flat plates are considered at very small plate separations for which the Debye layers are strongly overlapped, in the limit of small electrical potentials. If the plates are of infinite length, the disjoining pressure between the plates decays as an inverse power of the plate separation. If the plates are of finite length, we show that screening Debye layer charges close to the edge of the plates are no longer constrained to stay between the plates, but instead spill out into the surrounding electrolyte. The resulting change in the disjoining pressure is calculated analytically: the force between the plates is reduced by this edge correction when the charge density is uniform over the surface of the plates, and is increased when the surface is at constant potential. A similar change in disjoining pressure due to loss of lateral confinement of the Debye layer charges should occur whenever the sizes of the interacting charged objects become small enough to approach the Debye scale. We investigate the effect here in the context of a two-dimensional model problem that is sufficiently simple to yield analytical results.

Debye ring diffraction elucidation of 2D photonic crystal self-assembly and ordering at the air-water interface.

PubMed

Smith, N L; Coukouma, A; Dubnik, S; Asher, S A

2017-12-06

We fabricate 2D photonic crystals (2DPC) by spreading a dispersion of charged colloidal particles (diameters = 409, 570, and 915 nm) onto the surface of electrolyte solutions using a needle tip flow method. When the interparticle electrostatic interaction potential is large, particles self-assemble into highly ordered hexagonal close packed (hcp) monolayers. Ordered 2DPC efficiently forward diffract monochromatic light to produce a Debye ring on a screen parallel to the 2DPC. The diameter of the Debye ring is inversely proportional to the 2DPC particle spacing, while the Debye ring brightness and thickness depends on the 2DPC ordering. The Debye ring thickness increases as the 2DPC order decreases. The Debye ring ordering measurements of 2DPC attached to glass slides track measurements of the 2D pair correlation function order parameter calculated from SEM micrographs. The Debye ring method was used to investigate the 2DPC particle spacing, and ordering at the air-solution interface of NaCl solutions, and for 2DPC arrays attached to glass slides. Surprisingly, the 2DPC ordering does not monotonically decrease as the salt concentration increases. This is because of chloride ion adsorption onto the anionic particle surfaces. This adsorption increases the particle surface charge and compensates for the decreased Debye length of the electric double layer when the NaCl concentration is below a critical value.

A numerical method for electro-kinetic flow with deformable fluid interfaces

NASA Astrophysics Data System (ADS)

Booty, Michael; Ma, Manman; Siegel, Michael

2013-11-01

We consider two-phase flow of ionic fluids whose motion is driven by an imposed electric field. At a fluid interface, a screening cloud of ions develops and forms an electro-chemical double layer or Debye layer. The imposed field acts on this induced charge distribution, resulting in a strong slip flow near the interface. We formulate a ``hybrid'' or multiscale numerical method in the thin Debye layer limit that incorporates an asymptotic analysis of the electrostatic potential and fluid dynamics in the Debye layer into a boundary integral solution of the full moving boundary problem. Results of the method are presented that show time-dependent deformation and steady state drop interface shapes when the timescale for charge-up of the Debye layer is either much less than or comparable to the timescale of the flow.

Measurements of the Casimir-Lifshitz force in fluids: The effect of electrostatic forces and Debye screening

NASA Astrophysics Data System (ADS)

Munday, J. N.; Capasso, Federico; Parsegian, V. Adrian; Bezrukov, Sergey M.

2008-09-01

We present detailed measurements of the Casimir-Lifshitz force between two gold surfaces (a sphere and a plate) immersed in ethanol and study the effect of residual electrostatic forces, which are dominated by static fields within the apparatus and can be reduced with proper shielding. Electrostatic forces are further reduced by Debye screening through the addition of salt ions to the liquid. Additionally, the salt leads to a reduction of the Casimir-Lifshitz force by screening the zero-frequency contribution to the force; however, the effect is small between gold surfaces at the measured separations and within experimental error. An improved calibration procedure is described and compared with previous methods. Finally, the experimental results are compared with Lifshitz’s theory and found to be consistent for the materials used in the experiment.

Potential of an emissive cylindrical probe in plasma.

PubMed

Fruchtman, A; Zoler, D; Makrinich, G

2011-08-01

The floating potential of an emissive cylindrical probe in a plasma is calculated for an arbitrary ratio of Debye length to probe radius and for an arbitrary ion composition. In their motion to the probe the ions are assumed to be collisionless. For a small Debye length, a two-scale analysis for the quasineutral plasma and for the sheath provides analytical expressions for the emitted and collected currents and for the potential as functions of a generalized mass ratio. For a Debye length that is not small, it is demonstrated that, as the Debye length becomes larger, the probe potential approaches the plasma potential and that the ion density near the probe is not smaller but rather is larger than it is in the plasma bulk.

Importance of the Debye Screening Length on Nanowire Field Effect Transistor Sensors

PubMed Central

Stern, Eric; Wagner, Robin; Sigworth, Fred J.; Breaker, Ronald; Fahmy, Tarek M.; Reed, Mark A.

2009-01-01

Nanowire field effect transistors (NW-FETs) can serve as ultrasensitive detectors for label-free reagents. The NW-FET sensing mechanism assumes a controlled modification in the local channel electric field created by the binding of charged molecules to the nanowire surface. Careful control of the solution Debye length is critical for unambiguous selective detection of macromolecules. Here we show the appropriate conditions under which the selective binding of macromolecules is accurately sensed with NW-FET sensors. PMID:17914853

Importance of the Debye screening length on nanowire field effect transistor sensors.

PubMed

Stern, Eric; Wagner, Robin; Sigworth, Fred J; Breaker, Ronald; Fahmy, Tarek M; Reed, Mark A

2007-11-01

Nanowire field effect transistors (NW-FETs) can serve as ultrasensitive detectors for label-free reagents. The NW-FET sensing mechanism assumes a controlled modification in the local channel electric field created by the binding of charged molecules to the nanowire surface. Careful control of the solution Debye length is critical for unambiguous selective detection of macromolecules. Here we show the appropriate conditions under which the selective binding of macromolecules is accurately sensed with NW-FET sensors.

Propagation of monochromatic light in a hot and dense medium

NASA Astrophysics Data System (ADS)

Masood, Samina S.

2017-12-01

Photons, as quanta of electromagnetic fields, determine the electromagnetic properties of an extremely hot and dense medium. Considering the properties of the photons in the interacting medium of charged particles, we explicitly calculate the electromagnetic properties such as the electric permittivity, magnetic permeability, refractive index and the propagation speed of electromagnetic signals in an extremely hot and dense background. Photons acquire a dynamically generated mass in such a medium. The screening mass of the photon, the Debye shielding length and the plasma frequency are calculated as functions of the statistical parameters of the medium. We study the properties of the propagating particles in astrophysical systems of distinct statistical conditions. The modifications in the properties of the medium lead to the equation of state of the system. We mainly calculate all these parameters for extremely high temperatures of the early universe.

Thermodynamics of Thomas-Fermi screened Coulomb systems

NASA Technical Reports Server (NTRS)

Firey, B.; Ashcroft, N. W.

1977-01-01

We obtain in closed analytic form, estimates for the thermodynamic properties of classical fluids with pair potentials of Yukawa type, with special reference to dense fully ionized plasmas with Thomas-Fermi or Debye-Hueckel screening. We further generalize the hard-sphere perturbative approach used for similarly screened two-component mixtures, and demonstrate phase separation in this simple model of a liquid mixture of metallic helium and hydrogen.

Effect of screening on the transport of polyelectrolytes through nanopores

NASA Astrophysics Data System (ADS)

Oukhaled, G.; Bacri, L.; Mathé, J.; Pelta, J.; Auvray, L.

2008-05-01

We study the transport of dextran sulfate molecules (Mw=8000 Da) through a bacterial α-hemolysin channel inserted into a bilayer lipid membrane submitted to an external electric field. We detect the current blockades induced by the molecules threading through one pore and vary the ionic strength in an unexplored range starting at 10-3 M. In the conditions of the experiment, the polyelectrolyte molecules enter the pore only if the Debye screening length is smaller than the pore radius in agreement with theory. We also observe that large potentials favour the passage of the molecules. The distribution of blockade durations suggests that a complex process governs the kinetics of the molecules. The dwelling time increases sharply as the Debye length increases and approaches the pore radius.

Size, shape, and diffusivity of a single Debye-Hückel polyelectrolyte chain in solution.

PubMed

Soysa, W Chamath; Dünweg, B; Prakash, J Ravi

2015-08-14

Brownian dynamics simulations of a coarse-grained bead-spring chain model, with Debye-Hückel electrostatic interactions between the beads, are used to determine the root-mean-square end-to-end vector, the radius of gyration, and various shape functions (defined in terms of eigenvalues of the radius of gyration tensor) of a weakly charged polyelectrolyte chain in solution, in the limit of low polymer concentration. The long-time diffusivity is calculated from the mean square displacement of the centre of mass of the chain, with hydrodynamic interactions taken into account through the incorporation of the Rotne-Prager-Yamakawa tensor. Simulation results are interpreted in the light of the Odjik, Skolnick, Fixman, Khokhlov, and Khachaturian blob scaling theory (Everaers et al., Eur. Phys. J. E 8, 3 (2002)) which predicts that all solution properties are determined by just two scaling variables-the number of electrostatic blobs X and the reduced Debye screening length, Y. We identify three broad regimes, the ideal chain regime at small values of Y, the blob-pole regime at large values of Y, and the crossover regime at intermediate values of Y, within which the mean size, shape, and diffusivity exhibit characteristic behaviours. In particular, when simulation results are recast in terms of blob scaling variables, universal behaviour independent of the choice of bead-spring chain parameters, and the number of blobs X, is observed in the ideal chain regime and in much of the crossover regime, while the existence of logarithmic corrections to scaling in the blob-pole regime leads to non-universal behaviour.

Electron capture and excitation processes in H+-H collisions in dense quantum plasmas

NASA Astrophysics Data System (ADS)

Jakimovski, D.; Markovska, N.; Janev, R. K.

2016-10-01

Electron capture and excitation processes in proton-hydrogen atom collisions taking place in dense quantum plasmas are studied by employing the two-centre atomic orbital close-coupling (TC-AOCC) method. The Debye-Hückel cosine (DHC) potential is used to describe the plasma screening effects on the Coulomb interaction between charged particles. The properties of a hydrogen atom with DHC potential are investigated as a function of the screening strength of the potential. It is found that the decrease in binding energy of nl levels with increasing screening strength is considerably faster than in the case of the Debye-Hückel (DH) screening potential, appropriate for description of charged particle interactions in weakly coupled classical plasmas. This results in a reduction in the number of bound states in the DHC potential with respect to that in the DH potential for the same plasma screening strength, and is reflected in the dynamics of excitation and electron capture processes for the two screened potentials. The TC-AOCC cross sections for total and state-selective electron capture and excitation cross sections with the DHC potential are calculated for a number of representative screening strengths in the 1-300 keV energy range and compared with those for the DH and pure Coulomb potential. The total capture cross sections for a selected number of screening strengths are compared with the available results from classical trajectory Monte Carlo calculations.

Calculation of Energy Diagram of Asymmetric Graded-Band-Gap Semiconductor Superlattices.

PubMed

Monastyrskii, Liubomyr S; Sokolovskii, Bogdan S; Alekseichyk, Mariya P

2017-12-01

The paper theoretically investigates the peculiarities of energy diagram of asymmetric graded-band-gap superlattices with linear coordinate dependences of band gap and electron affinity. For calculating the energy diagram of asymmetric graded-band-gap superlattices, linearized Poisson's equation has been solved for the two layers forming a period of the superlattice. The obtained coordinate dependences of edges of the conduction and valence bands demonstrate substantial transformation of the shape of the energy diagram at changing the period of the lattice and the ratio of width of the adjacent layers. The most marked changes in the energy diagram take place when the period of lattice is comparable with the Debye screening length. In the case when the lattice period is much smaller that the Debye screening length, the energy diagram has the shape of a sawtooth-like pattern.

Direct measurement of sub-Debye-length attraction between oppositely charged surfaces.

PubMed

Kampf, Nir; Ben-Yaakov, Dan; Andelman, David; Safran, S A; Klein, Jacob

2009-09-11

Using a surface force balance with fast video analysis, we have measured directly the attractive forces between oppositely charged solid surfaces (charge densities sigma(+), sigma(-)) across water over the entire range of interaction, in particular, at surface separations D below the Debye screening length lambda(S). At very low salt concentration we find a long-ranged attraction between the surfaces (onset ca. 100 nm), whose variation at D

A molecular Debye-Hückel theory and its applications to electrolyte solutions: The size asymmetric case

DOE PAGES

Xiao, Tiejun; Song, Xueyu

2017-03-28

We developed a molecular Debye-Hückel theory for electrolyte solutions with size asymmetry, where the dielectric response of an electrolyte solution is described by a linear combination of Debye-Hückel-like response modes. Furthermore, as the size asymmetry of an electrolyte solution leads to a charge imbalanced border zone around a solute, the dielectric response to the solute is characterized by two types of charge sources, namely, a bare solute charge and a charge distribution due to size asymmetry. These two kinds of charge sources are screened by the solvent differently, our theory presents a method to calculate the mean electric potential asmore » well as the electrostatic contributions to thermodynamic properties. Finally, the theory was successfully applied to binary as well as multi-component primitive models of electrolyte solutions.« less

Debye screening in single-molecule carbon nanotube field-effect sensors.

PubMed

Sorgenfrei, Sebastian; Chiu, Chien-Yang; Johnston, Matthew; Nuckolls, Colin; Shepard, Kenneth L

2011-09-14

Point-functionalized carbon nanotube field-effect transistors can serve as highly sensitive detectors for biomolecules. With a probe molecule covalently bound to a defect in the nanotube sidewall, two-level random telegraph noise (RTN) in the conductance of the device is observed as a result of a charged target biomolecule binding and unbinding at the defect site. Charge in proximity to the defect modulates the potential (and transmission) of the conductance-limiting barrier created by the defect. In this Letter, we study how these single-molecule electronic sensors are affected by ionic screening. Both charge in proximity to the defect site and buffer concentration are found to affect RTN amplitude in a manner that follows from simple Debye length considerations. RTN amplitude is also dependent on the potential of the electrolyte gate as applied to the reference electrode; at high enough gate potentials, the target DNA is completely repelled and RTN is suppressed.

Debye screening in single-molecule carbon nanotube field-effect transistors

PubMed Central

Sorgenfrei, Sebastian; Chiu, Chien-yang; Johnston, Matthew; Nuckolls, Colin; Shepard, Kenneth L.

2013-01-01

Point-functionalized carbon nanotube field-effect transistors can serve as highly sensitive detectors for biomolecules. With a probe molecule covalently bound to a defect in the nanotube sidewall, two-level random telegraph noise (RTN) in the conductance of the device is observed as a result of a charged target biomolecule binding and unbinding at the defect site. Charge in proximity to the defect modulates the potential (and transmission) of the conductance-limiting barrier created by the defect. In this Letter, we study how these single-molecule electronic sensors are affected by ionic screening. Both charge in proximity to the defect site and buffer concentration are found to affect RTN amplitude in a manner that follows from simple Debye length considerations. RTN amplitude is also dependent on the potential of the electrolyte gate as applied to the reference electrode; at high enough repulsive potentials, the target DNA is completely repelled and RTN is suppressed. PMID:21806018

Renormalization group method based on the ionization energy theory

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

Arulsamy, Andrew Das, E-mail: sadwerdna@gmail.com; School of Physics, University of Sydney, Sydney, New South Wales 2006

2011-03-15

Proofs are developed to explicitly show that the ionization energy theory is a renormalized theory, which mathematically exactly satisfies the renormalization group formalisms developed by Gell-Mann-Low, Shankar and Zinn-Justin. However, the cutoff parameter for the ionization energy theory relies on the energy-level spacing, instead of lattice point spacing in k-space. Subsequently, we apply the earlier proofs to prove that the mathematical structure of the ionization-energy dressed electron-electron screened Coulomb potential is exactly the same as the ionization-energy dressed electron-phonon interaction potential. The latter proof is proven by means of the second-order time-independent perturbation theory with the heavier effective mass condition,more » as required by the electron-electron screened Coulomb potential. The outcome of this proof is that we can derive the heat capacity and the Debye frequency as a function of ionization energy, which can be applied in strongly correlated matter and nanostructures.« less

Electron screening and its effects on big-bang nucleosynthesis

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

Wang Biao; Bertulani, C. A.; Balantekin, A. B.

We study the effects of electron screening on nuclear reaction rates occurring during the big-bang nucleosynthesis epoch. The sensitivity of the predicted elemental abundances on electron screening is studied in detail. It is shown that electron screening does not produce noticeable results in the abundances unless the traditional Debye-Hueckel model for the treatment of electron screening in stellar environments is enhanced by several orders of magnitude. This work rules out electron screening as a relevant ingredient to big-bang nucleosynthesis, confirming a previous study [see Itoh et al., Astrophys. J. 488, 507 (1997)] and ruling out exotic possibilities for the treatmentmore » of screening beyond the mean-field theoretical approach.« less

Two loop renormalization of the magnetic coupling in hot QCD

NASA Astrophysics Data System (ADS)

Giovannangeli, P.

2004-04-01

Well above the critical temperature hot QCD is described by 3d electrostatic QCD with gauge coupling gE and Debye mass mE. We integrate out the Debye scales to two loop accuracy and find for the gauge coupling in the resulting magnetostatic action gM2=gE21-{1}/{48}{gE2N}/{πmE}-{17}/{4608}{gE2N}/{πmE}2+O{gE2N}/{πmE}3.

Angular Distribution and Linear Polarization of X-ray Radiation Resulting from Electron Impact Excitation of Highly Charged Ions in Debye Plasmas

NASA Astrophysics Data System (ADS)

Chen, Zhanbin

2018-05-01

Plasma-screening effects on the 1s _{1/2} → 2l (l = s , p ) and 1s _{1/2} → 3d _{3/2} electron-impact excitation of highly charged ions are investigated, together with their subsequent radiative decay. The analysis is performed based on the multi-configuration Dirac-Fock method and the fully relativistic distorted-wave method incorporating the Debye-Hückel potential. To explore the nature of the effects, calculations are carried out based on detailed analyses of the integrated total and magnetic sublevel cross sections, the alignment parameters, the linear polarizations, and the angular distribution of the X-ray photoemission, as well as on corresponding data calculated in various Debye lengths/environments, taking the 2p _{3/2}→ 1s _{1/2} and 3d _{3/2}→ 1s _{1/2} characteristic lines of H-like Fe^{25+} ion as an example. The present results are compared with experimental data and other theoretical predictions where available.

Kinetic Theory of Plasmas

DTIC Science & Technology

2009-09-01

RTO-EN-AVT-162 means of a Coulomb potential screened at the Debye length (Delcroix and Bers, 1984; Balescu , 1988). 4. The plasma is composed of...Theory of Plasmas 2 - 28 RTO-EN-AVT-162 References Balescu , R. (1988). Transport Processes in Plasmas. Elsevier, Amsterdam. Barth, T. (2008

Potential of mean force of DNA guided assemblies past Debye-Hückel regime

NASA Astrophysics Data System (ADS)

Girard, Martin; Seo, Soyoung; Li, Yaohua; Mirkin, Chad; Olvera de La Cruz, Monica

Many of the bioinspired systems make use of biopolymers such as polypeptides or DNA. The latter is widely used in self-assembled systems, from colloidal crystals to origami construction. In these systems, salt is commonly required to screen the electrostatic repulsion between the strands. In the classical Debye-Hückel picture, salt ions are point particles and the screening distance is a decreasing monotonic function of salt concentration. This picture breaks down at moderate salt concentrations, where the behavior becomes non-monotonic. In this talk, we will show results for potential of mean force of DNA grafted colloids obtained through multiscale molecular dynamics. In this picture, the highly charged DNA causes non-trivial behavior at moderate salt concentrations (c 0 . 3 - 0 . 7 M), namely increase of repulsion for non-complementary DNA strands while repulsion decreases for complementary strands. We will show spatial cluster distribution as function of size and charge as well as implications for experimental systems.

Influence of Plasma Environment on K-Line Emission in Highly Ionized Iron Atoms Evaluated Using a Debye-Huckel Model

NASA Technical Reports Server (NTRS)

Deprince, J.; Fritzsche, S.; Kallman, T. R.; Palmeri, P.; Quinet, P.

2017-01-01

The influence of plasma environment on the atomic parameters associated with the K-vacancy states has been investigated theoretically for several iron ions. To do this, a time-averaged Debye-Huckel potential for both the electron-nucleus and electron-electron interactions has been considered in the framework of relativistic multiconfiguration Dirac-Fock computations. More particularly, the plasma screening effects on ionization potentials, K-thresholds, transition energies, and radiative rates have been estimated in the astrophysical context of accretion disks around black holes. In the present paper, we describe the behavior of those atomic parameters for Ne-, Na-, Ar-, and K-like iron ions.

Coulomb interactions between cytoplasmic electric fields and phosphorylated messenger proteins optimize information flow in cells.

PubMed

Gatenby, Robert A; Frieden, B Roy

2010-08-11

Normal cell function requires timely and accurate transmission of information from receptors on the cell membrane (CM) to the nucleus. Movement of messenger proteins in the cytoplasm is thought to be dependent on random walk. However, Brownian motion will disperse messenger proteins throughout the cytosol resulting in slow and highly variable transit times. We propose that a critical component of information transfer is an intracellular electric field generated by distribution of charge on the nuclear membrane (NM). While the latter has been demonstrated experimentally for decades, the role of the consequent electric field has been assumed to be minimal due to a Debye length of about 1 nanometer that results from screening by intracellular Cl- and K+. We propose inclusion of these inorganic ions in the Debye-Huckel equation is incorrect because nuclear pores allow transit through the membrane at a rate far faster than the time to thermodynamic equilibrium. In our model, only the charged, mobile messenger proteins contribute to the Debye length. Using this revised model and published data, we estimate the NM possesses a Debye-Huckel length of a few microns and find this is consistent with recent measurement using intracellular nano-voltmeters. We demonstrate the field will accelerate isolated messenger proteins toward the nucleus through Coulomb interactions with negative charges added by phosphorylation. We calculate transit times as short as 0.01 sec. When large numbers of phosphorylated messenger proteins are generated by increasing concentrations of extracellular ligands, we demonstrate they generate a self-screening environment that regionally attenuates the cytoplasmic field, slowing movement but permitting greater cross talk among pathways. Preliminary experimental results with phosphorylated RAF are consistent with model predictions. This work demonstrates that previously unrecognized Coulomb interactions between phosphorylated messenger proteins and intracellular electric fields will optimize information transfer from the CM to the NM in cells.

Direct measurement of the plasma screening length and surface potential near the lunar terminator

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

Benson, J.

1977-05-01

Direct measurement of the lunar dayside surface potential and screening length has been made by the suprathermal ion detector experiment (Side) near the terminator. In a region 20degree--30degree from the terminator at the Apollo 14 and 15 sites the surface potential is found to be approximately 50 V negative, and the screening length to be about 1 km. This value of the screening length is more than 2 orders of magnitude greater than the solar wind 'Debye' length. The strong negative surface potential in this region may be due to enhanced temperature and density of the solar wind plasma.

Direct measurement of the plasma screening length and surface potential near the lunar terminator

NASA Technical Reports Server (NTRS)

Benson, J.

1977-01-01

Direct measurement of the lunar dayside surface potential and screening length has been made by the suprathermal ion detector experiment (Side) near the terminator. In a region 20-30 deg from the terminator at the Apollo 14 and 15 sites the surface potential is found to be approximately 50 V negative, and the screening length to be about 1 km. This value of the screening length is more than 2 orders of magnitude greater than the solar wind 'Debye' length. The strong negative surface potential in this region may be due to enhanced temperature and density of the solar wind plasma.

Transport of Multivalent Electrolyte Mixtures in Micro- and Nanochannels

DTIC Science & Technology

2013-11-08

equations for this process are the unsteady Navier-Stokes equations along with continuity and the Poisson- Nernst -Planck system for the electro- static part...about five times the Debye screening length D (the 1/e lengthscale for the potential from the solution of the linearized Poisson- Boltzmann equation

Quark and Gluon Relaxation in Quark-Gluon Plasmas

NASA Technical Reports Server (NTRS)

Heiselberg, H.; Pethick, C. J.

1993-01-01

The quasiparticle decay rates for quarks and gluons in quark-gluon plasmas are calculated by solving the kinetic equation. Introducing an infrared cutoff to allow for nonperturbative effects, we evaluate the quasiparticle lifetime at momenta greater than the inverse Debye screening length to leading order in the coupling constant.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length.

PubMed

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-10-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length

PubMed Central

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-01-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes. PMID:24465094

Screening effects on 12C+12C fusion reaction

NASA Astrophysics Data System (ADS)

Koyuncu, F.; Soylu, A.

2018-05-01

One of the important reactions for nucleosynthesis in the carbon burning phase in high-mass stars is the 12C+12C fusion reaction. In this study, we investigate the influences of the nuclear potentials and screening effect on astrophysically interesting 12C+12C fusion reaction observables at sub-barrier energies by using the microscopic α–α double folding cluster (DFC) potential and the proximity potential. In order to model the screening effects on the experimental data, a more general exponential cosine screened Coulomb (MGECSC) potential including Debye and quantum plasma cases has been considered in the calculations for the 12C+12C fusion reaction. In the calculations of the reaction observables, the semi-classical Wentzel-Kramers-Brillouin (WKB) approach and coupled channel (CC) formalism have been used. Moreover, in order to investigate how the potentials between 12C nuclei produce molecular cluster states of 24Mg, the normalized resonant energy states of 24Mg cluster bands have been calculated for the DFC potential. By analyzing the results produced from the fusion of 12C+12C, it is found that taking into account the screening effects in terms of MGECSC is important for explaining the 12C+12C fusion data, and the microscopic DFC potential is better than the proximity potential in explaining the experimental data, also considering that clustering is dominant for the structure of the 24Mg nucleus. Supported by the Turkish Science and Research Council (TÜBİTAK) with (117R015)

On the Debye-Hückel effect of electric screening

NASA Astrophysics Data System (ADS)

Campos, L. M. B. C.; Lau, F. J. P.

2014-07-01

The paper considers non-linear self-consistent electric potential equation (Sec. I), due to a cloud made of a single species of electric charges, satisfying a Boltzmann distribution law (Sec. II). Exact solutions are obtained in a simple logarithmic form, in three cases: (Sec. III) spherical radial symmetry; (Sec. IV) plane parallel symmetry; (Sec. V) a special case of azimuthal-cylindrical symmetry. All these solutions, and their transformations (Sec. VI), involve the Debye-Hückel radius; the latter was originally defined from a solution of the linearized self-consistent potential equation. Using an exact solution of the self-consistent potential equation, the distance at which the potential vanishes differs from the Debye-Hückel radius by a factor of √2 . The preceding (Secs. II-VI) simple logarithmic exact solutions of the self-consistent potential equations involve no arbitrary constants, and thus are special or singular integrals not the general integral. The general solution of the self-consistent potential equation is obtained in the plane parallel case (Sec. VII), and it involves two arbitrary constants that can be reduced to one via a translation (Sec. VIII). The plots of dimensionless potential (Figure 1), electric field (Figure 2), charge density (Figure 3), and total charge between ζ and infinity (Figure 4), versus distance normalized to Debye-Hückel radius ζ ≡ z/a, show that (Sec. IX) there is a continuum of solutions, ranging from a charge distribution concentrated inside the Debye-Hückel radius to one spread-out beyond it. The latter case leads to the limiting case of logarithmic potential, and stronger electric field; the former case, of very concentrated charge distribution, leads to a fratricide effect and weaker electric field.

Strong and weak adsorptions of polyelectrolyte chains onto oppositely charged spheres

NASA Astrophysics Data System (ADS)

Cherstvy, A. G.; Winkler, R. G.

2006-08-01

We investigate the complexation of long thin polyelectrolyte (PE) chains with oppositely charged spheres. In the limit of strong adsorption, when strongly charged PE chains adapt a definite wrapped conformation on the sphere surface, we analytically solve the linear Poisson-Boltzmann equation and calculate the electrostatic potential and the energy of the complex. We discuss some biological applications of the obtained results. For weak adsorption, when a flexible weakly charged PE chain is localized next to the sphere in solution, we solve the Edwards equation for PE conformations in the Hulthén potential, which is used as an approximation for the screened Debye-Hückel potential of the sphere. We predict the critical conditions for PE adsorption. We find that the critical sphere charge density exhibits a distinctively different dependence on the Debye screening length than for PE adsorption onto a flat surface. We compare our findings with experimental measurements on complexation of various PEs with oppositely charged colloidal particles. We also present some numerical results of the coupled Poisson-Boltzmann and self-consistent field equation for PE adsorption in an assembly of oppositely charged spheres.

Effects of laser radiation field on energies of hydrogen atom in plasmas

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

Bahar, M. K., E-mail: mussiv58@gmail.com

2015-09-15

In this study, for the first time, the Schrödinger equation with more general exponential cosine screened Coulomb (MGECSC) potential is solved numerically in the presence of laser radiation field within the Ehlotzky approximation using the asymptotic iteration method. The MGECSC potential includes four different potential forms in consideration of different sets of the parameters in the potential. By applying laser field, the total interaction potential of hydrogen atom embedded in plasmas converts to double well-type potential. The plasma screening effects under the influence of laser field as well as confinement effects of laser field on hydrogen atom in Debye andmore » quantum plasmas are investigated by solving the Schrödinger equation with the laser-dressed MGECSC potential. It is resulted that since applying a monochromatic laser field on hydrogen atom embedded in a Debye and quantum plasma causes to shift in the profile of the total interaction potential, the confinement effects of laser field on hydrogen atom in plasmas modeled by the MGECSC potential change localizations of energy states.« less

Structure determination from XAFS using high-accuracy measurements of x-ray mass attenuation coefficients of silver, 11 keV-28 keV, and development of an all-energies approach to local dynamical analysis of bond length, revealing variation of effective thermal contributions across the XAFS spectrum.

PubMed

Tantau, L J; Chantler, C T; Bourke, J D; Islam, M T; Payne, A T; Rae, N A; Tran, C Q

2015-07-08

We use the x-ray extended range technique (XERT) to experimentally determine the mass attenuation coefficient of silver in the x-ray energy range 11 kev-28 kev including the silver K absorption edge. The results are accurate to better than 0.1%, permitting critical tests of atomic and solid state theory. This is one of the most accurate demonstrations of cross-platform accuracy in synchrotron studies thus far. We derive the mass absorption coefficients and the imaginary component of the form factor over this range. We apply conventional XAFS analytic techniques, extended to include error propagation and uncertainty, yielding bond lengths accurate to approximately 0.24% and thermal Debye-Waller parameters accurate to 30%. We then introduce the FDMX technique for accurate analysis of such data across the full XAFS spectrum, built on full-potential theory, yielding a bond length accuracy of order 0.1% and the demonstration that a single Debye parameter is inadequate and inconsistent across the XAFS range. Two effective Debye-Waller parameters are determined: a high-energy value based on the highly-correlated motion of bonded atoms (σ(DW) = 0.1413(21) Å), and an uncorrelated bulk value (σ(DW) = 0.1766(9) Å) in good agreement with that derived from (room-temperature) crystallography.

Information-theoretic measures of hydrogen-like ions in weakly coupled Debye plasmas

NASA Astrophysics Data System (ADS)

Zan, Li Rong; Jiao, Li Guang; Ma, Jia; Ho, Yew Kam

2017-12-01

Recent development of information theory provides researchers an alternative and useful tool to quantitatively investigate the variation of the electronic structure when atoms interact with the external environment. In this work, we make systematic studies on the information-theoretic measures for hydrogen-like ions immersed in weakly coupled plasmas modeled by Debye-Hückel potential. Shannon entropy, Fisher information, and Fisher-Shannon complexity in both position and momentum spaces are quantified in high accuracy for the hydrogen atom in a large number of stationary states. The plasma screening effect on embedded atoms can significantly affect the electronic density distributions, in both conjugate spaces, and it is quantified by the variation of information quantities. It is shown that the composite quantities (the Shannon entropy sum and the Fisher information product in combined spaces and Fisher-Shannon complexity in individual space) give a more comprehensive description of the atomic structure information than single ones. The nodes of wave functions play a significant role in the changes of composite information quantities caused by plasmas. With the continuously increasing screening strength, all composite quantities in circular states increase monotonously, while in higher-lying excited states where nodal structures exist, they first decrease to a minimum and then increase rapidly before the bound state approaches the continuum limit. The minimum represents the most reduction of uncertainty properties of the atom in plasmas. The lower bounds for the uncertainty product of the system based on composite information quantities are discussed. Our research presents a comprehensive survey in the investigation of information-theoretic measures for simple atoms embedded in Debye model plasmas.

Dark/visible parallel universes and Big Bang nucleosynthesis

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

Bertulani, C. A.; Frederico, T.; Fuqua, J.

We develop a model for visible matter-dark matter interaction based on the exchange of a massive gray boson called herein the Mulato. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. A close study of big bang nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB) bounds, galaxy dynamics, together with the Standard Model assumptions, help us to set a limitmore » on the mass and width of the new gauge boson. Modification of the statistics underlying the kinetic energy distribution of particles during the BBN is also discussed. The changes in reaction rates during the BBN due to a departure from the Debye-Hueckel electron screening model is also investigated.« less

On thermal corrections to near-threshold annihilation

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

Kim, Seyong; Laine, M., E-mail: skim@sejong.ac.kr, E-mail: laine@itp.unibe.ch

2017-01-01

We consider non-relativistic ''dark'' particles interacting through gauge boson exchange. At finite temperature, gauge exchange is modified in many ways: virtual corrections lead to Debye screening; real corrections amount to frequent scatterings of the heavy particles on light plasma constituents; mixing angles change. In a certain temperature and energy range, these effects are of order unity. Taking them into account in a resummed form, we estimate the near-threshold spectrum of kinetically equilibrated annihilating TeV scale particles. Weakly bound states are shown to 'melt' below freeze-out, whereas with attractive strong interactions, relevant e.g. for gluinos, bound states boost the annihilation ratemore » by a factor 4 ... 80 with respect to the Sommerfeld estimate, thereby perhaps helping to avoid overclosure of the universe. Modestly non-degenerate dark sector masses and a way to combine the contributions of channels with different gauge and spin structures are also discussed.« less

Electrostatic attraction between overall neutral surfaces.

PubMed

Adar, Ram M; Andelman, David; Diamant, Haim

2016-08-01

Two overall neutral surfaces with positively and negatively charged domains ("patches") have been shown in recent experiments to exhibit long-range attraction when immersed in an ionic solution. Motivated by the experiments, we calculate analytically the osmotic pressure between such surfaces within the Poisson-Boltzmann framework, using a variational principle for the surface-averaged free energy. The electrostatic potential, calculated beyond the linear Debye-Hückel theory, yields an overall attraction at large intersurface separations, over a wide range of the system's controlled length scales. In particular, the attraction is stronger and occurs at smaller separations for surface patches of larger size and charge density. In this large patch limit, we find that the attraction-repulsion crossover separation is inversely proportional to the square of the patch-charge density and to the Debye screening length.

Dusty plasma ring model

NASA Astrophysics Data System (ADS)

Sheridan, T. E.

2009-12-01

A model of a dusty plasma (Yukawa) ring is presented. We consider n identical particles confined in a two-dimensional (2D) annular potential well and interacting through a Debye (i.e. Yukawa or screened Coulomb) potential. Equilibrium configurations are computed versus n, the Debye shielding parameter and the trap radius. When the particle separation exceeds a critical value the particles form a 1D chain with a ring topology. Below the critical separation the zigzag instability gives a 2D configuration. Computed critical separations are shown to agree well with a theoretical prediction for the zigzag threshold. Normal mode spectra for 1D rings are computed and found to be in excellent agreement with the longitudinal and transverse dispersion relations for unbounded straight chains. When the longitudinal and transverse dispersion relations intersect we observe a resonance due to the finite curvature of the ring.

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

Lee, Gyeong Won; Shim, Jaewon; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

The influence of renormalization plasma screening on the entanglement fidelity for the elastic electron-atom scattering is investigated in partially ionized dense hydrogen plasmas. The partial wave analysis and effective interaction potential are employed to obtain the scattering entanglement fidelity in dense hydrogen plasmas as functions of the collision energy, the Debye length, and the renormalization parameter. It is found that the renormalization plasma shielding enhances the scattering entanglement fidelity. Hence, we show that the transmission of the quantum information can be increased about 10% due to the renormalization shielding effect in dense hydrogen plasmas. It is also found that themore » renormalization shielding effect on the entanglement fidelity for the electron-atom collision increases with an increase of the collision energy. In addition, the renormalization shielding function increases with increasing collision energy and saturates to the unity with an increase of the Debye length.« less

Application of relativistic distorted-wave method to electron-impact excitation of highly charged Fe XXIV ion embedded in weakly coupled plasmas

NASA Astrophysics Data System (ADS)

Chen, Zhanbin

2018-05-01

The process of excitation of highly charged Fe XXIV ion embedded in weakly coupled plasmas by electron impact is studied, together with the subsequent radiative decay. For the target structure, the calculation is performed using the multiconfiguration Dirac-Hartree-Fock method incorporating the Debye-Hückel potential for the electron-nucleus interaction. Fine-structure levels of the 1s22p and 1s2s2p configurations and the transition properties among these levels are presented over a wide range of screening parameters. For the collision dynamics, the distorted-wave method in the relativistic frame is adopted to include the effect of plasma background, in which the interparticle interactions in the system are described by screened interactions of the Debye-Hückel type. The continuum wave function of the projectile electron is obtained by solving the modified Dirac equations. The influence of plasma strength on the cross section, the linear polarization, and the angular distribution of x-ray photon emission are investigated in detail. Comparison of the present results with experimental data and other theoretical predictions, when available, is made.

Ionic screening and dissociation are crucial for understanding chemical self-propulsion in polar solvents.

PubMed

Brown, Aidan T; Poon, Wilson C K; Holm, Christian; de Graaf, Joost

2017-02-08

Polar solvents like water support the bulk dissociation of themselves and their solutes into ions, and the re-association of these ions into neutral molecules in a dynamic equilibrium, e.g., H 2 O 2 ⇌ H + + HO 2 - . Using continuum theory, we study the influence of these association-dissociation reactions on the self-propulsion of colloids driven by surface chemical reactions (chemical swimmers). We find that association-dissociation reactions should have a strong influence on swimmers' behaviour, and therefore should be included in future modelling. In particular, such bulk reactions should permit charged swimmers to propel electrophoretically even if all species involved in the surface reactions are neutral. The bulk reactions also significantly modify the predicted speed of chemical swimmers propelled by ionic currents, by up to an order of magnitude. For swimmers whose surface reactions produce both anions and cations (ionic self-diffusiophoresis), the bulk reactions produce an additional reactive screening length, analogous to the Debye length in electrostatics. This in turn leads to an inverse relationship between swimmer radius and swimming speed, which could provide an alternative explanation for recent experimental observations on Pt-polystyrene Janus swimmers [S. Ebbens et al., Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2012, 85, 020401]. We also use our continuum theory to investigate the effect of the Debye screening length itself, going beyond the infinitely-thin-screening-length approximation used by previous analytical theories. We identify significant departures from this limiting behaviour for micron-sized swimmers under typical experimental conditions and find that the approximation fails entirely for nanoscale swimmers.

Spectra of confined positronium

NASA Astrophysics Data System (ADS)

Munjal, D.; Silotia, P.; Prasad, V.

2017-12-01

Positronium is studied under the effect of spherically confined plasma environment. Exponentially Cosine Screened Coulomb potential (ECSC) has been used to include the dense plasma screening effect on positronium. Time independent Schrodinger equation is solved numerically. Various physical parameters such as energy eigenvalues, radial matrix elements, oscillator strengths, and polarizability are well explored as a function of confinement parameters. Oscillator strength gets drastically modified under confinement. We have also obtained the results for Ps confined under spherically confined Debye potential and compared with results of ECSC potential. Also incidental degeneracy for different values of confinement parameters has been reported for the first time for positronium.

Underscreening in ionic liquids: a first principles analysis.

PubMed

Rotenberg, Benjamin; Bernard, Olivier; Hansen, Jean-Pierre

2018-02-07

An attempt is made to understand the underscreening effect, observed in concentrated electrolyte solutions or melts, on the basis of simple, admittedly crude models involving charged (for the ions) and neutral (for the solvent molecules) hard spheres. The thermodynamic and structural properties of these 'primitive' and 'semi-primitive' models are calculated within mean spherical approximation, which provides the basic input required to determine the partial density response functions. The screening length [Formula: see text], which is unambiguously defined in terms of the wave-number-dependent response functions, exhibits a cross-over from a low density, Debye-like regime, to a regime where [Formula: see text] increases with density beyond a critical density at which the Debye length [Formula: see text] becomes comparable to the ion diameter. In this high density regime the ratio [Formula: see text] increases according to a power law, in qualitative agreement with experimental measurements, albeit at a much slower rate.

Underscreening in ionic liquids: a first principles analysis

NASA Astrophysics Data System (ADS)

Rotenberg, Benjamin; Bernard, Olivier; Hansen, Jean-Pierre

2018-02-01

An attempt is made to understand the underscreening effect, observed in concentrated electrolyte solutions or melts, on the basis of simple, admittedly crude models involving charged (for the ions) and neutral (for the solvent molecules) hard spheres. The thermodynamic and structural properties of these ‘primitive’ and ‘semi-primitive’ models are calculated within mean spherical approximation, which provides the basic input required to determine the partial density response functions. The screening length λS , which is unambiguously defined in terms of the wave-number-dependent response functions, exhibits a cross-over from a low density, Debye-like regime, to a regime where λS increases with density beyond a critical density at which the Debye length λD becomes comparable to the ion diameter. In this high density regime the ratio λ_S/λD increases according to a power law, in qualitative agreement with experimental measurements, albeit at a much slower rate.

On the Debye–Hückel effect of electric screening

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

Campos, L. M. B. C.; Lau, F. J. P.

2014-07-15

The paper considers non-linear self-consistent electric potential equation (Sec. I), due to a cloud made of a single species of electric charges, satisfying a Boltzmann distribution law (Sec. II). Exact solutions are obtained in a simple logarithmic form, in three cases: (Sec. III) spherical radial symmetry; (Sec. IV) plane parallel symmetry; (Sec. V) a special case of azimuthal-cylindrical symmetry. All these solutions, and their transformations (Sec. VI), involve the Debye-Hückel radius; the latter was originally defined from a solution of the linearized self-consistent potential equation. Using an exact solution of the self-consistent potential equation, the distance at which the potentialmore » vanishes differs from the Debye-Hückel radius by a factor of √(2). The preceding (Secs. II–VI) simple logarithmic exact solutions of the self-consistent potential equations involve no arbitrary constants, and thus are special or singular integrals not the general integral. The general solution of the self-consistent potential equation is obtained in the plane parallel case (Sec. VII), and it involves two arbitrary constants that can be reduced to one via a translation (Sec. VIII). The plots of dimensionless potential (Figure 1), electric field (Figure 2), charge density (Figure 3), and total charge between ζ and infinity (Figure 4), versus distance normalized to Debye-Hückel radius ζ ≡ z/a, show that (Sec. IX) there is a continuum of solutions, ranging from a charge distribution concentrated inside the Debye-Hückel radius to one spread-out beyond it. The latter case leads to the limiting case of logarithmic potential, and stronger electric field; the former case, of very concentrated charge distribution, leads to a fratricide effect and weaker electric field.« less

Energy deposition of heavy ions in the regime of strong beam-plasma correlations.

PubMed

Gericke, D O; Schlanges, M

2003-03-01

The energy loss of highly charged ions in dense plasmas is investigated. The applied model includes strong beam-plasma correlation via a quantum T-matrix treatment of the cross sections. Dynamic screening effects are modeled by using a Debye-like potential with a velocity dependent screening length that guarantees the known low and high beam velocity limits. It is shown that this phenomenological model is in good agreement with simulation data up to very high beam-plasma coupling. An analysis of the stopping process shows considerably longer ranges and a less localized energy deposition if strong coupling is treated properly.

Ion extraction from a plasma

NASA Technical Reports Server (NTRS)

Aston, G.; Wilbur, P. J.

1981-01-01

The physical processes governing ion extraction from a plasma have been examined experimentally. The screen hole plasma sheath (the transition region wherein significant ion acceleration and complete electron retardation occurs) has been defined by equipotential plots for a variety of ion accelerator system geometries and operating conditions. It was found that the screen hole plasma sheath extends over a large distance, and influences ion and electron trajectories at least 15 Debye lengths within the discharge chamber. The electron density variation within the screen hole plasma sheath satisfied a Maxwell-Boltzmann density distribution at an effective electron temperature dependent on the discharge plasma primary-to-Maxwellian electron density ratio. Plasma ion flow up to and through the sheath was predominantly one-dimensional, and the ions entered the sheath region with a modified Bohm velocity. Low values of the screen grid thickness to screen hole diameter ratio were found to give good ion focusing and high extracted ion currents because of the effect of screen webbing on ion focusing.

Synthesis, spectroscopic characterization, DFT calculations and biological evaluation of benzothiazole derivative bearing Mn(II) and Ni(II) metal ions

NASA Astrophysics Data System (ADS)

El-Gamel, Nadia E. A.; Ali, Korany A.

2017-11-01

N-(benzo[d]thiazol-2-yl)-3-oxo-3-phenylpropanamide ligand and its Nickel and Manganese complexes have been synthesized and characterized by elemental and thermal analyses, IR, diffuse reflectance, mass and UV-Vis spectra, molar conductance and magnetic moment measurements. The decomposition mechanism and thermal stability of the investigated complexes are interpreted in terms of their structures. The thermal behaviour of the complexes has been studied and different thermodynamic parameters are calculated using Coats-Redfern method. N-(benzo[d]thiazol-2-yl)-3-oxo-3-phenylpropanamide is a neutral bidentate ligand coordinating metal ions via thiazole ring nitrogen and amide carbonyl O forming high spin octahedral complexes with Mn(II) (2) and distorted square planar in case of Ni(II) (1). Natural bond orbital analysis and geometry optimization were carried out at DFT/B3LYP/6-31G(d) level of theory for the ligand and the mentioned complexes. Ab inito computations at the HF/6-31G(d) level of the theory is conducted in order to detect any probability of a hydrogen bond formation in the ligand. The dipole moment of the Ni(II) and Mn(II) complexes is recorded to be 9.69 and 7.39 Debye, respectively, indicating that the complexes are more polarized than the ligand 2.39 Debye. The in vitro biological activity of the metal chelates is screened against the Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli), fungus (Aspergillus flavus, Candida albicans). Ni(II) complexes displayed the highest activity against Candida albicans and Staphylococcus aureus with MIC values of 13, 30 μg/cm3, respectively.

Critical screening in the one- and two-electron Yukawa atoms

NASA Astrophysics Data System (ADS)

Montgomery, H. E.; Sen, K. D.; Katriel, Jacob

2018-02-01

The one- and two-electron Yukawa atoms, also referred to as the Debye-Hückel or screened Coulomb atoms, have been topics of considerable interest both for intrinsic reasons and because of their relevance to terrestrial and astrophysical plasmas. At sufficiently high screening the one-electron Yukawa atom ceases to be bound. Some calculations appeared to suggest that as the screening increases in the ground state of the two-electron Yukawa atom (in which both the one-particle attraction and the interparticle repulsion are screened) the two electrons are detached simultaneously, at the same screening constant at which the one-electron atom becomes unbound. Our results rule this scenario out, offering an alternative that is not less interesting. In particular, it is found that for Z <1 a mild amount of screening actually increases the binding energy of the second electron. At the nuclear charge Zc≈0.911028 ... , at which the bare Coulomb two-electron atom becomes unbound, and even over a range of lower nuclear charges, an appropriate amount of screening gives rise to a bound two-electron system.

Dusty plasma (Yukawa) rings

NASA Astrophysics Data System (ADS)

Sheridan, T. E.; Gallagher, James C.

2016-11-01

One-dimensional and quasi-one-dimensional strongly coupled dusty plasma rings have been created experimentally. Longitudinal (acoustic) and transverse (optical) dispersion relations for the one-ring are measured and found to be in excellent agreement with the theory for an unbounded straight chain of particles interacting through a Yukawa (i.e., screened Coulomb or Debye-Hückel) potential. These rings provide a new experimental system to directly study one-dimensional and quasi-one-dimensional linear and nonlinear phenomena.

Electrostatic contribution to twist rigidity of DNA.

PubMed

Mohammad-Rafiee, Farshid; Golestanian, Ramin

2004-06-01

The electrostatic contribution to the twist rigidity of DNA is studied, and it is shown that the Coulomb self-energy of the double-helical sugar-phosphate backbone makes a considerable contribution-the electrostatic twist rigidity of DNA is found to be C(elec) approximately 5 nm, which makes up about 7% of its total twist rigidity ( C(DNA) approximately 75 nm). The electrostatic twist rigidity is found, however, to depend only weakly on the salt concentration, because of a competition between two different screening mechanisms: (1) Debye screening by the salt ions in the bulk, and (2) structural screening by the periodic charge distribution along the backbone of the helical polyelectrolyte. It is found that, depending on the parameters, the electrostatic contribution to the twist rigidity could stabilize or destabilize the structure of a helical polyelectrolyte.

Ion extraction from a plasma. Ph.D. Thesis. Progress Report, 1 Dec. 1979 - 1 Dec. 1980

NASA Technical Reports Server (NTRS)

Aston, G.

1980-01-01

An experimental investigation of the physical processes governing ion extraction from a plasma is presented. The screen hole plasma sheath of a multiaperture ion accelerator system is defined by equipotential plots for a variety of accelerator system geometries and operating conditions. A sheath thickness of at least fifteen Debye lengths is shown to be typical. The electron density variation within the sheath satisfies a Maxwell Boltzmann density distribution at an effective electron temperature dependent on the discharge plasma primary to Maxwellian electron density ratio. Plasma ion flow up to and through the sheath is predominately one dimensional and the ions enter the sheath with a modified Bohm velocity. Low values of the screen grid thickness to screen hole diameter ratio give good ion focusing and high extracted ion currents because of the effect of screen webbing on ion focusing.

Screening in ionic systems: simulations for the Lebowitz length.

PubMed

Kim, Young C; Luijten, Erik; Fisher, Michael E

2005-09-30

Simulations of the Lebowitz length, xiL (T, rho), are reported for the restricted primitive model hard-core (diameter a) 1:1 electrolyte for densities rho approximately < 4rho(c) and T(c) approximately < T approximately < 40T(c). Finite-size effects are elucidated for the charge fluctuations in various subdomains that serve to evaluate xiL. On extrapolation to the bulk limit for T approximately > 10T(c) the exact low-density expansions are seen to fail badly when rho > 1/10 rho(c) (with rho(c)a3 approximately = 0.08). At higher densities xiL rises above the Debye length, xiD proportional to square root(T/rho), by 10%-30% (up to rho approximately =1.3rho(c)); the variation is portrayed fairly well by the generalized Debye-Hückel theory. On approaching criticality at fixed rho or fixed T, xiL (T, rho) remains finite with xiL(c) approximately = 0.30a approximately = 1.3xiD(c) but displays a weak entropylike singularity.

Effect of surface charge density on the affinity of oxide nanoparticles for the vapor-water interface.

PubMed

Brown, Matthew A; Duyckaerts, Nicolas; Redondo, Amaia Beloqui; Jordan, Inga; Nolting, Frithjof; Kleibert, Armin; Ammann, Markus; Wörner, Hans Jakob; van Bokhoven, Jeroen A; Abbas, Zareen

2013-04-23

Using in-situ X-ray photoelectron spectroscopy at the vapor-water interface, the affinity of nanometer-sized silica colloids to adsorb at the interface is shown to depend on colloid surface charge density. In aqueous suspensions at pH 10 corrected Debye-Hückel theory for surface complexation calculations predict that smaller silica colloids have increased negative surface charge density that originates from enhanced screening of deprotonated silanol groups (≡Si-O(-)) by counterions in the condensed ion layer. The increased negative surface charge density results in an electrostatic repulsion from the vapor-water interface that is seen to a lesser extent for larger particles that have a reduced charge density in the XPS measurements. We compare the results and interpretation of the in-situ XPS and corrected Debye-Hückel theory for surface complexation calculations with traditional surface tension measurements. Our results show that controlling the surface charge density of colloid particles can regulate their adsorption to the interface between two dielectrics.

Automated combinatorial method for fast and robust prediction of lattice thermal conductivity

NASA Astrophysics Data System (ADS)

Plata, Jose J.; Nath, Pinku; Usanmaz, Demet; Toher, Cormac; Fornari, Marco; Buongiorno Nardelli, Marco; Curtarolo, Stefano

The lack of computationally inexpensive and accurate ab-initio based methodologies to predict lattice thermal conductivity, κl, without computing the anharmonic force constants or performing time-consuming ab-initio molecular dynamics, is one of the obstacles preventing the accelerated discovery of new high or low thermal conductivity materials. The Slack equation is the best alternative to other more expensive methodologies but is highly dependent on two variables: the acoustic Debye temperature, θa, and the Grüneisen parameter, γ. Furthermore, different definitions can be used for these two quantities depending on the model or approximation. Here, we present a combinatorial approach based on the quasi-harmonic approximation to elucidate which definitions of both variables produce the best predictions of κl. A set of 42 compounds was used to test accuracy and robustness of all possible combinations. This approach is ideal for obtaining more accurate values than fast screening models based on the Debye model, while being significantly less expensive than methodologies that solve the Boltzmann transport equation.

Observation of finite-wavelength screening in high-energy-density matter

DOE PAGES

Chapman, D. A.; Vorberger, J.; Fletcher, L. B.; ...

2015-04-23

A key component for the description of charged particle systems is the screening of the Coulomb interaction between charge carriers. First investigated in the 1920s by Debye and Hückel for electrolytes, charge screening is important for determining the structural and transport properties of matter as diverse as astrophysical and laboratory plasmas, nuclear matter such as quark-gluon plasmas, electrons in solids, planetary cores and charged macromolecules. For systems with negligible dynamics, screening is still mostly described using a Debye–Hückel-type approach. Here, we report the novel observation of a significant departure from the Debye–Hückel-type model in high-energy-density matter by probing laser-driven, shock-compressedmore » plastic with high-energy X-rays. We use spectrally resolved X-ray scattering in a geometry that enables direct investigation of the screening cloud, and demonstrate that the observed elastic scattering amplitude is only well described within a more general approach.« less

Three dimensional graphene transistor for ultra-sensitive pH sensing directly in biological media.

PubMed

Ameri, Shideh Kabiri; Singh, Pramod K; Sonkusale, Sameer R

2016-08-31

In this work, pH sensing directly in biological media using three dimensional liquid gated graphene transistors is presented. The sensor is made of suspended network of graphene coated all around with thin layer of hafnium oxide (HfO2), showing high sensitivity and sensing beyond the Debye-screening limit. The performance of the pH sensor is validated by measuring the pH of isotonic buffered, Dulbecco's phosphate buffered saline (DPBS) solution, and of blood serum derived from Sprague-Dawley rat. The pH sensor shows high sensitivity of 71 ± 7 mV/pH even in high ionic strength media with molarities as high as 289 ± 1 mM. High sensitivity of this device is owing to suspension of three dimensional graphene in electrolyte which provides all around liquid gating of graphene, leading to higher electrostatic coupling efficiency of electrolyte to the channel and higher gating control of transistor channel by ions in the electrolyte. Coating graphene with hafnium oxide film (HfO2) provides binding sites for hydrogen ions, which results in higher sensitivity and sensing beyond the Debye-screening limit. The 3D graphene transistor offers the possibility of real-time pH measurement in biological media without the need for desaltation or sample preparation. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of semiclassical plasma on the energy levels and radiative transitions in highly charged ions★

NASA Astrophysics Data System (ADS)

Hu, Hong-Wei; Chen, Zhan-Bin; Chen, Wen-Cong; Liu, Xiao-Bin; Fu, Nian; Wang, Kai

2017-11-01

Considering the quantum effects of diffraction and the collective screening effects, the potential of test charge in semiclassical plasmas is derived. It is generalized exponential screened Coulomb potential. Using the Ritz variational method incorporating this potential, the effects of semiclassical plasma on the energy levels and radiative transitions are investigated systematically, taking highly charged H-like ion as an example. The Debye plasma model is also employed for comparison purposes. Comparisons and analysis are made between these two sets of results and the differences are discussed. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

Effective screening length of isotropic liquid samples submitted to an applied voltage.

PubMed

Zola, R S; Evangelista, L R; Barbero, G

2006-05-25

A cell of isotropic liquid in the shape of a slab of thickness d and containing ionic impurities is considered. It is shown that the screening effect produced by the ionic charges on the external field is characterized by an effective surface length, lambda(S)(U), depending on the applied voltage U. The analysis indicates that lambda(S)(U)) < lambda(D) when the applied voltage is very large, and lambda(S)(U) --> lambda(D) for very small values of the applied voltage, where lambda(D) is the Debye screening length. The presence of the ions is responsible also for a counterpotential, v, that for small U is such to cancel the effective electric field in the sample, whereas in the opposite limit it is inversely proportional to the applied difference of potential.

Nonlocal electrostatics in ionic liquids: The key to an understanding of the screening decay length and screened interactions.

PubMed

Kjellander, Roland

2016-09-28

Screened electrostatic interactions in ionic liquids are investigated by means of exact statistical mechanical analysis combined with physical arguments that enhance the transparency and conceptual accessibility of the analysis and results. The constituent ions and immersed particles in the liquid can have arbitrary shapes and any internal charge distributions. The decay of the screened electrostatic potential and the free energy of interaction in ionic liquids can be exponentially damped oscillatory (like in molten simple salts) as well as plain exponential and long-ranged (like in dilute electrolyte solutions). Both behaviors are in agreement with the exact statistical mechanical analysis and reasons for their appearances are investigated. Exact but surprisingly simple expressions for the decay parameter κ of the screened electrostatics are obtained, which replace the classical expression for the Debye-Hückel parameter κ DH (the reciprocal Debye length). The expressions are applicable both for cases with plain exponential and oscillatory behaviors. The key importance of nonlocal electrostatics is thereby demonstrated explicitly. Dielectric properties of ionic liquids and other electrolytes are investigated, in particular the static dielectric function ϵ̃(k) and some effective relative permittivities (E r eff and E r ∗ ), which take roles that the dielectric constant ε r has for polar liquids consisting of electroneutral molecules. The dielectric constant in the latter case, which is the limit of ϵ̃(k) when the wave number k → 0, can be expressed solely in terms of dipolar features of the molecules. In contrast to this, the effective dielectric permittivities of ionic liquids have contributions also from quadrupolar, octupolar, and higher multipolar features of the constituent ions. The "dielectric constant" of electrolytes does not exist since ϵ̃(k)→∞ when k → 0, a well-known effect of perfect screening. The effective relative permittivities, E r eff , and E r ∗ of ionic liquids are obtained from the non-diverging part of ϵ̃(k), but not as a k → 0 limit. Influences of ion associations, especially pairing, are investigated for screened electrostatics and these permittivities. A general, multipolar expansion of ϵ̃(k) is derived and used to analyze dielectric properties of ionic liquids and other electrolytes.

Nonlocal electrostatics in ionic liquids: The key to an understanding of the screening decay length and screened interactions

NASA Astrophysics Data System (ADS)

Kjellander, Roland

2016-09-01

Screened electrostatic interactions in ionic liquids are investigated by means of exact statistical mechanical analysis combined with physical arguments that enhance the transparency and conceptual accessibility of the analysis and results. The constituent ions and immersed particles in the liquid can have arbitrary shapes and any internal charge distributions. The decay of the screened electrostatic potential and the free energy of interaction in ionic liquids can be exponentially damped oscillatory (like in molten simple salts) as well as plain exponential and long-ranged (like in dilute electrolyte solutions). Both behaviors are in agreement with the exact statistical mechanical analysis and reasons for their appearances are investigated. Exact but surprisingly simple expressions for the decay parameter κ of the screened electrostatics are obtained, which replace the classical expression for the Debye-Hückel parameter κDH (the reciprocal Debye length). The expressions are applicable both for cases with plain exponential and oscillatory behaviors. The key importance of nonlocal electrostatics is thereby demonstrated explicitly. Dielectric properties of ionic liquids and other electrolytes are investigated, in particular the static dielectric function ɛ ˜ ( k ) and some effective relative permittivities ( Er eff and Er ∗ ), which take roles that the dielectric constant ɛr has for polar liquids consisting of electroneutral molecules. The dielectric constant in the latter case, which is the limit of ɛ ˜ ( k ) when the wave number k → 0, can be expressed solely in terms of dipolar features of the molecules. In contrast to this, the effective dielectric permittivities of ionic liquids have contributions also from quadrupolar, octupolar, and higher multipolar features of the constituent ions. The "dielectric constant" of electrolytes does not exist since ɛ ˜ ( k ) → ∞ when k → 0, a well-known effect of perfect screening. The effective relative permittivities, Er eff , and Er ∗ of ionic liquids are obtained from the non-diverging part of ɛ ˜ ( k ) , but not as a k → 0 limit. Influences of ion associations, especially pairing, are investigated for screened electrostatics and these permittivities. A general, multipolar expansion of ɛ ˜ ( k ) is derived and used to analyze dielectric properties of ionic liquids and other electrolytes.

A Numerical Model of Laser-Induced Fluorescence in a Hydrogen Plasma

DTIC Science & Technology

1991-03-10

cross-sections. Lee, et al., cited screened Coulomb potential calculations by several groups to place an up- per limit of 30 A on the Debye length...intensity: RL(t)(1/sec) = B,,(cir 2/erg . sec) . (J,)(erg/sec .cm -. liz) (3.5) 35 The Einstein coefficients are related by the statistical weights of the...impact processes.) These rate matrices were then added together to obtain the total rate matrix for both groups of electrons. The total electron density

A dusty plasma 1-ring to rule them all

NASA Astrophysics Data System (ADS)

Sheridan, T. E.; Gallagher, James C.

2010-04-01

One-dimensional and quasi-one-dimensional strongly-coupled dusty plasma rings have been created experimentally in the DONUT (Dusty ONU experimenT) apparatus. Longitudinal (acoustic) and transverse (optical) dispersion relations for the 1-ring were measured and found to be in very good agreement with the theory for an unbounded straight chain of particles interacting through a Yukawa (i.e., screened Coulomb or Debye-H"uckel) potential. These rings provide a new system in which to study one-dimensional and quasi-one-dimensional physics.

Mie and debye scattering in dusty plasmas

PubMed

Guerra; Mendonca

2000-07-01

We calculate the total field scattered by a charged sphere immersed in a plasma using a unified treatment that includes the usual Mie scattering and the scattering by the Debye cloud around the particle. This is accomplished by use of the Dyadic Green function to determine the field radiated by the electrons of the Debye cloud, which is then obtained as a series of spherical vector wave functions similar to that of the Mie field. Thus we treat the Debye-Mie field as a whole and study its properties. The main results of this study are (1) the Mie (Debye) field dominates at small (large) wavelengths and in the Rayleigh limit the Debye field is constant; (2) the total cross section has an interference term between the Debye and Mie fields, important in some regimes; (3) this term is negative for negative charge of the grain, implying a total cross section smaller than previously thought; (4) a method is proposed to determine the charge of the grain (divided by a certain suppression factor) and the Debye length of the plasma; (5) a correction to the dispersion relation of an electromagnetic wave propagating in a plasma is derived.

On the non-exponentiality of the dielectric Debye-like relaxation of monoalcohols

NASA Astrophysics Data System (ADS)

Arrese-Igor, S.; Alegría, A.; Colmenero, J.

2017-03-01

We have investigated the Debye-like relaxation in a series of monoalcohols (MAs) by broadband dielectric spectroscopy and thermally stimulated depolarization current techniques in order to get further insight on the time dispersion of this intriguing relaxation. Results indicate that the Debye-like relaxation of MAs is not always of exponential type and conforms well to a dispersion of Cole-Davidson type. Apart from the already reported non-exponentiality of the Debye-like relaxation in 2-hexyl-1-decanol and 2-butyl-1-octanol, a detailed analysis of the dielectric permittivity of 5-methyl-3-heptanol shows that this MA also presents some extent of dispersion on its Debye-like relaxation which strongly depends on the temperature. Results suggest that the non-exponential character of the Debye-like relaxation might be a general characteristic in the case of not so intense Debye-like relaxations relative to the α relaxation. Finally, we briefly discuss on the T-dependence and possible origin for the observed dispersion.

