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Sample records for 3-4 day kelvin

  1. Unraveling nanoscale conduction and work function in a poly(3,4-ethylenedioxypyrrole)/carbon nanotube composite by Kelvin probe force microscopy and conducting atomic force microscopy

    Highlights: ► Counter ion effect on the nanoscale conduction of poly(3,4-ethylenedioxypyrrole) films. ► Local work function at nanometric spatial resolution by Kelvin probe force microscopy. ► Interconnected high current domains prevail in films with sulfonated carbon nanotubes. ► Enhanced redox activity and electrochromic contrast in carbon nanotube based films. ► Low work function of PEDOP/carbon nanotube film promotes uninhibited charge propagation. - Abstract: Poly(3,4-ethylenedioxypyrrole) or PEDOP films doped with triflate ions, dodecyl sulfate ions and benzyl sulfonate functionalized multiwalled carbon nanotubes (MWCNTs) have been synthesized by oxidative electropolymerization. The dynamic variation of local work function at the nanoscale has been followed by Kelvin probe force microscopy (KPFM) and the measure of heterogeneity of dopant distribution was assessed from the distinctive disparities in the current maps, using conductive atomic force microscopy (C-AFM). The surface potential profiles revealed a smaller work function for PEDOP-(MWCNT)SO3− film, and the current images showed a remarkably larger current sustaining capacity for this film, in contrast to PEDOP-CF3SO3− and PEDOP-C12H25)OSO3− films which, is a consequence of widespread interconnects between localized conducting domains of the polymer coated with carbon nanotubes. Functionalized nanotubes offer the prospect of conducting both electrons and ions, and therefore an almost seamless charge transport across PEDOP and (MWCNT)SO3− species is realized. Such an unhindered movement of charge is not realized in PEDOP films doped by the insulating triflate or dodecyl sulfate ions. Averaged point contact nanoscale I–V profiles confirmed this claim, as the PEDOP-(MWCNT)SO3− film showed carrier conductivity greater by four orders of magnitude, as compared to the PEDOP-CF3SO3− film. The enhanced electronic function and the reduced band gap of PEDOP-(MWCNT)SO3− film (0.19 eV) in

  2. Climatology of the ∼5-day Rossby and ∼6-day Kelvin waves seen in the SABER/TIMED temperatures (2002-2007)

    Complete text of publication follows. The presentation is focused on the global spatial (altitude and latitude) structure, seasonal and interannual variability of the ∼5-day Rossby (W1) and ∼6-day Kelvin (E1) waves derived from the SABER/TIMED temperature measurements for full 6 years (January 2002-December 2007). The latitude structure of the ∼5-day W1 wave is related to the gravest symmetric wave number 1 Rossby wave, i.e. the (1,1) mode. Its seasonal behavior is dominated by equinoctial amplifications; in the NH the wave amplifies in March-April and September, while in the SH - in March and November. The vertical structure of the ∼5-day Rossby wave amplitude revealed double-peaked maxima centered at ∼80-90 km in the mesosphere and ∼105-110 km in the lower thermosphere, as the lower thermospheric maximum is at least two times stronger than the mesospheric one. This is a vertically propagating wave from the stratosphere up to 120 km altitude with a mean vertical wavelength of ∼50-60 km. The ∼5-day Rossby wave at middle latitudes (40 deg) revealed some interannual variability and at least part of it is connected with the effect of QBO. The ∼6-day E1 wave is equatorially trapped wave located between 20 deg N and 20 deg S. Its seasonal behavior indicated some equinoctial and June solstice amplifications. The altitude structure of the ∼6-day Kelvin wave phase indicated that this is a vertically propagating wave up to 110 km altitude. The mean vertical wavelength in the stratosphere and mesosphere is ∼25 km, however above 95 km altitude the vertical wavelength shortened to 15 km. The ∼6-day Kelvin wave indicated significant SAO and QBO variability.

  3. PREFACE: Kelvin and Ireland

    Flood, Raymond; McCartney, Mark; Whitaker, Andrew

    2009-07-01

    Sir Joseph Larmor unveiling the Kelvin memorial in the Botanic Gardens, Belfast on a rainy day in 1913 Sir Joseph Larmor unveiling the Kelvin memorial in the Botanic Gardens, Belfast on a rainy day in 1913 © The Ulster Museum: Hogg collection William Thomson, later Lord Kelvin, was born in Belfast in 1824, and his family had lived near Ballynahinch in the north of Ireland, quite close to Belfast, from the seventeenth century. At the time of Kelvin's birth, James Thomson, his father, was Professor of Mathematics at the Belfast Royal Academical Institution (Inst). However, following the death of his wife in 1830, James took up a new position as Professor at the University of Glasgow, and he and his children moved there in 1832. Apart from three years studying at Cambridge, and a very brief period immediately afterwards travelling and teaching in Cambridge, Kelvin was to spend the rest of his life in Glasgow, where he occupied the Chair of Natural Philosophy (or Physics) for 53 years. The natural assumption might be that his birth in Ireland was irrelevant to Kelvin's life and work, and that the fine monument erected in his honour in Belfast's Botanic Gardens, which is pictured on the front cover of this volume, was more a demonstration of civic pride than a recognition of an aspect of Kelvin's life which was important to him. The purpose of the meeting was to demon strate that this was not the case, that, great Glaswegian as he undoubtedly became, Kelvin always delighted in the title of Irishman. The influence of his father, very much an Ulsterman, was immense, and Kelvin and his siblings were to follow his non-sectarian and reforming approach. Also important for Kelvin was his Christian upbringing, which began in Belfast, and his beliefs were to play a role of importance in his life and indeed in much of his most important work, in particular that on thermodynamics. Two of his siblings returned to Belfast and spent much of their lives there, and Kelvin was a

  4. Leapfrogging Kelvin waves

    Hietala, N; Salman, H; Barenghi, C F

    2016-01-01

    Two vortex rings can form a localized configuration whereby they continually pass through one another in an alternating fashion. This phenomenon is called leapfrogging. Using parameters suitable for superfluid helium-4, we describe a recurrence phenomenon that is similar to leapfrogging which occurs for two coaxial straight vortex filaments with the same Kelvin wave mode. For small amplitude Kelvin waves we demonstrate that our full Biot-Savart simulations closely follow predictions obtained from a simpified model that provides an analytical approximation developed for nearly parallel vortices. Our results are also relevant to thin-cored helical vortices in classical fluids.

  5. Pitfalls in Kelvin probe measurements

    We report on the interpretation of thickness-dependent surface potential profiles in insulators on metal substrates measured by Kelvin probe method. The electrical potentials are calculated within a self-consistent model taking both the conductive substrate and the insulator into account. It is shown that interpreting the Kelvin potentials for different layer thicknesses as the prevailing potential profile of a thick insulator film is generally wrong. Even more controversially, the reconstruction of the potential profile in a thick insulator layer on the basis of layer-thickness-dependent Kelvin measurements alone is per se impossible. This will be demonstrated exemplarily on the basis of doped and undoped organic films on conductive substrates.

  6. Lord Kelvin and Liberal Unionism

    Hutchison, Iain

    2009-04-01

    Kelvin had been a staunch Liberal until Gladstone's Irish Home Rule Bill of 1886 made him a Liberal Unionist. He believed the measure would damage Ireland's best interests and would create economic and social instability. He also rejected it on constitutional grounds. Concern for the position of Ulster's Protestants was, however, not a major issue for Kelvin. Between 1886 and 1890 he was the most prominent Liberal Unionist in the West of Scotland, and under his leadership, the party was highly effective in the region. It is likely that, to a certain extent, his peerage was a reward for his political work. After 1890, Kelvin became more of a party figurehead, while his views on many political issues drew him closer to those of the Conservatives.

  7. 3.4 Radiotherapy

    Kramer, H.-M.; Selbach, H.-J.; Vatnitsky, S.

    This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '3.4 Radiotherapy' of the Chapter '3 Dosimetry in Diagnostic Radiology and Radiotherapy' with the contents:

  8. Ultrasound estimation and FE analysis of elastic modulus of Kelvin foam

    Kim, Nohyu; Yang, Seung Yong [School of Mechatronics Engineering, Korea University of Technology and Education, Cheonan (Korea, Republic of)

    2016-02-15

    The elastic modulus of a 3D-printed Kelvin foam plate is investigated by measuring the acoustic wave velocity of 1 MHz ultrasound. An isotropic tetrakaidecahedron foam with 3 mm unit cell is designed and printed layer upon layer to fabricate a Kelvin foam plate of 14 mm thickness with a 3D CAD/printer using ABS plastic. The Kelvin foam plate is completely filled with paraffin wax for impedance matching, so that the acoustic wave may propagate through the porous foam plate. The acoustic wave velocity of the foam plate is measured using the time-of-flight (TOF) method and is used to calculate the elastic modulus of the Kelvin foam plate based on acousto-elasticity. Finite element method (FEM) and micromechanics is applied to the Kelvin foam plate to calculate the theoretical elastic modulus using a non-isotropic tetrakaidecahedron model. The predicted elastic modulus of the Kelvin foam plate from FEM and micromechanics model is similar, which is only 3-4% of the bulk material. The experimental value of the elastic modulus from the ultrasonic method is approximately twice as that of the numerical and theoretical methods because of the flexural deformation of the cell edges neglected in the ultrasonic method.

  9. Caustic graphene plasmons with Kelvin angle

    Shi, Xihang; Gao, Fei; Xu, Hongyi; Yang, Zhaoju; Zhang, Baile

    2015-01-01

    A century-long argument made by Lord Kelvin that all swimming objects have an effective Mach number of 3, corresponding to the Kelvin angle of 19.5 degree for ship waves, has been recently challenged with the conclusion that the Kelvin angle should gradually transit to the Mach angle as the ship velocity increases. Here we show that a similar phenomenon can happen for graphene plasmons. By analyzing the caustic wave pattern of graphene plasmons stimulated by a swift charged particle moving uniformly above graphene, we show that at low velocities of the charged particle, the caustics of graphene plasmons form the Kelvin angle. At large velocities of the particle, the caustics disappear and the effective semi-angle of the wave pattern approaches the Mach angle. Our study introduces caustic wave theory to the field of graphene plasmonics, and reveals a novel physical picture of graphene plasmon excitation during electron energy-loss spectroscopy measurement.

  10. Kelvin-Helmholtz instabilities with Godunov SPH

    Cha, Seung-Hoon; Inutsuka, Shu-Ichiro; Nayakshin, Sergei

    2009-01-01

    Numerical simulations for the non-linear development of Kelvin-Helmholtz instability in two different density layers have been performed with the particle-based method (Godunov SPH) developed by Inutsuka (2002). The Godunov SPH can describe the Kelvin-Helmholtz instability even with a high density contrast, while the standard SPH shows the absence of the instability across a density gradient (Agertz et al. 2007). The interaction of a dense blob with a hot ambient medium has been performed als...

  11. Kelvin wake pattern at large Froude numbers

    Darmon, Alexandre; Benzaquen, Michael; Raphaël, Elie

    2013-01-01

    Gravity waves generated by an object moving at constant speed at the water surface form a specific pattern commonly known as the Kelvin wake. It was proved by Lord Kelvin that such a wake is delimited by a constant angle $\\simeq 19.47^\\circ$. However a recent study by Rabaud and Moisy based on the observation of airborne images showed that the wake angle seems to decrease as the Froude number $Fr$ increases, scaling as $Fr^{-1}$ for large Froude numbers. To explain such observations the autho...

  12. Ship wakes: Kelvin or Mach angle?

    Rabaud, Marc; Moisy, Frédéric

    2013-05-24

    From the analysis of a set of airborne images of ship wakes, we show that the wake angles decrease as U(-1) at large velocities, in a way similar to the Mach cone for supersonic airplanes. This previously unnoticed Mach-like regime is in contradiction with the celebrated Kelvin prediction of a constant angle of 19.47° independent of the ship's speed. We propose here a model, confirmed by numerical simulations, in which the finite size of the disturbance explains this transition between the Kelvin and Mach regimes at a Froude number Fr=U/√[gL]~/=0.5, where L is the hull ship length. PMID:23745883

  13. Ship wakes: Kelvin or Mach angle?

    Rabaud, Marc

    2013-01-01

    From the analysis of a set of airborne images of ship wakes, we show that the wake angles decrease as $U^{-1}$ at large velocities, in a way similar to the Mach cone for supersonic airplanes. This previously unnoticed Mach-like regime is in contradiction with the celebrated Kelvin prediction of a constant angle of $19.47\\degree$ independent of the ship's speed. We propose here a model, confirmed by numerical simulations, in which the finite size of the disturbance explains this transition between the Kelvin and Mach regimes at a Froude number $Fr = U/\\sqrt{gL} \\simeq 0.5$, where $L$ is the hull ship length.

  14. Extended Kelvin theorem in relativistic magnetohydrodynamics

    Bekenstein, Jacob D.; Oron, Asaf

    2000-01-01

    We prove the existence of a generalization of Kelvin's circulation theorem in general relativity which is applicable to perfect isentropic magnetohydrodynamic flow. The argument is based on a new version of the Lagrangian for perfect magnetohydrodynamics. We illustrate the new conserved circulation with the example of a relativistic magnetohydrodynamic flow possessing three symmetries.

  15. Kelvin's Canonical Circulation Theorem in Hall Magnetohydrodynamics

    Shivamoggi, B K

    2016-01-01

    The purpose of this paper is to show that, thanks to the restoration of the legitimate connection between the current density and the plasma flow velocity in Hall magnetohydrodynamics (MHD), Kelvin's Circulation Theorem becomes valid in Hall MHD. The ion-flow velocity in the usual circulation integral is now replaced by the canonical ion-flow velocity.

  16. Periodic homogenization for Kelvin-Voigt viscoelastic media with a Kelvin-Voigt viscoelastic interphase

    Daridon, Loic; Licht, Christian; Orankitjaroen, Somsak; Pagano, Stéphane

    2016-01-01

    International audience We studied the effective behavior of a composite made of a periodic distribution of inclusions linked to a matrix by a very thin layer, with the three components being of linear Kelvin-Voigt viscoelastic type. The effective behavior, derived by a rigorous mathematical homogenization method, is not of Kelvin-Voigt type but instead involves an additional fading memory term. The influence of various parameters of the composite were numerically analyzed through a finite ...

  17. Radiochemistry days

    This document provides the 44 papers (transparencies used during the presentations and posters) presented at the Radiochemistry Days, held September 3-4, 1998 in Nantes, France. The main studied topics were problematic questions concerning the nuclear fuel cycle and in particular the management, storage of radioactive wastes and the environmental impact. (O.M.)

  18. Analysis of Kelvin Probe Operational Models

    Popescu, Eugeniu M.

    2011-01-01

    We present a study of several models on which Kelvin Probe instruments with flat and spherical tips rely for operation and for the determination of the contact potential difference. Using covariance analysis, we have investigated the precision limits of each model as imposed by the Cramer-Rao bound. Where the situation demanded, we have evaluated the bias introduced by the method in the estimation of the contact potential difference.

  19. Automatic kelvin probe compatible with ultrahigh vacuum

    Baikie, I.D.; Werf, van der, M.J.; Oerbekke, H.; Broeze, J.; Silfhout, van, A.

    1989-01-01

    This article describes a new type of in situ ultrahigh‐vacuum compatible kelvin probe based on a voice‐coil driving mechanism. This design exhibits several advantages over conventional mechanical feed‐through and (in situ) piezoelectric devices in regard to the possibility of multiple probe geometry, flexibility of probe geometry, amplitude of oscillation, and pure parallel vibration. Automatic setup and constant spacing features are achieved using a digital‐to‐analog converter (DAC) steered ...

  20. Heating a Plasma to 100 Million Kelvin

    Fröberg, Gunnar; Nygren, Thomas

    2014-01-01

    In this work techniques for heating the fusion reactor ITER to thermonuclear temperatures, over 100 million kelvin, is investigated. The temperature is numerically computed for different heating configurations. The heat leakage is modeled to occur only via diffusion. The diffusion is assumed to be a combination of Bohm and gyro-Bohm diffusion. Basic conditions for a fusion reactor has been studied. The power needed for the different heat sources for the plasma to ignite is computed. Plots of ...

  1. Kelvin-Helmholtz instabilities with Godunov SPH

    Cha, Seung-Hoon; Nayakshin, Sergei

    2009-01-01

    Numerical simulations for the non-linear development of Kelvin-Helmholtz instability in two different density layers have been performed with the particle-based method (Godunov SPH) developed by Inutsuka (2002). The Godunov SPH can describe the Kelvin-Helmholtz instability even with a high density contrast, while the standard SPH shows the absence of the instability across a density gradient (Agertz et al. 2007). The interaction of a dense blob with a hot ambient medium has been performed also. The Godunov SPH describes the formation and evolution of the fingers due to the combinations of Rayleigh-Taylor, Richtmyer-Meshkov, and Kelvin-Helmholtz instabilities. The blob test result coincides well with the results of the grid-based codes. An inaccurate handling of a density gradient in the standard SPH has been pointed out as the direct reason of the absence of the instabilities. An unphysical force happens at the density gradient even in a pressure equilibrium, and repulses particles from the initial density di...

  2. Kelvin Helmholtz Instability in Planetary Magnetospheres

    Johnson, Jay R.; Wing, Simon; Delamere, Peter A.

    2014-11-01

    Kelvin-Helmholtz instability plays a particularly important role in plasma transport at magnetospheric boundaries because it can control the development of a turbulent boundary layer, which governs the transport of mass, momentum, and energy across the boundary. Waves generated at the interface can also couple into body modes in the plasma sheet and inner magnetosphere where they can play an important role in plasma sheet transport and particle energization in the inner magnetosphere. Kinetic and electron-scale effects are important for the development of K-H instability, leading to secondary instabilities and plasma mixing. The development of vortices that entwine magnetosheath field lines with magnetospheric field lines also allows reconnection and the interchange of plasma blobs from open to closed field lines. Dawn-dusk asymmetries in Kelvin-Helmholtz development at planetary boundary layers may result from several effects including plasma corotation, kinetic effects, magnetic geometry, or asymmetric distribution of plasma. Examples are provided throughout the solar system illustrating the pervasive effects of the Kelvin-Helmholtz instability on plasma transport.

  3. N-(3,4-Dimethylphenylbenzamide

    B. Thimme Gowda

    2008-01-01

    Full Text Available The conformation of the NH bond in the structure of the title compound (N34DMPBA, C15H15NO, is anti to the meta-methyl substituent in the aniline ring, similar to that observed with respect to the meta-chloro substituent in N-(3,4-dichlorophenylbenzamide (N34DCPBA, but in contrast to the syn conformation observed with respect to the meta-methyl substituent in N-(3,4-dimethylphenylacetamide. The bond parameters in N34DMPBA are similar to those in N34DCPBA and other benzanilides. The molecules in N34DMPBA are packed into a column-like structure in the direction of the a axis through N—H...O hydrogen bonds.

  4. Kelvin probe’s stray capacitance and noise simulation

    Danyluk, S.; Dubanevich, A. V.; O. K. Gusev; A. I. Svistun; Tyavlovsky, A. K.; K. L. Tyavlovsky; R. I. Vorobey; A. L. Zharin

    2014-01-01

    Stray capacitance effects and their influence on Kelvin probe’s performance are studied using mathematical and computer simulation. Presence of metal surface, even grounded, in vicinity of vibrating Kelvin probe produces the additional stray signal of complex harmonic character. Mean value and amplitude of this stray signal depends mostly on the ratio of stray and measurement vibrating capacitors gaps d1/d0. The developed model can be used for theoretical analysis of Kelvin probe configuratio...

  5. Vertical propagation of baroclinic Kelvin waves along the west coast of India

    D Nethery; D Shankar

    2007-08-01

    A linear, continuously stratified ocean model is used to investigate vertical propagation of remotely forced, baroclinic Kelvin waves along the Indian west coast. The extent of vertical propagation over the length of the coast is found to be an increasing function of the forcing frequency. Simulations show that, over the length of the Indian west coast, vertical propagation is limited at annual and semi-annual periods, but significant at periods shorter than about 120 days. This has two major consequences. First, the depth of subsurface currents associated with these frequencies varies substantially along the coast. Second, baroclinic Kelvin waves generated in the Bay of Bengal at periods shorter than about 120 days have negligible influence on surface currents along the north Indian west coast.

  6. Equatorial atmospheric Kelvin waves during El Niño episodes and their effect on stratospheric QBO.

    Das, Uma; Pan, C J

    2016-02-15

    Equatorial atmospheric Kelvin waves are investigated during a positive El Niño Southern Oscillation (ENSO) episode using temperature data retrieved from GPS Radio Occultation (RO) observations of FORMOSAT-3/COSMIC during the period from August 2006 to December 2013. Enhanced Kelvin wave amplitudes are observed during the El Niño episode of 2009-2010 and it is also observed that these amplitudes correlate with the Niño 3.4 index and also with outgoing longwave radiation and trade wind index. This study indicates that the enhanced equatorial atmospheric Kelvin wave amplitudes might be produced by geophysical processes that were involved in the onset and development of the El Niño episode. Further, easterly winds above the tropopause during this period favored the vertically upward propagation of these waves that induced a fast descending westerly regime by the end of 2010, where the zero-wind line is observed to take only 5 months to descend from 10 to 50 hPa. The current study presents observational evidence of enhanced Kelvin wave amplitudes during El Niño that has affected the stratospheric quasi-biennial oscillation (QBO) through wave-mean flow interactions. Earlier El Niño episodes of 1987 and 1998 are also qualitatively investigated, using reanalysis data. It is found that there might have been an enhancement in the equatorial Kelvin wave amplitudes during almost all El Niño episodes, however, an effect of a fast descending westerly is observed in the QBO only when the ambient zonal winds in the lower stratosphere favor the upward propagation of the Kelvin waves and consequently they interact with the mean flow. This study indicates that the El Niño and QBO are not linearly related and wave mean flow interactions play a very important role in connecting these two geophysical phenomena. PMID:26771207

  7. High-resolution Kelvin probe microscopy in corrosion science: Scanning Kelvin probe force microscopy (SKPFM) versus classical scanning Kelvin probe (SKP)

    With the introduction of a Kelvin probe mode to atomic force microscopy, the so called scanning Kelvin probe force microscopy (SKPFM), the Kelvin probe technique finds application in a steadily increasing number of different fields, from corrosion science to microelectronics and biosciences. For many of these applications, high resolution is required as the relevant information lies in the sub-microscopic distribution of work functions or potentials, which explains the increasing interest in SKPFM. However, compared to the standard scanning Kelvin probe (SKP) technique SKPFM is prone to much more artefacts, which are often not taken into account in the interpretation of the results, as is also the case with the real physical nature of the measured data. A critical discussion of possible artefacts and on the interpretation of the data is presented in this paper, with the main focus on application in corrosion science

  8. CFD simulation of Kelvin-Helmholtz instability

    Kelvin-Helmholtz instability appears in stratified two-fluid flow at surface. When the relative velocity is higher than the critical relative velocity, the growth of waves occurs. The experiment of Thorpe [1] used as a benchmark in the present paper, is made in a rectangular glass tube filled with two immiscible fluids of various densities. We simulated the growth of instability with CFX-5.7 code and compared simulation with analytical solution. It was found that surface tension force, which stabilizes growth of waves, actually has a destabilizing effect in simulation, unless very small timestep and residual is used. In CFX code system of nonlinear Navier-Stokes equations is linearised and solved iterative in each timestep, until prescribed residual is achieved. On the other hand, simulation without surface tension force is more stable than analytical result predicts. (author)

  9. Automatic kelvin probe compatible with ultrahigh vacuum

    Baikie, I. D.; van der Werf, K. O.; Oerbekke, H.; Broeze, J.; van Silfhout, A.

    1989-05-01

    This article describes a new type of in situ ultrahigh-vacuum compatible kelvin probe based on a voice-coil driving mechanism. This design exhibits several advantages over conventional mechanical feed-through and (in situ) piezoelectric devices in regard to the possibility of multiple probe geometry, flexibility of probe geometry, amplitude of oscillation, and pure parallel vibration. Automatic setup and constant spacing features are achieved using a digital-to-analog converter (DAC) steered offset potential. The combination of very low driver noise pick-up and data-acquisition system (DAS) signal processing techniques results in a work function (wf ) resolution, under optimal conditions, of analysis techniques this design has numerous applications in surface studies, e.g., adsorption kinetics, sample topography and homogeneity, sputter profiles, etc. For semiconductor specimens the high wf resolution makes it eminently suitable for surface photovoltage (SPV) spectroscopy.

  10. KELVIN PROBE’S STRAY CAPACITANCE AND NOISE SIMULATION

    S. Danyluk

    2015-03-01

    Full Text Available Stray capacitance effects and their influence on Kelvin probe’s performance are studied using mathematical and computer simulation. Presence of metal surface, even grounded, in vicinity of vibrating Kelvin probe produces the additional stray signal of complex harmonic character. Mean value and amplitude of this stray signal depends mostly on the ratio of stray and measurement vibrating capacitors gaps d1/d0. The developed model can be used for theoretical analysis of Kelvin probe configuration and probe electrometer’s input circuit. 

  11. Ultrasonic Measurement of Elastic Modulus of Kelvin Foam

    Oh Sukwon

    2016-01-01

    Full Text Available Elastic modulus of 3D-printed Kelvin foam plate is investigated by measuring the acoustic wave velocity of 1 MHz ultrasound. An isotropic tetrakaidecahedron foam of 3 mm unit cell is designed and printed layer upon layer to fablicate a Kelvin foam plate of 14mm thickness by 3D CAD/printer using ABS plastic. The Kelvin foam plate is filled completely with paraffin wax for impedance matching, so that acoustic wave may propagate through the porous foam plate. The acoustic wave velocity of the foam plate is measured using the time-of-flight (TOF method to calculate the elastic modulus of the Kelvin foam plate based on acousto-elasticity.

  12. Observations of Equatorial Kelvin Wave Modes in FORMOSAT-3/COSMIC GPS RO Temperature Profiles

    Potula Sree Brahmanandam

    2010-01-01

    Full Text Available In this study, we analyze FORMOSAT-3/COSMIC (F3/C GPS radio occultation (RO derived temperature components for the period September 2006 to February 2008. Results show the presence of slow Kelvin waves (wave period > 10 days with higher zonal wavenumbers (either one or two in the upper troposphere and lower stratosphere (UTLS. The vertical wavelengths of these waves are found to be in the range of 5 - 12 km. The predominant Kelvin waves observed in the temperature fluctuations are in the altitude range between 15 and 28 km and centered on the tropical tropopause. The downward phase progression of these waves suggests that the derived waves are propagating upward, with the source region located at lower altitudes possibly due to tropical convective heating. The zonal winds retrieved using radiosonde observations over Singapore _ _ during this period show a periodicity of ~24 - 26 months in the stratosphere, and quasi-biennial oscillation (QBO characteristics with eastward zonal winds from March 2006 to May 2007 and westward winds from June 2007 to July 2008 respectively. Our results further show that the Kelvin wave characteristics are enhanced during the westward phase of QBO and diminish during the eastward phase, in line with the previous reported results. Furthermore, an examination of outgoing longwave radiation (OLR data shows that deep convection activity is developed episodically over the Indonesian archipelago during the observation period, thereby indicating that the Kelvin wave events observed in temperature fluctuations are either driven by convective activity (convectively coupled waves or by a broad spectrum of convective variability (free waves over the Indonesian region.

  13. Object size effect on the contact potential difference measured by scanning Kelvin probe method

    Polyakov, B.; Krutokhvostov, R.; Kuzmin, A.; Tamanis, E.; Muzikante, I.; Tale, I.

    2010-01-01

    Abstract Contact potential difference (CPD) was measured by macroscopic Kelvin probe instrument and scanning Kelvin probe microscope on Al, Ni and Pt on ITO substrates at ambient conditions. CPD values measured by scanning Kelvin probe microscope and macroscopic Kelvin probe are close within the error of about 10?30% for large studied objects, whereas scanning Kelvin probe microscope signal decreases, when the object size becomes smaller than 1.4 ?m. CPD and...

  14. A Validated Nonlinear Kelvin-Helmholtz Benchmark for Numerical Hydrodynamics

    Lecoanet, Daniel; Quataert, Eliot; Burns, Keaton J; Vasil, Geoffrey M; Oishi, Jeffrey S; Brown, Benjamin P; Stone, James M; O'Leary, Ryan M

    2015-01-01

    The nonlinear evolution of the Kelvin-Helmholtz instability is a popular test for code verification. To date, most Kelvin-Helmholtz problems discussed in the literature are ill-posed: they do not converge to any single solution with increasing resolution. This precludes comparisons among different codes and severely limits the utility of the Kelvin-Helmholtz instability as a test problem. The lack of a reference solution has led various authors to assert the accuracy of their simulations based on ad-hoc proxies, e.g., the existence of small-scale structures. This paper proposes well-posed Kelvin-Helmholtz problems with smooth initial conditions and explicit diffusion. We show that in many cases numerical errors/noise can seed spurious small-scale structure in Kelvin-Helmholtz problems. We demonstrate convergence to a reference solution using both Athena, a Godunov code, and Dedalus, a pseudo-spectral code. Problems with constant initial density throughout the domain are relatively straightforward for both cod...

  15. Multi-Scale Kelvin-Helmholtz Vortices Along Mercury's Magnetopause

    Gershman, D. J.; Raines, J. M.; Slavin, J. A.; Zurbuchen, T.; Sundberg, T.; Boardsen, S. A.; Anderson, B. J.; Korth, H.; Solomon, S. C.

    2014-12-01

    Data from the Fast Imaging Plasma Spectrometer (FIPS) and Magnetometer (MAG) sensors on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft have revealed stark differences in the Kelvin-Helmholtz (K-H) instability at Mercury compared with that at Earth. Although K-H vortices have been documented in planetary magnetospheres at the interface of magnetosheath and magnetospheric plasmas, such features at Mercury have been observed exclusively on the dusk side. From a survey of 58 K-H events, we find that these vortices have two distinct sets of behavior separated by the dusk terminator. On the dayside, the wave frequencies measured by MAG are nearly constant at ~0.025 Hz (~40 s period) under a variety of magnetosheath conditions, whereas the wave frequency measured on the nightside is correlated with the strength of the magnetic field near the magnetopause and matches the local Na+ gyrofrequency. The polarization of these waves inside the magnetosphere is distinctly right-handed, consistent with non-linear roll-up of K-H vortices as opposed to the left-handed ion-cyclotron wave mode. During these events, measurements from FIPS reveal strong (~30%) concentrations of Na+ in the nightside plasma sheet adjacent to the magnetopause. The keV energies of these planetary ions provide them with gyroradii that are ~500-1000 km, a scale at which a kinetic description of the K-H instability may be appropriate at Mercury. These data suggest a transition from fluid-scale to kinetic scale K-H vortices from day to night along Mercury's duskside magnetopause.

  16. A solution to the Kelvin wake angle controversy

    Darmon, Alexandre; Raphaël, Elie

    2014-01-01

    Gravity waves generated by an object moving at constant speed at the water surface form a specific pattern commonly known as the Kelvin wake. It was proved by Lord Kelvin that such a wake is delimited by a constant angle = 19.47{\\deg}. However a recent study by Rabaud and Moisy based on the observation of airborne images showed that the wake angle seems to decrease as the Froude number Fr increases, scaling as 1/Fr for large Froude numbers. To explain such observations the authors make the strong hypothesis that an object of size b cannot generate wavelengths larger than b thus leading to unrealistic pressure fields to model the object. With no need of such an assumption, we here analytically show that the angle corresponding to the maximum amplitude of the waves scales as 1/Fr for large Froude numbers whereas the Kelvin angle remains constant for all Fr.

  17. Characterization of interfacial bonding using a scanning Kelvin probe

    Interfaces play a crucial role in determining the ultimate properties and service life of coating and film materials. However, the characterization and measurement of interfacial bonding, in particular of the local strength, is difficult. The high sensitivity of the electron work function (EWF) to surface conditions has attracted increasing interest in applications of the Kelvin probing technique to investigate the mechanical behavior of materials. In this study, the Kelvin method was used to characterize the interfacial bond formed between pure copper and brass after annealing in argon gas. It was demonstrated that low EWF values, small EWF fluctuations, and narrow fluctuation ranges in interfacial regions corresponded to good bonding. Furthermore, there was a strong correlation between the EWF and the interfacial strength determined by the microindentation method using a universal microtribometer. The Kelvin probing technique could be a powerful tool for studying the local property and structure of interfaces

  18. AFM tip characterization by Kelvin probe force microscopy

    Reliable determination of the surface potential with spatial resolution is key for understanding complex interfaces that range from nanostructured surfaces to molecular systems to biological membranes. In this context, Kelvin probe force microscopy (KPFM) has become the atomic force microscope (AFM) method of choice for mapping the local electrostatic surface potential as it changes laterally due to variations in the surface work function or surface charge distribution. For reliable KPFM measurements, the influence of the tip on the measured electrostatic surface potential has to be understood. We show here that the mean Kelvin voltage can be used for a straightforward characterization of the electrostatic signature of neutral, charged and polar tips, the starting point for quantitative measurements and for tip-charge control for AFM manipulation experiments. This is proven on thin MgO(001) islands supported on Ag(001) and is supported by theoretical modeling, which shows that single ions or dipoles at the tip apex dominate the mean Kelvin voltage.

  19. Nuclear order in silver at pico-Kelvin temperature

    Siemensmeyer, K.; Clausen, K.N.; Lefmann, K.;

    1997-01-01

    Nuclear order in silver is observed by neutron diffraction at pico-Kelvin temperatures. The structure is a type-I antiferromagnet with critical field of 100 μT. The entropy-field phase diagram was determined using the spin-dependent absorption.......Nuclear order in silver is observed by neutron diffraction at pico-Kelvin temperatures. The structure is a type-I antiferromagnet with critical field of 100 μT. The entropy-field phase diagram was determined using the spin-dependent absorption....

  20. Nuclear order in silver at pico-Kelvin temperature

    Siemensmeyer, K.; Clausen, K.N.; Lefmann, K.; Lounasmaa, O.V.; Metz, A.; Nummila, K.K.; Rasmussen, F.B.; Steiner, M.; Tuoriniemi, J.T.; Vuorinen, R.T.

    Nuclear order in silver is observed by neutron diffraction at pico-Kelvin temperatures. The structure is a type-I antiferromagnet with critical field of 100 mu T. The entropy-field phase diagram was determined using the spin-dependent absorption.......Nuclear order in silver is observed by neutron diffraction at pico-Kelvin temperatures. The structure is a type-I antiferromagnet with critical field of 100 mu T. The entropy-field phase diagram was determined using the spin-dependent absorption....

  1. Nuclear order in silver at pico-Kelvin temperature

    Siemensmeyer, K.; Clausen, K.N.; Lefmann, K.;

    1997-01-01

    Nuclear order in silver is observed by neutron diffraction at pico-Kelvin temperatures. The structure is a type-I antiferromagnet with critical field of 100 mu T. The entropy-field phase diagram was determined using the spin-dependent absorption.......Nuclear order in silver is observed by neutron diffraction at pico-Kelvin temperatures. The structure is a type-I antiferromagnet with critical field of 100 mu T. The entropy-field phase diagram was determined using the spin-dependent absorption....

  2. Kelvin-Helmholtz and Buckling Instabilities for a Viscoelastic Liquid

    Keshavarz, Bavand

    2012-01-01

    In this fluid dynamics video prepared for the APS-DFD Gallery of Fluid Motion we study the Kelvin-Helmholtz instability for both Newtonian and viscoelastic jets. The nonlinear dynamics of the jet motion are slowed down by orders of magnitude using a synchronized strobe effect coupled with precise timing control of perturbation frequencies. Our results show that at high wave-numbers the imposed perturbations initially grow linearly with time and the jet axis remains straight while the Kelvin-Helmholtz wave amplitude grows and rolls up into bags that encapsulate the central jet within themselves. At low wave-numbers (long wave-lengths) the jet axis buckles under the action of viscous stresses and a coupling between the Kelvin-Helmholtz instability and bending of the jet leads to new concertina or chevron modes which grow with time as they move downstream. Addition of viscoelasticity to the jet leads to the pronounced inhibition of the Kelvin-Helmholtz instability as the jet perturbation amplitude grows and larg...

  3. Work function of colloidal semiconducting nanocrystals measured by Kelvin probe

    Colloidal suspensions of CdS, PbS, Cu2S, Ag2S and ZnO nanocrystals were prepared by chemical route in presence of organic capping ligands. The formation of nanocrystals was studied by using UV-visible absorption spectroscopy. Kelvin probe measurements of work function were performed on nanocrystals thin film on ITO (indium tin oxide) coated glass.

  4. 3,4-methylenedioxymethamphetamine (MDMA: current perspectives

    Meyer JS

    2013-11-01

    Full Text Available Jerrold S Meyer Department of Psychology, Neuroscience and Behavior Program, University of Massachusetts, Amherst, MA, USA Abstract: Ecstasy is a widely used recreational drug that usually consists primarily of 3,4-methylenedioxymethamphetamine (MDMA. Most ecstasy users consume other substances as well, which complicates the interpretation of research in this field. The positively rated effects of MDMA consumption include euphoria, arousal, enhanced mood, increased sociability, and heightened perceptions; some common adverse reactions are nausea, headache, tachycardia, bruxism, and trismus. Lowering of mood is an aftereffect that is sometimes reported from 2 to 5 days after a session of ecstasy use. The acute effects of MDMA in ecstasy users have been attributed primarily to increased release and inhibited reuptake of serotonin (5-HT and norepinephrine, along with possible release of the neuropeptide oxytocin. Repeated or high-dose MDMA/ecstasy use has been associated with tolerance, depressive symptomatology, and persisting cognitive deficits, particularly in memory tests. Animal studies have demonstrated that high doses of MDMA can lead to long-term decreases in forebrain 5-HT concentrations, tryptophan hydroxylase activity, serotonin transporter (SERT expression, and visualization of axons immunoreactive for 5-HT or SERT. These neurotoxic effects may reflect either a drug-induced degeneration of serotonergic fibers or a long-lasting downregulation in 5-HT and SERT biosynthesis. Possible neurotoxicity in heavy ecstasy users has been revealed by neuroimaging studies showing reduced SERT binding and increased 5-HT2A receptor binding in several cortical and/or subcortical areas. MDMA overdose or use with certain other drugs can also cause severe morbidity and even death. Repeated use of MDMA may lead to dose escalation and the development of dependence, although such dependence is usually not as profound as is seen with many other drugs of abuse

  5. The metabolite 3,4,3',4'-tetrachloroazobenzene (TCAB) exerts a higher ecotoxicity than the parent compounds 3,4-dichloroaniline (3,4-DCA) and propanil.

    Xiao, Hongxia; Kuckelkorn, Jochen; Nüßer, Leonie Katharina; Floehr, Tilman; Hennig, Michael Patrick; Roß-Nickoll, Martina; Schäffer, Andreas; Hollert, Henner

    2016-05-01

    3,4,3',4'-tetrachloroazobenzene (TCAB) is not commercially manufactured but formed as an unwanted by-product in the manufacturing of 3,4-dichloroaniline (3,4-DCA) or metabolized from the degradation of chloranilide herbicides, like propanil. While a considerable amount of research has been done concerning the toxicological and ecotoxicological effects of propanil and 3,4-DCA, limited information is available on TCAB. Our study examined the toxicity of TCAB in comparison to its parent compounds propanil and 3,4-DCA, using a battery of bioassays including in vitro with aryl hydrocarbon receptor (AhR) mediated activity by the 7-ethoxyresorufin-O-deethylase (EROD) assay and micro-EROD, endocrine-disrupting activity with chemically activated luciferase gene expression (CALUX) as well as in vivo with fish embryo toxicity (FET) assays with Danio rerio. Moreover, the quantitative structure activity response (QSAR) concepts were applied to simulate the binding affinity of TCAB to certain human receptors. It was shown that TCAB has a strong binding affinity to the AhR in EROD and micro-EROD induction assay, with the toxic equivalency factor (TEF) of 8.7×10(-4) and 1.2×10(-5), respectively. TCAB presented to be a weak endocrine disrupting compound with a value of estradiol equivalence factor (EEF) of 6.4×10(-9) and dihydrotestosterone equivalency factor (DEF) of 1.1×10(-10). No acute lethal effects of TCAB were discovered in FET test after 96h of exposure. Major sub-lethal effects detected were heart oedema, yolk malformation, as well as absence of blood flow and tail deformation. QSAR modelling suggested an elevated risk to environment, particularly with respect to binding to the AhR. An adverse effect potentially triggering ERβ, mineralocorticoid, glucocorticoid and progesterone receptor activities might be expected. Altogether, the results obtained suggest that TCAB exerts a higher toxicity than both propanil and 3,4-DCA. This should be considered when assessing the

  6. Wave fluxes of equatorial Kelvin waves and QBO zonal wind forcing derived from SABER and ECMWF temperature space-time spectra

    M. Ern

    2009-03-01

    Full Text Available The quasi-biennial oscillation (QBO of the zonal mean zonal wind is one of the most important processes in the dynamics of the middle atmosphere in the tropics. Influences of the QBO can even be found at mid and high latitudes. It is widely accepted that the phase descent of alternating tropical easterlies and westerlies is driven by atmospheric waves of both global scale (equatorial wave modes like Kelvin, equatorial Rossby, Rossby-gravity, or inertia-gravity waves, as well as mesoscale gravity waves. However, the relative distribution of the different types of waves to the forcing of the QBO winds is highly uncertain. This is the case because until recently there were no high resolution long-term global measurements in the stratosphere. In our study we estimate Kelvin wave momentum flux and the contribution of zonal wind forcing by Kelvin waves based on space-time spectra determined from both Sounding of the Atmosphere using Broadband Emission Radiometry (SABER temperature measurements as well as temperatures from European Centre for Medium-Range Weather Forecasts (ECMWF operational analyses. Peak values of total Kelvin wave zonal wind forcing found are about 0.2 m/s/day. There is good agreement between SABER and ECMWF results. Global distributions are shown and the results are compared to the total wave forcing required to balance the background atmosphere. Sometimes Kelvin wave forcing is sufficient to explain almost the whole total wave forcing required for the momentum balance during the transition from QBO easterly to westerly winds. This is especially the case during the later parts of the periods of westerly wind shear at the equator between 20 and 35 km altitude. During other phases of the westerly wind shear periods, however, the contribution of Kelvin waves can be comparably low and the missing wave forcing, which is often attributed to mesoscale gravity waves or intermediate scale waves, can be the by far dominant contribution of

  7. Magnetic moments of lanthanide 3-, 4-nitrobenzoates and 3,4-dinitrobenzoates

    The magnetic moments for lanthanide 3-nitro and 4-nitrobenzoates were determined at 298 K and those for 3,4-dinitrobenzoates of rare earth elements over the temperature range 77 - 296 K. The complexes of 3,4-dinitrobenzoates of rare earth were found to obey the Curie-Weiss law. The values of μ calculated for all complexes (except that for europium 3,4-dinitrobenzoates) are close to those obtained for Ln3+ ions by Hund and Van Vleck. The results reveal that irrespective of the kind of ligands (3-nitro, 4-nitro or 3,4-dinitrobenzoates) no influence of their field on lanthanide ions occurs. (author)

  8. Kelvin-Helmholtz instabilities in tokamak edge plasmas

    The parallel Kelvin-Helmholtz instability is investigated as a possible explanation for poloidal asymmetries of density fluctuations which reverse with the plasma current direction. It is shown that these modes are localised around the position where the radial gradient of parallel velocity is maximum. Two mechanisms lead to unstable Kelvin-Helmholtz modes: the acceleration of ions in a presheath and the anomalous Stringer spin-up due to asymmetries of the particle flux. Up-down asymmetries are explained by combining these two effects. Depending on the limiter configuration, the Stringer effect amplifies or weakens the flow due to presheath acceleration. This type of asymmetry reverses with the plasma current direction. (authors)

  9. Determination of the yield locus using a Kelvin probing method

    The high sensitivity of the electron work function (EWF) to surface condition has attracted increasing interest from materials scientists. In this study, application of a Kelvin probe, which is used to measure the EWF, for determination of the material's yielding under multiaxial plane stresses was explored. Yielding of copper was investigated using the EWF as an indicator of plastic deformation. It was demonstrated that the yield point of copper determined using this method was consistent with those given respectively by von Mises and Tresca yield criteria. Furthermore, the experimental results indicated that yielding was easier under a tensile stress than under a compressive stress. The Kelvin probing method is promising and could be very suitable for determining yield onset of materials under complex loading conditions

  10. Dense magnetospheric plasma and Kelvin-Helmholtz waves

    Walsh, B.

    2015-12-01

    The coupling of energy between the solar wind and a planetary magnetosphere is a function of the plasma parameters on both sides of the planet's magnetopause. Scientists routinely monitor the changing conditions in the solar wind in efforts to predict the dynamics at the magnetopause, but there can also be significant changes within the magnetosphere that play a role. On the magnetospheric side, the plasma density can change by several orders of magnitude (0.1cm-3 to 50cm-3). The current study investigates the role of dense magnetospheric plasma in the formation of Kelvin-Helmholtz waves at the magnetopause boundary. Spacecraft observations and SuperDARN radar measurements are presented showing the occurrence of Kelvin-Helmholtz waves on the dayside magnetopause under relatively low shear flows in the presence of a dense plasmaspheric plume.

  11. Radiochemistry days; Journees radiochimie

    NONE

    1998-09-01

    This document provides the 44 papers (transparencies used during the presentations and posters) presented at the Radiochemistry Days, held September 3-4, 1998 in Nantes, France. The main studied topics were problematic questions concerning the nuclear fuel cycle and in particular the management, storage of radioactive wastes and the environmental impact. (O.M.)

  12. The survival of interstellar clouds against Kelvin-Helmholtz instabilities

    Vietri, Mario; Ferrara, Andrea; Miniati, Francesco

    1997-01-01

    We consider the stability of clouds surrounded by a hotter confining medium with respect to which they are in motion, against Kelvin-Helmholtz instabilities (KHI). In the presence of cooling, sound waves are damped by dissipation. Whenever cooling times are shorter than sound crossing times, as they are in the normal interstellar medium, this implies that the instability generated at the interface of the two media cannot propagate far from the interface itself. To study how this influences th...

  13. KELVIN rare gas time-of-flight program

    The purpose of this appendix is to explain in detail the procedure for performing time-of-flight (TOF) calibration measurements. The result of the calibration measurements is to assign a correct length (L) to the path the molecules travel in a particular experimental configuration. In conjunction with time information (t) a velocity distribution (L/t) can then be determined. The program KELVIN is listed

  14. Charged-state dynamics in Kelvin probe force microscopy

    Ondráček, Martin; Hapala, Prokop; Jelínek, Pavel

    2016-01-01

    We present a numerical model which allows us to study the Kelvin force probe microscopy response to the charge switching in quantum dots at various time scales. The model provides more insight into the behavior of frequency shift and dissipated energy under different scanning conditions measuring a temporarily charged quantum dot on surface. Namely, we analyze the dependence of the frequency shift, its fluctuation and of the dissipated energy, on the resonance frequency of tip and electron tu...

  15. Noise performance of frequency modulation Kelvin force microscopy

    Heinrich Diesinger; Dominique Deresmes; Thierry Mélin

    2014-01-01

    Noise performance of a phase-locked loop (PLL) based frequency modulation Kelvin force microscope (FM-KFM) is assessed. Noise propagation is modeled step by step throughout the setup using both exact closed loop noise gains and an approximation known as “noise gain” from operational amplifier (OpAmp) design that offers the advantage of decoupling the noise performance study from considerations of stability and ideal loop response. The bandwidth can be chosen depending on how much noise is acc...

  16. AFM tip characterization by Kelvin probe force microscopy

    Barth, C.; Hynninen, T.; Bieletzki, M.; Henry, C.R.; Foster, Adam S.; Esch, F; Heiz, U.

    2010-01-01

    Reliable determination of the surface potential with spatial resolution is key for understanding complex interfaces that range from nanostructured surfaces to molecular systems to biological membranes. In this context, Kelvin probe force microscopy (KPFM) has become the atomic force microscope (AFM) method of choice for mapping the local electrostatic surface potential as it changes laterally due to variations in the surface work function or surface charge distribution. For reliable KPFM meas...

  17. The effect of sample resistivity on Kelvin probe force microscopy

    Weymouth, Alfred Jay; Giessibl, Franz J.

    2012-01-01

    Kelvin probe force microscopy (KPFM) is a powerful technique to probe the local electronic structure of materials with atomic force microscopy. One assumption often made is that the applied bias drops fully in the tip-sample junction. We have recently identified an effect, the Phantom force, which can be explained by an ohmic voltage drop near the tip-sample junction causing a reduction of the electrostatic attraction when a tunneling current is present. Here, we demonstrate the strong effect...

  18. High Spatial Resolution Kelvin Probe Force Microscopy With Coaxial Probes

    Westervelt, Robert M.; Brown, Keith A.; Satziner, Kevin J.

    2012-01-01

    Kelvin probe force microscopy (KPFM) is a widely used technique to measure the local contact potential difference (CPD) between an AFM probe and the sample surface via the electrostatic force. The spatial resolution of KPFM is intrinsically limited by the long range of the electrostatic interaction, which includes contributions from the macroscopic cantilever and the conical tip. Here, we present coaxial AFM probes in which the cantilever and cone are shielded by a conducting shell, confining...

  19. Visualisation of Local Charge Densities with Kelvin Probe Force Microscopy

    Milde, Peter

    2011-01-01

    For the past decades, Kelvin probe force microscopy (KPFM) developed from a sidebranch of atomic force microscopy to a widely used standard technique. It allows to measure electrostatic potentials on any type of sample material with an unprecedented spatial resolution. While the technical aspects of the method are well understood, the interpretation of measured data remains object of intense research. This thesis intends to prove an advanced view on how sample systems which are typical for ul...

  20. Quantitative Kelvin probe force microscopy of current-carrying devices

    Fuller, EJ; Pan, D; Corso, BL; Tolga Gul, O; Gomez, JR; Collins, PG

    2013-01-01

    Kelvin probe force microscopy (KPFM) should be a key tool for characterizing the device physics of nanoscale electronics because it can directly image electrostatic potentials. In practice, though, distant connective electrodes interfere with accurate KPFM potential measurements and compromise its applicability. A parameterized KPFM technique described here determines these influences empirically during imaging, so that accurate potential profiles can be deduced from arbitrary device geometri...

  1. Kelvin Probe Studies of Cesium Telluride Photocathode for AWA Photoinjector

    Wisniewski, Eric; Velazquez, Daniel; Yusof, Zikri; Spentzouris, Linda; Terry, Jeff; Harkay, Katherine

    2012-01-01

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (~50 nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin Probe technique. The study incl...

  2. Kelvin Probe Force Microscopy in liquid using Electrochemical Force Microscopy

    Liam Collins; Stephen Jesse; Kilpatrick, Jason I.; Alexander Tselev; M. Baris Okatan; Kalinin, Sergei V.; Rodriguez, Brian J

    2015-01-01

    Conventional closed loop-Kelvin probe force microscopy (KPFM) has emerged as a powerful technique for probing electric and transport phenomena at the solid–gas interface. The extension of KPFM capabilities to probe electrostatic and electrochemical phenomena at the solid–liquid interface is of interest for a broad range of applications from energy storage to biological systems. However, the operation of KPFM implicitly relies on the presence of a linear lossless dielectric in the probe–sample...

  3. Kelvin-Helmholtz wave generation beneath hovercraft skirts

    Sullivan, P. A.; Walsh, C.; Hinchey, M. J.

    1993-05-01

    When a hovercraft is hovering over water, the air flow beneath its skirts can interact with the water surface and generate waves. These, in turn, can cause the hovercraft to undergo violent self-excited heave motions. This note shows that the wave generation is due to the classical Kelvin-Helmholtz mechanism where, beyond a certain air flow rate, small waves at the air water interface extract energy from the air stream and grow.

  4. KELVIN rare gas time-of-flight program

    Vernon, M.

    1981-03-01

    The purpose of this appendix is to explain in detail the procedure for performing time-of-flight (TOF) calibration measurements. The result of the calibration measurements is to assign a correct length (L) to the path the molecules travel in a particular experimental configuration. In conjunction with time information (t) a velocity distribution (L/t) can then be determined. The program KELVIN is listed.

  5. Cavitation and bubble dynamics: the Kelvin impulse and its applications.

    Blake, John R; Leppinen, David M; Wang, Qianxi

    2015-10-01

    Cavitation and bubble dynamics have a wide range of practical applications in a range of disciplines, including hydraulic, mechanical and naval engineering, oil exploration, clinical medicine and sonochemistry. However, this paper focuses on how a fundamental concept, the Kelvin impulse, can provide practical insights into engineering and industrial design problems. The pathway is provided through physical insight, idealized experiments and enhancing the accuracy and interpretation of the computation. In 1966, Benjamin and Ellis made a number of important statements relating to the use of the Kelvin impulse in cavitation and bubble dynamics, one of these being 'One should always reason in terms of the Kelvin impulse, not in terms of the fluid momentum…'. We revisit part of this paper, developing the Kelvin impulse from first principles, using it, not only as a check on advanced computations (for which it was first used!), but also to provide greater physical insights into cavitation bubble dynamics near boundaries (rigid, potential free surface, two-fluid interface, flexible surface and axisymmetric stagnation point flow) and to provide predictions on different types of bubble collapse behaviour, later compared against experiments. The paper concludes with two recent studies involving (i) the direction of the jet formation in a cavitation bubble close to a rigid boundary in the presence of high-intensity ultrasound propagated parallel to the surface and (ii) the study of a 'paradigm bubble model' for the collapse of a translating spherical bubble, sometimes leading to a constant velocity high-speed jet, known as the Longuet-Higgins jet. PMID:26442141

  6. 3,4-methylenedioxymethamphetamine (MDMA): current perspectives

    Meyer JS

    2013-01-01

    Jerrold S Meyer Department of Psychology, Neuroscience and Behavior Program, University of Massachusetts, Amherst, MA, USA Abstract: Ecstasy is a widely used recreational drug that usually consists primarily of 3,4-methylenedioxymethamphetamine (MDMA). Most ecstasy users consume other substances as well, which complicates the interpretation of research in this field. The positively rated effects of MDMA consumption include euphoria, arousal, enhanced mood, increased sociability, and heighten...

  7. The application of the Kelvin probe in materials science

    This thesis reports on the application of the Kelvin probe in materials science and in particular on the study of metal and semiconductor surfaces in both ambient and UHV environments. The concept of the work function φ and its importance as a parameter in materials science is discussed in the context of novel technological applications. The various methods to determine the work function are reviewed. The main measurement technique used here - the Kelvin probe - is described in detail. The Kelvin probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (φtip) is not known. Therefore, a novel technique has been developed to measure φtip with the Kelvin probe via the photoelectric effect, thus combining the advantages of both methods to provide the absolute work function of the sample surface. High and low work function surfaces were generated as target materials for a novel ion source based on hyperthermal surface ionisation: oxidised rhenium exhibits the highest work function of 7.15eV at a temperature of ∼900K whereas the lowest work function of ∼2.54eV was measured on lanthanum hexaboride, LaB6. The process of thermal and hyperthermal surface ionisation (SI, HSI) as well as the generation of hyperthermal molecular beams is discussed and a model of the surface ionisation process is developed to estimate its efficiency. Experimental data of SI and HSI are presented. The application of the Kelvin probe for the detection of defects and impurities in semiconductors, namely iron contamination, is demonstrated via two methods based on the measurement of the surface photovoltage. We find that both methods yield a lower surface potential and surface charge for iron contaminated wafers compared to a clean sample and therefore can be

  8. A Review Paper: Contributions from the Gravity and the Kelvin Modes for the Vertical Motion Response.

    Julio Buchmann

    2009-10-01

    Full Text Available In earlier papers of a series of real data integrations of the National Center for Atmospheric Research (NCAR Community Climate Model (CCM with tropical heat anomalies display regions of pronounced subsidence and drying located several thousand kilometers westward poleward of the heating for cases of tropical Atlantic heating and tropical east Pacific heating. This highly predictable sinking response is established within the first five days of these integrations. The normal-modes of a set of nonlinear primitive equations for an atmosphere: Adiabatic, hydrostatic, incompressible, dry, without friction and viscosity are linearized about a basic state at rest and used to partition model response into gravity-inertia and Rossby modes. The emphasis of this review is given upon the contributions of the gravity and Kelvin modes for the vertical motion response.

  9. Sleeping body temperatures in 3-4 month old infants.

    Wailoo, M P; Petersen, S A; Whittaker, H.; Goodenough, P

    1989-01-01

    Rectal, skin, and ambient temperatures were continuously recorded overnight from 3-4 month old normal infants in their home cots under conditions of room temperature and wrapping chosen freely by parents. It was found that rectal temperature was above 37 degrees C when infants were put down, but fell rapidly to 36.4 degrees C within one and a half hours, then stabilised for a few hours before rising steadily. This pattern was tied more closely to the time of putting down than time of day. The...