Debye sheath mechanism at laser plasma interaction and generalization to nuclear forces and quark-gluon plasma

NASA Astrophysics Data System (ADS)

Osman, Frederick; Ghahramani, Nader; Hora, Heinrich

2005-10-01

The studies of laser ablation have lead to a new theory of nuclei, endothermic nuclei generation, and quark-gluon plasmas. The surface of ablated plasma expanding into vacuum after high power laser irradiation of targets contains an electric double layer having the thickness of the Debye length. This led to the discovery of surface tension in plasmas, and led to the internal dynamic electric fields in all inhomogeneous plasmas. The surface tension causes stabilization by short length surface wave smoothing the expanding plasma plume and to stabilization against the Rayleigh Taylor instability. Generalizing this to the degenerate electrons in a metal with the Fermi energy instead of the temperature resulted in the first quantum theory of surface tension of metals in agreement with measurements. Taking the Fermi energy in the Debye length for nucleons results in a theory of nuclei with stable confinement of protons and neutrons just at the well-known nuclear density, and the Debye lengths equal to the Hofstadter decay of the nuclear surface. Increasing the nuclear density by a factor of 10 leads to a change of the Fermi energy into its relativistic branch where no surface energy is possible and the particle mass is not defined, permitting the quark gluon plasma. Expansion of this higher density at the big bang or in super-nova results in nucleation and element generation. The Boltzmann equilibrium permits the synthesis of nuclei even in the endothermic range, however with the limit to about uranium. A relation for the magic numbers leads to a quark structure of nuclear shells that can be understood as a duality property of nuclei with respect to nucleons and quarks

Formation of H̅ in p̅-Ps collisions embedded in plasmas

NASA Astrophysics Data System (ADS)

Ratnavelu, Kuru; Ghoshal, Arijit; Nayek, Sujay; Bhattacharya, Arka; Mohamed Kamali, Mohd Zahurin

2016-04-01

Screening effects of plasmas on the formation of antihydrogen (H̅) in an arbitrary s-state from the ground state of the positronium atom (Ps) by antiproton (p̅) impact have been studied within the framework of charge-conjugation and time-reversal invariance. Two types of plasma environments have been considered, namely weakly coupled plasma and dense quantum plasma. For weakly coupled plasma, the interactions among the charged particles in plasma have been represented by Debye-Huckel screening model, whereas for dense quantum plasma, interactions among the charged particles in plasma have been represented by exponential cosine-screened Coulomb potentials. Effects of plasma screening on the antihydrogen formation cross section have been studied in the energy range 15-400 keV of incident antiproton. For the free atomic case, our results agree well with some of the most accurate results available in the literature. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

Effects of overlapping electric double layer on mass transport of a macro-solute across porous wall of a micro/nanochannel for power law fluid.

PubMed

Bhattacharjee, Saikat; Mondal, Mrinmoy; De, Sirshendu

2017-05-01

Effects of overlapping electric double layer and high wall potential on transport of a macrosolute for flow of a power law fluid through a microchannel with porous walls are studied in this work. The electric potential distribution is obtained by coupling the Poisson's equation without considering the Debye-Huckel approximation. The numerical solution shows that the center line potential can be 16% of wall potential at pH 8.5, at wall potential -73 mV and scaled Debye length 0.5. Transport phenomena involving mass transport of a neutral macrosolute is formulated by species advective equation. An analytical solution of Sherwood number is obtained for power law fluid. Effects of fluid rheology are studied in detail. Average Sherwood number is more for a pseudoplastic fluid compared to dilatant upto the ratio of Poiseuille to electroosmotic velocity of 5. Beyond that, the Sherwood number is independent of fluid rheology. Effects of fluid rheology and solute size on permeation flux and concentration of neutral solute are also quantified. More solute permeation occurs as the fluid changes from pseudoplastic to dilatant. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anti-screening optically allowed and forbidden collisional excitations in nonthermal astrophysical plasmas

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

Hong, Woo-Pyo; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr

2014-08-01

The influence of nonthermal shielding on the optically allowed and forbidden anti-screening channels for ion-ion collisional excitations is investigated in astrophysical Lorentzian plasmas. The semiclassical trajectory method and effective interaction Hamiltonian are employed to obtain the transition amplitudes, differential cross-sections, and momentum transfer-dependent effective projectile charges for the optically allowed and forbidden excitation channels as functions of the impact parameter, collision energy, Debye radius, and spectral index of nonthermal astrophysical plasmas. It is found that the nonthermal effect suppresses the ion-ion collisional excitation probability in astrophysical Lorentzian plasmas. Additionally, the influence of nonthermal shielding on the optically allowed transition ismore » found to be more significant than that on the optically forbidden transition. The variations of the nonthermal shielding effects on the optically allowed and forbidden anti-screening channels in astrophysical nonthermal plasmas are also discussed.« less

The origin of the Debye relaxation in liquid water and fitting the high frequency excess response.

PubMed

Elton, Daniel C

2017-07-19

We critically review the literature on the Debye absorption peak of liquid water and the excess response found on the high frequency side of the Debye peak. We find a lack of agreement on the microscopic phenomena underlying both of these features. To better understand the molecular origin of Debye peak we ran large scale molecular dynamics simulations and performed several different distance-dependent decompositions of the low frequency dielectric spectra, finding that it involves processes that take place on scales of 1.5-2.0 nm. We also calculated the k-dependence of the Debye relaxation, finding it to be highly dispersive. These findings are inconsistent with models that relate Debye relaxation to local processes such as the rotation/translation of molecules after H-bond breaking. We introduce the spectrumfitter Python package for fitting dielectric spectra and analyze different ways of fitting the high frequency excess, such as including one or two additional Debye peaks. We propose using the generalized Lydanne-Sachs-Teller (gLST) equation as a way of testing the physicality of model dielectric functions. Our attempts at fitting the experimental spectrum using the gLST relation as a constraint indicate that the traditional way of fitting the excess response with secondary and tertiary Debye relaxations is problematic. All of our work is consistent with the recent theory of Popov et al. (2016) that Debye relaxation is due to the migration of Bjerrum-like defects in the hydrogen bond network. Under this theory, the mechanism of Debye relaxation in liquid water is similar to the mechanism in ice, but the heterogeneity and power-law dynamics of the H-bond network in water results in excess response on the high frequency side of the peak.

Non Debye approximation on specific heat of solids

NASA Astrophysics Data System (ADS)

Bhattacharjee, Ruma; Das, Anamika; Sarkar, A.

2018-05-01

A simple non Debye frequency spectrum is proposed. The normalized frequency spectrum is compared to that of Debye spectrum. The proposed spectrum, provides a good account of low frequency phonon density of states, which gives a linear temperature variation at low temperature in contrast to Debye T3 law. It has been analyzed that the proposed model provides a good account of excess specific heat for nanostructure solid.

Combining the AFLOW GIBBS and elastic libraries to efficiently and robustly screen thermomechanical properties of solids

NASA Astrophysics Data System (ADS)

Toher, Cormac; Oses, Corey; Plata, Jose J.; Hicks, David; Rose, Frisco; Levy, Ohad; de Jong, Maarten; Asta, Mark; Fornari, Marco; Buongiorno Nardelli, Marco; Curtarolo, Stefano

2017-06-01

Thorough characterization of the thermomechanical properties of materials requires difficult and time-consuming experiments. This severely limits the availability of data and is one of the main obstacles for the development of effective accelerated materials design strategies. The rapid screening of new potential materials requires highly integrated, sophisticated, and robust computational approaches. We tackled the challenge by developing an automated, integrated workflow with robust error-correction within the AFLOW framework which combines the newly developed "Automatic Elasticity Library" with the previously implemented GIBBS method. The first extracts the mechanical properties from automatic self-consistent stress-strain calculations, while the latter employs those mechanical properties to evaluate the thermodynamics within the Debye model. This new thermoelastic workflow is benchmarked against a set of 74 experimentally characterized systems to pinpoint a robust computational methodology for the evaluation of bulk and shear moduli, Poisson ratios, Debye temperatures, Grüneisen parameters, and thermal conductivities of a wide variety of materials. The effect of different choices of equations of state and exchange-correlation functionals is examined and the optimum combination of properties for the Leibfried-Schlömann prediction of thermal conductivity is identified, leading to improved agreement with experimental results than the GIBBS-only approach. The framework has been applied to the AFLOW.org data repositories to compute the thermoelastic properties of over 3500 unique materials. The results are now available online by using an expanded version of the REST-API described in the Appendix.

Simulations of free-solution electrophoresis of polyelectrolytes with a finite Debye length using the Debye-Hückel approximation.

PubMed

Hickey, Owen A; Shendruk, Tyler N; Harden, James L; Slater, Gary W

2012-08-31

We introduce a mesoscale simulation method based on multiparticle collision dynamics (MPCD) for the electrohydrodynamics of polyelectrolytes with finite Debye lengths. By applying the Debye-Hückel approximation to assign an effective charge to MPCD particles near charged monomers, our simulations are able to reproduce the rapid rise in the electrophoretic mobility with respect to the degree of polymerization for the shortest polymer lengths followed by a small decrease for longer polymers due to charge condensation. Moreover, these simulations demonstrate the importance of a finite Debye length in accurately determining the mobility of uniformly charged polyelectrolytes and net neutral polyampholytes.

Electron-ion collision rates in noble gas clusters irradiated by femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Dey, R.; Roy, A. C.

2012-05-01

We report a theoretical analysis of electron-ion collision rates in xenon gas clusters irradiated by femtosecond laser pulses. The present analysis is based on the eikonal approximation (EA), the first Born approximation (FBA) and the classical (CL) methods. The calculations are performed using the plasma-screened Rogers potential introduced by Moll et al. [J. Phys. B. 43, 135103 (2010)] as well as the Debye potential for a wide range of experimental parameters. We find that the magnitudes of electron-ion collision frequency obtained in the EA do not fall as rapidly with the kinetic energy of electrons as in the FBA and CL methods for higher charge states of xenon ion (Xe8+ and Xe14+). Furthermore, EA shows that the effect of the inner structure of ion is most dominant for the lowest charge state of xenon ion (Xe1+). In the case of the present effective potential, FBA overestimates the CL results for all three different charge states of xenon, whereas for the Debye potential, both the FBA and CL methods predict collision frequencies which are nearly close to each other.

Debye-Scherrer simulation and its use for nano-materials testing

NASA Astrophysics Data System (ADS)

Kalabushkin, Alexander E.

2005-04-01

Nano-material specimens of metallic glass were tested with the Debye-Scherrer x-ray diffraction method. For data simulation and data treatment new Debye-Scherrer simulator was devised. The simulator and test results are discussed.

Attractive potential around a thermionically emitting microparticle.

PubMed

Delzanno, G L; Lapenta, G; Rosenberg, M

2004-01-23

We present a simulation study of the charging of a dust grain immersed in a plasma, considering the effect of thermionic electron emission from the grain. It is shown that the orbit motion limited theory is no longer reliable when electron emission becomes large: screening can no longer be treated within the Debye-Huckel approach and an attractive potential well can form, leading to the possibility of attractive forces on other grains with the same polarity. We suggest to perform laboratory experiments where emitting dust grains could be used to create nonconventional dust crystals or macromolecules.

Photorefractive Tungsten Bronze Crystals for Optical Limiters and Filters.

DTIC Science & Technology

1996-01-01

vector , X is the laser light wavelength, 0 is the half- angle between the two crossing laser beams, and k0 is the Debye screening wave vector given by...between the grating and the dielectric constant E’ = 950) such that the grating’ vector is interference pattern, the intensities of the output beams from...substituting Io, I, and Id into expression 0 ple d 2o0o 25i00 (8), we can calculate the phase shift between the grating and Applied Electric Feild in V

Free-energy functional of the Debye-Hückel model of simple fluids

NASA Astrophysics Data System (ADS)

Piron, R.; Blenski, T.

2016-12-01

The Debye-Hückel approximation to the free energy of a simple fluid is written as a functional of the pair correlation function. This functional can be seen as the Debye-Hückel equivalent to the functional derived in the hypernetted chain framework by Morita and Hiroike, as well as by Lado. It allows one to obtain the Debye-Hückel integral equation through a minimization with respect to the pair correlation function, leads to the correct form of the internal energy, and fulfills the virial theorem.

Effective surface Debye temperature for NiMnSb(100) epitaxial films

NASA Astrophysics Data System (ADS)

Borca, C. N.; Komesu, Takashi; Jeong, Hae-kyung; Dowben, P. A.; Ristoiu, D.; Hordequin, Ch.; Pierre, J.; Nozières, J. P.

2000-07-01

The surface Debye temperature of the NiMnSb (100) epitaxial films has been obtained using low energy electron diffraction, inverse photoemission, and core-level photoemission. The normal dynamic motion of the (100) surface results in a value for the effective surface Debye temperature of 145±13 K. This is far smaller than the bulk Debye temperature of 312±5 K obtained from wave vector dependent inelastic neutron scattering. The large difference between these measures of surface and bulk dynamic motion indicates a soft and compositionally different (100) surface.

Elucidation of spin echo small angle neutron scattering correlation functions through model studies.

PubMed

Shew, Chwen-Yang; Chen, Wei-Ren

2012-02-14

Several single-modal Debye correlation functions to approximate part of the overall Debey correlation function of liquids are closely examined for elucidating their behavior in the corresponding spin echo small angle neutron scattering (SESANS) correlation functions. We find that the maximum length scale of a Debye correlation function is identical to that of its SESANS correlation function. For discrete Debye correlation functions, the peak of SESANS correlation function emerges at their first discrete point, whereas for continuous Debye correlation functions with greater width, the peak position shifts to a greater value. In both cases, the intensity and shape of the peak of the SESANS correlation function are determined by the width of the Debye correlation functions. Furthermore, we mimic the intramolecular and intermolecular Debye correlation functions of liquids composed of interacting particles based on a simple model to elucidate their competition in the SESANS correlation function. Our calculations show that the first local minimum of a SESANS correlation function can be negative and positive. By adjusting the spatial distribution of the intermolecular Debye function in the model, the calculated SESANS spectra exhibit the profile consistent with that of hard-sphere and sticky-hard-sphere liquids predicted by more sophisticated liquid state theory and computer simulation. © 2012 American Institute of Physics

Kinetics of Diffusional Droplet Growth in a Liquid/Liquid Two-Phase System

NASA Technical Reports Server (NTRS)

Glicksman, M. E.; Fradkov, V. E.

1996-01-01

We address the problem of diffusional interactions in a finite sized cluster of spherical particles for volume fractions, V(sub v) in the range 0-0.01. We determined the quasi-static monopole diffusion solution for n particles distributed at random in a continuous matrix. A global mass conservation condition is employed, obviating the need for any external boundary condition. The numerical results provide the instantaneous (snapshot) growth or shrinkage rate of each particle, precluding the need for extensive time-dependent computations. The close connection between these snapshot results and the coarsegrained kinetic constants are discussed. A square-root dependence of the deviations of the rate constants from their zero volume fraction value is found for the higher V(sub v) investigated. This behavior is consistent with predictions from diffusion Debye-Huckel screening theory. By contrast, a cube-root dependence, reported in earlier numerical studies, is found for the lower V(sub v) investigated. The roll-over region of the volume fraction where the two asymptotics merge depends on the number of particles, n, alone. A theoretical estimate for the roll-over point predicts that the corresponding V(sub v) varies as n(sup -2), in good agreement with the numerical results.

Large divalent cations and electrostatic potentials adjacent to membranes. Experimental results with hexamethonium.

PubMed Central

Alvarez, O; Brodwick, M; Latorre, R; McLaughlin, A; McLaughlin, S; Szabo, G

1983-01-01

A simple extension of the Gouy-Chapman theory predicts that the ability of a divalent cation to screen charges at a membrane-solution interface decreases significantly if the distance between the charges on the cation is comparable with the Debye length. We tested this prediction by investigating the effect of hexamethonium on the electrostatic potential adjacent to negatively charged phospholipid bilayer membranes. The distance between the two charges of an extended hexamethonium molecule is approximately 1 nm, which is the Debye length in the 0.1 M monovalent salt solutions used in these experiments. Six different experimental approaches were utilized. We measured the electrophoretic mobility of multilamellar vesicles to determine the zeta potential, the line width of the 31P nuclear magnetic resonance (NMR) signal from sonicated vesicles to calculate the change in potential at the phosphodiester moiety of the lipid, and the conductance of planar bilayer membranes exposed to either carriers (nonactin) or pore formers (gramicidin) to estimate the change in potential within the membrane. We also measured directly the effect of hexamethonium on the potential above a monolayer formed from negative lipids, and attempted to calculate the change in the surface potential of a bilayer membrane from capacitance measurements. With the exception of the capacitance calculations, each of the techniques gave comparable results: hexamethonium exerts a smaller effect on the potential than that predicted by the classic screening theory. The results are consistent with the predictions of the extended Gouy-Chapman theory and are relevant to the interpretation of physiological and pharmacological experiments that utilize hexamethonium and other large divalent cations. PMID:6198001

Resumming the large-N approximation for time evolving quantum systems

NASA Astrophysics Data System (ADS)

Mihaila, Bogdan; Dawson, John F.; Cooper, Fred

2001-05-01

In this paper we discuss two methods of resumming the leading and next to leading order in 1/N diagrams for the quartic O(N) model. These two approaches have the property that they preserve both boundedness and positivity for expectation values of operators in our numerical simulations. These approximations can be understood either in terms of a truncation to the infinitely coupled Schwinger-Dyson hierarchy of equations, or by choosing a particular two-particle irreducible vacuum energy graph in the effective action of the Cornwall-Jackiw-Tomboulis formalism. We confine our discussion to the case of quantum mechanics where the Lagrangian is L(x,ẋ)=(12)∑Ni=1x˙2i-(g/8N)[∑Ni=1x2i- r20]2. The key to these approximations is to treat both the x propagator and the x2 propagator on similar footing which leads to a theory whose graphs have the same topology as QED with the x2 propagator playing the role of the photon. The bare vertex approximation is obtained by replacing the exact vertex function by the bare one in the exact Schwinger-Dyson equations for the one and two point functions. The second approximation, which we call the dynamic Debye screening approximation, makes the further approximation of replacing the exact x2 propagator by its value at leading order in the 1/N expansion. These two approximations are compared with exact numerical simulations for the quantum roll problem. The bare vertex approximation captures the physics at large and modest N better than the dynamic Debye screening approximation.

Model for screened, charge-regulated electrostatics of an eye lens protein: Bovine gammaB-crystallin

PubMed Central

Wahle, Christopher W.; Martini, K. Michael; Hollenbeck, Dawn M.; Langner, Andreas; Ross, David S.; Hamilton, John F.; Thurston, George M.

2018-01-01

We model screened, site-specific charge regulation of the eye lens protein bovine gammaB-crystallin (γ B) and study the probability distributions of its proton occupancy patterns. Using a simplified dielectric model, we solve the linearized Poisson-Boltzmann equation to calculate a 54 × 54 work-of-charging matrix, each entry being the modeled voltage at a given titratable site, due to an elementary charge at another site. The matrix quantifies interactions within patches of sites, including γB charge pairs. We model intrinsic pK values that would occur hypothetically in the absence of other charges, with use of experimental data on the dependence of pK values on aqueous solution conditions, the dielectric model, and literature values. We use Monte Carlo simulations to calculate a model grand-canonical partition function that incorporates both the work-of-charging and the intrinsic pK values for isolated γB molecules and we calculate the probabilities of leading proton occupancy configurations, for 4 < pH < 8 and Debye screening lengths from 6 to 20 Å. We select the interior dielectric value to model γB titration data. At pH 7.1 and Debye length 6.0 Å, on a given γB molecule the predicted top occupancy pattern is present nearly 20% of the time, and 90% of the time one or another of the first 100 patterns will be present. Many of these occupancy patterns differ in net charge sign as well as in surface voltage profile. We illustrate how charge pattern probabilities deviate from the multinomial distribution that would result from use of effective pK values alone and estimate the extents to which γB charge pattern distributions broaden at lower pH and narrow as ionic strength is lowered. These results suggest that for accurate modeling of orientation-dependent γB-γB interactions, consideration of numerous pairs of proton occupancy patterns will be needed. PMID:29346981

Model for screened, charge-regulated electrostatics of an eye lens protein: Bovine gammaB-crystallin.

PubMed

Wahle, Christopher W; Martini, K Michael; Hollenbeck, Dawn M; Langner, Andreas; Ross, David S; Hamilton, John F; Thurston, George M

2017-09-01

We model screened, site-specific charge regulation of the eye lens protein bovine gammaB-crystallin (γB) and study the probability distributions of its proton occupancy patterns. Using a simplified dielectric model, we solve the linearized Poisson-Boltzmann equation to calculate a 54×54 work-of-charging matrix, each entry being the modeled voltage at a given titratable site, due to an elementary charge at another site. The matrix quantifies interactions within patches of sites, including γB charge pairs. We model intrinsic pK values that would occur hypothetically in the absence of other charges, with use of experimental data on the dependence of pK values on aqueous solution conditions, the dielectric model, and literature values. We use Monte Carlo simulations to calculate a model grand-canonical partition function that incorporates both the work-of-charging and the intrinsic pK values for isolated γB molecules and we calculate the probabilities of leading proton occupancy configurations, for 4

Model for screened, charge-regulated electrostatics of an eye lens protein: Bovine gammaB-crystallin

NASA Astrophysics Data System (ADS)

Wahle, Christopher W.; Martini, K. Michael; Hollenbeck, Dawn M.; Langner, Andreas; Ross, David S.; Hamilton, John F.; Thurston, George M.

2017-09-01

We model screened, site-specific charge regulation of the eye lens protein bovine gammaB-crystallin (γ B ) and study the probability distributions of its proton occupancy patterns. Using a simplified dielectric model, we solve the linearized Poisson-Boltzmann equation to calculate a 54 ×54 work-of-charging matrix, each entry being the modeled voltage at a given titratable site, due to an elementary charge at another site. The matrix quantifies interactions within patches of sites, including γ B charge pairs. We model intrinsic p K values that would occur hypothetically in the absence of other charges, with use of experimental data on the dependence of p K values on aqueous solution conditions, the dielectric model, and literature values. We use Monte Carlo simulations to calculate a model grand-canonical partition function that incorporates both the work-of-charging and the intrinsic p K values for isolated γ B molecules and we calculate the probabilities of leading proton occupancy configurations, for 4

Electrostatic contribution to the persistence length of a semiflexible dipolar chain.

PubMed

Podgornik, Rudi

2004-09-01

We investigate the electrostatic contribution to the persistence length of a semiflexible polymer chain whose segments interact via a screened Debye-Hückel dipolar interaction potential. We derive the expressions for the renormalized persistence length on the level of a 1/D-expansion method already successfully used in other contexts of polyelectrolye physics. We investigate different limiting forms of the renormalized persistence length of the dipolar chain and show that, in, general, it depends less strongly on the screening length than in the context of a monopolar chain. We show that for a dipolar chain the electrostatic persistence length in the same regime of the parameter phase space as the original Odijk-Skolnick-Fixman (OSF) form for a monopolar chain depends logarithmically on the screening length rather than quadratically. This can be understood solely on the basis of a swifter decay of the dipolar interactions with separation compared to the monopolar electrostatic interactions. We comment also on the general contribution of higher multipoles to the electrostatic renormalization of the bending rigidity.

Correlation potential of a test ion near a strongly charged plate.

PubMed

Lu, Bing-Sui; Xing, Xiangjun

2014-03-01

We analytically calculate the correlation potential of a test ion near a strongly charged plate inside a dilute m:-n electrolyte. We do this by calculating the electrostatic Green's function in the presence of a nonlinear background potential, the latter having been obtained using the nonlinear Poisson-Boltzmann theory. We consider the general case where the dielectric constants of the plate and the electrolyte are distinct. The following generic results emerge from our analyses: (1) If the distance to the plate Δz is much larger than a Gouy-Chapman length, the plate surface will behave effectively as an infinitely charged surface, and the dielectric constant of the plate effectively plays no role. (2) If Δz is larger than a Gouy-Chapman length but shorter than a Debye length, the correlation potential can be interpreted in terms of an image charge that is three times larger than the source charge. This behavior is independent of the valences of the ions. (3) The Green's function vanishes inside the plate if the surface charge density is infinitely large; hence the electrostatic potential is constant there. In this respect, a strongly charged plate behaves like a conductor plate. (4) If Δz is smaller than a Gouy-Chapman length, the correlation potential is dominated by the conventional image charge due to the dielectric discontinuity at the interface. (5) If Δz is larger than a Debye length, the leading order behavior of the correlation potential will depend on the valences of the ions in the electrolyte. Furthermore, inside an asymmetric electrolyte, the correlation potential is singly screened, i.e., it undergoes exponential decay with a decay width equal to the Debye length.

One-dimensional conduction through supporting electrolytes: two-scale cathodic Debye layer.

PubMed

Almog, Yaniv; Yariv, Ehud

2011-10-01

Supporting-electrolyte solutions comprise chemically inert cations and anions, produced by salt dissolution, together with a reactive ionic species that may be consumed and generated on bounding ion-selective surfaces (e.g., electrodes or membranes). Upon application of an external voltage, a Faraday current is thereby established. It is natural to analyze this ternary-system process through a one-dimensional transport problem, employing the thin Debye-layer limit. Using a simple model of ideal ion-selective membranes, we have recently addressed this problem for moderate voltages [Yariv and Almog, Phys. Rev. Lett. 105, 176101 (2010)], predicting currents that scale as a fractional power of Debye thickness. We address herein the complementary problem of moderate currents. We employ matched asymptotic expansions, separately analyzing the two inner thin Debye layers adjacent to the ion-selective surfaces and the outer electroneutral region outside them. A straightforward calculation following comparable singular-perturbation analyses of binary systems is frustrated by the prediction of negative ionic concentrations near the cathode. Accompanying numerical simulations, performed for small values of Debye thickness, indicate a number unconventional features occurring at that region, such as inert-cation concentration amplification and electric-field intensification. The current-voltage correlation data of the electrochemical cell, obtained from compilation of these simulations, does not approach a limit as the Debye thickness vanishes. Resolution of these puzzles reveals a transformation of the asymptotic structure of the cathodic Debye layer. This reflects the emergence of an internal boundary layer, adjacent to the cathode, wherein field and concentration scaling differs from those of the Gouy-Chapman theory. The two-scale feature of the cathodic Debye layer is manifested through a logarithmic voltage scaling with Debye thickness. Accounting for this scaling, the complied current-voltage data collapses upon a single curve. This curve practically coincides with an asymptotically calculated universal current-voltage relation.

On behavior peculiarity of electron plasma

NASA Astrophysics Data System (ADS)

Gordeeva, N. M.; Yushkanov, A. A.

2018-03-01

The analysis of the analytical solution of the problem of the behavior of electron plasma in the AC electric field is fulfilled. Debye mode describes shielding of the external electric field in the plasma. The analysis of the region of existence of Debye mode, depending on the plasma parameters has been realized. A non-trivial dependence of the region of existence of Debye mode on the degree of degeneracy of the electron gas are revealed. For the case of nearly degenerate electron gas Debye mode has several areas of existence, depending on the frequency of the electric field.

A statistical model of a metallic inclusion in semiconducting media

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

Shikin, V. B., E-mail: shikin@issp.ac.ru

The properties of an isolated multicharged atom embedded into a semiconducting medium are discussed. The analysis generalizes the results of the known Thomas–Fermi theory for a multicharged (Z ≫ 1) atom in vacuum when it is immersed into an electron–hole gas of finite temperature. The Thomas–Fermi–Debye (TFD) atom problem is directly related to the properties of donors in low-doped semiconductors and is alternative in its conclusions to the ideal scenario of dissociation of donors. In the existing ideal statistics, an individual donor under infinitely low doping is completely ionized (a charged center does not hold its neutralizing counter-ions). A Thomas–Fermi–Debyemore » atom (briefly, a TFD donor) remains a neutral formation that holds its screening “coat” even for infinitely low doping level, i.e., in the region of n{sub d}λ{sub 0}{sup 3} ≪ 1, where n{sub d} is the concentration of the doping impurity and λ{sub 0} is the Debye length with the parameters of intrinsic semiconductor. Various observed consequences in the behavior of a TFD donor are discussed that allow one to judge the reality of the implications of the TFD donor model.« less

Inflation of the screening length induced by Bjerrum pairs.

PubMed

Zwanikken, Jos; van Roij, René

2009-10-21

Within a modified Poisson-Boltzmann theory we study the effect of Bjerrum pairs on the typical length scale [Formula: see text] over which electric fields are screened in electrolyte solutions, taking into account a simple association-dissociation equilibrium between free ions and Bjerrum pairs. At low densities of Bjerrum pairs, this length scale is well approximated by the Debye length [Formula: see text], with ρ(s) the free-ion density. At high densities of Bjerrum pairs, however, we find [Formula: see text], which is significantly larger than 1/κ due to the enhanced effective permittivity of the electrolyte, caused by the polarization of Bjerrum pairs. We argue that this mechanism may explain the recently observed anomalously large colloid-free zones between an oil-dispersed colloidal crystal and a colloidal monolayer at the oil-water interface.

Thermodynamic properties and theoretical rocket performance of hydrogen to 100,000 K and 1.01325 x 10 to the 8th power N/sq m

NASA Technical Reports Server (NTRS)

Patch, R. W.

1971-01-01

The composition and thermodynamic properties were calculated for 100 to 110,000 K and 1.01325 x 10 to the 2nd power to 1.01325 x 10 to the 8th power N/sq m for chemical equilibrium in the Debye-Huckel and ideal-gas approximations. Quantities obtained were the concentrations of hydrogen atoms, protons, free electrons, hydrogen molecules, negative hydrogen ions, hydrogen diatomic molecular ions, and hydrogen triatomic molecular ions, and the enthalpy, entropy, average molecular weight, specific heat at constant pressure, density, and isentropic exponent. Electronically excited states of H and H2 were included. Choked, isentropic, one-dimensional nozzle flow with shifting chemical equilibrium was calculated to the Debye-Huckel and ideal-gas approximations for stagnation temperatures from 2500 to 100,000 K. The mass flow per unit throat area and the sonic flow factor were obtained. The pressure ratio, temperature, velocity, and ideal and vacuum specific impulses at the throat and for pressure ratios as low as 0.000001 downstream were found. For high temperatures at pressures approaching 1.01325 x 10 to the 8th power N/sq m, the ideal-gas approximation was found to be inadequate for calculations of composition, precise thermodynamic properties, and precise nozzle flow. The greatest discrepancy in nozzle flow occurred in the exit temperature, which was as much as 21 percent higher when the Debye-Huckel approximation was used.

Fields in laser-ablated plasmas generalized to degenerate electrons and to Fermi energy in nuclei with change to quark-gluon plasma

NASA Astrophysics Data System (ADS)

Hora, Heinrich; Miley, George H.; Osman, Frederick; Hammerling, Peter X.

2004-09-01

The studies of laser ablation have lead to a new theory of nuclei, endothermic nuclei generation and quark-gluon plasmas. The surface of ablated plasma expanding into vacuum after high power laser irradiation of targets, contains an electric double layer having the thickness of the Debye length. This led to the discovery of surface tension of plasmas and to the internal dynamic electric fields in all inhomogeneous plasmas. The surface causes stabilization by short length surface waves smoothing the expanding plasma plume. Generalizing this to the degenerate electrons in a metal with the Fermi energy instead of the temperature, resulted in the surface tension of metals in agreement with measurements. Taking then the Fermi energy in the Debye length for nucleons results in a theory of nuclei with stable confinement of protons and neutrons just at the well known nuclear density, and in the Debye length equal to Hofstadter's decay of the nuclear surface. Increasing the nuclear density by a factor of 6 leads to the change of the Fermi energy into its relativistic branch where no surface energy is possible and the particle mass is not defined, permitting the quark-gluon plasma. Expansion of this higher density at the big band or in a supernova results in nucleation and element generation. The Boltzmann equilibrium permits the synthesis of nuclei even in the endothermic range limited to about uranium.

Self-Consistent Approach to Global Charge Neutrality in Electrokinetics: A Surface Potential Trap Model

NASA Astrophysics Data System (ADS)

Wan, Li; Xu, Shixin; Liao, Maijia; Liu, Chun; Sheng, Ping

2014-01-01

In this work, we treat the Poisson-Nernst-Planck (PNP) equations as the basis for a consistent framework of the electrokinetic effects. The static limit of the PNP equations is shown to be the charge-conserving Poisson-Boltzmann (CCPB) equation, with guaranteed charge neutrality within the computational domain. We propose a surface potential trap model that attributes an energy cost to the interfacial charge dissociation. In conjunction with the CCPB, the surface potential trap can cause a surface-specific adsorbed charge layer σ. By defining a chemical potential μ that arises from the charge neutrality constraint, a reformulated CCPB can be reduced to the form of the Poisson-Boltzmann equation, whose prediction of the Debye screening layer profile is in excellent agreement with that of the Poisson-Boltzmann equation when the channel width is much larger than the Debye length. However, important differences emerge when the channel width is small, so the Debye screening layers from the opposite sides of the channel overlap with each other. In particular, the theory automatically yields a variation of σ that is generally known as the "charge regulation" behavior, attendant with predictions of force variation as a function of nanoscale separation between two charged surfaces that are in good agreement with the experiments, with no adjustable or additional parameters. We give a generalized definition of the ζ potential that reflects the strength of the electrokinetic effect; its variations with the concentration of surface-specific and surface-nonspecific salt ions are shown to be in good agreement with the experiments. To delineate the behavior of the electro-osmotic (EO) effect, the coupled PNP and Navier-Stokes equations are solved numerically under an applied electric field tangential to the fluid-solid interface. The EO effect is shown to exhibit an intrinsic time dependence that is noninertial in its origin. Under a step-function applied electric field, a pulse of fluid flow is followed by relaxation to a new ion distribution, owing to the diffusive counter current. We have numerically evaluated the Onsager coefficients associated with the EO effect, L21, and its reverse streaming potential effect, L12, and show that L12=L21 in accordance with the Onsager relation. We conclude by noting some of the challenges ahead.

Thermodynamics of rough colloidal surfaces

NASA Astrophysics Data System (ADS)

Goldstein, Raymond E.; Halsey, Thomas C.; Leibig, Michael

1991-03-01

In Debye-Hückel theory, the free energy of an electric double layer near a colloidal (or any other) surface can be related to the statistics of random walks near that surface. We present a numerical method based on this correspondence for the calculation of the double-layer free energy for an arbitrary charged or conducting surface. For self-similar surfaces, we propose a scaling law for the behavior of the free energy as a function of the screening length and the surface dimension. This scaling law is verified by numerical computation. Capacitance measurements on rough surfaces of, e.g., colloids can test these predictions.

Stimulated Scattering and Phase Conjugation in Photorefractive Materials

DTIC Science & Technology

1992-01-31

than the grating in the deep traps. Bal’iO3 . 2 -15 Recently Brost et al. explained the intensity We predict that if the shallow traps can accumulate a...BSO and BaTiO 3 and induced transparency for Sr < so. Brost et al." ob- for I < 101 V/cm,. served that optical absorption of their BaTiO3 sample at A...flop crystal). Brost et al.’ showed 0 < 71 -< 1. In addition the Debye screening wave vector, that ko increased by -50%,’c between I = 2 x 10 - 3 W/cm

New Developments in the Theory of HTSC [High Temperature Superconductors

DOE R&D Accomplishments Database

Abrikosov, A.A.

1994-09-01

The superconductor is supposed to consist of alternating layers of two kinds: (1) layers with an attractive electron interaction and an effective mass of usual magnitude, (2) layers without interaction and with a large effective mass. The overlap between the layers is assumed to be small, its energy, t, being much less than {Delta}. It is shown, that such a model explains the most peculiar property found in experiments on electronic Raman light scattering in BSCCO 2212: different threshold values for the Raman satellite measured at two different polarizations of the incident and scattered light. The tunneling conductance G(V)= dJ/dV is analyzed for the same model. In order to fit the qualitative features of experimental data, it is assumed that the tunneling probability to the normal layers is much less, than to the superconducting layers. The conductance is calculated for the case t{much_lt}{Delta}. A brief analysis is given for the case t{approximately}{Delta}, which proves that such an assumption definitely contradicts the experimental data for BSCCO. The possible nature of the electronic states in the normal layers is discussed. In connection with the experimental discovery (angle resolved photoemission spectroscopy, ARPES) of the extended saddle point singularities in the electron spectrum of a variety of HTSC consequences are derived for T{sub c} and {Delta} in a simple model. A large enhancement of superconductivity is possible if the singularity has a sufficient extension and is located close to the Fermi energy. In order to explain the anisotropy of the energy gap, observed in ARPES experiments, on the basis of the "extended saddle point singularities" an assumption is done that the Coulomb interactions are weakly screened, i.e. the Debye screening radius is much larger than the lattice period; this makes the electron interaction long ranged (E-L model).

Electrostatic stability of electron-positron plasmas in dipole geometry

NASA Astrophysics Data System (ADS)

Mishchenko, Alexey; Plunk, Gabriel G.; Helander, Per

2018-04-01

The electrostatic stability of electron-positron plasmas is investigated in the point-dipole and Z-pinch limits of dipole geometry. The kinetic dispersion relation for sub-bounce-frequency instabilities is derived and solved. For the zero-Debye-length case, the stability diagram is found to exhibit singular behaviour. However, when the Debye length is non-zero, a fluid mode appears, which resolves the observed singularity, and also demonstrates that both the temperature and density gradients can drive instability. It is concluded that a finite Debye length is necessary to determine the stability boundaries in parameter space. Landau damping is investigated at scales sufficiently smaller than the Debye length, where instability is absent.

Important Variation in Vibrational Properties of LiFePO4 and FePO4 Induced by Magnetism

PubMed Central

Seifitokaldani, Ali; Gheribi, Aïmen E.; Phan, Anh Thu; Chartrand, Patrice; Dollé, Mickaël

2016-01-01

A new thermodynamically self-consistent (TSC) method, based on the quasi-harmonic approximation (QHA), is used to obtain the Debye temperatures of LiFePO4 (LFP) and FePO4 (FP) from available experimental specific heat capacities for a wide temperature range. The calculated Debye temperatures show an interesting critical and peculiar behavior so that a steep increase in the Debye temperatures is observed by increasing the temperature. This critical behavior is fitted by the critical function and the adjusted critical temperatures are very close to the magnetic phase transition temperatures in LFP and FP. Hence, the critical behavior of the Debye temperatures is correlated with the magnetic phase transitions in these compounds. Our first-principle calculations support our conjecture that the change in electronic structures, i.e. electron density of state and electron localization function, and consequently the change in thermophysical properties due to the magnetic transition may be the reason for the observation of this peculiar behavior of the Debye temperatures. PMID:27604551

Important Variation in Vibrational Properties of LiFePO4 and FePO4 Induced by Magnetism

NASA Astrophysics Data System (ADS)

Seifitokaldani, Ali; Gheribi, Aïmen E.; Phan, Anh Thu; Chartrand, Patrice; Dollé, Mickaël

2016-09-01

A new thermodynamically self-consistent (TSC) method, based on the quasi-harmonic approximation (QHA), is used to obtain the Debye temperatures of LiFePO4 (LFP) and FePO4 (FP) from available experimental specific heat capacities for a wide temperature range. The calculated Debye temperatures show an interesting critical and peculiar behavior so that a steep increase in the Debye temperatures is observed by increasing the temperature. This critical behavior is fitted by the critical function and the adjusted critical temperatures are very close to the magnetic phase transition temperatures in LFP and FP. Hence, the critical behavior of the Debye temperatures is correlated with the magnetic phase transitions in these compounds. Our first-principle calculations support our conjecture that the change in electronic structures, i.e. electron density of state and electron localization function, and consequently the change in thermophysical properties due to the magnetic transition may be the reason for the observation of this peculiar behavior of the Debye temperatures.

Important Variation in Vibrational Properties of LiFePO4 and FePO4 Induced by Magnetism.

PubMed

Seifitokaldani, Ali; Gheribi, Aïmen E; Phan, Anh Thu; Chartrand, Patrice; Dollé, Mickaël

2016-09-08

A new thermodynamically self-consistent (TSC) method, based on the quasi-harmonic approximation (QHA), is used to obtain the Debye temperatures of LiFePO4 (LFP) and FePO4 (FP) from available experimental specific heat capacities for a wide temperature range. The calculated Debye temperatures show an interesting critical and peculiar behavior so that a steep increase in the Debye temperatures is observed by increasing the temperature. This critical behavior is fitted by the critical function and the adjusted critical temperatures are very close to the magnetic phase transition temperatures in LFP and FP. Hence, the critical behavior of the Debye temperatures is correlated with the magnetic phase transitions in these compounds. Our first-principle calculations support our conjecture that the change in electronic structures, i.e. electron density of state and electron localization function, and consequently the change in thermophysical properties due to the magnetic transition may be the reason for the observation of this peculiar behavior of the Debye temperatures.

Electron Debye scale Kelvin-Helmholtz instability: Electrostatic particle-in-cell simulations

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

Lee, Sang-Yun; Lee, Ensang, E-mail: eslee@khu.ac.kr; Kim, Khan-Hyuk

2015-12-15

In this paper, we investigated the electron Debye scale Kelvin-Helmholtz (KH) instability using two-dimensional electrostatic particle-in-cell simulations. We introduced a velocity shear layer with a thickness comparable to the electron Debye length and examined the generation of the KH instability. The KH instability occurs in a similar manner as observed in the KH instabilities in fluid or ion scales producing surface waves and rolled-up vortices. The strength and growth rate of the electron Debye scale KH instability is affected by the structure of the velocity shear layer. The strength depends on the magnitude of the velocity and the growth ratemore » on the velocity gradient of the shear layer. However, the development of the electron Debye scale KH instability is mainly determined by the electric field generated by charge separation. Significant mixing of electrons occurs across the shear layer, and a fraction of electrons can penetrate deeply into the opposite side fairly far from the vortices across the shear layer.« less

Assessing the feasibility of low temperature XAFS experiments at Indus-2, India: First results

NASA Astrophysics Data System (ADS)

Ramanan, Nitya; Rajput, Parasmani; Jha, S. N.; Lahiri, Debdutta

2015-05-01

In this work, we report installation of displex cryostat XAFS sample holder at XAFS beamline (BL-09) of Indus-2 synchrotron facility, India and make critical assessment of feasibility of low-temperature XAFS experiments in terms of data quality and reproducibility, temperature range, calibration and attainable resolution. We adopted the Debye Model-based calibration method by measuring XAFS of standard Au foil with known Debye temperature (ΘDebye)Autheory = 165 K. The data is of good quality and reproducible with international data. By fitting Debye Waller Factor (σexpt2 (T)), we deduced (ΘDebye)Auexpt = 163 K which implies calibration within 2 K. Error bars for σexpt2 (T) correspond to temperature uncertainty ΔT ≤ 5 K, which defines the temperature resolution for low temperature XAFS experiments. Thus, from both calibration and resolution points-of-view, this work demonstrates the feasibility of low temperature XAFS experiments at BL-09, Indus-2. Feasibility of extending XAFS experiments to lower temperature and unknown samples is discussed.

Numerical experiments on charging of a spherical body in a plasma with Maxwellian distributions of charged particles

NASA Astrophysics Data System (ADS)

Krasovsky, Victor L.; Kiselyov, Alexander A.

2017-12-01

New results of numerical simulation of collisionless plasma perturbation caused by a sphere absorbing electrons and ions are presented. Consideration is given to nonstationary phenomena accompanying the process of charging as well as to plasma steady state reached at long times. Corresponding asymptotic values of charges of the sphere and trapped-ion cloud around it have been found along with self-consistent electric field pattern depending on parameters of the unperturbed plasma. It is established that contribution of the trapped ions to screening of the charged sphere can be quite significant, so that the screening becomes essentially nonlinear in nature. A simple interconnection between the sphere radius, electron and ion Debye lengths has been revealed as the condition for maximum trapped-ion effect. Kinetic structure of the space charge induced in the plasma is discussed with relation to the specific form of the unperturbed charged particle distribution functions.

Effective Coulomb force modeling for spacecraft in Earth orbit plasmas

NASA Astrophysics Data System (ADS)

Seubert, Carl R.; Stiles, Laura A.; Schaub, Hanspeter

2014-07-01

Coulomb formation flight is a concept that utilizes electrostatic forces to control the separations of close proximity spacecraft. The Coulomb force between charged bodies is a product of their size, separation, potential and interaction with the local plasma environment. A fast and accurate analytic method of capturing the interaction of a charged body in a plasma is shown. The Debye-Hückel analytic model of the electrostatic field about a charged sphere in a plasma is expanded to analytically compute the forces. This model is fitted to numerical simulations with representative geosynchronous and low Earth orbit (GEO and LEO) plasma environments using an effective Debye length. This effective Debye length, which more accurately captures the charge partial shielding, can be up to 7 times larger at GEO, and as great as 100 times larger at LEO. The force between a sphere and point charge is accurately captured with the effective Debye length, as opposed to the electron Debye length solutions that have errors exceeding 50%. One notable finding is that the effective Debye lengths in LEO plasmas about a charged body are increased from centimeters to meters. This is a promising outcome, as the reduced shielding at increased potentials provides sufficient force levels for operating the electrostatically inflated membrane structures concept at these dense plasma altitudes.

Temperature and pressure dependent thermodynamic behavior of 2H-CuInO2

NASA Astrophysics Data System (ADS)

Bhamu, K. C.

2018-05-01

Density functional theory and quasi-harmonic Debye model has been used to study the thermodynamic properties of 2H-CuInO2. At the optimized structural parameters, pressure (0 to 80 GPa) dependent variation in the various thermodynamic properties, i.e. unit cell volume (V), bulk modulus (B), specific heat (Cv), Debye temperature (θD), Grüneisen parameter (γ) and thermal expansion coefficient (α) are calculated for various temperature values. The results predict that the pressure has significant effect on unit cell volume and bulk modulus while the temperature shows negligible effect on both parameters. With increasing temperature thermal expansion coefficient increase while with increasing pressure it decreases. The specific heat remains close to zero for ambient pressure and temperature values and it increases with increasing temperature. It is observed that the pressure has high impact on Debye temperature and Grüneisen parameter instead of temperature. Debye temperature and Grüneisen parameter both remains almost constant for the temperature range (0-300K) while Grüneisen parameter decrease with increasing pressure at constant temperature and Debye temperature increases rapidly with increasing pressure. An increase in Debye temperature with respect to pressure shows that the thermal vibration frequency changes rapidly.

Detection beyond the Debye screening length in a high-frequency nanoelectronic biosensor.

PubMed

Kulkarni, Girish S; Zhong, Zhaohui

2012-02-08

Nanosensors based on the unique electronic properties of nanotubes and nanowires offer high sensitivity and have the potential to revolutionize the field of Point-of-Care (POC) medical diagnosis. The direct current (dc) detection of a wide array of organic and inorganic molecules has been demonstrated on these devices. However, sensing mechanism based on measuring changes in dc conductance fails at high background salt concentrations, where the sensitivity of the devices suffers from the ionic screening due to mobile ions present in the solution. Here, we successfully demonstrate that the fundamental ionic screening effect can be mitigated by operating single-walled carbon nanotube field effect transistor as a high-frequency biosensor. The nonlinear mixing between the alternating current excitation field and the molecular dipole field can generate mixing current sensitive to the surface-bound biomolecules. Electrical detection of monolayer streptavidin binding to biotin in 100 mM buffer solution is achieved at a frequency beyond 1 MHz. Theoretical modeling confirms improved sensitivity at high frequency through mitigation of the ionic screening effect. The results should promise a new biosensing platform for POC detection, where biosensors functioning directly in physiologically relevant condition are desired. © 2012 American Chemical Society

Quantum statistical effects in the mass transport of interstitial solutes in a crystalline solid

NASA Astrophysics Data System (ADS)

Woo, C. H.; Wen, Haohua

2017-09-01

The impact of quantum statistics on the many-body dynamics of a crystalline solid at finite temperatures containing an interstitial solute atom (ISA) is investigated. The Mori-Zwanzig theory allows the many-body dynamics of the crystal to be formulated and solved analytically within a pseudo-one-particle approach using the Langevin equation with a quantum fluctuation-dissipation relation (FDR) based on the Debye model. At the same time, the many-body dynamics is also directly solved numerically via the molecular dynamics approach with a Langevin heat bath based on the quantum FDR. Both the analytical and numerical results consistently show that below the Debye temperature of the host lattice, quantum statistics significantly impacts the ISA transport properties, resulting in major departures from both the Arrhenius law of diffusion and the Einstein-Smoluchowski relation between the mobility and diffusivity. Indeed, we found that below one-third of the Debye temperature, effects of vibrations on the quantum mobility and diffusivity are both orders-of-magnitude larger and practically temperature independent. We have shown that both effects have their physical origin in the athermal lattice vibrations derived from the phonon ground state. The foregoing theory is tested in quantum molecular dynamics calculation of mobility and diffusivity of interstitial helium in bcc W. In this case, the Arrhenius law is only valid in a narrow range between ˜300 and ˜700 K. The diffusivity becomes temperature independent on the low-temperature side while increasing linearly with temperature on the high-temperature side.

Field-Assisted Splitting of Pure Water Based on Deep-Sub-Debye-Length Nanogap Electrochemical Cells.

PubMed

Wang, Yifei; Narayanan, S R; Wu, Wei

2017-08-22

Owing to the low conductivity of pure water, using an electrolyte is common for achieving efficient water electrolysis. In this paper, we have fundamentally broken through this common sense by using deep-sub-Debye-length nanogap electrochemical cells to achieve efficient electrolysis of pure water (without any added electrolyte) at room temperature. A field-assisted effect resulted from overlapped electrical double layers can greatly enhance water molecules ionization and mass transport, leading to electron-transfer limited reactions. We have named this process "virtual breakdown mechanism" (which is completely different from traditional mechanisms) that couples the two half-reactions together, greatly reducing the energy losses arising from ion transport. This fundamental discovery has been theoretically discussed in this paper and experimentally demonstrated in a group of electrochemical cells with nanogaps between two electrodes down to 37 nm. On the basis of our nanogap electrochemical cells, the electrolysis current density from pure water can be significantly larger than that from 1 mol/L sodium hydroxide solution, indicating the much better performance of pure water splitting as a potential for on-demand clean hydrogen production.

Dependence of ion density in the wake of the AE-C satellite on the ratio of body size to Debye length in an (O/sup +/)-dominated plasma

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

Samir, U.; Kaufman, Y.J.; Brace, L.H.

Measurements of electron temperature, satellite potential, ion density and ion composition from the cylindrical electrostatic probe and the Bennett ion mass spectrometer on board the AE-C satellite were used to investigate the influence of the body size parameter R/sub D/=R/sub 0//lambda/sub D/ (where R/sub 0/ is the satellite radius and lambda/sub D/ is the ambient Debye length) on ion distribution in the very near wake. The investigation focused on (O/sup +/) plasmas. It was found that the ratio (..beta..) of density in the wake to ambient density varies with R/sub D/ and that the variation can be described by amore » simple exponential relationship of the form ..beta..=a/sub 0/ exp (a/sub 1/R/sub D/) for 37< or =R/sub D/< or =247 and a/sub 0/=0.006, a/sub 1/=-0.009. the present study extends that of Samir et al. (1979a).« less

Effect of magnon-phonon interactions on magnon squeezed states in ferromagnets

NASA Astrophysics Data System (ADS)

Mikhail, I. F. I.; Ismail, I. M. M.; Ameen, M.

2018-02-01

The squeezed states of dressed magnons in ferromagnets have been investigated. No effective Debye cutoff frequency has been assumed unlike what has been done hitherto. Instead, the results have been expressed throughout in terms of the reduced temperature. The effect of dressed magnon-phonon interactions on the formulation of these states has been studied. It has been shown that the magnon-phonon interactions play a significant role in determining the squeeze factor and the variation of the dressed magnon effective mass with temperature.

Nonperturbative finite-temperature Yang-Mills theory

NASA Astrophysics Data System (ADS)

Cyrol, Anton K.; Mitter, Mario; Pawlowski, Jan M.; Strodthoff, Nils

2018-03-01

We present nonperturbative correlation functions in Landau-gauge Yang-Mills theory at finite temperature. The results are obtained from the functional renormalisation group within a self-consistent approximation scheme. In particular, we compute the magnetic and electric components of the gluon propagator, and the three- and four-gluon vertices. We also show the ghost propagator and the ghost-gluon vertex at finite temperature. Our results for the propagators are confronted with lattice simulations and our Debye mass is compared to hard thermal loop perturbation theory.

Vibrationally averaged post Born-Oppenheimer isotopic dipole moment calculations approaching spectroscopic accuracy.

PubMed

Arapiraca, A F C; Jonsson, Dan; Mohallem, J R

2011-12-28

We report an upgrade of the Dalton code to include post Born-Oppenheimer nuclear mass corrections in the calculations of (ro-)vibrational averages of molecular properties. These corrections are necessary to achieve an accuracy of 10(-4) debye in the calculations of isotopic dipole moments. Calculations on the self-consistent field level present this accuracy, while numerical instabilities compromise correlated calculations. Applications to HD, ethane, and ethylene isotopologues are implemented, all of them approaching the experimental values.

Radiative transition of hydrogen-like ions in quantum plasma

NASA Astrophysics Data System (ADS)

Hu, Hongwei; Chen, Zhanbin; Chen, Wencong

2016-12-01

At fusion plasma electron temperature and number density regimes of 1 × 103-1 × 107 K and 1 × 1028-1 × 1031/m3, respectively, the excited states and radiative transition of hydrogen-like ions in fusion plasmas are studied. The results show that quantum plasma model is more suitable to describe the fusion plasma than the Debye screening model. Relativistic correction to bound-state energies of the low-Z hydrogen-like ions is so small that it can be ignored. The transition probability decreases with plasma density, but the transition probabilities have the same order of magnitude in the same number density regime.

Self-propulsion and interactions of catalytic particles in a chemically active medium.

PubMed

Banigan, Edward J; Marko, John F

2016-01-01

Enzymatic "machines," such as catalytic rods or colloids, can self-propel and interact by generating gradients of their substrates. We theoretically investigate the behaviors of such machines in a chemically active environment where their catalytic substrates are continuously synthesized and destroyed, as occurs in living cells. We show how the kinetic properties of the medium modulate self-propulsion and pairwise interactions between machines, with the latter controlled by a tunable characteristic interaction range analogous to the Debye screening length in an electrolytic solution. Finally, we discuss the effective force arising between interacting machines and possible biological applications, such as partitioning of bacterial plasmids.

Distributed databases for materials study of thermo-kinetic properties

NASA Astrophysics Data System (ADS)

Toher, Cormac

2015-03-01

High-throughput computational materials science provides researchers with the opportunity to rapidly generate large databases of materials properties. To rapidly add thermal properties to the AFLOWLIB consortium and Materials Project repositories, we have implemented an automated quasi-harmonic Debye model, the Automatic GIBBS Library (AGL). This enables us to screen thousands of materials for thermal conductivity, bulk modulus, thermal expansion and related properties. The search and sort functions of the online database can then be used to identify suitable materials for more in-depth study using more precise computational or experimental techniques. AFLOW-AGL source code is public domain and will soon be released within the GNU-GPL license.

Structure and dynamics of hyaluronic acid semidilute solutions: a dielectric spectroscopy study.

PubMed

Vuletić, T; Dolanski Babić, S; Ivek, T; Grgicin, D; Tomić, S; Podgornik, R

2010-07-01

Dielectric spectroscopy is used to investigate fundamental length scales describing the structure of hyaluronic acid sodium salt (Na-HA) semidilute aqueous solutions. In salt-free regime, the length scale of the relaxation mode detected in MHz range scales with HA concentration as c(HA)(-0.5) and corresponds to the de Gennes-Pfeuty-Dobrynin correlation length of polyelectrolytes in semidilute solution. The same scaling was observed for the case of long, genomic DNA. Conversely, the length scale of the mode detected in kilohertz range also varies with HA concentration as c(HA)(-0.5) which differs from the case of DNA (c(DNA)(-0.25)). The observed behavior suggests that the relaxation in the kilohertz range reveals the de Gennes-Dobrynin renormalized Debye screening length, and not the average size of the chain, as the pertinent length scale. Similarly, with increasing added salt the electrostatic contribution to the HA persistence length is observed to scale as the Debye length, contrary to scaling pertinent to the Odijk-Skolnick-Fixman electrostatic persistence length observed in the case of DNA. We argue that the observed features of the kilohertz range relaxation are due to much weaker electrostatic interactions that lead to the absence of Manning condensation as well as a rather high flexibility of HA as compared to DNA.

Free-Free Transitions of the e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident-Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Sinha, C.

2012-01-01

The free-free transition is studied for an electron-hydrogen atom in ground state when a low-energy electron (external) is injected into hydrogenic plasma in the presence of an external homogenous, monochromatic, and linearly polarized laser field. The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption or emission and no-photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

Vibrational properties of nanocrystals from the Debye Scattering Equation

DOE PAGES

Scardi, P.; Gelisio, L.

2016-02-26

One hundred years after the original formulation by Petrus J.W. Debije (aka Peter Debye), the Debye Scattering Equation (DSE) is still the most accurate expression to model the diffraction pattern from nanoparticle systems. A major limitation in the original form of the DSE is that it refers to a static domain, so that including thermal disorder usually requires rescaling the equation by a Debye-Waller thermal factor. The last is taken from the traditional diffraction theory developed in Reciprocal Space (RS), which is opposed to the atomistic paradigm of the DSE, usually referred to as Direct Space (DS) approach. Besides beingmore » a hybrid of DS and RS expressions, rescaling the DSE by the Debye-Waller factor is an approximation which completely misses the contribution of Temperature Diffuse Scattering (TDS). The present work proposes a solution to include thermal effects coherently with the atomistic approach of the DSE. Here, a deeper insight into the vibrational dynamics of nanostructured materials can be obtained with few changes with respect to the standard formulation of the DSE, providing information on the correlated displacement of vibrating atoms.« less

Influence of the Debye length on the interaction of a small molecule-modified Au nanoparticle with a surface-bound bioreceptor.

PubMed

Bukar, Natalia; Zhao, Sandy Shuo; Charbonneau, David M; Pelletier, Joelle N; Masson, Jean-Francois

2014-05-18

We report that a shorter Debye length and, as a consequence, decreased colloidal stability are required for the molecular interaction of folic acid-modified Au nanoparticles (Au NPs) to occur on a surface-bound receptor, human dihydrofolate reductase (hDHFR). The interaction measured using surface plasmon resonance (SPR) sensing was optimal in a phosphate buffer at pH 6 and ionic strength exceeding 300 mM. Under these conditions, the aggregation constant of the Au NPs was approximately 10(4) M(-1) s(-1) and the Debye length was below 1 nm, on the same length scale as the size of the folate anion (approximately 0.8 nm). Longer Debye lengths led to poorer SPR responses, revealing a reduced affinity of the folic acid-modified Au NPs for hDHFR. While high colloidal stability of Au NPs is desired in most applications, these conditions may hinder molecular interactions due to Debye lengths exceeding the size of the ligand and thus preventing close interactions with the surface-bound molecular receptor.

Thermodynamic properties of α-uranium

NASA Astrophysics Data System (ADS)

Ren, Zhiyong; Wu, Jun; Ma, Rong; Hu, Guichao; Luo, Chao

2016-11-01

The lattice constants and equilibrium atomic volume of α-uranium were calculated by Density Functional Theory (DFT). The first principles calculation results of the lattice for α-uranium are in agreement with the experimental results well. The thermodynamic properties of α-uranium from 0 to 900 K and 0-100 GPa were calculated with the quasi-harmonic Debye model. Volume, bulk modulus, entropy, Debye temperature, thermal expansion coefficient and the heat capacity of α-uranium were calculated. The calculated results show that the bulk modulus and Debye temperature increase with the increasing pressure at a given temperature while decreasing with the increasing temperature at a given pressure. Volume, entropy, thermal expansion coefficient and the heat capacity decrease with the increasing pressure while increasing with the increasing temperature. The theoretical results of entropy, Debye temperature, thermal expansion coefficient and the heat capacity show good agreement with the general trends of the experimental values. The constant-volume heat capacity shows typical Debye T3 power-law behavior at low temperature limit and approaches to the classical asymptotic Dulong-Petit limit at high temperature limit.

Boundary asymptotics for a non-neutral electrochemistry model with small Debye length

NASA Astrophysics Data System (ADS)

Lee, Chiun-Chang; Ryham, Rolf J.

2018-04-01

This article addresses the boundary asymptotics of the electrostatic potential in non-neutral electrochemistry models with small Debye length in bounded domains. Under standard physical assumptions motivated by non-electroneutral phenomena in oxidation-reduction reactions, we show that the electrostatic potential asymptotically blows up at boundary points with respect to the bulk reference potential as the scaled Debye length tends to zero. The analysis gives a lower bound for the blow-up rate with respect to the model parameters. Moreover, the maximum potential difference over any compact subset of the physical domain vanishes exponentially in the zero-Debye-length limit. The results mathematically confirm the physical description that electrolyte solutions are electrically neutral in the bulk and are strongly electrically non-neutral near charged surfaces.

Determination of molecular configuration by debye length modulation.

PubMed

Vacic, Aleksandar; Criscione, Jason M; Rajan, Nitin K; Stern, Eric; Fahmy, Tarek M; Reed, Mark A

2011-09-07

Silicon nanowire field effect transistors (FETs) have emerged as ultrasensitive, label-free biodetectors that operate by sensing bound surface charge. However, the ionic strength of the environment (i.e., the Debye length of the solution) dictates the effective magnitude of the surface charge. Here, we show that control of the Debye length determines the spatial extent of sensed bound surface charge on the sensor. We apply this technique to different methods of antibody immobilization, demonstrating different effective distances of induced charge from the sensor surface.

Debye-Waller Factor in Neutron Scattering by Ferromagnetic Metals

NASA Astrophysics Data System (ADS)

Paradezhenko, G. V.; Melnikov, N. B.; Reser, B. I.

2018-04-01

We obtain an expression for the neutron scattering cross section in the case of an arbitrary interaction of the neutron with the crystal. We give a concise, simple derivation of the Debye-Waller factor as a function of the scattering vector and the temperature. For ferromagnetic metals above the Curie temperature, we estimate the Debye-Waller factor in the range of scattering vectors characteristic of polarized magnetic neutron scattering experiments. In the example of iron, we compare the results of harmonic and anharmonic approximations.

Physics in Screening Environments

NASA Astrophysics Data System (ADS)

Certik, Ondrej

In the current study, we investigated atoms in screening environments like plasmas. It is common practice to extract physical data, such as temperature and electron densities, from plasma experiments. We present results that address inherent computational difficulties that arise when the screening approach is extended to include the interaction between the atomic electrons. We show that there may arise an ambiguity in the interpretation of physical properties, such as temperature and charge density, from experimental data due to the opposing effects of electron-nucleus screening and electron-electron screening. The focus of the work, however, is on the resolution of inherent computational challenges that appear in the computation of two-particle matrix elements. Those enter already at the Hartree-Fock level. Furthermore, as examples of post Hartree-Fock calculations, we show second-order Green's function results and many body perturbation theory results of second order. A self-contained derivation of all necessary equations has been included. The accuracy of the implementation of the method is established by comparing standard unscreened results for various atoms and molecules against literature for Hartree-Fock as well as Green's function and many body perturbation theory. The main results of the thesis are presented in the chapter called Screened Results, where the behavior of several atomic systems depending on electron-electron and electron-nucleus Debye screening was studied. The computer code that we have developed has been made available for anybody to use. Finally, we present and discuss results obtained for screened interactions. We also examine thoroughly the computational details of the calculations and particular implementations of the method.

The Debye light scattering equation's scaling relation reveals the purity of synthetic dendrimers

NASA Astrophysics Data System (ADS)

Tseng, Hui-Yu; Chen, Hsiao-Ping; Tang, Yi-Hsuan; Chen, Hui-Ting; Kao, Chai-Lin; Wang, Shau-Chun

2016-03-01

Spherical dendrimer structures cannot be structurally modeled using conventional polymer models of random coil or rod-like configurations during the calibration of the static light scattering (LS) detectors used to determine the molecular weight (M.W.) of a dendrimer or directly assess the purity of a synthetic compound. In this paper, we used the Debye equation-based scaling relation, which predicts that the static LS intensity per unit concentration is linearly proportional to the M.W. of a synthetic dendrimer in a dilute solution, as a tool to examine the purity of high-generational compounds and to monitor the progress of dendrimer preparations. Without using expensive equipment, such as nuclear magnetic resonance or mass spectrometry, this method only required an affordable flow injection set-up with an LS detector. Solutions of the purified dendrimers, including the poly(amidoamine) (PAMAM) dendrimer and its fourth to seventh generation pyridine derivatives with size range of 5-9 nm, were used to establish the scaling relation with high linearity. The use of artificially impure mixtures of six or seven generations revealed significant deviations from linearity. The raw synthesized products of the pyridine-modified PAMAM dendrimer, which included incompletely reacted dendrimers, were also examined to gauge the reaction progress. As a reaction toward a particular generational derivative of the PAMAM dendrimers proceeded over time, deviations from the linear scaling relation decreased. The difference between the polydispersity index of the incompletely converted products and that of the pure compounds was only about 0.01. The use of the Debye equation-based scaling relation, therefore, is much more useful than the polydispersity index for monitoring conversion processes toward an indicated functionality number in a given preparation.

Numerical study of the influence of solid polarization on electrophoresis at finite Debye thickness.

PubMed

Bhattacharyya, Somnath; De, Simanta

2015-09-01

The influence of solid polarization on the electrophoresis of a uniformly charged dielectric particle for finite values of the particle-to-fluid dielectric permittivity ratio is analyzed quantitatively without imposing the thin Debye length or weak-field assumption. Present analysis is based on the computation of the coupled Poisson-Nernst-Planck and Stokes equations in the fluid domain along with the Laplace equation within the solid. The electrophoretic velocity is determined through the balance of forces acting on the particle. The solid polarization of the charged particle produces a reduction on its electrophoretic velocity compared to a nonpolarizable particle of the same surface charge density. In accordance with the existing thin-layer analysis, our computed results for thin Debye layer shows that the solid polarization is important only when the applied electric field is strong. When the Debye length is in the order of the particle size, the electrophoretic velocity decreases with the rise of the particle permittivity and attains a saturation limit at large values of the permittivity. Our computed solution for electrophoretic velocity is in agreement with the existing asymptotic analyses based on a thin Debye layer for limiting cases.

The surface stability of Cr 2O 3 (0 0 0 1)

DOE PAGES

Cao, Shi; Wu, Ning; Echtenkamp, William; ...