  10. May Day

    王芳

    2009-01-01

    For Teacher: May Day occurs in May 1 and refers to any of several public holidays.In many countries, May Day is synonymous(同义词的)with International Workers' Day, or Labor Day, which celebrates the social and economic achievements(成就)of the labor movement.

  11. May Day

    王芳

    2009-01-01

    For Teachers: May Day occurs on May 1 and refers to any of several public holidays. In many coun- tries, May Day is synonymous (同义词的) with International Workers' Day, or Labor Day, which celebrates the social and economic achievements (成就) of the labor movement. As a day of celebration, the holiday has an- cient origins (起源), and it can relate to many customs that have survived into modem times.

  12. MATHEMATICAL MODELING OF A DISTANCE DEPENDENCE OF A SCANNING KELVIN PROBE LATERAL RESOLUTION

    Tyavlovsky, A. K.

    2015-01-01

    A mathematical model of cylindrical shaped plane-ended scanning Kelvin probe output signal is proposed considering the case of an infinite plane sample's surface with local defects represented by dot charges. Modeling results were obtained for the case of two closely situated dot charges anddifferent combinations of scanning Kelvin probe tip's diameter and sample-to-probe gap. It was found that the most effective way to improve the lateral resolution of a scanning Kelvin probe is to reduce th...

  13. 3, 4-methylenedioximethamphetamin reverses anxiety induced by chronic mild stress

    Laura Andrea León A

    2013-01-01

    Full Text Available Here we report the effects of subchronic 3, 4 methylenedioximethamphetamine (MDMA on the elevated plusmaze, a widely used animal model of anxiety. Rats exposed to a mild chronic stress (MCS protocol received intracerebroventricular microinjections of the selective serotonin reuptake inhibitor (SSRI – fluoxetine (2.0 ug/ul or MDMA, (2.0 ug/ul for seven days. On the eighth day rats were tested in the elevated plus-maze. Our results showed that sub chronic MDMA interacted with MCS leading to a decrease in anxiety related behaviors including: percentage of open arms entries (F [2, 26] = 4.00; p = 0.031, time spent in the open arms (F [2, 26] = 3.656; p = 0.040 and time spent in the open arms extremities (F [2, 26] = 5.842; p = 0.008. These results suggest a potential effect of MDMA in the reversion of the emotional significance of aversive stimuli.

  14. Kelvin-Helmholtz instabilities with Godunov smoothed particle hydrodynamics

    Cha, Seung-Hoon; Inutsuka, Shu-Ichiro; Nayakshin, Sergei

    2010-04-01

    Numerical simulations for the non-linear development of Kelvin-Helmholtz instability in two different density layers have been performed with the particle-based method (Godunov SPH) developed by Inutsuka. The Godunov SPH can describe the Kelvin-Helmholtz instability even with a high-density contrast, while the standard SPH shows the absence of the instability across a density gradient. The interaction of a dense blob with a hot ambient medium has been performed also. The Godunov SPH describes the formation and evolution of the fingers due to the combinations of Rayleigh-Taylor, Richtmyer-Meshkov and Kelvin-Helmholtz instabilities. The blob test result coincides well with the results of the grid-based codes. An inaccurate handling of a density gradient in the standard SPH has been pointed out as the direct reason of the absence of the instabilities. An unphysical force happens at the density gradient even in a pressure equilibrium, and repulses particles from the initial density discontinuity. Therefore, the initial perturbation damps, and a gap form at the discontinuity. The unphysical force has been studied in terms of the consistency of a numerical scheme. Contrary to the standard SPH, the momentum equation of the Godunov SPH does not use the particle approximation, and has been derived from the kernel convolution or a new Lagrangian function. The new Lagrangian function used in the Godunov SPH is more analogous to the real Lagrangian function for continuum. The momentum equation of the Godunov SPH has much better linear consistency, so the unphysical force is greatly reduced compared to the standard SPH in a high density contrast.

  15. Noise performance of frequency modulation Kelvin force microscopy

    Heinrich Diesinger

    2014-01-01

    Full Text Available Noise performance of a phase-locked loop (PLL based frequency modulation Kelvin force microscope (FM-KFM is assessed. Noise propagation is modeled step by step throughout the setup using both exact closed loop noise gains and an approximation known as “noise gain” from operational amplifier (OpAmp design that offers the advantage of decoupling the noise performance study from considerations of stability and ideal loop response. The bandwidth can be chosen depending on how much noise is acceptable and it is shown that stability is not an issue up to a limit that will be discussed. With thermal and detector noise as the only sources, both approaches yield PLL frequency noise expressions equal to the theoretical value for self-oscillating circuits and in agreement with measurement, demonstrating that the PLL components neither modify nor contribute noise. Kelvin output noise is then investigated by modeling the surrounding bias feedback loop. A design rule is proposed that allows choosing the AC modulation frequency for optimized sharing of the PLL bandwidth between Kelvin and topography loops. A crossover criterion determines as a function of bandwidth, temperature and probe parameters whether thermal or detector noise is the dominating noise source. Probe merit factors for both cases are then established, suggesting how to tackle noise performance by probe design. Typical merit factors of common probe types are compared. This comprehensive study is an encouraging step toward a more integral performance assessment and a remedy against focusing on single aspects and optimizing around randomly chosen key values.

  16. 29 CFR 3.4 - Submission of weekly statements and the preservation and inspection of weekly payroll records.

    2010-07-01

    ... inspection of weekly payroll records. 3.4 Section 3.4 Labor Office of the Secretary of Labor CONTRACTORS AND... STATES § 3.4 Submission of weekly statements and the preservation and inspection of weekly payroll... subcontractor, within seven days after the regular payment date of the payroll period, to a representative of...

  17. Strain analysis of nonlocal viscoelastic Kelvin bar in tension

    ZHAO Xue-chuan; LEI Yong-jun; ZHOU Jian-ping

    2008-01-01

    Based on viscoelastic Kelvin model and nonlocal relationship of strain and stress, a nonlocal constitutive relationship of viscoelasticity is obtained and the strain response of a bar in tension is studied. By transforming governing equation of the strain analysis into Volterra integration form and by choosing a symmetric exponential form of kernel function and adapting Neumann series, the closed-form solution of strain field of the bar is obtained. The creep process of the bar is presented. When time approaches infinite, the strain of bar is equal to the one of nonlocal elasticity.

  18. Open-loop band excitation Kelvin probe force microscopy

    A multidimensional scanning probe microscopy approach for quantitative, cross-talk free mapping of surface electrostatic properties is demonstrated. Open-loop band excitation Kelvin probe force microscopy (OL BE KPFM) probes the full response-frequency-potential surface at each pixel at standard imaging rates. The subsequent analysis reconstructs work function, tip–surface capacitance gradient and resonant frequency maps, obviating feedback-related artifacts. OL BE KPFM imaging is demonstrated for several materials systems with topographic, potential and combined contrast. This approach combines the features of both frequency and amplitude KPFM and allows complete decoupling of topographic and voltage contributions to the KPFM signal. (paper)

  19. Temperature calibration for diffusion experiments to sub-Kelvin precision.

    Zaum, Christopher; Bertram, Cord; Meyer Auf der Heide, Kastur M; Mehlhorn, Michael; Morgenstern, Karina

    2016-05-01

    Arrhenius plots are often used to determine energy barriers and prefactors of thermally activated processes. The precision of thus determined values depends crucially on the precision of the temperature measurement at the sample surface. We line out a procedure to determine the absolute temperature of a metal sample in a cryogenic scanning tunneling microscope between 5 K and 50 K with sub-Kelvin precision. We demonstrate the dependence of prefactor and diffusion energy on this calibration for diffusion of CO on Cu(111) and on Ag(100) measured in the temperature range from 30 K to 38 K and 19 K to 23 K, respectively. PMID:27250437

  20. Kelvin-Helmholtz instability and vortices in magnetized plasma

    Analytic theory and implicit particle simulations are used to describe the evolution of the Kelvin-Helmholtz instability and the plasma vortices driven by a nonuniform E x B flow velocity. Formulas for plasma convection arising from the self-consistent plasma electric field give the rate of anomalous momentum transport across the magnetic field. The momentum transport is shown to be controlled by the tilting angle of the elliptical vortex with respect to the direction of the parallel flow. Three stages of evolution are investigated and formulas for the final vortex state are given

  1. Kelvin--Helmholtz instability in an active region jet observed with \\emph{Hinode}

    Zhelyazkov, I; Srivastava, A K

    2015-01-01

    Over past ten years a variety of jet-like phenomena were detected in the solar atmosphere, including plasma ejections over a range of coronal temperatures being observed as extreme ultraviolet (EUV) and X-ray jets. We study the possibility for the development of Kelvin--Helmholtz (KH) instability of transverse magnetohydrodynamic (MHD) waves traveling along an EUV jet situated on the west side of NOAA AR 10938 and observed by three instruments on board Hinode on 2007 January 15/16 (Chifor et al., Astron. Astrophys.481, L57 (2008)). The jet was observed around LogT_e = 6.2 with up-flow velocities exceeded 150 km/s. Using Fe XII lambda186 and lambda195 line ratios, the measured densities were found to be above LogN_e = 11. We have modeled that EUV jet as a vertically moving magnetic flux tube (untwisted and weakly twisted) and have studied the propagation characteristics of the kink (m=1) mode and the higher m modes with azimuthal mode numbers m=2,3,4. It turns out that all these MHD waves can become unstable a...

  2. The influence of surface topography on Kelvin probe force microscopy

    Long-range electrostatic forces govern the imaging mechanism in electrostatic force microscopy as well as in Kelvin probe force microscopy. To improve the analysis of such images, simulations of the electrostatic field distribution have been performed in the past using a flat surface and a cone-shaped tip. However, the electrostatic field distribution between a tip and a sample depends strongly on the surface topography, which has been neglected in previous studies. It is therefore of general importance to study the influence of sample topography features on Kelvin probe force microscopy images, which we address here by performing finite element simulations. We show how the surface potential measurement is influenced by surface steps and surface grooves, considering potential variations in the form of a potential peak and a potential step. The influence of the topography on the measurement of the surface potential is found to be rather small compared to a typical experimental resolution. Surprisingly, in the case of a coinciding topography and potential step an improvement of the potential profile due to the inclusion of the topography is observed. Finally, based on the obtained results, suggestions for the realization of KPFM measurement are given.

  3. 3.4 Environmental impacts: energy industry

    The subchapter 3.4 'Environmental impact of the energy industry' of the 7th state of the environment report analyzes the current situation in Austria and briefly describes the following aspects: environmental policy targets, uniform taxation of energy, use of renewable energy sources, efficient use of energy, energy input, electricity supply and input, energy input into space heating and air conditioning systems, and renewable energy. In 2002, the input of final energy was risen by about 5 % in comparison to 1998. During this period, the largest increments in final energy inputs were recorded in the mobility sector with + 9.4 %, and in the private households sector with + 8.3 % . The goods production sector showed a slight decrease of about 1.3 % between 1998 and 2002. The 'goods production', 'mobility' and 'private households' sectors combined require about 87 % of the total final energy input. The final energy input for space heating and hot water in 2001 was 5.7 % above the input in 1998. Energy supply from renewable energy sources rose by about 13.8 % in 2002 compared to 1998. Domestic electricity consumption (excluding consumption for pumped-storage systems) in 2002 was about 10.5 % above consumption in 1998. Physical imports and physical exports in 2002 increased about 32 % and 8.6 % correspondingly compared to 1999. (nevyjel)

  4. The Lord Kelvin Project: Middle School Science for the 21st Century.

    Foti, Sebastian; Ledbetter, Ric; Taylor, Fred; Al-Kazemi, Ebraheem

    This paper introduces and reports upon lessons learned during the development phase of the Lord Kelvin Middle School Science Program. For the past two years, a set of tools to help middle school students learn science in a way that uses the full power of today's technology has been under development. Lord Kelvin is a robust collection of science…

  5. SDI Days

    Željko Hećimović

    2012-12-01

    Full Text Available NSDI and INSPIRE Days and Cartography and Geoinformation Conferences are traditionally organized every year. Three NSDI and INSPIRE Days and Cartography and Geoinformation Conferences have been organized so far: Varaždin (2009, Opatija (2010 and Split (2011. The Regional INSPIRE Training and Forum organized by EU INSPIRATION Project was also included this year. SDI Days were held in the Hotel International in Zagreb, September 25th – 29th, 2012.

  6. CEMI Days

    None

    2015-07-01

    CEMI Days are an important channel of engagement between DOE and the manufacturing industry to identify challenges and opportunities for increasing U.S. manufacturing competitiveness. CEMI Days that are held at manufacturing companies’ facilities can include tours of R&D operations or other points of interest determined by the host company.

  7. Effects of 3,4-Dichloroaniline on Testicle Enzymes as Biological Markers in Rats

    Bo ZHANG; SEN LIN

    2009-01-01

    Objective To investigate the effects of 3,4-dichlomaniline (3,4-DCA) on activities of testicle enzymes as biological markers in rats. Methods Fifty male rats were randomly divided into 5 groups (n=10). One group was left untreated and used as a solvent control (administered orally by corn oil), while the other 4 groups were treated with 3, 4-DCA. Corn oil was used as a solvent, and 3,4-DCA was diluted into tested concentrations (39, 81, 170, and 357 mg/kg). All the groups orally administered 3,4-DCA or corn oil, once a day for 4 weeks. The testicle tissue was homogenized in a 0.1 mol/L potassium phosphate buffer (0.1 mol/L, pH 7.2). The crude homogenate was centrifuged at 6000 rpm for 5 rain at 4 ℃. The supematant obtained was used as an enzyme extract for determination of the enzyme activities. Results Compared with the control, the activities of ALP, ACE and SDH were increased significantly at a lower level of 3,4-DCA, and decreased at a higher level of 3, 4-DCA, whreas the activities of LDH, LDH-X, and G6PDH were inhibited significantly with the increased 3,4-DCA concentration. Organ coefficient "organ weight/total body weight × 100" of testis, liver, and spleen increased significantly with the increased 3,4-DCA concentration. These results suggest that 3,4-DCA toxicity to the male reproductive system was associated with the activities of testicular enzymes which are the sensitive biochemical endpoints reflecting 3,4-DCA toxicity to the male reproductive system. Conclusion 3,4-DCA has toxicity to the reproductive system in male rats.

  8. The survival of interstellar clouds against Kelvin-Helmholtz instabilities

    Vietri, M; Miniati, F; Vietri, Mario; Ferrara, Andrea; Miniati, Francesco

    1997-01-01

    We consider the stability of clouds surrounded by a hotter confining medium with respect to which they are in motion, against Kelvin-Helmholtz instabilities (KHI). In the presence of cooling, sound waves are damped by dissipation. Whenever cooling times are shorter than sound crossing times, as they are in the normal interstellar medium, this implies that the instability generated at the interface of the two media cannot propagate far from the interface itself. To study how this influences the overall stability, first we derive an analytic dispersion relation for cooling media, separated by a shear layer. The inclusion of dissipation does not heal the instability, but it is shown that only a small volume around the interface is affected, the perturbation decaying exponentially with distance from the surface; this is confirmed by numerical simulations. Numerical simulations of spherical clouds moving in a surrounding intercloud medium by which they are pressure confined show that these clouds develop a core/ha...

  9. High spatial resolution Kelvin probe force microscopy with coaxial probes

    Kelvin probe force microscopy (KPFM) is a widely used technique to measure the local contact potential difference (CPD) between an AFM probe and the sample surface via the electrostatic force. The spatial resolution of KPFM is intrinsically limited by the long range of the electrostatic interaction, which includes contributions from the macroscopic cantilever and the conical tip. Here, we present coaxial AFM probes in which the cantilever and cone are shielded by a conducting shell, confining the tip–sample electrostatic interaction to a small region near the end of the tip. We have developed a technique to measure the true CPD despite the presence of the shell electrode. We find that the behavior of these probes agrees with an electrostatic model of the force, and we observe a factor of five improvement in spatial resolution relative to unshielded probes. Our discussion centers on KPFM, but the field confinement offered by these probes may improve any variant of electrostatic force microscopy. (paper)

  10. Band excitation Kelvin probe force microscopy utilizing photothermal excitation

    A multifrequency open loop Kelvin probe force microscopy (KPFM) approach utilizing photothermal as opposed to electrical excitation is developed. Photothermal band excitation (PthBE)-KPFM is implemented here in a grid mode on a model test sample comprising a metal-insulator junction with local charge-patterned regions. Unlike the previously described open loop BE-KPFM, which relies on capacitive actuation of the cantilever, photothermal actuation is shown to be highly sensitive to the electrostatic force gradient even at biases close to the contact potential difference (CPD). PthBE-KPFM is further shown to provide a more localized measurement of true CPD in comparison to the gold standard ambient KPFM approach, amplitude modulated KPFM. Finally, PthBE-KPFM data contain information relating to local dielectric properties and electronic dissipation between tip and sample unattainable using conventional single frequency KPFM approaches

  11. Reconstruction of surface potential from Kelvin probe force microscopy images

    We present an algorithm for reconstructing a sample surface potential from its Kelvin probe force microscopy (KPFM) image. The measured KPFM image is a weighted average of the surface potential underneath the tip apex due to the long-range electrostatic forces. We model the KPFM measurement by a linear shift-invariant system where the impulse response is the point spread function (PSF). By calculating the PSF of the KPFM probe (tip+cantilever) and using the measured noise statistics, we deconvolve the measured KPFM image to obtain the surface potential of the sample.The reconstruction algorithm is applied to measurements of CdS-PbS nanorods measured in amplitude modulation KPFM (AM-KPFM) and to graphene layers measured in frequency modulation KPFM (FM-KPFM). We show that in the AM-KPFM measurements the averaging effect is substantial, whereas in the FM-KPFM measurements the averaging effect is negligible. (paper)

  12. Kelvin Probe Studies of Cesium Telluride Photocathode for AWA Photoinjector

    Wisniewski, Eric; Yusof, Zikri; Spentzouris, Linda; Terry, Jeff; Harkay, Katherine

    2012-01-01

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (~50 nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin Probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.

  13. Analysis and simulation of the operation of a Kelvin probe

    Reasenberg, Robert D; Phillips, James D

    2013-01-01

    Experiments that measure extremely small gravitational forces are often hampered by the presence of non-gravitational forces that can neither be calculated nor separately measured. Among these spurious forces is electrostatic attraction between a test mass and its surroundings due to the presence of spatially varying surface potential known as the "patch effect." In order to make surfaces with small surface potential variation, it is necessary to be able to measure it. A Kelvin probe (KP) measures contact potential difference (CPD), using the time-varying capacitance between the sample and a vibrating tip that is biased with a backing potential. Assuming that the tip remains constant, this measures the sample's surface potential variation. We examine the operation of the KP from the perspective of parameter estimation in the presence of noise. We show that, when the CPD is estimated from measurements at two separate backing potentials, the standard deviation of the optimal estimate depends on the total observ...

  14. Kelvin-Helmholtz instability in non-Newtonian complex plasma

    Banerjee, D.; Garai, S.; Janaki, M. S.; Chakrabarti, N. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2013-07-15

    The Kelvin-Helmholtz (KH) instability is studied in a non-Newtonian dusty plasma with an experimentally verified model [Phys. Rev. Lett. 98, 145003 (2007)] of shear flow rate dependent viscosity. The shear flow profile used here is a parabolic type bounded flow. Both the shear thinning and shear thickening properties are investigated in compressible as well as incompressible limits using a linear stability analysis. Like the stabilizing effect of compressibility on the KH instability, the non-Newtonian effect in shear thickening regime could also suppress the instability but on the contrary, shear thinning property enhances it. A detailed study is reported on the role of non-Newtonian effect on KH instability with conventional dust fluid equations using standard eigenvalue analysis.

  15. MAY DAY

    李佳

    2009-01-01

    @@ May 1 is Intemational Labour Day.It is a great holiday for the working class.On this day working people all over the world demonstrate(显示)their power and solidarity(团结).It has its origins(起因,起源)in the struggle for shorter working hours.In 1884,eight Labour Unions of the United States and Canada held a convention(集会)in Chicago(芝加哥).Here it was decided to wage(开展)a united struggle to win the eight-hour day.A resolution(决议) was adopted (通过)fixing May1,1886,for a great nationwide(全国性的)demonstration(示威).

  16. MATHEMATICAL MODELING OF A DISTANCE DEPENDENCE OF A SCANNING KELVIN PROBE LATERAL RESOLUTION

    A. K. Tyavlovsky

    2015-04-01

    Full Text Available A mathematical model of cylindrical shaped plane-ended scanning Kelvin probe output signal is proposed considering the case of an infinite plane sample's surface with local defects represented by dot charges. Modeling results were obtained for the case of two closely situated dot charges anddifferent combinations of scanning Kelvin probe tip's diameter and sample-to-probe gap. It was found that the most effective way to improve the lateral resolution of a scanning Kelvin probe is to reduce the sample-to-probe gap in line with the reduction of sensor's vibration amplitude.

  17. Compensating electrostatic forces by single-scan Kelvin probe force microscopy

    We describe a novel method of single-scan Kelvin probe force microscopy, operating simultaneously with amplitude-modulation distance control in ambient air. A separate Kelvin probe feedback control loop compensates for potential differences between tip and sample by minimizing electrostatic forces. As a result, electrostatically induced height errors in topography are automatically cancelled. To prevent crosstalk from topography or errors in distance control, the Kelvin probe feedback employs phase information resulting from a combination of mechanical and electrical excitation of the cantilever at its second flexural eigenmode. The feedback for amplitude-modulation distance control operates as usual close to the first eigenfrequency

  18. Characterization of photovoltage evolution of ZnO films using a scanning Kelvin probe system

    Work function (WF) and surface photovoltage evolution of films can be measured using the Kelvin probe technique, and further analysis of the photoelectronic behavior can provide information on the energy level structure. In this paper, a theoretical analysis to measure surface photovoltage using Kelvin probe technique is presented. Based on this analysis, the surface photovoltage and its time-resolved evolution process as well as the energy level structure of ZnO films are determined using a scanning Kelvin probe. The present study therefore provides a simple and practical methodology for the characterization of the electronic behavior of films.

  19. 21 CFR 3.4 - Designated agency component.

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Designated agency component. 3.4 Section 3.4 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PRODUCT JURISDICTION Assignment of Agency Component for Review of Premarket Applications § 3.4 Designated...

  20. 34 CFR 3.4 - Use of the seal.

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Use of the seal. 3.4 Section 3.4 Education Office of the Secretary, Department of Education OFFICIAL SEAL § 3.4 Use of the seal. (a) Use by any person or...) Requests by any person or organization outside of the Department for permission to use the Seal must...

  1. 40 CFR 257.3-4 - Ground water.

    2010-07-01

    ... to sewage sludge that is not used or disposed through a practice regulated in 40 CFR part 503 may... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Ground water. 257.3-4 Section 257.3-4... and Practices § 257.3-4 Ground water. (a) A facility or practice shall not contaminate an...

  2. Mathematical justification of Kelvin-Voigt beam models by asymptotic methods

    Rodríguez-Arós, Á. D.; Viaño, J. M.

    2012-06-01

    The authors derive and justify two models for the bending-stretching of a viscoelastic rod by using the asymptotic expansion method. The material behaviour is modelled by using a general Kelvin-Voigt constitutive law.

  3. The Crossroads between the Galactic Disk and Interstellar Space, Ablaze in 3/4 keV Light

    Shelton, Robin L.

    2016-04-01

    The halo is the crossroads between the Galactic disk and intergalactic space. This region is inhabited by hot gas that has risen from the disk, gas heated in situ, and hot material that has fallen in from intergalactic space. Owing to high spectral resolution observations made by by XMM-Newton, Suzaku, and Chandra of the hot plasma's 3/4 keV emission and absorption, increasingly sophisticated and CPU intensive computer modeling, and an awareness that charge exchange can contaminate 3/4 keV observations, we are now better able to understand the hot halo gas than ever before.Spectral analyses indicate that the 3/4 keV emission comes from T ~ 2.2 million Kelvin gas. Although observations suggest that the gas may be convectively unstable and the spectra's temperature is similar to that predicted by recent sophisticated models of the galactic fountain, the observed emission measure is significantly brighter than that predicted by fountain models. This brightness disparity presents us with another type of crossroads: should we continue down the road of adding physics to already sophisticated modeling or should we seek out other sources? In this presentation, I will discuss the galactic fountain crossroads, note the latitudinal and longitudinal distribution of the hot halo gas, provide an update on charge exchange, and explain how shadowing observations have helped to fine tune our understanding of the hot gas.

  4. Experiments R285-3/4/5 (ILAS 3/4/5). Activity calculations

    In the irradiation experiments ILAS 3/4/5 a number of different austenitic stainless steel types and three types of vanadium samples for advanced nuclear systems will be irradiated at a temperature of 300 C up to dpa (displacements per atom) levels of 2.5 dpa for the steel samples and up to 6 dpa for the vanadium samples. In this report the results of the activity calculations of the sample holder material and of the different types of sample materials are presented. The activity of the holder material is calculated for the vertical average of the irradiation position. The activities of the sample materials are given for the vertical maximum of the irradiation position. A relation is given to convert these data to any vertical sample position. Also the changes in chemical composition of the different sample materials, due to nuclide transmutation, are given in this report. (orig.)

  5. Stabilization of nonhomogeneous beam by embedding patch of Kelvin-Voigt viscoelasticity%嵌有Kelvin-Voigt阻尼片的非均质梁的镇定

    陈叔平; 司守奎

    2003-01-01

    With the help of operator semigroup theory, the frequency domain method and the multiplier techniques wereapplied. When the Kelvin-Voigt damping was distributed locally on any subinterval of the region, the energy of the nonhomoge-neous Euler-Bernoulli beam was proved to decay uniformly exponentially.%借助于算子半群理论.应用频域方法和乘子技巧,证明了具有局部Kelvin-Voigt阻尼的非均质Euler-Bernoulli梁的能量是指数衰减的.

  6. A 10 Kelvin 3 Tesla Magnet for Space Flight ADR Systems

    Tuttle, Jim; Shirron, Peter; Canavan, Edgar; DiPirro, Michael; Riall, Sara; Pourrahimi, Shahin

    2003-01-01

    Many future space flight missions are expected to use adiabatic demagnetization refrigerators (ADRs) to reach detector operating temperatures well below one Kelvin. The goal is to operate each ADR with a mechanical cooler as its heat sink, thus avoiding the use of liquid cryogens. Although mechanical coolers are being developed to operate at temperatures of 6 Kelvin and below, there is a large efficiency cost associated with operating them at the bottom of their temperature range. For the multi-stage ADR system being developed at Goddard Space Flight Center, the goal is to operate with a 10 Kelvin mechanical cooler heat sink. With currently available paramagnetic materials, the highest temperature ADR stage in such a system will require a magnetic field of approximately three Tesla. Thus the goal is to develop a small, lightweight three Tesla superconducting magnet for operation at 10 Kelvin. It is important that this magnet have a low current/field ratio. Because traditional NbTi magnets do not operate safely above about six Kelvin, a magnet with a higher Tc is required. The primary focus has been on Nb3Sn magnets. Since standard Nb3Sn wire must be coated with thick insulation, wound on a magnet mandrel and then reacted, standard Nb,Sn magnets are quite heavy and require high currents Superconducting Systems developed a Nb3Sn wire which can be drawn down to small diameter, reacted, coated with thin insulation and then wound on a small diameter coil form. By using this smaller wire and operating closer to the wire s critical current, it should be possible to reduce the mass and operating current of 10 Kelvin magnets. Using this "react-then-wind" technology, Superconducting Systems has produced prototype 10 Kelvin magnets. This paper describes the development and testing of these magnets and discusses the outlook for including 10 Kelvin magnets on space-flight missions.

  7. Understanding the Atomic-Scale Contrast in Kelvin Probe Force Microscopy

    Nony, Laurent; Foster, Adam S.; Bocquet, Franck; Loppacher, Christian

    2009-01-01

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a noncontact atomic force microscope simulator including a Kelvin module. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and contact potential difference contrasts were reported. The local...

  8. Applying the Kelvin Probe to biological tissues: Theoretical and computational analyses

    Ahn, Andrew C; Gow, Brian J.; Martinsen, Ørjan G.; Zhao, Min; Grodzinsky, Alan J.; Baikie, Iain D.

    2012-01-01

    The Kelvin Probe measures surface electrical potential without making physical contact with the specimen. It relies on capacitive coupling between an oscillating metal tip that is normal to a specimen’s surface. Kelvin Probes have been increasingly used to study surface and electrical properties of metals and semiconductors and are capable of detecting material surface potentials with sub-millivolt resolution at a micrometer spatial scale. Its capability for measuring electrical potential wit...

  9. Determination of surface recombination velocities of organic monolayers on silicon through Kelvin probe

    Alderman, Nicholas; Adib Ibrahim, Mohd; Danos, Lefteris; Martin C. Grossel; Markvart, Tom

    2013-01-01

    We report the determination of the surface recombination velocity of electron-hole pairs for silicon samples passivated with organic monolayers using the Kelvin probe. The recombination velocity was determined from the surface photovoltage and incident photon flux. By scanning of the Kelvin probe tip over the sample, the change in surface recombination velocity can be measured allowing recombination lifetime mapping. Organic monolayers with different chain lengths and exhibiting various recom...

  10. KELVIN PROBE SELF-CALIBRATION MODE FOR SEMICONDUCTOR WAFERS PROPERTIES MONITORING

    R. I. Vorobey; O. K. Gusev; A. L. Zharin; A. N. Petlitsky; V. A. Pilipenko; A. S. Turtsevitch; Tyavlovsky, A. K.

    2015-01-01

    Improvement of repeatability and reliability of semiconductor wafers properties monitoring with a probe charge-sensitive methods is achieved by realization of Kelvin probe self-calibration mode using a wafer’s surface itself as a reference sample. Results of wafer surface scanning are visualized in the form of parameter distribution color map. A method of measurements based on Kelvin probe self-calibration mode is realized in a measurement installation for non-destructive non-contact monitori...

  11. Interaction and decay of Kelvin waves in the Gross-Pitaevskii model

    Proment, Davide; Barenghi, Carlo F.; Onorato, Miguel

    2013-01-01

    By solving numerically the governing Gross-Pitaevskii equation, we study the dynamics of Kelvin waves on a superfluid vortex. After determining the dispersion relation, we monitor the turbulent decay of Kelvin waves with energy initially concentrated at large length scales. At intermediate length scales, we find that the decay is consistent with scaling predictions of theoretical models. Finally we report the unexpected presence of large-length scale phonons in the system.

  12. Kelvin--Helmholtz instability in solar H-alpha surges

    Zhelyazkov, I; Chandra, R; Srivastava, A K; Mishonov, T

    2015-01-01

    We study the evolutionary conditions for Kelvin--Helmholtz (KH) instability in a H-alpha solar surge observed in NOAA AR 8227 on 1998 May 30. The jet with speeds in the range of 45--50 km/s, width of 7 Mm, and electron number density of 3.83 x 10^{10} cm^{-3} is assumed to be confined in a twisted magnetic flux tube embedded in a magnetic field of 7 G. The temperature of the plasma flow is of the order of 10^5 K while that of its environment is taken to be 2 x 10^6 K. The electron number density of surrounding magnetized plasma has a typical for the TR/lower corona region value of 2 x 10^{9} cm^{-3}. Under these conditions, the Alfven speed inside the jet is equal to 78.3 km/s. We model the surge as a moving magnetic flux tube for two magnetic field configurations: (i) a twisted tube surrounded by plasma with homogeneous background magnetic field, and (ii) a twisted tube which environment is plasma with also twisted magnetic field. The magnetic field twist in given region is characterized by the ratio of azim...

  13. Kelvin-Helmholtz Instabilities in Smoothed Particle Hydrodynamics

    Valcke, S.; de Rijcke, S.; Röediger, E.

    2011-07-01

    We have investigated whether Smoothed Particle Hydrodynamics (SPH), equipped with artificial conductivity, is able to capture the physics of density/energy discontinuities in the case of the so-called shearing layers test, a test for examining Kelvin-Helmholtz (KH) instabilities. We can trace back each failure of SPH to show KH rolls to two causes: i) shock waves travelling in the simulation box and ii) particle clumping, or more generally, particle noise. The probable cause of shock waves is the Local Mixing Instability (LMI), previously identified in the literature. Particle noise on the other hand is a problem because it introduces a large error in the SPH momentum equation. We show that setting up initial conditions with a suitably smoothed density gradient dramatically improves results. Particle clumping is easy to overcome, the most straightforward method being the use of a suitable smoothing kernel with non-zero first central derivative. We present results to that effect using a new smoothing kernel: the LInear Quartic (LIQ) kernel. Furthermore, we present new Artificial Conductivity signal velocities that lead to less diffusion. The effects of the shock waves and of particle disorder become less important as the time-scale of the physical problem (for the shearing layers problem: lower density contrast and higher Mach numbers) decreases. At the resolution of current galaxy formation simulations mixing is probably not important. However, mixing could become crucial for next-generation simulations.

  14. Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (≈50nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating. -- Highlights: ► The correlation between Quantum Efficiency (QE) and work function. ► How QE and work function evolve together. ► Rejuvenation of the photocathode via heating and the effect on work function. ► The effects on the work function due to exposure to UV light

  15. Scanning Kelvin probe study of metal/polymer interfaces

    A scanning Kelvin probe was used to study the metal/polymer contacts for models of epoxy, alkyd and polyaniline coatings. It was shown that the potential drop across the electrical double layer of oriented ionic dipoles at the metal/polymer interface contributes a major part of the measured Volta potentials. The Broensted acid/base interactions are responsible for the charge separation and the creation of a double electric layer. Polyaniline (an electron-conducting polymer) accepts electrons from the metal to its own Fermi level, thus producing a Schottky barrier. In this case, the Volta potential of the contact does not depend on the metal, but follows the polyaniline flat band potential. Exposure in water vapor neutralizes the potential drop at the interface due to water dipole orientation in a direction opposite to the intrinsic electric field. The kinetics of potential change during water uptake follow Fick's and Nernst's equations. After hydrolysis of the interfacial bonds, activation of the metal surface can takes place

  16. Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

    Wisniewski, Eric E., E-mail: ewisniew@anl.gov [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Velazquez, Daniel [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Yusof, Zikri, E-mail: zyusof@hawk.iit.edu [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Spentzouris, Linda; Terry, Jeff [Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Sarkar, Tapash J. [Rice University, 6100 Main, Houston, TX 77005 (United States); Harkay, Katherine [Accelerator Science Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States)

    2013-05-21

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (≈50nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating. -- Highlights: ► The correlation between Quantum Efficiency (QE) and work function. ► How QE and work function evolve together. ► Rejuvenation of the photocathode via heating and the effect on work function. ► The effects on the work function due to exposure to UV light.

  17. MESSENGER observations of multiscale Kelvin-Helmholtz vortices at Mercury

    Gershman, Daniel J.; Raines, Jim M.; Slavin, James A.; Zurbuchen, Thomas H.; Sundberg, Torbjörn; Boardsen, Scott A.; Anderson, Brian J.; Korth, Haje; Solomon, Sean C.

    2015-06-01

    Observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft in Mercury's magnetotail demonstrate for the first time that Na+ ions exert a dynamic influence on Mercury's magnetospheric system. Na+ ions are shown to contribute up to ~30% of the ion thermal pressure required to achieve pressure balance in the premidnight plasma sheet. High concentrations of planetary ions should lead to Na+ dominance of the plasma mass density in these regions. On orbits with northward-oriented interplanetary magnetic field and high (i.e., >1 cm-3) Na+ concentrations, MESSENGER has often recorded magnetic field fluctuations near the Na+ gyrofrequency associated with the Kelvin-Helmholtz (K-H) instability. These nightside K-H vortices are characteristically different from those observed on Mercury's dayside that have a nearly constant wave frequency of ~0.025 Hz. Collectively, these observations suggest that large spatial gradients in the hot planetary ion population at Mercury may result in a transition from a fluid description to a kinetic description of vortex formation across the dusk terminator, providing the first set of truly multiscale observations of the K-H instability at any of the diverse magnetospheric environments explored in the solar system.

  18. KELVIN-HELMHOLTZ INSTABILITY OF A CORONAL STREAMER

    Shear-flow-driven instability can play an important role in energy transfer processes in coronal plasma. We present for the first time the observation of a kink-like oscillation of a streamer that is probably caused by the streaming kink-mode Kelvin-Helmholtz instability (KHI). The wave-like behavior of the streamer was observed by the Large Angle and Spectrometric Coronagraph Experiment C2 and C3 on board the SOlar and Heliospheric Observatory. The observed wave had a period of about 70-80 minutes, and its wavelength increased from 2 R☉ to 3 R☉ in about 1.5 hr. The phase speeds of its crests and troughs decreased from 406 ± 20 to 356 ± 31 km s–1 during the event. Within the same heliocentric range, the wave amplitude also appeared to increase with time. We attribute the phenomena to the MHD KHI, which occurs at a neutral sheet in a fluid wake. The free energy driving the instability is supplied by the sheared flow and sheared magnetic field across the streamer plane. The plasma properties of the local environment of the streamer were estimated from the phase speed and instability threshold criteria

  19. Kelvin probe force and scanning capacitance microscopy on MOS structures

    Baumgart, Christine; Helm, Manfred; Schmidt, Heidemarie [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, Dresden (Germany); Jaensch, Stefan [ElKiDo, Skjern (Denmark)

    2009-07-01

    As the size of semiconductor devices is decreasing permanently, new techniques are required to probe their dopant profile reliably on a nanometer scale. Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM) are the most promising techniques for this demand. KPFM (LevelAFM from Anfatec) enables the detection of the contact potential difference (CPD) between tip and sample and SCM (DI3100 from Veeco Instruments) probes the capacitance of the metal oxide structures formed in contact. In order to demonstrate the complementary information obtained by KPFM and SCM measurements, we used the pn junction in a static random access memory integrated circuit device where the n-well with a donor concentration of 2.10{sup 17} cm{sup -3} has been fabricated by implanting the p-epi with a nominal acceptor concentration of 2.10{sup 16} cm{sup -3} with P{sup +} ions of energy 900 keV and a fluence of 1.7.10{sup 13} cm{sup -2}. As expected, KPFM yields a smooth variation of the CPD between the p-epi and the n-well amounting to 230 meV. SCM clearly shows the boxlike doping profile of this pn junction. The CPD variation can be modelled by assuming a partially compensated donor concentration in the n-well.

  20. Kelvin Notation for Stabilizing Elastic-Constant Inversion Notation Kelvin pour stabiliser l'inversion de constantes élastiques

    Dellinger J.

    2006-12-01

    Full Text Available Inverting a set of core-sample traveltime measurements for a complete set of 21 elastic constants is a difficult problem. If the 21 elastic constants are directly used as the inversion parameters, a few bad measurements or an unfortunate starting guess may result in the inversion converging to a physically impossible solution . Even given perfect data, multiple solutions may exist that predict the observed traveltimes equally well. We desire the inversion algorithm to converge not just to a physically possible solution, but to the best(i. e. most physically likely solution of all those allowed. We present a new parameterization that attempts to solve these difficulties. The search space is limited to physically realizable media by making use of the Kelvin eigenstiffness-eigentensor representation of the 6 x 6 elastic stiffness matrix. Instead of 21 stiffnesses, there are 6 eigenstiffness parametersand 15 rotational parameters . The rotational parameters are defined using a Lie-algebra representation that avoids the artificial degeneracies and coordinate-system bias that can occur with standard polar representations. For any choice of these 21 real parameters, the corresponding stiffness matrix is guaranteed to be physically realizable. Furthermore, all physically realizable matrices can be represented in this way. This new parameterization still leaves considerable latitude as to which linear combinations of the Kelvin parameters to use, and how they should be ordered. We demonstrate that by careful choice and ordering of the parameters, the inversion can be relaxedfrom higher to lower symmetry simply by adding a few more parameters at a time. By starting from isotropy and relaxing to the general result in stages (isotropy, transverse isotropy, orthorhombic, general, we expect that the method should find the solution that is closest to isotropy of all those that fit the data. L'inversion d'un ensemble de mesures du temps de parcours d

  1. Complexing 7,3',4'-tryoxiflavonol with cell phosphatidylcholine

    Nusratullin V. M.; Fahretdinova E. R.; Nasibullin R. S.; Galeeva R. I.

    2010-01-01

    Aim. To investigate the complex formation of 7,3',4'-try-oxyflavonol of flavonoids group with cellular phosphatidylcholine. Methods. Semi-empirical quantum chemistry, spectroscopy NMR. Results. The changes in conformational status of 7,3',4'-tryoxy- flavonol at complex formation have been shown. Conclusions. The conformational changes in phosphatidylcholine take place under the 7,3',4'-tryoxyflavonol/phosphatidylcholine complex formation.

  2. 基于分数阶微积分的Kelvin-Voigt流变模型%The Kelvin-Voigt Rheological Model Based on Fractional Calculus

    郭佳奇; 乔春生; 徐冲; 黄山秀

    2009-01-01

    为研究岩土材料的应力、应变和时间的关系,基于分数阶微积分理论,定义含分数阶导数的力学元件(FC元件),推导FC元件的蠕变柔量和松弛模量.与牛顿体元件相比,FC元件能更好地反映流变问题的非线性渐变过程.借鉴经典元件组合模型的建模思路,用FC元件取代整数阶微积分Kelvin-Voigt流变模型中的牛顿体元件,形成基于分数阶微积分的Kelvin-Voigt流变模型.应用离散化求Laplace逆变换的方法以及H-Fox函数,得出分数阶微积分Kelvin-Voigt流变模型的本构方程、蠕变方程、松弛方程、蠕变柔量及松弛模量的解析表达式.采用整数阶微积分Kelvin-Voigt流变模型、整数阶5参数开尔文流变模型和分数阶微积分Kelvin-Voigt流变模型对试验数据拟合的结果表明,分数阶微积分Kelvin-Voigt流变模型不但拟合精度高,能够克服整数阶微积分Kelvin-Voigt流变模型在蠕变初期及蠕变曲线拐点附近与试验数据不能很好吻合的弊端,而且能够在保证拟合精度的条件下,减少本构模型中的参数.

  3. Analysis and simulation of the operation of a Kelvin probe

    Experiments that measure extremely small gravitational forces are often hampered by the presence of non-gravitational forces that can neither be calculated nor separately measured. Among these spurious forces is electrostatic attraction between a test mass and its surroundings due to the presence of spatially varying surface potential known as the ‘patch effect’. In order to make surfaces with small surface potential variation, it is necessary to be able to measure it. A Kelvin probe (KP) measures contact potential difference (CPD), using the time-varying capacitance between the sample and a vibrating tip that is biased with a backing potential. Assuming that the tip remains constant, this measures the sample's surface potential variation. We examine the operation of the KP from the perspective of parameter estimation in the presence of noise. We show that, when the CPD is estimated from measurements at two separate backing potentials, the standard deviation of the optimal estimate depends on the total observing time. Further, the observing time may be unevenly divided between the two backing potentials, provided the values of those potentials are correspondingly set. We simulate a two-stage KP data analysis, including a sub-optimal estimator with advantages for real-time operation. Based on the real-time version, we present a novel approach to stabilizing the average distance of the tip from the sample. We also present the results of a series of covariance analyses that validate and bound the applicability of the suboptimal estimator, make a comparison with the results of an optimal estimator and guide the user. We discuss the application of the KP to the Laser Interferometer Space Antenna and to a test of the weak equivalence principle. (paper)

  4. Kelvin probe force microscopy in liquid using electrochemical force microscopy

    Liam Collins

    2015-01-01

    Full Text Available Conventional closed loop-Kelvin probe force microscopy (KPFM has emerged as a powerful technique for probing electric and transport phenomena at the solid–gas interface. The extension of KPFM capabilities to probe electrostatic and electrochemical phenomena at the solid–liquid interface is of interest for a broad range of applications from energy storage to biological systems. However, the operation of KPFM implicitly relies on the presence of a linear lossless dielectric in the probe–sample gap, a condition which is violated for ionically-active liquids (e.g., when diffuse charge dynamics are present. Here, electrostatic and electrochemical measurements are demonstrated in ionically-active (polar isopropanol, milli-Q water and aqueous NaCl and ionically-inactive (non-polar decane liquids by electrochemical force microscopy (EcFM, a multidimensional (i.e., bias- and time-resolved spectroscopy method. In the absence of mobile charges (ambient and non-polar liquids, KPFM and EcFM are both feasible, yielding comparable contact potential difference (CPD values. In ionically-active liquids, KPFM is not possible and EcFM can be used to measure the dynamic CPD and a rich spectrum of information pertaining to charge screening, ion diffusion, and electrochemical processes (e.g., Faradaic reactions. EcFM measurements conducted in isopropanol and milli-Q water over Au and highly ordered pyrolytic graphite electrodes demonstrate both sample- and solvent-dependent features. Finally, the feasibility of using EcFM as a local force-based mapping technique of material-dependent electrostatic and electrochemical response is investigated. The resultant high dimensional dataset is visualized using a purely statistical approach that does not require a priori physical models, allowing for qualitative mapping of electrostatic and electrochemical material properties at the solid–liquid interface.

  5. Kelvin probe force microscopy in liquid using electrochemical force microscopy.

    Collins, Liam; Jesse, Stephen; Kilpatrick, Jason I; Tselev, Alexander; Okatan, M Baris; Kalinin, Sergei V; Rodriguez, Brian J

    2015-01-01

    Conventional closed loop-Kelvin probe force microscopy (KPFM) has emerged as a powerful technique for probing electric and transport phenomena at the solid-gas interface. The extension of KPFM capabilities to probe electrostatic and electrochemical phenomena at the solid-liquid interface is of interest for a broad range of applications from energy storage to biological systems. However, the operation of KPFM implicitly relies on the presence of a linear lossless dielectric in the probe-sample gap, a condition which is violated for ionically-active liquids (e.g., when diffuse charge dynamics are present). Here, electrostatic and electrochemical measurements are demonstrated in ionically-active (polar isopropanol, milli-Q water and aqueous NaCl) and ionically-inactive (non-polar decane) liquids by electrochemical force microscopy (EcFM), a multidimensional (i.e., bias- and time-resolved) spectroscopy method. In the absence of mobile charges (ambient and non-polar liquids), KPFM and EcFM are both feasible, yielding comparable contact potential difference (CPD) values. In ionically-active liquids, KPFM is not possible and EcFM can be used to measure the dynamic CPD and a rich spectrum of information pertaining to charge screening, ion diffusion, and electrochemical processes (e.g., Faradaic reactions). EcFM measurements conducted in isopropanol and milli-Q water over Au and highly ordered pyrolytic graphite electrodes demonstrate both sample- and solvent-dependent features. Finally, the feasibility of using EcFM as a local force-based mapping technique of material-dependent electrostatic and electrochemical response is investigated. The resultant high dimensional dataset is visualized using a purely statistical approach that does not require a priori physical models, allowing for qualitative mapping of electrostatic and electrochemical material properties at the solid-liquid interface. PMID:25671164

  6. 机织建筑膜材料的广义Kelvin-Voigt蠕变模型%General Kelvin-Voigt creep model of fabric architectural membrane

    张伍连; 丁辛; 杨旭东

    2011-01-01

    The uniaxial tension creep tests of PVC coating membrane with plain architectural are experimented along the warp and weft direction at five different stresses. The general Kelvin -Voigt creep formulas are given. The experimental data are studied through the use of these creep formulas with three, five and seven parameters. The result shows: As the number of the parameters grew, prediction complexity is increased with grade. When the parameter is seven, the coefficients of determination are over 99.9% at different stresses. This shows that the general Kelvin-Voigt creep model with seven parameters can well predict creeping behavior of fabric architectural membrane.%对平纹组织为基布的PVC涂层膜材料进行了经纬两方向各自5种不同应力条件下的单轴向拉伸蠕变试验,给出了广义Kelvin-Voigt模型的具体蠕变方程,并利用广义三参数、五参数与七参数Kelvin-Voigt的蠕变方程对实验数据进行了分析.结果显示:随着模型参数个数的增加,预测效果也呈现出递增趋势;当模型参数为7个时,各应力拟合的确定系数均在99.9%以上,表明七参数广义Kelvin-Voigt蠕变模型已可以很好地预测膜材料的蠕变特性.

  7. Anthracen-9-ylmethylene-(3,4-dimethylisoxazol-5-ylamine

    Abdullah M. Asiri

    2011-09-01

    Full Text Available The title compound, anthracen-9-ylmethylene-(3,4-dimethylisoxazol-5-ylamine (3, was synthesized in high yield by reaction of anthracene-9-carbaldehyde and 5-amino-3,4-dimethyl­isoxazole in ethanol. The structure of this new compound was confirmed by elemental analysis, IR, 1H NMR, 13C NMR and GC-MS spectral analysis.

  8. Gyroresonance of Kelvin-Helmholtz vortices with Na+ in Mercury's magnetotail

    Gingell, Peter; Sundberg, Torbjorn; Burgess, David

    2015-04-01

    Observations of Mercury's plasma environment by the MESSENGER spacecraft have revealed that the planet hosts a strongly asymmetric magnetosphere as a result of an off-axis internal magnetic field, and significant finite Larmor radius effects at the boundary layer between magnetospheric and solar wind plasma environments. Linear analysis and global hybrid simulations suggest asymmetric growth of the Kelvin-Helmholtz instability between the dusk and dawn flanks of the magnetopause, and indeed Kelvin-Helmholtz waves have been observed almost exclusively at the dusk flank during northward IMF. A previous study has shown that Kelvin-Helmholtz waves at the dusk flank are observed predominantly at scales associated with the gyration of hot sodium ions - a population originating at the dayside exosphere, and distributed preferentially at the dusk flank. This suggests that a resonance may occur between sodium ion gyration and Kelvin-Helmholtz vortex growth. Using two- and three-dimensional local hybrid simulations of dusk and dawn boundaries, with varying magnetospheric sodium ion density, we have reproduced the main observational features: we see a strong peak in the Kelvin-Helmholtz wave spectra at sodium gyro scales at the dusk boundaries, and suppression of the growth of vortices at the dawn boundaries. We examine the mechanism of the resonant interaction between counter-gyrating sodium ions and K-H vortices using test particle simulations. Finally, we discuss the effect of the sodium ion population on cross-boundary particle transport.

  9. 3,4-Methylenedioxymethamphetamine facilitates fear extinction learning.

    Young, M B; Andero, R; Ressler, K J; Howell, L L

    2015-01-01

    Acutely administered 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') has been proposed to have long-term positive effects on post-traumatic stress disorder (PTSD) symptoms when combined with psychotherapy. No preclinical data support a mechanistic basis for these claims. Given the persistent nature of psychotherapeutic gains facilitated by MDMA, we hypothesized that MDMA improves fear extinction learning, a key process in exposure-based therapies for PTSD. In these experiments, mice were first exposed to cued fear conditioning and treated with drug vehicle or MDMA before extinction training 2 days later. MDMA was administered systemically and also directly targeted to brain structures known to contribute to extinction. In addition to behavioral measures of extinction, changes in mRNA levels of brain-derived neurotrophic factor (Bdnf) and Fos were measured after MDMA treatment and extinction. MDMA (7.8 mg kg(-1)) persistently and robustly enhanced long-term extinction when administered before extinction training. MDMA increased the expression of Fos in the amygdala and medial prefrontal cortex (mPFC), whereas increases in Bdnf expression were observed only in the amygdala after extinction training. Extinction enhancements were recapitulated when MDMA (1 μg) was infused directly into the basolateral complex of the amygdala (BLA), and enhancement was abolished when BDNF signaling was inhibited before extinction. These findings suggest that MDMA enhances fear memory extinction through a BDNF-dependent mechanism, and that MDMA may be a useful adjunct to exposure-based therapies for PTSD and other anxiety disorders characterized by altered fear learning. PMID:26371762

  10. Impact of atmospheric convectively coupled equatorial Kelvin waves on upper ocean variability

    Baranowski, Dariusz B.; Flatau, Maria K.; Flatau, Piotr J.; Matthews, Adrian J.

    2016-03-01

    Convectively coupled Kelvin waves (CCKWs) are atmospheric weather systems that propagate eastward along the equatorial wave guide with phase speeds between 11 and 14 m s-1. They are an important constituent of the convective envelope of the Madden-Julian oscillation (MJO), for which ocean-atmosphere interactions play a vital role. Hence, ocean-atmosphere interactions within CCKWs may be important for MJO development and prediction and for tropical climate, in general. Although the atmospheric structure of CCKWs has been well studied, their impact on the underlying ocean is unknown. In this paper, the ocean-atmosphere interactions in CCKWs are investigated by a case study from November 2011 during the CINDY/DYNAMO field experiment, using in situ oceanographic measurements from an ocean glider. The analysis is then extended to a 15 year period using precipitation data from the Tropical Rainfall Measuring Mission and surface fluxes from the TropFlux analysis. A methodology is developed to calculate trajectories of CCKWs. CCKW events are strongly controlled by the MJO, with twice as many CCKWs observed during the convectively active phase of the MJO compared to the suppressed phase. Coherent ocean-atmosphere interaction is observed during the passage of a CCKW, which lasts approximately 4 days at any given longitude. Surface wind speed and latent heat flux are enhanced, leading to a transient suppression of the diurnal cycle of sea surface temperature (SST) and a sustained decrease in bulk SST of 0.1°C. Given that a typical composite mean MJO SST anomaly is of the order of 0.3°C, and more than one CCKW can occur during the active phase of a single MJO event, the oceanographic impact of CCKWs is of major importance to the MJO cycle.

  11. Force gradient sensitive detection in lift-mode Kelvin probe force microscopy

    We demonstrate frequency modulation Kelvin probe force microscopy operated in lift-mode under ambient conditions. Frequency modulation detection is sensitive to force gradients rather than forces as in the commonly used amplitude modulation technique. As a result there is less influence from electric fields originating from the tip's cone and cantilever, and the recorded surface potential does not suffer from the large lateral averaging observed in amplitude modulated Kelvin probe force microscopy. The frequency modulation technique further shows a reduced dependence on the lift-height and the frequency shift can be used to map the second order derivative of the tip-sample capacitance which gives high resolution material contrast of dielectric sample properties. The sequential nature of the lift-mode technique overcomes various problems of single-scan techniques, where crosstalk between the Kelvin probe and topography feedbacks often impair the correct interpretation of the recorded data in terms of quantitative electric surface potentials.

  12. Determination of Contact Potential Difference by the Kelvin Probe (Part I I. Basic Principles of Measurements

    Vilitis O.

    2016-04-01

    Full Text Available Determination of electric potential difference using the Kelvin probe, i.e. vibrating capacitor technique, is one of the most sensitive measuring procedures in surface physics. Periodic modulation of distance between electrodes leads to changes in capacitance, thereby causing current to flow through the external circuit. The procedure of contactless, non-destructive determination of contact potential difference between an electrically conductive vibrating reference electrode and an electrically conductive sample is based on precise control measurement of Kelvin current flowing through a capacitor. The present research is devoted to creation of a new low-cost miniaturised measurement system to determine potential difference in real time and at high measurement resolution. Furthermore, using the electrode of a reference probe, the Kelvin method leads to both the indirect measurement of an electronic work function, or a contact potential of sample, and of a surface potential for insulator type samples.

  13. A validated non-linear Kelvin-Helmholtz benchmark for numerical hydrodynamics

    Lecoanet, D.; McCourt, M.; Quataert, E.; Burns, K. J.; Vasil, G. M.; Oishi, J. S.; Brown, B. P.; Stone, J. M.; O'Leary, R. M.

    2016-02-01

    The non-linear evolution of the Kelvin-Helmholtz instability is a popular test for code verification. To date, most Kelvin-Helmholtz problems discussed in the literature are ill-posed: they do not converge to any single solution with increasing resolution. This precludes comparisons among different codes and severely limits the utility of the Kelvin-Helmholtz instability as a test problem. The lack of a reference solution has led various authors to assert the accuracy of their simulations based on ad hoc proxies, e.g. the existence of small-scale structures. This paper proposes well-posed two-dimensional Kelvin-Helmholtz problems with smooth initial conditions and explicit diffusion. We show that in many cases numerical errors/noise can seed spurious small-scale structure in Kelvin-Helmholtz problems. We demonstrate convergence to a reference solution using both ATHENA, a Godunov code, and DEDALUS, a pseudo-spectral code. Problems with constant initial density throughout the domain are relatively straightforward for both codes. However, problems with an initial density jump (which are the norm in astrophysical systems) exhibit rich behaviour and are more computationally challenging. In the latter case, ATHENA simulations are prone to an instability of the inner rolled-up vortex; this instability is seeded by grid-scale errors introduced by the algorithm, and disappears as resolution increases. Both ATHENA and DEDALUS exhibit late-time chaos. Inviscid simulations are riddled with extremely vigorous secondary instabilities which induce more mixing than simulations with explicit diffusion. Our results highlight the importance of running well-posed test problems with demonstrated convergence to a reference solution. To facilitate future comparisons, we include as supplementary material the resolved, converged solutions to the Kelvin-Helmholtz problems in this paper in machine-readable form.

  14. Conductimetric immunosensor based on poly(3,4-ethylenedioxythiophene).

    Kanungo, Mandakini; Srivastava, Divesh N; Kumar, Anil; Contractor, A Q

    2002-04-01

    A conductimetric reagentless immunosensor using the biospecific binding pair of goat antirabbit IgG and rabbit IgG has been designed and fabricated using poly (3,4-ethylenedioxythiophene) as the immobilization matrix-cumtransducer. PMID:12119672

  15. Pump-probe Kelvin-probe force microscopy: Principle of operation and resolution limits

    Knowledge on surface potential dynamics is crucial for understanding the performance of modern-type nanoscale devices. We describe an electrical pump-probe approach in Kelvin-probe force microscopy that enables a quantitative measurement of dynamic surface potentials at nanosecond-time and nanometer-length scales. Also, we investigate the performance of pump-probe Kelvin-probe force microscopy with respect to the relevant experimental parameters. We exemplify a measurement on an organic field effect transistor that verifies the undisturbed functionality of our pump-probe approach in terms of simultaneous and quantitative mapping of topographic and electronic information at a high lateral and temporal resolution

  16. The work function of doped polyaniline nanoparticles observed by Kelvin probe force microscopy

    The work function of polyaniline nanoparticles in the emeraldine base state was determined by Kelvin probe force microscopy to be ∼270 meV higher than that of similar nanoparticles in the emeraldine salt state. Normal tapping mode atomic force microscopy could not be used to distinguish between the particles due to their similar morphologies and sizes. Moreover, other potential measurement systems, such as using zeta potentials, were not suitable for the measurement of surface charges of doped nanoparticles due to their encapsulation by interfering chemical groups. Kelvin probe force microscopy can be used to overcome these limitations and unambiguously distinguish between the bare and doped polyaniline nanoparticles. (paper)

  17. KELVIN PROBE SELF-CALIBRATION MODE FOR SEMICONDUCTOR WAFERS PROPERTIES MONITORING

    R. I. Vorobey

    2015-03-01

    Full Text Available Improvement of repeatability and reliability of semiconductor wafers properties monitoring with a probe charge-sensitive methods is achieved by realization of Kelvin probe self-calibration mode using a wafer’s surface itself as a reference sample. Results of wafer surface scanning are visualized in the form of parameter distribution color map. A method of measurements based on Kelvin probe self-calibration mode is realized in a measurement installation for non-destructive non-contact monitoring of semiconductor wafer defects. Method can be used to define defects’ physical properties including minority carrier diffusion length and lifetime, trapped charge density and energy distribution etc.

  18. Pump-probe Kelvin-probe force microscopy: Principle of operation and resolution limits

    Murawski, J.; Graupner, T.; Milde, P., E-mail: peter.milde@tu-dresden.de; Raupach, R.; Zerweck-Trogisch, U.; Eng, L. M. [Institute of Applied Physics, Technische Universität Dresden, D-01062 Dresden (Germany)

    2015-10-21

    Knowledge on surface potential dynamics is crucial for understanding the performance of modern-type nanoscale devices. We describe an electrical pump-probe approach in Kelvin-probe force microscopy that enables a quantitative measurement of dynamic surface potentials at nanosecond-time and nanometer-length scales. Also, we investigate the performance of pump-probe Kelvin-probe force microscopy with respect to the relevant experimental parameters. We exemplify a measurement on an organic field effect transistor that verifies the undisturbed functionality of our pump-probe approach in terms of simultaneous and quantitative mapping of topographic and electronic information at a high lateral and temporal resolution.

  19. The influence of microstructure on the corrosion behaviour of AZ91D studied by scanning Kelvin probe force microscopy and scanning Kelvin probe

    β-Mg17Al12, η-Al8Mn5 and an α-magnesium phase have been synthesized from pure components by controlled solidification procedures. These phases have been studied using different electrochemical techniques including the scanning Kelvin probe (SKP). From the results, it was possible to determine the nobility and the rate of the cathodic reaction of the different phases. Measurements have also been made on an AZ91D Mg-alloy using scanning Kelvin probe force microscopy (SKPFM) and field emission gun scanning electron microscopy (FEG-SEM). The results show that the Volta potentials measured with the scanning Kelvin probe (SKP) on bulk intermetallics are comparable with those recorded with the SKPFM on the AZ91D alloy. It is shown that SKPFM provides information on the local nobility of the different intermetallic particles and phases on the submicron scale. Both the η-Al8Mn5 phase and the β-Mg17Al12 phase in AZ91D showed a more noble potential than the α-magnesium phase. It is also shown that the aluminium-rich coring along the grain boundaries results in measurable changes in the Volta potential. Finally, the role of the β-Mg17Al12 phase and the η-Al8Mn5 phase in the corrosion behaviour of AZ91D is discussed in term of local nobility, surface coverage of the cathode and the cathodic activity of the different phases

  20. The subchronic effects of 3,4-methylendioxymethamphetamine on oxidative stress in rat brain

    Simić Ivan

    2014-01-01

    Full Text Available The aim of the present study was to evaluate the subchronic effects of 3,4-methylenedioxymethamphetamine on several oxidative stress markers: index of lipid peroxidation (ILP, superoxide dismutase (SOD activity, superoxide radical (O2.- levels, and reduced glutathione (GSH levels in the frontal cortex, striatum and hippocampus of the rat. The study included 64 male Wistar rats (200-250g. The animals were treated per os with of 5, 10, or 20 mg/kg of 3,4-methylenedioxymethamphetamine (MDMA every day for 15 days. The subchronic administration of MDMA resulted in an increase in ILP, SOD and O2.-, and a decrease in GSH, from which we conclude that oxidative stress was induced in rat brain.

  1. Preliminary evidence of motor impairment among polysubstance 3,4-methylenedioxymethamphetamine users with intact neuropsychological functioning

    Bousman, Chad A.; Cherner, Mariana; Emory, Kristen T; BARRON, DANIEL; Grebenstein, Patricia; Atkinson, J. Hampton; Heaton, Robert K.; Grant, Igor

    2010-01-01

    Neuropsychological disturbances have been reported in association with use of the recreational drug “ecstasy,” or 3,4-methylenedioxymethamphetamine (MDMA), but findings have been inconsistent. We performed comprehensive neuropsychological testing examining seven ability domains in 21 MDMA users (MDMA+) and 21 matched control participants (MDMA−). Among MDMA+ participants, median [interquartile range] lifetime MDMA use was 186 [111, 516] doses, with 120 [35–365] days of abstinence. There were ...

  2. Evaluation of Bcl-2 Family Gene Expression in Hippocampus of 3, 4-methylenedioxymethamphetamine Treated Rats

    Hamed Hashemi-Nasl; Mohammad Taghi Joghataei; Alireza Samzadeh-Kermani; Seyed Behnamedin Jameie; Mansoure Soleimani; Ali Samadikuchaksaraei; Mohammad Hassan Farhadi; Kazem Mousavizadeh; Sara Soleimani Asl; Mehdi Mehdizadeh

    2012-01-01

    Objective: 3,4-methylenedioxymethamphetamine (MDMA) is an illicit, recreational drug that causes cellular death and neurotoxicity. This study evaluates the effects of different doses of MDMA on the expression of apoptosis–related proteins and genes in the hippocampus of adult rats. Materials and Methods: In this expremental study,a total of 20 male Sprague Dawley rats (200-250 g ) were treated with MDMA (0, 5, 10, 20 mg/kg i.p. twice daily) for 7 days. Seven days after the last administration...

  3. Comment on ``Are there internal Kelvin waves in Lake Tanganyika?'' by Jaya Naithani and Eric Deleersnijder

    Antenucci, Jason P.

    2005-11-01

    Recent numerical modelling efforts have demonstrated the presence of Kelvin waves in Lake Tanganyika (Naithani and Deleersnijder, 2004), however it is claimed that these waves should not appear according to classical scaling arguments. Based on existing classical scaling arguments, supported by laboratory and field investigations, I will show why they can, and apparently do, appear in Lake Tanganyika.

  4. Characterization of interfacial strength of dissimilar metallic joints using a scanning Kelvin probe

    It is very important to understand the interfacial behavior for effective evaluation of welding quality. This letter reports a simple nondestructive characterization method of the interfacial strength of dissimilar metallic joints. Using a scanning Kelvin probe, the electron work function of Cu–steel joints was measured and a strong correlation between the electron work function and the interfacial tensile strength was found.

  5. Vertical propagation of baroclinic Kelvin waves along the west coast of India

    Nethery, D.; Shankar, D.

    -1 Vertical propagation of baroclinic Kelvin waves along the west coast of India DNethery1,2,asteriskmath and D Shankar1 1National Institute of Oceanography, Goa 403 004, India. 2Ecole Normale Sup?erieure, Paris, France. asteriskmathe-mail: daniel...

  6. 169 kelvin cryogenic microcooler empoying a condenser, evaporator, flow restriction and counterflow heat exchangers

    Burger, Johannes; Holland, Harry; Berenschot, Erwin; Seppenwolde, Jan-Henry; Brake, ter Marcel; Gardeniers, Han; Elwenspoek, Miko

    2001-01-01

    This paper presents the first cryogenic micromachined cooler that is suitable to cool from ambient temperature to 169 kelvin and below. The cooler operates with the vapor compression cycle. It consists of a silicon micromachined condenser, a flow restriction/evaporator and two miniature glass-tube c

  7. Reproductive solutions for the g-Navier-Stokes and g-Kelvin-Voight equations

    Luis Friz

    2016-01-01

    Full Text Available This article presents the existence of reproductive solutions of g-Navier-Stokes and g-Kelvin-Voight equations. In this way, for weak solutions, we reach basically the same result as for classic Navier-Stokes equations.

  8. Kelvin-Voigt均匀黏弹性介质中传播的地震波

    苑春方; 彭苏萍; 张中杰; 刘振宽

    2005-01-01

    研究了在小扰动的情况下, 地震波在Kelvin-Voigt均匀黏弹性介质中传播时的瞬态响应以及对应的三阶偏微分方程的解析解. 获得了在脉冲震源条件下Kelvin-Voigt均匀黏弹性三阶波动方程的平面波解. 运用脉冲叠加原理, 获得了在任意震源条件下Kelvin-Voigt均匀黏弹性三阶波动方程的平面波解. 讨论了地震波在Kelvin-Voigt均匀黏弹性介质中的传播速度和衰减, 推导出了地震波的衰减系数和传播速度与介质的密度、弹性模量和黏滞系数之间的精确关系. 这些结果能够用于地震勘探中黏弹性岩性参数的反演.

  9. Seismic wave propagating in Kelvin-Voigt homogeneous visco-elastic media

    2006-01-01

    This paper studies, under a small disturbance, the responses of seismic transient wave in the visco-elastic media and the analytic solution of the corresponding third-order partial differential equation. A plane wave solution of Kelvin-Voigt homogeneous visco-elastic third-order partial differential equation with a pulse source is obtained. By the principle of pulse stacking of particle vibration, the result is extended to the solution of Kelvin-Voigt homogeneous visco-elastic third-order partial differential equation with any source. The velocities of seismic wave propagating and the attenuation of seismic wave in Kelvin-Voigt homogeneous visco-elastic media are discussed. The velocities of seismic wave propagating and the coefficient of attenuation of seismic wave in Kelvin-Voigt homogeneous visco-elastic media are derived, expressed as functions of density of the media, elastic modulus and visco-elastic coefficient. These results can be applied in inversing lithology parameters in geophysical prospecting.

  10. EIGEN THEORY OF VISCOELASTIC DYNAMICS BASED ON THE KELVIN-VOIGT MODEL

    郭少华

    2004-01-01

    Using the eigen theory of solid mechanics, the eigen properties of anisotropic viscoelastic bodies with Kelvin-Voigt model were studied, and the generalized Stokes equation of anisotropic viscoelastic dynamics was obtained, which gives the threedimensional pattern of viscoelastical waves. The laws of viscoelastical waves of different anisotropical bodies were discussed. Several new conclusiones are given.

  11. Exponential stability of an elastic string with local Kelvin-Voigt damping

    Zhang, Qiong

    2010-12-01

    This paper is devoted to analyzing an elastic string with local Kelvin-Voigt damping. We prove the exponential stability of the system when the material coefficient function near the interface is smooth enough. Our method is based on the frequency method and semigroup theory.

  12. Extension of SGTE data for pure elements to zero Kelvin temperature - A case study

    Vřešťál, Jan; Štrof, J.; Pavlů, Jana

    2012-01-01

    Roč. 37, JUN (2012), s. 37-48. ISSN 0364-5916 R&D Projects: GA ČR(CZ) GAP108/10/1908 Institutional support: RVO:68081723 Keywords : Gibbs energy * Pure elements * Zero Kelvin * SGTE data * Heat capacity Subject RIV: BJ - Thermodynamics Impact factor: 1.433, year: 2012

  13. ANTIMICROBIAL ACTIVITIES OF 1,3,4-OXADIAZOLE : A REVIEW

    Bachwani Mukesh

    2011-06-01

    Full Text Available 1, 3, 4-Oxadiazole is a highly privileged structure the derivatives of which exhibit a wide range of biological activities including antibacterial, antitubercular, vasodialatory, antifungal, cytotoxic, anti-inflammatory and analgesic, hypolipidemic, anticancer and ulcerogenic activities. Resistance to number of antimicrobial agents among a variety of clinically significant species of bacteria is becoming increasingly important global problem. The search for new antimicrobial agents will consequently always remain as an important and challenging task for medicinal chemists. This Review has basic information about 1,3,4-oxadiazole and its antimicrobial activity work for further development in this field.

  14. Squaroglitter: A 3,4-Connected Carbon Net

    Prasad, Dasari L. V. K.

    2013-08-13

    Theoretical calculations are presented on a new hypothetical 3,4-connected carbon net (called squaroglitter) incorporating 1,4 cyclohexadiene units. The structure has tetragonal space group P4/mmm (No. 123) symmetry. The optimized geometry shows normal distances, except for some elongated bonds in the cyclobutane ring substructures in the network. Squaroglitter has an indirect bandgap of about 1.0 eV. The hypothetical lattice, whose density is close to graphite, is more stable than other 3,4-connected carbon nets. A relationship to a (4,4)nanotube is explored, as is a potential threading of the lattice with metal needles. © 2013 American Chemical Society.

  15. A Characterization of the SPARC T3-4 System

    van Tol, Michiel W

    2011-01-01

    This technical report covers a set of experiments on the 64-core SPARC T3-4 system, comparing it to two similar AMD and Intel systems. Key characteristics as maximum integer and floating point arithmetic throughput are measured as well as memory throughput, showing the scalability of the SPARC T3-4 system. The performance of POSIX threads primitives is characterized and compared in detail, such as thread creation and mutex synchronization. Scalability tests with a fine grained multithreaded runtime are performed, showing problems with atomic CAS operations on such physically highly parallel systems.

  16. Kelvin-Helmholtz instability at the magnetotail boundary: MHD simulation and comparison with Geotail observations

    Otto, A.; Fairfield, D. H.

    2000-09-01

    On March 24, 1995, the Geotail spacecraft observed large fluctuations of the magnetic field and plasma properties in the low-latitude boundary layer about 15 RE tailward of the dusk meridian. Although the magnetospheric and magnetosheath magnetic fields were strongly northward, the Bz component showed strong short-duration fluctuations in which Bz could even reach negative values. We have used two-dimensional magnetohydrodynamic simulations with magnetospheric and magnetosheath input parameters specifically chosen for this Geotail event to identify the processes which cause the observed boundary properties. It is shown that these fluctuations can be explained by the Kelvin-Helmholtz instability if the k vector of the instability has a component along the magnetic field direction. The simulation results show many of the characteristic properties of the Geotail observations. In particular, the quasi-periodic strong fluctuations are well explained by satellite crossings through the Kelvin-Helmholtz vortices. It is illustrated how the interior structure of the Kelvin-Helmholtz vortices leads to the rapid fluctuations in the Geotail observations. Our results suggest an average Kelvin-Helmholtz wavelength of about 5 RE, with a vortex size of close to 2 RE for an average repetition time of 2.5 min. The growth time for these waves implies a source region of about 10-16 RE upstream from the location of the Geotail spacecraft (i.e., near the dusk meridian). The results also indicate a considerable mass transport of magnetosheath material into the magnetosphere by magnetic reconnection in the Kelvin-Helmholtz vortices.

  17. Direct comparison of photoemission spectroscopy and in situ Kelvin probe work function measurements on indium tin oxide films

    The work function of commercially available indium tin oxide (ITO) films on glass substrates was measured using photoemission spectroscopy (PES) and ultra-high vacuum (UHV) Kelvin probe in direct comparison. Absolute Kelvin probe work function values were determined via calibration of the measured contact potential difference (CPD) using an in situ sputtered Au reference sample. The Kelvin probe data confirmed that ultraviolet photoemission spectroscopy (UPS) measurements change the work function of ITO surfaces previously exposed to ambient environment, when measured without in situ surface cleaning procedures. The results also demonstrate that both Kelvin probe and PES yield virtually identical work function values, as long as the Kelvin probe data are calibrated against a known standard. As a consequence, previously reported higher work function values determined with Kelvin probe as compared to values obtained with UPS on similar samples are likely related to a photochemically generated surface dipole during UPS measurements. Comparison between Kelvin probe and low intensity X-ray photoemission spectroscopy (LIXPS) work function measurements demonstrated that accurate work function measurements on ITO previously exposed to the ambient are possible with PES

  18. Synthesis of Novel Biologically Active s-Triazolo[3,4-b]-1,3,4-thiadiazole Derivatives

    SUN,Yi-Feng

    2004-01-01

    @@ Heterocycles bearing a symmetrical triazole or 1,3,4-thiadiazole ring system are reported to show a broad spectrum of biological activities.[1,2] The 1,2,4-triazole nucleus has been recently incorporated into a wide variety of therapeutically interesting drugs including H1/H2 histamine receptor blockers, cholinesterase active agents, CNS stimulants, antianxiety and sedatives[3] Coumarins are nowadays an important group of organic compounds that used as bactericides, fungicides,anti-inflammatory, anticoagulant, anti-HIV and antitumour agents.[4,5] Keeping in view the biological importance of the above mentioned heterocyclic compounds and in continuation of our search for biologically active nitrogen and sulphur heterocycles, a series of s-triazolo[3,4-b]-1,3,4-thiadiazole derivatives was synthesized.

  19. Poly(3,4-ethylenedioxythiophene)-based glucose biosensors

    Kros, A.; Nolte, R.J.M. [Nijmegen Univ. (Netherlands). Dept. of Organic Chemistry; Hoevell, S.W.F.M. van [TNO Nutrition and Food Research Inst., Zeist (Netherlands); Sommerdijk, N.A.J.M. [Eindhoven Univ. of Technology (Netherlands). Lab. of Macromolecular and Organic Chemistry

    2001-10-16

    Amperometric biosensors for the recognition of glucose oxidase (GOx) based on poly(3,4-ethylenedioxythiophene) (PEDOT) have for the first time been fabricated and are presented in this communication. This biosensor has potential applications for long-term glucose measurements, e.g., in the treatment of diabetes. (orig.)

  20. 20 TO 30-DAY AND 30 TO 60-DAY OSCILLATIONS IN ASSIMILATED GLOBAL DATASETS USING TRMM RAINFALL OBSERVATIONS

    TAO Li; Song YANG; LU Wei-song

    2010-01-01

    The influences of Tropical Rainfall Measuring Mission (TRMM) precipitation products on the structure and underlying physics of intraseasonal oscillation (ISO) are investigated with the U.S. National Aeronautics and Space Administration Goddard Earth Observing System model version 3 (GEOS-3) data assimilation system (DAS). The strong ISO phase in the 1998 summer is apparently located in the Asian monsoon region and the east equatorial Pacific region. The eastward propagation is a dominant feature for the tropical ISO at 20 to 30-day oscillation while the northeastward propagation is the salient ISO at 30 to 60-day oscillation over the 10°N to 25°N belt region. It appears that the Kelvin wave structure is for the tropical 20 to 30-day oscillation. The tropical 30 to 60-day oscillation has the characteristics of the Kelvin-Rossby wave. The impact of satellite-derived precipitation (and its associated latent heating) on the ISO intensity is limited in the GEOS-3 assimilation system. However, its impact on the ISO spatial structures is obvious. Overall, the results demonstrate a better eastward propagation and a northward propagation of ISO with the TRMM precipitation simulation, indicating that latent heating is very important in exciting the equatorial ISO.

  1. Synthesis and Crystal Structure of 3-(4-Ethoxyphenyl)-6-(phenoxymethyl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole

    LEI Xin-Xiang; LIU Miao-Chang; XIAO Hong-Ping; ZHANG An-Jiang; ZHANG Li-Xue

    2007-01-01

    The title compound C18H16N4O2S has been synthesized by the reaction of 4-amino-3-(4-ethoxyphenyl)-5-mercapto-1,2,4-triazole with phenoxyacetic acid in phospho- rus oxychloride, and characterized by IR, NMR spectra and elemental analysis. Its structure was determined by single-crystal X-ray diffraction. It crystallizes in monoclinic, space group P21/c with a = 1.4903(3), b = 1.5230(2), c = 0.9615(16) nm, Z = 4, V = 1.7769(5) nm3, Dc = 1.317 g/cm3, ( = 0.201 mm-1, F(000) = 736, R = 0.0795 and wR = 0.2233. In the title compound, all rings are essentially planar.

  2. Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system

    Drozdov, A. P.; Eremets, M. I.; Troyan, I. A.; Ksenofontov, V.; Shylin, S. I.

    2015-09-01

    A superconductor is a material that can conduct electricity without resistance below a superconducting transition temperature, Tc. The highest Tc that has been achieved to date is in the copper oxide system: 133 kelvin at ambient pressure and 164 kelvin at high pressures. As the nature of superconductivity in these materials is still not fully understood (they are not conventional superconductors), the prospects for achieving still higher transition temperatures by this route are not clear. In contrast, the Bardeen-Cooper-Schrieffer theory of conventional superconductivity gives a guide for achieving high Tc with no theoretical upper bound--all that is needed is a favourable combination of high-frequency phonons, strong electron-phonon coupling, and a high density of states. These conditions can in principle be fulfilled for metallic hydrogen and covalent compounds dominated by hydrogen, as hydrogen atoms provide the necessary high-frequency phonon modes as well as the strong electron-phonon coupling. Numerous calculations support this idea and have predicted transition temperatures in the range 50-235 kelvin for many hydrides, but only a moderate Tc of 17 kelvin has been observed experimentally. Here we investigate sulfur hydride, where a Tc of 80 kelvin has been predicted. We find that this system transforms to a metal at a pressure of approximately 90 gigapascals. On cooling, we see signatures of superconductivity: a sharp drop of the resistivity to zero and a decrease of the transition temperature with magnetic field, with magnetic susceptibility measurements confirming a Tc of 203 kelvin. Moreover, a pronounced isotope shift of Tc in sulfur deuteride is suggestive of an electron-phonon mechanism of superconductivity that is consistent with the Bardeen-Cooper-Schrieffer scenario. We argue that the phase responsible for high-Tc superconductivity in this system is likely to be H3S, formed from H2S by decomposition under pressure. These findings raise hope for the

  3. 具有Kelvin-Voigt阻尼的弱耦合系统的能量衰减估计%Energy decay estimates for the weakly coupled systems with Kelvin-Voigt damping

    樊美丽; 章春国; 谷尚武

    2014-01-01

    This paper studies the weakly coupled systems with Kelvin-Voigt damping. First, under the appro-priate hypothesis, we prove the well-posedness of the system by using the theory of linear operator semigroup. And then, we show that the energy of the weakly coupled system with Kelvin-Voigt damping is uniform expo-nential decay by applying the frequency domain result on Hilbert space.%研究具有 Kelvin-Voigt 阻尼的弱耦合系统。首先在合适的假设条件下,应用线性算子半群理论证明了系统的适定性;进而运用线性算子半群的频域定理证明了具有Kelvin-Voigt阻尼的弱耦合梁―弦系统的能量是一致指数衰减的。

  4. Photoinduced 1,2,3,4-tetrahydropyridine ring conversions.

    Turovska, Baiba; Lund, Henning; Lūsis, Viesturs; Lielpētere, Anna; Liepiņš, Edvards; Beljakovs, Sergejs; Goba, Inguna; Stradiņš, Jānis

    2015-01-01

    Stable heterocyclic hydroperoxide can be easily prepared as a product of fast oxidation of a 1,2,3,4-tetrahydropyridine by (3)O2 if the solution is exposed to sunlight. The driving force for the photoinduced electron transfer is calculated from electrochemical and spectroscopic data. The outcome of the reaction depends on the light intensity and the concentration of O2. In the solid state the heterocyclic hydroperoxide is stable; in solution it is involved in further reactions. PMID:26664638

  5. Study on the Synthesisof 3,4, 5-Trimethoxytol uene

    2001-01-01

    The 3,4,5-trimethoxytoluene(TMT) was systhesized using p-cresol by three steps including bromina-tion, methoxylation, and methylation with an overall yield of 84%. The structure of TMT was identified byNMR, GC/MS and IR. “One-pot”method was used in methoxylation and methylation for economical and conve-nient consideration. The mechanism for the methoxylation of 2,6-dibromo-4-methylphenol was discussed.

  6. Sub-Kelvin refrigeration with dry-coolers on a rotating system

    Oguri, S; Choi, J; Kawai, M; Tajima, O

    2014-01-01

    We developed a cryogenic system on a rotating table that achieves sub-Kelvin conditions. The cryogenic system consists of a helium sorption cooler and a pulse tube cooler in a cryostat mounted on a rotating table. Two rotary-joint connectors for electricity and helium gas circulation enable the coolers to be operated and maintained with ease. We performed cool-down tests under a condition of continuous rotation at 20 rpm. We obtained a temperature of 0.23 K with a holding time of more than 24 hours, thus complying with catalog specifications. We monitored the system's performance for four weeks; two weeks with and without rotation. A few-percent difference in conditions was observed between these two states. Most applications can tolerate such a slight difference. The technology developed is useful for various scientific applications requiring sub-Kelvin conditions on rotating platforms.

  7. Photoisomerization of azobenzene containing self-assembled monolayers investigated by Kelvin probe work function measurements

    Photoisomerization of asymmetric azobenzene disulfide self-assembled monolayer (SAM) on gold was characterized by the Kelvin probe work function measurements in ambient atmosphere. The reversible changes in work function between trans and cis azobenzene SAMs are reasonably interpreted by the molecular dipole moments normal to the surface based on the molecular conformational models. The different para-substituents of azobenzene with electron donating and electron-withdrawing properties induce opposite responses in work function against UV-vis photoirradiation, which is a direct evidence of functional SAMs being effective for the energy-level alignment at the organic/electrode interface. The Kelvin probe measurements in atmosphere eventually provide the work function value equivalent to that determined by ultraviolet photoelectron spectroscopy (UPS) in ultrahigh vacuum in our previous study.

  8. Heterojunction Effect in Weak Epitaxy Growth Thin Films Investigated by Kelvin Probe Force Microscopy

    We investigate the heterojunction effect between para-sexiphenyl (p-6P) and copper phthalocyanine (CuPc) using Kelvin probe force microscopy. CuPc films are grown on the inducing layer p-6P by a weak epitaxy growth technique. The surface potential images of Kelvin probe force microscopy indicate the band bending in CuPc, which reduces grain boundary barriers and lead to the accumulation of holes in the CuPc layer. The electrical potential distribution on the surface of heterojunction films shows negligible grain boundary barriers in the CuPc layers. The relation between band bending and grain boundary barrier in the weak epitaxy growth thin films is revealed. (condensed matter: structure, mechanical and thermal properties)

  9. Kelvin probe force microscopy of C60 on metal substrates: towards molecular resolution

    Surface workfunction changes upon C60 adsorption onto different metal single crystals are investigated by Kelvin probe force microscopy (KPFM). Literature values for similar metal/organic systems, showing a broad variation for both the measured metal workfunction and workfunction change, are compared to the acquired KPFM values. Good agreement is found between nanoscopic KPFM results and macroscopic photoelectron spectroscopy or Kelvin probe literature data. The model of a linear dependence between the metal substrate workfunction and the C60-induced workfunction change is confirmed. Former numerical simulations predicted a lateral quantitative KPFM resolution in the range of 10 nm, in this work results are published that show the achievement of this resolution with Cr coated, sharp tips. Furthermore, numerical simulations are presented that show the possibility of molecular contrast for KPFM

  10. Kelvin Probe Measurements on Solar Cells and Other Thin Film Devices

    Delk, John; Dils, D. W.; Lush, G. B.; Mackey, Willie R. (Technical Monitor)

    2001-01-01

    The Kelvin Probe (KP) has been used for years to measure the surface potential of metals and semiconductors. The KP is an elegantly simple but powerful tool invented by Lord Kelvin around the turn of the century. Using changes in surface potentials as a result of changing the intensity and wavelength of illumination, the KP returns data on material parameters such as band gap energies and the energy levels of interface states. We have employed the KP in the study of CdTe-based solar cells and quantum dot-based solar cells, as well as other thin-film devices. We hope eventually that the KP will be used as an in-line testing station for a fabrication process so that unfinished devices that will not meet requirements can be thrown out before the processing is completed, thus saving resources. Results of these studies will be presented.

  11. Numerical simulations of Kelvin-Helmholtz instability: a two-dimensional parametric study

    Tian, Chunlin

    2016-01-01

    Using two-dimensional simulations, we numerically explore the dependences of Kelvin-Helmholtz instability upon various physical parameters, including viscosity, width of sheared layer, flow speed, and magnetic field strength. In most cases, a multi-vortex phase exists between the initial growth phase and final single-vortex phase. The parametric study shows that the evolutionary properties, such as phase duration and vortex dynamics, are generally sensitive to these parameters except in certain regimes. An interesting result is that for supersonic flows, the phase durations and saturation of velocity growth approach constant values asymptotically as the sonic Mach number increases. We confirm that the linear coupling between magnetic field and Kelvin-Helmholtz modes is negligible if the magnetic field is weak enough. The morphological behaviour suggests that the multi-vortex coalescence might be driven by the underlying wave-wave interaction. Based on these results, we make a preliminary discussion about seve...

  12. THE DYNAMIC BEHAVIORS OF VISCOELASTIC PIPE CONVEYING FLUID WITH THE KELVIN MODEL

    Wang Zhongmin; Zhao Fengqun; Feng Zhenyu; Liu Hongzhao

    2000-01-01

    Based on the differential constitutive relationship of linear viscoelastic material, a solid-liquid coupling vibration equation for viscoelastic pipe conveying fluid is derived by the D'Alembert's principle. The critical flow velocities and natural frequencies of the cantilever pipe conveying fluid with the Kelvin model ( flutter instability) are calculated with the modified finite difference method in the form of the recurrence for mula. The curves between the complex frequencies of the first, second and third mode and flow velocity of the pipe are plotted. On the basis of the numerical calculation results, the dynamic behaviors and stability of the pipe are discussed. It should be pointed out that the delay time of viscoelastic material with the Kelvin model has a remarkable effect on the dynamic characteristics and stability behaviors of the cantilevered pipe conveying fluid, which is a gyroscopic non-conservative system.

  13. The effect of patch potentials in Casimir force measurements determined by heterodyne Kelvin probe force microscopy

    Garrett, Joseph L.; Somers, David; Munday, Jeremy N.

    2015-06-01

    Measurements of the Casimir force require the elimination of the electrostatic force between the surfaces. However, due to electrostatic patch potentials, the voltage required to minimize the total force may not be sufficient to completely nullify the electrostatic interaction. Thus, these surface potential variations cause an additional force, which can obscure the Casimir force signal. In this paper, we inspect the spatially varying surface potential of e-beamed, sputtered, sputtered and annealed, and template stripped gold surfaces with Heterodyne amplitude modulated Kelvin probe force microscopy (HAM-KPFM). It is demonstrated that HAM-KPFM improves the spatial resolution of surface potential measurements compared to amplitude modulated Kelvin probe force microscopy. We find that patch potentials vary depending on sample preparation, and that the calculated pressure can be similar to the pressure difference between Casimir force calculations employing the plasma and Drude models.

  14. On Advantages of the Kelvin Mapping in Finite Element Implementations of Deformation Processes

    Nagel, Thomas; Moerman, Kevin M; Kolditz, Olaf

    2016-01-01

    Classical continuum mechanical theories operate on three-dimensional Eu-clidian space using scalar, vector, and tensor-valued quantities usually up to the order of four. For their numerical treatment, it is common practice to transform the relations into a matrix-vector format. This transformation is usually performed using the so-called Voigt mapping. This mapping does not preserve tensor character leaving significant room for error as stress and strain quantities follow from different mappings and thus have to be treated differently in certain mathematical operations. Despite its conceptual and notational difficulties having been pointed out, the Voigt mapping remains the foundation of most current finite element programmes. An alternative is the so-called Kelvin mapping which has recently gained recognition in studies of theoretical mechanics. This article is concerned with benefits of the Kelvin mapping in numerical modelling tools such as finite element software. The decisive difference to the Voigt mapp...

  15. Two competing interpretations of Kelvin Probe Force Microscopy on semiconductors put to test

    Polak, Leo; Wijngaarden, Rinke J.

    2016-01-01

    Kelvin probe force microscopy (KPFM) is a popular tool for studying properties of semiconductors. However, the interpretation of its results is complicated by the possibility of so-called band bending and the presence of surface charges. In this work we study two different interpretations for KPFM on semiconductors: the contact potential difference (CPD) interpretation, which interprets the measured potential as the work function difference between the sample and the probe, and a newer, alter...

  16. Measuring Method of a Surface Property inside the Pore: Application of Kelvin's equation

    Amano, Ken-ichi

    2015-01-01

    Surface analyses inside the nanopore, micropore, and a very narrow pipe are important topics for development of the chemical engineering. Here, we propose a measuring method which evaluates the surface coverage of the chemically modified pore surface and the corrosion rate of the inner surface of the narrow pipe, etc. The method uses Kelvin's equation that expresses saturated vapor pressure of a liquid in the pore (pipe). The surface coverage and the corrosion rate are calculated by measuring...

  17. The dynamics of beltramized flows and its relation with the Kelvin waves

    Gonzalez, Rafael [Instituto de Desarrollo Humano, Universidad Nacional de General Sarmiento Pcia. de Buenos Aires, Argentina and Depto. de Fisica FCEyN, Universidad de Buenos Aires, Buenos Aires (Argentina); Santini, E Sergio, E-mail: rgonzale@ungs.edu.ar [Instituto de Ciencias, Universidad Nacional de General Sarmiento Pcia. de Buenos Aires (Argentina) and ICRA-BR, Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro (Brazil)

    2011-05-01

    We define the beltramized flow as the sum of an uniform translation and an uniform rotation with a Beltrami flow. Some of their features are studied by solving the Euler equations, for different geometries, taking into account the boundary conditions, and for different symmetries. We show that the Kelvin waves are beltramized flows. Finally, we show that the variational principle found in a previous work, remains valid for the beltramized flow.

  18. Kelvin-Tkachenko waves of few-vortex arrays in trapped Bose-Einstein condensates

    We have calculated the low-lying elementary excitations of three-dimensional few-vortex arrays in trapped Bose-Einstein condensates. The number of different Kelvin-Tkachenko vortex wave branches found matches the number of vortices in the condensate. The lowest odd-parity modes exhibit superfluid gyroscopic vortex motion. Experimentally, these modes could be excited and observed individually or in connection with the formation and decay of quantum turbulence.

  19. Why Was Kelvin's Estimate of the Earth's Age Wrong?

    Lovatt, Ian; Syed, M. Qasim

    2014-01-01

    This is a companion to our previous paper in which we give a published example, based primarily on Perry's work, of a graph of ln "y" versus "t" when "y" is an exponential function of "t". This work led us to the idea that Lord Kelvin's (William Thomson's) estimate of the Earth's age was…

  20. High-resolution superconducting single-flux quantum comparator for sub-Kelvin temperatures

    Savin, A. M.; Pekola, Jukka P.; Holmqvist, T.; Hassel, J.; Grönberg, L.; Helistö, P.; Kidiyarova-Shevchenko, A.

    2006-01-01

    A design of sub-Kelvin single-flux quantum (SFQ) circuits with reduced power dissipation and additional cooling of shunt resistors has been developed and characterized. The authors demonstrate operation of SFQ comparators with current resolution of 40nA at 2GHz sampling rate. Due to improved cooling the electron temperature in shunt resistors of a SFQ comparator is below 50mK when the bath temperature is about 30mK.

  1. Altimetric observations and model simulations of coastal Kelvin waves in the Bay of Bengal

    Nienhaus, M.J.; Subrahmanyam, B; Murty, V.S.N.

    , Columbia, SC 29208 1,2Department of Earth and Ocean Sciences, University of South Carolina, Columbia, SC 29208 3National Institute of Oceanography Regional Center (CSIR), Visakhapatnam 530 017, India Contact Information: Matthew J. Nienhaus, E...-mail: mnienhaus@geol.sc.edu Abstract Kelvin waves originating in the equatorial Indian Ocean propagate along the equatorial wave guide until reaching the Sumatra coast and follow the coastal waveguide counter clockwise around the perimeter of the Bay...

  2. The Kelvin-Helmholtz instability in weakly ionised plasmas II: multifluid effects in molecular clouds

    Jones, A. C.; Downes, T. P

    2011-01-01

    We present a study of the Kelvin-Helmholtz instability in a weakly ionised, multifluid MHD plasma with parameters matching those of a typical molecular cloud. The instability is capable of transforming well-ordered flows into disordered flows. As a result, it may be able to convert the energy found in, for example, bowshocks from stellar jets into the turbulent energy found in molecular clouds. As these clouds are weakly ionised, the ideal magnetohydrodynamic approximation does not apply at s...

  3. Local charge trapping in conjugated polymers resolved by scanning Kelvin probe microscopy

    Hallam, T.; Lee, M.; N. Zhao; Nandhakumar, I; Kemerink, M Martijn; Heeney, M.; McCulloch, I; Sirringhaus, H.

    2009-01-01

    The microstructure of conjugated polymers is heterogeneous on the length scale of individual polymer chains, but little is known about how this affects their electronic properties. Here we use scanning Kelvin probe microscopy with resolution-enhancing carbon nanotube tips to study charge transport on a 100 nm scale in a chain-extended, semicrystalline conjugated polymer. We show that the disordered grain boundaries between crystalline domains constitute preferential charge trapping sites and ...

  4. Simulating and interpreting Kelvin probe force microscopy images on dielectrics with boundary integral equations

    Shen, Yongxing; Barnett, David M.; Pinsky, Peter M.

    2008-01-01

    Kelvin probe force microscopy KPFM is designed for measuring the tip-sample contact potential differences by probing the sample surface, measuring the electrostatic interaction, and adjusting a feedback circuit. However, for the case of a dielectric insulating sample, the contact potential difference may be ill defined, and the KPFM probe may be sensing electrostatic interactions with a certain distribution of sample trapped charges or dipoles, leading to difficulty in interpr...

  5. Kelvin probe force microscopy of nanocrystalline TiO2 photoelectrodes

    Alex Henning; Gino Günzburger; Res Jöhr; Yossi Rosenwaks; Biljana Bozic-Weber; Housecroft, Catherine E.; Constable, Edwin C.; Ernst Meyer; Thilo Glatzel

    2013-01-01

    Dye-sensitized solar cells (DSCs) provide a promising third-generation photovoltaic concept based on the spectral sensitization of a wide-bandgap metal oxide. Although the nanocrystalline TiO2 photoelectrode of a DSC consists of sintered nanoparticles, there are few studies on the nanoscale properties. We focus on the microscopic work function and surface photovoltage (SPV) determination of TiO2 photoelectrodes using Kelvin probe force microscopy in combination with a tunable illumination sys...

  6. PREPARATIONS OF ZINC OXIDES AND CHARACTERIZATION OF THE PHOTOVOLTAIC BEHAVIOR USING A SCANNING KELVIN PROBE

    He, Y.; Zhi, W.; B. O. ZHOU

    2010-01-01

    Surface photovoltage of semiconductors depend strongly on their electronic structures, in particular, their Fermi energy level. This offers a possibility to characterize photoelectronic behavior using the Kelvin probe structure by measurements of work function (WF). In this paper, ZnO films were prepared using the CVD method and their microstructures and morphology were characterized using the XRD and SEM. Furthermore, photovoltage evolution and WF of selected ZnO samples were measured using ...

  7. Atomic force microscope based Kelvin probe measurements : application to an electrochemical reaction

    Böhmisch, Mathias; Burmeister, Frank; Rettenberger, Armin; Zimmermann, Jörg; Boneberg, Johannes; Leiderer, Paul

    1997-01-01

    An atomic force microscope (AFM) was utilized as a Kelvin probe to determine work functions of several metals and semiconductors quantitarively. Most of the experimental data show excellent agreement with published values measured by photoemission. Variations in work functions as low as 5 mV could be detected with a typical lateral resolution of 20 nm. This method allowed us to analyze and explain the energetics of an electrochemical reaction on the surface of WSe2, which could be in situ ind...

  8. Understanding the atomic-scale contrast in Kelvin Probe Force Microscopy

    Nony, Laurent; Foster, Adam; Bocquet, Franck; Loppacher, Christian

    2009-01-01

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy (KPFM) is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a non-contact Atomic Force Microscope/KPFM simulator. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and Contact Potential Difference (CPD) contrasts were reported. The local CPD do...

  9. Determination of the electrostatic lever arm of carbon nanotube field effect transistors using Kelvin Force Microscopy

    Brunel, David; Deresmes, Dominique; Melin, Thierry

    2009-01-01

    We use Kelvin Force Microscopy (KFM) to study the electrostatic properties of single-walled Carbon Nanotube Field Effect Transistor devices (CNTFETs) with backgate geometry at room temperature. We show that KFM maps recorded as a function of the device backgate polarization enable a complete phenomenological determination of the averaging effects associated with the KFM probe side capacitances, and thus, to obtain KFM measurements with quantitative character. The value of the electrostatic le...

  10. High resolution investigation of localized corrosion by in-situ Scanning Kelvin Probe Force Microscopy

    Senöz, Ceylan

    2011-01-01

    In dieser Arbeit wurde die Möglichkeit zur Nutzung der Scanning Kelvin Probe Force Microscopy (SKPFM) in der Korrosionforschung untersucht. Ein wesentlicher Nachteil dieser Technik ist die mangelnde Fähigkeit der Abbildbarkeit durch organische Beschichtungen hindurch. In dieser Arbeit wurde die Methodik zur Nutzung von SKPFM so weiter entwickelt, dass auch in-situ Untersuchungen in zwei verschiedenen Anwendungsfeldern möglich sind. Eine dieser Anwendungen beinhaltet den zugrunde l...

  11. Facile Preparation of a Platinum Silicide Nanoparticle-Modified Tip Apex for Scanning Kelvin Probe Microscopy

    Lin, Chun-Ting; Chen, Yu-Wei; Su, James; Wu, Chien-Ting; Hsiao, Chien-Nan; Shiao, Ming-Hua; Chang, Mao-Nan

    2015-01-01

    In this study, we propose an ultra-facile approach to prepare a platinum silicide nanoparticle-modified tip apex (PSM tip) used for scanning Kelvin probe microscopy (SKPM). We combined a localized fluoride-assisted galvanic replacement reaction (LFAGRR) and atmospheric microwave annealing (AMA) to deposit a single platinum silicide nanoparticle with a diameter of 32 nm on the apex of a bare silicon tip of atomic force microscopy (AFM). The total process was completed in an ambient environment...

  12. Electrical Potential of Acupuncture Points: Use of a Noncontact Scanning Kelvin Probe

    Gow, Brian J.; Cheng, Justine L.; Baikie, Iain D.; Ørjan G. Martinsen; Min Zhao; Stephanie Smith; Ahn, Andrew C

    2012-01-01

    Objective. Acupuncture points are reportedly distinguishable by their electrical properties. However, confounders arising from skin-to-electrode contact used in traditional electrodermal methods have contributed to controversies over this claim. The Scanning Kelvin Probe is a state-of-the-art device that measures electrical potential without actually touching the skin and is thus capable of overcoming these confounding effects. In this study, we evaluated the electrical potential profiles of ...

  13. Dual harmonic Kelvin probe force microscopy at the graphene-liquid interface

    Collins, Liam; Kilpatrick, J. I.; Vlassiouk, Ivan V.; Weber, Stefan A. L.; Rodriguez, Brian J; et al.

    2014-01-01

    Kelvin probe force microscopy (KPFM) is a powerful technique for the determination of the contact potential difference (CPD) between an atomic force microscope tip and a sample under ambient and vacuum conditions. However, for many energy storage and conversion systems, including graphene-based electrochemical capacitors, understanding electrochemical phenomena at the solid¿liquid interface is paramount. Despite the vast potential to provide fundamental insight for energy storage materials at...

  14. The Importance of Cantilever Dynamics in the Interpretation of Kelvin Probe Force Microscopy

    Brown, Keith A.; Westervelt, Robert M.; Satzinger, Kevin J.

    2012-01-01

    A realistic interpretation of the measured contact potential difference (CPD) in Kelvin probe force microscopy (KPFM) is crucial in order to extract meaningful information about the sample. Central to this interpretation is a method to include contributions from the macroscopic cantilever arm, as well as the cone and sharp tip of a KPFM probe. Here, three models of the electrostatic interaction between a KPFM probe and a sample are tested through an electrostatic simulation and compared with ...

  15. The role of the cantilever in Kelvin probe force microscopy measurements

    George Elias; Thilo Glatzel; Ernst Meyer; Alex Schwarzman; Amir Boag; Yossi Rosenwaks

    2011-01-01

    The role of the cantilever in quantitative Kelvin probe force microscopy (KPFM) is rigorously analyzed. We use the boundary element method to calculate the point spread function of the measuring probe: Tip and cantilever. The calculations show that the cantilever has a very strong effect on the absolute value of the measured contact potential difference even under ultra-high vacuum conditions, and we demonstrate a good agreement between our model and KPFM measurements in ultra-high vacuum of ...

  16. Kelvin probe study of laterally inhomogeneous dielectric charging and charge diffusion in RF MEMS capacitive switches

    Herfst, R.W.; Steeneken, P. G.; Schmitz, J; Mank, A.J.G.; Gils, van, S.H.

    2008-01-01

    In this paper we use scanning Kelvin probe microscopy (SKPM) to detect charge in the dielectric of RF MEMS capacitive switches. We observe a laterally inhomogeneous distribution. Laterally inhomogeneous dielectric charging leads to a narrowing of the C-V curve [1], and can lead to stiction of the membrane. The measurements show that trapped charges slowly diffuse, which reduces the inhomogeneity and shows that charge is vertically confined. From these measurements we estimate the lateral diff...

  17. Surface Potential Analysis of Nanoscale Biomaterials and Devices Using Kelvin Probe Force Microscopy

    Hyungbeen Lee; Wonseok Lee; Jeong Hoon Lee; Dae Sung Yoon

    2016-01-01

    In recent years, Kelvin probe force microscopy (KPFM) has emerged as a versatile toolkit for exploring electrical properties on a broad range of nanobiomaterials and molecules. An analysis using KPFM can provide valuable sample information including surface potential and work function of a certain material. Accordingly, KPFM has been widely used in the areas of material science, electronics, and biomedical science. In this review, we will briefly explain the setup of KPFM and its measuring pr...

  18. Determination of Contact Potential Difference by the Kelvin Probe (Part I) I. Basic Principles of Measurements

    Vilitis O.; Rutkis M.; Busenberg J.; Merkulov D.

    2016-01-01

    Determination of electric potential difference using the Kelvin probe, i.e. vibrating capacitor technique, is one of the most sensitive measuring procedures in surface physics. Periodic modulation of distance between electrodes leads to changes in capacitance, thereby causing current to flow through the external circuit. The procedure of contactless, non-destructive determination of contact potential difference between an electrically conductive vibrating reference electrode and an electrical...

  19. Sample preparation for scanning Kelvin probe microscopy studies on cross sections of organic solar cells

    Michael Scherer; Rebecca Saive; Dominik Daume; Michael Kröger; Wolfgang Kowalsky

    2013-01-01

    We prepared cross sections of P3HT:PCBM bulk heterojunction (BHJ) organic solar cells (OSCs) for the characterization of their potential distribution with scanning Kelvin probe microscopy. We compared results of samples obtained by microtome cutting of OSCs on plastic substrates, cleaving of OSCs on glass substrates, and milling with a focused ion beam. Their potential distributions were in good agreement with each other. Under short circuit conditions, potential gradients were detected in vi...

  20. Kelvin probe measurements of microcrystalline silicon on a nanometer scale using SFM

    Breymesser, A.; Schlosser, V.; Peiró, D.; Voz Sánchez, Cristóbal; Bertomeu i Balagueró, Joan; Andreu i Batallé, Jordi; Summhammer, J.

    2001-01-01

    Work function measurements on cross-sectioned microcrystalline pin silicon solar cells deposited by Hot-Wire CVD are presented. The experiment is realized by combining a modified Kelvin probe experiment and a scanning force microscope. The measured surface potential revealed that the built-in electric drift field is weak in the middle of the compensated intrinsic layer. A graded donor distribution and a constant boron compensation have to be assumed within the intrinsic layer in order to obta...

  1. Kelvin probe force microscopy for local characterisation of active nanoelectronic devices

    Tino Wagner; Hannes Beyer; Patrick Reissner; Philipp Mensch; Heike Riel; Bernd Gotsmann; Andreas Stemmer

    2015-01-01

    Frequency modulated Kelvin probe force microscopy (FM-KFM) is the method of choice for high resolution measurements of local surface potentials, yet on coarse topographic structures most researchers revert to amplitude modulated lift-mode techniques for better stability. This approach inevitably translates into lower lateral resolution and pronounced capacitive averaging of the locally measured contact potential difference. Furthermore, local changes in the strength of the electrostatic inter...

  2. Observation of equatorial Kelvin solitary waves in a slowly varying thermocline

    Zheng, Q; R. D. Susanto; X.-H. Yan; W. T. Liu; C.-R. Ho

    1998-01-01

    TOPEX/POSEIDON (T/P) sea level deviation (SLD) time series from 3 October 1992 to 15 May 1997 combined with upper ocean thermal structures are used to observe the characteristics and analyze the dynamics of equatorial waves in the Pacific Ocean. The evolution of the Kelvin wave propagating along an eastward shoaling thermocline in the equatorial Pacific is investigated. The behaviour of this wave as it propagates eastward can be approximately described with the solutions of the perturbed Kort...

  3. Global Regular Solutions to a Kelvin-Voigt Type Thermoviscoelastic System

    Pawlow, Irena

    2011-01-01

    A classical 3-D thermoviscoelastic system of Kelvin-Voigt type is considered. The existence and uniqueness of a global regular solution is proved without small data assumption. The existence proof is based on the successive approximation method. The crucial part constitute a priori estimates on an arbitrary finite time interval, which are derived with the help of the theory of anisotropic Sobolev spaces with a mixed norm.

  4. Approximate Kelvin-Voigt Fluid Driven by an External Force Depending on Velocity with Distributed Delay

    Yantao Guo

    2015-01-01

    Full Text Available We consider the approximate 3D Kelvin-Voigt fluid driven by an external force depending on velocity with distributed delay. We investigate the long time behavior of solutions to Navier-Stokes-Voigt equation with a distributed delay external force depending on the velocity of fluid on a bounded domain. By a prior estimate and a contractive function, we give a sufficient condition for the existence of pullback attractor of NSV equation.

  5. Quantitative dopant profiling in semiconductors: A new approach to Kelvin probe force microscopy

    Baumgart, Christine

    2013-01-01

    Failure analysis and optimization of semiconducting devices request knowledge of their electrical properties. To meet the demands of today’s semiconductor industry, an electrical nanometrology technique is required which provides quantitative information about the doping profile and which enables scans with a lateral resolution in the sub-10 nm range. In the presented work it is shown that Kelvin probe force microscopy (KPFM) is a very promising electrical nanometrology technique to face this...

  6. Synthesis of 4-aryl-3,4-dihydrocoumarin derivatives catalyzed by NbCl{sub 5}; Sintese de derivados 4-aril-3,4-di-hidrocuraminicos catalisada por NbCl{sub 5}

    Santos, Willian Henrique dos; Siqueira, Mayara de Souza; Silva-Filho, Luiz Carlos da, E-mail: lcsilva@fc.unesp.br [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Bauru, SP (Brazil). Faculdade de Ciencias

    2013-11-01

    Multicomponent reactions between phenols, {beta}-diesters and benzaldehydes for the synthesis of 4-aryl-3,4-dihydrocoumarin derivatives were carried out under mild conditions (room temperature) and presented moderate yields (38-88%) and reasonable reaction times (2-4 days), using niobium pentachloride as a catalyst. (author)

  7. Evaluation of the oral subchronic toxicity of AHTN (7-Acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene) in the rat.

    Api, Anne Marie; Smith, Robert L; Pipino, Sandra; Marczylo, Timothy; De Matteis, Francesco

    2004-05-01

    7-Acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN) is used as a fragrance material in a wide variety of consumer products. Because of its widespread exposure, a 90-day oral feeding study, with 4-week recovery periods for selected rats, was conducted. AHTN was added to the diet of rats at levels calculated to result in mean daily doses of 1.5, 5, 15 or 50 mg AHTN/kg body weight/day. On completion of the treatment period, 3 males and 3 females from each of the high dose groups and controls were maintained for a treatment free period of 4 weeks. There were no adverse effects revealed upon clinical examination or following extensive histopathological examinations. Histopathological examination of the prostate, seminal vesicles, mammary gland and testes of males and ovaries, mammary gland, uterus and vagina of females, undertaken on all animals in all test groups, revealed no evidence of hormonal effects of AHTN. A statistically significant decrease in body weight gain was observed in both sexes in the high dose group only. Statistically significant effects were observed in hematology and blood chemistry, although these effects were all within the range for historical controls and were not proportional to dose. A green to dark brown coloration in the livers and mesenteric lymph nodes was also seen in high dose animals. At the end of the treatment-free period, the color change was almost completely reversed; one high dose male still had green colored lymph nodes, but the liver appeared normal. A green coloration of the lacrimal glands in females, but not males, was also seen in 8/12, 4/15 and in 1 female given 50, 15 and 5 mg/kg body weight/day, respectively. This green color was still present in 2/3 of the high dose females after the treatment-free period. Microscopic examination of unstained sections of frozen livers under UV illumination did not reveal any fluorescence that might have been consistent with porphyrin accumulation. These findings were

  8. Impurities in Illicit Drug Preparations: 3,4-(Methylenedioxy)amphetamine and 3,4-(Methylenedioxy)methylamphetamine.

    Verweij, A M

    1992-12-01

    Attention is given here to the mass spectral data of impurities present in illicit drug preparations of 3,4-(methylenedioxy)amphetamine and 3,4-(methylenedioxy)methylamphetamine. These "designer" drugs, having emphatic properties, were synthesized following well-known procedures such as the reductive amination route, the Leuckart reaction, and the nitropropene and the bromopropane routes. Based on the structure elucidation of impurities - especially those so-called "route specific" ones - present in these illicit drug preparations conclusions can be drawn about the method of preparation of a drug sample. Furthermore, on the basis of this kind of information methods can be developed for the comparison of drug samples, by which questions about the origin of drug samples can be solved (commonly known as the signature method). PMID:26267375

  9. Comparison of mobility equivalent diameter with Kelvin-Thomson diameter using ion mobility data

    Mäkelä, Jyrki M.; Riihelä, Marko; Ukkonen, Ari; Jokinen, Vilho; Keskinen, Jorma

    1996-07-01

    Mobility distributions of both positive and negative cluster ions were studied in nitrogen gas enriched by ethanol, isopropanol, n-butanol and acetone vapours, respectively. The ions were generated into the system by a radioactive source normally used as a bipolar aerosol charger. The ion mobility distributions were measured with a time-of-flight mobility spectrometer (TOF). The measured ion mobility can be used to estimate the mobility equivalent diameter via conventional Millikan-Fuchs formula based on Stokes law corrected by molecule slip effects. When the vapour concentration is increased the cluster ions will get larger due to enhanced molecule attachment onto ions. Here the vapour concentration is assumed to be high enough so that the chemical tracer effects would become of minor importance. Therefore the Kelvin-Thomson equation for ion induced nucleation is first assumed to be valid. The Kelvin-Thomson diameter of the ions in all cases was found to be systematically smaller than the corresponding mobility equivalent diameter according to Millikan-Fuchs, indicating of inconsistencies between the formulas based on macroscopic quantities at 1 nm size range. Thereafter, other available mobility vs diameter relationships were surveyed. The closest agreement between mobility equivalent and Kelvin-Thomson diameters at this size was obtained using the relationship given by Tammet [J. Aerosol Sci. 26, 459 (1995)].