2015-05-28

The surface of chromia (Cr 2O 3) has a surface electronic structure distinct from the bulk and a packing density distinct from the bulk. More than a demarcation between the solid and the vacuum, the surface differs from the bulk of chromia, not just because of a partial occupancy of chromium sites, but also because of an increased number of unoccupied surface oxygen sites (vacancy sites), evident in angle-resolved core level photoemission. In spite of the structural differences that exist at the surface, there is, as yet, no evidence that these complications affect the surface Debye temperature beyond the mostmore » simple of assumptions regarding the lower coordination of the surface. Using low-energy electron diffraction (LEED), the effective surface Debye temperature (similar to 490 K) is found to be lower than the bulk (similar to 645 K) Debye temperature of Cr 2O 3(0 0 0 1). This surface effective Debye temperature, indicative of vibrations along the surface normal, uncorrected for anharmonic effects, has a value reduced from the effective bulk Debye temperature yet close to the value root 2 expected from a simple mean field argument.« less

Stern potential and Debye length measurements in dilute ionic solutions with electrostatic force microscopy.

PubMed

Kumar, Bharat; Crittenden, Scott R

2013-11-01

We demonstrate the ability to measure Stern potential and Debye length in dilute ionic solution with atomic force microscopy. We develop an analytic expression for the second harmonic force component of the capacitive force in an ionic solution from the linearized Poisson-Boltzmann equation. This allows us to calibrate the AFM tip potential and, further, obtain the Stern potential of sample surfaces. In addition, the measured capacitive force is independent of van der Waals and double layer forces, thus providing a more accurate measure of Debye length.

Assessing the contributions of surface waves and complex rays to far-field Mie scattering by use of the Debye series

NASA Technical Reports Server (NTRS)

Hovenac, Edward A.; Lock, James A.

1991-01-01

The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with the Debye series. Interference effects between surface waves, complex waves, and geometrical waves are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface wave-geometrical pattern is presented.

Static electric dipole polarizability of lithium atoms in Debye plasmas

NASA Astrophysics Data System (ADS)

Ning, Li-Na; Qi, Yue-Ying

2012-12-01

The static electric dipole polarizabilities of the ground state and n <= 3 excited states of a lithium atom embedded in a weekly coupled plasma environment are investigated as a function of the plasma screening radium. The plasma screening of the Coulomb interaction is described by the Debye—Hückel potential and the interaction between the valence electron and the atomic core is described by a model potential. The electron energies and wave functions for both the bound and continuum states are calculated by solving the Schrödinger equation numerically using the symplectic integrator. The oscillator strengths, partial-wave, and total static dipole polarizabilities of the ground state and n <= 3 excited states of the lithium atom are calculated. Comparison of present results with those of other authors, when available, is made. The results for the 2s ground state demonstrated that the oscillator strengths and the static dipole polarizabilities from np orbitals do not always increase or decrease with the plasma screening effect increasing, unlike that for hydrogen-like ions, especially for 2s→3p transition there is a zero value for both the oscillator strength and the static dipole polarizability for screening length D = 10.3106a0, which is associated with the Cooper minima.

Circular polarization of X-ray radiation emitted by longitudinally polarized electron impact excitation: Under a screened Coulomb interaction

NASA Astrophysics Data System (ADS)

Chen, Zhan-Bin

2017-12-01

Longitudinally polarized electron impact excitation from the ground state 1s2 to the excited state 1s2l (l =s,p) levels of highly charged He-like Fe24+ ions in weakly coupled hot-dense plasmas is investigated using a fully relativistic distorted-wave method. The Debye-Hückel potential is used to describe the plasma screening. Benchmark results such as the total cross sections, the magnetic sublevels cross sections, and the circular polarizations of corresponding X-ray radiations are presented. For the excitation process, results show that the plasma screening has an effect in reducing both the total and magnetic sublevels cross sections. For the de-excitation process, it is found that while the plasma screening as a slightly effect on the circular polarizations of radiations for the 1 s 2 s 3S1 → 1 s21S0,1 s 2 p 3P2 → 1 s21S0 , and 1 s 2 p 1P1 → 1 s21S0 transition lines, it gives a substantial contribution for the same properties of the 1 s 2 p 3P1 → 1 s21S0 line.

Determination of Debye temperatures and Lamb-Mössbauer factors for LnFeO3 orthoferrite perovskites (Ln  =  La, Nd, Sm, Eu, Gd)

NASA Astrophysics Data System (ADS)

Scrimshire, A.; Lobera, A.; Bell, A. M. T.; Jones, A. H.; Sterianou, I.; Forder, S. D.; Bingham, P. A.

2018-03-01

Lanthanide orthoferrites have wide-ranging industrial uses including solar, catalytic and electronic applications. Here a series of lanthanide orthoferrite perovskites, LnFeO3 (Ln  =  La Nd; Sm; Eu; Gd), prepared through a standard stoichiometric wet ball milling route using oxide precursors, has been studied. Characterisation through x-ray diffraction and x-ray fluorescence confirmed the synthesis of phase-pure or near-pure LnFeO3 compounds. 57Fe Mössbauer spectroscopy was performed over a temperature range of 10 K-293 K to observe hyperfine structure and to enable calculation of the recoil-free fraction and Debye temperature (θ D) of each orthoferrite. Debye temperatures (Ln  =  La 474 K Nd 459 K Sm 457 K Eu 452 K Gd 473 K) and recoil-free fractions (Ln  =  La 0.827; Nd 0.817; Sm 0.816; Eu 0.812; Gd 0.826) were approximated through minimising the difference in the temperature dependent experimental centre shift and theoretical isomer shift, by allowing the Debye temperature and isomer shift values to vary. This method of minimising the difference between theoretical and actual values yields Debye temperatures consistent with results from other studies determined through thermal analysis methods. This displays the ability of variable-temperature Mössbauer spectroscopy to approximate Debye temperatures and recoil-free fractions, whilst observing temperature induced transitions over the temperature range observed. X-ray diffraction and Rietveld refinement show an inverse relationship between FeO6 octahedral volume and approximated Debye temperatures. Raman spectroscopy show an increase in the band positions attributed to soft modes of Ag symmetry, Ag(3) and Ag(5) from La to GdFeO3 corresponding to octahedral rotations and tilts in the [0 1 0] and [1 0 1] planes respectively.

Determination of Cole-Cole parameters using only the real part of electrical impedivity measurements.

PubMed

Miranda, David A; Rivera, S A López

2008-05-01

An algorithm is presented to determine the Cole-Cole parameters of electrical impedivity using only measurements of its real part. The algorithm is based on two multi-fold direct inversion methods for the Cole-Cole and Debye equations, respectively, and a genetic algorithm for the optimization of the mean square error between experimental and calculated data. The algorithm has been developed to obtain the Cole-Cole parameters from experimental data, which were used to screen cervical intra-epithelial neoplasia. The proposed algorithm was compared with different numerical integrations of the Kramers-Kronig relation and the result shows that this algorithm is the best. A high immunity to noise was obtained.

Universal Non-Debye Scaling in the Density of States of Amorphous Solids.

PubMed

Charbonneau, Patrick; Corwin, Eric I; Parisi, Giorgio; Poncet, Alexis; Zamponi, Francesco

2016-07-22

At the jamming transition, amorphous packings are known to display anomalous vibrational modes with a density of states (DOS) that remains constant at low frequency. The scaling of the DOS at higher packing fractions remains, however, unclear. One might expect to find a simple Debye scaling, but recent results from effective medium theory and the exact solution of mean-field models both predict an anomalous, non-Debye scaling. Being mean-field in nature, however, these solutions are only strictly valid in the limit of infinite spatial dimension, and it is unclear what value they have for finite-dimensional systems. Here, we study packings of soft spheres in dimensions 3 through 7 and find, away from jamming, a universal non-Debye scaling of the DOS that is consistent with the mean-field predictions. We also consider how the soft mode participation ratio evolves as dimension increases.

First principles electronic and thermal properties of some AlRE intermetallics

NASA Astrophysics Data System (ADS)

Srivastava, Vipul; Sanyal, Sankar P.; Rajagopalan, M.

2008-10-01

A study on structural and electronic properties of non-magnetic cubic B 2-type AlRE (RE=Sc, Y, La, Ce, Pr and Lu) intermetallics has been done theoretically. The self-consistent tight binding linear muffin tin orbital method is used to describe the electronic properties of these intermetallics at ambient and at high pressure. These compounds show metallic behavior under ambient conditions. The variation of density of states under compression indicates some possibility of structural phase transformation in AlLa, AlCe and AlPr. Thermal properties like Debye temperature and Grüneisen constant are calculated at T=0 K and at ambient pressure within the Debye-Grüneisen model and compared with the others’ theoretical results. Our results are in good agreement. We have also performed a pressure-induced variation of Debye temperature and have found a decrease in Debye temperature around 40 kbar in AlRE (RE=La, Ce, Pr) intermetallics.

Estimation of Phonon and Carrier Thermal Conductivities for Bulk Thermoelectric Materials Using Transport Properties

NASA Astrophysics Data System (ADS)

Otsuka, Mioko; Homma, Ryoei; Hasegawa, Yasuhiro

2017-05-01

The phonon and carrier thermal conductivities of thermoelectric materials were calculated using the Wiedemann-Franz law, Boltzmann equation, and a method we propose in this study called the Debye specific heat method. We prepared polycrystalline n-type doped bismuth telluride (BiTe) and bismuth antimony (BiSb) bulk alloy samples and measured six parameters (Seebeck coefficient, resistivity, thermal conductivity, thermal diffusivity, magneto-resistivity, and Hall coefficient). The carrier density and mobility were estimated for calculating the carrier thermal conductivity by using the Boltzmann equation. In the Debye specific heat method, the phonon thermal diffusivity, and thermal conductivity were calculated from the temperature dependence of the effective specific heat by using not only the measured thermal conductivity and Debye model, but also the measured thermal diffusivity. The carrier thermal conductivity was also evaluated from the phonon thermal conductivity by using the specific heat. The ratio of carrier thermal conductivity to thermal conductivity was evaluated for the BiTe and BiSb samples, and the values obtained using the Debye specific heat method at 300 K were 52% for BiTe and <5.5% for BiSb. These values are either considerably larger or smaller than those obtained using other methods. The Dulong-Petit law was applied to validate the Debye specific heat method at 300 K, which is significantly greater than the Debye temperature of the BiTe and BiSb samples, and it was confirmed that the phonon specific heat at 300 K has been accurately reproduced using our proposed method.

The electrostatic persistence length of polymers beyond the OSF limit.

PubMed

Everaers, R; Milchev, A; Yamakov, V

2002-05-01

We use large-scale Monte Carlo simulations to test scaling theories for the electrostatic persistence length l(e) of isolated, uniformly charged polymers with Debye-Hückel intrachain interactions in the limit where the screening length kappa(-1) exceeds the intrinsic persistence length of the chains. Our simulations cover a significantly larger part of the parameter space than previous studies. We observe no significant deviations from the prediction l(e) proportional to kappa(-2) by Khokhlov and Khachaturian which is based on applying the Odijk-Skolnick-Fixman theories of electrostatic bending rigidity and electrostatically excluded volume to the stretched de Gennes-Pincus-Velasco-Brochard polyelectrolyte blob chain. A linear or sublinear dependence of the persistence length on the screening length can be ruled out. We show that previous results pointing into this direction are due to a combination of excluded-volume and finite chain length effects. The paper emphasizes the role of scaling arguments in the development of useful representations for experimental and simulation data.

Low Mach number fluctuating hydrodynamics for electrolytes

NASA Astrophysics Data System (ADS)

Péraud, Jean-Philippe; Nonaka, Andy; Chaudhri, Anuj; Bell, John B.; Donev, Aleksandar; Garcia, Alejandro L.

2016-11-01

We formulate and study computationally the low Mach number fluctuating hydrodynamic equations for electrolyte solutions. We are interested in studying transport in mixtures of charged species at the mesoscale, down to scales below the Debye length, where thermal fluctuations have a significant impact on the dynamics. Continuing our previous work on fluctuating hydrodynamics of multicomponent mixtures of incompressible isothermal miscible liquids [A. Donev et al., Phys. Fluids 27, 037103 (2015), 10.1063/1.4913571], we now include the effect of charged species using a quasielectrostatic approximation. Localized charges create an electric field, which in turn provides additional forcing in the mass and momentum equations. Our low Mach number formulation eliminates sound waves from the fully compressible formulation and leads to a more computationally efficient quasi-incompressible formulation. We demonstrate our ability to model saltwater (NaCl) solutions in both equilibrium and nonequilibrium settings. We show that our algorithm is second order in the deterministic setting and for length scales much greater than the Debye length gives results consistent with an electroneutral approximation. In the stochastic setting, our model captures the predicted dynamics of equilibrium and nonequilibrium fluctuations. We also identify and model an instability that appears when diffusive mixing occurs in the presence of an applied electric field.

Free-Free Transitions of e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Sinha, C.

2012-01-01

The free-free transition is studied for an electron-hydrogen in the ground state at low incident energies in the presence of an external homogenous, monochromatic, and linearly polarized laser-field inside a hot dense plasma.The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit, assuming that the plasma frequency is much higher than the laser frequency. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption /emission and no photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

Graphene decorated with mu-opioid receptor: the ionic screening effect and detection of enkephalin

NASA Astrophysics Data System (ADS)

Ping, Jinglei; Johnson, A. T. Charlie; Liu, Renyu; A. T. Charlie Johnson Team; Renyu Liu Collaboration

2015-03-01

We investigated the properties of graphene field effect transistors (GFETs) decorated with a computaionally redesigned, water-soluble variant of the human mu-opioid receptor (wsMOR) in physiological buffer solution. The shift of the Fermi level in the GFETs is quantitatively described by chemical-gating effect of charges on the wsMOR that are screened by the ionic solution. Our results suggest that sensitivity to the molecular target is lost when the Debye screening length of the solution is shorter than the distance from the graphene to the wsMOR; thus de-salting may be necessary when wsMOR decorated GFETs are used as biosensors in solution. We used this insight to detect DAMGO, a synthetic analog to the endogenous opioid peptide encephalin, at a concentration of 10 pM (5.1 pg/mL) in artificial cerebrospinal fluid (aCSF) diluted to 5% of its normal salt concentration. When the sensors were measured in a dry state, the limit of detection for DAGMO was 1 pM (0.5 pg/mL), one-third of the baseline in human body.Funding for this work was provided by DARPA.

Magnetic field tunable dielectric dispersion in successive field-induced magnetic phases of the geometrically frustrated magnet CuFeO2 up to 28 T

NASA Astrophysics Data System (ADS)

Tamatsukuri, H.; Mitsuda, S.; Hiroura, K.; Nakajima, T.; Fujihala, M.; Yamano, M.; Toshioka, Y.; Kaneko, C.; Takehana, K.; Imanaka, Y.; Terada, N.; Kitazawa, H.

2018-06-01

We find magnetic-field-dependent dielectric dispersions specific to successive field-induced magnetic phases of a geometrically frustrated magnet CuFeO2 up to 28 T. The dielectric dispersions in the three field-induced collinear-commensurate magnetic phases are well described by the superposition of Debye-type relaxations, and the number of contributions to the Debye-type dispersions differs in these phases. In contrast, the dielectric dispersions in the noncollinear-incommensurate phase, known as a spin-driven ferroelectric phase, cannot be simply described by the Debye-type relaxations. In addition, we find that the temperature dependence of the Debye relaxation frequencies follows the Arrhenius law, and that the activation energies derived from the Arrhenius equation also depend on the magnetic field. Considering the magnetostriction effect in combination with elongation/contraction of spins resulting from the application of a magnetic field, we show that the number of Debye relaxation components is equivalent to the number of states of local Fe3O clusters determined by oxygen displacement within a triangular Fe lattice. Based on this correspondence, we propose a possible explanation that excess charges resulting from a lack of stoichiometry hop over the double-well potentials within each local Fe3O cluster, like small polarons.

The Diagnostics of the External Plasma for the Plasma Rocket

NASA Technical Reports Server (NTRS)

Karr, Gerald R.

1997-01-01

Three regions of plasma temperature/energy are being investigated to understand fully the behavior of the plasma created by the propulsion device and the operation of the RPA. Each type of plasma has a RPA associated with it; i.e. a thermal RPA, a collimated RPA, and a high temperature RPA. Through the process of developing the thermal and collimated RPAs, the proper knowledge and experience has been gained to not only design a high temperature RPA for the plasma rocket, but to understand its operation, results, and uncertainty. After completing a literature search for, reading published papers on, and discussing the operation of the RPA with electric propulsion researchers, I applied the knowledge gained to the development of a RPA for thermal plasma. A design of a thermal RPA was made which compensates for a large Debye length and low ionized plasma. From this design a thermal RPA was constructed. It consists of an outer stainless steel casing, a phenolic insulator (outgases slightly), and stainless steel mesh for the voltage screens. From the experience and knowledge gained in the development of the thermal RPA, a RPA for collimated plasma was developed. A collimated RPA has been designed and constructed. It compensate for a smaller Debye length and much higher ionization than that existing in the thermal plasma. It is 17% of the size of the thermal RPA. A stainless steel casing shields the detector from impinging electrons and ions. An insulating material, epoxy resin, was utilized which has a negligible outgassing. This material can be molded in styrofoam and machined quite nicely. It is capable of withstanding moderately high temperatures. Attached to this resin insulator are inconel screens attached by silver plated copper wire to a voltage supply. All the work on the RPAs and thermal ion source, I performed in the University of Alabama in Huntsville's (UAH) engineering machine shop.

THERMODYNAMIC PROPERTIES OF MC (M = V, Nb, Ta): FIRST-PRINCIPLES CALCULATIONS

NASA Astrophysics Data System (ADS)

Cao, Yong; Zhu, Jingchuan; Liu, Yong; Long, Zhishen

2013-07-01

Through the quasi-harmonic Debye model, the pressure and temperature dependences of linear expansion coefficient, bulk modulus, Debye temperature and heat capacity have been investigated. The calculated thermodynamic properties were compared with experimental data and satisfactory agreement is reached.

Graphene Field Effect Transistors for Biomedical Applications: Current Status and Future Prospects.

PubMed

Forsyth, Rhiannan; Devadoss, Anitha; Guy, Owen J

2017-07-26

Since the discovery of the two-dimensional (2D) carbon material, graphene, just over a decade ago, the development of graphene-based field effect transistors (G-FETs) has become a widely researched area, particularly for use in point-of-care biomedical applications. G-FETs are particularly attractive as next generation bioelectronics due to their mass-scalability and low cost of the technology's manufacture. Furthermore, G-FETs offer the potential to complete label-free, rapid, and highly sensitive analysis coupled with a high sample throughput. These properties, coupled with the potential for integration into portable instrumentation, contribute to G-FETs' suitability for point-of-care diagnostics. This review focuses on elucidating the recent developments in the field of G-FET sensors that act on a bioaffinity basis, whereby a binding event between a bioreceptor and the target analyte is transduced into an electrical signal at the G-FET surface. Recognizing and quantifying these target analytes accurately and reliably is essential in diagnosing many diseases, therefore it is vital to design the G-FET with care. Taking into account some limitations of the sensor platform, such as Debye-Hükel screening and device surface area, is fundamental in developing improved bioelectronics for applications in the clinical setting. This review highlights some efforts undertaken in facing these limitations in order to bring G-FET development for biomedical applications forward.

Transient electromagnetic scattering by a radially uniaxial dielectric sphere: Debye series, Mie series and ray tracing methods

NASA Astrophysics Data System (ADS)

Yazdani, Mohsen

Transient electromagnetic scattering by a radially uniaxial dielectric sphere is explored using three well-known methods: Debye series, Mie series, and ray tracing theory. In the first approach, the general solutions for the impulse and step responses of a uniaxial sphere are evaluated using the inverse Laplace transformation of the generalized Mie series solution. Following high frequency scattering solution of a large uniaxial sphere, the Mie series summation is split into the high frequency (HF) and low frequency terms where the HF term is replaced by its asymptotic expression allowing a significant reduction in computation time of the numerical Bromwich integral. In the second approach, the generalized Debye series for a radially uniaxial dielectric sphere is introduced and the Mie series coefficients are replaced by their equivalent Debye series formulations. The results are then applied to examine the transient response of each individual Debye term allowing the identification of impulse returns in the transient response of the uniaxial sphere. In the third approach, the ray tracing theory in a uniaxial sphere is investigated to evaluate the propagation path as well as the arrival time of the ordinary and extraordinary returns in the transient response of the uniaxial sphere. This is achieved by extracting the reflection and transmission angles of a plane wave obliquely incident on the radially oriented air-uniaxial and uniaxial-air boundaries, and expressing the phase velocities as well as the refractive indices of the ordinary and extraordinary waves in terms of the incident angle, optic axis and propagation direction. The results indicate a satisfactory agreement between Debye series, Mie series and ray tracing methods.

Optical properties of soot particles: measurement - model comparison

NASA Astrophysics Data System (ADS)

Forestieri, S.; Lambe, A. T.; Lack, D.; Massoli, P.; Cross, E. S.; Dubey, M.; Mazzoleni, C.; Olfert, J.; Freedman, A.; Davidovits, P.; Onasch, T. B.; Cappa, C. D.

2013-12-01

Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. In order to accurately model the direct radiative impact of black carbon (BC), the refractive index and shape dependent scattering and absorption characteristics must be known. At present, the assumed shape remains highly uncertain because BC particles are fractal-like, being agglomerates of smaller (20-40 nm) spherules, yet traditional optical models such as Mie theory typically assume a spherical particle morphology. To investigate the ability of various optical models to reproduce observed BC optical properties, we measured light absorption and extinction coefficients of methane and ethylene flame soot particles. Optical properties were measured by multiple instruments: absorption by a dual cavity ringdown photoacoustic spectrometer (CRD-PAS), absorption and scattering by a 3-wavelength photoacoustic/nephelometer spectrometer (PASS-3) and extinction and scattering by a cavity attenuated phase shift spectrometer (CAPS). Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA) and mobility size was measured with a scanning mobility particle sizer (SMPS). Measurements were made for nascent soot particles and for collapsed soot particles following coating with dioctyl sebacate or sulfuric acid and thermal denuding to remove the coating. Wavelength-dependent refractive indices for the sampled particles were derived by fitting the observed absorption and extinction cross-sections to spherical particle Mie theory and Rayleigh-Debye-Gans theory. The Rayleigh-Debye-Gans approximation assumes that the absorption properties of soot are dictated by the individual spherules and neglects interaction between them. In general, Mie theory reproduces the observed absorption and extinction cross-sections for particles with volume equivalent diameters (VED) < ~160 nm, but systematically predicts lower absorption cross-sections relative to observations for larger particles with VED > ~160 nm. The discrepancy is most pronounced for measurements made at shorter wavelengths. In contrast, Rayleigh-Debye-Gans theory, which does not assume spherical particle morphology, exhibited good agreement with the observations for all particle diameters and wavelengths. These results indicate that the use of Mie theory to describe the absorption behavior of particles >160 nm VED will underestimate the absorption by these particles. Concurrent measurements of the absorption Angstrom exponent and the single scattering albedo, and their dependence on particle size, will also be discussed.

Eddies in a bottleneck: an arbitrary Debye length theory for capillary electroosmosis.

PubMed

Park, Stella Y; Russo, Christopher J; Branton, Daniel; Stone, Howard A

2006-05-15

Using an applied electrical field to drive fluid flows becomes desirable as channels become smaller. Although most discussions of electroosmosis treat the case of thin Debye layers, here electroosmotic flow (EOF) through a constricted cylinder is presented for arbitrary Debye lengths (kappa(-1)) using a long wavelength perturbation of the cylinder radius. The analysis uses the approximation of small potentials. The varying diameter of the cylinder produces radially and axially varying effective electric fields, as well as an induced pressure gradient. We predict the existence of eddies for certain constricted geometries and propose the possibility of electrokinetic trapping in these regions. We also present a leading-order criterion which predicts central eddies in very narrow constrictions at the scale of the Debye length. Eddies can be found both in the center of the channel and along the perimeter, and the presence of the eddies is a consequence of the induced pressure gradient that accompanies electrically driven flow into a narrow constriction.

Eddies in a Bottleneck: An Arbitrary Debye Length Theory for Capillary Electroosmosis

PubMed Central

Park, Stella Y.; Russo, Christopher J.; Branton, Daniel; Stone, Howard A.

2011-01-01

Using an applied electrical field to drive fluid flows becomes desirable as channels become smaller. Although most discussions of electroosmosis treat the case of thin Debye layers, here electroosmotic flow (EOF) through a constricted cylinder is presented for arbitrary Debye lengths (κ−1) using a long wavelength perturbation of the cylinder radius. The analysis uses the approximation of small potentials. The varying diameter of the cylinder produces radially and axially varying effective electric fields, as well as an induced pressure gradient. We predict the existence of eddies for certain constricted geometries and propose the possibility of electrokinetic trapping in these regions. We also present a leading-order criterion which predicts central eddies in very narrow constrictions at the scale of the Debye length. Eddies can be found both in the center of the channel and along the perimeter, and the presence of the eddies is a consequence of the induced pressure gradient that accompanies electrically driven flow into a narrow constriction. PMID:16376361

Calculation of Debye-Scherrer diffraction patterns from highly stressed polycrystalline materials

DOE PAGES

MacDonald, M. J.; Vorberger, J.; Gamboa, E. J.; ...

2016-06-07

Calculations of Debye-Scherrer diffraction patterns from polycrystalline materials have typically been done in the limit of small deviatoric stresses. Although these methods are well suited for experiments conducted near hydrostatic conditions, more robust models are required to diagnose the large strain anisotropies present in dynamic compression experiments. A method to predict Debye-Scherrer diffraction patterns for arbitrary strains has been presented in the Voigt (iso-strain) limit. Here, we present a method to calculate Debye-Scherrer diffraction patterns from highly stressed polycrystalline samples in the Reuss (iso-stress) limit. This analysis uses elastic constants to calculate lattice strains for all initial crystallite orientations, enablingmore » elastic anisotropy and sample texture effects to be modeled directly. Furthermore, the effects of probing geometry, deviatoric stresses, and sample texture are demonstrated and compared to Voigt limit predictions. An example of shock-compressed polycrystalline diamond is presented to illustrate how this model can be applied and demonstrates the importance of including material strength when interpreting diffraction in dynamic compression experiments.« less

XAFS Debye-Waller Factors Temperature-Dependent Expressions for Fe+2-Porphyrin Complexes

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas; Bunker, Grant

2007-02-01

We present an efficient and accurate method for directly calculating single and multiple scattering X-ray absorption fine structure (XAFS) thermal Debye-Waller factors for Fe+2 -porphiryn complexes. The number of multiple scattering Debye-Waller factors on metal porphyrin centers exceeds the number of available parameters that XAFS experimental data can support during fitting with simulated spectra. Using the Density Functional Theory (DFT) under the hybrid functional of X3LYP, phonon normal mode spectrum properties are used to express the mean square variation of the half-scattering path length for a Fe+2 -porphiryn complex as a function of temperature for the most important single and multiple scattering paths of the complex thus virtually eliminating them from the fitting procedure. Modeled calculations are compared with corresponding values obtained from DFT-built and optimized Fe+2 -porphyrin bis-histidine structure as well as from experimental XAFS spectra previously reported. An excellent agreement between calculated and reference Debye-Waller factors for Fe+2-porphyrins is obtained.

Ab Initio Study of Electronic Structure, Elastic and Transport Properties of Fluoroperovskite LiBeF3

NASA Astrophysics Data System (ADS)

Benmhidi, H.; Rached, H.; Rached, D.; Benkabou, M.

2017-04-01

The aim of this work is to investigate the electronic, mechanical, and transport properties of the fluoroperovskite compound LiBeF3 by first-principles calculations using the full-potential linear muffin-tin orbital method based on density functional theory within the local density approximation. The independent elastic constants and related mechanical properties including the bulk modulus ( B), shear modulus ( G), Young's modulus ( E), and Poisson's ratio ( ν) have been studied, yielding the elastic moduli, shear wave velocities, and Debye temperature. According to the electronic properties, this compound is an indirect-bandgap material, in good agreement with available theoretical data. The electron effective mass, hole effective mass, and energy bandgaps with their volume and pressure dependence are investigated for the first time.

Measurement of Debye length in laser-produced plasma.

NASA Technical Reports Server (NTRS)

Ehler, W.

1973-01-01

The Debye length of an expanded plasma created by placing an evacuated chamber with an entrance slit in the path of a freely expanding laser produced plasma was measured, using the slab geometry. An independent measurement of electron density together with the observed value for the Debye length also provided a means for evaluating the plasma electron temperature. This temperature has applications in ascertaining plasma conductivity and magnetic field necessary for confinement of the laser produced plasma. Also, the temperature obtained would be useful in analyzing electron-ion recombination rates in the expanded plasma and the dynamics of the cooling process of the plasma expansion.

Optical Simulation of Debye-Scherrer Crystal Diffraction

ERIC Educational Resources Information Center

Logiurato, F.; Gratton, L. M.; Oss, S.

2008-01-01

In this paper we describe and discuss simple, inexpensive optical experiments used to simulate x-ray and electron diffraction according to the Debye-Scherrer theory. The experiment can be used to address, at the high school level, important subjects related to fundamental quantum and solid-state physics.

Complex fluids with mobile charge-regulating macro-ions

NASA Astrophysics Data System (ADS)

Markovich, Tomer; Andelman, David; Podgornik, Rudi

2017-10-01

We generalize the concept of charge regulation of ionic solutions, and apply it to complex fluids with mobile macro-ions having internal non-electrostatic degrees of freedom. The suggested framework provides a convenient tool for investigating systems where mobile macro-ions can self-regulate their charge (e.g., proteins). We show that even within a simplified charge-regulation model, the charge dissociation equilibrium results in different and notable properties. Consequences of the charge regulation include a positional dependence of the effective charge of the macro-ions, a non-monotonic dependence of the effective Debye screening length on the concentration of the monovalent salt, a modification of the electric double-layer structure, and buffering by the macro-ions of the background electrolyte.

Persistence length changes dramatically as RNA folds.

PubMed

Caliskan, G; Hyeon, C; Perez-Salas, U; Briber, R M; Woodson, S A; Thirumalai, D

2005-12-31

We determine the persistence length l(p) for a bacterial group I ribozyme as a function of concentration of monovalent and divalent cations by fitting the distance distribution functions P(r) obtained from small angle x-ray scattering intensity data to the asymptotic form of the calculated P(WLC)(r) for a wormlike chain. The l(p) values change dramatically over a narrow range of Mg(2+) concentration from approximately 21 Angstroms in the unfolded state (U) to approximately 10 Angstroms in the compact (I(C)) and native states. Variations in l(p) with increasing Na(+) concentration are more gradual. In accord with the predictions of polyelectrolyte theory we find l(p) alpha 1/kappa(2) where kappa is the inverse Debye-screening length.

Precise energy eigenvalues of hydrogen-like ion moving in quantum plasmas

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

Dutta, S.; Saha, Jayanta K.; Mukherjee, T. K.

2015-06-15

The analytic form of the electrostatic potential felt by a slowly moving test charge in quantum plasma is developed. It has been shown that the electrostatic potential is composed of two parts: the Debye-Huckel screening term and the near-field wake potential. The latter depends on the velocity of the test charge as well as on the number density of the plasma electrons. Rayleigh-Ritz variational calculation has been done to estimate precise energy eigenvalues of hydrogen-like carbon ion under such plasma environment. A detailed analysis shows that the energy levels gradually move to the continuum with increasing plasma electron density whilemore » the level crossing phenomenon has been observed with the variation of ion velocity.« less

Static quark-antiquark potential in the quark-gluon plasma from lattice QCD.

PubMed

Burnier, Yannis; Kaczmarek, Olaf; Rothkopf, Alexander

2015-02-27

We present a state-of-the-art determination of the complex valued static quark-antiquark potential at phenomenologically relevant temperatures around the deconfinement phase transition. Its values are obtained from nonperturbative lattice QCD simulations using spectral functions extracted via a novel Bayesian inference prescription. We find that the real part, both in a gluonic medium, as well as in realistic QCD with light u, d, and s quarks, lies close to the color singlet free energies in Coulomb gauge and shows Debye screening above the (pseudo)critical temperature T_{c}. The imaginary part is estimated in the gluonic medium, where we find that it is of the same order of magnitude as in hard-thermal loop resummed perturbation theory in the deconfined phase.

Equilibrium swelling properties of polyampholytic hydrogels

NASA Astrophysics Data System (ADS)

English, Anthony E.; Mafé, Salvador; Manzanares, José A.; Yu, Xiahong; Grosberg, Alexander Yu.; Tanaka, Toyoichi

1996-06-01

The role of counter ions and ion dissociation in establishing the equilibrium swelling of balanced and unbalanced polyampholytic hydrogels has been investigated experimentally and theoretically. The swelling dependence on both the net charge offset and the external bath salt concentration has been examined using an acrylamide based polyampholytic hydrogels. By careful consideration of the swelling kinetics, we illustrate the effects of ion dissociation equilibria and counter ion shielding in polyampholytic hydrogels near their balance point where both polyelectrolyte and polyampholyte effects are present. The theory considers a Flory type swelling model where the Coulombic interactions between fixed ions in the hydrogel resemble those of an ionic solid with a Debye screening factor. Theoretical predictions from this model are in qualitative agreement with our experimental results.

Long-range electrostatic screening in ionic liquids

PubMed Central

Gebbie, Matthew A.; Dobbs, Howard A.; Valtiner, Markus; Israelachvili, Jacob N.

2015-01-01

Electrolyte solutions with high concentrations of ions are prevalent in biological systems and energy storage technologies. Nevertheless, the high interaction free energy and long-range nature of electrostatic interactions makes the development of a general conceptual picture of concentrated electrolytes a significant challenge. In this work, we study ionic liquids, single-component liquids composed solely of ions, in an attempt to provide a novel perspective on electrostatic screening in very high concentration (nonideal) electrolytes. We use temperature-dependent surface force measurements to demonstrate that the long-range, exponentially decaying diffuse double-layer forces observed across ionic liquids exhibit a pronounced temperature dependence: Increasing the temperature decreases the measured exponential (Debye) decay length, implying an increase in the thermally driven effective free-ion concentration in the bulk ionic liquids. We use our quantitative results to propose a general model of long-range electrostatic screening in ionic liquids, where thermally activated charge fluctuations, either free ions or correlated domains (quasiparticles), take on the role of ions in traditional dilute electrolyte solutions. This picture represents a crucial step toward resolving several inconsistencies surrounding electrostatic screening and charge transport in ionic liquids that have impeded progress within the interdisciplinary ionic liquids community. More broadly, our work provides a previously unidentified way of envisioning highly concentrated electrolytes, with implications for diverse areas of inquiry, ranging from designing electrochemical devices to rationalizing electrostatic interactions in biological systems. PMID:26040001

Screening of a dust particle charge in a humid air plasma created by an electron beam

NASA Astrophysics Data System (ADS)

Filippov, A. V.; Derbenev, I. N.; Kurkin, S. A.

2018-01-01

A kinetic model has been developed for charged particle reactions in a humid air plasma produced by a fast electron beam. The model includes over 550 reactions with electrons, 33 positive ion species and 14 negative ion species. The model has been tested by solving 48 non-steady state equations for number densities of charged particles in humid air electron beam plasma, and by comparing with the available experimental data. The system of 48 steady state equations has been solved by iterative method in order to define the main ion species of the humid air plasma. A reduced kinetic model has been developed to describe the processes with the main ions and electrons. Screening constants have been calculated on the basis of the reduced system by means of Leverrier-Fadeev method. The dependencies of screening constants on gas ionization rates have been found for the rates from 10 to 1018 cm-3s-1 and the fraction of water molecules from 0 to 2%. The analysis of the constants has revealed that one of them is close to the inverse Debye length, and the other constants are defined by the inverse diffusion lengths passed by ions in the characteristic times of the attachment, recombination, and ion conversion. Pure imaginary screening constants appear at low rates of gas ionization.

Debye potentials for heterogeneous media

NASA Astrophysics Data System (ADS)

Panamarev, N. S.; Donchenko, V. A.; Zemlyanov, Al. A.; Samokhvalov, I. V.; Apeksimov, D. V.; Panamaryova, A. N.; Trifonova, A. V.

2017-11-01

The paper presents the results of the Helmholtz equation solution by the method of perturbation theory in the spherical coordinate system for the Debye potentials for weakly heterogeneous media based on metal nanoparticles and the dielectric matrix. In that case, the dielectric function of a composite changes in space in the radial direction.

A molecular Debye-Hückel approach to the reorganization energy of electron transfer reactions in an electric cell

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

Xiao, Tiejun; Department of Chemistry, Iowa State University, Ames, Iowa 50011; Song, Xueyu

2014-10-07

Electron transfer near an electrode immersed in ionic fluids is studied using the linear response approximation, namely, mean value of the vertical energy gap can be used to evaluate the reorganization energy, and hence any linear response model that can treat Coulomb interactions successfully can be used for the reorganization energy calculation. Specifically, a molecular Debye-Hückel theory is used to calculate the reorganization energy of electron transfer reactions in an electric cell. Applications to electron transfer near an electrode in molten salts show that the reorganization energies from our molecular Debye-Hückel theory agree well with the results from MD simulations.

Correlated Debye model for atomic motions in metal nanocrystals

NASA Astrophysics Data System (ADS)

Scardi, P.; Flor, A.

2018-05-01

The Correlated Debye model for the mean square relative displacement of atoms in near-neighbour coordination shells has been extended to include the effect of finite crystal size. This correctly explains the increase in Debye-Waller coefficient observed for metal nanocrystals. A good match with Molecular Dynamics simulations of Pd nanocrystals is obtained if, in addition to the phonon confinement effect of the finite domain size, proper consideration is also given to the static disorder component caused by the undercoordination of surface atoms. The new model, which addresses the analysis of the Pair Distribution Function and powder diffraction data collected at different temperatures, was preliminarily tested on recently published experimental data on nanocrystalline Pt powders.

Interaction of colloidal nanoparticles with their local environment: the (ionic) nanoenvironment around nanoparticles is different from bulk and determines the physico-chemical properties of the nanoparticles

PubMed Central

Pfeiffer, Christian; Rehbock, Christoph; Hühn, Dominik; Carrillo-Carrion, Carolina; de Aberasturi, Dorleta Jimenez; Merk, Vivian; Barcikowski, Stephan; Parak, Wolfgang J.

2014-01-01

The physico-chemical properties of colloidal nanoparticles (NPs) are influenced by their local environment, as, in turn, the local environment influences the physico-chemical properties of the NPs. In other words, the local environment around NPs has a profound impact on the NPs, and it is different from bulk due to interaction with the NP surface. So far, this important effect has not been addressed in a comprehensive way in the literature. The vicinity of NPs can be sensitively influenced by local ions and ligands, with effects already occurring at extremely low concentrations. NPs in the Hückel regime are more sensitive to fluctuations in the ionic environment, because of a larger Debye length. The local ion concentration hereby affects the colloidal stability of the NPs, as it is different from bulk owing to Debye Hückel screening caused by the charge of the NPs. This can have subtle effects, now caused by the environment to the performance of the NP, such as for example a buffering effect caused by surface reaction on ultrapure ligand-free nanogold, a size quenching effect in the presence of specific ions and a significant impact on fluorophore-labelled NPs acting as ion sensors. Thus, the aim of this review is to clarify and give an unifying view of the complex interplay between the NP's surface with their nanoenvironment. PMID:24759541

Continuum limit of the vibrational properties of amorphous solids.

PubMed

Mizuno, Hideyuki; Shiba, Hayato; Ikeda, Atsushi

2017-11-14

The low-frequency vibrational and low-temperature thermal properties of amorphous solids are markedly different from those of crystalline solids. This situation is counterintuitive because all solid materials are expected to behave as a homogeneous elastic body in the continuum limit, in which vibrational modes are phonons that follow the Debye law. A number of phenomenological explanations for this situation have been proposed, which assume elastic heterogeneities, soft localized vibrations, and so on. Microscopic mean-field theories have recently been developed to predict the universal non-Debye scaling law. Considering these theoretical arguments, it is absolutely necessary to directly observe the nature of the low-frequency vibrations of amorphous solids and determine the laws that such vibrations obey. Herein, we perform an extremely large-scale vibrational mode analysis of a model amorphous solid. We find that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that follow another universal non-Debye scaling law.

Numerical analysis of finite Debye-length effects in induced-charge electro-osmosis.

PubMed

Gregersen, Misha Marie; Andersen, Mathias Baekbo; Soni, Gaurav; Meinhart, Carl; Bruus, Henrik

2009-06-01

For a microchamber filled with a binary electrolyte and containing a flat unbiased center electrode at one wall, we employ three numerical models to study the strength of the resulting induced-charge electro-osmotic (ICEO) flow rolls: (i) a full nonlinear continuum model resolving the double layer, (ii) a linear slip-velocity model not resolving the double layer and without tangential charge transport inside this layer, and (iii) a nonlinear slip-velocity model extending the linear model by including the tangential charge transport inside the double layer. We show that, compared to the full model, the slip-velocity models significantly overestimate the ICEO flow. This provides a partial explanation of the quantitative discrepancy between observed and calculated ICEO velocities reported in the literature. The discrepancy increases significantly for increasing Debye length relative to the electrode size, i.e., for nanofluidic systems. However, even for electrode dimensions in the micrometer range, the discrepancies in velocity due to the finite Debye length can be more than 10% for an electrode of zero height and more than 100% for electrode heights comparable to the Debye length.

Continuum limit of the vibrational properties of amorphous solids

PubMed Central

Mizuno, Hideyuki; Ikeda, Atsushi

2017-01-01

The low-frequency vibrational and low-temperature thermal properties of amorphous solids are markedly different from those of crystalline solids. This situation is counterintuitive because all solid materials are expected to behave as a homogeneous elastic body in the continuum limit, in which vibrational modes are phonons that follow the Debye law. A number of phenomenological explanations for this situation have been proposed, which assume elastic heterogeneities, soft localized vibrations, and so on. Microscopic mean-field theories have recently been developed to predict the universal non-Debye scaling law. Considering these theoretical arguments, it is absolutely necessary to directly observe the nature of the low-frequency vibrations of amorphous solids and determine the laws that such vibrations obey. Herein, we perform an extremely large-scale vibrational mode analysis of a model amorphous solid. We find that the scaling law predicted by the mean-field theory is violated at low frequency, and in the continuum limit, the vibrational modes converge to a mixture of phonon modes that follow the Debye law and soft localized modes that follow another universal non-Debye scaling law. PMID:29087941

Dark-field transmission electron microscopy and the Debye-Waller factor of graphene

PubMed Central

Hubbard, William A.; White, E. R.; Dawson, Ben; Lodge, M. S.; Ishigami, Masa; Regan, B. C.

2014-01-01

Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary. PMID:25242882

Dark-field transmission electron microscopy and the Debye-Waller factor of graphene.

PubMed

Shevitski, Brian; Mecklenburg, Matthew; Hubbard, William A; White, E R; Dawson, Ben; Lodge, M S; Ishigami, Masa; Regan, B C

2013-01-15

Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary.

Calculation of Debye-Scherrer diffraction patterns from highly stressed polycrystalline materials

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

MacDonald, M. J., E-mail: macdonm@umich.edu; SLAC National Accelerator Laboratory, Menlo Park, California 94025; Vorberger, J.

2016-06-07

Calculations of Debye-Scherrer diffraction patterns from polycrystalline materials have typically been done in the limit of small deviatoric stresses. Although these methods are well suited for experiments conducted near hydrostatic conditions, more robust models are required to diagnose the large strain anisotropies present in dynamic compression experiments. A method to predict Debye-Scherrer diffraction patterns for arbitrary strains has been presented in the Voigt (iso-strain) limit [Higginbotham, J. Appl. Phys. 115, 174906 (2014)]. Here, we present a method to calculate Debye-Scherrer diffraction patterns from highly stressed polycrystalline samples in the Reuss (iso-stress) limit. This analysis uses elastic constants to calculate latticemore » strains for all initial crystallite orientations, enabling elastic anisotropy and sample texture effects to be modeled directly. The effects of probing geometry, deviatoric stresses, and sample texture are demonstrated and compared to Voigt limit predictions. An example of shock-compressed polycrystalline diamond is presented to illustrate how this model can be applied and demonstrates the importance of including material strength when interpreting diffraction in dynamic compression experiments.« less

Effective Debye length in closed nanoscopic systems: a competition between two length scales.

PubMed

Tessier, Frédéric; Slater, Gary W

2006-02-01

The Poisson-Boltzmann equation (PBE) is widely employed in fields where the thermal motion of free ions is relevant, in particular in situations involving electrolytes in the vicinity of charged surfaces. The applications of this non-linear differential equation usually concern open systems (in osmotic equilibrium with an electrolyte reservoir, a semi-grand canonical ensemble), while solutions for closed systems (where the number of ions is fixed, a canonical ensemble) are either not appropriately distinguished from the former or are dismissed as a numerical calculation exercise. We consider herein the PBE for a confined, symmetric, univalent electrolyte and quantify how, in addition to the Debye length, its solution also depends on a second length scale, which embodies the contribution of ions by the surface (which may be significant in high surface-to-volume ratio micro- or nanofluidic capillaries). We thus establish that there are four distinct regimes for such systems, corresponding to the limits of the two parameters. We also show how the PBE in this case can be formulated in a familiar way by simply replacing the traditional Debye length by an effective Debye length, the value of which is obtained numerically from conservation conditions. But we also show that a simple expression for the value of the effective Debye length, obtained within a crude approximation, remains accurate even as the system size is reduced to nanoscopic dimensions, and well beyond the validity range typically associated with the solution of the PBE.

A new insight on the dynamics of sodium dodecyl sulfate aqueous micellar solutions by dielectric spectroscopy.

PubMed

Lanzi, Leandro; Carlà, Marcello; Lanzi, Leonardo; Gambi, Cecilia M C

2009-02-01

Aqueous sodium dodecyl sulfate micellar solutions were investigated by a recently developed double-differential dielectric spectroscopy technique in the frequency range 100 MHz-3 GHz at 22 degrees C, in the surfactant concentration range 29.8-524 mM, explored for the first time above 104 mM. The micellar contribution to dielectric spectra was analyzed according to three models containing, respectively, a single Debye relaxation, a Cole-Cole relaxation and a double Debye relaxation. The single Debye model is not accurate enough. Both Cole-Cole and double Debye models fit well the experimental dielectric spectra. With the double Debye model, two characteristic relaxation times were identified: the slower one, in the range 400-900 ps, is due to the motion of counterions bound to the micellar surface (lateral motion); the faster one, in the range 100-130 ps, is due to interfacial bound water. Time constants and amplitudes of both processes are in fair agreement with Grosse's theoretical model, except at the largest concentration values, where interactions between micelles increase. For each sample, the volume fraction of bulk water and the effect of bound water as well as the conductivity in the low frequency limit were computed. The bound water increases as the surfactant concentration increases, in quantitative agreement with the micellar properties. The number of water molecules per surfactant molecule was also computed. The conductivity values are in agreement with Kallay's model over the whole surfactant concentration range.

Electrostatic Inflation of Membrane Space Structures

NASA Astrophysics Data System (ADS)

Stiles, Laura A.

Membrane space structures provide a lightweight and cost effective alternative to traditional mechanical systems. The low-mass and high deployed-to-stored volume ratios allow for larger structures to be launched, expanding on-orbit science and technology capabilities. This research explores a novel method for deployment of membrane space structures using electrostatic pressure as the inflation mechanism. Applying electric charge to a layered gossamer structure provides an inflationary pressure due to the repulsive electrostatic forces between the charged layers. The electrostatic inflation of membrane structures (EIMS) concept is particularly applicable to non-precision structures such as sunshields or drag de-orbiting devices. This research addresses three fundamental topics: necessary conditions for EIMS in a vacuum, necessary conditions for EIMS in a plasma, and charging methods. Vacuum demonstrations show that less than 10 kiloVolts are required for electrostatic inflation of membrane structures in 1-g. On-orbit perturbation forces can be much smaller, suggesting feasible voltage requirements. Numerical simulation enables a relationship between required inflation pressure (to offset disturbances) and voltage. 100's of Volts are required for inflation in geosynchronous orbits (GEO) and a few kiloVolts in low Earth orbit (LEO). While GEO plasma has a small impact on the EIMS performance, Debye shielding at LEO reduces the electrostatic pressure. The classic Debye shielding prediction is far worse than actual shielding, raising the `effective' Debye length to the meter scale in LEO, suggesting feasibility for EIMS in LEO. Charged particle emission and remote charging methods are explored as inflation mechanisms. Secondary electron emission characteristics of EIMS materials were determined experimentally. Nonlinear fits to the Sternglass curve determined a maximum yield of 1.83 at 433 eV for Aluminized Kapton and a maximum yield of 1.78 at 511 eV for Aluminized Mylar. Remote charging was demonstrated to -500 V with a 5 keV electron beam. Charge emission power levels are below 1 Watt in GEO and from 10's of Watt to a kiloWatt in LEO.

Observations of low-energy ions in the wake of a magnetospheric satellite

NASA Technical Reports Server (NTRS)

Samir, U.; Comfort, R. H.; Chappell, C. R.; Stone, N. H.

1986-01-01

Measurements of low-energy ions made by the retarding ion mass spectrometer (RIMS) onboard the Dynamics Explorer 1 (DE 1) satellite are used to study some aspects of 'body-plasma interactions' in the terrestrial plasmasphere. Preliminary results are presented, yielding the degree of H+ and He+ ion depletion in the wake of the satellite in terms of specific and average ion Mach numbers, average ion mass, body size normalized to ionic Debye length, and body potential normalized to ion thermal energy. Some results from the RIMS measurements are compared with relevant results from the Explorer 31 and the Atmosphere Explorer C ionospheric satellites. Wake depletion is found to vary approximately linearly for small bodies (R-sub-Di less than about 12) and exponentially for large bodies (R-sub-Di greater than 50).

Plasmon mass scale and quantum fluctuations of classical fields on a real time lattice

NASA Astrophysics Data System (ADS)

Kurkela, Aleksi; Lappi, Tuomas; Peuron, Jarkko

2018-03-01

Classical real-time lattice simulations play an important role in understanding non-equilibrium phenomena in gauge theories and are used in particular to model the prethermal evolution of heavy-ion collisions. Above the Debye scale the classical Yang-Mills (CYM) theory can be matched smoothly to kinetic theory. First we study the limits of the quasiparticle picture of the CYM fields by determining the plasmon mass of the system using 3 different methods. Then we argue that one needs a numerical calculation of a system of classical gauge fields and small linearized fluctuations, which correspond to quantum fluctuations, in a way that keeps the separation between the two manifest. We demonstrate and test an implementation of an algorithm with the linearized fluctuation showing that the linearization indeed works and that the Gauss's law is conserved.

Transition energies and polarizabilities of hydrogen like ions in plasma

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

Das, Madhusmita

2012-09-15

Effect of plasma screening on various properties like transition energy, polarizability (dipole and quadrupole), etc. of hydrogen like ions is studied. The bound and free state wave functions and transition matrix elements are obtained by numerically integrating the radial Schrodinger equation for appropriate plasma potential. We have used adaptive step size controlled Runge-Kutta method to perform the numerical integration. Debye-Huckel potential is used to investigate the variation in transition lines and polarizabilities (dipole and quadrupole) with increasing plasma screening. For a strongly coupled plasma, ion sphere potential is used to show the variation in excitation energy with decreasing ion spheremore » radius. It is observed that plasma screening sets in phenomena like continuum lowering and pressure ionization, which are unique to ions in plasma. Of particular interest is the blue (red) shift in transitions conserving (non-conserving) principal quantum number. The plasma environment also affects the dipole and quadrupole polarizability of ions in a significant manner. The bound state contribution to polarizabilities decreases with increase in plasma density whereas the continuum contribution is significantly enhanced. This is a result of variation in the behavior of bound and continuum state wave functions in the presence of plasma. We have compared the results with existing theoretical and experimental data wherever present.« less

Confinement control mechanism for two-electron Hulthen quantum dots in plasmas

NASA Astrophysics Data System (ADS)

Bahar, M. K.; Soylu, A.

2018-05-01

In this study, for the first time, the energies of two-electron Hulthen quantum dots (TEHQdots) embedded in Debye and quantum plasmas modeled by the more general exponential cosine screened Coulomb (MGECSC) potential under the combined influence of electric and magnetic fields are investigated by numerically solving the Schrödinger equation using the asymptotic iteration method. To do this, the four different forms of the MGECSC potential, which set through the different cases of the potential parameters, are taken into consideration. We propose that plasma environments form considerable quantum mechanical effects for quantum dots and other atomic systems and that plasmas are important experimental arguments. In this study, by considering the quantum dot parameters, the external field parameters, and the plasma screening parameters, a control mechanism of the confinement on energies of TEHQdots and the frequency of the radiation emitted by TEHQdots as a result of any excitation is discussed. In this mechanism, the behaviors, similarities, the functionalities of the control parameters, and the influences of plasmas on these quantities are explored.

Structural Origin of Enhanced Dynamics at the Surface of a Glassy Alloy

NASA Astrophysics Data System (ADS)

Sun, Gang; Saw, Shibu; Douglass, Ian; Harrowell, Peter

2017-12-01

The enhancement of mobility at the surface of an amorphous alloy is studied using a combination of molecular dynamic simulations and normal mode analysis of the nonuniform distribution of Debye-Waller factors. The increased mobility at the surface is found to be associated with the appearance of Arrhenius temperature dependence. We show that the transverse Debye-Waller factor exhibits a peak at the surface. Over the accessible temperature range, we find that the bulk and surface diffusion coefficients obey the same empirical relationship with the respective Debye-Waller factors. Extrapolating this relationship to lower T , we argue that the observed decrease in the constraint at the surface is sufficient to account for the experimentally observed surface enhancement of mobility.

Inertial effects in systems with magnetic charge

NASA Astrophysics Data System (ADS)

Armitage, N. P.

2018-05-01

This short article sets out some of the basic considerations that go into detecting the mass of quasiparticles with effective magnetic charge in solids. Effective magnetic charges may be appear as defects in particular magnetic textures. A magnetic monopole is a defect in this texture and as such these are not monopoles in the actual magnetic field B, but instead in the auxiliary field H. They may have particular properties expected for such quasiparticles such as magnetic charge and mass. This effective mass may-in principle-be detected in the same fashion that the mass is detected of other particles classically e.g. through their inertial response to time-dependent electromagnetic fields. I discuss this physics in the context of the "simple" case of the quantum spin ices, but aspects are broadly applicable. Based on extensions to Ryzkhin's model for classical spin ice, a hydrodynamic formulation can be given that takes into account inertial and entropic forces. Ultimately, a form for the susceptibility is obtained that is equivalent to the Rocard equation, which is a classic form used to account for inertial effects in the context of Debye-like relaxation.

LETTER TO THE EDITOR: Green emission and bandgap narrowing due to two-photon excitation in thin film CdS formed by spray pyrolysis

NASA Astrophysics Data System (ADS)

Ullrich, B.; Schroeder, R.

2001-08-01

Thin (10 µm) film CdS on Pyrex® formed by spray pyrolysis is excited below the gap at 804 nm with 200 fs laser pulses at room temperature. Excitation intensities up to 250 GW cm-2 evoke green bandgap emission due to two-photon transitions. This two-photon photoluminescence does not show a red emission contribution in contrast to the single-photon excited emission, which is dominated by broad emission in the red spectral range. It is demonstrated that two-photon excitation causes photo-induced bandgap narrowing due to Debye screening. At 250 GW cm-2 bandgap narrowing of 47 meV is observed, which corresponds to an excited electron density of 1.6×1018 cm-3.

Theoretical study of interactions of BSA protein in a NaCl aqueous solution

NASA Astrophysics Data System (ADS)

Pellicane, Giuseppe; Cavero, Miguel

2013-03-01

Bovine Serum Albumine (BSA) aqueous solutions in the presence of NaCl are investigated for different protein concentrations and low to intermediate ionic strengths. Protein interactions are modeled via a charge-screened colloidal model, in which the range of the potential is determined by the Debye-Hückel constant. We use Monte Carlo computer simulations to calculate the structure factor, and assume an oblate ellipsoidal form factor for BSA. The theoretical scattered intensities are found in good agreement with the experimental small angle X-ray scattering intensities available in the literature. The performance of well-known integral equation closures to the Ornstein-Zernike equation, namely the mean spherical approximation, the Percus-Yevick, and the hypernetted chain equations, is also assessed with respect to computer simulation.

Quantum statistical mechanics of dense partially ionized hydrogen.

NASA Technical Reports Server (NTRS)

Dewitt, H. E.; Rogers, F. J.

1972-01-01

The theory of dense hydrogenic plasmas beginning with the two component quantum grand partition function is reviewed. It is shown that ionization equilibrium and molecular dissociation equilibrium can be treated in the same manner with proper consideration of all two-body states. A quantum perturbation expansion is used to give an accurate calculation of the equation of state of the gas for any degree of dissociation and ionization. In this theory, the effective interaction between any two charges is the dynamic screened potential obtained from the plasma dielectric function. We make the static approximation; and we carry out detailed numerical calculations with the bound and scattering states of the Debye potential, using the Beth-Uhlenbeck form of the quantum second virial coefficient. We compare our results with calculations from the Saha equation.

Method and system for nanoscale plasma processing of objects

DOEpatents

Oehrlein, Gottlieb S [Clarksville, MD; Hua, Xuefeng [Hyattsville, MD; Stolz, Christian [Baden-Wuerttemberg, DE

2008-12-30

A plasma processing system includes a source of plasma, a substrate and a shutter positioned in close proximity to the substrate. The substrate/shutter relative disposition is changed for precise control of substrate/plasma interaction. This way, the substrate interacts only with a fully established, stable plasma for short times required for nanoscale processing of materials. The shutter includes an opening of a predetermined width, and preferably is patterned to form an array of slits with dimensions that are smaller than the Debye screening length. This enables control of the substrate/plasma interaction time while avoiding the ion bombardment of the substrate in an undesirable fashion. The relative disposition between the shutter and the substrate can be made either by moving the shutter or by moving the substrate.

On the Numerical Analysis of Decay Rate Enhancement in Metallic Environment

NASA Astrophysics Data System (ADS)

Mehedinteanu, S.

2007-10-01

Motivated on the very recent experiments to determine the acceleration of the alpha decay of meta-stable radionuclides in metallic environment some work has been done to strengthten the importance in the process of electrons screening in metals. Thus, by combining the Gamow decay theory with electrostatic screening in Debye-Hückel approximation (jellium model) a formula for ``the shift'' in screening energy which enters in the decay enhancement factor expression that copes well with these experiments has been derived. It was established that to simulate the poly-atoms system containing decaying isotopes in QM&MD codes calculations, and to include ``the screening energy shift'' of protons, decay alpha, beta+ particles due to all surrounding interacting effects, it is sufficiently only to substitute the code ruly pseudo-potential input for hydrogen-like atoms (including alpha) by a screened Coulomb potential as from the well-known Gamow alpha decay theory. For demonstration is used the QM&MD code package which usually performs density-functional theory (DFT) total-energy calculations for materials ranging from insulators to transition metals. This package employs first-principles pseudo-potentials and a plane-wave basis-set, and it was used to do a special calculus for some metal environments (Pd) where protons-deuterons are implanted or when it is alloyed with a radionuclide-like isotopes (174Hf72), the results compare well with the existing experiments on the decay enhancement. These works give further arguments for a cheap solution to remove the transuranic waste (involving all alpha-decay) of used-up rods of fission reactors in a time period of a few years.

Comprehensive Urine Drug Screen by Gas Chromatography/Mass Spectrometry (GC/MS).

PubMed

Ramoo, Bheemraj; Funke, Melissa; Frazee, Clint; Garg, Uttam

2016-01-01

Drug screening is an essential component of clinical toxicology laboratory service. Some laboratories use only automated chemistry analyzers for limited screening of drugs of abuse and few other drugs. Other laboratories use a combination of various techniques such as immunoassays, colorimetric tests, and mass spectrometry to provide more detailed comprehensive drug screening. Mass spectrometry, gas or liquid, can screen for hundreds of drugs and is often considered the gold standard for comprehensive drug screening. We describe an efficient and rapid gas chromatography/mass spectrometry (GC/MS) method for comprehensive drug screening in urine which utilizes a liquid-liquid extraction, sample concentration, and analysis by GC/MS.

Some Debye temperatures from single-crystal elastic constant data

USGS Publications Warehouse

Robie, R.A.; Edwards, J.L.

1966-01-01

The mean velocity of sound has been calculated for 14 crystalline solids by using the best recent values of their single-crystal elastic stiffness constants. These mean sound velocities have been used to obtain the elastic Debye temperatures ??De for these materials. Models of the three wave velocity surfaces for calcite are illustrated. ?? 1966 The American Institute of Physics.

Analytical Debye-Huckel model for electrostatic potentials around dissolved DNA.

PubMed

Wagner, K; Keyes, E; Kephart, T W; Edwards, G

1997-07-01

We present an analytical, Green-function-based model for the electric potential of DNA in solution, treating the surrounding solvent with the Debye-Huckel approximation. The partial charge of each atom is accounted for by modeling DNA as linear distributions of atoms on concentric cylindrical surfaces. The condensed ions of the solvent are treated with the Debye-Huckel approximation. The resultant leading term of the potential is that of a continuous shielded line charge, and the higher order terms account for the helical structure. Within several angstroms of the surface there is sufficient information in the electric potential to distinguish features and symmetries of DNA. Plots of the potential and equipotential surfaces, dominated by the phosphate charges, reflect the structural differences between the A, B, and Z conformations and, to a smaller extent, the difference between base sequences. As the distances from the helices increase, the magnitudes of the potentials decrease. However, the bases and sugars account for a larger fraction of the double helix potential with increasing distance. We have found that when the solvent is treated with the Debye-Huckel approximation, the potential decays more rapidly in every direction from the surface than it did in the concentric dielectric cylinder approximation.

Dielectric relaxation of 2-ethyl-1-hexanol around the glass transition by thermally stimulated depolarization currents.

PubMed

Arrese-Igor, S; Alegría, A; Colmenero, J

2015-06-07

We explore new routes for characterizing the Debye-like and α relaxation in 2-ethyl-1-hexanol (2E1H) monoalcohol by using low frequency dielectric techniques including thermally stimulated depolarization current (TSDC) techniques and isothermal depolarization current methods. In this way, we have improved the resolution of the overlapped processes making it possible the analysis of the data in terms of a mode composition as expected for a chain-like response. Furthermore the explored ultralow frequencies enabled to study dynamics at relatively low temperatures close to the glass transition (Tg). Results show, on the one hand, that Debye-like and α relaxation timescales dramatically approach to each other upon decreasing temperature to Tg. On the other hand, the analysis of partial polarization TSDC data confirms the single exponential character of the Debye-like relaxation in 2E1H and rules out the presence of Rouse type modes in the scenario of a chain-like response. Finally, on crossing the glass transition, the Debye-like relaxation shows non-equilibrium effects which are further emphasized by aging treatment and would presumably emerge as a result of the arrest of the structural relaxation below Tg.

Characterizing Flexible and Instrinsically Unstructured Biological Macromolecules by SAS using the Porod-Debye Law

PubMed Central

Rambo, Robert P.; Tainer, John A.

2011-01-01

Unstructured proteins, RNA or DNA components provide functionally important flexibility that is key to many macromolecular assemblies throughout cell biology. As objective, quantitative experimental measures of flexibility and disorder in solution are limited, small angle scattering (SAS), and in particular small angle X-ray scattering (SAXS), provides a critical technology to assess macromolecular flexibility as well as shape and assembly. Here, we consider the Porod-Debye law as a powerful tool for detecting biopolymer flexibility in SAS experiments. We show that the Porod-Debye region fundamentally describes the nature of the scattering intensity decay, which captures information needed for distinguishing between folded and flexible particles. Particularly for comparative SAS experiments, application of the law, as described here, can distinguish between discrete conformational changes and localized flexibility relevant to molecular recognition and interaction networks. This approach aids insightful analyses of fully and partly flexible macromolecules that is more robust and conclusive than traditional Kratky analyses. Furthermore, we demonstrate for prototypic SAXS data that the ability to calculate particle density by the Porod-Debye criteria, as shown here, provides an objective quality assurance parameter that may prove of general use for SAXS modeling and validation. PMID:21509745

Peter J. W. Debye - a whole life devoted to science.

PubMed

Dalba, Giuseppe

2016-11-01

In 1915 P. Debye, one of the most prominent scientists in the field of condensed-matter physics and physical chemistry, published an X-ray scattering equation for randomly oriented scattering sites. This formula, since then used for describing the structure of powders, liquids and gases, has become a model for material analysis at the nanoscale. This paper re-examines briefly Debye's works on the origin and evolution of the scattering equation and its first uses. The career of the great scientist and some of his other numerous and diverse contributions to science are also reviewed. Additionally the paper addresses aspects of his life as a teacher, as a science manager and as a man, including the recent controversy about his conduct during the Third Reich regime.