  10. Kelvin probe force microscopy on electrically inhomogeneous Fe/W(001) films

    Noncontact scanning force microscopy can give information about the real topography of the sample. However, this is valid only when the dominant tip-sample interaction is due to the van der Waals force. If the sample is electrically inhomogeneous, e.g., the sample has an inhomogeneous electric charge distribution, it causes additional electrostatic forces between tip and sample, which prevent real topography measurement. To nullify the electrostatic effect, the tip bias can be regulated with a special feedback scheme called Kelvin probe force microscopy. Here we applied Kelvin probe force microscopy to the pseudomorphic Fe thin film grown on W(001). In this highly strained film, the electric properties depend on the number of layers, yielding different contact potentials in each layer. The samples were prepared and measured in-situ under ultra high vacuum condition without exposing them to the atmospheric environment. When the tip bias was not regulated, the apparent step height of the film changed depending on the tip-sample bias, and a reliable measurement of topography was impossible. With Kelvin probe force microscopy, the contact potentials different in each layer could be compensated, and the real topography image could be obtained

  11. A simultaneous Kelvin Probe and Raman spectroscopy approach for in situ surface and interface analysis

    A two-channel excitation and detection probe head for Raman spectroscopy was installed in the sample chamber of a height-regulated Kelvin Probe (KP). The beam of a 532 nm laser could be thereby focused on the sample area directly beneath the KP needle. Scattered light from the sample surface was collected by the Raman probe head and sent to a detector system via fiber optics. This allowed a simultaneous detection of surface potentials and Raman spectra for a localized investigation of the properties of oxide covered metal substrates in atmospheres of different relative humidity and oxygen partial pressure. Initial testing of the assembled setup revealed that both analytical methods can be operated independently of each other as long as the laser is not hitting the Kelvin Probe needle. The KP detected reversible and irreversible laser-induced drying, photoelectric and structural rearrangement effects that were correlated to equivalent Raman spectra recorded on bare steel sheets, steel covered with a powdery oxide layer and after that layer was wiped off. This showed that the combined Kelvin Probe–Raman spectroscopy approach can give additional information that is not available by each technique separately. As it has the potential to provide contributions to sophisticated analytical surface and interface studies, possible applications of this experimental tool are also discussed.

  12. Determination of Contact Potential Difference by the Kelvin Probe (Part I) I. Basic Principles of Measurements

    Vilitis, O.; Rutkis, M.; Busenberg, J.; Merkulov, D.

    2016-04-01

    Determination of electric potential difference using the Kelvin probe, i.e. vibrating capacitor technique, is one of the most sensitive measuring procedures in surface physics. Periodic modulation of distance between electrodes leads to changes in capacitance, thereby causing current to flow through the external circuit. The procedure of contactless, non-destructive determination of contact potential difference between an electrically conductive vibrating reference electrode and an electrically conductive sample is based on precise control measurement of Kelvin current flowing through a capacitor. The present research is devoted to creation of a new low-cost miniaturised measurement system to determine potential difference in real time and at high measurement resolution. Furthermore, using the electrode of a reference probe, the Kelvin method leads to both the indirect measurement of an electronic work function, or a contact potential of sample, and of a surface potential for insulator type samples. In the article, the first part of the research, i.e., the basic principles and prerequisites for establishment of such a measurement system are considered.

  13. Impact of MHD shock physics on magnetosheath asymmetry and Kelvin-Helmholtz instability

    Nykyri, K.

    2013-08-01

    We have performed 13 three-dimensional global magnetohydrodynamic (MHD) simulations of the magnetosheath plasma and magnetic field properties for Parker spiral (PS) and ortho-Parker spiral interplanetary magnetic field (IMF) orientations corresponding to a wide range of solar wind plasma conditions. To study the growth of the Kelvin-Helmholtz instability on the dawn and dusk flank magnetopause, we have performed 26 local two-dimensional MHD simulations, with the initial conditions taken from global simulations on both sides of the velocity shear layer at the dawn-dusk terminator. These simulations indicate that while the MHD physics of the fast shocks does not directly lead to strong asymmetry of the magnetosheath temperature for typical solar wind conditions, the magnetosheath on the quasi-parallel shock side has a smaller tangential magnetic field along the magnetosheath flow which enables faster growth of the Kelvin-Helmholtz instability (KHI). Because the IMF is statistically mostly in the PS orientation, the KHI formation may statistically favor the dawnside flank. For all the 26 simulations, the growth rates of the KHI correlated well with the ratio of the velocity shear and Alfvén speed along the wave vector, k. Dynamics of the KHI may subsequently lead to formation of kinetic Alfvén waves and reconnection in the Kelvin-Helmholtz vortices which can lead to particle energization. This may partly help to explain the observed plasma sheet asymmetry of cold-component ions, which are heated more on the dawnside plasma sheet.

  14. Properties of the average distribution of equatorial Kelvin waves investigated by ray tracing techniques

    M. Ern

    2009-06-01

    Full Text Available Kelvin waves excited by tropospheric convection are considered to be one of the main drivers of the stratospheric quasi-biennial oscillation (QBO. In this paper we combine several measured data sets with the Gravity wave Regional Or Global RAy Tracer (GROGRAT in order to study the forcing and vertical propagation of Kelvin waves. Launch distributions for the ray tracer at tropospheric altitudes are deduced from space-time spectra of European Centre for Medium-Range Weather Forecasts (ECMWF operational analyses, as well as outgoing longwave radiation (OLR and rainfall data measured by the Tropical Rainfall Measuring Mission (TRMM satellite. The resulting stratospheric Kelvin wave spectra are compared to ECMWF operational analyses and temperature measurements of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER satellite instrument. Questions addressed are: the relative importance of source variability versus wind modulation, the relative importance of radiative and turbulent damping versus wave breaking, and the minimum altitude where freely propagating waves dominate the spectrum.

  15. Chronic Unpredictable Stress Augments +3,4-Methylenedioxymethamphetamine (MDMA)-induced Monoamine Depletions: The Role of Corticosterone

    Johnson, Bethann N.; Yamamoto, Bryan K.

    2009-01-01

    Exposure to stress alters the behavioral and neurochemical effects of drugs of abuse. However, it is unknown if chronic stress can affect the serotonergic depletions induced by the psychostimulant drug 3,4-methylenedioxymethamphetamine (MDMA). Rats were exposed to 10 days of chronic unpredictable stress (CUS) which resulted in the predicted elevation of basal plasma corticosterone concentrations. On the 11th day, rats received 4 challenge doses of MDMA (5 mg/kg every 2 h, i.p.) or saline. Fiv...

  16. Developmental Effects of ±3,4-Methylenedioxymethamphetamine on Spatial Versus Path Integration Learning: Effects of Dose Distribution

    Vorhees, Charles V.; Schaefer, Tori L.; Williams, Michael T.

    2007-01-01

    We previously demonstrated that postnatal day 11–20 ±3,4-methylenedioxymethamphetamine (MDMA) exposure reduces locomotor activity and impairs path integration and spatial learning independent of the effects on activity. The effects were seen when the drug was administered twice per day, but the optimal dosing regimen is unknown. We tested whether the same total daily dose of MDMA administered in different patterns would equally affect later behavior. A split-litter design (15 litters) was use...

  17. Developmental effects of 3,4-methylenedioxymethamphetamine: a review

    Skelton, Matthew R.; Williams, Michael T; Vorhees, Charles V.

    2008-01-01

    ± 3,4-Methylenedioxymethamphetamine (MDMA) is a chemical derivative of amphetamine that has become a popular drug of abuse and has been shown to deplete serotonin in the brains of users and animals exposed to it. To date, most studies have investigated the effects of MDMA on adult animals. With a majority of users of MDMA being young adults, the chances of the users becoming pregnant and exposing the fetuses to MDMA are also a concern. Evidence to date has shown that developmental exposure to...

  18. AGR 3/4 Irradiation Test Final As Run Report

    Collin, Blaise P. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-06-01

    Several fuel and material irradiation experiments have been planned for the Idaho National Laboratory Advanced Reactor Technologies Technology Development Office Advanced Gas Reactor Fuel Development and Qualification Program (referred to as the INL ART TDO/AGR fuel program hereafter), which supports the development and qualification of tristructural-isotropic (TRISO) coated particle fuel for use in HTGRs. The goals of these experiments are to provide irradiation performance data to support fuel process development, qualify fuel for normal operating conditions, support development and validation of fuel performance and fission product transport models and codes, and provide irradiated fuel and materials for post irradiation examination and safety testing (INL 05/2015). AGR-3/4 combined the third and fourth in this series of planned experiments to test TRISO coated low enriched uranium (LEU) oxycarbide fuel. This combined experiment was intended to support the refinement of fission product transport models and to assess the effects of sweep gas impurities on fuel performance and fission product transport by irradiating designed-to-fail fuel particles and by measuring subsequent fission metal transport in fuel-compact matrix material and fuel-element graphite. The AGR 3/4 fuel test was successful in irradiating the fuel compacts to the burnup and fast fluence target ranges, considering the experiment was terminated short of its initial 400 EFPD target (Collin 2015). Out of the 48 AGR-3/4 compacts, 42 achieved the specified burnup of at least 6% fissions per initial heavy-metal atom (FIMA). Three capsules had a maximum fuel compact average burnup < 10% FIMA, one more than originally specified, and the maximum fuel compact average burnup was <19% FIMA for the remaining capsules, as specified. Fast neutron fluence fell in the expected range of 1.0 to 5.5×1025 n/m2 (E >0.18 MeV) for all compacts. In addition, the AGR-3/4 experiment was globally successful in keeping the

  19. 3,4-Diaminopyridinium 2-carboxy-4,6-dinitrophenolate

    Madhukar Hemamalini

    2010-11-01

    Full Text Available In the title salt, C5H8N3+·C7H3N2O7−, the pyridine N atom of the 3,4-diaminopyridine molecule is protonated. The 3,5-dinitrosalicylate anion shows whole-molecule disorder over two orientations with a refined occupancy ratio of 0.875 (4: 0.125 (4. In the crystal, the cations and anions are connected by intermolecular N—H...O and C—H...O hydrogen bonds, forming a three-dimensional network.

  20. Stereoselective Synthesis of 2,3,4,6-Tetrasubstituted Tetrahydropyrans

    GONG Jun-Fang; WU Yang-Jie; Véronique Micheletb; Jean-Pierre Genêt b

    2003-01-01

    @@ The construction of stereodefined, highly substituted tetrahydropyrans has attracted a lot of interest over the years since they constitute ubiquitous fragments of numerous biologically active natural products.[1] During the course of our synthetic studies toward ambruticin, a fascinating antibiotic[2] which came back in the front scene with three recent total synthesis, [3] we have been interested in the synthesis of 2,3,4,6-tetrasubstituted tetrahydropyrans 5 (Scheme 1). [4] Moreover, this kind of subunit is found to be embedded in several other natural products such as lasonolide A, polycavernoside A, ratjadone, or concanamycin A.

  1. Reliability of poly 3,4-ethylenedioxythiophene strain gauge

    Mateiu, Ramona Valentina; Lillemose, Michael; Hansen, Thomas Steen;

    2007-01-01

    -polymer Microsystems. The measurements are made on microfabricated test chips with PEDT resistors patterned by conventional UV-lithography and reactive ion etching (RIE). We determine a gauge factor of 3.41 ± 0.42 for the strained PEDT and we see an increase in resistivity from 1.98 · 104 X m to 2.22 · 104 X m when......We report on the experimentally observed reliability of the piezoresistive effect in strained poly 3,4-ethylenedioxythiophene (PEDT). PEDT is an intrinsic conductive polymer which can be patterned by conventional Cleanroom processing, and thus presents a promising material for all...

  2. Ultraporous poly(3,4-ethylenedioxythiophene) for nanometric electrochemical supercapacitor

    Ultrathin films of poly(3,4-ethylenedioxythiophene) (PEDOT) have been prepared by electropolymerization on steel and indium-tin oxide (ITO) substrates under identical experimental conditions. Scanning electron microscopy and atomic force microscopy indicate that the substrate affects dramatically both the morphology and topography of films when the polymerization times are very short. An ultraporous three-dimensional network involving ultrathin sticks with a fiber-like morphology was formed on ITO. Asymmetric and symmetric supercapacitors have been fabricated by assembling electrodes of PEDOT deposited on ITO and steel. The specific capacitance, electrochemical stability, supercapacitor behavior and Coulombic efficiency measured for devices with an ITO/steel configuration were similar to those reported for advanced PEDOT-inorganic hybrid composites. Furthermore, the performance of the ITO/steel assembly is higher than those determined for symmetric supercapacitors derived from two identical electrodes of PEDOT deposited on steel or on ITO. The unique properties of the asymmetric supercapacitors have been attributed to the ultraporous structure of the ultrathin films deposited on ITO, which is not significantly perturbed when the device is submitted to a very high number of consecutive oxidation–reduction processes, and the different electroactivities of the two electrodes. - Highlights: ► Ultrathin poly(3,4-ethylenedioxythiophene) (PEDOT) films show fiber-like morphology. ► The porosity of ultrathin PEDOT films induces a very high electrochemical stability. ► Asymmetric supercapacitors made of ultrathin PEDOT behave like hybrid nanocomposites.

  3. Uncertainty Quantification of Calculated Temperatures for the AGR 3/4 Experiment

    Pham, Binh Thi-Cam [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-01

    A series of Advanced Gas Reactor (AGR) irradiation experiments are being conducted within the Advanced Reactor Technology (ART) Fuel Development and Qualification Program. The main objectives of the fuel experimental campaign are to provide the necessary data on fuel performance to support fuel process development, qualify a fuel design and fabrication process for normal operation and accident conditions, and support development and validation of fuel performance and fission product transport models and codes (PLN 3636, “Technical Program Plan for INL Advanced Reactor Technologies Technology Development Office/Advanced Gas Reactor Fuel Development and Qualification Program”). The AGR 3/4 test was inserted in the Northeast Flux Trap position in the Advanced Test Reactor (ATR) core at Idaho National Laboratory (INL) in December 2011 and successfully completed irradiation in mid-April 2014, resulting in irradiation of the tristructural isotropic (TRISO) fuel for 369.1 effective full-power days (EFPDs) during approximately 2.4 calendar years. The AGR 3/4 data, including the irradiation data and calculated results, were qualified and stored in the Nuclear Data Management and Analysis System (NDMAS). To support the U.S. TRISO fuel performance assessment and to provide data for validation of fuel performance and fission product transport models and codes, the daily as run thermal analysis has been performed separately on each of twelve AGR 3/4 capsules for the entire irradiation as discussed in ECAR-2807, “AGR 3/4 Daily As Run Thermal Analyses”. The ABAQUS code’s finite element-based thermal model predicts the daily average volume average (VA) fuel temperature (FT), peak FT, and graphite matrix, sleeve, and sink temperature in each capsule. The JMOCUP simulation codes were also created to perform depletion calculations for the AGR 3/4 experiment (ECAR-2753, “JMOCUP As-Run Daily Physics Depletion Calculation for the AGR 3/4 TRISO Particle Experiment in ATR

  4. Uncertainty Quantification of Calculated Temperatures for the AGR 3/4 Experiment

    A series of Advanced Gas Reactor (AGR) irradiation experiments are being conducted within the Advanced Reactor Technology (ART) Fuel Development and Qualification Program. The main objectives of the fuel experimental campaign are to provide the necessary data on fuel performance to support fuel process development, qualify a fuel design and fabrication process for normal operation and accident conditions, and support development and validation of fuel performance and fission product transport models and codes (PLN 3636, 'Technical Program Plan for INL Advanced Reactor Technologies Technology Development Office/Advanced Gas Reactor Fuel Development and Qualification Program'). The AGR 3/4 test was inserted in the Northeast Flux Trap position in the Advanced Test Reactor (ATR) core at Idaho National Laboratory (INL) in December 2011 and successfully completed irradiation in mid-April 2014, resulting in irradiation of the tristructural isotropic (TRISO) fuel for 369.1 effective full-power days (EFPDs) during approximately 2.4 calendar years. The AGR 3/4 data, including the irradiation data and calculated results, were qualified and stored in the Nuclear Data Management and Analysis System (NDMAS). To support the U.S. TRISO fuel performance assessment and to provide data for validation of fuel performance and fission product transport models and codes, the daily as run thermal analysis has been performed separately on each of twelve AGR 3/4 capsules for the entire irradiation as discussed in ECAR-2807, 'AGR 3/4 Daily As Run Thermal Analyses'. The ABAQUS code's finite element-based thermal model predicts the daily average volume average (VA) fuel temperature (FT), peak FT, and graphite matrix, sleeve, and sink temperature in each capsule. The JMOCUP simulation codes were also created to perform depletion calculations for the AGR 3/4 experiment (ECAR-2753, 'JMOCUP As-Run Daily Physics Depletion Calculation for the AGR 3/4 TRISO Particle

  5. A Day For Love

    2009-01-01

    Young couples drive Valentine’s Day booms in China It is not clear when Chinese couplesstarted celebrating Valentine’s Day,but it has now firmly established itself as an important day around the Spring Festival,

  6. A modified Kelvin impact model for pounding simulation of base-isolated building with adjacent structures

    Ye Kun; Li Li; Zhu Hongping

    2009-01-01

    Base isolation can effectively reduce the seismic forces on a superstructure, particularly in low- to medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level between the base-isolated building (BIB) and its surrounding retaining walls. To effectively investigate the behavior of the BIB pounding with adjacent structures, after assessing some commonly used impact models, a modified Kelvin impact model is proposed in this paper. Relevant parameters in the modified Kelvin model are theoretically derived and numerically verified through a simple pounding case. At the same time, inelasticity of the isolated superstructure is introduced in order to accurately evaluate the potential damage to the superstructure caused by the pounding of the BIB with adjacent structures. The reliability of the modified Kelvin impact model is validated through numerical comparisons with other impact models. However, the difference between the numerical results from the various impact analytical models is not significant. Many numerical simulations of BIBs are conducted to investigate the influence of various design parameters and conditions on the peak inter-story drills and floor accelerations during pounding. It is shown that pounding can substantially increase floor accelerations, especially at the ground floor where impacts occur. Higher modes of vibration are excited during poundings, increasing the inter-story drifts instead of keeping a nearly rigid-body motion of the superstructure. Furthermore, higher ductility demands can be imposed on lower floors of the superstructure. Moreover, impact stiffness seems to play a significant role in the acceleration response at the isolation level and the inter-story drifts of lower floors of the superstructure. Finally, the numerical results show that excessive flexibility of the isolation system used to minimize the floor accelerations may cause the BIB to be more susceptible to pounding

  7. Tetrakis(μ-3,4-dimethoxyphenylacetatobis[(3,4-dimethoxyphenylacetato(1,10-phenanthrolineholmium(III

    Jian-Feng Liu

    2010-10-01

    Full Text Available In the centrosymmetric title compound, [Ho2(C10H11O46(C12H8N22], the HoIII atom is nine-coordinated by seven O atoms from the 3,4-dimethoxyphenylacetate (L anions and two N atoms from a 1,10-phenanthroline (phen molecule. The L ligands are coordinated to the HoIII ions in three modes: chelating, bridging and bridging–tridentate. Intramolecular C—H...O interactions occur. The crystal packing is stabilized by intermolecular C—H...O interactions and weak aromatic π–π interactions between phen molecules and the aromatic rings of the L ligands [centroid–centroid distance = 3.821 (2 Å].

  8. Sub-milliKelvin spatial thermometry of a single Doppler cooled ion in a Paul trap

    Knünz, S.; Herrmann, M; Batteiger, V.; Saathoff, G.; Hänsch, T. W.; Udem, Th.

    2012-01-01

    We report on observations of thermal motion of a single, Doppler-cooled ion along the axis of a linear radio-frequency quadrupole trap. We show that for a harmonic potential the thermal occupation of energy levels leads to Gaussian distribution of the ion's axial position. The dependence of the spatial thermal spread on the trap potential is used for precise calibration of our imaging system's point spread function and sub-milliKelvin thermometry. We employ this technique to investigate the l...

  9. Sub-milliKelvin spatial thermometry of a single Doppler cooled ion in a Paul trap

    Knünz, S; Batteiger, V; Saathoff, G; Hänsch, T W; Udem, Th; 10.1103/PhysRevA.85.023427

    2012-01-01

    We report on observations of thermal motion of a single, Doppler-cooled ion along the axis of a linear radio-frequency quadrupole trap. We show that for a harmonic potential the thermal occupation of energy levels leads to Gaussian distribution of the ion's axial position. The dependence of the spatial thermal spread on the trap potential is used for precise calibration of our imaging system's point spread function and sub-milliKelvin thermometry. We employ this technique to investigate the laser detuning dependence of the Doppler temperature.

  10. Measuring Method of a Surface Property inside the Pore: Application of Kelvin's equation

    Amano, Ken-ichi

    2015-01-01

    Surface analyses inside the nanopore, micropore, and a very narrow pipe are important topics for development of the chemical engineering. Here, we propose a measuring method which evaluates the surface coverage of the chemically modified pore surface and the corrosion rate of the inner surface of the narrow pipe, etc. The method uses Kelvin's equation that expresses saturated vapor pressure of a liquid in the pore (pipe). The surface coverage and the corrosion rate are calculated by measuring saturated vapor pressure of the liquid in the pore and the pipe, respectively. In this letter, we explain the concept of the method briefly.

  11. Charge behavior on insulating monocrystallic surfaces by Kelvin probe force microscopy

    Full text: Detailed knowledge on the contact charging behavior of dielectric materials is of great interest for technological applications like tribocharging separation. The underlying mechanisms are still not well understood. The charging of quartz and calcite single crystal surfaces upon contact with an Atomic Force Microscope tip has been investigated using Kelvin Probe Force Microscopy. It turned out that the charging is strongly influenced by the sample history. Especially contact with different forms of water (bulk water or humid air) and sample heat treatment change the charging/discharging behavior significantly. (author)

  12. Work function of few layer graphene covered nickel thin films measured with Kelvin probe force microscopy

    Eren, B. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Material Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Gysin, U.; Marot, L., E-mail: Laurent.marot@unibas.ch; Glatzel, Th.; Steiner, R.; Meyer, E. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2016-01-25

    Few layer graphene and graphite are simultaneously grown on a ∼100 nm thick polycrystalline nickel film. The work function of few layer graphene/Ni is found to be 4.15 eV with a variation of 50 meV by local measurements with Kelvin probe force microscopy. This value is lower than the work function of free standing graphene due to peculiar electronic structure resulting from metal 3d-carbon 2p(π) hybridization.

  13. COMPENSATION OF MEASUREMENT ERRORS WHEN REDUCING LINEAR DIMENSIONS OF THE KELVIN PROBE

    A. K. Tyavlovsky

    2013-01-01

    Full Text Available The study is based on results of modeling of measurement circuit containing vibrating-plate capacitor using a complex-harmonic analysis technique. Low value of normalized frequency of small-sized scanning Kelvin probe leads to high distortion factor of probe’s measurement signal that in turn leads to high measurement errors. The way to lower measurement errors is to register measurement signal on its second harmonic and to control the probe-to-sample gap by monitoring the ratio between the second and the first harmonics’ amplitudes.

  14. Analysis of Kelvin Probe operational models with application to SR-POEM

    We present a study of several models on which Kelvin Probe (KP) instruments with flat and spherical tips rely for operation and for the determination of the contact potential difference (CPD). The study is part of the development of a high-performance KP instrument that will be used in investigations of the patch effect for the sounding rocket principle of equivalence measurement experiment. Using covariance analysis for each model we investigate its performance as imposed by the Cramer-Rao bounds and the biases introduced in the estimation of the CPD, as well as its applicability to instrument control. (papers)

  15. Surface potential imaging of CNT-FET devices by scanning Kelvin probe microscopy

    We investigated the surface potential around nanotube channel during CNT-FET operation by scanning Kelvin probe microscopy (SKPM). The results demonstrate that the local surface potential distribution depends on the fabrication process of FET devices. We also measured the transfer characteristic of CNT-FET and compared with the surface potential image. In addition, we investigate the specific FET device with the closed CNT loops into which channel CNT penetrates. The surface potential distribution is completely different with that of a simple single CNT channel. We find that the closed loop of CNT has a capability of trapping the charge inside the loop

  16. Sample preparation for scanning Kelvin probe microscopy studies on cross sections of organic solar cells

    Michael Scherer

    2013-09-01

    Full Text Available We prepared cross sections of P3HT:PCBM bulk heterojunction (BHJ organic solar cells (OSCs for the characterization of their potential distribution with scanning Kelvin probe microscopy. We compared results of samples obtained by microtome cutting of OSCs on plastic substrates, cleaving of OSCs on glass substrates, and milling with a focused ion beam. Their potential distributions were in good agreement with each other. Under short circuit conditions, potential gradients were detected in vicinity of the electrode/organics interfaces, with negligible electric fields within the bulk. We contacted the OSCs in a defined manner and studied their potential distribution under operating conditions.

  17. Work function of few layer graphene covered nickel thin films measured with Kelvin probe force microscopy

    Few layer graphene and graphite are simultaneously grown on a ∼100 nm thick polycrystalline nickel film. The work function of few layer graphene/Ni is found to be 4.15 eV with a variation of 50 meV by local measurements with Kelvin probe force microscopy. This value is lower than the work function of free standing graphene due to peculiar electronic structure resulting from metal 3d-carbon 2p(π) hybridization

  18. The role of the cantilever in Kelvin probe force microscopy measurements

    George Elias

    2011-05-01

    Full Text Available The role of the cantilever in quantitative Kelvin probe force microscopy (KPFM is rigorously analyzed. We use the boundary element method to calculate the point spread function of the measuring probe: Tip and cantilever. The calculations show that the cantilever has a very strong effect on the absolute value of the measured contact potential difference even under ultra-high vacuum conditions, and we demonstrate a good agreement between our model and KPFM measurements in ultra-high vacuum of NaCl monolayers grown on Cu(111. The effect of the oscillating cantilever shape on the KPFM resolution and sensitivity has been calculated and found to be relatively small.

  19. Integrated scanning kelvin probe scanning electrochemical microscopy system : design, development and applications

    Maljusch, Artjom

    2012-01-01

    Ein integriertes System, das auf einer Kelvin-Sonde und einem elektrochemischen Rastermikroskop basiert, wurde entwickelt und aufgebaut. Der Vorteil dieses Systems besteht darin, dass es sequenzielle Experimente im SKP-Modus und unterschiedlichen SECM-Modi mit der gleichen Elektrode und über der gleichen Stelle auf der Probenoberfläche durchführen kann. Die speziell entwickelten "glasfreien" SKP-SECM-Elektroden ermöglichen eine hohe laterale Auflösung. Das System wurde für die Unt...

  20. COMPENSATION OF MEASUREMENT ERRORS WHEN REDUCING LINEAR DIMENSIONS OF THE KELVIN PROBE

    Tyavlovsky, A. K.; A. L. Zharin

    2015-01-01

    The study is based on results of modeling of measurement circuit containing vibrating-plate capacitor using a complex-harmonic analysis technique. Low value of normalized frequency of small-sized scanning Kelvin probe leads to high distortion factor of probe’s measurement signal that in turn leads to high measurement errors. The way to lower measurement errors is to register measurement signal on its second harmonic and to control the probe-to-sample gap by monitoring the ratio between the se...

  1. Note: Switching crosstalk on and off in Kelvin probe force microscopy

    In Kelvin Probe Force Microscopy (KPFM) electronic crosstalk can occur between the excitation signal and probe deflection signal. Here, we demonstrate how a small modification to our commercial instrument enables us to literally switch the crosstalk on and off. We study in detail the effect of crosstalk on open-loop KPFM and compare with closed-loop KPFM. We measure the pure crosstalk signal and verify that we can correct for it in the data-processing required for open-loop KPFM. We also demonstrate that open-loop KPFM results are independent of the frequency and amplitude of the excitation signal, provided that the influence of crosstalk has been eliminated

  2. Kelvin probe force microscopy study of ion implanted thermal oxide thin films on silicon

    Full text: Ion implantation through gate oxides may be used for future device fabrication. However, studies of the damage created have mostly been restricted to optical and magnetic studies with EPR, PL and IR absorption. We have studied the surface potential of keV energy P implanted 15 nm thermal oxides on silicon substrates with Kelvin probe Force Microscopy. Results have shown a surface potential change while there may not be any observed change in the topology. Analytical and numerical modeling has also been used to relate the change in potential to net charge. Copyright (2005) Australian Institute of Physics

  3. Investigation of the depletion layer by scanning capacitance force microscopy with Kelvin probe force microscopy

    Uruma, Takeshi; Satoh, Nobuo; Yamamoto, Hidekazu

    2016-08-01

    We have developed a scanning probe microscope (SPM) that combines atomic force microscopy (AFM) with both Kelvin probe force microscopy (KFM — to measure the surface potential) and scanning capacitance force microscopy (SCFM — to measure the differential capacitance). The surface physical characteristics of a commercial Si Schottky barrier diode (Si-SBD), with and without an applied reverse bias, were measured over the same area by our AFM/KFM/SCFM system. We thus investigated the discrete power device by calculating the depletion-layer width and drawing an energy-band diagram.

  4. Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: From fluid to kinetic modeling

    Henri, P.; Cerri, S.S.; Califano, F.; Pegoraro, F.; Rossi, C.; Faganello, M.; Šebek, Ondřej; Trávníček, Pavel M.; Hellinger, Petr; Frederiksen, J. T.; Nordlund, A.; Markidis, S.; Keppens, R.; Lapenta, G.

    2013-01-01

    Roč. 20, č. 10 (2013), 102118/1-102118/13. ISSN 1070-664X Grant ostatní: EU(XE) SWIFF Project No. 263340; European Commission(XE) HPC-EUROPA2 - No. 228398; EU(XE) RI-283493; NASA (US) NNX11A1164G Institutional support: RVO:67985815 ; RVO:68378289 Keywords : Kelvin-Helmholtz instability * plasma kinetic theory * plasma magnetohydrodynamics Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics; BL - Plasma and Gas Discharge Physics (UFA-U) Impact factor: 2.249, year: 2013

  5. Mixed initial-boundary value problem for equations of motion of Kelvin-Voigt fluids

    Baranovskii, E. S.

    2016-07-01

    The initial-boundary value problem for equations of motion of Kelvin-Voigt fluids with mixed boundary conditions is studied. The no-slip condition is used on some portion of the boundary, while the impermeability condition and the tangential component of the surface force field are specified on the rest of the boundary. The global-in-time existence of a weak solution is proved. It is shown that the solution is unique and depends continuously on the field of external forces, the field of surface forces, and initial data.

  6. Stability for the Timoshenko Beam System with Local Kelvin-Voigt Damping

    Hong Liang ZHAO; Kang Sheng LIU; Chun Guo ZHANG

    2005-01-01

    In this paper, we consider a vibrating beam with one segment made of viscoelastic material of a Kelvin-Voigt (shorted as K-V) type and other parts made of elastic material by means of the Timoshenko model. We have deduced mathematical equations modelling its vibration and studied the stability of the semigroup associated with the equation system. We obtain the exponential stability under certain hypotheses of the smoothness and structural condition of the coefficients of the system,and obtain the strong asymptotic stability under weaker hypotheses of the coefficients.

  7. Two- and three-dimensional behavior of Rayleigh-Taylor and Kelvin-Helmholtz instabilities

    Two- and three-dimensional behavior of the Rayleigh-Taylor (R-T) and Kelvin-Helmholts (K-H) instabilities is examined with a newly developed hydrodynamic code CIP (Cubic Interpolated Pseudoparticle). The mushroom structure owing to the K-H instability is quite different in two and three dimensions. The simulation without gravity show a similar behavior and hence this difference between two and three dimensions does not originate from the R-T instability. This difference cannot be explained by a linear analysis on the K-H instability also. (author)

  8. Day to Day Life of Transnational Couples

    Ferreira, Tatiana

    2016-01-01

    In this chapter we focus on the ways that transnational spatial mobility affects the production and reproduction of daily life of couples when one of the partners migrates alone. The aim is to examine the impact of male migration on day to day life of couples in which the partners are geographically separated across nation-state borders. V/e will adopt a transnational approach in order to recognize the importance of the connections between migrants and their family members b...

  9. Mother’s Day

    张萍

    2009-01-01

    Mother’s Day is a day for each family to honor (尊敬,给……以光荣) its mother ,celebrated (庆祝)on various days in many places around the world.It complements (补足,补充) Father’s Day,the celebration

  10. [Monograph for 3-(4-methylbenzylidene)camphor (4-MBC)--HBM values for the sum of metabolites 3-(4-carboxybenzylidene)camphor (3-4CBC) and 3-(4-carboxybenzylidene)-6-hydroxycamphor (3-4 CBHC) in the urine of adults and children. Statement of the HBM Commission of the German Federal Environment Agency].

    2016-01-01

    The substance 3-(4-methylbenzylidene)camphor (4-MBC, CAS-No. 36861-47-9 as well as 38102-62-4) is used as UV-filter in cosmetics, mainly in sunscreen lotions. National as well as European evaluations are available for the substance, especially from the Scientific Committee on Consumer Products (SCCP). The SCCP did not derive a TDI-value, but used for a MoS assessment a NOAEL of 25 mg/(kg bw · d) based on effects on the thyroid gland of rats in a subchronic study with oral administration. Newer studies, however, indicate lower NOAEL values, leading to tolerable daily intakes of 0,01 mg/kg bw. The HBM Commission established for the metabolite 3-(4-carboxybenzylidene)camphor (3-4CBC) HBM-I values of 0,09 mg/l urine for adults and 0,06 mg/l urine for children. HBM-I values for the metabolite 3-(4-carboxybenzylidene)-6-hydroxycamphor (3-4CBHC) were set at 0,38 mg/l urine for adults and 0,25 mg/l urine for children. The rounded HBM-I value for the sum of metabolites 3-4CBC und 3-4CBHC is accordingly 0,5 mg/l urine for adults and 0,3 mg/l urine for children. PMID:26721474

  11. AAS 227: Day 4

    Kohler, Susanna

    2016-01-01

    mean its not typical. While we wait for more and better observations of exoplanet systems, theory can help us understand why the Solar System formed the way it did, and where to look for systems that formed the same way. For example, some of Murray-Clays previous work has shown that metal-rich stars tend to host more hot Jupiters and eccentric giant planets (very different from Solar System architecture). So if we want to find more systems like our own, we need to search around stars with low-to-moderate metallicity.Extrasolar Planets: Hosts, Interactions, Formation, and Interiors (by Caroline Morley)This session was a mashup of a variety of planetary topics ranging from solar flares to interiors to habitability.Leslie Rogers kicked off the session by presenting work done in collaboration with her student Ellen Price to constrain the composition of the ultra-short period (4 hours!?!) planet candidate KOI 1843.03 using models of the objects interior. Since its so close to the star, it can only exist without being torn apart if its very dense, which allows them to calculate that it must be iron-rich like Mercury!Next Kevin Thielen, an undergrad at Eckerd College, presented results from a summer project to apply a variable polytrope index to planet models. Tom Barclay then showed models that demonstrate the huge effect that having giant planets in the outer solar system has on the formation of terrestrial planets. He finds that without Jupiter and Saturn, more planets would form (8 instead of 3-4!) and giant impacts (like the moon-forming impact) would be more frequent but less energetic.Aomawa Shields shifted to discuss her 3D GCM models to determine the orbital configurations that would lead to liquid water on the surface of the planet Kepler-62f. She determines the effect of eccentricity, axis tilt (obliquity), and rotation rate on habitability. Edward Guinan brought us closer to home discussing the potential for superflares solar flares up to hundreds of times more

  12. Stability of rotating magnetized jets in the solar atmosphere. I. Kelvin-Helmholtz instability

    Zaqarashvili, T V; Ofman, L

    2015-01-01

    Observations show various jets in the solar atmosphere with significant rotational motions, which may undergo instabilities leading to heat ambient plasma. We study the Kelvin-Helmholtz (KH) instability of twisted and rotating jets caused by the velocity jumps near the jet surface. We derive a dispersion equation with appropriate boundary condition for total pressure (including centrifugal force of tube rotation), which governs the dynamics of incompressible jets. Then, we obtain analytical instability criteria of Kelvin-Helmholtz instability in various cases, which were verified by numerical solutions to the dispersion equation. We find that twisted and rotating jets are unstable to KH instability when the kinetic energy of rotation is more than the magnetic energy of the twist. Our analysis shows that the azimuthal magnetic field of 1-5 G can stabilize observed rotations in spicule/macrospicules and X-ray/EUV jets. On the other hand, non-twisted jets are always unstable to KH instability. In this case, the ...

  13. Study of the Kelvin-Helmholtz instability through simulation with the code Athena

    Freitas-Lemes, P; Faúndez-Abans, M

    2013-01-01

    Kelvin-Helmholtz instabilities are common in astrophysical systems, ranging from jet black holes up to protoplanetary accretion disk. An astrophysical object with strong characteristics of the Kelvin-Helmholtz instability is Caraguejo Nebula, in which the material expansion was caused by the explosion of a supernova about 1000 years ago. This instability occurs at the boundary between two fluids of different densities when one of the fluids accelerated with respect to the other. In order to study this instability, we performed a simulation with the code ATHENA Eulerian mesh. For this simulation, we consider a square domain with periodic boundaries on the sides, and reflecting on the boundary of the top and bottom. The upper box is filled with a gas density {\\rho}=1.0, pressure P1 = 1.0, adiabatic index {\\gamma}=5/3, and velocity u1=0.03 in the x direction (to the right). The lower portion has a density {\\rho}=2.0, the same pressure, velocity, and adiabatic index, only in the opposite direction to the left. Sp...

  14. Interaction of Kelvin force and transport across a melting substrate in a microgravity environment.

    Burgess, Nicholas K; Premnath, Kannan N

    2010-10-01

    Gradients in magnetic field applied to electrically insulating fluids result in an effective body force-the Kelvin force, which can potentially be used to control flow and thermal processes, particularly in microgravity environments. We study the influence of the Kelvin force on the mass, momentum, and energy transport of fluid arising from the melting of a semi-infinite solid substrate subjected to temperature and magnetic-field gradients. The governing equations of the magnetothermal free convection of the melt under the boundary layer approximation with a suitable transformation lead to a similarity solution. Closed-form analytical solutions for the limiting case of smaller Prandtl numbers are presented. The nonlinear similarity equations are solved numerically using an iterative boundary-value technique based on a finite-difference approach. Based on the numerical results, the effect of various characteristic nondimensional parameters on the structure of the melt boundary layer and transport rates of heat and mass across the substrate are elucidated and discussed. PMID:21230386

  15. Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model

    R. L. Sriver

    2012-09-01

    Full Text Available Tropical cyclones (TCs actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air-sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

  16. Two competing interpretations of Kelvin probe force microscopy on semiconductors put to test

    Polak, Leo; Wijngaarden, Rinke J.

    2016-05-01

    Kelvin probe force microscopy (KPFM) is a popular tool for studying properties of semiconductors. However, the interpretation of its results is complicated by the possibility of so-called band bending and the presence of surface charges. In this work, we study two different interpretations for KPFM on semiconductors: the contact potential difference (CPD) interpretation, which interprets the measured potential as the work-function difference between the sample and the probe, and a newer, alternative interpretation proposed by Baumgart, Helm, and Schmidt (BHS). By performing model calculations, we demonstrate that these models generally lead to very different results. Hence it is important to decide which one is correct. We demonstrate that BHS predictions for the Kelvin voltage difference between the p and n parts of a p n junction are inconsistent with a set of experimental results from the literature. In addition, the BHS interpretation predicts an independence from the probe material as well as from surface treatments, which we both find to disagree with experiment. On the other hand, we present a theoretical argument for the validity of the CPD interpretation and we show that the CPD interpretation is able to accommodate all of these experimental results. Thus we posit that the BHS interpretation is generally not suitable for the analysis of KPFM on semiconductors and that the CPD interpretation should be used instead.

  17. Excitation of equatorial Kelvin and Yanai waves by tropical cyclones in an ocean general circulation model

    R. L. Sriver

    2013-01-01

    Full Text Available Tropical cyclones (TCs actively contribute to the dynamics of Earth's coupled climate system. They influence oceanic mixing rates, upper-ocean heat content, and air–sea fluxes, with implications for atmosphere and ocean dynamics on multiple spatial and temporal scales. Using an ocean general circulation model with modified surface wind forcing, we explore how TC winds can excite equatorial ocean waves in the tropical Pacific. We highlight a situation where three successive TCs in the western North Pacific region, corresponding to events in 2003, excite a combination of Kelvin and Yanai waves in the equatorial Pacific. The resultant thermocline adjustment significantly modifies the thermal structure of the upper equatorial Pacific and leads to eastward zonal heat transport. Observations of upper-ocean temperature by the Tropical Atmosphere Ocean (TAO buoy array and sea-level height anomalies using altimetry reveal wave passage during the same time period with similar properties to the modeled wave, although our idealized model methodology disallows precise identification of the TC forcing with the observed waves. Results indicate that direct oceanographic forcing by TCs may be important for understanding the spectrum of equatorial ocean waves, thus remotely influencing tropical mixing and surface energy budgets. Because equatorial Kelvin waves are closely linked to interannual variability in the tropical Pacific, these findings also suggest TC wind forcing may influence the timing and amplitude of El Niño events.

  18. The Magnetohydrodynamic Kelvin-Helmholtz Instability A Three-Dimensional Study of Nonlinear Evolution

    Ryu, D; Frank, A I; Ryu, Dongsu; Frank, Adam

    2000-01-01

    We investigate through high resolution 3D simulations the nonlinear evolution of compressible magnetohydrodynamic flows subject to the Kelvin-Helmholtz instability. We confirm in 3D flows the conclusion from our 2D work that even apparently weak magnetic fields embedded in Kelvin-Helmholtz unstable plasma flows can be fundamentally important to nonlinear evolution of the instability. In fact, that statement is strengthened in 3D by this work, because it shows how field line bundles can be stretched and twisted in 3D as the quasi-2D Cat's Eye vortex forms out of the hydrodynamical motions. In our simulations twisting of the field may increase the maximum field strength by more than a factor of two over the 2D effect. If, by these developments, the Alfv\\'en Mach number of flows around the Cat's Eye drops to unity or less, our simulations suggest magnetic stresses will eventually destroy the Cat's Eye and cause the plasma flow to self-organize into a relatively smooth and apparently stable flow that retains memo...

  19. Pressure Corrections for the Potential Flow Analysis of Electrohydrodynamic Kelvin-Helmholtz Instability

    Awasthi Mukesh Kumar

    2015-01-01

    Full Text Available The present paper deals with the study of the pressure corrections to the viscous potential flow analysis of Kelvin-Helmholtz instability with tangential electric field at the interface of two viscous fluids. Viscosity enters through normal stress balance in the viscous potential flow theory and tangential stresses for two fluids are not continuous at the interface. Here we have considered viscous pressure in the normal stress balance along with the irrotational pressure and it is assumed that the addition of this viscous pressure will resolve the discontinuity between the tangential stresses and the tangential velocities at the interface of two fluids. The viscous pressure is derived by mechanical energy balance equation and this pressure correction applied to compute the growth rate of electrohydrodynamic Kelvin-Helmholtz instability. A dispersion relation is obtained and stability criterion is given in the terms of critical value of relative velocity. It has been observed that the inclusion of irrotational shearing stresses have stabilizing effect on the stability of the system.

  20. Fractional Generalizations of Maxwell and Kelvin-Voigt Models for Biopolymer Characterization.

    Jóźwiak, Bertrand; Orczykowska, Magdalena; Dziubiński, Marek

    2015-01-01

    The paper proposes a fractional generalization of the Maxwell and Kelvin-Voigt rheological models for a description of dynamic behavior of biopolymer materials. It was found that the rheological models of Maxwell-type do not work in the case of modeling of viscoelastic solids, and the model which significantly better describes the nature of changes in rheological properties of such media is the modified fractional Kelvin-Voigt model with two built-in springpots (MFKVM2). The proposed model was used to describe the experimental data from the oscillatory and creep tests of 3% (w/v) kuzu starch pastes, and to determine the values of their rheological parameters as a function of pasting time. These parameters provide a lot of additional information about structure and viscoelastic properties of the medium in comparison to the classical analysis of dynamic curves G' and G" and shear creep compliance J(t). It allowed for a comprehensive description of a wide range of properties of kuzu starch pastes, depending on the conditions of pasting process. PMID:26599756

  1. Fractional Generalizations of Maxwell and Kelvin-Voigt Models for Biopolymer Characterization.

    Bertrand Jóźwiak

    Full Text Available The paper proposes a fractional generalization of the Maxwell and Kelvin-Voigt rheological models for a description of dynamic behavior of biopolymer materials. It was found that the rheological models of Maxwell-type do not work in the case of modeling of viscoelastic solids, and the model which significantly better describes the nature of changes in rheological properties of such media is the modified fractional Kelvin-Voigt model with two built-in springpots (MFKVM2. The proposed model was used to describe the experimental data from the oscillatory and creep tests of 3% (w/v kuzu starch pastes, and to determine the values of their rheological parameters as a function of pasting time. These parameters provide a lot of additional information about structure and viscoelastic properties of the medium in comparison to the classical analysis of dynamic curves G' and G" and shear creep compliance J(t. It allowed for a comprehensive description of a wide range of properties of kuzu starch pastes, depending on the conditions of pasting process.

  2. Modulation of 3,4-methylenedioxymethamphetamine effects by endocannabinoid system.

    Valverde, Olga; Rodríguez-Árias, Marta

    2013-01-01

    The amphetamine derivative 3, 4 Methylenedioxymethanphetamine (MDMA) is a powerful central nervous system stimulant that displays numerous pharmacological effects, including neurotoxicity. MDMA, or ecstasy, acts by inducing the release of different neurotransmitters depending on the animal species and, in particular, it produces the release of serotonin and dopamine. MDMA induces rewarding and reinforcing effects in rodents, primates and humans, and is currently consumed as an illicit psychostimulant among young people. One of the most reported side effects is the hyperthermic effect and the neurotoxicity on central serotonergic and dopaminergic neurons, depending on the species of animal. It seems that MDMA may also produce neurotoxic effects in humans. To date, the most consistent findings associated to MDMA consumption in humans relate to cognitive deficits in heavy users. MDMA when consumed as an illicit psychostimulant is commonly co-used with other abusers, being frequently associated with cannabinoids. The interaction between MDMA and cannabis effects is complex. Cannabis derivatives act on endocannabinoid system. Thus, at cellular levels, cannabinoids acting through CB1 cannabinoid receptors display opposite effects to those induced by MDMA, and they have been reported to develop neuroprotective actions, including the blockage of MDMA induced neurotoxicity, in laboratory animals. However, cannabis use is a recognized risk factor in the presentation and development of neuropsychiatric disorders, and also contributes to the development of psychological problems and cognitive failures observed in MDMA users. This paper represents a brief overview of the pharmacological interaction between MDMA and cannabis derivatives acting in the endocannabinoid system. We have evaluated recent findings in the literature of the most representative pharmacological effects displayed by both types of drugs. We analyze both, the synergic and opposite effects produced by these

  3. Valentine’s Day

    2007-01-01

    <正>February 14 is a day for people who have fallen in love.On this day, these men and women give gifts(presents) and cards to each other for Valentine’s Day(情人节). This day has been popular with people in love for a long time.At first,this holiday was called Lupercalia. Then the name of the day was changed to Saint Valentine’s Day.The man named Saint Valentine was killed on February 14,270 AD,because he was a Christian(基督教徒).

  4. Modelling and experimental verification of tip-induced polarization in Kelvin probe force microscopy measurements on dielectric surfaces

    Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

    2015-01-01

    Kelvin probe force microscopy is a widely used technique for measuring surface potential distributions on the micro- and nanometer scale. The data are, however, often analyzed qualitatively, especially for dielectrics. In many cases, the phenomenon of polarization and its influence on the measured...... signals is disregarded leading to misinterpretation of the results. In this work, we present a model that allows prediction of the surface potential on a metal/polymer heterostructure as measured by Kelvin probe force microscopy by including the tip-induced polarization of the dielectric that arises...

  5. Day Care Centers

    Department of Homeland Security — This database contains locations of day care centers for 50 states and Washington D.C. and Puerto Rico. The dataset only includes center based day care locations...

  6. Subtask 3.4 - Fischer - Tropsch Fuels Development

    Strege, Joshua; Snyder, Anthony; Laumb, Jason; Stanislowski, Joshua; Swanson, Michael

    2012-05-01

    Under Subtask 3.4, the Energy & Environmental Research Center (EERC) examined the opportunities and challenges facing FischerTropsch (FT) technology in the United States today. Work was completed in two distinct budget periods (BPs). In BP1, the EERC examined the technical feasibility of using modern warm-gas cleanup techniques for FT synthesis. FT synthesis is typically done using more expensive and complex cold-gas sweetening. Warm-gas cleanup could greatly reduce capital and operating costs, making FT synthesis more attractive for domestic fuel production. Syngas was generated from a variety of coal and biomass types; cleaned of sulfur, moisture, and condensables; and then passed over a pilot-scale FT catalyst bed. Laboratory and modeling work done in support of the pilot-scale effort suggested that the catalyst was performing suboptimally with warm-gas cleanup. Long-term trends showed that the catalyst was also quickly deactivating. In BP3, the EERC compared FT catalyst results using warm-gas cleanup to results using cold-gas sweetening. A gas-sweetening absorption system (GSAS) was designed, modeled, and constructed to sweeten syngas between the gasifier and the pilot-scale FT reactor. Results verified that the catalyst performed much better with gas sweetening than it had with warm-gas cleanup. The catalyst also showed no signs of rapid deactivation when the GSAS was running. Laboratory tests in support of this effort verified that the catalyst had deactivated quickly in BP1 because of exposure to syngas, not because of any design flaw with the pilot-scale FT reactor itself. Based on these results, the EERC concludes that the two biggest issues with using syngas treated with warm-gas cleanup for FT synthesis are high concentrations of CO{sub 2} and volatile organic matter. Other catalysts tested by the EERC may be more tolerant of CO{sub 2}, but volatile matter removal is critical to ensuring long-term FT catalyst operation. This subtask was funded through

  7. Is day surgery safe?

    Majholm, Birgitte; Engbæk, J; Bartholdy, Jens;

    2012-01-01

    Day surgery is expanding in several countries, and it is important to collect information about quality. The aim of this study was to assess morbidity and unanticipated hospital visits 0-30 days post-operatively in a large cohort.......Day surgery is expanding in several countries, and it is important to collect information about quality. The aim of this study was to assess morbidity and unanticipated hospital visits 0-30 days post-operatively in a large cohort....

  8. April Fools’ Day

    Abby

    2009-01-01

    April Fools’ Day,the day when mischief-makers(恶作剧的人)are ever so indulged(纵容),falls on April 1 every year.On that day,various pranks(恶作剧)are played on one another,and everybody has to be

  9. Valentine’s Day

    顾晓玲

    2009-01-01

    Valentine’s Day, which falls on February 14, is one of the most popular festivals of western society and even the whole world. It is a day for lovers, a day when people present chocolates, cards and candies to their beloved (心爱的人).

  10. A Day to Celebrate

    2010-01-01

    Participating countries at the 2010 World Expo in Shanghai can choose a day as their National Pavilion Day.The day is usually celebrated with ceremonies and performances,which bring the nation’s culture and its character to life.

  11. Popular Chat Day Q & A

    ... Popular Chat Day Q & A Popular Chat Day Q & A Read students’ most popular questions about drug ... Day Chat Day Participant FAQs Popular Chat Day Q & A Search Chat Day Transcripts Past Chat Day ...

  12. Satellite observations of the QBO wave driving by Kelvin waves and gravity waves

    Ern, Manfred; Preusse, Peter; Kalisch, Silvio; Riese, Martin

    2014-05-01

    The quasi-biennial oscillation (QBO) of the zonal wind in the tropical stratosphere is an important process in atmospheric dynamics influencing a wide range of altitudes and latitudes. Effects of the QBO are found also in the mesosphere and in the extra-tropics. The QBO even has influence on the surface weather and climate, for example during winter in the northern hemisphere at midlatitudes. Still, climate models have large difficulties in reproducing a realistic QBO. One reason for this deficiency are uncertainties in the wave driving by planetary waves and, in particular, gravity waves that are usually too small-scale to be resolved in global models. Different global equatorial wave modes (e.g., Kelvin waves) have been identified by longitude-time 2D spectral analysis in Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite temperature data, as well as ECMWF temperatures. We find good agreement between SABER satellite observations and ECMWF wave variances in both QBO-related temporal variations and their magnitude. Slow phase speed waves are strongly modulated by the QBO, higher phase speed waves are almost unaffected by the QBO, and ultra-fast equatorial waves can even reach the MLT region. Momentum fluxes and zonal wind drag due to Kelvin waves are derived, and the relative contribution of Kelvin waves to the QBO wind reversal from westward to eastward wind is estimated to be about 30% of the total wave driving. This is in good agreement with the general assumption that gravity waves (GWs) are probably more important for the QBO driving than global-scale waves. This is further supported by SABER and High Resolution Dynamics Limb Sounder (HIRDLS) satellite observations of gravity wave drag in the equatorial region. These observations are compared with the drag still missing in the ECMWF ERA Interim (ERAI) tropical momentum budget after considering zonal wind tendency, Coriolis force, advection terms and drag of resolved global

  13. Pathologic downstaging of T3-4Nx rectal cancer after chemoradiation: 5-fluorouracil vs. Tegafur

    Purpose: To describe downstaging effects in locally advanced rectal cancer induced by 2 fluopirimidine radiosensitizing agents given through different routes in conjunction with preoperative radiotherapy. Methods and Materials: From March 1995 to December 1999, two consecutive groups of patients with cT3-4Nx rectal cancer (94% CT scan, 71% endorectal ultrasound) were treated with either (1) 45-50 Gy (1.8 Gy/day, 25 fractions) and 5-fluorouracil (5-FU) (500-1,000 mg/m2 by 24-h continuous i.v. infusion on Days 1-4 and 21-25) or (2) oral Tegafur (1,200 mg/day on Days 1-35, including weekends). Surgery was performed 4 to 6 weeks after the completion of chemoradiation. Results: The total T downstaging rate was 46% in the 5-FU group and 53% in the Tegafur group. Subcategories were downstaged by the sensitizing agents (5-FU vs. Tegafur) as follows: pT0-1, 14% vs. 23%; pT2, 32% vs. 32%; pT3, 49% vs. 37%; pT4, 5% vs. 7%; and N0, 74% vs. 86%. Analysis of residual malignant disease in the specimen discriminated mic/mac subgroups (mic: <20% of microscopic cancer residue), with evident superior downstaging effects in the Tegafur-treated group: pTmic 23% vs. 58% (p 0.002). Conclusions: When administered concurrent with pelvic irradiation, oral Tegafur induced downstaging rates in both T and N categories superior to those induced by intermediate doses of 5-FU by continuous i.v. infusion. In this pilot experience, oral Tegafur reproduced the characteristics of downstaging described previously when full doses of 5-FU have been combined with radiotherapy

  14. Kint3-4 protein from human plasminogen delays Ehrlich tumor growth in mice Efeito da proteína Kint3-4 do plasminogênio humano no crescimento do tumor de Ehrlich

    Cristina Maria de Souza

    2011-08-01

    Full Text Available INTRODUCTION AND OBJECTIVE: Kint3-4 protein, originated from a genetic recombination of K1-3 and K1-4 human plasminogen segments, is recognized for its antiangiogenic and anti-inflammatory potential. This study aimed to evaluate the effect of Kint3-4 protein on tumor development in Swiss mice previously inoculated with Ehrlich tumor cells. METHODS: The protein fragment was obtained from Pichia pastoris cloning and transformation. After tumor cell inoculation three different protocols were used to assess tumor growth: beginning (0-6 days, peak (0-12 days and after peak (0-18 days. We analyzed tumor growth, histomorphological characteristics and immunohistochemistry by use of CDC47 (cellular proliferation marker and CD31 (blood vessel marker. RESULTS: Animals treated with Kint3-4 protein (150 µg/kg/48 h showed lower tumor growth in all protocols. Based on histological assessment, inflammation and tumor areas were also reduced. Moreover, both the lowest rate of tumor cell proliferation and low microvessel density were observed in animals treated with Kint3-4 protein compared with the untreated control group. CONCLUSION: The effect of Kint3-4 recombinant protein on tumor angiogenesis and control of malignant cell proliferation enhances the prospects of its use in clinical and antiangiogenic treatment.INTRODUÇÃO E OBJETIVO: A proteína Kint3-4 originou-se a partir de uma recombinação genética dos segmentos K1-3 e K1--4 do plasminogênio humano e é reconhecida por seu potencial anti-inflamatório e antiangiogênico. Este estudo teve como objetivo avaliar o efeito da proteína Kint3-4 no desenvolvimento de tumores em camundongos inoculados com células do tumor de Ehrlich. MÉTODOS: O fragmento de proteína foi obtido por uma técnica de clonagem e transformação de Pichia pastoris. Três diferentes protocolos foram avaliados após a inoculação das células tumorais: no início (0-6 dias, no pico (0-12 dias e após o pico (0-18 dias de

  15. Seasonal occurrence of sperm whales (Physeter macrocephalus) around Kelvin Seamount in the Sargasso Sea in relation to oceanographic processes

    Wong, Sarah N. P.; Whitehead, Hal

    2014-09-01

    Sperm whales (Physeter macrocephalus) are widely distributed in all oceans, but they are clumped geographically, generally in areas associated with high primary and secondary productivity. The warm, clear waters of the Sargasso Sea are traditionally thought to be low in productivity, however recent surveys have found large numbers of sperm whales there. The New England Seamount Chain bisects the north-western portion of the Sargasso Sea, and might influence the mesoscale eddies associated with the Gulf Stream; creating areas of higher productivity within the Sargasso Sea. We investigated the seasonal occurrence of sperm whales over Kelvin Seamount (part of the New England Seamount Chain) and how it is influenced by oceanographic variables. An autonomous recording device was deployed over Kelvin Seamount from May to June 2006 and November 2006 to June 2007. A total of 6505 hourly two-minute recordings were examined for the presence of sperm whale echolocation clicks. Sperm whales were more prevalent around Kelvin in the spring (April to June: mean=51% of recordings contained clicks) compared to the winter (November to March: mean=16% of recordings contained clicks). Sperm whale prevalence at Kelvin was related to chlorophyll-a concentration four weeks previous, eddy kinetic energy and month. The mesoscale activity associated with the Gulf Stream and the Gulf Stream's interaction with the New England Seamount Chain likely play an important role in sperm whale occurrence in this area, by increasing productivity and perhaps concentration of cephalopod species.