Calculation of Half-Metal, Debye and Curie Temperatures of Co2VAl Compound: First Principles Study

NASA Astrophysics Data System (ADS)

Arash, Boochani; Heidar, Khosravi; Jabbar, Khodadadi; Shahram, Solaymani; Masoud Majidiyan, Sarmazdeh; Rohollah Taghavi, Mendi; Sayed, Mohammad Elahi

2015-05-01

By FP-LAPW calculations, the structural, elastic, Debye and Curie temperatures, electronic and magnetic properties of Co2 VAl are investigated. The results indicate that Ferromagnetic (FM) phase is more stable than Anti-Ferromagnetic (AFM) and Non-magnetic (NM) ones. In addition, C11-C12 > 0, C44 > 0, and B > 0 so Co2VAl is an elastically stable material with high Debye temperature. Also, the B/G ratio exhibits a ductility behavior. The relatively high Curie temperature provides it as a favorable material for spintronic application. It's electronic and magnetic properties are studied by GGA+U approach leading to a 100% spin polarization at Fermi level. Supported by the simulation of Nano Physics Lab center of Kermanshah Branch, Islamic Azad University

Spectral lines behavior of Be I and Na I isoelectronic sequence in Debye plasma environment

NASA Astrophysics Data System (ADS)

Chaudhuri, Rajat K.; Chattopadhyay, Sudip; Sinha Mahapatra, Uttam

2012-08-01

We report the plasma screening effect on the first ionization potential (IP) and [He]2s2(1S0)→[He]2s2p /2s3p allowed (P11) and inter-combination transitions (P31) in some selected Be-like ions. In addition, we investigate the spectral properties of [Ne]3s (2S1/2)→[Ne]np(2P1/2 and P23/2 for n = 3, 4) transitions in Ca X and Fe XVI ions (Na I isoelectronic sequence) and [He]3s(2S1/2)→[He]np(2P1/2 and P23/2 for n = 2, 3) transitions in Li, B II, and N IV (Li I isoelectronic sequence) under plasma environment. The state-of-the-art relativistic coupled cluster calculations using the Debye model of plasma for electron-nucleus interaction show that (a) the ionization potential decreases sharply with increasing plasma strength and (b) the gap between the [He]2s2(1S0)→[He]2s2p(1,3P1) energy levels increases with increasing plasma potential and nuclear charge. It is found that the [He]2s2 (1S0)→2s3p(1,3P1) transition energy decreases uniformly with increasing plasma potential and nuclear charge. In other words, the spectral lines associated with 2s-2p (i.e., Δn=0, where n corresponds to principle quantum number) transitions in Be I isoelectronic sequence exhibit a blue-shift (except for Be I, B II, and the lowest inter-combination line in C III, which exhibit a red-shift), whereas those associated with 2s-3p (i.e., Δn≠0) transitions are red-shifted. Similar trend is observed in Li I and Na I isoelectronic sequences, where spectral lines associated with Δn=0 (Δn≠0) are blue-shifted (red-shifted). The effect of Coulomb screening on the spectral lines of ions subjected to plasma is also addressed.

Segregation of mass at the periphery of N -isopropylacrylamide-co-acrylic-acid microgels at high temperatures

DOE PAGES

Hyatt, John S.; Do, Changwoo; Hu, Xiaobo; ...

2015-09-29

Here, we investigate poly(N-isopropylacrylamide) (pNIPAM) microgels randomly copolymerized with large mol % of protonated acrylic acid (AAc), finding that above the lower critical solution temperature the presence of the acid strongly disrupts pNIPAM's collapse, leading to unexpected new behavior at high temperatures. We see a dramatic increase in the ratio between the radius of gyration and the hydrodynamic radius above the theoretical value for homogeneous spheres, and a corresponding increase of the network length scale, which we attribute to the presence of a heterogeneous polymer distribution that forms due to frustration of pNIPAM's coil-to-globule transition by the AAc. Finally, wemore » analyze this phenomenon using a Debye-Bueche-like scattering contribution as opposed to the Lorentzian term often used, interpreting the results in terms of mass segregation at the particle periphery.« less

On gel electrophoresis of dielectric charged particles with hydrophobic surface: A combined theoretical and numerical study.

PubMed

Majee, Partha Sarathi; Bhattacharyya, Somnath; Gopmandal, Partha Pratim; Ohshima, Hiroyuki

2018-03-01

A theoretical study on the gel electrophoresis of a charged particle incorporating the effects of dielectric polarization and surface hydrophobicity at the particle-liquid interface is made. A simplified model based on the weak applied field and low charge density assumption is also presented and compared with the full numerical model for a nonpolarizable particle to elucidate the nonlinear effects such as double layer polarization and relaxation as well as surface conduction. The main motivation of this study is to analyze the electrophoresis of the surface functionalized nanoparticle with tunable hydrophobicity or charged fluid drop in gel medium by considering the electrokinetic effects and hydrodynamic interactions between the particle and the gel medium. An effective medium approach, in which the transport in the electrolyte-saturated hydrogel medium is governed by the Brinkman equation, is adopted in the present analysis. The governing electrokinetic equations based on the conservation principles are solved numerically. The Navier-slip boundary condition along with the continuity condition of dielectric displacement are imposed on the surface of the hydrophobic polarizable particle. The impact of the slip length on the electrophoresis is profound for a thinner Debye layer, however, surface conduction effect also becomes significant for a hydrophobic particle. Impact of hydrophobicity and relaxation effects are higher for a larger particle. Dielectric polarization creates a reduction in its electrophoretic propulsion and has negligible impact at the thinner Debye length as well as lower gel screening length. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

From single Debye-Hückel chains to polyelectrolyte solutions: Simulation results

NASA Astrophysics Data System (ADS)

Kremer, Kurt

1996-03-01

This lecture will present results from simulations of single weakly charged flexible chains, where the electrostatic part of the interaction is modeled by a Debye-Hückel potential,( with U. Micka, IFF, Forschungszentrum Jülich, 52425 Jülich, Germany) as well as simulations of polyelectrolyte solutions, where the counterions are explicitly taken into account( with M. J. Stevens, Sandia Nat. Lab., Albuquerque, NM 87185-1111) ( M. J. Stevens, K. Kremer, JCP 103), 1669 (1995). The first set of the simulations is meant to clear a recent contoversy on the dependency of the persistence length LP on the screening length Γ. While the analytic theories give Lp ~ Γ^x with either x=1 or x=2, the simulations find for all experimentally accessible chain lengths a varying exponent, which is significantly smaller than 1. This causes serious doubts on the applicability of this model for weakly charged polyelectrolytes in general. The second part deals with strongly charged flexible polyelectrolytes in salt free solution. These simulations are performed for multichain systems. The full Coulomb interactions of the monomers and counterions are treated explicitly. Experimental measurements of the osmotic pressure and the structure factor are reproduced and extended. The simulations reveal a new picture of the chain structure based on calculations of the structure factor, persistence length, end-to-end distance, etc. Even at very low density, the chains show significant bending. Furthermore, the chains contract significantly before they start to overlap. We also show that counterion condensation dramatically alters the chain structure, even for a good solvent backbone.

Tight ceramic UF membrane as RO pre-treatment: the role of electrostatic interactions on phosphate rejection.

PubMed

Shang, Ran; Verliefde, Arne R D; Hu, Jingyi; Zeng, Zheyi; Lu, Jie; Kemperman, Antoine J B; Deng, Huiping; Nijmeijer, Kitty; Heijman, Sebastiaan G J; Rietveld, Luuk C

2014-01-01

Phosphate limitation has been reported as an effective approach to inhibit biofouling in reverse osmosis (RO) systems for water purification. The rejection of dissolved phosphate by negatively charged TiO2 tight ultrafiltration (UF) membranes (1 kDa and 3 kDa) was observed. These membranes can potentially be adopted as an effective process for RO pre-treatment in order to constrain biofouling by phosphate limitation. This paper focuses on electrostatic interactions during tight UF filtration. Despite the larger pore size, the 3 kDa ceramic membrane exhibited greater phosphate rejection than the 1 kDa membrane, because the 3 kDa membrane has a greater negative surface charge and thus greater electrostatic repulsion against phosphate. The increase of pH from 6 to 8.5 led to a substantial increase in phosphate rejection by both membranes due to increased electrostatic repulsion. At pH 8.5, the maximum phosphate rejections achieved by the 1 kDa and 3 kDa membrane were 75% and 86%, respectively. A Debye ratio (ratio of the Debye length to the pore radius) is introduced in order to evaluate double layer overlapping in tight UF membranes. Threshold Debye ratios were determined as 2 and 1 for the 1 kDa and 3 kDa membranes, respectively. A Debye ratio below the threshold Debye ratio leads to dramatically decreased phosphate rejection by tight UF membranes. The phosphate rejection by the tight UF, in combination with chemical phosphate removal by coagulation, might accomplish phosphate-limited conditions for biological growth and thus prevent biofouling in the RO systems. Copyright © 2013 Elsevier Ltd. All rights reserved.

High correlation of double Debye model parameters in skin cancer detection.

PubMed

Truong, Bao C Q; Tuan, H D; Fitzgerald, Anthony J; Wallace, Vincent P; Nguyen, H T

2014-01-01

The double Debye model can be used to capture the dielectric response of human skin in terahertz regime due to high water content in the tissue. The increased water proportion is widely considered as a biomarker of carcinogenesis, which gives rise of using this model in skin cancer detection. Therefore, the goal of this paper is to provide a specific analysis of the double Debye parameters in terms of non-melanoma skin cancer classification. Pearson correlation is applied to investigate the sensitivity of these parameters and their combinations to the variation in tumor percentage of skin samples. The most sensitive parameters are then assessed by using the receiver operating characteristic (ROC) plot to confirm their potential of classifying tumor from normal skin. Our positive outcomes support further steps to clinical application of terahertz imaging in skin cancer delineation.

Electronic structure, mechanical and thermodynamic properties of BaPaO3 under pressure.

PubMed

Khandy, Shakeel Ahmad; Islam, Ishtihadah; Gupta, Dinesh C; Laref, Amel

2018-05-07

Density functional theory (DFT)-based investigations have been put forward on the elastic, mechanical, and thermo-dynamical properties of BaPaO 3 . The pressure dependence of electronic band structure and other physical properties has been carefully analyzed. The increase in Bulk modulus and decrease in lattice constant is seen on going from 0 to 30 GPa. The predicted lattice constants describe this material as anisotropic and ductile in nature at ambient conditions. Post-DFT calculations using quasi-harmonic Debye model are employed to envisage the pressure-dependent thermodynamic properties like Debye temperature, specific heat capacity, Grüneisen parameter, thermal expansion, etc. Also, the computed Debye temperature and melting temperature of BaPaO 3 at 0 K are 523 K and 1764.75 K, respectively.

Mechanical and thermodynamic properties of AlX (X = N, P, As) compounds

NASA Astrophysics Data System (ADS)

Xu, Lifang; Bu, Wei

2017-09-01

The Vickers hardness of various AlX (X = N, P, As) compound polymorphs were calculated with the bond resistance model. Thermodynamic properties, such as vibrational entropy, constant volume specific heat and Debye temperatures, were calculated using phonon dispersion relations and phonon density of states (DOS). The calculated values are in good agreement with the previous experimental and theoretical data. For the same structure of AlX (X = N, P, As) compounds, their hardness and Debye temperatures both decrease with the X atomic number. The wurtzite (wz) and zincblende (zb) structures of the same compounds AlX share an almost identical hardness, but have different Debye temperatures. The difference between wz and zb structures increases as the atomic number of X increases. The thermodynamic properties reveal that the constant volume specific heat approaches the Dulong-Petit rule at high temperatures.

FDTD modelling of induced polarization phenomena in transient electromagnetics

NASA Astrophysics Data System (ADS)

Commer, Michael; Petrov, Peter V.; Newman, Gregory A.

2017-04-01

The finite-difference time-domain scheme is augmented in order to treat the modelling of transient electromagnetic signals containing induced polarization effects from 3-D distributions of polarizable media. Compared to the non-dispersive problem, the discrete dispersive Maxwell system contains costly convolution operators. Key components to our solution for highly digitized model meshes are Debye decomposition and composite memory variables. We revert to the popular Cole-Cole model of dispersion to describe the frequency-dependent behaviour of electrical conductivity. Its inversely Laplace-transformed Debye decomposition results in a series of time convolutions between electric field and exponential decay functions, with the latter reflecting each Debye constituents' individual relaxation time. These function types in the discrete-time convolution allow for their substitution by memory variables, annihilating the otherwise prohibitive computing demands. Numerical examples demonstrate the efficiency and practicality of our algorithm.

Ab-initio study of thermodynamic properties of boron nanowire at atomic scale

NASA Astrophysics Data System (ADS)

Bhuyan, Prabal D.; Gupta, Sanjeev K.; Sonvane, Y.; Gajjar, P. N.

2018-04-01

In the present work, we have optimized ribbon like zigzag structure of boron (B) nanowire (NW) and investigated vibrational and thermodynamic properties using quasi-harmonic approximations (QHA). All positive phonon in the phonon dispersive curve have confirmed dynamical stability of ribbon B-NW. The thermodynamic properties, like Debye temperature, internal energy and specific heat, are calculated as a function of temperature. The variation of specific heat is proportional to T3 Debye law at lower temperature for B-NW, while it becomes constant above room temperature at 1200K; obeys Dulong-Petit's law. The high Debye temperature of 1120K is observed at ambient temperature, which can be attributed to high thermal conductivity. Our study shows that B-NW with high thermal conductivity could be the next generation electron connector for nanoscale electronic devices.

Mass Media Campaign Improves Cervical Screening across All Socio-Economic Groups

ERIC Educational Resources Information Center

Anderson, Jenny O.; Mullins, Robyn M.; Siahpush, Mohammad; Spittal, Matthew J.; Wakefield, Melanie

2009-01-01

Low socio-economic status (SES) has been associated with lower cervical screening rates. Mass media is one known strategy that can increase cervical screening participation. This study sought to determine whether a mass media campaign conducted in Victoria, Australia, in 2005 was effective in encouraging women across all SES groups to screen. Data…

Electrostatic and hydrodynamics effects in a sedimented magnetorheological suspension.

PubMed

Domínguez-García, P; Pastor, J M; Melle, Sonia; Rubio, Miguel A

2009-08-01

We present experimental results on the equilibrium microstructure of a sedimented magnetorheological suspension, namely, an aqueous suspension of micron-sized superparamagnetic particles. We develop a study of the electrical interactions on the suspension by processing video-microscopy images of the sedimented particles. We calculate the pair distribution function, g(r), which yields the electrostatic pair potential u(r), showing an anomalous attractive interaction for distances on the order of twice the particle diameter, with characteristic parameters whose values show a dependence with the two-dimensional concentration of particles. The repulsive body of the potential is adjusted to a DLVO expression in order to calculate the Debye screening length and the effective surface charge density. Influence of confinement and variations on the Boltzmann sedimentation profile because of the electrostatic interactions appear to be essential for the interpretation of experimental results.

Analytical Debye-Huckel model for electrostatic potentials around dissolved DNA.

PubMed Central

Wagner, K; Keyes, E; Kephart, T W; Edwards, G

1997-01-01

We present an analytical, Green-function-based model for the electric potential of DNA in solution, treating the surrounding solvent with the Debye-Huckel approximation. The partial charge of each atom is accounted for by modeling DNA as linear distributions of atoms on concentric cylindrical surfaces. The condensed ions of the solvent are treated with the Debye-Huckel approximation. The resultant leading term of the potential is that of a continuous shielded line charge, and the higher order terms account for the helical structure. Within several angstroms of the surface there is sufficient information in the electric potential to distinguish features and symmetries of DNA. Plots of the potential and equipotential surfaces, dominated by the phosphate charges, reflect the structural differences between the A, B, and Z conformations and, to a smaller extent, the difference between base sequences. As the distances from the helices increase, the magnitudes of the potentials decrease. However, the bases and sugars account for a larger fraction of the double helix potential with increasing distance. We have found that when the solvent is treated with the Debye-Huckel approximation, the potential decays more rapidly in every direction from the surface than it did in the concentric dielectric cylinder approximation. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 7 PMID:9199767

Conditions for similitude and the effect of finite Debye length in electroosmotic flows.

PubMed

Oh, Jung Min; Kang, Kwan Hyoung

2007-06-15

Under certain conditions, the velocity field is similar to the electric field for electroosmotic flow (EOF) inside a channel. There was a disagreement between investigators on the necessity of the infinitesimal-Reynolds-number condition for the similarity when the Helmholtz-Smoluchowski relation is applied throughout the boundaries. What is puzzling is a recent numerical result that showed, contrary to the conventional belief, an evident Reynolds number dependence of the EOF. We show here that the notion that the infinitesimal-Reynolds-number condition is required originates from the misunderstanding that the EOF is the Stokes flow. We point out that the EOF becomes the potential flow when the Helmholtz-Smoluchowski relation is applied at the boundaries. We carry out a numerical simulation to investigate the effect of finiteness of the Debye length and the vorticity layer inherently existing at the channel wall. We show that the Reynolds number dependence of the previous numerical simulation resulted from the finiteness of the Debye length and subsequent convective transport of vorticity toward the bulk flow. We discuss in detail how the convection of vorticity occurs and what factors are involved in the transport process, after carrying out the simulation for different Reynolds numbers, Debye lengths, corner radii, and geometries.

Attempts to Manipulate the Decay Time of Radioactive Nuclei

NASA Astrophysics Data System (ADS)

Fallin, B.; Grabow, B.; Tornow, W.

2008-04-01

It has been known for 20 years that electron screening strongly changes nuclear reaction cross sections at sub-Coulomb charged-particle projectile energies. The screening energy can be increased considerably if the target atoms are implanted in a metallic host and cooled to low temperature (T˜10 K). The large screening in metals derives from the Debye plasma model applied to the quasi-free metallic electrons. If ``time reversed,'' this model implies that the lifetime of radioactive nuclei placed in a metallic host can be manipulated by orders of magnitude. For α and β^+ decay one expects a shorter half-life, while for β^- decay and EC, a longer half-life is expected. The results of prior experiments testing this theory are controversial; about half of the published data confirm an effect, while the other half observe no effect. We will report on our experimental studies using ^64Cu and ^65Zn nuclei produced at TUNL via the ^63Cu(d,p) and ^65Cu(p,n) reactions, respectively. For ^64Cu, we detected the 511 keV annihilation γ rays and for ^65Zn the 1115.5 keV γ rays using HPGe detectors. In both cases we did not observe a half-life change outside experimental uncertainties between measurements at room temperature and those with the samples cooled to T=12 K.

Critical role of electron heat flux on Bohm criterion

DOE PAGES

Tang, Xianzhu; Guo, Zehua

2016-12-05

Bohm criterion, originally derived for an isothermal-electron and cold-ion plasma, is often used as a rule of thumb for more general plasmas. Here, we establish a more precise determination of the Bohm criterion that are quantitatively useful for understanding and modeling collisional plasmas that still have collisional mean-free-path much greater than plasma Debye length. Specifically, it is shown that electron heat flux, rather than the isothermal electron assumption, is what sets the Bohm speed to bemore » $$\\sqrt{k_B(T_e||+3T_i||)/m_i}$$ with T e,i∥ the electron and ion parallel temperature at the sheath entrance and m i the ion mass.« less

Critical role of electron heat flux on Bohm criterion

NASA Astrophysics Data System (ADS)

Tang, Xian-Zhu; Guo, Zehua

2016-12-01

Bohm criterion, originally derived for an isothermal-electron and cold-ion plasma, is often used as a rule of thumb for more general plasmas. Here, we establish a more precise determination of the Bohm criterion that are quantitatively useful for understanding and modeling collisional plasmas that still have collisional mean-free-path much greater than plasma Debye length. Specifically, it is shown that electron heat flux, rather than the isothermal electron assumption, is what sets the Bohm speed to be √{ k B ( T e ∥ + 3 T i ∥ ) / m i } with T e , i ∥ the electron and ion parallel temperature at the sheath entrance and mi the ion mass.

Guidelines for Mass Screening of Congenital Hypothyroidism (2014 revision)

PubMed Central

Nagasaki, Keisuke; Minamitani, Kanshi; Anzo, Makoto; Adachi, Masanori; Ishii, Tomohiro; Onigata, Kazumichi; Kusuda, Satoshi; Harada, Shohei; Horikawa, Reiko; Minagawa, Masanori; Mizuno, Haruo; Yamakami, Yuji; Fukushi, Masaru; Tajima, Toshihiro

2015-01-01

Purpose of developing the guidelines: Mass screening for congenital hypothyroidism started in 1979 in Japan, and the prognosis for intelligence has been improved by early diagnosis and treatment. The incidence was about 1/4000 of the birth population, but it has increased due to diagnosis of subclinical congenital hypothyroidism. The disease requires continuous treatment, and specialized medical facilities should make a differential diagnosis and treat subjects who are positive in mass screening to avoid unnecessary treatment. The Guidelines for Mass Screening of Congenital Hypothyroidism (1998 version) were developed by the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology in 1998. Subsequently, new findings on prognosis and problems in the adult phase have emerged. Based on these new findings, the 1998 guidelines were revised in the current document (hereinafter referred to as the Guidelines). Target disease/conditions: Primary congenital hypothyroidism. Users of the Guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, physicians referring patients to pediatric practitioners, general physicians, laboratory technicians in charge of mass screening, and patients. PMID:26594093

Polarization-mediated Debye-screening of surface potential fluctuations in dual-channel AlN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Deen, David A.; Miller, Ross A.; Osinsky, Andrei V.; Downey, Brian P.; Storm, David F.; Meyer, David J.; Scott Katzer, D.; Nepal, Neeraj

2016-12-01

A dual-channel AlN/GaN/AlN/GaN high electron mobility transistor (HEMT) architecture is proposed, simulated, and demonstrated that suppresses gate lag due to surface-originated trapped charge. Dual two-dimensional electron gas (2DEG) channels are utilized such that the top 2DEG serves as an equipotential that screens potential fluctuations resulting from surface trapped charge. The bottom channel serves as the transistor's modulated channel. Two device modeling approaches have been performed as a means to guide the device design and to elucidate the relationship between the design and performance metrics. The modeling efforts include a self-consistent Poisson-Schrodinger solution for electrostatic simulation as well as hydrodynamic three-dimensional device modeling for three-dimensional electrostatics, steady-state, and transient simulations. Experimental results validated the HEMT design whereby homo-epitaxial growth on free-standing GaN substrates and fabrication of the same-wafer dual-channel and recessed-gate AlN/GaN HEMTs have been demonstrated. Notable pulsed-gate performance has been achieved by the fabricated HEMTs through a gate lag ratio of 0.86 with minimal drain current collapse while maintaining high levels of dc and rf performance.

Mapping HL7 CDA R2 Formatted Mass Screening Data to OpenEHR Archetypes.

PubMed

Kobayashi, Shinji; Kume, Naoto; Yoshihara, Hiroyuki

2017-01-01

Mass screening of adults was performed to manage employee healthcare. The screening service defined the data collection format as HL7 Clinical Document Architecture (CDA) R2. To capture mass screening data for nationwide electronic health records (her), we programmed a model within the CDA format and mapped the data items to the ISO13606/openEHR archetype for semantic interoperabiilty.

Limitations of the paraxial Debye approximation.

PubMed

Sheppard, Colin J R

2013-04-01

In the paraxial form of the Debye integral for focusing, higher order defocus terms are ignored, which can result in errors in dealing with aberrations, even for low numerical aperture. These errors can be avoided by using a different integration variable. The aberrations of a glass slab, such as a coverslip, are expanded in terms of the new variable, and expressed in terms of Zernike polynomials to assist with aberration balancing. Tube length error is also discussed.

The thermo-elastic instability model of melting of alkali halides in the Debye approximation

NASA Astrophysics Data System (ADS)

Owens, Frank J.

2018-05-01

The Debye model of lattice vibrations of alkali halides is used to show that there is a temperature below the melting temperature where the vibrational pressure exceeds the electrostatic pressure. The onset temperature of this thermo-elastic instability scales as the melting temperature of NaCl, KCl, and KBr, suggesting its role in the melting of the alkali halides in agreement with a previous more rigorous model.

Light scattering by cylindrical nanoparticles: Limits of applicability of the Rayleigh-Gans-Debye approximation

NASA Astrophysics Data System (ADS)

Kanevskii, V. I.; Rozenbaum, V. M.

2014-08-01

Applicability of the Rayleigh-Gans-Debye (RGD) approximation for describing light scattering by nanoparticles with large dielectric losses (such as carbon nanotubes) is analyzed. By a comparison of the approximate results with exact ones, it is shown that the presence of dielectric losses expands the range of applicability of the RGD approximation. This conclusion is illustrated by a differential cross-section diagram of scattering by a multiwall carbon nanotube.

Free-Free Transitions in the Presence of Laser Fields and Debye Potential at Very Low Incident Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, Anand

2012-01-01

We study the free-free transition in electron-helium ion in the ground state and embedded in a Debye potential in the presence of an external laser field at very low incident electron energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen as monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing Volkov wave function for it. The scattering wave function for the incident electron on the target embedded in a Debye potential is solved numerically by taking into account the effect of electron exchange. We calculate the laser-assisted differential and total cross sections for free-free transition for absorption/emission of a single photon or no photon exchange. The results will be presented at the conference.

Water promotes the sealing of nanoscale packing defects in folding proteins.

PubMed

Fernández, Ariel

2014-05-21

A net dipole moment is shown to arise from a non-Debye component of water polarization created by nanoscale packing defects on the protein surface. Accordingly, the protein electrostatic field exerts a torque on the induced dipole, locally impeding the nucleation of ice at the protein-water interface. We evaluate the solvent orientation steering (SOS) as the reversible work needed to align the induced dipoles with the Debye electrostatic field and computed the SOS for the variable interface of a folding protein. The minimization of the SOS is shown to drive protein folding as evidenced by the entrainment of the total free energy by the SOS energy along trajectories that approach a Debye limit state where no torque arises. This result suggests that the minimization of anomalous water polarization at the interface promotes the sealing of packing defects, thereby maintaining structural integrity and committing the protein chain to fold.

Formation of negative hydrogen ion: polarization electron capture and nonthermal shielding.

PubMed

Ki, Dae-Han; Jung, Young-Dae

2012-09-07

The influence of the nonthermal shielding on the formation of the negative hydrogen ion (H(-)) by the polarization electron capture are investigated in partially ionized generalized Lorentzian plasmas. The Bohr-Lindhard method has been applied to obtain the negative hydrogen formation radius and cross section as functions of the collision energy, de Broglie wave length, Debye length, impact parameter, and spectral index of the plasma. The result shows that the nonthermal character of the plasma enhances the formation radius of the negative hydrogen, especially, for small Debye radii. It is found that the nonthermal effect increases the formation cross section of the negative hydrogen. It is also found that the maximum position of the formation cross section approaches to the collision center with an increase of the spectral index. In addition, it is found that the formation cross section significantly decreases with an increase of the Debye length, especially, for small spectral indices.

First-principles investigations on structural, elastic, electronic properties and Debye temperature of orthorhombic Ni3Ta under pressure

NASA Astrophysics Data System (ADS)

Li, Pan; Zhang, Jianxin; Ma, Shiyu; Jin, Huixin; Zhang, Youjian; Zhang, Wenyang

2018-06-01

The structural, elastic, electronic properties and Debye temperature of Ni3Ta under different pressures are investigated using the first-principles method based on density functional theory. Our calculated equilibrium lattice parameters at 0 GPa well agree with the experimental and previous theoretical results. The calculated negative formation enthalpies and elastic constants both indicate that Ni3Ta is stable under different pressures. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν are calculated by the Voigt-Reuss-Hill method. The bigger ratio of B/G indicates Ni3Ta is ductile and the pressure can improve the ductility of Ni3Ta. In addition, the results of density of states and the charge density difference show that the stability of Ni3Ta is improved by the increasing pressure. The Debye temperature ΘD calculated from elastic modulus increases along with the pressure.

Electrostatic correlations in inhomogeneous charged fluids beyond loop expansion

NASA Astrophysics Data System (ADS)

Buyukdagli, Sahin; Achim, C. V.; Ala-Nissila, T.

2012-09-01

Electrostatic correlation effects in inhomogeneous symmetric electrolytes are investigated within a previously developed electrostatic self-consistent theory [R. R. Netz and H. Orland, Eur. Phys. J. E 11, 301 (2003)], 10.1140/epje/i2002-10159-0. To this aim, we introduce two computational approaches that allow to solve the self-consistent equations beyond the loop expansion. The first method is based on a perturbative Green's function technique, and the second one is an extension of a previously introduced semiclassical approximation for single dielectric interfaces to the case of slit nanopores. Both approaches can handle the case of dielectrically discontinuous boundaries where the one-loop theory is known to fail. By comparing the theoretical results obtained from these schemes with the results of the Monte Carlo simulations that we ran for ions at neutral single dielectric interfaces, we first show that the weak coupling Debye-Huckel theory remains quantitatively accurate up to the bulk ion density ρb ≃ 0.01 M, whereas the self-consistent theory exhibits a good quantitative accuracy up to ρb ≃ 0.2 M, thus improving the accuracy of the Debye-Huckel theory by one order of magnitude in ionic strength. Furthermore, we compare the predictions of the self-consistent theory with previous Monte Carlo simulation data for charged dielectric interfaces and show that the proposed approaches can also accurately handle the correlation effects induced by the surface charge in a parameter regime where the mean-field result significantly deviates from the Monte Carlo data. Then, we derive from the perturbative self-consistent scheme the one-loop theory of asymmetrically partitioned salt systems around a dielectrically homogeneous charged surface. It is shown that correlation effects originate in these systems from a competition between the salt screening loss at the interface driving the ions to the bulk region, and the interfacial counterion screening excess attracting them towards the surface. This competition can be quantified in terms of the characteristic surface charge σ _s^*=√{2ρ _b/(π ℓ _B)}, where ℓB = 7 Å is the Bjerrum length. In the case of weak surface charges σ _s≪ σ _s^* where counterions form a diffuse layer, the interfacial salt screening loss is the dominant effect. As a result, correlation effects decrease the mean-field density of both coions and counterions. With an increase of the surface charge towards σ _s^*, the surface-attractive counterion screening excess starts to dominate, and correlation effects amplify in this regime the mean-field density of both type of ions. However, in the regime σ _s>σ _s^*, the same counterion screening excess also results in a significant decrease of the electrostatic mean-field potential. This reduces in turn the mean-field counterion density far from the charged surface. We also show that for σ _s≫ σ _s^*, electrostatic correlations result in a charge inversion effect. However, the electrostatic coupling regime where this phenomenon takes place should be verified with Monte Carlo simulations since this parameter regime is located beyond the validity range of the one-loop theory.

Electrostatic correlations in inhomogeneous charged fluids beyond loop expansion.

PubMed

Buyukdagli, Sahin; Achim, C V; Ala-Nissila, T

2012-09-14

Electrostatic correlation effects in inhomogeneous symmetric electrolytes are investigated within a previously developed electrostatic self-consistent theory [R. R. Netz and H. Orland, Eur. Phys. J. E 11, 301 (2003)]. To this aim, we introduce two computational approaches that allow to solve the self-consistent equations beyond the loop expansion. The first method is based on a perturbative Green's function technique, and the second one is an extension of a previously introduced semiclassical approximation for single dielectric interfaces to the case of slit nanopores. Both approaches can handle the case of dielectrically discontinuous boundaries where the one-loop theory is known to fail. By comparing the theoretical results obtained from these schemes with the results of the Monte Carlo simulations that we ran for ions at neutral single dielectric interfaces, we first show that the weak coupling Debye-Huckel theory remains quantitatively accurate up to the bulk ion density ρ(b) ≃ 0.01 M, whereas the self-consistent theory exhibits a good quantitative accuracy up to ρ(b) ≃ 0.2 M, thus improving the accuracy of the Debye-Huckel theory by one order of magnitude in ionic strength. Furthermore, we compare the predictions of the self-consistent theory with previous Monte Carlo simulation data for charged dielectric interfaces and show that the proposed approaches can also accurately handle the correlation effects induced by the surface charge in a parameter regime where the mean-field result significantly deviates from the Monte Carlo data. Then, we derive from the perturbative self-consistent scheme the one-loop theory of asymmetrically partitioned salt systems around a dielectrically homogeneous charged surface. It is shown that correlation effects originate in these systems from a competition between the salt screening loss at the interface driving the ions to the bulk region, and the interfacial counterion screening excess attracting them towards the surface. This competition can be quantified in terms of the characteristic surface charge σ(s)*=√(2ρ(b)/(πl(B)), where l(B) = 7 Å is the Bjerrum length. In the case of weak surface charges σ(s)≪σ(s)* where counterions form a diffuse layer, the interfacial salt screening loss is the dominant effect. As a result, correlation effects decrease the mean-field density of both coions and counterions. With an increase of the surface charge towards σ(s)*, the surface-attractive counterion screening excess starts to dominate, and correlation effects amplify in this regime the mean-field density of both type of ions. However, in the regime σ(s)>σ(s)*, the same counterion screening excess also results in a significant decrease of the electrostatic mean-field potential. This reduces in turn the mean-field counterion density far from the charged surface. We also show that for σ(s)≫σ(s)*, electrostatic correlations result in a charge inversion effect. However, the electrostatic coupling regime where this phenomenon takes place should be verified with Monte Carlo simulations since this parameter regime is located beyond the validity range of the one-loop theory.

Symmetry energy in cold dense matter

NASA Astrophysics Data System (ADS)

Jeong, Kie Sang; Lee, Su Houng

2016-01-01

We calculate the symmetry energy in cold dense matter both in the normal quark phase and in the 2-color superconductor (2SC) phase. For the normal phase, the thermodynamic potential is calculated by using hard dense loop (HDL) resummation to leading order, where the dominant contribution comes from the longitudinal gluon rest mass. The effect of gluonic interaction on the symmetry energy, obtained from the thermodynamic potential, was found to be small. In the 2SC phase, the non-perturbative BCS paring gives enhanced symmetry energy as the gapped states are forced to be in the common Fermi sea reducing the number of available quarks that can contribute to the asymmetry. We used high density effective field theory to estimate the contribution of gluon interaction to the symmetry energy. Among the gluon rest masses in 2SC phase, only the Meissner mass has iso-spin dependence although the magnitude is much smaller than the Debye mass. As the iso-spin dependence of gluon rest masses is even smaller than the case in the normal phase, we expect that the contribution of gluonic interaction to the symmetry energy in the 2SC phase will be minimal. The different value of symmetry energy in each phase will lead to different prediction for the particle yields in heavy ion collision experiment.

Introduction to the theory and application of a unified Bohm criterion for arbitrary-ion-temperature collision-free plasmas with finite Debye lengths

NASA Astrophysics Data System (ADS)

Kos, L.; Jelić, N.; Kuhn, S.; Tskhakaya, D. D.

2018-04-01

At present, identifying and characterizing the common plasma-sheath edge (PSE) in the conventional fluid approach leads to intrinsic oversimplifications, while the kinetic one results in unusable over-generalizations. In addition, none of these approaches can be justified in realistic plasmas, i.e., those which are characterized by non-negligible Debye lengths and a well-defined non-negligible ion temperature. In an attempt to resolve this problem, we propose a new formulation of the Bohm criterion [D. Bohm, The Characteristics of Electrical Discharges in Magnetic Fields (McGraw-Hill, New York, 1949)], which is here expressed in terms of fluid, kinetic, and electrostatic-pressure contributions. This "unified" Bohm criterion consists of a set of two equations for calculating the ion directional energy (i.e., the mean directional velocity) and the plasma potential at the common PSE, and is valid for arbitrary ion-to-electron temperature ratios. It turns out to be exact at any point of the quasi-neutral plasma provided that the ion differential polytropic coefficient function (DPCF) of Kuhn et al. [Phys. Plasmas 13, 013503 (2006)] is employed, with the advantage that the DPCF is an easily measurable fluid quantity. Moreover, our unified Bohm criterion holds in plasmas with finite Debye lengths, for which the famous kinetic criterion formulated by Harrison and Thompson [Proc. Phys. Soc. 74, 145 (1959)] fails. Unlike the kinetic criterion in the case of negligible Debye length, the kinetic contribution to the unified Bohm criterion, arising due to the presence of negative and zero velocities in the ion velocity distribution function, can be calculated separately from the fluid term. This kinetic contribution disappears identically at the PSE, yielding strict equality of the ion directional velocity there and the ion sound speed, provided that the latter is formulated in terms of the present definition of DPCFs. The numerical values of these velocities are found for the Tonks-Langmuir collision-free, plane-parallel discharge model [Phys. Rev. 34, 876 (1929)], however, with the ion-source temperature extended here from the original (zero) value to arbitrary high ones. In addition, it turns out, that the charge-density derivative (in the potential "space") with respect to the potential exhibits two characteristic points, i.e., potentials, namely the points of inflection and maximum of that derivative (in the potential space), which stay "fixed" at their respective potentials independent of the Debye length until it is kept fairly small. Plasma quasi-neutrality appears well satisfied up to the first characteristic point/potential, so we identify that one as the plasma edge (PE). Adopting the convention that the sheath is a region characterized by considerable electrostatic pressure (energy density), we identify the second characteristic point/potential as the sheath edge (SE). Between these points, the charge density increases from zero to a finite value. Thus, the interval between the PE and SE, with the "fixed" width (in the potential "space") of about one third of the electron temperature, will be named the plasma-sheath transition (PST). Outside the PST, the electrostatic-pressure term and its derivatives turn out to be nearly identical with each other, independent of the particular values of the ion temperature and Debye length. In contrast, an increase in Debye lengths from zero to finite values causes the location of the sonic point/potential (laying inside the PST) to shift from the PE (for vanishing Debye length) towards the SE, while at the same time, the absolute value of the corresponding ion-sound velocity slightly decreases. These shifts turn out to be manageable with employing the mathematical concept of the plasma-to-sheath transition (different from, but related to our natural PST concept), resulting in approximate, but sufficiently reliable semi-analytic expressions, which are functions of the ion temperature and Debye length.

Breakdown of the Debye polarization ansatz at protein-water interfaces

NASA Astrophysics Data System (ADS)

Fernández Stigliano, Ariel

2013-06-01

The topographical and physico-chemical complexity of protein-water interfaces scales down to the sub-nanoscale range. At this level of confinement, we demonstrate that the dielectric structure of interfacial water entails a breakdown of the Debye ansatz that postulates the alignment of polarization with the protein electrostatic field. The tendencies to promote anomalous polarization are determined for each residue type and a particular kind of structural defect is shown to provide the predominant causal context.

Recovering refractive index correlation function from measurement of tissue scattering phase function (Conference Presentation)

NASA Astrophysics Data System (ADS)

Rogers, Jeremy D.

2016-03-01

Numerous methods have been developed to quantify the light scattering properties of tissue. These properties are of interest in diagnostic and screening applications due to sensitivity to changes in tissue ultrastructure and changes associated with disease such as cancer. Tissue is considered a weak scatterer because that the mean free path is much larger than the correlation length. When this is the case, all scattering properties can be calculated from the refractive index correlation function Bn(r). Direct measurement of Bn(r) is challenging because it requires refractive index measurement at high resolution over a large tissue volume. Instead, a model is usually assumed. One particularly useful model, the Whittle-Matern function includes several realistic function types such as mass fractal and exponential. Optical scattering properties for weakly scattering media can be determined analytically from Bn(r) by applying the Rayleigh-Gans-Debye (RGD) or Born Approximation, and so measured scattering properties are used to fit parameters of the model function. Direct measurement of Bn(r) would provide confirmation that the function is a good representation of tissue or help in identifying the length scale at which changes occur. The RGD approximation relates the scattering phase function to the refractive index correlation function through a Fourier transform. This can be inverted without approximation, so goniometric measurement of the scattering can be converted to Bn(r). However, geometric constraints of the measurement of the phase function, angular resolution, and wavelength result in a band limited measurement of Bn(r). These limits are discussed and example measurements are described.

Moderately nonlinear diffuse-charge dynamics under an ac voltage.

PubMed

Stout, Robert F; Khair, Aditya S

2015-09-01

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

Extrinsic Cation Selectivity of 2D Membranes

PubMed Central

2017-01-01

From a systematic study of the concentration driven diffusion of positive and negative ions across porous 2D membranes of graphene and hexagonal boron nitride (h-BN), we prove their cation selectivity. Using the current–voltage characteristics of graphene and h-BN monolayers separating reservoirs of different salt concentrations, we calculate the reversal potential as a measure of selectivity. We tune the Debye screening length by exchanging the salt concentrations and demonstrate that negative surface charge gives rise to cation selectivity. Surprisingly, h-BN and graphene membranes show similar characteristics, strongly suggesting a common origin of selectivity in aqueous solvents. For the first time, we demonstrate that the cation flux can be increased by using ozone to create additional pores in graphene while maintaining excellent selectivity. We discuss opportunities to exploit our scalable method to use 2D membranes for applications including osmotic power conversion. PMID:28157333

Identification of structural relaxation in the dielectric response of water

DOE PAGES

Hansen, Jesper S.; Kisliuk, Alexander; Sokolov, Alexei P.; ...

2016-06-09

One century ago pioneering dielectric results obtained for water and n-alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Here, comparing dielectric, viscoelastic, and light scattering results, we unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in monoalcohols.

Detection beyond Debye's length with an electrolyte-gated organic field-effect transistor.

PubMed

Palazzo, Gerardo; De Tullio, Donato; Magliulo, Maria; Mallardi, Antonia; Intranuovo, Francesca; Mulla, Mohammad Yusuf; Favia, Pietro; Vikholm-Lundin, Inger; Torsi, Luisa

2015-02-04

Electrolyte-gated organic field-effect transistors are successfully used as biosensors to detect binding events occurring at distances from the transistor electronic channel that are much larger than the Debye length in highly concentrated solutions. The sensing mechanism is mainly capacitive and is due to the formation of Donnan's equilibria within the protein layer, leading to an extra capacitance (CDON) in series to the gating system. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Size-dependent penetrant diffusion in polymer glasses.

PubMed

Meng, Dong; Zhang, Kai; Kumar, Sanat K

2018-05-18

Molecular Dynamics simulations are used to understand the underpinning basis of the transport of gas-like solutes in deeply quenched polymeric glasses. As found in previous work, small solutes, with sizes smaller than 0.15 times the chain monomer size, move as might be expected in a medium with large pores. In contrast, the motion of larger solutes is activated and is strongly facilitated by matrix motion. In particular, solute motion is coupled to the local elastic fluctuations of the matrix as characterized by the Debye-Waller factor. While similar ideas have been previously proposed for the viscosity of supercooled liquids above their glass transition, to our knowledge, this is the first illustration of this concept in the context of solute mass transport in deeply quenched polymer glasses.

[Evaluation of the usefulness for neonatal mass screening in light of 35 years personal experience].

PubMed

Bozkowa, K; Cabalska, B; Radomyska, B; Ołtarzewski, M; Lenartowska, I

1999-01-01

The results and the significance of neonatal mass-screening programmes for inborn errors of metabolism, conducted by the National Research Institute of Mother and Child (NRIMC), are discussed. As the first in Poland, in 1964, mass-screening for phenylketonuria (PKU) was introduced. The BIA-Guthrie test was used. Other Guthrie tests (GBIA) were applied in homocystinuria, tyrosinemia, histidinemia and leucinosis (Maple Syrup Urine Disease-MSUD). In the middle of the 60. the Beutler and Baluda test was introduced for galactosaemia, as well as the Efron urine test in infant screening for different inborn errors of metabolism. In the middle of the 70., neonatal mass-screening for cystic fibrosis (CF, mucoviscidosis) was started. Meconium tests and the sweat test with ion selective chloride electrode were used. Apart from inborn errors of metabolism, we also introduced a screening programme for neuroblastoma in which vaniline mandelic acid (VMA) in urine was estimated and for congenital hypothyroidism were TSH level was assessed. The results of screening are shown in the tables and in the figures. In our opinion the best clinical results are obtained with screening for congenital hypothyroidism and for PKU, since very early detection and treatment in these diseases prevents severe mental retardation. We therefore consider that both these screening programmes should be treated as obligatory examinations in all neonates. Taking into consideration the fact that there are different types of hyperhenylalaninemias, the principles of differential diagnosis are discussed. Molecular genetic investigations, carried out in the NRIMC Department of Genetics proved to be a very important procedure in the verification of diagnosis of different mutations. The authors also discuss the problem of dietary treatment duration in PKU. In our opinion the hypophenyloalanine diet regimen in girls, should not be discontinued during adolescence, since there is the problem of maternal PKU and the possibility of foetal damage. The results of our own investigations of maternal PKU are discussed. The significance of mass-screening for galactosemia is still under discussion. In our opinion, mass-screening for galactosemia is not useful and we have discontinued it. Selective screening has been started combined with molecular genetic studies in high risk families. In the future, we plan to prepare guidelines on the principles of diagnosis and treatment of galactosemia in children and women in the reproductive age. Mass-screening for cystic fibrosis is also still under discussion. The results of the early screening programmes were not satisfactory and the tests were discontinued. In 1998, after reorganisation of the whole system, CF screening, using tripsin-radioimmune assays, was started again. The new screening programme is combined with molecular genetic investigation of different mutations. It is still too early to assess the importance and success of this CF mass-screening programme. We decided to discontinue the screening for homocystinuria, histidinemia, tyrosinemia, leucinosis and for neuroblastoma, since these programmes did not comply with criteria of mass-screening. In 1997, major reorganisation of screening programmes for inborn errors of metabolism, at NRIMC, was undertaken. The Guthrie test for PKU was changed to a quantitative colorimetric method. The immuno-luminometric method is used for TSH estimation. The whole system is based on complete computer control of all the steps of screening, from blood sampling on filter paper until the final diagnosis. The advantages of this modern system of organisation of the screening programme are discussed.

Development of a Magnetic Microbead Affinity Selection Screen (MagMASS) Using Mass Spectrometry for Ligands to the Retinoid X Receptor-α

NASA Astrophysics Data System (ADS)

Rush, Michael D.; Walker, Elisabeth M.; Prehna, Gerd; Burton, Tristesse; van Breemen, Richard B.

2017-03-01

To overcome limiting factors in mass spectrometry-based screening methods such as automation while still facilitating the screening of complex mixtures such as botanical extracts, magnetic microbead affinity selection screening (MagMASS) was developed. The screening process involves immobilization of a target protein on a magnetic microbead using a variety of possible chemistries, incubation with mixtures of molecules containing possible ligands, a washing step that removes non-bound compounds while a magnetic field retains the beads in the microtiter well, and an organic solvent release step followed by LC-MS analysis. Using retinoid X receptor-α (RXRα) as an example, which is a nuclear receptor and target for anti-inflammation therapy as well as cancer treatment and prevention, a MagMASS assay was developed and compared with an existing screening assay, pulsed ultrafiltration (PUF)-MS. Optimization of MagMASS involved evaluation of multiple protein constructs and several magnetic bead immobilization chemistries. The full-length RXRα construct immobilized with amylose beads provided optimum results. Additional enhancements of MagMASS were the application of 96-well plates to enable automation, use of UHPLC instead of HPLC for faster MS analyses, and application of metabolomics software for faster, automated data analysis. Performance of MagMASS was demonstrated using mixtures of synthetic compounds and known ligands spiked into botanical extracts.

Charged plate in asymmetric electrolytes: One-loop renormalization of surface charge density and Debye length due to ionic correlations.

PubMed

Ding, Mingnan; Lu, Bing-Sui; Xing, Xiangjun

2016-10-01

Self-consistent field theory (SCFT) is used to study the mean potential near a charged plate inside a m:-n electrolyte. A perturbation series is developed in terms of g=4πκb, where band1/κ are Bjerrum length and bare Debye length, respectively. To the zeroth order, we obtain the nonlinear Poisson-Boltzmann theory. For asymmetric electrolytes (m≠n), the first order (one-loop) correction to mean potential contains a secular term, which indicates the breakdown of the regular perturbation method. Using a renormalizaton group transformation, we remove the secular term and obtain a globally well-behaved one-loop approximation with a renormalized Debye length and a renormalized surface charge density. Furthermore, we find that if the counterions are multivalent, the surface charge density is renormalized substantially downwards and may undergo a change of sign, if the bare surface charge density is sufficiently large. Our results agrees with large MC simulation even when the density of electrolytes is relatively high.

High-Temperature and High-Pressure Study of Electronic and Thermal Properties of PbTaO3 and SnAlO3 Metal Perovskites by Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Khandy, Shakeel Ahmad; Islam, Ishtihadah; Ganai, Zahid Saleem; Gupta, Dinesh C.; Parrey, Khursheed Ahmad

2018-01-01

First principles calculations on the thermodynamic properties of PbTaO3 and SnAlO3 in a temperature range from 0 K to 800 K and pressure range from 0 GPa to 30 GPa have been carried out within the framework of density functional theory (DFT). The band structures of these oxides at different pressures display an increase in metallic character with a concomitant decrease in lattice constants, while the bulk modulus increases with increasing pressure. The thermal concert of these materials has been analyzed in terms of the temperature and pressure variation in Debye temperature, thermal expansion, entropy, and the Grüneisen parameter. Debye temperatures have been calculated from the elastic parameters as well as the quasi-harmonic Debye model, which are 339.07 GPa for PbTaO3 and 714.36 GPa for SnAlO3.

First-principles study on the thermal expansion of Ni-X binary alloys based on the quasi-harmonic Debye model

NASA Astrophysics Data System (ADS)

Shin, Yongjin; Jung, Woo-Sang; Lee, Young-Su

2016-11-01

In this study, we use the quasi-harmonic Debye model to predict the coefficient of thermal expansion of Ni- X binary alloys. The method bridges between the macroscopic elastic behavior and thermodynamic properties of materials without an expensive calculation of the volume dependence of the phonon density of states. Furthermore, the Grüneisen parameter is derived from the volume dependence of the Debye temperature, which is calculated from the first-principles elastic stiffness constants. The experimental coefficient of thermal expansion (CTE) of pure nickel is well reproduced, especially in the low temperature region. Among the few alloying elements tested, Al is predicted to slightly decrease the CTE whereas Mo and W are more effective in reducing the CTE. For the cases of Ni-X binary alloy systems, where the variation in the CTE is relatively small, the method used here appears to perform better than certain other formulations that rely entirely on the energy vs. volume relationship.

Slow dielectric response of Debye-type in water and other hydrogen bonded liquids

NASA Astrophysics Data System (ADS)

Jansson, Helén; Bergman, Rikard; Swenson, Jan

2010-05-01

The slow dynamics of some hydrogen bonded glass-forming liquids has been investigated by broadband dielectric spectroscopy. We show that the polyalcohols glycerol, xylitol, and sorbitol, and mixtures of glycerol and water, and in fact, even pure water exhibit a process of Debye character at longer time-scales than the glass transition and viscosity related α-relaxation. Even if it is less pronounced, this process displays many similarities to the well-studied Debye-like process in monoalcohols. It can be observed in both the negative derivative of the real part of the permittivity or in the imaginary part of the permittivity, if the conductivity contribution is reduced. In the present study the conductivity contribution has been suppressed by use of a thin Teflon film placed between the sample and one of the electrodes. The new findings might have important implications for the structure and dynamics of hydrogen bonded liquids in general, and for water in particular.

Low temperature heat capacities and thermodynamic functions described by Debye-Einstein integrals.

PubMed

Gamsjäger, Ernst; Wiessner, Manfred

2018-01-01

Thermodynamic data of various crystalline solids are assessed from low temperature heat capacity measurements, i.e., from almost absolute zero to 300 K by means of semi-empirical models. Previous studies frequently present fit functions with a large amount of coefficients resulting in almost perfect agreement with experimental data. It is, however, pointed out in this work that special care is required to avoid overfitting. Apart from anomalies like phase transformations, it is likely that data from calorimetric measurements can be fitted by a relatively simple Debye-Einstein integral with sufficient precision. Thereby, reliable values for the heat capacities, standard enthalpies, and standard entropies at T  = 298.15 K are obtained. Standard thermodynamic functions of various compounds strongly differing in the number of atoms in the formula unit can be derived from this fitting procedure and are compared to the results of previous fitting procedures. The residuals are of course larger when the Debye-Einstein integral is applied instead of using a high number of fit coefficients or connected splines, but the semi-empiric fit coefficients keep their meaning with respect to physics. It is suggested to use the Debye-Einstein integral fit as a standard method to describe heat capacities in the range between 0 and 300 K so that the derived thermodynamic functions are obtained on the same theory-related semi-empiric basis. Additional fitting is recommended when a precise description for data at ultra-low temperatures (0-20 K) is requested.

Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions.

PubMed

Rinne, Klaus F; Gekle, Stephan; Netz, Roland R

2014-12-07

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into different water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.

Plasma effect on fast-electron-impact-ionization from 2p state of hydrogen-like ions

NASA Astrophysics Data System (ADS)

Qi, Y. Y.; Ning, L. N.; Wang, J. G.; Qu, Y. Z.

2013-12-01

Plasma effects on the high-energy electron-impact ionization process from 2p orbital of Hydrogen-like ions embedded in weakly coupled plasmas are investigated in the first Born approximation. The plasma screening of the Coulomb interaction between charged particles is represented by the Debye Hückel model. The screening of Coulomb interactions decreases the ionization energies and varies the wave functions for not only the bound orbital but also the continuum; the number of the summation for the angular-momentum states in the generalized oscillator strength densities is reduced with the plasma screening stronger when the ratio of ɛ /I2p (I2p is the ionization energy of 2p state and ɛ is the energy of the continuum electron) is kept, and then the contribution from the lower-angular-momentum states dominates the generalized oscillator strength densities, so the threshold phenomenon in the generalized oscillator strength densities and the double differential cross sections are remarkable: The accessional minima, the outstanding enhancement, and the resonance peaks emerge a certain energy region, whose energy position and width are related to the vicinity between δ and the critical value δnlc, corresponding to the special plasma condition when the bound state |nl⟩ just enters the continuum; the multiple virtual-state enhancement and the multiple shape resonances in a certain energy domain also appear in the single differential cross section whenever the plasma screening parameter passes through a critical value δnlc, which is similar to the photo-ionization process but different from it, where the dipole transition only happens, but multi-pole transition will occur in the electron-impact ionization process, so its multiple virtual-state enhancements and the multiple shape resonances appear more frequently than the photo-ionization process.

Early Detection and Mass Screening For Cancer

PubMed Central

Miller, A. B.

1972-01-01

The author reviews the evidence for the efficacy of early detection and mass screening programs in reducing morbidity and mortality from cancer. In cancer of the cervix, although screening reduces morbidity, we still do not have evidence for reduction in mortality. In cancer of the breast, one study suggests a reduction in mortality in the 50-59 year age group following screening by clinical examination and mammography. In other sites, especially lung, there is no evidence at present to support the adoption of mass screening programs. It is important that such programs should be carefully evaluated in the population, preferably in controlled studies. PMID:20468806

Regional Differences as Barriers to Body Mass Index Screening Described by Ohio School Nurses

ERIC Educational Resources Information Center

Stalter, Ann M.; Chaudry, Rosemary V.; Polivka, Barbara J.

2011-01-01

Background: Body mass index (BMI) screening is advocated by the National Association of School Nurses (NASN). Research identifying barriers to BMI screening in public elementary school settings has been sparse. The purpose of the study was to identify barriers and facilitating factors of BMI screening practices among Ohio school nurses working in…

Cosmic web and environmental dependence of screening: Vainshtein vs. chameleon

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

Falck, Bridget; Koyama, Kazuya; Zhao, Gong-Bo, E-mail: bridget.falck@port.ac.uk, E-mail: kazuya.koyama@port.ac.uk, E-mail: gong-bo.zhao@port.ac.uk

Theories which modify general relativity to explain the accelerated expansion of the Universe often use screening mechanisms to satisfy constraints on Solar System scales. We investigate the effects of the cosmic web and the local environmental density of dark matter halos on the screening properties of the Vainshtein and chameleon screening mechanisms. We compare the cosmic web morphology of dark matter particles, mass functions of dark matter halos, mass and radial dependence of screening, velocity dispersions and peculiar velocities, and environmental dependence of screening mechanisms in f(R) and nDGP models. Using the ORIGAMI cosmic web identification routine we find thatmore » the Vainshtein mechanism depends on the cosmic web morphology of dark matter particles, since these are defined according to the dimensionality of their collapse, while the chameleon mechanism shows no morphology dependence. The chameleon screening of halos and their velocity dispersions depend on halo mass, and small halos and subhalos can be environmentally screened in the chameleon mechanism. On the other hand, the screening of halos in the Vainshtein mechanism does not depend on mass nor environment, and their velocity dispersions are suppressed. The peculiar velocities of halos in the Vainshtein mechanism are enhanced because screened objects can still feel the fifth force generated by external fields, while peculiar velocities of chameleon halos are suppressed when the halo centers are screened.« less

Permanent electric dipole moments of PtX (X = H, F, Cl, Br, and I) by the composite approach

NASA Astrophysics Data System (ADS)

Deng, Dan; Lian, Yongqin; Zou, Wenli

2017-11-01

Using the FPD composite approach of Peterson et. al. we calculate the permanent electric dipole moments of PtX (X = H, F, Cl, Br, and I) at the equilibrium geometries of their ground states. The dipole moment of PtF is estimated to be 3.421 Debye, being very close to the experimental value of 3.42(6) Debye. This research also suggests the ordering of dipole moments of PtX being proportional to the electronegativity of X.

Screening College Students for Hypercholesterolemia.

ERIC Educational Resources Information Center

Faigel, Harris C.

1992-01-01

Describes one college's mandatory mass cholesterol screening for new students. Each year, over 30 beginning students with unknown hypercholesterolemia were detected. The program suggests that mass screening efficiently and economically identifies students who would benefit from cholesterol reduction, a modifiable risk in coronary artery disease.…

Newborn screening for sickling and other haemoglobin disorders using tandem mass spectrometry: A pilot study of methodology in laboratories in England.

PubMed

Daniel, Yvonne A; Henthorn, Joan

2016-12-01

To determine (i) if electrospray mass spectrometry-mass spectrometry with the SpOtOn Diagnostics Ltd reagent kit for sickle cell screening could be integrated into the English newborn screening programme, under routine screening conditions, and provide mass spectrometry-mass spectrometry results which match existing methods, and (ii) if common action values could be set for all manufacturers in the study, for all assessed haemoglobins, to indicate which samples require further investigation. Anonymised residual blood spots were analysed using the SpOtOn reagent kit as per manufacturer's instructions, in parallel with existing techniques at four laboratories. Mass spectrometry-mass spectrometry instrumentation at Laboratories A and B was AB Sciex (Warrington, UK) AP4000, and at Laboratories C and D, Waters Micromass (Manchester, UK), Xevo TQMS and Premier, respectively. There were 23,898 results accepted from the four laboratories. Excellent specificity at 100% sensitivity was observed for haemoglobin S, haemoglobin C, haemoglobin E and haemoglobin O Arab . A common action value was not possible for Hb C, but action values were set by manufacturer. The two haemoglobin D Punjab cases at Laboratory D were not detected using the common action value. Conversely, false-positive results with haemoglobin D Punjab were a problem at the remaining three laboratories. This multicentre study demonstrates that it is possible to implement mass spectrometry-mass spectrometry into an established screening programme while maintaining consistency with existing methods for haemoglobinopathy screening. However, one of the instruments investigated cannot be recommended for use with this application. © The Author(s) 2016.

Mass media campaign improves cervical screening across all socio-economic groups.

PubMed

Anderson, Jenny O; Mullins, Robyn M; Siahpush, Mohammad; Spittal, Matthew J; Wakefield, Melanie

2009-10-01

Low socio-economic status (SES) has been associated with lower cervical screening rates. Mass media is one known strategy that can increase cervical screening participation. This study sought to determine whether a mass media campaign conducted in Victoria, Australia, in 2005 was effective in encouraging women across all SES groups to screen. Data were obtained from the Victorian Cervical Cytology Registry for each Pap test registered during 2005 and categorized into SES quintiles using the Index of Socio-Economic Advantage/Disadvantage. Negative binomial regression was used to determine the impact of the campaign on the weekly number of Pap tests and whether the media campaign had a differential effect by SES, after adjusting for the number of workdays per week, age group and time since previous test. Cervical screening increased 27% during the campaign period and was equally effective in encouraging screening across all SES groups, including low-SES women. Mass media campaigns can prompt increased rates of cervical screening among all women, not just those from more advantaged areas. Combining media with additional strategies targeted at low-SES women may help lessen the underlying differences in screening rates across SES.

Native State Mass Spectrometry, Surface Plasmon Resonance, and X-ray Crystallography Correlate Strongly as a Fragment Screening Combination.

PubMed

Woods, Lucy A; Dolezal, Olan; Ren, Bin; Ryan, John H; Peat, Thomas S; Poulsen, Sally-Ann

2016-03-10

Fragment-based drug discovery (FBDD) is contingent on the development of analytical methods to identify weak protein-fragment noncovalent interactions. Herein we have combined an underutilized fragment screening method, native state mass spectrometry, together with two proven and popular fragment screening methods, surface plasmon resonance and X-ray crystallography, in a fragment screening campaign against human carbonic anhydrase II (CA II). In an initial fragment screen against a 720-member fragment library (the "CSIRO Fragment Library") seven CA II binding fragments, including a selection of nonclassical CA II binding chemotypes, were identified. A further 70 compounds that comprised the initial hit chemotypes were subsequently sourced from the full CSIRO compound collection and screened. The fragment results were extremely well correlated across the three methods. Our findings demonstrate that there is a tremendous opportunity to apply native state mass spectrometry as a complementary fragment screening method to accelerate drug discovery.

Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions

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

Rinne, Klaus F.; Netz, Roland R.; Gekle, Stephan

2014-12-07

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into differentmore » water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.« less

Quadrupole terms in the Maxwell equations: Debye-Hückel theory in quadrupolarizable solvent and self-salting-out of electrolytes.

PubMed

Slavchov, Radomir I

2014-04-28

If the molecules of a given solvent possess significant quadrupolar moment, the macroscopic Maxwell equations must involve the contribution of the density of the quadrupolar moment to the electric displacement field. This modifies the Poisson-Boltzmann equation and all consequences from it. In this work, the structure of the diffuse atmosphere around an ion dissolved in quadrupolarizable medium is analyzed by solving the quadrupolar variant of the Coulomb-Ampere's law of electrostatics. The results are compared to the classical Debye-Hückel theory. The quadrupolar version of the Debye-Hückel potential of a point charge is finite even in r = 0. The ion-quadrupole interaction yields a significant expansion of the diffuse atmosphere of the ion and, thus, it decreases the Debye-Hückel energy. In addition, since the dielectric permittivity of the electrolyte solutions depends strongly on concentration, the Born energy of the dissolved ions alters with concentration, which has a considerable contribution to the activity coefficient γ± known as the self-salting-out effect. The quadrupolarizability of the medium damps strongly the self-salting-out of the electrolyte, and thus it affects additionally γ±. Comparison with experimental data for γ± for various electrolytes allows for the estimation of the quadrupolar length of water: LQ ≈ 2 Å, in good agreement with previous assessments. The effect of quadrupolarizability is especially important in non-aqueous solutions. Data for the activity of NaBr in methanol is used to determine the quadrupolarizability of methanol with good accuracy.

First principles and Debye model study of the thermodynamic, electronic and optical properties of MgO under high-temperature and pressure

NASA Astrophysics Data System (ADS)

Miao, Yurun; Li, Huayang; Wang, Hongjuan; He, Kaihua; Wang, Qingbo

2018-02-01

First principles and quasi-harmonic Debye model have been used to study the thermodynamic properties, enthalpies, electronic and optical properties of MgO up to the core-mantle boundary (CMB) condition (137 GPa and 3700 K). Thermodynamic properties calculation includes thermal expansion coefficient and capacity, which have been studied up to the CMB pressure (137 GPa) and temperature (3700 K) by the Debye model with generalized gradient approximation (GGA) and local-density approximation (LDA). First principles with hybrid functional method (PBE0) has been used to calculate the electronic and optical properties under pressure up to 137 GPa and 0 K. Our results show the Debye model with LDA and first principles with PBE0 can provide accurate thermodynamic properties, enthalpies, electronic and optical properties. Calculated enthalpies show that MgO keep NaCl (B1) structure up to 137 GPa. And MgO is a direct bandgap insulator with a 7.23 eV calculated bandgap. The bandgap increased with increasing pressure, which will induce a blue shift of optical properties. We also calculated the density of states (DOS) and discussed the relation between DOS and band, optical properties. Equations were used to fit the relations between pressure and bandgaps, absorption coefficient (α(ω)) of MgO. The equations can be used to evaluate pressure after careful calibration. Our calculations can not only be used to identify some geological processes, but also offer a reference to the applications of MgO in the future.

Economic implications of three strategies for the control of taeniasis.

PubMed

Alexander, Anu; John, K R; Jayaraman, T; Oommen, Anna; Venkata Raghava, M; Dorny, Pierre; Rajshekhar, Vedantam

2011-11-01

To evaluate the cost-effectiveness of three strategies for the control of taeniasis in a community, in terms of cost per case treated. A study was conducted in South India to determine the prevalence of taeniasis by screening stool samples from 653 randomly chosen subjects, for coproantigens. The costs incurred in the project were used to estimate the cost per case screened and treated. A one-way sensitivity analysis was carried out for varying rates of taeniasis, different screening strategies and mass therapy. Further sensitivity analysis was carried out with different manpower and test costs. The rate of taeniasis as detected by ELISA for coproantigen was 3 per 1000 (2 of 653 samples). Our study showed that mass therapy without screening for taeniasis would be the most economical strategy in terms of cost per case treated if field workers are employed exclusively for either mass therapy or screening. For each strategy, costs per case treated are higher at low prevalence of taeniasis, with a sharp rise below 15%. In places that are endemic for taeniasis and neurocysticercosis, mass therapy or screening for taeniasis should be considered. Screening by stool microscopy is not cost-effective in terms of cost per case of taeniasis treated owing to its low sensitivity. Although the cost per case of taeniasis treated is high at low prevalence of taeniasis for all options, incorporating mass therapy into existing mass drug distribution programmes might prove to be the most cost-effective control strategy. © 2011 Blackwell Publishing Ltd.

The PHENIX muon spectrometer and J/psi production in 200 GeV center of mass energy proton-proton collisions at RHIC

NASA Astrophysics Data System (ADS)

Hoover, Andrew S.

The PHENIX experiment is one of the large detector projects at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. One of the unique features of the PHENIX detector is the muon tracking and identification system. No other RHIC experiment has a muon detection capability. Among the many physics topics explored by the observation of muons in Au-Au collisions are the effects of Debye screening on vector meson production, and the search for an enhancement in strangeness and heavy flavor production. In the collisions of polarized protons, the muon arms can explore the polarization of quarks and gluons in the proton through W boson production, the Drell-Yan process, and open heavy flavor production. The muon detector system covers the rapidity range -2.2 < y < -1.2 for the south arm and 1.2 < y < 2.4 for the north arm, with full azimuthal coverage. The detector provides muon tracking and identification in the momentum range 2 < p < 50 GeV, and pi/mu rejection of 10-4. The south muon arm was completed in 2001 for the second RHIC running period. The performance of the muon spectrometer during its first data taking period will be discussed. The production cross section for J/psi in proton-proton collisions at s = 200 GeV is measured. The measured value is in good agreement with the color evaporation model and QCD predictions. Although the number of J/psi currently available for study will not allow a definitive measurement of the J/psi polarization, a technique for performing the measurement is studied and a very low statistics analysis produces a result which is consistent with expectations.

A New Energy Ordering and the Dipole Moment of Gas Phase Glycine via Plane-Wave Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Min, Byeong June

2018-03-01

The abundance of glycine (Gly), the simplest amino acid, in meteorites leads us to the next question about its extraterrestrial origin. However, astronomers have not yet found glycine signature in interstellar medium. Laboratory microwave spectroscopy experiments report the most stable Gly conformer has a dipole moment of 4.5 - 5.45 Debye. Theoretical calculations, so far performed only with Gaussian basis functions, has predicted a dipole moment of about 1 Debye. This discrepancy has baffled astronomers. We study the energetics of glycine and its isomers and conformers via plane-wave density functional theory calculations. The geometric structures of the isomers and their conformers are identified, along with their relative stability and their dipole moment. In the case of glycine, we obtain the most stable conformer with a dipole moment of 5.76 Debye, close to the microwave spectroscopy experiments. If the plane wave energy cutoff is reduced to a lower value ( 400 eV) on purpose, the energy ordering reverses to the case with Gaussian basis calculations.

Compliance of the Stokes-Einstein model and breakdown of the Stokes-Einstein-Debye model for a urea-based supramolecular polymer of high viscosity.

PubMed

Świergiel, Jolanta; Bouteiller, Laurent; Jadżyn, Jan

2014-11-14

Impedance spectroscopy was used for the study of the static and dynamic behavior of the electrical conductivity of a hydrogen-bonded supramolecular polymer of high viscosity. The experimental data are discussed in the frame of the Stokes-Einstein and Stokes-Einstein-Debye models. It was found that the translational movement of the ions is due to normal Brownian diffusion, which was revealed by a fulfillment of Ohm's law by the electric current and a strictly exponential decay of the current after removing the electric stimulus. The dependence of the dc conductivity on the viscosity of the medium fulfills the Stokes-Einstein model quite well. An extension of the model, by including in it the conductivity relaxation time, is proposed in this paper. A breakdown of the Stokes-Einstein-Debye model is revealed by the relations of the dipolar relaxation time to the viscosity and to the dc ionic conductivity. The importance of the C=O···H-N hydrogen bonds in that breakdown is discussed.

Epoxy-based hydrogels investigated by high-frequency dielectric relaxation spectroscopy.

PubMed

Krakovský, Ivan; Shikata, Toshiyuki; Hasegawa, Ryuta

2013-11-14

Using high-frequency dielectric relaxation spectroscopy, nanophase-separated structures of epoxy-based hydrogels were investigated as a function of water content at 25 °C. The dielectric spectra resulting from the hydrogels were reasonably decomposed into two Debye-type and two Cole-Cole-type relaxation modes. The fastest Debye-type mode, found at 8.3 ps, was attributed to the rotational relaxation process of free water molecules in the bulk state. The other Debye-type mode, at ca. 20-34 ps, originates from the exchange process of water molecules that are hydrogen-bonded to the hydrophilic epoxy network portions for free bulk ones. The first Cole-Cole-type mode observed, at ca. 20-370 ps, was assigned to the complicated dynamics for electric dipole moments of the hydrophilic groups in the epoxy networks (mainly monomeric oxyethylene units). The slowest major Cole-Cole-type mode, at 5-29 ns, was attributed to the Maxwell-Wagner-Sillars polarization process and confirmed the presence of the nanophase-separated structures as revealed by the previous small-angle neutron scattering experiments.

Slow Debye-type peak observed in the dielectric response of polyalcohols

NASA Astrophysics Data System (ADS)

Bergman, Rikard; Jansson, Helén; Swenson, Jan

2010-01-01

Dielectric relaxation spectroscopy of glass forming liquids normally exhibits a relaxation scenario that seems to be surprisingly general. However, the relaxation dynamics is more complicated for hydrogen bonded liquids. For instance, the dielectric response of monoalcohols is dominated by a mysterious Debye-like process at lower frequencies than the structural α-relaxation that is normally dominating the spectra of glass formers. For polyalcohols this process has been thought to be absent or possibly obscured by a strong contribution from conductivity and polarization effects at low frequencies. We here show that the Debye-like process, although much less prominent, is also present in the response of polyalcohols. It can be observed in the derivative of the real part of the susceptibility or directly in the imaginary part if the conductivity contribution is reduced by covering the upper electrode with a thin Teflon layer. We report on results from broadband dielectric spectroscopy studies of several polyalcohols: glycerol, xylitol, and sorbitol. The findings are discussed in relation to other experimental observations of ultraslow (i.e., slower than the viscosity related α-relaxation) dynamics in glass formers.

Ab Initio Calculation of XAFS Debye-Waller Factors for Crystalline Materials

NASA Astrophysics Data System (ADS)

Dimakis, Nicholas

2007-02-01

A direct an accurate technique for calculating the thermal X-ray absorption fine structure (XAFS) Debye-Waller factors (DWF) for materials of crystalline structure is presented. Using the Density Functional Theory (DFT) under the hybrid X3LYP functional, a library of MnO spin—optimized clusters are built and their phonon spectrum properties are calculated; these properties in the form of normal mode eigenfrequencies and eigenvectors are in turn used for calculation of the single and multiple scattering XAFS DWF. DWF obtained via this technique are temperature dependent expressions and can be used to substantially reduce the number of fitting parameters when experimental spectra are fitted with a hypothetical structure without any ad hoc assumptions. Due to the high computational demand a hybrid approach of mixing the DFT calculated DWF with the correlated Debye model for inner and outer shells respectively is presented. DFT obtained DWFs are compared with corresponding values from experimental XAFS spectra on manganosite. The cluster size effect and the spin parameter on the DFT calculated DWFs are discussed.

Investigation of different physical aspects such as structural, mechanical, optical properties and Debye temperature of Fe2ScM (M=P and As) semiconductors: A DFT-based first principles study

NASA Astrophysics Data System (ADS)

Ali, Md. Lokman; Rahaman, Md. Zahidur

2018-04-01

By using first principles calculation dependent on the density functional theory (DFT), we have investigated the mechanical, structural properties and the Debye temperature of Fe2ScM (M=P and As) compounds under various pressures up to 60 GPa. The optical properties have been investigated under zero pressure. Our calculated optimized structural parameters of both the materials are in good agreement with other theoretical predictions. The calculated elastic constants show that Fe2ScM (M=P and As) compounds are mechanically stable under external pressure below 60 GPa. From the elastic constants, the shear modulus G, the bulk modulus B, Young’s modulus E, anisotropy factor A and Poisson’s ratio ν are calculated by using the Voigt-Reuss-Hill approximation. The Debye temperature and average sound velocities are also investigated from the obtained elastic constants. The detailed analysis of all optical functions reveals that both compounds are good dielectric material.

Study of microvascular non-Newtonian blood flow modulated by electroosmosis.

PubMed

Tripathi, Dharmendra; Yadav, Ashu; Anwar Bég, O; Kumar, Rakesh

2018-05-01

An analytical study of microvascular non-Newtonian blood flow is conducted incorporating the electro-osmosis phenomenon. Blood is considered as a Bingham rheological aqueous ionic solution. An externally applied static axial electrical field is imposed on the system. The Poisson-Boltzmann equation for electrical potential distribution is implemented to accommodate the electrical double layer in the microvascular regime. With long wavelength, lubrication and Debye-Hückel approximations, the boundary value problem is rendered non-dimensional. Analytical solutions are derived for the axial velocity, volumetric flow rate, pressure gradient, volumetric flow rate, averaged volumetric flow rate along one time period, pressure rise along one wavelength and stream function. A plug swidth is featured in the solutions. Via symbolic software (Mathematica), graphical plots are generated for the influence of Bingham plug flow width parameter, electrical Debye length and Helmholtz-Smoluchowski velocity (maximum electro-osmotic velocity) on the key hydrodynamic variables. This study reveals that blood flow rate accelerates with decreasing the plug width (i.e. viscoplastic nature of fluids) and also with increasing the Debye length parameter. Copyright © 2018 Elsevier Inc. All rights reserved.

q-deformed Einstein's model to describe specific heat of solid

NASA Astrophysics Data System (ADS)

Guha, Atanu; Das, Prasanta Kumar

2018-04-01

Realistic phenomena can be described more appropriately using generalized canonical ensemble, with proper parameter sets involved. We have generalized the Einstein's theory for specific heat of solid in Tsallis statistics, where the temperature fluctuation is introduced into the theory via the fluctuation parameter q. At low temperature the Einstein's curve of the specific heat in the nonextensive Tsallis scenario exactly lies on the experimental data points. Consequently this q-modified Einstein's curve is found to be overlapping with the one predicted by Debye. Considering only the temperature fluctuation effect(even without considering more than one mode of vibration is being triggered) we found that the CV vs T curve is as good as obtained by considering the different modes of vibration as suggested by Debye. Generalizing the Einstein's theory in Tsallis statistics we found that a unique value of the Einstein temperature θE along with a temperature dependent deformation parameter q(T) , can well describe the phenomena of specific heat of solid i.e. the theory is equivalent to Debye's theory with a temperature dependent θD.

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

Hyatt, John S.; Do, Changwoo; Hu, Xiaobo

Here, we investigate poly(N-isopropylacrylamide) (pNIPAM) microgels randomly copolymerized with large mol % of protonated acrylic acid (AAc), finding that above the lower critical solution temperature the presence of the acid strongly disrupts pNIPAM's collapse, leading to unexpected new behavior at high temperatures. We see a dramatic increase in the ratio between the radius of gyration and the hydrodynamic radius above the theoretical value for homogeneous spheres, and a corresponding increase of the network length scale, which we attribute to the presence of a heterogeneous polymer distribution that forms due to frustration of pNIPAM's coil-to-globule transition by the AAc. Finally, wemore » analyze this phenomenon using a Debye-Bueche-like scattering contribution as opposed to the Lorentzian term often used, interpreting the results in terms of mass segregation at the particle periphery.« less

Bohm velocity in the presence of a hot cathode

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

Palacio Mizrahi, J. H.; Krasik, Ya. E.

2013-08-15

The spatial distribution of the plasma and beam electrons in a region whose extension from a hot cathode is larger than the Debye length, but smaller than the electron mean free path, is analyzed. In addition, the influence of electrons thermionically emitted from a hot cathode and the ratio of electron-to-ion mass on the Bohm velocity and on the ion and electron densities at the plasma-sheath boundary in a gas discharge are studied. It is shown that thermionic emission has the effect of increasing the Bohm velocity, and this effect is more pronounced for lighter ions. In addition, it ismore » shown that the Bohm velocity cannot be increased to more than 24% above its value when there is no electron emission.« less

The defect level and ideal thermal conductivity of graphene uncovered by residual thermal reffusivity at the 0 K limit

NASA Astrophysics Data System (ADS)

Xie, Yangsu; Xu, Zaoli; Xu, Shen; Cheng, Zhe; Hashemi, Nastaran; Deng, Cheng; Wang, Xinwei

2015-05-01

Due to its intriguing thermal and electrical properties, graphene has been widely studied for potential applications in sensor and energy devices. However, the reported value for its thermal conductivity spans from dozens to thousands of W m-1 K-1 due to different levels of alternations and defects in graphene samples. In this work, the thermal diffusivity of suspended four-layered graphene foam (GF) is characterized from room temperature (RT) down to 17 K. For the first time, we identify the defect level in graphene by evaluating the inverse of thermal diffusivity (termed ``thermal reffusivity'': Θ) at the 0 K limit. By using the Debye model of Θ = Θ0 + C × e-θ/2T and fitting the Θ-T curve to the point of T = 0 K, we identify the defect level (Θ0) and determine the Debye temperature of graphene. Θ0 is found to be 1878 s m-2 for the studied GF and 43-112 s m-2 for three highly crystalline graphite materials. This uncovers a 16-43-fold higher defect level in GF than that in pyrolytic graphite. In GF, the phonon mean free path solely induced by defects and boundary scattering is determined as 166 nm. The Debye temperature of graphene is determined to be 1813 K, which is very close to the average theoretical Debye temperature (1911 K) of the three acoustic phonon modes in graphene. By subtracting the defect effect, we report the ideal thermal diffusivity and conductivity (κideal) of graphene presented in the 3D foam structure in the range of 33-299 K. Detailed physics based on chemical composition and structure analysis are given to explain the κideal-T profile by comparing with those reported for suspended graphene.Due to its intriguing thermal and electrical properties, graphene has been widely studied for potential applications in sensor and energy devices. However, the reported value for its thermal conductivity spans from dozens to thousands of W m-1 K-1 due to different levels of alternations and defects in graphene samples. In this work, the thermal diffusivity of suspended four-layered graphene foam (GF) is characterized from room temperature (RT) down to 17 K. For the first time, we identify the defect level in graphene by evaluating the inverse of thermal diffusivity (termed ``thermal reffusivity'': Θ) at the 0 K limit. By using the Debye model of Θ = Θ0 + C × e-θ/2T and fitting the Θ-T curve to the point of T = 0 K, we identify the defect level (Θ0) and determine the Debye temperature of graphene. Θ0 is found to be 1878 s m-2 for the studied GF and 43-112 s m-2 for three highly crystalline graphite materials. This uncovers a 16-43-fold higher defect level in GF than that in pyrolytic graphite. In GF, the phonon mean free path solely induced by defects and boundary scattering is determined as 166 nm. The Debye temperature of graphene is determined to be 1813 K, which is very close to the average theoretical Debye temperature (1911 K) of the three acoustic phonon modes in graphene. By subtracting the defect effect, we report the ideal thermal diffusivity and conductivity (κideal) of graphene presented in the 3D foam structure in the range of 33-299 K. Detailed physics based on chemical composition and structure analysis are given to explain the κideal-T profile by comparing with those reported for suspended graphene. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02012c

Non-Debye domain-wall-induced dielectric response in Sr0.61-xCexBa0.39Nb2O6

NASA Astrophysics Data System (ADS)

Kleemann, W.; Dec, J.; Miga, S.; Woike, Th.; Pankrath, R.

2002-06-01

Two different non-Debye dielectric spectra are observed in a polydomain relaxor-ferroelectric Sr0.61-xBa0.39Nb2O6:Ce3+x single crystal in the vicinity of its transition temperature, Tc~320 K. At infralow frequencies the susceptibility varies as χ*~ω-β, β~0.2, and is attributed to an irreversible creep-like viscous motion of domain walls, while logarithmic dispersion due to reversible wall relaxation [T. Nattermann, Y. Shapir, and I. Vilfan, Phys. Rev. B 42, 8577 (1990)] occurs at larger ω.

Ionization potential depression and optical spectra in a Debye plasma model

NASA Astrophysics Data System (ADS)

Lin, Chengliang; Röpke, Gerd; Reinholz, Heidi; Kraeft, Wolf-Dietrich

2017-11-01

We show how optical spectra in dense plasmas are determined by the shift of energy levels as well as the broadening owing to collisions with the plasma particles. In lowest approximation, the interaction with the plasma particles is described by the RPA dielectric function, leading to the Debye shift of the continuum edge. The bound states remain nearly un-shifted, their broadening is calculated in Born approximation. The role of ionization potential depression as well as the Inglis-Teller effect are shown. The model calculations have to be improved going beyond the lowest (RPA) approximation when applying to WDM spectra.

Computer-aided diagnosis workstation and network system for chest diagnosis based on multislice CT images

NASA Astrophysics Data System (ADS)

Satoh, Hitoshi; Niki, Noboru; Mori, Kiyoshi; Eguchi, Kenji; Kaneko, Masahiro; Kakinuma, Ryutarou; Moriyama, Noriyuki; Ohmatsu, Hironobu; Masuda, Hideo; Machida, Suguru

2007-03-01

Multislice CT scanner advanced remarkably at the speed at which the chest CT images were acquired for mass screening. Mass screening based on multislice CT images requires a considerable number of images to be read. It is this time-consuming step that makes the use of helical CT for mass screening impractical at present. To overcome this problem, we have provided diagnostic assistance methods to medical screening specialists by developing a lung cancer screening algorithm that automatically detects suspected lung cancers in helical CT images and a coronary artery calcification screening algorithm that automatically detects suspected coronary artery calcification. Moreover, we have provided diagnostic assistance methods to medical screening specialists by using a lung cancer screening algorithm built into mobile helical CT scanner for the lung cancer mass screening done in the region without the hospital. We also have developed electronic medical recording system and prototype internet system for the community health in two or more regions by using the Virtual Private Network router and Biometric fingerprint authentication system and Biometric face authentication system for safety of medical information. Based on these diagnostic assistance methods, we have now developed a new computer-aided workstation and database that can display suspected lesions three-dimensionally in a short time. This paper describes basic studies that have been conducted to evaluate this new system.

An Evaluation of Mass Screening Using Fecal Occult Blood Test for Colorectal Cancer in Japan: A Case‐Control Study

PubMed Central

Hiwatashi, Nobuo; Morimoto, Tomizo; Fukao, Akira; Sato, Hirofusa; Sugahara, Nobuyuki; Hisamichi, Shigeru; Toyota, Takayoshi

1993-01-01

There is as yet no firm evidence showing that mass screening for colorectal cancer using fecal occult blood tests (FOBTs) reduces the mortality from this cancer. Therefore we evaluated the effectiveness of the screening by a case‐control study in Miyagi Prefecture, Japan. The study included as case subjects 28 individuals who had died from colorectal cancer and had had an opportunity to participate in the mass screening before the date of diagnosis as colorectal cancer, and 3 controls for each case subject randomly selected from residents who were alive on the date of death of case subjects and matched by sex, age (within 3 years) and living area using residential files. For each set, i.e., a case subject and 3 controls, screening histories before the date of the diagnosis of the case as colorectal cancer were examined. Both the case subjects and the controls who had participated in the screening at least once within 3 years before the date of diagnosis of the case were classified as “screened.” The 28 case subjects consisted of 12 males and 16 females (average age: 60.8 years). The odds ratio of death from colorectal cancer for the screened versus the non‐screened persons was 0.24 (95% confidence interval = 0.08–0.76) by the Mantel‐Haenszel method. The present study suggests that mass screening using FOBTs for colorectal cancer significantly reduces the mortality from this cancer epidemiologically. PMID:8276715

Parent Reactions to a School-Based Body Mass Index Screening Program

ERIC Educational Resources Information Center

Johnson, Suzanne Bennett; Pilkington, Lorri L.; Lamp, Camilla; He, Jianghua; Deeb, Larry C.

2009-01-01

Background: This study assessed parent reactions to school-based body mass index (BMI) screening. Methods: After a K-8 BMI screening program, parents were sent a letter detailing their child's BMI results. Approximately 50 parents were randomly selected for interview from each of 4 child weight-classification groups (overweight, at risk of…

Influence of magnetic fields on the color screening masses

NASA Astrophysics Data System (ADS)

Bonati, Claudio; D'Elia, Massimo; Mesiti, Michele; Negro, Francesco; Rucci, Andrea; Sanfilippo, Francesco

2018-03-01

We present some recent results obtained in the study of the color magnetic and electric screening masses in the QCD plasma. In particular, we discuss how the masses get modified by strong external fields which are expected to be created in physical situations such as heavy-ion collisions.

Cost-effectiveness analysis of population-based screening of hepatocellular carcinoma: Comparing ultrasonography with two-stage screening

PubMed Central

Kuo, Ming-Jeng; Chen, Hsiu-Hsi; Chen, Chi-Ling; Fann, Jean Ching-Yuan; Chen, Sam Li-Sheng; Chiu, Sherry Yueh-Hsia; Lin, Yu-Min; Liao, Chao-Sheng; Chang, Hung-Chuen; Lin, Yueh-Shih; Yen, Amy Ming-Fang

2016-01-01

AIM: To assess the cost-effectiveness of two population-based hepatocellular carcinoma (HCC) screening programs, two-stage biomarker-ultrasound method and mass screening using abdominal ultrasonography (AUS). METHODS: In this study, we applied a Markov decision model with a societal perspective and a lifetime horizon for the general population-based cohorts in an area with high HCC incidence, such as Taiwan. The accuracy of biomarkers and ultrasonography was estimated from published meta-analyses. The costs of surveillance, diagnosis, and treatment were based on a combination of published literature, Medicare payments, and medical expenditure at the National Taiwan University Hospital. The main outcome measure was cost per life-year gained with a 3% annual discount rate. RESULTS: The results show that the mass screening using AUS was associated with an incremental cost-effectiveness ratio of USD39825 per life-year gained, whereas two-stage screening was associated with an incremental cost-effectiveness ratio of USD49733 per life-year gained, as compared with no screening. Screening programs with an initial screening age of 50 years old and biennial screening interval were the most cost-effective. These findings were sensitive to the costs of screening tools and the specificity of biomarker screening. CONCLUSION: Mass screening using AUS is more cost effective than two-stage biomarker-ultrasound screening. The most optimal strategy is an initial screening age at 50 years old with a 2-year inter-screening interval. PMID:27022228

Two independent measurements of Debye lengths in doped nonpolar liquids.

PubMed

Prieve, D C; Hoggard, J D; Fu, R; Sides, P J; Bethea, R

2008-02-19

Electric current measurements were performed between 2.5 cm x 7.5 cm parallel-plate electrodes separated by 1.2 mm of heptane doped with 0-15% w/w poly(isobutylene succinimide) (PIBS) having a molecular weight of about 1700. The rapid (microsecond) initial charging of the capacitor can be used to infer the dielectric constant of the solution. The much slower decay of current arising from the polarization of electrodes depends on the differential capacitance of the diffuse clouds of charge carriers accumulating next to each electrode and on the ohmic resistance of the fluid. Using the Gouy-Chapman model for the differential capacitance, Debye lengths of 80-600 nm were deduced that decrease with increasing concentration of PIBS. Values of the Debye lengths were confirmed by performing independent measurements of double-layer repulsion between a 6 microm polystyrene (PS) latex sphere and a PS-coated glass plate using total internal reflection microscopy in the same solutions. The charge carriers appear to be inverted PIBS micelles having apparent Stokes diameters of 20-40 nm. Dynamic light scattering reveals a broad distribution of sizes having an intensity-averaged diameter of 15 nm. This smaller size might arise (1) from overestimating the electrophoretic mobility of micelles by treating them as point charges or (2) because charged micelles are larger on average than uncharged micelles. When Faradaic reactions and zeta potentials on the electrodes can be neglected, such current versus time experiments yield values for the Debye length and ionic strength with less effort than force measurements. To obtain the concentration of charge carriers from measurements of conductivity, the mobility of the charge carriers must be known.

Weak polyelectrolyte complexation driven by associative charging.

PubMed

Rathee, Vikramjit S; Zervoudakis, Aristotle J; Sidky, Hythem; Sikora, Benjamin J; Whitmer, Jonathan K

2018-03-21

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly. In this study, we elucidate the novel interplay between weak polyelectrolyte charging and complexation behavior through coupled molecular dynamics and Monte Carlo simulations. Specifically, we investigate a model of two equal-length and oppositely charging polymer chains in an implicit salt solution represented through Debye-Hückel interactions. The charging tendency of each chain, along with the salt concentration, is varied to determine the existence and extent of cooperativity in charging and complexation. Strong cooperation in the charging of these chains is observed at large Debye lengths, corresponding to low salt concentrations, while at lower Debye lengths (higher salt concentrations), the chains behave in apparent isolation. When the electrostatic coupling is long-ranged, we find that a highly charged chain strongly promotes the charging of its partner chain, even if the environment is unfavorable for an isolated version of that partner chain. Evidence of this phenomenon is supported by a drop in the potential energy of the system, which does not occur at the lower Debye lengths where both potential energies and charge fractions converge for all partner chain charging tendencies. The discovery of this cooperation will be helpful in developing "smart" drug delivery mechanisms by allowing for better predictions for the dissociation point of delivery complexes.

Weak polyelectrolyte complexation driven by associative charging

NASA Astrophysics Data System (ADS)

Rathee, Vikramjit S.; Zervoudakis, Aristotle J.; Sidky, Hythem; Sikora, Benjamin J.; Whitmer, Jonathan K.

2018-03-01

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly. In this study, we elucidate the novel interplay between weak polyelectrolyte charging and complexation behavior through coupled molecular dynamics and Monte Carlo simulations. Specifically, we investigate a model of two equal-length and oppositely charging polymer chains in an implicit salt solution represented through Debye-Hückel interactions. The charging tendency of each chain, along with the salt concentration, is varied to determine the existence and extent of cooperativity in charging and complexation. Strong cooperation in the charging of these chains is observed at large Debye lengths, corresponding to low salt concentrations, while at lower Debye lengths (higher salt concentrations), the chains behave in apparent isolation. When the electrostatic coupling is long-ranged, we find that a highly charged chain strongly promotes the charging of its partner chain, even if the environment is unfavorable for an isolated version of that partner chain. Evidence of this phenomenon is supported by a drop in the potential energy of the system, which does not occur at the lower Debye lengths where both potential energies and charge fractions converge for all partner chain charging tendencies. The discovery of this cooperation will be helpful in developing "smart" drug delivery mechanisms by allowing for better predictions for the dissociation point of delivery complexes.

The defect level and ideal thermal conductivity of graphene uncovered by residual thermal reffusivity at the 0 K limit.

PubMed

Xie, Yangsu; Xu, Zaoli; Xu, Shen; Cheng, Zhe; Hashemi, Nastaran; Deng, Cheng; Wang, Xinwei

2015-06-14

Due to its intriguing thermal and electrical properties, graphene has been widely studied for potential applications in sensor and energy devices. However, the reported value for its thermal conductivity spans from dozens to thousands of W m(-1) K(-1) due to different levels of alternations and defects in graphene samples. In this work, the thermal diffusivity of suspended four-layered graphene foam (GF) is characterized from room temperature (RT) down to 17 K. For the first time, we identify the defect level in graphene by evaluating the inverse of thermal diffusivity (termed "thermal reffusivity": Θ) at the 0 K limit. By using the Debye model of Θ = Θ0 + C× e(-θ/2T) and fitting the Θ-T curve to the point of T = 0 K, we identify the defect level (Θ0) and determine the Debye temperature of graphene. Θ0 is found to be 1878 s m(-2) for the studied GF and 43-112 s m(-2) for three highly crystalline graphite materials. This uncovers a 16-43-fold higher defect level in GF than that in pyrolytic graphite. In GF, the phonon mean free path solely induced by defects and boundary scattering is determined as 166 nm. The Debye temperature of graphene is determined to be 1813 K, which is very close to the average theoretical Debye temperature (1911 K) of the three acoustic phonon modes in graphene. By subtracting the defect effect, we report the ideal thermal diffusivity and conductivity (κideal) of graphene presented in the 3D foam structure in the range of 33-299 K. Detailed physics based on chemical composition and structure analysis are given to explain the κideal-T profile by comparing with those reported for suspended graphene.

Propagation of a plasma streamer in catalyst pores

NASA Astrophysics Data System (ADS)

Zhang, Quan-Zhi; Bogaerts, Annemie

2018-03-01

Although plasma catalysis is gaining increasing interest for various environmental applications, the underlying mechanisms are still far from understood. For instance, it is not yet clear whether and how plasma streamers can propagate in catalyst pores, and what is the minimum pore size to make this happen. As this is crucial information to ensure good plasma-catalyst interaction, we study here the mechanism of plasma streamer propagation in a catalyst pore, by means of a two-dimensional particle-in-cell/Monte Carlo collision model, for various pore diameters in the nm-range to μm-range. The so-called Debye length is an important criterion for plasma penetration into catalyst pores, i.e. a plasma streamer can penetrate into pores when their diameter is larger than the Debye length. The Debye length is typically in the order of a few 100 nm up to 1 μm at the conditions under study, depending on electron density and temperature in the plasma streamer. For pores in the range of ∼50 nm, plasma can thus only penetrate to some extent and at very short times, i.e. at the beginning of a micro-discharge, before the actual plasma streamer reaches the catalyst surface and a sheath is formed in front of the surface. We can make plasma streamers penetrate into smaller pores (down to ca. 500 nm at the conditions under study) by increasing the applied voltage, which yields a higher plasma density, and thus reduces the Debye length. Our simulations also reveal that the plasma streamers induce surface charging of the catalyst pore sidewalls, causing discharge enhancement inside the pore, depending on pore diameter and depth.

Electron collection theory for a D-region subsonic blunt electrostatic probe

NASA Technical Reports Server (NTRS)

Wai-Kwong Lai, T.

1974-01-01

Blunt probe theory for subsonic flow in a weakly ionized and collisional gas is reviewed, and an electron collection theory for the relatively unexplored case, Deybye length approximately 1, which occurs in the lower ionosphere (D-region), is developed. It is found that the dimensionless Debye length is no longer an electric field screening parameter, and the space charge field effect can be negelected. For ion collection, Hoult-Sonin theory is recognized as a correct description of the thin, ion density-perturbed layer adjacent the blunt probe surface. The large volume with electron density perturbed by a positively biased probe renders the usual thin boundary layer analysis inapplicable. Theories relating free stream conditions to the electron collection rate for both stationary and moving blunt probes are obtained. A model based on experimental nonlinear electron drift velocity data is proposed. For a subsonically moving probe, it is found that the perturbed region can be divided into four regions with distinct collection mechanisms.

Rovibrational states of Wigner molecules in spherically symmetric confining potentials

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

Cioslowski, Jerzy

2016-08-07

The strong-localization limit of three-dimensional Wigner molecules, in which repulsively interacting particles are confined by a weak spherically symmetric potential, is investigated. An explicit prescription for computation of rovibrational wavefunctions and energies that are asymptotically exact at this limit is presented. The prescription is valid for systems with arbitrary angularly-independent interparticle and confining potentials, including those involving Coulombic and screened (i.e., Yukawa/Debye) interactions. The necessary derivations are greatly simplified by explicit constructions of the Eckart frame and the parity-adapted primitive wavefunctions. The performance of the new formalism is illustrated with the three- and four-electron harmonium atoms at their strong-correlation limits.more » In particular, the involvement of vibrational modes with the E symmetry is readily pinpointed as the origin of the “anomalous” weak-confinement behavior of the {sup 1}S{sub +} state of the four-electron species that is absent in its {sup 1}D{sub +} companion of the strong-confinement regime.« less

Extended Solution Gate OFET-based Biosensor for Label-free Glial Fibrillary Acidic Protein Detection with Polyethylene Glycol-Containing Bioreceptor Layer.

PubMed

Song, Jian; Dailey, Jennifer; Li, Hui; Jang, Hyun-June; Zhang, Pengfei; Wang, Jeff Tza-Huei; Everett, Allen D; Katz, Howard E

2017-05-25

A novel organic field effect transistor (OFET) -based biosensor is described for label-free glial fibrillary acidic protein (GFAP) detection. We report the first use of an extended solution gate structure where the sensing area and the organic semiconductor are separated, and a reference electrode is not needed. Different molecular weight polyethylene glycols (PEGs) are mixed into the bio-receptor layer to help extend the Debye screening length. The drain current change was significantly increased with the help of higher molecular weight PEGs, as they are known to reduce the dielectric constant. We also investigated the sensing performance under different gate voltage (V g ). The sensitivity increased after we decreased V g from -5 V to -2 V, because the lower V g is much closer to the OFET threshold voltage and the influence of attached negatively charged proteins become more apparent. Finally, the selectivity experiments toward different interferents were performed. The stability and selectivity are promising for clinical applications.

Beyond the Debye length in high ionic strength solution: direct protein detection with field-effect transistors (FETs) in human serum.

PubMed

Chu, Chia-Ho; Sarangadharan, Indu; Regmi, Abiral; Chen, Yen-Wen; Hsu, Chen-Pin; Chang, Wen-Hsin; Lee, Geng-Yen; Chyi, Jen-Inn; Chen, Chih-Chen; Shiesh, Shu-Chu; Lee, Gwo-Bin; Wang, Yu-Lin

2017-07-12

In this study, a new type of field-effect transistor (FET)-based biosensor is demonstrated to be able to overcome the problem of severe charge-screening effect caused by high ionic strength in solution and detect proteins in physiological environment. Antibody or aptamer-immobilized AlGaN/GaN high electron mobility transistors (HEMTs) are used to directly detect proteins, including HIV-1 RT, CEA, NT-proBNP and CRP, in 1X PBS (with 1%BSA) or human sera. The samples do not need any dilution or washing process to reduce the ionic strength. The sensor shows high sensitivity and the detection takes only 5 minutes. The designs of the sensor, the methodology of the measurement, and the working mechanism of the sensor are discussed and investigated. A theoretical model is proposed based on the finding of the experiments. This sensor is promising for point-of-care, home healthcare, and mobile diagnostic device.

Line of charges in electrolyte solution near a half-space I. Counterion condensation.

PubMed

Tang, Tian; Jagota, Anand; Hui, Chung-Yuen

2006-07-15

The effect of a half-space on counterion condensation around a line of charges in electrolyte solution is examined in the framework of Debye-Hückel electrostatics. The half-space substrate is allowed to be a conductor, a dielectric, or a semiconductor. Counterions are predicted to be released completely as the line of charges approaches a conducting substrate. When it approaches a dielectric substrate, depending on the ratio of solvent to substrate dielectric constant, there are three possibilities: (1) epsilon(sol)/epsilon(sub) < 1; the counterions are partially (or completely) released; (2) epsilon(sol)/epsilon(sub) = 1; the amount of condensation remains unchanged; and (3) epsilon(sol)/epsilon(sub) > 1; more counterions condense. Depending on the relative magnitude of screening lengths in the semiconductor and in the solution, its effect on condensation follows either that of a metal or that of a dielectric. For the case of a moderately doped silicon substrate, condensation is predicted to be similar to that for a dielectric.

Glass transition of charged particles in two-dimensional confinement.

PubMed

Yazdi, Anoosheh; Heinen, Marco; Ivlev, Alexei; Löwen, Hartmut; Sperl, Matthias

2015-05-01

The glass transition of mesoscopic charged particles in two-dimensional confinement is studied by mode-coupling theory. We consider two types of effective interactions between the particles, corresponding to two different models for the distribution of surrounding ions that are integrated out in coarse-grained descriptions. In the first model, a planar monolayer of charged particles is immersed in an unbounded isotropic bath of ions, giving rise to an isotropically screened Debye-Hückel (Yukawa)-type effective interaction. The second, experimentally more relevant system is a monolayer of negatively charged particles that levitate atop a flat horizontal electrode, as frequently encountered in laboratory experiments with complex (dusty) plasmas. A steady plasma current toward the electrode gives rise to an anisotropic effective interaction potential between the particles, with an algebraically long-ranged in-plane decay. In a comprehensive parameter scan that covers the typical range of experimentally accessible plasma conditions, we calculate and compare the mode-coupling predictions for the glass transition in both kinds of systems.

The human peripheral subunit-binding domain folds rapidly while overcoming repulsive Coulomb forces

PubMed Central

Arbely, Eyal; Neuweiler, Hannes; Sharpe, Timothy D; Johnson, Christopher M; Fersht, Alan R

2010-01-01

Peripheral subunit binding domains (PSBDs) are integral parts of large multienzyme complexes involved in carbohydrate metabolism. PSBDs facilitate shuttling of prosthetic groups between different catalytic subunits. Their protein surface is characterized by a high density of positive charges required for binding to subunits within the complex. Here, we investigated folding thermodynamics and kinetics of the human PSBD (HSBD) using circular dichroism and tryptophan fluorescence experiments. HSBD was only marginally stable under physiological solvent conditions but folded within microseconds via a barrier-limited apparent two-state transition, analogous to its bacterial homologues. The high positive surface-charge density of HSBD leads to repulsive Coulomb forces that modulate protein stability and folding kinetics, and appear to even induce native-state movement. The electrostatic strain was alleviated at high solution-ionic-strength by Debye-Hückel screening. Differences in ionic-strength dependent characteristics among PSBD homologues could be explained by differences in their surface charge distributions. The findings highlight the trade-off between protein function and stability during protein evolution. PMID:20662005

Transport properties of liquid metal hydrogen under high pressures

NASA Technical Reports Server (NTRS)

Brown, R. C.; March, N. H.

1972-01-01

A theory is developed for the compressibility and transport properties of liquid metallic hydrogen, near to its melting point and under high pressure. The interionic force law is assumed to be of the screened Coulomb type, because hydrogen has no core electrons. The random phase approximation is used to obtain the structure factor S(k) of the system in terms of the Fourier transform of this force law. The long wavelenth limit of the structure factor S(o) is related to the compressibility, which is much lower than that of alkali metals at their melting points. The diffusion constant at the melting point is obtained in terms of the Debye frequency, using a frequency spectrum analogous with the phonon spectrum of a solid. A similar argument is used to obtain the combined shear and bulk viscosities, but these depend also on S(o). The transport coefficients are found to be about the same size as those of alkali metals at their melting points.

Charge ordering in ionic fluids mediate repulsive surface interactions

NASA Astrophysics Data System (ADS)

Dasbiswas, Kinjal; Ludwig, Nicholas B.; Zhang, Hao; Talapin, Dmitri; Vaikuntanathan, Suri

Recent experiments on ionic fluids, such as surface force measurements in organic ionic liquids and the observation of colloidal stability in inorganic molten salts, suggest the presence of long-ranged repulsive forces. These cannot be explained within the classical Debye-Hückel theory for dilute electrolytes. We argue that such repulsive interactions can arise from long-range (several nm) charge density oscillations induced by a surface that preferentially binds one of the ionic species in an ionic fluid. We present a continuum theory that accounts for such charge layering based on a frustrated Ising model that incorporates both long-range Coulombic and short-range steric interactions. The mean-field analytic treatment qualitatively matches results from molecular simulations. A careful analysis of the ionic correlation functions arising from such charge ordering may also explain the long electrostatic screening lengths observed in various ionic fluids and their non-monotonic dependence on the electrolyte concentration. We acknowledge the University of Chicago for support.

Variational extension of the mean spherical approximation to arbitrary dimensions

NASA Astrophysics Data System (ADS)

Velázquez, Esov S.; Blum, Lesser; Frisch, Harry L.

1997-10-01

We generalize a variational principle for the mean spherical approximation for a system of charged hard spheres in 3D to arbitrary dimensions. We first construct a free energy variational trial function from the Debye-Hückel excess charging internal energy at a finite concentration and an entropy obtained at the zero-concentration limit by thermodynamic integration. In three dimensions the minimization of this expression with respect to the screening parameter leads to the mean spherical approximation, usually obtained by solution of the Ornstein-Zernike equation. This procedure, which interpolates naturally between the zero concentration/coupling limit and the high-concentration/ coupling limit, is extended to arbitrary dimensions. We conjecture that this result is also equivalent to the MSA as originally defined, although a technical proof of this point is left for the future. The Onsager limit T ΔS MSA / ΔE MSA → 0 for infinite concentration/coupling is satisfied for all d ≠ 2, while for d=2 this limit is 1.

Study of phonon modes and elastic properties of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 rare-earth bulk metallic glasses

NASA Astrophysics Data System (ADS)

Suthar, P. H.; Gajjar, P. N.; Thakore, B. Y.; Jani, A. R.

2013-04-01

A phonon modes and elastic properties of two different rare-earth based bulk metallic glasses Sc36Al24Co20Y20 and Gd36Al24Co20Y20 are computed using Hubbard-Beeby approach and our well established model potential. The local field correlation functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar Sen et al (S) are employed to investigate the influence of the screening effects on the vibrational dynamics of Sc36Al24Co20Y20 and Gd36Al24Co20Y20 bulk metallic glasses. The results for bulk modulus BT, modulus of rigidity G, Poisson's ratio ξ, Young's modulus Y, Debye temperature ΘD, propagation velocity of elastic waves and dispersion curves are reported. The computed elastic properties are found to be in good agreement with experimental and other available data.

Gravitational lensing by a smoothly variable three-dimensional mass distribution

NASA Technical Reports Server (NTRS)

Lee, Man Hoi; Paczynski, Bohdan

1990-01-01

A smooth three-dimensional mass distribution is approximated by a model with multiple thin screens, with surface mass density varying smoothly on each screen. It is found that 16 screens are sufficient for a good approximation of the three-dimensional distribution of matter. It is also found that in this multiscreen model the distribution of amplifications of single images is dominated by the convergence due to matter within the beam. The shear caused by matter outside the beam has no significant effect. This finding considerably simplifies the modeling of lensing by a smooth three-dimensional mass distribution by effectively reducing the problem to one dimension, as it is sufficient to know the mass distribution along a straight light ray.

21 CFR 862.1055 - Newborn screening test system for amino acids, free carnitine, and acylcarnitines using tandem...

Code of Federal Regulations, 2012 CFR

2012-04-01

... mass spectrometry is a device that consists of stable isotope internal standards, control materials..., free carnitine, and acylcarnitines using tandem mass spectrometry. 862.1055 Section 862.1055 Food and... screening test system for amino acids, free carnitine, and acylcarnitines using tandem mass spectrometry. (a...

21 CFR 862.1055 - Newborn screening test system for amino acids, free carnitine, and acylcarnitines using tandem...

Code of Federal Regulations, 2014 CFR

2014-04-01

... mass spectrometry is a device that consists of stable isotope internal standards, control materials..., free carnitine, and acylcarnitines using tandem mass spectrometry. 862.1055 Section 862.1055 Food and... screening test system for amino acids, free carnitine, and acylcarnitines using tandem mass spectrometry. (a...

Gauge-invariant screening masses and static quark free energies in Nf=2 +1 QCD at nonzero baryon density

NASA Astrophysics Data System (ADS)

Andreoli, Michele; Bonati, Claudio; D'Elia, Massimo; Mesiti, Michele; Negro, Francesco; Rucci, Andrea; Sanfilippo, Francesco

2018-03-01

We discuss the extension of gauge-invariant electric and magnetic screening masses in the quark-gluon plasma to the case of a finite baryon density, defining them in terms of a matrix of Polyakov loop correlators. We present lattice results for Nf=2 +1 QCD with physical quark masses, obtained using the imaginary chemical potential approach, which indicate that the screening masses increase as a function of μB. A separate analysis is carried out for the theoretically interesting case μB/T =3 i π , where charge conjugation is not explicitly broken and the usual definition of the screening masses can be used for temperatures below the Roberge-Weiss transition. Finally, we investigate the dependence of the static quark free energy on the baryon chemical potential, showing that it is a decreasing function of μB, which displays a peculiar behavior as the pseudocritical transition temperature at μB=0 is approached.

Drug screening in medical examiner casework by high-resolution mass spectrometry (UPLC-MSE-TOF).

PubMed

Rosano, Thomas G; Wood, Michelle; Ihenetu, Kenneth; Swift, Thomas A

2013-10-01

Postmortem drug findings yield important analytical evidence in medical examiner casework, and chromatography coupled with nominal mass spectrometry (MS) serves as the predominant general unknown screening approach. We report screening by ultra performance liquid chromatography (UPLC) coupled with hybrid quadrupole time-of-flight mass spectrometer (MS(E)-TOF), with comparison to previously validated nominal mass UPLC-MS and UPLC-MS-MS methods. UPLC-MS(E)-TOF screening for over 950 toxicologically relevant drugs and metabolites was performed in a full-spectrum (m/z 50-1,000) mode using an MS(E) acquisition of both molecular and fragment ion data at low (6 eV) and ramped (10-40 eV) collision energies. Mass error averaged 1.27 ppm for a large panel of reference drugs and metabolites. The limit of detection by UPLC-MS(E)-TOF ranges from 0.5 to 100 ng/mL and compares closely with UPLC-MS-MS. The influence of column recovery and matrix effect on the limit of detection was demonstrated with ion suppression by matrix components correlating closely with early and late eluting reference analytes. Drug and metabolite findings by UPLC-MS(E)-TOF were compared with UPLC-MS and UPLC-MS-MS analyses of postmortem blood in 300 medical examiner cases. Positive findings by all methods totaled 1,528, with a detection rate of 57% by UPLC-MS, 72% by UPLC-MS-MS and 80% by combined UPLC-MS and UPLC-MS-MS screening. Compared with nominal mass screening methods, UPLC-MS(E)-TOF screening resulted in a 99% detection rate and, in addition, offered the potential for the detection of nontargeted analytes via high-resolution acquisition of molecular and fragment ion data.

First-principles calculations for elastic properties of OsB 2 under pressure

NASA Astrophysics Data System (ADS)

Yang, Jun-Wei; Chen, Xiang-Rong; Luo, Fen; Ji, Guang-Fu

2009-11-01

The structure, elastic properties and elastic anisotropy of orthorhombic OsB 2 are investigated by density functional theory method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation (GGA) as well as local density approximation (LDA). The obtained structural parameters, elastic constants, elastic anisotropy and Debye temperature for OsB 2 under pressure are consistent with the available experimental data and other theoretical results. It is found that the elastic constants, bulk modulus and Debye temperature of OsB 2 tend to increase with increasing pressure. It is predicted that OsB 2 is not a superhard material from our calculations.

The polarized Debye sheath effect on Kadomtsev-Petviashvili electrostatic structures in strongly coupled dusty plasma

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

Shahmansouri, M.; Alinejad, H.

2015-04-15

We give a theoretical investigation on the dynamics of nonlinear electrostatic waves in a strongly coupled dusty plasma with strong electrostatic interaction between dust grains in the presence of the polarization force (i.e., the force due to the polarized Debye sheath). Adopting a reductive perturbation method, we derived a three-dimensional Kadomtsev-Petviashvili equation that describes the evolution of weakly nonlinear electrostatic localized waves. The energy integral equation is used to study the existence domains of the localized structures. The analysis provides the localized structure existence region, in terms of the effects of strong interaction between the dust particles and polarization force.

Theoretical investigations on structural, elastic and electronic properties of thallium halides

NASA Astrophysics Data System (ADS)

Singh, Rishi Pal; Singh, Rajendra Kumar; Rajagopalan, Mathrubutham

2011-04-01

Theoretical investigations on structural, elastic and electronic properties, viz. ground state lattice parameter, elastic moduli and density of states, of thallium halides (viz. TlCl and TlBr) have been made using the full potential linearized augmented plane wave method within the generalized gradient approximation (GGA). The ground state lattice parameter and bulk modulus and its pressure derivative have been obtained using optimization method. Young's modulus, shear modulus, Poisson ratio, sound velocities for longitudinal and shear waves, Debye average velocity, Debye temperature and Grüneisen parameter have also been calculated for these compounds. Calculated structural, elastic and other parameters are in good agreement with the available data.

Solvent free tin oxide nanoparticle for gas sensing application

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

Ranjan, Pranay, E-mail: pranjan@iitp.ac.in; Thakur, Ajay D.; Centre for Energy and Environment, Indian Institute of Technology Patna, Patliputra, Patna 800013 India

2016-05-06

A new modified technique of synthesizing tin oxide nanoparticles with crystallite size of 2 nm to 6 nm has been developed. Surface area of the nanoparticle has been increased as we approached towards the Debye length. Such a techniques for approaching the Debye length is expected to bring remarkable changes in the properties of resistive based gas sensors. The technique used here is less toxic, economical and has high yield. Phase purity, size, shape and composition has been investigated using x-ray diffraction, micro Raman, scanning electron microscopy and energy dispersive x ray spectroscopy. While surface area has been calculated through Brunaur-Emmett-Teller (BET).

Thermodynamic properties of fullerite C70

NASA Astrophysics Data System (ADS)

Rekhviashvili, S. Sh.

2017-08-01

A new expression for the isochoric heat capacity and the equation of state of fullerite C70 are obtained in the framework of a quantum-statistical method. Analogs of the Debye law and Dulong-Petit law for this fullerite are formulated. Fullerene C70 molecules are modeled by isotropic quantum oscillators under the assumption that their nonsphericity weakly influences the thermodynamic properties of the condensed phase. The intramolecular oscillations of carbon atoms are described using the Debye theory and the cold contribution to the free energy of fullerite is calculated using the Lennard-Jones pair potential for fullerene molecules. A comparison of the proposed theory to experiment shows good agreement.

A modified Rayleigh-Gans-Debye formula for small angle X-ray scattering by interstellar dust grains

NASA Astrophysics Data System (ADS)

Sharma, Subodh K.

2015-05-01

A widely used approximation in studies relating to small angle differential scattering cross-section of X-rays scattered by interstellar dust grains is the well known Rayleigh-Gans-Debye approximation (RGDA). The validity of this approximation, however, is limited only to X-ray energies greater than about 1 keV. At lower energies, this approximation overestimates the exact results. In this paper a modification to the RGDA is suggested. It is shown that a combination of the RGDA with Ramsauer approximation retains the formal simplicity of the RGDA and also yields good agreement with Mie computations at all X-ray energies.

Thermodynamic properties of semiconductor compounds studied based on Debye-Waller factors

NASA Astrophysics Data System (ADS)

Van Hung, Nguyen; Toan, Nguyen Cong; Ba Duc, Nguyen; Vuong, Dinh Quoc

2015-08-01

Thermodynamic properties of semiconductor compounds have been studied based on Debye-Waller factors (DWFs) described by the mean square displacement (MSD) which has close relation with the mean square relative displacement (MSRD). Their analytical expressions have been derived based on the statistical moment method (SMM) and the empirical many-body Stillinger-Weber potentials. Numerical results for the MSDs of GaAs, GaP, InP, InSb, which have zinc-blende structure, are found to be in reasonable agreement with experiment and other theories. This paper shows that an elements value for MSD is dependent on the binary semiconductor compound within which it resides.

Debye temperature of metallic nanowires--an experimental determination from the resistance of metallic nanowires in the temperature range 4.2 K-300 K.

PubMed

Bid, Aveek; Bora, Achyut; Raychaudhuri, A K

2007-06-01

We have studied the resistance of metallic nanowires (silver and copper) as a function of the wire diameter in the temperature range 4.2 K-300 K. The nanowires with an average diameter of 15 nm-200 nm and length 6 microm were electrochemically deposited using polycarbonate membranes as template from AgNO3 and CuSO4, respectively. The wires after growth were removed from the membranes by dissolving the polymer in dichloromethane and their crystalline nature confirmed by XRD and TEM studies. The TEM study establishes that the nanowires are single crystalline and can have twin in them. The resistivity data was fitted to Bloch-Gruneisen theorem with the values of Debye temperature and the electron-acoustic phonon coupling constant as the two fit variables. The value of the Debye temperature obtained for the Ag wires was seen to match well with that of the bulk while for Cu wires a significant reduction was observed. The observed increase in resistivity with a decrease in the wire diameter could be explained as due to diffuse surface scattering of the conduction electrons.

Low temperature and high pressure thermoelastic and crystallographic properties of SrZrO3 perovskite in the Pbnm phase

NASA Astrophysics Data System (ADS)

Knight, Kevin S.; Bull, Craig L.

2016-12-01

The thermoelastic and structural properties of SrZrO3 perovskite in the Pnma (Pbnm) phase have been studied using neutron powder diffraction at 82 temperatures between 11 K and 406 K at ambient pressure, and at sixteen pressures between 0.07 and 6.7 GPa at ambient temperature. The bulk modulus, derived by fitting the equation of state to a second order Birch-Murnaghan equation-of-state, 157(5) GPa, is in excellent agreement with that deduced in a recent resonant ultrasound investigation. Experimental axial compressional moduli are in agreement with those calculated from the elastic stiffness coefficients derived by ab-initio calculation, although the experimental bulk modulus is significantly softer than that calculated. Following low temperature saturation for temperatures less than 40 K, the unit cell monotonically increases with a predicted high temperature limit in the volume expansivity of ∼2.65 × 10-5 K-1. Axial linear thermal expansion coefficients are found to be in the order αb < αc < αa for all temperatures greater than 20 K with the b axis indicating a weak, low temperature negative expansion coefficient at low temperatures. The thermoelastic properties of SrZrO3 can be approximated by a two-term Debye model for the phonon density of states with Debye temperatures of 238(4) K and 713(6) K derived in a self-consistent manner by simultaneously fitting the isochoric heat capacity and the unit cell volume. Atomic displacement parameters have been fitted to a modified Debye model in which the zero-point term is an additional refinable variable and shows the cations and anions have well separated Debye temperatures, mirroring the need for two Debye-like distributions in the vibrational density of states. The temperature dependence of the crystal structure is presented in terms of the amplitudes of the seven symmetry-adapted basis vectors of the aristotype phase that are consistent with space group Pbnm, thus permitting a direct measure of the order parameter evolution in SrZrO3. The temperature variation of the in-phase tilt, which is lost at the phase transition at 973 K, is consistent with tricritical behaviour, in agreement with published results based on high temperature crystallographic data.

First-principles simulations of electrostatic interactions between dust grains

NASA Astrophysics Data System (ADS)

Itou, H.; Amano, T.; Hoshino, M.

2014-12-01

We investigated the electrostatic interaction between two identical dust grains of an infinite mass immersed in homogeneous plasma by employing first-principles N-body simulations combined with the Ewald method. We specifically tested the possibility of an attractive force due to overlapping Debye spheres (ODSs), as was suggested by Resendes et al. [Phys. Lett. A 239, 181-186 (1998)]. Our simulation results demonstrate that the electrostatic interaction is repulsive and even stronger than the standard Yukawa potential. We showed that the measured electric field acting on the grain is highly consistent with a model electrostatic potential around a single isolated grain that takes into account a correction due to the orbital motion limited theory. Our result is qualitatively consistent with the counterargument suggested by Markes and Williams [Phys. Lett. A 278, 152-158 (2000)], indicating the absence of the ODS attractive force.

Optical phonon modes and polaron related parameters in GaxIn1-xP

NASA Astrophysics Data System (ADS)

Bouarissa, N.; Algarni, H.; Al-Hagan, O. A.; Khan, M. A.; Alhuwaymel, T. F.

2018-02-01

Based on a pseudopotential approach under the virtual crystal approximation that includes the effect of compositional disorder, the optical lattice vibration frequencies and polaron related parameters in zinc-blende GaxIn1-xP have been studied. Our findings showed generally reasonably good accord with data in the literature. Other case, our results are predictions. The composition dependence of longitudinal optical (LO) and transverse optical (TO) phonon modes, LO-TO splittings, Frӧhlich coupling parameter, Debye temperature of LO phonon frequency, and polaron effective mass has been analyzed and discussed. While a non-monotonic behavior has been noticed for the LO and TO phonon frequencies versus Ga concentration x, a monotonic behavior has been observed for the rest of the features of interest. The information derived from this investigation may be useful for optoelectronic technological applications.

A Novel Method of Extraction of Blend Component Structure from SANS Measurements of Homopolymer Bimodal Blends.

PubMed

Smerdova, Olga; Graham, Richard S; Gasser, Urs; Hutchings, Lian R; De Focatiis, Davide S A

2014-05-01

A new method is presented for the extraction of single-chain form factors and interchain interference functions from a range of small-angle neutron scattering (SANS) experiments on bimodal homopolymer blends. The method requires a minimum of three blends, made up of hydrogenated and deuterated components with matched degree of polymerization at two different chain lengths, but with carefully varying deuteration levels. The method is validated through an experimental study on polystyrene homopolymer bimodal blends with [Formula: see text]. By fitting Debye functions to the structure factors, it is shown that there is good agreement between the molar mass of the components obtained from SANS and from chromatography. The extraction method also enables, for the first time, interchain scattering functions to be produced for scattering between chains of different lengths. [Formula: see text].

Laser-driven two-electron quantum dot in plasmas

NASA Astrophysics Data System (ADS)

Bahar, M. K.; Soylu, A.

2018-06-01

We have investigated the energies of two-electron parabolic quantum dots (TEPQdots) embedded in plasmas characterized by more general exponential cosine screened Coulomb (MGECSC) potential under the action of a monochromatic, linearly polarized laser field by solving the corresponding Schrödinger equation numerically via the asymptotic iteration method. The four different cases of the MGECSC potential constituted by various sets of the potential parameters are reckoned in modeling of the interactions in the plasma environments which are Debye and quantum plasmas. The plasma environment is a remarkable experimental argument for the quantum dots and the interactions in plasma environments are different compared to the interactions in an environment without plasma and the screening specifications of the plasmas can be controlled through the plasma parameters. These findings constitute our major motivation in consideration of the plasma environments. An appreciable confinement effect is made up by implementing the laser field on the TEPQdot. The influences of the laser field on the system are included by using the Ehlotzky approximation, and then Kramers-Henneberger transformation is carried out for the corresponding Schrödinger equation. The influences of the ponderomotive force on two-electron quantum dots embedded in plasmas are investigated. The behaviours, the similarities and the functionalities of the laser field, the plasma environment, and the quantum dot confinement are also scrutinized. In addition, the role of the plasma environments in the mentioned analysis is also discussed in detail.

[Screening and confirmation of 24 hormones in cosmetics by ultra high performance liquid chromatography-linear ion trap/orbitrap high resolution mass spectrometry].

PubMed

Li, Zhaoyong; Wang, Fengmei; Niu, Zengyuan; Luo, Xin; Zhang, Gang; Chen, Junhui

2014-05-01

A method of ultra high performance liquid chromatography-linear ion trap/orbitrap high resolution mass spectrometry (UPLC-LTQ/Orbitrap MS) was established to screen and confirm 24 hormones in cosmetics. Various cosmetic samples were extracted with methanol. The extract was loaded onto a Waters ACQUITY UPLC BEH C18 column (50 mm x 2.1 mm, 1.7 microm) using a gradient elution of acetonitrile/water containing 0.1% (v/v) formic acid for the separation. The accurate mass of quasi-molecular ion was acquired by full scanning of electrostatic field orbitrap. The rapid screening was carried out by the accurate mass of quasi-molecular ion. The confirmation analysis for targeted compounds was performed with the retention time and qualitative fragments obtained by data dependent scan mode. Under the optimal conditions, the 24 hormones were routinely detected with mass accuracy error below 3 x 10(-6) (3 ppm), and good linearities were obtained in their respective linear ranges with correlation coefficients higher than 0.99. The LODs (S/N = 3) of the 24 compounds were < or = 10 microg/kg, which can meet the requirements for the actual screening of cosmetic samples. The developed method was applied to screen the hormones in 50 cosmetic samples. The results demonstrate that the method is a useful tool for the rapid screening and identification of the hormones in cosmetics.

Technical aspects of neonatal screening using tandem mass spectrometry. Report from the 4th meeting of the International Society for Neonatal Screening.

PubMed

Simonsen, H; Jensen, U G

1999-12-01

Quantitative analysis of amino acids (AA) and acylcarnitines using tandem mass spectrometry is an emerging technology used to screen neonatal dried blood spot samples for disorders in the metabolism of AA, organic acids and fatty acids. This paper provides a brief review of some of the technically oriented issues which emerged at the 4th meeting of the International Society for Neonatal Screening in Stockholm, 1999. The information covers sample preparation, instrumentation, data acquistion modes, internal standards, interpretation, confounding factors and practical screening experience.

A SIMPLE AND RAPID MATRIX-ASSISTED LASER DESORPTION/IONIZATION TIME OF FLIGHT MASS SPECTROMETRY METHOD TO SCREEN FISH PLASMA SAMPLES FOR ESTROGEN-RESPONSIVE BIOMARKERS

EPA Science Inventory

In this study, we describe and evaluate the performance of a simple and rapid mass spectral method for screening fish plasma for estrogen-responsive biomarkers using matrix assisted laster desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) couopled with a short...

Outcomes from a mass media campaign to promote cervical screening in NSW, Australia.

PubMed

Morrell, Stephen; Perez, Donna A; Hardy, Margaret; Cotter, Trish; Bishop, James F

2010-09-01

Despite the decline in the incidence of cervical cancer in Australia as a result of population screening, a substantial proportion of women in NSW screen less regularly than the recommended two-yearly interval or do not screen. With higher rates of cervical cancer in unscreened and underscreened women, and despite the introduction of the human papillomavirus vaccine, there remains a need to continue to remind women to screen. The mass media has been shown to be effective at improving participation in cervical screening. A 2007 television advertising campaign to promote cervical screening in New South Wales (NSW) was examined. Data from the NSW Papanicolaou (Pap) Test Register were used to compare weekly numbers of Pap tests for NSW overall and in metropolitan local government areas with low screening rates by age group and by time since the last Pap test. Time series regression analysis incorporating seasonal effects was used to estimate the strength of the association between screening and the media campaign. Overall during the advertising campaign, 15% more screens (16 700) occurred than expected for 2007 without the advertising campaign. Increases were evident among unscreened and underscreened women, with little overscreening occurring. Women living in low screening areas also showed a significant increase in mean weekly screens of 21% (388) over that expected in the absence of the media campaign. Despite the ecological nature of this study, the mass media campaign appears to have been successful in increasing screening in unscreened and underscreened women in NSW.

Large Subpectoral Lipoma on Screening Mammography

PubMed Central

Su, Andres; Margolies, Laurie

2017-01-01

A 61 year-old woman presenting for bilateral screening mammogram was found to have an oval fat-density mass in the posterior right breast, partially visualized, with anterior displacement and thinning of the pectoralis major muscle. This mass was found on CT and MRI correlation to represent a large fat-containing mass, likely a lipoma, deep to the pectoralis major. On subsequent screening mammograms, the visualized portion of the mass remained stable. Subpectoral lipomas and intramuscular lipomas within the pectoralis major are rare, and their appearance on mammography may not be familiar to most radiologists. A review of the literature and a discussion of their appearance on multiple imaging modalities is provided. PMID:29299106

A new mass screening method for methylmercury poisoning using mercury-volatilizing bacteria from Minamata Bay.

PubMed

Nakamura, K; Naruse, I; Takizawa, Y

1999-09-01

A simplified mass screening method for methylmercury exposure was developed using methylmercury-volatilizing bacteria from Minamata Bay. Some bacteria can transform methylmercury into mercury vapor. Most mercury in the hair is methylmercury, which is readily extracted with HCl solution. Black spots are formed on X-ray film due to the reduction of Ag(+) emulsion with mercury vapor produced by methylmercury-volatilizing bacteria. By exploiting these characteristics, a screening method was developed, whereby the fur of rats injected with methylmercury chloride formed clear black spots on X-ray film, whereas the fur of rats injected with saline did not. Subsequently, 50 human hair samples were examined using this mass screening method. The method identified people who had high mercury concentration, over 20 microg/g. A few thousand hair samples may be screened in a day using this method because it is rapid, simple, and economical. This method, therefore, enables screening of persons with methylmercury poisoning in mercury-polluted areas. Copyright 1999 Academic Press.

Development of a fully automatic scheme for detection of masses in whole breast ultrasound images.

PubMed

Ikedo, Yuji; Fukuoka, Daisuke; Hara, Takeshi; Fujita, Hiroshi; Takada, Etsuo; Endo, Tokiko; Morita, Takako

2007-11-01

Ultrasonography has been used for breast cancer screening in Japan. Screening using a conventional hand-held probe is operator dependent and thus it is possible that some areas of the breast may not be scanned. To overcome such problems, a mechanical whole breast ultrasound (US) scanner has been proposed and developed for screening purposes. However, another issue is that radiologists might tire while interpreting all images in a large-volume screening; this increases the likelihood that masses may remain undetected. Therefore, the aim of this study is to develop a fully automatic scheme for the detection of masses in whole breast US images in order to assist the interpretations of radiologists and potentially improve the screening accuracy. The authors database comprised 109 whole breast US imagoes, which include 36 masses (16 malignant masses, 5 fibroadenomas, and 15 cysts). A whole breast US image with 84 slice images (interval between two slice images: 2 mm) was obtained by the ASU-1004 US scanner (ALOKA Co., Ltd., Japan). The feature based on the edge directions in each slice and a method for subtracting between the slice images were used for the detection of masses in the authors proposed scheme. The Canny edge detector was applied to detect edges in US images; these edges were classified as near-vertical edges or near-horizontal edges using a morphological method. The positions of mass candidates were located using the near-vertical edges as a cue. Then, the located positions were segmented by the watershed algorithm and mass candidate regions were detected using the segmented regions and the low-density regions extracted by the slice subtraction method. For the removal of false positives (FPs), rule-based schemes and a quadratic discriminant analysis were applied for the distribution between masses and FPs. As a result, the sensitivity of the authors scheme for the detection of masses was 80.6% (29/36) with 3.8 FPs per whole breast image. The authors scheme for a computer-aided detection may be useful in improving the screening performance and efficiency.

Mass spectrometric-based stable isotopic 2-aminobenzoic acid glycan mapping for rapid glycan screening of biotherapeutics.