  16. Numerical simulations of the Kelvin-Helmholtz instability with the Gadget-2 SPH code

    Gabbasov, Ruslan F; Suarez-Cansino, Joel; Sigalotti, Leonardo Di G

    2013-01-01

    The method of Smoothed Particle Hydrodynamics (SPH) has been widely studied and implemented for a large variety of problems, ranging from astrophysics to fluid dynamics and elasticity problems in solids. However, the method is known to have several deficiencies and discrepancies in comparison with traditional mesh-based codes. In particular, there has been a discussion about its ability to reproduce the Kelvin-Helmholtz Instability in shearing flows. Several authors reported that they were able to reproduce correctly the instability by introducing some improvements to the algorithm. In this contribution, we compare the results of Read et al. (2010) implementation of the SPH algorithm with the original Gadget-2 N-body/SPH code.

  17. Kelvin-Helmootz instability of double perturbed cylindrical self-gravitating fluids

    The Kelvin-Helmholtz instability of a self-gravitating gas cylinder (radius R and density ρ(1), co-axial with a perturbed fluid cylinder (density ρ(2) and radius q R with 1 (2) = 0 is obtained as a limiting case. Here the streaming has a strong destabilizing effect. As U = 0, the marginal stability occurred as ρ(1) = ρ(2). While as U ≠ 0, the marginal stability states do not occur at ρ(1) = ρ(2). As q values are increased for the case 0 (2)/ρ(1) (1) (2), the principle of exchange of instability is valid for the most cases especially for large values of q. The result is (physically interpreted) related to the behavior of the spiral arm of galaxy.

  18. Kelvin Helmholtz instability in an ultrathin air film causes drop splashing on smooth surfaces

    Liu, Yuan; Xu, Lei

    2015-01-01

    When a fast-moving drop impacts onto a smooth substrate, splashing will be produced at the edge of the expanding liquid sheet. This ubiquitous phenomenon lacks a fundamental understanding. Combining experiment with model, we illustrate that the ultrathin air film trapped under the expanding liquid front triggers splashing. Because this film is thinner than the mean free path of air molecules, the interior airflow transfers momentum with an unusually high velocity comparable to the speed of sound and generates a stress 10 times stronger than the airflow in common situations. Such a large stress initiates Kelvin Helmholtz instabilities at small length scales and effectively produces splashing. Our model agrees quantitatively with experimental verifications and brings a fundamental understanding to the ubiquitous phenomenon of drop splashing on smooth surfaces.

  19. Kelvin-probe force microscopy of the pH-dependent charge of functional groups

    Stone, Alexander D. D.; Mesquida, Patrick

    2016-06-01

    Kelvin-probe Force Microscopy (KFM) is an established method to map surface potentials or surface charges at high, spatial resolution. However, KFM does not work in water, which restricts its applicability considerably, especially when considering common, functional chemical groups in biophysics such as amine or carboxy groups, whose charge depends on pH. Here, we demonstrate that the KFM signal of such groups taken in air after exposure to water correlates qualitatively with their expected charge in water for a wide range of pH values. The correlation was tested with microcontact-printed thiols exposing amine and carboxy groups. Furthermore, it was shown that collagen fibrils, as an example of a biological material, exhibit a particular, pH-sensitive surface charge pattern, which could be caused by the particular arrangement of ionizable residues on the collagen fibril surface.

  20. Kelvin-Helmholtz instability in solar chromospheric jets: theory and observation

    Kuridze, D; Henriques, V; Mathioudakis, M; Keenan, F P; Hanslmeier, A

    2016-01-01

    Using data obtained by the high resolution CRisp Imaging SpectroPolarimeter instrument on the Swedish 1-m Solar Telescope, we investigate the dynamics and stability of quiet-Sun chromospheric jets observed at disk center. Small-scale features, such as Rapid Redshifted and Blueshifted Excursions, appearing as high speed jets in the wings of the H$\\alpha$ line, are characterized by short lifetimes and rapid fading without any descending behavior. To study the theoretical aspects of their stability without considering their formation mechanism, we model chromospheric jets as twisted magnetic flux tubes moving along their axis, and use the ideal linear incompressible magnetohydrodynamic approximation to derive the governing dispersion equation. Analytical solutions of the dispersion equation indicate that this type of jet is unstable to Kelvin-Helmholtz instability (KHI), with a very short (few seconds) instability growth time at high upflow speeds. The generated vortices and unresolved turbulent flows associated...

  1. Scanning Kelvin-probe study of the hydrogen-terminated diamond surface in ultrahigh vacuum

    Atomic-force and Kelvin-probe microscopies were employed in ultrahigh vacuum to image the surface topography and contact potential of the hydrogen-terminated and unterminated surfaces of diamond. A variation of about 25 meV in the contact potential was measured on a length scale of 20 nm and ascribed to differently orientated surface domains resulting from hydrogen-plasma processing of the sample. Shifts in the work function arising from sample heating in vacuum and the adsorption of C60 were measured. The Fermi level was found to be 0.7 and 1.1 eV below the valence band maximum for C60 coverages of 1 and 4 monolayer, respectively.

  2. Accurate determination of the Boltzmann constant by Doppler spectroscopy: Towards a new definition of the kelvin

    Darquié, Benoît; Sow, Papa Lat Tabara; Lemarchand, Cyril; Triki, Meriam; Tokunaga, Sean; Bordé, Christian J; Chardonnet, Christian; Daussy, Christophe

    2015-01-01

    Accurate molecular spectroscopy in the mid-infrared region allows precision measurements of fundamental constants. For instance, measuring the linewidth of an isolated Doppler-broadened absorption line of ammonia around 10 $\\mu$m enables a determination of the Boltzmann constant k B. We report on our latest measurements. By fitting this lineshape to several models which include Dicke narrowing or speed-dependent collisional effects, we find that a determination of k B with an uncertainty of a few ppm is reachable. This is comparable to the best current uncertainty obtained using acoustic methods and would make a significant contribution to any new value of k B determined by the CODATA. Furthermore, having multiple independent measurements at these accuracies opens the possibility of defining the kelvin by fixing k B, an exciting prospect considering the upcoming redefinition of the International System of Units.

  3. Suppression mechanism of Kelvin-Helmholtz instability in compressible fluid flows

    Karimi, Mona; Girimaji, Sharath S.

    2016-04-01

    The transformative influence of compressibility on the Kelvin-Helmholtz instability (KHI) at the interface between two fluid streams of different velocities is explicated. When the velocity difference is small (subsonic), shear effects dominate the interface flow dynamics causing monotonic roll-up of vorticity and mixing between the two streams leading to the KHI. We find that at supersonic speed differentials, compressibility forces the dominance of dilatational (acoustic) rather than shear dynamics at the interface. Within this dilatational interface layer, traveling pressure waves cause the velocity perturbations to become oscillatory. We demonstrate that the oscillatory fluid motion reverses vortex roll-up and segregates the two streams leading to KHI suppression. Analysis and illustrations of the compressibility-induced suppression mechanism are presented.

  4. Study on magnetohydrodynamic Kelvin-Helmholtz instability with mass transfer through porous media

    Kumar Awasthi, Mukesh

    2013-09-01

    We study the linear analysis of Kelvin-Helmholtz instability of the interface between two viscous and magnetic fluids in a fully saturated porous medium using viscous potential flow theory, when the fluids are subjected to a constant tangential magnetic field, and when there is heat and mass transfer across the interface. The Darcy-Brinkman model has been used for the investigation. A dispersion relation has been derived and stability is discussed theoretically as well as numerically. The stability criterion is given in terms of a critical value of relative velocity as well as the critical value of applied magnetic field. It has been observed that both tangential magnetic field and vapor fraction have stabilizing effect on the stability of the system while heat and mass transfer destabilizes the interface. Porosity stabilizes the interface while the porous medium has destabilizing effect.

  5. Real-space measurement of potential distribution in PECVD ONO electrets by Kelvin probe force microscopy

    Emmerich, F.; Thielemann, C.

    2016-05-01

    Multilayers of silicon oxide/silicon nitride/silicon oxide (ONO) are known for their good electret properties due to deep energy traps near the material interfaces, facilitating charge storage. However, measurement of the space charge distribution in such multilayers is a challenge for conventional methods if layer thickness dimensions shrink below 1 μm. In this paper, we propose an atomic force microscope based method to determine charge distributions in ONO layers with spatial resolution below 100 nm. By applying Kelvin probe force microscopy (KPFM) on freshly cleaved, corona-charged multilayers, the surface potential is measured directly along the z-axis and across the interfaces. This new method gives insights into charge distribution and charge movement in inorganic electrets with a high spatial resolution.

  6. Kelvin probe force microscopy for conducting nanobits of NiO thin films

    We demonstrated the writing and reading of conducting nanobits on a NiO thin film deposited on Pt/TiO2/SiO2/Si substrates for a resistive random access memory (RRAM) application using conducting atomic force microscopy (CAFM) and Kelvin probe force microscopy (KFM). A Pt/NiO/Pt RRAM capacitor showed a typical unipolar switching behavior with bistable resistances. Conducting nanobits with diameters of 22 nm written with a bias of 3.0 V on the NiO thin film were observed with CAFM. The conducting nanobits observed by KFM exhibited negative potentials relative to the insulating regions when there was no bias at the Pt bottom electrode because image charges were induced by charges formed at the end of the KFM tip by the reference AC bias. Enhancement of the KFM signals for conducting nanobits was achieved using specific biases at the Pt bottom electrode, which provided clear KFM images for conducting nanobits.

  7. Fast, high-resolution surface potential measurements in air with heterodyne Kelvin probe force microscopy

    Garrett, Joseph L.; Munday, Jeremy N.

    2016-06-01

    Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths.

  8. Dual harmonic Kelvin probe force microscopy at the graphene–liquid interface

    Kelvin probe force microscopy (KPFM) is a powerful technique for the determination of the contact potential difference (CPD) between an atomic force microscope tip and a sample under ambient and vacuum conditions. However, for many energy storage and conversion systems, including graphene-based electrochemical capacitors, understanding electrochemical phenomena at the solid–liquid interface is paramount. Despite the vast potential to provide fundamental insight for energy storage materials at the nanoscale, KPFM has found limited applicability in liquid environments to date. Here, using dual harmonic (DH)-KPFM, we demonstrate CPD imaging of graphene in liquid. We find good agreement with measurements performed in air, highlighting the potential of DH-KPFM to probe electrochemistry at the graphene–liquid interface

  9. A milliKelvin scanning Hall probe microscope for high resolution magnetic imaging

    The design and performance of a novel scanning Hall probe microscope for milliKelvin magnetic imaging with submicron lateral resolution is presented. The microscope head is housed in the vacuum chamber of a commercial 3He-refrigerator and operates between room temperature and 300 mK in magnetic fields up to 10 T. Mapping of the local magnetic induction at the sample surface is performed by a micro-fabricated 2DEG Hall probe equipped with an integrated STM tip. The latter provides a reliable mechanism of surface tracking by sensing and controlling the tunnel currents. We discuss the results of tests of the system and illustrate its potential with images of suitable reference samples captured in different modes of operation.

  10. Understanding the atomic-scale contrast in Kelvin Probe Force Microscopy

    Nony, Laurent; Bocquet, Franck; Loppacher, Christian; 10.1103/PhysRevLett.103.036802

    2009-01-01

    A numerical analysis of the origin of the atomic-scale contrast in Kelvin probe force microscopy (KPFM) is presented. Atomistic simulations of the tip-sample interaction force field have been combined with a non-contact Atomic Force Microscope/KPFM simulator. The implementation mimics recent experimental results on the (001) surface of a bulk alkali halide crystal for which simultaneous atomic-scale topographical and Contact Potential Difference (CPD) contrasts were reported. The local CPD does reflect the periodicity of the ionic crystal, but not the magnitude of its Madelung surface potential. The imaging mechanism relies on the induced polarization of the ions at the tip-surface interface owing to the modulation of the applied bias voltage. Our findings are in excellent agreement with previous theoretical expectations and experimental observations.

  11. Ammonia Sensing by PANI-DBSA Based Gas Sensor Exploiting Kelvin Probe Technique

    Anju Yadav

    2015-01-01

    Full Text Available Dodecyl benzene sulfonic acid (DBSA doped polyaniline (PANI-DBSA has been synthesized by chemical oxidative polymerization of aniline monomer in the presence of DBSA. The UV-visible spectroscopy and X-ray diffraction measurements confirm the formation of PANI and its doping by DBSA. SEM images show the formation of submicron size rod shaped PANI particles. A vibrating capacitor based ammonia gas sensor was prepared by spin coating PANI-DBSA film over copper (Cu substrate. The sensor exploited Kelvin probe technique to monitor contact potential difference between PANI and Cu as a function of time and ammonia concentration. Upon exposure to 30 ppm ammonia, the sensor displays response time of 329 s, recovery time of 3600 s, and sensitivity value of 1.54 along with good repeatability.

  12. Surface Potential Analysis of Nanoscale Biomaterials and Devices Using Kelvin Probe Force Microscopy

    Hyungbeen Lee

    2016-01-01

    Full Text Available In recent years, Kelvin probe force microscopy (KPFM has emerged as a versatile toolkit for exploring electrical properties on a broad range of nanobiomaterials and molecules. An analysis using KPFM can provide valuable sample information including surface potential and work function of a certain material. Accordingly, KPFM has been widely used in the areas of material science, electronics, and biomedical science. In this review, we will briefly explain the setup of KPFM and its measuring principle and then survey representative results of various KPFM applications ranging from material analysis to device analysis. Finally, we will discuss some possibilities of KPFM on whether it is applicable to various sensor systems. Our perspective shed unique light on how KPFM can be used as a biosensor as well as equipment to measure electrical properties of materials and to recognize various molecular interactions.

  13. A scanning Kelvin probe study of charge trapping in zone-cast pentacene thin film transistors

    We have used scanning Kelvin probe microscopy (SKPM) as a local probe to study charge trapping in zone-cast pentacene field effect transistors on both SiO2 and benzocyclobutene (BCB) substrates. Annealing at 130 deg. C was found to reduce the threshold voltage, susceptibility to negative gate bias stress and trapping of positive charges within single pentacene grains. We conclude that oxygen is able to penetrate and disassociatively incorporate into crystalline pentacene, chemically creating electrically active defect states. Screening of a positive gate bias caused by electron injection from Au into pentacene was directly observed with SKPM. The rate of screening was found to change significantly after annealing of the film and depended on the choice of gate dielectric.

  14. Charging and discharging behavior in dielectric-coated MEMS electrodes probed by Kelvin probe force microscopy

    The charging and discharging behavior of silicon dioxide, silicon nitride and aluminum nitride dielectric coatings on microfabricated aluminum electrodes in response to an applied voltage, thermal treatment, operating environment and monolayer coating have been investigated through Kelvin probe force microscopy (KPFM) techniques. Correlated results from surface potential measurements and finite element simulations demonstrate the existence of capacitive coupling between the KPFM probe tip assembly and the device sample which give rise to as much as 20–40% difference between the applied bias and the measured surface potential. Surface charge mobility on the three material systems has been differentiated focusing on the influence of bulk and surface water and the relevant physicochemical properties. The merits and limitations of proposed schemes for mitigating the effects of dielectric charging, including thermal treatment and monolayer coating, are presented. (paper)

  15. Measuring minority-carrier diffusion length using a Kelvin probe force microscope

    A method based on Kelvin probe force microscopy for measuring minority-carrier diffusion length in semiconductors is described. The method is based on measuring the surface photovoltage between the tip of an atomic force microscope and the surface of an illuminated semiconductor junction. The photogenerated carriers diffuse to the junction and change the contact potential difference between the tip and the sample, as a function of the distance from the junction. The diffusion length L is then obtained by fitting the measured contact potential difference using the minority-carrier continuity equation. The method was applied to measurements of electron diffusion length in GaP pn and Schottky junctions. The measured diffusion length was found to be ∼2 μm, in good agreement with electron beam induced current measurements

  16. Nanoscale surface photovoltage of organic semiconductors with two pass Kelvin probe microscopy

    Kelvin probe microscopy implemented with controlled sample illumination is used to study nanoscale surface photovoltage effects. With this objective a two trace method, where each scanning line is measured with and without external illumination, is proposed. This methodology allows a direct comparison of the contact potential images acquired in darkness and under illumination and, therefore, the surface photovoltage is simply inferred. Combined with an appropriate data analysis, the temporal and spatial evolution of reversible and irreversible photo-induced processes can be obtained. The potential and versatility of this technique is applied to MEH-PPV thin films. Photo-physical phenomena such as the mesoscale polymer electronic light-induced response as well as the local nanoscale electro-optical properties are studied.

  17. Potential profile and photovoltaic effect in nanoscale lateral pn junction observed by Kelvin probe force microscopy

    Nanoscale pn junctions have been investigated by Kelvin probe force microscopy and several particular features were found. Within the depletion region, a localized noise area is observed, induced by temporal fluctuations of dopant states. Electronic potential landscape is significantly affected by dopants with ground-state energies deeper than in bulk. Finally, the effects of light illumination were studied and it was found that the depletion region shifts its position as a function of light intensity. This is ascribed to charge redistribution within the pn junction as a result of photovoltaic effect and due to the impact of deepened-level dopants. - Highlights: • In pn nano-junctions, temporal potential fluctuations are found in depletion layer. • Fluctuations are due to frequent capture and emission of free carriers by dopants. • Depletion layer position shifts as a function of the intensity of irradiated light. • The depletion layer shifts are due to changes of deep-level dopants' charge states

  18. Exploratory Data Analysis of The KelvinHelmholtz instability in Jets

    Tirunagari, Santosh

    2015-01-01

    The KelvinHelmholtz (KH) instability is a fundamental wave instability that is frequently observed in all kinds of shear layer (jets, wakes, atmospheric air currents etc). The study of KH-instability, coherent flow structures has a major impact in understanding the fundamentals of fluid dynamics. Therefore there is a need for methods that can identify and analyse these structures. In this Final assignment, we use machine-learning methods such as Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) to analyse the coherent flow structures. We used a 2D co-axial jet as our data, with Reynolds number corresponding to Re: 10,000. Results for POD modes and DMD modes are discussed and compared.

  19. Singularity formation on a fluid interface during the Kelvin-Helmholtz instability development

    Zubarev, N M

    2014-01-01

    The dynamics of singularity formation on the interface between two ideal fluids is studied for the Kelvin-Helmholtz instability development within the Hamiltonian formalism. It is shown that the equations of motion derived in the small interface angle approximation (gravity and capillary forces are neglected) admit exact solutions in the implicit form. The analysis of these solutions shows that, in the general case, weak root singularities are formed on the interface in a finite time for which the curvature becomes infinite, while the slope angles remain small. For Atwood numbers close to unity in absolute values, the surface curvature has a definite sign correlated with the boundary deformation directed towards the light fluid. For fluids with comparable densities, the curvature changes its sign in a singular point. In the particular case of fluids with equal densities, the obtained results are consistent with those obtained by Moore based on the Birkhoff-Rott equation analysis.

  20. Fast, high-resolution surface potential measurements in air with heterodyne Kelvin probe force microscopy.

    Garrett, Joseph L; Munday, Jeremy N

    2016-06-17

    Kelvin probe force microscopy (KPFM) adapts an atomic force microscope to measure electric potential on surfaces at nanometer length scales. Here we demonstrate that Heterodyne-KPFM enables scan rates of several frames per minute in air, and concurrently maintains spatial resolution and voltage sensitivity comparable to frequency-modulation KPFM, the current spatial resolution standard. Two common classes of topography-coupled artifacts are shown to be avoidable with H-KPFM. A second implementation of H-KPFM is also introduced, in which the voltage signal is amplified by the first cantilever resonance for enhanced sensitivity. The enhanced temporal resolution of H-KPFM can enable the imaging of many dynamic processes, such as such as electrochromic switching, phase transitions, and device degredation (battery, solar, etc), which take place over seconds to minutes and involve changes in electric potential at nanometer lengths. PMID:27159082

  1. Kelvin probe studies of cesium telluride photocathode for the AWA photoinjector

    Velazquez, D.; Wisniewski, E. E.; Yusof, Z.; Harkay, K.; Spentzouris, L.; Terry, J. [Physics Department at Illinois Institute of Technology, Chicago, IL 60616 and High Energy Physics Division at Argonne National Laboratory, Lemont, IL 60439 (United States); High Energy Physics Division at Argonne National Laboratory, Lemont, IL 60439 (United States); Accelerator Science Division at Argonne National Laboratory, Lemont, IL 60439 (United States); Physics Department at Illinois Institute of Technology, Chicago, IL 60616 (United States)

    2012-12-21

    Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (> 1%), is robust in a photoinjector, and long lifetime. This photocathode is fabricated in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch ({approx}50 nC) in a long bunch train. We present some results from a study of the work function of cesium telluride photocathode using the Kelvin Probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV light exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.

  2. Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: from fluid to kinetic modeling

    Henri, P; Califano, F; Pegoraro, F; Rossi, C; Faganello, M; Šebek, O; Trávníček, P M; Hellinger, P; Frederiksen, J T; Nordlund, Å; Markidis, S; Keppens, R; Lapenta, G

    2013-01-01

    The nonlinear evolution of collisionless plasmas is typically a multi-scale process where the energy is injected at large, fluid scales and dissipated at small, kinetic scales. Accurately modelling the global evolution requires to take into account the main micro-scale physical processes of interest. This is why comparison of different plasma models is today an imperative task aiming at understanding cross-scale processes in plasmas. We report here the first comparative study of the evolution of a magnetized shear flow, through a variety of different plasma models by using magnetohydrodynamic, Hall-MHD, two-fluid, hybrid kinetic and full kinetic codes. Kinetic relaxation effects are discussed to emphasize the need for kinetic equilibriums to study the dynamics of collisionless plasmas in non trivial configurations. Discrepancies between models are studied both in the linear and in the nonlinear regime of the magnetized Kelvin-Helmholtz instability, to highlight the effects of small scale processes on the nonl...

  3. Observation of Impact Ionization of Shallow States in Sub-Kelvin, High-Purity Germanium

    Phipps, A.; Sadoulet, B.; Sundqvist, K. M.

    2016-07-01

    We report on the observation of impact ionization processes involving shallow impurity states in a sub-Kelvin, high-purity n-type germanium detector similar to those used by direct detection dark matter experiments such as the Cryogenic Dark Matter Search. An optical fiber is used to generate packets of charge carriers near one surface of the detector. The charge carriers drift to the opposite surface by application of an electric field. The resulting drift current is measured by a high-speed charge amplifier. The onset of impact ionization for both electron and hole transport is clearly observed in the drift current as the applied electric field is increased above ≈ 5 V/cm. We present the effective charge collection efficiency and trapping length as a function of applied electric field for electrons and holes. We estimate the impact ionization cross section to be on the order of 5× 10^{-13} mathrm {cm}^2.

  4. Observation of Impact Ionization of Shallow States in Sub-Kelvin, High-Purity Germanium

    Phipps, A.; Sadoulet, B.; Sundqvist, K. M.

    2016-01-01

    We report on the observation of impact ionization processes involving shallow impurity states in a sub-Kelvin, high-purity n-type germanium detector similar to those used by direct detection dark matter experiments such as the Cryogenic Dark Matter Search. An optical fiber is used to generate packets of charge carriers near one surface of the detector. The charge carriers drift to the opposite surface by application of an electric field. The resulting drift current is measured by a high-speed charge amplifier. The onset of impact ionization for both electron and hole transport is clearly observed in the drift current as the applied electric field is increased above ≈ 5 V/cm. We present the effective charge collection efficiency and trapping length as a function of applied electric field for electrons and holes. We estimate the impact ionization cross section to be on the order of 5× 10^{-13} {cm}^2.

  5. Application of Kelvin Probe to Studies of Fusion Reactor Materials under Irradiation

    Luo Guangnan; K. Yamaguchi; T. Terai; M. Yamawaki

    2005-01-01

    Recently, the work function (WF) changes in metallic and ceramic materials to be potentially used in future fusion reactors have been examined by means of Kelvin probe (KP),under He ion irradiation in high energy (MeV) and / or low energy (500 eV) ranges. The results of polycrystalline Ni samples indicate that the 1 MeV beam only induces decrease in the WF within the experimental fluence range; whereas the irradiation of 500 eV beam results in decrease in the WF firstly, then increase till saturation. A dual layer surface model is employed to explain the observed phenomena, together with computer simulation results by SRIM code. Charges buildup on the surface of lithium ceramics has been found to greatly influence the probe output, which can be explained qualitatively using a model concerning an induction electric field due to external field and free charges on the ceramic surface.

  6. Effects of Coriolis forces on the Kelvin-Helmholtz instability in a stratified plasma

    In this note the instability in the Kelvin-Helmnholtz configuration of a stratified plasma has been studied to include the joint influence of effects of F.L.R. and the Coriolis forces. The plasma is assumed to be moving with a uniform streaming velocity and the axis of rotation is taken along the direction of the horizontal magnetic field. The dispersion relation has been solved numerically and it is found that the Coriolis forces have dual rule, stabilizing for small wave numbers and destabilizing for large wave numbers. The plasma can in fact be stabilized by these effects over a certain small wave number range over which it is unstable in their absence. (author)

  7. Bending vibration of axially loaded Timoshenko beams with locally distributed Kelvin-Voigt damping

    Chen, Wei-Ren

    2011-06-01

    Utilizing the Timoshenko beam theory and applying Hamilton's principle, the bending vibration equations of an axially loaded beam with locally distributed internal damping of the Kelvin-Voigt type are established. The partial differential equations of motion are then discretized into linear second-order ordinary differential equations based on a finite element method. A quadratic eigenvalue problem of a damped system is formed to determine the eigenfrequencies of the damped beams. The effects of the internal damping, sizes and locations of damped segment, axial load and restraint types on the damping and oscillating parts of the damped natural frequency are investigated. It is believed that the present study is valuable for better understanding the influence of various parameters of the damped beam on its vibration characteristics.

  8. Thermal consolidation of porous medium with a rheological kelvin-voigt skeleton

    Bartlewska-Urban, Monika; Strzelecki, Tomasz

    2012-10-01

    This study presents calculations results of thermal consolidation process of the porous medium with the rheological Kelvin-Voigt skeleton, obtained numerically with the use of Flex.PDE software. The investigated calculation scheme consisted of the porous column filled with a liquid. The vertical load was applied to the top surface of the column through a porous plate allowing the free flow of liquid through this surface. Numerical solution is based on compression of the sample at appropriately defined boundary conditions. The aim of this study was to describe the influence of external load and temperature gradient on the deformation tests progress at different values of three parameters: λ, rs and cv. The results obtained, in the context of further research, can also be used for the determination of the influence of other parameters of the state and model parameters on the process of thermo poroelasticity of Biot model with rheological skeleton.

  9. Lack of exponential stability to Timoshenko system with viscoelastic Kelvin-Voigt type

    Malacarne, Andréia; Muñoz Rivera, Jaime Edilberto

    2016-06-01

    We study the Timoshenko systems with a viscoelastic dissipative mechanism of Kelvin-Voigt type. We prove that the model is analytical if and only if the viscoelastic damping is present in both the shear stress and the bending moment. Otherwise, the corresponding semigroup is not exponentially stable no matter the choice of the coefficients. This result is different to all others related to Timoshenko model with partial dissipation, which establish that the system is exponentially stable if and only if the wave speeds are equal. Finally, we show that the solution decays polynomially to zero as {t^{-1/2}} , no matter where the viscoelastic mechanism is effective and that the rate is optimal whenever the initial data are taken on the domain of the infinitesimal operator.

  10. Kelvin probe force microscopy on doped semiconductor nanostructures with local, carrier-depleted space charge regions

    Baumgart, Christine; Helm, Manfred; Schmidt, Heidemarie [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institut fuer Ionenstrahlphysik und Materialforschung, P.O. Box 510119, 01314 Dresden (Germany); Mueller, Anne-Dorothea; Mueller, Falk [Anfatec Instruments AG, Melanchthonstr. 28, 08606 Oelsnitz (Germany)

    2011-07-01

    Failure analysis and optimization of semiconducting devices require knowledge of their electrical properties. Kelvin probe force microscopy (KPFM) is the most promising non-contact electrical nanometrology technique to meet the demands of today's semiconductor industry. We present its applicability to locally doped silicon structures. Quantitative dopant profiling by means of KPFM measurements is successfully demonstrated on a conventional static random access memory (SRAM) cell and on cross-sectionally prepared Si epilayers by applying a recently introduced new explanation of the measured KPFM signal. Additionally, the influence of local, carrier-depleted space charge regions and of the electric fields across them is discussed. It is explained how drift and diffusion of injected charge carriers in intrinsic electric fields influence the surface region of the investigated semiconductor and thus may disturb the detected KPFM bias.

  11. The Fourier Kelvin Stellar Interferometer (FKSI): A Progress Report and Update

    Danchi, William C.; Barry, R. K.; Traub, W. A.; Unwin, S.

    2008-01-01

    The Fourier-Kelvin Stellar Interferometer (FKSI) mission is a two-telescope infrared space interferometer with a 12.5 meter baseline on a boom, operating from 3-8 (or 10) microns, and passively cooled to about 60 K. The main goals for the mission are the measurement an characterization of the exozodiacal light around nearby stars, debris disks, and characterization of the atmospheres of known exoplanets. We discuss progress on this mission in the context of the recent call from NASA for mission concepts for the upcoming National Academy of Sciences Decadal Survey, where it is considered a medium class mission ($600-800 million) in terms of the overall budget.

  12. Requirements Formulation and Dynamic Jitter Analysis for Fourier-Kelvin Stellar Interferometer

    Liu, Kuo-Chia; Hyde, Tristram; Blaurock, Carl; Bolognese, Jeff; Howard, Joseph; Danchi, William

    2004-01-01

    The Fourier-Kelvin Stellar Interferometer (FKSI) has been proposed to detect and characterize extra solar giant planets. The baseline configuration for FKSI is a two- aperture, structurally connected nulling interferometer, capable of providing null depth less than lo4 in the infrared. The objective of this paper is to summarize the process for setting the top level requirements and the jitter analysis performed on FKSI to date. The first part of the paper discusses the derivation of dynamic stability requirements, necessary for meeting the FKSI nulling demands. An integrated model including structures, optics, and control systems has been developed to support dynamic jitter analysis and requirements verification. The second part of the paper describes how the integrated model is used to investigate the effects of reaction wheel disturbances on pointing and optical path difference stabilities.

  13. Magnetic Field Generation in Core-Sheath Jets via the Kinetic Kelvin-Helmholtz Instability

    Nishikawa, K -I; Dutan, I; Niemiec, J; Medvedev, M; Mizuno, Y; Meli, A; Sol, H; Zhang, B; Pohl, M; Hartmann, D H

    2014-01-01

    We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas we find generation of strong large-scale DC currents and magnetic fields which extend over the entire shear-surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates transverse structure similar to that produced by the Weibel instability.

  14. A Deposited Magnetic Thermometer for Temperatures Below 0.1 Kelvin

    Tuttle, J. G.; Stevenson, T. R.; Canavan, E. R.; DiPirro, M. J.; Franz, D. E.; Shirron, P. J.

    2003-01-01

    Magnetic thermometers are less sensitive to self-heating due to rf noise than are traditional resistive thermometers. This makes them appealing at temperatures well below 0.1 Kelvin in the operating range of many space-flight detectors. We have built and tested a magnetic thermometer which is deposited directly onto a substrate. This device, which uses the temperature dependence of iron-doped palladium s magnetic susceptibility, includes self-shielding deposited coils surrounding a sputtered palladium layer. It is read out using a SQUID to achieve high resolution. Its small size and very good heat-sinking should eventually make it useful for the temperature control of space flight detector arrays, in particular those already using SQUID readouts. The design and test results for this device are discussed.

  15. Sub-Kelvin magnetic and electrical measurements in a diamond anvil cell with in situ tunability

    Palmer, A; Silevitch, D M; Feng, Yejun; Wang, Y; Jaramillo, R.; Banerjee, A.; Ren, Y.; Rosenbaum, T. F.

    2015-09-01

    We discuss techniques for performing continuous measurements across a wide range of pressure–field–temperature phase space, combining the milli-Kelvin temperatures of a helium dilution refrigerator with the giga-Pascal pressures of a diamond anvil cell and the Tesla magnetic fields of a superconducting magnet. With a view towards minimizing remnant magnetic fields and background magnetic susceptibility, we characterize high-strength superalloy materials for the pressure cell assembly, which allows high fidelity measurements of low-field phenomena such as superconductivity below 100 mK at pressures above 10 GPa. In situ tunability and measurement of the pressure permit experiments over a wide range of pressure, while at the same time making possible precise steps across abrupt phase transitions such as those from insulator to metal.

  16. Sub-Kelvin magnetic and electrical measurements in a diamond anvil cell with in situ tunability

    Palmer, A.; Silevitch, D. M.; Feng, Yejun; Wang, Yishu; Jaramillo, R.; Banerjee, A.; Ren, Y.; Rosenbaum, T. F.

    2015-09-01

    We discuss techniques for performing continuous measurements across a wide range of pressure-field-temperature phase space, combining the milli-Kelvin temperatures of a helium dilution refrigerator with the giga-Pascal pressures of a diamond anvil cell and the Tesla magnetic fields of a superconducting magnet. With a view towards minimizing remnant magnetic fields and background magnetic susceptibility, we characterize high-strength superalloy materials for the pressure cell assembly, which allows high fidelity measurements of low-field phenomena such as superconductivity below 100 mK at pressures above 10 GPa. In situ tunability and measurement of the pressure permit experiments over a wide range of pressure, while at the same time making possible precise steps across abrupt phase transitions such as those from insulator to metal.

  17. Integrated scanning Kelvin probe-scanning electrochemical microscope system: development and first applications.

    Maljusch, Artjom; Schönberger, Bernd; Lindner, Armin; Stratmann, Martin; Rohwerder, Michael; Schuhmann, Wolfgang

    2011-08-01

    The integration of a scanning Kelvin probe (SKP) and a scanning electrochemical microscope (SECM) into a single SKP-SECM setup, the concept of the proposed system, its technical realization, and first applications are presented and discussed in detail. A preloaded piezo actuator placed in a grounded stainless steel case was used as the driving mechanism for oscillation of a Pt disk electrode as conventionally used in SECM when the system was operated in the SKP mode. Thus, the same tip is recording the contact potential difference (CPD) during SKP scanning and is used as a working electrode for SECM imaging in the redox-competition mode (RC-SECM). The detection of the local CPD is established by amplification of the displacement current at an ultralow noise operational amplifier and its compensation by application of a variable backing potential (V(b)) in the external circuit. The control of the tip-to-sample distance is performed by applying an additional alternating voltage with a much lower frequency than the oscillation frequency of the Kelvin probe. The main advantage of the SKP-SECM system is that it allows constant distance measurements of the CPD in air under ambient conditions and in the redox-competition mode of the SECM in the electrolyte of choice over the same sample area without replacement of the sample or exchange of the working electrode. The performance of the system was evaluated using a test sample made by sputtering thin Pt and W films on an oxidized silicon wafer. The obtained values of the CPD correlate well with known data, and the electrochemical activity for oxygen reduction is as expected higher over Pt than W. PMID:21675763

  18. Convectively coupled Kelvin and easterly waves in a regional climate simulation of the tropics

    Tulich, Stefan N.; Kiladis, George N.; Suzuki-Parker, Asuka

    2011-01-01

    This study evaluates the performance of a regional climate model in simulating two types of synoptic tropical weather disturbances: convectively-coupled Kelvin and easterly waves. Interest in these two wave modes stems from their potential predictability out to several weeks in advance, as well as a strong observed linkage between easterly waves and tropical cyclogenesis. The model is a recent version of the weather research and forecast (WRF) system with 36-km horizontal grid spacing and convection parameterized using a scheme that accounts for key convective triggering and inhibition processes. The domain spans the entire tropical belt between 45°S and 45°N with periodic boundary conditions in the east-west direction, and conditions at the meridional/lower boundaries specified based on observations. The simulation covers 6 years from 2000 to 2005, which is long enough to establish a statistical depiction of the waves through space-time spectral filtering of rainfall data, together with simple lagged-linear regression. Results show that both the horizontal phase speeds and three-dimensional structures of the waves are qualitatively well captured by the model in comparison to observations. However, significant biases in wave activity are seen, with generally overactive easterly waves and underactive Kelvin waves. Evidence is presented to suggest that these biases in wave activity (which are also correlated with biases in time-mean rainfall, as well as biases in the model's tropical cyclone climatology) stem in part from convection in the model coupling too strongly to rotational circulation anomalies. Nevertheless, the model is seen to do a reasonable job at capturing the genesis of tropical cyclones from easterly waves, with evidence for both wave accumulation and critical layer processes being importantly involved.

  19. Convectively coupled Kelvin and easterly waves in a regional climate simulation of the tropics

    Tulich, Stefan N. [University of Colorado, CIRES, Boulder, CO (United States); NCAR, Boulder, CO (United States); CIRES-NOAA/ESRL R/PSD1, Boulder, CO (United States); Kiladis, George N. [CIRES-NOAA/ESRL R/PSD1, Boulder, CO (United States); Suzuki-Parker, Asuka [Georgia Institute of Technology, Atlanta, GA (United States)

    2011-01-15

    This study evaluates the performance of a regional climate model in simulating two types of synoptic tropical weather disturbances: convectively-coupled Kelvin and easterly waves. Interest in these two wave modes stems from their potential predictability out to several weeks in advance, as well as a strong observed linkage between easterly waves and tropical cyclogenesis. The model is a recent version of the weather research and forecast (WRF) system with 36-km horizontal grid spacing and convection parameterized using a scheme that accounts for key convective triggering and inhibition processes. The domain spans the entire tropical belt between 45 S and 45 N with periodic boundary conditions in the east-west direction, and conditions at the meridional/lower boundaries specified based on observations. The simulation covers 6 years from 2000 to 2005, which is long enough to establish a statistical depiction of the waves through space-time spectral filtering of rainfall data, together with simple lagged-linear regression. Results show that both the horizontal phase speeds and three-dimensional structures of the waves are qualitatively well captured by the model in comparison to observations. However, significant biases in wave activity are seen, with generally overactive easterly waves and underactive Kelvin waves. Evidence is presented to suggest that these biases in wave activity (which are also correlated with biases in time-mean rainfall, as well as biases in the model's tropical cyclone climatology) stem in part from convection in the model coupling too strongly to rotational circulation anomalies. Nevertheless, the model is seen to do a reasonable job at capturing the genesis of tropical cyclones from easterly waves, with evidence for both wave accumulation and critical layer processes being importantly involved. (orig.)

  20. A moving finite element model of the incompressible Kelvin-Helmholtz instability

    The Kelvin-Helmholtz instability, caused by the sheared flow of fluids and plasmas, is of considerable practical importance. It may play a role in the edge turbulence associated with anomalous transport in the scrapeoff layer of tokamaks. Many features of this problem cause it to be one of the classic challenges to Computational Fluid Dynamics (CFD). The interesting behavior is localized to a narrow shear layer. For large Reynolds numbers, turbulence develops in this region, with thin ribbons of fluid interacting locally. In the incompressible limit, Poisson's equation must be solved for the stream function, along with the equation for convection of vorticity. Attempts to deal with the problem with adaptive and Lagrangian grids have a tendency to fail because the sheared flow can tear the grid apart. The authors treat the incompressible Kelvin-Helmholtz instability primarily as an interesting challenge in their development of the methods of Moving Finite Elements and Graph Massage as a general-purpose technique for difficult 2D problems in CFD. Moving Finite Elements provides a continuously adaptive motion of the unstructured triangular grid, concentrating it in regions of sharp gradients associated with the shear layer and the thin ribbons. Graph Massage allows the grid to break and reconnect occasionally, giving it the topological flexibility to avoid tangling. Periodic boundary conditions avoid interference of the boundaries with the flow, and Graph Massage allows one to take portions of the grid which flow out one side and put them back on the other side. The results now appear robust and believable. The 3D color movie shows vortices developing, merging, and circulating. The grid surges and boils around with the vortices with no difficulty. Vorticity is conserved to about 1 part in 1,000 for the duration of a long run at a Reynolds number of 1,000, with nonconservation of vorticity due primarily to Graph Massage rather than Moving Finite elements

  1. AAS 227: Day 4

    Kohler, Susanna

    2016-01-01

    mean its not typical. While we wait for more and better observations of exoplanet systems, theory can help us understand why the Solar System formed the way it did, and where to look for systems that formed the same way. For example, some of Murray-Clays previous work has shown that metal-rich stars tend to host more hot Jupiters and eccentric giant planets (very different from Solar System architecture). So if we want to find more systems like our own, we need to search around stars with low-to-moderate metallicity.Extrasolar Planets: Hosts, Interactions, Formation, and Interiors (by Caroline Morley)This session was a mashup of a variety of planetary topics ranging from solar flares to interiors to habitability.Leslie Rogers kicked off the session by presenting work done in collaboration with her student Ellen Price to constrain the composition of the ultra-short period (4 hours!?!) planet candidate KOI 1843.03 using models of the objects interior. Since its so close to the star, it can only exist without being torn apart if its very dense, which allows them to calculate that it must be iron-rich like Mercury!Next Kevin Thielen, an undergrad at Eckerd College, presented results from a summer project to apply a variable polytrope index to planet models. Tom Barclay then showed models that demonstrate the huge effect that having giant planets in the outer solar system has on the formation of terrestrial planets. He finds that without Jupiter and Saturn, more planets would form (8 instead of 3-4!) and giant impacts (like the moon-forming impact) would be more frequent but less energetic.Aomawa Shields shifted to discuss her 3D GCM models to determine the orbital configurations that would lead to liquid water on the surface of the planet Kepler-62f. She determines the effect of eccentricity, axis tilt (obliquity), and rotation rate on habitability. Edward Guinan brought us closer to home discussing the potential for superflares solar flares up to hundreds of times more

  2. General Rushes Open Days Day II

    2013-01-01

    General Footage during the Open Days 2013 (Day 2 -29/09/2013) Images: Antoine Nouel, Clément Sbaffe, Victor Prunier, David Guerazzi, Basile Manent, Réemi Richarme, Noemi Caraban 00:00:00 00:08:56 Interviews 00:08:56 00:20:47 ALICE 00:20:47 00:26:52 ATLAS 00:26:52 00:28:07 Workshops 00:28:07 00:33:13 Crystal Lab 00:33:13 00:44:19 Superconductivity 00:44:19 01:04:42 Cryogenics 01:04:42 01:12:39 Transports 01:12:39 01:16:30 LEIR 01:16:30 01:18:28 LMF 01:18:28 01:19:50 Vacuum 01:19:50 01:36:39 Superconducting magnets (F1) 01:36:39 01:46:06 The idea filled world of vacuum (F2) 01:46:06 01:49:55 CCC 01:49:55 01:52:41 Safety Training Center 01:52:41 01:55:00 COMPASS 01:55:00 02:09:19 Robotics 02:09:19 02:18:36 LHC Point 6 (with DG) 02:18:36 02:25:16 LHC Point 4 02:25:16 02:29:29 LHCb 02:29:29 02:33:12 Control Center 02:33:12 02:39:57 Streets

  3. 3,4-Methylenedioxymethamphetamine and 3,4-methylenedioxyamphetamine destroy serotonin terminals in rat brain: quantification of neurodegeneration by measurement of [3H]paroxetine-labeled serotonin uptake sites

    This study examines the effects of repeated systemic administration (20 mg/kg s.c., twice daily for 4 days) of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) on levels of brain monoamines, their metabolites and on the density of monoamine uptake sites in various regions of rat brain. Marked reductions (30-60%) in the concentration of 5-hydroxyindoleacetic acid were observed in cerebral cortex, hippocampus, striatum, hypothalamus and midbrain at 2 weeks after a 4-day treatment regimen of MDMA or MDA; less consistent reductions in serotonin (5-HT) content were observed in these brain regions. In addition, both MDMA and MDA caused comparable and substantial reductions (50-75%) in the density of [3H]paroxetine-labeled 5-HT uptake sites in all brain regions examined. In contrast, neither MDMA nor MDA caused any widespread or long-term changes in the content of the catecholaminergic markers (i.e., norepinephrine, dopamine, 3,4 dihydroxyphenylacetic acid and homovanillic acid) or in the number of [3H]mazindol-labeled norepinephrine or dopamine uptake sites in the brain regions examined. These data demonstrate that MDMA and MDA cause long-lasting neurotoxic effects with respect to both the functional and structural integrity of serotonergic neurons in brain. Furthermore, our measurement of reductions in the density of 5-HT uptake sites provides a means for quantification of the neurodegenerative effects of MDMA and MDA on presynaptic 5-HT terminals

  4. 3,4-Methylenedioxymethamphetamine and 3,4-methylenedioxyamphetamine destroy serotonin terminals in rat brain: quantification of neurodegeneration by measurement of (/sup 3/H)paroxetine-labeled serotonin uptake sites

    Battaglia, G.; Yeh, S.Y.; O' Hearn, E.; Molliver, M.E.; Kuhar, M.J.; De Souza, E.B.

    1987-09-01

    This study examines the effects of repeated systemic administration (20 mg/kg s.c., twice daily for 4 days) of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) on levels of brain monoamines, their metabolites and on the density of monoamine uptake sites in various regions of rat brain. Marked reductions (30-60%) in the concentration of 5-hydroxyindoleacetic acid were observed in cerebral cortex, hippocampus, striatum, hypothalamus and midbrain at 2 weeks after a 4-day treatment regimen of MDMA or MDA; less consistent reductions in serotonin (5-HT) content were observed in these brain regions. In addition, both MDMA and MDA caused comparable and substantial reductions (50-75%) in the density of (/sup 3/H)paroxetine-labeled 5-HT uptake sites in all brain regions examined. In contrast, neither MDMA nor MDA caused any widespread or long-term changes in the content of the catecholaminergic markers (i.e., norepinephrine, dopamine, 3,4 dihydroxyphenylacetic acid and homovanillic acid) or in the number of (/sup 3/H)mazindol-labeled norepinephrine or dopamine uptake sites in the brain regions examined. These data demonstrate that MDMA and MDA cause long-lasting neurotoxic effects with respect to both the functional and structural integrity of serotonergic neurons in brain. Furthermore, our measurement of reductions in the density of 5-HT uptake sites provides a means for quantification of the neurodegenerative effects of MDMA and MDA on presynaptic 5-HT terminals.

  5. Delivery of RANKL-Binding Peptide OP3-4 Promotes BMP-2-Induced Maxillary Bone Regeneration.

    Uehara, T; Mise-Omata, S; Matsui, M; Tabata, Y; Murali, R; Miyashin, M; Aoki, K

    2016-06-01

    Although bone morphogenetic protein 2 (BMP-2) is known to stimulate osteogenesis, there is evidence that high doses of BMP-2 can lead to side effects, including inflammation and carcinogenesis. The supplementation of other bone-augmenting agents is considered helpful in preventing such side effects by reducing the amount of BMP-2 required to obtain a sufficient amount of bone. We recently showed that a receptor activator of nuclear factor κB ligand (RANKL)-binding peptide promotes osteoblast differentiation. In the present study, we aimed to investigate whether OP3-4, a RANKL-binding peptide, promotes BMP-2-induced bone formation in the murine maxilla using an injectable gelatin hydrogel (GH) carrier. A GH carrier containing OP3-4 with BMP-2 was subperiosteally injected into the murine maxillary right diastema between the incisor and the first molar. The mice were sacrificed 28 d after the injections. The local bone formation in the OP3-4-BMP-2-injected group was analyzed in comparison to the carrier-injected, BMP-2-injected, and control-peptide-BMP-2-injected groups. The GH carrier containing OP3-4 with BMP-2 enlarged the radio-opaque area and increased the bone mineral content and density in the radiological analyses in comparison to the other experimental groups. Interestingly, fluorescence-based histological analyses revealed that the mineralization had started from the outside, then proceeded inward, suggesting that the size of the newly formed bone had already been set before calcification started and that the effects of OP3-4 might be involved in accelerating the early steps of osteogenesis. Actually, OP3-4 enhanced the BMP-2-induced 5-bromo-2'-deoxyuridine (BrdU)-positive cell numbers at the injected site on day 7 and the expression of Runx2 and Col1a1, which are early osteogenic cell markers, on day 10 after the subperiosteal injections. In summary, we demonstrated, for the first time, that the application of OP3-4 by subperiosteal injection promoted BMP

  6. Simultaneous polysubstance use among Danish 3,4-methylenedioxymethamphetamine and hallucinogen users

    Licht, Cecilie L; Christoffersen, Maria; Okholm, Mads;

    2012-01-01

    To describe patterns of simultaneous polysubstance use (SPU) among Danish 3,4-methylenedioxymethamphetamine (MDMA) ("Ecstasy") and hallucinogen users.......To describe patterns of simultaneous polysubstance use (SPU) among Danish 3,4-methylenedioxymethamphetamine (MDMA) ("Ecstasy") and hallucinogen users....

  7. First Day of Life

    ... Know About Zika & Pregnancy The First Day of Life KidsHealth > For Parents > The First Day of Life Print A A A Text Size What's in ... usually begin within the first few hours of life. previous continue Your Feelings Having a baby is ...

  8. Science Challenge Day

    Siegel, Deborah

    2013-01-01

    Science fairs can be good motivators, but as extracurricular activities, they leave some students behind. However, by staging a Science Challenge Day at school, educators can involve all students in doing everything from choosing activities to judging projects. This article presents a model for running a successful Science Challenge Day. The…

  9. NO TOBACCO DAY

    Medical Service

    2002-01-01

    The CERN Medical Service is joining in with the world no tobacco day, which takes place on 31 May 2002. We encourage you to take this opportunity to stop smoking for good. Nurses and Doctors will be present on that day to give out information on methods to stop smoking and to assist you in your efforts.

  10. April Fools Day

    艾群

    2005-01-01

    April Fools' Day is traditionally a day to play practical jokes on others, send people on fools'things,and fool the unsuspecting(信任的)。No one knows how this holiday began but it was thought to have originated(起源)in France.

  11. Father's Day

    北辰

    2004-01-01

    The idea of a special day to honour mothers was first put forward in America in 1907.Tow years later a woman,Mrs.John Bruce Dodd,in the state of Washington,proposed a similar day to honour the head of the family—the father.

  12. My Lucky Day

    Olvey, Maura

    2010-01-01

    Teaching based on problem solving brings challenges for the teacher, primarily that of finding problems with multiple access points that accommodate all students. This article narrates the author's lucky day as she discovers the Four fours problem which impacted her passion for teaching math. The day she presented the Four fours problem to her…

  13. Valentine's Day

    顾晓玲

    2009-01-01

    Valentine’s Day,which falls on February14,is one of the most popular festivals of western society and even the whole world.It is a day for lovers,a day when people present chocolates,cards and can-dies to their beloved(心爱的人).

  14. Rainy Day Activities.

    Texas Child Care, 1997

    1997-01-01

    Experienced caregivers plan ahead for rainy days. This article describes specific rainy day activities for young children, such as books and crafts to learn about rain (rain in a jar, making a rainbow), simple cooking activities (taffy pull, cinnamon candy tea), and games (mummy wrap, hunt the thimble, rain lotto). (EV)

  15. General Rushes Open Days Day I

    2013-01-01

    General Footage during Open Days 2013 (Day 1 -28/09/2013) Images: Cameramen: Antoine Nouel, Clément Sbaffe, Victor Prunier, David Guerazzi, Basile Manent, Réemi Richarme, Noemi Caraban 00:00:00 00:03:40 Interviews 00:03:40 00:06:54 Beam Instrumentation 00:06:54 00:07:16 Globe 00:07:16 00:10:28 Microcosme 00:10:28 00:12:59 Lectures 00:12:59 00:27:52 Fun with physics 00:27:52 00:28:19 International Village 00:28:19 00:34:18 Fun Zone 00:34:18 00:47:50 ATLAS Surface 00:47:50 00:56:57 ATLAS underground 00:56:57 00:58:53 Detector technologies 00:58:53 01:04:39 CLIC 01:04:39 01:05:56 CMS surface 01:05:56 01:09:32 LINAC 2-3 01:09:32 01:15:29 LINAC 4 01:15:29 01:20:41 Computer Center 01:20:41 01:25:53 Clubs 01:25:53 01:31:49 Beam Instrumentation 01:31:49 01:35:27 Music Festival 01:35:27 01:37:31 SPS 01:37:31 01:46:13 CCC 01:46:13 01:48:24 Safety Trainig Center 01:48:24 01:52:38 COMPASS 01:52:38 01:56:09 EHN1 01:56:09 02:01:42 AMS 02:01:42 02:10:52 Robotics 02:10:52 02:22:48 LHC Point 4 02:22:48 02:23:48 Control Cent...

  16. Biodegradation of 3,4 dichloroaniline by fungal isolated from the preconditioning phase of winery wastes subjected to vermicomposting.

    Castillo, Jean Manuel; Nogales, Rogelio; Romero, Esperanza

    2014-02-28

    A hazardous contaminant, 3,4-dichloroaniline (DCA) is widespread in the environment due to its extensive use in the manufacture of chemicals and its application in different sectors. The ability of fungi grow on in winery wastes in the preconditioning period of vermicomposting to degrade DCA was investigated. Three filamentous fungi (F1, F2, and F3) were isolated and one identified as Aspergillus niger and two as Fusarium sp. strains. The culture media with the fungus alone or in consortium (Fmix) with DCA as the nitrogen source were analyzed by solid-phase microextraction and gas chromatography-mass spectrometry (SPME-GC/MS). The fastest degradation rate was measured in Fmix with a DT50 of 0.85day(-1). Fusarium sp. and A. niger differed in the metabolism of DCA. Five metabolites were identified as a result of oxidation, co-denitrification, N-acetylation, and polymerization reactions. The major metabolites were 3,4-dichloroacetanilide and dichloroquinolines. The azo-metabolites tetrachloroazobenzene and tetracloroazoxybenzene and 3,4-dichloronitrobenzene were found in minor amounts but appeared to be the most persistent in the Fusarium cultures (half-lives ranging from 8.3 to 30.9 days). This study highlights the metabolic potential of microorganisms in the preconditioning period of the vermicomposting process and its possible application for in situ bioremediation strategies. PMID:24440653

  17. AGR-3/4 Final Data Qualification Report for ATR Cycles 151A through 155B-1

    Pham, Binh T. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-03-01

    This report provides the qualification status of experimental data for the entire Advanced Gas Reactor 3/4 (AGR 3/4) fuel irradiation. AGR-3/4 is the third in a series of planned irradiation experiments conducted in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) for the AGR Fuel Development and Qualification Program, which supports development of the advanced reactor technology under the INL ART Technology Development Office (TDO). The main objective of AGR-3/4 irradiation is to provide a known source of fission products for subsequent transport through compact matrix and structural graphite materials due to the presence of designed-to-fail fuel particles. Full power irradiation of the AGR 3/4 test began on December 14, 2011 (ATR Cycle 151A), and was completed on April 12, 2014 (end of ATR Cycle 155B) after 369.1 effective full power days of irradiation. The AGR-3/4 test was in the reactor core for eight of the ten ATR cycles between 151A and 155B. During the unplanned outage cycle, 153A, the experiment was removed from the ATR northeast flux trap (NEFT) location and stored in the ATR canal. This was to prevent overheating of fuel compacts due to higher than normal ATR power during the subsequent Powered Axial Locator Mechanism cycle, 153B. The AGR 3/4 test was inserted back into the ATR NEFT location during the outage of ATR Cycle 154A on April 26, 2013. Therefore, the AGR-3/4 irradiation data received during these 2 cycles (153A and 153B) are irrelevant and their qualification status isnot included in this report. Additionally, during ATR Cycle 152A the ATR core ran at low power for a short enough duration that the irradiation data are not used for physics and thermal calculations. However, the qualification status of irradiation data for this cycle is still covered in this report. As a result, this report includes data from 8 ATR Cycles: 151A, 151B, 152A, 152B, 154A, 154B, 155A, and 155B, as recorded in the Nuclear Data Management and

  18. Novel 2,5-disubstituted-1,3,4-oxadiazoles as anti-inflammatory drugs

    Ega Durgashivaprasad

    2014-01-01

    Full Text Available Objective: 1,3,4-oxadiazole ring is a versatile moiety with a wide range of pharmacological properties. The present work deals with the synthesis and evaluation of the anti-inflammatory activity of two novel 2,5-disubstituted-1,3,4-oxadiazoles (OSD and OPD. Materials and Methods: Carrageenan-induced rat hind paw edema was employed as an acute model of inflammation. For evaluating sub-acute anti-inflammatory activity, carrageenan-induced inflammation in rat air pouch was employed. Complete Freund′s adjuvant-induced arthritis in rats was used as a model of chronic inflammation. To evaluate in vitro anti-inflammatory activity, lipopolysaccharide (LPS-stimulated RAW264.7 cells were used. Results: OSD (100 mg/kg reduced carrageen-induced paw edema by 60%, and OPD (100 mg/kg produced a modest 32.5% reduction. OSD also reduced leukocyte influx and myeloperoxidase in carrageenan-induced rat air pouch model. In complete Freund′s adjuvant-induced arthritis model, both OSD and OPD (200 mg/kg for 14 days reduced paw edema and NO levels. In LPS-stimulated RAW264.7 cells, OSD and OPD inhibited formation of nitric oxide and reactive oxygen species, with OPD showing a better activity in comparison to OSD. Conclusions: OSD was the better of the two compounds in in vivo models of inflammation. The o-phenol substitution at position 2 of oxadiazole ring in OSD may be responsible for its better in vivo anti-inflammatory activity. The ability of the compounds to inhibit LPS-induced pro-inflammatory mediator release suggests an anti-inflammatory mechanism targeting LPS-TLR4-NF-κB signalling pathway, which needs to be explored in detail. The disparate efficacy in vitro and in vivo also requires in-depth evaluation of the pharmacokinetics of these novel oxadiazoles.

  19. Metformin Prevented Dopaminergic Neurotoxicity Induced by 3,4-Methylenedioxymethamphetamine Administration.

    Porceddu, Pier Francesca; Ishola, Ismail Ogunbayode; Contu, Liliana; Morelli, Micaela

    2016-07-01

    Metformin, a well-known antidiabetic drug, has recently been proposed to promote neurogenesis and to have a neuroprotective effect on the neurodegenerative processes induced by the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in models of Parkinson's disease. Interestingly, metformin has antioxidant properties and is involved in regulating the production of cytokines released during the neuroinflammatory process. Several studies have reported that 3,4-methylenedioxymethamphetamine (MDMA), a recreational drug mostly consumed by young adults, produces a persistent loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) and caudate putamen (CPu) of mice. The aim of this study was to investigate the potential neuroprotective effect of metformin against short- and long-term neurotoxicity induced by MDMA and its role on MDMA-induced hyperthermia. Adult mice received metformin (2 × 200 mg/kg, 11-h intervals, administered orally), MDMA (4 × 20 mg/kg, 2-h interval, administered intraperitoneally), or MDMA plus metformin (2 × 200 mg/kg, 1 h before the first MDMA administration and 4 h after the last). On the second and third day, mice were treated with vehicle or metformin (1 × 200 mg/kg) and sacrificed 48 h and 7 days after the last MDMA administration. The neuroprotective effect of metformin on MDMA-induced dopaminergic damage was evaluated by dopamine transporter (DAT) and tyrosine hydroxylase (TH) immunohistochemistry in SNc and CPu. Metformin prevented the MDMA-induced loss of TH-positive neurons in the SNc and TH- and DAT-positive fibers in CPu, both at 48 h and 7 days after the last MDMA administration. These results show that metformin is neuroprotective against the short- and long-lasting dopaminergic neurodegeneration induced by MDMA. PMID:27251371

  20. Effect of hydrostatic pressure on N(CH3)4+ cation motion in ferroelectric N(CH3)4H(Cl3CCOO)2.

    Zdanowska-Fraczek, M; Lewicki, S; Jakubas, R; Wasicki, J

    2000-06-01

    The proton spin-lattice relaxation time in ferroelectric N(CH3)4H(Cl3CCOO)2 has been studied under isobaric conditions at pressures 0.1, 200 and 400 MPa over a wide range of temperature. The data indicate that the dominant relaxation mechanism for T1 can be attributed to the classical CH3 group reorientation of N(CH3)4+ cation. The influence of pressure on methyl group reorientation of N(CH3)4+ cation was analysed. PMID:10868567

  1. Angular Distributions for 3,4 Lambda H Bound States in the 3,4 He(e,e'K+) reaction

    Dohrmann, Frank; Ahmidouch, Abdellah; Armstrong, Christopher; Arrington, John; Asaturyan, Razmik; Avery, Steven; Bailey, Kevin; Hu, Bitao; Breuer, Herbert; Brown, Daniel; Carlini, Roger; Cha, Jinseok; Chant, Nicholas; Christy, Michael; Cochran, Anthony; Cole, Leon; Crowder, J.; Danagoulian, Samuel; Elaasar, Mostafa; Ent, Rolf; Fenker, Howard; Fujii, Yu; Gan, Liping; Garrow, Kenneth; Gueye, Paul; Hafidi, Kawtar; Hinton, Wendy; Juengst, Henry; Keppel, Cynthia; Liang, Yongguang; Liu, Jinghua; Lung, Allison; Mack, David; Markowitz, Pete; Mitchell, Joseph; Miyoshi, Toshinobu; Mkrtchyan, Hamlet; Mtingwa, Sekazi; Mueller, Robert; Niculescu, Gabriel; Niculescu, Maria-Ioana; Potterveld, David; Raue, Brian; Reimer, Paul; Reinhold, Joerg; Roche, Julie; Sarsour, Murad; Sato, Yoshinori; Segel, Ralph; Semenov, Andrei; Stepanyan, Samuel; Tadevosyan, Vardan; Tajima, Shigeyuki; Tang, Liguang; Uzzle, Alicia; Wood, Stephen; Yamaguchi, Hiroshi; Yan, Chen; Yuan, Lulin; Zeidman, Benjamin; Zeier, Markus; Zihlmann, Benedikt

    2004-12-01

    The 3Lambda H and 4Lambda H hypernuclear bound states have been observed for the first time in kaon electroproduction on 3,4He targets. The production cross sections have been determined at Q**2= 0.35 GeV**2 and W= 1.91 GeV. For either hypernucleus the nuclear form factor is determined by comparing the angular distribution of the 3,4He(e,e'K+)3,4Lambda H processes to the elementary cross section 1H(e,e'K+) Lambda on the free proton, measured during the same experiment.

  2. Bad Air Day

    ... link, please review our exit disclaimer . Subscribe Bad Air Day Air Quality and Your Health In many parts of the country, summer has the worst air quality of any season. When the forecast says ...

  3. Mother’s Day

    李瑞海

    2011-01-01

    难度指数:★★★☆☆词数:408建议阅读时间:5分钟Mother’s Day is a time of commemoration(纪念)and celebration for mothers.It is a time of breakfastin bed,family gatherings,and crayons scribbled"ILove You".The earliest Mother’s Day celebrations can betraced back to the spring celebrations of ancient

  4. An extended day program

    Ševkušić-Mandić Slavica G.

    2002-01-01

    Full Text Available The paper presents the results of a pilot project evaluation, carried out as an action investigation whose aim was to provide a better quality extended day for primary school students. The project included the training of teachers involved in extended day program, designing of special activities performed by teachers with children once a week as well as changes and equipping of premises where children stay. The aims of the program were conception and performance of activities in a less formal way than during regular instructional days, linking of learning at school and acquired knowledge to everyday experiences, and work on contents contributing to the development of child's interests and creativity. The program was accomplished in a Belgrade primary school during the 2001/2002 academic year, comprising students of 1st and 2nd grades (N=77. The effects of the program were monitored throughout the academic year (observation and teachers' reports on accomplished workshops and at the end of the academic year (teachers and students' opinions of the program, academic achievement and creativity of students attending the extended day program compared with students not attending it. Findings about positive effects of the program on students' broadening of interests and willingness to express themselves creatively, indicate unequivocally that there is a need for developing special extended day programs. The extended day program is an opportunity for school to exert greater educational influence that has yet to be tapped.

  5. Open Day: General Information

    2004-01-01

    http://www.cern.ch/cern50/ With 50 visit points, including theatre performances, debates and visits to installations that have never before been opened to the public, CERN's 50th anniversary Open Day is set to be a day to remember. Seven hundred volunteers have signed up to help for the day. The Open Day team truly appreciates this wonderful show of support! The Open Day would not be possible without their help. Car parking and Access Cars with a CERN sticker can access all CERN sites as normal. However, to avoid congestion on Meyrin site, we ask you to park in areas that will not be open to the public (see below) and to use the shuttle services wherever possible for your transport during the day. Private cars on the French side of the border without a CERN sticker will be diverted to a car park area in the Prévessin site. There is a shuttle service connecting the Meyrin and Prévessin sites via SM18 every 20 minutes. Private cars on the Swiss side of the border without a CERN sticker will be diverte...

  6. Preparation of QTi4.3-4Graghite Composite by Semi-solid Casting Technology

    ZHANG Peng; DU Yunhui; LIU Hanwu; ZENG Daben; BA Limin

    2005-01-01

    The electromagnetic-mechanical stirring technology was employed for preparing QTi4.3-4 graghite composite slurry, and QTi4.3-4 graghite composite with uniform distribution of graphite particles was prepared using the semi-solid casting technology successfully. The structure of this QTi4.3-4 graghite composite was studied and the condition for uniform distribution of graphite particles was got. The experimental results show that there exists a linear relationship between the solid fraction aud the stirring temperature of QTi4.3-4 graphite slurry. With the decreasing of stirring temperature, the solid fraction of QTi4.3-4 graghite slurry increases constantly. In casting, with the iucreasing of solid fraction of QTi4.3-4graghite slurry, the agglomeration of graphite particles is removed gradually. When the solid fraction is higher than 40% , graphite particles can distribute evenly in QTi4.3-4 graghite composite.

  7. Application of scanning Kelvin probe microscopy for the electrical characterization of microcrystalline silicon for photovoltaics

    In the last years microcrystalline silicon thin films have attracted great attention as a new photovoltaic material. With this material it is possible to combine simple and cheap low temperature deposition techniques known from amorphous silicon with the long-term stability of the photovoltaic performance like in bulk crystalline silicon solar cells. The critical point is the deposition procedure with numerous tunable parameters influencing the quality and character of the produced diode structures. Additionally there is a great uncertainty about unintentionally incorporated defects, which is not affected by the deposition parameters. Extended investigation of the material, diode and solar cell characteristics is essential in order to correlate the impact of deposition conditions with the quality of the devices. The situation is complicated due to the anisotropic and inhomogeneous character of microcrystalline silicon. Scanning Kelvin probe microscopy (SKPM) is a work function measurement method based on a scanning force microscope (SFM) and a modified Kelvin probe technique. Due to the excellent lateral resolution of the SFM work function measurements with resolutions far below the micrometer level can be carried out. Applied on doped microcrystalline silicon structures it is possible to visualize the position of the Fermi level within the band gap and the influence of the deposition conditions on it. Within this work a SKPM based on a commercially available SFM was constructed and built. Great effort was concentrated on the characterization of the SKPM experiment. On the basis of an extended knowledge about the performance investigations concentrated on cross sections of microcrystalline silicon diode structures produced by hot-wire chemical vapor deposition (HW-CVD). A pin structure for the diodes was chosen due to the low diffusion lengths within this rather defective material. The evolution of the built-in electric drift field within the intrinsic absorber is

  8. Kelvin probe force microscopy of DNA-capped nanoparticles for single-nucleotide polymorphism detection

    Lee, Hyungbeen; Lee, Sang Won; Lee, Gyudo; Lee, Wonseok; Lee, Jeong Hoon; Hwang, Kyo Seon; Yang, Jaemoon; Lee, Sang Woo; Yoon, Dae Sung

    2016-07-01

    Kelvin probe force microscopy (KPFM) is a robust toolkit for profiling the surface potential (SP) of biomolecular interactions between DNAs and/or proteins at the single molecule level. However, it has often suffered from background noise and low throughput due to instrumental or environmental constraints, which is regarded as limiting KPFM applications for detection of minute changes in the molecular structures such as single-nucleotide polymorphism (SNP). Here, we show KPFM imaging of DNA-capped nanoparticles (DCNP) that enables SNP detection of the BRCA1 gene owing to sterically well-adjusted DNA-DNA interactions that take place within the confined spaces of DCNP. The average SP values of DCNP interacting with BRCA1 SNP were found to be lower than the DCNP reacting with normal (non-mutant) BRCA1 gene. We also demonstrate that SP characteristics of DCNP with different substrates (e.g., Au, Si, SiO2, and Fe) provide us with a chance to attenuate or augment the SP signal of DCNP without additional enhancement of instrumentation capabilities.Kelvin probe force microscopy (KPFM) is a robust toolkit for profiling the surface potential (SP) of biomolecular interactions between DNAs and/or proteins at the single molecule level. However, it has often suffered from background noise and low throughput due to instrumental or environmental constraints, which is regarded as limiting KPFM applications for detection of minute changes in the molecular structures such as single-nucleotide polymorphism (SNP). Here, we show KPFM imaging of DNA-capped nanoparticles (DCNP) that enables SNP detection of the BRCA1 gene owing to sterically well-adjusted DNA-DNA interactions that take place within the confined spaces of DCNP. The average SP values of DCNP interacting with BRCA1 SNP were found to be lower than the DCNP reacting with normal (non-mutant) BRCA1 gene. We also demonstrate that SP characteristics of DCNP with different substrates (e.g., Au, Si, SiO2, and Fe) provide us with a

  9. Study of semiconductor and metal surfaces using a novel scanning Kelvin probe

    This thesis reports design and construction of a novel Scanning Kelvin probe (SKP) compatible with the Ultra-High-Vacuum (UHV) environment - the first automatic, high resolution, UHV-SKP in the UK. The Kelvin Probe is a capacitor device used to measure the work function φ between a vibrating reference electrode (the tip) and the surface under investigation. It utilises a non-contact, non-destructive measurement mode allowing work function measurements at temperatures in the range from (300 - 1100) K. The work function is a multi-parameter variable highly sensitive to changes in surface and interface chemical composition, adsorbate induced surface dipole and surface atomic geometry. We have also followed the variable temperature oxidation kinetics of Si(111) in the range (100 - 600) K and show that magnitude of the Δφpeak during the initial adsorption curve decreases in a linear fashion with increasing substrate temperature. Moreover, the transient work function measurements on the O2/Si(111) surface at 300 K show that the lifetime of the precursor states depend strongly on oxygen exposure. We examined high (Rhenium Re, Tungsten W, Molybdenum Mo and Platinum Pt) and low (Calcium Ca, Lanthanum Hexaboride LaB6, Gadolinium Gd) work function materials as target surfaces for Hyperthermal Surface Ionisation (HSI) used in a new mass spectroscopy ionisation technique. We particularly investigated the high work function materials with respect to their oxidation behaviour as it substantially increases their φ's. We present and discuss the following experimental evidence: a) the magnitude and sign of φ changes in terms of adsorbate induced dipoles, b) the effect of molecular hydrogen exposure on the clean surface, and c) the effect of subsequent oxygen exposure. The oxidised Rhenium exhibited the highest work function with φ = (7.15 ± 0.1) eV at a temperature of ∼900 K. LaB6 indicated the lowest work function with φ = (2.45 ± 0.1) eV, while Ca gave the best results

  10. Synthesis and antimicrobial activity of some novel fused heterocyclic 1,2,4-triazolo [3,4-b][1,3,4] thiadiazine derivatives

    Jagdish K. Sahu

    2014-01-01

    Full Text Available In the present investigation, the synthesis and antimicrobial evaluation of 1,2,4-triazolo [3,4-b][1,3,4] thiadiazine including different pharmacophores are aimed at. In this study, a series of 6-aryl-3- (3,4 -dialkoxyphenyl-7H -[1,2,4]triazolo [3,4-b][1,3,4] thiadiazine (7a-7k was synthesized by condensing 4-amino-5-(3,4-dialkoxyphenyl-4H-[1,2,4]- triazole-3-thiol (6 with various aromatic carboxylic acids in the presence of phenacyl bromides through one-pot reaction. Eleven fused heterocyclic derivatives were successfully synthesized. The structures of these newly synthesized compounds were characterized by IR, 1 H NMR and mass spectroscopic studies. All the synthesized compounds were screened for their antimicrobial evaluation. Some of the compounds exhibited promising antimicrobial activity. From the present study it may be concluded that synthesized compounds are fruitful in terms of their structural novelty and marked biological activities. These compounds could be further modified to develop potential and safer antifungal agents.

  11. 4th Optimization Day

    Eberhard, Andrew; Ralph, Daniel; Glover, Barney M

    1999-01-01

    Although the monograph Progress in Optimization I: Contributions from Aus­ tralasia grew from the idea of publishing a proceedings of the Fourth Optimiza­ tion Day, held in July 1997 at the Royal Melbourne Institute of Technology, the focus soon changed to a refereed volume in optimization. The intention is to publish a similar book annually, following each Optimization Day. The idea of having an annual Optimization Day was conceived by Barney Glover; the first of these Optimization Days was held in 1994 at the University of Ballarat. Barney hoped that such a yearly event would bring together the many, but widely dispersed, researchers in Australia who were publishing in optimization and related areas such as control. The first Optimization Day event was followed by similar conferences at The University of New South Wales (1995), The University of Melbourne (1996), the Royal Melbourne Institute of Technology (1997), and The University of Western Australia (1998). The 1999 conference will return to Ballarat ...

  12. Development of nonlinear two fluid interfacial structures by combined action of Rayleigh-Taylor, Kelvin-Helmholtz and Richtmyer-Meshkov instabilities:Oblique shock

    Gupta, M R; Roy, Sourav; Banerjee, Rahul; Khan, Manoranjan

    2010-01-01

    The nonlinear evolution of two fluid interfacial structures like bubbles and spikes arising due to the combined action of Rayleigh-Taylor and Kelvin-Helmholtz instability or due to that of Richtmyer-Meshkov and Kelvin-Helmholtz instability resulting from oblique shock is investigated. Using Layzer's model analytic expressions for the asymptotic value of the combined growth rate are obtained in both cases for spikes and bubbles. However, if the overlying fluid is of lower density the interface perturbation behaves in different ways. Depending on the magnitude of the velocity shear associated with Kelvin-Helmholtz instability both the bubble and spike amplitude may simultaneously grow monotonically (instability) or oscillate with time or it may so happen that while this spike steepens the bubble tends to undulate. In case of an oblique shock which causes combined action of Richtmyer-Meshkov instability arising due to the normal component of the shock and Kelvin Helmholtz instability through creation of velocity...

  13. Noncontact atomic force and Kelvin probe force microscopy on MgO(100) and MgO(100)-supported Ba

    Pang, Chi Lun; Sasahara, Akira; Onishi, Hiroshi

    2016-08-01

    Atomically-flat MgO(100) surfaces were prepared by sputtering and annealing. Noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) were used to characterize the MgO(100) surfaces. The NC-AFM images revealed the presence of point defects on an atomically-resolved surface. The surface potential at these point defects, as well as features such as step edges and deposited Ba nanoparticles were mapped using KPFM. The Kelvin images show that the surface potential increases at the point defects and at the step edges. On the other hand, a decrease in the potential was found over Ba nanoparticles which can be explained by electron charge transfer from the Ba to the MgO.

  14. In-situ Kelvin probe study of the SnO2/p (a-Si:H) interface

    The authors present an in-situ Kelvin probe study of the effects of hydrogen and argon plasma treatments on fluorine doped tin-oxide (SnO2 substrates, as well as the consequences of these treatments on the subsequent growth of a-Si:H. They found that the effect of both hydrogen and argon plasmas is to enhance the reactivity of SnO2 substrates in a silane plasma. Moreover, the doping level (Fermi level) of boron doped a-Si:H layers deposited on SnO2 is reached more quickly when the substrate has been treated previously with an argon plasma. As a consequence, the authors expect a higher open circuit voltage (Voc) for SnO2/p-i-n solar cells in which the substrate has been treated by an argon plasma. The Kelvin probe results have been confirmed by Voc measurements on solar cells deposited on treated and untreated substrates

  15. Methods for measurement of electron emission yield under low energy electron-irradiation by collector method and Kelvin probe method

    Secondary electron emission yield of gold under electron impact at normal incidence below 50 eV was investigated by the classical collector method and by the Kelvin probe method. The authors show that biasing a collector to ensure secondary electron collection while keeping the target grounded can lead to primary electron beam perturbations. Thus reliable secondary electron emission yield at low primary electron energy cannot be obtained with a biased collector. The authors present two collector-free methods based on current measurement and on electron pulse surface potential buildup (Kelvin probe method). These methods are consistent, but at very low energy, measurements become sensitive to the earth magnetic field (below 10 eV). For gold, the authors can extrapolate total emission yield at 0 eV to 0.5, while a total electron emission yield of 1 is obtained at 40±1 eV.

  16. The Kelvin-Helmholtz instability under Parker-Spiral Interplanetary Magnetic Field conditions at the magnetospheric flanks

    Adamson, E.; Nykyri, K.; Otto, A.

    2016-07-01

    We have generated fully three-dimensional, high-resolution magnetohydrodynamic (MHD) simulations of the Kelvin-Helmholtz (KH) Instability during Parker-Spiral Interplanetary Magnetic Field (IMF) conditions at the dawnside magnetospheric flank magnetopause. Results of these simulations show that, although the draping of a strong tangential magnetic field component around the magnetopause, tailward of the terminator (due to the Parker-Spiral orientation), tends to stabilize the growth of such instabilities within the shear-flow plane, Kelvin-Helmholtz waves with a k -vector tilted out of this plane may, nonetheless, develop into the nonlinear phase. This result suggests that obliquely propagating KH waves may contribute to the dawn-dusk asymmetries observed in plasma sheet parameters.

  17. Wave simulation in biologic media based on the Kelvin-Voigt fractional-derivative stress-strain relation.

    Caputo, Michele; Carcione, José M; Cavallini, Fabio

    2011-06-01

    The acoustic behavior of biologic media can be described more realistically using a stress-strain relation based on fractional time derivatives of the strain, since the fractional exponent is an additional fitting parameter. We consider a generalization of the Kelvin-Voigt rheology to the case of rational orders of differentiation, the so-called Kelvin-Voigt fractional-derivative (KVFD) constitutive equation, and introduce a novel modeling method to solve the wave equation by means of the Grünwald-Letnikov approximation and the staggered Fourier pseudospectral method to compute the spatial derivatives. The algorithm can handle complex geometries and general material-property variability. We verify the results by comparison with the analytical solution obtained for wave propagation in homogeneous media. Moreover, we illustrate the use of the algorithm by simulation of wave propagation in normal and cancerous breast tissue. PMID:21601139

  18. Light yield of an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin

    Liu, Jing; Soma, Arun Kumar

    2016-01-01

    A light yield of 20.4 $\\pm$ 0.8 photoelectrons/keV was achieved with an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin. This is by far the largest yield in the world achieved with CsI crystals. An energy threshold that is several times lower than the current dark matter experiments utilizing CsI(Tl) crystals may be achievable using this technique. Together with novel CsI crystal purification methods, the technique may be used to improve the sensitivities of dark matter and coherent elastic neutrino-nucleus scattering experiments. Also measured were the scintillation light decay constants of the undoped CsI crystal at both room temperature and 77 Kelvin. The results are consistent with those in the literature.

  19. The effect of oxidation on charge carrier motion in PbS quantum dot thin films studied with Kelvin Probe Microscopy

    Nguyen Hoang, Lan Phuong; Williams, Pheona; Moscatello, Jason; Aidala, Kathy; Aidala group Team

    We developed a technique that uses scanning probe microscopy (SPM) to study the real-time injection and extraction of charge carriers in thin film devices. We investigate the effects of oxidation on thin films of Lead Sulfide (PbS) quantum dots with tetrabutyl-ammonium-iodide (TBAI) ligands in an inverted field effect transistor geometry with gold electrodes. By positioning the SPM tip at an individual location and using Kelvin Probe Force Microscopy (KPFM) to measure the potential over time, we can record how the charge carriers respond to changing the backgate voltage with grounded source and drain electrodes. We see relatively fast screening for negative backgate voltages because holes are quickly injected into the PbS film. The screening is slower for positive gate voltages, because some of these holes are trapped and therefore less mobile. We probe these trapped holes by applying different gate voltages and recording the change in potential at the surface. There are mixed reports about the effect of air exposure on thin films of PbS quantum dots, with initial exposure appearing to be beneficial to device characteristics. We study the change in current, mobility, and charge injection and extraction as measured by KPFM over hours and days of exposure to air. This work is supported by NSF Grant DMR-0955348, and the Center for Heirarchical Manufacturing at the University of Massachusetts, Amherst (NSF CMMI-1025020).

  20. The acute and subchronic effect of 3,4-methylenedioxymethamphetamine on body temperature in rats

    Simić Ivan

    2009-01-01

    Full Text Available Introduction. The consumption of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy is known to cause severe hyperthermia in humans. This is of extreme importance since ecstasy is often consumed at 'rave' parties, where dancing takes place in a warm environment, which may exacerbate the effect of MDMA on thermoregulation. The present study was performed in order to evaluate the effects of single and repeated administration of MDMA on body temperature in Wistar rats. Material and methods. The study included 72 male Wistar rats, housed in groups of four in cages at a room temperature of 222oC. They were divided in two groups. The rats in the first group were treated with oral solution of MDMA (5 mg/kg, 10 mg/kg, 20 mg/kg, 40 mg/kg and their temperature was measured hourly until 8th hour. The rats in the second group were treated with oral solution of MDMA (5 mg/kg, 10 mg/kg, 20 mg/kg every day during 15 days and their temperature was measured daily at 0th, 1st, 3rd, 5th and 8th hour. Temperature was measured by inserting a thermocouple probe 2,5 cm into the rectum. Results. Both groups showed dose dependent increase of body temperature, determined by rectal temperature measurements. The magnitude of hyperthemic response caused by subchronic administration of MDMA was markedly diminished during the experiment. Conclusion. The hyperthermic effect of MDMA was dose-dependent. The magnitude of the hyperthermic response was markedly diminished in subchronic administration.

  1. Effects of 3,4-methylenedioxymethamphetamine administration on retinal physiology in the rat.

    Martins, João; Castelo-Branco, Miguel; Batista, Ana; Oliveiros, Bárbara; Santiago, Ana Raquel; Galvão, Joana; Fernandes, Eduarda; Carvalho, Félix; Cavadas, Cláudia; Ambrósio, António F

    2011-01-01

    3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) is known to produce euphoric states, but may also cause adverse consequences in humans, such as hyperthermia and neurocognitive deficits. Although MDMA consumption has been associated with visual problems, the effects of this recreational drug in retinal physiology have not been addressed hitherto. In this work, we evaluated the effect of a single MDMA administration in the rat electroretinogram (ERG). Wistar rats were administered MDMA (15 mg/kg) or saline and ERGs were recorded before (Baseline ERG), and 3 h, 24 h, and 7 days after treatment. A high temperature (HT) saline-treated control group was also included. Overall, significantly augmented and shorter latency ERG responses were found in MDMA and HT groups 3 h after treatment when compared to Baseline. Twenty-four hours after treatment some of the alterations found at 3 h, mainly characterized by shorter latency, tended to return to Baseline values. However, MDMA-treated animals still presented increased scotopic a-wave and b-wave amplitudes compared to Baseline ERGs, which were independent of temperature elevation though the latter might underlie the acute ERG alterations observed 3 h after MDMA administration. Seven days after MDMA administration recovery from these effects had occurred. The effects seem to stem from specific changes observed at the a-wave level, which indicates that MDMA affects subacutely (at 24 h) retinal physiology at the outer retinal (photoreceptor/bipolar) layers. In conclusion, we have found direct evidence that MDMA causes subacute enhancement of the outer retinal responses (most prominent in the a-wave), though ERG alterations resume within one week. These changes in photoreceptor/bipolar cell physiology may have implications for the understanding of the subacute visual manifestations induced by MDMA in humans. PMID:22216322

  2. Effects of 3,4-methylenedioxymethamphetamine administration on retinal physiology in the rat.

    João Martins

    Full Text Available 3,4-Methylenedioxymethamphetamine (MDMA; ecstasy is known to produce euphoric states, but may also cause adverse consequences in humans, such as hyperthermia and neurocognitive deficits. Although MDMA consumption has been associated with visual problems, the effects of this recreational drug in retinal physiology have not been addressed hitherto. In this work, we evaluated the effect of a single MDMA administration in the rat electroretinogram (ERG. Wistar rats were administered MDMA (15 mg/kg or saline and ERGs were recorded before (Baseline ERG, and 3 h, 24 h, and 7 days after treatment. A high temperature (HT saline-treated control group was also included. Overall, significantly augmented and shorter latency ERG responses were found in MDMA and HT groups 3 h after treatment when compared to Baseline. Twenty-four hours after treatment some of the alterations found at 3 h, mainly characterized by shorter latency, tended to return to Baseline values. However, MDMA-treated animals still presented increased scotopic a-wave and b-wave amplitudes compared to Baseline ERGs, which were independent of temperature elevation though the latter might underlie the acute ERG alterations observed 3 h after MDMA administration. Seven days after MDMA administration recovery from these effects had occurred. The effects seem to stem from specific changes observed at the a-wave level, which indicates that MDMA affects subacutely (at 24 h retinal physiology at the outer retinal (photoreceptor/bipolar layers. In conclusion, we have found direct evidence that MDMA causes subacute enhancement of the outer retinal responses (most prominent in the a-wave, though ERG alterations resume within one week. These changes in photoreceptor/bipolar cell physiology may have implications for the understanding of the subacute visual manifestations induced by MDMA in humans.

  3. Kelvin modes as NambuGoldstone modes along superfluid vortices and relativistic strings: Finite volume size effects

    Kobayashi, Michikazu; Nitta, Muneto

    2014-01-01

    We study Kelvin modes and translational zero modes excited along a quantized vortex and relativistic global string in superfluids and a relativistic field theory, respectively, by constructing the low-energy effective theory of these modes. We find that they become exact gapless Nambu-Goldstone modes only in a system with infinite volume limit. On the other hand, in a system with the finite volume, we find an imaginary massive gap causing the tachyonic instability above some critical waveleng...

  4. Fractal Nature of Metallic and Insulating Domain Configurations in a VO2 Thin Film Revealed by Kelvin Probe Force Microscopy

    Sohn, Ahrum; Kanki, Teruo; Sakai, Kotaro; Tanaka, Hidekazu; Kim, Dong-Wook

    2015-01-01

    We investigated the surface work function (W S ) and its spatial distribution for epitaxial VO2/TiO2 thin films using Kelvin probe force microscopy (KPFM). Nearly grain-boundary-free samples allowed observation of metallic and insulating domains with distinct W S values, throughout the metal–insulator transition. The metallic fraction, estimated from W S maps, describes the evolution of the resistance based on a two-dimensional percolation model. The KPFM measurements also revealed the fracta...

  5. Combined Kelvin probe force microscopy and secondary ion mass spectrometry for hydrogen detection in corroded 2024 aluminium alloy

    Larignon, Céline; Alexis, Joël; Andrieu, Eric; Lacroix, Loïc; Odemer, Grégory; Blanc, Christine

    2013-01-01

    The capability of Kelvin probe force microscopy (KFM) to detect and locate hydrogen in corroded 2024 aluminium alloy was demonstrated. Hydrogen was introduced inside the 2024 alloy following a cyclic corrosion test consisting of cycles of immersion in 1 M NaCl solution followed by exposure to air at -20 °C. The combination of scanning electron microscopy, secondary ion mass spectrometry and KFM demonstrated that the grain and subgrain boundaries were preferential pathways for the short-circui...

  6. Investigating atomic contrast in atomic force microscopy and Kelvin probe force microscopy on ionic systems using functionalized tips

    Gross, Leo; Schuler, Bruno; Mohn, Fabian; Moll, Nikolaj; Pavliček, Niko; Steurer, Wolfram; Scivetti, Ivan; Kotsis, Konstantinos; Persson, Mats; Meyer, Gerhard

    2014-01-01

    Noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) have become important tools for nanotechnology; however, their contrast mechanisms on the atomic scale are not entirely understood. Here we used chlorine vacancies in NaCl bilayers on Cu(111) as a model system to investigate atomic contrast as a function of applied voltage, tip height, and tip functionalization. We demonstrate that the AFM contrast on the atomic scale decisively depends on both the tip termin...

  7. The resistive switching in TiO2 films studied by conductive atomic force microscopy and Kelvin probe force microscopy

    Yuanmin Du; Amit Kumar; Hui Pan; Kaiyang Zeng; Shijie Wang; Ping Yang; Andrew Thye Shen Wee

    2013-01-01

    The resistive switching characteristics of TiO2 thin films were investigated using conductive atomic force microscopy (CAFM) and Kelvin probe force microscopy (KPFM). The as-prepared TiO2 thin films were modulated into higher and lower resistance states by applying a local electric field. We showed that the resistive switching results from charge injection and release assisted by electro-migration of oxygen ions. An integrated model combined with filamentary and interfacial effects was utiliz...

  8. Directly created electrostatic micro-domains on hydroxyapatite: probing with a Kelvin Force probe and a protein

    Plecenik, Tomas; Robin, Sylvain; Gregor, Maros; Truchly, Martin; Lang, Sidney; Gandhi, Abbasi; Zahoran, Miroslav; Laffir, Fathima; Soulimane, Tewfik; Vargova, Melinda; Plesch, Gustav; Kus, Peter; Plecenik, Andrej; Tofail, S. A. M.

    2013-01-01

    Micro-domains of modified surface potential (SP) were created on hydroxyapatite (HAp) films by direct patterning by midenergy focused electron beam, typically available as a microprobe of Scanning Electron Microscopes. The SP distribution of these patterns has been studied on sub-micrometer scale by the Kelvin Probe Force Microscopy method as well as lysozyme adsorption. Since the lysozyme is positively charged at physiological pH, it allows us to track positively and negatively charged areas...

  9. Investigation of Kelvin probe force microscopy efficiency for the detection of hydrogen ingress by cathodic charging in an aluminium alloy

    Larignon, Céline; Alexis, Joël; Andrieu, Eric; Lacroix, Loïc; Odemer, Grégory; Blanc, Christine

    2013-01-01

    Detecting and locating absorbed hydrogen in aluminium alloys is necessary for evaluating the contribution of hydrogen embrittlement to the degradation of the mechanical properties for corroded or cathodically hydrogen-charged samples. The capability of Kelvin probe force microscopy (KFM) to overcome this issue was demonstrated. Aluminium alloy samples were hydrogenated by cathodic polarisation in molten salts (KHSO4/NaHSO4.H2O). The presence of absorbed hydrogen was revealed; the affected zon...

  10. Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination

    Narchi, Paul; Alvarez, José; Chrétien, Pascal; Picardi, Gennaro; Cariou, Romain; Foldyna, Martin; Prod’homme, Patricia; Kleider, Jean-Paul; i Cabarrocas, Pere Roca

    2016-01-01

    Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 10...

  11. Study of electric field distribution in AlGalnP light-emitting diode by Kelvin probe force microscopy

    This work presents results of study of different AlGaInP light-emitting diodes by using Kelvin force probe microscopy. Study of current-voltage characteristics and electric field distribution had shown that for all type of experimental samples containing multiple quantum wells the most significant series resistance of heterostructures is determined by p-isotype heterojunction and confinement p-layer

  12. Modelling and experimental verification of tip-induced polarization in Kelvin probe force microscopy measurements on dielectric surfaces

    Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

    2015-01-01

    Kelvin probe force microscopy is a widely used technique for measuring surface potential distributions on the micro- and nanometer scale. The data are, however, often analyzed qualitatively, especially for dielectrics. In many cases, the phenomenon of polarization and its influence on the measured signals is disregarded leading to misinterpretation of the results. In this work, we present a model that allows prediction of the surface potential on a metal/polymerheterostructure as measured by ...

  13. Nanoscale Structural and Electronic Properties of Ultrathin Blends of Two Polyaromatic Molecules: A Kelvin Probe Force Microscopy Investigation

    Palermo, Vincenzo; Morelli, Susanna; Palma, Matteo; Simpson, Christopher; Nolde, Fabian; Herrmann, Andreas; Müllen, Klaus; Samorì, Paolo

    2006-01-01

    We describe a Kelvin Probe Force Microscopy (KPFM) study on the morphological and electronic properties of complex mono and bi-molecular ultrathin films self-assembled on mica. These architectures are made up from an electron-donor (D), a synthetic all-benzenoid polycyclic aromatic hydrocarbon, and an electron-acceptor (A), perylene-bis-dicarboximide. The former molecule self-assembles into fibers in single component films, while the latter molecule forms discontinuous layers. Taking advantag...

  14. Evaluation of Bcl-2 Family Gene Expression in Hippocampus of 3, 4-methylenedioxymethamphetamine Treated Rats

    Hamed Hashemi-Nasl

    2012-01-01

    Full Text Available Objective: 3,4-methylenedioxymethamphetamine (MDMA is an illicit, recreational drugthat causes cellular death and neurotoxicity. This study evaluates the effects of differentdoses of MDMA on the expression of apoptosis–related proteins and genes in the hippocampusof adult rats.Materials and Methods: In this expremental study,a total of 20 male Sprague Dawley rats(200-250 g were treated with MDMA (0, 5, 10, 20 mg/kg i.p. twice daily for 7 days. Sevendays after the last administration of MDMA, the rats were killed. Bax and Bcl-2 genesin addition to protein expressions were detected by western blot and reverse transcriptionpolymerasechain reaction (RT-PCR.Results were analyzed using one-way ANOVA andp≤0.05 was considered statistically significant.Results: Our results showed that MDMA caused dose dependent up-regulation of Baxand down-regulation of Bcl-2 in the hippocampus. There was a significant alteration inbcl-2 and bax genes density.Conclusion: Changes in apoptosis-related proteins and respective genes relating to Baxand Bcl-2 might be involved in the molecular mechanism of MDMA-induced apoptosis.

  15. Kinetic plasma turbulence during the nonlinear stage of the Kelvin-Helmholtz instability

    Kemel, Koen; Lapenta, Giovanni; Califano, Francesco; Markidis, Stefano

    2014-01-01

    Using a full kinetic, implicit particle-in-cell code, iPiC3D, we studied the properties of plasma kinetic turbulence, such as would be found at the interface between the solar wind and the Earth magnetosphere at low latitude during northwards periods. In this case, in the presence of a magnetic field B oriented mostly perpendicular to the velocity shear, turbulence is fed by the disruption of a Kelvin-Helmholtz vortex chain via secondary instabilities, vortex pairing and non-linear interactions. We found that the magnetic energy spectral cascade between ion and electron inertial scales, $d_i$ and $d_e$, is in agreement with satellite observations and other previous numerical simulations; however, in our case the spectrum ends with a peak beyond $d_e$ due to the occurrence of the lower hybrid drift instability. The electric energy spectrum is influenced by effects of secondary instabilities: anomalous resistivity, fed by the development of the lower hybrid drift instability, steepens the spectral decay and, de...

  16. Observation of three distinct ion populations at the Kelvin-Helmholtz-unstable magnetopause

    M. G. G. T. Taylor

    2008-06-01

    Full Text Available We report Double Star spacecraft observations of the dusk-flank magnetopause and its boundary layer under predominantly northward interplanetary magnetic field (IMF. Under such conditions the flank low-latitude boundary layers (LLBL of the magnetosphere are known to broaden. The primary candidate processes associated with the transport of solar wind plasma into the LLBL are: (1 local diffusive plasma transport associated with the Kelvin-Helmholtz instability (KHI, (2 local plasma penetration owing to magnetic reconnection in the vicinity of the KHI-driven vortices, and (3 via a pre-existing boundary layer formed through double high-latitude reconnection on the dayside. Previous studies have shown that a cold population of solar wind origin is typically mixed with a hot population of magnetospheric origin in the LLBL. The present observations show the coexistence of three distinct ion populations in the dusk LLBL, during an interval when the magnetopause is unstable to the KHI: (1 a typical hot magnetospheric population, (2 a cold population that shows parallel temperature anisotropy, and (3 a distinct third cold population that shows perpendicular temperature anisotropy. Although no unambiguous conclusion may be drawn from this single event, we discuss the possible mechanisms at work and the origin of each population by envisaging three likely sources: hot magnetospheric plasma sheet, cold magnetosheath of solar wind origin, and cold plasma of ionospheric origin.

  17. Evaluating gyro-viscosity in the Kelvin-Helmholtz instability by kinetic simulations

    Umeda, Takayuki; Yamauchi, Natsuki; Wada, Yasutaka; Ueno, Satoshi

    2016-05-01

    In the present paper, the finite-Larmor-radius (gyro-viscous) term [K. V. Roberts and J. B. Taylor, Phys. Rev. Lett. 8, 197-198 (1962)] is evaluated by using a full kinetic Vlasov simulation result of the Kelvin-Helmholtz instability (KHI). The velocity field and the pressure tensor are calculated from the high-resolution data of the velocity distribution functions obtained by the Vlasov simulation, which are used to approximate the Finite-Larmor-Radius (FLR) term according to Roberts and Taylor [Phys. Rev. Lett. 8, 197-198 (1962)]. The direct comparison between the pressure tensor and the FLR term shows an agreement. It is also shown that the anisotropic pressure gradient enhanced the linear growth of the KHI when the inner product between the vorticity of the primary velocity shear layer and the magnetic field is negative, which is consistent with the previous FLR-magnetohydrodynamic simulation result. This result suggests that it is not sufficient for reproducing the kinetic simulation result by fluid simulations to include the FLR term (or the pressure tensor) only in the equation of motion for fluid.

  18. Kelvin probe characterization of buried graphitic microchannels in single-crystal diamond

    Bernardi, E.; Battiato, A.; Olivero, P.; Picollo, F.; Vittone, E.

    2015-01-01

    In this work, we present an investigation by Kelvin Probe Microscopy (KPM) of buried graphitic microchannels fabricated in single-crystal diamond by direct MeV ion microbeam writing. Metal deposition of variable-thickness masks was adopted to implant channels with emerging endpoints and high temperature annealing was performed in order to induce the graphitization of the highly-damaged buried region. When an electrical current was flowing through the biased buried channel, the structure was clearly evidenced by KPM maps of the electrical potential of the surface region overlying the channel at increasing distances from the grounded electrode. The KPM profiling shows regions of opposite contrast located at different distances from the endpoints of the channel. This effect is attributed to the different electrical conduction properties of the surface and of the buried graphitic layer. The model adopted to interpret these KPM maps and profiles proved to be suitable for the electronic characterization of buried conductive channels, providing a non-invasive method to measure the local resistivity with a micrometer resolution. The results demonstrate the potential of the technique as a powerful diagnostic tool to monitor the functionality of all-carbon graphite/diamond devices to be fabricated by MeV ion beam lithography.

  19. Kelvin-Helmholtz instability with mass transfer through porous media:Effect of irrotational viscous pressure

    AWASTHI Mukesh Kumar

    2014-01-01

    This paper studies the effect of the irrotational viscous pressure on Kelvin-Helmholtz instability of the plane interface of two viscous and incompressible fluids in a fully saturated porous media with mass and heat transfers across the interface. In the earlier work, the instability of the plane interface of two viscous and streaming miscible fluids through porous media was studied by assuming that the motion and the pressure are irrotational and the viscosity enters the normal stress balance. This theory is called the viscous potential flow theory. Here, we use another irrotational theory in which the discontinuities in the irrotational tangential velocity and shear stress are eliminated in the global energy balance by considering viscous contributions of the irrotational pressure. The Darcy-Brinkman model is used in the investigation and the stability criterion is formulated in terms of a critical value of the relative velocity. It is observed that the heat and mass transfer has a destabilizing effect on the stability of the system while the irrotational shearing stresses stabilize the system.

  20. The effect of Prandtl number on mixing in low Reynolds number Kelvin-Helmholtz billows

    Rahmani, M.; Seymour, B. R.; Lawrence, G. A.

    2016-05-01

    The effect of Prandtl number on mixing in temporally evolving Kelvin-Helmholtz (KH) instabilities at low to moderate Reynolds numbers is studied through direct numerical simulation. We distinguish between the mixing induced by the primary billow and the mixing generated by three-dimensional motions by performing each simulation in two and three dimensions. The results indicate that the time evolution of the rate of two- and three-dimensional mixing through different stages of the life cycle of KH flow is significantly influenced by the Prandtl number. As the Prandtl number increases, the final amount of mixing increases for Reynolds that are too low to support active three-dimensional motions. This trend is the opposite in sufficiently high Reynolds number KH flows that can overcome viscous effects and develop significant three-dimensional instabilities. While the mixing generated in the two-dimensional flows, uniform in the span-wise direction, is not significantly dependent on the Prandtl number, the turbulent mixing induced by three-dimensional motions is a function of the Prandtl number. We observe a steady increase in the total amount of mixing for buoyancy Reynolds numbers above 7, consistent with the results of Shih et al. ["Parameterization of turbulent fluxes and scales using homogeneous sheared stably stratified turbulence simulations," J. Fluid Mech. 525, 193-214 (2005)]. Both maximum instantaneous and cumulative mixing efficiencies exhibit a decreasing trend with increasing Prandtl number. We compare the dependence of the mixing efficiency on Prandtl number to previous studies.

  1. The effect of Prandtl number on mixing in low Reynolds number Kelvin-Helmholtz billows

    Rahmani, Mona; Seymour, Brian

    2014-01-01

    The effect of Prandtl number on the evolution of Kelvin-Helmholtz (KH) billows and the amount of mixing they generate is studied through direct numerical simulation (DNS). The results indicate that the time evolution of the rate of mixing through different stages of the life-cycle of KH flow is significantly influenced by the Prandtl number. As the Prandtl number increases, the final amount of mixing increases for Reynolds that are too low to support active three-dimensional motions. This trend is the opposite in sufficiently high Reynolds number KH flows that can overcome viscous effects, and develop significant three-dimensional instabilities. While the mixing generated in the two-dimensional flows, uniform in the span-wise direction, is not significantly dependent on the Prandtl number, the turbulent mixing induced by three-dimensional motions is a function of the Prandtl number. The turbulent mixing efficiency near the end of the turbulence decay phase approaches 0.2, the commonly observed value in the oc...

  2. Buried polymer/metal interfaces examined with Kelvin Probe Force Microscopy

    Device performance in organic electronics depends on electronic properties of buried interfaces between thin (< 100 nm) polymer films and metal. Such properties are determined here for two model systems using Kelvin Probe Force Microscopy. First, three types of micro-patterns of self-assembled monolayer (SAM) on Au (COOH-SAM/Au, COOH-SAM/CH3-SAM, CH3-SAM/COOH-SAM), all covered by polystyrene (PS), are detected with Contact Potential Difference (CPD) to yield maps with different (enhanced or reversed) contrasts. In turn, capacitance gradient signal dC/dz is uniform and PS topography is flat (except for ∼ 1 nm variation on COOH-SAM/Au). Second, domains rich in PS and polyaniline (doped with camphorsulfonic acid) (PANI(CSA)), phase-separated in film blends cast on Au, are reflected by topography and dC/dz maps. Surprisingly, CPD signal varies between individual PANI(CSA) domains, indicating their modified interaction with metal substrate. - Highlights: ► Buried interfaces between thin (< 100 nm) polymer films and Au are revealed. ► Micro-patterns of self-assembled monolayer on Au covered by polystyrene are detected. ► Different interactions between individual polyaniline domains and Au are shown

  3. Spin Dynamics of Kelvin's Pebbles, Jellett's Eggs, and Shiva's Lingam Stones

    Brecher, Kenneth

    2015-04-01

    Study of the problem of the rise of the center of mass (COM) of spinning objects is said to have begun in the late nineteenth century. These early mathematical treatments aimed to explain the motion of the newly invented and patented ``tippe top.'' This semi-spheroidal top will invert when spun on a smooth surface while raising its COM. Because of the importance of friction in their dynamics, such non-holonomic systems are not readily amenable to analytic treatment, or of intuitive understanding. In notes written in 1844 - before the invention of the tippe top - Lord Kelvin (William Thomson) discussed the problem of the rising COM of spinning objects. He experimented with both oblate and prolate ellipsoidal pebbles, but did not publish a complete theoretical treatment of the problem. J. H. Jellett, in his 1872 book ``Theory of Friction,'' provided a partial account of the related problem of the rise of the COM for an egg-shaped (ovoid) object, making use of a new (adiabatic) invariant of the motion that he devised. Naturally occurring prolate ellipsoidal ``Lingam stones'' from the Narmada River in India exhibit similar counter-intuitive dynamical behavior. When spun around its minor axis in a horizontal plane, a Lingam stone will stand erect and spin around its major axis in a vertical position. This presentation will explore the history and some of the experimental facts and theoretical ideas about the rotational dynamics of such physical objects.

  4. Instabilidade de Kelvin-Helmholtz em Raios Cometários

    Matsuura, O. T.; Shigueoka, H.; Voelzke, M. R.

    1995-08-01

    Raios cometários são estruturas finas e longas da cauda de cometas do Tipo I (ou de plasma). Como eles apresentam simetria cilíndrica, admitem modelos MHD simples. Este trabalho explora essa possibilidade, apresentando um estudo sistemático da estabilidade e das oscilações de raios cometários na aproximação de plasma homogêneo. O critério de estabilidade, combinado com dados observacionais de perturbações (ondas, hélices, rupturas etc), constitui um importante diagnóstico da velocidade do plasma cometário em relação ao vento solar circundante, contribuindo assim para esclarecer questões fundamentais, tais como, o papel da instabilidade de Kelvin-Helmholtz na aceleração do plasma cometário, a propagação, conversão de modos e amortecimento de certas ondas do espectro MHD nos raios cometários. Os resultados deste estudo nortearão a análise de um grande número de imagens do Cometa Halley arquivadas em CD-ROM pela equipe dos fenômenos de grande escala do International Halley W!

  5. What is the angle of a nonlinear Kelvin ship wave pattern?

    Pethiyagoda, Ravindra; Moroney, Timothy J

    2014-01-01

    While the half-angle which encloses a Kelvin ship wave pattern is commonly accepted to be 19.47 degrees, recent observations and calculations for sufficiently fast-moving ships suggest that the apparent wake angle decreases with ship speed. One explanation for this decrease in angle relies on the assumption that a ship cannot generate wavelengths much greater than its hull length. An alternative interpretation is that the wave pattern that is observed in practice is defined by the location of the highest peaks; for wakes created by sufficiently fast-moving objects, these highest peaks no longer lie on the outermost divergent waves, resulting in a smaller apparent angle. In this paper, we focus on the problem of free surface flow past a submerged point source. In the linear case, we measure the apparent wake angle formed by the highest peaks, and observe the following three regimes: a small Froude number pattern, in which the divergent waves are not visible; standard wave patterns for which the maximum peaks o...

  6. Instability of Supersonic Cold Streams Feeding Galaxies I: Linear Kelvin-Helmholtz Instability with Body Modes

    Mandelker, Nir; Dekel, Avishai; Birnboim, Yuval; Burkert, Andreas; Krumholz, Mark R; Steinberg, Elad

    2016-01-01

    Massive galaxies at high redshift are predicted to be fed from the cosmic web by narrow, dense, cold streams. These streams penetrate supersonically through the hot medium encompassed by a stable shock near the virial radius of the dark-matter halo. Our long-term goal is to explore the heating and dissipation rate of the streams and their fragmentation and possible breakup, in order to understand how galaxies are fed, and how this affects their star-formation rate and morphology. We present here the first step, where we analyze the linear Kelvin-Helmholtz instability (KHI) of a cold, dense slab or cylinder flowing through a hot, dilute medium in the transonic regime. The current analysis is limited to the adiabatic case with no gravity and assuming equal pressure in the stream and the medium. By analytically solving the linear dispersion relation, we find a transition from a dominance of the familiar rapidly growing surface modes in the subsonic regime to more slowly growing body modes in the supersonic regim...

  7. A Reversible Thermally Driven Pump for Use in a Sub-Kelvin Magnetic Refrigerator

    Miller, Franklin K.

    2012-01-01

    A document describes a continuous magnetic refrigerator that is suited for cooling astrophysics detectors. This refrigerator has the potential to provide efficient, continuous cooling to temperatures below 50 mK for detectors, and has the benefits over existing magnetic coolers of reduced mass because of faster cycle times, the ability to pump the cooled fluid to remote cooling locations away from the magnetic field created by the superconducting magnet, elimination of the added complexity and mass of heat switches, and elimination of the need for a thermal bus and single crystal paramagnetic materials due to the good thermal contact between the fluid and the paramagnetic material. A reliable, thermodynamically efficient pump that will work at 1.8 K was needed to enable development of the new magnetic refrigerator. The pump consists of two canisters packed with pieces of gadolinium gallium garnet (GGG). The canisters are connected by a superleak (a porous piece of VYCOR glass). A superconducting magnetic coil surrounds each of the canisters. The configuration enables driving of cyclic thermodynamic cycles (such as the sub-Kelvin Active Magnetic Regenerative Refrigerator) without using pistons or moving parts.

  8. Kelvin--Helmholtz instability of magnetohydrodynamic waves propagating on solar surges

    Zhelyazkov, I; Srivastava, A K; Mishonov, T

    2014-01-01

    In the present paper, we study the evolutionary conditions for Kelvin--Helmholtz (KH) instability in a high-temperature solar surge observed in NOAA AR11271 using the Solar Dynamics Observatory data on 2011 August 25. We study the propagation of normal MHD modes in a flux tube considering the two cases, notably of untwisted magnetic flux tube and the twisted one. The numerical solution to the dispersion relation shows that the kink ($m = 1$) wave traveling in an untwisted flux tube becomes unstable if the jet speed exceeds $1060$ km\\,s$^{-1}$ -- a speed which is inaccessible for solar surges. A weak twist (the ratio of azimuthal to longitudinal magnetic field component) of the internal magnetic field in the range of $0.025$--$0.2$ does not change substantially the critical flow velocity. Thus, one implies that, in general, the kink mode is stable against the KH instability. It turns out, however, that the $m = -2$ and $m = -3$ MHD modes can become unstable when the twist parameter has values between $0.2$ and...

  9. Quantitative dopant profiling in semiconductors. A new approach to Kelvin probe force microscopy

    Baumgart, Christine

    2012-07-01

    Failure analysis and optimization of semiconducting devices request knowledge of their electrical properties. To meet the demands of today's semiconductor industry, an electrical nanometrology technique is required which provides quantitative information about the doping profile and which enables scans with a lateral resolution in the sub-10 nm range. In the presented work it is shown that Kelvin probe force microscopy (KPFM) is a very promising electrical nanometrology technique to face this challenge. The technical and physical aspects of KPFM measurements on semiconductors required for the correct interpretation of the detected KPFM bias are discussed. A new KPFM model is developed which enables the quantitative correlation between the probed KPFM bias and the dopant concentration in the investigated semiconducting sample. Quantitative dopant profiling by means of the new KPFM model is demonstrated by the example of differently structured, n- and p-type doped silicon. Additionally, the transport of charge carriers during KPFM measurements, in particular in the presence of intrinsic electric fields due to vertical and horizontal pn junctions as well as due to surface space charge regions, is discussed. Detailed investigations show that transport of charge carriers in the semiconducting sample is a crucial aspect and has to be taken into account when aiming for a quantitative evaluation of the probed KPFM bias.

  10. Screening properties of graphene layers studied by Kelvin Probe Force Microscopy and Landau Level Spectroscopy

    Vetick, John; Lu, Chih-Pin; Altvater, Michael; Duan, Junxi; Li, Guohong; Andrei, Eva Y.

    2015-03-01

    Graphene is one of the best conductors known, but due to its two dimensional structure and the need to support it on insulating substrates, its electronic properties are often masked by substrate-induced random potential fluctuations. In order to realize graphene's full potential for electronic application it is therefore important to understand its screening properties and to find ways to minimize substrate invasiveness. We employed Kelvin Probe Force microscopy (KPFM) to investigate the screening properties of CVD grown graphene crystals as a function of layer number and substrate material using a gated device geometry. The KPFM study was complemented by low temperature scanning tunneling microscopy and Landau level spectroscopy in similar samples and device configurations. Measurements were carried out on single layer, bilayer, trilayer and twisted bilayer samples deposited on SiO2 and hBN substrates. Our findings show that twisted graphene layers provide superior screening of charged impurities and random potentials while at the same time preserving the unique electronic band structure of single layer graphene. Work Supported by DOE-FG02-99ER45742 and NSF DMR 1207108.