PubMed

Prien, Justin M; Prater, Bradley D; Qin, Qiang; Cockrill, Steven L

2010-02-15

Fast, sensitive, robust methods for "high-level" glycan screening are necessary during various stages of a biotherapeutic product's lifecycle, including clone selection, process changes, and quality control for lot release testing. Traditional glycan screening involves chromatographic or electrophoretic separation-based methods, and, although reproducible, these methods can be time-consuming. Even ultrahigh-performance chromatographic and microfluidic integrated LC/MS systems, which work on the tens of minute time scale, become lengthy when hundreds of samples are to be analyzed. Comparatively, a direct infusion mass spectrometry (MS)-based glycan screening method acquires data on a millisecond time scale, exhibits exquisite sensitivity and reproducibility, and is amenable to automated peak annotation. In addition, characterization of glycan species via sequential mass spectrometry can be performed simultaneously. Here, we demonstrate a quantitative high-throughput MS-based mapping approach using stable isotope 2-aminobenzoic acid (2-AA) for rapid "high-level" glycan screening.

Generic sample preparation combined with high-resolution liquid chromatography-time-of-flight mass spectrometry for unification of urine screening in doping-control laboratories.

PubMed

Peters, R J B; Oosterink, J E; Stolker, A A M; Georgakopoulos, C; Nielen, M W F

2010-04-01

A unification of doping-control screening procedures of prohibited small molecule substances--including stimulants, narcotics, steroids, beta2-agonists and diuretics--is highly urgent in order to free resources for new classes such as banned proteins. Conceptually this may be achieved by the use of a combination of one gas chromatography-time-of-flight mass spectrometry method and one liquid chromatography-time-of-flight mass spectrometry method. In this work a quantitative screening method using high-resolution liquid chromatography in combination with accurate-mass time-of-flight mass spectrometry was developed and validated for determination of glucocorticosteroids, beta2-agonists, thiazide diuretics, and narcotics and stimulants in urine. To enable the simultaneous isolation of all the compounds of interest and the necessary purification of the resulting extracts, a generic extraction and hydrolysis procedure was combined with a solid-phase extraction modified for these groups of compounds. All 56 compounds are determined using positive electrospray ionisation with the exception of the thiazide diuretics for which the best sensitivity was obtained by using negative electrospray ionisation. The results show that, with the exception of clenhexyl, procaterol, and reproterol, all compounds can be detected below the respective minimum required performance level and the results for linearity, repeatability, within-lab reproducibility, and accuracy show that the method can be used for quantitative screening. If qualitative screening is sufficient the instrumental analysis may be limited to positive ionisation, because all analytes including the thiazides can be detected at the respective minimum required levels in the positive mode. The results show that the application of accurate-mass time-of-flight mass spectrometry in combination with generic extraction and purification procedures is suitable for unification and expansion of the window of screening methods of doping laboratories. Moreover, the full-scan accurate-mass data sets obtained still allow retrospective examination for emerging doping agents, without re-analyzing the samples.

Screening Methods for Metal-Containing Nanoparticles in Water

EPA Science Inventory

Screening-level analysis of water for metal-containing nanoparticles is achieved with single particle-inductively coupled plasma mass spectrometry (SP-ICPMS). This method measures both the concentration of nanoparticles containing an analyte metal and the mass of the metal in eac...

Plasma effect on fast-electron-impact-ionization from 2p state of hydrogen-like ions

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

Qi, Y. Y.; Ning, L. N.; Wang, J. G.

2013-12-15

Plasma effects on the high-energy electron-impact ionization process from 2p orbital of Hydrogen-like ions embedded in weakly coupled plasmas are investigated in the first Born approximation. The plasma screening of the Coulomb interaction between charged particles is represented by the Debye Hückel model. The screening of Coulomb interactions decreases the ionization energies and varies the wave functions for not only the bound orbital but also the continuum; the number of the summation for the angular-momentum states in the generalized oscillator strength densities is reduced with the plasma screening stronger when the ratio of ε/I{sub 2p} (I{sub 2p} is the ionizationmore » energy of 2p state and ε is the energy of the continuum electron) is kept, and then the contribution from the lower-angular-momentum states dominates the generalized oscillator strength densities, so the threshold phenomenon in the generalized oscillator strength densities and the double differential cross sections are remarkable: The accessional minima, the outstanding enhancement, and the resonance peaks emerge a certain energy region, whose energy position and width are related to the vicinity between δ and the critical value δ{sub nl}{sup c}, corresponding to the special plasma condition when the bound state |nl just enters the continuum; the multiple virtual-state enhancement and the multiple shape resonances in a certain energy domain also appear in the single differential cross section whenever the plasma screening parameter passes through a critical value δ{sub nl}{sup c}, which is similar to the photo-ionization process but different from it, where the dipole transition only happens, but multi-pole transition will occur in the electron-impact ionization process, so its multiple virtual-state enhancements and the multiple shape resonances appear more frequently than the photo-ionization process.« less

Structural, electronic and thermal properties of super hard ternary boride, WAlB

NASA Astrophysics Data System (ADS)

Rajpoot, Priyanka; Rastogi, Anugya; Verma, U. P.

2018-04-01

A first principle study of the structural, electronic and thermal properties of Tungsten Aluminum Boride (WAlB) using full-potential linearized augmented plane wave (FP-LAPW) in the frame work of density function theory (DFT) have been calculated. The calculated equilibrium structural parameters are in excellent agreement with available experimental results. The calculated electronic band structure reveals that WAlB is metallic in nature. The quasi-harmonic Debye model is applied to study of the temperature and pressure effect on volume, Debye temperature, thermal expansion coefficient and specific heat at constant volume and constant pressure. To the best of our knowledge theoretical investigation of these properties of WAlB is reported for the first time.

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

Filippov, A. V., E-mail: fav@triniti.ru

The interaction of two charged point macroparticles located in Wigner–Seitz cells of simple cubic (SC), body-centered cubic (BCC), or face-centered cubic (FCC) lattices in an equilibrium plasma has been studied within the Debye approximation or, more specifically, based on the linearized Poisson–Boltzmann model. The shape of the outer boundary is shown to exert a strong influence on the pattern of electrostatic interaction between the two macroparticles, which transforms from repulsion at small interparticle distances to attraction as the interparticle distance approaches half the length of the computational cell. The macroparticle pair interaction potential in an equilibrium plasma is shown tomore » be nevertheless the Debye one and purely repulsive for likely charged macroparticles.« less

A Surrogate for Debye-Waller Factors from Dynamic Stokes Shifts

PubMed Central

Zhong, Qin; Johnson, Jerainne; Aamer, Khaled A.; Tyagi, Madhusudan

2011-01-01

We show that the short-time behavior of time-resolved fluorescence Stokes shifts (TRSS) are similar to that of the intermediate scattering function obtained from neutron scattering at q near the peak in the static structure factor for glycerol. This allows us to extract a Debye-Waller (DW) factor analog from TRSS data at times as short as 1 ps in a relatively simple way. Using the time-domain relaxation data obtained by this method we show that DW factors evaluated at times ≥ 40 ps can be directly influenced by α relaxation and thus should be used with caution when evaluating relationships between fast and slow dynamics in glassforming systems. PMID:21701673

Nanostructured Drugs Embedded into a Polymeric Matrix: Vinpocetine/PVP Hybrids Investigated by Debye Function Analysis.

PubMed

Hasa, Dritan; Giacobbe, Carlotta; Perissutti, Beatrice; Voinovich, Dario; Grassi, Mario; Cervellino, Antonio; Masciocchi, Norberto; Guagliardi, Antonietta

2016-09-06

Microcrystalline vinpocetine, coground with cross-linked polyvinylpyrrolidone, affords hybrids containing nanosized drug nanocrystals, the size and size distributions of which depend on milling times and drug-to-polymer weight ratios. Using an innovative approach to microstructural characterization, we analyzed wide-angle X-ray total scattering data by the Debye function analysis and demonstrated the possibility to characterize pharmaceutical solid dispersions obtaining a reliable quantitative view of the physicochemical status of the drug dispersed in an amorphous carrier. The microstructural properties derived therefrom have been successfully employed in reconciling the enigmatic difference in behavior between in vitro and in vivo solubility tests performed on nanosized vinpocetine embedded in a polymeric matrix.

Optical equivalence of isotropic ensembles of ellipsoidal particles in the Rayleigh-Gans-Debye and anomalous diffraction approximations and its consequences

NASA Astrophysics Data System (ADS)

Paramonov, L. E.

2012-05-01

Light scattering by isotropic ensembles of ellipsoidal particles is considered in the Rayleigh-Gans-Debye approximation. It is proved that randomly oriented ellipsoidal particles are optically equivalent to polydisperse randomly oriented spheroidal particles and polydisperse spherical particles. Density functions of the shape and size distributions for equivalent ensembles of spheroidal and spherical particles are presented. In the anomalous diffraction approximation, equivalent ensembles of particles are shown to also have equal extinction, scattering, and absorption coefficients. Consequences of optical equivalence are considered. The results are illustrated by numerical calculations of the angular dependence of the scattering phase function using the T-matrix method and the Mie theory.

Order-disorder effects on the elastic properties of CuMPt6 (M=Cr and Co) compounds

NASA Astrophysics Data System (ADS)

Huang, Shuo; Li, Rui-Zi; Qi, San-Tao; Chen, Bao; Shen, Jiang

2014-04-01

The elastic properties of CuMPt6 (M=Cr and Co) in disordered face-centered cubic (fcc) structure and ordered Cu3Au-type structure are studied with lattice inversion embedded-atom method. The calculated lattice constant and Debye temperature agree quite well with the comparable experimental data. The obtained formation enthalpy demonstrates that the Cu3Au-type structure is energetically more favorable. Numerical estimates of the elastic constants, bulk/shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy, and Debye temperature for both compounds are performed, and the results suggest that the disordered fcc structure is much softer than the ordered Cu3Au-type structure.

Webinar Presentation: Suspect Screening of Environmental Organic Acids in Human Serum Using High-resolution Mass Spectrometry (HRMS)

EPA Pesticide Factsheets

This presentation, Suspect Screening of Environmental Organic Acids in Human Serum Using High-resolution Mass Spectrometry (HRMS), was given at the NIEHS/EPA Children's Centers 2016 Webinar Series: Exposome held on May 11, 2016.

Evaluation of Abdominal Ultrasonography Mass Screening for Hepatocellular Carcinoma in Taiwan

PubMed Central

Yeh, Yen-Po; Hu, Tsung-Hui; Cho, Po-Yuan; Chen, Hsiu-Hsi; Yen, Amy Ming-Fang; Chen, Sam Li-Sheng; Chiu, Sherry Yueh-Hsia; Fann, Jean Ching-Yuan; Su, Wei-Wen; Fang, Yi-Jen; Chen, Shih-Tien; San, Hsiao-Ching; Chen, Hung-Pin; Liao, Chao-Sheng

2014-01-01

Mass screening with abdominal ultrasonography (AUS) has been suggested as a tool to control adult hepatocellular carcinoma (HCC) in individuals, but its efficacy in reducing HCC mortality has never been demonstrated. This study aimed to assess the effectiveness of reducing HCC mortality by mass AUS screening for HCC based on a program designed and implemented in the Changhua Community-based Integrated Screening (CHCIS) program with an efficient invitation scheme guided by the risk score. We invited 11,114 (27.0%) of 41,219 eligible Taiwanese subjects between 45 and 69 years of age who resided in an HCC high-incidence area to attend a risk score-guided mass AUS screening between 2008 and 2010. The efficacy of reducing HCC mortality was estimated. Of the 8,962 AUS screening attendees (with an 80.6% attendance rate), a total of 16 confirmed HCC cases were identified through community-based ultrasonography screening. Among the 16 screen-detected HCC cases, only two died from HCC, indicating a favorable survival. The cumulative mortality due to HCC (per 100,000) was considerably lower in the invited AUS group (17.26) compared with the uninvited AUS group (42.87) and the historical control group (47.51), yielding age- and gender-adjusted relative mortality rates of 0.69 (95% confidence interval [CI]: 0.56-0.84) and 0.63 (95% CI: 0.52-0.77), respectively. Conclusion: The residents invited to community-based AUS screening for HCC, compared with those who were not invited, showed a reduction in HCC mortality by ∼31% among subjects aged 45-69 years who had not been included in the nationwide vaccination program against hepatitis B virus infection. (Hepatology 2014;59:1840–1849) PMID:24002724

Screen time and adiposity in adolescents in Mexico

PubMed Central

Lajous, Martín; Chavarro, Jorge; Peterson, Karen E; Hernández-Prado, Bernardo; Cruz-Valdéz, Aurelio; Hernández-Ávila, Mauricio; Lazcano-Ponce, Eduardo

2014-01-01

Objective To assess the association of time spent viewing television, videos and videogames with measures of fat mass [body mass index (BMI)] and distribution [triceps and subscapular skin folds (TSF, SSF)]. Design Cross-sectional validated survey, self-administered to students to assess screen time (TV, videos and videogames) and lifestyle variables. Trained personnel obtained anthropometry. The association of screen time with fat mass and distribution, stratified by sex, was modeled with multivariable linear regression, adjusting for potential confounders and correlation of observations within schools. Subjects and setting 3519 males and 5613 females aged 11 to 18 years attending urban and rural schools in the State of Morelos, Mexico Results In males, ≥5 hr/day compared with < 2 hr/day of screen time, was significantly associated with a 0.13 (95%CI 0.04, 0.23) higher BMI z score, 0.73 mm (95% CI 0.24, 1.22) higher SSF and 1.08 mm (95% CI 0.36, 1.81) higher TSF. The positive association of screen time with SSF was strongest in males 11–12 yr. Sexual maturity appeared to modify the association in females; a positive between screen time and SSF was observed in those who had not undergone menarche (p-trend 0.04) but not among sexually mature females (p-trend 0.75). Conclusion Screen time is associated with fat mass and distribution among adolescent males in Mexico. Maturational tempo appears to affect the relationship of screen time with adiposity in boys and girls. Findings suggest obesity preventive interventions in the Mexican context should explore strategies to reduce screen time among youth in early adolescence. PMID:19232154

Investigate the electrical and thermal properties of the low temperature resistant silver nanowire fabricated by two-beam laser technique

NASA Astrophysics Data System (ADS)

He, Gui-Cang; Dong, Xian-Zi; Liu, Jie; Lu, Heng; Zhao, Zhen-Sheng

2018-05-01

A two-beam laser fabrication technique is introduced to fabricate the single silver nanowire (AgNW) on polyethylene terephthalate (PET) substrate. The resistivity of the AgNW is (1.31 ± 0.05) × 10-7 Ω·m, which is about 8 times of the bulk silver resistivity (1.65 × 10-8 Ω·m). The AgNW electrical resistance is measured in temperature range of 10-300 K and fitted with the Bloch-Grüneisen formula. The fitting results show that the residue resistance is 153 Ω, the Debye temperature is 210 K and the electron-phonon coupling constant is (5.72 ± 0.24) × 10-8 Ω·m. Due to the surface scattering, the Debye temperature and the electron-phonon coupling constant are lower than those of bulk silver, and the residue resistance is bigger than that of bulk silver. Thermal conductivity of the single AgNW is calculated in the corresponding temperature range, which is the biggest at the temperature approaching the Debye temperature. The AgNW on PET substrate is the low temperature resistance material and is able to be operated stably at such a low temperature of 10 K.

The Debye-Huckel Approximation in Electroosmotic Flow in Micro- and Nano-channels

NASA Astrophysics Data System (ADS)

Conlisk, A. Terrence

2002-11-01

In this work we consider the electroosmotic flow in a rectangular channel. We consider a mixture of water or other neutral solvent and a salt compound such as sodium chloride and other buffers for which the ionic species are entirely dissociated. Results are produced for the case where the channel height is much greater than the electric double layer(EDL)(microchannel) and for the case where the channel height is of the order or slightly greater than the width of the EDL(nanochannel). At small cation, anion concentration differences the Debye-Huckel approximation is appropriate; at larger concentration differences, the Gouy-Chapman picture of the electric double emerges naturally. In the symmetric case for the electroosmotic flow so induced, the velocity field and the potential are similar. We specifically focus in this paper on the limits of the Debye-Huckel approximation for a simplified version of a phosphate buffered saline(PBS) mixture. The fluid is assumed to behave as a continuum and the volume flow rate is observed to vary linearly with channel height for electrically driven flow in contrast to pressure driven flow which varies as height cubed. This means that very large pressure drops are required to drive flows in small channels. However, useful volume flow rates may be obtained at a very low driving voltage.

Optimised analytical models of the dielectric properties of biological tissue.

PubMed

Salahuddin, Saqib; Porter, Emily; Krewer, Finn; O' Halloran, Martin

2017-05-01

The interaction of electromagnetic fields with the human body is quantified by the dielectric properties of biological tissues. These properties are incorporated into complex numerical simulations using parametric models such as Debye and Cole-Cole, for the computational investigation of electromagnetic wave propagation within the body. These parameters can be acquired through a variety of optimisation algorithms to achieve an accurate fit to measured data sets. A number of different optimisation techniques have been proposed, but these are often limited by the requirement for initial value estimations or by the large overall error (often up to several percentage points). In this work, a novel two-stage genetic algorithm proposed by the authors is applied to optimise the multi-pole Debye parameters for 54 types of human tissues. The performance of the two-stage genetic algorithm has been examined through a comparison with five other existing algorithms. The experimental results demonstrate that the two-stage genetic algorithm produces an accurate fit to a range of experimental data and efficiently out-performs all other optimisation algorithms under consideration. Accurate values of the three-pole Debye models for 54 types of human tissues, over 500 MHz to 20 GHz, are also presented for reference. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Nonlinear effects on electrophoresis of a charged dielectric nanoparticle in a charged hydrogel medium

NASA Astrophysics Data System (ADS)

Bhattacharyya, S.; De, Simanta

2016-09-01

The impact of the solid polarization of a charged dielectric particle in gel electrophoresis is studied without imposing a weak-field or a thin Debye length assumption. The electric polarization of a dielectric particle due to an external electric field creates a non-uniform surface charge density, which in turn creates a non-uniform Debye layer at the solid-gel interface. The solid polarization of the particle, the polarization of the double layer, and the electro-osmosis of mobile ions within the hydrogel medium create a nonlinear effect on the electrophoresis. We have incorporated those nonlinear effects by considering the electrokinetics governed by the Stokes-Brinkman-Nernst-Planck-Poisson equations. We have computed the governing nonlinear coupled set of equations numerically by adopting a finite volume based iterative algorithm. Our numerical method is tested for accuracy by comparing with several existing results on free-solution electrophoresis as well as results based on the Debye-Hückel approximation. Our computed result shows that the electrophoretic velocity decreases with the rise of the particle dielectric permittivity constant and attains a saturation limit at large values of permittivity. A significant impact of the solid polarization is found in gel electrophoresis compared to the free-solution electrophoresis.

A Hierarchical Algorithm for Fast Debye Summation with Applications to Small Angle Scattering

PubMed Central

Gumerov, Nail A.; Berlin, Konstantin; Fushman, David; Duraiswami, Ramani

2012-01-01

Debye summation, which involves the summation of sinc functions of distances between all pair of atoms in three dimensional space, arises in computations performed in crystallography, small/wide angle X-ray scattering (SAXS/WAXS) and small angle neutron scattering (SANS). Direct evaluation of Debye summation has quadratic complexity, which results in computational bottleneck when determining crystal properties, or running structure refinement protocols that involve SAXS or SANS, even for moderately sized molecules. We present a fast approximation algorithm that efficiently computes the summation to any prescribed accuracy ε in linear time. The algorithm is similar to the fast multipole method (FMM), and is based on a hierarchical spatial decomposition of the molecule coupled with local harmonic expansions and translation of these expansions. An even more efficient implementation is possible when the scattering profile is all that is required, as in small angle scattering reconstruction (SAS) of macromolecules. We examine the relationship of the proposed algorithm to existing approximate methods for profile computations, and show that these methods may result in inaccurate profile computations, unless an error bound derived in this paper is used. Our theoretical and computational results show orders of magnitude improvement in computation complexity over existing methods, while maintaining prescribed accuracy. PMID:22707386

Experimental studies of Debye-like process and structural relaxation in mixtures of 2-ethyl-1-hexanol and 2-ethyl-1-hexyl bromide

NASA Astrophysics Data System (ADS)

Preuß, M.; Gainaru, C.; Hecksher, T.; Bauer, S.; Dyre, J. C.; Richert, R.; Böhmer, R.

2012-10-01

Binary solutions of 2-ethyl-1-hexanol (2E1H) with 2-ethyl-1-hexyl bromide (2E1Br) are investigated by means of dielectric, shear mechanical, near-infrared, and solvation spectroscopy as well as dielectrically monitored physical aging. For moderately diluted 2E1H the slow Debye-like process, which dominates the dielectric spectra of the neat monohydroxy alcohol, separates significantly from the α-relaxation. For example, the separation in equimolar mixtures amounts to four decades in frequency. This situation of highly resolved processes allows one to demonstrate unambiguously that physical aging is governed by the α-process, but even under these ideal conditions the Debye process remains undetectable in shear mechanical experiments. Furthermore, the solvation experiments show that under constant charge conditions the microscopic polarization fluctuations take place on the time scale of the structural process. The hydrogen-bond populations monitored via near-infrared spectroscopy indicate the presence of a critical alcohol concentration, xc ≈ 0.5-0.6, thereby confirming the dielectric data. In the pure bromide a slow dielectric process of reduced intensity is present in addition to the main relaxation. This is taken as a sign of intermolecular cooperativity probably mediated via halogen bonds.

Screening for celiac disease in the general population and in high-risk groups

PubMed Central

Card, Timothy R; Kaukinen, Katri; Bai, Julio; Zingone, Fabiana; Sanders, David S; Murray, Joseph A

2015-01-01

Background Celiac disease (CD) occurs in approximately 1% of the Western population. It is a lifelong disorder that is associated with impaired quality of life (QOL) and an excessive risk of comorbidity and death. Objectives To review the literature on screening for CD in relation to the current World Health Organization (WHO) criteria for mass screening. Methods We performed a PubMed search to identify indexed papers on CD screening with a publication date from 1900 until 1 June 2014. When we deemed an abstract relevant, we read the corresponding paper in detail. Results CD fulfills several WHO criteria for mass screening (high prevalence, available treatment and difficult clinical detection), but it has not yet been established that treatment of asymptomatic CD may reduce the excessive risk of severe complications, leading to higher QOL nor that it is cost-effective. Conclusions Current evidence is not sufficient to support mass screening for CD, but active case-finding may be appropriate, as we recognize that most patients with CD will still be missed by this strategy. Although proof of benefit is still lacking, screening for CD may be appropriate in high-risk groups. PMID:25922671

Electron spin relaxation governed by Raman processes both for Cu2+ ions and carbonate radicals in KHCO3 crystals: EPR and electron spin echo studies

NASA Astrophysics Data System (ADS)

Hoffmann, Stanislaw K.; Goslar, Janina; Lijewski, Stefan

2012-08-01

EPR studies of Cu2+ and two free radicals formed by γ-radiation were performed for KHCO3 single crystal at room temperature. From the rotational EPR results we concluded that Cu2+ is chelated by two carbonate molecules in a square planar configuration with spin-Hamiltonian parameters g|| = 2.2349 and A|| = 18.2 mT. Free radicals were identified as neutral HOCOrad with unpaired electron localized on the carbon atom and a radical anion CO3·- with unpaired electron localized on two oxygen atoms. The hyperfine splitting of the EPR lines by an interaction with a single hydrogen atom of HOCOrad was observed with isotropic coupling constants ao = 0.31 mT. Two differently oriented radical sites were identified in the crystal unit cell. Electron spin-lattice relaxation measured by electron spin echo methods shows that both Cu2+ and free radicals relax via two-phonon Raman processes with almost the same relaxation rate. The temperature dependence of the relaxation rate 1/T1 is well described with the effective Debye temperature ΘD = 175 K obtained from a fit to the Debye-type phonon spectrum. We calculated a more realistic Debye temperature value from available elastic constant values of the crystal as ΘD = 246 K. This ΘD-value and the Debye phonon spectrum approximation give a much worse fit to the experimental results. Possible contributions from a local mode or an optical mode are considered and it is suggested that the real phonon spectrum should be used for the relaxation data interpretation. It is unusual that free radicals in KHCO3 relax similarly to the well localized Cu2+ ions, which suggests a small destruction of the host crystal lattice by the ionizing irradiation allowing well coupling between radical and lattice dynamics.

Modeling impacts of NH{sub 3} on uptake of H{sub 2}SO{sub 4} by charged nucleating nanoparticles in the Earth's atmosphere

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

Nadykto, A. B., E-mail: anadykto@gmail.com; Department of Applied Mathematics, Moscow State University of Technology “STANKIN”, Vadkovsky per. 1, Moscow 127055; Nazarenko, K. M.

2016-06-08

The understanding of the role of ammonia, a well-known stabilizer of binary sulfuric acid-water clusters, in the gas-to-nanoparticle conversion in the Earth atmosphere is critically important for the assessment of aerosol radiative forcing associated with the climate changes. The sulfuric acid H{sub 2}SO{sub 4} is present in the atmosphere in the form of the gas-phase hydrates (H{sub 2}SO{sub 4})(H{sub 2}O){sub n}, whose interaction with NH{sub 3} leads to the formation of more stable bisulfate clusters (NH{sub 3})(H{sub 2}SO{sub 4})(H{sub 2}O){sub n}. Although the impact of NH{sub 3} on the thermochemical stability of binary clusters nucleating homogeneously has been studied inmore » some detail in the past, the effect of ammonia on other microphysical properties relevant to nucleation remains insufficiently well understood. In the present study, the effect of ammonia on the electrical dipole moment controlling the nucleation of airborne ions via the dipole-charge interaction has been investigated using the Density Functional Theory (DFT), ab initio MP2 and model chemistry G3 methods. The presence of ammonia in (H{sub 2}SO{sub 4})(H{sub 2}O){sub n} is found to lead to very large enhancement in the dipole moment, which exceeds 2.0-2.5 Debyes (∼60-80%), 3.7-5.0 Debyes (∼90-180%), 1.4-4.5 Debyes (∼50-150%) and 2.1-5.5 Debyes (∼60-700%) for n = 0, n = 1, n = 2 and n = 3, respectively. The implications of this include the significantly increased uptake of the sulfuric acid, the key atmospheric nucleation precursor, by airborne ions and neutrals (due to dipole-dipole interaction), enhanced nucleation rates and the elevated production of ultrafine particles, which cause adverse health impacts.« less

Direct mass spectrometric screening of antibiotics from bacterial surfaces using liquid extraction surface analysis.

PubMed

Kai, Marco; González, Ignacio; Genilloud, Olga; Singh, Sheo B; Svatoš, Aleš

2012-10-30

There is a need to find new antibiotic agents to fight resistant pathogenic bacteria. To search successfully for novel antibiotics from bacteria cultivated under diverse conditions, we need a fast and cost-effective screening method. A combination of Liquid Extraction Surface Analysis (LESA), automated chip-based nanoelectrospray ionization, and high-resolution mass or tandem mass spectrometry using an Orbitrap XL was tested as the screening platform. Actinobacteria, known to produce well-recognized thiazolyl peptide antibiotics, were cultivated on a plate of solid medium and the antibiotics were extracted by organic solvent mixtures from the surface of colonies grown on the plate and analyzed using mass spectrometry (MS). LESA combined with high-resolution MS is a powerful tool with which to extract and detect thiazolyl peptide antibiotics from different Actinobacteria. Known antibiotics were correctly detected with high mass accuracy (<4 ppm) and structurally characterized using tandem mass spectra. Our method is the first step toward the development of a novel high-throughput extraction and identification tool for antibiotics in particular and natural products in general. The method described in this paper is suitable for (1) screening the natural products produced by bacterial colonies on cultivation plates within the first 2 min following extraction and (2) detecting antibiotics at high mass accuracy; the cost is around 2 Euro per sample. Copyright © 2012 John Wiley & Sons, Ltd.

Development and Validation of a Qualitative Method for Target Screening of 448 Pesticide Residues in Fruits and Vegetables Using UHPLC/ESI Q-Orbitrap Based on Data-Independent Acquisition and Compound Database.

PubMed

Wang, Jian; Chow, Willis; Chang, James; Wong, Jon W

2017-01-18

A semiautomated qualitative method for target screening of 448 pesticide residues in fruits and vegetables was developed and validated using ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC/ESI Q-Orbitrap). The Q-Orbitrap Full MS/dd-MS 2 (data dependent acquisition) was used to acquire product-ion spectra of individual pesticides to build a compound database or an MS library, while its Full MS/DIA (data independent acquisition) was utilized for sample data acquisition from fruit and vegetable matrices fortified with pesticides at 10 and 100 μg/kg for target screening purpose. Accurate mass, retention time and response threshold were three key parameters in a compound database that were used to detect incurred pesticide residues in samples. The concepts and practical aspects of in-spectrum mass correction or solvent background lock-mass correction, retention time alignment and response threshold adjustment are discussed while building a functional and working compound database for target screening. The validated target screening method is capable of screening at least 94% and 99% of 448 pesticides at 10 and 100 μg/kg, respectively, in fruits and vegetables without having to evaluate every compound manually during data processing, which significantly reduced the workload in routine practice.

Screening and identification of glyceollins and their metabolites by electrospray ionization tandem mass spectrometry with precursor ion scanning

USDA-ARS?s Scientific Manuscript database

A method has been developed for screening glyceollins and their metabolites based upon precursor ion scanning. Under higher-energy collision conditions, employing a triple quadrupole mass spectrometer in the negative ion mode, deprotonated glyceollin precursors yield a diagnostic radical product ion...

Analyzing Screening Policies for Childhood Obesity

PubMed Central

Yang, Yan; Goldhaber-Fiebert, Jeremy D.; Wein, Lawrence M.

2013-01-01

Due to the health and economic costs of childhood obesity, coupled with studies suggesting the benefits of comprehensive (dietary, physical activity and behavioral counseling) intervention, the United States Preventive Services Task Force recently recommended childhood screening and intervention for obesity beginning at age six. Using a longitudinal data set consisting of the body mass index of 3164 children up to age 18 and another longitudinal data set containing the body mass index at ages 18 and 40 and the presence or absence of disease (hypertension and diabetes) at age 40 for 747 people, we formulate and numerically solve – separately for boys and girls – a dynamic programming problem for the optimal biennial (i.e., at ages 2, 4, …, 16) obesity screening thresholds. Unlike most screening problem formulations, we take a societal viewpoint, where the state of the system at each age is the population-wide probability density function of the body mass index. Compared to the biennial version of the task force’s recommendation, the screening thresholds derived from the dynamic program achieve a relative reduction in disease prevalence of 3% at the same screening (and treatment) cost, or – due to the flatness of the disease vs. screening tradeoff curve – achieves the same disease prevalence at a 28% relative reduction in cost. Compared to the task force’s policy, which uses the 95th percentile of body mass index (from cross-sectional growth charts tabulated by the Centers for Disease Control and Prevention) as the screening threshold for each age, the dynamic programming policy treats mostly 16 year olds (including many who are not obese) and very few males under 14 years old. While our results suggest that adult hypertension and diabetes are minimized by focusing childhood obesity screening and treatment on older adolescents, the shortcomings in the available data and the narrowness of the medical outcomes considered prevent us from making a recommendation about childhood obesity screening policies. PMID:23956465

Effects of dielectric inhomogeneity on electrostatic twist rigidity of a helical biomolecule in Debye-Hückel regime

NASA Astrophysics Data System (ADS)

Rezaie-Dereshgi, Amir; Mohammad-Rafiee, Farshid

2018-04-01

The electrostatic interactions play a crucial role in biological systems. Here we consider an impermeable dielectric molecule in the solvent with a different dielectric constant. The electrostatic free energy in the problem is studied in the Debye-Hückel regime using the analytical Green function that is calculated in the paper. Using this electrostatic free energy, we study the electrostatic contribution to the twist rigidity of a double stranded helical molecule such as a DNA and an actin filament. The dependence of the electrostatic twist rigidity of the molecule to the dielectric inhomogeneity, structural parameters, and the salt concentration is studied. It is shown that, depending on the parameters, the electrostatic twist rigidity could be positive or negative.

Experimental confirmation of stable, small-debye-length, pure-electron-plasma equilibria in a stellarator.

PubMed

Kremer, J P; Pedersen, T Sunn; Lefrancois, R G; Marksteiner, Q

2006-09-01

The creation of the first small-Debye length, low temperature pure electron plasmas in a stellarator is reported. A confinement time of 20 ms has been measured. The long confinement time implies the existence of macroscopically stable equilibria and that the single particle orbits are well confined despite the lack of quasisymmetry in the device, the Columbia non-neutral torus. This confirms the beneficial confinement effects of strong electric fields and the resulting rapid E x B rotation of the electrons. The particle confinement time is presently limited by the presence of bulk insulating materials in the plasma, rather than any intrinsic plasma transport processes. A nearly flat temperature profile is seen in the inner part of the plasma.

Prediction study of structural, elastic and electronic properties of FeMP (M = Ti, Zr, Hf) compounds

NASA Astrophysics Data System (ADS)

Tanto, A.; Chihi, T.; Ghebouli, M. A.; Reffas, M.; Fatmi, M.; Ghebouli, B.

2018-06-01

First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy indexes, Pugh's criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal.

Ab initio study of the electron-phonon coupling at the Cr(001) surface

NASA Astrophysics Data System (ADS)

Peters, L.; Rudenko, A. N.; Katsnelson, M. I.

2018-04-01

It is experimentally well established that the Cr(001) surface exhibits a sharp resonance around the Fermi level. However, there is no consensus about its physical origin. It is proposed to be either due to a single particle dz2 surface state renormalized by electron-phonon coupling or the orbital Kondo effect involving the degenerate dx z/ dy z states. In this paper we examine the electron-phonon coupling of the Cr(001) surface by means of ab-initio calculations in the form of density functional perturbation theory. More precisely, the electron-phonon mass-enhancement factor of the surface layer is investigated for the 3d states. For the majority and minority spin dz2 surface states we find values of 0.19 and 0.16. We show that these calculated electron-phonon mass-enhancement factors are not in agreement with the experimental data even if we use realistic values for the temperature range and surface Debye frequency for the fit of the experimental data. More precisely, then experimentally an electron-phonon mass-enhancement factor of 0.70 ±0.10 is obtained, which is not in agreement with our calculated values of 0.19 and 0.16. Our findings suggest that the experimentally observed resonance at the Cr(001) surface is not due to electron-phonon effects but due to electron-electron correlation effects.

Supplement to MTI study on selective passenger screening in the mass transit rail environment.

DOT National Transportation Integrated Search

2010-01-01

This supplement updates and adds to MTIs 2007 report on Selective Screening of Rail Passengers (Jenkins and Butterworth MTI 06-07: Selective Screening of Rail Passengers). The report reviews current screening programs implemented (or planned) by n...

Sedentary Screen Time and Left Ventricular Structure and Function: the CARDIA Study

PubMed Central

Gibbs, Bethany Barone; Reis, Jared P.; Schelbert, Erik B.; Craft, Lynette L.; Sidney, Steve; Lima, Joao; Lewis, Cora E.

2013-01-01

Sedentary screen time (watching TV or using a computer) predicts cardiovascular outcomes independently from moderate and vigorous physical activity and could impact left ventricular structure and function through the adverse consequences of sedentary behavior. Purpose To determine whether sedentary screen time is associated with measures of left ventricular structure and function. Methods The Coronary Artery Risk Development in Young Adults (CARDIA) Study measured screen time by questionnaire and left ventricular structure and function by echocardiography in 2,854 black and white participants, aged 43–55 years, in 2010–2011. Generalized linear models evaluated cross-sectional trends for echocardiography measures across higher categories of screen time and adjusting for demographics, smoking, alcohol, and physical activity. Further models adjusted for potential intermediate factors (blood pressure, antihypertensive medication use, diabetes, and body mass index (BMI). Results The relationship between screen time and left ventricular mass(LVM) differed in blacks vs. whites. Among whites, higher screen time was associated with larger LVM (P<0.001), after adjustment for height, demographics, and lifestyle variables. Associations between screen time and LVM persisted when adjusting for blood pressure, antihypertensive medication use, and diabetes (P=0.008) but not with additional adjustment for BMI (P=0.503). Similar relationships were observed for screen time with LVM indexed to height2.7, relative wall thickness, and mass-to-volume ratio. Screen time was not associated with left ventricular structure among blacks or left ventricular function in either race group. Conclusions Sedentary screen time is associated with greater LVM in white adults and this relationship was largely explained by higher overall adiposity. The lack of association in blacks supports a potential qualitative difference in the cardiovascular consequences of sedentary screen-based behavior. PMID:23863618

Plasma constraints on the cosmological abundance of magnetic monopoles and the origin of cosmic magnetic fields

NASA Astrophysics Data System (ADS)

Medvedev, Mikhail V.; Loeb, Abraham

2017-06-01

Existing theoretical and observational constraints on the abundance of magnetic monopoles are limited. Here we demonstrate that an ensemble of monopoles forms a plasma whose properties are well determined and whose collective effects place new tight constraints on the cosmological abundance of monopoles. In particular, the existence of micro-Gauss magnetic fields in galaxy clusters and radio relics implies that the scales of these structures are below the Debye screening length, thus setting an upper limit on the cosmological density parameter of monopoles, ΩM lesssim 3 × 10-4, which precludes them from being the dark matter. Future detection of Gpc-scale coherent magnetic fields could improve this limit by a few orders of magnitude. In addition, we predict the existence of magnetic Langmuir waves and turbulence which may appear on the sky as ``zebra patterns'' of an alternating magnetic field with k·B ≠ 0. We also show that magnetic monopole Langmuir turbulence excited near the accretion shock of galaxy clusters may be an efficient mechanism for generating the observed intracluster magnetic fields.

Simulating the thermodynamics of charging in weak polyelectrolytes: the Debye-Hückel limit

NASA Astrophysics Data System (ADS)

Rathee, Vikramjit S.; Sikora, Benjamin J.; Sidky, Hythem; Whitmer, Jonathan K.

2018-01-01

The coil-globule transition in weak (annealed) polyelectrolytes involves a subtle balance of pH, charge strength, and solvation forces. In this work, we utilize a coarse-grained hybrid grand-canonical Monte Carlo and molecular dynamics approach to explore the swelling behavior of weak linear and star polyelectrolytes under different ionic screening conditions and pH. Importantly, we are able to quantify topology-dependent effects in charging which arise at the core of star polymers. Our results are suggestive of suppression of charging in star weak polyelectrolytes in comparison to linear weak polyelectrolytes. Furthermore, we characterize the coil-globule transition in linear and star weak polyelectrolyte through expanded ensemble density-of-states simulations which suggest a change from a first order to second order phase transition moving from linear to star polyelectrolytes. Lastly, we characterize the inhomogeneous charging across the weak star polyelectrolyte through observed shifts in {{Δ }}{{{pK}}}{{o}}, and compare with experimental work. We discuss these results in relation to surfaces functionalized by weak polyelectrolyte brushes and weak polyelectrolyte-based drug delivery applications.

Design, synthesis and in vitro evaluation of 18β-glycyrrhetinic acid derivatives for anticancer activity against human breast cancer cell line MCF-7.

PubMed

Yadav, Dharmendra Kumar; Kalani, Komal; Singh, Abhishek K; Khan, Feroz; Srivastava, Santosh K; Pant, Aditya B

2014-01-01

In the present work, QSAR model was derived by multiple linear regression method for the prediction of anticancer activity of 18β-glycyrrhetinic acid derivatives against the human breast cancer cell line MCF-7. The QSAR model for anti-proliferative activity against MCF-7 showed high correlation (r(2)=0.90 and rCV(2)=0.83) and indicated that chemical descriptors namely, dipole moment (debye), steric energy (kcal/mole), heat of formation (kcal/mole), ionization potential (eV), LogP, LUMO energy (eV) and shape index (basic kappa, order 3) correlate well with activity. The QSAR virtually predicted that active derivatives were first semi-synthesized and characterized on the basis of their (1)H and (13)C NMR spectroscopic data and then were in-vitro tested against MCF-7 cancer cell line. In particular, octylamide derivative of glycyrrhetinic acid GA-12 has marked cytotoxic activity against MCF-7 similar to that of standard anticancer drug paclitaxel. The biological assays of active derivative selected by virtual screening showed significant experimental activity.

Specific detection of biomolecules in physiological solutions using graphene transistor biosensors

PubMed Central

Gao, Ning; Gao, Teng; Yang, Xiao; Dai, Xiaochuan; Zhou, Wei; Zhang, Anqi; Lieber, Charles M.

2016-01-01

Nanomaterial-based field-effect transistor (FET) sensors are capable of label-free real-time chemical and biological detection with high sensitivity and spatial resolution, although direct measurements in high–ionic-strength physiological solutions remain challenging due to the Debye screening effect. Recently, we demonstrated a general strategy to overcome this challenge by incorporating a biomolecule-permeable polymer layer on the surface of silicon nanowire FET sensors. The permeable polymer layer can increase the effective screening length immediately adjacent to the device surface and thereby enable real-time detection of biomolecules in high–ionic-strength solutions. Here, we describe studies demonstrating both the generality of this concept and application to specific protein detection using graphene FET sensors. Concentration-dependent measurements made with polyethylene glycol (PEG)-modified graphene devices exhibited real-time reversible detection of prostate specific antigen (PSA) from 1 to 1,000 nM in 100 mM phosphate buffer. In addition, comodification of graphene devices with PEG and DNA aptamers yielded specific irreversible binding and detection of PSA in pH 7.4 1x PBS solutions, whereas control experiments with proteins that do not bind to the aptamer showed smaller reversible signals. In addition, the active aptamer receptor of the modified graphene devices could be regenerated to yield multiuse selective PSA sensing under physiological conditions. The current work presents an important concept toward the application of nanomaterial-based FET sensors for biochemical sensing in physiological environments and thus could lead to powerful tools for basic research and healthcare. PMID:27930344

General strategy for biodetection in high ionic strength solutions using transistor-based nanoelectronic sensors.

PubMed

Gao, Ning; Zhou, Wei; Jiang, Xiaocheng; Hong, Guosong; Fu, Tian-Ming; Lieber, Charles M

2015-03-11

Transistor-based nanoelectronic sensors are capable of label-free real-time chemical and biological detection with high sensitivity and spatial resolution, although the short Debye screening length in high ionic strength solutions has made difficult applications relevant to physiological conditions. Here, we describe a new and general strategy to overcome this challenge for field-effect transistor (FET) sensors that involves incorporating a porous and biomolecule permeable polymer layer on the FET sensor. This polymer layer increases the effective screening length in the region immediately adjacent to the device surface and thereby enables detection of biomolecules in high ionic strength solutions in real-time. Studies of silicon nanowire field-effect transistors with additional polyethylene glycol (PEG) modification show that prostate specific antigen (PSA) can be readily detected in solutions with phosphate buffer (PB) concentrations as high as 150 mM, while similar devices without PEG modification only exhibit detectable signals for concentrations ≤10 mM. Concentration-dependent measurements exhibited real-time detection of PSA with a sensitivity of at least 10 nM in 100 mM PB with linear response up to the highest (1000 nM) PSA concentrations tested. The current work represents an important step toward general application of transistor-based nanoelectronic detectors for biochemical sensing in physiological environments and is expected to open up exciting opportunities for in vitro and in vivo biological sensing relevant to basic biology research through medicine.

Specific detection of biomolecules in physiological solutions using graphene transistor biosensors.

PubMed

Gao, Ning; Gao, Teng; Yang, Xiao; Dai, Xiaochuan; Zhou, Wei; Zhang, Anqi; Lieber, Charles M

2016-12-20

Nanomaterial-based field-effect transistor (FET) sensors are capable of label-free real-time chemical and biological detection with high sensitivity and spatial resolution, although direct measurements in high-ionic-strength physiological solutions remain challenging due to the Debye screening effect. Recently, we demonstrated a general strategy to overcome this challenge by incorporating a biomolecule-permeable polymer layer on the surface of silicon nanowire FET sensors. The permeable polymer layer can increase the effective screening length immediately adjacent to the device surface and thereby enable real-time detection of biomolecules in high-ionic-strength solutions. Here, we describe studies demonstrating both the generality of this concept and application to specific protein detection using graphene FET sensors. Concentration-dependent measurements made with polyethylene glycol (PEG)-modified graphene devices exhibited real-time reversible detection of prostate specific antigen (PSA) from 1 to 1,000 nM in 100 mM phosphate buffer. In addition, comodification of graphene devices with PEG and DNA aptamers yielded specific irreversible binding and detection of PSA in pH 7.4 1x PBS solutions, whereas control experiments with proteins that do not bind to the aptamer showed smaller reversible signals. In addition, the active aptamer receptor of the modified graphene devices could be regenerated to yield multiuse selective PSA sensing under physiological conditions. The current work presents an important concept toward the application of nanomaterial-based FET sensors for biochemical sensing in physiological environments and thus could lead to powerful tools for basic research and healthcare.

Mass spectrometric screening of ligands with lower off-rate from a clicked-based pooled library.

PubMed

Arai, Satoshi; Hirosawa, Shota; Oguchi, Yusuke; Suzuki, Madoka; Murata, Atsushi; Ishiwata, Shin'ichi; Takeoka, Shinji

2012-08-13

This paper describes a convenient screening method using ion trap electrospray ionization mass spectrometry to classify ligands to a target molecule in terms of kinetic parameters. We demonstrate this method in the screening of ligands to a hexahistidine tag from a pooled library synthesized by click chemistry. The ion trap mass spectrometry analysis revealed that higher stabilities of ligand-target complexes in the gas phase were related to lower dissociation rate constants, i.e., off-rates in solution. Finally, we prepared a fluorescent probe utilizing the ligand with lowest off-rate and succeeded in performing single molecule observations of hexahistidine-tagged myosin V walking on actin filaments.

Multifactorial Analysis of Mortality in Screening Detected Lung Cancer.

PubMed

Digumarthy, Subba R; De Man, Ruben; Canellas, Rodrigo; Otrakji, Alexi; Wang, Ge; Kalra, Mannudeep K

2018-01-01

We hypothesized that severity of coronary artery calcification (CAC), emphysema, muscle mass, and fat attenuation can help predict mortality in patients with lung cancer participating in the National Lung Screening Trial (NLST). Following regulatory approval from the Cancer Data Access System (CDAS), all patients diagnosed with lung cancer at the time of the screening study were identified. These subjects were classified into two groups: survivors and nonsurvivors at the conclusion of the NLST trial. These groups were matched based on their age, gender, body mass index (BMI), smoking history, lung cancer stage, and survival time. CAC, emphysema, muscle mass, and subcutaneous fat attenuation were quantified on baseline low-dose chest CT (LDCT) for all patients in both groups. Nonsurvivor group had significantly greater CAC, decreased muscle mass, and higher fat attenuation compared to the survivor group ( p < 0.01). No significant difference in severity of emphysema was noted between the two groups ( p > 0.1). We thus conclude that it is possible to create a quantitative prediction model for lung cancer mortality for subjects with lung cancer detected on screening low-dose CT (LDCT).

Radiologic findings of screen-detected cancers in an organized population-based screening mammography program in Turkey

PubMed Central

Kayhan, Arda; Arıbal, Erkin; Şahin, Cennet; Taşçı, Ömür Can; Gürdal, Sibel Özkan; Öztürk, Enis; Hatipoğlu, Hayat Halide; Özaydın, Nilüfer; Cabioğlu, Neslihan; Özçınar, Beyza; Özmen, Vahit

2016-01-01

PURPOSE Bahçeşehir Breast Cancer Screening Program is a population based organized screening program in Turkey, where asymptomatic women aged 40–69 years are screened biannually. In this prospective study, we aimed to determine the mammographic findings of screen-detected cancers and discuss the efficacy of breast cancer screening in a developing country. METHODS A total of 6912 women were screened in three rounds. The radiologic findings were grouped as mass, focal asymmetry, calcification, and architectural distortion. Masses were classified according to shape, border, and density. Calcifications were grouped according to morphology and distribution. Cancers were grouped according to the clinical stage. RESULTS Seventy cancers were detected with an incidence of 4.8/1000. Two cancers were detected in other centers and three were not visualized mammographically. Mammographic presentations of the remaining 65 cancers were mass (47.7%, n=31), calcification (30.8%, n=20), focal asymmetry (16.9%, n=11), architectural distortion (3.1%, n=2), and skin thickening (1.5%, n=1). The numbers of stage 0, 1, 2, 3, and 4 cancers were 13 (20.0%), 34 (52.3%), 14 (21.5%), 3 (4.6%), and 1 (1.5%), respectively. The numbers of interval and missed cancers were 5 (7.4%) and 7 (10.3%), respectively. CONCLUSION A high incidence of early breast cancer has been detected. The incidence of missed and interval cancers did not show major differences from western screening trials. We believe that this study will pioneer implementation of efficient population-based mammographic screenings in developing countries. PMID:27705880

Development of a Clinical Forecasting Model to Predict Comorbid Depression Among Diabetes Patients and an Application in Depression Screening Policy Making.

PubMed

Jin, Haomiao; Wu, Shinyi; Di Capua, Paul

2015-09-03

Depression is a common but often undiagnosed comorbid condition of people with diabetes. Mass screening can detect undiagnosed depression but may require significant resources and time. The objectives of this study were 1) to develop a clinical forecasting model that predicts comorbid depression among patients with diabetes and 2) to evaluate a model-based screening policy that saves resources and time by screening only patients considered as depressed by the clinical forecasting model. We trained and validated 4 machine learning models by using data from 2 safety-net clinical trials; we chose the one with the best overall predictive ability as the ultimate model. We compared model-based policy with alternative policies, including mass screening and partial screening, on the basis of depression history or diabetes severity. Logistic regression had the best overall predictive ability of the 4 models evaluated and was chosen as the ultimate forecasting model. Compared with mass screening, the model-based policy can save approximately 50% to 60% of provider resources and time but will miss identifying about 30% of patients with depression. Partial-screening policy based on depression history alone found only a low rate of depression. Two other heuristic-based partial screening policies identified depression at rates similar to those of the model-based policy but cost more in resources and time. The depression prediction model developed in this study has compelling predictive ability. By adopting the model-based depression screening policy, health care providers can use their resources and time better and increase their efficiency in managing their patients with depression.

Anomalous properties of the acoustic excitations in glasses on the mesoscopic length scale.

PubMed

Monaco, Giulio; Mossa, Stefano

2009-10-06

The low-temperature thermal properties of dielectric crystals are governed by acoustic excitations with large wavelengths that are well described by plane waves. This is the Debye model, which rests on the assumption that the medium is an elastic continuum, holds true for acoustic wavelengths large on the microscopic scale fixed by the interatomic spacing, and gradually breaks down on approaching it. Glasses are characterized as well by universal low-temperature thermal properties that are, however, anomalous with respect to those of the corresponding crystalline phases. Related universal anomalies also appear in the low-frequency vibrational density of states and, despite a longstanding debate, remain poorly understood. By using molecular dynamics simulations of a model monatomic glass of extremely large size, we show that in glasses the structural disorder undermines the Debye model in a subtle way: The elastic continuum approximation for the acoustic excitations breaks down abruptly on the mesoscopic, medium-range-order length scale of approximately 10 interatomic spacings, where it still works well for the corresponding crystalline systems. On this scale, the sound velocity shows a marked reduction with respect to the macroscopic value. This reduction turns out to be closely related to the universal excess over the Debye model prediction found in glasses at frequencies of approximately 1 THz in the vibrational density of states or at temperatures of approximately 10 K in the specific heat.

First-Principles Calculations on the Origin of Mechanical Properties and Electronic Structures of 5d Transition Metal Monocarbides MC (M = Hf, Ta, W, Re, Os, Ir, and Pt)

NASA Astrophysics Data System (ADS)

Fukuichi, Masayuki; Momida, Hiroyoshi; Geshi, Masaaki; Michiuchi, Masato; Sogabe, Koichi; Oguchi, Tamio

2018-04-01

Much is not systematically known about the origin of mechanical properties among 5d transition metal carbides including tungsten carbide. In order to understand the microscopic origin of hardness, the mechanical properties and electronic structures of 5d transition metal monocarbides MC (M = Hf, Ta, W, Re, Os, Ir, and Pt) in five different structures (NaCl, WC, ZnS, CsCl, and NiAs type) are analyzed using first-principles calculations based on the density functional theory. Our results would indicate that WC-type WC and NiAs-type ReC have the highest and second highest hardness among all of the MC, respectively, in terms of the Debye temperature. By examining the Debye temperature in the series, it is found that MC in the range of less and more than half filled 5d shells are brittle and ductile, respectively. Our results would indicate that filling in the bonding and anti-bonding states contributes to brittleness and ductility. The Debye temperature could be a key to understanding hardness in terms of bulk and shear moduli. In addition, we evaluate some other structural properties such as equilibrium volume, formation enthalpy, and elastic constant to investigate structural stability. Based on the theoretical findings, the microscopic mechanisms of hardness and brittleness in the transition metal carbides are discussed.

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

NASA Astrophysics Data System (ADS)

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

2011-01-01

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

Breast cancer biology varies by method of detection and may contribute to overdiagnosis.

PubMed

Hayse, Brandon; Hooley, Regina J; Killelea, Brigid K; Horowitz, Nina R; Chagpar, Anees B; Lannin, Donald R

2016-08-01

Recently, it has been suggested that screening mammography may result in some degree of overdiagnosis (ie, detection of breast cancers that would never become clinically important within the lifespan of the patient). The extent and biology of these overdiagnosed cancers, however, is not well understood, and the effect of newer screening modalities on overdiagnosis is unknown. We performed a retrospective review of a prospectively collected database of breast cancers diagnosed at the Yale Breast Center from 2004-2014. The mode of initial presentation was categorized into 5 groups: screening mammogram, screening magnetic resonance imaging, screening ultrasonography, self-detected masses, and physician-detected masses. Compared with cancers presenting with masses, cancers detected by image-based screening were more likely to present with ductal carcinoma-in-situ or T1 cancers (P < .001). In addition to a simple stage shift, however, cancers detected by image-based screening were also more likely to be luminal and low-grade cancers; symptomatic cancers were more likely high-grade and triple-negative (P < .001, respectively). On a multivariate analysis, adjusting for age, race, and tumor size, cancers detected by mammogram, US, and magnetic resonance imaging had greater odds of being luminal (odds ratio 1.8, 95% confidence interval, 1.5-2.3; odds ratio 2.2, 95% confidence interval, 1.1-4.7; and odds ratio 4.7, 95% confidence interval, 2.1-10.6, respectively), and low-grade (odds ratio 2.2, 95% confidence interval, 1.6-2.9; odds ratio 4.9, 95% confidence interval, 2.7-8.9; and odds ratio 4.6, 95% confidence interval, 2.6-8.1, respectively) compared with cancers presenting with self-detected masses. Screening detects cancers with more indolent biology, potentially contributing to the observed rate of overdiagnosis. With magnetic resonance imaging and US being used more commonly for screening, the rate of overdiagnosis may increase further. Copyright © 2016. Published by Elsevier Inc.

Regional differences as barriers to body mass index screening described by Ohio school nurses.

PubMed

Stalter, Ann M; Chaudry, Rosemary V; Polivka, Barbara J

2011-08-01

Body mass index (BMI) screening is advocated by the National Association of School Nurses (NASN). Research identifying barriers to BMI screening in public elementary school settings has been sparse. The purpose of the study was to identify barriers and facilitating factors of BMI screening practices among Ohio school nurses working in suburban, rural, and urban public elementary schools. This descriptive study used focus groups with 25 school nurses in 3 geographic regions of Ohio. An adapted Healthy People 2010 model guided the development of semistructured focus group questions. Nine regional themes related to BMI screening emerged specific to suburban, rural, and/or urban school nurses' experiences with BMI screening practice, policy, school physical environment, school social environment, school risk/protection, and access to quality health care. Key facilitating factors to BMI screening varied by region. Key barriers to BMI screening were a lack of privacy, time, policy, and workload of school nurses. Regionally specific facilitating factors to BMI screening in schools provide opportunities for schools to accentuate the positive and to promote school health. © 2011, American School Health Association.

Non-Target Screening of Veterinary Drugs Using Tandem Mass Spectrometry on SmartMass

NASA Astrophysics Data System (ADS)

Xia, Bing; Liu, Xin; Gu, Yu-Cheng; Zhang, Zhao-Hui; Wang, Hai-Yan; Ding, Li-Sheng; Zhou, Yan

2013-05-01

Non-target screening of veterinary drugs using tandem mass spectrometric data was performed on the SmartMass platform. This newly developed software uses the characteristic fragmentation patterns (CFP) to identify chemicals, especially those containing particular substructures. A mixture of 17 sulfonamides was separated by ultra performance liquid chromatography (UPLC), and SmartMass was used to process the tandem mass spectrometry (MS/MS) data acquired on an Orbitrap mass spectrometer. The data were automatically extracted, and each sulfonamide was recognized and analyzed with a prebuilt analysis rule. By using this software, over 98 % of the false candidate structures were eliminated, and all the correct structures were found within the top 10 of the ranking lists. Furthermore, SmartMass could also be used to identify slightly modified contraband drugs and metabolites with simple prebuilt rules. [Figure not available: see fulltext.

Sedentary Behavior Is Independently Related to Fat Mass among Children and Adolescents in South China.

PubMed

Xue, Hongmei; Tian, Guo; Duan, Ruonan; Quan, Liming; Zhao, Li; Yang, Min; Libuda, Lars; Muckelbauer, Rebecca; Cheng, Guo

2016-10-25

We aim to explore the independent associations of sedentary behaviors (SB) with body mass distribution among Chinese children. Data on the screen-based sedentary time (television viewing and computer use) and doing homework, physical activities and dietary intake of 1586 Chinese children (50.3% girls) aged 7-15 years were obtained through validated questionnaires. Skin-fold thickness, body height, and weight were measured to calculate percent body fat (%BF), fat mass index (FMI), and fat-free mass index (FFMI). Parental characteristics were collected by questionnaires. Among girls, time of SB (screen time or doing homework) was positively related to %BF, FMI, and FFMI ( p < 0.03) after adjusting for maternal overweight, the average annual income of family, moderate-to-vigorous physical activity energy expenditure, and energy intake: Girls in the highest tertile of screen time/homework had 16.7%/23.3% higher relative FMI and 2.9%/2.9% higher relative FFMI than girls in the lowest tertile. Among boys, screen time was positively associated with FFMI ( p < 0.003), but not related to %BF and FMI ( p > 0.09), while time of doing homework was positively related to %BF and FMI ( p = 0.03). Sedentary behaviors might be positively and independently related to fat mass among Chinese children, and were more pronounced in girls.

Current use of high-resolution mass spectrometry in drug screening relevant to clinical and forensic toxicology and doping control.

PubMed

Ojanperä, Ilkka; Kolmonen, Marjo; Pelander, Anna

2012-05-01

Clinical and forensic toxicology and doping control deal with hundreds or thousands of drugs that may cause poisoning or are abused, are illicit, or are prohibited in sports. Rapid and reliable screening for all these compounds of different chemical and pharmaceutical nature, preferably in a single analytical method, is a substantial effort for analytical toxicologists. Combined chromatography-mass spectrometry techniques with standardised reference libraries have been most commonly used for the purpose. In the last ten years, the focus has shifted from gas chromatography-mass spectrometry to liquid chromatography-mass spectrometry, because of progress in instrument technology and partly because of the polarity and low volatility of many new relevant substances. High-resolution mass spectrometry (HRMS), which enables accurate mass measurement at high resolving power, has recently evolved to the stage that is rapidly causing a shift from unit-resolution, quadrupole-dominated instrumentation. The main HRMS techniques today are time-of-flight mass spectrometry and Orbitrap Fourier-transform mass spectrometry. Both techniques enable a range of different drug-screening strategies that essentially rely on measuring a compound's or a fragment's mass with sufficiently high accuracy that its elemental composition can be determined directly. Accurate mass and isotopic pattern acts as a filter for confirming the identity of a compound or even identification of an unknown. High mass resolution is essential for improving confidence in accurate mass results in the analysis of complex biological samples. This review discusses recent applications of HRMS in analytical toxicology.

Dressing effects on the occurrence scattering time retardation and advance in a dusty plasma

NASA Astrophysics Data System (ADS)

Lee, Myoung-Jae; Jung, Young-Dae; Hanyang Plasma Team

2017-10-01

The dressing effects on the occurrence scattering time for the dust-dust interaction are investigated in a complex plasma. The first-order eikonal analysis is applied to obtain the scattering amplitude and the occurrence scattering time for the dust-dust interaction. The result shows that dressing effect enhances the retardation phenomena of the occurrence scattering time in the forward scattering domain. It is shown that the oscillatory behavior of the scaled occurrence scattering time is getting more significant with an increase of the Debye length. It is also found that the retardation domain of the occurrence scattering time increases with a decrease of the Debye length. The variation of the occurrence scattering time retardation and advance due to the dressing effect is also discussed.

Study of 57Fe Mössbauer effect in RFe 2Zn 20 ( R = Lu, Yb, Gd)

DOE PAGES

Bud’ko, Sergey L.; Kong, Tai; Ma, Xiaoming; ...

2015-08-04

In this document we report measurements of 57Fe Mössbauer spectra for RFe 2Zn 20 ( R = Lu, Yb, Gd) from ~ 4.5 K to room temperature. The obtained isomer shift values are very similar for all three compounds, their temperature dependence was analyzed within the Debye model and resulted in an estimate of the Debye temperatures of 450-500 K. The values of quadrupole splitting at room temperature change with the cubic lattice constant a in a linear fashion. For GdFe 2Zn 20, ferromagnetic order is seen as an appearance of a sextet in the spectra. The 57Fe site hyperfinemore » field for T → 0 was evaluated to be ~ 2.4 T.« less

Interactive visualization of multi-data-set Rietveld analyses using Cinema:Debye-Scherrer.

PubMed

Vogel, Sven C; Biwer, Chris M; Rogers, David H; Ahrens, James P; Hackenberg, Robert E; Onken, Drew; Zhang, Jianzhong

2018-06-01

A tool named Cinema:Debye-Scherrer to visualize the results of a series of Rietveld analyses is presented. The multi-axis visualization of the high-dimensional data sets resulting from powder diffraction analyses allows identification of analysis problems, prediction of suitable starting values, identification of gaps in the experimental parameter space and acceleration of scientific insight from the experimental data. The tool is demonstrated with analysis results from 59 U-Nb alloy samples with different compositions, annealing times and annealing temperatures as well as with a high-temperature study of the crystal structure of CsPbBr 3 . A script to extract parameters from a series of Rietveld analyses employing the widely used GSAS Rietveld software is also described. Both software tools are available for download.

Interactive visualization of multi-data-set Rietveld analyses using Cinema:Debye-Scherrer

PubMed Central

Biwer, Chris M.; Rogers, David H.; Ahrens, James P.; Hackenberg, Robert E.; Onken, Drew; Zhang, Jianzhong

2018-01-01

A tool named Cinema:Debye-Scherrer to visualize the results of a series of Rietveld analyses is presented. The multi-axis visualization of the high-dimensional data sets resulting from powder diffraction analyses allows identification of analysis problems, prediction of suitable starting values, identification of gaps in the experimental parameter space and acceleration of scientific insight from the experimental data. The tool is demonstrated with analysis results from 59 U–Nb alloy samples with different compositions, annealing times and annealing temperatures as well as with a high-temperature study of the crystal structure of CsPbBr3. A script to extract parameters from a series of Rietveld analyses employing the widely used GSAS Rietveld software is also described. Both software tools are available for download. PMID:29896062

Lattice distortions in complex oxides and their relation to the thermal properties

NASA Astrophysics Data System (ADS)

Srivastava, Archana; Gaur, N. K.

2018-05-01

We have investigated the various lattice distortions in complex oxides Ca1-xLaxMnO3 and its effect on elastic and thermal properties of these perovskite manganites, especially Debye temperature of these complex oxides. The revealed data on Bulk modulus and Debye temperature studied as a function of lattice distortions using a novel atomistic approach of Atom in Molecules(AIM) theory and Modified Rigid Ion Model (MRIM) are in closer agreement with the available experimental data for some concentrations (x) of Ca1-xLaxMnO3. We demonstrate that the distortions introduced due to electron concentration, size mismatch and JT effects are the dominant factor, whereas charge mismatch and buckling of Mn-O-Mn angle influence the thermal properties to a lesser degree in the ferromagnetic state.

Long Range Debye-Hückel Correction for Computation of Grid-based Electrostatic Forces Between Biomacromolecules

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

Mereghetti, Paolo; Martinez, M.; Wade, Rebecca C.

Brownian dynamics (BD) simulations can be used to study very large molecular systems, such as models of the intracellular environment, using atomic-detail structures. Such simulations require strategies to contain the computational costs, especially for the computation of interaction forces and energies. A common approach is to compute interaction forces between macromolecules by precomputing their interaction potentials on three-dimensional discretized grids. For long-range interactions, such as electrostatics, grid-based methods are subject to finite size errors. We describe here the implementation of a Debye-Hückel correction to the grid-based electrostatic potential used in the SDA BD simulation software that was applied to simulatemore » solutions of bovine serum albumin and of hen egg white lysozyme.« less

Finite-element time-domain algorithms for modeling linear Debye and Lorentz dielectric dispersions at low frequencies.

PubMed

Stoykov, Nikolay S; Kuiken, Todd A; Lowery, Madeleine M; Taflove, Allen

2003-09-01

We present what we believe to be the first algorithms that use a simple scalar-potential formulation to model linear Debye and Lorentz dielectric dispersions at low frequencies in the context of finite-element time-domain (FETD) numerical solutions of electric potential. The new algorithms, which permit treatment of multiple-pole dielectric relaxations, are based on the auxiliary differential equation method and are unconditionally stable. We validate the algorithms by comparison with the results of a previously reported method based on the Fourier transform. The new algorithms should be useful in calculating the transient response of biological materials subject to impulsive excitation. Potential applications include FETD modeling of electromyography, functional electrical stimulation, defibrillation, and effects of lightning and impulsive electric shock.