  11. Depth-sensitive subsurface imaging of polymer nanocomposites using second harmonic Kelvin probe force microscopy.

    Castañeda-Uribe, Octavio Alejandro; Reifenberger, Ronald; Raman, Arvind; Avila, Alba

    2015-03-24

    We study the depth sensitivity and spatial resolution of subsurface imaging of polymer nanocomposites using second harmonic mapping in Kelvin Probe Force Microscopy (KPFM). This method allows the visualization of the clustering and percolation of buried Single Walled Carbon Nanotubes (SWCNTs) via capacitance gradient (∂C/∂z) maps. We develop a multilayered sample where thin layers of neat Polyimide (PI) (∼80 nm per layer) are sequentially spin-coated on well-dispersed SWCNT/Polyimide (PI) nanocomposite films. The multilayer nanocomposite system allows the acquisition of ∂C/∂z images of three-dimensional percolating networks of SWCNTs at different depths in the same region of the sample. We detect CNTs at a depth of ∼430 nm, and notice that the spatial resolution progressively deteriorates with increasing depth of the buried CNTs. Computational trends of ∂C/∂z vs CNT depth correlate the sensitivity and depth resolution with field penetration and spreading, and enable a possible approach to three-dimensional subsurface structure reconstruction. The results open the door to nondestructive, three-dimensional tomography and nanometrology techniques for nanocomposite applications. PMID:25591106

  12. Design Enhancements of the Fourier Kelvin Stellar Interferometer to Enable Detection of Earth Twins

    Barry, Richard K.; Danchi, William C.; Lopez, Bruno; Rinehart, Stephan; Augereau, Jean-Charles; Beust, Herve; Bonfils, Xavier; Borde, Pascal; Kern, Pierre; Leger, Alain; Monin, Jean-Louis; Mourard, Denis; Ollivier, Marc; Petrov, Roman; Vakhili, Farrokh

    2009-01-01

    During the last few years, considerable effort has been directed towards very large-scale (> $5 billion) missions to detect and characterize Mars-radius to Earth-radius planets around nearby stars; such as the Terrestrial Planet Finder Interferometer and Darwin missions. However, technological issues such as formation flying and control of systematic noise sources will likely prevent these missions from entering Phase A until at least the end of the next decade. Presently more than 350 planets have been discovered by a variety of techniques, and little is known about the majority of them other than their approximate mass. However, a simplified nulling interferometer operating in the near- to mid-infrared (e.g. approx. 5-15 microns), like the enhanced version of the Fourier Kelvin Stellar Interferometer (FKSI), can characterize the atmospheres of a large sample of the known planets - including Earth twins. Many other scientific problems can be addressed with a system like FKSI, including the studies of debris disks, active galactic nuclei, and low mass companions around nearby stars. We report results of a recent engineering study on an enhanced version of FKSI that includes 1-meter primary mirrors, 20-meter boom length, and an advanced sun shield that will provide a 45-degree FOR and 40K operating temperature for all optics including siderostats.

  13. Global reconnection topology as inferred from plasma observations inside Kelvin-Helmholtz vortices

    M. B. Bavassano Cattaneo

    2010-04-01

    Full Text Available During a long lasting period of northward interplanetary magnetic field and high solar wind speed (above 700 km/s, the Cluster spacecraft go across a number of very large rolled-up Kelvin-Helmholtz (KH vortices at the dusk magnetopause, close to the terminator. The peculiarity of the present event is a particular sequence of ions and electrons distribution functions observed repeatedly inside each vortex. In particular, whenever Cluster crosses the current layer inside the vortices, multiple field-aligned ion populations appear, suggesting the occurrence of reconnection. In addition, the ion data display a clear velocity filter effect both at the leading and at the trailing edge of each vortex. This effect is not present in the simultaneous electron data. Unlike other KH studies reported in the literature in which reconnection occurs within the vortices, in the present event the observations are not compatible with local reconnection, but are accounted for by lobe reconnection occurring along an extended X-line at the terminator in the Southern Hemisphere. The reconnected field lines "sink" across the magnetopause and then convect tailward-duskward where they become embedded in the vortices. Another observational evidence is the detected presence of solar wind plasma on the magnetospheric side of the vortices, which confirms unambiguously the occurrence of mass transport across the magnetopause already reported in the literature. The proposed reconnection scenario accounts for all the observational aspects, regarding both the transport process and the kinetic signatures.

  14. Gold nanoparticle coated silicon tips for Kelvin probe force microscopy in air

    The tip apex dimensions and geometry of the conductive probe remain the major limitation to the resolution of Kelvin probe force microscopy (KPFM). One of the possible strategies to improve the spatial resolution of surface potential images consists in the development of thinner and more durable conductive tips. In an effort to improve the lateral resolution of topography and surface potential maps, we have evaluated high aspect ratio conductive tips created by depositing gold nanoparticles on standard silicon tips. Besides the already known general topographic resolution enhancement offered by these modified tips, an improvement of surface potential lateral resolution and signal-to-noise ratio is reported here for a variety of samples as compared to other regular conductive probes. We have also observed that the modified conductive tips have a significant auto-regeneration capability, which stems from a certain level of mobility of the nanoparticle coating. This property makes the modified tips highly resistant to degradation during scanning, thus increasing their durability. As demonstrated by the heterogeneous set of structures measured in the present study performed in air, the nanoparticle coated tips are suitable for KPFM analysis. In particular, surface potential difference determination on graphene deposited on silicon, gold sputtered on a salt surface, large and mildly rough areas of ZnO films and small DNA molecules on insulating mica have been achieved with enhanced resolution. (paper)

  15. Experimental determination of conduction and valence bands of semiconductor nanoparticles using Kelvin probe force microscopy

    The ability to determine a semiconductor’s band edge positions is important for the design of new photocatalyst materials. In this paper, we introduced an experimental method based on Kelvin probe force microscopy to determine the conduction and valence band edge energies of semiconductor nanomaterials, which has rarely been demonstrated. We tested the method on six semiconductor nanoparticles (α-Fe2O3, CeO2, Al2O3, CuO, TiO2, and ZnO) with known electronic structures. The experimentally determined band edge positions for α-Fe2O3, Al2O3, and CuO well matched the literature values with no statistical difference. Except CeO2, all other metal oxides had a consistent upward bias in the experimental measurements of band edge positions because of the shielding effect of the adsorbed surface water layer. This experimental approach may outstand as a unique alternative way of probing the band edge energy positions of semiconductor materials to complement the current computational methods, which often find limitations in new synthetic or complex materials. Ultimately, this work provides scientific foundation for developing experimental tools to probe nanoscale electronic properties of photocatalytic materials, which will drive breakthroughs in the design of novel photocatalytic systems and advance the fundamental understanding of material properties.

  16. Carrier density distribution in silicon nanowires investigated by scanning thermal microscopy and Kelvin probe force microscopy.

    Wielgoszewski, Grzegorz; Pałetko, Piotr; Tomaszewski, Daniel; Zaborowski, Michał; Jóźwiak, Grzegorz; Kopiec, Daniel; Gotszalk, Teodor; Grabiec, Piotr

    2015-12-01

    The use of scanning thermal microscopy (SThM) and Kelvin probe force microscopy (KPFM) to investigate silicon nanowires (SiNWs) is presented. SThM allows imaging of temperature distribution at the nanoscale, while KPFM images the potential distribution with AFM-related ultra-high spatial resolution. Both techniques are therefore suitable for imaging the resistance distribution. We show results of experimental examination of dual channel n-type SiNWs with channel width of 100 nm, while the channel was open and current was flowing through the SiNW. To investigate the carrier distribution in the SiNWs we performed SThM and KPFM scans. The SThM results showed non-symmetrical temperature distribution along the SiNWs with temperature maximum shifted towards the contact of higher potential. These results corresponded to those expressed by the distribution of potential gradient along the SiNWs, obtained using the KPFM method. Consequently, non-uniform distribution of resistance was shown, being a result of non-uniform carrier density distribution in the structure and showing the pinch-off effect. Last but not least, the results were also compared with results of finite-element method modeling. PMID:26381074

  17. Theoretical simulation of Kelvin probe force microscopy for Si surfaces by taking account of chemical forces

    A new method of theoretical simulation for Kelvin probe force microscopy (KPFM) imaging on semiconductor or metal samples is proposed. The method is based on a partitioned real space (PR) density functional based tight binding (DFTB) calculation of the electronic states to determine the multi-pole electro-static force, which is augmented with the chemical force obtained by a perturbation treatment of the orbital hybridization. With the PR-DFTB method, the change of the total energy is calculated together with the induced charge distribution in the tip and the sample by their approach under an applied bias voltage, and the KPFM images, namely the patterns of local contact potential difference (LCPD) distribution, are obtained with the minimum condition of the interaction force. However, since the interaction force is due to electro-static multi-poles, the spatial resolution of the KPFM images obtained by PR-DFTB is limited to the nano-scale range and an atom-scale resolution cannot be attained. By introducing an additional chemical force, i.e., the force due to the orbital hybridization, we succeeded in reproducing atom-scale resolution of KPFM images. Case studies are performed for clean and impurity embedded Si surfaces with Si tip models. (paper)

  18. Facile Preparation of a Platinum Silicide Nanoparticle-Modified Tip Apex for Scanning Kelvin Probe Microscopy.

    Lin, Chun-Ting; Chen, Yu-Wei; Su, James; Wu, Chien-Ting; Hsiao, Chien-Nan; Shiao, Ming-Hua; Chang, Mao-Nan

    2015-12-01

    In this study, we propose an ultra-facile approach to prepare a platinum silicide nanoparticle-modified tip apex (PSM tip) used for scanning Kelvin probe microscopy (SKPM). We combined a localized fluoride-assisted galvanic replacement reaction (LFAGRR) and atmospheric microwave annealing (AMA) to deposit a single platinum silicide nanoparticle with a diameter of 32 nm on the apex of a bare silicon tip of atomic force microscopy (AFM). The total process was completed in an ambient environment in less than 3 min. The improved potential resolution in the SKPM measurement was verified. Moreover, the resolution of the topography is comparable to that of a bare silicon tip. In addition, the negative charges found on the PSM tips suggest the possibility of exploring the use of current PSM tips to sense electric fields more precisely. The ultra-fast and cost-effective preparation of the PSM tips provides a new direction for the preparation of functional tips for scanning probe microscopy. PMID:26471480

  19. ac driving amplitude dependent systematic error in scanning Kelvin probe microscope measurements: Detection and correction

    The dependence of the contact potential difference (CPD) reading on the ac driving amplitude in scanning Kelvin probe microscope (SKPM) hinders researchers from quantifying true material properties. We show theoretically and demonstrate experimentally that an ac driving amplitude dependence in the SKPM measurement can come from a systematic error, and it is common for all tip sample systems as long as there is a nonzero tracking error in the feedback control loop of the instrument. We further propose a methodology to detect and to correct the ac driving amplitude dependent systematic error in SKPM measurements. The true contact potential difference can be found by applying a linear regression to the measured CPD versus one over ac driving amplitude data. Two scenarios are studied: (a) when the surface being scanned by SKPM is not semiconducting and there is an ac driving amplitude dependent systematic error; (b) when a semiconductor surface is probed and asymmetric band bending occurs when the systematic error is present. Experiments are conducted using a commercial SKPM and CPD measurement results of two systems: platinum-iridium/gap/gold and platinum-iridium/gap/thermal oxide/silicon are discussed

  20. Kelvin probe characterization of buried graphitic microchannels in single-crystal diamond

    In this work, we present an investigation by Kelvin Probe Microscopy (KPM) of buried graphitic microchannels fabricated in single-crystal diamond by direct MeV ion microbeam writing. Metal deposition of variable-thickness masks was adopted to implant channels with emerging endpoints and high temperature annealing was performed in order to induce the graphitization of the highly-damaged buried region. When an electrical current was flowing through the biased buried channel, the structure was clearly evidenced by KPM maps of the electrical potential of the surface region overlying the channel at increasing distances from the grounded electrode. The KPM profiling shows regions of opposite contrast located at different distances from the endpoints of the channel. This effect is attributed to the different electrical conduction properties of the surface and of the buried graphitic layer. The model adopted to interpret these KPM maps and profiles proved to be suitable for the electronic characterization of buried conductive channels, providing a non-invasive method to measure the local resistivity with a micrometer resolution. The results demonstrate the potential of the technique as a powerful diagnostic tool to monitor the functionality of all-carbon graphite/diamond devices to be fabricated by MeV ion beam lithography

  1. Resonant multi-frequency method for Kelvin probe force microscopy in air

    The multi-frequency method, recently introduced in atomic force microscopy (AFM), has shown remarkable enhancement of sensitivity and resolution of microscopy with a variety of heterogeneous materials. Under ambient conditions, Kelvin probe force microscopy (KPFM) is commonly carried out using only the first flexural eigenmode of the micro-cantilever probe. Here we report a resonant multi-frequency method for KPFM in air. To implement this method, the first eigenmode of the cantilever probe is used for topography imaging, whereas the second one is used to measure the local contact potential difference in the two-pass mode with the tip lifted. By introducing an additional feedback controller, a multi-frequency KPFM (MF-KPFM) is developed upon a commercial AFM. The performance of MF-KPFM, including the feedback controller, sensitivity and noise, lift height of the cantilever and lateral resolution, is evaluated and optimized. The capabilities of MF-KPFM are demonstrated by characterizing a charge pattern on a polymer electret. The results show that the lateral resolution of KPFM in air can be improved by the resonant multi-frequency method. (paper)

  2. Kelvin probe force microscopy for characterizing doped semiconductors for future sensor applications in nano- and biotechnology

    Kelvin probe force microscopy (KPFM) is one of the most promising non-contact electrical nanometrology techniques to characterize doped semiconductors. By applying a recently introduced explanation of measured KPFM signals, we show the applicability of KPFM to determine and control surface-near electrostatic forces in planar doped silicon and in doped silicon nanostructures. Surface-near electrostatic forces may be used for the immobilization of nano- and biomaterials in future sensor applications in nano- and biotechnology. Additionally, the influence of the electrostatic potential distribution in doped semiconductor nanostructures, e.g. in horizontal Si nanowires, and its influence on the surface-near electrostatic forces are discussed. It is explained how drift and diffusion of injected electrons and holes in intrinsic electric fields influence the detected KPFM signal. For example KPFM is successfully employed to locate p+p and n+p junctions along B-doped and As-doped p-Si nanowires, respectively. As an outlook the physical immobilization and the transport of biomaterials above arrays of separately addressable doped semiconductor cells will be discussed.

  3. Deconvolution of Kelvin probe force microscopy measurements—methodology and application

    Kelvin probe force microscopy (KPFM) is a method to detect the surface potential of micro- and nanostructured samples using a common atomic force microscope (AFM). The electrostatic force has a very long range compared to other surface forces. By using AFM systems under ambient conditions, KPFM measurements are performed using a non-contact regime at surface distances greater than 10 nm. This paper deals with a method to deconvolve the measured KPFM data with the objective to increase the lateral resolution. The KPFM signal is a convolution of an effective surface potential and a microscopic intrinsic point spread function, which allows the restoration of the measured data by linear deconvolution. In contrast to other papers [4], we have developed a new method to use the measured AFM tip shape as a basis to construct the point spread function. The linear shift-invariant channel is introduced as a signal formation model and a Wiener-supported deconvolution algorithm is applied to the measured data. The new method was demonstrated on a nanoscale test stripe pattern for lateral resolution and calibration of length scales (BAM-L200) manufactured by the Federal Institute for Materials Research and Testing, Germany. For the first time, a two-dimensional deconvolution of the KPFM data was able to be demonstrated. An increase in the lateral resolution compared to Strassburg et al (2005 Rev. Sci. Instrum. 76 083705) was accomplished. The results demonstrate the necessity of deconvolving the virtually topography-free probe data under ambient conditions

  4. Open loop Kelvin probe force microscopy with single and multi-frequency excitation

    Conventional Kelvin probe force microscopy (KPFM) relies on closed loop (CL) bias feedback for the determination of surface potential (SP). However, SP measured by CL-KPFM has been shown to be strongly influenced by the choice of measurement parameters due to non-electrostatic contributions to the input signal of the bias feedback loop. This often leads to systematic errors of several hundred mV and can also result in topographical crosstalk. Here, open loop (OL)-KPFM modes are investigated as a means of obtaining a quantitative, crosstalk free measurement of the SP of graphene grown on Cu foil, and are directly contrasted with CL-KPFM. OL-KPFM operation is demonstrated in both single and multi-frequency excitation regimes, yielding quantitative SP measurements. The SP difference between single and multilayer graphene structures using OL-KPFM was found to be 63 ± 11 mV, consistent with values previously reported by CL-KPFM. Furthermore, the same relative potential difference between Al2O3-coated graphene and Al2O3-coated Cu was observed using both CL and OL techniques. We observed an offset of 55 mV between absolute SP values obtained by OL and CL techniques, which is attributed to the influence of non-electrostatic contributions to the input of the bias feedback used in CL-KPFM. (paper)

  5. Multifrequency spectrum analysis using fully digital G Mode-Kelvin probe force microscopy

    Collins, Liam; Belianinov, Alex; Somnath, Suhas; Rodriguez, Brian J.; Balke, Nina; Kalinin, Sergei V.; Jesse, Stephen

    2016-03-01

    Since its inception over two decades ago, Kelvin probe force microscopy (KPFM) has become the standard technique for characterizing electrostatic, electrochemical and electronic properties at the nanoscale. In this work, we present a purely digital, software-based approach to KPFM utilizing big data acquisition and analysis methods. General mode (G-Mode) KPFM works by capturing the entire photodetector data stream, typically at the sampling rate limit, followed by subsequent de-noising, analysis and compression of the cantilever response. We demonstrate that the G-Mode approach allows simultaneous multi-harmonic detection, combined with on-the-fly transfer function correction—required for quantitative CPD mapping. The KPFM approach outlined in this work significantly simplifies the technique by avoiding cumbersome instrumentation optimization steps (i.e. lock in parameters, feedback gains etc), while also retaining the flexibility to be implemented on any atomic force microscopy platform. We demonstrate the added advantages of G-Mode KPFM by allowing simultaneous mapping of CPD and capacitance gradient (C‧) channels as well as increased flexibility in data exploration across frequency, time, space, and noise domains. G-Mode KPFM is particularly suitable for characterizing voltage sensitive materials or for operation in conductive electrolytes, and will be useful for probing electrodynamics in photovoltaics, liquids and ionic conductors.

  6. Determination of effective tip geometries in Kelvin probe force microscopy on thin insulating films on metals

    In scanning probe techniques, accurate height measurements on heterogeneous surfaces are a major requirement. Different electrostatic potentials of various materials have a significant influence on the measured force/current and therefore a direct influence on the tip-sample distance. Kelvin probe force microscopy (KPFM) is based on a dynamic compensation of the electrostatic force while performing non-contact atomic force microscopy measurements. Thus, the influence of the electrostatic potentials can be minimized and accurate height measurements become possible. Here, the study of ultra-thin alkali halide films on Cu(111) investigated by KPFM is presented. This work is focused on the interface between areas of bare Cu(111) and the first layers of salt. The compensation of the electrostatic potential allow us to determine layer heights with high accuracy. The second objective was to elaborate on the characterization of tip geometries across suitable nanostructures. Simulations of measured images are performed with different input parameters, which gives a direct estimation of the effective tip radius and geometry used for the measurements.

  7. Kelvin probe force microscopy for the nano scale characterization of chalcopyrite solar cell materials and devices

    Kelvin probe force microscopy allows to determine not only the surface topography as does atomic force microscopy, but in addition also delivers images of the surface work function on a nanometer scale. Operation in ultrahigh vacuum improves the lateral and energy resolution and allows to obtain absolute work function values. In this paper we will introduce the method and give examples for the application to solar cell materials and devices. We review examples where the surface of an oriented CuGaSe2 film showed distinct work function values for differently oriented facets of single grains, with differences as high as 250 meV, possibly affecting the power conversion efficiency of a solar cell. A cross-sectional study of a complete solar cell device based on the CuGaSe2 absorber material revealed the formation of an additional MoSex layer between the Mo back contact and the absorber. We will present results of measurements at individual grain boundaries of the absorber material. Furthermore, band bending effects at these grain boundaries are discussed and compared to results from transport studies

  8. Characterizing defects and transport in Si nanowire devices using Kelvin probe force microscopy

    Si nanowires (NWs) integrated in a field effect transistor device structure are characterized using scanning electron (SEM), atomic force, and scanning Kelvin probe force (KPFM) microscopy. Reactive ion etching (RIE) and vapor–liquid–solid (VLS) growth were used to fabricate NWs between predefined electrodes. Characterization of Si NWs identified defects and/or impurities that affect the surface electronic structure. RIE NWs have defects that both SEM and KPFM analysis associate with a surface contaminant as well as defects that have a voltage dependent response indicating impurity states in the energy bandgap. In the case of VLS NWs, even after aqua regia, Au impurity levels are found to induce impurity states in the bandgap. KPFM data, when normalized to the oxide-capacitance response, also identify a subset of VLS NWs with poor electrical contact due to nanogaps and short circuits when NWs cross that is not observed in AFM images or in current–voltage measurements when NWs are connected in parallel across electrodes. The experiments and analysis presented outline a systematic method for characterizing a broad array of nanoscale systems under device operation conditions. (paper)

  9. Microelectrical characterizations of junctions in solar cell devices by scanning Kelvin probe force microscopy

    Scanning Kelvin probe force microscopy was applied to the microelectrical characterizations of junctions in solar cell devices. Surface Fermi-level pinning effects on the surface potential measurement were avoided by applying a bias voltage (Vb) to the device and taking the Vb-induced potential and electric field changes. Two characterizations are presented: the first is a direct measurement of Bi-induced junction shift in GaInNAs(Bi) cells; the second is a junction-uniformity measurement in a-Si:H devices. In the first characterization, using Bi as a surfactant during the molecular beam epitaxy growth of GaInNAs(Bi) makes the epitaxial layer smoother. However, the electrical potential measurement exhibits a clear Bi-induced junction shift to the back side of the absorber layer, which results in significant device degradation. In the second characterization, the potential measurement reveals highly non-uniform electric field distributions across the n-i-p junction of a-Si:H devices; the electric field concentrates much more at both n/i and i/p interfaces than in the middle of the i-layer. This non-uniform electric field is due possibly to high defect concentrations at the interfaces. The potential measurements further showed a significant improvement in the electric field uniformity by depositing buffer layers at the interfaces, and this indeed improved the device performance.

  10. The stray capacitance effect in Kelvin probe force microscopy using FM, AM and heterodyne AM modes

    The effect of stray capacitance on potential measurements was investigated using Kelvin probe force microscopy (KPFM) at room temperature under ultra-high vacuum (UHV). The stray capacitance effect was explored in three modes, including frequency modulation (FM), amplitude modulation (AM) and heterodyne amplitude modulation (heterodyne AM). We showed theoretically that the distance-dependence of the modulated electrostatic force in AM-KPFM is significantly weaker than in FM- and heterodyne AM-KPFMs and that the stray capacitance of the cantilever, which seriously influences the potential measurements in AM-KPFM, was almost completely eliminated in FM- and heterodyne AM-KPFMs. We experimentally confirmed that the contact potential difference (CPD) in AM-KPFM, which compensates the electrostatic force between the tip and the surface, was significantly larger than in FM- and heterodyne AM-KPFMs due to the stray capacitance effect. We also compared the atomic scale corrugations in the local contact potential difference (LCPD) among the three modes on the surface of Si(111)-7 × 7 finding that the LCPD corrugation in AM-KPFM was significantly weaker than in FM- and heterodyne AM-KPFMs under low AC bias voltage conditions. The very weak LCPD corrugation in AM-KPFM was attributed to the artefact induced by topographic feedback. (paper)

  11. Numerical simulation of Kelvin-Helmholtz instability using an implicit, non-dissipative DNS algorithm

    An in-house, fully parallel compressible Navier-Stokes solver was developed based on an implicit, non-dissipative, energy conserving, finite-volume algorithm. PETSc software was utilized for this purpose. To be able to handle occasional instances of slow convergence due to possible oscillating pressure corrections on successive iterations in time, a fixing procedure was adopted. To demonstrate the algorithms ability to evolve a linear perturbation into nonlinear hydrodynamic turbulence, temporal Kelvin-Helmholtz Instability problem is studied. KHI occurs when a perturbation is introduced into a system with a velocity shear. The theory can be used to predict the onset of instability and transition to turbulence in fluids moving at various speeds. In this study, growth rate of the instability was compared to predictions from linear theory using a single mode perturbation in the linear regime. Effect of various factors on growth rate was also discussed. Compressible KHI is most unstable in subsonic/transonic regime. High Reynolds number (low viscosity) allows perturbations to develop easily, in consistent with the nature of KHI. Higher wave numbers (shorter wavelengths) also grow faster. These results match with the findings of stability analysis, as well as other results presented in the literature.

  12. Striations in the Taurus molecular cloud: Kelvin-Helmholtz instability or MHD waves?

    Heyer, M; Yildiz, U A; Snell, R L; Falgarone, E; Pineda, J

    2016-01-01

    The origin of striations aligned along the local magnetic field direction in the translucent envelope of the Taurus molecular cloud is examined with new observations of 12CO and 13CO J=2-1 emission obtained with the 10~m submillimeter telescope of the Arizona Radio Observatory. These data identify a periodic pattern of excess blue and redshifted emission that is responsible for the striations. For both 12CO and 13CO, spatial variations of the J=2-1 to J=1-0 line ratio are small and are not spatially correlated with the striation locations. A medium comprised of unresolved CO emitting substructures (cells) with a beam area filling factor less than unity at any velocity is required to explain the average line ratios and brightness temperatures. We propose that the striations result from the modulation of velocities and the beam filling factor of the cells as a result of either the Kelvin-Helmholtz instability or magnetosonic waves propagating through the envelope of the Taurus molecular cloud. Both processes ar...

  13. Study on the sputter-cleaning processes of Ni by means of Kelvin probe

    Luo, G.-N.; Yamaguchi, K.; Terai, T.; Yamawaki, M.

    2002-05-01

    A new device has been established to study the surface properties of materials under low energy ion irradiation by means of a Kelvin probe. The serious impact of space charging on the probe was observed, and verified unambiguously via a simulation test. The appropriate measures applied to the system function quite well, and suppress the detrimental influence effectively. The preliminary experiment of helium ion irradiation on nickel resulted in a decrease in work function (WF) at the low fluence, followed by an increase with increasing the fluence till the final saturation was achieved. The behavior can be explained using a two-layer surface model, i.e., the desorption of the topmost loosely bound adsorbed layer due to the irradiation decreases the surface dipole moment towards the bulk, in turn the WF decreases; then the native oxide layer on the bulk is sputtered away gradually, which induces the increase in the WF; finally, the saturation is reached as a result of the balance between the sputtering and the adsorption of the species from the residual gases. The desorption/adsorption experiment further verified the validity of the model.

  14. Scanning Kelvin probe measurements on As-doped CdTe solar cells

    Scanning Kelvin probe microscopy (SKPM) has been used to study the Fermi level shift in arsenic (As) doped cadmium telluride (CdTe) photovoltaic devices. The contact potential difference (CPD) between probe tip and sample surface revealed that increasing As concentrations in CdTe led to a decrease in CPD. This highlighted a downward shift in the CdTe Fermi level and an increase in the CdTe work function. Using a highly oriented pyrolytic graphite sample in ambient conditions as a reference, the absolute work functions of the CdTe samples were estimated to vary from 3.88 to 4.09 eV. High-resolution SKPM measurements revealed localized shifts in CPD at CdTe grain boundaries. This was directly correlated to As doping concentrations, and indicated the segregation of As to grain boundaries. A mechanism is proposed where localized band bending at grain boundaries channels minority carriers away from the grain boundary, leading to reduced carrier recombination. (paper)

  15. Kelvin probe force microscopy for local characterisation of active nanoelectronic devices

    Tino Wagner

    2015-11-01

    Full Text Available Frequency modulated Kelvin probe force microscopy (FM-KFM is the method of choice for high resolution measurements of local surface potentials, yet on coarse topographic structures most researchers revert to amplitude modulated lift-mode techniques for better stability. This approach inevitably translates into lower lateral resolution and pronounced capacitive averaging of the locally measured contact potential difference. Furthermore, local changes in the strength of the electrostatic interaction between tip and surface easily lead to topography crosstalk seen in the surface potential. To take full advantage of the superior resolution of FM-KFM while maintaining robust topography feedback and minimal crosstalk, we introduce a novel FM-KFM controller based on a Kalman filter and direct demodulation of sidebands. We discuss the origin of sidebands in FM-KFM irrespective of the cantilever quality factor and how direct sideband demodulation enables robust amplitude modulated topography feedback. Finally, we demonstrate our single-scan FM-KFM technique on an active nanoelectronic device consisting of a 70 nm diameter InAs nanowire contacted by a pair of 120 nm thick electrodes.

  16. Kelvin probe force microscopy for local characterisation of active nanoelectronic devices.

    Wagner, Tino; Beyer, Hannes; Reissner, Patrick; Mensch, Philipp; Riel, Heike; Gotsmann, Bernd; Stemmer, Andreas

    2015-01-01

    Frequency modulated Kelvin probe force microscopy (FM-KFM) is the method of choice for high resolution measurements of local surface potentials, yet on coarse topographic structures most researchers revert to amplitude modulated lift-mode techniques for better stability. This approach inevitably translates into lower lateral resolution and pronounced capacitive averaging of the locally measured contact potential difference. Furthermore, local changes in the strength of the electrostatic interaction between tip and surface easily lead to topography crosstalk seen in the surface potential. To take full advantage of the superior resolution of FM-KFM while maintaining robust topography feedback and minimal crosstalk, we introduce a novel FM-KFM controller based on a Kalman filter and direct demodulation of sidebands. We discuss the origin of sidebands in FM-KFM irrespective of the cantilever quality factor and how direct sideband demodulation enables robust amplitude modulated topography feedback. Finally, we demonstrate our single-scan FM-KFM technique on an active nanoelectronic device consisting of a 70 nm diameter InAs nanowire contacted by a pair of 120 nm thick electrodes. PMID:26734511

  17. Mechanical stability of a microscope setup working at a few kelvins for single-molecule localization

    Hinohara, Takuya; Hamada, Yuki I.; Nakamura, Ippei; Matsushita, Michio, E-mail: matsushita@phys.titech.ac.jp; Fujiyoshi, Satoru

    2013-06-20

    Highlights: ► Localization precision of the image of a point source is free from diffraction. ► Prerequisite for the precision is stability of the sample and objective at 1.5 K. ► We developed a rigid imaging unit to make image of scattering of a sample bead. ► The centroid of the scattering image of a bead was determined for 800 images. ► The standard deviation of the 800 centroids measured in 17 min was 0.85 nm. - Abstract: A great advantage of single-molecule fluorescence imaging is the localization precision of molecule beyond the diffraction limit. Although longer signal-acquisition yields higher precision, acquisition time at room temperature is normally limited by photobleaching, thermal diffusion, and so on. At low temperature of a few kelvins, much longer acquisition is possible and will improve precision if the sample and the objective are held stably enough. The present work examined holding stability of the sample and objective at 1.5 K in superfluid helium in the helium bath. The stability was evaluated by localization precision of a point scattering source of a polymer bead. Scattered light was collected by the objective, and imaged by a home-built rigid imaging unit. The standard deviation of the centroid position determined for 800 images taken continuously in 17 min was 0.5 nm in the horizontal and 0.9 nm in the vertical directions.

  18. Full data acquisition in Kelvin Probe Force Microscopy: Mapping dynamic electric phenomena in real space.

    Collins, Liam; Belianinov, Alex; Somnath, Suhas; Balke, Nina; Kalinin, Sergei V; Jesse, Stephen

    2016-01-01

    Kelvin probe force microscopy (KPFM) has provided deep insights into the local electronic, ionic and electrochemical functionalities in a broad range of materials and devices. In classical KPFM, which utilizes heterodyne detection and closed loop bias feedback, the cantilever response is down-sampled to a single measurement of the contact potential difference (CPD) per pixel. This level of detail, however, is insufficient for materials and devices involving bias and time dependent electrochemical events; or at solid-liquid interfaces, where non-linear or lossy dielectrics are present. Here, we demonstrate direct recovery of the bias dependence of the electrostatic force at high temporal resolution using General acquisition Mode (G-Mode) KPFM. G-Mode KPFM utilizes high speed detection, compression, and storage of the raw cantilever deflection signal in its entirety at high sampling rates. We show how G-Mode KPFM can be used to capture nanoscale CPD and capacitance information with a temporal resolution much faster than the cantilever bandwidth, determined by the modulation frequency of the AC voltage. In this way, G-Mode KPFM offers a new paradigm to study dynamic electric phenomena in electroactive interfaces as well as a promising route to extend KPFM to the solid-liquid interface. PMID:27514987

  19. Practical aspects of single-pass scan Kelvin probe force microscopy

    Li, Guangyong; Mao, Bin; Lan, Fei; Liu, Liming

    2012-11-01

    The single-pass scan Kelvin probe force microscopy (KPFM) in ambient condition has a few advantages over the dual-pass lift-up scan KPFM. For example, its spatial resolution is expected to be higher; and its topographical errors caused by electrostatic forces are minimized because electrostatic forces are actively suppressed during the simultaneous topographical and KPFM measurement. Because single-pass scan KPFM in ambient condition is relatively new, it received little attention in the literature so far. In this article, we discuss several major practical aspects of single-pass scan KPFM especially in ambient condition. First, we define the resolution using a point spread function. With this definition, we analyze the relation between the resolution and the scanning parameters such as tip apex radius and tip-surface distance. We further study the accuracy of KPFM based on the point spread function. Then, we analyze the sensitivity of KPFM under different operation modes. Finally, we investigate the crosstalk between the topographical image and the surface potential image and demonstrate the practical ways to minimize the crosstalk. These discussions not only help us to understand the single-pass scan KPFM but also provide practical guidance in using single-pass scan KPFM.

  20. Electroviscoelastic Instability of a Kelvin Fluid Layer Influenced by a Periodic Electric Force.

    Mohamed; Elshehawey; El-Dib

    1998-11-01

    The electroviscoelastic stability of a Kelvin fluid layer is discussed in the presence of the field periodicity. The surface elevations are governed by two transcendental coupled equations of Mathieu type which have not been attempted before. Analysis for the surface waves in axisymmetric modes and antisymmetric deformation which are governed by a single transcendental Mathieu equation is considered. The method of multiple scales expansion is applied to the stability analysis. The solution and the characteristic curves are obtained analytically. It is shown that the region between the two branches of the characteristic curves is unstable, whereas all points which lie outside the characteristic curves are stable. The special case of large viscosity is introduced for numerical calculations. It is found that the increase of kinematic viscosity, field frequency, and the elasticity parameter possesses a dual role in a damping nature. The phenomena of the coupled resonance is observed. The resonance region and the resonance points are functions of viscosity, elasticity, and field frequency, with nonlinear relations in the wavenumber. Copyright 1998 Academic Press. PMID:9778390

  1. The two-dimensional magnetohydrodynamic Kelvin-Helmholtz instability: compressibility and large-scale coalescence effects

    Baty, H; Comte, P

    2003-01-01

    The Kelvin-Helmholtz (KH) instability occurring in a single shear flow configuration that is embedded in a uniform flow-aligned magnetic field, is revisited by means of high resolution two-dimensional (2D) magnetohydrodynamic (MHD) simulations. First, the calculations extend previous studies of magnetized shear flows to a higher compressibility regime. The nonlinear evolution of an isolated KH billow emerging from the fastest growing linear mode for a convective sonic Mach number $M_{cs}=0.7$ layer is in many respects similar to its less compressible counterpart (Mach $M_{cs}=0.5$). In particular, the disruptive regime where locally amplified, initially weak magnetic fields, control the nonlinear saturation process is found for Alfv\\'en Mach numbers $4\\simlt M_A \\simlt 30$. The most notable difference between $M_{cs}=0.7$ versus $M_{cs}=0.5$ layers is that higher density contrasts and fast magnetosonic shocklet structures are observed. Second, the use of adaptive mesh refinement allows to parametrically explo...

  2. The Kelvin-Helmholtz instability of boundary-layer plasmas in the kinetic regime

    Steinbusch, Benedikt; Gibbon, Paul; Sydora, Richard D.

    2016-05-01

    The dynamics of the Kelvin-Helmholtz instability are investigated in the kinetic, high-frequency regime with a novel, two-dimensional, mesh-free tree code. In contrast to earlier studies which focused on specially prepared equilibrium configurations in order to compare with fluid theory, a more naturally occurring plasma-vacuum boundary layer is considered here with relevance to both space plasma and linear plasma devices. Quantitative comparisons of the linear phase are made between the fluid and kinetic models. After establishing the validity of this technique via comparison to linear theory and conventional particle-in-cell simulation for classical benchmark problems, a quantitative analysis of the more complex magnetized plasma-vacuum layer is presented and discussed. It is found that in this scenario, the finite Larmor orbits of the ions result in significant departures from the effective shear velocity and width underlying the instability growth, leading to generally slower development and stronger nonlinear coupling between fast growing short-wavelength modes and longer wavelengths.

  3. Real-time charge carrier motion in P3HT studied with Kelvin Probe Microscopy

    Castaneda, Chloe; Zaidi, Alyina; Moscatello, Jason; Aidala, Katherine

    We have developed a technique that uses scanning probe microscopy (SPM) to study the real-time injection and extraction of charge carriers in organic semiconductor devices. We investigate P3HT (full name) in an inverted field effect transistor geometry with gold electrodes. By positioning the SPM tip at an individual location and using Kelvin probe microscopy to record the potential over time, we can record how the charge carriers respond to changing the backgate voltage while the source and drain electrodes are grounded. We see relatively fast screening for negative backgate voltages because holes are quickly injected into the P3HT film. The screening is slower for positive gate voltages, because some of these holes are trapped and therefore less mobile. We compare P3HT transistors with different fabrication procedures that are expected to change the trap distribution: no silanization of the oxide and no annealing, silanization and no annealing, and both silanization and annealing. By incrementally stepping the gate voltage, we probe different trap depths. The recorded change in potential over time is best fit by a double exponential, suggesting two physical mechanisms involved in screening. This work is supported by NSF Grant DMR-0955348, and the Center for Heirarchical Manufacturing at the University of Massachusetts, Amherst (NSF CMMI-1025020).

  4. Kelvin probe force microscopy of metallic surfaces used in Casimir force measurements

    Behunin, R. O.; Dalvit, D. A. R.; Decca, R. S.; Genet, C.; Jung, I. W.; Lambrecht, A.; Liscio, A.; López, D.; Reynaud, S.; Schnoering, G.; Voisin, G.; Zeng, Y.

    2014-12-01

    Kelvin probe force microscopy at normal pressure was performed by two different groups on the same Au-coated planar sample used to measure the Casimir interaction in a sphere-plane geometry. The obtained voltage distribution was used to calculate the separation dependence of the electrostatic pressure Pres(D ) in the configuration of the Casimir experiments. In the calculation it was assumed that the potential distribution in the sphere has the same statistical properties as the measured one, and that there are no correlation effects on the potential distributions due to the presence of the other surface. The result of this calculation, using the currently available knowledge, is that Pres(D ) does not explain the magnitude or the separation dependence of the difference Δ P (D ) between the measured Casimir pressure and the one calculated using a Drude model for the electromagnetic response of Au. We discuss in the conclusions the points which have to be checked out by future work, including the influence of pressure and a more accurate determination of the patch distribution, in order to confirm these results.

  5. The effect of compressibility on magnetohydrodynamic jets and Kelvin-Helmholtz instability

    Praturi, Divya Sri; Girimaji, Sharath

    2015-11-01

    We investigate the effect of compressibility and magnetic field on the evolution of planar magnetohydrodynamic (MHD) jets. These jets are susceptible to Kelvin-Helmholtz (KH) instability when subjected to an in-plane transverse velocity perturbation. Various linear stability analyses have shown that compressibility and magnetic field along the jet have a stabilizing influence on the KH instability. We performed three-dimensional numerical simulations using magneto gas kinetic method (MGKM) to study the effect of the Mach number, Alfvén Mach number, and the orientation of the magnetic field with respect to the jet velocity direction on the flow-field evolution. In MGKM, the magnetic effects are added as source terms in the hydrodynamic gas kinetic scheme which also take into account the non-ideal MHD terms for finite plasma conductivity and the Hall effects. An in-depth analysis of linear and nonlinear physics is presented. The first author was supported by Texas A&M University Institute for Advanced Study HEEP fellowship.

  6. A Numerical Method of the Euler-Bernoulli Beam with Optimal Local Kelvin-Voigt Damping

    Xin Yu

    2014-01-01

    Full Text Available This paper deals with the numerical approximation problem of the optimal control problem governed by the Euler-Bernoulli beam equation with local Kelvin-Voigt damping, which is a nonlinear coefficient control problem with control constraints. The goal of this problem is to design a control input numerically, which is the damping and distributes locally on a subinterval of the region occupied by the beam, such that the total energy of the beam and the control on a given time period is minimal. We firstly use the finite element method (FEM to obtain a finite-dimensional model based on the original PDE system. Then, using the control parameterization method, we approximate the finite-dimensional problem by a standard optimal parameter selection problem, which is a suboptimal problem and can be solved numerically by nonlinear mathematical programming algorithm. At last, some simulation studies will be presented by the proposed numerical approximation method in this paper, where the damping controls act on different locations of the Euler-Bernoulli beam.

  7. Homogenization of a thermo-chemo-viscoelastic Kelvin-Voigt model

    Amosov, Andrey; Kostin, Ilya; Panasenko, Grigory; Smyshlyaev, Valery P.

    2013-08-01

    The paper is devoted to a model for the procedure of formation of a composite material constituted of solid fibers and of a solidifying matrix. The solidification process for the matrix depends on the temperature and on the degree of cure, which are used for the modeling of the mechanical properties of the matrix. Namely, the mechanical properties are described by Kelvin-Voigt viscoelastic equation with rapidly oscillating periodic coefficients depending on the temperature and the degree of cure. The latter are in turn solutions of a thermo-chemical problem with rapidly varying coefficients. We prove an error estimate for approximation of the viscoelastic problem by the same equation but with the coefficients depending on solution to the homogenized thermo-chemical problem. This estimate, in combination with our recent estimates for the viscoelastic (with time-dependent coefficients) and thermo-chemical homogenization problems, generates the overall error bound for the asymptotic solution to the full coupled thermo-chemo-viscoelastic model.

  8. Mechanical stability of a microscope setup working at a few kelvins for single-molecule localization

    Highlights: ► Localization precision of the image of a point source is free from diffraction. ► Prerequisite for the precision is stability of the sample and objective at 1.5 K. ► We developed a rigid imaging unit to make image of scattering of a sample bead. ► The centroid of the scattering image of a bead was determined for 800 images. ► The standard deviation of the 800 centroids measured in 17 min was 0.85 nm. - Abstract: A great advantage of single-molecule fluorescence imaging is the localization precision of molecule beyond the diffraction limit. Although longer signal-acquisition yields higher precision, acquisition time at room temperature is normally limited by photobleaching, thermal diffusion, and so on. At low temperature of a few kelvins, much longer acquisition is possible and will improve precision if the sample and the objective are held stably enough. The present work examined holding stability of the sample and objective at 1.5 K in superfluid helium in the helium bath. The stability was evaluated by localization precision of a point scattering source of a polymer bead. Scattered light was collected by the objective, and imaged by a home-built rigid imaging unit. The standard deviation of the centroid position determined for 800 images taken continuously in 17 min was 0.5 nm in the horizontal and 0.9 nm in the vertical directions

  9. Gas sensing characterization of tellurium thin films by the Kelvin probe technique

    The sensing behavior of tellurium films at room temperature was tested with environmental pollutant gases, such as NO2, CO, O3, and water vapor, using the Kelvin probe technique. A significant sensitivity was observed for nitrogen dioxide. The detection range for NO2 was between 0.5-5.0 ppm in air with controlled humidity. The response and the recovery time are rapid with good reproducibility and high sensibility. The work function measurements showed that chalcogenide semiconductors in question are well-suited materials for the detection of not only small concentrations of NO2, but also for humidity sensing. The relative humidity of 45% induces the work function change Δ φ of approximately 200 mV at room temperature. It is shown that the 'strong' chemisorption of nitrogen dioxide results in an increase in both work function change Δ Φ > 0 and electrical conductivity Δ c > 0 because of the additional charging of the surface and band bending. The effect of water vapor is due to a simple physical adsorption of polar water molecules oriented perpendicular to the surface with a negative pole inward. As a result, the dipole component of the work function increases, i.e., Δ Φ > 0, but the free lattice holes become more localized at the surface and the conductivity of the p-type chalcogenide layer decreases Δ c < 0. (authors)

  10. Kelvin-Helmholtz instability and kinetic internal kink modes in tokamaks

    The m=1 (poloidal mode number) and n=1 (toroidal mode number) kinetic internal kink (KIK) mode in the presence of a density gradient is studied with the cylindrical version of the gyro-reduced MHD code, which is one of the extended MHD codes being able to treat the physics beyond resistive MHD. Electron inertia and electron finite temperature effects are included. The unstable KIK mode is observed in the parameter range in which the linear theory predicts complete stabilization due to the electron diamagnetic effect. The electrostatic potential profile in the linear stage of the KIK instability has the sheared poloidal flow with the m=1 mode structure. The vortexes are generated due to the Kelvin-Helmholtz (K-H) instability. The KIK is stabilized when the vortexes are formed, but it is destabilized again as the vortexes diminish due to the charge neutralizing electron motion along the magnetic field. These phenomena are observed in the early nonlinear stage of the KIK instability in which the width of the m=1 magnetic island is sufficiently small compared with the radial extent of the vortexes. The strong coupling between the vortexes and the KIK instability can be one of the candidates explaining the sudden onset of the sawtooth crash. (author)

  11. Kelvin probe force microscopy imaging of cross-sections of Si multilayer structures

    Baumgart, Christine; Helm, Manfred; Schmidt, Heidemarie [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, Dresden (Germany); Mueller, Anne-Dorothea; Mueller, Falk [Anfatec Instruments AG, Oelsnitz (Germany); Moeller, Andre [SGS Institute Fresenius GmbH, Dresden (Germany)

    2009-07-01

    Kelvin probe force microscopy (KPFM) is a standard technique for the investigation of surface potentials. We present its applicability to cross-sectionally prepared p-p{sup +} Si multilayer structures. The contact potential difference (CPD) image between tip and sample has been recorded by means of an Anfatec Level-AFM with a 2nd amplifier and NSC15 probes from MikroMash. Using an active mixer, the excitation amplitude of the NSC15 probes is almost independent on the working frequency. The probed CPD signal difference between the layers ranges between 60 meV and 850 meV and can be correlated to the variation of the diffusion potential in the Si multilayer structure. The p-type of majority charge carriers and the corresponding acceptor dopant profile have been pinpointed by scanning capacitance measurements. Starting from the known donor dopant concentration in the NSC15 probe, we simulated the CPD and determined the acceptor concentration in the whole p-p{sup +} Si multilayer structure. From the frequency dependence of the CPD we can clearly distinguish between surface and bulk effects.

  12. Kelvin probe force microscopy for characterizing doped semiconductors for future sensor applications in nano- and biotechnology

    Schmidt, Heidemarie, E-mail: Heidemarie.Schmidt@etit.tu-chemnitz.de [Chemnitz University of Technology, Department of Materials for Nanoelectronics, Faculty of Electrical Engineering and Information Technology, 09126 Chemnitz (Germany); Habicht, Stefan; Feste, Sebastian [Forschungszentrum Jülich, Peter Grünberg Institute 9 (PGI-9-IT), 52425 Jülich (Germany); JARA-FIT, Fundamentals of Future Information Technology (Germany); Müller, Anne-Dorothea [Anfatec Instruments AG, Melanchthonstr. 28, 08606 Oelsnitz (Germany); Schmidt, Oliver G. [Chemnitz University of Technology, Department of Materials for Nanoelectronics, Faculty of Electrical Engineering and Information Technology, 09126 Chemnitz (Germany); Institute for Integrative Nanosciences, IFW Dresden, Helmholtzstraße 20, 01069 Dresden (Germany)

    2013-09-15

    Kelvin probe force microscopy (KPFM) is one of the most promising non-contact electrical nanometrology techniques to characterize doped semiconductors. By applying a recently introduced explanation of measured KPFM signals, we show the applicability of KPFM to determine and control surface-near electrostatic forces in planar doped silicon and in doped silicon nanostructures. Surface-near electrostatic forces may be used for the immobilization of nano- and biomaterials in future sensor applications in nano- and biotechnology. Additionally, the influence of the electrostatic potential distribution in doped semiconductor nanostructures, e.g. in horizontal Si nanowires, and its influence on the surface-near electrostatic forces are discussed. It is explained how drift and diffusion of injected electrons and holes in intrinsic electric fields influence the detected KPFM signal. For example KPFM is successfully employed to locate p{sup +}p and n{sup +}p junctions along B-doped and As-doped p-Si nanowires, respectively. As an outlook the physical immobilization and the transport of biomaterials above arrays of separately addressable doped semiconductor cells will be discussed.

  13. Kelvin probe force microscopy for characterizing doped semiconductors for future sensor applications in nano- and biotechnology

    Schmidt, Heidemarie; Habicht, Stefan; Feste, Sebastian; Müller, Anne-Dorothea; Schmidt, Oliver G.

    2013-09-01

    Kelvin probe force microscopy (KPFM) is one of the most promising non-contact electrical nanometrology techniques to characterize doped semiconductors. By applying a recently introduced explanation of measured KPFM signals, we show the applicability of KPFM to determine and control surface-near electrostatic forces in planar doped silicon and in doped silicon nanostructures. Surface-near electrostatic forces may be used for the immobilization of nano- and biomaterials in future sensor applications in nano- and biotechnology. Additionally, the influence of the electrostatic potential distribution in doped semiconductor nanostructures, e.g. in horizontal Si nanowires, and its influence on the surface-near electrostatic forces are discussed. It is explained how drift and diffusion of injected electrons and holes in intrinsic electric fields influence the detected KPFM signal. For example KPFM is successfully employed to locate p+p and n+p junctions along B-doped and As-doped p-Si nanowires, respectively. As an outlook the physical immobilization and the transport of biomaterials above arrays of separately addressable doped semiconductor cells will be discussed.

  14. Liquid entrainment by an expanding core disruptive accident bubble--a Kelvin/Helmholtz phenomenon

    The final stage of a postulated energetic core disruptive accident (CDA) in a liquid metal fast breeder reactor is believed to involve the expansion of a high-pressure core-material bubble against the overlying pool of sodium. Some of the sodium will be entrained by the CDA bubble which may influence the mechanical energy available for damage to the reactor vessel. The following considerations of liquid surface instability indicate that the Kelvin-Helmholtz (K-H) mechanism is primarily responsible for liquid entrainment by the expanding CDA bubble. First, an instability analysis is presented which shows that the K-H mechanism is faster than the Taylor acceleration mechanism of entrainment at the high fluid velocities expected within the interior of the expanding CDA bubble. Secondly, a new model of liquid entrainment by the CDA bubble is introduced which is based on spherical-core-vortex motion and entrainment via the K-H instability along the bubble surface. The model is in agreement with new experimental results presented here on the reduction of nitrogen-gas-simulant CDA bubble work potential. Finally, a one-dimensional air-over-water parallel flow experiment was undertaken which demonstrates that the K-H instability results in sufficiently rapid and fine liquid atomization to account for observed CDA gas-bubble work reductions. An important byproduct of the theoretical and experimental work is that the liquid entrainment rate is well described by the Ricou-Spalding entrainment law

  15. The ultra-fast Kelvin waves in the equatorial ionosphere: observations and modeling

    A. N. Onohara

    2013-02-01

    Full Text Available The main purpose of this study is to investigate the vertical coupling between the mesosphere and lower thermosphere (MLT region and the ionosphere through ultra-fast Kelvin (UFK waves in the equatorial atmosphere. The effect of UFK waves on the ionospheric parameters was estimated using an ionospheric model which calculates electrostatic potential in the E-region and solves coupled electrodynamics of the equatorial ionosphere in the E- and F-regions. The UFK wave was observed in the South American equatorial region during February–March 2005. The MLT wind data obtained by meteor radar at São João do Cariri (7.5° S, 37.5° W and ionospheric F-layer bottom height (h'F observed by ionosonde at Fortaleza (3.9° S; 38.4° W were used in order to calculate the wave characteristics and amplitude of oscillation. The simulation results showed that the combined electrodynamical effect of tides and UFK waves in the MLT region could explain the oscillations observed in the ionospheric parameters.

  16. NATIONAL HEARING DAY

    2003-01-01

    The 12th of June 2003 Is the French National Hearing Day. The Medical Service invites everyone working at CERN to come and have an ear test at the infirmary. Bld. 57, ground floor, between 9h00 and 16h00 Tel. 73802

  17. National hearing day

    2003-01-01

    The 12th of June 2003 Is the French National Hearing Day. The Medical Service invites everyone working at CERN to come and have an ear test at the infirmary. Bld. 57, ground floor, between 9h00 and 16h00 Tel. 73802

  18. April Fool's Day

    2004-01-01

    @@ While popular in the U.S., the April Fool's Day tradition is even more popular in European countries, such as France and Great Britain. Although the roots(起源) of the traditional tricks (恶作剧) are unclear, the French and the British both have claims(声称) on the origin(起源) of the celebration.

  19. 90-Day Cycle Handbook

    Park, Sandra; Takahashi, Sola

    2013-01-01

    90-Day Cycles are a disciplined and structured form of inquiry designed to produce and test knowledge syntheses, prototyped processes, or products in support of improvement work. With any type of activity, organizations inevitably encounter roadblocks to improving performance and outcomes. These barriers might include intractable problems at…

  20. My Days in Tibet

    Rosemary; Adang

    1999-01-01

    Early on the morning of July 27, 1999, my travel companion, Moira Fulton.and I (two American women) flew to Lhasa. We had been anticipating this dayfor months, and finally we were headed for a five-day visit on "The Roof of theWorld."

  1. CERN openlab Open Day

    Purcell, Andrew Robert

    2015-01-01

    The CERN openlab Open Day took place on 10 June, 2015. This was the first in a series of annual events at which research and industrial teams from CERN openlab can present their projects, share achievements, and collect feedback from their user communities.

  2. Scheduling: Seven Period Day

    Williamson, Ronald

    2010-01-01

    Driven by stable or declining financial resources many school districts are considering the costs and benefits of a seven-period day. While there is limited evidence that any particular scheduling model has a greater impact on student learning than any other, it is clear that the school schedule is a tool that can significantly impact teacher…

  3. European Antibiotic Awareness Day

    Earnshaw, S; Mancarella, G; Mendez, A;

    2014-01-01

    Awareness Day (EAAD) on 18 November as platform to support national campaigns across Europe. This article provides an overview of EAAD tools, materials, and activities developed during the first five years. It shows that EAAD has been successful due to good cooperation between ECDC and national institutions...

  4. "A Day Without Immigrants"

    Heiskanen, Benita

    2009-01-01

    Abstract This article considers the debates surrounding the "Day Without Immigrants" protests organized in major U.S. cities on 1 May 2006, prompted by H.R. 4437, the Border Protection, Anti-Terrorism, and Illegal Immigration Control Act of 2005, from the multiple perspectives of scholars, pundits...

  5. World Heart Day

    2009-09-01

    For World Heart Day, learn more about what heart-healthy steps you can take in the workplace.  Created: 9/1/2009 by National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP).   Date Released: 9/9/2009.

  6. Fabulous Weather Day

    Marshall, Candice; Mogil, H. Michael

    2007-01-01

    Each year, first graders at Kensington Parkwood Elementary School in Kensington, Maryland, look forward to Fabulous Weather Day. Students learn how meteorologists collect data about the weather, how they study wind, temperature, precipitation, basic types/characteristics of clouds, and how they forecast. The project helps the students grow in…

  7. Pemerolehan Leksikal Nomina Bahasa Angkola Anak Usia 3-4 Tahun: Analisis Psikolinguistik

    Lumbanraja, Novelina

    2011-01-01

    Penelitian ini dilakukan untuk menganalisis pemerolehan leksikal nomina bahasa Angkola anak usia 3-4 tahun: analisis psikolinguistik dengan tujuan mendeskripsikan bagaimana pemerolehan leksikal nomina bahasa Angkola anak usia 3-4 tahun dan bagaimana urutan lpemerolehan leksikal nomina bahasa Angkola anak usia 3-4 tahun. Pengumpulan data dilakukan terlebih dahulu dengan melakukan observasi. Hal ini dilakukan untuk mengamati pemahaman kata benda yang diucapkan anak-anak dengan kata benda ya...