Parents of Elementary School Students Weigh in on Height, Weight, and Body Mass Index Screening at School

ERIC Educational Resources Information Center

Kubik, Martha Y.; Fulkerson, Jayne A.; Story, Mary; Rieland, Gayle

2006-01-01

School-based body mass index (BMI) screening and parent notification programs have been recommended as a childhood overweight prevention strategy. However, there are little empirical data available to guide decision making about the acceptability and safety of programs. A pilot study was conducted using a quasiexperimental research design. In fall…

Making the Case for Objective Performance Metrics in Newborn Screening by Tandem Mass Spectrometry

ERIC Educational Resources Information Center

Rinaldo, Piero; Zafari, Saba; Tortorelli, Silvia; Matern, Dietrich

2006-01-01

The expansion of newborn screening programs to include multiplex testing by tandem mass spectrometry requires understanding and close monitoring of performance metrics. This is not done consistently because of lack of defined targets, and interlaboratory comparison is almost nonexistent. Between July 2004 and April 2006 (N = 176,185 cases), the…

Mass Screening: An Aid to Competency Based Program Development.

ERIC Educational Resources Information Center

Siehl, Peterann M.; Studer, Jeannine

Adolescent suicide is the second leading cause of death in the adolescent population and is on the rise. This study used a mass screening concept as a pre-test identifier of at risk clients for suicide ideation and depressions; development of a competency-based prevention group treatment program, and the post-testing of the identified at-risk…

Real-time detection method and system for identifying individual aerosol particles

DOEpatents

Gard, Eric E [San Francisco, CA; Coffee, Keith R [Patterson, CA; Frank, Matthias [Oakland, CA; Tobias, Herbert J [Kensington, CA; Fergenson, David P [Alamo, CA; Madden, Norm [Livermore, CA; Riot, Vincent J [Berkeley, CA; Steele, Paul T [Livermore, CA; Woods, Bruce W [Livermore, CA

2007-08-21

An improved method and system of identifying individual aerosol particles in real time. Sample aerosol particles are collimated, tracked, and screened to determine which ones qualify for mass spectrometric analysis based on predetermined qualification or selection criteria. Screening techniques include one or more of determining particle size, shape, symmetry, and fluorescence. Only qualifying particles passing all screening criteria are subject to desorption/ionization and single particle mass spectrometry to produce corresponding test spectra, which is used to determine the identities of each of the qualifying aerosol particles by comparing the test spectra against predetermined spectra for known particle types. In this manner, activation cycling of a particle ablation laser of a single particle mass spectrometer is reduced.

Imaging and Screening of Cancer of the Gallbladder and Bile Ducts.

PubMed

Sandrasegaran, Kumar; Menias, Christine O

2017-11-01

Biliary cancers include gallbladder cancer (GBC) and cholangiocarcinoma (CCA). GBC may appear as a mass replacing the gallbladder, thickened gallbladder wall, or polypoid lesion in the gallbladder. Gallbladder polyps with low risk of GBC (eg, 6- to 10-mm polyps without other risk factors) are screened with sonography. In general, polyps smaller than 5 mm are ignored and those larger than 10 mm require surgical consideration. Screening for CCA is less well-established. On imaging, CCA may be divided into mass-forming, periductal infiltrating, and intraductal types. This review discusses the current state of screening and diagnosis of GBC and CCA. Copyright © 2017 Elsevier Inc. All rights reserved.

Cost-Effectiveness between Double and Single Fecal Immunochemical Test(s) in a Mass Colorectal Cancer Screening.

PubMed

Cai, Shan-Rong; Zhu, Hong-Hong; Huang, Yan-Qin; Li, Qi-Long; Ma, Xin-Yuan; Zhang, Su-Zhan; Zheng, Shu

2016-01-01

This study investigated the cost-effectiveness between double and single Fecal Immunochemical Test(s) (FIT) in a mass CRC screening. A two-stage sequential screening was conducted. FIT was used as a primary screening test and recommended twice by an interval of one week at the first screening stage. We defined the first-time FIT as FIT1 and the second-time FIT as FIT2. If either FIT1 or FIT2 was positive (+), then a colonoscopy was recommended at the second stage. Costs were recorded and analyzed. A total of 24,419 participants completed either FIT1 or FIT2. The detection rate of advanced neoplasm was 19.2% among both FIT1+ and FIT2+, especially high among men with age ≥55 (27.4%). About 15.4% CRC, 18.9% advanced neoplasm, and 29.9% adenoma missed by FIT1 were detected by FIT2 alone. Average cost was $2,935 for double FITs and $2,121 for FIT1 to detect each CRC and $901 for double FITs and $680 for FIT1 to detect each advanced neoplasm. Double FITs are overall more cost-effective, having significantly higher positive and detection rates with an acceptable higher cost, than single FIT. Double FITs should be encouraged for the first screening in a mass CRC screening, especially in economically and medically underserved populations/areas/countries.

A high-sensitivity ultra-high performance liquid chromatography/high-resolution time-of-flight mass spectrometry (UHPLC-HR-TOFMS) method for screening synthetic cannabinoids and other drugs of abuse in urine.

PubMed

Sundström, Mira; Pelander, Anna; Angerer, Verena; Hutter, Melanie; Kneisel, Stefan; Ojanperä, Ilkka

2013-10-01

The continuing emergence of designer drugs imposes high demands on the scope and sensitivity of toxicological drug screening procedures. An ultra-high performance liquid chromatography/high-resolution time-of-flight mass spectrometry (UHPLC-HR-TOFMS) method was developed for screening and simultaneous confirmation of both designer drugs and other drugs of abuse in urine samples in a single run. The method covered selected synthetic cannabinoids and cathinones, amphetamines, natural cannabinoids, opioids, cocaine and other important drugs of abuse, together with their main urinary metabolites. The database consisted of 277 compounds with molecular formula and exact monoisotopic mass; retention time was included for 192 compounds, and primary and secondary qualifier ion exact mass for 191 and 95 compounds, respectively. Following a solid-phase extraction, separation was performed by UHPLC and mass analysis by HR-TOFMS. MS, and broad-band collision-induced dissociation data were acquired at m/z range 50-700. Compound identification was based on a reverse database search with acceptance criteria for retention time, precursor ion mass accuracy, isotopic pattern and abundance of qualifier ions. Mass resolving power in spiked urine samples was on average FWHM 23,500 and mass accuracy 0.3 mDa. The mean and median cut-off concentrations determined for 75 compounds were 4.2 and 1 ng/mL, respectively. The range of cut-off concentrations for synthetic cannabinoids was 0.2-60 ng/mL and for cathinones 0.7-15 ng/mL. The method proved to combine high sensitivity and a wide scope in a manner not previously reported in drugs of abuse screening. The method's feasibility was demonstrated with 50 authentic urine samples.

Relationship between echocardiographic LV mass and ECG based left ventricular voltages in an adolescent population: related or random?

PubMed

Czosek, Richard J; Cnota, James F; Knilans, Timothy K; Pratt, Jesse; Guerrier, Karine; Anderson, Jeffrey B

2014-09-01

In attempts to detect diseases that may place adolescents at risk for sudden death, some have advocated for population-based screening. Controversy exists over electrocardiography (ECG) screening due to the lack of specificity, cost, and detrimental effects of false positive or extraneous outcomes. Analyze the relationship between precordial lead voltage on ECG and left ventricle (LV) mass by echocardiogram in adolescent athletes. Retrospective cohort analysis of a prospectively obtained population of self-identified adolescent athletes during sports screening with ECG and echocardiogram. Correlation between ECG LV voltages (R wave in V6 [RV6] and S wave in lead V1 [SV1]) was compared to echocardiogram-based measurements of left ventricular mass. Potential effects on ECG voltages by body anthropometrics, including weight, body mass index (BMI), and body surface area were analyzed, and ECG voltages indexed to BMI were compared to LV mass indices to analyze for improved correlation. A total of 659 adolescents enrolled in this study (64% male). The mean age was 15.4 years (14-18). The correlations between LV mass and RV6, SV1, and RV6 + SV1 were all less than 0.20. The false positive rate for abnormal voltages was relatively high (5.5%) but improved if abnormal voltages in both RV6 and SV1 were mandated simultaneously (0%). Indexing ECG voltages to BMI significantly improved correlation to LV mass, though false positive findings were increased (12.9%). There is poor correlation between ECG precordial voltages and echocardiographic LV mass. This relationship is modified by BMI. This finding may contribute to the poor ECG screening characteristics. ©2014 Wiley Periodicals, Inc.

Understanding Pediatricians' Views toward School-Based BMI Screening in Massachusetts: A Pilot Study

ERIC Educational Resources Information Center

Pietras, Stefanie A.; Rhodes, Erinn T.; Meyers, Alan; Goodman, Elizabeth

2012-01-01

Background: Massachusetts (MA) mandated body mass index (BMI) screening in schools in 2010. However, little is known about pediatricians' views on school-based screening or how the pediatricians' perspectives might affect the school-based screening process. We assessed MA pediatricians' knowledge, attitudes, beliefs, and practices concerning BMI…

Body Mass Index and Cancer Screening in Older American Indian and Alaska Native Men

ERIC Educational Resources Information Center

Muus, Kyle J.; Baker-Demaray, Twyla; McDonald, Leander R.; Ludtke, Richard L.; Allery, Alan J.; Bogart, T. Andy; Goldberg, Jack; Ramsey, Scott D.; Buchwald, Dedra S.

2009-01-01

Context: Regular screenings are important for reducing cancer morbidity and mortality. There are several barriers to receiving timely cancer screening, including overweight/obesity. No study has examined the relationship between overweight/obesity and cancer screening among American Indian/Alaska Natives (AI/ANs). Purpose: To describe the…

Electrostatic interactions between diffuse soft multi-layered (bio)particles: beyond Debye-Hückel approximation and Deryagin formulation.

PubMed

Duval, Jérôme F L; Merlin, Jenny; Narayana, Puranam A L

2011-01-21

We report a steady-state theory for the evaluation of electrostatic interactions between identical or dissimilar spherical soft multi-layered (bio)particles, e.g. microgels or microorganisms. These generally consist of a rigid core surrounded by concentric ion-permeable layers that may differ in thickness, soft material density, chemical composition and degree of dissociation for the ionogenic groups. The formalism allows the account of diffuse interphases where distributions of ionogenic groups from one layer to the other are position-dependent. The model is valid for any number of ion-permeable layers around the core of the interacting soft particles and covers all limiting situations in terms of nature of interacting particles, i.e. homo- and hetero-interactions between hard, soft or entirely porous colloids. The theory is based on a rigorous numerical solution of the non-linearized Poisson-Boltzmann equation including radial and angular distortions of the electric field distribution within and outside the interacting soft particles in approach. The Gibbs energy of electrostatic interaction is obtained from a general expression derived following the method by Verwey and Overbeek based on appropriate electric double layer charging mechanisms. Original analytical solutions are provided here for cases where interaction takes place between soft multi-layered particles whose size and charge density are in line with Deryagin treatment and Debye-Hückel approximation. These situations include interactions between hard and soft particles, hard plate and soft particle or soft plate and soft particle. The flexibility of the formalism is highlighted by the discussion of few situations which clearly illustrate that electrostatic interaction between multi-layered particles may be partly or predominantly governed by potential distribution within the most internal layers. A major consequence is that both amplitude and sign of Gibbs electrostatic interaction energy may dramatically change depending on the interplay between characteristic Debye length, thickness of ion-permeable layers and their respective protolytic features (e.g. location, magnitude and sign of charge density). This formalism extends a recent model by Ohshima which is strictly limited to interaction between soft mono-shell particles within Deryagin and Debye-Hückel approximations under conditions where ionizable sites are completely dissociated.

Computer-aided diagnosis workstation and database system for chest diagnosis based on multi-helical CT images

NASA Astrophysics Data System (ADS)

Satoh, Hitoshi; Niki, Noboru; Mori, Kiyoshi; Eguchi, Kenji; Kaneko, Masahiro; Kakinuma, Ryutarou; Moriyama, Noriyuki; Ohmatsu, Hironobu; Masuda, Hideo; Machida, Suguru; Sasagawa, Michizou

2006-03-01

Multi-helical CT scanner advanced remarkably at the speed at which the chest CT images were acquired for mass screening. Mass screening based on multi-helical CT images requires a considerable number of images to be read. It is this time-consuming step that makes the use of helical CT for mass screening impractical at present. To overcome this problem, we have provided diagnostic assistance methods to medical screening specialists by developing a lung cancer screening algorithm that automatically detects suspected lung cancers in helical CT images and a coronary artery calcification screening algorithm that automatically detects suspected coronary artery calcification. We also have developed electronic medical recording system and prototype internet system for the community health in two or more regions by using the Virtual Private Network router and Biometric fingerprint authentication system and Biometric face authentication system for safety of medical information. Based on these diagnostic assistance methods, we have now developed a new computer-aided workstation and database that can display suspected lesions three-dimensionally in a short time. This paper describes basic studies that have been conducted to evaluate this new system. The results of this study indicate that our computer-aided diagnosis workstation and network system can increase diagnostic speed, diagnostic accuracy and safety of medical information.

A strategy for screening and identifying mycotoxins in herbal medicine using ultra-performance liquid chromatography with tandem quadrupole time-of-flight mass spectrometry.

PubMed

Fang, Lian-xiang; Xiong, Ai-zhen; Wang, Rui; Ji, Shen; Yang, Li; Wang, Zheng-tao

2013-09-01

The objective of this study was to develop an effective strategy for screening and identifying mycotoxins in herbal medicine (HM). Here, Imperatae Rhizoma, a commonly used Chinese herb, was selected as a model HM. A crude drug contaminated with fungi was analyzed by comparing with uncontaminated ones. Ultra-performance LC coupled to tandem quadrupole TOF-MS (UPLC-Q-TOF-MS) with collision energy function was applied to analyze different samples from Imperatae Rhizoma. Then, MarkerLynx(TM) software was employed to screen the excess components in analytes, compared with control samples, and those selected markers were likely to be the metabolites of fungi. Furthermore, each of the accurate masses of the markers obtained from MarkerLynx(TM) was then searched in a mycotoxins/fungal metabolites database established in advance. The molecular formulas with relative mass error between the measured and theoretical mass within 5 ppm were chosen and then applied to MassFragment(TM) analysis for further confirmation of their structures. With the use of this approach, five mycotoxins that have never been reported in HM were identified in contaminated Imperatae Rhizoma. The results demonstrate the potential of UPLC-Q-TOF-MS coupled with the MarkerLynx(TM) software and MassFragment(TM) tool as an efficient and convenient method to screen and identify mycotoxins in herbal materials and aid in the quality control of HM. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Child's Weight Status and Parent's Response to a School-Based Body Mass Index Screening and Parent Notification Program

ERIC Educational Resources Information Center

Lee, Jiwoo; Kubik, Martha Y.

2015-01-01

This study examined the response of parents of elementary school-aged children to a school-based body mass index (BMI) screening and parent notification program conducted in one Minnesota school district in 2010-2011 and whether parent's response was moderated by child's weight status. Randomly selected parents (N = 122) of second- and…

Headspace screening of fluid obtained from the gut during colonoscopy and breath analysis by proton transfer reaction-mass spectrometry: A novel approach in the diagnosis of gastro-intestinal diseases

NASA Astrophysics Data System (ADS)

Lechner, M.; Colvin, H. P.; Ginzel, C.; Lirk, P.; Rieder, J.; Tilg, H.

2005-05-01

Background: The diagnosis of many gastro-intestinal diseases is difficult and can often be confirmed only by using invasive diagnostic means. In contrast, the headspace screening of fluid obtained from the gut during colonoscopy and the analysis of exhaled air may be a novel approach for the diagnosis of these diseases.Materials and methods: The screening was performed by using proton transfer reaction-mass spectrometry (PTR-MS) which allows rapid and sensitive measurement. Fluid samples obtained from the gut during colonoscopy were collected from 76 and breath samples from 70 subjects. Mass spectra of healthy controls were created. Afterwards these spectra were compared with those of patients suffering from inflammatory bowel diseases (IBD; Crohn's disease and ulcerative colitis; n = 10) and irritable bowel syndrome (IBS; n = 7).Results: Significant differences in the mass spectra could be observed both in the headspace of the fluid and in the exhaled air comparing patients with healthy controls.Conclusions: This study is the first describing headspace screening of fluid obtained from the gut during colonoscopy, possibly presenting a novel diagnostic tool in the differential diagnosis of gastro-intestinal diseases.

Current applications of high-resolution mass spectrometry for the analysis of new psychoactive substances: a critical review.

PubMed

Pasin, Daniel; Cawley, Adam; Bidny, Sergei; Fu, Shanlin

2017-10-01

The proliferation of new psychoactive substances (NPS) in recent years has resulted in the development of numerous analytical methods for the detection and identification of known and unknown NPS derivatives. High-resolution mass spectrometry (HRMS) has been identified as the method of choice for broad screening of NPS in a wide range of analytical contexts because of its ability to measure accurate masses using data-independent acquisition (DIA) techniques. Additionally, it has shown promise for non-targeted screening strategies that have been developed in order to detect and identify novel analogues without the need for certified reference materials (CRMs) or comprehensive mass spectral libraries. This paper reviews the applications of HRMS for the analysis of NPS in forensic drug chemistry and analytical toxicology. It provides an overview of the sample preparation procedures in addition to data acquisition, instrumental analysis, and data processing techniques. Furthermore, it gives an overview of the current state of non-targeted screening strategies with discussion on future directions and perspectives of this technique. Graphical Abstract Missing the bullseye - a graphical respresentation of non-targeted screening. Image courtesy of Christian Alonzo.

Screening of environmental contaminants in honey bee wax comb using gas chromatography-high-resolution time-of-flight mass spectrometry.

PubMed

Gómez-Ramos, M M; García-Valcárcel, A I; Tadeo, J L; Fernández-Alba, A R; Hernando, M D

2016-03-01

This study reports an analytical approach intended to be used for investigation of non-targeted environmental contaminants and to characterize the organic pollution pattern of bee wax comb samples. The method comprises a generic extraction followed by detection with gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC-TOF-MS), operated in electron impact ionization (EI) mode. The screening approach for the investigation of non-targeted contaminants consisted of initial peak detection by deconvolution and matching the first-stage mass spectra EI-MS(1) with a nominal mass spectral library. To gain further confidence in the structural characterization of the contaminants under investigation, the molecular formula of representative ions (molecular ion when present in the EI spectrum) and, for at least other two fragment ions, was provided for those with an accurate mass scoring (mass error < 5 ppm). This methodology was applied for screening environmental contaminants in 50 samples of bee wax comb. This approach has allowed the tentative identification of some GC-amenable contaminants belonging to different chemical groups, among them, phthalates and polycyclic aromatic hydrocarbons (PAHs), along with residues of veterinary treatments used in apiculture.

[Rapid screening the alkaloids of poppy shell in hot pot condiment, beef noodle soup and seasoning by direct analysis in real time-tandem mass spectrometry].

PubMed

Zhang, Baile; Gao, Lihong; Xie, Yingshuang; Zhou, Wei; Chen, Xiaofeng; Lei, Chunni; Zhang, Huan

2017-07-08

A direct analysis in real time tandem mass spectrometry (DART-MS/MS) method was established for quickly screening five illegally added alkaloids of poppy shell from the hot pot condiment, beef noodle soup and seasoning. The samples were extracted and purified by acetonitrile, and then injected under the conditions of ionization temperature of 300℃, grid electrode voltage of 150 V and sampling rate of 0.8 mm/s using DART in the positive ion mode. The determination was conducted by tandem mass spectrometry in positive ESI mode under multiple reaction monitoring (MRM) mode. The method is simple and rapid, and can meet the requirement of rapid screening and analysis of large quantities of samples.

Sedentary Behavior Is Independently Related to Fat Mass among Children and Adolescents in South China

PubMed Central

Xue, Hongmei; Tian, Guo; Duan, Ruonan; Quan, Liming; Zhao, Li; Yang, Min; Libuda, Lars; Muckelbauer, Rebecca; Cheng, Guo

2016-01-01

We aim to explore the independent associations of sedentary behaviors (SB) with body mass distribution among Chinese children. Data on the screen-based sedentary time (television viewing and computer use) and doing homework, physical activities and dietary intake of 1586 Chinese children (50.3% girls) aged 7–15 years were obtained through validated questionnaires. Skin-fold thickness, body height, and weight were measured to calculate percent body fat (%BF), fat mass index (FMI), and fat-free mass index (FFMI). Parental characteristics were collected by questionnaires. Among girls, time of SB (screen time or doing homework) was positively related to %BF, FMI, and FFMI (p < 0.03) after adjusting for maternal overweight, the average annual income of family, moderate-to-vigorous physical activity energy expenditure, and energy intake: Girls in the highest tertile of screen time/homework had 16.7%/23.3% higher relative FMI and 2.9%/2.9% higher relative FFMI than girls in the lowest tertile. Among boys, screen time was positively associated with FFMI (p < 0.003), but not related to %BF and FMI (p > 0.09), while time of doing homework was positively related to %BF and FMI (p = 0.03). Sedentary behaviors might be positively and independently related to fat mass among Chinese children, and were more pronounced in girls. PMID:27792134

Near Wake Depletion of Non-Magnetized Bodies Immersed in Mesosonic Plasma Flow

NASA Technical Reports Server (NTRS)

Wright, K. H.; Stone, N. H.; Samir, U.; Sorensen, J.; Winningham, J. D.

1997-01-01

During the recent TSS-1R mission, measurements of ion depletion in the near wake were obtained at a downstream distance of two body radii from the satellite center. The ratio of satellite radius to Debye length is approximately 150. Similar measurements were also obtained at the same downstream location in the wake of the shuttle during the Spacelab 2 mission of August 1985. In the case of the shuttle, the ratio of body radius to Debye length is greater than 1000. The wake depletion observed in the these two cases, together with data obtained from previous ionospheric satellites and from applicable laboratory experiments involving small bodies, will be compared in order to determine the influence of body size on wake filling. Extrapolation of these results to the case of the moon in the solar wind will be noted.

First principle study of structural, elastic and electronic properties of APt3 (A=Mg, Sc, Y and Zr)

NASA Astrophysics Data System (ADS)

Benamer, A.; Roumili, A.; Medkour, Y.; Charifi, Z.

2018-02-01

We report results obtained from first principle calculations on APt3 compounds with A=Mg, Sc, Y and Zr. Our results of the lattice parameter a are in good agreement with experimental data, with deviations less than 0.8%. Single crystal elastic constants are calculated, then polycrystalline elastic moduli (bulk, shear and Young moduli, Poisson ration, anisotropy factor) are presented. Based on Debye model, Debye temperature ϴD is calculated from the sound velocities Vl, Vt and Vm. Band structure results show that the studied compounds are electrical conductors, the conduction mechanism is assured by Pt-d electrons. Different hybridisation states are observed between Pt-d and A-d orbitals. The study of the charge density distribution and the population analysis shows the coexistence of ionic, covalent and metallic bonds.

Estimation of the reduction of sputtering for fusion grade materials after disappearance of the Debye sheath

NASA Astrophysics Data System (ADS)

Adhikari, S.; Moulick, R.; Goswami, K. S.

2018-02-01

The effect of grazing angle on a solid surface (divertor) erosion due to ion sputtering is studied by 1D-3V fluid approach. For an oblique magnetic field, there exists a region in front of the solid surface called Chodura sheath (CS). It is assumed that the CS is additive to the Debye sheath (DS). For a certain value of the grazing angle, it has been observed that the DS vanishes and the entire potential drop occurs across the CS. This new analysis of the event provides some facts of pragmatic importance in improving the solutions of edge impurity codes. Important factors, such as ion energy, impact angle for physical sputtering are highlighted. The dependence of these two parameters on the grazing angle is also investigated in detail.

Effect of hydrostatic pressure on physical properties of strontium based fluoroperovskites for novel applications

NASA Astrophysics Data System (ADS)

Erum, Nazia; Azhar Iqbal, Muhammad

2018-02-01

Density functional theory (DFT) is employed to calculate the effect of pressure variation on electronic structure, elastic parameters, mechanical durability, and thermodynamic aspects of SrRbF3, in combination with Quasi-harmonic Debye model. The pressure effects are determined in the range of 0-25 GPa, in which cubic stability of SrRbF3 fluoroperovskite remains valid. Significant influence of compression on wide range of elastic parameters and related mechanical properties have been discussed, to utilize this material in low birefringence lens fabrication technology. Apart of linear dependence on elastic coefficients, transition from brittle to ductile behavior is also observed at elevated pressure ranges. Moreover, successful prediction of important thermodynamic aspects such as volume expansion coefficient (α), Debye temperature (θ D), heat capacities (Cp and Cv) are also done within wide pressure and temperature ranges.

Full-Potential Calculation of Structural, Electronic, and Thermodynamic Properties of Fluoroperovskite { CsMF}3 (M = Be and Mg)

NASA Astrophysics Data System (ADS)

Harmel, M.; Khachai, H.; Ameri, A.; Baki, N.; Haddou, A.; Khalfa, M.; Abbar, B.; Omran, S. Bin; Uğur, G.; Uğur, Ş.; Khenata, R.

2012-12-01

The structural and electronic properties of the cubic fluoroperoveskite { CsBeF}3 and { CsMgF}3 have been investigated using the full-potential-linearized augmented plane wave method within the density functional theory. The exchange-correlation potential was treated with the local density approximation and the generalized gradient approximation. The calculations of the electronic band structures show that { CsBeF}_{3 } has an indirect bandgap, whereas { CsMgF}3 has a direct bandgap. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the effect of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and the heat capacity for { CsBeF}3 and { CsMgF}3 compounds are investigated for the first time.

Analysis of terahertz dielectric properties of pork tissue

NASA Astrophysics Data System (ADS)

Huang, Yuqing; Xie, Qiaoling; Sun, Ping

2017-10-01

Seeing that about 70% component of fresh biological tissues is water, many scientists try to use water models to describe the dielectric properties of biological tissues. The classical water dielectric models are Debye model, Double Debye model and Cole-Cole model. This work aims to determine a suitable model by comparing three models above with experimental data. These models are applied to fresh pork tissue. By means of least square method, the parameters of different models are fitted with the experimental data. Comparing different models on both dielectric function, the Cole-Cole model is verified the best to describe the experiments of pork tissue. The correction factor α of the Cole-Cole model is an important modification for biological tissues. So Cole-Cole model is supposed to be a priority selection to describe the dielectric properties for biological tissues in the terahertz range.

Plasma interaction with emmissive surface with Debye-scale grooves

NASA Astrophysics Data System (ADS)

Schweigert, Irina; Burton, Thomas S.; Thompson, Gregory B.; Langendorf, Samuel; Walker, Mitchell L. R.; Keidar, Michael

2018-04-01

The sheath development over emissive grooved surface in dc discharge plasma controlled by an electron beam is studied in the experiment and in 2D kinetic simulations. Grooved hexagonal boron nitride surfaces with different aspect ratios, designed to mimic the erosion channels, were exposed to an argon plasma. The characteristic size of the grooves (1 mm and 5 mm) is about of the Debye length. The secondary electrons emission from the grooved surfaces is provided by the bombardment with energetic electrons originated from the heated powered cathode. The transition between a developed and a collapsed sheaths near emissive surface takes place with an increase of the beam electron energy. For grooved emissive surfaces, the sheath transition happens at essentially higher voltage compared to the planar one. This phenomenon is analyzed in the terms of the electron energy distribution function.

LEO high voltage solar array arcing response model, continuation 5

NASA Technical Reports Server (NTRS)

Metz, Roger N.

1989-01-01

The modeling of the Debye Approximation electron sheaths in the edge and strip geometries was completed. Electrostatic potentials in these sheaths were compared to NASCAP/LEO solutions for similar geometries. Velocity fields, charge densities and particle fluxes to the biased surfaces were calculated for all cases. The major conclusion to be drawn from the comparisons of our Debye Approximation calculations with NASCAP-LEO output is that, where comparable biased structures can be defined and sufficient resolution obtained, these results are in general agreement. Numerical models for the Child-Langmuir, high-voltage electron sheaths in the edge and strip geometries were constructed. Electrostatic potentials were calculated for several cases in each of both geometries. Velocity fields and particle fluxes were calculated. The self-consistent solution process was carried through one cycle and output electrostatic potentials compared to NASCAP-type input potentials.

Computer models of the spacecraft wake

NASA Technical Reports Server (NTRS)

Rubin, A. G.; Heinemann, M.; Tautz, M.; Cooke, D.

1986-01-01

Until recently, computations of space plasma flow over a spacecraft have been unstable for ratios of spacecraft dimension to Debye length typical of the low Earth orbit environment. Calculations are presented of the spacecraft/environment interaction based on two computer codes, MACH and POLAR. MACH, an inside-out particle tracking code, was developed for the purpose of validating the physics of POLAR in regimes where these are no comprehensive theoretical or experimental results. While the spacecraft which can be treated by MACH are restricted to simple geometries, the methodology is more fundamental than POLAR. MACH generates self-consistent solutions within the context of quasisteady Vlasov plasma flow and achieves Debye ratios previously unobtainable. POLAR uses a three-dimensional finite-element representation of the vehicle in a staggered mesh. The plasma sheath is modeled by outside-in particle tracking. Solutions for the plasma flow, wake and vehicle charging are obtained by Vlasov-Poisson iteration; charge stabilization techniques make the results virtually insensitive to the Debye ratio. POLAR reproduces the Laframboise static plasma solutions for sperical probes and fits the Makita-Kuriki probe data for spheres in a flowing plasma in regions where comparisons are valid. POLAR and MACH solutions for the particle and electrostatic potential structure of the wake of a charged disk in a low-altitude flow are shown for Mach numbers 4, 5, and 8. New features of the solutions include ion focussing in the wake and a definitive determination of the sheath edge in the wake which shows that the sheath is not an equipotential.

Small Angle Neutron Scattering Studies on Blends of Poly (Styrene-ran-Vinyl Phenol) with Liquid Crystalline Polyurethane

NASA Astrophysics Data System (ADS)

Mehta, Rujul

2005-03-01

Molecular composites, composed of uniformly dispersed rigid-rod liquid crystalline polymer (LCP) molecules in a flexible amorphous polymer matrix, have remained hitherto elusive due to a scarcity of miscible systems containing a LCP and an amorphous polymer. The production of such a blend, with an experimentally accessible miscibility window, has become possible by modifying the architecture of the flexible polymer, so as to induce favorable intermolecular hydrogen bonding. Specifically, liquid crystalline polyurethanes (LCPU) are found to be miscible with a copolymer of styrene and vinyl phenol; with optimum hydrogen bonding between the carbonyl groups of the urethane linkages and the hydroxyl groups present in the styrenic matrix. Availability of a truly miscible molecular composite presents a unique opportunity of studying the confirmation of polymer chains containing rigid-rods that are uniformly dispersed in a flexible coil matrix. A system consisting of the LCPU and the deuterated styrenic copolymer containing 20% vinyl phenol is examined by Small Angle Neutron Scattering at the National Center for Neutron Research at Gaithersburg and Technology, and the Institute of Solid State Research (IFF) at Jülich. Scattering curves for neat dPS-VPh did not fit the Debye-Bueche model; indicating complex structure. A two correlation length Debye-Bueche model was considered to accommodate for this nonlinear behavior. This model utilizes four fitting parameters, including two correlation lengths a1 and a2, corresponding to a Debye-Bueche model and Guinier model.

21 CFR 862.1055 - Newborn screening test system for amino acids, free carnitine, and acylcarnitines using tandem...

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Newborn screening test system for amino acids... screening test system for amino acids, free carnitine, and acylcarnitines using tandem mass spectrometry. (a) Identification. A newborn screening test system for amino acids, free carnitine, and acylcarnitines using tandem...

21 CFR 862.1055 - Newborn screening test system for amino acids, free carnitine, and acylcarnitines using tandem...

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Newborn screening test system for amino acids... screening test system for amino acids, free carnitine, and acylcarnitines using tandem mass spectrometry. (a) Identification. A newborn screening test system for amino acids, free carnitine, and acylcarnitines using tandem...

Cost and Efficacy Assessment of an Alternative Medication Compliance Urine Drug Testing Strategy.

PubMed

Doyle, Kelly; Strathmann, Frederick G

2017-02-01

This study investigates the frequency at which quantitative results provide additional clinical benefit compared to qualitative results alone. A comparison between alternative urine drug screens and conventional screens including the assessment of cost-to-payer differences, accuracy of prescription compliance or polypharmacy/substance abuse was also included. In a reference laboratory evaluation of urine specimens from across the United States, 213 urine specimens with provided prescription medication information (302 prescriptions) were analyzed by two testing algorithms: 1) conventional immunoassay screen with subsequent reflexive testing of positive results by quantitative mass spectrometry; and 2) a combined immunoassay/qualitative mass-spectrometry screen that substantially reduced the need for subsequent testing. The qualitative screen was superior to immunoassay with reflex to mass spectrometry in confirming compliance per prescription (226/302 vs 205/302), and identifying non-prescription abuse (97 vs 71). Pharmaceutical impurities and inconsistent drug metabolite patterns were detected in only 3.8% of specimens, suggesting that quantitative results have limited benefit. The percentage difference between the conventional testing algorithm and the alternative screen was projected to be 55%, and a 2-year evaluation of test utilization as a measure of test order volume follows an exponential trend for alternative screen test orders over conventional immunoassay screens that require subsequent confirmation testing. Alternative, qualitative urine drug screens provide a less expensive, faster, and more comprehensive evaluation of patient medication compliance and drug abuse. The vast majority of results were interpretable with qualitative results alone indicating a reduced need to automatically reflex to quantitation or provide quantitation for the majority of patients. This strategy highlights a successful approach using an alternative strategy for both the laboratory and physician to align clinical needs while being mindful of costs.

Comparison of clinical and survival characteristics between prostate cancer patients of PSA-based screening and clinical diagnosis in China.

PubMed

Xu, Libo; Wang, Jinguo; Guo, Baofeng; Zhang, Haixia; Wang, Kaichen; Wang, Ding; Dai, Chang; Zhang, Ling; Zhao, Xuejian

2018-01-02

Prostate-specific antigen (PSA)-based mass screening remains the most controversial topic in prostate cancer. PSA-based mass screening has not been widely used in China yet. The aim of our study was to evaluate the effect of the PSA-based screening in China. The cohort consisted of 1,012 prostate cancer patients. Data were retrospectively collected and clinical characteristics of the cohorts were investigated. Survival was analyzed for prostatic carcinoma of both PSA screened and clinically diagnosed patients according to clinical characteristics and the National Comprehensive Cancer Network (NCCN) risk classification. Cox Proportional Hazards Model analysis was done for risk predictor identification. The median age was 71 years old. Five-year overall and prostate-cancer-specific survival in prostatic adenocarcinoma patients were 77.52% and 79.65%; 10-year survivals were 62.57% and 68.60%, respectively. Survival was significantly poorer in patients with metastases and non-curative management. T staging and Gleason score by NCCN classification effectively stratified prostatic adenocarcinoma patients into different risk groups. T staging was a significant predictor of survival by COX Proportional Hazard Model. PSA screened patients had a significantly higher percentage diagnosed in early stage. PSA screened prostatic adenocarcinoma patients had a better prognosis in both overall and prostate cancer-specific survivals. This Chinese cohort had a lower overall and prostate cancer survival rate than it is reported in western countries. The incidence of early-stage prostate cancer found in PSA-based mass screening was high and there were significant differences in both overall and prostate cancer-specific survival between the PSA-screened and clinically diagnosed patients.

Comparison of clinical and survival characteristics between prostate cancer patients of PSA-based screening and clinical diagnosis in China

PubMed Central

Xu, Libo; Wang, Jinguo; Guo, Baofeng; Zhang, Haixia; Wang, Kaichen; Wang, Ding; Dai, Chang; Zhang, Ling; Zhao, Xuejian

2018-01-01

Prostate-specific antigen (PSA)-based mass screening remains the most controversial topic in prostate cancer. PSA-based mass screening has not been widely used in China yet. The aim of our study was to evaluate the effect of the PSA-based screening in China. The cohort consisted of 1,012 prostate cancer patients. Data were retrospectively collected and clinical characteristics of the cohorts were investigated. Survival was analyzed for prostatic carcinoma of both PSA screened and clinically diagnosed patients according to clinical characteristics and the National Comprehensive Cancer Network (NCCN) risk classification. Cox Proportional Hazards Model analysis was done for risk predictor identification. The median age was 71 years old. Five-year overall and prostate-cancer-specific survival in prostatic adenocarcinoma patients were 77.52% and 79.65%; 10-year survivals were 62.57% and 68.60%, respectively. Survival was significantly poorer in patients with metastases and non-curative management. T staging and Gleason score by NCCN classification effectively stratified prostatic adenocarcinoma patients into different risk groups. T staging was a significant predictor of survival by COX Proportional Hazard Model. PSA screened patients had a significantly higher percentage diagnosed in early stage. PSA screened prostatic adenocarcinoma patients had a better prognosis in both overall and prostate cancer-specific survivals. This Chinese cohort had a lower overall and prostate cancer survival rate than it is reported in western countries. The incidence of early-stage prostate cancer found in PSA-based mass screening was high and there were significant differences in both overall and prostate cancer-specific survival between the PSA-screened and clinically diagnosed patients. PMID:29416625

With the Advent of Tomosynthesis in the Workup of Mammographic Abnormality, is Spot Compression Mammography Now Obsolete? An Initial Clinical Experience.

PubMed

Ni Mhuircheartaigh, Neasa; Coffey, Louise; Fleming, Hannah; O' Doherty, Ann; McNally, Sorcha

2017-09-01

To determine if the routine use of spot compression mammography is now obsolete in the assessment of screen detected masses, asymmetries and architectural distortion since the availability of digital breast tomosynthesis. We introduced breast tomosynthesis in the workup of screen detected abnormalities in our screening center in January 2015. During an initial learning period with tomosynthesis standard spot compression views were also performed. Three consultant breast radiologists retrospectively reviewed all screening mammograms recalled for assessment over the first 6-month period. We assessed retrospectively whether there was any additional diagnostic information obtained from spot compression views not already apparent on tomography. All cases were also reviewed for any additional lesions detected by tomosynthesis, not detected on routine 2-view screening mammography. 548 women screened with standard 2-view digital screening mammography were recalled for assessment in the selected period and a total of 565 lesions were assessed. 341 lesions were assessed by both tomosynthesis and routine spot compression mammography. The spot compression view was considered more helpful than tomosynthesis in only one patient. This was because the breast was inadequately positioned for tomosynthesis and the area in question was not adequately imaged. Apart from this technical error there was no asymmetry, distortion or mass where spot compression provided more diagnostic information than tomosynthesis alone. We detected three additional cancers on tomosynthesis, not detected by routine screening mammography. From our initial experience with tomosynthesis we conclude that spot compression mammography is now obsolete in the assessment of screen detected masses, asymmetries and distortions where tomosynthesis is available. © 2017 Wiley Periodicals, Inc.

Value of screening endoscopy in evaluation of esophageal, gastric and colon cancers

PubMed Central

Ro, Tae H; Mathew, Michelle A; Misra, Subhasis

2015-01-01

Esophageal, gastric, and colorectal cancers are deadly diseases that continue to plague our world today. The value of screening endoscopy in evaluating these types of cancers is a critical area of discussion due to a potential reduction in morbidity and mortality. This article describes how to identify a good screening test and explains what are important criteria in the field of screening endoscopy. Furthermore, the current status and progress of screening endoscopy for esophageal, gastric, and colorectal cancer will be evaluated and discussed. Mass screening programs have not been implemented for esophageal and gastric carcinomas in those with average or low risk populations. However, studies of high-risk populations have found value and a cost-benefit in conducting screening endoscopy. Colorectal cancer, on the other hand, has had mass screening programs in place for many years due to the clear evidence of improved outcomes. As the role of endoscopy as a screening tool has continued to develop, newer technology and techniques have emerged to improve its utility. Many new image enhancement techniques and computer processing programs have shown promise and may have a significant role in the future of endoscopic screening. These developments are paving the way for improving the diagnostic and therapeutic capability of endoscopy in the field of gastroenterology. PMID:26361416

Value of screening endoscopy in evaluation of esophageal, gastric and colon cancers.

PubMed

Ro, Tae H; Mathew, Michelle A; Misra, Subhasis

2015-09-07

Esophageal, gastric, and colorectal cancers are deadly diseases that continue to plague our world today. The value of screening endoscopy in evaluating these types of cancers is a critical area of discussion due to a potential reduction in morbidity and mortality. This article describes how to identify a good screening test and explains what are important criteria in the field of screening endoscopy. Furthermore, the current status and progress of screening endoscopy for esophageal, gastric, and colorectal cancer will be evaluated and discussed. Mass screening programs have not been implemented for esophageal and gastric carcinomas in those with average or low risk populations. However, studies of high-risk populations have found value and a cost-benefit in conducting screening endoscopy. Colorectal cancer, on the other hand, has had mass screening programs in place for many years due to the clear evidence of improved outcomes. As the role of endoscopy as a screening tool has continued to develop, newer technology and techniques have emerged to improve its utility. Many new image enhancement techniques and computer processing programs have shown promise and may have a significant role in the future of endoscopic screening. These developments are paving the way for improving the diagnostic and therapeutic capability of endoscopy in the field of gastroenterology.

A Comprehensive Review of School-Based Body Mass Index Screening Programs and Their Implications for School Health: Do the Controversies Accurately Reflect the Research?

ERIC Educational Resources Information Center

Ruggieri, Dominique G.; Bass, Sarah B.

2015-01-01

Background: Whereas legislation for body mass index (BMI) surveillance and screening programs has passed in 25 states, the programs are often subject to ethical debates about confidentiality and privacy, school-to-parent communication, and safety and self-esteem issues for students. Despite this debate, no comprehensive analysis has been completed…

Computer-aided diagnosis workstation and network system for chest diagnosis based on multislice CT images

NASA Astrophysics Data System (ADS)

Satoh, Hitoshi; Niki, Noboru; Eguchi, Kenji; Moriyama, Noriyuki; Ohmatsu, Hironobu; Masuda, Hideo; Machida, Suguru

2008-03-01

Mass screening based on multi-helical CT images requires a considerable number of images to be read. It is this time-consuming step that makes the use of helical CT for mass screening impractical at present. To overcome this problem, we have provided diagnostic assistance methods to medical screening specialists by developing a lung cancer screening algorithm that automatically detects suspected lung cancers in helical CT images, a coronary artery calcification screening algorithm that automatically detects suspected coronary artery calcification and a vertebra body analysis algorithm for quantitative evaluation of osteoporosis likelihood by using helical CT scanner for the lung cancer mass screening. The function to observe suspicious shadow in detail are provided in computer-aided diagnosis workstation with these screening algorithms. We also have developed the telemedicine network by using Web medical image conference system with the security improvement of images transmission, Biometric fingerprint authentication system and Biometric face authentication system. Biometric face authentication used on site of telemedicine makes "Encryption of file" and Success in login" effective. As a result, patients' private information is protected. Based on these diagnostic assistance methods, we have developed a new computer-aided workstation and a new telemedicine network that can display suspected lesions three-dimensionally in a short time. The results of this study indicate that our radiological information system without film by using computer-aided diagnosis workstation and our telemedicine network system can increase diagnostic speed, diagnostic accuracy and security improvement of medical information.

Accurate mass screening and identification of emerging contaminants in environmental samples by liquid chromatography-hybrid linear ion trap Orbitrap mass spectrometry.

PubMed

Hogenboom, A C; van Leerdam, J A; de Voogt, P

2009-01-16

The European Reach legislation will possibly drive producers to develop newly designed chemicals that will be less persistent, bioaccumulative or toxic. If this innovation leads to an increased use of more hydrophilic chemicals it may result in higher mobilities of chemicals in the aqueous environment. As a result, the drinking water companies may face stronger demands on removal processes as the hydrophilic compounds inherently are more difficult to remove. Monitoring efforts will also experience a shift in focus to more water-soluble compounds. Screening source waters on the presence of (emerging) contaminants is an essential step in the control of the water cycle from source to tap water. In this article, some of our experiences are presented with the hybrid linear ion trap (LTQ) FT Orbitrap mass spectrometer, in the area of chemical water analysis. A two-pronged strategy in mass spectrometric research was employed: (i) exploring effluent, surface, ground- and drinking-water samples searching for accurate masses corresponding to target compounds (and their product ions) known from, e.g. priority lists or the scientific literature and (ii) full-scan screening of water samples in search of 'unknown' or unexpected masses, followed by MS(n) experiments to elucidate the structure of the unknowns. Applications of both approaches to emerging water contaminants are presented and discussed. Results are presented for target analysis search for pharmaceuticals, benzotriazoles, illicit drugs and for the identification of unknown compounds in a groundwater sample and in a polar extract of a landfill soil sample (a toxicity identification evaluation bioassay sample). The applications of accurate mass screening and identification described in this article demonstrate that the LC-LTQ FT Orbitrap MS is well equipped to meet the challenges posed by newly emerging polar contaminants.

Screening of the binding of small molecules to proteins by desorption electrospray ionization mass spectrometry combined with protein microarray.

PubMed

Yao, Chenxi; Wang, Tao; Zhang, Buqing; He, Dacheng; Na, Na; Ouyang, Jin

2015-11-01

The interaction between bioactive small molecule ligands and proteins is one of the important research areas in proteomics. Herein, a simple and rapid method is established to screen small ligands that bind to proteins. We designed an agarose slide to immobilize different proteins. The protein microarrays were allowed to interact with different small ligands, and after washing, the microarrays were screened by desorption electrospray ionization mass spectrometry (DESI MS). This method can be applied to screen specific protein binding ligands and was shown for seven proteins and 34 known ligands for these proteins. In addition, a high-throughput screening was achieved, with the analysis requiring approximately 4 s for one sample spot. We then applied this method to determine the binding between the important protein matrix metalloproteinase-9 (MMP-9) and 88 small compounds. The molecular docking results confirmed the MS results, demonstrating that this method is suitable for the rapid and accurate screening of ligands binding to proteins. Graphical Abstract ᅟ.

In situ superexchange electron transfer through a single molecule: a rectifying effect.

PubMed

Kornyshev, Alexei A; Kuznetsov, Alexander M; Ulstrup, Jens

2006-05-02

An increasingly comprehensive body of literature is being devoted to single-molecule bridge-mediated electronic nanojunctions, prompted by their prospective applications in molecular electronics and single-molecule analysis. These junctions may operate in gas phase or electrolyte solution (in situ). For biomolecules, the latter is much closer to their native environment. Convenient target molecules are aromatic molecules, peptides, oligonucleotides, transition metal complexes, and, broadly, molecules with repetitive units, for which the conducting orbitals are energetically well below electronic levels of the solvent. A key feature for these junctions is rectification in the current-voltage relation. A common view is that asymmetric molecules or asymmetric links to the electrodes are needed to acquire rectification. However, as we show here, this requirement could be different in situ, where a structurally symmetric system can provide rectification because of the Debye screening of the electric field in the nanogap if the screening length is smaller than the bridge length. The Galvani potentials of each electrode can be varied independently and lead to a transistor effect. We explore this behavior for the superexchange mechanism of electron transport, appropriate for a wide class of molecules. We also include the effect of conformational fluctuations on the lowest unoccupied molecular orbital (LUMO) energy levels; that gives rise to non-Arrhenius temperature dependence of the conductance, affected by the molecule length. Our study offers an analytical formula for the current-voltage characteristics that demonstrates all these features. A detailed physical interpretation of the results is given with a discussion of reported experimental data.

Ionic liquids behave as dilute electrolyte solutions

PubMed Central

Gebbie, Matthew A.; Valtiner, Markus; Banquy, Xavier; Fox, Eric T.; Henderson, Wesley A.; Israelachvili, Jacob N.

2013-01-01

We combine direct surface force measurements with thermodynamic arguments to demonstrate that pure ionic liquids are expected to behave as dilute weak electrolyte solutions, with typical effective dissociated ion concentrations of less than 0.1% at room temperature. We performed equilibrium force–distance measurements across the common ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTf2]) using a surface forces apparatus with in situ electrochemical control and quantitatively modeled these measurements using the van der Waals and electrostatic double-layer forces of the Derjaguin–Landau–Verwey–Overbeek theory with an additive repulsive steric (entropic) ion–surface binding force. Our results indicate that ionic liquids screen charged surfaces through the formation of both bound (Stern) and diffuse electric double layers, where the diffuse double layer is comprised of effectively dissociated ionic liquid ions. Additionally, we used the energetics of thermally dissociating ions in a dielectric medium to quantitatively predict the equilibrium for the effective dissociation reaction of [C4mim][NTf2] ions, in excellent agreement with the measured Debye length. Our results clearly demonstrate that, outside of the bound double layer, most of the ions in [C4mim][NTf2] are not effectively dissociated and thus do not contribute to electrostatic screening. We also provide a general, molecular-scale framework for designing ionic liquids with significantly increased dissociated charge densities via judiciously balancing ion pair interactions with bulk dielectric properties. Our results clear up several inconsistencies that have hampered scientific progress in this important area and guide the rational design of unique, high–free-ion density ionic liquids and ionic liquid blends. PMID:23716690

When does mass screening for open neural tube defects in low-risk pregnancies result in cost savings?

PubMed Central

Tosi, L L; Detsky, A S; Roye, D P; Morden, M L

1987-01-01

Using a decision analysis model, we estimated the savings that might be derived from a mass prenatal screening program aimed at detecting open neural tube defects (NTDs) in low-risk pregnancies. Our baseline analysis showed that screening v. no screening could be expected to save approximately $8 per pregnancy given a cost of $7.50 for the maternal serum alpha-feto-protein (MSAFP) test and a cost of $42,507 for hospital and rehabilitation services for the first 10 years of life for a child with spina bifida. When a more liberal estimate of the costs of caring for such a child was used, the savings with the screening program were more substantial. We performed extensive sensitivity analyses, which showed that the savings were somewhat sensitive to the cost of the MSAFP test and highly sensitive to the specificity (but not the sensitivity) of the test. A screening program for NTDs in low-risk pregnancies may result in substantial savings in direct health care costs if the screening protocol is followed rigorously and efficiently. PMID:2433011

Focus Article: Oscillatory and long-range monotonic exponential decays of electrostatic interactions in ionic liquids and other electrolytes: The significance of dielectric permittivity and renormalized charges

NASA Astrophysics Data System (ADS)

Kjellander, Roland

2018-05-01

A unified treatment of oscillatory and monotonic exponential decays of interactions in electrolytes is displayed, which highlights the role of dielectric response of the fluid in terms of renormalized (effective) dielectric permittivity and charges. An exact, but physically transparent statistical mechanical formalism is thereby used, which is presented in a systematic, pedagogical manner. Both the oscillatory and monotonic behaviors are given by an equation for the decay length of screened electrostatic interactions that is very similar to the classical expression for the Debye length. The renormalized dielectric permittivities, which have similar roles for electrolytes as the dielectric constant has for pure polar fluids, consist in general of several entities with different physical meanings. They are connected to dielectric response of the fluid on the same length scale as the decay length of the screened interactions. Only in cases where the decay length is very long, these permittivities correspond approximately to a dielectric response in the long-wavelength limit, like the dielectric constant for polar fluids. Experimentally observed long-range exponentially decaying surface forces are analyzed as well as the oscillatory forces observed for short to intermediate surface separations. Both occur in some ionic liquids and in concentrated as well as very dilute electrolyte solutions. The coexisting modes of decay are in general determined by the bulk properties of the fluid and not by the solvation of the surfaces; in the present cases, they are given by the behavior of the screened Coulomb interaction of the bulk fluid. The surface-fluid interactions influence the amplitudes and signs or phases of the different modes of the decay, but not their decay lengths and wavelengths. The similarities between some ionic liquids and very dilute electrolyte solutions as regards both the long-range monotonic and the oscillatory decays are analyzed.

Band-limited Bouguer gravity identifies new basins on the Moon

NASA Astrophysics Data System (ADS)

Featherstone, W. E.; Hirt, C.; Kuhn, M.

2013-06-01

Spectral domain forward modeling is used to generate topography-implied gravity for the Moon using data from the Lunar Orbiter Laser Altimeter instrument operated on board the Lunar Reconnaissance Orbiter mission. This is subtracted from Selenological and Engineering Explorer (SELENE)-derived gravity to generate band-limited Bouguer gravity maps of the Moon so as to enhance the gravitational signatures of anomalous mass densities nearer the surface. This procedure adds evidence that two previously postulated basins on the lunar farside, Fitzgerald-Jackson (25°N, 191°E) and to the east of Debye (50°N, 180°E), are indeed real. When applied over the entire lunar surface, band-limited Bouguer gravity reveals the locations of 280 candidate basins that have not been identified when using full-spectrum gravity or topography alone, showing the approach to be of utility. Of the 280 basins, 66 are classified as distinct from their band-limited Bouguer gravity and topographic signatures, making them worthy of further investigation.

First-Principles Determination of Ultralow Thermal Conductivity of monolayer WSe2

NASA Astrophysics Data System (ADS)

Zhou, Wu-Xing; Chen, Ke-Qiu

2015-10-01

By using first-principles calculations combined with the phonon Boltzmann transport equation, we systematically investigate the phonon transport of monolayer WSe2. Compared with other 2D materials, the monolayer WSe2 is found to have an ultralow thermal conductivity due to the ultralow Debye frequency and heavy atom mass. The room temperature thermal conductivity for a typical sample size of 1 μm is 3.935  W/m K, which is one order of magnitude lower than that of MoS2. And the room temperature thermal conductivity can be further decreased by about 95% in 10 nm sized samples. Moreover, we also find the ZA phonons have the dominant contribution to the thermal conductivity, and the relative contribution is almost 80% at room temperature, which is remarkably higher than that for monolayer MoS2. This is because the ZA phonons have longer lifetime than that of LA and TA phonons in monolayer WSe2.

The effect of complex black carbon microphysics on the determination of the optical properties of brown carbon

NASA Astrophysics Data System (ADS)

Liu, Dantong; Taylor, Jonathan W.; Young, Dominque E.; Flynn, Michael J.; Coe, Hugh; Allan, James D.

2015-01-01

of the impacts of brown carbon (BrC) requires accurate determination of its physical properties, but a model must be invoked to derive these from instrument data. Ambient measurements were made in London at a site influenced by traffic and solid fuel (principally wood) burning, apportioned by single particle soot photometer data and optical properties measured using multiwavelength photoacoustic spectroscopy. Two models were applied: a commonly used Mie model treating the particles as single-coated spheres and a Rayleigh-Debye-Gans approximation treating them as aggregates of smaller-coated monomers. The derived solid fuel BrC parameters at 405 nm were found to be highly sensitive to the model treatment, with a mass absorption cross section ranging from 0.47 to 1.81 m2/g and imaginary refractive index from 0.013 to 0.062. This demonstrates that a detailed knowledge of particle morphology must be obtained and invoked to accurately parameterize BrC properties based on aerosol phase measurements.

Dissociation of 1P states in hot QCD Medium Using Quasi-Particle Model

NASA Astrophysics Data System (ADS)

Nilima, Indrani; Agotiya, Vineet Kumar

2018-03-01

We extend the analysis of a very recent work [1] to study the dissociation phenomenon of 1P states of the charmonium and bottomonium spectra (χc and χb) in a hot QCD medium using Quasi-Particle Model. This study employed a medium modified heavy quark potential which has quite different form in the sense that it has a lomg range Coulombic tail in addition to the Yukawa term even above the deconfinement temperature. Then we study the flavor dependence of their binding energies and explore the nature of dissociation temperatures by employing the Quasi-Particle debye mass for pure gluonic and full QCD case. Interestingly, the dissociation temperatures obtained by employing EoS1 and EoS2 with the Γ criterion, is closer to the upper bound of the dissociation temperatures which are obtained by the dissolution of a given quarkonia state by the mean thermal energy of the quasi-partons in the hot QCD/QGP medium.

Eliciting population preferences for mass colorectal cancer screening organization.

PubMed

Nayaradou, Maximilien; Berchi, Célia; Dejardin, Olivier; Launoy, Guy

2010-01-01

The implementation of mass colorectal cancer (CRC) screening is a public health priority. Population participation is fundamental for the success of CRC screening as for any cancer screening program. The preferences of the population may influence their likelihood of participation. The authors sought to elicit population preferences for CRC screening test characteristics to improve the design of CRC screening campaigns. A discrete choice experiment was used. Questionnaires were compiled with a set of pairs of hypothetical CRC screening scenarios. The survey was conducted by mail from June 2006 to October 2006 on a representative sample of 2000 inhabitants, aged 50 to 74 years from the northwest of France, who were randomly selected from electoral lists. Questionnaires were sent to 2000 individuals, each of whom made 3 or 4 discrete choices between hypothetical tests that differed in 7 attributes: how screening is offered, process, sensitivity, rate of unnecessary colonoscopy, expected mortality reduction, method of screening test result transmission, and cost. Complete responses were received from 656 individuals (32.8%). The attributes that influenced population preferences included expected mortality reduction, sensitivity, cost, and process. Participants from high social classes were particularly influenced by sensitivity. The results demonstrate that the discrete choice experiment provides information on patient preferences for CRC screening: improving screening program effectiveness, for instance, by improving test sensitivity (the most valued attribute) would increase satisfaction among the general population with regard to CRC screening programs. Additional studies are required to study how patient preferences actually affect adherence to regular screening programs.

The effects of gray scale image processing on digital mammography interpretation performance.

PubMed

Cole, Elodia B; Pisano, Etta D; Zeng, Donglin; Muller, Keith; Aylward, Stephen R; Park, Sungwook; Kuzmiak, Cherie; Koomen, Marcia; Pavic, Dag; Walsh, Ruth; Baker, Jay; Gimenez, Edgardo I; Freimanis, Rita

2005-05-01

To determine the effects of three image-processing algorithms on diagnostic accuracy of digital mammography in comparison with conventional screen-film mammography. A total of 201 cases consisting of nonprocessed soft copy versions of the digital mammograms acquired from GE, Fischer, and Trex digital mammography systems (1997-1999) and conventional screen-film mammograms of the same patients were interpreted by nine radiologists. The raw digital data were processed with each of three different image-processing algorithms creating three presentations-manufacturer's default (applied and laser printed to film by each of the manufacturers), MUSICA, and PLAHE-were presented in soft copy display. There were three radiologists per presentation. Area under the receiver operating characteristic curve for GE digital mass cases was worse than screen-film for all digital presentations. The area under the receiver operating characteristic for Trex digital mass cases was better, but only with images processed with the manufacturer's default algorithm. Sensitivity for GE digital mass cases was worse than screen film for all digital presentations. Specificity for Fischer digital calcifications cases was worse than screen film for images processed in default and PLAHE algorithms. Specificity for Trex digital calcifications cases was worse than screen film for images processed with MUSICA. Specific image-processing algorithms may be necessary for optimal presentation for interpretation based on machine and lesion type.

Recent developments and new applications of tandem mass spectrometry in newborn screening.

PubMed

Rinaldo, Piero; Tortorelli, Silvia; Matern, Dietrich

2004-08-01

To summarize recent developments in the field of newborn screening related to the use of tandem mass spectrometry as an analytic platform. Novel inborn errors of metabolism with informative amino acid and/or acylcarnitine profiles have been characterized, increasing the complexity of the differential diagnosis of abnormal results. In addition, methods have been developed for the analysis in dried blood spots of steroids and lysosomal enzymes. Previously unrecognized genotype/phenotype correlations have been found among cohorts of patients whose conditions were diagnosed by screening rather than clinically. Several government entities and professional organizations have issued position statements on newborn screening, and worldwide outcome studies continue to underscore the clinical and financial benefits of expanded newborn screening. Although it is done inconsistently, newborn screening in the United States is undergoing a rapid expansion driven by the introduction of tandem mass spectrometry in at least 34 state programs. This technology is also used to detect disease markers beyond acylcarnitines and amino acids, as both primary and second-tier tests. In addition to analytic improvements, there is a trend toward the development of joint programs not limited to contiguous geographic areas, often based upon public-private partnerships. This review will summarize several new developments in the field that have occurred since early 2003 and will mention others likely to occur in the near future.

High-throughput tandem mass spectrometry multiplex analysis for newborn urinary screening of creatine synthesis and transport disorders, Triple H syndrome and OTC deficiency.

PubMed

Auray-Blais, Christiane; Maranda, Bruno; Lavoie, Pamela

2014-09-25

Creatine synthesis and transport disorders, Triple H syndrome and ornithine transcarbamylase deficiency are treatable inborn errors of metabolism. Early screening of patients was found to be beneficial. Mass spectrometry analysis of specific urinary biomarkers might lead to early detection and treatment in the neonatal period. We developed a high-throughput mass spectrometry methodology applicable to newborn screening using dried urine on filter paper for these aforementioned diseases. A high-throughput methodology was devised for the simultaneous analysis of creatine, guanidineacetic acid, orotic acid, uracil, creatinine and respective internal standards, using both positive and negative electrospray ionization modes, depending on the compound. The precision and accuracy varied by <15%. Stability during storage at different temperatures was confirmed for three weeks. The limits of detection and quantification for each biomarker varied from 0.3 to 6.3 μmol/l and from 1.0 to 20.9 μmol/l, respectively. Analyses of urine specimens from affected patients revealed abnormal results. Targeted biomarkers in urine were detected in the first weeks of life. This rapid, simple and robust liquid chromatography/tandem mass spectrometry methodology is an efficient tool applicable to urine screening for inherited disorders by biochemical laboratories. Copyright © 2014 Elsevier B.V. All rights reserved.

Nontargeted Screening Method for Illegal Additives Based on Ultrahigh-Performance Liquid Chromatography-High-Resolution Mass Spectrometry.

PubMed

Fu, Yanqing; Zhou, Zhihui; Kong, Hongwei; Lu, Xin; Zhao, Xinjie; Chen, Yihui; Chen, Jia; Wu, Zeming; Xu, Zhiliang; Zhao, Chunxia; Xu, Guowang

2016-09-06

Identification of illegal additives in complex matrixes is important in the food safety field. In this study a nontargeted screening strategy was developed to find illegal additives based on ultrahigh-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS). First, an analytical method for possible illegal additives in complex matrixes was established including fast sample pretreatment, accurate UHPLC separation, and HRMS detection. Second, efficient data processing and differential analysis workflow were suggested and applied to find potential risk compounds. Third, structure elucidation of risk compounds was performed by (1) searching online databases [Metlin and the Human Metabolome Database (HMDB)] and an in-house database which was established at the above-defined conditions of UHPLC-HRMS analysis and contains information on retention time, mass spectra (MS), and tandem mass spectra (MS/MS) of 475 illegal additives, (2) analyzing fragment ions, and (3) referring to fragmentation rules. Fish was taken as an example to show the usefulness of the nontargeted screening strategy, and six additives were found in suspected fish samples. Quantitative analysis was further carried out to determine the contents of these compounds. The satisfactory application of this strategy in fish samples means that it can also be used in the screening of illegal additives in other kinds of food samples.

Characteristics of invasive breast cancer and overall survival of patients eligible for mass breast cancer screening in Guadeloupe compared to those of the preceding age group.

PubMed

Kadhel, Philippe; Borja De Mozota, Daphné; Gaumond, Stéphanie; Deloumeaux, Jacqueline

2017-10-01

Mass breast cancer screening is offered to French women between the ages of 50 and 74. In the French overseas department of Guadeloupe, where the population is of mostly African ancestry, a low age at diagnosis of breast cancer has been reported, as for African-Americans. This raises the question of whether breast cancer is more aggressive in the age group preceding that eligible for mass screening (40-49) in Guadeloupe. We compared the tumor-related prognostic factors, first line therapy and overall survival rates of breast cancer cases diagnosed between the 40-49 and 50-74 age groups, based on reports of the cancer registry of Guadeloupe for the period 2008-2013. The characteristics studied, risk of death after breast cancer (HR 0.84 [95% CI: 0.58-1.22] and overall survival, did not differ significantly between the two groups, except for higher tumor size (28.8 vs 24.0; p=0.004) in the younger group. These results do not show a pattern of more aggressive breast cancer in the age group preceding that eligible for mass screening in Guadeloupe. Copyright © 2017 Elsevier Ltd. All rights reserved.

Practical application of in silico fragmentation based residue screening with ion mobility high-resolution mass spectrometry.

PubMed

Kaufmann, Anton; Butcher, Patrick; Maden, Kathry; Walker, Stephan; Widmer, Mirjam

2017-07-15

A screening concept for residues in complex matrices based on liquid chromatography coupled to ion mobility high-resolution mass spectrometry LC/IMS-HRMS is presented. The comprehensive four-dimensional data (chromatographic retention time, drift time, mass-to-charge and ion abundance) obtained in data-independent acquisition (DIA) mode was used for data mining. An in silico fragmenter utilizing a molecular structure database was used for suspect screening, instead of targeted screening with reference substances. The utilized data-independent acquisition mode relies on the MS E concept; where two constantly alternating HRMS scans (low and high fragmentation energy) are acquired. Peak deconvolution and drift time alignment of ions from the low (precursor ion) and high (product ion) energy scan result in relatively clean product ion spectra. A bond dissociation in silico fragmenter (MassFragment) supplied with mol files of compounds of interest was used to explain the observed product ions of each extracted candidate component (chromatographic peak). Two complex matrices (fish and bovine liver extract) were fortified with 98 veterinary drugs. Out of 98 screened compounds 94 could be detected with the in silico based screening approach. The high correlation among drift time and m/z value of equally charged ions was utilized for an orthogonal filtration (ranking). Such an orthogonal ion mobility based filter removes multiply charged ions (e.g. peptides and proteins from the matrix) as well as noise and artefacts. Most significantly, this filtration dramatically reduces false positive findings but hardly increases false negative findings. The proposed screening approach may offer new possibilities for applications where reference compounds are hardly or not at all commercially available. Such areas may be the analysis of metabolites of drugs, pyrrolizidine alkaloids, marine toxins, derivatives of sildenafil or novel designer drugs (new psychoactive substances). Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Ultrafast visualization of the structural evolution of dense hydrogen towards warm dense matter

NASA Astrophysics Data System (ADS)

Fletcher, Luke

2016-10-01

Hot dense hydrogen far from equilibrium is ubiquitous in nature occurring during some of the most violent and least understood events in our universe such as during star formation, supernova explosions, and the creation of cosmic rays. It is also a state of matter important for applications in inertial confinement fusion research and in laser particle acceleration. Rapid progress occurred in recent years characterizing the high-pressure structural properties of dense hydrogen under static or dynamic compression. Here, we show that spectrally and angularly resolved x-ray scattering measure the thermodynamic properties of dense hydrogen and resolve the ultrafast evolution and relaxation towards thermodynamic equilibrium. These studies apply ultra-bright x-ray pulses from the Linac Coherent Light (LCLS) source. The interaction of rapidly heated cryogenic hydrogen with a high-peak power optical laser is visualized with intense LCLS x-ray pulses in a high-repetition rate pump-probe setting. We demonstrate that electron-ion coupling is affected by the small number of particles in the Debye screening cloud resulting in much slower ion temperature equilibration than predicted by standard theory. This work was supported by the DOE Office of Science, Fusion Energy Science under FWP 100182.

Swelling of biological and semiflexible polyelectrolytes.

PubMed

Dobrynin, Andrey V; Carrillo, Jan-Michael Y

2009-10-21

We have developed a theoretical model of swelling of semiflexible (biological) polyelectrolytes in salt solutions. Our approach is based on separation of length scales which allowed us to split a chain's electrostatic energy into two parts that describe local and remote electrostatic interactions along the polymer backbone. The local part takes into account interactions between charged monomers that are separated by distances along the polymer backbone shorter than the chain's persistence length. These electrostatic interactions renormalize chain persistence length. The second part includes electrostatic interactions between remote charged pairs along the polymer backbone located at distances larger than the chain persistence length. These interactions are responsible for chain swelling. In the framework of this approach we calculated effective chain persistence length and chain size as a function of the Debye screening length, chain degree of ionization, bare persistence length and chain degree of polymerization. Our crossover expression for the effective chain's persistence length is in good quantitative agreement with the experimental data on DNA. We have been able to fit experimental datasets by using two adjustable parameters: DNA ionization degree (α = 0.15-0.17) and a bare persistence length (l(p) = 40-44 nm).

Plasma Constraints on the Cosmological Abundance of Magnetic Monopoles and the Origin of Cosmic Magnetic Fields

NASA Astrophysics Data System (ADS)

Medvedev, Mikhail; Loeb, Abraham

2017-10-01

Existing theoretical and observational constraints on the abundance of magnetic monopoles are limited. Here we demonstrate that an ensemble of monopoles forms a plasma whose properties are well determined and whose collective effects place new tight constraints on the cosmological abundance of monopoles. In particular, the existence of micro-Gauss magnetic fields in galaxy clusters and radio relics implies that the scales of these structures are below the Debye screening length, thus setting an upper limit on the cosmological density parameter of monopoles, ΩM <= 3 ×10-4 , which precludes them from being the dark matter. Future detection of Gpc-scale coherent magnetic fields could improve this limit by a few orders of magnitude. In addition, we predict the existence of magnetic Langmuir waves and turbulence which may appear on the sky as ``zebra patterns'' of an alternating magnetic field with k . B ≠ 0 . We also show that magnetic monopole Langmuir turbulence excited near the accretion shock of galaxy clusters may be an efficient mechanism for generating the observed intracluster magnetic fields. The authors acknowledge DOE partial support via Grant DE-SC0016368.

Plasma constraints on the cosmological abundance of magnetic monopoles and the origin of cosmic magnetic fields

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

Medvedev, Mikhail V.; Loeb, Abraham, E-mail: mmedvedev@cfa.harvard.edu, E-mail: aloeb@cfa.harvard.edu

Existing theoretical and observational constraints on the abundance of magnetic monopoles are limited. Here we demonstrate that an ensemble of monopoles forms a plasma whose properties are well determined and whose collective effects place new tight constraints on the cosmological abundance of monopoles. In particular, the existence of micro-Gauss magnetic fields in galaxy clusters and radio relics implies that the scales of these structures are below the Debye screening length, thus setting an upper limit on the cosmological density parameter of monopoles, Ω {sub M} {sub ∼<} {sub 3} {sub ×} {sub 10}{sup −4}, which precludes them from being themore » dark matter. Future detection of Gpc-scale coherent magnetic fields could improve this limit by a few orders of magnitude. In addition, we predict the existence of magnetic Langmuir waves and turbulence which may appear on the sky as ''zebra patterns'' of an alternating magnetic field with k·B ≠ 0. We also show that magnetic monopole Langmuir turbulence excited near the accretion shock of galaxy clusters may be an efficient mechanism for generating the observed intracluster magnetic fields.« less

Direct, Label-Free, and Rapid Transistor-Based Immunodetection in Whole Serum.

PubMed

Gutiérrez-Sanz, Óscar; Andoy, Nesha M; Filipiak, Marcin S; Haustein, Natalie; Tarasov, Alexey

2017-09-22

Transistor-based biosensors fulfill many requirements posed upon transducers for future point-of-care diagnostic devices such as scalable fabrication and label-free and real-time quantification of chemical and biological species with high sensitivity. However, the short Debye screening length in physiological samples (<1 nm) has been a major drawback so far, preventing direct measurements in serum. In this work, we demonstrate how tailoring the sensing surface with short specific biological receptors and a polymer polyethylene glycol (PEG) can strongly enhance the sensor response. In addition, the sensor performance can be dramatically improved if the measurements are performed at elevated temperatures (37 °C instead of 21 °C). With this novel approach, highly sensitive and selective detection of a representative immunosensing parameter-human thyroid-stimulating hormone-is shown over a wide measuring range with subpicomolar detection limits in whole serum. To the best of our knowledge, this is the first demonstration of direct immunodetection in whole serum using transistor-based biosensors, without the need for sample pretreatment, labeling, or washing steps. The presented sensor is low-cost, can be easily integrated into portable diagnostics devices, and offers a competitive performance compared to state-of-the-art central laboratory analyzers.

Long-ranged electrostatic repulsion and crystallization of emulsion droplets in an ultralow dielectric medium supercritical carbon dioxide.

PubMed

Ryoo, Won; Webber, Stephen E; Bonnecaze, Roger T; Johnston, Keith P

2006-01-31

Electrostatic repulsion stabilizes micrometer-sized water droplets with spacings greater than 10 microm in an ultralow dielectric medium, CO2 (epsilon = 1.5), at elevated pressures. The morphology of the water/CO2 emulsion is characterized by optical microscopy and laser diffraction as a function of height. The counterions, stabilized with a nonionic, highly branched, stubby hydrocarbon surfactant, form an extremely thick double layer with a Debye screening length of 8.9 microm. As a result of the balance between electrostatic repulsion and the downward force due to gravity, the droplets formed a hexagonal crystalline lattice at the bottom of the high-pressure cell with spacings of over 10 microm. The osmotic pressure, calculated by solving the Poisson-Boltzmann equation in the framework of the Wigner-Seitz cell model, is in good agreement with that determined from the sedimentation profile measured by laser diffraction. Thus, the long-ranged stabilization of the emulsion may be attributed to electrostatic stabilization. The ability to form new types of colloids in CO2 with electrostatic stabilization is beneficial because steric stabilization is often unsatisfactory because of poor solvation of the stabilizers.

Hawking radiation from the holographic screen

NASA Astrophysics Data System (ADS)

Zhao, Ying-Jie

2017-10-01

In this paper, we generalize the Parikh-Wilczek scheme to a holographic screen in the framework of the ultraviolet self-complete quantum gravity. We calculate that the tunneling probability depends on the energy of the particle and the mass of the holographic screen. The radiating temperature has not been the standard Hawking temperature.

EVALUATION OF GROUNDWATER FLOW PATTERNS AROUND A DUAL-SCREENED GROUNDWATER CIRCULATION WELL

EPA Science Inventory

Dual-screened groundwater circulation wells (GCWs) can be used to remove contaminant mass and to mix reagents in situ. GCWs are so named because they force water in a circular pattern between injection and extraction screens. The radial extent, flux and direction of the effective...

Facilitating Factors and Barriers to BMI Screening in Schools

ERIC Educational Resources Information Center

Stalter, Ann M.; Chaudry, Rosemary V.; Polivka, Barbara J.

2010-01-01

The National Association of School Nurses advocates for body mass index (BMI) screening. Little research describes school nurse practice of BMI screening. In this descriptive study, 25 Ohio school nurses participated in three focus groups. An adapted "Healthy People 2010" Determinants of Health Model guided the research questions. School…

FREQUENCY-DEPENDENT ABSORPTION OF ELECTROMAGNETIC ENERGY IN BIOLOGICAL TISSUE

EPA Science Inventory

The frequency-dependent absorption of electromagnetic energy in biological tissue is illustrated by use of the Debye equations, model calculations for different irradiation conditions, and measured electrical properties (conductivity and permittivity) of different tissues. Four s...

Accuracy of RGD approximation for computing light scattering properties of diffusing and motile bacteria. [Rayleigh-Gans-Debye

NASA Technical Reports Server (NTRS)

Kottarchyk, M.; Chen, S.-H.; Asano, S.

1979-01-01

The study tests the accuracy of the Rayleigh-Gans-Debye (RGD) approximation against a rigorous scattering theory calculation for a simplified model of E. coli (about 1 micron in size) - a solid spheroid. A general procedure is formulated whereby the scattered field amplitude correlation function, for both polarized and depolarized contributions, can be computed for a collection of particles. An explicit formula is presented for the scattered intensity, both polarized and depolarized, for a collection of randomly diffusing or moving particles. Two specific cases for the intermediate scattering functions are considered: diffusing particles and freely moving particles with a Maxwellian speed distribution. The formalism is applied to microorganisms suspended in a liquid medium. Sensitivity studies revealed that for values of the relative index of refraction greater than 1.03, RGD could be in serious error in computing the intensity as well as correlation functions.

Thermodynamic properties of OsB under high temperature and high pressure

NASA Astrophysics Data System (ADS)

Chen, Hai-Hua; Li, Zuo; Cheng, Yan; Bi, Yan; Cai, Ling-Cang

2011-09-01

The energy-volume curves of OsB have been obtained using the first-principles plane-wave ultrasoft-pseudopotential density functional theory (DFT) within the generalized gradient approximation (GGA) and local density approximation (LDA). Using the quasi-harmonic Debye model we first analyze the specific heat, the coefficients of thermal expansion as well as the thermodynamic Grüneisen parameter of OsB in a wide temperature range at high pressure. At temperature 300 K, the coefficients of thermal expansion αV by LDA and GGA calculations are 1.67×10 -5 1/K and 2.01×10 -5 1/K, respectively. The specific heat of OsB at constant pressure (volume) is also calculated. Meanwhile, we find that the Debye temperature of OsB increases monotonically with increasing pressure. The present study leads to a better understanding of how the OsB materials respond to pressure and temperature.

Elastic, thermodynamic and optical behavior of V2AC (A = Al, Ga) MAX phases

NASA Astrophysics Data System (ADS)

Khatun, M. R.; Ali, M. A.; Parvin, F.; Islam, A. K. M. A.

This article reports the first-principles calculations of yet unexplored Mulliken bond population, Vickers hardness, thermodynamic and optical properties of MAX phases V2AC (A = Al, Ga). We have also revisited the structural and elastic properties of these phases in order to assess the reliability of our calculations. The temperature and pressure dependence of bulk modulus, Debye temperature, specific heats, and thermal expansion coefficient have been successfully estimated through the quasi-harmonic Debye model in the temperature range from 0 to 1000 K and the pressure range from 0 to 50 GPa. The optical properties such as the dielectric function, refractive index, photoconductivity, absorption coefficients, reflectivity and loss function are also evaluated for the first time. The reflectivity is found to be high which indicates that V2AC (A = Al, Ga) having the same characteristics could be good candidate materials to reduce solar heating up to ∼15 eV.

Laboratory observation of electron phase-space holes during magnetic reconnection.

PubMed

Fox, W; Porkolab, M; Egedal, J; Katz, N; Le, A

2008-12-19

We report the observation of large-amplitude, nonlinear electrostatic structures, identified as electron phase-space holes, during magnetic reconnection experiments on the Versatile Toroidal Facility at MIT. The holes are positive electric potential spikes, observed on high-bandwidth ( approximately 2 GHz) Langmuir probes. Investigations with multiple probes establish that the holes travel at or above the electron thermal speed and have a three-dimensional, approximately spherical shape, with a scale size approximately 2 mm. This corresponds to a few electron gyroradii, or many tens of Debye lengths, which is large compared to holes considered in simulations and observed by satellites, whose length scale is typically only a few Debye lengths. Finally, a statistical study over many discharges confirms that the holes appear in conjunction with the large inductive electric fields and the creation of energetic electrons associated with the magnetic energy release.

Simulation of radial expansion of an electron beam injected into a background plasma

NASA Technical Reports Server (NTRS)

Koga, J.; Lin, C. S.

1989-01-01

A 2-D electrostatic particle code was used to study the beam radial expansion of a nonrelativistic electron beam injected from an isolated equipotential conductor into a background plasma. The simulations indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. The simulations also suggest that the charge buildup at the beam stagnation point causes the beam radial expansion. From a survey of the simulation results, it is found that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. This dependence is explained in terms of the ratio of the beam electron Debye length to the ambient electron Debye length. These results are most applicable to the SEPAC electron beam injection experiments from Spacelab 1, where high charging potential was observed.

Molecular physics. Production of trilobite Rydberg molecule dimers with kilo-Debye permanent electric dipole moments.

PubMed

Booth, D; Rittenhouse, S T; Yang, J; Sadeghpour, H R; Shaffer, J P

2015-04-03

Permanent electric dipole moments are important for understanding symmetry breaking in molecular physics, control of chemical reactions, and realization of strongly correlated many-body quantum systems. However, large molecular permanent electric dipole moments are challenging to realize experimentally. We report the observation of ultralong-range Rydberg molecules with bond lengths of ~100 nanometers and kilo-Debye permanent electric dipole moments that form when an ultracold ground-state cesium (Cs) atom becomes bound within the electronic cloud of an extended Cs electronic orbit. The electronic character of this hybrid class of "trilobite" molecules is dominated by degenerate Rydberg manifolds, making them difficult to produce by conventional photoassociation. We used detailed coupled-channel calculations to reproduce their properties quantitatively. Our findings may lead to progress in ultracold chemistry and strongly correlated many-body physics. Copyright © 2015, American Association for the Advancement of Science.

Surface forces between colloidal particles at high hydrostatic pressure

NASA Astrophysics Data System (ADS)

Pilat, D. W.; Pouligny, B.; Best, A.; Nick, T. A.; Berger, R.; Butt, H.-J.

2016-02-01

It was recently suggested that the electrostatic double-layer force between colloidal particles might weaken at high hydrostatic pressure encountered, for example, in deep seas or during oil recovery. We have addressed this issue by means of a specially designed optical trapping setup that allowed us to explore the interaction of a micrometer-sized glass bead and a solid glass wall in water at hydrostatic pressures of up to 1 kbar. The setup allowed us to measure the distance between bead and wall with a subnanometer resolution. We have determined the Debye lengths in water for salt concentrations of 0.1 and 1 mM. We found that in the pressure range from 1 bar to 1 kbar the maximum variation of the Debye lengths was <1 nm for both salt concentrations. Furthermore, the magnitude of the zeta potentials of the glass surfaces in water showed no dependency on pressure.

Electrostatic Debye layer formed at a plasma-liquid interface

NASA Astrophysics Data System (ADS)

Rumbach, Paul; Clarke, Jean Pierre; Go, David B.

2017-05-01

We construct an analytic model for the electrostatic Debye layer formed at a plasma-liquid interface by combining the Gouy-Chapman theory for the liquid with a simple parabolic band model for the plasma sheath. The model predicts a nonlinear scaling between the plasma current density and the solution ionic strength, and we confirmed this behavior with measurements using a liquid-anode plasma. Plots of the measured current density as a function of ionic strength collapse the data and curve fits yield a plasma electron density of ˜1019m-3 and an electric field of ˜104V /m on the liquid side of the interface. Because our theory is based firmly on fundamental physics, we believe it can be widely applied to many emerging technologies involving the interaction of low-temperature, nonequilibrium plasma with aqueous media, including plasma medicine and various plasma chemical synthesis techniques.

Comparative Evaluation of Preliminary Screening Methods for Colorectal Cancer in a Mass Program.

PubMed

Ye, Ding; Huang, Qiuchi; Li, Qilong; Jiang, Xiyi; Mamat, Mayila; Tang, Mengling; Wang, Jianbing; Chen, Kun

2017-09-01

The fecal immunochemical test (FIT) has been widely used in preliminary screening for colorectal cancer (CRC). The high-risk factor questionnaire (HRFQ) and quantitative risk-assessment method (QRAM) are recommended for estimating the risk of CRC qualitatively and quantitatively in China. We aimed to prospectively compare the diagnostic values of CRC preliminary screening methods to identify which method is preferable as a screening strategy. Individuals aged 40-74 years old were enrolled in a mass CRC screening program from January 1, 2007 to December 31, 2014, in Jiashan County, Zhejiang Province, China. FIT of two stool specimens at 1-week intervals was performed by laboratory personnel and face-to-face interviews were conducted by trained investigators. Screening data in the program were linked to a CRC surveillance and registry system, and CRC cases reported in the system were regarded as true patients. A total of 96,043 subjects were included. The sensitivity and specificity of FIT for detecting CRC cases were 75.49% (95% CI 69.84-80.39) and 90.36% (95% CI 90.17-90.54), respectively. QRAM was more sensitive (p < 0.001) and less specific (p < 0.001) than HRFQ. The sensitivity and specificity of FIT along with HRFQ were 86.56% (95% CI 81.81-90.22) and 81.37% (95% CI 81.12-81.62), and those of FIT along with QRAM were 88.93% (95% CI 84.47-92.23) and 73.95% (95% CI 73.67-74.23). Our findings suggest that CRC preliminary screening with FIT and QRAM in parallel has high sensitivity and satisfactory specificity, and is a useful strategy in mass screening programs.

Computer-aided diagnosis workstation and telemedicine network system for chest diagnosis based on multislice CT images

NASA Astrophysics Data System (ADS)

Satoh, Hitoshi; Niki, Noboru; Eguchi, Kenji; Ohmatsu, Hironobu; Kakinuma, Ryutaru; Moriyama, Noriyuki

2009-02-01

Mass screening based on multi-helical CT images requires a considerable number of images to be read. It is this time-consuming step that makes the use of helical CT for mass screening impractical at present. Moreover, the doctor who diagnoses a medical image is insufficient in Japan. To overcome these problems, we have provided diagnostic assistance methods to medical screening specialists by developing a lung cancer screening algorithm that automatically detects suspected lung cancers in helical CT images, a coronary artery calcification screening algorithm that automatically detects suspected coronary artery calcification and a vertebra body analysis algorithm for quantitative evaluation of osteoporosis likelihood by using helical CT scanner for the lung cancer mass screening. The functions to observe suspicious shadow in detail are provided in computer-aided diagnosis workstation with these screening algorithms. We also have developed the telemedicine network by using Web medical image conference system with the security improvement of images transmission, Biometric fingerprint authentication system and Biometric face authentication system. Biometric face authentication used on site of telemedicine makes "Encryption of file" and "Success in login" effective. As a result, patients' private information is protected. We can share the screen of Web medical image conference system from two or more web conference terminals at the same time. An opinion can be exchanged mutually by using a camera and a microphone that are connected with workstation. Based on these diagnostic assistance methods, we have developed a new computer-aided workstation and a new telemedicine network that can display suspected lesions three-dimensionally in a short time. The results of this study indicate that our radiological information system without film by using computer-aided diagnosis workstation and our telemedicine network system can increase diagnostic speed, diagnostic accuracy and security improvement of medical information.

Whole organism high content screening identifies stimulators of pancreatic beta-cell proliferation.

PubMed

Tsuji, Naoki; Ninov, Nikolay; Delawary, Mina; Osman, Sahar; Roh, Alex S; Gut, Philipp; Stainier, Didier Y R

2014-01-01

Inducing beta-cell mass expansion in diabetic patients with the aim to restore glucose homeostasis is a promising therapeutic strategy. Although several in vitro studies have been carried out to identify modulators of beta-cell mass expansion, restoring endogenous beta-cell mass in vivo has yet to be achieved. To identify potential stimulators of beta-cell replication in vivo, we established transgenic zebrafish lines that monitor and allow the quantification of cell proliferation by using the fluorescent ubiquitylation-based cell cycle indicator (FUCCI) technology. Using these new reagents, we performed an unbiased chemical screen, and identified 20 small molecules that markedly increased beta-cell proliferation in vivo. Importantly, these structurally distinct molecules, which include clinically-approved drugs, modulate three specific signaling pathways: serotonin, retinoic acid and glucocorticoids, showing the high sensitivity and robustness of our screen. Notably, two drug classes, retinoic acid and glucocorticoids, also promoted beta-cell regeneration after beta-cell ablation. Thus, this study establishes a proof of principle for a high-throughput small molecule-screen for beta-cell proliferation in vivo, and identified compounds that stimulate beta-cell proliferation and regeneration.

Detection of weapons of mass destruction

NASA Astrophysics Data System (ADS)

Bjorkholm, Paul J.

2003-07-01

High Energy X-ray cargo screening is a mature technology that has proven its value in the detection of contraband material hidden within cargo including fully loaded sea containers. To date high energy screening has been largely applied to manifest verification and to drug detection. However, the dramatic change in world terrorism has altered the application. Now it is essential that weapons of mass destruction (WMD"s) be interdicted with incredibly high accuracy. The implication of a missed detection has gone from loss of revenue or the lowering of the street price of drugs to potentially stopping, at least for some significant time, most world commerce. Screening containers with high energy x-rays (~250+ mm of steel penetration) is capable of detecting all nuclear threats at a fraction of the strategically important mass. The screening operation can be automated so that no human decisions are required with very low false alarms. Finally, the goal of 100% inspection of cargo inbound to the United States from the twenty largest international ports is an achievable goal with hardware costs in the area of that already spent on airport security.

[Evaluation of mass screening activity for cardiovascular disease risk factors in a rural environment].

PubMed

Boudreau, F

2001-01-01

The aim of this study was to evaluate the immediate and short-term impacts of a cardiovascular mass screening activity in a rural environment. A posttest-only control group design was used. Concerning the immediate impact, the results showed that the participants of the experimental group had, compared to the participants in the control group, a higher intention to participate regularly in physical activities and a higher intention to reduce their fat consumption. The participants' intention to stop smoking was not modified by the screening activity. After four months, the results revealed an increase in participation in physical activities and a decrease in fat consumption. The proportion of participants who smoked did not decrease. In conclusion, it is suggested that a cardiovascular mass screening activity such as the one performed in this study could be effective in motivating a population to adopt heart health-related behaviours. Others studies are necessary however to confirm the short-term impact of this type of activity on behaviour modification with regard to cardiovascular health.

Added value of shear-wave elastography for evaluation of breast masses detected with screening US imaging.

PubMed

Lee, Su Hyun; Chang, Jung Min; Kim, Won Hwa; Bae, Min Sun; Seo, Mirinae; Koo, Hye Ryoung; Chu, A Jung; Gweon, Hye Mi; Cho, Nariya; Moon, Woo Kyung

2014-10-01

To evaluate the additional value of shear-wave elastography (SWE) to B-mode ultrasonography (US) and to determine an appropriate guideline for the combined assessment of screening US-detected breast masses. This study was conducted with institutional review board approval, and written informed consent was obtained. From March 2010 to February 2012, B-mode US and SWE were performed in 159 US-detected breast masses before biopsy. For each lesion, Breast Imaging Reporting and Data System (BI-RADS) category on B-mode US images and the maximum stiffness color and elasticity values on SWE images were assessed. A guideline for adding SWE data to B-mode US was developed with the retrospective cohort to improve diagnostic performance in sensitivity and specificity and was validated in a distinct prospective cohort of 207 women prior to biopsy. Twenty-one of 159 masses in the development cohort and 12 of 207 breast masses in the validation cohort were malignant. In the development cohort, when BI-RADS category 4a masses showing a dark blue color or a maximum elasticity value of 30 kPa or less on SWE images were downgraded to category 3, specificity increased from 9.4% (13 of 138) to 59.4% (82 of 138) and 57.2% (79 of 138) (P < .001), respectively, without loss in sensitivity (100% [21 of 21]). In the validation cohort, specificity increased from 17.4% (34 of 195) to 62.1% (121 of 195) and 53.3% (104 of 195) (P < .001) respectively, without loss in sensitivity (91.7% [11 of 12]). The addition of SWE to B-mode US improved diagnostic performance with increased specificity for screening US-detected breast masses. BI-RADS category 4a masses detected at US screening that showed a dark blue color or a maximum elasticity value of 30 kPa or less on SWE images can be safely followed up instead of performing biopsy. © RSNA, 2014.

Development of a new screening method for the detection of antibiotic residues in muscle tissues using liquid chromatography and high resolution mass spectrometry with a LC-LTQ-Orbitrap instrument.

PubMed

Hurtaud-Pessel, D; Jagadeshwar-Reddy, T; Verdon, E

2011-10-01

A liquid chromatography-high resolution mass spectrometry (LC-HRMS) method was developed for screening meat for a wide range of antibiotics used in veterinary medicine. Full-scan mode under high resolution mass spectral conditions using an LTQ-Orbitrap mass spectrometer with resolving power 60,000 full width at half maximum (FWHM) was applied for analysis of the samples. Samples were prepared using two extraction protocols prior to LC-HRMS analysis. The scope of the method focuses on screening the following main families of antibacterial veterinary drugs: penicillins, cephalosporins, sulfonamides, macrolides, tetracyclines, aminoglucosides and quinolones. Compounds were successfully identified in spiked samples from their accurate mass and LC retention times from the acquired full-scan chromatogram. Automated data processing using ToxId software allowed rapid treatment of the data. Analyses of muscle tissues from real samples collected from antibiotic-treated animals was carried out using the above methodology and antibiotic residues were identified unambiguously. Further analysis of the data for real samples allowed the identification of the targeted antibiotic residues but also non-targeted compounds, such as some of their metabolites.

Broad screening of illicit ingredients in cosmetics using ultra-high-performance liquid chromatography-hybrid quadrupole-Orbitrap mass spectrometry with customized accurate-mass database and mass spectral library.

PubMed

Meng, Xianshuang; Bai, Hua; Guo, Teng; Niu, Zengyuan; Ma, Qiang

2017-12-15

Comprehensive identification and quantitation of 100 multi-class regulated ingredients in cosmetics was achieved using ultra-high-performance liquid chromatography (UHPLC) coupled with hybrid quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS). A simple, efficient, and inexpensive sample pretreatment protocol was developed using ultrasound-assisted extraction (UAE), followed by dispersive solid-phase extraction (dSPE). The cosmetic samples were analyzed by UHPLC-Q-Orbitrap HRMS under synchronous full-scan MS and data-dependent MS/MS (full-scan MS 1 /dd-MS 2 ) acquisition mode. The mass resolution was set to 70,000 FWHM (full width at half maximum) for full-scan MS 1 and 17,500 FWHM for dd-MS 2 stage with the experimentally measured mass deviations of less than 2ppm (parts per million) for quasi-molecular ions and 5ppm for characteristic fragment ions for each individual analyte. An accurate-mass database and a mass spectral library were built in house for searching the 100 target compounds. Broad screening was conducted by comparing the experimentally measured exact mass of precursor and fragment ions, retention time, isotopic pattern, and ionic ratio with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. The developed methodology was evaluated and validated in terms of limits of detection (LODs), limits of quantitation (LOQs), linearity, stability, accuracy, and matrix effect. The UHPLC-Q-Orbitrap HRMS approach was applied for the analysis of 100 target illicit ingredients in 123 genuine cosmetic samples, and exhibited great potential for high-throughput, sensitive, and reliable screening of multi-class illicit compounds in cosmetics. Copyright © 2017 Elsevier B.V. All rights reserved.

About the singular behavior of the ionic condensation of sodium chondroitin sulfate: Conductivity study in water and water dioxane mixture

NASA Astrophysics Data System (ADS)

M'halla, Jalel; Besbes, Rafik; Bouazzi, Ramzi; Boughammoura, Sondes

2006-01-01

In this work, we generalized the (Bjerrum-Debye-Fuoss-MSA) double layer model to an ellipsoidal polyion (chondroitin sulfate) of (∣ Zs∣ e) structural charge, Ls structural length, R minor axe and ( R2 + L2/4) 1/2 major axe. With L ⩽ Ls. Na + counter ions are distributed on the contact (or condensed) layer and on the Debye layer (ionic atmosphere). Both layers are ellipsoidal equipotentials of, respectively, R and d minor axes and are concentric to the polyion. With d = ( R + 1/2 Γ), Γ is the Debye-MSA screen parameter. The equilibrium distribution of Na + ions is derived from a "two states" statistical approach, leading to a general implicit expression for the rate of condensation (1 - α). The generality of this formula results from the fact that it takes into account the finite size of the polyion ( L ≠ ∞ and R ≠ 0) and allows to calculate α for different conformations of the polyion: (ellipsoidal L ≠ 0, cylindrical: L = Ls, spherical: L → 0, and Manning's model: RL-1 → 0). The main conclusion of this model is that, α obeys to the Ostwald's principle of dilution ( α → 1 when CNa+ → 0). This result is contrary to Manning's theory, for which α is a constant αM independent on the concentration Ci: αM = bS/(∣ Zi∣ Lb), with bS = Ls/∣ Zs∣ and Lb = e2/( ɛkT) is the Bjerrum length. However, our analysis shows that the rate of variation: (∂ α/∂ Ci) in a given range of concentration, depends on the structural parameter bS. Indeed, the critical Manning condition ( α-1αM = 1, ⇒(∂ α/∂ Ci) ≈ 0), is compatible with the general following "rod-like model" approximation: (1-α)≈|Zi|(πbS)[4πZi2Lb][αCiR2];withbS″=αM-1 only for some peculiar values of bS and Lb (i.e., dielectric constant: ɛ). In water at 25 °C ( ɛ = 78.3), this singular behavior occurs for a range of a relative low or moderate concentration for some polyelectrolytes of bS structural parameter of about 5.8 Å. This is the case of sodium chondroitin sulfate in water ( bS = 5.72 Å). The addition of dioxane increases Lb, consequently, α is shifted from its Manning's value. In order to verify this dioxane effect, we have compared experimental equivalent conductibilities Λexp of sodium chondroitin sulfate in water ( no shift) and water-dioxane (60 wt%) mixture ( positive shift), to their theoretical values ΛM, ΛcthandΛsth corresponding, respectively, to the Manning, cylindrical and spherical models. This comparison allows also, to explain the conformation "chosen" by the polyion, in order to minimizing the friction effects (due to: viscosity; ionic and dielectric relaxations) and therefore, to optimize its mobility by the shift of its rate of ionic condensation α.

Screening of lysosomal storage disorders: application of the online trapping-and-cleanup liquid chromatography/mass spectrometry method for mucopolysaccharidosis I.

PubMed

Ombrone, Daniela; Malvagia, Sabrina; Funghini, Silvia; Giocaliere, Elisa; Della Bona, Maria Luisa; Forni, Giulia; De Luca, Alessio; Villanelli, Fabio; Casetta, Bruno; Guerrini, Renzo; la Marca, Giancarlo

2013-01-01

In recent years, new treatments have become available to treat some lysosomal storage disorders (LSDs) and many studies suggest that there is a benefit with starting therapy early. Newborn screening should detect diseases early enough for prompt treatment. Some countries include additional conditions, such as some LSDs, into their newborn screening panels. Mucopolysaccharidosis Type I (MPS I) is an autosomal recessive disorder caused by the deficiency of α-L-iduronidase (IDUA) activity. Currently, enzyme replacement therapy (ERT) or bone marrow transplantation is available and this has raised a growing interest for the development of a newborn screening test. In 2009, we reported a new fast and simplified tandem mass spectrometry-based method for quantifying five enzyme activities on dried blood spots. Here, we describe the inclusion of IDUA activity determination for the simultaneous detection of six lysosomal storage diseases. We have defined reference normal ranges by testing 680 healthy newborns and 240 adults. The assay was checked through three confirmed MPS I patients whose IDUA activity was below the normal range. Reproducibility of the assays has been established by assessing the intra-day and inter-day assay imprecisions. This quick assay has been devised to be implemented in newborn screening by liquid chromatography tandem mass spectrometry.

Validation of a nutrition risk screening tool for children and adolescents with cystic fibrosis ages 2-20 years.

PubMed

McDonald, Catherine M

2008-04-01

According to the 2002 Cystic Fibrosis (CF) Foundation nutrition consensus report, children with CF should grow normally. Cross-sectional data from the foundation's patient registry concluded that a body mass index at or greater than the 50th percentile is associated with better lung function. A consistent, evidence-based screening process can identify those individuals with CF having nutrition risk factors associated with a decrease in pulmonary function, target early intervention, and prevent further decline. A tool for screening nutrition risk is described to identify those children with CF who would benefit from more extensive nutrition intervention. The proposed screening tool is a risk-based classification system with 3 categories: weight gain, height velocity, and body mass index. The CF Foundation recommendations regarding these parameters are incorporated, with risk points assigned when minimum body mass index, weight gain, and/or height gain standards are unmet. An interrater measure of agreement determined a satisfactory level of reliability (kappa = 0.85). Patient records (n = 85) were reviewed to determine nutrition status category (no risk or at risk) of this tool compared with the CF Foundation 2002 Nutrition Consensus, yielding sensitivity and specificity at 84% and 75%, respectively. A second comparison was made with combined, independent nutrition risk factors not included in the screening tool. The sensitivity and specificity of the screening tool compared with the combined risk factors were 86% and 78%, respectively. This tool for screening nutrition risk for CF is reliable and valid, with consistent, reproducible results, free from subject or observer bias.

Mammographic findings of women recalled for diagnostic work-up in digital versus screen-film mammography in a population-based screening program.

PubMed

Lipasti, Seppo; Anttila, Ahti; Pamilo, Martti

2010-06-01

Limited information is available concerning differences in the radiological findings of women recalled for diagnostic work-up in digital mammography (DM) versus screen-film mammography (SFM) screening. To compare the radiological findings, their positive predictive values (PPVs) for cancer and other process indicators of DM screening performed by computed radiography (CR) technology and SFM screening in a population-based program. The material consisted of women, 50-59 years of age, who were invited for screening: 30 153 women with DM in 2007-2008 and 32 939 women with SFM in 1999-2000. The attendance rate was 77.7% (23 440) in the DM arm and 83.8% (27 593) in the SFM arm. In the DM arm, 1.71% of those screened (401) and in the SFM arm 1.59% (438) were recalled for further work-up. The images resulting in the recall were classified as: 1) tumor-like mass, 2) parenchymal distortion/asymmetry, 3) calcifications, and 4) combination of mass and calcifications. The distributions of the various radiological findings and their PPVs for cancer were compared in both study groups. The recall rates, cancer detection rates, test specificities, and PPVs of the DM and SFM groups were also compared. Women were recalled for diagnostic work-up most often due to tumor-like mass. It was more common in SFM (1.08% per woman screened) than in DM (0.93%). The second most common finding was parenchymal distortion and asymmetry, more often in DM (0.58%) than in SFM (0.37%). Calcifications were the third most common finding. DM exposed calcifications more often (0.49%) than SFM (0.26%). The PPVs for cancer of the recalls were higher in DM than in SFM in all subgroups of radiological findings. The test specificities were similar (DM 98.9%, SFM 98.8%). Significantly more cancers were detected by DM (cancer detection rate 0.623% per woman screened, n=146) than by SFM (cancer detection rate 0.406% per woman screened, n=112). The PPVs for cancer of all recalls for diagnostic work-up were significantly higher in DM (36%) than in SFM (26%). In DM women were recalled for diagnostic work-up more often for calcifications, parenchymal distortions, and asymmetries than in SFM. In the case of tumor-like masses, more women were recalled in SFM. DM detected more cancers than SFM, and the PPVs for cancer were higher in DM than in SFM in all subgroups of radiological findings.

Screening for trace explosives by AccuTOF™-DART®: an in-depth validation study.

PubMed

Sisco, Edward; Dake, Jeffrey; Bridge, Candice

2013-10-10

Ambient ionization mass spectrometry is finding increasing utility as a rapid analysis technique in a number of fields. In forensic science specifically, analysis of many types of samples, including drugs, explosives, inks, bank dye, and lotions, has been shown to be possible using these techniques [1]. This paper focuses on one type of ambient ionization mass spectrometry, Direct Analysis in Real Time Mass Spectrometry (DART-MS or DART), and its viability as a screening tool for trace explosives analysis. In order to assess viability, a validation study was completed which focused on the analysis of trace amounts of nitro and peroxide based explosives. Topics which were studied, and are discussed, include method optimization, reproducibility, sensitivity, development of a search library, discrimination of mixtures, and blind sampling. Advantages and disadvantages of this technique over other similar screening techniques are also discussed. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Rapid screening of pharmaceutical drugs using thermal desorption - SALDI mass spectrometry

NASA Astrophysics Data System (ADS)

Grechnikov, A. A.; Kubasov, A. E.; Georgieva, V. B.; Borodkov, A. S.; Nikiforov, S. M.; Simanovsky, Ya O.; Alimpiev, S. S.

2012-12-01

A novel approach to the rapid screening of pharmaceutical drugs by surface assisted laser desorption-ionization (SALDI) mass spectrometry with the rotating ball interface coupled with temperature programmed thermal desorption has been developed. Analytes were thermally desorbed and deposited onto the surface of amorphous silicon substrate attached to the rotating ball. The ball was rotated and the deposited analytes were analyzed using SALDI. The effectiveness of coupling SALDI mass spectrometry with thermal desorption was evaluated by the direct and rapid analysis of tablets containing lidocaine, diphenhydramine and propranolol without any sample pretreatment. The overall duration of the screening procedure was 30÷40 sec. Real urine samples were studied for drug analysis. It is shown that with simple preparation steps, urine samples can be quantitatively analyzed using the proposed technique with the detection limits in the range of 0.2÷0.5 ng/ml.

First-Principles Study of Structural, Electronic, Optical, and Thermal Properties of BeSiSb2 and MgSiSb2

NASA Astrophysics Data System (ADS)

Benlamari, S.; Boukhtouta, M.; Taïri, L.; Meradji, H.; Amirouche, L.; Ghemid, S.

2018-03-01

Structural, electronic, optical, and thermal properties of ternary II-IV-V2 (BeSiSb2 and MgSiSb2) chalcopyrite semiconductors have been calculated using the full-potential linearized augmented plane wave scheme␣in the generalized gradient approximation. The optimized equilibrium structural parameters ( a, c, and u) are in good agreement with theoretical results obtained using other methods. The band structure and density of states reveal that BeSiSb2 has an indirect (Γ-Z) bandgap of about 0.61 eV, whereas MgSiSb2 has a direct (Γ-Γ) bandgap of 0.80 eV. The dielectric function, refractive index, and extinction coefficient were calculated to investigate the optical properties, revealing that BeSiSb2 and MgSiSb2 present very weak birefringence. The temperature dependence of the volume, bulk modulus, Debye temperature, and heat capacities ( C v and C p) was predicted using the quasiharmonic Debye model at different pressures. Significant differences in properties are observed at high pressure and high temperature. We predict that, at 300 K and 0 GPa, the heat capacity at constant volume C v, heat capacity at constant pressure C P, Debye temperature θ D, and Grüneisen parameter γ will be about 94.91 J/mol K, 98.52 J/mol K, 301.30 K, and 2.11 for BeSiSb2 and about 96.08 J/mol K, 100.47 J/mol K, 261.38 K, and 2.20 for MgSiSb2, respectively.

Redshift of the Heα emission line of He-like ions under a plasma environment

NASA Astrophysics Data System (ADS)

Fang, T. K.; Wu, C. S.; Gao, X.; Chang, T. N.

2017-11-01

By carefully following the spatial and temporal criteria of the Debye-Hückel (DH) approximation, we present a detailed theoretical study on the redshifts of the spectroscopically isolated Heα lines corresponding to the 1 s 2 p 1P →1 s21S emission from two-electron ions embedded in external dense plasma. We first focus our study on the ratio R =Δ ωα/ωo between the redshift Δ ωα due to the external plasma environment and the energy ωo of the Heα line in the absence of the plasma. Interestingly, the result of our calculation shows that this ratio R turns out to vary as a nearly universal function of a reduced Debye length λD(Z ) =(Z -1 ) D . Since the ratio R dictates the necessary energy resolution for a quantitative measurement of the redshifts and, at the same time, the Debye length D is linked directly to the plasma density and temperature, the dependence of R on D should help to facilitate the potential experimental efforts for a quantitative measurement of the redshifts for the Heα line of the two-electron ions. In addition, our study has led to a nearly constant redshift Δ ωα at a given D for all He-like ions with Z between 5 and 18 based on our recent critical assessment of the applicability of the DH approximation to atomic transitions. These two general features, if confirmed by observation, would offer a viable and easy alternative in the diagnostic efforts of the dense plasma.

Calculation of NaCl, KCl and LiCl Salts Activity Coefficients in Polyethylene Glycol (PEG4000)-Water System Using Modified PHSC Equation of State, Extended Debye-Hückel Model and Pitzer Model

NASA Astrophysics Data System (ADS)

Marjani, Azam

2016-07-01

For biomolecules and cell particles purification and separation in biological engineering, besides the chromatography as mostly applied process, aqueous two-phase systems (ATPS) are of the most favorable separation processes that are worth to be investigated in thermodynamic theoretically. In recent years, thermodynamic calculation of ATPS properties has attracted much attention due to their great applications in chemical industries such as separation processes. These phase calculations of ATPS have inherent complexity due to the presence of ions and polymers in aqueous solution. In this work, for target ternary systems of polyethylene glycol (PEG4000)-salt-water, thermodynamic investigation for constituent systems with three salts (NaCl, KCl and LiCl) has been carried out as PEG is the most favorable polymer in ATPS. The modified perturbed hard sphere chain (PHSC) equation of state (EOS), extended Debye-Hückel and Pitzer models were employed for calculation of activity coefficients for the considered systems. Four additional statistical parameters were considered to ensure the consistency of correlations and introduced as objective functions in the particle swarm optimization algorithm. The results showed desirable agreement to the available experimental data, and the order of recommendation of studied models is PHSC EOS > extended Debye-Hückel > Pitzer. The concluding remark is that the all the employed models are reliable in such calculations and can be used for thermodynamic correlation/predictions; however, by using an ion-based parameter calculation method, the PHSC EOS reveals both reliability and universality of applications.

Order parameters from image analysis: a honeycomb example

NASA Astrophysics Data System (ADS)

Kaatz, Forrest H.; Bultheel, Adhemar; Egami, Takeshi

2008-11-01

Honeybee combs have aroused interest in the ability of honeybees to form regular hexagonal geometric constructs since ancient times. Here we use a real space technique based on the pair distribution function (PDF) and radial distribution function (RDF), and a reciprocal space method utilizing the Debye-Waller Factor (DWF) to quantify the order for a range of honeycombs made by Apis mellifera ligustica. The PDFs and RDFs are fit with a series of Gaussian curves. We characterize the order in the honeycomb using a real space order parameter, OP 3 , to describe the order in the combs and a two-dimensional Fourier transform from which a Debye-Waller order parameter, u, is derived. Both OP 3 and u take values from [0, 1] where the value one represents perfect order. The analyzed combs have values of OP 3 from 0.33 to 0.60 and values of u from 0.59 to 0.69. RDF fits of honeycomb histograms show that naturally made comb can be crystalline in a 2D ordered structural sense, yet is more ‘liquid-like’ than cells made on ‘foundation’ wax. We show that with the assistance of man-made foundation wax, honeybees can manufacture highly ordered arrays of hexagonal cells. This is the first description of honeycomb utilizing the Debye-Waller Factor, and provides a complete analysis of the order in comb from a real-space order parameter and a reciprocal space order parameter. It is noted that the techniques used are general in nature and could be applied to any digital photograph of an ordered array.

High impact technologies for natural products screening.

PubMed

Koehn, Frank E

2008-01-01

Natural products have historically been a rich source of lead molecules in drug discovery. However, natural products have been de-emphasized as high throughput screening resources in the recent past, in part because of difficulties in obtaining high quality natural products screening libraries, or in applying modern screening assays to these libraries. In addition, natural products programs based on screening of extract libraries, bioassay-guided isolation, structure elucidation and subsequent production scale-up are challenged to meet the rapid cycle times that are characteristic of the modern HTS approach. Fortunately, new technologies in mass spectrometry, NMR and other spectroscopic techniques can greatly facilitate the first components of the process - namely the efficient creation of high-quality natural products libraries, bimolecular target or cell-based screening, and early hit characterization. The success of any high throughput screening campaign is dependent on the quality of the chemical library. The construction and maintenance of a high quality natural products library, whether based on microbial, plant, marine or other sources is a costly endeavor. The library itself may be composed of samples that are themselves mixtures - such as crude extracts, semi-pure mixtures or single purified natural products. Each of these library designs carries with it distinctive advantages and disadvantages. Crude extract libraries have lower resource requirements for sample preparation, but high requirements for identification of the bioactive constituents. Pre-fractionated libraries can be an effective strategy to alleviate interferences encountered with crude libraries, and may shorten the time needed to identify the active principle. Purified natural product libraries require substantial resources for preparation, but offer the advantage that the hit detection process is reduced to that of synthetic single component libraries. Whether the natural products library consists of crude or partially fractionated mixtures, the library contents should be profiled to identify the known components present - a process known as dereplication. The use of mass spectrometry and HPLC-mass spectrometry together with spectral databases is a powerful tool in the chemometric profiling of bio-sources for natural product production. High throughput, high sensitivity flow NMR is an emerging tool in this area as well. Whether by cell based or biomolecular target based assays, screening of natural product extract libraries continues to furnish novel lead molecules for further drug development, despite challenges in the analysis and prioritization of natural products hits. Spectroscopic techniques are now being used to directly screen natural product and synthetic libraries. Mass spectrometry in the form of methods such as ESI-ICRFTMS, and FACS-MS as well as NMR methods such as SAR by NMR and STD-NMR have been utilized to effectively screen molecular libraries. Overall, emerging advances in mass spectrometry, NMR and other technologies are making it possible to overcome the challenges encountered in screening natural products libraries in today's drug discovery environment. As we apply these technologies and develop them even further, we can look forward to increased impact of natural products in the HTS based drug discovery.

Dipole Relaxation in an Electric Field.

ERIC Educational Resources Information Center

Neumann, Richard M.

1980-01-01

Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)

Systematic screening and characterization of flavonoid glycosides in Carthamus tinctorius L. by liquid chromatography/UV diode-array detection/electrospray ionization tandem mass spectrometry.

PubMed

Jin, Yu; Xiao, Yuan-sheng; Zhang, Fei-fang; Xue, Xing-ya; Xu, Qing; Liang, Xin-miao

2008-02-13

The traditional Chinese medicine (TCM) is a complex system, which always consists of numerous compounds with significant difference in the content and physical and chemical properties. In this paper, a screening method based on target molecular weights was developed to characterize the flavonoid glycosides in the flower of Carthamus tinctorius L. The screening tables of aglycone and glycan were designed, respectively, in order to select and combine freely. The multiple reaction monitoring (MRM) scan mode with higher sensitivity and selectivity was adopted in the screening, which benefit the characterization for the minor components. Seventy-seven flavonoid glycosides were screened out finally, and their structures were characterized by tandem mass spectrometric method in both positive and negative ion modes. The glycosylation mode, aglycone, sequence and/or the interglycosidic linkages of the glycan portion and glycosylation position were elucidated by the fragmentation rule in the MS. Numerous compounds screened out with this method showed the structure variety in secondary plant metabolites, and the purposeful screening systemically and subsequent structure characterization offered more information about the chemical constitutions of TCM.

Is School-Based Height and Weight Screening of Elementary Students Private and Reliable?

ERIC Educational Resources Information Center

Stoddard, Sarah A.; Kubik, Martha Y.; Skay, Carol

2008-01-01

The Institute of Medicine recommends school-based body mass index (BMI) screening as an obesity prevention strategy. While school nurses have provided height/weight screening for years, little has been published describing measurement reliability or process. This study evaluated the reliability of height/weight measures collected by school nurses…

Sickle Cell Screening: Medical, Legal, Ethical, Psychological and Social Problems; A Sickle Cell Crisis.

ERIC Educational Resources Information Center

Bowman, James E.

In recent years, sickle cell screening programs have been initiated by community groups, health centers, hospitals, medical schools, health departments, school systems, city and State governments, various branches of the Federal Government, fraternal and social clubs, and other organizations. Problems have resulted from mass sickle cell screening,…

10 CFR 960.3-2-1 - Site screening for potentially acceptable sites.

Code of Federal Regulations, 2010 CFR

2010-01-01

... POTENTIAL SITES FOR A NUCLEAR WASTE REPOSITORY Implementation Guidelines § 960.3-2-1 Site screening for... first repository, the process shall begin with site-screening activities that consider large land masses... repositories, the Secretary shall first identify the State within which the site is located in a decision-basis...

Screening of polar components of petroleum products by electrospray ionization mass spectrometry

USGS Publications Warehouse

Rostad, Colleen E.

2005-01-01

The polar components of fuels may enable differentiation between fuel types or commercial fuel sources. Screening for these components in the hydrocarbon product is difficult due to their very low concentrations in such a complex matrix. Various commercial fuels from several sources were analyzed by flow injection analysis/electrospray ionization/mass spectrometry without extensive sample preparation, separation, or chromatography. This technique enabled screening for unique polar components at very low concentrations in commercial hydrocarbon products. This analysis was then applied to hydrocarbon samples collected from the subsurface with a different extent of biodegradation or weathering. Although the alkane and isoprenoid portion had begun to biodegrade or weather, the polar components had changed little over time. Because these polar compounds are unique in different fuels, this screening technique can provide source information on hydrocarbons released into the environment.

An integrated high resolution mass spectrometric data acquisition method for rapid screening of saponins in Panax notoginseng (Sanqi).

PubMed

Lai, Chang-Jiang-Sheng; Tan, Ting; Zeng, Su-Ling; Qi, Lian-Wen; Liu, Xin-Guang; Dong, Xin; Li, Ping; Liu, E-Hu

2015-05-10

The aim of this study was to develop a convenient method without pretreatments for nontarget discovery of interested compounds. The segment and exposure strategy, coupled with two mass spectrometer data acquisition methods was firstly proposed for screening the saponins in extract of Panax notoginseng (Sanqi) via high-performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry (HPLC-QTOF/MS). By gradually removing certain major or moderate interference compounds, the developed segment and exposure strategy could significantly improve the detection efficiency for trace compounds. Moreover, the newly developed five-point screening approach based on a modified mass defect filter strategy and the visual isotopic ion technique was verified to be efficient and reliable in picking out the interested precursor ions. In total, 234 ginsenosides including 67 potential new ones were characterized or tentatively identified from the extract of Sanqi. Particularly, some unusual compounds containing the branched glycosyl group or new substituted acyl groups were firstly reported. The proposed integrated strategy held a strong promise for analyses of the complex mixtures. Copyright © 2015 Elsevier B.V. All rights reserved.

Detection and identification of 700 drugs by multi-target screening with a 3200 Q TRAP LC-MS/MS system and library searching.

PubMed

Dresen, S; Ferreirós, N; Gnann, H; Zimmermann, R; Weinmann, W

2010-04-01

The multi-target screening method described in this work allows the simultaneous detection and identification of 700 drugs and metabolites in biological fluids using a hybrid triple-quadrupole linear ion trap mass spectrometer in a single analytical run. After standardization of the method, the retention times of 700 compounds were determined and transitions for each compound were selected by a "scheduled" survey MRM scan, followed by an information-dependent acquisition using the sensitive enhanced product ion scan of a Q TRAP hybrid instrument. The identification of the compounds in the samples analyzed was accomplished by searching the tandem mass spectrometry (MS/MS) spectra against the library we developed, which contains electrospray ionization-MS/MS spectra of over 1,250 compounds. The multi-target screening method together with the library was included in a software program for routine screening and quantitation to achieve automated acquisition and library searching. With the help of this software application, the time for evaluation and interpretation of the results could be drastically reduced. This new multi-target screening method has been successfully applied for the analysis of postmortem and traffic offense samples as well as proficiency testing, and complements screening with immunoassays, gas chromatography-mass spectrometry, and liquid chromatography-diode-array detection. Other possible applications are analysis in clinical toxicology (for intoxication cases), in psychiatry (antidepressants and other psychoactive drugs), and in forensic toxicology (drugs and driving, workplace drug testing, oral fluid analysis, drug-facilitated sexual assault).

The current revolution in newborn screening: new technology, old controversies.

PubMed

Tarini, Beth A

2007-08-01

Newborn screening has provided a model of a successful public health screening program for the past 40 years. However, the history of newborn screening is not without controversy. Many of these controversies have been rekindled with the introduction of tandem mass spectrometry, a technology that has greatly increased our ability to detect potential disease in asymptomatic newborns. This review highlights the challenges raised by this and future technological advances as we strive to maintain the success of newborn screening in the 21st century.

Electrical transport, electrothermal transport, and effective electron mass in single-crystalline In2O3 films

NASA Astrophysics Data System (ADS)

Preissler, Natalie; Bierwagen, Oliver; Ramu, Ashok T.; Speck, James S.

2013-08-01

A comprehensive study of the room-temperature electrical and electrothermal transport of single-crystalline indium oxide (In2O3) and indium tin oxide (ITO) films over a wide range of electron concentrations is reported. We measured the room-temperature Hall mobility μH and Seebeck coefficient S of unintentionally doped and Sn-doped high-quality, plasma-assisted molecular-beam-epitaxy-grown In2O3 for volume Hall electron concentrations nH from 7×1016 cm-3 (unintentionally doped) to 1×1021 cm-3 (highly Sn-doped, ITO). The resulting empirical S(nH) relation can be directly used in other In2O3 samples to estimate the volume electron concentration from simple Seebeck coefficient measurements. The mobility and Seebeck coefficient were modeled by a numerical solution of the Boltzmann transport equation. Ionized impurity scattering and polar optical phonon scattering were found to be the dominant scattering mechanisms. Acoustic phonon scattering was found to be negligible. Fitting the temperature-dependent mobility above room temperature of an In2O3 film with high mobility allowed us to find the effective Debye temperature (ΘD=700 K) and number of phonon modes (NOPML=1.33) that best describe the polar optical phonon scattering. The modeling also yielded the Hall scattering factor rH as a function of electron concentration, which is not negligible (rH≈1.4) at nondegenerate electron concentrations. Fitting the Hall-scattering-factor corrected concentration-dependent Seebeck coefficient S(n) for nondegenerate samples to the numerical solution of the Boltzmann transport equation and to widely used, simplified equations allowed us to extract an effective electron mass of m*=(0.30±0.03)me (with free electron mass me). The modeled mobility and Seebeck coefficient based on polar optical phonon and ionized impurity scattering describes the experimental results very accurately up to electron concentrations of 1019 cm-3, and qualitatively explains a mobility plateau or local maximum around 1020 cm-3. Ionized impurity scattering with doubly charged donors best describes the mobility in our unintentionally doped films, consistent with oxygen vacancies as unintentional shallow donors, whereas singly charged donors best describe our Sn-doped films. Our modeling yields a (phonon-limited) maximum theoretical drift mobility and Hall mobility of μ=190 cm2/Vs and μH=270 cm2/Vs, respectively. Simplified equations for the Seebeck coefficient describe the measured values in the nondegenerate regime using a Seebeck scattering parameter of r=-0.55 (which is consistent with the determined Debye temperature), and provide an estimate of the Seebeck coefficient to lower electron concentrations. The simplified equations fail to describe the Seebeck coefficient around the Mott transition (nMott=5.5×1018 cm-3) from nondegenerate to degenerate electron concentrations, whereas the numerical modeling accurately describes this region.

Radiologists' preferences for digital mammographic display. The International Digital Mammography Development Group.

PubMed

Pisano, E D; Cole, E B; Major, S; Zong, S; Hemminger, B M; Muller, K E; Johnston, R E; Walsh, R; Conant, E; Fajardo, L L; Feig, S A; Nishikawa, R M; Yaffe, M J; Williams, M B; Aylward, S R

2000-09-01

To determine the preferences of radiologists among eight different image processing algorithms applied to digital mammograms obtained for screening and diagnostic imaging tasks. Twenty-eight images representing histologically proved masses or calcifications were obtained by using three clinically available digital mammographic units. Images were processed and printed on film by using manual intensity windowing, histogram-based intensity windowing, mixture model intensity windowing, peripheral equalization, multiscale image contrast amplification (MUSICA), contrast-limited adaptive histogram equalization, Trex processing, and unsharp masking. Twelve radiologists compared the processed digital images with screen-film mammograms obtained in the same patient for breast cancer screening and breast lesion diagnosis. For the screening task, screen-film mammograms were preferred to all digital presentations, but the acceptability of images processed with Trex and MUSICA algorithms were not significantly different. All printed digital images were preferred to screen-film radiographs in the diagnosis of masses; mammograms processed with unsharp masking were significantly preferred. For the diagnosis of calcifications, no processed digital mammogram was preferred to screen-film mammograms. When digital mammograms were preferred to screen-film mammograms, radiologists selected different digital processing algorithms for each of three mammographic reading tasks and for different lesion types. Soft-copy display will eventually allow radiologists to select among these options more easily.

Rapid Screening and Characterization of Acetylcholinesterase Inhibitors from Yinhuang Oral Liquid Using Ultrafiltration-liquid Chromatography-electrospray Ionization Tandem Mass Spectrometry

PubMed Central

Zhang, Haomin; Guo, Yinan; Meng, Lingwen; Sun, Hui; Yang, Yinping; Gao, Ying; Sun, Jiaming

2018-01-01

Background: At present, approximately 17–25 million people in the world suffer from Alzheimer's disease (AD). The most efficacious and acceptable therapeutic drug clinically are the acetylcholinesterase inhibitors (AChEIs). Yinhuang oral liquid is a Chinese medicine preparation which contains AChEIs according to the literatures. However, no strategy has been presented for rapid screening and identification of AChEIs from Yinhuang oral liquid. Objective: To develop a method for rapid screening and identification of AChEIs from Yinhuang oral liquid using ultrafiltration–liquid chromatography–electrospray ionization tandem mass spectrometry (UF-LC-ESI-MS/MS). Materials and Methods: In this study, UF incubation conditions such as enzyme concentration, incubation time, and incubation temperature were optimized so as to get better screening results. The AChEIs from Yinhuang oral liquid were identified by high-performance liquid chromatography-ESI-MS and the improved Ellman method was used for the AChE inhibitory activity test in vitro. Results: The results showed that Yinhuang oral liquid can inhibit the activity of AChE. We screened and identified seven compounds with potential AChE inhibitory activity from Yinhuang oral liquid, which provided experimental basis for the treatment and prevention of AD. Conclusion: The current technique was used to directly screen the active ingredients with acetylcholinesterase inhibition from complex traditional Chinese medicine, which was simple, rapid, accurate, and suitable for high-throughput screening of AChEI from complex systems. SUMMARY A UF-LC-ESI-MS/MS method for rapid screening and identification of AChEIs from Yinhuang oral liquid was developedSeven compounds were screened and identified with potential AChE inhibitory activity from Yinhuang oral liquidIt provided experimental basis of Yinhuang oral liquid for the treating and preventing AD. Abbreviations used: (AD): Alzheimer's disease; (UF-LC-ESI-MS/MS): ultrafiltration–liquid chromatography–electrospray ionization tandem mass spectrometry; (AChEIs): acetylcholinesterase inhibitors. PMID:29720840

The shape dependence of chameleon screening

NASA Astrophysics Data System (ADS)

Burrage, Clare; Copeland, Edmund J.; Moss, Adam; Stevenson, James A.

2018-01-01

Chameleon scalar fields can screen their associated fifth forces from detection by changing their mass with the local density. These models are an archetypal example of a screening mechanism, and have become an important target for both cosmological surveys and terrestrial experiments. In particular there has been much recent interest in searching for chameleon fifth forces in the laboratory. It is known that the chameleon force is less screened around non-spherical sources, but only the field profiles around a few simple shapes are known analytically. In this work we introduce a numerical code that solves for the chameleon field around arbitrary shapes with azimuthal symmetry placed in a spherical vacuum chamber. We find that deviations from spherical symmetry can increase the chameleon acceleration experienced by a test particle, and that the least screened objects are those which minimize some internal dimension. For the shapes considered in this work, keeping the mass, density and background environment fixed, the accelerations due to the source varied by a factor of ~ 3.

Newborn screening by tandem mass spectrometry for glutaric aciduria type 1: a cost-effectiveness analysis.

PubMed

Pfeil, Johannes; Listl, Stefan; Hoffmann, Georg F; Kölker, Stefan; Lindner, Martin; Burgard, Peter

2013-10-17

Glutaric aciduria type I (GA-I) is a rare metabolic disorder caused by inherited deficiency of glutaryl-CoA dehydrogenase. Despite high prognostic relevance of early diagnosis and start of metabolic treatment as well as an additional cost saving potential later in life, only a limited number of countries recommend newborn screening for GA-I. So far only limited data is available enabling health care decision makers to evaluate whether investing into GA-I screening represents value for money. The aim of our study was therefore to assess the cost-effectiveness of newborn screening for GA-I by tandem mass spectrometry (MS/MS) compared to a scenario where GA-I is not included in the MS/MS screening panel. We assessed the cost-effectiveness of newborn screening for GA-I against the alternative of not including GA-I in MS/MS screening. A Markov model was developed simulating the clinical course of screened and unscreened newborns within different time horizons of 20 and 70 years. Monte Carlo simulation based probabilistic sensitivity analysis was used to determine the probability of GA-I screening representing a cost-effective therapeutic strategy. Within a 20 year time horizon, GA-I screening averts approximately 3.7 DALYs (95% CI 2.9 - 4.5) and about one life year is gained (95% CI 0.7 - 1.4) per 100,000 neonates screened initially . Moreover, the screening programme saves a total of around 30,682 Euro (95% CI 14,343 to 49,176 Euro) per 100,000 screened neonates over a 20 year time horizon. Within the limitations of the present study, extending pre-existing MS/MS newborn screening programmes by GA-I represents a highly cost-effective diagnostic strategy when assessed under conditions comparable to the German health care system.

Modelling magnetic reconnection events relevant for solar physics with the new Energy Conserving Moment Implicit Method

NASA Astrophysics Data System (ADS)

Boella, Elisabetta; Herrero-Gonzalez, Diego; Innocenti, Maria Elena; Bemporad, Alessandro; Lapenta, Giovanni

2017-04-01

Fully kinetic simulations of magnetic reconnection events in the solar environment are especially challenging due to the extreme range of spatial and temporal scales that characterises them. As one moves from the photosphere to the chromosphere and the corona, the temperature increases from sub eV to 10-100 eV, while the mass density decreases from 10-4 to 10-12 kg/m3 and further. The intrinsic scales of kinetic reconnection (inertial length and gyroradius) are tremendously smaller than the maximum resolution available in observations. Furthermore, no direct information is available on the size of reconnection regions, plasmoids and reconnection fronts, while observations suggest that the process can cascade down to very small scale te{Bemporad}. Resolving the electron and ion scales while simulating a sufficiently large domain is a great challenge facing solar modelling. An especially challenging aspect is the need to consider the Debye length. The very low temperature of the electrons and the large spatial and temporal scales make these simulations hard to implement within existing Particle in Cell (PIC) methods. The limit is the ratio of the grid spacing to the Debye length. PIC methods show good stability and energy conservation when the grid does not exceed the Debye length too much. Semi-implicit methods te{Brackbill, Langdon} improve on this point. Only the recently developed fully energy conserving implicit methods have solved the problem te{Markidis, Chen}, but at a high computational cost. Very recently, we have developed an efficient new semi-implicit algorithm, which has been proven to conserve energy exactly to machine precision te{Lapenta}. In this work, we illustrate the main steps that enabled this great breakthrough and report the implementation on a new massively parallel three dimensional PIC code, called ECsim te{Lapenta2}. The new approach is applied to the problem of reconnection in the solar environment. We compare results of a simple 2D configuration similar to the so-called GEM challenge for different ranges of electron temperature, density and magnetic field, relative to different distances from the photosphere, demonstrating the capability of the new code. Finally, we report on the first results (to the authors' knowledge) of realistic magnetic 3D reconnection simulations in the solar environment, considering a large domain sufficient to describe the interaction of large scale dynamics with the reconnection process. A. Bemporad, ApJ 689, 572 (2008). J.U. Brackbill and D.W. Forslund, J. Comput. Phys. 46, 271 (1982). A. Langdon et al., J. Comput. Phys. 51, 107 (1983). S. Markidis and G. Lapenta, J. Comput. Phys. 230, 7037 (2011). G. Chen et al., J. Comput. Phys. 230, 7018 (2011). G. Lapenta, arXiv preprint arXiv:1602.06326 (2016). G. Lapenta et al., arXiv preprint arXiv:1612.08289 (2016).