  8. Synthesis and Antimicrobial Activity of Some New 1,3,4-Thiadiazole Derivatives

    Mohamed R. Abdel Aziz

    2012-12-01

    Full Text Available New series of 1,3,4-thiadiazoles have been prepared via reaction of 1,3,4-thiadiazolenaminones 1 with N-phenyl 2-oxopropanehydrazonoyl chloride (2 in dioxane in the presence of triethylamine. Also, some new heterocycles incorporating 1,3,4-thiadiazole ring were obtained by reaction of 1,3,4-thiadiazolenaminones 1 with nitrogen-nucleophiles like hydrazine hydrate, 3-amino-1,2,4-triazole and 2-aminobenzimidazole. The structure of the new products was established based on elemental and spectral analysis. The relation between the structure of the products and their activity towards some microorganisms was studied and promising results were obtained.

  9. The SAO and Kelvin waves in the EuroGRIPS GCMS and the UK Met. Office analyses

    M. Amodei

    Full Text Available We compare the tropical oscillations and planetary scale Kelvin waves in four troposphere-stratosphere climate models and the assimilated dataset produced by the United Kingdom Meteorological Office (UKMO. The comparison has been made in the GRIPS framework "GCM-Reality Intercomparison Project for SPARC", where SPARC is Stratospheric Processes and their Role in Climate, a project of the World Climate Research Program. The four models evaluated are European members of GRIPS: the UKMO Unified Model (UM, the model of the Free University in Berlin (FUB–GCM, the ARPEGE-climat model of the French National Centre for Meteorological Research (CNRM, and the Extended UGAMP GCM (EUGCM of the Centre for Global Atmospheric Modelling (CGAM. The integrations were performed with different, but annually periodic external conditions (e.g., sea-surface temperature, sea ice, and incoming solar radiation. The structure of the tropical winds and the strengths of the Kelvin waves are examined. In the analyses where the SAO (Semi-Annual Oscillation and the QBO (Quasi-Biennal Oscillation are reasonably well captured, the amplitude of these analysed Kelvin waves is close to that observed in independent data from UARS (Upper Atmosphere Research Satellite. In agreement with observations, the Kelvin waves generated in the models propagate into the middle atmosphere as wave packets, consistent with a convective forcing origin. In three of the models, slow Kelvin waves propagate too high and their amplitudes are overestimated in the upper stratosphere and in the mesosphere, the exception is the UM which has weaker waves. None of the modelled waves are sufficient to force realistic eastward phases of the QBO or SAO. Although the SAO is represented by all models, only two of them are able to generate westerlies between 10 hPa and 50 hPa. The importance of the role played in the SAO by unresolved gravity waves is emphasized. Although it exhibits some unrealistic features, the

  10. Synthesis of 1-Substituted Carbazolyl-1,2,3,4-tetrahydro- and Carbazolyl-3,4-dihydro-β-carboline Analogs as Potential Antitumor Agents

    Ji-Wang Chern

    2011-02-01

    Full Text Available A series of 1-substituted carbazolyl-1,2,3,4-tetrahydro- and carbazolyl-3,4-dihydro-b-carboline analogs have been synthesized and evaluated for antitumor activity against human tumor cells including KB, DLD, NCI-H661, Hepa, and HepG2/A2 cell lines. Among these, compounds 2, 6, 7, and 9 exhibited the most potent and selective activity against the tested tumor cells. As for inhibition of topoisomerase II, compounds 1–14 and 18 showed better activity than etoposide. Among them, compounds 3, 4, 7, 9, and 10 exhibited potent activity. The structure and activity relationship (SAR study revealed correlation between carbon numbers of the side chain and biological activities. The molecular complex with DNA for compound 2 was proposed.

  11. Computer Security Day

    CERN Bulletin

    2010-01-01

      Viruses, phishing, malware and cyber-criminals can all threaten your computer and your data, even at CERN! Experts will share their experience with you and offer solutions to keep your computer secure. Thursday, 10 June 2010, 9.30, Council Chamber Make a note in your diary! Presentations in French and English: How do hackers break into your computer? Quels sont les enjeux et conséquences des attaques informatiques contre le CERN ? How so criminals steal your money on the Internet? Comment utiliser votre ordinateur de manière sécurisée ? and a quiz: test your knowledge and win one of the many prizes that will be on offer! For more information and to follow the day's events via a live webcast go to: http://cern.ch/SecDay.  

  12. One Day on Earth

    2011-01-01

    In collaboration with the CineGlobe Film Festival, the One Day on Earth global film project invites you to share your story of scientific inspiration, scientific endeavors and technological advancement on 11 November 2011 (11.11.11).   Technology in the 21st century continuously inspires us to re-imagine the world. From outer-space to cyberspace, new ideas that we hope will improve the lives of future generations keep us in a state of change. However, these new technologies may alter the nature of our shared existence in ways not yet known. On 11.11.11, we invite you to record the exciting ways that science is a part of your life, together with people around the world who will be documenting their lives on this day of global creation. See www.onedayonearth.org for details on how to participate.

  13. CERN Heart Days

    2003-01-01

    14 & 15 OCTOBER 2003 The Medical Service and the Fire Brigade invite everyone working at CERN to participate in the above event. INFIRMARY 9 am to 16.30 pm Building 57, ground floor No need to book HEALTHY HEART? Evaluation of personal cardiac risks through the monitoring of: Blood pressure Cholesterol and sugar levels Body Mass Index ... and more Leaflets, information and advice concerning cardiac issues FIRE BRIGADE 9 to 12am - Building 65 Please book (limited to 15 people/day) FIRST AID COURSES What to do in a Cardiac Emergency (3 h. duration) Places are limited and on reservation only (15 people/day). To book, e-mail the Medical Services on: service.medical@cern.ch

  14. CERN Heart Days

    2003-01-01

    14 & 15 OCTOBER 2003 The Medical Service and the Fire Brigade invite everyone working at CERN to participate in the above event. INFIRMARY 9 am to 16.30 pm Building 57, ground floor no need to book HEALTHY HEART? • Evaluation of personal cardiac risks through the monitoring of: Blood pressure Cholesterol and sugar levels Body Mass Index ... and more • Leaflets, information and advice concerning cardiac issues FIRE BRIGADE 9 to 12 am - Building 65 Please book (limited to 15 people/day) FIRST AID COURSES • What to do in a Cardiac Emergency (3 h. duration) Places are limited and on reservation only (15 people/day). To book, e-mail the Medical Services on: service.medical@cern.ch

  15. Governing To‐day

    Turner, Kevin

    Governing To-day denotes a domain of research, and what the thesis undertakes is a theoretical discussion of some questions of method vis-à-vis researching this domain. There are two aspects to the title that enfold one another. Firstly, “governing to-day” signposts that it is to!day that is to be...... takes as its reference point and means of critique the “will not to be governed like that”. Consequently, the approach thus outlined is firmly situated within that rather loosely affiliated body of work that goes under the title studies in governmentality. Studies in governmentality have their point of...... departure in the research and writing of the French philosopher and historian, Michel Foucault. It is primarily within the writings of Foucault that the thesis seeks to find a workaround to the problem thrown forth by the aforementioned questions of method....

  16. Open Days in 2008

    Corinne Pralavorio

    CERN will be organising two Open Days in 2008, one for CERN employees and their families on Saturday, 5 April, and another for the general public on Sunday, 6 April. This is the one last chance to see the LHC and its experiments. In addition to the surface facilities, visitors will be able to go underground to see the accelerator and will have acces to the experiment caverns. Exceptionally, most of the points along the ring will be open. We need a large number of volunteers to ensure the success of these two very special days. Full details of the events will be published in the first January edition of the Bulletin. Volunteers will be able to register by completing an electronic form and an information session will be organised.

  17. Innovation and Entrepreneurship Day

    Di Meglio, Alberto

    2015-01-01

    Scientific Research is one of the strongest drivers behind innovation, but innovation cannot be fully exploited without providing a fertile ground for ideas to develop and mature. What can be done at CERN to maximize the human and technological assets that naturally gather together to work on the next frontiers of Physics research. The Innovation and Entrepreneurship Day is the first event co-organized by CERN openlab, the CERN KT group, IdeaSquare and Intel, a CERN openla industrial partner,...

  18. National HIV Testing Day

    2011-06-09

    Dr. Kevin A. Fenton, Director of CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, discusses National HIV Testing Day, an annual observance which raises awareness of the importance of knowing one's HIV status and encourages at-risk individuals to get an HIV test.  Created: 6/9/2011 by National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention (NCHHSTP).   Date Released: 6/9/2011.

  19. A long day

    Fahy, John

    2014-01-01

    My fieldwork is based in Mayapur, West Bengal where the Hare Krishnas have their international headquarters. Once a week the devotees leave their compound for ‘Food for Life’, distributing food to villagers along the Ganges. The kids often come on the boat across the river to help out. After a long day of kirtan and cooking, these kids take a break on the cart on the way back to the boat.

  20. World AIDS Day 2004

    CynthiaKirk; 刘保行

    2005-01-01

    December first was World AIDS Day. Last year, the campaign (运动;活动) centered on women and girls. They made up almost half of all people infected with the virus HIV that causes AIDS. And H1V was spreading faster among women than men in most areas of the world. These findings (发现) werefrom the yearly report by the United Nations and the World Health Organization, a UN agency

  1. 'EU divertor celebration day'

    The meeting 'EU divertor celebration day' organized on 16 January 2002 at Plansee AG, Reutte, Austria was held on the occasion of the completion of manufacturing activities of a complete set of near full-scale prototypes of divertor components including the vertical target, the dome liner and the cassette body. About 30 participants attended the meeting including Dr. Robert Aymar, ITER Director, representatives from EFDA, CEA, ENEA, IPP and others

  2. Governing To‐day

    Turner, Kevin

    Governing To-day denotes a domain of research, and what the thesis undertakes is a theoretical discussion of some questions of method vis-à-vis researching this domain. There are two aspects to the title that enfold one another. Firstly, “governing to-day” signposts that it is to!day that is to be...... governed, that it is ourselves in our actuality that form the target of government, hence it is this government of ourselves in our present that we are to enquire into. Secondly, “governing to-day” highlights the fact that it is thus the state of contemporary arts of government, government at this moment...... in time, in the present!day, in this time that is our own, and so forth, that forms the object of enquiry. Accordingly, “governing to!day” denotes both a government of the present and government in the present. In working through said questions of method, the thesis sketches out an approach that...

  3. 3,4-DGE is cytotoxic and decreases HSP27/HSPB1 in podocytes.

    Sanchez-Niño, Maria Dolores; Poveda, Jonay; Sanz, Ana Belen; Carrasco, Susana; Ruiz-Ortega, Marta; Selgas, Rafael; Egido, Jesus; Ortiz, Alberto

    2014-03-01

    Hyperglycemia is the key driver of diabetic complications and increased concentrations of glucose degradation products. The study of peritoneal dialysis solution biocompatibility has highlighted the adverse biological effects of glucose degradation products. Recently, 3,4-dideoxyglucosone-3-ene (3,4-DGE) was identified as the most toxic glucose degradation product in peritoneal dialysis fluids. In addition, 3,4-DGE is present in high-fructose corn syrup, and its precursor 3-deoxyglucosone is increased in diabetes. The role of 3,4-DGE in glomerular injury had not been addressed. We studied the effects of 3,4-DGE on cultured human podocytes and in vivo in mice. 3,4-DGE induced apoptosis in podocytes in a dose- and time-dependent manner. 3,4-DGE promoted the release of cytochrome c from mitochondria and activation of caspase-3. While high glucose concentrations increased the levels of the podocyte intracellular antiapoptotic protein HSP27/HSPB1, 3,4-DGE decreased the expression of podocyte HSP27/HSPB1. Apoptosis induced by 3,4-DGE was caspase-dependent and could be prevented by the broad-spectrum caspase inhibitor zVAD-fmk. Antagonism of Bax by a Ku-70-derived peptide also prevented apoptosis. Intravenous administration of 3,4-DGE to healthy mice resulted in a decreased expression of HSP27/HSPB1 and caspase-3 activation in whole kidney and in podocytes in vivo. In conclusion, 3,4-DGE induces apoptotic cell death in cultured human podocytes, suggesting a potential role in glomerular injury resulting from metabolic disorders. PMID:24337777

  4. Synthesis and thermolysis of oxo chloro-2-ethyl-1.3.4-thiadiazole rhenium complex

    Present article is devoted to synthesis and thermolysis of oxo chloro-2-ethyl-1.3.4-thiadiazole rhenium complex. The synthesis method of oxo chloro-2-ethyl-1.3.4-thiadiazole rhenium complex is elaborated. The kinetics of its thermolysis process is studied. The thermodynamic functions of thermolysis process are evaluated.

  5. Three-dimensional photochemical microfabrication of poly(3,4-ethylene- dioxythiophene) in transparent polymer sheet

    Yamada, Katsumi, E-mail: kyamada@chem.t-kougei.ac.jp [Department of Life Science and Sustainable Chemistry, Tokyo Polytechnic University, 1583 Iiyama, Atsugi, Kanagawa, 243-0297 (Japan); Yamada, Yumiko [Department of Life Science and Sustainable Chemistry, Tokyo Polytechnic University, 1583 Iiyama, Atsugi, Kanagawa, 243-0297 (Japan); Sone, Junji [Department of Applied Computer Science, Tokyo Polytechnic University, 1583 Iiyama, Atsugi, Kanagawa, 243-0297 (Japan)

    2014-03-03

    A dimeric compound of 3,4-ethylenedioxythiophene was polymerized to form poly(3,4-ethylenedioxythiophene) by multi-photon sensitized polymerization using a femtosecond laser. In contrast, photopolymerization could not be achieved using 3,4-ethylenedioxythiophene as the starting material, because it has a more positive oxidation peak potential compared to the redox potential of the tris(2,2′-bipyridyl)ruthenium complex used as the photosensitizer. Furthermore, three-dimensional micropatterns of poly(3,4-ethylenedioxythiophene) could be produced in a transparent polymer sheet by scanning the laser focal point. - Highlights: • Multi-photon sensitized polymerization of 3,4-ethylenedioxythiophene (EDOT). • Three-dimensional microstructures of poly(EDOT) in the transparent polymer sheet. • The dimeric compound of EDOT was employed as the starting material. • The lateral precision of this system exceeded the diffraction limit.

  6. The Fourier-Kelvin Stellar Interferometer (FKSI): A Discovery Class TPF/DARWIN Pathfinder Mission Concept

    Danchi, W. C.; Allen, R. J.; Benford, D. J.; Deming, D.; Gezan, D. Y.; Kuchner, M.; Leisawitz, D. T.; Linfield, R.; Millan-Gabet, R.; Monnier, J. D.

    2003-01-01

    The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging and nulling interferometer for the mid-infrared spectral region (5-30 microns). FKSI is conceived as a scientific and technological pathfinder to TPF/DARWIN as well as SPIRIT, SPECS, and SAFIR. It will also be a high angular resolution system complementary to NGST. The scientific emphasis of the mission is on the evolution of protostellar systems, from just after the collapse of the precursor molecular cloud core, through the formation of the disk surrounding the protostar, the formation of planets in the disk, and eventual dispersal of the disk material. FKSI will also search for brown dwarfs and Jupiter mass and smaller planets, and could also play a very powerful role in the investigation of the structure of active galactic nuclei and extra-galactic star formation. We have been studying alternative interferometer architectures and beam combination techniques, and evaluating the relevant science and technology tradeoffs. Some of the technical challenges include the development of the cryocooler systems necessary for the telescopes and focal plane array, light and stiff but well-damped truss systems to support the telescopes, and lightweight and coolable optical telescopes. We present results of detailed design studies of the FKSI starting with a design consisting of five one meter diameter telescopes arranged along a truss structure in a linear non-redundant array, cooled to 35 K. A maximum baseline of 20 meters gives a nominal resolution of 26 mas at 5 microns. Using a Fizeau beam combination technique, a simple focal plane camera could be used to obtain both Fourier and spectral data simultaneously for a given orientation of the array. The spacecraft will be rotated to give sufficient Fourier data to reconstruct complex images of a broad range of astrophysical sources. Alternative and simpler three and two telescope designs emphasizing nulling and spectroscopy also have been

  7. Pervaporation from a dense membrane: roles of permeant-membrane interactions, Kelvin effect, and membrane swelling.

    Sharma, Ashutosh; Thampi, Sumesh P; Suggala, Satyanarayana V; Bhattacharya, Prashant K

    2004-05-25

    Dense polymeric membranes with extremely small pores in the form of free volume are used widely in the pervaporative separation of liquid mixtures. The membrane permeation of a component followed by its vaporization on the opposite face is governed by the solubility and downstream pressure. We measured the evaporative flux of pure methanol and 2-propanol using dense membranes with different free volumes and different affinities (wettabilities and solubilities) for the permeant. Interestingly, the evaporative flux for different membranes vanished substantially (10-75%) below the equilibrium vapor pressure in the bulk. The discrepancy was larger for a smaller pore size and for more wettable membranes (higher positive spreading coefficients). This observation, which cannot be explained by the existing (mostly solution-diffusion type) models ofpervaporation, suggests an important role for the membrane-permeant interactions in nanopores that can lower the equilibrium vapor pressure. The pore sizes, as estimated from the positron annihilation, ranged from 0.2 to 0.6 nm for the dry membranes. Solubilities of methanol in different composite membranes were estimated from the Flory-Huggins theory. The interaction parameter was obtained from the surface properties measured by the contact angle goniometry in conjunction with the acid-base theory of polar surface interactions. For the membranes examined, the increase in the "wet" pore volume due to membrane swelling correlates almost linearly with the solubility of methanol in these membranes. Indeed, the observations are found to be consistent with the lowering of the equilibrium vapor pressure on the basis of the Kelvin equation. Thus, a higher solubility or selectivity of a membrane also implies stronger permeant-membrane interactions and a greater retention of the permeant by the membrane, thus decreasing its evaporative flux. This observation has important implications for the interpretation of existing experiments and in

  8. Instability of Supersonic Cold Streams Feeding Galaxies I: Linear Kelvin-Helmholtz Instability with Body Modes

    Mandelker, Nir; Padnos, Dan; Dekel, Avishai; Birnboim, Yuval; Burkert, Andreas; Krumholz, Mark R.; Steinberg, Elad

    2016-09-01

    Massive galaxies at high redshift are predicted to be fed from the cosmic web by narrow, dense streams of cold gas that penetrate through the hot medium encompassed by a stable shock near the virial radius of the dark-matter halo. Our long-term goal is to explore the heating and dissipation rate of the streams and their fragmentation and possible breakup, in order to understand how galaxies are fed, and how this affects their star-formation rate and morphology. We present here the first step, where we analyze the linear Kelvin-Helmholtz instability (KHI) of a cold, dense slab or cylinder in 3D flowing supersonically through a hot, dilute medium. The current analysis is limited to the adiabatic case with no gravity. By analytically solving the linear dispersion relation, we find a transition from a dominance of the familiar rapidly growing surface modes in the subsonic regime to more slowly growing body modes in the supersonic regime. The system is parametrized by three parameters: the density contrast between stream and medium, the Mach number of stream velocity with respect to the medium, and the stream width with respect to the halo virial radius. A realistic choice for these parameters places the streams near the mode transition, with the KHI exponential-growth time in the range 0.01-10 virial crossing times for a perturbation wavelength comparable to the stream width. We confirm our analytic predictions with idealized hydrodynamical simulations. Our linear estimates thus indicate that KHI may be effective in the evolution of streams before they reach the galaxy. More definite conclusions await the extension of the analysis to the nonlinear regime and the inclusion of cooling, thermal conduction, the halo potential well, self-gravity and magnetic fields.

  9. A Robust Cooling Platform for NIS Junction Refrigeration and sub-Kelvin Cryogenic Systems

    Wilson, B.; Atlas, M.; Lowell, P.; Moyerman, S.; Stebor, N.; Ullom, J.; Keating, B.

    2014-08-01

    Recent advances in Normal metal-insulator-superconductor (NIS) tunnel junctions (Clark et al. Appl Phys Lett 86: 173508, 2005, Appl Phys Lett 84: 4, 2004) have proven these devices to be a viable technology for sub-Kelvin refrigeration. NIS junction coolers, coupled to a separate cold stage, provide a flexible platform for cooling a wide range of user-supplied payloads. Recently, a stage was cooled from 290 to 256 mK (Lowell et al. Appl Phys Lett 102: 082601 2013), but further mechanical and electrical improvements are necessary for the stage to reach its full potential. We have designed and built a new Kevlar suspended cooling platform for NIS junction refrigeration that is both lightweight and well thermally isolated; the calculated parasitic loading is pW from 300 to 100 mK. The platform is structurally rigid with a measured deflection of 25 m under a 2.5 kg load and has an integrated mechanical heat switch driven by a superconducting stepper motor with thermal conductivity G W/K at 300 mK. An integrated radiation shield limits thermal loading and a modular platform accommodates enough junctions to provide nanowatts of continuous cooling power. The compact stage size of 7.6 cm 8.6 cm 4.8 cm and overall radiation shield size of 8.9 cm 10.0 cm 7.0 cm along with minimal electrical power requirements allow easy integration into a range of cryostats. We present the design, construction, and performance of this cooling platform as well as projections for coupling to arrays of NIS junctions and other future applications.

  10. Electrical characterisitics of ferritin cores investegated by Kelvin Probe force microscopy

    We fabricated Fe (iron metal) cores structure by using a low energy Ar+ ion beam. A monolayer of ferritin molecule (Fe2O3: iron oxide) was adsorbed on the thermal silicon oxide layer. The bombardment energy was optimized using Ar gas by changing the input power after the protein of the monolayer was eliminated with UV/O3. Though it was resulted in a poor reduction when the time of ion beam was less than 30 sec, Ar+ ion beam enabled completely reduction when the time of ion beam was in 60 sec. We reduced the core particles to conductive Fe nanodots. X-ray photoelectron spectroscopy (XPS) measurements confirmed the reduction of the cores. As a result, the diameter of the ferritin nano-structure was 7 nm, which was not identical to that of the iron core in the ferritin after ion beam. Additionally, the Kelvin Probe Force microscopy (KFM) profile was not almost identical between Fe2O3 and Fe cores. It is very difficult for conventional Ar+ beam processes to fabricate such fine structure of Fe cores, because the high energy ions enhanced the bombardment damage of the iron core in the conventional reduction processes. The results that the change of lattice constant from 0.25 to 0.2 nm corresponds from ferrihydrite (110) to α-Fe(111), respectively, which suggests the ferrihydrite cores reduced to Fe nanodots after ion beam process. Furthurmore, the diameter of the ferritin core decreased from 7 nm to 5 nm after the ion beam process

  11. Kelvin probe measurements: investigations of the patch effect with applications to ST-7 and LISA

    One of the possible noise sources for the space-based gravitational wave detector LISA (the Laser Interferometer Space Antenna), associated with its test masses, is that due to spatial variations in surface potential (or patch effect) across the surfaces of the test mass and its housing. Such variations will lead to force gradients which may result in a significant acceleration noise term. Another noise source is that due to temporal variations in the surface potential, which in conjunction with any ambient dc voltage or net free charge on the test mass may also produce a significant acceleration noise term. The ST-7 demonstrator mission is designed to test technologies for LISA, including the gravitational reference sensor, which contains a gold-coated gold/platinum (Au/Pt) alloy test mass, surrounded by a housing that carries the electrodes for sensing and control. We have used a Kelvin probe at the Goddard Space Flight Center to make spatial and temporal measurements of contact potential differences for a selection of materials (Au/Pt, beryllia, alumina, titanium) and coatings (gold, diamond-like carbon, indium tin oxide, titanium carbide). Our investigations indicate that subject to certain assumptions all of these coatings appear to satisfy the ST-7 requirement that patch effect spatial variations should be less than 100 mV. The data also revealed evidence of behavioural trends with pressure and possible contamination effects. Regarding temporal variations, the current accuracy of the instrument is limiting the measurements at a level above the likely LISA requirements. We discuss our results and draw some conclusions of relevance to LISA

  12. Excluding Contact Electrification in Surface Potential Measurement Using Kelvin Probe Force Microscopy.

    Li, Shengming; Zhou, Yusheng; Zi, Yunlong; Zhang, Gong; Wang, Zhong Lin

    2016-02-23

    Kelvin probe force microscopy (KPFM), a characterization method that could image surface potentials of materials at the nanoscale, has extensive applications in characterizing the electric and electronic properties of metal, semiconductor, and insulator materials. However, it requires deep understanding of the physics of the measuring process and being able to rule out factors that may cause artifacts to obtain accurate results. In the most commonly used dual-pass KPFM, the probe works in tapping mode to obtain surface topography information in a first pass before lifting to a certain height to measure the surface potential. In this paper, we have demonstrated that the tapping-mode topography scan pass during the typical dual-pass KPFM measurement may trigger contact electrification between the probe and the sample, which leads to a charged sample surface and thus can introduce a significant error to the surface potential measurement. Contact electrification will happen when the probe enters into the repulsive force regime of a tip-sample interaction, and this can be detected by the phase shift of the probe vibration. In addition, the influences of scanning parameters, sample properties, and the probe's attributes have also been examined, in which lower free cantilever vibration amplitude, larger adhesion between the probe tip and the sample, and lower cantilever spring constant of the probe are less likely to trigger contact electrification. Finally, we have put forward a guideline to rationally decouple contact electrification from the surface potential measurement. They are decreasing the free amplitude, increasing the set-point amplitude, and using probes with a lower spring constant. PMID:26824304

  13. Kelvin probe force microscopy of nanocrystalline TiO2 photoelectrodes

    Alex Henning

    2013-07-01

    Full Text Available Dye-sensitized solar cells (DSCs provide a promising third-generation photovoltaic concept based on the spectral sensitization of a wide-bandgap metal oxide. Although the nanocrystalline TiO2 photoelectrode of a DSC consists of sintered nanoparticles, there are few studies on the nanoscale properties. We focus on the microscopic work function and surface photovoltage (SPV determination of TiO2 photoelectrodes using Kelvin probe force microscopy in combination with a tunable illumination system. A comparison of the surface potentials for TiO2 photoelectrodes sensitized with two different dyes, i.e., the standard dye N719 and a copper(I bis(imine complex, reveals an inverse orientation of the surface dipole. A higher surface potential was determined for an N719 photoelectrode. The surface potential increase due to the surface dipole correlates with a higher DSC performance. Concluding from this, microscopic surface potential variations, attributed to the complex nanostructure of the photoelectrode, influence the DSC performance. For both bare and sensitized TiO2 photoelectrodes, the measurements reveal microscopic inhomogeneities of more than 100 mV in the work function and show recombination time differences at different locations. The bandgap of 3.2 eV, determined by SPV spectroscopy, remained constant throughout the TiO2 layer. The effect of the built-in potential on the DSC performance at the TiO2/SnO2:F interface, investigated on a nanometer scale by KPFM measurements under visible light illumination, has not been resolved so far.

  14. Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy–magnetic force microscopy combination

    Miriam Jaafar

    2011-09-01

    Full Text Available The most outstanding feature of scanning force microscopy (SFM is its capability to detect various different short and long range interactions. In particular, magnetic force microscopy (MFM is used to characterize the domain configuration in ferromagnetic materials such as thin films grown by physical techniques or ferromagnetic nanostructures. It is a usual procedure to separate the topography and the magnetic signal by scanning at a lift distance of 25–50 nm such that the long range tip–sample interactions dominate. Nowadays, MFM is becoming a valuable technique to detect weak magnetic fields arising from low dimensional complex systems such as organic nanomagnets, superparamagnetic nanoparticles, carbon-based materials, etc. In all these cases, the magnetic nanocomponents and the substrate supporting them present quite different electronic behavior, i.e., they exhibit large surface potential differences causing heterogeneous electrostatic interaction between the tip and the sample that could be interpreted as a magnetic interaction. To distinguish clearly the origin of the tip–sample forces we propose to use a combination of Kelvin probe force microscopy (KPFM and MFM. The KPFM technique allows us to compensate in real time the electrostatic forces between the tip and the sample by minimizing the electrostatic contribution to the frequency shift signal. This is a great challenge in samples with low magnetic moment. In this work we studied an array of Co nanostructures that exhibit high electrostatic interaction with the MFM tip. Thanks to the use of the KPFM/MFM system we were able to separate the electric and magnetic interactions between the tip and the sample.

  15. Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: From fluid to kinetic modeling

    The nonlinear evolution of collisionless plasmas is typically a multi-scale process, where the energy is injected at large, fluid scales and dissipated at small, kinetic scales. Accurately modelling the global evolution requires to take into account the main micro-scale physical processes of interest. This is why comparison of different plasma models is today an imperative task aiming at understanding cross-scale processes in plasmas. We report here the first comparative study of the evolution of a magnetized shear flow, through a variety of different plasma models by using magnetohydrodynamic (MHD), Hall-MHD, two-fluid, hybrid kinetic, and full kinetic codes. Kinetic relaxation effects are discussed to emphasize the need for kinetic equilibriums to study the dynamics of collisionless plasmas in non trivial configurations. Discrepancies between models are studied both in the linear and in the nonlinear regime of the magnetized Kelvin-Helmholtz instability, to highlight the effects of small scale processes on the nonlinear evolution of collisionless plasmas. We illustrate how the evolution of a magnetized shear flow depends on the relative orientation of the fluid vorticity with respect to the magnetic field direction during the linear evolution when kinetic effects are taken into account. Even if we found that small scale processes differ between the different models, we show that the feedback from small, kinetic scales to large, fluid scales is negligible in the nonlinear regime. This study shows that the kinetic modeling validates the use of a fluid approach at large scales, which encourages the development and use of fluid codes to study the nonlinear evolution of magnetized fluid flows, even in the collisionless regime

  16. Evolution of Kelvin-Helmholtz instability at Venus in the presence of the parallel magnetic field

    Two-dimensional MHD simulations were performed to study the evolution of the Kelvin-Helmholtz (KH) instability at the Venusian ionopause in response to the strong flow shear in presence of the in-plane magnetic field parallel to the flow direction. The physical behavior of the KH instability as well as the triggering and occurrence conditions for highly rolled-up vortices are characterized through several physical parameters, including Alfvén Mach number on the upper side of the layer, the density ratio, and the ratio of parallel magnetic fields between two sides of the layer. Using these parameters, the simulations show that both the high density ratio and the parallel magnetic field component across the boundary layer play a role of stabilizing the instability. In the high density ratio case, the amount of total magnetic energy in the final quasi-steady status is much more than that in the initial status, which is clearly different from the case with low density ratio. We particularly investigate the nonlinear development of the case that has a high density ratio and uniform magnetic field. Before the instability saturation, a single magnetic island is formed and evolves into two quasi-steady islands in the non-linear phase. A quasi-steady pattern eventually forms and is embedded within a uniform magnetic field and a broadened boundary layer. The estimation of loss rates of ions from Venus indicates that the stabilizing effect of the parallel magnetic field component on the KH instability becomes strong in the case of high density ratio

  17. Evolution of Kelvin-Helmholtz instability at Venus in the presence of the parallel magnetic field

    Lu, H. Y. [Space Science Institute, School of Astronautics, Beihang University, Beijing 100191 (China); Key Laboratory of Planetary Sciences, Chinese Academy of Sciences, Nanjing 210008 (China); Cao, J. B.; Fu, H. S. [Space Science Institute, School of Astronautics, Beihang University, Beijing 100191 (China); Zhang, T. L. [Space Research Institute, Austrian Academy of Sciences, Graz A-8042 (Austria); Ge, Y. S. [Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 (China)

    2015-06-15

    Two-dimensional MHD simulations were performed to study the evolution of the Kelvin-Helmholtz (KH) instability at the Venusian ionopause in response to the strong flow shear in presence of the in-plane magnetic field parallel to the flow direction. The physical behavior of the KH instability as well as the triggering and occurrence conditions for highly rolled-up vortices are characterized through several physical parameters, including Alfvén Mach number on the upper side of the layer, the density ratio, and the ratio of parallel magnetic fields between two sides of the layer. Using these parameters, the simulations show that both the high density ratio and the parallel magnetic field component across the boundary layer play a role of stabilizing the instability. In the high density ratio case, the amount of total magnetic energy in the final quasi-steady status is much more than that in the initial status, which is clearly different from the case with low density ratio. We particularly investigate the nonlinear development of the case that has a high density ratio and uniform magnetic field. Before the instability saturation, a single magnetic island is formed and evolves into two quasi-steady islands in the non-linear phase. A quasi-steady pattern eventually forms and is embedded within a uniform magnetic field and a broadened boundary layer. The estimation of loss rates of ions from Venus indicates that the stabilizing effect of the parallel magnetic field component on the KH instability becomes strong in the case of high density ratio.

  18. Kelvin Absolute Temperature Scale Identified as Length Scale and Related to de Broglie Thermal Wavelength

    Sohrab, Siavash

    Thermodynamic equilibrium between matter and radiation leads to de Broglie wavelength λdβ = h /mβvrβ and frequency νdβ = k /mβvrβ of matter waves and stochastic definitions of Planck h =hk =mk c and Boltzmann k =kk =mk c constants, λrkνrk = c , that respectively relate to spatial (λ) and temporal (ν) aspects of vacuum fluctuations. Photon massmk =√{ hk /c3 } , amu =√{ hkc } = 1 /No , and universal gas constant Ro =No k =√{ k / hc } result in internal Uk = Nhνrk = Nmkc2 = 3 Nmkvmpk2 = 3 NkT and potential pV = uN\\vcirc / 3 = N\\ucirc / 3 = NkT energy of photon gas in Casimir vacuum such that H = TS = 4 NkT . Therefore, Kelvin absolute thermodynamic temperature scale [degree K] is identified as length scale [meter] and related to most probable wavelength and de Broglie thermal wavelength as Tβ =λmpβ =λdβ / 3 . Parallel to Wien displacement law obtained from Planck distribution, the displacement law λwS T =c2 /√{ 3} is obtained from Maxwell -Boltzmann distribution of speed of ``photon clusters''. The propagation speeds of sound waves in ideal gas versus light waves in photon gas are described in terms of vrβ in harmony with perceptions of Huygens. Newton formula for speed of long waves in canals √{ p / ρ } is modified to √{ gh } =√{ γp / ρ } in accordance with adiabatic theory of Laplace.

  19. CERN hearing day

    2005-01-01

    1 in 10 people suffer from hearing loss - do you? The Medical Service invites everyone working on CERN premises to participate in the National Hearing Day on: Thursday 10th March From 9am to 4pm The Infirmary, Blg. 57, Gr.Fl. We will be offering hearing tests (audiogram); information, advice on hearing loss, tinnitus and more. Deafness does not just affect the elderly: in Europe, 50% the hearing-impaired are under the age of 55. Exposure to excessive noise is one of the main reasons for hearing loss. But prevention is possible and effective: for example, Hearing protection devices could reduce tinnitus cases by 80%.

  20. CERN hearing day

    2005-01-01

    1 in 10 people suffer from hearing loss ? do you? The Medical Service invites everyone working on the CERN site to participate in the NATIONAL HEARING DAY on: Thursday 10th March 2005 From 9am to 4pm The Infirmary, Blg. 57, Ground Floor We will be offering hearing tests (audiograms), as well as information and advice on hearing loss, tinnitus, etc. Deafness does not just affect the elderly: in Europe, 50% of the hearing-impaired are under the age of 55. Exposure to excessive noise is one of the main reasons for hearing problems but prevention is possible. For example, hearing protection devices can prevent 80% of tinnitus cases.

  1. CERN hearing day

    2005-01-01

    1 in 10 people suffer from hearing loss - do you? The Medical Service invites everyone working on the CERN site to participate in the NATIONAL HEARING DAY on: Thursday 10th March 2005 From 9am to 4pm The Infirmary, Blg. 57, Ground Floor We will be offering hearing tests (audiograms), as well as information and advice on hearing loss, tinnitus, etc. Deafness does not just affect the elderly: in Europe, 50% of the hearing-impaired are under the age of 55. Exposure to excessive noise is one of the main reasons for hearing problems but PREVENTION IS POSSIBLE. For example, hearing protection devices can prevent 80% of tinnitus cases.

  2. CERN hearing day

    2005-01-01

    1 in 10 people suffer from hearing loss - do you? The Medical Service invites everyone working on CERN premises to participate in the National Hearing Day on: Thursday 10th March From 9am to 4pm The Infirmary, Blg. 57, Gr.Fl. We will be offering hearing tests (audiogram); information, advice on hearing loss, tinnitus and more. Deafness does not just affect the elderly: in Europe, 50% the hearing-impaired are under the age of 55. Exposure to excessive noise is one of the main reasons for hearing loss. But PREVENTION IS POSSIBLE AND EFFECTIVE: for example, Hearing protection devices could reduce tinnitus cases by 80%.

  3. Have a Good Day

    王秋海

    2002-01-01

    几次在一些场合和学生交谈,分手时道一声:Have a good day!,然而令我哑然的是,多数人竟反问我:I beg your pardon?让我啼笑皆非,弄得双方都很尴尬。有些人反应片刻似乎明白了此话的意思,但却不知如何作答,只好嗫嚅着发窘。

  4. The climatology, propagation and excitation of ultra-fast Kelvin waves as observed by meteor radar, Aura MLS, TRMM and in the Kyushu-GCM

    R. N. Davis

    2012-02-01

    Full Text Available Wind measurements from a meteor radar on Ascension Island (8° S, 14° W and simultaneous temperature measurements from the Aura MLS instrument are used to characterise ultra-fast Kelvin waves (UFKW of zonal wavenumber 1 (E1 in the mesosphere and lower thermosphere (MLT in the years 2005–2010. These observations are compared with some predictions of the Kyushu-general circulation model. Good agreement is found between observations of the UFKW in the winds and temperatures, and also with the properties of the waves in the Kyushu-GCM. UFKW are found at periods between 2.5–4.5 days with amplitudes of up to 40 m s−1 in the zonal winds and 6 K in the temperatures. The average vertical wavelength is found to be 44 km. Amplitudes vary with latitude in a Gaussian manner with the maxima centred over the equator. Dissipation of the waves results in monthly-mean eastward accelerations of 0.2–0.9 m s−1 day−1 at heights around 95 km, with 5-day mean peak values of 4 m s−1 day−1. Largest wave amplitudes and variances are observed over Indonesia and central Africa and may be a result of very strong moist convective heating over those regions. Rainfall data from TRMM are used as a proxy for latent-heat release in an investigation of the excitation of these waves. No strong correlation is found between the occurrence of large-amplitude mesospheric UFKW events and either the magnitude of the equatorial rainfall or the amplitudes of E1 signatures in the rainfall time series, indicating that either other sources or the propagation environment are more important in determining the amplitude of UFKW in the MLT. A strong semiannual variation in wave amplitudes is observed. Intraseasonal oscillations (ISOs with periods 25–60 days are evident in the zonal background winds, zonal-mean temperature, UFKW amplitudes, UFKW accelerations and the rainfall rate. This suggests that UFKW play a role in

  5. 5th Optimization Day

    Mees, Alistair; Fisher, Mike; Jennings, Les

    2000-01-01

    'Optimization Day' (OD) has been a series of annual mini-conferences in Australia since 1994. The purpose of this series of events is to gather researchers in optimization and its related areas from Australia and their collaborators, in order to exchange new developments of optimization theories, methods and their applications. The first four OD mini-conferences were held in The Uni­ versity of Ballarat (1994), The University of New South Wales (1995), The University of Melbourne (1996) and Royal Melbourne Institute of Technology (1997), respectively. They were all on the eastern coast of Australia. The fifth mini-conference Optimization Days was held at the Centre for Ap­ plied Dynamics and Optimization (CADO), Department of Mathematics and Statistics, The University of Western Australia, Perth, from 29 to 30 June 1998. This is the first time the OD mini-conference has been held at the west­ ern coast of Australia. This fifth OD preceded the International Conference on Optimization: Techniques and Applica...

  6. A day to celebrate

    Laëtitia Pedroso

    2010-01-01

    After several weeks of preparations and hard work on the part of many people, the events to mark International Women's Day at CERN on 8 March were a genuine success. They were followed with great interest by the outside world, judging by the flurry of activity on twitter, various blogs and the media coverage they generated.   Women on shift in the CERN control rooms. Women were overwhelmingly in the majority at the controls of the experiments and accelerators throughout the day, as well as acting as the guides for all official visits. There was no shortage of enthusiasm! "I'm very happy that CERN has supported the project, and I'm especially encouraged by the enthusiastic response from everyone who's taken part", says Pauline Gagnon, a physicist from the Indiana University group and a member of the ATLAS collaboration, who was behind the idea. "I hope that this kind of initiative will help to show that women have a place in science and that young women thinkin...

  7. Higgs Boson Pizza Day

    Stefania Pandolfi

    2016-01-01

    CERN celebrated the fourth anniversary of the historical Higgs boson announcement with special pizzas.    400 pizzas were served on Higgs pizza day in Restaurant 1 at CERN to celebrate the fourth anniversary of the announcement of the discovery of the Higgs Boson (Image: Maximilien Brice/ CERN) What do the Higgs boson and a pizza have in common? Pierluigi Paolucci, INFN and CMS collaboration member, together with INFN president Fernando Ferroni found out the answer one day in Naples: the pizza in front of them looked exactly like a Higgs boson event display. A special recipe was then created in collaboration with the chef of the historic “Ettore” pizzeria in the St. Lucia area of Naples, and two pizzas were designed to resemble two Higgs boson decay channel event displays. The “Higgs Boson Pizza Day” was held on Monday, 4 July 2016, on the fourth anniversary of the announcement of the discovery of the Higgs boso...

  8. 基于Kelvin-Voigt模型的粘弹性波动力学的本征化理论%Eigen Theory of Viscoelastic Dynamics Based on the Kelvin-Voigt Model

    郭少华

    2004-01-01

    利用固体力学本征化理论,研究了具有Kelvin-Voigt粘弹性质的各向异性固体的本征特性,并由此得到了各向异性粘弹性波动力学的广义Stokes方程,展现了波动过程的立体图像.讨论了几类常见各向异性固体的粘弹性波动规律,给出了一些新的结论.

  9. Boronic, diboronic, and α-amino-boronic acids derived from 1-ethynyl-3, 4-dimethoxybenzene

    This work was undertaken with the intention of synthesizing (α-amino-β-(3, 4-dihydroxyphenyl) ethylboronic acid. Unfortunately, the goal could not be attained since the isolation of the target compound could not be achieved though some information suggested its existence in the final product. The methods of synthesis used in the second half of the attempted preparation are described here (compounds in the first half have been published elsewhere). In this procedure, (β-(3, 4-dimethoxyphenyl)) ethenylboronic acid is esterified and azeotropic distillation is conducted to provide diethyl (β-(3, 4-dimethoxyphenyl)) ethenylboronate. This compound is dissolved in diglyme and diborane gas is introduced. The hydroboration product is then subjected to amination with hydroxylamine-0-sulfonic acid. (β-(3, 4-dimethoxyphenyl)) ethyl-α, α-diboronic acid is obtained from the residue of acetone extraction. The acetone extract is concentrated to a solid caramel, from which (α-borono-β-(3, 4-dimethoxyphenyl)) ethylammonium tetraphenylborate is formed. Conversion from the tetraphenylborate salt to (α-amino-β-(3, 4-dimethoxyphenyl)) ethylboronic acid hydrochloride is attempted by the double decomposition RH BPh4 + CsCl -- RH Cl + CsBPh4. The product is subjected to demethylation and treated with sodium tetraphenylborate to precipitate (α-borono-β-(3, 4-dihydroxyphenyl)) ethylammonium tetraphenylborate. Conversion of this to the target compound is tried by double decomposition. (Nogami, K.)

  10. Analysis of common cause failure in Wolsong 2/3/4 NPPs PSA

    Wolsong 2/3/4 Nuclear Power Plants (WS 2/3/4 NPPs) are CANDU 6 type Pressurized Heavy Water Reactors (PHWRs) being built in Wolsong site of Korea by Korea Power Electric Corporation (KEPCO). WS 2/3/4 NPPs are designed by Atomic Energy of Canada Ltd. (AECL). AECL performs Probabilistic Safety Assessment (PSA) for these NPPs. In this PSA, however, the effect of Common Cause Failure (CCF) is not analyzed due to the limitation of CANDU reliability data. Since the CCF is regarded as one of the most dominant contributors to the total core damage frequency (CDF) in Pressurized Water Reactor (PWR) PSA. KEPCO and Korea Atomic Energy Research Institute (KAERI) initiated WS 2/3/4 NPPs Level 2 PSA which includes the CCF analysis and detailed HRA. In WS 2/3/4 NPPs Level 2 PSA, the authors reviewed the CCF data used in PWR PSA, and applied these data for WS 2/3/4 NPPs Level 2 PSA. The MGL method is implemented for the CCF analysis of WS 2/3/4 NPPs. The analyzed results show that the effect of CCF is not negligible in CANDU PSA as well as in PWR PSA. So the CCF data of CANDU plants should be collected and incorporated into CANDU PSA

  11. ITER days in Moscow

    In connection with the successful completion of the Engineering Design of the International Thermonuclear Reactor (ITER) and the 50th anniversary of fusion research in the USSR, the Ministry of the Russian Federation for Atomic Energy (Minatom) with the participation of the Russian Academy of Sciences, organized the International Symposium 'ITER days in Moscow' on 7-8 June 2001. About 250 people from more than 20 states took part in the Meeting. The participants welcomed the R and D results of the ITER project and considered it as a necessary step to establish a basis for a fusion energy source. There were also some scientific presentations on the following topics: ITER physics basis; Effect of fusion research on general physics; Fusion power reactors; US interests in burning plasma

  12. CERN Heart Days

    2003-01-01

    14 & 15 OCTOBER 2003 The Medical Service and the Fire Brigade invite everyone working at CERN to participate in the above event. INFIRMARY 9 am to 16.30 pm Building 57, ground floor HEALTHY HEART? ♥ Evaluation of personal cardiac risks through the monitoring of: • Blood pressure • Cholesterol and sugar levels • Body Mass Index ... and more ♥ Leaflets, information and advice concerning cardiac issues FIRE BRIGADE 9 to 12am Building 65 FIRST AID COURSES ♥ What to do in a Cardiac Emergency (3 h duration) Places are limited and on reservation only (15 people / day) To book, E-mail the Medical Services on: service.medical@cern.ch

  13. Nuclear Power Day '86

    The proceedings in two volumes of the event ''Nuclear Power Day '86'' held in the Institute of Nuclear Research, contain full texts of 13 papers which all fall under the INIS Scope. The objective of the event was to acquaint broad technical public with the scope of the State Research and Development Project called ''Development of Nuclear Power till the Year 2000''. The papers were mainly focused on increased safety and reliability of nuclear power plants with WWER reactors, on the development of equipment and systems for disposal and burial of radioactive wastes, the introduction of production of nuclear power facilities of an output of 1,000 MW, and on the construction of nuclear heat sources. (Z.M.)

  14. World AIDS Day 1998.

    1999-01-01

    Excerpts of speeches given at a public rally on World AIDS Day 1998 underscore the need to energize support for those living with HIV/AIDS, emphasize the importance of increasing public education efforts, and memorialize those lost to the disease. Reverend Pat Bumgardner stressed the need to educate children about practicing safe sex and the dangers of drug use. He also focused attention on AIDS as a worldwide crisis, with the 30 million people who have HIV or AIDS. Councilwoman Margarita Lopez spoke about achieving objectives and securing resources through activism. She also condemned New York City's Mayor for trying to hinder the rally. Anne Chelimsky, who did not speak at the rally but attended it, reflected on her new role as an activist, and on how the rally affected her. PMID:11367196

  15. A map of the large day-night temperature gradient of a super-Earth exoplanet.

    Demory, Brice-Olivier; Gillon, Michael; de Wit, Julien; Madhusudhan, Nikku; Bolmont, Emeline; Heng, Kevin; Kataria, Tiffany; Lewis, Nikole; Hu, Renyu; Krick, Jessica; Stamenković, Vlada; Benneke, Björn; Kane, Stephen; Queloz, Didier

    2016-04-14

    Over the past decade, observations of giant exoplanets (Jupiter-size) have provided key insights into their atmospheres, but the properties of lower-mass exoplanets (sub-Neptune) remain largely unconstrained because of the challenges of observing small planets. Numerous efforts to observe the spectra of super-Earths--exoplanets with masses of one to ten times that of Earth--have so far revealed only featureless spectra. Here we report a longitudinal thermal brightness map of the nearby transiting super-Earth 55 Cancri e (refs 4, 5) revealing highly asymmetric dayside thermal emission and a strong day-night temperature contrast. Dedicated space-based monitoring of the planet in the infrared revealed a modulation of the thermal flux as 55 Cancri e revolves around its star in a tidally locked configuration. These observations reveal a hot spot that is located 41 ± 12 degrees east of the substellar point (the point at which incident light from the star is perpendicular to the surface of the planet). From the orbital phase curve, we also constrain the nightside brightness temperature of the planet to 1,380 ± 400 kelvin and the temperature of the warmest hemisphere (centred on the hot spot) to be about 1,300 kelvin hotter (2,700 ± 270 kelvin) at a wavelength of 4.5 micrometres, which indicates inefficient heat redistribution from the dayside to the nightside. Our observations are consistent with either an optically thick atmosphere with heat recirculation confined to the planetary dayside, or a planet devoid of atmosphere with low-viscosity magma flows at the surface. PMID:27027283

  16. A map of the large day-night temperature gradient of a super-Earth exoplanet

    Demory, Brice-Olivier; Gillon, Michael; de Wit, Julien; Madhusudhan, Nikku; Bolmont, Emeline; Heng, Kevin; Kataria, Tiffany; Lewis, Nikole; Hu, Renyu; Krick, Jessica; Stamenković, Vlada; Benneke, Björn; Kane, Stephen; Queloz, Didier

    2016-04-01

    Over the past decade, observations of giant exoplanets (Jupiter-size) have provided key insights into their atmospheres, but the properties of lower-mass exoplanets (sub-Neptune) remain largely unconstrained because of the challenges of observing small planets. Numerous efforts to observe the spectra of super-Earths—exoplanets with masses of one to ten times that of Earth—have so far revealed only featureless spectra. Here we report a longitudinal thermal brightness map of the nearby transiting super-Earth 55 Cancri e (refs 4, 5) revealing highly asymmetric dayside thermal emission and a strong day-night temperature contrast. Dedicated space-based monitoring of the planet in the infrared revealed a modulation of the thermal flux as 55 Cancri e revolves around its star in a tidally locked configuration. These observations reveal a hot spot that is located 41 ± 12 degrees east of the substellar point (the point at which incident light from the star is perpendicular to the surface of the planet). From the orbital phase curve, we also constrain the nightside brightness temperature of the planet to 1,380 ± 400 kelvin and the temperature of the warmest hemisphere (centred on the hot spot) to be about 1,300 kelvin hotter (2,700 ± 270 kelvin) at a wavelength of 4.5 micrometres, which indicates inefficient heat redistribution from the dayside to the nightside. Our observations are consistent with either an optically thick atmosphere with heat recirculation confined to the planetary dayside, or a planet devoid of atmosphere with low-viscosity magma flows at the surface.

  17. Toxicokinetics and biotransformation of 3-(4-methylbenzylidene)camphor in rats after oral administration

    3-(4-Methylbenzylidene)camphor (4-MBC) is an UV-filter frequently used in sunscreens and cosmetics. Equivocal findings in some screening tests for hormonal activity initiated a discussion on a possible weak estrogenicity of 4-MBC. In this study, the toxicokinetics and biotransformation of 4-MBC were characterized in rats after oral administration. Male and female Sprague-Dawley rats (n = 3 per group) were administered single oral doses of 25 or 250 mg/kg bw of 4-MBC in corn oil. Metabolites formed were characterized and the kinetics of elimination for 4-MBC and its metabolites from blood and with urine were determined. Metabolites of 4-MBC were characterized by 1H NMR and LC-MS/MS as 3-(4-carboxybenzylidene)camphor and as four isomers of 3-(4-carboxybenzylidene)hydroxycamphor containing the hydroxyl group located in the camphor ring system with 3-(4-carboxybenzylidene)-6-hydroxycamphor as the major metabolite. After oral administration of 4-MBC, only very low concentrations of 4-MBC were present in blood and the peak concentrations of 3-(4-carboxybenzylidene)camphor were approximately 500-fold above those of 4-MBC; blood concentrations of 3-(4-carboxybenzylidene)-6-hydroxycamphor were below the limit of detection. Blood concentration of 4-MBC and 3-(4-carboxybenzylidene)camphor peaked within 10 h after 4-MBC administration and then decreased with half-lives of approximately 15 h. No major differences in peak blood levels between male and female rats were seen. In urine, one isomer of 3-(4-carboxybenzylidene)hydroxycamphor was the predominant metabolite [3-(4-carboxybenzylidene)-6-hydroxycamphor], the other isomers and 3-(4-carboxybenzylidene)camphor were only minor metabolites excreted with urine. However, urinary excretion of 4-MBC-metabolites represents only a minor pathway of elimination for 4-MBC, since most of the applied dose was recovered in feces as 3-(4-carboxybenzylidene)camphor and, to a smaller extent, as 3-(4-carboxybenzylidene)-6-hydroxycamphor

  18. On the incidence of Kelvin-Helmholtz instability for mass exchange process at the Earth’s magnetopause

    R. Smets

    Full Text Available Due to the velocity shear imposed by the solar wind flowing around the magnetosphere, the magnetopause flanks are preferred regions for the development of a Kelvin-Helmholtz instability. Since its efficiency for momentum transfer across the magnetopause has already been established, we investigate its efficiency for mass transfer. Using nonresistive magnetohydrodynamic simulations to describe the magnetic field shape in the instability region, we use test-particle calculations to analyse particle dynamics. We show that the magnetopause thickness and the instability wave-length are too large to lead to nonadiabatic motion of thermal electrons from the magnetosphere. On the other hand, the large mass of H+, He+ and O+ ions leads to such nonadiabatic motion and we thus propose the Kelvin-Helmholtz instability as a mechanism for either magnetospheric ion leakage into the magnetosheath or solar wind ion entry in the magnetosphere. Test-particle calculations are performed in a dimensionless way to discuss the case of each type of ion. The crossing rate is of the order of 10%. This rate is anti-correlated with shear velocity and instability wavelength. It increases with the magnetic shear. The crossing regions at the magnetopause are narrow and localized in the vicinity of the instability wave front. As a Kelvin-Helmholtz instability allows for mass transfer through the magnetopause without any resistivity, we propose it as an alternate process to reconnection for mass transfer through magnetic boundaries.

    Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; MHD waves and instabilities – Space plasma physics (numerical simulation studies

  19. Collision-Induced Infrared Absorption by Collisional Complexes in Dense Hydrogen-Helium Gas Mixtures at Thousands of Kelvin

    Abel, Martin; Frommhold, Lothar; Li, Xiaoping; Hunt, Katharine L. C.

    2011-06-01

    The interaction-induced absorption by collisional pairs of H{_2} molecules is an important opacity source in the atmospheres of the outer planets and cool stars. The emission spectra of cool white dwarf stars differ significantly in the infrared from the expected blackbody spectra of their cores, which is largely due to absorption by collisional H{_2}-H{_2}, H{_2}-He, and H{_2}-H complexes in the stellar atmospheres. Using quantum-chemical methods we compute the atmospheric absorption from hundreds to thousands of kelvin. Laboratory measurements of interaction-induced absorption spectra by H{_2} pairs exist only at room temperature and below. We show that our results reproduce these measurements closely, so that our computational data permit reliable modeling of stellar atmosphere opacities even for the higher temperatures. L. Frommhold, Collision-Induced Absorption in Gases, Cambridge University Press, Cambridge, New York, 1993 and 2006 Xiaoping Li, Katharine L. C. Hunt, Fei Wang, Martin Abel, and Lothar Frommhold, "Collision-Induced Infrared Absorption by Molecular Hydrogen Pairs at Thousands of Kelvin", International Journal of Spectroscopy, vol. 2010, Article ID 371201, 11 pages, 2010. doi: 10.1155/2010/371201 M. Abel, L. Frommhold, X. Li, and K. L. C. Hunt, "Collision-induced absorption by H{_2} pairs: From hundreds to thousands of Kelvin," J. Phys. Chem. A, published online, DOI: 10.1021/jp109441f L. Frommhold, M. Abel, F. Wang, M. Gustafsson, X. Li, and K. L. C. Hunt, "Infrared atmospheric emission and absorption by simple molecular complexes, from first principles", Mol. Phys. 108, 2265, 2010

  20. Microgalvanic activity of an Mg-Al-Ca-based alloy studied by scanning Kelvin probe force microscopy

    An Mg-Al-Ca based alloy was investigated by scanning electron microscopy, energy dispersive spectroscopy and scanning Kelvin probe force microscopy following extrusion. The investigations revealed two main intermetallics, i.e. Al-Ca(Sn,Sr) and Al-Mn-Fe, both distributed along the extrusion direction and having distinctive morphology. The microgalvanic couples, i.e. Al-Ca(Sn,Sr)/α-Mg and Al-Mn-Fe/α-Mg showed positive Volta potential differences with the Al-Mn-Fe intermetallic being the noblest (i.e. 262 ± 18 mV vs 62 ± 7 mV)